Graded absorption and purity improvement coupling system for ester exchange reaction ethylene glycol extract

Abstract

The invention discloses a graded absorption and purity improvement coupling system for ester exchange reaction ethylene glycol extraction liquid, and relates to the technical field of separation and purification of biological medicine chemical raw materials. Comprising an extraction liquid pretreatment module, a countercurrent grading absorption module, a purity improvement coupling module, a solvent recycling module and an environment-friendly terminal treatment module which are sequentially connected along the material flow direction, and an intelligent cooperative control module for monitoring and optimizing the whole system. In the invention, in the aspect of separation and purification, the system adopts a light-to-heavy gradient absorption strategy and a rectification-membrane separation coupling process, so that the thermodynamic limitation of a traditional single separation means is broken through, and high-precision purification of a carboxylic ester product and efficient selective recovery of ethylene glycol can be synchronously realized; therefore, the final purity of the target product is greatly improved, the target product can meet the harsh standard in the high-end application field, and the volatilization loss of light components and the entrainment of ethylene glycol are remarkably reduced by optimizing the mass transfer process.

Description

A coupled system for fractional absorption and purity enhancement of ethylene glycol extract from transesterification reaction Technical Field

[0001] This invention relates to the field of chemical separation and purification technology, specifically to a coupled system for the fractional absorption and purity enhancement of ethylene glycol extract for transesterification products, which is particularly suitable for the efficient separation and resource recovery of ethylene glycol extract during the preparation of carboxylic acid esters. Background Technology

[0002] In chemical production, carboxylic acid esters are an important class of organic compounds, widely used as solvents, plasticizers, fragrances and pharmaceutical intermediates. Industrially, carboxylic acid esters are often prepared by transesterification. In this process, ethylene glycol is usually used as an extractant to extract the reaction mixture to enrich the target product, forming a complex extraction system containing ethylene glycol, carboxylic acid esters, unreacted alcohols, byproducts and impurities.

[0003] However, in existing technologies, the treatment of this type of extract mainly adopts single distillation or simple absorption processes. Due to the easy volatilization and loss of low-boiling-point light components during the separation process, the yield of carboxylic acid esters decreases, the separation of ethylene glycol and carboxylic acid esters is difficult, the recovery rate is low, and the recycling of raw materials is affected. The purity of the product is difficult to meet the requirements of high-end industries such as pharmaceuticals and electronics. In addition, the treatment of waste gas and waste liquid in the process is incomplete, resulting in high environmental pollution pressure, and the stability of system operation also needs to be improved.

[0004] Therefore, there is an urgent need to develop an integrated system that can efficiently separate ethylene glycol, recover carboxylic acid esters, realize the resource utilization of light components, and meet environmental protection requirements, so as to improve the overall process level and economic and environmental benefits of transesterification for the preparation of carboxylic acid esters. Summary of the Invention

[0005] The purpose of this invention is to provide a coupled system for the fractional absorption and purity enhancement of ethylene glycol extract from transesterification reactions, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a staged absorption and purity enhancement coupling system for ethylene glycol extract from transesterification reaction. The system includes an extract pretreatment module, a countercurrent staged absorption module, a purity enhancement coupling module, a solvent recovery and utilization module, and an environmentally friendly end-of-pipe treatment module connected sequentially along the material flow direction, as well as an intelligent collaborative control module for monitoring and optimizing the entire system. The modules are closely connected through pipelines and signal lines, forming a complete production system with a closed loop of materials and energy and seamless information flow.

[0007] Preferably, the outlet of the extract pretreatment module is connected to the inlet of the countercurrent staged absorption module. Its function is to homogenize, purify and condition the raw ethylene glycol extract from the upstream process, including stabilizing the flow rate and composition through a buffer tank, removing solid catalyst residues and mechanical impurities through a multi-stage filter, and adjusting the temperature and pH of the material through a heat exchange and dosing unit, so as to create stable and clean feeding conditions for subsequent precision separation.

[0008] Preferably, the countercurrent staged absorption module is one of the core separation units of the system, employing a two-stage countercurrent, selective absorption strategy. This includes a light component absorption unit and an ethylene glycol selective absorption unit arranged in series. The light component absorption unit (e.g., a packed absorber) primarily utilizes a dedicated inert absorbent oil (e.g., white oil) to selectively absorb low-boiling-point light components such as methanol and ethanol from the extract through countercurrent contact. Its bottom outlet outputs an intermediate liquid with most of the light components removed. The ethylene glycol selective absorption unit (e.g., a plate column or a structured packed column) uses a compounded polar absorbent (e.g., a mixture of water and a specific organic solvent) to countercurrently contact the intermediate liquid from the preceding stage, selectively absorbing ethylene glycol. Its top outlet outputs a "crude ester liquid" with light components and most of the ethylene glycol removed, while its bottom outlet outputs an "ethylene glycol-rich absorbent." This module achieves gradient and selective removal of light and heavy impurities (light components and ethylene glycol).

[0009] Preferably, the purity enhancement coupling module receives two key streams from the previous module, processes them in parallel, and purifies them simultaneously. It includes an ester product distillation and purification unit and an ethylene glycol stripping and purification unit. The inlet of the ester product distillation and purification unit (e.g., a vacuum distillation column) is connected to the top outlet of the ethylene glycol selective absorption unit, responsible for deep purification of the "crude ester liquid." By precisely controlling the temperature, pressure, and reflux ratio, a high-purity (e.g., ≥99.8%) carboxylic acid ester product is collected via a side stream. The inlet of the ethylene glycol stripping and purification unit is connected to the bottom outlet of the ethylene glycol selective absorption unit, responsible for processing the "ethylene glycol-rich absorbent." It typically includes a stripping column (e.g., a vacuum stripping column) and an ethylene glycol distillation column, sequentially completing the desorption of ethylene glycol from the absorbent and the purification of the crude ethylene glycol after desorption, ultimately obtaining a high-purity ethylene glycol product (e.g., ≥99.5%), which can be directly reused in transesterification reactions.

[0010] Preferably, to meet the extreme purity requirements of specific fields, the purity enhancement coupling module may optionally include a membrane-assisted purification unit. This unit is connected after the high-purity ester product outflow from the ester product distillation and purification unit, and typically includes nanofiltration and / or reverse osmosis membrane modules. Utilizing the selective sieving effect of the membrane, it removes impurities such as trace ions and polar organic compounds that are difficult to remove through distillation, thereby enhancing the product purity to electronic or pharmaceutical grade standards (e.g., ≥99.95%).

[0011] Preferably, the solvent recovery module is responsible for the internal material circulation of the system. Its inlet receives absorbent liquid rich in light components from the light component absorption unit and regenerated lean absorbent from the ethylene glycol desorption and refining unit. The solvent recovery module realizes the recovery of light components (such as methanol) as by-products and the regeneration and recycling of absorbents (inert absorbent oil and compound polar absorbent) through flash evaporation, distillation and other operations, which greatly reduces the consumption of fresh solvent.

[0012] Preferably, the environmentally friendly end-of-pipe treatment module enables the system to operate in a green manner. It collects waste gas (VOCs), process wastewater, and a small amount of solid waste from each process unit through a closed pipeline network, and performs advanced treatment on each of them.

[0013] Preferably, the intelligent collaborative control module is signal-connected to all the aforementioned physical modules, and collects massive amounts of data in real time from various sensors (temperature, pressure, flow rate, liquid level) and online analyzers (such as gas chromatographs). The core of the intelligent collaborative control module lies in its built-in predictive control model and optimization algorithm based on the process mechanism. The intelligent collaborative control module can not only perform basic loop control and safety interlocks, but also dynamically calculate and issue optimal control commands by solving a rolling time-domain multivariate optimization problem. It coordinates key operating parameters in real time, such as the absorbent ratio and flow rate in the countercurrent staged absorption module, the rectification reflux ratio, the reboiler temperature, and the desorption pressure in the purity enhancement coupling module. This enables the entire complex coupled system to automatically, quickly, and accurately adjust to the globally optimal operating point when faced with feed fluctuations.

[0014] A coupled system for fractional absorption and purity enhancement of ethylene glycol extract from transesterification reactions, executed by the intelligent collaborative control module, includes the following steps:

[0015] S1: Dynamic Model Establishment: Based on mass conservation, energy conservation and mass and heat transfer dynamics, a simplified mathematical model is established to describe the dynamic coupling relationship between key manipulated variables (such as absorbent flow rate, reflux ratio, reboiler heat load) and controlled variables (such as product purity, key component concentration, equipment temperature and pressure).

[0016] S2: Data Acquisition: In each set control cycle (e.g., 1-5 minutes), the current status measurement values ​​of the system are acquired in real time, including feed composition, temperature and pressure of key trays in each tower, and online product analysis values.

[0017] S3: Based on the current state and the dynamic model, predict a future time period (prediction time domain). The behavior of the internal system; by solving a constrained rolling time-domain optimization problem online, a series of future control action manipulator adjustment sequences are calculated. The objective function of the optimization problem for:

[0018] ;

[0019] In the formula, ) represents the vector of controlled variables predicted by the model. Set its value vector. and This is the weight matrix. To predict the time domain, To control the time domain; The index of the future prediction time is used to traverse the prediction time domain 1~P and accumulate the tracking error at each future time. The sequence number of the control step to be executed is used to traverse the control time domain from 0 to M-1 and accumulate the adjustment range of the control quantity for each step.

[0020] S4: Command Execution and Feedback: The first increment in the control action sequence obtained from the above optimization calculation. The command is immediately sent to the corresponding actuator (such as a regulating valve or variable frequency pump). The next control cycle then begins.

[0021] S5: Repeat steps S2 to S4 in the next control cycle to form a closed-loop predictive, optimization, and feedback control.

[0022] S6: Model self-updating: Periodically (e.g., daily or weekly) using historical data accumulated during system operation, the parameters in the prediction model are corrected and updated, enabling the model to adapt to slow process changes such as catalyst activity decay and equipment scaling, and maintain long-term control accuracy.

[0023] Preferably, the controlled variable vector This includes at least the purity of the carboxylic acid ester product and the concentration of the ethylene glycol recovery solution.

[0024] Preferably, the manipulated variable adjustment vector This includes at least the adjustment amount of the composite absorbent ratio, the adjustment amount of the distillation column reflux ratio, and the adjustment amount of the stripping column operating pressure.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. In this invention, at the separation and purification level, the system adopts a gradient absorption strategy of light components first and heavy components later, coupled with a distillation-membrane separation process. This breaks through the thermodynamic limitations of traditional single separation methods and can simultaneously achieve high-precision purification of carboxylic acid ester products and efficient selective recovery of ethylene glycol. This not only significantly improves the final purity of the target product, enabling it to meet the stringent standards of high-end applications, but also significantly reduces the volatilization loss of light components and the entrainment of ethylene glycol by optimizing the mass transfer process, thereby comprehensively improving the total yield of key materials. In addition, the application of the intelligent collaborative control module enables this multi-unit strongly coupled system to have adaptive optimization and anti-interference control capabilities, effectively ensuring the stability of process parameters and the continuous optimization of separation efficiency under complex operating conditions. This fundamentally solves the common industry problem of large fluctuations in the operation of traditional separation devices and unstable product quality.

[0027] 2. In this invention, the efficient regeneration and recycling of the absorbent within the system, the resource recovery of light components, and the closed-loop reuse of ethylene glycol minimize the consumption of fresh raw materials and the generation of waste, directly reducing the material costs and waste disposal expenses of production and operation. At the same time, the fully enclosed design and the environmentally friendly end-of-pipe treatment module with hierarchical treatment curb fugitive emissions at the source, achieving deep purification and compliant discharge of volatile organic compounds and wastewater, fully complying with increasingly stringent environmental protection regulations. This technical solution not only has a competitive advantage in terms of energy and material consumption per unit product, but also provides a transformation and upgrading path for the industrial production of carboxylic acid esters by transesterification, which combines high economic returns and sustainable development characteristics, by improving resource utilization and enhancing environmental friendliness. Attached Figure Description

[0028] Figure 1 is a flowchart of the process of a coupled system for graded absorption and purity enhancement of ethylene glycol extract from transesterification reaction according to the present invention.

[0029] Figure 2 is a block diagram of a coupling system for graded absorption and purity enhancement of ethylene glycol extract from transesterification reaction according to the present invention.

[0030] In the diagram: 1. Extract pretreatment module; 2. Countercurrent fractionation absorption module; 21. Light component absorption unit; 22. Ethylene glycol selective absorption unit; 3. Purity enhancement coupling module; 31. Ester product distillation and purification unit; 32. Ethylene glycol desorption and purification unit; 33. Membrane-assisted purification unit; 4. Solvent recovery and utilization module; 5. Environmental end-of-pipe treatment module; 6. Intelligent collaborative control module. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1: Referring to Figures 1 and 2: A staged absorption and purity enhancement coupling system for ethylene glycol extract from transesterification reaction includes an extract pretreatment module 1, a countercurrent staged absorption module 2, a purity enhancement coupling module 3, a solvent recovery and utilization module 4, and an environmentally friendly end-of-pipe treatment module 5, connected sequentially along the material flow direction, as well as an intelligent collaborative control module 6.

[0033] The outlet of the extract pretreatment module 1 is connected to the inlet of the countercurrent staged absorption module 2. The countercurrent staged absorption module 2 includes a light component absorption unit 21 and an ethylene glycol selective absorption unit 22 arranged in series. The light component absorption unit 21 is used to remove light components from the extract, and its bottom outlet is connected to the inlet of the ethylene glycol selective absorption unit 22. The ethylene glycol selective absorption unit 22 is used to selectively absorb ethylene glycol, and its top outlet outputs crude ester liquid, and its bottom outlet outputs ethylene glycol-rich absorbent liquid.

[0034] The purity enhancement coupling module 3 includes an ester product distillation and purification unit 31 and an ethylene glycol desorption and purification unit 32. The inlet of the ester product distillation and purification unit 31 is connected to the top outlet of the ethylene glycol selective absorption unit 22 to process the crude ester liquid, and the inlet of the ethylene glycol desorption and purification unit 32 is connected to the bottom outlet of the ethylene glycol selective absorption unit 22 to process the ethylene glycol-rich absorption liquid.

[0035] The inlet of the solvent recovery module 4 is connected to the top outlet of the light component absorption unit 21 and the desorbent outlet of the ethylene glycol desorption and purification unit 32, respectively, for the regeneration of the absorbent and the recovery of light components.

[0036] The inlet of the environmental protection end-of-pipe treatment module 5 is connected to the exhaust gas, wastewater and solid waste discharge outlets of each module in the system, and the intelligent collaborative control module 6 is connected to the signals of the above modules.

[0037] The light component absorption unit 21 is a packed absorption tower that uses inert absorbent oil as the absorbent, while the ethylene glycol selective absorption unit 22 is a plate tower or a structured packed tower that uses a compound polar absorbent.

[0038] The ester product distillation and purification unit 31 is a vacuum distillation column; the ethylene glycol desorption and purification unit 32 includes a desorption column and an ethylene glycol distillation column connected in sequence; the purity enhancement coupling module 3 also includes a membrane-assisted purification unit 33, the inlet of which is connected to the outlet of the ester product distillation and purification unit 31, for membrane separation and purification of the ester product from the ester product distillation and purification unit 31; the membrane-assisted purification unit 33 includes at least one of a nanofiltration membrane module and a reverse osmosis membrane module.

[0039] The intelligent collaborative control module 6 is used to receive sensor signals and online analyzer data, perform calculations based on the built-in predictive control model, and output control commands for dynamically adjusting the absorbent parameters in the countercurrent staged absorption module 2 and the distillation and desorption parameters in the purity enhancement coupling module 3.

[0040] The working principle of this scheme is as follows: The system is designed for the complex mixture formed after the transesterification reaction products are extracted with ethylene glycol. This mixture usually contains ethylene glycol (the main extractant), target carboxylic acid esters (such as DMC, BHET, etc.), unreacted low alcohols (such as methanol, ethanol), by-product diethylene glycol, catalyst residues, and trace amounts of coloring agents.

[0041] The system adopts a modular series coupling design, with materials flowing sequentially along the path of pretreatment, graded absorption, deep purification, solvent recovery, and environmental protection treatment. This design follows the basic principle of chemical separation: from easy to difficult and from coarse to fine.

[0042] The pretreatment module 1 removes solid impurities and stabilizes the operating conditions, creating conditions for subsequent precision separation. The countercurrent fractional absorption module 2, based on the significant differences in polarity and solubility between components, uses different absorbents for selective and gradient separation, prioritizing the removal of lighter components and then selectively enriching ethylene glycol, avoiding mutual interference from simultaneous separation of multiple components. The purity enhancement coupling module 3 processes the two key streams after preliminary separation in parallel, achieving high product purification through distillation and analytical purification, respectively, thus improving overall processing efficiency. The solvent recovery and utilization module 4 and the environmental end-of-pipe treatment module 5 realize internal material circulation and compliant waste discharge, forming a closed-loop process of resources, products, and recycled resources. The intelligent collaborative control module 6 dynamically coordinates the operation of each unit through real-time data acquisition and model prediction optimization, ensuring that this complex coupled system can operate stably, efficiently, and adaptively. The modules are closely connected through pipelines and signal lines, forming an organic whole that integrates material flow, energy flow, and information flow, rather than a simple combination of equipment.

[0043] The countercurrent staged absorption module 2 is the core module for achieving efficient and selective preliminary separation of light components and ethylene glycol in complex extracts. The light component absorption unit 21 utilizes a packed absorption tower, which provides a large gas-liquid contact area and low pressure drop, making it ideal for absorption processes with high flow rates and high mass transfer efficiency. The liquid film distribution on the packing surface facilitates the diffusion and mass transfer of light components from the gas phase to the absorbent oil phase. It uses inert absorbent oil as the absorbent; light components typically have good oil solubility, while the target carboxylic esters and ethylene glycol have extremely low solubility in the oil phase. Therefore, selecting a chemically stable, low-volatility, high-boiling-point inert absorbent oil enables highly selective absorption of light components while maximizing the retention of the target product in the original phase, ensuring the yield of subsequent stages. The countercurrent operation mode ensures the maximum concentration gradient throughout the tower, providing a continuous and stable driving force for mass transfer.

[0044] The ethylene glycol selective absorption unit 22 is designed using either a plate tower or a structured packed tower, both of which offer good interstage mass transfer and operational flexibility. Plate towers are easy to maintain and allow for side-stream sampling, while structured packed towers offer high throughput, low pressure drop, and high efficiency, allowing selection based on the specific system and throughput. It employs a compounded polar absorbent, as ethylene glycol is a strongly polar molecule. Using a selective absorbent composed of water and one or more polar organic solvents in a specific ratio, the "like dissolves like" principle can be utilized to significantly improve the absorption capacity and selectivity for ethylene glycol. By adjusting the absorbent composition online, fluctuations in the ethylene glycol concentration in the feed can be flexibly accommodated, maintaining high absorption efficiency. This unit removes ethylene glycol while exhibiting very low solubility for the target ester, thus achieving effective separation of ethylene glycol and the target ester.

[0045] Removing the lighter components first avoids their competitive dissolution in the second-stage absorption tower, which could interfere with the selective absorption of ethylene glycol. It also reduces the load on subsequent distillation units. This gradient absorption strategy, prioritizing lighter components over heavier ones, is key to the system's efficient separation.

[0046] The purity enhancement coupling module 3 receives the two streams after fractional absorption and performs further processing on each, simultaneously producing high-purity products. Firstly, the ester product distillation purification unit 31 employs a vacuum distillation process. The target carboxylic acid ester product may be heat-sensitive and has a boiling point close to that of residual trace amounts of ethylene glycol and heavy components. Vacuum distillation lowers the boiling point of the material, preventing the decomposition of heat-sensitive substances, while simultaneously increasing the relative volatility between components, making separation easier.

[0047] Precise control of reflux ratio, temperature, and pressure: Through intelligent control modules, these three key parameters are adjusted in tandem to precisely control the gas-liquid balance and separation accuracy within the column. For example, increasing the reflux ratio can improve the purity of the top product, but it also increases energy consumption; the system needs to perform online optimization to find the lowest energy consumption operating point that meets product specifications.

[0048] The ethylene glycol desorption and purification unit 32 utilizes a desorption tower to break the binding force between ethylene glycol and the compound absorbent. A vacuum stripping process is employed, reducing the system pressure and / or introducing inert gas to lower the partial pressure of ethylene glycol in the liquid phase, thus promoting its desorption from the rich absorbent. This process enables online regeneration of the absorbent; the regenerated lean absorbent can be directly reused after cooling, reducing solvent consumption costs.

[0049] The crude ethylene glycol obtained from the analysis is then subjected to conventional distillation in an ethylene glycol distillation column to remove trace amounts of absorbent, water, and ester impurities, thereby obtaining high-purity ethylene glycol that can be directly reused in the upstream transesterification reaction, thus completing the closed-loop recycling of raw materials.

[0050] Finally, the membrane separation technology of the membrane-assisted purification unit 33, based on molecular size exclusion and dissolution-diffusion mechanism, can efficiently remove trace ions, small molecule polar organics, pigments, etc. that are difficult to remove by distillation at room temperature;

[0051] By placing the membrane unit after distillation, redundant purification processes are performed on the distillation product. This coupled purification route of distillation and membrane separation breaks through the purity limit of single distillation, enabling the final product to meet the ultra-high standards required by fields such as electronic chemicals and high-end pharmaceutical intermediates. The concentrate retained by the membrane is returned to the pretreatment system, avoiding material loss.

[0052] Solvent recovery module 4 and environmental end-of-pipe treatment module 5 work together to form the key support for the system to achieve closed-loop material management and clean production. Specifically, the inlet of solvent recovery module 4 receives the light component-rich absorbent from the top of the light component absorption unit 21 and the lean absorbent after desorption from the ethylene glycol desorption and purification unit 32. Through physical methods such as flash evaporation and distillation, solvent recovery module 4 regenerates the absorbent (achieving a recycling rate of >99%) and purifies the recovered methanol and other light components into recyclable chemical raw materials, while reducing the volume of a small amount of high-boiling-point residue. Closely connected to this, environmental end-of-pipe treatment module 5 collects and classifies the waste gas, wastewater, and solid waste generated at each node of the system. Environmental end-of-pipe treatment module 5 adopts a fully closed-loop design. Waste gas is condensed and recovered, and a combination of adsorption / catalytic oxidation processes are used to achieve efficient removal of VOCs. Wastewater is discharged in compliance with standards after pretreatment and biochemical treatment, and solid waste is disposed of in a standardized manner. The coordinated operation of the two modules not only significantly reduces the consumption of fresh materials and the cost of waste disposal, but also ensures that all emissions meet stringent environmental regulations at the system level.

[0053] As the nerve center of the entire coupled system, the intelligent collaborative control module 6 plays a core role in solving the control challenges caused by material circulation and energy coupling between the countercurrent staged absorption module 2 and the purity enhancement coupling module 3 through an advanced multivariate predictive control (MPC) strategy, thereby ensuring stable and optimized system operation. First, it constructs a comprehensive data sensing layer by collecting data in real time through sensors and online analyzers (such as the gas chromatograph installed at the product outlet of the ester product distillation and purification unit 31). Second, it establishes a simplified dynamic model of the embedded coupling relationship based on the process mechanism and solves a rolling time-domain optimization problem (optimization objective function) in each control cycle. Under strict adherence to process constraints, the module dynamically calculates coordinated optimization adjustment commands for absorbent parameters (such as the flow rate and ratio of the compound absorbent entering the ethylene glycol selective absorption unit 22) and distillation and purification parameters (such as the reflux ratio of the ester product distillation and purification unit 31 and the purification pressure of the ethylene glycol purification unit 32). Subsequently, the first control increment in the optimization sequence is sent to the actuator to achieve precise control. Simultaneously, historical data is used to periodically update model parameters, enabling the system to adapt to slowly changing operating conditions through self-learning. Through this mechanism, the module does not control individual units in isolation, but rather treats the coupled system as a whole for global optimization, thereby minimizing system energy and material consumption while ensuring product purity and yield.

[0054] Example 2: As shown in Figures 1 and 2, a coupled system for the fractional absorption and purity enhancement of ethylene glycol extract from transesterification reactions is executed by an intelligent collaborative control module 6, including the following steps:

[0055] S1: Establish a dynamic model of the system, which describes the coupling relationship between the key manipulated variables and the controlled variables;

[0056] S2: In each control cycle k, obtain the current state measurement value of the system;

[0057] S3: Based on the dynamic model, solve the rolling time-domain optimization problem to obtain the sequence of manipulator adjustment amounts in the future control time domain. The objective function is optimized. for:

[0058] ;

[0059] In the formula, The vector of controlled variables predicted by the model. Set its value vector. and This is the weight matrix. To predict the time domain, To control the time domain; The index of the future prediction time is used to traverse the prediction time domain 1~P and accumulate the tracking error at each future time. The sequence number of the control step to be executed is used to traverse the control time domain from 0 to M-1 and accumulate the adjustment range of the control quantity for each step.

[0060] S4: Set the first control increment in the sequence Apply to the system;

[0061] S5: Repeat steps S2 to S4 in the next control cycle;

[0062] S6: Periodically update the parameters in the dynamic model using historical data from system operation.

[0063] In step S3, when solving the optimization problem, the applied constraints include: upper and lower bound constraints on the manipulated variables and their rates of change, and upper and lower bound constraints on the controlled variables; the controlled variable vector At least including the purity of the carboxylic acid ester product and the concentration of the ethylene glycol recovery solution; the manipulated variable adjustment vector This includes at least the adjustment amount of the composite absorbent ratio, the adjustment amount of the distillation column reflux ratio, and the adjustment amount of the stripping column operating pressure.

[0064] The working principle of this technical solution is as follows: the outlet of the extract pretreatment module 1 is connected to the inlet of the countercurrent staged absorption module 2, providing a stable and clean feed to the module. Inside the countercurrent staged absorption module 2, the bottom outlet of the light component absorption unit 21 is connected in series with the inlet of the ethylene glycol selective absorption unit 22 to achieve gradient removal of light components and ethylene glycol; wherein, the top outlet of the ethylene glycol selective absorption unit 22 outputs crude ester liquid, and the bottom outlet outputs ethylene glycol-rich absorbent liquid.

[0065] These two key streams enter the ester product distillation and purification unit 31 and the ethylene glycol desorption and purification unit 32 of the purity enhancement coupling module 3, respectively, for deep purification. Optionally, a membrane-assisted purification unit 33 is connected after the ester product distillation and purification unit 31 for maximizing product purity. After the core separation is completed, the solvent recovery and utilization module 4 receives the rich absorbent from the top of the light component absorption unit 21 and the regenerator from the ethylene glycol desorption and purification unit 32, realizing solvent recycling and resource recovery.

[0066] Meanwhile, the environmental end-of-pipe treatment module 5 collects and treats the three wastes generated throughout the system to meet standards. The intelligent collaborative control module 6 runs through and coordinates the operation of all the above physical modules, monitoring and optimizing the operation of each unit in real time via signal connections. This clearly defined structural correspondence, indicated by labels, clearly outlines the material flow, energy flow, and control flow paths of the system, providing a clear and complete physical foundation for the technical solution described in the claims.

[0067] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A coupled system for fractional absorption and purity enhancement of ethylene glycol extract from transesterification reactions, characterized in that, The system includes an extract pretreatment module (1), a countercurrent staged absorption module (2), a purity enhancement coupling module (3), a solvent recovery and utilization module (4), and an environmentally friendly end-of-pipe treatment module (5), connected sequentially along the material flow direction, as well as an intelligent collaborative control module (6). The outlet of the extract pretreatment module (1) is connected to the inlet of the countercurrent staged absorption module (2). The countercurrent staged absorption module (2) includes a light component absorption unit (21) and an ethylene glycol selective absorption unit (22) arranged in series. The light component absorption unit (21) is used to remove light components from the extract, and its bottom outlet is connected to the inlet of the ethylene glycol selective absorption unit (22). The ethylene glycol selective absorption unit (22) is used to selectively absorb ethylene glycol, and its top outlet outputs crude ester liquid, and its bottom outlet outputs ethylene glycol-rich absorbent liquid. The purity enhancement coupling module (3) is connected to the inlet of the countercurrent staged absorption module (4), a solvent recovery and utilization module (5), and an environmentally friendly end-of-pipe treatment module (6). The integrated module (3) includes an ester product distillation and purification unit (31) and an ethylene glycol desorption and purification unit (32). The inlet of the ester product distillation and purification unit (31) is connected to the top outlet of the ethylene glycol selective absorption unit (22) to treat the crude ester liquid. The inlet of the ethylene glycol desorption and purification unit (32) is connected to the bottom outlet of the ethylene glycol selective absorption unit (22) to treat the ethylene glycol-rich absorbent. The inlet of the solvent recovery and utilization module (4) is connected to the top outlet of the light component absorption unit (21) and the desorption agent outlet of the ethylene glycol desorption and purification unit (32) respectively, for the regeneration of the absorbent and the recovery of light components. The inlet of the environmental protection end-of-pipe treatment module (5) is connected to the exhaust gas, wastewater and solid waste discharge outlets of each module of the system respectively. The intelligent collaborative control module (6) is signal-connected to each of the above modules.

2. The fractional absorption and purity enhancement coupling system for ethylene glycol extract from transesterification reaction according to claim 1, characterized in that: The light component absorption unit (21) is a packed absorption tower, using inert absorbent oil as the absorbent, and the ethylene glycol selective absorption unit (22) is a plate tower or a structured packed tower, using a compound polar absorbent.

3. The fractional absorption and purity enhancement coupling system for ethylene glycol extract from transesterification reaction according to claim 1, characterized in that: The ester product distillation and purification unit (31) is a vacuum distillation column; the ethylene glycol desorption and purification unit (32) includes a desorption column and an ethylene glycol distillation column connected in sequence.

4. The fractional absorption and purity enhancement coupling system for ethylene glycol extract from transesterification reaction according to claim 3, characterized in that: The purity enhancement coupling module (3) further includes a membrane-assisted purification unit (33), the inlet of which is connected to the outlet of the ester product distillation purification unit (31), for membrane separation purification of the ester product from the ester product distillation purification unit (31); the membrane-assisted purification unit (33) includes at least one of nanofiltration membrane module and reverse osmosis membrane module.

5. The fractional absorption and purity enhancement coupling system for ethylene glycol extract from transesterification reaction according to claim 1, characterized in that: The intelligent collaborative control module (6) is used to receive sensor signals and online analyzer data, perform calculations based on the built-in predictive control model, and output control commands for dynamically adjusting the absorbent parameters in the countercurrent staged absorption module (2) and the distillation and analysis parameters in the purity enhancement coupling module (3).

6. The fractional absorption and purity enhancement coupling system for ethylene glycol extract from transesterification reaction according to claim 5, characterized in that, It is executed by the intelligent collaborative control module (6). Includes the following steps: S1: Establish a dynamic model of the system, which describes the coupling relationship between the key manipulated variables and the controlled variables; S2: In each control cycle S3: Based on the dynamic model, solve the rolling time-domain optimization problem to obtain the sequence of manipulator adjustment amounts in the future control time domain. The objective function is optimized. for: In the formula, The vector of controlled variables predicted by the model. Set its value vector. and This is the weight matrix. To predict the time domain, To control the time domain; The index of the future prediction time is used to traverse the prediction time domain 1~P and accumulate the tracking error at each future time. The sequence number of the control step to be executed is used to traverse the control time domain from 0 to M-1, and to accumulate the adjustment range of the control quantity for each step; S4: The first control increment in the sequence is... S5: Repeat steps S2 to S4 in the next control cycle; S6: Periodically update the parameters in the dynamic model using historical data from system operation.

7. The method for the coupled system of fractionated absorption and purity enhancement of ethylene glycol extract from transesterification reaction according to claim 6, characterized in that: When solving the optimization problem in step S3, the applied constraints include: upper and lower bound constraints on the manipulated variable and its rate of change, and upper and lower bound constraints on the controlled variable.

8. The method for the coupled system of fractionated absorption and purity enhancement of ethylene glycol extract from transesterification reaction according to claim 6, characterized in that: The controlled variable vector This includes at least the purity of the carboxylic acid ester product and the concentration of the ethylene glycol recovery solution.

9. The method for the coupled system of fractionated absorption and purity enhancement of ethylene glycol extract from transesterification reaction according to claim 6, characterized in that: The manipulator adjustment vector This includes at least the adjustment amount of the composite absorbent ratio, the adjustment amount of the distillation column reflux ratio, and the adjustment amount of the stripping column operating pressure.

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