Combustion of Rechargeable Metal Fuels in Fluidized Bed Boilers (CORAL)

The cyclic reduction/oxidation of metal oxide/metal is a promising approach for energy storage and flexible CO2-free provision of heat and power. The project explores a novel concept of metal oxidation utilising retrofitted coal-fired fluidized bed power plants. A hydrogen-based process will be used for the direct reduction of metal oxides. In periods of power surplus, a metal oxide (e.g., hematite) is reduced to pure metal by the addition of green hydrogen (and heat) that stems from electrolysis (or gasification of residues). In periods of lack of power, the metal (e.g., iron) is oxidized in a fluidized bed furnace, and the released heat is used for power and heat generation in a power plant process. The reduction/oxidation process in fluidized beds is tested at various scales up to 1 MW thermal power. Various numerical models are developed, validated by experiments, and applied to design modifications. The concept is assessed regarding electrical efficiency, economics, environmental and social impact.