Removal of NO from flue gas using heat-activated ammonium persulfate aqueous solution in a bubbling reactor

Abstract

Ammonium persulfate aqueous solution was used for the first time for NO removal from flue gas in a bubbling bed due to its low cost compared with other persulfate salts (sodium persulfate, potassium persulfate and ammonium persulfate). The effects of ammonium persulfate concentration, solution temperature, initial pH value, additive concentration, NO concentration, O₂ concentration and SO₂ concentration on NO removal were investigated systematically. The increased pH had a significant and negative effect on NO removal. The optimal solution temperature was 50 °C and increased ammonium persulfate concentration greatly promoted the NO removal efficiency. Urea showed a better performance on NO removal efficiency than ammonium hydroxide. The NO concentration and O₂ concentration affected NO removal slightly while the increased SO₂ concentration weakened NO removal efficiency. NO generation in alkaline ammonium persulfate aqueous solution was detected. The detection of free radicals in ammonium persulfate solution using the HPLC method and the effect of O₂ concentration on NO generation was carried out with the initial pH value increased. Due to the reducibility of ammonia, the solution pH and O₂ concentration in the flue gas were proven to play a major role in NO generation using ammonium persulfate. The NO generation mechanism and the possible reactions in the aqueous solution were elucidated and speculated. The experimental results indicated that the proposed technology using heat-activated ammonia persulfate in acidic aqueous solution might be a feasible method for the NO removal from flue gas.