In spite of its established role in reliably providing high-throughput, high-purity oxygen for gasification, cryogenic distillation-based air separation is costly and energy-intensive to operate, accounting for up to 15% of the total gasification plant capital cost, and consuming a major portion of in-plant power use. Moreover, any outages of the air separation unit (ASU) can disrupt the entire gasification plant process. Other oxygen supply technologies, such as pressure swing adsorption (PSA) and polymeric membranes are available, but at present commercially available offerings are limited in applicability to much smaller scales or cannot provide oxygen at a high enough purity (>95%) for gasification.
Since the cryogenic oxygen production patent issued to Carl Von Linde in 1903, the technology has been refined in engineering configuration and optimized in terms of efficiency to reduce costs to the greatest possible extent. Presently, the thermodynamic efficiency of state-of-the-art cryogenic air separation plants approaches theoretical limits as near as is practicable; therefore, a technical breakthrough that would significantly lower its costs is unlikely. Accordingly, there is great incentive to develop a new approach or technology for oxygen separation.
Accordingly, DOE/NETL recognized a need and an opportunity, and has been exploring alternative options for producing low-cost oxygen via several approaches. Ion transport membrane (ITM) technology is one such option started in the 1990s and is moving forward at engineering demonstration scale. Several other options are being explored, primarily at the proof-of-principle scales via Small Business Innovation Research (SBIR) grants. For example, in 2013 and 2014, SBIR Phase I grant applications were invited for proposals exploring novel approaches such as oxygen separation under magnetic gradients, via redox swing, sorbents, and biomimetic approaches.
The current DOE/NETL portfolio in gasifier feed systems includes important oxygen separation technology development projects.