THF three-stage rectification system and production process

Abstract

The invention relates to the technical field of THF rectification, in particular to a THF three-stage rectification system and a production process, the THF three-stage rectification system comprises a raw material tank, a first-stage rectification tower, a feeding pipeline, a second-stage rectification tower, a second-stage rectification tower feeding pipeline, a third-stage rectification tower and a third-stage rectification tower feeding pipeline, according to the system, the steam flow distribution proportion can be rapidly and accurately adjusted by means of the three-way temperature control proportional valve according to real-time temperature feedback of all rectification stages, it is ensured that all tower plates and related equipment can obtain steam at the appropriate temperature in the different rectification stages, the mass transfer and heat transfer processes in the rectification towers are optimized to a great extent, and the product purity is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of THF rectification, and particularly relates to a THF three-stage rectification system and a production process. Background Art

[0002] In the field of industrial production, rectification, as a key separation technology, is widely used in multiple industries such as chemical engineering, pharmaceuticals, and petroleum. The efficient and stable operation of its process is directly related to product quality and production efficiency. With the booming development of the manufacturing industry, the market has increasingly stringent requirements for the purity of rectified products, and at the same time, higher standards are put forward for energy consumption control in the production process. However, traditional rectification technologies have gradually shown deficiencies in many aspects and are difficult to meet the needs of industrial upgrading.

[0003] Currently, most rectification processes mainly rely on relatively basic methods for steam temperature control. It is difficult to accurately match the complex and changeable working conditions, resulting in frequent fluctuations in steam temperature. The instability of steam temperature will seriously interfere with the gas-liquid equilibrium in the rectification column, making the mass transfer and heat transfer processes unable to proceed efficiently; in terms of flow regulation, conventional valves have the problem of lagging response speed. During the production process, the steam demand will change in real time with the change of process conditions, but traditional valves cannot quickly sense and adapt to these dynamic changes, resulting in the disconnection between steam supply and actual demand. This will not only cause waste of energy, but also may lead to production abnormalities. Due to the inaccurate regulation of steam parameters, the rectification equipment is prone to fluctuations during operation. Being in an unstable operation state for a long time will accelerate the wear of the equipment, increase the equipment maintenance cost and repair frequency, and shorten the service life of the equipment. Therefore, we propose a THF three-stage rectification system and a production process. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a THF three-stage rectification system and a production process, thereby solving the technical problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A THF three-stage rectification system includes a raw material tank, a primary rectification column, a feed pipeline, a secondary rectification column, a secondary rectification column feed pipeline, a tertiary rectification column, and a tertiary rectification column feed pipeline; The outlet of the raw material tank is connected to the primary rectification column through the feed pipeline. The steam outlet at the top of the primary rectification column is connected to the steam inlet of a primary condenser. The bottom outlet of the column is connected to a bottom residue discharge pipeline. The condensate outlet of the primary condenser is respectively connected to a primary fraction collection tank and a reflux pipeline through pipelines, and the reflux pipeline is connected to the reflux port of the primary rectification column; The primary fraction collection tank is connected to the feed inlet of the secondary rectification column through a secondary rectification column feed pipeline; the steam outlet at the top of the secondary rectification column is connected to the steam inlet of the secondary condenser; the condensate outlet of the secondary condenser is respectively connected to a secondary fraction collection tank and a reflux pipeline through pipelines, and the reflux pipeline is connected to the reflux inlet of the secondary rectification column; The secondary fraction collection tank is connected to the feed inlet of the tertiary rectification column through a tertiary rectification column feed pipeline; the steam outlet at the top of the tertiary rectification column is connected to the steam inlet of the tertiary condenser; the condensate outlet of the tertiary condenser is respectively connected to a finished product collection tank and a reflux pipeline through pipelines, and the reflux pipeline is connected to the reflux inlet of the tertiary rectification column.

[0006] In a possible implementation manner, it further includes a steam pipeline, a three-way temperature control proportional valve, a pneumatic control valve, a temperature transmitter, a pressure transmitter, and a control system. The steam pipeline is respectively connected to the primary rectification column, the secondary rectification column, and the tertiary rectification column. The three-way temperature control proportional valve and the pneumatic control valve are installed on the steam pipeline. The temperature transmitter is respectively installed on each rectification column and the steam pipeline, and the pressure transmitter is installed on each rectification column. The control system receives the signals from the temperature transmitter and the pressure transmitter.

[0007] In a possible implementation manner, it further includes an ice water pipeline, a flow control valve, and a liquid level transmitter; the ice water pipeline is respectively connected to the primary condenser, the secondary condenser, and the tertiary condenser. The flow control valve is installed on the ice water pipeline, and the liquid level transmitter is respectively installed on the raw material tank, the primary fraction collection tank, the secondary fraction collection tank, and the finished product collection tank.

[0008] In a possible implementation manner, it further includes a vacuum pipeline, a vacuum pump, a vacuum gauge, a bottom residue discharge pipeline, and a waste liquid collection tank; valves and a vacuum gauge are provided on the vacuum pipeline. The bottom residue discharge pipeline is connected to the bottom of each rectification column, and the residue enters the waste liquid collection tank through the bottom residue discharge pipeline. A valve is provided on the bottom residue discharge pipeline.

[0009] In a possible implementation manner, a THF three-stage rectification production process includes the following steps: S1: Raw material preparation. Use a gas chromatograph and a mass spectrometer to detect the purity, impurities, and moisture content of the raw materials. Adopt extraction, filtration, and drying methods to purify different impurities. Store the qualified raw materials in the raw material tank, keep them at room temperature, keep them sealed, monitor the liquid level through the liquid level transmitter, and regularly check the equipment; S2: Primary rectification stage. Open the valve of the feed pipeline to transport the raw materials to the primary rectification column, adjust the flow rate and pay attention to the filtration device, introduce steam for heating, monitor the temperature and pressure and automatically adjust them. The steam and the substances in the column undergo gas-liquid mass transfer. After the steam condenses, part of it returns, and the rest flows into the primary fraction collection tank; S3: In the secondary rectification stage, when the liquid level in the primary fraction collection tank reaches 70%-80%, open the valve to transport the primary fraction to the secondary rectification column. Monitor the flow rate and pipeline sealing, introduce steam for heating. After the steam condenses, part of it flows back, and the rest flows into the secondary fraction collection tank. Regularly check the heat exchange efficiency of the condenser. S4: In the tertiary rectification stage, when the liquid level in the secondary fraction collection tank reaches 60%-70%, transport the secondary fraction to the tertiary rectification column. Adjust the feed rate with reference to the data of the previous two stages. Heat with steam. After the steam condenses, part of it flows back, and the rest flows into the finished product collection tank. Monitor the liquid level and sample and test the product. S5: Storage of finished products and treatment of residual liquid. Transport the product in the finished product collection tank to the storage container or for production. Ensure the pipeline is sealed and clean. Regularly clean the tank body and calibrate the equipment. Store in a cool and dry place. The residual liquid at the bottom of each rectification column is discharged through the pipeline for bottom residual liquid, collected separately, and THF is recovered by extraction and rectification. The impurities are treated harmlessly.

[0010] In a possible implementation, in the primary rectification stage, the steam temperature is 110-130°C, the pressure is 0.2-0.4MPa. Monitor and control the temperature at the top of the column at 60-70°C and the temperature at the bottom of the column at 80-100°C, and maintain a vacuum degree of -0.08MPa to -0.06MPa.

[0011] In a possible implementation, in the secondary rectification stage, the steam temperature is 100-120°C, the pressure is 0.1-0.3MPa. Monitor and control the temperature at the top of the column at 50-60°C and the temperature at the bottom of the column at 70-90°C, and maintain a vacuum degree of -0.09MPa to -0.07MPa.

[0012] In a possible implementation, in the tertiary rectification stage, the steam temperature is 90-110°C, the pressure is 0.05-0.2MPa. Monitor and control the temperature at the top of the column at 40-50°C and the temperature at the bottom of the column at 60-80°C, and maintain a vacuum degree of -0.1MPa to -0.08MPa.

[0013] Beneficial effects compared with the prior art: 1. In this solution, through the three-way temperature control proportional valve and the pneumatic control valve, in the complex process of tertiary rectification, the system can, according to the real-time temperature feedback of each rectification stage, quickly and accurately adjust the steam flow distribution ratio with the help of the three-way temperature control proportional valve. Ensure that in different rectification stages, each tray and related equipment can obtain steam with appropriate temperature, greatly optimizing the mass transfer and heat transfer processes in the rectification column and significantly improving the purity of the product. 2. In this solution, through the pneumatic control valve, the flow rate of the main steam pipeline or branch pipeline can be quickly and accurately adjusted, ensuring that the steam supply always closely matches the actual demand, effectively avoiding various production anomalies caused by flow imbalance, and greatly improving the stability of the entire steam transmission and use system. 3. In this solution, energy waste caused by excessively high steam temperature or large steam flow is avoided, the steam demand of each device in different operating states is accurately matched, the utilization efficiency of steam energy in industrial production is maximally improved, the energy cost of enterprises is reduced, and green and sustainable production is facilitated. Description of the Drawings

[0014] The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly and to be able to implement it according to the content of the description, the following describes in detail with reference to the preferred embodiments of the present invention and the accompanying drawings.

[0015] Figure 1 It is a schematic diagram of the overall structure of the rectification system of the present invention; Figure 2 For the present invention Figure 1 Enlarged schematic diagram of the structure at A in Figure 3 For the present invention Figure 1 Enlarged schematic diagram of the structure at B in Figure 4 For the present invention Figure 1 Enlarged schematic diagram of the structure at C in

[0016] Legend: 1, raw material tank; 2, feed pipeline; 3, primary rectification tower; 4, primary condenser; 5, primary fraction collection tank; 6, feed pipeline for secondary rectification tower; 7, secondary rectification tower; 8, secondary condenser; 9, secondary fraction collection tank; 10, feed pipeline for tertiary rectification tower; 11, tertiary rectification tower; 12, tertiary condenser; 13, finished product collection tank; 14, steam pipeline; 15, vacuum pipeline; 16, ice water pipeline; 17, reflux pipeline; 18, bottom residue discharge pipeline; 19, pressure transmitter; 20, temperature transmitter; 21, liquid level transmitter; 22, waste liquid collection tank. Detailed Embodiment

[0017] The preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention can be implemented in various different forms. Therefore, the present invention is not limited to the embodiments described below. In addition, in order to describe the present invention more clearly, components not connected to the invention will be omitted from the drawings; The technical solutions in the embodiments of the present application are to solve the problems in the above background technology, and the general idea is as follows: This embodiment introduces a THF three-stage distillation system and production process. The distillation system includes a raw material tank 1, which is made of stainless steel and has good corrosion resistance to ensure long-term storage of THF raw materials without chemical reactions. The raw material tank is equipped with a feed inlet, a discharge outlet, a liquid level gauge interface, a pressure gauge interface, etc. The feed inlet is used to supplement raw materials, and the discharge outlet is connected to the first-stage distillation column 3 through a feed pipeline 2. The feed pipeline 2 is generally made of seamless stainless steel pipe, which has high strength and corrosion resistance and can withstand a certain pressure and temperature.

[0018] On the feed pipeline 2, a pneumatic butterfly valve is installed. This valve is a valve that drives the butterfly plate to rotate through a pneumatic actuator to achieve the opening, closing, and adjustment functions. In addition, in order to prevent solid impurities in the raw materials from entering the distillation column, a filtering device is also installed on the feed pipeline. The filtering device can effectively filter out rust, granular impurities, etc., to prevent these impurities from entering the first-stage distillation column 3, affecting the gas-liquid mass transfer process in the column, and even clogging the trays or packing, thereby ensuring the normal operation and distillation effect of the distillation column.

[0019] The first-stage distillation column 3 has a cylindrical tower body. The feed inlet of the first-stage distillation column 3 is connected to the feed pipeline 2 to receive the raw materials from the raw material tank 1. Inside the column, steam is introduced through a steam pipeline 14 for heating. The steam pipeline 14 is led out from a steam source, and a three-way temperature control proportional valve and a pneumatic regulating valve are provided on the steam pipeline 14. The main function of the three-way temperature control proportional valve is to accurately adjust the distribution of steam flow according to the temperature change of the steam. The three-way temperature control proportional valve can automatically adjust the valve opening according to the signal feedback by the temperature sensor. The pneumatic regulating valve is used to adjust the steam flow. The pneumatic regulating valve can adjust the steam flow according to the load change of the equipment, thereby controlling the operating power of the equipment. The steam temperature is controlled at 110 - 130 °C, and the steam pressure is controlled at 0.2 - 0.4 MPa. Within this temperature and pressure range, the low-boiling components in the THF raw materials and part of the THF will vaporize and rise first.

[0020] The vaporized steam is discharged from the top steam outlet of the tower and enters the first-stage condenser 4 through a pipeline. The first-stage condenser 4 adopts a shell-and-tube heat exchanger structure, which consists of a shell, a tube bundle, a tube sheet, etc. The shell is cylindrical and made of stainless steel, which can accommodate the tube bundle and withstand a certain pressure. The tube bundle is composed of multiple heat exchange tubes. The heat exchange tubes are made of copper tubes or stainless steel tubes, which have good heat conduction performance. The tube sheet is used to fix the tube bundle and divide the shell into a steam chamber and a cooling medium chamber. The steam inlet of the first-stage condenser 4 is connected to the pipeline at the top steam outlet of the first-stage distillation column, and an ice water pipeline 16 provides cooling ice water for it.

[0021] The ice water pipeline 16 is made of stainless steel and has good low-temperature resistance. A flow regulating valve is installed on the ice water pipeline to adjust the flow rate of the cooling water, thereby controlling the cooling effect of the primary condenser 4. The temperature of the cooling ice water is maintained at 5 - 15 °C. By adjusting the flow regulating valve, the temperature of the cooling ice water can be kept within this range to ensure effective condensation of the steam. The condensate outlet of the primary condenser 4 is connected to the primary fraction collection tank 5 and the reflux pipeline 17 through two pipelines respectively. A check valve is installed on the pipeline connected to the primary fraction collection tank 5 to prevent liquid backflow and ensure smooth collection of the fractions; a three-way temperature control proportional valve is set on the pipeline connected to the reflux pipeline 17 to accurately control the amount of liquid refluxing to the primary distillation column 3 by adjusting its opening degree, that is, to control the reflux ratio. The reflux ratio is controlled between 1 - 3.

[0022] The primary fraction collection tank 5 is used to store the THF fraction obtained from the primary distillation. Its structure is similar to that of the raw material tank, made of stainless steel, and is equipped with a feed inlet, a discharge outlet, a liquid level gauge interface, a pressure gauge interface, etc. The discharge outlet of the primary fraction collection tank 5 is connected to the secondary distillation column 7 through the secondary distillation column feed pipeline 6. A valve is installed on the secondary distillation column feed pipeline 6 to control the flow rate of the primary fraction entering the secondary distillation column 7, so that the primary fraction can stably enter the secondary distillation column 7 for secondary distillation.

[0023] The structure and working principle of the secondary distillation column 7 are similar to those of the primary distillation column 3. Its feed inlet receives the primary fraction from the primary fraction collection tank 5. Steam is introduced through the steam pipeline 14 for heating to further vaporize and separate the fraction. The top steam outlet is connected to the secondary condenser 8, the bottom discharge outlet is connected to the bottom residue discharge pipeline 18, and the bottom residue is discharged from the distillation column through the bottom residue discharge pipeline 18 into the waste liquid collection tank 22. The reflux port is connected to the secondary condenser 8 through the reflux pipeline 17. The structure and working principle of the secondary condenser 8 are the same as those of the primary condenser 4. The steam is condensed by the cooling ice water provided by the ice water pipeline 16. Part of the condensate flows back to the secondary distillation column 7 through the reflux pipeline 17, and the other part enters the secondary fraction collection tank 9.

[0024] The secondary fraction collection tank 9 stores the THF fraction obtained from the secondary distillation. Its discharge outlet is connected to the tertiary distillation column 11 through the tertiary distillation column feed pipeline 10. A valve is installed on the tertiary distillation column feed pipeline 10 to control the flow rate of the secondary fraction entering the tertiary distillation column 11. The tertiary distillation column 11 performs the final distillation on the secondary fraction. The top steam outlet is connected to the tertiary condenser 12, the bottom discharge outlet is connected to the bottom residue discharge pipeline 18, and the bottom residue is discharged from the distillation column through the bottom residue discharge pipeline 18 into the waste liquid collection tank 22. The reflux port is connected to the tertiary condenser 12 through the reflux pipeline 17. The tertiary condenser 12 uses the cooling ice water provided by the ice water pipeline 16 to condense the steam. Part of the condensate flows back through the reflux pipeline 17, and part enters the finished product collection tank 13.

[0025] The finished product collection tank 13 is used to store the high-purity THF product obtained after three-stage rectification. Its structure is similar to that of the raw material tank, made of stainless steel, and is equipped with a feed inlet, a discharge outlet, a liquid level gauge interface, a pressure gauge interface, etc. During the operation of the entire system, the pressure transmitter 19, the temperature transmitter 20, and the liquid level transmitter 21 continuously monitor the pressure, temperature, and liquid level data of each rectification column, condenser, and each storage tank, and transmit these data to the control system in real time.

[0026] The pressure transmitter 19 is respectively installed on each rectification column to measure the pressure inside the rectification column. It converts the pressure signal into an electrical signal and transmits it to the control system. The temperature transmitter 20 is installed at different positions of each rectification column (such as the top, bottom, and feed inlet, etc.) and on the inlet and outlet pipes of the condenser to measure the temperature of the material inside the rectification column and the temperature of the cooling ice water inside the condenser. The temperature transmitter converts the temperature signal into an electrical signal and transmits it to the control system. The liquid level transmitter 21 is respectively installed on the raw material tank, the primary fraction collection tank, the secondary fraction collection tank, and the finished product collection tank to monitor the liquid level height inside the tank. The liquid level transmitter converts the liquid level signal into an electrical signal and transmits it to the control system.

[0027] The control system is the control part of the entire THF three-stage rectification system, consisting of an industrial computer, a PLC (programmable logic controller), a sensor interface, an actuator interface, etc. The industrial computer is used to run the control software to implement a human-machine interface. Operators can set process parameters and monitor the system operation status through this interface. The PLC is the core controller of the control system. It receives signals from sensors (such as pressure transmitters, temperature transmitters, liquid level transmitters, etc.), performs calculations and controls according to preset process parameters, and then controls the opening of valves on each pipeline and the operation of related equipment through the actuator interface to achieve automatic control and monitoring of the entire rectification system.

[0028] The vacuum tube 15 is connected to the top of each rectification column to maintain a vacuum environment inside the rectification column through a vacuum pump. The vacuum tube is generally made of stainless steel and has good sealing performance and corrosion resistance. A valve is set on the vacuum tube to control the adjustment of the vacuum degree. At the same time, a vacuum gauge is installed on the vacuum tube line to display the vacuum degree inside the rectification column in real time. Operators can adjust the valve on the vacuum tube according to the reading of the vacuum gauge to control the vacuum degree, ensure that the rectification is carried out under appropriate vacuum conditions, thereby reducing the boiling point of THF, reducing energy consumption and the risk of product decomposition. The bottom residue discharge pipe 18 is used to discharge the bottom residue of each rectification column and has good corrosion resistance. A valve is provided on the pipe to periodically open and discharge the residue to prevent the accumulation of residue from affecting the rectification effect. The discharged residue can be subjected to subsequent treatment. The production process of this rectification production process is as follows: S1: Raw material preparation Raw material detection: Before THF distillation, the raw materials need to be quality checked. Use precision analytical instruments such as gas chromatographs and mass spectrometers to detect the purity, impurity types and contents, moisture content and other indicators of the THF raw materials to be distilled. The gas chromatograph can separate and detect the various components in the THF raw materials, and accurately determine the contents of each component by comparing with standard samples to determine the purity of the raw materials. The mass spectrometer can further analyze the types and structures of impurities. If the raw material purity is low and the impurity content is too high, preliminary purification treatment is required. Specifically, when it is detected that the raw materials contain more water-soluble impurities, the extraction method can be used to separate the impurities from the THF raw materials using an extractant that is immiscible with THF and has good solubility for impurities. Commonly used extractants include ether, ethyl acetate, etc. If the raw material contains solid particulate impurities, it is removed by filtration. If the moisture content exceeds the standard, it can be dehydrated by drying with a desiccant or azeotropic distillation. Desiccant drying generally uses desiccants such as anhydrous sodium sulfate and anhydrous calcium chloride, which can absorb the moisture in the THF raw material. Azeotropic distillation uses substances that form azeotropes with water (such as benzene, cyclohexane, etc.) to remove water through distillation, thereby achieving the purpose of dehydration.

[0029] Raw material storage: After ensuring that the quality of the raw materials meets the requirements of distillation, store them in the raw material tank 1. The storage temperature of the raw material tank 1 is within the normal temperature range to avoid the impact of too high or too low temperature on the quality of the raw materials. At the same time, it is necessary to ensure that the raw material tank is well sealed to prevent outside air, moisture, etc. from entering the tank, causing the raw materials to be oxidized or damp. The liquid level in the raw material tank 1 is monitored in real time by the liquid level transmitter 21 to ensure that the raw material reserve can meet the production needs for a certain period of time. In addition, it is necessary to regularly check the sealing of the raw material tank 1, and whether the pressure gauge, thermometer and other equipment are working properly to ensure safe and stable storage of raw materials.

[0030] S2: primary distillation stage Raw material transportation: After confirming that the raw materials are ready, open the valve on the feed pipe 2 to transport the THF raw material in the raw material tank 1 to the primary distillation tower 3. During the transportation process, adjust the valve opening to allow the raw material to enter the primary distillation tower 3 at a stable flow rate. At the same time, observe the operation of the filter device to prevent it from being blocked and affecting the raw material transportation. If the filter device is found to be blocked, it should be cleaned or the filter element replaced in time.

[0031] Heating and vaporization: After the raw materials enter the first-stage rectification column 3, the valve on the steam pipeline 14 is opened, and steam is introduced into the column for heating. The steam temperature is controlled at 110 - 130 °C, and the steam pressure is controlled at 0.2 - 0.4 MPa. Under these temperature and pressure conditions, the low-boiling components in the THF raw materials and part of the THF will vaporize and rise first. During the steam heating process, the steam temperature is monitored in real time through the temperature transmitter 20, and the steam pressure is monitored in real time through the pressure transmitter 19 to ensure that the temperature and pressure of the steam are within the set range. If the temperature or pressure fluctuates, the control system will automatically adjust the valve opening of the steam pipeline to restore the temperature and pressure to the set value.

[0032] Gas-liquid mass transfer: Inside the first-stage rectification column 3, the vaporized steam comes into full contact with the trays or packing in the column for the gas-liquid mass transfer process. During the gas-liquid mass transfer process, the temperature at different positions inside the first-stage rectification column 3, especially the temperatures at the top and bottom of the column, is monitored in real time through the temperature transmitter 20. The top temperature is controlled at 60 - 70 °C. This temperature range allows THF and some low-boiling impurities to vaporize and rise, while preventing too many high-boiling impurities from entering the steam flow. The bottom temperature is controlled at 80 - 100 °C to ensure that the raw materials can be fully vaporized. At the same time, the pressure transmitter 19 monitors the pressure inside the column in real time, and by adjusting the valve on the vacuum pipe 15, the pressure inside the first-stage rectification column 3 is maintained in a vacuum environment of -0.08 MPa to -0.06 MPa. Under vacuum conditions, the boiling point of THF decreases, which helps with rectification at a lower temperature, reducing energy consumption and thermal decomposition of THF.

[0033] Condensation, reflux, and collection: As the rectification progresses, the vaporized THF steam is discharged from the top steam outlet and enters the first-stage condenser 4. The ice water pipeline 16 supplies low-temperature ice water to the first-stage condenser 4, and by adjusting the flow control valve on the ice water pipeline, the temperature of the cooling medium is maintained at 5 - 15 °C. During the cooling process, the steam gradually condenses into a liquid. Part of the condensate flows back to the first-stage rectification column 3 through the reflux pipeline 17, and the reflux ratio is precisely controlled by adjusting the valve on the reflux pipeline. The reflux ratio is controlled between 1 - 3. The refluxed condensate and the rising steam carry out full gas-liquid mass transfer inside the column, further separating THF from impurities and improving the rectification effect and product purity. The remaining condensate then flows into the first-stage fraction collection tank 5 for storage. At this time, the purity of THF in the first-stage fraction is initially improved, removing most of the low-boiling impurities and some high-boiling impurities. During this process, the inlet and outlet temperatures of the cooling ice water are monitored through the temperature transmitter 20 to ensure that the temperature of the cooling ice water is within the appropriate range and guarantee that the steam can be fully condensed. At the same time, pay attention to observing the operation of the reflux pipeline and the first-stage fraction collection tank to prevent problems such as pipeline blockage or tank leakage.

[0034] S3: Second-stage rectification stage Fraction transportation: When the liquid level in the primary fraction collection tank 5 reaches a certain height, specifically 70%-80% of the tank volume, the valve on the feed pipeline 6 of the secondary rectification column is opened to transport the primary fraction to the secondary rectification column 7. During transportation, the flow rate and velocity of the primary fraction are monitored through the flowmeter installed on the feed pipeline 6 of the secondary rectification column and based on parameters such as feed time and pipeline flow velocity, and the amount of the primary fraction entering the secondary rectification column 7 is monitored. At the same time, check whether the pipeline connections are well-sealed to prevent losses and safety hazards caused by fraction leakage.

[0035] Re-heating, gasification and mass transfer: The secondary rectification column 7 is heated by introducing steam through the steam pipeline 14. The steam temperature is controlled at 100-120°C and the pressure is controlled at 0.1-0.3 MPa. This temperature and pressure range are determined according to the component characteristics of the primary fraction and the requirements for further purification. Under these conditions, THF and residual impurities in the fraction are further gasified and separated. Since the composition and purity of the fraction have changed at this time, the specific effects of gas-liquid mass transfer and the separation difficulty are also different. The temperature transmitter 20 is used to monitor the top temperature of the column at 50-60°C and the bottom temperature at 70-90°C. Controlling the top temperature within this range can further separate THF from trace impurities that are difficult to separate, while the bottom temperature ensures that the fraction can be fully gasified. The pressure transmitter 19, in cooperation with the valve on the vacuum pipe 15, maintains the pressure in the column at a vacuum degree of -0.09 MPa to -0.07 MPa. By maintaining a certain vacuum degree, the boiling point of THF is reduced, the rectification efficiency is improved, and at the same time, the energy consumption and the possibility of product thermal decomposition are reduced. Condensation and reflux: The steam at the top of the secondary rectification column 7 enters the secondary condenser 8. The ice water pipeline 16 provides cooling ice water for the secondary condenser 8. By adjusting the flow control valve on the ice water pipeline, the temperature of the cooling medium is maintained at 5-15°C to condense the steam. Part of the condensate flows back to the secondary rectification column 7 through the reflux pipeline 17, and the reflux ratio is controlled between 2 and 4. The other part of the condensate flows into the secondary fraction collection tank 9. During this process, the heat transfer efficiency of the secondary condenser 8 should be regularly checked, and it can be evaluated by comparing parameters such as the temperature difference between the inlet and outlet of the cooling ice water and the temperature after the steam is condensed. If it is found that the heat transfer efficiency has decreased, check whether the ice water pipeline is blocked, whether the surface of the heat exchange tube is fouled, etc., and clean or repair it in time. At the same time, closely monitor the working status of the valve on the reflux pipeline to ensure that it can accurately adjust the reflux ratio.

[0036] S4: Tertiary rectification stage Fraction Introduction: After a certain amount of fraction accumulates in the secondary fraction collection tank 9, specifically reaching 60%-70% of the tank volume, the valve on the feed pipeline 10 of the tertiary rectification column is opened to transfer the secondary fraction to the tertiary rectification column 11. At this point, the secondary fraction has undergone the first two stages of rectification and has a relatively high purity, but still contains a small amount of impurities, which need to be finally purified in depth in the tertiary rectification column. During the transfer process, attention should also be paid to the stability of the feed and the tightness of the pipeline. Additionally, based on the data recorded in the control system for the first two stages of rectification, the feed rate and feed volume for this time can be appropriately adjusted to optimize the rectification effect in the tertiary rectification column.

[0037] Final Rectification and Purification: The steam heating temperature of the tertiary rectification column 11 is controlled at 90 - 110°C, and the steam pressure is controlled at 0.05 - 0.2 MPa. These temperature and pressure conditions are more precise and are aimed at deeply purifying the secondary fraction to remove almost all remaining impurities. The top temperature of the column is monitored at 40 - 50°C and the bottom temperature at 60 - 80°C through the temperature transmitter 20. The low top temperature helps to separate the high-purity THF vapor from the extremely small amount of impurity vapor, while the bottom temperature ensures the full vaporization of the fraction. The pressure transmitter 19 and the valve on the vacuum pipe 15 maintain the pressure inside the column at -0.1 MPa to -0.08 MPa, creating a high-vacuum rectification environment. The high vacuum not only further reduces the boiling point of THF but also decreases the dissolution of impurities in the vapor, improving the product purity.

[0038] Final Condensation and Collection: The vapor at the top of the tertiary rectification column 11 enters the tertiary condenser 12, and the ice water pipeline 16 continues to supply chilled ice water for condensation. By adjusting the flow rate and temperature of the chilled ice water, it is ensured that the vapor is completely condensed. Part of the condensate flows back to the tertiary rectification column 11, with the reflux ratio controlled between 3 - 5. The other part of the condensate flows into the finished product collection tank 13. At this time, the purity of the obtained THF product has reached a relatively high level, meeting the production requirements. During this process, the liquid level of the finished product collection tank 13 should be monitored in real-time. When the liquid level reaches 90% of the tank volume, the product should be promptly transferred and stored. At the same time, the finished product is sampled and tested, and through analytical methods such as gas chromatography and mass spectrometry, the purity and impurity content of the THF product are reconfirmed to ensure that the product quality meets the standards.

[0039] S5: Storage of Finished Product and Treatment of Residual Liquid Product storage: The high-purity THF product in the finished product collection tank 13 is transported through the discharge port to subsequent storage containers or directly used in production. During transportation, ensure the tightness and cleanliness of the pipeline to prevent product contamination. The transportation pipeline is generally made of stainless steel and is cleaned and disinfected before and after use. Regularly clean and inspect the finished product collection tank 13. When cleaning, thoroughly remove the residual liquid and impurities in the tank, and check whether there is corrosion, cracks, etc. on the tank body. At the same time, calibrate and maintain the equipment such as liquid level gauges and pressure gauges in the tank to ensure their normal operation. The storage temperature of the finished product is in a cool and dry environment, avoiding direct sunlight and high temperature to prevent the product from decomposing or deteriorating. The storage container usually uses a stainless steel tank with good sealing performance or other suitable material containers, and is equipped with corresponding protective facilities such as fire prevention and explosion protection devices.

[0040] Residual liquid treatment: The residual liquid at the bottom of each distillation column is regularly discharged through the bottom residual liquid discharge pipeline 18. The residual liquid contains unevaporated high-boiling impurities and a small amount of THF. First, classify and collect the residual liquid. The residual liquid discharged from different distillation columns may have different compositions and needs to be treated separately. For the recovery of THF in the residual liquid, methods such as extraction and distillation are used. Specifically, when using the extraction method, select a suitable extractant, and through multiple extractions, enrich the THF in the residual liquid, and then further purify it by distillation. The recovered THF can re-enter the production process to improve the utilization rate of raw materials. For the part of impurities that cannot be recovered, it needs to be harmlessly treated according to environmental protection requirements. According to the nature of the impurities, physical treatment, chemical treatment or biological treatment methods can be used to ensure that the treated emissions meet environmental protection standards and prevent environmental pollution. During the residual liquid treatment process, comply with safety operation procedures to prevent safety accidents such as leakage, fire, and explosion.

[0041] Finally, it should be noted that: Obviously, the above embodiments are only examples for clearly illustrating the present invention, rather than limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A THF three-stage rectification system, characterized in that, It includes a raw material tank (1), a primary distillation column (3), a feed pipeline (2), a secondary distillation column (7), a feed pipeline (6) for the secondary distillation column, a tertiary distillation column (11), and a feed pipeline (10) for the tertiary distillation column; The outlet of the raw material tank (1) is connected to the primary distillation column (3) through the feed pipeline (2). The steam outlet at the top of the primary distillation column (3) is connected to the steam inlet of a primary condenser (4). The condensate outlet of the primary condenser (4) is respectively connected to a primary fraction collection tank (5) and a reflux pipeline (17) through pipelines, and the reflux pipeline (17) is connected to the reflux port of the primary distillation column (3); The primary fraction collection tank (5) is connected to the feed port of the secondary distillation column (7) through the feed pipeline (6) for the secondary distillation column. The steam outlet at the top of the secondary distillation column (7) is connected to the steam inlet of a secondary condenser (8). The condensate outlet of the secondary condenser (8) is respectively connected to a secondary fraction collection tank (9) and a reflux pipeline (17) through pipelines, and the reflux pipeline (17) is connected to the reflux port of the secondary distillation column (7); The secondary fraction collection tank (9) is connected to the feed port of the tertiary distillation column (11) through the feed pipeline (10) for the tertiary distillation column. The steam outlet at the top of the tertiary distillation column (11) is connected to the steam inlet of a tertiary condenser (12). The condensate outlet of the tertiary condenser (12) is respectively connected to a finished product collection tank (13) and a reflux pipeline (17) through pipelines, and the reflux pipeline (17) is connected to the reflux port of the tertiary distillation column (11).

2. The THF three-stage rectification system according to claim 1, wherein, It also includes a steam pipeline (14), a three-way temperature control proportional valve, a pneumatic control valve, a temperature transmitter (20), a pressure transmitter (19), and a control system. The steam pipeline (14) is respectively connected to the primary distillation column (3), the secondary distillation column (7), and the tertiary distillation column (11). The three-way temperature control proportional valve and the pneumatic control valve are installed on the steam pipeline (14). The temperature transmitter (20) is respectively installed on each distillation column and the steam pipeline (14), and the pressure transmitter (19) is installed on each distillation column. The control system receives the signals from the temperature transmitter (20) and the pressure transmitter (19).

3. A THF three-stage rectification system according to claim 1, wherein It also includes an ice water pipeline (16), a flow control valve, and a liquid level transmitter (21); the ice water pipeline (16) is respectively connected to the primary condenser (4), the secondary condenser (8), and the tertiary condenser (12). The flow control valve is installed on the ice water pipeline (16), and the liquid level transmitter (21) is respectively installed on the raw material tank (1), the primary fraction collection tank (5), the secondary fraction collection tank (9), and the finished product collection tank (13).

4. The THF three-stage rectification system according to claim 1, characterized in that, It also includes a vacuum pipeline (15), a vacuum pump, a vacuum gauge, a bottom residue discharge pipeline (18), and a waste liquid collection tank (22); valves and a vacuum gauge are provided on the vacuum pipeline (15). The bottom residue discharge pipeline (18) is connected to the bottom of each distillation column, and the residue enters the waste liquid collection tank (22) through the bottom residue discharge pipeline (18), and a valve is provided on the bottom residue discharge pipeline (18).

5. A THF three-stage rectification production process, characterized in that, It includes the following steps: S1: Raw material preparation. Use a gas chromatograph and a mass spectrometer to detect the purity, impurities and moisture content of the raw materials. For different impurities, adopt extraction, filtration and drying methods for purification. Store the qualified raw materials in the raw material tank (1), keep them at room temperature, sealed, monitor the liquid level through the liquid level transmitter (21) and regularly check the equipment; S2: The first-stage rectification stage. Open the valve of the feed pipeline (2) to transport the raw materials to the first-stage rectification tower (3), adjust the flow rate and pay attention to the filtration device, introduce steam for heating, monitor the temperature and pressure and automatically adjust. The steam and the substances in the tower carry out gas-liquid mass transfer. After the steam condenses, part of it returns, and the rest flows into the first-fraction collection tank (5); S3: The second-stage rectification stage. When the liquid level in the first-fraction collection tank (5) reaches 70%-80%, open the valve to transport the first fraction to the second-stage rectification tower (7), monitor the flow rate and the pipeline seal, introduce steam for heating, after the steam condenses, part of it returns, and the rest flows into the second-fraction collection tank (9), and regularly check the heat exchange efficiency of the condenser; S4: The third-stage rectification stage. When the liquid level in the second-fraction collection tank (9) reaches 60%-70%, transport the second fraction to the third-stage rectification tower (11), adjust the feed according to the data of the previous two stages, heat with steam, after the steam condenses, part of it returns, and the rest flows into the finished product collection tank (13), monitor the liquid level and sample and detect the product; S5: Finished product storage and residue treatment. Transport the product in the finished product collection tank (13) to the storage container or use it for production, ensure the pipeline is sealed and clean, regularly clean the tank body and calibrate the equipment, store it in a cool and dry place. The bottom residues of each rectification tower are discharged through the bottom residue discharge pipeline (18), collected separately, adopt extraction and rectification to recover THF, and harmlessly treat the impurities.

6. The THF three-stage rectification production process according to claim 5, characterized in that, In the said first-stage rectification stage, the steam temperature is 110-130°C, the pressure is 0.2-0.4MPa, monitor and control the top of the tower at 60-70°C, the bottom of the tower at 80-100°C, and maintain a vacuum degree of -0.08MPa to -0.06MPa.

7. The THF three-stage rectification production process according to claim 5, characterized in that, In the said second-stage rectification stage, the steam temperature is 100-120°C, the pressure is 0.1-0.3MPa, monitor and control the top of the tower at 50-60°C, the bottom of the tower at 70-90°C, and maintain a vacuum degree of -0.09MPa to -0.07MPa.

8. The THF three-stage rectification production process according to claim 5, characterized in that, In the said third-stage rectification stage, the steam temperature is 90-110°C, the pressure is 0.05-0.2MPa, monitor and control the top of the tower at 40-50°C, the bottom of the tower at 60-80°C, and maintain a vacuum degree of -0.1MPa to -0.08MPa.

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