CO2 sequestration using brine impacted fly fish
Muriithi, Grace Nyambura
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It was hypothesized that South African FA and brine could sequester CO2 through mineral carbonation. A statistical approach was undertaken to optimize the % CaCO3 formed from FA/brine/CO2 interaction with input parameters of temperature, pressure, particle size and solid/liquid ratio (S/L) being varied. The ranges adopted for the input parameters were: temperature of 30 ºC or 90 ºC; pressure of 1 Mpa or 4 Mpa; four particle sizes namely bulk ash, > 150 μm, < 20 μm and 20 μm- 150 μm particle size range; S/L ratios of 0.1, 0.5 or 1. The FA/ brine dispersions were carbonated in a high pressure reactor varying the above mentioned input parameters. The fresh Secunda FA of various size fractions was characterized morphologically using scanning electron microscopy, chemically using X-ray fluorescence and mineralogically using qualitative X-ray diffraction. The carbonated solid residues on the other hand were characterized using quantitative X-ray diffraction, scanning electron microscopy, thermal gravimetic analysis and Chittick tests. The raw brine from Tutuka together with the carbonation leachates were characterized using inductively coupled mass spectrometry and ion chromatography. Total acid digestion was carried out to evaluate the differences in the total elemental content in both the fresh ash and the carbonated solid residues. The results suggested that South African FA from Secunda belongs to class F based on the CaO content as well as the total alumina, silica and ferric oxide content, while the RO brine from Tutuka were classified as NaSO4 waters.