FIELD: producing oxidized lignin.
SUBSTANCE: invention is related to a method for producing oxidized lignin in a kraft pulp mill, the method comprising at least: separating unwashed kraft lignin obtained by CO2 precipitation in a kraft pulp mill; dissolving the unwashed kraft lignin in oxidized or unoxidized white liquor to produce an alkaline lignin solution; oxidizing the lignin solution under alkaline conditions with a) oxygen gas O2 under excess pressure, and b) NaOH and/or oxidized white liquor as an alternative source of alkali; treating the oxidized lignin solution by membrane filtration; extracting a concentrated lignin solution; recovery of by-products and chemicals as such or reuse of by-products and chemicals in the kraft pulp mill.
EFFECT: method for producing oxidized ligning at a kraft pulp plant is proposed.
7 cl, 5 dwg, 4 tbl
