Modeling the Influence of Heat Transfer on Gas Hydrate Formation

Abstract

Abstract Gas hydrates are crystalline structures of water and gas which form at high pressures and low temperatures. Hydrates have important applications in carbon sequestration, desalination, gas separation, gas transportation and influence flow assurance in oil-gas production. Formation of gas hydrates involves mass diffusion, chemical kinetics and phase change (which necessitates removal of the heat of hydrate formation). When hydrates are synthesized artificially inside reactors, the heat released raises the temperature of the water inside the reactor and reduces the rate of hydrate formation (since the driving force is reduced). An examination of literature shows that there is inadequate understanding of the coupling between heat and mass transfer during hydrate formation. Current models treat heat and mass transfer separately during hydrate formation. In this study, we develop a first principles-based mathematical framework to couple heat and mass transfer during hydrate formation. Our model explores the difference between “actual subcooling” and “apparent subcooling” in the hydrate forming system. The apparent subcooling depends on the targeted reactor temperature and is supposedly, the driving force for hydrate growth. However, due to the increase in temperature of the reactor, the actual subcooling is lower than the apparent subcooling. All these effects are modeled for a 1-D hydrate forming reactor. Results of our simulations are compared with some experimental observations from literature. We also present mathematical scaling to determine the temperature rise in a hydrate-forming reactor. In addition to artificial synthesis of hydrates, the mathematical framework developed can also be applied to other hydrate forming systems (flow assurance, hydrate formation in nature).