One of the methods used to fire natural solid fuel (coal) in furnace devices is its combustion in pulver ized form. In this case, aerosuspension is supplied to the burners, which consists of a mixture of air and polydisperse pulverized coal. Combustion of pulver ized fuel is a complex set of physicochemical phenom ena, such as heat transfer between particles, gases, and enclosing surfaces, release of moisture and volatiles in the course of heating, combustion of volatiles and coke residue accompanied by a multitude of various reactions and intense mass transfer, conversion of the fuel mineral part, etc. These processes may run either sequentially in time or concurrently with each other and have a strong influence on each other. In this con nection, those carrying out a theoretical analysis face the need to simultaneously consider equations describing the motion of gases with particles, heat transfer between particles, gases, and walls, chemical kinetics that takes into account, apart from coke resi due combustion, also the release and combustion of volatiles, etc. Since some processes are still poorly understood, we can state that it is almost impossible to construct an exact mathematical model, and an attempt to decrease the number of simplifying assumptions will inevitably result in obtaining an excessively complicated model. Thus, we should take only those simplifying assumptions that do not have an essential effect on the main processes and that will allow us to obtain satisfactory agreement between cal culation and experiment.A polydisperse composition of fuel gives rise to cer tain difficulties in calculating a pulverized coal flame. The sizes of pulverized fuel obtained in milling coal may differ from one another by as mush as one or two orders of magnitude. Since the intensity of heat trans fer between particles, gases, and enclosing surfaces, release of volatiles, and other processes depend on the size of particles, particles belonging to different frac tions burn under different conditions. Fine fractions are heated and ignited more rapidly than large frac tions, thus increasing the general temperature level in the system and consuming part of oxidizer. It should also be pointed out that both sizes of particles and their quantity vary during the combustion process.Matters concerned with studying the combustion of polydispersed solid fuel systems were addressed in many works. In some studies [1, 2], polydispersed composition was taken into account by introducing a conditional "monodispersed" system averaged according to the initial distribution function based on the Rosin-Rammler law, whereas other researchers [3] took polidispersity into account by subdividing a system into certain number of fractions with finding the average size within each of them. The authors of [3] stated and solved problems concerned with analyz ing the ignition and burnout of both individual parti cles and "monofractions" at short process periods. To this end, systems of equations written for each fraction were solved numericall...
