Pulverised coal and corresponding fly-ash collected from the stack precipitator of thermal power plants were analysed for eight heavy metals. Fly-ash was separated into various sized fractions which were then chemically characterized. The fly-ash contained higher concentrations of heavy metals with respect to their coal. Except in the case of Pb, Cd and Co, the heavy metals were more concentrated in the <53 µm than in the >150 µm fraction. For the probable contribution of these metals to atmospheric emission and waste ash, it is necessary to estimate the enrichment factors from coal to fly-ash.
INTRODUCTIONCoal is undoubtedly the prime source of energy in our country. At present, coal-fired power generating plants account for 55 percent of the total generating capacity. 1 The increased use of coal will produce additional quantities of fly-ash, one of the waste products of burning pulverised coal. India produces mostly poor quality coal with a 25-30 percent ash content. It is estimated that ten percent of the resultant fly-ash is released into the atmosphere, whereas the rest of solid fly-ash is available for disposal. 1 ' 2 The fly-ash generated by these plants is and will continue to be a disposal problem. Emission from thermal power stations is a major source of particulates and gaseous pollutants. Apart from gaseous pollutants thermal power plants add particulate matter to the air. Of all types of particulates the presence of toxic trace metal like, As, Cd, Cr, Cu, Co, Zn, Mn, Ni and Pb constitutes the greatest health hazard. Moreover, inhalation of metals is more harmful than ingestion by way of food or water.Analysis of heavy metals concentrations in pulverised coal, fly-ash and in different size fractions of the fly-ash produced from power plants was carried out to assess the probable contribution of these metals through coal burning to atmospheric emission and waste ash.
MATERIALS AND METHODThe material used for the present investigation was pulverised coal from different mines and corresponding fly-ash collected from the stack precipitator of power plants. The coal, fly-ash and its component size fractions were analysed to characterise their chemical composition. The fly-ash (No. 1) was fractionated by mechanical sieving into the following particle sizes >150, 150-106, 106-75, 75-53 and <53 /im. Known volumes of all the samples were digested with hydrofluoric aqua regia, 3 and the digested samples were analysed for Cr, Mn, Ni, Pb, Cd, Cu, Co and Zn by the Perkin Elmer (703) Atomic Absorption Spectrophotometer. 4
