COOKING OF CHEMICAL PULP IN SULPHUR-FREE LIQUOR CONTAINING A DELIGNIFICATION-ACCELERATING COMPOUND

摘要

The invention relates to a process for producing chemical pulp from comminuted cellulose-containing material without using sulphur-containing cooking liquids, thereby removing the problems, for example smell problems, which are associated with sulphur-containing liquids. The process comprises at least one impregnation stage followed by at least one cooking stage, with a delignification-accelerating compound being supplied to at least one of the said stages. In the process, a first cooking liquid, which has been extracted from a position downstream of the impregnation stage, which liquid primarily contains OH<-> ions as the active substance, is supplied to the impregnation stage. This makes it possible to achieve a higher concentration of OH<-> ions than in the case of conventional soda-anthraquinone cooking and to use a lower process temperature. The process is suitable for producing chemical pulp from essentially all generally available raw materials for cellulose production and also for producing pulp from non-Scandinavian raw materials as well as for producing pulp from alternative fibrous raw materials. The process is suitable both for producing pulp which is intended for ECF bleaching or TCF bleaching and for producing unbleached high-yield pulp.