Patent ID: 8486224
Filing Date: 2013-07-16
Classification: D21C,Y02P

Abstract:
1. A method for separation of lignin from black liquor comprising the following steps: a) precipitating lignin by acidifying black liquor to about a pH of 10 and thereupon dewatering to obtain a first lignin cake; b) suspending the first lignin cake obtained in step a) while keeping the suspension on an acidic side whereupon a second lignin suspension is obtained and adjusting a pH level to approximately the pH level of the washing water of step d) below; c) dewatering of the second lignin suspension to obtain a second lignin cake; d) addition of washing water and performing a displacement washing at substantially constant conditions without any dramatic gradients in the pH; and e) dewatering of the second lignin cake produced in step d) into dryness to obtain a third lignin cake and displacement of the remaining washing liquid in said third lignin cake, whereby a lignin product is obtained which has a higher dryness than after the displacement washing of step d).