Dumping the pith into irrigation systems
is a good solution if the pith can be
distributed over a large area and the
irrigated land is ploughed regularly as
the pith, being organic material. acts as
a soil conditioner. If this is not
feasible. then the wet pith must be
dewatered and pressed before being
trucked away for land fill or before
incineration.
The best method for dewatering the wet
pith is to pass the pith and water over
DSM screens or gravity disk—tyPe rotary
strainers. DSM screens work well in the
case of wet pith from a wet depithing
operation immediately following moist
depithing. The wet pith removed after
long—term wet bulk storage tends to be
slimy and DSM screens may blind. The
gravity disk—type rotary strainers are
better for thickening wet pith removed
after longsterm wet bulk storage. For
final thickening to a high consistency.
twin—wire sludge belt thickeners can be
used. Unfortunately. belt thickeners
currently available are unable to Press
wet pith to a moisture content low enough
to sustain combustion; the moisture
content remains at about 75 — 60% despite
claims that moisture contents of 65 — 70%
and lower can be achieved.
Land fill is not a good solution unless
the pith is buried. Wet pith dries to a
fine, light powder that may cause dust
problems. lncineration of the wet pith
may be the only solution.
If wet depithing is immediately after
moist depithing. the thickened and
pressed wet pith can be mixed with the
pith from moist depithing and burned.
This, of course. reduces the fuel value
of the pith from moist depithing. If wet
depithing is after wet bulk storage and
the cane crushing season is relatively
short. the wet pith must be incinerated
separately. A fluidized bed reactor is a
good but expensive solution.
Figure 5 shows a typical bagasse
depithing, handling and wet bulk storage
system.