Impact of modified dry water material ratios on gas separation and recovery kinetics via the hydrate method
To enhance the efficiency of separating and recovering low-concentration coal mine gas using the hydrate method and to boost the gas content of gas hydrate,dry water was modified by incorporating carbon nanotubes and copper powder at four different mass fractions.This modification was achieved through compounding with Tetrahydrofuran(THF)at a molar fraction of 5.56％.Five cycles of gas hydrate separation and recovery experiments were conducted using modified dry water as the liquid phase to explore its impact on the separation and recovery kinetics of a molar fraction 25％CH4/67％N2/8％O2 mixture.Building upon these experiments,the reusability of modified dry water was also investigated.The findings revealed that the system utilizing dry water modified with a 0.5％mass fraction of carbon nanotubes exhibited the most favorable kinetics in gas hydrate formation.Additionally,at the initial stage of gas hydrate separation,the reaction rate reached 1.007 mmol/(mol·h),and the amount of gas consumption reached 4.992 mmol/mol.These values are two and three times higher,respectively,compared to the unmodified dry water system.The modified dry water underwent partial dissociation during multiple cycles of gas hydrate formation.For the quaternary mixture comprising silica nanoparticles,water,modified material,and modified dry water,there exists an optimal ratio at which the kinetic target parameters of gas hydrate formation can be optimized.The optimal reusability of modified dry water was observed when the mass fraction of modified material was 1％.A comparison was conducted,revealing that the recovery rate through gas hydration separation reached up to 1.264 mmol/(mol·h)in the gellan gum-modified dry water system with a mass fraction of 10％.According to the pressure-driven preferential experiment conducted in this system,the kinetic parameters and the recovery outcome failed to exhibit a trend of gradual increase with a rise in the initial gas-phase pressure.Specifically,in the system with an initial gas-phase pressure of 6 MPa,gas consumption and recovery rate were relatively higher,reaching 10.958 mmol/mol and 58.14％,respectively.
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