METHOD FOR ACID-BASE TREATMENT OF BLACK LIQUOR FROM SULPHATE CELLULOSE PRODUCTION Russian patent published in 2017 - IPC D21C11/00 

FIELD: chemistry.

SUBSTANCE: invention relates to sulphate cellulose production. Disclosed is an acid-base method of recovering chemicals, which includes separating organic compounds from black liquor solutions from cellulose production, treating the solution with sulphuric acid to pH>1-5 to obtain a suspension of organic compounds (lignin etc.), filtering and washing the solid phase from the solution, followed by processing into a commercial product. The obtained acidic solution is treated with alkali metal salts, e.g. KOH, to pH>7 and evaporated with crystallisation of the salts to 100-500 g water per 100 g dry salt. The mother salt solution after separating the solid and liquid phases and correcting the solution is fed for cooking pulp chips, and the solid product after separation and drying thereof is removed from the process as a commercial product.

EFFECT: invention improves production efficiency based on reducing power consumption when producing cellulose, providing environmental safety of the alkali recovery process by excluding high energy consuming and environmentally hazardous processes from the process chain: burning black liquor in a soda recovery boiler, decarbonisation of limestone, causticisation of soda liquor; reduces material consumption and improves diversification of production.

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