Mercury in Polish Coking Bituminous Coals
2018
Burmistrz, Piotr | Kogut, Krzysztof | Marczak, Marta | Dziok, Tadeusz | Górecki, Jerzy
Poland emits 10.58 Mg of mercury to the atmosphere annually. More than 90% of this emission is generated by combustion and thermochemical usage of coal, including coking. In Poland, the coking industry consumes more than 12 million Mg of bituminous coals each year. Contrary to lignites and subbituminous coals used in power plants, there is not much reliable data on mercury content in Polish bituminous coals. The purpose of this paper was to determine mercury content in bituminous coals delivered to Polish coke plants and to analyze possible removal of mercury during coal cleaning processes. Eighty-two samples from 9 mines were analyzed. The average mercury content varied from 28.4 to 182.6 μg kg–¹, with a mean value of 75.9 μg kg–¹. The analysis of mercury content in three coals treated by (i) flotation, (ii) dense-media washing, and (iii) jig washer cleaning, revealed that mercury content in relation to net calorific value can be reduced by 27% (flotation) to 71% (dense-media washing). In addition, distribution of mercury, ash, and sulfur between products and rejects in the process of coal cleaning was determined. For this purpose samples of raw coals, clean coals, middling products and rejects derived from six coal preparation plants were examined (67 samples). The publication presents the mercury balance results for bituminous coal coking. The mercury is transferred to coal tar (75%, mean mercury content 2007 μg kg–¹), coke (6%, 7.5 μg kg–¹), sulfur (2%, 2998 μg kg–¹) and purified coke oven gas (3%, 7.5 μg m–³). Balance data shows that almost 14% of mercury is emitted to the atmosphere during the process of filling the coke oven chambers with coal.
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