A cleaving c9 fraction rectification column side line take-off device

Abstract

The present application relates to rectifying column technical field, specifically to a kind of cracking C9 fraction rectifying column side line take-out device, including tower section, collecting tray, air pipe and take-out pipe;The tower section is connected with collecting tray, the collecting tray is evenly distributed with air pipe for balancing liquid level, the air pipe side wall is equipped with liquid inlet located above collecting tray, the opening size of the liquid inlet gradually decreases from upper end to lower end;The take-out pipe is communicated with tower section, take-out pipe lower end is higher than collecting tray, upper end is lower than the lower end of liquid inlet.The present application is installed on cracking C9 fraction rectifying column and is used for side line to take out liquid phase, installation requirement is low, even if certain installation deviation occurs, can also guarantee liquid distribution uniform, maintain the stability of rectification process.

Description

Technical Field

[0001] This invention relates to the field of distillation column technology, and more specifically to a side stream extraction device for a cracked C9 fraction distillation column. Background Technology

[0002] Currently, the main method for processing cracked C9 fractions in China is to separate the cracked C9 fractions according to their distillation range, generally into three distillation ranges. The first distillation range is 140-160℃, which mainly consists of light C8 components such as styrene and o-xylene. The second distillation range is 160-185℃, which mainly consists of components such as methylstyrene, vinyltoluene, dicyclopentadiene, and indene. The third distillation range is above 185℃, which mainly consists of heavy components such as polycyclic olefins, naphthalene, and anthracene.

[0003] Existing distillation columns are typically packed columns or plate columns. Packed columns are widely used in chemical and oil refining industries due to their advantages such as high operational flexibility, high energy density, high efficiency, low pressure drop, simple structure, and low cost. However, some products require side-stream distillation from the middle of the column due to the presence of multiple components. To facilitate side-stream distillation, plate columns have traditionally been used instead of packed columns. However, plate columns increase the cost of the column. Therefore, solving the problem of liquid side-stream distillation in packed columns is particularly important to save money.

[0004] In the existing technology, experts and scholars have conducted relevant research in this area, such as a side-stream extraction device for a packed tower with application number 202022509950.0 and a side-stream extraction or intermediate feeding device placed in the packing layer with application number 201120148275. Both of these are side-stream extraction devices. However, the above two side-stream extraction devices have very high installation requirements. If there is a slight tilt during installation, it will cause the downward discharge (rinsing) liquid phase to be discharged from a single or a limited number of drain pipes. This can easily lead to uneven liquid distribution in the lower packing layer while the liquid phase is being extracted, which will affect the distillation. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a side-stream sampling device for a cracked C9 fraction distillation column. This device is installed on the cracked C9 fraction distillation column for side-stream sampling of the liquid phase. It has low installation requirements and can ensure uniform liquid distribution and maintain the stability of the distillation process even if there are certain installation deviations.

[0006] The technical solution adopted in this application to address this technical problem is as follows:

[0007] A side stream extraction device for a cracked C9 fraction distillation column includes a column section, a liquid collection tray, a vent pipe, and an extraction pipe; the column section is connected to a liquid collection tray, and the liquid collection tray is evenly distributed with vent pipes for balancing the liquid level. The side wall of the vent pipe is provided with a liquid inlet located above the liquid collection tray, and the opening size of the liquid inlet gradually decreases from the top to the bottom.

[0008] The extraction pipe is connected to the tower section, with the lower end of the extraction pipe higher than the liquid collection tray and the upper end lower than the lower end of the liquid inlet.

[0009] Furthermore, there are multiple liquid inlets, which are distributed in a circular array along the vent pipe. The sidewall of the vent pipe between each two adjacent liquid inlets is twisted, and the gap between each two adjacent twisted sidewalls of the vent pipe constitutes the opening size of the liquid inlet, which gradually decreases from the top to the bottom.

[0010] Furthermore, the liquid collection tray is also evenly distributed with multiple drain holes and connection holes. The connection holes are used to connect to the vent pipe, and the ratio of the number of connection holes to the number of drain holes is 4-5:1.

[0011] Furthermore, the connecting hole and the vent pipe are connected via a threaded pipe, the threaded pipe is fixedly connected in the connecting hole, the inner wall of the threaded pipe is provided with an internal thread, the outer wall of the vent pipe is provided with an external thread, the vent pipe is connected in the threaded pipe via the external thread, the vent pipe moves up and down in the threaded pipe by rotation to adjust the height difference between the upper end of the vent pipe and the extraction pipe, and the tower section is provided with a viewing window facing the vent pipe.

[0012] Furthermore, the outer wall of the vent pipe is provided with a vertical first groove, and a limiting ring is provided on the outer sleeve of the vent pipe. The inner wall of the limiting ring is provided with protruding teeth that extend into the first groove. The limiting ring slides up and down along the first groove outside the vent pipe. The lower end face of the limiting ring is arrayed with first teeth, and the upper end face of the threaded pipe is arrayed with second teeth. The first teeth and the second teeth mesh with each other.

[0013] Furthermore, the outer contour of the limiting ring is hexagonal.

[0014] Furthermore, the lower end of the vent pipe is provided with a third tooth.

[0015] Furthermore, the third tooth is inclined radially outward along the ventilator.

[0016] Furthermore, the inner wall of the vent pipe is provided with a second annular groove located below the liquid inlet, and the inner wall of the vent pipe below the second groove is provided with vertical third grooves, the upper end of the third grooves being connected to the second grooves.

[0017] Furthermore, it also includes a storage tank, which is connected to a pipeline, and the upper end of the storage tank is provided with a return gas pipeline connected to the tower section.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. The present invention has a vertical liquid inlet on the vent pipe with a smaller opening at the bottom and a larger opening at the top, which ensures uniform liquid distribution and maintains the stability of the distillation process even when there is installation deviation.

[0020] 2. The vent pipe of the present invention can be adjusted up and down. Even if there is a deviation in the installation, it can be balanced by adjusting the vent pipe up and down to achieve a more stable distillation operation.

[0021] 3. The side-line extraction device of the present invention can also enhance gas-liquid contact and improve mass and heat transfer during the extraction process. Attached Figure Description

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

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

[0024] Figure 3 This is a schematic diagram of the ventilation mechanism of the present invention;

[0025] Figure 4 This is a schematic diagram (cross-sectional view) of the structure connecting the ventilation mechanism and the liquid collection tray of the present invention;

[0026] Figure 5 yes Figure 4 Enlarged view of part A.

[0027] The attached diagram is labeled as follows: 1. Tower section; 2. Liquid collection tray; 3. Outlet pipe; 4. Storage tank; 5. Drain hole; 6. Connection hole; 7. Vent pipe; 8. Liquid inlet; 9. Threaded pipe; 10. First groove; 11. Limiting ring; 12. First tooth; 13. Second tooth; 14. Third tooth; 15. Second groove; 16. Third groove. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0029] like Figure 1 and Figure 2As shown, a side-stream sampling device for a C9 fraction distillation column includes a column section 1, a collection tray 2, a venting mechanism, a sampling pipe 3, and a storage tank 4. The column section 1 is a cylindrical body with flanges at both ends, used to connect between two packing sections of a packed column. The collection tray 2 is connected to the inner wall of the column section 1. The collection tray 2 is provided with multiple drain holes 5 and multiple connection holes 6. The drain holes 5 are used to drain the liquid phase below the collection tray 2 and are also used when the distillation column is shut down. When the liquid phase on the collection tray 2 is discharged, a venting mechanism is connected to the connecting hole 6. The venting mechanism includes a vent pipe 7. The side wall of the vent pipe 7 is provided with a liquid inlet 8 located above the collection tray 2. The opening size of the liquid inlet 8 gradually decreases from the top to the bottom. Because the liquid inlet 8 is located on the side wall of the vent pipe 7, and the lower opening is small while the upper opening is large, when the liquid level of the liquid phase is close to the lower end of the liquid inlet 8, the amount of liquid discharged from the vent pipe 7 is very small, and the liquid level of the liquid phase is close to the lower end of the liquid inlet 8. Near the upper end of the liquid inlet 8, the discharge volume in the vent pipe 7 is large. Even if there is a deviation in installation accuracy causing the liquid collection plate 2 to tilt or other situations, the liquid inlet 8 is in a vertical state and the lower opening of the liquid inlet is small, resulting in less discharge. This offsets the tilt of the liquid collection plate 2 or the height difference of the vent pipe 7, ensuring that liquid phase is discharged from all vent pipes 7 and the discharge volume is not significantly different. This ensures that the liquid phase is distributed through each vent pipe 7, unlike existing technologies where, when there is a deviation in installation, the liquid phase is discharged from one or a limited number of vent pipes 7, resulting in an uneven distribution of the liquid phase, which affects the gas-liquid heat transfer in the packing below. This problem is more likely to occur when the side line output is large and the liquid phase leaks downward less. The output pipe 3 is connected to the tower section 1 above the liquid collection plate 2. The upper end of the output pipe 3 is lower than the upper end of the vent pipe 7. The outer end of the output pipe 3 is connected to the storage tank 4. The upper end of the storage tank 4 is provided with a return gas pipeline connected to the tower section 1.

[0030] Because of fluctuations in the production status of the upstream processes (ethylene section and cracking section), the fractions in different temperature ranges within the packed tower also change, which cannot be determined by theoretical calculations. Existing side-stream extraction devices only have a liquid phase inlet at the top of the vent pipe 7. When the fraction fluctuates and the extraction rate does not change in time, there may even be a situation where no liquid phase flows down, leading to increased impurities in the extracted liquid phase and disrupting the overall operational stability of the packed tower. This invention mitigates these problems because the liquid inlet 8 is located on the side wall of the vent pipe 7, with a small opening at the bottom and a large opening at the top. Therefore, even if the fraction fluctuates and the rate does not change in time, causing the liquid level to drop, liquid phase will continue to flow downwards due to the lower bottom of the liquid inlet 8 (at this time, the extraction pipe 3 may extract some gas phase, but this does not affect the use of this invention or the operation of the distillation tower). Figure 1 and Figure 2(The return gas pipeline at the top of the storage tank is designed for this purpose.) When the tower's operating conditions change, this invention has better adaptability than the side-line extraction device in the prior art, and plays a role in maintaining the stability of tower operation.

[0031] like Figure 3 As shown, there are multiple liquid inlets 8, which are arranged in a circular array along the vent pipe 7. In addition to directly cutting material from the vent pipe 7 to make the liquid inlets 8, the liquid inlets 8 of the present invention can also be set in another form, namely: the side wall of the vent pipe 7 between each two adjacent liquid inlets 8 is twisted, and the gap between each two adjacent twisted side walls of the vent pipe 7 constitutes the opening size of the liquid inlet 8, which gradually decreases from the top to the bottom.

[0032] The liquid inlet 8 of the present invention is formed by twisting the side wall of the vent pipe 7. After twisting, the liquid inlet 8 is formed between the side walls of two adjacent vent pipes 7, and the liquid phase entering the vent pipe 7 through the liquid inlet 8 flows down along the inner wall of the vent pipe 7 to form a liquid film on the inner wall of the vent pipe 7. The liquid film contacts the gas phase rising along the vent pipe 7 to transfer heat and mass, reduce the impact between the airflows, and reduce the pressure drop and airflow entrainment problems.

[0033] The ratio of the number of connecting holes 6 to the number of drain holes 5 is 4-5:1. Compared with connecting holes 6, the number of drain holes 5 is very small. The main function of drain holes 5 is to discharge liquid phase when the packed tower is shut down, rather than to make the liquid phase descend during the production process. In this invention, the liquid phase mainly flows downward through the vent hole to form a liquid film, which enhances gas-liquid contact, rather than being discharged mainly through drain holes 5.

[0034] The ventilation mechanism also includes a threaded pipe 9, which is fixedly connected to the connecting hole 6. The inner wall of the threaded pipe 9 is provided with an internal thread, and the outer wall of the ventilation pipe 7 is provided with an external thread. The ventilation pipe 7 is connected to the threaded pipe 9 through the external thread. The ventilation pipe 7 moves up and down in the threaded pipe 9 by rotation to adjust the height difference between the upper end of the ventilation pipe 7 and the extraction pipe 3. The tower section 1 is provided with a viewing window facing the ventilation mechanism.

[0035] This invention adjusts the vent pipe 7 into a structure that can be moved up and down for adjustment. This can also reduce the problem of insufficient equipment installation accuracy. After the equipment is installed, by adjusting the height of the vent pipe 7, the tilting deviation caused by insufficient equipment accuracy can be reduced. For example, the liquid collection plate 2 is tilted, the liquid collection plate 2 is in a state of low center and high outer edge due to liquid phase accumulation, and the liquid inlet 8 on the vent pipe 7 is of different sizes. The height of the vent pipe 7 can be adjusted to make the liquid inlet of each vent pipe 7 more consistent, reducing the design and installation difficulty.

[0036] The C9 fraction contains components that are prone to self-polymerization, such as CPD, MCPD, DCPD, DMCPD, and styrene. Therefore, it is necessary to minimize the residence time of this fraction on the collection tray 2 while ensuring that it can be extracted, so as to avoid self-polymerization. Therefore, a viewing window is provided on the column section 1 of this invention to observe the stable operating conditions in actual production. Then, when the column is shut down, the height of the vent pipe 7 is adjusted. The optimal distillation conditions can be achieved by adjusting the height of the vent pipe 7.

[0037] The outer wall of the vent pipe 7 is provided with a vertical first groove 10, and a limiting ring 11 is provided on the outer sleeve of the vent pipe 7. The inner wall of the limiting ring 11 is provided with protruding teeth that extend into the first groove 10. The limiting ring 11 slides up and down along the first groove 10 outside the vent pipe 7. The lower end face of the limiting ring 11 is arranged with first teeth 12, and the upper end face of the threaded pipe 9 is arranged with second teeth 13. The first teeth 12 and the second teeth 13 mesh with each other.

[0038] Because the vent pipe 7 and the threaded pipe 9 of the present invention are connected by threads, the packing tower is prone to rotation due to vibration during operation, which causes the height of the vent pipe 7 to change. Therefore, a limiting ring 11 is set to limit the vent pipe 7 and prevent the height of the vent pipe 7 from changing due to vibration during operation.

[0039] The outer contour of the limiting ring 11 is hexagonal, which is used to limit the vent pipe 7 and can also be used as an auxiliary tool for adjusting the vent pipe 7. Simply use a wrench to clamp the limiting ring 11, lift it up a certain distance and then rotate it to rotate the vent pipe 7. This avoids the oil or impurities generated during the distillation process affecting the grip on the circular vent pipe 7 and ensures smooth adjustment.

[0040] The lower end of the vent pipe 7 is provided with a third tooth 14; the third tooth 14 at the lower end of the vent pipe 7 is used to disperse the liquid film on the inner wall of the vent pipe 7 into droplets. After the liquid phase leaves the vent pipe 7, it is guided by the third tooth 14 to form multiple downward dripping liquid phase drop lines, instead of being concentrated into a relatively thick liquid flow. This can increase the contact area between the liquid phase and the gas phase, and increase mass transfer and heat transfer.

[0041] like Figure 5 As shown, the third tooth 14 is radially outward along the vent pipe 7, that is, the inner wall of the third tooth 14 gradually increases in diameter from top to bottom, so that the liquid phase has an outward component during the downward flow along the inner wall of the vent pipe 7.

[0042] The outwardly inclined third tooth 14 not only disperses the liquid film into a liquid phase droplet line, but also guides the droplets, so that the droplets have a horizontal component that moves outward away from the vent pipe 7 when they fall, reducing the probability of being carried by the gas phase that is about to enter the vent pipe 7, reducing airflow entrainment and reducing pressure drop.

[0043] like Figure 4As shown, the inner wall of the vent pipe 7 is provided with a second annular groove 15 located below the liquid inlet 8. The inner wall of the vent pipe 7 below the second groove 15 is provided with vertical third grooves 16, the upper end of the third groove 16 being connected to the second groove 15.

[0044] The second groove 15 on the inner wall of the vent pipe 7 is used to collect the liquid phase entering through the liquid inlet 8 and to distribute the liquid phase evenly in multiple third grooves 16 to form a liquid film. The vertical third grooves 16 are beneficial for guiding the liquid film and preventing the liquid phase from flowing down in streams. This is especially suitable for enhancing the distribution of liquid phase when the side line output is large and the amount of downward flowing liquid phase is small. For the specific principle, please refer to "Study on Statistical Characteristics of Liquid Film Flow on Complex Surfaces" - Yuan Meng, Master's Thesis, East China University of Science and Technology.

[0045] The working principle of this invention is as follows:

[0046] This invention connects two adjacent packing sections on a packed tower, replacing a liquid redistributor. During distillation, when liquid phase refluxes from the packing above the collecting pan 2, the collecting pan 2 collects this refluxed liquid phase, concentrating it on the collecting pan 2. A portion of the liquid phase is discharged downwards through the drain hole 5, while the other portion accumulates in the collecting pan 2, causing the liquid level to rise. When the liquid level rises to the lower end of the inlet 8 of the first vent pipe 7, a portion of the liquid phase begins to enter the vent pipe 7 and flow down along the inner wall of the vent pipe 7. At this point, the flow rate is extremely small, and the liquid level continues to rise to a certain height. After reaching a certain temperature, the liquid level is higher than the lower end of the inlet 8 of all vent pipes 7. Liquid phase enters each vent pipe 7. Even at this time, the liquid phase flow rate in each vent pipe 7 is still not much different. As the liquid level continues to rise, the liquid phase flow rate in each vent pipe 7 also increases. At this time, the liquid phase level exceeds the upper end of the extraction pipe 3, and liquid phase can be extracted. The extracted liquid phase is temporarily transported to the storage tank 4 for subsequent cooling and transfer. However, it can be ensured that liquid phase flows out of each vent pipe 7 and disperses downwards, and the liquid phase flow rate in all vent pipes 7 is not much different.

[0047] When the liquid enters the vent pipe 7 through the inlet 8, it forms a liquid film and flows downward along the inner wall of the vent pipe 7 under the guidance of the twisting state of the side wall of the vent pipe 7. It then disperses into multiple downward dripping liquid drop lines at the third tooth at the lower end of the vent pipe 7 and continues to fall. During this period, the falling liquid comes into contact with the gas phase below the collecting pan 2 and the gas phase rising along the vent pipe 7, and performs heat and mass transfer. In the case of side stream extraction, it can also ensure a certain degree of distillation.

[0048] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Claims

1. A side stream extraction device for a cracked C9 fraction distillation column, characterized in that, It includes a tower section (1), a liquid collection tray (2), a vent pipe (7), and a collection pipe (3); the tower section (1) is connected to the liquid collection tray (2), and the liquid collection tray (2) is evenly distributed with vent pipes (7) for balancing the liquid level. The side wall of the vent pipe (7) is provided with a liquid inlet (8) located above the liquid collection tray (2), and the size of the opening of the liquid inlet (8) gradually decreases from the top to the bottom. The extraction pipe (3) is connected to the tower section (1). The lower end of the extraction pipe (3) is higher than the liquid collection plate (2), and the upper end is lower than the lower end of the liquid inlet (8). There are multiple liquid inlets (8), which are arranged in a circular array along the vent pipe (7). The sidewall of the vent pipe (7) between each two adjacent liquid inlets (8) is twisted. The gap between each two adjacent twisted sidewalls of the vent pipe (7) constitutes the opening size of the liquid inlet (8), which gradually decreases from the top to the bottom. The liquid collection tray (2) is evenly distributed with multiple drain holes (5) and connecting holes (6). The connecting holes (6) are connected to the vent pipe (7) via a threaded pipe (9). The threaded pipe (9) is fixedly connected inside the connecting hole (6). The inner wall of the threaded pipe (9) is provided with an internal thread. The outer wall of the vent pipe (7) is provided with an external thread. The vent pipe (7) is connected inside the threaded pipe (9) via the external thread. The vent pipe (7) moves up and down inside the threaded pipe (9) by rotation to adjust the height difference between the upper end of the vent pipe (7) and the extraction pipe (3). The tower section (1) is provided with a viewing window facing the vent pipe (7).

2. The side-stream extraction device for the cracked C9 fraction distillation column according to claim 1, characterized in that, The connecting hole (6) is used to connect the vent pipe (7), and the ratio of the number of connecting holes (6) to the number of vent holes (5) is 4-5:

1.

3. The side-stream extraction device for the cracked C9 fraction distillation column according to claim 1, characterized in that, The outer wall of the vent pipe (7) is provided with a vertical first groove (10), and a limiting ring (11) is provided on the outer sleeve of the vent pipe (7). The inner wall of the limiting ring (11) is provided with protruding teeth that extend into the first groove (10). The limiting ring (11) slides up and down along the first groove (10) outside the vent pipe (7). The lower end face of the limiting ring (11) is arranged with first teeth (12), and the upper end face of the threaded pipe (9) is arranged with second teeth (13). The first teeth (12) and the second teeth (13) mesh with each other.

4. The side-stream extraction device for the cracked C9 fraction distillation column according to claim 3, characterized in that, The outer contour of the limiting ring (11) is hexagonal.

5. The side-stream extraction device for the cracked C9 fraction distillation column according to claim 1, characterized in that, The lower end of the vent pipe (7) is provided with a third tooth (14).

6. The side-stream extraction device for the cracked C9 fraction distillation column according to claim 5, characterized in that, The third tooth (14) is inclined radially outward along the ventilator (7).

7. The side-stream extraction device for the cracked C9 fraction distillation column according to claim 1, characterized in that, The inner wall of the vent pipe (7) is provided with a second groove (15) in the shape of an annulus located below the liquid inlet (8). The inner wall of the vent pipe (7) below the second groove (15) is provided with vertical third grooves (16), and the upper end of the third groove (16) is connected to the second groove (15).

8. The side-stream extraction device for the cracked C9 fraction distillation column according to claim 1, characterized in that, It also includes a storage tank (4), which is connected to a pipeline, and the upper end of the storage tank (4) is provided with a return gas pipeline connected to the tower section.

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