Experimental Study Of Plasma-catalytic Removal Of Hydrogen Sulfide Odor

In recent years,the problem of odor pollution in China has become increasingly prominent,which has seriously jeopardized human health and social livelihood.With the further improvement of regulatory standards,the control of odor pollution has drawn wide attention from all over the society.Among the odor pollutants,hydrogen sulfide has the characteristics of wide source,low olfactory threshold and great harm to the human body,and is the most important treatment.Plasma control technology has the advantages of convenient start-stop,fast response,large injection power and small floor space.It is especially suitable for the emission characteristics of typical hydrogen sulfide odor,high concentration,low concentration and strong odor.It has broad application prospects.In the previous studies,there were problems in understanding the mechanism path and strengthening means of plasma reactive groups,the use of plasma active groups was not efficient,and the energy efficiency was low.In this paper,the key steps and control methods for the efficient generation of reactive groups are studied by numerical simulation of plasma reaction history.The utilization of reactive groups is enhanced by comprehensive optimization of reactor design and operating conditions,and further enhanced by coupling of perovskite catalysts.Hydrogen removal effect.The main conclusions are as follows:The reaction history of the removal of hydrogen sulfide by corona plasma was simulated by various simulation methods.The multi-field coupling was used to solve the electronic characteristics,the overall electronic reaction and the simulation of the primary and secondary radical reactions after discharge.The study found that:The electron density near the anode is about three orders of magnitude higher.The discharge can be separated in two regions:most of the ionization occurs in an area less than 0.5 cm near the electrode.There is a strong electric field in the positive charge separation region that accelerates electrons to the energy that can ionize the background gas.Discharge occurred in 10^-8s,secondary electron excitation occurred in 10^-5s,and10^-4s discharge reached relative steady state.The region within 0.5 cm in the radial direction has a higher electron temperature and a stronger electric field.In areas outside the radial 0.5 cm,the electrons do not have enough energy to effectively ionize or attach to form an anion.The area outside the radial direction of 0.5 cm largely depends on the drift of the ions to the ground.The active group quenching reaction is mainly concentrated in 10^-710^-4s,and the ozone reaches steady state in 10^-3s.The quenching rate of the active group:OH>N>O,the oxide species play a key role in the process of pollutants reaction.N+OH?NO+H,O+HO2?OH+O2,OH+O?O2+H are key reactive group quenching reactions.By studying different input voltages,the influence of reactor outer diameter,air humidity and gas residence time on the volt-ampere characteristics of the plasma reactor was obtained.It is studied to remove hydrogen sulfide by plasma oxidization by a circular sawtooth electrode,and the arrangement of the high-voltage electrode disk sawtooth of the reactor is preferably selected.On this basis,the central composite design?CCD?method was used to study the effects of different plasma reaction conditions including discharge power,gas residence time and initial hydrogen sulfide concentration on plasma oxidation removal of hydrogen sulfide.The interaction between them was studied.It has been found that the smaller the diameter of the reactor,the lower the dizzying voltage and the breakdown voltage,and the lower voltage required to obtain the same specific corona current.The smaller the reactor diameter,the steeper the volt-ampere characteristic curve.The relative humidity of the air has a great influence on the volt-ampere characteristics.As the relative humidity increases,the corona voltage and the breakdown voltage decrease simultaneously,and the corona current increases at the same voltage.The stun voltage has little relationship with the gas residence time.As the residence time increases,the breakdown voltage gradually decreases,and the corona current decreases at the same voltage.The addition of the serrated tooth fitting can effectively increase the tip curvature of the discharge electrode,thereby enhancing the discharge of the plasma reaction region,thereby achieving the purpose of strengthening the electric field,thereby strengthening the electron reaction,generating more active radicals,and finally improving the reaction effect of hydrogen sulfide.In all of the electrical configurations screened by the experiment,the optimum disc electrode spacing was 15 mm,10mm,and 20 mm,respectively,when the outer diameters were 30 mm,40 mm,and 50 mm,respectively.As the density of the serrated electrodes increases,the processing efficiency tends to rise first and then decrease.Among the three,the reactor with a 40 mm outer diameter and a 10mm spacer circular sawtooth electrode has the best effect,while the 50 mm outer diameter reactor has a relatively poor relative effect.Through the comprehensive optimization of the influence of the response surface model,the obtained model has a high coefficient of determination?removal efficiency R²=0.9849,energy efficiency R²=0.9868?,and it can be considered that the regression model obtained has good fitting with the actual data.ANOVA results show that in the process of plasma degradation of hydrogen sulfide,discharge power is the most significant factor affecting the removal efficiency,and gas residence time is the most significant factor affecting energy efficiency.The process of oxidative removal of hydrogen sulfide by plasma-coupled LaMO3?M=Mn,Fe,Co?perovskite catalyst was studied.The effects of energy density,relative humidity and other factors on the removal efficiency of hydrogen sulfide and sulfur selectivity were investigated.Based on the analysis of by-products,the reaction of the plasma-coupled LaMO3?M=Mn,Fe,Co?catalyst for the degradation of hydrogen sulfide was proposed.The physical structure and redox characteristics of the catalyst were analyzed by various characterization methods such as BET,XRD,XPS and H2-TPR.It was found that the addition of LaMO3?M=Mn,Fe,Co?perovskite catalyst promoted the complete oxidation of formaldehyde in plasma environment.Compared with plasma alone,LaMO3?M=Mn,Fe,Co?perovskite catalyst greatly improved the degradation efficiency and sulfur selection of plasma oxidation degradation of hydrogen sulfide.Sex.When LaCoO3 catalyst is used,the effect of plasma degradation of hydrogen sulfide is the best,which can reach 96.4%at an energy density of 593.7J/L.The LaMO3?M=Mn,Fe,Co?perovskite catalyst has a non-stoichiometric effect.With the increase of the La/Mn molar ratio,the efficiency of plasma catalytic degradation of hydrogen sulfide decreases.The LaMO3?M=Mn,Fe,Co?catalyst has a smaller crystallite size than the LaFeO3 and LaMnO3 catalyst.The characterization results of the catalyst show LaCoO3 perovskite catalyst possess higher Oads/?Oads+Olat?and H2 consumption,which is benefit the plasma oxidation process to remove hydrogen sulfide.The by-products of the plasma-assisted LaMO3?M=Mn,Fe,Co?perovskite catalyst for the degradation of hydrogen sulfide are mainly S,SO2 and SO3.In the process of plasma degradation of hydrogen sulfide alone,the removal efficiency and sulfur balance of hydrogen sulfide increase with the increase of energy density.The addition of LaMO3?M=Mn,Fe,Co?perovskite catalyst further improved the sulfur balance and significantly inhibited the formation of by-products O3 and NOx,with inhibition levels of 32% and 21%,respectively.