The replacement process of CH4 from CH4 hydrate formed in NaCl solution by using pressurized CO2 was investigated with a self-designed device at temperatures of 271.05, 273.15 and 275.05 K and a constant pressure of 3.30 MPa. The mass fraction of the NaCl solution was either 0.5 wt% or 1.0 wt%. The effects of temperature and concentration of NaCl solution on the replacement process were investigated. Experimental results showed that high temperature was favorable to the replacement reaction but high NaCl concentration had a negative effect on the replacement process. Based on the experimental data, kinetic models of CH4 hydrate decomposition and CO2 hydrate formation in NaCl solution were established. The calculated activation energies suggested that both CH4 hydrate decomposition and CO2 hydrate formation are dominated by diffusion in the hydrate phase.
Termodynamic data on methane hydrate formation in the presence of ammonia are very important for upgrading of ammonia synthesis vent gas using hydrate formation. This paper is focused on the formation conditions of methane hydrate in the presence of ammonia and the effects of gas-liquid ratio and temperature on the separation of vent gas by hydrate formation. Equilibrium data for methane hydrate within an ammonia mole concentration range from 1% to 5 % were obtained. The experimental results indicated that ammonia has an inhibitive effect on hydrate formation. The higher the ammonia concentration, the higher is the pressure reguired for methane hydrate formation would be. The primary experimental results showed that when volume ratio of gas to liquid was 80：1 and temperature was 283.15 K, total mole fraction of （H2＋N2） in gas phase could reach 96.9 %.
Dong Taibin Wang Leiyan Liu Aixian Guo Xuqiang Ma Qinglan Li Guowen Sun Qiang
