Studies on the Effectiveness of Mercury Removal from Hard Coal with the Rejects in the Washing and Dry Deshaling Processes

Abstract

Due to the toxicity of mercury a reduction of its emission is the objective of many legislative actions. In the case of power plants, there are well-known methods allowing for the removal of mercury from flue gases (post-combustion). In the case of households and small- scale combustion installations these methods are not used, which is caused by high investment costs. The most effective solution for this group of customers is the removal of mercury from coal (pre-combustion). This can be obtained in the washing and deshaling processes. The coal-cleaning equipment which is commonly used in Polish coal preparation plants was analyzed, i.e. dense media separators, grain and fine coal jigs, flotation machines, as well as the pneumatic vibrating FGX type separator. The effectiveness of the coal clean - ing process was assessed with the use of the RF factor (the ratio of the mercury content in the rejects to the mercury content in the feed coal). The obtained values of the RF factors show that mercury has a tendency to remain in the rejects, while higher values of the RF factors were obtained for the dry deshaling process (from 0.83 to 2.82) than for the washing process (from 0.53 to 2.24).