Leaching and indirect mineral carbonation performance of coal fly ash-water solution system

• Wet indirect mineral carbonation is conducted using fly ash (FA) as source materials.
• Overall CO2 storage capacity of FA suspended solution is 31.1 mg CO2/g FA.
• Maximum mineral carbonation capacity of FA suspended in solution is 17.4 mg CO2/g FA.
• Alkaline components are leached from suspended FA during mineral carbonation.
• Tiny particles in FA strongly affect the mineral carbonation performance.

The leaching and carbonation performances of indirect mineral carbonation are investigated using coal fly ash (FA) as the raw source and water as the solvent. The reactions were conducted at ambient temperature and pressure with a gas mixture comprised of 15 and 33 mol% CO2. The overall CO2 storage and mineral carbonation capacities of FA suspended solution in which alkaline components had been previously leached for 2 h (2S33) were 31.06 and 17.36 mg CO2/g FA, respectively. The mineral carbonation capacity of FA in 2S33 was 18% of the theoretical value and its mineral carbonation storage capacity ratio was 55.9%. The performance of 2S33 was higher than that of its filtrate because the alkaline components were leached from the suspended FA simultaneously with the mineral carbonation. Submicrometer-sized particles were present in raw FA and their size was reduced by stirring during the leaching, as well as slightly increased, compared to the original raw FA, due to the carbonation. These submicro FA particles strongly affected the performance of the mineral carbonation of the FA-water solution.