Carbon dioxide capture and storage by pH swing mineralization using recyclable ammonium salts and flue gas mixtures

CO₂ mineral sequestration through the employment of silicate rocks such as serpentine is an important technology for the mitigation of CO₂ emissions. Most mineral carbonation works in this study use pure CO₂. The indirect carbonation process employed different flue gases (5, 15, 25% CO₂) and the presence of SOx and NOx. Also, the direct contact of CO₂ with the Mg source was compared to the indirect reaction of Mg with CO₂ as NH₄CO₃. The impact of variables such as temperature, solid-liquid ration (S/L), and molar ratio of additives on carbonation rate and degree was studied. An average carbonation efficiency of about 90% was achieved at 80°C after 30 min for indirect mineral carbonation process. The carbonation efficiency decreased to 50-60% when the process was directly employed. The carbonation efficiency obtained in the presence of 15-25% CO₂ was very similar to that with 100% CO₂ at 140°C, while at 80°C, the carbonation efficiency in presence of flue gas (40-55%) was much larger compared to that using pure C0₂ (10% after 3 h). SOx and NOx co-removal efficiency was 54.4% and 18% at 140°C and 20 bar, respectively.