Experimental Study On The Removal Of Arsenic In Coal-fired Flue Gas

Arsenic produced by coal-fired power plants have serious harm to human body and ecological environment and caused widespread concern.Hence,the removal of arsenic from coal-fired flue gas has become another hot topic of mercury emission control in China.Up to now,in order to remove arsenic in flue gas,the activated carbon adsorption method was mainly used at home and abroad,but the method exits the shortage of high cost operation and poor stability of the system.The fly ash adsorption method has significant impact on the internal factors,such as composition of fly ash and particle size,and the adsorption capacity of metal oxide method is greatly affected by the environment.Therefore,the development of the process for arsenic removal with less investment,lower running cost and environmental friendly,has become a very important topic in the air pollution control field.Based on large investigations and series of experiments,some oxidants for removal of arsenic were prepared in a self-designed bubbing reactor,including H2O2?NaCIO?NaClO2 and various complex oxidants including H2O2/Na2S2O8 and NaClO2/NaC10 were synthesized.And the effects of preparation conditions of oxidants,and then the optimal reaction conditions for the oxidant were established.(1)The optimal reaction conditions are that concentration of H2O2 is 0.2 mol/L,solution pH is 7.5,reaction temperature is 50 ? simulated flue gas flow is 1.0 L/min,arsenic concentration at the entrance is 427 ?g/m3,and the obtained removal efficiency is 92.6%for arsenic.(2)The optimal reaction conditions are that concentration of NaCIO is 0.1 mol/L,solution pH is 6.0,reaction temperature is 60 ?,simulated flue gas flow is 1.0 L/min,arsenic concentration at the entrance is 427 ?g/m3,and the obtained removal efficiency is 97.5%for arsenic.(3)The optimal experiment conditions are that concentration of NaClO2 is 0.1 mol/L,solution pH is 5.5,reaction temperature is 50 ?,simulated flue gas flow is 1.0 L/min,arsenic concentration at the entrance is 427 ?g/m3,and the obtained removal efficiency for is 85.8%for arsenic.(4)The optimal experiment conditions are that the molar ratio of Na2S2O8 and H2O2 is 0.01/1 mol/mol,complex oxidant pH is 5.5,reaction temperature is 50?,simulated flue gas flow is 1.0 L/min,arsenic concentration at the entrance is 427?/m3 and the obtained removal efficiency is 96.3%for arsenic.(5)The optimal experiment conditions are that the molar ratio of NaClO2 and NaClO is 0.01/1 mol/mol,complex oxidant pH is 5.5,reaction temperature is 50 ?,simulated flue gas flow is 1.0 L/min,arsenic concentration at the entralce is 427 ?g/m3,and the obtained removal efficiency is 100.0%for arsenic.According to the above studies,new kinds of methods to remove arsenic in flue gas was proposed.According to the characterizations of removal products determined by HPLC-HG-AFS,the reaction mechanisms of removal of arsenic was speculated.Based on the characterizations of products by HPLC-HG-AFS,the main products were As(V).