| Coal-fired power plant is a major emission sources of heavy metal pollution. Due to differences in physical and chemical properties of heavy metals, part of heavy metals emit with flu gas, part of heavy metals enrich in fly ash, bottom ash and FGD gypsum during combustion. Since Mercury arsenic, lead, cadmium and chromium is volatile, advanced environmental protection equipment (SCR, ESP, FGD) can not capture them effectively. It is a great pollution to the environment emitting heavy metals without control. In this work, we focused on the transformation behavior of arsenic, lead, cadmium and chromium in coal-fired power plant.By BCR method to anaiyze the chemical speciation of the five heavy metal elements in fly ash of five different plants, compare the influence of different combustion, coal and other factors on distribution of the different existing status of heavy metal elements. Comparing the difference of the existing status of the five heavy metal elements in the fly ash and FGD gypsum. According to the experimental data, we found that where most of Hg, Pb in fly ash were in stable solid-state, but Pb, Cr, Cd were evenly distributed, comparing with Hg, Pb their stability decreasedESP electrode ash of two coal-fired power plants were analyzed. It can be found that the existing status of Hg were oxidizable and residual state. For A power plant, reducing of unburned carbon in fly ash leads to reducing of Hg. For B power plant, HgS in fly ash causes increasing of Hg. The four existing statuses of As in the electrode fly ash can be evenly distributed. Where most of Pb in fly ash were in stable solid-state, and with the increase of the electrode, Pb content is incremented. The oxidizable state of Cr, Cd is relatively less, with the increase of the electrode Cr, Cd content is incremented. Results of these studies show a theory that the main existing status of heavy metals in fly ash were stable solid-state, the proportion of about 60% or more to 90%. |
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