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Coal injection systems for blast furnace tuyeres have been available in some form for many years, but only recently has improved technology and increased oil prices made them economically feasible. At BSC Scunthorpe Works trials were successfully carried out using granular - not pulverised - coal, and full scale operation of the system on three blast furnaces is now being commissioned.
Commissioning began this month (September 1984) of a major pneumatic granular coal injection system for the blast furnace at British Steel Corporation's Scunthorpe Works.
This system has been designed, developed and installed by Doncaster based Macawber Combustion Systems Ltd, a member company of the international Macawber group, in close cooperation with the British Steel Corporation (BSC). Macawber has a respected worldwide reputation for its dense phase pneumatic conveying systems for a wide variety of industry bulk materials.
In common with many steelmakers around the world, BSC decided to go ahead with conversion of its furnaces to coal injection largely because of the continuing high costs of oil and matallurgical coke. Granular coal can replace to a typical ratio 1.1kg coal to 1 .Okg of coke and despite fluctuations on the world spot market for oil, coal is a much cheaper fuel.
Coal injection systems for blast furnaces are not new. Some systems have been available for decades. Others have been established since the 1970's. These systems operate with different mechanisms but they do have a common factor in that they use pulverised fuel of typically 80% less than 75 microns (200 mesh) dried to less than 1% moisture. While such systems still allow coal to replace oil and coke, it is nevertheless hoped that a system could be developed which, in addition to handling pulverised fuel, would also be able to inject coarser coal. In this way the overall economic advantages of handling granular coal could be exploited.
Earlier attempts to inject granular coal into blast furnaces met with limited success either due to operating problems on the furnace or practicaf engineering problems encountered with the equipment.
Macawber, with its well proven record of handling materials which are often impossible to convey through conventional pneumatic systems, were a natural selection to investigate the possibilities of developing such a system. The company's proximity to Scunthorpe...