STUDIES ON THE LOWER EXPLOSION LIMIT OF COAL DUST CLOUDS (PART II). INFLUENCE OF ASH CONTENT AND A SIMPLIFIED ESTIMATION METHOD OF LOWER EXPLOSION LIMIT CONCENTRATION OF COAL DUST CLOUDS.

A similar technique to that used in considering the explosion limit of coal dust-rock dust mixtures was used to investigate the influence of ash content on the lower explosion limit concentration of coals. On the basis of the results obtained by a theoretical calculation of lower explosion limit concentrations of coal dust clouds reported in the previous paper, a simplified method of estimation of lower explosion limit concentrations of coals was developed. Then experimental data were used for comparison. Evaluation of the influence of ash content on the lower explosion limit concentration in the simplified estimation method is presented. It may be concluded that the simplified estimation method can be applicable for coals, the ash content of which is less than roughly 30 pct.