Method and system for continuous pre-reduction of solid particulate material
By using the pre-reduction gas from the reduction furnace to countercurrently reduce the solid granular material in the reactor and reusing the exhaust gas for waste heat, the problems of insufficient reduction gas application and unutilized waste heat are solved, and an efficient reduction process and energy optimization are achieved.
Patent Information
- Application Number
- CN202380094248.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-02-16
- Filing Date
- 2023-12-22
- Publication Date
- 2025-10-03
AI Technical Summary
The existing technology fails to effectively utilize the reducing gas from the self-reduction furnace in the reduction of metal oxides, and the waste heat of the exhaust gas is not fully reused.
By continuously passing the solid granular material through the reactor and pre-reducing it with the pre-reduction gas from the iron and steel metallurgical self-reduction furnace, combined with countercurrent heat and mass transfer, an efficient reduction process is achieved, and the waste gas is used for post-combustion to reuse the remaining heat.
It achieves efficient pre-reduction of solid granular materials, improves reduction efficiency, and effectively utilizes waste heat resources of exhaust gas, reducing energy loss.
Smart Images
Figure CN120752354A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to ferrous metallurgy processes. More particularly, the present invention relates to methods and systems for reusing gases from ferrous metallurgical furnaces. Background Art
[0002] The classical methods for obtaining primary iron from iron oxides are known in the prior art. Traditionally, blast furnaces are used as reduction reactors to produce pig iron. In addition, direct reduction reactors are used to produce sponge iron (direct reduced iron - DRI). The most commonly used iron-containing raw materials in these processes are sintered ore, pelletized ore, and granulated iron ore.
[0003] The blast furnace is a vertical reactor operated in countercurrent mode. Ore in the form of sinter, pellets and granules, as well as reducing agents (coke / coal) and fluxes (limestone, etc.) are sequentially charged through the upper part of the furnace to form staggered layers of iron-containing charge and reducing agent. Preheated air is introduced into the lower part of the blast furnace through tuyeres located in the area above the crucible (combustion zone). Auxiliary fuels such as pulverized coal injection (PCI) are used together with the blown air. The reaction between the heated air and the carbon in the coke / coal in the combustion zone produces reducing gases that rise up the reactor, thereby promoting the energy transfer of the hot gases to the solid charge, the reduction of the iron ore to metallic iron, and the formation of hot metal, in addition to the formation of a slag phase.
[0004] Some more modern furnaces use self-reducing pellets, which provide much more favorable reduction conditions. Such equipment is called an autoreducing furnace. The closer contact between the iron oxide and the carbonaceous material provides favorable reaction kinetics because the diffusion path for CO to enter the pellets is reduced. Therefore, the reducing gas generation and oxide reduction reactions, as shown below, occur within the pellets themselves.
[0005] 2MeO (s) +C (s) →2Me (s) +CO 2(g)
[0006] CO 2(g) +C (s) →2CO (g)
[0007] MeO (s) +CO (g) →Me (s) +CO 2(g)
[0008] In this respect, the agglomerate itself effectively establishes a semi-closed system in which the atmosphere remains reducing throughout the period that carbon is available therein. Thus, the self-reducing agglomerate acts as a microreactor.
[0009] The off-gas from an autogenous reduction furnace typically has a higher CO / CO2 ratio than the off-gas from a blast furnace, resulting in a greater reducing power.
[0010] Currently, some industrial processes utilize the gas from autogenous reduction furnaces to generate electricity through combustion. However, the use of this reducing power of the gas in metal oxide reduction applications has not been explored.
[0011] The proposed invention solves the above-mentioned problems of the prior art in a simple and effective manner. Summary of the Invention
[0012] The main object of the present invention is to provide a method and system for the continuous pre-reduction of solid particulate materials, which utilizes the reducing potential of a fuel- and reducing gas-rich gas from a ferrous metallurgical autoreduction furnace.
[0013] A secondary object of the invention is to utilize the waste gases in other processes, such as post-combustion and reuse of residual calorific value.
[0014] In order to achieve the above-mentioned objectives, the present invention provides a method for continuous pre-reduction of solid granular materials, comprising the steps of (i) continuously passing the solid granular material through a reactor and (ii) pre-reducing the solid granular material by injecting a pre-reduction gas into the reactor when the solid granular material passes through the reactor, wherein the pre-reduction gas comes from a ferrous metallurgical autoreduction furnace.
[0015] The present invention also provides a system for continuous pre-reduction of solid granular materials. The system includes a pre-reduction reactor fed by exhaust gas from a ferrous metallurgical reduction furnace. The solid granular materials continuously pass through the reactor and are pre-reduced by the pre-reduction gas. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The following detailed description refers to the accompanying drawings and their corresponding reference numerals.
[0017] Figure 1 A flow chart of a method according to a preferred embodiment of the present invention is shown. DETAILED DESCRIPTION
[0018] It should be noted at the outset that the following description will be based on a preferred embodiment of the present invention, which will be apparent to anyone skilled in the art. However, the present invention is not limited to this particular embodiment.
[0019] Therefore, the present invention provides a method for the continuous pre-reduction of solid particulate material 10, the flow diagram of which is shown in FIG. Figure 1. In a first step, the method of the present invention comprises the step of continuously passing a solid particulate material 10 through a reactor 20. Preferably, the solid particulate material 10 is iron ore. Such solid particulate material 10 may include a variety of particle sizes, including fine and ultrafine. Alternatively, the solid particulate material 10 is a solid agglomerate, such as a self-reducing briquette.
[0020] Preferably, the reactor 20 is a rotating cylindrical reactor or any other reactor capable of pre-reducing the solid particulate material 10 .
[0021] In the second step, the method of the present invention includes a step of pre-reducing the solid granular material 10 by injecting a pre-reduction gas 30 into the reactor 20 as the solid granular material 10 passes through the reactor 20. The pre-reduction gas used in the step of pre-reducing the solid granular material 10 originates from a ferrous metallurgical autoreduction furnace 40. This ensures a reducing atmosphere favorable for the pre-reduction of the solid granular material 10 due to the CO / CO₂ ratio present in the exhaust gas composition of this type of furnace. Preferably, the CO / CO₂ mass ratio present in the gas composition from the ferrous metallurgical autoreduction furnace 40 ranges from 1.5 to 3. Thermodynamically, this ratio is sufficient to achieve a satisfactory degree of metallization.
[0022] In addition to the large amount of CO in its composition, the gas from the ferrous metallurgical autoreduction furnace 40 has an outlet temperature in the range of 600 to 800° C., which is sufficient for the pre-reduction of the solid particulate material 10. Therefore, the gas from the ferrous metallurgical autoreduction furnace 40 can be directly injected into the reactor 20 without the need for a cooling / heating system. It is worth noting that in a blast furnace, the temperature of the outlet gas can vary between 100 and 200° C., which makes it difficult to use it in the pre-reduction process.
[0023] Preferably, the step of continuously passing the solid granular material 10 through the reactor 20 comprises continuously moving the solid granular material 10 from a first end of the reactor 20 toward a second end of the reactor 20. In this case, the first end of the reactor 20 is an inlet end for the solid granular material 10, and the second end of the reactor 20 is an outlet end for the solid granular material 10.
[0024] Still preferably, the first end of the reactor 20 (where the solid particulate material is added) is the gas outlet after pre-reduction. The second end of the reactor 20 is the inlet for the pre-reduction gas 30 from the ferrous metallurgical autoreduction furnace 40. Therefore, the pre-reduction gas 30 preferably flows through the reactor 20 in a countercurrent flow to the solid particulate material 10, thereby facilitating heat and mass transfer between the two materials and thus improving the efficiency of the pre-reduction process. Furthermore, there is the possibility of using an auxiliary fuel to minimize the loss of energy efficiency of the top gas during the entire pre-reduction process.
[0025] Preferably, after the step of pre-reducing the solid particulate material 10 inside the reactor 20, the off-gas leaving the pre-reduction system can be used for another application, such as by reusing its remaining heat through post-combustion. The generated heat can be used for various applications within the steelmaking plant.
[0026] Preferably, after the step of pre-reducing the solid particulate material 10 inside the reactor 20 , it is directly guided to the ferrous metallurgical autoreduction furnace 40 for material reduction.
[0027] Alternatively, it is possible to use comminution, separation and / or magnetic separation techniques, followed by a step of agglomeration of the pre-reduced material for its subsequent transport to the reduction furnace. This option allows (i) avoiding the generation of agglomerate fines caused by crystallization transformations due to phase changes during pre-reduction, and / or (ii) a possible low iron concentration in the pre-reduced agglomerates (if the solid particulate material is, for example, iron ore or iron agglomerates).
[0028] Alternatively, the material may be pre-reduced to a fine / ultrafine particle size and then agglomeration performed.
[0029] The present invention also provides a system related to the above method, which includes a reactor 20 and a metallurgical autoreduction furnace 40, wherein the solid particulate material 10 continuously passes through the interior of the reactor 20 and is pre-reduced by the pre-reduction gas 30 from the metallurgical autoreduction furnace 40.
[0030] The system according to the present invention also includes all pipes for connecting and conveying the solid particulate material and the pre-reduction gas between the reactor 20 and the metallurgical autoreduction furnace 40 .
[0031] Optionally, after the pre-reduction of the solid particulate material 10 and before this material enters the metallurgical autoreduction furnace 40 , a magnetic separation step 50 is provided, the purpose of which is to concentrate the magnetic material and separate it from gangue originating from the magnetic material itself.
[0032] Thus, as described above, the present invention primarily provides a method and system for the continuous pre-reduction of solid particulate materials that utilizes the reducing potential of gases from a metallurgical autoreduction furnace rich in fuel and reducing gas. As described above, the gases from the autoreduction furnace have a favorable CO2 concentration compared to CO2 and other compounds, thereby ensuring a reducing atmosphere in the reactor. Furthermore, the outlet temperature of the gases from the autoreduction furnace meets the criteria for direct injection into the reactor, eliminating the need for a gas heating system.
[0033] Several variations are possible that may affect the scope of protection of the present application. Therefore, it is emphasized that the present invention is not limited to the particular configurations / embodiments described above.
Claims
1. A method for the continuous pre-reduction of a solid particulate material (10), comprising the following steps: passing a solid particulate material (10) continuously through a reactor (20); and pre-reducing the solid particulate material (10) by injecting a pre-reduction gas (30) into the reactor (20) as the solid particulate material (10) passes through the reactor (20); It is characterized in that the pre-reduction gas (30) comes from a steel metallurgical self-reduction furnace (40).
2. The method according to claim 1, characterized in that The step of continuously passing the solid particulate material (10) through the reactor (20) comprises continuously moving the solid particulate material (10) from a first end of the reactor (20) towards a second end of the reactor (20).
3. The method according to claim 2, characterized in that The first end of the reactor (20) is an inlet end for the solid granular material (10) and an outlet end for the pre-reduction gas (30) from the ferrous metallurgical self-reduction furnace (40).
4. The method according to claim 2 or 3, characterized in that The second end of the reactor (20) is an outlet end for the solid granular material (10) and an inlet end for the pre-reduction gas (30) from the ferrous metallurgical self-reduction furnace (40).
5. The method according to any one of claims 1 to 4, characterized in that An additional step of post-combustion of the pre-reduction gas (30) for heat generation is included after the step of pre-reducing the solid particulate material (10) within the reactor (20).
6. The method according to any one of claims 1 to 5, characterized in that The invention comprises the additional step of guiding the pre-reduced solid particulate material (10) in the reactor (20) to the ferrous metallurgical autoreduction furnace (40).
7. The method according to any one of claims 1 to 6, characterized in that The reactor (20) is a rotating cylindrical reactor.
8. The method according to any one of claims 1 to 7, characterized in that An additional step of comminuting the pre-reduced solid particulate material (10) is included.
9. The method according to claim 8, characterized in that Include the following additional steps: separating and / or magnetically separating the pulverized material and / or fines and ultrafines produced in the pre-reduction step; and The separated and / or magnetically selected material is agglomerated.
10. A continuous pre-reduction system for solid particulate material (10), comprising: Reactor (20); Iron and steel metallurgy self-reduction furnace (40); wherein a solid particulate material (10) is continuously passed through a reactor (20); It is characterized in that the solid granular material (10) is pre-reduced by the pre-reduction gas (30) originating from the iron and steel metallurgical self-reduction furnace (40).
11. The system according to claim 10, wherein: The reactor (20) comprises a first end and a second end, wherein continuous movement of the solid particulate material (10) occurs from the first end towards the second end.
12. The system according to claim 11, wherein: The first end of the reactor (20) is an inlet end for the solid particulate material (10) and an outlet end for the pre-reduction gas (30) originating from the ferrous metallurgical self-reduction furnace (40).
13. The system according to claim 11 or 12, characterized in that The second end of the reactor (20) is an outlet end for the solid granular material (10) and an inlet end for the pre-reduction gas (30) from the ferrous metallurgical self-reduction furnace (40).
14. The system according to any one of claims 11 to 13, characterized in that The pre-reduced solid granular material (10) in the reactor (20) is guided to the ferrous metallurgical autoreduction furnace (40).