Process and direct reduction plant for the production of sponge iron

Abstract

The invention relates to a process for producing sponge iron from iron ore-containing material (20) by direct reduction using at least one reducing gas in a reactor (16) of a direct reduction plant (12), wherein the reducing gas or at least one of the reducing gases is generated by in-situ reforming in the reactor (16). It is planned that, at least during the start-up of the corresponding direct reduction process, the reactor (16) will be supplied with sponge iron material (22) in addition to the iron ore-containing material (20). The invention further relates to a direct reduction plant (12) for the production of sponge iron from iron ore-containing material (20) by direct reduction using at least one reducing gas in a reactor (16) of the direct reduction plant (12).

Description

[0001] The invention relates to a process for producing sponge iron from material containing iron ore by direct reduction using at least one reducing gas in a reactor of a direct reduction plant, in which the reducing gas or at least one of the reducing gases is produced by in-situ reforming in the reactor.

[0002] The invention further relates to a corresponding direct reduction plant for producing sponge iron from material containing iron ore by direct reduction by means of at least one reducing gas in a reactor of the direct reduction plant, wherein the plant further comprises a feed device for feeding the material containing the iron ore into the reactor and is designed to produce the reducing gas or at least one of the reducing gases by in-situ reforming in the reactor.

[0003] In direct reduction, solid sponge iron (DRI: Direct Reduced Iron) is produced from iron ore by reducing the oxidation state of Fe. The production of sponge iron in the reactor comprises two basic steps: In a first step, the iron ore is reduced to sponge iron in a reduction zone using a suitable hot reducing gas. Such a reducing gas typically comprises H2 (hydrogen) and CO (carbon monoxide) at temperatures in the range of 850 °C to 1100 °C. In a second step, the produced sponge iron is cooled in a cooling zone using a cooling gas to temperatures that are often below 100 °C. The iron ore is fed to the reactor in the form of iron ore-containing material in particulate form, such as lump ore, pellets, and / or sintered material particles. The corresponding direct reduction plant is a type of shaft furnace.

[0004] In the debate about low-CO2 steel production due to climate change, the direct reduction process is becoming increasingly important.

[0005] The reducing gas used in direct reduction is typically a mixture of hydrogen (H2) and carbon monoxide (CO), which is obtained by reforming natural gas (NG) either in an external catalytic inline or offline reformer or in situ within the reactor (so-called "zero reformer" ZR process). Nevertheless, a corresponding direct reduction plant can also be designed to utilize other suitable gases containing H2 and / or CO. In the context of the invention, the focus is naturally on direct reduction processes in which the reducing gas, or at least one of the reducing gases, is generated by in-situ reforming in the reactor (ZR process).

[0006] A challenge in the operation of such direct reduction plants, in which reducing gas is generated by in-situ reforming in the reactor, is the start-up phase of the direct reduction process when starting up the plant, since at this point in time the in-situ reforming in the reactor has not yet started to a sufficient extent due to the lack of metallic iron, which is intended to act as a catalyst in the reactor, and therefore there is too little reducing gas available for the direct reduction process.

[0007] Document EP 3 494 238 B1 describes a process for producing sponge iron from iron ore-containing material by direct reduction using at least one reducing gas in a reactor of a direct reduction plant, in which the reducing gases are generated by in-situ reforming in the reactor. During startup of the corresponding direct reduction process, in addition to the gas from which the reducing gases are generated by in-situ reforming, pre-reformed reducing gas(es) are also introduced into the reactor. In this way, the plant can start up from a plant shutdown more quickly and with greater stability than a conventionally operated direct reduction plant for such an in-situ process.

[0008] However, the prerequisite for such an approach is the availability of an appropriately pre-reformed reducing gas and a system for the targeted admixture of this pre-reformed reducing gas.

[0009] The object of the invention is to provide a method for producing sponge iron from particles containing iron ore by direct reduction and a corresponding direct reduction plant for producing sponge iron, in which the direct reduction process or the corresponding plant can be started up quickly and reliably from standstill using simple means.

[0010] According to the invention, the object is achieved by the features of the independent claims. Preferred embodiments of the invention are specified in the subclaims, each of which may represent an aspect of the invention individually or in combination.

[0011] In the method according to the invention for producing sponge iron from material containing iron ore by direct reduction using at least one reducing gas in a reactor of a direct reduction plant, in which the reducing gas or at least one of the reducing gases is generated by in-situ reforming in the reactor, it is provided that sponge iron material is also fed to the reactor in addition to the material containing iron ore, at least when starting up the corresponding direct reduction process.

[0012] The additional sponge iron material added to the reactor during startup, i.e., the start-up phase, and possibly even beyond this phase, supports the in-situ reforming of an introduced gas such as methane (CH4) into reducing gases, thus shortening the startup phase and achieving stable normal operation more quickly. The addition of sponge iron material is therefore primarily a temporary addition.

[0013] According to a preferred embodiment of the invention, the sponge iron material is fed into the reactor parallel to the feed of the material containing the iron ore. The term "parallel feed" in this context can be understood both spatially and temporally. The sponge iron material is fed into the reactor via the same or a parallel path as the material containing the iron ore.

[0014] In particular, it is envisaged that the sponge iron material and the iron ore-containing material are fed into the reactor using one and the same feed device. This allows for the simple and coordinated feeding of both types of material.

[0015] According to a further preferred embodiment of the invention, both the sponge iron material and the iron ore-containing material are fed into the reactor via feed inlets on the top side of the reactor. The usual path for feeding the iron ore-containing material leads via the top side of the reactor and has proven successful in practice. It has been found that using such a path is also advantageous for feeding the sponge iron material.

[0016] According to yet another preferred embodiment of the invention, the sponge iron material fed into the reactor is based on sponge iron previously produced in the direct reduction plant. Thus, the sponge iron for this sponge iron material does not need to be procured separately.

[0017] In particular, it is envisaged that a maximum of 5% of the sponge iron produced in the direct reduction plant is subsequently fed into the reactor as sponge iron material.

[0018] Finally, with regard to the process, it is advantageously provided that – at least during the start-up of the corresponding direct reduction process – in addition to a gas from which the at least one reducing gas is generated by in-situ reforming in the reactor, a pre-reformed reducing gas is also introduced into the reactor. In this way, the start-up of the process / plant can be further accelerated.

[0019] In the direct reduction plant according to the invention for producing sponge iron from material containing iron ore by direct reduction using at least one reducing gas in a reactor of the direct reduction plant, in which the plant further comprises a feed device for feeding the material containing the iron ore into the reactor and is configured to generate the reducing gas or at least one of the reducing gases by in-situ reforming in the reactor, it is provided that this plant further comprises means for feeding sponge iron material into the reactor. In this way, additional sponge iron material can be fed to the reactor during start-up, i.e., a start-up phase, and optionally also beyond this start-up phase. This supports the in-situ reforming of a corresponding gas into reducing gas(es), so that the start-up or start-up phase is shortened and stable normal operation is achieved more quickly.

[0020] According to a preferred embodiment of the plant according to the invention, the feed device is a feed device for feeding the iron ore-containing material and the sponge iron material into the reactor, wherein the feed device comprises said means for feeding the sponge iron material. In the simplest case, the feed device feeds a mixture prepared in the ore deposit containing the two aforementioned types of material (iron ore-containing material and sponge iron material) to the reactor.

[0021] According to a further preferred embodiment of the plant according to the invention, it is provided that the plant has feed inlets on an upper side of the reactor, via which the feeding of the sponge iron material and the feeding of the material containing the iron ore to the reactor is made possible.

[0022] According to yet another preferred embodiment of the plant according to the invention, the direct reduction plant is configured to feed sponge iron material to the reactor, which material is based on sponge iron previously produced in the direct reduction plant. For this purpose, the direct reduction plant provides a corresponding path for a material flow of sponge iron / sponge iron material to the feed device or the means for feeding the sponge iron material.

[0023] Finally, it is advantageous that the direct reduction plant comprises a system for the targeted admixture of a pre-reformed reducing gas to the gas from which the at least one reducing gas is produced by the in-situ reforming in the reactor. The pre-reformed gas can contain from 0% to 100% CO and from 0% to 100% H2.

[0024] The invention will now be explained by way of example with reference to the accompanying drawings using a preferred embodiment, wherein the features presented below may represent an aspect of the invention both individually and in combination. They show: Fig. 1 an electric steelmaking plant with electric arc furnace and direct reduction plant according to a preferred embodiment of the invention.

[0025] The Fig.Figure 1 shows central components of a steelmaking plant 10, namely a direct reduction plant 12 and an electric arc furnace 14, in an exemplary, schematic representation. The direct reduction plant 12 is used to produce sponge iron (DRI: Direct Reduced Iron) and comprises a reactor 16 for the actual reaction, i.e., the direct reduction, and a feed device 18 arranged above the reactor 16 for feeding iron ore-containing material 20 and additional material 22 into the reactor 16, wherein this material 20, 22 is each in the form of bulk material. In the present case, the additional material is sponge iron material 22. The feed device 18 is arranged above the reactor 16 for this purpose. The reactor 16 extends vertically from a top side 24 along its central longitudinal axis 26 to a lower end 28.It comprises a reactor vessel 30, in whose interior—that is, the interior of reactor 16—the corresponding reactions take place. For this purpose, an upper part 32 of reactor 16 contains a reduction zone in which the Fe is reduced from the iron ore, and a lower part 34 of reactor 16 contains a cooling zone in which the resulting sponge iron can be / is cooled. The lower part 34 of reactor 16 is conical in shape and converges at the lower end 28 into an outlet 36 for the optionally still hot or cold sponge iron, which can be removed from reactor 16 there (path 38).

[0026] The feed device 18 has at least one storage container 40, 42 for the materials 20, 22 (in the example shown, two storage containers 40, 42). The storage container 40 is intended to hold the material 20 containing the iron ore, and the storage container 42 is intended to hold the sponge iron material 22. Each outlet of the respective storage container 40, 42 is connected via a respective lock device 44, 46 of the feed device 18 to an associated feed inlet 48, 50 into the reactor 16, wherein these feed inlets 48, 50 are located on the top side 24 of the reactor 16. The lock devices 44, 46 serve for the gas-tight introduction of the materials 20, 22 present as bulk material into the reactor 16. The combination of the components storage container 42, lock device 46 and feed access 50 can also be referred to as means 42, 46, 50 for feeding the sponge iron material 22 to the reactor 16.

[0027] In the example shown, the electric arc furnace 14 is designed as an alternating current furnace with three graphite electrodes 52 in a cover 54 that can be opened and closed.

[0028] In furnace 14, steel is produced from sponge iron (path 38) and steel scrap (path 56) at approximately 1500 to 1800 °C; accordingly, the process is also referred to as electric steelmaking. The resulting steel (crude steel) is then poured into a steel ladle 58 for further transport.

[0029] The direct reduction device 12 has the following function: The iron ore-containing material 20 is fed to the reactor 16 from the storage container 40 via the lock device 44. The individual particles of the thus fed material 20 sink downward through the reduction zone of the reactor 16 and react at high temperature (850 °C to 1100 °C) in countercurrent contact with a reducing gas, which generally contains carbon monoxide (CO) and / or hydrogen (H2), which is formed in parallel in-situ in the reactor from supplied gas (for example, natural gas, methanol, or ammonia). The gas for forming this reducing gas is introduced into the reactor 16 at an inlet via a line 60, which opens into the lower part of the reduction zone, and is removed from the reactor 16 at an outlet in the upper part of the reduction zone via another line 62.However, a major portion of this extracted gas retains its reducing potential and is then returned to the reactor 16 at the inlet in a recirculating system via line 60. A pre-reformed reducing gas can be admixed to the gas from which the at least one reducing gas is generated by the in-situ reforming in the reactor 16 via an admixer 64 before being introduced into the reactor 16. In this way, the start-up of the process / plant 12 can be further accelerated.

[0030] The cooling zone is located in the lower part 34 of the reactor 16. This part 34 is preferably conical in shape and converges to the outlet 36, through which the already reduced ore, i.e. the sponge iron or the DRI, is discharged hot or cold. In the cooling zone in the lower part 34 of the reactor 16, a cooling gas stream (containing any non-oxidizing, inert or reducing gas, e.g. natural gas) is normally circulated in countercurrent to, among other things, extract heat from the hot sponge iron / DRI. This cooling gas is introduced through a cooling gas line 66 into a lower section of the conically shaped lower part 34 of the reactor 16 and removed in heated form from an upper section of the lower part 34 of the reactor 16 through a further cooling gas line 68 and then returned to line 66 in a closed circuit.In this resulting cooling circuit 66, 68, 70, 72, the hot gas is cleaned and cooled before being reintroduced into the reactor 16. For this purpose, the cooling circuit 66, 68, 70, 72 comprises a cooler 70 and a compressor 72. If it is desired to discharge the sponge iron / DRI at high temperature, the cooling circuit 66, 68, 70, 72 is shut down, and the DRI does not undergo any type of active cooling before being discharged from the reactor 16 via the outlet 36, for example, for hot coupling to the electric arc furnace (EAF).

[0031] The following function of the means 42, 46, 50 for feeding the sponge iron material 22 to the reactor 16 now arises: If at any time during the direct reduction process there is a deficit of reducing gas in the reactor 16, then in addition to the iron ore-containing material 20, sponge iron material 22 can also be fed into the reduction zone, i.e., the upper part 32 of the reactor 16, via the means 42, 46, 50 for feeding the sponge iron material 22 of the feed device 18. In this way, more catalyst material for the in-situ reformation is provided at a suitable location. The sponge iron material 22 is fed to the reactor 16 from the storage container 42 via the lock device 46 and the feed inlet 50. The individual particles of the material 22 thus fed in sink downwards through the reduction zone of the reactor 16 and promote the formation of reducing gas there.A typical time at which there is a deficit of reducing gas in the reactor 16 during the direct reduction process is the start-up of the direct reduction process or the direct reduction plant 12 after a shutdown.

[0032] The sponge iron material 22 fed to the reactor 16 can be based on sponge iron previously produced in the direct reduction plant 12, but external sources are also conceivable. In this way, the sponge iron for this sponge iron material does not need to be specially procured. For this purpose, the direct reduction plant 12 has a corresponding path 74 for a material flow of sponge iron / sponge iron material 22 to the feed device 18 or the means 42, 46, 50 for feeding the sponge iron material 22. This path branches off from the usual path 38 for the sponge iron, which leads to the electric arc furnace 14.

[0033] As an alternative to the electric arc furnace 14 shown here, another electrically heated furnace, such as a melter (not shown), can also be connected downstream of the direct reduction device 12 in the steelmaking plant 10. Reference symbol 10 steel production plant 12 Direct reduction device 14 electric arc furnace 16 reactor 18 Feeding device 20 iron ore material, 22 Sponge iron material 24 Top (Reactor) 26 Longitudinal axis (reactor) 28 lower end (reactor) 30 reactor vessels 32 upper part 34 lower part 36 Outlet 38 Path (Sponge Iron) 40 storage containers 42 Arrow 44 Lock system 46 Lock facility 48 Feed access 50 Feed access 52 Graphite electrode 54 lids 56 Path (Scrap) 58 steel pan 60 gas pipeline 62 additional guest management 64 proportioners 66 Cooling gas line 68 additional cooling gas lines 70 coolers 72 Compressor 74 Path (sponge iron material) QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3 494 238 B1

[0007]

Claims

[1] A process for producing sponge iron from iron ore-containing material (20) by direct reduction using at least one reducing gas in a reactor (16) of a direct reduction plant (12), in which the reducing gas or at least one of the reducing gases is produced by in-situ reforming in the reactor (16), characterized by that sponge iron material (22) is also fed to the reactor (16) in addition to the material (20) containing iron ore, at least when the corresponding direct reduction process is started up. [2] Method according to claim 1, wherein the feeding of the sponge iron material (22) to the reactor (16) takes place in parallel with the feeding of the iron ore-containing material (20) to the reactor (16). [3] Method according to claim 1 or 2, wherein the feeding of the sponge iron material and the feeding of the iron ore-containing material (20) to the reactor (16) are carried out by means of one and the same feeding device (18). [4] Method according to one of claims 1 to 3, wherein the feeding of the sponge iron material (20) and the feeding of the iron ore-containing material (22) to the reactor (16) takes place via feed inlets (48, 50) on an upper side (24) of the reactor (16). [5] Process according to one of claims 1 to 4, wherein the sponge iron material (22) supplied to the reactor is based on sponge iron previously produced in the direct reduction plant (12). [6] Process according to claim 5, wherein at most 5% of the sponge iron produced in the direct reduction plant (12) is subsequently fed to the reactor (16) as sponge iron material (22). [7] Direct reduction plant (12) for producing sponge iron from iron ore-containing material by direct reduction by means of at least one reducing gas in a reactor (16) of the direct reduction plant (12), wherein the plant (12) further comprises a feed device (18) for feeding the iron ore-containing material (20) into the reactor (16) and is designed to produce the reducing gas or at least one of the reducing gases by in-situ reforming in the reactor (16), characterized by Means (42, 46, 50) for feeding sponge iron material (22) into the reactor (16). [8] Direct reduction plant according to claim 7, wherein the feeding device (18) is a feeding device (18) for feeding the iron ore-containing material (20) and the sponge iron material (22) into the reactor (16), which comprises said means (42, 46, 50) for feeding the sponge iron material (22). [9] Direct reduction plant according to claim 7 or 8, with feed inlets (48, 50) on an upper side (24) of the reactor (16), via which the sponge iron material (22) and the iron ore-containing material (20) are fed to the reactor. [10] Direct reduction plant according to one of claims 7 to 9, which is arranged to supply the reactor (16) with sponge iron material (22) which is based on sponge iron previously produced in the direct reduction plant (12).

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