Significance of Low Stirring Modes on the Kinetics of Methane Hydrate Formation

We studied the kinetics of methane (CH4) gas clathrate hydrate formation and its morphology at low pressure, temperature, and low stirring speeds. A typical jacket cooling high-pressure reactor was used to form the hydrate in low stirring mode (LSM) at speeds of 100, 150, and 200 rpm and in unstirring mode (USM) under a pressure of 50 bar and a temperature of 2 ± 0.5 °C. A fixed mole ratio of cyclopentane to deionized water (CP/water) of 1:3.14 was maintained for all tests. The kinetics of hydrate formation among LSM and USM time of the hydrate was compared at the same conditions. Due to the volatile nature of CP, each experiment was carried out three times to ensure the repeatability of the experimental results. The results reveal that the employment of LSM resulted in a shorter hydrate formation time with enhanced stability of the CP/CH4 hydrate. In addition, the use of LSM enhanced the diffusion rate of CH4 within the two distinct polarity solvent phases. Moreover, higher CH4 gas consumption and an improved CP/CH4 hydrate formation rate were achieved. Under LSM conditions, four distinct morphological characteristics of CP/CH4 hydrate were observed, showing the evolution of morphology from a hazy emulsion to hydrate crystal slurry, hydrate agglomeration, and then, finally, complete solid hydrate blocks.