Preparation And Characterization Research On CMC/ZrCit/GDL Gel Used In Mine Fire Preventing And Extinguishing

The spontaneous combustion of coal is one of the main disasters that affecting mine safety production.It poses a great threat to the safety production of coal mine.It not only causes a lot of waste of coal resources and serious environmental pollution,but also causes heavy casualties and economic losses.In order to prevent spontaneous combustion of coal,various fire-fighting technologies have emerged,such as grouting,inert gas,foam,colloids,and inhibitors.Among them,gel has received attention as a new type of fire-fighting material.Based on this,this thesis carried out the research on the preparation and characteristics of CMC/Zr Cit/GDL fire-fighting gel for mines.Through variable control and orthogonal compounding experiments,the formula of CMC/Zr Cit/GDL gel was optimized and analyzing the basic characteristics and hydrodynamic properties.Explaining the gel forming mechanism from the perspective of polymerization and cross-linking mechanism,and finally investigate its inhibition effect and analyze the fire extinguishing mechanism through the inhibition experiment and fire extinguishing experiment.(1)This paper uses sodium carboxymethyl cellulose as the polymer,zirconium citrate as the cross-linking agent and glucono-?-lactone as the p H modifier to prepare a new type of mineral gel.The formula of the gel was determined by the compound experiment.The gelation time of the gel was tested by the drip timing method.According to the test results of the gelation time and the actual needs,the suitable ratio can be selected,and the formation and stability of three-dimensional structure of the gel was analyzed from the structure of the polymer and the crosslinking agent.(2)The thermal stability of the gel under high temperature conditions was tested,and the weight loss rate of the gel during the temperature program was obtained.It was found that the gel would shrink into a film on the surface under high temperature conditions,which has a greater binding force for the absorbed water,and the gel has good water solidity and thermal stability,which can effectively reduce the evaporation of water.Tested the adhesion of the gel at different temperatures,and found that the adhesion rate of No.23 gel can reach 20.9%?30%,and the adhesion rate of No.32 gel can reach 27%?34.6%.The gel and coal body can be bonded into a whole.The self-made plugging experiment test device was used to test the pressure that the gel can bear on the coal body,and it was found that the No.23 gel can withstand the air pressure of 2355 mm H₂O,and the No.32 gel can withstand the air pressure of 2587 mm H₂O.The permeability of the gel was tested with a self-made experimental device,and it was found that different gels would penetrate different amounts from the coal.Due to the high polymer concentration and high viscosity,gels No.23 and No.32 are more likely to remain in the coal,thus blocking the air leak and isolates contact between coal and oxygen(3)The rheological properties experiment of the gel was carried out with a rheometer,and it was found that the gel is a pseudoplastic fluid.The higher the mass fraction of the gel,the greater the viscosity of the gel and the faster of the gel formation.The viscosity of the gel will decrease with the increase of shear,showing the characteristics of shear thinning.The Herschel-Bulkley equation of yield pseudoplastic fluid is used to fit and analyze the rheological curve of the steady state rheological experiment of the gel.The greater the concentration of the gel,the greater the shear stress,the stronger the pseudoplasticity,the greater the gel yield stress,the higher the consistency coefficient and the lower the flow index.1.2% strain is a critical value.Before 1.2% strain,G' is greater than G'',and the elasticity of the gel is dominant.The gel is in a solid state and it is difficult to flow.After 1.2%strain,G''starts to be greater than G',but the difference is relatively small,indicating that the structure of the gel is damaged to a certain extent when subjected to external forces.The shear rate of No.23 gel when flowing in a 1000-meter pipeline is 104.675s^-1,the pressure drop of the pipeline is 3.622MPa,and the shear rate of No.32 gel when flowing in a 1000-meter pipeline is 100.891s^-1.(4)The temperature programmed experiment shows that the gel has a significant effect on the heating process.The coal samples treated with different gels have reduced the CO gas generated by oxidation to varying degrees,and the maximum oxygen consumption rate can be reduced by 54.91%.Through thermogravimetric experiments,it is found that the addition of gel slows down the change of coal sample quality,delays the reaction process,and the activation energy increases by 3.16%?15.22%.Through the FTIR experiment,it was found that the number of active groups and oxygen-containing functional groups in the coal sample added to the gel was reduced.Gaussian software simulates and calculates the changes in the lowest unoccupied orbital and the highest occupied orbital.It is found that the addition of gel has higher molecular stability.The reaction is not easy to occur,which increases the difficulty of the reaction between coal and oxygen.Finally,a simulated fire extinguishing experiment of the gel was carried out to verify the good fire extinguishing effect of the gel,and summarize the fire extinguishing mechanism of the gel.