biotreatment downstream processing and modelling advances in biochemical engineering

[...]... phase-out of chlorine will occur in the pulp and paper industry [13] In the end, the deciding factors will be the success of environmental groups in their moves against the use of chlorine and consumer demands for chlorine-free paper The success of pulp and paper industry in informing the general population and overcoming the more emotive issues with clear scientific data will also have an influence Regardless... before use Because the bleaching process is costly and results in some weight loss, bleached kraft pulp sells for about 10-20% more than unbleached pulp Bleaching is done by processes employing mainly chlorine and its oxides The residual lignin is degraded and dissolved in various sequences of bleaching and extraction steps in which chlorine, hypochlorite, chlorine dioxide, oxygen and hydrogen peroxide are... Z Chlorination Chlorination, with addition of a small amount of chlorine dioxide Chlorination, with a mixture of chlorine and chlorine dioxide with chlorine in excess Sequential bleaching, with chlorine and subsequent treatment with chlorine dioxide without washing between the addition of chemicals Chlorine dioxide treatment Chlorine dioxide treatment with addition of a small amount of chlorine Sequential... by subjecting the pulp to preliminary oxygen bleaching and enzyme treatment and replacing the part of the chlorine gas conventionally used in bleaching with chlorine dioxide Furthermore, in the bleaching procedure, the liquid obtained from washing stages after oxygen and enzyme treatment can be treated in a soda recovery boiler Thus, the use of enzyme enables the amounts of toxic compounds in the spent... kraft pulp In European Patent No 0395792 [74], a process is described by Enso Gutzeit OY in which oxygen is used in the first oxidation stage of the bleaching process The pulp is then treated with hemicellulase enzyme and washed The subsequent oxidation stage is carried out using bleaching chemicals containing chlorine, e.g chlorine gas and/ or chlorine dioxide The amount of chlorine in the bleaching process... Research Centre of Finland was focusing on lignin degrading biochemical processes It was found that treatment of chemical pulps with xylanases leads to savings in the consumption of bleaching chemicals, decreased environmental loadings or increased final brightness of pulp [32-34] Since then various papers have been published describing the benefits of xylanase treatments in pulp bleaching These benefits... using lower amounts of chlorine-containing compounds and affords the opportunity to eliminate the use of elemental chlorine, thereby reducing the pollution load Realities and Trends in EnzymaticPrebleachingof Kraft Pulp 21 Also, a greater extent of delignification is achieved while retaining acceptable pulp strength properties Johnson examined new processes for bleaching including pretreatment with xylanase... Improved strength and brightness Chances of reduction in yield due to some loss of hemicellulose innovative answer to chlorine-reduced and chlorine-free bleaching of kraft pulp In this article, an overview of the recent developments in the application of enzymes in kraft pulp bleaching is presented The results of international research on the use of enzymes in bleaching, the opportunities for using enzymes,... degrade and solubilize the lignin [1, 2] The lignin undergoes a variety of reactions but the most important of these results in partial depolymerization and formation of ionizable (mainly phenolic hydroxyl) groups; these changes lead to the dissolution of lignin in the alkaline pulping liquor The lignin reactions involved in kraft pulping have been studied extensively [3~6] About 90% of the lignin is... reductions in chlorine, chlorine dioxide, hypochlorite), economic (decreased chlorine dioxide and/ or peroxide requirements), improved pulp quality (higher brightness ceiling) and improved mill flexibility Mill trials began as early as 1989 in Finland and since 1991, commercial use of xylanase has become a reality As reported by Jurasek and Paice [35] at the International Symposium on Pollution Prevention in . prebleaching are reviewed here within an engineering context. Advances in Biochemical Engineering Biotechnology, Vol. 56 Managing Editor: Th. Scheper 9 Springer-Verlag Berlin Heidelberg 1997 2 List. of lignin in the alkaline pulping liquor. The lignin reactions involved in kraft pulping have been studied extensively [3~6]. About 90% of the lignin is removed, the 10% or so remaining in the. were responsible for the initial interest in new technologies or biochemical solutions for eliminating chlorine-containing chemicals, which may still be the case in certain parts of the world,