Patent ID: 6503369
Filing Date: 2003-01-07
Classification: C05D,D21C

Abstract:
A process for producing cellulose and a fertilizer by-product by using a closed cycle of cooking chemicals and process waters, which process comprises(1) cellulose cooking using a process based on formic acid and/or other organic solvents, cellulose washing and bleaching based on hydrogen peroxide bleaching with alkaline stages, (2) recovery of cooking chemicals and wash waters as well as lignin and other organic matter formed as a by-product in pulp production, (3) recycling of the recovered cooking chemicals and process waters, and (4) burning of the recovered lignin and other organic matter recovered from pulp production as a by-product, which process further comprises (i) at least partly using potassium hydroxide as alkali in the bleaching, (ii) separating the used bleach liquor into an aqueous fraction and a potassium-containing bleach concentrate, (iii) returning the aqueous fraction to the bleaching and (iv) mixing the potassium-containing bleach concentrate obtained from step (ii) with ashes obtained from the burning of lignin and possibly other organic matter recovered from pulp production as a by-product obtained from step (4), in order to be used as raw material for a potash fertilizer.