Demonstration Of Long-Term Stability of Solid Adsorbents For Direct Air Capture of Carbon Dioxide Under Real-World Working Conditions

Problem being addressed: CO2 capture is necessary for CO2 sequestration, utilization, and conversion. On-site capture is an attractive approach, because it is not limited by CO2 sources or transport infrastructure. However, CO2 concentration in air is 300 times less than in flue gas. Such low CO2 concentration amplifies the challenge and technology breakthroughs are needed to make on-demand CO2 production economically competitive. The adsorbent stability is one of major technical risks for adsorption process commercialization pursuit, which is regarded as one promising approach in the field. However, it is very expensive to conduct the long-term stability testing with current gas/solid reactor or contactor technologies known in the literature. Approaches: The adsorption and heat exchange (AHX) reactor design developed at MWI addresses the above challenge. An adsorbent material is loaded into the AHX module that is installed inside a compact reactor vessel for real-world performance testing. The adsorbent stability can be assessed by conducting long-time repeated capture/regeneration cyclic testing under practical process conditions. The AHX modular unit operates with air and water at low temperature and low pressure, and renders safe and environmentally benign operation. What is to be done in Phase I: In phase I, a small-scale AHX testing apparatus will be built with automated un-attended capture/regeneration operation. The solid adsorbents showing excellent performance in the previous work will be loaded into a miniature AHX module. A few different adsorbent formulations will be tested under the same capture conditions and regeneration conditions for a few months. The most stable adsorbent will be identified. The spent and fresh adsorbent materials will be characterized to understand correlation of the material composition and structures with the adsorbent performance and develop technical insights for further improvements.. Commercial Applications and Other Benefits: The stable adsorbent will facilitate commercialization of direct air capture (DAC) units with potential for widespread adoption. The possible applications include i) capturing CO2 at sequestration sites, ii) concentrating CO2 for greenhouse agriculture and micro-algal growth, iii) providing the carbon source for production of hydrocarbon fuels with renewable power (solar, wind power, etc.) and other renewable products.