Multi-fuelled hydrogen production
Hydrocarbon fuels such as natural gas, biogas and bioethanol, aside from being combustible, contain hydrogen atoms. These fuels are therefore ideal feedstock to produce hydrogen fuel that can be used to support the transition from a fossil fuel-based to a renewable energy economy. EU-funded scientists working on the project COMETHY (Compact multifuel-energy to hydrogen converter) have developed a compact, low-temperature steam reformer. This reformer can utilise different types of fuels, including fuels derived from biomass, and is driven by heat obtained from energy resources, including solar energy. Steam reforming, a widespread hydrogen production method, has been revised to exploit renewable energy. Hence, a mixture of molten nitrate salts is used as heat transfer fluid up to 550°C as this fluid is today widely used to capture, store and dispatch solar heat in Concentrating Solar plants. Positive features include low cost, high heat transfer/storage capacity and minor implications about environmental impact, safety and toxicity. This result was obtained after extensive research, going from the development of basic components (catalysts and membranes) to their integration in an innovative membrane reformer heated with molten salts, where both hydrogen production and purification occurred in a single stage. Besides the high degree of compactness, the device developed is also highly flexible as far as the feedstock to be converted to hydrogen is concerned, which can be either clean methane (e.g. from natural gas) or a biomass-derived fuel such as clean biogas (methane/CO2 mixtures) or bioethanol. The steam reforming technology developed in COMETHY allows enables easy changeover of both the feedstock and the external heat source (solar or fossil/biomass back up) where start-up, stand-by and shut-down operations are facilitated. The reactors developed in COMETHY were successfully tested with different prototypes, one of which realised up to the pilot scale (3.5 Nm3/h hydrogen production) and integrated in a molten salt loop, thereby proving the concept of development. With the input of solar energy, use of COMETHY technology substantially saves primary fuels and reduces CO2 emissions in hydrogen production (compared to traditional reforming technology). The process was evaluated to be economically attractive for both decentralised and centralised applications.
Keywords
Hydrogen production, COMETHY, multifuel-energy, steam reformer, palladium
