(283g) Component Development for the Reformer Steam Iron Process for Decentralised Sustainable Hydrogen Production

In a world with an increasing population and energy demand, fuel cells have the potential to realise high efficient and emission-free power generation based on renewable hydrogen. At present the majority of the worldwide hydrogen production is based on fossil fuels which are converted in centralised plants and delivered to a small number of large-scale consumers. The future energy system will be based on hydrogen produced onsite near the customer, based on renewable energy carriers. This avoids the emission of carbon dioxide and the long distance transport of hydrogen.

The steam reforming of biogas is one promising process for renewable decentralised hydrogen production. It can be seen as a combination of the conventional steam methane reforming reaction (1), the dry reforming reaction (2) and the water gas shift reaction (3).

CH₄ + H₂O → CO + 3H₂                          ΔH₂₉₈= +206 kJ                          (1)

CH₄ + CO₂ → 2CO + 2H₂                        ΔH₂₉₈= +247 kJ                          (2)

CO + H₂O  → CO₂ + H₂                           ΔH₂₉₈= -41 kJ                            (3)

The conventional steam methane reformer requires additional purification steps in order to remove the produced carbon dioxide and unreacted carbon monoxide and methane. The steam iron process enables the production, purification and storage of hydrogen produced from any hydrocarbon containing feedstock in one single unit. At this chemical looping process a solid contact mass that consists of magnetite (Fe₃O₄) is reduced by hydrogen and carbon monoxide which is produced at the reforming process (4). The steam oxidation of the newly formed iron leads to the formation of pure hydrogen (5).

Fe₃O₄ + 4H₂/CO → 3Fe⁰ + 4H₂O/CO₂                                                        (4)

3Fe⁰ + 4H₂O→ Fe₃O₄ + 4H₂                                                                     (5)

The reaction conditions at the reformer stage have high influence on the reactivity and stability of the solid contact mass. In order to reach high reaction rates in the steam iron reactor the amount of carbon dioxide and steam in the syngas have to be minimised by working at low steam to CH₄ (S/C)ratios and high temperatures. On the other hand low S/C ratios reduces the CH₄conversion and may cause coke formation on the reforming catalyst and the contact mass which in turn reduces the purity of the produced hydrogen. By increasing the process temperature these effects can be minimised but particular attention has to be given to the stability of all components. In this work different process conditions are investigated in order to optimise the system.

Acknowledgment: This work is funded by the Research Studios Austria program of the Austrian Federal Ministry of Economy, Family and Youth.