Simultaneous Removal of SO₂ and NO Using H₂O₂/Urea Activated by Vacuum Ultraviolet Light in a Pilot-Scale Spraying Tower

Abstract

A study on simultaneous removal of SO 2 and NO from flue gas using H 2 O 2 /urea activated by vacuum ultraviolet (VUV) light was carried out in a pilot-scale photochemical spraying tower. The effects of different operational variables on simultaneous removal efficiencies of SO 2 and NO were investigated. The gaseous and liquid removal products were detected by the flue gas analyzer and ion chromatography (IC), respectively. The removal pathways of SO 2 and NO were analyzed. The application prospect of this new method was also preliminarily discussed. Results show that under most of the process conditions tested, SO 2 can attain complete removal. Removal efficiency of NO is enhanced under increasing the VUV irradiation intensity and H 2 O 2 concentration, but it is inhibited by an increase of the flue gas flow and NO concentration. The urea concentration and liquid−gas ratio have a dual influence on NO removal, and its removal efficiency increases first and then decreases. SO 2 concentration has little impact on NO removal. IC results show that SO 4 2− and NO 3 − are the main removal products in solution. • OH derived from VUV activation of H 2 O 2 plays the crucial role in NO removal.

Comparison of various chemical compounds for the removal of SO2 and NOx with wet scrubbing for marine diesel engines

“…H 2 O 2 was not effective in oxidizing NO to NO 2 in this study. On top of using a high concentration, studies involving H 2 O 2 usually required some sort of activation either with UV radiation or ozone (Wen et al 2019 ; Xie et al 2019 ). Without these, it can be seen that H 2 O 2 was inferior compared to other types of chemical oxidants of the same concentration studied here.…”

“…Out of these, a significant amount of work focused on gas–liquid reactions where strong oxidizing agents were used to oxidize NO to a more soluble NO 2 form. The more common chemical compounds studied included chlorine-based oxidizing agents such as chlorite and hypochlorite (Brogren et al 1998 ; Chien and Chu 2000 ; Chu et al 2003 ; Deshwal and Lee 2009 ; Gong et al 2020 ; Jin et al 2006 ; Mondal and Chelluboyana 2013 ; Park et al 2015 ; Wei et al 2009 ; Yang et al 2018 ; Zhao et al 2010 ; Zhao et al 2011 ; Zhao et al 2015 ; Zhao et al 2016 ), permanganates (Brogren et al 1997 ; Chu et al 2001 ; Fang et al 2013 ), ozone (Han et al 2020 ; Kang et al 2020 ; Lin et al 2016 ; Shao et al 2019 ; Sun et al 2017 ; Sun et al 2015 ), and hydrogen peroxide (Liu et al 2014 ; Liu and Zhang 2011 ; Wen et al 2019 ; Wu et al 2018 ; Xie et al 2019 ).…”

Comparison of various chemical compounds for the removal of SO2 and NOx with wet scrubbing for marine diesel engines.

“…H2O2 was not effective in oxidizing NO to NO2 in this study. On top of using a high concentration, studies involving H2O2 usually required some sort of activation either with UV radiation or ozone (Wen et al 2019;Xie et al 2019). Without these, it can be seen that H2O2 was inferior compared to other types of chemical oxidants of the same concentration studied here.…”

“…Already in the R&D scene, there are many upcoming methods for treating SOx and NOx simultaneously (Chang et al 2004;Chu et al 2001;Cui et al 2018;Cui et al 2019;Deshwal et al 2008;Fang et al 2013;Fang et al 2011;Han et al 2019;Hao et al 2017;Hao et al 2016;Kang et al 2020;Kang et al 2018;Liémans and Thomas 2013;Liu et al 2014;Liu et al 2018;Mondal and Chelluboyana 2013;Park et al 2015;Wang et al 2015;Xi et al 2020;Xie et al 2019;Yan et al 2020;Yang et al 2016;Yang et al 2018;Zhao et al 2010;Zhao et al 2015). Apart from the marine sector, the industry involving land-based small and medium sized coal-fired boilers are also actively researching this area due to shortcomings encountered in existing control technologies (Kang et al 2020;Shao et al 2019;Sun et al 2015;Wu et al 2018;Xie et al 2019). A significant portion of research in this area is focused on finding a powerful oxidizing agent that can be added into the scrubber so that NO gas can be simultaneously scrubbed along with SO2.…”

Combining ozone and UV-light for energy efficient removal of SOx in low-temperature flue gas

“…Advanced oxidation processes (AOPs) that use hydroxyl radicals ( OH) for water purification and disinfection have been employed for wastewater treatment for over three decades [16,17]. Recently, this knowledge has been applied to the gas-phase removal of exhaust gas pollutants with notable success [18,19,20]. Here, direct exposure of the primary oxidant, usually hydrogen peroxide (H 2 O 2 ), to ultraviolet (UV) light at a particular wavelength creates OH.…”