Experimental and simulation studies of iron oxides for geochemical fixation of CO2-SO2 gas mixtures

Abstract

Iron-bearing minerals are reactive phases of the subsurface environment and could potentially trap CO 2 –SO 2 gas mixtures derived from fossil fuel combustion processes by their conversion to siderite (FeCO 3 ) and dissolved sulfate. Changes in fluid and mineral compositions resulting from reactions, involving the co-injection of SO 2 with CO 2 were observed both theoretically and experimentally. Experiments were conducted with a natural hematite (α-Fe 2 O 3 ) sample. A high pressure-high temperature apparatus was used to simulate conditions in geologic formations deeper than 800 m, where CO 2 is in the supercritical state. Solid samples were allowed to react with a NaCl–NaOH brine and SO 2 -bearing CO 2 -dominated gas mixtures. The predicted equilibrium mineral assemblage at 100 °C and 250 bar became hematite, dawsonite (NaAl(OH) 2 CO 3 ), siderite (FeCO 3 ) and quartz (SiO 2 ). Experimentally, siderite and dawsonite, derived from the presence of kaolinite (Al 2 Si 2 O 5 (OH) 4 ) in the parent material, were present in residual solids at longer reaction time intervals, which agreed well with results from the modelling work.