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RENERTECH RESEARCH.

Renewable Energy Sources.

Technology For Rural Development.

Electronics for Agricultural Efficiency.

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Gasification of Coffee Hulls

for Electricity as well as Heat.

Most coffee countries utilising the wet process for production of high grade Arabica coffee utilise the coffee hulls as a source of heat for drying their parchment coffee.

If the situation has a wet climate, as in Asia and the Pacific territories, they often do not have enough hulls to dry all their product. If it is a dry climate, like the Nations on the East coast of the African continent, there are great mountains of coffee hulls clogging up the factory yards.

The major problem with all of these areas is that their coffee hulls, or husks for that matter, are burnt very inefficiently. The burners for coffee hulls do not have good combustion and produce lots of smoke. Therefore they have to use a heat exchanger, which is even more inefficient and rusts out very quickly. By designing a burner with 100% clean combustion the expense and inefficiency of a heat exchanger is not required. Even in a very wet climate, it should be possible todry drained wet parchment with the hulls that can be taken off it. It is all about the efficiency of burning those same hulls, and that can be handled very easily by gasification.

The process of gasification is where biomass such as the hulls from coffee parchment is combusted with a restriction of air to make ‘producer gas’. Producer gas is a mix of carbon monoxide, nitrogen and hydrogen usually made on a single large gas producer and piped around the factory and reburnt with additional air in engines to generate electricity and in hot air heaters to dry ones coffee. It is the process of ‘double combustion, burning the hulls to make gas, and then being able to establish critical control when reburning that combustible gas with more air that 100% of the heat available from that fuel can be used to ‘direct dry’ ones coffee with a stream of hot air that will not taint or spoil the product.

Indeed, the most efficient usage is burn the producer gas through an engine to generate ones electricity, if that is required, and then use the waste heat from the engine to dry the coffee. Far too much coffee is overheated, starts sweating oils and suffers premature aging etc. by using too much heat. Heat from engine exhaust and radiators is much more gentle and will vastly improve the keeping quality of the green bean, leading on to massive advantages all around. Its not just the efficiency of the process, it is the greatly reduced costs of maintenance. The gasification process is conducted at about half the temperature of burning hulls directly in an air stream and heat damage, corrosion, buckling and heat distortion of the furnaces are entirely eliminated. A gasification furnace will outlast an Asaro, Wilkinson, XXXX or any other coffee drying furnace by a factor of 3-1.

Write to me if you are interested and I will help you through. Ken C.

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