Cyclohexanone rectification and purification method based on high-tower segmented packing

Abstract

The invention relates to the technical field of chemical separation, in particular to a cyclohexanone rectification and purification method based on high-tower segmented packing, which comprises the following steps: step 1, filtering a cyclohexanone raw material containing impurities to remove solid particles, and dynamically adjusting the filtering precision according to the viscosity of the raw material; 2, arranging a bottom section, a middle section and a top section in the vertical high tower; the temperature gradient of each section is regulated and controlled through an independent temperature control unit, so that the temperature gradient of the middle section is matched with the relative volatility of the cyclohexanone-light component; 3, dynamically adjusting the reflux ratio based on the real-time detection result of the purity of the tower top distillate, and controlling an intermittent discharge valve according to the density change of the tower bottom heavy component enrichment liquid so as to continuously remove the heavy components; and 4, recycling the waste heat of the steam at the top of the tower for preheating the raw materials, and inhibiting the tower pressure fluctuation through a buffer tank. Through the innovative design of sectional packing of the high tower, the separation efficiency is improved, the energy consumption is reduced, and meanwhile, the equipment reliability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical separation, and particularly to a method for rectifying and purifying cyclohexanone based on segmented packing in a tall tower. Background Art

[0002] As an important chemical intermediate, cyclohexanone is widely used in the fields of nylon, caprolactam and solvent production. The core of its rectification and purification process lies in the efficient separation of light components (such as cyclohexane, water) and heavy components (such as phenol derivatives, cyclohexenone), while reducing energy consumption and improving product purity. However, the following key problems still exist in the practical application of the existing technology: Traditional rectification towers mostly adopt single packing or conventional plate tower structures, and the surface characteristics of the packing lack targeted design, resulting in low separation selectivity between cyclohexanone and impurities. For example, the existing packing has limited adsorption capacity for heavy components (such as cyclohexenone), and heavy components at the bottom of the tower are easily entrained into the product, affecting the purity of cyclohexanone. In addition, the wall flow effect leads to uneven liquid phase distribution, further reducing the mass transfer efficiency. Some devices need to rely on multi-tower series processes (such as the combination of light tower 1, light tower 2, and ketone tower), increasing the equipment complexity and energy consumption.

[0003] The existing process often compensates for the insufficient separation efficiency by increasing the reflux ratio or steam volume, but this significantly increases energy consumption. For example, the steam consumption of a 60,000-ton / year cyclohexanone device before optimization was as high as 5.53 kg / s, and the annual operating cost exceeded tens of millions of yuan. At the same time, when the raw material composition fluctuates, the traditional static control strategy (such as a fixed reflux ratio) is difficult to respond dynamically, resulting in frequent operation adjustments and affecting the stability of continuous production.

[0004] Therefore, there is an urgent need for a method for rectifying and purifying cyclohexanone based on segmented packing in a tall tower to break through the "trade-off" dilemma between separation efficiency and energy consumption, and at the same time realize the resource utilization of heavy components and reduce the environmental load. Summary of the Invention

[0005] Based on the above object, the present invention provides a method for rectifying and purifying cyclohexanone based on segmented packing in a tall tower, including the following steps: Step 1: Filter the cyclohexanone raw material containing impurities to remove solid particles, and dynamically adjust the filtration accuracy according to the viscosity of the raw material; preheat the filtered raw material to the bubble point temperature range, and the preheating temperature is dynamically set based on the light component content in the raw material; Step 2: Set a bottom section, a middle section and a top section in a vertical tall tower, and fill each section with packing having different surface characteristics. The packing in the bottom section preferentially adsorbs heavy component impurities, the packing in the middle section selectively adsorbs cyclohexanone, and the packing in the top section promotes the desorption of light components; regulate the temperature gradient of each section through an independent temperature control unit, so that the temperature gradient in the middle section matches the relative volatility of cyclohexanone-light components; Step 3: Dynamically adjust the reflux ratio based on the real-time detection result of the purity of the top distillate, and at the same time control the intermittent discharge valve according to the change in the density of the heavy component enrichment liquid at the bottom of the column to continuously remove heavy components; Step 4: Recover the waste heat of the top steam of the column for raw material preheating, and suppress the column pressure fluctuation through a buffer tank.

[0006] Preferably, the specific process of dynamically adjusting the filtration accuracy in Step 1 is as follows: Install differential pressure sensors at the inlet and outlet of the multi-stage filtration device to monitor the filtration differential pressure in real time; Judge the fluctuation trend of the raw material viscosity according to the differential pressure change rate. When the differential pressure change rate increases positively and exceeds the preset threshold, expand the filter mesh aperture. When the differential pressure change rate increases negatively and exceeds the preset threshold, reduce the filter mesh aperture; The preset threshold is determined by experimental calibration. The calibration method is: input simulated raw materials with different viscosities into the filtration device, record the corresponding relationship between the differential pressure change rate and the filter mesh aperture adjustment amount, and establish a differential pressure-viscosity-aperture mapping table.

[0007] Preferably, the specific process of dynamically setting the preheating temperature in Step 1 is as follows: Install an on-line chromatographic analyzer on the raw material conveying pipeline to detect the light component concentration in real time; Calculate the lower limit of the target preheating temperature based on the correlation model between the light component concentration and the bubble point temperature. The correlation model is established in the following way: a. Configure cyclohexanone mixed solutions with different light component concentrations in the laboratory; b. Measure the bubble point temperature of each mixed solution under the set pressure; c. Use a non-linear regression algorithm to fit the concentration-temperature curve to generate a bubble point temperature prediction equation; Set the target preheating temperature to 1.05 - 1.15 times the calculated value of the prediction equation, and the specific multiple is adaptively adjusted according to the difference between the initial temperature of the raw material and the bubble point temperature.

[0008] Preferably, the surface property design of the bottom section packing in Step 2 includes: Use corrugated plate packing as the base material, and its surface is coated with a hydrophobic-lipophilic composite coating; The hydrophobic layer of the coating is composed of fluorocarbon resin, and the lipophilic layer is composed of modified silane coupling agent; The optimization method of the coating thickness is: calculate the adsorption energy between the heavy component molecules and the coating through molecular dynamics simulation, and select the coating thickness range corresponding to the peak adsorption energy; The input parameters of the molecular dynamics simulation include the polar distribution data of the heavy component molecules, and the data is obtained by measuring the functional group type and content of the heavy components in the raw material with a Fourier transform infrared spectrometer.

[0009] Preferably, the surface property design of the intermediate section packing in step 2 includes: Using structured wire mesh packing as the substrate, and loading a cyclohexanone selective adsorbent on its surface; The adsorbent is a modified molecular sieve with adjustable pore size, and the method for optimizing its pore size is as follows: a. Measuring the diffusion coefficient of cyclohexanone molecules in the molecular sieve by gas adsorption method; b. Adjusting the calcination temperature and time of the molecular sieve so that the ratio of the peak value of the pore size distribution to the kinetic diameter of cyclohexanone molecules is 1.2 - 1.5; c. The kinetic diameter is calculated by measuring the crystal structure of cyclohexanone by X-ray diffraction method.

[0010] Preferably, the specific process of the temperature gradient matching in step 2 is as follows: Arranging a thermocouple array at equal intervals in the vertical direction in the intermediate section packing layer to monitor the temperature distribution in real time; Calculating the theoretical temperature gradient slope according to the curve of the relative volatility of cyclohexanone and light components changing with temperature; By adjusting the steam flow rate of the reboiler, controlling the deviation between the measured temperature gradient slope and the theoretical slope within ±5%; The calculation method of the theoretical temperature gradient slope is: measuring the vapor-liquid equilibrium data of cyclohexanone and light components under a set pressure, plotting the relative volatility - temperature curve, and taking the tangent slope at the inflection point of the curve as the theoretical reference value.

[0011] Preferably, the specific process of dynamically adjusting the reflux ratio in step 3 is as follows: Installing an on-line refractometer at the outlet of the top condenser to detect the refractive index of the distillate in real time; Inputting the refractive index data into the light component concentration - reflux ratio correlation model to output the real-time reflux ratio adjustment amount; The correlation model is trained in the following way: a. Collecting historical production data, including the refractive index, tower pressure, inter-stage temperature gradient and the optimal reflux ratio under different light component concentrations; b. Using a machine learning algorithm to establish a prediction model with the refractive index, tower pressure and temperature gradient as inputs and the reflux ratio adjustment amount as the output; c. Optimizing the model parameters through cross-validation until the prediction error is less than 3%.

[0012] Preferably, the control logic of the intermittent discharge valve in step 3 is: Setting a two-stage liquid seal device at the bottom of the tower. The height of the first-stage liquid seal is adaptively adjusted according to the bottom pressure fluctuation. The adjustment method is: monitoring the bottom pressure through a pressure sensor, and when the pressure change amplitude exceeds the set range, adjusting the liquid seal height to restore the pressure to the steady-state value; The second - stage liquid seal connects a density sensor, which triggers the opening of the discharge valve when the density of the heavy - component enriched liquid exceeds the threshold value. The threshold value is determined through material balance simulation. The simulation method is as follows: Calculate the density threshold value according to the initial concentration of heavy components in the raw material, the residence time at the bottom of the tower, and the sedimentation rate of heavy components.

[0013] Preferably, the specific process of waste heat recovery in step 4 is as follows: Introduce the overhead steam into a shell - and - tube heat exchanger to form a thermal coupling with the raw material pre - heater. Calculate the current waste heat recovery efficiency according to the real - time data of the steam flow sensor and the raw material temperature sensor. By adjusting the opening degree of the heat exchanger bypass valve, maintain the waste heat recovery efficiency in the range of 85% - 95%. The calculation formula for the waste heat recovery efficiency is: the ratio of the recovered heat to the total heat of the steam, where the recovered heat is obtained by calculating the temperature rise of the raw material and its specific heat capacity.

[0014] Preferably, the method for designing the volume of the buffer tank in step 4 is as follows: Calculate the theoretical buffer volume base number according to the proportional relationship between the tower diameter and the designed processing capacity. Taking the theoretical buffer volume base number as the reference value, generate a volume range of ±30% as the input range for fluid dynamics simulation. Based on the historical data of tower pressure fluctuations, simulate the tower pressure stability effect at different volumes through fluid dynamics simulation. Select the minimum volume that can reduce the tower pressure fluctuation amplitude by more than 80% from the simulation results as the final design value. The input parameters of the fluid dynamics simulation include steam flow rate, the gas - liquid two - phase flow pattern in the tower, and the pressure difference between the inlet and outlet of the buffer tank.

[0015] The beneficial effects of the present invention: 1. By adopting the high - tower segmented packing technology and optimizing the design of the packing surface, the present invention greatly improves the separation selectivity between cyclohexanone and impurities. Especially, the adsorption capacity for heavy components is significantly enhanced, effectively avoiding the entrainment problem of heavy components such as cyclohexenone, thereby improving the purity of the product.

[0016] 2. The present invention realizes the uniformity of liquid - phase distribution, effectively reduces the influence of the wall - flow effect, optimizes the efficiency of gas - liquid contact, and thus improves the mass transfer efficiency in the tower. This optimized design makes the functions of each section of the packing in the tower more reasonable, avoiding the problem of unsatisfactory separation effect caused by low mass transfer efficiency in some areas.

[0017] 3. The present invention adopts the high tower sectional packing technology, which can achieve efficient separation within a single tower, avoiding the complexity of multi-tower series connection. By optimizing the packing structure, higher separation efficiency can be achieved within the same tower, thus reducing the need for additional equipment, simplifying the process flow, and lowering the overall equipment investment and maintenance costs.

[0018] 4. In the present invention, by improving the structure and performance of the sectional packing, the separation efficiency can be enhanced without relying on increasing the reflux ratio and steam volume. This can effectively reduce steam consumption and operating energy consumption, reduce energy waste in the production process, and lower production costs. For example, after implementing the present invention, the steam consumption of the cyclohexanone plant has been significantly reduced, thus achieving significant energy savings.

[0019] 5. Through the method of the present invention, the operating state of the sectional packing can be dynamically adjusted according to real-time operating conditions, enabling the rectifying column to maintain good operating stability when the raw material composition fluctuates. This dynamic response mechanism not only improves the continuity and stability of production but also avoids frequent adjustment of control parameters such as the reflux ratio, improving the operating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 is the flow chart of the steps of the method of the present invention; Figure 2 is the flow chart of the steps of the dynamic adjustment of the filtration accuracy described in step 1 of the method of the present invention; Figure 3 is the flow chart of the control logic of the intermittent discharge valve described in step 3 of the method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The present invention will be described in detail below in conjunction with the drawings and specific embodiments. At the same time, it should be noted here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments. For some well-known technologies, those skilled in the art can also adopt other alternative methods for implementation; and the drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0023] Please refer to Figures 1-3, An embodiment of the present invention provides a method for rectifying and purifying cyclohexanone based on high - tower sectional packing. In step 1, first, the cyclohexanone raw material containing impurities is filtered to remove solid particulate matter. The filtration accuracy is dynamically adjusted according to the change in the viscosity of the raw material. For this purpose, a differential pressure sensor is set to monitor the change in differential pressure during the filtration process in real - time. When the viscosity fluctuates, the aperture of the filter screen will be adjusted accordingly to ensure the best filtration effect under different raw material conditions. This process ensures that solid impurities in cyclohexanone are effectively removed without affecting the filtration efficiency due to the change in raw material viscosity.

[0024] The filtered raw material is pre - heated to the bubble - point temperature range. The setting of the pre - heating temperature is dynamically adjusted according to the content of light components in the raw material. An on - line chromatographic analyzer is installed to detect the concentration of light components in real - time. According to the relationship between light components and the bubble - point temperature, the lower limit of the target pre - heating temperature is calculated. The set pre - heating temperature is between 1.05 - 1.15 times this value, ensuring that the pre - heating temperature of the raw material always matches the actual required bubble - point temperature, thereby improving the thermal efficiency and separation effect during the distillation process.

[0025] In step 2, in a vertical high - tower, the packings in the bottom, middle, and top sections have different surface characteristics. The packing in the bottom section is specifically designed to adsorb heavy - component impurities, the packing in the middle section selectively adsorbs cyclohexanone, and the packing in the top section helps with the desorption of light components. This packing design ensures that each component can be optimally separated in different sections. In addition, the temperature gradient of each section is controlled by an independent temperature control unit. Especially, the temperature gradient in the middle section is matched with the volatility of cyclohexanone and light components to ensure a more precise separation effect.

[0026] In step 3, the purity of the overhead distillate is used to dynamically adjust the reflux ratio based on the real - time detection results. By controlling the reflux ratio, the quality of the overhead distillate is ensured to be stable. At the same time, according to the density change of the heavy - component enriched liquid at the bottom of the tower, the opening of the intermittent discharge valve is controlled to continuously remove heavy - component impurities, further improving the purity of the product. This process can effectively improve the stability of the entire rectification process and ensure that impurities in the separation process are effectively removed.

[0027] In step 4, the waste heat of the steam at the top of the tower is recovered and used for pre - heating the raw material, thereby reducing energy consumption and improving the overall energy efficiency. At the same time, by setting a buffer tank, the differential pressure fluctuation in the tower is suppressed, and the pressure in the tower is kept stable. This measure reduces the operation instability caused by pressure fluctuations and further improves the operation efficiency of the entire rectification system.

[0028] In a possible implementation, differential pressure sensors are installed at the inlet and outlet of the multi-stage filtration device. These sensors are responsible for monitoring the change in differential pressure during the filtration process in real time and accurately recording the differential pressure values when the raw material enters and leaves the filter. Since the viscosity fluctuation of the raw material directly affects the fluid flow rate in the filter, the change in differential pressure can reflect the change trend of the raw material viscosity. Through these differential pressure data, the filtration state of the raw material can be evaluated in real time.

[0029] According to the monitored differential pressure change rate, the fluctuation trend of the raw material viscosity can be judged. If it is detected that the differential pressure change rate suddenly increases and exceeds the preset threshold, it indicates that the viscosity of the raw material has fluctuated violently. At this time, it is necessary to restore the filtration effect by dynamically adjusting the filter mesh aperture.

[0030] When the differential pressure change rate exceeds the preset threshold, the system drives the filter mesh support through a servo motor to automatically reduce or increase the aperture of the filter mesh. The process of aperture adjustment is real-time. Through the precise control of the servo motor, the aperture can be adjusted within a few seconds to adapt to the current raw material viscosity. This measure can effectively avoid the decrease in filtration efficiency or blockage caused by excessive fluctuation of the raw material viscosity.

[0031] The preset threshold is calibrated through experiments. The calibration process first inputs simulated raw materials with different viscosities into the filtration device and records the relationship between the differential pressure change rate and the filter mesh aperture adjustment amount at different viscosities. Through this experiment, a mapping relationship table between differential pressure, viscosity, and aperture adjustment amount is established. This mapping table can be used for real-time calculation and adjustment of the filter mesh aperture to ensure that the aperture can be accurately adjusted according to the differential pressure change during actual operation.

[0032] In a possible implementation, an on-line chromatographic analyzer is installed on the raw material conveying pipeline to monitor the concentration of light components in the raw material in real time. The concentration of light components has a great influence on the bubble point temperature, so it must be continuously detected during the rectification process. The chromatographic analyzer can accurately identify the content changes of different components and provide data support for subsequent temperature adjustment.

[0033] Based on the relationship between the concentration of light components and the bubble point temperature, an association model is established using laboratory data. The specific steps of this process are as follows: In the laboratory, cyclohexanone mixed solutions with different light component concentrations are prepared. These mixed solutions cover different samples from low concentration to high concentration to ensure that the influence of concentration on the bubble point temperature can be fully reflected. At the set pressure, the bubble point temperature of each mixed solution is measured. Through accurate measurement of the bubble point temperature, the relationship data between concentration and bubble point temperature can be obtained. The relationship data between concentration and bubble point temperature is fitted using a non-linear regression algorithm to generate an accurate bubble point temperature prediction equation. This prediction equation can predict the bubble point temperature according to different concentrations of light components.

[0034] Calculate the lower limit value of the target preheating temperature according to the established bubble point temperature prediction equation. The lower limit of the target preheating temperature should be 1.05 - 1.15 times the calculated value of the prediction equation. The setting of this multiple can be adaptively adjusted according to the difference between the initial temperature of the raw material and the bubble point temperature. For example, if the raw material temperature is low, the multiple can be appropriately increased to ensure that premature boiling or too low temperature during the rectification process can be effectively avoided, which may affect the rectification effect.

[0035] In a possible implementation, in the bottom section of the rectification column, corrugated plate packing is used as the base material. This corrugated plate packing has a large surface area and good fluid distribution characteristics, which can improve the contact efficiency between liquid and gas, thereby enhancing the separation effect. The structure of the corrugated plate packing can effectively increase the mass transfer area and optimize the mass exchange during the rectification process.

[0036] A hydrophobic-lipophilic composite coating is coated on the surface of the corrugated plate packing. This coating consists of two different functional layers: The hydrophobic layer of the coating is composed of fluorocarbon resin. Fluorocarbon resin has excellent hydrophobicity and can effectively prevent the adsorption of moisture, thereby reducing the interference of moisture on the separation process and improving the operation efficiency of the rectification column.

[0037] The lipophilic layer of the coating is composed of a modified silane coupling agent, which can enhance the affinity between the coating and organic solvents. This lipophilic layer helps to enhance the adsorption of heavy component molecules and improve the separation efficiency. Especially when dealing with compounds with high lipophilicity such as cyclohexanone, it can effectively promote the distribution and separation of heavy components.

[0038] The selection of the coating thickness is crucial for improving the performance of the packing. Molecular dynamics simulation is used to calculate the adsorption energy between heavy component molecules and the coating surface. Through simulation calculations, the optimal thickness range of the coating is found when the adsorption energy reaches the peak value. In the specific implementation process, the simulation will consider the polarity distribution data of heavy component molecules, which can be obtained by measuring the functional group type and content of heavy components in the raw material using a Fourier transform infrared spectrometer (FTIR). Through these detailed calculations and analyses, the most suitable coating thickness can be selected to ensure that the coating is neither too thin to result in insufficient adsorption effect nor too thick to affect the gas-liquid flow and mass transfer efficiency.

[0039] In a possible implementation, in the middle section of the rectification column, structured wire mesh packing is used as the base material. The structured wire mesh packing has good structural stability and uniform gas-liquid distribution performance. Its regular mesh structure is conducive to the full contact of gas and liquid on the packing surface, improving the separation efficiency. In addition, the surface of the wire mesh packing can effectively load adsorbents, enhancing the selective adsorption ability of the packing, thereby improving the separation effect of cyclohexanone.

[0040] A selective adsorbent with cyclohexanone surface-loaded on the packing. The adsorbent is a modified molecular sieve with the ability to adjust the pore size. The molecular sieve has excellent adsorption performance and can efficiently adsorb cyclohexanone molecules during the rectification process, thereby improving the separation purity of cyclohexanone. The design of the loaded adsorbent can further promote the separation effect of cyclohexanone through selective adsorption.

[0041] To improve the adsorption effect of the molecular sieve, its pore size needs to be precisely optimized. The specific optimization steps are as follows: First, measure the diffusion coefficient of cyclohexanone molecules in the molecular sieve by the gas adsorption method. The diffusion coefficient reflects the movement ability of molecules in the pore channels. Measuring this value can understand the diffusion rate of cyclohexanone molecules in the molecular sieve, thereby judging the applicability of the molecular sieve to cyclohexanone.

[0042] Optimize its pore size distribution by adjusting the calcination temperature and time of the molecular sieve. Specifically, by appropriately controlling the calcination conditions, the ratio of the peak value of the molecular sieve pore size distribution to the molecular kinetic diameter of cyclohexanone is maintained between 1.2 and 1.5. The optimization of this ratio can make the adsorption ability of the molecular sieve to cyclohexanone molecules reach the best state, while avoiding the reduction of adsorption efficiency caused by too large pore size or the pore blockage of the molecular sieve caused by too small pore size.

[0043] First, measure the structure of cyclohexanone crystals by X-ray diffraction method and calculate the molecular kinetic diameter of cyclohexanone. The molecular kinetic diameter is a basic physical quantity describing the propagation of molecules in different media. It directly affects the matching degree between molecules and the pores of the molecular sieve, thereby determining the adsorption efficiency.

[0044] In a possible implementation, a thermocouple array is arranged at equal intervals in the vertical direction in the packing layer in the middle section of the rectification column. The thermocouples are used to monitor the temperature distribution at different height positions in the rectification column in real time. The arrangement of the thermocouple array ensures that the temperature information of each layer of packing can be accurately obtained, thereby providing data support for the subsequent calculation of the temperature gradient.

[0045] Based on the curve of the relative volatility of cyclohexanone and light components changing with temperature, calculate the slope of the theoretical temperature gradient. The relative volatility is a key parameter in the rectification process, reflecting the volatility difference of different components at a specific temperature. By plotting the relationship curve between the relative volatility and temperature through experimental data, the volatility changes of cyclohexanone and light components at different temperatures can be obtained. Through the analysis of the curve, the slope of the theoretical temperature gradient in this temperature range, that is, the tangent slope of the curve, can be calculated. This slope reflects the relationship between the temperature gradient and the volatility change in the rectification column.

[0046] By adjusting the steam flow rate of the reboiler, ensure that the deviation between the actually measured temperature gradient slope and the theoretical slope is controlled within ±5%. The adjustment of the reboiler steam flow rate directly affects the heat input in the tower, thereby affecting the temperature distribution and temperature gradient. By precisely controlling the reboiler steam flow rate, an optimized matching of the temperature gradient can be achieved, making the temperature distribution in the tower more in line with the theoretical requirements and improving the separation efficiency.

[0047] Under the set pressure, first measure the vapor-liquid equilibrium data of cyclohexanone and light components, and draw the relative volatility-temperature curve based on these data. By calculating the tangent slope of the curve at the inflection point, the reference value of the theoretical temperature gradient slope is obtained. This reference value is used as a reference for subsequent adjustment to ensure that the temperature gradient in the distillation column is consistent with the theoretical expectation.

[0048] In a possible implementation, install an on-line refractometer at the outlet of the top condenser of the distillation column to detect the refractive index of the distillate in real time. The refractive index, as an indirect characterization parameter of the light component concentration, can reflect the component change of the distillate with high frequency and low delay, which helps to capture the fluctuation of the light component content in the distillation process in a timely manner.

[0049] Input the refractive index data obtained in real time into the correlation model of light component concentration-reflux ratio, and combine operation parameters such as the current tower pressure and the temperature gradient between sections to quickly output the adjustment amount of the reflux ratio. After the reflux ratio is adjusted, it is directly fed back to the operation control, thereby realizing the dynamic optimization control of the distillation process.

[0050] Widely collect historical operation data, and the data content includes: the refractive index of the distillate, the operating tower pressure, the temperature gradient between each section under different light component concentration conditions, and the optimal reflux ratio obtained under these conditions. Through sufficient data coverage, ensure that there is a stable correlation between the model input and output.

[0051] Based on the collected data, use machine learning algorithms (such as gradient boosting tree, support vector machine or neural network, etc.) to construct the model. The model takes the refractive index, tower pressure and temperature gradient as input variables, and the output variable is the suggested adjustment amount of the reflux ratio.

[0052] Evaluate the generalization ability of the model through cross-validation technology, and continuously optimize the model parameters to make it have high prediction accuracy on both the training set and the validation set. After the model is finally determined, its prediction error is controlled within 3%, ensuring that the output adjustment amount of the reflux ratio has high credibility and practicability.

[0053] By monitoring with an online refractometer, it can instantaneously respond to minute changes in the concentration of light components in the distillate, avoiding control lags caused by traditional analysis delays. The prediction model built based on historical data can fully integrate various influencing factors, improving the accuracy and rationality of reflux ratio adjustment, keeping the rectification process in an optimal state at all times. Ultimately, the energy consumption of the overall rectification process is reduced, the purity of cyclohexanone products is improved, and production stability is enhanced, significantly increasing the operating efficiency and economic benefits.

[0054] In a possible implementation, a two-stage liquid seal device is installed at the bottom of the rectification column, and the first and second stage liquid seal devices perform different functions respectively.

[0055] The height of the first-stage liquid seal is automatically adjusted according to the pressure fluctuation at the bottom of the column. Through the pressure sensor installed at the bottom of the column, the pressure change at the bottom of the column is monitored in real time. When the pressure change amplitude exceeds the set range, the system automatically adjusts the height of the first-stage liquid seal to restore the pressure to the steady-state value. The function of the liquid seal is to maintain the stability of the bottom pressure of the column and prevent excessive or too low pressure fluctuations, which helps the stable operation of the rectification column.

[0056] The second-stage liquid seal device is connected to a density sensor. When the density of the heavy-component enriched liquid at the bottom of the column exceeds the preset threshold, the density sensor can accurately detect this change and immediately trigger the opening of the discharge valve. By discharging the heavy-component enriched liquid, the purpose of maintaining the material balance in the column is achieved, preventing excessive accumulation of heavy components in the bottom liquid and affecting the efficiency and purity of the rectification process.

[0057] The density threshold is determined by the material balance simulation method. Specifically, the simulation process includes: calculating the critical density value of the heavy component based on the initial concentration of the heavy component in the raw material, the residence time at the bottom of the column, and the sedimentation rate of the heavy component. This critical value serves as the threshold for the second-stage liquid seal to trigger the discharge valve. When the density sensor detects that the density of the liquid exceeds this critical value, the system will automatically open the discharge valve to release the excess heavy-component enriched liquid, ensuring the stability of the operation in the column.

[0058] In a possible implementation, the steam at the top of the rectification column is introduced into a shell-and-tube heat exchanger through a pipeline. The function of this heat exchanger is to transfer the heat of the top steam to the raw material preheater, thereby realizing the recovery and reuse of thermal energy. Through such thermal coupling, the heat in the top steam is effectively transferred to the preheated raw material, reducing the external energy input required for raw material heating and improving the energy utilization efficiency.

[0059] The waste heat recovery process relies on the data from the steam flow sensor and the raw material temperature sensor. The steam flow entering the heat exchanger is monitored by the steam flow sensor, while the temperature data of the raw material entering the preheater is obtained through the raw material temperature sensor. Based on these data, the waste heat recovery efficiency can be calculated in real time. The calculation formula for the recovery efficiency is the ratio of the recovered heat to the total heat of the steam, where the recovered heat is calculated by the temperature rise of the raw material and the specific heat capacity of the raw material.

[0060] To ensure that the waste heat recovery efficiency is within the optimal range (85% - 95%), the opening degree of the bypass valve of the heat exchanger can be adjusted according to the calculated real-time waste heat recovery efficiency. The adjustment of the opening degree of the bypass valve makes the heat exchange process between the steam and the raw material more efficient. If the recovery efficiency is low, the opening degree of the bypass valve can be increased to increase the steam flow and recover more heat; if the recovery efficiency is too high, the opening degree of the bypass valve can be reduced to decrease the heat recovery and keep the efficiency within a reasonable range.

[0061] In a possible implementation, first, by analyzing the relationship between the tower diameter and the designed throughput, the base number of the theoretical buffer volume is initially calculated. The tower diameter is usually directly related to the processing capacity of the distillation column, while the designed throughput represents the material flow rate passing through the tower per unit time. According to the proportional relationship between these two parameters, the preliminary value of the required buffer volume can be estimated.

[0062] To optimize the volume design of the buffer tank, next, taking the base number of the theoretical buffer volume as the reference value, a volume range of ±30% is generated as the input range for the hydrodynamic simulation. Then, using the historical data of the tower pressure fluctuation, the tower pressure stability effect under different buffer volumes is simulated through the hydrodynamic simulation. The historical data includes the pressure fluctuation information inside the tower, and these data can reflect the change trend of the tower pressure during the normal operation of the distillation column. Through the simulation, the suppression effect of different volume designs on the tower pressure fluctuation can be predicted, and a basis for the reasonable selection of the volume can be provided.

[0063] According to the results of the hydrodynamic simulation, the minimum buffer volume that can reduce the tower pressure fluctuation amplitude by at least 80% is selected as the final design value. This selection of the minimum volume is based on the trade-off between the amplitude of the tower pressure fluctuation and the volume, ensuring that the buffer tank has sufficient volume to absorb the pressure fluctuation inside the tower while avoiding unnecessary space waste caused by an overly large volume.

[0064] When conducting the simulation, the input parameters include the steam flow rate, the gas-liquid two-phase flow pattern inside the tower, and the pressure difference between the inlet and outlet of the buffer tank. These parameters reflect the gas-liquid flow state and pressure change inside the tower and are key data for accurate simulation.

[0065] The present invention encompasses any alternatives, modifications, equivalent methods, and solutions that are within the spirit and scope of the present invention. For the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention. However, those skilled in the art can fully understand the present invention even without the description of these details. Additionally, well-known methods, processes, procedures, components, and circuits, etc., are not described in detail to avoid unnecessary confusion with the essence of the present invention.

[0066] The above description is only a preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as within the protection scope of the present invention.

Claims

1. A method for rectifying and purifying cyclohexanone based on tower-section fillers, characterized in that, It includes the following steps: Step 1: Filter the cyclohexanone raw material containing impurities to remove solid particles, and dynamically adjust the filtration accuracy according to the raw material viscosity; preheat the filtered raw material to the bubble point temperature range, and the preheating temperature is dynamically set based on the light component content in the raw material; Step 2: Set a bottom section, a middle section and a top section in a vertical high tower, and fill each section with packings with different surface characteristics. The packings in the bottom section preferentially adsorb heavy component impurities, the packings in the middle section selectively adsorb cyclohexanone, and the packings in the top section promote the desorption of light components; regulate the temperature gradient of each section through an independent temperature control unit to make the temperature gradient in the middle section match the relative volatility of cyclohexanone-light components; Step 3: Dynamically adjust the reflux ratio based on the real-time detection result of the purity of the overhead distillate, and at the same time control the intermittent discharge valve according to the density change of the heavy component enrichment liquid at the bottom of the tower to continuously remove heavy components; Step 4: Recover the waste heat of the overhead steam for raw material preheating, and suppress the tower pressure fluctuation through a buffer tank.

2. The cyclohexanone rectification and purification method based on tower-section packing according to claim 1, wherein The specific process of dynamically adjusting the filtration accuracy in Step 1 is as follows: Set differential pressure sensors at the inlet and outlet of the multi-stage filtration device to monitor the filtration differential pressure in real time; Judge the fluctuation trend of the raw material viscosity according to the differential pressure change rate. When the differential pressure change rate increases positively and exceeds the preset threshold, expand the filter screen aperture. When the differential pressure change rate increases negatively and exceeds the preset threshold, reduce the filter screen aperture; The preset threshold is determined by experimental calibration. The calibration method is: input simulated raw materials with different viscosities into the filtration device, record the corresponding relationship between the differential pressure change rate and the filter screen aperture adjustment amount, and establish a differential pressure-viscosity-aperture mapping table.

3. A method for rectifying and purifying cyclohexanone based on high tower segmented packing according to claim 1, characterized in that, The specific process of dynamically setting the preheating temperature in Step 1 is as follows: Install an on-line chromatographic analyzer on the raw material conveying pipeline to detect the light component concentration in real time; Calculate the lower limit of the target preheating temperature based on the correlation model between the light component concentration and the bubble point temperature. The correlation model is established by the following methods: a. Configure cyclohexanone mixed solutions with different light component concentrations; b. Measure the bubble point temperature of each mixed solution under the set pressure; c. Use a non-linear regression algorithm to fit the concentration-temperature curve to generate a bubble point temperature prediction equation; Set the target preheating temperature to 1.05-1.15 times the calculated value of the prediction equation, and the specific multiple is adaptively adjusted according to the difference between the initial temperature of the raw material and the bubble point temperature.

4. A method for rectifying and purifying cyclohexanone based on tower-section packing according to claim 1, characterized in that, The surface characteristic design of the packings in the bottom section in Step 2 includes: Use corrugated plate packings as the base material, and its surface is coated with a hydrophobic-lipophilic composite coating; The hydrophobic layer of the coating is composed of fluorocarbon resin, and the lipophilic layer is composed of modified silane coupling agent; The optimization method of the coating thickness is: calculate the adsorption energy between the heavy component molecules and the coating through molecular dynamics simulation, and select the coating thickness range corresponding to the peak adsorption energy; The input parameters of the molecular dynamics simulation include the polar distribution data of the heavy component molecules, and the data are obtained by measuring the functional group type and content of the heavy components in the raw material with a Fourier transform infrared spectrometer.

5. A method for rectifying and purifying cyclohexanone based on tower-section packing according to claim 1, characterized in that, The surface characteristic design of the packings in the middle section in Step 2 includes: Use regular wire mesh packings as the base material, and its surface is loaded with a cyclohexanone selective adsorbent; The adsorbent is a modified molecular sieve with adjustable pore size. The pore size optimization method is: a. Determine the diffusion coefficient of cyclohexanone molecules in molecular sieve by gas adsorption method; b. Adjust the calcination temperature and time of molecular sieve to make the ratio of the peak value of pore size distribution to the kinetic diameter of cyclohexanone molecules be 1.2 - 1.5; c. The kinetic diameter is calculated after determining the crystal structure of cyclohexanone by X-ray diffraction method.

6. A method for rectifying and purifying cyclohexanone based on a tower section packing according to claim 1, characterized in that, The specific process of the temperature gradient matching in Step 2 is as follows: Arrange a thermocouple array at equal intervals in the vertical direction in the middle section packing layer to monitor the temperature distribution in real time; Calculate the theoretical temperature gradient slope according to the curve of the relative volatility of cyclohexanone and light components varying with temperature; By adjusting the steam flow rate of the reboiler, control the deviation between the measured temperature gradient slope and the theoretical slope within ±5%; The calculation method of the theoretical temperature gradient slope is: measure the vapor-liquid equilibrium data of cyclohexanone and light components under a set pressure, draw the relative volatility - temperature curve, and take the tangent slope at the inflection point of the curve as the theoretical reference value.

7. A cyclohexanone rectification and purification method based on tower-section packing according to claim 1, wherein, The specific process of the dynamic adjustment of reflux ratio in Step 3 is as follows: Install an on-line refractometer at the outlet of the top condenser to detect the refractive index of the distillate in real time; Input the refractive index data into the light component concentration - reflux ratio correlation model to output the real-time reflux ratio adjustment amount; The correlation model is trained in the following way: a. Collect historical production data, including refractive index, tower pressure, inter-stage temperature gradient and the optimal reflux ratio under different light component concentrations; b. Establish a prediction model with refractive index, tower pressure and temperature gradient as inputs and reflux ratio adjustment amount as output by using machine learning algorithm; c. Optimize the model parameters through cross-validation until the prediction error is less than 3%.

8. A method for rectifying and purifying cyclohexanone based on tower-section packing according to claim 1, characterized in that, The control logic of the intermittent discharge valve in Step 3 is: Set a double-stage liquid seal device at the bottom of the tower. The height of the first-stage liquid seal is adjusted adaptively according to the fluctuation of the bottom pressure of the tower. The adjustment method is: monitor the bottom pressure of the tower through a pressure sensor, and when the pressure change amplitude exceeds the set range, adjust the liquid seal height to make the pressure return to the steady-state value; The second-stage liquid seal is connected to a density sensor. When the density of the heavy component enrichment liquid exceeds the threshold value, trigger the opening of the discharge valve; The threshold value is determined by material balance simulation. The simulation method is: calculate the density threshold value according to the initial concentration of heavy components in the raw material, the residence time at the bottom of the tower and the sedimentation rate of heavy components.

9. A method for rectifying and purifying cyclohexanone based on tower-section packing according to claim 1, characterized in that The specific process of the waste heat recovery in Step 4 is as follows: Introduce the top steam into a shell-and-tube heat exchanger to form a thermal coupling with the raw material preheater; Calculate the current waste heat recovery efficiency according to the real-time data of the steam flow sensor and the raw material temperature sensor; By adjusting the opening degree of the heat exchanger bypass valve, maintain the waste heat recovery efficiency in the range of 85% - 95%; The calculation formula of the waste heat recovery efficiency is: the ratio of the recovered heat to the total heat of the steam, where the recovered heat is calculated through the temperature rise of the raw material and specific heat capacity.

10. A method for rectifying and purifying cyclohexanone based on high tower segmented packing according to claim 1, characterized in that, The method for designing the volume of the buffer tank in Step 4 is: Calculate the theoretical buffer volume base number according to the proportional relationship between the tower diameter and the designed processing capacity; Taking the theoretical buffer volume base number as the reference value, generate a volume range of ±30% as the input range for hydrodynamic simulation; Based on the historical data of tower pressure fluctuation, simulate the tower pressure stability effect at different volumes through hydrodynamic simulation; Select the minimum volume that reduces the tower pressure fluctuation amplitude by more than 80% from the simulation results as the final design value; The input parameters for the hydrodynamic simulation include steam flow rate, gas-liquid two-phase flow regime in the tower, and pressure difference between the inlet and outlet of the buffer tank.

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