Negative pressure self-balancing collaborative control method and system of sludge disc drying system

Abstract

This invention proposes a negative pressure self-balancing collaborative control method and system for a sludge disc drying system. The method includes: collecting the negative pressure value of each branch pipe, calculating the negative pressure value deviation of each branch pipe, and if the negative pressure value deviation is greater than a preset deviation value, calculating the change in the opening of the corresponding branch regulating valve and simultaneously calculating the coupling interference of each branch pipe, and adjusting the opening of the branch regulating valve; if the opening of any branch regulating valve is detected to exceed the preset opening range, triggering the coordinated adjustment of the main regulating valve, adjusting the opening of the main regulating valve according to the change in the opening of the main regulating valve, and adjusting the opening of each branch regulating valve according to the feedforward compensation value of the branch regulating valve. This invention solves the technical problem of mutual influence between the main regulating valve and the branch regulating valves in the prior art. By establishing a mathematical model between the negative pressure of the branch pipe, the opening of the branch regulating valve, and the opening of the main regulating valve, and adding decoupling control and feedforward compensation mechanisms, this invention eliminates the coupling interference between loops and stabilizes the negative pressure of the branch pipe at the target value.

Description

Technical Field

[0001] This invention relates to the field of sludge treatment, and in particular to a negative pressure self-balancing coordinated control method and system for a sludge disc drying system. Background Technology

[0002] In the new sludge drying project, the disc drying system is one of the core technologies. This system mainly includes a disc dryer, a waste gas cyclone dust collector, a waste gas condenser, and a waste gas induced draft fan. The process primarily involves feeding municipal wet sludge via a shaftless screw conveyor to the steam disc dryer. The steam disc dryer dries the 80% moisture content sludge to below 40% moisture content. A saturated steam indirect heat transfer process is employed, where saturated steam indirectly exchanges heat with the wet sludge through the metal walls of the hollow hot shaft and hollow blades, transferring heat to the wet sludge inside the sludge dryer. The saturated steam enters the dryer and, together with the moisture evaporated from the material, forms waste gas. This waste gas enters the waste gas cyclone dust collector for dust removal through a waste gas pipeline, and after being cooled by the primary and secondary waste gas condenser heat exchangers, it is introduced into the waste gas exhaust header by the waste gas induced draft fan and sent to the inlet duct of the wet scrubber. The dried sludge is fed into the power plant's raw coal bunker via a dry sludge scraper, and then transported to the coal mill for grinding by a coal feeder to ensure complete combustion of the sludge.

[0003] Modern sludge drying systems are typically equipped with relatively simple control systems. The outlet negative pressure of the disc dryer is controlled within the optimal operating range (usually -150 to -200 Pa) based on the varying quality of the municipal sludge supply. Controlling the airflow of the induced draft fan in the sludge drying system requires coordinating the opening of the main control valve and the control valves of the three branch pipes to maintain stable negative pressure in the branch pipes. The main control valve of the induced draft fan controls the negative pressure of the entire system, while each branch pipe has its own branch control valve to regulate and maintain stable negative pressure. This coordinated control of the main and branch control valves means that when the main control valve is adjusted, the negative pressure in each branch pipe will be affected at its original opening value. Therefore, the opening of the branch control valves needs to be adjusted according to the changes in negative pressure in each branch pipe. Increasing the opening of the main control valve may increase the total airflow, leading to a decrease in total negative pressure. In this case, the branch control valves need to be appropriately closed to maintain stable negative pressure in each branch pipe. Conversely, closing the main control valve may increase the total negative pressure, requiring the branch control valves to be opened wider to maintain negative pressure in each branch pipe.

[0004] In sludge drying systems, the negative pressure of the exhaust gas at the outlet of the disc dryer is a key parameter affecting system operating efficiency, energy consumption, safety, and equipment lifespan. Its optimal negative pressure range needs to be precisely controlled according to process requirements, and its main impacts are as follows: Excessive negative pressure can cause the following problems: 1. Shortened material residence time: High-speed airflow may cause wet sludge particles to be carried out of the dryer prematurely, resulting in incomplete drying and insufficient moisture content. 2. Reduced heat exchange efficiency: Excessive airflow speed reduces the heat contact time between the sludge and the drying trays, lowering thermal energy utilization. 3. Increased induced draft fan load: Maintaining high negative pressure requires the induced draft fan to operate continuously at high speed, significantly increasing power consumption and exacerbating heat loss. 4. Excessive extraction of exhaust gas will remove more heat, requiring the replenishment of more saturated steam to maintain balance, leading to an increase in overall energy consumption. 5. Dust explosion risk: High-speed airflow can easily stir up fine dust after drying; if mixed with air and reaching the explosion limit, it poses a safety hazard. 6. Fan surge: Extreme negative pressure may cause the induced draft fan to enter the surge zone, causing severe vibration and damaging the equipment.

[0005] Excessive negative pressure can cause: 1. Obstructed moisture removal: The dryer cannot effectively remove evaporated moisture, leading to increased humidity and a decreased drying rate. 2. Condensation risk: Moisture condenses in pipes or cold areas of equipment, potentially causing sludge adhesion or equipment corrosion. 3. Increased indirect energy consumption: The drying time is prolonged, and the energy consumption per unit processing capacity may actually increase.

[0006] The existing technical problems include: if the opening of the main control valve needs to be adjusted due to operating conditions, the total negative pressure of the entire system will change, which will affect the negative pressure of each branch pipe. At this time, it may be necessary to adjust the opening of the branch control valve repeatedly to compensate for the impact of the change in the main control valve in order to maintain the stability of the negative pressure of each branch pipe. Manual control is frequent and the degree of automation control is weak. Monitoring personnel need to pay close attention to the operating conditions of the exhaust gas negative pressure of the disc dryer at all times. According to the different qualities of the municipal sludge, timely adjustments need to be made to the inlet control valve of the induced draft fan and the upstream branch control valve. This increases the monitoring burden on the operators and requires them to be vigilant at all times. It is difficult to stably control the reasonable negative pressure value of the exhaust gas at the outlet of each disc dryer, and it is difficult to balance the stability of the negative pressure of each branch. Coordination between upper and lower layers is required, and mutual interference is significant. Summary of the Invention

[0007] Based on the above problems, this invention proposes a negative pressure self-balancing coordinated control method and system for a sludge disc drying system. This invention solves the technical problem in the prior art where the main control valve and each branch control valve influence each other and require repeated manual adjustments; it also solves the technical problem of requiring operators to monitor the discs and the difficulty in stably controlling the reasonable negative pressure value of the exhaust gas at the outlet of each disc dryer.

[0008] This invention proposes a negative pressure self-balancing coordinated control method for a sludge disc drying system, comprising: Collect the negative pressure value of each branch pipe, calculate the negative pressure value deviation of each branch pipe, and if the negative pressure value deviation is greater than the preset deviation value, calculate the change in the opening of the branch regulating valve corresponding to the branch pipe, and at the same time calculate the coupling interference of each branch pipe. Adjust the opening of the branch regulating valve corresponding to the branch pipe according to the change in the opening of the branch regulating valve and the coupling interference. The coupling interference is the amount of coupling interference caused by the change in the opening of the main regulating valve and other branch regulating valves on the calculated negative pressure of the branch pipe. If the opening of any branch gate is detected to exceed the preset opening range, the coordinated adjustment of the main gate is triggered. The coordinated adjustment of the main gate includes: calculating the change in the opening of the main gate according to the main gate opening formula, calculating the feedforward compensation value of the branch gate, adjusting the opening of the main gate according to the change in the opening of the main gate, and adjusting the opening of each branch gate according to the feedforward compensation value of the branch gate.

[0009] In addition, the negative pressure value of each branch pipe is collected, and the deviation of the negative pressure value of each branch pipe is calculated, including: The negative pressure deviation is obtained by subtracting the negative pressure value from the preset negative pressure value.

[0010] In addition, if the negative pressure deviation is greater than the preset deviation value, the change in the opening of the branch regulating valve corresponding to the branch pipe is calculated, including: The change in the opening of the control gate is calculated using an incremental formula. , , in, , and All are PID proportional coefficients for the control gate. Let be the negative pressure deviation at time i.

[0011] In addition, the coupling interference of each branch pipe is calculated using the following formula. : , in, Let ΔX0 be the influence coefficient of the main control valve on branch pipe i, and ΔX0 be the change in the opening of the main control valve between the current time and the previous time. Let ΔXj be the interference coefficient of branch pipe j on branch pipe i, and let ΔXj be the change in the opening of branch valve j between the current time and the previous time.

[0012] In addition, the amount of coupling interference in each branch pipe It is determined by the branch negative pressure coupling model at time i. The value at time i-1 The difference is obtained by subtracting the values; The branch negative pressure coupling model is as follows: ; in, This is the negative pressure value of the branch pipe. Let X0 be the base negative pressure constant, Xj be the opening degree of the main regulating valve at the current moment, and Xj be the opening degree of other branch regulating valves at the current moment. This represents the number of random perturbations.

[0013] In addition, the calculation of the change in the total control valve opening ΔX0 according to the total control valve opening formula includes: , in, This is the overall damping ratio coefficient. The integral coefficient of the total tuning. This is the average of the negative pressure deviations of multiple control valves.

[0014] In addition, the calculation of the feedforward compensation value of the control gate includes: Calculate the feedforward compensation coefficient , , The PID proportional coefficient of the control gate. The influence coefficient of the main control valve on branch pipe i; Feedforward compensation value ΔXif= ΔX0 represents the total change in the gate opening between the current time and the previous time.

[0015] In addition, after collecting the negative pressure value of each branch pipe and before calculating the negative pressure value deviation of each branch pipe, negative pressure extreme value tracking is performed, including: Within each control cycle of the PID controller, identify the branch pipe with the largest deviation from the target negative pressure value and assign its corresponding branch regulating valve PID proportional coefficient. Temporary reinforcement is applied until the negative pressure in the branch pipe converges to the target value, at which point it is restored. Return to the original value, and then perform the same treatment on the other branches in sequence.

[0016] In addition, if the opening of any branch damper is detected to exceed the preset opening range, it is determined whether the excess is the maximum boundary value or the minimum boundary value. If the excess is the maximum boundary value, the opening of the branch damper is adjusted to the maximum boundary value; if the excess is the minimum boundary value, the opening of the branch damper is adjusted to the minimum boundary value.

[0017] This invention proposes a system employing a negative pressure self-balancing collaborative control method for a sludge disc drying system as described in any of the preceding claims. The system startup sequence includes: After startup, first set the main control valve and branch control valve to the preset opening, collect multiple sets of working condition data, input them into the branch negative pressure coupling model, calculate the parameters of the branch negative pressure coupling model, and set the target negative pressure value. Based on the target negative pressure value, adjust the branch regulating valve to approach the target negative pressure value, and adjust the main regulating valve to stabilize it near the main regulating valve threshold. If no faults are found in any of the components within the system, the system enters the negative pressure self-balancing collaborative control mode. The negative pressure self-balancing collaborative control mode adopts the negative pressure self-balancing collaborative control method of the sludge disc drying system for control.

[0018] This invention solves the technical problems in existing technologies where the main control valve and branch control valves influence each other and require repeated manual adjustments; it also solves the technical problems of requiring operators to monitor the system and the difficulty in stably controlling the reasonable negative pressure value of the exhaust gas at the outlet of each disc dryer. The negative pressure self-balancing collaborative control method for the sludge disc drying system provided by this invention establishes a mathematical model between the branch pipe negative pressure, the branch control valve opening, and the main control valve opening, and incorporates decoupling control and feedforward compensation mechanisms to eliminate coupling interference between loops, thus stabilizing the negative pressure of the exhaust gas branch pipes at the outlet of the disc dryer at the target value. Attached Figure Description

[0019] Figure 1 A flowchart of a negative pressure self-balancing collaborative control method for a sludge disc drying system provided in an embodiment of the present invention; Figure 2 A schematic diagram of a sludge disc drying system; Figure 3 This is a flowchart illustrating the startup sequence of a negative pressure self-balancing collaborative control method for a sludge disc drying system, provided as an embodiment of the present invention. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. This description is intended only to illustrate specific embodiments of the invention and does not constitute any limitation on the invention. The scope of protection of the invention is defined by the claims.

[0021] Reference Figure 1 This invention proposes a negative pressure self-balancing coordinated control method for a sludge disc drying system, comprising: Step S001: Collect the negative pressure value of each branch pipe and calculate the negative pressure value deviation of each branch pipe; Step S002: Determine whether the negative pressure value deviation is greater than the preset deviation value. If it is greater, proceed to step S003; if it is not greater, proceed to step S004. Step S003: Calculate the change in the opening of the branch regulating valve corresponding to the branch pipe, and at the same time calculate the coupling interference of each branch pipe. Adjust the opening of the branch regulating valve corresponding to the branch pipe according to the change in the opening of the branch regulating valve and the coupling interference. The coupling interference is the amount of coupling interference caused by the change in the opening of the main regulating valve and other branch regulating valves on the negative pressure of the calculated branch pipe. Branch regulating valve is short for branch regulating valve. Step S004; Maintain the opening degree unchanged; Step S005: Monitor whether the opening of any regulating valve exceeds the preset opening range. If yes, proceed to step S006; otherwise, proceed to step S007. Step S006: Trigger the coordinated adjustment of the main control gate. The coordinated adjustment of the main control gate includes: calculating the change in the opening of the main control gate according to the formula of the main control gate opening, calculating the feedforward compensation value of the branch control gate, adjusting the opening of the main control gate according to the change in the opening of the main control gate, and adjusting the opening of each branch control gate according to the feedforward compensation value of the branch control gate.

[0022] Step S007: Maintain the opening degree unchanged.

[0023] Because the proper control of the exhaust negative pressure at the outlet of the disc dryer in a sludge disc drying system directly affects drying efficiency, energy consumption, and system safety requirements. Adjustments to the main control valve affect the negative pressure of each branch pipe. Therefore, this invention introduces a feedforward compensation mechanism (feedback compensation) to establish a mathematical decoupling relationship between inputs and outputs. This ensures that each input primarily affects its corresponding expected output, while eliminating the cross-influence of other inputs on that output. This allows the adjustment of the main control valve to be compensated by the branch control valves, maintaining stable negative pressure in the branch pipes. By combining dynamic adjustments, multi-parameter coordination, and the introduction of decoupling control based on operating conditions, the system achieves economical, safe, and stable operation while ensuring effective sludge drying.

[0024] Meanwhile, the negative pressure at the outlet of the disc dryer is a multivariate control problem. The main control valve and the control valves of each branch are controlled variables, while the negative pressure of each branch pipe is the controlled variable. This invention can adjust the opening of the main control valve and the branch control valves in real time based on the feedback of the negative pressure of each branch pipe. This invention achieves energy optimization by adjusting the opening of the intermediate control valve and the control valves of each branch in real time according to the negative pressure demand, avoiding energy waste caused by over-powered valves.

[0025] In step S001, the negative pressure value of each branch pipe is collected, and the negative pressure value deviation of each branch pipe is calculated; The DCS control system collects the negative pressure value of each branch pipe and calculates the negative pressure deviation of each branch pipe. Optionally, the DCS control system embeds a PID control algorithm. PID (Proportional Integral Derivative) is used in automatic control algorithms (closed-loop control of temperature, speed, position, etc.). DCS is an abbreviation for Distributed Control System.

[0026] Optionally, when calculating the negative pressure deviation for each branch pipe, the negative pressure value is subtracted from the preset negative pressure value to obtain the negative pressure deviation. The preset negative pressure value is, for example, -180 Pa.

[0027] Step S002: Determine whether the negative pressure value deviation is greater than the preset deviation value. If it is greater, proceed to step S003; if it is not greater, proceed to step S004. When the negative pressure deviation is greater than the preset deviation value, it means that simply adjusting the branch valve corresponding to the branch pipe is not enough. It is necessary to adjust the main valve to bring the negative pressure deviation of the branch pipe back to a condition where it is less than the preset deviation value.

[0028] The preset deviation value is, for example, 5 Pa. In engineering, the preset deviation value is called the "dead zone". The purpose of setting the dead zone is to prevent the control valve from being adjusted frequently and to filter out small fluctuations.

[0029] Optionally, when determining whether the negative pressure deviation is greater than a preset deviation value, if the deviation is greater than and continues to exceed a preset time period (e.g., 5 minutes), then proceed to step S003. By setting a preset time period, frequent adjustments to the control valve caused by short-term fluctuations are avoided.

[0030] In step S003, the change in the opening of the branch regulating valve corresponding to the branch pipe is calculated, and the coupling interference of each branch pipe is also calculated. The opening of the branch regulating valve corresponding to the branch pipe is adjusted according to the change in the opening of the branch regulating valve and the coupling interference. The coupling interference is the amount of coupling interference caused by the change in the opening of the main regulating valve and other branch regulating valves on the negative pressure of the calculated branch pipe. Since changes in the opening of the main control valve affect the negative pressure values ​​of all branch pipes, and changes in the opening of other branch pipes also slightly affect the negative pressure values ​​of the branch pipes being calculated, a "feedback decoupling algorithm" is used to counteract the coupling effect. This means that while calculating the change in the opening of the corresponding branch control valve, the coupling interference of each branch pipe is also calculated. The coupling interference caused by each change in the opening of the main control valve is compensated for in each branch pipe in the next control cycle.

[0031] Optionally, the calculation of the change in the opening of the branch control valve corresponding to the branch pipe includes: The change in the opening of the control gate is calculated using an incremental formula. , , in, , and All are PID proportional coefficients for the control gate. Let be the negative pressure deviation at time i.

[0032] The following formula is derived: , in, The calculated opening of the control valve. The difference between the opening of the control valve before calculation is the valve opening. , - for , The preset deviation value, This is the negative pressure value of the branch pipe.

[0033] Optionally, the coupling interference of each branch pipe can be calculated using the following formula. : , in, The influence coefficient of the main control valve on branch pipe i. This represents the total change in the gate opening between the current moment and the previous moment. Let ΔXj be the interference coefficient of branch pipe j on branch pipe i, and let ΔXj be the change in the opening of branch valve j between the current time and the previous time.

[0034] Optionally, the coupling interference amount of each branch pipe It is determined by the branch negative pressure coupling model at time i. The value at time i-1 The difference is obtained by subtracting the values; The branch negative pressure coupling model is as follows: ; in, This is the negative pressure value of the branch pipe. Let X0 be the base negative pressure constant, Xj be the opening degree of the main regulating valve at the current moment, and Xj be the opening degree of other branch regulating valves at the current moment. This represents the number of random perturbations.

[0035] In step S005, it is monitored whether the opening degree of any regulating valve exceeds the preset opening degree range.

[0036] The preset opening range is, for example, [30%, 70%], and the automatic limit is 30% (lower limit) or 70% (upper limit).

[0037] In step S006, the coordinated adjustment of the main control gate is triggered. The coordinated adjustment of the main control gate includes: calculating the change in the opening of the main control gate according to the formula of the main control gate opening, calculating the feedforward compensation value of the branch control gate, adjusting the opening of the main control gate according to the change in the opening of the main control gate, and adjusting the opening of each branch control gate according to the feedforward compensation value of the branch control gate.

[0038] Optionally, an example illustrates the process by which the DCS monitors whether the opening of any branch control valve exceeds the preset opening range and determines whether to adjust it: The opening values ​​X1, X2, and X3 of the branch control valve are acquired in real time (assuming the entire system includes three branch control valves, with openings denoted as X1, X2, and X3 respectively). The DCS executes the following logic: Maintain opening condition: When X1≤70% and X2≤70% and X3≤70% (the case where all branch gates have an upward adjustment margin), the main gate (denoted as V0) maintains its current opening (the opening of V0 and X0 remain unchanged). Increase opening action: When X1>71% or X2>71% or X3>71% (when there is no upward adjustment margin in any branch), start the PID increase operation of the main control valve. At this time, ΔX0 is positive, and increase the opening of V0 (that is, increase the total exhaust volume and reduce the branch adjustment pressure). Maintain opening condition: When X1≥30% and X2≥30% and X3≥30% (when all branches have downward adjustment margin), V0 maintains the current opening; Reduce opening action: When X1<30% or X2<30% or X3<30% (when there is no downward adjustment margin in any branch), the PID reduction operation of the main control valve is started. At this time, ΔX0 is negative, and the opening of V0 is reduced (that is, the total exhaust volume is reduced to match the branch adjustment requirements).

[0039] Optionally, calculating the change in the total control valve opening ΔX0 according to the total control valve opening formula includes: , in, This is the overall damping ratio coefficient. The integral coefficient of the total tuning. This is the average of the negative pressure deviations of multiple control valves.

[0040] ΔX0 is derived using the following formula: , X0 is the total valve opening after calculation, and X1 is the total valve opening before calculation. The difference between the two is ΔX0. - for , The preset deviation value, This is the negative pressure value of the branch pipe. In engineering, this is also known as a "dead zone".

[0041] The reason for simultaneously calculating the feedforward compensation value of the branch gate is to avoid V0 action causing... Significant fluctuations can be compensated for by adjusting each branch gate before the main gate operates. Optionally, an example can be used to illustrate the feedforward compensation process: Set feedforward compensation coefficient Based on the overall damping influence coefficient (The influence coefficient of the main control valve on branch pipe i) and the PID proportional coefficient of the branch control valve make The calculation formula is: , The PID proportional coefficient of the control gate. The influence coefficient of the main control valve on branch pipe i; Feedforward compensation value ΔXif= ΔX0 represents the total change in the gate opening between the current time and the previous time.

[0042] Example: =4.0, =-2.5Pa / %, then =-4.0×(-2.5)=10 (% / Pa), which means that for every 1% change in V0, V1 (the regulating valve) needs to act 10% / Pa in advance to offset the negative pressure change; Feedforward compensation execution: When the DCS controller output ΔX0≠0, synchronously calculate the branch control valve feedforward increment ΔXif: Example: ΔX0 = 5% (V0 increases by 5%), then ΔXif = 10 × 5% = 50% (because...) There is a maximum limit of 70%, if If the original value is greater than 20%, then the actual compensation will be... =70%) Compensation logic: Feedforward compensation value ΔXif and change in valve opening. The sum is added as the total increase, that is = +ΔXif+ΔXi, where... The calculated opening of the control valve. Before calculation, the opening of the lateral control gate is determined. The V0 action and the feedforward compensation of the lateral control gate are executed synchronously to counteract the coupling disturbance.

[0043] This invention solves the technical problems in existing technologies where the main control valve and branch control valves influence each other and require repeated manual adjustments; it also solves the technical problems of requiring operators to monitor the system and the difficulty in stably controlling the reasonable negative pressure value of the exhaust gas at the outlet of each disc dryer. The negative pressure self-balancing collaborative control method for the sludge disc drying system provided by this invention establishes a mathematical model between the branch pipe negative pressure, the branch control valve opening, and the main control valve opening, and incorporates decoupling control and feedforward compensation mechanisms to eliminate coupling interference between loops, thus stabilizing the negative pressure of the exhaust gas branch pipes at the outlet of the disc dryer at the target value.

[0044] In one embodiment, the negative pressure value of each branch pipe is collected, and the deviation of the negative pressure value of each branch pipe is calculated, including: The negative pressure deviation is obtained by subtracting the negative pressure value from the preset negative pressure value.

[0045] The calculation of the negative pressure deviation provides a basis for the next step of judgment.

[0046] For example, the negative pressure value of the branch pipe The preset negative pressure value is -150Pa. The negative pressure value is -180Pa. Optionally, in order to stabilize the negative pressure value of the branch pipe within -180Pa±20Pa, the negative pressure value deviation is set to 5Pa. The negative pressure value deviation is also called the "dead zone" in engineering. By setting the "dead zone", small fluctuations are filtered out.

[0047] In one embodiment, if the negative pressure deviation is greater than a preset deviation value, the calculation of the change in the opening of the branch regulating valve corresponding to the branch pipe includes: The change in the opening of the control gate is calculated using an incremental formula. , , in, , and All are PID proportional coefficients for the control gate. Let be the negative pressure deviation at time i.

[0048] This embodiment first requires establishing a mathematical model, which is based on the linear correlation between valve opening and negative pressure. The model is calibrated using three sets of on-site operating data (no load, 50% load, and full load). The model accuracy error is ≤ ±8%, as shown in the following formula: 1. Branch negative pressure coupling model (describes the relationship between the main control valve, branch control valves, and branch negative pressure): ; in, This is the negative pressure value of the branch pipe. Let X0 be the base negative pressure constant, Xj be the opening degree of the main regulating valve at the current moment, and Xj be the opening degree of other branch regulating valves at the current moment. For random perturbation numbers, The influence coefficient of the main control valve on branch pipe i. Let be the interference coefficient of branch j on branch i.

[0049] The basic negative pressure constant (Pa) of branch pipe i is determined by no-load conditions (example: a1=a2=a3=-100Pa). The influence coefficient (Pa / %) of the main control valve on branch pipe i represents the change in negative pressure of branch i for every 1% change in the opening of the main control valve (Example: = = =-2.5Pa / %, the negative sign indicates that as X0 increases, reduce); The influence coefficient (Pa / %) of valve j on the negative pressure of branch i represents the change in negative pressure of branch i for every 1% change in the opening of valve j (Example: = = = = = =-0.3Pa / %, coupling interference is relatively weak); : Random disturbance number, i.e. system disturbance error (≤±5Pa, compensated by DCS in real time).

[0050] By collecting three sets of operating condition data (X0 / X1 / X2 / X3, P1 / P2 / P3), substituting them into the branch negative pressure coupling model, and calibrating using the least squares method, the model was calibrated. , , (See the mathematical model for example results).

[0051] 2. Optimal valve opening calculation model (core solution formula): Objective function: , Constraints: 30%≤X1 / X2 / X3≤70%, 0%≤X0≤100%. The optimal opening is solved iteratively using the following formula: , , , and These are all PID proportional coefficients for the control gate, for example, values ​​of 4.0, 0.05, and 0.8 respectively. This is the overall damping ratio coefficient. This is the integral coefficient for the overall tuning, and can take values ​​such as 2.5 and 0.03. Based on this, the change in the opening of the control gate is calculated using an incremental formula. , , By calculating the change in the opening of the control door The branch adjustment gate of the control branch is used to adjust the opening degree.

[0052] In one embodiment, the coupling interference of each branch pipe is calculated using the following formula. : , in, Let ΔX0 be the influence coefficient of the main control valve on branch pipe i, and ΔX0 be the change in the opening of the main control valve between the current time and the previous time. Let ΔXj be the interference coefficient of branch pipe j on branch pipe i, and let ΔXj be the change in the opening of branch valve j between the current time and the previous time.

[0053] Coupling interference Incorporate into the calculation to obtain the corrected deviation. , , Then reconstruct the change in the opening of the control valve. , Example: If V0 increases by 5% (ΔX0 = 5%), then = ×5+( × + × = -2.5 × 5 + 0 = -12.5 Pa, = - =-180-(-160)=-20Pa, after correction =-20 - (-12.5)=-7.5Pa, PID output If the value is negative, the opening of V1 is reduced to offset the decrease in negative pressure caused by the increase of V0.

[0054] Through coupling interference amount The main valve adjustment can compensate for the negative pressure of the branch pipes, and it can also compensate for the negative pressure of other branch pipes caused by the opening adjustment of each branch valve, thereby reducing the coupling degree and ensuring that each adjustment only affects itself.

[0055] In one embodiment, the coupling interference amount of each branch pipe It is determined by the branch negative pressure coupling model at time i. The value at time i-1 The difference is obtained by subtracting the values; The branch negative pressure coupling model is as follows: ; in, This is the negative pressure value of the branch pipe. Let X0 be the base negative pressure constant, Xj be the opening degree of the main regulating valve at the current moment, and Xj be the opening degree of other branch regulating valves at the current moment. This represents the number of random perturbations.

[0056] A mathematical model is established to link the main control valve opening, branch control valve opening, and branch pipe negative pressure. (When it is not possible to conduct a complete calibration of the three sets of working conditions on site, the initial coefficients can be quickly obtained using an expert knowledge base.)

[0057] In one embodiment, calculating the change in the total control valve opening ΔX0 according to the total control valve opening formula includes: , in, This is the overall damping ratio coefficient. The integral coefficient of the total tuning. This is the average of the negative pressure deviations of multiple control valves.

[0058] , By establishing a calculation model for the main control valve opening formula, a correlation is established between the main control valve opening, the branch control valve opening, and the branch pipe negative pressure.

[0059] In one embodiment, calculating the feedforward compensation value of the control gate includes: Calculate the feedforward compensation coefficient , , The PID proportional coefficient of the control gate. The influence coefficient of the main control valve on branch pipe i; Feedforward compensation value ΔXif= ΔX0 represents the total change in the gate opening between the current time and the previous time.

[0060] To avoid negative pressure in the branch pipe caused by the operation of the main control valve V0. Significant fluctuations require compensation to be provided to each sub-gate before the main gate operates.

[0061] In one embodiment, after acquiring the negative pressure value of each branch pipe and before calculating the negative pressure value deviation of each branch pipe, negative pressure extreme value tracking is performed, including: Within each control cycle of the PID controller, identify the branch pipe with the largest deviation from the target negative pressure value and assign its corresponding branch regulating valve PID proportional coefficient. Temporary reinforcement is applied until the negative pressure in the branch pipe converges to the target value, at which point it is restored. Return to the original value, and then perform the same treatment on the other branches in sequence.

[0062] An example illustrating the negative pressure extreme value tracking process: 1. The DCS collects the negative pressure extreme values ​​of the three branches in real time: minimum value Pmin=min(P1,P2,P3) and maximum value Pmax=max(P1,P2,P3). 2. Prioritize adjusting extreme value branches: For the branch corresponding to Pmin, the PID proportional coefficient is... Temporarily boosted by 1.2 times, quickly pulling back to the target value; Pmin- After | ≤ 10Pa, the same weighted adjustment is performed on the branch corresponding to Pmax; 3. Iterative convergence: Repeat extreme value tracking until all negative pressure deviation values ​​are reached. - ≤20Pa, recovery Initial value.

[0063] By prioritizing the allocation of adjustment resources to the "worst" branch, the system avoids the situation where, when all branches adjust synchronously with the same force, the extreme branch's slow adjustment speed can drag down the overall system balance in the long run. Compared to conventional PID control (where all branches adjust synchronously with the same force), this approach offers a more efficient and effective control. (Using a consistent value approach), extreme value tracking can shorten the settling time of the system from a non-equilibrium state to full convergence by about 30% to 50%.

[0064] In one embodiment, if the opening of any branch gate is detected to exceed the preset opening range, it is determined whether the exceeding value is the maximum boundary value or the minimum boundary value. If the exceeding value is the maximum boundary value, the opening of the branch gate is adjusted to the maximum boundary value; if the exceeding value is the minimum boundary value, the opening of the branch gate is adjusted to the minimum boundary value.

[0065] The preset opening range is, for example, [30%, 70%], which is the branch valve constraint range [30%, 70%]. When the branch valve exceeds this range, it can no longer improve the negative pressure deviation through its own adjustment. Therefore, the system will promptly trigger the main valve to coordinate with the main valve to avoid branch valve adjustment failure.

[0066] Reference Figure 3 This invention proposes a system employing a negative pressure self-balancing collaborative control method for a sludge disc drying system as described in any of the preceding claims. The system startup sequence includes: Step S101: After startup, first set the main control gate and branch control gate to the preset opening, collect multiple sets of working condition data, input them into the branch negative pressure coupling model, calculate the parameters of the branch negative pressure coupling model, and set the target negative pressure value. Step S102: Based on the target negative pressure value, adjust the branch valve to approach the target negative pressure value, and adjust the main valve to stabilize near the main valve threshold. Step S103: If no faults are found in any of the components in the system, the system enters the negative pressure self-balancing collaborative control mode. The negative pressure self-balancing collaborative control mode adopts the negative pressure self-balancing collaborative control method of the sludge disc drying system for control.

[0067] The system hardware includes: 1. Controlled objects: 1 exhaust gas induced draft fan inlet main control valve (denoted as V0), 3 primary / secondary exhaust gas condenser outlet branch control valves (denoted as V1, V2, V3, corresponding to 3 disc dryers); 2. Controlled parameters: negative pressure of exhaust gas at the outlet of the three disc dryers (denoted as P1, P2, P3, target value Ps=-180Pa), and total negative pressure of the main pipe (denoted as P0, auxiliary reference); 3. Hardware configuration: 3 negative pressure sensors (accuracy ±5Pa, installed at the branch pipe outlet), 1 main negative pressure sensor (installed at the main pipe), 4 electric actuators (opening control accuracy ±1%), 1 set of DCS control system; 4. Description of each functional layer: Sensing layer: Negative pressure sensors collect P1 / P2 / P3 / P0 signals; Control layer: The DCS control system incorporates PID algorithm, decoupling module, and feedforward compensation module; Execution layer: Electric actuators drive V0 / V1 / V2 / V3 to move; Feedback layer: Real-time acquisition of valve opening (denoted as X0 / X1 / X2 / X3, range 0~100%) and negative pressure signal to form a closed loop.

[0068] System startup procedure 1: Preparations before powering on 1) Start the exhaust gas induced draft fan, keep the exhaust gas induced draft fan inlet regulating valve V0 open at 50%, and the #1, #2, #3 primary and secondary exhaust gas condenser outlet regulating valves open at 50%, and run stably for 30 minutes; 2) Collect three sets of operating condition data (X0 / X1 / X2 / X3, P1 / P2 / P3), substitute them into the branch negative pressure coupling model, and calibrate using the least squares method. , , , The branch negative pressure coupling model is as follows:

[0069] Different systems require different calibration methods using the least squares method. , , It needs to be recalibrated.

[0070] 3) Set core parameters: target negative pressure Ps=-180Pa, PID dead zone ±5Pa (to avoid frequent valve operation), branch valve constraint range [30%, 70%], and delay judgment time 5min.

[0071] 2: Manual coarse adjustment for stability 1) Based on the sludge quality (e.g., moisture content 80%), refer to expert experience to set the initial opening of the inlet regulating valve of the exhaust gas fan (example: X0=45%), and observe that the main pipe P0 is stable at -220Pa±10Pa; 2) Manually adjust the outlet regulating valves of the primary and secondary exhaust gas condensers one by one until the exhaust gas pressure at the outlet of the primary and secondary exhaust gas condensers is stable at -180Pa±20Pa. Record the valve opening at this time (Example: X1=48%, X2=52%, X3=46%). 3) Once it is confirmed that all sensors and actuators are fault-free (signal drift ≤ ±3Pa, actuator action response time ≤ 2s), the negative pressure self-balancing collaborative control mode is entered. The negative pressure self-balancing collaborative control mode adopts the negative pressure self-balancing collaborative control method of the sludge disc drying system for control.

[0072] 3: System stability criteria and shutdown protection 1. Stability criterion: Within 10 minutes, P1 / P2 / P3 are all within -180Pa±20Pa, and X0 / X1 / X2 / X3 do not have frequent movements (≤3 movements every 5 minutes). 2. Shutdown Protection: The DCS will issue an alarm and switch to manual mode when the following conditions occur: Negative pressure sensor signal loss or drift >±20Pa within 3 seconds; The deviation between the valve opening and the command is >5% (actuator jamming); Exceeding -100Pa to -250Pa (limit range); X0 reaches 0% or 100% (no adjustment margin).

[0073] Definitions: Decoupling PID control: This is a method that uses a PID controller to perform decoupling operations. It is a method for multivariable control systems, and its core purpose is to reduce or eliminate the mutual coupling between control loops in the system. In a multivariable control system, each controlled parameter may be affected by multiple control parameters, and each control parameter may also affect multiple controlled parameters. Coupling refers to the phenomenon in a closed-loop system where, when a setpoint changes, in addition to the corresponding output variable response, other output variables also produce responses; the degree of this internal interaction reflects the degree of coupling.

[0074] This invention solves the technical problems in existing technologies where the main control valve and branch control valves influence each other and require repeated manual adjustments; it also solves the technical problems of requiring operators to monitor the system and the difficulty in stably controlling the reasonable negative pressure value of the exhaust gas at the outlet of each disc dryer. The negative pressure self-balancing collaborative control method for the sludge disc drying system provided by this invention establishes a mathematical model between the branch pipe negative pressure, the branch control valve opening, and the main control valve opening, and incorporates decoupling control and feedforward compensation mechanisms to eliminate coupling interference between loops, thus stabilizing the negative pressure of the exhaust gas branch pipes at the outlet of the disc dryer at the target value.

[0075] As needed, the above technical solutions can be combined to achieve the best technical effect.

[0076] The above description is merely the principle and preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several other modifications can be made based on the principle of the present invention, and these modifications should also be considered within the scope of protection of the present invention.

Claims

1. A negative pressure self-balancing coordinated control method for a sludge disc drying system, comprising: Collect the negative pressure value of each branch pipe, calculate the negative pressure value deviation of each branch pipe, and if the negative pressure value deviation is greater than the preset deviation value, calculate the change in the opening of the branch regulating valve corresponding to the branch pipe, and at the same time calculate the coupling interference of each branch pipe. Adjust the opening of the branch regulating valve corresponding to the branch pipe according to the change in the opening of the branch regulating valve and the coupling interference. The coupling interference is the amount of coupling interference caused by the change in the opening of the main regulating valve and other branch regulating valves on the calculated negative pressure of the branch pipe. If the opening of any branch gate is detected to exceed the preset opening range, the coordinated adjustment of the main gate is triggered. The coordinated adjustment of the main gate includes: calculating the change in the opening of the main gate according to the main gate opening formula, calculating the feedforward compensation value of the branch gate, adjusting the opening of the main gate according to the change in the opening of the main gate, and adjusting the opening of each branch gate according to the feedforward compensation value of the branch gate.

2. The negative pressure self-balancing coordinated control method for the sludge disc drying system according to claim 1, characterized in that, Collect the negative pressure value of each branch pipe and calculate the deviation of the negative pressure value of each branch pipe, including: The negative pressure deviation is obtained by subtracting the negative pressure value from the preset negative pressure value.

3. The negative pressure self-balancing coordinated control method for the sludge disc drying system according to claim 1, characterized in that, If the negative pressure deviation is greater than the preset deviation value, the change in the opening of the branch regulating valve corresponding to the branch pipe is calculated, including: The change in the opening of the control gate is calculated using an incremental formula. , , in, , and All are PID proportional coefficients for the control gate. Let be the negative pressure deviation at time i.

4. The negative pressure self-balancing coordinated control method for the sludge disc drying system according to claim 1, characterized in that, The coupling interference of each branch pipe is calculated using the following formula. : ， in, Let ΔX0 be the influence coefficient of the main control valve on branch pipe i, and ΔX0 be the change in the opening of the main control valve between the current time and the previous time. Let ΔXj be the interference coefficient of branch pipe j on branch pipe i, and let ΔXj be the change in the opening of branch valve j between the current time and the previous time.

5. The negative pressure self-balancing coordinated control method for the sludge disc drying system according to claim 4, characterized in that, Coupling interference in each branch It is determined by the branch negative pressure coupling model at time i. The value at time i-1 The difference is obtained by subtracting the values; The branch negative pressure coupling model is as follows: ； in, This is the negative pressure value of the branch pipe. Let X0 be the base negative pressure constant, Xj be the opening degree of the main regulating valve at the current moment, and Xj be the opening degree of other branch regulating valves at the current moment. This represents the number of random perturbations.

6. The negative pressure self-balancing coordinated control method for the sludge disc drying system according to claim 1, characterized in that, The calculation of the change in the total control valve opening ΔX0 according to the formula includes: ， in, This is the overall damping ratio coefficient. The integral coefficient of the total tuning. This is the average of the negative pressure deviations of multiple control valves.

7. The negative pressure self-balancing coordinated control method for the sludge disc drying system according to claim 1, characterized in that, The calculation of the feedforward compensation value of the control gate includes: Calculate the feedforward compensation coefficient , , The PID proportional coefficient of the control gate. The influence coefficient of the main control valve on branch pipe i; Feedforward compensation value ΔXif= ΔX0 represents the total change in the gate opening between the current time and the previous time.

8. The negative pressure self-balancing coordinated control method for the sludge disc drying system according to claim 7, characterized in that, After collecting the negative pressure value of each branch pipe and before calculating the negative pressure value deviation of each branch pipe, negative pressure extreme value tracking is performed, including: Within each control cycle of the PID controller, identify the branch pipe with the largest deviation from the target negative pressure value and assign its corresponding branch regulating valve PID proportional coefficient. Temporary reinforcement is applied until the negative pressure in the branch pipe converges to the target value, at which point it is restored. Return to the original value, and then perform the same treatment on the other branches in sequence.

9. The negative pressure self-balancing coordinated control method for the sludge disc drying system according to claim 1, characterized in that, If the opening of any branch damper is detected to exceed the preset opening range, it is determined whether the excess is the maximum boundary value or the minimum boundary value. If the excess is the maximum boundary value, the opening of the branch damper is adjusted to the maximum boundary value; if the excess is the minimum boundary value, the opening of the branch damper is adjusted to the minimum boundary value.

10. A system employing the negative pressure self-balancing coordinated control method for the sludge disc drying system as described in any one of claims 1-9, characterized in that, The system startup sequence includes: After startup, first set the main control valve and branch control valve to the preset opening, collect multiple sets of working condition data, input them into the branch negative pressure coupling model, calculate the parameters of the branch negative pressure coupling model, and set the target negative pressure value. Based on the target negative pressure value, adjust the branch regulating valve to approach the target negative pressure value, and adjust the main regulating valve to stabilize it near the main regulating valve threshold. If no faults are found in any of the components within the system, the system enters the negative pressure self-balancing collaborative control mode. The negative pressure self-balancing collaborative control mode adopts the negative pressure self-balancing collaborative control method of the sludge disc drying system for control.

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