Argon-Selective CMS for High Purity Oxygen Production

U.S. Department of Energy (DOE) is developing innovative, flexible, and small-scale (1-5 MW), modular gasification systems for converting diverse types of US domestic energy resources into value-added products with greatly reduced or negative CO2 emissions. Production of high purity (>95%) oxygen at modular scale is an enabling technology for successful development and deployment of these systems. Cryogenic air separation units are the standard commercial technology for large scale, high purity oxygen production with unit O2 cost between $33-$70 per ton/day. However, there is no cost-effective offering for cryogenic system at such small range (10 – 50 ton/day oxygen), therefore, it is not an economically viable option for modular gasification application. The commercial non-cryogenic separation in this range is mostly based on conventional pressure-swing adsorption (PSA) and/or vacuum-pressure-swing adsorption (VPSA) and they can produce 90-93% purity oxygen at reasonable costs (~$50 to $70 per ton), but not high-purity oxygen, which does not meet DOE target. This proposed project addresses this specific need. Our technology concept involves use of a novel 1-stage/2-layer rapid cycle PSA (RPSA) process using unique fiber structured adsorbents to both enhance the oxygen productivity of a conventional PSA system (thus reducing the overall capital and operating cost) and enable the production of required high purity (>95%) for oxygen. The introduction of a unique argon (Ar)- selective cellulose-derived carbon molecular sieve (CMS) fiber, following a first layer of LiX fiber, ensures the effective and thorough adsorptive-purification of air to cost-effectively produce high purity oxygen. In SBIR Phase 1 of this project, we plan to build on our developed LiX and CMS-based fiber adsorbents for N2- and Ar-selective adsorption. Pyrolysis carbonation conditions will be screened to optimize Ar-selectivity for the cellulose-derived CMS materials. The dual-layer fiber modules will be tested in a lab-scale RPSA unit to measure adsorption breakthrough and O2 purity to obtain necessary engineering design data and confirm techno-economic analysis. A 10 kg O2/day prototype system is planned to be designed, built, and tested in the SBIR Phase 2. Its successful demonstration will pave the way for our design and deployment of a 10-50 ton/day commercial modular system to meet the DOE’s goal for distributed power production of 1 to 5 MW, in collaboration with our partners, Georgia Institute of Technology and Generon. The anticipated benefits of the proposed technology will be development of a cost-effective modular high purity oxygen production technology for a number of industrial applications (such as medical oxygen supply and wastewater treatment, etc.) in addition to modular gasification for clean hydrogen and negative carbon emissions. Key factors for market acceptance and penetration of this technology will be its compact size, robustness, and lower cost of high purity oxygen production.