Circulating cooling water path control system for sintering furnace in magnetic material production

Abstract

The invention discloses a circulating cooling water path control system for a sintering furnace in magnetic material production, which belongs to the technical field of magnetic material production equipment and adopts three cooling water branches arranged in parallel: a first branch and a third branch which are automatically controlled, and a second branch and a third branch which are manually controlled, and the flow of the third branch is smaller than that of the first branch. The PLC control host receives working signals of the sintering furnace in real time, the first branch is closed and the third branch is opened in the temperature rise and heat preservation stages of the sintering furnace, and the first branch is opened and the third branch is closed in the temperature reduction stage; when the first branch circuit or the third branch circuit breaks down or flow is insufficient, the PLC control host automatically generates a manual intervention instruction, and the second branch circuit is manually started to provide standby cooling. According to the system, by means of a branch on-demand switching and manual backup mechanism, the accurate requirement for the cooling strength in each stage of the magnetic material sintering process is effectively guaranteed, the reliability of temperature control and the process stability are ensured, and therefore the quality and production safety of magnetic material products are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic material production equipment, and is specifically used for the circulating cooling water path control system of a sintering furnace in magnetic material production. Background Art

[0002] During the operation of the sintering furnace used in magnetic material production, circulating water cooling is required to remove the heat generated by the furnace body and the internal products during high-temperature treatment, maintain the stable operation of the equipment, and ensure the sintering quality of the products. However, the sintering process usually includes different stages such as heating, heat preservation, and cooling. The heat intensity generated in the furnace and the requirements for cooling vary significantly in each stage. Specifically, in the heating and heat preservation stages, the furnace body is in a high-temperature state, and the cooling intensity needs to be strictly controlled. Usually, only a small flow rate of cooling water is required to maintain basic heat dissipation, avoiding over-cooling from interfering with the set temperature curve in the furnace or causing product defects. In the cooling stage, in order to quickly and safely cool the products after high-temperature sintering and prevent abnormal grain growth or deterioration of magnetic properties, a large flow rate of cooling water needs to be provided instantaneously to quickly remove a large amount of heat.

[0003] This differential demand for the flow rate of cooling water, especially the requirement for rapid switching from a small flow rate to a large flow rate, poses challenges to traditional cooling water path control systems. The common single cooling water circuit combined with a regulating valve in the prior art is difficult to efficiently and smoothly adapt to such drastic flow rate changes. The main reasons are as follows: On the one hand, relying on a single regulating valve to frequently and rapidly act within a large opening range (from nearly closed to fully open) to achieve a large-scale switching of the flow rate not only requires extremely high response speed and control accuracy of the valve itself, increasing equipment costs and maintenance difficulties, but also in extreme working conditions (such as when a very low flow rate is required), the valve may be in a slightly open state, with poor control stability, prone to oscillation or inaccurate flow rate control, resulting in furnace temperature fluctuations exceeding the process allowable range. On the other hand, when the system needs to quickly switch from the small flow rate in the heat preservation stage to the large flow rate required in the cooling stage, even when the single valve is fully open, the rate of flow rate increase may be limited by the pipeline design and pump capacity, resulting in a response lag problem and being unable to meet the cooling intensity requirements for rapid cooling in a timely manner.

[0004] In addition, the cooling system of the sintering furnace has extremely high requirements for operating reliability. Once the cooling fails or the flow rate is insufficient, the temperature inside the furnace may quickly get out of control, resulting in the scrapping of the entire furnace of magnetic material products at the least, and at the worst, damaging the expensive sintering furnace equipment. However, a system relying on a single automatic control water circuit (or a single valve) has a risk of single-point failure. If a failure (such as jamming, leakage, signal distortion, etc.) occurs in this automatic control part (such as valves, actuators or related sensors), causing insufficient flow or complete interruption, the system often lacks a fast and effective backup cooling means. Although the conventional alarm and shutdown mechanism can prevent further damage to the equipment, it cannot save the sintering products in progress, resulting in production losses. And trying to add a completely redundant backup in a single loop is too costly.

[0005] Therefore, in the field of magnetic material sintering, how to design a cooling water circuit control system that can reliably and accurately meet the small-flow cooling requirements during the heating / holding stage of the sintering furnace and the large-flow cooling requirements during the cooling stage, and effectively cope with possible failures in the automatic control part, avoiding temperature control failure and production accidents caused by insufficient cooling, has become a technical problem to be solved urgently. In particular, it is necessary to overcome the difficulties such as the control stability of rapid flow switching, the accuracy of small-flow regulation, and the risk of single failure points. The present invention improves and develops the cooling water pipeline in combination with the working characteristics of the sintering furnace, aiming to solve the above problems. Summary of the Invention

[0006] An object of an embodiment of the present invention is to solve at least the above problems and / or defects, and provide at least the advantages described later.

[0007] Another object of the present invention is to provide a circulating cooling water circuit control system for a sintering furnace used in magnetic material production.

[0008] Solve the problem that a single water circuit cannot quickly switch and lacks a fault backup when the sintering furnace requires small-flow cooling during the heating / holding stage and large-flow cooling during the cooling stage.

[0009] Solve the problems of unstable cooling efficiency caused by fluctuations in the temperature of circulating water, and the mismatch between the energy consumption of the water pump and the branch state.

[0010] Solve the problems of temperature shock caused by too fast valve action during the switching of the heating and cooling stages, and insufficient small-flow cooling at high heating rates.

[0011] Solve the problem that the temperature drop rate gets out of control or the response is delayed due to improper initial opening setting at the beginning of cooling.

[0012] Solve the problem that the lack of a hierarchical emergency mechanism during branch failures is likely to cause cooling interruption or blindness in manual operation.

[0013] Solve the problem of the complexity of multi-variable coupling control of water temperature, refrigeration intensity, and water pump frequency, and avoid overload or energy consumption waste.

[0014] Solve the problems of temperature control failure caused by single-point water temperature detection error and insufficient cooling capacity under high-temperature working conditions.

[0015] Solve the problems of the water pump operating overload under high water temperature and multi-branch working conditions and lacking forced protection when the flow demand surges.

[0016] Solve the problem that the flow rate upper limit of a single branch cannot meet the process requirements under extreme cooling requirements.

[0017] Solve the problems of low adjustment accuracy and poor flow stability of small-flow branches.

[0018] For this reason, the present invention is implemented by the following technical solutions: A circulating cooling water path control system for a sintering furnace in magnetic material production, including: Three cooling water branches, which are arranged in parallel between the water inlet 10 and the water outlet 20 of the sintering furnace. The three cooling water branches include: an automatically controlled first branch and a third branch, and a manually controlled second branch. Among them, the flow rate of the third branch is less than that of the first branch. A PLC control host, which is connected to the working signal of the sintering furnace and the actuators for automatic control of the water branches. The PLC control host is configured as follows: during the heating and heat preservation stages of the sintering furnace in magnetic material production, the first branch is closed and the third branch is opened; during the cooling stage of the sintering furnace, the first branch is opened and the third branch is closed. Among them, when a failure or insufficient flow rate occurs in the first branch, or when a failure or insufficient flow rate occurs in the third branch, the PLC control host generates a manual intervention instruction to manually start the second branch.

[0019] Preferably, the circulating cooling water path control system for a sintering furnace in magnetic material production further includes: A cooling air conditioner, which is arranged on the circulating water return pipe between the water outlet 20 and the water inlet 10 of the sintering machine and is used to reduce the temperature of the circulating cooling water. A water temperature sensor is arranged on the return pipe. The cooling air conditioner and the water temperature sensor are both connected to the PLC control host. The PLC control host controls the start-stop and refrigeration intensity of the cooling air conditioner according to the water temperature detection data transmitted by the water temperature sensor to maintain the circulating water temperature within a set range. A circulating water pump, which is connected to the PLC control host. The circulating water pump is provided with a circulating water pump frequency converter, and the PLC control host adjusts the working frequency of the circulating water pump according to the switching state of the cooling water branch.

[0020] Preferably, in the circulating cooling water path control system for a sintering furnace in magnetic material production, during the heating and heat preservation stages of the sintering furnace: when the temperature change rate α of the sintering furnace > 1.5 °C / min, perform dynamic tuning control of the third branch: Keep the first branch closed, increase the opening of the third branch from the reference value of 30% to (30 + 5×(α - 1.5))%, with a maximum not exceeding 50%; When detecting the signal that the process stage switches to the cooling stage, perform gradient switching: Within t0 = 0 - 30 seconds, linearly reduce the opening of the third branch from the current value to 10%; Within t1 = 30 - 60 seconds, the first branch opens at a rate of (10 + 0.5×(T 初始 -T 目标 ))%, and at the same time, the third branch maintains an opening of 10%; When the opening of the first branch ≥ 80%, completely close the third branch.

[0021] Preferably, in the circulating cooling water path control system of the sintering furnace used in magnetic material production, at the initial stage of the sintering furnace cooling stage, a branch flow - temperature gradient mapping table is also established based on historical data, and the initial opening γ of the first branch is dynamically calculated according to the following formula: Wherein, T 当前 is the temperature of the sintering furnace detected in real time, T 目标 is the target temperature of the current process stage, Δ T max is the preset maximum allowable temperature drop rate (unit: °C / min), is the average temperature change rate within the sliding time window of the previous 5 minutes.

[0022] Preferably, in the circulating cooling water path control system of the sintering furnace used in magnetic material production, when the PLC control host detects a branch fault, a three - level response mechanism is executed: Level I: The flow rate of the faulty branch drops to 70% - 60% of the theoretical value, generate a first - level manual intervention instruction, manually start the second branch and adjust it to an opening of 30%; Level II: The flow rate of the faulty branch drops to 60% - 40% of the theoretical value, generate a second - level manual intervention instruction, manually adjust the second branch to an opening of 60%; Level III: The flow rate of the faulty branch < 40%, generate a third - level manual intervention instruction, close the faulty branch and manually fully open the second branch.

[0023] Preferably, in the circulating cooling water path control system of the sintering furnace used in magnetic material production, the cooling air conditioner uses a variable - frequency compressor, and the evaporator of the cooling air conditioner is connected in series at a position 20 close to the water outlet of the sintering furnace in the return water pipeline; the PLC control host also performs the following steps: When the detected value of the water temperature sensor ≥ 35°C, start the cooling air conditioner and operate it at 100% cooling intensity; When 30°C ≤ the detected value of the water temperature sensor < 35°C, start the cooling air conditioner and operate it at 50%-80% cooling intensity; When the detected value of the water temperature sensor < 30°C, turn off the cooling air conditioner; The frequency converter of the circulating water pump adopts closed-loop PID control, and the corresponding relationship between its frequency adjustment range and the number of opened cooling water branches is as follows: When only the third branch is opened: 30Hz - 40Hz; When only the first branch is opened: 40Hz - 50Hz; When the first branch and the third branch are opened simultaneously: 45Hz - 55Hz; When the first branch, the second branch, and the third branch are opened simultaneously: 50Hz - 60Hz; Among them, during the gradient switching process in the cooling stage, when the first branch and the third branch are opened simultaneously, the frequency of the circulating water pump is adjusted according to 45Hz - 55Hz; after the gradient switching is completed, it is adjusted according to 40Hz - 50Hz when only the first branch is opened.

[0024] Preferably, in the circulating cooling water path control system of the sintering furnace used in magnetic material production, two water temperature sensors are arranged in parallel on the water temperature sensor on the return water pipe, and the two water temperature sensors are respectively located at the water inlet end and the water outlet end of the evaporator of the cooling air conditioner; when the difference between the detected values of the two water temperature sensors ≥ 2°C, the PLC control host controls the cooling air conditioner according to the temperature value data of the water temperature sensor with the higher temperature, and triggers a sensor calibration alarm; In the cooling stage of the sintering furnace, if the average value of the detected values of the two water temperature sensors ≥ 40°C, start the second branch and synchronously increase the frequency of the circulating water pump to 55Hz - 60Hz.

[0025] Preferably, in the circulating cooling water path control system of the sintering furnace used in magnetic material production, the frequency converter of the circulating water pump is set with an overload protection threshold linked to the water temperature, and its maximum allowable frequency is determined according to the following rules: When the water temperature of the return water pipe is in the range of 25°C to 40°C, the maximum allowable frequency linearly decreases from 60Hz to 54Hz; When the water temperature > 40°C, the maximum allowable frequency is fixed at 54Hz; Operation constraint rules: When the following two conditions are met simultaneously: a) The number of opened cooling water branches ≥ 2, b) The water temperature ≥ 35°C, The working frequency of the circulating water pump shall not exceed the maximum allowable frequency corresponding to the current water temperature; Fault prevention rules: If the following two conditions are met simultaneously: i) The opening degree of the first branch ≥ 90%, ii) The actual operating frequency of the circulating water pump reaches more than 97% of the maximum allowable frequency corresponding to the current water temperature, then the PLC control host forcibly generates a start instruction for the second branch. Manual start only refers to manually operating the valve, and the PLC can automatically generate instructions.

[0026] Preferably, in the circulating cooling water path control system of the sintering furnace used in magnetic material production, when the absolute value of the real-time temperature change rate during the cooling stage of the sintering furnace ≥ 4 °C / min, and it lasts for ≥ 90 seconds, the opening degree of the first branch ≥ 95% and the actual operating frequency of the circulating water pump ≥ 90% of the maximum allowable frequency corresponding to the current water temperature occur simultaneously, the PLC control host executes the three-branch coordinated opening protocol, The coordinated opening protocol includes: Send start instructions for the second branch and the third branch, automatically open the third branch, manually open the second branch, and adjust the opening degree of the second branch to 50% of it; When the water temperature in the return water pipe ≥ 35 °C, the operating frequency of the circulating water pump is allowed to exceed the 60Hz upper limit, and the excess amount is calculated as an increase of 2Hz for every 5 °C increase.

[0027] Preferably, in the circulating cooling water path control system of the sintering furnace used in magnetic material production, a first pneumatic ball valve is provided on the first branch, a manual ball valve is provided on the second branch, and a third pneumatic ball valve is provided on the third branch. The ratio of the diameter D1 of the first pneumatic ball valve on the first branch to the diameter D3 of the third pneumatic ball valve on the third branch is 5:1 ≤ D1 / D3 ≤ 8:1, The ratio of the theoretical maximum flow rate Q1 of the first branch to the theoretical maximum flow rate Q3 of the third branch Q1 / Q3 ≥ 15.

[0028] Compared with the prior art, the advantages and beneficial technical effects of the present invention are: By setting three parallel branches with different flow rates and a PLC staged control strategy, the present invention ensures precise control of small flow rates during the heating / holding stage, rapid response of large flow rates during the cooling stage, and at the same time, the manual backup branch provides redundant cooling capacity in case of automatic branch failure, significantly improving the system reliability and process adaptability.

[0029] By integrating the closed-loop control of the cooling air conditioner and the variable-frequency circulating water pump, the present invention realizes the suppression of water temperature fluctuations and the dynamic matching of the pump frequency, ensuring both the stability of the cooling efficiency and the reduction of ineffective energy consumption under high-load conditions.

[0030] Through a dynamic tuning algorithm and a gradient switching timing sequence, the present invention adaptively increases the opening degree of the small-flow branch during the high-speed heating stage and achieves a smooth transition between valve actions and the temperature curve during stage switching, effectively avoiding damage to the microstructure of magnetic materials caused by temperature shocks.

[0031] Through a composite calculation model of historical data mapping and temperature drop rate feedback, the present invention accurately predicts the required opening degree of the branch at the initial stage of cooling, suppresses the risk of out-of-control temperature drop rate from the source, and improves the predictability of temperature control.

[0032] Through a three-level progressive fault response mechanism, the present invention triggers manual intervention instructions according to the degree of flow loss, avoiding energy waste caused by premature activation of standby branches and ensuring timely takeover of cooling capacity in case of serious faults.

[0033] By establishing a multi-variable coordination rule of water temperature - refrigeration intensity - pump frequency - number of branches, the present invention realizes global parameter optimization under complex working conditions, and maximally avoids overloading of equipment while ensuring cooling requirements.

[0034] Through a redundant detection of dual water temperature sensors and a calibration mechanism triggered by the difference value, the present invention improves the credibility of temperature data, and at the same time, the high-temperature linkage emergency strategy enhances the system robustness under extreme working conditions.

[0035] Through a frequency protection threshold and a forced start rule associated with water temperature, the present invention intelligently restricts the pump load under high-temperature multi-branch working conditions, prevents overheating damage of the motor, and actively activates standby resources when the flow demand is critically saturated.

[0036] Through a three-branch collaborative opening protocol, the present invention breaks through the limitation of the single-branch flow rate upper limit on rapid cooling, uses a frequency elasticity improvement mechanism to meet transient large-load demands, and ensures strict compliance with the process curve.

[0037] Through the tapered flow channel design and the optimized path ratio of the small-flow branch, the present invention improves the flow linear regulation characteristics and fluid stability under low-opening conditions, and avoids temperature fluctuations caused by valve oscillations.

[0038] Other advantages, objectives, and features of the embodiments of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through research and practice of the embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic structural diagram of a circulating cooling water control system for a sintering furnace used in magnetic material production in one embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] To further elaborate on the technical means and effects adopted by the present invention, the present invention will be further described below in conjunction with embodiments and the accompanying drawings. The specific implementation manners described herein are only used to explain the present invention, rather than limiting the present invention.

[0041] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials, unless otherwise specified, can all be obtained from commercial channels.

[0042] As Figure 1 shown, the present invention provides a circulating cooling water path control system for a sintering furnace in magnetic material production, which is characterized by including: Three cooling water branches, which are arranged in parallel between the water inlet 10 and the water outlet 20 of the sintering furnace. The three cooling water branches include: an automatically controlled first branch and a third branch, and a manually controlled second branch. Among them, the flow rate of the third branch is less than that of the first branch. A PLC control host, which is connected to the working signal of the sintering furnace and the actuators for automatic control of the water branches. The PLC control host is configured to: during the heating and heat preservation stages of the sintering furnace in magnetic material production, close the first branch and open the third branch; during the cooling stage of the sintering furnace, open the first branch and close the third branch. Among them, when a failure or insufficient flow rate occurs in the first branch, or when a failure or insufficient flow rate occurs in the third branch, the PLC control host generates a manual intervention instruction to manually start the second branch.

[0043] Optionally, the three cooling water branches are installed in parallel on the circulating pipeline between the water inlet 10 and the water outlet 20 of the sintering furnace. The first branch adopts a pneumatic ball valve with a nominal diameter of 50 mm (a 304 stainless steel valve body and PTFE seals can be selected), and is connected by a flange at a position 0.5 - 1 meter downstream of the water inlet 10. The theoretical maximum flow rate is 60 m 3 / h; the third branch adopts a pneumatic ball valve with a nominal diameter of 8 mm (the same material as the first branch), is installed at a position 1.2 meters away from the first branch on the same side, and a tapered flow channel (the length of the necking section is 22 - 30 mm) is configured at the inlet end. The theoretical maximum flow rate is 3.8 m³ / h; the second branch adopts a manual ball valve with a nominal diameter of 40 mm (a carbon steel valve body) and is arranged at the middle position between the two automatic branches. The PLC control host (an industrial programmable controller can be selected) is connected to the temperature control system of the sintering furnace and the pneumatic ball valve actuator through a 4 - 20 mA signal line. A turbine flowmeter is installed at the outlet of the circulating water pump (a centrifugal water pump can be selected), and the flow signal is connected to the analog input module of the PLC.

[0044] When the sintering furnace enters the heating or heat preservation stage (judgment condition: PLC receives that the furnace temperature ≥ 600°C and the heating rate < 0.5°C / min), the PLC outputs a closing instruction to close the pneumatic ball valve of the first branch to 0% opening, and at the same time opens the third branch to the reference opening of 30%. In the cooling stage (when the furnace temperature drops from the target value and the rate > 1°C / min), the PLC immediately opens the first branch to 100% opening and closes the third branch. Flow monitoring is achieved by comparing the set value with the feedback value of the flowmeter in real time: If the actual flow of the first branch is continuously lower than 70% of the set value (such as 42 m³ / h) for 120 seconds, or the third branch is lower than 70% of the set value (such as 2.66 m³ / h), it is determined that the flow is insufficient. At this time, the PLC generates a red alarm text "Please manually open the second branch" on the human-machine interface, and at the same time records the fault code F101.

[0045] After the operator receives the manual intervention instruction, rotate the handle of the manual ball valve of the second branch according to the regulations. The corresponding relationship between the opening angle and the flow rate has been calibrated: 30° opening corresponds to 15 m 3 / h, 60° opening corresponds to 30 m 3 / h, fully open 90° corresponds to 40 m 3 / h. During system verification, simulate the stuck spool fault of the third branch in the heating stage (set flow rate 2.8 m 3 / h, actually drops to 1.2 m 3 / h), the PLC triggers an alarm within 90 seconds; after manually opening the second branch to 45°, the flow rate recovers to 18 m 3 / h, and the furnace temperature fluctuation is controlled within ±5°C. The response time of the pneumatic ball valve is measured by a stopwatch: the full-stroke switch action takes 2.1 - 2.5 seconds, meeting the time requirement for stage switching.

[0046] This embodiment ensures the precise matching of the cooling requirements in each process stage of the sintering furnace through the hardware layout of the flow diversion branch and the staged automatic switching, and cooperates with the manual emergency mechanism to maintain the basic cooling capacity when the automatic control fails, improving the reliability of the system operation.

[0047] In another embodiment of the present invention, preferably, it further includes: A cooling air conditioner, which is arranged on the circulating water return pipeline between the water outlet 20 and the water inlet 10 of the sintering machine, is used to reduce the temperature of the circulating cooling water. A water temperature sensor is arranged on the return pipeline. The cooling air conditioner and the water temperature sensor are both connected to the PLC control host. The PLC control host controls the start-stop and refrigeration intensity of the cooling air conditioner according to the water temperature detection data transmitted by the water temperature sensor to maintain the circulating water temperature within the set range; A circulating water pump, which is connected to the PLC control host. The circulating water pump is provided with a circulating water pump frequency converter. The PLC control host adjusts the working frequency of the circulating water pump according to the switching state of the cooling water branch.

[0048] For example, a cooling air conditioner (an air-cooled chiller can be selected) is connected to the return water pipeline 1.2 - 1.5 meters downstream of the outlet 20 of the sintering furnace through a flange, and its evaporator (the material can be 316L stainless steel) is connected in series to the pipeline. Water temperature sensors (PT100 platinum resistance type can be selected) are installed 0.5 meters before the water inlet end of the evaporator and another one is installed 0.5 meters after the water outlet end, and the signal lines are connected to the AI module of the PLC control host. A circulation water pump (a horizontal centrifugal pump can be selected) is set at a position 2 meters downstream of the cooling air conditioner, equipped with a frequency converter (a vector control type can be selected), and the control terminal of the frequency converter is connected to the DO module of the PLC host. The pipeline insulation layer uses rubber and plastic materials (with a thickness of 25 mm) and is wrapped with an aluminum foil protective layer.

[0049] The PLC collects the data of the water temperature sensor every 10 seconds: when the detected value ≥ 35°C (such as 35.2°C), it sends a start command to the cooling air conditioner and sets the refrigeration intensity to 100%; when the temperature drops to the range of 30 - 34.9°C (such as 32.5°C), it adjusts the refrigeration intensity to 65%; when it is lower than 30°C (such as 29.8°C), it turns off the air conditioner. At the same time, the PLC adjusts the pump frequency according to the branch state: when only the third branch is open, it sets 35 Hz (with a fluctuation range of ±3 Hz); when only the first branch is open, it sets 45 Hz; when two branches are open simultaneously, it sets 50 Hz; when all three branches are fully open, it sets 55 Hz. During the gradient switching process in the cooling stage (i.e., the coexistence period of the first and third branches), the frequency is fixed at 50 Hz for operation, and after the switching is completed, it switches to the 45 Hz mode.

[0050] In this embodiment, the closed-loop regulation of the water temperature and the refrigeration intensity is used to maintain the stability of the temperature of the cooling medium, and at the same time, the pump frequency is dynamically matched based on the branch state, optimizing the equipment energy consumption level on the premise of ensuring the cooling efficiency.

[0051] In another embodiment of the present invention, preferably, during the heating and heat preservation stages of the sintering furnace: when the temperature change rate α of the sintering furnace > 1.5°C / min, the third branch dynamic tuning control is executed: Keep the first branch in the closed state, and increase the opening degree of the third branch from the reference value of 30% to (30 + 5×(α - 1.5))%, with a maximum not exceeding 50%; When detecting the signal of the process stage switching to the cooling stage, execute the gradient switching: Within t0 = 0 - 30 seconds, linearly reduce the opening degree of the third branch from the current value to 10%; Within t1 = 30 - 60 seconds, the first branch opens at a rate of (10 + 0.5×(T 初始 -T 目标 ))%, and at the same time, the third branch maintains an opening degree of 10%; When the opening degree of the first branch ≥ 80%, the third branch is completely closed.

[0052] Optionally, when the sintering furnace is in the heating or heat preservation stage, the PLC collects the furnace temperature change rate data every 20 seconds. If it is detected that the change rate α > 1.5 °C / min (for example, α = 2.0 °C / min), then start the dynamic tuning of the third branch: keep the pneumatic ball valve of the first branch (a stainless steel valve with a nominal diameter of 8 mm can be selected) in the fully closed state, and raise the pneumatic ball valve of the third branch from the reference opening degree of 30% to the new opening degree value. The opening degree calculation formula is: 30 + 5×(α - 1.5), and the calculation result is rounded up (for example, when α = 2.0, the opening degree = 30 + 5×0.5 = 32.5% → 33%). The upper limit of the opening degree is limited to 50%, and when the calculation result exceeds 50%, it is executed according to 50%. The valve positioner (a model with analog feedback can be selected) receives a 4 - 20 mA signal to execute the opening degree adjustment, and the response time ≤ 1 second.

[0053] When the PLC receives the start signal for the cooling stage (triggered when the furnace temperature drops from the peak and the rate ≥ 1.2 °C / min), immediately execute the gradient switching program: Within 0 - 30 seconds: The opening degree of the third branch linearly decreases from the current value (such as 40%) to 10%, with a decrease of 1% opening degree per second; Within 30 - 60 seconds: The pneumatic ball valve of the first branch (with a nominal diameter of 50 mm) operates at a rate of opening 40% per minute, while the opening degree of the third branch remains unchanged at 10%. The opening rate is adjusted according to the initial temperature difference, and the formula is: 10 + 0.5×|Tinitial - Ttarget| (for example, when the temperature difference is 200 °C, the rate = 10 + 0.5×200 = 110% / min); When the opening degree of the first branch reaches 80% (confirmed by the valve position feedback signal), the PLC outputs an instruction to close the third branch to 0% within 2 seconds. This embodiment adapts to high heating rate conditions through a dynamic tuning algorithm, uses the gradient switching timing to achieve a smooth transition of the branches, effectively avoids the impact of sudden temperature changes on the sintering process, and maintains the stability of the magnetic material crystallization process.

[0054] In another embodiment of the present invention, preferably, in the initial stage of the cooling stage of the sintering furnace, a mapping table of branch flow - temperature gradient is also established based on historical data, and the initial opening degree γ of the first branch is dynamically calculated according to the following formula: Wherein, T 当前 is the sintering furnace temperature detected in real - time, T 目标 is the target temperature of the current process stage, Δ T max is the preset maximum allowable temperature drop rate (unit: °C / min), is the average temperature change rate within the first 5-minute sliding time window.

[0055] Optionally, at the initial stage of the cooling phase of the sintering furnace (defined as the first 5 minutes when the furnace temperature drops from the peak), the PLC calls the records of the last 10 cooling processes stored in the historical database to establish a mapping relationship table between the branch flow rate and the temperature gradient. The temperature of the sintering furnace collected in real time is measured by a K-type thermocouple (nickel-chromium-nickel-silicon material can be selected), installed at the geometric center point of the furnace chamber, and the signal is converted by the transmitter and input into the PLC. The preset maximum allowable temperature drop rate ΔTmax = 6 °C / min, and the average temperature change rate β within the sliding time window is calculated by sampling the furnace temperature data once every 30 seconds (the average value of the last 10 sampling points).

[0056] When running for the first time without historical data, the calculation can be carried out according to the current stage. In this embodiment, through the composite calculation of historical data mapping and real-time parameter feedback, the opening degree of the branch at the initial stage of cooling is accurately set, the fluctuation of the temperature drop rate is effectively suppressed, and the process stability is improved.

[0057] In another embodiment of the present invention, preferably, when the PLC control host detects a branch fault, a three-level response mechanism is executed: Level I: The flow rate of the faulty branch drops to 70%-60% of the theoretical value, generating a first-level manual intervention instruction to manually start the second branch and adjust it to 30% opening. Level II: The flow rate of the faulty branch drops to 60%-40% of the theoretical value, generating a second-level manual intervention instruction to manually adjust the second branch to 60% opening. Level III: The flow rate of the faulty branch < 40%, generating a third-level manual intervention instruction to close the faulty branch and manually fully open the second branch. The second branch is a temporary standby, and the faulty branch needs to be repaired synchronously.

[0058] Optionally, the PLC control host monitors the flow rate of each branch in real time through a turbine flowmeter (DN15 caliber stainless steel shell can be selected), and the flowmeter is installed 0.8-1.2 meters downstream of the water outlet of each branch. When the flow rate of the first or third branch is detected to be abnormal, the fault level is determined according to the following theoretical maximum flow rate reference value: the theoretical value of the first branch is 60 m³ / h, and the theoretical value of the third branch is 3.8 m³ / h. The three-level response threshold is set as: Level I fault flow rate range 42-36 m³ / h (first branch) or 2.66-2.28 m³ / h (third branch); Level II 36-24 m³ / h or 2.28-1.52 m³ / h; Level III < 24 m³ / h or < 1.52 m³ / h. The manual control second branch ball valve (DN40 carbon steel handle valve can be selected) is installed at a height of 1.5 meters on the operation console, and the valve body surface is marked with an opening degree scale line.

[0059] The PLC refreshes the flow data every 5 seconds and compares it with the threshold value: When a level-I fault is triggered (such as the flow rate of the first branch drops to 45 m³ / h), the PLC pops up a yellow alarm "Please manually open the second branch to 30% opening" on the HMI interface, and at the same time writes the code F201 to the log. The operator rotates the handle of the second branch to align the pointer with the 30% scale line (corresponding to a flow meter reading of approximately 15 m³ / h). When entering a level-II fault (such as the flow rate continues to drop to 32 m³ / h), the alarm is upgraded to orange and prompts "Please adjust the second branch to 60% opening", and the operator turns the handle to the 60% scale line (flow rate approximately 30 m³ / h). When reaching a level-III fault (such as the flow rate < 22 m³ / h), the PLC outputs a red alarm "Please close the faulty branch and fully open the second branch". The operator closes the manual stop valve in front of the pneumatic valve of the faulty branch (installed 0.5 meters upstream of the pneumatic valve), and turns the handle of the second branch to the 90° fully open position (flow rate approximately 40 m³ / h). This embodiment adopts a three-level progressive fault response strategy, which precisely matches the intensity of manual intervention with the degree of flow loss. It not only avoids the premature activation of standby resources but also ensures the reliable replacement of the cooling capacity in case of serious faults, maintaining the continuity of the sintering process.

[0060] In another embodiment of the present invention, preferably, the cooling air conditioner adopts a variable-frequency compressor, and the evaporator of the cooling air conditioner is serially arranged at a position close to the water outlet 20 of the sintering furnace in the return water pipeline; the PLC control host also performs the following steps: When the detected value of the water temperature sensor ≥ 35 °C, start the cooling air conditioner and operate it at 100% cooling intensity; When 30 °C ≤ the detected value of the water temperature sensor < 35 °C, start the cooling air conditioner and operate it at 50%-80% cooling intensity; When the detected value of the water temperature sensor < 30 °C, turn off the cooling air conditioner; The frequency converter of the circulating water pump adopts closed-loop PID control, and the corresponding relationship between its frequency adjustment range and the number of opened cooling water branches is as follows: When only the third branch is opened: 30 Hz - 40 Hz; When only the first branch is opened: 40 Hz - 50 Hz; When the first branch and the third branch are opened simultaneously: 45 Hz - 55 Hz; When the first branch, the second branch, and the third branch are opened simultaneously: 50 Hz - 60 Hz; Among them, during the gradient switching process in the cooling stage, when the first branch and the third branch are opened simultaneously, the frequency of the circulating water pump is adjusted according to 45 Hz - 55 Hz; after the gradient switching is completed, it is adjusted according to 40 Hz - 50 Hz when only the first branch is opened.

[0061] Optionally, the cooling air conditioner can be an air-cooled screw chiller. Its evaporator uses a 316L stainless steel plate heat exchanger, which is installed in series through a flange on the return water pipeline 1.5 - 2 meters downstream of the outlet 20 of the sintering furnace. The distance between the inlet and outlet 20 of the evaporator is maintained at 0.8 meters. The water temperature sensor can be a PT1000 platinum resistance. The first one is installed 0.3 meters before the inlet 10 of the evaporator, and the second one is installed 0.3 meters after the outlet 20. The sensor wires are connected to the RTD input module of the PLC. The circulating water pump can be a vertical multistage centrifugal pump, and the supporting frequency converter can be a vector control type with an IP55 protection level. The frequency converter is installed within 10 meters of the water pump motor in the control cabinet. The pipeline insulation layer can be a closed-cell rubber and plastic material with a thickness of 30mm. The PLC reads the data of the water temperature sensor every 15 seconds: when the detected value ≥ 35°C (such as 35.5°C), it sends a start command to the cooling air conditioner and sets the compressor frequency to 50Hz (100% cooling intensity); when the temperature is in the range of 30 - 34.9°C (such as 33.2°C), it sets the compressor frequency to 30Hz (60% cooling intensity); when it is below 30°C (such as 29.4°C), it outputs a stop command. The water pump frequency control rule is: when only the third branch is open, it is set to 35Hz ± 2Hz; when only the first branch is open, it is set to 45Hz ± 2Hz; when the first and third branches are open simultaneously, it is set to 50Hz ± 2Hz; when all three branches are open, it is set to 55Hz ± 2Hz. During the gradient switching process in the cooling stage (that is, during the period when the first branch is open and the third branch is not completely closed), regardless of the change in the branch state, the water pump frequency is fixed at 50Hz. This embodiment realizes precise temperature control through the hierarchical matching of water temperature and cooling intensity, dynamically adjusts the water pump frequency in combination with the branch state, optimizes the operation efficiency of the equipment while meeting the cooling requirements, and avoids hydraulic fluctuations through the frequency locking mechanism during the gradient switching period.

[0062] In another embodiment of the present invention, preferably, two water temperature sensors are arranged in parallel on the water temperature sensor on the return water pipeline. The two water temperature sensors are respectively located at the inlet end and the outlet end of the evaporator of the cooling air conditioner; when the difference between the detected values of the two water temperature sensors ≥ 2°C, the PLC control host controls the cooling air conditioner according to the temperature value data of the water temperature sensor with a higher temperature, and triggers a sensor calibration alarm; In the cooling stage of the sintering furnace, if the average value of the detected values of the two water temperature sensors ≥ 40°C, the second branch is started and the frequency of the circulating water pump is synchronously increased to 55Hz - 60Hz.

[0063] Optionally, in the return water pipeline, two water temperature sensors can be PT100 platinum resistance thermometers, which are respectively installed 0.3 meters before the water inlet end and 0.3 meters after the water outlet end of the evaporator of the cooling air conditioner. The sensor probe is vertically inserted into the center of the pipeline and fixed through a stainless steel sleeve. The wires are connected to the RTD input module of the PLC (an 8-channel isolation type can be selected) using shielded twisted pair. The sensor range covers 0 - 100 °C with an accuracy of ±0.5 °C. The pipeline maintains a 1.5-meter straight pipe section at the sensor installation section to avoid the influence of elbow disturbance on measurement. The PLC synchronously reads the data of the two sensors every 10 seconds: When the temperature difference between the water inlet end and the water outlet end ≥ 2 °C (for example, 42.3 °C at the water inlet end / 39.7 °C at the water outlet end), the PLC automatically selects the higher value of 42.3 °C as the control reference, and performs the start / stop and intensity adjustment of the cooling air conditioner according to this value (start 100% refrigeration when 42.3 °C ≥ 35 °C). At the same time, an alarm code E305 "Temperature difference exceeds the limit and needs to be calibrated" is triggered on the HMI interface. During the cooling stage of the sintering furnace, the average value of the two sensors is calculated in real time: If the average value ≥ 40 °C (for example, the average is 40.5 °C when the water inlet end is 43 °C / the water outlet end is 38 °C), the PLC immediately outputs an opening instruction to the second branch (regardless of whether the automatic branch is faulty), and sets the target frequency of the water pump frequency converter to 58 Hz (the allowable range is 55 - 60 Hz). At this time, the operator needs to manually adjust the opening of the second branch ball valve to the 70% scale line position (corresponding to a flow rate of about 28 m³ / h). This embodiment improves the reliability of temperature data through dual-sensor redundant detection and temperature difference-triggered calibration mechanism, and actively activates the standby cooling resources under high-temperature working conditions, enhancing the system's ability to cope with extreme working conditions.

[0064] In another embodiment of the present invention, preferably, the circulating water pump frequency converter is set with an overload protection threshold linked to the water temperature, and its maximum allowable frequency is determined according to the following rules: When the water temperature in the return water pipeline is in the range of 25 °C to 40 °C, the maximum allowable frequency linearly decreases from 60 Hz to 54 Hz; When the water temperature > 40 °C, the maximum allowable frequency is fixed at 54 Hz; Operation constraint rules: When the following two conditions are met simultaneously: a) The number of opened cooling water branches ≥ 2, b) The water temperature ≥ 35 °C, The working frequency of the circulating water pump shall not exceed the maximum allowable frequency corresponding to the current water temperature; Fault prevention rules: If the following two conditions are met simultaneously: i) The opening of the first branch ≥ 90%, ii) When the actual working frequency of the circulating water pump reaches more than 97% of the maximum allowable frequency corresponding to the current water temperature, the PLC control host forcibly generates a second branch start instruction.

[0065] The frequency converter of the circulating water pump can be of the vector control type, and its overload protection module presets the water temperature - frequency correlation threshold: when the water temperature of the return water pipe is in the range of 25°C to 40°C, the maximum allowable frequency f max is calculated according to the formula f max = 60 - 0.3×(T - 25) (T is the real-time water temperature, unit °C). For example: when T = 25°C, f max = 60Hz; when T = 32°C, f max = 60 - 0.3×7 = 57.9Hz; when T ≥ 40°C, f max is fixed at 54Hz.

[0066] The frequency converter control cabinet is installed on a moisture-proof base within 5 meters of the water pump motor. The temperature sensor in the cabinet can use an NTC thermistor to monitor the ambient temperature. The circulating water pump can be a horizontal centrifugal pump (the material can be selected as a cast iron housing / stainless steel impeller), and the distance between the water inlet 10 and the outlet of the evaporator of the cooling air conditioner is maintained at a straight pipe section of 1.5 meters.

[0067] The PLC detects the water temperature and the branch status every 10 seconds: when both a) the number of opened branches ≥ 2 (such as the first branch + the third branch), b) the water temperature ≥ 35°C (such as 36.2°C) are satisfied, calculate the current f max value (when T = 36.2°C, f_max = 60 - 0.3×11.2 = 56.64Hz), and limit the working frequency of the water pump ≤ 56.6Hz (if the set value is higher than this, automatic peak shaving will be performed).

[0068] In this embodiment, through the frequency protection threshold related to the water temperature and the multi-condition trigger mechanism, the overload damage of the water pump is effectively prevented under high-temperature and multi-branch working conditions, and the continuity of the cooling capacity is ensured through the forced start strategy of the standby branch In another embodiment of the present invention, preferably, when the absolute value of the real-time temperature change rate during the cooling stage of the sintering furnace ≥ 4°C / min, and it lasts for ≥ 90 seconds, the opening degree of the first branch ≥ 95% and the actual working frequency of the circulating water pump ≥ 90% of the maximum allowable frequency corresponding to the current water temperature occur simultaneously, the PLC control host executes the three-branch coordinated opening protocol, The coordinated opening protocol includes: Sending the opening instructions for the second branch and the third branch, automatically opening the third branch, manually opening the second branch, and adjusting the opening degree of the second branch to 50% of it; When the water temperature of the return water pipe ≥ 35°C, the working frequency of the circulating water pump is allowed to exceed the 60Hz upper limit, and the excess amount is calculated as an increase of 2Hz for every 5°C increase.

[0069] During the cooling stage of the sintering furnace, the PLC monitors three parameters in real time: the furnace temperature change rate is calculated by sampling every second through a K-type thermocouple (nickel-chromium-nickel-silicon material can be selected); the first branch opening is fed back in real time by a valve positioner (4-20mA feedback type can be selected); the circulating water pump frequency is transmitted by a frequency converter (vector control type can be selected) via Modbus communication. The trigger threshold for coordinated opening is: The absolute value of the temperature change rate is ≥4.0℃ / min (e.g. -4.2℃ / min) Duration ≥ 90 seconds The first branch opening ≥ 95% Water pump frequency ≥54Hz (90% of the preset upper limit of 60Hz) The four conditions must be met at the same time. The circulating water pump can be a vertical multi-stage centrifugal pump (the shell material can be ductile iron), and the outlet pressure sensor is installed 0.5 meters downstream of the pump flange. When the trigger conditions are met (for example, -4.3℃ / min is monitored for 95 seconds, the first branch opening is 96%, and the frequency is 55.2Hz), the PLC executes the three-branch coordinated opening protocol: 1. Automatically open the third branch: output a 100% opening command to the pneumatic ball valve (diameter 8mm) of the third branch, and the valve will be fully opened within 2 seconds; 2. Generate manual instructions: A red alarm pops up on the HMI interface, "Please open the second branch to 50% opening immediately", and at the same time, the opening of the first branch is locked and no longer increased; 3. Frequency elastic adjustment: If the water temperature of the return pipe is ≥35℃ (such as 36℃), the upper limit of the allowable frequency is calculated according to the formula = 60 + 2×(T-35) / 5 (such as the upper limit at 36℃ = 60+2×1 / 5=60.4Hz), and the actual set frequency is the range of 58-60.4Hz. After receiving the instruction, the operator needs to rotate the second branch manual ball valve to the 50% scale position (corresponding to a flow rate of approximately 20m³ / h) within 60 seconds.

[0070] This implementation method uses a multi-threshold joint trigger mechanism to break through the single-branch flow limitation under extreme working conditions, and utilizes the backup resource coordination and frequency elasticity improvement strategy to ensure the strict requirements of the magnetic material sintering process for rapid cooling.

[0071] In another embodiment of the present invention, preferably, a first pneumatic ball valve 1 is provided on the first branch, a manual ball valve 2 is provided on the second branch, and a third pneumatic ball valve 3 is provided on the third branch. The ratio of the diameter D1 of the first pneumatic ball valve 1 of the first branch to the diameter D3 of the third pneumatic ball valve 3 of the third branch is 5:1≤D1 / D3≤8:1.

[0072] The ratio Q1 / Q3 of the theoretical maximum flow rate Q1 of the first branch to the theoretical maximum flow rate Q3 of the third branch is Q1 / Q3 ≥ 15; The inlet end of the third branch is provided with a tapered flow channel structure, and the relationship between the length L of its necking section and the nominal diameter D3 is L = 2.7D3 to 3.7D3.

[0073] The first branch uses a pneumatic ball valve with a nominal diameter of 50 mm (a 304 stainless steel valve body and a PTFE valve seat can be selected), and is connected by a flange to the straight pipe section 0.8 m downstream of the water inlet of the sintering furnace. The theoretical maximum flow rate is 60 m³ / h (when the medium is water and the pressure is 0.4 MPa). The third branch uses a pneumatic ball valve with a nominal diameter of 8 mm (same material), which is installed at a distance of 1.5 m from the first branch. The theoretical maximum flow rate is 3.8 m³ / h, and the nominal diameter ratio D1 / D3 = 6.25 (meeting the range of 5:1 to 8:1). The inlet end of the third branch is provided with a tapered flow channel structure (a brass H62 material can be selected). The length L of the necking section is 30 mm (when D3 = 8 mm, L / D3 = 3.75), the tapered transition angle is 15°, and the nominal diameter of the inlet flange gradually changes from 20 mm to 8 mm. The manual ball valve of the second branch has a nominal diameter of 40 mm (carbon steel WCB material), and the installation height is 1.2 m from the ground. Through the optimization of the nominal diameter ratio and the design of the tapered flow channel, this embodiment improves the regulation accuracy and fluid stability of the small-flow branch while ensuring the flow rate difference requirement, and avoids valve oscillation under low-opening conditions.

[0074] The present invention uses a multi-channel controller to provide different cooling water flow rates for the equipment. According to different working stages of the equipment, control switching is carried out to provide cooling for the equipment more precisely. The water inlet of the equipment is divided into three parallel branches. The first branch is a full-flow automatic control pipeline (the first pneumatic ball valve is large), the second branch is a full-flow manual control pipeline (manual ball valve 2), and the third branch is a small-flow automatic control pipeline (the third pneumatic ball valve 3 is small). When the equipment is in the heating and heat preservation stages, the large ball valve is closed and the small ball valve is opened to reduce the cooling water flow rate. When the equipment is in the cooling stage, the large ball valve is opened and the small ball valve is closed to use full-flow cooling. In each stage, the PLC host of the equipment controls the frequency converter to adjust the working frequency and temperature of the circulating water pump and the cooling air conditioner, effectively reducing the energy consumption of the equipment and saving production costs. And it is horizontally promoted to other similar equipment, which has a positive effect on the overall cost reduction and efficiency improvement of the factory. The present invention can effectively reduce the energy consumption of the equipment and save production costs while ensuring the normal operation of the equipment. And it is horizontally promoted as an improvement of lean production.

[0075] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the embodiments of the present invention. For those skilled in the art, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and their equivalents, the embodiments of the present invention are not limited to specific details.

Claims

1. A circulating cooling water circuit control system for a sintering furnace in magnetic material production, characterized in that, Including: Three cooling water branches, which are arranged in parallel between the water inlet and outlet of the sintering furnace. The three cooling water branches include: an automatically controlled first branch and a third branch, and a manually controlled second branch. Among them, the flow rate of the third branch is less than that of the first branch. A PLC control host, which is connected to the working signal of the sintering furnace and the actuator for automatic control of the water branch. The PLC control host is configured to: during the heating and heat preservation stages of the sintering furnace in magnetic material production, close the first branch and open the third branch; during the cooling stage of the sintering furnace, open the first branch and close the third branch. Among them, when a fault occurs in the first branch or the flow rate is insufficient, or when a fault occurs in the third branch or the flow rate is insufficient, the PLC control host generates a manual intervention instruction to manually start the second branch.

2. The circulating cooling water path control system for a sintering furnace used in magnetic material production according to claim 1, characterized in that, It also includes: A cooling air conditioner, which is arranged on the circulating water return pipeline between the water outlet and inlet of the sintering machine and is used to reduce the temperature of the circulating cooling water. A water temperature sensor is arranged on the return pipeline. The cooling air conditioner and the water temperature sensor are both connected to the PLC control host. The PLC control host controls the start-stop and refrigeration intensity of the cooling air conditioner according to the water temperature detection data transmitted by the water temperature sensor to maintain the circulating water temperature within a set range. A circulating water pump, which is connected to the PLC control host. The circulating water pump is equipped with a circulating water pump frequency converter, and the PLC control host adjusts the working frequency of the circulating water pump according to the switching state of the cooling water branch.

3. The circulating cooling water path control system for a sintering furnace used in magnetic material production according to claim 1, characterized in that, During the heating and heat preservation stages of the sintering furnace: when the temperature change rate α of the sintering furnace > 1.5 °C / min, perform dynamic tuning control of the third branch: Keep the first branch in the closed state, and increase the opening degree of the third branch from the reference value of 30% to (30 + 5×(α - 1.5))%, with a maximum not exceeding 50%. When detecting a signal indicating the process stage switches to the cooling stage, perform gradient switching: Within t0 = 0 - 30 seconds, linearly reduce the opening degree of the third branch from the current value to 10%. Within t1 = 30 - 60 seconds, the first branch opens at a rate of (10 + 0.5×(T 初始 -T 目标 ))%, while the third branch maintains an opening of 10%; When the opening degree of the first branch ≥ 80%, completely close the third branch.

4. The circulating cooling water path control system for the sintering furnace used in magnetic material production according to claim 3, wherein In the initial stage of the cooling stage of the sintering furnace, a mapping table of branch flow rate - temperature gradient is also established based on historical data, and the initial opening degree γ of the first branch is dynamically calculated according to the following formula: Among them, T 当前 is the temperature of the sintering furnace detected in real time, T 目标 is the target temperature of the current process stage, Δ T max is the preset maximum allowable temperature drop rate, is the average temperature change rate within the 5-minute sliding time window.

5. The circulating cooling water path control system for a sintering furnace used in magnetic material production according to claim 4, wherein, When the PLC control host detects a branch fault, execute a three-level response mechanism: Level I: The flow rate of the faulty branch drops to 70% - 60% of the theoretical value, generate a first-level manual intervention instruction, manually start the second branch and adjust it to an opening degree of 30%. Level II: The flow rate of the faulty branch drops to 60% - 40% of the theoretical value, generate a second-level manual intervention instruction, and manually adjust the second branch to an opening degree of 60%. Level III: The flow rate of the faulty branch < 40%, generate a third-level manual intervention instruction, close the faulty branch and manually fully open the second branch.

6. The circulating cooling waterway control system for the sintering furnace used in magnetic material production according to claim 2, wherein, The cooling air conditioner uses a variable frequency compressor, and the evaporator of the cooling air conditioner is connected in series in the return pipeline at a position close to the water outlet of the sintering furnace; the PLC control host also performs the following steps: When the detection value of the water temperature sensor ≥ 35 °C, start the cooling air conditioner and operate it at 100% refrigeration intensity. When 30 °C ≤ the detection value of the water temperature sensor < 35 °C, start the cooling air conditioner and operate it at a refrigeration intensity of 50% - 80%. When the detected value of the water temperature sensor < 30°C, turn off the cooling air conditioner; The frequency converter of the circulating water pump adopts closed-loop PID control, and the corresponding relationship between its frequency adjustment range and the number of opened cooling water branches is as follows: When only the third branch is opened: 30Hz - 40Hz; When only the first branch is opened: 40Hz - 50Hz; When the first branch and the third branch are opened simultaneously: 45Hz - 55Hz; When the first branch, the second branch, and the third branch are opened simultaneously: 50Hz - 60Hz; Among them, during the gradient switching process in the cooling stage, when the first branch and the third branch are opened simultaneously, the frequency of the circulating water pump is adjusted according to 45Hz - 55Hz; after the gradient switching is completed, it is adjusted according to 40Hz - 50Hz when only the first branch is opened.

7. The circulating cooling water path control system for a sintering furnace used in magnetic material production according to claim 6, wherein, Two water temperature sensors are connected in parallel on the water temperature sensor on the return water pipe. The two water temperature sensors are respectively located at the water inlet end and the water outlet end of the evaporator of the cooling air conditioner; when the difference between the detected values of the two water temperature sensors ≥ 2°C, the PLC control host controls the cooling air conditioner based on the temperature value data of the water temperature sensor with a higher temperature, and triggers a sensor calibration alarm; In the cooling stage of the sintering furnace, if the average value of the detected values of the two water temperature sensors ≥ 40°C, start the second branch and synchronously increase the frequency of the circulating water pump to 55Hz - 60Hz.

8. The circulating cooling water path control system for a sintering furnace used in magnetic material production according to claim 6, characterized in that, The frequency converter of the circulating water pump is set with an overload protection threshold linked to the water temperature, and its maximum allowable frequency is determined according to the following rules: When the water temperature of the return water pipe is in the range of 25°C to 40°C, the maximum allowable frequency linearly decreases from 60Hz to 54Hz; When the water temperature > 40°C, the maximum allowable frequency is fixed at 54Hz; Operation constraint rules: When the following two conditions are met simultaneously: a) The number of opened cooling water branches ≥ 2, b) The water temperature ≥ 35°C, The working frequency of the circulating water pump shall not exceed the maximum allowable frequency corresponding to the current water temperature; Fault prevention rules: If the following two conditions are met simultaneously: i) The opening degree of the first branch ≥ 90%, ii) The actual working frequency of the circulating water pump reaches more than 97% of the maximum allowable frequency corresponding to the current water temperature, Then the PLC control host forcibly generates a start instruction for the second branch.

9. The circulating cooling waterway control system for the sintering furnace used in magnetic material production according to claim 2, wherein, When the absolute value of the real-time temperature change rate in the cooling stage of the sintering furnace ≥ 4°C / min and lasts for ≥ 90 seconds, and the opening degree of the first branch ≥ 95% and the actual working frequency of the circulating water pump ≥ 90% of the maximum allowable frequency corresponding to the current water temperature occur simultaneously, the PLC control host executes a three-branch collaborative opening protocol. The collaborative opening protocol includes: Send start instructions for the second branch and the third branch, automatically open the third branch, manually open the second branch, and adjust the opening degree of the second branch to 50%; When the water temperature of the return water pipe ≥ 35°C, the working frequency of the circulating water pump is allowed to exceed the 60Hz upper limit, and the excess amount is calculated as an increase of 2Hz for every 5°C increase.

10. The circulating cooling water path control system for a sintering furnace used in magnetic material production according to claim 1, characterized in that, A first pneumatic ball valve is installed on the first branch, a manual ball valve is installed on the second branch, and a third pneumatic ball valve is installed on the third branch. The ratio of the diameter D1 of the first pneumatic ball valve on the first branch to the diameter D3 of the third pneumatic ball valve on the third branch is 5:1 ≤ D1 / D3 ≤ 8:

1. The ratio Q1 / Q3 of the theoretical maximum flow rate Q1 of the first branch to the theoretical maximum flow rate Q3 of the third branch is Q1 / Q3 ≥ 15.

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