Method for controlling the stirring of molten metal in a steelmaking furnace and related steel production plant

Abstract

A method (100) for controlling stirring within a container (22) of a steelmaking furnace (20), the container (22) comprising a metal bath (1) containing molten metal (3) and a slag layer (5), the method (100) comprising: - measuring at least two parameters representing the metal bath (1) contained within the container (22) during stirring; - detecting the formation of an opening (8) in the slag layer (5) based on the measurement of the at least two parameters; - adjusting the stirring based on the detection of the formation of the opening (8); wherein the at least two parameters include visual parameters measured on an image of the slag layer (5) captured during stirring, and mechanical parameters representing mechanical waves generated within the container (22) during stirring.

Description

Technical Field

[0001] This invention relates to a method for controlling the stirring of molten metal inside a vessel in a steelmaking furnace. Background Technology

[0002] Currently, steel can be produced via two main manufacturing routes. The most commonly used route today, known as the "BF-BOF route," involves producing molten iron in a blast furnace (BF) by reducing iron oxides using a reducing agent (primarily coke), and then converting the molten iron into steel in a converter process or a basic oxygen converter (BOF). This route releases significant amounts of CO2 in both the coking plant (producing coke from coal) and the iron production process.

[0003] The second main route involves the so-called "direct reduction method." This includes methods according to brands such as MIDREX®, FINMET®, ENERGIRON® / HYL, COREX®, and FINEX®, in which sponge iron is produced from an iron oxide carrier through direct reduction in the form of HDRI (hot direct reduced iron), CDRI (cold direct reduced iron), or HBI (hot pressed iron). The sponge iron in HDRI, CDRI, and HBI forms is then further processed in EAF (Extractable Iron Forming) to produce steel.

[0004] Therefore, one of the main options chosen by steel manufacturers to reduce CO2 emissions is the shift from the BF-BOF route to the DRI-EAF route. However, there are some limitations to using DRI products with iron-containing scrap in conventional electric arc furnaces. In reality, scrap steel contains a significant amount of impurities, and the resulting molten steel will require further processing to produce high-quality steel grades. Furthermore, electric arc furnaces have so far been used primarily for producing specific steel grades for long product applications, and they do not have the same metallurgical constraints as steel grades, especially those used in automotive products.

[0005] After treatment in the EAF, the molten metal is placed into a ladle furnace or stirred furnace. There, a floating slag layer covers the surface of the molten metal. The slag acts as a barrier between the molten metal and the ambient air.

[0006] In such a furnace, the molten metal undergoes agitation. This agitation allows the molten metal to be homogenized and / or cleaned by reducing the content of undesirable chemicals such as phosphorus, carbon, and / or sulfur. This agitation enables the transfer of phosphorus, carbon, and / or sulfur into the slag layer. However, excessive agitation can lead to the formation of open-eyes in the slag—open areas through the slag layer where the molten metal can be in direct contact with ambient air. This can promote nitrogen absorption or oxidation of the molten metal, potentially resulting in a final nitrogen or oxygen content that does not meet the requirements of the final product.

[0007] For example, molten steel produced by a basic oxygen converter contains 20 to 90 parts per million (ppm) of nitrogen by weight, compared to 100 to 140 ppm by weight for steel produced in an electric arc furnace. Therefore, current electric arc furnace (EAF) steels have significantly higher nitrogen content than basic oxygen converter (BOF) steels and fail to meet the requirements for high-grade steels. High nitrogen content can lead to inconsistent mechanical properties in hot-rolled steels, embrittlement of the heat-affected zone (HAZ) in welded steels, and poor cold formability.

[0008] Currently, stirring power is adjusted by human operators based on visual observation. However, such adjustments are not satisfactory. They require constant operator attention and are susceptible to human error. Summary of the Invention

[0009] One of the objectives of this invention is to address this problem by proposing a method for controlling the stirring of molten metal, which achieves optimal stirring while ensuring low nitrogen uptake and low oxidation of the molten metal during stirring.

[0010] Therefore, the present invention relates to a method for controlling the stirring of molten metal in a vessel of a steelmaking furnace, the vessel comprising a metal bath containing molten metal and a slag layer at least partially covering the molten metal, the method comprising the following steps:

[0011] - Measure at least two parameters representing the metal bath contained within the container during stirring;

[0012] - Based on the measurement of the at least two parameters, the formation of openings in the slag layer is detected;

[0013] - Adjust stirring based on the detection of open-eye formation;

[0014] Among them, at least two parameters include at least one visual parameter measured on an image of the slag layer captured during stirring, and at least one mechanical parameter representing the mechanical waves generated within the vessel during stirring.

[0015] Because of these characteristics, the formation of open eyes can be effectively detected based on visual parameters measured on the slag layer image and mechanical parameters representing the mechanical waves generated within the vessel during agitation. The visual parameters enable visual detection of open eye formation. Some of the mechanical waves generated within the vessel represent agitation. Monitoring these mechanical waves allows it to be determined whether agitation leads to open eye formation.

[0016] Furthermore, relying on both visual and mechanical parameters allows for more precise control over the stirring process.

[0017] For example, in the case of gas agitation, monitoring at least one mechanical parameter enables the determination of the effective amount of agitating gas injected into the bath, regardless of the agitating gas flow rate setpoint, which may be affected by, for example, the state of the gas injection device (e.g., the corresponding porous plug may be blocked), while monitoring visual parameters enables consideration of slag characteristics that affect the formation of the opening, such as its viscosity or its thickness.

[0018] For example, even with gas agitation, if only mechanical parameters are considered to control the agitation flow rate, the maximum acceptable flow rate to avoid opening formation for some slags may not be the same as the maximum acceptable flow rate to avoid opening formation for another, thicker slag. Therefore, for thicker slags, a higher flow rate can be used without forming openings, and agitation efficiency can be improved without the risk of exposing molten metal to air.

[0019] Therefore, monitoring at least one visual parameter and at least one mechanical parameter enables more accurate adjustment of the stirring according to different conditions of the metal bath.

[0020] The method may also include the following features, either individually or in any technically feasible combination:

[0021] - The stirring of the molten metal is carried out over a period of time, during which the method is executed at several control moments.

[0022] - At each control moment, during the adjustment step, if no eye formation is detected, the stirring power is increased or kept constant; if eye formation is detected, the stirring power is decreased.

[0023] - Images of the slag layer were captured by a thermal imager, and at least one visual parameter included the emissivity of the slag layer;

[0024] - Mechanical waves are vibrations that propagate within the walls of a container, and these vibrations depend on stirring;

[0025] - The detection step is also based on the value of at least one additional parameter representing the metal bath, which includes at least one of the following:

[0026] - At least one stirring parameter representing stirring power;

[0027] - At least one chemical parameter representing the compositional properties of the slag layer;

[0028] - At least one geometric parameter representing the width of the slag layer;

[0029] - At least one thermal parameter representing the temperature of the metal bath;

[0030] - The method also includes the step of measuring at least one additional parameter to obtain the value of at least one additional parameter;

[0031] - The detection process is based on a machine learning model that considers:

[0032] - Multiple previous values ​​of at least two parameters and / or at least one additional parameter during a previous time of stirring of molten metal contained in a container and / or during a previous time of stirring of molten metal contained in another container;

[0033] - Detect the formation of openings in the corresponding slag layer based on multiple previous values;

[0034] - Stirring is achieved by blowing a stirring gas, such as argon, into the molten metal; and

[0035] - Stirring is performed to desulfurize the molten metal.

[0036] The present invention also relates to steel production equipment, which includes at least:

[0037] - A steelmaking furnace, comprising a vessel designed to contain a bath of molten metal and a slag layer at least partially covering the molten metal; and

[0038] - A stirring device, comprising:

[0039] - A stirring tool configured to stir molten metal within a container;

[0040] - At least two sensors configured to generate data representing at least two parameters representing the metal bath during stirring;

[0041] - Control module, configured as follows:

[0042] - Receives data representing at least two parameters;

[0043] - Based on data representing at least two parameters, detect the formation of openings in slag layers; and

[0044] - Adjust the stirring power of the stirring tool based on the detection of eye formation.

[0045] The at least two sensors include at least one camera configured to capture images of the slag layer, and at least one accelerometer configured to measure mechanical waves generated within the vessel during stirring.

[0046] The steel production equipment may also include the following features, either individually or in any technically feasible combination:

[0047] - The stirring tool is configured to stir molten metal within a time period, and the control module is configured to receive data representing at least two parameters at several control moments within that time period, detect the formation of openings in the slag layer, and adjust the stirring power of the stirring tool.

[0048] - At each control moment, the control module is configured as follows:

[0049] - If no eye formation is detected, increase or maintain a constant stirring power; and

[0050] - If eye formation is detected, reduce the stirring power;

[0051] - At least one camera is a thermal imager configured to measure the emissivity of the slag layer; and

[0052] - At least one accelerometer is configured to measure vibrations propagating in the walls of the container, the vibrations being dependent on agitation. Attached Figure Description

[0053] Other aspects and advantages of the invention will become apparent after reading the following description, which is given by way of example and with reference to the accompanying drawings, in which:

[0054] - Figure 1 A schematic cross-sectional view of a portion of a steel production apparatus according to an embodiment of the present invention; and

[0055] - Figure 2 This is a schematic diagram of a method for controlling the stirring of molten metal inside a vessel in a steelmaking furnace according to an embodiment of the present invention. Detailed Implementation

[0056] refer to Figure 1 The steel production equipment 10 according to the present invention is described.

[0057] The steel production equipment 10 includes at least a steelmaking furnace 20 and a stirring device 40.

[0058] The steelmaking furnace 20 is designed to receive a metal bath 1 containing molten metal 3 and a slag layer 5. The metal bath 1 is obtained, for example, in another steelmaking furnace (not shown), such as a basic oxygen converter (BOF) or an electric arc furnace (EAF). The metal bath 1 is obtained from metallic materials.

[0059] Preferably, the steel production equipment 10 includes an EAF (not shown) in which a metal bath 1 is obtained.

[0060] For example, steelmaking furnace 20 is a ladle furnace or a stirring furnace.

[0061] The steelmaking furnace 20 includes a container 22 defining an internal volume 24, within which the metal bath 1 is housed. (Example) Figure 1As shown in the example, container 22 includes a bottom wall 26 and side walls 27. For example, container 22 also includes a removable furnace top (not shown) designed to cooperate with the side walls 27 and the bottom wall 26 to define an internal volume 24.

[0062] The slag layer 5 at least partially covers the molten metal 3.

[0063] For example, the metallic material includes scrap steel. The scrap steel may be melted together with pig iron and / or direct reduced iron (DRI). For example, the scrap steel that can be used is referred to as old scrap (E1 or E3), new scrap (E8), shredded scrap (E40), or fragmented scrap (E46) in the EU-21 scrap steel specification. In a preferred embodiment, the material melted into the EAF comprises at least 40% DRI by weight, preferably 40% to 60% DRI by weight.

[0064] The percentage of DRI and / or pig iron in the charge is highly dependent on the quality of the scrap steel available and the type of steel to be produced. If the levels of impurities such as copper, chromium, molybdenum, nickel, tin, antimony, zinc, and / or arsenic are low, the amount of scrap steel to be charged can be increased, thereby reducing the amount of DRI.

[0065] The stirring device 40 includes a stirring tool 42, at least two sensors 50, and a control module 70. Advantageously, the stirring device 40 also includes at least one additional sensor 60.

[0066] The stirring tool 42 is configured to stir the molten metal 3 within the container 22. In particular, the stirring tool 42 is configured to stir the molten metal 3 for a period of time.

[0067] For example, the stirring tool 42 includes a gas blower 44 configured to blow stirring gas 46 into the molten metal 3. Figure 1 As shown in the example, a gas blower 44 is arranged on the bottom wall 26 of container 22, located in the bottom portion 25 of the internal volume 24, opposite to the slag layer 5. For example, the stirring gas is argon.

[0068] At least two sensors 50 are configured to generate data representing at least two parameters of the metal bath 1 during stirring.

[0069] At least two sensors 50 include at least one camera 52 configured to capture images of the slag layer 5, and at least one accelerometer 54 configured to measure mechanical waves generated within the container 22 during stirring. The accelerometer 54 may be located directly on the container 22 or on a structure supporting the container 22.

[0070] For example, at least one camera 52 is a thermal imager configured to measure the emissivity of the slag layer 5.

[0071] For example, at least one accelerometer 54 is configured to measure vibrations propagating in the walls 26, 27.

[0072] At least one additional sensor 60 is configured to generate data representing at least one additional parameter representing the metal bath 1.

[0073] For example, the at least one additional parameter includes at least one of the following:

[0074] - At least one stirring parameter representing the stirring power used to stir the molten metal 3, such as stirring gas flow rate and / or stirring gas back pressure;

[0075] - At least one chemical parameter representing the compositional properties of the slag layer 5 contained within container 22, such as the oxygen activity of the slag and / or the oxide content of the slag;

[0076] - At least one geometric parameter representing the width W of the slag layer 5;

[0077] - At least one thermal parameter representing the temperature of metal bath 1;

[0078] Advantageously, such as Figure 1 As shown in the example, at least one additional sensor 60 includes at least one of the following:

[0079] - At least one sensor 60A for generating data representing at least one stirring parameter;

[0080] - At least one sensor 60B for generating data representing at least one chemical parameter, such as an analyzer and / or a device configured to determine at least one chemical parameter by online LIBS (Laser Induced Breakdown Spectroscopy) measurement, spectroscopy or by electrochemical measurement;

[0081] - At least one sensor 60C for generating data representing geometric parameters;

[0082] - At least one sensor 60D, such as a thermal imager or pyrometer, used to generate data representing thermal parameters.

[0083] Control module 70 is configured as follows:

[0084] - Receives data representing at least two parameters;

[0085] - Based on data representing at least two parameters, the formation of openings 8 in slag layer 5 is detected; and

[0086] - Adjust the stirring power of the stirring tool 42 based on the detection of the formation of the open eye 8.

[0087] "Open eye 8" refers to the open area through the slag layer 5, in which the molten metal can come into direct contact with the ambient air.

[0088] Advantageously, the control module 70 is also configured to receive data representing at least one additional parameter. For example, the control module 70 is configured to detect the formation of the eye opening 8 based on data representing at least two parameters and / or data representing at least one additional parameter.

[0089] Specifically, the control module 70 is configured to receive data representing at least two parameters at several control moments within the time period, detect the formation of openings 8 in the slag layer 5, and adjust the stirring power of the stirring tool 42.

[0090] Advantageously, at each control moment, the control module 70 is configured to increase or maintain a constant stirring power if no eye formation is detected, and to decrease the stirring power if eye formation is detected.

[0091] For example, control module 70 is configured to detect the formation of eye opening 8 based on a machine learning model, which at least considers:

[0092] - At a previous moment during the previous stirring of molten metal 3 contained in container 22 and / or during the previous stirring of molten metal contained in another container, at least two parameters and / or at least one additional parameter with multiple previous values;

[0093] - The formation of open holes 8 in the corresponding slag layer 5 is detected based on multiple previous values.

[0094] exist Figure 1 In the example shown, the control module 70 is made in the form of software or a software module, which can be executed by the processor of an electronic device (not shown). The memory of the electronic device is then able to store the control software. The processor is then able to execute the software.

[0095] In variations not shown, the control module is manufactured as a programmable logic component such as a FPGA (Field Programmable Gate Array) or an integrated circuit such as an ASIC (Application Specific Integrated Circuit).

[0096] When an electronic device is implemented as one or more software programs (i.e., as a computer program, also known as a computer program product), it can also be recorded on a computer-readable medium (not shown). A computer-readable medium is, for example, a medium capable of storing electronic instructions and coupled to a bus of a computer system. Examples of readable media include optical discs, magneto-optical discs, ROM memory, RAM memory, any type of non-volatile memory (e.g., FLASH or NVRAM), or magnetic cards. The computer program containing the software instructions is stored on the readable medium.

[0097] refer to Figure 2 A method 100 for controlling the stirring of molten metal 3 inside a container 22 of a steelmaking furnace 20 is described.

[0098] Advantageously, method 100 is performed at each of several control moments during the time period of stirring the molten metal 3.

[0099] For example, stirring is performed by blowing stirring gas 46 into the molten metal 3. Advantageously, stirring is performed to desulfurize the molten metal 3.

[0100] Method 100 includes a step 110 of measuring at least two parameters representing the metal bath 1 contained within container 22 during stirring. The at least two parameters include at least one visual parameter measured on an image of the slag layer 5 captured during stirring, and at least one mechanical parameter representing mechanical waves generated within container 22 during stirring. For example, at least one visual parameter is measured by camera 52, and at least one mechanical parameter is measured by accelerometer 54.

[0101] For example, at least one visual parameter includes the emissivity of the slag layer 5.

[0102] For example, mechanical waves are vibrations that propagate in the walls 26, 27 of container 22, and these vibrations depend on stirring.

[0103] Advantageously, method 100 also includes step 120 of measuring at least one additional parameter representing metal bath 1.

[0104] For example, at least one stirring parameter is measured by sensor 60A, at least one chemical parameter is measured by sensor 60B, at least one geometric parameter is measured by sensor 60C, and at least one thermal parameter is measured by sensor 60D.

[0105] Method 100 further includes step 130 of detecting the formation of an opening 8 in the slag layer 5 based on measurements of at least two parameters, advantageously based on measurements of at least two parameters and / or at least one additional parameter.

[0106] For example, high emissivity in certain regions of slag layer 5 indicates the formation of an opening 8 in said regions of slag layer 5. For example, typical vibration modes in the walls 26, 27 of container 22 indicate the formation of an opening 8 in said regions of slag layer 5.

[0107] Advantageously, detection step 130 is based on the aforementioned machine learning model.

[0108] For example, the formation of the eye 8 is detected when the actual value of the parameter and / or additional parameter representing the metal bath 1 is substantially equal to the value of the parameter and / or additional parameter associated with the formation of the eye 8.

[0109] Method 100 also includes step 140 of adjusting the stirring, particularly the stirring power, based on the detection of the formation of the open eye 8.

[0110] For example, at each control moment, if no eye formation is detected, the stirring power is increased or kept constant, and if eye formation is detected, the stirring power is decreased.

[0111] By reducing the stirring power upon detecting the formation of an opening, this invention enables the prevention of further formation / expansion of the opening, or the closure of the opening (i.e., the formation of a new slag layer within the opening to block it). This allows for optimal slag coverage of the metal bath and reduces direct contact between the molten metal and air.

[0112] Thanks to the invention described above, the formation of the open eye 8 can be effectively detected. The stirring power can be automatically adjusted without human operator intervention. This optimizes stirring while reducing the risk of the molten metal 3 absorbing unwanted compounds such as nitrogen or oxygen.

Claims

1. A method (100) for controlling the stirring of molten metal (3) in a container (22) of a steelmaking furnace (20), the container (22) comprising a metal bath (1) containing the molten metal (3) and a slag layer (5) at least partially covering the molten metal (3), the method (100) comprising the following steps: - Measure (110) at least two parameters representing the metal bath (1) contained in the container (22) during stirring; - Based on the measurement of the at least two parameters, the formation of an opening (8) in the slag layer (5) is detected (130); - Adjust the stirring (140) based on the detection of the formation of the open eye (8); The at least two parameters include at least one visual parameter measured on an image of the slag layer (5) captured during stirring, and at least one mechanical parameter representing the mechanical waves generated within the container (22) during stirring.

2. The method (100) according to claim 1, wherein, The stirring of the molten metal (3) is carried out over a period of time, and the method (100) is performed at several control moments within the period of time.

3. The method (100) according to claim 2, wherein, At each control moment, during the adjustment step (140), if no eye formation is detected, the stirring power is increased or kept constant; if eye formation is detected, the stirring power is decreased.

4. The method (100) according to any one of the preceding claims, wherein, The image of the slag layer (5) is captured by a thermal imager (52), and the at least one visual parameter includes the emissivity of the slag layer (5).

5. The method (100) according to any one of the preceding claims, wherein, The mechanical wave is a vibration that propagates in the walls (26, 27) of the container, and the vibration depends on the stirring.

6. The method (100) according to any one of the preceding claims, wherein, The detection step (130) is also based on the value of at least one additional parameter representing the metal bath (1), said at least one additional parameter including at least one of the following: - At least one stirring parameter representing stirring power; - At least one chemical parameter representing the compositional properties of the slag layer (5); - At least one geometric parameter representing the width (W) of the slag layer (5); - At least one thermal parameter representing the temperature of the metal bath (1).

7. The method (100) of claim 6, comprising the step (120) of measuring the at least one additional parameter to obtain a value of the at least one additional parameter.

8. The method (100) according to claim 6 or 7, wherein, The detection step (130) is based on a machine learning model, which considers: - Multiple previous values ​​of the at least two parameters and / or the at least one additional parameter during a previous stirring of the molten metal (3) contained in the container (22) and / or at a previous moment during a previous stirring of the molten metal contained in another container; - The formation of openings (8) in the corresponding slag layer (5) is detected based on the multiple prior values.

9. The method (100) according to any one of the preceding claims, wherein, The stirring is carried out by blowing a stirring gas (46), such as argon, into the molten metal (3).

10. The method (100) according to any one of the preceding claims, wherein, The stirring is performed to desulfurize the molten metal (3).

11. A steel production equipment (10), comprising at least: - A steelmaking furnace (20), comprising a vessel (22) designed to contain a metal bath (1) containing molten metal (3) and a slag layer (5) at least partially covering the molten metal (3); and - A stirring device (40), comprising: - A stirring tool (42) configured to stir the molten metal (3) within the container; - At least two sensors (50) configured to generate data representing at least two parameters representing the metal bath (1) during stirring; - Control module (70), configured as follows: - Receive data representing at least two of the parameters; - Based on data representing the at least two parameters, detect the formation of openings (8) in the slag layer (5); and - Adjust the stirring power of the stirring tool (42) based on the detection of the formation of the opening (8). The at least two sensors (50) include at least one camera (52) configured to capture an image of the slag layer (5), and at least one accelerometer (54) configured to measure mechanical waves generated within the container (22) during stirring.

12. The steel production equipment (10) according to claim 11, wherein, The stirring tool (42) is configured to stir the molten metal (3) for a period of time, and the control module (70) is configured to receive data representing the at least two parameters at several control moments during the period of time, detect the formation of openings (8) in the slag layer (5), and adjust the stirring power of the stirring tool (42).

13. The steel production equipment (10) according to claim 12, wherein, At each control moment, the control module (70) is configured as follows: - If no eye-opening formation is detected, increase or maintain the stirring power constant; and - If eye formation is detected, reduce the stirring power.

14. The steel production equipment (10) according to any one of claims 11 to 13, wherein, The at least one camera (52) is a thermal imager configured to measure the emissivity of the slag layer (5).

15. The steel production equipment (10) according to any one of claims 11 to 14, wherein, The at least one accelerometer (54) is configured to measure vibrations propagating in the walls (26, 27) of the container (22), the vibrations depending on the stirring.

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