METHOD FOR RECOVERY OF CHEMICALS FROM BLACK LIQUOR IN CELLULOSE ALKALINE PROCESS AND CLEANING AGENT Russian patent published in 2006 - IPC D21C11/04 D21C11/10 D21C11/12 C01F11/18 C01D1/20 

FIELD: pulp-and-paper industry, in particular black liquor purification in cellulose alkaline process.

SUBSTANCE: claimed method includes step of introducing of green liquor and lime before causticization reaction and two-step causticization in conventional process of chemicals recovery. Method of present invention makes it possible to eliminate formation of exhaust residue (lime slurry), needs no steps of collection and treatment of lime slurry and allows the production some products based on deposited calcium carbonate having different particle size by controlling recovery process conditions. Exemplary abovementioned products represent CaCO₃ useful in production of chalk overlay paper wherein at least 90 % CaCO₃ has particle size less than 2 mum and ultrafine CaCO₃ with particle size less than 1 mum. Claimed cleaning agent for green liquor refining in cellulose alkaline process includes all substances which may provide Ca²⁺ ions and representing solution, suspension or solids containing any soluble calcium salt, CaO and Ca(OH)₂ or mixture thereof. When only slurry containing Ca(OH)₂ is used as green liquor mass ratio of Ca(OH)₂ (calculated as CaO) to Na₂CO₃ in green liquor_{is (0.01-1):106.}

EFFECT: decreased energy consumption and equipment cost; additional product based on calcium carbonate of improved quality.

3 cl, 1 dwg, 1 tbl, 5 ex