Study On Distribution Law And Harmful Control Of Harmful Gas In Urban Sewage Discharge Pipeline

With the acceleration of China’s urbanization process, the urban population are growing with each passing day, a large number of sewage, manure and other waste accumulate and ferment in the underground sewage pipeline, producing large amounts of harmful gases, such as carbon dioxide, methane, hydrogen sulfide, etc. Safety accidents in recent years about the drainage pipes,caused by harmful gases occurs frequently. Therefore, It is necessary to study the harmful gases distribution law of the underground sewage pipe and the damage control measures.At present, the domestic and foreign research on the underground sewage pipelines harmful gases, are mostly about gas detection, gas spillover law, gas production capacity calculation, gas early warning model research, etc. The study of the distribution law of harmful gas in sewage pipe is very little, and there has no people to explore the diffusion rule and the risk control measures from the angle of ventilation. Therefore, Based on the previous studies, first of all, this paper make more detailed research on harmful gas distribution of the underground sewage pipes, then it makes more detailed research on the diffusion of harmful gas in the pipeline and the control measures by Ventsim software.This topic comes from the National Natural Science Foundation of China "Explosion mechanism and prevention of oil and gas misture in urban drainage culvert". This paper mainly adopts the method of field measurement method, theoretical analysis method, the control variable method, the ideal model, Origin data processing software, Ventsim software simulation, the innovations and the main conclusions of this article are:(1)the V=AVo+B (V is the diffusion speed of pollutants in underground sewage pipes,Vo is the speed of air flow rate of underground sewage pipes; Among them, A, V and B is constant, it has no tie to the position of the pollutant source changes, the initial release of pollution source, the sewage pipe’s shape and cross-sectional area).(2)Increasing the air volume of the underground sewage pipe on the wind or opening the manhole cover of each district at the intersection can speed up the flow of harmful gases in sewage pipes, in case of harmful gas gathered in the sewage pipe.(3)Opening a regional manhole cover can effectively accelerate the diffusion of harmful gas of the region sewage pipe, and in a certain range, the more the increase of the number of the opened manhole cover, the better the effect of diffusion of harmful gas.(4) Under the condition of keeping the underground sewage pipe cross-sectional area unchanged, compared with the square pipe, arched pipe and irregular shape pipe, the circular sewage pipe is most beneficial to the diffusion of harmful gas of the underground sewage pipe.(5) Simulate the present situation of ventilation of underground sewage pipes,and we can found where is of poor ventilation and where is capable of accumulating the harmful gas, it provides a basis for the safety hazard investigation and the implementation of control measures.