Vacuum Moisture Swing
The goal of this project is to design and build a direct air capture device that utilizes a vacuum moisture swing process to separate CO2 from ambient air. This process utilizes common sorbent materials to bind to CO2 as air passes through them, and then it leverages a process in which moisture unbinds the CO2 from the sorbents. The intent is to have a scalable design which will be practical and energy-efficient for large-scale deployment near high CO2 areas such as factories.
The project has two primary goals: to design a structured sorbent bed that will be more energy efficient than the standard packed bed, and to build a functioning, lab-scale device which will perform the vacuum moisture swing process. The structured sorbent beds will be designed as CAD models and run through CFD simulations to optimize their structures. The device will be designed to run the full direct air capture cycle, with most aspects automated.
The device will run through a five step cycle: adsorption, evacuation, desorption, final evacuation, and pressurization. During adsorption, ambient air will be pulled through the sorbent bed. The sorbent bed will then be isolated from atmosphere and a vacuum pump will draw down to complete evacuation. A water reservoir will then be exposed, causing the water to vaporize and unbind the CO2 from the sorbents in the desorption stage. The water reservoir will then be isolated and a final draw-down of the sorbent chamber will complete the final evacuation. Finally the sorbent bed will be exposed to ambient pressure, which will pressurize the system. The system can then repeat the cycles.
The new designs of the structured sorbent beds are intended to provide a lower resistance to flow, thereby decreasing the power requirement to run the cycle. A primary intent of this project is as a proof-of-concept that a vacuum moisture swing process can be a viable option for removing CO2 from air in large-scale, real-world applications.
As of writing this document, the design is still in development. Initial CFD simulations have been run, generating pressure drop numbers for monolith, laminate, and packed bed sorbent structures. A full PLC program has been written on run on a PLC emulator, and is prepared for deployment in a physical PLC. Initial sorbent bed designs have been 3D printed using just plastic. The Bill of Materials is nearly complete, and parts purchasing is intended to be the primary next step.
Sponsor: Project funding has been provided by Arizona's Salt River Project
Advisor: NAU Professor, Jennifer Lynn Wade - Jennifer.Wade@nau.edu
Mentor: NAU PHD Candidate, Stephano Sinyangwe - sks459@nau.edu
