Study On Formation Mechanism And Inhibitory Property Of Gel Foam For Coal Mine Fire Prevention And Extinguishing

Coal spontaneous combustion is a major safety problem affecting the production of coal mines.Currently,the main technologies for prevention and control of coal mines are grouting,inerting gas,using inhibitors and gels.However,the above technology has some defects.The new technology of gel foam combined with the technical advantages of gel and foam can effectively control the spontaneous combustion of coal.In this paper,the factors affecting the performance of gel foam were studied,and the new gel foam was applied in the field.In this paper,a total of 12 basic foaming agents were tested by Ross-Miles method.According to the principles of foaming agent's environmental performance,classification and foaming ability,four types of foaming agents,PSLC-3,PLAK-1,PAEX-3 and PAOM-2,were selected to prepare gel foam for each other.The foaming properties of the gel foam were studied by changing the concentration,temperature and proportion of four kinds of foaming agents.The intrinsic reasons for the influence of concentration and temperature on foam foaming amount and half life were analyzed from the angle of surface tension,and the best formula of foaming agent for preparation of gel foam was determined.The performance of Fang gel foam coal fire prevention and extinguishing is applied to 4 existing mined out areas with large amount of coal remaining to verify the practicability of the new formula gel foam fire extinguishing material.The main conclusions are as follows:1.The Ross-Miles method was used to test the single foaming agent.From the point of view of surface tension and theoretical analysis,the following conclusions were drawn:(1)At a certain temperature,the optimal concentration of foaming agent has the maximum foaming volume,and the optimal foaming concentration is after the concentration of CMC.When the solution concentration reaches CMC,the surface tension does not decrease but increases slightly with the increase of the concentration,which may lead to the decrease of foaming volume.(2)When the temperature is constant,the best concentration of foaming agent has the best stability.(3)At the same concentration,the surface tension decreases obviously with the increase of temperature.At the same concentration,the foaming agent has the best working temperature range of the best foaming ability.(4)At the same concentration,the foaming agent has the best stable working temperature.Under certain conditions,surface tension affects the stability of foam by reducing the pressure difference of foam gas interface,but when the concentration exceeds CMC,surface tension is no longer the dominant factor to control the change of half-life,and the influence of temperature on half-life becomes dominant.(5)Under the combined action of concentration and temperature,foaming agent has the best performance point of foam performance,and when the blowing agent concentration exceeds CMC,it coincides with the working point of the optimum value of foam half life.Ross-Miles method was used to test the foaming agent compatibility.Compared with the same foaming agent at the same temperature,the half life and foam performance of the matching foaming agent are improved obviously.Moreover,we obtained the best formula for the preparation of gel foam.2.At the same temperature,the CO released from the coal samples treated with gel foam is much lower than that of raw coal.It shows that the gel foam has a good retarding effect,which inhibits the oxidation of coal and the release of CO.Moreover,the new formula high performance gel foam has better blocking effect than ordinary two-phase foam.3.Field application of 4 coal mined out areas with a large amount of residual coal was carried out.The cause of spontaneous combustion was analyzed thoroughly,and the coal seam oxidation ignition area was determined.Combined with the actual situation,the comprehensive scheme was adopted,and high performance gel foam was used for prevention and control.From the perspective of the effect,the new fire-fighting material,high performance gel foam,has the advantages of many kinds of fire prevention and extinguishing materials,and can fully cover the large,middle and low positions of the oxidized coal remaining in the goaf.It effectively prevents the further oxidation of the remaining coal in the goaf and can take away the large amount of heat in the goaf,and the CO concentration in the return air tunnel is reduced to a safe value,which can ensure the safe withdrawal of the working face and at the same time.Effectively prevent the reburning of oxidized coal in goaf.