MetaSol

Metallurgy accounts for 7% of global greenhouse gas emissions, and its decarbonation is a major issue. We propose to develop processes based on the direct use of concentrated solar energy for process heat and of different carbon-free (hydrogen, ammonia) or bio-sourced (urea, bio-methane) reducers, and to assess their environmental impacts. This will allow us to identify a sustainable process for producing iron and / or cast iron from iron oxide ore with minimized environmental impacts. Firstly, the optimal temperatures and kinetic data of the various envisaged reactions will be studied in a solar simulator (350 W thermal) and in the high-temperature environmental chamber of an X-ray diffractometer. Two classes of reactions will be studied, corresponding to two different temperature ranges: reactions leading to the production of pure iron in solid form (600-1200°C) and reactions leading to the production of liquid cast iron at high temperature (> 1500°C). The reaction products will be analyzed (phase, purity) and the ease of separating the iron-rich phase (pure iron or cast iron) from the other by-products evaluated. In parallel, two solar continuous-flow reactors based on different technologies (heating by direct or indirect radiation) and designed for a solar thermal power of 1.5 kW will be developed. They will allow the continuous injection of iron ore powder and the continuous extraction of reaction products. The most suitable materials for the construction of the receiver / reactor will be determined. The reactors will be tested in real conditions using the PROMES solar facilities (Odeillo), and the influence of the various experimental parameters (particle size, reducing agent, reactant flow rate, temperature) on the yields and the quality of the products determined. The solar metallurgical process will be modeled by two approaches (CFD model (Computational Fluid Dynamics) and global dynamic simulation) which will be validated by comparison with experimental results. The CFD model will notably allow determining the temperature profiles in the flow in order to size reactors suitable for industrial production. The dynamic simulation of the system will make it possible to provide the data necessary for the life cycle analysis (LCA) of the process, and in particular to predict the possible productions by taking into account the seasonal and daily variability of solar irradiation. Finally, the environmental impacts of large-scale solar metallurgy will be studied. To this end, complete mass-energy balances of the processes, estimated from previous experiments and models, will be carried out. Production units at different scales (from 100 kW to 100 MW) will be modeled and their environmental impacts assessed by LCA. The impacts related to the use of different types of reducers will be assessed, either from existing databases, or by detailing the processes in the case of reducers produced from renewable bio-resources. Two production regimes will also be studied and compared: i) discontinuous production due to intermittency; ii) continuous production with energy storage or hybridization. Different scenarios will be studied by combining the size of the plant, the reducer type, its production mode, and the production regime. The global impacts of these different scenarios will be compared with each other, but also with those of blast furnaces and direct reduction processes. Economic conclusions will also be drawn from these results, since solar metallurgy can only become economically profitable if environmental impacts are taken into account in the economic study, notably via the increase of the carbon tax.