Occurrence Of Uranium In Coals And Its Emissions From Coal-Fired Power Plants

Coal is China’s major energy source. Uranium is a trace elemental in coal and its concentration in coal has an important impact on coal mining and utilization. Moreover, reports on the release characteristics of uranium from coal combustion and the occurrence and distribution of uranium from the different effluents in coal-fired power plants is also limited.this paper reports measurements performed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) on uranium concentration in a variety of coal samples and samples of a coal-fired power plant. The paper also reports the release characteristics of uranium from coal combustion in a tube furnace and uranium mass balance characteristics of coal combustion in a drop tube furnace. A round of field measurements was performed of coal, fly ash, bottom ash, limestone, gypsum and flue gas samples of a coal-fired power plant. Material samples were collected,measured and analyzed, and the distribution and mass balance characteristics of uranium is discussed. Moreover, a detailed method for the measurement of uranium in coal samples by inductively coupled plasma atomic emission spectrometry (ICP-AES) and TCP extraction resin was developed in this paper.Chinese coal samples from eigh-teen coal mines were collected and analyzed for uranium and it was found that the uranium content for most of the coals was in the range from 1 to 3 mg/kg. Laboratory experiments with a tubular furnace indicate that the amount of uranium released from heated coal increases with temperature and with the retention time, when it combust. Full-scale field tests were carried out at a coal-fired power plant to investigate the uranium distribution (and mass balance) in the coal, limestone, fly ash, bottom ash, gypsum and the flue gas. Almost all the uranium in the coal concentrated in the fly ash (about 80%) and the bottom ash (about 10%). The uranium content in the flue gas was less than 1/1000 of the total elemental input, between 0.043 and 0.069 lg/m3, which is much lower than the typical concentration of mercury or arsenic in flue gas of coal-fired power plant. The uranium content in the desulfurization gypsum product was found to be slightly larger than the uranium content of the limestone. Using inductively coupled plasma atomic emission spectrometry (ICP-AES) and TBP extraction resin, uranium content in 2 kinds of coal samples was measured and the results were accurate.