A Predictive Model for Hydrate Formation Conditions in Alcohol-Containing Systems Based on the Cubic-Plus-Association State Equation

Abstract

In alcohol-containing systems, the association of polar molecules significantly influences the calculation of water activity, leading to substantial deviations from ideal solution behavior. This makes it challenging for traditional hydrate formation condition models to accurately predict hydrate formation temperatures and pressures. To address this issue, we propose a novel unified thermodynamic framework based on the Parrish-Prausnitz (P-P) model and the Cubic-Plus-Association (CPA) equation of state (EoS) for calculating the hydrate formation condition in systems containing gas/water/alcohol, by using the advantages of the CPA EoS to characterize the association interaction of polar molecules. In addition, we utilize experimental data to model the molecular association in alcohol-containing systems and conduct regression analysis for binary interaction coefficients among alcohol, water, and gas. Multiple sets of experimental data on component fractions and hydrate formation conditions for methane-alcohol-water systems are used for validation. The proposed model shows an average relative error of 1.17–6.42% for predicting alcohol/methane component fractions in the liquid phase and 1.93–4.78% for predicting hydrate formation conditions in alcohol-containing systems. Compared to traditional models, this model demonstrates a significant improvement in accuracy and performs well in predicting hydrate formation conditions in alcohol-containing systems.