Preparation and Characteristics of Biomass Gel Foam with High Foaming and Film-Forming Properties for Preventing Coal Spontaneous Combustion

To overcome the problem of poor biocompatibility of inorganic gel foam, a biomass gel foam was prepared using carboxymethyl chitosan, tannic acid, and ammonium ferric citrate as raw materials. The results indicated that the gel foam exhibited optimal comprehensive performance when the mass concentrations of foaming agent, stabilizer, gelling agent, and crosslinking agent were 0.8, 0.2, 0.9, and 0.6 wt%, respectively. At this point, the foaming multiple was up to 8 and the half-life was 7.79 days. Compared to pure foam, the gel foam demonstrated excellent water retention and film-forming properties. After continuous heating at 80 degrees C for 10 hours, its water retention rate remained as high as 49.34%. The foam film formed after 120 hours of room temperature drying reached a thickness of 1 cm without any liquid separation phenomenon. The gel foam exhibited a good inhibition effect on the spontaneous combustion and oxidation process of coal. The CO inhibition rate reached 67.43% at 100 degrees C, and the cross-point temperature was effectively delayed by 18.2 degrees C. Moreover, the gel foam exhibited excellent burn resistance properties.