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

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, NO_x, and particulate matter (PM). SO₂ and NO_x 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.