Downflow type washing tower device for solid-liquid separation and purification

Abstract

This utility model relates to the field of washing tower technology, specifically to a co-current washing tower device for solid-liquid separation and purification. Firstly, the device adopts a co-current structure, eliminating the need for piston-driven operation. Crystal movement is controlled by the pressure heads of the feed pump and solvent pump, as well as the rotation speed of the scraper disc, simplifying the mechanical structure, reducing costs, and improving operational stability and ease of use. Secondly, the device precisely controls the pressure difference between each section through a pressure stabilizing tank, ensuring stable pressure during production. Furthermore, the co-current washing method allows for a longer contact time between the solid and liquid phases during material and energy exchange. Through the synergistic effect of the solid-liquid separation section, the first solvent replacement section, the second solvent replacement section, and the crystal scraping and melting section, the separation effect and product purity are significantly improved.

Description

Technical Field

[0001] This utility model relates to the field of washing tower technology, and in particular to a co-current type washing tower device for solid-liquid separation and purification. Background Technology

[0002] In the field of solid-liquid separation and purification of crystal slurry composed of crystals and mother liquor, commonly used methods include centrifugal filtration, pressure filtration, and vacuum filtration. Among these, piston-type and hydraulic washing towers have certain advantages in pressure filtration devices. Piston-type washing towers rely on the movement of the piston to provide power for pushing the crystals towards the product end. This design can achieve the purpose of solid-liquid separation to a certain extent, and because its power source is clear, it has a relatively direct control method for pushing the crystals to move. Hydraulic washing towers rely on the static pressure head of the feed pump to provide power for pushing the crystals towards the product end. Its mechanical parts are relatively simple and do not require a complex piston structure, which makes the construction and maintenance of the equipment more convenient. At the same time, it can also complete the basic functions of solid-liquid separation and purification.

[0003] However, firstly, piston-type washing towers typically rely on the movement of a piston to propel the crystals towards the product end, resulting in complex mechanical components and high mechanical costs. Furthermore, their control programs are complex, hindering simplification of production operations and improvement of stability. Secondly, hydraulic washing towers typically rely on the static pressure head of a feed pump to propel the crystals towards the product end. While their mechanical components are simpler, the pressure control in each section and part is complex, leading to unstable pressure during production. Thirdly, both piston-type and hydraulic washing towers involve countercurrent washing and separation processes between solids and liquids. The contact time between the solid and liquid phases during mass and energy exchange is relatively short, resulting in poor separation efficiency. Utility Model Content

[0004] The purpose of this invention is to provide a co-current washing tower device for solid-liquid separation and purification, aiming to solve the following problems in the prior art: First, piston-type washing towers typically rely on the movement of a piston to provide power for pushing crystals towards the product end, resulting in complex mechanical components and high mechanical costs; at the same time, their control programs are also complex, making it difficult to simplify production operations and improve stability. Second, hydraulic washing towers typically rely on the static pressure head of a feed pump to provide power for pushing crystals towards the product end. Although their mechanical components are relatively simple, the pressure control of each section and part is complex, resulting in unstable pressure during production operation. Third, both piston-type and hydraulic washing towers involve counter-current washing and separation processes of solids and liquids, resulting in short contact time between the solid and liquid phases during mass and energy exchange, leading to poor separation effects.

[0005] To achieve the above objectives, this utility model employs a co-current scrubbing tower device for solid-liquid separation and purification, comprising a solid-liquid separation cylinder, a first solvent replacement cylinder, and a second solvent replacement cylinder. The solid-liquid separation cylinder is provided with a feed inlet and a first solvent return inlet. A feed pump is installed at the feed inlet. A first solvent return distribution network is installed inside the solid-liquid separation cylinder. Filter rods are installed between the solid-liquid separation cylinder, the first solvent replacement cylinder, and the second solvent replacement cylinder. A filter rod sealing layer is installed between the filter rods and the solid-liquid separation cylinder. The filter rod is provided with a second solvent secondary replacement outlet. A first filter screen assembly is provided between the solid-liquid separation cylinder and the first solvent replacement cylinder. A second filter screen assembly is provided between the first solvent replacement cylinder and the second solvent replacement cylinder. A secondary replacement filter screen, a scraper disc, and a melting section cylinder are arranged sequentially from top to bottom below the second solvent replacement cylinder. The scraper disc is connected to a motor. The melting section cylinder is provided with a molten liquid inlet and a molten liquid outlet. A molten liquid circulation pump and a melter are connected between the molten liquid inlet and the molten liquid outlet.

[0006] The first filter assembly includes a solid-liquid separation filter and a first solvent filter section. The first solvent filter section has a first solvent outlet. The solid-liquid separation filter is disposed inside the first solvent filter section. The first solvent filter section is disposed between the solid-liquid separation section and the first solvent replacement section. The first solvent return port is connected to the first solvent outlet, and a first solvent pump is disposed between the first solvent return port and the first solvent outlet.

[0007] The second filter assembly includes a primary replacement filter and a second solvent filter cylinder. The second solvent filter cylinder is provided with a second primary solvent replacement inlet. The primary replacement filter is disposed inside the second solvent filter cylinder. The second solvent filter cylinder is disposed between the first solvent replacement cylinder and the second solvent replacement cylinder. The second secondary solvent replacement outlet is connected to the second primary solvent replacement inlet, and a second solvent return pump is provided between the second secondary solvent replacement outlet and the second primary solvent replacement inlet.

[0008] The solid-liquid separation filter is a cylindrical wedge-shaped filter with a pore size of 100µm to 300µm; the primary replacement filter is a cylindrical wedge-shaped filter with a pore size of 100µm to 300µm; the secondary replacement filter is a cylindrical perforated mesh with 100µm to 300µm oblique holes; and the first solvent return distribution mesh is a 50-150 mesh straight-hole perforated mesh.

[0009] A first pressure stabilizing tank is provided between the first solvent outlet and the second solvent primary replacement inlet, and a second pressure stabilizing tank is provided between the second solvent primary replacement inlet and the molten liquid outlet.

[0010] This invention discloses a co-current washing tower device for solid-liquid separation and purification. Firstly, the device adopts a co-current structure, eliminating the need for piston-driven operation. Crystal movement is controlled by the pressure heads of the feed pump and solvent pump, as well as the rotation speed of the scraper disc, simplifying the mechanical structure, reducing costs, and improving operational stability and ease of use. Secondly, the device precisely controls the pressure difference between each section through a pressure stabilizing tank, ensuring stable pressure during production. Furthermore, the co-current washing method allows for a longer contact time between the solid and liquid phases during material and energy exchange. Through the synergistic effect of the solid-liquid separation section, the first solvent replacement section, the second solvent replacement section, and the crystal scraping and melting section, the separation effect and product purity are significantly improved. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the structure of the co-current type scrubbing tower device for solid-liquid separation and purification according to this utility model.

[0013] 1-Feed pump, 2-Second solvent secondary displacement outlet, 3-Filter rod, 4-Filter rod seal, 5-First solvent return distribution net, 6-Feed inlet, 7-Solid-liquid separation cylinder section, 8-Solid-liquid separation filter screen, 9-First solvent filter cylinder section, 10-First solvent displacement cylinder section, 11-Primary displacement filter screen, 12-Second solvent filter cylinder section, 13-Second solvent displacement cylinder section, 14-Secondary displacement filter screen, 15-Scraper disc, 16-Melting section cylinder section, 17-Melted liquid inlet, 18-Motor, 1 9-Melting liquid circulation pump, 20-Second solvent return pump, 21-First solvent return port, 22-First solvent pump, 23-First solvent outlet, 24-First pressure stabilizing tank, 25-Second solvent primary replacement inlet, 26-Second pressure stabilizing tank, 27-Melting liquid outlet, 28-Melter, A-Solid-liquid separation section, B-Second solvent primary replacement section, C-Second solvent secondary replacement section, D-Crystal scraping and melting section, E-First solvent, F-Crystal slurry feed, G-Crystal melting liquid. Detailed Implementation

[0014] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0015] Please see Figure 1 This utility model provides a co-current type washing tower device for solid-liquid separation and purification, including a solid-liquid separation cylinder 07, a first solvent replacement cylinder 10, and a second solvent replacement cylinder 13. The solid-liquid separation cylinder 07 is provided with a feed inlet 06 and a first solvent return inlet 21. A feed pump 01 is provided on the feed inlet 06. A first solvent return distribution network 05 is provided inside the solid-liquid separation cylinder 07. A filter rod 03 is arranged between the solid-liquid separation cylinder 07, the first solvent replacement cylinder 10, and the second solvent replacement cylinder 13. A filter rod sealing layer 04 is provided between the filter rod 03 and the solid-liquid separation cylinder 07. The filter rod 03 is equipped with... A second solvent secondary replacement outlet 02 is provided. A first filter assembly is provided between the solid-liquid separation cylinder 07 and the first solvent replacement cylinder 10. A second filter assembly is provided between the first solvent replacement cylinder 10 and the second solvent replacement cylinder 13. A secondary replacement filter 14, a scraper disc 15 and a melting section cylinder 16 are arranged sequentially from top to bottom below the second solvent replacement cylinder 13. The scraper disc 15 is connected to a motor 18. The melting section cylinder 16 is provided with a molten liquid inlet 17 and a molten liquid outlet 27. A molten liquid circulation pump 19 and a melter 28 are connected between the molten liquid inlet 17 and the molten liquid outlet 27.

[0016] In this embodiment, the solid-liquid separation cylinder 07 achieves preliminary solid-liquid separation through the synergistic action of the feed pump 01 and the first solvent return port 21, combined with the solid-liquid separation filter 08; the first solvent replacement cylinder 10 completes the first round of replacement of impurities on the crystal surface using the primary replacement filter 11; the second solvent replacement cylinder 13 further purifies the crystal through the secondary replacement filter 14. The three are designed with a co-current pressure gradient to ensure that the crystal and solvent are in full contact during axial flow, solving the problem of short contact time in countercurrent washing. At the same time, it avoids the mechanical complexity of piston-type equipment and the pressure fluctuation problem of hydraulic equipment, significantly improving separation efficiency and operational stability.

[0017] In this embodiment, the bottom of the filter rod 03 is integrally connected to the scraper disc 15. When the scraper disc 10 rotates, the filter rod 03 also rotates. Thus, the upper part of the filter rod 03 is connected to the top flange cover of the solid-liquid separation cylinder section 07 via the filter rod seal 04, ensuring the airtightness of the device. The opening direction of the secondary replacement filter screen 14 at the lower part of the filter rod 03 is tangential to the axis of rotation. Therefore, under the action of centrifugal force, the liquid can easily pass through the filter screen openings while crystals are intercepted. Preferably, the distance between the lower end of the secondary replacement filter screen 14 and the scraper disc 10 is 100~300mm.

[0018] Furthermore, the solid-liquid separation cylinder 07 achieves preliminary solid-liquid separation through the synergistic action of the feed pump 01 and the first solvent return port 21, combined with the solid-liquid separation filter 08; the first solvent replacement cylinder 10 completes the first round of replacement of impurities on the crystal surface using the primary replacement filter 11; the second solvent replacement cylinder 13 further purifies the crystal through the secondary replacement filter 14. The three are designed with a co-current pressure gradient, which allows the crystal and solvent to fully contact each other in the axial flow, solving the problem of short contact time in countercurrent washing. At the same time, it avoids the mechanical complexity of piston-type equipment and the pressure fluctuation problem of hydraulic equipment, significantly improving separation efficiency and operational stability.

[0019] In this embodiment, the solid-liquid separation filter 08 adopts a 100-300μm wedge-shaped hole structure, which effectively intercepts crystal particles while allowing the mother liquor to be discharged through the jacketed first solvent filter section 09, thus achieving efficient solid-liquid separation. The first solvent filter section 09 is connected to the solid-liquid separation section 07 through a flange to form a detachable sealed structure, which not only ensures the convenience of cleaning the filter screen, but also avoids the problem of difficult filter screen replacement in traditional piston-type equipment, thereby reducing maintenance costs.

[0020] Furthermore, the second filter assembly includes a primary replacement filter 11 and a second solvent filter cylinder 12. The second solvent filter cylinder 12 is provided with a second primary solvent replacement inlet 25. The primary replacement filter 11 is disposed inside the second solvent filter cylinder 12. The second solvent filter cylinder 12 is disposed between the first solvent replacement cylinder 10 and the second solvent replacement cylinder 13. The second secondary solvent replacement outlet 02 is connected to the second primary solvent replacement inlet 25, and a second solvent return pump 20 is provided between the second secondary solvent replacement outlet 02 and the second primary solvent replacement inlet 25.

[0021] In this embodiment, the primary replacement filter 11, with its 100-300μm wedge-shaped hole design, can uniformly distribute the solvent flow field when fresh solvent is injected into the secondary solvent primary replacement inlet 25, thereby enhancing the replacement effect of impurities on the crystal surface. The secondary solvent filter section 12 and the primary solvent replacement section 10 are connected by a filter rod 03 to form a continuous co-current channel, allowing the crystals to fall naturally under the action of gravity and pressure difference, avoiding the crystal accumulation problem caused by pressure fluctuations in hydraulic equipment, and improving the replacement efficiency.

[0022] Furthermore, the solid-liquid separation filter 08 is a cylindrical wedge-shaped filter with a pore size of 100um~300um; the primary replacement filter 11 is a cylindrical wedge-shaped filter with a pore size of 100um~300um; the secondary replacement filter 14 is a cylindrical perforated mesh with 100um~300um oblique holes; and the first solvent return distribution mesh 05 is a 50~150 mesh straight hole perforated mesh.

[0023] In this embodiment, the solid-liquid separation filter 08 adopts a wedge-shaped pore structure of 100μm~300μm. Its involute channel design can reduce crystal accumulation on the filter surface through the shearing effect of the wedge-shaped edge while ensuring crystal retention rate, thus extending the continuous operation cycle. The primary replacement filter 11 and the secondary replacement filter 14 both adopt a wedge-shaped / oblique pore structure with the same pore size range. The wedge-shaped pores of the primary replacement filter 11 can enhance the scouring and removal of initial impurities on the crystal surface by the solvent, while the oblique pores of the secondary replacement filter 14... The perforated mesh (with the opening direction along the axial tangent) utilizes centrifugal force to accelerate solvent penetration and improve the purity of the final product. The first solvent return distribution mesh 05 uses a 50-150 mesh straight-hole perforated mesh. Its uniformly distributed circular channels allow the returned solvent to be injected into the solid-liquid separation zone in a laminar flow state, avoiding crystal breakage caused by turbulence. At the same time, this pore size range can prevent large particles of impurities from entering the system, and will not cause rapid blockage due to excessively small pore size. The three work together to achieve an efficient, stable, and low-maintenance solid-liquid separation and solvent replacement process.

[0024] Furthermore, a first pressure stabilizing tank 24 is provided between the first solvent outlet 23 and the second solvent primary replacement inlet 25, and a second pressure stabilizing tank 26 is provided between the second solvent primary replacement inlet 25 and the molten liquid outlet 27.

[0025] In this embodiment, the first pressure stabilizing tank 24 maintains a pressure difference of 50-250 kPa between the solid-liquid separation cylinder 07 and the first solvent replacement cylinder 10, ensuring the stability of solid-liquid separation. The second pressure stabilizing tank 26 controls the pressure gradient between the second solvent replacement cylinder 13 and the melting section cylinder 16, allowing the crystals to continuously receive solvent washing during the downstream process, thus avoiding operational fluctuations caused by the complex multi-stage pressure control of hydraulic equipment. The synergistic effect of the two tanks enables the device to achieve a stable crystal delivery effect similar to piston-driven operation without the need for a complex piston mechanism.

[0026] In this invention, it is divided into a solid-liquid separation section A, a second solvent primary replacement section B, a second solvent secondary replacement section C, and a crystal scraping and melting section D.

[0027] In the solid-liquid separation section A of this invention, there are two feed streams. The first stream of crystal slurry feed is sent to the feed inlet 06 via the feed pump 01. The second stream of first solvent return feed is fed in through the upper first solvent return inlet 21 and after being distributed by the solid-liquid distribution filter screen. The crystal slurry feed inlet 06 is located on the side of the solid-liquid separation cylinder 07, and the first solvent return inlet 21 is located at the top of the solid-liquid separation cylinder 07. The lower part of the solid-liquid separation cylinder 07 is connected to the first solvent filter cylinder 09 via a flange. The first solvent filter cylinder 09 is a jacketed type, with a filter screen on the inner wall. The first solvent (i.e., filtrate) of the solid-liquid separation passes through the solid-liquid separation filter screen 08 on the inner wall and then into the jacket. Inside the casing, the first solvent is drawn into the inlet of the first solvent pump 22 through the first solvent outlet 23. After passing through the first solvent pump 22, part of the first solvent material is returned as return liquid to the first solvent return port 21, and the remaining first solvent material is discharged to other processes outside the boundary area. In this section, under the driving force of the feed pump 01 and the pressure head of the first solvent pump 22, the solid and liquid phases exchange materials and energy in a co-current manner in the solid-liquid separation cylinder 07 and the first solvent filter cylinder 09, ensuring the residence time of the initial solid-liquid separation (the serpentine arrow indicates the direction of liquid flow, and the straight arrow indicates the direction of crystal pushing).

[0028] In the second solvent primary replacement section B of this invention, the crystals after solid-liquid separation flow through the first solvent replacement cylinder section 10 and then enter the second solvent filter cylinder section 12. Inside the second solvent filter cylinder section 12, the second solvent liquid phase material from the second solvent return pump 20 enters through the first solvent primary replacement inlet, and then, after being distributed through the primary replacement filter 11, enters the inner cylinder, where it replaces and washes the impurities on the crystal surface. In this section, under the driving force of the preceding section, the crystals, rich in liquid phase impurities, undergo thorough surface impurity replacement and energy exchange with the second solvent in a co-current manner within the second solvent filter cylinder section 12.

[0029] In the second solvent secondary replacement section C of this invention, the crystals after the first solvent primary replacement flow together with the second solvent through the second solvent replacement cylinder 13 region. The replaced second solvent then passes through the secondary replacement filter 14 and exits from the second solvent secondary replacement outlet 02 before entering the second solvent return pump 20. A portion of the molten liquid remains in the liquid phase passing through the secondary replacement filter 14. The concentrations of the molten liquid, the secondary replacement liquid, and the primary replacement liquid decrease in that order. In this section, the crystals, whose surface liquid phase impurities have been reduced, undergo thorough surface impurity replacement and energy exchange with the second solvent in a co-current manner within the second solvent replacement cylinder 13 under the driving force from the front section.

[0030] In the crystal scraping and melting section D of this invention, the motor 18 drives the scraper disc 15 to rotate. The scraper disc 15 has serrated scrapers. As the scraper disc 15 rotates, it scrapes the crystals, causing them to fall from below and mix into the molten liquid circulation pipe. The molten liquid is then heated by the melter 28 and completely melted into a liquid phase. It is then pumped by the molten liquid circulation pump 19 to the molten liquid inlet 17 for further rinsing and as a mixture of scraped crystals. Part of the molten liquid enters the molten liquid cylinder through the molten liquid inlet 17 and passes through the secondary replacement filter 14, undergoing a secondary replacement process on the crystal feed in the second solvent replacement cylinder 13. The portion of the molten liquid melted by the melter 28 is discharged as a qualified product outside the boundary area.

[0031] In this invention, the co-current flow of the co-current scrubbing tower is achieved through the pressure or pressure difference of each section. First, by controlling the pressure of the feed pump 01 and the first solvent return port 21, as well as the rotation speed of the bottom scraper disc 15, a total driving force is provided for the crystals in each section of the device to move from top to bottom. Then, controlling the pressure of the first solvent outlet 23 provides a pressure difference for the solid-liquid separation of the crystals and the liquid, so that the first solvent and the uppermost crystals flow downward together. The crystals continue to be pushed downward to the area of ​​the first solvent replacement section 10, while the first solvent is discharged from the first solvent outlet. Next, under the combined action of the driving force from the upper part and the pressure difference maintained by the first pressure stabilizing tank 24, the crystals in the first solvent replacement section 10 continue to flow downward together with the second solvent from the second solvent primary replacement inlet 25. The process involves moving the crystal while simultaneously replacing impurities on its surface, resulting in fewer and purer crystals. After passing through the second solvent filter section 12, the crystals, driven by the pressure and pressure difference created by the second solvent pressure tank and the melting circulating liquid, continue to flow downstream together in the second solvent replacement section 13 for further material and energy replacement, further enhancing crystal purity. Finally, the crystals are scraped into powder by a scraper and mixed into the melting circulating liquid. Controlling the pressure difference between the circulating liquid and the pressure at the second solvent replacement outlet 02, a portion of the melting circulating liquid passes through the second solvent replacement filter, ultimately replacing impurities on the crystal surface. This process removes almost all impurities, resulting in a nearly perfect pure crystal melt that is discharged as a product outside the boundary area.

[0032] In this invention, pressure values ​​(unit: kPaG) at each control point are also provided, as shown in Table 1 below:

[0033] The following examples use L-lactide as feed material, but the apparatus is not limited to the separation and purification of L-lactide; it is applicable to any solid-liquid phase feed with the same separation principle.

[0034] This utility model also provides five embodiments, as follows: Example 1 A 90wt% L-lactide crystal slurry with a solid content of 50% and a flow rate of 1000 kg / h at a temperature of 90°C enters the upper part of a co-current scrubbing tower after being fed by feed pump 01. The separated liquid phase material is discharged from the first solvent outlet 23 and then pumped by the first solvent pump 22. The first solvent, at a temperature of 90°C and a flow rate of 500 kg / h, is discharged outside the boundary area, while a stream with a flow rate of 2 m³ / h returns to the first solvent return outlet 21. The molten liquid circulating at the bottom with a flow rate of 20 m³ / h enters the molten liquid inlet 17. The flow rate of the second solvent at the second solvent secondary replacement outlet 02 is controlled at 2 m³ / h and the temperature at 100°C, and the flow rate of the molten crystal liquid discharged outside the boundary area is controlled at 500 kg / h. The pressure values ​​at each control point are operated according to the data in the Example 1 column of Table 1. Analysis revealed that the L-lactide content in the first solvent discharged outside the boundary area was 81.6 wt%, and the L-lactide content in the molten crystal discharged outside the boundary area was 98.4 wt%.

[0035] Example 2 A 90wt% L-lactide crystal slurry with a solid content of 50% and a flow rate of 1000 kg / h at a temperature of 90°C enters the upper part of a co-current scrubbing tower after being fed by feed pump 01. The separated liquid phase material is discharged from the first solvent outlet 23 and then pumped by the first solvent pump 22. The first solvent, at a temperature of 90°C and a flow rate of 500 kg / h, is discharged outside the boundary area, while a stream with a flow rate of 2 m³ / h returns to the first solvent return outlet 21. The molten liquid circulating at the bottom with a flow rate of 20 m³ / h enters the molten liquid inlet 17. The flow rate of the second solvent at the second solvent secondary replacement outlet 02 is controlled at 2 m³ / h and the temperature at 100°C, and the flow rate of the molten crystal liquid discharged outside the boundary area is controlled at 500 kg / h. The pressure values ​​at each control point are operated according to the data in column 2 of Example 1 in Table 1. Analysis revealed that the L-lactide content in the first solvent discharged outside the boundary area was 81.1 wt%, and the L-lactide content in the molten crystal discharged outside the boundary area was 98.9 wt%.

[0036] Example 3 A 90wt% L-lactide crystal slurry with a solid content of 50% and a flow rate of 1000 kg / h at a temperature of 90℃ enters the upper part of a co-current scrubbing tower after being fed by feed pump 01. The separated liquid phase material is discharged from the first solvent outlet 23 and then pumped by the first solvent pump 22. The first solvent, at a temperature of 90℃ and a flow rate of 500 kg / h, is discharged outside the boundary area, while a stream with a flow rate of 2 m³ / h returns to the first solvent return outlet 21. The molten liquid circulating at the bottom with a flow rate of 20 m³ / h enters the molten liquid inlet 17. The flow rate of the second solvent at the second solvent secondary replacement outlet 02 is controlled at 2 m³ / h and the temperature at 100℃, and the flow rate of the molten crystal liquid discharged outside the boundary area is controlled at 500 kg / h. The pressure values ​​at each control point are operated according to the data in the Example 3 column of Table 1. Analysis revealed that the L-lactide content in the first solvent discharged outside the boundary area was 80.4 wt%, and the L-lactide content in the crystal melt discharged outside the boundary area was 99.6 wt%.

[0037] Example 4 A 90wt% L-lactide crystal slurry with a solid content of 50% and a flow rate of 1000 kg / h at a temperature of 90°C enters the upper part of a co-current scrubbing tower after being fed by feed pump 01. The separated liquid phase material is discharged from the first solvent outlet 23 and then pumped by the first solvent pump 22. The first solvent, at a temperature of 90°C and a flow rate of 500 kg / h, is discharged outside the boundary area, while a stream with a flow rate of 2 m³ / h returns to the first solvent return outlet 21. The molten liquid circulating at the bottom with a flow rate of 20 m³ / h enters the molten liquid inlet 17. The flow rate of the second solvent at the second solvent secondary replacement outlet 02 is controlled at 2 m³ / h and the temperature at 100°C, and the flow rate of the molten crystal liquid discharged outside the boundary area is controlled at 500 kg / h. The pressure values ​​at each control point are operated according to the data in column 4 of Example 1 in Table 1. Analysis revealed that the L-lactide content in the first solvent discharged outside the boundary area was 80.6 wt%, and the L-lactide content in the crystal melt discharged outside the boundary area was 99.4 wt%.

[0038] Example 5 A 90wt% L-lactide crystal slurry with a solid content of 50% and a flow rate of 1000 kg / h at a temperature of 90°C enters the upper part of a co-current scrubbing tower after being fed by feed pump 01. The separated liquid phase material is discharged from the first solvent outlet 23 and then pumped by the first solvent pump 22. The first solvent, at a temperature of 90°C and a flow rate of 500 kg / h, is discharged outside the boundary area, while a stream with a flow rate of 2 m³ / h returns to the first solvent return outlet 21. The molten liquid circulating at the bottom with a flow rate of 20 m³ / h enters the molten liquid inlet 17. The flow rate of the second solvent at the second solvent secondary replacement outlet 02 is controlled at 2 m³ / h and the temperature at 100°C, and the flow rate of the molten crystal liquid discharged outside the boundary area is controlled at 500 kg / h. The pressure values ​​at each control point are operated according to the data in column 5 of Example 1 in Table 1. Analysis revealed that the L-lactide content in the first solvent discharged outside the boundary area was 80.9 wt%, and the L-lactide content in the molten crystal discharged outside the boundary area was 99.1 wt%.

[0039] The above-disclosed embodiments are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of the present utility model. Those skilled in the art can understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present utility model are still within the scope of the utility model.

Claims

1. A co-current scrubbing tower device for solid-liquid separation and purification, characterized in that, The system includes a solid-liquid separation cylinder, a first solvent replacement cylinder, and a second solvent replacement cylinder. The solid-liquid separation cylinder has an inlet and a first solvent return outlet. A feed pump is installed at the inlet. A first solvent return distribution network is installed inside the solid-liquid separation cylinder. A filter rod is installed between the solid-liquid separation cylinder, the first solvent replacement cylinder, and the second solvent replacement cylinder. A filter rod sealing layer is installed between the filter rod and the solid-liquid separation cylinder. A second solvent secondary replacement outlet is installed on the filter rod. A first filter screen assembly is installed between the solid-liquid separation cylinder and the first solvent replacement cylinder. A second filter screen assembly is installed between the first solvent replacement cylinder and the second solvent replacement cylinder. Below the second solvent replacement cylinder, from top to bottom, a secondary replacement filter screen, a scraper disc, and a melting section cylinder are sequentially arranged. The scraper disc is connected to a motor. The melting section cylinder has a molten liquid inlet and a molten liquid outlet. A molten liquid circulation pump and a melter are connected between the molten liquid inlet and the molten liquid outlet.

2. The co-current scrubbing tower device for solid-liquid separation and purification as described in claim 1, characterized in that, The first filter assembly includes a solid-liquid separation filter and a first solvent filter section. The first solvent filter section is provided with a first solvent outlet. The solid-liquid separation filter is disposed inside the first solvent filter section. The first solvent filter section is disposed between the solid-liquid separation section and the first solvent replacement section. The first solvent return port is connected to the first solvent outlet, and a first solvent pump is provided between the first solvent return port and the first solvent outlet.

3. The co-current scrubbing tower device for solid-liquid separation and purification as described in claim 2, characterized in that, The second filter assembly includes a primary replacement filter and a second solvent filter cylinder. The second solvent filter cylinder is provided with a second primary solvent replacement inlet. The primary replacement filter is disposed inside the second solvent filter cylinder. The second solvent filter cylinder is disposed between the first solvent replacement cylinder and the second solvent replacement cylinder. The second secondary solvent replacement outlet is connected to the second primary solvent replacement inlet, and a second solvent return pump is provided between the second secondary solvent replacement outlet and the second primary solvent replacement inlet.

4. The co-current scrubbing tower device for solid-liquid separation and purification as described in claim 3, characterized in that, The solid-liquid separation filter is a cylindrical wedge-shaped filter with a pore size of 100um to 300um; the primary replacement filter is a cylindrical wedge-shaped filter with a pore size of 100um to 300um; the secondary replacement filter is a cylindrical perforated mesh with 100um to 300um oblique holes; and the first solvent return distribution mesh is a 50 to 150 mesh straight-hole perforated mesh.

5. The co-current scrubbing tower device for solid-liquid separation and purification as described in claim 4, characterized in that, A first pressure stabilizing tank is provided between the first solvent outlet and the second solvent primary displacement inlet, and a second pressure stabilizing tank is provided between the second solvent primary displacement inlet and the molten liquid outlet.

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