Ash management in coal-fired power plants (Couch, 10-2006)

The presence of troublesome impurities in coal affect its behaviour during combustion and hence the performance of coal-fired boilers. The report discusses how the quantity and composition of the ash varies in the world´s major coals. Ways of minimising the amount of mineral matter in the coal are outlined. The mineral transformations which take place in a pulverised coal fired boiler are described together with the behaviour of various ash-forming components which can cause slagging or fouling deposits. Various management methods can be used to minimise and/or control the adverse effects of deposition. These include modelling coal quality impacts and using advanced measurement devices and control systems. Intelligent sootblowing where the boiler cleaning blowers are actuated when required is being increasingly used. Ash management in circulating fluidised bed boilers is also discussed, together with various aspects of ash use. There is increasing pressure to make use of the ash formed in boilers to reduce the need for disposal sites.