Coconut Shell Charcoal

Introduction

Shell Charcoal is an important product obtained from coconut shell. Shell charcoal is used widely as domestic and industrial fuel. It is also used by blacksmiths and goldsmiths and in laundries. Shell Charcoal is also used to produce activated carbon. Activated Carbon produced from coconut shell has certain specific advantages as the raw material can adsorb certain molecular species. Shell is carbonized by using methods like pit method, drum method, destructive distillation etc. The shell charcoal is the raw material required for the manufacture of activated carbon. The shell charcoal is manufactured by burning shells of fully matured nuts in limited supply of air sufficient only for carbonisation, but not for complete destruction. The output of charcoal in the traditional pith method is just below 30 per cent of the weight of the original shells. In VietNam the average output in the traditional method has been found to be 35kg of charcoal from 1000 whole shells or about 30,000 whole shells yield 1 tonne of charcoal. Sometimes, especially when the processing is defective, the output is still lower and nearly 50,000 shells are required to produce one tonne of charcoal. To obtain good quality charcoal, fully dried, clean, mature shells should be used. Now several modern methods are in vogue for the production of charcoal. In the modern waste heat recovery unit the heat generated by the burning of coconut shells is used for drying copra and shell charcoal is obtained as by-product. A simple and efficient method adopted for the production of charcoal on cottage scale is given below.

Process (Drum Method)

A M.S. Drum kiln is used for carbonization of shells. The drum consists of three sets of six 1" dia holes provided at its bottom, middle and upper layers and a lid. A detachable chimney is provided which is installed on the lid after closing the drum. The manufacture of charcoal requires optimum carbonization of raw shells in a limited supply of air so that there is neither unburnt shell nor ash due to complete combustion. The steel drum is filled with raw shells after placing temporarily a four inch diameter wooden pole in the centre of the drum. The wooden pole is then removed, leaving a hollow space in the centre which allows the flow of smoke during carbonization. To start carbonization, a piece of burning rag is dropped to the bottom of the drum through the hollow space in the centre. When the fire is well underway, the lid with the chimney is placed into position and the upper and the middle sets of holes are closed. Carbonization which starts at the bottom progresses as it goes up as well as radially from the hollow space. When carbonization is complete in a particular zone, a persistent glow can be seen in all the six holes of a set. When the bottom most set of holes indicate this situation, the middle set of holes is opened and the bottom set closed. The stoppage of air flowing into the bottom region avoids over-carbonization in that region. The progressive carbonization results in reduction in volume of contents and therefore more shells are added from the top. When the middle region is carbonized well, the top set of holes is opened while the middle set is now closed. A further addition of raw shells is done to fill the volume reduction to maximize capacity for burning. When the top region is well carbonized, the top set of holes is also closed, resulting in complete stoppage of air inflow to the drum. The drum is then cooled for about eight hours after which the product is ready for discharge.