Chapter 12 Large-scale and Industrial Utilisation - Anamed

less brittle product than with water hyacinth alone, see Shah and Bhattacharya
(1983). The briquetting takes place because the compression of the screw
together with the heating coils raise the temperature to 250 degrees centigrade. It
is believed that the high temperature softens the lignin, which behaves as a
waterproof glue. They use an extruding machine that produces 2 briquettes per
minute, each 50cm long and 0.5kg in weight. The heat content of the briquettes
is about 85% that of wood charcoal The energy output of each briquette exceeds
the energy used in its production by a
factor of about ten.
In Thailand also briquettes
are made which are a mixture of
ground lignite, dried water
hyacinth and binder in the ratio
6:3:1. The binder is 4% glue,
3% resin and 3% a synthetic
compound made from tapioca.
Such briquettes, which are very
strong, have four times more
heat than wood charcoal and
cost 30% less than wood
charcoal.
In Kenya, briquettes are
produced from coffee husks. It
is possible that such briquettes
could be produced in all coffee
Figure 12.3 Piston Press
producing countries, and that water hyacinth could be combined with coffee
husks.
Depending on the particular briquetting machine used, to work effectively
they require a feedstock that
- has a moisture content of less than 18% (some require between 4 and
8%).
- consists of pieces of between 2 and 20 mm in size, and can include
some dust.
- is free of such materials as sand, earth, stones and metal.
The optimum particle size and moisture content, and the latitude, must be
determined through experience.
Briquetting machines can usually handle between 150 and 550 kg per hour,
but the Danish firm below manufacture a machine that handles 1300 kg/hr. As a
guide, a machine that produces 250kg of bricks per hour will, in a 40 hour week,
produce 5 tons of briquettes, and in a 50 week year will produce 250 tons of
briquettes.
The additional equipment required includes a hammar mill, inclusive of filter
and cyclone, drying equipment, conveyors and screw feeds, storage bins (wet
and dry), bagging equipment, exhaust fans, an electrical control panel, cutting
Chapter 12 Large Scale and Industrial Utilisation Page 81