Catalyst Facilitation And Reduction Effect In Plasma CF₄ Removal Process

Carbon tetrafluoride (CF4) is gaseous pollutants emitted from modern industries, because of it strong infrared absorption and long atmospheric lifetimes. Thus CF4 will cause strong greenhouse effect directly into the atmosphere. Microwave plasma, which is the new technology on decomposing CF4 from 1990. It is characteristic that the catalyst can improve the efficiency and energy utilization CF4, also can reduce the efficiency of by-products NO_X generation. So It is a very practical prospect of environment-friendly technology. In this investigation, the use of atmospheric pressure microwave plasma decompose CF4 with catalyst Al₂O₃,Ag/Al₂O₃,MnO₂/Al₂O₃ and MnO₂/2wt%Ag/Al₂O₃ respectively, and study on the impact of by-products NO_X. The results showed:(1) Introduction of catalyst Al₂O₃ did not influence to the by-products NO_X, and the concentration of NO_X from emission is in the 100ml/m³. However, catalyst Ag/Al₂O₃,MnO₂/Al₂O₃,MnO₂/2wt%Ag/Al₂O₃ play a significant role in the reaction, under the catalyst 2wt%Ag/Al₂O₃,2wt% MnO₂/Al₂O₃ or 2wt%/MnO₂/2wt%Ag/Al₂O₃ action, the DRE of NO_X is respectively 90%,89% and 98%. The loading Ag of catalyst sample NO_X alkali liquor absorption effect is better than the loading MnO₂, and the absorption is not obviously to the loading MnO₂. Three kinds of catalyst samples were without dropped significantly by using catalyst for long-time, so catalyst using life is good.(2) The CF4 decomposition that combined the atmospheric microwave plasma with Ag/ Al2O₃,MnO₂/Al₂O₃,MnO₂/2wt%Ag/Al₂O₃ catalyst respectively which were investigated: The DRE of CF4 reduced with increase the loading of Ag in the Ag/Al₂O₃ catalyst, and it dropped 19.5% when the loading of Ag increased from 0 to 4wt%. The loading of MnO₂ over catalyst carriers has obvious facilitation for CF4 decomposition. The DRE of CF4 reached 98.2%, which was the best effect over 2wt%MnO₂/Al₂O₃ catalyst, and reached 97.2% by 2wt%MnO₂/2wt%Ag/Al₂O₃.(3) The synergy of the atmospheric microwave plasma and 2wt%MnO₂/2wt%Ag/Al₂O₃ for CF4 decomposition was obvious effect. The DRE of CF4 was enhanced about 21.9% by the synergistic effect, and was 45.2% by plasma stimulation alone.The action decomposed CF4 which combined the atmospheric microwave plasma with catalyst, the highest energy efficiency for CF4 decomposition was 2.546g/kWh, and enhanced about 63.1% after adding catalyst.