Fate of cadmium in coal-fired power plants in Guizhou, Southwest China: With emphasis on updated atmospheric emissions

摘要

Coal-fired power plants (CFPPs) are important source of anthropogenic atmospheric releases of various pollutants, including cadmium (Cd). In this research, the distribution of Cd in seven CFPPs in Guizhou province, southwest China and the atmospheric Cd emissions from this source category in this province was studied. Among the boilers, one was a circulating fluidized bed boiler (CFB) and the others were pulverized coal-fired boilers (PC). All CFPPs are equipped with De-NOx, De-dust, and De-SO2 devices. Solid samples including feed fuel (coal, gangue, and coal slime), limestone, bottom ash, fly ash, gypsum, as well as stack flue gas samples were simultaneously collected and analyzed. Cd in feed coal, bottom ash, fly ash, limestone, gypsum, and stack flue gas were in the range of 0.15–0.68, 0.08–0.42, 0.43–2.03, 0.01–0.67, 0.02–0.41?mg?kg?1, and 0.005–0.03?μg·Nm?3, respectively. Cd release ratio during the coal combustion in the boiler was in the range of 95.91–98.77% for PC, but only 76.94% for CFB. Cd atmospheric emission factors were in the range of 0.03–0.2?mg Cd·t?1 coal, 0.02–0.1?μg·(kW·h)?1 or 0.002–0.01?g Cd·TJ?1 for the seven CFPPs, lower values were found for CFB boiler than that of PC boilers. In 2017, the amount of Cd emitted from CFPPs in Guizhou province was estimated to be 51.4?kg?y?1 (CFB: 2.4?kg?y?1 and PC: 49?±?32?kg?y?1), significantly lower than previous reports.