Study On Performance Of Gel Foam Fire-extinguishing Material For Preventing Spontaneous Combustion Of Coal Gangue

Coal gangue is one of the main solid wastes in China.At present,more than 1/3of coal gangue hills in China are experiencing combustion,and the combustion of coal gangue will emit a large number of toxic gases,such as H₂S,CO,SO₂.In the use of fire extinguishing materials for the prevention and control of spontaneous combustion of coal gangue,three-phase fire extinguishing materials,foam fire extinguishing materials and ordinary gel foam fire extinguishing materials are widely used in China and abroad to extinguish the spontaneous combustion of coal gangue.However,the combustion of coal gangue hill belongs to internal spontaneous combustion,and the combustion time is long.At present,the fire extinguishing materials on the market have defects such as poor fluidity,high consumption,poor sealing and easy reburning.Therefore,research on spontaneous combustion prevention of coal gangue has been carried out in China and abroad.Gel foam fire prevention and extinguishing materials combine the advantages of foam and gel,which not only have the plugging and viscosity of gel,but also retain the advantages of large volume of foam.The gel foam described in this paper is mainly composed of foaming system and foam stabilizer.The foam stabilizer is a super absorbent hydrogel of chitosan grafted acrylic acid.In this paper,Waring-Blender method was used to test the single foaming performance of eight selected foaming agents,and then the comprehensive value of the foam was compared.Finally,the foaming agent with large volume and long half-life of the starting foam was screened,and four of them were selected to carry out the pairwise compounding experiment of the foaming agent.Then the ratio of different foaming agents was changed,and the foaming system of gel foam was determined according to the foaming performance and salt resistance.The foam stabilizer was prepared by chemical crosslinking-aqueous solution polymerization with chitosan and acrylic acid as the main raw materials,ammonium persulfate as the initiator,and N,N-methylene bisacrylamide as the crosslinking agent.Through orthogonal experiment and single factor analysis experiment,changing the ratio of chitosan and acrylic acid,crosslinking agent concentration,initiator concentration,neutralization degree of four influencing factors,the water absorption effect of hydrogel was detected,and the suitable concentration was selected.The synthesized hydrogel was used as foam stabilizer for gel foam,and the structure of the synthesized material was characterized by thermogravimetric analyzer and infrared spectroscopy.The effect of foam stabilizer was detected,the optimal concentration of foam stabilizer was determined,and the combination of foaming system and foam stabilizer in gel foam was determined.The heat resistance of gel foam was studied by redesigning the chemical thermal stability and constant temperature dehydration performance test of gel foam.The experimental results show that the heat resistance time of gel foam is about twice of that of ordinary foam.Under the condition of different multiples of gel foam,the heat resistance of low multiple gel foam is better than that of high multiple gel foam,and the heat resistance of foam stabilizer at 5‰concentration is better than that at 7‰and 3‰concentration.The relationship between temperature and foam stabilizer concentration and gel foam viscosity was observed by measuring the viscosity of gel foam.Through self-made coal spontaneous combustion temperature programmed experiment,the flame retardant properties of coal treated by water,ordinary two-phase foam and gel foam were observed.The results showed that the flame retardant effect of gel foam was better than that of two-phase foam and water.Finally,a small fire extinguishing test bench was set up to observe the fire extinguishing effect of gel foam by comparing gel foam with two-phase foam and water.