In the process of coupling disaster prevention and control of gas and coal spontaneous combustion in goaf, there is a great contradiction between the gas drainage and carbon dioxide inerting technology. The key performance indexes are put forward to solve the coupling disaster, such as the air quantity of the intake airway (A), the gas drainage rate (B), the carbon dioxide injection rate (C), and the injection depth (D). Using the numerical simulation method and the orthogonal test of four factors and three levels, we establish the coupling disaster model of the no. 7436 working face in the Kongzhuang coal mine. Using a combination of the relative membership degree method and range analysis, the optimal level of each factor is determined, which is A II B III C II D II . Furthermore, the distribution law of the airflow field is obtained under the conditions of different gas drainage rates and carbon dioxide injection rates. The results show that the gas concentration decreases with an increase in gas drainage in the upper corner, but it has little impact on the width of the oxidation zone. The gas concentration can be reduced to 1%, while the gas drainage rate is higher than 35 m 3 /min. With an increase in gas injection rate, the carbon dioxide emission rate increases in the upper corner, but the width of the oxidation zone decreases. Also, the gas injection rate should be less than 800 m 3 /h. Moreover, with an increase in injection time in the upper corner during the injection process, the carbon dioxide and gas concentrations increase, and the maximum carbon dioxide concentration is 1.3%, and the maximum gas concentration is 0.42%, which is consistent with the results of numerical simulations.

The utilization of CO2 is extremely important to solve the environmental problems and coal spontaneous combustion in goaf. There are three kinds of CO2 utilization in goaf: adsorption, diffusion, and seepage. Since adsorption will consume CO2 in goaf, the optimization of CO2 injection amount is very critical. A self-developed adsorption experimental device was used to determine the CO2 adsorption capacity of three different particle sizes of lignite coal samples at 30–60 °C and 0.1–0.7 MPa. The factors affecting CO2 adsorption by coal and its thermal effect were studied. In the coal and CO2 system, the CO2 adsorption characteristic curve is not affected by temperature, but there are differences in that with different particle sizes. The adsorption capacity increases with the increase of pressure, while it decreases with the increase of temperature and particle size. Under atmospheric pressure, the adsorption capacity of coal is a logistic function relationship with temperature. Furthermore, the average adsorption heat of CO2 on lignite shows that the interaction force between CO2 molecules has a stronger effect on CO2 adsorption than the effect of heterogeneity and anisotropy on the coal surface. Finally, the existing gas injection equation is improved theoretically with CO2 dissipation, which provides a new idea for the work of CO2 prevention and fire suppression in goaf.

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