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Show The NCB's initial development of fbc from 1965 to 1972 was concerned primarily with the application to power generation. A 75 MW demonstration boiler was designed in 1971 and a site identified at the NCB's Grimethorpe Power Station. However, Government finance was not made available for it, the development programme was terminated, and subsequent effort on fbc boilers was directed towards industrial use, as already described. The successful operation of industrial water tube boilers now provides a basis from which fbc power generation boilers can be designed with confidence. A 124 MW boiler (140 t/h) is at present being built by Deutsche Babcock for a power and heating scheme at Hameln and a 200 MW (electrical) demonstration is planned by the Tennessee Valley Authority, based on their 20 MW (electrical) pilot plant which is scheduled for commissioning in 1982. Operation of the fbc unit at elevated pressure gives a prospect of increasing the efficiency of steam power generation by utilising the hot combustion gases to drive a gas turbine. This is expected to be possible because alkali metal salts, which would condense on turbine blades with conventional coal firing (cf. boiler fouling), are not volatilised from the ash in fluidised combustion. The NCB initiated work on pressurised fbc in 1969 using a 2 MW unit, and this demonstrated that static blades in the hot gas stream were not subject to excessive corrosion or erosion. Subsequently, this unit has been used to obtain detailed information on combustion, heat transfer and emission control at operating pressures up to 6 bar. To demonstrate pressurised fbc on a larger scale, an 80 MW facility has been built at the NCB's Grimethorpe site, jointly financed with the US and Germany. It was commissioned in 1980 and is being used, initially without a turbine, to study scale-up of combustion, heat transfer and emission control. At the same time, alternative gas cleaning devices to attain the low dust loading necessary for a turbine will be assessed. In parallel with this programme, gas turbines will be operated in the US and Germany using cleaned fbc combustion gases diluted with air heated in tube banks in a fluidised bed. Subsequently, a turbine will be added to the Grimethorpe unit. It is expected that pressurised fbc will lead to a fuel saving in power generation of more than 6%. 20-20 |