(389b) Mineralization in Sequestration: Effect of Rock Composition

Kinetics of mineralogical reactions of pure CO2 with limestone, sandstone, arkose and peridotite were examined in a high-temperature, high-pressure system. Mineralogically complex arkose was most reactive. Layers of calcite were seen growing on the surface of arkose. Analcime deposits were omnipresent, either occurring as large connected aggregates or as deposits on surfaces of other minerals. Ankerite and calcite were observed as amorphous deposits intergrown with starting minerals. With limestone, continuous dissolution was seen with the release of CO2 gas, indicated by increase of reactor pressure. This occurs due to the lack of a source of alkali to buffer the solution. With sandstone, the decrease in pH of the solution was moderate compared to arkose and limestone, but there was no evident precipitation due to the lack of necessary cations. In peridotite experiments, carbonation of peridotite forming calcium and magnesium carbonates along with serpentine was evident. However, peridotite is not a commonly occurring mineral. Arkose has the geochemical complexity for permanent sequestration of CO2 as carbonates and is an ideal choice. Geochemists workbench (GWB) was used for kinetic modeling of these reactions. A full factorial statistical analysis was carried out to identify the most sensitive parameters (kinetic rates and reactive surface areas) in the arkose. The choice of the base parameter in brine governs the mineral that drives the geochemical process. Simulations predict faster reactions than those observed experimentally. Hence, caution should be exercised when using the calculated rates of reaction for making long-term process predictions.