The Potential for Separation and Capture of Carbon Dioxide at High Temperatures Using Inorganic Membranes

摘要

Gas separation has been identified as a critical enabling technology for Vision 21 and various technologies that might be included in some Vision 21 plant configurations. Principal among these is the separation of hydrogen from reformed natural gas and coal-derived synthesis gas. Also of interest is the pre- and postcombustion separation and capture of carbon dioxide. Oak Ridge National Laboratory (ORNL) is engaged in the development of both high-temperature and low-temperature gas separation devices. ORNL has developed high-temperature (>600℃) inorganic membranes for gas separations of interest in fossil energy systems. For many processes of interest, particularly natural gas reforming and coal gasification, hydrogen and CO_2 are in the same process streams. Thus, separation of these components is of considerable interest. The Hr-CO_2 separation is addressed in this paper. At least two approaches may be used for the separation of CO_2 by using these membranes. For separation of H_2 and CO_2, the usual approach has been to fabricate inorganic membranes with sufficiently small pore size, i.e., ～ 0.5 nm diameter, so that they function as molecular sieves for H_2. Another approach has been to fabricate surface flow membranes in which CO_2 adsorbs on the pore surfaces and is transported through the membranes. Only molecular sieving, i.e., the high-temperature approach, is discussed in this paper. Results of these efforts are presented as well as a discussion of the potential for the use of these membranes.