| Coal and gas outburst accidents seriously threaten the coal mine production safety,which is supposed to be a vital problem to be solved in the development of mining industry.The new technology of gas hydrate curing is aimed at preventing the occurrence of coal and gas outburst.In this paper,gas hydrate distribution characteristics are accurately determined and the changing laws of gas hydrate growth rate,saturation bearing hydrate in coal and gas content are effectively acquired accompanied with the variation factors of coal structure,gas occurrence characteristics and water injection parameters.Together with the clarification of gas hydrate formation mechanism,all the above elements could provide theoretical basis for optimizing the process of gas hydrate curing on prevention the gas outburst,achieving the goal of target elimination in dangerous areas of coal outburst,which exhibits a significant effect on engineering application.Moreover,the author designs and constructs gas hydrate phase equilibrium visible testing devices with volume variable;high pressure experiment system of gas hydrate kinetics and impedance monitoring system of gas hydrate curing respectively,which is dedicated to measure the distribution characteristics of pores and fissures in accordance with the outburst samples of different mines.Based on the hydrate formation conditions,solution composition for impedance monitoring system is confirmed as well.Meanwhile,investigate these influencing rules of the factors including the porosity and fissures in coal,gas pressure/concertation and saturation bearing water in coal acting on these perspectives,which are gas hydrate growth rate,gas content and saturation bearing hydrate.The main researches of this paper are as follows:(1)Adding Na Cl solution into liquid phase of gas hydrate curing system serves the purpose that it is feasible to determine and calculate the following aspects the gas hydrate growth rate,gas content,saturation bearing hydrate applying the impedance testing method.It is found that the pressure of phase equilibrium rises and the induction period is prolonged when Na Cl mass fraction is increased,together with the consequence the reduction of nucleation rate and the enhancement of the impedance system stability.Composition of compound solution with 3% Na Cl and 500mg/L SDS is the optimum ratio in the gas hydrate curing under the impedance monitoring system.(2)The growth rate of gas hydrate formation is faster when the coal bears a larger porosity and fissures.In the meantime,the gas content and the saturation of hydrate are higher.The hydration index of gas hydrate in different pores and fissures is greater than the theoretical value of 5.75.(3)During the period of gas hydrate nucleation,the induction time of gas hydrate formation decreases initially,followed by an increase as the CH4 concentration reduces and it also presents the increase tendency with the raise of gas phase pressure,due to the effect of gas concentration and pressure.In the stage of gas hydrate growth,the gas hydrate formation is more massive and the saturation of hydrate is higher in the system with gas pressure and CH4 concentration both higher.Gas pressure takes on a less effect on gas fraction of gas hydrate.It performs that gas content rate and cavity filling rate are higher in the system with a low concentration of CH4.(4)The quantity of gas hydrate formation and its growth rate both appear a rising complexion complied with the increase of saturation bearing water under the circumstance of same pressure.When the coal containing water is not saturated,the distribution area of gas hydrate is enlarged and the saturation bearing hydrate of each layer decreases.(5)Saturation calculation model of gas hydrate is established to figure up the saturation bearing hydrate in coal,which provides a technical support for the field application of gas hydrate curing.Construction of theoretical model of gas hydration kinetics optimizes the theoretical basis of gas hydrate curing technology. |
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