Rapid Nucleation and Growth of Tetrafluoroethane Hydrate in the Cyclic Process of Boiling–Condensation

Abstract

Conceptually a new method to promote rapid nucleation and growth of hydrates was proposed and investigated to deal with the existing condition of complex hydrate growth and nucleation. It is based on self-circulation of tetrafluoroethane boiling-condensation process in enclosed water volume. Under this cyclic system, hydrate formation interface increased from two to four, which included the water–gas tetrafluoroethane, water–liquid tetrafluoroethane, water–bubble, and water–droplet interfaces. A number of nucleation sites provided by bubbles and droplets accompanied by energy disturbance effectively strengthened the hydrate nucleation. Thus, the accumulation of hydrates can be completed efficiently and rapidly by an order of magnitude at non-additive and non-mechanical conditions. The experimental results indicate that 1.703 mol of hydrate was generated within 35 min, and the rate of hydrates increased by 4000 times. Furthermore, the hydrate reformation presented a different nucleation and growth morphology and promoted the hydrate conversion amount. The experiments also obtained the optimum hydrate formation condition by comparing the hydrate conversion amount and induction time at different tested temperatures and thermal stimulation temperatures. Thus, the new method of boiling–condensing has greatly accelerated the application of gas hydrates in cold storage, seawater desalination, and gas separation.