Research On The Kinetics Of Ethylene Hydrate Formation

The condition of ethylene (temperature and pressure) to form hydrate is very special. It covers normal gaseous area, near-critical area and supercritical area. The ethylene hydrate formation behavior in supercritical condition has its own characteristic. The new separation technology combined ethylene hydrate formation with supercritical extraction has a good application prospect. In this paper, the ethylene hydrate formation behavior in pure water were researched through hydrate formation experiment.The 31 kinetic data of hydrate formation in gaseous, near-critical and supercritical condition and 4 solubility data were measured. The experiments were conducted at temperature ranging from 5.57-15.42 ℃ , pressure ranging from 2.033~6.020MPa.The experimental results show that: Solution, nucleation and crystal growth are a continuous process. The induction effect is not apparent in the ethylene hydrate formation. The kinetic curves of ethylene in gaseous condition are very smooth with second nucleation happened in lower temperature and higher pressure. The second nucleation happens constantly in near-critical condition. The hydrate formation behavior of ethylene becomes more complex in supercritical condition.The hydrate formation behavior of methane and gaseous ethylene were compared, including solution rate, nucleation and crystal growth. The differences of their hydrate formation behavior were explained combined with the proposed hydrate formation mechanism in normal gaseous condition.A novel dissolution viewpoint was developed to explain the mechanism of hydrate formation in supercritical condition. The hydrate former in supercritical fluid phase doesn't dissolve into the aqueous phase in the form of single molecule. The fluid molecular clusters near the interface crack to form smaller fluid molecular clusters through collision, and then fall into the aqueous phase. The smaller fluid molecular clusters continue breaking through disturbance, collisions and attraction by the neighboring molecular clusters. The process continues until a single fluid molecule is formed.