A generalized model for leaching of chlorine from Illinois coal and the effect of particle size

Abstract

Experimental leaching data are presented for an Illinois No. 6 coal at four temperature levels and different particle sizes. A generalized model based on diffusion and relaxation has been fitted to Sample C8601 of Illinois No. 6 coal with a wt% of chlorine of 0.42. The experimental data on this sample covered a temperature range of 297–370 K and a particle size range of − 20 to − 325 mesh. Based on the type of coal and the conditions of leaching, it was found that 40–80% of the original chlorine could be leached from the coal matrix. The model based on diffusion-relaxation concept predicted the leaching data within 5% average absolute deviation (AAD). The diffusion rate constants at different temperatures were correlated to Arrhenius type relations. Attempts made to correlate the constants in the Arrhenius equations with the chlorine content in coal and particle size are discussed. The water leaching data were used to calculate Fickian diffusivities based on the time required for 50 per cent desorption. The calculated diffusivity values ranged from 0.6 to 3 × 10 − 11 cm 2s − 1.