Preparation and characterization of antioxidant gel foam for preventing coal spontaneous combustion

Abstract

New antioxidant gel foam is prepared to improve its stability and effectiveness in preventing coal spontaneous combustion. The physicochemical composite inhibitor is prepared by introducing procyanidins into a super absorbent polymer. And then the inhibitor is incorporated into the gel foam (surfactant, foam stabilizer, and gel system), the combined properties of foam, gel and inhibitor are utilized to prevent coal spontaneous combustion. The optimal composition ratio of antioxidant gel foam is obtained by single-factor experiments and response surface methodology. The microstructure of the foam is characterized. The properties of antioxidant gel foam in preventing coal spontaneous combustion are compared and analyzed through cementation, film-forming, and temperature-programmed experiments. The results reveal that the foam properties of the antioxidant gel foam are better when the mass fractions of surfactant, foam stabilizer, gel system, and inhibitor are 0.92 %, 0.49 %, 0.34 %, and 0.55 %, respectively. The inhibitor constitutes a high-water retention skeleton structure of foam wall and stabilizes the platform boundary. The antioxidant gel foam has small bubble size, uniform distribution, and excellent stability. The foam coarsening process is slow, which can fully wet the coal and reduce the coal temperature. Simultaneously, the antioxidant has better cementation and film-forming properties, which can cement the crushed coal and form a complete gel film, blocking the air leakage channels and isolating the contact between the coal and oxygen. Besides, the inhibition effect of antioxidant on coal spontaneous is better than that of water-based foam, polymer-stabilized foam, and ordinary gel foam. It can effectively slow down the oxygen consumption rate, gas production rate, and exothermic intensity during coal oxidation, the inhibition rate at 100 °C is 74.48 %. This study provides an antioxidant gel foam with good foam properties and inhibition effect, which can effectively reduce the oxidation rate of coal and prevent its spontaneous combustion through the physical effects on covering, wetting, and cementing, as well as inhibiting the chemical reaction between coal and oxygen.