Annealing furnace pressure control method

Abstract

The application relates to an annealing furnace pressure control method, which comprises the following steps: in the production process of an annealing furnace unit, determining whether the unit speed changes, if the unit speed changes, executing the annealing furnace pressure control operation; for the hydrogen-containing area of the annealing furnace, controlling the area furnace pressure by adjusting the opening of the first diffusion adjusting valve of the hydrogen-containing area; for the non-hydrogen-containing area of the annealing furnace, controlling the area furnace pressure by controlling the opening of the nitrogen cut-off valve of the area; for the isolation section of the annealing furnace, controlling the area furnace pressure by adjusting the opening of the second diffusion adjusting valve of the isolation section. The unit speed change condition is used as the feedforward of the furnace pressure regulation, when the unit speed changes, the high-pressure nitrogen cut-off valve and the diffusion adjusting valve of different furnace sections are processed correspondingly, the extremely high furnace pressure control response speed can be obtained, the condition that the furnace pressure greatly fluctuates is avoided, and the stability and reliability of the annealing furnace production can be improved.

Description

Technical Field

[0001] This invention belongs to the field of annealing furnace production technology, specifically relating to a method for controlling furnace pressure in an annealing furnace. Background Technology

[0002] Silicon steel annealing furnaces typically have multiple sections, and the furnace pressure varies depending on the annealing process, but there is a certain correlation between them. For each section, the commonality is that it needs to maintain a slightly positive pressure and keep the pressure stable; however, in annealing furnace production, pressure fluctuations frequently occur. Currently, the main method for adjusting the furnace pressure is: when the pressure transmitter detects a pressure fluctuation, it controls the furnace pressure by adjusting the opening of the regulating valves in the heating and isolation sections. This method has a slow response time and is prone to causing large fluctuations in furnace pressure. When the pressure in any section reaches the low alarm setpoint, an interlock is triggered, causing the high-pressure nitrogen shut-off valve to open for a period of time to maintain a slightly positive pressure. However, this method leads to a significant increase in furnace pressure, and because of the large amount of nitrogen introduced, the atmosphere inside the furnace also changes, which is detrimental to the entire annealing process. Summary of the Invention

[0003] This invention relates to a method for controlling furnace pressure in an annealing furnace, which can at least solve some of the defects of the prior art.

[0004] This invention relates to a method for controlling furnace pressure in an annealing furnace, comprising:

[0005] During the production process of the annealing furnace unit, it is determined whether the unit speed has changed. If the unit speed changes, the furnace pressure control operation of the annealing furnace is executed.

[0006] Specifically, for the hydrogen-containing area of ​​the annealing furnace, the furnace pressure is controlled by adjusting the opening of the first venting regulating valve of the hydrogen-containing area; for the non-hydrogen-containing area of ​​the annealing furnace, the furnace pressure is controlled by controlling the opening of the nitrogen shut-off valve of the area; and for the isolation section of the annealing furnace, the furnace pressure is controlled by adjusting the opening of the second venting regulating valve of the isolation section.

[0007] As one implementation method, the annealing furnace pressure control operation includes:

[0008] Determine whether the change in unit speed is an increase or a decrease;

[0009] If the unit speed changes to increase, the speed increase control strategy is executed; if the unit speed changes to decrease, the speed decrease control strategy is executed.

[0010] As one implementation method, the acceleration control strategy includes:

[0011] For the hydrogen-containing area of ​​the annealing furnace, when an increase in unit speed is detected, the opening of the first venting regulating valve is increased in advance; after the unit is running stably, the first venting regulating valve is restored to an opening that can maintain stable furnace pressure.

[0012] For the non-hydrogen-containing area of ​​the annealing furnace, when the unit speeds up, the nitrogen shut-off valve in this area should be kept closed;

[0013] For the isolation section, when the unit speeds up, the second venting regulating valve is kept in automatic control mode.

[0014] As one implementation method, the deceleration control strategy includes:

[0015] For the hydrogen-containing area of ​​the annealing furnace, when a decrease in unit speed is detected, the opening of the first venting regulating valve is reduced in advance; after the unit is running stably, the first venting regulating valve is restored to an opening that can maintain stable furnace pressure.

[0016] For the non-hydrogen-containing area of ​​the annealing furnace, when the unit speed is reduced, the nitrogen shut-off valve on the furnace outlet section is opened, and the opening degree of the remaining nitrogen shut-off valves in the area is increased; after the unit is running stably, the nitrogen shut-off valve on the furnace outlet section is closed, and the remaining nitrogen shut-off valves in the area are restored to the opening degree that can maintain furnace pressure stability.

[0017] For the isolation section, when the unit speed is reduced, the opening of the second venting regulating valve is reduced. When the second venting regulating valve is closed, the nitrogen shut-off valve on the isolation section is opened. After the unit is running stably, the nitrogen shut-off valve on the isolation section is closed, and the second venting regulating valve is restored to an opening that can maintain stable furnace pressure.

[0018] As one implementation method, for the non-hydrogen-containing area of ​​the annealing furnace, except for the nitrogen shut-off valve on the furnace outlet section, the remaining nitrogen shut-off valves constitute a valve group for common control, and the valve group is controlled by PID control.

[0019] As one embodiment, the annealing furnace includes a furnace zone inlet section, a first hydrogen-containing atmosphere furnace section, a second hydrogen-containing atmosphere furnace section, an isolation section, an air-cooling section, a first cooling section, a second cooling section, and a furnace zone outlet section connected in sequence, wherein the first hydrogen-containing atmosphere furnace section is equipped with the first venting regulating valve.

[0020] As one of the implementation methods, each furnace section is equipped with a pressure detection unit.

[0021] As one implementation method, the first cooling section and the second cooling section constitute a cooling zone controlled as a whole, and the minimum furnace pressure of the two is selected as the actual furnace pressure value of the cooling zone.

[0022] The present invention has at least the following beneficial effects:

[0023] In this invention, the change in unit speed is used as the feedforward for furnace pressure regulation. When the unit speed changes, the furnace pressure of each furnace section will change sequentially and with the same trend. Based on this trend of furnace pressure change, the high-pressure nitrogen shut-off valve and venting regulating valve of different furnace sections can be treated accordingly, which can achieve a very high furnace pressure control response speed, avoid large fluctuations in furnace pressure, and improve the stability and reliability of annealing furnace production. Attached Figure Description

[0024] 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.

[0025] Figure 1 This is a schematic diagram of the partitioning of an annealing furnace provided in an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the annealing furnace pressure control method provided in an embodiment of the present invention. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] like Figure 2 This invention provides a method for controlling furnace pressure in an annealing furnace, comprising:

[0029] During the production process of the annealing furnace unit, it is determined whether the unit speed has changed. If the unit speed changes, the furnace pressure control operation of the annealing furnace is executed.

[0030] Specifically, for the hydrogen-containing area of ​​the annealing furnace, the furnace pressure is controlled by adjusting the opening of the first venting regulating valve 41 of the hydrogen-containing area; for the non-hydrogen-containing area of ​​the annealing furnace, the furnace pressure is controlled by controlling the opening of the nitrogen shut-off valve 50 of the area; and for the isolation section 2 of the annealing furnace, the furnace pressure is controlled by adjusting the opening of the second venting regulating valve 42 of the isolation section 2.

[0031] In one embodiment, such as Figure 1The annealing furnace includes a furnace inlet section 11, a first hydrogen-containing atmosphere furnace section 12, a second hydrogen-containing atmosphere furnace section 13, an isolation section 2, an air-cooling section 31, a first cooling section 32, a second cooling section 33, and a furnace outlet section 34 connected in sequence. The furnace inlet section 11, the first hydrogen-containing atmosphere furnace section 12, and the second hydrogen-containing atmosphere furnace section 13 are hydrogen-containing areas, while the air-cooling section 31, the first cooling section 32, the second cooling section 33, and the furnace outlet section 34 are non-hydrogen-containing areas.

[0032] Each furnace section is equipped with a pressure detection unit, which can detect the furnace pressure in the corresponding furnace section; the pressure detection unit includes, but is not limited to, pressure transmitters.

[0033] Preferably, such as Figure 1 The first hydrogen-containing atmosphere furnace section 12 is equipped with a first venting regulating valve 41; the isolation section 2 is equipped with a second venting regulating valve 42; the furnace inlet section 11, the first hydrogen-containing atmosphere furnace section 12, the isolation section 2, and the furnace outlet section 34 are each equipped with a nitrogen shut-off valve 50; the first cooling section 32 and the second cooling section 33 are each equipped with multiple nitrogen shut-off valves 50. In a more specific embodiment, such as Figure 1 The first cooling section 32 is equipped with three nitrogen shut-off valves 50, and the second cooling section 33 is equipped with four nitrogen shut-off valves 50.

[0034] The valves are numbered as follows: the first venting regulating valve 41 is PV-F02, and the second venting regulating valve 42 is PV-F04. The nitrogen shut-off valve 50 at the furnace inlet section 11 is XV-N21, the nitrogen shut-off valve 50 at the first hydrogen-containing atmosphere furnace section 12 is XV-N22, the nitrogen shut-off valve 50 at the isolation section 2 is XV-N23, the three nitrogen shut-off valves 50 at the first cooling section 32 are XV-N24, XV-N25, and XV-N26 respectively, the four nitrogen shut-off valves 50 at the second cooling section 33 are XV-N27, XV-N28, XV-N29, and XV-N2A respectively, and the nitrogen shut-off valve 50 at the furnace outlet section 34 is XV-N2B.

[0035] Understandably, in the above description of the furnace section being equipped with a venting regulating valve / nitrogen shut-off valve 50, it means that the furnace section is equipped with a venting pipe with a venting regulating valve / a nitrogen supply pipe with a nitrogen shut-off valve 50.

[0036] Whether the unit speed has changed can be determined by monitoring the speed changes of the unit's process section. The PLC control system continuously monitors the speed change of the unit's process section, a = ΔV / Δt, where Δt is the scan time and ΔV is the speed change value from t to t+Δt. When a changes, it means that the unit speed has changed. a > 0 means the unit speed has increased, and a < 0 means the unit speed has decreased.

[0037] In this embodiment, the change in unit speed is used as the feedforward for furnace pressure regulation. When the unit speed changes, the furnace pressure of each furnace section will change sequentially and with the same trend. Based on this trend of furnace pressure change, the high-pressure nitrogen shut-off valve 50 and the venting regulating valve of different furnace sections can be processed accordingly, which can achieve a very high furnace pressure control response speed, avoid large fluctuations in furnace pressure, and improve the stability and reliability of annealing furnace production.

[0038] When the unit speed remains unchanged, furnace pressure adjustment is generally not performed.

[0039] Furthermore, the furnace pressure control operation of the annealing furnace includes:

[0040] Determine whether the change in unit speed is an increase or a decrease;

[0041] If the unit speed changes to increase, the speed increase control strategy is executed; if the unit speed changes to decrease, the speed decrease control strategy is executed.

[0042] When the unit speeds up, the furnace pressure in each section increases sequentially from the furnace inlet section 11 to the furnace outlet section 34. Based on the trend of the furnace pressure change, different measures can be taken for the high-pressure nitrogen shut-off valve 50 and the venting regulating valve in different furnace sections. In one embodiment, the speed-up control strategy includes:

[0043] a. For the hydrogen-containing area of ​​the annealing furnace, when the unit speed is detected to increase, the opening of the first venting regulating valve 41 is increased in advance.

[0044] Before the unit speed changes, the first venting regulating valve 41 is usually automatically controlled (e.g., automatically controlled by a primary automation program); when the unit speed changes, the first venting regulating valve 41 can be set to manual control for easier control, for example, the opening degree of the first venting regulating valve 41 can be controlled by CV. 20 Adjust to CV 21 Preferably, CV 21 It is calculated from a curve fitted from historical data.

[0045] After the unit is running stably, the first venting regulating valve 41 is restored to an opening that can maintain stable furnace pressure; for example, the opening of the first venting regulating valve 41 is changed from CV... 21 Adjust to CV 22 And set the valve to automatic, wherein, preferably, CV 22 It is calculated from a curve fitted from historical data.

[0046] b. For the non-hydrogen-containing area of ​​the annealing furnace, it is only necessary to ensure that the furnace pressure in this area is higher than that in the hydrogen-containing area to prevent hydrogen from flowing into this area; specifically, when the unit speeds up, the nitrogen shut-off valve 50 in this area should be kept closed; since this area does not contain hydrogen, the increase in furnace pressure will not cause external oxygen to enter or cause instability in the furnace atmosphere.

[0047] c. For isolation section 2, its main function is to maintain the pressure difference between the front and rear areas to prevent hydrogen from flowing from the hydrogen-containing area to the non-hydrogen-containing area. Additionally, it needs to prevent oxygen-containing atmosphere from flowing from the non-hydrogen-containing area to the hydrogen-containing area, thus affecting the strip quality. Therefore, the furnace pressure in this section needs to be higher than the pressures of the preceding and following sections. As the unit speed increases, the furnace pressure in isolation section 2 will also rise. To ensure that the pressure in this section is simultaneously higher than the pressures of the preceding and following areas, it is not necessary to increase the opening of its second venting regulating valve 42; automatic control of the second venting regulating valve 42 is sufficient (e.g., automatic control of the second venting regulating valve 42 can be achieved through a primary automation program). Correspondingly, when the unit speed increases, the second venting regulating valve 42 remains in automatic control mode.

[0048] When the unit speed decreases, the furnace pressure in each furnace section decreases sequentially from the furnace outlet section 34 to the furnace inlet section 11. Based on the trend of furnace pressure change, different actions can be taken for the high-pressure nitrogen shut-off valve 50 and the venting regulating valve in different furnace sections. In one embodiment, the speed reduction control strategy includes:

[0049] A. For the hydrogen-containing area of ​​the annealing furnace, in addition to stabilizing the furnace pressure, it is also necessary to ensure the stability of the atmosphere inside the furnace. Therefore, the furnace pressure cannot be easily maintained by opening the high-pressure nitrogen shut-off valve 50. In this embodiment, the furnace pressure is mainly regulated by the first venting regulating valve 41. Specifically, when a decrease in unit speed is detected, the opening of the first venting regulating valve 41 is reduced in advance; for example, the opening of the first venting regulating valve 41 is determined by CV. 20 Adjust to CV 23 Preferably, CV 23 It is calculated from a curve fitted from historical data.

[0050] After the unit is running stably, the first venting regulating valve 41 is restored to an opening that can maintain stable furnace pressure; for example, the opening of the first venting regulating valve 41 is changed from CV... 23 Adjust to CV 24 And set the valve to automatic, wherein, preferably, CV 24 It is calculated from a curve fitted from historical data.

[0051] B. For the non-hydrogen-containing area of ​​the annealing furnace, in addition to maintaining stable furnace pressure, it is also necessary to ensure that the furnace pressure in this area is higher than that in the hydrogen-containing area to prevent hydrogen from flowing into this area.

[0052] Accordingly, when the unit slows down, the nitrogen shut-off valve 50 on the furnace outlet section 34 is opened, and the opening degree of the remaining nitrogen shut-off valves 50 in the same section is increased; after the unit is running stably, the nitrogen shut-off valve 50 on the furnace outlet section 34 is closed, and the remaining nitrogen shut-off valves 50 in the same section are restored to the opening degree that can maintain the furnace pressure stability.

[0053] Preferably, for the non-hydrogen-containing area of ​​the annealing furnace, except for the nitrogen shut-off valve 50 on the furnace outlet section 34, the remaining nitrogen shut-off valves 50 constitute a valve group for common control, and the valve group is controlled by PID control.

[0054] In one embodiment, the valve assembly is controlled based on the following table:

[0055] PID Output and Valve Status Comparison Table

[0056] For the valve group PV-F06 mentioned above, when the unit speed changes, PV-F06 can be switched from automatic to manual, and its opening degree can be changed from CV... 60 Adjust to CV 61 Preferably, CV 61 The opening degree of PV-F06 is calculated from the curve fitted from historical data; after the unit is running stably, the opening degree of PV-F06 is adjusted from CV. 61 Adjust to CV 62 Preferably, CV 62 It is calculated from a curve fitted from historical data.

[0057] C. For isolation section 2, when the unit speed is reduced, the opening of the second venting regulating valve 42 is reduced. When the second venting regulating valve 42 is closed, the nitrogen shut-off valve 50 on isolation section 2 is opened. After the unit is running stably, the nitrogen shut-off valve 50 on isolation section 2 is closed, and the second venting regulating valve 42 is restored to the opening that can maintain the furnace pressure.

[0058] In one embodiment, the first cooling section 32 and the second cooling section 33 constitute a cooling zone under overall control, and the minimum furnace pressure of the two is selected as the actual furnace pressure value of the cooling zone. This method can improve the response speed and stability of furnace pressure control.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling furnace pressure in an annealing furnace, characterized in that, include: During the production process of the annealing furnace unit, it is determined whether the unit speed has changed. If the unit speed changes, the furnace pressure control operation of the annealing furnace is executed. Specifically, for the hydrogen-containing area of ​​the annealing furnace, the furnace pressure is controlled by adjusting the opening of the first venting regulating valve of the hydrogen-containing area; for the non-hydrogen-containing area of ​​the annealing furnace, the furnace pressure is controlled by adjusting the opening of the nitrogen shut-off valve of the area; and for the isolation section of the annealing furnace, the furnace pressure is controlled by adjusting the opening of the second venting regulating valve of the isolation section. The annealing furnace pressure control operation includes: Determine whether the change in unit speed is an increase or a decrease; If the unit speed change is an increase, the speed increase control strategy is executed; if the unit speed change is a decrease, the speed decrease control strategy is executed. The acceleration control strategy includes: For the hydrogen-containing area of ​​the annealing furnace, when an increase in unit speed is detected, the opening of the first venting regulating valve is increased in advance; after the unit is running stably, the first venting regulating valve is restored to an opening that can maintain stable furnace pressure. For the non-hydrogen-containing area of ​​the annealing furnace, when the unit speeds up, the nitrogen shut-off valve in this area should be kept closed; For the isolation section, when the unit speeds up, the second venting regulating valve remains in automatic control mode; The deceleration control strategy includes: For the hydrogen-containing area of ​​the annealing furnace, when a decrease in unit speed is detected, the opening of the first venting regulating valve is reduced in advance; after the unit is running stably, the first venting regulating valve is restored to an opening that can maintain stable furnace pressure. For the non-hydrogen-containing area of ​​the annealing furnace, when the unit speed is reduced, the nitrogen shut-off valve on the furnace outlet section is opened, and the opening degree of the remaining nitrogen shut-off valves in the area is increased; after the unit is running stably, the nitrogen shut-off valve on the furnace outlet section is closed, and the remaining nitrogen shut-off valves in the area are restored to the opening degree that can maintain furnace pressure stability. For the isolation section, when the unit speed is reduced, the opening of the second venting regulating valve is reduced. When the second venting regulating valve is closed, the nitrogen shut-off valve on the isolation section is opened. After the unit is running stably, the nitrogen shut-off valve on the isolation section is closed, and the second venting regulating valve is restored to an opening that can maintain stable furnace pressure.

2. The annealing furnace pressure control method as described in claim 1, characterized in that: For the non-hydrogen-containing area of ​​the annealing furnace, except for the nitrogen shut-off valve on the furnace outlet section, the remaining nitrogen shut-off valves constitute a valve group for common control, and the valve group is controlled by PID control.

3. The annealing furnace pressure control method as described in claim 1, characterized in that: The annealing furnace includes a furnace zone inlet section, a first hydrogen-containing atmosphere furnace section, a second hydrogen-containing atmosphere furnace section, an isolation section, an air-cooling section, a first cooling section, a second cooling section, and a furnace zone outlet section connected in sequence. The first hydrogen-containing atmosphere furnace section is equipped with the first venting regulating valve.

4. The annealing furnace pressure control method as described in claim 3, characterized in that: Each furnace section is equipped with a pressure detection unit.

5. The annealing furnace pressure control method as described in claim 4, characterized in that: The first cooling section and the second cooling section constitute a cooling zone under overall control, and the minimum furnace pressure of the two is selected as the actual furnace pressure value of the cooling zone.

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