Environmental Geochemistry Of Aluminous Argillite And Carbonate In The Late Carboniferous Taiyuan Formation From Huainan Coalfield

The aluminous argillite and carbonate of the Taiyuan Formation in Huainan coalfield are developed widespread, and their economic values are generally attractive. With more and more attention focused on the deep resources and the coal economic industry restructuring, the study on the environmental geochemistry of aluminous argillite and carbonate in the Taiyuan Formation has both theoretical and practical significances. Several large-scale coal-fired power plants have been built in Huainan city which is one of the most important bases in the East China. Given the huge amounts of coal consumption and the low installation percentage of air pollutant-control devices (APCDs), there is an urgent need to evaluate the emission rate of Hg and the enrichment degree of Hg during coal combustion, to investigate the fractional distillation of Hg during coal combustion in depth and evaluate the Hg removal efficiencies of the typical APCDs, and finally estimate the Hg emission inventory of Huainan coal-fired power plants.The survey region of this study is the Huainan Coal field. Aluminous argillite and carbonate of the Taiyuan Formation in Huainan coalfield, and the feed coal and the coal-combustion residues (CCRs) in typical coal-fired power plants in Huainan city were selected as the research objects. Combined with interdisciplinary theories of mineralogy, lithology, geochemistry and so on, this article systematically studied the physic-chemical properties and formation mechanisms of aluminous argillite and carbonate and the environmental geochemical characteristics and according to the principle of mass balance analyzed the release and emission characteristics and the migration fractional distillation characteristics, and then carried out systematic analysis of the Huainan coal industry from the aspects of resource utilization and environmental protection. The main achievements are as follows:(1) Through analysis of the aluminous argillite samples from the Taiyuan Formation using microscopy scanning, mineralogical composition and tests of major and minor elements, it indicates that the studied aluminous argillites probably derived from the common parent rocks composed of felsic to intermediate igneous rocks. These argillites were presumably deposited under anoxic environments. After the trace elemental and stable isotopic analysis of carbonates from 13 layers in Huainan Coalfield, it is obtained that along the carbonate succession upward,818O shows a decreased trend, suggesting a gradual rise of sea levels in a warm climate. Lower part of the Taiyuan Fonnation is suggested to be formed in the Late Carboniferous Epoch, while middle and upper parts should belong to the Lower Permian Series.(2) Based on the research on the content distribution and the migration charactersitics of Hg during coal combustion in 2 large-scale coal-fired power plants in Huainan city, mass balance calculation shows that the shares of Hg in bottom ash, fly ash, WFGD products (gypsum, effluents, sludge), and stack emissions were<2,17-32, 7-22, and 54-82 %, respectively. The Hg-removal efficiencies of ESPs, WFGD, and ESPs + WFGD were 17-32,10-29, and 36-46 %, respectively. We estimated that Hg emissions in all Huainan coal-fired power plants varied from 1.8 Mg in 2003 to 7.3 Mg in 2010.