Method for lignin separation from black liquor having multiple acidification steps

US9266917B2 · kind B2 · utility

Assignee

• VALMET AB · SE

Inventors

• Peter Björklund · Espoo, FI
• Martin Wimby · Torslanda, SE
• Henrik Wallmo · Hagfors, SE

Key dates

• Filing date: Jun 22, 2011
• Grant date: Feb 23, 2016
• Expiry date: Dec 1, 2031

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y02P40/40
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

The method is for separation of lignin from original black liquor (BLIN) having the following phases in sequence; a first precipitation phase (PR1) for precipitation of lignin by a first acidification of the original black liquor by adding a first acid or mixture of acids (G1a); followed by a second precipitation phase (PR2) for precipitation of lignin by a further acidification of the original black liquor by adding a second acid or mixture of acids (G1b). The first phase is implemented to lower the pH while avoiding any larger amount of precipitation, i.e. less than 2-5%, while the second phase is implemented in order to obtain the larger part of the precipitation. In total is 40-70% of the total lignin content of the original black liquor precipitated while the residual black liquor after precipitation is still strongly alkaline.