Fly ash suspensions stabilized by hydroxypropyl guar gum and xanthan gum for retarding spontaneous combustion of coal

This study evaluated the potential application of hydroxypropyl guar gum (HPG) and xanthan gum (XG) (HPG/XG weight ratio 1:1) to stabilize highly concentrated fly ash suspensions (FAS) (300 g/L) used for retarding spontaneous combustion of coal. The rheological behaviors of FAS were measured with different HPG/XG mixture concentrations including 1.2, 1.4, 1.6, 1.8, and 2 g/L, respectively. The effects of concentrations on the static stability of FAS were investigated to determine the optimal concentration. It was found that increasing HPG/XG concentration was beneficial to the viscoelasticity of FAS as evidenced by higher elastic modulus (G′), and FAS can be stabilized over 72 h when HPG/XG concentration increased to 1.6 g/L. Retarding spontaneous combustion experiments indicated that FAS significantly elevated the crossing point temperature of coal and reduced the carbon monoxide during low-temperature oxidation, efficiently retarding spontaneous combustion of coal.