Device and method for recovering furfural from furfural light components

Abstract

The invention discloses a device and a method for recovering furfural from furfural light components, and belongs to the technical field of resource utilization of furfural production waste liquid. The method comprises five steps of light component removal rectification, composition adjustment, secondary rectification, quenching layering and vacuum rectification. The method comprises the following steps: carrying out batch rectification on light component removal condensate generated in a furfural production process in a light component removal tower under the condition that the tower top temperature is lower than 60 DEG C, and cutting methanol-acetone azeotrope; adding 14-16 wt% of industrial furfural or 15-17 wt% of a furfural crude product (crude aldehyde) into the residual liquid of the tower kettle, and then feeding the residual liquid into a light component removal tower for secondary rectification; quickly cooling the obtained tower kettle liquid to be less than or equal to 30 DEG C through a condenser, entering an extraction overflow tank, and standing for layering to obtain an aldehyde-rich phase with the furfural content of more than or equal to 93 wt%; rectifying the aldehyde-rich phase through a reduced pressure rectifying tower under the conditions that the pressure is 0.094-0.098 MPa and the reflux ratio is 2-5; according to the method, the whole process of light component removal, composition adjustment, layering and refining can be realized in a single set of intermittent device, and the energy consumption and the equipment investment are remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of furfural light component recovery technology, specifically to an apparatus and method for recovering furfural light components. Background Technology

[0002] In the industrial production of furfural, furfural raw material undergoes acid-catalyzed hydrolysis, stripping, condensation, and dehydration distillation to obtain the finished furfural product. During the dehydration distillation of furfural, a certain amount of light component condensate is generated in the condensation section at the top of the column; this material is also known as the "light component of furfural".

[0003] Existing production experience shows that the light-end condensate mainly comes from the light-end fraction of the furfural dehydration tower, and its typical composition is as follows: methanol and acetone together account for about 40%, of which the ratio of methanol to acetone is about 2:1; water accounts for about 45%; furfural accounts for about 10%; and the remaining 5% is acetic acid and other organic impurities.

[0004] Currently, most furfural producers in China outsource the disposal of the light component condensate to hazardous waste treatment. The outsourcing cost for each ton of light component is approximately 5,000 yuan, which not only significantly increases the production cost of furfural but also poses a risk of odor and VOC emissions during the temporary storage, transfer, and disposal of the light component, due to its strong pungent odor and volatility. This increases the environmental pressure and safety management risks for these companies.

[0005] Existing patent document CN116534933A discloses an apparatus and process for recovering and extracting furfural from process wastewater. The system includes a wastewater feeding unit, a light-light-removal distillation column, a recovery distillation column, an aldehyde separation tank, a liquid separation tank, and a storage tank, used to recover furfural from furfural-containing wastewater. The main technical feature of this patent is the use of a multi-stage distillation and condensation separation combination to treat the wastewater, achieving furfural enrichment. This scheme is similar to the present invention in that it also achieves the recovery and extraction of furfural-containing systems. However, its process flow does not involve the step of adding industrial furfural or crude aldehyde to adjust the composition, nor does it explicitly mention the operation steps of methanol-acetone azeotropic separation and rapid cooling stratification. Therefore, it differs significantly from the present invention in terms of overall separation efficiency and material recovery rate.

[0006] Patent document CN102417496A discloses improved operating conditions for the removal of light components from furfural stock solution. This method involves distillation at a bottom temperature of 100–105°C, a top temperature of 65–70°C, and a reflux ratio of 1:20 to remove light components from the furfural stock solution. While this invention focuses on the "light component removal" operation of the furfural stock solution, and its distillation parameters are similar to the primary light component removal steps of this invention, it does not involve innovative measures such as azeotropic separation control, furfural replenishment for composition adjustment, or low-temperature rapid quenching for stratification. Therefore, its technical effect is mainly limited to improving the stability of furfural distillation, without achieving the reuse of light component resources.

[0007] Patent document CN102675265A deals with furfural main product liquid or crude aldehyde refining process, rather than the recovery of light components from the light component removal condensate in furfural production; furthermore, it uses a multi-tower continuous distillation system, which is complex and requires high equipment investment, failing to reflect the simplified feature of this invention that completes multi-step separation and recovery within a single batch unit. Patent CN114805257A does not involve the recovery and separation of light components such as methanol and acetone, nor does it propose a resource utilization scheme for the effective components in the light component removal condensate; it has the same technical problems as the above.

[0008] Furthermore, since the production volume of light condensate is relatively large, and some of its components (such as furfural, methanol, and acetone) have high recycling value, if the separation and reuse of these effective components can be achieved, not only can production costs be significantly reduced, but also the amount of hazardous waste generated and the environmental burden can be reduced.

[0009] In summary, although various improvement schemes for furfural waste liquid or distillation processes have been proposed in the prior art, none of them involve the comprehensive technical measures adopted in this invention, such as adding furfural to adjust the composition, rapid cooling and stratification, methanol-acetone azeotropic cutting, and multi-step separation and recovery in a single unit. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to overcome the existing defects and provide an apparatus and method for recovering furfural light components. The method forms a synergistic chain of "light component removal distillation - composition adjustment - second distillation - rapid cooling and stratification - vacuum distillation", which not only solves the low-boiling azeotropic separation of methanol / acetone, but also pushes the system to a favorable aldehyde-water separation range by adjusting the composition. Finally, high-purity furfural is recovered in vacuum distillation, and the separation efficiency and recovery rate are significantly improved, which can effectively solve the problems in the background technology.

[0011] To achieve the above objectives, the present invention provides the following technical solution: an apparatus and method for recovering furfural light components, comprising an apparatus for recovering furfural light components, the apparatus including a light component removal tower, a tower bottom liquid storage tank, an extraction overflow tank, and an aldehyde recovery tower. The inlet of the light component removal tower is connected to the pipeline for conveying the light component removal condensate generated during the furfural production process. The inlet of the tower bottom liquid storage tank is connected to the lower outlet of the light component removal tower, and the outlet of the tower bottom liquid storage tank is connected to the inlet of the light component removal tower via a pipeline. This method realizes a secondary distillation cycle of the material. The tower bottom liquid storage tank is equipped with a stirring device for receiving the residual liquid from the light component removal tower and adding 14-16 wt% industrial furfural or 15-17 wt% of the residual liquid mass. The crude furfural product (wt%) is stirred evenly and then pumped into the light phase removal tower via pipeline. The stirring device in the bottom liquid storage tank of this tower is a conventional technology and will not be described in detail here. The bottom outlet of the light phase removal tower is connected to a second condenser, and the outlet of the second condenser is connected to the extraction overflow tank. This second condenser is used to rapidly cool the bottom liquid of the light phase removal tower to ≤30℃ after the second distillation. The upper light phase overflow port of the extraction overflow tank is connected to the bottom liquid storage tank or wastewater treatment system via pipeline, and the lower heavy phase outlet of the extraction overflow tank is connected to the inlet of the aldehyde recovery tower via a transfer pump. This extraction overflow tank is used for static stratification, with the upper layer being the aqueous phase and the lower layer being the aldehyde-rich phase, wherein the furfural content is ≥93%. The aldehyde recovery tower has a purity ≥98.0 wt% and a moisture content ≤0.2 wt%. The top of the aldehyde recovery tower is connected to a reflux controller via a condenser. The reflux outlet of the reflux controller is connected to the reflux port at the top of the aldehyde recovery tower. The outlet of the reflux controller is connected to a furfural tank via a pipeline. The furfural tank is used to store the recovered furfural product. The aldehyde recovery tower operates under a pressure of -0.094 to -0.098 MPa with a reflux ratio of 2 to 5. It is used for vacuum distillation of the aldehyde-rich phase. The furfural product is collected at the top of the tower with a purity ≥98.0 wt% and a moisture content ≤0.2 wt%. The method includes the following steps: Step 1: Light-light component removal and distillation separation. The light-light component removal condensate produced during furfural production is used as raw material and fed into the light-light component removal column for batch distillation under atmospheric pressure. The bottom temperature of the column is controlled at 58-63℃ and the top temperature is below 60℃. The top condensate is collected as acetone and methanol-acetone azeotropic fractions. The bottom liquid of the light-light component removal column is a mixture mainly containing furfural, methanol and water. Step 2: Composition adjustment. Add 14-16 wt% industrial furfural or 15-17 wt% crude furfural product (coarse furfural) to the residue in the bottom of the column, stir and mix evenly to adjust the composition of the mixture to be close to the furfural-water azeotropic composition, and then send it back to the light-light distillation column for a second distillation. Step 3: Second distillation: Distillation is carried out under atmospheric pressure, with the bottom temperature controlled at 85-95℃ and the top temperature below 80℃. Heating is stopped when the bottom temperature reaches 97.8℃, and the bottom liquid is obtained. Step 4: Rapid Cooling and Separation: The bottom liquid of the tower is rapidly cooled to ≤30℃ via condenser II and then enters the extraction overflow tank for separation. The upper layer is the aqueous phase, and the lower layer is the aldehyde-rich phase. The upper aqueous phase is discharged through the overflow port, and the lower aldehyde-rich phase is sent to the aldehyde recovery tower via a transfer pump; the furfural content in the aldehyde-rich phase is ≥93 wt%. Step 5: Recover furfural by vacuum distillation. The aldehyde-rich phase is fed into a vacuum distillation column and subjected to intermittent distillation under a pressure of -0.094 to -0.098 MPa. The reflux ratio is controlled at 2 to 5, and the furfural product is collected by condensation at the top of the column.

[0012] Through the above steps, the purity of the furfural product is ≥98.0 wt%, and the moisture content is ≤0.2 wt%.

[0013] The furfural tank is equipped with an inert gas protection system, with nitrogen or carbon dioxide as the inert gas, to prevent furfural from oxidizing and deteriorating. The furfural tank is also equipped with an online sampling port for monitoring product purity.

[0014] Furthermore, the light-weight removal tower is a packed tower structure, and the packing uses stainless steel Pall rings or metal stepped rings.

[0015] Furthermore, the bottom liquid storage tank is a horizontal stirred tank structure, equipped with a variable frequency stirrer with a stirring speed of 50-200 r / min. The tank is equipped with a level gauge and a reflux pipeline to control the stability of the system composition after adding furfural. The stirred tank structure, variable frequency stirrer and control method configured in the bottom liquid storage tank are existing conventional technologies and will not be described in detail here.

[0016] Furthermore, the second condenser is a shell-and-tube heat exchanger or a spiral plate heat exchanger, with circulating cooling water or ethylene glycol solution as the cooling medium, a temperature of 10-20°C, and a heat exchange area of ​​5-15 m², used to reduce the temperature of the bottom liquid in the tower to ≤30°C within 3 minutes.

[0017] Furthermore, the top of the light component removal tower is connected to the light component tank via a condenser. This light component removal tower is used for intermittent distillation of the light component removal condensate under atmospheric pressure, controlling the bottom temperature of the tower to be 58-63°C and the top temperature to be below 60°C. The acetone and methanol-acetone azeotrope are condensed at the top of the tower and then enter the light component tank, while the bottom liquid retains furfural, methanol and water components.

[0018] Furthermore, the extraction overflow tank (6) is a vertical cylindrical gravity stratification tank with a phase separation baffle and an overflow weir inside. The upper light phase is discharged through the overflow port, and the lower heavy phase is pumped into the aldehyde recovery tower (7) through the bottom outlet. The stratification time is 20 to 60 minutes.

[0019] Furthermore, during the second distillation or aldehyde recovery process, 0.5–3 wt% of a water-capturing agent is introduced into the bottom of the column. The water-capturing agent is ethyl formate, ethyl acetate, or acetic anhydride. The reaction-separation coupling operation is carried out under the conditions of a bottom temperature of 85–100°C and a top temperature of 75–80°C. The water-capturing agent reacts with water to produce acetic acid and ethanol, forming a low-boiling-point acetic acid-ethanol azeotrope, which is continuously removed with the distillate from the top of the column. This disrupts the furfural-water azeotropic equilibrium, achieving a reaction-driven separation process. This results in a furfural product purity ≥ 98.5 wt%, a 25% reduction in system energy consumption compared to traditional distillation processes, and eliminates the need for additional pressure reduction operations.

[0020] This invention proposes a reactive distillation process for aldehyde-water decoupling based on the reaction-separation coupling principle, addressing the challenges of complete separation and high energy consumption in furfural-water azeotropic systems. The process introduces a water-capturing reactant into the bottom of the second distillation column or aldehyde recovery column, allowing water in the azeotropic system to undergo a controlled chemical reaction with the reactant under high-temperature conditions in the bottom of the column, thereby achieving chemical transformation and removal of water. This effectively disrupts the stable azeotropic equilibrium between furfural and water, altering the vapor-liquid equilibrium and enabling efficient separation and enrichment of furfural components in the bottom of the column under normal pressure. Unlike traditional distillation methods that rely solely on physical evaporation, this invention achieves simultaneous reactive dehydration and separation through a "chemical reaction-driven thermodynamic equilibrium migration" approach, significantly improving the purity and energy utilization efficiency of furfural.

[0021] In this invention, the water-capturing agent is selected from one or more of ethyl formate, ethyl acetate, or acetic anhydride, and its addition amount is 0.5–3 wt% of the mass of the liquid in the bottom of the column, preferably 1.5 wt%. The water-capturing agent reacts with water in the aldehyde-water mixture at a bottom temperature of 85–100°C to produce acetic acid and ethanol, as shown in the following reaction equation: H2O+CH3COOC2H5⇌CH3COOH+C2H5OH The acetic acid-ethanol produced in the reaction forms a new low-boiling azeotrope with a boiling point of approximately 78°C, lower than the aldehyde-water azeotropic point (97.8°C). Therefore, while the reaction proceeds in the bottom of the column, the generated acetic acid-ethanol azeotrope is continuously distilled off from the top and recovered by condensation. As the reaction continues, water in the bottom of the column is continuously consumed, significantly reducing the system's water activity and disrupting the aldehyde-water azeotropic relationship, thus gradually enriching furfural. The synergistic effect of the reaction and separation leads to a dynamic equilibrium shift in the system, allowing furfural to achieve high-purity separation under normal pressure without the need for additional vacuum distillation.

[0022] The integrated reaction-separation distillation process of this invention enables the high-purity recovery of furfural products. Experimental results show that when ethyl acetate is used as the water-capturing agent at a concentration of 1.5 wt% of the bottom liquid, after 1.2 hours of operation under conditions of a top temperature controlled at 75–80°C and a bottom temperature controlled at 90–95°C, the purity of furfural in the bottom of the column can reach over 98.5 wt%, with a moisture content ≤0.2 wt%. Compared with traditional vacuum distillation processes, this invention reduces system energy consumption by approximately 25%, shortens separation time by 20%, and avoids the equipment complexity and energy loss associated with vacuum operation. Furthermore, the acetic acid-ethanol mixture collected from the top of the column can be recycled as a by-product solvent, achieving closed-loop resource recycling and green production. This integrated reaction-separation process not only achieves complete separation of the aldehyde-water azeotropic system but also forms an innovative "reaction-driven separation" mechanism, exhibiting significant advantages in energy saving, consumption reduction, and process simplification.

[0023] Furthermore, the extraction overflow tank is equipped with a layered enhancement module, which includes: an ultrasonic oscillation device installed at the bottom or inside the tank wall, with an ultrasonic frequency of 20–40 kHz and a power density of 10–30 W / L, used to apply ultrasonic disturbance to the aldehyde-water mixture, generating microbubble disturbance through cavitation effect to destroy the aldehyde-water interfacial emulsion layer; a low-polarity oil film auxiliary system located above the liquid surface inside the tank, which forms an oil film layer with a thickness of 1–3 mm by spraying or dripping low-polarity oily additives to reduce the interfacial tension of the system, inhibit reemulsification, and promote phase separation; the tank is equipped with a temperature and amplitude control unit to control the temperature inside the tank at 25–35°C, and the ultrasonic oscillation duration is 3–5 minutes; Working principle and effect The ultrasonic device is activated when the distillate from the bottom of the column enters the extraction overflow tank. Ultrasound generates cavitation in liquids, forming a large number of microbubbles, and local pressure pulses disrupt the aldehyde-water emulsion interface. At the same time, the low polarity oil film reduces the surface tension of the system, making the stratification driven by the density difference between the aqueous phase and the aldehyde phase faster and more stable. After ultrasonic disturbance for 3–5 minutes, the oscillation is stopped, and the liquid is allowed to settle naturally. The stratification time has been reduced from 20–60 min to 5–10 min; The purity of furfural in the lower aldehyde-rich phase was increased to ≥95 wt%, and the entrained moisture was significantly reduced; The upper aqueous phase is clear and free of obvious aldehyde phase entrainment, reducing the burden of subsequent processing.

[0024] Furthermore, the column bottom liquid temporary storage tank is equipped with an adaptive composition adjustment module, which includes: The online analysis unit uses a near-infrared (NIR) or Fourier transform infrared (FTIR) concentration analyzer. The probe is inserted into the bottom liquid storage tank to detect the concentration of furfural, methanol, and water in the bottom liquid in real time. The measurement cycle is 10-30 seconds, and the measurement error is ≤±0.5%. The control and calculation unit includes a programmable logic controller (PLC) and a stoichiometric model. The control and calculation unit automatically calculates the required proportion of furfural to be added based on real-time detection data and adjusts the addition amount dynamically within the range of 12-18 wt% to keep the composition of the mixture in the bottom of the tower within the azeotropic ratio range of furfural and water. The execution unit includes a variable frequency addition pump and a stirring linkage system, which is used to automatically add industrial furfural according to the control signal and mix it evenly. After addition, the system automatically re-measures the concentration and forms a closed-loop feedback. The adaptive composition adjustment module enables azeotropic point self-locking control of the bottom liquid composition, ensuring that the composition fluctuation of the mixed liquid entering the light-light removal tower does not exceed ±0.3%, thereby improving the azeotropic separation efficiency and furfural recovery rate of the light-light removal tower.

[0025] Furthermore, a dynamic azeotropic point migration control system is installed within the light-weight removal tower. This system includes: The microwave energy field module has a frequency of 2450 MHz and a power of 200-500 W. The microwave energy is radiated through the tower wall to the liquid-gas mixing zone inside the tower, selectively absorbing the highly polar water molecules in the system and forming a local temperature gradient of 0.5-1.0℃. The variable pressure control module controls the tower top pressure to fluctuate periodically within the range of 0.095 to 0.105 MPa via a servo valve, and is synchronized with the microwave power adjustment signal. The temperature and pressure feedback unit is used to monitor the temperature distribution and pressure changes in the column in real time, forming a closed loop of microwave power and pressure coordinated control, thereby forming a dynamic azeotropic adjustment zone in the middle of the column to achieve non-azeotropic distillation separation of the furfural-methanol-water system. Among them, through the dynamic azeotropic point migration control system, the separation efficiency of azeotropic components is improved by 15-20%, the furfural content in the top fraction of the column is ≤0.05 wt%, and the total energy consumption of the system is reduced by 10-15%.

[0026] To achieve a uniform distribution of microwave energy field inside the tower, the outer wall of the light-removing tower in this embodiment is covered with a microwave radiation cavity; the cavity adopts a stainless steel shielding structure and is equipped with waveguides and reflectors to uniformly couple microwave energy into the tower along the tower wall.

[0027] A pressure servo valve is installed at the top of the tower, and the servo valve adjusts the pressure at the top of the tower in real time by a PID control system. The tower body is equipped with three temperature sampling points (top, middle, and bottom) and one pressure sensor along the height direction to form a temperature-pressure closed-loop feedback system. The microwave power adjustment and the servo valve action are synchronously controlled by a PLC, with a control accuracy of ±0.1℃ and ±0.002 MPa, thereby realizing dynamic azeotropic point migration control within the tower.

[0028] Operating parameters: Microwave frequency: 2450 MHz; Power: 300 W; Top pressure: 0.095–0.105 MPa; Modulation period: 30–60 s; Reflux ratio: 2.0–3.5; Distillation time: 3–4 h.

[0029] Control logic: When the temperature at the top of the tower deviates from the target value by ±0.3℃, the system automatically adjusts the microwave power by ±50W; synchronously adjusts the servo valve opening by ±2% to control the slight fluctuation of the pressure inside the tower; generates a "microwave power - tower top pressure" coordinated curve in real time; and automatically maintains the optimal dynamic separation state.

[0030] This invention is a process control type invention. The tower structure and cavity arrangement can be realized using existing industrial standard equipment. Those skilled in the art can directly implement this technical solution based on existing technology and the above description.

[0031] Compared with the prior art, the beneficial effects of the present invention are: 1. This method fully utilizes the differences in boiling points and azeotropic properties among the components. First, the methanol-acetone azeotrope is effectively cut in the light component removal column under conditions where the top temperature is below 60°C. Then, 14–16 wt% of industrial furfural or 15–17 wt% of crude furfural product is added to the bottom of the column to adjust the composition, making the mixture composition close to the furfural-water azeotropic composition, thereby improving the separation equilibrium conditions. After two distillations, combined with rapid quenching and vacuum distillation, efficient separation of the multi-component system of furfural, acetone, and methanol is achieved. Compared with existing processes, the furfural recovery rate can reach 8–9% of the total amount of light component removal condensate, the furfural yield is increased by about 0.8–1.0 percentage points, and the separation efficiency is increased by about 20–30%.

[0032] 2. In traditional furfural production, the light components are generally sold off as hazardous waste, with disposal costs as high as approximately 5,000 yuan per ton, leading to resource waste and environmental burden. This invention reduces the amount of hazardous waste to be treated by more than 70% through the graded recovery of the main recyclable materials (furfural, acetone, and methanol) in the light components. By rationally controlling the temperature range between the top and bottom of the column, reducing repeated heating processes, and adopting a design for rapid cooling heat exchange and vacuum distillation energy reuse, the system energy consumption is reduced by approximately 25-30% compared to conventional multi-tower distillation. Based on the production of one ton of furfural, the overall cost is reduced by approximately 40 yuan, demonstrating significant energy-saving and consumption-reducing effects and good economic viability for industrial applications.

[0033] 3. By employing low-temperature rapid cooling stratification technology in the aldehyde-water separation stage, the bottom liquid of the tower is rapidly cooled to below 30°C via a heat exchanger, allowing the furfural layer to completely separate from the aqueous phase within 3-5 minutes. The purity of the furfural layer can reach over 93 wt%, and the stratification time is shortened by 80% compared to traditional natural cooling. At the same time, it reduces the risk of furfural thermal polymerization and ensures stable product quality. The entire unit integrates four functional modules: light-light distillation, composition adjustment, rapid cooling stratification, and vacuum distillation. It achieves secondary distillation of materials by pipeline circulation, resulting in a compact structure and a reduction of approximately 40% in the number of equipment. It can be directly used to upgrade existing furfural production lines, achieving the synergistic goal of waste liquid reduction and resource utilization. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the connection structure of the recycling device of the present invention.

[0035] In the diagram: 1. Condenser I, 2. Light component tank, 3. Light component removal tower, 4. Tower bottom liquid temporary storage tank, 5. Condenser II, 6. Extraction overflow tank, 7. Aldehyde recovery tower, 8. Furfural tank, 9. Reflux controller, 10. Condenser III. Detailed Implementation

[0036] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0037] Please see Figure 1This invention provides a technical solution: an apparatus and method for recovering furfural light components, comprising an apparatus for recovering furfural light components, the apparatus including a light component removal tower 3, a tower bottom liquid storage tank 4, and an extraction overflow tank 6. The inlet of the light component removal tower 3 is connected to the light component removal condensate conveying pipeline generated during the furfural production process. The inlet of the tower bottom liquid storage tank 4 is connected to the lower outlet of the light component removal tower 3, and the outlet of the tower bottom liquid storage tank 4 is connected to the inlet of the light component removal tower 3 through a pipeline to achieve secondary distillation circulation of the material. The tower bottom liquid storage tank 4 is equipped with a stirring device for receiving the residual liquid from the bottom of the light component removal tower 3 and adding 14-16 wt% industrial furfural or 15-17 wt% of the residual liquid mass. Crude furfural (wt%) is stirred evenly and pumped into the light phase removal tower 3. The bottom outlet of the light phase removal tower 3 is connected to condenser 5, and the outlet of condenser 5 is connected to the extraction overflow tank 6 to rapidly cool the bottom liquid after the second distillation to ≤30℃. The upper light phase overflow port of the extraction overflow tank 6 is connected to the bottom liquid temporary storage tank 4 or the wastewater treatment system via a pipeline, and the lower heavy phase outlet of the extraction overflow tank 6 is connected to the inlet of the aldehyde recovery tower 7 via a transfer pump. The extraction overflow tank 6 is used for static stratification, with the upper layer being the aqueous phase and the lower layer being the aldehyde-rich phase, wherein the furfural content is ≥93 wt%. The top of the aldehyde recovery tower 7 is connected to the reflux controller 9 via condenser 3 10, and the reflux outlet of the reflux controller 9 is connected to the top reflux port of the aldehyde recovery tower 7 via a pipeline. The outlet of the reflux controller 9 is connected to the furfural tank 8 via a pipeline. The furfural tank 8 is used to store the recovered furfural product. The aldehyde recovery tower 7 operates at -0.094 to -0.098 °C. Operating under MPa pressure conditions with a reflux ratio of 2–5, it is used for vacuum distillation of aldehyde-rich phases, with furfural product collected at the top of the column. The furfural purity is ≥98.0 wt%, and the moisture content is ≤0.2 wt%. The method includes: Step 1, light-light phase removal distillation separation: The condensate from the light-light phase removal is fed into the light-light phase removal column 3 for batch distillation under atmospheric pressure, controlling the bottom temperature at 58–63℃ and the top temperature at <60℃. The condensate collected at the top of the column is acetone and methanol-acetone azeotropic fraction; the bottom residue is a mixture containing furfural, methanol, and water; Step 2, composition adjustment: 14–16 wt% of industrial furfural or 15–17 wt% of the residue mass is added to the bottom residue. wt% furfural is stirred evenly to make the mixture composition close to the furfural-water azeotrope, and then returned to the light-light content removal tower 3 for a second distillation; Step 3, second distillation: heating distillation under atmospheric pressure, controlling the bottom temperature of the tower to 85-95℃ and the top temperature of the tower to <80℃. When the temperature of the tower bottom reaches 97.8℃, heating is stopped to obtain the tower bottom liquid; Step 4, rapid cooling and separation: the tower bottom liquid is rapidly cooled to ≤30℃ by condenser 5 and then enters the extraction overflow tank 6 for separation. The upper layer is the aqueous phase and the lower layer is the aldehyde-rich phase. The upper aqueous phase is discharged through the overflow port, and the lower aldehyde-rich phase is sent to the aldehyde recovery tower 7 by the transfer pump; the furfural content in the aldehyde-rich phase is ≥93 wt%; Step 5, vacuum distillation to recover furfural: the aldehyde-rich phase is in the range of −0.094 to −0.Intermittent distillation is performed at 0.98 MPa, with a reflux ratio controlled at 2–5. Furfural product is collected by condensation at the top of the column. The furfural product obtained through the above steps has a purity ≥98.0 wt% and a moisture content ≤0.2 wt%. Furfural tank 8 is equipped with inert gas (nitrogen or carbon dioxide) protection and an online sampling port to monitor product purity.

[0038] Implementation in stages: (1) Separation of furfural from methanol and acetone (light weight removal distillation) The light-light condensate produced during furfural production is used as raw material and distilled in a batch distillation unit (light-light condensate removal column) under atmospheric pressure. Acetone has a boiling point of 56.05℃, and methanol has a boiling point of 64.7℃. The two can form an azeotrope (azeotropic point 55.7℃; methanol 12.1 wt%, acetone 87.9 wt%). The raw material contains approximately 40 wt% methanol and acetone (methanol:acetone ≈ 2:1), approximately 45 wt% water, and approximately 10 wt% furfural. By controlling the column top temperature to <60℃, acetone and the methanol-acetone azeotrope are selectively condensed and collected from the top of the column, leaving a mixture mainly composed of furfural, methanol, and water in the bottom of the column.

[0039] (2) Separation of methanol and aldehyde azeotropic system (composition adjustment + second distillation) Methanol and water do not form an azeotrope, nor do methanol and furfural; furfural and water do form an azeotrope (97.8℃, furfural approximately 35 wt%, water approximately 65 wt%). Given that the original column bottom composition usually deviates from this azeotropic ratio, which is detrimental to subsequent aldehyde-water separation, 14.25 wt% industrial furfural or 15.50 wt% crude furfural product (raw aldehyde) is added to the column bottom mixture and thoroughly stirred to bring the system composition close to the furfural-water azeotropic point. A second distillation is then carried out under atmospheric pressure, controlling the bottom temperature at 85–95℃ and the top temperature at <80℃. Heating is stopped when the column bottom temperature reaches 97.8℃ (the furfural-water azeotropic point under atmospheric pressure, with an allowable deviation of ±0.5℃). The resulting bottom condensate is an aldehyde-water azeotrope.

[0040] (3) Rapid cooling and stratification of aldehyde-water azeotrope After heating is stopped, the bottom liquid is rapidly passed through a cooler with a temperature ≤30℃ to quickly cool the aldehyde-water azeotrope. After rapid cooling, the system undergoes gravity stratification: the upper layer is the aqueous phase, and the lower layer is the aldehyde phase (furfural phase), with a furfural content of ≥93 wt%. The aldehyde-rich phase (≥93 wt%) is separated from the upper aqueous phase by extraction or overflow separation, achieving preliminary separation of aldehyde and water.

[0041] (4) Vacuum distillation for aldehyde recovery The resulting aldehyde-water mixture (aldehyde-rich phase) with a content of ≥93 wt% was pumped into a vacuum distillation column and operated under set reflux and collection conditions. Furfural product was collected by condensation at the top of the column, achieving high-quality recovery of furfural from the light components.

[0042] This implementation method is based on a multi-stage synergistic separation mechanism: First, utilizing the relatively low boiling point of methanol and acetone and the low boiling point behavior of the methanol-acetone azeotrope, the light-end azeotrope is selectively cut off in the light-end distillation column 3 under the condition that the column top temperature is below 60°C, so that furfural is mainly retained in the column bottom residue; then, by adding a certain proportion of industrial furfural or coumarin to the column bottom residue, the composition of the mixture is pushed closer to the furfural-water azeotropic point, so that the vapor-liquid balance in the column during the subsequent atmospheric pressure second distillation is more conducive to the upward migration of water and trace amounts of light end products, and furfural is enriched on the column bottom side; when the column bottom temperature reaches the furfural-water azeotropic point of 97.8°C, heating is terminated to avoid furfural overheating and self-condensation; then, rapid heat exchange cooling (≤3°C) is implemented. The temperature is reduced to ≤30℃ within min. Utilizing the density and miscibility differences between the furfural and aqueous phases, gravity stratification is achieved within the extraction overflow tank 6, rapidly obtaining a stable state where the aldehyde-rich phase and aqueous phase are separated. The aldehyde-rich phase is then fed into the aldehyde recovery tower 7, where it is processed under reduced pressure (−0.094~−0.098℃). To reduce the relative volatility and heat load of the system under pressure (MPa), a reflux ratio of 2-5 is set to further remove trace water and impurities. Furfural reaching the target purity is collected at the top of the column, while high-boiling impurities are collected at the bottom. In the whole process, the pipeline loop of the bottom liquid storage tank 4 and the light-weight removal column 3 forms a closed loop of primary light-weight removal, composition adjustment, and secondary distillation, allowing the material to enter the column twice. The furfural tank 8 is covered with inert gas and sampled online to limit oxidative polymerization and achieve quality monitoring. The key control points include: temperature windows of each column section (58-63℃, <60℃, 85-95℃, <80℃ and 97.8℃ endpoint), cooling end temperature ≤30℃, liquid level and overflow height of the stratification tank, pressure reduction and reflux ratio stability. Through the coupling of the above thermodynamic separation, composition adjustment and physical property stratification, the continuous connection of light-weight end cutting, azeotropic elimination and high-purity purification is completed.

[0043] This implementation method achieves a series operation of "light component removal—composition adjustment—re-distillation—quenching and stratification—reduced pressure purification" within a single batch unit: ① After light component removal, furfural mainly remains in the bottom of the distillation column, reducing the loss of target components; ② Adding furfural brings the mixture closer to the furfural-water azeotropic composition, improving relative volatility and plate efficiency requirements, and increasing the driving force for water migration during the second distillation; ③ Quenching to ≤30℃ reduces the risk of furfural condensation and oxidation, obtaining clear two phases within 3-5 minutes, with the aldehyde-rich phase containing ≥93 wt% furfural, significantly shortening the stratification time and reducing entrainment; ④ Reduced pressure distillation achieves deep dehydration at a lower temperature, and the product can stably reach ≥98.0 wt% purity and ≤0.2 wt% moisture; ⑤ The combination of pipeline circulation and batch operation requires fewer pieces of equipment and is easy to modify, making it suitable for upgrading existing furfural production lines, significantly reducing the amount of hazardous waste sold and improving VOCs management; ⑥ Inert protection and online sampling enhance quality consistency and operational safety, reducing the risk of finished product discoloration and acid value increase.

[0044] In one possible implementation, the light-light removal tower 3 is a packed tower structure, with stainless steel Pall rings or metal stepped rings as packing. High specific surface area packing is used in the light-light removal rectification section to enhance mass transfer. The Pall rings or stepped rings form a fully wetted liquid film and turbulent gas phase in the tower, increasing the equivalent value of interphase contact area and plate efficiency, making it easier for methanol-acetone azeotropes to migrate from the top of the tower and be condensed and cut off. At the same time, it reduces the pressure drop, which is beneficial for stable operation at atmospheric pressure and low tower top temperature (<60°C).

[0045] Compared to tray towers, packed towers can achieve a higher number of mass transfer units at the same tower height, shorten the cutting time, and reduce the amount of reboiling steam used; the stainless steel material is resistant to furfural and organic acid corrosion, has a long service life, and is easy to maintain.

[0046] The packing can be replaced with structured packing (such as stainless steel corrugated structured packing). The specific surface area and porosity of the packing are checked according to the throughput and allowable pressure drop. A liquid redistributor can be added inside the tower to suppress channeling.

[0047] In one possible implementation, the bottom liquid storage tank 4 is a horizontal stirred tank structure equipped with a variable frequency stirrer with a stirring speed of 50-200 r / min. The tank is equipped with a level gauge and a reflux line to control the stability of the system composition after furfural addition. The horizontal structure increases the interfacial residence area, which is conducive to the rapid and uniform mixing of industrial furfural or aldehyde with the bottom liquid. The variable frequency speed regulation adjusts the shear in the range of 50-200 r / min in the low viscosity system to avoid excessive aeration and volatilization loss. The level gauge and reflux line form a linkage control between the material quantity and composition to ensure that the mixture before being sent back to the light removal tower 3 is close to the furfural-water azeotropic composition.

[0048] In one possible implementation, condenser 5 is a shell-and-tube heat exchanger or a spiral plate heat exchanger, with circulating cooling water or ethylene glycol solution as the cooling medium, a temperature of 10–20°C, and a heat exchange area of ​​5–15 m². It is used to reduce the temperature of the bottom liquid to ≤30°C within 3 minutes. Through a reasonable design of the heat transfer area and logarithmic mean temperature difference, the bottom liquid can complete sensible heat removal in a short time and quickly cross the easily polymerizable temperature range of furfural. The ethylene glycol solution can still provide a stable cold source even under high ambient temperatures in summer. This shortens the stratification cycle, reduces the risk of thermal polymerization and discoloration, and stably obtains ≥93 wt% aldehyde-rich phase.

[0049] In one possible implementation, the top of the light component removal tower 3 is connected to the light component tank 2 via a condenser 1. The light component removal tower 3 performs intermittent distillation on the light component removal condensate under normal pressure, controlling the bottom temperature of the tower to be 58-63°C and the top temperature to be below 60°C. The acetone and methanol-acetone azeotrope are condensed at the top of the tower and then enter the light component tank 2. The bottom liquid of the tower retains furfural, methanol and water components.

[0050] By controlling the low top temperature and appropriate reflux, methanol, acetone and their azeotropic products are selectively ejected using their low boiling characteristics; condenser 1 condenses the top vapor into a light component liquid phase and collects it into light component tank 2. Condenser 1 can be equipped with a variable frequency circulating water pump and a PID temperature control valve to maintain a stable reflux temperature at the top of the tower; light component tank 2 can be equipped with a breather valve and a flame arrester to improve safety.

[0051] In one possible implementation, the extraction overflow tank 6 is a vertical cylindrical gravity stratification tank with a phase separation baffle and an overflow weir inside. The upper light phase is discharged through the overflow port, and the lower heavy phase is pumped into the aldehyde recovery tower 7 through the bottom outlet. The stratification time is 20 to 60 minutes.

[0052] In one possible implementation, during the second distillation or aldehyde recovery process, 0.5–3 wt% of a water-capturing agent is introduced into the bottom of the column. The water-capturing agent is ethyl formate, ethyl acetate, or acetic anhydride. The reaction-separation coupling operation is carried out under the conditions of a bottom temperature of 85–100°C and a top temperature of 75–80°C. The water-capturing agent reacts with water to produce acetic acid and ethanol, forming a low-boiling acetic acid-ethanol azeotrope, which is continuously removed with the top of the column, thereby disrupting the furfural-water azeotropic equilibrium and achieving reaction-driven separation. This results in a furfural product purity ≥98.5 wt%, a 25% reduction in system energy consumption compared to traditional distillation processes, and the elimination of the need for additional pressure reduction operations.

[0053] By introducing esters or anhydrides that can react with water into the bottom of the column, the water in the system is consumed and an acetic acid-ethanol azeotrope with a lower boiling point is generated, causing water to be continuously carried out from the top. The vapor-liquid equilibrium is disturbed by the chemical reaction, which effectively increases the relative volatility of furfural, thus achieving high-purity separation under normal pressure.

[0054] While maintaining normal pressure operation, it can obtain ≥98.5 wt% furfural and ≤0.2 wt% water, save about 25% of energy consumption, shorten the separation time by about 20%, and simplify the configuration of the vacuum system; the by-product acetic acid-ethanol at the top of the column can be recovered and reused.

[0055] The water-catching agent is added by dripping or by a continuous low-flow metering pump; the preferred dosage of ethyl acetate is about 1.5 wt%; a selective condensation-phase separation unit can be added at the top of the column to recover the acetic acid-ethanol azeotrope.

[0056] This invention proposes a reactive distillation process for aldehyde-water decoupling based on the reaction-separation coupling principle, which addresses the problems of incomplete separation and high energy consumption in the furfural-water azeotropic system. The process introduces a water-capturing reactant into the bottom of the second distillation column or aldehyde recovery column, allowing water in the azeotropic system to undergo a controlled chemical reaction with the reactant under high-temperature conditions in the bottom of the column, thereby achieving chemical transformation and removal of water. This effectively disrupts the stable azeotropic equilibrium between furfural and water, altering the vapor-liquid equilibrium of the system, enabling efficient separation and enrichment of furfural components in the bottom of the column under normal pressure. Unlike traditional distillation methods that rely solely on physical evaporation, this invention achieves simultaneous reactive dehydration and separation through a "chemical reaction-driven thermodynamic equilibrium migration" approach, significantly improving the purity and energy utilization efficiency of furfural.

[0057] In this invention, the water-capturing agent is selected from one or more of ethyl formate, ethyl acetate, or acetic anhydride, and its addition amount is 0.5–3 wt% of the mass of the liquid in the bottom of the column, preferably 1.5 wt%. The water-capturing agent reacts with water in the aldehyde-water mixture at a bottom temperature of 85–100°C to produce acetic acid and ethanol, and the reaction equation is as follows: H2O+CH3COOC2H5⇌CH3COOH+C2H5OH The acetic acid-ethanol produced in the reaction forms a new low-boiling azeotrope with a boiling point of approximately 78°C, which is lower than the aldehyde-water azeotropic point (97.8°C). Therefore, while the reaction is proceeding in the bottom of the column, the acetic acid-ethanol azeotrope is continuously distilled off from the top of the column and recovered by condensation. As the reaction continues, the water in the bottom of the column is continuously consumed, the water activity of the system decreases significantly, the aldehyde-water azeotropic relationship is disrupted, and furfural gradually accumulates. The synergistic effect of reaction and separation leads to the dynamic equilibrium shift of the system, enabling high-purity separation of furfural under normal pressure conditions without the need for additional vacuum distillation.

[0058] The integrated reaction-separation distillation process of this invention enables the high-purity recovery of furfural products. Experimental results show that when ethyl acetate is used as the water-capturing agent at a concentration of 1.5 wt% of the bottom liquid, after 1.2 hours of operation under conditions of a top temperature controlled at 75–80°C and a bottom temperature controlled at 90–95°C, the purity of furfural in the bottom of the column can reach over 98.5 wt%, with a water content ≤0.2 wt%. Compared with traditional vacuum distillation, this invention reduces system energy consumption by approximately 25%, shortens separation time by 20%, and avoids the equipment complexity and energy loss associated with vacuum operation. Furthermore, the acetic acid-ethanol mixture collected from the top of the column can be recycled as a by-product solvent, achieving closed-loop resource recycling and green production. This integrated reaction-separation process not only achieves complete separation of the aldehyde-water azeotropic system but also forms an innovative "reaction-driven separation" mechanism, exhibiting significant advantages in energy saving, consumption reduction, and process simplification. This invention proposes an aldehyde-water decoupling reactive distillation process based on the reaction-separation coupling principle to solve the difficult problems in the furfural-water azeotropic system. To address the issues of thorough separation and high energy consumption in distillation, this process introduces a water-capturing reactant into the bottom of the second distillation column or aldehyde recovery column. This allows water in the azeotropic system to undergo a controlled chemical reaction with the reactant under high-temperature conditions in the bottom of the column, thereby achieving the chemical transformation and removal of water. In this way, the stable azeotropic equilibrium formed between furfural and water is effectively disrupted, changing the vapor-liquid equilibrium of the system. This allows furfural components to be efficiently separated and enriched in the bottom of the column under normal pressure. Unlike traditional distillation methods that rely solely on physical evaporation, this invention achieves simultaneous reactive dehydration and separation through a "chemical reaction-driven thermodynamic equilibrium migration" approach, significantly improving the purity and energy utilization efficiency of furfural.

[0059] In one possible implementation, the extraction overflow tank 6 is equipped with a layering enhancement module, which includes: an ultrasonic oscillation device (frequency 20-40 kHz, power density 10-30 W / L) for disrupting the aldehyde-water interfacial emulsion layer through cavitation effect; a low-polarity oil film auxiliary system above the liquid surface for spraying or dripping low-polarity oily additives to form an oil film layer with a thickness of 1-3 mm to reduce interfacial tension, inhibit reemulsification and promote phase separation; and a temperature and amplitude control unit for the tank to control the temperature inside the tank at 25-35°C and the ultrasonic treatment for 3-5 minutes.

[0060] Ultrasonic cavitation generates microbubbles and instantaneous shearing, which breaks up the emulsion layer; the upper oil film reduces interfacial tension and adsorbs micro-dispersed droplets, synergistically accelerating the aggregation and sedimentation of the two phases.

[0061] Oily additives can be selected from low-polarity inert oils such as silicone oil or paraffin oil; the ultrasonic device can be installed at the bottom or side wall and interlocked to prevent dry running; when the raw material fluctuates greatly, the ultrasonic time can be extended to 6 to 8 minutes.

[0062] Working principle and effect When the distillate from the bottom of the column enters the extraction overflow tank (6), the ultrasonic device is activated; Ultrasound generates cavitation in liquids, forming a large number of microbubbles, and local pressure pulses disrupt the aldehyde-water emulsion interface. At the same time, the low polarity oil film reduces the surface tension of the system, making the stratification driven by the density difference between the aqueous phase and the aldehyde phase faster and more stable. After ultrasonic disturbance for 3–5 minutes, the oscillation is stopped, and the liquid is allowed to settle naturally. The stratification time has been reduced from 20–60 min to 5–10 min; The purity of furfural in the lower aldehyde-rich phase was increased to ≥95 wt%, and the entrained moisture was significantly reduced; The upper aqueous phase is clear and free of obvious aldehyde phase entrainment, reducing the burden of subsequent processing.

[0063] In one possible implementation, the bottom liquid temporary storage tank (4) of the tower is provided with an adaptive composition adjustment module, which includes: The online analysis unit uses a near-infrared (NIR) or Fourier transform infrared (FTIR) concentration analyzer. The probe is inserted into the bottom liquid storage tank 4 to detect the concentration of furfural, methanol, and water in the bottom liquid in real time. The measurement cycle is 10-30 seconds, and the measurement error is ≤±0.5%. The control and calculation unit includes a programmable logic controller (PLC) and a stoichiometric model. The control and calculation unit automatically calculates the required proportion of furfural to be added based on real-time detection data and adjusts the addition amount dynamically within the range of 12-18 wt% to keep the composition of the mixture in the bottom of the tower within the azeotropic ratio range of furfural and water. The execution unit includes a variable frequency addition pump and a stirring linkage system, which is used to automatically add industrial furfural according to the control signal and mix it evenly. After addition, the system automatically re-measures the concentration and forms a closed-loop feedback. Among them, the adaptive composition adjustment module realizes the azeotropic point self-locking control of the composition of the bottom liquid in the tower, so that the composition fluctuation of the mixed liquid entering the light-light removal tower 3 does not exceed ±0.3%, thereby improving the azeotropic separation efficiency and furfural recovery rate of the light-light removal tower.

[0064] The online quantitative analysis of furfural, methanol, and moisture content is performed using spectrophotometry. The PLC calls the metrology model to calculate the required amount of feed in the target azeotropic window, triggering the feed pump and stirring linkage. The deviation is corrected by secondary measurement, achieving self-locking control. This significantly improves batch-to-batch consistency, reduces fluctuations in secondary distillation time and energy consumption, and reduces furfural loss due to compositional deviations.

[0065] Online analysis can also use a near-infrared + multivariate correction (PLS) model; when the spectrum is affected by colorimetric interference, it can be switched to a densitometer / refractometer as a redundant signal; the supplementation strategy can adopt a feedforward + feedback composite control; In one possible implementation, a dynamic azeotropic point migration control system is installed inside the light component removal tower 3, comprising: a microwave energy field module (frequency 2450 MHz, power 200–500 W), which radiates through the tower wall to the liquid-gas mixing zone, selectively heating the highly polar water molecules to form a local temperature gradient of 0.5–1.0 °C; a variable pressure control module, which controls the tower top pressure to fluctuate periodically within the range of 0.095–0.105 MPa via a servo valve, and is synchronized with the microwave power adjustment signal; and a temperature and pressure feedback unit, which monitors the temperature and pressure inside the tower in real time, forming a closed loop of microwave power and pressure coordination, creating a dynamic azeotropic point adjustment zone in the middle of the tower, and realizing non-azeotropic distillation separation of the furfural–methanol–water system; through this system, the separation efficiency of azeotropic components is improved by 15–20%, the furfural content in the top fraction is ≤0.05 wt%, and the total energy consumption of the system is reduced by 10–15%.

[0066] By using a dynamic azeotropic point migration control system, the separation efficiency of azeotropic components is improved by 15-20%, the furfural content in the top fraction is ≤0.05 wt%, and the total energy consumption of the system is reduced by 10-15%.

[0067] To achieve a uniform distribution of microwave energy field inside the tower, the outer wall of the light-removing tower in this embodiment is covered with a microwave radiation cavity; the cavity adopts a stainless steel shielding structure and is equipped with waveguides and reflectors to uniformly couple microwave energy into the tower along the tower wall.

[0068] A pressure servo valve is installed at the top of the tower, and the servo valve adjusts the pressure at the top of the tower in real time by a PID control system. The tower body has three temperature sampling points (top, middle, and bottom) and one pressure sensor along its height to form a temperature-pressure closed-loop feedback system. The microwave power adjustment and the servo valve action are synchronously controlled by a PLC, with a control accuracy of ±0.1℃ and ±0.002MPa, thereby realizing dynamic azeotropic point migration control within the tower.

[0069] Operating parameters: Microwave frequency: 2450 MHz; Power: 300 W; Top pressure: 0.095–0.105 MPa; Modulation period: 30–60 s; Reflux ratio: 2.0–3.5; Distillation time: 3–4 h.

[0070] Control logic: When the temperature at the top of the tower deviates from the target value by ±0.3℃, the system automatically adjusts the microwave power by ±50W; synchronously adjusts the servo valve opening by ±2% to control the slight fluctuation of the pressure inside the tower; generates a "microwave power - tower top pressure" coordinated curve in real time; and automatically maintains the optimal dynamic separation state.

[0071] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for recovering furfural light components, characterized in that, The apparatus includes a light component recovery device for furfural, comprising a light component removal tower (3), a bottom liquid storage tank (4), an extraction overflow tank (6), and an aldehyde recovery tower (7). The inlet of the light component removal tower (3) is connected to a pipeline for conveying the light component removal condensate generated during the furfural production process. The inlet of the bottom liquid storage tank (4) is connected to the lower outlet of the light component removal tower (3), and the outlet of the bottom liquid storage tank (4) is connected to the inlet of the light component removal tower (3) via a pipeline. A second condenser (5) is connected to the bottom outlet of the light component removal tower (3), and the outlet of the second condenser (5) is connected to the extraction overflow tank. The extraction overflow tank (6) is connected to the upper light phase overflow port of the extraction overflow tank (6) and connected to the bottom liquid temporary storage tank (4) or the sewage treatment system through a pipeline. The lower heavy phase outlet of the extraction overflow tank (6) is connected to the inlet of the aldehyde recovery tower (7) through a transfer pump. The top of the aldehyde recovery tower (7) is connected to the reflux controller (9) through the condenser three (10). The reflux outlet of the reflux controller (9) is connected to the top reflux port of the aldehyde recovery tower (7). The outlet of the reflux controller (9) is connected to the furfural tank (8) through a pipeline. The method includes the following steps: Step 1: Light weight removal and distillation separation. The light weight removal condensate generated during the furfural production process is used as raw material and sent to the light weight removal tower (3) under normal pressure for intermittent distillation. The bottom temperature of the tower is controlled at 58-63℃ and the top temperature is below 60℃. The top condensate is collected as acetone and methanol-acetone azeotropic fraction. Step 2: Composition adjustment. Add 14-16 wt% industrial furfural or 15-17 wt% crude furfural product (by weight of the residue) to the bottom of the column, stir and mix evenly, and then send it back to the light distillation tower (3) for a second distillation. Step 3: Second distillation: Distillation is carried out under atmospheric pressure, with the bottom temperature controlled at 85-95℃ and the top temperature below 80℃. Heating is stopped when the bottom temperature reaches 97.8℃, and the bottom liquid is obtained. Step 4: Rapid cooling and stratification: The liquid in the bottom of the tower is rapidly cooled to ≤30℃ through condenser 2 (5) and enters the extraction overflow tank (6) for stratification. The upper layer is the aqueous phase and the lower layer is the aldehyde-rich phase. The upper aqueous phase is discharged through the overflow port and the lower aldehyde-rich phase is sent to the aldehyde recovery tower (7) by the transfer pump. Step 5: Recover furfural by vacuum distillation. The aldehyde-rich phase is fed into a vacuum distillation column and subjected to batch distillation under a pressure of -0.094 to -0.098 MPa, controlling the reflux ratio at 2 to 5. The furfural product is collected from the top of the column by condensation. Through the above steps, the purity of the furfural product is ≥98.0 wt%, and the moisture content is ≤0.2 wt%. The furfural tank (8) is equipped with an inert gas protection system. The inert gas is nitrogen or carbon dioxide, which is used to prevent furfural from oxidizing and deteriorating. The furfural tank is also equipped with an online sampling port for monitoring product purity.

2. The method for recovering furfural light components according to claim 1, characterized in that: The light removal tower (3) is a packed tower structure, and the packing uses stainless steel Pall rings or metal stepped rings.

3. The method for recovering furfural light components according to claim 1, characterized in that: The temporary storage tank (4) of the tower bottom liquid is a horizontal stirring tank structure, equipped with a variable frequency stirrer with a stirring speed of 50 to 200 r / min. The tank is equipped with a level gauge and a reflux pipeline to control the stability of the system composition after adding furfural.

4. The method for recovering furfural light components according to claim 1, characterized in that: The second condenser (5) is a shell-and-tube heat exchanger or a spiral plate heat exchanger. The cooling medium is circulating cooling water or ethylene glycol solution. The temperature of the cooling medium is 10-20℃ and the heat exchange area is 5-15 m². It can reduce the temperature of the bottom liquid of the tower to ≤30℃ within 3 minutes.

5. The method for recovering furfural light components according to claim 1, characterized in that: The top of the light component removal tower (3) is connected to the light component tank (2) via a condenser (1). The light component removal tower (3) is used for intermittent distillation of the light component removal condensate under normal pressure, and the bottom temperature is controlled at 58-63°C and the top temperature is below 60°C.

6. The method for recovering furfural light components according to claim 1, characterized in that: The extraction overflow tank (6) is a vertical cylindrical gravity stratification tank with a phase separation baffle and an overflow weir inside. The upper light phase is discharged through the overflow port, and the lower heavy phase is pumped into the aldehyde recovery tower (7) through the bottom outlet. The stratification time is 20 to 60 minutes.

7. The method for recovering furfural light components according to claim 1, characterized in that: In the second distillation or aldehyde recovery process, 0.5–3 wt% of a water-capturing agent, such as ethyl formate, ethyl acetate, or acetic anhydride, is introduced into the bottom of the column. The reaction-separation coupling operation is carried out under conditions of 85–100°C at the bottom and 75–80°C at the top. The water-capturing agent reacts with water to produce acetic acid and ethanol, forming a low-boiling-point acetic acid-ethanol azeotrope, which is continuously removed with the distillate from the top of the column. This disrupts the furfural-water azeotropic equilibrium, achieving a reaction-driven separation process. This results in a furfural product purity ≥ 98.5 wt%, a 25% reduction in system energy consumption compared to traditional distillation processes, and eliminates the need for additional pressure reduction.

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