Patent ID: 6245196
Filing Date: 2001-06-12
Classification: D21C

Abstract:
A method for processing alkaline cellulosic pulp to cause a precipitation of lignin onto pulp fibers, comprising the steps of:(a) washing the pulp in a series of washer stages to sequentially remove entrained lignin therefrom;(b) between each washer stage, adding dilution water to repulp a pulp mat exiting from a prior washer stage and to create a pulp stream for a next washer stage, said pulp stream containing said entrained lignin;(c) after at least one of the washer stages, adding an acidifying agent to said pulp stream to form a pulp product by precipitating said entrained lignin onto cellulosic fibers contained in said pulp stream; and(d) removing said pulp product from said series of washer stages with said pulp product having at least about a 1 unit increase in Kappa number, said increase in Kappa number arising from said precipitating of said entrained lignin.