Desorption and mineralization of CO2 in amine-based solution by Ca(OH)2

Abstract

Aiming at the shortage of CO2 desorption process, a new desorption method, fixing CO2 by adding calcium hydroxide CO2-loaded amine solution (MDEA + MEA), was proposed in this paper. The emitted CO2 was converted into CO32- using amine solution (MDEA + MEA), and then made into carbonate, a product of mineralization, by combining the Ca(OH)2 with Ca2+ and the OH− released by Ca(OH)2 which can neutralize the protonated amines and convert them into fresh amines at 20 °C and ambient pressure. And the associated desorption mechanisms by adding calcium hydroxide into CO2-loaded amine solution (MDEA + MEA) was investigated. The effects of CO2 loading, C/Ca molar ratio, reacting time, temperature and stirring rate on CO2 desorption rate were systematically investigated in desorption and mineralisation process. The results indicated that changing the C/Ca molar ratio, CO2 loading, reacting time, temperature and stirring rate have an effectively influence the desorption efficiency. The performance stability of the amine solution (MDEA + MEA) was verified in multicycle-cycle experiments. In addition, CO2 capture efficiency of different amine solutions was also studied. The results indicated that a capture efficiency of 1 mol/L MEA + 1 mol/L MDEA as high as 61.03% was achieved which is 19.28% higher than that of its counterpart (0.2 mol/L MEA + 1 mol/L MDEA). Multiple-cycle experiments showed that CO2-loaded amine solution (MDEA + MEA) achieved stable cyclic loading (0.537molCO2/L) and regeneration efficiency (72.47%). This further confirmed the coordinated mechanism of carbonation reaction between CO2 and Ca(OH)2 using mineral composition analysis (XRD), thermogravimetric analysis (TGA) and transmission electron microscope (TEM). It is verified that calcium hydroxide can reduce and reuse emitted CO2, thereby making CO2 a potential future resource.