A review of removing SO2 and NOX by wet scrubbing

Zhao, Mengjing; Xue, Peng; Liu, Junjie; Liao, Junhua; Guo, Jiamin

doi:10.1016/j.seta.2021.101451

Cited by 29 publications

(25 citation statements)

References 83 publications

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“…One alternative NO x reduction strategy is based on absorption in aqueous solutions. 14,15 The solubility of NO in water is low, but various additives have been investigated to improve the solubility and removal of NO. 16−20 Alternatively, to the direct absorption of NO, NO can be selectively oxidized to NO 2 , which has a higher solubility in water.…”

Section: Introductionmentioning

confidence: 99%

“…One alternative NO x reduction strategy is based on absorption in aqueous solutions. , The solubility of NO in water is low, but various additives have been investigated to improve the solubility and removal of NO. − Alternatively, to the direct absorption of NO, NO can be selectively oxidized to NO 2 , which has a higher solubility in water. ,, NO can be selectively oxidized to NO 2 by, e.g., ClO 2 , NaClO, NaClO 2 , NaClO 3 , O 3 , etc. − However, even with the higher solubility of NO 2 , NO 2 absorption rates may be too low. Various chemical compounds have been investigated as additives to further improve the absorption rates of NO 2 .…”

Section: Introductionmentioning

confidence: 99%

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Role of Sulfite Oxidation in NO₂ Absorption in a pH-Neutral Scrubber Solution

et al. 2022

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Nitrogen dioxide (NO2) absorption in aqueous sulfite solutions has recently gained more attention to reduce NO x emissions. The NO2 removal efficiency is strongly influenced by the competing reactions of NO2 absorption and sulfite oxidation. The present study investigates the role of sulfite oxidation in NO2 absorption at neutral pH. The effects of sulfite concentration, thiosulfate, pH, NO2 inlet concentration, oxygen concentration on NO2 absorption efficiency, and sulfite oxidation rates were investigated under well-controlled conditions at 25 °C in a laboratory-scale wet scrubbing system. NO2 absorption rates showed a strong dependence on the sulfite concentration and increased linearly with increasing NO2 inlet concentrations between 25 and 150 ppm. At the highest investigated sulfite concentration, 20 mM, the NO2 removal efficiency was around 80%. Oxidation rates of sulfite during NO2 absorption in the presence of 5 vol % O2 increased with increasing sulfite concentrations in the scrubbing solution and ranged from 20 mg·L–1·min–1 with 1 mM sulfite to 200 mg·L–1·min–1 with 20 mM sulfite. The oxidation rate decreased significantly when thiosulfate was added, while the oxidation rates were independent of the oxygen concentration between 2–10 vol % O2. The NO2 absorption rate decreased with decreasing pH between pH 6 and 8 proportionally to the sulfite concentration as predicted by the sulfite–bisulfite equilibrium. The implication from these results is that significantly less sulfite feeding is needed in industrial NO2 absorption if the pH can be maintained at neutral pH, instead of lower pH such as in simultaneous SO2 and NO2 scrubbing.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Role of Sulfite Oxidation in NO₂ Absorption in a pH-Neutral Scrubber Solution

et al. 2022

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“…NO 2 absorption in aqueous sulfite solutions has recently gained more attention in order to reduce NO x emissions from thermal conversion of non-recyclable waste and fuels with high nitrogen contents. − The NO x in flue gases consists mostly of NO. Due to the low solubility of NO in water, NO is oxidized to NO 2 which has a higher solubility in water. , NO 2 reacts with water forming nitrite and nitrate (see R ).…”

Section: Introductionmentioning

confidence: 99%

Role of Thiosulfate in NO₂ Absorption in Aqueous Sulfite Solutions

Schmid

Hupa

Paavola

et al. 2022

Ind. Eng. Chem. Res.

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NOx emissions continues to be a major challenge in order to reduce the environmental impact of thermal conversion of non-recyclable waste and fuels with high nitrogen contents. Oxidation of NO to NO2 followed by absorption of NO2 in aqueous solutions with sulfur compounds as additives has recently gained more attention in order to reduce NOx emissions from flue gases. One major challenge in NO2 absorption is the high consumption of sulfite, requiring sulfite oxidation inhibitors such as thiosulfate. The present study clarifies the chemistry and consumption of thiosulfate in wet scrubbing of NO2 with buffered solutions under well-controlled conditions at neutral pH at 25 °C. Absorption rates for the reaction of thiosulfate and NO2 in the scrubber were determined, and the ability of thiosulfate to inhibit the sulfite oxidation was investigated and quantified. With 1 mM thiosulfate (no sulfite) in the scrubber solution, the NO2 absorption rate increased by 30% as compared to pure water and by 160% with 100 mM thiosulfate. The absorption rate increased with time in the presence of oxygen. With 1 mM sulfite (no thiosulfate), the initial NO2 absorption rate increased by 200% as compared to pure water. However, the absorption rate decreases significantly after short periods of time due to the high consumption of sulfite through undesired oxidation by O2. In tests with sulfite and thiosulfate as an oxidation inhibitor, high removal efficiencies could be maintained over extended periods of time. With a 10 mM sulfite solution, 1 mM thiosulfate decreased the sulfite oxidation rate from 130 to 31 mg·L–1·min–1, and 2 mM thiosulfate decreased the rate to 16 mg·L–1·min–1. For the investigated conditions, the consumption of thiosulfate did not change significantly when higher sulfite concentrations were used. The results of the study demonstrate high NO2 absorption rates for low concentrations of sulfite and thiosulfate at neutral pH.

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“…These pollutants in a certain range significantly affect human health, such as the body's respiratory system, especially in children and the elderly 8) . Meanwhile, the concern for the environment is acid rain resulting from photocatalytic reactions produced by air pollutants above, especially NOx gas 9) . Among several types of Nitrogen Oxides, the gases most found in atmospheric air are Nitrogen Monoxide (NO) and Nitrogen Dioxide (NO2), where Nitrogen Monoxide takes up a percentage above 80% of NOx gas 10) .…”

Section: Introductionmentioning

confidence: 99%

The Feed Gas Flow Effects on the NOx Removal Performance through the Polyvinylidene Fluoride Hollow Fiber Membrane Module using H_2O_2 and HNO_3 as an Absorbent

Purnawan¹,

Wibowo²,

Ramadhani³

et al. 2022

Evergreen

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Nitrogen oxides (NOx), which can be found in the combustion process of coal-fired power plants, are pollutant gases that are dangerous to the environment and human life. The conventional technology used the dry method such as SCR (Selective Catalytic Reduction) and SNCR (Selective Non-Catalytic Reduction) to clean the gas stream from NOx contents. Alternatively, the polyvinylidene fluoride (PVDF) membrane module can be utilized to remove the NOx using oxidant solutions to absorb the NOx. The study aims to investigate the performance of the PVDF hollow fiber membrane module (HFMM) in removing NOx using absorbent solutions consists of H2O2 and HNO3. Throughout the experiment, the feed gas having 600 ppm NOx in nitrogen was introduced to the membrane fiber, then diffused in the pores of membrane to the outer surface of the fiber in the shell side of the HFMM, where the reaction between oxidant and NOx took place. The experimental results revealed that the efficiency of NOx elimination declines as the feed gas flow rate is increased. This study's maximum NOx reduction efficiency was 99.8%, at a 100 cm 3 /min feed gas flow.

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A review of removing SO2 and NOX by wet scrubbing

Cited by 29 publications

References 83 publications

Role of Sulfite Oxidation in NO₂ Absorption in a pH-Neutral Scrubber Solution

Role of Sulfite Oxidation in NO₂ Absorption in a pH-Neutral Scrubber Solution

Role of Thiosulfate in NO₂ Absorption in Aqueous Sulfite Solutions

The Feed Gas Flow Effects on the NOx Removal Performance through the Polyvinylidene Fluoride Hollow Fiber Membrane Module using H_2O_2 and HNO_3 as an Absorbent

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A review of removing SO2 and NOX by wet scrubbing

Cited by 29 publications

References 83 publications

Role of Sulfite Oxidation in NO2 Absorption in a pH-Neutral Scrubber Solution

Role of Sulfite Oxidation in NO2 Absorption in a pH-Neutral Scrubber Solution

Role of Thiosulfate in NO2 Absorption in Aqueous Sulfite Solutions

The Feed Gas Flow Effects on the NOx Removal Performance through the Polyvinylidene Fluoride Hollow Fiber Membrane Module using H_2O_2 and HNO_3 as an Absorbent

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Resources

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Role of Sulfite Oxidation in NO₂ Absorption in a pH-Neutral Scrubber Solution

Role of Sulfite Oxidation in NO₂ Absorption in a pH-Neutral Scrubber Solution

Role of Thiosulfate in NO₂ Absorption in Aqueous Sulfite Solutions