RESUMEN
The implementation of the Gob-Side Entry Retaining Mining Mode with Roof Cutting and Pressure Relief (GERRCPR) results in the gob connecting to the retaining roadway, creating an open space that causes significant air leakage and increases the risk of spontaneous combustion. A study was conducted during the implementation of the GERRCPR in the Xiaonan Coal Mine N1-1502 working face to investigate spontaneous combustion characteristics, along with fire prevention and extinguishing measures. To analyze gob airflow, Computational Fluid Dynamics (CFD) was employed to collect data on airflow conditions, O2 concentration, and temperature. Based on this, this study focuses on exploring the effects of nitrogen injection treatment under various rates and positions to optimize parameters for buried pipe nitrogen injection. Results indicated that within the GERRCPR, air leakage in the gob increased, leading to an increase in O2 concentration, expansion of the oxidation zone, and an elevated risk of spontaneous combustion. Air leakage primarily occurred from the retaining roadway and the working face near the intake-air roadway, peaking at a retaining roadway length of 500 m, with a flow rate of 226 m3/min. Following nitrogen injection treatment, the oxidation zone was significantly reduced, with optimal treatment achieved at a nitrogen injection depth of 70 m and a rate of 600 m3/h. Field monitoring data showed that the inertization measure of using porous long pipes, a nitrogen injection spacing of 30 m, and a nitrogen injection rate of 600 m3/h significantly decreased the O2 concentration within the gob. This reduction meets safety production requirements and outperforms the effectiveness of traditional buried-pipe nitrogen injection methods, thereby validating the simulation accuracy. Understanding the laws governing spontaneous coal combustion in the GERRCPR and enacting preventive measures for nitrogen injection can improve safety standards in mining operations. This proactive approach can effectively prevent spontaneous coal combustion accidents, resulting in substantial social benefits.
RESUMEN
A programmed temperature-increase experiment was conducted on coal samples from four coal mines in the Zhalainuoer mining area to improve the accuracy of predicting and forecasting lignite spontaneous combustion. The gases produced during the coal tests were analyzed, and logistic, exponential, Boltzmann, and fourth-degree polynomial functions were selected to develop predictive models for the gas data. Additionally, the Boltzmann function was used to predict the occurrence of fire. The results revealed that the initial appearance temperature of CO was approximately 50 °C, and it exhibited an exponential growth trend with increasing temperature. The initial appearance temperature of C2H4 was approximately 140 °C, which could serve as an indicator of coal entering the accelerated oxidation stage. Applying the selection principle to gas indicators, CO and C2H4 were identified as single gas indicators for lignite spontaneous combustion in the Zhalainuoer mining area, whereas CO/CO2 and C2H4/C2H6 were identified as composite gas indicators. Among the four functions, the Boltzmann function model exhibited the best fitting effect for CO and CO/CO2 within the temperature range of 0-200 °C. The values of the four parameters (A 1, A 2, dx, and x 0) were determined based on their statistical characteristics, and a functional equation describing the relationship between gas concentration and coal temperature was derived. This indicates that the Boltzmann function model can be effectively used to predict the spontaneous combustion of lignite in the Zhalainuoer mining area.
