Study on CO₂ absorption-mineralization characteristics of mixed amine solution coupled with CaO and key influencing factors in mineralization process

Amine CO₂ capture is an effective post-combustion carbon capture (PCC) technology, while CO₂ mineral carbonation is a safe and stable method for CO₂ storage. In this paper, these two methods were combined, and the CO₂ absorption-mineralization performance of mixed amine solution coupled with CaO under different ratios of mixed amine solution, temperature, reaction time and CaO addition ratio were studied by using MEA/MDEA mixed amine solution as the CO₂ absorbent and using CaO as the CO₂ mineralizing raw material. The results show that CaO could effectively mineralize the CO₂ absorbed in MEA/MDEA solution, realizing the regeneration of MEA/MDEA solution simultaneously under normal temperature and pressure. Meanwhile, the MEA/MDEA solution can still maintain a high CO₂ conversion rate (77.4%) and CO₂ cycle loading (1.03 mol/L) after five cycles of absorption-mineralization experiments. The FT-IR and XRD analyses reveal that the addition of CaO makes a large amount of Ca²⁺ and OH^- into the MEA/MDEA solution, which could react with CO_3^2\rm - /HCO_3^\rm - and protonated amine in the solution to form calcium carbonate precipitate and free amine respectively, thus realizing the mineralization of CO₂ and the regeneration of MEA/MDEA solution. The main component of solid products obtained is calcium carbonate, and calcite is its main crystal form.