An Investigation of Factors Affecting the Physical Characteristics of Flyash Formed in a Laboratory Scale Combustor

Abstract

An Australian bituminous coal was burnt in a laboratory drop-tube combustor at 1400, 1500 and 1600°C to determine the effect of p.f. properties and combustion temperature on the character and particle size of the flyash. The experiments showed that the mass mean particle size of the flyash was approximately proportional to that of the p.f., and almost independent of combustion temperature. In contrast, the proportion of fine ash (< 10 μ) was independent of p.f. size but increased markedly with increased combustion temperature. The upper size of the ash was determined by unburnt char for the 175 μm and 240 μm p.f. and by the mineral matter for the 29 μm p.f. Cenosphere formation increased with combustion temperature and dominated the ash formed at 1600°C. The work emphasises the need for more detailed p.f. analysis during laboratory and pilot-scale combustion studies into flyash formation and related phenomena such a's fouling, filtration and precipitability. Additional research is required to quantify cenosphere formation and its influence on the formation of fine flyash.