Device for recovering and extracting furfural from process wastewater

Abstract

The utility model discloses a device for recovering and extracting furfural from process wastewater. A pre-process dehydration and deacidification tower is connected with an inlet of a process wastewater storage tank, an outlet of the process wastewater storage tank is connected with a process wastewater feeding pump, an outlet of the process wastewater feeding pump is connected with an inlet of a preheater, an outlet of the preheater is connected with an inlet of a light component removal rectifying tower, and a tower kettle liquid phase of the light component removal rectifying tower is connected with an inlet of a recovery distillation tower; a gas phase at the top of the recovery distillation tower is connected with an inlet of a recovery condenser, the recovery condenser is connected with an inlet of an aldehyde separation tank, and a lower outlet of the aldehyde separation tank is connected with an inlet of a crude furfural removal storage tank; a steam gas phase at the top of the light component removal rectifying tower is connected with an inlet of a light component removal condenser, an outlet of the light component removal condenser is connected with an inlet of a liquid separation tank, an outlet of the liquid separation tank is connected with an inlet of a light component storage tank, and an outlet of the light component storage tank is connected with a light component delivery pump. And the tower is distilled in a stable temperature range, so that the technological process of recovering the wastewater to extract the furfural is realized, the refining yield can be improved by 3-6%, and the relative economic benefit is improved by 3-5%.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a device for recovering and extracting furfural from process wastewater. Background Technology

[0002] CN102086180B discloses a production process for improving furfural yield. The process involves distilling a dilute furfural-containing aldehyde hydrolysate in a primary distillation column, separating it using an aldehyde-water separation device, and then further processing the lower aldehyde phase into finished furfural product after washing in a water washing column and dehydration in a dehydration column. The upper aqueous phase from the aldehyde-water separation device is further washed and de-lightened before being recycled back into the primary distillation column. This invention also discloses a dedicated aldehyde-water separation device for the above process, comprising an outer cylinder, a middle cylinder, and an inner cylinder. The inner cylinder has multiple sieve holes distributed on its wall. The inlet is connected to the inner cylinder. A first settling chamber is located between the inner and middle cylinders, and a second settling chamber is located between the middle and outer cylinders. However, the lightened-light ...

[0003] Currently, in China, the crude furfural produced by initial distillation in furfural production plants typically contains around 90% furfural. This crude furfural is then refined into commercial furfural through various distillation methods (including intermittent distillation with alkali neutralization and deacidification, continuous distillation with alkali neutralization and deacidification, and continuous distillation without alkali neutralization in a tower for deacidification and dehydration). The refining yield is generally between 82% and 85%, while the theoretical yield should be above 89%. The reason for this low yield is that the first step of the distillation process, vacuum distillation and dehydration (deacidification), produces process wastewater containing a large amount of furfural (accounting for 15% to 20% of the weight of crude furfural, with a furfural content of 8% to 20%), which is discharged into the plant's wastewater treatment system. This wastewater results in the loss of furfural, leading to a low yield and poor production efficiency for the company.

[0004] To address the issue of low refining yield, analysis of the process wastewater containing furfural revealed that it primarily contains a large amount of water, followed by furfural, acetic acid, acetone, methanol, and other components. Because the content of these mixed components is relatively similar, conventional distillation methods would be insufficient to recover and extract furfural from the wastewater. Summary of the Invention

[0005] To overcome the above-mentioned defects, the purpose of this invention is to provide a device for recovering and extracting furfural from process wastewater, so as to improve the furfural purification rate. It is applicable to any furfural production enterprise. The comprehensive calculation shows that the purification yield can be increased by 3 to 6 percentage points on the original basis, and the relative economic benefits can be increased by 3 to 5%.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An apparatus for recovering and extracting furfural from process wastewater includes a process wastewater storage tank, a process wastewater feed pump, a preheater, a light component removal distillation column, a recovery distillation column, a recovery condenser and a light component removal condenser, an aldehyde separation tank, a crude furfural removal storage tank, a liquid separation tank, a light component storage tank, and a light component transfer pump. The upstream dehydration and deacidification tower is connected to the inlet of the process wastewater storage tank; the outlet of the process wastewater storage tank is connected to the process wastewater feed pump; the outlet of the process wastewater feed pump is connected to the inlet of the preheater; and the outlet of the preheater is connected to the inlet of the light component removal distillation column. The liquid phase at the bottom of the light component removal distillation column is connected to the inlet of the recovery distillation column; the vapor phase at the top of the recovery distillation column is connected to the inlet of the recovery condenser; the recovery condenser is connected to the inlet of the aldehyde separation tank; and the lower outlet of the aldehyde separation tank is connected to the inlet of the crude furfural storage tank. The vapor phase distilled from the top of the light component removal distillation column is connected to the inlet of the light component removal condenser; the outlet of the light component removal condenser is connected to the inlet of the liquid separator; the outlet of the liquid separator is connected to the inlet of the light component storage tank; and the outlet of the light component storage tank is connected to the light component transfer pump.

[0008] Optionally, the light-light distillation column includes, from top to bottom, a top vapor outlet, a distillation process liquid reflux outlet, a rectification section, a process wastewater inlet, a stripping section, a reboiler, a reboiler heater, and a reboiler liquid outlet; the internal components of the stripping section adopt the structure of float valves, perforated plates, tongue-shaped plates, or packing; the reboiler heater adopts the structure of external circulation, central circulation, or coil; the internal components of the rectification section adopt the structure of float valves, perforated plates, tongue-shaped plates, or packing.

[0009] Optionally, the capacity of the process wastewater storage tank is 10-40 m³. 3 The process wastewater feed pump is set with a flow rate range of 500–3000 L / h; the temperature of the light precipitate removal distillation column is controlled at 110℃–90℃; the amount of water-aldehyde solution collected accounts for 70%–90% of the feed amount; the vapor condensation temperature at the top of the recovery distillation column is 60℃–40℃; and the temperature of the recovery distillation column is controlled at 110℃–90℃.

[0010] Optionally, the light-weight distillation column includes a bottom level gauge connector, a top conical head, a top instrument interface, a bottom observation mirror, a bottom heating steam inlet, and a bottom vapor outlet. The top conical head is located at the top of the rectification section, narrower at the top and wider at the bottom. The top instrument interface is located on the side of the top conical head. The bottom level gauge connector is located on the upper and lower sides of the bottom, and the bottom heating steam inlet is located on the other side of the bottom. The bottom vapor outlet is located at the bottom of the bottom, above the bottom liquid outlet. The bottom observation mirror is located on the upper outer side of the bottom.

[0011] The positive and beneficial effects of this new technology:

[0012] The distillation process is carried out in a column within a stable temperature range. The vapor phase at the top of the column condenses and enters the aldehyde separation tank. After stratification in the aldehyde separation tank, the crude furfural at the bottom is metered by a mass flow meter and sent to a crude furfural storage tank. This process realizes the recovery and extraction of furfural from process wastewater and improves the furfural purification rate. This new distillation equipment is suitable for any furfural production enterprise in China. Comprehensive calculations show that the purification yield can be increased by 3-6 percentage points compared to the original method, resulting in a relative increase in economic benefits of 3-5%. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a process for recovering and extracting furfural from process wastewater, provided in Embodiment 1 of this invention.

[0014] Figure 2 This is a schematic diagram of the structure of a light-light distillation column provided in Embodiment 1 of this invention;

[0015] Figure 3 This is a schematic diagram of a light distillation column provided in Embodiment 2 of this invention.

[0016] 1. Process wastewater storage tank; 2. Process wastewater feed pump; 3. Preheater; 4. Light component removal distillation column; 5. Recovery distillation column; 6. Recovery condenser; 7. Aldehyde separation tank; 8. Light component removal condenser; 9. Separating tank; 10. Light component storage tank; 11. Light component transfer pump; 12. Reboiler; 13. Stripping section; 14. Rectifying section; 15. Top vapor outlet; 16. Distillation process liquid reflux port; 17. Process wastewater inlet; 18. Reboiler heater; 19. Reboiler liquid outlet; 20. Top conical head; 21. Top instrument interface; 22. Reboiler sight glass; 23. Reboiler level gauge connection; 24. Reboiler heating steam inlet; 25. Reboiler vapor outlet. Detailed Implementation

[0017] The present invention will be further explained below with reference to some specific implementation methods.

[0018] Example 1

[0019] like Figure 1 and Figure 2As shown, an apparatus for recovering and extracting furfural from process wastewater includes a process wastewater storage tank 1, a process wastewater feed pump 2, a preheater 3, a light component removal distillation column 4, a recovery distillation column 5, a recovery condenser 6, a light component removal condenser 8, an aldehyde separation tank 7, a crude furfural removal storage tank, a liquid separation tank 9, a light component storage tank 10, and a light component transfer pump 11. The upstream dehydration and deacidification tower is connected to the inlet of the process wastewater storage tank 1, the outlet of the process wastewater storage tank 1 is connected to the process wastewater feed pump 2, the outlet of the process wastewater feed pump 2 is connected to the inlet of the preheater 3, the outlet of the preheater 3 is connected to the inlet of the light component removal distillation column 4, and the liquid phase of the bottom 12 of the light component removal distillation column 4 is connected to the inlet of the recovery distillation column 5. The top vapor phase of the recovery distillation column 5 is connected to the inlet of the recovery condenser 6, the recovery condenser 6 is connected to the inlet of the aldehyde separation tank 7, and the lower outlet of the aldehyde separation tank 7 is connected to the inlet of the crude furfural storage tank; the top vapor phase of the light component removal distillation column 4 is connected to the inlet of the light component removal condenser 8, the outlet of the light component removal condenser 8 is connected to the inlet of the liquid separator 9, the outlet of the liquid separator 9 is connected to the inlet of the light component storage tank 10, and the outlet of the light component storage tank 10 is connected to the light component transfer pump 11, which can send the light components to the plant's light component (waste liquid) disposal system; the liquid wastewater (containing 0.05% furfural) from the bottom 12 of the recovery distillation column 5 is discharged to the plant's wastewater treatment system.

[0020] The upstream dehydration and deacidification tower is connected to the inlet of the process wastewater storage tank. The upstream dehydration and deacidification tower stores the process wastewater generated in the crude furfural refining process in the process wastewater storage tank. This invention has improved the light distillation tower. The new process distillation device is suitable for any furfural production enterprise in China. The comprehensive calculation shows that the refining yield can be increased by 3 to 6 percentage points on the original basis, and the relative economic benefits can be increased by 3 to 5%.

[0021] Specifically, the recovery distillation column 5 is a valve-type column; the light-weight condenser 8 is a tubular or plate type structure; the device includes a water cooling circulation system (water for condenser cooling) and a steam heating system (steam for heating the column bottom 12); Reference Figure 2 The light-light distillation column 4 includes, from top to bottom, a top vapor outlet 15, a distillation process liquid reflux outlet 16, a rectification section 14, a process wastewater inlet 17, a stripping section 13, a reboiler 12, a reboiler heater 18, and a reboiler liquid outlet 19. The internal components of the stripping section 13 adopt structural forms such as float valves, perforated plates, tongue-shaped plates, or packing. The reboiler heater 18 adopts structural forms such as external circulation, central circulation, coil, or straight pipe. The internal components of the rectification section 14 adopt structural forms such as float valves, perforated plates, tongue-shaped plates, or packing.

[0022] Distillation and rectification columns facilitate interphase mass transfer between the vapor and liquid phases. A condenser at the top partially condenses the vapor phase distilled at the top, with some condensate returning to the top as reflux, and the remaining distillate being the top product. A heater at the bottom partially vaporizes the liquid, causing the vapor to rise along the column, while the remaining liquid becomes the bottom product. Feed is added in the middle of the column; the liquid in the feed descends along with the liquid from the upper section, while the vapor in the feed rises along with the vapor from the lower section. Throughout the distillation column, the vapor and liquid phases come into countercurrent contact for interphase mass transfer. Volatile components in the liquid phase enter the vapor phase, while less volatile components in the vapor phase transfer to the liquid phase. For systems that do not form azeotropes, with proper design and operation, the top distillate will contain high-purity volatile components (low-boiling, light components), and the bottom product will contain high-purity less volatile components (high-boiling components). The section of the column above the feed inlet further concentrates the volatile components in the rising vapor and is called the rectification section 14; the section below the feed inlet extracts the volatile components from the descending liquid and is called the stripping section 13. The combination of these two sections allows for more complete separation of the components in the liquid mixture, producing two products of the desired purity.

[0023] The key to the relatively complete separation of liquid mixtures in distillation lies in the application of reflux. Reflux involves returning both the high-concentration, volatile liquid component from the top of the column and the high-concentration, non-volatile vapor component from the bottom to the column. This gas-liquid reflux creates countercurrent contact between the gas and liquid phases, resulting in relatively pure single-component products at both ends of the column. The ratio of the amount of liquid refluxed from the top of the column to the amount of product from the top is called the reflux ratio. It is a crucial control parameter in distillation operations, and its variation affects the separation efficiency and energy consumption.

[0024] Example 2

[0025] like Figure 3 As shown, the light distillation column 4 includes a bottom level gauge connector 23, a top conical head 20, a top instrument interface 21, a bottom observation mirror 22, a bottom heating steam inlet 24, and a bottom vapor outlet 25. The top conical head 20 is located at the top of the rectification section 14, and is narrower at the top and wider at the bottom. The top instrument interface 21 is provided on the side of the top conical head 20, which can be used to install instruments such as thermocouples and thermometers. The bottom level gauge connector 23 is respectively located on the upper and lower sides of the bottom, and the bottom heating steam inlet 24 is located on the other side of the bottom. The bottom vapor outlet 25 is located at the bottom of the bottom, above the bottom liquid outlet 19. The bottom observation mirror 22 is located on the upper outer side of the bottom, allowing real-time observation of the inside of the bottom.

[0026] Example 3

[0027] A process for recovering and extracting furfural from industrial wastewater includes the following steps:

[0028] S1. The process wastewater distilled from the dehydration and deacidification tower is stored in a process wastewater storage tank (the process wastewater generated during the crude furfural refining process is stored in the process wastewater storage tank), and is fed by a process wastewater feed pump (flow rate 3m³ / h). 3 Wastewater is fed into the light-duty distillation tower at the set flow rate ( / h, head 10-40m);

[0029] S2. Passing primary steam into the reboiler heater, the column is distilled to remove light components within a stable temperature range (110℃~70℃). The water-aldehyde solution continuously collected from the reboiler (collected amount accounts for 70~90% of the feed) enters the recovery distillation column.

[0030] S3. Simultaneously, primary steam is introduced into the heater of the recovery distillation tower to distill the tower within a stable temperature range (110℃~90℃). After the vapor phase at the top of the tower condenses (60℃~40℃), it enters the aldehyde separation tank. After stratification in the aldehyde separation tank, the lower crude furfural is metered by a mass flow meter and sent to the crude furfural storage tank.

[0031] Furthermore, the capacity of the process wastewater storage tank is 10m³. 3 -40m 3 The process wastewater feed pump is set with a flow rate range of 500L / h to 3000L / h; the primary steam pressure is controlled between 0.5MPa and 0.3MPa; the temperature of the light precipitate removal distillation column is controlled between 110℃ and 90℃; the amount of water-aldehyde solution collected accounts for 70% to 90% of the feed amount; the vapor condensation temperature at the top of the recovery distillation column is between 60℃ and 40℃; and the temperature of the recovery distillation column is controlled between 110℃ and 90℃.

[0032] The process wastewater distilled from the dehydration and deacidification tower is fed into the middle section of the light component removal distillation tower via a feed pump. Primary steam is introduced into the heater of the light component removal distillation tower to bring the gas and liquid phases into contact and carry out interphase mass transfer, enabling the tower to remove light components through distillation within a stable temperature range. The vapor phase at the top of the tower is condensed to obtain the distilled light components. The water-aldehyde solution continuously collected from the bottom of the tower enters the recovery distillation tower. Simultaneously, primary steam is introduced into the heater of the recovery distillation tower to distill within a stable temperature range. The vapor phase at the top of the tower is condensed and enters the aldehyde separation tank. After stratification in the aldehyde separation tank, the crude furfural at the bottom is metered by a mass flow meter and sent to the crude furfural storage tank, realizing the process of recovering and extracting furfural from the process wastewater.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the new technical solution of this invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the new technical solution of this invention, as long as they do not depart from the spirit and scope of the new technical solution of this invention, should be covered within the scope of the claims of this invention.

Claims

1. An apparatus for recovering and extracting furfural from process wastewater, characterized in that, Includes process wastewater storage tanks, process wastewater feed pumps, preheaters, light component removal distillation columns, recovery distillation columns, recovery condensers and light component removal condensers, aldehyde separation tanks, crude furfural removal storage tanks, liquid separation tanks, light component storage tanks and light component transfer pumps. The dehydration and deacidification tower of the preceding process is connected to the inlet of the process wastewater storage tank. The outlet of the process wastewater storage tank is connected to the process wastewater feed pump. The outlet of the process wastewater feed pump is connected to the inlet of the preheater. The outlet of the preheater is connected to the inlet of the light component removal distillation tower. The bottom liquid phase of the light component removal distillation tower is connected to the inlet of the recovery distillation tower. The top vapor phase of the recovery distillation tower is connected to the inlet of the recovery condenser. The recovery condenser is connected to the inlet of the aldehyde separation tank. The lower outlet of the aldehyde separation tank is connected to the inlet of the crude furfural removal storage tank. The top vapor phase of the light component removal distillation tower is connected to the inlet of the light component removal condenser. The outlet of the light component removal condenser is connected to the inlet of the liquid separator. The outlet of the liquid separator is connected to the inlet of the light component storage tank. The outlet of the light component storage tank is connected to the light component transfer pump. The light-light-removal distillation column includes, from top to bottom, a top vapor outlet, a distillation process liquid reflux outlet, a rectification section, a process wastewater inlet, a stripping section, a reboiler, a reboiler heater, and a reboiler liquid outlet. The stripping section internals utilize float valves, perforated plates, tongue-shaped plates, or packing structures. The reboiler heater employs an external circulation, central circulation, or coil-type structure. The rectification section internals utilize float valves, perforated plates, tongue-shaped plates, or packing structures. The light-light distillation column also includes a bottom level gauge connector, a top conical head, a top instrument interface, a bottom observation mirror, a bottom heating steam inlet, and a bottom gas phase outlet; the top conical head is located at the top of the distillation section, and is narrower at the top and wider at the bottom; the top instrument interface provided on the side of the top conical head is used to install a thermocouple thermometer; The level gauge connector is used to install the level gauge and is respectively located on the upper and lower sides of the column bottom; the heating steam inlet of the column bottom is located on the other side of the column bottom; the gas phase outlet of the column bottom is located at the bottom of the column bottom, above the liquid phase outlet of the column bottom; and the observation mirror of the column bottom is located on the upper outer side of the column bottom.

2. The apparatus for recovering and extracting furfural from process wastewater as described in claim 1, characterized in that, The capacity of the process wastewater storage tank is 10-40 m³; the flow rate of the process wastewater feed pump is set to 500-3000 L / h; the temperature of the light volatile organic compound (LDC) removal distillation column is controlled at 110℃-90℃; the amount of water-aldehyde solution collected from the bottom of the LDC removal distillation column accounts for 70%-90% of the feed amount; the vapor condensation temperature at the top of the recovery distillation column is 60℃-40℃; the temperature of the recovery distillation column is controlled at 110℃-90℃.

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