PROCESS AND ALKALINE SULFITE-SULFIDE COOKING LIQUOR FOR THE PREPARATION OF PULP OUT OF LIGNIN-CONTAINING CELLULOSE RAW-MATERIAL

摘要

Abstract of the DisclosureDescribed herein are a process for the preparationof pulp out of a lignin-containing cellulose raw-materialand a sulfide-sulfite cooking liquor to be used in theprocess. According to the process, the cellulose raw-material is split into chips, the chips are treatedso as to constitute a starting material suitable forcooking, the chips are cooked in an alkaline sulfite-sulfide cooking liquor, which contains 70 to 400 g ofsodium sulfite per kg of dry wood, 35 to 110 g ofsodium sulfide per kg of dry wood, 20 to 150 g ofsodium carbonate per kg of dry wood, as well as thequantity of sodium hydroxide required for raising thepH of the cooking liquor to a value of 9 to 13, andthe delignified fibrous material is ground to anappropriate drainability. According to the inventionthe sodium sulfide is introduced into the cookingliquor as white liquor, and 0.05 to 0.3 % ofanthraquinone, based on the quantity of wood, is added tothe alkaline sulfite-sulfide cooking liquor in order toaccelerate the cooking, to lower the concentration of thecooking chemicals, and to inhibit the formation ofthiosulfate.