Residual heat boiler flue gas heat feedforward steam temperature control method and device, computer equipment, storage medium and computer program product

Abstract

The application relates to a waste heat boiler flue gas heat feedforward steam temperature control method and device, computer equipment, a storage medium and a computer program product. The method comprises the following steps: obtaining an operating parameter of a flue gas side, determining flue gas side heat release, flue gas side heat change amount and flue gas side heat change rate based on the operating parameter of the flue gas side; determining a primary economizer outlet temperature preliminary set value of the steam side based on a main steam temperature deviation of the steam side; determining a feedforward gain coefficient based on the main steam temperature deviation and the flue gas side heat change rate; determining a feedforward compensation amount based on the flue gas side heat change amount and the feedforward gain coefficient; superimposing the feedforward compensation amount on the primary economizer outlet temperature preliminary set value to obtain a final economizer outlet temperature set value; and generating a valve opening degree instruction based on the final economizer outlet temperature set value and a measured economizer outlet temperature value to control the steam side steam temperature. The method can improve the steam side steam temperature control accuracy.

Description

Technical Field

[0001] This application relates to the field of automatic control technology, and in particular to a method, device, computer equipment, storage medium and computer program product for controlling the feedforward steam temperature of waste heat boiler flue gas. Background Technology

[0002] In waste heat power generation systems, stable control of boiler superheated steam temperature is a key factor in ensuring the safe operation of the steam turbine.

[0003] In scenarios such as waste heat power generation in glass kilns, flue gas parameters fluctuate frequently with changes in the operating conditions of the glass kiln, directly affecting the heat exchange process of the boiler, which in turn causes the superheated steam temperature to deviate from the set value, requiring timely control by adjusting the desuperheating water volume.

[0004] Currently, the control of superheated steam temperature in waste heat power generation boilers mainly adopts a cascade PID control scheme. Some systems have introduced a steam flow feedforward signal on this basis to adjust the desuperheating water volume in advance.

[0005] However, the control signal of the above scheme comes from the steam side. When the flue gas temperature or flue gas flow fluctuates significantly due to the glass kiln fire change, operating condition adjustment, etc., the steam temperature will deviate significantly before the regulation action can be triggered, which makes it difficult for the steam temperature control to meet the turbine's accuracy requirements for steam parameters.

[0006] Therefore, the existing technology has the technical problem of low accuracy in steam side temperature control. Summary of the Invention

[0007] Based on this, it is necessary to provide a waste heat boiler flue gas heat feedforward steam temperature control method, device, computer equipment, computer-readable storage medium, and computer program product that can improve the accuracy of steam temperature control on the steam side, addressing the aforementioned technical problems.

[0008] In a first aspect, this application provides a method for controlling the steam temperature of a waste heat boiler by feeding forward the heat from the flue gas. The method includes: Obtain the operating parameters on the flue gas side, and based on the operating parameters on the flue gas side, determine the heat released on the flue gas side, the amount of heat change on the flue gas side, and the rate of heat change on the flue gas side; Obtain the main steam temperature deviation on the steam side, and determine the initial set value of the desuperheater outlet temperature on the steam side based on the main steam temperature deviation; The feedforward gain coefficient is determined based on the main steam temperature deviation and the flue gas side heat change rate. The feedforward compensation amount on the flue gas side is determined based on the change in heat on the flue gas side and the feedforward gain coefficient. The feedforward compensation is added to the initial set value of the desuperheater outlet temperature to obtain the final set value of the desuperheater outlet temperature. Based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature, a valve opening command is generated; the valve opening command is used to adjust the desuperheating water regulating valve on the steam side to control the steam temperature on the steam side.

[0009] In an exemplary embodiment, the operating parameters on the flue gas side include the flue gas inlet temperature, the flue gas outlet temperature, and the induced draft fan operating frequency signal; based on the operating parameters on the flue gas side, the heat released on the flue gas side, the change in heat on the flue gas side, and the rate of change in heat on the flue gas side are determined, including: The flue gas volumetric flow rate is determined based on the operating frequency signal of the induced draft fan; Obtain the flue gas side density and flue gas side isobaric specific heat capacity, and determine the flue gas side heat release in the current cycle based on the flue gas side volume flow rate, flue gas side density, flue gas side isobaric specific heat capacity, flue gas side inlet temperature and flue gas side outlet temperature; The change in flue gas heat is determined based on the difference between the heat released on the flue gas side in the current cycle and the heat released on the flue gas side in the previous cycle. The rate of change of heat on the flue gas side is determined based on the ratio of the change in heat on the flue gas side to the control cycle.

[0010] In one exemplary embodiment, determining the flue gas side volumetric flow rate based on the induced draft fan operating frequency signal includes: The induced draft fan speed is determined based on the induced draft fan operating frequency signal; The reference volumetric flow rate on the flue gas side is determined based on the characteristic curves of the induced draft fan frequency, rotation speed and flow rate. The average temperature of the flue gas side and the pressure difference between the inlet and outlet of the flue gas side induced draft fan are obtained. Based on the average temperature of the flue gas side and the pressure difference between the inlet and outlet of the flue gas side induced draft fan, the reference volumetric flow rate of the flue gas side is corrected for temperature and pressure to obtain the flue gas side volumetric flow rate under actual operating conditions.

[0011] In an exemplary embodiment, the feedforward gain coefficient is determined based on the main steam temperature deviation and the flue gas side heat change rate, including: Determine the steam temperature deviation correction coefficient based on the main steam temperature deviation; Determine the rate of change correction coefficient based on the rate of change of heat on the flue gas side; The feedforward gain coefficient is determined based on the basic feedforward gain coefficient, steam temperature deviation correction coefficient, and rate of change correction coefficient.

[0012] In one exemplary embodiment, a valve opening command is generated based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature, including: Based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature, an initial valve opening command is generated. Obtain the correspondence between the opening degree and flow rate of the desuperheating water regulating valve on the steam side, and perform linearization compensation on the initial valve opening command based on the correspondence between the opening degree and flow rate to obtain the compensated valve opening command. The valve opening command is obtained by limiting the high and low amplitude and the rate of change of the compensated valve opening command.

[0013] In one exemplary embodiment, the method further includes: When the flue gas inlet temperature is detected to rise above the first temperature threshold within a preset time, the feedforward gain coefficient is increased and the control cycle used to generate the initial set value of the desuperheater outlet temperature is shortened. When the flue gas inlet temperature is detected to drop more than the second temperature threshold within a preset time, the feedforward compensation amount is reversed to generate an instruction to reduce the output of desuperheating water. When any abnormality is detected in the signal of any sensor involved in the control, the feedforward compensation is cut off, and the system switches to feedback control mode or manual control mode.

[0014] Secondly, this application provides a waste heat boiler flue gas heat feedforward steam temperature control device, the device comprising: The parameter acquisition module is used to acquire the operating parameters of the flue gas side, and based on the operating parameters of the flue gas side, determine the heat released by the flue gas side, the amount of heat change of the flue gas side, and the rate of heat change of the flue gas side. The numerical determination module is used to obtain the main steam temperature deviation on the steam side and determine the preliminary set value of the desuperheater outlet temperature on the steam side based on the main steam temperature deviation. The coefficient determination module is used to determine the feedforward gain coefficient based on the main steam temperature deviation and the flue gas side heat change rate. The compensation amount determination module is used to determine the feedforward compensation amount on the flue gas side based on the change in heat on the flue gas side and the feedforward gain coefficient. The compensation superposition module is used to superimpose the feedforward compensation amount onto the initial set value of the desuperheater outlet temperature to obtain the final set value of the desuperheater outlet temperature. The instruction generation module is used to generate valve opening instructions based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature. The valve opening instructions are used to adjust the desuperheating water regulating valve on the steam side to control the steam temperature on the steam side.

[0015] Thirdly, this application provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method.

[0016] Fourthly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0017] Fifthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the above-described method.

[0018] The aforementioned waste heat boiler flue gas heat feedforward steam temperature control method, device, computer equipment, storage medium, and computer program product acquires the operating parameters of the flue gas side in real time and calculates the released heat, heat change, and heat change rate of the flue gas side. Simultaneously, it determines the initial set value of the desuperheater outlet temperature based on the main steam temperature deviation on the steam side. Then, based on the main steam temperature deviation and the flue gas heat change rate, it adaptively determines the feedforward gain coefficient, converting the flue gas heat change into a feedforward compensation amount and adding it to the desuperheater outlet temperature set value, ultimately generating a valve opening command. In this way, the traditional feedback control relying solely on steam side measurements is extended to a composite control architecture integrating flue gas side heat feedforward. By directly sensing the heat change on the flue gas side and pre-adjusting the desuperheating water flow, intervention is performed before the flue gas disturbance causes a significant deviation in the main steam temperature. This effectively solves the technical problem of large response lag and large overshoot in steam temperature control caused by large fluctuations in flue gas parameters in waste heat boilers, significantly improving the speed and stability of steam temperature control. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating a waste heat boiler flue gas heat feedforward steam temperature control method in one embodiment. Figure 2 This is a schematic diagram of the application architecture of a waste heat boiler flue gas heat feedforward steam temperature control method provided in one embodiment; Figure 3 This is a schematic diagram of a cascade feedback control branch provided in one embodiment; Figure 4 This is a flowchart illustrating a waste heat boiler flue gas heat feedforward steam temperature control method in another embodiment. Figure 5 This is a structural block diagram of a waste heat boiler flue gas heat feedforward steam temperature control device in one embodiment. Figure 6 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments.

[0022] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0023] In one exemplary embodiment, such as Figure 1 As shown, a method for controlling the steam temperature by feeding forward the heat from the flue gas of a waste heat boiler is provided. Taking the application of this method to a DCS control system as an example, the method includes the following steps S102 to S112. Wherein: Step S102: Obtain the operating parameters on the flue gas side, and based on the operating parameters on the flue gas side, determine the heat released on the flue gas side, the amount of heat change on the flue gas side, and the rate of heat change on the flue gas side.

[0024] Among them, the operating parameters on the flue gas side refer to the real-time measurement signals reflecting the thermal state of the flue gas collected by sensors installed on the flue gas passage of the waste heat boiler, including at least the flue gas side inlet temperature T_in, the flue gas side outlet temperature T_out, and the induced draft fan operating frequency signal.

[0025] Among them, the heat released on the flue gas side refers to the heat power released to the working medium by the flue gas through convection heat transfer during the process of the flue gas flowing through the heating surface of the waste heat boiler, denoted as Q.

[0026] The change in heat on the flue gas side refers to the difference between the heat released on the flue gas side calculated in the current control cycle and the heat released on the flue gas side calculated in the previous control cycle, denoted as ΔQ.

[0027] Among them, the flue gas side heat change rate refers to the rate of change of heat released by the flue gas side per unit time, denoted as dQ / dt, which is obtained by dividing the flue gas side heat change by the control period.

[0028] Optionally, in each control cycle, the control system first collects the operating parameters on the flue gas side, including the flue gas inlet temperature T_in (0-600°C), the flue gas outlet temperature T_out (0-400°C), and the induced draft fan operating frequency signal. Based on these operating parameters, the system calculates the heat released on the flue gas side in the current cycle, and then determines the amount of heat change and the rate of heat change on the flue gas side.

[0029] Step S104: Obtain the main steam temperature deviation on the steam side, and determine the preliminary set value of the desuperheater outlet temperature on the steam side based on the main steam temperature deviation.

[0030] Among them, the main steam temperature deviation on the steam side refers to the difference between the set value T_sp and the actual measured value T_pv of the main steam temperature at the superheater outlet, denoted as e, and its absolute value is denoted as |e|.

[0031] The set value T_sp is the rated main steam temperature of 450°C, and the actual measured value T_pv is the measured value of GT751CH05.

[0032] The initial set value of the desuperheater outlet temperature refers to the target value of the desuperheater outlet temperature determined by the preset steam-side temperature control strategy based on the main steam temperature deviation, before the feedforward compensation is added. It can be represented as T_sp_initial.

[0033] Optionally, the control system collects the measured value of the main steam temperature on the steam side, calculates the main steam temperature deviation, and determines the preliminary set value of the desuperheater outlet temperature based on the main steam temperature deviation.

[0034] In practical applications, the method of this application can be implemented based on a cascaded PID control structure.

[0035] The cascaded PID control structure includes a main loop and a secondary loop. The two control loops work together to achieve precise control of steam temperature.

[0036] The main circuit primarily controls the main steam temperature at the superheater outlet.

[0037] The main circuit is set to the rated main steam temperature (e.g., 450°C), which is manually set by the operator on the DCS operation screen or automatically given by the AGC command.

[0038] The measurement signal of the main circuit is the real-time acquisition value of the main steam temperature at the superheater outlet. The main circuit uses a PID1 controller, which performs feedback control calculations based on the deviation of the main steam temperature, and its output is the preliminary set value of the desuperheater outlet temperature.

[0039] The control cycle of the main circuit is 5 seconds, and the action mode is reverse action. That is, when the measured value of the main steam temperature increases, the output of PID1 decreases to reduce the initial set value of the desuperheater outlet temperature, thereby increasing the desuperheating water volume and suppressing the upward trend of the main steam temperature.

[0040] The secondary circuit uses the desuperheater outlet temperature (inlet steam temperature) as the secondary control object.

[0041] The measurement signal for the secondary circuit is the real-time acquired value of the desuperheater outlet temperature.

[0042] The secondary loop uses a PID2 controller, which performs feedback control calculations based on the deviation between the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature. Its output is the opening command of the desuperheating water regulating valve, which is directly output to the analog output card (such as the GT721AO card) to drive the desuperheating water regulating valve.

[0043] The control cycle of the secondary loop is 1 second, and the action mode is reverse action. That is, when the measured value of the desuperheater outlet temperature increases, the output of PID2 increases to increase the opening of the desuperheating water regulating valve, increase the desuperheating water volume, and suppress the rising trend of the upstream steam temperature.

[0044] The feedforward signal is superimposed after the output of the main circuit and before the set value of the secondary circuit.

[0045] The superposition formula is: secondary circuit setpoint = main circuit PID1 output + feedforward compensation.

[0046] The output of the main loop PID1 is the initial set value of the desuperheater outlet temperature. The feedforward compensation is obtained by multiplying the change in heat on the flue gas side by the feedforward gain coefficient (i.e., feedforward compensation = K_ff × ΔQ). The result obtained by superimposing these values ​​is the final set value of the desuperheater outlet temperature, which is used as the given value of the secondary loop PID2.

[0047] In the above cascade control structure, the control cycle of the secondary loop (1 second) is shorter than that of the primary loop (5 seconds), which enables the secondary loop to respond quickly to changes in the inlet steam temperature. In the early stage of flue gas disturbance causing fluctuations in the inlet steam temperature, the control is suppressed by adjusting the opening of the desuperheating water regulating valve, which effectively shortens the response time of the control system.

[0048] Meanwhile, the main loop uses a longer control cycle to precisely correct the main steam temperature, eliminating steady-state deviations and forming a hierarchical control architecture of "rapidly suppressing disturbances in the inner loop and precisely eliminating deviations in the outer loop".

[0049] Step S106: Determine the feedforward gain coefficient based on the main steam temperature deviation and the flue gas side heat change rate.

[0050] Among them, the feedforward gain coefficient is a coefficient used to adjust the influence of the change in heat on the flue gas side on the desuperheating water control loop, denoted as K_ff.

[0051] Optionally, the control system adaptively determines the feedforward gain coefficient K_ff based on the magnitude of the main steam temperature deviation e and the rate of change of heat on the flue gas side.

[0052] Step S108: Determine the feedforward compensation amount on the flue gas side based on the change in heat on the flue gas side and the feedforward gain coefficient.

[0053] Among them, the feedforward compensation amount refers to the compensation signal obtained by multiplying the change in heat on the flue gas side by the feedforward gain coefficient, which is used to superimpose the initial set value of the desuperheater outlet temperature.

[0054] Optionally, the control system multiplies the feedforward gain coefficient by the change in heat on the flue gas side to obtain the feedforward compensation.

[0055] Step S110: The feedforward compensation is superimposed on the initial set value of the desuperheater outlet temperature to obtain the final set value of the desuperheater outlet temperature.

[0056] The final set value of the desuperheater outlet temperature refers to the signal obtained by adding the initial set value of the desuperheater outlet temperature to the feedforward compensation amount, which serves as the target value for controlling the desuperheater outlet temperature. It can be represented as T_sp_final.

[0057] Optionally, the control system adds the feedforward compensation to the initial set value of the desuperheater outlet temperature to obtain the final set value of the desuperheater outlet temperature.

[0058] Step S112: Based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature, a valve opening command is generated; the valve opening command is used to adjust the desuperheating water regulating valve on the steam side to control the steam temperature on the steam side.

[0059] Among them, the desuperheater outlet temperature measurement value refers to the guide steam temperature signal collected in real time by the temperature sensor installed at the desuperheater outlet.

[0060] Among them, the valve opening command refers to the control signal that the control system finally outputs to the desuperheating water regulating valve positioner, which is used to change the valve opening to regulate the desuperheating water flow.

[0061] Among them, the desuperheating water regulating valve refers to the actuator installed on the desuperheating water pipeline, which is used to regulate the flow rate of desuperheating water injected into the superheater to control the steam temperature.

[0062] Optionally, the control system calculates and outputs a valve opening command based on the deviation between the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature, and adjusts the opening of the desuperheating water regulating valve to control the steam temperature on the steam side.

[0063] In the aforementioned waste heat boiler flue gas heat feedforward steam temperature control method, the operating parameters of the flue gas side are acquired in real time, and the released heat, heat change, and heat change rate of the flue gas side are calculated. At the same time, the initial set value of the desuperheater outlet temperature is determined based on the main steam temperature deviation on the steam side. Then, the feedforward gain coefficient is adaptively determined based on the main steam temperature deviation and the flue gas heat change rate, and the flue gas heat change is converted into a feedforward compensation amount and added to the desuperheater outlet temperature set value, finally generating a valve opening command. In this way, the traditional feedback control that only relies on steam side measurement is extended to a composite control architecture that integrates flue gas side heat feedforward. By directly sensing the heat change on the flue gas side and adjusting the desuperheating water volume in advance, intervention is carried out before the flue gas disturbance causes a significant deviation in the main steam temperature. This effectively solves the technical problem of large response lag and large overshoot in steam temperature control caused by large fluctuations in flue gas parameters in waste heat boilers, and significantly improves the speed and stability of steam temperature control.

[0064] In an exemplary embodiment, the operating parameters on the flue gas side include the flue gas inlet temperature, the flue gas outlet temperature, and the induced draft fan operating frequency signal. Based on the flue gas side operating parameters, the heat released on the flue gas side, the change in heat on the flue gas side, and the rate of change in heat on the flue gas side are determined, including: determining the flue gas side volumetric flow rate based on the induced draft fan operating frequency signal; obtaining the flue gas side density and the flue gas side isobaric specific heat capacity, and determining the heat released on the flue gas side in the current cycle based on the flue gas side volumetric flow rate, flue gas side density, flue gas side isobaric specific heat capacity, flue gas side inlet temperature, and flue gas side outlet temperature; determining the change in heat on the flue gas side based on the difference between the heat released on the flue gas side in the current cycle and the heat released on the flue gas side in the previous cycle; and determining the rate of change in heat on the flue gas side based on the ratio of the change in heat on the flue gas side to the control cycle.

[0065] The flue gas inlet temperature refers to the flue gas temperature signal measured by the temperature sensor installed at the flue gas inlet of the waste heat boiler, denoted as T_in, and the unit is ℃.

[0066] The flue gas outlet temperature refers to the flue gas temperature signal measured by the temperature sensor installed at the flue gas outlet of the waste heat boiler, denoted as T_out, and the unit is ℃.

[0067] Among them, the induced draft fan operating frequency signal refers to the analog signal that is fed back from the induced draft fan frequency converter and represents the current operating frequency of the induced draft fan.

[0068] The flue gas volumetric flow rate refers to the actual volume of flue gas flowing through the boiler heating surface per unit time, with the unit being Nm³ / h, denoted as V.

[0069] Among them, the flue gas side density refers to the mass density of flue gas under actual operating conditions, with the unit being kg / Nm³, denoted as ρ.

[0070] The density of flue gas can be calculated based on the ideal gas law with temperature correction, expressed as ρ=P0×M / [R×(T_g+273)], where P0 is the standard atmospheric pressure (101325Pa), M is the average molar mass of flue gas (kg / mol), R is the universal gas constant (8.314J / (mol·K)), and T_g is the average temperature on the flue gas side (°C).

[0071] Among them, the specific heat capacity at constant pressure of flue gas refers to the amount of heat required to increase the temperature of a unit mass of flue gas by 1 K under constant pressure, with the unit being kJ / (kg·K), denoted as Cp.

[0072] The isobaric specific heat capacity of flue gas can be calculated by weighted summation of the volume fraction of each component of the flue gas and the specific heat capacity of each component at the corresponding temperature, expressed as Cp=Σ(Xi×Cpi), where Xi is the volume fraction of the i-th component of the flue gas, and Cpi is the isobaric specific heat capacity of the i-th component at the average temperature of the flue gas. The Cpi of each component can be determined by looking up a table or by empirical polynomial formula based on the temperature.

[0073] Considering that changes in the fuel-air ratio may alter the flue gas composition and its specific heat capacity during glass furnace fire changes or operating condition adjustments, in a more preferred embodiment, the flue gas composition volume fraction Xi can be updated in real time based on signals such as fuel flow rate and air-fuel ratio, thereby dynamically correcting the flue gas constant pressure specific heat capacity Cp to further improve the calculation accuracy of feedforward heat.

[0074] The heat released from the flue gas side in the current cycle refers to the heat transfer from flue gas convection, calculated based on the flue gas parameters collected in the current control cycle, denoted as Q_now, with units of kW.

[0075] The heat released from the flue gas side in the previous cycle refers to the heat released from the flue gas calculated and stored in the previous control cycle, denoted as Q_prev, with the unit being kW.

[0076] The change in heat on the flue gas side refers to the difference between the heat released on the flue gas side in the current cycle and the heat released on the flue gas side in the previous cycle, denoted as ΔQ, with the unit being kW.

[0077] The control cycle refers to the time interval between the control system performing one complete control operation.

[0078] Among them, the flue gas side heat change rate refers to the rate of change of heat released from the flue gas side per unit time, denoted as dQ / dt, with the unit being kW / s, and is obtained by dividing the flue gas side heat change by the control period.

[0079] For example, dQ / dt=(Q_now-Q_prev) / Δt, where Q_now is the heat value of the current cycle, Q_prev is the heat value of the previous cycle, and Δt is the control cycle, which can be 5 seconds.

[0080] Optionally, the control system performs the following calculation logic in the heat calculation.

[0081] First, based on the operating frequency signal of the induced draft fan and combined with the frequency-speed-flow characteristic relationship of the induced draft fan, the volumetric flow rate of the flue gas side is determined.

[0082] Meanwhile, based on the flue gas inlet and outlet temperatures, the average flue gas temperature T_g = (T_in + T_out) / 2 is calculated.

[0083] Then, based on the average temperature and composition information of the flue gas side, the density and specific heat capacity of the flue gas side at constant pressure are determined.

[0084] The density of flue gas can be calculated based on the ideal gas law with temperature correction, and the specific heat capacity of flue gas at constant pressure can be calculated by weighted summation of the volume fraction of each component of the flue gas and the specific heat capacity of each component at the corresponding temperature.

[0085] The formula for calculating the heat released by flue gas is: Q = V_actual × ρ_actual × Cp × (T_in - T_out).

[0086] In the formula, Q is the heat released by the flue gas, in kW; V is the flue gas volumetric flow rate under actual operating conditions, in Nm³ / h; ρ_actual is the flue gas density under actual operating conditions, in kg / Nm³; Cp is the flue gas specific heat capacity at constant pressure, in kJ / (kg·K); T_in is the flue gas inlet temperature, in °C; and T_out is the flue gas outlet temperature, in °C.

[0087] The actual flue gas density can be obtained by correcting the density under standard conditions for temperature and pressure. For example, the formula ρ_actual=ρ_std×(273 / (T_g+273))×(P_abs / P_std) can be used, where P_abs is the absolute pressure of the flue gas and P_std is the standard atmospheric pressure.

[0088] Substituting the flue gas side volumetric flow rate, flue gas side density, flue gas side isobaric specific heat capacity, and the difference between the flue gas side inlet temperature and outlet temperature into the above formula, we can obtain the heat released by the flue gas side in the current cycle, Q_now.

[0089] Subtract the heat released from the flue gas side in the current cycle, Q_now, from the heat value of the previous cycle, Q_prev, stored in memory, to obtain the change in heat on the flue gas side, ΔQ = Q_now - Q_prev.

[0090] Dividing the change in heat on the flue gas side by the control period, we obtain the rate of change in heat on the flue gas side: dQ / dt = ΔQ / Δt.

[0091] Finally, the heat released from the flue gas side in the current cycle, Q_now, is stored in memory for use in the calculation of the next cycle.

[0092] In this embodiment, the volumetric flow rate of the flue gas is indirectly determined by the operating frequency signal of the induced draft fan, and the heat released on the flue gas side is calculated by combining the flue gas physical properties and the inlet and outlet temperature difference, thus realizing real-time soft measurement of flue gas heat.

[0093] This heat calculation method based on existing instrument signals can obtain heat information reflecting changes in flue gas side conditions without the need to install an expensive flue gas flow meter. This allows the control system to detect heat change trends in the early stages of flue gas condition fluctuations, providing a direct and timely source of disturbance signals for subsequent feedforward compensation. It effectively solves the problem of control response lag caused by the lack of direct flue gas side measurement.

[0094] In an exemplary embodiment, determining the feedforward gain coefficient based on the main steam temperature deviation and the flue gas side heat change rate includes: determining a steam temperature deviation correction coefficient based on the main steam temperature deviation; determining a change rate correction coefficient based on the flue gas side heat change rate; and determining the feedforward gain coefficient based on the basic feedforward gain coefficient, the steam temperature deviation correction coefficient, and the change rate correction coefficient.

[0095] The main steam temperature deviation refers to the absolute value of the difference between the set value IN1 (450°C) and the actual measured value IN2 (0-500°C) of the main steam temperature at the superheater outlet, denoted as |e|.

[0096] Among them, the steam temperature deviation correction coefficient refers to the coefficient that adjusts the feedforward gain in stages according to the magnitude of the main steam temperature deviation, denoted as α, α = f(|T_sp - T_pv|).

[0097] The purpose of this design is to ensure system stability when the steam temperature deviation is large, as excessive feedforward contribution may cause reverse overshoot.

[0098] Among them, the rate of change of heat on the flue gas side refers to the rate of change of heat released on the flue gas side per unit time, denoted as dQ / dt.

[0099] Among them, the rate of change correction coefficient refers to the coefficient that dynamically corrects the feedforward gain according to the magnitude of the rate of change of heat on the flue gas side, denoted as β, β = 1 + k ×IN3, IN3 = dQ / dt, and k can be taken as 0.01.

[0100] The base feedforward gain coefficient refers to the uncorrected feedforward gain reference value determined by thermal balance calculations or engineering debugging, denoted as K_base.

[0101] The feedforward gain coefficient refers to the final feedforward gain value after temperature deviation correction and rate of change correction, denoted as K_ff.

[0102] Optionally, the control system performs the following steps in the adaptive adjustment of the feedforward coefficient: First, it determines the magnitude of the main steam temperature deviation e. When e is less than or equal to the first threshold 5, the steam temperature deviation correction coefficient α is taken as the first correction value 1. When e is greater than the first threshold 5 and less than or equal to the second threshold 10, α is taken as the second correction value 0.8. When e is greater than the second threshold 10, α is taken as the third correction value 0.6.

[0103] The first correction value is greater than the second correction value, and the second correction value is greater than the third correction value. The logic behind this design is as follows: when the steam temperature deviation is small, it indicates that the coordination between the feedforward and feedback is good, and the feedforward can maintain a strong gain to fully utilize its rapid compensation function; when the steam temperature deviation is large, it indicates that the current operating condition may be more complex or the feedforward has an overshooting tendency, and the feedforward gain needs to be appropriately reduced to avoid excessive feedforward leading to reverse overshoot.

[0104] Then, the correction coefficient β for the rate of change of heat of flue gas is calculated based on the rate of change of heat of flue gas dQ / dt. The calculation formula is β=1+k×dQ / dt, where k is the rate of change sensitivity coefficient, which can be adjusted according to the actual debugging effect.

[0105] The β is limited. If β is greater than 2, then β is controlled to be 2. If β is less than 0.5, then β is controlled to be 0.5, so that it is kept within the preset lower and upper limits to prevent the feedforward gain from being amplified to an unreasonable level when the heat change is too drastic.

[0106] Finally, the basic feedforward gain coefficient K_base (which can be 0.15) is multiplied by the steam temperature deviation correction coefficient α and the rate of change correction coefficient β to obtain the final feedforward gain coefficient K_ff. K_ff is then limited to ensure that it is within a safe and reasonable range.

[0107] In this embodiment, the adaptive adjustment of the feedforward gain is achieved by adjusting the steam temperature deviation correction coefficient in stages according to the magnitude of the main steam temperature deviation, and by dynamically adjusting the rate of change correction coefficient according to the rate of change of heat on the flue gas side.

[0108] When the steam temperature deviation is small, the feedforward gain is kept at a large value to give full play to the rapid compensation effect of the feedforward; when the steam temperature deviation is large, the feedforward gain is appropriately reduced to avoid aggravating the steam temperature fluctuation due to excessive feedforward.

[0109] Meanwhile, the introduction of a rate of change correction coefficient can enhance the feedforward effect for rapid response when flue gas conditions change drastically, and weaken the feedforward effect to improve system stability when flue gas conditions are stable.

[0110] This adaptive gain algorithm effectively solves the problem that fixed feedforward gain is difficult to balance response speed and stability under complex operating conditions, and avoids the deterioration of control quality caused by excessive or insufficient feedforward.

[0111] In one exemplary embodiment, determining the flue gas side volumetric flow rate based on the induced draft fan operating frequency signal includes: determining the induced draft fan speed according to the induced draft fan operating frequency signal; determining the flue gas side reference volumetric flow rate based on the characteristic curve of induced draft fan frequency, speed and flow rate; obtaining the flue gas side average temperature and the flue gas side induced draft fan inlet and outlet pressure difference, and performing temperature correction and pressure correction on the flue gas side reference volumetric flow rate based on the flue gas side average temperature and the flue gas side induced draft fan inlet and outlet pressure difference to obtain the flue gas side volumetric flow rate under actual operating conditions.

[0112] Among them, the induced draft fan operating frequency signal refers to the analog signal that represents the current operating frequency fed back from the induced draft fan frequency converter.

[0113] The induced draft fan speed refers to the actual rotational speed of the induced draft fan impeller, measured in r / min and denoted as n, which is calculated from the induced draft fan operating frequency signal.

[0114] Among them, the characteristic curves of the induced draft fan frequency, speed and flow rate refer to the functions provided by the fan manufacturer or obtained through on-site calibration, which describe the volumetric flow rate relationship of the induced draft fan at different frequencies and speeds.

[0115] Among them, the flue gas side reference volumetric flow rate refers to the uncorrected volumetric flow rate value determined according to the characteristic curve of the induced draft fan under standard operating conditions, denoted as V_base.

[0116] The average temperature on the flue gas side refers to the arithmetic mean of the flue gas inlet temperature and the flue gas outlet temperature, denoted as T_g, which is used to correct the volumetric flow rate for temperature.

[0117] Among them, the pressure difference between the inlet and outlet of the flue gas side induced draft fan is the difference between the outlet pressure and the inlet pressure of the induced draft fan, denoted as ΔP, which is used to correct the volumetric flow rate by pressure.

[0118] Temperature correction refers to the correction of the reference volumetric flow rate based on the difference between the actual flue gas temperature and the standard state temperature, according to the ideal gas law.

[0119] Pressure correction refers to the correction of the reference volumetric flow rate based on the difference between the actual flue gas pressure and the standard atmospheric pressure.

[0120] The actual flue gas volumetric flow rate refers to the flue gas volumetric flow rate after temperature and pressure correction, reflecting the actual operating conditions, denoted as V_actual.

[0121] Optionally, the control system performs the following steps in the flue gas flow calculation function block: First, convert the induced draft fan operating frequency signal into the induced draft fan speed.

[0122] Then, based on the fan frequency-speed-flow characteristic curve provided by the manufacturer or the field calibration data, establish the correspondence between the benchmark volumetric flow rate and the frequency or speed of the induced draft fan.

[0123] The reference volumetric flow rate can be expressed as the product of the induced draft fan speed and the fan characteristic coefficient.

[0124] Next, the inlet and outlet temperatures of the flue gas are collected, and the average temperature T_g of the flue gas is calculated.

[0125] Based on the ideal gas law, a temperature correction is applied to the reference volumetric flow rate. The correction formula includes a factor representing the ratio of the average temperature on the flue gas side to the standard state temperature.

[0126] Finally, the reference volumetric flow rate is multiplied by the temperature correction factor and the pressure correction factor to obtain the flue gas volumetric flow rate under actual operating conditions.

[0127] In practical applications, temperature correction is performed using the formula V_actual=k×n×(T_g+273) / 273, where k is the fan characteristic coefficient (provided by the manufacturer or obtained through calibration), n is the induced draft fan speed (r / min), obtained from the frequency converter feedback signal, and T_g is the average flue gas temperature (°C).

[0128] In this embodiment, by establishing the characteristic relationship between the frequency, rotational speed, and flow rate of the induced draft fan and supplementing it with temperature and pressure corrections, indirect measurement of the volumetric flow rate of the flue gas side is achieved without installing a flue gas flow meter.

[0129] This soft measurement method utilizes the existing induced draft fan frequency converter feedback signal and temperature and pressure measuring points in the control system to obtain the flue gas volume flow signal that meets the accuracy requirements of feedforward control without the need for additional hardware. It solves the problem that waste heat boilers usually lack flue gas flow measuring points and cannot directly obtain flue gas heat change information. It provides a key calculation basis for flue gas side heat feedforward control, making the feedforward control scheme feasible and scalable in practical engineering.

[0130] In an exemplary embodiment, the method further includes: when the flue gas inlet temperature is detected to rise above a first temperature threshold within a preset time, increasing the feedforward gain coefficient and shortening the control cycle used to generate the preliminary set value of the desuperheater outlet temperature; when the flue gas inlet temperature is detected to fall below a second temperature threshold within a preset time, reversing the feedforward compensation amount to generate an instruction to indicate a reduction in the output of desuperheating water; and when any abnormality is detected in the signal of any sensor involved in the control, cutting off the feedforward compensation amount and switching to feedback control mode or manual control mode.

[0131] The preset time refers to the monitoring time window used to determine whether the change in flue gas temperature is an abnormal sudden change, and it can be set to 30 seconds.

[0132] The first temperature threshold refers to the temperature change limit for determining a sudden increase in the flue gas inlet temperature, which can be set to 50℃.

[0133] The second temperature threshold refers to the limit value for determining the temperature change that causes a sudden drop in the flue gas inlet temperature, which can be set to 40℃.

[0134] The first and second temperature thresholds mentioned above are exemplary settings. In actual engineering, they can be adjusted and modified based on field data such as the process characteristics of the glass kiln and the rate of change of flue gas temperature during normal fire replacement.

[0135] Even better, it can be combined with the identification of ignition switching signals or flue gas temperature change patterns to distinguish between normal ignition switching operations and abnormal temperature surges, thus avoiding triggering protection actions during normal operations.

[0136] Increasing the feedforward gain coefficient means multiplying the current feedforward gain coefficient by a preset amplification factor when a sudden rise in flue gas temperature is detected, in order to accelerate the response speed of adding desuperheating water. The amplification factor can be set to 2 times.

[0137] Shortening the control cycle refers to reducing the control cycle of the control loop that generates the initial set value of the desuperheater outlet temperature from the normal value when a sudden rise in flue gas temperature is detected, so as to speed up the response frequency of the control loop. The control cycle can be shortened from 5 seconds to 2 seconds.

[0138] The reverse output of the feedforward compensation means that when a sudden drop in flue gas temperature is detected, the sign of the feedforward compensation is reversed, so that the desuperheating water volume is adjusted to decrease.

[0139] The pause integral action refers to temporarily freezing the accumulation of integral components in the control loop when a sudden drop in flue gas temperature is detected, in order to prevent integral saturation caused by continuous accumulation of deviations.

[0140] Among them, abnormal sensor signal means that the control system detects that the quality of the sensor signal is bad, such as signal disconnection or exceeding the range.

[0141] Among them, cutting off the feedforward compensation means forcibly setting the feedforward compensation to zero, causing the control system to degenerate into a feedback control mode that relies solely on the steam side deviation for adjustment.

[0142] Among them, the feedback control mode refers to the cascade control mode that relies solely on the main steam temperature deviation and the desuperheater outlet temperature deviation for adjustment.

[0143] Among them, the manual control mode refers to the control method in which the operator directly sets the opening degree of the desuperheating water regulating valve based on experience.

[0144] Optionally, the control system performs the following steps in the abnormal operating condition protection function block: First, continuously record the historical value of the flue gas side inlet temperature and store it in memory.

[0145] In each control cycle, the difference between the current flue gas inlet temperature and the historical value before the preset time is calculated and denoted as ΔT_gas=T_gas_in-T_gas_prev. It is then determined whether the difference exceeds the preset temperature threshold.

[0146] Specifically, protection can be provided against sudden increases in flue gas temperature. When ΔT_gas is greater than 50°C and the temperature change occurs within 30 seconds, a sudden increase in flue gas temperature is determined to have occurred, triggering the sudden increase protection action.

[0147] Increase the feedforward gain coefficient K_ff to twice the normal value to quickly increase the desuperheating water volume; shorten the control cycle of the control loop that generates the initial set value of the desuperheater outlet temperature from the normal 5 seconds to 2 seconds to speed up the response frequency of the control loop; at the same time, trigger an alarm to notify the operators that "the flue gas temperature has suddenly increased and the steam temperature is being adjusted".

[0148] Ten seconds after the sudden temperature rise protection is triggered, the control system checks whether the main steam temperature deviation e = |450 - T_main| exceeds 10°C. If e is greater than 10°C, the alarm is escalated to an emergency alarm, displaying the message "Steam temperature deviation is too large, manual intervention is recommended"; if e is not greater than 10°C, the control parameters are gradually restored, decreasing the feedforward gain coefficient K_ff by 0.1 each time. When K_ff recovers to 1.0, the control cycle is restored to 5 seconds, and the alarm is deactivated.

[0149] It can protect against sudden drops in flue gas temperature. When ΔT_gas is less than -40°C and the temperature change occurs within 30 seconds, a sudden drop in flue gas temperature is determined to have occurred, triggering the sudden drop protection action.

[0150] The feedforward compensation is superimposed on the initial set value of the desuperheater outlet temperature to make the generated valve opening command adjust in the closing direction (i.e., the direction of reducing desuperheating water); the integral action in the control loop that generates the initial set value of the desuperheater outlet temperature is suspended, that is, the integral enable flag is set to the prohibited state to prevent integral saturation caused by continuous deviation accumulation.

[0151] At the same time, it checks whether the main steam temperature T_main is below 430°C. If so, it triggers a low temperature alarm and prompts "Main steam temperature is too low, please monitor carefully".

[0152] The control system continuously monitors the main steam temperature. When the main steam temperature rises above 440°C, the reduction adjustment of the feedforward compensation is canceled, the integral action is restored, and the alarm is deactivated.

[0153] It can protect against sensor malfunctions. The control system continuously monitors the quality indicators of the signals from each sensor involved in the control.

[0154] When the quality indicator of any sensor signal becomes bad quality, differentiated processing is performed based on the type of faulty sensor.

[0155] If the fault is in the flue gas temperature signal, the feedforward compensation will be forcibly reset to zero, the feedforward control will be cut off, and the system will switch to a pure feedback cascade control mode that relies solely on the main steam temperature deviation and the desuperheater outlet temperature deviation for adjustment. An alarm message will be triggered indicating "Flue gas temperature signal fault, feedforward cut off". If the fault is in the main steam temperature signal, the system will switch to manual control mode, maintain the desuperheating water regulating valve at a preset safe opening (e.g., 50%), and trigger an emergency alarm message indicating "Main steam temperature signal fault, please handle manually".

[0156] If the desuperheating water flow signal is faulty, close the desuperheating water regulating valve to the preset safe opening (e.g., 20%) and trigger an alarm message "Desuperheating water flow signal fault, awaiting manual handling".

[0157] In this embodiment, by setting up multi-level abnormal operating condition protection logic, the feedforward effect is rapidly enhanced and the control loop response is accelerated when the flue gas temperature rises suddenly; the feedforward is adjusted in the opposite direction and integral saturation is prevented when the flue gas temperature drops suddenly; and the control mode is automatically downgraded or switched to manual operation when the sensor fails, thus comprehensively improving the robustness and safety of the control system.

[0158] After the sudden rise protection action, a recovery judgment mechanism is also set up. When the steam temperature deviation does not exceed the limit, the control parameters are gradually restored to the normal value to avoid long-term operation under abnormal control parameters.

[0159] This graded protection mechanism effectively solves the problem that under extreme operating conditions or abnormal signals, a single feedforward-feedback composite control may lead to steam temperature runaway due to mismatched control parameters or signal distortion. It ensures that the steam temperature is always within a controllable range under various abnormal conditions, avoiding serious safety accidents such as superheater overheating and tube rupture or turbine water ingress.

[0160] In one exemplary embodiment, a valve opening command is generated based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature. This includes: generating an initial valve opening command based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature; obtaining the correspondence between the opening and flow rate of the steam-side desuperheating water regulating valve, and performing linearization compensation processing on the initial valve opening command according to the correspondence between the opening and flow rate to obtain a compensated valve opening command; and applying high and low amplitude limits and change rate limits to the compensated valve opening command to obtain the valve opening command.

[0161] The final set value of the desuperheater outlet temperature refers to the target value of the desuperheater outlet temperature control after the feedforward compensation is added.

[0162] Among them, the desuperheater outlet temperature measurement value refers to the guide steam temperature signal collected in real time by the temperature sensor installed at the desuperheater outlet.

[0163] The initial valve opening command refers to the valve opening signal that is directly calculated and output by a preset control algorithm based on the deviation between the final set value and the measured value of the desuperheater outlet temperature, without compensation or amplitude limiting.

[0164] The relationship between valve opening and flow rate refers to the inherent flow characteristic function of the desuperheating water regulating valve, which describes the relationship between the valve opening and the flow rate of the medium passing through the valve.

[0165] Linearization compensation refers to performing an inverse function operation on the initial valve opening command based on the valve's flow characteristic function, so that the compensated opening command and the actual flow present an approximately linear relationship, thereby improving control quality.

[0166] Among them, the compensated valve opening command refers to the valve opening signal that has undergone linearization compensation processing but has not yet been subjected to amplitude limiting processing.

[0167] Among them, high and low limits refer to setting the upper and lower limits of the output for the valve opening command to prevent the safety risks caused by the valve being fully open or fully closed.

[0168] Among them, the rate of change limit refers to setting an upper limit on the amount of change of the valve opening command per unit time to prevent the valve from moving too fast and causing water hammer and other impact phenomena.

[0169] Among them, the valve opening command refers to the control signal that is finally output to the positioner of the desuperheating water regulating valve.

[0170] Optionally, the control system performs the following steps in the valve characteristic compensation and limiting function block: First, based on the deviation between the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature, the control algorithm calculates and outputs the initial valve opening command.

[0171] Then, obtain the relationship between the opening degree of the desuperheating water regulating valve and the flow rate.

[0172] If the control valve has an equal percentage flow characteristic, its relative flow rate and relative stroke have an exponential relationship, which is determined by the turnability ratio (R).

[0173] To achieve linear control, the required relative stroke needs to be calculated from the required relative flow rate.

[0174] The initial valve opening command is mapped to the required relative flow rate. Substituting this into the inverse function formula of the equal percentage valve characteristic, the compensated relative stroke is calculated. Then, the relative stroke is converted into the compensated valve opening command.

[0175] Next, the valve opening command after compensation is subjected to high and low amplitude limit processing.

[0176] The high limit is set to not exceed the preset maximum opening limit to ensure that the valve has an adjustment margin and to prevent the valve from being fully open and unable to respond when a rapid increase in desuperheating water is needed; the low limit is set to not be lower than the preset minimum opening limit to ensure valve sealing and prevent internal leakage caused by the valve being fully closed.

[0177] Finally, the rate of change of the amplitude-limited signal is limited.

[0178] Calculate the difference between the valve opening command of the current cycle and the previous cycle. If the absolute value of the difference exceeds the preset maximum rate of change, adjust the output value of the current cycle according to the maximum rate of change to prevent water hammer caused by excessively rapid valve action from impacting and damaging pipelines and equipment.

[0179] In practical applications, desuperheating water regulating valves are selected based on equal percentage flow characteristics.

[0180] The adjustable ratio (R) refers to the ratio of the maximum flow rate to the minimum adjustable flow rate when the valve is fully open, reflecting the adjustment range of the valve. In this example, R is set to 30.

[0181] The relationship between the relative flow rate (q) and the relative stroke (l) of an equal percentage valve is q=R^(l-1), where the relative stroke l=L / 100, L is the valve opening percentage, and the value ranges from 0 to 1; the relative flow rate q=Q / Qmax is the ratio of the actual flow rate through the valve to the maximum flow rate, and the value ranges from 0 to 1.

[0182] To achieve linear compensation, the required relative travel needs to be calculated from the required relative flow rate. The inverse function formula is l=1+ln(q) / ln(R).

[0183] The specific compensation process is as follows: Divide the initial valve opening command U by 100 to obtain the required relative flow rate q_req=U / 100.

[0184] When q_req is greater than the linearization compensation trigger threshold of 0.01, the relative stroke after compensation is calculated by substituting into the inverse function formula: l_calc = 1 + ln(q_req) / ln(R). Then, the relative stroke is converted into the valve opening percentage: L = l_calc × 100. When q_req is less than or equal to 0.01, the valve opening command is directly set to 0, i.e., the valve is fully closed.

[0185] The valve opening command after compensation is initially limited. If L is greater than 100, then 100 is used; if L is less than 0, then 0 is used.

[0186] Then, the valve opening command after the initial limit is processed with high and low limits: the high limit is set to 95%, that is, the valve opening does not exceed 95%, in order to retain the adjustment margin and avoid the valve being in a fully open state and unable to respond when it is necessary to quickly increase the desuperheating water; the low limit is set to 5%, that is, the valve opening is not less than 5%, in order to ensure the valve sealing and prevent internal leakage caused by the valve being fully closed.

[0187] Finally, the rate of change of the valve opening command after the amplitude limit is applied.

[0188] The maximum rate of change refers to the maximum amount of change allowed in the valve opening command per unit time. In this example, it is set to 5% / s, and the execution cycle is 1s.

[0189] Calculate the difference ΔL between the valve opening command L_limit after the current cycle limit and the valve opening command L_prev finally output in the previous cycle. ΔL = L_limit - L_prev.

[0190] If the absolute value of ΔL is greater than 5%, the output value of this cycle is adjusted according to the maximum rate of change of 5%. That is, if ΔL>0, then L_final=L_prev+5; if ΔL<0, then L_final=L_prev-5; if the absolute value of ΔL is not greater than 5%, then L_final=L_limit is output directly.

[0191] Save the L_final of this cycle as L_prev for use in the next cycle.

[0192] The final output valve opening command L_final is sent to the desuperheating water regulating valve positioner.

[0193] In this embodiment, by performing linearization compensation on the desuperheating water regulating valve, the inherent nonlinear flow characteristics of the valve are compensated, so that the control output and the actual flow through the valve present a good linear relationship, thereby obtaining a stable control gain throughout the entire stroke range, avoiding the problem of overly sensitive control at small openings and overly slow control at large openings caused by valve nonlinearity.

[0194] Meanwhile, by setting high and low limits and change rate restrictions, the problem of interruption of desuperheating water or excessive water spraying that may be caused by fully opening or closing the valve is prevented, and the impact damage to pipelines and equipment caused by water hammer caused by excessively rapid valve action is avoided.

[0195] This valve coordination control strategy effectively solves the problems of poor control effect and equipment safety hazards caused by the nonlinear characteristics and unreasonable actions of regulating valves, and further improves the accuracy of steam temperature control and the long-term operational reliability of the system.

[0196] Figure 2 This is a schematic diagram of the application architecture of a waste heat boiler flue gas heat feedforward steam temperature control method provided in an embodiment of this application.

[0197] like Figure 2 As shown, the method is implemented based on a DCS control system, which is equipped with an AI analog input card (GT711), an RTD thermal resistance input card (GT751), an AO analog output card (GT721), and a DO digital output card (GT741).

[0198] Among them, the GT711AI card is used to collect the induced draft fan operating frequency signal, the desuperheating water flow signal, and the induced draft fan inlet and outlet pressure difference signal; the GT751RTD card is used to collect the flue gas side inlet temperature signal, the flue gas side outlet temperature signal, the main steam temperature signal, and the guide steam temperature signal; the GT721AO card is used to output the desuperheating water regulating valve opening command; and the GT741DO card is used to output the dry contact protection signal under abnormal operating conditions.

[0199] All calculation and control logic for implementing the method in this application is based on the existing AI / RTD / AO cards and standard function blocks of the DCS system, without the need for additional dedicated controllers or instruments, which effectively reduces the system implementation cost and improves the maintainability and long-term operational reliability of the system.

[0200] The DCS control system includes a feedforward calculation branch and a cascade feedback control branch.

[0201] The feedforward calculation branch includes a flue gas heat calculation module and a feedforward coefficient adaptive module.

[0202] The inputs to the flue gas heat calculation module include: induced draft fan operating frequency signal (converted to rotational speed n), flue gas inlet temperature T_in, flue gas outlet temperature T_out, induced draft fan inlet and outlet pressure difference ΔP, standard atmospheric pressure P0 (constant), fan characteristic coefficient k (provided by the manufacturer or calibrated on-site), average flue gas temperature T_g=(T_in+T_out) / 2, flue gas density ρ, and flue gas specific heat capacity at constant pressure Cp.

[0203] This module calculates the heat released by the flue gas in the current cycle, Q_now, based on the formulas V=k×n×(T_g+273) / 273 and Q=V×ρ×Cp×(T_in-T_out). It also stores the heat value Q_prev from the previous cycle into memory and outputs the change in heat on the flue gas side, ΔQ=Q_now-Q_prev, and the rate of change in heat on the flue gas side, dQ / dt=ΔQ / Δt.

[0204] The inputs to the feedforward coefficient adaptive module include: main steam temperature setpoint T_sp=450°C, main steam temperature measurement T_pv (from GT751RTD channel 05), main steam temperature deviation e=T_sp-T_pv, flue gas side heat change rate dQ / dt (from flue gas heat calculation module), and basic feedforward gain coefficient K_base=0.15.

[0205] The internal calculation logic of this module is as follows: steam temperature deviation correction coefficient α=f(|e|), when |e|≤5°C α=1.0, when 5°C<|e|≤10°C α=0.8, when |e|>10°C α=0.6; change rate correction coefficient β=1+0.01×dQ / dt, and limited to 0.5≤β≤2.0.

[0206] This module calculates the feedforward gain coefficient according to the formula K_ff=K_base×α×β and outputs the feedforward compensation amount=K_ff×ΔQ.

[0207] The control system adds the feedforward compensation to the initial set value of the desuperheater outlet temperature to obtain the final set value of the secondary loop, i.e., the final set value of the desuperheater outlet temperature. The superposition formula is: T_sp_final=T_sp_initial+(K_ff×ΔQ).

[0208] Figure 3 A schematic diagram of a cascade feedback control branch is shown.

[0209] The outer loop is the main steam temperature PID controller (PID1), whose setpoint (SP) is the rated main steam temperature of 450°C, and the measured value (PV) is the main steam temperature measured value T_pv (from GT751RTD channel 05). The deviation is e=T_sp-T_pv, the control cycle is 5 seconds, and the action mode is reverse action, that is, the output decreases when the temperature rises.

[0210] The controller outputs the initial setpoint T_sp_initial for the desuperheater outlet temperature, which is then fed into the summation point and superimposed with the feedforward compensation.

[0211] The inner loop is a PID controller for the lead steam temperature (PID2). Its setpoint (SP) is the final setpoint T_sp_final from the subloop at the summing point, and its measured value (PV) is the lead steam temperature measurement (from GT751RTD channel 06). The deviation e2 = T_sp_final - T_pv_leader, the control cycle is 1 second, and the action mode is reverse-acting, meaning the output increases as the temperature rises. This controller outputs an initial valve opening command (0-100%).

[0212] The valve characteristic compensation and limiting module of the cascade feedback control branch takes the initial valve opening command as input and executes the following three steps in sequence: Step 1: Linearization compensation processing. The desuperheating water regulating valve adopts an equal percentage flow characteristic with an adjustable ratio R=30.

[0213] Let the valve opening percentage be L, the relative stroke be l = L / 100, and the relative flow rate be q = R^(l-1).

[0214] Based on the required relative flow rate q_req, the compensated relative stroke is calculated using the inverse function formula l_calc=1+ln(q_req) / ln(R), and then converted into a compensated valve opening command.

[0215] Step 2: High and low amplitude limiting processing.

[0216] The upper limit is set at 95% to reserve adjustment margin; the lower limit is set at 5% to ensure valve sealing. Step 3: Rate of change limitation.

[0217] The maximum rate of change is set to 5% / second to prevent water hammer caused by excessively rapid valve action.

[0218] This module outputs the final valve opening command, which is then transmitted via the GT721AO card to the desuperheating water regulating valve positioner. This drives the regulating valve core to adjust the flow rate of the desuperheating water injected into the superheater, thereby controlling the steam temperature.

[0219] In the above cascade control structure, the control cycle of the secondary loop is shorter than that of the primary loop, forming a hierarchical control architecture of "rapidly suppressing disturbances in the inner loop and accurately eliminating deviations in the outer loop".

[0220] By adopting a feedforward-feedback composite control architecture, compared with traditional pure feedback cascade control, the response lag time of the control system to flue gas disturbances is shortened from 60 to 90 seconds to 15 to 25 seconds, effectively solving the technical problem of large response lag in steam temperature control caused by large fluctuations in flue gas parameters in waste heat boilers.

[0221] In another embodiment, such as Figure 4As shown, a method for controlling the steam temperature by feeding forward the heat from the flue gas of a waste heat boiler is provided. Taking the application of this method to a DCS control system as an example, the method includes the following steps:

[0222] Step S402: Obtain the flue gas inlet temperature, flue gas outlet temperature, and induced draft fan operating frequency signals.

[0223] Step S404: Determine the flue gas volume flow rate based on the induced draft fan operating frequency signal.

[0224] Step S406: Obtain the flue gas side density and flue gas side isobaric specific heat capacity, and determine the heat released by the flue gas side in the current cycle based on the flue gas side volume flow rate, flue gas side density, flue gas side isobaric specific heat capacity, flue gas side inlet temperature and flue gas side outlet temperature.

[0225] Step S408: Determine the change in heat on the flue gas side based on the difference between the heat released on the flue gas side in the current cycle and the heat released on the flue gas side in the previous cycle.

[0226] Step S410: Determine the rate of change of heat on the flue gas side based on the ratio of the change in heat on the flue gas side to the control cycle.

[0227] Step S412: Obtain the main steam temperature deviation on the steam side, and determine the preliminary set value of the desuperheater outlet temperature on the steam side based on the main steam temperature deviation.

[0228] Step S414: Determine the steam temperature deviation correction coefficient based on the main steam temperature deviation.

[0229] Step S416: Determine the rate of change correction coefficient based on the rate of change of heat on the flue gas side.

[0230] Step S418: Determine the feedforward gain coefficient based on the basic feedforward gain coefficient, steam temperature deviation correction coefficient, and rate of change correction coefficient.

[0231] Step S420: Determine the feedforward compensation amount on the flue gas side based on the change in heat on the flue gas side and the feedforward gain coefficient.

[0232] Step S422: The feedforward compensation is added to the initial set value of the desuperheater outlet temperature to obtain the final set value of the desuperheater outlet temperature.

[0233] Step S424: Based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature, generate a valve opening command; the valve opening command is used to adjust the desuperheating water regulating valve on the steam side to control the steam temperature on the steam side.

[0234] It should be noted that the specific limitations of the above steps can be found in the above description of the specific limitations of a waste heat boiler flue gas heat feedforward steam temperature control method.

[0235] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows.

[0236] Unless otherwise specified in this document, there is no strict order in which these steps are performed, and they may be performed in any other order.

[0237] Moreover, at least some steps in the flowcharts involved in the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but may be executed at different times. The execution order of these steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least some of the steps or stages in other steps.

[0238] Based on the same inventive concept, this application also provides a waste heat boiler flue gas heat feedforward steam temperature control device for implementing the waste heat boiler flue gas heat feedforward steam temperature control method mentioned above.

[0239] The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations of one or more waste heat boiler flue gas heat feedforward steam temperature control device embodiments provided below can be found in the limitations of the waste heat boiler flue gas heat feedforward steam temperature control method above, and will not be repeated here.

[0240] In one exemplary embodiment, such as Figure 5 As shown, a waste heat boiler flue gas heat feedforward steam temperature control device is provided, including: a parameter acquisition module 502, a value determination module 504, a coefficient determination module 506, a compensation amount determination module 508, a compensation amount superposition module 510, and an instruction generation module 512, wherein: The parameter acquisition module 502 is used to acquire the operating parameters of the flue gas side, and based on the operating parameters of the flue gas side, determine the heat released by the flue gas side, the amount of heat change of the flue gas side, and the rate of heat change of the flue gas side. The numerical determination module 504 is used to obtain the main steam temperature deviation on the steam side and determine the preliminary set value of the desuperheater outlet temperature on the steam side based on the main steam temperature deviation. The coefficient determination module 506 is used to determine the feedforward gain coefficient based on the main steam temperature deviation and the flue gas side heat change rate. The compensation amount determination module 508 is used to determine the feedforward compensation amount on the flue gas side based on the change in heat on the flue gas side and the feedforward gain coefficient. The compensation amount superposition module 510 is used to superimpose the feedforward compensation amount onto the initial set value of the desuperheater outlet temperature to obtain the final set value of the desuperheater outlet temperature. The instruction generation module 512 is used to generate valve opening instructions based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature; the valve opening instructions are used to adjust the desuperheating water regulating valve on the steam side to control the steam temperature on the steam side.

[0241] In an exemplary embodiment, the operating parameters on the flue gas side include the flue gas inlet temperature, the flue gas outlet temperature, and the induced draft fan operating frequency signal. The parameter acquisition module 502 is specifically used to determine the flue gas volumetric flow rate based on the induced draft fan operating frequency signal; acquire the flue gas density and the flue gas isobaric specific heat capacity, and determine the flue gas heat released in the current cycle based on the flue gas volumetric flow rate, flue gas density, flue gas isobaric specific heat capacity, flue gas inlet temperature, and flue gas outlet temperature; determine the flue gas heat change amount based on the difference between the flue gas heat released in the current cycle and the flue gas heat released in the previous cycle; and determine the flue gas heat change rate based on the ratio of the flue gas heat change amount to the control cycle.

[0242] In an exemplary embodiment, the parameter acquisition module 502 is specifically used to determine the induced draft fan speed based on the induced draft fan operating frequency signal; determine the flue gas side reference volumetric flow rate based on the characteristic curve of the induced draft fan frequency, speed and flow rate; acquire the flue gas side average temperature and the flue gas side induced draft fan inlet and outlet pressure difference, and perform temperature correction and pressure correction on the flue gas side reference volumetric flow rate based on the flue gas side average temperature and the flue gas side induced draft fan inlet and outlet pressure difference to obtain the flue gas side volumetric flow rate under actual operating conditions.

[0243] In an exemplary embodiment, the coefficient determination module 506 is specifically used to determine the steam temperature deviation correction coefficient based on the main steam temperature deviation; determine the rate of change correction coefficient based on the flue gas side heat change rate; and determine the feedforward gain coefficient based on the basic feedforward gain coefficient, the steam temperature deviation correction coefficient, and the rate of change correction coefficient.

[0244] In an exemplary embodiment, the instruction generation module 512 is specifically used to generate an initial valve opening instruction based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature; obtain the correspondence between the opening and flow rate of the steam-side desuperheating water regulating valve, and perform linearization compensation processing on the initial valve opening instruction according to the correspondence between the opening and flow rate to obtain a compensated valve opening instruction; and apply high and low amplitude limits and change rate limits to the compensated valve opening instruction to obtain a valve opening instruction.

[0245] In an exemplary embodiment, the device further includes: a detection module, configured to: increase the feedforward gain coefficient and shorten the control cycle for generating the preliminary set value of the desuperheater outlet temperature when the flue gas inlet temperature is detected to rise above a first temperature threshold within a preset time; reverse the feedforward compensation amount to generate an instruction for indicating a reduction in desuperheating water output when the flue gas inlet temperature is detected to fall below a second temperature threshold within a preset time; and cut off the feedforward compensation amount and switch to feedback control mode or manual control mode when any abnormal sensor signal involved in the control is detected.

[0246] Each module in the aforementioned waste heat boiler flue gas heat feedforward steam temperature control device can be implemented entirely or partially through software, hardware, or a combination thereof.

[0247] The above modules can be embedded in the processor of the computer device in hardware form or independent of it, or they can be stored in the memory of the computer device in software form, so that the processor can call and execute the corresponding operations of the above modules.

[0248] In one exemplary embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 6 As shown.

[0249] The computer device includes a processor, memory, input / output interfaces (I / O), and communication interfaces.

[0250] The processor, memory, and input / output interfaces are connected via the system bus, and the communication interface is connected to the system bus via the input / output interface.

[0251] The processor of this computer device provides computing and control capabilities. The memory of this computer device includes non-volatile storage media and internal memory.

[0252] The non-volatile storage medium stores the operating system, computer programs, and databases. This internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage medium.

[0253] The database of this computer device is used to store feedforward steam temperature control data for waste heat boiler flue gas heat.

[0254] The computer device's input / output interface is used for exchanging information between the processor and external devices.

[0255] The communication interface of this computer device is used to communicate with external terminals via a network connection.

[0256] When the computer program is executed by the processor, it implements a waste heat boiler flue gas heat feedforward steam temperature control method.

[0257] Those skilled in the art will understand that Figure 6 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0258] In one embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, which, when executed by the processor, causes the processor to perform the steps of the above-described waste heat boiler flue gas heat feedforward steam temperature control method.

[0259] The steps of the waste heat boiler flue gas heat feedforward steam temperature control method described above can be the steps in the waste heat boiler flue gas heat feedforward steam temperature control method of the above embodiments.

[0260] In one embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, causes the processor to perform the steps of the above-described waste heat boiler flue gas heat feedforward steam temperature control method.

[0261] The steps of the waste heat boiler flue gas heat feedforward steam temperature control method described above can be the steps in the waste heat boiler flue gas heat feedforward steam temperature control method of the above embodiments.

[0262] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, causes the processor to perform the steps of the above-described waste heat boiler flue gas heat feedforward steam temperature control method.

[0263] The steps of the waste heat boiler flue gas heat feedforward steam temperature control method described above can be the steps in the waste heat boiler flue gas heat feedforward steam temperature control method of the above embodiments.

[0264] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods.

[0265] Any references to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory.

[0266] Non-volatile memories can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc.

[0267] Volatile memory may include random access memory (RAM) or external cache memory, etc.

[0268] By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0269] The databases involved in the various embodiments provided in this application may include at least one of relational databases and non-relational databases.

[0270] Non-relational databases can include, but are not limited to, blockchain-based distributed databases.

[0271] The processors involved in the various embodiments provided in this application may be general-purpose processors, central processing units, graphics processors, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited thereto.

[0272] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0273] The above-described embodiments are merely examples of several implementation methods of this application. They are described in a relatively specific and detailed manner, but should not be construed as limiting the scope of this application's patent.

[0274] It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the scope of protection of this application.

[0275] Therefore, the scope of protection of this application shall be determined by the appended claims.

Claims

1. A method for controlling the steam temperature of a waste heat boiler by feeding forward flue gas heat, characterized in that, The method includes: Obtain the operating parameters on the flue gas side, and based on the operating parameters on the flue gas side, determine the heat released on the flue gas side, the amount of heat change on the flue gas side, and the rate of heat change on the flue gas side; Obtain the main steam temperature deviation on the steam side, and determine the preliminary set value of the desuperheater outlet temperature on the steam side based on the main steam temperature deviation; The feedforward gain coefficient is determined based on the main steam temperature deviation and the flue gas heat change rate. Based on the change in heat on the flue gas side and the feedforward gain coefficient, the feedforward compensation amount on the flue gas side is determined; The feedforward compensation is added to the initial set value of the desuperheater outlet temperature to obtain the final set value of the desuperheater outlet temperature. Based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature, a valve opening command is generated; the valve opening command is used to adjust the desuperheating water regulating valve on the steam side to control the steam temperature on the steam side.

2. The method according to claim 1, characterized in that, The operating parameters on the flue gas side include the flue gas inlet temperature, the flue gas outlet temperature, and the induced draft fan operating frequency signal; the determination of the heat released on the flue gas side, the amount of heat change on the flue gas side, and the rate of heat change on the flue gas side based on the operating parameters on the flue gas side includes: The flue gas volume flow rate is determined based on the operating frequency signal of the induced draft fan; Obtain the flue gas side density and flue gas side isobaric specific heat capacity, and determine the flue gas side heat release in the current cycle based on the flue gas side volume flow rate, flue gas side density, flue gas side isobaric specific heat capacity, flue gas side inlet temperature and flue gas side outlet temperature; The change in flue gas heat is determined based on the difference between the heat released on the flue gas side in the current cycle and the heat released on the flue gas side in the previous cycle. The rate of change of heat on the flue gas side is determined based on the ratio of the change in heat on the flue gas side to the control cycle.

3. The method according to claim 2, characterized in that, The determination of flue gas volumetric flow rate based on the operating frequency signal of the induced draft fan includes: The induced draft fan speed is determined based on the induced draft fan operating frequency signal; The reference volumetric flow rate on the flue gas side is determined based on the characteristic curves of the induced draft fan frequency, rotation speed and flow rate. The average temperature of the flue gas side and the pressure difference between the inlet and outlet of the flue gas side induced draft fan are obtained. Based on the average temperature of the flue gas side and the pressure difference between the inlet and outlet of the flue gas side induced draft fan, the reference volumetric flow rate of the flue gas side is corrected for temperature and pressure to obtain the flue gas side volumetric flow rate under actual operating conditions.

4. The method according to claim 1, characterized in that, The determination of the feedforward gain coefficient based on the main steam temperature deviation and the flue gas side heat change rate includes: Based on the main steam temperature deviation, determine the steam temperature deviation correction coefficient; Determine the rate of change correction coefficient based on the rate of change of heat on the flue gas side; The feedforward gain coefficient is determined based on the basic feedforward gain coefficient, the steam temperature deviation correction coefficient, and the rate of change correction coefficient.

5. The method according to claim 1, characterized in that, The step of generating a valve opening command based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature includes: Based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature, an initial valve opening command is generated. Obtain the correspondence between the opening degree and flow rate of the desuperheating water regulating valve on the steam side, and perform linearization compensation processing on the initial valve opening command based on the correspondence between the opening degree and flow rate to obtain the compensated valve opening command. The valve opening command is obtained by limiting its high and low amplitude and the rate of change after compensation.

6. The method according to claim 1, characterized in that, The method further includes: When the flue gas inlet temperature is detected to rise above the first temperature threshold within a preset time, the feedforward gain coefficient is increased and the control cycle used to generate the initial set value of the desuperheater outlet temperature is shortened. When the flue gas inlet temperature is detected to drop below the second temperature threshold within the preset time, the feedforward compensation amount is reversed to generate an instruction to reduce the output of desuperheating water. When any abnormality is detected in the signal of any sensor involved in the control, the feedforward compensation is cut off, and the system switches to feedback control mode or manual control mode.

7. A waste heat boiler flue gas heat feedforward steam temperature control device, characterized in that, The device includes: The parameter acquisition module is used to acquire the operating parameters of the flue gas side, and based on the operating parameters of the flue gas side, determine the heat released by the flue gas side, the amount of heat change of the flue gas side, and the rate of heat change of the flue gas side. The numerical determination module is used to obtain the main steam temperature deviation on the steam side and determine the preliminary set value of the desuperheater outlet temperature on the steam side based on the main steam temperature deviation. The coefficient determination module is used to determine the feedforward gain coefficient based on the main steam temperature deviation and the flue gas side heat change rate. The compensation amount determination module is used to determine the feedforward compensation amount on the flue gas side based on the change in heat on the flue gas side and the feedforward gain coefficient; The compensation amount superposition module is used to superimpose the feedforward compensation amount onto the initial set value of the desuperheater outlet temperature to obtain the final set value of the desuperheater outlet temperature. The instruction generation module is used to generate a valve opening instruction based on the final set value of the desuperheater outlet temperature and the measured value of the desuperheater outlet temperature; the valve opening instruction is used to adjust the desuperheating water regulating valve on the steam side to control the steam temperature on the steam side.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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