Study on multi field coupling numerical simulation of nitrogen injection in goaf and fire-fighting technology

Area of Science:

• Mining Engineering
• Geotechnical Engineering
• Fire Safety Engineering

Background:

• Spontaneous combustion of residual coal in goaf poses a significant fire hazard in mining operations.
• Effective prevention strategies are crucial for ensuring mine safety and operational continuity.

Purpose of the Study:

• To investigate the effectiveness of nitrogen injection in preventing spontaneous coal combustion in goaf.
• To determine optimal nitrogen injection parameters (depth and volume) for controlling spontaneous combustion zones.
• To validate simulation results through engineering applications.

Main Methods:

• Establishment of a multi-field coupling numerical model for nitrogen injection in goaf using FLUENT software.
• Simulation of spontaneous combustion zone variations under dynamic mining conditions with varying nitrogen injection parameters.
• Analysis of temperature and CO concentration changes at measurement points.

Main Results:

• Nitrogen injection significantly reduces the width of the spontaneous combustion zone and extreme temperature values.
• Optimal nitrogen injection at 40m depth and 1000 m³/h volume reduced the spontaneous combustion zone width from 49m to 22m.
• An injection rate of 690 m³/h at 40m depth met inert cooling requirements, with a zone width of 31m and temperature of 309.95K.
• Field application confirmed successful control of spontaneous combustion, with CO concentrations and temperatures significantly reduced.

Conclusions:

• Nitrogen injection is a viable and effective method for preventing spontaneous coal combustion in goaf.
• The study provides critical data for optimizing nitrogen injection parameters in mining operations.
• The developed numerical model accurately predicts the impact of nitrogen injection on spontaneous combustion control.