(733e) CO2 Capture Via Gas Hydrate Crystallization

A. Basdeo ¹, P. Naidoo¹, A.H Mohammadi^{1, 2}, D. Ramjugernath¹

¹ Thermodynamics Research Unit, School of Chemical Engineering, University of KwaZulu-Natal, Howard College Campus, King George V Avenue, Glenwood, Durban, 4041, South Africa.

² MINES ParisTech, CEP/TEP - Centre Énergétique et Procédés, 35 Rue Saint Honoré, 77305 Fontainebleau, France.

Corresponding Author: Email: annelinebasdeo@gmail.com; Tel:+27 31 260 2969. Fax : +27 31 260 1118

Carbon dioxide (CO₂), in addition to other gases, allows for the transfer of solar radiation through the earth’s atmosphere but prohibits the escape of heat. As a result the global surface temperature is increased. Since the Industrial Revolution, the combustion of fossil fuels has led to release of billions of tons of CO₂ into the atmosphere. According to the International Energy Agency (IEA), CO₂ emissions in 2050 may rise to twice those of 2007, if no mitigation options are implemented (IEA, 2010). The concerns of climate change have led to interest in mitigation strategies such as carbon dioxide capture and storage (CCS). Reports by the IEA proclaim that in order to stabilize CO₂ concentrations, carbon dioxide capture and storage (CCS) will need to contribute to one-fifth of the total reductions by 2050 (IEA, 2010).

CCS involves the capturing of CO₂, emitted from large industrial sources, before release into the atmosphere and storing it in secure geological formations deep underground. Gas hydrate crystallization is an attractive technology for capturing CO₂.Gas hydrates are non-stiochiometric crystalline compounds that consist of a lattice of water molecules that physically encage molecules of another component i.e. CO₂ (Lee et al., 2010).

Tetra-n-butyl ammonium chloride (TBAC) and tetra-n-butyl ammonium fluoride (TBAF) are additives that can reduce hydrate formation pressures to feasible industrial conditions however there is insufficient phase data available on (CO₂+TBAC) and (CO₂+TBAF) systems (Li et al., 2010).

Due to the current interest in CO₂ capture and storage by gas hydrate crystallization; there is a demand in experimental phase equilibrium data for the relevant CO₂ hydrate systems. In order to design efficient CCS processes, reliable and accurate phase equilibrium data is required. The present study involves the examination of CO₂ capture from a CO₂+N₂ mixture via gas hydrate crystallization and the measurement of hydrate phase equilibrium data for CO₂+N₂+TBAC+H₂O and CO₂+N₂+TBAF+H₂O systems by employing an isochoric pressure search method using static high pressure equipment.  The effect of TBAF and TBAC concentrations on the CO₂ hydrate formation pressures and the CO₂+N₂ separation efficiency will be investigated.

A MATLAB programme will be developed to fit the measured hydrate phase equilibrium data. An ASPEN Tech simulation will be performed to simulate and predict results of the overall carbon capture process. In order to determine the efficiency of CO₂ capture, compositions of the gas phase will be measured using a ROLSI^TM capillary sampling device and analysed with a gas chromatograph. A material balance will be employed to determine the compositions of the hydrate and aqueous phases. The material balance will be solved using a mathematical algorithm which employs Newton’s numerical method and differential evolution optimization strategy.