The Effect Of Pore Structure And Modified Of Activated Carbons On Mercury Removal In Flue Gas And Adsorption Mechanism

Mercury emissions from coal-fired power plants are believed to be the largest source of anthropogenic mercury emissions. Among the variety of potential methods for Hg capture, activated carbon injection as a viable, ready technology. The adsorption capacity of activated carbon come from high specific surface area and pore size distribution. There is not ideal absorption efficiency of activated carbons for mercury removal which results high price in industrial applications. As a result, it’s necessary to have a deep study about the properties of activated carbons in order to better mercury removal.In this paper, coconut shell, Taixi anthracite and Datong weakly caking coal are used as raw materials respectively to prepared activated carbons, which is aim to study the relationship between pore size distribution and ability of mercury removal of activated carbons. The effect of conditions, such as different raw material, burn off, activation media, preparation process on the adsorption properties, pore size distribution and the capability of mercury removal are investigated. Moreover, activated carbons modified with 0.5%KBr are investigated through compare the pore size distribution and capability of mercury removal with virgin activated carbons. The samples are characterized by nitrogen absorption-desorption, Fourier transform infrared spectroscopy and search engine marketing. The capacity Experiments were conducted to study the mercury adsorption capacity of activated carbons by using a bench-scale fixed bed. The research results shows:Compare the activated carbons from different raw material, YK activated carbons with highest SBET and pore size distribution, DT activated carbons with the second, TX with the least. Though for ability of mercury removal, YK is the worst, TX and DT with the same mercury removal ability. For the different burn off activated carbons, 50% of burn off activated carbon has the highest SBET and pore size distribution while 66% of burn off the least. The mercury removal results show that 50% of burn off activated carbon is the best; the activated carbons activation with steam is better than activation with carbon dioxide both on pore size distribution and mercury removal. Columnar activated carbon is richer than granular activated carbons in pore size distribution, granular activated carbon with higher initial removal efficiency, as the adsorption time goes on, removal efficiency decreased quickly while the columnar activated carbon decreased slowly. Activated carbons prepared with the same raw material, the ability of mercury removal is related with the pore volume of 0.61-1.0nm, the bigger V0.61-1.0, the higher ability of mercury removal. For activated carbons with different raw material, the effect of material is bigger than the pore volume.The result of activated carbons modified with KBr shows that: The modification process had no significant effect on the pore size distribution, the type of surface functional groups of activated carbons. Mercury results on fix-bed show that: Due to modified with KBr, the ability of mercury removal improved greatly. DT activated carbons modified with KBr has the best mercury removal performance while YK is the worst. For modified activated carbons with the same materials, the bigger specific surface area the better mercury removal performance.