Research on collaborative control of Hg, As, Pb and Cr by electrostatic-fabric-integrated precipitator and wet flue gas desulphurization in coal-fired power plants

Abstract

A full-scale field investigation studying the emission of trace elements was carried out at a coal-fired power plant equipped with a wet flue gas desulfurization (WFGD) system and an electrostatic-fabric-integrated precipitator (EFIP). The results indicated that 76%–94% of the As, Pb and Cr are present in the fly ash, and that Hg is distributed in the gypsum and fly ash. The concentrations of As, Pb, Cr and Hg in the electrostatic precipitation ash are 2–4times higher than what was present in the fabric filtration ash. The results indicated that 2.73% of the As and 4.69% of the Hg are released after the FGD system. The Pb and Cr content in the post-FGD flue gas were identified as extremely low. The BCR leaching results indicated that fly ash with a smaller particle size will release more As. Therefore, fly ash collected by fabric filtration should be regarded as serious concern, and treated seriously. The proportion of Pb in the non-mobile fraction increased with particle size, and a larger portion of Pb was present in the oxidizable fraction as compared to As and Cr. Trace element concentrations in the EFIP under low load (75% load) were measured 3%–25% higher than under the full load. The trace element concentrations in the WFGD decreased with the decreased load.