International Journal of Chemical Reactor Engineering

Published by De Gruyter

Volume 9 Issue 1

August 2011

Issue of International Journal of Chemical Reactor Engineering

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Contents
Journal Overview

Review

March 2, 2011

Kinetic Modeling and Reactor Simulation and Optimization of Industrially Important Polymerization Processes: a Perspective

Manojkumar Ramteke, Santosh K. Gupta

Abstract

The field of what is now referred to as polymer reaction engineering started in the early 1930s with Staudingers discovery of macromolecules. Though the earlier work was related primarily to synthesis and kinetics, the field started growing at increasing rates, possibly in the late 1950s or early 1960s. In the early years, this field provided a challenging area of research. It has evolved from the modeling of simple polymerizations to that of more complex systems, to experimentation for filling the gaps in our knowledge, to optimization. This mini-review summarizes a small sampling of the literature in polymerization reaction engineering over the last about four decades using a personal perspective. The concepts in this area are now being applied in a variety of specialized domains, e.g., polymerization at the nano scale, design and control of chain macrostructure and rapid optimal switch-over of grades being manufactured, molecular simulation and computational fluid dynamics, etc.

September 28, 2011

Multiphase Flow Measurement Techniques for Slurry Transport

Katherine J. Albion, Lauren Briens, Cedric Briens, Franco Berruti

Abstract

Multiphase flow measurement techniques are required to monitor slurry transport in industrial processes. Monitoring methods are used to ensure that the slurry is transported under specific conditions, and as an indicator of potential problems. Intrusive and non-intrusive sensors are used to measure solids concentration, mass flowrates, velocities and flow patterns. Sensing techniques are based on pressure, electrical, sound, imaging and nuclear properties. In this literature review, measurement techniques examined for horizontal pipelines include pressure measurements, the Coriolis mass flowmeter, acoustic sensors, capacitance, conductivity and microwave probes, electrical resistance tomography, laser Doppler imaging and the Pulsed Neutron Activation Technique. The principles of operation are described along with experimental results and a critique of the sensors and technology.

Article

January 8, 2011

Mathematical Modeling of Coal Gasification in a Fluidized Bed Reactor Using a Eulerian Granular Description

Pablo Cornejo, Oscar Farías

Abstract

A three-dimensional computational model was developed to describe the coal-gasification processes inside fluidized-bed reactors. The commercial multi-purpose CFD code FLUENT 6.3 was employed, taking into account drying, volatilization, combustion and gasification processes. Both gas phase and solid phase were described using a eulerian approach to model the exchanges of mass, energy and momentum between phases. The disperse phase was described using the kinetic theory of granular flows. The chemical model involved five heterogeneous and five homogeneous chemical reactions, tracking seven species in the gas phase (CO2, CO, H2O, CH4, H2, O2 and N2) and one specie in the solid phase (C(s)). Drying and volatilization rates were estimated by mass conservation. Heterogeneous reaction-rates were determined by combining an Arrhenius kinetic-rate and a diffusion rate using the kinetics/diffusion Surface Reaction Model; the model was implemented within FLUENT through UDFs (User Defined Functions). Homogeneous reaction-rates were described by a turbulent mixing rate using the Eddy Dissipation Model available in FLUENT. Calibration and validation were performed by using existing experimental data from a benchmark coal-gasification case available in the literature. Results are in good agreement with experimental data, capturing known phenomena like fluidization-bed height, temperature distribution and species concentrations. The main contribution of the present work was implementing the necessary sub-models within the FLUENT code in order to handle reactive fluidized-beds in complex geometries. This allowed combining the flexibility of a commercial CFD code with the accuracy of simplified models developed in academic frameworks.

January 8, 2011

Modeling and Optimizing of Mechanically Agitated Vessels by Central Composite Rotatable Design Method

Ramin Zadghaffari, Jafarsadegh Moghaddas, F. Fakheri, H. Razmi, H. Heidari

Abstract

A central composite rotatable design (CCRD) methodology was used to analyze the effect of some operating variables on gas-liquid two phase mixing time in an agitated tank driven by dual 6-blade Rushton turbines. The variables chosen were the impellers rotational speed (x1), gas flow rate (x2), probe location (x3) and tracer injection point (x4). The mathematical relationship of mixing time on the four significant independent variables can be approximated by a nonlinear polynomial model. Predicted values were found to be in good agreement with the experimental values (R-sq of 95.9 percent and R-Sq (Adj) of 95.7 percent for response Y). This study has shown that central composite design could efficiently be applied for the modeling of mixing time, and it is an economical way of obtaining the maximum amount of information with the fewest number of experiments.

February 3, 2012

Comparison of Lumping Approaches to Predict the Product Yield in a Dual Bed VGO Hydrocracker

Sepehr Sadighi, Arshad Ahmad, Mansoor Shirvani

Abstract

In this research, to predict the product yields of a pilot scale VGO hydrocracking reactor charged with mono functional hydrotreating and hydrocracking catalysts, two different four-lump models are developed. The first one, called combined bed model, is a simplex in which there is no boundary between hydrotreating and hydrocracking reactions through the reactor. The second one, called dual bed model, is a rigorous model in which hydrogen consumption and hydrotreating reactions are included. In this way, the reactor is subdivided into two different layers, so the effect of hydrotreating reactions on the hydrocracking section can be considered. Results show that the absolute average deviation (AAD%) of the yield prediction for the combined bed and the dual bed models are 8.23 percent and 5.87 percent, respectively. The main reason for the lower average deviation of the dual bed model is its higher accuracy to predict the yield of gas which is also the major advantage of this approach. However, the simplicity of the combined bed model can make it more applicable and attractive, especially when hydrogen consumption as well as sulfur, nitrogen and aromatic specifications of the feed and products are not accessible.

January 16, 2011

Adsorption Thermodynamics of Toxin (65 kDa) and Protoxin (130 kDa) from Bacillus thuringiensis by Several Minerals

Xueyong Zhou, Ning Liu, Jianbao Gao, Mei Zhang, Fei Cao

Abstract

The adsorption thermodynamics of toxin (65 kDa) and protoxin (130 kDa) from Bacillus thuringiensis (Bt) by several minerals (montmorillonite, kaolinite and silica) were investigated. The adsorption of toxin and protoxin by minerals was a spontaneous process in the range of temperature from 278K to 318K. The ?G0ads values of the toxin adsorption by above minerals ranged from -35.30 to -43.81 kJ mol-1, and the protoxin adsorption ranged from -35.87 to -44.83 kJ mol-1. The adsorption isotherms of both proteins followed Langmuir equation and the maximum adsorbed amount (Nadsmax) of protoxin were lower than those of toxin. The adsorption of Bt proteins on minerals was exothermic process, companying a negative value of ?H0ads. The ?H0ads values of the adsorption of toxin were between -3.85 and -4.98 kJ mol-1 and the protoxin were between -2.60 and -4.53 kJ mol-1. The standard adsorption entropy changes (?S0ads) of toxin ranged from 110.73 to 122.16 J mol-1 K-1, and of protoxin ranged from 122.57 to 132.77 J mol-1 K-1. The positive standard entropy (?S0ads) indicated that the freedom increased when the insecticidal proteins from B. thuringiensis adsorbed minerals. The Kads, ?G0ads and ?S0ads of toxin in value were lower than those of protoxin, suggesting that the spontaneous trend and the affinity between protoxin and minerals were larger than those of toxin.

January 16, 2011

Non Linear State and Parameters Estimation in Chemical Processes: Analysis and Improvement of Three Estimation Structures Applied to a CSTR

Héctor Botero, Hernán Álvarez

Abstract

This paper proposes a new composite observer capable of estimating the states and unknown (or changing) parameters of a chemical process, using some input-output measurements, the phenomenological based model and other available knowledge about the process. The proposed composite observer contains a classic observer (CO) to estimate the state variables, an observer-based estimator (OBE) to obtain the actual values of the unknown or changing parameters needed to tune the CO, and an asymptotic observer (AO) to estimate the states needed as input to the OBE. The proposed structure was applied to a CSTR model with three state variables. With the proposed structure, the concentration of reactants and other CSTR parameters can be estimated on-line if the reactor and jacket temperatures are known. The procedure for the design of the proposed structure is simple and guarantees observer convergence. In addition, the convergence speed of state and parameter estimation can be adjusted independently.

January 23, 2011

Simulation and Optimization of an Auto-Thermal Ammonia Synthesis Reactor

Rakesh Angira

Abstract

This paper deals with the simulation and optimization of an auto-thermal ammonia synthesis reactor. In the present study, three methods, viz., Eulers method, Runge-Kutta method (4th order with fixed step size) and NAG subroutine (D02EJF) in MATLAB, are used for simulation. A software package POYMATH is also used to solve three coupled model equations. The effect of top temperature on the optimal reactor length is discussed and results are compared with that reported in literature. Also, the Differential Evolution (DE) in combination with Runge-Kutta method is used for optimization, considering both reactor length and top temperature simultaneously as independent variables. The new results obtained for optimal reactor length and top temperature are presented.

January 23, 2011

Parameteric Optimization of Dye Removal by Electrocoagulation Using Taguchi Methodology

Vimal Chandra Srivastava, Digvijay Patil, Kaushal Kumar Srivastava

Abstract

This paper utilizes a statistical approach, the Taguchi optimization methodology (L16 orthogonal array), to determine the optimum conditions for the orange-G (OG) dye removal from aqueous solution by electrocoagulation (EC) using iron plate electrodes. The experimental parameters investigated were initial dye concentration (C0): 50-200 mg/l; initial pH (pH0): 2-8; supporting electrolyte (NaCl) concentration (m): 0-1.5 g/l; electrode gap (g):1-2.5 cm; and applied voltage (Vap): 6-24 V. These parameters were varied at four levels to see their effects on the removal efficiency (RE). Vap was found to be the most significant factor with a 24.6 percent contribution, followed by parameter C0 with 20.2 percent contribution to the RE. The predicted optimum value of RE for C0 = 200 mg/l was found to be 84.9 percent. Confirmation experiments have been performed to prove the effectiveness of the Taguchi technique after the optimum levels of process parameters are determined.

January 23, 2011

Experimental Study of Hydrodynamic Characteristics and CO₂ Absorption in Producer Gas Using CaO-sand Mixture in a Bubbling Fluidized Bed Reactor

M.M. Mahadzir, Z.A. Zainal

Abstract

Producer gas, from biomass gasification process can be used to generate power as an alternative to fossil fuel. Carbon dioxide (CO2) content in the producer gas is acts as a diluent gas resulted in low heating value. We used limestone (which is of rather wide occurrence in Malaysia) that consisted mainly of the mineral calcite (calcium oxide, CaO) as calcium based sorbent to absorb CO2 in the producer gas. Removing the CO2 from the producer gas will improved its heating value. In this paper, the first step was to study the behavior of CaO-sand mixtures in a cold model experiment. The effects of the CaO-sand mixtures, the CaO particle sizes, the volume flow rate and the pressure of air intake were investigated experimentally. Then, the hot model experimental was conducted to investigate CO2 absorption at the optimum condition obtained from the cold model experiment resulted. The CaO percentages of 50 and 40 in sand were found to have a good fluidization at all air pressures (200-600 kNm-2). In addition to that, the 1000 micron particle size of the CaO-sand mixture and the volume flow rate of air between 0.00025- 0.00092 m3s-1 were also found to give a good fluidization. In the hot model experiment, the best CO2 absorption occurred at 50 percent CaO mixture with simulated gas pressure of 300 kNm-2 and the volume flow rate of 0.00075 m3s-1 at 650-750°C in a bubbling fluidized bed reactor (BFBR).

January 23, 2011

Maximum Power Output of Multistage Continuous and Discrete Isothermal Endoreversible Chemical Engine System with Linear Mass Transfer Law

Lingen Chen, Shaojun Xia, Fengrui Sun

Abstract

The maximum power output of a multistage isothermal endoreversible chemical engine system operating between a finite potential capacity high-chemical-potential reservoir and an infinite potential capacity low-chemical-potential environment with the linear mass transfer law is investigated in this paper. For the fixed initial time and fixed initial concentration of the key component in the high-chemical-potential reservoir, the continuous model is optimized by applying Hamilton-Jacobi-Bellman (HJB) theory and Euler-Lagrange equation, respectively, and the discrete model is optimized by applying dynamic programming method and discrete maximum principle, respectively. Numerical examples for the discrete model with three different boundary conditions are provided, and the results are also compared with those for the continuous model. The results show that both of the maximum power outputs of the limiting continuous and multistage discrete isothermal endoreversible chemical engine systems are equal to the difference between their classical reversible thermodynamic performance limits and a dissipation term. The relative concentration of the key component in the high-chemical-potential reservoir for the maximum power outputs of the continuous and discrete models decreases with the increase of time linearly. The relationships among the maximum power output of the system, the process period and the final concentration of the key component in the high-chemical-potential fluid reservoir are discussed in detail.

January 23, 2011

A Novel Route for Conversion of Free Fatty Acids in Acidic Oils to Methyl Esters by In-Situ Hydrolysis of Methyl Acetate

Vijaya Lakshmi Ch, Uday Bhaskar R.V.S, Viswanath Kotra, Satyavathi Bankupalli

Abstract

Biodiesel from clean oils is comparatively easier than production from crude and non-edible oils. To achieve maximum yield of biodiesel, a two stage process is adopted in which non-edible oils are used as feed-stock: an acid catalyzed esterification of free fatty acids followed by base catalyzed transesterification. Presence of water formed during esterification reaction is detrimental to a viable transesterification process. In the present work, an alternate method for removal of water by in situ hydrolysis reaction of methyl acetate is introduced. The dehydration using methyl acetate during esterification has yielded good results as the soap formed during transesterification was minimal. The results indicated high conversion of triglycerides to methyl ester for lower oil to methanol ratio and at a lower temperature. For 1:3 molar ratio of oil to methanol, the conversion obtained was less than 90 percent and is equivalent to conversions with higher alcohol ratios during esterification in the absence of methyl acetate. These results are indicative of the fact that use of methyl acetate reduces the alcohol to oil ratio without affecting the conversions. Moreover, higher conversions are possible at lower temperatures in the presence of methyl acetate. It is further observed that the oils that are subjected to free fatty acid conversions in the presence of methyl acetate record very little soap formation during the transesterification reactions, thereby resulting in higher grade of biodiesel.

January 23, 2011

Compatibility of Transport and Reaction in Membrane Reactors Used for the Oxidative Dehydrogenation of Short-Chain Hydrocarbons

Christof Hamel, Tanya Wolff, Andreas Seidel-Morgenstern

Abstract

The possibility of process intensification by enhancing selectivity and yield in networks of parallel and series reactions was investigated applying asymmetric multilayer ceramic and sintered metal membranes in a dead-end configuration for a controlled distributed reactant feeding. The oxidative dehydrogenation of ethane to ethylene was selected as a model reaction applying three different doped and/or active VOx/?-Al2O3 catalysts. Experimental investigations were performed in a pilot scale in order to evaluate the potential of a distributed dosing via membranes with respect to operation conditions and compatibility of reaction and membrane properties. It was demonstrated that the rates of reaction and trans-membrane mass transfer have to be compatible for an optimal membrane reactor operation avoiding back diffusion of reactants out of the catalytic zone as well as achieving safety aspects. Therefore, a detailed modeling of the trans-membrane mass transfer under reaction conditions was carried out. As a main result, it was found metal membranes possess a favorable mechanical stability, relatively low costs for production and the possibility to control mass transfer if the rate of reaction and mass transfer in the membrane is compatible which can adjusted by the trans-membrane pressure and the catalyst activity, respectively.

February 7, 2012

Determination of Kinetic Parameters for Enzymatic Cellulose Hydrolysis Using Hybrid Differential Evolution

Yu-Ting Chen, Feng-Sheng Wang

Abstract

A kinetic model could provide a dynamical description of mechanism in that it is required for analysis, design, optimization and control. Temperature and pH could affect the cellulose activity. In this study, we have introduced the kinetic model, which includes temperature and pH effects, to describe dynamic behaviors of the enzymatic hydrolysis of cellulose to glucose. A commercial enzyme was applied to the hydrolysis process. Various batch time-series observations were collected and used to estimate the model parameters of the kinetic model. Hybrid differential evolution with a geometric mean mutation was applied to determine optimal estimates, and then such estimates were used as the initial starting for a gradient-based method to obtain the refined solution. The approach is capable of predicting the dynamic behaviors of the cellulose hydrolysis process as observed extra experimental validations. Furthermore, the time-average sensitivities were applied to evaluate accuracy and robustness of the mathematical model.

January 23, 2011

Unsteady Flow Mixing Effect in Bionic Micro-Flow Channel

Chin-Tsan Wang, C. T. Chang, Tzu-Yang Hu, Tzong-Shyng Leu

Abstract

Micro-mixers are studied extensively due to their high mixing efficiency. A periodic flow variation at the channel entrance will be used to drive fluids in this study to achieve a mixing effect. Numerical analysis is used and verified by experiment in the study to identify the group of operating factors, such as Reynolds number Re, the driving phase difference ? and the driving frequency ratio Fr, needed for the fluid to achieve the best mixing result for a bionic micro-mixer. It is found in this study that the mixing efficiency is related to the velocity period distribution; the more even the velocity period distribution becomes, the better the mixing efficiency and the best group of operating factors is found (Re2 = 1, Rer = 0.85, Fr = 1, F2 = 50 Hz, I/Am = 1, ? = 3/4 ?). Furthermore, a larger aspect ratio results in a better mixing efficiency. The influence of wall-effect on the flow mixing decreases with AR. It is found that there exists an optimal mixing efficiency at aspect ratio AR = 10. These research results could be used to improve the design of a bionic micro-mixer.

January 23, 2011

The Homotopy Analysis Method for Fractional Cauchy Reaction-Diffusion Problems

Subir Das, Rajnesh Kumar, Praveen Kumar Gupta

Abstract

In this article, homotopy analysis method is successfully applied to obtain the approximate analytical solutions of the characteristic Cauchy reaction-diffusion equation with fractional time derivative. The beauty of the article is the wonderful application of Caputo fractional order time derivative. The linear interactions of the merging populations are examined using perturbation theory and the method of matched asymptotic expansions. The solutions of the problem for different particular cases are presented graphically.

February 5, 2011

Numerical Study of Bubbling Gas-Solid Fluidized Beds Hydrodynamics: Influence of Immersed Horizontal Tubes and Data Analysis

Teklay W. Asegehegn, Matthias Schreiber, Hans J. Krautz

Abstract

Numerical simulations of two dimensional gas-solid bubbling fluidized beds with and without immersed horizontal tubes were performed using Eulerian - Eulerian Two Fluid Model (TFM). The influences of immersed horizontal tubes and different data analyses techniques on the bed and bubble hydrodynamics were investigated. The results were compared with experimental data and correlations available in the literature.Different ways for extracting and defining hydrodynamic properties, such as bed expansion ratio and bubble properties, were found to influence the simulation results. Furthermore, the time-averaged values showed greater sensitivity to the length of averaging time in the first few seconds. With regard to tube influence, immersed tubes were found to be the main source of bubble breakup. Thus, the calculated mean bubble diameters and rise velocities were found to be lower with tubes than without for the same bed geometry and superficial velocity. The bubble shapes were observed to elongate in the vertical direction in the tube bank region compared to the bed region below and above the tube bank. In addition, the TFM was found to successfully predict the overall time-averaged solid motion and distribution. For beds with immersed tubes, defluidized regions were observed at the upper part of the tubes where solid particles rested without moving. On the other hand, the lower parts of the tubes were usually covered with gas pockets. These effects were seen to reduce with increasing superficial velocity.

February 5, 2011

The Characteristic of Power Spectral of Pressure Fluctuation Signal in CFB Riser with Fractal Analysis

Liping Ma, Yanfu Shi, Huarui Yu

Abstract

Hydrodynamics plays a crucial role in defining the performance of circulating fluidized beds (CFB), and pressure fluctuation signal has been used to analyze the dynamic behavior in it. From this point of view, in the present study, the power spectral characteristic of pressure fluctuation signal in CFB is analyzed based on fractal theory. Analysis also takes into account the power spectrum and correlation analysis of pressure fluctuation signal. Results show that the pressure fluctuation signal has the characteristic of 1/f noise when the solid circulating flow is smaller. Elsewhere when the solid circulating flow is increased, pressure fluctuation signal has the characteristic of Fractal Brownian Motion (FBM). The value of power spectral exponent ? is between 2~7, this value is fluctuant in the upper and bottom zone of riser, and it is somewhat steady in the middle zone of riser, which could be used to judge the transition of flow regimes from thin pneumatic flow to dense pneumatic conveying. Correlation analysis exteriorly indicated the chaos characteristic of pressure fluctuation signal in CFB.

February 5, 2011

Three-Dimensional Flamelet Simulation of Polycyclic Aromatic Hydrocarbons Formation in DI-Diesel Engines

Beijing Zhong, Shuai Dang, Jun Xi

Abstract

In this study, numerical simulations for an n-heptane fueled Chaochai 6102bzl direct injection diesel engine are performed in order to predict the chemical details of the combustion process and resulting polycyclic aromatic hydrocarbons (such as benzene, naphthalene, phenanthrene and pyrene) formation. The diesel geometry and reduced kinetic mechanism of n-heptane oxidation, which includes only 86 reactions and 57 species, have been developed and incorporated into the computational fluid dynamics code, FLUENT. The diesel unsteady laminar flamelet model, turbulence model and spray model have been employed in the numerical simulations. The numerical simulation results showed that the polycyclic aromatic hydrocarbons were firstly increased with the increase of diesel crank angel and then decreased, which was mostly located at the bottom of diesel combustion chamber wall.

February 5, 2011

Mass Transport Properties of a Flow-Through Electrolytic Reactor Using Zinc Reduction System

Abbas H. Sulaymon, Mumtaz A. Zablouk, Anaam A. Sabri, Ali H. Abbar

Abstract

An electrolytic process for the removal of Zn(II) from aqueous solution using a parallel amalgamated copper screens cathode operated in the flow through mode is proposed. The current-potential curves recorded at a rotating amalgamated copper disc electrode were used to determine diffusion coefficient of Zn(II). The performance of electrolytic reactor was investigated by using different flow rates at initial zinc ion concentration(48 mg/L). Taking into account the residential Zn(II) concentration, the best results were obtained for cathode potential of (-1.35 V vs. SCE) at flow rate (320 L/h). Zinc ion concentration was found to decrease from 48 mg/L to 1 mg/L during 120 min. of electrolysis. The experimental data are well correlated in term of Sherwood and Reynolds numbers based on the wire diameter of woven screen for characteristic length .Empirical correlation characterized the mass transport properties of the reactor is: Sh = 8.077 Re0.363.

February 5, 2011

Some Exact Solutions for Helical Flows of Maxwell Fluid in an Annular Pipe due to Accelerated Shear Stresses

Muhammad Jamil, Constantin Fetecau, Najeeb Alam Khan, Amir Mahmood

Abstract

Some exact solutions corresponding to helical flows of Maxwell fluid between two infinite coaxial circular cylinders are determined by means of finite Hankel transform, presented in series form, satisfied all imposed initial and boundary conditions. The motion is produced by the inner cylinder that applies the torsional and longitudinal time-dependent accelerated shear stresses to the fluid. The corresponding solutions for Newtonian fluid and large-time solutions are also obtained as limiting cases and effect of material parameters on the large-time solutions are discussed. Finally, the influence of pertinent parameters as well as a comparison between Maxwell and Newtonian fluids on the velocity components and shear stresses profiles is also examined by graphical illustrations.

February 5, 2011

CFD Modeling and Simulation of a Catalytic Micro-Monolith

Almerinda Di Benedetto, Valeria Di Sarli

Abstract

In this work, a first step in modeling and simulating the thermal behavior of an entire catalytic micro-monolith was performed. In particular, a Computational Fluid Dynamics (CFD) model was developed for simulating three-channel and five-channel micro-combustors. For both configurations, the operating maps were built as functions of the inlet gas velocity and compared to the operating map of a single-channel configuration.Results show that, due to the relevance of heat losses in micro-devices, it is not possible to extrapolate the behavior of the multi-channel configurations from that of the single channel. Therefore, simulation of the entire catalytic micro-monolith is needed. However, this is computationally demanding: it has been found that the CPU time almost linearly increases with the number of channels simulated.Finally, for a fixed total mass flow rate, it has been demonstrated the opportunity to maximize the overall fuel conversion by means of a non-uniform distribution of mass flow rates among the channels.

March 5, 2011

Production of Acid Silica Sols and Gels by Using a Y-shaped Reactor and Dilution Technique

Takashi Saeki, Saori Kikuchi, Masahiro Ishida, Aya Kaide

Abstract

Silica sols were produced continuously by using a Y-shaped reactor. Diluted sodium silicate and sulfuric acid were forced to collide with each other at the intersection of the reactor. The produced silica sols gradually increase in the viscosity and finally form silica gels. In this study, the gelation process of silica sols was considered by rheological measurements. The onset time of gelling was strongly affected by both the concentration of SiO2 and the excessive rate of sulfuric acid. Also, the gelation time can be controlled by the addition of appropriate amount of water of sulfuric acid solution.

March 5, 2011

Molecular Dynamics Simulation of Water and Ions in Nanopores of Lysozyme Protein Crystal

Nafiseh Farhadian, Mojtaba Shariaty-niassar, Kourosh Malek, Ali Maghari

Abstract

Highly porous cross-linked protein crystals are a novel class of nanoporous materials with vast applications in biocatalysis and selective separation membranes. Long time equilibrium molecular dynamics (MD) simulations were performed to study the behavior of water and ions in the nanopores of lysozyme protein crystals. Pore size profile along different axes showed that the main pores lie along the z-axis consisting of an anisotropic structure. The morphology of pore network and pore sizes, influence water dynamics in protein crystals. Transport properties of water molecules were investigated under two diffusion regimes around protein surface, i.e. surface and core zone. Results showed that water molecules near the surface zone had the anomalous diffusion behavior while the behavior in the core zone was diffusive. Moreover, an anisotropic diffusion behavior was occurred along different axes in accordance to experimental predictions. Simulations demonstrated that nearly 16 percent of water molecules have the residence time above 100 ps at the first hydration layer around the protein crystal, while 3.3 percent of those remain in the cavities over a longer time of about 1400 ps. The behavior of chloride counter ions in the first hydration layer around the protein crystal or on the specific residues of the crystal was investigated as well. The simulation results were in a good agreement with the previous theoretical studies and experimental data. This study provides valuable insights into understanding the transport phenomena in the protein crystals in view of the nature of solvent-protein and ion-protein interactions.

March 5, 2011

Study on a Coupling Reactor for Catalytic Partial Oxidation of Natural Gas to Syngas

Weisheng Wei, Wei Du, Jian Xu, Xiaojun Bao

Abstract

In the current paper, engineering issues for catalytic partial oxidation of natural gas to syngas have been investigated in a pilot plant. In contrast to the microreactor for catalyst evaluation, for a large scale fixed bed reactor operated under high temperature and pressure, attentions should be paid to: introduction method of feeding gases, preheat temperature of feeds, and the coupling of exothermic oxidation reactions with endothermic reforming reactions. As indicated by thermodynamic calculations at a pressure of 2.0 MPa, the reaction temperature should reach at least 1273 K in order to obtain a yield of CO higher than 80 percent. To reach such a high reaction temperature under adiabatic conditions, the feeding gases need to be preheated to a temperature within the range of 773-923 K. With safety considerations of explosion potential, a newly designed nozzle that can premix reactant gases well and thus is suitable for natural gas catalytic partial oxidation process, has been adopted in this pilot unit. A thermally coupled fixed bed reactor is then proposed and proved to be feasible based on thermodynamic calculations and experimental validations.

March 5, 2011

A Three-Dimensional Model Frame for Modelling Combustion and Gasification in Circulating Fluidized Bed Furnaces

Kari Myöhänen, Timo Hyppänen

Abstract

In a large-scale circulating fluidized bed furnace, the local feeding of fuel, air, and other input materials, and the limited mixing rate of different reactants produce spatially non-uniform process conditions. To simulate the real conditions, the furnace should be modelled three-dimensionally or the three-dimensional effects should be accounted for. The fluidized beds can be studied by different model approaches, ranging from micro-scale particle models and meso-scale two-fluid models to macro-scale engineering models. The fundamentals-oriented micro- and meso-scale models are not yet capable for practical comprehensive calculations of industrial scale circulating fluidized bed units, including modelling of reactions, attrition of particles, and heat transfer. The following paper introduces a three-dimensional semi-empirical steady state model for modelling combustion and gasification in circulating fluidized bed processes. The incorporated submodels include fluid dynamics of solids and gases, fuel combustion and limestone reactions, comminution of solid materials, homogeneous reactions, heat transfer within suspension and to surfaces, models for separators and external heat exchangers, and a model for nitrogen oxide chemistry. The model structure and the main features together with a sample calculation are described. A review of the currently used model approaches for fluidized bed systems at different scales is included to relate the presented model to other modelling field and to justify the need for semi-empirical modelling approach.

March 5, 2011

Numerical Investigation of Flow Friction and Heat Transfer in a Channel with Various Shaped Ribs Mounted on Two Opposite Ribbed Walls

Khwanchit Wongcharee, Wayo Changcharoen, Smith Eiamsa-ard

Abstract

Heat transfer and fluid flow characteristics through a channel with two - dimensional transverse ribs are numerically investigated. The effects of different shaped ribs (rectangular rib, triangular rib, cylindrical rib, concave-concave rib, convex-concave rib, long convex-short concave rib and long concave-short concave rib) are examined. The investigation is performed for the ribs mounted on top and bottom walls with rib pitch to height ratio (P/e) of 6.67, in Reynolds number between 3000 and 7000, under constant wall temperature condition. For the present case, the data predicted by SST k-omega turbulence model show better agreement with the experimental data, than those predicted by RNG k-epsilon turbulence model. The mean heat transfer, flow friction, temperature fields and the local heat transfer coefficients as well as the flow structure behaviors are reported. For the ribs considered, the channel with triangular-ribs yields the highest Nusselt number, the one with concave-concave rib provides the highest friction and the one with cylindrical rib show the best thermal enhancement. At the similar condition, the triangular rib gives higher Nusselt number than that provided by the cylindrical one by around 29.3 percent, while the cylindrical rib offers the highest thermal enhancement factor of 1.4 which is higher than that of the cylindrical one by around 1.33 percent while the cylindrical rib offers the highest thermal enhancement factor of 1.33 which is higher than that of the triangular one by around 9.6 percent. In addition, in spite of their high heat transfer, the concave-concave rib and long concave-concave rib yield low thermal performance factors, due to the prominent effect of high friction factor.

March 10, 2011

Non-Newtonian Flow Behavior on Frictional Pressure in Packed Bed

Suresh Kumar Patel, Subrata Kumar Majumder

Abstract

The packed bed columns with non-Newtonian liquid are increasing importance as a simple and inexpensive means of achieving yield of different chemical and biochemical processes though their hydrodynamic behavior is complex and not yet fully understood. In this article non-Newtonian flow behavior on frictional pressure was investigated in packed bed within a range of liquid velocity 0.004-0.04 m/s. The frictional pressure loss in non-Newtonian liquid system has been analyzed by modified Ergun equation. The modification of the Ergun equation is incorporated with the flow behavior index of non-Newtonian liquid. The degree of frictional pressure loss decreases with increase in flow behavior index. A correlation has been developed to interpret the degree of effect on the frictional pressure loss. The correlation may be useful for further understanding and scale-up of the packed bed column for its industrial application.

April 14, 2011

Investigation of Picolinic Acid Extraction by Trioctylamine

Amaç Fatih Tuyun, Hasan Uslu

Abstract

Picolinic acid is a pyridine compound with a carboxyl side chain at the 2-position. It is an isomer of nicotinic acid, which has the carboxyl side chain at the 3-position. Picolinic acid acts as a chelating agent of elements such as chromium, zinc, manganese, copper, iron, and molybdenum in the human body. It is involved in phenylalanine, tryptophan, and alkaloid production, and for the quantitative detection of calcium. In this study, picolinic acids aqueous solution was extracted by a method reactive extraction. All experiments were reported on the extraction of picolinic acid by trioctylamine (TOA) dissolved in two different aliphatic hydrocarbons (n-octane and n-decane), two different alcohols (octan-1-ol and decan-1-ol), and two different ketones (diisobutyl ketone (DIBK) and octan-2-one), as well as single diluents. Experimental results of batch extraction experiments were calculated and reported as distribution coefficients (KD=C*PA/CPA ), loading factors (Z), and extraction efficiency (E). The highest synergistic extraction efficiency was found as 89.199 for TOA+ isoamyl alcohol extractant system with KD value of 8.259 and Z value of 0.530.

April 14, 2011

Reaction Kinetics of Simultaneous Removal of SO₂ and NO from Flue Gas by NaClO₂ Solution

Yi Zhao, Liu Feng, Guo Tianxiang, Zhao Yin

Abstract

Experiments of simultaneous removal of SO2 and NO from simulated flue gas, using NaClO2 solution as the absorbent, were carried out in a self-designed bubble reactor, and removal efficiencies of 100 percent for SO2 and 95.2 percent for NO were obtained under the optimal experimental conditions. The mechanism of simultaneous removal of SO2 and NO using NaClO2 acid solutions was proposed by analyzing the removal products. The reaction kinetics for simultaneous desulfurization and denitrification were investigated, and the results indicated that the oxidation-absorption processes of SO2 and NO were divided into two zones, as the fast and slow reaction zones. In the slow reaction zones, both were zero order reactions, and in the fast reaction zones, the reaction order, rate constant and activation energy of SO2 removal reaction with absorbent were 1.4, 1.22 (mol L-1)-0.4 s-1 and 66.25 kJ mol-1, respectively, and 2, 3.15×103 (mol L-1)-1 s-1, and 42.50 kJ mol-1 for NO removal reaction, respectively.

April 14, 2011

The Potential of Different Saline Solution on the Extraction of the Moringa oleifera Seed's Active Component for Water Treatment

Grasiele Scaramal Madrona, Rosangela Bergamasco, Vanessa Jurca Seolin, Marcia R. Fagundes Klen

Abstract

The main objective of the present work is to study the efficiency in terms of removing color and turbidity of raw water in order to obtain drinking water. For this purpose, different coagulant solutions were obtained utilizing different salts, NaCl, KCl and MgCl2, in concentration 1M, distilled water combined with the Moringa oleifera Lam seed. Each coagulant solution obtained was studied with concentrations ranging from 25 to 300 mg/L of Moringa in salt solution. The tests were performed in the Jar Test, and the efficiency of the process was assessed in terms of color and turbidity. The results show no difference in the coagulation for extracts using the salts KCl, NaCl and MgCl2 1 Molar. The best results were found employing the coagulant solutions extracted with salt, in various concentration ranges (125 to 300 mg/L); as the concentration of protein in solution becomes higher, the greater is its power as a coagulant. The lowest content of protein was found in the solution extracted with water, which consequently had the lowest values of color and turbidity removal. Finally, the results obtained by the present work show that the seed of Moringa oleifera Lam is a great alternative for use as a coagulant in drinking water treatment systems.

April 14, 2011

Experimental Flow Measurements of a Spouted Bed Using Pressure Transducer and X-Ray CT Scanner

Bangyou Wu, Ana Orta, Apostolos Kantzas

Abstract

Flow behaviour of an air-glass bead spouted bed (20 cm diameter, 1.31 m high) was investigated using wall pressure fluctuation measurements and X-ray Computed Tomography (CT) scanning. Spout shape, spout dimension, fountain shape and fountain height were visualized from CT images. Statistical and spectral analyses were applied to pressure fluctuation series measured along the column wall. Local and global gas-solids flow dynamics were compared. Gas velocity greatly affects hydrodynamics of the spout bed. A stable spouting regime was identified. This study enhances the understanding of gas-solid flow patterns and provides detail hydrodynamics for further modelling work.

April 14, 2011

Removal of Remazol Turquoise Blue (G-133) and Polyvinyl Alcohol (PVA) by Electrocoagulation using Monopolar and Bipolar Electrodes

Sureyya Altin

Abstract

This study aims to investigate color and COD removal efficiencies of electrocoagulation (EC) process for dye solutions simulated by using polyvinyl alcohol (PVA) and reactive dyestuff of Remazol Turquoise Blue (G-133). The two different electrode configurations, namely monopolar and bipolar, were examined to find out the better alternative intensifying the performance of the process. The results obtained from these tests show that an EC cell with bipolar electrodes has produced slightly higher color and COD removal efficiencies than that of an EC cell with monopolar electrodes. The best removal efficiencies have been found for the both electrode configurations under the conditions that the time of electrolysis is 30 min, the constant direct current (DC) value 0.75 A and the initial pH value 3. Consequently, the bipolar electrode configuration (BPEC) has yielded 72.7 percent COD and 99.8 percent color removals while the monopolar electrode configuration (MPEC) producing 65.2 percent COD and 99.6 percent color removals.

May 6, 2011

Experimental Characteristics of Pneumatic Pulse Jet Pumping Systems with a Venturi-Like Reverse Flow Diverter

Cong Xu, Yi Huang

Abstract

The effects of area ratio of the diffuser entrance to the nozzle exit, displacement vessel volume, and suction gap configuration on the performance of pumping systems with a Venturi-like reverse flow diverter are investigated experimentally. The performance of a pumping system with area ratio of 1.5 is greater than one with area ratio of 1.0, but when the jet outlet velocity ranges from 1225 m/s, the performance of a suction gap in the shape of an axially-symmetric cylinder is the same as one with an arch-like configuration. The effective lifting factor should be more than 1.0, which means that the effective volume of the displacement vessel must be at least 1/(q-1) times the riser tube volume.

May 7, 2011

Comparative Study of Numerical Simulations of the RESS Process: The Supercritical Pure Fluid Expansion

Ksibi Hatem

Abstract

We present a review of numerical models and related (CFD) simulations for the so-called RESS process (rapid expansion of supercritical solutions), which has been attracted with so much attention in the literature for the potential applications related to the production of microparticulates of selected materials with controllable morphology and narrow-size distributions (using supercritical fluids, especially the carbon dioxide). The numerical computation of supercritical fluid flows in general is extremely challenging because of the complexity of the involved physical processes and the different space and time scales. The aim of this study is the focused analysis of advanced mathematical modeling of the supercritical fluid expansion in the RESS process with the specific intent of delineating a possible strategy for optimizing operating parameters. In particular, temperature, pressure, composition, flow rate and reactor dimensions are considered as variables potentially impacting the transport and growth of crystallized particles.

May 11, 2011

Facile Preparation of P-25 Films Dip-Coated Nickel Foam and High Photocatalytic Activity for the Degradation of Quinoline and Industrial Wastewater

Suiyi Zhu, Xia Yang, Gu-Ning Wang, Lei-Lei Zhang, He-Feng Zhu, Ming-Xin Huo

Abstract

A kind of P-25 TiO2 films coated nickel foam was synthesized by a facile dip-coating/calcination route, and used to fabricate a continuous-flow three-phase photocatalytic reactor. The morphology, crystal phase structure, surface composition and specific surface area of P-25 films coated nickel foam were investigated by field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption-desorption measurements, respectively. The results indicated that the coated/ calcined P-25 films had the porous surface structure fabricated by nano-sized titanium dioxide consisted of two crystal phases and incorporated with a NiO interlayer. The increase of P-25 contents enhanced the specific surface area; however, 20 percent of initial P-25 sol would result in visible large cracks because of too high P-25 content and consequently cause the peeling of films. The photocatalytic activities of nickel foam with different coating amounts of P-25 for the degradation of quinoline aqueous solutions were investigated with a continuous-flow three-phase photocatalytic reactor based on the P-25 films coated nickel foam. The results suggested that nickel foam coated with 10 percent of P-25 sol had an optimal photocatalytic activity for the degradation of quinoline aqueous solutions. The continuous-flow three-phase photocatalytic reactor fabricated with P-25 films coated nickel foam with an optimal P-25 coating amount shows high photocatalytic activity and stability for the degradation of quinoline aqueous solutions and industrial wastewater. The treated industrial wastewater meets the international discharge standard.

May 12, 2011

Kinetic Modelling of Phenol Oxidation in a Bioremediation Medium Using Fenton's Reagent

Pardeep Kumar, Hossein Nikaktari, Mehdi Nemati, Gordon A. Hill

Abstract

The present study is aimed at kinetic modeling of phenol oxidation using Fentons reagent in a medium suitable for bioremediation of organic pollutants. Batch experiments were conducted to study the effects of H2O2 concentration (29.26 to 146.31 mM), temperature (5 to 35°C), and to compare the oxidation of phenol in a bioremediation medium to that in pure water. The reaction mechanism used for kinetic modeling is based on the intermediate oxidation products identified in this study using LC-MS and ion chromatography. Progress of the chemical oxidation by Fentons reagent was monitored by determining the residual phenol concentration and concentrations of evolved intermediate compounds (catechol and hydroquinone) at regular time intervals. The rate of phenol oxidation and ultimate conversion of phenol were found to increase with increase in hydrogen peroxide concentration. The increase in temperatures has a positive effect on phenol oxidation and the rate of phenol oxidation was found to increase with temperature in the range of 5-35°C. Kinetic parameters, namely rate constants and activation energies for reactions involved, were determined by best-fitting the experimental data to the proposed reaction model. The values of the rate constants for oxidation of phenol and intermediate compounds, k1 (phenol to catechol), k2 (phenol to hydroquinone), k3 (catechol to maleic acid), k4 (hydroquinone to maleic acid) at 25°C were found to be 7.02x10-5±4.63x10-5, 7.22x10-4±6.09x10-4, 1.82x10-4±1.08x10-4, 1.68x10-3±1.29x10-3 L/mM min, respectively.

May 15, 2011

Augmentation of the Performance of Batch Electrocoagulation Unit by Using Gas Sparging

Ahmed Hassan Elshazly

Abstract

The present work investigates the effect of gas sparging in improving the performance of a batch electrocoagulation unit used to treat wastewater generated from the dyeing industry. Monopolar cylindrical aluminum electrodes were used. Many variables were investigated such as superficial gas velocity, current density, initial dye concentration, area ratio (cathode/anode), time of operation and the effect of adding chemical coagulant as FeSO4. The results show that the percentage of dye removal has been increased by a factor ranging from 2.52 to 5.14 by increasing the gas flow rate from 0.4 to 0.8 liter/min respectively and that about 93.5 percent of the dye can be removed within 60 minutes. Also it was found that using gas sparging is more efficient than adding chemical coagulant as ferrous sulfate for the removal of dye from wastewater. The power consumption for the unit was measured for different gas flow rates and different current densities; the results show that lower gas flow rate can improve the economy of the process.

May 15, 2011

Validation of CFD Model for Polysilicon Deposition and Production of Silicon Fines in a Silane Deposition FBR

James M. Parker

Abstract

In this work, a CFD model for simulating industrial scale particle-fluid systems is used to model a fluidized bed reactor for the deposition of high-purity silicon from silane gas. The performance of these reactors is directly dependent on a large number of factors and parameters which make the design and optimization of the deposition reactors an engineering challenge. Using the reactor design and experimental data from work performed at the Jet Propulsion Laboratory as a basis for validation, the CFD model was found to accurately model the deposition rate, silicon fines production, and temperature distribution within a silane deposition reactor. Additionally, the CFD model is demonstrated to be an effective tool for comparing different reactor designs on the basis of fluidization mode, reaction conversion, heat transfer, and particle mixing.

May 15, 2011

Membrane Contactor as Reactor for CO₂ Capture

Jian-Gang Lu, Fan Fan, Cong Liu, Yan Ji, Hui Zhang

Abstract

A novel composite solution consisting of N-methylmonoethanolamine (MM-EA) and 2-amino-2-methyl-1-propanol (AMP) as a CO2 absorbent was proposed. Coupling process of membrane contactor and the composite solution was investigated. The performance of the coupling was experimentally compared between the single and composite solution. Overall mass transfer coefficients were determined. Effects of various factors, such as flow rates and operation temperatures on mass transfer of membrane contactor, were studied. Comparison of prediction for overall mass transfer coefficients using a resistance in series model with experimental values was performed. Results show that performance of the composite solution is evidently better than that of the single MMEA solution. The overall mass transfer coefficient with the composite solution is much higher than that with the single MMEA solution. Higher operation temperature can enhance mass transfer of membrane contactor. Operation parameters such as flow rates can promote mass transfer, but the promotion is limited. Enhance of mass transfer relies essentially on chemical reaction. Model values are in good agreement with experimental ones.

May 16, 2011

Self-Cleaning Tests of Zn-Fe/Anatase-Coated Glass Plates under Direct and Diffuse Sunlight

Jorge Medina-Valtierra, Jorge Ramírez-Ortiz, Claudio Frausto-Reyes

Abstract

Thin films of anatase (TiO2) doped with 1 wt. percent of zinc ferrite (ZnFe2O4) were formed on glass plates by deposition of a sol-gel mixture using an ultra-spinning technique. After the preparation, the TiO2 films with a thickness of 168-232 nm were investigated with respect to their UV absorption capability and photo-degradation of organic molecules. Microscope observations of the surface of TiO2 films showed that they exhibit a micro-granular surface. To test the self-cleaning properties of the doped TiO2 films, a layer of fluoranthene of around 6.5 mg was sprayed over the glass and then exposed to direct or diffuse solar radiation. While the coated-glass transparency was totally recovered at 88 h of direct solar exposure for the undoped anatase film, the covering of fluoranthene on the 1 wt. percent ZnFe2O4-doped TiO2 film was degraded totally at 52 h of exposure time. As complementary experiments, the same glass plates with metal oxide-doped anatase films, after spraying with a similar layer of the organic contaminant, were placed under diffuse sunlight. In a typical experiment, the covering of fluoranthene was degraded almost 100 percent at an exposure time of 48 days and the transparency of glass plates was recovered totally at 55 days of indirect solar exposure. A correlation was found between the weight losses of the solid contaminant and the intensity of the Raman vibration at 672 cm-1. It was found that under diffuse solar irradiation is possible to remove completely a fluoranthene layer generating an expected application of these active surfaces under extreme conditions.

June 5, 2011

Low-Temperature Pyrolysis and Gasification of Biomass: Numerical Evaluation of the Process Intensification Potential of Rotating- and Circulating Rotating Fluidized Beds in a Static Fluidization Chamber

Nicolas Staudt, Axel De Broqueville, Waldo Rosales Trujillo, Juray De Wilde

Abstract

The process intensification potential of rotating- and circulating rotating fluidized beds in a static fluidization chamber when used for the low-temperature pyrolysis and gasification of biomass is numerically evaluated. The species continuity equations and energy balance equations are based on complete mixing for the particles within given zones of the particle bed and plug flow for the gas. The reaction mechanism accounts for pyrolysis of biomass and tar, gas-phase combustion, the water gas shift reaction, and combustion and gasification of char. A comparison with current circulating fluidized bed riser technology is made. The circulation of inert solid with a high heat capacity and the separation of the flue gas from the production gas are also studied.

June 5, 2011

Numerical Investigation of Radiation Effects in Monolithic Catalytic Combustion Reactors

Sandip Mazumder, Michael Grimm

Abstract

In modeling catalytic combustion in a monolithic catalytic converter, it is generally assumed that the gas within the individual monolith channels does not interfere with thermal radiation. To date, no quantitative study has been undertaken to validate this assumption. Past studies for carbon monoxide combustion also appear to indicate that the emissivity of the washcoat has little effect on the thermal radiation field. In order to investigate these two issues, methane-air combustion on platinum is modeled inside a single channel of a monolith using a detailed surface reaction mechanism comprised of 24 reactions between 19 species. Radiation transport is modeled using the Discrete Ordinates Method and a gray formulation. Planck-mean absorption coefficients of the gases, calculated from the HITEMP and HITRAN databases, are used to investigate participating medium effects. All calculations were performed using the commercial CFD code, CFD-ACE+, supplemented by user-subroutines for calculating the radiative properties of the gas mixture. Results show that the conversion percentages and temperature distributions are unaltered by the inclusion of participating medium radiation effects, verifying the commonly held belief, stated earlier. However, in strong contrast with carbon monoxide combustion, the emissivity of the washcoat was found to significantly affect flammability limits in the case of methane combustionthe flame being hotter and more stable for smaller values of emissivity.

June 27, 2011

Synthesis and Physicochemical Characterization of Nanostructured Pt/CeO₂ Catalyst Used for Total Oxidation of Toluene

Zahra Abbasi, Mohammad Haghighi, Esmaeil Fatehifar, Saeed Saedy

Abstract

Nanostructured Pt/CeO2 with different loadings of platinum was successfully synthesized via redox reaction along with wet impregnation method. The catalytic performance of the synthesized nanocatalysts was evaluated for abatement of toluene from waste gas stream. The synthesized nanocatalysts were characterized using XRD, FESEM, TEM, N2 adsorption, FTIR and TPR-H2 techniques. Crystallographic analysis confirmed the formation of CeO2 as crystalline phase with average crystallite size of 10.5 nm. Morphological analysis showed that majority of the synthesized CeO2 particles were less than 100 nm with average particle size of 50.62 nm. TEM analysis illustrated that platinum particles were fairly well dispersed with an average size of 5-15 nm. Specific surface analysis revealed that the synthesized nanocatalysts had large enough surface area for catalytic oxidation of toluene. Temperature programmed reduction profiles indicated that Pt/CeO2 had more reducibility compared to pure ceria. The results of catalytic experiments showed that the synthesized catalysts had the ability to remove 99% of toluene via total oxidation. According to these results, the best loading of Pt on ceria was 0.5 wt% with higher activity compared to pure ceria.

July 6, 2011

Study on Pyrolysis Characteristics of Corn Straw

Zhengqi Li, Zhichao Chen, Chunlong Liu, Zhiyong Hu, Wei Zhao, Guangbo Zhao

Abstract

Pyrolysis characteristics of corn straw samples (corn stalks skins, corn stalks cores, corn bracts and corn leaves) was performed using thermogravimetric analysis Three heating rates (20, 50 and 100 k min-1) were applied with a final temperature of 900°C. The maximum pyrolysis rates increased with the heating rate increasing and the temperature at the peak pyrolysis rate also increased. The activation energy and the temperature interval of pyrolysis for these samples had only slightly increasing at different heating rates. The one-step model was used to obtain the pre-exponential and the activation energy. Through calculating, we obtain the mass loss ratio curve. The three models have similar results. The one-step model is simpler and suitable for the simulation of the mass loss ratio curve.

July 6, 2011

Orthogonal Flow Impinging on a Wall with Suction or Blowing

Najeeb Alam Khan, Asmat Ara, Syed Anwer Ali, Muhammad Jamil

Abstract

The goal of this work is the approximate solutions of a viscous incompressible fluid impinging orthogonally on a porous flat plate. The equation governing the flow of an incompressible fluid is investigated using the homotopy perturbation method (HPM) with the aid of Padé-approximants. The approximate solutions can be successfully applied to provide the value of the skin-friction. The reliability and efficiency of the approximate solutions were verified using numerical solutions in the literature.

November 14, 2011

Theoretical and Empirical Studies on the Catalytic Partial Oxidation of Methane Promoted by FeY and Fe(piperazine)Y Complexes (Y = Y-zeolite)

Marcio Eduardo Berezuk, Carla C. R. S. Rossi, Nakédia M. F. Carvalho, Pedro Augusto Arroyo, Cláudio Dariva, Adolfo Horn, Lúcio Cardozo-Filho

Abstract

In this study, we synthesized and characterized zeolite-encapsulated Fe(III) complexes containing piperazine-derived ligands. The catalytic activity of these complexes was tested in the partial oxidation of methane to methanol using O2 as a low-pressure oxidant. Values for methane conversion of up to 1.2% with methanol selectivity of up to 6.7% were obtained. The experimental data were compared with thermodynamic simulation results for the reaction that takes place as a basic principle, the minimization of Gibbs free energy.

July 6, 2011

Development of an All-in-One Type Adsorption Heat Pump for Heating Application

Lihua Dong, Hongyu Huang, Noriyuki Kobayashi

Abstract

The present research of adsorption heat pump system for heating application mainly focuses on its miniaturization and high output. When the adsorption heat pump is downsized the heat energy is insufficient to meet heating application. In addition, a large amount of low-temperature heat energy in industry has not been utilized but discharged into the atmosphere as waste heat. To improve energy efficiency and reduce carbon dioxide emission, it is important to effectively utilize the low-temperature heat source which is usually discarded as waste heat. In order to solve the problem between the miniaturization and the high output, a miniature all-in-one type adsorption heat pump which can effectively utilize waste heat is designed. In this design, a heat exchanger coated with adsorption material is used as an adsorber or desorber, and another heat exchanger is used as an evaporator or condenser. A seal unit is formed by assembling two heat exchangers into a vacuum tight container and is connected to the surroundings only by hydraulic piping. Moreover, the adsorbent is a functional adsorbent material-zeolite (AQSOA FAM-Z02, Mitsubishi Plastics) which can be regenerated by utilizing the low-temperature heat energy between 75 and 100°C. In this paper the design and experimental performance of this all-in-one type adsorption heat pump are described.

July 6, 2011

Effect of Operating Conditions for Higher Alcohols Synthesis from Synthesis Gas over Alkali-Modified Co-Rh-Mo Trimetallic Catalyst Supported on Multi-Walled Carbon Nanotubes

Venkateswara Rao Surisetty, Janusz Kozinski, Ajay K. Dalai

Abstract

The effects of operating conditions on the higher alcohols synthesis reaction from synthesis gas were studied in a single-pass tubular downflow fixed-bed reactor, using sulfided K-promoted trimetallic Co-Rh-Mo catalyst supported on multi-walled carbon nanotubes (MWCNTs). The p CO conversion increased monotonically with increasing reaction temperature (from 275 to 350°C) and pressure (from 800 to 1400 psi), while decreasing monotonically with increasing GHSV (from 2.4 to 4.2 m3 (STP)/(kg of cat./h)). To maximize the ethanol STY and selectivity, the optimum operating conditions were determined as 330°C, 1320 psi, and 3.8 m3 (STP)/kg of cat./h). Maximum ethanol STY and selectivity were obtained using gas with H2 to CO molar ratio around 1.25.

July 7, 2011

Dye Decolorization by Immobilized Laccase: Statistical Optimization and Effect of Impeller Geometry

Nur Atiqah Ismail, M. Suffian M. Annuar, Shaliza Ibrahim

Abstract

Laccase enzyme from Trametes versicolor was immobilized using calcium-alginate entrapment method to decolorize triphenylmethane dye. Selected variables namely initial dye concentration (ppm), agitation speed (rpm) and process time (day) were optimized using response surface methodology (RSM) Box-Behnken design protocol. Under optimal conditions, good percentage of crystal violet decolorization was observed. Experiments were scaled up to a one litre (1 L) stirred tank reactor (STR) to examine the effects of impeller speed and geometry. In both the shake flask and stirred vessel study, lower initial dye concentration showed greater removal of dye. The dye removal achieved in the stirred tank ranged from 14 percent to 36 percent. A 6-blade mixed flow impeller (6MFD) showed better removal than a radial 6-curved blade (6CB) impeller, at the same agitation speeds, albeit with higher power demand. The effect of impeller speed depended on level of dye concentration and impeller type; speed was important at low concentration for the 6MFD while the exact opposite was true for the 6CB.

July 7, 2011

A Skeletal Chemical Kinetic Model of PRF Oxidation for HCCI Engines

Qingfeng Zhang, Zhaolei Zheng, Zuwei He, Ying Wang

Abstract

A skeletal chemical kinetic mechanism, including 42 species and 71 reactions for the oxidation of primary reference fuel (PRF), was developed and applied to model homogeneous charge compression ignition (HCCI) combustion after various experiments and available mechanisms for PRF oxidation being reviewed and the performance of mechanisms applied to experiments relevant to HCCI engines being analyzed. The ignition delay predicted by the skeletal mechanism showed good agreement with experiments for different fuels over the temperature range 667-1350K. Validation was also performed with experiments from HCCI engines, and good agreement was obtained for the primary reference fuels. The results show that the present PRF mechanism gives reliable performance for HCCI combustion predictions. Sensitivity analysis indicates that for PRF70 and PRF91.8 under HCCI conditions, H-atom abstraction from iso-octane molecule reaction and OH addition to n-heptane molecule have large influence, and CH2O, CH3 are very important intermediate species.

July 7, 2011

CFD Simulation of Mass Transfer around Spherical Particles in Fluidized Bed

Zoha Vatani, Majid Taghizadeh, Reza Orouj

Abstract

In this study, the mass transfer of three-dimensional nonreactive gas-solid fluidized bed was investigated computationally. The influence of the inlet gas velocity and temperature on mass transfer of air to wet particles was analyzed. The simulation results indicated that the mass transfer coefficients of air to spherical sand particles was decreased from 2.12 to 1.66 m/s with increment of temperature from 300 to 360 K. Sherwood numbers of gas to cluster increased with the increase of inlet air velocity. CFD model of the gas-particle heat transfer have been implemented, the result showed that the heat flux of gas to particles increased with the increase of Reynolds number. Distributions of water vapor concentration and velocity in this bed were numerically predicted and the computed Sherwood and Nusselt numbers were compared with the estimated values from empirical equations.

July 9, 2011

Experimental and Theoretical Study on Fluidization of Stalk-Shaped Biomass Particle in a Fluidized Bed

Yong Zhang, Wenqi Zhong, Baosheng Jin

Abstract

Detailed knowledge of the fluidization mechanics of biomass itself, or of mixtures of biomass and inert particles is critical to successful design and operation of fluidized bed involving biomass. In this study, the fluidization behaviors of biomass alone and sand-biomass mixture were experimentally and theoretically studied. A segmented fluidized bed equipped with multiple pressure transducers was used as the experimental apparatus. The cotton stalk with a shape of stalk was employed as biomass material, and three different sizes of sand were utilized as inert particle. By mixing cotton stalk and sand, three binary systems were obtained, in which only the weight percentage of biomass particle in each mixture is different. The fluidized beds experienced the following states, depending on gas superficial velocity and initial mixture fraction: fixed, bubbling fluidization and turbulent fluidization. It is found that the additive of sand has positive influence on the fluidization of biomass and the initial arrangement of bed has influence on the development of pressure drop with the gas velocity. The developed equation for predicting the minimum fluidization velocity (Umf) of binary mixture quite satisfactorily predicts the Umf values of mixture with low biomass concentration. In addition, the correlation expressed in terms of Reynolds and Archimedes numbers to predict transition velocity (Uc) is proposed. Calculated Uc is in excellent agreement with the experimental data.

July 11, 2011

CO₂ Capture by Calcined Dolomite in a Fluidized Bed: Experimental Data and Numerical Simulations

Luca Di Felice, Pier U. Foscolo, Larry Gibilaro

Abstract

The capture of CO2 by particles of calcined dolomite in a gas-fluidized bed was investigated experimentally in a laboratory-scale reactor. Step-response experiments were performed to determine CaO conversion rates in the bed as a function of time and dolomite particle diameter. It was found that the CO2 capture dynamics in the fluidized bed itself could be extracted from the overall system response curves by making use of a blank testperformed under identical flow and temperature profile conditions but with no calcined dolomite present. A simple flow-with-reaction model of the process was proposed; it provided a good description of the transient behaviour in terms of an empirical transfer coefficient, which was found to depend linearly on dolomite particle diameter. A shrinking core model was then developed and applied, to evaluate the individual effect of chemical kinetics and pore diffusion on the global reaction rate. The chemical process was found to control the smallest particle size carbonation test, in very good agreement with the kinetic constant value proposed in literature (Bhatia and Perlmutter, 1983), whereas the diffusion coefficient, needed to describe CO2 uptake as particle grows, appeared to be a function of sorbent size: this points to the need of more sophisticated SRD (simultaneous reaction and diffusion) models to describe the real behaviour of systems at hand.

July 12, 2011

Response Surface Methodology for Optimization of Epoxidized Trimethylolpropane Ester Synthesis from Palm Oil

Ferra Naidir, Robiah Yunus, Irmawati Ramli, Tinia I. Mohd. Ghazi

Abstract

To improve the oxidative stability of the palm oil-based biolubricant, the fatty acid double bonds in palm oil-based trimethylolpropane ester (TMP ester) was converted into an oxirane ring via an in-situ epoxidation method. The epoxidized TMP ester was produced from a reaction between TMP ester and peracetic acid which was prepared in-situ by reacting glacial acetic acid with hydrogen peroxide in the presence of concentrated sulphuric acid. The response surface methodology was applied using a central composite design technique to optimize the conditions of the epoxidation reaction to produce the epoxidized TMP ester. The effects of four independent variables namely concentration of acetic acid (0-2 mol), concentration of hydrogen peroxide (1.5-9.5 mol), temperature of reaction (30-110°C) and reaction time (0.5-26.5 h) on the three dependent variables; percentage of oxirane oxygen, iodine value, and hydroxyl value were studied. A second-order polynomial multiple regression model was employed to predict the three dependent variables under optimum conditions of 0.59 mol of glacial acetic acid, 7.5 mol of hydrogen peroxide concentration, at temperature of 50°C and reaction times of 7 h. The optimum values of percentage of oxirane oxygen, iodine value, and hydroxyl value were 4.01%, 1.94%, and 0.43% respectively. The analysis of variance yielded a high coefficient of determination value of 0.9395-0.9880, hence indicating the fitness of the second-order regression model to the experimental data.

July 12, 2011

Development of UV Distribution Model for the Non-Contact Type UV Disinfection System

Sung Hong Kim, Young Gyun Choi, Dooil Kim

Abstract

Fouling on the quartz sleeve reduces the transmittance of UV light through the sleeve into the water in submerged UV disinfection system. The concept of a non-contact type of UV disinfection system was introduced in this study. UV lamps and their quartz sleeves hang over the water surface and there is no interface between the sleeve and water. Indeed, there is no fouling. Based on optical laws and UV distribution model, a detailed mathematical model for a non-contact type UV disinfection system was developed and simulated in this study. UV light passes through 4 media of air-quartz-air and water in case of non-contact type irradiation system. By the simulation of the mathematical model of the system, it is known that the non-contact type of UV system requires 2.5 times more powerful UV lamp or a lamp with longer exposure time than that of the submerged type of UV system. In a non-contact type of UV system, high-reflective ceiling material can increase the UV intensity of the water layer as much as 28 percent more than the case of non-reflective ceiling material. The non-contact type UV irradiation system requires more powerful lamp or one that have longer exposure time. Nevertheless, considering the fouling attenuation and maintenance problem associated with the fouling, non-contact type of UV disinfection system deserves to be practically considered, especially in a small to middle scale water or wastewater treatment plant.

July 12, 2011

Mitigating NH₃ Vaporization from an Aqueous Ammonia Process for CO₂ Capture

Wojciech M. Budzianowski

Abstract

An aqueous ammonia process (AAP) offers several advantageous technological features over other existing reactive absorption-based CO2 capture processes such as increased CO2 absorption loading capacity, no oxidative solvent degradation, no corrosion problems, high CO2 absorption fluxes and low energy input needed for solvent regeneration. It has also the potential of capturing multiple flue gas components (SO2, NOX, and CO2) and producing value added chemicals, such as ammonium sulfate, ammonium nitrate and ammonium bicarbonate, which are commonly used as fertilizers. Unfortunately, a major drawback of the AAP is NH3 volatility resulting in NH3vaporization to the flue gas. Therefore, the current article presents the results of experimental and numerical investigations directed at in-depth understanding of the AAP and at developing of new methods for mitigating the unwanted NH3 vaporization. For this purpose three types of reactor configurations are studied: (i) packed bed, (ii) falling film and (iii) membrane. The bench-scale experiments realized in the counter-current packed bed reactor reveal, that NH3 vaporization can be minimized under the conditions of low temperature, pH, and flow rate of flue gas and under the conditions of high pressure and flow rate of aqueous ammonia. Further, from the detailed 2D modeling of the AAP realized in the falling film reactor it is found, that NH3 vaporization can be mitigated by making use of the mechanisms of negative enhancement of mass transfer and of migrative mass transport. Finally, the potential benefits of using membrane facilitated AAP reactors are discussed.

July 15, 2011

Theoretical/Experimental Study of an Upflow Anaerobic Sludge Blanket Reactor Treating Domestic Wastewater

Maria Gorethe Sousa Lima, Severino Rodrigues de Farias Neto, Antonio Gilson Barbosa de Lima, Flávio César Brito Nunes, Luciano de Andrade Gomes

Abstract

This work reports a theoretical and experimental study to evaluate the fluid dynamic of an Upflow Anaerobic Sludge Blanket reactor (UASB), treating domestic wastewater in a pilot scale. Simulations were developed using the Ansys CFX 10.0. For validating the numerical results, an experimental study was conducted by monitoring the total concentration of suspended solids in the effluent and pressure along the reactor. The comparative analysis between the numerical and experimental results of the pressure and sludge concentration in the outlet of the reactor presented few differences, being considered satisfactory.

July 15, 2011

Experimental Study of Reactive Absorption of Carbon Dioxide in a Lab Scale Spray Dryer

Leila Kavoshi, Mohammad S. Hatamipour, Amir Rahimi

Abstract

Reactive absorption of CO2 with NaOH as absorbent was evaluated experimentally in a lab scale spray dryer. Taguchi method was used for design of experiments. Results showed that the most important factors are inlet CO2 concentration, nozzle size, absorbent concentration and temperature, respectively. The optimum conditions are 150°C for temperature, 10% (w/w) for NaOH concentration, 10% for CO2 concentration, and 0.5 mm for nozzle diameter. By conducting experiments under the optimum conditions, the removal efficiency was obtained as 69.4%.

July 15, 2011

Fermentation of Groundnut Shell Enzymatic Hydrolysate for Fuel Ethanol Production by Free and Sorghum Stalks Immobilized Cells of Pichia stipitis NCIM 3498

Chandrasekhar Gajula, Anuj Kumar Chandel, Radhika Konakalla, Ravinder Rudravaram, Ravindra Pogaku, Lakshmi Narasu Mangamoori

Abstract

Groundnut shell (GS), after separation of pod, is readily available as a potential feedstock for production of fermentable sugars. The substrate was delignified with sodium sulfite. The delignified substrate released 670 mg/g of sugars after enzymatic hydrolysis (50°C, 120 rpm, 50 hrs) using commercial cellulases (Dyadic® Xylanase PLUS, Dyadic Inc. USA). The groundnut shell enzymatic hydrolysate (45.6 g/L reducing sugars) was fermented for ethanol production with free and sorghum stalks immobilized cells of Pichia stipitis NCIM 3498 under submerged cultivation conditions. Immobilization of yeast cells on sorghum stalks were confirmed by scanning electron microscopy (SEM). A maximum of ethanol production (17.83 g/L, yield 0.44 g/g and 20.45 g/L, yield 0.47 g/g) was observed with free and immobilized cells of P. stipitis respectively in batch fermentation conditions. Recycling of immobilized cells showed a stable ethanol production (20.45 g/L, yield 0.47 g/g) up to 5 batches followed by a gradual downfall in subsequent cycles.

July 15, 2011

Tank Car Conversion to a Reactor

Dale L. Schruben, Jaime Garcia

Abstract

Tank car conversion into a reactor is undertaken herein for some large scale industrial processes of solids reacting with liquids to yield liquid products. The model loads liquid directly to the tank car, using it as the reactor as well. Savings accrue over the usual unit operation where the solids in the tank car are off-loaded to a reactor, then liquid is added to the reactor for solid conversion into a liquid product before reloading product to the tank car for customer delivery. Several analytical tools are used together to yield a sound picture of fluid flow in the tank car and its bed mass profile during the progress of bed reaction. This provides a basis for business and plant operation decisions.

July 18, 2011

Self-Diffusion Coefficient and Viscosity in Fluids

Lawrence Novak

Abstract

Rate-based models suitable for equipment or transport-reaction modeling require a capability for predicting transport coefficients over a sufficient range of temperature and pressure. This paper demonstrates a relatively simple novel approach to correlate and estimate transport coefficients for pure components over the entire fluid region.The use of Chapman-Enskog transport coefficients for reducing self-diffusion coefficient and viscosity to dimensionless form results in relatively simple mathematical relationships between component dimensionless transport coefficients and residual entropy over the entire fluid region. Dimensionless self-diffusion coefficients and viscosities were calculated from extensive molecular dynamics simulation data and experimental data on argon, methane, ethylene, ethane, propane, and n-decane. These dimensionless transport coefficients were plotted against dimensionless residual entropy calculated from highly accurate reference equations of state.Based on experimental data, the new scaling model introduced here shows promise as: (1) an equation of state-based transport coefficient correlation over the entire fluid region (liquid, gas, and critical fluid), (2) a component transport coefficient correlation for testing transport data consistency, and (3) a component transport coefficient correlation for interpolation and extrapolation of self-diffusion coefficient and viscosity.

February 3, 2012

Optimization of Styrene Reactor Using Tabu Search and Genetic Algorithm Methods

Shahrokh Shahhosseini, Samaneh Vakili

Abstract

This paper deals with multi-objective optimization of styrene reactor using Tabu search (TS) and genetic algorithm (GA) methods. Styrene is produced commercially by catalytic dehydrogenation of ethyl benzene. As styrene is an important monomer, the capacity of the plant is usually very high, as a result the investment cost is also very high, and even a small enhancement in the plant operation can generate major income. The adiabatic reactor using the pseudo homogeneous model was considered in this study for maximizing the styrene conversion and selectivity. A computer program was written to simulate an adiabatic reactor in order to evaluate the possibility of optimizing the process in simulation environment. The simulation results were compared with the experimental data. This comparison indicated that the value of overall mean squarer of errors for conversion of the compounds was 7.09E-05 and overall means relative error of them was 2.18 percent. In order to optimize the performance of the reactors, conversion of styrene was adopted as the objective function. Six decision variables, namely, ethyl benzene feed temperature at the entrance of each bed, pressure, the ratio of steam to ethyl benzene and initial ethyl benzene flow rate were used for the optimization. The results of GA optimization showed final conversion of styrene increased from an initial value of 0.710 to 0.75 after 100 generation of population. Applying Tabu algorithm optimization, the value rose from 0.725 to 0.813 after generation of 100 neighborhoods. The results revealed that the CPU time needed to optimize the reactor for TS was shorter than that of GA method. In addition, using the same iteration numbers for both methods, the optimum value of styrene conversion was greater when TS method was applied.

July 20, 2011

Asymptotic Analysis of Flow Processes at Drawing of Single Optical Microfibres

Giovanni Luzi, Philipp Epple, Michael Scharrer, Ken Fujimoto, Cornelia Rauh, Antonio Delgado

Abstract

Microstructured optical fibres (i.e. fibres that contain holes) have assumed a high profile in recent years, and given rise to many novel optical devices. The problem of manufacturing such fibres by heating and then drawing a preform is considered for both the cases of annular microfibres and annular capillaries. A fluid-mechanics model suggested in literature that uses asymptotic analysis based on the small aspect ratio of capillaries is analysed and revised. The leading-order equations are examined in some asymptotic limits, many of which give valuable practical information about the control parameters that influence the drawing process. Additionally, the solution obtained for a single capillary provides a suitable basis for describing more complicated fibre structures.

July 23, 2011

MHD Free Convective Heat and Mass Transfer of a Chemically-Reacting Fluid from Radiate Stretching Surface Embedded in a Saturated Porous Medium

A.M. Rashad, M. Modather M. Abdou, Ali Chamkha

Abstract

Magneto-hydrodynamic free convective heat and mass transfer of a viscous, incompressible, electrically conducting and chemically-reacting fluid adjacent to a vertical stretching sheet embedded in a saturated porous medium in the presence of a thermal radiation effect are investigated. The sheet is linearly stretched with uniform constant of temperature and concentration. The governing partial differential equations are transferred into a system of ordinary differential equations, which are solved numerically using a fourth order Runge-Kutta scheme with the shooting method. The effects of various parameters entering into the problem have been examined on the velocity and temperature profiles as well as the skin-friction coefficient, and Nusselt and Sherwood numbers are presented graphically and in tabular form.

September 28, 2011

Realization of Non Linear Controllers in Batch Reactor using GA and SVM

S. Sujatha, N. Pappa

Abstract

This paper presents the application of machine learning schemes, namely SVM and GA, for realization of non linear control schemes and optimization of Batch reactor. Batch reactor is an essential unit operation in almost all batch- processing industries such as chemical and pharmaceuticals. In this approach, the temperature profile of the batch reactor is optimized using Genetic Algorithm (GA) with a view to maximize the desired product and minimize the waste product as a multi -objective function. Generic Model Control is implemented by using SVM Estimator, and it includes the non-linear model of a process to determine the control action. SVM estimator will predict the current value of the heat release makes the control performance to be more robust. The robustness performance of GMC has been experienced. Other non linear control schemes, such as Direct Inverse Control and Internal Model Control, are also implemented.

July 23, 2011

Sonochemical Degradation of Methylene Blue and P-Nitrophenol in Aqueous Medium

Rajanandam K. S, Madhu G.M, Ashly Thomas

Abstract

The presence of dyes in aqueous system causes aesthetic pollution, hydrolysis or other chemical reactions leading to the formation of products which are non degradable, and accumulate in water. A number of methods have been devised for degradation of dyes in aqueous streams which can cater to the never ending necessities of water worldwide. The methods include biological treatment, chemical oxidation, electrochemical decomposition, photocatalytic and chemical coagulation, physical and physico-chemical treatment. These methods are successful to a certain extent. In the present work, an attempt was made towards the sonochemical degradation of azo dyes such as methylene blue and p-nitro phenol. Further sonication experiments were carried out in combination with advanced oxidation processes. Sonication was performed at 20 and 70 kW power ratings. Percentage degradation was found to increase with increase in power ratings. Degradation of azo dyes was improved in presence UV source. Maximum degradation was observed when sonication was carried out in presence of UV source and hydrogen peroxide which was used as an oxidant. Increase in dye concentration decreased degradation rate and decrease in pH (acid medium) increased the degradation rate.

July 23, 2011

High-Temperature Pyrolysis of Liquified Petroleum Gases in the Fast-Mixing Reactor

Marat Ktalkherman, Igor Namyatov, Vladimir Emel'kin

Abstract

Experimental study and computational analysis of a pyrolysis of liquefied petroleum gases (LPG) in a high-enthalpy heat carrier flow are presented. The experiments on a small-scale device were carried out within the temperature range at the reactor inlet of 1,350-1,500 K, which is essentially higher than the typical values in the conventional method of steam cracking. Increased initial temperatures required to realize in the experiments the ultra-fast mixing of the feedstock with heat carrier (~0.05 ms). The rate of feedstock temperature growth in the mixer was about 107 K/s. The ethylene mass fraction in pyrolysis products in our experiments reached 47%.

July 23, 2011

Intrinsic Mode Entropy Analysis of Tube-Wall Pressure Fluctuation Signals in the Kenics Static Mixer

Hui-Bo Meng, Zhi-Qiang Liu, Yan-Fang Yu, Qiang Xiong, Jian-Hua Wu

Abstract

The multi-scale nonlinear hydrodynamics in Kenics Static Mixer (KSM) with 100 mm in diameter and 2 in aspect ratio was investigated in this work. The time series of tube-wall pressure fluctuation signals were measured at different flow rates ranged of 100~600 Lh-1 and at different axial positions in the range of 420~580 mm away from the cross-section of mixer inlet. It is difficult for composite signals to make an effective analysis by Sample Entropy (SampEn) based on a single scale. The complexity of tube-wall pressure fluctuation signals in a Kenics static mixer was investigated using Intrinsic Mode Entropy (IMEn) based on Sample Entropy algorithm and Empirical Mode Decomposition (EMD) method. Data sampling length and tolerance are optimized based on intrinsic mode entropy. Results of multi-scale analysis of pressure fluctuations indicated that the Sample entropy reaches maximum in the first scale and progressively decreases according to increase of the decomposed order. It is clear that the movement of high frequency component of the pressure signal is the most complicated and is rich in randomness. With the decomposition scales increasing, the complexity of signal decreases and approaches periodic motion eventually. The intrinsic mode entropy of the tube wall pressure signals in KSM has similar development tendencies in different flow rates. Besides, as the flow rates increased, the macro-scale vortexes play a more and more important role and guide the system to develop toward the stable state.

July 23, 2011

Synthesis of Biodiesel Using Castor Oil under Microwave Radiation

Hong Yuan, Bolun Yang, Hailiang Zhang, Xiaowei Zhou

Abstract

The castor oil was adopted to synthesize biodiesel (Fatty Acid Methyl Ester, FAME) under microwave radiation. Acid catalysts (NaHSO4H2O and AlCl3) and heterogeneous base catalyst (Na2CO3) were evaluated in the present study. The amounts of FAME in the product were analyzed by high performance liquid chromatography (HPLC). Experimental results show that the microwave radiation was an efficient method to enhance the reaction process. When the transesterification was carried out at 338 K, with 18:1 molar ratio of methanol to castor oil, 7.5wt% mass ratio of catalyst to castor oil, 200w microwave radiation power and 120 minutes reaction time, yields of 74, 73, 90% were obtained respectively using catalysts of NaHSO4H2O, AlCl3 and Na2CO3. The energy consumed by microwave heating and conventional heating in transesterification were measured, and the results showed that the microwave heating consumed less energy than the conventional heating to achieve the same amount of FAME.

July 23, 2011

Studies on Minimum Fluidization Velocity and Liquid Hold in an Internal Loop Airlift Fluidized Bed Reactor

Sivakumar Venkatachalam, Akilamudhan Palianiappan, Senthilkumar Kandasamy

Abstract

The influence of superficial gas and liquid velocities, particle diameter and sphericity, physical and rheological properties of liquids on minimum fluidization velocity and liquid holdup were studied in an internal loop airlift fluidized bed reactor. Spheres, Bearl saddles and Raschig rings were used as solid phases. Water, n-Butanol, two concentrations of Glycerol (60 and 80%) were used as Newtonian liquids and three concentrations (0.25%, 0.6% and 1.0%) of Carboxy Methyl Cellulose (CMC) solutions were used as non-Newtonian liquids. Superficial gas velocity was varied from 0.142 x 10-3 m/s to 5.662 x 10-3 m/s and superficial liquid velocity was varied from 0.001 to 0.12 m/s. The experimental results showed that increase in particle size and sphericity increased minimum fluidization velocity whereas increase in superficial gas velocity decreased minimum fluidization velocity. The liquid holdup increased with increase in particle size and superficial liquid velocity. An increase in superficial gas velocity decreased the liquid holdup for Newtonian and non-Newtonian systems. Based on the experimental results separate correlations were developed for the prediction of minimum fluidization velocity and liquid holdup for both Newtonian and non-Newtonian liquids for a wide range of operating conditions.

July 23, 2011

Production of L-asparaginase from Natural Substrates by Aspergillus terreus MTCC 1782: Optimization of Carbon Source and Operating Conditions

Baskar Gurunathan, Renganathan Sahadevan

Abstract

In the present work, the effect of different carbon sources, namely glucose, sucrose, maltose, fructose and lactose, was studied for extracellular L-asparaginase production by Aspergillus terreus MTCC 1782 in submerged fermentation. The best carbon source and operating conditions such as initial pH, inoculum size, temperature and agitation rate were optimized. Glucose was found to be the best carbon source for L-asparaginase production using modified Czapek-Dox media containing L-proline as substrate. Sucrose was found to be the best carbon source for L-asparaginase production using modified Czapek-Dox media containing groundnut oil cake flour as substrate. Glucose was found to be the best carbon source for maximum L-asparaginase production using modified Czapek-Dox media containing soya bean meal flour as substrate. The soya bean meal flour was found to be the best natural substrate for maximum L-asparaginase activity of 35.3 IU/mL using 0.6% glucose as carbon source at the optimal culture conditions of initial pH 6, inoculum size 2%, temperature 35°C and agitation rate 160 rpm.

July 23, 2011

Enhancement of DME Production in an Optimized Membrane Isothermal Fixed-Bed Reactor

Mohammad Farsi, Abdolhossein Jahanmiri

Abstract

Dimethyl ether is a colorless gas at the ambient condition that is easily liquefied under light pressure. Currently, DME as a green fuel has been suggested as one of the most promising candidates for substitution of LPG and diesel fuel. In this paper, a water cooled membrane fixed bed reactor is proposed and modeled heterogeneously for large scale production of DME from methanol dehydration. The proposed reactor is modeled one-dimensionally based on mass and energy conservation laws at steady state condition. Also, the efficacy of the proposed membrane reactor is investigated and the results of the proposed reactor are compared with an isothermal and commercial adiabatic reactor. The simulation results of the proposed membrane reactor indicate that the methanol conversion is improved about 6.2 percent compared to the conventional industrial reactor. Also, water vapor removal from reaction zone in the membrane reactor yields lower water concentration over the catalyst pellets and higher quality of outlet product. These can lead to higher catalyst lifetime and lower cost in purification stage.

February 3, 2011

Synthesis and Characterization of Manganese Oxide and Investigation of its Catalytic Activities for Oxidation of Benzyl Alcohol in Liquid Phase

Mohammad Ilyas, Muhammad Saeed

Abstract

Manganese oxide was prepared by mechano-chemical process in solid state and was characterized by chemical and physical techniques. Chemical techniques include determination of oxygen content while physical techniques, includes surface area and pore size analyses, particle size, XRD, FTIR and SEM analyses. The synthesized manganese oxide was shown to have octahedral layered structure. The catalytic activity of manganese oxide was studied by carrying out the oxidation of benzyl alcohol in liquid phase using n-octane as solvent at temperature (<373) and oxygen pressure of up to one atmosphere. Benzaldehyde and benzoic acid were identified as the reaction products. However, benzoic acid appeared in reaction mixture after complete conversion of benzyl alcohol to benzaldehyde. Influence of different reaction parameters like comparison of reduced and unreduced catalyst, leaching of catalyst, effect of air, oxygen and nitrogen, effect of catalyst loading, life span of catalyst, effect of time and effect of partial pressure of oxygen on the reaction performance was studied. The catalyst can easily be separated from the reaction mixture by filtration, and can be regenerated by washing with water and ethanol and drying at 323 K.

August 5, 2011

On The Behavior of Partial Oxidation of Methane in a Pd-Membrane Reactor under Periodic Operation Conditions

Lemnouer Chibane, Brahim Djellouli

Abstract

In the current study, a theoretical analysis of the behavior of the reaction of partial oxidation of methane performed in a palladium membrane reactor, operating under periodic conditions was carried out. The periodic operations in the pd-membrane reactor are supposed to be created by forcing some inputs cyclically using a sinusoidal function. The concerned inputs are the composition and mainly the steam and oxygen in the reactor inlet and the sweeping gas in the permeation side. It was found that the periodic operations applied to these inputs are beneficial since the predicted performance is improved. When the steam to methane ratio and the sweeping gas are running periodically both in phase, the conversion of methane and the pure hydrogen recovery can exceed the steady state levels and the H2/CO ratio is significantly reduced compared to the steady state operation.

December 1, 2011

Optimization of Chiral Resolution of (+/-)-1-Phenylethanol by Statistical Methods

Ganapati D. Yadav, Jyoti B. Sontakke

Abstract

Optically active 1-phenylethanol is used as a chiral building block and synthetic intermediate in pharmaceutical and fine-chemical industries. Lipase - catalyzed kinetic resolution of (R,S)-1-phenylethanol with vinyl acetate as an acyl donor and Candida antarctica immobilized lipase as a biocatalyst in a batch reactor was optimized using Response Surface Methodology (RSM). Four-factor-five-level central composite rotatable design (CCRD) was employed to evaluate the effect of synthesis parameters such as speed of agitation, enzyme loading, temperature and acyl donor/alcohol molar ratio, on conversion, enantiomeric excess (ee), enantioselectivity and initial rate. Optimum reaction conditions obtained were; mole ratio of acyl donor: ester of 2:1, temperature of 42.5 °C, catalyst loading of 1.6x10 -3 g.cm -3 and speed of agitation of 336 rpm. Analysis of variance was performed to determine significantly affecting variables and interactions between the process parameters.

August 8, 2011

A Comparative Study of the Flow Dynamics in Two Observation Cells for Measuring the Kinetics of the Fast Redox Reaction between Cu²⁺ and S₂O₃^2-

Mihaela-Ligia M. Unguresan

Abstract

For the study of Cu2+ - S2O32- reaction kinetics was used an experimental stopped flow apparatus with two types of observation cells. The first has a toroidal mixing chamber, and the other, with a separate mixing chamber has the entrance of the reactants on two perpendicular directions. The reaction rate and the residence time have been calculated during the flow in the mixing chambers and the observation cells. The calculated values have been compared with the real formation and decomposition time of the reaction intermediate. The deviations due to the residence-time in the toroidal chamber and in the observation cell respectively are smaller than those for the cell with separate mixing chamber due to its different geometry. The shape of the experimental curves I = f(t) with the toroidal cell lead to kinetic parameters which are different than the ones obtained with the other cell.

August 8, 2011

Hydrodynamic Studies on Three-Phase Combined (Internal & External) Loop Airlift Fluidized Bed Reactor Using Newtonian and non-Newtonian Liquids: Minimum Fluidization Velocity and Liquid Holdup

Sivakumar Venkatachalam, Akilamudhan Palaniappan, Kannan Kandasamy

Abstract

A novel combined airlift loop fluidized bed reactor was proposed in this work. The internal and external loops were combined and the hydrodynamic parameters like minimum fluidization velocity and liquid holdup were studied for Newtonian and non-Newtonian fluids. Studies were conducted using Newtonian fluids of water, n-butanol, 60% and 80% glycerol and non - Newtonian fluids such as 0.25%, 0.6% and 1.0% Carboxy Methyl Cellulose (CMC) aqueous solutions were employed in the liquid phases. Spheres, Bearl saddle and Raschig ring with different sizes were used as solid phase. The experimental results indicated that the increase in particle size and sphericity increased minimum fluidization velocity whereas increase in superficial gas velocity decreased minimum fluidization velocity. In addition, the liquid holdup increased with increase in particle size and superficial liquid velocity. Furthermore, an increase in superficial gas velocity decreased the liquid holdup for Newtonian and non-Newtonian systems. Two separate correlations were developed to predict the minimum fluidization velocity and liquid holdup based on the experimental results for both Newtonian and non-Newtonian liquids for a wide range of operating conditions. The capability of the proposed correlation for minimum fluidization velocity and liquid holdup was examined and reasonable agreement between predicted and experimental results of Newtonian and non-Newtonian liquids suggested the applicability of the proposed correlations.

August 8, 2011

Design Optimization of an LPG Thermal Cracker for Multiple Objectives

Reza Nabavi, G. P. Rangaiah, Aligholi Niaei, Darioush Salari

Abstract

Ethylene and propylene, building blocks of the petrochemical industries, are mostly produced by steam cracking of hydrocarbons. In our recent work (Nabavi, Rangaiah, Niaei and Salari, Multiobjective Optimization of an Industrial LPG Thermal Cracker using a First Principles Model, Ind. Eng. Chem. Res. 2009, 48, 9523-9533), operation of an industrial liquefied petroleum gas (LPG) cracker was optimized for several sets of two and three objectives. In this work, optimization of an LPG cracker design is investigated for multiple objectives. The objectives considered are maximization of annual ethylene and propylene production, selectivity and run length, and minimization of severity and total heat duty per year. The elitist non-dominated sorting genetic algorithm adapted with the jumping gene operator, NSGA-II-aJG is used to solve the multi-objective optimization problems. The results of design optimization for multiple objectives are compared with those for operation optimization.

August 8, 2011

Multi-Objective Optimization of an Ethylene Oxide Reactor

Allan Vandervoort, Jules Thibault, Yash P. Gupta

Abstract

In this study, multi-objective optimization is performed for a reactor producing ethylene oxide from ethylene. The optimization considered three objectives: the maximization of the ethylene oxide production and selectivity, and the maximization of a safety factor related to the presence of oxygen in the reactor. The Pareto domain for this optimization problem was first approximated using the Objective-Based Gradient Algorithm, and the Pareto-optimal solutions were ranked using the Net-Flow procedure to determine the best operating conditions. From the optimization results, it is recommended that the ethylene oxide reactor be operated at high inlet pressure and gas temperature, and low inlet volumetric gas flowrate and chemical reaction moderator concentration. These operating conditions led to the highest ranked compromise solution, balancing the trade-off between each of the three objectives. Finally, it was found that a decrease in the inlet pressure or variation in the volumetric gas flowrate could readily lead to operating conditions outside of the Pareto domain, and these input variables should therefore be carefully controlled throughout operation of the reactor.

August 8, 2011

A Stochastic Model of Microbial Bioconversion Process in Batch Culture

Lei Wang, Zhilong Xiu, Enmin Feng

Abstract

The stochastic counterpart to the deterministic description of batch fermentation with ordinary differential equation is investigated in the process of glycerol bio-dissimilation to 1,3-propanediol by Klebsiella pneumonia. We briefly discuss the batch fermentation process driven by five-dimensional Brownian motion and Lipschitz coefficient, which is suitable for the actual fermentation. Subsequently, we study the existence and uniqueness of solutions for the stochastic system as well as the boundedness of the Two-order Moment and the Markov property of the solution. Finally, computer simulation results reveal the peculiar role of randomness in the dynamical responses of the batch culture.

August 16, 2011

Nanopowders Production in the Plasmachemical Reactor: Modelling and Simulation

Andrei V. Kolesnikov, Joshua Kekana

Abstract

A mathematical model capable of determining suitable operating conditions to produce TiO2 nanoparticles with specified average diameter is presented. The model consists of mass, momentum and energy conservation equations. Particle dynamics processes under consideration include particle formation by nucleation, growth by both condensation and coagulation as well as the loss of the product particles due to deposition on the reactor wall. The aim of this model is to predict the effect of inlet temperature and reactants concentrations on the average diameter of TiO2 nanoparticle products taking into account particle deposition on the wall due to thermophoresis. Strong non-linear coupling between energy and mass balance equations makes numerical integration of the stiff ordinary differential equations (ODE) a problem. The simulation results obtained provide useful information about the influence of the operational conditions (initial temperature and TiCl4 concentration) and particle wall deposition rate on the average nanoparticle diameter at reasonable computational time. The performance of the present monodisperse model was validated by comparing its predicted results with previously published numerical data. Good correlations between the predicted and numerical results were achieved.

August 16, 2011

Composite Distribution Solution for Minimizing Heat Loss in a Pyrolysis Reactor

Werner O. Filtvedt, Morten Melaaen, Arve Holt, Massoud Javidi, Birger Retterstøl Olaisen

Abstract

The article presents a novel design for a distribution plate. The solution is suitable for a reactor vessel where a reactant gas needs to be maintained at a different temperature from the reaction chamber in order to avoid unwanted occurrences, such as clogging of the distribution plate. A normal procedure involves cooling of the distribution plate which is reported to either increase heat loss substantially or yield insufficient temperature in parts of the reaction chamber. The problem is especially important for reactors where the difference in reactant inlet temperature and desired reaction temperature is large. The investigated design utilized materials of very different thermal conductivity to only cool specific parts of the distribution arrangement and thereby minimize heat loss. Our system is a distribution plate for use in a fluidized bed reactor for silane pyrolysis. However, the solution is general and may be utilized in many types of vessels and chemical reactors.

September 1, 2011

Study of Chemical Quench of High Temperature Syngas

Zhen Yang, Yinhe Liu, Zidong Cao

Abstract

Quench of high temperature raw syngas to a certain degree is of great importance for the availability of a gasifier, and it influences the economical running of whole energy utilization system. Chemical quench is one of the best choices for high temperature syngas quench. Based on the Gibbs free energy minimization approach, thermodynamic analyses are carried out to elucidate the quench process of high temperature syngas. The optimal quench temperature and optimal feeding rate of coal are achieved with the consideration of effects such as inlet syngas temperature, steam input and moisture content in the coal. The results show that chemical quench is an effective way for high temperature syngas quench. The higher the temperature of syngas is, the better the chemical quench effect is. Steam input to the syngas can enhance the chemical quench reaction for the same coal feeding rate, while the effect of moisture content in coal on chemical quench is negligible.

September 1, 2011

Medium Optimization for the Production of Phytase by Recombinant Pichia pastoris Grown on Glycerol

Min Liu, Gabriel Potvin, Yiru Gan, Zhanbin Huang, Zisheng Zhang

Abstract

Based on statistical designs, minimal salts medium, commonly used for yeast cultivation, was optimized to maximize GAP promoter-mediated phytase production by recombinant Pichia pastoris grown on glycerol. A Plackett-Burman design was followed to screen medium components to determine those that significantly affected phytase production. Of the 8 components studied, the concentrations of K2SO4, CaSO4•2H2O and MgSO4•7H2O were identified as having a significant effect. These three components were subsequently optimized by response surface methodology using a central composite design. The optimal concentrations of the three components, leading to a maximal extracellular phytase activity of 161.64 U/ml, were K2SO4 13.25g/l, CaSO4•2H2O 1.03g/l and MgSO4•7H2O 17.94g/l. The activity measured in cultures using optimized growth medium is significantly higher than the 73.31 U/ml measured in cultures using standard minimal salts media. The theoretical phytase yields predicted by the developed model were very close to experimentally obtained values.

September 14, 2011

Critical Analysis of Kinetic Modeling Procedures

José Carlos Pinto, Marcos W. Lobao, Andre L. Alberton, Marcio Schwaab, Marcelo Embiruçu, Silvio Vieira de Melo

Abstract

In this work, issues related to the mathematical modeling and statistical analyses of kinetic data are discussed. Firstly, problems related to the combinatorial explosion of the number of plausible kinetic models are analyzed, when complex reaction mechanisms are taken into consideration and distinct rate determining steps are assumed. Although modeling procedures based on rate-determining steps can lead to oversimplification of kinetic models, these procedures are still very popular because the existence of multiple rate-determining steps usually renders the analytical derivation of kinetic rate expressions impossible. However, if the derived kinetic models are too simple, one can face serious difficulties to fit the proposed models to available experimental data. Secondly, problems related to the statistical analyses of experimental data are discussed. Particularly, very often statistical tools are used even when some of the fundamental assumptions required for their validity are violated. For this reason, the fundamental grounds that support some of the most popular statistical tools are discussed in the framework of the kinetic analysis.

September 14, 2011

Kinetic Modeling of Fischer-Tropsch Synthesis over Fe/Ce/Al₂O₃

Hossein Atashi, Farhad Fazlollahi, Majid Sarkari, Ali A. Mirzaei, Mohsen Allahyari Shahrasb

Abstract

In this experimental study, a kinetic model has been developed for Fischer-Tropsch synthesis reactions by using Fe/Ce/Al2O3 as the catalyst (80% Fe/20% Ce/5wt%Al2O3) in a fixed-bed micro reactor assuming no internal or external diffusion. Operating conditions of the reactor are as follows: reactor total pressure 6-22 atm; Temperature 543-573 K; H2/CO feed ratio 1.5-2 and space velocity 4200 hr-1. Light alkenes were successfully produced due to high activity and selectivity of the catalyst. Considering the mechanism of the process and Langmuir-Hinshelwood- Hogan-Watson (LHHW) approach, four different mechanisms, namely carbide, enol, combined carbide-enol, and parallel carbide-enol were defined for CO consumption rate equations. The rate expressions for the CO hydrogenation reactions are based on elementary reaction corresponding to the carbid-enol mechanism. The obtained rate expressions for the CO hydrogenation reactions from nonlinear regression analysis and Levenberg-Marquardt method demonstrate that the formation of monomer species (HCOs) due to CO hydrogenation reaction has controlled the FTS reaction rate. The activation energy and adsorption enthalpy were calculated as 58.38 kJ/mol and -22.26 kJ/mol, respectively. Also, the effects of temperature and pressure variation on selectivity and production rate of light products are presented.

September 14, 2011

Modeling, Simulation and Optimization of a Three-Phase Catalytic Slurry Intensified Continuous Reactor

Li Shi

Abstract

A dynamic model of three-phase catalytic slurry intensified continuous reactor is proposed, performing the o-cresol hydrogenation. Dynamic simulations are performed to describe the reactor behaviors from start-up to steady-state operating point, and also dynamic behaviors in response of steps disturbances of three effective input variables. An off-line optimization is solved through non-linear programming used of Sequential Quadratic Programming (SQP), a new operating point is obtained with higher productivity and conversion.

September 16, 2011

Kinetic and Thermodynamic Modeling of Cd⁺² and Ni⁺² Biosorption by Raw Chicken Feathers

Hilda E. Reynel-Avila, Guadalupe de la Rosa, Cintia K. Rojas-Mayorga, Irene Cano-Aguilera, Adrian Bonilla-Petriciolet

Abstract

Batch experiments were performed to model kinetic and thermodynamic data for Cd+2 and Ni+2 biosorption by raw chicken feathers (CFs) under different conditions. Results indicated that Cd+2 and Ni+2 sorption onto CFs occurred on the external surface of the biosorbent. Ion removal increased with pH, whereas both endothermic and exothermic stages where observed depending on temperature. Our calculated thermodynamic parameters showed that, below the temperature of 30°C, the metal uptake of Cd+2 and Ni+2 ions may be mainly controlled by a chemisorption process. However, for temperatures higher than 30°C, it is likely that sorption of both metals onto CFs is caused by a combination of both physical and chemical processes, especially for Ni+2 ions. Maximum sorption capacities were of 0.039 (Cd+2 ) and 0.065 mmol/g (Ni+2) at pH 5 and 30°C. Using 0.1 M HCl or CH3COOH as desorbing agents, approximately a 50% recovery for Cd+2 was achieved. The pseudo-second order and the general rate law models best fit the sorption kinetics data. The equilibrium metal uptake data was best described by the Sips isotherm.

September 16, 2011

Explicit Solution for Time-Fractional Batch Reactor System

Najeeb Alam Khan, Muhammad Jamil, Asmat Ara, Subir Das

Abstract

In this paper, the new homotopy perturbation method (NHPM) has been successively applied for finding approximate analytical solutions of the fractional order batch reactor system. An approximate analytical solution for the concentration of reactants and products that is valid for a time interval. The approximate analytical procedure is depends only on two components. The behavior of the solution and effects of different parameters and fractional index are shown graphically. Numerical solutions of ordinary batch reactor system verify our approximate solution with good agreement.

September 16, 2011

Numerical Approximations to Solution of Biochemical Reaction Model

Ahmet Yildirim, Ahmet Gökdogan, Mehmet Merdan

Abstract

In this paper, approximate analytical solution of biochemical reaction model is used by the multi-step differential transform method (MsDTM) based on classical differential transformation method (DTM). Numerical results are compared to those obtained by the fourth-order Runge-Kutta method to illustrate the preciseness and effectiveness of the proposed method. Results are given explicit and graphical form.

September 16, 2011

Removal of Cadmium (II) Ions from Aqueous Phase by Biosorption on Biological Activated Dates' Pedicels (Kinetic, Equilibrium and Thermodynamic Study)

Hynda Yazid, Zahra Sadaoui, Rachida Maachi

Abstract

The preparation of biological activated dates’ pedicels (ADP) adsorbents and its biosorption behaviour of cadmium (II) was the topic of this study. The raw (RDP) and activated (ADP) dates’ pedicels were characterized by SEM, XRF, FTIR and surface area analysis. SEM analysis revealed a heterogeneous structure for ADP and a cellular aspect different from that of RDP, due to the deposit of the bacterial film which has been constituted during the biological treatment of the material. The XRF results show the presence of potassium, calcium in RPD, and sodium in APD which could favour the retention of heavy metals in aqueous solutions by ions exchange. The FT-IR spectra showed that there are different functional groups in adsorbents, which are able to react with metal ions in aqueous solution. Biological pretreatment was carried out in nitrate enriched solution; allowing to enhance the development of denitrifying micro-organisms already existing on the organic support without the need for biomass inoculation. Biological pretreatment allowed the appearance of a bacterial film at the surface of the date pedicel particles, which improved their biosorption capacity. Indeed, the biosorption yields of cadmium (II) ions obtained at equilibrium (60 min) were 70.4 and 57.4% for ADP and RDP, respectively. The experimental data were analyzed by the Langmuir and Freundlich isotherm models and the model constants were evaluated. The maximum biosorption capacity as calculated using the Langmuir isotherm model was 10.75 mg g-1 which is greater than that of commercial and granular activated carbon. The kinetic data obtained at different initial cadmium concentrations and different temperatures were analyzed using pseudo-second-order and intra-particle diffusion models. The biosorption kinetics followed a pseudo-second-order kinetic model. The biosorption of cadmium ion was endothermic and spontaneous. Elution efficiencies with different concentrations of CaCl2, KCl and NaCl were evaluated. The desorption studies showed the reversibility of biosorption and CaCl2 was the most efficient desorbent for elution and desorption of cadmium from the biosorbant.

September 28, 2011

Evaluating and Estimating the Complex Dynamic Phenomena in Nonlinear Chemical Systems

Rama Rao Karri

Abstract

Successful operation and control of complex dynamic systems heavily rely on the availability of fast and accurate evaluation of the system performance. The measurement problems and the delays associated with these systems require the need for on-line state estimators as alternative measurement tools. In this work, a state estimation method based on extended Kalman filter (EKF) is presented for nonlinear dynamical systems that are characterized by complex dynamic phenomena such as multiple steady state behavior, limit cycle oscillations and chaos. The estimator uses the mathematical model of the process in conjunction with the known process measurements to provide the unmeasured process states that capture the fast changing nonlinear dynamics of the process. The design and performance of the state estimator is evaluated by applying two typical continuous non-isothermal nonlinear processes, a chemical reactor and a polymerization reactor, which show rich dynamical behavior ranging from stable situations to chaos. In order to understand the dynamic phenomena and to analyze the conditions that lead to an improved operation, prior to state estimation, these processes are thoroughly analyzed for multiplicity, stability and bifurcation studies. The sensitivity of the state estimator is also studied towards the effect of the design parameters involved in the method. The results demonstrate the efficacy of the model based method for state estimation in nonlinear chemical processes associated with complex dynamic behavior.

September 29, 2011

Novel Batch Reactor for the Dilute Acid Pretreatment of Lignocellulosic Feedstocks with Improved Heating and Cooling Kinetics

John C. Degenstein, Srinivas Kamireddy, Melvin P. Tucker, Yun Ji

Abstract

The pretreatment of lignocellulosic biomass is an important part of the process of utilizing a renewable and abundant feedstock. This paper aims to provide a novel lab-scale batch pretreatment reactor that significantly improves heating and cooling kinetics over typical batch pretreatment reactors, yet made from readily available parts. The heating and cooling kinetics of a batch pretreatment reactor are important for emulating the behavior of a large scale continuous reactor system. The heat transfer performance has been quantified and presented here as a tool for aiding the design of a similar reactor system. One important lignocellulosic feedstock is corn stover, which was used in this study to validate the reactor performance. The pretreatment method that was used in this study is the dilute acid pretreatment. The pretreatment runs were enzymatically saccharified to evaluate the pretreatment effectiveness. The results from this enzymatic saccharification were compared with several literature sources to validate the reactor performance. The pretreatment conditions that were used are 0.5 wt% sulfuric acid, 10 minute pretreatment time, and 10 wt% solids loading. The enzymatic digestibility of the cellulose in the pretreated solids was 53.3% at 150°C and 72.1% at 160°C.

September 29, 2011

Continuous Production of Biodiesel with Supercritical Methanol: a Simple Compressible Flow Model for Tubular Reactors

Ruengwit Sawangkeaw, Witsanee Satayanon, Kunchana Bunyakiat, Séverine Camy, Jean-Stéphane Condoret, Somkiat Ngamprasertsith

Abstract

From an industrial point of view, the continuous process for biodiesel production with supercritical methanol (SCM) is more appropriate than the batch process. However, lab-scale studies on the continuous process have shown that the maximum conversion always remains slightly lower than that obtained in the batch process. This work proposes a simple compressible flow model to predict the conversion of methanol and oils into methyl esters (ME) along the length of a tubular reactor and further demonstrates the effect of the development of the compressibility factor of the reaction mixture upon the conversion efficiency to ME. The governing equation was derived from a general molar balance in the tubular reactor using transesterification kinetics of refined-bleached-deodorized (RBD) palm oil in SCM coupled with a suitable thermodynamic model with adjusted binary interaction parameters. Vapor-liquid equilibrium data for triolein + methanol, methyl oleate + methanol and glycerol + methanol mixtures were obtained from the literature and then refitted with the thermodynamic model consisting of the Peng-Robinson equation of state and MHV2 mixing rules to find the set of adequate interaction parameters. In order to check the validity of the proposed model, the predicted ME contents were compared with observed values in a lab-scale continuous reactor at various operating temperatures, pressures and methanol to oil molar ratios. The proposed model proved to be adequate for predicting the final conversion to ME for operating temperatures below 320°C, when the thermal degradation reactions of unsaturated fatty acids did not interfere. Our results also illustrate the importance of taking into account the development of the compressibility factor with time and reactor length, since this was shown to be the cause of the lower transesterification reaction rate in the tubular SCM process. The findings in this work could be employed as a knowledgebase to further develop a better model for continuous production of biodiesel with SCM in a tubular reactor.

October 4, 2011

Pressure Effect on Hydrodynamics of a High Pressure X-ray Transparent Polyethylene Fluidized Bed

Ana Orta, Bangyou Wu, Mahfam Ghods, Adriana Guerrero, Celine Bellehumeur, Apostolos Kantzas

Abstract

Hydrodynamics of a polyethylene fluidized bed were studied at different operating pressures (191-2908 kPa) and constant temperature of 30°C. Minimum fluidization velocity (Umf) decreased with increasing of operating pressures. Measured Umf agree well with calculated Umf as derived from the standard deviation of pressure fluctuations using Puncochar’s Method (1985). As expected, with the increase of superficial velocity, amplitude and standard deviation of pressure fluctuation series also increase, which is indication of more vigorous bubbling behavior inside the bed. Power spectral density of pressure fluctuation series indicates similar frequency distribution of the bubbling behavior at different superficial velocities. The dominant frequency from the power spectral was found to be around 1 Hz. Bubble diameter and bubble velocity were estimated from X-ray fluoroscopy images. Bubble diameter and bubble velocity increase with increasing bed height and superficial gas velocity due to bubble coalescence and more gas flowing upwards. At the same fluidization number, the average bubble size slightly decreases with increasing pressure at all bed heights because there is less gas flowing and the bubbles coalesce less rapidly. The bubble velocity is observed to have a small decrease from 191 kPa up to 2200 kPa, and then a substantial increase due to the fact that at higher pressure, the solid circulation increases at the bed.

October 4, 2011

Catalytic Activity of Sulfated Iron-Tin Mixed Oxide for Esterification of Free Fatty Acids in Crude Palm Oil: Effects of Iron Precursor, Calcination Temperature and Sulfate Concentration

Kamchai Nuithitikul, Worawoot Prasitturattanachai, Jumras Limtrakul

Abstract

The activities of sulfated iron-tin mixed oxide catalysts for esterification of free fatty acids in crude palm oil were investigated. The iron-tin mixed oxides were prepared from co-precipitation method when the iron content was fixed at 10 mol%. Types of iron precursor, sulfate concentration and calcination temperature were varied. The optimum study in the esterification reaction variables (stirring speed, reaction time, catalyst loading, methanol/oil molar ratio and reaction temperature) was also conducted with the best sulfated iron-tin mixed oxide catalyst. The findings show that iron sulfate is the best precursor. The activities of sulfated iron-tin mixed oxide catalysts increase with sulfate concentration. The optimum calcination temperature to prepare sulfated iron-tin mixed oxides is 450°C. The addition of iron oxide into sulfated tin oxide improves the stability of the catalyst during the reusability process. Therefore, sulfated iron-tin mixed oxide is a better candidate than sulfated tin oxide for esterification of free fatty acids. For the esterification study, the optimum reaction conditions are: the stirring speed of 250 rpm, the catalyst loading of 4.5 wt% of the oil, the methanol/oil molar ratio of 14.2, the reaction temperature of 80°C and the reaction time of 3 h.

October 9, 2011

Modeling and Optimization of Polyphenol Extraction for Tannin-Formaldehyde Resin Synthesis

Nana S. A. Derkyi, Daniel Sekyere, Nicholas A. Darkwa, Nana B. Boakye

Abstract

The properties of plywood depend on many factors, including the quality of resin applied, and the curing or pressing conditions. The bark extracts of various commercially important trees containing polyphenolics in the form of tannins can be condensed with formaldehyde to produce wood resins. In the present work, aqueous ethanol was used as solvent to extract formaldehyde-condensable polyphenolics from Pinus caribaea Morelet bark. The contents of the co-extracted tannin and sugars were determined as well as the Stiasny number. Applying response surface methodology, a four factor, five level central composite rotatable design (CCRD) was employed to examine the optimum conditions of extraction variables for the pine bark polyphenolics. To study the effect of extraction optimization conditions on the resin quality, resins were processed from tannins extracted at the following response parameters; i) only tannin content was optimized, ii) only sugar content was optimized, iii) only Stiasny number was optimized and iv) tannin content, sugar content and Stiasny number were optimized simultaneously. The resins were characterized by viscosity, pot life and plywood bond strength. Each experiment was done in triplicate. Industrial grade phenol-formaldehyde adhesive was used as the control. The optimization models developed were found to adequately represent the extraction of polyphenolic compounds from P. caribaea bark. The quality of resin prepared from the extracted polyphenolics was found to be dependent on the extraction process parameters employed. The extraction process that gave a high tannin yield (18.85%) with a corresponding good quality resin (shear strength = 2.26 MPa, 11.4% delamination) similar to that of the control (industrial phenol-formaldehyde resin) was found for the optimization model when the objective function was to maximize both the tannin yield and Stiasny number and minimize the sugar content simultaneously. This corresponded to optimum extraction conditions of 52.2°C extraction temperature, 150 min extraction time, 43.6% solvent concentration and 10:1 liquid-solid ratio.

October 9, 2011

PIV Investigation of Liquid Flow Field in Off-Centered Shaft Stirred Tanks with Floating Particles

Rajab Abd alsalam Atibeni, Zhengming Gao, Yuyun Bao

Abstract

The local behavior of continuous phase in a stirred tank with floating particles was investigated by using PIV technique. The effect of solid concentration and off-centered shaft position on the fluid field were studied. Experimental measurements were carried out in a fully baffled cylindrical vessel equipped with a flat bottom and an up-pumping 4-Wide-blade Hydrofoil impeller (WHU). The diameter of the vessel, the diameter of the impeller, and the vertical clearance of the bottom were 0.192 m, 0.075 m, and 0.064 m, respectively. The liquid phase was water, and low density polyethylene flat cylindrical particles were used as the floating particles at different concentrations (0.0, 0.6, 0.8, and 1.0 vol.%) and different shaft positions (0.0, 0.0096, 0.0192, and 0.0288 m away from the center of the tank, corresponding to the eccentricities of 0%, 5%, 10%, and 15%, respectively). PIV measurements showed that the velocity increases by approximately 50% in the tank with the most eccentric shaft. Axial and radial mean velocities for the carrier liquid phase were also measured by using fluorescent particles. Results indicated that as the increase of floating particle concentration, the velocity decreases by about 16% in the main flow direction. In addition, the flow behavior is not affected by the presence of floating particles, and the circulation pattern is similar in both the absence and the presence of floating particles.

October 13, 2011

Synthesis and Kinetic Studies on Controlled Release of 6-Thioguanine Entrapped Polyethylene Glycol-Co-Polylactic Acid Polymer Nanoparticles

Sathishkumar Kannaiyan, T.G.Ashwin Narayanan, P.Karthick Sarathy, Nagarjun Sudhakar, Rama Krishnan

Abstract

Poly lactic acid-polyethylene glycol (PLA-co-PEG) copolyester was synthesized from oligomer of L-lactic acid and poly ethylene glycol (PEG) using stannous octoate as catalyst. 6-Thioguanine containing Poly lactic acid-polyethylene glycol (PLA-co-PEG) nanocapsules were prepared in the presence and absence of gold nanoparticles via the W/O/W emulsification solvent-evaporation method. The morphologies of prepared nanocapsules changed substantially because of the presence of gold nanoparticles. From SEM and TEM measurements, the average size of the polymer nanocapsules and gold nanoparticles were found to be in range of 230-260 nm and 18-20 nm, respectively. In general the drug release was quicker in Phosphate buffer saline (pH 7.4) compared to 0.1M hydrochloric acid and this may be due to higher solubility, higher swelling and penetration properties of PLA-co-PEG in PBS compared to HCl. Polymer nanocapsules with gold show a prolonged controlled release with higher encapsulation efficiency (75%) compared to that of polymer nanocapsules (45%) in the absence of gold nanoparticles. It may be due to the more entrapping efficiency of gold and less diffusivity of drugs from the nanocapsules. Application of in vitro drug release data to various kinetic equations indicated Higuchi model, indicating a uniform distribution of thioguanine in the nanocapsules.

October 25, 2011

Study on Direct Hydration of Camphene to Isoborneol by Cation Exchange Resins

Yong Liu, Zheng Zhou, Gaodong Yang, Zhibing Zhang

Abstract

The direct hydration of camphene to isoborneol has been studied in the presence of strong acidic cation exchange resins as catalyst. The effect of various parameters such as temperature, catalyst loading, mass ratio of the reactants, and reaction time on the conversion of camphene was investigated to optimize the reaction conditions. Based on the optimized reaction conditions, a novel pilot-scale jet reactor was used to study the direct hydration of camphene. The kinetic studies of direct hydration reaction have been discussed in detail. A pseudo-homogeneous (PH) model was used to correlate the experimental data in the temperature range from 353.15 K to 383.15 K. The kinetic parameters were evaluated, which made the calculated results in excellent agreement with the experimental results.

October 30, 2011

Behavior of Phosphate in Uranium-Bearing Organophosphorus Solvents in the Pyrolysis and Combustion Reactors

Hee-Chul Yang, Wang-Gyu Choi, Kune-Woo Lee

Abstract

This study investigated the behavior of phosphate in uranium-bearing organo phosphorus solvents under pyrolysis and combustion conditions. The volatilization characteristics of phosphate and the reaction between uranium oxide and phosphate oxide were established based on the results of a thermogravimetric analysis of tributyl phosphate (TBP) and uranium-bearing TBP-dodecane solutions. Uranium dioxide, UO2, functioned as a sorbent for the capture of vaporized phosphate oxide, P4O10(g). A significant fraction of phosphate remained in the form of uranium pyrophosphate (UP2O7) and uranium metaphosphate (U(PO3)4). The P4O10(g) capturing capacity of UO2 was 0.96-0.84 g/g for pyrolysis and 0.60 g/g for combustion, respectively. The relatively low phosphate-capturing capacity of combustion was due to the dissociation of P4O10(g) from (U(PO3)4) at flame temperatures higher than 1300K. Pyrolysis appears to be a better method than combustion for a thermal destruction of uranium-bearing TBP solutions while affording minimized problems associated with the condensation of corrosive phosphoric acid.

November 3, 2011

Hydrodynamic Characteristics of a Novel Circulating Fluidized Bed Steam Reformer Operating in the Fast Fluidization Regime

Moataz Bellah M. Mousa, Seif-Eddeen K. Fateen, Essam A. Ibrahim

Abstract

Circulating Fluidized Bed Steam Reformers (CFBSRs) represent an important alternative for the production of syngas for the Fisher-Tropsch (FT) process and for hydrogen production. Most research regarding this novel CFBSRs did not consider its hydrodynamic characteristics. In this work, the riser Computational Fluid Dynamics (CFD) simulations were investigated using two phase Eulerian-Eulerian approach coupled with kinetic theory of granular flow with k-epsilon model to describe the turbulence of each phase. The model equations were solved via the commercial CFD package FLUENT, which uses the finite volume numerical approach. Cold flow simulations were carried out under the fast fluidization regime and results were validated qualitatively against available experimental data. The radial segregation of the catalyst, the velocity distribution of both phases and other characteristics of the flow were captured by the simulation. This work showed that for operation under high density and high flux conditions, solids flux should be higher than 300 kg/m2s and inlet void fraction lower than 85%.

November 7, 2011

Biological Treatment of Wastewater from Sugar Production Process by using Three-Phase Fluidized Bed Reactor

Kun Hu, Changyi Jin, Yong Guo, Weixing Huang

Abstract

The biodegradation of wastewater from the sugar industry is investigated in a three-phase biological fluidized bed reactor. In the inoculation experiment, the immobilized biofilm was found to keep dominant over the suspended biomass, and a stable biofilm of 175 microns thick was formed after 12 days. The continuous experiments for biodegradation of wastewater showed that, under the operation with hydraulic retention time of 3 h, the average COD and NH3-N removals reached to 85% and 80%, respectively, and the resultant effluent COD and NH3-N achieved the Chinese Discharge Standard of Water Pollutants for Sugar Industry (GB 21909-2008). The experiment for impact load showed that as the influent COD load changed stepwise from 2.3 to 5.1 kgCOD/m3·d, the reactor achieved the treatment effect without being affected in the performance. Finally, tracer experiments were performed to measure the internal circulation and residence time distribution (RTD) of wastewater in the reactor. It was found that the internal circulation of wastewater evidently exists in the reactor. Meanwhile, the RTD characteristics were described with the tanks-in-series model, and under the operating conditions, the calculated model parameter n was ranged from 1.19 to 1.27, which indicated that the flow pattern in the reactor is close to that in a CSTR. The internal circulation causes the organic matters in the influent to be effectively diluted within the reactor, and also promotes the organic matters to be fully degraded, so that the reactor can present high adaptability to the variation of organic load and high removal efficiency to COD and NH3-N. As a result, the biological fluidized bed reactor is suggested to be a prospective unit for the treatment of wastewater from sugar production process.

November 14, 2011

Unified Description of Isothermal Endoreversible Chemical Cycles with Linear Mass Transfer Law

Dan Xia, Lingen Chen, Fengrui Sun

Abstract

An isothermal endoreversible four-reservoir chemical pump cycle operating between a finite potential capacity high-chemical-potential mass reservoir and three infinite potential capacity mass reservoirs is established in this paper. Optimal control theory is applied to determine the optimal cycle configuration corresponding to the maximum energy output per cycle for the fixed total cycle time and transferred energy of high-chemical-potential mass reservoir in which the mass transfer between working fluid and mass reservoirs obey linear mass transfer law. The optimal cycle configuration is an isothermal endoreversible four-reservoir chemical pump cycle, in which the chemical potential (the concentration) of the key component in the finite potential capacity high-chemical-potential mass reservoir and that in the working fluid change nonlinearly with time and the difference between the chemical potential (the ratio of the concentration) of the key component in the finite potential capacity mass reservoir and (to) that in the working fluid is a constant, and the chemical potentials (the concentration) of the key component in the working fluid at the infinite potential capacity mass reservoir sides are also constants. Moreover, the numerical example is provided to reveal the influences of concentration and chemical potential change of the finite potential capacity high-chemical-potential mass reservoir on the optimal configuration of the four-reservoir chemical pump cycle. Then, a unified description of various isothermal endoreversible chemical cycles with linear mass transfer law is obtained. They include ten type of isothermal endoreversible chemical cycles: four-reservoir chemical pumps with finite potential capacity mass reservoirs and infinite potential capacity mass reservoirs, four-reservoir chemical potential transformers with finite potential capacity mass reservoir and infinite potential capacity mass reservoirs, three- reservoir chemical pumps with finite potential capacity mass reservoirs and infinite potential capacity mass reservoirs, three-reservoir chemical potential transformers with finite potential capacity mass reservoir and infinite potential capacity mass reservoirs, two-reservoir chemical pump with infinite potential capacity mass reservoirs, and chemical engine with infinite potential capacity mass reservoirs. The results can provide some guidelines for optimal design and operation of real chemical cycles and devices.

November 16, 2011

Fluid Viscosity-Residual Entropy Correlation

Lawrence T. Novak

Abstract

Chemical reaction engineering, process engineering, and product engineering models are used for design and analysis. Often, transport coefficient models are needed in equipment and in-situ models to account for the importance of momentum, heat, and mass transfer. Previous work+ demonstrated a novel component-based reference equation of state approach for correlating self-diffusion coefficient and viscosity over the entire fluid region (liquid, gas, and critical fluid). In this paper, a segment-based approach is used to extend the previous work+ from a limited number of individual component correlations to a predictive fluid viscosity correlation for a class of components consisting of n-alkanes, up to 1300 molecular weight, covering a wide range of components, temperatures, and pressures. A scaled segment viscosity-segment residual entropy correlation (V-S model) was introduced and evaluated here. PC-SAFT segment parameters and residual entropy were used in a correlation model linking viscosity to the PC-SAFT equation of state. Experimental evaluation of this V-S model used 3122 data points for eighteen n-alkanes, ranging from methane up to 2390 molecular weight linear polyethylene. Temperatures ranged from 96 °K to 650 °K, and pressures ranged from 10-4 atmospheres to 4990 atmospheres. The conditions studied are relevant to oil and gas reservoir engineering and other in-situ processes. Based on this work, covering the entire fluid region, the V-S model was found to result in a group correlation squared (R2) of -0.998 and group average absolute deviation (AAD) of 3.9%. Individual viscosity segment correlation parameters (Bseg and Aseg) were fitted to molecular weight and used in the predictive mode. In the predictive mode, a group AAD of 6.7% was obtained for n-alkanes from methane up to 1300 molecular weight linear polyethylene, over the entire fluid region. The scaled segment viscosity-segment residual entropy model introduced here has potential for a much broader range of applications. In addition, this model would be easy to embed in existing in-house and commercial simulators to provide predictive properties and rate-based modeling capability. + Novak, http://www.bepress.com/ijcre/vol9/A63

November 16, 2011

A Novel Biodiesel and Glycerol Carbonate Production Plant

Nghi T. Nguyen, Yaşar Demirel

Abstract

Crude glycerol is the byproduct of biodiesel production plant and the economic value of glycerol may affect the profitability of the biodiesel production plant. As the production rate of bioglycerol increases, its market values drop considerably. Therefore, conversion of bioglycerol into value-added products can reduce the overall cost, hence, leading to a more economical biodiesel production plant. In a direct carboxylation reaction, CO2 reacts with glycerol to produce glycerol carbonate and water. This study presents a direct comparison of the economic analysis of the conventional biodiesel production plant and the possible next generation biodiesel-glycerol carbonate production plant. At the end of 15-year project, the net present value of the biodiesel-glycerol carbonate production plant is $13.21 million higher than the conventional biodiesel plant. The stochastic model has predicted that the biodiesel-glycerol carbonate and conventional biodiesel production plants has about 30% and 63% chance of getting negative net present value, respectively. Heterogeneous catalyst, Ca3La1, is used for transesterification reaction to reduce separation steps in the biodiesel production process.

November 29, 2011

Frictional Pressure Drop of Gas-Newtonian and Gas-Non Newtonian Slug Flow in Vertical Pipe

Subrata Kumar Majumder, Sandip Ghosh, Gautam Kundu, Arun Kumar Mitra

Abstract

Experimental study on two-phase pressure drop in a vertical pipe with air-Newtonian and non-Newtonian liquid in slug flow regime has been carried out within a range of gas and liquid flowrate of 0.5×10-4 to 1.92×10-4 m-3/s and 1.6×10-4 to 6.7×10-4 m3/s respectively. In the present study air and four types of liquids such as water, amyl alcohol, glycerin (two different concentrations), and CMC (Sodium Carboxymethyl Cellulose) are used. The present data were analyzed by two-phase friction method. To predict the two-phase pressure drop, correlations have been developed with Newtonian and non-Newtonian liquid. A general correlation was also developed to predict the two-phase pressure drop in a vertical column of diameter 0.01905 m and 3.4 m height combining both the Newtonian and non-Newtonian liquid systems.

December 1, 2011

The Effect of Gas Flow Rate on the Thin Film Deposition Rate on Carbon Steel Using Thermal CVD

Mohammad A. Chowdhury, Dewan M. Nuruzzaman, Mohammad L. Rahaman

Abstract

Solid thin films have been deposited on carbon steel substrates in a chemical vapor deposition (CVD) reactor where natural gas, mostly methane (CH4), was used as a precursor gas. The effect of gas flow rate on the thin film deposition rate has been investigated experimentally. The effect of gap between activation heater and substrate on the deposition rate has also been observed. To do so, a hot filament thermal chemical vapor deposition unit is used. The flow rate of natural gas varies from 0.5 to 2 l/min at normal temperature and pressure (NTP) and the gap between activation heater and substrate varies from 4 to 6.5 mm. Results show that the deposition rate on carbon steel increases with the increase of gas flow rate. It is also seen that deposition rate increases with the decrease of gap between activation heater and substrate within the observed range. These results are analyzed by dimensional analysis to correlate the deposition rate with gas flow rate, surface roughness and film thickness. In addition, friction coefficient and wear rate of carbon steel sliding against SS 304 under different normal loads are also investigated before and after deposition. The obtained results reveal that in general, the values of friction coefficient and wear rate are lower after deposition than that of before deposition.

December 1, 2011

Performance Analysis of Immobilized Enzyme Semifluidised Bed Bioreactors

C.M. Narayanan, Maneka Banik, Sayani Halder

Abstract

In spite of the many-sided advantages of semifluidised bed bioreactors, no attempt has been made to simulate their performance mathematically. Only scattered experimental data are available in literature. In the present study, therefore, attempts have been made to simulate immobilized enzyme semifluidised bed bioreactors’ performance as equivalent to CSTR – PFR combinations, but with due allowances for the heterogeneity of the system. Bioconversions that follow Michaelis – Menten kinetics (with and without substrate inhibition) and reversible Michaelis – Menten kinetics have been considered. Substrate transfer into the particle (that accommodates the immobilized enzyme) is governed by the magnitude of effectiveness factor which is evaluated based on the generalized integral for the estimation of Thiele – type modulus and the corresponding correlation for effectiveness factor (as a hyperbolic tangent function) and also based on the analytical expression proposed by Gottifredi and Gonzo. Parameters such as operating semifluidisation velocity, porosity of fluidized section, height ratio of packed section to fluidized section are estimated from experimental correlations that are selected through elaborate trial and error procedure. Though the simulation model involves simplifications and empirical estimation of a few parameters, model results are found to exhibit reasonably good agreement with data collected through extensive experimental investigations, the maximum deviation being ±12.5 %. This confirms the acceptability of the software package developed. The developed software could be, therefore, recommended for the design and installation of industrial semifluidised bed bioreactors and also for the performance analysis of existing industrial bioreactors.

December 1, 2011

Kinetics Study of Esterification Reaction of 2-Methyl-4-Chlorophenoxyacetic Acid (MCPA Acid)

Pei San Kong, Mohamed Kheireddine Aroua, Aziz Abdul Raman

Abstract

MCPA ester is a postemergence and selective herbicide widely used in controlling weed growth. This is due to the low solubility of MCPA ester in water which differs from majority of the other herbicides. With low solubility, the chance of water pollution is lesser comparatively. MCPA ester can degrade in soil by biological and biotic mechanism which reduces the soil pollution. Despite the wide application of this ester, the kinetic data on synthesis of MCPA ester is still considered as a proprietary data and it is not available in the open literature. Therefore kinetic studies are conducted in this work. MCPA ester was synthesized by reacting MCPA acid and 2-ethylhexanol in the presence of sulfuric acid as a catalyst. The parameters studied were reaction temperature, catalyst concentration and alcohol to acid molar ratio. The reaction was conducted in a jacketed batch reactor and samples were taken at an appropriate time intervals. The concentration MCPA ester was determined by gas chromatography mass spectrometry (GC-MSD) analysis. The experimental data were fitted with proposed homogeneous integrated second order kinetic model and the fitting accuracy at 373K, 383K and 393K were 0.99, 0.95 and 0.99 respectively. The activation energy and frequency factor were estimated to be 71.559 kJmol-1 and 1.221 x 107 Lmol-1 min-1 respectively. Kinetic constant values were 0.844 x 103 to 6.331 x 103 Lmol-1 min-1 within the range of the temperature and concentration studied. As predicted, the activation energy decreases with increases in catalyst concentration and the values at 0.01M, 0.1M and 0.5M catalyst concentration were 73.6, 71.7 and 69.4 kJmol-1 respectively.

December 1, 2011

Melting Effect on Unsteady Hydromagnetic Flow of a Nanofluid Past a Stretching Sheet

Ali J. Chamkha, A.M. Rashad, Eisa Al-Meshaiei

Abstract

This paper considers unsteady, laminar, boundary-layer flow with heat and mass transfer of a nanofluid along a horizontal stretching plate in the presence of a transverse magnetic field, melting and heat generation or absorption effects. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis. The governing partial differential equations are transformed into a set of non-similar equations and solved numerically by an efficient implicit, iterative, finite-difference method. A parametric study illustrating the influence of various physical parameters is performed. Numerical results for the steady-state velocity, temperature and nanoparticles volume fraction profiles as well as the time histories of the skin-friction coefficient, Nusselt number and the Sherwood number are presented graphically and discussed.

December 1, 2011

Quantification of Mixing in RIM Using a Non-Diffusive Two-Phase Flow Numerical Model

Cláudio P. Fonte, Ricardo J. Santos, Madalena M. Dias, José Carlos B. Lopes

Abstract

Mixing in RIM is made mainly by advective mechanisms, rather than diffusion. In this paper, the advective mechanisms that enable reducing the mixing scales down to the values required for the complete chemical reaction of the two monomers inside the RIM mixing chamber are identified and studied. From Computational Fluid Dynamics (CFD) simulations of non-diffusive two-phase flow using the Volume-of-Fluid (VOF) model, a linear scale of segregation is determined as a measure of the degree of mixing and the effect of the Reynolds number is studied.

December 17, 2011

Unsteady Rotating Flows of Oldroyd-B Fluids with Fractional Derivatives

Muhammad Jamil, Najeeb Alam Khan, Muhammad Imran Asjad

Abstract

Exact solutions corresponding to the unsteady flows of an Oldroyd-B fluid with fractional derivatives, between two infinite coaxial circular cylinders are obtained by means of Laplace and finite Hankel transforms. The motion of the fluid is produced by the inner cylinder that, at time t=0+, is applied a time dependent rotational shear stress to the fluid. The expressions of the velocity field and the shear stress are presented in series form in term of generalized G_{a,b,c}(•,t) and R_{a,b}(•,t) functions. The solutions that have been obtained satisfy all imposed initial and boundary conditions. The corresponding solutions for ordinary Oldroyd-B, fractional Maxwell, ordinary Maxwell, fractional second grade, ordinary second grade and Newtonian fluids performing the same motion are obtained as limiting cases of general solutions. Moreover, as a check of our calculi, our present solutions for ordinary second grade and Oldroyd-B fluids are compared with known solutions form the literature. Finally, the influence of the pertinent parameters on the fluid motion as well as a comparison between the models is underlined by graphical illustrations.

Short Communication or Note

January 16, 2011

Fe Containing ZSM-5 Zeolite as Catalyst for Wet Peroxide Oxidation of Orange II

Emre Bolova, Gonul Gunduz, Meral Dukkanci, Selahattin Yilmaz, Yadigar Ceyda Yaman

Abstract

This study presents the catalytic performances of iron containing ZSM-5 zeolites, prepared by ion exchange or hydrothermal synthesis, in catalytic Fenton-like oxidation of Orange II in aqueous solution. The catalyst, ZSM-5 zeolite with Si/Al ratio of 42 loaded with iron by ion exchange, showed the highest activity. The decolorization of 99.7 percent, degradation of 87.0 percent and COD removal of 81.2 percent were achieved over this catalyst at an initial pH of 3.5. Incorporation of iron into ZSM-5 structure increased its catalytic activity. The hydrothermally prepared FeZSM-5 catalyst was more stable against leaching at low pH value due to the iron being in the framework.

March 10, 2011

Solid to Gas Temperature Gradient in a Microwave Fluidized Bed

Zeljko Pajkic, Achim Schmidt, Thorsten Gerdes, Monika Willert-Porada

Abstract

Convective heat transfer from solid to gas was investigated in a microwave heated fluidized bed and compared to an identical conventionally heated bed. Fluidizing gas was fed at room temperature and heated in contact with the bed solid phase. Solid phase temperature was varied in range of 300-600°C. Temperature difference of the two phases and heat loss by gas stream were measured in both heating types and discussed regarding chemical reaction engineering and energy efficiency. Advantages of microwave heating in such systems were elaborated with an outlook to perspective applications of the process in field of materials science and engineering.

May 2, 2011

Dynamic Technique to Determine Hexadecane Transfer Rate from Organic Phase to Aqueous Phase in a Three-Phase Bioreactor

Manuel Alejandro Lizardi-Jiménez, Gerardo Saucedo-Castañeda, Frederic Thalasso, Mariano Gutiérrez-Rojas

Abstract

Determination of mass transfer of non-water soluble substrates, as hexadecane (HXD), is an important constraint in three-phase airlift bioreactor. A new simple dynamic technique able to measure the hexadecane transfer rate (HTR) in a three-phase airlift bioreactor (ALB) was studied in this work. The image analyses technique allowed measuring the resulting specific mass transfer area (aHXD). Gas chromatography was used to measure time-dependent transferred HXD and therefore the HXD transfer coefficient (kLHXD). Finally, HTR was calculated by using the equation HTR = kLaHXD(CHXD* - CHXD) where CHXD* and CHXD are the saturation HXD-aqueous interphase and HXD aqueous phase concentration, respectively. As case study, we successfully applied to the measurement of HTR during a typical ALB microbial consortium culture; values from 0.010 to 0.042 mg HXD (L h)-1 were found. This technique could be used to compare similar simultaneously occurring parameters to assess mass transfer constraints in three-phase systems.

May 15, 2011

Optimisation of C:N Ratio for Co-Digested Processed Industrial Food Waste and Sewage Sludge Using the BMP Test

Zuhaib Siddiqui, N.J. Horan, Kofi Anaman

Abstract

Biomethane production from processed industrial food waste (IFW) in admixture with sewage sludge (primary and waste activated sludge: PS and WAS) was evaluated at a range of C:N ratios using a standard biochemical methane potential (BMP) test. IFW alone had a C:N of 30 whereas for WAS it was 5.4 and thus the C:N ratio of the blends fell in that range. Increasing the IFW content in mix improves the methane potential by increasing both the cumulative biogas production and the rate of methane production. Optimum methane yield 239 mL/g VSremoved occurred at a C:N ratio of 15 which was achieved with a blend containing 11 percent (w/w) IFW. As the fraction of IFW in the blend increased, volatile solids (VS) destruction was increased and this led to a reduction in methane yield and amount of production. The highest destruction of volatile solids of 93 percent was achieved at C:N of 20 followed by C:N 30 and 15. A shortened BMP test is adequate for evaluating optimum admixtures.

May 20, 2011

Sol-gel Synthesis and Photocatalytic Properties of the Nano-ZnO Network

Ying Liang, Zhigao Tian, Ying Liu, Huajun Liu

Abstract

The fluffy porous structure ZnO nanocrystals have been successfully synthesized using citric acid assisted sol-gel method. The ZnO nanocrystals were systematically characterized by XRD, SEM, UVS, and TGA/DSC. Finally, the ZnO nanocrystals were investigated in the photodegradation experiment. The results indicated that the highly photocatalytic activity was exhibited using ZnO nanocrystals as photocatalyst.

May 24, 2011

Esterification Catalysis through Functionalized Membranes

Elham Abouel Fetouh El-Zanati, Stephen M. Ritchie, Heba Mohamed Abdallah, Rim Ettouny, Mahmoud A. El-Rifai

Abstract

Breaking the thermodynamic equilibrium in reversible esterification reactions is achieved through water adsorption on a functionalized membrane. The used functionalized catalytic membrane contains sulfonated polystyrene grafts which act as an alternative to conventional esterification process catalysts. A set of parameters influencing the esterification reaction have been studied. These include feed reactants molar ratio, temperature, different styrene percentages in the membrane, and membrane area. The results show that the increase of molar ratio, temperature, styrene percentage, and membrane surface area increases the reaction conversion and product yield. The high reaction rate obtained on the onset of the reaction, which is attributable to water removal by adsorption, is offset as the reaction proceeds owing to the deactivation of the catalytic active sites by the water adsorbed within the membrane. Therefore, the conversion rate increases up to a maximum and then decreases owing to catalyst deactivation as the membrane becomes progressively saturated with the adsorbed water. The maximum conversion reached was 93.78 percent after a processing time of 10 sec when using 10:1 molar ratio ethanol to acetic acid, 5 percent styrene in the grafted membrane having a diameter of 14.2 cm (1.52 meq of catalyst/g) at 30ºC, and a membrane internal adsorption surface area of 252,450 cm2.

July 8, 2011

The Influence of Boria and EDTA on the Hydrodesulfurization Activity on CoMoS Supported Catalysts

Matin Parvari, Peyman Moradi

Abstract

The hydrodesulfurization of dibenzothiophene (HDS of DBT) in a high pressure batch reactor at 320°C was carried out over CoMo/Al2O3-B2O3 catalysts with different B2O3 contents (4, 10, and 16 wt%). Ethylenediaminetetraacetic acid (EDTA) with different EDTA/Co mole ratios (0.6, 1.2 and 1.8) was used as a chelating ligand during the preparation of CoMo/Al2O3-B2O3. XRD studies, FTIR, TPD of NH3, and BET experiments were used to investigate the catalyst samples. The results showed that the catalyst using the support with 4 wt% B2O3 and an EDTA/Co mole ratio of 1.2 had a hydrodesulfurization activity (in pseudo first order kinetic constant basis) value of ~2.96 times higher than that of the simple CoMo/Al2O3 catalyst.

July 8, 2011

Adsorption and UV-Visible Light Induced Degradation of Methylene Blue over ZnO Nano-Particles

Muhammad Amirul Islam, Iqbal Ahmed Siddiquey, Md. Azizur Rahman Khan, Md. Mahbubul Alam, Saiful S.M. Islam, Mohammad A. Hasnat

Abstract

Photocatalytic degradation of a heteropolyaromatic dye (methylene blue) in aqueous ZnO suspension was investigated under UV and visible light irradiation. Adsorption behavior was found to be well fitted with the Langmuir and Freundlich isotherms. Free energy of adsorption was found to be negative which indicates that adsorption was spontaneous. Under UV light irradiation for 6 hours, the catalytic process produced a net decolorization and mineralization (50 µM MB) of about 98% and 89% respectively. Meanwhile, under visible light irradiation (10 µM MB) for 8 hours these resulted ca. 95% and 77% decolorization and mineralization, respectively. Degradation efficiency was found to be highest at basic pH (8.6). Catalyst loading of 1.0 gl-1 was found to be optimum for the degradation of 100 µM MB solution. In all conditions the UV irradiation showed much better photo-assistance than the visible light irradiation.

July 15, 2011

Alkali Metal Exchanged Zeolite as Heterogeneous Catalyst for Biodiesel Production from Sunflower Oil and Waste Oil: Studies in a Batch/Continuous Slurry Reactor System

M. E. Borges, A. Brito, A. Hernández, L. Díaz

Abstract

Biodiesel as an alternative fuel has become more important in recent times due to the increasing awareness of fossil fuel resources and the environmental benefits. The main disadvantages are its cost and availability of fats and oils resources. By collecting used frying oils and converting them to biodiesel fuel, the cost of biodiesel is significantly lowered and the negative impact of disposing used oil to environment reduced.The aim of this study was to analyse the performance of several alkali metal exchanged zeolites as heterogeneous catalysts for biodiesel production from sunflower oil and waste oil. Several catalysts studied showed a high activity for transesterification reaction with batch or continuous flow reactor operation conditions performed: temperature (100- 155°C), methanol/oil molar ratio (12:1- 72:1 mol/mol) and catalyst concentration (3-6 wt %). Results indicated that biodiesel production using waste oil as feedstock has good potential because it is an inexpensive and available feedstock.

August 8, 2011

Use of Liquid Marbles as Micro-Reactors

Edward Bormashenko, Revital Balter, Doron Aurbach

Abstract

Liquid marbles are droplets coated with hydrophobic micro-scaled powder. Micro-scaled particles of polyvinylidene fluoride formed highly permeable shell enwrapping 100 microliter droplet. This fact was used for converting liquid marbles into micro-reactors. Marbles containing the mixture of ammonia acetate, acetic acid and acetylacetone were exposed to formaldehyde vapor. Formaldehyde vapor absorbed by the liquid surface promoted the chemical reaction accompanied by marble coloring. Thus, mobile sliding and floating micro-reactors were produced. Liquid marbles can be used for remote sensing of gaseous organic contaminants.

September 16, 2011

Removal of Carbon Monoxide by Oxidation from Excess Hydrogen Gas on Co₃O₄-NiO/AC Catalyst

Guilin Zhou, Hongmei Xie, Tingting Wan, Guizhi Zhang, Shengmin Chen, Xuxi Zheng

Abstract

The present work investigates the catalytic properties of the Co-Ni-supported activated carbon (AC) catalyst for the oxidation removal of CO in excess hydrogen gas to obtain High purity hydrogen. X-ray diffraction (XRD), temperature-programmed desorption of O2 (O2-TPD), and temperature-programmed reduction (TPR) were used to study the properties of the prepared catalyst. XRD, and TPR results indicate that the highly dispersed NiO and Co3O4 are the main phase in the prepared catalyst. The O2-TPD results show that the Co3O4-NiO/AC catalyst has strong adsorption and activation capacity to O2 molecules. Active oxygen species can be formed on the surface of Co3O4-NiO/AC catalyst, which is the active species to oxidize CO molecules. CO conversion can exceed 99.5% in the temperature range of 443~463 K, and CO oxidation selectivity exceeds 62.2% in less than 463 K.

November 14, 2011

An Integral Formulation Approach for Numerical Solution of Tubular Reactors Models

Eliseo Hernandez-Martinez, Jose Alvarez-Ramirez, Francisco J. Valdes-Parada, Hector Puebla

Abstract

In this paper, we derive an integral formulation approach based on Green’s function for the numerical solution of tubular reactor models described by reaction-diffusion-convection (RDC) equations with Danckwerts-type boundary conditions. The integral formulation approach allows the direct incorporation of boundary conditions and leads to a stable and accurate numerical integration with smooth round-off error. Numerical simulations of two of tubular reactors models are presented in order to illustrate the numerical accuracy of the method. The results are compared with those resulting from using standard finite difference method. Our results show that the integral formulation approach improves the performance of classical FD schemes.

NCC3 2010 Catalysis Congress

January 8, 2011

The Investigation of Electrochemical Oxidation of Formic Acid on Pt, Pd and PtRu Modified Gas Diffusion Layer

Fatih Köleli, Anya Beytaroglu, Derya Röpke, Thorsten Röpke, Rezzan Aydin

Abstract

Catalytic activities of platinum (Pt), palladium (Pd) and platinum-ruthenium (PtRu black) modified gas diffusion layers (GDL), so called gas diffusion electrodes (GDE),were studied for electrooxidation of formic acid in aqueous acidic solution. The effects of formic acid concentration and medium temperature on the oxidation were investigated. Additionally, cyclic voltammetric investigation (CV), electrochemical impedance spectroscopy (EIS) and amperometric measurements were carried out by using modified catalysts. Electrochemical measurements indicated that the modified PtRu/C black exhibits higher electrocatalytic activity than Pt/C and Pd/C catalysts.

March 10, 2011

Effects of Catalyst Precursor Type and Preparation Conditions, and Solvent Type on Activity and Selectivity of Pt/SiO2 Catalyst in Citral Hydrogenation

Can O. Depboylu, Selahattin Yilmaz, Sedat Akkurt

Abstract

In this study, citral hydrogenation reaction in liquid phase over silica gel supported Pt catalysts was investigated. It was desired to hydrogenate carbonyl group selectively to produce valuable unsaturated alcohols, namely geraniol and nerol. Pt/SiO2 catalysts were prepared by impregnation method. The effects of parameters investigated in the present study included Pt precursor type (hexachloroplatinic acid (HCLPA), platinum II acetylacetonate (PAA)), catalyst activation temperature (350°C and 450°C), catalyst activation without calcination, catalyst washing with 0.1 M NaOH and solvent type (ethanol, 2-pentanol). The catalysts activities and selectivities were affected by the type of precursor and activation temperature. The maximum citral conversion (89.50 percent) was achieved at lower activation temperature (350°C) with PAA precursor based catalyst. It was observed that higher activation temperature provided lower citral conversion but higher selectivity to unsaturated alcohols; increasing the activation temperature to 450°C decreased citral conversion to 26.10 percent. But selectivity to unsaturated alcohols, geraniol and nerol, increased from 7.06 to 54.60 percent. Catalyst washing and 2-pentanol prevented acetal formation. Catalyst activation without calcination gave lower citral conversion (20.84 percent) and selectivity to unsaturated alcohols (30.00 percent).

May 7, 2011

Carbon Nanotube Structures as Support for Ethanol Electro-Oxidation Catalysis

Hilal Kivrak, Sadig Kuliyev, Hermann Tempel, Joerg Schneider, Deniz Uner

Abstract

In the present study, the effect of support for ethanol electro-oxidation reaction was investigated on 20 percent Pt/C (E-Tek), 20 percent Pt/commercial CNT, and 20 percent Pt/home-made CNTs. Homemade CNTs were prepared by template synthesis method via chemical vapor deposition (CVD) method. Twenty percent Pt/commercial CNTs and 20 percent Pt/home-made CNTs were prepared by polyol method. The metal dispersions were determined from volumetric chemisorption measurements. These catalysts were tested as anode catalysts for the ethanol electro-oxidation reaction at room temperature by cyclic voltammetry. An optimization study was conducted to find out the optimum scan rate and optimum potential change for ethanol electro-oxidation reaction on 20 percent Pt/C (E-Tek) catalyst. Then, ethanol electro-oxidation measurements were performed on 20 percent Pt/C (E-Tek), 20 percent Pt/commercial CNTs, and 20 percent Pt/home-made CNTs catalysts in 0.5 M H2SO4 +0.5 M ethanol solution at 0.05 V/s scan rate and 1.2 V vs. NHE. Although the raw data indicated that the 20 percent Pt/commercial CNTs exhibited the worst performance, the performances of all of the catalysts were identical after normalizing the current values with respect to the exposed Pt site obtained from the volumetric hydrogen chemisorption measurements. These results indicate that only the metal dispersions improved ethanol electro-oxidation reaction and support did not have any effect on ethanol electro-oxidation reaction under the conditions used in this study.

About this journal

Objective
The International Journal of Chemical Reactor Engineering covers the broad fields of theoretical and applied reactor engineering. The IJCRE covers topics drawn from the substantial areas of overlap between catalysis, reaction and reactor engineering. The journal is presently edited by Hugo de Lasa and Charles Xu, counting with an impressive list of Editorial Board leading specialists in chemical reactor engineering. Authors include notable international professors and R&D industry leaders.

Topics

Chemical reaction engineering
Single-phase and multi-phase reactor design
Catalytic reactors
Operation and control of chemical reactors
New chemical reactor concepts for green chemical processes
Fluid mechanics and fluid dynamics
Computational fluid dynamics
Low and high pressure and temperature chemical reactor operation.

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Original research and development articles, research and special events reports, book reviews etc.

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Volume 9 Issue 1

Issue of International Journal of Chemical Reactor Engineering

Kinetic Modeling and Reactor Simulation and Optimization of Industrially Important Polymerization Processes: a Perspective

Abstract

Multiphase Flow Measurement Techniques for Slurry Transport

Abstract

Mathematical Modeling of Coal Gasification in a Fluidized Bed Reactor Using a Eulerian Granular Description

Abstract

Modeling and Optimizing of Mechanically Agitated Vessels by Central Composite Rotatable Design Method

Abstract

Comparison of Lumping Approaches to Predict the Product Yield in a Dual Bed VGO Hydrocracker

Abstract

Adsorption Thermodynamics of Toxin (65 kDa) and Protoxin (130 kDa) from Bacillus thuringiensis by Several Minerals

Abstract

Non Linear State and Parameters Estimation in Chemical Processes: Analysis and Improvement of Three Estimation Structures Applied to a CSTR

Abstract

Simulation and Optimization of an Auto-Thermal Ammonia Synthesis Reactor

Abstract

Parameteric Optimization of Dye Removal by Electrocoagulation Using Taguchi Methodology

Abstract

Experimental Study of Hydrodynamic Characteristics and CO2 Absorption in Producer Gas Using CaO-sand Mixture in a Bubbling Fluidized Bed Reactor

Abstract

Maximum Power Output of Multistage Continuous and Discrete Isothermal Endoreversible Chemical Engine System with Linear Mass Transfer Law

Abstract

A Novel Route for Conversion of Free Fatty Acids in Acidic Oils to Methyl Esters by In-Situ Hydrolysis of Methyl Acetate

Abstract

Compatibility of Transport and Reaction in Membrane Reactors Used for the Oxidative Dehydrogenation of Short-Chain Hydrocarbons

Abstract

Determination of Kinetic Parameters for Enzymatic Cellulose Hydrolysis Using Hybrid Differential Evolution

Abstract

Unsteady Flow Mixing Effect in Bionic Micro-Flow Channel

Abstract

The Homotopy Analysis Method for Fractional Cauchy Reaction-Diffusion Problems

Abstract

Numerical Study of Bubbling Gas-Solid Fluidized Beds Hydrodynamics: Influence of Immersed Horizontal Tubes and Data Analysis

Abstract

The Characteristic of Power Spectral of Pressure Fluctuation Signal in CFB Riser with Fractal Analysis

Abstract

Three-Dimensional Flamelet Simulation of Polycyclic Aromatic Hydrocarbons Formation in DI-Diesel Engines

Abstract

Mass Transport Properties of a Flow-Through Electrolytic Reactor Using Zinc Reduction System

Abstract

Some Exact Solutions for Helical Flows of Maxwell Fluid in an Annular Pipe due to Accelerated Shear Stresses

Abstract

CFD Modeling and Simulation of a Catalytic Micro-Monolith

Abstract

Production of Acid Silica Sols and Gels by Using a Y-shaped Reactor and Dilution Technique

Abstract

Molecular Dynamics Simulation of Water and Ions in Nanopores of Lysozyme Protein Crystal

Abstract

Study on a Coupling Reactor for Catalytic Partial Oxidation of Natural Gas to Syngas

Abstract

A Three-Dimensional Model Frame for Modelling Combustion and Gasification in Circulating Fluidized Bed Furnaces

Abstract

Numerical Investigation of Flow Friction and Heat Transfer in a Channel with Various Shaped Ribs Mounted on Two Opposite Ribbed Walls

Abstract

Non-Newtonian Flow Behavior on Frictional Pressure in Packed Bed

Abstract

Investigation of Picolinic Acid Extraction by Trioctylamine

Abstract

Reaction Kinetics of Simultaneous Removal of SO2 and NO from Flue Gas by NaClO2 Solution

Abstract

The Potential of Different Saline Solution on the Extraction of the Moringa oleifera Seed's Active Component for Water Treatment

Abstract

Experimental Flow Measurements of a Spouted Bed Using Pressure Transducer and X-Ray CT Scanner

Abstract

Removal of Remazol Turquoise Blue (G-133) and Polyvinyl Alcohol (PVA) by Electrocoagulation using Monopolar and Bipolar Electrodes

Abstract

Experimental Characteristics of Pneumatic Pulse Jet Pumping Systems with a Venturi-Like Reverse Flow Diverter

Abstract

Comparative Study of Numerical Simulations of the RESS Process: The Supercritical Pure Fluid Expansion

Abstract

Facile Preparation of P-25 Films Dip-Coated Nickel Foam and High Photocatalytic Activity for the Degradation of Quinoline and Industrial Wastewater

Abstract

Kinetic Modelling of Phenol Oxidation in a Bioremediation Medium Using Fenton's Reagent

Abstract

Augmentation of the Performance of Batch Electrocoagulation Unit by Using Gas Sparging

Abstract

Validation of CFD Model for Polysilicon Deposition and Production of Silicon Fines in a Silane Deposition FBR

Abstract

Experimental Study of Hydrodynamic Characteristics and CO₂ Absorption in Producer Gas Using CaO-sand Mixture in a Bubbling Fluidized Bed Reactor

Reaction Kinetics of Simultaneous Removal of SO₂ and NO from Flue Gas by NaClO₂ Solution

Membrane Contactor as Reactor for CO₂ Capture

Synthesis and Physicochemical Characterization of Nanostructured Pt/CeO₂ Catalyst Used for Total Oxidation of Toluene

CO₂ Capture by Calcined Dolomite in a Fluidized Bed: Experimental Data and Numerical Simulations

Mitigating NH₃ Vaporization from an Aqueous Ammonia Process for CO₂ Capture