Effects of surface tension on the kinetics of methane hydrate formation with APG additive in an impinging stream reactor

To elucidate the mechanisms underlying the formation of methane hydrate and to facilitate its efficient synthesis, the study initiated by quantifying the surface tension of Alkyl Polyglucoside (APG). The study examined the influence of surface tension on methane hydration, as well as the impact of impinging flow-coupled surface tension on hydrate generation kinetics. Additionally, it investigated the effects of subcooling and initial pressure. The addition of APGs and the increase of carbon chain length were found to make significant and moderate effects on reducing the gas-liquid tension, respectively. Specifically, at a temperature of 275.15 K, the surface tension shows an order of APG08 > APG0810 > APG06 > APG1214 > APG0814. The reduction in surface tension effectively enhances both the total methane consumption (Delta n) and the rate of hydrate formation (R-H), albeit the augmentative effect was relatively confined, with a maximum increase of 0.0084 mol and 0.0039 mol/h per unit decrease in surface tension. Moreover, the incorporation of impact flow into the APGs system determinately accelerated the R-H, where the reaction rate showed the increase of 166.76 %, 160.08 %, and 144.23 % for APG08, APG0810, and APG0814 system, respectively, at the maximum value of beta = 0.30. The synergistic coefficient between impact flow and APGs surface tension was larger than 1, with optimal synergy manifested at beta = 0.21. Furthermore, elevating subcooling substantially enhanced Delta n up to 0.47 mol and increasing initial pressure significantly boosted R-H to 0.40 mol/h. The kinetic promoting effects of subcooling and initial pressure surpassed those induced by reducing surface tension.