| As a global toxic pollutants, mercury emissions has referred to the agenda. In October 2013,under the organization of the UN Environment Programme(UNEP), the international community reached an agreement about the “Minamata Convention About Mercury”. This convention shall manage and control the worldwide use, emissions and release of mercury and its compounds which are all related to human activities. The UNEP report 2013, thinks that China’s contribution to the global mercury emissions is more than a third, making China face a great international pressure in performing the agreement in the future. The main reasons for the dilemma is that our country is a big one of mercury and energy consumption as well as metal smelting and cement production, but in the past for screening of atmospheric mercury pollution problems is not clear.Therefore, to accurately calculate the emission factor of the mercury emission source, to establish a complete list of emissions, formulate corresponding mercury emission reduction measures and set up perfect supervision and management mechanism, is one of the important measures to cope with the “Minamata Convention”.Chongqing is one of the largest industrial city in southwest of China, with the development of the economy, the energy consumption with coal and cement production industry growing rapidly year by year involving mercury emissions in recent years, there also exits the mercury emission reduction pressure. Therefore, the study on atmospheric mercury anthropogenic source emission inventory in Chongqing is necessary. To finish the work tasks, the study of key industries mercury emission factor is the foundation. For this purpose, on the basis of investigating the atmospheric mercury anthropogenic emission source in Chongqing, we are clear that steel smelting, coal-fired power plants and cement production are the three industries for atmospheric mercury in Chongqing key anthropogenic emission source, and select representative enterprise, through to the enterprise production process, raw materials, slag and fly ash, etc. A detailed investigation and sample analysis, adopts the material of the mass balance calculation method, studied the key industries of mercury emission factor, and calculated the industry of atmospheric mercury emissions. Aim is tobuild Chongqing artificial source atmospheric mercury emission list, specify the corresponding mercury emission reduction measures to provide basic data and improve the supervision and management mechanism.According to the existing production technology of key industries in Chongqing, 1 selected the iron and steel enterprises, 4 four coal-fired power plants and cement factories, research on mercury emission factors, the results obtained are as follows:1)There is only one of iron and steel enterprises in Chongqing. Including input materials in each production process technology of iron and steel enterprises, used in blast furnace ore mercury content in the highest, 159.11 μg·kg-1±6.95 μg·kg-1, followed by sintering and coal of blast furnace.Dust mercury content was the highest in the output material, 18.13 μg·kg-1±1.42 μg·kg-1, followed by slag. In the process of iron and steel production, the sintering process of mercury total input accounted for 68.06% of total iron and steel production input mercury, far higher than other processes. Besides, there’s a large amount of mercury output of solid products in sintering process,accounting for 22.61% of the total mercury solid product output. There’s a large amount of the coal consumption in their own coking plant of iron and steel enterprises, and a lot of mercury input. Mercury input 1346.74 g·d-1±36.95 g·d-1, total mercury solid product output is 177.42g·d-1±13.73 g·d-1. Mercury emission factors for iron and steel enterprise flue gas was estimated preliminarily to be 0.092 g·t-1 steel production in Chongqing, slightly higher than the mercury emission factor of steel industry abroad. According to the mercury emission factor to estimate, in2014 in Chongqing iron and steel smelting process emissions of atmospheric mercury is 732.68 kg.To control mercury emissions, iron and steel enterprises should be combined with production practice, further reduce energy consumption of coking and sintering process level, or improve the quality of raw materials, and reduce the input of mercury.2)Chongqing is currently in production, the size of coal-fired power plants, a total of 42, among them, 32 power plant using circulating fluidized bed boiler, 10 power plants using the pulverized coal furnace. The different process of power plant are chosen as 2 different representative power plant capacity in this study. Coal-fired power plants all input materials, the raw coal contained mercury content is the highest, four that coal mercury content of the average of 208.77 μg·kg-1. The output of solid waste ash and desulfurization gypsum mercury content in the highest, dust removal device and has a great effect on the mercury removal desulfurization device. Emissions of mercury from coal-fired power plants and coal consumption, the types of boiler, flue gas purification devices are closely related. According to the quality of material balance calculation, four coal-fired power plants(A, B, C, D) of mercury emissions were 19.01 g·d-1, 6.85 g·d-1, 40.63 g·d-1, 981.55 g·d-1,according to the production process, the installed capacity of power plants to weighted, mercuryAbstract emission factors were 3.91 μg·(kw·h)-1、19.23 μg·(kw·h)-1、6.12 μg·(kw·h)-1、32.98 μg·(kw·h)-1.Circulating fluidized bed boiler power plant(A and B from coal-fired power plants) of mercury emission factors are much smaller than pulverized coal furnace power plant coal-fired power plants(C, D), two types of mercury emissions from coal-fired power plants were 11.52μg·(kw·h)-1. and28.01μg·(kw·h)-1..Based on mercury emission factor to estimate, in Chongqing in 2014 coal-fired power plants of atmospheric mercury emissions of 981.48 kg, the circulating fluidized bed boiler power plant power plant pulverized coal and furnace of 90.71 kg and 890.77 kg respectively. In addition to improve the efficiency of coal-fired power plant flue gas purification equipment in addition to the mercury to reduce flue gas mercury emissions, should also strengthen the wastes such as fly ash and the desulfurization gypsum regulation, thus reducing the waste of mercury on surrounding the secondary pollution of atmosphere, soil and groundwater.3)The cement plants whose annual output is more than 1 million t in chongqing, total 27,and their production technology is the new type of dry process rotary kiln.These cement plants’ annual output account for 86.47% of the total output of cement, and dozens of small shaft kiln cement plants, only 13.53% of its production, and will be phased out. Therefore, we chose four representative NSP cement plants as research object, doing research on mercury emission factor. Of all the input materials in Cement plants’ production process, limestone and desulfurization gypsum containing mercury content was the highest, followed by coal, limestone and coal in the mercury into the quantity of cement products and a greater role in flue gas mercury emissions. The mercury content of preheated ash was the highest in the output material, followed by cement products, most of mercury into the preheated ashes. Four cement plants(A, B, C, D) of mercury emissions were 49.7 g·d-1, 40.15 g·d-1, 50.1 g·d-1, 113.73 g·d-1, mercury emission factors were 8.22mg·t-1, 6.27 mg·t-1, 9.64 mg·t-1, 11.61 mg·t-1. B cement plant meets the standards of American EPA new cement plant mercury emissions, A, C, D cement plant are in accordance with the existing cement plants mercury emission factor. According to the capacity of NSP we estimate that in Chongqing cement plants’ mercury emission factor,on average, is 8.94 mg·t-1cement.According to the mercury emission factor estimation, in Chongqing in 2014 NSP cement production of atmospheric mercury emissions is 515.36 kg. NSP cement production process as the mainstream of the modern cement production, should increase the promotion in the cement industry in Chongqing, so as to reduce the comprehensive energy consumption of cement industry in Chongqing and to implement environmental protection. |
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