Managing Wastes from Coal Use

Burning coal, such as for power generation, gives rise to a variety of wastes which must be controlled or at least accounted for. Thus, coal plants, in addition to gaseous and liquid wastes, also produce solid wastes which either must be removed or serious attempts be made to mitigate the problem (Saroff and Robey, 1992). Some of this solid waste is removed with the bed ash through the bottom of the boiler. Small ash particles, or fly ash, that escape the boiler are captured with dust collectors (cyclones and baghouses). More than 90% of the sulfur released from coal can be captured in this manner. 

While it is possible to control some of the toxic emissions released by coal-fired power plants, the resulting waste creates more problems for the environment. The pollution controls used to capture harmful emissions concentrate toxins and heavy metals such as mercury into coal ash and sludge. Toxic substances in ash and sludge include arsenic, mercury, chromium, and cadmium. 

The clean coal technologies are a variety of evolving responses to late twentieth century environmental concerns, including that of global warming due to carbon dioxide releases to the atmosphere. However, many of the elements have in fact been applied for many years, and they will be only briefly mentioned here  

Coal cleaning by washing has been standard practice in developed countries for some time. It reduces emissions of ash and sulfur dioxide when the coal is burned. 

Electrostatic precipitators and fabric filters can remove 99% of the fly ash from the flue gases these technologies are in widespread use. 

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