A method for controlling the furnace bottom and reducing the end-point carbon-oxygen concentration product by separately controlling the flow of the bottom blowing branch

Abstract

The application discloses a method for controlling the bottom of a furnace and reducing the end-point carbon-oxygen concentration product by separately controlling the flow of bottom blowing branch pipes, and belongs to the field of metallurgical manufacturing. In the application, m kinds of bottom blowing modes are arranged at the bottom of a converter, and each mode corresponds to each production process, and each mode is selected to separately control or jointly control v bottom blowing branch pipes. When the joint control is performed, the flow setting parameters of the v branch pipes are the same, and the m kinds of mode parameters are selected. When the separate control is performed, the flow of the v branch pipes is separately controlled, and the m*v kinds of mode parameters are selected. By reforming the bottom blowing control system of the converter, each gas supply element is designed to realize independent automatic control of the gas flow, the bottom gas supply intensity can be adjusted in a large range, the stirring force in the converter can be controlled, the bottom blowing effect can be maximally exerted, the slag-steel reaction balance can be promoted, the oxygen content in the steel can be reduced, and the steel quality can be improved.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical manufacturing and relates to bottom and side blowing methods for smelting furnaces. More specifically, it relates to a method for controlling the furnace bottom and reducing the final carbon-oxygen concentration product by separately controlling the flow rate of the bottom blowing branch pipe. Background Technology

[0002] The 300t top-and-bottom combined blowing converter of Maanshan Iron & Steel No. 4 Steel Rolling Mill adopts the double-ring slit bottom blowing gas supply element product developed by Beijing Iron & Steel Research Institute. Each converter is equipped with 16 double-ring slit bottom blowing gas supply elements. After adopting the combined blowing process, the molten pool is uniformly stirred, and the bottom gas supply intensity can be adjusted within a large range to control the stirring force in the converter, making it suitable for smelting various steel grades from low carbon steel to high carbon steel.

[0003] The Fourth Steel Rolling Mill primarily produces low-carbon and ultra-low-carbon steel products, with stringent final requirements. The high temperature and high oxygen levels at the furnace bottom make control difficult, resulting in a constant downward trend and damage to the bottom-blowing elements. Frequent maintenance can further clog these elements, hindering the full realization of metallurgical efficiency. To maximize the effectiveness of bottom blowing, promote slag-steel reaction equilibrium, reduce oxygen content in steel, and improve steel quality, it is essential to address the issues of burnout, clogging, and maintenance of the bottom-blowing gas supply elements, ensuring their lifespan matches the furnace's lifespan.

[0004] Currently, the converter is equipped with 16 double-ring-slit bottom-blowing gas supply elements. The gas supply mode is singular, and the flow rate is the same at all process nodes. When furnace conditions are poor or the bottom-blowing gas supply elements become clogged, dynamic control is impossible. Due to the technological and operational characteristics of the converter smelting process, the corrosion of different parts of the furnace lining is asynchronous. In recent years, the Fourth Steel Rolling Mill has become Maanshan Iron & Steel's largest steel manufacturing unit in terms of both product variety and output. However, the long-term effectiveness of the top and bottom blowing in the converter process severely restricts product development, upgrading, and further efficiency improvement, making it difficult to achieve high-quality development requirements. The failure of bottom blowing in the later stages of furnace operation prevents the realization of the expected metallurgical effects and significant economic benefits of bottom blowing.

[0005] A search revealed that patent CN105441621B discloses an automatic control system and method for bottom blowing gas flow in a single-branch converter. This technology mainly relies on the relationship between pressure and flow rate. When the pressure value is abnormal, the opening of the corresponding branch pipe regulating valve is increased to increase the gas flow rate. The impact force of the high-flow-rate gas pressure is used to break up the slag covering the corresponding branch pipe blowing port. This method mainly solves the problem of easy clogging of the bottom blowing element. Patent CN114262762A discloses a method, apparatus, medium, and equipment for adjusting the bottom blowing flow rate of a converter. It determines the erosion rate of the furnace bottom lining bricks based on the furnace bottom thickness; adjusts the flow rate of the main bottom blowing pipe according to the erosion rate; and during the smelting process, adjusts the bottom blowing flow rate of each branch pipe in real time based on the carbon-oxygen product at the converter endpoint, using a preset smelting heat. Thus, a macroscopic adjustment (coarse adjustment) is first made to the flow rate of the main pipe based on the erosion rate, and then the bottom blowing flow rate of each branch pipe is adjusted in real time based on the carbon-oxygen product, which is equivalent to fine-tuning the bottom blowing flow rate. Therefore, the converter bottom blowing flow rate can be precisely controlled, thereby ensuring steelmaking quality. The above process is based on certain principles. First, the bottom blowing flow rate of the main pipe is adjusted, and then the flow rate of each branch pipe is adjusted in a chain reaction based on the abnormal pressure value of each branch pipe to prevent blockage of the furnace bottom branch pipes. Although the flow rate of different branch pipes deviates according to the pressure value, the overall bottom blowing flow rate adjustment trend is the same for all branch pipes. However, in practice, this still makes it difficult to meet the required performance. Summary of the Invention

[0006] 1. The problem to be solved

[0007] In view of the current situation where the bottom blowing process of converter is not effective and it is difficult to guarantee the long-term effect, the present invention proposes to provide a method to control the flow of the bottom blowing branch pipe and reduce the carbon-oxygen concentration product at the end point. By modifying the converter bottom blowing control system, each gas supply element is designed to achieve independent automatic control of gas flow. The bottom gas supply intensity can be adjusted within a large range, the stirring force in the converter can be controlled, the bottom blowing effect can be maximized, the slag-steel reaction balance can be promoted, the oxygen content in the steel can be reduced, and the steel quality can be improved.

[0008] 2. Technical Solution

[0009] To solve the above problems, the present invention adopts the following technical solution.

[0010] The present invention discloses a method for controlling the furnace bottom and reducing the final carbon-oxygen concentration product by individually controlling the flow rate of the bottom blowing branch pipes. The converter bottom blowing has m bottom blowing modes. In each mode, for each production process, v bottom blowing branch pipes are selected for individual control or joint control. In joint control, the flow rate setting parameters of the v branch pipes are the same, and m mode parameters are available for selection. In individual control, the flow rate of the v branch pipes is controlled separately, and m*v mode parameters are available for selection.

[0011] Furthermore, the converter bottom blowing control process is as follows:

[0012] M = a, b, ..., m represents the m bottom blowing modes selected by the host computer, j = 1, 2, ..., j represents the j production processes automatically identified by the control system; L = 1 represents the combined adjustment of bottom blowing branch pipes, T represents true, and F represents no;

[0013] S1. At the start of the furnace cycle, if the host computer selects bottom blowing mode a, the control system determines whether j=1 is true. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then, the set value a1 of the joint control of mode a and process 1 is assigned to the bottom blowing v root branch pipe to perform flow regulation.

[0014] S2. If L=1 is F, it means single control. Then, assign the v setpoints of single control in mode a and process 1 to the v root branch pipe of bottom blowing to perform independent flow regulation.

[0015] S3. If j=1 is F, then determine whether j=2 is true. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then assign the set value a2 of the joint control of mode a and process 2 to the root branch pipe of bottom blow v to perform flow regulation.

[0016] S4. If L=1 is F, it means single control. Then, assign the v setpoints of single control in mode a and process 2 to the v root branch pipes of the bottom blower to perform independent flow regulation.

[0017] S5, and so on, adjust and control the bottom blowing branch pipes for different production processes under different modes.

[0018] Furthermore, the converter bottom blowing system has 7 bottom blowing modes, each mode allowing for single or combined control of 16 bottom blowing branch pipes; M = a, b, ..., g represents the 7 bottom blowing modes selected by the host computer; j = 1, 2, ..., 13 represents the 13 production processes automatically identified by the control system, including charging, early SiMn oxidation, early C oxidation, mid-oxidation, mid-late oxidation, late oxidation, auxiliary blowing, post-stirring, measurement, tapping, slag splashing, slag dumping, and waiting; L = 1 represents the combined adjustment of bottom blowing branch pipes, T is true, and F is false.

[0019] The control process is as follows:

[0020] S1. At the start of the furnace cycle, if the host computer selects bottom blowing mode a, the control system determines whether j=1 is true. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then, the set value a1 of joint control in mode a and process 1 is assigned to V01, V02, ... V16 of the 16 bottom blowing branch pipes to perform flow regulation.

[0021] S2. If L=1 is F, it means single control. Then, the set values ​​a101, a102, ..., a116 of single control in mode a and process 1 are assigned to V01, V02, ..., V16 of the 16 bottom blowing branches to perform flow regulation.

[0022] S3. If j=1 is F, then determine j=2. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then assign the set value a2 of the joint control of mode a and process 2 to V01, V02, ... V16 of the 16 bottom blowing branches to perform flow regulation.

[0023] S4. If L=1 is F, it means single control. Then, the single control settings a201, a202, ..., a216 of mode a and process 2 are assigned to V01, V02, ..., V16 of the 16 bottom blowing branches to perform flow regulation.

[0024] S5. Following this logic, if j=12 is F, then check j=13. If it is true, the next step is to check if L=1 is true. If it is T, it indicates joint control. Then, assign the setpoint a13 of the joint control in mode a and process 13 to V01, V02, ... V16 of the 16 bottom blowing branch pipes respectively. If L=1 is F, it indicates single control. Then, assign the setpoint a1301, a1302, ..., a1316 of the single control in mode a and process 13 to V01, V02, ... V16 of the 16 bottom blowing branch pipes respectively to perform flow regulation.

[0025] Furthermore, the bottom blowing flow rate of each branch pipe section is adjusted based on the thickness measurement data of that section. When the thickness measurement data of a certain branch pipe section is less than 600mm, the bottom blowing flow rate of that section is adjusted by 0.02m³. 3 / t.min-0.16m 3 Between / t.min; the bottom blowing flow rate remains unchanged in other parts.

[0026] 3. Beneficial effects

[0027] The control method of this invention, by modifying the converter bottom blowing control system and designing independently controlled bottom blowing gas supply elements, with each gas supply element having an independent automatic gas flow control system, makes the bottom blowing equipment compact, reduces equipment costs, automates operation, simplifies maintenance, and ensures uniform stirring of the molten pool. Simultaneously, it allows for adjustment of the bottom gas supply intensity within a wide range, controlling the stirring force within the converter, maximizing the bottom blowing effect, promoting slag-steel reaction equilibrium, reducing oxygen content in steel, and improving steel quality. In practice, compared to existing technologies, the bottom blowing effect of a 300t converter is significantly improved, the production process of IF steel is optimized, and higher quality molten steel is provided for the RH furnace: the bottom blowing life is synchronized with the furnace age, the carbon-oxygen product at the converter endpoint for low-carbon steel smelting is reduced to 0.0016; the residual manganese at the smelting endpoint is increased by 0.018%, and the FeO in the final slag is reduced by 2.50%, resulting in significant economic benefits. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the thickness measurement data distribution at the bottom of the converter in this invention;

[0029] Figure 2 This is a schematic diagram of the control method of the present invention. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] Example

[0032] This embodiment utilizes a method for controlling the flow rate of the bottom blowing branch pipes individually to control the furnace bottom and reduce the final carbon-oxygen concentration product. The converter bottom blowing system has m bottom blowing modes. In each mode, corresponding to each production process, individual or combined control of v bottom blowing branch pipes can be selected. In combined control, the flow rate setting parameters for the v branch pipes are the same, with m mode parameters available for selection. In individual control, the flow rate of each of the v branch pipes is controlled separately, with m*v mode parameters available for selection. The converter bottom blowing control process is as follows:

[0033] M = a, b, ..., m represents the m bottom blowing modes selected by the host computer, j = 1, 2, ..., j represents the j production processes automatically identified by the control system; L = 1 represents the combined adjustment of bottom blowing branch pipes, T represents true, and F represents no;

[0034] S1. At the start of the furnace cycle, if the host computer selects bottom blowing mode a, the control system determines whether j=1 is true. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then, the set value a1 of the joint control of mode a and process 1 is assigned to the bottom blowing v root branch pipe to perform flow regulation.

[0035] S2. If L=1 is F, it means single control. Then, assign the v setpoints of single control in mode a and process 1 to the v root branch pipe of bottom blowing to perform independent flow regulation.

[0036] S3. If j=1 is F, then determine whether j=2 is true. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then assign the set value a2 of the joint control of mode a and process 2 to the root branch pipe of bottom blow v to perform flow regulation.

[0037] S4. If L=1 is F, it means single control. Then, assign the v setpoints of single control in mode a and process 2 to the v root branch pipes of the bottom blower to perform independent flow regulation.

[0038] S5, and so on, adjust and control the bottom blowing branch pipes for different production processes under different modes.

[0039] Taking practical application as an example, the converter bottom blowing design has 7 modes (a to g), each allowing for individual or combined control of 16 branch pipes. In combined control, the setting parameters for all 16 branch pipes are identical, with 7 sets of parameters available. In individual control, there are 7 × 16 = 112 sets of parameters to choose from, greatly enriching the converter bottom blowing control and meeting the smelting requirements under different operating conditions. In this embodiment, the 16 converter branch pipes are controlled independently, with each branch pipe having its own strength coefficient. Data is transmitted to the PLC via WINCC communication. The control program automatically calculates the set flow rate for each branch pipe based on the loading amount and the set strength coefficient, using this as the input value for the branch pipe regulating valve PID controller. The controller performs real-time deviation calculations between the set value and the actual feedback flow rate, and then outputs instructions based on the deviation. When the deviation exceeds the set standard, a 4-20mA standard signal is continuously output to control the field regulating valve to operate continuously; when the deviation is very small or nonexistent, the controller outputs no signal, and the regulating valve opening remains unchanged.

[0040] Specifically, when the host computer selects joint control, it sets the bottom blowing intensity using a 7x13 matrix table with seven modes (a, b, c, d, e, f, and g) as columns and 13 bottom blowing processes (charging, SiMn pre-oxidation, C pre-oxidation, mid-oxidation, mid-late oxidation, late oxidation, auxiliary blowing, post-stirring, measurement, tapping, slag splashing, slag dumping, and waiting) as rows. When a mode (a to g) is selected and the converter enters a bottom blowing process, the PLC assigns the intensity coefficient corresponding to the mode and process to the set value of the PID controller of the 16 branch pipes. If the HMI selects single control, the above matrix table can be set separately for each of the 16 branch pipes, with one matrix table for each branch pipe. Similarly, after selecting a mode, when the converter enters a bottom blowing process, the PLC assigns the intensity coefficient corresponding to the mode and process to the set value of the PID controller of the corresponding branch pipe.

[0041] Combination Figure 2 The control process is as follows:

[0042] S1. At the start of the furnace cycle, if the host computer selects bottom blowing mode a, the control system determines whether j=1 is true. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then, the set value a1 of joint control in mode a and process 1 is assigned to V01, V02, ... V16 of the 16 bottom blowing branch pipes to perform flow regulation.

[0043] S2. If L=1 is F, it means single control. Then, the set values ​​a101, a102, ..., a116 of single control in mode a and process 1 are assigned to V01, V02, ..., V16 of the 16 bottom blowing branches to perform flow regulation.

[0044] S3. If j=1 is F, then determine j=2. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then assign the set value a2 of the joint control of mode a and process 2 to V01, V02, ... V16 of the 16 bottom blowing branches to perform flow regulation.

[0045] S4. If L=1 is F, it means single control. Then, the single control settings a201, a202, ..., a216 of mode a and process 2 are assigned to V01, V02, ..., V16 of the 16 bottom blowing branches to perform flow regulation.

[0046] S5. Following this logic, if j=12 is F, then check j=13. If it is true, the next step is to check if L=1 is true. If it is T, it indicates joint control. Then, assign the setpoint a13 of the joint control in mode a and process 13 to V01, V02, ... V16 of the 16 bottom blowing branch pipes respectively. If L=1 is F, it indicates single control. Then, assign the setpoint a1301, a1302, ..., a1316 of the single control in mode a and process 13 to V01, V02, ... V16 of the 16 bottom blowing branch pipes respectively to perform flow regulation.

[0047] In practice, due to process and operational reasons, the damage, maintenance requirements, and effectiveness of bottom-blowing elements arranged at the furnace bottom cannot be completely consistent. This embodiment adopts a self-designed independent control technology for bottom-blowing elements, allowing each branch pipe to independently adjust its gas supply intensity, achieving a relatively consistent bottom-blowing effect and avoiding the impact caused by uneven actual gas supply intensity. Figure 1 The diagram shows the daily thickness measurement of the converter bottom based on the thickness measurement chart. Each dot represents a bottom-blowing component, totaling 16 components. When the thickness measurement data for a certain branch pipe is below 600mm, the bottom-blowing flow rate of that component is adjusted. The bottom-blowing flow rate can be adjusted from 0.02m based on the actual thickness measurement data. 3 / t.min-0.16m 3Adjust the flow rate between / t.min; while adjusting the flow rate at this location, keep the bottom blowing flow rate at other locations unchanged.

[0048] The current industry standard design is that when the thickness value of a certain part is low, in order to avoid accidents such as the furnace bottom falling too fast and causing the furnace bottom to penetrate steel, the flow rate of all 16 branch pipes needs to be adjusted from strong bottom blowing to weak bottom blowing. This cannot guarantee the full-cycle full-re-blowing effect of the furnace, nor can it guarantee the stability of the carbon-oxygen product.

[0049] In this embodiment, when the furnace condition is poor and the furnace bottom is difficult to control, and it is always on a downward trend, which also causes damage to the bottom blowing elements, the overall gas supply intensity of this branch pipe can be reduced while the other branches remain unchanged. This ensures both the bottom blowing effect and the stability of the furnace condition, stabilizes the converter furnace bottom control, significantly improves the carbon-oxygen product control, and reduces the fluctuation range. In three of the converters, the carbon-oxygen product was consistently controlled below 0.0020 throughout the entire furnace service life. Even after 5500 heats, the carbon-oxygen product did not fluctuate significantly, and the bottom-blowing system maintained good permeability. The "mushroom head" permeable bricks in the bottom-blowing system of each converter were visualized throughout the entire furnace service life. The practical application effects are also reflected in the following aspects: the bottom-blowing equipment is compact, has low equipment costs, is automated in operation, and is easy to maintain; it is suitable for smelting various steel grades from low-carbon to high-carbon steel, ensuring the effectiveness of bottom blowing; and the bottom-blowing flow rate is optimized by dynamically adjusting the bottom-blowing intensity of each branch pipe; it reduces the oxidizability of molten steel and final slag, significantly reducing the frequency and amount of converter refractory maintenance, especially effectively improving the erosion degree at the molten pool and slag line. The long-service, long-compound blowing technology adopted in this embodiment provides important technical support for improving the quality of steel products and developing high-end products, laying the foundation for the production of clean steel.

[0050] The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A method for controlling the furnace bottom and reducing the final carbon-oxygen concentration product by individually controlling the flow rate of the bottom blowing branch pipe, characterized in that: The converter bottom blowing has m bottom blowing modes. In each mode, for each production process, v bottom blowing branch pipes can be individually controlled or jointly controlled. When jointly controlled, the flow rate setting parameters of v branch pipes are the same, and m mode parameters are available for selection. When individually controlled, the flow rate of v branch pipes is controlled separately, and m*v mode parameters are available for selection. The converter bottom blowing control process is as follows: M=a,b,...,m represents the m bottom blowing modes selected by the host computer, j=1,2,...,j represents the j production processes automatically identified by the control system; L=1 represents the combined adjustment of bottom blowing branch pipes, T represents true, and F represents no; S1. At the start of the furnace cycle, if the host computer selects bottom blowing mode a, the control system determines whether j=1 is true. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then, the set value a1 of joint control in mode a and process 1 is assigned to the bottom blowing v root branch pipe to perform flow regulation. S2. If L=1 is F, it means single control. Then, assign the v set values ​​of single control in mode a and process 1 to the v root branch pipe of bottom blower to perform independent flow regulation. S3. If j=1 is F, then determine whether j=2 is true. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then assign the set value a2 of the joint control of mode a and process 2 to the root branch pipe of bottom blow v to perform flow regulation. S4. If L=1 is F, it means single control. Then, assign the v set values ​​of single control in mode a and process 2 to the v root branch pipe of bottom blowing to perform independent flow regulation. S5. Similarly, adjust and control the bottom blowing branch pipes for different production processes under different modes. The converter bottom blowing system has 7 bottom blowing modes, each mode allowing for single-hole or joint control of 16 bottom blowing branch pipes; M=a,b,...,g represents the 7 bottom blowing modes selected by the host computer; j=1,2,...,13 represents the 13 production processes automatically identified by the control system, including charging, early SiMn oxidation, early C oxidation, mid-oxidation, mid-late oxidation, late oxidation, auxiliary blowing, post-stirring, measurement, tapping, slag splashing, slag dumping, and waiting; L=1 represents the joint adjustment of bottom blowing branch pipes, T is true, F is false; the control process is as follows: S1. At the start of the furnace cycle, if the host computer selects bottom blowing mode a, the control system determines whether j=1 is true. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then, the set value a1 of joint control in mode a and process 1 is assigned to V01, V02, ... V16 of the 16 bottom blowing branch pipes to perform flow regulation. S2. If L=1 is F, it means single control. Then, the single control settings a101, a102, ..., a116 of mode a and process 1 are assigned to V01, V02, ..., V16 of the 16 bottom blowing branches to perform flow regulation. S3. If j=1 is F, then determine j=2. If it is true, the next step is to determine whether L=1 is true. If it is T, it indicates joint control. Then assign the set value a2 of the joint control of mode a and process 2 to V01, V02, ... V16 of the 16 bottom blower branches to perform flow regulation. S4. If L=1 is F, it means single control. Then, the single control settings a201, a202, ..., a216 of mode a and process 2 are assigned to V01, V02, ..., V16 of the 16 bottom blowing branches to perform flow regulation. S5. Similarly, if j=12 is F, then check j=13. If it is true, the next step is to check if L=1 is true. If it is T, it indicates joint control. Then, the set value a13 of the joint control of mode a and process 13 is assigned to V01, V02, ... V16 of the 16 bottom blowing branch pipes respectively. If L=1 is F, it indicates single control. Then, the set value a1301, a1302, ..., a1316 of the single control of mode a and process 13 is assigned to V01, V02, ... V16 of the 16 bottom blowing branch pipes respectively to perform flow regulation. The bottom blowing flow rate of each branch pipe section is adjusted according to the thickness measurement data of that section. When the thickness measurement data of a certain branch pipe section is less than 600mm, the bottom blowing flow rate of that section is adjusted to between 0.02m³ / t.min and 0.16m³ / t.min; the bottom blowing flow rate of other sections remains unchanged.

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