Steelmaking method and related plant network

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 steel making method and associated network of plants. [Background technology]

[0002] Steel can currently be produced through two main production routes. The production route that is currently most commonly used, called the "BF-BOF route", involves producing hot metal in a blast furnace by using a reducing agent, mainly coke, reducing the iron oxide in a converter process or basic oxygen furnace (BOF), and then converting the hot metal into steel. This route requires the use of large amounts of CO2 for both the production of coke from coal in the coking plant and the production of hot metal. 2 is released.

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

[0004] The currently predominant blast furnace-basic oxygen furnace (BF-BOF) pathway relies on coal as a reductant and fuel, and therefore requires CO2 reduction to meet climate change targets. 2 Reducing emissions is difficult. 2 There are two options to reduce emissions: maintain the BF-BOF route and use carbon capture and / or CO 2 The key to success is to implement carbon capture and storage (CCS or CCU) technologies or to explore new low-emission processes.

[0005] Therefore, CO 2A first step in reducing 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 in terms of process, so not all blast furnaces can be replaced with direct reduction equipment at once. Also, this switch from one route to the other represents both technical and economic challenges that must first be solved before a carbon-neutral production route is available. Therefore, there will be plants where different equipment coexists.

[0006] And while 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, CO 2 There is a need for a method that allows steel to be produced according to a hybrid BF / DRI route with a reduced footprint. [Means for solving the problem]

[0008] This problem is now solved by the method according to the invention, which involves the production of hot metal and blast furnace top gas in a blast furnace, in which a direct reduction plant produces direct reduced iron and reduction furnace top gas with the aid of reducing gas, in which the reduction furnace top gas is at least partially reused as reducing gas, and which has a reduction rate of 200 Nm3 / tonne of hot metal produced. 3 ~700Nm 3 of hydrogen is injected, the top gas of the blast furnace is at least partially 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 gases in an electric furnace.

[0009] The method of the invention may also have the following optional features, taken 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 production process of hot metal, the coke oven gas being the or one of the hydrogen source for the hydrogen injected into the blast furnace, - Reducing gas for the direct reduced iron production process includes coke oven gas; - The reducing furnace gas is the source or one of the sources of hydrogen injected into the blast furnace; - the 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 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 recovering in a gas hub all gases released during steel production and redirecting them for reuse in 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 gas using reducing gas, and a reduction furnace gas having a gas content of 200 Nm3 / tonne of hot metal produced. 3 ~700Nm 3 the hydrogen injection means of the blast furnace and the blast furnace top gas are fed to the hydrogen injection means of the blast furnace and the blast furnace top gas is fed to the hydrogen injection means of the blast furnace and the blast furnace top gas is fed to the hydrogen injection means of the blast furnace and the blast furnace top gas is fed to the hydrogen injection means of the blast furnace and the blast furnace top gas is fed to the hydrogen injection means of the blast furnace and the blast furnace top gas is fed to the hydrogen injection means of the blast furnace and the blast furnace top gas is fed to the biochemical plant ...

[0011] Other characteristics and advantages of the 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 description of the drawings]

[0012] [Figure 1] 1 shows a network of plants making it possible to carry out the method according to the invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 device 5. In working mode, iron oxide ore and pellets 10 containing around 30% by weight of oxygen are charged at the top of the shaft furnace 9 and are allowed to fall by gravity via a reducing gas 11. This reducing gas 11, prepared by the gas preparation device 5, is injected into the furnace 9 in a countercurrent flow from the charged iron oxide. The oxygen contained in the ore and pellets is removed by stepwise reduction of the iron oxide in a countercurrent reaction of gas with the oxide. The oxidant content of the gas increases while the gas is moving to the top of the furnace. Reduced iron, also called DRI product 12, leaves the bottom of the furnace 9, whereas reduced top gas 13 leaves 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 main purpose is to produce hot metal 22, which is then converted into steel by reducing its carbon content. The blast furnace 2 is conventionally fed with solid materials, mainly sinter, pellets, iron ore, and carbonaceous materials, generally coke, which are charged at the top, called the throat of the blast furnace. Liquids, consisting of hot metal and slag, are removed from a basin at the bottom of the blast furnace 2. The iron-containing blast furnace charge (sinter, pellets and iron ore) is conventionally treated with reducing gases, notably CO, H, to convert the iron oxides into reducing gases. 2 and N 2 The hot metal 22 is converted into molten iron by reduction with a gas containing argon (including argon gas), which is formed by partial combustion of carbonaceous materials thanks to hot air 20 injected by a tuyere located at the bottom of the blast furnace, usually at a temperature between 1000 and 1300 °C. The injection of the reducing agent may also take place at the top of the blast furnace, above the tuyere, which is called 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 a 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 type of electric furnace 3 may be different. 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 part 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 charged cold. The electric furnace 3 may also be charged with hot metal 22 produced by a blast furnace and / or scrap. According to the technology and charge material used, the produced molten metal can either be sent to a converter to reduce the carbon content and / or sent to secondary metallurgy to refine the steel and bring it to the appropriate composition for further processing steps.

[0019] The biochemical plant 4 is a plant that converts the blast furnace gas 21A into alcohol using biology. It converts the CO or CO of the BFG into alcohol using microorganisms, bacteria or algae. 2 and H 2 It may be a fermentation or electrofermentation plant that converts the contents 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 so-called "coke ovens", which are insulated chambers. 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 sources that are naturally replenished on human timescales, including sources such as sunlight, wind, rain, tides, waves, and geothermal heat. 2 Since it does not emit any heat, electricity derived from nuclear sources can be used.

[0022] In the method according to the invention, at least a part 13A of the direct reduction furnace 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 Hydrogen between the two is injected into the blast furnace 2 and at least a portion 12A of the blast furnace top gas is sent to a biochemical plant 4.

[0023] Nm 3 is a unit of measurement for the amount of gas corresponding to the contents of one cubic metre of volume 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 the reducing gas 11. In a preferred embodiment, the direct reduction furnace gas 13 is recycled to a water removal unit and a CO 2 It is captured and treated in a first gas treatment unit 7, which may comprise a separation unit. The treated gas may be split into at least two streams, a first stream 13A being reused in the direct reduction plant as reducing gas 11 and a second stream 13B being 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 directly reduced top gas 13 may also be split into three or more streams and used as described in the previous embodiment.

[0026] 200-700Nm 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 in 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 the wustite content of the ferrous blast furnace charge at an early stage in the furnace, thus carrying out an in-situ metallization of the ferrous charge in the furnace. It therefore reduces the required charge of fossil carbon in the form of fine coal and coke, thus reducing the CO2 content of the process. 2 Reducing emissions and carbon footprint.

[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 inhomogeneous metallization of the iron-based blast furnace charge. 3 Injecting 700 Nm3 / 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 1000 / thm provides no additional benefit as this hydrogen does not react with the iron oxides and only contributes to heating 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, respectively, injected into the blast furnace 2.

[0030] In another embodiment, the hydrogen is provided by waste gas originating from a chemical plant, such as a plant for the production of hydrocarbons. This chemical plant may be independent of the steel plant. This allows to create synergies with the existing industrial environment of the steel plant and to further reduce the carbon footprint globally. The waste gas is gas resulting from chemical production that is not used in the chemical plant and may for example be directed to a flare with the aim of disposing of the gas.

[0031] In a further embodiment, the hydrogen is green hydrogen, which is a hydrogen-producing fuel obtained from the electrolysis of water by 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 tonne of hot metal in BF 3 The use of hydrogen reduces the required charge of fossil carbon in the form of powdered coal and coke, thus reducing the CO 2 Reduce emissions and carbon footprint.

[0034] In a preferred embodiment, the reduction 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 aforementioned hydrogen sources, but preferentially is green hydrogen.

[0035] In the method according to the invention, the blast furnace gas 21 or BFG is at least partially sent to a biochemical plant 4 to produce hydrocarbons. The blast furnace gas 21 is recovered and processed in a second gas processing unit 8. This second gas processing unit 8 comprises, among others, a dust filter unit, a water remover, a CO 2 removal device such as a pressure swing adsorption device, 2 and a separation unit. The BFG can be split into two streams 21A, 21B, the first stream 21A being sent to the biochemical plant 4 and the remaining stream 21B being sent to the direct reduction plant 1, where 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 tuyere level. The BFG can also be split into three streams that are 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 is able to recover all the gases released in the steel making process, as well as the available external gases, and redirect them for reuse within the steel making process, according to each gas composition and each process's needs, both in terms of 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 an improved overall management of the different gases and energy needs of the system, and therefore a reduction of the carbon footprint.

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

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

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

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

Claims

1. A method for producing steel, comprising the steps of: a. Producing direct reduced iron (12) and reduction furnace gas (13) in a direct reduction plant (1), the reduction furnace gas (13) being at least partially (13A) recycled as the reducing gas (11); 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 / tonne of hot metal to be produced. ３ ~700Nm ３ of hydrogen (20) is injected and the blast furnace top gas (21A) is sent at least in part to a biochemical plant (4) to produce hydrocarbons, 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); The method includes:

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

3. 3. The method according to claim 1 or 2, wherein hydrogen (20) is injected into the shaft of the blast furnace (2).

4. The method according to any one of claims 1 to 3, wherein the or one of the sources of hydrogen (20) injected into the blast furnace (2) is waste gas from the chemical industry.

5. 5. The method according to claim 1, further comprising a 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, the coke oven gas (62) being the or one of the sources of hydrogen (20) injected into the blast furnace (2).

6. 6. The method of claim 5, wherein the reducing gas (11) for the direct reduced iron production process comprises coke oven gas (62).

7. The method according to any one of the preceding claims, wherein the reduced furnace top gas (13C) is the or one of the sources of hydrogen (20) injected into the blast furnace (2).

8. The method according to any one of the preceding claims, wherein the reducing top gas (13) is injected at least partially as a reducing agent into the shaft of the blast furnace (2).

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

10. The method according to any one of the preceding claims, wherein the hydrogen is added to the blast furnace gas (21) before its use in the biochemical plant (4).

11. The method according to any one of the preceding claims, 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.

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

14. The method according to any one of the preceding claims, wherein green hydrogen is injected into the blast furnace (2).

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

16. 16. The method according to any one of claims 1 to 15, further comprising the step of recovering all gases released during steel production in a gas hub and redirecting them for reuse within the steel production process.

17. The method according to any one of claims 1 to 16, wherein all steps are supplied with renewable energy.

18. The method according to any one of the preceding claims, wherein the hot metal (22) is used in an electric furnace (3) to produce molten metal.

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

20. A network of a plant, comprising: a. a direct reduction plant (1) for producing direct reduced iron (12) and reduction furnace gas (13) using a reducing gas (11); b. 200 Nm per tonne of hot metal produced ３ ~700Nm ３ a blast furnace (2) for producing molten iron and blast furnace top gas (21), comprising means for injecting hydrogen (20) between c. an electric furnace for producing molten metal and electric furnace gases using at least a portion of the produced direct reduced iron (12); 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 a hydrogen injection means of the blast furnace (2); iii. The blast furnace gas (21A) is at least partially sent to a biochemical plant (4) for the production of hydrocarbons. A gas distribution system designed to enable The plant network includes:

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