Advanced Exergy Analysis of the Flash Ironmaking Process

Abstract

The growing demand for renewable energy highlights the importance of green energy carriers in mitigating the temporal and geographic imbalances between renewable energy supply and demand. Iron, as a metal fuel, offers a promising solution by enabling the storage of electrical energy from renewables through the thermochemical reduction of iron oxides with green hydrogen. This stored energy can be later converted back into electricity via thermochemical oxidation, such as in retrofitted coal-fired power plants. Transporting the iron/iron oxide in a closed cycle allows for spatial and temporal separation of renewable energy storage and release. To maximize the system efficiency of this energy-iron cycle, it is crucial to achieve high storage efficiencies during the thermochemical reduction of iron oxides. The flash ironmaking process is a promising method for this, as it allows for the reduction of fine iron oxide particles with green hydrogen without the need for pre- or post-treatment. Conventional exergy analyses, as well as advanced exergy analysis, are used to analyze the flash ironmaking process. The results reveal an exergetic system efficiency of 53.7 % for a defined base case, with the largest share of exergy destruction attributed to unavoidable exergy destruction at 82.2 % of the total exergy destruction. Additionally, most of the exergy destruction was endogenous at 89.4 % of the total exergy destruction. These assessments indicate that the overall potential for improvement of the reduction plant is moderate, and component improvements should be prioritized over structural improvements to reduce avoidable endogenous exergy destruction.