A purification control method and system based on furnace bottom air leakage recycling

Abstract

This invention discloses a purification control method and system based on the recovery and utilization of bottom air leakage, belonging to the field of industrial furnace and kiln automatic control technology. This purification control method based on the recovery and utilization of bottom air leakage collects signals of the operating frequency, pressure difference, furnace negative pressure, and dust concentration of the recovery fan and the main induced draft fan. It uses a parallel pressure source coupling identification algorithm to obtain the parallel pressure source coupling coefficient, a positive feedback trend prediction algorithm to obtain the positive feedback trend value, and a dynamic decoupling control algorithm to generate the frequency adjustment step size of the recovery fan and the frequency compensation step size of the main induced draft fan (which has the opposite direction). The operating frequency is then superimposed with the adjustment step size and the compensation step size and output synchronously to the corresponding strain gauge. This invention, through parallel pressure source coupling identification and dynamic decoupling control, cuts off the positive feedback loop between the recovery fan and the main induced draft fan at the control architecture level, achieving both efficient waste heat recovery from air leakage and stable furnace negative pressure.

Description

Technical Field

[0001] This invention relates to the field of automatic control technology for industrial furnaces and kilns, specifically to a purification control method and system based on the recovery and utilization of air leakage from the furnace bottom. Background Technology

[0002] During operation, industrial boilers and heating furnaces inevitably experience gaps between the mechanical seal at the furnace bottom and the material layer, resulting in bottom air leakage. This leakage contains waste heat and residual oxygen, and direct discharge would lead to energy waste. Therefore, existing technologies typically incorporate a bottom air leakage recovery system, which uses a recovery fan to draw the leaked air into the main air duct, thus achieving waste heat recovery and utilization.

[0003] A furnace bottom air leakage recovery system typically consists of a recovery fan, recovery duct, regulating damper, and bypass vent valve. The recovery fan is connected in parallel with the main induced draft fan at the same furnace negative pressure node. Under normal operating conditions, the recovery fan adjusts according to the furnace negative pressure or a preset air volume, sending the leaked air into the main duct for combustion. A dust concentration monitoring device is usually installed in the recovery duct to determine the ash content in the leaked air.

[0004] In actual operation, the air leakage at the furnace bottom is affected by various factors, including grate speed, bed thickness, fuel type, and mechanical seal condition. Changes in these factors can cause the air leakage to fluctuate within a wide range. Simultaneously, the dust concentration in the recovery duct also changes dynamically with variations in bed condition and combustion status. When changes occur in air leakage or dust concentration, the operating parameters of the recovery system need to be adjusted to adapt to the new conditions.

[0005] The limitations of existing technologies include at least the following problems: In the design of the control architecture of the furnace bottom air leakage recovery system, the recovery fan and the main induced draft fan are only controlled independently based on the series flow relationship of the main air duct. This fails to recognize that when they are connected in parallel at the same furnace negative pressure node, they form a coupled parallel pressure source. When the recovery fan increases its speed to increase suction, the pipeline pressure decreases, which passively increases the flow of the main induced draft fan, forming a positive feedback loop that mutually excites the enhanced suction and the deepening of the furnace negative pressure. Existing control architectures cannot suppress this positive feedback mechanistically; they can only passively maintain system stability by reducing the fan response speed, setting a negative pressure dead zone, or limiting the recovery air volume. This results in low waste heat recovery efficiency from air leakage, furnace negative pressure fluctuations disturbing combustion stability, and the recovery system's inability to dynamically adjust to air leakage conditions, leading to increased wear and ash accumulation on the heating surfaces. Consequently, it is difficult to ensure the efficient and stable operation of industrial furnaces under varying conditions. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a purification control method and system based on the recovery and utilization of leaking air from the furnace bottom. This solves the problem that existing technologies, which control the recovery fan and the main induced draft fan in series flow relationships, are unable to suppress the positive feedback loop of the parallel pressure source and can only passively balance recovery efficiency and negative pressure stability.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a purification control method based on the recovery and utilization of furnace bottom leakage air, comprising the following steps: collecting the operating frequencies of the recovery fan and the main induced draft fan, the pressure difference between the recovery fan outlet and the furnace negative pressure node, the real-time pressure value of the furnace negative pressure node, and the dust concentration signal of the recovery air duct; employing a parallel pressure source coupling identification algorithm, obtaining the coupling strength characterization value based on the operating frequency and pressure difference of the recovery fan, obtaining the system impedance characterization value based on the operating frequency of the main induced draft fan and the real-time pressure value of the furnace negative pressure, and correlating the coupling strength characterization value with the system impedance characterization value to obtain the parallel pressure source coupling coefficient; employing a positive feedback trend prediction algorithm, correlating the parallel pressure source coupling coefficient with... The positive feedback trend value is obtained by weighted fusion of the dust concentration signal in the recovery duct. A dynamic decoupling control algorithm is adopted to generate the frequency adjustment step size of the recovery fan based on the deviation between the coupling coefficient of the parallel pressure source and the preset target coupling coefficient. The coupling coefficient of the parallel pressure source and the frequency adjustment step size are calculated together to obtain the frequency compensation step size of the main induced draft fan in opposite directions. The operating frequencies of the recovery fan and the main induced draft fan are respectively superimposed with the corresponding adjustment step size and compensation step size to obtain the target frequencies of both and output synchronously to the corresponding strain gauge. A safety clamp prediction algorithm is adopted to control the bypass vent valve to open and limit the maximum operating frequency of the recovery fan when the dust concentration signal in the recovery duct is greater than the preset dust concentration threshold and the positive feedback trend value is greater than the preset trend threshold.

[0008] Furthermore, the specific steps for obtaining the coupling strength characterization value based on the operating frequency and pressure difference of the recovery fan are as follows: filter the operating frequency and pressure difference of the recovery fan to obtain the estimated coupling strength value; normalize and compare the estimated coupling strength value with the preset rated operating frequency and rated pressure difference of the recovery fan to obtain the coupling strength characterization value.

[0009] Furthermore, the specific steps for obtaining the system impedance characterization value based on the main induced draft fan operating frequency and the real-time pressure value of the furnace negative pressure are as follows: the absolute values ​​of the main induced draft fan operating frequency and the real-time pressure value of the furnace negative pressure are filtered to obtain the system impedance estimate; the system impedance estimate is normalized and compared with the preset rated operating frequency of the main induced draft fan and the rated value of the furnace negative pressure to obtain the system impedance characterization value.

[0010] Furthermore, the specific steps for obtaining the positive feedback trend value by weighted fusion of the parallel pressure source coupling coefficient and the dust concentration signal of the recovery duct are as follows: perform change rate analysis on the dust concentration signal of the recovery duct to obtain the dust concentration change rate; dynamically allocate weighting coefficients according to the magnitude of the parallel pressure source coupling coefficient, and weightedly fuse the parallel pressure source coupling coefficient and the dust concentration change rate to obtain the positive feedback trend value.

[0011] Furthermore, the specific steps for generating the frequency adjustment step size of the recovery fan based on the deviation between the parallel pressure source coupling coefficient and the preset target coupling coefficient are as follows: Analyze the deviation between the parallel pressure source coupling coefficient and the preset target coupling coefficient to obtain the coupling deviation value; perform correlation calculation between the coupling deviation value and the preset proportional coefficient to obtain the initial frequency adjustment step size; perform correlation calculation between the positive feedback trend value and the preset correction proportional coefficient to obtain the correction coefficient; and perform comprehensive processing of the initial frequency adjustment step size and the correction coefficient to obtain the frequency adjustment step size of the recovery fan.

[0012] Furthermore, the specific steps for obtaining the main induced draft fan frequency compensation step size in opposite directions through the collaborative calculation of the parallel pressure source coupling coefficient and the frequency adjustment step size are as follows: The parallel pressure source coupling coefficient and the frequency adjustment step size are analyzed collaboratively to obtain the compensation base value; the compensation base value is correlated with a preset basic compensation coefficient to obtain the initial compensation step size; the rate of change of the parallel pressure source coupling coefficient is analyzed to obtain the coupling coefficient change rate; the rate of change of the coupling coefficient is correlated with a preset dynamic compensation coefficient to obtain the dynamic compensation factor; the initial compensation step size and the dynamic compensation factor are fused to obtain the main induced draft fan frequency compensation step size; the direction of the main induced draft fan frequency compensation step size is set to be opposite to the direction of the frequency adjustment step size, and the response speed of the compensation step size is adjusted synchronously with the rate of change of the coupling coefficient.

[0013] Furthermore, the specific steps for controlling the opening of the bypass vent valve and limiting the maximum operating frequency of the recovery fan are as follows: The dust concentration signal in the recovery duct is compared with a preset dust concentration threshold to obtain a dust exceedance judgment result; the positive feedback trend value is compared with a preset trend threshold to obtain a positive feedback trend exceedance judgment result; when both the dust exceedance judgment result and the positive feedback trend exceedance judgment result are satisfied, a bypass vent valve opening command is generated, and the vent valve opening degree is adjusted in stages according to the magnitude of the positive feedback trend value; the maximum operating frequency of the recovery fan is locked to a preset percentage of the current operating frequency, and the preset percentage decreases progressively as the positive feedback trend value increases.

[0014] Furthermore, the specific steps for generating the frequency adjustment step size of the recovery fan based on the deviation between the parallel pressure source coupling coefficient and the preset target coupling coefficient are as follows: Analyze the deviation between the parallel pressure source coupling coefficient and the preset target coupling coefficient to obtain the coupling deviation value; perform correlation calculation between the coupling deviation value and the preset adjustment ratio coefficient to obtain the initial adjustment step size; perform correlation calculation between the positive feedback trend value and the preset correction ratio coefficient to obtain the correction coefficient; perform comprehensive processing of the initial adjustment step size and the correction coefficient, and introduce the real-time fluctuation value of the furnace negative pressure for secondary correction to obtain the frequency adjustment step size of the recovery fan.

[0015] Furthermore, the specific steps for obtaining the main induced draft fan frequency compensation step size in opposite directions through the collaborative calculation of the parallel pressure source coupling coefficient and the frequency adjustment step size are as follows: The parallel pressure source coupling coefficient and the frequency adjustment step size are analyzed collaboratively to obtain the compensation base value; the compensation base value is correlated with a preset basic compensation coefficient to obtain the initial compensation step size; the rate of change of the parallel pressure source coupling coefficient is analyzed to obtain the coupling coefficient change rate; the rate of change of the coupling coefficient is correlated with a preset dynamic compensation coefficient to obtain the dynamic compensation factor; the initial compensation step size and the dynamic compensation factor are fused to obtain the main induced draft fan frequency compensation step size; the direction of the main induced draft fan frequency compensation step size is set to be opposite to the direction of the frequency adjustment step size, and the response speed of the compensation step size is adjusted synchronously with the rate of change of the coupling coefficient.

[0016] A purification and control system based on furnace bottom air leakage recovery and utilization includes: a parameter acquisition unit for acquiring the operating frequencies of the recovery fan and the main induced draft fan, the pressure difference between the recovery fan outlet and the furnace negative pressure node, the real-time pressure value of the furnace negative pressure node, and the dust concentration signal of the recovery air duct; a parallel pressure source coupling identification unit connected to the parameter acquisition unit for obtaining a coupling strength characterization value based on the recovery fan operating frequency and pressure difference, obtaining a system impedance characterization value based on the main induced draft fan operating frequency and the real-time pressure value of the furnace negative pressure, and performing a correlation calculation between the coupling strength characterization value and the system impedance characterization value to obtain the parallel pressure source coupling coefficient; a positive feedback trend prediction unit connected to the parallel pressure source coupling identification unit for weighted fusion of the parallel pressure source coupling coefficient and the dust concentration signal of the recovery air duct to obtain a positive feedback trend value; and a dynamic solution unit. The coupling control unit, connected to the positive feedback trend prediction unit, generates the frequency adjustment step size of the recovery fan based on the deviation between the parallel pressure source coupling coefficient and the preset target coupling coefficient. It then calculates the frequency compensation step size of the main induced draft fan in the opposite direction by coordinating the parallel pressure source coupling coefficient and the frequency adjustment step size. The command output unit, connected to the dynamic decoupling control unit, superimposes the corresponding adjustment step size and compensation step size on the operating frequencies of the recovery fan and the main induced draft fan to obtain their target frequencies, and outputs the target frequencies synchronously to the corresponding strain gauge. The safety clamp control unit, connected to the positive feedback trend prediction unit and the parameter acquisition unit, controls the bypass vent valve to open and limits the maximum operating frequency of the recovery fan when the dust concentration signal in the recovery duct is greater than the preset dust concentration threshold and the positive feedback trend value is greater than the preset trend threshold.

[0017] The present invention has the following beneficial effects:

[0018] (1) The purification control method based on the recovery and utilization of furnace bottom air leakage decouples the recovery fan and the main induced draft fan according to the parallel pressure source relationship through the parallel pressure source coupling identification algorithm. It abandons the mode of independent control of the two according to the series flow relationship in the existing technology. The existing control architecture fails to identify that the two are connected in parallel at the same furnace negative pressure node and form a coupled parallel pressure source. When the recovery fan increases the suction, the pipeline pressure decreases and the flow of the main induced draft fan will passively increase, forming a positive feedback loop of mutual excitation between enhanced suction and deepened furnace negative pressure. The system stability can only be maintained passively by reducing the fan response speed, setting a negative pressure dead zone, or limiting the recovery air volume. This invention introduces the parallel pressure source coupling coefficient, directly identifies and quantifies this coupling relationship at the control architecture level, and changes the control of the recovery fan and the main induced draft fan from mutual interference to coordinated cooperation. It cuts off the formation conditions of the positive feedback loop from the mechanism and achieves both the efficiency of air leakage waste heat recovery and the stability of furnace negative pressure.

[0019] (2) The purification control method based on the recovery and utilization of bottom leakage air in the furnace obtains the positive feedback trend value by weighted fusion of the coupling coefficient of the parallel pressure source and the dust concentration signal of the recovery air duct through the positive feedback trend prediction algorithm. This realizes the early prediction of the formation trend of the positive feedback loop. The existing technology only compensates after the positive feedback has occurred or the negative pressure exceeds the limit, which is a post-event suppression. The control action is always lagging behind the disturbance change. The present invention introduces the dust concentration change rate into the calculation of the positive feedback trend value and dynamically allocates the weighting coefficient according to the size of the coupling coefficient of the parallel pressure source. When the coupling degree is high and the dust concentration rises rapidly, the positive feedback trend value can reflect the accelerated formation trend of the positive feedback loop in advance. The dynamic decoupling control algorithm adaptively shrinks the frequency adjustment step of the recovery fan and performs reverse compensation on the main induced draft fan, so that the control action intervenes before the positive feedback is formed, turning passive suppression into active avoidance.

[0020] (3) The purification control method based on the recovery and utilization of bottom leakage air uses the safety clamp prediction algorithm to take the dust concentration signal of the recovery air duct and the positive feedback trend value as dual triggering conditions. The opening of the vent valve and the limit of the maximum operating frequency of the recovery fan are adjusted in stages according to the magnitude of the positive feedback trend value. The existing safety clamp mechanism only relies on the dust concentration or negative pressure exceeding the limit to trigger, which is a post-event protection and a switch control. Once triggered, the recovery path is completely cut off, resulting in waste of residual heat. The present invention introduces the positive feedback trend value as a prediction condition when the dust concentration exceeds the standard. The safety protection is triggered only when both conditions are met at the same time, avoiding the invalid action caused by the false triggering of a single condition. After triggering, the opening of the vent valve and the frequency limit are adjusted in stages according to the strength of the positive feedback trend value. The stronger the positive feedback trend, the greater the protection force. When the trend weakens, the protection force is reduced synchronously, realizing the dynamic matching of protection force and risk level.

[0021] (4) The purification control system based on the bottom leakage air recovery and utilization acquires multi-dimensional information such as the operating frequency of the recovery fan and the main induced draft fan, the negative pressure of the furnace, the pressure difference and the dust concentration in real time through the parameter acquisition unit. The parallel pressure source coupling identification unit integrates them into a coupling coefficient that characterizes the coupling strength of the parallel pressure source. The positive feedback trend prediction unit predicts the formation trend of the positive feedback loop based on this. The dynamic decoupling control unit generates synchronous and reverse cooperative control commands. The safety clamp control unit implements graded protection under extreme working conditions. A control link combining feedforward and feedback is formed between each unit, so that the recovery system can dynamically adjust the control strategy according to the changes in the leakage working conditions.

[0022] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0023] Figure 1 This is a flowchart of a purification control method based on the recovery and utilization of air leakage from the furnace bottom according to the present invention.

[0024] Figure 2 This is a flowchart illustrating the specific steps in a purification control method based on the recovery and utilization of bottom air leakage in the present invention to obtain the coupling strength characterization value based on the operating frequency and pressure difference of the recovery fan.

[0025] Figure 3 This is a block diagram of a purification control system based on the recovery and utilization of air leakage from the furnace bottom according to the present invention. Detailed Implementation

[0026] Please see Figure 1 This invention provides a technical solution: a purification control method based on the recovery and utilization of furnace bottom air leakage, comprising the following steps: collecting the operating frequencies of the recovery fan and the main induced draft fan, the pressure difference between the recovery fan outlet and the furnace negative pressure node, the real-time pressure value of the furnace negative pressure node, and the dust concentration signal of the recovery air duct; employing a parallel pressure source coupling identification algorithm, obtaining the coupling strength characterization value based on the operating frequency and pressure difference of the recovery fan, obtaining the system impedance characterization value based on the operating frequency of the main induced draft fan and the real-time pressure value of the furnace negative pressure, and correlating the coupling strength characterization value with the system impedance characterization value to obtain the parallel pressure source coupling coefficient; employing a positive feedback trend prediction algorithm, correlating the parallel pressure source coupling coefficient with the recovery air duct... The positive feedback trend value is obtained by weighted fusion of dust concentration signals. A dynamic decoupling control algorithm is adopted to generate the frequency adjustment step size of the recovery fan based on the deviation between the coupling coefficient of the parallel pressure source and the preset target coupling coefficient. The coupling coefficient of the parallel pressure source and the frequency adjustment step size are calculated together to obtain the frequency compensation step size of the main induced draft fan in opposite directions. The operating frequencies of the recovery fan and the main induced draft fan are respectively superimposed with the corresponding adjustment step size and compensation step size to obtain the target frequencies of both and output synchronously to the corresponding strain gauge. A safety clamp prediction algorithm is adopted to control the bypass vent valve to open and limit the maximum operating frequency of the recovery fan when the dust concentration signal of the recovery air duct is greater than the preset dust concentration threshold and the positive feedback trend value is greater than the preset trend threshold.

[0027] The coupling coefficient of the parallel pressure source ranges from 0 to 1. When the coupling coefficient is 0, it indicates that the recovery fan and the main induced draft fan are not coupled. When the coupling coefficient is 1, it indicates that the two are in a fully coupled state.

[0028] The preset target coupling coefficient is set according to the rated load of the industrial furnace, and the value range is 0.3~0.6;

[0029] For example, when the rated load of the furnace is 300MW, the preset target coupling coefficient is set to 0.45;

[0030] The frequency converter adopts vector control mode. After receiving the target frequency command, the response time is ≤50ms, which ensures that the fan speed can quickly follow the frequency adjustment and avoids the triggering of positive feedback loop.

[0031] The parallel pressure source coupling identification algorithm, positive feedback trend prediction algorithm, dynamic decoupling control algorithm, and safety clamp prediction algorithm are all integrated into the PLC controller. The sampling period of the PLC controller is set to 100ms to ensure the real-time performance of parameter acquisition and command output.

[0032] Specifically, such as Figure 2 As shown, the specific steps for obtaining the coupling strength characterization value based on the operating frequency and pressure difference of the recovery fan are as follows:

[0033] The coupling strength estimate is obtained by filtering the operating frequency and pressure difference of the recovery fan. Specifically:

[0034] A first-order low-pass filter algorithm is used to analyze the operating frequency of the recovery fan. The pressure difference between the outlet of the recovery fan and the negative pressure node of the furnace. Filtering is performed to remove high-frequency noise caused by electromagnetic interference and airflow disturbances in the industrial environment. The filtering formula is as follows:

[0035] ;

[0036] in, The current filtered operating frequency of the recovery fan. This is the original value of the operating frequency of the recovery fan collected at the current moment;

[0037] The filtered pressure difference at the current moment. This is the raw value of the differential pressure collected at the current moment;

[0038] These represent the filtered operating frequency and pressure difference of the recovery fan at the previous moment. These are the filter coefficients, with values ​​ranging from 0.1 to 0.3.

[0039] For example: when The operating frequency of the recovery fan after filtering at the previous moment The raw frequency collected at the current moment Then the current filtered frequency ;

[0040] Similarly, the pressure difference after filtering at the previous moment The raw pressure difference collected at the current moment The current filtered pressure difference ;

[0041] After filtering and Perform a product operation to obtain the estimated coupling strength. Based on the above example, ;

[0042] The coupling strength estimate is normalized and compared with the preset rated operating frequency and rated pressure difference of the recovery fan to obtain the coupling strength characterization value, which is as follows:

[0043] Set the rated operating frequency of the recovery fan (e.g., 50Hz), rated differential pressure of the recovery fan (e.g., 5 kPa), calculate the rated coupling reference value:

[0044] ;

[0045] Based on the above example Then, a normalization formula is used to estimate the coupling strength. Convert to coupling strength characterization value The normalization formula is ,make sure The value range is 0 to 1. Based on the example above, This indicates that the coupling between the current recovery fan and the furnace negative pressure node is at a moderate level.

[0046] In this implementation scheme, by incorporating filtering into the calculation of coupling strength characterization, the problem of electromagnetic interference and airflow disturbance in the industrial field contaminating the original acquired signal is effectively solved. The introduction of the first-order low-pass filtering algorithm filters out high-frequency noise in the operating frequency and differential pressure signals of the recovery fan, ensuring that the data used in subsequent product calculations truly reflects the actual operating status of the equipment and avoiding misjudgment of coupling strength due to signal jumps. The normalized comparison method is used to associate the estimated coupling strength with the preset rated parameters, so that the obtained coupling strength characterization value always falls within a uniform numerical range, eliminating the influence of differences in rated parameters of different equipment on the judgment of coupling strength.

[0047] Specifically, the steps to obtain the system impedance characterization value based on the main induced draft fan operating frequency and the real-time pressure value of the furnace negative pressure are as follows:

[0048] The system impedance prediction is obtained by filtering the absolute values ​​of the main induced draft fan operating frequency and the real-time negative pressure value of the furnace. Specifically:

[0049] A first-order low-pass filtering algorithm is used to filter the operating frequency of the main induced draft fan. The absolute value of the real-time pressure at the negative pressure node of the furnace. Perform filtering processing, filter coefficients Similarly, for values ​​ranging from 0.1 to 0.3 (e.g., 0.2), the filtering formula is:

[0050] ;

[0051] in, This represents the filtered operating frequency of the main induced draft fan at the current moment. This is the raw value of the main induced draft fan's operating frequency collected at the current moment;

[0052] This represents the absolute value of the furnace negative pressure after filtering at the current moment. This is the original absolute value of the furnace negative pressure collected at the current moment;

[0053] These are the operating frequency of the main induced draft fan and the absolute value of the furnace negative pressure after filtering at the previous moment, respectively.

[0054] For example: the filtered operating frequency of the main induced draft fan at the previous moment. The raw frequency collected at the current moment Then the current filtered frequency ;

[0055] The absolute value of the furnace negative pressure after filtering at the previous moment The absolute value of the original negative pressure collected at the current moment. The absolute value of the current filtered negative pressure ;

[0056] After filtering and By performing ratio calculations, the estimated system impedance is obtained. Based on the above example, ;

[0057] The system impedance estimate is normalized and compared with the preset rated operating frequency of the main induced draft fan and the rated negative pressure of the furnace to obtain the system impedance characterization value, which is as follows:

[0058] Set the rated operating frequency of the main induced draft fan (e.g., 50Hz), absolute value of furnace negative pressure rating (e.g., 4kPa), calculate the reference value for rated impedance. Based on the above example, ;

[0059] The system impedance prediction is obtained using a normalized formula. Convert to system impedance characterization value The normalization formula is Based on the above example, This indicates that the current system impedance is higher than the rated impedance, and the main induced draft fan load is slightly high.

[0060] In this implementation scheme, by placing the filtering process before the calculation of the system impedance characterization value, the pollution of the main induced draft fan operating frequency and furnace negative pressure acquisition signals by electromagnetic interference and airflow disturbance in the industrial site is effectively eliminated. The introduction of the first-order low-pass filtering algorithm filters out high-frequency noise in the original signal, ensuring that the data on which the subsequent ratio calculation is based truly reflects the actual impedance relationship between the main induced draft fan and the furnace negative pressure. By using the ratio calculation to correlate the main induced draft fan operating frequency with the absolute value of the furnace negative pressure, the obtained system impedance prediction value can intuitively reflect the output required by the main induced draft fan to overcome the furnace negative pressure under the current operating conditions. By using a normalized comparison method to correlate the system impedance prediction value with the preset rated parameters, the obtained system impedance characterization value eliminates the influence of the difference in rated parameters of different equipment on the impedance judgment.

[0061] Specifically, the steps for obtaining the positive feedback trend value by weighted fusion of the parallel pressure source coupling coefficient and the dust concentration signal in the recovery duct are as follows:

[0062] The rate of change of dust concentration was obtained by analyzing the change signal of dust concentration in the recovery duct, and the specific details are as follows:

[0063] The dust concentration signal in the recovery duct was calculated using the first-order difference method. rate of change The calculation formula is:

[0064] ;

[0065] in, This represents the dust concentration value collected at the current moment (unit: mg / m³). This represents the dust concentration value collected at the previous moment. The sampling period for the PLC controller is set to 100ms, or 0.1s.

[0066] For example: dust concentration at the current moment Dust concentration at the previous moment The rate of change of dust concentration This indicates that the dust concentration is on the rise.

[0067] The weighting coefficients are dynamically allocated based on the magnitude of the coupling coefficients of the parallel pressure sources. The positive feedback trend value is obtained by weighting and fusing the coupling coefficients of the parallel pressure sources with the dust concentration change rate. Specifically:

[0068] Set two weighting coefficients (corresponding to the coupling coefficient of parallel pressure sources) )and (corresponding dust concentration change rate) ), and satisfy ;

[0069] Weighting coefficients Based on the coupling coefficient Dynamic allocation, the allocation formula is:

[0070] ;

[0071] ;

[0072] That is, coupling coefficient The larger, The larger the value, the higher the weight (the stronger the coupling, the more significant the impact of the coupling coefficient on the positive feedback trend).

[0073] Positive feedback trend value The calculation formula is:

[0074] ;

[0075] in, The preset maximum rate of change in dust concentration (e.g., 100 mg / (m³·s)) is used to... Perform normalization processing to ensure The value range is 0 to 1;

[0076] For example: if the coupling coefficient of the parallel pressure sources ,but , Based on the above example ,but Positive feedback trend value ( The closer the value is to 1, the more pronounced the positive feedback trend, and the higher the risk of getting out of control.

[0077] In this implementation scheme, by incorporating the dust concentration change rate into the calculation of the positive feedback trend value, a leap from static state judgment to dynamic trend prediction is achieved. The first-order difference method is used to analyze the dust concentration change rate, enabling the system to capture the upward trend of dust concentration rather than just focusing on the current value. This provides a leading time indicator for the early identification of the positive feedback loop. The practice of dynamically allocating weighting coefficients based on the coupling coefficient of parallel pressure sources solves the problem that fixed weights are difficult to adapt to changes in operating conditions. When the coupling strength is high, the coupling coefficient has a greater weight in the positive feedback trend judgment, while when the coupling strength is low, the dust concentration change rate plays a dominant role. This allows the calculation of the positive feedback trend value to be adaptively adjusted according to the actual coupling state of the system. The normalization of the dust concentration change rate ensures the dimensional consistency with the coupling coefficient, so that the final positive feedback trend value can intuitively reflect the risk level of the positive feedback loop formation.

[0078] Specifically, the steps for generating the frequency adjustment step size of the recovery fan based on the deviation between the parallel pressure source coupling coefficient and the preset target coupling coefficient are as follows:

[0079] The coupling deviation value is obtained by analyzing the deviation between the coupling coefficient of the parallel pressure sources and the preset target coupling coefficient. Specifically:

[0080] Set the preset target coupling coefficient as (Value range: 0.3~0.6, e.g., 0.45), Coupling bias value The calculation formula is:

[0081] ;

[0082] in, The coupling coefficient of the parallel pressure sources at the current moment;

[0083] For example: if the current , ,but This indicates that the current coupling coefficient is higher than the target value, and the frequency of the recovery fan needs to be reduced to weaken the coupling.

[0084] like ,but This indicates that the current coupling coefficient is lower than the target value, and the frequency of the recovery fan needs to be increased to enhance the coupling.

[0085] The initial frequency adjustment step size is obtained by correlating the coupling deviation value with a preset scaling factor, specifically as follows:

[0086] Set the scaling factor (Value range: 0.1~0.5Hz, e.g., 0.2Hz), initial frequency adjustment step size The calculation formula is ;

[0087] Based on the above example, when hour, That is, the initial adjustment step size is 0.01Hz, and the direction is decreasing ( When the value is positive, it indicates a reduction in the operating frequency of the recovery fan.

[0088] when hour, The negative sign indicates that the adjustment direction is to increase ( A negative value indicates an increase in the operating frequency of the recovery fan.

[0089] The correction coefficient is obtained by correlating the positive feedback trend value with a preset correction ratio coefficient. Specifically:

[0090] Set the correction ratio coefficient (Value range: 0.8~1.2, e.g., 1.0), correction factor The calculation formula is:

[0091] ;

[0092] in, This represents the current positive feedback trend value. The median value of the positive feedback trend is 0.5.

[0093] For example: if ,but This indicates that the positive feedback trend is slightly below the median value, and the adjustment step size needs to be appropriately reduced.

[0094] like ,but This indicates that the positive feedback trend is slightly higher than the median value, and the adjustment step size needs to be increased appropriately;

[0095] The frequency adjustment step size of the recovery fan is obtained by comprehensively processing the initial frequency adjustment step size and the correction coefficient. Specifically:

[0096] Frequency adjustment step size of the recovery fan The calculation formula is:

[0097] ;

[0098] Based on the above example ,but

[0099] ;

[0100] like ,but ;

[0101] Simultaneously limited The value range is -0.05Hz to 0.05Hz to avoid system fluctuations caused by excessively large adjustment steps.

[0102] In this implementation scheme, by incorporating the positive feedback trend value into the calculation process of the frequency adjustment step size of the recovery fan, a dynamic correlation between the adjustment amplitude and the degree of positive feedback risk is achieved. First, the initial adjustment step size is calculated based on the deviation between the coupling coefficient of the parallel pressure source and the preset target value, ensuring that the adjustment direction of the recovery fan is consistent with the direction of the coupling deviation, and ensuring that the coupling coefficient always converges towards the target value. On this basis, the positive feedback trend value is introduced as a correction coefficient. When the positive feedback trend is higher than the intermediate value, the adjustment step size is appropriately increased to accelerate the response speed. When the positive feedback trend is lower than the intermediate value, the adjustment step size is appropriately decreased to avoid over-adjustment. This allows the adjustment step size to be dynamically adjusted according to the formation risk of the positive feedback loop. This adjustment method, which combines coupling deviation control with positive feedback trend correction, avoids the response lag or over-adjustment problems caused by fixed step size control. It enables the frequency adjustment of the recovery fan to not only respond quickly to changes in coupling deviation, but also automatically adjust the adjustment intensity according to the degree of positive feedback risk, achieving a dynamic balance between control accuracy and adjustment speed.

[0103] Specifically, the steps for calculating the frequency compensation step size of the main induced draft fan in opposite directions by coordinating the coupling coefficient of the parallel pressure sources with the frequency adjustment step size are as follows:

[0104] The compensation base value is obtained by synergistic analysis of the coupling coefficient of the parallel pressure sources and the frequency adjustment step size, specifically as follows:

[0105] Compensation base value The calculation formula is:

[0106] ;

[0107] in, To recover the absolute value of the frequency adjustment step size of the fan, The coupling coefficient of the parallel pressure sources;

[0108] For example: if ,but The larger the coupling coefficient, the larger the compensation base value, ensuring that the compensation strength matches the coupling strength.

[0109] The initial compensation step size is obtained by performing a correlation calculation between the compensation base value and the preset basic compensation coefficient, specifically as follows:

[0110] Set the basic compensation coefficient (Value range: 1.5~3.0, e.g., 2.0), Initial compensation step size The calculation formula is:

[0111] ;

[0112] Based on the above example ;

[0113] The rate of change of the coupling coefficient of the parallel pressure sources is obtained by performing a rate-of-change analysis. The rate of change of the coupling coefficient is then correlated with a preset dynamic compensation coefficient to obtain the dynamic compensation factor, which is as follows:

[0114] The rate of change of coupling coefficients was calculated using the first-order difference method. The calculation formula is:

[0115] ;

[0116] in, The coupling coefficient at the current moment. The coupling coefficient at the previous time step. ;

[0117] For example: Current The previous moment ,but ;

[0118] Set dynamic compensation coefficient (Value range: 0.5~1.5, e.g., 1.0), Dynamic compensation factor The calculation formula is:

[0119] ;

[0120] Based on the above example The greater the rate of change of the coupling coefficient, the larger the dynamic compensation factor and the faster the compensation step response;

[0121] The initial compensation step size and the dynamic compensation factor are fused to obtain the main induced draft fan frequency compensation step size, which is as follows:

[0122] Main induced draft fan frequency compensation step size The calculation formula is:

[0123] ;

[0124] Based on the above example ;

[0125] Simultaneously limited The value range is -0.08Hz to 0.08Hz to ensure that the compensation range of the main induced draft fan is reasonable;

[0126] The direction of the frequency compensation step size for the main induced draft fan is opposite to the direction of the frequency adjustment step size, and the response speed of the compensation step size is adjusted synchronously with the rate of change of the coupling coefficient. Specifically:

[0127] Define the direction of frequency adjustment step size — A positive value indicates a reduction in the operating frequency of the recovery fan;

[0128] A negative value indicates an increase in the operating frequency of the recovery fan; the corresponding compensation step direction is:

[0129] like If the value is positive (reducing the frequency of the recovery fan), then the frequency compensation step size of the main induced draft fan is... A negative value (increase the frequency of the main induced draft fan);

[0130] like If the value is negative (increase the frequency of the recovery fan), then A positive value (reduce the frequency of the main induced draft fan);

[0131] For example: (Reducing the frequency of the recovery fan) (Increase the frequency of the main induced draft fan);

[0132] Response speed of compensation step size (Unit: Hz / ms, referring to the adjustment rate of frequency compensation) and the rate of change of coupling coefficient The correlation formula is:

[0133] ;

[0134] in, Based on the basic response speed (e.g., 0.01Hz / ms), continuing from the above... ,but , The larger, The larger the value, the faster the compensation response, and the faster the positive feedback loop is suppressed.

[0135] In this implementation scheme, by coordinating the frequency compensation step size of the main induced draft fan with the frequency adjustment step size of the recovery fan and the coupling coefficient of the parallel pressure source, dynamic matching of compensation intensity and coupling strength is achieved. The compensation base value is determined by the product of the absolute value of the adjustment step size and the coupling coefficient, so that the stronger the coupling, the larger the compensation base value, ensuring that the compensation intensity can offset the excitation intensity of the positive feedback loop. Based on the initial compensation step size, the rate of change of the coupling coefficient is introduced as a dynamic compensation factor, so that the compensation step size can be adjusted synchronously with the changing trend of the coupling coefficient. When the coupling coefficient rises rapidly, the compensation step size increases accordingly, and when the coupling coefficient tends to stabilize, the compensation step size converges accordingly. The direction of the compensation step size is explicitly set to be opposite to the direction of the adjustment step size, directly offsetting the furnace negative pressure fluctuation caused by the adjustment of the recovery fan in terms of action timing. The response speed of the compensation step size is linked with the rate of change of the coupling coefficient, so that the speed of the compensation action can follow the formation speed of the positive feedback loop. It intervenes quickly when the positive feedback accelerates and transitions smoothly when the positive feedback slows down, achieving a comprehensive dynamic matching from compensation intensity to compensation speed.

[0136] Specifically, the steps for controlling the opening of the bypass vent valve and limiting the maximum operating frequency of the recovery fan are as follows:

[0137] The dust concentration signal from the recovery duct is compared with a preset dust concentration threshold to obtain the dust exceeding the standard judgment result, specifically:

[0138] Set preset dust concentration threshold (Value range 80~120mg / m³, e.g., 100mg / m³), the comparison logic is as follows:

[0139] If the current dust concentration If the dust exceeds the standard, the result of the judgment is "true" (meaning that the dust exceeds the standard);

[0140] like If so, the result is "false" (meaning the dust level is not exceeded).

[0141] For example, If the dust exceeds the standard, the result is "true".

[0142] If so, the result is "false";

[0143] The positive feedback trend value is compared with a preset trend threshold to obtain the result of the positive feedback trend exceeding the limit. Specifically:

[0144] Set preset trend threshold (Value range: 0.6~0.8, e.g., 0.7), the comparison logic is as follows:

[0145] If the current positive feedback trend value If the positive feedback trend exceeds the standard, the judgment result is "true" (indicating that the positive feedback trend is obvious and there is a risk of getting out of control).

[0146] like If so, the result is "false";

[0147] For example, If the result is true, then the judgment result is "true";

[0148] If so, the result is "false";

[0149] When both the dust exceedance judgment result and the positive feedback trend exceedance judgment result are met simultaneously, a bypass vent valve opening command is generated, and the vent valve opening degree is adjusted in stages according to the magnitude of the positive feedback trend value, specifically as follows:

[0150] The bypass vent valve opening command is only generated when both judgment results are "true" to avoid false triggering due to a single indicator exceeding the limit.

[0151] Combined with preset trend thresholds , the opening of the vent valve is divided into 3 levels, and the grading logic and opening setting are as follows:

[0152] Level 1 (0.7<T≤0.75): opening 30%;

[0153] For example: , the opening of the vent valve is adjusted to 30%;

[0154] Level 2 (0.75<T≤0.8): opening 60%;

[0155] For example: , the opening of the vent valve is adjusted to 60%;

[0156] Level 3 (T>0.8): opening 100%;

[0157] For example: , the opening of the vent valve is adjusted to 100%;

[0158] The opening adjustment adopts a linear adjustment mode, with an adjustment time ≤1s, so as to ensure rapid pressure relief and reduce dust concentration;

[0159] The maximum operating frequency of the recovery fan is locked to a preset percentage of the current operating frequency, and the preset percentage decreases stepwise as the positive feedback trend value increases, which is specifically as follows:

[0160] The preset percentage is divided into 3 levels, corresponding to the opening levels of the vent valve, and the level setting is as follows:

[0161] Level 1 (0.7<T≤0.75): preset percentage 80%;

[0162] For example: the current operating frequency of the recovery fan is 45Hz, and the maximum operating frequency after locking is ;

[0163] Level 2 (0.75<T≤0.8): preset percentage 70%;

[0164] For example: the current operating frequency is 45Hz, and the maximum operating frequency after locking is ;

[0165] Level 3 (T>0.8): preset percentage 60%;

[0166] For example: the current operating frequency is 45Hz, and the maximum operating frequency after locking is ;

[0167] After locking, the operating frequency of the recovery fan shall not exceed this maximum limit until the dust concentration and the positive feedback trend value , the lock is automatically released.

[0168] In this implementation scheme, by using both the dust concentration signal and the positive feedback trend value as the safety clamp trigger condition, the problem of malfunction caused by triggering a single indicator is effectively solved. Only when the dust concentration exceeds the standard and the positive feedback trend is obvious is the condition determined to require intervention and protection. This avoids ineffective protection actions caused by instantaneous fluctuations in dust or occasional jumps in the positive feedback trend. After the protection is triggered, the opening of the vent valve and the limit of the maximum operating frequency of the recovery fan are adjusted according to the strength of the positive feedback trend value. The stronger the positive feedback trend, the larger the opening of the vent valve and the stricter the frequency limit. When the positive feedback trend weakens, the protection intensity is reduced accordingly. This achieves dynamic matching between protection intensity and risk level. The graded adjustment method avoids the waste of residual heat caused by completely cutting off the recovery path upon triggering in on / off control. This allows the system to effectively suppress risks and maintain some recovery capacity under extreme conditions. When the dust concentration and the positive feedback trend fall back to the safe range at the same time, the system automatically unlocks and restores normal operation, avoiding the response lag caused by manual reset.

[0169] Specifically, the steps for generating the frequency adjustment step size of the recovery fan based on the deviation between the parallel pressure source coupling coefficient and the preset target coupling coefficient are as follows:

[0170] The coupling deviation value is obtained by analyzing the deviation between the coupling coefficient of the parallel pressure sources and the preset target coupling coefficient. Specifically:

[0171] Set the preset target coupling coefficient (Value range: 0.3~0.6, e.g., 0.45), Coupling bias value ;

[0172] For example: Current ,but ;

[0173] The initial adjustment step size is obtained by correlating the coupling deviation value with a preset adjustment ratio coefficient, specifically as follows:

[0174] Set adjustment ratio coefficient (Value range: 0.15~0.6Hz, e.g., 0.3Hz), initial adjustment step size The calculation formula is:

[0175] ;

[0176] Based on the above example The direction is downward ( When the value is positive, it indicates a reduction in the operating frequency of the recovery fan.

[0177] The correction coefficient is obtained by correlating the positive feedback trend value with a preset correction ratio coefficient. Specifically:

[0178] Set the correction ratio coefficient (Value range: 0.9~1.3, e.g., 1.1), correction factor The calculation formula is:

[0179] ;

[0180] in, ;

[0181] For example: ,but ;

[0182] The initial adjustment step size and correction coefficient are combined and then further corrected by incorporating the real-time fluctuation value of the furnace negative pressure to obtain the frequency adjustment step size of the recovery fan, which is as follows:

[0183] Calculate the adjustment step size after the initial correction:

[0184] ;

[0185] Based on the above example ;

[0186] Introducing real-time fluctuation values ​​of furnace negative pressure:

[0187] ;

[0188] in, This is the current real-time value of the furnace negative pressure. The rated negative pressure of the furnace (range -5~-2kPa, for example: -3kPa, absolute value 3kPa);

[0189] For example: ,but ;

[0190] Set negative pressure correction factor (Value range: 0.05~0.2kPa) -1 For example: 0.1 kPa -1 Secondary correction factor:

[0191] ;

[0192] Based on the above example ;

[0193] Final frequency adjustment step size for the recovery fan:

[0194] ;

[0195] Based on the above example ;

[0196] limited The value range is -0.06Hz to 0.06Hz, balancing adjustment accuracy and system stability.

[0197] In this implementation scheme, a secondary correction is further introduced by incorporating real-time fluctuations in furnace negative pressure, on top of the dual corrections of coupling deviation and positive feedback trend. This allows the frequency adjustment step size of the recovery fan to simultaneously respond to changes in three dimensions: coupling state, positive feedback trend, and negative pressure disturbance. When furnace negative pressure fluctuates, the secondary correction coefficient dynamically scales the adjustment step size according to the fluctuation amplitude. The larger the fluctuation, the larger the correction amplitude. This ensures that the frequency adjustment of the recovery fan appropriately converges when negative pressure fluctuations are severe and returns to normal response when negative pressure is stable. This multi-dimensional correction mechanism solves the problem in traditional control where relying solely on a single feedback signal makes it difficult to accommodate multiple disturbances. It enables the frequency adjustment step size of the recovery fan to automatically match the optimal adjustment intensity according to the real-time system status, avoiding over-adjustment or under-adjustment caused by negative pressure fluctuation interference.

[0198] Specifically, the steps for calculating the frequency compensation step size of the main induced draft fan in opposite directions by coordinating the coupling coefficient of the parallel pressure sources with the frequency adjustment step size are as follows:

[0199] The compensation base value is obtained by synergistic analysis of the coupling coefficient of the parallel pressure sources and the frequency adjustment step size, specifically as follows:

[0200] Compensation base value The calculation formula is:

[0201] ;

[0202] For example: , ,but ;

[0203] The initial compensation step size is obtained by performing a correlation calculation between the compensation base value and the preset basic compensation coefficient, specifically as follows:

[0204] Set the basic compensation coefficient (Value range: 1.8~3.5, e.g., 2.5), Initial compensation step size The calculation formula is:

[0205] ;

[0206] Based on the above example ;

[0207] The rate of change of the coupling coefficient of the parallel pressure sources is obtained by performing a rate-of-change analysis. The rate of change of the coupling coefficient is then correlated with a preset dynamic compensation coefficient to obtain the dynamic compensation factor, which is as follows:

[0208] Rate of change of coupling coefficient:

[0209] ;

[0210] For example: Current The previous moment ,but ;

[0211] Set dynamic compensation coefficient (Value range: 0.6~1.6, e.g., 1.2), Dynamic compensation factor ;

[0212] Based on the above example ;

[0213] The initial compensation step size and the dynamic compensation factor are fused to obtain the main induced draft fan frequency compensation step size, which is as follows:

[0214] Main induced draft fan frequency compensation step size The calculation formula is:

[0215] ;

[0216] Based on the above example ;

[0217] limited The value range is -0.1Hz to 0.1Hz to ensure that the compensation amplitude is adapted to the load characteristics of the main induced draft fan;

[0218] The direction of the frequency compensation step size for the main induced draft fan is opposite to the direction of the frequency adjustment step size, and the response speed of the compensation step size is adjusted synchronously with the rate of change of the coupling coefficient. Specifically:

[0219] A positive value indicates a reduction in the operating frequency of the recovery fan;

[0220] A negative value indicates an increase in the operating frequency of the recovery fan;

[0221] Corresponding compensation step direction: If If it is a positive value (reducing the frequency of the recovery fan), then A negative value (increase the frequency of the main induced draft fan);

[0222] like If the value is negative (increase the frequency of the recovery fan), then A positive value (reduce the frequency of the main induced draft fan);

[0223] For example: (Reducing the frequency of the recovery fan) (Increase the frequency of the main induced draft fan);

[0224] Response speed of compensation step size (Unit: Hz / ms, referring to the adjustment rate of frequency compensation) and the rate of change of coupling coefficient The correlation formula is:

[0225] ;

[0226] in, Based on the base response speed (e.g., 0.012 Hz / ms), based on the example above. ,but This ensures that the compensation response speed matches the coupling fluctuation intensity, quickly blocking the positive feedback loop.

[0227] In this implementation scheme, by linking the frequency compensation step size of the main induced draft fan with the rate of change of the coupling coefficient and the dynamic compensation factor, the frequency adjustment action of the main induced draft fan can be made to better match the real-time changes of the furnace top operating conditions. This avoids the problem of over-adjustment or under-adjustment caused by a fixed compensation step size, maintains stable adjustment when the operating conditions fluctuate slightly, and responds quickly to compensation when the operating conditions fluctuate significantly, effectively improving the stability and adjustment accuracy of the main induced draft fan during the furnace top gas recovery process.

[0228] Please see Figure 3This invention provides a technical solution: a purification control system based on the recovery and utilization of furnace bottom air leakage, comprising: a parameter acquisition unit, used to acquire the operating frequency of the recovery fan and the main induced draft fan, the pressure difference between the outlet of the recovery fan and the furnace negative pressure node, the real-time pressure value of the furnace negative pressure node, and the dust concentration signal of the recovery air duct; a parallel pressure source coupling identification unit, connected to the parameter acquisition unit, used to obtain a coupling strength characterization value based on the operating frequency and pressure difference of the recovery fan, obtain a system impedance characterization value based on the operating frequency of the main induced draft fan and the real-time pressure value of the furnace negative pressure, and perform a correlation calculation between the coupling strength characterization value and the system impedance characterization value to obtain a parallel pressure source coupling coefficient; and a positive feedback trend prediction unit, connected to the parallel pressure source coupling identification unit, used to weightedly fuse the parallel pressure source coupling coefficient and the dust concentration signal of the recovery air duct to obtain a positive and negative trend prediction value. The system includes: a trend value; a dynamic decoupling control unit connected to the positive feedback trend prediction unit, used to generate the frequency adjustment step size of the recovery fan based on the deviation between the parallel pressure source coupling coefficient and the preset target coupling coefficient, and to obtain the frequency compensation step size of the main induced draft fan in opposite directions by coordinating the parallel pressure source coupling coefficient and the frequency adjustment step size; a command output unit connected to the dynamic decoupling control unit, used to superimpose the corresponding adjustment step size and compensation step size on the operating frequencies of the recovery fan and the main induced draft fan respectively to obtain their target frequencies, and to synchronously output the target frequencies to the corresponding strain gauge; and a safety clamp control unit connected to the positive feedback trend prediction unit and the parameter acquisition unit, used to control the bypass vent valve to open and limit the maximum operating frequency of the recovery fan when the dust concentration signal in the recovery duct is greater than the preset dust concentration threshold and the positive feedback trend value is greater than the preset trend threshold.

[0229] The parameter acquisition unit includes a frequency sensor, a differential pressure sensor, a pressure sensor, and a dust concentration sensor. The frequency sensor is a Hall effect frequency sensor, which is installed on the motor shaft of the recovery fan and the main induced draft fan, respectively. The measurement range is 0~60Hz, and the measurement accuracy is ±0.1Hz.

[0230] The differential pressure sensor is a diffused silicon differential pressure sensor, which is installed on the pipeline between the outlet of the recovery blower and the negative pressure node of the furnace. The measurement range is 0~10kPa and the measurement accuracy is ±0.01kPa.

[0231] The pressure sensor is a capacitive pressure sensor, installed at the negative pressure node of the furnace, with a measurement range of -5~0 kPa and a measurement accuracy of ±0.01 kPa;

[0232] The dust concentration sensor is a laser scattering dust sensor, installed in the middle of the recovery air duct, with a measurement range of 0~200mg / m³ and a measurement accuracy of ±1mg / m³.

[0233] All sensors are connected to the PLC controller via 4-20mA analog signals to ensure the accuracy and real-time performance of parameter acquisition.

[0234] The parallel pressure source coupling identification unit, positive feedback trend prediction unit, dynamic decoupling control unit, safety clamp control unit, and instruction output unit are all integrated into the PLC controller. The PLC controller adopts the Siemens S7-1500 series with a main frequency of ≥1GHz and a memory of ≥16GB to ensure the high efficiency of algorithm operation and instruction processing.

[0235] The command output unit is connected to the frequency converter of the recovery fan and the frequency converter of the main induced draft fan via the CAN bus. The output signal is a 0~10V analog signal, which is used to control the output frequency of the frequency converter.

[0236] The safety gear control unit is connected to the actuator of the bypass vent valve through a relay output module. The control signal is a switching signal with a response time of ≤100ms.

[0237] The units are connected via an internal bus with a data transmission rate of ≥100Mbps, ensuring the synchronization of the units' collaborative work and avoiding control instability caused by signal delay.

[0238] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0239] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A purification and control method based on the recovery and utilization of air leakage from the furnace bottom, characterized in that, Includes the following steps: The system collects the operating frequency of the recovery fan and the main induced draft fan, the pressure difference between the recovery fan outlet and the furnace negative pressure node, the real-time pressure value of the furnace negative pressure node, and the dust concentration signal of the recovery air duct. A parallel pressure source coupling identification algorithm is adopted. The coupling strength characterization value is obtained based on the operating frequency and pressure difference of the recovery fan. The system impedance characterization value is obtained based on the operating frequency of the main induced draft fan and the real-time pressure value of the furnace negative pressure. The coupling strength characterization value and the system impedance characterization value are correlated and calculated to obtain the coupling coefficient of the parallel pressure source. A positive feedback trend prediction algorithm is used to obtain the positive feedback trend value by weighted fusion of the coupling coefficient of the parallel pressure source and the dust concentration signal of the recovery air duct; A dynamic decoupling control algorithm is adopted to generate the frequency adjustment step size of the recovery fan based on the deviation between the coupling coefficient of the parallel pressure source and the preset target coupling coefficient. The coupling coefficient of the parallel pressure source and the frequency adjustment step size are calculated together to obtain the frequency compensation step size of the main induced draft fan with opposite direction. The operating frequencies of the recovery fan and the main induced draft fan are superimposed with the corresponding adjustment step size and compensation step size respectively to obtain the target frequencies of the two and output synchronously to the corresponding strain gauge. Using a safety clamp prediction algorithm, when the dust concentration signal in the recovery duct is greater than the preset dust concentration threshold and the positive feedback trend value is greater than the preset trend threshold, the bypass vent valve is opened and the maximum operating frequency of the recovery fan is limited.

2. The purification and control method based on the recovery and utilization of air leakage from the furnace bottom according to claim 1, characterized in that, The specific steps for obtaining the coupling strength characterization value based on the operating frequency of the recovery fan and the pressure difference are as follows: The coupling strength estimate is obtained by filtering the operating frequency and pressure difference of the recovery fan. The coupling strength is characterized by normalizing and comparing the estimated value with the preset rated operating frequency and rated pressure difference of the recovery fan.

3. The purification and control method based on the recovery and utilization of air leakage from the furnace bottom as described in claim 1, characterized in that, The specific steps to obtain the system impedance characterization value based on the main induced draft fan operating frequency and the real-time pressure value of the furnace negative pressure are as follows: The system impedance estimate is obtained by filtering the absolute values ​​of the main induced draft fan operating frequency and the real-time negative pressure value of the furnace. The system impedance estimate is normalized and compared with the preset rated operating frequency of the main induced draft fan and the rated negative pressure of the furnace to obtain the system impedance characterization value.

4. The purification and control method based on the recovery and utilization of air leakage from the furnace bottom according to claim 1, characterized in that, The specific steps for obtaining the positive feedback trend value by weighted fusion of the parallel pressure source coupling coefficient and the dust concentration signal of the recovery duct are as follows: The rate of change of dust concentration was obtained by analyzing the rate of change of dust concentration signal in the recovery air duct. The weighting coefficients are dynamically allocated based on the magnitude of the coupling coefficients of the parallel pressure sources, and the positive feedback trend value is obtained by weighting and fusing the coupling coefficients of the parallel pressure sources with the dust concentration change rate.

5. The purification and control method based on the recovery and utilization of air leakage from the furnace bottom according to claim 1, characterized in that, The specific steps for generating the frequency adjustment step size of the recovery fan based on the deviation between the parallel pressure source coupling coefficient and the preset target coupling coefficient are as follows: The coupling deviation value is obtained by analyzing the deviation between the coupling coefficient of the parallel pressure source and the preset target coupling coefficient; The initial frequency adjustment step size is obtained by correlating the coupling deviation value with a preset proportional coefficient. The correction coefficient is obtained by correlating the positive feedback trend value with the preset correction ratio coefficient. The frequency adjustment step size of the recovery fan is obtained by combining the initial frequency adjustment step size and the correction coefficient.

6. The purification and control method based on the recovery and utilization of air leakage from the furnace bottom according to claim 1, characterized in that, The specific steps for calculating the frequency compensation step size of the main induced draft fan in opposite directions by coordinating the coupling coefficient of the parallel pressure source with the frequency adjustment step size are as follows: The compensation base value is obtained by performing a joint analysis of the coupling coefficient of the parallel pressure source and the frequency adjustment step size. The initial compensation step size is obtained by performing a correlation calculation between the compensation base value and the preset basic compensation coefficient. The rate of change of the coupling coefficient of the parallel pressure sources is obtained by performing a rate of change analysis. The rate of change of the coupling coefficient is then correlated with the preset dynamic compensation coefficient to obtain the dynamic compensation factor. The initial compensation step size and the dynamic compensation factor are fused together to obtain the frequency compensation step size of the main induced draft fan. The direction of the frequency compensation step size of the main induced draft fan is opposite to the direction of the frequency adjustment step size, and the response speed of the compensation step size is adjusted synchronously with the rate of change of the coupling coefficient.

7. The purification and control method based on the recovery and utilization of air leakage from the furnace bottom according to claim 1, characterized in that, The specific steps for controlling the opening of the bypass vent valve and limiting the maximum operating frequency of the recovery fan are as follows: The dust concentration signal in the recovery duct is compared with the preset dust concentration threshold to obtain the dust exceeding the standard judgment result; The positive feedback trend value is compared with the preset trend threshold to obtain the result of the positive feedback trend exceeding the standard; When the dust exceedance judgment result and the positive feedback trend exceedance judgment result are met simultaneously, a bypass vent valve opening command is generated, and the vent valve opening degree is adjusted in stages according to the magnitude of the positive feedback trend value. The maximum operating frequency of the recovery fan is locked at a preset percentage of the current operating frequency, and the preset percentage decreases gradually as the positive feedback trend value increases.

8. The purification and control method based on the recovery and utilization of air leakage from the furnace bottom according to claim 1, characterized in that, The specific steps for generating the frequency adjustment step size of the recovery fan based on the deviation between the parallel pressure source coupling coefficient and the preset target coupling coefficient are as follows: The coupling deviation value is obtained by analyzing the deviation between the coupling coefficient of the parallel pressure source and the preset target coupling coefficient; The initial adjustment step size is obtained by correlating the coupling deviation value with the preset adjustment ratio coefficient. The correction coefficient is obtained by correlating the positive feedback trend value with the preset correction ratio coefficient. The initial adjustment step size and correction coefficient are combined and then the real-time fluctuation value of the furnace negative pressure is introduced for secondary correction to obtain the frequency adjustment step size of the recovery fan.

9. The purification and control method based on the recovery and utilization of air leakage from the furnace bottom according to claim 1, characterized in that, The specific steps for calculating the frequency compensation step size of the main induced draft fan in opposite directions by coordinating the coupling coefficient of the parallel pressure source with the frequency adjustment step size are as follows: The compensation base value is obtained by performing a joint analysis of the coupling coefficient of the parallel pressure source and the frequency adjustment step size. The initial compensation step size is obtained by performing a correlation calculation between the compensation base value and the preset basic compensation coefficient. The rate of change of the coupling coefficient of the parallel pressure sources is obtained by performing a rate of change analysis. The rate of change of the coupling coefficient is then correlated with the preset dynamic compensation coefficient to obtain the dynamic compensation factor. The initial compensation step size and the dynamic compensation factor are fused together to obtain the frequency compensation step size of the main induced draft fan. The direction of the frequency compensation step size of the main induced draft fan is opposite to the direction of the frequency adjustment step size, and the response speed of the compensation step size is adjusted synchronously with the rate of change of the coupling coefficient.

10. A purification control system based on the recovery and utilization of furnace bottom air leakage, employing the purification control method based on the recovery and utilization of furnace bottom air leakage as described in any one of claims 1-9, characterized in that, include: The parameter acquisition unit is used to acquire the operating frequency of the recovery fan and the main induced draft fan, the pressure difference between the outlet of the recovery fan and the negative pressure node of the furnace, the real-time pressure value of the negative pressure node of the furnace, and the dust concentration signal of the recovery air duct. The parallel pressure source coupling identification unit is connected to the parameter acquisition unit. It is used to obtain the coupling strength characterization value based on the operating frequency and pressure difference of the recovery fan, and to obtain the system impedance characterization value based on the operating frequency of the main induced draft fan and the real-time pressure value of the furnace negative pressure. The coupling strength characterization value and the system impedance characterization value are correlated and calculated to obtain the parallel pressure source coupling coefficient. The positive feedback trend prediction unit is connected to the parallel pressure source coupling identification unit and is used to weighted fuse the parallel pressure source coupling coefficient with the dust concentration signal of the recovery air duct to obtain the positive feedback trend value. The dynamic decoupling control unit is connected to the positive feedback trend prediction unit. It is used to generate the frequency adjustment step size of the recovery fan based on the deviation between the coupling coefficient of the parallel pressure source and the preset target coupling coefficient. The coupling coefficient of the parallel pressure source and the frequency adjustment step size are calculated together to obtain the frequency compensation step size of the main induced draft fan in opposite directions. The command output unit, connected to the dynamic decoupling control unit, is used to superimpose the operating frequencies of the recovery fan and the main induced draft fan with the corresponding adjustment step size and compensation step size to obtain the target frequencies of the two, and output the target frequencies synchronously to the corresponding strain gauge. The safety clamp control unit, connected to the positive feedback trend prediction unit and the parameter acquisition unit, is used to control the bypass vent valve to open and limit the maximum operating frequency of the recovery fan when the dust concentration signal in the recovery duct is greater than the preset dust concentration threshold and the positive feedback trend value is greater than the preset trend threshold.

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