Experimental and simulation studies of iron oxides for geochemical fixation of CO_2-SO_2 gas mixtures

摘要

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_2O_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 250bar became hematite, dawsonite (NaAl(OH)_2CO_3), siderite (FeCO_3) and quartz (SiO_2). Experimentally, siderite and dawsonite, derived from the presence of kaolinite (Al_2Si_2O_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.