Experiment design as a tool for hydrate phase equilibria prediction of CO2 + CH4 gas mixture in the presence of tera-butylammonium bromide in LW–H–V systems

Abstract

In this study, we introduce experimental design as a novel approach to derive an equation that predicts the hydrate phase equilibrium temperature in a LW–H–V (liquid water, hydrate, vapor) system, based on pressure, gas composition, and the concentration of tetra-n-butylammonium bromide (TBAB). Our phase equilibria model is informed by experiments under nine different conditions, varying in gas compositions (CH4, CO2, and a 50/50 mole % CH4/CO2 mixture) and TBAB concentrations (15 and 30 wt.%). From these, we calculated temperature responses for 13 experiments, leading to the formulation of two models: a model without pressure transformation, which lacked predictive accuracy, and a more accurate model incorporating a natural logarithm pressure transformation (NLPT). The NLPT model demonstrated exceptional predictive power, with R2, adjusted R2, and predicted R2 values of 0.9975, 0.9958, and 0.9914, respectively. Additionally, it achieved an F-value of 565.90 in the analysis of variance (ANOVA). Validation diagrams, comparing predicted results to experimental data, confirmed the ability of the NLPT model to accurately predict hydrate phase equilibria, underscoring the efficacy of our experimental design approach.