Effect of rock composition on mineralization in sequestration

摘要

The reactive behavior of pure CO_2 with limestone, sandstone, arkose and peridotite wasexamined in this study. The experimental apparatus consists of series of high-pressurereactors with pure CO_2 as feed gas at 1000C to evaluate the dependence of kinetics andmineralogical changes on rock composition. Arkose was observed to exhibit the highesttendency of participating in these reactions, which can be attributed to the geochemicalcomplexity of its initial mineral assemblage. Layers of calcite were seen growing on thesurface of the arkose. Analcime deposits are almost omnipresent either occurring as largeconnected aggregates or as deposits on surfaces of other minerals. Ankerite and calcitedeposition were observed as amorphous mass intergrown with starting minerals.Continuous dissolution of limestone was seen with the release of CO_2 gas, indicated bythe increasing pressure in the reactor (formation of a gas chamber), which occurs due tothe lack of any source of alkali to buffer the solution. With sandstone, there was slightincrease in pH due to dissolution of feldspars. The rate of carbonation of feldspars ispretty slow compared to the dissolution. Hence the precipitation of carbonates at the measured time scale is not evident. In peridotite experiments, carbonation of peridotiteforming calcium and magnesium carbonates along with serpentine was evident. Hence,arkose has the geochemical complexity for permanent sequestration of CO_2 as carbonatesand is an ideal choice. The study provides useful laboratory data when considering CO_2sequestration in different geologic The brine chemistry results for the experiments withdifferent initial rock compositions are presented in this report. These results complementthe changes in the rock chemistry.