Automatic temperature and steam regulating method for steam heater

Abstract

The present application relates to the technical field of thermal automatic control, and discloses a steam air heater wind temperature and steam automatic regulating method, comprising: executing a multi-source parameter acquisition step to obtain thermodynamic parameters and time domain differential pressure signals; executing a fluidization evaluation step to convert the frequency domain differential pressure signals and integrate to obtain a fluidization stability index; executing a phase change calculation step to combine steam-water property parameters to calculate the current dimensionless height coordinate; executing a mapping calculation step to calculate the target phase change critical surface height based on negative feedback and feedforward compensation; executing a coordination execution step to build a mixture enthalpy model to establish a water seal safety margin and adjust the opening degree of the double-sided valve; and executing a freeze protection step to trigger an over-riding execution strategy to forcibly set the valve opening degree through a risk identification mechanism, wherein the present application can output heat in advance to improve the fluidization stability of the wind powder, prevent the mixed medium from breaking through the water seal device, and completely avoid the freezing of the condensate water under extremely cold working conditions.

Description

Technical Field

[0001] This invention relates to the field of thermal automatic control technology, specifically to a method for automatically adjusting the air temperature and steam of a steam heater. Background Technology

[0002] In coal-fired power generating units, steam heaters are commonly used to heat the primary air entering the coal mill to ensure the dryness and fluidized transport of pulverized coal. Existing steam heater control systems mainly rely on the actual air temperature at the heater's air outlet for closed-loop negative feedback regulation. Due to the significant thermal inertia and large delay characteristics of the steam condensation heat exchange process, when the moisture content of the pulverized coal entering the coal mill fluctuates and increases, conventional temperature feedback logic cannot make an anticipatory response. This results in the system being unable to provide sufficient transient high enthalpy heat in time, which in turn causes the pulverized coal particles in the air-coal mixing pipeline to agglomerate, reducing the fluidization stability during the pulverized coal transport process.

[0003] When steam heaters implement dual-side control of steam and water, existing valve adjustment strategies often lack prediction and constraint on the thermodynamic load-bearing capacity of the condensate recovery pipeline. When the system adjusts the steam inlet valve and the condensate outlet valve simultaneously to increase the heat exchange area, the sudden drop in back pressure on the condensate side will cause transient flash evaporation of condensate in the pipe. The large amount of high-enthalpy steam-water mixture discharged can easily damage the downstream physical water seal device, thereby inducing strong steam-liquid impact vibration, which poses a serious threat to the physical safety of the condensate pipeline and related equipment.

[0004] In extremely cold conditions and when the unit is operating at low load, the steam heater requires a small flow of heating steam. At this time, the actual steam condensation rate in the heat exchange tube bundle often exceeds the physical replenishment rate of the heating steam. The sudden volume reduction caused by the steam phase change will create a slight negative pressure at the end of the tube bundle. This local vacuum will cause external cold air to backflow along the condensate recovery pipe, causing the condensate accumulated at the bottom of the tube bundle to freeze due to phase change, ultimately leading to the freezing and cracking of the heat exchange tube bundle. Traditional control methods always lock the control target to wind temperature tracking and lack a mandatory overriding intervention mechanism for the slight negative pressure physical state, which cannot fundamentally eliminate the risk of cold air backflow under extremely cold conditions. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for automatically regulating the air temperature and steam of a steam heater. This method solves the problems in existing technologies, such as poor fluidization stability of pulverized coal due to delayed temperature feedback regulation, unrestrained operation of valves on both the gas and water sides which easily damages the water seal device and causes steam-liquid impact vibration, and condensate freezing caused by the slight negative pressure at the end of the tube bundle drawing in cold air under extremely cold and low-load conditions.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A method for automatically regulating the air temperature and steam of a steam heater, wherein the automatic regulation method is executed by a distributed control system, and the automatic regulation method includes: Perform multi-source parameter acquisition steps to acquire in real time the thermodynamic boundary conditions, boundary environment parameters, and time-domain differential pressure signal in the air-powder mixing pipeline of the steam heater body on both the gas and water sides. The fluidization evaluation step involves frequency domain conversion and energy integration of the time-domain differential pressure signal to obtain the fluidization stability index. The phase change calculation steps are performed, and the current dimensionless height coordinates of the physical interface between pure steam and saturated water are dynamically calculated and characterized by combining the physical property parameters of steam and water with the physical geometric characteristics of the integrally extruded spiral finned tube bundle. The mapping calculation step is performed, and the cross-field mapping calculation is carried out based on the negative feedback adjustment of the actual air temperature at the air outlet of the heater and the nonlinear feedforward compensation of the fluidization stability index to calculate the height of the target phase change critical surface. The coordinated execution steps are implemented to construct a prediction model for the enthalpy of the steam-water mixture discharged into the water seal device to establish the safety margin of the water seal device. Under the constraint of the safety margin of the water seal device, the opening degree of the steam inlet electric regulating valve and the opening degree of the condensate electric shut-off valve are adjusted through the valve asynchronous action logic and asymmetric action logic. The antifreeze protection steps are executed. The overreaching execution strategy of forcibly moving the phase change boundary upward is triggered by the extreme cold and micro negative pressure risk identification mechanism, which cuts off the conventional temperature tracking link and forcibly sets the opening of the steam inlet electric regulating valve and the opening of the condensate electric shut-off valve.

[0008] In the fluidization evaluation step, the distributed control system extracts and smooths the time-domain differential pressure signal, then converts it to the frequency domain to generate a complex frequency domain sequence. The power spectral density function is calculated by extracting and normalizing the complex frequency domain amplitude. The distributed control system sets a lower threshold for the high-frequency band and an upper limit for the full-band integral, performs definite integral operations on the power spectral density function, and divides the high-frequency band pulsating energy integral value by the total full-band pulsating energy integral value to obtain the fluidization stability index. The distributed control system incorporates the local turbulent dissipation characteristics caused by increased pulsated coal moisture in the air-coal mixing pipeline into the regulation logic through the fluidization stability index.

[0009] In the phase change calculation and mapping steps, the distributed control system uses thermodynamic state parameters as a joint addressing index to obtain the inlet steam enthalpy, outlet condensate enthalpy, and latent heat of vaporization from the steam thermodynamic property data table. Combining the dimensionless structural constant established by the internal flow cross-sectional area and the overall heat transfer coefficient of the heater, the distributed control system calculates the current dimensionless height coordinates based on the difference between the inlet steam enthalpy and the outlet condensate enthalpy, the latent heat of vaporization, and the dimensionless structural constant. The distributed control system performs proportional-integral-differential calculations on the deviation between the preset target air temperature and the actual air temperature at the heater outlet to output a basic liquid level height command. It also introduces a fluidization stability index to perform nonlinear logarithmic decay calculations to calculate the target phase change critical surface height. When the fluidization stability index increases, the target phase change critical surface height is lowered, and the integrally extruded spiral finned tube bundle is controlled to accelerate the discharge of condensate to increase the latent heat transfer area, outputting high enthalpy heat into the air-coal mixing pipeline to disrupt the coal powder agglomeration structure.

[0010] In the coordinated execution step, the distributed control system combines the sudden change in the opening of the condensate-cooled electric shut-off valve with the flow characteristic constant to calculate the transient flash enthalpy increment caused by the valve action, predict the total specific enthalpy of the steam-water mixture discharged into the water seal device, and compare the total specific enthalpy of the steam-water mixture with the critical breakdown specific enthalpy corresponding to the current working pressure to establish the safety margin of the water seal device. When the safety margin of the water seal device is greater than zero, the normal coordination mode is triggered. By connecting a time delay element and a slope limiter to the output channel of the steam inlet electric regulating valve, asynchronous rate regulation is performed where the rate of change of the steam inlet electric regulating valve is less than the rate of change of the condensate-cooled electric shut-off valve. When the safety margin of the water seal device is less than or equal to zero, the interlocking restriction conditions of the safety protection mode are triggered, forcibly locking or reducing the opening of the condensate-cooled electric shut-off valve, and switching the controller parameters to execute the asymmetric action logic of separately adjusting the steam inlet electric regulating valve to prevent the medium in the pipe from breaking through the water seal device.

[0011] During the antifreeze protection process, when the air inlet temperature of the heater is lower than the critical antifreeze temperature and the actual heating steam flow rate is lower than the steady-state flow rate threshold for maintaining condensation balance, the distributed control system determines that a slight negative pressure physical state exists in the end cavity of the integrally extruded spiral finned tube bundle due to the volume contraction caused by steam phase change. The distributed control system triggers an overriding execution strategy to force the phase change boundary upward, cutting off the closed-loop negative feedback regulation link and acquiring priority control authority for both valves. Based on the extreme cold equivalent heat dissipation constant, the actual heating steam flow rate, and the saturated steam temperature, the forced safe phase change height is recalculated. The distributed control system reduces the opening of the condensate electric shut-off valve by outputting a valve-closing command, blocking the discharge path and allowing condensate to submerge the bottom cavity to raise the physical phase change boundary. Simultaneously, it outputs a feedforward compensation opening command to increase the opening of the steam inlet electric regulating valve, blocking the cold air backflow path and maintaining the thermodynamic pressure balance within the tube.

[0012] This invention provides a method for automatically adjusting the air temperature and steam of a steam heater. It has the following beneficial effects: 1. This invention obtains the fluidization stability index by performing frequency domain conversion and energy integration on the time-domain differential pressure signal in the air-coal mixing pipeline. The fluidization stability index is then introduced as a feedforward compensation term into the cross-field mapping calculation. When the increased moisture content of the coal powder entering the pulverizer is detected, causing agglomeration, the distributed control system actively lowers the target phase change critical surface height through nonlinear logarithmic decay calculation. This guides the system to accelerate the discharge of condensate to increase the latent heat transfer area in the pure steam state. This control method can output high enthalpy heat to the air-coal mixing pipeline in advance to destroy the physical structure of coal powder agglomeration. It overcomes the large thermodynamic delay problem caused by the traditional reliance on air temperature feedback regulation and significantly improves the air-coal fluidization stability of the system under fluctuating coal powder moisture conditions.

[0013] 2. This invention constructs a prediction model for the enthalpy of the steam-water mixture discharged into the water seal device. By comparing the total specific enthalpy of the steam-water mixture with the critical destruction specific enthalpy, the safety margin of the water seal device is established. Under the constraint of the safety margin of the water seal device, the asynchronous and asymmetric action logic of the steam inlet electric regulating valve and the condensate electric shut-off valve is executed. In the conventional coordination mode, the asynchronous rate adjustment of the condensate valve opening quickly and the steam valve opening slowly approaches the target phase change critical surface height. When the safety margin is insufficient, the interlocking restriction condition is triggered, the condensate discharge rate is forcibly locked and the steam valve opening is adjusted separately. This coordinated execution mechanism effectively avoids the sudden drop in pipe pressure and transient flash evaporation caused by the synchronous large-scale action of the valves on both sides, prevents the high-enthalpy mixed medium from breaking through the water seal device and causing steam-liquid impact vibration, and ensures the physical safety of the condensate recovery pipeline during the control and regulation process.

[0014] 3. This invention designs a micro-negative pressure risk identification mechanism and an overstepping execution strategy for forced upward movement of the phase change boundary under extremely cold and low-load conditions. When the air inlet temperature of the heater and the actual heating steam flow rate are lower than the set antifreeze and steady-state thresholds, the distributed control system determines that a micro-negative pressure physical state has appeared at the end of the integrally extruded spiral finned tube bundle. It then cuts off the conventional closed-loop negative feedback regulation link and seizes the priority control authority of the valve. By rapidly reducing the opening of the condensate electric shut-off valve, it causes condensate to submerge the bottom of the tube bundle to raise the physical phase change boundary. At the same time, it increases the opening of the steam inlet electric regulating valve to inject steam dynamic pressure. This overstepping protection action reduces the effective heat dissipation area on the steam side and blocks the backflow path of cold air, eliminating the local vacuum suction force generated by the sudden shrinkage of the steam phase change volume, fundamentally avoiding the phase change freezing of water at the bottom of the tube bundle. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Please see Figure 1 This invention provides a method for automatically regulating the air temperature and steam flow of a steam heater. The main body executing the automatic regulation method is a distributed control system. The distributed control system is electrically connected to the pressure transmitter and the first thermocouple on the steam inlet side, the pressure transmitter and the second thermocouple on the condensate outlet side, the anemometer and the air temperature sensor in the air duct, and the differential pressure transmitter arranged on both sides of the air-powder coupled flow field disturbance mixing compensator. At the same time, the distributed control system is communicatively connected to the steam inlet electric regulating valve installed on the steam supply pipeline and the condensate electric shut-off valve installed on the condensate recovery pipeline. For the wired or wireless communication network connection between the distributed control system and various sensors and actuators, those skilled in the art can select and configure according to the actual working conditions. The signal transmission and conversion technology of the communication network connection is a well-known technology in the field and will not be described in detail here. The distributed control system executes a complete automatic regulation process by acquiring data signals from hardware feedback, thereby achieving matching control of air temperature and steam flow.

[0018] The overall control logic of the automatic adjustment method consists of a series of steps including multi-source parameter acquisition, fluidization evaluation, phase change calculation, mapping calculation, coordinated execution, and antifreeze protection. The automatic adjustment method specifically includes the following macroscopic steps.

[0019] In step S100, the distributed control system performs a multi-source parameter acquisition step to acquire in real time the thermodynamic boundary conditions, boundary environment parameters, and aerodynamic pressure difference changes in the air-powder mixing pipeline of the steam heater body on both sides.

[0020] In step S200, the distributed control system performs a fluidization assessment step, which obtains the fluidization stability index by performing frequency domain conversion and energy integration calculation on the differential pressure signal, and quantitatively characterizes the degree of coal powder agglomeration and moisture state at the inlet of the downstream coal mill.

[0021] In step S300, the distributed control system performs a phase change calculation step, combining the steam-water physical property parameters with the physical and geometric characteristics of the integrally extruded spiral finned tube bundle, and dynamically calculates the current dimensionless height coordinates of the physical interface between pure steam and saturated water after complete condensation.

[0022] In step S400, the distributed control system performs a mapping calculation step, and performs a cross-field mapping calculation based on the negative feedback adjustment of the actual wind temperature and the nonlinear feedforward compensation of the fluidization stability index to calculate the target phase change critical surface height for air-water dual-side coordinated control.

[0023] In step S500, the distributed control system performs a coordinated execution step, constructs a prediction model of the enthalpy of the steam-water mixture discharged into the water seal device to establish the safety margin of the water seal device, and achieves accurate tracking of the height of the target phase change critical surface through asynchronous and asymmetric valve action logic under safety constraints.

[0024] In step S600, the distributed control system executes the antifreeze protection step, triggering an overreach execution strategy that forces the phase change boundary to move upward through the extreme cold and micro-negative pressure risk identification mechanism, cutting off the conventional temperature tracking link and forcibly intervening in the valve opening to eliminate the micro-negative pressure physical state.

[0025] The following describes in detail each macroscopic execution step of the above-mentioned automatic adjustment method, with specific sub-steps.

[0026] For the multi-source parameter acquisition step S100, the distributed control system acquires the thermodynamic boundary conditions and external environmental parameters of the steam heater body on both the gas and water sides. Sub-step S110 in the multi-source parameter acquisition step S100 includes the real-time acquisition process of thermodynamic parameters. The distributed control system acquires the heating steam inlet pressure through the inlet pressure transmitter arranged on the steam supply pipeline. The inlet pressure transmitter is installed between the steam inlet electric regulating valve and the steam inlet flange of the integrally extruded spiral finned tube bundle to obtain the actual steam pressure entering the integrally extruded spiral finned tube bundle. The distributed control system obtains the heating steam inlet temperature through the inlet thermocouple arranged on the steam supply pipeline. For the acquisition of thermodynamic parameters on the hydrophobic side, the distributed control system obtains the hydrophobic outlet pressure through an outlet pressure transmitter arranged on the hydrophobic recovery pipeline. The outlet pressure transmitter is installed between the condensate outlet flange of the integrally extruded spiral finned tube bundle and the condensate electric shut-off valve to monitor the back pressure inside the condensate tube after heat exchange. The distributed control system obtains the condensate outlet temperature through the outlet thermocouple arranged on the condensate recovery pipeline. For the on-site installation, power supply wiring, and analog-to-digital conversion of the inlet pressure transmitter, inlet thermocouple, outlet pressure transmitter, and outlet thermocouple, those skilled in the art can perform conventional matching and selection based on the on-site pipe diameter. The physical installation and signal transmission conversion of the inlet pressure transmitter, inlet thermocouple, outlet pressure transmitter, and outlet thermocouple are well-known technologies in this field and will not be elaborated here.

[0027] Sub-step S120 in the multi-source parameter acquisition step S100 includes the continuous acquisition process of aerodynamic parameters. The distributed control system acquires the pressure difference change data in the air-coal mixing pipeline downstream of the steam heater body and before entering the coal mill. An air-coal coupled flow field disturbance mixing compensator is fixedly installed inside the air-coal coupled flow field disturbance mixing compensator. A first static pressure sampling probe is installed on the pipe wall of the air inlet section of the air-coal coupled flow field disturbance mixing compensator, and a second static pressure sampling probe is installed on the pipe wall of the air outlet section of the air-coal coupled flow field disturbance mixing compensator. To prevent high-frequency pulsation signal distortion caused by high-concentration coal powder blockage, both the first and second static pressure sampling probes are... A flush-mounted, anti-clogging, anti-wear sampling probe is used. The first static pressure sampling probe is connected to the high-pressure side interface of the differential pressure transmitter via a pre-mounted pressure tap, and the second static pressure sampling probe is connected to the low-pressure side interface of the differential pressure transmitter via a post-mounted pressure tap. The differential pressure transmitter measures and converts the actual static pressure difference between the inlet and outlet of the air-powder coupled flow field disturbance mixing compensator at a preset sampling frequency. The distributed control system reads the digital feedback signal output by the differential pressure transmitter in real time. The data register inside the distributed control system stores the differential pressure values ​​in chronological order, generating a time-domain differential pressure signal composed of discrete time points and the corresponding differential pressure value sequences. ,in The time step is a variable, and the time-domain differential pressure signal is continuously acquired. The distributed control system acquires basic data on resistance fluctuations during the mixing process of pulverized coal particles and primary air. For the reverse purging configuration of the pre-pressure tap and the post-pressure tap, as well as the low-pass filter circuit of the differential pressure transmitter, those skilled in the art can make conventional selections based on the dust concentration in the air-powder mixing pipeline. The physical installation and basic data acquisition technology attached to the pressure tap are well-known technologies in this field and will not be described in detail here.

[0028] Sub-step S130 in the multi-source parameter acquisition step S100 includes the acquisition process of boundary environment parameters, and the distributed control system acquires the air inlet temperature of the heater. and the actual air temperature at the heater's air outlet Because the air duct at the heater interface is large and an expansion and reduction duct is installed in front of the air-powder mixing pipe, there are temperature distribution differences in the cross-section of the air flowing through the integrally extruded spiral finned tube bundle. The temperature sensing element adopts a multi-point grid measurement method. Uniformly distributed temperature sensor matrices are arranged on the air inlet cross-section of the expansion and reduction duct and the air outlet cross-section of the integrally extruded spiral finned tube bundle. The distributed control system synchronously reads the measurement values ​​of the temperature sensor matrix on the air inlet cross-section, and the logic processor inside the distributed control system calculates the arithmetic mean of the summed temperature sensor matrix values. The distributed control system sets the arithmetic mean of the air inlet cross-section as the air inlet temperature of the heater. Simultaneously, the distributed control system reads the measured values ​​from the temperature sensor matrix on the air outlet section, calculates the arithmetic mean of the summed measured values, and sets this arithmetic mean as the actual air temperature at the heater outlet. By using multi-point grid measurement and average value calculation, the single-point temperature measurement error caused by uneven local wind speed behind the flow equalization guide plate is eliminated, providing an accurate temperature feedback benchmark for calculating the height of the target phase change critical surface.

[0029] For the fluidization evaluation step S200, in sub-step S210, the distributed control system performs frequency domain conversion of the differential pressure signal to extract high-frequency flow characteristics in the resistance fluctuation of the air-powder mixing pipeline.

[0030] In sub-step S211, the frequency domain analysis module of the distributed control system extracts a time-domain differential pressure signal with a preset time window length from its internal data register. This forms discrete data frames. To adapt to the computational structure of the Fast Fourier Transform algorithm, the total number of sampling points contained in the discrete data frames is... To suppress spectral leakage caused by non-integer multiple period truncation during the Fast Fourier Transform, the distributed control system applies a window function to the discrete data frame for smoothing, resulting in a windowed discrete time series. The window function is either a Hanning window or a Hamming window, which is used to attenuate abrupt changes in the time series signal at both ends of the discrete data frame.

[0031] In sub-step S212, the distributed control system calls its internal Fast Fourier Transform (FFT) algorithm processor to perform a Discrete Fourier Transform (DFT) on the windowed discrete-time series. The FFT algorithm will be based on the time step variable. Time-domain differential pressure signal The mapping is transformed to the frequency domain space, generating a complex frequency domain sequence containing phase and amplitude information.

[0032] In sub-step S213, the distributed control system extracts each frequency variable from the complex frequency domain sequence. The corresponding complex frequency domain amplitude Calculate the amplitude of the complex number in the frequency domain. The square of the value is then normalized using the sampling parameters to obtain the power spectral density function characterizing the pulsating energy distribution of the gas-solid two-phase mixing flow field. Power spectral density function The specific calculation formula is as follows:

[0033] In the formula, the absolute value sign represents the magnitude of the complex number in the frequency domain. Take the mold. To ensure the accuracy of time-frequency conversion and prevent high-frequency aliasing distortion, the physical sampling frequency of the differential pressure transmitter is set to be greater than twice the highest characteristic pulsation frequency of the gas-solid two-phase flow in the air-powder mixing pipeline, in order to determine the time interval for acquiring adjacent time-series data points by the differential pressure transmitter. The distributed control system constructs the power spectral density function... When, the power spectral density function The effective spectrum limit is set at half the physical sampling frequency of the differential pressure transmitter. As for the underlying matrix operation code, discrete convolution rules, and data addressing methods inside the microprocessor of the fast Fourier transform algorithm, those skilled in the art can perform conventional configuration based on the main frequency computing power of the distributed control system. The underlying time-frequency discrete mathematical operation rules are well-known technologies in this field and will not be elaborated here.

[0034] For the fluidization evaluation step S200, in sub-step S220, the distributed control system calculates the fluidization stability index. The calculation results were used to quantitatively characterize the degree of coal powder agglomeration and moisture state at the inlet of the downstream coal mill.

[0035] In sub-step S221, the distributed control system establishes a mapping relationship between the frequency domain energy distribution and the physical state of the gas-solid two-phase flow. When the moisture content of the pulverized coal entering the mill increases, the pulverized coal particles agglomerate to form aggregates. These aggregates collide with the primary air within the air-powder coupled flow field disturbance mixing compensator, increasing local turbulent dissipation within the flow field. This local turbulent dissipation manifests as an increase in pulsating energy in the high-frequency band in terms of drag fluctuation characteristics. The distributed control system then applies the power spectral density function... The integral area in the high-frequency band is used as the benchmark data for assessing the degree of deterioration in pulverized coal fluidization.

[0036] In sub-step S222, the distributed control system determines the frequency band boundary parameters used for energy integration calculation. The distributed control system reads the Nyquist cutoff frequency determined by the sampling system and sets the Nyquist cutoff frequency as the upper limit of integration across the entire frequency band. The distributed control system calls the fundamental frequency domain cutoff frequency pre-stored in the memory. This fundamental frequency domain cutoff frequency is the critical value of the no-coal-powder disturbance resistance obtained through pre-calibration tests under no-load conditions where the coal mill is shut down and only ventilated. The distributed control system sets the fundamental frequency domain cutoff frequency as the lower limit threshold of the high-frequency band. High frequency band lower limit threshold It is used to distinguish between the low-frequency energy generated by macroscopic pulsation of primary wind and the high-frequency energy generated by disturbance of pulverized coal aggregates.

[0037] In sub-step S223, the numerical integrator inside the distributed control system modulates the power spectral density function. The distributed control system performs definite integral calculations, calculating the integral value of pulsating energy in the high-frequency band and simultaneously calculating the total integral value of pulsating energy across the entire frequency band. The distributed control system then divides the integral value of pulsating energy in the high-frequency band by the total integral value of pulsating energy across the entire frequency band to obtain the dimensionless fluidization stability index. Fluidization stability index The specific calculation formula is as follows:

[0038] In the formula Let be the power spectral density function. For frequency variables, This is the lower limit threshold for the high-frequency band. The fluidization stability index is the upper limit of the integral across the entire frequency band. The numerical domain is distributed in to Between, fluidization stability index The higher the value, the higher the proportion of high-frequency disturbances in the air-coal mixing pipeline, indicating that the current coal powder has higher moisture content and more severe agglomeration. The distributed control system will then adjust the fluidization stability index. The data is stored in the data register and used as a feedforward trigger variable for the subsequent calculation of the critical surface height of the target phase transition. For the numerical approximation algorithm for the microprocessor to perform definite integral operations, those skilled in the art can compile the code according to the calculation accuracy requirements of the distributed control system. The underlying numerical definite integral algorithm is a well-known technology in this field and will not be described in detail here.

[0039] For phase change calculation step S300, the distributed control system performs real-time calling and status determination of the physical properties of the steam and water.

[0040] Sub-step S310 includes the analysis process of the heating steam inlet state parameters, whereby the phase change calculation module of the distributed control system receives the heating steam inlet pressure. and heating steam inlet temperature The distributed control system's internal read-only memory is pre-written with a data table of the thermodynamic properties of steam, including the superheated steam zone, saturated zone, and subcooled water zone. The phase change calculation module calculates the heating steam inlet pressure. and heating steam inlet temperature As a joint addressing index, a two-dimensional interpolation operation is performed within the superheated steam region of the steam thermodynamic properties data table to calculate the inlet steam specific enthalpy entering the integrally extruded spiral finned tube bundle. Enthalpy of inlet steam Used to characterize the thermodynamic energy carried by a unit mass of heating steam in its inlet physical state.

[0041] Sub-step S320 includes the analysis process of hydrophobic outlet state parameters and phase transition characteristic parameters, and the distributed control system receives the hydrophobic outlet pressure. and hydrophobic outlet temperature The phase change calculation module will calculate the hydrophobic outlet pressure. and hydrophobic outlet temperature As a joint addressing index, the outlet hydrophobic specific enthalpy is calculated by two-dimensional interpolation within the subcooled water or saturated region of the water vapor thermodynamic properties data table. Meanwhile, the phase change calculation module uses the heating steam inlet pressure As a univariate index, one-dimensional interpolation is performed within the saturation region of the steam thermodynamic property data table to extract the heating steam inlet pressure. The phase change calculation module calculates the difference between the saturated steam specific enthalpy and the saturated liquid specific enthalpy, and outputs this difference as the current heating steam inlet pressure. The corresponding latent heat of vaporization of steam Latent heat of vaporization of steam The latent heat value used to characterize the condensation of a unit mass of pure steam into saturated water under constant pressure inside an integrally extruded spiral finned tube bundle is described. For the data structure array of the water vapor thermodynamic property data table in the underlying register of the distributed control system and the interpolation approximation mathematical operation code executed by the microprocessor, those skilled in the art can perform conventional configuration according to the calculation accuracy of the controller. The underlying database lookup addressing and numerical interpolation algorithm are well-known technologies in this field and will not be described in detail here.

[0042] For phase change calculation step S300, in sub-step S330, the distributed control system performs dynamic calculation of the phase change critical surface inside the heater tube.

[0043] In sub-step S331, the phase change calculation module of the distributed control system sets the integrally extruded spiral finned tube bundle as a thermodynamic control body with a one-dimensional dynamic phase change boundary, and establishes a dimensionless height coordinate system along the vertical heat transfer direction of the integrally extruded spiral finned tube bundle. The origin coordinate of the dimensionless height coordinate system (zero) corresponds to the bottom condensate drain port of the integrally extruded spiral finned tube bundle, and the endpoint coordinate (one) corresponds to the top steam inlet of the integrally extruded spiral finned tube bundle. The current dimensionless height coordinate... Used to characterize the physical interface location where the pure steam condensation process inside the integrally extruded spiral finned tube bundle ends and is completely converted into saturated water.

[0044] In sub-step S332, the distributed control system reads the internal flow cross-sectional area, the overall heat transfer coefficient of the heater, and the design heat transfer area of ​​the integrally extruded spiral finned tube bundle, which are pre-stored in the data register. The phase change calculation module calculates the dimensionless structural constant by combining the internal flow cross-sectional area, the overall heat transfer coefficient of the heater, and the design heat transfer area. The specific calculation logic is a dimensionless structure constant. The proportionality coefficient is directly proportional to the product of the overall heat transfer coefficient and the designed heat transfer area of ​​the heater, and inversely proportional to the reference heat capacity flow rate corresponding to the internal flow cross-sectional area. Accurate proportionality coefficient values ​​are obtained through pre-conducting steady-state thermal balance calibration tests under rated operating conditions. This is a dimensionless structural constant. It is used to correct the geometric ratio between the theoretical condensation phase change length and the actual physical tube length in order to compensate for the nonlinear heat fluid resistance loss in the actual countercurrent heat exchange process.

[0045] In sub-step S333, the distributed control system retrieves the acquired inlet steam specific enthalpy. Enthalpy of hydrophobic outlet and the latent heat of steam vaporization The phase transition calculation module combines dimensionless structural constants. The calculations were performed to obtain the current dimensionless height coordinates. Current dimensionless height coordinates The range of values ​​is limited to to Between, the current dimensionless height coordinates The specific calculation formula is as follows:

[0046] The difference in the numerator in the formula represents the actual enthalpy drop of the heat exchange medium released inside the tube, while the denominator represents the theoretical latent heat required for the heat exchange medium to undergo a complete gas-liquid phase change. The ratio of the difference in the numerator to the denominator reflects the proportion of the thermodynamic phase change process completed.

[0047] In sub-step S334, the distributed control system calculates the current dimensionless height coordinates. The data is stored in the data register as the modulated reference variable for performing subsequent cross-field mapping calculations and collaborative execution actions. For the underlying logic gate circuits that perform division operations and coordinate system variable mapping within the distributed control system, those skilled in the art can perform conventional configurations based on the microprocessor's instruction set architecture. The operation rules of the underlying arithmetic logic unit are well-known technologies in the field and will not be elaborated here.

[0048] For the mapping calculation step S400, in the sub-step S410, the distributed control system performs negative feedback regulation of the basic phase transition boundary.

[0049] In sub-step S411, the cross-field mapping module of the distributed control system reads the actual air temperature at the heater outlet stored in the data register. Meanwhile, the distributed control system acquires the preset target air temperature set by the operator. The cross-field mapping module sets the preset target wind temperature Actual air temperature at the heater's air outlet Perform the difference operation to calculate the temperature deviation value. Temperature deviation value The specific calculation formula is as follows:

[0050] In the formula The time step variable is the temperature deviation value. Used to quantify the actual heat exchange capacity surplus or deficit of the steam heater body under current operating conditions.

[0051] In sub-step S412, the cross-field mapping module maps the temperature deviation value. The input is fed into an internally integrated proportional-integral-derivative (PID) controller, which, based on pre-tuned proportional gain, integral time constant, and derivative time constant, processes the temperature deviation value. and temperature deviation value The time series data is continuously subjected to proportional, integral, and differential operations. The proportional-integral-derivative controller linearly superimposes the output results of the proportional, integral, and differential operations to calculate and generate an effective heat transfer area correction for the integrally extruded spiral finned tube bundle. The effective heat transfer area correction corresponds to the size of the pure steam latent heat release space required inside the integrally extruded spiral finned tube bundle to compensate for thermal disturbances caused by changes in air inlet air volume or ambient temperature.

[0052] In sub-step S413, the distributed control system converts the effective heat transfer area correction output by the proportional-integral-derivative controller into a dimensionless height coordinate control signal. Specifically, the distributed control system obtains the pre-stored total design heat transfer area of ​​the integrally extruded spiral finned tube bundle, divides the effective heat transfer area correction by the total design heat transfer area to obtain the dimensionless height change increment, adds the historical phase change boundary height from the previous calculation cycle to the dimensionless height change increment, and outputs a basic liquid level height command. Basic liquid level height command The range of values ​​is limited to to Between, basic liquid level height instructions Characterization is performed without considering the gas-solid two-phase fluidization disturbance in the downstream air-powder mixing pipeline, solely to maintain the actual air outlet temperature of the heater. Approaching the preset target wind temperature The distributed control system will use the base liquid level height command to maintain the physical phase transition boundary height required to achieve steady-state equilibrium. The parameters are stored in the data register and used as the basis for subsequent calculation of the target phase change critical surface height. For the parameter tuning methods of the proportional coefficient, integral time constant and derivative time constant of the proportional-integral-derivative controller, those skilled in the art can make conventional configurations based on the response delay characteristics of the on-site thermal equipment. The underlying closed-loop negative feedback regulation operation rules are well-known technologies in this field and will not be described in detail here.

[0053] For the mapping calculation step S400, in the sub-step S420, the distributed control system performs a nonlinear mapping calculation between the fluidized feedforward and the target phase transition boundary.

[0054] In sub-step S421, the distributed control system calls the basic liquid level height instruction stored in the data register. With fluidization stability index The distributed control system will use the fluidization stability index An aerodynamic feedforward variable, used to characterize the degree of coal powder agglomeration in the air-coal mixing pipeline, is introduced into the thermodynamic control logic.

[0055] In sub-step S422, the distributed control system obtains the pre-tuned first feedforward decoupling gain coefficient. Decoupling gain coefficient with second feedforward The cross-field mapping module of the distributed control system performs nonlinear logarithmic decay calculations to calculate the height of the target phase transition critical surface. Target phase transition critical surface height The specific calculation formula is as follows:

[0056] In the formula Based on the basic liquid level height command The fluidization stability index, The first feedforward decoupling gain coefficient is... The second feedforward decoupling gain coefficient and the first feedforward decoupling gain coefficient are given. Decoupling gain coefficient with second feedforward The dimensionless system constant, the first feedforward decoupling gain coefficient, is obtained by pre-determining the optimal transient heat increase required to disrupt the physical structure of pulverized coal agglomerates under different pulverized coal moisture conditions in the air-coal mixing pipeline, and then using the least squares method to perform curve fitting on the experimental data. Used to adjust the height of the target phase transition critical surface With fluidization stability index The absolute decrease in the change, the second feedforward decoupling gain coefficient Used to adjust the decay curvature of nonlinear logarithmic decay operations.

[0057] In sub-step S423, the distributed control system establishes the execution benchmark for the gas-water dual-side control based on the result of the nonlinear logarithmic decay calculation, when the fluidization stability index... When the height is increased, the cross-field mapping module reduces the height of the target phase transition critical surface through nonlinear logarithmic decay calculation. Target phase transition critical surface height The distributed control system accelerates the discharge of condensate in subsequent execution stages by reducing the physical length of the integrally extruded spiral finned tube bundle in a pure steam state, thereby increasing the latent heat transfer area. This allows for the output of high enthalpy heat into the air-coal mixing pipeline to disrupt the agglomeration of pulverized coal. The distributed control system will then calculate the target phase change critical surface height. The parameters are sent to the coordination execution module as target constraint input parameters for the coordinated adjustment of the opening of the gas and water dual-sided electric valves. For the floating-point Taylor expansion approximation algorithm that performs natural logarithmic operations inside the microprocessor, those skilled in the art can perform conventional configuration according to the instruction cycle of the control chip. The underlying nonlinear mathematical mapping operation code is a well-known technology in this field and will not be described in detail here.

[0058] For the coordinated execution step S500, the distributed control system performs the establishment and calculation of the water seal saturation margin model to ensure the safety of the condensate recovery pipeline in the gas-water dual-side control process.

[0059] In sub-step S510, the coordinated execution module of the distributed control system reads the current opening feedback value of the steam inlet electric regulating valve and the current opening feedback value of the drain electric shut-off valve. The distributed control system, combined with the transient medium flow rate in the steam supply pipeline, constructs a prediction model for the enthalpy of the steam-water mixture to be discharged into the water seal device. The coordinated execution module calculates the total specific enthalpy of the steam-water mixture to be discharged into the water seal device based on the prediction model. Total enthalpy of a soft drink mixture The specific calculation formula is as follows:

[0060] In the formula For the hydrophobic specific enthalpy of the outlet, The flow characteristic constant of the pre-calibrated hydrostatic shut-off valve is given by [reference to a specific parameter]. The constant was obtained by conducting flow tests on the hydrophobic electric shut-off valve under different differential pressure conditions in advance, and fitting the mapping relationship between the sudden change in valve opening and the increase in the enthalpy of the flowing medium. For control commands of hydrophobic electric shut-off valve The difference between the current opening feedback value and the current opening value. For the inlet steam specific enthalpy, in the formula The product term is used to quantify the transient flash enthalpy increase caused by the sudden drop in pipe pressure when the opening of the hydrophobic electric shut-off valve increases abruptly.

[0061] In sub-step S520, the distributed control system obtains the current operating pressure of the water seal device through a pressure transmitter arranged inside the water seal device. The coordination and execution module will manage the current workload. As a univariate addressing index, one-dimensional interpolation is performed within the saturation region of the water vapor thermodynamic property data table to extract the current working pressure. The corresponding saturated liquid specific enthalpy, the coordinated execution module will adjust the current working pressure The corresponding saturated liquid specific enthalpy is set as the critical destruction specific enthalpy. Critical destruction specific enthalpy The upper limit of energy characterizing the liquid phase physical equilibrium within a water seal device without boiling or vaporization destruction; the critical destruction specific enthalpy of the distributed control system. Total enthalpy of the mixture with soda By performing a difference operation, the safety margin of the water seal device can be calculated. Safety margin of water seal device The specific calculation formula is as follows:

[0062] Safety margin of water seal device The highest priority hard constraint condition for quantitatively assessing whether the medium inside the pipe will cause vapor-liquid impact vibration is to be established. For the equipment selection of the pressure transmitter inside the water seal device and the installation method of the opening on the container wall, those skilled in the art can make conventional configurations based on the geometric container shape of the water seal device. The physical sealing installation of the pressure transmitter and the basic electrical signal acquisition are well-known technologies in this field and will not be described in detail here.

[0063] For the coordinated execution step S500, the distributed control system executes the conventional coordination mode in sub-step S530 to achieve the target phase transition critical surface height. It enables precise tracking and prevents damage to the water seal device.

[0064] In sub-step S531, the coordination execution module of the distributed control system continuously monitors the safety margin of the water seal device. When the distributed control system determines the safety margin of the water seal device When the value is greater than zero, the coordination execution module determines that the hydrophobic recovery pipeline has sufficient thermodynamic capacity, and the distributed control system triggers the normal coordination mode.

[0065] In sub-step S532, the distributed control system calculates the current dimensionless height coordinates in normal coordination mode. Height of the target phase transition critical surface Positional deviation, when the current dimensionless height coordinate Greater than the height of the target phase transition critical surface This indicates that the integrally extruded spiral finned tube bundle needs to increase the effective heat exchange area, and the coordinating execution module simultaneously outputs the first control command for the steam inlet electric regulating valve. and the second control command for the hydrophobic electric shut-off valve The distributed control system uses the first control command. Increase the opening of the steam inlet electric regulating valve and simultaneously issue a second control command. Increase the opening degree of the hydrostatic shut-off valve.

[0066] In sub-step S533, to prevent sudden pressure changes inside the pipe, the first control command... With the second control command An asynchronous rate regulation mechanism is adopted, and the specific implementation logic is that the distributed control system uses the first control command. A time delay circuit and a slope limiter are connected in series in the logic output channel. The distributed control system sets the rate of change of the steam inlet electric regulating valve to be less than the rate of change of the condensate electric shut-off valve. The distributed control system actively reduces the internal back pressure of the condensate recovery pipeline by prioritizing the rapid opening of the condensate electric shut-off valve, thus accelerating the discharge of condensate accumulated in the pipeline. At the same time, the distributed control system controls the steam inlet electric regulating valve to follow up with steam replenishment at a slower rate after the time delay circuit has elapsed, so that the current dimensionless height coordinate... Smoothly approaching the target phase transition critical surface height .

[0067] For the coordinated execution step S500, the distributed control system executes the safety protection mode in sub-step S540.

[0068] In sub-step S541, when the distributed control system determines the safety margin of the water seal device... When the total enthalpy of the steam-water mixture is less than or equal to zero, the coordination execution module determines the total enthalpy of the steam-water mixture to be discharged into the water seal device. This will cause the water seal device to boil and vaporize, damaging it and triggering the interlocking restrictions of the safety protection mode in the distributed control system.

[0069] In sub-step S542, under interlocking constraints, the distributed control system cuts off the target phase transition critical surface height. For the second control command The feedback control link, the distributed control system forcibly locks the second control command. The corresponding opening increment is zero, or the second control command decreases in the negative direction. The corresponding opening degree of the hydrophobic electric shut-off valve, the distributed control system forces the saturated condensate to accumulate and cool at the lower end of the integrally extruded spiral finned tube bundle by limiting the hydrophobic discharge, and prevents the high enthalpy mixed medium from breaking through the water seal device and causing vapor-liquid impact vibration.

[0070] In sub-step S543, while locking the opening of the hydrophobic electric shut-off valve, the distributed control system initiates asymmetric action logic to compensate for the heat transfer gap. Specifically, the compensation logic involves the distributed control system switching its internally integrated proportional-integral-derivative controller to a second set of control parameters pre-tuned for large delay conditions. The distributed control system adjusts the first control command solely based on the position deviation. The corresponding steam inlet electric regulating valve opening is passively compensated for by increasing the steam compression density in the pipe and extending the heat exchange response time in the distributed control system. For the decoupling algorithm of the multi-output channel of the underlying proportional-integral-derivative controller, the parameter disturbance-free switching algorithm, and the dead zone compensation control of the actuator, those skilled in the art can perform conventional configuration based on the hardware response curve of the electric actuator. The hardware-level amplitude limiting interlock and single-loop asymmetric fault-tolerant execution technology of the control loop are well-known technologies in the field and will not be described in detail here.

[0071] For the antifreeze protection step S600, the distributed control system executes the extreme cold and micro-negative pressure risk identification mechanism in sub-step S610.

[0072] In sub-step S611, the distributed control system continuously reads the air inlet temperature of the heater obtained in the multi-source parameter acquisition step. The distributed control system calls the preset antifreeze critical temperature in the internal memory. Among them, the critical temperature for antifreeze The temperature boundary value is obtained based on the historical extreme minimum temperature of the region where the steam heater is located and the environmental heat dissipation rate of the integrally extruded spiral finned tube bundle. The anti-freeze protection logic unit of the distributed control system sets the air inlet temperature of the heater. Critical temperature for antifreeze Perform real-time comparison calculations.

[0073] In sub-step S612, the distributed control system obtains the actual heating steam flow rate entering the integrally extruded spiral finned tube bundle through flow meters arranged on the steam supply pipeline. The distributed control system invokes a preset steady-state flow threshold. Among them, steady-state flow threshold The minimum theoretical steam replenishment flow rate required to maintain the internal pressure of the integrally extruded spiral finned tube bundle above the ambient atmospheric pressure, obtained through thermodynamic condensation equilibrium calculations, is the actual heating steam flow rate. It characterizes the thermal input state of the steam heater body under the current unit load conditions.

[0074] In sub-step S613, the distributed control system constructs risk determination logic. When the distributed control system detects the air inlet temperature of the heater... Below the critical temperature for antifreeze And the actual heating steam flow rate Less than the steady-state flow threshold When the antifreeze protection logic unit determines that the steam condensation rate inside the integrally extruded spiral finned tube bundle exceeds the actual heating steam flow rate, the antifreeze protection logic unit will determine that the steam condensation rate inside the integrally extruded spiral finned tube bundle exceeds the actual heating steam flow rate. Based on the corresponding physical replenishment rate, the distributed control system determines that a slight negative pressure physical state occurs in the end cavity of the integrally extruded spiral finned tube bundle due to the volume shrinkage caused by the vapor phase change.

[0075] In sub-step S614, given that the micro-negative pressure physical state will cause cold air from the external environment to backflow through the hydrophobic recovery pipeline, thereby triggering the phase change and freezing of the condensate at the bottom of the integrally extruded spiral finned tube bundle, the distributed control system generates an extreme cold operation state trigger signal based on the micro-negative pressure physical state determination result. The distributed control system writes the extreme cold operation state trigger signal into the data register to trigger subsequent protection actions. For the selection of the flow meter and the requirements for the straight pipe section length for installation, as well as the determination and calculation of the internal logic gate circuit of the distributed control system, those skilled in the art can perform conventional configuration based on the pipe diameter and the instruction set of the control chip. The underlying logic state judgment and flow physical acquisition technology are well-known technologies in this field and will not be described in detail here.

[0076] For the antifreeze protection step S600, the distributed control system executes an overriding execution strategy in sub-step S620 to force the phase change boundary to move upward in order to eliminate the micro-negative pressure physical state.

[0077] In sub-step S621, the antifreeze protection logic unit of the distributed control system receives the extreme cold operation state trigger signal written in the data register. The antifreeze protection logic unit cuts off the closed-loop negative feedback regulation link from the target phase change critical surface height output by the cross-field mapping module to the coordinated execution module. The antifreeze protection logic unit obtains the priority control authority of the steam inlet electric regulating valve and the condensate electric shut-off valve. The distributed control system decouples the conventional temperature deviation control. In the specific lower-level feature implementation, under the extreme cold micro-negative pressure condition, the distributed control system stops tracking the actual air temperature at the air outlet of the heater and converts the control objective of the distributed control system into maintaining the thermodynamic pressure balance inside the integrally extruded spiral finned tube bundle.

[0078] In sub-step S622, the antifreeze protection logic unit recalculates the safe phase change boundary based on the current thermodynamic input conditions, and retrieves the actual heating steam flow rate obtained in the multi-source parameter acquisition step and the phase change calculation step. Inlet steam specific enthalpy Enthalpy of hydrophobic outlet The antifreeze protection logic unit calls the equivalent heat dissipation constant pre-stored in the controller. The equivalent heat dissipation constant The heat transfer mapping coefficient is obtained by conducting wind-side heat dissipation calibration tests on the integrally extruded spiral finned tube bundle under extremely cold environmental temperatures. The antifreeze protection logic unit extracts the current heating steam inlet pressure and retrieves the saturated steam temperature corresponding to the current heating steam inlet pressure from the steam thermodynamic property data table. The antifreeze protection logic unit is combined with the equivalent heat dissipation constant. With saturated steam temperature The forced safe phase transition height was calculated. Forced safety phase transition height The specific calculation formula is as follows:

[0079] In the formula This represents the saturated steam temperature corresponding to the current heating steam inlet pressure. Forced safe phase change height for air inlet temperature of the heater This is used to characterize the proportion of the maximum pure steam residence space that an integrally extruded spiral finned tube bundle can maintain an internal pressure no lower than atmospheric pressure under actual heating steam flow conditions where heat is scarce.

[0080] In sub-step S623, the antifreeze protection logic unit calculates the forced safety phase transition height. The output execution command, the antifreeze protection logic unit outputs a valve-closing forced command to the hydrostatic shut-off valve, reducing the opening of the hydrostatic shut-off valve at a preset maximum action rate. This reduces the opening of the hydrostatic shut-off valve, blocking the discharge path of condensate, and causing the condensate to rapidly submerge at the bottom of the integrally extruded spiral finned tube bundle. The submersion process pushes the physical phase change boundary upward, forcing the actual phase change boundary inside the integrally extruded spiral finned tube bundle to approach the forced safe phase change height. The forced upward shift of the phase change boundary reduces the effective heat dissipation surface area on the steam side, causing the actual steam condensation rate to differ from the actual heating steam flow rate. Achieving physical equilibrium eliminates the local vacuum suction force generated by the sudden volume reduction during vapor phase change.

[0081] In sub-step S624, while the phase change boundary is forced upward, the antifreeze protection logic unit outputs a feedforward compensation opening command to the steam inlet electric regulating valve. The feedforward compensation opening command drives the steam inlet electric regulating valve to increase its opening. The distributed control system uses the additional injected steam dynamic pressure to block the backflow path of cold air in the condensate recovery pipeline, ensuring that the water at the bottom of the integrally extruded spiral finned tube bundle is maintained in a saturated water thermodynamic state, thus preventing the water from freezing due to phase change. For the highest control authority priority configuration code and the maximum action rate limiting circuit of the electric actuator in the antifreeze protection logic unit, those skilled in the art can make conventional selection and configuration based on the interrupt service mechanism of the controller. The underlying control handover and command limiting output logic are well-known technologies in the field and will not be described in detail here.

[0082] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for automatically adjusting the air temperature and steam of a steam heater, wherein the main body executing the automatic adjustment method is a distributed control system, characterized in that, The automatic adjustment method includes: Perform multi-source parameter acquisition steps to acquire in real time the thermodynamic boundary conditions, boundary environment parameters, and time-domain differential pressure signal in the air-powder mixing pipeline of the steam heater body on both the gas and water sides. Perform a fluidization evaluation step, and perform frequency domain transformation and energy integration on the time-domain differential pressure signal to obtain the fluidization stability index; The phase change calculation steps are performed, and the current dimensionless height coordinates of the physical interface between pure steam and saturated water are dynamically calculated and characterized by combining the physical property parameters of steam and water with the physical geometric characteristics of the integrally extruded spiral finned tube bundle. The mapping calculation step is performed, and the cross-field mapping calculation is carried out based on the negative feedback adjustment of the actual air temperature at the air outlet of the heater and the nonlinear feedforward compensation of the fluidization stability index to calculate the height of the target phase change critical surface. The coordinated execution steps are implemented to construct a prediction model of the enthalpy of the steam-water mixture discharged into the water seal device to establish the safety margin of the water seal device. Under the constraint of the safety margin of the water seal device, the opening of the steam inlet electric regulating valve and the opening of the condensate electric shut-off valve are adjusted through the valve asynchronous action logic and asymmetric action logic. The antifreeze protection steps are executed by triggering an overreach execution strategy that forces the phase change boundary to move upward through the extreme cold and micro negative pressure risk identification mechanism, cutting off the conventional temperature tracking link, and forcibly setting the opening degree of the steam inlet electric regulating valve and the opening degree of the condensate electric shut-off valve.

2. The method for automatic adjustment of air temperature and steam in a steam heater according to claim 1, characterized in that, The multi-source parameter acquisition step includes: The inlet pressure and temperature of the heating steam are obtained in real time by an inlet pressure transmitter and an inlet thermocouple arranged on the steam supply pipeline. The outlet pressure and outlet temperature of the condensate are obtained by an outlet pressure transmitter and an outlet thermocouple arranged on the condensate recovery pipeline. The time-domain differential pressure signal is generated by continuously measuring the actual static pressure difference at a preset sampling frequency through differential pressure transmitters at both ends of the inlet and outlet of the air-powder coupled flow field disturbance mixing compensator arranged inside the air-powder mixing pipeline. The air inlet temperature of the heater and the actual air outlet temperature of the heater are obtained by a matrix of temperature sensors arranged on the air inlet section of the expanded and variable diameter air duct and the air outlet section of the integrally extruded spiral finned tube bundle.

3. The method for automatic adjustment of air temperature and steam in a steam heater according to claim 1, characterized in that, The fluidization evaluation step includes: The time-domain differential pressure signal is truncated into discrete data frames, smoothed by applying a window function, and then mapped to the frequency domain space through discrete Fourier transform to generate a complex frequency domain sequence. Extract the complex frequency domain amplitude corresponding to each frequency variable in the complex frequency domain sequence, calculate the square of the complex frequency domain amplitude and perform normalization processing to obtain the power spectral density function; The predetermined Nyquist cutoff frequency is extracted and set as the upper limit of the full-band integration, and the critical value of the no-coal-powder disturbance resistance frequency obtained in the pre-calibrated no-load condition is extracted and set as the lower limit threshold of the high-frequency band. The power spectral density function is subjected to definite integral operation. The high-frequency band pulsating energy integral value within the interval from the lower threshold of the high-frequency band to the upper limit of the full-frequency band integral is divided by the total pulsating energy integral value of the full-frequency band within the interval from zero to the upper limit of the full-frequency band integral, and the fluidization stability index is calculated.

4. The method for automatic adjustment of air temperature and steam in a steam heater according to claim 2, characterized in that, The phase transition calculation steps include: Using the heating steam inlet pressure and heating steam inlet temperature as joint addressing indexes, two-dimensional interpolation is performed in the superheated steam region of the steam thermodynamic property data table to calculate the inlet steam specific enthalpy. Using the hydrophobic outlet pressure and the hydrophobic outlet temperature as joint addressing indexes, two-dimensional interpolation is performed in the subcooled water region or saturated region of the water vapor thermodynamic property data table to calculate the outlet hydrophobic specific enthalpy. Using the heating steam inlet pressure as a univariate index, the saturated steam specific enthalpy and the saturated liquid specific enthalpy are extracted, and the difference between the saturated steam specific enthalpy and the saturated liquid specific enthalpy is calculated as the latent heat of vaporization of steam. The dimensionless structural constant is calculated by combining the internal flow cross-sectional area of ​​the pre-stored integral extrusion-molded spiral finned tube bundle, the comprehensive heat transfer coefficient of the heater, and the designed heat transfer area. Calculate the difference between the inlet steam enthalpy and the outlet hydrophobic enthalpy, divide the difference between the inlet steam enthalpy and the outlet hydrophobic enthalpy by the latent heat of vaporization of the steam, multiply by the dimensionless structural constant, and subtract the result of the multiplication to obtain the current dimensionless height coordinates.

5. The method for automatic adjustment of air temperature and steam in a steam heater according to claim 1, characterized in that, The execution mapping calculus step includes: The temperature deviation value is calculated by subtracting the preset target air temperature from the actual air outlet temperature of the heater. The temperature deviation value is then input into the internal proportional-integral-derivative controller for continuous proportional, integral, and derivative operations. The output results are then linearly superimposed to generate an effective heat exchange area correction. The dimensionless height change increment is obtained by dividing the effective heat exchange area correction by the pre-stored total design heat exchange area. The historical phase change boundary height of the previous calculation cycle is added to the dimensionless height change increment, and the basic liquid level height command is output. The first and second feedforward decoupling gain coefficients, which are pre-tuned, are obtained. The nonlinear logarithmic decay operation is then performed to calculate the height of the target phase transition critical surface. Specifically, the second feedforward decoupling gain coefficient is multiplied by the fluidization stability index and then one is added. The natural logarithm of the result after adding one is taken and multiplied by the first feedforward decoupling gain coefficient. Finally, the result of multiplication is subtracted from the basic liquid level height command to obtain the height of the target phase transition critical surface.

6. The method for automatic adjustment of air temperature and steam in a steam heater according to claim 4, characterized in that, The construction of the enthalpy prediction model for the steam-water mixture discharged into the water seal device to establish the safety margin of the water seal device includes: The difference between the control command and the current opening feedback value of the hydrophobic electric shut-off valve is read. The difference between the control command and the current opening feedback value is multiplied by the pre-fitted flow characteristic constant of the hydrophobic electric shut-off valve. The product is multiplied by the difference between the inlet steam specific enthalpy and the outlet condensate specific enthalpy. The final product is added to the outlet condensate specific enthalpy to calculate the total specific enthalpy of the steam-water mixture discharged into the water seal device. Obtain the current working pressure of the water seal device, perform one-dimensional interpolation calculation within the saturation region of the water vapor thermodynamic property data table, and extract the corresponding saturated liquid specific enthalpy as the critical destruction specific enthalpy; The safety margin of the water seal device is calculated by subtracting the total specific enthalpy of the steam-water mixture from the critical destruction specific enthalpy.

7. The method for automatic adjustment of air temperature and steam in a steam heater according to claim 6, characterized in that, The adjustment of the opening degree of the steam inlet electric regulating valve and the condensate electric shut-off valve through the valve asynchronous action logic and asymmetric action logic includes: When the safety margin of the water seal device is determined to be greater than zero, the normal coordination mode is triggered. Calculate the positional deviation between the current dimensionless height coordinates and the height of the target phase transition critical surface; When the current dimensionless height coordinate is greater than the target phase change critical surface height, a first control command for the steam inlet electric regulating valve and a second control command for the condensate electric shut-off valve are output simultaneously. A time delay circuit and a slope limiter are connected in series in the logic output channel of the first control command. The rate of change of the action of the steam inlet electric regulating valve is set to be less than the rate of change of the action of the condensate electric shut-off valve. The opening degree of the condensate electric shut-off valve is increased first, and the steam inlet electric regulating valve is controlled to increase its opening degree after the delay time set by the time delay circuit.

8. The method for automatic adjustment of air temperature and steam in a steam heater according to claim 6, characterized in that, The method of adjusting the opening of the steam inlet electric regulating valve and the condensate electric shut-off valve through asynchronous valve action logic and asymmetric action logic also includes: When the safety margin of the water seal device is determined to be less than or equal to zero, the interlocking restriction condition of the safety protection mode is triggered. Disconnect the feedback control link between the target phase change critical surface height and the hydrophobic electric shut-off valve, forcibly lock the opening increment of the hydrophobic electric shut-off valve to zero, or reduce the opening of the hydrophobic electric shut-off valve in the negative direction. The asymmetric action logic is activated, and the internally integrated proportional-integral-derivative controller is switched to the second set of control parameters pre-tuned for large delay conditions, adjusting only the opening of the steam inlet electric regulating valve.

9. The method for automatic adjustment of air temperature and steam in a steam heater according to claim 4, characterized in that, The extreme cold micro-negative pressure risk identification mechanism includes: The air inlet temperature of the heater is continuously compared with the pre-set antifreeze critical temperature based on historical extreme minimum temperatures. The actual heating steam flow rate is obtained by a flow meter installed on the steam supply pipeline, and the steady-state flow rate threshold obtained by condensation balance calculation is called. When it is determined that the air inlet temperature of the heater is less than the antifreeze critical temperature and the actual heating steam flow rate is less than the steady-state flow rate threshold, a slight negative pressure physical state is determined to occur in the end cavity of the integrally extruded spiral finned tube bundle, and an extreme cold operation state trigger signal is generated.

10. The method for automatic adjustment of air temperature and steam in a steam heater according to claim 9, characterized in that, The overriding execution strategy that triggers the forced upward shift of the phase transition boundary, cutting off the conventional temperature tracking link and forcibly intervening in the valve opening to eliminate the micro-negative pressure physical state, includes: Upon receiving the extreme cold operating state trigger signal, the closed-loop negative feedback regulation link is cut off, and priority control authority is obtained for the steam inlet electric regulating valve and the condensate electric shut-off valve. The equivalent heat dissipation constant calibrated for extreme cold is called, and the corresponding saturated steam temperature is obtained by addressing the data table of thermodynamic properties of water vapor; Calculate the product of the actual heating steam flow rate and the difference between the inlet steam specific enthalpy and the outlet condensate specific enthalpy, calculate the product of the equivalent heat dissipation constant and the difference between the saturated steam temperature and the air inlet temperature of the heater, divide the two products and subtract the result of the division, and calculate the forced safety phase change height. The output valve closing command reduces the opening of the hydrophobic electric shut-off valve, forcing the actual phase change boundary to approach the forced safe phase change height; A feedforward compensation opening command is output to the steam inlet electric regulating valve to increase the opening.

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