Forsterite Carbonation in Zones with Transport Limited
by Diffusion
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Abstract
Fractures
in rocks could provide substantial surface area for reactions
that lead to carbonate mineral precipitation in geologic carbon sequestration.
Diffusion-limited transport of solutes in such zones affects the spatial
and temporal distribution of mineral dissolution rates and carbonation
products, thus influencing the overall carbon sequestration process.
A tube with a packed bed of forsterite and exposed at one end to a
solution in equilibrium with 100 bar of CO<sub>2</sub> at 100 °C
was used to explore the timing and spatial localization of carbonate
precipitation along a one-dimensional diffusion-limited zone. The
identity and quantity of carbonate minerals as a function of depth
were determined using Raman spectroscopy and total carbon analysis.
Carbonate was observed within the packed bed as early as day 1. Hydromagnesite
formed in the bed first and was replaced by magnesite within 5 days.
Carbonate was spatially localized with the largest amount formed 0.5
cm into the packed bed. The overall carbonation rate in the bed did
not decline until day 30