Coconut shells free from contamination of coir pith, etc., are broken into small
pieces and fed into a pulveriser.
The powder from the pulveriser is fed into a
cyclone and the parallel product is collected in bag filters. The shell powder is
then fed into a vibrating sieving machine and packed according to mesh size
requirements for various end uses.
The rejects from the sieving machine can be
recycled in the pulverizer for size reduction. The main requirements for
consistent good quality of coconut shell powder are proper selection of shell of
proper stage of maturity and efficient machinery
Shell Charcoal is obtained by burning the shell of fully matured
coconuts with a limited supply of air so that they do not burn away to
ash but are only carbonized.
The manufacture of shell charcoal
shows from the coconut shell has become a very important
economic and commercial activity. Furthermore, coconut shell
charcoal, which was relatively a minor product in the past, has now
developed into a general commercial commodity due to its intrinsic
value as a raw material for the manufacture of activated carbon.
Coconut shell charcoal are of two types: viz Coconut shell charcoal
and granulated shell charcoal.
The process of activation is carried out in two stages. Firstly the
coconut shell is converted into shell charcoal by carbonization
process which is usually carried out in mud-pits, brick kilns and
metallic portable kilns. The coconut shell charcoal is activated by
reaction with steam at a temperature of 900oC -1100oC under
controlled atmosphere in a rotary kiln. The reaction between steam
and charcoal takes place at the internal surface area, creating more
sites for adsorption. The temperature factor, in the process of
activation is very important. Below 900oC the reaction becomes too
slow and is very uneconomical. Above 1100°C the reaction becomes
diffusion controlled and therefore takes place on the outer surface of
the charcoal resulting in loss of charcoal.