Abstract
A thermodynamic property of Ca2Fe2O5 was exploited to improve the efficiency of the steam-iron process to produce hydrogen. The ability of reduced Ca2Fe2O5 to convert a higher fraction of steam to hydrogen than chemically unmodified Fe was demonstrated in a packed bed. At 1123K, the use of Ca2Fe2O5 achieved an equilibrium conversion of steam to hydrogen of 75%, in agreement with predicted thermodynamics and substantially higher than that theoretically achievable by iron oxide, viz. 62%. Furthermore, in Ca2Fe2O5, the full oxidation from Fe(0) to Fe(III) can be utilised for hydrogen production – an improvement from the Fe to Fe3O4 transition for unmodified iron. Thermodynamic considerations demonstrated in this study allow for the rational design of oxygen carriers in the future. Modifications of reactors to capitalise on this new material are discussed.
Highlights
The use of hydrogen as an energy vector is dependent on efficiently minimising the carbon emissions associated with its production [1]
This paper focuses on Ca2Fe2O5, a phase recently studied for its potential in chemical looping [8]
The performance of a rationally-designed oxygen carrier Ca2Fe2O5 was verified by comparison with 60 wt% Fe2O3-ZrO2 (Fe60Zr)
Summary
The use of hydrogen as an energy vector is dependent on efficiently minimising the carbon emissions associated with its production [1]. A proposed alternative to steam reforming is to use the chemical looping of iron oxide to produce H2, otherwise known as the steam-iron process. Use of looping reactions for this purpose dates back to the late 19th and early 20th Century [4]. This process is summarised in the following scheme:.
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