A wonderful storm

COULD something regarded as a bane by the farmer be a boon to the industrialist? Cyclones, provided they occur in furnaces, could be just that something. Cyclone-type furnaces are known for their versatility and efficient combustion of solid, liquid and gaseous fuels. Such a combustion system is particularly suitable for burning high-ash, non-coking coal and has already proved its utility elsewhere in the world.

In a cyclone furnace, the fuel and the combustion air undergoes a strong, swirling motion. The high degree of turbulence and the consequent mixing result in stable and high-intensity combustion. A good rate of combustion efficiency and high temperature is normally attained.

The Bhubaneswar- based Regional Research Laboratory (RRL) of the Council for Scientific dnd Industrial Research has taken up research and development (R&D) work with the objective of developing a cyclone combustion process to burn high - ash and high-volatile Indian coals. But this could find other applications too. Cyclone furnaces could prove their mettle not just in coal-fired but chemical and metallurgical industries too, where at present, oil-firing systems are in operation.

Cyclone combustion is also considered as an alternative system for achieving the very high temperatures necessary in coal-fired magneto hydrodynamic (MHD) power generation. A cyclone system has a number of advantages over the conventional pulverised coal firing systems. The latter is usually slow and the temperature in the furnace is usually limited to 1,200-1,3000c. The cyclone furnace, which overcomes these shortcomings, ensures a much faster combustion. The ash-handling system is also much more simplified, with flyash carryover being minimised. In general, a cyclone furnace is capable of providing operational flexibility with the possibility of using different types of coal with varying ash and moisture content.

Various types of cyclone furnaces have been developed in many countries, They are mostly used in fired boilers and gas turbine systems. In addition, developmental work on cyclone-type furnaces is being done to use them as process heaters in industries. The cyclone furnaces in these countries burn coal whose ash content ranges from 10- 30 per cent and ash silica content from 55-65 per cent. The furnace temperatures required are 1,500-1,7000c. The Indian non-coking coal, on the other hand, has 30-45 per cent ash content, while the silica content stands at a very high 75-83 per cent. Therefore, the slag tap firing of these coals obviously requires a much higher furnace temperature along with the need for special design considerations.

By undertaking an in-house R&D programme, the Rat. has developed an experimental cyclone furnace with 100 kg/hr coal burning capacity. This furnace has been tested with coals of varying ash content. The experimental cyclone furnace has to a large extent been able to meet the expected performance standards. Plans to develop the design of an industrial-scale cyclone furnace have been chalked out for the future.