STOCHASTIC MODELING OF DEVOLATILIZATION-INDUCED COAL FRAGMENTATION DURING FLUIDIZED-BED COMBUSTION

The breakage of coal particles into smaller fragments during the devolatilization stage mostly occurs randomly due to the heterogenous structure of coal, thereby necessitating a stochastic approach for modeling. In the present work, the master equation approach has been proposed for predicting the statistics of the size distribution of the coal particles during their stepwise degradation. The particle-size distribution has been lumped into a limited number of states, each representing a particular volume range. The master equation and the equations for the means, variances, and covariances of the random variables, each representing the number of particles in the individual states in the system, have also been derived from the stochastic population balance. Simulation has been performed with a stiff differential equation solver to predict the dynamic particle number statistics at any time. By fitting the model to experimental data, the transition intensity function is found to be inversely proportional to the square of particle radius.