Separation of mercury in industrial processes of Polish hard steam coals cleaning

Coal use is regarded as one of main sources of anthropogenic propagation of mercury in the environment. The coal cleaning is listed among methods of the mercury emission reduction. The article concerns the statistical assessment of mercury separation between coal cleaning products. Two industrial processes employed in the Polish coal preparation plants are analysed: coal cleaning in heavy media vessels and coal cleaning in jigs. It was found that the arithmetic mean mercury content in coarse and medium coal size fractions for clean coal from heavy media vessels, amounts 68.9 mu g/kg, and most of the results lay below the mean value, while for rejects it amounts 95.5 mu g/kg. It means that it is for around 25 mu g/kg greater than in the clean coal. The arithmetic mean mercury content in raw coal smalls amounts around 118 pg/kg. The cleaning of smalls in jigs results in clean coal and steam coal blends characterized by mean mercury content 96.8 mu g/kg and rejects with mean mercury content 184.5 mu g/kg.