A multi-stage membrane-in-coupling rectification device

Abstract

The utility model belongs to chemical engineering technical field relates to a kind of multi-section membrane inlay coupling rectification device. Including rectifying column and membrane separation unit;The membrane separation unit is inlaid at least installed on the tray of at least two rectifying columns;And the two trays are respectively located in the tower section in rectifying section and in rectifying section in tower section;The permeation side of membrane separation unit is respectively connected to vacuum pump by being located in the tower section interface of rectifying section and rectifying section;The top of the rectifying column is provided with reflux ratio control system, and the top of rectifying column is connected to distillate tank by condenser;The membrane separation unit is used to separate water or organic matter. Coupling to rectifying column inside simultaneously by multi-section membrane unit, different types of membrane unit can also be inlaid according to the characteristics of separation system, multi-section structure gives full play to the role of membrane separation, saves membrane area, enhances the synergistic effect of membrane unit and rectifying unit, improves the separation performance of membrane inlay coupling device, also reduces the energy consumption of rectification.

Description

Technical Field

[0001] This utility model relates to a multi-stage membrane embedded coupling distillation device and distillation method, belonging to the field of separation technology. Background Technology

[0002] Membrane separation offers advantages such as high separation efficiency, good thermal stability, and small footprint. Combining membrane separation with distillation technology can generate a synergistic effect, overcoming the shortcomings of each and further improving separation efficiency. Distillation-membrane coupling can be divided into two processes based on the embedding location of the membrane unit: external coupling and internal coupling. External coupling, as the most important coupling process, has developed rapidly. However, this approach is more like a combination of separation methods and cannot achieve in-situ separation. Furthermore, research on the synergistic mechanism between membrane separation and distillation is lacking, thus hindering the full realization of the separation potential of distillation-membrane coupling.

[0003] The distillation-membrane coupling process is a relatively recent development. This process embeds membrane units inside the distillation column, allowing the in-situ dehydration of the membrane units to shift the vapor-liquid equilibrium within the column, thereby improving distillation separation efficiency. Compared to external coupling processes, the intramembrane coupling process enhances the synergistic effect between distillation and membrane units, reduces energy costs, and improves the integration of the apparatus. While the intramembrane coupling process improves distillation separation efficiency, the impact of membrane unit embedding on the interior of the distillation column is poorly studied, limiting the performance improvement of the internal coupling process to some extent.

[0004] Currently, internal coupling processes embed membrane units entirely within the distillation column. Due to variations in vapor-liquid composition distribution and flow rate within the column, the vapor phase composition encountered by the membrane unit differs at different locations. This can lead to insufficient contact between the membrane unit and the vapor phase components, or incomplete removal of contacted components, thus hindering the full separation efficiency of the membrane unit. Existing technologies can further improve separation efficiency by increasing the membrane area at the optimal embedding location in the separation system to achieve the separation target. However, this does not fundamentally solve the problem, increasing process costs and potentially wasting membrane area. Furthermore, the membrane units embedded in the column can only separate specific systems; changing the separation system requires replacing the embedded membrane units. This problem is even more pronounced when separating multi-component components, as only one component can be removed by the membrane unit before further separation is achieved through subsequent operations, limiting the application range of this process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a multi-stage membrane-embedded coupling distillation device that embeds multiple membrane units inside a distillation column. This device can be applied to the separation of ethanol / water systems, thereby improving the separation efficiency.

[0006] A multi-stage membrane-embedded coupled distillation device includes a distillation column and a membrane separation unit;

[0007] The membrane separation unit is embedded in at least two distillation columns on at least one tray; and these two trays are located in columns within the rectification section and the stripping section, respectively.

[0008] The permeate side of the membrane separation unit is connected to the vacuum pump through column section interfaces located in the rectification section and the stripping section, respectively;

[0009] The distillation column is equipped with a reflux ratio control system at the top, and the top of the distillation column is connected to the distillate tank via a condenser.

[0010] The membrane separation unit is used to separate water or organic matter.

[0011] The membrane separation unit is equipped with a hydrophilic membrane or a hydrophobic membrane.

[0012] The hydrophilic membrane is made of one of NaA, T-type, MOR, CHA, NaY or ZSM-5 molecular sieves; the hydrophobic membrane is made of PDMS.

[0013] The carrier configuration of the separation membrane installed in the membrane separation unit is one of sheet type, tubular type or hollow fiber type.

[0014] The membrane separation unit in the rectification section is equipped with a hydrophobic membrane, while the membrane separation unit in the stripping section is equipped with a hydrophilic membrane; the multi-stage membrane embedded coupling rectification device is used to separate a mixed system of polar organic solvent-nonpolar organic solvent-water.

[0015] A multi-stage membrane-embedded coupled distillation method includes the following steps:

[0016] Using the above-mentioned distillation apparatus, water-containing organic materials are fed into the distillation column, and the raw materials are heated by an oil bath; the reflux ratio control system controls the reflux ratio of the distillate; the membrane separation units in the rectification section and the stripping section dehydrate the materials in the column section.

[0017] The membrane separation unit uses a vacuum pump to draw in osmotic pressure, with the operating pressure not exceeding 2000 Pa.

[0018] The material at the top of the tower is condensed, and the condensation medium is water.

[0019] The heating medium in the tower bottom is dimethyl silicone oil.

[0020] The beneficial effects of this invention are as follows: This invention employs a multi-segment membrane-embedded coupled distillation device, which can simultaneously embed multiple membrane units within the distillation column. The multi-segment structure allows the membrane units to contact more water in the vapor phase, increasing the overall water-driven force and enabling the membrane units to remove more water. This enhances the effect of the packing material within the column, thereby saving membrane area and strengthening the synergistic effect between the membrane units and the distillation unit, further improving the separation performance of the coupled device. The multi-segment structure also reduces the amount of circulating material within the column, thus lowering distillation energy consumption.

[0021] This invention utilizes multi-segment membrane units embedded within the column. These units can be of the same type of hydrophilic membrane or different types of membrane depending on the characteristics of the separation system. Besides separating binary systems, the embedded multi-segment membranes of various types can selectively separate specific substances in different segments. Therefore, the multi-segment embedded coupled distillation device has a wider range of applications and provides a new approach for the separation of multiple components. The area of ​​each membrane unit embedded within the column can be freely adjusted based on process simulation results. Furthermore, the impact of different membrane area distribution methods on the separation performance of the device can be investigated, thereby determining the optimal membrane area ratio and optimizing the membrane area according to different feed conditions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the distillation-membrane coupled distillation apparatus and simulated process used in Example 1 for ethanol / water;

[0023] Figure 2 This is a schematic diagram of the multi-stage membrane embedded coupling distillation device and simulated process applied to ethanol / water in Example 2;

[0024] Figure 3 This is a diagram showing the vapor-liquid composition distribution inside the multi-stage membrane embedded coupling distillation unit used in Example 2 for ethanol / water.

[0025] Figure 4 This is a schematic diagram of the multi-stage membrane embedded coupling distillation device and simulated process applied to ethanol / water in Example 3;

[0026] Figure 5 This is a schematic diagram of the small-scale multi-stage membrane embedded coupling distillation device and experimental process used in Example 4 (ethanol / water);

[0027] Figure reference numerals: 1-Feed tank; 2-Distillation column section; 3-Hydrophilic membrane (VP1); 4-Hydrophilic membrane (VP2); 5-Hydrophilic membrane (VP3); 6-Hydrophilic membrane (VP4); 7-Condenser; 8-Reflux ratio control system; 9-Distillate tank; 10-Vacuum pump; 11-VP1 column section interface; 12-VP2 column section interface. Detailed Implementation

[0028] The device and working method used in this utility model are described in detail below: Example 1

[0029] This example illustrates a process simulation and energy consumption analysis for the separation of an ethanol / water binary system using a distillation-membrane coupling method. It uses a feed rate of 200 kg per hour, with a feed composition of 50 wt.% ethanol and 50 wt.% water. The process flow diagram is shown below. Figure 1 As shown, when NaA molecular sieve membrane 3 is coupled to the upper section of a distillation column, after the combined effects of distillation and membrane separation, the ethanol content at the top of the column is 99.00 wt.%, the water content on the permeate side of the molecular sieve membrane is greater than 99.00 wt.%, and the required NaA membrane area is 6.4 m². 2 The permeate flow rate is 11.81 kg per hour. This process requires 1.06 tons of low-pressure steam to produce one ton of product. Example 2

[0030] This example illustrates the process simulation and energy consumption analysis of a multi-stage membrane-embedded coupled distillation system for the separation of an ethanol / water binary system. It uses a feed rate of 200 kg per hour, with a feed composition of 50 wt.% ethanol and 50 wt.% water. The process flow diagram is shown below. Figure 2 As shown, the membrane area is 6.4 m². 2 The NaA molecular sieve membrane was differentially embedded and coupled into the distillation column. Through the combined action of distillation and separation by membrane units 3, 4, 5, and 6, the final distillate from the top of the column had an ethanol content greater than 99.00 wt.%, a water content greater than 99.00 wt.% on the permeate side of the molecular sieve membrane, and a water content greater than 99.00 wt.% in the bottom distillate. The effect of multi-stage embedded coupling on the distillation separation effect in the above process flow was analyzed, and the results are shown in Table 1. The results show that, with the same membrane area, using multi-stage membrane units can increase the permeate flow rate of the membrane units and increase the ethanol content of the top distillate. The effect of multi-stage embedded coupling on the vapor-liquid composition distribution within the column is analyzed as follows: Figure 3 As shown, the vapor-liquid composition distribution within the column indicates that the multi-stage coupling structure allows the membrane unit to contact more water vapor, thereby obtaining a higher water-driven force and enabling the membrane unit to remove more water. This is consistent with the results of the permeate flow measurement, enhancing the synergistic effect between the membrane unit and distillation. The increased ethanol content in the top distillate further improves the separation performance of the coupling device. Simultaneously, the multi-stage structure allows the membrane unit to remove more water, reducing material circulation within the column and thus lowering distillation energy consumption. Energy consumption calculations show that 1.03 tons of low-pressure steam are required to obtain 1.0 ton of ethanol in this example. Compared to the coupling process in Example 1, this method saves 2.8% of low-pressure steam for the same membrane area.

[0031] Table 1. Multi-stage membrane embedded coupling distillation separation performance

[0032] Example 3

[0033] This example illustrates the process simulation and energy consumption analysis of a multi-stage membrane-embedded coupled distillation system for the separation of an ethanol / water binary system. It uses a feed rate of 200 kg per hour, with a feed composition of 50 wt.% ethanol and 50 wt.% water. The process flow diagram is shown below. Figure 3 As shown, the membrane area is 6.4 m². 2 The NaA molecular sieve membrane was divided into two membrane units, which were embedded in the upper section (VP1) 3 and the middle section (VP2) 4 of the distillation column, respectively. After distillation and the combined action of the two membrane units, the ethanol content of the distillate at the top of the column was greater than 99.00 wt.%. The above process flow was simulated to analyze the impact of different membrane area distribution schemes on the distillation separation effect and energy consumption when multiple membrane units were embedded. The simulation results are shown in Table 2. The results show that when multiple membrane units are embedded, although Scheme 1 has the largest overall permeate flow rate because its VP2 membrane area is the largest and the water content in the vapor phase is high, thus removing more water, the separation effect is the worst. Scheme 3 has the highest energy consumption, while Scheme 2 has the highest ethanol content in the distillate and moderate energy consumption. Therefore, by comprehensively comparing the energy consumption and distillation separation effect of the three schemes, it is concluded that the optimal solution for multi-stage membrane embedding coupling is to distribute the membrane area evenly.

[0034] Table 2. Separation performance of multi-stage membrane embedded coupling distillation with different membrane area distribution methods

[0035] Example 4

[0036] This example illustrates a specific experimental implementation of a small-scale, multi-stage membrane-embedded coupled distillation device for the separation of an ethanol / water binary system. Taking a feed mass of 1.4 kg and a feed composition of 50 wt.% ethanol and 20 wt.% water as an example, the total membrane area is 7.5 cm². 2 The experimental setup diagram is as follows: Figure 5 As shown, the system includes a feed tank 1, a distillation column section 2, hydrophilic membranes 3 and 4, a condenser 7, a reflux ratio control system 8, a distillate tank 9, and a vacuum pump 10. The lower part of the distillation column section is connected to the feed tank, and the upper part is connected to the condenser. The vacuum pump is connected to the hydrophilic membranes 3 and 4 through a cold trap. The hydrophilic membranes 3 and 4 are connected to the distillation column section interfaces 11 and 12, respectively. The reflux ratio control system 8 controls the distillate reflux ratio. The feed tank 1 is heated by a heater. The area of ​​the hydrophilic membranes 3 and 4 embedded in the distillation column is freely adjustable.

[0037] The above apparatus was used for ethanol / water system separation. The heating temperature was 105 °C, and the reflux ratio was set to 5. Hydrophilic membranes with different membrane areas were embedded in the middle and upper sections of the distillation column, respectively. The vapor permeation device was turned on, and the experimental results are shown in Table 3. Analysis of the experimental results shows that Scheme 1 has the largest permeate mass. This is because Scheme 1 has the largest VP2 membrane area, resulting in a higher water content in the vapor phase and thus removing more water, but the separation effect is the worst. Scheme 2 has the highest ethanol content in the distillate and the best distillation separation effect. The experimental results are consistent with the simulation, indicating that the optimal method for multi-stage membrane embedding coupling is to distribute the membrane area evenly.

[0038] Table 3. Distillation separation performance with different membrane area distribution methods

[0039]

[0040] This study demonstrates the feasibility of using the multi-segment membrane embedded coupling device for the separation of ethanol / water systems, proposes a multi-segment membrane embedded coupling method, and investigates the impact of multi-segment membrane embedding on the distillation separation effect and energy consumption through simulation and experiments. It also examines the influence of different membrane area distribution methods on multi-segment membrane embedded coupled distillation, and determines that evenly distributing the membrane unit area in multi-segment membrane embedding yields the best separation effect. Example 5

[0041] The separation process of the ethanol / water / acetone ternary system, with a total mass of 200 kg / h and a composition of 30 wt.% ethanol, 40 wt.% water, and 30 wt.% acetone, is carried out in feed tank 1 and heated to 110°C. Distillation column section 2 is divided into a lower section (rectifying section), a middle section (feed section), and an upper section (rectifying section). A hydrophilic NaA molecular sieve membrane (VP1, membrane area 3.2 m²) is embedded in the lower part of the column, with interface 11 connecting to vacuum pump 10. An acetone-selective PDMS membrane (VP2, membrane area 1.6 m²) is embedded in the upper part of the column, with interface 12 connecting to vacuum pump 10. A side stream outlet in the middle section is used to collect high-purity ethanol. The column bottom temperature is 115°C (silicone oil heating medium); the column top pressure is atmospheric pressure; the reflux ratio is 4; the vacuum pump pressure is 500 Pa on the VP1 side and 800 Pa on the VP2 side. During the dehydration process at the bottom of the column, water molecules in the vapor phase permeate through the VP1 membrane, and water vapor is collected on the permeate side (flow rate 25.3 kg / h, water content >99.5%). In the upper part of the column, acetone is removed: the remaining vapor phase rises to the top of the column, and acetone permeates through the VP2 membrane, with acetone vapor collected on the permeate side (flow rate 18.7 kg / h, acetone content >98.2%). Ethanol is collected via a side stream: the unpermeated ethanol accumulates in the middle section of the column and is collected via a side stream (flow rate 62.0 kg / h, ethanol content >99.6%, water content <0.3%, acetone content <0.1%). This embodiment achieves one-step separation of the ethanol / water / acetone ternary system by segmented embedding of hydrophilic membranes and acetone-selective membranes.

Claims

1. A multi-stage membrane-in-coupling rectification apparatus, characterized by, The system includes a distillation column and a membrane separation unit; the membrane separation unit is embedded in at least two trays of the distillation column; and these two trays are respectively located in sections within the rectification section and the stripping section; the permeate side of the membrane separation unit is connected to a vacuum pump through interfaces located in the sections within the rectification section and the stripping section; the top of the distillation column is equipped with a reflux ratio control system, and the top of the distillation column is connected to a distillate tank through a condenser; the membrane separation unit is used to separate water or organic matter.

2. The multi-stage membrane in-coupling rectifier apparatus according to claim 1, wherein, The membrane separation unit is equipped with a hydrophilic membrane or a hydrophobic membrane.

3. The multi-stage membrane-embedded coupled distillation apparatus according to claim 2, characterized in that, The hydrophilic membrane is made of one of the following molecular sieves: NaA, T-type, MOR, CHA, NaY, or ZSM-5.

4. The multi-stage membrane-integrated coupled distillation apparatus according to claim 1, wherein, The hydrophobic membrane is made of PDMS.

5. The multi-stage membrane-integrated coupled distillation apparatus according to claim 1, wherein, The carrier configuration of the separation membrane installed in the membrane separation unit is one of sheet type, tubular type or hollow fiber type.

6. The multi-stage membrane in-coupling rectifier apparatus according to claim 1, wherein, The membrane separation unit in the rectification section is equipped with a hydrophobic membrane, while the membrane separation unit in the stripping section is equipped with a hydrophilic membrane; the multi-stage membrane embedded coupling rectification device is used to separate a mixed system of polar organic solvent-nonpolar organic solvent-water.

Images