Multiobjective optimization of membrane in hybrid cryogenic CO₂ separation process for coal-fired power plants

Post-combustion carbon dioxide (CO₂) capture is considered a potential method to mitigate CO₂ emissions from fossil fuels burned in power plants. In recent years, combining two different methods of post-combustion CO₂ capture such as membrane and cryogenic distillation has been explored for availing the advantages of each method. This study focuses on the optimization of membranes for developing the membrane-cryogenic distillation process. For this purpose, a process flow sheet is developed, and simulation with model components such as compressor, heat exchanger, turbo expander, and distillation column is carried out using Aspen Plus. A membrane model is developed using in-house MATLAB code, and optimization is done to achieve higher concentration and recovery of CO₂ using the MOJAYA algorithm. The membrane model is coupled to Aspen Plus through component object model (COM) technology. In this investigation, a hollow fiber membrane is considered. The optimized specifications of membrane modules are length, number of hollow fibers, feed pressure, and permeate pressure which are 0.3 m, 100,000, 5.76 bar, and 0.1 bar, respectively. This analysis results in the purity and recovery of the process of 99.8 and 90%, respectively, and an energy penalty of around 1.74 MJ/kg of CO₂. A comparison of other processes available in the literature reveals that the current study renders maximum purity and recovery with a minimum energy penalty.