Tadeusz Dziok*, Andrzej Strugała*, Ireneusz Baic**, Wiesław Blaschke**
*AGH University of Science and Technology, Krakow, Poland; **Łukasiewicz Research Network – Institute of Mechanised Construction and Rock Mining, Katowice Branch, Poland
corresponding author’s e-mail:
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 processes which is commonly used in Polish coal preparation plants were analyzed, i.e. dense media separation, grain and fine coal jigging, flotation, as well as dry deshaling using the pneumatic vibrating FGX type separator. The first four are the washing processes and the last one is the dry separation process. The effectiveness of the coal cleaning 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 with the average of 1.15) than for the washing process (from 0.53 to 2.24 with the average of 1.50). This shows the possibility of the effective removal of mercury occurring in the adventitious inorganic constituents of the analyzed Polish hard coals. However, it should be noted, that the obtained results varied within a relatively high range, which should be explained by the difference in the mode of mercury occurrence in individual coals.
Keywords
hard coal, washing, deshaling, mercury, removal
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