Opportunities for CO2-Selective Membranes in Hydrogen Purification

Syngas operations require separation of CO₂ from hydrogen for various reasons, not only for CO₂ capture from IGCC operations, but for a number of existing refinery and petrochemical applications.  Membrane technology is an attractive approach to CO₂ capture because of inherent advantages such as modularity, high energy efficiency and good reliability.  MTR has been developing CO₂-selective Polaris^TM membranes, which are highly permeable to CO₂ and reject the other major components of syngas, including H₂, CO and CH₄.  Polaris membranes have CO₂ permeances approximately ten times higher than other commercial CO₂-selective membranes.  This combination of permeance and selectivity meets the target range necessary to yield a competitive membrane-based process for hydrogen purification and/or CO₂ capture and sequestration.

This presentation will describe how multi-stage and multi-step membrane process designs can be used to minimize membrane area, compressor power requirements, and hydrogen loss during hydrogen recovery from syngas.  A preliminary process simulation study shows that a Polaris-based membrane process can achieve 99% hydrogen recovery, and capture 97% of CO₂ as a sequestration-ready liquid stream, at an energy cost lower than conventional technologies such as Selexol.  Currently, MTR is working with the U.S. DOE National Carbon Capture Center (NCCC, operated by Southern Company) to conduct field tests of Polaris membranes at a coal-fired gasification plant.  The membrane demonstration system processes 500 lb/hr syngas (equivalent to 0.15 MWe IGCC power plant).  Results of the tests will be summarized, and critical issues such as long-term stability in practical applications and the impact of contaminants on system performance will be addressed.