Ironmaking methods and related plants

Abstract

A method for producing molten iron in at least one blast furnace (1) comprising at least two levels of gas injection (3A, 3B) and releasing a blast furnace top gas (10) during operation, the method comprising at least the steps of: charging the blast furnace with an iron-containing charge (4) and a first carbon-based reductant (5), injecting at the first level (3A) hot blast (11) having a temperature of at least 1000° C., said hot blast containing oxygen (6), recovering the blast furnace top gas and extracting hydrogen to produce a H2-rich stream (13) containing more than 90%v of hydrogen and a H2-lean stream (12), injecting the H2-rich stream (11) into the blast furnace at the second level (3B) of gas injection. Related network of plants.

Description

[Technical Field]

[0001] The present invention relates to a method of making iron and an associated ironmaking plant. [Background technology]

[0002] In blast furnaces, the conversion of iron-containing charges (sinter, pellets and iron ore) into cast iron or hot metal is traditionally carried out by the reduction of iron oxide with reducing gases (including, among others, CO, H2 and N2), which are formed by the partial combustion of coke and ultimately auxiliary reducing agents in tuyeres located at the bottom of the blast furnace, where air preheated to temperatures between 1000°C and 1300°C, called hot blast, is injected.

[0003] Auxiliary reducing agents that can be injected into the tuyere to improve productivity and reduce costs can be coal in pulverized form, fuel oil, natural gas or other fuels in combination with oxygen enrichment of the hot blast.

[0004] The gas recovered at the top of the blast furnace is called top gas and consists mainly of CO, CO2, H2 and N2 in proportions of 20-28%v, 17-25%v, 1-5%v and 48-55%v, respectively. Despite the partial use of this gas as fuel in other plants such as power plants, the blast furnace remains a significant producer of CO2.

[0005] Considering the considerable increase in atmospheric CO2 concentrations since the beginning of the last century and the subsequent greenhouse effect, it is essential to reduce CO2 emissions where CO2 is produced in large quantities, especially in blast furnaces.

[0006] To this end, the consumption of reducing agents in blast furnaces has been halved over the past 50 years, so that today, in conventionally configured blast furnaces, the carbon consumption has reached the lower limit associated with the laws of thermodynamics.

[0007] One solution that has been considered to further reduce this carbon-based reducing agent consumption, and therefore the CO2 footprint of blast furnace ironmaking production, is to capture the top gas, remove the CO2, and reinject it into the blast furnace shaft, which is at an elevation above the normal tuyere injection height of the hot air. However, with this solution, the reduction in reducing agent consumption remains less than 30% compared to production in a conventional blast furnace (without top gas recycling), according to numerous calculations and trials that have been carried out. In terms of the global CO2 footprint, this corresponds to a reduction of less than 20% by volume of CO2 emitted. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, there is a need for an ironmaking method that allows for a significant reduction in the consumption of carbon-based reducing agents in the blast furnace. [Means for solving the problem]

[0009] This problem is solved by a method according to the invention for producing hot metal in at least one blast furnace comprising at least two levels of gas injection and which, in operation, emits blast furnace top gas, the method comprising at least the following steps: charging an iron-containing charge and a first carbon-based reductant into the blast furnace; injecting, at a first level, hot blast having a temperature of at least 1000°C, the hot blast containing oxygen; recovering the blast furnace top gas; extracting hydrogen from the blast furnace top gas to produce an H-rich stream and an H-lean stream containing more than 90%v of hydrogen; and injecting the H-rich stream into the blast furnace at a second level of gas injection.

[0010] The method of the invention may also have the following optional features, considered separately or according to all possible technical combinations: - the first carbon-based reductant comprises coke; the first carbon-based reductant comprises a non-fossil carbon reductant; the hot air further comprises at least one second carbon-based reducing agent; the second carbon-based reductant comprises a non-fossil carbon reductant; - Hydrogen produced in the hydrogen production process is added to the H2-rich stream before it is injected into the blast furnace; - the hydrogen production process is a water decomposition process that produces hydrogen and oxygen; - The hot air contains oxygen produced in the water splitting process. - The water splitting process is an electrolysis reaction. - The electrolysis reaction is powered by renewable energy, - The H2-rich stream is injected into the blast furnace at a temperature of 750°C to 1100°C. - 200 Nm per tonne of hot metal to be produced 3 ~700Nm 3 of hydrogen is injected into the blast furnace, - More than 50% by volume of the hydrogen injected into the blast furnace is hydrogen extracted from the blast furnace top gas; - Hydrogen extracted from the reduction furnace top gas of the direct reduced iron production process is added to the H2-rich stream before it is injected into the blast furnace.

[0011] The present invention also relates to a network of plants comprising at least one blast furnace producing molten iron and discharging blast furnace top gas, the blast furnace comprising first and second gas injection means respectively arranged at two different levels over the height of the blast furnace, the first injection means designed to inject hot blast air having a temperature of at least 1000°C into the blast furnace, the hot blast air comprising oxygen, the blast furnace comprising gas recovery and treatment equipment capable of capturing blast furnace top gas and extracting hydrogen from the blast furnace top gas to produce an H2-rich stream and an H2-lean stream, the second injection means designed to inject the H2-rich stream into the blast furnace.

[0012] The network of plants according to the invention may also have the following optional characteristics, which are considered separately or according to all possible technical combinations: the plant further comprises a hydrogen production plant and a hydrogen gas line making it possible to mix the hydrogen produced in the hydrogen production plant with the H2-rich stream before the H2-rich stream is injected into the blast furnace via the second injection means, - a hydrogen production plant is a water splitting plant that produces hydrogen and oxygen; the plant further comprises an oxygen gas line making it possible to inject the produced oxygen into the hot air before the hot air is injected into the blast furnace through the first injection means, The plant further comprises a direct reduction furnace producing direct reduced iron and a reduction furnace top gas, a second gas recovery and treatment device capturing the reduction furnace top gas and capable of extracting hydrogen from the reduction furnace top gas to produce a directly reduced H2 stream, and mixing means enabling the directly reduced H2 stream to be mixed with an H2-rich stream before the H2-rich stream is injected into the blast furnace.

[0013] Other characteristics and advantages of the invention will become apparent from the description thereof given below by way of indication and in no way limiting, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0014] [Figure 1] 1 shows an ironmaking plant making it possible to carry out a method according to one embodiment of the present invention; [Figure 2] 1 shows an iron-making plant making it possible to carry out a method according to a second embodiment of the invention; [Figure 3] 1 shows an iron-making plant making it possible to carry out a method according to a third embodiment of the invention; DETAILED DESCRIPTION OF THE INVENTION

[0015] First, it should be noted that on the drawings, the same reference numerals refer to the same elements regardless of the figure they feature in and regardless of the shape of those elements. Similarly, if elements are not specifically referenced in one of the figures, their reference can be easily found by referring to another figure.

[0016] It should also be noted that the drawings primarily represent one embodiment of the subject matter of the invention, but that other embodiments may exist that correspond to the definition of the invention. The elements in the drawings are illustrative and may not be drawn to scale.

[0017] 1 shows an iron-making plant making it possible to carry out a method according to one embodiment of the present invention. The plant comprises at least one blast furnace 1 in which an iron-bearing charge 4, such as sinter, pellets, iron ore, etc., is charged into the throat of the blast furnace 1 together with a first carbon-based reductant 5. This first carbon-based reductant may be coke, but is preferentially a non-fossil carbon-based reductant, such as biochar or biocoal or waste plastic.

[0018] Biochar or biocoal refers to charcoal produced by pyrolysis of biomass in the absence of oxygen. Biomass is renewable organic material derived from plants and animals. Biomass sources for energy include, among others, wood and wood processing waste (firewood, wood pellets, and wood chips, sawdust and waste from lumber and furniture factories, and black liquor, agricultural crops, and waste from pulp and paper mills), corn, soybeans, sugarcane, switchgrass, woody plants, and algae, as well as crop and food processing residues, biomaterials in municipal solid waste (paper, cotton, and wool products, as well as food, yard, and wood waste, and animal manure and human sewage).

[0019] The iron-bearing charge 4 is converted to hot metal by reduction of the iron oxide. According to the invention, this reduction is carried out as a result of three inputs: the first is the injection of a first carbonaceous reducing agent 5, the second is the injection of hot blast gas 11 at a first injection level 3A, and finally the injection of hydrogen at a second gas injection level 3B. For clarity, the reference signs 3A and 3B indicate both the injection levels and the associated injection means at the considered levels.

[0020] Furthermore, even though both gas injection heights 3A and 3B are shown as a pair of arrows in the figure, it should be noted that this is for illustrative purposes only, and that these two gas injections take place preferentially at their respective heights around the periphery of the blast furnace 1.

[0021] The hot blast 11 has a temperature above 1000°C, preferably between 1000°C and 1300°C, and contains oxygen 6 and preferably a second carbonaceous reductant 7. It is preferentially injected at the level of the generally known tuyeres, which are located at the bottom of the blast furnace 1. This second carbonaceous reductant 7 is preferentially in finely divided form and can be coal, but is preferentially a non-fossil carbonaceous reductant such as biochar or biocoal according to the explanation given above or waste plastic.

[0022] In a preferred embodiment, the hot blast is between 35 and 70 Nm3 per tonne of hot metal to be produced. 3 The oxygen content of the hot blast is 100%. Although higher levels are possible, adding oxygen within this range allows the hot blast flow rate to be maintained at a level that is compatible with good gas distribution in the lower part of the furnace, resulting in satisfactory operation of the blast furnace. The remaining component of the hot blast is air. This oxygen is preferentially mixed with the air before heating. This hot blast allows the combustion of coke in the tuyere, which is then converted into reducing gas that allows the reduction of iron ore.

[0023] Therefore, in the process according to the invention, there is a third input for the reduction of iron, consisting of hydrogen injected at the second height 3B of the blast furnace, preferentially at a shaft height above the tuyere level, at a temperature preferentially between 750°C and 1100°C, more preferentially between 900°C and 1000°C.

[0024] 200 Nm per ton of hot metal produced 3 ~700Nm 3 This hydrogen introduction allows partial reduction of the wustite in the ferrous blast furnace charge material at an early stage in the furnace, and performs in situ metallization of the ferrous charge in the furnace. 3Below 700 Nm / thm there are some problems with the homogeneous distribution of reducing gas around the blast furnace, which may lead to failures caused by inhomogeneous metallization of the iron-based blast furnace charge material. 3 Injecting 700 Nm / thm of hydrogen is sufficient to convert all iron oxide in the ferrous blast furnace charge material to metallic iron at the injection level. 3 Injecting hydrogen above 1 / thm would not provide any additional benefit since this hydrogen would not react with the iron oxides; it would only contribute to heating of the blast furnace top gas.

[0025] According to the present invention, this hydrogen originates at least in part from the blast furnace top gas 10. The top gas 10 is captured at the outlet of the blast furnace 1 and sent to a gas recovery and treatment device 30, where it is split between an H-rich stream 11 and an H-lean stream 12. This H-rich stream 11, which preferentially contains more than 90% H by volume, is then injected into the blast furnace 1 at a second injection height 3B. The H-lean stream is sent to a further gas treatment device, for example, to remove CO, which may then be stored or used for chemical production. Recovering and injecting H from the top gas allows for a reduction in the need for an external source of hydrogen and thus reduces the operating costs of the process. The inventors have discovered that even if the top gas 10 contains a small amount of hydrogen, for a given hydrogen injection rate into the furnace shaft, and therefore for a given reduction in the facility's CO emissions, it is already sufficient to split the amount of external hydrogen required by more than two.

[0026] As a matter of illustration, the top gas 10 may contain between 15-25% v CO, between 20-30% v CO, between 2-32% H, and greater than 30% v N. This composition will vary greatly depending on the amount of hydrogen injected. In a preferred embodiment, the H-lean stream contains less than 0.1% v H.

[0027] The gas recovery and processing unit 30 may comprise at least one compressor, an impurity removal device such as a hydrolysis bed or a ZnO bed, a CO2 and / or CO removal device such as a PSA or VPSA, and a PSA dedicated to H2 recovery.

[0028] In a preferred embodiment shown in Figure 2, hydrogen 21 produced in a hydrogen production plant 20 is added to the H2-rich stream 13 before it is injected into the blast furnace 1. This makes it possible to further reduce the need for the addition of carbon-based reductants. Preferably, less than 50% by volume of the total amount of hydrogen injected by the second injection means 3B comes from the hydrogen production plant 20.

[0029] In the most preferred embodiment, the hydrogen production plant 20 is a water splitting plant that produces hydrogen 21 and oxygen 22 from water, for example by electrolysis. As shown in Figure 2, the produced oxygen 22 can be used as an oxygen source 6 for hot air 11. This makes it possible to reduce the overall operating costs of the plant, as the need for external purchase of oxygen is eliminated or reduced.

[0030] In a most preferred embodiment, the hydrogen production plant 20 is 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, the use of electricity derived from nuclear sources can be used, as the CO2 produced does not emit.

[0031] In another embodiment, shown in FIG. 3, the plant further comprises a direct reduction furnace 40. In operation, iron oxide ore and pellets 41 containing approximately 30% oxygen by weight are charged to the top of the furnace 40 and descend by gravity through reducing gas 42. This reducing gas 42 is injected into the furnace 40 countercurrently from 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 43, exits the bottom of the furnace 40, while reduced furnace top gas 44 exits the top of the furnace 40. This reduced furnace top gas 44 is captured and processed in a second gas processing unit 50, where hydrogen is extracted and mixed with the H2-rich stream 13. The composition of the reduced furnace top gas 44 varies depending on the composition of the reducing gas 42 injected into the furnace 40. In a preferred embodiment, the reducing gas 42 comprises more than 90%v hydrogen, which hydrogen is preferentially green hydrogen.

[0032] Using the method according to the invention, it is possible to reduce CO2 emissions by at least 35% by volume, and even more than 50%, in accordance with the various embodiments described, compared to production in a conventional blast furnace (without top gas recycle).

Claims

1. A method for producing hot metal (2) in at least one blast furnace (1) comprising at least two levels (3A, 3B) of gas injection and releasing blast furnace top gas (10) during operation, comprising at least the following steps: A. Charging an iron-containing charge (4) and a first carbon-based reducing agent (5) into the blast furnace (1); B. A step of injecting hot air (11) having a temperature of 1000°C or more at a first height (3A) which is the height of a tuyere located at the bottom of the blast furnace (1), wherein the hot air (11) contains oxygen (6); C. Recovering the blast furnace top gas (10); D. Extracting hydrogen from the blast furnace top gas (10) to obtain H2O containing more than 90% hydrogen. ２ The H-rich stream (13) and ２ generating a lean stream (12); E. The above H ２ injecting the rich stream (13) into the blast furnace at a second level of gas injection (3B) at a shaft height higher than the level of the tuyere. A method comprising:

2. 2. The method of claim 1, wherein the first carbon-based reductant (5) comprises coke.

3. 3. The method of claim 1 or 2, wherein the first carbon-based reductant (5) comprises a non-fossil carbon reductant.

4. The method according to any one of claims 1 to 3, wherein in step B, the hot air (11) further comprises at least one second carbon-based reducing agent (7).

5. 5. The method of claim 4, wherein the second carbon-based reductant (7) comprises a non-fossil carbon reductant.

6. The H ２ Before the H-rich stream (13) is injected into the blast furnace (1), hydrogen (21) produced in the hydrogen production step is added to the H ２ The method according to any one of claims 1 to 5, wherein the hydroxybenzoate is added to the rich stream (13).

7. 7. The method of claim 6, wherein the hydrogen production process is a water splitting process to produce hydrogen (21) and oxygen (22).

8. 8. The method according to claim 7, wherein the hot air (11) contains oxygen (22) produced in the water splitting step.

9. The method according to claim 7 or 8, wherein the water splitting step is an electrolysis reaction.

10. 10. The method of claim 9, wherein the electrolysis reaction is powered by renewable energy.

11. The H ２ The method according to any one of the preceding claims, wherein the rich stream (13) is injected into the blast furnace (1) at a temperature between 750°C and 1100°C.

12. 200 Nm per tonne of hot metal to be produced ３ ~700Nm ３ The method according to any one of claims 1 to 11, wherein hydrogen is injected into the blast furnace.

13. 12. The method of claim 11, wherein more than 50% by volume of the hydrogen injected into the blast furnace (1) is hydrogen extracted from the blast furnace top gas (10).

14. The H ２ Before the H-rich stream (13) is injected into the blast furnace (1), hydrogen (45) extracted from the reduction furnace top gas (44) of the direct reduced iron production process is added to the H ２ The method according to any one of claims 1 to 13, wherein the hydroxybenzoate is added to the rich stream (13).

15. 1. A pig iron production plant comprising: a. at least one blast furnace (1) producing molten iron (2) and discharging blast furnace top gas (10), the blast furnace (1) comprising first and second gas injection means (3A, 3B) respectively positioned at two different heights across the height of the blast furnace (1); b. The first injection means (3A) is designed to inject hot air (11) having a temperature of 1000°C or more into the blast furnace (1) at a first height (3A) which is the height of a tuyere located at the bottom of the blast furnace (1), and the hot air (11) contains oxygen (6); c. Capturing the blast furnace top gas (10) and extracting hydrogen from the blast furnace top gas (10) to produce a H2O mixture containing more than 90% hydrogen. ２ The H-rich stream (13) and ２ a gas recovery and treatment system (30) capable of producing a lean stream (12); d. The blast furnace (1) is injected with the H gas at a second level (3B) of gas injection, which is at a shaft height higher than the height of the tuyere. ２ said second injection means (3B) designed to inject a stream (13) rich in A pig iron production plant equipped with:

16. A hydrogen generation plant (20) and a hydrogen supplying plant (3B) are connected to the hydrogen supplying plant (20) and the ... and the hydrogen supplying plant (3B) are connected to the hydrogen supplying plant (20). ２ The hydrogen (21) produced in the hydrogen production plant (20) is added to the H2-rich stream (13) before it is injected into the blast furnace (1). ２ 16. The ironmaking production plant of claim 15, further comprising a hydrogen gas line allowing mixing with the iron-rich stream (13).

17. 17. The ironmaking production plant of claim 16, wherein the hydrogen production plant (20) is a water splitting plant that produces hydrogen and oxygen.

18. 18. The ironmaking production plant according to claim 17, further comprising an oxygen gas line (22) making it possible to inject the produced oxygen into the hot blast (11) before it is injected into the blast furnace (1) through the first injection means (3A).

19. a. a direct reduction furnace (40) producing direct reduced iron (43) and reduction furnace top gas (44); b. Capturing the reduction furnace top gas (44) and extracting hydrogen from the reduction furnace top gas (44) to directly reduce H ２ a second gas recovery and treatment device (50) capable of producing stream (45); c. The H ２ before the direct reduction H rich stream (13) is injected into the blast furnace (1). ２ Stream (45) ２ a mixing means for allowing the mixture to be mixed with the rich stream (13) The ironmaking production plant according to any one of claims 15 to 18, further comprising:

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