1. Introduction
Chemical looping hydrogen production typically utilises iron
oxide as an oxygen carrier as this material has several thermodynamically
favourable phase changes that can be exploited [1–4].
In this process a carbonaceous fuel, here carbon monoxide, is used
to reduce the iron oxide (producing carbon dioxide). Then water is
used to re-oxidise the iron and produce hydrogen. This is performed
in a cyclic manner. In order to have good utilisation of
the redox capacity of the material, we need to use an oxygen carrier
material (OCM) particle size, l, that is similar to or less than the
effective oxygen diffusional lengthscale (effective diffusion coeffi-
cient, D, divided by an equivalent first order surface rate constant,
k) such that the surface rate is controlling, e.g. l is similar to or less
than D/k
1. IntroductionChemical looping hydrogen production typically utilises ironoxide as an oxygen carrier as this material has several thermodynamicallyfavourable phase changes that can be exploited [1–4].In this process a carbonaceous fuel, here carbon monoxide, is usedto reduce the iron oxide (producing carbon dioxide). Then water isused to re-oxidise the iron and produce hydrogen. This is performedin a cyclic manner. In order to have good utilisation ofthe redox capacity of the material, we need to use an oxygen carriermaterial (OCM) particle size, l, that is similar to or less than theeffective oxygen diffusional lengthscale (effective diffusion coeffi-cient, D, divided by an equivalent first order surface rate constant,k) such that the surface rate is controlling, e.g. l is similar to or lessthan D/k
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