These slides were presented at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

Carbon capture, utilization and storage (CCUS) is considered as an effective approach to reduce greenhouse gas emissions. CCUS is a multistep process involving the capturing of carbon dioxide produced by industrial sources, such as power plants or factories, before being released into the atmosphere, transporting it to a storage location, and then securely storing it underground or in other suitable reservoirs. Ongoing research and development activities are focused on improving the efficiency and scalability of carbon capture systems. Separation through membranes is one of the most widespread methods for isolation. There are different types of membranes for CO2 separation: The most frequently used ones are made from polymers of organic compounds. Nevertheless, inorganic formulations (e.g. zeolites) can provide very high thermal and chemical stability (generally at the cost of lower permeability), and new advanced membrane materials are emerging, including composite, MOF (metal-organic framework), ZIF (zeolitic imidazolate framework) or CMS (carbon molecular sieve) membranes. Compared to other carbon dioxide isolation methods, like amine washing, membrane separation has the advantage of being highly energy efficient, as typically no heating is required. This paper presents an approach for simulating carbon dioxide membrane separation. Firstly, the relevant membrane properties are investigated with the help of computational chemistry. A zeolite membrane and a polymer membrane are examined. The membrane permeability is determined using a multiscale computational chemistry approach. In doing so, various length and time scales and reactions, from atomistic level up to micrometer scale are represented, taking into account quantum mechanical properties as well as molecular mechanics behavior. The approach is validated through successful comparison with properties documented in literature. In the next step, permeability properties are derived from the computational chemistry simulation for the membrane. These are then used within a finite volume based CFD (Computational Fluid Dynamics) simulation of a separation unit. To model the membrane, a baffle interface which is selectively permeable is applied inside a cavity. Flue gas modelled as a mixture containing several species is introduced into the system, which has two outlets. The permeate passes the membrane and can leave the system through an outlet on the other side of the membrane. The goal of the simulation is to be able to assess the efficiency of the separation process regarding the design and dimensions of the ducts and cavities as well as process parameters like flue gas concentration and flow velocities. It allows also to virtually design and test new membrane materials. In this way, a digital twin of the CO2 separator including the detailed membrane formulation can be realized.