Experimental investigation of the flow and extinguishment characteristics of gel-stabilized foam used to control coal fire

Abstract

For understanding the extinguishing effectiveness of gel-stabilized foam fluids, the rheological law, flow characteristics, and extinguishment process were analyzed systematically in this study. The results revealed that gel-stabilized foam was non-Newton fluids, and the foam demonstrated shear-thinning behavior due to the orientation changes in molecular chains and structure destruction of three-dimensional gel at high shear rate. By fitting shear rate-shear stress curves, it was found that power-law equation of pseudoplastic fluid could descript the rheological behavior of foam well, and coefficients of determination for fitting results in all expansion ratios were lager than 0.9950. In addition, a simplified experiment platform of the goaf filled with coals was employed to investigate the flow characteristics of the foam fluids to extinguish coal fire. Analysis showed that gel-stabilized foam presented the hemispherical diffusion shape in porous media, and foam fluids would quickly cover to extinguish the open coal fire with excellent thermal stability. Moreover, the foam fluids also captured the hidden fire source efficiently in porous media by the quick seepage, finally cooling the high-temperature coal fire from 760 °C to 30 °C after injecting foam. The research would provide theoretical guidance for extinguishing coal fire using gel-stabilized foam.