A solid sorbent-based multi-stage fluidized bed process with inter-stage heat integration as an energy efficient carbon capture process

• A novel energy-efficient carbon capture process with multi-stages is proposed.
• K2CO3, Na2CO3 promoted MgO, and Li4SiO3 were used as the sorbents for each stage.
• A flow-sheet simulator based on a mathematical model was developed.
• The heating demand for three-stage process was estimated to be1.73 GJ/ton-CO2.
• The net electrical efficiency loss of the retrofitted coal power plant was 9.5%.

A thermally coupled multi-stage fluidized bed process was developed as a viable option for the carbon capture process with reduced energy consumption. The process is composed of multiple stages that operate at different temperature levels. Each stage consists of an absorber, a regenerator, and a heat exchanger for intra-stage heat recovery. Between adjacent stages, an absorber at a higher temperature stage is thermally integrated with a regenerator at a lower temperature stage to balance the supply and demand of thermal energy. A conceptual scheme of the process and an associated mathematical model was developed. Case studies of two- and three-stage fast fluidized bed processes are presented. For each stage, K2CO3, Na2CO3 promoted MgO, and Li4SiO4 are used as low-, medium-, and high-temperature solid sorbents which undergo independent gas-solid reaction pathways but with thermally coupled. The sorbents were chosen based on the availability of data on their kinetics and properties. A flow-sheet simulation of the developed process for a 500-MWe pulverized coal-based power plant was conducted using the Aspen Custom Modeler, to produce a process design study and a sensitivity analysis. Finally, the energy efficiency, including the net electrical efficiency, of the retrofitted power plant is compared with those of optimized MEA-based carbon capture processes and the calcium looping process.