Experimental Study On The Removal Of Arsenic In Flue Gas

The air pollution in China can be geared to typical coal-smoke pollution,in which pollutants produced in the combustion process,such as SO₂,NO_x,particulates,trace heavy metals,VOCs,have severely impaired the ecological environment and human health.Listed as the first category of carcinogens by the international agency for research on cancer,arsenic is one of the most volatile harmful trace elements in coal,which should attract serious attention of people.Relatively there is a lack of research on the arsenic pollution control in coal-fired power plants.Hence the development of the process for arsenic removal with less investment,lower running cost and environmental friendly,has a very important significance for the removal of arsenic in coal-fired power plants and the ultimate realization of a variety of pollutants removal.Based on large investigations,the experimental programs and apparatus of arsenic removal were prepared.Screening various suitable oxidants,the complex oxidant was made for arsenic removal with H₂O₂ as the fundamental substance and Na₂S₂O₈ as the addition agent.And the effects of the concentration ratio of the complex oxidant and reaction conditions on the arsenic removal efficiency were investigated through a self-design experimental platform,and then the optimal experiment conditions for the complex oxidant were established.The optimal experiment conditions were that the molar ratio of Na₂S₂O₈ and H₂O₂ was 0.01/1?mol/mol?,complex oxidant pH was 5.5,reaction temperature was 50?,simulated flue gas flow was 1.0L/min,arsenic concentration at the entrance was 0.421 mg/m³,and the obtained arsenic removal efficiency was 96.3%.Simulating the actual conditions of coal-fired power plants,it was investigated that the influences of the concentration of O₂,CO₂,SO₂ and NO on the arsenic removal efficiency.It was shown by experimental results that: with the increase of the concentration of O₂ and CO₂,the efficiency of arsenic removal was almost unaffected;purification efficiency decreased as SO₂ concentration elevated;and with the concentration of NO increase,the arsenic removal efficiency had a slow upward trend after an initial decrease.According to the characterizations of reaction products by AFS,HPLC-HG-AFS and XRD,the product of dearsenization was identified as calcium arsenate.And then the reaction mechanisms of H₂O₂/Na₂S₂O₈ complex oxidant removing arsenic were speculated according to the characterizations results and related references.