Ironmaking process 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 for making iron and an associated iron-making plant. [Background technology]

[0002] In blast furnaces, the conversion of iron-containing charges (sinter, pellets and iron ore) into cast iron or molten iron has traditionally been achieved using reducing gases (especially CO, H 2 and N 2 The reduction is carried out by the reduction of iron oxide with iron oxides (including iron oxides), the reducing gas being formed by partial combustion of coke and finally auxiliary reducing agents in the tuyere located at the bottom of the blast furnace, where air preheated to a temperature between 1000 °C and 1300 °C, called hot blast, is injected.

[0003] Supplementary reducing agents that may be injected into the tuyere to increase productivity and reduce costs may 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, CO in proportions of 20-28%v, 17-25%v, 1-5%v and 48-55%v. 2 , H 2 and N 2 Despite the partial use of this gas as fuel in other plants, such as power plants, blast furnaces still produce CO 2 It is a remarkable production device.

[0005] Atmospheric CO since the beginning of the last century 2 Considering the significant increase in concentration and subsequent greenhouse effect, CO 2 Where large amounts of CO are produced, especially in blast furnaces, 2 It is essential to reduce emissions.

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

[0007] This further reduces the carbon-based reducing agent consumption and therefore the CO2 emissions from blast furnace ironmaking production. 2 One solution being considered to reduce the footprint is to capture top gas and reduce CO 2 The solution is to remove the top gas and reinject it into the blast furnace shaft, which is at a height 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 carried out. 2 In terms of footprint, this is the CO emitted 2 This corresponds to a reduction of less than 20% by volume. Summary of the Invention [Problem to be solved by the invention]

[0008] There is therefore a need for an ironmaking process which 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, which comprises a method for producing hot metal in at least one blast furnace comprising at least two levels of gas injection and releasing blast furnace top gas during operation, said method comprising at least the following steps: charging an iron-containing charge and a first carbon-based reductant into the blast furnace, injecting hot blast at a first level having a temperature of at least 1000° C., said hot blast containing oxygen, recovering the blast furnace top gas, extracting hydrogen from the blast furnace top gas to obtain a H2O mixture containing more than 90% hydrogen. 2 Rich flow and H 2 generating a lean stream; 2 injecting the 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, taken 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; - Before being injected into the blast furnace, the hydrogen produced in the hydrogen production process is 2 added to the rich stream, - the hydrogen production process is a water splitting process to produce hydrogen and oxygen; - The hot air contains the oxygen produced in the water splitting process. - The water splitting process is an electrolysis reaction; - The electrolysis reaction is powered by renewable energy, -H 2 The rich stream is injected into the blast furnace at temperatures between 750°C and 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 hydrogen injected into the blast furnace is hydrogen extracted from the blast furnace top gas; -H 2 Hydrogen extracted from the reduction furnace top gas of the direct reduced iron production process is added to the H 2 is added to the rich stream.

[0011] The invention also relates to a network of plants including at least one blast furnace producing molten iron and discharging blast furnace top gas, the blast furnace comprising first and second gas injection means arranged at two different heights over the height of the blast furnace, the first injection means being designed to inject hot blast having a temperature of 1000° C. or more into the blast furnace, the hot blast containing oxygen, the blast furnace capturing the blast furnace top gas and extracting hydrogen from the blast furnace top gas to produce H 2 Rich flow and H 2 a gas recovery and treatment apparatus capable of producing a H2-poor stream, and the second injection means is adapted to inject the H2 into the blast furnace. 2The present invention relates to a network of plants designed to inject a stream rich in

[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 comprises a hydrogen production plant and a second injection means for injecting H 2 Before the hydrogen-rich stream is injected into the blast furnace, hydrogen produced in a hydrogen generation plant is added to the H 2 and a hydrogen gas line allowing mixing with the hydrogen-rich stream. - a hydrogen production plant is a water splitting plant which produces hydrogen and oxygen; the plant further comprises an oxygen gas line making it possible to inject the generated oxygen into the hot air before the latter is injected into the blast furnace through the first injection means, - The plant consists of a direct reduction furnace that produces direct reduced iron and reduction furnace top gas, and a direct reduction H 2 a second gas recovery and treatment apparatus capable of producing a H 2 The H2O-rich stream is directly reduced before being injected into the blast furnace. 2 Flow H 2 and mixing means for enabling mixing of the enriched stream with the enriched stream.

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

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

[0015] First, it should be noted that on the drawings, like reference numerals refer to like 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 readily found by reference 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] Figure 1 shows an iron-making plant making it possible to carry out a method according to an embodiment of the invention. The plant comprises at least one blast furnace 1 in which an iron-bearing charge 4, such as sinter, pellets, iron ore, 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 a renewable organic material derived from plants and animals. Biomass sources for energy include, among others, wood and wood processing wastes (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, as well as 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 being the injection of a first carbonaceous reducing agent 5, the second being 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 references 3A and 3B indicate both the injection level and the associated injection means at the level considered.

[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 circumference of the blast furnace 1.

[0021] The hot blast 11 has a temperature of more than 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 tuyere 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 preferentially is a non-fossil carbonaceous reductant such as biochar or biocoal according to the description given previously or waste plastics.

[0022] In a preferred embodiment, the hot blast is between 35 and 70 Nm3 per tonne of hot metal to be produced. 3 of oxygen. Although higher heights are possible, adding oxygen within this range makes it possible to maintain the hot blast flow rate at a height compatible with good distribution of gases 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 gases that allow the reduction of the iron ore.

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

[0024] 200 Nm per tonne 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. 3 Below 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 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 above 1000 / thm would not provide any additional benefit since this hydrogen would not react with the iron oxides; it would only contribute to heating the blast furnace top gas.

[0025] According to the invention, this hydrogen originates at least in part from the blast furnace top gas 10, which is captured at the outlet of the blast furnace 1 and sent to a gas recovery and treatment device 30, where H 2 Rich flow 11 and H 2 This H is divided between the inflow and outflow 12. 2 The H-rich stream 11 preferentially contains more than 90 vol.% H 2 and then injected into the blast furnace 1 at a second injection height 3B. 2 The lean stream is sent to further gas treatment equipment, e.g. 2 H from the top gas may be removed and stored or used for chemical production. 2The recovery and injection of hydrogen makes it possible to reduce the need for an external source of hydrogen and therefore to reduce the operating costs of the process. The inventors have found that even if the top gas 10 contains a small amount of hydrogen, for a given hydrogen injection rate into the shaft of the furnace, the CO 2 It has been found that for a given reduction in emissions, it is already sufficient to divide the amount of external hydrogen required by more than two.

[0026] As a matter of explanation, the top gas 10 may be comprised of between 15 and 25% CO, between 20 and 30% CO 2 , H between 2 and 32% 2 , and more than 30%v N 2 This composition can vary greatly depending on the amount of hydrogen implanted. In a preferred embodiment, H 2 The poor flow rate is less than 0.1% H 2 Includes.

[0027] The gas recovery and treatment unit 30 includes at least one compressor, an impurity removal device such as a hydrolysis bed or a ZnO bed, a CO scavenger such as a PSA or VPSA, and a CO scavenger. 2 and / or CO removal equipment, and H 2 It can have a dedicated PSA for collection.

[0028] In a preferred embodiment shown in FIG. 2, hydrogen 21 produced in a hydrogen production plant 20 is mixed with H 2 The hydrogen-rich stream 13 is added to the hydrogen-rich stream 13. 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 originates from the hydrogen production plant 20.

[0029] In the most preferred embodiment, the hydrogen production plant 20 is a water splitting plant producing hydrogen 21 and oxygen 22 from water, for example by electrolysis. As shown in Figure 2, said produced oxygen 22 can be used as oxygen source 6 for hot air 11. This allows to reduce the operating costs of the whole plant, since there is no or reduced need for external purchase of oxygen.

[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. 2 Since it does not emit any heat, the use of electricity derived from nuclear sources can be used.

[0031] In another embodiment, shown in FIG. 3, the plant further comprises a direct reduction furnace 40. In the operating mode, iron oxide ore and pellets 41, containing about 30% oxygen by weight, are charged to the top of the furnace 40 and fall by gravity through a reducing gas 42, which is injected into the furnace 40 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 the gas with the oxide. The oxidant content of the gas increases as it travels to the top of the furnace. Reduced iron, also called DRI product 43, leaves the bottom of the furnace 40, while reduced top gas 44 leaves the top of the furnace 40. This reduced top gas 44 is captured and treated in a second gas treatment unit 50, where hydrogen is extracted, which is H 2 The reduced top gas 44 is mixed with the enriched stream 13. The composition of the reduced 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 is preferentially green hydrogen.

[0032] Using the method according to the invention, it is possible to reduce CO by at least 35% by volume, and even by more than 50%, according to the various embodiments described, compared to production in a conventional blast furnace (without top gas recycle).2 It is possible to reduce emissions.

Claims

1. A method for producing molten iron (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. Injecting hot air (11) having a temperature of 1000° C. or more at a first height (3A), said hot air (11) containing oxygen (6); C. Recovering the blast furnace top gas (10); D. Extract 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 (11) into the blast furnace at a second level of gas injection (3B). The method includes:

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

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. 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 process is added to the H ２ The method according to any one of claims 1 to 5, wherein the oxidizing agent 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) comprises oxygen (22) produced in the water splitting process.

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 according to 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 the preceding claims, wherein the oxidizing agent is added to a stream (13) rich in nitric acid.

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 arranged at two different heights over the height of the blast furnace (1); b. the first injection means (3A) designed to inject hot air (11) having a temperature of 1000° C. or more into the blast furnace (1), the hot air (11) containing oxygen (6); c. Capturing the blast furnace top gas (10) and extracting hydrogen from the blast furnace top gas (10) to produce H ２ The H-rich stream (13) and ２ a gas recovery and treatment apparatus (30) capable of producing a lean stream (12); d. The H ２ said second injection means (3B) designed to inject a stream (13) rich in A pig iron production plant equipped with:

16. A hydrogen production plant (20) and the H ２ The hydrogen (21) produced in the hydrogen production plant (30) is added to the H2O-rich stream (13) before it is injected into the blast furnace (1). ２ 14. The ironmaking production plant of claim 13, further comprising a hydrogen gas line enabling mixing with the rich stream (13).

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

18. 18. 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 reduced furnace top gas (44); b. Capturing the reduction furnace top gas (44) and extracting hydrogen from the reduction furnace top gas (44) to produce directly reduced H ２ a second gas recovery and treatment apparatus (50) capable of producing stream (45); c. The H ２ before the direct reduction H enriched stream (13) is injected into the blast furnace (1). ２ The flow (45) is ２ a mixing means enabling the mixture with the rich stream (13) The ironmaking production plant according to any one of claims 1 to 18, further comprising:

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