Mini-Encyclopedia of Papermaking Wet-End
Part Two: Definitions and Concepts
The word "drainage" refers to the ease with which water is released from papermaking furnish, especially in the early part of a paper machine's forming section. The word "dewatering" is more general, including the effects of vacuum and pressing as means of getting water out of the wet web. Drainage tends to be inhibited by the presence of fiber fines, high basis weight webs, high levels of refining, and any excess of polyelectrolytes remaining in the solution phase. Drainage rates often can be increased by the use of highly cationic chemicals such as alum, polyamines, or PEI products. Microparticle programs are designed to increase drainage rates. Factors that increase fiber flocculation are likely to increase initial drainage rates, but they are also likely to hurt the performance of vacuum dewatering and pressing.
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