Energy & Fuels, Vol.33, No.3, 1722-1733, 2019
Integrated (C)O2 Capture, Conversion, and Storage To Produce Calcium Carbonate Using an Amine Looping Strategy
One of the critical and emerging needs for sustainable energy production is the development of novel integrated approaches for the capture, conversion, and storage of CO2. In this context, carbon mineralization, which is a thermodynamically downhill route for the accelerated conversion of CO2 to water-insoluble and stable calcium and magnesium carbonates, is a sustainable approach for permanently storing CO2. However, one of the challenges with carbon mineralization has been the need for higher concentrations of CO2 to accelerate the formation of calcium and magnesium carbonates. In this study, we propose a direct integrated approach in which amine-bearing solvents, such as monoethanolamine (MEA), and alkaline Ca-bearing solids, such as calcium oxide and calcium silicate, are reacted in a slurry reaction system in two modes. These two modes involve in situ changes in the aqueous chemistry to facilitate the capture of CO2 using MEA and the release of CO2 into the aqueous phase to produce higher conversions of calcium carbonate. In the first mode, continuous CO2 flow at 1 atm is provided such that MEA in the aqueous phase captures CO2 and supplies the captured carbon-bearing species for reaction with dissolved calcium. In the second mode, MEA pre-loaded with CO2 was introduced into the system without a continuous supply of CO2. Complete conversion of calcium oxide to calcium carbonate was achieved using both modes. Further, the extent of carbon mineralization achieved with calcium silicate was 36% in mode 1 as opposed to 20% in mode 2 at 50 degrees C for a reaction time of 3 h. These data suggested that amine-bearing solvents undergo continuous looping between the CO2-loaded and release states, which facilitate the accelerated conversion of calcium-bearing oxides and silicates to calcium carbonate. The formation of calcium carbonate and calcium hydroxide phases was noted when less than complete conversions of calcium oxide were achieved. Calcium carbonate was the only phase formed on the complete conversion of calcium oxide and the carbon mineralization of carbon dioxide.