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Summary

It may be possible to lower costs of carbon capture and sequestration by keeping constituents such as sulfur dioxide (SO₂) in the flue-gas stream. The reactive behavior of pure carbon dioxide (CO₂) and CO₂+SO₂ mixtures within a geologically realistic environment was examined in this paper. The experimental apparatus consisted of a series of high-pressure reactors operated at different conditions and with different feed-gas compositions to observe changes in both the rock and water compositions. The rock consisted of equal proportions of quartz, calcite, andesine, dolomite, chlorite, and magnesite (constituents in arkose or dirty sandstone). The brine was prepared from laboratory-grade sodium chloride. Several long-term batch experiments with pure CO₂ were carried out at different temperatures. Each mineral in the mixture showed evidence of participating in the geochemical reactions. Layers of calcite were seen growing on the surface of the arkose. Analcime deposits were omnipresent, occurring either as large connected aggregates or as deposits on the surfaces of other minerals (quartz). Calcite depositions were observed as amorphous masses intergrown with the feed. The CO₂+SO₂ mixture experiments showed growth of euhedral anhydrite crystals and pronounced dissolution patterns over the examined surfaces. The growth of these new phases would lead to significant changes in the petrophysical properties of the rock. The trends in ionic-concentration changes in the aqueous phase complemented the changes in the rock chemistry.