Process for producing steel in an integrated steelworks

Abstract

Method for producing steel in an integrated steelworks (1), comprising at least one direct reduction reactor (2) for directly reducing iron ore to sponge iron, at least one electric furnace (3) for melting the sponge iron to pig iron or crude steel, at least one blast furnace (4) for melting iron ore to pig iron and at least one converter (5) for refining pig iron to crude steel, characterized in that the process gas (2.2, 2.3, 2.4, 2.5, 2.9) discharged from the direct reduction reactor (2) is at least partly added to the hot blast (4.1*) and / or at least partly to a feed material (4.3) which is / or is blown into the blast furnace (4), wherein the process gas (4.4) discharged from the blast furnace (4) is at least partly used as fuel gas (4.6, 4.7) for firing a Reduction gas heater (20) of the direct reduction reactor (2).

Description

[0001] The invention relates to a method for producing steel in an integrated steelworks.

[0002] A generic process for steel production in an integrated steelworks is disclosed, for example, in EP 1 641 945 B1. The use of an additional melter in an integrated steelworks is shown on the applicant's website https: / / www.thyssenkrupp-steel.com / de / unternehmen / nachhaltigkeit / klimastrategie / "Two technology paths - one goal."

[0003] Further exemplary embodiments of steelworks are disclosed in the documents EP 1 285 096 B1, AT 385 051 B and DE 44 21 673 A1.

[0004] The object of the present invention is to further develop a generic method in such a way that the energetically and materially valuable process gases present in an existing integrated steelworks can be used in an economically optimized manner.

[0005] This object is achieved by a method for producing steel in an integrated steelworks, comprising at least one direct reduction reactor for directly reducing iron ore to sponge iron, at least one electric furnace for melting the sponge iron to crude steel or pig iron, at least one blast furnace for melting iron ore to pig iron and at least one converter for refining the pig iron to crude steel, wherein according to the invention the process gas discharged from the direct reduction reactor is at least partly admixed to the hot blast and / or at least partly to a feed material which is blown into the blast furnace.

[0006] Furthermore, at least part of the process gas discharged from the blast furnace is provided as fuel gas for firing the reducing gas heater of a direct reduction reactor.

[0007] In at least one direct reduction reactor, sponge iron is produced from iron ore using a reducing gas, which can consist of hydrogen and / or methane (natural gas). This sponge iron is then melted in at least one smelter to produce crude steel or pig iron. Furthermore, iron ore and coke, which is produced from coal in a coking plant, are melted in at least one blast furnace to produce pig iron, which in turn is refined in a converter, particularly an oxygen converter, and thus converted into crude steel by removing, in particular, carbon, sulfur, and / or phosphorus. The individual units and corresponding processes mentioned are state-of-the-art and established processes in practice.

[0008] It was surprisingly discovered that the process gas discharged from the direct reduction reactor is of high energy and material value and can therefore be optimally utilized in an integrated steelworks in the blast furnace process via the tuyeres, in particular via the injection lances, in an economical and ecological manner.

[0009] The process gas discharged from the direct reduction reactor can be at least partially mixed with or replaced by a feed material. This allows high-cost feed components, such as hydrogen, or CO2-intensive components, such as coal and / or natural gas, to be partially or completely substituted, thereby reducing the costs and CO2 footprint of the feed materials.

[0010] Air is typically used as the cold blast. Before being blown into the blast furnace as hot blast via the tuyeres, it is heated to the required temperature in a cowper. If necessary, additional oxygen can be added before and / or after the heating process. The pressure can also be increased before and / or after the heating process. Depending on the capacity of the blast furnace, two or more cowper heaters are installed, operating alternately (their mode of operation is known). Alternatively or additionally, the process gas discharged from the direct reduction reactor can be mixed, at least in part, with the hot blast.

[0011] Whether the hot blast and / or the feed material can be completely replaced by the process gas discharged from the direct reduction reactor depends on the design and operating mode of the corresponding equipment in the integrated steelworks. At least a portion of the discharged process gas is fed into the blast furnace via the tuyeres, resulting in a mixed gas consisting of process gas, hot blast, and feed material.

[0012] At least a part of the discharged process gas means that either only a part of the discharged process gas is fed to the blast furnace and the remainder is used outside the blast furnace process or can be fed entirely to the blast furnace process.

[0013] Adding can also be understood as adding.

[0014] Depending on the composition of the reducing gas used, the process gas discharged from the direct reduction reactor contains unreacted components which can be economically used in the blast furnace process for the reduction and melting of iron ore, coke and other additives, in particular compounds or mixtures of carbon and oxygen (CO, CO2), methane (CH4), hydrogen (H2) and / or water vapor (H2O) as well as process-related unavoidable impurities.

[0015] According to one embodiment of the invention, at least a portion of the discharged process gas is directly added to the hot blast and / or at least a portion is directly added to the feed material. This means that the process gas, as discharged from the direct reduction reactor, is fed directly, in particular via appropriate supply lines, to the blast furnace process, preferably without having to undergo a process gas treatment stage.

[0016] According to an alternative embodiment of the invention, the discharged process gas is first dehumidified and then, as dehumidified process gas, at least partially added to the hot blast and / or at least partially to the feed material. The discharged process gas is passed through a unit, for example, a condenser, and cooled accordingly, so that the water vapor present in the process gas condenses and is thus separated from the process gas. Condensing and discharging the condensate "dehumidifies" the process gas. This can improve the quality of the process gas.

[0017] A further embodiment of the invention provides that the CO2 content contained in the discharged process gas or in the dehumidified process gas is separated and then, as carbon dioxide-free process gas, at least partially added to the hot blast and / or at least partially added to the blast furnace feed. The process gas is passed through a unit in which compounds or mixtures of carbon and oxygen, such as carbon dioxide (CO2), are separated, for example, by CO2 separation in the form of amine scrubbing, carbonate scrubbing, membrane separation technology, such as selective membranes, or PSA (pressure swing absorption).To further improve the carbon footprint, the carbon dioxide captured from the process gas can be stored in a suitable environment, for example, using CCS (Carbon Capture and Storage), or utilized as a material in a CCU (Carbon Capture and Utilization) process. Furthermore, the carbon dioxide (CO2) can also be utilized as a potential cooling gas or as part of a potential cooling gas in an optional cooling zone in the direct reduction process.

[0018] In the direct reduction reactor, a reducing gas is fed in to reduce the iron ore to sponge iron, which is first heated to an appropriate temperature in a reducing gas heater before being fed into the reduction zone of the direct reduction reactor.

[0019] For this purpose, according to one embodiment of the invention, the process gas discharged from the electric furnace can be provided, at least in part, as fuel gas or as additional gas to the fuel gas for firing the reducing gas heater of the direct reduction reactor. Alternatively or additionally, at least part of the process gas discharged from the electric furnace can be blown into the blast furnace via the tuyeres.

[0020] The integrated steelworks further comprises a coking plant, which produces the coke for the blast furnace process from coal in the immediate vicinity. According to an alternative embodiment of the invention, at least a portion of the process gas discharged from the coking plant can be provided as fuel gas for firing the reduction gas heater of the direct reduction reactor. Alternatively or additionally, at least a portion of the process gas discharged from the coking plant can be injected into the blast furnace via the tuyeres.

[0021] The integrated steelworks further comprises a steelworks with at least one converter, for example, an LD converter (also called a BOF converter), in which the pig iron is optimized to produce crude steel for further processing. According to a further alternative embodiment of the invention, at least a portion of the process gas discharged from the converter can be provided as fuel gas for firing the reduction gas heater of the direct reduction reactor. Alternatively or additionally, at least a portion of the process gas discharged from the converter can be injected into the blast furnace via the tuyeres.

[0022] The use of the exhausted process gas from electric furnaces, coking plants, converters or blast furnaces can significantly improve the energy balance of an integrated steelworks.

[0023] A further improvement in the energy balance can be achieved if, according to one embodiment of the invention, at least two process gases discharged from the electric furnace, coking plant, converter, and blast furnace are combined and at least partially provided as fuel gas for firing the reduction gas heater of the direct reduction reactor. Alternatively or additionally, at least two process gases discharged from the electric furnace, coking plant, and converter can be combined and at least partially injected into the blast furnace via the tuyeres.

[0024] The invention is explained in more detail using the following embodiments in conjunction with the Fig. 1. The Fig. 1 shows an example of a method according to the invention in a schematic representation of an integrated steelworks for producing steel or pig iron.

[0025] The integrated steelworks (1) comprises at least one direct reduction reactor (2) for directly reducing iron ore (io) to sponge iron, at least one electric furnace (3) for melting the sponge iron to produce crude steel or pig iron, at least one blast furnace (4) for melting iron ore (io), in particular with coke, injected coal, and other additives, to produce pig iron, and at least one converter (5) for refining pig iron to produce crude steel. Furthermore, the integrated steelworks (1) comprises at least one coking plant (6) for coking coal to produce coke.

[0026] Iron ore (io) is fed into the direct reduction reactor (2), which can be designed as a shaft furnace, for example, and is thus appropriately loaded at the upper end, and into the blast furnace (4) together with coke from the coking plant (6) and other additives, such as limestone, in particular in layers over the burden. At the lower end of the direct reduction reactor (2), the sponge iron produced is removed and fed to an electric furnace (3) to melt the sponge iron, in particular with the addition of other additives such as steel scrap. The pig iron obtained from the blast furnace (4) must be refined into crude steel in a converter (5). Both the crude steel and thePig iron from the direct reduction and smelting plant as well as from the blast furnace process is fed into the secondary metallurgy in the integrated steelworks (1) as quickly as possible in order to process the desired steel and cast it into semi-finished products, such as flat or long products.

[0027] In addition to iron ore (io), the direct reduction reactor (2) must also be fed with a reducing gas to expel the oxygen from the ore. This reducing gas can consist of hydrogen and / or hydrocarbon-containing and / or carbonaceous compounds or mixtures (2.7) and flows through the reactor (2) from bottom to top in a countercurrent flow. The reducing gas (2.1) is heated to the required operating temperature, for example, between 600 and 1300 °C, in a reducing gas heater (20) before being fed.

[0028] Unused reducing gas, along with any gaseous reaction products, is removed from the direct reduction reactor (2) as process gas (2.2). The removed process gas (2.2) may contain hydrogen (H2), a compound or mixture of carbon and oxygen (CO, CO2), and / or at least one hydrogen-containing compound (H2O), as well as unavoidable impurities. In the standard process, the removed process gas (2.2) would be recycled to the direct reduction reactor (2), with fresh gas (2.7) additionally added to improve the reduction potential.

[0029] According to the invention, the process gas (2.2, 2.3, 2.4, 2.5, 2.9) discharged from the direct reduction reactor (2) is at least partially mixed with the hot blast (4.1*) and / or at least partially with a feed material (4.2) which is / or is blown into the blast furnace (4). The process gas (2.2) discharged from the direct reduction reactor (2) is of particularly high energy and material value and can therefore be economically and ecologically utilized in the blast furnace process.

[0030] The cold blast (4.1) is heated to the required temperature in a blast heater (10) before being injected into the blast furnace (4) and then injected as hot blast (4.1*) through the tuyeres. The process gas (2.2, 2.3, 2.4, 2.5, 2.9) discharged from the direct reduction reactor (2) can be at least partially mixed with the hot blast (4.1*). Alternatively or additionally, the process gas (2.2, 2.3, 2.4, 2.5, 2.9) discharged from the direct reduction reactor (2) can be at least partially mixed with a feed material (4.3). Hydrogen, oil, natural gas, and / or coal powder (injected coal), for example, can be used as (additional) feed material (4.3), which can then be injected, particularly as a mixture (4.2), in addition to the hot blast (4.1*). The hot blast (4.1*) can be additionally enriched with oxygen (4.9) if required.

[0031] There are therefore several variants for economically and ecologically introducing the energetically and materially high-quality process gas (2.2, 2.3, 2.4, 2.5, 2.9) from the direct reduction reactor (2) into the blast furnace (4), which depend in particular on the operating mode (partial / full load) of the individual units (2, 4) and on the units present or not present (H2O, CO2 separation).

[0032] For example, the feed material (4.3) can be completely replaced by the process gas (2.2, 2.3, 2.4, 2.5) discharged from the direct reduction reactor (2). However, typically only a portion of the discharged process gas (2.2, 2.3, 2.4, 2.5) is added to the feed material (4.3), so that a mixed gas consisting of process gas (2.2, 2.3, 2.4, 2.5), feed material (4.3), and hot blast (4.1*) is injected into the blast furnace (4).

[0033] In the simplest variant, at least a portion of the discharged process gas (2.3, 2.9) is directly added to the hot blast (4.1*) and / or at least a portion directly to the feed material (4.3). This ensures direct supply via appropriate supply lines, without having to pass through a process gas conditioning stage (2.3, 2.9).

[0034] In a further variant, the discharged process gas (2.2) is passed through a water / vapor separation unit, for example, a condenser, and cooled accordingly, so that the water vapor (H2O) contained in the process gas (2.2) condenses and is thus separated. By condensing and discharging the condensate, the process gas (2.2) is "dehumidified" and then, as dehumidified process gas (2.4, 2.9), at least partially added to the hot blast (4.1*) and / or at least partially to the feed material (4.3).

[0035] In a further variant, the discharged process gas (2.2) is passed through a unit for carbon dioxide separation, for example through an amine scrubber, in order to separate the CO2 content, so that it can then be added as carbon dioxide-free process gas (2.5, 2.9) at least in part to the hot blast (4.1*) and / or at least in part to the feed material (4.3).

[0036] If only a portion of the discharged process gas (2.2) from the direct reduction process is recycled either via one of the variants (2.3, 2.9), (2.4, 2.9), or (2.5, 2.9), the remainder (2.6) can be recycled to the direct reduction reactor (2), particularly mixed with fresh gas (2.7), as mixed gas (2.8) to the reduction gas heater (20), and then fed to the direct reduction reactor (2) as warm reduction gas (2.1). If necessary, the warm reduction gas (2.1) can be additionally enriched with oxygen (2.10).

[0037] Furthermore, the energy balance of the integrated steelworks (1) can be substantially improved by using or recycling the process gas (3.1, 4.4, 5.1, 6.1) discharged from the electric furnace (3), coking plant (6), converter (5), and / or blast furnace (4). Furthermore, according to the invention, at least part of the process gas (4.4, 4.5) discharged from the blast furnace (4) is provided as fuel gas (4.6, 4.7) for firing the reduction gas heater (20) of the direct reduction reactor (2). For example, in addition to the fuel gas (4.6, 4.7) or as additional gas (4.6, 4.7) to the fuel gas for firing the reducing gas heater (20), the process gas (3.1) discharged from the electric furnace (3) can be used at least in part as fuel gas (4.6, 4.7) and / or the process gas (5.1) discharged from the converter (5) can be used at least in part as fuel gas (4.6, 4.7) and / or the process gas (6.1) discharged from the coking plant (6) can be used at least in part as fuel gas (4.6, 4.7).7) for firing the reduction gas heater (20) of the direct reduction reactor (2). Depending on the operating mode, the discharged process gas (3.1, 4.4, 5.1, 6.1) can be used for firing by only one unit (3, 4, 5, 6) or by several units (3, 4, 5, 6). Additional fuel gas (4.8) can be added or supplied as needed.

[0038] The process gas (4.4) discharged from the blast furnace (4), also called blast furnace gas, is used as standard, among other things, to fire the hot blast heaters (10), so that a part (4.5) can be diverted to fire the reduction gas heaters (20) and the remainder (4.4), in particular with further fuel gas (not shown), is used to fire the hot blast heaters (10).

[0039] The process gas (4.6) can be passed through a carbon dioxide separation unit to separate the CO2 content, so that a carbon dioxide-free process gas (4.7) with improved efficiency compared to (4.6) can then be provided for firing the reduction gas heater (20).

[0040] Furthermore, it is also possible (not in Fig.1), to provide the discharged process gas (3.1, 5.1, 6.1) from the electric furnace (3), coking plant (6) and / or converter (5) not only as fuel gas (4.6, 4.7) or as additional gas (4.6, 4.7) to the fuel gas for firing the reduction gas heater (20), but additionally or even alternatively to feed it to the blast furnace (4) via the tuyeres together with the hot blast (4.1*), the process gas (2.2, 2.3, 2.4, 2.5, 2.9) discharged from the direct reduction reactor (2) and the feed material (4.3) in order to economically utilize the process gases (3.1, 5.1, 6.1), in particular those low in nitrogen. Depending on the operating mode, the discharged process gas (3.1, 5.1, 6.1) can be used by only one unit (3, 5, 6) for blowing into the blast furnace (4) or by several units (3, 5, 6).

Claims

[1] A process for producing steel in an integrated steelworks (1), comprising at least one direct reduction reactor (2) for directly reducing iron ore to sponge iron, at least one electric furnace (3) for melting the sponge iron to pig iron or crude steel, at least one blast furnace (4) for melting iron ore to pig iron and at least one converter (5) for refining pig iron to crude steel, characterized by that the process gas (2.2, 2.3, 2.4, 2.5, 2.9) discharged from the direct reduction reactor (2) is at least partly admixed with the hot blast (4.1*) and / or at least partly with a feed material (4.3) which is blown into the blast furnace (4), wherein the process gas (4.4) discharged from the blast furnace (4) is at least partly provided as fuel gas (4.6, 4.7) for firing a reduction gas heater (20) of the direct reduction reactor (2). [2] Method according to claim 1, wherein the process gas (2.3, 2.9) is at least partly added directly to the hot blast (4.1*) and / or at least partly added directly to the feed material (4.3). [3] Method according to claim 1, wherein the process gas (2.2) is first dehumidified and then, as dehumidified process gas (2.4, 2.9), is added at least in part to the hot blast (4.1*) and / or at least in part to the feed material (4.3). [4] Method according to claim 1 or 3, wherein the CO2 content contained in the process gas (2.2) or in the dehumidified process gas (2.2) is separated and then added as carbon dioxide-free process gas (2.5, 2.9) at least in part to the hot blast (4.1*) and / or at least in part to the feed material (4.3). [5] Method according to one of claims 1 to 4, wherein the process gas (3.1) discharged from the electric furnace (3) is provided at least in part as fuel gas (4.6, 4.7) for firing the reducing gas heater (20) of the direct reduction reactor (2) and / or is fed at least in part to the blast furnace (4). [6] Method according to one of claims 1 to 4, wherein the integrated steelworks (1) comprises a coking plant (6) and wherein the process gas (6.1) discharged from the coking plant (6) is provided at least in part as fuel gas (4.6, 4.7) for firing the reducing gas heater (20) of the direct reduction reactor (2) and / or is fed at least in part to the blast furnace (4). [7] Method according to one of claims 1 to 4, wherein the process gas (5.1) discharged from the converter (5) is provided at least in part as fuel gas (4.6, 4.7) for firing the reducing gas heater (20) of the direct reduction reactor (2) and / or is fed at least in part to the blast furnace (4). [8] Method according to one of claims 5 to 7, wherein at least two discharged process gases (3.1, 4.4, 5.1, 6.1) are provided at least in part as fuel gas (4.6, 4.7) for firing the reducing gas heater (20) of the direct reduction reactor (2) and / or at least two discharged process gases (3.1, 5.1, 6.1) are fed at least in part to the blast furnace (4).

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