METHOD AND APPARATUS FOR PRODUCING CHEMICAL PULP

PROBLEM TO BE SOLVED: To reduce energy and cost in a method for producing chemical pulp by steaming wood chips with knots in a digester. SOLUTION: The method for producing chemical pulp is to digest wood chips with knots in the digester to produce the chemical pulp and comprises the following steps (a) to (e). In the step (a), a low pressure slurry comprising crushed cellulose-based fiber material is formed by mixing a liquid with the crushed cellulose-based fiber material in a vessel or a pipe practically acting at an atmospheric pressure. In the step (b), the slurry is fed to a low pressure inlet of a slurry-transfer device. In the step (c), a high pressure slurry comprising the crushed cellulose-based material is formed in a transfer device. In the step (d), the high pressure slurry is discharged from the transfer device and fed to the digester. In the step (e), knots are removed from the slurry containing digesting cellulose material with knots at practically atmospheric pressure, subsequently, the removed knots are directly transferred to the vessel, the pipe or down stream of those and are brought to a part of the low pressure slurry fed to the transfer device. COPYRIGHT: (C)2004,JPO&NCIPI