Cracking C9 fraction rectifying tower side withdrawing device

Abstract

The invention relates to the technical field of rectifying towers, in particular to a cracking C9 fraction rectifying tower side line extraction device which comprises tower sections, a liquid collecting tray, a breather pipe and an extraction pipe. A liquid collecting tray is connected in the tower section, vent pipes for balancing the liquid level are uniformly distributed on the liquid collecting tray, a liquid inlet positioned above the liquid collecting tray is formed in the side wall of each vent pipe, and the opening size of each liquid inlet is gradually reduced from the upper end to the lower end; the lower end of the extraction pipe is higher than the liquid collecting tray, and the upper end of the extraction pipe is lower than the lower end of the liquid inlet. The device is mounted on a cracking C9 fraction rectifying tower and used for side-draw liquid phase production, the mounting requirement is low, even if certain mounting deviation occurs, uniform liquid distribution can be ensured, and the stability of the rectifying process is maintained.

Description

Technical Field

[0001] The invention relates to the technical field of distillation towers, and in particular to a side-line extraction device of a cracking C9 fraction distillation tower. Background Art

[0002] At present, the main treatment method for cracking C9 fraction in China is to separate the cracking C9 into different coarse and fine fractions according to the distillation range. It is generally separated into three distillation sections. The first distillation section is 140-160℃, which is mainly C8 light components such as styrene and o-xylene. The second distillation section is 160-185℃, which is mainly methyl styrene, vinyl toluene, dicyclopentadiene, indene and other components. The third distillation section is above 185℃, which is mainly heavy components such as condensed ring olefins, naphthalene, anthracene and other heavy components.

[0003] Existing distillation towers are usually packed towers or plate towers. Packed towers are widely used in chemical and oil refining industries due to their advantages of large operating flexibility, large energy, high efficiency, low pressure drop, simple structure, and low cost. However, in the distillation of some products, due to the presence of multiple components, the middle part of the tower needs to be side-lined. In order to facilitate the side-line, plate towers are used instead of packed towers. However, plate towers will increase the cost of the tower. Therefore, in order to save money, it is particularly important to solve the problem of side-line extraction of liquid phase in packed towers.

[0004] Experts and scholars have conducted relevant research in this regard in the prior art, such as a side-line extraction device for a packed tower with application number 202022509950.0 and a side-line extraction or intermediate feeding device placed in a packing layer with application number 201120148275. Both are side-line extraction devices, but the above two side-line extraction devices have very high installation requirements. If there is a slight tilt during installation, the liquid phase discharged (flushing) downward will be discharged from a single or a limited number of drainage pipes, which will easily cause uneven liquid distribution in the lower layer of packing when the liquid phase is extracted, affecting distillation. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a side line extraction device for a cracking C9 fraction distillation tower, which is installed on the cracking C9 fraction distillation tower for side line extraction of liquid phase. The installation requirements are low, and even liquid distribution can be guaranteed evenly even if a certain installation deviation occurs, thereby maintaining the stability of the distillation process.

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

[0007] A side-line extraction device for a cracking C9 fraction distillation tower comprises a tower section, a liquid collecting tray, a vent pipe and an extraction pipe; the tower section is connected with a liquid collecting tray, the liquid collecting tray is evenly provided with vent pipes for balancing the liquid level, the vent pipe side wall is provided with a liquid inlet located above the liquid collecting tray, and the opening size of the liquid inlet gradually decreases from the upper end to the lower end;

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

[0009] Furthermore, there are multiple liquid inlets, which are distributed in an array along the circumference of the ventilation pipe. The side wall of the ventilation pipe between each two adjacent liquid inlets is in a twisted state, and the gap between each two adjacent twisted ventilation pipe side walls constitutes the opening size of the liquid inlet, which gradually decreases from the upper end to the lower end.

[0010] Furthermore, the liquid collecting tray is evenly distributed with a plurality of leakage holes and connecting holes, the connecting holes are used to connect the ventilation pipes, and the ratio of the number of the connecting holes to the number of the leakage holes is 4-5:1.

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

[0012] Furthermore, a vertical first groove is provided on the outer wall of the ventilation pipe, a limiting ring is provided on the outer sleeve of the ventilation pipe, and a protruding tooth extending into the first groove is provided on the inner wall of the limiting ring. The limiting ring slides up and down along the first groove outside the ventilation pipe, and a first tooth array is provided on the lower end face of the limiting ring, and a second tooth array is provided on the upper end face of the threaded tube, and the first tooth and the second tooth are meshed with each other.

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

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

[0015] Furthermore, the third teeth are inclined radially outward along the ventilation pipe.

[0016] Furthermore, a second annular groove is provided on the inner wall of the ventilation pipe and is located below the liquid inlet. Vertical third grooves are evenly distributed on the inner wall of the ventilation pipe below the second groove, and the upper end of the third groove is connected to the second groove.

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

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention provides a vertical liquid inlet on the ventilation pipe, and the opening of the liquid inlet is small at the lower end and large at the upper end, so that even when there is an installation deviation, the liquid distribution can be guaranteed to be uniform, and the stability of the distillation process can be maintained.

[0020] 2. The ventilation 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 ventilation pipe up and down to achieve a more stable distillation operation state.

[0021] 3. The side line extraction device of the present invention can also strengthen the gas-liquid contact during the extraction process, and improve the mass transfer and heat transfer effects. 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 structural schematic diagram of the ventilation mechanism of the present invention;

[0025] Figure 4 It is a structural schematic diagram (cross-sectional view) of the ventilation mechanism of the present invention connected to the liquid collecting tray;

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

[0027] The numbers in the attached drawings are: 1, tower section; 2, liquid collecting tray; 3, production pipe; 4, storage tank; 5, leakage hole; 6, connecting hole; 7, ventilation 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 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 2As shown, a side-line extraction device for a cracking C9 fraction distillation tower comprises a tower section 1, a liquid collecting tray 2, a ventilation mechanism, an extraction pipe 3 and a storage tank 4. The tower section 1 is a cylindrical body with flanges at both ends, which is used to be connected between two packing sections of a packing tower. The inner wall of the tower section 1 is connected to the liquid collecting tray 2, and the liquid collecting tray 2 is provided with a plurality of leakage holes 5 and a plurality of connecting holes 6. The leakage holes 5 are used to discharge the liquid phase to the bottom of the liquid collecting tray 2, and are also used to stop the distillation tower. When the liquid phase on the liquid collecting tray 2 is discharged, the connecting hole 6 is connected to a ventilation mechanism, and the ventilation mechanism includes a ventilation pipe 7. The side wall of the ventilation pipe 7 is provided with a liquid inlet 8 located above the liquid collecting tray 2. The opening size of the liquid inlet 8 gradually decreases from the upper end to the lower end. Because the liquid inlet 8 is located on the side wall of the ventilation pipe 7, and the lower end opening is small and the upper end opening is large, when the liquid level of the liquid phase approaches the lower end of the liquid inlet 8, the amount of liquid discharged in the ventilation pipe 7 is very small, and the liquid level of the liquid phase is close to When near the upper end of the liquid inlet 8, the amount of liquid discharged from the vent pipe 7 is large. Even if there is an installation accuracy deviation that causes the liquid collecting tray 2 to tilt or other situations, because the liquid inlet 8 is in a vertical state and the opening at the lower end of the liquid inlet is small, the amount of liquid discharged is small, thereby offsetting the tilt of the liquid collecting tray 2 or the height difference of the vent pipe 7, ensuring that liquid is discharged from all vent pipes 7 and the difference in the amount of liquid discharged is not large, ensuring that the liquid phase is distributed through each vent pipe 7, unlike the prior art, when there is an installation deviation, the liquid phase is discharged from one or a limited number of vent pipes 7, and there is an uneven distribution of liquid phase, which affects the gas-liquid heat transfer in the packing below, especially when the side line production volume is large and the liquid phase leaks downward less, the above problem is more likely to occur; the production pipe 3 is connected to the tower section 1 above the liquid collecting tray 2, the upper end of the production pipe 3 is lower than the upper end of the vent pipe 7, the outer end of the production pipe 3 is connected to the storage tank 4, and the upper end of the storage tank 4 is provided with a return air pipeline connected to the tower section 1.

[0030] Because the production state fluctuates in the front-end process (ethylene section and cracking section), the fractions in different temperature sections in the packed tower also change, which cannot be determined by theoretical calculation. The side-line extraction device in the prior art is only provided with a liquid phase through port at the top of the vent pipe 7. When the fraction fluctuates and the extraction amount is not changed in time, there may even be a situation where no liquid phase is dripping down, resulting in an increase in impurities in the liquid phase extraction, destroying the stable operation of the entire packed tower; the present invention can alleviate the occurrence of the above-mentioned problem, because the liquid inlet 8 is located on the side wall of the vent pipe 7, and the lower end opening is small and the upper end is large. Therefore, even if the fraction fluctuates and the amount is not changed in time, resulting in a drop in the liquid level, the lower end of the liquid inlet 8 is relatively low and the liquid phase is always discharged and washed downward (at this time, the extraction pipe 3 may extract a part of the gas phase, but it does not affect the use of the present invention and the operation of the distillation tower, Figure 1 and Figure 2In the embodiment, the return air pipeline at the upper end of the storage tank is provided for this purpose). When the operating conditions of the tower change, the present invention has better adaptability than the side line extraction device in the prior art, and has a maintaining effect on the stability of the tower operation.

[0031] like Figure 3 As shown, there are multiple liquid inlets 8, and the multiple liquid inlets 8 are distributed in an array along the circumference of the ventilation tube 7. In addition to directly cutting material on the ventilation tube 7 to make the liquid inlet 8, the liquid inlet 8 of the present invention also has another form to realize the setting of the liquid inlet 8, namely: the side wall of the ventilation tube 7 between each two adjacent liquid inlets 8 is in a twisted state, and the gap between each two adjacent twisted side walls of the ventilation tube 7 constitutes the opening size of the liquid inlet 8 which gradually decreases from the upper end to the lower end.

[0032] The liquid inlet 8 of the present invention is formed by twisting the side wall of the vent pipe 7. Not only is the liquid inlet 8 formed between the side walls of two adjacent vent pipes 7 after twisting, but the liquid phase entering the vent pipe 7 from the liquid inlet 8 also flows down along the inner wall of the vent pipe 7, forming a liquid film on the inner wall of the vent pipe 7, and contacting with the gas phase rising along the vent pipe 7 for heat and mass transfer, thereby reducing the impact between the air flows and reducing the pressure drop and air flow entrainment problems.

[0033] The ratio of the number of the connecting holes 6 to the number of the leakage holes 5 is 4-5:1. Compared with the connecting holes 6, the number of the leakage holes 5 is very small. The main function of the leakage holes 5 is to discharge the liquid phase when the packed tower is stopped, rather than being mainly used to make the liquid phase descend during the production process. The liquid phase of the present invention mainly forms a liquid film in the vent hole and flows downward to enhance the gas-liquid contact, rather than being mainly discharged from the leakage holes 5.

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

[0035] The present invention adjusts the vent pipe 7 to a structure that can be moved up and down and adjusted, which can also achieve the goal of eliminating the problem of insufficient equipment installation accuracy. After the equipment is installed, by adjusting the height of the end of the vent pipe 7, the tilt deviation caused by insufficient equipment accuracy can be eliminated. For example, the liquid collecting tray 2 is tilted, the liquid collecting tray 2 is accumulated by the liquid phase and is low in the middle and high at the outer edge, the liquid inlet 8 on the vent pipe 7 is of different sizes, etc. The height of the vent pipe 7 can be adjusted to achieve a consistent amount of liquid inlet to each vent pipe 7, thereby reducing the difficulty of design and installation.

[0036] The C9 fraction contains components such as CPD, MCPD, DCPD, DMCPD, styrene, etc. that are easy to self-polymerize. Therefore, it is necessary to minimize the residence time of the fraction on the liquid collecting tray 2 as much as possible under the premise of meeting the extraction requirements to avoid self-polymerization. Therefore, a window is set on the tower section 1 of the present invention to observe the stable working conditions in actual production, and then the height of the vent pipe 7 is adjusted when the vehicle is stopped. The best distillation working conditions can be achieved by adjusting the height of the vent pipe 7.

[0037] A vertical first groove 10 is provided on the outer wall of the vent pipe 7, and a limiting ring 11 is provided on the outer sleeve of the vent pipe 7. A protruding tooth extending into the first groove 10 is provided on the inner wall of the limiting ring 11. The limiting ring 11 slides up and down along the first groove 10 outside the vent pipe 7. A first tooth 12 is arrayed on the lower end face of the limiting ring 11, and a second tooth 13 is arrayed on the upper end face of the threaded tube 9. The first tooth 12 and the second tooth 13 are meshed with each other.

[0038] Because the vent pipe 7 of the present invention is threadedly connected to the threaded pipe 9, the packed tower is prone to rotate due to vibration during operation, causing the vent pipe 7 to change in height. Therefore, a limiting ring 11 is provided to limit the vent pipe 7 to prevent the vent pipe 7 from changing in height due to operating vibration.

[0039] The outer contour of the limiting ring 11 is a hexagon, which is used to limit the vent pipe 7 and can also be used as an auxiliary tool for adjusting the vent pipe 7. The vent pipe 7 can be rotated by clamping the limiting ring 11 with a wrench, lifting it up a certain distance and then rotating it, thereby avoiding the influence of oil or impurities generated during the distillation process on the grip of the circular vent pipe 7 and ensuring smooth adjustment.

[0040] The third teeth 14 are provided at the lower end of the ventilation pipe 7; the third teeth 14 at the lower end of the ventilation pipe 7 are used to disperse the liquid film on the inner wall of the ventilation pipe 7 into droplets. After the liquid phase leaves the ventilation pipe 7, it is guided by the third teeth 14 to form a plurality of liquid phase dripping lines dripping downwards, rather than being concentrated into a thicker liquid flow, which 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 teeth 14 are inclined radially outward along the vent pipe 7 , that is, the inner wall of the third teeth 14 gradually increases in diameter from top to bottom, so that the liquid phase has an outward moving component during the process of flowing downward along the inner wall of the vent pipe 7 .

[0042] The outwardly inclined third tooth 14 can not only disperse the liquid film into a liquid phase dripping line, but also guide the droplets so that the droplets have a horizontal component outward away from the ventilation pipe 7 when falling, reducing the probability of being carried by the gas phase that is about to enter the ventilation pipe 7, reducing air flow entrainment, and reducing pressure drop.

[0043] like Figure 4As shown, a second annular groove 15 is provided on the inner wall of the vent pipe 7 below the liquid inlet 8 , and vertical third grooves 16 are evenly distributed on the inner wall of the vent pipe 7 below the second groove 15 . The upper ends of the third grooves 16 are connected to the second grooves 15 .

[0044] The second groove 15 on the inner wall of the vent pipe 7 is used to collect the liquid phase entering from the liquid inlet 8, and evenly distribute the liquid phase in the multiple third grooves 16 to form a liquid film. The vertical third grooves 16 are conducive to guiding the liquid film to prevent the liquid phase from flowing down in strands. It is particularly suitable for enhancing the liquid phase distribution when the side line production volume is large and the amount of liquid phase flowing downward is small. For the specific principle, please refer to "Research on Statistical Characteristics of Liquid Film Flow on Complex Surfaces" - Yuan Meng, master's thesis of East China University of Science and Technology.

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

[0046] The present invention is connected between two adjacent packing sections on the packed tower to replace the liquid redistributor. During the distillation process, when there is liquid reflux on the packing above the liquid collecting plate 2, the liquid collecting plate 2 collects the refluxed liquid and concentrates it on the liquid collecting plate 2. A part of the liquid is discharged downward through the drain hole 5, and the other part of the liquid accumulates in the liquid collecting plate 2, causing the liquid level to rise. When the liquid level rises to the lower end of the liquid inlet 8 of the first vent pipe 7, a part of the liquid begins to enter the vent pipe 7 and flows down along the inner wall of the vent pipe 7. At this time, the flow rate is extremely small, and the liquid level continues to rise to a certain height. After the temperature reaches 300 °C, the liquid level is higher than the lower end of the liquid inlet 8 of all the vent pipes 7, and liquid enters each vent pipe 7. Even at this time, the liquid flow rate in each vent pipe 7 is still not much different. The liquid level continues to rise, and the liquid flow rate in each vent pipe 7 also increases accordingly. At this time, the liquid level exceeds the upper end of the production pipe 3, and liquid can be produced. The produced liquid is temporarily transported to the storage tank 4 for subsequent cooling and transfer. However, it can be ensured that liquid flows out of each vent pipe 7 and disperses downward, and the liquid flow rates flowing through all the vent pipes 7 are not much different.

[0047] When the liquid phase enters the vent pipe 7 through the liquid inlet 8, a liquid film is formed along the inner wall of the vent pipe 7 under the guidance of the twisted state of the side wall of the vent pipe 7 and flows downward, and is dispersed into multiple downward dripping liquid phase dripping lines at the third teeth at the lower end of the vent pipe 7, and continues to fall downward. During this period, the falling liquid phase contacts the gas phase under the liquid collecting tray 2 and the gas phase upward along the vent pipe 7 to carry out heat and mass transfer, and a certain distillation effect can also be guaranteed in the case of side line extraction.

[0048] 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 side line extraction device for a cracking C9 fraction distillation tower, characterized in that: The tower section (1) comprises a liquid collecting tray (2), a vent pipe (7) and a production pipe (3); the tower section (1) is connected with a liquid collecting tray (2), the liquid collecting tray (2) is evenly provided with vent pipes (7) for balancing the liquid level, the vent pipe (7) is provided with a liquid inlet (8) located above the liquid collecting tray (2) on the side wall, and the opening size of the liquid inlet (8) gradually decreases from the upper end to the lower end; The extraction pipe (3) is in communication with the tower section (1); the lower end of the extraction pipe (3) is higher than the liquid collecting tray (2) and the upper end is lower than the lower end of the liquid inlet (8).

2. The cracking C9 fraction distillation tower side line extraction device according to claim 1, characterized in that: There are a plurality of liquid inlets (8), which are distributed in an array along the circumference of the ventilation pipe (7), the side wall of the ventilation pipe (7) between each two adjacent liquid inlets (8) is in a twisted state, and the gap between each two adjacent twisted side walls of the ventilation pipe (7) constitutes an opening size of the liquid inlet (8) that gradually decreases from the upper end to the lower end.

3. The cracking C9 fraction distillation tower side line extraction device according to claim 1, characterized in that: The liquid collecting tray (2) is evenly distributed with a plurality of drainage holes (5) and connection holes (6), the connection holes (6) being used to connect to the ventilation pipe (7), and the ratio of the number of the connection holes (6) to the number of the drainage holes (5) is 4-5:

1.

4. The cracking C9 fraction distillation tower side line extraction device according to claim 3, characterized in that: The connection hole (6) is connected to the vent pipe (7) via a threaded pipe (9). The threaded pipe (9) is fixedly connected in the connection hole (6). An internal thread is provided on the inner wall of the threaded pipe (9). An external thread is provided on the outer wall of the vent pipe (7). The vent pipe (7) is connected in the threaded pipe (9) via the external thread. The vent pipe (7) moves up and down in the threaded pipe (9) by rotation to adjust the height difference between the upper end of the vent pipe (7) and the production pipe (3). A viewing window facing the vent pipe (7) is provided on the tower section (1).

5. The cracking C9 fraction distillation tower side line extraction device according to claim 4, characterized in that: The outer wall of the vent pipe (7) is provided with a vertical first groove (10), the outer sleeve of the vent pipe (7) is provided with a limiting ring (11), the inner wall of the limiting ring (11) is provided with a protruding tooth extending 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 surface of the limiting ring (11) is provided with a first tooth array (12), the upper end surface of the threaded tube (9) is provided with a second tooth array (13), and the first tooth (12) and the second tooth (13) are meshed with each other.

6. The cracking C9 fraction distillation tower side line extraction device according to claim 5, characterized in that: The outer contour of the limiting ring (11) is a hexagon.

7. The cracking C9 fraction distillation tower side line extraction device according to claim 1, characterized in that: The lower end of the ventilation pipe (7) is provided with a third tooth (14).

8. The cracking C9 fraction distillation tower side line extraction device according to claim 7, characterized in that: The third teeth (14) are inclined radially outward along the vent pipe (7).

9. The side line extraction device of the cracking C9 fraction distillation tower according to claim 1, characterized in that: The inner wall of the ventilation pipe (7) is provided with a second annular groove (15) located below the liquid inlet (8); vertical third grooves (16) are evenly distributed on the inner wall of the ventilation pipe (7) below the second groove (15); the upper ends of the third grooves (16) are connected to the second grooves (15).

10. The cracking C9 fraction distillation tower side line extraction device according to claim 1, characterized in that: It also comprises a storage tank (4), the storage tank (4) is connected to a pipeline, and an air return pipeline connected to the tower section is provided at the upper end of the storage tank (4).

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