EVALUATION OF COAL PROPERTIES USED IN A CEMENT PLANT

Coal is not only a heat source for clinker burning but also the coal ash after combustion plays a large role in the quality of clinker mixed with hot meals in the kiln. Since the properties of coal vary depending on the coalification and environment in which it was sedimented, the quality of coal supplying to cement plant can change greatly depending on the coal seam even if it is from the same coal mine. Therefore, the coal used in a cement plant should have its properties measured accurately through representative sampling whenever it is supplied to the plant, and it should be possible to ensure stable kiln operation with stable coal quality. Based on the properties of coal used in 'A' plant for more than 10 years, the permissible coal qualities used in cement plants are evaluated. In order to efficiently utilize the calorific value of coal in the kiln process, the lowest possible intrinsic moisture content is preferred to reduce heat loss due to evaporation of the intrinsic moisture of the coal. In particular, it is examined on the AFT (ash fusion temperature) to obtain the stable clinker quality through well mixing and melting between the coal ash remaining after coal combustion and hot meals in the kiln, and correlation equations for predicting AFTs are suggested according to the chemical components (SiO2, Al2O3, Fe2O3, CaO) in coal ash. In addition, the criteria of chlorine concentration in feeding coal into the kiln process is suggested, so as not to cause process instability due to coating formation within the kiln process caused by repeated volatilization and condensation of chlorine and sulfur compounds due to the circulation behavior of volatile matters, and to enable the stable and continuous kiln process operation.