Four-tower furfural refining and byproduct steam device

Abstract

The utility model discloses a four-tower device for refining furfural and byproduct steam. The device comprises a steam pocket, and a primary tower, a light component removal tower, a refining tower and a recovery tower which are sequentially connected with the steam pocket, the steam pocket comprises a first pipeline and a second pipeline, the inlet end of the first pipeline is connected with an aldehyde steam heat source pipeline, and the outlet end of the first pipeline is connected with a stock solution tank playing a buffering role in front of the primary tower; the inlet end of the second pipeline is connected with a boiler water pipeline, the outlet end of the second pipeline is connected with a third pipeline and a fourth pipeline through a tee joint, the outlet end of the third pipeline is connected with a steam compressor, and the outlet end of the fourth pipeline is connected with a reboiler; the reboiler is positioned at the bottom of the primary distillation tower and is used for heating materials at the bottom of the primary distillation tower. Compared with the traditional furfural production process, the device has the advantages that the process flow is simplified, the process separation process of the light component removal tower, the neutralization kettle and the dehydration tower is simplified into one light component removal tower, the investment of the neutralization kettle, the dehydration tower and corollary equipment is reduced, and meanwhile, the energy consumption is also reduced.

Description

Technical Field

[0001] This utility model belongs to the field of biomass utilization technology, specifically relating to a four-tower refining device for furfural and producing steam as a byproduct. Background Technology

[0002] Furfural is an organic compound with the chemical formula C5H4O2. It is a colorless, transparent, oily liquid with a distinctive odor similar to benzaldehyde. It is mainly used as an industrial solvent and can also be used to produce furfuryl alcohol, furoic acid, tetrahydrofuran, γ-valerolactone, pyrrole, tetrahydropyrrole, etc.

[0003] Furfural is primarily produced from agricultural waste such as corn cobs, rice husks, and straw. After pretreatment including drying and crushing, furfural is extracted through hydrolysis under acid and then separated by distillation. The process mainly includes raw material preparation, hydrolysis extraction, and furfural refining. The aldehyde vapor generated by the hydrolysis reaction is condensed to form a raw liquid. This liquid is then concentrated to produce crude furfural, which contains water, methanol, acetone, formic acid, acetic acid, and 5-methylfurfural. High-quality furfural is obtained through initial distillation, removal of light components, neutralization and deacidification, dehydration, and refining. Energy conservation and environmental protection factors must also be considered during production to ensure sustainable development.

[0004] In the existing process, aldehyde vapor from the hydrolysis reactor typically passes through a slag separator to remove solid dust before directly entering the reboiler of the primary distillation tower as a heat source. Unused waste heat is exchanged with circulating cooling water in the raw liquid condenser, and the condensed raw liquid is then sent to the raw liquid tank. This results in a significant amount of heat energy from the aldehyde vapor being carried away by the circulating cooling water, leading to substantial energy waste. Secondly, the existing process for removing light components, acids, and water from furfural mainly consists of four steps: light component removal, neutralization and deacidification, settling and separation, and dehydration. This process is complex, involves numerous pieces of equipment, and consumes a large amount of energy. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of existing furfural refining processes, such as complex processes, numerous equipment, and high energy consumption, and to provide a device for refining furfural and producing by-product steam. This device first recovers the heat energy of the aldehyde vapor to produce by-product steam, and then obtains qualified furfural through distillation, which greatly reduces energy waste and improves the yield of furfural.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] An apparatus for refining furfural using four towers and producing steam as a byproduct includes a steam boiler and a primary distillation tower, a light component removal tower, a refining tower, and a recovery tower connected sequentially to the steam boiler. The steam boiler includes a first pipeline and a second pipeline. The inlet end of the first pipeline is connected to an aldehyde vapor heat source pipeline, and the outlet end of the first pipeline is connected to the primary distillation tower. The inlet end of the second pipeline is connected to a boiler water pipeline, and the outlet end of the second pipeline is connected to a third pipeline and a fourth pipeline via a tee. The outlet end of the third pipeline is connected to a steam compressor, and the outlet end of the fourth pipeline is connected to a first reboiler. The first reboiler is located at the bottom of the primary distillation tower and is used to heat the bottom material of the primary distillation tower. The bottom of the refining tower is provided with a heavy component outlet, and the bottom of a first reflux tank connected to the light component removal tower is provided with a light component outlet. The recovery tower is connected to the light component outlet of the light component removal tower and the heavy component outlet of the refining tower, respectively, and is used to recover furfural from the light components and furfural from the heavy components.

[0008] Preferably, a raw liquid tank is installed on the pipeline connecting the primary distillation tower and the first pipeline.

[0009] Preferably, the primary distillation column is provided with an upper feed inlet, a lower feed inlet, a top gas outlet, and a bottom drain outlet. The upper feed inlet of the primary distillation column is connected to the raw liquid tank, and the lower feed inlet of the primary distillation column is connected to the first condenser. The other end of the first condenser is connected to the bottom drain outlet of the primary distillation column via a tee. The top gas outlet of the primary distillation column is connected to the light aldehyde removal column in sequence via a water-aldehyde vapor compressor, the first condenser, and an aldehyde-water separator.

[0010] Preferably, the aldehyde-water separator includes a feed inlet, an aqueous phase outlet, and an oil phase outlet. The aqueous phase outlet of the aldehyde-water separator is connected to the upper feed inlet of the primary distillation column, the oil phase outlet of the aldehyde-water separator is connected to the light phase removal column, and the feed inlet of the aldehyde-water separator is connected to the outlet of the water-aldehyde vapor compressor through the first condenser.

[0011] Preferably, the recovery tower is a batch distillation tower, the bottom of the tower is a jacketed conical tank, the jacket is heated by steam, the bottom of the tower has a built-in stirring device, and the steam outlet of the recovery tower is provided with a distillation section.

[0012] Preferably, the bottom of the light-light-removal tower is provided with a second reboiler, the bottom of the refining tower is provided with a third reboiler, the top of the light-light-removal tower is provided with a second condenser, the top of the refining tower is provided with a third condenser, and the top of the recovery tower is provided with a fourth condenser and a third reflux tank. The second condenser is connected to the light-light-removal tower and the recovery tower respectively through the first reflux tank, and the third condenser is connected to the furfural outlet of the refining tower and the third reflux tank through the second reflux tank.

[0013] Compared with the prior art, the technical effects of this utility model are as follows:

[0014] 1) The aldehyde vapor from the hydrolysis reactor is first sent to the steam package to produce by-product steam. Most of the by-product steam is used as a heat source, or it can be sold after being pressurized by a steam compressor.

[0015] 2) Most of the heat energy in the aldehyde vapor at the top of the primary distillation column is recovered. The vapor at the top of the primary distillation column is compressed by the water-aldehyde vapor compressor and then sent to the condenser as a heat source to heat the material at the bottom of the column. This not only recovers most of the heat energy in the aldehyde vapor at the top of the column, but also saves energy consumption of the reboiler in the primary distillation column.

[0016] 4) The methanol, acetone, water and acetic acid in the aldehyde are removed together in the light component removal tower. The three processes of light component removal, neutralization and deacidification and dehydration in the traditional process are combined into one process, which simplifies the process flow, reduces the investment in neutralization kettle, dehydration tower and supporting equipment, and reduces energy consumption.

[0017] 5) The recovery tower adopts a batch distillation tower device: the bottom of the tower is a jacketed conical storage tank with steam heating inside the jacket and internal stirring. The steam outlet has a rectification section for reflux, which recovers furfural in the light components and furfural in the heavy components, reduces furfural loss, and maximizes efficiency. Attached Figure Description

[0018] Figure 1 It is a four-tower refining unit that produces furfural and generates steam as a byproduct.

[0019] In the diagram, 01-Steam Bundle, 02-Soil Tank, 03-Preliminary Distillation Column, 04-First Reboiler, 05-First Condenser, 06-Aldehyde-Water Separator, 07-Light Oxygen Extraction Column, 08-Second Reboiler, 09-Second Condenser, 10-First Reflux Tank, 11-Refining Column, 12-Third Reboiler, 13-Third Condenser, 14-Second Reflux Tank, 15-Recovery Column, 16-Fourth Condenser, 17-Third Reflux Tank, 18-Steam Compressor, 19-Water-Aldehyde Steam Compressor, 151-Rectification Section. Detailed Implementation

[0020] The following will combine Figure 1 This device should be described clearly and completely.

[0021] Example 1

[0022] A four-tower refining apparatus for furfural and producing steam as a byproduct, such as... Figure 1As shown, the structure includes a steam boiler 01 and, in sequence connected to the steam boiler 01, a primary distillation column 03, a light precipitator 07, a refining column 11, and a recovery column 15. The steam boiler includes a first pipeline and a second pipeline. The inlet end of the first pipeline is connected to an aldehyde vapor heat source pipeline, and the outlet end of the first pipeline is connected to the primary distillation column 03. The inlet end of the second pipeline is connected to a boiler water pipeline, and the outlet end of the second pipeline is connected to a third pipeline and a fourth pipeline via a tee. The outlet end of the third pipeline is connected to a steam compressor 18, and the outlet end of the fourth pipeline is connected to a first reboiler 04. The first reboiler 04 is located at the bottom of the primary distillation column 03 and is used to heat the bottom material of the primary distillation column 03. A buffer tank 02 is installed on the pipeline connecting the primary distillation column 03 and the first pipeline.

[0023] The primary distillation column 03 has an upper feed inlet on one side of its upper middle section and a lower feed inlet on its lower middle section. It also has a top gas outlet and a bottom liquid outlet at the top and bottom, respectively. The upper feed inlet of the primary distillation column 03 is connected to the raw material tank 02, and the lower feed inlet of the primary distillation column 03 is connected to the first condenser 05. The other end of the first condenser 05 is connected to the bottom liquid outlet of the primary distillation column via a tee. The top gas outlet of the primary distillation column 03 is connected to the light aldehyde removal column 07 sequentially via the water-aldehyde vapor compressor 19, the first condenser 05, and the aldehyde-water separator 06.

[0024] The aldehyde-water separator 06 includes a feed inlet, an upper aqueous phase outlet, and a lower oil phase outlet. The upper aldehyde-water outlet pipe of the aldehyde-water separator 06 is connected to the upper feed inlet of the primary distillation column 03, and the lower outlet of the aldehyde-water separator 06 is connected to the light phase removal column 07. The feed inlet of the aldehyde-water separator 06 is connected to the outlet of the water-aldehyde vapor compressor 19 through the first condenser 05.

[0025] The bottom of the light component removal tower 07 is equipped with a second reboiler 08, the bottom of the refining tower 11 is equipped with a third reboiler 12, the top of the light component removal tower 07 is equipped with a second condenser 09, the top of the refining tower 11 is equipped with a third condenser 13, and the top of the recovery tower 15 is equipped with a fourth condenser 16 and a third reflux tank 17. The second condenser 09 is connected to the light component removal tower 07 and the recovery tower (15) through the first reflux tank 10, respectively. The third condenser 13 is connected to the furfural outlet of the refining tower 11 and the third reflux tank 17 through the second reflux tank 14. The second condenser 09 and the third condenser 13 are mainly used for heating and boiling the materials in the light component removal process and the refining process to improve the separation effect of light components and furfural.

[0026] The bottom of the refining tower 11 is provided with a heavy component outlet, and the first reflux tank 10 connected to the light component removal tower 07 is provided with a light component outlet; the recovery tower 15 is connected to the light component outlet of the light component removal tower 07 and the heavy component outlet of the refining tower (11) respectively, and is used to recover furfural in the light component and furfural in the heavy component. The recovery tower 15 is a batch distillation tower, the tower bottom is a jacketed conical tank, the jacket is heated by steam, the tower bottom has a built-in stirring device, and the steam outlet of the recovery tower 15 is provided with a rectification section 151.

[0027] The working process of the above device is as follows:

[0028] 1) The high-temperature hydrolyzed aldehyde vapor from the hydrolysis reactor enters the steam package 01 as a heat source to heat the boiler water pipeline to generate low-pressure steam. Part of the low-pressure steam is pressurized by the steam compressor 18 and used as a heat source, while the other part of the low-pressure steam enters the first reboiler 04 to heat the material in the primary distillation tower 03. The high-temperature hydrolyzed aldehyde vapor is condensed to obtain furfural raw liquid, which enters the raw liquid tank 02.

[0029] 2) The obtained furfural stock solution enters the primary distillation column 03 from the stock solution tank 02 for atmospheric pressure primary distillation. The resulting water and furfural azeotrope vapor is compressed by the water-aldehyde vapor compressor 19 and then enters the first condenser 05 for heat exchange as a heat source to heat the bottom material of the primary distillation column 03. The water and furfural liquid after heat exchange and condensation enter the aldehyde-water separator 06 for aldehyde-water separation to obtain an aldehyde-water mixture and crude aldehyde. The aldehyde-water mixture is returned to the primary distillation system of the primary distillation column 03 for reflux.

[0030] 3) The aldehyde obtained by aldehyde-water separation in aldehyde-water separator 06 enters light component removal tower 07 for light component removal treatment, and obtains light components such as methanol, acetone, water, acetic acid, and a small amount of furfural, as well as a mixture of furfural and heavy components.

[0031] 4) The obtained furfural and heavy component mixture enters the refining tower 11 for refining. After separating the aldehyde residue, heavy component and a small amount of furfural, the target product furfural product is obtained.

[0032] 5) The light components from the light component removal tower 07 and the heavy components from the refining tower 11 are alternately fed into the recovery tower for recovery. The recovery tower 15 is a batch distillation tower, which operates under both atmospheric and negative pressure. The vessel is a jacketed conical tank with steam heating inside the jacket and built-in stirring. The steam outlet has a rectification section 151, which can achieve high-purity separation through reflux. Light component separation is carried out using atmospheric pressure batch distillation, while heavy component distillation is carried out using negative pressure batch distillation.

[0033] A method for refining furfural using the above-mentioned four-tower apparatus and producing steam as a byproduct:

[0034] 1) High-temperature hydrolyzed aldehyde vapor from the hydrolysis reactor enters steam boiler 01 as a heat source to heat the boiler water pipeline, generating low-pressure steam. Part of the low-pressure steam is pressurized by steam compressor 18 and used as a heat source, while the other part enters the first reboiler 04 to heat the material in the primary distillation column 03. The high-temperature hydrolyzed aldehyde vapor is condensed to obtain furfural stock solution, which enters the stock solution tank 02. The pressure of the aldehyde vapor is 0.6–1.3 MPa, the temperature is 126.5–195.6℃, and the furfural mass content is 3–16%. The pressure of the low-pressure steam is 0.1–0.7 MPa.

[0035] 2) The obtained furfural stock solution enters the primary distillation column 03 from the stock solution tank 02 for atmospheric distillation at a temperature of 90-99.5℃. The resulting water and furfural azeotropic vapor is compressed and heated by 15-20℃ by the water-aldehyde vapor compressor 19 and then enters the first condenser 05 for heat exchange as a heat source to heat the bottom material of the primary distillation column 03. The water and furfural liquid after heat exchange and condensation enter the aldehyde-water separator 06 for aldehyde-water separation to obtain an aldehyde-water mixture and crude aldehyde. The aldehyde-water mixture is returned to the primary distillation system of the primary distillation column 03 for reflux.

[0036] 3) The aldehyde obtained by aldehyde-water separation in aldehyde-water separator 06 enters light component removal tower 07, and is subjected to light component removal treatment at pressure -0.095 to -0.05 MPa and temperature 40 to 75℃ to obtain light components such as methanol, acetone, water, acetic acid, and a small amount of furfural, as well as a mixture of furfural and heavy components.

[0037] 4) The obtained furfural and heavy component mixture enters the refining tower 11 and is refined at a pressure of -0.098 to -0.06 MPa and a temperature of 85 to 99°C. After separating the aldehyde residue, heavy components and a small amount of furfural, the target product furfural is obtained.

[0038] 5) The mixture of light components obtained from the light component removal tower 07 and the mixture of aldehyde residue, heavy components, and a small amount of furfural from the bottom of the refining tower are recovered and treated. Specifically, the light components from the light component removal and the heavy components from the refining tower are alternately fed into the recovery tower for recovery. The recovery tower 15 is a batch distillation tower, which operates at atmospheric pressure and pressures of -0.095 to -0.05 MPa, respectively. The kettle is a jacketed conical tank with steam heating inside the jacket and built-in stirring. The steam outlet has a rectification section 151, which can achieve high-purity separation through reflux. Light component separation adopts atmospheric pressure batch distillation, while heavy component distillation adopts negative pressure batch distillation.

[0039] Example 2

[0040] use Figure 1 A method for producing furfural by continuous distillation in a four-tower system and generating steam as a byproduct includes the following steps:

[0041] 1) The aldehyde vapor from the hydrolysis reactor has a pressure of 0.4 MPa, a temperature of 151.6℃, and a furfural content of 5.1%. The aldehyde vapor enters the steam package 01 as a heat source to heat the boiler water pipeline to generate 0.2 MPa low-pressure steam. The low-pressure steam is pressurized by the steam compressor (18) and used as a heat source. The aldehyde vapor is condensed and then sent to the original liquid tank 02.

[0042] 2) The primary distillation column 03 operates under atmospheric pressure. The primary distillation temperature is 96.5℃. The raw liquid enters the primary distillation column 03 from the upper part. The water-furfural azeotrope vapor collected at the top of the column is compressed by the water-aldehyde vapor compressor 19 and sent to the first condenser 05 as a heat source to heat the bottom material of the primary distillation column 03. After condensation, the liquid enters the aldehyde-water separator 06. The upper aldehyde-water mixture is used as reflux for the primary distillation column 03, and the lower crude aldehyde is sent to the light removal column 07. Wastewater is collected from the bottom of the primary distillation column 03.

[0043] 3) The crude aldehyde from the aldehyde-water separator 06 enters from the middle of the light component removal tower 07. This tower operates at a pressure of -0.085 MPa and a temperature of 45.7℃. The methanol, acetone, water, acetic acid, and a small amount of furfural produced at the top of the tower are condensed and sent to the recovery tower 15. The furfural and heavy components collected at the bottom of the tower are sent to the purification tower 11 for distillation.

[0044] 4) Furfural and heavy components from the light component removal tower 07 enter the middle of the refining tower 11. This tower operates at a pressure of -0.09 MPa and a temperature of 91.2℃. Qualified furfural is collected from the top of the tower. Aldehyde residue, heavy components, and a small amount of furfural are collected from the bottom of the tower.

[0045] 5) The light component from the top of the light component removal column is fed into recovery column 15. The separation process of this light component is atmospheric pressure batch distillation. The light component is collected from the top of the column, and the furfural and water collected from the bottom of the column are returned to the system for separation. The heavy component from the bottom of purification column 11 is fed into recovery column 15. The heavy component is distilled under negative pressure at -0.095MPa in a batch process. Furfural is collected from the top of the column, and the heavy component is collected from the bottom of the column.

[0046] Example 3

[0047] use Figure 1 A method for producing furfural by continuous distillation in a four-tower system and generating steam as a byproduct includes the following steps:

[0048] 1) The aldehyde vapor from the hydrolysis reactor has a pressure of 0.8 MPa, a temperature of 175.4℃, and a furfural content of 7.8%. The aldehyde vapor enters the steam boiler 01 as a heat source to heat the boiler water pipeline and generate low-pressure steam of 0.4 MPa. The low-pressure steam is pressurized by the steam compressor 18 and used as a heat source. The aldehyde vapor is condensed and then sent to the raw liquid tank 02.

[0049] 2) The primary distillation column 03 operates under atmospheric pressure. The primary distillation temperature is 96.2℃. The raw liquid enters the primary distillation column 03 from the upper part. The water-furfural azeotrope vapor collected at the top of the column is compressed by the water-aldehyde vapor compressor 19 and sent to the first condenser 05 as a heat source to heat the bottom material of the primary distillation column 03. After condensation, the liquid enters the aldehyde-water separator 06. The upper aldehyde-water mixture is used as reflux in the primary distillation column 03, and the lower crude aldehyde is sent to the light removal column 07. Wastewater is collected from the bottom of the primary distillation column 03.

[0050] 3) The crude aldehyde from the aldehyde-water separator 06 enters from the middle of the light component removal tower 07. This tower operates at a pressure of -0.06 MPa and a temperature of 68°C. The methanol, acetone, water, acetic acid, and a small amount of furfural produced at the top of the tower are condensed and sent to the recovery tower 15. The furfural and heavy components collected at the bottom of the tower are sent to the purification tower 11 for distillation.

[0051] 4) Furfural and heavy components from the light component removal tower 07 enter the middle of the refining tower 11. This tower operates at a pressure of -0.07 MPa and a temperature of 98℃. Qualified furfural is collected from the top of the tower. Aldehyde residue, heavy components, and a small amount of furfural are collected from the bottom of the tower.

[0052] 5) The light component from the top of the light component removal column is fed into recovery column 15. The separation process of this light component is atmospheric pressure batch distillation. The light component is collected from the top of the column, and the furfural and water collected from the bottom of the column are returned to the system for separation. The heavy component from the bottom of purification column 11 is fed into recovery column 15. The heavy component is distilled under negative pressure (-0.05 MPa) batch distillation. Furfural is collected from the top of the column, and the heavy component is collected from the bottom of the column.

[0053] Obviously, the embodiments described above are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A four-tower refining apparatus for furfural and producing steam as a byproduct, characterized in that, It includes a steam package (01) and a primary distillation column (03), a light-light removal column (07), a refining column (11), and a recovery column (15) connected in sequence to the steam package (01); the steam package includes a first pipeline and a second pipeline, the inlet end of the first pipeline is connected to an aldehyde vapor heat source pipeline, and the outlet end of the first pipeline is connected to the primary distillation column (03); the inlet end of the second pipeline is connected to a boiler water pipeline, and the outlet end of the second pipeline is connected to a third pipeline and a fourth pipeline respectively through a tee, wherein the outlet end of the third pipeline is connected to a steam compressor (18), and the outlet end of the fourth pipeline is connected to a first reboiler (04); the first reboiler (04) is located at the bottom of the primary distillation column (03) and is used to heat the bottom material of the primary distillation column (03).

2. The apparatus for refining furfural with four towers and producing steam as a byproduct according to claim 1, characterized in that, The bottom of the refining tower (11) is provided with a heavy component outlet, and the bottom of the first reflux tank (10) connected to the light component removal tower (07) is provided with a light component outlet; the recovery tower (15) is connected to the light component outlet of the light component removal tower (07) and the heavy component outlet of the refining tower (11) respectively, and is used to recover furfural in the light component and furfural in the heavy component.

3. The apparatus for refining furfural using four towers and producing steam as a byproduct according to claim 1, characterized in that, The primary distillation tower (03) is connected to the first pipeline by a raw liquid tank (02).

4. The apparatus for refining furfural using four towers and producing steam as a byproduct according to claim 2, characterized in that, The primary distillation column (03) is provided with an upper feed inlet, a lower feed inlet, a top gas outlet, and a bottom liquid outlet. The upper feed inlet of the primary distillation column (03) is connected to the raw liquid tank (02), and the lower feed inlet of the primary distillation column (03) is connected to the first condenser (05). The other end of the first condenser (05) is connected to the bottom liquid outlet of the primary distillation column (03) through a tee. The top gas outlet of the primary distillation column (03) is connected to the light aldehyde removal column (07) in sequence through the water-aldehyde vapor compressor (19), the first condenser (05), and the aldehyde-water separator (06).

5. The apparatus for refining furfural using four towers and producing steam as a byproduct according to claim 4, characterized in that, The aldehyde-water separator (06) includes a feed inlet, an oil phase outlet, and a water phase outlet. The water phase outlet of the aldehyde-water separator (06) is connected to the upper feed inlet of the primary distillation tower (03). The oil phase outlet of the aldehyde-water separator (06) is connected to the light phase removal tower (07). The feed inlet of the aldehyde-water separator (06) is connected to the outlet of the water-aldehyde vapor compressor (19) through the first condenser (05).

6. The apparatus for refining furfural using four towers and producing steam as a byproduct according to claim 1, characterized in that, The recovery tower (15) is an intermittent distillation tower. The bottom of the tower is a conical tank with a jacket. Steam is passed through the jacket for heating. The bottom of the tower has a built-in stirring device. The steam outlet of the recovery tower (15) is equipped with a distillation section (151).

7. The apparatus for refining furfural using four towers and producing steam as a byproduct according to claim 6, characterized in that, The bottom of the light-light removal tower (07) is provided with a second reboiler (08), the bottom of the refining tower (11) is provided with a third reboiler (12), the top of the light-light removal tower (07) is provided with a second condenser (09), the top of the refining tower (11) is provided with a third condenser (13), and the top of the recovery tower (15) is provided with a fourth condenser (16) and a third reflux tank (17). The second condenser (09) is connected to the light-light removal tower (07) and the recovery tower (15) respectively through the first reflux tank (10). The third condenser (13) is connected to the furfural outlet of the refining tower (11) and the third reflux tank (17) through the second reflux tank (14).

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