A Novel Rapid Pressure Swing Adsorption (RPSA) System for Modular Oxygen Production
- Georgia Inst. of Technology, Atlanta, GA (United States). Georgia Tech Research Institute
The worldwide oxygen (O2) market stood at $10.80 billion in 2014 with production of over 100 million metric tons per year of pure O2 from air. The US oxygen market, which holds around 23% of global share, is expected to grow at a compound annual growth rate (CAGR) of 2% and reach 42.63 million tons by 2023. Oxygen is used for diverse applications as a catalyst and oxidizing agent in the chemical industry, in food and beverage, mineral processing and mining, water treatment and healthcare industries, etc. For large-scale oxygen production, standard cryogenic air separation technologies offer the lowest production cost and energy requirements for oxygen. At oxygen production levels of less than 200 tons/day (TPD), the capital cost and energy penalty for cryogenic air separation become too high to compete with pressure swing adsorption (PSA) or vacuum pressure swing adsorption (VPSA) oxygen production systems. Commercial PSA plants have seen incremental improvement in the past 20 years; however, much lower capital costs and energy requirements are still needed to support the DOE’s modular gasification platform for small scale (10-50 TPD O2 level) distributed power and chemical production from fossil fuel. This project is aimed at developing a novel structured rapid PSA (RPSA) design with a microporous N2-selective Lithium-Low-Silica-X type (LiLSX) zeolite-containing fiber membrane separating N2 from air, resulting in a highly efficient oxygen production process. The RPSA process by using novel structured adsorbents has the potential to improve oxygen productivity of a conventional PSA system by almost an order of magnitude. Structured adsorbents allow high gas throughput with low pressure drop and effectively provide more gas/adsorbent contact resulting in higher mass and heat transfer and adsorbent utilization. In this phase I project, we incorporated commercially available LiLSX materials into a structured continuous adsorbent structure—as opposed to the discrete nature of a beaded bed—to eliminate issues related to pressure drop, crush strength and dusting and improved adsorption kinetics. One key benefit of structured adsorbents is handling target flow rates within a much smaller footprint, which will reduce CAPEX and OPEX. In Phase I of this project, working with our research institute partner, Georgia Institute of Technology , we synthesized and screened a number of fibrous adsorbent structures, with two different fabrication routes. These lab-made fiber modules were then tested in a lab-scale RPSA unit to measure their breakthrough and O2 separation performance. Experimental results clearly show that oxygen production from air can be achieved with high N2 selectivity via the use of our novel fiber module system. The O2 purity of fiber modules can be in the range of 80-95% depending on the cycle conditions, with significant reduction of bed-size-factor. Upon proper RPSA cycling optimization, the fiber sorbent technology showed a 4-fold increase in mass transfer rate as well as a 20-fold reduction in bed pressure drop. Based on the experimental data, Susteon developed preliminary process models through Aspen Adsim™ and incorporated industrial standard 12-step advanced VPSA cycles that cannot be replicated in lab PSA system at this stage. Simulation confirmed lab findings and showed that the low system void is one of the key factors to achieve high O2 purity and cyclic performance, both of which can be achieved on our fiber modules with proper packing. The RPSA results in 10% higher product recovery as compared to conventional PSA based on packed bed with beads. The experimental and modeling work done in this SBIR Phase I project provided valuable insights for the design of a protype pilot oxygen production system for commercial-relevant deployment of this process technology. Some of these insights will be further investigated in Phase II of this project. Preliminary techno-economic analysis in the Phase I study showed that the distributed, modular O2 production facility at 50 TPD O2 capacity for a 5 MW gasification plant has a corresponding specific power consumption of 206 kWh/ton, with unit O2 cost of $37-40/ton. The current state-of-the-art (SOTA) PSA production price for oxygen is $45-52 per ton depending on the specific gas supplier, with power consumption up to 250 kWh/ton. Such potential shall be the focus of a Phase II project, with a successful demonstration at 10-20 kg/day pilot scale to pave the way for the 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 industrial partners, Generon and Praxair. The anticipated benefits of the proposed technology will be the development of a modular oxygen technology for gasification and other applications, including metal and glass industries, pulp and paper, chemical and refining, medical oxygen supply, oxygen for ozone production, water purification and wastewater treatment, etc.
- Research Organization:
- Susteon Inc., Cary, NC
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- SC0020515
- OSTI ID:
- 1845341
- Type / Phase:
- SBIR (Phase I)
- Report Number(s):
- DOE-SUSTEON-20515; 10005
- Country of Publication:
- United States
- Language:
- English
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