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

Abstract

A new technology (called here, spray-and-scattered-bubble technology) based on preozonation was designed and tested for simultaneous removal of SO 2 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 SO 2 /NOx removal in the spray zone and then undergoes further removal in the bubble zone. Factors that affect the simultaneous removal of SO 2 /NOx were investigated through lab-scale experiments, by varying the O 3 /NO molar ratio, liquid/gas ratio and the immersion depth. The results showed the removal of SO 2 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 SO 2 , for liquid/gas ratio of 4 dm 3 /m 3 or immersion depth of 100 mm. The O 3 /NO molar ratio had little effect on the SO 2 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 Nm 3 /h). Increasing SO 2 concentration in flue gas can promote the removal efficiency of NOx, but the SO 2 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 joint advantages of reducing emissions and saving energy.

Techno-Economic Evaluation of Co-Removal of NOx and SOx Species from Flue Gases via Enhanced Oxidation of NO by ClO2—Case Studies of Implementation at a Pulp and Paper Mill, Waste-to-Heat Plant and a Cruise Ship

“…Furthermore, Si et al performed experiments at pilot scale, 5000 Nm 3 /h, using a newly designed scrubber where SO 2 and NO x was removed using O 3 for oxidation of NO. They confirmed that increasing amount of SO 2 in the flue gas increases NO 2 absorption and they reached almost complete SO 2 absorption and >80% absorption of NO x [10].…”

Simultaneous Removal of SO2 and NO by O3 Oxidation Combined with Wet Absorption

“…Then, as the pH increased to 9, the removal rates increased to 80.40, 37.58, and 46.35%, respectively. This suggested that acidic conditions were not conducive to the removal of nitrogen oxides, which may be due to the fact that acidic conditions were detrimental to NO absorption and that nitrous acid may be accelerated under the strong acidic conditions (24). The optimum denitration efficiency was observed at a pH of 12.13.…”

“…23 Si et al studied a method of simultaneously removing NO x and SO 2 by using O 3 as an oxidant and a limestone slurry as an absorbent. 24 As the SO 2 concentrations increased from 2200 to 4500 mg/m 3 , the NO x removal efficiency increased by more than 10%.…”

Treatment of Flue Gas from an Infectious Waste Incinerator using the Ozone System

“…This work is primarily concerned with more serious applications of ozone gas generators with wet scrubbing technology in industries. (Wang and Zhong, 2016), such as carbon black drying kiln furnaces (Ma et al, 2016), marine emissions (Xi et al, 2019;Zhou et al, 2016), glass melting furnaces (Yamamoto et al, 2016), and pulverized coal boilers (Si et al, 2019).…”