Use of tail gas produced from the exhaust gas of a reduction process for iron oxide-containing materials
By separating and mixing tail gas with melt off-gas to increase its calorific value, the method addresses the inefficiencies in utilizing tail gas from hydrogen-based reducing processes, enabling effective thermal utilization and resource conservation.
Patent Information
- Application Number
- JP2025536373
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-04-27
- Filing Date
- 2023-12-13
- Publication Date
- 2026-01-21
Smart Images
Figure 2026502144000001_ABST
Abstract
Description
[Technical Field]
[0001] This application relates to a process for producing molten iron, which involves the production of a metallized product by reducing an iron oxide-containing material using a reducing gas consisting at least primarily of hydrogen, i.e., H2, which reduction generates a top gas. [Background technology]
[0002] The reduction of metal oxide-containing materials, such as iron oxide-containing materials, i.e., ores, oxide briquettes, or pellets, using a reducing gas is known. For example, reduction by direct reduction in a fixed or fluidized bed with a reducing gas. In conventional pre-reduction and direct reduction processes currently used on a large industrial scale, the reducing gas is based not only on hydrogen but also primarily on carbon, for example, carbon monoxide (CO) and / or methane (CH4) derived from natural gas. This therefore generates large amounts of carbon dioxide (CO2), which is undesirable, especially for environmental policy reasons.
[0003] One known means for reducing CO2 emissions in the direct reduction of metal oxide-containing materials is to use hydrogen, i.e., H2, as the reducing gas. In this case, hydrogen can be used as the sole reducing gas or in combination with other gases based on carbon, coal, or coke, for example, derived from natural gas. The higher the proportion of CO2-neutral hydrogen, i.e., H2, in the reducing gas, the lower the CO2 emissions. Depending on the availability of natural gas or other gases and hydrogen, the contribution of these gases to the reducing gas can be varied by changing the mixture amounts.
[0004] The higher the amount of hydrogen available, the greater the potential for avoiding carbon from natural gas or other gases from contributing to climate problems.
[0005] It would be advantageous to operate existing plants and processes in which the reducing gas is primarily carbon-based and partially hydrogen-based from natural gas or other gases with an increased proportion of hydrogen in the reducing gas. This would allow flexibility in responding to the availability of natural gas or other gases and hydrogen, and would allow capital investments already made in the plant to be utilized. At least until sufficient hydrogen becomes available to use a reducing gas based entirely on hydrogen, the reducing gas will still need to utilize reducing components contained in natural gas or other gases in addition to hydrogen.
[0006] To conserve resources, it is common practice in direct reduction processes to prepare the reducing gas using spent reducing gas, known as top gas. For this purpose, the top gas, optionally after processing steps such as dedusting or compression, is mixed with fresh reducing gas components, such as gas from a reformer for reforming natural gas, hydrogen (H2) from a hydrogen production plant, or ammonia (NH3). The reducing components remaining in the top gas can then be sent to direct reduction and reused as reducing agents. The drawback of such top gas recycling is that the top gas also contains non-reducing components, such as nitrogen (N2) or carbon dioxide (CO2). Recycling further accumulates these components in the reducing gas. To prevent condensation, a portion of the top gas is discharged from this circulation as so-called exhaust gas, also known as bleed gas.
[0007] To conserve resources, it is desirable to utilize this exhaust gas, especially when using a hydrogen-rich reducing gas, since increasing the hydrogen content in the reducing gas will also increase the hydrogen content in the top gas.
[0008] It is known to utilize the heat by burning the exhaust gases with an oxidant, such as air, and to use that heat to heat a medium, which may be, for example, a reducing gas precursor.
[0009] It is also known to separate hydrogen, or H2, from other components in the exhaust gas and use this hydrogen to produce reducing gas. The portion of the exhaust gas that remains after hydrogen, or H2, separation, known as tail gas, is not suitable for thermal use alone due to its low heating value and is therefore combusted after the addition of fuel. Summary of the Invention [Problem to be solved by the invention]
[0010] The problem that the present invention seeks to solve is to provide a process and apparatus that allows for the use of tail gas when using a reducing gas that is primarily hydrogen, i.e., H2. [Means for solving the problem]
[0011] The present invention is achieved by a method for producing molten iron, the method comprising the steps of: The production of the metallized product is carried out by reducing the iron oxide-containing material using a reducing gas consisting at least primarily of hydrogen, i.e., H2; Reduction produces top gas, Optionally, after the top gas is treated, a first portion of the top gas is mixed with a reducing gas component to prepare a reducing gas, and a second portion of the top gas as an exhaust gas is separated into a hydrogen-rich gas stream and a hydrogen-depleted tail gas stream; The metallized product of the reduction is mixed with a carbon support and melted in a melting device to produce molten iron and generate melting off-gas. mixing at least a portion of the tail gas stream with at least a portion of the melt off-gas to form a tail gas mixture; At least a portion of the tail gas mixture is sent to thermal utilization. It is characterized by:
[0012] The reducing gas consists at least mainly of hydrogen, i.e., H. This should be understood to mean that the reducing gas contains hydrogen as a reducing gas component, and that the hydrogen content in volume % is higher than any other reducing gas components optionally present. The hydrogen content is preferably at least 50 volume %, particularly preferably more than 50 volume %, and very particularly preferably at least 60 volume %.
[0013] Other reducing gas components optionally present that may also have a reducing effect include, for example, carbon monoxide, CO, or hydrocarbons, or ammonia, NH3.
[0014] Preferably, the metallized product is direct reduced iron or DRI, also known as sponge iron.
[0015] The optional processing of the top gas includes, for example, processing types such as dedusting, compression, heat exchange, cooling, which may be performed in a wet or dry manner, and the processing may be single-stage or multi-stage, and one or more processing types may be utilized.
[0016] The first and second subquantities of top gas may have the same composition or may differ in composition.
[0017] It is preferred that the first and second partial quantities of top gas have the same composition, ie the volumetric flow is simply divided into two partial quantities.
[0018] The metallized product of this reduction is mixed with a carbon support and melted in a melter to produce molten iron. Mixing with the carbon support may be performed prior to introduction into the melter or within the melter.
[0019] The melting device may be, for example: Electric Arc Furnace (EAF), Submerged Arc Furnace (SAF), Open slag bath furnace (OSBF), a melting unit, and converter and so on, for example, one element of the group consisting of
[0020] A melting unit performs melting based at least in part on electrical energy.
[0021] In the context of this application, the EAF, SAF and OSBF should not be understood as melting units.
[0022] Converter is to be understood as meaning, for example, a steel converter for producing steel.
[0023] The heat utilization is an exothermic reaction with a reactant, such as combustion with oxygen or another oxidizing reactant.
[0024] Preferably, the heat utilization is carried out in the process environment for producing molten iron, such as for heating a process gas stream or for steam generation to generate the power required for the process. [Effects of the Invention]
[0025] Due to the presence of carbon carriers during melting, the melting off-gas contains, for example, carbon monoxide (CO) and therefore has a higher calorific value than the tail gas. Therefore, the tail gas mixture obtained according to the present invention has a higher calorific value than the tail gas and is suitable for thermal utilization. By mixing the two gases generated during the process for producing molten iron according to the present invention, the tail gas can be utilized.
[0026] Heat utilization is reformer, reducing gas heating device, Drying equipment for iron oxide-containing materials, Heating devices for iron oxide-containing materials, a processing device for iron oxide-containing materials; and Steam or hot water generator Preferably, the method includes providing heat to one element of the group consisting of:
[0027] The heat required for reforming may be provided, for example, in a reformer.
[0028] Reaching a desired temperature for the reducing gas may be done, for example, in a reducing gas heating device.
[0029] Heat may be provided in the drying device for the iron oxide-containing material to facilitate drying.
[0030] The heat required for heating may be supplied in a heating device for the iron oxide-containing material, and it is possible to carry out heating, for example, to promote pre-oxidation of the material.
[0031] The heat required for the treatment may be provided in a treatment facility for iron oxide-containing materials, such as a sintering plant or a pelletizing plant.
[0032] The heat required for the production of steam or hot water may be provided in a steam or hot water generator, which may be used directly or may be used, for example, to generate electricity.
[0033] The thermal utilization of the tail gas mixture produces a first off-gas.
[0034] Preferably, at least a portion of the tail gas mixture is used in an inert gas generator.
[0035] In an inert gas generator, the tail gas mixture is combusted with air to produce an inert gas, for example, carbon dioxide or CO2, an inert gas that is substantially non-reactive under conditions of use.
[0036] The inert gas may be used, for example, for purging, in a reduction unit or melter that reduces iron oxide-containing material to produce a metallized product.
[0037] Following the formation of the tail gas mixture described above, it is also possible in principle to use all of the tail gas mixture in the inert gas generator, thereby preventing a portion of the inert gas mixture from being sent to thermal utilization.
[0038] Preferably, at least a portion of the melt off-gas is used in the reformer.
[0039] The reformer may provide a reducing component for the reducing gas.
[0040] for example, CO2+CH4→2CO+2H2 or H2O+CH4→CO+3H2 Use in accordance with may be carried out.
[0041] Carbon dioxide, i.e., CO2, or water vapor, i.e., H2O, in the melt off-gas reacts with natural gas, for example, in a reformer, to produce the reducing components carbon monoxide, i.e., CO, and hydrogen, i.e., H2, which serve as reducing components of the reducing gas.
[0042] In principle, it is also possible to use all of the melting off-gas from the melting device in which the metallized product of the reduction is mixed with a carbon support and melted to produce molten iron in the reformer to provide the reducing component of the reducing gas that carries out the reduction.
[0043] However, in this case, when a melting apparatus in which the metallized product of reduction is mixed with a carbon support and melted to produce molten iron is connected to the formation of the tail gas mixture, the melt off-gas is not used for mixing with the tail gas at all.
[0044] The iron oxide-containing material is reduced to a metallized product in a reduction unit. The reduction unit that reduces the iron oxide-containing material to a metallized product may be, for example, a fixed-bed shaft or a moving-bed reactor or a fluidized-bed reactor. Process-specific vent gas is generated when the metallized product, such as direct reduced iron (DRI), is pneumatically conveyed from the reduction unit into a DRI bunker, where the solids and gases are separated. The vent gas may be used as fuel, optionally after wet or dry dedusting.
[0045] In one embodiment, the exhaust gas is mixed with at least a portion of a process-specific vent gas prior to gas separation into a hydrogen-rich gas stream and a hydrogen-depleted tail gas stream, where the mixture of exhaust gas and process-specific vent gas is gas-separated into a hydrogen-rich gas stream and a hydrogen-depleted tail gas stream.
[0046] The heat utilization is preferably carried out in conjunction with the supply of at least one fuel, such as natural gas or process-specific vent gas, to the tail gas mixture.
[0047] This allows the heating value of the tail gas mixture to be increased.
[0048] Preferably, the tail gas mixture is sent to a gas storage means prior to thermal utilization and withdrawn from the gas storage means for thermal utilization, thereby allowing for compensation for changes over time in the composition and / or generation of the tail gas stream and / or melt gas stream and / or fuel (such as process-specific vent gas and / or natural gas).
[0049] Both tail gas and melt off-gas streams, as well as fuel streams such as process-specific vent gas and / or natural gas, may undergo changes in composition and amount over time.
[0050] Preferably, at least one fuel is also introduced into the gas storage means. In this case, a mixture of the fuel and the tail gas mixture can be sent to heat utilization. Variations in the heating value of the tail gas stream and / or the melt gas stream and / or the fuel (such as, for example, process-specific vent gas or natural gas), and thus of the tail gas mixture, can thus be compensated for in the gas storage means. Preferably, the introduction into the gas storage means is controlled so that the heating value of the mixture of the tail gas mixture and the fuel withdrawn from the gas storage means corresponds to the value desired for heat utilization.
[0051] The invention will now be described by way of example with reference to the schematic drawings.
[0052] The above-mentioned characteristics, features, and advantages of the present invention, as well as the manner in which they are realized, will become clearer and more understandable in combination with the following description of the embodiments, which are more particularly illustrated in combination with the schematic and exemplary drawings. [Brief explanation of the drawings]
[0053] [Figure 1] 1 is a schematic diagram of one embodiment of a process according to the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0054] Example FIG. 1 is a schematic diagram of a method for producing molten iron 20 in a melting apparatus 10. For this production, a metallized product 30, e.g., DRI, is obtained from an iron oxide-containing material 50 by reduction in a reduction unit 40 using a reducing gas primarily composed of hydrogen. The top gas 60 produced in this reduction is discharged from the reduction unit 40 and split into two portions after a multi-stage process consisting of heat exchange 70, dry dedusting 80, and water cooling 90. The first portion 100 is mixed with a reducing gas component 110, and the second portion 120 is sent to a gas separation device 130, where a hydrogen-rich gas stream 140 and a hydrogen-depleted tail gas stream 150 are generated. As shown, the hydrogen-rich gas stream 140 is sent to a supply of the reducing gas component 110, which may be one of several reducing gas components or may be the only component.
[0055] Following mixing with the reducing gas component, the resulting reducing gas precursor is heated by heat exchange 70 and electrical heating 160, and the resulting reducing gas 170 is supplied to the reduction unit 40.
[0056] The metallized product 30 is fed to the melter 10, mixed with a carbon carrier, and melted in the melter 10 to produce the molten iron 20. The addition of the carbon carrier is indicated by the wavy arrow. In this figure, two variations are shown: one in which the metallized product is mixed with the carbon carrier before being introduced into the melter 10, and one in which the metallized product is mixed with the carbon carrier in the melter 10. Each of these variations may exist alone, or both variations may exist in combination.
[0057] Melt off-gas 180 generated in melter 10 is mixed with tail gas stream 150 to form tail gas mixture 190. Tail gas mixture 190 is sent to heat utilization 200. Prior to heat utilization 200, it is optionally sent to gas storage means 210.
[0058] The tail gas mixture 190 and / or the gas storage means 210 are optionally mixed with fuel, as indicated by the dashed arrows. [Explanation of symbols]
[0059] 10 Melting device 20 Molten iron 30 Metallized products 40 Redemption Units 50 Iron oxide-containing materials 60 Top Gas 70 Heat Exchange 80 Dry dust removal 90 Cooling 100 First Partial Amount 110 Reducing gas components 120 Second Partial Amount 130 Gas Separator 140 Hydrogen-rich gas stream 150 tail gas flow 160 Electric heating 170 Reducing Gas 180 Melt Offgas 190 Tail Gas Mixture 200 Heat utilization 210 Gas storage means
Claims
1. A method for producing molten iron (20), comprising the steps of: The production of the metallized product (30) is carried out by reducing the iron oxide-containing material (50) using a reducing gas consisting at least primarily of hydrogen, i.e., H2; The reduction generates a top gas (60); Optionally, after processing the top gas (60), a first portion (100) of the top gas (60) is mixed with a reducing gas component (110) to prepare a reducing gas, and a second portion (120) of the top gas (60) is separated as an exhaust gas into a hydrogen-rich gas stream (140) and a hydrogen-depleted tail gas stream (150); The metallized product (30) produced by the reduction is mixed with a carbon carrier and melted in a melting device (10) to produce molten iron (20) and generate melting off-gas (180), mixing at least a portion of the tail gas stream (150) with at least a portion of the melt off-gas (180) to form a tail gas mixture (190); At least a portion of the tail gas mixture (190) is sent to a heat utilization (200). A method characterized by:
2. The heat utilization (200) is reformer, reducing gas heating device, Drying equipment for iron oxide-containing materials, Heating devices for iron oxide-containing materials, a processing device for iron oxide-containing materials; and Steam or hot water generator 10. The method of claim 1, comprising providing heat to one element of the group consisting of:
3. 3. The method according to claim 1 or 2, characterized in that at least a portion of the tail gas mixture (190) is utilized in an inert gas generator.
4. 4. The method according to any one of claims 1 to 3, characterized in that at least a portion of the melt off-gas (180) is utilized in a reformer.
5. 5. The method according to claim 1, wherein the exhaust gas is mixed with at least a portion of a process-specific vent gas before the gas separation into a hydrogen-enriched gas stream (140) and a hydrogen-depleted tail gas stream (150) takes place.
6. 6. The method according to any one of claims 1 to 5, characterized in that the heat utilization (200) is carried out in conjunction with the supply of at least one fuel to the tail gas mixture (190).
7. 7. The method according to any one of claims 1 to 6, characterized in that the tail gas mixture (190) is sent to a gas storage means (210) before the heat utilization (200) and is withdrawn from the gas storage means (210) for the heat utilization (200).
8. 8. The method according to claim 7, characterized in that at least one fuel is further introduced into the gas storage means (210).