A circulating pump valve linkage control method, system, product and medium

Abstract

A method, system, product, and medium for the coordinated control of a circulating pump and its valves are disclosed, relating to the field of electronic digital data processing. The method includes: acquiring the flow-head characteristics of the circulating pump, the flow-pressure loss characteristics of the pipeline system, and the flow coefficient characteristics of the flow-regulating and pressure-regulating valve; establishing a pressure balance relationship between the circulating pump outlet pressure and the pipeline pressure loss and valve pressure drop, and setting a target value for the nozzle inlet pressure; determining the target slurry flow rate based on the flue gas flow rate and pollutant concentration; calculating the circulating pump speed that satisfies the target slurry flow rate and nozzle inlet pressure target value based on the pressure balance relationship, and adjusting the circulating pump to the specified speed using a frequency converter; and real-time monitoring of the actual nozzle inlet pressure value. When the actual nozzle inlet pressure deviates from the target value, the valve pressure drop is changed by adjusting the opening of the flow-regulating and pressure-regulating valve to bring the actual nozzle inlet pressure back to the target value. Implementing this method allows for more precise simultaneous control of the circulating pump's flow and pressure.

Description

Technical Field

[0001] This application relates to the field of electronic digital data processing, and in particular to a method, system, product, and medium for the linkage control of a circulating pump valve. Background Technology

[0002] In wet flue gas desulfurization (FGD) systems of coal-fired power plants, circulating pumps deliver desulfurization slurry to the spray layer of the absorber tower. After atomization through nozzles, the slurry comes into full contact with the flue gas, achieving the absorption and removal of sulfur dioxide. Desulfurization efficiency and system energy consumption are directly affected by two key parameters: slurry flow rate and nozzle inlet pressure. The slurry flow rate determines the amount of slurry participating in the desulfurization reaction, while the nozzle inlet pressure determines the atomization effect and the uniformity of droplet coverage. With increasingly stringent environmental standards and higher requirements for energy conservation and emission reduction, accurately controlling these two parameters has become a core issue for optimizing the operation of desulfurization systems.

[0003] In related technologies, variable frequency drives (VFDs) can be used to adjust the speed of the circulating pump to regulate the slurry flow rate, while regulating valves are installed in the pipeline system to adjust the nozzle inlet pressure. Specifically, the required slurry flow rate is determined based on changes in the flue gas load, and the VFD adjusts the circulating pump speed to achieve the target flow rate. When the nozzle inlet pressure deviates from the set value, the valve opening is adjusted to change the pipeline resistance, thereby regulating the pressure. This method controls flow rate and pressure separately through the independent adjustment of the pump and valves.

[0004] However, in actual operation, changes in the circulating pump speed not only alter the slurry flow rate but also the pump outlet pressure and pipeline pressure loss, thus affecting the nozzle inlet pressure. Similarly, changes in the regulating valve opening alter the pipeline resistance and pressure regulation, also changing the slurry flow rate. Therefore, when the frequency converter adjusts the pump speed to regulate the flow rate, the nozzle inlet pressure fluctuates accordingly; conversely, when the valve is adjusted to stabilize the pressure, the slurry flow rate deviates. Under conditions of frequent flue gas load changes, this mutual interference causes repeated fluctuations in flow and pressure, requiring multiple iterative adjustments to stabilize the system. This adjustment process is slow and makes it difficult to achieve precise simultaneous control of both flow and pressure. Summary of the Invention

[0005] This application provides a method, system, product, and medium for the coordinated control of a circulating pump and its valves, which enables more precise simultaneous control of the flow and pressure of the circulating pump.

[0006] In a first aspect, this application provides a circulating pump valve linkage control method applied to a desulfurization system. The desulfurization system includes an absorption tower, a circulating pump, a pipeline system, a flow regulating valve, and a spray layer. The circulating pump delivers slurry to the spray layer through the pipeline system. The flow regulating valve is installed in the pipeline system. The spray layer includes several nozzles. The method includes: acquiring the flow-head characteristics of the circulating pump, the flow-pressure loss characteristics of the pipeline system, and the flow coefficient characteristics of the flow regulating valve; establishing a pressure balance relationship between the circulating pump outlet pressure and the pipeline pressure loss and valve pressure drop, and setting a target value for the nozzle inlet pressure; determining the target slurry flow rate based on the flue gas flow rate and pollutant concentration; calculating the circulating pump speed that satisfies the target slurry flow rate and nozzle inlet pressure target value based on the pressure balance relationship, and adjusting the circulating pump to the circulating pump speed using a frequency converter; and real-time monitoring of the actual value of the nozzle inlet pressure. When the actual value of the nozzle inlet pressure deviates from the target value, the valve pressure drop is changed by adjusting the opening of the flow regulating valve to bring the actual value of the nozzle inlet pressure back to the target value.

[0007] In the above embodiments, the coordinated control of pump speed and valve opening is achieved by establishing a pressure balance relationship. The combination of frequency conversion coarse adjustment of flow rate and valve fine adjustment of pressure decouples flow regulation and pressure regulation, avoiding the repeated fluctuation problem caused by mutual interference between pump speed change and valve adjustment in traditional methods. This achieves simultaneous and precise control of flow rate and pressure, ensuring stable nozzle atomization effect and reliable desulfurization efficiency.

[0008] In conjunction with some embodiments of the first aspect, in some embodiments, the step of establishing a pressure balance relationship between the circulating pump outlet pressure and pipeline pressure loss and valve pressure drop, and setting a target value for the nozzle inlet pressure, specifically includes: obtaining the flow-head characteristic curve of the circulating pump at different speeds, the flow-pressure loss characteristic curve of the pipeline system at different flow rates, and the valve pressure drop characteristics of the flow regulating and pressure regulating valve at different opening degrees and flow rates; establishing a pressure balance equation based on the principle of energy conservation in fluid mechanics, which states that the sum of the circulating pump head and the pipeline pressure loss head, the valve pressure drop head and the nozzle inlet pressure head is equal; and setting a target value for the nozzle inlet pressure based on the nozzle atomization performance requirements.

[0009] In the above embodiments, by acquiring complete characteristic data of the circulating pump, pipeline system and flow regulating valve, an accurate pressure balance equation was established based on the principle of energy conservation in fluid mechanics. This equation clearly describes the energy balance relationship between the head of the circulating pump and the head of each pressure loss component, providing a reliable theoretical basis and calculation basis for subsequent pump-valve linkage control, enabling the control system to accurately predict the operating status under different working conditions.

[0010] In conjunction with some embodiments of the first aspect, in some embodiments, the step of calculating the circulating pump speed that satisfies the target slurry flow rate and nozzle inlet pressure target values ​​based on the pressure balance relationship, and adjusting the circulating pump to the circulating pump speed via a frequency converter, specifically includes: determining a range of candidate operating points based on the target slurry flow rate on the circulating pump flow-head characteristic curve; for each operating point within the candidate operating point range, calculating the pressure drop value that the flow-regulating and pressure-regulating valve needs to bear in reverse according to the pressure balance equation, and calculating the corresponding valve opening value through the valve flow coefficient characteristic of the flow-regulating and pressure-regulating valve; eliminating candidate operating points whose valve opening value exceeds the adjustable range of the flow-regulating and pressure-regulating valve, and selecting the operating point with the lowest circulating pump operating power from the remaining candidate operating points as the optimal operating point; adjusting the circulating pump to the speed corresponding to the optimal operating point, and adjusting the flow-regulating and pressure-regulating valve to the opening corresponding to the optimal operating point.

[0011] In the above embodiments, by screening and optimizing the selection from candidate operating points, infeasible operating points with excessive valve opening are eliminated, and the optimal operating point with the minimum operating power of the circulating pump is selected from the feasible operating points. Under the premise of meeting the target flow and pressure requirements, the circulating pump operates in the high-efficiency zone, which not only ensures the process requirements of the desulfurization system, but also minimizes the system energy consumption.

[0012] In conjunction with some embodiments of the first aspect, in some embodiments, the step of adjusting the opening of the flow regulating valve to change the valve pressure drop and bring the actual value of the nozzle inlet pressure back to the target value when the actual value of the nozzle inlet pressure deviates from the target value specifically includes: real-time acquisition of the actual value of the nozzle inlet pressure and calculation of the deviation between the actual value of the nozzle inlet pressure and the target value of the nozzle inlet pressure; when the actual value of the nozzle inlet pressure is lower than the target value of the nozzle inlet pressure, and under the condition that the zero flow head of the circulating pump is greater than or equal to the sum of the pipeline pressure loss head, the valve pressure drop head, and the nozzle inlet pressure head, reducing the valve opening of the flow regulating valve to bring the actual value of the nozzle inlet pressure back to the target value. The operating point of the circulating pump shifts to the left along the flow-head characteristic curve. When the increase in the circulating pump head is greater than the increase in the valve pressure drop, the nozzle inlet pressure increases. When the actual value of the nozzle inlet pressure is higher than the target value, and the actual head of the circulating pump is greater than the sum of the pipeline pressure loss head, the valve pressure drop head, and the nozzle inlet pressure head, the valve opening of the flow-regulating and pressure-regulating valve is increased to shift the operating point of the circulating pump to the right along the flow-head characteristic curve. When the decrease in the circulating pump head is greater than the decrease in the valve pressure drop, the nozzle inlet pressure decreases. The above steps are repeated until the actual value of the nozzle inlet pressure returns to the allowable deviation range of the target value of the nozzle inlet pressure.

[0013] In the above embodiments, by monitoring the nozzle inlet pressure deviation in real time, and taking corresponding valve adjustment strategies according to the deviation direction, the operating point position of the circulating pump is changed by adjusting the valve opening through the pump characteristic curve law and the influence of valve on pipeline resistance. This achieves rapid and precise adjustment of the nozzle inlet pressure without changing the pump speed, effectively compensating for pressure fluctuations during operation.

[0014] In some embodiments of the first aspect, after adjusting the opening of the flow-regulating and pressure-regulating valve to change the valve pressure drop and bring the actual value of the nozzle inlet pressure back to the target value, the method further includes: obtaining the slope of the flow-head characteristic curve of the circulating pump at the current operating point and the rate of change of flow-pressure loss of the pipeline system at the current estimated flow rate; calculating the change of valve pressure drop based on the change in the opening of the flow-regulating and pressure-regulating valve and the current estimated flow rate, and calculating the flow deviation caused by the change in opening based on the slope of the flow-head characteristic curve and the rate of change of flow-pressure loss; simultaneously calculating the circulating pump speed compensation required to bring the flow back to the target slurry flow rate, and the influence of the head change caused by the speed compensation on the nozzle inlet pressure, based on the flow deviation and the pressure balance relationship; and simultaneously sending the speed compensation and the secondary valve opening compensation required to offset the influence as a set of linkage correction commands to the frequency converter and the flow-regulating and pressure-regulating valve, so that the flow rate and the nozzle inlet pressure return to their respective target values ​​in one correction.

[0015] In the above embodiments, changes in valve opening synchronously alter the resistance characteristics of the pipeline system, causing the operating point of the circulating pump to deviate along the flow-head characteristic curve, resulting in coupled disturbances between the slurry flow rate and the nozzle inlet pressure. If the flow and pressure deviations are corrected step-by-step in sequence, each correction introduces new cross-coupling errors, causing repeated oscillations and slow convergence. This embodiment calculates the flow deviation, speed compensation, and secondary valve opening compensation immediately after valve adjustment, and integrates the speed compensation and secondary valve opening compensation into a set of linked correction commands, issuing them synchronously. This allows the flow rate and nozzle inlet pressure to return to their respective target values ​​simultaneously within the same control cycle, fundamentally eliminating the flow-pressure cross-coupling oscillations caused by step-by-step adjustment, shortening the adjustment convergence time, and improving the dynamic response performance of the control system.

[0016] In some embodiments of the first aspect, after adjusting the opening of the flow regulating valve to change the valve pressure drop and bring the actual value of the nozzle inlet pressure back to the target value, the method further includes: when the rotational speed of the circulating pump and the opening of the flow regulating valve are both in a steady state, monitoring the pressure residual between the actual value of the nozzle inlet pressure and the target value; when the pressure residual exceeds a preset threshold and the duration exceeds a preset time, calculating the current slurry density estimate using the pressure balance relationship based on the current pump speed, valve opening, and current estimated flow rate; comparing the slurry density estimate with the initial density value used in the pressure balance relationship, and if the deviation between the two exceeds the density deviation threshold, updating the slurry density parameter in the pressure balance relationship to the slurry density estimate; and recalculating the target opening of the flow regulating valve and / or the target rotational speed of the circulating pump based on the updated pressure balance relationship to eliminate the nozzle inlet pressure deviation caused by changes in slurry density.

[0017] In the above embodiments, the slurry density continuously drifts due to factors such as fluctuations in limestone slurry concentration and changes in the desulfurization reaction process. If the density parameter in the pressure balance relationship uses a fixed initial value for a long period, the control system will generate a systemic pressure deviation that is difficult to eliminate, causing the nozzle inlet pressure to deviate from the target value. This embodiment monitors the pressure residual under steady-state conditions, uses the current pump speed, valve opening, and current estimated flow rate to back-calculate the estimated slurry density value, and automatically updates the density parameter in the pressure balance relationship when the density deviation exceeds a threshold. This allows the control model to adaptively track the long-term drift of the slurry density, eliminating the steady-state deviation of the nozzle inlet pressure caused by density changes without the need for additional density sensors, and improving the long-term control accuracy of the system under complex operating conditions.

[0018] In conjunction with some embodiments of the first aspect, in some embodiments, after the step of changing the valve pressure drop by adjusting the opening of the flow regulating and pressure regulating valve to bring the actual value of the nozzle inlet pressure back to the target value, the method further includes: obtaining the pressure drop ratio between the valve pressure drop of the flow regulating and pressure regulating valve and the total head of the circulating pump under the current operating conditions;

[0019] When the pressure drop ratio exceeds the preset energy-saving re-optimization trigger threshold, based on the pressure balance relationship, using the current nozzle inlet pressure target value and the current flow rate value as equality constraints, and the rotational speed of the circulating pump and the opening of the flow regulating valve as variables to be solved, the target rotational speed and target opening combination that minimizes the valve pressure drop is solved. Based on the difference between the current rotational speed of the circulating pump and the target rotational speed, and the difference between the current opening of the flow regulating valve and the target opening, a step-by-step migration path is generated. This step-by-step migration path includes multiple intermediate steps, each corresponding to a set of intermediate rotational speed values ​​and intermediate opening values. In this step-by-step migration path, two adjacent intermediate steps... The changes in rotational speed and valve opening between steps are determined based on the ratio between the partial derivative of pump speed with respect to nozzle inlet pressure and the partial derivative of valve opening with respect to nozzle inlet pressure in the pressure balance relationship. This ensures that the changes in nozzle inlet pressure caused by the change in rotational speed in each intermediate step cancel each other out. The rotational speed of the circulating pump and the opening of the flow regulating valve are adjusted sequentially according to the step-by-step migration path. After each intermediate step is executed, the actual value of the nozzle inlet pressure is detected. If the deviation between the actual value and the target value exceeds the preset migration tolerance, the migration is paused, and the deviation is corrected through the flow regulating valve before continuing to execute the next intermediate step.

[0020] In the above embodiments, when the pressure drop ratio borne by the flow regulating and pressure regulating valve is too high, a large amount of head output by the circulating pump is dissipated by the valve throttling, resulting in unnecessary energy waste. Furthermore, if the pump is moved to a low-throttling condition by increasing the speed and opening the valve wider, the asynchronous changes in speed and opening during the migration process will cause transient deviations in the nozzle inlet pressure, affecting desulfurization efficiency. This embodiment solves for an optimized speed-opening combination constrained by nozzle inlet pressure and flow rate, with the goal of minimizing valve pressure drop. Based on the ratio of the partial derivatives of the two variables with respect to nozzle inlet pressure in the pressure balance relationship, a step-by-step migration path is constructed. This ensures that the pressure disturbances caused by changes in speed and opening in each intermediate step cancel each other out, maintaining stable nozzle inlet pressure throughout the migration process. Simultaneously, the migration safety is ensured through measured verification and deviation correction mechanisms after each step, achieving energy-saving re-optimization of the circulating pump without affecting the desulfurization process performance.

[0021] In a second aspect, embodiments of this application provide a desulfurization system, which includes: one or more processors and a memory; the memory is coupled to the one or more processors, and the memory is used to store computer program code, which includes computer instructions, and the one or more processors call the computer instructions to cause the desulfurization system to perform the method described in the first aspect and any possible implementation thereof.

[0022] Thirdly, embodiments of this application provide a computer program product containing instructions that, when the computer program product is run on a desulfurization system, cause the desulfurization system to perform the method described in the first aspect and any possible implementation thereof.

[0023] Fourthly, embodiments of this application provide a computer-readable storage medium including instructions that, when executed on a desulfurization system, cause the desulfurization system to perform the method described in the first aspect and any possible implementation thereof.

[0024] Understandably, the desulfurization system provided in the second aspect, the computer program product provided in the third aspect, and the computer storage medium provided in the fourth aspect are all used to execute the methods provided in the embodiments of this application. Therefore, the beneficial effects they can achieve can be referred to the beneficial effects in the corresponding methods, and will not be repeated here.

[0025] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0026] 1. This application establishes a complete pressure balance relationship between the circulating pump outlet pressure, pipeline pressure loss, and valve pressure drop. Based on this relationship, it implements coordinated control of pump speed and valve opening. Therefore, it can accurately maintain stable nozzle inlet pressure while adjusting slurry flow rate. This effectively solves the problem in existing technologies where mutual interference between pump speed regulation and valve regulation leads to repeated fluctuations in flow and pressure, requiring multiple iterative adjustments to achieve stability. Thus, it achieves decoupled control of flow and pressure. This method combines the continuous flow adjustment capability of frequency converter regulation with the rapid pressure compensation capability of valve regulation. Coarse flow adjustment is achieved by regulating the circulating pump speed using a frequency converter, and the valve opening is preset based on the pressure balance relationship. When pressure deviation occurs during operation, fine pressure adjustment is performed by rapidly adjusting the valve opening. The fast response of the valve compensates for pressure fluctuations in a timely manner, ensuring that the nozzle inlet pressure is always maintained within the target range, thus guaranteeing stable nozzle atomization effect and desulfurization efficiency.

[0027] 2. This application dynamically determines the number of circulating pumps in operation based on the target slurry flow rate and the flow range of a single circulating pump. It intelligently starts and stops the standby pump when the operating circulating pump reaches the variable frequency control capability limit. Therefore, it enables the system to maintain high-efficiency operation across a wide load range, effectively solving problems such as discontinuous flow regulation, large fluctuations in slurry pH caused by pump start-stop, and energy waste due to low-load, low-efficiency operation of multiple pumps caused by existing power frequency pump start-stop control methods. This achieves continuous flow regulation, system stability, and energy economy. This method organically combines pump number adjustment with variable frequency control. When the load changes significantly beyond the variable frequency control range of the existing operating pump group, the number of pumps is adjusted by starting and stopping the pumps. Within the load range after determining the number of pumps, continuous and precise flow adjustment is achieved through variable frequency control, reducing the flow regulation range from 16% to 50% in traditional power frequency pump start-stop methods to 4.8% to 15%. The power of a single pump can be reduced to 53% of its rated power when operating at the lowest frequency.

[0028] 3. This application addresses the issue that when the pressure drop ratio borne by the flow regulating and pressure regulating valve is too high, a large amount of head output by the circulating pump is dissipated by the valve throttling, resulting in unnecessary energy waste. Furthermore, if the pump is moved to a low-throttling condition by increasing the speed and opening the valve more fully, the asynchronous changes in speed and opening during the migration process will cause transient deviations in the nozzle inlet pressure, affecting desulfurization efficiency. This embodiment solves for an optimized speed-opening combination constrained by nozzle inlet pressure and flow rate, with the goal of minimizing valve pressure drop. Based on the ratio of the partial derivatives of the two variables with respect to nozzle inlet pressure in the pressure balance relationship, a step-by-step migration path is constructed. This ensures that the pressure disturbances caused by changes in speed and opening in each intermediate step cancel each other out, maintaining stable nozzle inlet pressure throughout the migration process. Simultaneously, a measurement verification and deviation correction mechanism after each step ensures migration safety, achieving energy-saving re-optimization of the circulating pump without affecting the desulfurization process performance. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating a circulating pump valve linkage control method in an embodiment of this application.

[0030] Figure 2 This is another schematic flowchart of the circulating pump valve linkage control method in the embodiments of this application;

[0031] Figure 3 This is a schematic diagram of the physical device structure of a desulfurization system in an embodiment of this application. Detailed Implementation

[0032] The terminology used in the following embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in the specification of this application, the singular expressions “a,” “an,” “the,” “the,” and “this” are intended to include the plural expressions as well, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this application refers to any or all possible combinations including one or more of the listed items.

[0033] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature, and in the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0034] To facilitate understanding, the application scenarios of the embodiments of this application are described below.

[0035] After coal-fired power units complete ultra-low emission retrofitting, the target for SO2 concentration control in clean flue gas narrows, leading to increased start-up and shutdown frequency of desulfurization tower circulating pumps. Affected by factors such as deep peak shaving by thermal power plants, electricity market fluctuations, and changes in coal sulfur content, under most operating conditions, it is difficult to precisely match the outlet SO2 concentration with the number of operating pumps in the desulfurization tower. This results in problems such as excessive energy consumption from adding a pump and insufficient desulfurization efficiency from removing a pump, leading to energy waste.

[0036] In the existing technology, the operation optimization of slurry circulation pumps relies on the accumulation of experience under different operating conditions and is achieved by screening the pump group combination mode. This method has the following technical problems: the adjustment of the liquid-gas ratio of the desulfurization tower by the industrial frequency slurry circulation pump is discrete, making it difficult to achieve the optimal liquid-gas ratio; frequent start-up and shutdown of the circulation pump causes fluctuations in the pH value of the desulfurization tower slurry, affecting the SO2 absorption reaction rate; when the unit load changes rapidly, the response time of switching the pump group combination mode is long, making it difficult to achieve stable control of SO2 concentration.

[0037] To facilitate understanding, the method provided in this implementation will be described in detail below, using the above scenario as an example. Please refer to [link / reference]. Figure 1 This is a flowchart illustrating a circulating pump valve linkage control method in an embodiment of this application.

[0038] S101. Obtain the flow-head characteristics of the circulating pump, the flow-pressure loss characteristics of the pipeline system, and the flow coefficient characteristics of the flow regulating valve.

[0039] The flow-head characteristic of a circulating pump indicates the relationship between the flow rate and head provided by the pump at different speeds. According to the proportional law of centrifugal pumps, flow rate changes are directly proportional to speed changes, pressure changes are directly proportional to the square of the speed change, and motor power changes are directly proportional to the cube of the speed change. The flow-pressure loss characteristic of a pipeline system refers to the pressure loss generated by the slurry at different flow rates during pipeline flow, including friction loss and local resistance loss. The flow coefficient characteristic of a flow regulating and pressure regulating valve indicates the valve's flow capacity at different opening degrees. This valve uses a streamlined valve core designed based on three-dimensional fluid dynamics, which can effectively reduce eddies and local resistance during slurry flow. The target value of the nozzle inlet pressure is determined based on the design data provided by the nozzle manufacturer. The nozzle design pressure is 0.7 bar, and the normal operating pressure range is 0.5-0.8 bar. Within this pressure range, the slurry particle size at the nozzle outlet can be guaranteed to be between 2300-2500 micrometers, meeting the requirements for atomization effect and spray coverage area.

[0040] Flow rate and head data at different speeds were extracted from the performance parameter tables provided by the circulating pump manufacturer. Based on the proportional law of centrifugal pumps, which states that flow rate is proportional to speed, a family of flow rate and head characteristic curves was formed. Considering the pipe diameter, length, bends, and other components, the Darcy-Weisbach formula was used to calculate friction loss and local pressure loss, establishing a correlation between flow rate and pressure loss. Flow coefficient values ​​at different opening degrees were obtained from the product catalog of the flow regulating valve. Due to the valve's streamlined design, the adjustment of the flow area of ​​the valve core and body allows for continuous linear control of the circulating flow. Based on the nozzle technical requirements, the target nozzle inlet pressure was set to 0.7 bar, with an allowable fluctuation range of 0.5-0.8 bar. According to the proportional law of centrifugal pumps, which states that pressure is proportional to the square of speed, this pressure range corresponds to a circulating pump head adjustment range of approximately 3 meters. In the DCS system, the valve opening of the electric flow regulating valve and the remote pressure gauge were interlocked using logic configuration, enabling the valve to respond to the pressure gauge signal in real time and dynamically correct the opening to ensure that the nozzle pressure remains stable within the design range. In addition, differential pressure detection devices are installed at both ends of the flow regulating and pressure regulating valve. The differential pressure difference, i.e., the valve pressure drop, is measured in real time through a differential pressure transmitter. Since desulfurization circulating pump pipelines usually do not have online flow measurement instruments, this application utilizes three field-obtainable parameters: the speed fed back by the frequency converter, the valve pressure drop measured in real time by the differential pressure detection device, and the nozzle inlet pressure measurement value. Based on the pressure balance equation, the current slurry flow rate is obtained by solving the equation simultaneously, realizing soft flow measurement under the condition of no flow meter. Specifically, according to the pressure balance equation H_pump(Q,n)=h_pipeline(Q)+h_valve+H_nozzle, where H_pump(Q,n) is the known pump flow-head characteristic function, h_pipeline(Q) is the known pipeline flow-pressure loss characteristic function, h_valve is the direct measurement value of the differential pressure transmitter, and H_nozzle=P_nozzle / (ρ×g) is obtained by converting the nozzle inlet pressure, only the flow rate Q is the only unknown quantity in the equation. The current estimated flow rate value can be obtained by numerical solution. For example, under a certain operating condition, the frequency converter feedback speed n = 1450 rpm, the differential pressure transmitter measures the valve pressure drop h_valve = 3.50 m, and the nozzle inlet pressure P_nozzle = 0.72 bar. Substituting these measured values ​​into the pressure balance equation, the equation simplifies to a univariate equation containing only the flow rate Q, yielding Q ≈ 3246 m³ / h. In the DCS control system, this solution process is executed once per control cycle, achieving real-time soft measurement of the flow rate. When the circulating pump speed is not at its rated value, the pump characteristic curve is first converted to the current speed according to the similarity law before being substituted into the solution.

[0041] In some embodiments, characteristic parameters can be obtained in multiple ways. Optionally, offline testing can be used to measure the performance of the circulating pump on a test bench using flow meters and pressure sensors, record the data, and then fit and generate characteristic curves; the pipeline system can be simulated using fluid dynamics calculation software to extract pressure loss values ​​under various flow conditions; and flow coefficient calibration data can be obtained from the valve supplier. Optionally, during system operation, online data acquisition can be used to obtain estimated flow values ​​based on pressure balance relationships by utilizing feedback signals from valve differential pressure detection devices, nozzle inlet pressure transmitters, and frequency converters. After data cleaning and curve fitting, an actual operating characteristic model can be established, and the characteristic parameters can be periodically corrected. It is understood that other methods can also be used to obtain characteristic parameters, and this is not limited here.

[0042] The electric flow and pressure regulating valve also features the following technical characteristics: In terms of material selection, both the valve core and body are made of super duplex stainless steel 2205 / C276, resistant to corrosion and wear from desulfurization slurry (chloride ions, acidic media), ensuring long-term operation. Regarding structural processing, the streamlined contour of the valve core is machined using five-axis linkage to ensure streamlined precision; the valve body flow channel is polished (roughness Ra≤0.8μm) to reduce slurry adhesion and wear. For sealing design, a hard seal structure is adopted, combined with an elastic compensation device to prevent slurry leakage and adapt to the scouring of solid particles in the slurry. In terms of drive configuration, an electric actuator (protection level IP65) is selected, with a response time ≤1s, meeting the requirements for rapid adjustment under operating conditions. The actuator torque matches the resistance torque at the valve's maximum opening. Regarding pressure characteristics, automatic adjustment is achieved through pressure feedback from a pressure sensor on the slurry pipeline, with a fast response speed (≤1s), adapting to 50%–100% flow fluctuations while maintaining nozzle pressure stable at 0.5bar–0.8bar. In terms of flow characteristics, it features equal percentage characteristics and a constant flow rate change rate, avoiding excessive pressure at low flow rates and excessive pressure at high flow rates.

[0043] S102. Establish the pressure balance relationship between the circulating pump outlet pressure, pipeline pressure loss, and valve pressure drop, and set the target value for the nozzle inlet pressure.

[0044] The circulating pump outlet pressure represents the pressure generated at the pump outlet. Pipeline pressure loss refers to the pressure lost by the slurry due to resistance in the pipeline system. Valve pressure drop represents the pressure reduction experienced when the slurry flows through a flow regulating valve. The nozzle inlet pressure target value is the pressure setting required to ensure the nozzle atomization effect; it is determined based on the nozzle performance curve and is typically set to 0.7 bar.

[0045] This step establishes a pressure balance equation based on the law of conservation of energy in fluid mechanics. After the circulating pump head is converted into pressure, it overcomes pipeline pressure loss and valve pressure drop sequentially during the delivery process, ultimately forming residual pressure at the nozzle inlet. The pressure balance equation is established as follows: circulating pump head equals pipeline pressure loss head plus valve pressure drop head plus nozzle inlet pressure head. The target value for the nozzle inlet pressure is set at 0.7 bar, based on the requirement that the nozzle can produce droplet sizes of 2300 μm to 2500 μm within a pressure range of 0.5 bar to 0.8 bar. When using a simplified model, the pipeline is divided into four regions: pump outlet section, main pipe section, branch pipe section, and spray layer inlet section. The pressure loss of each region is calculated separately and then summed to obtain the total pressure loss, thus establishing the pressure balance equation. The target value is set based on the median of the nozzle's rated operating pressure range, with an allowable deviation range of ±0.05 bar. When using a dynamic model, changes in physical properties such as slurry temperature, density, and viscosity are considered, and correction coefficients for these physical properties are introduced. The friction coefficient and pressure loss of the pipeline are corrected by real-time measurement using an online density meter and temperature sensor. The target value of the nozzle inlet pressure is dynamically adjusted according to the concentration of sulfur dioxide.

[0046] In some embodiments, the step of establishing a pressure balance relationship between the circulating pump outlet pressure and the pipeline pressure loss and valve pressure drop, and setting a target value for the nozzle inlet pressure, specifically includes: obtaining the flow-head characteristic curve of the circulating pump at different speeds, the flow-pressure loss characteristic curve of the pipeline system at different flow rates, and the valve pressure drop characteristics of the flow regulating and pressure regulating valve at different opening degrees and flow rates; establishing a pressure balance equation based on the principle of energy conservation in fluid mechanics, which states that the sum of the circulating pump head and the pipeline pressure loss head, the valve pressure drop head and the nozzle inlet pressure head is equal; and setting a target value for the nozzle inlet pressure based on the nozzle atomization performance requirements.

[0047] S103. Determine the target slurry flow rate based on flue gas flow rate and pollutant concentration.

[0048] Flue gas flow rate refers to the volume of flue gas entering the absorption tower per unit time. Pollutant concentration refers to the mass concentration of sulfur dioxide in the flue gas. Target slurry flow rate represents the slurry circulation flow rate required to achieve the set desulfurization efficiency. Liquid-to-gas ratio represents the ratio of slurry circulation flow rate to flue gas flow rate, and is a key design parameter for the desulfurization system, with typical values ​​ranging from 10 L / Nm³ to 15 L / Nm³.

[0049] Real-time data on flue gas flow rate and sulfur dioxide concentration are collected through a continuous emission monitoring system. Flue gas flow rate is obtained through a flow measurement device in the inlet flue of the absorption tower, and sulfur dioxide concentration is measured using an online flue gas analyzer. The total amount of sulfur dioxide to be removed is calculated based on the flue gas flow rate and sulfur dioxide concentration, and the required desulfurization efficiency is obtained by consulting the design parameters. The required liquid-to-gas ratio to achieve this efficiency is calculated based on the desulfurization reaction kinetics. The target slurry flow rate is obtained by multiplying the flue gas flow rate by the liquid-to-gas ratio, with a safety margin of 5% to 10%. When using a segmented liquid-to-gas ratio strategy, the sulfur dioxide concentration is divided into three intervals: low, medium, and high, each corresponding to a different liquid-to-gas ratio setpoint. The interval is determined based on the real-time concentration, and the corresponding liquid-to-gas ratio value is selected. The target slurry flow rate is calculated by multiplying the selected liquid-to-gas ratio by the real-time flue gas flow rate. When using a closed-loop control method based on desulfurization efficiency, the actual desulfurization efficiency is calculated by real-time monitoring of the outlet sulfur dioxide concentration. The actual efficiency is compared with the target efficiency, and the liquid-to-gas ratio adjustment is calculated based on the deviation using a proportional-integral control algorithm. The target slurry flow rate is obtained by multiplying the adjusted liquid-to-gas ratio by the flue gas flow rate.

[0050] S104. Calculate the circulating pump speed that meets the target slurry flow rate and nozzle inlet pressure target value according to the pressure balance relationship, and adjust the circulating pump to the circulating pump speed through the frequency converter.

[0051] Candidate operating points refer to a series of possible operating states on the flow-head characteristic curve of a circulating pump that satisfy the target slurry flow rate. The optimal operating point is the operating point with the lowest operating power among all candidate operating points that meet the flow and pressure requirements. The frequency converter changes the motor speed by adjusting the power supply frequency. Depending on the motor type, the speed of an asynchronous motor is equal to 60 multiplied by the frequency, divided by the number of pole pairs, multiplied by 1, and then subtracted from the slip rate. The speed of a permanent magnet synchronous motor is equal to 60 multiplied by the frequency, divided by the number of pole pairs. According to the proportional law of centrifugal pumps, the operating power of a circulating pump is proportional to the cube of its speed.

[0052] Based on the target slurry flow rate, the operating point that meets the flow rate requirement is found on the flow-head characteristic curve of the circulating pump. According to the proportional law of centrifugal pumps, the flow rate is directly proportional to the rotational speed, and there are multiple candidate operating points that meet the flow rate requirement on different speed curves. For each operating point within the candidate operating point range, the pressure drop value required by the flow regulating and pressure regulating valve is calculated in reverse according to the pressure balance equation. The calculation formula is: valve pressure drop equals circulating pump outlet pressure minus pipeline pressure loss minus the target value of nozzle inlet pressure. The target value of nozzle inlet pressure is set to 0.7 bar to ensure that the slurry particle size at the nozzle outlet is maintained at approximately 2200 micrometers. According to the nozzle technical requirements, the nozzle pressure operating range is 0.5-0.8 bar. According to the proportional law of centrifugal pumps, the pressure is directly proportional to the square of the rotational speed, and this range corresponds to a circulating pump head adjustment range of approximately 3 meters. Therefore, when selecting candidate operating points, it is necessary to ensure that the head difference between each operating point is within 3 meters. The valve opening value is calculated by inversely using the valve flow coefficient characteristics based on the target flow rate. Because the flow regulating valve employs a streamlined valve core design, the flow area and valve opening are linearly related, avoiding the sudden flow changes common in traditional valve regulation. Candidate operating points with valve openings exceeding the adjustable range are eliminated. For the retained operating points, pump efficiency is checked based on speed and flow rate to calculate operating power. According to the proportional law of centrifugal pumps, power is proportional to the cube of speed; operating points with lower speeds typically have lower energy consumption. The operating point with the lowest power is selected as the optimal operating point, and setting commands are sent to the frequency converter and valve actuator to complete the coordinated pump-valve regulation.

[0053] In some embodiments, the step of calculating the circulating pump speed that satisfies the target slurry flow rate and nozzle inlet pressure target values ​​based on the pressure balance relationship, and adjusting the circulating pump to the circulating pump speed via a frequency converter, specifically includes: determining a range of candidate operating points based on the target slurry flow rate on the circulating pump flow-head characteristic curve; for each operating point within the candidate operating point range, calculating the pressure drop value that the flow-regulating and pressure-regulating valve needs to bear in reverse according to the pressure balance equation, and calculating the corresponding valve opening value through the valve flow coefficient characteristic of the flow-regulating and pressure-regulating valve; eliminating candidate operating points whose valve opening value exceeds the adjustable range of the flow-regulating and pressure-regulating valve, and selecting the operating point with the lowest circulating pump operating power from the remaining candidate operating points as the optimal operating point; adjusting the circulating pump to the speed corresponding to the optimal operating point, and adjusting the flow-regulating and pressure-regulating valve to the opening corresponding to the optimal operating point.

[0054] Based on the target slurry flow rate, all operating points satisfying this flow rate are identified on the family of flow-head characteristic curves of the circulating pump. According to the proportional law of centrifugal pumps, flow rate is directly proportional to rotational speed; multiple operating points satisfying the flow rate requirement exist on different speed curves, forming a candidate operating point range. For each operating point within the candidate range, its corresponding rotational speed and head values ​​are extracted. The pipeline pressure loss value is calculated based on the pipeline geometry parameters and the target slurry flow rate. The Darcy-Weisbach formula is used to calculate the friction loss and local pressure loss. The pressure drop value required by the flow regulating valve is calculated in reverse using the pressure balance equation. The formula is: valve pressure drop equals the pressure corresponding to the circulating pump head minus the pipeline pressure loss minus the target nozzle inlet pressure of 0.7 bar. The valve pressure drop and the target slurry flow rate are substituted into the valve flow coefficient formula. The flow coefficient Kv equals the flow rate divided by the square root of the pressure drop. The corresponding valve opening value is found based on the flow coefficient characteristic curve. The calculated valve opening is checked to ensure it is within the adjustable range of 5% to 90%, and candidate operating points with valve openings outside this range are eliminated.

[0055] Power calculations and comparisons were performed on the candidate operating points that met the valve opening constraints. The operating efficiency η of the slurry circulation pump is equal to the ratio of the pump's output power P_output to its rated power P_rated. The output power P_output is calculated based on the required pump head and flow rate at the production site. The approximate formula for the relative operating efficiency η of the slurry circulation pump is η=C1(Q* / n*)+C2, where Q is the relative value of the flow rate, n is the relative value of the rotational speed, and C1 and C2 are constants. From this formula, it can be seen that the relative operating efficiency of the slurry circulation pump is mainly determined by the ratio of the pump's flow rate to its rotational speed. When the rotational speed is kept constant (n*=1), and the flow rate is reduced by controlling the valve opening, Q* / n*=Q*. When the pump flow rate is adjusted only by regulating the pipe resistance characteristics of the valve, the operating efficiency will drop to 80% when the flow rate decreases to 60% of the rated flow rate. The operating efficiency of the circulation pump decreases as the flow rate decreases. When the outlet valve of the slurry circulation pump is fully open and remains unchanged, Q and n are proportional. When the pump speed is adjusted by adjusting the frequency of the frequency converter, the efficiency is equal when the working flow of the circulation pump drops to 60% of the rated flow and when the flow is 100%. The desulfurization circulation pump then enters the high-efficiency working zone again.

[0056] Based on the proportional law of centrifugal pumps, which states that the change in motor power is proportional to the cube of the change in speed, the operating power of the circulating pump is calculated for each candidate operating point. The power ratio is equal to the cube of the speed ratio, i.e., the power at that operating point equals the rated power multiplied by the speed at that operating point divided by the cube of the rated speed. The operating power values ​​of all retained candidate operating points are compared, and the operating point with the lowest operating power is identified as the optimal operating point. This optimal operating point simultaneously meets the target slurry flow rate requirements, the nozzle inlet pressure range of 0.5 bar to 0.8 bar, valve opening constraints, and optimal energy consumption requirements. The circulating pump speed and the opening parameters of the flow and pressure regulating valve corresponding to the optimal operating point are extracted. The control system converts the speed setpoint into the frequency setpoint required by the frequency converter and sends a frequency setting command to the frequency converter through the communication interface. After receiving the command, the frequency converter adjusts the output frequency according to the set acceleration and deceleration time, driving the circulating pump speed to change to the target value. Simultaneously, the control system converts the opening setpoint into the control signal required by the valve actuator and sends an opening setting command to the valve actuator. The actuator drives the valve core to move, adjusting the valve opening to the target value, thus achieving coordinated pump and valve regulation.

[0057] S105. Real-time detection of the actual value of the nozzle inlet pressure. When the actual value of the nozzle inlet pressure deviates from the target value of the nozzle inlet pressure, the valve pressure drop is changed by adjusting the opening of the flow regulating valve, so that the actual value of the nozzle inlet pressure returns to the target value.

[0058] The actual value of the nozzle inlet pressure represents the pressure value at the spray layer inlet position measured in real time by a remote pressure gauge. The opening degree of the flow regulating and pressure regulating valve represents the percentage of the valve core relative to the fully open position. This valve adopts a streamlined valve core structure, achieving continuous linear control of the flow rate by precisely adjusting the flow area between the valve core and the valve body. The operating point of the circulating pump refers to the actual operating position of the circulating pump on the flow-head characteristic curve. According to the proportional law of centrifugal pumps, the head changes proportionally to the square of the speed when the rotational speed changes. The target value of the nozzle inlet pressure is 0.7 bar, with an allowable fluctuation range of 0.5-0.8 bar. Within this pressure range, the nozzle outlet slurry particle size can be maintained at 2300-2500 micrometers, meeting the atomization effect requirements.

[0059] The nozzle inlet pressure is measured in real time using a remote pressure gauge. This gauge signal is interlocked with the electric flow and pressure regulating valve via a DCS system. The control system calculates the pressure deviation at fixed intervals; the deviation equals the actual value minus the target value of 0.7 bar. A pressure dead zone is set, and valve regulation is initiated when the absolute value of the deviation exceeds the dead zone value. When the actual value is lower than the target value, the valve opening is reduced, increasing the valve pressure drop. Due to the streamlined valve design, the reduced opening decreases the flow area between the valve core and body, increasing local resistance and thus raising the valve pressure drop. According to the pressure balance relationship, the increased valve pressure drop results in a relatively larger share of pressure allocated to the nozzle inlet, achieving a pressure increase. When the circulating pump speed increases, according to the proportional law of centrifugal pumps, pressure is proportional to the square of the speed, and the circulating pump outlet pressure increases accordingly. At this time, the valve opening needs to be increased to reduce the valve pressure drop and absorb the excess pressure. When the actual value is higher than the target value, the valve opening is increased to reduce the valve pressure drop. The increased flow area reduces local resistance, lowering the valve pressure drop and consequently reducing the nozzle inlet pressure. The valve opening adjustment employs a proportional-integral-derivative (PID) control algorithm, utilizing the valve's continuous linear adjustment characteristics to avoid sudden flow changes. The system continuously monitors the pressure and repeatedly adjusts it until the actual value falls within the allowable range of 0.5-0.8 bar. Within this pressure range, the nozzles can guarantee an atomized particle size of 2300-2500 micrometers and sufficient spray coverage area to meet desulfurization efficiency requirements.

[0060] In some embodiments, the step of adjusting the opening of the flow regulating valve to change the valve pressure drop and bring the actual value of the nozzle inlet pressure back to the target value when the actual value of the nozzle inlet pressure deviates from the target value specifically includes: real-time acquisition of the actual value of the nozzle inlet pressure and calculation of the deviation between the actual value of the nozzle inlet pressure and the target value of the nozzle inlet pressure; when the actual value of the nozzle inlet pressure is lower than the target value of the nozzle inlet pressure, and the zero flow head of the circulating pump is greater than or equal to the sum of the pipeline pressure loss head, the valve pressure drop head, and the nozzle inlet pressure head, reducing the valve opening of the flow regulating valve to make the operating point of the circulating pump move along the target value. The flow-head characteristic curve shifts to the left. When the increase in the circulating pump head is greater than the increase in the valve pressure drop, the nozzle inlet pressure increases. When the actual value of the nozzle inlet pressure is higher than the target value, and the actual head of the circulating pump is greater than the sum of the pipeline pressure loss head, the valve pressure drop head, and the nozzle inlet pressure head, the valve opening of the flow-regulating and pressure-regulating valve is increased to shift the operating point of the circulating pump to the right along the flow-head characteristic curve. When the decrease in the circulating pump head is greater than the decrease in the valve pressure drop, the nozzle inlet pressure decreases. The above steps are repeated until the actual value of the nozzle inlet pressure returns to the allowable deviation range of the target value of the nozzle inlet pressure.

[0061] In some embodiments, after step S105, the method may further include:

[0062] Obtain the slope of the flow-head characteristic curve of the circulating pump at the current operating point and the rate of change of flow-pressure loss of the pipeline system at the current estimated flow rate; calculate the change of valve pressure drop based on the change in opening of the flow-regulating and pressure-regulating valve and the current estimated flow rate; combine the slope of the flow-head characteristic curve and the rate of change of flow-pressure loss to calculate the flow deviation caused by the change in opening; based on the flow deviation and the pressure balance relationship, simultaneously calculate the amount of circulating pump speed compensation required to return the flow rate to the target slurry flow rate, and the impact of the head change caused by the speed compensation on the nozzle inlet pressure; use the speed compensation and the secondary valve opening compensation required to offset the impact as a set of linkage correction commands, and simultaneously send them to the frequency converter and the flow-regulating and pressure-regulating valve, so that the flow rate and the nozzle inlet pressure return to their respective target values ​​in one correction.

[0063] The slope of the flow-head characteristic curve refers to the first derivative of the head H of the circulating pump with respect to the flow rate Q at the current operating point, denoted as Spump = dH / dQ, with units of m / (m³ / h). It is a negative value, reflecting the magnitude of the head change caused by each unit change in flow rate near the operating point. By fitting the pump performance curve with a quadratic polynomial H = a × Q² + b × Q + c, and substituting the current operating point flow rate Q0 to find the derivative, we get Spump = 2a × Q0 + b. For example, at Q0 = 5000 m³ / h and H0 = 20 m, Spump = −0.002 m / (m³ / h), meaning that for every 1 m³ / h increase in flow rate, the head decreases by 0.002 m. The rate of change of pressure drop in a pipeline system refers to the first derivative of the pipeline resistance pressure drop ΔP with respect to the flow rate Q. From the pipeline resistance characteristic equation ΔP_pipeline = k_pipeline × Q², differentiating with respect to Q yields dΔP_pipeline / dQ = 2 × k_pipeline × Q. This is converted to the head slope as dH_sys / dQ = 2 × k_pipeline × Q ÷ (ρ × g), with units of m / (m³ / h), and is a positive value; for example, k_pipeline = 4 × 10⁻⁻⁴. 8 bar·h² / m 6 When Q0 = 5000 m³ / h, dΔP_pipeline / dQ = 4 × 10⁻ 4 bar / (m³ / h), corresponding to the head slope dH_sys / dQ=4×10⁻ 4 ×10 5÷(1050×9.81)=0.00388m / (m³ / h). The change in valve pressure drop refers to the change in the pressure difference across the valve after the opening degree of the flow regulating valve is changed by Δα, denoted as ΔΔP_valve, with the unit being bar. Under the current estimated flow rate Q0, ΔΔP_valve is calculated from the Kv characteristic curve as ΔΔP_valve = Q0²×(ρ / ρwater)×[1 / Kv(α+Δα)²−1 / Kv(α)²]. For example, if the opening degree is increased by 5%, causing Kv to rise from 8531 to 9200, the valve pressure drop will decrease from 0.36 bar to 0.31 bar under Q0=5000m³ / h, and ΔΔP_valve = −0.05 bar. Flow offset refers to the change in flow rate caused by the change in valve opening altering the system resistance characteristics, resulting in the circulating pump's operating point shifting along the flow-head characteristic curve to a new equilibrium point. It is denoted as ΔQ and measured in m³ / h. For example, if the valve is opened 5% larger, the system curve shifts downwards, the pump's operating point shifts to the right, and the flow rate increases from 5000 m³ / h to 5083 m³ / h. The flow offset ΔQ = +83 m³ / h. Speed ​​compensation refers to the adjustment of the circulating pump's speed required to eliminate the flow offset and restore the flow rate to the target slurry flow rate Q0. It is denoted as Δn and measured in rpm. It is approximately calculated using the pump similarity law Q∝n, yielding Δn = −ΔQ ÷ Q0 × n0. For example, when ΔQ = +83 m³ / h and n0 = 1480 rpm, Δn = −83 ÷ 5000 × 1480 = −24.6 rpm, meaning a speed reduction of approximately 25 rpm is required. The effect of head change on nozzle inlet pressure refers to the change in nozzle inlet pressure caused by the change in pump head with the square of the speed after the speed compensation Δn is applied. This is denoted as ΔP effect. Linearizing this at flow rate Q0 using the similarity law H∝n², we get the head change ΔH = 2 × H0 × Δn ÷ n0, which can then be converted to ΔP effect = ρ × g × ΔH ÷ 10. 5 For example, when Δn = −25 rpm, ΔH = 2 × 20 × (−25) ÷ 1480 = −0.676 m, and ΔP influence = 1050 × 9.81 × (−0.676) ÷ 10 5 =−0.070bar. The secondary compensation amount for valve opening refers to the additional valve opening correction amount applied to offset the pressure disturbance at the nozzle inlet caused by the influence of ΔP, denoted as Δα2. It is derived from the pressure balance relationship ∂P_nozzle / ∂α=−∂ΔP_valve / ∂α, so Δα2=ΔP_influence ÷(∂ΔP_valve / ∂α), where ∂ΔP_valve / ∂α is approximated by the difference at the current opening through the Kv-α characteristic curve; for example, when ∂ΔP_valve / ∂α=−0.010bar / %, ΔP_influence=−0.070bar, Δα2=(−0.070)÷(−0.010)=+7.0%, that is, the valve needs to be opened by an additional 7% to compensate for the pressure drop caused by the deceleration. The linkage correction command integrates the speed compensation amount Δn and the valve opening secondary compensation amount Δα2 into a set of commands, and sends them synchronously to the frequency converter and the flow and pressure regulating valve actuator within the same control cycle, thereby eliminating the transient deviation of flow-pressure cross-coupling caused by the timing difference in step-by-step regulation.

[0064] This section describes the flow-pressure coupling feedforward compensation process after valve adjustment in S105. In S105, the control system maintains the target nozzle inlet pressure by adjusting the opening of the flow and pressure regulating valve (change Δα). However, changes in valve opening synchronously alter the pipeline system resistance characteristic curve, causing the circulating pump's operating point to shift from its original equilibrium point to a new equilibrium point. This results in the actual slurry flow rate deviating from the target value Q0. Therefore, a feedforward calculation process is required to derive the speed compensation Δn and the secondary valve opening compensation Δα2, which are then executed synchronously with a linkage correction command. The control system first uses the inverter feedback speed n0, the valve pressure drop h_valve, and the actual nozzle inlet pressure P_nozzle measured in real-time by the valve differential pressure detection device. Based on the pressure balance equation, it solves simultaneously to obtain the current estimated flow rate Q0. Then, it reads the slope of the circulating pump flow-head characteristic curve S_pump and the pipeline system flow-pressure loss change rate dH_sys / dQ at the current operating point (Q0, n0). S_pump is determined by the pump performance curve fitting polynomial H=a×Q²+b×Q+c stored in the control system. Substituting coefficients a and b into the current operating point flow rate Q0, we obtain S_pump = 2a × Q0 + b. Coefficients a and b are determined by fitting the pump's factory calibration data and are corrected for changes in speed using a similarity law. The pipeline flow pressure drop change rate is calculated by substituting the pipeline resistance coefficient k_pipeline (obtained through multi-flow measurement point calibration during system commissioning) into dΔP_pipeline / dQ = 2 × k_pipeline × Q0, and then dividing by (ρ × g) to convert it into the head slope dH_sys / dQ. Both parameters are directly read from the control system cache when the operating conditions remain unchanged. After S105 completes the valve opening adjustment, using the current estimated flow rate Q0 and the Kv value corresponding to the old and new openings, we calculate the valve pressure drop change (bar) using ΔΔP_valve = Q0² × (ρ / ρwater) × [1 / Kv(α + Δα)² − 1 / Kv(α)²], and then convert it to head units: ΔH_valve = ΔΔP_valve × 10 5 ÷(ρ×g)(m), The change in valve opening causes the overall pipeline system resistance curve to shift by ΔH_valve. The operating point of the circulating pump moves along the flow-head characteristic curve to a new equilibrium point. Taylor expansions are performed on the pump curve and the system curve at Q0 respectively. The pump side is H_pump(Q0, n0) + S_pump × ΔQ, and the system side is H_sys(Q0, α) + dH_sys / dQ × ΔQ + ΔH_valve. The common term on both sides is eliminated: H_pump(Q0, n0) = H_sys After rearranging (Q0, α), we get (S_pump − dH_sys / dQ) × ΔQ = ΔH_valve. The flow offset calculation formula is ΔQ = ΔH_valve ÷ (S_pump − dH_sys / dQ). Substituting specific values ​​for verification: S_pump = −0.002 m / (m³ / h), dH_sys / dQ = 0.00388 m / (m³ / h), Δα = +5% to make ΔP_valve = −0.05 bar, then ΔH_valve = −0.05 × 10 5÷(1050×9.81)=−0.486m, ΔQ=−0.486÷(−0.002−0.00388)=−0.486÷(−0.00588)=+82.7m³ / h, that is, after the valve is opened by 5%, the flow rate is about 83m³ / h higher. To restore the offset flow rate Q0+ΔQ to Q0, the circulating pump speed needs to be reduced. According to the pump similarity law Q∝n, under the premise that the system resistance curve remains approximately unchanged, the flow rate change is proportional to the speed change. The speed compensation is Δn=−ΔQ÷Q0×n0, which gives Δn=−82.7÷5000×1480=−24.5rpm. The speed change will cause a change in head, which in turn affects the nozzle inlet pressure. According to the pump similarity law H∝n², linearized at the flow rate Q0, the head change ΔH_Δn=2×H0×Δn÷n0=2×20×(−24.5)÷1480=−0.661m, which is converted to the nozzle inlet pressure influence ΔP_influence=ρ×g×ΔH_Δn÷10 5 =1050×9.81×(−0.661)÷10 5=−0.068bar. If only speed compensation Δn is performed without valve correction, the nozzle inlet pressure will be 0.068bar lower, exceeding the allowable deviation of ±0.05bar, and needs to be eliminated through secondary valve compensation. From the pressure balance relationship P_nozzle = P_pump − ΔP_pipe − ΔP_valve, when the pump speed and flow rate are fixed, ∂P_nozzle / ∂α = −∂ΔP_valve / ∂α. Let the secondary compensation opening Δα2 satisfy (−∂ΔP_valve / ∂α)×Δα2 = −ΔP_influence. Simplifying, we get Δα2 = ΔP_influence ÷ (∂ΔP_valve / ∂α). ∂ΔP_valve / ∂α is approximated by difference at the current opening α using the Kv-α characteristic curve. Taking the difference step size Δα_test = 1%, we calculate ΔP_valve(α+1%) = Q0² × (ρ / ρ_water) ÷ Kv(α+1%)² and ΔP_valve(α−1%) = Q0² × (ρ_water) ÷ Kv(α+1%)² respectively. After dividing / ρwater)÷Kv(α−1%)², we take ∂ΔPvalve / ∂α≈[ΔPvalve(α+1%)−ΔPvalve(α−1%)]÷2. From the known 5% change in opening of S105, the pressure drop change caused by the change is −0.05bar, so we get ∂ΔPvalve / ∂α=−0.050÷5=−0.010bar / %, and substituting it, we get Δα2=(−0.068)÷(−0.010)=+6.8%. That is, on the basis of the already adjusted opening Δα of S105, the valve needs to be opened by an additional 6.8% to reduce the valve pressure drop by another 0.068bar to completely offset the decrease in nozzle inlet pressure caused by speed compensation. The speed compensation amount Δn (speed reduced from 1480 rpm to 1455.5 rpm) and the valve opening secondary compensation amount Δα2 (an additional 6.8% increase on the existing opening) are combined into a set of linkage correction commands, which are synchronously issued to the frequency converter and the flow and pressure regulating valve actuator within the same control cycle. The frequency converter drives the motor according to the target speed n0 + Δn, and the flow and pressure regulating valve actuator adjusts the opening according to the target opening α + Δα + Δα2. This enables the slurry flow rate and nozzle inlet pressure to return to their respective target values ​​simultaneously in one correction, fundamentally eliminating the problem of repeated coupling oscillation caused by flow correction affecting pressure and pressure correction affecting flow rate in step-by-step regulation.

[0065] The following provides a more detailed description of the process of the method provided in this implementation. Please refer to [link / reference]. Figure 2 This is another flowchart illustrating the circulating pump valve linkage control method in this application embodiment.

[0066] S201. When the rotational speed of the circulating pump and the opening degree of the flow regulating and pressure regulating valve are both in a steady state, monitor the pressure residual between the actual value of the nozzle inlet pressure and the target value.

[0067] Steady state refers to the operating state where the speed of the circulating pump and the opening of the flow and pressure regulating valve no longer change. The criteria for determination are that within multiple consecutive sampling cycles (e.g., 30 consecutive times with a 1-second sampling interval), the change in the circulating pump speed does not exceed 0.1% of the rated speed, and the change in the valve opening does not exceed 0.5%. Meeting these conditions constitutes a steady state. The actual nozzle inlet pressure is a slurry pressure measurement continuously collected by a remote pressure transmitter installed at the inlet pipe of the spray layer, in bar, reflecting the actual pressure state of the current spray operation. For example, a measurement value of 0.72 bar at a certain moment. The target nozzle inlet pressure is a pressure setpoint preset according to the nozzle atomization performance requirements. In this method, it is set to 0.7 bar, with an allowable deviation range of ±0.05 bar, corresponding to an atomized particle size of 2300~2500 μm. Pressure residual is the difference between the actual value and the target value of the nozzle inlet pressure. The calculation formula is "pressure residual = P actual - P target". A positive value indicates that the actual pressure is too high, and a negative value indicates that the actual pressure is too low. For example, when the actual value is 0.72 bar, the residual is +0.02 bar.

[0068] After valve adjustment in S105 is completed, the control system continuously monitors the circulating pump speed and the opening of the flow and pressure regulating valve at a fixed sampling period. Steady-state determination uses a sliding window method: within a window of length N sampling points, if the speed range does not exceed 0.1% of the rated speed and the opening range does not exceed 0.5%, the system is confirmed to have entered steady state. The window length N is adjusted based on the system response time; for example, N=30 (corresponding to 30 seconds). After confirming steady state, the pressure residual is calculated using the real-time measurement value from the remote pressure transmitter. The calculation formula is "Pressure residual = P actual - P target", and the residual value and its duration are continuously recorded. If the absolute value of the residual is within ±0.05 bar, the system is considered to be operating normally, and subsequent correction procedures are not triggered. If the absolute value of the residual continuously exceeds the allowable range, the residual value and its duration are transmitted to S202 as input data for slurry density deviation diagnosis. The purpose of steady-state pre-judgment is to distinguish between the deviation of the actual physical property parameters and the transient pressure disturbance during the dynamic adjustment transition process, so as to avoid the density correction process being mistakenly triggered by the short-term pressure deviation during the adjustment transition period.

[0069] S202. When the pressure residual exceeds the preset threshold and the duration exceeds the preset time, the current slurry density estimate is calculated using the pressure balance relationship based on the current pump speed, valve opening and current estimated flow rate.

[0070] The preset threshold is the pressure residual threshold that triggers the slurry density back-calculation process. It is determined based on the measurement and control accuracy of the pressure sensor, for example, set to 0.02 bar, meaning that the process is triggered when the absolute value of the residual is greater than 0.02 bar. The preset duration is the duration condition for excluding transient interference, for example, set to 60 seconds, meaning that the residual exceeding the limit must last for more than 60 seconds before the density back-calculation is initiated, preventing the correction process from being mistakenly triggered due to brief operating disturbances. The slurry density estimate is the result of inversely solving the pressure balance equation under the condition that the current pump speed, valve opening, and flow rate are known. It is denoted as ρ estimate and the unit is kg / m³. It reflects the actual physical properties of the slurry after changes in the content of solid particles such as gypsum and calcium carbonate. For example, if the initial density is set to 1050 kg / m³, and the back-calculated density is 1071 kg / m³, it indicates that the solid content of the slurry has increased.

[0071] When the absolute value of the pressure residual continuously exceeds a preset threshold (e.g., 0.02 bar) during steady-state operation and the duration exceeds a preset duration (e.g., 60 seconds), the slurry density back-calculation program is initiated. The theoretical basis for density back-calculation is that in the pressure balance equation expressed in terms of head (unit: m water column), the circulating pump head Hpump(Q, n), the pipeline pressure drop head hpipe(Q), and the valve pressure drop head hvalve(Q, α) are all independent of the slurry density; while the conversion relationship between the nozzle inlet pressure Pnozzle(unit: Pa) and its corresponding head is "Pnozzle = ρ × g × Hnozzle", where "Hnozzle = Hpump - hpipe - hvalve". Therefore, the back-calculation formula for the density estimate is:

[0072] ρ estimate = P_nozzle actual ÷ (g × (H_pump(Q, n) - h_pipeline(Q) - h_valve(Q, α)))

[0073] The specific steps are as follows: ① Read the inverter feedback speed n, valve opening α, and valve pressure drop h_valve measured in real time by the valve differential pressure detection device, as well as the actual value of nozzle inlet pressure P_nozzle. Solve the pressure balance equation simultaneously to obtain the current estimated flow rate Q; ② Calculate Hpump(Q, n) by looking up or interpolating the flow-head characteristic curve family of circulating pumps; ③ Calculate the pipeline pressure loss head by the pipeline resistance characteristic "hpipeline = kpipeline × Q²"; ④ The valve pressure drop head hvalve is directly measured by the valve differential pressure detection device (this item is independent of density in head units); ⑤ Calculate the nozzle inlet head Hnozzle = Hpump - hpipeline - hvalve; ⑥ Substitute the actual P_nozzle collected by the remote pressure transmitter into the above formula to solve for ρ estimation. For example, when the pressure balance equation is solved simultaneously to obtain Q=5000m³ / h, n=1450rpm, and α=65%, the calculated nozzle H=7.14m, while the actual nozzle P=0.75bar=75000Pa, then the estimated ρ=75000÷(9.81×7.14)≈1071kg / m³, which is about 2% higher than the initial density setting of 1050kg / m³.

[0074] S203. Compare the estimated slurry density with the initial density value used in the pressure balance relationship. If the deviation between the two exceeds the density deviation threshold, update the slurry density parameter in the pressure balance relationship to the estimated slurry density.

[0075] The initial density value, denoted as ρ0, is the baseline parameter for slurry density set when establishing the pressure balance relationship. It is typically taken as a typical value of slurry density under the system's design conditions, such as 1050 kg / m³ (approximately 1.05 g / cm³). This value is used for the initial calculation of various pressure quantities in the pressure balance equation and remains unchanged after the system's initial commissioning or the last parameter update until a new update is triggered. The density deviation threshold, denoted as Δρ threshold, is the threshold for determining whether the slurry density has significantly deviated. For example, it is set to 20 kg / m³. This means that if the difference between the estimated density and the initial density exceeds 20 kg / m³, a substantial change in density is considered, triggering a parameter update; if it is below this threshold, it is considered measurement noise or a temporary fluctuation, and no update operation is performed.

[0076] The estimated slurry density ρ, obtained from the back-calculation of S202, is compared with the density parameter ρ0 currently used in the pressure balance relationship, and the density deviation "Δρ = |ρ_estimated - ρ0|" is calculated. If Δρ does not exceed the Δρ threshold (e.g., 20 kg / m³), it is determined to be a measurement error or a temporary operating condition disturbance, and the density parameter ρ0 in the pressure balance relationship remains unchanged, without being updated. If Δρ exceeds the Δρ threshold, the slurry density parameter in the pressure balance relationship is updated from ρ0 to ρ_estimated, and all subsequent pressure calculations involving density use ρ_estimated. For example, if the initial density ρ0 = 1050 kg / m³, the estimated value ρ_estimated = 1071 kg / m³, and the deviation Δρ = 21 kg / m³, exceeding the threshold of 20 kg / m³, an update is triggered, the density parameter is corrected to 1071 kg / m³, and written into the pressure balance equation. The update operation only modifies the density parameter, while other model parameters such as the pipeline resistance coefficient k, the pipeline and valve Kv characteristic curves remain unchanged. This ensures that the structural integrity of the pressure balance equation is not affected, and only the density-related calculation terms are corrected, thereby eliminating the impact of slurry property drift on the model accuracy.

[0077] S204. Recalculate the target opening degree of the flow regulating valve and / or the target speed of the circulating pump based on the updated pressure balance relationship to eliminate the nozzle inlet pressure deviation caused by changes in slurry density.

[0078] The target opening degree, denoted as α*, is the setpoint for the flow and pressure regulating valve, recalculated based on the new pressure balance relationship after the density parameters are updated. It is used to rematch the nozzle inlet pressure target under the current actual slurry properties. The target rotational speed, denoted as n*, is the setpoint for the circulating pump speed, recalculated based on the new pressure balance relationship after the density parameters are updated. When the target opening degree exceeds the valve's adjustable range, the rotational speed is adjusted synchronously to ensure the system simultaneously meets both flow and pressure targets under the new density conditions.

[0079] Substitute the updated density value ρ estimate into the pressure balance equation, and constrain the current target slurry flow rate Q and the nozzle inlet pressure target value P (0.7 bar), recalculate the target opening and / or target rotational speed according to the following steps: First, based on the current pump rotational speed n and the target Q, calculate the circulating pump head Hpump(Qtarget, n) from the circulating pump flow-head characteristic curve, and convert it to pressure: "Ppump = ρ estimate × g × Hpump". Second, calculate the pipeline pressure loss using the updated density: "ΔPpipeline = ρ estimate × g × kpipeline × Qtarget²". Third, calculate the pressure drop required by the valve based on the pressure balance equation: "ΔPvalve = Ppump - ΔPpipeline - Ptarget". Fourth, substitute ΔPvalve and the target Q into the valve flow coefficient formula: "Kv = Qtarget ÷ √(ΔPvalve ÷ (ρ estimate / ρwater))", and find the corresponding target opening α* from the Kv-α characteristic curve. If α is within the valve's adjustable range (5%~90%), then α is used as the new valve setting value and executed. If α exceeds the adjustable range, then the boundary value (5% or 90%) is taken, and the pump speed n is solved in reverse simultaneously. Under the condition of keeping the target Q unchanged, the valve pressure drop is adjusted to fall back into the adjustable range. After obtaining the target speed n, it is simultaneously sent to the frequency converter and valve actuator to eliminate the nozzle inlet pressure deviation caused by the change in slurry density.

[0080] S205. Obtain the pressure drop ratio between the valve pressure drop of the flow regulating valve and the total head of the circulating pump under the current operating conditions.

[0081] Valve pressure drop is the pressure difference consumed when slurry flows through the regulating valve, denoted as ΔP_valve, in bar. A larger value indicates more severe valve throttling and more wasted energy on the valve. Valve pressure drop is calculated using the pressure balance equation from the pump outlet pressure, pipeline pressure loss, and nozzle inlet pressure, rather than being directly measured by pressure sensors on both sides of the valve. The total head equivalent pressure of the circulating pump is the total pressure provided by the circulating pump at the current operating point, denoted as P_p_total, in bar. It is obtained by substituting the current pump speed and flow rate into the performance curve to obtain the head, and then converting it using "P_p_total = ρ_estimated × g × H_p_pump". The pressure drop ratio is the ratio of valve pressure drop to the total head equivalent pressure of the circulating pump, denoted as "r = ΔP_valve ÷ P_p_total". It is dimensionless and reflects the proportion of valve throttling losses to the total output pressure of the circulating pump under the current operating conditions. It is the basis for determining whether energy-saving re-optimization is triggered.

[0082] Under steady-state operating conditions, the pressure drop ratio r is calculated through the following steps: Read the inverter feedback speed n, the valve pressure drop h_valve measured in real time by the valve differential pressure detection device, and the actual value of the nozzle inlet pressure P_nozzle collected by the remote pressure transmitter; solve the pressure balance equation simultaneously to obtain the current estimated flow rate Q; calculate the pipeline pressure loss "ΔP_pipeline = ρ_estimated × g × k_pipeline × Q²" from the pipeline resistance characteristics; calculate the valve pressure drop "ΔP_valve = ρ_estimated × g × H_pump(Q, n) - ΔP_pipeline - P_nozzle" from the pressure balance equation; calculate the total head converted to pressure "P_pump_total = ρ_estimated × g × H_pump(Q, n)" from the circulating pump performance curve; finally, calculate the pressure drop ratio "r = ΔP_valve ÷ P_pump_total". For example, when the total head of the circulating pump is equivalent to a pressure of 3.0 bar, the pipeline pressure loss is 1.5 bar, and the nozzle inlet pressure is 0.7 bar, the valve pressure drop is 0.8 bar, and the pressure drop ratio r = 0.8 ÷ 3.0 ≈ 26.7%. This ratio is continuously calculated at a fixed period (e.g., updated every 30 seconds) and compared with the energy-saving re-optimization trigger threshold. When r exceeds the trigger threshold (e.g., 25%), it indicates that the valve throttling loss is too large, and there is room for energy-saving optimization by reducing the pump speed and increasing the valve opening, thus triggering the re-optimization solution process of S206.

[0083] S206. When the pressure drop ratio exceeds the preset energy-saving re-optimization trigger threshold, based on the pressure balance relationship, the current nozzle inlet pressure target value and the current flow rate value are used as equality constraints, and the rotational speed of the circulating pump and the opening degree of the flow regulating valve are used as variables to be solved, to solve the combination of target rotational speed and target opening degree that minimizes the pressure drop of the valve.

[0084] The energy-saving re-optimization trigger threshold is the pressure drop ratio threshold for initiating energy-saving optimization solutions. For example, it is set to 25%. If the pressure drop is below this threshold, re-optimization will not be performed to avoid excessively frequent adjustments that could affect system stability. Equality constraints are fixed conditions that must be met during the optimization solution, including the nozzle inlet pressure equaling the target value (P_nozzle = P_target = 0.7 bar) and the current calculated flow rate remaining constant (Q = Q_current), ensuring that the optimized system still meets the desulfurization process requirements. The target speed and target opening combination (n, α)** is the optimal combination of circulating pump speed and valve opening that minimizes the valve pressure drop ΔP_valve, provided that the above equality and boundary constraints are satisfied.

[0085] When r exceeds the trigger threshold (e.g., 25%), with Q (current) and P (target) as equality constraints, and n and α as decision variables, an optimization problem is established: the objective function is to minimize ΔPvalve(Qcurrent, α, ρestimated), the constraints are the pressure balance equation "ρestimated × g × Hpump(Qcurrent, n) - ΔPpipeline(Qcurrent, ρestimated) - ΔPvalve = Ptarget", and the boundary constraints "minimum n ≤ n ≤ maximum n, 5% ≤ α ≤ 90%". From the constraint equations, it can be seen that under the condition that Qcurrent and Ptarget are fixed, "ΔPvalve = ρestimated × g × Hpump - ΔPpipeline - Ptarget", minimizing ΔPvalve is equivalent to minimizing Hpump(Qcurrent, n), that is, reducing the pump speed to the lowest feasible value that satisfies the constraints. The solution steps are as follows: Within the feasible range of n, candidate speeds are discretized and enumerated with a fixed step size (e.g., 10 rpm); for each candidate n, the performance curve is used to calculate the pump H (Q_current, n), and the corresponding ΔP_valve is calculated by substituting it into the constraint equation; ΔP_valve and Q_current are substituted into the valve flow coefficient formula "Kv*=Q_current ÷ √(ΔP_valve × ρ_water ÷ ρ_estimated)", and the corresponding valve opening α is found by reverse lookup from the Kv-α characteristic curve; it is checked whether α is within 5%~90%; all (n, α) combinations that satisfy the constraints are retained, and the combination with the smallest ΔP_valve (i.e., the smallest n) is taken as the optimal solution (n*, α*). For example, if the current operating point is (n0=1480 rpm, α0=40%), ΔP_valve=0.8 bar, after solving, we get (n*=1380 rpm, α*=78%), ΔP_valve*=0.2 bar, which reduces the valve pressure drop by 0.6 bar, corresponding to a pump shaft power reduction of about 15%, achieving the energy-saving optimization goal.

[0086] S207. Based on the difference between the current speed of the circulating pump and the target speed, and the difference between the current opening degree of the flow regulating valve and the target opening degree, a step-by-step migration path is generated. The step-by-step migration path includes multiple intermediate steps, each intermediate step corresponding to a set of intermediate speed values ​​and intermediate opening degree values. The speed change and opening change between two adjacent intermediate steps in the step-by-step migration path are determined according to the ratio between the partial derivative of the pump speed with respect to the nozzle inlet pressure and the partial derivative of the valve opening degree with respect to the nozzle inlet pressure in the pressure balance relationship, so that the nozzle inlet pressure change caused by the speed change in each intermediate step cancels out the nozzle inlet pressure change caused by the opening degree change.

[0087] The step-by-step migration path is an ordered adjustment sequence that smoothly migrates the operating point from the current state (n0, α0) to the target state (n*, α*). By decomposing the total adjustment into M consecutive intermediate steps, it avoids drastic fluctuations in nozzle inlet pressure caused by a single large adjustment. Each intermediate step corresponds to a set of intermediate speed values ​​and intermediate valve opening values, forming intermediate operating points on the path. The partial derivative ratio is the ratio of the partial derivatives of the nozzle inlet pressure with respect to pump speed and valve opening in the pressure balance relationship, i.e., the ratio of (∂P_nozzle / ∂n) to (∂P_nozzle / ∂α). This ratio quantifies the relative influence of unit speed change and unit opening change on nozzle inlet pressure at the current operating point, determining the ratio of the changes in the two in each step, so that their influence on pressure cancels each other out.

[0088] The total speed change Δntotal = n * - n0 and the total opening change Δαtotal = α * - α0 are decomposed into M steps (e.g., M = 10). The basic speed change for each step is "δn = Δntotal ÷ M". The corresponding opening change for each step is determined by the ratio of partial derivatives, and the calculation process is as follows: For the partial derivative ∂Pnozzle / ∂n, under the condition of fixed Q and α, according to the centrifugal pump proportional law Hpump is proportional to n², and the partial derivative of the pump outlet pressure "Ppump = ρestimated × g × Hpump(Q, n)" with respect to n is "∂Ppump / ∂n = 2 × ρestimated × g × Hpump ÷ n". The pipeline pressure loss and valve pressure drop do not change with n when Q and α are fixed, so "∂Pnozzle / ∂n = 2 × ρestimated × g × Hpump ÷ n > 0". For the partial derivative ∂P_nozzle / ∂α, under the condition of fixed Q and n, the valve pressure drop "ΔP_valve = (Q ÷ Kv(α))² × (ρ_estimated ÷ ρ_water) × 10⁻ 5 The partial derivative with respect to α is obtained by differential approximation of the Kv characteristic curve at the current opening degree. Since P_nozzle = P_pump - ΔP_pipeline - ΔP_valve, the valve pressure drop decreases when the valve is opened wider, and the nozzle pressure increases, therefore ∂P_nozzle / ∂α > 0. Based on the constant pressure condition "(∂P_nozzle / ∂n)×δn + (∂P_nozzle / ∂α)×δα = 0", the change in opening degree at each step is obtained:

[0089] δα = -(∂P_nozzle / ∂n) ÷ (∂P_nozzle / ∂α) × δn

[0090] Since n* < n0 (deceleration), δn < 0, deceleration causes the P nozzle to decrease; while α* > α0 (opening the valve), δα > 0, opening the valve makes ΔP valve decrease and the P nozzle increase, and the two offset each other. For example, at the current operating point, ∂P nozzle / ∂n = 0.0030 bar / rpm and ∂P nozzle / ∂α = 0.0050 bar / %, then the partial derivative ratio is 0.60. When δn = -10 rpm per step, δα = 0.60×10 = +6%. Generate the migration path for 10 intermediate steps: the i-th intermediate step corresponds to (ni, αi) = (n0 + i×δn, α0 + i×δα), i = 1, 2, …, 10, that is, gradually migrate from (1480 rpm, 40%) by each step of (-10 rpm, +6%). The influence of the rotational speed change and the opening change on the nozzle inlet pressure at each step on the path is equal in magnitude and opposite in direction, ensuring that the nozzle inlet pressure remains theoretically unchanged during the migration process.

[0091] S208. Adjust the rotational speed of the circulating pump and the opening of the flow regulating and pressure regulating valve in sequence according to this step-by-step migration path. After each intermediate step is executed, detect the actual value of the nozzle inlet pressure. If the deviation between the actual value and the target value exceeds the preset migration tolerance deviation, suspend the migration and correct the deviation through the flow regulating and pressure regulating valve, and then continue to execute the next intermediate step.

[0092] The migration tolerance deviation is the maximum range allowed for the nozzle inlet pressure to deviate from the target value during the step-by-step migration execution, which is determined according to the stability requirement of the nozzle pressure in the desulfurization process. For example, it is set to ±0.03 bar, which is less than the allowable deviation of the nozzle during normal operation (±0.05 bar), providing an additional safety margin during the migration process. Suspending the migration means that when the nozzle inlet pressure deviation exceeds the migration tolerance deviation after a certain intermediate step is executed, stop issuing subsequent intermediate step instructions and transfer to the operation state of the valve single adjustment and correction mode. After the pressure deviation is corrected, resume the migration process.

[0093] Following the step-by-step migration path generated in S207, each intermediate step is executed sequentially. The execution flow of step i is as follows: An intermediate speed command ni is sent to the frequency converter, and an intermediate opening command αi is simultaneously sent to the flow regulating and pressure regulating valve actuator; wait for the actuator to complete its response, ensuring both the speed and opening reach the set values ​​(response time not exceeding 1 second); collect the measured value Pactual from the remote pressure transmitter and calculate the pressure deviation "δi = Pactual - Ptarget". If |δi| does not exceed 0.03 bar, the command for step i+1 (n(i+1), α(i+1)) is sent to advance the migration process. If |δi| exceeds 0.03 bar, the migration is paused, the current speed ni remains unchanged, and only the opening of the flow regulating and pressure regulating valve is adjusted to correct the pressure deviation: when δi > 0 (pressure too high), the valve opening is increased; when δi < 0 (pressure too low), the valve opening is decreased, using proportional-integral control until |δi| does not exceed 0.03 bar. After the correction is completed, record the actual valve opening αi correction. Using (ni, αi correction) as the new reference point, based on the remaining migration amount Δn_remaining = n* - ni and Δα_remaining = α* - αi correction, and the remaining number of steps Mi, recalculate δn and δα for each subsequent step according to the partial derivative ratio method in S207, update the remaining part in the step-by-step migration path, and then continue to execute step i+1. Until all M intermediate steps are completed, the circulating pump speed reaches n*, and the flow regulating and pressure regulating valve opening reaches α*, the step-by-step migration process of energy saving re-optimization is completed. The valve pressure drop is reduced from the high value before optimization to the minimum target value, and the circulating pump operates at a lower speed, achieving the energy saving target.

[0094] The desulfurization system in the embodiments of this invention is described below from the perspective of hardware processing. Please refer to [link / reference needed]. Figure 3 This is a schematic diagram of the physical device structure of a desulfurization system in an embodiment of this application.

[0095] It should be noted that, Figure 3 The structure of the desulfurization system shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of the present invention.

[0096] like Figure 3As shown, the desulfurization system includes a Central Processing Unit (CPU) 301, which can perform various appropriate actions and processes based on a program stored in a Read-Only Memory (ROM) 302 or a program loaded from a storage section 308 into a Random Access Memory (RAM) 303, such as performing the methods described in the above embodiments. The RAM 303 also stores various programs and data required for system operation. The CPU 301, ROM 302, and RAM 303 are interconnected via a bus 304. An Input / Output (I / O) interface 305 is also connected to the bus 304.

[0097] The following components are connected to I / O interface 305: input section 306 including audio input devices, push-button switches, etc.; output section 307 including liquid crystal display (LCD) and audio output devices, indicator lights, etc.; storage section 308 including hard disks, etc.; and communication section 309 including network interface cards such as LAN (Local Area Network) cards, modems, etc. Communication section 309 performs communication processing via a network such as the Internet. Drive 310 is also connected to I / O interface 305 as needed. Removable media 311, such as disks, optical disks, magneto-optical disks, semiconductor memories, etc., are installed on drive 310 as needed so that computer programs read from them can be installed into storage section 308 as needed.

[0098] In particular, according to embodiments of the present invention, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of the present invention include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing computer programs for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication section 309, and / or installed from removable medium 311. When the computer program is executed by central processing unit (CPU) 301, it performs the various functions defined in the present invention.

[0099] It should be noted that specific examples of computer-readable storage media may include, but are not limited to: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), flash memory, optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0100] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. Each block in a flowchart or block diagram may represent a module, program segment, or portion of code, which contains one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those shown in the drawings.

[0101] Specifically, the desulfurization system in this embodiment includes a processor and a memory. The memory stores a computer program. When the computer program is executed by the processor, it implements the circulating pump valve linkage control method provided in the above embodiment.

[0102] In another aspect, the present invention also provides a computer-readable storage medium, which may be included in the desulfurization system described in the above embodiments; or it may exist independently and not assembled into the desulfurization system. The storage medium carries one or more computer programs that, when executed by a processor of the desulfurization system, cause the desulfurization system to implement the circulating pump valve linkage control method provided in the above embodiments.

[0103] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0104] As used in the above embodiments, depending on the context, the term "when..." can be interpreted as meaning "if...", "after...", "in response to determining...", or "in response to detecting...". Similarly, depending on the context, the phrase "when determining..." or "if (the stated condition or event) is interpreted as meaning "if determining...", "in response to determining...", "when (the stated condition or event) is detected", or "in response to detecting (the stated condition or event)".

[0105] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. This program can be stored in a computer-readable storage medium, and when executed, it can include the processes described in the above method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM or random access memory (RAM), magnetic disks, or optical disks.

Claims

1. A method for coordinated control of a circulating pump and its valves, characterized in that, The method is applied to a desulfurization system, which includes an absorption tower, a circulating pump, a pipeline system, a flow regulating and pressure regulating valve, and a spray layer. The circulating pump delivers slurry to the spray layer through the pipeline system. The flow regulating and pressure regulating valve is installed in the pipeline system. The spray layer includes a plurality of nozzles. The flow rate and head characteristics of the circulating pump, the flow rate and pressure loss characteristics of the pipeline system, and the flow coefficient characteristics of the flow regulating and pressure regulating valve are obtained. Establish a pressure balance relationship between the circulating pump outlet pressure and pipeline pressure loss and valve pressure drop, and set a target value for the nozzle inlet pressure; The target slurry flow rate is determined based on the flue gas flow rate and pollutant concentration; The circulating pump speed that satisfies the target slurry flow rate and the target nozzle inlet pressure is calculated based on the pressure balance relationship, and the circulating pump is adjusted to the circulating pump speed by means of a frequency converter; The actual value of the nozzle inlet pressure is detected in real time. When the actual value of the nozzle inlet pressure deviates from the target value of the nozzle inlet pressure, the valve pressure drop is changed by adjusting the opening of the flow regulating and pressure regulating valve so that the actual value of the nozzle inlet pressure returns to the target value.

2. The method according to claim 1, characterized in that, The steps of establishing a pressure balance relationship between the circulating pump outlet pressure and pipeline pressure loss and valve pressure drop, and setting a target value for the nozzle inlet pressure, specifically include: Obtain the flow-head characteristic curve of the circulating pump at different speeds, the flow-pressure loss characteristic curve of the pipeline system at different flow rates, and the valve pressure drop characteristics of the flow regulating and pressure regulating valve at different opening degrees and flow rates; A pressure balance equation is established based on the principle of energy conservation in fluid mechanics. The pressure balance equation states that the sum of the circulating pump head and the pipeline pressure loss head, the valve pressure drop head and the nozzle inlet pressure head is equal. The target value of the nozzle inlet pressure is set according to the nozzle atomization performance requirements of the nozzle.

3. The method according to claim 1, characterized in that, The step of calculating the circulating pump speed to meet the target slurry flow rate and the target nozzle inlet pressure based on the pressure balance relationship, and adjusting the circulating pump to the specified circulating pump speed via a frequency converter, specifically includes: The range of candidate operating points is determined based on the target slurry flow rate on the flow-head characteristic curve of the circulating pump. For each operating point within the candidate operating point range, the pressure drop value that the flow regulating valve needs to bear is calculated in reverse according to the pressure balance equation, and the corresponding valve opening value is calculated through the valve flow coefficient characteristics of the flow regulating valve. Candidate operating points whose valve opening values ​​exceed the adjustable range of the flow and pressure regulating valve are eliminated, and the operating point with the lowest circulating pump operating power is selected as the optimal operating point from the remaining candidate operating points. Adjust the circulating pump to the speed corresponding to the optimal operating point, and adjust the flow and pressure regulating valve to the opening degree corresponding to the optimal operating point.

4. The method according to claim 1, characterized in that, The step of adjusting the opening of the flow regulating and pressure regulating valve to change the valve pressure drop when the actual value of the nozzle inlet pressure deviates from the target value, so that the actual value of the nozzle inlet pressure returns to the target value, specifically includes: Real-time acquisition of the actual value of the nozzle inlet pressure and calculation of the deviation between the actual value of the nozzle inlet pressure and the target value of the nozzle inlet pressure; When the actual value of the nozzle inlet pressure is lower than the target value of the nozzle inlet pressure, and the zero flow head of the circulating pump is greater than or equal to the sum of the pipeline pressure loss head, the valve pressure drop head, and the nozzle inlet pressure head, the valve opening of the flow regulating valve is reduced so that the operating point of the circulating pump shifts to the left along the flow head characteristic curve. When the increase in the circulating pump head is greater than the increase in the valve pressure drop, the nozzle inlet pressure increases. When the actual value of the nozzle inlet pressure is higher than the target value of the nozzle inlet pressure, and the actual head of the circulating pump is greater than the sum of the pipeline pressure loss head, the valve pressure drop head, and the nozzle inlet pressure head, the valve opening of the flow regulating and pressure regulating valve is increased to shift the operating point of the circulating pump to the right along the flow head characteristic curve. When the decrease in the head of the circulating pump is greater than the decrease in the valve pressure drop, the nozzle inlet pressure decreases. Repeat the above steps until the actual value of the nozzle inlet pressure returns to the allowable deviation range of the nozzle inlet pressure target value.

5. The method according to any one of claims 1-4, characterized in that, After the step of changing the valve pressure drop by adjusting the opening of the flow regulating and pressure regulating valve to bring the actual value of the nozzle inlet pressure back to the target value, the method further includes: The slope of the flow-head characteristic curve of the circulating pump at the current operating point and the rate of change of flow-pressure loss of the pipeline system at the current estimated flow rate are obtained. The current estimated flow rate is obtained by solving the current speed of the circulating pump fed back by the frequency converter, the valve pressure drop measured in real time by the valve differential pressure detection device, and the actual value of the nozzle inlet pressure, based on the pressure balance relationship. The change in valve pressure drop is calculated based on the change in the opening of the flow regulating valve and the current estimated flow rate. The flow offset caused by the change in opening is then calculated by combining the slope of the flow head characteristic curve and the flow pressure loss change rate. Based on the flow rate offset and the pressure balance relationship, the amount of circulating pump speed compensation required to bring the flow rate back to the target slurry flow rate is calculated synchronously, as well as the impact of the head change caused by the speed compensation on the nozzle inlet pressure. The speed compensation amount and the valve opening secondary compensation amount required to offset the influence amount are treated as a set of linkage correction commands and simultaneously sent to the frequency converter and the flow and pressure regulating valve, so that the flow rate and nozzle inlet pressure return to their respective target values ​​in one correction.

6. The method according to any one of claims 1-4, characterized in that, After the step of changing the valve pressure drop by adjusting the opening of the flow regulating and pressure regulating valve to bring the actual value of the nozzle inlet pressure back to the target value, the method further includes: When the rotational speed of the circulating pump and the opening degree of the flow regulating and pressure regulating valve are both in a steady state, monitor the pressure residual between the actual value of the nozzle inlet pressure and the target value; When the pressure residual exceeds the preset threshold and the duration exceeds the preset time, the current slurry density estimate is calculated back using the pressure balance relationship based on the current pump speed, valve opening and current estimated flow rate. The estimated slurry density is compared with the initial density value used in the pressure balance relationship. If the deviation between the two exceeds the density deviation threshold, the slurry density parameter in the pressure balance relationship is updated to the estimated slurry density. The target opening of the flow regulating valve and / or the target rotational speed of the circulating pump are recalculated based on the updated pressure balance relationship to eliminate the nozzle inlet pressure deviation caused by changes in slurry density.

7. The method according to any one of claims 1-4, characterized in that, After the step of changing the valve pressure drop by adjusting the opening of the flow regulating and pressure regulating valve to bring the actual value of the nozzle inlet pressure back to the target value, the method further includes: Obtain the pressure drop ratio between the valve pressure drop of the flow regulating and pressure regulating valve and the total head of the circulating pump under the current operating conditions; When the pressure drop ratio exceeds the preset energy-saving re-optimization trigger threshold, based on the pressure balance relationship, the current nozzle inlet pressure target value and the current flow rate value are used as equality constraints, and the rotational speed of the circulating pump and the opening of the flow regulating and pressure regulating valve are used as variables to be solved, to solve for the target rotational speed and target opening combination that minimizes the valve pressure drop. A step-by-step migration path is generated based on the difference between the current rotational speed of the circulating pump and the target rotational speed, and the difference between the current opening degree of the flow regulating and pressure regulating valve and the target opening degree. The step-by-step migration path includes multiple intermediate steps, each intermediate step corresponding to a set of intermediate rotational speed values ​​and intermediate opening degree values. The rotational speed change and opening degree change between two adjacent intermediate steps in the step-by-step migration path are determined based on the ratio between the partial derivative of the pump rotational speed with respect to the nozzle inlet pressure and the partial derivative of the valve opening degree with respect to the nozzle inlet pressure in the pressure balance relationship, so that the change in nozzle inlet pressure caused by the change in rotational speed in each intermediate step cancels out the change in nozzle inlet pressure caused by the change in opening degree. According to the step-by-step migration path, the speed of the circulating pump and the opening of the flow regulating and pressure regulating valve are adjusted sequentially. After each intermediate step is executed, the actual value of the nozzle inlet pressure is detected. If the deviation between the actual value and the target value exceeds the preset migration allowable deviation, the migration is paused and the deviation is corrected by the flow regulating and pressure regulating valve before continuing to execute the next intermediate step.

8. A desulfurization system, characterized in that, The desulfurization system includes: one or more processors and a memory; the memory is coupled to the one or more processors, the memory is used to store computer program code, the computer program code including computer instructions, and the one or more processors call the computer instructions to cause the desulfurization system to perform the method as described in any one of claims 1-7.

9. A computer-readable storage medium comprising instructions, characterized in that, When the instruction is executed on the desulfurization system, it causes the desulfurization system to perform the method as described in any one of claims 1-7.

10. A computer program product, characterized in that, When the computer program product is run on the desulfurization system, it causes the desulfurization system to perform the method as described in any one of claims 1-7.

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