ABSTRACT
Papermaking is essentially a massive dehydration
operation. A fiber-water suspension with initial con-
sistencies of 0.2 to 1.0% (consistency ¼ grams of fiber per gram of fiber-water suspension) is delivered to a
screen, where, with the application of vacuum, much
of the free water is drained off and the consistencies
rise to about 18 to 23%. Then, more of the free water
is removed by mechanical ‘‘squeezing’’ at the press
section. The sheet is then transferred to the drying
section, with a consistency of 33 to 55% to remove the
remaining excess water to obtain the final product
with 6 to 9% moisture content. In the United States,
the production of over 60 million tons of paper per
year entails the removal of over 80 million tons of
water by thermal dryers. Considering that for a typ-
ical newsprint machine the water removed in the
dryers is less than 1% of the original water, one can
easily realize the amount of water that must be re-
moved in the papermaking process.
