Removal of sulfur dioxide and nitrogen oxides by using ozone injection and absorption-reduction technique

摘要

A two-step process capable of removing NO_x and SO_2 simultaneously was proposed,which was made up of an ozonizing chamber and an absorber containing a reducing agent solution.Nitrogen oxides (NO plus NO_2)in most practical exhaust gases consist chiefly of NO.The injection of ozone into the exhaust gas gives rise to a rapid oxidation of NO to NO_2.Compared to NO,NO_2 has relatively high solubility in water,and it can readily be reduced to N_2 when the NO_2-rich exhaust gas is brought into contact with the reducing agent solution.Sodium sulfide (Na_2S)used as the reducing agent in this study can also remove SO_2,effectively.As the exhaust gas passed through the ozonizing chamber and the absorber sequentially,NO_x removal efficiency of about 95% and SO_2 removal efficiency of 100% were obtained.The formation of H_2S from sodium sulfide could be suppressed by using a basic reagent,together with the reducing agent.The rate of depletion of the reducing agent during the treatment of the exhaust gas was much faster than expected by reaction stoichiometry,obviously due to the oxygen in the exhaust gas.The amount of sodium sulfide required was found to be about four times the amount of NOX and SO_2 removed.