Scraper-type crystallizer

Abstract

The application provides a scraper type crystallizer, and belongs to the technical field of petroleum chemical industry.The crystallizer has a plurality of crystallization tubes, the plurality of crystallization tubes are arranged in a barrel, the internal space of the crystallization tubes is isolated from the internal space of the barrel into two independent spaces, the internal space of the barrel is used for containing a refrigerant, and the internal space of the crystallization tubes is used for crystallization.The plurality of small-diameter crystallization tubes replace the inner wall of a traditional crystallizer to perform crystallization, all the crystallization tubes share the refrigerant in the barrel, and the structure is simpler and more reliable, and the volume is smaller.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, and more specifically, relates to a scraper-type crystallizer. Background Technology

[0002] Para-xylene (PX) is an important basic organic chemical raw material. Downstream industries require PX to have a purity of over 99.7%, making efficient PX separation a crucial step in PX industrial production. Since the boiling point difference among the four isomers of C8 aromatics is only about 2°C, separating para-xylene from C8 aromatics using distillation methods is extremely difficult. Industrially, two main methods are employed for PX separation: crystallization and adsorption.

[0003] For the separation of PX by crystallization, existing technologies are divided into two main categories: suspension crystallization and layer-by-layer crystallization. Layer-by-layer crystallization is a discontinuous and unsteady-state process. A mixed aromatic liquid first forms a crystal layer within the crystallizer, then the crystallizer is heated to remove some impurities through evaporation, followed by melting and release. This process is difficult to scale up or maintain continuously. Suspension melt crystallization technology is represented by the crystallization technology of BP & Lummus. CN1216837C discloses a crystallization method for preparing high-purity para-xylene, wherein the crystallizer is a scraped crystallizer, and the outer shell is cooled by propylene.

[0004] In practical industrial applications, the cooling jacket on the outer shell of the crystallizer is usually directly welded to the crystallizer, which is difficult to design, challenging to control during manufacturing, and significantly affects the roundness of the shell. Furthermore, an excessively large shell diameter makes crystallizer installation and scraper control difficult. These factors have affected the application of crystallization for PX separation. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a scraper-type crystallizer that solves the problems of excessively large shell diameter, difficulty in crystallizer installation, and scraper control in existing technologies.

[0006] To achieve the above objectives, the present invention provides a scraper-type crystallizer, comprising:

[0007] The cylinder has an upper tube sheet at the top and a lower tube sheet at the bottom, and is equipped with a refrigerant inlet and a refrigerant outlet. The refrigerant can flow into the cylinder from the refrigerant inlet and out of the cylinder from the refrigerant outlet.

[0008] Multiple crystallizing tubes are vertically arranged inside the cylinder, with their upper ends sealed to the upper tube sheet and their lower ends sealed to the lower tube sheet. The internal space of the crystallizing tubes is isolated from the internal space of the cylinder.

[0009] Multiple scraper stirring components, the same number as the number of crystallization tubes, are respectively set inside the crystallization tubes, which can scrape off the crystals attached to the inner wall of the crystallization tubes;

[0010] The driving component is capable of driving multiple of the scraper stirring assemblies to operate;

[0011] The feeding component is connected to the upper inlet of each crystallizer tube, allowing material to flow into each crystallizer tube through the feeding component;

[0012] The discharge component is connected to the lower port of each crystallization tube, allowing the material to flow out from the discharge component after crystallization inside the crystallization tube.

[0013] The feeding component is an upper end cap, which is sealed to the upper tube sheet and forms a first space. The first space is connected to the upper tube openings of multiple crystallizing tubes. The upper end cap is provided with a feeding port.

[0014] The discharge component is a lower end cap, which is sealed to the lower tube sheet to form a second space. The second space is connected to the lower tube openings of multiple crystallizing tubes, and the lower end cap is provided with a discharge port.

[0015] The second space has a conical structure.

[0016] The number of crystallization tubes is 3-55.

[0017] The inner diameter of the crystallization tube is 150mm-1800mm.

[0018] Multiple crystallization tubes are arranged in a uniform parallel manner.

[0019] The scraper stirring assembly is rotary.

[0020] The scraper stirring assembly includes: a main shaft, an upper bearing fixing structure, a scraper stirring blade, and a lower bearing fixing structure. The upper part of the main shaft is connected to the upper part of the crystallization tube through the upper bearing fixing structure, and the lower part of the main shaft is connected to the lower part of the crystallization tube through the lower bearing fixing structure. The scraper stirring blade is located in the middle of the main shaft, and the driving component can drive the main shaft to rotate.

[0021] The scraper stirring assembly is reciprocating.

[0022] The present invention provides a scraper-type crystallizer, which has the following advantages: the crystallizer has multiple crystallization tubes, which are arranged in a cylinder. The internal space of the crystallization tubes is isolated from the internal space of the cylinder as two independent spaces. The internal space of the cylinder is used to contain refrigerant, and the internal space of the crystallization tubes is used for crystallization. Multiple crystallization tubes with smaller diameters replace the traditional inner wall of the crystallizer for crystallization. All crystallization tubes share the refrigerant in the cylinder. The structure is simpler and more reliable, and the volume is smaller.

[0023] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0024] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0025] Figure 1 A side view of a scraper crystallizer according to an embodiment of the present invention is shown.

[0026] Figure 2 A top view of a scraper-type crystallizer apparatus according to an embodiment of the present invention is shown.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1. Shell; 11. Upper tube sheet; 12. Lower tube sheet; 13. Refrigerant inlet; 14. Refrigerant outlet;

[0029] 2. Crystallization tube;

[0030] 3. Scraper stirring assembly; 31. Main shaft; 32. Bearing upper fixing structure; 33. Scraper stirring paddle; 34. Bearing lower fixing structure.

[0031] 4. Drive components;

[0032] 5. Feeding component; 51. Feed inlet;

[0033] 6. Discharge component; 61. Discharge port. Detailed Implementation

[0034] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0035] The following example, taking the separation of p-xylene from mixed aromatics (C8 aromatics mass fraction above 95%, p-xylene mass fraction above 17%), further illustrates the technical solution of the present invention.

[0036] This invention provides a scraper-type crystallizer, comprising:

[0037] The cylinder 1 has an upper tube sheet 11 at the top and a lower tube sheet 12 at the bottom. It is provided with a refrigerant inlet 13 and a refrigerant outlet 14. The refrigerant can flow into the cylinder 1 from the refrigerant inlet 13 and flow out of the cylinder 1 from the refrigerant outlet 14.

[0038] Multiple crystallizing tubes 2 are vertically arranged inside the cylinder 1, with their upper ends sealed to the upper tube sheet 11 and their lower ends sealed to the lower tube sheet 12. The internal space of the crystallizing tubes 2 is isolated from the internal space of the cylinder 1.

[0039] Multiple scraper stirring components 3, the same number as the crystallization tubes 2, are respectively installed inside the crystallization tubes 2, which can scrape off the crystals attached to the inner wall of the crystallization tubes 2;

[0040] The driving component 4 is capable of driving multiple scraper stirring assemblies 3 to work;

[0041] The feeding component 5 is connected to the upper opening of each crystallization tube 2, allowing material to flow into each crystallization tube 2 through the feeding component 5;

[0042] The discharge component 6 is connected to the lower port of each crystallization tube 2, and the material can flow out from the discharge component 6 after crystallization in the crystallization tube 2.

[0043] Specifically, multiple crystallizer tubes 2 are sealed to the upper tube sheet 11 and the lower tube sheet 12, dividing the space inside the cylinder 1 into two independent spaces: the tube side and the shell side. Mixed aromatics enter the crystallizer tube 2 through the feed component 5 on the tube side, flow downwards through the tube 2 while crystallizing, and the crystal slurry mixture flows out of the crystallizer tube 2 through the discharge component 6 on the tube side. Refrigerant enters the cylinder 1 through the refrigerant inlet 13 on the shell side and flows out of the cylinder 1 through the refrigerant outlet 14 on the shell side. The refrigerant can be low-carbon hydrocarbons such as propylene and ethylene, or non-phase-change media such as chilled water and chilled oil; the type of refrigerant is not limited. Generally, it is more reasonable for the refrigerant to enter from the bottom and flow out from the top, but the flow direction can be adjusted according to the specific crystallization temperature. This scheme uses multiple smaller-diameter crystallizer tubes 2 instead of the traditional crystallizer inner wall for crystallization. The outer side of the crystallizer tubes 2 is not directly welded with a jacket for refrigeration; instead, all crystallizer tubes 2 share the refrigerant on the shell side, resulting in a simpler, more reliable, and smaller structure.

[0044] Since PX crystals adhere to the inner wall of the crystallization tube 2 and need to be removed in time, a scraper stirring assembly 3 is installed in each crystallization tube 2.

[0045] Optionally, the driving component 4 can be a single unit, connected to multiple scraper stirring assemblies 3 via a transmission structure, capable of driving multiple scraper stirring assemblies 3 to work simultaneously; the driving component 4 can also be multiple units, the number of which is the same as the number of scraper stirring assemblies 3, each connected to multiple scraper stirring assemblies 3, capable of driving multiple scraper stirring assemblies 3 to work separately.

[0046] Furthermore, the feeding component 5 is an upper end cap, which is sealed to the upper tube sheet 11 to form a first space. The first space is connected to the upper tube openings of multiple crystallizing tubes 2. The upper end cap is provided with a feeding port 51.

[0047] The discharge component 6 is a lower end cap, which is sealed to the lower tube sheet 12 to form a second space. The second space is connected to the lower tube openings of multiple crystallizing tubes 2. The lower end cap is provided with a discharge port 61.

[0048] Specifically, by setting an upper end cap, multiple crystallizing tubes 2 can share a single feed inlet 51; by setting a lower end cap, multiple crystallizing tubes 2 can share a single discharge outlet 61. This design simplifies the structure and reduces the size of the equipment.

[0049] Furthermore, the second space has a conical structure, with the cone angle preferably less than 60°. Specifically, the conical structure facilitates the outflow of the crystal slurry mixture and prevents its accumulation within the second space.

[0050] Furthermore, the number of crystallization tubes 2 is 3-55. Specifically, the number of crystallization tubes 2 is no less than 3, which can better utilize the space of the shell; theoretically there is no upper limit to the number of crystallization tubes 2, but if it exceeds 55, the arrangement of crystallization tubes 2 becomes too difficult, which is not conducive to industrial applications.

[0051] Furthermore, the inner diameter of the crystallization tube 2 is 150mm-1800mm. Specifically, an inner diameter of not less than 150mm facilitates scraper installation, and theoretically there is no upper limit to the maximum size, but if it exceeds 1800mm, the scraper cantilever system will be difficult to install and debug.

[0052] In a typical design, such as Figure 2 As shown, 19 crystallization tubes 2 are arranged inside the shell, each with an inner diameter of 600mm. The crystallization tubes 2 are closely arranged together. The shell size is Φ3000mm×8000mm. Such a crystallizer has a similar processing capacity to the Φ3600mm×25000mm external jacket scraper crystallizer in the comparative technology, but the size is greatly reduced, the structure is simpler, and on-site installation and commissioning are more convenient.

[0053] In another typical design, 55 crystallization tubes 2 are arranged inside the housing. The scraper is driven by a horizontal crankshaft-driven connecting rod, which drives the reciprocating scraper. The diameter of the crystallization tube 2 is selected as 150mm. Thus, the housing size is Φ1400mm×11000mm, which is more compact in structure compared with the external jacket scraper crystallizer.

[0054] Furthermore, multiple crystallization tubes 2 are arranged uniformly in parallel.

[0055] Optionally, the scraper agitator assembly 3 is rotary. The scraper agitator 33 can be a plate scraper, a frame scraper, or a spiral scraper, and the drive component 4 is an electric motor. The electric motor can be shared by multiple spindles 31 through a transmission structure, or each spindle 31 can be set up individually. The electric motor needs to be reduced to a suitable speed and obtain greater torque through a reducer, generally 4-80 r / min, and also needs to have a speed regulation function to cope with abnormal situations in the crystallizer.

[0056] Furthermore, the scraper agitation assembly 3 includes: a main shaft 31, an upper bearing fixing structure 32, a scraper agitator 33, and a lower bearing fixing structure 34. The upper part of the main shaft 31 is connected to the upper part of the crystallization tube 2 via the upper bearing fixing structure 32, and the lower part of the main shaft 31 is connected to the lower part of the crystallization tube 2 via the lower bearing fixing structure 34. The scraper agitator 33 is located in the middle of the main shaft 31, and the drive component 4 can drive the main shaft 31 to rotate. Specifically, the motor drives the scraper agitator 33 through the main shaft 31 to scrape off the paraxylene crystals adhering to the inner wall of the crystallization tube 2. The upper bearing fixing structure 32 is used to control the radial oscillation of the main shaft 31 when it rotates. It can be located at the lower end of the motor or the upper end of the crystallization tube 2. If it is located at the upper end of the crystallization tube 2, it needs to have a large flow area. The lower bearing fixing structure 34 is the main structure that bears the load of the main shaft 31. In a typical design, the lower bearing fixing structure 34 is welded to the lower end of the tube sheet in the form of a triangular bracket, and the large perforated area can ensure that the crystal slurry can flow smoothly. Other structures with large flow areas and the ability to effectively bear the load of the spindle 31 can also be considered, but this is not an important factor.

[0057] Optionally, the scraper agitator assembly 3 is reciprocating. The scraper agitator 33 is a plate scraper or a frame scraper. The scraper's support structure also has a large flow area to facilitate the flow of crystal slurry.

[0058] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A scraper-type crystallizer, characterized in that, include: The cylinder (1) has an upper tube sheet (11) at the top and a lower tube sheet (12) at the bottom. It is provided with a refrigerant inlet (13) and a refrigerant outlet (14). The refrigerant can flow into the cylinder (1) from the refrigerant inlet (13) and flow out of the cylinder (1) from the refrigerant outlet (14). Multiple crystallizing tubes (2) are vertically arranged inside the cylinder (1), with their upper ends sealed to the upper tube sheet (11) and their lower ends sealed to the lower tube sheet (12). The internal space of the crystallizing tubes (2) is isolated from the internal space of the cylinder (1). Multiple scraper stirring components (3), the same number as the number of crystallization tubes (2), are respectively set inside the crystallization tubes (2) and can scrape off the crystals attached to the inner wall of the crystallization tubes (2); The driving component (4) is capable of driving multiple scraper stirring assemblies (3) to work; The feeding component (5) is connected to the upper port of each crystallization tube (2), and the material can flow into each crystallization tube (2) through the feeding component (5); The discharge component (6) is connected to the lower port of each crystallization tube (2), and the material can flow out from the discharge component (6) after crystallization in the crystallization tube (2).

2. A scraper-type crystallizer according to claim 1, characterized in that, The feeding component (5) is an upper end cap, which is sealed to the upper tube sheet (11) and forms a first space. The first space is connected to the upper tube openings of multiple crystallizing tubes (2). The upper end cap is provided with a feeding port (51). The discharge component (6) is a lower end cap, which is sealed to the lower tube plate (12) to form a second space. The second space is connected to the lower tube openings of multiple crystallizing tubes (2). The lower end cap is provided with a discharge port (61).

3. A scraper-type crystallizer according to claim 2, characterized in that, The second space has a conical structure.

4. A scraper-type crystallizer according to claim 3, characterized in that, The second spatial cone angle is less than 60°.

5. A scraper-type crystallizer according to claim 1, characterized in that, The number of crystallization tubes (2) is 3-55.

6. A scraper-type crystallizer according to claim 1, characterized in that, The inner diameter of the crystallization tube (2) is 150mm-1800mm.

7. A scraper-type crystallizer according to claim 1, characterized in that, Multiple crystallization tubes (2) are arranged in a uniform parallel manner.

8. A scraper-type crystallizer according to claim 1, characterized in that, The scraper stirring assembly (3) is a rotary type.

9. A scraper-type crystallizer according to claim 8, characterized in that, The scraper stirring assembly (3) includes: a main shaft (31), a bearing upper fixing structure (32), a scraper stirring paddle (33), and a bearing lower fixing structure (34). The upper part of the main shaft (31) is connected to the upper part of the crystallizing tube (2) through the bearing upper fixing structure (32), and the lower part of the main shaft (31) is connected to the lower part of the crystallizing tube (2) through the bearing lower fixing structure (34). The scraper stirring paddle (33) is located in the middle of the main shaft (31), and the driving component (4) can drive the main shaft (31) to rotate.

10. A scraper-type crystallizer according to claim 1, characterized in that, The scraper stirring assembly (3) is reciprocating.

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