Aqueous Ammonia Capture Integrated With ex-Situ Mineralisation Using Recyclable Salts for Industrial CCS

AbstractCarbon dioxide capture and storage by mineralization (CCSM), also known as ex-situ mineralization, is an important technology for industrial CCS. The feedstocks for CCSM can not only be Mg/Ca-silicate minerals, but can also include waste materials from industries, such as steel slags and waste cement. Aqueous ammonia capture is preferred for industrial CCS, since industrial emissions present high CO2 concentrations (around 25 vol.%) and more impurities (SO2/NOx) than that from power plants. Aqueous ammonia CO2 capture integrated with ex-situ mineralisation avoids stripping CO2 as pure gas from absorbents and compression of CO2, and therefore reduces the high energy consumption of capture. In this study, optimization experiments were conducted on this process. The dissolution efficiency of Mg from serpentine using 2.8M NH4HSO4 at 100g/l solid to liquid ratio for 1h was around 80%. The decrease in dissolution efficiencies is because of the Si passive layer on the surface of serpentine particles. The molar ratio of Mg: NH4+ salts: NH3 is the key factor controlling carbonation efficiency, and when using the molar ratio of Mg: NH4+ salts: NH3 is 1:1.5:2, the carbonation efficiency was 96%