Salting-out crystallizer

Abstract

The utility model relates to a solution separation device, in particular to a salting-out crystallizer, and aims to overcome the defects that in the prior art, solid-liquid distribution in a crystallizer is not uniform, the crystallization effect is not ideal, and solid-liquid partition cannot be realized. The salting-out crystallizer comprises a tank body, N discharge ports, a feed pipe, an overflow weir and a central guide cylinder, the overflow weir and the central guide cylinder are arranged in the tank body, and N is larger than or equal to 1. A clear liquid area, a settling area and a crystal suspension area are sequentially arranged in the tank body from top to bottom along the central axis; one end of the discharge hole is communicated with the crystal suspension area; the overflow weir is located at the upper part of the clear liquid area and comprises a bottom plate arranged along the circumferential direction of the inner side wall of the tank body, the bottom plate has a gradient along the circumferential direction of the tank body, and the inner end is higher than the outer end; the central guide cylinder is arranged along the central axis of the tank body, the upper end of the central guide cylinder is lower than the upper end of the overflow weir, and the lower end of the central guide cylinder is located in the crystal suspension area.

Description

Technical Field

[0001] This utility model relates to a solution separation device, specifically a salting-out crystallizer. Background Technology

[0002] Traditional methods for separating salt solutions involve evaporation or cooling crystallization. The salting-out effect on liquid-liquid equilibrium demonstrates that adding salt can achieve phase separation. Similarly, adding a solvent to a salt solution can crystallize out another salt. The precipitated crystal slurry is then transported to an external centrifuge to achieve solid-liquid separation. However, existing salting-out crystallizers suffer from uneven solid-liquid distribution, resulting in suboptimal crystallization and an inability to achieve solid-liquid separation. Utility Model Content

[0003] The purpose of this invention is to address the shortcomings of existing technologies, such as uneven solid-liquid distribution within the crystallizer, unsatisfactory crystallization effect, and inability to achieve solid-liquid zoning. Based on the principle that adding solvent to a salt-containing solution can crystallize salt out of the solution, this invention provides a salt precipitation crystallizer.

[0004] To achieve the above objectives, the technical solution provided by this utility model is as follows:

[0005] A salt-precipitation crystallizer is characterized by comprising a tank body, N discharge ports, a feed pipe, and an overflow weir and a central guide cylinder disposed within the tank body, wherein N ≥ 1; the tank body comprises, from top to bottom, a clear liquid zone, a sedimentation zone, and a crystal suspension zone along its central axis; one end of each discharge port is connected to the crystal suspension zone, and the other end is connected to external equipment; the overflow weir is located above the clear liquid zone and includes a bottom plate arranged circumferentially along the inner side wall of the tank body and a surrounding weir disposed at the inner end of the bottom plate; the bottom plate has a slope along the circumference of the tank body, and an overflow port is disposed at the lowest point of the tank body side wall corresponding to the slope direction; the inner end of the bottom plate is higher than its outer end, and multiple salt discharge holes are evenly distributed circumferentially at the outer end; the central guide cylinder is disposed along the central axis of the tank body, with its upper end located in the clear liquid zone and lower than the upper end of the overflow weir, and its lower end located in the crystal suspension zone; one end of the feed pipe is connected to the central guide cylinder, and the other end is connected to an external feeding device.

[0006] Furthermore, it also includes a circulating liquid input pipe and Q circulating liquid discharge pipes, wherein Q≥2;

[0007] One end of the circulating feed liquid input pipe is connected to the outlet of the external heat exchanger, and the other end is connected to the position of the crystal suspension zone near the lower end of the central guide tube, with the opening facing downwards;

[0008] One end of the circulating liquid discharge pipe is located above the clear liquid zone and is lower than the upper end of the cofferdam. The other end passes through the side wall of the tank and connects to the inlet of the external heat exchanger.

[0009] Furthermore, the circulating liquid input pipe includes L connecting pipes and an annular pipe, wherein L≥2. One end of the connecting pipe passes through the side wall of the tank and connects to the outlet of the external heat exchanger, and the other end connects to the side wall of the annular pipe. The annular pipe surrounds the central guide cylinder and is coaxially arranged with it, located near the lower end of the central guide cylinder. Multiple sets of through holes are evenly opened on the side wall of the annular pipe along its annular axis, with the through holes facing downwards.

[0010] One end of the circulating liquid discharge pipe faces upwards.

[0011] Furthermore, the tank body includes a large-diameter section, a variable-diameter section, and a small-diameter section arranged sequentially from top to bottom along the central axis. The diameters at both ends of the variable-diameter section are matched with the diameters of the large-diameter section and the small-diameter section, respectively. The clear liquid zone is located in the upper part of the large-diameter section and the variable-diameter section, the sedimentation zone is located in the lower part of the variable-diameter section and the upper part of the small-diameter section, and the crystal suspension zone is located in the lower part of the small-diameter section.

[0012] Furthermore, the bottom of the tank is uniformly provided with an annular sedimentation hopper along the circumference, and the bottom of the sedimentation hopper is uniformly provided with P cleaning and drain ports along the circumference, wherein P≥3, for draining or backwashing the crystals deposited at the bottom of the tank.

[0013] Furthermore, the opening of the cleaning drain outlet faces outwards, and the angle between its central axis and the central axis of the tank is less than 5°.

[0014] Furthermore, a flared opening is provided at the lower end of the central guide tube;

[0015] A protective cover is provided above the central guide tube. The protective cover is a horn-shaped structure with the large end facing down, and the upper end of the central guide tube is located inside the large end of the horn opening.

[0016] The connection point between the feed pipe and the central guide tube is one-third higher than the bottom of the central guide tube.

[0017] Furthermore, Q=3, L=3, one end of the three circulating liquid discharge pipes is evenly distributed along the circumference of the tank, the three connecting pipes are evenly distributed along the annular axis of the annular pipe, and each group of through holes in the annular pipe includes three through holes located in the same radial section.

[0018] The number N is 4, and the four discharge ports are evenly distributed along the circumference of the tank.

[0019] Furthermore, it also includes a stirring motor M and stirring blades. The output end of the stirring motor M is connected to the stirring blades, which are located in the central guide tube and are used to stir the materials therein evenly.

[0020] The beneficial effects of this utility model are:

[0021] 1. In this utility model, the overflow weir is sloped, and the inner end of the bottom plate is higher than the outer end, which facilitates the complete discharge of the overflow liquid from the overflow port. A salt discharge hole is provided at the outer end of the bottom plate. Fine crystals in the upper clear liquid settle to the bottom of the overflow weir and can re-enter the salt precipitation crystallizer through the salt discharge hole, minimizing the amount of fine crystals in the overflow liquid.

[0022] 2. The feed position of this utility model is located in the central guide tube. The feed is fully mixed with the clear liquid in the inner circulation in the guide tube, and some crystal nuclei are initially formed, thereby improving the crystallization efficiency.

[0023] 3. This utility model is equipped with a circulating liquid input pipe and a circulating liquid discharge pipe, which are used to take out a portion of the clear liquid from the clear liquid zone for external circulation to achieve temperature control in the salting-out crystallizer, generate supersaturation, and then enter the crystallizer to fully mix with the internal circulating liquid. The liquid in the tank gradually rises to eliminate the supersaturation of the solution and achieve crystal growth.

[0024] 4. The bottom of this utility model is equipped with an annular sedimentation hopper and a cleaning and sewage discharge port to prevent crystal deposition and facilitate online tank washing and brushing. Attached Figure Description

[0025] Figure 1 This is a structural schematic diagram of an embodiment of the present utility model;

[0026] Figure 2 yes Figure 1 A top view (the central deflector and protective cover are not shown);

[0027] Figure 3 This is a schematic diagram of the structure of the circulating liquid input pipe in an embodiment of the present invention, wherein a is a top view of the circulating liquid input pipe and b is a radial sectional view of the annular tube of the circulating liquid input pipe.

[0028] Figure 4 This is a schematic diagram of the overflow weir in an embodiment of this utility model.

[0029] Explanation of reference numerals in the attached figures:

[0030] 1-Tank body, 11-Discharge port, 12-Infeed pipe, 13-Circulating liquid discharge pipe, 14-Circulating liquid input pipe, 141-Connecting pipe, 142-Annular pipe, 2-Overflow weir, 21-Bottom plate, 22-Dike, 23-Overflow port, 24-Salt discharge hole, 3-Central guide cylinder, 31-Protective cover, 4-Sediment hopper, 41-Cleaning and sewage discharge port. Detailed Implementation

[0031] This utility model discloses a salt precipitation crystallizer structure as follows: Figure 1 and Figure 2As shown, it includes a tank body 1, N discharge ports 11, a feed pipe 12, a central guide tube 3 and an overflow weir 2 set inside the tank body 1, wherein N≥1, and the number of discharge ports 11 is determined according to the diameter of the tank body 1 and the crystal production.

[0032] Because the material storage capacity inside the salting-out crystallizer is large, it is very inconvenient to completely empty and clean the bottom deposits. Therefore, a ring-shaped sedimentation hopper 4 is provided circumferentially at the bottom of the tank 1. P cleaning and drain ports 41 are evenly arranged circumferentially at the bottom of the sedimentation hopper 4, where P ≥ 3. The openings of the cleaning and drain ports 41 face outwards, and the angle between their central axis and the central axis of the tank 1 is generally less than 5°. The cleaning and drain ports 41 can be used for both drainage and reverse flow of cleaning liquid into the salting-out crystallizer. This causes the cleaning liquid or material to rotate in the tank, sweeping up the crystals deposited at the bottom and discharging them out of the crystallizer through the discharge port. This serves to clean and scrub the tank. Periodically blowing the crystals deposited in the sedimentation hopper 4 through the cleaning and drain ports 41 can achieve online anti-deposition in the salting-out crystallizer.

[0033] The tank body 1 includes a large-diameter section, a variable-diameter section, and a small-diameter section arranged sequentially from top to bottom along the central axis. The diameters at both ends of the variable-diameter section match the diameters of the large-diameter section and the small-diameter section, respectively. The internal regions of the tank body 1 are, from top to bottom, a clear liquid zone, a settling zone, and a crystal suspension zone. The clear liquid zone is located in the upper part of the large-diameter section and the variable-diameter section, the settling zone is located in the lower part of the variable-diameter section and the upper part of the small-diameter section, and the crystal suspension zone is located in the lower part of the small-diameter section. This invention increases the cross-section of the settling zone and the clear liquid zone by reasonably setting different diameters, thereby reducing the rising speed of the liquid inside the crystallizer and promoting crystal settling.

[0034] The overflow weir 2 is located in the large-diameter section and includes a bottom plate 21 arranged circumferentially along the inner wall of the tank 1 and a cofferdam 22 located at the inner end of the bottom plate 21. The bottom plate 21 has a slope along the circumference of the tank 1, and an overflow port 23 is provided on the side wall of the tank 1 corresponding to the lowest point of the slope. The inner end of the bottom plate 21 is higher than its outer end, and multiple salt discharge holes 24 are evenly opened circumferentially at the outer end. Figure 4 As shown. The upper clear liquid enters the overflow weir 2 through the cofferdam 22, and the fine crystals in it settle to the bottom of the overflow weir 2. They then re-enter the salt precipitation crystallizer through the salt discharge hole 24 to minimize the amount of fine crystals in the overflow liquid. The overflow liquid is discharged from the overflow port 23.

[0035] The central guide tube 3 is set along the central axis of the tank 1. The upper end of the central guide tube 3 is located in the large diameter section of the tank 1 and is lower than the upper end of the cofferdam 22. The lower end of the central guide tube 3 is provided with a flared mouth. The opening of the flared mouth is located in the lower part of the crystal suspension zone. The central guide tube 3 is used for internal circulation of the clear liquid that has been desaturated inside the crystallizer. A protective cover 31 is set above the central guide tube 3. The protective cover 31 is set as a flared structure with the large end facing down. The upper end of the central guide tube 3 is located inside the large end of the flared mouth, so as to avoid the fine crystals from diffusing due to the fast flow rate when the clear liquid enters the central guide tube 3, which would increase the fine crystal content in the overflow liquid.

[0036] One end of the feed pipe 12 is connected to the central guide cylinder 3, and the other end is connected to an external feeding device. In this embodiment, three feed pipes 12 are provided, which are used to transport different salt solutions or solid salts into the guide pipes respectively. The feed is fully mixed with the internal circulating clear liquid in the central guide cylinder 3 to form a feed mixture, which enters the tank 1 from the lower end of the central guide cylinder 3. Due to the high feed temperature, some crystal nuclei will initially form after the feed is fully mixed with the clear liquid. The connection between the feed pipe 12 and the central guide cylinder 3 is preferably higher than 1 / 3 of the height of the central guide cylinder 3 from bottom to top, with sufficient distance to facilitate uniform mixing of the feed. To improve the uniformity of material mixing in the central guide cylinder 3, a stirring motor M is also provided, with its output end connected to stirring blades that extend into the central guide cylinder 3.

[0037] To achieve temperature control in the salting-out crystallizer, a portion of the clear liquid is externally circulated. Therefore, Q circulating liquid discharge pipes 13 are set in the clear liquid zone, where Q≥2. A circulating liquid input pipe 14 is set in the crystal suspension zone. One end of the circulating liquid discharge pipe 13 is located in the upper part of the clear liquid zone, with the pipe opening facing upwards and its height lower than the upper end of the cofferdam 22. At least two circulating liquid discharge pipes 13 are evenly distributed along the circumference of the tank 1 to ensure the stability of the clear liquid in the tank 1. The other end of the circulating liquid discharge pipe 13 passes through the side wall of the tank 1 and is connected to the inlet of the external heat exchanger. The circulating feed inlet pipe 14 includes L connecting pipes 141 and an annular pipe 142, where L ≥ 2. One end of each connecting pipe 141 passes through the side wall of the tank 1 and connects to the outlet of the external heat exchanger, while the other end connects to the annular pipe 142. At least two connecting pipes 141 are evenly distributed along the annular axis of the annular pipe 142. The annular pipe 142 is coaxially arranged around the central guide cylinder 3 and is located near the lower end of the central guide cylinder 3. Multiple sets of through holes are evenly opened on the side wall of the annular pipe 142 along its annular axis, such as... Figure 3As shown, each group of through holes includes multiple through holes located on the same radial cross section and facing downwards, used for inputting external circulating clear liquid. The external circulating clear liquid mixes with the feed mixture from the central guide tube 3 here, forming a supersaturated liquid. The supersaturation is then eliminated by the slurry flow in the salting-out crystallizer, generating a large number of crystals that gradually settle. The number of through holes is adjusted according to the flow rate or equipment specifications. In this embodiment, three circulating liquid discharge pipes 13 are provided, and the circulating liquid input pipe 14 includes three connecting pipes 141, all of which are dual-use and one-standby. Each group of through holes includes three through holes.

[0038] N discharge ports 11 are located on the side wall of the tank 1 corresponding to the lower part of the small-diameter section. One end of each discharge port 11 is connected to the crystal suspension zone, and the other end is connected to external equipment for discharging the crystal slurry from the crystal suspension zone. Since the outlets of both the internal and external circulating clear liquids are in the crystal suspension zone, the crystal slurry can remain in a suspended state in this area, thus ensuring smooth discharge from the discharge ports 11 and discharging the crystal slurry from the discharge ports 11 to other external equipment. To ensure the stability of the crystal suspension state in the tank 1, in this embodiment, four discharge ports 11 are evenly arranged along the circumference of the tank 1.

[0039] The working principle of salting-out crystallization is as follows: Type B salt is added to a Type A salt solution. By raising or lowering the temperature, Type A salt precipitates out, or Type C salt precipitates after a reaction. This novel salting-out crystallizer controls the temperature through an external heat exchanger, eliminating the unsaturation of the salt solution and allowing Type A or Type C salt to crystallize and grow. The crystals are then discharged through outlet 11. The crystal slurry from outlet 11 is then filtered by a centrifuge or other methods to separate the crystals. Specifically, the external heat exchanger controls the temperature by circulating the clarified liquid: a portion of the clarified liquid is taken from the clarified liquid zone and enters the external heat exchanger through the circulating liquid discharge pipe 13. After being heated or cooled, it returns to the crystal suspension zone. Due to the temperature decrease or increase, the circulating liquid becomes supersaturated. This supersaturation is then fully contacted with the crystal nuclei in the feed mixture, eliminating the supersaturation. Crystals precipitate on the crystal nuclei, achieving crystal growth. Different crystal sizes have different settling rates; larger particles settle to the crystal suspension zone and are then pumped to the separation equipment.

[0040] High-temperature feed is added to the internal circulation clear liquid, and the clear liquid and feed are fully mixed, resulting in supersaturation or a small number of crystal nuclei. Due to the decrease or increase in temperature, the clear liquid in the external circulation will produce supersaturation or a small number of fine crystals. When the two circulating liquids come into full contact in the crystal suspension zone of the crystallizer, a large number of crystals are generated on the basis of fine crystals or crystal nuclei. At the same time, the crystals in the crystal suspension zone enter the settling zone upward along the flow field direction. In the settling zone, the supersaturation of the liquid is eliminated. Crystals of different sizes settle at different speeds. Large crystals fall back to the crystal suspension zone and are sent to the centrifugal system by the external discharge pump through the discharge port 11.

[0041] The above description is only a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this utility model, and these modifications or substitutions should all be covered within the protection scope of this utility model.

Claims

1. A salting-out crystallizer, characterized in that: It includes a tank body (1), N discharge ports (11), a feed pipe (12), an overflow weir (2) and a central guide tube (3) set in the tank body (1), wherein N≥1; The tank (1) consists of a clear liquid zone, a sedimentation zone, and a crystal suspension zone, arranged from top to bottom along the central axis. One end of the discharge port (11) is connected to the crystal suspension zone, and the other end is connected to external equipment; The overflow weir (2) is located in the upper part of the clear liquid area, including a bottom plate (21) arranged circumferentially along the inner side wall of the tank (1) and a weir (22) arranged at the inner end of the bottom plate (21). The bottom plate (21) is sloped circumferentially along the tank (1), and an overflow port (23) is provided at the lowest point of the side wall of the tank (1) corresponding to the slope direction. The inner end of the bottom plate (21) is higher than its outer end, and multiple salt discharge holes (24) are evenly opened circumferentially at the outer end. The central guide tube (3) is set along the central axis of the tank (1), with its upper end located in the clear liquid zone and lower than the upper end of the overflow weir (2), and its lower end located in the crystal suspension zone; One end of the feed pipe (12) is connected to the central guide tube (3), and the other end is connected to the external feed device.

2. The salting-out crystallizer according to claim 1, characterized in that: It also includes a circulating liquid input pipe (14) and Q circulating liquid discharge pipes (13), wherein Q≥2; One end of the circulating liquid input pipe (14) is connected to the outlet of the external heat exchanger, and the other end is connected to the position of the crystal suspension zone near the lower end of the central guide tube (3), with the opening facing downward; One end of the circulating liquid discharge pipe (13) is located above the clear liquid zone and is lower than the upper end of the cofferdam (22). The other end passes through the side wall of the tank (1) and is connected to the inlet of the external heat exchanger.

3. The salting-out crystallizer according to claim 2, characterized in that: The circulating liquid input pipe (14) includes L connecting pipes (141) and an annular pipe (142), wherein L≥2. One end of the connecting pipe (141) passes through the side wall of the tank (1) and connects to the outlet of the external heat exchanger, and the other end connects to the side wall of the annular pipe (142). The annular pipe (142) surrounds the central guide cylinder (3) and is coaxially arranged with it, located near the lower end of the central guide cylinder (3). Multiple sets of through holes are evenly opened on the side wall of the annular pipe (142) along its annular axis, with the through holes facing downwards. One end of the circulating liquid discharge pipe (13) faces upward.

4. A salting-out crystallizer according to any one of claims 1-3, characterized in that: The tank (1) includes a large-diameter section, a variable-diameter section, and a small-diameter section arranged sequentially from top to bottom along the central axis. The diameters at both ends of the variable-diameter section are matched with the diameters of the large-diameter section and the small-diameter section, respectively. The clear liquid zone is located in the upper part of the large-diameter section and the variable-diameter section, the sedimentation zone is located in the lower part of the variable-diameter section and the upper part of the small-diameter section, and the crystal suspension zone is located in the lower part of the small-diameter section.

5. The salting-out crystallizer according to claim 4, characterized in that: The bottom of the tank (1) is uniformly provided with an annular sedimentation hopper (4) along the circumference. The bottom of the sedimentation hopper (4) is uniformly provided with P cleaning and drain ports (41) along the circumference, wherein P≥3, for draining or backwashing the crystals deposited at the bottom of the tank (1).

6. The salting-out crystallizer according to claim 5, characterized in that: The opening of the cleaning drain (41) faces outward, and the angle between its central axis and the central axis of the tank (1) is less than 5°.

7. A salting-out crystallizer according to claim 6, characterized in that: The lower end of the central guide tube (3) is provided with a flared mouth; A protective cover (31) is provided above the central guide tube (3). The protective cover (31) is a horn-shaped structure with the large end facing down. The upper end of the central guide tube (3) is located inside the large end of the horn opening. The connection point between the feed pipe (12) and the central guide cylinder (3) is one-third higher than the bottom of the central guide cylinder (3).

8. A salting-out crystallizer according to claim 3, characterized in that: Q=3, L=3, one end of the three circulating liquid discharge pipes (13) is evenly distributed along the circumference of the tank body (1), and the three connecting pipes (141) are evenly distributed along the annular axis of the annular pipe (142). Each group of through holes in the annular pipe (142) includes three through holes located in the same radial section. The N=4, and the four discharge ports (11) are evenly arranged around the tank body (1).

9. The salting-out crystallizer according to claim 1, characterized in that: It also includes a stirring motor M and stirring blades. The output end of the stirring motor M is connected to the stirring blades, which are located in the central guide tube (3) for stirring the materials therein evenly.

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