If the digesters are continuous, the wet
depithed bagasse, with a dry fiber
content of 12 — 15%. can be fed directly
to the digesters. as the digester feed
screw will press the bagasse to a dry
content of 30 — 35%. If batch digesters
are used, presses are required ahead of
the digesters to reduce the water content
of the bagasse to decrease steam
consumption.
Fiber losses (as distinct from losses of
residual sugars and dirt) are 6 — 12% for
bale handling and storage; fiber losses
in wet bulk storage piles are 2.5 to 5%.
The amount of insoluble material removed
on wet depithing is usually 5 — 10%. If
the bagasse has been stored in wet bulk
piles. the material removed by wet
“depithing“ is fine dirt and about equal
portions of fines and pith. If the
bagasse is wet depithed immediately after
moist depithing or the bagasse is from
bale storage, the amount of bagasse fines
removed will exceed the amount of pith
removed: and it may be necessary to
increase rejection rate to 15% to attain
the desired degree of pith removal. The
residual pith content after moist
depithing should be in the order of 12 —
16% but is often as high as 18%.
Disposal of pith from wet depithing can
be a problem. Wet pith is slow draining,
especially wet pith from the wet
depithing of bagasse stored in wet bulk
piles. The simplest solution is to dump
the wet pith into an old quarry or other
depression, a large swamp or a desert
area. Where this is not permitted or not
feasible, other means of disposal must be
applied.