Study of the preparation and extinguishment characteristic of the novel high-water-retaining foam for controlling spontaneous combustion of coal

Abstract

For enhancing the wetting effect of foam on residual coal in goaf to control spontaneous combustion of coal efficiently, this study proposed the novel high-water-retaining foam with excellent water retention and extinguishment performance. Polymer composite (PC) as thickening agent and organic boron complex (OBC) as crosslinking agent were introduced into foam system to form gel structure by borate/cis-hydroxy bonds in foam film to hold water. Preparation experiments indicated that high-water-retaining foam with the component range of 3.4 ~ 4.8 g/L PC and 2.0 ~ 3.4 g/L OBC showed the crosslinking time more than 30 min, which was conducive for foam to spread fully to cover and wet the residual coal in goaf. Considering the foam foamability and stability, this study revealed that the optimal component proportion of high-water-retaining foam was 4.0 g/L PC and 3.0 g/L OBC, exhibiting the largest foam comprehensive value of 529.82 and best foam performance. Water retention capacity of foam tests indicated that high-water-retaining foam could hold the water in foam system above 60% after placing 120 h, while traditional aqueous foam had lost 98% water. And coal-fire extinguishing tests indicated better extinguishment characteristic of high-water-retaining foam than that of traditional aqueous foam as evidenced by faster cooling and extinguishment rate to burning coal for the novel foam. Moreover, high-water-retaining foam would cover the coal fully for a long term to prevent oxygen from feeding the fire, finally controlling spontaneous combustion of coal efficiently.