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Method for separating lignin from black liquor (United States Patent 8486224)

Wednesday, July 31, 2013   (0 Comments)
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United States Patent 8486224
Method for separating lignin from black liquor includes the following steps: a) precipitating lignin by acidifying black liquor and thereupon dewatering, b) suspending the lignin filter cake obtained in step a) to obtain a second lignin suspension and adjusting the pH level to approximately that of the washing water of step d) below, c) dewatering of the second lignin suspension, d) adding washing water and performing a displacement washing at substantially constant conditions without any dramatic gradients in the pH, and e) dewatering the lignin cake produced in step d) into a high dryness and displacing the remaining washing liquid in the filter cake, whereby a lignin product is obtained which has an even higher dryness after the displacement washing of step d). The lignin product or an intermediate lignin product obtained by the method, and its use, preferably for the production of heat or chemicals is also disclosed.
Öhman, Fredrik (Gavle, SE), Theliander, Hans (Gothenburg, SE), Tomani, Per (Huddinge, SE), Axegard, Peter (Solna, SE),    2013    Method for separating lignin from black liquor    United States    LignoBoost AB (Stockholm, SE)    8486224