Modeling vapor-liquid-solid phase behavior in natural gas systems
Chapman, Walter G.
Master of Science
This thesis proposes modeling phase behavior, including the solid phase, during gas processing. Failure to accurately predict solid phase formation or freezing of CO2, hydrates, and water ice causes plugging and equipment failure. Vapor-liquid-solid phase behaviors of hydrocarbons are modeled using the Perturbed Chain-SAFT (PC-SAFT) equation of state in the presence of carbon dioxide at cryogenic temperatures. PC-SAFT does an excellent job predicting vapor-liquid equilibria (VLE), vapor-solid equilibria (VSE), and liquid-solid equilibria (LSE) using binary interaction parameters fit to the vapor-liquid equilibria data. Using these parameters produces excellent results for LSE and VSE for hydrocarbon + carbon dioxide systems over the entire range of measured temperatures and pressures. Predicting accurate solid phase behavior will help in design and optimization of processes for cryogenic systems especially when data are lacking at process conditions. Further, modeling at extreme high temperatures and pressures demonstrates the usefulness of PC-SAFT for deepwater reservoirs.
Chemical engineering; Petroleum engineering