| The leakage of gas containing H2S is more harmful than that of ordinary natural gas,so it is necessary to study the law of H2S gas leakage diffusion,which is of great significance to environmental protection and emergency repair.Because of the difference in physical properties between H2S and other components of natural gas,the diffusion of H2S natural gas in air is uneven.However,in previous studies,the gas containing H2S was considered as a single component gas,which could not accurately reflect the H2S diffusion concentration distribution.In view of the above problems,the paper carried out a study on the diffusion of natural gas containing H2S:(1)Based on the mechanism of gas diffusion,the diffusion coefficient matrix of multi component gas is first considered,and the interaction diffusion coefficient of two elements,the matrix of multicomponent diffusion coefficient and thermodynamic correction factor matrix are analyzed and studied.As for the CH4+H2S+ air system,the influence of molar fraction and pressure on MS diffusion coefficient matrix and thermodynamic correction factor matrix is studied,and the diffusion coefficient matrix of CH4+H2S+ Air system is obtained.Finally,the diffusion coefficient matrix of multicomponent gas containing H2S is obtained,which is the theoretical basis for the simulation of the leakage and diffusion.(2)Aiming at the diffusion of H2S natural gas in the air,two models have been established under a constant leakage source:one-component gas diffusion model,which considers natural gas containing H2S as one component and multicomponet gas diffusion model,which considers natural gas containing H2S as multicomponent.The difference of H2S concentration of distribution of these two models under a constant leakage source is compared.Then,the influence of pipeline transportation on H2S concentration distribution difference is studied,the difference of H2S concentration distribution between two models under different wind speed is discussed.The results show that the maximum error of the horizontal diffusion range of H2S critical concentration is 10.9 m under the two models,and the maximum error of the vertical diffusion range of H2S critical concentration is 24.8 m.The difference of H2S concentration under the two models indicates that one-component gas diffusion model cannot accurately represent H2S diffusion concentration distribution.(3)Aiming at the change of the leakage source in the actual process,the coupling model of pipeline leakage and air diffusion is established,and the relationship between leakage flow rate and pipe diameter,leakage aperture and pressure of pipeline was studied,and the pressure and leakage flow rate at different pipe pressure is analyzed.The distribution of H2S concentration at different time under different operating conditions when valve closes is studied,and the change of H2S concentration distribution at different time is explored.The results show that closing the valve leads to the decrease of pipe pressure,causing the leakage gas flow rate to decrease gradually,when the pipeline pressure is equal to the ambient pressure,the leakage flow rate is close to zero.The greater the difference between pipeline pressure and ambient pressure,the longer the flow rate reduces to zero.After closing the valve,the horizontal and vertical diffusion influence range of H2S are decreasing,and the extent of H2S horizontal and vertical diffusion decrease with the increase of pipeline pressure and ambient pressure in the same time.(4)In view of the actual complex environment of the pipeline and considering the environmental conditions,the method of establishing a three-dimensional leakage diffusion model for complex terrain is established.The distribution of H2S gas diffusion concentration in the complex terrain adopting multicomponent diffusion model is studied by an example,and the distribution of the surface H2S concentration at different time under different wind directions is compared.The results show that the maximum width of H2S diffusion over the critical concentration is smaller than that in the flat area because of the block of the complex terrain,and the difference between them is increasing with time.Under the combined action of topography and wind,the gas would diffuse along the wind direction,between the hills and the low lands.It has a guiding function for the actual rush repair. |
