Assessment of CO₂ absorption characteristics and carbon sequestration potential of fly ash mineralization reaction from different coal types

The particle size distribution and chemical composition of fly ash from different coal types are known to directly influence the carbon sequestration performance in mineralization reactions. Investigating the CO₂ absorption characteristics of mineralization reactions is considered crucial for assessing the carbon sequestration potential of fly ash. Fly ash samples from several coal-fired power plants in Shijiazhuang, China, are analyzed using pressure drop and thermogravimetric analysis methods to comprehensively characterize the CO₂ absorption characteristics and carbon sequestration performance of mineralization reactions. The experimental results indicate that increasing the pressure and temperature of mineralization reactions enhances the carbon sequestration performance of fly ash. When the initial pressure is increased from 1.0 MPa to 2.0 MPa, the average CO₂ absorption of fly ash from different coal types increases by 7.18 g/kg. When the temperature is raised from 40 ℃ to 60 ℃, the average CO₂ absorption increases by 4.28 g/kg. The pressure drop method is found to result in non-mineralized CO₂ absorption, leading to an overestimation of carbon sequestration performance compared to the thermogravimetric analysis method. Smaller particle sizes are observed to provide higher specific surface areas, promoting the interaction between CO₂ and active components, which enhances carbon sequestration performance. A positive correlation is identified between the CO₂ absorption of fly ash and Ca content, while a negative correlation is observed with S content. High-Ca fly ash exhibits superior carbon sequestration performance due to its abundance of reactive materials. Sulfur in fly ash, primarily in the form of sulfates, competes with calcium during reactions, inhibiting carbonate formation and reducing carbon sequestration performance. Among the fly ash samples analyzed, fly ash from Anhuaneng Thermal Power Plant (AH) exhibits stable CO₂ absorption and mineralization carbon sequestration efficiency. Fly ash from Huadian Thermal Power Plant (HD) demonstrates relatively high CO₂ absorption capacity. Fly ash from Xibaipo Thermal Power Plant (XB) shows the highest and most stable CO₂ absorption and mineralization carbon sequestration efficiency, indicating the greatest potential for carbon sequestration in mineralization reactions.