Abstract
A novel process scheme is analysed for the production of hydrogen from methane, while obtaining a separate stream of CO2, which is suitable for a subsequent reuse and/or for its permanent geological storage. This system comprises three interconnected fluidized-bed reactors operating at atmospheric pressure. H2 is produced in a sorption enhanced reforming (SER) stage, where the presence of a CaO-based sorbent allows the CO2 to be removed as it is formed. The main novelty of the process concerns the regeneration of the CaCO3, required to carry out a multicycle operation. A redox chemical loop supplies the heat necessary for the calcination. The CaCO3 formed in the SER is put in contact with a very high-temperature solids stream, which is mainly composed of Fe2O3 resulting from the exothermic oxidation of Fe3O4 with air in a separate reactor (at 950 °C - 1,200 °C). The calciner also acts as a fuel reactor, where Fe2O3 is reduced again to Fe3O4 by feeding a fuel gas, which is converted to CO2 and steam. A preliminary thermodynamic assessment of the proposed system has been carried out reaching H2 equivalent efficiencies of up to 79 %, which are around 9 % points above the efficiency of a reference H2 production plant based on conventional steam reforming including CO2 capture with MDEA. Carbon capture efficiencies of around 98 % can be obtained, which are significantly higher than those obtained in the reference plant that uses MDEA absorption (around 85 %). These results confirm the potential of this novel system for a future development as hydrogen production process with CO2 capture.
