Research on N2-inhibitor-water mist fire prevention and extinguishing technology and equipment in coal mine goaf

Research on the Low-Temperature Oxygen Consumption and Low-Oxygen Gas Emission Law in Goaf of Ultrathick Coal Seams

Low-oxygen (oxygen concentration below 18.5%) phenomena often occur in the top coal caving working face of ultrathick coal seams, posing a serious threat to the safety of workers. The characteristics of oxygen consumption and gas production at low-constant temperature and the corresponding functional group evolution of residual coal in goaf were studied by temperature-programmed and infrared spectrum experiments. The influence of different factors on the emission of low-oxygen gases was studied through numerical calculation. The results show that low-temperature oxygen consumption and gas production occurred when the coal was about 40 °C. When the temperature was constant, the oxygen consumption and gas production rate increased with the extension of time. In the early stage of coal oxidation, the aliphatic C-H components were attacked by oxygen molecules and reacted with them. The asymmetric methyl and methylene groups were more likely to oxidize and produce carbonyl compounds. With the increase of nitrogen injection, the overall width of the oxidation zone (oxygen concentration was defined as 10-18%) narrowed, and the range of the oxidation zone moved forward from the depth of the goaf. The oxygen concentration in the air return corner decreased gradually, and the low-oxygen area in the air return corner expanded gradually. The distance between the low-oxygen area of the working face and the air intake corner was gradually shortened. With the increase of air intake, the width of the oxidation zone increased and moved to the depth of goaf, and the degree of low oxygen in the air return corner increased. The research results are of great significance for the understanding and prevention of the low-oxygen phenomenon in ultrathick coal seams.

Study on Inerting Characteristics of Gas Coal by the Inerting Concentration and Ratio of an Inert Gas Mixture

To study the effect of the inert gas mixture concentration and ratio on the spontaneous combustion reaction of gas coal, a combination of experimental research and theoretical analysis was used to study the pyrolysis and combustion kinetics characteristics of gas coal and further explore the influence of inert gas on the inerting characteristics of gas coal. Research has shown that during the entire heating reaction process of gas coal, the concentration of inert gases has little effect on the drying and desorption stages, but there is a significant lag phenomenon in the characteristic temperature points of active decomposition and degassing stages. Under the same concentration of mixed inert gases, the higher the relative percentage content of CO2, the more significant the change and the better the inhibitory effect. The higher the volume fraction of the inert gas, the higher the cross-temperature point. In the late stage of rapid heating of coal samples, when the volume fraction of inert gas is 40%, the rate of temperature rise increases rapidly. In a pure air environment, CO begins to be released at 80 °C, and when the temperature rises to 130 ∼ 140 °C, the concentration of CO begins to rapidly increase. Under inert conditions, the higher the relative percentage content of inert gas is, the higher the temperature point at which CO is generated. When the experimental conditions are a mixture of 30% N2 and 10% CO2 as inert gas, the optimal inerting effect has been achieved. The research results provide a theoretical basis for determining the optimal ratio of inert gas inerting concentrations to achieve fire prevention and extinguishing.

Global evolutional trend of safety in coal mining industry: a bibliometric analysis

Mining safety is recognized as one of the factors influencing the mining industry's long-term viability. Therefore, we did a bibliometric analysis to take stock of safety management in the coal mining industry. This study suggests a three-step strategy, comprising literature extraction and screening, bibliometric analysis, and discussion, to provide an in-depth understanding of the present state and development trend of mine safety research. The findings raise additional concerns which include the following: (i) Coal dust pollution has a direct and indirect impact on the environment. (ii) Most research projects have prioritized technology innovation and development over safety norms. (iii) Most works have come from advanced countries such as China, the USA, the UK, and Australia to the neglect of developing nations, leaving a significant vacuum in the literature. (iv) There are more major safety principles in the food business than in the mining industry, indicating a weak safety culture in the mining industry. Additionally, future research goals are provided, such as creating safer policy guidelines to support technological advancements, constructing effective safety mines, and creating solutions to dust pollution and human errors.