Hydrogen production from fossil and renewable sources using an oxygen transport membrane

摘要

Oxygen transport membranes (OTMs) made of mixed ion-electron conductors can be used to increase the production of hydrogen from fossil and renewable sources. This study describes two methods for producing hydrogen with La_(0.7)Sr_(0.3)Cu_(0.2)Fe_(0.8)O_(3-δ) (LSCF7328), an OTM material that is easily-prepared, exhibits good mechanical properties, and is stable in severe gas conditions. In tests with thin-film (thickness ≈22 μm) LSCF7328 membranes, hydrogen was produced by flowing simulated product streams from CO_2 gasification of coal on one side of the OTM and steam on the other side. In this method, the so-called coal gas on the oxygen-permeate side drives the removal of oxygen from the other 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 rate was measured to be ≈4.7 cm~3/min-cm~2 at 900 ℃, indicating that hydrogen can be produced at a significant rate by using product streams from coal gasification. This process also yields a CO_2-rich product stream that is ready for sequestration. In another test, a tubular LSCF7328 was found to increase the hydrogen production from ethanol reforming by supplying high-purity oxygen from air.