Experimental and modeling phase equilibria of gas hydrate systems for post-combustion CO2 capture

Accurate knowledge of hydrate phase equilibria is of fundament in terms of the hydrate-based gas separation process (HBGS) for post-combustion CO2 capture. In this work, we experimentally investigated the phase equilibria of flue gas during hydrate-based CO2 capture. Additionally, new experimental data for dissociation pressure of flue gases with different CO2 concentration were reported. Subsequently, a more accurate thermodynamic model combining Cubic-Plus-Association Equation of State (CPA-EoS) and Chen-Guo model was employed to predict the dissociation pressure of flue gases. To better perform the hydrate equilibria, a temperature dependent binary interaction parameter kij and new parameters for Chen-Guo model were developed. The results showed that the general tender of the new experimental data was in line with previous results. In addition, an improved accuracy was noticed for the mixtures with an Average Absolution Deviation (AAD) approximately to 4.07%, through comparing the predicted results with the experimental data. Especially, in terms of the gases with a CO2 concentration less than 85.32%, the improvement was significant. Lastly, this work also utilized the thermodynamic model and the Clausius-Clapeyron equation to predict the dissociation enthalpies of CO2 hydrate. The results showed that the prediction results were located in the margin of experimental data, which demonstrated the thermodynamic model proposed in our work was capable of describing the gas hydrate behavior with high accuracy.