Wet carbonation of recycled concrete fines for low-carbon cement production: process design and techno-economic analysis

The cement industry is a major contributor to global CO2 emissions, responsible for approximately 7% of the total annual emissions. The decarbonization of this sector can be achieved through a range of technologies, such as carbon capture and storage to mitigate process-related emissions, and the electrification of the heat demand or adoption of alternative fuels to reduce energy-related emissions. This thesis investigates the techno-economic feasibility of implementing a wet carbonation plant of recycled concrete fines to address the CO2 emissions from the rotary kiln within an electrified-calciner cement plant. Recycled concrete fines, generated as the fine fractions during the concrete recycling process, exhibit the potential for partial CO2 capture, while also serving as supplementary cementitious material when blended with clinker. The proposed design configuration is modelled and simulated using the gPROMS process simulation software to evaluate both technical and economic performances. In this study, the process is also compared with an electrified cement plant with carbon capture system based on absorption with monoethanolamine to provide a benchmark for performance evaluation. The technical results reveal a limited carbon capture rate achievable by the carbonation process, reducing total equivalent CO2 emissions by approximately 15.2 % compared with an electrified cement plant without carbon capture. This performance is notably lower than that of the amine-based case (33.2 %). Nevertheless, the carbonation process demonstrates promising economic potential, characterized by a 3.3 % reduction in capital expenditures and 1.5 % for the operational requirements, with respect to the reference configuration with amine-based carbon capture unit. Overall, the study emphasizes the potential of wet carbonation as a promising pathway for CO2 mitigation within the cement industry, provided that further research and technological development are pursued to enhance its environmental performance.