Development of an environmentally friendly gel foam and assessment of its thermal stability and fire suppression properties in liquid pool fires

Large-scale tank fires are one of the most challenging firefighting scenarios and pose significant threats to the safety of personnel and the integrity of equipment. The development of effective extinguishing agents is thus of both fundamental and practical importance in the controlling, mitigation, and suppression of tank fires. In this study, a novel environmentally friendly fire suppression foam based on gel-glycoside was developed using alpha-olefin sulfonate (AOS) and alkyl ethoxy polyglycosides (AEG) as the foaming agents, and sodium silicate, and sodium bicarbonate as the gelling and cross-linking agents respectively. The optimal ratios of the foaming agents were determined firstly by examining the foam expansion ratio and foam comprehensive value. Subsequently, the foamability, thermal stability, cross-linking time, and spreadability of the optimized formulations were analyzed. Finally, the fire extinguishing effects and performance in suppressing burnback of these formulations were examined and compared with those of a traditional film-forming fluoroprotein foam (FFFP). The experimental results indicated that the gel-glycoside foam, consisting of a composite foaming agent (AOS:AEG=1:9), sodium silicate, and sodium bicarbonate at concentrations of 0.6, 2.4 and 3.7wt%, respectively, exhibited the best spreadability and thermal stability. This formulation also showed excellent performance in cooling and suppressing burnback in the fire extinguishing tests, with a 90% burnback time of 485s, 45% higher than that of FFFP. The present results clearly demonstrated that gel-glycoside foams can effectively control and suppress liquid pool fires and hence reduce the risk in potential re-ignition. These findings are also important for the further development of gel foams for extinguishing large-scale oil storage tank fires.