An experimental study of temperature of burning coal particle in fluidized bed

The purpose of this study was to investigate the temperature of coal particle during combustion in fluidized bed (FB). It is necessary to know the coal particle temperature in order to predict kinetics of chemical reactions within and at the surface of coal particle, accurate NO _x and SO ₂ emission, fragmentation, attrition, the possibility of ash melting, etc. The experimental investigations were conducted in order to obtain the reliable data on the temperature of particle burning in the FB. A method using thermocouple was developed and applied for measurements. Thermocouple was inserted in the center of the particle shaped into spherical form with various diameters: 5, 7, 8, and 10 mm. Two characteristic types of low-rank Serbian coals were investigated. Experiments were done at the FB temperature in the range of 590-710 °C. Two types of experiments were performed: (i) combustion using air as fluidization gas and (ii) devolatilization with N ₂ followed by combustion of obtained char in air. The temperature histories of particles during all stages after introducing in the FB were analyzed. Temperature difference between the burning particle and the FB was defined as a criterion, for comparison. It was shown that the temperature profile depends on the type of the coal and the particle size. The higher temperature difference between the burning particle and the FB was obtained for smaller particles and for lignite (130-180 °C) in comparison to the brown coal (70-130 °C). The obtained results indicated that a primary role in the temperature history of coal particle have the mass and heat transfer through combusting particle.