Analysis of the explosion risk of low-concentration oxygen-bearing coal bed methane in the low-temperature environment

Abstract

In the process of deep cooling and liquefaction of low-concentration (concentration <30 %) oxygen-bearing coal bed methan, there is a risk of explosion because the methane concentration in the ultra-low temperature environment is within the explosion limit. It is of great guiding significance to study the occurrence mechanism and accident-causing process of such accidents. Firstly, the experimental system of low-temperature methane explosion characteristics is constructed, and it is found that when ignition energy exceeds a certain range, the process of deep cooling and liquefaction of low-concentration oxygen-bearing coal bed methane will cause explosion. Then, the occurrence of the gas explosion accident in low-temperature environment is briefly described, and the causes of the accident are analyzed preliminarily, and the dynamic characteristics of methane explosion propagation under ultra-low temperature conditions are studied by Fluent numerical simulation, and it is obtained that ultra-low temperature conditions have a promotion effect on the explosion pressure. Finally, based on the analysis of catastrophe theory, the traditional accident causation cusp catastrophe model is improved, and the “experimental safety state" and the “internal causes of explosion-external cause of explosion" are taken as the state variables and control variables respectively, and the explosion risk analysis model for deep cooling and liquefaction of low-concentration oxygen-bearing coal bed methane based on the cusp catastrophe theory is constructed. Based on the accident case, the process of accidents caused by risk factors is described, and the evolution mechanism of such disasters and accidents is clarified. Finally, the hazard state evaluation method for liquefaction explosion of low-concentration oxygen-bearing coal bed methane is proposed based on the catastrophe theory, and this evaluation model is applied to evaluate and analyze the hazard state of accident case. The evaluation results are consistent with the actual hazard state, confirming the rationality and feasibility of this evaluation method. In this paper, the key hazards of such accidents are found out in detail and provides support for safety decision-making in the deep cooling and liquefaction process of low-concentration oxygen-bearing coal bed methane.