The effect of microwave radiation on the triboelectrostatic separation of coal

The triboelectrostatic separation and extraction of Slovak brown coal samples—untreated and microwave-treated, were analyzed. The changes in the coal structure as a result of interaction between the microwave radiation and the coal facilitated improvements to the process of separation and extraction of the coal. In the case of microwave-treated coal at a power of 900 W for a period of 10 min it was possible to obtain increased content of volatile substances to 44 wt% compared to 30 wt% in the untreated sample and decrease of ash content from 49 to 18.3 wt%. The quality of triboelectrostatic separation of microwave irradiated and non-irradiated coal samples was evaluated by comparing the recoveries of the combustible matter and ash. The influence of microwaves on the extraction of coal was also positive: the preliminary thin layer chromatographic analysis of 2 min microwave irradiated and non-irradiated coal extracts confirmed the effect of microwaves on qualitative organic matter composition in the extracts utilizable for special purposes.