(204a) Development of Dense Membranes for Hydrogen Separation from Coal Gasification Streams

We are developing dense cermet (i.e., ceramic-metal composite) membranes for separating hydrogen from product streams generated during coal gasification. Hydrogen separation with these membranes is nongalvanic (i.e. requires no electrical power), and the hydrogen separated from the feed stream is of high purity, making post-separation purification steps unnecessary. Using various feed gas mixtures, we measured the hydrogen permeation rate, or flux, for the membranes in the temperature range of 500-900°C. This rate varied linearly with the inverse of membrane thickness and reached ≈33 cm³[STP]/min-cm² at 900°C for an ≈15-µm-thick membrane when 100% H₂ at ambient pressure was used as the feed gas. When membranes were tested in a gas mixture that contained CH₄, CO, and CO₂ for times approaching ≈500 h, performance did not degrade. Because the membranes will encounter H2S, we also tested the membranes in gas mixtures that contained H₂, CH₄, CO₂, CO, and H₂S. Hydrogen flux measurements showed that at 900°C, the membranes are stable for up to 1200 h in gases that contain 400 ppm H₂S. The cermet membranes are found to be stable in the temperature range of 500-800°C in simulated synthesis gas mixtures containing ≈21% steam. The present status of membrane development will be presented in this talk.

Work supported by the U.S. Department of Energy, Office of Fossil Energy, National Energy Technology Laboratory's Hydrogen and Syngas Technology Program, under Contract DE-AC02-06CH11357.