Response surface optimizing XG/HPMC fly ash colloid to inhabit coal spontaneous combustion: An experimental study

Fly ash grouting is an effective technical to prevent the coal spontaneous combustion. However, fly ash slurry has its problems such as being prone to sedimentation and not easy to solidify, which has a negative impact on the prevention and control of coal spontaneous combustion. To enhance fly ash colloid's efficacy in preventing coal spontaneous combustion, an XG/HPMC fly ash colloid incorporating polymer xanthan gum (XG) and hydroxypropyl methylcellulose (HPMC) is developed. The ratio of the XG/HPMC fly ash colloid is optimized by integrating single -factor experiments and response surface analysis. The microstructure and rheological behavior of the XG/HPMC fly ash colloid are characterized, and its anti - spontaneous combustion properties are compared and analyzed. The results reveal that the gelling properties of XG/HPMC fly ash colloid are better during the colloid concentration is 0.78 %, the colloid mass ratio is 65:35, and the water-cement ratio is 10.38:1, respectively. Microscopic tests indicate that the functional groups of XG and HPMC have been successfully graft-polymerized onto the surface of the fly ash colloid. XG/HPMC fly ash colloid belongs to yield pseudoplastic fluid. It exhibits shear - thinning behavior, allowing it to flow easily and cover the coal surface, thereby effectively preventing oxygen from contacting coal. Moreover, the inhibition rate of XG/HPMC fly ash colloid on is 77.47 % higher than of raw coal in 100 °C. XG/HPMC fly ash colloid treated coal maximum weight loss rate is reduced by 4.41 % that compared with the raw coal. Furthermore, the XG/HPMC fly ash colloid lowers the content of oxygen-containing functional groups in coal and prevents chain reactions, thus curbing coal spontaneous combustion. The results provide support for achieving efficient fire prevention performance of fly ash colloid.