Production of nitrided sponge iron

Abstract

The invention relates to a method for nitriding sponge iron by direct reduction using reducing gas which comprises hydrogen H2 and the hydrogen H2 of which originates at least in part from splitting of ammonia NH3. After the direct reduction in a reduction reactor, the sponge iron is cooled to a temperature below 450°C. Ammonia NH3 contributes to this cooling. Cooling waste gas arising during the cooling is removed and is subjected to separation into a hydrogen-enriched first gas stream and a nitrogen-enriched second gas stream. The first gas stream contributes hydrogen H2 to the reducing gas. An apparatus for nitriding sponge iron comprises: an apparatus for the direct reduction of iron oxide-containing material to form sponge iron, having a reduction reactor (1) and a feed line (3) for feeding reducing gas and / or a precursor of the reducing gas to the reduction reactor (1); and a cooling apparatus (4) for cooling the sponge iron to a temperature below 450°C. An ammonia feed line (6) opens into the cooling apparatus (4). A cooling waste gas line (7) proceeds from the cooling apparatus (4) and opens into a gas separation apparatus (8). A hydrogen gas stream discharge line (9) for discharging the first gas stream proceeds from the gas separation apparatus (8) and has an opening into the feed line (3).

Description

[0001] 202400244

[0002] Description

[0003] Production of nitrided sponge iron

[0004] field of technology

[0005] The application relates to a method and a device for the nitriding of sponge iron.

[0006] State of the art

[0007] It is known to reduce iron oxide-containing materials – such as ores – using reducing gas, also called reducing gas. This can be done, for example, by direct reduction with reducing gas in a reduction unit, such as a reduction shaft. In currently used, conventional processes on a large industrial scale, the reducing gas is predominantly based on natural gas. Therefore, large quantities of carbon dioxide (CO2) are produced, which is undesirable for environmental reasons, among others.

[0008] The solid product of a direct reduction of iron oxide-containing material without the production of a melt is called sponge iron or DRI direct reduced iron.

[0009] To reduce CO2 emissions during the reduction of iron oxide-containing materials, it is known to use hydrogen (H2) as a reducing gas. Hydrogen (H2) can be used as the sole reducing gas or in combination with other gases, such as natural gas-based or synthesis gas-based reducing gases. The greater the proportion of CO2-neutral hydrogen (H2) in the reducing gas, the less CO2 is emitted.

[0010] However, storing hydrogen (H2) and transporting it from its place of production to consumers is problematic and involves great effort due to its physical properties.

[0011] To reduce CO2 emissions during the reduction of iron oxide-containing materials, ammonia (NH3) is also known to be used as a reducing agent. Ammonia (NH3) offers significant advantages over hydrogen (H2) with regard to storage and transport.

[0012] Ammonia NH3 can be split into nitrogen f N2 and hydrogen f H2

[0013] 2 NH3-> N2+ 3 H2.

[0014] Hydrogen (H2) can react as a reducing agent with metal oxides, for example iron oxides:

[0015] 3 Fe2O3 + H2 → 2 Fe3O4 + H2O

[0016] Fe3O4+ H2-> 3 FeO + H2O FeO + H2-> Fe + H2O .

[0017] Ammonia (NH3) can also act as a reducing agent itself:

[0018] 9 Fe2O3+ 2 NH3-> 6 Fe3O4+ N2+ 3 H2O

[0019] 3 Fe3O4+ 2 NH3-> 9 FeO + N2+ 3 H2O

[0020] Ammonia (NH3)-containing reducing gas can consist of ammonia (NH3) or a mixture of ammonia (NH3) with one or more other gases – preferably one or more of which can have a reducing effect on iron oxide-containing material. In principle, reducing gas obtained using ammonia (NH3) can be used to reduce iron oxide-containing material; such a reducing gas can, for example, be ammonia (NH3) or a mixture of ammonia (NH3) with one or more other gases – preferably one or more of which can have a reducing effect on iron oxide-containing material – which would be the case, for example, with a mixture of ammonia (NH3) and its fission products hydrogen (H2) and nitrogen (N2), whereby, of course, other gases could also be present in the mixture.

[0021] It is known that the presence of ammonia (NH3) during the reduction of iron oxide-containing material can lead to the formation of iron nitrides. For example, the following reactions with metallic iron lead to the formation of iron nitrides:

[0022] 4 Fe + NH3 => Fe3N + 3 / 2 H2 ( 6 , 3 % weight increase )

[0023] 3 Fe + NH3 => Fe3N + 3 / 2 H2 ( 8 , 3 % weight increase )

[0024] 2 Fe + NH3 => Fe2N + 3 / 2 H2 ( 12.5% ​​weight increase )

[0025] Similarly, in the presence of ammonia (NH3), reactions can occur even in already reduced material, forming iron nitrides. For example, on reduced DRI pellets, contact with ammonia (NH3) can lead to the formation of an iron nitride or iron nitride layer on the surface or within the porous iron sponge pellets.

[0026] It is known that the process associated with nitridation

[0027] Passivation of sponge iron against, for example,

[0028] Utilizing reactions with atmospheric oxygen or moisture 202400244

[0029] 4. This can be achieved by dispensing with the hot briquetting process, which is also passivating and is used to produce a transportable product.

[0030] Summary of the invention

[0031] Technical task

[0032] The object of the present invention is to present a process which allows an energy- and resource-efficient process for a hydrogen-based direct reduction process in which ammonia NH3 is used as the hydrogen source, with the provision of nitrided sponge iron.

[0033] Technical solution

[0034] The problem is solved by a process for the nitriding of sponge iron, comprising direct reduction of iron oxide-containing material to sponge iron, wherein hydrogen-containing reduction gas (H2) is used, wherein at least a subset of the hydrogen (H2) originates from the cracking of ammonia (NH3), and wherein the reduction gas is supplied to a reduction reactor containing the iron oxide-containing material in an interior space, and comprising

[0035] Cooling of the iron sponge to a temperature below 450 °C, characterized in that 202400244

[0036] 5. The cooling of the sponge iron to a temperature below 450 °C is carried out using a cooling gas containing ammonia (NH3), and the cooling takes place in at least one member of the group consisting of a) the cooling zone of the reduction reactor, b) the cooling reactor, and the cooling gas generated during the cooling process is at least partially discharged from a) and / or b), and at least a subset of the discharged cooling gas is separated, optionally after treatment, into a hydrogen-enriched first gas stream and a nitrogen-enriched second gas stream, and the first gas stream contributes hydrogen (H2) to the reducing gas.

[0037] The term "nitrided sponge iron" refers to an iron sponge that contains or consists of iron nitride(s). Nitridation refers to the formation of iron nitride. Therefore, "nitrided sponge iron" can be understood as an iron sponge containing iron nitrides.

[0038] Iron oxide-containing material is directly reduced to sponge iron with a reducing gas containing hydrogen (H₂). Due to the thermodynamic and kinetic conditions necessary for the industrial implementation of direct reduction, the resulting sponge iron has a property of 202400244.

[0039] 6

[0040] Temperatures exceeding 450 °C. For example, the temperature of the sponge iron produced by the direct reduction of the iron oxide-containing material is 700 °C or more, or at least 550 °C or more.

[0041] The reducing gas can be pure hydrogen (H₂) or a mixture of hydrogen (H₂) and one or more other gases. These other gases can be, for example, CO or CH₄. Hydrogen (H₂) can be obtained from ammonia (NH₃), but it can also be produced by electrolysis, from the reforming of natural gas, or from other sources such as syngas. At least a portion of the hydrogen (H₂) originates from ammonia (NH₃), being released through the splitting of ammonia (NH₃).

[0042] Preferably, the reducing gas contains at least 15 volumes of hydrogen (H2), particularly preferably 50 volumes, and most preferably 70 volumes.

[0043] The sponge iron obtained from direct reduction is cooled to a temperature below 450 °C using a cooling gas containing ammonia (NH3). The cooling takes place in at least one member of the group consisting of a) the cooling zone of the reduction reactor, b) the cooling reactor. Ammonia (NH3) makes one or more contributions to this cooling; one contribution may, for example, consist of bringing ammonia (NH3) at a lower temperature into contact with the sponge iron.

[0044] 7

[0045] The sponge iron cools down through heat transfer, while the ammonia (NH3) heats up. One way this cooling can occur is for ammonia (NH3) to come into contact with the sponge iron, resulting in endothermic decomposition reactions of the ammonia (NH3) – this cools the sponge iron.

[0046] For cooling, a cooling gas containing ammonia (NH3) is supplied to the iron sponge to be cooled – which was produced by direct reduction using the reducing gas supplied to the section of the reduction reactor containing the iron oxide material. This direct reduction takes place in the so-called reduction zone of the reduction reactor. For example, a gas mixture containing ammonia (NH3) or pure ammonia (NH3) can be supplied.

[0047] The reduction zone and cooling zone are different zones of the reduction reactor.

[0048] The sponge iron to be cooled may already contain iron nitrides; in this case, the existing iron nitride content will increase during cooling with the addition of ammonia. However, it is also possible that the sponge iron to be cooled does not contain iron nitrides; in this case, the iron nitride content will increase from a zero level during cooling with the addition of ammonia. In any case, after cooling to below 450 °C, to which ammonia (NH3) contributes, nitrided sponge iron is present; and after cooling to below 450 °C, to which ammonia (NH3) contributes, the iron nitride content in the sponge iron is greater than before this cooling.

[0049] The iron nitride content is given, for example, as the weight of iron nitrides in a quantity of sponge iron. 202400244

[0050] As explained at the beginning, contact between iron and

[0051] Ammonia (NH3) reacts with iron to form iron nitrides, thus nitriding the sponge iron. The occurrence of nitridation depends on the temperature range in which the contact between ammonia (NH3) and iron takes place. Within the temperature range traversed during cooling according to the invention, nitridation of the sponge iron occurs. Accordingly, a nitrided sponge iron is obtained, which exhibits the advantages associated with its passivation achieved through nitridation.

[0052] Preferably, the nitrided iron sponge, after cooling to a temperature below 450 °C, has an iron nitride content of over 20 wt! , particularly preferably over 50 wt! , very preferably over 70 wt! , and most preferably over 90 wt! .

[0053] In the reduction reactor, the reducing gas causes the reduction of the iron oxide-containing material; its reducing components are at least partially consumed in the process. A so-called top gas, containing the spent reducing gas, is drawn off from the reduction zone of the reactor.

[0054] Cooling gas is produced during the cooling process. This cooling gas originates from the refrigerant gas while the refrigerant gas exerts a cooling effect. The cooling gas differs from the fresh refrigerant gas supplied for cooling at least in its temperature—it is warmer—but it can also differ in its composition. The cooling gas can contain one or more of the following components:

[0055] - Ammonia NH3, which is heated compared to its temperature when supplied for cooling; 202400244

[0056] Nitrogen f N2;

[0057] - Hydrogen f H2.

[0058] Nitrogen (N2) and hydrogen (H2) are therefore the products of a splitting of ammonia (NH3).

[0059] Cooling can take place in a cooling zone of the reduction reactor, or it can take place in a cooling reactor separate from the reduction reactor - in this case, the sponge iron produced in the reduction reactor at a temperature above 450 °C is fed to the cooling reactor.

[0060] Cooling gas is used to cool the sponge iron being cooled. The cooling gas contains ammonia (NH3), or it can consist entirely of ammonia (NH3). The degree of cooling depends on the amount of cooling gas supplied to the sponge iron. Preferably, the cooling process is regulated and / or controlled to achieve an optimal temperature profile for nitriding by changing the amount of cooling gas and / or the amount of ammonia (NH3) added.

[0061] Preferably, the cooling process is controlled and / or regulated using information about the composition of the cooling exhaust gas, and / or temperature measurements inside the cooling zone or cooling reactor, and / or temperature measurements of the cooling exhaust gas. For example, a limit value can be set for the ammonia (NH3) content of the cooling exhaust gas – for example, 0.1 volumes. A higher content indicates incomplete conversion of the ammonia (NH3) supplied for cooling; accordingly, the flow of ammonia (NH3) for cooling could be reduced if more complete conversion is desired.

[0062] According to the invention, cooling exhaust gas generated during cooling is removed - at least partially - from a) and / or b) 202400244

[0063] 10. Discharged to the outside; it is discharged from the reduction reactor or the cooling reactor to the outside. Discharge to the outside means that the cooling exhaust gas leaves the reduction reactor or the cooling reactor during discharge; "outside" is to be understood as outside the reduction reactor or the cooling reactor. In the case of the reduction reactor, the cooling exhaust gas leaves the cooling zone of the reduction reactor to the outside.

[0064] During discharge, a gas stream of the cooling exhaust gas is extracted. When extracted from the reduction reactor, the gas stream of the discharged cooling exhaust gas is not extracted from the reduction zone of the reduction reactor, but rather from the cooling zone; the gas stream of the discharged cooling exhaust gas does not pass through any other zones of the reduction reactor during discharge. Top gas and discharged cooling exhaust gas are different gas streams.

[0065] According to the invention, at least a subset of the discharged cooling exhaust gas is separated into a

[0066] A hydrogen-enriched first gas stream and a nitrogen-enriched second gas stream. This separation can be carried out after processing; the processing can, for example, include one or more steps from the following list:

[0067] - Cooling;

[0068] - Dust removal;

[0069] - Compression.

[0070] Each of the steps can be repeated multiple times.

[0071] For example, 202400244 can be used to separate cooling exhaust gas into a hydrogen-enriched first gas stream and a nitrogen-enriched second gas stream.

[0072] 11 a membrane process or a pressure swing adsorption (PSA) process or a vacuum pressure swing adsorption (VPSA) process or a cryogenic separation process may be used.

[0073] The hydrogen-enriched first gas stream contributes hydrogen to the reducing gas; this hydrogen, H₂, is a component of the reducing gas. According to the invention, it is at least partially used in the production of the reducing gas. The reducing gas can also contain other components, for example, hydrogen (H₂) from other sources; it can also contain hydrogen (H₂) derived from the cracking of ammonia (NH₃) occurring outside of the cooling process. The hydrogen (H₂) can also be obtained by electrolysis, by reforming natural gas, or from other sources such as syngas or coke oven gas. During the production of the reducing gas, its components are combined. Besides hydrogen (H₂), other components of the reducing gas can be other gases; these other gases can be, for example, CO or CH₄.

[0074] Preferably, the hydrogen content of the hydrogen-enriched first gas stream is over 90 volumsi .

[0075] The hydrogen-enriched first gas stream can be used entirely to contribute hydrogen to the reducing gas; however, only a portion of the hydrogen-enriched first gas stream can be used to contribute hydrogen to the reducing gas. The remainder of the hydrogen-enriched first gas stream can be used for other purposes.

[0076] Other uses include, for example: 202400244

[0077] 12

[0078] - Use as fuel gas for preheating the reducing gas in a reducing gas furnace or a reformer;

[0079] - Use as fuel gas for preheating higher hydrocarbons - for example, natural gas which is subsequently added to the process gas cycle to carry out or promote carburization of the sponge iron;

[0080] - Use as fuel gas for preheating or splitting ammonia NH3, which contributes to the preparation of the reducing gas - for example as a component of the reducing gas;

[0081] - Use as fuel gas for preheating inert gases used in the direct reduction process - for example nitrogen, where the inert gases are intended for use in the bottom seal leg or top seal leg of a MIDREX process;

[0082] - Use as fuel gas for the generation of heat, steam, or hot water;

[0083] - Use as fuel gas in a power plant, for example for electricity generation, steam generation or heat generation - for example district heating;

[0084] - Use as fuel gas in a steelworks, wherever heat is needed, for example for ladle heating, roller hearth furnaces, in a pelletizing or sintering plant or other industrial steps in iron and steel production;

[0085] - Use in a synthesis process, for example for the production of synthetic natural gas, synthetic fuels, in a Fischer-Tropsch synthesis, for the production of ethanol, hydrocracking;

[0086] - Use for the export of hydrogen, for example after bottling, tank wagons or other containers;

[0087] - Use as fuel gas for preheating, drying, and oxidizing ores;

[0088] - Use as fuel gas for other processes. 202400244

[0089] 13

[0090] The remainder of the hydrogen-enriched first gas stream does not need to be used for other purposes; it can also be used for combustion or release at a flare without further use.

[0091] It is also possible to use the entire hydrogen-enriched first gas stream for the other uses listed or to feed it into a flare without further use for combustion or release.

[0092] The process according to the invention comprises separating at least a subset of the discharged cooling exhaust gas; the entire discharged cooling exhaust gas can be subjected to separation, or there can also be cooling exhaust gas that has not been subjected to separation. Cooling exhaust gas that has not been subjected to separation can also be used for the other applications listed above for the first gas stream enriched with hydrogen, or can be fed to combustion or release at a flare without further use.

[0093] The nitrogen-enriched second gas stream can be used for the following purposes, for example:

[0094] - Use as an inert gas in an industrial process - for example for purging or inerting;

[0095] - as a pressure maintenance measure for storage in hydrocarbon reservoirs, for example during the extraction of crude oil, natural gas, condensates;

[0096] - if the second gas stream contains at least some hydrogen, enriched with nitrogen, this can - 202400244

[0097] 14 analogous to the preceding list for the hydrogen-enriched first gas stream - can be used as fuel gas or for chemical processes such as syntheses.

[0098] A hydrogen-based direct reduction process is presented, in which ammonia (NH3) is used as the hydrogen source and nitrided sponge iron is provided, with the process being carried out in an energy- and resource-efficient manner. By utilizing the heat content of the sponge iron to crack ammonia (NH3) during the cooling step, which passes through a temperature range necessary for the production of iron nitrides in the sponge iron, and subsequently using the resulting hydrogen (H2) for the direct reduction – largely avoiding the input of the nitrogen (N2) produced in the process – the need for other cracking energy and / or a separate cracking device for ammonia cracking is reduced. The dual use of ammonia (NH3) on the one hand as a coolant and on the other hand as a hydrogen supplier is resource-efficient.

[0099] A further advantage of the process according to the invention is that, as a result of the passivation of nitrided sponge iron, briquetting to achieve passivation can be omitted. Since briquetting can adversely affect the processability of the sponge iron in subsequent processing steps – for example, melting – the possibility of dispensing with briquetting is advantageous.

[0100] Preferably, a portion of the discharged cooling exhaust gas contributes to the cooling process. For this purpose, the portion is fed to the sponge iron to be cooled, optionally with the addition of ammonia (NH3). This results in 202400244

[0101] 15 for example the possibility of making the ammonia NH3 contained in the cooling exhaust gas available again for cooling.

[0102] According to one implementation method, in such a recirculation of a subset of the discharged cooling exhaust gas, a control and / or regulation of the subset of the discharged cooling exhaust gas supplied to the separation is carried out.

[0103] Preferably, the gas pressure during cooling – for example, in the cooling zone of the reduction reactor or in the cooling reactor – is controlled and / or regulated by controlling and / or regulating the quantity of the subset of the discharged cooling exhaust gas fed to the separation process. Controlling and / or regulating the gas pressure during cooling is necessary for the controlled operation of any industrial process.

[0104] The first gas stream contributes hydrogen (H₂) to the reducing gas; it is preferred to heat the hydrogen (H₂) of the first gas stream by heat exchange with the discharged cooling exhaust gas. In this process, the hydrogen (H₂) in the first gas stream can be heated, i.e., the first gas stream itself can be heated – but it can also be a precursor of the reducing gas, which contains the hydrogen (H₂) of the first gas stream, that is heated.

[0105] The hydrogen (H2) of the first gas stream can also be heated by means of a heating device – for example, a reduction gas furnace or electric heater. When using a reduction gas furnace with fuel combustion, a second gas stream can be heated – completely or partially.

[0106] 16

[0107] - can be used as fuel or fuel component. The hydrogen H2 in the first gas stream can be heated, i.e., the first gas stream can be heated – but a precursor of the reducing gas, which contains the hydrogen H2 of the first gas stream, can also be heated.

[0108] A further subject matter of the present application is a device for the nitriding of sponge iron, comprising a device for the direct reduction of iron oxide-containing material to sponge iron with a reduction reactor and a supply line for supplying reducing gas and / or a precursor of the reducing gas to the reduction reactor, and comprising a cooling device for cooling the sponge iron to a temperature below 450 °C, wherein an ammonia supply line opens into the cooling device, characterized in that a cooling exhaust gas line extends from the cooling device for the discharge of cooling exhaust gas generated during cooling to the outside, which opens into a gas separation device for separating, optionally treated, cooling exhaust gas into a hydrogen-enriched first gas stream and a nitrogen-enriched second gas stream, wherein a 202400244

[0109] 17

[0110] The hydrogen gas stream outlet is used to discharge the first gas stream, and the hydrogen gas stream outlet has an opening into the supply line.

[0111] The inventive method can be carried out with such a device for the nitriding of sponge iron.

[0112] A reduction reactor is, for example, a reduction shaft – such as in a direct reduction process using a reduction shaft containing a fixed bed of iron oxide-containing material. Alternatively, a reduction reactor can be a fluidized bed reactor – for example, in a direct reduction process using a reduction reactor containing a fluidized bed of iron oxide-containing material. The fluidized bed reactor can also comprise several individual sub-reactors, which may be connected in parallel or sequentially, forming the fluidized bed reactor.

[0113] The reduction reactor is, for example, a fluidized bed reactor – for instance, when carrying out a direct reduction process with a reduction reactor containing a fluidized bed of iron oxide-containing material. The fluidized bed reactor can also comprise several individual sub-reactors, which are connected, for example, in parallel or sequentially and together form the fluidized bed reactor.

[0114] The reducing gas is the gas introduced into the reduction reactor, or rather its interior containing iron oxide material – in which the reduction reactions take place – with its composition and temperature present at the time of introduction. Before this 202400244

[0115] 18

[0116] Given the composition and temperature of the precursor, a precursor to the reducing gas is present, from which the reducing gas is prepared. If it is a precursor, further steps are required, such as adding additional components, heating to the desired temperature for introduction into the reduction reactor, or chemical reactions leading to a change in composition. Preparation can be achieved, for example, by adding further components or heating. Preparation can also occur through chemical reactions taking place within the precursor without external intervention, which, for example, change the chemical composition or the temperature.

[0117] The supply line serves to supply hydrogen-containing (H2) reduction gas to the reduction reactor or to supply a precursor of the reduction gas to the reduction reactor.

[0118] The ammonia supply line serves to supply ammonia-containing gas to the cooling device. This allows the ammonia (NH3), which is intended to contribute to cooling, to be supplied.

[0119] A cooling exhaust line extends from the cooling device to the outside for the removal of cooling exhaust gases produced during the cooling process. The cooling exhaust line terminates at least in a gas separator. The gas separator serves to separate the cooling exhaust gas into at least a hydrogen-enriched first gas stream and a nitrogen-enriched second gas stream. The cooling exhaust gas contains hydrogen (H₂) and nitrogen (N₂). The hydrogen-enriched first gas stream is, with respect to 202400244

[0120] 19

[0121] Nitrogen content depleted; the nitrogen-enriched second gas stream is depleted with respect to hydrogen content. The gas separation device can be, for example, a device for carrying out a membrane process, a pressure swing adsorption (PSA) process, a vacuum pressure swing adsorption (VPSA) process, or a cryogenic separation process. Preferably, a gas separation device is understood to be a device in which various molecularly and / or atomically present components of a gas stream, which is a mixture of several gases, are separated from one another, so that several streams enriched or depleted with respect to these components are produced. The process step of separating the discharged cooling exhaust gas into a hydrogen-enriched first gas stream and a nitrogen-enriched second gas stream is also preferably understood in this sense.

[0122] If necessary, one or more treatment devices are present in the cooling exhaust gas line; the treatment devices serve, for example, to:

[0123] - Cooling;

[0124] - Dust removal;

[0125] - Compression.

[0126] A hydrogen gas stream outlet leads from the gas separation device to discharge the first gas stream. The hydrogen gas stream outlet has at least one opening into the supply line. This allows the hydrogen-enriched first gas stream to contribute hydrogen (H₂) to the reducing gas; this hydrogen (H₂) becomes a component of the reducing gas and is used in its preparation.

[0127] 20

[0128] At least a subset of the hydrogen-enriched first gas stream is used as a component in the preparation of the reducing gas.

[0129] The use of a subset occurs both when, with an unchanged composition of the top gas, only a subset of the resulting volume of the first gas stream is used, and when not all components of the first gas stream are used – for example, when an enrichment of a component – ​​such as enrichment of hydrogen H2- – takes place and the correspondingly enriched gas stream is used completely or partially.

[0130] One step in the preparation of the reducing gas can therefore be the mixing of the first gas stream with other components of the reducing gas; either the gas mixture obtained in this way forms the reducing gas, or the reducing gas is prepared on the basis of this gas mixture, whereby further steps such as the addition of additional components or heating to the temperature desired for introduction into the reduction reactor, or chemical reactions leading to a change in the composition take place.

[0131] In one embodiment, the cooling device for cooling the sponge iron is designed as a subsection of the reduction reactor. The cooling device is thus integrated into the reduction reactor; it can be referred to as the cooling zone of the reduction reactor.

[0132] In another embodiment, the cooling device for cooling the sponge iron is designed as a cooling reactor. The cooling reactor differs from the reduction reactor; both the reduction reactor and the cooling reactor are designated 202400244.

[0133] 21 two different reactors, the cooling reactor is not integrated into the reduction reactor.

[0134] A material feed line connects the reduction reactor and the cooling reactor; it serves to supply sponge iron from the reduction reactor to the cooling reactor.

[0135] Preferably, a device for controlling and / or regulating the temperature profile in the cooling device that is optimal for nitriding is provided by changing the amount of cooling gas and / or the amount of ammonia NH3 added.

[0136] Preferably, this device is suitable for control and / or regulation using information about the composition of the cooling exhaust gas, and / or temperature measurements inside the cooling device, and / or temperature measurements on the cooling exhaust gas.

[0137] Preferably, a recirculation line is provided, branching off from the cooling exhaust gas line and leading into the cooling device and / or the ammonia supply line. This allows a portion of the discharged cooling exhaust gas to contribute to the cooling process. For this purpose, the portion is fed to the sponge iron being cooled, optionally with the addition of ammonia (NH3). This makes it possible to reuse the ammonia (NH3) contained in the cooling exhaust gas for the cooling process.

[0138] It is preferred to provide a device for controlling and / or regulating the size of the portion of the discharged cooling exhaust gas supplied to the gas separation device.

[0139] It is preferred if the device for controlling and / or regulating the size of the portion of the discharged cooling exhaust gas supplied to the gas separation device is a 202400244

[0140] 22

[0141] A device for controlling and / or regulating the gas pressure during cooling is .

[0142] According to one design, a heat exchanger is provided in the hydrogen gas stream discharge and / or the supply line for heating the hydrogen H2 of the first gas stream by heat exchange with the discharged cooling exhaust gas.

[0143] According to one design, a heating device - for example a reduction gas furnace, electric heater - is provided in the hydrogen gas stream outlet and / or the supply line for heating hydrogen H2 of the first gas stream.

[0144] When using a reduction gas furnace with combustion of a fuel fs, a feed line for supplying a second gas stream - completely or partially - as fuel f or fuel f component to the reduction gas furnace may be provided.

[0145] Another subject matter of the present application is a signal processing device with machine-readable program code, characterized in that it includes control and / or regulation commands for carrying out a method according to the invention. A further subject matter is a signal processing device for carrying out a method according to any one of claims 1 to 9.

[0146] Another subject matter of the present application is a machine-readable program code for a signal processing device, characterized in that the program code includes control and / or regulation commands which cause the signal processing device to carry out a method according to the invention. In the case of 202400244

[0147] 23. The further object is a computer program product comprising commands for a signal processing device which, when the program for the signal processing device is executed, cause it to carry out the method according to one of claims 1 to 9.

[0148] Another subject matter of the present application is a storage medium with machine-readable program code according to the invention stored thereon. A further subject matter is a storage medium with a computer program stored thereon for carrying out a method according to any one of claims 1 to 9.

[0149] Brief descriptions of the drawings

[0150] The invention will now be explained in more detail using exemplary illustrations. The drawing is exemplary and is intended to illustrate the inventive concept, but in no way to restrict or even exhaustively represent it. It shows:

[0151] Fig. 1 is a schematic representation of a process according to the invention.

[0152] Fig. 2 shows a schematic representation of another variant of a process sequence according to the invention.

[0153] Fig. 3 shows a schematic representation of a further variant of a process sequence according to the invention.

[0154] Figure 1 schematically shows the process sequence according to the invention. Iron oxide-containing material 1 is placed in a reduction reactor 2 – shown schematically as an example. 202400244

[0155] 24 is a reduction shaft, but it could also be a fluidized bed reactor or a fluidized bed reactor – where hydrogen (H₂) is directly reduced to sponge iron using a hydrogen-containing reduction gas. A portion of the hydrogen (H₂) originates from the cracking of ammonia (NH₃). The reduction gas is supplied to the reduction reactor 2, which contains the iron oxide-containing material, via feed line 3. The sponge iron is cooled to a temperature below 450 °C in a cooling device 4. The cooling device 4 is shown as a separate cooling reactor from the reduction reactor 2; the sponge iron from the reduction reactor 2 is fed to the cooling reactor via material feed line 5. An ammonia supply line 6 leads into the cooling device 4; it serves to supply ammonia NH3 into the cooling device 4, where the ammonia NH3 contributes to cooling.In the cooling device, nitrided iron sponge is produced from the iron sponge, which is the product of direct reduction in reduction reactor 2. Preferably, the nitrided iron sponge, after cooling to a temperature below 450 °C, has an iron nitride content of over 20 by weight!, and more preferably, it has an iron nitride content of over 50 by weight!.

[0156] Cooling exhaust gas produced during cooling is discharged via the cooling exhaust gas line 7 leading from the cooling device 4. This line opens into a gas separator 8 for separating the cooling exhaust gas into a hydrogen-enriched first gas stream and a nitrogen-enriched second gas stream. A hydrogen gas stream outlet 9 extends from the gas separator 8 for the discharge of the first gas stream. The hydrogen gas stream outlet 9 has an opening into the supply line 3. This allows the 202400244

[0157] 25

[0158] Hydrogen (H2) of the first gas stream contributes to the reducing gas.

[0159] The cooling exhaust gas line may contain one or more treatment devices – for example, for cooling, dust removal, or compression – which are not shown separately for clarity. In this case, the appropriately treated cooling exhaust gas is fed to the gas separation device 8.

[0160] A device for controlling and / or regulating the cooling device to achieve an optimal temperature profile for nitriding by changing the amount of cooling gas and / or the amount of ammonia (NH3) added may be provided, preferably being suitable for controlling and / or regulating using information about the composition of the cooling exhaust gas, and / or temperature measurements inside the cooling device, and / or temperature measurements of the cooling exhaust gas. For clarity, this is not shown in Figure 1.

[0161] Figure 2 schematically shows another variant of a process sequence according to the invention. Figure 2 is largely analogous to Figure 1, but differs, among other things, in that a recirculation line 10 is present, which branches off from the cooling exhaust gas line 7 and opens into the ammonia supply line 6. This allows a portion of the discharged cooling exhaust gas to contribute to the cooling process.

[0162] Optionally, a device is provided for controlling and / or regulating the quantity of the discharged cooling exhaust gas supplied to the gas separation device. 202400244

[0163] 26

[0164] This can be a device for controlling and / or regulating the gas pressure during cooling.

[0165] This is not shown separately for the sake of clarity.

[0166] A heat exchanger for heating the hydrogen (H₂) of the first gas stream by heat exchange with the discharged cooling exhaust gas may be provided in the hydrogen gas stream outlet 9 and / or the supply line 3. This is not shown for clarity.

[0167] A heating device – for example, a reducing gas furnace or electric heater – can be provided in the hydrogen gas stream outlet 9 and / or the supply line 3 for heating the hydrogen H₂ of the first gas stream. An example of such an optionally present reducing gas furnace 11 in the hydrogen gas stream outlet 9 is shown with dashed lines.

[0168] The reduction gas furnace 11 operates by combustion of a fuel fs. In the example shown, a feed line 12 supplies a second gas stream as

[0169] Fuel component to the reduction gas furnace 11 from the gas separation device 8.

[0170] Figure 3 schematically shows another variant of a process sequence according to the invention, largely analogous to Figure 1. Figure 3 differs from Figure 1 in that the cooling device for cooling the sponge iron is designed as a section 13 of the reduction reactor 2. The cooling device is thus integrated into the reduction reactor 2; it is a cooling zone of the reduction reactor 2. 202400244

[0171] 27

[0172] Reference character list

[0173] 1 iron oxide-containing material

[0174] 2 Reduction reactor

[0175] 3 Supply line

[0176] 4 Cooling device

[0177] 5 Material supply line

[0178] 6 Ammonia supply line

[0179] 7 Cooling exhaust pipe

[0180] 8 Gas separator device

[0181] 9 Hydrogen gas st stromaus le itung

[0182] 10 Recirculation line

[0183] 11 Reduction gas furnaces

[0184] 12 Feed line

[0185] 13 Subsection ( of the

[0186] Reduction reactor 29

Claims

202400244 28 Claims 1. A process for the nitriding of sponge iron, comprising direct reduction of iron oxide-containing material ( 2 ) to sponge iron, wherein hydrogen-containing reduction gas (H2) is used, wherein at least a subset of the hydrogen (H2) originates from the cracking of ammonia (NH3), and wherein the reduction gas is supplied to a reduction reactor containing the iron oxide-containing material in an interior space. (1) is supplied, and comprising cooling the sponge iron to a temperature below 450 °C, characterized in that the cooling of the sponge iron to a temperature below 450 °C is carried out using a cooling gas containing ammonia (NH3), and the cooling takes place in at least one member of the group consisting of a) cooling zone of the reduction reactor, b) cooling reactor, cooling gas generated during cooling is at least partially discharged from a) and / or b), and at least a subset of the discharged cooling gas is separated, optionally after treatment, into a hydrogen-enriched first gas stream and a nitrogen-enriched second gas stream. 202400244 29 and the first gas stream hydrogen H2 contributes to the reducing gas.

2. Method according to claim 1, characterized in that the nitrided iron sponge, after cooling to a temperature below 450 °C, has an iron nitride content of over 20 by weight, particularly preferably over 50 by weight, very preferably over 70 by weight, and most preferably over 90 by weight.

3. Method according to claim 1 or 2, characterized in that during cooling, regulation and / or control is carried out to adjust a temperature profile optimal for nitriding by changing the amount of cooling gas and / or the amount of ammonia NH3 added.

4. Method according to one of claims 1 to 3, characterized in that the cooling is controlled and / or regulated using information about the composition of the cooling exhaust gas, and / or temperature measurements inside the cooling zone or the cooling reactor, and / or temperature measurements on the cooling exhaust gas.

5. Method according to one of claims 1 to 4, characterized in that a subset of the discharged cooling exhaust gas contributes to the cooling.

6. Method according to one of claims 1 to 5, characterized in that, in the case of recirculation of a subset of the discharged cooling exhaust gas for cooling, a control and / or regulation of the subset of the discharged cooling exhaust gas supplied to the separation is carried out. 202400244 30 7. Method according to claim 6, characterized in that the gas pressure during cooling is controlled and / or regulated by controlling and / or regulating the size of the quantity of the subset of the discharged cooling exhaust gas supplied to the separation.

8. Method according to one of claims 1 to 7, characterized in that hydrogen H2 of the first gas stream is heated by heat exchange with discharged cooling exhaust gas.

9. Method according to one of claims 1 to 8, characterized in that hydrogen H2 of the first gas stream is heated by means of a heating device.

10. Device for the nitriding of sponge iron, comprising a device for the direct reduction of iron oxide-containing material to sponge iron with a reduction reactor (1) and a supply line (3) for supplying reducing gas and / or a precursor of the reducing gas to the reduction reactor (1), and comprising a cooling device (4) for cooling the sponge iron to a temperature below 450°C, wherein an ammonia supply line (6) opens into the cooling device (4), characterized in that 202400244 31. A cooling exhaust gas line (7) extends from the cooling device (4) for the discharge of cooling exhaust gas generated during cooling to the outside, which leads into a gas separation device (8) for the separation of, if necessary, treated cooling exhaust gas into a hydrogen-enriched first gas stream and a nitrogen-enriched second gas stream, wherein a hydrogen gas stream outlet (9) extends from the gas separation device (8) for the discharge of the first gas stream, and the hydrogen gas stream outlet (9) has an opening into the supply line (3).

11. Device according to claim 10, characterized in that the cooling device (4) for cooling the iron sponge is designed as a subsection of the reduction reactor (1).

12. Device according to claim 10, characterized in that the cooling device (4) for cooling the iron sponge is designed as a cooling reactor.

13. Device according to one of claims 10 to 12, characterized in that a device for controlling and / or regulating the temperature profile in the cooling device (4) that is optimal for nitriding is provided by changing the amount of cooling gas and / or the amount of ammonia NH3 added.

14. Device according to one of claims 10 to 13, characterized in that a recirculation line (10) is provided which branches off from the cooling exhaust gas line (7) and leads into the cooling device (4) and / or into the ammonia supply line (6). 202400244 32 15. Device according to one of claims 10 to 14, characterized in that a device for controlling and / or regulating the size of the partial quantity of the discharged cooling exhaust gas supplied to the gas separation device (8) is provided.

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