An Experimental Study on the Combustion Kinetics and Ash Melting Characteristics of Two Kinds of South Korean Coal Gangue using TGA and TMA

Coal gangue has a potential to be used as fuel in a circulating fluidized bed boiler. However, there are few studies on it in South Korea. In this study, the combustion characteristics and kinetics of coal gangue were investigated by thermogravimetric analysis at different heating rates (20, 30, and 40 degrees C/min) under air atmosphere. The experimental results indicated that a higher heating rate would improve the oxidation reaction ratio of coal gangue. And the combustion characteristic index (S) indicates that coal has better combustion performance than coal gangue. The kinetic behavior was evaluated with the model-free (Flynn-Wall-Ozawa methods) and model-fitting (Coats-Redfern methods). The activation energy values obtained from the Flynn-Wall-Ozawa method showed the activation energy of coal is less than coal gangue. This result is the same as that of the Coats-Redfern methods. In addition, ash melting temperature, slagging, and fouling are related to ash deposition. In order to predict the ash deposition characteristics of coal gangue in this study was researched by using Thermo-Mechanical Analysis. The results showed that coal gangue has higher ash melting temperature than coal. However, coal gangue has a higher K2O content of ash. Therefore, as a circulating fluidized bed fuel should pay attention to the occurrence of slagging.