Study On The Removal Of Carbonyl Sulfur From Coke Oven Gas By Dielectric Barrier Discharge With Cu-Cd/γ-Al₂O₃

Coke oven gas is rich in H₂,CO,CH₄,etc.has great application value,but coke oven gas exists carbonyl sulfide（COS）and other sulfide-containing impurity gases,COS has the characteristics of low reactivity,long life,etc.,which is more difficult to remove than other sulfide-containing gases.COS not only affects the quality of chemical products,causing damage to the environment,but also affects human organs to some extent.Among the existing technologies for COS removal,low temperature plasma has the advantages of reaction temperature close to room temperature,better adaptability to polluting gases and higher conversion rate.Therefore,Dielectric barrier discharge（DBD）plasma synergistic catalyst was used to remove COS from coke oven gas.In this paper,Dielectric barrier discharge plasma was used in synergistic catalyst to remove COS from coke oven gas.Through catalyst screening,Cu-Cd/γ-Al₂O₃ catalysts with good catalytic activity and elemental sulfur selectivity were obtained,and in-depth research was carried out,mainly investigating the effects of four systems:DBD plasma alone,Cu-Cd/γ-Al₂O₃ thermal catalytic hydrogenation,Cu-Cd/γ-Al₂O₃ catalyst-coupled DBD plasma and Cu-Cd/γ-Al₂O₃photocatalytic on COS removal under hydrogen atmosphere,and the effects of different active components,loading and roasting temperature were also studied,Effects of COS concentration,airspeed,humidity and oxygen concentration on the removal of carbonyl sulfur from coke oven gas by DBD plasma and Cu-Cd/γ-Al₂O₃ catalyst.The surface material changes of Cu-Cd/γ-Al₂O₃catalysts were analyzed by XRD,XPS,BET and other characterizations,and the mechanism of COS removal by dielectric barrier discharge and Cu-Cd/γ-Al₂O₃ catalyst was discussed by plasma in situ infrared detection,optical fiber spectrometer and gas chromatography detection results.The experimental results and conclusions are as follows:Firstly,the products generated by COS in DBD plasma in the absence of catalyst were studied and found to have by-products of H₂S,CO and CO₂ generation and highly selective generation of singlet sulfide.The Cu-Cd/γ-Al₂O₃ catalysts with high activity,inhibition of H₂S generation and high selectivity for the generation of singlet sulfide were prepared by screening different carriers,active components,loading amounts and roasting temperatures.Among them,γ-Al₂O₃ has the highest catalytic activity with 98.37%COS removal efficiency at low SED and can effectively inhibit the generation of H₂S.The Cu-Cd/γ-Al₂O₃ catalyst with a roasting temperature of 450°C and a loading of 7.5 wt.%Cu and 5 wt.%Cd had the best COS removal efficiency,achieving over98%COS removal efficiency within 7.5 h with no H₂S generation and highly selective generation of singlet sulfide.The heat and UV light generated by the plasma did not have a significant effect on the COS removal efficiency.Secondly,the effects of COS concentration,reaction airspeed,relative humidity and oxygen concentration on the COS removal efficiency of the Cu-Cd/γ-Al₂O₃ catalyst were investigated.It was found that the COS removal efficiency decreased with increasing COS concentration in the range of 250-1000 ppm,and was highest at 250 ppm,which was close to 100%.The COS removal efficiency decreased with increasing air velocity in the range of 5000-20000 h^-1 and was only 91.11%at an air velocity of 20000 h^-1 and low SED.In addition,the COS removal efficiency was not greatly affected by humidity in the range of 15-65%and oxygen in the range of 0.2-0.8%,indicating that the catalyst has good resistance to water and oxygen.In a study in simulated coke oven gas,it was found that 50%H₂ concentration had some effect on COS removal,but did not affect the inhibition of H₂S by the Cu-Cd/γ-Al₂O₃ catalyst.the addition of CO had some effect on COS removal,especially at 9%CO concentration,COS removal efficiency decreased by about35%,but the catalyst was effective in inhibiting H₂S production.The simultaneous addition of CO and O₂ can effectively improve the COS removal efficiency.Finally,the surface states,lattice spacing and other properties of theγ-Al₂O₃,Cu/γ-Al₂O₃,Cd/γ-Al₂O₃ and Cu-Cd/γ-Al₂O₃ catalysts were characterised and analysed,confirming that the introduction of Cu and Cd did not affect the crystal structure ofγ-Al₂O₃ and that Cu₂S,Cu S and Cd S were formed on the catalyst surface.in addition,with the large amount of singlet sulphur deposition made the catalyst mesopores blocked and a large number of HS groups were generated,which was the reason for the partial H₂S generation after the long-term reaction.