METHOD FOR PRODUCING HIGH PURITY LIGNIN

The present invention relates to a method for separation of lignin from original black liquor (BLIN) comprising a first precipitation stage (PR) for precipitation of lignin by a first acidification using acidifier AC， preferably using CO2， at alkaline conditions， then separating a lignin cake with subsequent suspension of the lignin cake in a strong acid in order to leach our metals from the lignin followed by dewatering and obtaining a clean lignin product LP. According to the invention is the process further improved by intensified hydrolysis of lignin cake such that most of the carbohydrates are broken down to dissolvable monomers that could be separated from the lignin in the filtrate from a filtering stage subsequent to the hydrolysis. The improved hydrolysis could reduce as much as 90% of the carbohydrate content using a moderately increased temperature and increased charge of acidifier while avoiding any larger lignin yield losses.

本发明涉及一种从原黑液（original black liquor，BLIN）中分离木质素的方法。该方法包含第一沉淀阶段（PR）：在碱性条件下，通过酸化剂AC（优选采用二氧化碳）进行初次酸化以沉淀木质素；随后分离得到木质素滤饼，将该滤饼悬浮于强酸中以从木质素中浸出金属，经脱水后得到清洁木质素产品（LP）。本发明进一步对该工艺进行了优化：通过对木质素滤饼实施强化水解，使绝大多数碳水化合物降解为可溶性单体，可在水解后过滤阶段的滤液中与木质素分离。该优化后的水解工艺可在适度升高温度、提升酸化剂投加量的前提下，将碳水化合物含量降低多达90%，同时避免出现显著的木质素收率损失。