WO2022122030A1

WO2022122030A1 - Method and device for purifying maltol grignard procedure intermediate

Info

Publication number: WO2022122030A1
Application number: PCT/CN2021/137217
Authority: WO
Inventors: 詹见; 陈金林; 谢国柱
Original assignee: 安徽金禾实业股份有限公司
Priority date: 2020-12-11
Filing date: 2021-12-10
Publication date: 2022-06-16
Also published as: CN112409304A; CN116261559A

Abstract

Disclosed is a method for purifying a maltol Grignard procedure intermediate characterized by comprising the following steps: step 1: an intermediate enters a distillation tower for coarse separation of furfuryl alcohol and a solvent, the temperature at the bottom of the distillation tower is higher than the temperature at the top of the tower; step 2: a fluid from the bottom of the distillation tower enters a first-stage flash distillation kettle, the temperature of the first-stage flash distillation kettle is higher than the temperature at the bottom of the distillation tower, and a gas phase of the first-stage flash distillation kettle is condensed and then enters a second-stage flash distillation kettle; step 3: the temperature of the second-stage flash distillation kettle is lower than the temperature of the first-stage flash distillation kettle, and a gas phase of the second-stage flash distillation kettle is condensed and then enters the third-stage flash distillation kettle; step 4: the temperature of the third-stage flash distillation kettle is lower than the temperature of the second-stage flash distillation kettle, and a gas phase of the third-stage flash distillation kettle is condensed and then collected. Also disclosed is a device for purifying a maltol Grignard procedure intermediate. The present method and device may increase the content and yield of furfuryl alcohol.

Description

A kind of maltol Grignard section intermediate purification method and device

This application claims the priority of a Chinese invention patent whose title is filed on December 11, 2020, and whose application number is 202011442706.5, and whose title is a method for purifying a maltol Grignard section intermediate. The above application is incorporated herein by reference in its entirety.

technical field

The invention relates to a method for purifying an intermediate of a maltol Grignard section.

Background technique

In the production process of maltol, the traditional furfural method is used. Grignard reagent reacts with furfural in toluene and tetrahydrofuran solvent to generate furfuryl alcohol intermediate, and then the furfuryl alcohol is purified by distillation.

Chinese patent document CN110790732A discloses a method for refining and purifying furfuryl alcohol in the production of maltol. The first tetrahydrofuran tank; a high-concentration furfuryl alcohol solution containing tetrahydrofuran is extracted from the bottom of the rectification tower, and pumped to the distillation kettle to control the temperature at 68 ℃-75 ℃ and vacuum degree -0.095 to -0.099MPa for distillation, and the reduced The solvent tetrahydrofuran steamed from the still is pumped to the second tetrahydrofuran tank, and then the tetrahydrofuran is pumped back to the rectifying tower for circulating rectification through pipelines.

Chinese patent document CN209317065U discloses a vacuum distillation device for ethyl maltol that reduces energy consumption, including a furfuryl propanol dilute solution receiving tank, a vacuum distillation still, a tube condenser, a furfuryl propanol storage tank and a solvent recovery device , the furfuryl propanol dilute solution receiving tank is connected to the vacuum distillation kettle, the liquid outlet end of the vacuum distillation kettle top is connected to the liquid and gas inlet end of the gas-liquid separator, and the gas outlet end of the gas-liquid separator is connected to the liquid inlet end of the tube condenser The liquid outlet end of the tube condenser is connected with the liquid inlet end of the solvent recovery device; the liquid outlet of the gas-liquid separator is connected with the top of the vacuum distillation kettle, and the liquid outlet end at the bottom of the vacuum distillation kettle is connected with the furfuryl propanol storage tank.

In the prior art, the energy consumption of the separation and purification method is relatively high, and the content of the purified furfuryl alcohol is not high, and there are many impurities. The recovered solvent also contains more furfuryl alcohol. As a result, the yield of furfuryl alcohol is low and the quality is not high. Seriously affect the yield and yield of maltol.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method for purifying a maltol Grignard section intermediate, which can improve the content and yield of furfuryl alcohol, solve intermittent repetitive operations, and reduce labor intensity of personnel.

In order to solve the above-mentioned technical problems, the present invention provides a method for purifying a maltol Grignard section intermediate, which is characterized in that, comprising the following steps:

(1) the intermediate enters the rectifying tower at a flow rate of 2 m ³ /h to carry out the rough separation of furfuryl alcohol and the solvent, and the temperature at the bottom of the rectifying tower is 60° C. and the temperature at the top of the tower is 40° C.;

(2) Then it is extracted from the bottom of the rectifying tower and entered into the first-level flash tank, the extraction flow rate is 1.5 m ³ /h, the temperature of the first-level flash tank is 85°C, and the gas phase of the first-level flash tank is condensed and then enters the second-level flash tank Flash kettle, the temperature of the secondary flash kettle is 65°C, the gas phase of the secondary flash kettle is condensed and then enters the tertiary flash kettle, and the temperature of the third flash kettle is 60°C. , the freezing medium temperature of above-mentioned gas phase condensation is -5 ℃～-8 ℃, all above-mentioned flashing stills all adopt vacuum distillation, and vacuum degree is -0.08MPa;

(3) Return the materials in the secondary flash kettle and the third flash kettle to the primary flash kettle every 3h;

(4) The qualified furfuryl alcohol is extracted from the bottom of the first-stage flash tank according to the flow rate of 0.5 m ³ /h, and the content of the extracted furfuryl alcohol is analyzed every hour.

The solvent separated in step (1) is recycled for production needs.

In step (2), the solvent after the vapor phase condensation of the three-stage flash tank is used for washing magnesium slag in production.

For the sake of simple description, the following method for purifying a maltol Grignard section intermediate of the present invention is abbreviated as this method.

The advantages of the method: the present invention realizes continuous production, has strong operability, reduces consumption, and improves the yield and quality of furfuryl alcohol. It plays a decisive role in improving the yield of the whole maltol product.

1. The furfuryl alcohol content is increased from 91% to 95%.

2. The yield of furfuryl alcohol in one kettle has been increased from 960kg to 980kg.

3. The solvent consumption is reduced, the cost is reduced, and an average of 300 liters of solvent are recovered per day.

4. It realizes continuous production, reduces labor intensity, and facilitates more stable production control.

Description of drawings

FIG. 1 is a flow chart of the equipment of this method.

Detailed ways

Referring to FIG. 1 , the equipment corresponding to this method includes a rectifying tower 1, a first flash tank 41, a second flash tank 42, a third flash tank 43, a first condenser 21, and a second condenser 22 , the third condenser 23, the fourth condenser 24, the first pump 51, the second pump 52, the first solvent tank 31, the second solvent tank 32, the furfuryl alcohol tank 33, and a reboiler 11 is provided on the side of the rectifying tower 1 And connected with the rectification tower 1 through the circulation pipeline, the upper outlet of the rectification tower 1 is connected with the first condenser 21, the other end of the first condenser 21 is connected with the first solvent tank 31, and the lower outlet of the rectification tower 1 is connected with the first condenser 21. The first pump 51 is connected to the inlet end of the first flash still 41, the lower outlet of the first flash still is connected to the furfuryl alcohol tank 33, the upper outlet of the first flash still 41 is connected to the second condenser 22, and the second condenser 22 The other end is connected with the inlet end of the second flash vessel 42, the upper outlet of the second flash vessel 42 is connected with the third condenser 23, the other end of the third condenser 23 is connected with the inlet end of the third flash vessel 43, and the third condenser 23 is connected with the inlet end of the third flash vessel 43. The upper outlet of the flash vessel 43 is connected to the fourth condenser 24, the other end of the fourth condenser 24 is connected to the second solvent tank 32, and the lower outlet of the second flash vessel 42 is merged with the lower outlet of the third flash vessel 43 , and is connected to the inlet end of the first flash tank 41 through the second pump 52 . The intermediate of the maltol Grignard section is connected to the inlet ends of the first flash tank 41 , the second flash tank 42 and the third flash tank 43 through an atomizing injector.

In the document CN110790732A, it is reported that the furfuryl alcohol tetrahydrofuran mixed solution is pumped into the atmospheric rectifying tower for rectification, and the tetrahydrofuran recovered by the rectification at the top of the tower enters the first tetrahydrofuran tank; The furfuryl alcohol solution of tetrahydrofuran is pumped into the steam-reducing still to control the temperature at 68 ℃-75 ℃, vacuum degree-0.095 to -0.099MPa to carry out distillation, and the solvent tetrahydrofuran steamed from the steam-reducing still is pumped to the second tetrahydrofuran tank, Then, the tetrahydrofuran is pumped back to the rectifying tower for circulating rectification through the pipeline. In the document of CN209317065U, in the process of producing ethyl maltol, the filtrate (that is, the dilute solution of furfuryl propanol) after the hydrolysis reaction is transferred into the vacuum distillation still, and the control temperature is less than or equal to 65°C, and the pressure is less than or equal to -0.088 MPa, the vacuum distillation still distillate is cooled through the condenser, and the benzene and tetrahydrofuran solvent are separated, and the concentrated solution at the bottom of the vacuum distillation still is the purified furfuryl propanol intermediate. Then the separated solvent is re-distilled, and the temperature is controlled to 100 ° C. After the distillation is completed, the residual liquid at the bottom of the still contains furfuryl propanol intermediate, which is then transferred to the vacuum distillation still for secondary distillation, and the residual liquid is separated. of benzene and tetrahydrofuran solvent, and extract the furfuryl propanol inside again. The intermediate content of furfuryl propanol extracted by the secondary re-steaming is low, the impurities are many, and the color is dark. The reason is that furfuryl propanol is decomposed and oxidized by secondary heating (high temperature) in the process of atmospheric re-distillation.

The prior art fully recognizes the importance of lowering the separation temperature in separating furfuryl alcohol and solvent. When the separation temperature is high, more by-reaction products will be produced, and the by-reaction products will generate pitch in the subsequent reaction, which wastes raw materials on the one hand, and increases the difficulty of waste disposal on the other hand.

However, the prior art does not recognize the importance of reducing separation time. For example, in the document CN110790732A, the vacuum distillation temperature is 68°C-75°C; in the document CN209317065U, the control (decompression distillation) temperature is less than or equal to 65°C. However, no attention was paid to the importance of shortening the distillation time.

Based on the above characteristics, the present invention improves the ordinary vacuum distillation into the distillation in the flash tank. In the flash evaporation process, after the intermediate containing the solvent enters the flash tank, the separation of the gas phase and the liquid phase is achieved in a very short time. The liquid phase gradually falls into the bottom of the flash vessel, and the gas phase is output from the flash vessel and condensed to continue processing.

In the process of heating distillation, reducing the pressure can reduce the boiling point, but this is due to the reduction of the vapor pressure, which reduces the boiling point of the entire system; from the point of view of the heating position, it takes a long time to heat at a higher temperature to realize the distillation of the entire system. Completed; the continuous heating of the heating position causes the decomposition and side reactions of furfuryl alcohol, which makes the entire color of the liquid phase darker, and the finished product has many impurities and poor quality.

For the flash distillation process, the liquid to be separated is misty when entering the flash tank, so relatively high temperature and relatively low pressure are required to realize solvent distillation in a very short time. Based on the above considerations, the inventors of the present invention increased the flash evaporation temperature to 85 degrees Celsius in order to achieve rapid separation, so that the distillation of the solvent can be achieved in a very short time (almost instantaneously). At the same time, the inventor also found that, due to the increase of the flash temperature, the pressure in the flash tank was simultaneously increased (-0.08MPa). The increase of the pressure in the flash tank reduces the requirement of the system on the vacuum device and reduces the energy consumption of the vacuum generating device.

The separation of liquid mixtures with different boiling points is carried out using a rectification column, and the separation process is continuous. The general rectification column is fed from the middle, the high-boiling material is collected at the bottom of the column, and the low-boiling material is collected at the top of the column. Continuing to use vacuum distillation to separate the high-boiling substances collected in the rectification tower, it is necessary to wait for the continuous working rectification tower to collect the substances in the whole kettle, and then distill the substances in the whole kettle under reduced pressure. It can be seen from this point that ordinary vacuum distillation is used after the rectification column, which is a discontinuous operation; there are the process of collecting intermediates until the volume meets the volume of vacuum distillation, and the process of vacuum distillation. These two processes usually Takes a long time.

In the present invention, after the separation in the rectifying tower, the material extracted from the bottom of the tower is directly fed into the flashing kettle for flashing; the flashing is also a continuous process. The invention does not collect the intermediate until the volume of the intermediate meets the amount of vacuum distillation, and after the rectifying column runs smoothly, the material can be directly extracted from the bottom of the rectifying column and enter the flash kettle for flash distillation; When the substance enters the flash tank, the flash evaporation is completed in a very short speed, which is a continuous working process.

The present invention adopts such a method, so that the whole reaction process is carried out continuously, changing the two-stage waiting time necessary for the vacuum distillation of the whole still, on the one hand, reducing the time-consuming (with waiting process) of the distillation separation process, and on the other hand, continuous The chemical operation improves the operation efficiency of the entire production line. For example, if the whole-pot vacuum distillation method is adopted, the continuous operation of the same rectifying tower requires at least two sets of vacuum distillation kettles to realize the continuous work of the pre-stage and subsequent sections of distillation and separation. , so the present invention reduces the equipment cost.

After furfuryl alcohol is obtained by separation in the primary flash tank, it can be directly recovered without further separation of the gas phase; however, the gas phase condensation product of the primary flash tank still contains more furfuryl alcohol. In the present invention, in order to obtain a purer solvent, the second-stage flash evaporation and the third-stage flash evaporation are continued for the vapor-phase condensation product of the first-stage flash tank, so as to finally obtain a solvent with higher purity; due to the flash treatment, the side reaction of the solvent There is also a corresponding reduction. Calculated at an initial flow rate of 2 m ³ /h, about 13 liters of solvent can be recovered per hour.

The maltol Grignard section intermediate purification method of the present invention comprises the following steps:

(1) The intermediate enters the rectifying tower at a flow rate of 2 m ³ /h to carry out the rough separation of furfuryl alcohol and the solvent. The temperature at the bottom of the rectifying tower is 60° C. and the temperature at the top of the tower is 40° C. In this process, about 25% The liquid collected at the top of the tower, the main component of this part of the liquid is solvent, and also contains a part of furfuryl alcohol; about 75% of the liquid is collected at the bottom of the tower, and this part of the liquid contains more furfuryl alcohol.

(2) Then it is extracted from the bottom of the rectifying tower and entered into the first-level flash tank, and the extraction flow rate is 1.5m ³ /h, and the intermediate is sprayed into the first-level flash using a pump using an atomizing injector, such as a venturi tube. In the kettle, the temperature of the primary flash kettle is 85°C, the gas phase of the primary flash kettle enters the secondary flash kettle after condensation, and the temperature of the secondary flash kettle is 65°C, and the gas phase of the secondary flash kettle is condensed. Enter the three-stage flash distillation still, the temperature of the three-stage flash distillation still is 60 ℃, and the collection after the gas phase condensation of the three-stage flash distillation still, the freezing medium temperature of the above-mentioned vapor phase condensation is -5 to -8 ℃, and all the above-mentioned flash stills are Using vacuum distillation, the vacuum degree is -0.08MPa;

By adopting the above method, the original whole-pot underpressure distillation mode was changed, and the continuous separation of furfuryl alcohol was realized. On the one hand, the reaction time was reduced; The side reactions are greatly reduced, and unnecessary impurities are reduced.

Example 1:

A method for purifying a maltol Grignard section intermediate, comprising the following steps:

(2) Then it is extracted from the bottom of the rectifying tower and entered into the first-level flash tank, the extraction flow rate is 1.5 m ³ /h, the temperature of the first-level flash tank is 85°C, and the gas phase of the first-level flash tank is condensed and then enters the second-level flash tank Flash kettle, the temperature of the secondary flash kettle is 65°C, the gas phase of the secondary flash kettle is condensed and then enters the tertiary flash kettle, and the temperature of the third flash kettle is 60°C. , the freezing medium temperature of above-mentioned gas phase condensation is -5 ℃, all above-mentioned flashing stills all adopt vacuum distillation, and vacuum degree is -0.08MPa;

Randomly collect data for ten hours, and analyze the content of furfuryl alcohol at the bottom of the flash kettle. The average content of furfuryl alcohol is 95.34%, impurities are 0.42%, and the balance is solvent. In addition, the furfuryl alcohol content in the first solvent tank was detected to be 1.41%, and the furfuryl alcohol content in the second solvent tank was 0.72% (both by mass).

Embodiment 2:

(1) the intermediate enters the rectifying tower at the flow rate of 2m ³ /h to carry out the rough separation of furfuryl alcohol and the solvent, and the temperature at the bottom of the rectifying tower is 60° C.,

(2) Then it is extracted from the bottom of the rectifying tower and entered into the first-level flash tank, the extraction flow rate is 1.5 m ³ /h, the temperature of the first-level flash tank is 85°C, and the gas phase of the first-level flash tank is condensed and then enters the second-level flash tank Flash kettle, the temperature of the secondary flash kettle is 65°C, the gas phase of the secondary flash kettle is condensed and then enters the tertiary flash kettle, and the temperature of the third flash kettle is 60°C. , the freezing medium temperature of above-mentioned gas phase condensation is -6.5 ℃, all above-mentioned flashing stills all adopt vacuum distillation, and vacuum degree is -0.08MPa;

Ten hours of data were collected randomly, and the content of furfuryl alcohol at the bottom of the flash tank was analyzed. The average content of furfuryl alcohol was 95.48%, and the impurities were 0.39%. In addition, the furfuryl alcohol content in the first solvent tank was detected to be 1.39%, and the furfuryl alcohol content in the second solvent tank was 0.71% (both by mass).

Embodiment three:

(2) Then it is extracted from the bottom of the rectifying tower and entered into the first-level flash tank, the extraction flow rate is 1.5 m ³ /h, the temperature of the first-level flash tank is 85°C, and the gas phase of the first-level flash tank is condensed and then enters the second-level flash tank Flash kettle, the temperature of the secondary flash kettle is 65°C, the gas phase of the secondary flash kettle is condensed and then enters the tertiary flash kettle, and the temperature of the third flash kettle is 60°C. , the freezing medium temperature of above-mentioned gas phase condensation is -8 ℃, all above-mentioned flashing stills all adopt vacuum distillation, and vacuum degree is -0.08MPa;

Ten hours of data were collected randomly, and the content of furfuryl alcohol at the bottom of the flash kettle was analyzed. The average content of furfuryl alcohol was 95.61%, impurities were 0.31%, and the remainder was mainly solvent. In addition, the furfuryl alcohol content in the first solvent tank was detected to be 1.35%, and the furfuryl alcohol content in the second solvent tank was 0.68% (both by mass).

Comparative example four:

(2) then take out from the bottom of the rectifying tower and enter into the vacuum distillation still by pipeline pumping to carry out vacuum distillation, and the control vacuum distillation still temperature is 85 ℃, and vacuum tightness-0.082MPa to-0.078MPa; with the whole still 4m3, it takes about 5 hours to complete the whole still distillation.

The data of three consecutive vacuum distillation kettles were collected, and the furfuryl alcohol content was analyzed. The furfuryl alcohol content of the liquid separated from the top of the rectification column is 1.26%, 1.28% and 1.31%.

By adopting the method and device of the present invention, the time of distillation and separation is reduced, and the utilization rate of equipment is improved; because the heating time of distillation and separation is reduced, the content of impurities contained in furfuryl alcohol is obviously reduced, and the cost of separation of impurities in the subsequent process is reduced; at the same time, The reduction of the impurity amount of furfuryl alcohol conversion increases the output of furfuryl alcohol, as in still kettle volume 4m , according to the present invention about ² hours of reaction can complete the amount of a kettle, with the above impurity quantity calculation, single kettle output by the original 960kg increased to 980kg; using multi-stage flash evaporation, the solvent can be recovered by about 300 liters per day.

The above descriptions are only specific implementations of the present application, and those skilled in the art can make other improvements or modifications on the basis of the above-mentioned embodiments under the above teachings of the present application. Those skilled in the art should understand that the above-mentioned specific description is only to better explain the purpose of the present application, and the protection scope of the present application should be subject to the protection scope of the claims.

Furthermore, those skilled in the art will appreciate that although some of the embodiments described herein include certain features, but not others, included in other embodiments, that combinations of features of different embodiments are intended to be within the scope of the present application within and form different embodiments. For example, in the following claims, any of the claimed embodiments may be used in any combination.

Claims

A method for purifying a maltol Grignard section intermediate, comprising the following steps:

Step 1: the intermediate enters the rectifying tower and carries out the rough separation of furfuryl alcohol and the solvent, and the temperature at the bottom of the rectifying tower is higher than the temperature at the top of the tower;

Step 2: the produced fluid from the bottom of the rectifying tower enters the first-level flash still, the temperature of the first-stage flash still is higher than the temperature at the bottom of the rectifying tower, and the gas phase of the first-stage flash still enters the second-stage flash still after condensation;

Step 3: the temperature of the secondary flash kettle is lower than the temperature of the primary flash kettle, and the gas phase of the secondary flash kettle is condensed and then enters the third flash kettle;

Step 4: the temperature of the third-stage flash tank is lower than the temperature of the second-level flash tank, and the third-level flash tank is collected after gas-phase condensation.
The method for purifying a maltol Grignard section intermediate according to claim 1, characterized in that: in step 2, qualified furfuryl alcohol is extracted from the bottom of the primary flash tank.
The method for purifying a maltol Grignard section intermediate according to claim 1, characterized in that: after step 3 and step 4, the materials in the secondary flash still and the tertiary flash still are regularly returned to the primary flash still .
The method for purifying a maltol Grignard section intermediate according to claim 1, wherein in step 4, the temperature of the gas-phase condensation medium is -5°C to -8°C.
The method for purifying a maltol Grignard section intermediate according to claim 1, characterized in that: the first-level flash still, the second-level flash tank, and the third-level flash tank all adopt vacuum distillation, and the degree of vacuum is-0.08MPa .
The method for purifying a maltol Grignard section intermediate according to claim 1, wherein the temperature at the bottom of the rectifying tower is 60°C, and the temperature at the top of the tower is 40°C.
The method for purifying a maltol Grignard section intermediate according to claim 1, characterized in that: the temperature of the first-level flash tank is 85 ℃, the temperature of the second-level flash tank is 65 ℃, and the temperature of the third-level flash tank is 60 ℃ .
A maltol Grignard section intermediate purification equipment, characterized in that it comprises a rectifying tower (1), a first flash still (41), a second flash still (42), a rectifying tower (1), a first flash still (41), a second flash still (42), A flash distillation kettle (41) and a second flash distillation kettle (42) are connected in sequence; the outlet on the lower side of the first flash distillation kettle is connected to a furfuryl alcohol tank (33).
Maltol Grignard section intermediate purification equipment according to claim 8, is characterized in that: rectification tower (1) lower outlet is connected with the first flash kettle (41) inlet end through first pump (51); The upper outlet of the first flash vessel (41) is connected to the second condenser (22), and the other end of the second condenser (22) is connected to the inlet end of the second flash vessel (42); the second flash vessel (42) ) upper outlet is connected with the third condenser (23), the other end of the third condenser (23) is connected with the inlet end of the third flash kettle (43), and the upper outlet of the third flash kettle (43) is connected with the fourth The condenser (24) is connected, and the other end of the fourth condenser (24) is connected with the second solvent tank (32).
The maltol Grignard section intermediate purification equipment according to claim 8, characterized in that: the lower outlet of the second flash kettle (42) is merged with the lower outlet of the third flash kettle (43), and passes through the second A pump (52) is connected to the inlet end of the first flash tank (41).
The maltol Grignard section intermediate purification equipment according to claim 8 is characterized in that: a reboiler 11 is arranged on the side of the rectification tower 1 and is connected with the rectification tower 1 through a circulation pipeline, and the upper side of the rectification tower 1 The outlet is connected to the first condenser 21 , and the other end of the first condenser 21 is connected to the first solvent tank 31 .
The maltol Grignard section intermediate purification equipment according to claims 8-12 is characterized in that: the Grignard section intermediate is connected to the inlet of the flash kettle through an atomizing injector.
A method for purifying a maltol Grignard section intermediate, comprising the following steps:

(1) the intermediate enters the rectifying tower at a flow rate of 2 m 3 /h to carry out the rough separation of furfuryl alcohol and the solvent, and the temperature at the bottom of the rectifying tower is 60° C. and the temperature at the top of the tower is 40° C.;

(2) Then it is extracted from the bottom of the rectifying tower and entered into the first-level flash tank, the extraction flow rate is 1.5 m 3 /h, the temperature of the first-level flash tank is 85°C, and the gas phase of the first-level flash tank is condensed and then enters the second-level flash tank Flash kettle, the temperature of the secondary flash kettle is 65°C, the gas phase of the secondary flash kettle is condensed and then enters the tertiary flash kettle, and the temperature of the third flash kettle is 60°C. , the freezing medium temperature of above-mentioned gas phase condensation is -5 ℃～-8 ℃, all above-mentioned flashing stills all adopt vacuum distillation, and vacuum degree is -0.08MPa;

(3) Return the materials in the secondary flash kettle and the third flash kettle to the primary flash kettle every 3h;

(4) The qualified furfuryl alcohol is extracted from the bottom of the first-stage flash tank according to the flow rate of 0.5 m 3 /h, and the content of the extracted furfuryl alcohol is analyzed every hour.