Abstract
In this work, the feasibility of the simultaneous removal of NOx and SO2 through a simple process using a composite absorbent (NaClO2/Na2S2O8) was evaluated. Factors affecting the removal of NOx and SO2, such as NaClO2 and Na2S2O8 concentrations, solution temperature, the initial pH of solution, gas flow rate, and SO2, NO, and O2 concentrations were studied, with a special attention to NOx removal. Results indicate that a synergistic effect on NOx removal has been obtained through combination of NaClO2 and Na2S2O8. NaClO2 in the solution played a more important role than did Na2S2O8 for the removal of NOx. The above factors had an important impact on the removal of NOx, especially the solution temperature, the initial pH of the solution, and the oxidant concentrations. The optimum experimental conditions were established, and a highest efficiency of NOx removal of more than 80% was obtained. Meanwhile, tandem double column absorption experiments were conducted, and a NOx removal efficiency of more than 90% was reached, using NaOH solution as an absorbant in the second reactor. A preliminary reaction mechanism for NOx and SO2 removal was deduced, based on experimental results. The composite absorbent has the potential to be used in the wet desulfurization and denitration process, to realize the synergistic removal of multi-pollutants.
Highlights
NOx and SO2 released from the fossil fuels burning process, are becoming increasingly well-known as the precursors for photochemical smog and regional haze [1,2]
The results indicate that all oxidant solutions had a good level of efficiency of removal on SO2, where the removal efficiency was close to 100%
Different oxidant solutions had different effects on NOx removal, and the capacity on the NOx removal of three oxidant solutions was NaClO2 > KMnO4 > Na2S2O8, with the average NOx removal efficiencies being at 48.69%, 48.13%, and 23.98%, respectively
Summary
NOx (mainly NO) and SO2 released from the fossil fuels burning process, are becoming increasingly well-known as the precursors for photochemical smog and regional haze [1,2]. Coal-fired power plants, industrial boilers and furnaces are considered to be the main anthropogenic sources of these pollutants. Wet flue gas desulfurization (WFGD) technology and selective catalytic reduction (SCR) technology are the mature commercial technologies for controlling SO2 and NOx, and they are widely used in the flue gas treatment of power plant boilers in worldwide [3]. Flue gas pollutants emitted from power plant are being effectively controlled. WFGD technology is often used to control SO2 emitted from other industrial sources, such as industrial boilers and industrial furnaces; there is a lack of cost-effective NOx treatment technology. Due to the high investment and operating costs, a complicated system, and the large area required, the application of the SCR system in the field of industrial boilers and furnaces flue gas treatment is limited. It is urgent that a cost-effective NOx control technology is developed, and it is better to develop an economical, and simplified method to achieve synergistic removal NOx and SO2
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