Double diaphragm valve linkage control method for controlling temperature of material liquid in feeding tank

Abstract

The application provides a kind of double thin film valve linkage control's feed tank liquid temperature control method, comprising: the sealing interlayer of feed tank is connected with heating steam pipeline and heat dissipation steam pipeline, the first steam film valve is arranged in the heating steam pipeline, and the second steam film valve is arranged in the heat dissipation steam pipeline;Determine whether there is liquid in the feed tank, if so, obtain the actual liquid weight and actual liquid temperature in the tank;Establish the PID liquid temperature model of feed tank, process standard liquid temperature and the actual liquid temperature are regarded as the input value of the PID liquid temperature model and are adjusted by PID, and the intermediate control variable CV is used as output value;According to the intermediate control variable, the opening of the first steam film valve and / or the second steam film valve is adjusted, and the temperature of the liquid in the feed tank is controlled.The application can realize the rapid heating and rapid heat dissipation of the feed tank, and improve the stability and accuracy of the liquid temperature control.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of temperature control of material liquid of feeding tank, and particularly relates to a method for controlling temperature of material liquid of feeding tank with double thin film valve linkage control. BACKGROUND

[0002] The feeding machine is a device for atomizing and adding material liquid to tobacco sheets in the tobacco processing technology, and the feeding tank is used for storing material liquid and maintaining constant temperature of the material liquid. The tank temperature is collected from a temperature sensor, and the tank temperature is controlled by opening and closing of a steam on-off valve. The steam enters the peripheral sealed interlayer of the tank, and the heat of the tank wall is used for indirectly heating the material liquid. When the material liquid in the tank is more, the heating process is relatively slow. When the material liquid in the tank is less, the heating is rapid and easy to overheat. The existing technology controls the temperature of the feeding tank by using a single steam on-off valve. When the tank temperature is higher than 55 DEG C, the steam on-off valve is closed. When the tank temperature is lower than 54 DEG C, the steam on-off valve is opened. This temperature control model has defects. When the remaining amount of material liquid is small at the end of production, a large amount of steam entering after the steam on-off valve is opened will continuously heat the small amount of material liquid, resulting in temperature rising of the tank at the end of the batch, overheat of the material liquid, and influence on product quality. Meanwhile, the opening and closing of the valve determines the amount of steam added, and all the heat of the steam is transferred to the tank and the material liquid, and the excess heat is stored in the tank steam pipe wall and cannot be consumed. The temperature control property of the feeding tank determines that the tank can only be rapidly heated and cannot be rapidly cooled. The current process requires that the material liquid should not be overheated and should be continuously and stably maintained at a small range of the process set temperature. Therefore, it is of great significance to realize the bidirectional temperature control of the material liquid which can rapidly heat and rapidly cool, and to achieve the purpose of stably controlling the temperature of the material liquid. SUMMARY

[0003] The present application provides a method for controlling temperature of material liquid of feeding tank with double thin film valve linkage control, solves the problems existing in the temperature control of the material liquid of the existing feeding tank, and can realize rapid heating and rapid cooling of the tank, and improve the stability and accuracy of the temperature control of the material liquid.

[0004] To achieve the following purposes, the present application provides the following technical solutions:

[0005] A method for controlling temperature of material liquid of feeding tank with double thin film valve linkage control, comprising:

[0006] A heating steam pipeline and a heat dissipation steam pipeline are connected to the sealed interlayer of the feeding tank. The heating steam pipeline is used for feeding steam into the sealed interlayer of the feeding tank to heat the material liquid in the feeding tank. The heat dissipation steam pipeline is used for discharging excess steam in the pipe wall insulation layer.

[0007] The heating steam pipeline is provided with a first steam film valve, and the heat dissipation steam pipeline is provided with a second steam film valve;

[0008] determining whether the feed tank contains liquid, and if so, obtaining the actual liquid weight and the actual liquid temperature in the tank;

[0009] establishing a PID liquid temperature model of the feed tank, taking the process standard liquid temperature and the actual liquid temperature as input values of the PID liquid temperature model for PID adjustment, and taking the output value CV as an intermediate control variable;

[0010] adjusting the opening degree of the first steam film valve and / or the second steam film valve according to the intermediate control variable to control the temperature of the liquid in the feed tank.

[0011] Preferably, it further comprises:

[0012] obtaining the pulse carrier caused by the opening and closing of the first steam film valve and / or the second steam film valve, and correcting the opening degree value of the first steam film valve and / or the second steam film valve with the pulse carrier.

[0013] Preferably, the adjustment of the opening degree of the first steam film valve and / or the second steam film valve according to the intermediate control variable comprises:

[0014] when the output value CV of the PID liquid temperature model is greater than 50%, the first steam film valve is controlled to open, and the opening degree of the first steam film valve is Va1=(CV-50%)*2;

[0015] and the second steam film valve is controlled to close, and the opening degree of the second steam film valve is Va2=0.

[0016] Preferably, the adjustment of the opening degree of the first steam film valve and / or the second steam film valve according to the intermediate control variable further comprises:

[0017] when the output value CV of the PID liquid temperature model is less than 50%, the first steam film valve is controlled to close, and the opening degree of the first steam film valve is Va1=0;

[0018] and the second steam film valve is controlled to open, and the opening degree of the second steam film valve is Va2=(CV-50%)*2.

[0019] Preferably, it further comprises:

[0020] If the formula for constructing the pulse carrier F is:

[0021] TOFF is the duration when the pulse carrier takes low level, and TON is the duration when the pulse carrier takes high level;

[0022] The opening value correction value of the first steam film valve is Value1=Va1·F1, and the opening value correction value of the first steam film valve is Value2=Va2·F2, wherein F1 is the heating pipeline pulse carrier, and F2 is the heat dissipation pipeline pulse carrier.

[0023] Preferably, it further comprises:

[0024] According to the value range of the actual feed liquid weight or the actual feed liquid temperature, the selective PID control in the form of limited integral, non-integral or complete integral of the weighted weight value is selected to control the feed liquid temperature.

[0025] Preferably, the selective PID control in the form of limited integral, non-integral or complete integral of the weighted weight value comprises:

[0026] When the actual feed liquid temperature Tt∈(Ttemp-YU2, Ttemp-YU1), that is, the actual feed liquid temperature Tt is greater than (Temp-YU2) and less than (Temp-YU1), the heating steam pipeline adopts PD control on the first steam film valve.

[0027] When the actual feed liquid temperature Tt∈(Ttemp-YU3, Ttemp-YU2), that is, the actual feed liquid temperature Tt is greater than (Temp-YU3) and less than (Temp-YU2), the percentage weight limited integral algorithm is adopted.

[0028] Preferably, the selective PID control in the form of limited integral, non-integral or complete integral of the weighted weight value further comprises:

[0029] When the actual feed liquid weight Y∈(Weight2, Weight1), that is, the actual feed liquid weight Y value is greater than Weight2 and less than Weight1, the limited integral algorithm assigns a weight value K1, and CV is a large weight value limited integral algorithm, and the CV calculation formula is:

[0030]

[0031] The opening value definition formula of the first steam film valve is:

[0032]

[0033] The opening value definition formula of the first steam film valve after pulse carrier modulation is:

[0034]

[0035] Preferably, the selective PID control in the form of weighted limit integral, non-integral or complete integral, further comprises:

[0036] When the actual liquid weight Y is in (Weight3, Weight2), that is, the actual liquid weight Y is greater than Weight3 and less than Weight2, the limit integral algorithm assigns a weight value of K2, and CV is the limit integral algorithm with a medium weight value, and the CV calculation formula is:

[0037]

[0038] The opening value definition formula of the first steam film valve is:

[0039]

[0040] The opening value definition formula of the first steam film valve after pulse carrier modulation is:

[0041]

[0042] Preferably, the selective PID control in the form of weighted limit integral, non-integral or complete integral, further comprises:

[0043] When the actual liquid weight Y is in (0, Weight3), that is, the actual liquid weight Y is less than Weight3, the limit integral algorithm assigns a weight value of K3, and CV is the limit integral algorithm with a small weight value, and the CV calculation formula is:

[0044]

[0045] The opening value definition formula of the first steam film valve is:

[0046]

[0047] The opening value definition formula of the first steam film valve after pulse carrier modulation is:

[0048]

[0049] The present application provides a kind of double thin film valve linkage control's feeding tank liquid temperature control method, using PID liquid temperature model is adjusted to the steam film valve opening on the heating steam pipeline and heat dissipation heating pipeline connected to feeding tank, to carry out steam quantity regulation, so that the liquid temperature in feeding tank is controlled, solve the problems existing in the liquid temperature control of current cut tobacco feeding tank, can realize the rapid heating and rapid heat dissipation of material tank, improve the stability and accuracy of liquid temperature control. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the specific embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments.

[0051] Figure 1 A schematic diagram of a double thin film valve linkage control method for controlling the temperature of the liquid in a feeding tank provided by the present application.

[0052] Figure 2 A schematic diagram of a feeding tank provided by the embodiment of the present application, which is installed with heating and heat dissipation double steam pipelines.

[0053] Figure 3 A schematic diagram of a PID liquid temperature control algorithm provided by the embodiment of the present application. DETAILED DESCRIPTION

[0054] In order to make the person skilled in the art better understand the scheme of the embodiment of the present application, the following will further describe the embodiment of the present application in combination with the drawings and the embodiments.

[0055] In view of the problems existing in the current liquid temperature control of the feeding tank, the present application provides a double thin film valve linkage control method for controlling the temperature of the liquid in a feeding tank, which solves the problems existing in the current liquid temperature control of the feeding tank in the process of making tobacco, and can realize the rapid heating and rapid heat dissipation of the feeding tank, and improve the stability and accuracy of the liquid temperature control.

[0056] As shown in Figure 1 A double thin film valve linkage control method for controlling the temperature of the liquid in a feeding tank, which comprises:

[0057] S1: The heating steam pipeline and the heat dissipation steam pipeline are connected to the sealing interlayer of the feeding tank, the heating steam pipeline is used to send steam into the sealing interlayer of the feeding tank to heat the liquid in the feeding tank, and the heat dissipation steam pipeline is used to discharge the excess steam in the pipe wall insulation layer.

[0058] S2: The heating steam pipeline is provided with a first steam thin film valve, and the heat dissipation steam pipeline is provided with a second steam thin film valve.

[0059] S3: It is judged whether there is liquid in the feeding tank, if yes, the actual liquid weight and the actual liquid temperature in the tank are obtained.

[0060] S4: A PID liquid temperature model of the feeding tank is established, the process standard liquid temperature and the actual liquid temperature are taken as the input values of the PID liquid temperature model for PID adjustment, and the output value CV is taken as the intermediate control variable.

[0061] S5: The opening degree of the first steam thin film valve and / or the second steam thin film valve is adjusted according to the intermediate control variable, so as to control the temperature of the liquid in the feeding tank.

[0062] In an embodiment, as shown in Figure 2 The heating steam pipe is used to add steam, and a steam film valve Y1 (percentage opening control) and other necessary devices must be provided on the heating steam pipe. The heat dissipation steam pipe is used to discharge excess steam in the pipe wall insulation layer, and a steam film valve Y2 (percentage opening control) and other necessary devices must be provided.

[0063] Firstly, it is determined whether the feed tank contains liquid, which is determined by a liquid level switch, a liquid level meter or a manual confirmation method. If the feed tank contains liquid, the following steps are executed; otherwise, the process returns to the waiting state until the production conditions are met.

[0064] Next, the actual liquid mass in the tank is obtained according to the existing method, which is defined as Y value. The Y value changes over time with the production of the feed tank.

[0065] Next, a general PID liquid temperature control algorithm is introduced, as shown in Figure 3 The method is as follows:

[0066] Since the liquid temperature is not allowed to exceed the temperature and needs to be continuously controlled at the specified process standard liquid temperature, a special improved PID algorithm is selected for temperature control. The process standard liquid temperature TEMP is used as the set value SP of the PID module, the actual liquid temperature Tt is used as the actual value PV of the PID module, and the PID output result is used as the control value CV. The value range of CV is defined as 0%-100%. CV is used as an intermediate control variable, which is combined with other algorithms to control the opening value of the steam film valve Y1 on the heating steam pipe and the opening value of the steam film valve Y2 on the heat dissipation steam pipe. Due to the slow absorption process, the residual heat in the tank will cause the temperature to rise by a certain temperature threshold, which is defined as YU0. Generally, this temperature threshold can be measured by experiment. Therefore, the control system sets the input standard value r(t) to be lower than the process standard liquid temperature by YU0 temperature points.

[0067] Therefore, the formula of r(t) is: r(t)=SP-YU0=TEMP-YU0;

[0068] Define e(t) as the control deviation, and its formula is:

[0069] e(t)=r(t)-c(t)=SP-YU0-PV=TEMP-YU0-Tt; where r(t) is the input standard value of the control system, and c(t) is the actual value of the control system.

[0070] The method further comprises: acquiring a pulse carrier caused by opening and closing of the first steam film valve and / or the second steam film valve, and correcting the opening degree value of the first steam film valve and / or the second steam film valve with the pulse carrier.

[0071] Further, the adjusting the opening degree of the first steam film valve and / or the second steam film valve according to the intermediate control variable comprises:

[0072] when the output value CV of the PID feed liquid temperature model is greater than 50%, controlling the first steam film valve to open, and the opening degree of the first steam film valve being Va1=(CV-50%)*2;

[0073] and controlling the second steam film valve to close, and the opening degree of the second steam film valve being Va2=0.

[0074] Further, the adjusting the opening degree of the first steam film valve and / or the second steam film valve according to the intermediate control variable further comprises:

[0075] when the output value CV of the PID feed liquid temperature model is less than 50%, controlling the first steam film valve to close, and the opening degree of the first steam film valve being Va1=0;

[0076] and controlling the second steam film valve to open, and the opening degree of the second steam film valve being Va2=(CV-50%)*2.

[0077] When the PID is activated, the initial value of CV must be assigned as 50%. When the value of the actual feed liquid temperature Tt continuously increases from a value lower than TEMP-YU0 until approaching the value of TEMP-YU0, the value of CV is immediately assigned as 50%. When the value of the actual feed liquid temperature Tt continuously decreases from a value higher than TEMP-YU0 until approaching the value of TEMP-YU0, the value of CV is immediately assigned as 50%.

[0078] Since the tank temperature is heated through steam heat transfer to the pipe wall, and then through heat transfer to the feed liquid, the transmission process is relatively slow and easy to overshoot, and therefore continuously assigning the film valve opening degree with the CV output value will cause a large range of overshoot, and therefore constructing a modified value after pulse carrier modulation and then assigning the film valve opening degree can better solve the overshoot problem.

[0079] Defining a pulse carrier F, and defining the time length of F=1 as TON, and defining the time length of F=0 as TOFF, then repeatedly opening and closing in a timed manner to form the pulse carrier F, and finally correcting the opening degree values of the steam film valves Y1 and Y2 in the form of the carrier.

[0080] The method further comprises:

[0081] If the formula of the pulse carrier F is:

[0082] TOFF is the duration of the pulse carrier taking low level, and TON is the duration of the pulse carrier taking high level;

[0083] The opening value correction value of the first steam film valve is Value1=Va1·F1, and the opening value correction value of the first steam film valve is Value2=Va2·F2, wherein F1 is the heating pipeline pulse carrier, and F2 is the heat dissipation pipeline pulse carrier.

[0084] Therefore, the formula definition of the heating pipeline pulse carrier F1 is:

[0085]

[0086] Therefore, the formula definition of the heat dissipation pipeline pulse carrier F2 is:

[0087]

[0088] The method further comprises: according to the value range of the actual feed liquid weight or the actual feed liquid temperature, selectively performing PID control in the form of limited integral, non-integral or complete integral of weighted value to perform feed liquid temperature control.

[0089] In practical application, the method is as follows: when the output value CV of the PID is less than 50%, the steam film valve Y2 of the heat dissipation steam pipeline adopts general PID control without correction, and the output of the double film valve is as follows:

[0090] CV maintains the original value, and the calculation formula is:

[0091]

[0092] Among them, KP, TI and TD are respectively the PID proportion, integral and differential coefficient.

[0093] The opening value definition formula of the steam film valve Y1 is Va1=0.

[0094] The opening value Value1 of the steam film valve Y1 after pulse carrier modulation is 0.

[0095] The opening value definition formula of the steam film valve Y2 is:

[0096]

[0097] The opening value definition formula of the steam film valve Y2 after pulse carrier modulation is:

[0098]

[0099] A feed liquid temperature comparison threshold YU0, YU1, YU2, YU3 is set, wherein YU0<YU1<YU2<YU3.

[0100] A feed liquid weight comparison threshold Weight1, Weight2, Weight3 is set, wherein Weight3<Weight2<Weight1.

[0101] The selective PID control in the form of limited integral, non-integral or complete integral of the weighted value includes:

[0102] When the actual feed liquid temperature Tt∈(Ttemp-YU2, Ttemp-YU1), that is, the actual feed liquid temperature Tt is greater than (Temp-YU2) and less than (Temp-YU1), the heating steam pipeline adopts PD control on the first steam film valve;

[0103] When the actual feed liquid temperature Tt∈(Ttemp-YU3, Ttemp-YU2), that is, the actual feed liquid temperature Tt is greater than (Temp-YU3) and less than (Temp-YU2), the integral algorithm is limited in the form of percentage weight.

[0104] Wherein, the integral is removed, and the calculation formula is:

[0105]

[0106] The opening value definition formula of the steam film valve Y1 after pulse carrier modulation:

[0107]

[0108] The opening value definition formula of the steam film valve Y1 after pulse carrier modulation:

[0109]

[0110] The opening value definition formula of the steam film valve Y2: Va2=0;

[0111] The opening value of the steam film valve Y2 after pulse carrier modulation: Value2=0.

[0112] The limited integral of different weight ratios is carried out in different regions of the feed liquid weight, and the method is as follows:

[0113] The weight coefficients K1, K2, K3 are defined, and the relationship is K1>K2>K3.

[0114] When the actual liquid weight Y ∈ (Weight2, Weight1), that is, the actual liquid weight Y value is greater than Weight2 and less than Weight1, the limit integral algorithm assigns a weight value of K1, CV is a limit integral algorithm with a large weight value, and the CV calculation formula is:

[0115]

[0116] The opening value definition formula of the first steam film valve is:

[0117]

[0118] The opening value definition formula of the first steam film valve after pulse carrier modulation is:

[0119]

[0120] The opening value definition formula of the steam film valve Y2 is Va2 = 0.

[0121] The opening value of the steam film valve Y2 after pulse carrier modulation is Value2 = 0.

[0122] When the actual liquid weight Y ∈ (Weight3, Weight2), that is, the actual liquid weight Y value is greater than Weight3 and less than Weight2, the limit integral algorithm assigns a weight value of K2, CV is a limit integral algorithm with a medium weight value, and the CV calculation formula is:

[0123]

[0124] The opening value definition formula of the first steam film valve is:

[0125]

[0126] The opening value definition formula of the first steam film valve after pulse carrier modulation is:

[0127]

[0128] The opening value definition formula of the steam film valve Y2 is Va2 = 0.

[0129] The opening value of the steam film valve Y2 after pulse carrier modulation is Value2 = 0.

[0130] When the actual liquid weight Y ∈ (0, Weight3), that is, the actual liquid weight Y value is less than Weight3, the limit integral algorithm assigns a weight value of K3, CV is a limit integral algorithm with a small weight value, and the CV calculation formula is:

[0131]

[0132] The opening value definition formula of the first steam film valve:

[0133]

[0134] The opening value definition formula of the first steam film valve after pulse carrier modulation:

[0135]

[0136] The opening value definition formula of the steam film valve Y2: Va2=0.

[0137] The opening value of the steam film valve Y2 after pulse carrier modulation: Value2=0.

[0138] When the actual liquid temperature Tt∈(0, Ttemp-YU3), that is, the actual liquid temperature Tt is less than (Temp-YU3), the PID adopts a general type PID control, and no restriction is made to the integral algorithm.

[0139] The CV adopts a general type algorithm, and no integral is removed or limited, and the calculation formula is:

[0140]

[0141] The opening value definition formula of the steam film valve Y1:

[0142]

[0143] The opening value definition formula of the steam film valve Y1 after pulse carrier modulation:

[0144]

[0145] The opening value definition formula of the steam film valve Y2: Va2=0.

[0146] The opening value of the steam film valve Y2 after pulse carrier modulation: Value2=0.

[0147] Finally, the steam film valve Y1 opening value Value1 after pulse carrier modulation is used to control the opening of the steam film valve Y1, and the steam film valve Y2 opening value Value2 after pulse carrier modulation is used to control the opening of the steam film valve Y2.

[0148] The method is improved based on a general PID, solves the PID set value over-temperature problem in the form of fixed threshold subtraction, and selectively controls the PID in the form of weighted value limited integral, non-integral and complete integral according to the value range of the liquid temperature and the liquid weight, so as to continuously and accurately control the liquid temperature. A pulse carrier modulation is also constructed, different pulse signals are used to modulate the analog signal of the thin film valve opening value according to different heating and heat dissipation characteristics, so as to solve the problem of system overshoot caused by heat transmission lag, and finally realize the bidirectional action of rapid heating and rapid heat dissipation of the liquid temperature control.

[0149] It can be seen that the application provides a kind of double thin film valve linkage control's feeding tank liquid temperature control method, PID liquid temperature model is used to adjust the steam film valve opening on the heating steam pipeline and heat dissipation heating pipeline connected with the feeding tank, to adjust the steam quantity, so as to control the liquid temperature in the feeding tank, solve the existing problems of the feeding tank liquid temperature control in the silk making, can realize the rapid heating and rapid heat dissipation of the feeding tank, and improve the stability and accuracy of the liquid temperature control.

[0150] The above describes the structure, features and effects of the application according to the embodiments shown in the drawings, the above is only the preferred embodiment of the application, but the application is not limited by the drawings, any change or modification within the scope of the application, or the equivalent embodiment of the equivalent change, still within the scope of the application.

Claims

1. A method for controlling the temperature of liquid in a feeding tank using a dual-diaphragm valve linkage control system, characterized in that, include: The sealing jacket of the feeding tank is connected to a heating steam pipeline and a cooling steam pipeline. The heating steam pipeline is used to supply steam into the sealing jacket of the feeding tank to heat the liquid in the feeding tank. The cooling steam pipeline is used to discharge excess steam from the insulation layer of the pipe wall. The heating steam pipeline is equipped with a first steam diaphragm valve, and the heat dissipation steam pipeline is equipped with a second steam diaphragm valve. Determine if there is liquid in the feeding tank. If so, obtain the actual weight and temperature of the liquid in the tank. A PID feed temperature model for the feeding tank is established. The standard feed temperature and the actual feed temperature are used as input values ​​for the PID feed temperature model for PID regulation, and the output value CV is used as an intermediate control variable. Adjust the opening degree of the first steam diaphragm valve and / or the second steam diaphragm valve according to the intermediate control variable to control the temperature of the liquid in the feeding tank; The pulse carrier wave caused by the opening and closing of the first steam diaphragm valve and / or the second steam diaphragm valve is obtained, and the opening value of the first steam diaphragm valve and / or the second steam diaphragm valve is corrected with the pulse carrier wave. The step of adjusting the opening degree of the first steam diaphragm valve and / or the second steam diaphragm valve according to the intermediate control variable includes: When the output value CV of the PID feed temperature model is greater than 50%, the first steam diaphragm valve is controlled to open, and the opening degree of the first steam diaphragm valve is Va1=(CV-50%)*2. And control the second steam diaphragm valve to close, with the opening degree of the second steam diaphragm valve being Va2=0; When the output value CV of the PID feed temperature model is less than 50%, the first steam diaphragm valve is controlled to close, and the opening degree of the first steam diaphragm valve is Va1=0. And control the second steam diaphragm valve to open, the opening degree of the second steam diaphragm valve is Va2=(CV-50%)*2; If the formula for constructing the pulse carrier F is: TOFF is the duration of the pulse carrier when it is low, and TON is the duration of the pulse carrier when it is high. The correction value for the opening degree of the first steam diaphragm valve is then: The correction value for the opening degree of the first steam diaphragm valve is: F1 is the pulse carrier of the heating pipe, and F2 is the pulse carrier of the heat dissipation pipe. The actual liquid weight or actual liquid temperature range is divided into regions, and selective PID control is performed in the form of weighted integral, non-integral, or full integral to control the liquid temperature. The selective PID control, which uses weighted values ​​to limit integration, non-integration, or full integration, includes: When the actual liquid temperature When the actual liquid temperature Tt is greater than (Temp-YU2) and less than (Temp-YU1), the heating steam pipeline uses PD to control the first steam diaphragm valve. When the actual liquid temperature When the actual liquid temperature Tt is greater than (Temp-YU3) and less than (Temp-YU2), a percentage weighting method is used to limit the integral algorithm, where YU1, YU2, and YU3 are the comparison thresholds for liquid temperatures, and YU1... <YU2<YU3; The selective PID control, which uses weighted values ​​to limit integration, non-integration, or full integration, further includes: When the actual weight of the liquid material When the actual liquid weight Y is greater than Weight2 and less than Weight1, the weight assigned to the restricted integral algorithm is K1, and CV is the restricted integral algorithm with a large weight value. The CV calculation formula is: ； The formula for defining the opening value of the first steam diaphragm valve is: ； The formula for defining the opening value of the first steam diaphragm valve after pulse carrier modulation is as follows: ； When the actual weight of the liquid material When the actual liquid weight Y is greater than Weight3 and less than Weight2, the weight assigned to the restricted integral algorithm is K2, and CV is the restricted integral algorithm with assigned weights. The formula for calculating CV is: ； The formula for defining the opening value of the first steam diaphragm valve is as follows: ； The formula for defining the opening value of the first steam diaphragm valve after pulse carrier modulation is as follows: ； When the actual weight of the liquid material When the actual weight Y of the liquid is less than Weight3, the weight assigned to the restricted integral algorithm is K3, and CV is a restricted integral algorithm with a smaller weight. The formula for calculating CV is: ； The formula for defining the opening value of the first steam diaphragm valve is as follows: ； The formula for defining the opening value of the first steam diaphragm valve after pulse carrier modulation is as follows: ； Among them, Weight1, Weight2, and Weight3 are the weight comparison thresholds of the liquid and feed, with Weight3 < Weight2 < Weight1, and KP, TI, and TD are the proportional, integral, and derivative coefficients of the PID, respectively, with K1 > K. 2> K3.

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