Novel waste bone recovery system for CO2 and SOx utilization in cement plants using microbubble carbonation reactor

Abstract

Cement has been widely used as a primary building material to construct various types of infrastructure. However, cement plants emit excessive carbon dioxide (CO2) and sulfur oxide (SOx) during calcination of limestone. Animal bone residues can reduce air pollutants as they contain calcium hydroxyapatite (Ca10(PO4)6(OH)2), which can capture and utilize CO2 and SOx. Therefore, brushite cement (CaHPO4∙2 H2O) and raw materials of cement, such as calcium carbonate (CaCO3) and calcium sulfate (CaSO4), can be recovered. In this study, a novel waste bone recovery system for CO2 and SOx utilization using cement plant flue gas was developed using a microbubble carbonation reactor (MCR). The system was designed using a process simulation model with the experimental results of the proposed MCR. Using an MCR with a high carbonation rate increases economic feasibility by decreasing the capacity of the conventional cost-intensive carbonation process. The proposed model involves the following steps: (1) waste bone dissolution and synthesis of CaHPO4∙2 H2O; (2) SOx capture and utilization; (3) CO2 capture and utilization using MCR. The total annualized cost (TAC) was determined to validate the economic feasibility of the system. Consequently, 99% of SOx and 94% of CO2 were captured using the production of CaSO4 and CaCO3 at the MCR, respectively. Additionally, the TAC of the proposed system can be decreased by 44% and 27% compared to the base cases 1 and 2 corresponding to the conventional SOx and CO2 capture processes.