Dynamic simulation of a solar-based iron producing plant using hydrogen as reductant

• Decarbonation of industrial steelmaking by using H 2 reductant and solar thermal energy. • A dynamic model of an upscaled 10 MW solar iron-making reactor was developed. • Simulations predict the annual reactor performance under variable solar power input. • A global solar thermochemical efficiency of 20% was reached with heat losses below 10%. • The annual Fe production capacity was 30,000 tons using typical solar irradiation data. Steel metallurgy is a high consumer of fossil energy and a major emitter of CO 2 . The process of direct reduction of iron oxide using concentrated solar power and H 2 as reductant is a promising path for carbon–neutral steel making. This study aims to evaluate for the first time the potential of large-scale solar iron-producing plant through dynamic modelling to predict annual process performance under real fluctuating solar irradiation. The model, based on unsteady mass and energy balance equations, was first validated for a lab-scale reactor. An upscaled 10 MW solar reactor operating continuously was then designed and simulated with a loaded mass of 4.5 tons of iron oxide, reaching an equilibrium temperature around 1000 °C. The equilibrium temperature decreased (1530–680 °C) when increasing the quantity of loaded iron oxide (1–22.5 tons), while iron production still increased (0.8–1.8 kg/kWh of solar energy). The effect of decreasing the direct normal irradiation (DNI) (1000 to 500 W/m 2 ) on the decrease of the equilibrium temperature (1016 to 840 °C) and thus on the decrease of the reaction rate and production was emphasized. Dynamic simulation yielded an annual Fe production capacity of almost 30,000 tons in design conditions using representative solar meteorological data. Step-by-step steady-state simulations were compared to dynamic simulations, giving equivalent results for long term process yield assessment. Annually, 20 % of the solar energy was dedicated to the reaction and 70 % to reactants heating, with less than 10 % of heat losses. The instantaneous iron production was chiefly proportional to the DNI. The developed dynamic model successfully predicted the global production capacity and annual performance of large-scale solar metallurgical plants.