Micro-particles stabilized aqueous foam for coal spontaneous combustion control and its flow characteristics

•MSAF are prepared in batch mode using a home-made foam generating column.•Micro-particles can disperse well in surfactant diluents with the concentration of 0.25 wt.%.•The diffusions of MSAF in the Y direction and Z direction occur simultaneously.•Mathematical model of MSAF flowing in inclined fracture was derived and amended. The goaf is the location where coal mines are most prone to coal spontaneous combustion, 60 % of the spontaneous combustion fire occur in the goaf. The coal has a greater crushing degree at the top of the goaf, where the heat accumulation is not easy to dissipate and mine fires are more likely to occur. In order to prevent coal spontaneous combustion in goaf efficiently and comprehensively, the uniform and dense micro-particles stabilized aqueous foams with the bubble diameter of 350–400 micrometers are prepared in batch mode using a home-made foam generating column with an internal hollow tube. The micro-particles can disperse well in surfactant diluents with the concentration of 0.25 wt.% and have strong wettability with the contact angle of 82.2°. Similar simulation experiments for flow characteristics indicated that the foam fluid does not appear to flow as low as ordinary cement paste, the diffusions in the Y direction and Z direction occur simultaneously, and the whole high fracture of loose gangue heap can be fully accumulated and seeped by foam fluid. Based on the micro-element force analysis of foam fluid in highly inclined fractures, the relationship equations between pressure difference, time, shear force and dynamic viscosity under different fracture dip angles and azimuth angles are derived and amended. The error was compared with the residual measurement points, and the error value is 0.05 %–9.72 %, indicating the amended fitting formula has universal applicability.