FIELD: pulp- and-paper industry. SUBSTANCE: nonbleached pulp is diluted with alkali material to pulp consistence below 10 wt %, amount of alkali material being sufficient for its uniform distribution across all fiber mass. Consistence of thus obtained pulp is then raised to at least 13 wt %. Liquid phase is removed, and high-consistence pulp is treated with oxygen. Content of alkali material in said high- consistence pulp is ranged from 0.8 to 7 wt % or higher based on absolutely dry stuff. More than 50% of liquid phase is returned directly to the stage of pulp dilution with alkali material. EFFECT: enhanced efficiency of process. 9 tbl, 1 dwg
