METHOD OF OBTAINING ALKALI LIGNIN

FIELD: chemistry. ^ SUBSTANCE: method pertains to obtaining alkali lignin from used alkaline solution of sulphate or alkaline pulping and can be used in the pulp and paper industry. Sulphate or soda liquor at temperature of 40-95°C and concentration of 7-40% of solid matter is treated at pressure of 3.0-7.0 atm with a liquid saturated with carbon dioxide. The treatment is carried out in a throttling device, preferably in an injector with obtaining of foamed alkali liquor at the output. The separated alkali lignin is separated from the liquid phase with the floating foam. The liquid saturated with carbon dioxide can be used alkaline solution from sulphate or alkaline pulping with concentration of 14-17% or waste water from washing pulp of sulphate or alkaline pulping with concentration of solid matter of 3-7%. A gas mixture is used, containing carbon dioxide in quantity ranging from 3.0 to 99.9% of its overall content. Carbon dioxide is separated from the stream of foamed alkali liquor when it comes out of the injector and is repeatedly used. ^ EFFECT: proposed method allows for eliminating the process of sedimentation of soda liquor after treating it with carbon dioxide and filtering alkali lignin residue, as well as the possibility of using flowing action equipment. ^ 3 cl, 1 dwg, 3 ex