Study on Highly Stable Biomass Gel Foam with Ultra-Strong Film-Forming Performance Based on the Double Network Structure to Inhibit Coal Spontaneous Combustion

To further enhance gel foam stability, an ultra-strong film-forming stabilized biomass gel foam (PE/SA-Ca) with the double network structure was achieved by using pectin (PE), sodium alginate (SA), calcium L-lactate (Ca-L) and biomass foaming systems (BS). The results showed that the double network gel foam had ultra-strong film-forming and stability performances than the single network gel foam. Specifically, when the PE:SA ratio of the double network gel matrix was 5:5, the film thickness of PE/SA-Ca increased from 1 to 4.25 mm and the half-life increased from 3 to 22 days compared to the single network gel foam. In addition, PE/SA-Ca could maintain film integrity at high temperature up to 120 degrees C. The water retention rate of PE/SA-Ca was increased by 79.5% compared to pure foam. The inhibition rate of PE/SA-Ca in the coal low-temperature oxidation experiment was as high as 78.06% at 180 degrees C. Fire extinguishing experiment showed that PE/SA-Ca could rapidly reduce the coal fire temperature from 960 to 68.9 degrees C within 20 min and effectively prevent prevention of coal re-ignition. This research provides a technical method for the development of highly stable, ultra-strong film-forming and eco-friendly gel foam.