Influence of particle size distribution on the combustion rates in a batch fed fluidized bed

The design of such FBC's is based on the practical experience gained from pilot plant studies and also on the predictions of mathematical models. Central to any model of coal combustion in FBC's is the rate at which particles burn in the bed which determines the carbon loading and hence pollutant emissions, heat release rates, coal feed rates and elutriation rates. Particle size and temperature usually indicate the controlling mechanism of combustion; large particles and high temperature suggest that diffusion is dominant whereas chemical kinetics became important for small particles and low temperatures. In a typical FBC the particle sizes range from that of the maximum of the input feed down to that of particles which are about to be elutriated and particle temperatures can have a value anywhere between the bed temperature T/sub b/ and T/sub b/ + 200K. The particle size distribution of the coal feed is a parameter which is important in the design of FBC's but whose influence on the combustion rates in the bed has not been studied. It is the purpose of this paper therefore, to develop a theory to predict the burnaway, burnout time and particulate phase oxygen concentration in a batch fedmore » FBC and show their dependence on the input particle size distribution which is accurately known.« less