Process to remove particles from fibrous paper suspension by pressure washing with cold water in sieve assembly

摘要

In a papermaking process a fibrous suspension (S, S') contains unwanted impurities e.g. 'Stickies' that are washed from the suspension by a pressure sorting assembly (3, 4) with fine slits. In the process, colder dilution water (W) is admixed to the pre-washed suspension before the sieve (1, 2). The temperature of the pre-washed suspension is reduced by 8C by the admixture of cold water. The washing operation is a two-stage process in which material rejected (R1) from the first stage is re-introduced to the inlet of the second stage. Water is cooled in a heat exchanger (5) and is then admixed at the second stage inlet. The heat exchanger (5) is cooled with fresh water (6) which is subsequently used in the papermaking machine. The return water (10) is cooled by about 20C. The sieve slit width is less than 0.2 mm.