Study On Preparation And Characteristics Of Inorganic Salt Enhanced Inhibitory Foam For Preventing Coal Spontaneous Combustion

Coal mine fires caused by coal spontaneous combustion not only burn a large number of coal resources,but also directly threaten production safety,causing significant casualties and property losses.Therefore,research on prevention and control of coal spontaneous combustion technology is crucial.The inhibitor foam technology combines the advantages of inhibitor technology and foam technology.It can make full use of the good fluidity and accumulation of foam to transport the inhibitor to the closed goaf,so as to prevent the coal left in the goaf.It is an important technical means to prevent coal spontaneous combustion.However,the inorganic salt ions contained in mine water and inorganic salt inhibitor have salting out effect on foam,which seriously affects the foaming performance and stability of foam,thus reducing the inhibition effect.In view of the above problems,this paper develops a kind of inorganic salt enhanced foam,which has important practical significance for preventing coal spontaneous combustion in goaf.Firstly,a composite foaming agent was prepared by selecting lauryl propyl betaine（LAB）and sulfonate foaming agent（S）with an extended half-life in inorganic salt solution.When the ratio of LAB to S is 7:3 and the total concentration is 8g/L,put it into 5g/L inorganic salt solution,the foaming volume is 1400m L,and the half-life of foam is 543min,which is 37%and 22%higher than that of foam in pure water.To analyze the effect of different inorganic salt inhibitors on the interface of composite foam,four inorganic salt inhibitors,Na Cl,Ca Cl₂,Na₂SO₄,and Na HCO₃,were added to the composite foam.It was found that Ca Cl₂ could inhibit bubble aggregation and reduce the surface tension to below 30m N/m.Therefore,Ca Cl₂ is selected as the inhibitor component in the inorganic salt enhanced foam system.Then,to improve the resistance performance,melatonin（MLT）,a free radical scavenger,was introduced as a composite inhibitor.The experimental results showed that when the ratio of Ca Cl₂ to MLT was 4:1,the average inhibition rate of the composite inhibitor was 65.8%between 80℃and 170℃,which had the best inhibition effect.When LAB,S,Ca Cl₂,and MLT were 0.56g/L,0.24g/L,16%,and 4%,respectively,the foam half-life reached 3067 minutes,which was 6.89 times that of pure water composite foam.Finally,the effects of inhibiting foam on preventing coal spontaneous combustion was discussed by studying the wettability,inhibiting performance of the inhibiting foam,the changes of the microscopic morphology of coal samples before and after the inhibition,the changes of thermal weightlessness and functional groups.According to the experimental results,the contact angle of the inhibition foam solution could quickly drop to 31.5°within 2s,which could quickly infiltrate the coal and improve the inhibition performance.When ratio of coal to inhibited foam was 3:1,the inhibition rate was above 60%at 70℃,and the CO release at 200℃was reduced by 63.17%,which had a good inhibition effect.The surface of the coal sample was smoother after inhibition,and the inhibition foam could effectively block the pores of the coal.The thermogravimetric experiment showed that the inhibition foam could significantly delay the characteristic temperature point,extend the ignition point temperature by11℃,and reduce the weight change during the decomposition stage by 12.8%.The change of functional groups of coal during low-temperature oxidation shows that the content of active functional groups such as aliphatic group in coal can be significantly reduced by inhibiting foam,thus preventing chain reaction and effectively preventing coal spontaneous combustion.Figure[38]Table[9]Reference[97]...