Growth Kinetics of Methane Hydrate in a Pilot-Scale Flow Loop

Methane hydrate growth kinetics and deposition behavior were investigated in a pilot-scale high-pressure flow loop under an isothermal and isobaric operating condition. The pressure range was from 3 to 7 MPa with temperature ranging from 273.15 to 281.15 K. The growth kinetics was characterized by the variation in the methane gas consumption with time. The effects of liquid loading (LL, the percentage of total volume of liquid water used in the experiments compared to the total volume of the flow loop), flow rate, pressure, and temperature on the growth rate were systematically studied. The formation of methane hydrate mainly took place at the interface of gas and water, and a layer of methane hydrate film was also found to form on the wetted inner wall of the flow loop. A threshold LL was found to exist below which the growth rate of methane hydrate was significantly higher, and here, all of the water could convert to methane hydrate in less than 2 h. The deposition behavior of the methane hydrate varied over the course of an experiment that also depended upon the operating conditions. Two mechanisms of methane hydrate growth and plugging in the flow loop were proposed on the basis of the experimental results. Decreasing LL and increasing flow rate increased the growth rate of methane hydrate, whereas the pressure and temperature had no clear effects in the range studied. Both the mass transfer limitation across the methane hydrate layer and the heat transfer resistance became limiting factors at different stages of the growth of methane hydrate.