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| Titel |
Surface area changing during CO2 water-mineral interaction: an inverse modelling approach |
| VerfasserIn |
A. Rocha Scislewski, P. Zuddas |
| 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 |
250026053
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| Zusammenfassung |
| Several physical and chemical mechanisms control the potential storage of CO2 in
geological media. The CO2 dissolution in the aquifers produces a decreasing on pH
enhancing the dissolution of minerals present in the host rock. This complex process
consists on a set of reactions that produces an increase in the fluid alkalinity and
facilitates the formation of metal complexes in solution. Reactions of gas dissolution
and mineral trapping are considerably slow but their relative effectiveness may be
increased over longer time frames given a faster sequestration. The reactive mineral
surface area, representing the area that really participates on the overall process,
is difficult to estimate. In this work, we applied a conceptual model to estimate
the mineral surface area participating in the reaction of dissolution-precipitation
during the geochemical interactions in multi-mineral systems using water chemistry
data.
In our schematic modeling, the chemical evolution of the dissolved phases is
reconstructed with a reaction progress chart defined by a fractional degree of advancement
(ζ) of the irreversible mass-transfer process and attaining the continuum limit during
water-rock interaction. The system is solved in terms of a transported reaction rate vector,
introducing the experimental rate constants for every single mineral and solving for the
surface areas of dissolving plagioclase, biotite, k-feldspar and calcite. This is done assuming
the activities of dissolved silica and aluminum ions as constrained by the instantaneous
equilibrium with quartz and kaolinite.
We applied our modeling to previous analytical results of a flow-through experiment
carried out with Caetité (Brazil) granite samples, at the temperature of 22Ë +/- 2Ë C and
using fluids at different CO2 fugacity. Preliminary results indicate that the surface area
dramatically changes by several orders of magnitude during several months of interactions for
albite and biotite minerals. In addition, this inverse modeling approach reveals that the
changing in the surface area is about 3-4 orders of magnitude higher when compared to the
mineral dissolution rate variation. |
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