Patent ID: 8815052
Filing Date: 2014-08-26
Classification: D21C

Abstract:
1. A method for separation of lignin from a lignin containing black liquor slurry, comprising the following steps: i) precipitating lignin by adding one or more compounds comprising sulphate or sulphate ions, or a mixture comprising said compound, said compound being selected from the group consisting of recovery boiler ashes, Na ii) suspending the first lignin filter cake whereupon a second suspension is obtained having a pH level below 6, iii) dewatering of the second suspension to obtain a second lignin filter cake; iv) adding washing water to the second lignin filter cake and performing a displacement washing at more or less constant conditions at the pH level below 6; and v) dewatering of the second filter cake to dryness and displacement of remaining washing liquid in said second lignin filter cake, whereby a lignin product or an intermediate lignin product is obtained.