Method for producing steel in an integrated metallurgical plant

Abstract

The invention relates to a method for producing steel in an integrated metallurgical plant (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 obtain pig iron or crude steel, at least one blast furnace (4) for smelting iron ore to obtain pig iron, and at least one converter (5) for refining the pig iron to obtain crude steel. According to the invention, process gases (2.2, 2.3, 2.4, 2.5, 2.9) discharged from the direct reduction reactor (2) are at least partially mixed with hot blast air (4.1 * ) blown into the blast furnace (4) and / or at least partially mixed with optional charging material (4.3) blown into the blast furnace (4).

Description

Technical Field

[0001] This invention relates to a method for producing steel in an integrated metallurgical plant. Background Technology

[0002] For example, EP 1 641 945 B1 discloses a method for producing steel in an integrated metallurgical plant. The use of an additional furnace in the integrated metallurgical plant is shown on the applicant's homepage https: / / www.thyssenkrupp-steel.com / de / unternehmen / nachhaltigkeit / klimastrategie / “Zwei Technologiepfade-ein Ziel”. Summary of the Invention

[0003] The purpose of this invention is to further develop this method so that the process gases with energy and material value present in existing integrated metallurgical plants can be utilized in an economically optimized manner.

[0004] This objective is achieved by a method for producing steel in an integrated metallurgical plant comprising at least one direct reduction reactor for directly reducing iron ore to sponge iron; at least one electric furnace for melting sponge iron to obtain pig iron or crude steel; at least one blast furnace for smelting iron ore to obtain pig iron; and at least one converter for refining pig iron to obtain crude steel, wherein, according to the invention, process gases discharged from the direct reduction reactor are at least partially incorporated with hot blast and / or at least partially incorporated with selective charging materials, said hot blast and / or said charging materials being blown into the blast furnace.

[0005] In at least one direct reduction reactor, sponge iron is produced from iron ore using a reducing gas, which may consist of hydrogen and / or methane (natural gas), and then melted in at least one furnace to obtain crude steel or pig iron. Alternatively, in at least one blast furnace, iron ore and coke produced from coal from a coking plant are smelted into pig iron, which is then converted into crude steel in a converter, particularly an oxygen converter, through refining, and thereby through decarburization, desulfurization, and / or dephosphorization, in particular. The aforementioned equipment and corresponding methods are existing technologies and processes commonly used in practice.

[0006] Surprisingly, it has been recognized that the process gases discharged from the direct reduction reactor have high energy and material value, and can therefore be utilized in an economical and ecological manner in the blast furnace process in an integrated metallurgical plant, through tuyeres, especially through blast torches.

[0007] The process gas discharged from the direct reduction reactor can be at least partially incorporated into or replace selective feed materials. This can, in particular, partially or completely replace expensive components used in the feed, such as hydrogen or carbon dioxide-intensive components, such as coal and / or natural gas, thereby reducing feedstock costs and the carbon footprint.

[0008] Standard practice uses air as cold blast, which is heated to the required temperature in a blast heater (Cowper) before being blown into the blast furnace as hot blast through the tuyeres. If necessary, additional oxygen may be mixed in before and / or after heating. Pressure may also be increased before and / or after heating. Depending on the blast furnace capacity, two or more blast heaters operate alternately (their function is known). Alternatively or additionally, process gases discharged from the direct reduction reactor may be at least partially mixed with the hot blast.

[0009] Whether the hot blast and / or selective charging materials can be completely replaced by process gases discharged from the direct reduction reactor depends on the design and operation of the corresponding equipment in the integrated metallurgical plant. At least a portion of the discharged process gases is supplied to the blast furnace through tuyeres, allowing a mixture of process gases, hot blast, and selective charging materials to be blown in.

[0010] The expression "at least a portion of the discharged process gases" means that only a portion of the discharged process gases are supplied to the blast furnace, while the remainder are used outside the blast furnace process, or are supplied entirely to the blast furnace process.

[0011] Mixing can also be understood as supplying.

[0012] The process gas discharged from the direct reduction reactor contains unreacted portions, depending on the composition of the reducing gas used. These portions can be economically used in the blast furnace process to reduce and smelt iron ore, coke and other additives. In particular, it contains compounds or mixtures of carbon and oxygen (CO, CO2), methane (CH4), hydrogen (H2) and / or water vapor (H2O), as well as impurities that are unavoidable due to process limitations.

[0013] According to one design of the invention, at least a portion of the discharged process gas is directly mixed with hot blast and / or at least a portion is directly mixed with selective charging materials. This means that the process gas discharged from the direct reduction reactor can be directly, especially via corresponding supply lines, supplied to the blast furnace process, preferably without needing to go through a stage for processing the process gas.

[0014] According to an alternative design of the invention, the discharged process gas is first dehumidified, and then at least partially blended with hot blast and / or at least partially blended with a selective charge material. The discharged process gas passes through a unit, such as a condenser, and is accordingly cooled, causing water vapor in the process gas to condense and be removed from the process gas. The process gas is "dehumidified" through condensation and condensate discharge. This improves the quality of the process gas.

[0015] In another embodiment of the invention, the discharged CO2 component contained in the process gas or dehumidified process gas is removed, and then the gas is at least partially blended with hot blast and / or at least partially blended with selective charging materials in a blast furnace as a CO2-free process gas. The process gas passes through at least one unit in which a compound or mixture of carbon and oxygen, such as carbon dioxide (CO2), is separated, for example by amine washing, carbonate washing, various membrane separation technologies (e.g., selective membranes), or pressure swing absorption (PSA). To further improve climate balance, the carbon dioxide separated from the process gas can be stored in a suitable environment, for example, by carbon capture and storage (CCS), or used for material utilization in a carbon capture and utilization (CCU) process. Furthermore, carbon dioxide (CO2) can also be utilized as a cooling gas or as part of the cooling gas in the selective cooling zone of a direct reduction process.

[0016] In a direct reduction reactor, a reducing gas is introduced to reduce iron ore to obtain sponge iron. This reducing gas is first heated to an appropriate temperature in a reducing gas heater before being introduced into the reduction zone of the direct reduction reactor.

[0017] Therefore, according to one design of the present invention, the process gas discharged from the electric furnace, serving as fuel gas or auxiliary gas for the combustion reducing gas heater, can at least partially provide fuel gas for the reducing gas heater of the combustion direct reduction reactor. Alternatively or additionally, at least a portion of the process gas discharged from the electric furnace can be blown into the blast furnace through a tuyer.

[0018] The integrated metallurgical plant also includes a coking plant that produces coke from coal in a nearby location for use in the blast furnace process. According to an alternative design of the invention, process gases discharged from the coking plant can at least partially serve as fuel gas for a reducing gas heater used to burn the direct reduction reactor. Alternatively or additionally, at least a portion of the process gases discharged from the coking plant can be blown into the blast furnace through tuyeres.

[0019] The integrated metallurgical plant also includes a steelmaking plant with at least one converter, such as an LD converter (also known as a BOF converter), in which pig iron is optimized to obtain crude steel for subsequent processing; wherein, according to another alternative design according to the invention, the process gas discharged from the converter can be at least partially provided as fuel gas for combustion of the reducing gas heater in the direct reduction reactor. Alternatively or additionally, the process gas discharged from the converter can be at least partially blown into the blast furnace through a tuyer.

[0020] According to another alternative design of the invention, at least a portion of the process gas discharged from the blast furnace may be provided as fuel gas for a reducing gas heater used to burn the direct reduction reactor.

[0021] Using process gases discharged from electric furnaces, coking plants, converters, or blast furnaces can greatly improve the energy balance of integrated metallurgical plants.

[0022] According to one embodiment of the invention, if at least two process gases discharged from electric furnaces, coking plants, converters, and blast furnaces are combined and at least partially provided as fuel gas for a reducing gas heater used to burn the reducing gas in a direct reduction reactor, the energy balance can be further improved. Alternatively or additionally, at least two process gases discharged from electric furnaces, coking plants, and converters can be combined and at least partially blown into the blast furnace through tuyeres. Attached Figure Description

[0023] The following is combined with Figure 1 The invention will be described in detail with the aid of the following embodiments. Figure 1 An example of the method of the present invention is shown in a schematic diagram of an integrated metallurgical plant for producing steel or pig iron. Detailed Implementation

[0024] The integrated metallurgical plant (1) includes at least one direct reduction reactor (2) for directly reducing iron ore (io) to sponge iron; at least one electric furnace (3) for melting sponge iron to obtain crude steel or pig iron; at least one blast furnace (4) for smelting iron ore (io), especially using coke, pulverized coal and other additives, to obtain pig iron; and at least one converter (5) for refining pig iron to obtain crude steel. In addition, the integrated metallurgical plant (1) also includes at least one coking plant (6) for coking coal into coke.

[0025] Iron ore (io) is introduced into a direct reduction reactor (2), designed as a vertical shaft furnace and thus charged at the top, and also into a blast furnace (4) along with coke from a coking plant (6) and other additives, such as limestone, especially through stratified charge. At the bottom of the direct reduction reactor (2), the resulting sponge iron is removed and fed into an electric furnace (3) to melt the sponge iron, especially with the addition of other additives such as scrap steel. The pig iron obtained from the blast furnace (4) must be refined in a converter (5) to obtain crude steel. The crude steel or pig iron obtained from the direct reduction and melting equipment, together with the crude steel or pig iron obtained from the blast furnace process, is supplied to the secondary metallurgical plant (1) in the fastest way possible for processing into the required steel products and casting into semi-finished products, such as flats or longs.

[0026] In addition to iron ore (io), the direct reduction reactor (2) must also be equipped with a reducing gas to remove oxygen from the ore. This reducing gas may consist of hydrogen and / or hydrocarbon and / or carbon compounds or mixtures (2.7) and flows through the reactor (2) from bottom to top in a countercurrent manner. Before loading, 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).

[0027] Unconsumed reducing gas, along with any possible gaseous reaction products, is discharged from the direct reduction reactor (2) as process gas (2.2). The discharged process gas (2.2) may contain hydrogen (H2), compounds or mixtures of carbon and oxygen (CO, CO2), and / or at least one hydrogen-containing compound (H2O), as well as unavoidable impurities. In standard processes, the discharged process gas (2.2) is recirculated back to the direct reduction reactor (2) in a loop, with additional fresh gas (2.7) blended in to enhance reduction potential.

[0028] According to the present invention, the process gases (2.2, 2.3, 2.4, 2.5, 2.9) discharged from the direct reduction reactor (2) are at least partially mixed with the hot blast (4.1). * The hot blast and / or at least partially mixed with selective charging material (4.2) is blown into the blast furnace (4). The process gas (2.2) discharged from the direct reduction reactor (2) has particularly high energy and material value, and therefore can be used in an economical and ecological manner in the blast furnace process.

[0029] Before being blown into the blast furnace (4), the cold blast (4.1) is heated to the required temperature in the air heater (10) and then used as hot blast (4.1). * The process gases (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).* ) Blending. Alternatively or additionally, the process gases (2.2, 2.3, 2.4, 2.5, 2.9) discharged from the direct reduction reactor (2) may be blended at least partially with selective feed materials (4.3). For example, hydrogen, petroleum, natural gas and / or pulverized coal (Einblaskohle) may be used as (further) feed materials (4.3), especially as mixtures (4.2) in the hot blast (4.1). * In addition to the above, additional air should be blown in. If necessary, hot air (4.1) should be used. * It is also rich in oxygen (4.9).

[0030] Therefore, there are many variant schemes that economically and ecologically introduce process gases of high energy and material value into the blast furnace (4) from the direct reduction reactor (2) (2.2, 2.3, 2.4, 2.5, 2.9). These variant schemes depend in particular on the operating mode (partial load / full load) of the individual equipment (2, 4) and the presence or absence of units (removal of H2O, CO2).

[0031] Thus, for example, the process gases (2.2, 2.3, 2.4, 2.5) discharged from the direct reduction reactor (2) can completely replace the selective charge material (4.3). However, in general, only a portion of the discharged process gases (2.2, 2.3, 2.4, 2.5) are mixed with the selective charge material (4.3), therefore, the mixture consists of the process gases (2.2, 2.3, 2.4, 2.5), the selective charge material (4.3), and the hot air (4.1). * The mixture of gases was blown into the blast furnace (4).

[0032] In the simplest variant, the discharged process gases (2.3, 2.9) are at least partially directly mixed with the hot blast (4.1). * It can be mixed directly with (4.3) and / or at least partially directly with optional charge materials. Therefore, it can be supplied directly for use via appropriate supply lines without going through the stages for processing process gases (2.3, 2.9).

[0033] In another variant, the discharged process gas (2.2) passes through a unit for removing water / water vapor, such as a condenser, and is accordingly cooled, causing the water vapor (H2O) in the process gas (2.2) to be condensed and thus separated. Through condensation and the discharge of the condensate, the process gas (2.2) is "dehumidified" and subsequently, as dehumidified process gas (2.4, 2.9), is at least partially mixed with hot blast air (4.1). * ) and / or at least partially mixed with selective charge material (4.3).

[0034] In another variant, the discharged process gas (2.2) passes through a unit for removing carbon dioxide, such as an amine scrubber, to remove the CO2 component, so that it can subsequently be used as a carbon dioxide-free process gas (2.5, 2.9) at least partially mixed with hot blast (4.1). * ) and / or at least partially mixed with selective charge material (4.3).

[0035] If only a portion of the process gas (2.2) discharged during the direct reduction process is utilized through one of the variant schemes (2.3, 2.9), (2.4, 2.9), or (2.5, 2.9), the remainder (2.6) can be looped to the direct reduction reactor (2), particularly mixed with fresh gas (2.7) as a mixed gas (2.8) and then fed to the reducing gas heater (20), and subsequently as hot reducing gas (2.1) to the direct reduction reactor (2). The hot reducing gas (2.1) can be further enriched with oxygen (2.10) if needed.

[0036] In addition, the energy balance of the integrated metallurgical plant (1) can be significantly improved by using and / or utilizing process gases (3.1, 4.4, 5.1, 6.1) emitted from the electric furnace (3), coking plant (6), converter (5) and / or blast furnace (4). For example, as fuel gas (4.6, 4.7) or auxiliary gas (4.6, 4.7) for igniting the reducing gas heater (20), at least part of the process gas (3.1) discharged from the electric furnace (3) can be provided as fuel gas (4.6, 4.7), and / or at least part of the process gas (5.1) discharged from the converter (5) can be provided as fuel gas (4.6, 4.7), and / or at least part of the process gas (4.4, 4.5) discharged from the blast furnace (4) can be provided as fuel gas (4.6, 4.7), and / or at least part of the process gas (6.1) discharged from the coking plant (6) can be provided as fuel gas (4.6, 4.7) for igniting the reducing gas heater (20) of the direct reduction reactor (2). Depending on the operating mode, the discharged process gases (3.1, 4.4, 5.1, 6.1) can be used for combustion by only one device (3, 4, 5, 6), or they can be utilized by multiple devices (3, 4, 5, 6). Additional fuel gases (4.8) can be mixed or supplied when needed.

[0037] The process gas (4.4) discharged from the blast furnace (4) is also called the furnace top gas. Its standard uses include combustion blast heaters (10), etc. Therefore, a portion (4.5) can be separated for combustion reducing gas heaters (20), and the remainder (4.4) can be used for combustion blast heaters (10) in particular, along with other fuel gases (not shown).

[0038] The process gas (4.6) can be decomposed by a unit for separating carbon dioxide to remove the CO2 component, so that a carbon dioxide-free process gas (4.7) can be subsequently provided, which is more efficient than the process gas (4.6) used for combustion in the reducing gas heater (20).

[0039] In addition, it can also ( Figure 1 (Not shown in the text) Process gases (3.1, 5.1, 6.1) discharged from the electric furnace (3), coking plant (6), and / or converter (5) are not only provided as fuel gases (4.6, 4.7) or auxiliary gases (4.6, 4.7) for the combustion reducing gas heater (20), but may also be additionally or even alternatively supplied with hot blast (4.1) through tuyeres. * The process gases (2.2, 2.3, 2.4, 2.5, 2.9) discharged from the direct reduction reactor (2) along with selective charging materials (4.3) are supplied to the blast furnace (4) to make economical use of process gases (3.1, 5.1, 6.1), especially those with low nitrogen content. Depending on the operating mode, the discharged process gases (3.1, 5.1, 6.1) can be blown into the blast furnace (4) by only one device (3, 5, 6) or by multiple devices (3, 5, 6).

Claims

1. A method for producing steel in an integrated metallurgical plant (1), said integrated metallurgical plant comprising at least one direct reduction reactor (2) for directly reducing iron ore to sponge iron; at least one electric furnace (3) for melting sponge iron to obtain pig iron or crude steel; at least one blast furnace (4) for smelting iron ore to obtain pig iron; and at least one converter (5) for refining pig iron to obtain crude steel, characterized in that, The process gases (2.2, 2.3, 2.4, 2.5, 2.9) discharged from the direct reduction reactor (2) are at least partially mixed with the hot blast (4.1). * The hot blast and / or the charging material is mixed and / or at least partially mixed with selective charging material (4.3), wherein the hot blast and / or the charging material is blown into the blast furnace (4) through a tuyer, wherein the process gas (3.1) discharged from the electric furnace (3) is at least partially provided as fuel gas (4.6, 4.7) for combustion of the reducing gas heater (20) of the direct reduction reactor (2) and / or at least partially provided to the blast furnace (4), and / or wherein the process gas (5.1) discharged from the converter (5) is at least partially provided as fuel gas (4.6, 4.7) for combustion of the reducing gas heater (20) of the direct reduction reactor (2) and / or at least partially supplied to the blast furnace (4).

2. The method of claim 1, wherein the process gas (2.3, 2.9) is at least partially directly reacted with the hot blast (4.1). * ) Blending and / or at least partially directly blended with selective charge materials (4.3).

3. The method of claim 1, wherein the process gas (2.2) is first dehumidified, and then, as the dehumidified process gas (2.4, 2.9), is at least partially mixed with hot blast air (4.1). * ) Blending and / or at least partially blending with selective charge materials (4.3).

4. The method of claim 1 or 3, wherein the CO2 component contained in the process gas (2.2) or the dehumidified process gas (2.4, 2.9) is removed, and then at least partially reacted with hot blast (4.1) as a carbon dioxide-free process gas (2.5, 2.9). * ) Blending and / or at least partially blending with selective charge materials (4.3).

5. The method of claim 1, wherein, The integrated metallurgical plant (1) includes a coking plant (6), and the process gas (6.1) discharged from the coking plant (6) is at least partially provided as fuel gas (4.6, 4.7) for combustion of the reducing gas heater (20) of the direct reduction reactor (2) and / or at least partially supplied to the blast furnace (4).

6. The method of claim 5, wherein at least a portion of the process gas (4.4) discharged from the blast furnace (4) is provided as fuel gas (4.6, 4.7) for combustion of the reducing gas heater (20) of the direct reduction reactor (2).

7. The method of claim 6, wherein at least two of the discharged process gases (3.1, 4.4, 5.1, 6.1) are at least partially provided as fuel gases (4.6, 4.7) for combustion of the reducing gas heater (20) of the direct reduction reactor (2) and / or at least two of the discharged process gases (3.1, 5.1, 6.1) are at least partially supplied to the blast furnace (4).

Images