Enhancement Mechanism of SO2 on NO2 Removal by Calcium Hydroxide at Low Temperature

Oxidizing NO to more soluble NO₂ has been proposed as a promising method for enhancing NO removal in conventional FGD processes. In this paper, the roles of gas components (O₂, H₂O) and reaction temperature in NO₂ removal were discussed by comparing the NO₂ absorption characteristics in and without the presence of SO₂. It was found that the presence of SO₂ in the flue gas could enhance NO₂ removal. The effects of O₂, H₂O and reaction temperature had a high dependence on the presence of SO₂. Without the presence of SO₂, H₂O and O₂ concentration had negligible influence on NO₂ removal, while higher reaction temperature could accelerate NO₂ absorption. However, reaction temperature did not affect NO₂ removal in the presence of SO₂, and NO₂ removal increased with increasing relative humidity but decrease with O₂ concentration increasing.