Direct Reduction Plant and Method for Producing Direct Reduced Iron in a Direct Reduction Plant

Description

1 / 12 “DIRECT REDUCTION PLANT AND METHOD FOR PRODUCING DIRECT REDUCED IRON IN A DIRECT REDUCTION PLANT”

[001] The invention relates to a plant for manufacturing Direct Reduced Iron (DRI) and the associated method.

[002] Currently, steel can be produced through two main manufacturing routes. Currently, the most widely used production route consists of hot metal production in a blast furnace, using a reducing agent, mainly coke, to reduce iron oxides. In this method, approximately 450 to 600 kg of total fuel are consumed per metric ton of hot metal; this method, both in the production of coke from coal in a coke oven and in the production of hot metal, releases significant amounts of CO2.

[003] The second main route involves the so-called “direct reduction methods”. Among these are methods, notably those of the MIDREX or ENERGIRON / HYL brands, in which sponge iron is produced in the form of HDRI (Hot Direct Reduced Iron), CDRI (Cold Direct Reduced Iron) or HBI (Hot Briquetted Iron) from the direct reduction of iron oxide carriers. Sponge iron in the form of HDRI, CDRI or HBI generally undergoes further processing in electric arc furnaces.

[004] There are three zones in each direct reduction tank with cold discharge: reduction zone at the top, transition zone in the middle and cooling zone at the bottom in a cone shape. In hot discharge DRI, this lower part is mainly used for homogenization of the product before discharge.

[005] The reduction of iron oxides occurs in the upper section of the furnace, at temperatures up to 950 °C. Iron ores, in the form of lump ores and / or pellets, containing about 30% oxygen by weight, are loaded into the upper part of a direct reduction shaft furnace and descend, Petition 870250111041, dated 03 / 12 / 2025, page 10 / 31 2 / 12 by gravity, through a reducing gas. This reducing gas enters the furnace from the bottom of the reduction zone and flows countercurrently to the loaded iron ores. The oxygen contained in the iron ore is removed by the gradual reduction of iron oxides by the gaseous reducing agents. The oxidant content of the gas phase increases as the gas moves towards the top of the furnace.

[006] Reducing gas generally comprises hydrogen and carbon monoxide and is obtained by reforming natural gas. For example, in the MIDREX method, methane is first transformed into a reformer according to the following reactions to produce synthesis gas or reducing gas: CH4 + CO2 -> 2CO + 2H CH4 + H2O -> CO + 3H2 and the iron oxide reacts with the reducing gas, for example, according to the following reactions: 3Fe2O3 + CO / H2 -> 2Fe3O4+ CO2 / H2O Fe3O4 + CO / H2 -> 3FeO + CO2 / H2O FeO + CO / H2 -> Fe + CO2 / H2O at the end of the reduction zone, the ore is metallized.

[007] A transition section is found below the reduction section; this section is long enough to separate the reduction section from the cooling section, allowing independent control of both sections. In this section, the carburization of the metallized product occurs. Carburization is the process of increasing the carbon content of the direct reduction product within the reduction furnace through the following reactions: 3Fe + CH4 ^ Fe3C + 2H2 (Endothermic) 3Fe + 2CO ^ Fe3C + CO2 (Exothermic) 3Fe + CO + H2 ^ Fe3C + H2O (Exothermic)

[008] The injection of natural gas into the transition zone utilizes heat Petition 870250111041, dated 03 / 12 / 2025, page 11 / 31 3 / 12 of the direct reduction product in the transition zone is sensitive to promoting hydrocarbon cracking and carbon deposition. Due to the relatively low concentration of oxidants, natural gas from the transition zone is more likely to crack into H2 and carbon than to reform into H2 and CO. Natural gas cracking provides carbon for DRI carburization and, at the same time, adds a reducing agent (H2) to the gas, which increases the gas reduction potential.

[009] In view of the considerable increase in the concentration of CO2 in the atmosphere since the beginning of the last century and the consequent greenhouse effect, it is essential to reduce CO2 emissions where it is produced in large quantities and, therefore, in particular during the manufacture of DRI.

[010] One solution currently under development is the progressive increase of the hydrogen content in the reducing gas, aiming to obtain a pure hydrogen reducing gas. The following reduction reaction will then occur: Fe2O3 + 3H2 = 2Fe + 3H2O, thus releasing harmless H2O instead of the greenhouse gas CO2.

[011] As mentioned below, this shift from methane-based DRI to H2-based DRI will be phased in for several reasons. Existing plants need to adapt their equipment and assess the impact on subsequent stages of steel production. The most preferable source of hydrogen is green hydrogen to reduce the overall carbon footprint, but it is currently not available in sufficient quantities to meet all needs. Although the future availability of green hydrogen depends heavily on the capacity of renewable energy sources.

[012] Consequently, plants will have to operate in a hybrid mode between NG-based DRI and DRI-H2 technologies.

[013] There is therefore a need for equipment that Petition 870250111041, dated 03 / 12 / 2025, page 12 / 31 4 / 12 allows operation with a variable hydrogen content in the reducing gas. There is also a need for a direct reduction method that allows operation with a higher hydrogen content in the reducing gas without detrimental impact on productivity compared to existing natural gas-based methods.

[014] This problem is solved by a plant according to the invention, comprising a direct reduction furnace and a reformer, this reformer comprising several tubes provided with gas supply means, at least one of said tubes being provided with at least one gas supply means capable of supplying said tube with a stream of gaseous hydrogen and at least one other tube being provided with at least one gas supply means capable of supplying said other tube with a methane-containing gas.

[015] The invention plant may also comprise the following optional features, considered separately or in combination with all possible technical options: - at least one of the tubes is provided with gas supply means capable of supplying said tube with a stream of hydrogen gas or with gas containing methane, said gas supply means further comprising selection means that allow supplying only the stream of hydrogen gas or only the gas containing methane to said tube, - at least one of the tubes is provided with gas supply means capable of supplying said tube exclusively with a stream of gaseous hydrogen, - The gas supply means designed to supply the pipes with a stream of gaseous hydrogen are equipped with means to control the flow rate of H2. - at least one of the aforementioned pipes, in which the current of Petition 870250111041, dated 03 / 12 / 2025, page 13 / 31 5 / 12 hydrogen is exclusively supplied, it is filled with solid particles, The solid particles are made of ceramic or a high-temperature alloy.

[016] The invention also relates to a method for manufacturing direct reduced iron in a direct reduction plant, according to any of the foregoing combinations, wherein oxidized iron is reduced in the direct reduction furnace using a reducing gas to produce direct reduced iron, the method comprising supplying a methane-containing gas with the gas supply medium to at least one of the reformer tubes to subject said methane-containing gas to a reforming step to produce a reformed gas, supplying a hydrogen gas stream with the gas supply medium to at least one of the reformer tubes to heat said hydrogen gas stream to a temperature of 800 °C to 1100 °C, mixing at least the reformed gas and the heated hydrogen gas stream to form the reducing gas and injecting the reducing gas into the direct reduction furnace.

[017] The method of the invention may also comprise the following optional features, considered separately or in combination with all possible technical combinations: Oxygen is injected into the reducing gas before it is injected into the direct reduction furnace. - the gaseous hydrogen stream comprises more than 70% hydrogen by volume, - the reducing gas comprises at least 50% by volume of H2, - a direct reduction top gas exits the direct reduction furnace and the methane-containing gas comprises at least a portion of said direct reduction top gas, Petition 870250111041, dated 03 / 12 / 2025, page 14 / 31 6 / 12 - the stream of gaseous hydrogen is green hydrogen.

[018] Other features and advantages of the invention will become clear from the description given below by way of indication, and which is in no way restrictive, with reference to the accompanying figures, in which: Figure 1 illustrates a direct reduction plant that allows the implementation of a method according to the invention; Figure 2 illustrates one embodiment of a reformer that allows for the execution of a method in accordance with the invention; Figure 3A illustrates another reformer that allows the execution of a method according to the invention; Figure 3B is an enlarged view of the reformer injection means shown in Figure 3A.

[019] The elements in the figures are illustrative and may not have been drawn to scale.

[020] Figure 1 illustrates a direct reduction (DR) plant according to the invention. This DR plant includes a DR tank or furnace (1) comprising, from top to bottom, a loading device (10) for oxidized ore, such as iron ore, said iron ore traveling through the tank (1) by gravity, a reduction section located at the top of the tank, a transition section located in the central part of the tank and, optionally, a cooling section located at the bottom and an outlet from which the directly reduced iron (12) is finally extracted.

[021] The direct reduction furnace (or shaft furnace) (1) is charged at its top with iron ore containing oxidized iron, such as hematite or magnetite. This oxidized iron is reduced in the furnace (1) by a reducing gas (11) injected into the furnace and flowing countercurrent to the oxidized iron. If cold DRI is expected as the final product, the directly reduced iron needs to be cooled in the cooling zone. When such a cooling region is Petition 870250111041, dated 03 / 12 / 2025, page 15 / 31 7 / 12 present, the reduced iron (12) exits through the bottom of the furnace (1) at a temperature below 65 °C, preferably from 30 °C to 65 °C, for further processing, such as briquetting, before being used in subsequent steelmaking stages. The reducing gas, after the reduction of the iron, exits through the top of the furnace as a top gas (20) (TG).

[022] The direct reduction plant (1) further comprises a reformer (33) comprising several tubes (51) provided with gas supply means (64, 65). At least one of the tubes (51A) is provided with at least one gas supply means (64), allowing the associated tube (51A) to be supplied with a hydrogen gas stream (25), and at least one other tube (51B) is provided with at least one gas supply means (65), allowing this other tube (51B) to be supplied with a methane-containing gas (24).

[023] The reducing gas (11) then comprises a reformed gas (41) resulting from the reforming of the methane-containing gas (24) in the reformer (33) and a heated hydrogen gas stream. This heated hydrogen gas stream has a temperature of 800 °C to 1100 °C and results from heating the hydrogen gas stream (25) in the same reformer (33) used for reforming the methane-containing gas (24).

[024] Methane reforming is a well-known technology in which methane reacts with steam and / or carbon dioxide in the presence of a catalyst to form carbon oxides and hydrogen.

[025] In a preferred embodiment, the hydrogen gas stream (25) is green hydrogen. Green hydrogen (GH or GH2) is hydrogen generated by renewable energy or low-carbon energy. This H2 stream can be supplied by a plant dedicated to H2 production, such as an electrolysis plant. It can be a water or steam electrolysis plant. It is preferably operated with CO2-neutral electricity, which includes, Petition 870250111041, dated 03 / 12 / 2025, page 16 / 31 8 / 12 Notably, electricity from renewable sources, defined as energy produced from renewable resources that are naturally replenished on a human timescale, including sources such as sunlight, wind, rain, tides, waves, and geothermal heat. In some embodiments, electricity from nuclear sources can be used, since it does not emit CO2 during its production.

[026] In a preferred embodiment, the H2 stream (25) enters the reformer at a temperature ranging from ambient to 400 °C. It may have been preheated before its injection into the reformer (33). This preheating is preferably an electric heating powered by CO2-neutral electricity.

[027] Before its injection into the furnace, oxygen (27) can be added to the reducing gas (11). This addition allows the temperature of the reducing gas to be increased thanks to the oxygen-induced exothermic reactions.

[028] The reducing gas (1) is preferably injected into the furnace at a temperature of 900 to 1200 °C. It preferably comprises more than 50% by volume of hydrogen.

[029] The top gas (20) exiting the DRI tank (1) is collected in a pipeline and, after optionally undergoing a water removal stage in a scrubber (30), can be split into a process gas stream (21A) and a top fuel gas stream (21B). This top fuel gas stream (21B) can be supplied as fuel to the burners (53) in the reformer (33). The process gas stream (21A), after optionally undergoing a CO2 removal stage in a CO2 removal equipment (31) and a second water removal stage in a scrubber (32), can be mixed with natural gas (23) to form the methane-containing gas (24) supplied to the reformer (33). The process gas stream (21A) can also be sent directly to the reformer (33). Petition 870250111041, dated 03 / 12 / 2025, page 17 / 31 9 / 12 without the addition of natural gas (23).

[030] The top gas exiting the DRI shaft furnace generally comprises H2, CO, CH4, H2O, CO2 and N2 in various proportions. The top gas scrubbing operation allows the removal of water vapor from the remaining stream, improving its reduction potential.

[031] The top gas (21), after the scrubber (30), generally comprises, by volume, 43 to 57% H2, 13 to 28% CO, 12 to 18% CO2, 2 to 12% CH4, 1 to 4% H2O and 0 to 3% N2. If subjected to a partial CO2 removal step in the CO2 removal equipment (22), it generally comprises 50 to 69% H2, 15 to 20% CO, 2 to 13% CO2, 9 to 14% CH4, 1 to 4% H2O and 0 to 3% N2.

[032] Figure 2 illustrates one embodiment of a reformer (33) according to the invention. The reformer (33) comprises gas supply means (64, 65), allowing the supply of gas to a series of reforming tubes (51B, 51A), and at least one main collector tube (52), allowing the collection of the gas existing in the tubes (51A, 51B). The reformer also comprises fuel-fed burners (53) (not shown) and a combustion exhaust collector (54) to recover the exhaust gases from the combustion. In this first embodiment, at least one reforming tube (51A) is fed only with the hydrogen stream (25) by means of hydrogen gas injection means (65), and at the outlet a heated hydrogen gas stream (42) with a temperature of 800 °C to 1100 °C is collected, this tube being operated in hydrogen heating mode.The other reforming tubes (51B) are supplied by appropriate gas injection means (64) with methane-containing gas (24), as done in the prior art, and a reformed gas (41) is collected at the outlet; these tubes are operated in reforming mode. The typical composition of a reformed gas (41), before mixing with the heated H2 stream (42), is expressed in percentages as follows: Petition 870250111041, dated 03 / 12 / 2025, page 18 / 31 10 / 12 volume, 54 to 75% H2, 14 to 35% CO; 2 to 7% CO2; up to 5% CH4, up to 6% H2O and up to 3% N2. Both the reformed gas (41) and the heated hydrogen stream (42) are mixed to form a reducing gas (26) which exits the reformer (33).

[033] In a preferred embodiment, the reformer (33) is a catalytic reformer and at least one reforming tube (51A) supplied with the hydrogen stream is used to heat the H2 stream. The H2 heating tube (51A) is preferably provided with means to adjust the gas flow rate and is preferably filled with inert particles, such as ceramic or metallic particles, such as alumina particles or high-temperature alloys. High-temperature alloys are alloys capable of withstanding temperatures above 500 °C. With the use of these particles, the heat exchange between the hydrogen gas and the tube wall is improved. In addition, the particles also help to reduce the gas velocity, avoiding possible problems in the main collector (52).

[034] In Figure 2, only five tubes are represented, one of them being supplied with hydrogen, but the invention obviously covers embodiments in which the reformer comprises several series of tubes and in which one of the tubes in the series or one of the series is dedicated to heating hydrogen.

[035] Figures 3A and 3B illustrate another embodiment of a reformer that allows the execution of a method according to the invention. The same references will be used when referring to the same element of the previous embodiment.

[036] In this embodiment, the reformer (33), as in the previous embodiment, comprises main collector tubes (52), allowing the collection of gas exiting the tubes (51), burners (not shown) fed with fuel (not shown) and an exhaust manifold of Petition 870250111041, dated 03 / 12 / 2025, page 19 / 31 11 / 12 combustion (54) to recover the exhaust gases from combustion. In this embodiment, at least one reforming tube (51) is provided with two gas supply means (64, 65), capable of supplying, respectively, the hydrogen gas stream (25) and the methane-containing gas (24). These two gas supply means are equipped with selection means, such as opening / closing devices, which allow the supply of either the hydrogen stream (25) or the methane-containing gas (24) to the tube (51). This results in the supply of either only the hydrogen gas stream or only the methane-containing gas (24) to the tube. In this embodiment, the methane-containing gas (24) is the process gas (21).

[037] Both the hydrogen supply medium (65) and the process gas supply medium (64) are connected to a gas injection device (66) designed to inject the required gas into the tube (51). The hydrogen supply medium (65) is connected to a hydrogen source which may be a storage tank or an H2 distribution network.Each gas supply means (64, 65) is equipped, respectively, with a hydrogen opening device and a methane opening device, and when sufficient hydrogen is available, the hydrogen opening device is opened while the methane opening device is closed, so that only the hydrogen stream (25) flows through the tube, which operates in hydrogen heating mode, whereas, when hydrogen is absent, the hydrogen opening device is closed and the methane opening device is opened, so that only the methane-containing gas (24) flows through the tube, which then operates in reforming mode. When several tubes are equipped with this dual supply means, it is possible that some of them operate in hydrogen heating mode while others operate in reforming mode.

[038] This allows flexibility in installation according to the Petition 870250111041, dated 03 / 12 / 2025, page 20 / 31 12 / 12 hydrogen availability and the ability to operate in total methane, total hydrogen, or methane / hydrogen hybrid modes.

[039] In both embodiments, it is clear to the person skilled in the art that the means of gas supply are related to the main gas supplied to the tubes, namely hydrogen and methane-containing gases, so that the tubes are operated in the so-called hydrogen heating mode or reforming mode. In the case of a tube operated in reforming mode, steam or top process gas may, for example, be supplied together with the methane-containing gas to carry out the reforming reaction.

[040] With the plant according to the invention, it is possible to adapt the existing direct reduction plant for hydrogen reduction with minimal investment and equipment, and it is also possible to operate with variable reducing gas compositions and adapt to hydrogen availability without detrimental impact on productivity. Petition 870250111041, dated 03 / 12 / 2025, pages 21 / 31

Claims

1 / 3 Claims 1. DIRECT REDUCTION PLANT, characterized by comprising a direct reduction furnace (1) and a reformer (33), the reformer (33) comprising several tubes (51) provided with gas supply means (64, 65), at least one of the tubes (51A) being provided with at least one gas supply means (65) capable of supplying the tube (51A) with a gaseous hydrogen stream (25) and at least one other tube (51B) being provided with at least one gas supply means (64) capable of supplying the other tube (51B) with a methane-containing gas (24).

2. DIRECT REDUCTION PLANT, according to claim 1, characterized in that at least one of the tubes (51) is provided with gas supply means (65, 64) capable of supplying the tube (51) with the hydrogen gas stream (25) or with the methane-containing gas (24), the gas supply means (65, 64) further comprising selection means that allow supplying only the hydrogen gas stream (25) or only the methane-containing gas (24) to the tube (51).

3. DIRECT REDUCTION PLANT, according to claim 1, characterized in that at least one of the tubes (51) is provided with a gas supply means (65) capable of supplying the tube (51) exclusively with the gaseous hydrogen stream (25).

4. DIRECT REDUCTION PLANT, according to any one of claims 1 to 3, characterized by the gas supply means (64), designed to supply the tubes (51A) with a stream of gaseous hydrogen (25), being equipped with means to control the flow rate of H2.

5. DIRECT REDUCTION PLANT, according to claim 3, characterized in that at least one of the tubes (51A), in which the hydrogen stream (25) is exclusively supplied, is filled with solid particles. Petition 870250111041, dated 03 / 12 / 2025, page 22 / 31 2 / 3 6. DIRECT REDUCTION PLANT, according to claim 5, characterized in that the particles are made of ceramic or a high-temperature alloy.

7. METHOD FOR PRODUCING DIRECT REDUCED IRON (12) IN A DIRECT REDUCTION PLANT, as defined in any one of claims 1 to 6, characterized in that oxidized iron (10) is reduced in the direct reduction furnace (1) using a reducing gas (11) to produce direct reduced iron (12), the method comprising: - supplying a methane-containing gas (24) with the gas supply medium (64) to at least one of the reformer tubes (51B) (33) to subject the methane-containing gas (24) to a reforming step to produce a reformed gas (41), - supplying a hydrogen gas stream (25) with the gas supply medium (65) to at least one of the reformer tubes (51A) (33) to heat the hydrogen gas stream (25) to a temperature of 800 °C to 1100 °C, - mixing at least the reformed gas (41) and the heated gaseous hydrogen stream (42) to form the reducing gas (11), - inject the reducing gas (11) into the direct reduction furnace (1).

8. METHOD, according to claim 7, characterized in that oxygen (27) is injected into the reducing gas (11) before its injection into the direct reduction furnace (1).

9. METHOD, according to any one of claims 7 to 8, characterized in that the gaseous hydrogen stream (25) comprises more than 70% by volume of hydrogen.

10. METHOD, according to any one of claims 7 to 9, characterized in that the reducing gas (11) comprises at least 50% by volume of H2. Petition 870250111041, dated 03 / 12 / 2025, page 23 / 31 3 / 3 11. METHOD, according to any one of claims 7 to 10, characterized in that a direct reduction top gas (20) exits the direct reduction furnace (1) and the methane-containing gas (24) comprises at least a portion (21A) of the direct reduction top gas (20).

12. METHOD, according to any one of claims 7 to 10, characterized in that the gaseous hydrogen stream (25) is green hydrogen. Petition 870250111041, dated 03 / 12 / 2025, page 24 / 31

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