Design and optimization of membrane processes for carbon capture purposes

There has been an increasing interest in the application of membrane systems to CO2 capture for significantly reducing greenhouse gases emissions, and their success depends in large part on how the process is designed. This thesis proposes a superstructure optimization approach based on mathematical programming to design optimal multistage membrane systems for CO2 capture in Aspen Plus. The membrane system is defined with reference to a bio-based PEBA-type membrane developed within BioCoMem Horizon project. Three separation processes are taken into account: biogas upgrading, natural gas sweetening, and post-combustion carbon capture. For biogas upgrading and post-combustion carbon capture the optimal structure comprises three stages, while in the sweetening of natural gas, different designs involving two or three stages show comparable performances. The processing cost for natural gas sweetening and biogas upgrading is twice as much that of competing technologies, while the energy requirements are comparable. In post-combustion carbon capture, both processing cost and energy demand are much higher than those of conventional technologies. Results highlight that, in order to reach commercial maturity, membrane features must be improved and the development effort should focus more on enhancing membrane permeance rather than its selectivity.