模拟烟气中气态痕量元素污染物发生方法的研究现状

Research status of methods for generating gaseous trace element pollutants in simulated flue gas

  • 摘要: 目前燃煤电厂对于SO2、NOx和PM等主要污染物已经有较为成熟的控制方法,但针对具有长期环境危害性的痕量污染物尚缺乏有效的排放控制手段。为全面掌握痕量污染物在煤燃烧过程中的释放、迁移和转化规律并开发相应的控制技术,建立稳定可靠的模拟烟气痕量污染物发生方法是开展相关研究的前提条件。通过文献调研,对常见痕量污染物的四种发生方法进行了总结、归纳和对比:溶液蒸发法较为简单易用,但产物中易含有副产物,这些副产物会带来一定的影响;燃烧法产生的痕量污染物最接近实际情况,但受实验条件影响较大,并且产物成分较为复杂;升华法获得的产物浓度较为准确,但适用范围较窄,仅用于某几种气态痕量污染物的发生;氢化物氧化法可准确地控制产物的发生速率,但也仅适用于少量痕量污染物,并且装置较为复杂。分析比较了不同方法的适用情形,最后提出多种方法联用的思路以期得到更加接近实际情形并且成分可控的结果。

     

    Abstract: Technologies for the emission and control of pollutants have been widely applied in coal-fired power plants in China to control the emissions of SO2, NOx, and particulate matter (PM). SO2 and NOx belong to the pollutants of major elements, with PM pertaining to the solid products. Control technologies for the above three pollutants, such as flue gas desulfurization, selective catalytic reduction, and electrostatic precipitators, have been proven to be highly efficient at removing the abovementioned pollutants in practical settings. The emission and control of Hg pollutants have also been extensively studied. However, control technologies for pollutants from trace elements, including Cd, Cr, Pb, Se, and As, which are also hazardous to long-term human health and the ecosystem, must be further developed both experimentally and theoretically. As a first step in future studies and analyses, the development of accurate and reliable methods for generating trace element pollutants is extremely important for the development of their future control technologies. In this paper, different ways of generating trace elements pollutants in simulated flue gas have been summarized and compared, including solution evaporation, combustion, sublimation, and hydride oxidization methods. The detailed procedures of these methods have been presented, and the advantages and disadvantages of each method have been discussed in detail. The findings indicate that the solution evaporation method is simple and feasible, but includes water vapor and other possible gaseous by-products that will have a negative effect on the results of subsequent experiments. The combustion method offers a realistic simulated flue gas, although factors related to the fuel or combustion conditions might influence the results and the product constituents are somewhat complex. The sublimation and hydride oxidation methods provide the most accurate trace element pollutants, but they are only suitable for the generation of certain types of gaseous trace pollutants and the installation of the hydride oxide apparatus is complicated. The applicability of these methods has also been discussed carefully in this study. A joint method for generating trace element pollutants has been proposed to obtain results that are closer to the actual situation and more precise than those obtained using any single method.

     

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