Mini-Encyclopedia of Papermaking Wet-End Chemistry
Part Three: Equipment & Unit Operations

Drainage and Dewatering

The words "drainage" and "dewatering" refer to the removal of water from the wet web during the formation of paper. Sometimes papermakers refer to "gravity drainage," i.e. the removal of water without use of vacuum. The action of hydrofoils is usually considered to fall within the heading of gravity drainage. The more general term "dewatering" includes not only gravity drainage, but also the effects of vacuum boxes, the couch roll, and wet-pressing. Chemical factors that increase dewatering by gravity do not necessarily achieve an overall benefit, since the effectiveness of vacuum dewatering is highly dependent on the uniformity of the paper. Fiber flocs or pin-holes in paper can make vacuum dewatering less effective.

For more information, see also an essay titled "Retention and Drainage Chemicals."

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This page is maintained by Martin hubbe, Associate Professor of Wood and Paper Science, NC State University, m_hubbe@ncsu.edu .