(69e) Inorganic Membranes to Facilitate the Production of Hydrogen Using Nuclear Energy

There
are several processes being investigated for using the heat from the next
generation nuclear reactors to produce hydrogen.  The efficient separation of
gases at high temperatures can improve the efficiency of at least two of the
leading candidates, thermochemical water splitting and high temperature
electrolysis.  Through a series of reactions, the Sulfur-Iodine (SI)
thermochemical process facilitates the splitting of water into hydrogen and
oxygen. In the SI process all the chemicals are recycled except for water. The SI
process is efficient, scalable to large sizes, and consumes no expensive
chemical reagents; however, it has one major disadvantage.  The thermal
decomposition of sulfuric acid requires high temperatures (800 to 900 °C).  However,
there is a potential to lower the peak temperature by 200+ °C if the
decomposition products of sulfuric acid, O₂, H₂O, and SO₂,
can be separated from SO₃ using an inorganic membrane. First
generation membranes have been fabricated and we will present preliminary
separation data showing the potential to separate the product gases from SO₃. 
We will also present results of the stability of these membranes under simulated
operational conditions.

High
temperature electrolysis employs a solid oxide electrolyzer to split water into
hydrogen and oxygen.  As the oxygen is produced, it transports through the
electrolyte layer of the electrolyzer leaving behind on the feed side a mixture
of only the product hydrogen and the residual steam.  The efficiency of this
process can be improved by recovering the unreacted steam and feeding it back
to the inlet to the electrolyzer without costly cooling and reheat steps. 
Inorganic membranes have the potential to separate the hydrogen from the steam at
the operating temperature of 800°C. Preliminary data showing membrane
separation performance and thermal stability will be presented.