Thermodynamic modeling of CO2 hydrates

CO2 hydrates are a nuisance in the petroleum industry, but also constitute a great opportunity as they form the basis for a new technology for capturing CO2 from flue gases. Both the understanding of the problems caused by CO2 hydrates and their exploitation require high quality experimental thermodynamic data and rigorous models, which can be used over an extensive range of conditions (temperature and pressure) and chemicals (used as gas hydrate formers and inhibitors).

The objectives of the FTP project is to build a solid experimental and theoretical framework for fully understanding and addressing the problems of CO2 hydrates in the petroleum industry and for enhancing the future utilization of hydrate crystallization as a CO2 capture technology. Two research groups, one from DTU (Denmark) and one from Ecole des Mines (France) will closely work towards the above objective.

The objectives during the PhD project will be to develop a molecular thermodynamic model, based on the Cubic Plus Association (CPA) Equation of State (EoS), for modeling mixtures related to CO2 hydrates. However, it is currently necessary to assume that CO2 is associating, which it is not, to describe its behavior. It is suspected that this discrepancy is due to the fact, that CO2 has a large quadrupole moment, which is currently unaccounted for in the CPA. To correct this, and gain a more physically consistent model, the proposed model is expected to include the effect of the quadrupole. The proposed model will be first tested for mixtures containing CO2 with water and alkanes and then incorporated in the van der Waals- Platteeuw theory for the description of CO2 hydrates. It is expected that the Van der Waals and Platteuw’s theory will be modified to describe, more accurately, mixtures containing hydrate formers, since the composition of gas in the hydrate phase is currently insufficiently described. Experimental thermodynamic data for complex hydrate mixtures with inhibitors will be acquired at Ecole des Mines, and used to test the full model.

Supervisor: Prof. Georgios Kontogeorgis,