Experimental Study On Increasing Mercury Removal Performance Of Activated Carbon By Loading Sulfur By Non-thermal Plasma

Elemental mercury（Hg⁰）from coal-fired flue gas is difficult to be removed due to its low solubility and high volatility.Activated carbon injection technology has been regarded as one of the most efficient ways to capture Hg⁰ in coal-fired flue gas.But the mercury removal efficiency of raw activated carbon is low.Some researchers put forward halogen impregnated methods to improve mercury removal performance.However,the modification process of impregnated methods is time-consuming and high energy consumption.Mercury adsorbed on the surface of modified AC by impregnated methods will be released under acid conditions.In view of the above factors,non-thermal plasma was applied to modify activated carbon in the presence of sulfur-containing gas.Then,the effect of modification conditions,flue gas components and adsorption temperature on Hg⁰ removal efficiency were investigated.Finally,the mechanism of Hg⁰ removal was analyzed.Activated carbon was first modified by non-thermal plasma in the presence of H₂S to investigate Hg⁰ removal performance.The experimental results showed that the non-thermal plasma treatment in the presence of H₂S increased the relative content of elemental S of activated carbon.The mercury removal efficiency of modified activated carbon increased with the enhancement of H₂S concentration during non-thermal plasma treatment process.When the modification time was 1min and adsorption temperature was 140℃,modified activated carbon had better mercury removal performance.The possible mechanism of mercury removal was that Hg⁰ reacted with elemental S which was produced by ionization of H₂S to form Hg S.To improve the mercury removal performance of activated carbon more effectively,this paper modified activated carbon with non-thermal plasma in the presence of H₂S and SO₂ to increase the content of elemental sulfur.The results showed that non-thermal plasma treatment could accelerate the reaction rate of H₂S and SO₂ to generate more elemental S on the surface of activated carbon.The most suitable non-thermal plasma treatment voltage and time were 3.0 k V and 1 min.When the mixed ratio of H₂S and SO₂ was 2:1,modified activated carbon had better mercury removal performance at 140℃.In summary,the mercury removal mechanism of the modified activated carbon（AC treated by non-thermal plasma in the presence of H₂S and SO₂）was investigated and it was that the elemental S which was generated by the reaction of H₂S and SO₂ reacted with Hg⁰ to form chemically stable HgS.