Predicting the Combustion Behaviour of Coal Particles

Abstract

A mathematical model has been formulated to describe the combustion behaviour of single particles of pulverised bituminous coal and the predictions have been compared with experimental values obtained using a small tube furnace. The model was programmed for an analogue computer and incorporates data, much of it recently acquired, on the physical changes undergone by coal particles which are rapidly healed. It is concluded that for 60 μm diameter particles burning within the chemical control regime, increase in the radiating surface of the particles is of major importance in controlling their temperature and that this surface may be accounted for by fragmentation at an advanced stage of burnout. Between 1325° and 1450 °K the values for the surface reaction rate coefficient of the two chars investigated are between 0·04 and 0·14 times those of published data for carbon surfaces other than pyrolytic graphites. It is suggested that the differences may be attributed to the porous nature of the chars.