Partitioning and Migration of Trace Elements during Coal Combustion in Two Coal-Fired Power Plants in Hefei City, Anhui Province, Eastern China

Abstract

Coal-fired thermal power plants that meet the huge energy demand of China largely contribute to carbon emissions, environmental pollution, and human health issues. To investigate the impact of coal-fired power plants on the environment in the most developed region of eastern China, samples of feed coal, limestone, slag, fly ash, and flue gas desulfurization (FGD) gypsum were collected from two coal-fired power plants in Hefei City, Anhui Province, China. The concentrations of trace elements in these samples were determined using inductively coupled plasma mass spectrometry (ICP-MS). The results show that the feed coal was slightly rich in V, Cr, Se, In, Sb, Pb, and Ga compared to common Chinese coal. Most trace elements were concentrated in fly ash, especially in the fine particles. Only Sc, Cr, Rb, and Ba were enriched in slag. The smaller the particle size of the fly ash, the higher the fraction of volatile trace elements. The elemental concentrations of old fly ash, which was precipitated in the well of the flue gas pipeline, did not show noticeable differences from fresh fly ash. In addition, the short-time storage of fly ash did not influence the trace elements. To understand the possibility of recovering rare earth elements from coal combustion by-products, the outlook coefficients (Coutl) of coal combustion by-products for the Wanneng (WN) and Tianyuan (TY) power plants were calculated, and they were found to be promising for rare earth elements plus yttrium (REY) recovery. However, as per the evaluation diagram of cut-off grade and Coutl values, all feed coal and its by-products from these two coal-fired power plants are projected to be ‘unpromising’. Therefore, the coal combustion by-products from the WN and TY coal-fired power plants were not candidates for REY recovery.