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Licensed Unlicensed Requires Authentication Published by De Gruyter November 19, 2015

Modeling of Non-catalytic Supercritical Water Oxidation of Phenol

S.M. Ghoreishi, S.M. Shariatmadar Mortazavi and Ali Hedayati

Abstract

The non-catalytic supercritical water oxidation (SCWO) of phenol was modeled using Gopalan-Savage and Thornton-Savage global and network rates. Comparison of experimental data for the phenol conversion with the numerical predictions of this study indicated very close compatibility. Applying the validated model, the phenol conversion and selectivity of various products were studied as a function of effective parameters such as feed phenol concentration, reactor residence time, feed temperature, and feed oxygen concentration. The results of modeling analysis show that an appropriate elevated temperature range (460°C < T <500°C) and long residence time (≈90 s) reduce the concentration of hazardous products (i.e., dimers, dibenzofuran, dibenzo-p-dioxin) and maximize the selectivity of environmental benign products such as water and carbon dioxide. Also, high oxygen concentration (≈0.01 mol/L) increase water and carbon dioxide yield. Moreover, high feed phenol concentrations cause a shortcoming for the SCWO system in terms of phenol conversion and selectivity of desirable environmental products. As a consequence, the feed phenol concentration of ≤2 × 10−3 mol/L is recommended as the appropriate condition.

Acknowledgements

The financial support provided for this project by Isfahan University of Technology (IUT) is gratefully acknowledged.

Nomenclature

AM0.58-a-b.s−1pre-frequency factor
CAmol/m3reactant concentration
[CA o]mol/m3feed reactant concentration
CP,H2OkJ/mol.°Cconstant pressure heat capacity for water
Dmreactor diameter
EakJ/molactivation energy
Ftmol/sfeed molar flow rate
Gg/s.m2mass velocity
hwkJ/s.m2. °Cconvective heat transfer coefficient
ΔHkJ/molenthalpy change
Ks−1(mol/lit)1-nrate constant
i(-)Number of reaction
Lmreactor length
NPec(-)Peclet number (uIL/Dz)
Pbarpressure
rAmol/m3.srate of reaction of component A per unit volume
rPhenolmol/m3.sglobal rate reaction
T°Ctemperature
um/sinterstitial fluid velocity
UW/m2.koverall heat transfer
Vm3reactor volume
x(-)conversion
zmreactor axial dimension
(-)experimental data
yˆi(-)model predicted data
yˉ(-)average of the experimental data
Greek letters
ρkg/m3fluid density
ρpkg/m3particle density
μkg/m.sfluid viscosity
νA(-)stoichiometric coefficient of A in each reaction
τ(s)residence time

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Published Online: 2015-11-19
Published in Print: 2015-12-1

©2015 by De Gruyter