Formation condition data for methane hydrate in ammonia-water system is very important for the process development and determination of operation condition for recycling the vent gas of ammonia synthesis using the hydrate method.This paper focuses on the formation conditions of methane hydrate in the presence of ammonia.Equilibrium data of methane hydrate in the temperature

pressure and concentration ranges from 277—281 K

4—8 MPa

1.018%

3.171% and 5.278%(mole) ammonia

were obtained.The experimental results indicated that ammonia had an inhibitive effect on hydrate formation.The higher the concentration of ammonia

the higher the formation pressure for methane hydrate.The Chen-Guo hydrate model was extended to this methane hydrate system containing ammonia in water.It was shown that the model could be used to predict the formation pressure for methane hydrate.