Study On Model Of Sewage Pipeline Gas Safety Risk Assessment Of Chongqing City

As China’s economic development, urban capacity continues to expand, citysewers toxic flammable and explosive gases such as invisible time bomb at any timethreatening people’s lives and property safety, there is a serious safety hazard. Urbansewage pipes, due to the silting of sludge, industrial wastes and so on, easy to producetoxic and flammable and explosive gas, such as hydrogen sulfide, carbon monoxide,ammonia, methane and carbon dioxide. They are asphyxiating gas, can cause the bodyto hypoxia and death, especially hydrogen sulfide, the greatest harm to human body, aretoxic gases, high concentrations of hydrogen sulfide makes hyposmia, and instantly youcan make the poisoning, carbon monoxide and methaneflammable and explosive gas, itis easy to gather in the sewers explosion encountered in flame. In view of this situation,the establishment of a comprehensive risk assessment index system and improve therisk assessment model is particularly important.At present, domestic and international research on the safety of the sewage pipelinegas is still stuck in the rapid detection of the field or on-line monitoring, have not of theformation of a comprehensive evaluation index system and assessment model. In orderto protect the safety of sewage pipeline gas and establish a comprehensive riskassessment index system and improve the risk assessment model, this research throughthe sewers scene detection, sewage pipeline gas explosion theory analysis andnumerical simulation and experimental study to analyze the impact of sewage pipelinegas safety, the factors and hazard rating affecting the eventual establishment of sewersgas safety risk assessment model based on the risk matrix. The main results are:The gas that threats sewage pipeline safety, is mainly methane and hydrogensulfide, methane caused the main reason of the sewage pipe bombings, hydrogen sulfideis caused by the staff underground work poisoning the main reason to do the focus ofthe sewage pipeline gas safety work is to prevent methane andthe generation ofhydrogen sulfide, as soon as possible to rule out excessive methane and hydrogensulfide concentration.There are many factors threat sewage pipeline gas security, obtained to the threat offactors analyzed in this study are mainly methane, carbon dioxide, hydrogen sulfide,temperature, and the regional environment and check the well location.This study theoretically analyzes the factors affecting the explosion, base on the blast wave model, the theoretically calculated on the basis of the limits of the explosionlimit of the sewage pipe system. establish a numerical simulation of the basic physicaland mathematical models, using fluent software to simulate the explosion process,pointing out that the impact of CO₂on CH₄explosion.Sewers may contain dozens or even hundreds of mg/m³of H₂S, but4.3%lowerexplosive limit for H₂S is almost negligible, the experimental studies confirmed thepresence of H₂S in the sewage pipeline explosion did not affect, the threat of H₂S on thesewage pipeline gas safety performance in its toxicity, is the main reason for downholeoperation poisoning. Inhibition of CO₂on the sewage pipeline gas explosion in themixed gas of low concentrations of CH₄, CO₂can effectively inhibit the occurrence ofexplosion, but a higher concentration of CH₄gas mixture, a small amount of CO₂inhibition is not obvious. In the sewers there is a certain concentration of CO₂sewershave a protective effect.Based on experimental studies, the sewage pipe the of CH₄explosion threshold todetermine at around5.5%, compared to the previous scholars have measured the lowerexplosion limit increase, mainly due to the sewers gas condition and previous scholarstests different, in the sewage pipeline of toxic and explosive gas monitoring andwarning system the CH₄threshold value is set at5.5%is more appropriate.Based on the risk matrix sewage pipe gas safety risk assessment model, and takingChongqing City Commercial District3#biochemical pool inspection well regarded asan example calculation. According to the risk weight sorting draw: the inspection wellof methane and hydrogen sulfide is the key risk factors, should be ahead in the aspect ofprevention measures.