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WO2024246143A1 - Procédé de réduction assisté par des champs magnétiques alternatifs - Google Patents

Procédé de réduction assisté par des champs magnétiques alternatifs Download PDF

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Publication number
WO2024246143A1
WO2024246143A1 PCT/EP2024/064804 EP2024064804W WO2024246143A1 WO 2024246143 A1 WO2024246143 A1 WO 2024246143A1 EP 2024064804 W EP2024064804 W EP 2024064804W WO 2024246143 A1 WO2024246143 A1 WO 2024246143A1
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WIPO (PCT)
Prior art keywords
reactor
reduction
reducible
reducible material
reduced
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2024/064804
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English (en)
Inventor
Francesco Torre
María TAEÑO
Ali MARGOT
Eduardo J. GARCÍA-SUAREZ
Stefania DOPPIU
Elena PALOMO
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Fundacion Centro De Investigacion Cooperativa De Energias Alternativas Cic Energigune Fundazioa
Original Assignee
Fundacion Centro De Investigacion Cooperativa De Energias Alternativas Cic Energigune Fundazioa
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Publication of WO2024246143A1 publication Critical patent/WO2024246143A1/fr
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B11/00—Making pig-iron other than in blast furnaces
    • C21B11/10—Making pig-iron other than in blast furnaces in electric furnaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/12—Making spongy iron or liquid steel, by direct processes in electric furnaces
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B15/00—Obtaining copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B19/00—Obtaining zinc or zinc oxide
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B23/00—Obtaining nickel or cobalt
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B47/00—Obtaining manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B5/00—General methods of reducing to metals
    • C22B5/02—Dry methods smelting of sulfides or formation of mattes
    • C22B5/08—Dry methods smelting of sulfides or formation of mattes by sulfides; Roasting reaction methods
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B5/00—General methods of reducing to metals
    • C22B5/02—Dry methods smelting of sulfides or formation of mattes
    • C22B5/12—Dry methods smelting of sulfides or formation of mattes by gases
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
    • C22B9/003—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals by induction
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
    • C22B9/006—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals with use of an inert protective material including the use of an inert gas

Definitions

  • the present invention relates to the field of energy storage and conversion, in particular through the use of alternating magnetic fields in a low temperature method that allows the easy and economical production of thermochemical reactive materials for thermal energy storage or the production of valuable chemicals and fuels.
  • Thermal energy storage is a cheap way of storing renewable energy that may assist the decarbonization of both industrial and domestic heat.
  • storage in chemical energy carriers opens a huge range of possibilities.
  • electrolyzers e.g. alkaline electrolyzers, PEM or Proton-Exchange Membrane electrolyzer, SOEC or Solid-Oxide Electrolyzers
  • SOEC Solid-Oxide Electrolyzers
  • fuel cells e.g., SOFC or Solid-Oxide Fuel Cells
  • SOFC Solid-Oxide Fuel Cells
  • thermochemical cycles which produce fuels and feedstocks from solar radiation.
  • microwave and/or suitable reducing agents may facilitate the reduction process in Power-to-X transformations.
  • reducing agents is a widespread method to lower the working temperature in reduction processes.
  • Commonly used reducing agents are hydrogen, carbon monoxide, gaseous ammonia, and hydrocarbons. By using gaseous streams of H2 or CO, the reduction process may take place at temperature which are considerably lower than in absence of reducing agents. For example, Seo et al.
  • microwave-assisted reduction is a strategy where microwaves (frequency range: 0.9-25 GHz) interact with the material to be reduced modifying its electrical conductivity and promoting its reduction at low to moderate temperatures without the use of reducing agents or contact electrodes.
  • Document JP2010173930A discloses a method for generating hydrogen at a temperature as low as at most 500°C.
  • a magnetic raw material Mn-Zn ferrite or the like
  • IR infrared
  • a magnetic raw material Mn-Zn ferrite or the like
  • oscillation wavelength is amplified, which induces resonance of hydrogen, carbon, nitrogen and oxygen molecules included in the gas with the surface molecules of the magnetic raw material. Hydrogen is then generated from the methane, ammonia or steam.
  • the inventors have devised a new method for the reduction of materials based on the surprising finding that reducible materials (such as a magnetic oxide) exposed to the effects of an alternating magnetic field enables the low temperature reduction of said materials.
  • the new reduction process may not require the presence of reducing agents and/or contact electrodes, solving the issues that have been, so far, associated with current technologies, such as high temperatures, complex installations, high investments and operating costs, low energy and mass efficiencies.
  • the present invention takes advantage of the interaction of alternating magnetic fields with the magnetic nature of target materials for their reduction at low temperatures, in some cases below 100 °C, whereas temperatures above 1000 °C would be required by conventional heating techniques.
  • the invention relates to a method for reducing a reducible material, wherein the reducible material is a magnetic material, said method comprising the following steps: i) introducing the reducible material into a reactor cavity; ii) subjecting the reducible material to an alternating magnetic field; iii) heating the reducible material to at least the temperature at which the reduction of said material starts, thereby forming a reduced material and oxidized products; and iv) releasing from the reactor the generated oxidized products and, optionally, the reduced material, provided that only the reducible material is responsive to the alternating magnetic field and the reducible material is not subjected to an electric field.
  • Figure 1 Apparatus for carrying out the induction-assisted reduction of the present invention: A) Fixed bed reactor; B) Moving bed reactor.
  • Figure 4 A) XRD spectrum of the sample after the induction-assisted reduction; B) Zoomed-in insert of the XRD spectrum of panel A.
  • FIG. 1 Water splitting process. Upper panel: hydrogen release over time; lower part: time dependence of material weight (solid line) and temperature (dotted line).
  • any ranges given include both the lower and the upper end-points of the range. Ranges or values given, such as temperatures, times, molar ratio, volume ratio and the like, should be considered approximate when they are defined by the term “about” (i.e. with a 5% margin of variation around indicated point).
  • low temperature refers to a temperature comprised between room temperature and 600 °C
  • high temperature refers to temperatures higher than 600 °C.
  • the invention relates to a method for reducing a reducible material, wherein the reducible material is a magnetic material, said method comprising the following steps: i) introducing the reducible material into a reactor cavity; ii) subjecting the reducible material to an alternating magnetic field; iii) heating the reducible material to at least the temperature at which the reduction of said material starts, thereby forming a reduced material and oxidized products; and iv) releasing from the reactor the generated oxidized products and, optionally, the reduced material, provided that only the reducible material is responsive to the alternating magnetic field and the reducible material is not subjected to an electric field.
  • the method has the advantage that no other elements other than the reducible material are “responsive” to, i.e. are inductively heated by, the alternating magnetic field.
  • the magnetic material may be a magnetic susceptor, that is a material or component which absorbs magnetic energy and converts it into heat; more particularly, no other magnetic susceptor materials are employed in the method.
  • the magnetic material is inductively heated by the alternating magnetic field and reduced, provided that no other magnetic susceptor materials are employed in the method.
  • the reducible material is the only material being a magnetic susceptor responsive to the alternating magnetic field, being inductively heated by the alternating magnetic field and then reduced, while is not subjected to an electric field.
  • the reducible material of the first aspect of the invention is selected from a ferromagnetic, ferromagnetic and superparamagnetic material. The ferromagnetic, ferrimagnetic or superparamagnetic properties of the reducible material ensure that, when exposed to an alternating magnetic field, the reducible material will start heating up due to the rotation of the magnetic moments, appearance of hysteresis losses, or the generation of induction currents.
  • the reducible material comprises inorganic cations susceptible to reduction.
  • the reducible material may be in a solid state, in a molten state or suspended or dissolved in a fluid.
  • solid state materials they may be in powder form, porous structures or even mechanically supported on other non-active materials.
  • the reducible material is solid.
  • a metal oxide such as iron nitride, Fe x N y
  • a metal oxyfluoride such as XQFeOF
  • X is a trivalent metal and Q is a divalent metal
  • the structure of the reducible material may comprise dopants, such as transition metals, which alter the original physical-chemical properties of the reducible material.
  • dopants include Fe, Co, V, Mn, Ni, Cr.
  • metal oxides and mixed metal oxides with magnetic properties include, but are not limited to, those having general formula MO, AB2O4 or ABO3, where M, A and B refer to metals or combination of metals with the particularly defined stoichiometry.
  • Metal oxides also comprise M-MO (metal-metal oxide) and MO-MO (metal oxide-metal oxide) combinations.
  • Reducible oxides are solid state materials that are characterized by the reversible oxidation state of the metal. Because of the reversibility, these materials are promising for storing and releasing oxygen, as well as, for a huge variety of catalytic processes.
  • the metal oxides and mixed metal oxides are selected from FesO4, CrO2, TiO2, SnO2, ZnO, CeO2, ImOs, MmOs-MnO, CoFe2O4, NiFe2O4, CuFe2O4, MnFe2O4, Ni-MgFe2O4, ZnFe2O4, ZrO2-supported NiFe2O4, Sr/Ca-LaFeOs, YsFesOn, BaFenOw, Lao.vSro.sMnOs, S ⁇ FeMoOe, combinations and doped variants thereof.
  • the following table summarizes the preferred metal oxides and mixed metal oxides and specifies their magnetic properties.
  • the reducible material is a ferrimagnetic material. More preferably, the reducible material is a mixed metal oxide AB2O4 selected from the table above, i.e. selected from CoFe2O4, NiFe2O4, CuFe2O4, MnFe2C>4, Ni-MgFe2O4 and ZnFe2O4. Even more preferably, the reducible material is CoFe2O4.
  • the reducible material is introduced into a reactor cavity.
  • the reactor may be a fixed bed reactor (e.g. the reducible material stays in a fixed position and does not undergo any translational or rotational movement) or a moving bed reactor (the reducible material undergoes translational and/or rotational movements).
  • the reducible material is introduced in a fixed bed reactor, such as a quartz reactor.
  • a fixed bed reactor such as a quartz reactor.
  • the reducible material is placed on top of a mechanical and inert support, such as quartz wool or other porous materials (e.g., porous ceramic membranes, ceramic foams, fiber meshes or filters, micro-perforated plates) which is placed at the bottom of the reactor.
  • a mechanical and inert support such as quartz wool or other porous materials (e.g., porous ceramic membranes, ceramic foams, fiber meshes or filters, micro-perforated plates) which is placed at the bottom of the reactor.
  • the reducible material is introduced in a moving bed reactor, along with a carrier gas through an inlet opening, so as the reducible material is circulating within the reactor.
  • a moving bed reactor along with a carrier gas through an inlet opening, so as the reducible material is circulating within the reactor.
  • This can be made, for example, by means of a conveyor belt, a pneumatic conveyor or a screw conveyor.
  • the amount of reducible material and, optionally, of mechanical support material will depend on the size of the reactor and on the desired amount of reduced material and oxidized products to be obtained. A skilled person would possess the required knowledge to decide what the suitable amount of reducible material is.
  • the weight of the reducible material may be pre-determined before its introduction into the reactor cavity.
  • a gas flow such as argon
  • argon is passed through suitable openings of the reactor prior to or after introducing the reducible material with the aim of removing air and moisture from the reactor or calibrating and/or sensing a certain gas (e.g. oxygen).
  • a certain gas e.g. oxygen
  • An inert gas flow can be kept constant or varied throughout the method of the invention; in a particular embodiment, argon is used at a constant flow, more particularly the flow is kept at about 75 mL/min.
  • the reduction process may further comprise chemical reductants.
  • a chemical reductant is a substance that can donate electrons to another chemical species (such as the reducible material), thereby causing the reduction of the latter.
  • the chemical reductants is selected from the group consisting of H2, CO, ammonia, hydrocarbons, methanol, ethanol and any combination thereof.
  • graphite is not used in the reduction method.
  • graphite and coal are not used in the reduction method.
  • solid carbon-containing chemical reductants are not used in the reduction method (wherein “solid” refers to ambient conditions).
  • the reduction process is carried out without using graphite, CO, H2, CH4, natural gas, coal, brown-coal dust, hydrocarbons, ammonia and combinations thereof.
  • the reduction process is carried out without any additional chemical reductant; this means that the reducible material is heated by the alternating magnetic fields to at least the temperature at which the reduction of said material starts, said reduction taking place without the assistance of any further chemical reductant.
  • the reducible material is then subjected to an alternating magnetic field.
  • This is generated by an AC (alternating current) power generator which is activated at the desired power.
  • the power of the AC generator is comprised between 2 kW and 30 MW, more preferably between 2 kW and 1 MW, even more preferably between 2 and 4 kW. In the most preferred embodiment, the power of the AC generator is about 3.5 kW.
  • the power unit can also be expressed as 1 joule per second or 1 kg-m 2 -s 3 .
  • the frequency of the alternated magnetic field is lower than 30 MHz.
  • the present invention requires that no electric field is applied in the reduction method and a skilled person would be familiar with induction heating techniques and, therefore, how to apply an alternating magnetic field without, at the same time, applying an electric field.
  • the following scenarios may apply:
  • the magnetic field can be predominantly alternating with the electric field components being relatively weak and at right angles (Far-Field Approximation);
  • an alternating magnetic field can be created inside a shielded environment (e.g., using mu-metal or superconducting shields) that prevents the electric field components from entering or exiting (Shielded Environment);
  • a shielded environment e.g., using mu-metal or superconducting shields
  • the frequency of the alternated magnetic field is very low, i.e. equal to or lower than 800 kHz, preferably comprised between 100 kHz and 800 kHz, more preferably between 200 kHz and 600 kHz; even more preferably, the frequency is about 400 kHz.
  • such low frequencies ensure that the reducible material is subjected to an alternating magnetic field in absence of an electric field.
  • a sensor for the detection of signals due to oxidized products may be present and activated prior to or simultaneously with the AC generator.
  • the alternating magnetic field causes the heating of the reducible material by induction heating.
  • a further source of heating can be used in combination with induction heating originated from the applied magnetic field; in this regard, conventional sources of heating, such as industrial waste heat, solar or electrical heating, combustion, are known to a person skilled in the art.
  • heating sources selected from microwave irradiation, plasma/electric arc, metallurgical furnace, or heating by oxidation reactions are not used in the method.
  • no further heating sources other than the alternating magnetic field is used in the method.
  • the reducible material is inductively heated by the alternating magnetic field and reduced with no further chemical reductants. This is also caused by non-thermal effects of the alternating magnetic field on the reducible material.
  • no further heating sources other than the alternating magnetic field and no further chemical reductants, as defined above, are used in the method.
  • the temperature of the reducible material and the amount of oxidized products released can be continuously monitored.
  • the reduction of the reducible material takes place at low temperature, particularly at a temperature of less than 250 °C, less than 150 °C, less than 100 °C.
  • the reduction of the reducible material starts at a temperature comprised between 50 and 100 °C, more preferably between 60 and 90 °C, even more preferably between 80 and 90 °C.
  • the method of the invention comprises steps i-iv, provided that: only the reducible material is responsive to the alternating magnetic field, the frequency of the alternating magnetic field is lower than 30 MHz, preferably, less than or equal to 800 KHz, more preferably between 200 and 600 KHz; and the alternating magnetic field has also a non-thermal effect on the reducible material, so that the reduction starts at a temperatures of less than 250 °C, preferably less than 150 °C, more preferably less than 100 °C.
  • the reduction of the reducible material starts shortly after subjecting it to an alternating magnetic field, preferably after at least 5, at least 10, at least 15, at least 20, at least 25, at least 30 seconds; more preferably, the reduction starts after an amount of time between 5 and 60 seconds, more preferably between 10 and 50 seconds, even more preferably between 20 and 40 seconds, yet even more preferably after about 30 seconds from applying an alternating magnetic field.
  • the reduction starts at a temperature between 50 and 100 °C and after an amount of time between 5 and 60 seconds from applying an alternating magnetic field.
  • the heating goes up to a maximum which reflects the peak of reduction of the reducible material (hence the maximum formation of reduced materials) and release of oxidized products.
  • the maximum reduction temperature is lower than or equal to 600 °C.
  • the maximum reduction temperature is comprised between 50 °C and 600 °C, more preferably between 100 °C and 500 °C, even more preferably between 50 °C and 400 °C.
  • the term “maximum temperature” refers to the temperature at which the maximum amount of reduced material is reached.
  • the method of the invention may afford nearly quantitative reduction of the reducible material.
  • >20 wt% of the material is reduced; preferably >50 wt% of the material is reduced; more preferably, > 70 wt% of the material is reduced; even more preferably, >80 wt% of the material is reduced.
  • the resulting reduced material comprises at least a metal oxide, i.e., a metal oxide having a lower valence than the corresponding reducible material from which it originates; preferably, a mixture of metal oxides.
  • the reduced material comprises at least a metal in an elemental state; preferably, wherein more than 80 wt.% of the reducible material has been converted into at least a metal in an elemental state.
  • the oxidized products are preferably in the form of a gas stream, and preferably comprise molecules such as O2, Ch, F2, Br2, S, H2, CO, CO or syngas; more preferably the oxidized products essentially consist of O2 molecules or syngas.
  • the process of the invention further comprises the release of the oxidized products from the reactor.
  • the release of the oxidized products is made by one of the following means or a combination thereof: application of vacuum, the use of a carrier gas, the use of a reactive stream that can react with the generated oxidized products, the use of a selective separator for separating the reduced material from the oxidized product.
  • the release of the oxidized products is made by using a carrier gas.
  • carrier gases include argon and nitrogen.
  • Said carrier gas is introduced in the reactor through at least an inlet opening. As the reaction takes place, the resulting oxidized products are released from the reactor by the carrier gas through at least an outlet opening.
  • the reducible material when the reaction takes place in a moving bed reactor, can be introduced into the reactor along with the carrier gas through the same or different inlet openings.
  • the carrier gas allows releasing both the reduced material and the oxidized products from the reactor through at least an outlet opening.
  • the resulting mixture is then subjected to a separation step in order to separate the reduced material from the oxidized products.
  • cyclone separators or porous filters can be used for such separation.
  • the release of the oxidized products from the reactor can also be made by applying vacuum.
  • vacuum pumps can be placed connected to an outlet opening provided in the reactor.
  • the AC-power generator may be turned off while the reduced material can be cooled down under an inert gas flow.
  • the completion of the reaction can be monitored by sensors, e.g. when the signal of the sensor detecting the oxidized products returns to its baseline.
  • the process of the invention may also be accompanied by in-situ measurement of the temperature of the reducible material, the induced magnetic field, and the composition of the oxidized products generated.
  • the process can include the continuous adjustment of the intensity of the applied external magnetic field to improve the efficiency of the process.
  • the reduction process is carried out in an apparatus comprising:
  • an induction furnace comprising an alternating current power generator, and an applicator (2);
  • reactor selected from fixed bed reactor and moving bed reactor, said reactor comprising means for introducing a reducible material into a reactor cavity and at least an outlet opening.
  • the induction furnace is responsible for the generation and application of the alternating magnetic fields to the reducible materials and may be assembled in different ways, provided that the induction furnace comprises an alternating current (AC) power generator and an applicator.
  • AC alternating current
  • the induction furnace may also comprise power control elements and a cooling station.
  • Power control elements may be present in order to tune the generated AC current, while a cooling station may be needed in order to cool down the electrical elements of the induction furnace and thereby prevent overheating of said elements.
  • the operating frequency range can go from 50 Hz to 1 MHz.
  • the generated AC current is then transmitted to the applicator.
  • applicator can be understood a element that allows conducting the current to the reactor. Applicators are known to have different geometries (i.e. planar, helicoidal) depending on the design of the reactor, however a skilled person would recognize suitable geometries among the various possibilities.
  • the applicator is made of metallic elements, preferably the applicator is a metal coil, more preferably is a copper coil.
  • the diameter of the applicator may be comprised between 1 and 5 cm, preferably between 2 and 4.0 cm, more preferably the diameter is 2.5 cm.
  • the reactor is made from an inert material that i) does not interact with the magnetic field; ii) does not react with the reducible material or with the oxidized products generated during the reduction; and iii) withstands the expected working temperatures.
  • the reactor is a quartz or alumina reactor; even more preferably, the reactor is a quartz tube; such tube may have different diameters depending on the application scale.
  • the reactor has means for introducing a reducible material into a reactor cavity and at least an outlet opening.
  • the means for introducing the reducible material into the reactor can be varied and include, for example, an opening gate or at least one inlet opening.
  • said at least one inlet opening also allows introducing a carrier and/or inert gas and/or optional chemical reductants into the reactor.
  • the at least one outlet opening allows releasing the oxidized products generated in the reduction reaction and, optionally, the generated reduced materials.
  • a carrier and/or inert gas is introduced in the reactor through the at least one inlet opening, the carrier and/or inert gas can also be released through the at least one outlet opening along with the oxidized products.
  • the reactor may be a fixed bed reactor or a moving bed reactor.
  • the reactor is a fixed bed reactor.
  • Figure 1(A) schematically depicts the components of the apparatus of the invention in a fixed bed configuration.
  • the apparatus comprises an induction furnace comprising an alternating current (AC) power generator (1) and an applicator (2) as defined herein above, wherein the applicator (2) is preferably in the form of metallic coils.
  • the induction furnace may also comprise power control elements and a cooling station (not shown) such as also mentioned above.
  • the reducible material is introduced in the reactor (3), for example through an opening gate of said reactor, thus forming a reducible material bed (6).
  • the reducible material can be placed on an inert support (7) inside the reactor (3), preferably homogeneously distributed as a layer with varying thickness.
  • the inert support can be quartz wool or other porous mediums (e.g., porous ceramic membranes, ceramic foams, fiber meshes or filters, micro-perforated plates) and is placed in the bottom part of the reactor (3).
  • the reactor (3) may be provided with at least one inlet opening (4) which allows the introduction of a carrier and/or inert gas, such as argon, in the reactor.
  • the fixed bed reactor also includes at least one outlet opening (5) for releasing the oxidized products resulting from the reduction reaction.
  • the at least one outlet opening also allows releasing said carrier and/or inert gas, along with the oxidized products.
  • a fixed bed type reactor may additionally comprise elements to evacuate the oxidized products generated during the reduction process, such as vacuum pumps or pumps for the dragging and circulation of fluids.
  • the reactor is a moving bed reactor.
  • Figure 1(B) schematically depicts the components of the apparatus of the invention in a moving bed configuration.
  • the apparatus also comprises an induction furnace comprising an alternating current (AC) power generator (1) and an applicator (2) as defined herein above, wherein the applicator (2) is preferably in the form of metallic coils.
  • the induction furnace may also comprise power control elements and a cooling station (not shown) such as also mentioned above.
  • the reducible material is introduced in the reactor (3) along with a carrier gas through at least an opening inlet (4) of said reactor, thus allowing the reducible material (6) to circulate within the reactor (3).
  • the reactor comprises means of conveying the reducible material to the inlet opening (4) of the reactor (3).
  • said means of conveying include, for example, conveyor belt, a pneumatic conveyor or a screw conveyor.
  • the moving bed reactor also includes at least one outlet opening (5) for releasing the oxidized products resulting from the reduction reaction, along with the carrier gas.
  • the apparatus of the invention further comprises a separator (8) at the reactor outlet opening (5) where the reduced material is separated from the oxidized products generated during the reduction process.
  • Cyclone separators or porous filters can be used for the separation of the reduced material from the oxidized products generated during the reduction process.
  • optional sensing means placed at the outlet opening of the reactor may allow the quantification of the oxidized products.
  • the sensing means are O2 sensors which detect variations in the O2 released at the outlet opening.
  • the apparatus may further comprise temperature sensing means (such as a pyrometer) which provide contactless external measurement of the temperature inside the reactor.
  • the temperature sensing means are preferably connected to the AC generator so to regulate the output power to reach/maintain the programmed temperature.
  • the temperature sensing means are placed on one side of the reactor and perpendicular to it.
  • the sensor is directed on one side of the reduced material inside the reactor.
  • the temperature measured externally can be significantly lower than the one inside of the reactor.
  • the external layer of the reducible material may be more susceptible to heat-losses, particularly:
  • the rate of the heat flow dissipated through the reactor can be comparable with the rate of the energy flow absorbed by the reducible material.
  • the reactor may be equipped with a top opening with a gas-tight connection that allows the introduction of temperature sensing means along the vertical axis of the reactor and permits the direct internal temperature measurement.
  • the apparatus of the invention can be further equipped with process monitoring and control elements selected from temperature sensors (e.g., infrared thermometer), video cameras for the observation of the material during the reduction process, devices for the analysis of the composition of the products of the reduction method.
  • process monitoring and control elements selected from temperature sensors (e.g., infrared thermometer), video cameras for the observation of the material during the reduction process, devices for the analysis of the composition of the products of the reduction method.
  • Another disclosure of the invention refers to a reduced material obtainable by the method of the first aspect of the invention.
  • the reduced materials are characterized by comprising metals or a mixture of metals at a lower oxidation state or even elemental state.
  • the reducible material is CoFe2O4
  • the reduced material may comprise elemental iron, cobalt and unconverted CoFe2O4; more preferably, elemental iron ranges from 60 to 90 wt%, while elemental cobalt ranges from 1 to 10 wt%.
  • the reduced material comprises about 80 wt% Fe, about 7 % Co and unconverted CoFe2O4.
  • the reduced material displays a specific diffractogram.
  • reduced material obtained by reduction of CoF e2O4 according to the method of the invention displays peaks at 30.2°, 35.5°, 43.2°, 53.5°, 57.1°, 62.7° and 73.9° corresponding to CoFe2O4, peaks at 44.9° and 65.2° corresponding to metal iron and peaks at 44.1° and 51.5° corresponding to cobalt.
  • the reduced material obtained by the process of the invention can be subjected to subsequent steps in order to further produce a variety of new reduced products or be used in different applications in the energy industry.
  • the invention also relates to the use of the reduced material obtained according to the process of the invention, in thermal energy storage, in the production of hydrogen, syngas and/or hydrocarbons, and as selective absorbent of impurities in gaseous streams.
  • Most of these uses involve the re-oxidation of the reduced material, mainly for producing new reduced materials.
  • the process of the invention further comprises the re-oxidation of the reduced material obtained in step iii), and separated from the oxidized products, in the presence of at least an oxidizing agent or of a molecule susceptible of being reduced.
  • the oxidizing agent or the molecule susceptible of being reduced will be selected accordingly.
  • Thermal energy storage For example, the reduced materials find use in thermal energy storage involving their redox cycling.
  • a redox cycle of reducible materials involves two steps: 1) the charging step of the storage system, in which heat is supplied to reducible materials and both reduced materials and fluid oxidized products are generated (endothermic step, corresponding to the method of the invention); and 2) the discharging step of the storage system, in which the reduced material is then re-oxidized in the presence of O2 releasing heat (exothermic step).
  • the invention also relates to the use of the reduced material obtained by the process of the invention in thermal energy storage.
  • the process of the invention further comprises the re-oxidation of the reduced material obtained in step iii), and separated from the oxidized products, in the presence of oxygen as oxidizing agent.
  • the reduced materials of the invention are obtained at lower temperature compared to those obtained in the prior art requiring very high temperatures (i.e. > 1000 °C to reduce metal oxides).
  • High reduction temperature lead to problems related to the stability of the storage material (e.g., sintering over successive cycles of use) and to the cost of the materials needed to build the tank and heat/mass exchangers, which must withstand very high working temperatures.
  • the use of the reduced materials of the present invention represents a considerable practical and economical advantage.
  • the invention relates to the use of the reduced materials obtained by the process of the invention in H2 production.
  • the production of H2 is made by thermochemical watersplitting cycles.
  • the process of the invention further comprises the re-oxidation of the reduced material obtained in step iii), and separated from the oxidized products, by bringing it into contact with water vapor to produce H2.
  • the production of H2 is made by using H2S as oxidizing agent.
  • the process of the invention further comprises the re-oxidation of the reduced material obtained in step iii), and separated from the oxidized products, in the presence of H2S as oxidizing agent to produce H2.
  • the method of the present invention achieves the reduction of reducible materials at low-to-moderate temperatures ( ⁇ 600 °C), which is very competitive with the high temperatures employed in the prior art, where the heat sources needed are limited in number (e.g., solar concentrators, waste heat from intensive industry) and the methods involve problems with durability and cost of materials.
  • the present invention may compete with electrolyzers in the production of green H2.
  • the invention relates to the use of the reduced material obtainable by the process of the invention for CO2 splitting or co-splitting of water and CO2.
  • the reduced materials of the present invention can be used in thermochemical cycles for CO2 splitting, or co-splitting of water and CO2.
  • the process of the invention further comprises the re-oxidation of the reduced material obtained in step iii), and separated from the oxidized products, by bringing it into contact with CO2 or with a mixture of CO2 and water, to produce CO and/or syngas.
  • the reduced material is brought into contact with CO2, being reoxidized to a reducible material and simultaneously producing CO (or syngas).
  • the reduced material is brought into contact with a mixture of CO2 and H2O, being reoxidized to a reducible material and simultaneously producing syngas (CO and H2).
  • CO is a powerful reducing agent with multiple uses in the industry.
  • syngas is commonly used to produce methanol or hydrocarbons (e.g., alkanes, olefins, aromatic compounds, waxes, etc.).
  • the reduced materials of the present invention allow low temperature thermochemical cycles for CO2 valorization as opposed to prior art methods which require high temperatures required in the reduction of the reducible material.
  • the reduced materials obtained according to the process of the invention can also be used to produce reduced products with new functionalities while also being oxidized.
  • the reduced material is brought into contact with a molecule susceptible of being reduced.
  • Molecules such as alkanes, alkenes, naphthene or aromatic hydrocarbons could be suitable substrates to form reduced products with new functionalities.
  • reaction of the reduced material with methane or ethane will give olefins, hydrogen, synthesis gas or aromatic hydrocarbons.
  • Selective absorption of a gaseous stream In another embodiment, the invention relates to the use of the reduced material obtainable by the process of the invention as a selective absorbent of impurities in gaseous streams.
  • the reduced material obtained by the process of this invention can react with and/or remove impurities from a gaseous stream selectively by fixing them in their structure.
  • the impurities are selected from O2, O3, Ch, F2, Br2, HC1, H2S, N2O, NO X or mixtures thereof.
  • the reduced material acts as an absorbent material and can be regenerated when subjected to the action of an alternating magnetic field according to the method of the first aspect of the invention.
  • a method for reducing a reducible material wherein the reducible material is a magnetic material, said method comprising the following steps: i) introducing the reducible material into a reactor cavity; ii) subjecting the reducible material to an alternating magnetic field; iii) heating to at least the temperature at which the reduction of the reducible material starts, thereby forming a reduced material and oxidized products; and iv) releasing from the reactor the generated oxidized products and, optionally, the reduced material.
  • the reducible material is a ferromagnetic, ferrimagnetic or superparamagnetic material selected from a metal oxide, a mixed metal oxide, a metal nitride, a metal oxyfluoride or a double perovskite halide.
  • the reducible material is selected from CoFe2O4, NiFe2O4, CuFe2O4, MnFe2C>4, Ni-MgFe2O4, ZnFe2C>4 or ZrCh supported NiFe2O4; preferably, the reducible material is CoFe2O4. 4.
  • the frequency of the alternated magnetic field in step ii) is comprised between 100 kHz and 800 kHz, more preferably between 200 kHz and 600 kHz; even more preferably, the frequency is about 400 kHz.
  • oxidized products comprise at least a molecule selected from O2, Ch, F2, E and S.
  • the reduced material comprises at least a metal oxide; preferably, a mixture of metal oxides.
  • the reduced material comprises at least a metal in an elemental state; preferably, wherein more than 80 wt.% of the reducible material has been converted into at least a metal in an elemental state.
  • an induction furnace comprising an AC power generator (1) and an applicator (2);
  • reactor (3) selected from a fixed bed reactor and a moving bed reactor, said reactor comprising means for introducing a reducible material into a reactor cavity, and an outlet opening (5);
  • the reactor (3) is a fixed bed reactor which further comprises at least one inlet opening (4) which allows the introduction of a carrier and/or inert gas in the reactor (3), and wherein the apparatus optionally further comprises elements to evacuate oxidized products, said elements being selected from vacuum pumps or pumps for the dragging and circulation of fluids.
  • the reactor is a moving bed reactor
  • the means for introducing the reducible material to the inlet opening (4) of the reactor (3) are selected from a conveyor belt, a pneumatic conveyor and a screw conveyor, and wherein the apparatus further comprises a separator (7) at the reactor outlet opening (5).
  • control elements are temperature sensors outside the reactor providing external measurement of the temperature inside the reactor.
  • CoFe2O4 supplied by Inframat® Advanced MaterialsTM LLC (USA) has been used.
  • the main features of CoFe2O4 are the following:
  • the equipment for carrying out the reduction process can be depicted in figure 2.
  • the apparatus included a power generator of alternated current (not shown in the figure) with maximum power of 3500 W and frequency range from 375 to 575 KHz (Ceia).
  • the generated AC current is transmitted to a copper coil (2) of around 2.5 cm of diameter.
  • the material to be reduced (6) is placed inside a quartz tube reactor (3) with external diameter of 2 cm. To keep the material particles in place at the desired height, a portion of quartz wool (7) is placed in the bottom part of the quartz reactor.
  • the quartz reactor is equipped with:
  • the experimental setup for induction heating relies on the contactless external measurement of the temperature, which can be performed by placing a pyrometer on one side of the reactor and perpendicular to it.
  • the quartz reactor is equipped of a top opening (12) with a customized gas-tight connection that allows introducing a pyrometer (13) along the vertical axis of the reactor and permits the direct internal temperature measurement.
  • Example 1 Procedure for the reduction process.
  • the inlet and the outlet openings of the reactor were closed and connected to the Ar reservoir and to the O2 microsensor, which was previously calibrated by using a two-point calibration.
  • pure argon and synthetic air (20 vol.% O2 in N2) were used.
  • Fig. 3 the temperature of the sample and the amount of O2 released were continuously monitored. The results achieved are shown in Fig. 3, where the sample started to heat-up as soon as the alternating magnetic field was applied (power on) and progresses steadily and smoothly until the Curie temperature of the material was reached. At such temperature, the material loses its magnetic properties, and it does not continue to heat up. During heating, oxygen was generated, meaning that the reduction of the material was taking place. As shown in Fig. 3, the reduction started after about 0.5 min and at very low temperature ( ⁇ 88 °C). O2 release occured from the beginning of the reduction process until a maximum value of 0.65 pmol/gcoFe2O4 at 170 °C was reached. Then, it slowed down. The reduction process was fast, ending after ca. 9 min.
  • the reduced sample was analyzed by XRD to identify and quantify the crystalline phases.
  • the experimental conditions for XRD analysis are described in the “Material characterization” section.
  • the quantification was performed using the Rietveld method. As shown in Fig. 4, the major phase of the sample was metallic iron (80.1 wt.%). Also 6.6 wt.% cobalt and 13.3 wt.% of original CoFe2O4were present. This indicates that an extensive reduction of the cobaltite was achieved, which is unusual when the reduction is performed by a conventional heating method. This is further highlighted in Table 1, which shows the advantages of the reduction method proposed in the present invention compared with a conventional heating method. In the latter case, results may vary slightly depending on the synthesis method and experimental conditions.
  • Example 2 Equipment and procedure for water splitting with the reduced material.
  • the reduced CoFe2O4 was removed from the quartz reactor to test the H2 production in a water splitting reaction.
  • Water splitting experiments were performed using an STA 449 F3 Jupiter (NETZSCH) thermobalance coupled with a water vapour generator provided by aDROP GmbH.
  • the outlet gas of the STA oven was connected to an H2 Clark-type microsensor (detection limit ⁇ 10' 3 vol.%) interfaced with an amplifier (Unisense, Denmark).
  • the sensor was calibrated before each measurement by using a two-point calibration. To this aim, pure Ar and an Ar with 2 vol.% H2 standards were used.
  • the samples were heated at 10 °C min' 1 up to 650 °C under a 75 mL/min argon flow. Water vapour was then introduced into the gas flow at a rate of 2 g H2O/hour for 3 hours. When the water supply was stopped, the argon flow was maintained, and the sample was cooled to room temperature.
  • the sample was first heated at 10 K/min up to 650 °C under a 75 mL/min Ar flow. Steam was then introduced into the Ar flow at a rate of 2 g H2O/I1 while the temperature is keeping constant (isothermal conditions) and the H2 content in the outlet gas of the thermobalance oven is continuously monitored.
  • the lower part of figure 5 shows the temperature evolution of the sample as well as its weight changes, whereas H2 generation over time is plotted in the upper part.
  • the total amount ofH2 released was equal to 3.9 mmol/g (8 gH2/g CoFe2O4 approx.), which largely surpassed the values obtained when CoFe2O4 is reduced by conventional heating at high temperature (0.83 mmol/g) and under comparable water splitting conditions.
  • the time required to complete the re-oxidation of the material is much lower.
  • the duration of the water dissociation process was less than 60 min, whereas it takes several hours for the material reduced by conventional heating method at high temperature.

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Abstract

La présente invention concerne un procédé de réduction directe de matériaux réductibles à de basses températures (< 600 °C environ) au moyen de champs magnétiques alternatifs. Il peut, en outre, ne pas nécessiter d'agents de réduction chimiques ou d'électrodes à contact. L'invention se rapporte également à l'équipement utilisé pour mettre en œuvre ladite réduction, aux matériaux obtenus par ledit procédé de réduction et à l'utilisation de tels matériaux pour produire des produits chimiques présentant un intérêt industriel et/ou en tant que porteur d'énergie.
PCT/EP2024/064804 2023-05-30 2024-05-29 Procédé de réduction assisté par des champs magnétiques alternatifs Pending WO2024246143A1 (fr)

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JP2010173930A (ja) 2009-01-27 2010-08-12 Buhei Kono メタン、アンモニア、水蒸気から磁性体フェライト及び金属酸化物磁性体にマイクロ波を照射した場合の赤外線、遠赤外線、テラヘルツの波長輻射による触媒反応を利用し、輻射する波長振動の密度を高め低温の１５０℃〜４００℃の低温帯で水素を効率よく発生させる方法
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