Research Of The Reactions Of H₂S And O₂ In Flue Gas

Fire flooding is one of the important measures to increase production in heavy oil reservoirs,and a large amount of gas will be produced in the process of fire flooding.During the whole process of fire flooding,the composition of the produced gas changes continuously with the mining time.H₂S and O₂ react to form sulfur during the pressurization process of fire flooding gas reinjection compressor.When passing through the air cooler,the sulfur condenses to the pipe wall in solid state,causing blockage of the air cooler.Therefore,the study of the reaction between hydrogen sulfide and oxygen is of great significance to pay attention to the problems encountered in the large-scale experiment of fire flooding gas return in oil field.In this paper,the reaction of hydrogen sulfide with oxygen was studied by means of molecular simulation and experiment.According to the actual composition of the gas produced by fire flooding,a 3D periodic model was established.The kinetic parameters of hydrogen sulfide reaction with oxygen at different temperatures and pressures were simulated by using the molecular dynamics method based on Reax FF reaction force field.It was found that the kinetic equation of H₂S oxidation under simulated conditions(30??150?,no catalyst and two components)was very accurate,which proved that the reaction was first-order reaction,and the activation energy of hydrogen sulfide reaction was 187 k J/mol.The orthogonal simulation of two components shows that the composition is the most important factor affecting the reaction of H₂S and O₂,the pressure is the second,and the temperature has the least effect on the reaction.The reaction mechanism of hydrogen sulfide with oxygen can be directly obtained by statistical analysis of the dynamic simulated trajectory in the reaction kinetics.At the same time,the space configurations of three kinds of hydrogen sulfide and oxygen molecules were obtained by quantum mechanics calculation and density functional theory method,and the lowest energy position was selected to calculate the quantum mechanics.It is concluded that hydrogen sulfide and oxygen react to form the minimum unit S₂ of elemental sulfur,which requires a five-step reaction and a comprehensive exothermic heat of 421 k J/mol.Among the five elementary reactions,the highest energy barrier appeared in the fourth step of the reaction,and the exothermic reaction reached 182 k J/mol.Then the S₂ would continue react to form S₈.The reaction process of forming stable structure sulfur is all heating reaction.According to the simulation results,in order to obtain the influence of various factors on the reaction,we also carried out the orthogonal experiment and the fifteen groups of kinetic data were obtained.Under this experimental condition(30??150?,no catalyst in flue gas),the reaction of hydrogen sulfide with oxygen is the first order reaction,which is consistent with the simulated results.The activation energy of hydrogen sulfide reaction is 197k J/mol.Temperature has the greatest effect on the reaction,the second is the composition,and the pressure has the least effect on the reaction.At last,through the comparison of experiment and simulation calculation,it is concluded that temperature has a great influence on the reaction between hydrogen sulfide and oxygen.The conversion of the reaction increases with the increase of temperature.The conversion decreases with the increase of pressure at low temperature.Sulphur is most difficult to form at pressure of 14 MPa?20 MPa and temperature of30?.It can guide cooling treatment and pressurizing treatment before flue gas reinjection.In this way,the influence of sulphur formation on the injection process can be avoided.