Study on the effects of coal-ash-slag deposition on boiler tubes in a coal-fired thermal power plant

Coal combustion in a thermal power plant generates plenty of ashes, which gets melted at high temperature. These melted ashes, i.e. slag, gets deposited on the external surface of the boiler tube in the furnace and stick to it. This slag greatly affect the heat transfer, which leads to reduction in the efficiency of the boiler. Also, slag deposition slowly corrodes the external surface of the tube. In this paper, a typical slag deposited tube was collected from a coal fired thermal power plant and metallographic analysis was carried out on this tube and the results were compared with an unexposed tube of same material, diameter and thickness. It is concluded from the analysis that there are no significant changes in microstructure, hardness values as well as inslag compositions.