Economics of Removal of Coal Moisture in Thermal Power Generation with Waste Heat Recovery

The techno-economic aspects of coal drying with cost effective waste heat recovery mechanism is one of the challenging issues faced while using lignite or high ash brown coal for direct combustion in coal fired thermal power plant. Coal being hygroscopic in nature, re-adsorbs considerable moisture even after conventional drying post wet coal washing condition affecting boiler performance. Particularly moisture in coal affects the pulverization where pulverized coal (PC) firing is adopted. In this paper the impact of coal moisture on useful heat value for PC fired steam generation is evaluated for some typical steam coals so that related change in direct firing coal throughput can be estimated for application of suitable online coal drying mechanism. This assessment can be further used to determine usefulness of pre-combustion coal drying methods like integrated drying and partial coal gasification method, particularly for coal processed through dry or wet coal washing to improve the heat value with the exhaust flue gas immediate upstream of stack.