Patent ID: 9260464
Filing Date: 2016-02-16
CPC Classification: C07G,C08H,C08L,D21C

Claim Text:
1. A process for recovering purified, solid lignin from black liquor from a paper mill comprising: a. carbonating said black liquor at a temperature between about 80° C. and 200° C. and a pressure between about 50 psig and about 200 psig in a carbonation column with an amount of carbon dioxide sufficient to reduce the pH to between 9.0 and 10.5; b. subjecting said carbonated black liquor to a phase separation at the bottom of said carbonation column wherein a dense liquid-lignin phase is formed, a lignin-depleted liquid phase is formed, and NaOH and other basic components are neutralized; c. returning said lignin-depleted liquid phase to said paper mill; d. removing said dense liquid-lignin phase and neutralized NaOH and other basic components from the bottom of said column and acidifying said dense liquid-lignin phase with sulfuric acid at a temperature between about 100° C. and 130° C. to a pH less than 4 to neutralize residual NaOH and other basic components, thereby generating a granular lignin; e. washing said granular lignin granules to remove residual acid and ash content, thereby generating purified a lignin.