CE05 - Une énergie durable, propre, sûre et efficace

Solar iron metallurgy based on renewable or bio-sourced reducers – MetaSol

Can we completely decarbonize the steel industry?

Coal-based steel industry - one of the biggest polluters of the Earth.

Reducing iron ore with non-carbon or bio-sourced reducers, and with solar energy

The present project addresses an emblematic and central energy-demanding process of our society: metallurgy. The reduction of iron oxide into metallic iron, steel and cast iron using coke is the process that gave rise to the industrial revolution, clearly taking advantage of the high-energy density enclosed into cheap coal and despite its considerable environmental and societal impacts. Current standard metallurgy process presents several problems that cannot be easily solved. First, producing 1.7 billion tons of steel per year (2017) leads to the release of twice as much CO2 (7% of world emissions). There are currently no low-CO2 alternatives to steel or cast iron production at large scale despite efforts from several researchers and founders around the world (see below). Second, coal is a non-renewable resource which is, contrary to the iron ore itself, unevenly distributed in the world.<br />1) Replacement of coke and charcoal with i) carbon-free reductants (hydrogen (H2) or ammonia (NH3)) or ii) bio-sourced reductants other than charcoal (bio-methane (CH4) or urea (CH4N2O)).<br />2) Design of a continuous flow reactor suitable for direct use of concentrated solar energy where the output products would be solid iron or liquid melt. The developed solar reactor must allow the injection of particles and the continuous extraction of products in a controlled atmosphere. It will be tested in the focus of a solar concentrator with direct irradiation of iron oxide particles to determine performance such as yields and product quality under different operating parameters. <br />3) Life cycle assessment (LCA) and eco-design of each alternative process (including production, supply and storage of reagents, construction of infrastructure and equipment).

In a first step, the optimal temperatures and kinetic data of the different reduction reactions will be studied in a solar simulator. Two families 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 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 pig iron) from the other by-products will be evaluated.
In parallel, a solar reactor with continuous material flow, and adapted to a solar thermal power of 1.5 kW will be developed. It will allow the continuous injection of ore powder and the continuous extraction of reaction products. The reactors will be tested in real conditions using the solar installations of PROMES (Odeillo), and the influence of the various experimental parameters on the yields and the quality of the products will be determined.
The solar metallurgy 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 be used to determine the temperature profiles in the flow in order to size reactors adapted to industrial production. The dynamic simulation of the system will provide the data necessary for the life cycle analysis (LCA) of the process, in particular to predict the possible productions by taking into account the seasonal and daily variability of the solar irradiation.
The complete mass-energy balances of the processes, estimated from the previous experiments and modelling, will be used in the LCA. Production units at different scales (from 100 kW to 100 MW) will be modeled and their environmental impacts evaluated by LCA. The impacts related to the use of different types of reducers will be evaluated, 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 type of gearbox, its production mode, and the production regime. The overall impacts of these different scenarios will be compared with those of blast furnaces and direct reduction processes. Economic conclusions will also be drawn from these results, as solar metallurgy can only become economically viable if environmental impacts are taken into account in the economic analysis, notably through an increase in the carbon tax.

The main results already achieved are as follows:
- the solar simulator is fully completed and is operating routinely (April 2021).
- the reduction of industrial iron oxide pellets has been successfully completed, using hydrogen and ammonia as reducing agents. An analysis of the influence of temperature on the reduction rate was performed in a variable temperature X-ray diffraction. Experiments in the solar simulator confirmed the possibility of reducing iron oxide under light flux (September 2021)
- the reduced pellets were characterized by X-ray diffraction and scanning electron microscopy. After optimization of the process, iron oxide conversion rates of more than 90% were obtained (July 2022). The writing of an article will start.
- the continuous reactor has been designed internally at PROMES (between fall 2021 and spring 2022). The construction of the reactor is carried out through the supply of a set of mechanically welded parts, awarded to the company REMCO after a tender procedure. The manufacture of the various components of the reactor began in July 2022.
- The life cycle assessment (LCA) of a solar dish intended for firing has been carried out as a preliminary step before the LCA of the solar metallurgy process (September 2022). The solar process was compared to conventional methods (induction, gas burner, electric plate). An article is currently being finalized.

In the coming months, experimental results of ore reduction on a laboratory scale will be refined.
The pilot reactor using concentrated solar energy will be built and put into operation for the first tests.
In parallel, the LCA of the production channels of the selected reductants will be carried out, with the modeling of the solar reactor.
At the end of the project, we will have an overall vision of the feasibility of the decarbonization of the steel industry in the coming decades.

The first works carried out gave rise to two communications in international conferences.

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.

Project coordination

Ligia BARNA (Toulouse Biotechnology Institute)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

TBI Toulouse Biotechnology Institute
PROMES Laboratoire procédés, matériaux, énergie solaire
LPCNO LABORATOIRE DE PHYSIQUE ET CHIMIE DES NANO-OBJETS

Help of the ANR 465,620 euros
Beginning and duration of the scientific project: January 2021 - 48 Months

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