SODA PULPING OF BAGASSE - DELIGNIFICATION PHASES AND KINETICS

The aim of this work has been to ascertain the effect of hemicellulose removal and bagasse drying on selectivity, extension and rate of soda delignification. To this end, three bagasse samples (standard, air dr ied and partially hydrolysed) were pulped at different temperature and active alkali doses according to a three-level factorial design. It w as concluded that bagasse delignification occurs only in two phases (' 'bulk'' and ''residual''), lignin being removed from,the very beginnin g of pulping. The initial polysaccharides removal stage, present in wo od delignification, does not take place for bagasse. A two phases expo nential equation has been found suitable for modeling bagasse delignif ication kinetics. Results confirm that bagasse drying renders delignif ication difficult because of diffusion restrictions, while hemicellulo ses removal makes it easier.