Method for precipitating lignin from black liquor by utilizing waste gases
AssigneeValmet Power AB
InventorsAnders Littorin, Henrik Wallmo, Hanna Kristina Karlsson, Martin Wimby
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Abstract
The method is for separation of lignin from original black liquor. Lignin is precipitated in a first acidification stage followed by dewatering a first lignin suspension while forming a first filter cake. The first lignin filter cake is suspended in a second acidification stage whereupon a second lignin suspension is obtained. The second lignin suspension is dewatered to form a second filter cake. The second filter cake is washed and the washed second lignin cake is dewatered to obtain a lignin product. Waste gases from the second acidification stage is recirculated back to the first acidification stage and mixed with the original black liquor.
Claims14
A method for separation of lignin from original black liquor, comprising:
- precipitating lignin in a first acidification stage of an original black liquor by adding a first acid or mixture of acids and obtaining a first lignin suspension,
- dewatering the first lignin suspension while forming a first filter cake with a high content of lignin,
- suspending the first filter cake in a second acidification stage using a second acid or mixture of acids,
- obtaining a second lignin suspension,
- dewatering the second lignin suspension while forming a second filter cake with a high content of lignin,
- washing the second filter cake,
- dewatering of the washed second filter cake and obtaining a lignin product,
- re-circulating waste gases emitted from the second acidification stage, and
- mixing the waste gases with the original black liquor.
Dependencies are inferred from the claim text.