Aqueous three-phase foam supported by fly ash for coal spontaneous combustion prevention and control

This work deals with the preparation and characterization of fly ash (FA) supported aqueous three-phase foams containing N₂ for coal spontaneous combustion prevention and control. Uniform and dense three-phase foams featuring FA contents between 20 wt.% and 33 wt.% are prepared in batch mode using a home-made foam generating column with an internal Venturi tube. The effect of FA on the foamability, static and dynamic stability of the three-phase foams is discussed. Compared with two phase foams, the FA supported three-phase foams manifest higher static and dynamic stability, which increases with the FA content. Base on the excellent static and dynamic stability, a structure model to attach FA particles at the N₂–water interfaces of the three-phase foams was proposed to elucidate the observed behaviors. The as prepared FA supported three-phase foams, exhibiting excellent coal fire extinguishing characteristic, can be used as a promising fire extinguishing material, especially for preventing the large coal area spontaneous combustion or extinguishing fire in high and unknown locations in goaf.