Method for producing direct reduced iron for iron and steel plants

Abstract

1. A direct iron ore reduction process, in which an NH3-containing gas feed (24a) is fed to a gas reformer (25) where it is reformed to obtain a hydrogen-containing reducing gas (25a, 25b), at least a portion of which is fed to a direct reduction reactor (1) where iron ore (2) is subjected to direct reduction with the reducing gas (25a, 25b) to obtain directly reduced iron (30), and during reforming of the hydrogen-containing reducing gas (25a), NH3 in the gas feed (24a) is subjected to the dissociation reaction 2NH3 → N2 + 3H2.

Description

[Technical field]

[0001] The present invention relates to the production of iron by direct reduction. [Background technology]

[0002] The process of producing iron by reduction of iron oxide in iron ore below the melting point of the produced iron is known as the direct reduction process. The product obtained is known as direct reduced iron or DRI. Due to its structure with a very high specific surface area, direct reduced iron is also called sponge iron.

[0003] In practice, DRI is often compacted into denser briquettes, referred to in the art as hot briquetted iron or HBI. In practice, the high specific surface area of ​​uncompacted DRI makes it susceptible to spontaneous combustion and therefore a transportation hazard if it reacts with water. Passivation is achieved, at least in part, by briquetting the DRI into fairly dense briquettes with a fairly low specific surface area.

[0004] The present invention more specifically relates to a direct reduction process in which the reducing gas is generated outside the iron reduction reactor or furnace.

[0005] Known examples of such direct reduction processes are the Wiberg-Soderfors process, the Midrex process, the HYL ZR process, the HYL III process, the Armco process, the NSC process, the Profar process, the HYL I and HYL II processes, the Fiol process, and the HIB process.

[0006] In the majority of these known direct reduction processes, natural gas is reformed in a catalyst bed with steam and / or gaseous reduction products discharged from an iron reduction reactor to produce a reducing gas, which is fed to the iron reduction reactor to react with the iron oxides in the iron ore to generate reduced metallic iron. Partial oxidation processes for gasifying liquid hydrocarbons, heavy residues, or coal have also been proposed for the production of reducing gas.

[0007] In both cases, a reducing gas containing CO and H2 is obtained.

[0008] Direct reduction processes have been of particular interest in areas where suitable iron ore and cheap natural gas, non-coking coal, and / or renewable energy sources such as hydroelectric power are available.

[0009] As the steel industry moves to reduce CO2 emissions gain momentum, non-coal-based direct reduction processes are expected to grow in importance.

[0010] However, there remains a need to reduce the CO2 emissions of DRI production, or more generally of DRI production and subsequent melting in electric arc furnaces (EAFs) for steel production. Summary of the Invention [Problem to be solved by the invention]

[0011] It is an object of the present invention to provide such a direct reduction process and a corresponding steel production process with reduced CO2 emissions. [Means for solving the problem]

[0012] In contrast, the present invention proposes a new direct iron ore reduction process.

[0013] According to the process, a gas feed is fed to a gas reformer, where it is reformed to obtain a hydrogen-containing reducing gas which is discharged from the gas reformer.

[0014] The iron ore is fed to a direct reduction reactor, to which at least a portion of the reducing gas is also fed, in which the iron ore is subjected to reduction of the incorporated iron oxide by reaction with the reducing gas, and the direct reduced iron thus obtained is discharged from the direct reduction reactor.

[0015] According to the present invention, the gas feed provided to the gas reformer contains NH3. In the gas reformer, the NH3 in the gas feed undergoes the following dissociation reaction: 2NH3→N2+3H2(1).

[0016] A hydrogen-containing reducing gas is thus obtained.

[0017] The hydrogen-containing reducing gas is discharged from the gas reformer, and at least a portion of the hydrogen-containing reducing gas is supplied to a direct reduction reactor.

[0018] In the direct reduction reactor, hydrogen present in the reducing gas acts as a reducing agent for the reduction of iron oxide in the iron ore to metallic iron by direct reduction.

[0019] The nitrogen in the reducing gas acts as a ballast gas and does not participate in the direct reduction. In the direct reduction reactor, the gas composition is reducing and therefore not conducive to NOx formation, which is a highly undesirable pollutant to the environment.

[0020] The ammonia fed to the gas reformer can be of any origin. According to a preferred embodiment, the ammonia is produced using hydrogen with a low carbon footprint and / or using renewable energy sources. Thus, the ammonia is advantageously produced using blue hydrogen or, more preferably, using green hydrogen.

[0021] If it were possible to replace 100% of the reducing agent currently used in direct reduction reactors with green hydrogen, CO2 emissions could potentially be reduced by 63%-95% via the DRI / EAF route versus the traditional blast furnace / BOF route.

[0022] However, the availability of green hydrogen depends on local sustainable energy resources, whether that be hydroelectric, wind, solar, tidal, and / or even, arguably, nuclear.

[0023] It would be desirable to extend the ecological benefits of using green hydrogen in steelmaking to other regions with less sustainable energy sources.

[0024] According to the present invention, this can be achieved in that green hydrogen is used to produce ammonia and that the hydrogen is recovered from the ammonia for use as a reducing agent in a direct reduction reactor as described above.

[0025] As ammonia is easier to transport than hydrogen, the invention enables more widespread, cost-effective use of green hydrogen in iron and steelmaking.

[0026] The same advantages, although to a lesser extent, are obtained when blue hydrogen is used to produce ammonia.

[0027] Hydrogen obtained by ammonia dissociation and used as a reductant in the direct reduction reactor can partially or completely replace the use of CO and / or hydrocarbon-based hydrogen or other high carbon footprint hydrogen as reductants in DRI production.

[0028] According to a preferred embodiment, the direct reduction reactor is a continuous direct reduction reactor.

[0029] The gas reformer is preferably a catalytic gas reformer, in particular a gas reformer having a catalyst containing, for example, nickel or a nickel alloy.

[0030] The gas feed to the gas reformer may contain at least one hydrocarbon in addition to NH3. The gas feed specifically comprises a hydrocarbon selected from the group consisting of gaseous hydrocarbons such as methane, ethane, propane, butane, pentane, etc., or a combination of two or more of said hydrocarbons, e.g., natural gas.

[0031] When such a hydrocarbon-containing gas feed is reformed in a gas reformer, the resulting reducing gas further contains CO, which acts as a further reducing agent for the reduction of iron oxide in the iron ore to metallic iron by direct reduction in the direct reduction reactor.

[0032] The gas feed to the gas reformer may also include steam and / or CO2.

[0033] The gas feed to the gas reformer may contain CO2, for example, when the gas feed to the gas reformer comprises a CO2-containing flue gas or a CO2-containing fraction thereof from a direct reduction reactor.

[0034] The reducing gas is typically discharged from the gas reformer at a temperature above ambient temperature, for example 700-900° C. According to an advantageous embodiment, at least a portion of the discharge reducing gas fed to the direct reduction reactor may be further heated before being introduced into the direct reduction reactor. Preferably, on-site available waste heat is used to heat the gas reformer and / or to heat the discharge reducing gas upstream of the direct reduction reactor.

[0035] The reducing gas is advantageously supplied to the direct reduction reactor at a temperature in particular between 600°C and 1100°C, preferably between 750°C and 1100°C, more preferably between 950°C and 1050°C.

[0036] The flue gas from the direct reduction reactor, also referred to as "top gas", or a fraction thereof, may also be used as a fuel to heat the gas reformer. Thus, according to a specific embodiment, a fraction of the flue gas from the direct reduction reactor is used as a fuel to heat the gas reformer, and another fraction of said flue gas is added to the gas feed of the gas reformer. Other fuels, for example those containing undissociated ammonia, may be used as fuel to heat the gas reformer.

[0037] The direct reduction reactor can be a shaft furnace. Examples of shaft furnaces suitable for use in the present invention include moving bed shaft furnaces and fluidized bed shaft furnaces. In a countercurrent moving bed shaft furnace, the gas phase flows countercurrently to the iron ore solid charge, and DRI is a particularly useful example of such a moving bed shaft furnace.

[0038] The direct reduced iron produced in and discharged from the reactor can be briquette to obtain HBI.

[0039] The direct reduced iron produced in and discharged from the reactor may be used to produce steel, optionally after being briquetted into HBI.

[0040] The present invention also covers a steel production process, in which direct reduced iron, optionally briquetted to HBI, is produced using the direct iron ore reduction process according to the invention, and steel is produced from said direct reduced iron, for example in an electric arc furnace.

[0041] The present invention relates to a method or process for producing direct reduced iron (DRI) with low / reduced CO2 emissions in a direct reduction reactor, preferably a continuously operated DRI reactor, also referred to herein as a DRI reactor, in which hydrogen (H2), optionally in combination with carbon monoxide (CO), acts as a reducing agent for the reduction of iron oxide contained in iron ore. The iron ore can be, for example, in the form of iron ore lumps and / or iron ore pellets or a mixture thereof (hereinafter referred to without distinction as "iron ore"). At least a portion of the hydrogen used as reducing agent is produced by dissociation of ammonia (NH3) in a gas reformer.

[0042] The gas reformer may be a non-catalytic thermal gas reformer or a catalytic gas reformer. A catalytic gas reformer may, for example, contain nickel or a nickel alloy as the catalyst.

[0043] The gas feed to the gas reformer may contain ammonia in combination with gaseous hydrocarbons (eg, natural gas), along with H2 and / or CO and / or CO2 and / or H2O.

[0044] reaction: (a) CH4 + H2O ⇔ CO + 3H2 (b) CH4⇔C (s) +2H2 (c) CO2 + CH4 ⇔ 2H2 + 2CO (d) C (s) ⇔[C] (e) 3Fe+[C] ⇔ Fe3C (wherein [C] represents carbon dissolved in solid solution with iron). (f) 3Fe2O3+CO (g) ⇔2Fe3O4+CO 2(g) ,T=400~700℃ (g) 2Fe3O4+2CO (g) ⇔6FeO+2CO 2(g) ,T=700~900℃ (h) FeO+CO (g) ⇔Fe+CO 2(g) ,T=850~1000℃ (i) 3Fe2O3+H 2(g)⇔2Fe3O4+H2O (g) ,T=400~700℃ (j) 2Fe3O4+2H 2(g) ⇔6FeO+2H2O (g) ,T=700~900℃ (k) 6FeO+6H 2(g) ⇔6Fe+6H2O (g) ,T=850~1000℃

[0045] DRI production and subsequent melting in an EAF will require the use of low carbon or renewable hydrogen as the reducing agent to reduce the CO2 emissions of the combined DRI reactor / EAF below current emissions typical of this steel production method.

[0046] The availability of green hydrogen depends on local resources, whether they be hydroelectric, wind, solar, tidal, and / or even nuclear, which could limit the availability of industrial quantities of green hydrogen to regions rich in sustainable energy. Unless efficient and safe ways of transporting green hydrogen can be found, its use to mitigate CO2 emissions from industrial activities, specifically steelmaking, will remain limited to such regions.

[0047] One of the more promising ways to efficiently and safely transport hydrogen around the world takes the form of ammonia, made with three hydrogen atoms chemically bonded to a single nitrogen atom. Ammonia made from blue hydrogen is also referred to herein as blue ammonia, and ammonia from green hydrogen is also referred to as green ammonia.

[0048] Hydrogen, which may be blue or green hydrogen, can then be recovered by decomposing ammonia, specifically blue or green ammonia, as long as due care is taken to keep the carbon footprint of the transportation methods / vehicles used to transport the ammonia to user areas and to keep the energy used in the endothermic ammonia decomposition / dissociation reaction as low as possible. [Brief description of the drawings]

[0049] [Figure 1] FIG. 1 is a schematic diagram of an embodiment of a direct iron ore reduction process according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Gas feed stream 24 contains ammonia 19 in an amount greater than 0% and up to 100% vol (ammonia only) relative to stream 24, preferably between 50% vol and 100% vol.

[0051] The gas feed stream 24 may further comprise a hydrocarbon-containing gas 20, such as natural gas or coke oven gas or a mixture thereof. The proportion of each of the natural gas and coke oven gas in the hydrocarbon-containing gas 20 may be between 0 and 100% vol. The proportion of the hydrocarbon-containing gas 20 in the stream 24 may vary between 0% vol and 50% vol. The gas feed stream 24 may also contain additional gaseous hydrogen 21 (e.g., gray H2, preferably blue H2, more preferably green H2), particularly in a proportion between 0% vol and 50% vol of the stream 24. The gas feed stream 24 may also contain additional steam 22. Such additional steam may be added to the reforming stream 24 to provide a suitable amount of hydrogen atoms in the stream 24, including any gaseous hydrocarbon-containing gas 20 (e.g., natural gas and / or coke oven gas) contained therein. Gas feed stream 24 may also contain reformed gas 23, the proportion of which in stream 24 may vary from 0% vol to 50% vol. Gas feed stream 24 may also contain any other gases that may be advantageously added to gas feed stream 24 to improve the efficiency of reducing gas production in gas reformer 25 or to adjust the composition of the reducing gas so produced.

[0052] It will be appreciated that the sum of the percentages of the components of gas feed stream 24 will be exactly 100% vol for gas feed stream 24, and that the sum of the percentages of any compounds other than ammonia for gas feed stream 24 will be less than 100% vol, the balance being ammonia (totaling 100% vol).

[0053] In the gas reformer 25, ammonia in the gas stream 24 undergoes a dissociation reaction (m):

number

[0054] When the gas stream 24 contains hydrocarbons such as methane, the hydrocarbons are chemically reacted in the gas reformer 25, which can be a steam reformer or a dry reformer (see reactions (a) and (c)). (a) CH4 + H2O ⇔ CO + 3H2 (b) CH4⇔C (s) +2H2 (c) CO2 + CH4 ⇔ 2H2 + 2CO (d) C (s) ⇔[C] (e) 3Fe+[C] ⇔ Fe3C

[0055] A catalyst can be used in the gas reformer 25 to increase the kinetics of the reactions. In particular, a nickel or nickel alloy based catalyst can be present in the gas reformer 25 to increase the reaction rates of reactions ((m) and / or (a) and / or (c)). Additionally, the metallic iron produced in the DRI reactor 1 can be useful as a catalyst for the dissociation reaction (m), but also for reactions (a) and / or (c).

[0056] The reducing gases 25 a and 25 b generated in the gas reformer 25 are supplied to the DRI reactor 1 .

[0057] The DRI reactor 1 is further charged with iron ore 2.

[0058] In the illustrated embodiment, the DRI reactor 1 is a moving bed reactor, where the iron ore 2 is fed to the DRI reactor 1 at the top of the reactor and then moves downward within the DRI reactor 1.

[0059] In the DRI reactor 1, iron ore 2 is contacted with a reducing gas 3a. The result is a mixture of unreduced iron ore, partially reduced iron ore, and metallic iron (DRI).

[0060] The reactions that occur when reducing gas 3a contacts iron ore 2 depend on the composition of reducing gas stream 25c fed to DRI reactor 1 and are described in reactions (fh) and (i-k). (f) 3Fe2O3+CO (g) ⇔2Fe3O4+CO 2(g) ,T=400~700℃ (g) 2Fe3O4+2CO (g) ⇔6FeO+2CO 2(g) ,T=700~900℃ (h) 6FeO+6CO (g) ⇔6Fe+6CO 2(g) ,T=850~1000℃ (i) 3Fe2O3+H 2(g) ⇔2Fe3O4+H2O (g) ,T=400~700℃ (j) 2Fe3O4+2H 2(g) ⇔6FeO+2H2O (g) ,T=700~900℃ (k) 6FeO+6H 2(g) ⇔6Fe+6H2O (g) ,T=850~1000℃

[0061] The DRI reactor 1 may be equipped with heating means (not shown) to maintain the iron ore 2 and reducing gas 3a within a temperature range suitable for the direct ore reduction reaction.

[0062] The top gas 5 leaves the top of the DRI reactor 1 at a temperature between 100°C and 600°C, preferably between 250°C and 500°C, and more preferably between 300°C and 450°C.

[0063] The top gas 5 may be dedusted in a dust catcher and / or scrubber 6. According to an advantageous embodiment illustrated in FIG. 1, the optionally dedusted top gas 6a is then passed to a heat recovery system 7 where the temperature of the top gas is reduced to a temperature between 25° C. and 100° C., but preferably between 25° C. and 40° C. The energy recovered in the heat recovery system 7 may be used for any of a variety of purposes, such as, but not limited to, to make steam or to preheat air and / or fuel that may be used in the gas reformer 25. The cooled top gas 7a is optionally dehydrated to produce a dehydrated and cooled gas stream 8a.

[0064] The cooled and dehydrated top gas stream 8a is split into stream 11 and stream 9a.

[0065] The flow rate of stream 11 can be between 0 and 100% vol of stream 8a, but preferably between 20% vol and 90% vol of stream 8a, more preferably between 30% vol and 80% vol of stream 8a. Combustible gas, for example natural gas 8b and / or even ammonia 8c, can be added to stream 11 to modify the heating value of stream 11 as required. Stream 11 is burned in one or more combustion chambers, represented in the figure by 11a, 11b, 11c of the gas reformer 25, to provide heat to the gas reformer 25 and thus to the chemical reactions taking place therein. An alternative combustible gas that does not contain a fraction of the top gas from the DRI reactor 1 can be used to heat the gas reformer 25. An optional heat exchanger 12 can be used to preheat stream 11 upstream of the gas reformer 25. In the illustrated embodiment, flue gases 13a, 13b, and 13c exiting combustion chambers 11a, 11b, and 11c pass through an optional heat exchanger 12 to preheat stream 11 and produce a cooler flue gas stream 13, which then flows to stack 14 and out into the atmosphere 15. If natural gas, coke oven gas, or any other gaseous hydrocarbon is used as part of the mixture 11, the flue gas 13 will contain CO2, which should preferably be extracted from stream 13 prior to release into the atmosphere 15 (extraction not shown).

[0066] In the exemplary embodiment, another portion of the cooled and dehydrated top gas stream 8a is compressed in compressor 9 to produce compressed stream 9a.

[0067] Stream 9a needs to be at a pressure of 2-10 Bar (i.e., 200-1000 kPa), preferably 4-8 Bar (i.e., 400-800 kPa), in order to separate CO2 from stream 9a using a vacuum pressure swing adsorption (VPSA) or pressure swing adsorption (PSA) machine to produce a CO2-lean stream 10a. A further option is to separate CO2 from stream 9a using a chemical absorption unit, for example through the use of amines, to produce a CO2-lean stream 10a. CO2 can also be separated from stream 9a using polymeric membranes or through cryogenic separation.

[0068] Since CO2 contributes favorably to the production of reducing gases in the gas reformer 25 and is involved in reaction (c), the CO2 separation step 10 may also be omitted or the amount of CO2 removed from stream 9a in step 10 may be limited, in which case due care would be taken to avoid or limit reaction (b).

[0069] The DRI reactor 1 is advantageously operated at a pressure between 100 and 400 kPa gauge, more preferably between 100 and 200 kPa gauge.

[0070] In the illustrated embodiment, stream 10a is added to an ammonia-containing gas feed stream 24. Natural gas, coke oven gas, other hydrocarbon-containing gas, or mixtures thereof 20 is also part of stream 24, typically in an amount between 0% vol and 50% vol of stream 24. Hydrogen (Grey H2, preferably Blue H2, more preferably Green H2) 21 may also be included in stream 24, in a proportion between 0% vol and 50% vol of stream 24. Additional steam 22 may be added to stream 24 as needed, particularly to aid in the hydrocarbon reforming in gas reformer 25.

[0071] The reformed gas 23 may also be included in the stream 24 at a ratio of 0% to 50% of the stream 24.

[0072] Stream 24, optionally with the addition of stream 10a, is fed in multiple substreams 24a to a gas reformer 25 to produce reducing gas in the gas reformer 25 by utilizing reaction (1) and optionally one or more of reactions (a) and (c) depending on the composition of the substreams.

[0073] The resulting reducing gases 25a and 25b are suitable for reducing iron ore in the DRI reactor 1.

[0074] According to a particularly advantageous and distinct embodiment of the present invention, the ammonia 19 in stream 24 is green (or low carbon) ammonia 19, thus providing a significant reduction in CO2 emissions / carbon footprint compared to conventional hydrocarbon-based DRI operations.

[0075] Stream 24 is optionally preheated in heat exchanger 12 to produce preheated gas stream 24a. Such preheating advantageously utilizes excess heat exiting the combustion chamber of the gas reformer 25, thus reducing the additional energy required to heat the gas reformer 25.

[0076] The optionally preheated gas mixture 24a is reformed in a gas reformer 25 that utilizes a catalyst to reform the gas stream 24a into reducing gases 25a and 25b suitable for the reduction of iron ore 2 in the DRI reactor 1 according to reactions (1), (a), and (c).

[0077] The reducing gases 25a and 25b are optionally mixed with additional gaseous hydrocarbons 23b and / or oxygen 23a upstream of the DRI reactor 1 to further adjust the composition and temperature of the final reducing gas 25c before being introduced into the bustle 3 of the DRI reactor 1. The temperature at which the mixture 25c is introduced into the DRI reactor 1 can be between 600°C and 1100°C, preferably between 750°C and 1100°C, and more preferably between 950°C and 1050°C. This is desirable to increase the kinetics of the reduction reaction in the DRI reactor 1. The bustle serves as a manifold to distribute the final reducing gas 25c evenly around the circumference of the DRI reactor 1.

[0078] At the bottom of the DRI reactor 1, the mixture 4 of unreduced, partially reduced, and fully reduced iron ore from the upper portion of the DRI reactor 1 is converted to substantially all of the iron ore into hot metallic DRI 26a after reactions (f)-(k) have been substantially completed. 85%-99%, preferably 90%-97%, and more preferably 94%-97% of the iron in the DRI 26a is metallic iron, and the remaining iron is non-metallic iron oxide (Fe x O y ) form.

[0079] Although desirable in principle, it is generally impractical in practice to completely react iron ore to obtain 100% of its iron content as metallic iron, since doing so would significantly reduce the productivity of the DRI process and significantly increase the reducing gas consumption of the process. Therefore, a compromise should be found regarding the degree of iron ore reduction.

[0080] The hot DRI 26a enters a conical cooling zone 26 where it is cooled by cooling gas 27 to a temperature that depends on the immediate use of the DRI after discharge from the DRI reactor 1. If the DRI 30 is immediately charged to an adjacent EAF (not shown) at a temperature in the range of 400°C to 800°C, more preferably 600°C to 800°C, it is advantageous to limit the cooling to a temperature required for safe transport of the DRI 30 to the EAF while taking advantage of the sensible heat already present in the hot DRI. Alternatively, the hot DRI can be subjected to limited cooling before being formed into briquettes (HBI). Such briquetting makes the DRI more suitable for storage and / or transport to an EAF site located remotely from the DRI reactor 1.

[0081] The cooling gas 27 may be substantially inert so as not to react with the hot DRI 26a. The cooling gas 27 may also be or contain a gas that imparts desired properties to the DRI while cooling. An example of such a gas is natural gas, which may decompose according to reaction (b) to deposit carbon in the DRI, where it dissolves in the iron as a solid solution. As discussed above, the carbon provides operational and energy saving benefits to the EAF process during melting of the DRI. The cooling gas 27 may also include a portion of the top gas 5.

[0082] At the top of the cooling zone 26 of the DRI reactor 1, cooling gas 27 is extracted from the cooling zone 26 as spent cooling gas stream 28, which is then cooled and then augmented with make-up cooling gas and compressed for reinjection at the bottom of the cooling zone 26.

[0083] The DRI 30 is extracted at the bottom of the conical cooling zone 26 at a temperature most suitable for its subsequent use.

[0084] Advantages and distinguishing features of the present invention include the following: 1. Blue or green ammonia can be used to partially or completely replace carbon-bearing hydrocarbons, thereby reducing CO2 emissions in DRI reactors and iron and steel plants. 2. Partially or completely replacing blue or green hydrogen with blue or green ammonia as a method to produce low-emission DRI. 3. Compared to (blue / green) hydrogen, (blue / green) ammonia can be more easily stored and transported to areas around the world that do not have the natural resources / sufficient natural resources to produce green hydrogen.

[0085] Liquid hydrogen is very costly to prepare and store on long voyages due to the cryogenic temperature of liquid hydrogen required for transportation (-253°C). Liquid ammonia boils at (-33°C). Liquid ammonia is less costly to transport due to its higher transportation and storage temperatures. Furthermore, with existing infrastructure on a global scale, NH3 is more easily available compared to liquid hydrogen. 1. Ammonia can be mixed with gaseous hydrocarbons, such as natural gas, coke oven gas, steam, and syngas, in proportions of up to 90% vol ammonia, and still produce DRI that advantageously contains a desired and controllable amount of dissolved carbon (in solid solution) and / or iron carbide (FeC) via reaction (e). The desired carbon content of the DRI depends on the end use of the DRI. 2. The DRI reactor can be advantageously operated 100% free of direct CO2 emissions by replacing 100% of the traditional gaseous components (hydrocarbons, natural gas, coke oven gas, and other carbon-containing gases) with the ammonia dissociation product in the reforming process. 3. Hydrogen is a gas that is mixed with water in a unit volume (Nm 3 Hydrogen is a light gas capable of carrying / transporting only a limited amount of heat / thermal energy per tonne. Therefore, hydrogen is not effective as a heat transfer medium for heat transfer to a mixture of unreduced iron ore, reduced iron ore, or fully reduced ore 4. Thus, feeding 100% hydrogen as the reducing gas to a DRI reactor would result in low top gas temperatures approaching 100°C. Since DRI top gas contains a lot of water vapor, there is a risk that condensation of such moisture may occur. Conventional DRI operations exhibit top gas temperatures in the range of 300-600°C.

[0086] When ammonia is dissociated in a gas reformer, a mixture of hydrogen and nitrogen is produced. Compared to hydrogen, nitrogen is much more dense per unit volume (Nm 3) can carry / transport significantly more heat / thermal energy per 1000 sq. m. The problems mentioned above can be easily avoided because the mixture of hydrogen and nitrogen (and optionally other components) supplied as the reducing gas to the DRI reactor can be used as an effective heat transfer medium for the supply of thermal energy to the DRI reactor.

[0087] Notes: Unless otherwise indicated, percentages of compounds in gas streams are percentages by volume (% vol).

[0088] A distinction is made between continuously operated DRI reactors / processes and batch DRI reactors / processes.

[0089] The gas stream injected into a continuously operated DRI reactor is generally injected continuously during operation of the DRI reactor.

[0090] Method embodiments of the present invention The present invention includes a process for producing direct reduced iron (DRI) in a (preferably continuous) DRI reactor using hydrogen (H2) as the reducing gas to reduce iron oxide contained in iron ore, in which at least a portion of the hydrogen is produced in a gas reformer by dissociation of ammonia (NH3) into nitrogen (N2) and hydrogen (H2) (reaction (1)).

[0091] Continuous DRI reactors suitable for use in the present process are known in the art.

[0092] To that end, the ammonia-containing stream is subjected to a dissociation reaction (1) upstream of the DRI reactor, and the dissociation product stream containing hydrogen and nitrogen is injected into the DRI reactor, whereby hydrogen produced by the dissociation reaction is used as a reducing agent for the reduction of iron oxide in the iron ore in the DRI reactor.

[0093] The ammonia-containing stream is applied upstream of the DRI reactor and the dissociation reaction (1) can be non-catalytic or catalytic.

[0094] Thermal energy for the reaction can be provided, for example, by combustion in a fired heater as described above.

[0095] The temperature of the dissociation product (reducing gas) stream can be adjusted upstream of the DRI reactor by injecting fuel and / or oxidant into the stream upstream of the DRI reactor.

[0096] Hydrogen other than that generated by ammonia dissociation can also be injected into the DRI reactor as a reducing gas for the reduction of iron oxide in the iron ore.

[0097] Hydrogen not generated by ammonia dissociation may be injected into the DRI reactor separately from the dissociation product streams listed above. Hydrogen not generated by ammonia dissociation may also be mixed with the ammonia-containing stream and / or the dissociation product stream.

[0098] This supplemental hydrogen preferably has a low carbon footprint, for example hydrogen produced by electrolysis with electricity from renewable energy sources.

[0099] Another useful supplemental hydrogen source is coke oven gas.

[0100] A further supplemental hydrogen source is syngas.

[0101] The last two gases also contain CO, which is also useful as a reducing agent for the reduction of iron oxide.

[0102] According to one embodiment of the method, CO is used in the DRI reactor as an additional reducing agent in addition to the H2 generated by dissociation of ammonia as described above.

[0103] The CO may be injected into the DRI reactor separately from the dissociation product stream and / or may be mixed with the dissociation product stream.

[0104] Useful sources of CO are coke oven gas, syngas, and recycled top gas from the DRI reactor.

[0105] As such, a CO-containing gas, such as coke oven gas and / or syngas, may be mixed with the dissociation product stream.

[0106] Preferably, a syngas comprising a mixture of CO and H2 is generated.

[0107] The CO-containing syngas is preferably generated by dry or steam reforming of hydrocarbons, particularly gaseous hydrocarbons such as CH4 / natural gas, preferably by catalytic dry reforming or catalytic steam reforming. Syngas can also be formed by partial oxidation of hydrocarbon gases, preferably using oxygen as the combustion oxidant.

[0108] Syngas may be produced separately from the ammonia dissociation and the produced syngas may be mixed with the dissociation product stream.

[0109] Gaseous hydrocarbons, typically along with steam and / or CO2, may also be injected into the gas reformer and undergo reforming into syngas along with ammonia dissociation therein.

[0110] Gaseous hydrocarbons, particularly CH4 / natural gas, may be fed separately to the gas reformer or may be mixed with the ammonia-containing stream.

[0111] In the present method, the top gas generated by the DRI reactor, which contains H and, in certain embodiments, significant levels of CO, can be used as an additional / supplement reducing gas for the reduction of iron oxide in the DRI reactor.

[0112] The H2 and optionally CO present in the top gas may be used as fuel, in particular to heat the gas reformer and / or to preheat the gas fed to the gas reformer and / or to preheat the reducing gas prior to introduction into the DRI reactor.

[0113] In the context of the present invention, the expression "top gas" means the spent reducing gas discharged from a DRI reactor after it has been used in the direct reduction of iron ore in said reactor.

[0114] The H2 and optionally CO present in the top gas can also be recycled as reducing gas to the DRI reactor, for example by mixing said H2 and any CO with an ammonia-containing stream to a gas reformer or with a dissociation product stream upstream of the DRI reactor.

[0115] To increase the concentration of H2 and any CO, water is typically removed from the top gas by condensation before the top gas is used as a fuel and / or recycled as a reducing gas.

[0116] Similarly, when the top gas contains a significant amount of CO2, CO2 may also be removed from the top gas before it is used as a fuel and / or before it is recycled as a reducing gas, particularly before the top gas is recycled as a reducing gas.

[0117] The iron ore may specifically be fed to the DRI reactor in the form of lumps and / or pellets.

[0118] The produced DRI may be subjected to briquetting.

[0119] The produced DRI, whether briquette- ized or not, is typically used in the production of steel.

Claims

1. - feeding a gas feed (24a) to a gas reformer (25); - reforming said gas feed (24a) in said gas reformer (25) to obtain a hydrogen-containing reducing gas (25a, 25b); - discharging said reducing gas (25a, 25b) from said gas reformer (25); - feeding iron ore (2) into a direct reduction reactor (1); - feeding at least a portion of said reducing gas (25a, 25b) into said direct reduction reactor (1); - subjecting said iron ore (2) to direct reduction by said reducing gas (25a, 25b) in said direct reduction reactor (1) to obtain direct reduced iron (30); - discharging the direct reduced iron (30) from the direct reduction reactor (1); 1. A direct iron ore reduction process comprising: The gas feed to the gas reformer (25) is NH ３ and NH in the gas feed (24a) in the gas reformer (25) ３ is a dissociation reaction (1) <h2 style=";text-align:left;direction:ltr">2NH<h2 style=";text-align:left;direction:ltr"> ３ <h2 style=";text-align:left;direction:ltr"> →N<h2 style=";text-align:left;direction:ltr"> ２ <h2 style=";text-align:left;direction:ltr"> +3H<h2 style=";text-align:left;direction:ltr"> ２ <h2 style=";text-align:left;direction:ltr"> (1) and A direct iron ore reduction process.

2. 2. The direct iron ore reduction process according to claim 1, wherein the direct reduction reactor (1) is a continuous direct reduction reactor.

3. 2. The direct iron ore reduction process of claim 1, wherein the gas reformer (25) is a catalytic reformer.

4. 4. The direct iron ore reduction process of claim 3, wherein the gas reformer (25) comprises a nickel or nickel alloy containing catalyst.

5. 2. The direct iron ore reduction process of claim 1, wherein the reforming process is accomplished via partial oxidation. Process.

6. 2. The direct iron ore reduction process of claim 1, wherein the gas feed (24a) to the gas reformer (25) comprises at least one hydrocarbon (20).

7. 7. The direct iron ore reduction process of claim 6, wherein the gas feed (24a) to the gas reformer (25) comprises gaseous hydrocarbons selected from the group consisting of methane, ethane, propane, butane, and pentane, or a combination of two or more of said hydrocarbons.

8. 7. The direct iron ore reduction process of claim 6, wherein the gas feed (24a) to the gas reformer (25) further comprises steam.

9. The gas feed (24a) to the gas reformer (25) is ２ 7. The direct iron ore reduction process of claim 6, comprising:

10. 2. The direct iron ore reduction process according to claim 1, wherein the reducing gas (25a, 25b) discharged from the gas reformer (25) is heated before being fed to the direct reduction reactor (1).

11. 2. The direct iron ore reduction process according to claim 1, wherein the reducing gas (25a, 25b) is supplied to the direct reduction reactor (1) at a temperature between 600°C and 1100°C.

12. 2. The direct iron ore reduction process according to claim 1, wherein the flue gas (5) or a fraction thereof from the direct reduction reactor (1) is used as fuel to heat the gas reformer (25).

13. 2. The direct iron ore reduction process according to claim 1, wherein the direct reduction reactor (1) is a shaft furnace.

14. The direct iron ore reduction process according to any one of claims 1 to 13, wherein the direct reduced iron is briquettered after being removed from the direct reduction reactor (1).

15. 14. A process for producing steel, wherein direct reduced iron (30) is produced using the direct iron ore reduction process according to any one of claims 1 to 13, and optionally after the direct reduced iron has been briquette, steel is produced from the direct reduced iron (30) in an electric arc furnace.

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