Research On The Preparation,performance And Mechanism Of Environment-friendly And High-efficient Foam Extinguishing Agent

The petrochemical fire is a typical liquid fire,which is difficult to extinguish due to its high heat release,fast burning speed,flowability and splashing.The scientific and efficient control and extinguishing of petrochemical fires is a major demand in the field of national firefighting and disaster relief,and it is also a hot and difficult issue for researchers to study.Foam extinguishing technology is proved to be the most common and effective way to extinguish liquid fires with the development of research.However,the traditional AFFF is mainly composed of perfluorooctyl sulfonate（PFOS）surfactant which possesses a complex environmentally harmful behavior and has been banned by the European Union in 2006.Hence,it is necessary to develop an environmental AFFF without PFOS surfactant,especially fluoride-free AFFF.In this paper,an environment-friendly foam extinguishing agent was prepared by using the hydrocarbon and silicone surfactant mixed system as the foaming agent,together with foam stabilizer,cosolvent,antifreeze,flame retardant and other additives to replace the traditional AFFF and solve the environmental pollution of the traditional AFFF.The major works of this study are summarized as follows:（1）Three types of silicone surfactants were successfully synthesized and compounded with anionic,cationic and amphoteric hydrocarbon surfactants,respectively,to prepare surfactant mixed systems.The results show that there is a synergistic effect between hydrocarbon and silicone surfactants,and the mixed systems exhibit the excellent critical micelle concentration,surface tension foaming ability and foam stability.（2）Both polysaccharide polymers and inorganic salts were used as the proposed foam stabilizers in environment-friendly foam extinguishing agents.The effect of foam stabilizer type,addition ratio and compounding method on viscosity,surface tension,foaming ability and foam stability of foam extinguishing agent was discussed by various analytical methods.The results shown that the addition of xanthan gum and sodium alginate improves the viscosity and the 25%drainage time of the foam extinguishing agent.The addition of individual polysaccharide polymer cannot improve the foam properties,while the combination of xanthan gum and gelatin can effectively balance the foaming ability and foam stability of foam extinguishing agent.The mixed system of inorganic salt and polysaccharide polymer can further improve the foam stability of foam extinguishing agent,while the foam stabilization mechanism of 0.025%xanthan gum/0.125%gelatin/0.1%Mg Cl₂ is ascribed to the formation of hydrogen bonds between xanthan gum and gelatin in foam solutions that greatly increases the viscosity as well as enhances the surface strength of the foam solution film and slows down the diffusion of water in the liquid film,thus effectively slowing down the drainage rate and bubbles coarsening of foam.Furthermore,there are a strong electrostatic interaction between Mg²⁺and surfactant head group.At the same time,Mg²⁺is adsorbed around the surfactant head group,which weakens the electrostatic repulsion between the head groups and increases the concentration of surfactants at gas-liquid interface,improving the foam stability ulteriorly.（3）The effects of gas-liquid ratio,flame retardant content,mixing chamber angle and particle size inside the rectifier on extinguishing efficiency of foam extinguishing agent were investigated by a self-assembled compressed nitrogen fire extinguishing system.The results shown that the expansion ratio of foam extinguish agent increases with increasing the gas-liquid ratio.Hence,an excessive low or high gas-liquid ratio is not conductive to exert the optimum fluidity,stability as well as fire-extinguishing performance of foam extinguishing agent.Namely,the foam shows the best fire extinguishing performance corresponding to the mixing chamber placed horizontally and the particle size in the rectifier is5 mm.（4）The fire extinguishing performance and burn-back performance of the environment-friendly foam extinguishing agent developed in this research meet the requirement of Chinese national standards and are better than that of traditional AFFF and protein foam extinguishing agents.The results of this study can guide the development of environment-friendly fluorine-free foam in liquid fuel fires.There are 107 figures,34 tables and 137 references in the paper.