Reforming in fuel cell systems is used to produce hydrogen-rich fuel gas for use in PEMFC, HT-PEMFC, and SOFC systems from liquid or gaseous energy sources such as methanol, ethanol, propane, or biogas.
Compared to large-scale natural gas reforming, fuel cell reformers typically operate at more moderate temperatures. These depend on the reforming process used, the type of catalyst employed, and the respective fuel cell technology.
Methanol and ethanol steam reforming enable operation at comparatively low temperatures and are often used in combination with copper or precious metal-based catalyst systems. These processes are particularly suitable for PEMFC and HT-PEMFC applications.
Autothermal reforming combines endothermic steam reforming with exothermic partial oxidation and allows thermally balanced operation. It is particularly suitable for compact and dynamically operated systems, for example in mobile applications.
In SOFC systems, reforming can take place directly in the fuel cell stack. This internal reforming uses the high operating temperature and waste heat of the stack to efficiently convert the fuel.
In addition to H₂, the reformed gas produced also contains CO₂, CO, H₂O, and unreformed hydrocarbons. To comply with strict CO limits, especially in PEMFC systems, downstream gas treatment stages such as the water-gas shift reaction and selective oxidation (PROX) are used.
The selection of suitable reforming, shift, and gas purification processes depends largely on the fuel used, the available temperature window, the requirements of the fuel cell, and the dynamic operating conditions of the overall system. In addition, adsorbents and molecular sieves are used for gas purification, CO and CO₂ separation, and the recovery of residual hydrogen.
