Experimental
In a coal-fired electricity power plant, coal is burned at up to
17001C, the combustion process leading to the major part of the
mineral matter in coal being fused into a vitrified ash. Most of
the by-product and any unburned matter sink to the bottom of the
furnace, forming bottom ash or slag, the bottom ash sometimes
being moved to ash ponds for storage. The lighterfly ash is carried
along by the hot gases, from the furnace up the stack. Most of the
fly ash can then be expected to be collected by emission control
devices (e.g., electrostatic precipitators, sometimes referred to as
scrubbers), only a small fraction then escaping to be dispersed into
the atmosphere. The present study makes investigations for a
power plant that uses electrostatic precipitators with efficiency in
excess of 99.2% (TNB Generation, 2003). The finer particles constitute a particular concern, being less efficiently removed by
electrostatic precipitators but typically containing greater
TENORM concentrations (the surface area per unit volume increasing with reducing particle size)