Patent ID: 11866456
Assignee: LIQUID LIGNIN COMPANY
Field: Biotechnology (Chemistry)
Classification: CPC C  D | IPC C  D

Claim 0:
1. A process for recovering purified, solid lignin from black liquor comprising:
(a) in a pre-carbonation column, pre-carbonating said black liquor in a first carbonation step with CO2 to reduce a pH to between about 11.5 and about 12.5 to form a partially carbonated black liquor;
(b) transferring an entire volume of said pre-carbonation column to a carbonation column;
(c) in said carbonation column, further carbonating said partially carbonated black liquor in a second carbonation step with CO2 sufficient to reduce the pH to between about 9.0 and about 10.5 to form carbonated black liquor;
(d) subjecting said carbonated black liquor to a phase separation in a carbonation settler, wherein a dense liquid-lignin phase and a light lignin-depleted liquid phase are formed;
(e) transferring said dense liquid-lignin phase from said carbonation settler to an acidification reactor;
(e) in said acidification reactor, neutralizing basic components from said dense liquid-lignin phase with sufficient acid to reduce said pH to below 4 and evolve gaseous CO2, thereby generating a porous, solid lignin; and
(f) washing said porous, solid lignin to remove residual acid and ash content.