Series-parallel pressure control method and system for air preheater preceding tube heating furnace

Abstract

The application provides a series-parallel pressure control method and system of a pipe heating furnace pre-air preheater, relates to the thermal control technical field of a pipe heating furnace combustion system, and the method comprises the following steps: collecting pressure, hot water flow and temperature data of each temperature section preheater in real time during the operation of the heating furnace; calculating the heat load value and the pressure difference parameter based on the data, and generating a pressure prediction sequence of a future time step by using the system dynamics equation of the MPC model; processing the prediction sequence by using a rolling horizon optimization algorithm to obtain an optimal control instruction sequence that meets the constraint condition; generating the opening degree instruction of the stop valve on the bypass pipeline according to the sequence, combining the branch pipe pressure state, and dynamically adjusting the valve opening degree through a distributed control architecture to realize the pressure balance and coordinated control of the series-parallel structure of the pipe heating furnace pre-air preheater. The application improves the pressure control precision and the system thermal efficiency of the pipe heating furnace pre-air preheater in the series-parallel structure.

Description

Technical Field

[0001] This application relates to the field of thermal control technology for combustion systems of tubular furnaces, and in particular to a series-parallel pressure control method and system for a preheater of a tubular furnace. Background Technology

[0002] In large tubular furnace systems in the petrochemical industry, the preheater plays a crucial role in reducing energy consumption by recovering waste heat to raise the temperature of the combustion air. Due to the high heat load and numerous burners in the furnace, the preheaters are often arranged in groups. The pressure balance and flow distribution among the preheater units directly affect the system's thermal efficiency and operational stability. Therefore, a control method is needed that can coordinate the hydraulic conditions among multiple preheater groups in real time and adapt to variable load operation.

[0003] Currently, related systems often employ a branch pipe pressure control method based on fixed-parameter PID regulation. This scheme sets pressure detection points on the supply and return water branch pipes, and performs independent closed-loop control of each branch regulating valve based on the deviation between the measured pressure and the set value, thereby maintaining the branch pipe pressure within the allowable range and ensuring the basic hydraulic balance of the preheater.

[0004] However, when dealing with the operation of multiple preheaters in series and parallel and the frequent fluctuation of heat load, this type of method has problems such as delayed adjustment response, inter-group coupling effect, and frequent valve operation, which leads to large system pressure fluctuations, and the actual flow of some preheater units deviates from the design conditions, affecting the overall heat recovery effect, while increasing the equipment regulation load and energy consumption. Summary of the Invention

[0005] This application provides a series-parallel pressure control method and system for a preheater of a tubular furnace, which solves the problems of low pressure control accuracy and poor system thermal efficiency of the preheater of a tubular furnace in a series-parallel structure in the prior art.

[0006] To address the aforementioned technical problems, in a first aspect, this application provides a method for controlling the series and parallel pressure of a preheater for a tubular heating furnace, comprising:

[0007] During the operation of the tubular heater, pressure data at the corresponding locations are collected in real time by pressure sensors installed in the water supply branch pipe, return branch pipe, inlet and outlet of the series pre-air preheater group, and bypass pipe. At the same time, the hot water flow data flowing through each branch and the temperature data of the two temperature-section pre-air preheaters are monitored. The bypass pipe is located between the two temperature-section pre-air preheaters in the series pre-air preheater group.

[0008] Based on the pressure data, the hot water flow rate data, and the temperature data, calculate the heat load value and pressure difference parameter;

[0009] The system dynamics equations of the MPC model are used to process the heat load value and the pressure difference parameter to generate a pressure prediction sequence for future time steps;

[0010] Based on the pressure prediction sequence, a rolling time-domain optimization algorithm is used to perform multi-step prediction optimization processing to obtain the optimal control command sequence that meets the preset optimization conditions.

[0011] Based on the optimal control command sequence, an opening command for the shut-off valve on the bypass pipeline is generated. Based on the opening command and the pressure status of the water supply branch and the return branch, a distributed control architecture is used to adjust the valve opening on the bypass pipeline to achieve pressure balance and coordinated control within the series preheater group and among multiple parallel series preheater groups.

[0012] Optionally, the process of using the system dynamics equations of the MPC model to process the heat load value and the pressure difference parameter to generate a pressure prediction sequence for future time steps includes:

[0013] Based on the heat load value and the pressure difference parameter, the fluid mass conservation equation and momentum conservation equation in the system dynamics equation of the MPC model are used to establish the dynamic coupling relationship between pressure, flow rate and temperature.

[0014] Based on the dynamic coupling relationship, and combined with the current water supply branch pressure, return branch pressure, hot water flow rate, and temperature data of the two temperature-segment preheaters, the pressure change trajectory of the water supply branch and return branch in multiple consecutive time steps is predicted through forward iterative calculation.

[0015] In each iteration of the calculation, the pressure change trajectory is dynamically corrected based on the heat load value, and a pressure prediction sequence is formed based on the corrected pressure change trajectory.

[0016] Optionally, based on the dynamic coupling relationship, and combining the current water supply branch pressure, return branch pressure, hot water flow rate, and temperature data of the two temperature-section pre-air preheaters, the pressure change trajectory of the water supply branch and return branch over multiple consecutive time steps is predicted through forward iterative calculation, including:

[0017] The initial system state is based on the current water supply branch pressure, return branch pressure, hot water flow rate, and temperature data of the two temperature-section preheaters.

[0018] Based on the dynamic coupling relationship, the changes in pressure of the supply branch pipe and the return branch pipe within the first time step are calculated.

[0019] The change is superimposed on the initial system state to obtain the predicted values ​​of the supply branch pressure and return branch pressure at the end of the first time step.

[0020] Using the system state at the end of the first time step as the new initial system state, the process of calculating the change and superimposing the system state is repeated to obtain the predicted values ​​of the water supply branch pressure and the return branch pressure for the second to Nth time steps in sequence, where N is an integer greater than 1.

[0021] Arrange the predicted pressure values ​​of the supply branch pipes and return branch pipes for all time steps in chronological order to form a pressure change trajectory.

[0022] Optionally, dynamically correcting the pressure change trajectory based on the heat load value includes:

[0023] Based on the heat load value and the specific heat capacity parameter of the hot water, calculate the temperature change caused by the hot water flowing through the preheater of each temperature range.

[0024] Based on the temperature change, combined with the fluid thermal expansion coefficient, the first pressure change component caused by the change in hot water density is calculated, and the second pressure change component caused by the change in fluid resistance is calculated through the viscosity-temperature characteristics.

[0025] The first pressure change component and the second pressure change component are combined to obtain the pressure change correction amount;

[0026] The pressure change correction is superimposed on the pressure prediction value at the corresponding time step in the pressure change trajectory to generate the corrected pressure change trajectory.

[0027] Optionally, calculating the heat load value and pressure difference parameter based on the pressure data, the hot water flow rate data, and the temperature data includes:

[0028] Extract the mass flow rate value from the hot water flow rate data, and extract the inlet and outlet temperature difference value from the temperature data;

[0029] Using the mass flow rate and the inlet / outlet temperature difference, the total heat transferred by the hot water in the preheater unit per unit time is calculated using the thermodynamic heat transfer formula, and the total heat value is used as the heat load value.

[0030] Based on the pressure data, the first pressure difference between the inlet of the high-temperature section pre-air ...

[0031] Optionally, the step of performing multi-step prediction optimization processing using a rolling time-domain optimization algorithm based on the pressure prediction sequence to obtain an optimal control command sequence that satisfies preset optimization conditions includes:

[0032] Calculate the pressure deviation between the pressure prediction value in the pressure prediction sequence and the pressure setpoint at the corresponding time step, and construct an optimization function with the objective of minimizing the pressure deviation;

[0033] Multiple physical constraints are introduced into the optimization function. The optimization function with the multiple physical constraints is solved by the rolling time-domain optimization algorithm to generate a sequence of shut-off valve control commands for multiple future time steps. The sequence of shut-off valve control commands is then used as the optimal control command sequence.

[0034] Optionally, the step of generating an opening command for the shut-off valve on the bypass pipeline based on the optimal control command sequence, and adjusting the valve opening on the bypass pipeline using a distributed control architecture based on the opening command and the pressure status of the supply and return branch pipes, includes:

[0035] The optimal control command sequence is converted into an opening percentage value, and the opening percentage value is used as the opening command.

[0036] The opening command is distributed to the local controller of the corresponding bypass pipeline, so that the local controller can generate a corresponding control signal according to the opening command, and drive the actuator of the shut-off valve to adjust the valve to the specified opening position based on the control signal;

[0037] The pressure status of the supply and return water branch pipes is monitored in real time. When the pressure status of any branch pipe deviates from the preset range, the opening correction amount is calculated by the central coordinator based on the pressure data of all series-connected pre-air preheater groups.

[0038] Based on the opening correction amount, the opening command is corrected to obtain a corrected opening command. The corrected opening command is then synchronously sent to the local controllers of the affected parallel series pre-air preheater groups through the distributed control architecture. Each local controller coordinates and adjusts the opening of the shut-off valve on its bypass pipeline according to the corrected opening command, so as to maintain pressure balance between the high-temperature section pre-air preheater and the low-temperature section pre-air preheater within the series pre-air preheater group, and at the same time, to achieve dynamic balance of branch pipe pressure among the parallel series pre-air preheater groups.

[0039] Secondly, this application provides a series-parallel pressure control system for a preheater of a tubular furnace, comprising:

[0040] The data acquisition module is used to collect pressure data in real time at the corresponding locations of the water supply branch pipe, return branch pipe, inlet and outlet of the series pre-air preheater group, and bypass pipe during the operation of the tubular heater. At the same time, it monitors the hot water flow data through each branch and the temperature data of the two temperature-section pre-air preheaters. The bypass pipe is located between the two temperature-section pre-air preheaters in the series pre-air preheater group.

[0041] The calculation module is used to calculate the heat load value and pressure difference parameter based on the pressure data, the hot water flow data, and the temperature data;

[0042] The generation module is used to process the heat load value and the pressure difference parameter using the system dynamics equations of the MPC model to generate a pressure prediction sequence for future time steps.

[0043] The optimization module is used to perform multi-step prediction optimization processing based on the pressure prediction sequence using a rolling time-domain optimization algorithm to obtain the optimal control command sequence that meets the preset optimization conditions.

[0044] The adjustment module is used to generate the opening command of the shut-off valve on the bypass pipeline according to the optimal control command sequence, and adjust the valve opening on the bypass pipeline according to the opening command and the pressure status of the water supply branch and the return branch, using a distributed control architecture, so as to achieve pressure balance and coordinated control within the series pre-air preheater group and among multiple series pre-air preheater groups in parallel.

[0045] Thirdly, this application provides an electronic device, comprising:

[0046] Memory, used to store computer programs;

[0047] A processor is configured to execute the computer program to implement the steps of the series-parallel pressure control method for the preheater of the tubular furnace as described in the first aspect above.

[0048] Fourthly, this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, can implement the steps of the series-parallel pressure control method for the preheater of a tubular furnace as described in the first aspect above.

[0049] This application provides a series-parallel pressure control method for a preheater of a tubular boiler. The method includes: during boiler operation, real-time pressure data is collected from pressure sensors located on the supply branch pipe, return branch pipe, inlet and outlet of the series preheater group, and bypass pipe; simultaneously, hot water flow data flowing through each branch pipe and temperature data of the two temperature-section preheaters are monitored. The bypass pipe is located between the two temperature-section preheaters within the series preheater group. Based on the pressure data, hot water flow data, and temperature data, a heat load value and pressure difference parameter are calculated; and M is used... The system dynamics equations of the PC model process the heat load value and the pressure difference parameter to generate a pressure prediction sequence for future time steps. Based on the pressure prediction sequence, a rolling time-domain optimization algorithm is used for multi-step prediction optimization to obtain an optimal control command sequence that meets preset optimization conditions. According to the optimal control command sequence, an opening command for the shut-off valve on the bypass pipeline is generated. Based on the opening command and the pressure status of the supply and return water branches, a distributed control architecture is used to adjust the valve opening on the bypass pipeline to achieve pressure balance and coordinated control within the series pre-air preheater group and among multiple parallel series pre-air preheater groups.

[0050] The technical solution provided in this application has the following beneficial effects:

[0051] This application achieves comprehensive perception of the system's operating status, providing a data foundation for precise control. It quantifies the system's thermodynamic and hydraulic characteristics, providing crucial input for model prediction. It anticipates system pressure change trends, providing a basis for active control decisions. It generates optimal control strategies that consider multiple objective constraints, improving control quality. Finally, it enables rapid, accurate, and coordinated control of system pressure, ensuring stable operation.

[0052] Furthermore, this application integrates heat load and pressure difference parameters, uses system dynamic equations based on the fluid conservation law to construct a dynamic coupling model of pressure, flow rate and temperature, and performs forward iterative calculations based on the current system state to predict future pressure trajectories. At the same time, dynamic corrections for the influence of heat load are introduced in the iterations, ultimately forming an accurate pressure prediction sequence.

[0053] Furthermore, by establishing an accurate dynamic coupling model and making forward-looking predictions, this method can effectively capture the inherent dynamic characteristics and thermodynamic effects of the system, improve the accuracy of pressure prediction and adaptability to changes in operating conditions, and lay a reliable foundation for subsequent optimized control.

[0054] These or other aspects of this application will become more apparent in the following description of the embodiments. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 A flowchart illustrating a series-parallel pressure control method for a preheater of a tubular furnace, provided as an embodiment of this application;

[0057] Figure 2 A schematic diagram illustrating a specific implementation of a series-parallel pressure control method for a preheater of a tubular furnace, provided in this application embodiment;

[0058] Figure 3 This is a schematic diagram of another specific implementation of a series-parallel pressure control method for a preheater of a tubular heating furnace, provided in an embodiment of this application.

[0059] Figure 4 This is a schematic diagram of the series-parallel pressure control system for a preheater of a tubular furnace, provided as an embodiment of this application. Detailed Implementation

[0060] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0061] The core of this application is to provide a series-parallel pressure control method for a preheater of a tubular heating furnace, and a flowchart of one specific embodiment is shown below. Figure 1 As shown, the method includes:

[0062] Step 101: During the operation of the tubular heater, pressure data at the corresponding locations are collected in real time by pressure sensors installed in the water supply branch pipe, return branch pipe, inlet and outlet of the series pre-air preheater group, and bypass pipe. At the same time, the hot water flow data flowing through each branch and the temperature data of the two temperature-section pre-air preheaters are monitored. The bypass pipe is located between the two temperature-section pre-air preheaters in the series pre-air preheater group.

[0063] In step 101, the series-connected preheater group is formed by connecting two adjacent preheaters in series, including a high-temperature preheater and a low-temperature preheater. The two temperature-section preheaters within the series-connected preheater group are interconnected via a bypass pipe, which is equipped with a shut-off valve. Pressure data is a measured value reflecting the pressure of the hot water within the pipe. "Flowing through each branch" refers to the hot water flowing through the parallel-connected supply and return water branch pipes; hot water flow rate data is the amount of hot water flowing through a certain cross-section of the pipe per unit time. "Two temperature-section preheaters" specifically refers to the high-temperature and low-temperature sections connected in series to form a preheater group, while "series-connected preheater group" is a complete functional unit composed of these two specific sections connected in series. Temperature data is the measured temperature of the hot water at the preheater inlet and outlet. The bypass pipe is an auxiliary pipe connecting the two preheaters in the series-connected preheater group.

[0064] In this embodiment of the application, during the operation of the tubular heater, pressure data at each point is first obtained by pressure sensors installed at the inlet and outlet positions of the water supply branch pipe, return branch pipe, and series preheater group. At the same time, flow meters are used to monitor the flow of hot water in each branch and record the flow data. Then, temperature sensors are used to collect the inlet and outlet temperature data of the two preheater sections in the series preheater group. A bypass pipe is connected between the two preheater sections of the series preheater group to realize the diversion and regulation of hot water.

[0065] For example, in a tubular heater system of a petrochemical plant, pressure sensors installed at points P1 (supply branch pipe), P2 (return branch pipe), P3 (inlet of the series preheater group), P4 (outlet), and P5 (bypass connection point) measured pressure values ​​of 1.2 MPa, 1.1 MPa, 1.15 MPa, 1.05 MPa, and 1.12 MPa, respectively. Simultaneously, the hot water flow rate through the branch pipe was monitored to be 50 tons per hour. Temperature sensors measured the inlet temperature of the high-temperature preheater to be 150 degrees Celsius and the outlet temperature of the low-temperature preheater to be 90 degrees Celsius. These data provide a basis for subsequent calculations and analyses.

[0066] Step 102: Calculate the heat load value and pressure difference parameter based on the pressure data, the hot water flow rate data and the temperature data.

[0067] In step 102, the heat load value is the total heat transferred by the hot water in the preheater per unit time. The pressure difference parameter is the pressure difference between the inlet and outlet of the series preheater group.

[0068] In this embodiment, based on the collected pressure data, hot water flow data, and temperature data, the heat load value is first calculated using the hot water flow value and the temperature difference between the inlet and outlet of the preheater to reflect the heat exchange capacity of the preheater; at the same time, the pressure difference parameter is calculated based on the inlet and outlet pressure data of the series preheater group to characterize the fluid flow resistance; these two parameters together describe the thermodynamic and hydraulic characteristics of the system.

[0069] For example, based on the data measured in step 101, a hot water flow rate of 50 tons / hour is converted to 13.89 kg / second, the inlet and outlet temperature difference is 60 degrees Celsius, and the specific heat capacity of water is 4.18 kJ / (kg·°C). This can be calculated using the formula... Calculate the heat load value, where This is the heat load value. For quality flow, For specific heat capacity, For the temperature difference, the calculation is as follows =13.89×4.18×60=3482.5 kJ / s; at the same time, the pressure difference parameter of the series preheater group is calculated as P3-P4=1.15-1.05=0.1 MPa.

[0070] Step 103: Process the heat load value and the pressure difference parameter using the system dynamics equations of the MPC model to generate a pressure prediction sequence for future time steps.

[0071] In step 103, the system dynamics equations establish the pressure-flow relationship based on fluid mechanics formulas. The pressure prediction sequence is a sequence of pressure values ​​predicted at multiple future time points based on the current system state.

[0072] In this embodiment, the heat load value and pressure difference parameter are input into the system dynamic equation of the model predictive control model. This equation establishes the dynamic relationship between pressure, flow rate and temperature through the principles of fluid mass conservation and momentum conservation. Based on the system state data at the current moment, the pressure changes at multiple consecutive time points in the future are predicted through forward iterative calculation. In each iteration, the influence of heat load on temperature is considered, and the prediction results are dynamically corrected to finally form a complete pressure prediction sequence.

[0073] For example, the heat load value of 3482.5 kJ / s and the pressure difference parameter of 0.1 MPa obtained in step 102 are input into the system dynamic equation. Combined with the current state data such as the supply water branch pressure of 1.2 MPa and the return water branch pressure of 1.1 MPa, the pressure values ​​at the next 5 time points (interval of 10 seconds) are predicted by iterative calculation, and the pressure prediction sequence [1.19, 1.18, 1.17, 1.16, 1.15] MPa is obtained.

[0074] Step 104: Based on the pressure prediction sequence, a rolling time-domain optimization algorithm is used to perform multi-step prediction optimization processing to obtain the optimal control command sequence that meets the preset optimization conditions.

[0075] In step 104, the preset optimization condition represents minimizing the pressure deviation (setpoint vs. actual value), while the constraints include the preheater temperature range (to prevent overheating or efficiency reduction) and valve opening limits. The optimal control command sequence is a sequence of control commands at multiple future time points that satisfy the system constraints and achieve the best control effect.

[0076] In this embodiment, based on the pressure prediction sequence, a rolling time-domain optimization algorithm is used to establish an optimization function with the goal of minimizing the pressure deviation, while considering constraints such as the preheater temperature range and valve opening limits. The optimization problem is resolved in each control cycle to generate the optimal control command sequence for multiple future time steps, ensuring that the system achieves the best control effect while meeting various physical constraints.

[0077] For example, based on the pressure prediction sequence [1.19, 1.18, 1.17, 1.16, 1.15] MPa obtained in step 103, with a pressure setpoint of 1.2 MPa as the target, and under the constraints of preheater temperature not exceeding 160 degrees Celsius and valve opening degree 0-100%, the control command sequence [45%, 50%, 55%, 60%, 65%] for the next 5 time points is generated through optimization calculation.

[0078] Step 105: Based on the optimal control command sequence, generate the opening command of the shut-off valve on the bypass pipeline, and based on the opening command and the pressure status of the water supply branch and the return branch, use a distributed control architecture to adjust the valve opening on the bypass pipeline to achieve pressure balance coordination control within the series preheater group and among multiple parallel series preheater groups.

[0079] In step 105, the opening command is a signal that controls the degree of valve opening. Branch pipe pressure status refers to the actual pressure value of hot water in the supply or return branch pipe, measured by a sensor, relative to a preset pressure range. The distributed control architecture is a collaborative control system composed of multiple local controllers and a central coordinator.

[0080] In this embodiment, the opening command of the shut-off valve on the bypass pipeline is generated according to the optimal control command sequence, and the command is sent to each local controller through a distributed control architecture. The local controller drives the actuator to adjust the valve opening, while the central coordinator monitors the branch pressure status and corrects the command when necessary, so as to realize the pressure balance coordination control within the series preheater group and between the parallel preheater groups.

[0081] For example, the first instruction 45% is taken from the control instruction sequence obtained in step 104 as the current opening instruction, and is sent to the local controller of the bypass pipeline through the distributed control architecture. The controller drives the shut-off valve to adjust to the 45% opening. At the same time, the central coordinator monitors that the branch pressure is 1.19 MPa, which is close to the set range, and maintains the current instruction to achieve pressure balance within the series preheater group and between the parallel preheater groups.

[0082] The first instruction, 45%, is taken from the control instruction sequence obtained in step 104 as the current opening instruction. It is then sent to the local controller of the bypass pipeline through the distributed control architecture. The controller drives the shut-off valve to adjust to the 45% opening. At the same time, the central coordinator monitors that the branch pressure is 1.19 MPa, which is close to the set range. The current instruction is maintained to achieve pressure balance within the series preheater group and between the parallel preheater groups.

[0083] To address the lag and coupling issues in existing pressure control methods when dealing with multiple preheaters operating in series and parallel, and to further improve the accuracy and foresight of pressure prediction, in some embodiments, step 103: processing the heat load value and the pressure difference parameter using the system dynamics equations of the MPC model to generate a pressure prediction sequence for future time steps includes:

[0084] Step 201: Based on the heat load value and the pressure difference parameter, the fluid mass conservation equation and momentum conservation equation in the system dynamics equation of the MPC model are used to establish the dynamic coupling relationship between pressure, flow rate and temperature.

[0085] In step 201, the dynamic coupling relationship refers to the correlation characteristics between pressure, flow rate, and temperature, described by mathematical equations. The fluid mass conservation equation reflects the law that the mass of a fluid remains constant during flow. The momentum conservation equation reflects the law that the fluid's motion state changes under the action of forces.

[0086] In this embodiment, the key influencing factors of the system's thermodynamic and hydraulic characteristics are first determined based on the heat load value and pressure difference parameters. Then, using the fluid mass conservation equation and momentum conservation equation contained in the system dynamics equation of the model predictive control model, a dynamic coupling relationship model reflecting the interaction between pressure, flow rate, and temperature is constructed. This model can accurately describe the dynamic behavior characteristics of the system under different operating conditions. The specific implementation process is as follows: the heat load value... As a source term in the energy equation, temperature is established. Over time Differential equations of change ,in Indicates fluid temperature. Indicates time, Indicates the heat load value. Indicates fluid density, This represents the specific heat capacity at constant pressure of a fluid. This represents the volume occupied by the fluid; the pressure difference parameter As boundary conditions for the momentum conservation equation, flow rate is established. With pressure relational equations ,in Indicates fluid flow rate. Indicates the flow coefficient. Indicates the pressure difference parameter; via temperature For fluid density and viscosity Influence relationship and ,in This represents the fluid density at the reference temperature. Indicates the coefficient of fluid volume expansion. Indicates reference temperature. Indicates fluid dynamic viscosity, This represents the fluid dynamic viscosity at the reference temperature. The viscosity temperature coefficient is represented by the energy equation and the mass conservation equation. and momentum conservation equation Solve simultaneously, where, This represents the local rate of change of density over time. Indicates mass flux divergence, Represents the fluid velocity vector. This represents the local rate of change of velocity over time, forming pressure. ,flow With temperature The dynamic coupling relationship between them. A specific example is: when the heat load Q increases, the temperature... Increased density A decrease in density, according to the law of conservation of mass, will cause a decrease in pressure. Decrease, while viscosity Changes will affect the resistance term in the momentum equation. Finally, by solving these three equations simultaneously, the future trend of branch pressure changes can be predicted.

[0087] Step 202: Based on the dynamic coupling relationship, and combined with the current water supply branch pressure, return branch pressure, hot water flow rate, and temperature data of the two temperature-section preheaters, the pressure change trajectory of the water supply branch and return branch in multiple consecutive time steps is predicted through forward iterative calculation.

[0088] In step 202, the current water supply branch pressure, return branch pressure, hot water flow rate, and temperature data of the two temperature-section preheaters refer to: the real-time measured pressure values ​​of hot water in the water supply branch, the pressure values ​​of hot water in the return branch, the volumetric flow rate of hot water flowing through the branch per unit time, and the temperature values ​​of hot water at the inlet and outlet of the high-temperature and low-temperature preheaters, respectively, measured by the corresponding position sensors. Forward iterative calculation refers to a calculation method that, starting from the current moment, progressively extrapolates the future system state in chronological order. "Continuous" in multiple consecutive time steps refers to multiple predicted time periods arranged in a fixed time interval sequence. For example, setting the control cycle to 5 seconds, starting from the current moment, continuously predicting the pressure values ​​at the 5th, 10th, 15th, and 20th seconds in the future, these equally spaced time points constitute a continuous time step sequence. The pressure change trajectory refers to the continuous path of system pressure change over time in the future.

[0089] In this embodiment, based on the establishment of a dynamic coupling relationship, and combined with the pressure data of the water supply branch pipe, the pressure data of the return water branch pipe, the hot water flow data, and the temperature data of the two temperature-section preheaters collected at the current moment, the system pressure state at each future time point is calculated sequentially through a forward iterative calculation method, thereby forming a complete pressure change trajectory of the water supply branch pipe and the return water branch pipe in multiple consecutive time steps in the future.

[0090] Step 203: In each iteration of the calculation, the pressure change trajectory is dynamically corrected according to the heat load value, and a pressure prediction sequence is formed based on the corrected pressure change trajectory.

[0091] In step 203, dynamic correction refers to the process of adjusting the prediction results in a timely manner based on the real-time changes in influencing factors.

[0092] In the embodiments of this application, during the forward iterative calculation, the predicted results of the pressure change trajectory are adjusted in real time according to the influence of the heat load value on the system temperature field. By considering the changes in fluid characteristics caused by the heat exchange process, the pressure prediction is ensured to accurately reflect the actual operating conditions. Finally, based on the dynamically corrected pressure change trajectory, a pressure prediction sequence that accurately reflects the future pressure state of the system is formed.

[0093] Here is a specific example:

[0094] In a tubular heater system of a petrochemical plant, based on the measured heat load of 3482.5 kJ / s and pressure difference of 0.1 MPa, the dynamic coupling relationship between pressure, flow rate, and temperature is established using the fluid mass conservation equation and momentum conservation equation in the system dynamics equations of the model predictive control model. The fluid mass conservation equation is expressed as follows: This equation describes the conservation properties of fluid mass in spacetime; the momentum conservation equation is expressed as follows: This equation describes the equilibrium relationship between fluid momentum change and pressure gradient, viscous force, and gravity. Based on this dynamic coupling relationship, and combined with the current system state data (supply branch pressure 1.2 MPa, return branch pressure 1.1 MPa, hot water flow rate 50 tons / hour converted to 13.89 kg / s), high-temperature section pre-air preheater inlet temperature 150°C, low-temperature section pre-air preheater outlet temperature 90°C), the pressure change trajectory of the supply and return branch pipes is predicted over five consecutive time steps through forward iterative calculation, with a time step interval of 10 seconds. In each iteration, the influence of the heat load value of 3482.5 kJ / s on the temperature field is calculated using thermodynamic relationships. Dynamically correct pressure change trajectory, where The unit representing temperature change is degrees Celsius. The unit for heat load is kilojoules per second. The unit for mass flow rate is kilograms per second. The isobaric specific heat capacity of water is taken as 4.18 kJ / kg Celsius. Based on the corrected pressure change trajectory, the final pressure prediction sequence is formed, resulting in a supply branch pressure prediction sequence of [1.19, 1.18, 1.17, 1.16, 1.15] MPa and a return branch pressure prediction sequence of [1.09, 1.08, 1.07, 1.06, 1.05] MPa. These prediction values ​​accurately reflect the future pressure change trend of the system by taking into account the interaction of thermodynamic and hydraulic factors.

[0095] In the embodiments of this application, by establishing an accurate dynamic coupling model and making forward-looking predictions that take into account the influence of heat load, the inherent dynamic characteristics and thermodynamic effects of the system can be effectively captured, improving the accuracy of pressure prediction and adaptability to changes in operating conditions, and providing a reliable decision basis for subsequent optimization control.

[0096] To further improve the accuracy and continuity of pressure change trajectory prediction, in some embodiments, step 202: based on the dynamic coupling relationship, combined with the current supply branch pressure, return branch pressure, hot water flow rate, and temperature data of the two temperature-segment preheaters, the pressure change trajectory of the supply and return branch pipes within multiple consecutive time steps is predicted through forward iterative calculation, including:

[0097] Step 301: Use the current water supply branch pressure, return branch pressure, hot water flow rate, and temperature data of the two temperature-section preheaters as the initial system state.

[0098] In step 301, the initial system state refers to the initial operating conditions of the system when the predictive calculation begins, including the measured values ​​of the supply water branch pressure, return water branch pressure, hot water flow rate, and temperature data of the two temperature-section preheaters.

[0099] In this embodiment, the pressure data of the water supply branch pipe, the pressure data of the return water branch pipe, the hot water flow data, and the temperature data of the high-temperature section pre-air preheater and the low-temperature section pre-air preheater collected at the current moment are first used as the initial system state to provide a reference starting point for subsequent prediction calculations.

[0100] Step 302: Based on the dynamic coupling relationship, calculate the changes in the pressure of the water supply branch pipe and the return branch pipe within the first time step.

[0101] In step 302, the change refers to the magnitude of the change in system parameters within a time step.

[0102] In this embodiment of the application, based on the dynamic coupling relationship established in step 201, the changes in the pressure of the water supply branch pipe and the return branch pipe within the first time step are calculated according to the current system state. This calculation takes into account the physical laws of fluid mass conservation and momentum conservation, and reflects the trend of system parameters changing with time.

[0103] Step 303: Superimpose the change with the initial system state to obtain the predicted values ​​of the supply branch pressure and return branch pressure at the end of the first time step.

[0104] In step 303, the predicted value refers to the estimated value of the system parameters at a future point in time obtained through calculation.

[0105] In this embodiment of the application, the change calculated in step 302 is superimposed with the initial system state in step 301 to obtain the predicted values ​​of the water supply branch pressure and the return branch pressure at the end of the first time step. This predicted value includes both the initial state information and the trend of parameter changes.

[0106] Step 304: Using the system state at the end of the first time step as the new initial system state, repeat the process of calculating the change and superimposing the system state to obtain the predicted pressure values ​​of the water supply branch pipe and the return water branch pipe from the second time step to the Nth time step in sequence, where N is an integer greater than 1.

[0107] In step 304, the new initial system state refers to the latest system state used for the next round of prediction calculations.

[0108] In this embodiment of the application, the system state obtained at the end of the first time step is taken as the new initial system state, and the calculation process of steps 302 and 303 is repeated to obtain the predicted values ​​of the water supply branch pressure and the return branch pressure from the second time step to the Nth time step in sequence, where N is an integer greater than 1. Multi-step prediction is achieved through this recursive calculation.

[0109] Step 305: Arrange the predicted pressure values ​​of the supply branch pipes and return branch pipes of all time steps in chronological order to form a pressure change trajectory.

[0110] In this embodiment of the application, the predicted pressure values ​​of the water supply branch pipe and the return water branch pipe obtained in all time steps from steps 301 to 304 are arranged in chronological order to form a complete pressure change trajectory, which intuitively shows the trend of system pressure change over a period of time.

[0111] Here is a specific example:

[0112] In a tubular heater system of a petrochemical plant, the initial system state is initially set as follows: supply branch pressure of 1.2 MPa, return branch pressure of 1.1 MPa, hot water flow rate of 50 tons per hour (converted to 13.89 kg per second), inlet temperature of the high-temperature section preheater of 150 degrees Celsius, and outlet temperature of the low-temperature section preheater of 90 degrees Celsius. Based on the established dynamic coupling relationship, the fluid mass conservation equation is solved. and momentum conservation equation The changes in pressure in the supply and return branch pipes within the first 10 seconds of the first time step are calculated. The calculated pressure change in the supply branch pipe is -0.01 MPa, and the pressure change in the return branch pipe is also -0.01 MPa. These two changes are then superimposed with the corresponding pressure values ​​in the initial system state to obtain the predicted pressure values ​​for the supply branch pipe (1.19 MPa) and return branch pipe (1.09 MPa) at the end of the first time step. Using these predicted values ​​as the new initial system state, the process of calculating the changes and superimposing the system state is repeated to obtain the predicted pressure values ​​for the supply branch pipe (1.18 MPa) for the second to fifth time steps. The predicted pressure values ​​for the supply and return water branches are 1.17 MPa, 1.16 MPa, 1.15 MPa, and 1.08 MPa, 1.07 MPa, 1.06 MPa, and 1.05 MPa, respectively. Finally, the predicted pressure values ​​for the supply and return water branches at all five time steps are arranged in chronological order to form the pressure change trajectory of the supply branch [1.19, 1.18, 1.17, 1.16, 1.15] MPa and the pressure change trajectory of the return water branch [1.09, 1.08, 1.07, 1.06, 1.05] MPa. These trajectory data fully demonstrate the pressure change trend of the system in the next 50 seconds.

[0113] In this embodiment, by using a recursive forward iterative calculation, continuous prediction of future pressure changes is achieved from the current state, forming a complete pressure change trajectory. This provides accurate pressure change trend information for subsequent optimized control, enhancing the system's predictability and adaptability to changes in operating conditions.

[0114] To further improve the accuracy of pressure change trajectory prediction, especially considering the impact of heat exchange processes on fluid characteristics, in some embodiments, step 203: dynamically correcting the pressure change trajectory based on the heat load value includes:

[0115] Step 401: Based on the heat load value and the specific heat capacity parameter of the hot water, calculate the temperature change caused by the hot water flowing through the preheater of each temperature range.

[0116] In step 401, the temperature change refers to the temperature change caused by heat exchange when hot water flows through the preheater.

[0117] In this embodiment of the application, the temperature change per unit time of hot water as it flows through the preheater of each temperature range is obtained by thermodynamic calculation based on the heat load value and the specific heat capacity parameter of hot water. This calculation reflects the actual impact of the heat exchange process on the water temperature.

[0118] Step 402: Based on the temperature change and the fluid thermal expansion coefficient, calculate the first pressure change component caused by the change in hot water density, and simultaneously calculate the second pressure change component caused by the change in fluid resistance through viscosity-temperature characteristics.

[0119] In step 402, the first pressure change component is the pressure change caused by the change in fluid density due to the temperature change, and the second pressure change component is the pressure change caused by the change in fluid viscosity due to the temperature change, which in turn affects the flow resistance.

[0120] In this embodiment, based on the temperature change obtained in step 401, the first pressure change component caused by the change in hot water density is calculated using the fluid thermal expansion coefficient. Simultaneously, the second pressure change component caused by the change in fluid resistance is calculated using the correlation between viscosity and temperature. These two components reflect the influence of temperature change on pressure from different physical mechanisms. The specific implementation process is as follows: First, based on the temperature change... and fluid thermal expansion coefficient Through formula Calculate the change in hot water density, where As a reference density, then based on the density change through hydrostatic relations The first pressure change component was calculated, where Bulk modulus This represents the first component of pressure change; simultaneously, it is based on the temperature change. viscosity-temperature relationship ,in For reference viscosity, The viscosity temperature coefficient is used to calculate the viscosity change, which is then applied using the Darcy-Weisbach formula. Calculate the change in fluid resistance, where the coefficient of friction is... With viscosity Related, Indicates the length of the pipe. This represents the pipe's inner diameter, from which the second pressure change component is obtained. A specific example is: when hot water flows through the high-temperature preheater and its temperature rises by 10°C, the pressure decrease due to the decrease in density can be calculated using the above process. And the increase in pressure due to decreased viscosity and reduced flow resistance. The two are combined to obtain the net pressure change correction.

[0121] Step 403: Combine the first pressure change component with the second pressure change component to obtain the pressure change correction amount.

[0122] In step 403, the pressure change correction is the total effect of density change and flow resistance change on pressure.

[0123] In this embodiment of the application, the first pressure change component and the second pressure change component calculated in step 402 are combined to obtain a complete pressure change correction amount, which includes the comprehensive impact of temperature change on system pressure through different pathways.

[0124] Step 404: Superimpose the pressure change correction amount with the pressure prediction value at the corresponding time step in the pressure change trajectory to generate the corrected pressure change trajectory.

[0125] In step 404, the corrected pressure change trajectory is a more accurate pressure prediction trajectory after correction for the effects of heat load.

[0126] In this embodiment of the application, the pressure change correction obtained in step 403 is superimposed with the pressure prediction value of the corresponding time step in the original pressure change trajectory to generate a corrected pressure change trajectory, so that the pressure prediction result is more consistent with the actual heat exchange conditions.

[0127] Here is a specific example:

[0128] In a tubular heater system of a petrochemical plant, based on a heat load of 3482.5 kJ / s and a specific heat capacity of hot water of 4.18 kJ / kg Celsius, the thermodynamic relationship is used... Calculate the temperature change, and obtain the temperature change. Based on this temperature change and the fluid's thermal expansion coefficient Taking 0.0002 per degree Celsius, the density change formula is used. Calculate the density change, and obtain Furthermore, through hydrostatic relationships Calculate the first pressure change component, and obtain Simultaneously, based on the temperature change, the viscosity-temperature relationship is used. Calculate the viscosity change, and obtain Then through Darcy's formula Calculate the second pressure change component, and obtain The pressure change correction is obtained by combining the first pressure change component (-0.002 MPa) with the second pressure change component (+0.0013 MPa). The pressure change correction is then superimposed on the pressure prediction values ​​for each time step in the pressure change trajectory. For example, the predicted pressure value of the supply branch pipe in the first time step (1.19 MPa) is corrected to 1.1893 MPa, and the predicted pressure value of the return branch pipe (1.09 MPa) is corrected to 1.0893 MPa. This correction is applied sequentially to all time steps to generate the corrected pressure change trajectory. The pressure change trajectory of the supply branch pipe is corrected to [1.1893, 1.1793, 1.1693, 1.1593, 1.1493] MPa, and the pressure change trajectory of the return branch pipe is corrected to [1.0893, 1.0793, 1.0693, 1.0593, 1.0493] MPa.

[0129] In this embodiment, by considering the dual effects of heat load on fluid density and flow resistance, the pressure change trajectory is dynamically corrected, which improves the accuracy of pressure prediction and makes the prediction results more realistically reflect the system behavior under actual working conditions.

[0130] To accurately quantify the system's thermodynamic and hydraulic characteristics and provide key input parameters for subsequent predictive control, in some embodiments, step 102: calculating the heat load value and pressure difference parameter based on the pressure data, the hot water flow rate data, and the temperature data, includes:

[0131] Step 501: Extract the mass flow rate value from the hot water flow rate data and extract the inlet and outlet temperature difference value from the temperature data.

[0132] In step 501, the mass flow rate refers to the mass of hot water flowing through the pipe cross-section per unit time. The inlet and outlet temperature difference refers to the difference between the inlet temperature and the outlet temperature of the hot water when it flows through the preheater unit.

[0133] In this embodiment, the mass flow rate value is first extracted from the hot water flow data, which reflects the mass flow of the hot water; at the same time, the difference between the inlet temperature of the high-temperature section preheater and the outlet temperature of the low-temperature section preheater is extracted from the temperature data, which reflects the temperature change range of the heat exchange process.

[0134] Step 502: Using the mass flow rate value and the inlet and outlet temperature difference value, calculate the total heat transferred by the hot water in the preheater unit per unit time using the thermodynamic heat transfer formula, and use the total heat value as the heat load value.

[0135] In step 502, the total heat value refers to the total amount of heat transferred by the hot water per unit time as it flows through the preheater unit.

[0136] In this embodiment of the application, the mass flow rate value and inlet / outlet temperature difference value obtained in step 501 are used to calculate the total heat value transferred by hot water in the preheater unit per unit time using the thermodynamic heat transfer formula, and the total heat value is used as the heat load value to characterize the thermodynamic characteristics of the system.

[0137] Step 503: Based on the pressure data, calculate the first pressure difference between the inlet of the high-temperature section pre-air ...

[0138] In step 503, the first pressure difference refers to the pressure difference between the inlet of the high-temperature section preheater and the outlet of the low-temperature section preheater in the series-connected preheater group. The second pressure difference refers to the pressure difference between multiple series-connected preheater groups connected in parallel.

[0139] In this embodiment of the application, based on pressure data, the first pressure difference between the inlet of the high-temperature section pre-air ...

[0140] Here is a specific example:

[0141] In a tubular heater system at a petrochemical plant, a volumetric flow rate of 50 tons per hour was extracted from the hot water flow data. This was converted to a mass flow rate of 13.89 kilograms per second (kg / s). One ton per hour equals 1000 kilograms per 3600 seconds, or 0.2778 kilograms per second. Therefore, 50 multiplied by 0.2778 equals 13.89 kilograms per second. From the temperature data, the inlet temperature of the high-temperature preheater (150 degrees Celsius) and the outlet temperature of the low-temperature preheater (90 degrees Celsius) were extracted, resulting in a temperature difference of 60 degrees Celsius. Using the mass flow rate of 13.89 kilograms per second and the inlet-outlet temperature difference of 60 degrees Celsius, the thermodynamic heat transfer formula was applied... ,in The unit for mass flow rate is kilograms per second. Indicates the volumetric flow rate of hot water. This indicates the density of water. ,in This represents the total heat value (i.e., the heat load value). This represents the specific heat capacity of water at constant pressure, calculated as follows: The total heat value is used as the heat load value. Based on the pressure data, the first pressure difference between the inlet pressure of the high-temperature section pre-air ...

[0142] In this embodiment, a systematic parameter calculation process accurately obtains key parameters reflecting the thermodynamic and hydraulic characteristics of the system, providing a reliable quantitative basis for subsequent model prediction and optimized control, and enhancing the scientificity and accuracy of the entire control system.

[0143] To further improve the accuracy and adaptability of control commands and ensure stable system operation under various constraints, in some embodiments, step 104: based on the pressure prediction sequence, a rolling time-domain optimization algorithm is used to perform multi-step prediction optimization processing to obtain the optimal control command sequence that satisfies preset optimization conditions, including:

[0144] Step 601: Calculate the pressure deviation between the pressure prediction value in the pressure prediction sequence and the pressure setpoint at the corresponding time step, and construct an optimization function with the goal of minimizing the pressure deviation.

[0145] In step 601, pressure deviation refers to the degree of difference between the predicted pressure value and the pressure setpoint. The optimization function is a mathematical expression used to quantify the control objective and guide the optimization process.

[0146] In the embodiments of this application, the pressure deviation between the pressure prediction value and the pressure setpoint at each time step in the pressure prediction sequence is first calculated. Then, an optimization function is constructed with the objective of minimizing the cumulative value of these pressure deviations. This function transforms the system control objective into a mathematical extremum problem.

[0147] Step 602: Introduce multiple physical constraints into the optimization function, solve the optimization function with the multiple physical constraints using a rolling time-domain optimization algorithm, generate a sequence of shut-off valve control commands for multiple future time steps, and use the sequence of shut-off valve control commands as the optimal control command sequence.

[0148] In step 602, physical constraints refer to the physical limitations that must be followed during system operation, including: the temperature of the preheater of each temperature section must not exceed its maximum allowable operating temperature and must not be lower than its minimum required operating temperature; the opening of the shut-off valve on the bypass pipeline must be maintained within the effective range of 0% to 100%; and the pressure difference between the high-temperature section and the low-temperature section of the series preheater group must be maintained within the set tolerance range.

[0149] In this embodiment, multiple physical constraints are introduced into the optimization function, including preheater temperature range limitations and valve opening range limitations. Then, a rolling time-domain optimization algorithm is used to solve the optimization function with these constraints, generating a sequence of shut-off valve control commands for multiple future time steps. This sequence is then output as the optimal control command sequence. Specifically, the implementation process is as follows: First, three physical constraints are introduced into the optimization function—the temperature of each preheater section must be between its allowable upper and lower limits, the bypass valve opening must be within the range of 0% to 100%, and the pressure difference between the series preheater groups must remain within a set range. Then, a rolling time-domain optimization algorithm is used to solve the optimization problem that minimizes the pressure deviation under these constraints in each control cycle based on the latest pressure prediction sequence, obtaining the optimal valve opening sequence for multiple future time steps. A specific example is as follows: when the prediction shows that the branch pipe pressure will exceed the upper limit within the next 30 seconds, the optimization algorithm calculates the valve opening sequence [60%, 70%, 75%, 80%, 85%] for the next 5 time steps (6 seconds each) under the premise that the preheater temperature does not exceed the limit and the valve opening does not exceed 100%, and then diverts the flow to reduce the pressure by gradually increasing the opening.

[0150] Here is a specific example:

[0151] In a tubular heater system of a petrochemical plant, based on five predicted pressure values ​​(1.19 MPa, 1.18 MPa, 1.17 MPa, 1.16 MPa, and 1.15 MPa) in a pressure prediction sequence and the corresponding time step pressure setpoint (1.2 MPa), the pressure deviations at each time step were calculated to be 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa, and 0.05 MPa, respectively. An optimization function was constructed with the objective of minimizing the sum of squares of the pressure deviations. ,in This represents the value of the objective function as a dimensionless number. The pressure setpoint is represented by megapascals (MPA). The pressure prediction value is represented by megapascals (MPa), and the summation symbol ∑ indicates the summation of the squared deviations over five time steps. Several physical constraints are introduced into this optimization function, including that the temperature of each preheater section must not exceed 160 degrees Celsius and must not be lower than 80 degrees Celsius; the opening of the shut-off valve on the bypass pipeline must be maintained within the range of 0% to 100%; and the pressure difference between the high-temperature and low-temperature sections of the series preheater group must be maintained within ±0.05 MPa. The optimization function with these physical constraints is solved using a rolling time-domain optimization algorithm, generating a shut-off valve control command sequence of 45%, 50%, 55%, 60%, and 65% for the next five time steps. This shut-off valve control command sequence is then output as the optimal control command sequence for subsequent valve regulation control.

[0152] In this embodiment, by constructing an optimization problem that considers multiple constraints and solving it using a rolling optimization method, an optimal instruction sequence that satisfies both the system's safe operation requirements and the control objective is generated, thereby improving the accuracy and reliability of the control.

[0153] To further improve the accuracy and system coordination of valve control, and ensure the real-time performance and stability of pressure balance control, in some embodiments, step 105: generating an opening command for the shut-off valve on the bypass pipeline based on the optimal control command sequence, and adjusting the valve opening on the bypass pipeline using a distributed control architecture based on the opening command and the pressure status of the supply and return water branch pipes, includes:

[0154] Step 701: Convert the optimal control command sequence into an opening percentage value, and use the opening percentage value as the opening command.

[0155] In step 701, the opening percentage value refers to the percentage of the valve's opening degree relative to the fully open state. The opening command is the specific instruction signal that controls the valve's operation.

[0156] In this embodiment of the application, the control command values ​​in the optimal control command sequence are converted into corresponding opening percentage values, and these opening percentage values ​​are used as the actual opening commands executed, providing a clear control target for valve regulation.

[0157] Step 702: Distribute the opening command to the local controller of the corresponding bypass pipeline, so that the local controller can generate a corresponding control signal according to the opening command, and drive the actuator of the shut-off valve to adjust the valve to the specified opening position based on the control signal.

[0158] In step 702, the local controller for the bypass pipeline refers to an independent control unit installed near each bypass pipeline, specifically for controlling the shut-off valves on that pipeline. Its core function is to receive control commands and directly drive the valve actuator. The "pressure sensor" is a detection device used to measure the fluid pressure in the pipeline. It provides the collected pressure data to the local controller and the central coordinator as a control basis; the two form a cooperative relationship of detection and execution. The control signal is an electrical signal that drives the actuator. The actuator is a mechanical device that receives the control signal and drives the valve.

[0159] In this embodiment of the application, the opening command is distributed to the local controller of the corresponding bypass pipeline. The local controller generates a corresponding control signal based on the received opening command, and drives the actuator of the shut-off valve based on the control signal to precisely adjust the valve to the opening position specified by the command.

[0160] Step 703: Monitor the pressure status of the supply and return water branch pipes in real time. When the pressure status of any branch pipe deviates from the preset range, the opening correction amount is calculated by the central coordinator based on the pressure data of all series-connected pre-air preheater groups.

[0161] In step 703, the opening correction amount is the adjustment amount made to the original opening command to maintain pressure balance. The "pressure state" in the context of detecting a deviation of the pressure state of any branch pipe from the preset range refers to the operating condition category corresponding to the pressure measurement value obtained through continuous monitoring. This category is divided according to whether the pressure value is within a preset numerical range (e.g., 1.2-1.5 MPa), such as "normal state," "high pressure state," or "low pressure state." The central coordinator refers to the main control computer deployed in the central control room of the tubular furnace. It is connected to all local controllers through a communication network, responsible for aggregating data from various pressure sensors, executing global optimization algorithms, and issuing coordinated control commands to each local controller.

[0162] In this embodiment, the pressure status of the water supply branch pipe and the return branch pipe is monitored in real time. When the pressure status of any branch pipe deviates from the preset range, the central coordinator analyzes the system pressure distribution based on the pressure data of all series-connected pre-air preheater groups and calculates an appropriate opening correction amount.

[0163] Step 704: Based on the opening correction amount, the opening command is corrected to obtain the corrected opening command. The corrected opening command is then synchronously sent to the local controllers of the affected parallel series pre-air preheater groups through the distributed control architecture. Each local controller coordinates and adjusts the opening of the shut-off valve on its bypass pipeline according to the corrected opening command, so as to maintain pressure balance between the high-temperature section pre-air preheater and the low-temperature section pre-air preheater within the series pre-air preheater group, and at the same time, to achieve dynamic balance of branch pipe pressure among the parallel series pre-air preheater groups.

[0164] In step 704, the corrected opening command is the final control command after pressure adjustment. The affected parallel series preheater groups refer to the set of all preheater groups directly connected to a branch pipe and requiring coordinated adjustment, as determined by hydraulic analysis when the pressure of a branch pipe is abnormal. These groups will experience pressure linkage due to sharing the water network, and their bypass valve openings need to be adjusted uniformly to restore system balance.

[0165] In this embodiment, the original opening command is modified based on the opening correction amount to obtain the modified opening command. The modified opening command is then synchronously sent to the local controllers of the affected parallel and series preheater groups through a distributed control architecture. Each local controller coordinates and adjusts the opening of the shut-off valve on its bypass pipeline according to the modified opening command to achieve system pressure balance.

[0166] Here is a specific example:

[0167] In a tubular heater system of a petrochemical plant, the first command (45%) in the optimal control command sequence of 45%, 50%, 55%, 60%, 65% is converted into an opening percentage value, which is used as the current opening command. This opening command is distributed to the local controller of the corresponding bypass pipe. The local controller generates a corresponding 12.6 mA control signal based on the 45% opening command, and drives the actuator of the shut-off valve to adjust the valve to the 45% opening position. The pressure status of the supply water branch pipe (1.19 MPa) and the return water branch pipe (1.09 MPa) is monitored in real time. When the supply water branch pipe pressure (1.19 MPa) deviates from the preset range of 1.2 ± 0.02 MPa, the opening correction is calculated by the central coordinator based on the pressure data of all series-connected preheater groups, including the first group pressure (1.19 MPa) and the second group pressure (1.17 MPa). The specific formula is used. Calculation, where The opening correction amount is expressed as a percentage. The representative adjustment coefficient is 0.6 per megapascal. This represents a pressure setpoint of 1.2 MPa. Representing an actual pressure value of 1.19 MPa, the calculation yielded... Based on this opening correction, the original opening command is modified from 45% to 45.6%. The modified opening command is then synchronously sent to the local controllers of the two parallel series pre-air preheater groups through a distributed control architecture. Each local controller coordinates and adjusts the opening of the shut-off valve on its bypass pipeline to 45.6% according to the modified 45.6% opening command. This ensures that the high-temperature section pre-air preheater and the low-temperature section pre-air preheater within the series pre-air preheater group maintain pressure balance, while also achieving dynamic balance in the branch pipe pressure between the two parallel series pre-air preheater groups.

[0168] In this embodiment, a distributed architecture is used to achieve precise execution and coordinated control of instructions. Combined with real-time pressure monitoring and dynamic correction mechanisms, this ensures that the system can maintain a stable pressure balance under various operating conditions.

[0169] Figure 4 A schematic diagram of the series-parallel pressure control system for a preheater of a tubular furnace, provided in an embodiment of this application, is shown below. Figure 4 As shown, the detailed implementation section describes:

[0170] The data acquisition module 41 is used to collect pressure data in real time at the corresponding locations through pressure sensors installed in the water supply branch pipe, return branch pipe, inlet and outlet of the series pre-air preheater group, and bypass pipe during the operation of the tubular heater. At the same time, it monitors the hot water flow data flowing through each branch and the temperature data of the two temperature-section pre-air preheaters. The bypass pipe is located between the two temperature-section pre-air preheaters in the series pre-air preheater group.

[0171] The calculation module 42 is used to calculate the heat load value and pressure difference parameter based on the pressure data, the hot water flow data and the temperature data.

[0172] The generation module 43 is used to process the heat load value and the pressure difference parameter using the system dynamics equations of the MPC model to generate a pressure prediction sequence for future time steps.

[0173] The optimization module 44 is used to perform multi-step prediction optimization processing based on the pressure prediction sequence using a rolling time-domain optimization algorithm to obtain the optimal control command sequence that meets the preset optimization conditions.

[0174] The adjustment module 45 is used to generate the opening command of the shut-off valve on the bypass pipeline according to the optimal control command sequence, and adjust the valve opening on the bypass pipeline according to the opening command and the pressure status of the water supply branch and the return branch, using a distributed control architecture, so as to achieve pressure balance coordination control within the series pre-air preheater group and among multiple series pre-air preheater groups in parallel.

[0175] Specific examples are as follows:

[0176] Currently, the heat loads of tubular heaters in China's petrochemical industry, such as those used in hydrocracking, EDC cracking, ethylene cracking, styrene, (PDH) propane dehydrogenation, and hydrogen conversion, are all in the MW range or higher. Therefore, these tubular heaters are equipped with a large number of burners, which are generally arranged in several rows, with multiple burners on each row located at the bottom of the heater. The hot water inlet and outlet water for each preheater are connected in parallel to the hot water branch pipes on each row. Figure 2 As shown in the diagram. Among them, 1 is the main water supply pipe, 2 is the main water return pipe, 3 is the branch water supply pipe, 4 is the branch water return pipe, 5 is the inlet pipe of each preheater, and 6 is the outlet pipe of each preheater.

[0177] In China's domestic petrochemical industry, the preheaters for the burners of these tubular heaters are all connected in parallel with the water supply and return lines. Figure 2 As shown in numbers 5 and 6. The hot water used by each preheater is: plant condensate, wastewater, low-pressure steam, etc.

[0178] While parallel-connected preheater piping provides stable pressure, the large number of preheaters means each preheater receives a limited amount of hot water. Since the designed heat load cannot be reduced, the outlet water temperature must be lowered to meet the preheater's heat load, resulting in decreased temperature and pressure. To meet the designed heat load, the heating surface needs to be increased, leading to the following drawbacks: First, it increases the amount of preheater material used, thus increasing costs. Second, it increases the preheater's size, as the burners in this type of tubular furnace are located at the bottom of the furnace, where space is limited. If the preheater is too large, combined with the feed and return water pipes, it may not fit, reducing the furnace's efficiency and increasing fuel consumption. Third, it increases air-side resistance, further increasing the induced draft fan's power consumption.

[0179] This application addresses and adjusts numerous problems existing in tubular heaters of this type, such as low outlet hot water temperature due to the parallel connection of preheaters, large preheater volume, material waste, and large footprint.

[0180] The load of this type of tubular heater determines that the number of burners cannot be reduced, and the amount of hot water used by this type of tubular heater is also a fixed quantity. To increase the preheater outlet temperature, the only solution is to increase the flow rate of hot water through the preheater. Therefore, the water inlet of two preheaters can be combined into one, and these two preheaters can be connected in series. The two series preheaters can then be connected in parallel with two other series preheaters on the 3-supply branch pipe and the 4-return branch pipe. This can achieve the goals of stabilizing the pressure of the parallel preheater pipeline, increasing the hot water flow rate, reducing the preheater volume, and reducing the amount of preheater materials used.

[0181] The preheater of this type of tubular heater actually uses a series-parallel busbar system for water supply and return to solve the problems of stabilizing preheater pipeline pressure, increasing hot water flow, reducing preheater volume, and reducing preheater material usage. For example... Figure 3 As shown. In addition to ensuring a consistent outlet hot air temperature for the preheater of this type of tubular heater, this application also addresses issues such as stable preheater pipeline pressure, reduced preheater volume, and lower preheater material usage.

[0182] The specific contents are as follows: 1. The hot water inlet and outlet pipes of two adjacent preheaters are connected in series, divided into a high-temperature section (stage 1) and a low-temperature section (stage 2). The hot water inlet and outlet pipes of these two preheaters are connected in parallel to the branch pipes of the other two adjacent preheaters; 2. The air inlet and outlet air temperature, flow rate, and differential pressure of the high-temperature section (stage 1) and the low-temperature section (stage 2) preheaters connected in series by the two adjacent preheaters should be completely consistent; 3. The hot water inlet and return pipes of the series preheater composed of two adjacent preheaters are connected in parallel to the series preheater composed of the other two adjacent preheaters; 4. There is a bypass pipe between the hot water inlet of the high-temperature section (stage 1) and the hot water inlet of the low-temperature section (stage 2) preheater composed of two adjacent preheaters, and a shut-off valve is installed on the bypass pipe.

[0183] The series-parallel pressure control system of the preheater of the tubular heating furnace in this application embodiment is used to implement the aforementioned series-parallel pressure control method of the preheater of the tubular heating furnace. Therefore, the specific implementation of the series-parallel pressure control system of the preheater of the tubular heating furnace can be found in the embodiment section of the series-parallel pressure control method of the preheater of the tubular heating furnace mentioned above. The specific implementation can be referred to the description of the corresponding embodiments, which will not be repeated here.

[0184] This application also provides an electronic device, comprising: a memory for storing a computer program; and a processor for executing the computer program to implement the steps of the series-parallel pressure control method for the preheater of the tubular furnace as described above.

[0185] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the series-parallel pressure control method for the preheater of the tubular furnace described above.

[0186] In one exemplary embodiment, the aforementioned computer-readable storage medium may include, but is not limited to, various media capable of storing computer programs, such as USB flash drives, read-only memory, random access memory, portable hard drives, magnetic disks, or optical disks.

[0187] The embodiments of this application also provide a computer program product, which includes a computer program that, when executed by a processor, implements the steps in the embodiments of the series-parallel pressure control method for any of the tubular furnace preheaters described above.

[0188] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0189] The foregoing has provided a detailed description of the series-parallel pressure control method, system, electronic equipment, and storage medium for a preheater of a tubular heating furnace provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and its core ideas. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of this application.

Claims

1. A method for controlling the series and parallel pressure of a preheater for a tubular heating furnace, characterized in that, include: During the operation of the tubular heater, pressure data at the corresponding locations are collected in real time by pressure sensors installed in the water supply branch pipe, return branch pipe, inlet and outlet of the series pre-air preheater group, and bypass pipe. At the same time, the hot water flow data flowing through each branch and the temperature data of the two temperature-section pre-air preheaters are monitored. The bypass pipe is located between the two temperature-section pre-air preheaters in the series pre-air preheater group. Based on the pressure data, the hot water flow rate data, and the temperature data, calculate the heat load value and pressure difference parameter; The system dynamics equations of the MPC model are used to process the heat load value and the pressure difference parameter to generate a pressure prediction sequence for future time steps; Based on the pressure prediction sequence, a rolling time-domain optimization algorithm is used to perform multi-step prediction optimization processing to obtain the optimal control command sequence that meets the preset optimization conditions. According to the optimal control command sequence, the opening command of the shut-off valve on the bypass pipeline is generated. Based on the opening command and the pressure status of the water supply branch and the return branch, a distributed control architecture is used to adjust the valve opening on the bypass pipeline to achieve pressure balance coordination control within the series pre-air preheater group and among multiple parallel series pre-air preheater groups. The process of using the system dynamics equations of the MPC model to process the heat load value and the pressure difference parameter to generate a pressure prediction sequence for future time steps includes: Based on the heat load value and the pressure difference parameter, the fluid mass conservation equation and momentum conservation equation in the system dynamics equation of the MPC model are used to establish the dynamic coupling relationship between pressure, flow rate and temperature. Based on the dynamic coupling relationship, and combined with the current water supply branch pressure, return branch pressure, hot water flow rate, and temperature data of the two temperature-segment preheaters, the pressure change trajectory of the water supply branch and return branch in multiple consecutive time steps is predicted through forward iterative calculation. In each iteration of the calculation, the pressure change trajectory is dynamically corrected based on the heat load value, and a pressure prediction sequence is formed based on the corrected pressure change trajectory.

2. The method according to claim 1, characterized in that, Based on the dynamic coupling relationship, and combining the current water supply branch pressure, return branch pressure, hot water flow rate, and temperature data of the two temperature-section preheaters, the system predicts the pressure change trajectories of the water supply and return branches over multiple consecutive time steps through forward iterative calculations, including: The initial system state is based on the current water supply branch pressure, return branch pressure, hot water flow rate, and temperature data of the two temperature-section preheaters. Based on the dynamic coupling relationship, the changes in pressure of the supply branch pipe and the return branch pipe within the first time step are calculated. The change is superimposed on the initial system state to obtain the predicted values ​​of the supply branch pressure and return branch pressure at the end of the first time step. Using the system state at the end of the first time step as the new initial system state, the process of calculating the change and superimposing the system state is repeated to obtain the predicted values ​​of the water supply branch pressure and the return branch pressure for the second to Nth time steps in sequence, where N is an integer greater than 1. Arrange the predicted pressure values ​​of the supply branch pipes and return branch pipes for all time steps in chronological order to form a pressure change trajectory.

3. The method according to claim 1, characterized in that, The step of dynamically correcting the pressure change trajectory based on the heat load value includes: Based on the heat load value and the specific heat capacity parameter of the hot water, calculate the temperature change caused by the hot water flowing through the preheater of each temperature range. Based on the temperature change, combined with the fluid thermal expansion coefficient, the first pressure change component caused by the change in hot water density is calculated, and the second pressure change component caused by the change in fluid resistance is calculated through the viscosity-temperature characteristics. The first pressure change component and the second pressure change component are combined to obtain the pressure change correction amount; The pressure change correction is superimposed on the pressure prediction value at the corresponding time step in the pressure change trajectory to generate the corrected pressure change trajectory.

4. The method according to claim 1, characterized in that, The calculation of heat load and pressure difference parameters based on the pressure data, the hot water flow rate data, and the temperature data includes: Extract the mass flow rate value from the hot water flow rate data, and extract the inlet and outlet temperature difference value from the temperature data; Using the mass flow rate and the inlet / outlet temperature difference, the total heat transferred by the hot water in the preheater unit per unit time is calculated using the thermodynamic heat transfer formula, and the total heat value is used as the heat load value. Based on the pressure data, the first pressure difference between the inlet of the high-temperature section pre-air ...

5. The method according to claim 1, characterized in that, The step of performing multi-step prediction optimization processing based on the pressure prediction sequence using a rolling time-domain optimization algorithm to obtain an optimal control command sequence that satisfies preset optimization conditions includes: Calculate the pressure deviation between the pressure prediction value in the pressure prediction sequence and the pressure setpoint at the corresponding time step, and construct an optimization function with the objective of minimizing the pressure deviation; Multiple physical constraints are introduced into the optimization function. The optimization function with the multiple physical constraints is solved by the rolling time-domain optimization algorithm to generate a sequence of shut-off valve control commands for multiple future time steps. The sequence of shut-off valve control commands is then used as the optimal control command sequence.

6. The method according to claim 1, characterized in that, The step of generating an opening command for the shut-off valve on the bypass pipeline based on the optimal control command sequence, and adjusting the valve opening on the bypass pipeline using a distributed control architecture based on the opening command and the pressure status of the supply and return branch pipes, includes: The optimal control command sequence is converted into an opening percentage value, and the opening percentage value is used as the opening command. The opening command is distributed to the local controller of the corresponding bypass pipeline, so that the local controller can generate a corresponding control signal according to the opening command, and drive the actuator of the shut-off valve to adjust the valve to the specified opening position based on the control signal; The pressure status of the supply and return water branch pipes is monitored in real time. When the pressure status of any branch pipe deviates from the preset range, the opening correction amount is calculated by the central coordinator based on the pressure data of all series-connected pre-air preheater groups. Based on the opening correction amount, the opening command is corrected to obtain a corrected opening command. The corrected opening command is then synchronously sent to the local controllers of the affected parallel series pre-air preheater groups through the distributed control architecture. Each local controller coordinates and adjusts the opening of the shut-off valve on its bypass pipeline according to the corrected opening command, so as to maintain pressure balance between the high-temperature section pre-air preheater and the low-temperature section pre-air preheater within the series pre-air preheater group, and at the same time, to achieve dynamic balance of branch pipe pressure among the parallel series pre-air preheater groups.

7. A series-parallel pressure control system for a preheater of a tubular heating furnace, characterized in that, include: The data acquisition module is used to collect pressure data in real time at the corresponding locations of the water supply branch pipe, return branch pipe, inlet and outlet of the series pre-air preheater group, and bypass pipe during the operation of the tubular heater. At the same time, it monitors the hot water flow data through each branch and the temperature data of the two temperature-section pre-air preheaters. The bypass pipe is located between the two temperature-section pre-air preheaters in the series pre-air preheater group. The calculation module is used to calculate the heat load value and pressure difference parameter based on the pressure data, the hot water flow data, and the temperature data; The generation module is used to process the heat load value and the pressure difference parameter using the system dynamics equations of the MPC model to generate a pressure prediction sequence for future time steps. The optimization module is used to perform multi-step prediction optimization processing based on the pressure prediction sequence using a rolling time-domain optimization algorithm to obtain the optimal control command sequence that meets the preset optimization conditions. The adjustment module is used to generate the opening command of the shut-off valve on the bypass pipeline according to the optimal control command sequence, and adjust the valve opening on the bypass pipeline according to the opening command and the pressure status of the water supply branch and the return branch, using a distributed control architecture, so as to achieve pressure balance coordination control within the series pre-air preheater group and among multiple series pre-air preheater groups in parallel. The process of using the system dynamics equations of the MPC model to process the heat load value and the pressure difference parameter to generate a pressure prediction sequence for future time steps includes: Based on the heat load value and the pressure difference parameter, the fluid mass conservation equation and momentum conservation equation in the system dynamics equation of the MPC model are used to establish the dynamic coupling relationship between pressure, flow rate and temperature. Based on the dynamic coupling relationship, and combined with the current water supply branch pressure, return branch pressure, hot water flow rate, and temperature data of the two temperature-segment preheaters, the pressure change trajectory of the water supply branch and return branch in multiple consecutive time steps is predicted through forward iterative calculation. In each iteration of the calculation, the pressure change trajectory is dynamically corrected based on the heat load value, and a pressure prediction sequence is formed based on the corrected pressure change trajectory.

8. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the series-parallel pressure control method for the preheater of a tubular furnace as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, enables the series-parallel pressure control method for the preheater of a tubular furnace as described in any one of claims 1 to 6.

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