Process for separating lignins and dissolved organic compounds from kraft spent liquor
AssigneeBountiful Applied Research Corporation
InventorHassan E. Shall
Life of this patent
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Abstract
Digestion liquor is used in the paper pulping process to dissolve lignins and free the cellulose fiber from raw wood chips. After pulping, spent digestion liquor is laden with lignins. Heretofore, it was known that lignins could be coagulated by acidification of the digestion liquor, but such method coagulated the lignins in a slimy gelatinous mass that was difficult to separate from the liquor. It has been discovered that the addition of water soluble, surface active, polymeric agents to the digestion liquor prior to acidification, results in an easily separable lignin coagulant after acidification.
Claims15
A process for treating a spent Kraft alkaline digestion liquor containing lignins and liquid, comprising the steps of:
- (a) mixing into said spent Kraft digestion liquor a water soluble, surface active, polymeric coagulant agent;
- (b) acidifying the spent digestion liquor of step (a) to a pH below 7 to cause lignins and other dissolved organic compounds of the spent digestion liquor to coagulate as solids and float to the surface of the spent digestion liquor;
- and
- (c) separating the coagulated solids and the residual liquid of the acidified spent digestion liquor, one from the other.
A process for treating a kraft spent alkaline digestion liquor containing lignins and liquid, comprising the steps of:
- (a) mixing into said kraft spent digestion liquor a water soluble, surface active, polymeric coagulant agent;
- (b) acidifying the spent digestion liquor of step (a) to a pH of about 3.0, whereby the lignins and other dissolved organic compounds of the spent digestion liquor coagulate as solids and float to the surface of the spent digestion liquor;
- and
- (c) separating the coagulated solids and the residual liquid of the acidified spent digestion liquor, one from the other.
Dependencies are inferred from the claim text.