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/tonne of pulp of which 3 comes from wet barking, 12 from the fibre separation (stone groundwood) and 10 from the bleaching operation. The ellluent has a low colour and the amount of suspended solids is normally in the range 20-30 kg/tonne of pulp. In the chemical pulping process ·150-600 kg BOD,/tonne is generated. The lower figure applies to semi-chemical pulping and the higher to the production of viscose pulps. Normally, however, the spent Iiquor is collected, evaporated and burnt leading to at least 95% reduction of the BOD discharge. The total BOD, of the

effect of fungal pretreatment on the energy consumption of refiners used for mechanical pulps and their corresponding paper properties have been investiga- ted in the literature (Akhtar et al. 1992, 1997a, 1997b). Also, the fungal pretreatment of wood fibers prior to chemical pulping have been assessed in the literature (Ferraz et al. 2000; Mendonça et al. 2004; Wolfaardt et al. 2004; Villalba et al. 2006; Çöpür, Tozluo¤lu 2007). It was reported that the pretreatment of wood chips with fungi in biochemical processes facilitated delignification (Scott et al. 1995

: A step towards an optimised precipitation operation Henrik Wallmo, Tobias Richards and Hans Theliander, Chalmers University of Technology, Gothenburg, Sweden Chemical pulping 5208 09-06-15 14.02 Sida 158 Nordic Pulp and Paper Research Journal Vol 24 no. 2/2009 159 the precipitation process influences both the absorption of CO2 in black liquor and the average specific filtration resistance of the precipitated lignin. The main parameters evaluated were the mixing conditions and the CO2 concentration of the precipitation gas. Additionally, the influence of the

, filtration and washing Precipitation The precipitation experiments were carried out at atmos- pheric pressure in a tank reactor with a total volume of 2.5 litres and equipped with four baffles. The reactor was immersed in an oil bath to control the temperature during The influence of hemicelluloses during the precipitation of lignin in kraft black liquor Henrik Wallmo and Hans Theliander, Chalmers Univerity of Technology, Gothenburg, Sweden, A.-S. Jönsson and O. Wallberg, Lund University, Sweden, K. Lindgren, STFI-Packforsk AB , Stockholm, Sweden Chemical pulping 5308 09

larger amount of inorganic compounds to be recovered without having to increase the capacity of the recovery boiler. This may, in Using the Pitzer method to estimate the boiling point rise in black liquor solutions Marta Bialik, Ali Moosavifar, Maria Sedin and Hans Theliander, Chalmers University of Technology, Gothenburg, Sweden Chemical pulping 5608 09-06-15 14.12 Sida 172 Nordic Pulp and Paper Research Journal Vol 24 no. 2/2009 173 turn, allow the existing pulp mill to increase its output without the need for a costly retrofit of the boiler section. The

Rickard Fornell and Thore Berntsson, Chalmers University of Technology, Gothenburg, Sweden Chemical pulping 7108 09-06-15 14.16 Sida 183 184 Nordic Pulp and Paper Research Journal Vol 24 no. 2/2009 chemical recovery according to pulp mill process design. Possible positive aspects of this, compared to other etha- nol processes, could be lower investment cost, sulphur- free process, simplified distillation, and less inhibition in hydrolysis/ fermentation (von Schenck et al. 2007). The main part of the study presented here is a techno- economic analysis of the ethanol

Ivo Valchev Chapter 4 Chemical pulp bleaching 4.1 Introduction The main objective of bleaching is to remove encrusted substances to obtain a pure white product; therefore, the manufacturing process requires further delignification and bleaching of the fibers, as residual lignin is a major contributing factor to color. Unbleached chemical pulps still contain lignin in an amount of 2−4.5% on oven dry (o.d.) pulp depending on the wood species and process details. The bleaching process can best be regarded as a continued pulping in which a series of alternating

Nordic Pulp and Paper Research Journal Vol 23 no. 1/2008 91 KEYWORDS: Modelling, Simulation, Bleaching, Deligni- fication, Pulp suspension, Computational, Phenomenon models SUMMARY: Conventional pulp bleaching processes consist of the following unit operations: chemical mixing, bleaching reac- tions (retention towers) and pulp washing. The quality and pro- fitability of chemical pulp bleaching depends on how well one is able to utilise the physico-chemical phenomena (chemical reactions, fluid dynamics, thermodynamics, mass and heat transfer) that determine

4 Bleaching of chemical pulp 4.1 Bleaching stages and sequences Historically chemical pulp bleaching was a single stage treatment with chlorine or hypochlorite. However, it is advantageous to apply moderate amounts of chemical repeatedly. Low charges of chemical cause fewer side reactions, therefore, the amount applied is consumed more economically. Consequently, multistep processes were soon developed. A one step treatment is mostly made if either the brightness gain required is low or the material to be bleached is already rather clean or bright, and responds

105 5.6.2 Alkaline Hydrolysis 106 5.6.3 Hexenuronic Acid 107 5.6.4 Stabilization Reactions with Polysulphide 108 5.7 Pulping with Anthraquinone (AQ) 109 5.8 The Final Delignification Phase in Kraft Pulping 111 5.9 Oxidizable Structures in the Pulp 112 5.10 Structure of the Residual Pulp Lignin 112 5.11 Sulphite Pulping 115 5.11.1 Lignin Chemistry 115 5.11.2 Carbohydrate Chemistry 118 5.12 Further Reading 118 5.12.1 General Literature 118 5.12.2 Ph.D. Theses 119 5.12.3 References 119 92 RKN==fåíêçÇìÅíáçå In chemical pulping