Simultaneous removal of SO2 and NOx by a new combined spray-and-scattered-bubble technology based on preozonation: From lab scale to pilot scale

Tong Si, Chunbo Wang, Xuenan Yan, Yue Zhang, Yujie Ren, Jian Hu and Edward J. Anthony

Applied Energy, 2019, vol. 242, issue C, 1528-1538

Abstract: A new technology (called here, spray-and-scattered-bubble technology) based on preozonation was designed and tested for simultaneous removal of SO2 and NOx from power plant flue gas. It combines the advantages of the common spray tower and the jet bubble reactor, in which the flue gas experiences an initial SO2/NOx removal in the spray zone and then undergoes further removal in the bubble zone. Factors that affect the simultaneous removal of SO2/NOx were investigated through lab-scale experiments, by varying the O3/NO molar ratio, liquid/gas ratio and the immersion depth. The results showed the removal of SO2 and NOx can be significantly improved as compared to a separate spray column or bubble reactor, by as much as 17%, for the spray column and 18% for the bubble reactor for NOx and 11% for the spray column, and 13% for the bubble reactor for SO2, for liquid/gas ratio of 4 dm3/m3 or immersion depth of 100 mm. The O3/NO molar ratio had little effect on the SO2 removal, but it strongly affected the removal efficiency of NOx especially when it was less than 1.0. Both the liquid/gas ratio and immersion depth demonstrated a positive correlation with the removal efficiency. However, a balance must be maintained between efficiency and economics, since the liquid/gas ratio directly influences the performance and number of the circulating pumps, and the depth is closely related to the flue gas pressure drop, and both factors affect energy requirements. To further confirm its industrial feasibility, a 30 h test using real coal-fired flue gas was conducted in a pilot-scale experimental facility (flue gas volume of 5000 Nm3/h). Increasing SO2 concentration in flue gas can promote the removal efficiency of NOx, but the SO2 removal was almost complete under all conditions tested. Finally, taking a 300 MW unit as an example, the total energy cost of this new technology is estimated as being 10% lower than that of the common spray tower technology, based on an analysis using Aspen Plus™, with the largest difference reflected in the energy requirements of the circulating pumps and the ozonizer. Over all, the new technology offers the collaborative advantages of reducing emissions and saving energy.

Keywords: Simultaneous SO2 and NOx removal; Wet scrubber; Spray-and-scattered-bubble; Energy consumption (search for similar items in EconPapers)
Date: 2019
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Citations: View citations in EconPapers (2)

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DOI: 10.1016/j.apenergy.2019.03.186

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