Studying the Slagging Properties of Mechanically Activated Coals

Abstract—

Intense mechanical pretreatment of coal is among promising technologies in thermal engineering owing to its ability to achieve essentially higher coal reactivity. In being subjected to such treatment, the coal’s mineral part becomes significantly transformed, and a change occurs in the gas and ash flows during combustion, which may result in either lower or higher fouling of the boiler’s heating surface. Till now, there have been no activities in the world practices on studying the effect that the “mechanical activation” of coals has on the deposit formation intensity. For coals characterized by different degrees of metamorphism, specifically, brown coal from the Kansk–Achinsk basin and black coal from the Ekibastuz basin, regularities pertinent to the change in the slagging onset temperature after pulverization in mills having different degrees of energy intensity are established. Results from studying the slagging intensity in burning the dust of brown coals after their having been pulverized in a disintegrating mill are given. The numerical analyses were carried out by applying the universal SigmaFlow CFD software package. The mathematical model used in carrying out the studies comprised the submodels of a reacting turbulent gas flow and models of motion, heat transfer, coal particle combustion, and slag deposit formation. For taking into account the specific features pertinent to the combustion of “mechanically activated” coals, the model was supplemented with the reaction properties, volatile release rates, and coal residue burning rates. The numerical analyses of slagging intensity in burning pulverized brown coals have shown that the slagging onset temperature becomes by 40–60°С higher after having been pulverized in a disintegrator.