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| Titel |
Modeling Dissolution and Precipitation Dynamics During Dedolomitization |
| VerfasserIn |
Yaniv Edery, Harvey Scher, Brian Berkowitz |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047298
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| Zusammenfassung |
| We simulate the processes of dedolomitization and calcium carbonate precipitation using
particle tracking. The study is stimulated by the results of a laboratory experiment
that examined reactive transport of injected CaCl2/HCl, into a column of sucrosic
dolomite particles, with a constant flow field. The injected fluid supplies Ca2+ and H+.
Dedolomitization is a protonation reaction yielding carbonic acid, which in a deprotonation
reaction yields CO32-; reaction with the abundant Ca2+ forms the precipitate CaCO3. The
novelty of the simulation is to treat the dynamics of the rate-limiting reactants with a particle
tracking method; the dedolomitization and precipitation processes involve multi-step,
multi-species chemical reactions, with both irreversible and reversible stages. At each time
step the local concentration of H+ determines the probability (assuming local carbonate
equilibria) of precipitation and dissolution. The precipitation changes the porosity which in
turn changes the local flow field. The particle tracking is governed by spatial and
temporal distributions within a continuous time random walk framework. This
includes the option of either advective-dispersive (Fickian) transport or the effects
of disorder of heterogeneous media — non-Fickian behavior. The dynamics of
dedolomitization are examined for different flow conditions. The fluctuations in the
local velocity distributions, due to porosity changes, create conditions for positive
feedbacks leading to preferential pathways, large-scale nonlinearity and precipitation
banding. These features have been observed in the laboratory experiments and are now
accounted for by the simulation results at similar time frames, velocities and pH levels. |
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