Experimental Study On Catalytic Filter Media For Denitration And Chlorobenzene Decomposition

Nitrogen oxides（NO_x）and dioxins（PCDD/F）generated in the process of waste incineration power generation are discharged into the atmosphere,which will cause serious harm to the environment and human health.As a traditional industrial flue gas denitration technology,SCR can also oxidize and decompose dioxin and its precursor chlorobenzene when reducing NO_x,but the decomposition efficiency of SCR device is low when removing pollutants under low temperature and complex flue gas conditions.Fiber filter media have been widely used in the field of fine particle capture and removal.The preparation of composite catalytic fiber filter material by combining catalytic technology with filter material fiber,and the combined removal of dust,NO_x and dioxin with the existing dust removal device is one of the important ways to achieve low-cost and efficient collaborative treatment of multi pollutants in flue gas.Using Mn as basic element,Ti O₂ as carrier and Ce as promoter,the powder catalyst was prepared after calcination.Taking o-dichlorobenzene（1,2-DCBz）as the substitute of dioxin,the effects of preparation method,Mn loading,Mn/Ce ratio and flue gas composition on the efficiency of denitration and synergistic removal of chlorobenzene were studied on a fixed bed test bench,so as to determine the optimal catalyst formula.The activity of the catalyst prepared by sol-gel method is slightly higher than that prepared by impregnation method,both of which can achieve good catalytic efficiency at 200℃.The catalyst with a Mn/Ti ratio of 0.2 can achieve 100%denitration efficiency at 140℃,but the removal efficiency of chlorobenzene is less than 15%.The results show that the activity of the catalyst at low temperature is obviously improved after adding Ce element.Under the reaction conditions of Mn/Ce ratio of 0.5:0.5 and200℃,the catalyst can achieve 100%denitration and dechlorination efficiency.The increase of NH₃ content in flue gas is conducive to the improvement of denitration efficiency,but NH₃ will compete with 1,2-DCBz on the catalytic active site for adsorption,which has a certain inhibitory effect on the removal of 1,2-DCBz.P84 filter material has the best oxidation resistance and acid resistance.Under the same loading method,P84 can support more catalyst than PPS and glass fiber.The catalytic activity of the catalyst prepared by impregnation method is higher than that of the catalyst prepared by in-situ method.At 200℃,the catalytic filter prepared by impregnation method achieves 92.3%denitration efficiency and 92.1%dechlorination efficiency.By adding PTFE concentrated solution to the impregnation solution,only0.7%of the catalyst particles fall off from the modified impregnation method,while the catalyst particles fall off seriously from the in-situ method.Under the condition of220℃,the denitration efficiency of the enhanced catalyst decreased from 94.8%to94.4%.Therefore,the addition of PTFE has little effect on the catalytic activity of the filter media.The doping of Fe,Co and Cu can enhance the catalytic activity of the filter media in the absence of SO₂ and H₂O,but the catalytic activity varies greatly in the presence of different concentrations of SO₂.Under the condition of 150ppm SO₂,the denitrification and dechlorination performance of the three elements modified catalytic filter media are better than that of the unmodified catalytic filter media.When the SO₂concentration is increased to 300ppm and 450ppm respectively,only Fe modified catalytic filter media can maintain a denitration efficiency of more than 95%and a dechlorination efficiency of more than 90%at 200℃.Under the condition of the same H₂O vapor content in the flue gas,the higher the reaction temperature,the weaker the catalytic activity of H₂O on the catalytic filter material.When the reaction temperature is 200°C,the H₂O vapor concentration increases from 0vol.%to 4vol.%,and then to 12vol.%,and the denitration efficiency of the Mn-Ce-Fe catalytic filter decreases from 98.2%to 87.7%,and then further drops to74.1%,the dechlorination efficiency of benzene dropped from 96%to 93.2%,and then increased to 97.1%.H₂O inhibits the denitration effect of the catalytic filter,but there is a certain concentration range of H₂O,so that H₂O can promote the removal of Cl^-on the surface of the catalytic filter,thereby improving the performance of the catalytic filter to remove chlorobenzene.