A method for controlling thermal power of a distillation tower reboiler

Abstract

The present invention belongs to the technical field of distillation and purification, and specifically relates to a method for controlling the thermal power of a distillation tower reboiler, which is used for controlling the power of a reboiler in a distillation tower provided with a vacuum cover and a vacuum insulation layer, and comprises the following steps: Step S1, executing the safety judgment logic, judging whether the heater temperature of the reboiler and the pressure of the vacuum insulation layer are within the safety threshold range, and if they are within the safety threshold range, executing Step S2; if they are not within the safety threshold range, stopping the power output of the heater to avoid the risk of weak insulation breakdown; Step S2, executing the power control logic, and adjusting the power of the reboiler in real time according to the predetermined value of the target variable, and the target variable is the distillation tower parameter that needs to be controlled by the power adjustment of the reboiler, including tower pressure, tower temperature and power. The present invention improves the effectiveness of the power adjustment of the reboiler working in a high vacuum state, ensures the stable operation of the distillation tower, and reduces safety risks.

Description

Technical Field

[0001] The invention belongs to the technical field of distillation and purification, and in particular relates to a method for controlling the thermal power of a distillation tower reboiler. Background Art

[0002] A distillation tower is a tower-type gas-liquid contact device that performs distillation operations. It utilizes the difference in volatility of the components in the mixture and continuously contacts and transfers mass between the gas and liquid phases to enrich the low-boiling-point components in the gas phase and the high-boiling-point components in the liquid phase, thereby achieving the purpose of separation.

[0003] Tower temperature is an important factor affecting gas-liquid mass transfer in the tower. Temperature fluctuations will destroy the equilibrium state of the separation system in the tower, causing changes in product composition and affecting the separation effect. The insulation of the distillation tower is very important, which is related to the separation and purification effect, as well as energy saving, especially for distillation systems whose operating temperature is far from the ambient temperature, such as deep cryogenic distillation towers working at extremely low temperatures. The insulation effect will directly determine the separation performance and overall energy consumption of the tower.

[0004] In order to maintain a stable operating environment, the distillation tower needs thermal insulation measures. The vacuum insulation layer is a very convenient and efficient insulation method, which is widely used in low-temperature distillation towers. A vacuum hood is installed outside the distillation tower, and a high vacuum is drawn inside the vacuum hood to form a vacuum insulation layer to reduce the heat leakage of the distillation tower to the outside world and achieve the purpose of saving cooling capacity.

[0005] Under high vacuum environment, the change of gas pressure and the accumulation of heat will have a great impact on the insulation performance of the heating element of the distillation tower bottom reboiler located in the vacuum cover using direct electric heating:

[0006] (1) According to Paschen's law, there is a relationship between the gap voltage withstand strength and the gas pressure and gap distance. When the gas composition and the gap bipolar material are constant, the gas gap breakdown voltage is a function of the product of the gas pressure and the interpolar distance. There is a valley point in the relationship curve, that is, when the interpolar distance is constant, the gas gap breakdown voltage has a minimum value at a certain gas pressure. As the gas pressure changes, the voltage withstand strength between the gap bipolars at a certain distance will change accordingly, making the live parts with good insulation performance have the risk of breakdown under certain pressure conditions.

[0007] (2) Under vacuum conditions, when the environment does not dissipate enough heat and there is no heat-absorbing load, the heater is prone to accumulate heat and heat up, causing aging of the cold end of the armored heater, seal failure, affecting insulation performance, and creating a risk of breakdown.

[0008] For distillation towers with direct electric heating reboilers, although insulating powder is filled between the armored heater power cord and the protective shell, there is still a gap atmosphere, and the atmosphere medium also has the risk of breakdown under vacuum conditions. Once the above breakdown occurs, the leakage current of the heater may cause the non-insulated parts of the entire tower to be charged, making the reboiler heater unable to work normally, and at the same time creating a huge safety risk.

[0009] At present, the distillation system using vacuum insulation does not consider the additional effect of the vacuum environment in the power control of the electric heater of the bottom reboiler, which poses a high safety risk. Summary of the invention

[0010] The purpose of the present invention is to provide a method for realizing segmented heterogeneous target variable adjustment of the thermal power of a distillation tower reboiler, and simultaneously performing effective measurement of the actual power of the distillation tower reboiler under the action of an AC power supply; at the same time, effectively avoiding the breakdown risk between the power line of the reboiler armored heater and the protective tube due to the pressure change that may exist in the vacuum casing, and the breakdown risk caused by insulation deterioration due to the high temperature accumulated in the vacuum, thereby effectively protecting the distillation system.

[0011] To achieve the above objectives, the technical solution of the present invention provides a method for controlling the thermal power of a distillation tower reboiler, which is used to control the power of a reboiler in a distillation tower provided with a vacuum cover and a vacuum isolation layer, comprising the following steps:

[0012] Step S1, executing the safety judgment logic to determine whether the heater temperature of the reboiler and the pressure of the vacuum insulation layer are within the safety threshold range. If they are within the safety threshold range, step S2 is executed; if they are not within the safety threshold range, the power output of the heater is stopped to avoid the risk of weak insulation breakdown;

[0013] Step S2, execute the power control logic, and adjust the power of the reboiler in real time according to the predetermined value of the target variable, wherein the target variable is the distillation tower parameter that needs to be controlled by the power adjustment of the reboiler, including tower pressure, tower temperature and power.

[0014] Further, the safety decision logic includes the following steps:

[0015] Step S1.1, before the distillation tower is officially put into use, the insulation strength-working pressure performance test is performed on the heater of the reboiler to obtain the insulation performance parameters of the heater when it works within the pressure range of the vacuum insulation layer, and determine the pressure range where there is a risk of breakdown between the power line of the heater and the protective tube;

[0016] Step S1.2, before the heater of the reboiler is officially put into use, the insulation strength-vacuum heat accumulation performance test is performed on the heater, the insulation performance parameters thereof at high temperature caused by heat accumulation under the high vacuum working environment of the vacuum cover are obtained, and the temperature range in which there is a risk of breakdown between the power line of the heater and the protective tube is determined;

[0017] Step S1.3, monitoring the pressure of the vacuum insulation layer where the reboiler is located, and writing it into the reboiler power control logic: when the pressure of the vacuum insulation layer is within the pressure range determined in step S1.1, stopping the power output of the heater to avoid the risk of weak insulation breakdown;

[0018] Step S1.4, monitor the temperature of the heater of the reboiler and write it into the reboiler power control logic: when the temperature of the heater is within the temperature range determined in step S1.2, stop the power output of the heater to avoid the risk of weak insulation breakdown.

[0019] Further, the power control logic comprises the following steps:

[0020] Step S2.1, segmenting the reboiler according to control requirements, and clarifying the target variable type and target value of each segment;

[0021] Step S2.2, each segment independently sets a PID controller, and determines the input variable and output variable of the PID controller according to the target variable of each segment;

[0022] Step S2.3, real-time monitoring of the target variable, and transmitting the measured value of the target variable to the input end of the PID controller, and obtaining the value of the output variable through calculation by the PID controller;

[0023] Step S2.4, according to the specific form of the power regulation loop, the output variable of the PID controller is converted into a suitable form and sent into the power regulation loop to adjust the power output heating of the heater; the power regulation loop is formed by a combination of physical devices that perform power regulation, and is responsible for converting the required power calculated and output by the PID controller into actual operation of the power supply of the heater, including on / off and voltage / current regulation;

[0024] Step S2.5, looping through the steps S2.3 and S2.4, and performing real-time power regulation based on the target variable through the closed-loop logic of the PID controller.

[0025] Furthermore, the power supply form of the heater is not limited. When the heater adopts an AC power supply, the actual power measurement value is obtained by the moving average of the effective current and voltage product, the voltage / current effective value measurement is performed at a frequency not lower than the operating frequency of the heater, and the effective heating power of the reboiler heater is calculated synchronously and by moving average, which serves as a real-time feedback input when the PID controller uses the reboiler power as the target variable; specifically, the measurement of the voltage / current effective value is completed through a mutual inductor.

[0026] Furthermore, when the heater adopts an AC power supply, power regulation output is performed through a solid-state relay in cooperation with a PLC pulse width modulation; or power regulation output is performed through a PLC analog output module in cooperation with a power regulator.

[0027] Furthermore, when the heater adopts a DC power supply, the output power value calculated by the PID controller can be converted into a current / voltage demand value according to the resistance of the heater, and transmitted to the DC power supply of the heating circuit to execute the output to achieve power regulation; for power supply equipment with embedded script programming capabilities, the output power value calculated by the PID controller is directly transmitted to the loop DC power supply for execution.

[0028] Furthermore, the input variables of the PID controller are demand target variables, including power, tower pressure and tower temperature, and the output variables of the PID controller are demand power or pulse signal duty cycle; when the heater adopts an AC power supply, if the output variable of the PID controller is the demand power, the duty cycle needs to be determined according to the rated power of the heater; after the PLC device receives the duty cycle and performs pulse width modulation, it outputs a pulse switching signal to the solid-state relay for execution.

[0029] Furthermore, the PID controller is a proportional power controller, that is, the required power is only a specific proportion of the rated power. At this time, the duty cycle information can be calculated and output to the DO module of the PLC device, the pulse level signal can be adjusted, the solid-state relay can be driven, and the loop current of the heater can be controlled to be on and off, thereby realizing power regulation.

[0030] The beneficial effects of the present invention are:

[0031] 1. The power output control of the reboiler heater of the distillation tower working under high vacuum conditions takes into account the breakdown risk of the heating components caused by changes in insulation strength due to changes in working pressure and temperature, improves the effectiveness of reboiler power regulation, ensures the smooth operation of the distillation tower, and reduces safety risks.

[0032] 2. The reboiler heat power of the distillation tower is adjusted in sections with heterogeneous target variables, and the liquid level distribution of the reboiler heating power is adjusted according to demand to achieve flexible control of the distillation tower operating parameters such as evaporation rate and discharge temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a logic block diagram of the power control of the distillation tower reboiler using an AC power supply and PLC pulse width modulation as described in a specific embodiment of the present invention;

[0034] Figure 2 It is a logic block diagram of the power control of the distillation tower reboiler using an AC power supply and a power regulator as described in a specific embodiment of the present invention;

[0035] Figure 3 It is a logic block diagram of power control of a distillation tower reboiler using a DC power supply as described in a specific embodiment of the present invention;

[0036] Figure 4 It is a logic diagram of regulating heating power by pulse width modulation using a non-zero-crossing shutoff type SSR as described in a specific embodiment of the present invention;

[0037] Figure 5 It is a logic diagram of regulating heating power by pulse width modulation using a zero-crossing turn-off SSR as described in a specific embodiment of the present invention;

[0038] Figure 6 It is a schematic diagram of the multi-stage heterogeneous target variable reboiler power regulation form described in the embodiment part of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0040] The present invention provides a method for controlling the thermal power of a distillation tower reboiler, which is used to control the power of a reboiler in a distillation tower provided with a vacuum cover and a vacuum isolation layer, and comprises the following steps:

[0041] Step S1, execute the safety judgment logic to determine whether the heater temperature and vacuum insulation layer pressure of the reboiler are within the safety threshold range. If they are within the safety threshold range, execute step S2; if the heater temperature and vacuum insulation layer pressure of the reboiler are not within the safety threshold range (that is, within the risk range), stop the power output of the heater to avoid the risk of weak insulation breakdown. The safety judgment logic mainly involves the identification and control of the breakdown risk of the reboiler electrical heating components;

[0042] Step S2, execute the power control logic, and adjust the power of the reboiler in real time according to the predetermined value of the target variable. The target variable is the distillation tower parameter that needs to be controlled by the power adjustment of the reboiler, including tower pressure, tower temperature and power, etc.; the judgment logic uses the heater temperature and the space pressure as reference factors. When the reference factor is within the safety threshold range, the reboiler output power adjustment based on the custom target is performed.

[0043] The safety decision logic includes the following steps:

[0044] Step S1.1, before the distillation tower is officially put into use, the insulation strength-working pressure performance test is performed on the heater of the reboiler to obtain the insulation performance parameters of the heater when it works within the pressure range of the vacuum insulation layer, and to determine the pressure range where there is a risk of breakdown between the power line of the heater and the protective tube;

[0045] Step S1.2, before the heater of the reboiler is officially put into use, the insulation strength-vacuum heat accumulation performance test is performed on the heater, and its insulation performance parameters at high temperatures that may be caused by heat accumulation in the high vacuum working environment of the vacuum cover are obtained, and the temperature range in which there is a risk of breakdown between the power line and the protective tube of the heater is determined;

[0046] Step S1.3, monitoring the pressure of the vacuum insulation layer where the reboiler is located, and writing it into the reboiler power control logic: when the pressure of the vacuum insulation layer is within the pressure range determined in step S1.1, stopping the power output of the heater to avoid the risk of weak insulation breakdown;

[0047] Step S1.4, monitor the temperature of the heater of the reboiler and write it into the reboiler power control logic: when the temperature of the heater is within the temperature range determined in step S1.2, stop the power output of the heater to avoid the risk of weak insulation breakdown.

[0048] The power control logic includes the following steps:

[0049] Step S2.1, segment the reboiler (i.e., the heating section in the figure) according to the control requirements, and clarify the target variable type and target value of each section;

[0050] Step S2.2, each segment independently sets a PID controller, and determines the input variable and output variable of the PID controller according to the target variable of each segment;

[0051] Step S2.3, real-time monitoring of the target variable, and transmitting the measured value of the target variable to the input end of the PID controller, and the value of the output variable is obtained by the PID controller calculation;

[0052] Step S2.4, according to the specific form of the power regulation loop, the output variable of the PID controller is converted into a suitable form and sent into the power regulation loop to adjust the power output heating of the heater; the power regulation loop is formed by the combination of physical devices that perform power regulation, and is responsible for converting the required power calculated and output by the PID controller into the actual operation of the power supply of the heater, including on-off and voltage / current regulation, etc.;

[0053] Step S2.5, looping through steps S2.3 and S2.4, and performing real-time power regulation based on the target variable through the closed-loop logic of the PID controller.

[0054] The power control logic is based on the PID controller, with the predetermined value of the target variable as the input variable and the ratio of the heater power of the reboiler / heater power to the rated power as the direct output variable; the PID controller receives the instantaneous value of the target variable in real time, compares it with the preset value of the target variable to determine the deviation, and calculates the output variable value with the goal of minimizing the deviation between the instantaneous value and the preset value, and passes it to the power regulation loop for execution.

[0055] The reboiler power is adjusted by a segmented independent PID (proportional-integral-differential) controller: the heating devices are arranged in segments, and each segment is independently configured with a PID controller. The number of segments of the reboiler can be designed and determined according to the reboiler specifications (such as volume, height, etc.) and process control requirements. For example, for a smaller reboiler, only single-stage power control can be performed; for a large reboiler, a segmented heating method is adopted, and each segment is independently configured with a PID controller and a power regulation loop, which has the ability to independently control and adjust the heating power, and each segment PID controller can select different target variables.

[0056] There is no limit to the power supply form of the heater. When the heater adopts AC power supply, the actual power measurement value can be obtained by the moving average of the effective current and voltage product, and the voltage / current effective value measurement is performed at a frequency not lower than the operating frequency of the heater. The effective heating power of the reboiler heater is calculated synchronously and by moving average, which serves as the real-time feedback input of the PID controller when the reboiler power is used as the target variable; specifically, the measurement of the AC voltage / current effective value can be completed through a mutual inductor.

[0057] When the heater uses AC power, the power regulation output can be performed through the solid-state relay (SSR) in conjunction with the PLC pulse width modulation (PWM); or the power regulation output can be performed through the PLC analog output (AO) module in conjunction with the power regulator (SCR).

[0058] Figure 1This is a logic block diagram of the power control of the distillation tower reboiler using AC power supply and PLC pulse width modulation. The power regulation is performed by solid-state relay (SSR) in conjunction with PLC pulse width modulation (PWM). After the output power is modulated by pulse width (PWM), the duty cycle is obtained, and the level signal is output in the form of pulse switch through the PLC digital output (DO) module to drive the solid-state relay (SSR) to adjust the current on and off of the loop heater to achieve power regulation.

[0059] The logic of regulating the heating power by driving the solid-state relay (SSR) through pulse width modulation is as follows Figure 4 , 5 As shown, as the switch actuator of the electric power heating component, preferably, the solid-state relay (SSR) has zero-crossing shutdown capability; a dual-channel output type is used to cut off the lines at both ends of the heater at the same time.

[0060] Figure 2 This is a logic block diagram of the power control of the distillation tower reboiler using an AC power supply and a power regulator (SCR). The PLC analog output (AO) module cooperates with the power regulator (SCR) to perform power regulation. The PLC analog output (AO) module converts the PID's required power into a 4-20mA DC signal and sends it to the power regulator (SCR), which drives it to adjust the current on and off of the loop heater to achieve power regulation.

[0061] When the heater uses a DC power supply, such as Figure 3 , the output power value calculated by the PID controller can be converted into a current / voltage demand value according to the resistance of the heater, and transmitted to the DC power supply of the heating circuit for output execution to achieve power regulation; in particular, for some power supply devices with built-in script programming capabilities, the output power value calculated by the PID controller can be directly transmitted to the loop DC power supply for execution.

[0062] The input variable of the PID controller can be the required target variable, including power, tower pressure and tower temperature, and the output variable of the PID controller can be the required power or the duty cycle of the pulse signal. When the heater uses an AC power supply, if the output variable of the PID controller is the required power, the duty cycle must be determined based on the rated power of the heater. After the PLC device receives the duty cycle and performs pulse width modulation (PWM), it outputs a pulse switching signal to the solid-state relay (SSR) for execution.

[0063] The PID controller can be a proportional power controller, that is, the required power is only a specific proportion of the rated power, such as 1 / 2, 1 / 3, 1 / 5, etc. At this time, the duty cycle information can be calculated and output to the DO module of the PLC device, the pulse level signal can be adjusted, the solid-state relay (SSR) can be driven, and the loop current of the heater can be controlled to achieve power regulation.

[0064] Example

[0065] According to the reboiler heater insulation strength-working pressure performance test results, determine the pressure range (P min ,P max ); According to the test results of the insulation strength-operating temperature performance of the reboiler heater, determine the minimum temperature T at which there is a risk of breakdown between the heater power line and the protection tube max (K).

[0066] Use Figure 6 The heterogeneous target variable reboiler power regulation form shown in the figure performs reboiler power control in three stages. The three-stage PID controller information is as follows:

[0067]

[0068] 380V / 50HZ industrial AC is used as the power supply for the reboiler heater, and a dual solid-state relay (SSR) is used as the switch actuator of the electric power heating component. A current transformer is set in the AC circuit where the heater is located to determine the effective value of the AC current acting on the heating element. Heaters P1, P2, and P3 are arranged from top to bottom, and each section is independently equipped with a PID controller, SSR contactless switch, and AC current transformer, and output power control is performed in the form of pulse switching.

[0069] The effective current of the loop obtained by the mutual inductor is sent to the corresponding analog input (AI) module of the PLC device to calculate and obtain the effective heating power. In order to eliminate the influence of abnormal values, the effective power value within a certain number of points is processed by moving average, and the average value obtained is used as the measured effective value of the heater power.

[0070] Pulse switch power control is achieved through the pulse width modulation (PWM) function of the PLC device. The PID controller calculates the duty cycle by comparing the input variable with the target variable. After pulse width modulation (PWM), it is sent to the digital output (DO) module of the PLC device for execution.

[0071] (1) For the PID controller P1, the logic of the reboiler power control method is as follows:

[0072] Obtain the reboiler temperature and ambient pressure values ​​in real time and make safety judgments. When the monitored temperature or pressure is outside the safe action range, directly adjust the PLC equipment DO module, disconnect the SSR two-way switch, and stop the power supply to the heating element; when the monitored temperature and pressure are within the safe action range, execute the reboiler power control logic based on the preset target.

[0073] The reboiler power is set as the target variable, the actual power acting on the P1 section is used as the input variable, and the PID controller calculates the pulse signal duty cycle as the output variable.

[0074] The measured power value H1 is obtained through the AI ​​module of the PLC device as the input variable, which is compared with the preset target value SH1 to calculate the duty cycle RH1; RH1 is sent to the PLC for PWM, and the DO module is controlled to output pulses based on it; the pulse signal acts on the SSR contactless switch to perform dual-channel on-off control of the heating element circuit, modulate the power-on heating time of the heating element, and then adjust the heating power.

[0075] The above process is executed cyclically with the PID controller calculation period as the period.

[0076] (2) For the PID controller P2, the logic of the reboiler power control method is as follows:

[0077] Obtain the reboiler temperature and ambient pressure values ​​in real time and make safety judgments. When the monitored temperature or pressure is outside the safe action range, directly adjust the PLC equipment DO module, disconnect the SSR two-way switch, and stop the power supply to the heating element; when the monitored temperature and pressure are within the safe action range, execute the reboiler power control logic based on the preset target.

[0078] The reboiler temperature is set as the target variable, the actual temperature of the P2 stage heater is used as the input variable, and the PID controller calculates the pulse signal duty cycle as the output variable.

[0079] The measured temperature value T is obtained through the AI ​​module of the PLC equipment as the input variable, which is compared with the preset target value ST to calculate the duty cycle RT; RT is sent to the PLC for PWM, and the DO module is controlled to output pulses based on it; the pulse signal acts on the SSR contactless switch to perform dual-channel on-off control of the heating element circuit, modulate the power-on heating time of the heating element, and then adjust the heating power.

[0080] The above process is executed cyclically with the PID controller calculation period as the period.

[0081] (3) PID controller P3 is a proportional controller, that is, it fixes the power value of the rated power ratio of the output. The logic of its power control method is as follows:

[0082] Obtain the reboiler temperature and ambient pressure values ​​in real time and make safety judgments. When the monitored temperature or pressure is outside the safe action range, directly adjust the PLC equipment DO module, disconnect the SSR two-way switch, and stop the power supply to the heating element; when the monitored temperature and pressure are within the safe action range, execute the reboiler power control logic based on the preset target.

[0083] The proportion of the reboiler power to the rated power is set, and the duty cycle RH2 is obtained synchronously.

[0084] The measured power value H2 is obtained through the AI ​​module of the PLC device as the input variable, and the input variable is only for display observation; the DO module of the PLC device is controlled to output pulses based on the constant duty cycle RH2; the pulse signal acts on the SSR contactless switch to perform dual-channel on-off control of the heating element circuit, modulate the power-on heating time of the heating element, and then adjust the heating power.

[0085] The above process is executed in a loop.

[0086] The device described in the present invention is not limited to the embodiments described in the specific implementation manner. Those skilled in the art may derive other implementation manners based on the technical solution of the present invention, which also fall within the technical innovation scope of the present invention.

Claims

1. A method for controlling the thermal power of a reboiler in a distillation tower, which is used to control the power of a reboiler in a distillation tower provided with a vacuum cover and a vacuum insulation layer, comprising the following steps: Step S1, executing the safety judgment logic to determine whether the heater temperature of the reboiler and the pressure of the vacuum insulation layer are within the safety threshold range. If they are within the safety threshold range, step S2 is executed; if they are not within the safety threshold range, the power output of the heater is stopped to avoid the risk of weak insulation breakdown; Step S2, executing the power control logic to adjust the power of the reboiler in real time according to a predetermined value of a target variable, wherein the target variable is a distillation column parameter that needs to be controlled by the power adjustment of the reboiler, including column pressure, column temperature and power; The safety decision logic includes the following steps: Step S1.1, before the distillation tower is officially put into use, the insulation strength-working pressure performance test is performed on the heater of the reboiler to obtain the insulation performance parameters of the heater when it works within the pressure range of the vacuum insulation layer, and determine the pressure range where there is a risk of breakdown between the power line of the heater and the protective tube; Step S1.2, before the heater of the reboiler is officially put into use, the insulation strength-vacuum heat accumulation performance test is performed on the heater, the insulation performance parameters thereof at high temperature caused by heat accumulation under the high vacuum working environment of the vacuum cover are obtained, and the temperature range in which there is a risk of breakdown between the power line of the heater and the protective tube is determined; Step S1.3, monitoring the pressure of the vacuum insulation layer where the reboiler is located, and writing it into the reboiler power control logic: when the pressure of the vacuum insulation layer is within the pressure range determined in step S1.1, stopping the power output of the heater to avoid the risk of weak insulation breakdown; Step S1.4, monitoring the temperature of the heater of the reboiler and writing it into the reboiler power control logic: when the temperature of the heater is within the temperature range determined in step S1.2, stopping the power output of the heater to avoid the risk of weak insulation breakdown; The power control logic comprises the following steps: Step S2.1, segmenting the reboiler according to control requirements, and clarifying the target variable type and target value of each segment; Step S2.2, each segment independently sets a PID controller, and determines the input variable and output variable of the PID controller according to the target variable of each segment; Step S2.3, real-time monitoring of the target variable, and transmitting the measured value of the target variable to the input end of the PID controller, and obtaining the value of the output variable through calculation by the PID controller; Step S2.4, according to the specific form of the power regulation loop, the output variable of the PID controller is converted into a suitable form and sent into the power regulation loop to adjust the power output heating of the heater; the power regulation loop is formed by a combination of physical devices that perform power regulation, and is responsible for converting the required power calculated and output by the PID controller into actual operation of the power supply of the heater, including on / off and voltage / current regulation; Step S2.5, looping through the steps S2.3 and S2.4, and performing real-time power regulation based on the target variable through the closed-loop logic of the PID controller.

2. A method for controlling heat power of a distillation tower reboiler according to claim 1, characterized in that: The power supply form of the heater is not limited. When the heater adopts an AC power supply, the actual power measurement value is obtained by the moving average of the effective current and voltage product, the voltage / current effective value measurement is performed at a frequency not lower than the operating frequency of the heater, and the effective heating power of the reboiler heater is calculated synchronously and by moving average, which serves as the real-time feedback input of the PID controller when the reboiler power is used as the target variable; specifically, the voltage / current effective value measurement is completed by a mutual inductor.

3. A method for controlling heat power of a distillation tower reboiler as claimed in claim 2, characterized in that: When the heater adopts AC power supply, the power regulation output is performed through the solid-state relay in cooperation with the PLC pulse width modulation; or the power regulation output is performed through the PLC analog output module in cooperation with the power regulator.

4. A method for controlling heat power of a distillation tower reboiler according to claim 3, characterized in that: When the heater uses a DC power supply, the output power value calculated by the PID controller can be converted into a current / voltage demand value according to the resistance of the heater, and transmitted to the DC power supply of the heating circuit to execute the output to achieve power regulation; for power supply equipment with embedded script programming capabilities, the output power value calculated by the PID controller is directly transmitted to the loop DC power supply for execution.

5. A method for controlling heat power of a distillation tower reboiler according to claim 4, characterized in that: The input variables of the PID controller are the required target variables, including power, tower pressure and tower temperature, and the output variables of the PID controller are the required power or the duty cycle of the pulse signal; when the heater adopts an AC power supply, if the output variable of the PID controller is the required power, the duty cycle needs to be determined according to the rated power of the heater; After receiving the duty cycle and performing pulse width modulation, the PLC device outputs a pulse switch signal to the solid-state relay for execution.

6. A method for controlling heat power of a distillation tower reboiler according to claim 5, characterized in that: The PID controller is a proportional power controller, that is, the required power is only a specific proportion of the rated power. At this time, the duty cycle information can be calculated and output to the DO module of the PLC device, the pulse level signal can be adjusted, the solid-state relay can be driven, and the loop current of the heater can be controlled to be on and off, thereby realizing power regulation.

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