Rectifying tower for cracking C9 fraction

Abstract

The invention relates to the technical field of rectification, in particular to a rectifying tower for cracking C9 fractions, which comprises a tower body and a tower plate, the tower plate is arranged in the tower body, a CPD extraction device is arranged at the top end of the tower body, a DCPD side line extraction device is arranged in the middle of the tower body, and the lower part of the tower body is communicated with a solvent side line extraction device; a partition plate is arranged in the bottom end of the tower body, the space at the bottom of the tower body is divided into a flash evaporation space and a concentration space by the partition plate, the flash evaporation space is communicated with a C9 fraction supply pipeline through a cracking reactor, and the flash evaporation space is communicated with a tower kettle liquid return pipeline; a solvent extracted by the solvent side-draw device is mixed with tower bottoms extracted from the tower bottoms reflux pipeline, and then is heated by the reboiler and refluxed to the concentration space, and the concentration space is provided with a tower bottoms discharge pipeline; the influence of coking of materials in the rectifying tower or polymers on the rectifying operation can be reduced, and the stability of the rectifying operation is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of distillation, and in particular to a distillation tower for cracking C9 fraction. Background Art

[0002] The ethylene cracking C9 fraction is a by-product of the ethylene plant. It is the remaining fraction after the cracked naphtha is extracted and separated into the C5 fraction and the C6-C8 fraction (hydrogenation to produce BTX), accounting for about 10% to 20% of the total ethylene production. The composition of the C9 fraction is very complex. Currently, there are more than 150 components of the C9 fraction that can be detected, and the distribution is very scattered. Due to the complexity of the cracked C9 components, it is impossible to separate it into fine monomer substances. From the perspective of synthetic chemistry, the cracked C9 can be divided into two categories: active components that can be polymerized and inactive components that can be used as solvents.

[0003] At present, the main treatment method used in China is to separate the cracked C9 according to the distillation range, which is generally separated into three distillation sections. The first distillation section is 140-160℃, mainly C8 light components such as styrene and o-xylene, the second distillation section is 160-185℃, mainly methyl styrene, vinyl toluene, dicyclopentadiene, indene and other components, and the third distillation section is above 185℃, mainly condensed ring olefins, naphthalene, anthracene and other heavy components. Among them, the fraction of the second distillation section is further distilled to separate DCPD and methylcyclopentadiene from the cracked C9 fraction, and the remaining resin material is finely separated into resin materials for different purposes, so that high-quality resins can be produced, and DCPD and methylcyclopentadiene components are separated from the cracked C9 fraction to produce medium-purity or high-purity DCPD and methylcyclopentadiene, so as to achieve the purpose of comprehensive utilization of the cracked C9 fraction.

[0004] During the distillation process, there are many components that are easy to self-polymerize in the second distillation section of the cracking C9 fraction. The coking or viscous polymers produced are easy to deposit on the bottom or plates of the tower, affecting the operating stability of the distillation tower. Therefore, a distillation tower dedicated to the cracking C9 fraction is needed for the purification and refining of the second distillation section of the cracking C9 fraction. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a distillation tower for cracking C9 fraction, which is used for purification and refining of the second distillation process in the cracking C9 fraction. When separating the C9 fraction, the influence of coking or polymer of materials in the distillation tower on the distillation operation is reduced, thereby ensuring the stability of the distillation operation.

[0006] The technical solution adopted in this application to solve this technical problem is:

[0007] A distillation tower for cracking C9 fraction comprises a tower body and a tower plate, wherein the tower body is provided with tower plates which are installed in a staggered manner in sequence, the top of the tower body is provided with a CPD extraction device, the middle of the tower body is provided with a DCPD side-line extraction device, and the lower part of the tower body is connected with a solvent side-line extraction device; a partition plate located below the tower plate is provided in the bottom end of the tower body, and the partition plate divides the space at the bottom of the tower body into a flash space and a concentration space, the flash space is connected with a C9 fraction supply pipeline via a cracking reactor, the flash space is vertically opposite to a downcomer of a lowermost tower plate in the tower body, the flash space is connected with a bottom liquid reflux pipeline, the solvent extracted by the solvent side-line extraction device is mixed with the bottom liquid extracted from the bottom liquid reflux pipeline, and then heated by a reboiler and refluxed to the concentration space, and the concentration space is provided with a bottom liquid external discharge pipeline.

[0008] Furthermore, the partition plate is a plate body with strip corrugations, the strip corrugations are arranged along the vertical direction, and the lower end of the partition plate and two side edges of the partition plate are connected to the inner wall of the tower body.

[0009] Furthermore, the hot fluid inlet end of the reboiler is connected to the C9 fraction delivery pipeline through the cracking reactor, and the hot fluid outlet end of the reboiler is connected to the flash space of the tower kettle.

[0010] Furthermore, the tower plate is evenly distributed with air lifting holes, the air lifting holes are installed with guide floating tongues, the guide floating tongue is provided with air ports, and the air ports face the upper surface of the tower plate.

[0011] Furthermore, the length direction of the air riser is consistent with the flow direction of the liquid phase.

[0012] Furthermore, the guide floating tongue includes a main board, a connecting plate and a limiting plate, the main board corresponds to the shape of the air lift hole, the two ends of the main board are respectively connected to the connecting plate and the limiting plate, the end of the main board is also connected to the limiting end, the limiting end is an extension formed by cutting from the connecting plate and the limiting plate, and is integral with the main board, the limiting end and the main board are on the same plane, and when the connecting plate and the limiting plate are bent to form an angle with the main board, the position of the connecting plate and the limiting plate after cutting the limiting end constitutes an air outlet.

[0013] Furthermore, after the connecting plate is bent, the vertical distance between the end of the connecting plate and the limiting end is greater than the thickness of the tower plate.

[0014] Furthermore, triangular guide plates are connected to two side edges of the main board, and the outer end sharp corners of the guide plates are close to the limiting plates and inclined downward.

[0015] Furthermore, the limiting plate is arc-shaped and is provided with a cutting slit, which cuts the limiting plate into a frame and a tongue plate connected to each other. The tongue plate is bent inwardly to form an air outlet between the tongue plate and the frame.

[0016] Furthermore, the C9 fraction supply pipeline is provided with an inhibitor adding device located upstream of the cracking reactor.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention is used for the purification and refining of the second distillation process in the cracking C9 fraction. When separating the C9 fraction, the influence of coking or polymer of the material in the distillation tower on the distillation operation is reduced, and the stability of the distillation operation is ensured. Because the influence of coking and polymer is reduced, the maintenance frequency of the distillation tower of the present invention is reduced, and the service life is extended.

[0019] 2. The present invention does not have a stripping section, but divides the tower bottom into two spaces by setting a partition plate, one for flash evaporation and the other for concentration, which can improve the distillation efficiency while reducing the impact of coking or polymer on the distillation tower.

[0020] 3. The present invention does not use the existing technology in the reboiler, but uses the temperature of cracked C9 to heat the bottom liquid, fully recovers the waste heat, and improves the operation stability.

[0021] 4. The guide floating tongue of the present invention has an air port, and the air flow blown out of the air port can keep the liquid phase away from the rising air hole at the beginning and end of distillation, avoiding the adhesion of coke or polymer therein to the guide floating tongue and the tower plate, reducing the number of maintenance times and extending the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of the present invention;

[0023] Figure 2 is a sectional front view of the present invention;

[0024] Figure 3 It is a schematic structural diagram of a tower plate of the present invention;

[0025] Figure 4 It is a schematic structural diagram of the guide floating tongue of the present invention;

[0026] Figure 5 It is a cross-sectional view of the connection between the guide floating tongue and the tower plate of the present invention.

[0027] The numbers in the attached drawings are: 1. tower body; 2. tower plate; 3. partition plate; 4. flash space; 5. concentration space; 6. cracking reactor; 7. CPD extraction device; 8. solvent side-line extraction device; 9. tower bottom liquid reflux pipeline; 10. reboiler; 11. tower bottom liquid external discharge pipeline; 12. air riser; 13. guide floating tongue; 14. air outlet; 15. main board; 16. connecting plate; 17. limit plate; 18. limit end; 19. guide plate; 20. frame; 21. tongue plate; 22. inhibitor addition device; 23. DCPD side-line extraction device. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0029] like Figure 1 and Figure 2 As shown, a distillation tower for cracking C9 fraction comprises a tower body 1 and a tower plate 2, wherein the tower body 1 is provided with the tower plates 2 which are installed in a staggered manner in sequence, the top of the tower body 1 is provided with a CPD extraction device 7, the middle of the tower body 1 is provided with a DCPD side-line extraction device 23, and the lower part of the tower body 1 is connected with a solvent side-line extraction device 8; the bottom end of the tower body 1 is provided with a partition plate 3 located below the tower plate 2, and there is a gap between the upper end of the partition plate 3 and the lowermost tower plate 2, and the partition plate 3 separates the air at the bottom of the tower body 1 The chamber is divided into a flash space 4 and a concentration space 5. The flash space 4 is connected to the C9 fraction supply pipeline via a cracking reactor 6. The flash space 4 is vertically opposite to the downcomer of the lowest tower plate 2 in the tower body 1. The flash space 4 is connected to a bottom liquid reflux pipeline 9. The solvent extracted from the solvent side-line extraction device 8 is mixed with the bottom liquid extracted from the bottom liquid reflux pipeline 9 and then heated by a reboiler 10 and refluxed to the concentration space 5. The concentration space 5 is provided with a bottom liquid external discharge pipeline 11.

[0030] Instead of setting a stripping section, the tower kettle is divided into two spaces by setting a partition plate, one for flash evaporation and the other for concentration. The flash evaporation space 4 is used to receive the liquid phase flowing down from the tower plate 2. The flash evaporation space 4 is connected to the C9 fraction supply pipeline. The incoming material of the C9 fraction supply pipeline is subjected to high-temperature cracking, and the temperature reaches 260-300°C. The inside of the C9 fraction supply pipeline contains cracked CPD, MCPD and solvents with low activity. Because of the high pressure in the pipeline, it maintains a liquid state. After entering the flash evaporation space 4, it can be quickly vaporized. CPD, MCPD and solvent vapor rise, leaving some The high boiling point components absorb the latent heat of vaporization due to the temperature drop and remain at the bottom of the tower. At this time, the liquid phase flowing down from the tower plate 2 received by the flash space 4 is a solvent-type material with a boiling point of 170-185°C. Its main components are n-propylbenzene, m-ethyltoluene, p-ethyltoluene, mesitylene and a small amount of DCPD, etc. It has good thermal stability and is not easy to polymerize. In addition, the liquid phase can reduce the temperature of the tower bottom liquid and dilute the tower bottom liquid, thereby avoiding rapid polymerization or coking of materials such as indene in the tower bottom liquid due to excessive concentration and high temperature, thereby reducing the probability of polymerization and coking.

[0031] Although the flash space 4 can quickly flash out CPD and MCPD, it still cannot flash out completely. A part of CPD, MCPD and DCPD will still remain in the bottom liquid and cannot be completely flashed. At this time, if the bottom liquid is directly discharged, it will cause a large waste. Therefore, the present invention is provided with a concentration space 5, which is separated from the flash space 4 and does not directly receive the liquid phase on the tower plate 2, but receives the bottom liquid transferred from the flash space and reheated. The bottom liquid stays in the concentration space 5 for a period of time, and the DCPD liquid phase therein continues to depolymerize and release CPD and MCPD before being discharged, thereby improving the processing efficiency and processing depth and reducing the cost. At the same time, a part of the solvent is extracted and mixed with the bottom liquid of the flash space 4 and then heated by a reboiler, which is also beneficial to diluting the material and reducing the occurrence of thermal coking of the material.

[0032] The partition plate 3 is a plate body with strip-shaped corrugations, and the strip-shaped corrugations are arranged along the vertical direction. The lower end of the partition plate 3 and two side edges of the partition plate 3 are connected to the inner wall of the tower body 1.

[0033] The corrugated partition plate 3 can increase the heat transfer area, which is beneficial for the material in the concentration space 5 to be continuously heated by the material in the flash space 4 .

[0034] The hot fluid inlet end of the reboiler 10 is connected to the C9 fraction delivery pipeline through the cracking reactor, and the hot fluid outlet end of the reboiler 10 is connected to the flash space 4 of the tower bottom.

[0035] The reboiler used in the present invention is different from that in the prior art and does not require fuel or heat transfer oil. Instead, the C9 fraction after cracking is used as a thermal fluid to heat the material, thereby avoiding the waste of resources caused by the use of cooling water, and reducing the problem of coking of the C9 fraction after cracking in the flash space due to the high temperature, thereby improving operational stability.

[0036] like Figure 3 , Figure 4 and Figure 5 As shown, the tower plate 2 is evenly distributed with air lifting holes 12 , and a guide floating tongue 13 is installed in the air lifting hole 12 . The guide floating tongue 13 is provided with an air port 14 , and the air port 14 faces the upper surface of the tower plate 2 .

[0037] An air inlet 14 is provided on the guide floating tongue 13, and the air inlet 14 faces the surface of the tower plate 2. When the gas volume is small, gas escapes from the air inlet 14, which can blow the liquid phase on the tower plate 2 away from the rising air hole 12, thereby preventing the presence of easily coked or viscous polymers in the liquid phase from adhering to the guide floating tongue 13 and the tower plate 2.

[0038] The air riser 12 is preferably trapezoidal, and the length direction of the air riser 12 is consistent with the flow direction of the liquid phase.

[0039] The trapezoidal air lifting hole 12 cooperates with the guide floating tongue 13 to produce a guiding effect. When the airflow is discharged from the bottom of the guide floating tongue 13, there is a component flowing along the liquid phase, which has the effect of promoting the movement of the liquid phase.

[0040] like Figure 4 and Figure 5 As shown, the guide floating tongue 13 includes a main board 15, a connecting plate 16 and a limiting plate 17. The main board 15 corresponds to the shape of the air lift hole 12. The two ends of the main board 15 are respectively connected to the connecting plate 16 and the limiting plate 17. The end of the main board 15 is also connected to the limiting end 18. The limiting end 18 is an extension formed by cutting from the connecting plate 16 and the limiting plate 17 and is integrated with the main board. The limiting end 18 and the main board 15 are on the same plane. When the connecting plate 16 and the limiting plate 17 are bent to form an angle with the main board 15, the position of the connecting plate 16 and the limiting plate 17 after cutting the limiting end 18 constitutes the air port 14.

[0041] After the connecting plate 16 is bent, the vertical distance between the end of the connecting plate 16 and the limiting end 18 is greater than the thickness of the tower plate 2 .

[0042] After the guide floating tongue 13 is blown up by the airflow, the air port 14 at one end of the connecting plate 16 of the guide floating tongue 13 can form air blowing to one side of the connecting plate 16 to prevent one end of the connecting plate 16 from being adhered.

[0043] The two side edges of the main board 15 are connected to triangular guide plates 19 , and the outer sharp corners of the guide plates 19 are close to the limiting plates 17 and tilted downward.

[0044] The guide plate 19 presses the airflow downward, reduces the upward flow of the airflow, and reduces the possibility of gas-liquid entrainment. The guide plate 19 makes the air outlet end of the guide float tongue 13 rise upward at a certain angle to expose the air port 14. When the airflow is small, it can facilitate the airflow to pass through and promote the heat transfer of the filled gas and liquid. At the same time, because the guide plate 19 makes the guide float tongue 13 rise upward at a smaller angle, liquid leakage will not occur.

[0045] The limiting plate 17 is arc-shaped and is provided with a cutting seam, which cuts the limiting plate 17 into a frame 20 and a tongue plate 21 connected to each other. The tongue plate 21 is bent inwardly, and a blowing port is formed between the tongue plate 21 and the frame 20 .

[0046] The arc-shaped limiting plate 17 has a stronger limiting effect than other guide floating tongues 13, which can prevent the guide floating tongue 13 from falling out and extend the service life.

[0047] The C9 fraction supply pipeline is provided with an inhibitor adding device 22 located upstream of the cracking reactor 6 .

[0048] The use principle of the present invention is as follows: the incoming material of the C9 fraction supply pipeline is subjected to high-temperature cracking, and the temperature reaches 260-300°C. The interior thereof contains cracked CPD, MCPD and solvents with low activity, etc., which are maintained in a liquid state due to the high pressure in the pipeline. After entering the flash evaporation space 4, they can be quickly vaporized, and CPD, MCPD and solvent vapors rise, leaving some high-boiling point components. Because CPD, MCPD and solvent absorb the latent heat of vaporization, the temperature drops and they remain at the bottom of the tower. As the CPD and MCPD gas phases rise, the temperature on the tower plate drops step by step. Many solvent-type stable substances flow on the tower plate with a tower plate temperature of about 160°C and begin to reflux. The CPD and MCPD gas phases continue to rise. When the temperature drops to about 130°C, CPD and MCPD self-polymerize to generate DCPD, DMCPD, etc., which are liquefied due to their high boiling points. At a temperature of 100 Reflux begins on the tower plate at about -130°C, CPD and MCPD that have not self-polymerized are extracted from the top of the tower, DCPD and DMCPD are extracted from the upper part of the tower, and a low-activity solvent at about 160°C is extracted from the lower part of the tower. The solvent contains less self-polymerizing components and less polymers. After extraction, it is mixed with the bottom liquid extracted from the bottom liquid reflux pipeline 9 and heated by the reboiler 10 to reflux to the concentration space 5, where it continues to crack and release CPD and MCPD gas phase. The concentration space 5 does not receive the C9 fraction cracked by high temperature, but only depolymerizes the DCPD and DMCPD in itself. If the solvent is not extracted from the side line, but the bottom liquid is directly transferred from the flash space into the concentration space, the concentration of the self-polymerizable material in the bottom liquid is high, and the DCPD and DMCPD content is high, which is transferred to the concentration space and is easily discharged as bottom liquid before depolymerization, resulting in waste.

[0049] The guide floating tongue can blow the liquid phase on the tower plate 2 away from the gas lift hole 12 to prevent the presence of easily coked or viscous polymers in the liquid phase from causing adhesion between the guide floating tongue 13 and the tower plate 2 .

[0050] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

Claims

1. A distillation tower for cracking a C9 fraction, comprising a tower body (1) and tower plates (2), wherein the tower body (1) is provided with tower plates (2) which are sequentially staggered, characterized in that: The top of the tower body (1) is provided with a CPD extraction device (7), the middle of the tower body (1) is provided with a DCPD side-line extraction device (23), and the lower part of the tower body (1) is connected to a solvent side-line extraction device (8); the bottom of the tower body (1) is provided with a partition plate (3) located below the tower plate (2), the partition plate (3) divides the space at the bottom of the tower body (1) into a flash space (4) and a concentration space (5), and the flash space (4) is connected to the C9 fraction supply pipe (6). The flash space (4) is connected to the downcomer of the lowest tower plate (2) in the tower body (1) in vertical relation, the flash space (4) is connected to the tower bottom liquid reflux pipeline (9), the solvent extracted by the solvent side-line extraction device (8) is mixed with the tower bottom liquid extracted from the tower bottom liquid reflux pipeline (9), and then heated and refluxed to the concentration space (5) through the reboiler (10), and the concentration space (5) is provided with a tower bottom liquid external discharge pipeline (11).

2. A distillation tower for cracking C9 fraction according to claim 1, characterized in that: The partition plate (3) is a plate body with strip-shaped corrugations, the strip-shaped corrugations are arranged in the vertical direction, and the lower end of the partition plate (3) and two side edges of the partition plate (3) are connected to the inner wall of the tower body (1).

3. A distillation tower for cracking C9 fraction according to claim 1, characterized in that: The hot fluid inlet end of the reboiler (10) is connected to the C9 fraction delivery pipeline via the cracking reactor (6), and the hot fluid outlet end of the reboiler (10) is connected to the flash space (4) of the tower bottom.

4. A distillation tower for cracking C9 fraction according to claim 1, characterized in that: The tower plate (2) is evenly distributed with gas lifting holes (12), the gas lifting holes (12) are provided with guide floating tongues (13), the guide floating tongues (13) are provided with gas outlets (14), and the gas outlets (14) face the upper surface of the tower plate (2).

5. A distillation tower for cracking C9 fraction according to claim 4, characterized in that: The length direction of the gas riser (12) is consistent with the flow direction of the liquid phase.

6. A distillation tower for cracking C9 fraction according to claim 4, characterized in that: The guide floating tongue (13) comprises a main board (15), a connecting plate (16) and a limiting plate (17). The main board (15) matches the shape of the air lifting hole (12). The two ends of the main board (15) are respectively connected to the connecting plate (16) and the limiting plate (17). The end of the main board (15) is also connected to a limiting end (18). The limiting end (18) is an extension formed by cutting from the connecting plate (16) and the limiting plate (17) and is integral with the main board (15). The limiting end (18) and the main board (15) are on the same plane. When the connecting plate (16) and the limiting plate (17) are bent to form an angle with the main board (15), the position after the connecting plate (16) and the limiting plate (17) cut the limiting end (18) constitutes the air port (14).

7. A distillation tower for cracking C9 fraction according to claim 6, characterized in that: After the connecting plate (16) is bent, the vertical distance between the end of the connecting plate (16) and the limiting end (18) is greater than the thickness of the tower plate (2).

8. A distillation tower for cracking C9 fraction according to claim 6, characterized in that: The two side edges of the main board (15) are also connected to triangular guide plates (19), and the outer end sharp corners of the guide plates (19) are close to the limiting plates (17) and tilted downward.

9. A distillation tower for cracking C9 fraction according to claim 6, characterized in that: The limiting plate (17) is arc-shaped and is provided with a cutting slit, wherein the cutting slit cuts the limiting plate (17) into a frame (20) and a tongue plate (21) connected to each other, wherein the tongue plate (21) is bent inwardly, and an air blowing port (14) is formed between the tongue plate (21) and the frame (20).

10. A distillation tower for cracking C9 fraction according to claim 1, characterized in that: The C9 fraction supply pipeline is provided with an inhibitor adding device (22) located upstream of the cracking reactor (6).

Images