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

The breakage of coal particles into smaller fragments during the devol atilization stage mostly occurs randomly due to the heterogenous struc ture 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 par ticles during their stepwise degradation. The particle-size distributi on has been lumped into a limited number of states, each representing a particular volume range. The master equation and the equations for t he means, variances, and covariances of the random variables, each rep resenting the number of particles in the individual states in the syst em, have also been derived from the stochastic population balance. Sim ulation has been performed with a stiff differential equation solver t o predict the dynamic particle number statistics at any time. By fitti ng the model to experimental data, the transition intensity function i s found to be inversely proportional to the square of particle radius.