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| Titel |
Natural Gas Hydrates as CH4 Source and CO2 Sink - What do SO2 Impurities do? |
| VerfasserIn |
B. Beeskow-Strauch, J. M. Schicks, E. Spangenberg, J. Erzinger |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250021482
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| Zusammenfassung |
| The large amounts of gas hydrates stored in natural reservoirs are thought to be a promising
future energy source. The recently discussed idea of methane extraction from these
formations, together with the subsequent storage of CO2 in form of gas hydrates is an elegant
approach to bring forward.
A number of experiments have been performed on lab scale showing the replacement of CH4
by CO2 and vice versa. For instance, Graue and Kvamme (2006) demonstrated with Magnetic
Resonance Images of core plug experiments the possibility of CH4 extraction by using liquid
CO2. Laser Raman investigations of Schicks et al. (2007) showed, on the other hand, the
ineffectiveness and slowness of the CH4 exchange reaction with gaseous CO2. After 120
hours, only 20% CH4 were exchanged for CO2. Natural methane hydrates which include
often higher hydrocarbons tend to be even more stable than pure methane hydrates (Schicks
et al., 2006).
Contrary to lab conditions, industrial emitted CO2 contains - despite much effort to clean it –
traces of impurities. For instance, CO2 emitted from the state-of-the-art Vattenfall
Oxyfuel pilot plant in Schwarze Pumpe should reach a quality of >99.7% CO2
but still contains small amounts of N2, Ar, O2, SOx and NOx (pers. comm. Dr.
Rolland).
Here we present a microscopic and laser Raman study in a p-T range of 1 to 4 MPa and
271 to 280K focussing on CO2 hydrate formation and CH4-exchange reaction in
the presence of 1% SO2. The experiments have been performed in a small-scale
cryocell.
The Raman spectra show that CO2 and SO2 occupy both large and small cages of the hydrate
lattice. SO2 occurs strongly enriched in the hydrate clathrate, compared to its concentration in
the feed gas which causes a strong acidification of the liquid phase after hydrate
dissociation.
Our study reveals that the hydrate formation rate from impure CO2 is similar to that of pure
CO2 hydrate but that the stability of the CO2-SO2-hydrate exceeds that of pure CO2
hydrate.
The improved stability of impure CO2 hydrate might also boost the exchange reaction with
CH4 hydrate.
These significant parameters - changes of hydrate stability and CO2-CH4 exchange rate as
well as the acidification of the environment - have to be considered in future concepts for
CO2 sequestration combined with CH4 recovery.
Reference:
Graue, A., Kvamme, B. 2006. Conference Paper presented at the Offshore Technology
Conference in Houston, Texas, U.S.A.
Schicks, J.M., Naumann, R., Erzinger, J., Hester, K.C., Koh, C.A. Sloan, E.D., 2006. Journal
of Physical Chemistry, 110, 11468-11474
Schicks, J. M.; Spangenberg, E.; Erzinger, J. 2007. American Geophysical Union, Fall
Meeting, abstract #OS12A-08 |
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