A study of the effects of thermal shocks on liberation characteristics of high coal ash particles

Abstract The influence of thermal shocks on the liberation characteristics of a by-product/discard from a coking coal preparation plant, known as coal middlings were investigated. The coal middlings are characterized by very high ash content (>45%), low carbon content ( 80 of around 2 mm. In case of cryogenic grinding, liquid nitrogen was used and soaking time was varied from 20 min to 60 min. Microscopic analysis revealed the presence of cracks and fragmentations in both vitrinite and inertinite particles. However, minor reduction in size was observed with d 80 reaching up to a minimum of 6.5 mm with 60 min exposure time. In addition to this marginal increase in BET surface area and pore size of the sample was achieved because of the both pre-treatments. Study reveals that microwave heating is more effective technique than the cryogenic cooling for sizing and liberation of ash particles of coal.