Absorption of nitrogen dioxide via a non-packing scrubber using a sulfite/thiosulfate complex absorbent

The conventional packing-type scrubber was found to exhibit high efficiency in treating exhaust gases. However, achieving effective performance requires large surface areas of packing materials, leading to a substantial pressure drop and a large energy consumption. Therefore, the present study demonstrates the advantages of a non-packing scrubbing system and investigates the effect of thiosulfate (S₂O₃^2-) ion on NO₂ absorption using a sulfite solution. The efficiency of the system with 0.1 M Na₂SO₃ solution increased substantially upon the addition of 0.1 M Na₂S₂O₃ and maintained an efficiency of 90 % over extended periods. It also improved the absorbent oxidation ratio of O₂ to NO₂ from 13.6 to 3.9 mol O₂ (mol NO₂^-1) because the Na₂S₂O₃ was regarded as an effective oxidation inhibitor. Therefore, the total chemical usage for 450 min was lowered by a factor of 11.3 (to 0.192 mol d^-1) when 0.1 M Na₂S₂O₃-assisted 0.1 M Na₂SO₃ solution was used. This analysis showed that the addition of S₂O₃^2- ion can improve the NO₂ removal efficiency and lower the chemical usage. In addition, because the implementation of the PHRS substantially reduces the pressure drop below 0.01 hPa in the scrubbing system, the cost-effective adaptation of the PHRS is feasible.