Study On Application Of Atmospheric Pressure Microwave Plasma Torch In Hydrogen Production By Hydrogen Sulfide Decomposition

With the increasing demand for energy from oil,gas and coal in China,the safe exploitation of oil and gas fields containing H₂S has been put on the agenda gradually.Coal and petroleum processing enterprises will collect acid gas in different ways to meet industrial requirements to ensure personnel safety and reduce H₂S emissions.Taking the economic and environmental issues into accounts,the reutilization of H₂S is considered to be the best choice at present.Atmospheric pressure microwave plasma does not need expensive vacuum equipment,operates in high discharge stability,and is characterized by gas temperature suitable for the reaction in gas phase,so the study of gas modification with atmospheric pressure microwave plasma has been widely paid attention to.In this paper,the physicochemical process of hydrogen production from H₂S Decomposition by microwave plasma torch at atmospheric pressure is investigated.Firstly,the discharge of N₂-H₂S mixed gas in atmospheric pressure microwave plasma torch is studied,and the change of discharge morphology at various discharge conditions is presented.At the same time,the emission spectra of N₂-H₂S plasma discharge are acquired,and the variations of the emission intensity and characteristic molecular bands along the axial and radial direction are delivered.LIFBASE software is used to fit the CN Violet(0,0)band,thereby the characteristic gas temperature of N₂-H₂S plasma torch is determined to be 5900?300 K.Through analysis,it is concluded that the decomposition of H₂S is promoted by both thermal and ionization decomposition in the microwave plasma torch at atmospheric pressure.Furthermore,the composition of the tail gas after H₂S Decomposition is identified by Fourier Transform Infrared Spectrometer(FTIR),and the concentration of H₂ in the decomposed products of H₂S in the plasma torch is measured by means of gas chromatograph(GC).The conversion rate of H₂S into H₂ was calculated by the conservation of particle number from the measured concentration of H₂ in exhaust gas.Considering that the sulfur element products of H₂S decomposition in the plasma torch are deposited in a variety of solid compounds,the special cooling measurements are introduced in chemical reaction buffer room,the resulting effects by introducing a spiral water-cooling tube and a water-cooling cylindrical rod in chamber,respectively,are compared with the natural cooling from chamber wall.It is found that the introduction of the cylindrical water-cooling rod along the axial afterglow of plasma discharge has the best effect on obtaining more solid sulfide,inhibiting the reverse reaction and obtaining higher hydrogen conversion rate.Under the conditions of H₂S:N₂=1:9,gas flow rate of 10 L/min,discharge power of 1200 W,and distance of the end of cylindrical rod from discharge tube of 4 mm,the maximum concentration of H₂ in exhaust gas is achieved to be6.87%,and the corresponding H₂S conversion rate to H₂ is highest with value of 66.4%.Under the conditions of H₂S:N₂=1:9,gas flow rate of 20 L/min,discharge condition of 800 W,the distance of the end of cooling cylindrical rod from discharge tube of 11 mm,the lowest SER of H₂S Decomposition is 21.4 e V/molec,and when the discharge power is raised to 1800 W,the maximum yield of H₂ is obtained at the value of 1.065 L/min.