An automatic control method for power supply to an electric arc furnace

Abstract

This invention relates to the field of automatic control technology, specifically to an automatic control method for power supply to an electric arc furnace. This application divides the electric arc furnace power supply process into an arc ignition stage, a penetration stage, a melting stage, an oxidation stage, and a heating stage. Then, according to user instructions, voltage levels are set for each of these stages. During power supply, the height of the power supply electrode, current stability, the composition of the molten steel being smelted in the electric arc furnace, and the time signal of the power supply clock are acquired. Finally, based on the electrode height, current stability, molten steel composition, and time signal, the power supply stage of the electric arc furnace is switched automatically throughout the entire process. This solves the problem of manual operation relying on human experience for judgment, lacking quantitative indicators, and having poor accuracy.

Description

Technical Field

[0001] This invention relates to the field of automatic control technology, and specifically to an automatic control method for power supply to an electric arc furnace. Background Technology

[0002] Power supply operation is one of the main operations in electric arc furnace steelmaking. Different smelting stages have different requirements for the power supply level. The arc ignition stage requires a rapid and stable arc to form between the electrode and the steel charge; the penetration stage requires a sufficiently high arc temperature to quickly melt the scrap steel below, allowing the electrode to descend rapidly; the melting stage requires a long arc and high power to rapidly melt the scrap steel; the oxidation stage requires a reduced heating rate of the molten pool to provide good dephosphorization conditions; and the heating stage requires rapid heating in conjunction with thicker foam slag. Reasonable power supply operation can accelerate scrap steel melting, reduce electrode consumption, improve energy utilization, and reduce furnace lining erosion. Therefore, improving the level of power supply operation is of great significance for reducing electric arc furnace smelting costs and improving smelting efficiency. Currently, power supply operation is achieved manually by the electric arc furnace operator based on experience, switching between power supply levels.

[0003] However, manual operation is greatly influenced by subjective consciousness. Different operators have different understandings of the steelmaking process and different operating habits, making it difficult to achieve standardized operation. In addition, relying on human experience for judgment lacks quantitative indicators and has poor accuracy, especially when there are large variations in the raw materials fed into the furnace, which often leads to significant deviations in judgment. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an automatic control method for power supply of electric arc furnaces, so as to overcome the problems of current manual operation relying on human experience for judgment, lacking quantitative indicators, and having poor accuracy.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An automatic control method for power supply to an electric arc furnace includes:

[0007] The electric arc furnace power supply process is divided into the arc ignition stage, the well penetration stage, the melting stage, the oxidation stage, and the heating stage.

[0008] The voltage levels are set for the arc initiation stage, the well drilling stage, the melting stage, the oxidation stage, and the heating stage according to user instructions.

[0009] Acquire the power supply electrode height, current stability, steel composition in the electric arc furnace, and power supply clock time signal;

[0010] The power supply phase of the electric arc furnace is switched according to the electrode height, the current stability, the steel composition, and the time signal.

[0011] Furthermore, the method described above, wherein switching the power supply stage of the electric arc furnace based on the electrode height, the current stability, the molten steel composition, and the time signal includes:

[0012] When power is supplied and the power supply clock starts counting, the arc initiation phase is determined to have begun.

[0013] Obtain the actual height of the electrode and the arc initiation height;

[0014] When the ratio of the actual height of the electrode to the arc-starting height of the electrode is less than the preset well-penetration setting value, and the time signal is greater than the minimum setting value of the energization time of the arc-starting stage, the arc-starting stage is determined to end and the well-penetration stage begins.

[0015] When the ratio of the actual height of the electrode to the arc initiation height of the electrode is less than the preset melting setting value, and the time signal is greater than the minimum setting value of the energizing time during the well penetration stage, the well penetration stage is determined to end and the melting stage begins.

[0016] After the melting stage begins, the average value of the three-phase current is sampled according to the preset sampling period;

[0017] Determine the number of stable current measurements from the sampled data;

[0018] When the number of stable current cycles exceeds the preset oxidation setting value, and the time signal exceeds the minimum setting value for the energizing time of the melting stage, the melting stage is determined to end and the oxidation stage is determined to begin.

[0019] Obtain the composition of molten steel;

[0020] When the phosphorus content in the molten steel meets the endpoint phosphorus content requirement, and the time signal is greater than the minimum set value of the energizing time in the oxidation stage, the oxidation stage is determined to end and the heating stage begins.

[0021] When the user's smelting end signal is received, the heating phase is determined to be over.

[0022] Furthermore, in the method described above, determining the number of stable current measurements of the sampled data includes:

[0023] Establish a sampling queue;

[0024] The sampled data is placed in the sampling queue, and each time a new sampled data is sampled, the new sampled data is placed at the tail of the queue, and the original sampled data at the head of the queue is discarded.

[0025] Obtain the maximum and minimum values ​​of the sampled data in the sampling queue;

[0026] Calculate the difference between the maximum and minimum values ​​in the sampling queue, and increment the number of stable current determinations by one when the difference is less than a preset stable current difference.

[0027] Furthermore, in the method described above, determining the start of the arc initiation phase when power is supplied and the power supply clock starts counting includes:

[0028] When the user's smelting start signal is received and the sum of the three-phase currents is greater than zero, the power supply clock starts timing, and the arc initiation stage is determined to have begun.

[0029] Furthermore, the methods described above also include:

[0030] The power supply clock resets the time signal and restarts timing after the voltage level switch is completed.

[0031] Furthermore, in the above-described method, determining the end of the heating phase upon receiving a smelting completion signal from the user includes:

[0032] When the user's smelting end signal is received, the power supply clock stops counting and the time signal is cleared to determine that the heating stage has ended.

[0033] Furthermore, in the method described above, the three-phase current is the secondary current of the transformer.

[0034] Furthermore, in the above-described method, obtaining the actual height of the electrode and the arc initiation height includes:

[0035] During the power supply process, the distance between the bottom of the electrode and the surface of the molten steel is obtained, and the distance is the actual height of the electrode;

[0036] The distance between the bottom of the electrode and the surface of the molten steel when the electrode initiates an arc is obtained, and the distance is the arc initiation height of the electrode.

[0037] The beneficial effects of the automatic power supply control method for an electric arc furnace of the present invention are as follows:

[0038] This application divides the electric arc furnace power supply process into an arc ignition stage, a penetration stage, a melting stage, an oxidation stage, and a heating stage. Then, according to user instructions, voltage levels are set for each of these stages. During power supply, the application acquires signals such as the height of the power supply electrodes, current stability, the composition of the molten steel in the electric arc furnace, and the power supply clock. Finally, based on these signals, the application automatically switches between the electric arc furnace's power supply stages, thus solving the problem of manual operation relying on experience and lacking quantitative indicators, resulting in poor accuracy. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a flowchart provided in one embodiment of an automatic power supply control method for an electric arc furnace according to the present invention;

[0041] Figure 2 This is a voltage level setting table for each stage provided in one embodiment of an automatic control method for power supply to an electric arc furnace according to the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0043] Manual operation is greatly influenced by subjective consciousness. Different operators have different understandings of the steelmaking process and different operating habits, making it difficult to achieve standardized operation. In addition, relying on human experience for judgment lacks quantitative indicators and has poor accuracy, especially when there are large variations in the raw materials fed into the furnace, which often leads to significant deviations in judgment.

[0044] In view of this, the purpose of this invention is to provide an automatic control method for power supply of electric arc furnaces, so as to overcome the problems of current manual operation relying on human experience for judgment, lacking quantitative indicators, and having poor accuracy.

[0045] like Figure 1 As shown, Figure 1 This is a flowchart of an embodiment of an automatic power supply control method for an electric arc furnace according to the present invention. This embodiment may include the following steps:

[0046] S1. The electric arc furnace power supply process is divided into the arc ignition stage, the well penetration stage, the melting stage, the oxidation stage, and the heating stage.

[0047] S2. Set the voltage level for the arc initiation stage, well penetration stage, melting stage, oxidation stage and heating stage according to the user's instructions.

[0048] S3. Acquire the power supply electrode height, current stability, steel composition in the electric arc furnace, and power supply clock time signals.

[0049] S4. Switch the power supply stage of the electric arc furnace according to the electrode height, current stability, molten steel composition and time signal.

[0050] Understandably, this application divides the electric arc furnace power supply process into an arc ignition stage, a penetration stage, a melting stage, an oxidation stage, and a heating stage. Then, according to user instructions, voltage levels are set for each of the arc ignition stage, penetration stage, melting stage, oxidation stage, and heating stage. During power supply, the power supply electrode height, current stability, steel composition in the electric arc furnace, and power supply clock time signals are acquired. Finally, based on the electrode height, current stability, steel composition, and time signals, the power supply stage of the electric arc furnace is switched automatically throughout the entire process. This solves the problem of manual operation relying on human experience for judgment, lacking quantitative indicators, and having poor accuracy.

[0051] Preferably, step S4 is as follows:

[0052] When power is supplied and the power supply clock starts counting, the arc initiation phase is determined to have begun.

[0053] Obtain the actual height of the electrode and the arc initiation height;

[0054] When the ratio of the actual height of the electrode to the arc-starting height of the electrode is less than the preset well-penetration setting value, and the time signal is greater than the minimum setting value of the energization time of the arc-starting stage, the arc-starting stage is determined to end and the well-penetration stage begins.

[0055] When the ratio of the actual height of the electrode to the arc-starting height of the electrode is less than the preset melting setting value, and the power supply time signal is greater than the minimum setting value of the power supply time in the well-drilling stage, the well-drilling stage is determined to end and the melting stage begins.

[0056] After the melting stage begins, the average value of the three-phase current is sampled according to the preset sampling period;

[0057] Determine the number of times the sampled data stabilizes at the current level;

[0058] When the number of stable current cycles exceeds the preset oxidation setting value and the time signal exceeds the minimum setting value for the energizing time of the melting stage, the melting stage is determined to end and the oxidation stage is determined to begin.

[0059] Obtain the composition of molten steel;

[0060] When the phosphorus content in the molten steel meets the endpoint phosphorus content requirement, and the time signal is greater than the minimum set value of the energizing time in the oxidation stage, the oxidation stage is determined to be over and the heating stage is started.

[0061] When the user's smelting end signal is received, the heating phase is determined to be over.

[0062] Understandably, by setting the starting conditions for each power supply stage, the entire power supply process can be automatically switched, thus eliminating the need to rely on manual experience to judge the power supply voltage. Furthermore, the settings for well penetration, minimum energizing time during the arc initiation stage, melting, oxidation, melting, and oxidation stages are all set by the user according to their own needs.

[0063] In some optional embodiments, the number of times the current is stabilized is determined by establishing a sampling queue; placing the sampled data into the sampling queue, and each time a new sampled data is sampled, the new sampled data is placed at the end of the queue and the original sampled data at the head of the queue is discarded; obtaining the maximum and minimum values ​​of the sampled data in the sampling queue; calculating the difference between the maximum and minimum values ​​in the sampling queue, and when the difference is less than a preset stable current difference, the number of times the current is stabilized is incremented by one.

[0064] It is understandable that by judging the difference between the maximum and minimum sampled data in a sampling queue, it is possible to determine whether a sampling queue has a stable voltage, thereby ensuring the stability of the power supply to the electric arc furnace and reducing errors caused by unstable power supply.

[0065] Preferably, when the user's smelting start signal is received and the sum of the three-phase currents is greater than zero, the power supply clock starts timing to determine the start of the arc initiation stage.

[0066] In some optional embodiments, the power supply clock resets the time signal and restarts timing after the voltage level switch is completed; at the same time, when the user's smelting end signal is obtained, the power supply clock stops timing and resets the time signal, determining that the heating stage has ended.

[0067] Preferably, the three-phase current is the secondary current of the transformer.

[0068] Preferably, the distance between the bottom of the electrode and the surface of the molten steel during the power supply process is obtained, and the distance is the actual height of the electrode; the distance between the bottom of the electrode and the surface of the molten steel when the electrode starts to arc is obtained, and the distance is the arc height of the electrode.

[0069] In practice, the power supply levels for different smelting stages of an electric arc furnace are as follows: Figure 2As shown, the power supply levels are set to 8 for the arc initiation stage, 12 for the well penetration stage, 15 for the melting stage, 6 for the oxidation stage, and 13 for the heating stage. The well penetration setting is 80%, and the minimum energizing time for the well penetration stage is 1 minute; the melting setting is 25%, and the stable current determination condition is not less than 15 kA; the oxidation setting is 100%, and the minimum energizing time for both the melting and oxidation stages is 0.5 minutes. The automatic power supply control process is as follows:

[0070] After smelting preparations are completed, the electric arc furnace operator issues a smelting start signal, the vacuum switch is closed, and the arc ignition stage begins. The voltage level is switched to level 8. The electrodes begin to descend, and the electrode displacement detection device located on the three-phase electrode columns collects the displacement data of the three-phase electrodes in real time and uploads it to the electric arc furnace PLC. The PLC calculates and converts the displacement data into electrode height data based on the rated molten steel level. When all three-phase currents are greater than zero, the current electrode height data is recorded and marked as the arc ignition height. The power supply clock starts timing, with the clock timed in minutes and updating at a rate of 1 second (i.e., automatically incrementing by 1 / 60 of a minute every second).

[0071] As the scrap steel melts, the electrode descends continuously. When the ratio of the actual electrode height to the arc-starting height is less than 80% of the arc-starting set value, if the power supply clock is greater than the minimum set value of 1 minute for the arc-starting stage power-on time, the arc-starting stage is determined to be over and the well-penetrating stage begins, and the power supply level is switched to level 12. If the power supply clock is less than 1 minute, the power supply level is switched to level 12 after the power supply clock is greater than 1 minute. After the level is switched to level 12, the power supply clock is reset to zero and the timing restarts.

[0072] When the ratio of the actual electrode height to the arc initiation height is less than 25% of the well penetration setting, if the power supply clock is greater than the minimum setting value of the well penetration stage power-on time by 0.5 minutes, the well penetration stage is determined to be over and the melting stage to begin, and the power supply level is switched to level 15; if the power supply clock is less than 0.5 minutes, the power supply level is switched to level 15 after the power supply clock is greater than 0.5 minutes, and the power supply clock is reset to zero and the timing restarts after the level is switched to level 15.

[0073] After the melting stage begins, the scrap steel at the bottom melts faster, causing the upper scrap steel to collapse due to loss of support, resulting in large current fluctuations. Once the scrap steel in the furnace is mostly melted, the current fluctuations decrease. Electric arc furnace process engineers analyze the stability of the current to determine the timing of the switch between the melting and oxidation stages. Specifically, after the melting stage begins, the PLC samples the average three-phase current at a 1-second interval, with 20 samples forming a queue. Each time a new data point is sampled, it is placed at the end of the queue, and the previous data point at the head of the queue is discarded. The difference between the maximum and minimum values ​​in the queue is calculated. If this difference is not greater than 15, the current is considered stable, and the stable current determination count is incremented by 1. When the stable current determination count exceeds 100, if the power supply clock exceeds the minimum set value for the melting stage energizing time by 1 minute, the melting stage is considered to have ended, the oxidation stage to begin, and the power supply level is switched to level 6. If the power supply clock is less than 1 minute, the power supply level is switched to level 6 after the power supply clock exceeds 1 minute. After switching to gear 6, the power clock is reset to zero and the timing restarts.

[0074] Upon entering the oxidation stage, the PLC automatically detects the steel composition. When the phosphorus content in the molten steel meets the tapping requirements, if the power supply clock exceeds the minimum set value for the oxidation stage power-on time by 0.5 minutes, the oxidation stage is considered complete, the heating stage begins, and the power supply level switches to level 13. If the power supply clock is less than 0.5 minutes, the power supply level switches to level 13 after the power supply clock exceeds 0.5 minutes. After switching to level 13, the power supply clock is reset to zero and restarts.

[0075] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0076] It should be noted that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.

[0077] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0078] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0079] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0080] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0081] The storage media mentioned above can be read-only memory, disk, or optical disk, etc.

[0082] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0083] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An automatic control method for power supply to an electric arc furnace, characterized in that, include: The electric arc furnace power supply process is divided into the arc ignition stage, the well penetration stage, the melting stage, the oxidation stage, and the heating stage. The voltage levels are set for the arc initiation stage, the well drilling stage, the melting stage, the oxidation stage, and the heating stage according to user instructions. Acquire the power supply electrode height, current stability, steel composition in the electric arc furnace, and power supply clock time signal; The power supply stage of the electric arc furnace is switched according to the electrode height, the current stability, the steel composition, and the time signal. The step of switching the power supply stage of the electric arc furnace based on the electrode height, the current stability, the molten steel composition, and the time signal includes: When power is supplied and the power supply clock starts counting, the arc initiation phase is determined to have begun. Obtain the actual height of the electrode and the arc initiation height; When the ratio of the actual height of the electrode to the arc-starting height of the electrode is less than the preset well-penetration setting value, and the time signal is greater than the minimum setting value of the energization time of the arc-starting stage, the arc-starting stage is determined to end and the well-penetration stage begins. When the ratio of the actual height of the electrode to the arc initiation height of the electrode is less than the preset melting setting value, and the time signal is greater than the minimum setting value of the energizing time during the well penetration stage, the well penetration stage is determined to end and the melting stage begins. After the melting stage begins, the average value of the three-phase current is sampled according to the preset sampling period; Determine the number of stable current measurements from the sampled data; When the number of stable current cycles exceeds the preset oxidation setting value, and the time signal exceeds the minimum setting value for the energizing time of the melting stage, the melting stage is determined to end and the oxidation stage is determined to begin. Obtain the composition of molten steel; When the phosphorus content in the molten steel meets the endpoint phosphorus content requirement, and the time signal is greater than the minimum set value of the energizing time in the oxidation stage, the oxidation stage is determined to end and the heating stage begins. When the user's smelting end signal is received, the heating phase is determined to be over.

2. The method according to claim 1, characterized in that, The determination of the number of stable current values ​​in the sampled data includes: Establish a sampling queue; The sampled data is placed in the sampling queue, and each time a new sampled data is sampled, the new sampled data is placed at the tail of the queue, and the original sampled data at the head of the queue is discarded. Obtain the maximum and minimum values ​​of the sampled data in the sampling queue; Calculate the difference between the maximum and minimum values ​​in the sampling queue, and increment the number of stable current determinations by one when the difference is less than a preset stable current difference.

3. The method according to claim 2, characterized in that, The determination that the arc initiation phase begins when power is supplied and the power supply clock starts counting includes: When the user's smelting start signal is received and the sum of the three-phase currents is greater than zero, the power supply clock starts timing, and the arc initiation stage is determined to have begun.

4. The method according to claim 1, characterized in that, Also includes: The power supply clock resets the time signal and restarts timing after the voltage level switch is completed.

5. The method according to claim 1, characterized in that, The determination of the end of the heating phase upon receiving the user's smelting completion signal includes: When the user's smelting end signal is received, the power supply clock stops counting and the time signal is cleared to determine that the heating stage has ended.

6. The method according to claim 1, characterized in that, The three-phase current is the secondary current of the transformer.

7. The method according to claim 1, characterized in that, The acquisition of the actual height and arc initiation height of the electrode includes: During the power supply process, the distance between the bottom of the electrode and the surface of the molten steel is obtained, and the distance is the actual height of the electrode; The distance between the bottom of the electrode and the surface of the molten steel when the electrode initiates an arc is obtained, and the distance is the arc initiation height of the electrode.

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