Co-absorption and Reduction Mechanism of SO2 and NO2 from Flue Gas Using a Na2SO3 Solution with an Oxidation Inhibitor

Herein, a novel Na2SO3 process enhanced with an oxidation inhibitor was proposed for the synergic removal of SO2 and NO2 from nonferrous smelting flue gas. The co-absorption and reduction characteristics and mechanism of SO2 and NO2 were investigated. Results showed that when 80.59, 161.17, and 241.76 mM Na2S2O3 was added into 2% of Na2SO3 solution, NO2 absorption capacity increased to 264%, 300%, and 330%, and that of SO2 increased to 162%, 198%, and 232%, respectively. The inhibition action of Na2S2O3 was achieved by reacting S2O32-with center dot SO3- to form an inert substance polythionate that prevents center dot SO3- from reacting with dissolved oxygen. The co-absorption and reduction characteristics of SO2 and NO2 revealed that similar to 42.5% of NO2(N) was reduced to N-2, 21.5% of NO2(N) combined with SO32- to form ONSO3- compounds, 5% of NO2(N) formed NO3- in solution, and 22.6% of NO2(N) was reduced to NO into flue gas. Therefore, the enhanced Na2SO3 process shows potential for synergistic desulfurization and NO2 removal from the nonferrous metal smelting industry.