Application of Inorganic Solidified Foam to Control the Coexistence of Unusual Methane Emission and Spontaneous Combustion of Coal in the Luwa Coal Mine, China

Unusual methane emission and spontaneous combustion of coal induced by the air leakage are both hazards during mining. The most common practice has been to improve mine safety is sealing the mining fractures. In this paper, the methane and geology, coal spontaneous combustion characteristics and the coexistence of methane emission and spontaneous combustion of coal were analyzed. The preparation system of inorganic solidified foam (ISF) in field applications is studied and the working principle of generating device consists of foam generator and mixer was expounded. The technical plan of site construction is that the foam fluid was injected to respectively seal the mining fractures behind hydraulic supports, the cavities of air return corner, and the fractures nearby the coal pillar. After the foam fluid injection, the two stress values in the coal pillar eventually maintained above 15.5 Mpa and 13 Mpa, respectively. It indicated that the ISF can enhance the bearing stress ability of the coal pillar by transforming the stress state from two dimensional to three dimensional. The methane concentration in the air return corner and air return roadway declined significantly to 0.63% and 0.25%. The differential pressure inside and outside of the 4301(1) goaf fluctuated between −100 pa and 150 pa and the concentration of CO and O₂ declined to 9 ppm and 6%. The CO concentration in the air return corner finally reached a stable level of 6 ppm. What that all means, the foam fluids can seal the air leakage and inhibit spontaneous combustion of coal effectively.