Integrated device and method for multi-stage separation and waste heat of alcohol wastewater

Abstract

The application discloses a kind of alcohol wastewater multistage separation and waste heat integration device and method, device includes vertical coaxial tower body, gas purification section, extraction rectification section, pre-concentration section and heat exchange liquid collection section are integrated from top to bottom in it.The extraction rectification section is equipped with self-cleaning tray system, and the inclined hole is prevented from being blocked in cooperation with the injection cover.The heat exchange liquid collection section is built-in spiral coil type reboiler, and the heat medium inlet is connected with the extraction section bottom rich solvent outlet, to form internal energy circulation;Device outside is equipped with multi-section jacketed preheating heat exchange unit, recovers system waste heat gradient preheats raw material wastewater, forms external energy recovery network.The method includes raw material preheating, pre-concentration, extraction separation, internal energy circulation and discharge steps.The application highly integrates multistage separation function, substantially reduces energy consumption by internal and external double-circulation energy network, and uses self-cleaning tray to ensure long-term stable operation, with the advantages of compact equipment, significant energy saving, reliable operation.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment and resource recycling technology, specifically to a method and apparatus for treating alcohol wastewater, and particularly to an energy-saving treatment apparatus capable of multi-stage separation and deep energy integration. Background Technology

[0002] The waste liquid generated during alcohol production typically contains 5%-15% alcohol. Direct discharge not only wastes resources but also causes environmental pollution. Recovering the alcohol from this waste liquid has both economic and environmental value. Currently, industrial processes mainly use distillation or extractive distillation to treat it.

[0003] A typical traditional process system consists of multiple independent units connected in series: a pre-concentration tower for initial concentration of wastewater; an extractive distillation tower for adding a selective solvent to separate alcohol and water; and a solvent recovery tower for distilling alcohol from the rich solvent and regenerating the solvent. In addition, multiple reboilers, condensers, feed preheaters, and product coolers are required. This multi-tower series configuration has significant drawbacks: a large number of units, a large footprint, complex piping connections, and high initial investment. More importantly, heat is supplied and discharged independently between each unit, resulting in low overall system thermal efficiency. The distillation process requires the evaporation of a large amount of water, with energy consumption accounting for over 60% of production costs, leading to high operating expenses. Furthermore, impurities such as fibers, bacteria, and inorganic salts often found in alcohol wastewater can easily clog trays or packing, requiring frequent cleaning and affecting continuous and stable operation.

[0004] Therefore, there is an urgent need in this field to develop a new device that can overcome the above-mentioned defects, achieve efficient alcohol recovery, significantly reduce equipment complexity and operating energy consumption, and improve anti-clogging ability and operational stability. Summary of the Invention

[0005] To address the technical problems of existing technologies, such as complex equipment, high energy consumption, and susceptibility to clogging, the present invention aims to provide a highly integrated multi-stage separation and waste heat recovery device and method for alcohol wastewater. This device, through a compact structural design, highly integrates the functions of a traditional multi-tower system and achieves cascaded and cyclical energy utilization, aiming to significantly reduce equipment investment and operating energy consumption, thus achieving the comprehensive goals of equipment compactness, energy minimization, and stable operation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a multi-stage separation and waste heat integration device for alcohol wastewater, characterized in that it includes a vertically arranged single coaxial tower body, the interior of which, from top to bottom, is provided with a gas purification section, an extractive distillation section, a pre-concentration section, and a heat exchange collection section. The gas purification section has a purified waste gas outlet at its top. The extractive distillation section has an extractant inlet at its top, a multi-layer tray system inside, and a solvent-rich outlet at its bottom. The pre-concentration section has a raw material wastewater inlet on its upper side wall. The heat exchange collection section has a built-in spiral coil reboiler, and a treated wastewater outlet at its bottom. A preheating heat exchange unit is also included, wherein the raw material channel inlet of the preheating heat exchange unit is used to receive raw material wastewater, and its raw material channel outlet is connected to the raw material wastewater inlet of the pre-concentration section. The heat source channel of the preheating heat exchange unit is configured to receive waste heat from the process stream inside the device.

[0007] Preferably, the heat medium inlet of the spiral coil reboiler is connected to the rich solvent outlet at the bottom of the extractive distillation section via a pipeline, and its heat medium outlet is connected to the raw material channel of the preheating heat exchange unit via a pipeline.

[0008] Preferably, the preheating heat exchange unit includes a multi-segment jacket fitted outside the tower body, and the inner wall of the multi-segment jacket is divided into three independent heating chambers (upper, middle, and lower) by an annular partition between the outer wall of the tower body and the inner wall of the multi-segment jacket. The raw material channel of the preheating heat exchange unit is a raw material wastewater coil that extends in a serpentine manner and sequentially winds around the upper, middle, and lower heating chambers. At least one of the heating chambers is connected to a cooling medium circulation pipe from the condenser of the gas purification section or a cooling medium circulation pipe from the product outlet cooler.

[0009] Preferably, the tray system is a self-cleaning tray system, comprising a tray body and a spray hood; the tray body has downwardly inclined holes; the spray hood is positioned above the inclined holes, and its bottom end forms an annular gap with the upper surface of the tray body. Further, the angle between the axis of the inclined holes and the tray plane is 30-60 degrees; the spray hood is a cap-shaped structure with a closed top, and the diameter of its lower opening is larger than the diameter of the inclined holes.

[0010] As a further optimization, the device also includes an integrated interface for connecting an external solvent recovery tower; the integrated interface is configured to selectively connect the heat medium circuit of the reboiler of the solvent recovery tower to at least one heating chamber of the multi-segment jacket, and to selectively connect the cooling medium outlet of the top condenser of the solvent recovery tower to the raw material wastewater coil.

[0011] Preferably, the pre-concentration section is filled with structured packing, and the raw material wastewater inlet is connected to a liquid distributor located above the structured packing; the diameter of the heat exchange collection section is larger than that of the section above it, and its bottom is tapered to form a collection hopper, with the treated wastewater outlet located at the bottom of the collection hopper.

[0012] The present invention also provides a method for treating alcohol wastewater using the above-mentioned apparatus, characterized by comprising the following steps: (S1) Preheating raw material wastewater: The alcohol wastewater is flowed through the raw material channel of the preheating heat exchange unit and preheated using the waste heat from the process stream inside the device; (S2) Pre-concentration: The preheated wastewater is introduced into the pre-concentration section, so that it comes into countercurrent contact with the rising steam from the heat exchange collection section for preliminary concentration; (S3) Extraction and separation: Steam from the pre-concentration section is introduced into the extractive distillation section, and extractant is introduced from the extractant inlet, so that the steam and the extractant from top to bottom are in countercurrent contact on the tray system, and the alcohol in the steam is absorbed by the extractant. (S4) Internal energy circulation: The high-temperature rich solvent collected from the bottom of the extractive distillation section flows into the spiral coil reboiler as a heat medium in part or all of the solvent, providing reboiling heat for the heat exchange collection section. (S5) Emission and resource recovery: The purified gas is discharged from the exhaust gas outlet of the gas purification section, and the treated wastewater is discharged from the wastewater outlet of the heat exchange liquid collection section; the rich solvent collected from the rich solvent collection outlet is subjected to subsequent resource recovery treatment.

[0013] Compared with existing technologies, the beneficial effects of this invention are as follows: First, by innovatively integrating four functional sections—pre-concentration, extractive distillation, gas purification, and heat exchange—into a single coaxial tower, it replaces the traditional multi-tower series system. This significantly reduces the number of devices, connecting pipes, and instruments, reducing the floor space by 40%-50% and equipment investment costs by 30%-40%. Second, it constructs a dual internal and external energy circulation network. The internal circulation utilizes the high-temperature solvent-rich sensible heat generated during the extraction process as the main heat source for the spiral coil reboiler, greatly reducing dependence on external steam or electric heating. The external circulation, through a multi-stage jacketed system, recovers waste heat from the gas purification condenser, product cooler, and even the external solvent recovery tower in stages, for preheating the raw material wastewater, thus realizing the utilization of system waste heat. The overall energy-saving effect can reach 40%-60%. Third, the unique self-cleaning tower plate design, utilizing downward-sloping orifices and high-speed jets generated by the spray hood, effectively prevents the adhesion and accumulation of solid impurities on the tower plate, solving the industry problem of easy clogging of towers when treating complex wastewater, ensuring long-term continuous and stable operation of the device, and reducing maintenance costs. Fourth, the integrated design simplifies the process and facilitates centralized control and optimization. The functional sections are naturally coupled vertically, ensuring efficient heat and mass transfer, and the device exhibits good adaptability to feed wastewater of varying concentrations. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view of the coaxial tower of the multi-stage separation and waste heat integration device for alcohol wastewater of the present invention; Figure 2 for Figure 1 Schematic diagram of external pipe connections; Figure 3 This is a cross-sectional view of the extractive distillation section inside the coaxial column; Figure 4 This is a schematic diagram of a self-cleaning tray system; Figure 5 This is a cross-sectional view of the pre-concentration section inside the coaxial tower. Figure 6 This is a schematic diagram of the heat exchange base liquid section inside the coaxial tower. Figure 7 This is a schematic diagram of a preheating heat exchange unit; Figure 8 This is a schematic diagram of an external solvent recovery tower; Figure 9 This is a flowchart illustrating the integrated process of wastewater classification treatment and preheating in this invention.

[0015] Explanation of the labels in the diagram: 1. Tower body; 11. Gas purification section; 111. Waste gas outlet; 12. Extractive distillation section; 121. Rich solvent outlet; 122. Extractant inlet; 13. Pre-concentration section; 131. Raw material wastewater inlet; 132. Structured packing; 133. Liquid distributor; 14. Heat exchange collection section; 141. Spiral coil reboiler; 142. Treated wastewater outlet; 143. Collection hopper; 2. Preheating heat exchange unit; 21. Multi-stage jacket; 211. Heating chamber; 22. Raw material wastewater coil; 3. Self-cleaning tray system; 31. Tray body; 32. Spray hood; 33. Inclined hole; 34. Bottom clearance; 4. Solvent recovery tower; 41. Alcohol product outlet. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Example

[0017] Integrated Separation and Deep Energy Recovery Implementation This embodiment demonstrates the complete configuration and operational performance of the device of the present invention in achieving high-efficiency separation and extreme energy saving. The core of the device is a vertically arranged single coaxial tower 1, designed for a pressure of 0.3 MPa, made of stainless steel, with a total height of approximately 28 meters. The tower 1 has an inner diameter of 1.6 meters and is clearly divided into four functional sections from top to bottom by internal components.

[0018] The gas purification section 11 is 3 meters high, and a DN150 exhaust gas outlet 111 is provided at the center of its top. A stainless steel wire mesh demister is installed inside to remove liquid droplets entrained in the rising steam.

[0019] The extractive distillation section 12 is 10 meters high. A DN80 extractant inlet 122 is located on the top wall of this section. Twenty layers of the self-cleaning tray system 3 of this invention are installed within the section. Each tray body 31 has multiple regularly arranged circular oblique holes 33, each with a diameter of 12 mm, whose central axis is inclined downwards at a 45-degree angle to the horizontal tray plane. A top-closed cap-shaped spray hood 32 is fixed directly above each oblique hole 33. The lower opening diameter of the spray hood 32 is 20 mm, and its bottom edge forms a uniform annular gap 34 with a height of 10 mm between it and the upper surface of the tray body 31. A collection tray is located at the bottom of this section, connected to a DN100 rich solvent outlet 121.

[0020] The pre-concentration section 13, with a height of 7 meters, is located below the extractive distillation section 12. The upper wall of this section has a DN150 feed wastewater inlet 131. The section is filled with stainless steel 250Y perforated plate corrugated structured packing 132, with a total packing height of 5.5 meters. A tubular liquid distributor 133 is installed at the top of the packing layer and connected to the feed wastewater inlet 131.

[0021] The heat exchange and collection section 14 is an expanded section, with the tower diameter increased to 2.0 meters and the height to 8 meters. A conical collection hopper 143 is welded to the bottom of this section, and a DN150 treated wastewater outlet 142 is located at the bottom of the hopper. Within this section, a spiral coil reboiler 141 is installed. This reboiler is constructed from Φ45×3.5 mm stainless steel tubing, with a total heat exchange area of ​​approximately 120 square meters, and is submerged below the operating liquid level in the tower bottom.

[0022] In this embodiment, the preheating heat exchange unit 2 adopts a highly integrated multi-segment jacket design. A cylindrical jacket shell 21 is concentrically fitted onto the outside of the column body 1, covering the extractive distillation section 12 and the pre-concentration section 13. A 120 mm wide annular space is formed between the inner wall of the jacket and the outer wall of the column body. This space is precisely divided into three independent and sealed heating chambers 211—upper, middle, and lower—by two annular partitions welded to the column wall. A stainless steel raw material wastewater coil 22, approximately 180 meters long and with a diameter of Φ32×3 mm, is arranged in a serpentine pattern (6 round trips) and sequentially winds through the interiors of the lower, middle, and upper heating chambers 211, and is fixed by a bracket.

[0023] The energy connections are as follows: the inlet and outlet of the upper heating chamber 211 are connected in parallel to the cooling water circulation pipeline of the condenser at the top of the gas purification section 11. After the cooling water is heated from 40°C to approximately 72°C in the condenser, a portion is diverted into this chamber to heat the wastewater in coil 22. The middle heating chamber 211 is connected in parallel to the cooler circulation water pipeline of the final alcohol product storage tank, receiving cooling return water at approximately 58°C. The lower heating chamber 211 serves as a buffer or for future connection to a lower-grade heat source.

[0024] The coaxial tower assembly achieves deep energy integration with an external solvent recovery tower 4. The solvent recovery tower 4 is a Φ1.0-meter atmospheric pressure packed tower. Approximately 60% of the ethylene glycol at approximately 95°C collected from the rich solvent outlet 121 of the main tower is directed to the spiral coil reboiler 141 as a heat transfer medium. After releasing sensible heat, it cools to approximately 78°C and is then mixed with the remaining rich solvent before being sent to the feed inlet of the solvent recovery tower 4. The bottom of the solvent recovery tower 4 is heated by 0.3MPa saturated steam. The condensate from this steam at approximately 105°C is refluxed through a three-way regulating valve and connected to the inlet pipe of the upper chamber 211 of the multi-section jacket 21 as a supplementary high-temperature heat source. Meanwhile, the cooling water outlet of the condenser at the top of the solvent recovery tower 4, which condenses alcohol vapor at about 78°C, has a water temperature of about 45°C. It is connected to the inlet of the raw material wastewater coil 22, which runs through the lower chamber 211 of the multi-section jacket 21, and is used to preheat the lowest temperature raw material.

[0025] The process and results are as follows: Alcohol wastewater with a concentration of 10% (v / v) and a temperature of 30°C enters the serpentine coil 22 within the multi-section jacket 21 at a flow rate of 15 m³ / h. Inside the coil, the wastewater is heated in stages: first, it is preheated by a heat source of approximately 45°C in the lower chamber; then, it is heated further by a heat source of approximately 58°C in the middle chamber; and finally, it is heated to 70°C by a mixed heat source of approximately 72°C and 105°C in the upper chamber. The preheated wastewater is then evenly distributed onto the packing of the pre-concentration section 13 by the distributor 133, where it comes into countercurrent contact with hot steam from the bottom of the column, achieving initial concentration. The concentrated steam then enters the extractive distillation section 12, where it comes into countercurrent contact with a 50°C lean ethylene glycol extractant added from the top at a flow rate of 5 m³ / h on the self-cleaning tray system 3. The alcohol is efficiently absorbed, forming ethylene glycol rich at approximately 95°C.

[0026] A portion of the high-temperature rich solvent serves as the core heat medium to drive the spiral coil reboiler 141, providing rising steam for the entire tower, which is then cooled after heat exchange. All the rich solvent is ultimately regenerated in the solvent recovery tower 4 to obtain an alcohol product with a concentration higher than 95%. The regenerated extractant is cooled and recycled.

[0027] Through actual operation testing and energy balance calculations, the device in this embodiment, compared to a traditional independent system consisting of a pre-concentration tower, extraction tower, solvent recovery tower, and multiple heat exchangers, reduces the external steam consumption required to drive the main tower reboiling by approximately 65% ​​while achieving the same throughput and product purity. Simultaneously, over 80% of the system's low-grade waste heat is recovered through a multi-stage jacket system for raw material preheating. The device has achieved over 5000 hours of continuous and stable operation, verifying its superior energy-saving effect and reliability. Example

[0028] This embodiment provides a detailed description of the self-cleaning tray system 3 described in claims 4 and 5. This system is the core component for achieving long-term stable operation of the device of the present invention. Its structural design addresses the problem of easy deposition and clogging of suspended solids, colloids, and heavy organic compounds that may be present in alcohol wastewater, achieving fully automatic online cleaning through a purely mechanical method.

[0029] The system mainly consists of a tray body 31 and a spray hood 32. The tray body has multiple inclined holes 33 with their axes tilted downwards at 30 to 60 degrees, preferably 45 degrees. These inclined holes are covered by a cap-shaped spray hood 32 with a closed top. An annular gap 34 with a height of 5 to 10 mm is formed between the bottom of the spray hood and the upper surface of the tray body. During operation, the cleaning function automatically activates and continues to work. Its mechanism is a dynamic and continuous physical process. First, trace solid impurities in the wastewater gradually deposit on the surface of the tray body 31. As the deposits accumulate, their own weight overcomes the adhesion force to the tray surface, and with the help of the inherent downward tilt of the inclined holes 33, they begin to slide and accumulate towards the orifice under the action of gravity. Simultaneously, high-speed process steam rising from the lower tray is sprayed upwards through the inclined holes 33. This fluid shears and disturbs the deposits at the orifice, loosening them and maintaining the patency of the orifice. Subsequently, the loosened sediment clumps, under the influence of gravity, completely slide off along the inclined channel and leave the current tray through the bottom gap 34, falling into the liquid layer of the next tray. This process repeats on each tray with the same structure, allowing solid impurities to be transferred layer by layer from the top to the bottom of the column, eventually all of which collect in the heat exchange collection section 14 at the bottom of the column and are discharged from the system along with the purified wastewater or residual liquid.

[0030] Through the anti-clogging performance test of the self-cleaning tray, except that the self-cleaning tray system 3 in the extractive distillation section 12 of Example 1 was replaced with a conventional F1 type floating valve tray, the other structures, dimensions and operating conditions of the comparative device, such as feed concentration, flow rate and temperature, were kept the same as in Example 1. In this comparative experiment, the energy integration of the external solvent recovery tower 4 was not activated for the time being, and the rich solvent was directly sent out for processing.

[0031] The experiment used the same batch of alcohol wastewater containing yeast residues, fiber, and other suspended solids at a concentration of 8%, and conducted a long-term comparative operation under the same process parameters.

[0032] The F1 type floating valve tray unit operated smoothly initially after startup. However, after approximately 360 hours of continuous operation, the differential pressure monitoring value in the extractive distillation section 12 rose continuously from the initial 4.5 kPa to 7.8 kPa, an increase of 73%. Along with the increase in differential pressure, the tray mass transfer efficiency decreased, and the separation effect fluctuated. Shutdown and disassembly revealed that a large amount of fibrous material was entangled around the floating valve legs and orifices, resulting in a significant reduction in the effective flow area of ​​some orifices, and even restricting the movement of some floating valves.

[0033] In this embodiment of the invention, a self-cleaning tray system 3 is used. During the same 360-hour operating cycle, the pressure difference in the extractive distillation section 12 remains stable within a narrow range of 4.7 kPa to 5.1 kPa, with a maximum increase of less than 10%. The device operates smoothly throughout the entire process, and no decrease in separation efficiency is observed. Shutdown inspection shows that the oblique holes 33 on the tray remain unobstructed, and only a small amount of soft deposits are present on the inner wall of the spray hood 32 and at the bottom gap 34; there is no hard scaling or structural blockage, which can be easily restored by simple rinsing.

[0034] This comparative experiment powerfully demonstrates that, when faced with complex and easily clogged industrial alcohol wastewater, the self-cleaning tray system of this invention, thanks to its unique downward-sloping jet and active flushing mechanism, can maintain a good hydrodynamic state within the tower for a long period. This characteristic is the core foundation for ensuring the long-term, maintenance-free, and stable operation of the entire highly integrated device, and is an advantage that traditional tray designs cannot match. Example

[0035] This embodiment illustrates the workflow, energy integration method, and operation control logic of the preheating heat exchange unit 2. This unit is the core energy-saving module for achieving ultra-low energy consumption operation in this invention. Its function is to systematically recover waste heat at each stage of the process and to perform precise gradient preheating of raw material wastewater.

[0036] The preheating heat exchange unit 2 preferably adopts a multi-segment jacket 21 structure fitted outside the tower body 1, with its inner wall divided into three independent heating chambers 211 (upper, middle, and lower) by an annular partition. The raw material wastewater coil 22 extends in a serpentine manner and sequentially winds around these three chambers.

[0037] During the start-up phase of the unit, the raw wastewater is first pumped into the coil section that runs through the lower heating chamber 211. At this time, low-pressure steam is injected into the chamber through the auxiliary steam inlet to initially heat the wastewater to 50-60°C.

[0038] Once the main tower is operating stably and internal waste heat is generated, the system switches to a highly efficient integrated recovery mode. Cooled, rich solvent from the heat medium outlet of the spiral coil reboiler 141, at approximately 85-95°C, is introduced into the lower chamber, replacing auxiliary steam as the primary heat source to preheat the wastewater to 60-70°C. Subsequently, the wastewater flows into the coils in the middle heating chamber 211, which is connected to the cooling medium circuit of the product outlet cooler, receiving warm water at approximately 50-65°C to further heat the wastewater to 70-80°C. Finally, the wastewater enters the coils on the upper heating chamber 211, which is connected to the cooling medium circuit of the condenser in the gas purification section 11. Utilizing the high-grade condensation heat at approximately 70-85°C, the wastewater is ultimately heated to the target feed temperature of 80-90°C, and then piped into the pre-concentration section 13.

[0039] When the unit needs to treat wastewater with higher concentrations or requires a higher degree of solvent regeneration and thus activates the external solvent recovery tower 4, its integrated interface comes into play. This interface can introduce the condensation heat of the low-temperature steam generated by the reboiler of the solvent recovery tower into the middle or lower chamber of the multi-stage jacket as a supplementary heat source; at the same time, it can also connect the cooling water outlet of its top condenser to the front end of the raw material wastewater coil 22 for additional preheating. This design deeply integrates the external equipment into the overall energy network, avoiding additional energy consumption.

[0040] The preheating integration process is remarkably effective. By recovering over 75% of the usable waste heat within the system, it significantly enhances the thermal properties of the raw material wastewater, reducing external steam consumption of the reboiler in the main column's extractive distillation section by more than 40%. This embodiment fully demonstrates how the invention, through structural innovation, transforms dispersed waste heat of varying grades into ordered and efficient driving energy, which is the core of achieving optimal overall energy efficiency for the entire system.

[0041] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technical principles disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A multi-stage separation and waste heat integration device for alcohol wastewater, characterized in that, include: A single coaxial tower body (1) is arranged vertically. The tower body (1) has a gas purification section (11), an extractive distillation section (12), a pre-concentration section (13) and a heat exchange liquid collection section (14) arranged from top to bottom. The top of the gas purification section (11) is provided with a purified exhaust gas outlet (111). The top of the extractive distillation section (12) is provided with an extractant inlet (122), which is equipped with a multi-layer tray system (3) and a rich solvent outlet (121) at the bottom. The pre-concentration section (13) has a raw material wastewater inlet (131) on the upper side wall. The heat exchange liquid collection section (14) is equipped with a spiral coil reboiler (141), and the bottom of the reboiler is provided with a treated wastewater outlet (142). And a preheating heat exchange unit (2), the raw material channel inlet of the preheating heat exchange unit (2) is used to receive raw material wastewater, and its raw material channel outlet is connected to the raw material wastewater inlet (131) of the pre-concentration section (13). The heat source channel of the preheating heat exchange unit (2) is configured to receive waste heat from the process stream inside the device.

2. The apparatus according to claim 1, characterized in that, The heat medium inlet of the spiral coil reboiler (141) is connected to the rich solvent outlet (121) at the bottom of the extractive distillation section (12) via a pipe, and its heat medium outlet is connected to the raw material channel of the preheating heat exchange unit (2) via a pipe.

3. The apparatus according to claim 1, characterized in that, The preheating heat exchange unit (2) includes a multi-segment jacket (21) fitted outside the tower body (1). The inner wall of the multi-segment jacket (21) and the outer wall of the tower body (1) are divided into three independent heating chambers (211) of the upper, middle and lower sections by an annular partition. The raw material channel of the preheating heat exchange unit (2) is a raw material wastewater coil (22) that extends in a serpentine manner and passes through the three heating chambers (211) of the upper, middle and lower sections in sequence. At least one of the heating chambers (211) is connected to a cooling medium circulation pipe. The cooling medium circulation pipe is selected from one or two of the cooling medium circulation pipes of the condenser from the gas purification section (11) and the cooling medium circulation pipes of the product extraction cooler.

4. The apparatus according to claim 1, characterized in that, The tray system is a self-cleaning tray system (3), including a tray body (31) and a spray hood (32); the tray body (31) has downward inclined holes (33); the spray hood (32) covers the inclined holes (33) and its bottom end forms an annular bottom gap (34) with the upper surface of the tray body (31).

5. The apparatus according to claim 4, characterized in that, The angle between the axis of the inclined hole (33) and the plane of the tower plate is 30-60 degrees; the spray hood (32) is a cap-shaped structure with a closed top, and the diameter of the opening at its lower end is larger than the diameter of the inclined hole (33).

6. The apparatus according to claim 3, characterized in that, It also includes an integrated interface for connecting an external solvent recovery tower (4); the integrated interface is configured to selectively connect the heat medium circuit of the reboiler of the solvent recovery tower (4) to at least one heating chamber (211) of the multi-section jacket (21), and selectively connect the cooling medium outlet of the top condenser of the solvent recovery tower (4) to the raw material wastewater coil (22).

7. The apparatus according to claim 1, characterized in that, The pre-concentration section (13) is filled with structured packing (132), and the raw material wastewater inlet (131) is connected to a liquid distributor (133) located above the structured packing (132); the diameter of the heat exchange collection section (14) is larger than that of the section above it, and its bottom is tapered to form a collection hopper (143), and the treated wastewater outlet (142) is located at the bottom of the collection hopper (143).

8. A method for treating alcohol wastewater using the apparatus described in any one of claims 1-7, characterized in that, Includes the following steps: (S1) Preheat raw material wastewater: The alcohol wastewater flows through the raw material channel of the preheating heat exchange unit (2) and is preheated by the waste heat from the process flow inside the device. (S2) Pre-concentration: The preheated wastewater is introduced into the pre-concentration section (13) so that it comes into countercurrent contact with the rising steam from the heat exchange collection section (14) for preliminary concentration; (S3) Extractive distillation: Steam from the pre-concentration section (13) is introduced into the extractive distillation section (12), and extractant is introduced from the extractant inlet (122) so that the steam and the extractant from top to bottom are in countercurrent contact on the tray system (3), and the alcohol in the steam is absorbed by the extractant. (S4) Internal energy circulation: The high-temperature rich solvent collected from the bottom of the extractive distillation section (12) flows into the spiral coil reboiler (141) as a heat medium in part or all, providing reboiling heat to the heat exchange collection section (14); (S5) Discharge and subsequent treatment: The purified gas is discharged from the exhaust gas outlet (111) of the gas purification section (11), the treated wastewater is discharged from the wastewater outlet (142) of the heat exchange liquid collection section (14), and the rich solvent collected from the rich solvent outlet (121) is used for subsequent regeneration treatment.

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