SYSTEM AND METHOD FOR THE DIRECT REDUCTION OF IRON OXIDE POWDER BY HYDROGEN

Abstract

A direct hydrogen reduction system for iron oxide powder, comprising a reduction reactor (3) arranged to (i) receive the iron oxide powder, hydrogen gas (H2), and a heat input, and to (ii) deliver pure iron and water in vapor form. The heat input is provided by a solar tower (5a) comprising at its summit a solar receiver (9a) designed to receive at its focal point solar radiation reflected by a plurality of heliostats (1) arranged around this solar tower (5a). Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: SYSTEM AND DIRECT HYDROGEN REDUCTION PROCESS OF IRON OXIDE POWDER FIELD OF INVENTION

[0001] The present invention relates to a direct hydrogen reduction system for iron oxide powder (a mixture of Fe2O3 / Fe3O4 / FeO). It also relates to a direct reduction process implemented in this system. STATE OF THE ART

[0002] Most current energy production systems use fuels that emit CO2 (natural gas, coal, fuel oil, etc.). Furthermore, the rising cost of energy and the risk of shortages linked to the energy dependencies of many countries worldwide are a reason for seeking a green alternative energy source for generating steam for industrial applications.

[0003] In this context, metallic fuels, as detailed in the 2015 Applied Energy article "Direct combustion of recyclable metal fuels for zero-carbon heat and power," are a proposed solution for producing CO2-free combustion for all types of energy production applications. Metallic fuels (magnesium, aluminum, iron) have the advantage of generating only solid metal oxides during combustion, which are easily recovered in a combustion system. These oxides can then be recycled using renewable energy via an inert anode electrolysis process or a zero-CO2 thermal reduction process using solar energy.Using hydrogen in this reduction process as a reducing agent allows the role of energy carrier to be transferred from this gas, which is very complex to store and transport, to highly energy-dense iron powder, which is easy to store and transport and whose energy production systems are less expensive.

[0004] Direct reduction systems for iron oxides, conventionally used in metallurgy to produce "iron sponges," employ coal or gas (from methane cracking), composed primarily of hydrogen and carbon monoxide, as reducing agents. These processes are highly emissive in terms of greenhouse gas emissions, and projects for producing iron from green hydrogen (GravitHy, SSAB, etc.) or electrolysis (Electra, Boston Metals, etc.), aimed at decarbonizing this activity, are already emerging worldwide.

[0005] Research in the field of metal oxide reduction has also explored the application of heat by solar means and with gaseous reducing agents (monoxide) of carbon, methane) or solids (biochar). Without a reducing agent, the reduction temperatures of certain metal oxides are far too high for the use of concentrated solar power (CSP) processes (tower solar power plants can reach temperatures between 500 and 1000°C, and the parabolic mirror at the PROMES laboratory in Odeillo can heat up to over 2300°C). Indeed, the reduction temperature is around 3400°C for magnesia (MgO) and 3700°C for alumina (Al₂O₃). With a reducing agent such as methane, the reduction temperature can be lowered to 1500°C for both types of oxides (Y. Berro et al., Energy Conversion and Management, 2022). However, the process used is a parabolic solar array that concentrates a large amount of radiation onto a small volume in order to reach very high temperatures (above 2300°C). And it's a process that doesn't yet exist in this form on an industrial scale.

[0006] The aim of the present invention is to propose a new device and method for the direct reduction of iron oxide powder which makes it possible to produce an efficient energy vector and which can be deployed on an industrial scale. Description of the invention

[0007] This objective is achieved with a direct hydrogen reduction system of an iron oxide powder, comprising a reduction reactor arranged to (i) receive the iron oxide powder, hydrogen gas H2 and a heat input and to (ii) deliver pure iron and water in vapor form, characterized in that the heat input is provided by a solar tower comprising at its summit a solar receiver intended to receive at its focus solar radiation reflected by a plurality of heliostats arranged around this solar tower.

[0008] In a first configuration of the invention, the reduction reactor comprises a fluidized bed disposed in the solar receiver and connected on one side to the outlet of an iron oxide reservoir and on the other side to the inlet of a reservoir to receive the pure iron from the reduction of the iron oxides.

[0009] The reduction system may further advantageously include, downstream of the fluidized bed, means for condensing water vapor and, downstream of said condensing means, means for separating, on the one hand, liquid water from the condensing means and, on the other hand, excess hydrogen which has not been recombined in the reduction reactor.

[0010] It may also include, upstream of the fluidized bed, hydrogen gas storage means designed to receive excess hydrogen from the separator means. It may further include, downstream of these separator means, means for electrolyzing the liquid water from said separator means and means water storage in order to deliver the hydrogen gas thus produced to the hydrogen storage facilities.

[0011] The solar tower may further comprise:

[0012] -a supply conduit for iron oxides from an iron oxide reservoir to the fluidized bed,

[0013] -a supply conduit for reducing hydrogen from hydrogen storage means located near the base of the tower to the fluidized bed,

[0014] -a pure iron discharge conduit from the fluidized bed to an iron reservoir, said iron oxide and pure iron reservoirs respectively being disposed near the base of said tower, and

[0015] - means of extraction for the evacuation of water vapor from the fluidized bed.

[0016] The fluidized bed may further include a fluidization grid for iron oxides and a high-temperature filter at the outlet of water vapor and excess hydrogen.

[0017] The fluidized bed may further include a perforated plate (or other means of distributing the fluidizing gas) for the fluidization of iron oxides and a high-temperature filter at the outlet of water vapor and excess hydrogen.

[0018] The solar receiver and the fluidized bed can be arranged so that said fluidized receives solar energy in a concentrated manner over its entire circumference.

[0019] The solar receiver and the fluidized bed can be arranged so that said fluidized receives solar energy from the heliostats in a concentrated manner over its entire circumference.

[0020] In another configuration of a reduction system according to the invention, the reduction reactor can be disposed in whole or in part in a bath of molten salts (arranged in the form of a molten salts / oxide reactor exchanger) located near the solar tower and thermally coupled to the solar receiver via a closed circuit of molten salts.

[0021] The reduction reactor may further include means for conducting excess steam and hydrogen from the reduction reactor to means for separating hydrogen from water, said separating means being connected at the outlet on the one hand to water storage means and on the other hand to hydrogen gas storage means intended to supply hydrogen to the reduction reactor.

[0022] The reduction system according to the invention may further include, downstream of the water storage means, electrolyzer means intended to produce hydrogen gas and deliver it to the hydrogen storage means.

[0023] The electrolyzing means can also be provided to receive an external water input.

[0024] The reduction system according to the invention may further include an electrical power generation unit by converting part of the heat present in the reduction reactor.

[0025] This electrical power generation unit may include a steam circuit comprising a steam generator thermally coupled to the reduction reactor, a steam turbine mechanically coupled to an electric generator, and steam condensation equipment from said turbine to deliver liquid water to the inlet of the steam generator.

[0026] According to another aspect of the invention, a process for the direct hydrogen reduction of an iron oxide powder is proposed, implemented in a reduction system according to the invention, comprising steps for:

[0027] - bringing iron oxide powder and hydrogen gas H2 into a reactor reduction designed to deliver pure iron and water in steam form,

[0028] - supply heat to said reduction reactor,

[0029] characterized in that the heat input is provided by a solar tower comprising at its summit a solar receiver designed to receive at its focus solar radiation reflected by a plurality of heliostats arranged around this solar tower.

[0030] In a first configuration of the invention, the reduction of iron oxides is carried out at the top of the solar tower, in the form of a fluidized bed of iron oxides included in the solar receiver.

[0031] In another configuration of the invention, the reduction of iron oxides is carried out in a reduction plant installed near the solar tower, within a bath of molten salts thermally coupled to the solar receiver.

[0032] The reduction process according to the invention may further advantageously include the production of electrical energy from the heat present in the reduction reactor. The reduction process may also include the production of hydrogen from the steam exiting the reduction reactor, to contribute to the supply of hydrogen required for the reduction of iron oxides.

[0033] According to the invention, a system for the direct reduction of iron oxides to hydrogen by solar means is thus provided, comprising a tower receiving solar radiation (at the level of a receiver near the top) from the heliostats (located around the tower), a device for fluidizing iron oxide powder in the heated volume of the tower receiver thus promoting the gas-solid reaction mixing, a device for transporting the oxides and emptying the metal produced, a thermal recovery system at the exhaust to recover the calories during the condensation of the water vapors, and a device for recovering the unreacted hydrogen by means of a phase separator (separation of liquid water and gaseous hydrogen).

[0034] The system according to the invention makes it possible to use the basic structure and design of a solar power plant tower that normally heats molten salts, and adapt it to heat instead fluidized iron oxide powder with hydrogen in order to reduce it to pure iron without emitting any greenhouse gases in the process (and to fully exploit the capacity of a solar tower plant). This tower, whose initial function is the thermal storage of solar radiation in molten salts, is thus converted to an iron production function in order to allow renewable energy storage for a longer period than by heating molten salts (whose thermal storage time is on the order of 8 to 10 hours). This would also allow the transport of this energy, in the form of pure iron, over long distances (to areas with low renewable energy concentration but high energy demand).The local or non-local use of this recycled iron can be achieved using an iron-burning power plant or other energy conversion processes.

[0035] Advantageously, in this same variant, the unreacted hydrogen is returned to the reservoir which supplies the iron oxide reduction plant.

[0036] In another variant of the system for the direct reduction of iron oxides by solar means, the water from the hydrogen oxidation reaction can be reused to produce hydrogen by in-situ green electrolysis.

[0037] In another variant of the direct solar reduction system for iron oxides, a power generation unit using a steam cycle turbine can be placed at the system's exhaust. This energy can be used to operate the power plant or distributed to the electrical grid, thereby improving the system's overall energy efficiency.

[0038] Advantageously, in this same variant, the water from the hydrogen oxidation reaction can be reused to produce hydrogen by in-situ green electrolysis.

[0039] Advantageously, the fluidized bed located in the hot zone of the solar tower receiver is supplied with iron oxides by a powder transport system that may consist of a screw conveyor or a blower system (or any other suitable system). This operation is carried out after the fluidized bed has been emptied of the iron powder resulting from the reduction process, using a metal transport system to its storage tank. These two operations are performed successively after the reduction operation has converted all the iron oxide powder in the tank into pure iron. It is preferable to perform them before starting the hydrogen fluidization of the bed.

[0040] In the case of the reduction of iron oxides, based on a mixture of more than 99% Fe2O3 (as is the case in hematite or in oxide powder) Iron (resulting from the complete combustion of iron), whose reduction is the most energy-intensive (among the three iron oxides), undergoes a reaction at a much lower temperature than the two other metals mentioned above (between 400 and 1000°C depending on the reducing agent chosen and the quality of the reaction mixture). This has the advantage of allowing the use of solar concentrating towers, which are widespread throughout the world (Noor III in Ouarzazate, Ivanpah in California, etc.) and whose solar concentrating technology has already been proven at high power levels (several hundred megawatts). The use of hydrogen as a reducing agent at a sufficiently high temperature (between 700 and 900°C) allows for a more rapid, near-total conversion of iron oxides to pure iron, which would correspond to production objectives on an industrial scale (Daniel Spreitzer et al., "Reduction of Iron Oxides with Hydrogen—A Review").The main advantage of this process, which uses hydrogen as a reducing agent, is that it does not emit CO2 during the production of pure iron.

[0041] In another configuration of a direct hydrogen reduction system for iron oxides using solar energy, in which the oxide reduction is carried out in a power plant located at the base of or near a solar tower, the system comprises a tower receiving solar radiation (at a receiver near the top) from heliostats (located around the tower) to heat molten salts in a conventional manner. A fluidization device for iron oxide powder heated by the molten salts is located in a reduction power plant situated near the tower. This reduction power plant is located and positioned similarly to a thermal power plant that conventionally converts the heat from the molten salts into electricity.The reduction system contains a device for transporting oxides and emptying the produced metal, a heat recovery system at the exhaust to recover heat during the condensation of water vapors, and a device for recovering unreacted hydrogen using a phase separator (separation of liquid water and gaseous hydrogen).

[0042] Advantageously, in this same variant, the unreacted hydrogen is returned to the reservoir which supplies the iron oxide reduction plant.

[0043] Advantageously, in this same variant, the water from the hydrogen oxidation reaction can be reused to produce hydrogen by in-situ green electrolysis.

[0044] Advantageously, the fluidized bed is supplied with iron oxides by a powder transport system which may consist of a screw conveyor or a blower system (or any other suitable system). This operation is carried out when the fluidized bed has been previously emptied of the iron powder resulting from the reduction, or continuously, by means of a metal transport system to its storage tank.

[0045] In another variant of the device for the direct reduction of iron oxides by solar means, the water from the hydrogen oxidation reaction can be reused to produce electricity in parallel by means of simultaneous heating of the oxide reactor and a steam generator by the molten salts.

[0046] The present invention enables the storage of solar energy through the production of iron, which will serve as an energy carrier, allowing for decentralized use (e.g., oxide reduction in North Africa, local energy production, and transport of some of the iron to Europe) and time-shifted use (the iron can be stored for months without difficulty). The combustion of powdered iron is the means of producing energy without CO2 emissions for a wide variety of applications (heat and electricity production, mobility, etc.). The production of iron without greenhouse gas emissions (via solar energy) also makes it possible to decarbonize the metallurgy sector (steel production). DESCRIPTION OF THE FIGURES

[0047] Other features and advantages will become apparent from the following description of two particular embodiments and two non-limiting modes of operation of the invention, made with reference to the figures in which:

[0048] - Fig. 1 is a schematic representation of a first embodiment of the invention;

[0049] - [Fig.2] is a schematic representation of a variant of the first mode of realization of the invention presented in [Fig.1];

[0050] - [Fig. 3] is a schematic representation of a first mode of operation of the solar-concentrated iron oxide reduction plant;

[0051] - [Fig. 4] is a schematic representation of a second mode of operation of the solar-concentrated iron oxide reduction plant;

[0052] - [Fig. 5] is a schematic representation of a third mode of operation of the solar-concentrated iron oxide reduction plant;

[0053] - [Fig. 6] is a schematic representation of a variant of the solar power plant tower presented in [Fig.3], [Fig.4] and [Fig.5];

[0054] - Figure 7 schematically represents another configuration of a system of reduction of iron oxides according to the invention, in which the molten salts directly heat a reduction plant near the solar tower;

[0055] - Figure 8 schematically represents a variant of this other configuration, including cogeneration of electrical energy.

[0056] DETAILED DESCRIPTION OF IMPLEMENTATION EXAMPLES

[0057] We will now describe, with reference to [Fig.1], a first embodiment of the hydrogen reduction plant of iron oxides by solar means.

[0058] Such a system is based on the hydrogen reduction of iron oxides, which does not emit CO2 and allows for the storage of solar energy in the iron produced for long periods and for possible transport over long distances. Thus, the system makes it possible to reduce pollution from both metallurgical and energy production activities while enabling a circular economy where the metallic fuel (iron in this invention) is regenerated at each use cycle thanks to the oxides recovered during combustion.

[0059] Hydrogen is transported from a reservoir 0 to a powder iron oxide fluidization system located in the solar receiver 9a of a tower 5a. Before this fluidization operation, a fluidized bed 3 is fed by an iron oxide reservoir 2 and a transport system (possibly with a screw conveyor).

[0060] The iron oxide powder located in the receiver is heated to very high temperatures (above 500°C) using the concentration of solar radiation made possible by a field of heliostats 1 which individually track the sun and reflect it precisely towards the receiver at the top of the solar tower 9a.

[0061] The hydrogen reduction reaction of iron oxides in a solar power plant tower is accompanied by the production of very high-temperature steam. This steam can be condensed in 5 to recover the heat from this change of state and improve the energy efficiency of the system. The iron from the reduction is collected in an iron reservoir 4.

[0062] The water vapor exiting the fluidized bed 3 is mixed with unreacted hydrogen. A phase separator 6 at the condenser outlet recovers the excess hydrogen for reinjection into the reservoir 0. The liquid water is stored in a reservoir 7 downstream of the separator.

[0063] Figure [Fig. 2] presents a variant of the first embodiment, illustrated in [Fig. 1], An electrolyzer 8, producing hydrogen from green electricity, transforms water from storage tank 7 into hydrogen for reinjection into tank 0. This limits the need for water or hydrogen supply to power the plant (and avoids water stress). In a first operating mode of the invention illustrated in [Fig. 3], the fluidized bed 3 is fed with iron oxides from a tank 2 alongside the solar tower 5a (by a screw conveyor, blower, or other powder transport system). The solar tower 5a also includes a duct with extraction 8a for venting water vapor and hydrogen to a water vapor treatment facility.

[0064] In a second operating mode of the invention illustrated in [Fig. 4], the hydrogen from reservoir 0 is transported along the solar tower 5a and then passes through a fluidization grid (distributor) 6a in order to fluidize the iron oxide powder in the fluidized bed and promote mixing and thus the reduction reaction. Heliostats 1 reflect the radiation towards the receiver 9a, where the fluidized bed 3 is located, in order to reach the reduction temperature of the iron oxides. The produced water vapor and unreacted hydrogen pass through a high-temperature filter 7a to prevent particles from the fluidized bed from escaping. This filtration is achieved by minimizing pressure losses through an extraction system 8a. The water vapor and hydrogen are then transferred to the condensation, separation, and storage units.

[0065] In a third mode of operation of the invention illustrated in [Fig.5], once the reduction of iron oxides is almost total, the iron is drained from the fluidized bed 3 to a storage tank 4 (by a screw or suction system or other powder transport system).

[0066] In a variant of the type of solar tower power plant shown in [Fig. 3], [Fig. 4], and [Fig. 5], [Fig. 6] presents the invention within a solar tower 5a in which the receiver 9a receives concentrated solar radiation reflected by a heliostat field 1 distributed over 360° around the tower to heat the entire fluidized bed 3 around its circumference. Excess steam and hydrogen are discharged at 10, iron oxides are inlet at 11, hydrogen is inlet at 12, and iron is discharged at 13.

[0067] We will now describe, with reference to [Fig. 7], another configuration of an iron oxide reduction system 90 in which a molten salt heat exchanger 915 is installed in a reduction plant (to heat the fluidized bed) located at the base of or near a solar tower 910 equipped at its summit with a focal point 910 receiving solar radiation from a set of heliostats 92. The molten salt bath 915 is connected to a circuit 96 carrying cold salts from the bath via a cold salt reservoir 94 to the focal point 910 designed to heat this cold salt. The salt thus heated is returned to the molten salt bath (or salt / oxide fluidized bed heat exchanger) 915 via a hot salt reservoir 93 and a hot salt injection circuit 95.

[0068] The molten salt exchanger 915 heats a reduction reactor 990 (from inside and / or outside the reactor) containing iron oxides and equipped with an iron oxide filling inlet 97 and an iron metal discharge outlet 98.

[0069] The reduction reactor 990 is equipped with a hydrogen injection conduit 99 from a hydrogen reservoir 914 and an outlet conduit 980 for water H2O and excess hydrogen H2.

[0070] The outlet conduit 980 is connected to the inlet of a hydrogen / water separator 911 which has a hydrogen outlet connected via a conduit to a hydrogen tank 914 and a water outlet connected to a water tank 912.

[0071] The iron oxide reduction system 90 further comprises an electrolyzer 913 receiving water as input from the water reservoir 912 and from an input external water 916 and generating at the output hydrogen which is stored in the hydrogen tank 914.

[0072] In a variant of this other configuration, illustrated by [Fig. 8], the iron oxide reduction system 100 according to the invention further comprises an electrical generation system 930 including a steam generator 917 thermally coupled to the molten salts 915 (the molten salts are distributed in parallel or in series between the reactor heating and the steam generation) and receiving water stored in a water tank 918. The steam from the steam generator 917 is admitted into the inlet of a turbine 919 driving an electrical generator 920 connected to a transformer system 922 and delivering electrical power to an electrical power grid. The turbine 919 is connected to an air-cooled condenser 921 which delivers water that is admitted into the inlet of the water tank 918.

[0073] Of course, the present invention is not limited to the examples of embodiments that have just been described and other embodiments can be considered without departing from the scope of the present invention.

[0074] Other methods of hydrogen production besides electrolysis can therefore be considered. In particular, water splitting technologies could be implemented.

Claims

Demands

1. A direct hydrogen reduction system for an iron oxide powder, comprising a reduction reactor (3) arranged to (i) receive the iron oxide powder, hydrogen gas H2 and a heat input and to (ii) deliver iron and water in vapor form, characterized in that the heat input is provided by a solar tower (5a) comprising at its summit a solar receiver (9a) designed to receive at its focus solar radiation reflected by a plurality of heliostats (1) arranged around this solar tower (5a).

2. Reduction system according to the preceding claim, characterized in that the reduction reactor (3) comprises a fluidized bed disposed in the solar receiver (9a) and connected on one side to the outlet of an iron oxide reservoir (2) and on the other side to the inlet of a reservoir (4) to receive the pure iron from the reduction of the iron oxides.

3. Reduction system according to claim 2, characterized in that it further comprises, downstream of the fluidized bed, means (5) for condensing water vapor and, downstream of said condensing means (5), means (6) for separating, on the one hand, liquid water from the condensing means (5) and, on the other hand, excess hydrogen which has not been recombined in the reduction reactor (3).

4. Reduction system according to the preceding claim, characterized in that it further comprises, upstream of the fluidized bed, means (0) for storing hydrogen gas intended to receive excess hydrogen from the separator means (6).

5. Reduction system according to claim 3 or 4, characterized in that it further comprises, downstream of the separating means (6), means (8) for electrolyzing the liquid water from said separating means (6) and water storage means (7) in order to deliver the hydrogen gas thus produced into the hydrogen storage means (0).

6. Reduction system according to any one of claims 2 to 5, characterized in that the solar tower (5a) further comprises: - a conduit for supplying iron oxides from an iron oxide reservoir (2) to the fluidized bed, - a supply conduit for reducing hydrogen from hydrogen storage means located near the base of the tower (5a) to the fluidized bed (3), - a discharge conduit for pure iron from the fluidized bed (3) to an iron reservoir (4), said reservoirs (2,4) respectively of iron oxides and pure iron being disposed near the base of said tower (5a), and - extraction means (8a) for the evacuation of water vapor from the fluidized bed (3).

7. Reduction system according to any one of claims 2 to 6, characterized in that the fluidized bed (3) comprises a perforated plate or other means for distributing the fluidizing gas (6a) for the fluidization of iron oxides and a high-temperature filter (7a) at the outlet of the water vapor and excess hydrogen.

8. Reduction system according to any one of claims 2 to 7, characterized in that the solar receiver (9a) and the fluidized bed (3) are arranged so that said fluidized receives solar energy from the heliostats (1) in a concentrated manner over its entire circumference.

9. Reduction system (90,100) according to claim 1, characterized in that the reduction reactor (990) is disposed in whole or in part in a molten salt bath (915) disposed near the solar tower (910) and thermally coupled to the solar receiver via a closed circuit of molten salts (95,96).

10. Reduction system (90,100) according to the preceding claim, characterized in that the reduction reactor (990) further comprises means (980) for conducting excess water vapor and hydrogen from the reduction reactor (990) to means (911) for separating hydrogen from water, said separating means (911) being connected at the outlet on the one hand to water storage means (912) and on the other hand to gas hydrogen storage means (914) intended to supply hydrogen to the reduction reactor (990).

11. Reduction system (90,100) according to the preceding claim, characterized in that it further comprises, downstream of the water storage means (912), electrolyzing means (913) provided for producing hydrogen gas and delivering it to the hydrogen storage means (914).

12. Reduction system according to the preceding claim, characterized in that the electrolyzing means (913) are further provided to receive an external water input (916).

13. Reduction system (100) according to any one of the preceding claims, characterized in that it further comprises an electrical power generation unit (930) by conversion of a portion of the heat present in the reduction reactor.

14. Reduction system according to the preceding claim, characterized in that the electrical power generation unit (930) comprises a steam circuit including a steam generator (917) thermally coupled to the reduction reactor, a steam turbine (919) mechanically coupled to an electrical generator (920), and equipment (921) for condensing steam from said turbine (919) to deliver liquid water to the inlet of the steam generator (917).

15. A method for the direct hydrogen reduction of an iron oxide powder, implemented in a reduction system according to any one of the preceding claims, comprising steps for: - bringing iron oxide powder and hydrogen gas H2 into a reduction reactor (3,990) intended to deliver pure iron and water in vapor form, - supplying heat to said reduction reactor (3,990), characterized in that the heat supply is provided by a solar tower (5a) comprising at its summit a solar receiver (9a) intended to receive at its focus solar radiation reflected by a plurality of heliostats (1) arranged around this solar tower (5a).

16. Reduction method according to the preceding claim, wherein the reduction of iron oxides is carried out at the top of the solar tower (5a), in the form of a fluidized bed (3) of iron oxides included in the solar receiver (9a).

17. Reduction method according to claim 15, wherein the reduction of iron oxides is carried out in a reduction plant installed near the solar tower (910), within a bath of molten salts (915) thermally coupled to the solar receiver.

18. A reduction method according to any one of claims 15 to 17, characterized in that it further comprises the production of electrical energy (930) from the heat present at the level of the reduction reactor (990).

19. A reduction process according to any one of claims 15 to 18, characterized in that it further comprises a production of hydrogen from the steam from the reduction reactor (3,990), to contribute to the supply of hydrogen required for the reduction of iron oxides.

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