METHOD AND APPARATUS FOR PRODUCING CHEMICAL PULP

PROBLEM TO BE SOLVED: To reduce energy costs in a method for producing a chemical pulp by cooking wood chips including knots in a digester. SOLUTION: This method for producing the chemical pulp comprises (a) a step for forming a low pressure slurry composed of a liquid and a comminuted cellulosic fibrous material in a vessel operating at essentially atmospheric pressure, (b) a step for supplying the slurry to a low pressure inlet 23 of a high pressure transfer device 24 while removing liquid from the slurry through a low pressure outlet 25 thereof, (c) a step for supplying a high pressure liquid to the high pressure transfer device and forming a high pressure slurry of the comminuted cellulosic material, (d) a step for discharging the high pressure slurry from a high pressure outlet 27 of the high pressure transfer device and (e) a step for removing knots from a slurry containing uncooked cellulosic material at essentially atmospheric pressure, and thereafter transferring the removed knots to the vessel so that the knots become part of the low pressure slurry supplied to the low pressure inlet 23 of the high pressure transfer device. COPYRIGHT: (C)2003,JPO