Research On Transformation And Mobility Of Trace Elements During Power-generation Utilization Of Huainan Coal

Huainan with the pillar industry of coal exploitation is the significant industrial city in Anhui province, moreover, is one of the large scale fossil power lands in China. The total installed capability of Huainan will be increased to 2000KW by 2020, which will bring tremendous impacts on the Huainan eco-environment when it supplies a steady flow of electric power by means of coal-combustion. Trace elements can easily be released into surrounding environment in the process of coal preparation, coal combustion, and the disposition of coal-combusted products. Therefore, the study on the release rule of trace elements in coal combustion and by-products disposition is quite significant to the construction of eco-Huainan.In this study, I put my emphasizes on the mobility and release law of trace elements in the process of coal combustion and coal combustion by-products in disposal site according to the samples sampled from Pingwei and Tianji thermal power plants. Moreover, the results of this study will be the theories support to the eco-Huainan construction.With the methods of hydride generation atom fluorescence spectrometry method (HG-AFS) and inductively coupled plasma atomic emission spectrometry(ICP-AES, we can get the contents of trace elements in samples.â‘ By the method of relative enrichment factor, I can classify the elements by their volatile ability into volatile elements and nonvolatile elements. By analyzing the characteristic of trace elements distribution in combustion by-products, I get a conclusion of the mobility and release law of trace elements;â‘¡By analyzing the characteristic of trace elements distribution in ash disposal site, I draw a conclusion that the mobility and release law of trace elements under ash disposal condition which is comprised of vertical direction and the direction along the discharging fly ash of ash channel. In order to give supports to the above two laws, I did relativity analysis between ash content and trace elements (the higher the related coefficient is, the more of trace elements combines with organic materials, and the elements are easily escaped from coal in combustion).I come to a conclusion that the occurrence mode of trace elements are(the higher content of elements in form of exchange state, the easier the elements mobile in leaching condition, and the second is oxidation state). The results are that, firstly, the contents of As, Co, Cd, Hg, Mn, Se, Zn in coal are decreased, especially the removal rate in washing processing of As, Hg is higher than the others, such as 74.9% and 75.1%, 99.4% and 96.5% respectively in Pingwei and Tianji thermal power plants. Secondly, in the combustion progress, As, Co, Cu, Mo, V and Zn are concentred in smaller particles; the contents of Ba, Co, Cu, Pb, V, Zn are higher than preboiler coal and remarkably Huainan coal; Cr, Hg are partly released to the atomosphere and exhausted in the combustion products. Thirdly, the ability of mobility and releasement and rule of trace elements in raw fly ash in the disposal process: As, Co, Cr, Cu, Hg, Pb, Se, Zn are able to released from ash into water, in which the subtractive ratio of As, Hg are higher in wet-ash dischargement; the further from ash-discharging port, the higher contents of As, Co, Cr, Hg, Pb, Cu and the lower contents of Mn, Se and Zn is basically not changing in the surface distribution; in the vertical distribution, Co is the highest in upper layer, Cu, Mn, Cu are between upper and bottom and bottom is higher than upper, Cr, Pb, As, Hg are the highest in the middle layer, Se is the higest in bottom layer and Zn is changing little. The reasons for the above are closely related to the geochemical characteristic of trace elements and the specific disposal circumstance in field.In the end, I put forward my conclusion that the law of transformation and mobility of trace elements during power-generation utilization of Huainan coal through the above works that will be the scientific theory to eco-Huainan construction and be available to put forward and carry out the pollution-controlled measures.