Modeling, simulation and design of the rotating packed bed for MEA-based carbon capture system

Abstract

Mitigation technologies of greenhouse gas emissions have been actively researched due to the rising concerns for climate change and global warming. For carbon capture, several technologies are already developed and commercialized. For conventional power plants, post-combustion capture using absorption is most popular because an existing power plant can easily be retrofitted to accommodate it. Even though chemical absorption based on amine solvents is a mature technology, the large volume of packed beds and extra costs needed for the conventional MEA process for carbon capture are the obstacles to applying the technology to industrial plants. To lower the costs of the process, there are many outstanding issues, such as solvent selection-design, developing advanced process units and, process operability. The rotating packed bed (RPB) is an intensified equipment that can reduce the volume of the packed bed significantly and maybe a good alternative for certain industrial situations. The RPB has been suggested as the rotational force can enhance the mass transfer rate by increasing the interfacial area. Since the rotating packed bed can use a high viscosity solvent, a high concentration of the absorbent that can decrease the solvent flowrate as well as regeneration energy can be applied. For widespread industrial adoption of the monoethanolamine (MEA) process with RPBs, an investigation of its rotation cost and the operation conditions is needed. In this study, the design and operation related to the energy consumption of the MEA-based carbon dioxide capture process applied with RPBs are analyzed through modeling and simulation. The rigorous model of RPB for carbon capture is developed in the simulator. A thermodynamic model and physical properties models that can simulate the physical and chemical phenomena of a mixture of MEA and water and carbon dioxide are used. The mass transfer coefficients models and hydraulic models that can express the effect of the rotation are employed. The developed process model is validated with steady-state experimental data in the literature and the whole process including RPB absorber, stripper, and other process units are integrated into the simulator. The preliminary designs of the RPBs are suggested based on the consideration of flooding and capture rate, and then key operating variables are optimized to minimize the total energy consumption. The RPB cannot handle large gas flows with one unit since the RPB has size limitations. Therefore, the maximum gas flow rate that a single carbon capture process with RPB units can treat are examined. The module concept is applied to the RPB process. Depending on the treating gas flowrate, three different module designs are suggested. The cost estimation model for each module is obtained. The number of each module for processing a given gas flowrate is investigated based on cost estimation models.