Coal Gas Assisted Hydrogen Production Using Mixed-Conducting Oxygen Transport Membranes

COAL GAS ASSISTED HYDROGEN PRODUCTION USING MIXED-CONDUCTING OXYGEN TRANSPORT MEMBRANES

C.Y. Park, T.H. Lee, S.E. Dorris, Y. Lu, and U. (Balu) Balachandran

Energy Systems Division

Argonne National Laboratory

Argonne, IL  60439-4838

ABSTRACT

Due to their ability to separate oxygen without a need for electrodes, or electrical circuitry, oxygen transport membranes (OTMs) attract considerable interest in applications such as oxygen separation from air, upgrading of natural gas for production of liquid fuels, and oxygen-enriched combustion. The objective of this study is to develop dense OTMs that can produce hydrogen via coal/coal gas-assisted water dissociation. 

Tubular-type OTMs were used to produce hydrogen via water splitting. Two different OTM materials, La_0.7Sr_0.3Cu_0.2Fe_0.8O_3-d (LSCF) and BaFe_0.9Zr_0.1O_3-d (BFZ), were prepared by a conventional solid-state technique. In tests with an LSCF thin-film tube (thickness of »30 mm, active area of 15.3 cm²) and a BFZ self-supporting tube (thickness of 1.05 mm, active area of 13.5 cm²) as the OTMs, hydrogen was produced by flowing CO/CO₂ gas mixtures on the oxygen-permeation side of the OTM and steam on the other side, the so-called hydrogen-generation side. In this method, the simulated coal gas on the oxygen-permeate side drives the removal of oxygen from the hydrogen-generation side of the OTM, where hydrogen and oxygen are produced by water splitting. With CO (99.5% purity) flowing on the oxygen-permeate side, the hydrogen production rates of LSCF and BFZ at 900 °C were measured to be »19.6 and »22.0 cm³/min, respectively, indicating that hydrogen can be produced at a significant rate by using product streams from coal gasification.

To be practical for hydrogen production, OTMs must remain chemically and mechanically stable in corrosive environments at elevated temperatures. The OTMs also should be available in a shape with a large active area, like a tubular film. Details on the preparation of thin films, microstructural behavior, flow rate effects, and stability tests will be discussed. Also, the oxygen permeation flux values of new promising membrane materials will be presented in this talk.

Work supported by the U.S. Department of Energy (DOE), Office of Fossil Energy, National Energy Technology Laboratory's Advanced Fuels Program, and Energy Efficiency and Renewable Energy, Office of Fuel Cell Technologies Program, under Contract DE-AC02-06CH11357.