Development of an implicit least squares optimisation scheme for the determination of Kihara potential parameters using gas hydrate equilibrium data

Abstract

An implicit optimisation scheme is formulated to find the Kihara potential parameters for methane and ethane, using experimental hydrate formation data from both pure methane and ethane hydrates and hydrates formed from mixtures of methane and ethane. In this method, all three Kihara potential parameters, for both methane and ethane, are allowed to be adjustable parameters. Phase equilibria calculations, using the new Kihara potential parameters, exhibit a transition from structure I to structure II in hydrates formed from methane/ethane mixtures. This is consistent with experimentally observed behaviour. The use of Microsoft ® Excel, an easily available tool, is illustrated for the determination of the Kihara potential parameters by implementing the formulated implicit optimisation scheme using gas hydrate equilibrium data.