| 摘要 |
Method for the preparation of cellulose pulp comprises a pre-treatment step with an impregnation liquid containing hydrogen sulphide and/or sodium bisulphide, carried out in an impregnation zone at 100-160 deg. C, pressure greater than 3 atmospheres and a pH of 5-10, followed by an alkali cooking step.The impregnation liquid comprises filtrate from the bleaching plant or leftover acid from chlorine dioxide processing. The cooking step contains a cooking zone with unidirectional flow and at least one cooking zone with a counter-flow. Cooking temperature is 165 deg. C for coniferous wood and 155 deg. C for deciduous wood. The temperature in the final counter-flow cooking zone is the same as the highest temperature in the cooking step. Dwell time in the counter-flow cooking zone is >30 minutes. |
