(321l) Prediction of N2 and Co2 Gas Hydrate Equilibria

The sequestration of CO2 is essential to reducing greenhouse effects. According to recent reports [1-2], 80% of total greenhouse emissions come from CO2 and CO2 emissions have increased by 15% from 1980 to 2002 in the US. Global warming due to CO2 emissions has become a hot issue and, last year, it has manifested as severe weather changes and strong hurricanes. There has been active research on the geological and ocean storage of CO2 [3-5] and Japan has already been injecting CO2 into the aquifer since 2003 [6]. However, the separation process for CO2 prior to geological or ocean injection has not actively been studied. In other words, their separation process from actual plant sites has yet to be developed. One possible separation process of CO2 from industrial flue/tail gases would be a gas hydrate separation technique since the equilibrium conditions of CO2 hydrate is very moderate (around 10 atm at 273K). Also, the process has several merits. The same flue gas pressure or a little compression according to different sources can be used to produce their hydrates and the transportation of CO2 in the hydrate form requires much less compression or freezing than the transportation of its gas or liquid form. In the presentation, we predict the equilibrium condition of N2 and CO2 binary mixture hydrate at various conditions in order to apply this information for the development of CO2 separation process using gas hydrates. The Peng-Robinson equation of state is employed for the calculation of fugacity in the gas phase and the Lee-Holder distortion model [7] is used to predict the binary gas hydrate (N2 and CO2) equilibrium condition with two empirical parameters. In a model, we use the assumption that the water cavity can be distorted as a function of gas molecule in it. With the optimized empirical parameters we could predict the equilibrium condition of N2 and CO2 gas hydrate in 10% error.

BIBLIOGRAPHY

1. http://www.netl.doe.gov/coal/Carbon%20Sequestration/pubs/project%20portf..., seen in December 2004.

2. U.S. Department of Energy, ?Carbon Sequestration Technology Roadmap and Program Plan-2004?, Office of Fossil Fuel, NETL, April 2004.

3. S. Bachu, ?Screening and Ranking of Sedimentary Basins for Sequestration of CO2 in Geological Media?, Environmental Geology, vol 44(3), 277-289(2003).

4. P. Brewer, G. Frederic, E. Pelzer, and F. Orr, ?Direct Experiments on the Ocean Disposal of Fossil Fuel CO2, Science, vol 284 (5416), 943-945 (1999).

5. S-Y Lee, L. Liang , D. Riestenberg, O. R. West, C. Tsouris, and E. Adams, ?CO2 Hydrate Composite for Ocean Carbon Sequestration?, Environ. Sci. Technol., vol 37, 3701-3708 (2003).

6. http://www.rite.or.jp/English/E-home-frame.html, seen in December 2004.

7. S.-Y. Lee and G. D. Holder, "A Generalized Model For Gas Hydrate Equilibria", Gas Hydrates: Challenges for the Future, Ann. of the New York Academy of Science, Vol 912, 614-622, 2000.