Patent ID: 9574303
Date: 2017-02-21
CPC Classifications: C01D,D21C,Y02P

Claim:
1. A method of recovering wood pulping chemicals from black liquor produced in a wood pulping process in a pulp mill comprising: burning the black liquor in a recovery boiler and forming ash containing carbonate, sodium, potassium and chloride; dissolving at least a portion of the ash to form a dissolved ash solution; directing the dissolved ash solution to a first stage crystallization unit and concentrating the dissolved ash solution and precipitating sodium carbonate and burkeite and forming a concentrated dissolved ash solution including the precipitated sodium carbonate and burkeite; directing at least a portion of the concentrated dissolved ash solution to a downstream second stage crystallization unit and further concentrating the concentrated dissolved ash solution to form glaserite crystals which are directed from the second stage crystallization unit in a glaserite slurry; separating the glaserite crystals from the glaserite slurry; and reducing the tendency of sodium carbonate and burkeite to crystalize in the second stage crystallization unit and encouraging pure glaserite to crystallize in the second crystallization unit by adding sodium sulfate or a sulfate reagent to the concentrated dissolved ash solution or to the dissolved ash solution.