Heat exchange control method and system for evaporator

Abstract

The present application relates to the technical field of evaporator heat exchange control, and specifically to a heat exchange control method and system for an evaporator. The method comprises: collecting various relevant data sequences within each adjustment time period through a built-in sensor in the evaporator and preprocessing the data; calculating the evaporation transfer effect of the evaporator using the degree of change of the solution level sequence and steam flow sequence in the subsequences divided into different time periods, as well as the difference between the solution temperature sequence and the steam temperature sequence; calculating the evaporator's steam flow variation using the numerical difference between the elements in the solution temperature sequence and the preset solution temperature, as well as the evaporator's evaporation transfer effect; and adjusting the current steam flow using the evaporator's steam flow variation in different adjustment time periods. The present application aims to precisely control the steam flow so that the solution temperature is more stable during the evaporation process.

Description

Technical Field

[0001] The present application relates to the technical field of evaporator heat exchange control, and in particular to a heat exchange control method and system for an evaporator. Background Art

[0002] An evaporator is a common piece of chemical equipment, primarily used to remove solvents from solutions through heating and evaporation, thereby concentrating the solution. It is widely used in a variety of fields, including chemical, pharmaceutical, food, and environmental protection. For example, in the pharmaceutical industry, it is used to extract active ingredients from liquid medicines, and in the food industry, it is used to concentrate fruit juices. The process begins by introducing the solution to be concentrated into the evaporator's heating chamber. Heating steam flows outside the heating tubes, transferring heat through the tube walls to the solution within, raising the solution's temperature and initiating vaporization. The resulting secondary steam is discharged from the top of the evaporator, condensed in the condenser, and then discharged from the system, while the concentrated solution is discharged from the bottom of the evaporator. When using an evaporator to evaporate a solution, the efficiency of the heat exchange between the heating steam and the solution determines the efficiency of the concentration.

[0003] Traditionally, evaporator heat exchange control uses a valve controller to control the flow of heating steam into the heating chamber to maintain temperature balance. However, as the liquid evaporates, heat exchange efficiency is affected. Traditional valve controllers can only adjust the steam flow rate based on preset values. This method fails to fully account for the low heat exchange efficiency and heat accumulation caused by the concentration of the solution. As a result, traditional valve controllers cannot accurately perform adaptive adjustments, resulting in suboptimal evaporator heat exchange efficiency. Summary of the Invention

[0004] In order to solve the above technical problems, the present application provides a heat exchange control method and system for an evaporator. The technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides a heat exchange control method for an evaporator, the method comprising the following steps:

[0006] Various relevant data sequences within each adjustment time period are collected through the built-in sensor of the evaporator and pre-processed; the relevant data include solution temperature, steam temperature, solution level and steam flow rate;

[0007] The heat exchange synchronization degree of the evaporator is calculated by using the variation degree of the solution level sequence and steam flow sequence in the subsequences divided into different time periods.

[0008] The evaporation transfer effect of the evaporator is calculated by using the difference between the solution temperature series and the steam temperature series and the heat exchange synchronization degree of the evaporator.

[0009] The steam flow variation of the evaporator is calculated by using the numerical difference between the elements in the solution temperature sequence and the preset solution temperature, as well as the evaporation transfer effect of the evaporator;

[0010] The current steam flow is adjusted using the steam flow variation of the evaporator in different adjustment time periods.

[0011] Preferably, the steam flow sequence and the solution level sequence are evenly divided into N subsequences, and the steam flow variation and liquid level variation of each subsequence are calculated. The similarity between the sequences composed of the steam flow variation and liquid level variation of all subsequences is calculated using the cosine similarity function, and the similarity is used as the heat exchange synchronization degree of the evaporator.

[0012] Preferably, the method for calculating the steam flow variation degree is: calculating the cumulative sum and variance of all elements in each subsequence in the steam flow sequence; calculating the sum of the variance and a preset first zero division adjustment factor; and taking the ratio of the cumulative sum to the sum as the steam flow variation degree of each subsequence in the steam flow sequence.

[0013] Preferably, the method for calculating the liquid level variation degree is: taking the numerical difference between the first element and the last element of each subsequence in the solution liquid level sequence as the liquid level variation degree of each subsequence in the solution liquid level sequence.

[0014] Preferably, the difference change is determined by subtracting the solution temperature sequence from the steam temperature sequence to obtain an internal and external temperature difference sequence, and normalizing the slope of the fitting line of the internal and external temperature difference sequence.

[0015] Preferably, the evaporation transfer effect of the evaporator is determined by the ratio of the heat exchange synchronization degree to the difference change.

[0016] Preferably, the calculation method of the steam flow variation of the evaporator is:

[0017]

[0018] Where, Indicates the steam flow variation of the evaporator; represents the number of elements in the solution temperature series; represents the jth element in the solution temperature sequence; T represents the preset temperature of the solution; Indicates the evaporation transfer effect of the evaporator; Indicates the preset second division-by-zero adjustment factor; Represents the normalization function.

[0019] Preferably, the result of subtracting 1 from the ratio of the steam flow variation between the current adjustment time period and the previous adjustment time period is used as the adjustment coefficient of the steam flow in the current adjustment time period; and the current steam flow is adjusted according to the adjustment coefficient.

[0020] Preferably, the method of adjusting the current steam flow according to the adjustment coefficient is: when the adjustment coefficient is negative, the current steam flow is reduced; when the adjustment coefficient is positive, the current steam flow is increased; when the adjustment coefficient is 0, the current steam flow is not adjusted.

[0021] In the second aspect, another embodiment of the present application also provides a heat exchange control system for an evaporator, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, it implements a heat exchange control method for an evaporator as described above.

[0022] This application has at least the following beneficial effects:

[0023] By calculating the evaporator's heat exchange synchronization and evaporation transfer efficiency, the relationship between steam flow rate and solution level and temperature fluctuations is accurately analyzed, enabling dynamic steam flow rate adjustment. Compared to traditional fixed flow rate control methods, this intelligent adjustment method more closely matches steam heat with solution evaporation requirements, avoiding heat waste, significantly improving evaporator heat exchange efficiency, accelerating solution concentration, and enhancing production efficiency. Based on the evaporation transfer efficiency and solution temperature fluctuations, the steam flow rate fluctuation is precisely calculated, enabling fine-grained adjustment of the steam flow rate. While maintaining evaporation efficiency, it avoids overheating and steam waste, reducing energy consumption. Furthermore, it reduces equipment impact caused by frequent steam flow rate adjustments, reduces equipment wear, extends equipment life, and reduces maintenance costs. Through real-time monitoring and dynamic adjustment, this solution ensures that the evaporator always operates at optimal conditions. Precise steam flow control ensures more stable solution temperature during the evaporation process, preventing uneven evaporation caused by localized overheating or underheating, thereby improving product quality consistency and effectively enhancing product quality and market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1 A flow chart of a heat exchange control method for an evaporator provided in one embodiment of the present application;

[0026] Figure 2 A flowchart of a process for constructing an indicator for regulating the current steam flow is provided in one embodiment of the present application. DETAILED DESCRIPTION

[0027] An embodiment of the present application provides a heat exchange control method for an evaporator, which is specifically referred to in Figure 1 , the method comprises the following steps:

[0028] Step 1: Collect various relevant data sequences within each adjustment time period through the built-in sensor of the evaporator and preprocess the data.

[0029] The temperature of the solution in each adjustment time period in the heating tube of the heating chamber and the temperature of the steam outside the heating tube are collected respectively through the temperature sensor built into the evaporator, and the liquid level height of the solution in each adjustment time period in the heating tube is collected through the liquid level sensor; a flow sensor is installed at the steam inlet of the heating chamber to collect the flow rate of the heating steam in each adjustment time period.

[0030] In this embodiment, the frequency of data acquisition is 10 Hz, and the acquisition time is 1 minute, that is, an adjustment time period. The collected data are arranged in the order of acquisition time. Due to the complex environment in which each sensor is located, the collected data is prone to noise. Therefore, a denoising algorithm is used to denoise the arranged data. The denoised data are recorded as solution temperature sequence, steam temperature sequence, solution level sequence, and steam flow sequence respectively.

[0031] Among them, the denoising algorithm includes SG (Savitzky-Golay) filtering, mean filtering, polynomial filtering, etc. SG filtering is adopted in this embodiment. The calculation process of SG filtering is a well-known technology, and the specific calculation steps are not repeated here.

[0032] Step 2: Calculate the heat exchange synchronization degree of the evaporator using the variation degree of the solution level sequence and the steam flow sequence in the subsequences divided into different time periods.

[0033] During the evaporation process of the solution, the hot steam contacts the heating tube and transfers the heat to the solution. The absorbed heat accelerates the movement of the molecules in the solution, causing the solvent in the solution to continuously vaporize, thus achieving the heat exchange process in the evaporator. During the continuous heat exchange, the heated steam continuously enters the heating chamber. The steam that has absorbed the heat and the evaporated gas of the solution flow into the condensation infusion, condensing the steam and realizing the recycling of solvent resources.

[0034] As the solution continuously absorbs heat, the solvent in the solution continuously flows away, the solution level continuously drops, the solute concentration increases, and the viscosity increases, which will increase the flow resistance of the solution in the heating tube, reduce the heat transfer coefficient, and deteriorate the heat transfer efficiency. At the same time, the drop in the solution level will also reduce the contact area between the solution heating tubes, making the heat transfer efficiency even lower. In this case, it is necessary to reduce the steam flow rate so that the temperature in the steam can fully exchange with the solution. Therefore, when the steam rate and the drop in the solution level maintain a certain synchronization, it means that the evaporator is fully evaporating the solution. At this time, the steam flow control adjustment is relatively small.

[0035] Accordingly, in this application, the steam flow rate sequence and the solution level sequence are evenly divided into N subsequences. In this embodiment, N is set to 30. These subsequences are used to characterize the changes in steam flow rate and solution level over different time periods. When the state of steam flow rate variation and solution level variation over different time periods are similar, it indicates that the evaporator is operating smoothly and efficiently.

[0036] Therefore, the heat exchange synchronization degree of the evaporator is calculated as follows: Where, Indicates the heat exchange synchronization degree of the evaporator. It represents the steam flow rate change sequence in which all steam flow rate changes are arranged in chronological order. It represents the liquid level change sequence in which all liquid level changes are arranged in chronological order. represents the cosine similarity function. The calculation of the cosine similarity function is a well-known technique, and the specific calculation steps are not repeated here.

[0037] Among them, the steam flow rate variation of the steam flow subsequence in the i-th time period is The calculation expression is: Where, Represents the cumulative sum of all elements in the steam flow subsequence in the i-th time period. It represents the degree of dispersion of all elements in the steam flow subsequence in the i-th time period. The algorithms for the degree of dispersion include variance, standard deviation, mean absolute deviation, coefficient of dispersion, etc. In this embodiment, variance is used as the evaluation algorithm for the degree of dispersion. It represents the preset first zero division adjustment factor, which is used to prevent the denominator from being 0. In this embodiment, the value is 1.

[0038] Among them, the liquid level change degree of the solution level subsequence in the i-th time period is The calculation expression is: Where, , They represent the first and last elements in the solution level subsequence in the i-th time period respectively.

[0039] During the evaporator's heat exchange process, the more stable and larger the steam flow rate entering the heating chamber, the greater the steam flow rate variation, and the more heat the heating chamber can provide per unit time. The more heat the solution absorbs within a time period, the greater the total amount of solvent vaporized, resulting in a greater liquid level variation within that time period. The more consistent the steam flow rate variation and liquid level variation at different time periods, the greater the evaporator's heat exchange synchronization, indicating a more balanced heat exchange process within the evaporator and requiring less steam flow control adjustments.

[0040] Step 3: Calculate the evaporation transfer effect of the evaporator using the difference between the solution temperature sequence and the steam temperature sequence and the heat exchange synchronization of the evaporator.

[0041] As the solvent evaporates, the solution becomes thicker. To effectively evaporate the solvent, it needs to absorb more heat. Therefore, the smaller the temperature difference between the inside and outside of the heating tube, the less heat the steam can provide. The opening of the steam valve can be controlled to reduce the steam flow and minimize energy waste.

[0042] Therefore, for the temperature series of the solution and steam inside and outside the heating tube, the internal and external temperature difference series is obtained by subtracting the solution temperature series from the steam temperature series. This series is used to characterize the temperature difference between the inside and outside of the heating tube. When the value of the element in the internal and external temperature difference series continuously decreases, it indicates that the efficiency of heat exchange between the steam and the solution through the temperature difference is continuously decreasing, and the effect of the steam is continuously decreasing. As a result, the steam flow rate per unit time can be reduced.

[0043] Based on this, this application uses the internal and external temperature difference sequence as input for a linear least squares method, performing a straight-line fit. The output is the slope of the fitted line, which represents the changing state of the internal and external temperature difference of the heating tube. A larger slope indicates a faster change in the internal and external temperature difference of the heating tube, and the steam cannot provide sufficient heat for the solution to evaporate the solvent. The calculation of the linear least squares fitting line is a well-known technique, and the specific calculation steps are not repeated here.

[0044] At the same time, in order to avoid the dimensionless quantity of the data, the slope of the fitting line is normalized by a normalization function, and the normalized value is used to characterize the difference between the solution temperature series and the steam temperature series. In this embodiment, the sigmoid normalization function is used, wherein the calculation of the sigmoid normalization is a well-known technology, and the specific calculation steps are not repeated here.

[0045] Therefore, the evaporation transfer effect of the evaporator is calculated as follows: Where, Indicates the evaporation transfer effect of the evaporator. Indicates the heat exchange synchronization degree of the evaporator. Indicates the difference between the solution temperature series and the steam temperature series.

[0046] During evaporator operation, the smoother the evaporator's operation, the more synchronized the steam flow rate and solution level changes are, resulting in a greater degree of heat exchange synchronization. Furthermore, higher evaporator efficiency reduces the temperature difference between the inside and outside of the heating tube, resulting in a smaller slope of the temperature difference series. This results in a greater evaporative transfer efficiency and less need for steam flow control. This state improves product quality stability, reduces energy consumption and equipment wear, extends equipment life, and increases production efficiency.

[0047] Step 4: Calculate the steam flow rate variation of the evaporator using the numerical difference between the elements in the solution temperature sequence and the preset solution temperature, as well as the evaporation transfer effect of the evaporator.

[0048] During the middle and late stages of the evaporation process, the maximum evaporation effect is achieved when the temperature of the solution in the heating tube is maintained at around 80°C. Therefore, in this embodiment, the solution temperature is preset at 80°C. During evaporation, when the solution temperature falls below the set value, the steam flow rate is appropriately increased; when the solution temperature rises above the set value, the steam flow rate is reduced. This prevents the temperature from falling below the optimal level, resulting in suboptimal evaporation, and consequently, energy loss and reduced production efficiency.

[0049] Therefore, the steam flow variation of the evaporator is calculated based on the above indicators. The expression is:

[0050]

[0051] Where, Indicates the steam flow rate fluctuation of the evaporator. Represents the number of elements in the solution temperature series. represents the jth element in the solution temperature sequence. T represents the preset solution temperature, which is 80 in this embodiment. Indicates the evaporation transfer effect of the evaporator. It represents the preset second zero division adjustment factor, which is used to prevent the denominator from being 0. In this embodiment, the value is 1. represents a normalization function, and in this embodiment, a sigmoid normalization function is adopted.

[0052] When the steam flow in the evaporator is adjusted, the more smoothly the evaporator runs, the more synchronized the steam flow of the evaporator and the rate of liquid level drop are, and the temperature difference between the inside and outside of the heating tube changes more slowly, which makes the evaporation transfer effect of the evaporator larger. At the same time, the difference between the temperature inside the heating tube and the preset temperature is smaller, which makes the steam flow change of the evaporator smaller. This shows that the steam flow control adjustment ratio of the evaporator is smaller during operation.

[0053] Step 5: Use the steam flow rate variation of the evaporator in different adjustment time periods to adjust the current steam flow rate.

[0054] The steam flow rate change of the evaporator in each adjustment time period is calculated by the above method, and the ratio of the steam flow rate change between the current adjustment time period and the previous adjustment time period minus 1 is used as the adjustment coefficient of the steam flow rate in the current adjustment time period. In this application, the process flow chart of the index construction process for adjusting the current steam flow rate is shown in the attached figure. Figure 2 shown.

[0055] Among them, when the adjustment coefficient is negative, the current steam flow is reduced; when the adjustment coefficient is positive, the current steam flow is increased; when the adjustment coefficient is 0, the current steam flow is not adjusted.

[0056] Therefore, the calculated adjustment coefficient will be used as the input of the steam valve controller. The steam valve controller will adjust the opening of the current steam valve through the adjustment coefficient and adjust the steam flow of the evaporator to ensure that the evaporator maintains a stable and efficient operating state during the heat exchange process.

[0057] Based on the same inventive concept as the above-mentioned heat exchange control method for an evaporator, another embodiment of the present application also provides a heat exchange control system for an evaporator, including a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the computer program, it implements any one of the above-mentioned heat exchange control methods for an evaporator.

[0058] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention herein. This application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of the present application and include common knowledge or customary techniques in the art not invented herein.

[0059] It will be understood that the present application is not limited to the exact construction that has been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof.

Claims

1. A heat exchange control method for an evaporator, characterized in that: The method comprises the following steps: Various relevant data sequences within each adjustment time period are collected through the built-in sensor of the evaporator and pre-processed; the relevant data include solution temperature, steam temperature, solution level and steam flow rate; The heat exchange synchronization degree of the evaporator is calculated by using the variation degree of the solution level sequence and steam flow sequence in the subsequences divided into different time periods. The evaporation transfer effect of the evaporator is calculated by using the difference between the solution temperature series and the steam temperature series and the heat exchange synchronization degree of the evaporator. The steam flow variation of the evaporator is calculated by using the numerical difference between the elements in the solution temperature sequence and the preset solution temperature, as well as the evaporation transfer effect of the evaporator; The current steam flow is adjusted using the steam flow variation of the evaporator in different adjustment time periods.

2. The heat exchange control method for an evaporator according to claim 1, characterized in that: The steam flow rate sequence and the solution level sequence are evenly divided into N subsequences respectively. The steam flow rate variation and the liquid level variation of each subsequence are calculated. The similarity between the sequences composed of the steam flow rate variation and the liquid level variation of all subsequences is calculated using the cosine similarity function. The similarity is used as the heat exchange synchronization degree of the evaporator.

3. The heat exchange control method for an evaporator according to claim 2, characterized in that: The method for calculating the steam flow rate variation degree is as follows: calculating the cumulative sum and variance of all elements in each subsequence in the steam flow rate sequence; calculating the sum of the variance and a preset first zero division adjustment factor; and using the ratio of the cumulative sum to the sum as the steam flow rate variation degree of each subsequence in the steam flow rate sequence.

4. The heat exchange control method for an evaporator according to claim 2, wherein: The method for calculating the liquid level variation degree is as follows: the numerical difference between the first element and the last element of each subsequence in the solution liquid level sequence is used as the liquid level variation degree of each subsequence in the solution liquid level sequence.

5. The heat exchange control method for an evaporator according to claim 1, wherein: The difference change is determined by subtracting the solution temperature sequence from the steam temperature sequence to obtain an internal and external temperature difference sequence, and normalizing the slope of the fitting line of the internal and external temperature difference sequence.

6. The heat exchange control method for an evaporator according to claim 5, characterized in that: The evaporation transfer efficiency of the evaporator is determined by the ratio of the heat exchange synchronization degree to the difference change.

7. The heat exchange control method for an evaporator according to claim 1, characterized in that: The calculation method of the steam flow variation of the evaporator is: Where, Indicates the steam flow variation of the evaporator; represents the number of elements in the solution temperature series; represents the jth element in the solution temperature sequence; T represents the preset temperature of the solution; Indicates the evaporation transfer effect of the evaporator; Indicates the preset second division-by-zero adjustment factor; Represents the normalization function.

8. The heat exchange control method for an evaporator according to claim 1, wherein: The result of subtracting 1 from the ratio of the steam flow change between the current adjustment time period and the previous adjustment time period is used as the adjustment coefficient of the steam flow in the current adjustment time period; the current steam flow is adjusted according to the adjustment coefficient.

9. The heat exchange control method for an evaporator according to claim 8, characterized in that: The method for adjusting the current steam flow according to the adjustment coefficient is as follows: when the adjustment coefficient is negative, the current steam flow is reduced; when the adjustment coefficient is positive, the current steam flow is increased; when the adjustment coefficient is 0, the current steam flow is not adjusted.

10. A heat exchange control system for an evaporator, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the heat exchange control method for an evaporator according to any one of claims 1 to 9 is implemented.

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