Steelmaking methods and related plant networks

Abstract

In a direct reduction plant (1), reducing gas (11) is used to produce direct reduced iron (12) and reduction furnace top gas (13), the reduction furnace top gas (13) being at least partially (13A) recycled as the reducing gas (11) to produce hot metal and blast furnace top gas (21) in a blast furnace (2), where a reduction gas concentration of 200 Nm3 / tonne of hot metal produced is reached. 3 ~700Nm 3 and at least a portion of the direct reduced iron (12) produced is used to produce molten metal and electric furnace gas in an electric furnace (3).

Description

[Technical Field]

[0001] The present invention relates to a steelmaking method and an associated network of plants. [Background technology]

[0002] Steel can currently be produced through two main production routes. The most commonly used route, known as the "BF-BOF route," involves producing molten iron in a blast furnace by using a reducing agent, primarily coke, and then converting it into hot metal in a converter process. ,for example The first is to reduce the iron oxide in a basic oxygen furnace (BOF) and then convert the hot metal to steel. This route releases large amounts of CO2, both in the production of coke from coal in a coking plant and in the production of hot metal.

[0003] The second main route involves the so-called "direct reduction process", which involves the direct reduction of an iron oxide support to produce sponge iron in the form of HDRI (hot direct reduced iron), CDRI (cold direct reduced iron) or HBI (hot briquette iron), among others, under brands such as MIDREX, FINMET, ENERGIRON / HYL, COREX, FINEX, etc. Sponge iron in the form of HDRI, CDRI and HBI is usually subjected to further processing in an electric furnace.

[0004] The currently dominant blast furnace-basic oxygen furnace (BF-BOF) pathway relies on coal as a reducing agent and fuel, making it difficult to reduce CO2 emissions to meet climate change targets. There are two options for reducing CO2 emissions from steelmaking: maintaining the BF-BOF pathway and implementing carbon capture and / or storage (CCS or CCU) technologies, or exploring new low-emission processes.

[0005] Therefore, a first step in reducing CO2 emissions could be to switch from the BF-BOF route to the DRI route. This represents a major change both in terms of equipment and process, so not all blast furnaces can be replaced with direct reduction equipment at once. Also, this switch from one route to another represents both technical and economic challenges that must first be overcome before a carbon-neutral production route becomes available. Therefore, there will likely be plants where different equipment coexists.

[0006] Also, although an ever-increasing portion of steel demand will be covered by scrap / DRI-based production, the need for steel production remains high and traditional BF technology is still expected to be the primary production route for decades to come. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, there is a need for a method that allows steel to be produced according to a hybrid BF / DRI route with a reduced CO2 footprint. [Means for solving the problem]

[0008] This problem is now solved by a method according to the invention, which involves producing hot metal and blast furnace top gas in a blast furnace using reducing gas in a direct reduction plant, in which the reducing gas is at least partially reused as reducing gas, and the hot metal and blast furnace top gas are produced in a direct reduction plant with a reduction rate of 200 Nm3 per tonne of hot metal produced. 3 ~700Nm 3 of hydrogen is injected, at least a portion of the blast furnace top gas is sent to a biochemical plant to produce hydrocarbons, and at least a portion of the produced direct reduced iron is used to produce molten metal and electric furnace gas in an electric furnace.

[0009] The method of the invention may also have the following optional features, considered separately or according to all possible technical combinations: - Hydrogen is injected into the blast furnace at a temperature comprised between 750 and 1100°C. - Hydrogen is injected into the shaft of the blast furnace, - the source or sources of hydrogen injected into the blast furnace are waste gases from the chemical industry; - the method further comprises the step of producing coke and coke oven gas in a coke plant, the coke being at least partially charged into a blast furnace for the process of producing hot metal, and the coke oven gas being the or one of the hydrogen source for the hydrogen injected into the blast furnace, - Reducing gases for direct reduced iron production processes include coke oven gas; - The reducing furnace top gas is the source or one of the sources of hydrogen injected into the blast furnace; - reducing furnace top gas is injected into the shaft of the blast furnace at least partially as a reducing agent; - the reduced furnace top gas is at least partially sent to a biochemical plant to produce hydrocarbons; - Hydrogen is added to the blast furnace top gas before its use in the biochemical plant; - the reducing gas for the direct reduced iron production process contains at least 70% v hydrogen; - the hydrogen is green hydrogen, - The molten metal produced in the electric furnace is converted into molten steel in the converter. - Green hydrogen will be injected into blast furnaces, - Blast furnace top gas is reused as a reducing agent in the blast furnace. - the method further comprises the step of collecting in a gas hub all gases released during steel production and redirecting them for reuse within the steel production process, - All processes are powered by renewable energy; - Hot metal is used in electric furnaces to produce molten metal, - Scrap is used in electric furnaces to produce molten metal.

[0010] The present invention also relates to a direct reduction plant for producing direct reduced iron and reduction furnace top gas using reducing gas, and a reduction furnace top gas having a gas content of 200 Nm3 per ton of hot metal produced. 3 ~700Nm 3 the direct reduction plant is at least partially recycled as reducing gas in the direct reduction plant, hydrogen is supplied to the hydrogen injection means of the blast furnace, and the blast furnace top gas is at least partially sent to the biochemical plant for hydrocarbon production.

[0011] Other characteristics and advantages of the present invention will become apparent from the following description of the invention, given by way of example and in no way limiting, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows a network of plants making it possible to implement the method according to the invention; DETAILED DESCRIPTION OF THE INVENTION

[0013] Elements in the figures are illustrative and may not be drawn to scale.

[0014] FIG. 1 shows a network of plants comprising a direct reduction plant 1 , a blast furnace 2 , an electric furnace 3 and a biochemical plant 4 .

[0015] The direct reduction plant 1 comprises a shaft furnace 9 and a gas preparation unit 5. In operation, iron oxide ore and pellets 10 containing approximately 30% oxygen by weight are charged to the top of the shaft furnace 9 and allowed to descend by gravity via reducing gas 11. This reducing gas 11, prepared by the gas preparation unit 5, is injected into the furnace 9 countercurrently to the charged iron oxide. The oxygen contained in the ore and pellets is removed by gradually reducing the iron oxide in a countercurrent reaction between the gas and the oxide. The oxidant content of the gas increases as the gas moves to the top of the furnace. Reduced iron, also referred to as DRI product 12, exits the bottom of the furnace 9, while reduced top gas 13 exits the top of the furnace 9. This reduced top gas 13 is captured and treated in a first gas treatment unit 7. The composition of this reduced top gas 13 varies depending on the composition of the reducing gas 11 injected into the shaft furnace 9.

[0016] The blast furnace 2 is a gas-liquid-solid countercurrent chemical reactor whose primary purpose is to produce hot metal 22, which is then converted to steel by reducing its carbon content. The blast furnace 2 is conventionally fed with solid materials, primarily sinter, pellets, iron ore, and carbonaceous materials, commonly coke, charged into the upper part of the furnace, known as the throat. Liquids, consisting of hot metal and slag, are removed from a basin at the bottom of the furnace. The iron-containing blast furnace charge (sinter, pellets, and iron ore), is conventionally converted to hot metal 22 by reducing iron oxide with reducing gas (particularly CO, H2, and N2), which is formed by partial combustion of the carbonaceous materials thanks to hot air 20 injected through tuyeres located at the bottom of the furnace, typically at temperatures between 1000 and 1300°C. Reducing agent injection may also occur at the top of the furnace, above the tuyeres, known as shaft injection.

[0017] The resulting gas is discharged at the top of the blast furnace and is called blast furnace top gas 21. This blast furnace top gas 21 is captured and treated in the second gas treatment unit 8. The composition of this blast furnace top gas 21 varies depending on the composition of the reducing agent injected into the blast furnace 2.

[0018] The electric furnace 3 may be of different types. In particular, it may be an electric arc furnace (EAF), a smelting furnace, a submerged arc furnace (SAF) or an open slag bath furnace (OSBF). The purpose of this furnace is to melt the charge material, which is at least a portion of the direct reduced iron 12 produced by the direct reduction plant 1. This direct reduced iron 12 can be charged hot directly at the outlet of the direct reduction plant 1 or cold. The electric furnace 3 may also be charged with hot metal 22 produced by a blast furnace and / or scrap. Depending on the technology and charge material used, the molten metal produced can either be sent to a converter to reduce the carbon content and / or sent to secondary metallurgy to refine the steel and make it of the appropriate composition for further processing steps.

[0019] Biochemical plant 4 is a plant that uses biology to convert blast furnace top gas 21A into alcohol. It can be a fermentation or electrofermentation plant that uses microorganisms, bacteria, or algae to convert the CO or CO2 and H2 content of the BFG into hydrocarbons, such as ethanol.

[0020] In the embodiment of Figure 1, the plant further comprises a coke plant 6, which is optional for carrying out the method according to the invention. Coke 61 is produced by heating coal to very high temperatures, typically around 1000°C, in a so-called "coke oven", which is an insulated chamber. During the processing of the coal, organic material in the coal blend evaporates or decomposes, producing coke oven gas (COG) 62 and coal tar, a thick, dark liquid used in industry and medicine.

[0021] In preferred embodiments, these plants are all powered by renewable energy, which is defined as energy collected from renewable resources that are naturally replenished on human timescales, including sources such as sunlight, wind, rain, tides, waves, and geothermal heat. In some embodiments, electricity derived from nuclear sources can be used, as no CO2 is produced.

[0022] In the method according to the present invention, at least a part 13A of the direct reduction furnace top gas is recycled as reducing gas 11, and the reduction gas is 200 to 700 Nm3 per ton of hot metal to be produced. 3 The hydrogen between them is injected into the blast furnace 2 and at least a portion 12A of the blast furnace top gas is sent to the biochemical plant 4.

[0023] Nm 3 is a unit of measure of the amount of gas corresponding to the contents of a volume of one cubic meter under normal conditions of temperature and pressure (0°C and 1 atmosphere).

[0024] The combination of these different features makes it possible to use both DRI and blast furnace processes while reducing the overall carbon footprint of the process.

[0025] At least a portion 13A of the direct reduction furnace gas 13 is recycled as reducing gas 11. In a preferred embodiment, the direct reduction furnace gas 13 is captured and processed in a first gas processing unit 7, which may include, among other things, a water remover and a CO2 separation unit. The processed gas may be split into at least two streams: a first stream 13A is recycled as reducing gas 11 in the direct reduction plant, and a second stream 13B is sent to the biochemical plant 4 for conversion to hydrocarbons. In another embodiment, this second stream 13C may also be sent to the blast furnace 2 for use in the hot blast 20 or may be injected into the blast furnace shaft as a reducing agent after heating. The direct reduction top gas 13 may also be split into three or more streams and used as described in the previous embodiment.

[0026] 200-700 Nm per ton of hot metal produced 3 of hydrogen is injected into the blast furnace 2 as reducing gas. This hydrogen is preferentially injected at a temperature comprised between 750 and 1100°C, preferentially between 900 and 1000°C. This hydrogen may be injected into the shaft of the blast furnace 2 and / or at tuyere level as part of the hot blast.

[0027] This introduction of hydrogen allows partial reduction of wustite in the ferrous blast furnace charge at an early stage in the furnace, thus performing in situ metallization of the ferrous charge in the furnace, which therefore reduces the required charge of fossil carbon in the form of pulverized coal and coke, and therefore recue the CO2 emissions and carbon footprint of the process.

[0028] 200Nm 3 Below 700 Nm / thm there are some problems with the homogeneous distribution of reducing gas around the blast furnace, which may lead to disturbances caused by the heterogeneous metallization of the iron-based blast furnace charge. 3 Injecting 700 Nm / thm of hydrogen is sufficient to convert all the iron oxide in the ferrous blast furnace charge to metallic iron at the injection level. 3 Injecting hydrogen in excess of / thm does not provide any additional benefit as this hydrogen does not react with the iron oxides and only contributes to heating of the blast furnace top gas.

[0029] This hydrogen can come from several sources: it can be provided by or extracted from the coke oven gas 61. It can also come from the direct reduction top gas 13C and / or the blast furnace top gas 21C, with the composition of said gases depending on the composition of the reducing gas 11 and the reducing agent 20 injected into the blast furnace 2, respectively.

[0030] In another embodiment, the hydrogen is provided by waste gases originating from a chemical plant, such as a plant for hydrocarbon production. This chemical plant may be unrelated to the steel plant. This allows for synergies to be created with the existing industrial environment of the steel plant, further reducing the carbon footprint globally. The waste gases are gases resulting from chemical production that are not used in the chemical plant and may, for example, be directed to a flare for disposal purposes.

[0031] In a further embodiment, the hydrogen is green hydrogen, which is a hydrogen-producing fuel obtained from the electrolysis of water with electricity produced by a low-carbon power source, including in particular electricity from renewable sources as defined above.

[0032] All these different sources of hydrogen mentioned above can be mixed with each other to obtain the necessary reducing conditions in the blast furnace.

[0033] 200-700, preferably 200-670 Nm per ton of hot metal in BF 3 The use of hydrogen reduces the required charge of fossil carbon in the form of pulverized coal and coke, thus reducing the CO2 emissions and carbon footprint of the process.

[0034] In a preferred embodiment, the reducing gas 11 used in the direct reduction plant 1 also contains at least 70% by volume of hydrogen. This hydrogen can come from all the hydrogen sources mentioned above, but is preferentially green hydrogen.

[0035] In the method according to the invention, blast furnace top gas 21 or BFG is at least partially sent to a biochemical plant 4 to produce hydrocarbons. The blast furnace top gas 21 is recovered and processed in a second gas processing unit 8. This second gas processing unit 8 may comprise, among other things, a dust filter unit, a water remover, and a CO2 separation unit such as a pressure swing adsorption device. The BFG can be split into two streams 21A and 21B: the first stream 21A is sent to the biochemical plant 4, and the remaining stream 21B is sent to the direct reduction plant 1. There, the second stream can be used to heat the reducing gas 11 in the gas preparation unit 5 by direct heat exchange or by use as fuel in a burner. In another embodiment, this second stream 21C is reinjected into the blast furnace at the tuyere level. The BFG can also be split into three streams that can be used as described in the previous embodiment.

[0036] In a preferred embodiment, hydrogen from one of the aforementioned sources, such as coke oven gas 62A, 62B, can be added to the blast furnace top gas 21A and optionally to the direct reduction furnace top gas 13B to increase the hydrogen content before being sent to the biochemical plant 4. This makes it possible to optimize the production of hydrocarbons in the biochemical plant 4.

[0037] In a preferred embodiment, the steel plant comprises a gas hub (not shown), which recovers all gases released in the steel making process as well as available external gases and can redirect them for reuse within the steel making process according to each gas composition and each process's needs in terms of both reactants and energy. The hub is defined as a trading point that allows interchangeability between several streams. The gas hub is a conversion, conditioning and storage facility for internal and external wastes as well as multiple energy carriers such as flue gas, recovered hydrogen or green hydrogen. The presence of such an interconnected inlet / outlet system for gas supplies allows for an improved overall management of the different gas and energy needs of the system and therefore a reduction in the carbon footprint.

[0038] In a preferred embodiment, all gases emitted by the steel plant can be treated in a gas treatment unit to produce hydrogen, which is then reused within the steel plant, for example as a reducing agent in a blast furnace or direct reduction furnace.

[0039] The method according to the invention makes it possible to produce steel using a hybrid BF / DRI route with a reduced carbon footprint, which also allows for a sustainable transition from the most commonly used BF / BOF route to a DRI-based carbon-neutral route.

[0040] In the embodiment of Figure 1, all plants are shown together, but they may be located at different manufacturing sites and different gases and materials may be transported from one plant to another by suitable means.

[0041] All the different embodiments described can be used in combination with one another, where technically possible.

Claims

1. 1. A method of manufacturing steel, comprising the steps of: a. Producing direct reduced iron (12) and reduction furnace top gas (13) in a direct reduction plant (1) using a reducing gas (11), and the reduction furnace top gas (13) is at least partially recycled as the reducing gas (11) (13A); b. A process for producing hot metal and blast furnace top gas (21) in a blast furnace (2), with a gas pressure of 200 Nm3 per ton of hot metal to be produced. ３ ~700Nm ３ the hydrogen (20) is injected into a blast furnace, the blast furnace top gas (21A) is sent at least in part to a biochemical plant (4) to produce hydrocarbons, and the reduced furnace top gas (13C) is the or one of the sources of hydrogen (20) injected into the blast furnace (2), c) Producing molten metal and electric furnace gas in an electric furnace (3) using at least a portion of the produced direct reduced iron (12) and molten iron produced in a blast furnace; A method comprising:

2. 2. The method of claim 1, wherein the hydrogen (20) is injected into the blast furnace (2) at a temperature comprised between 750 and 1100°C.

3. 2. The method of claim 1, wherein the hydrogen (20) is injected into a shaft located at the top of the blast furnace (2) and above the tuyere.

4. 3. The method of claim 2, wherein the hydrogen (20) is injected into the shaft located at the top of the blast furnace (2) and above the tuyere.

5. The method according to any one of claims 1 to 4, wherein the or one of the sources of hydrogen (20) injected into the blast furnace (2) is waste gas from the chemical industry.

6. 5. The method according to claim 1, further comprising the step of producing coke (61) and coke oven gas (62) in a coke plant (6), the coke (61) being at least partially charged into a blast furnace (2) for a hot metal production process, and the coke oven gas (62) being the or one of the sources of hydrogen for the hydrogen (20) injected into the blast furnace (2).

7. 7. The method of claim 6, wherein the reducing gas (11) for the direct reduced iron production process comprises coke oven gas (62).

8. 5. The method according to any one of claims 1 to 4, wherein the reducing top gas (13) is injected at least partially as a reducing agent into the upper part of the blast furnace (2) and into a shaft located above the tuyere.

9. The method according to any one of claims 1 to 4, wherein the reduced furnace top gas (13B) is at least partly sent to a biochemical plant (4) to produce hydrocarbons.

10. A method described in any one of claims 1 to 4, wherein the hydrogen is added to the blast furnace gas (21) before the blast furnace gas (21) is used in the biochemical plant (4).

11. The method according to any one of claims 1 to 4, wherein the reducing gas (11) for the direct reduced iron production process comprises at least 70%v hydrogen.

12. 12. The method of claim 11, wherein the hydrogen is green hydrogen obtained from the electrolysis of water with electricity produced by a low-carbon power source.

13. A method according to any one of claims 1 to 4, wherein the molten metal produced in the electric furnace (3) is converted into molten steel in a converter.

14. 5. The method according to any one of claims 1 to 4, wherein green hydrogen is injected into the blast furnace (2), the green hydrogen being hydrogen obtained from the electrolysis of water using electricity produced by a low-carbon power source.

15. The method according to any one of claims 1 to 4, wherein the blast furnace top gas (21C) is reused as a reducing agent in the blast furnace.

16. The method according to any one of claims 1 to 4, wherein the scrap is used in an electric furnace (3) to produce molten metal.

17. A plant, a. A direct reduction plant (1) that uses a reducing gas (11) to produce direct reduced iron (12) and a reduction furnace top gas (13); b. 200 Nm per tonne of hot metal produced ３ ~700Nm ３ a blast furnace (2) for producing hot metal and blast furnace top gas (21), equipped with means for injecting hydrogen (20) between c. an electric furnace that produces molten metal and electric furnace gas using at least a portion of the produced direct reduced iron (12) and molten iron produced in the blast furnace; d. A biochemical plant (4) capable of producing hydrocarbons; e. A gas distribution system comprising: i. The reduction furnace gas (13) is at least partially (13A) recycled as reducing gas (11) in the direct reduction plant (1); ii. Hydrogen is supplied to the hydrogen injection means of the blast furnace (2); iii. The blast furnace top gas (21A) is at least partially sent to a biochemical plant (4) for hydrocarbon production; iv. The reduced furnace top gas (13) is used as a source of hydrogen to be injected into the blast furnace. A gas distribution system designed to allow Plants including.

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