| 摘要 |
A method for the production of cellulosic pulp comprises defibration of a fibrous raw material consisting of wood chips, straw, bagasse, reed or the like. The fibrous raw material is impregnated by an aqueous solution of sodium carbonate. The fibrous raw material impregnated with sodium carbonate is fed to a pressure vessel (5). The material in the pressure vessel (5) is acidified by supplying sulphur dioxide to the pressure vessel (5), said sulphur dioxide reacting with said sodium carbonate to generate sodium sulphite and carbon dioxide, said reaction at least partly taking place in situ in the fibrous raw material. The material in the pressure vessel (5) thereafter for a short period of time is heated by saturated steam at a pressure of 20-100 bar, which further promotes said reaction. Thereafter the material is rapidly discharged and caused to expand in a second vessel (22) under a substantially lower and substantially constant pressure. |
