Feed mixing distributor of ethylbenzene / styrene tower top heat recovery heat exchanger

Abstract

The utility model discloses a feed mixing distributor of an ethylbenzene / styrene tower top heat recovery heat exchanger, which is characterized in that a vertical tube type fixed tube plate heat exchanger is adopted, a shell side medium is an ethylbenzene / styrene separation tower incoming material, a tube pass medium is a water and ethylbenzene mixture, and a lower tube box of the tower top heat recovery heat exchanger is provided with a horizontal feed port and a bottom feed port. Water and ethylbenzene enter the lower tube box from the horizontal feeding port or the bottom feeding port, the horizontal feeding port is connected with a liquid distributor, a secondary mixer is arranged above the liquid distributor and provided with a plurality of hollow tubular parts, the upper end of each tubular part is connected with the heat exchange tube, the lower end of each tubular part is provided with a blocking plate, the blocking plate is provided with a bottom overflowing hole, and the side wall of each tubular part is provided with a side overflowing hole. The total flow passing area of the side flow passing holes is larger than the total flow passing area of the bottom flow passing holes. The device has the beneficial effects that through twice mixing of the calandria liquid distributor and the secondary mixer, the mixing effect of water and ethylbenzene is improved, and azeotrope is easier to form.

Description

Technical Field

[0001] The utility model belongs to the field of heat exchangers and relates to an improvement on the feed structure of an ethylbenzene / styrene tower top heat recovery heat exchanger. Background Art

[0002] Styrene is an important chemical raw material used in resin production, and is also used in the pharmaceutical, dye and other industries. At present, the main styrene synthesis process in the world is the ethylbenzene dehydrogenation method, where ethylene (which can be produced by dehydration of ethanol) reacts with benzene to form ethylbenzene, and ethylbenzene is catalytically dehydrogenated to form a mixture of ethylbenzene and styrene, which needs to be separated by distillation.

[0003] The difference in boiling points between ethylbenzene and styrene is very small, only 9 degrees Celsius under normal pressure. Therefore, in order to separate ethylbenzene / styrene, the separation tower in industry often adopts negative pressure operation, the number of theoretical plates of the separation tower is more than 80, and the reflux ratio is >6.5. Since the ethylbenzene / styrene separation tower operates under negative pressure conditions, the top temperature of the tower is relatively low. Usually, the top operating pressure of the ethylbenzene / styrene separation tower is 6~40 kPa (absolute pressure), and the corresponding operating temperature is 60~103 degrees Celsius. Due to the low top temperature (<100 degrees Celsius), a large amount of low-temperature heat is difficult to recover by conventional methods such as steam generation. Even if the ethylbenzene styrene separation tower adopts high vacuum operation (tower top pressure <10 kPa (absolute pressure)), the operating energy consumption of the ethylbenzene / ethylene separation tower system is still very high, and its low-pressure steam consumption accounts for more than 30% of the entire styrene unit, and the cooling water consumption also accounts for nearly 35% of the entire styrene unit, and the comprehensive energy consumption accounts for 30~40% of the styrene unit.

[0004] In order to fully recover a large amount of low-temperature heat at the top of the ethylbenzene / styrene separation tower, U.S. Patent No. 4,628,136 discloses a method for recovering low-temperature heat at the top of an ethylbenzene / styrene separation tower. The method uses the top steam to evaporate the azeotropic mixture of ethylbenzene and water, and the azeotropic mixture of ethylbenzene and water is sent to the ethylbenzene dehydrogenation reaction system after evaporation. Under normal pressure, 33.3% (mass) water and 66.7% (mass) ethylbenzene can form an azeotrope with a minimum constant boiling point of 91.8°C. The ethylbenzene / water mixture forms an azeotrope and can boil at a temperature lower than the standard boiling point of any component. It is precisely because of its lower boiling point that the mixture can absorb the heat of the material at the top of the tower, thereby saving energy. In actual applications, if the top heat recovery heat exchanger is not well mixed with ethylbenzene and water, the heat exchange effect will not be ideal, and the purpose of fully recovering a large amount of low-temperature heat at the top of the tower cannot be achieved, and even the normal operation of the device is affected. The key to solving this problem is to ensure the rapid and full mixing of ethylbenzene and water. In the prior art, liquid distributors have tubular and disc structures to improve the mixing efficiency of liquids. They can generally fully mix liquids with good solubility, but are not enough for organic and inorganic mixing. Stirring, ultrasound and other methods are not applicable on separation towers. Utility Model Content

[0005] The utility model aims to provide a feed mixing distributor for an ethylbenzene / styrene tower top heat recovery heat exchanger to improve the mixing rate of ethylbenzene and water.

[0006] The technical solution of the utility model is as follows: a feed mixing distributor for an ethylbenzene / styrene tower top heat recovery heat exchanger, the structure of the tower top heat recovery heat exchanger is a vertical tube-in-tube fixed tube sheet heat exchanger, the shell side medium is the incoming material of the ethylbenzene / styrene separation tower, the tube side medium is a mixture of water and ethylbenzene, the lower tube box of the tower top heat recovery heat exchanger is provided with a horizontal feed port and a bottom feed port, water and ethylbenzene enter the lower tube box from the horizontal feed port or the bottom feed port respectively, and the utility model is characterized in that the horizontal feed port is connected to a liquid distributor, a secondary mixer is provided above the liquid distributor, the secondary mixer contains a plurality of hollow tubular members, each tubular member has an upper end connected to a heat exchange tube and a blocking plate provided at the lower end, the blocking plate is provided with a bottom flow hole, the side wall of the tubular member is provided with a side flow hole, and the total flow area of ​​the side flow holes is greater than the total flow area of ​​the bottom flow holes.

[0007] Preferably, there is one bottom flow hole and more than two side flow holes, which are arranged up and down in the same vertical area of ​​the wall of the tubular member. By adjusting the aperture diameter of the bottom flow hole and the aperture diameter and number of the side flow holes, an area difference between the total flow areas of the two is achieved.

[0008] Furthermore, the side flow holes are oriented toward the center of the tube sheet.

[0009] Preferably, the tubular member is a round tube, the connection between the tubular member and the heat exchange tube is plug-in, the outer diameter of the tubular member is 0-2 mm larger than the inner diameter of the heat exchange tube, a step is machined on the upper part of the tubular member, an inclined cone is machined at the end of the step, and the circumferential wall between the step and the inclined cone is interference-fitted with the heat exchange tube. The step is further welded to the contact seam of the heat exchange tube.

[0010] Preferably, the connection between the tubular member and the heat exchange tube is welding, the tubular member and the heat exchange tube are of the same size, the outer edge of the tube mouth is chamfered, and the tubes are aligned and welded.

[0011] The liquid distributor is of pipe arrangement type, comprising a main distribution pipe and a liquid distribution pipe. The main distribution pipe is horizontally placed in the middle of the lower pipe box, one end of which is connected to the pipe opening extending into the lower pipe box from the horizontal feed port, and the other end is fixed to the bracket on the inner wall of the pipe box. The liquid distribution pipes are distributed on both sides of the main distribution pipe. The length of the liquid distribution pipe is adapted according to the distance between the inner wall of the lower pipe box and the liquid distribution pipe. The diameter of the liquid distribution pipe is smaller than that of the main distribution pipe. A certain number and diameter of liquid distribution holes are provided on the liquid distribution pipe and the main distribution pipe.

[0012] The longer liquid distribution pipe is placed on the cross bar, both ends of the cross bar are fixed to the brackets on the inner wall of the pipe box, and the liquid distribution pipe and the cross bar are fastened by U-bolts.

[0013] The beneficial effects of the utility model are as follows: 1. Through the double mixing of the tube-type liquid distributor and the secondary mixer, the mixing effect of water and ethylbenzene is improved, and the safe and stable operation of the equipment is guaranteed. 2. The mixing effect of water and ethylbenzene is good, and it is easier to form an azeotrope, which can make the azeotrope composition in the heat exchange tube uniform, reduce the average boiling point of the medium, improve the efficiency of the heat exchanger, and improve the energy recovery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is an overall schematic diagram of a shell-and-tube fixed tube sheet heat exchanger;

[0015] Figure 2 It is a cross-sectional view of the interior of the downtube box;

[0016] Figure 3 is a schematic diagram of the shape of the tubular member of the secondary mixer;

[0017] Figure 4 It is a schematic diagram of the relationship between the side flow holes and the center position of the tube sheet;

[0018] Figure 5 It is a cross-sectional schematic diagram of the connection between the tubular member and the heat exchange tube;

[0019] Figure 6 It is a cross-sectional schematic diagram of the connection between the tubular part and the heat exchange tube by welding;

[0020] Figure 7 is a top view schematic diagram of a tube-type liquid distributor;

[0021] Reference numerals in the figure: 1-lower tube box, 2-horizontal feed inlet, 3-bottom feed inlet, 4-liquid distributor, 5-secondary mixer, 6-heat exchange tube, 7-heat exchanger tube sheet, 8-blocking plate, 9-bottom flow hole, 10-side flow hole, 11-step, 12-inclined cone, 13-center of tube sheet, 14-main distribution pipe, 15-liquid distribution pipe, 16-liquid distribution hole, 17-bracket, 18-cross bar, 19-U-bolt. DETAILED DESCRIPTION

[0022] like Figure 1 , 2 A feed mixing distributor for an ethylbenzene / styrene tower top heat recovery heat exchanger. The structure of the tower top heat recovery heat exchanger is a vertical tube-in-tube fixed tube sheet heat exchanger. The shell side medium is the feed from the ethylbenzene / styrene separation tower. The tube side medium is a mixture of water and ethylbenzene. The lower tube box 1 of the tower top heat recovery heat exchanger is provided with a horizontal feed port 2 and a bottom feed port 3. Water and ethylbenzene enter the lower tube box 1 from the horizontal feed port 2 or the bottom feed port 3 respectively (water and ethylbenzene enter from one of the horizontal feed port 2 or the bottom feed port 3, and can enter separately), and exit from the upper tube box.

[0023] The horizontal feed port 2 is connected to the liquid distributor 4. A secondary mixer 5 is arranged above the liquid distributor 4. The secondary mixer 5 contains a plurality of hollow tubular members. The upper end of each tubular member is connected to the heat exchange tube 6, and the lower end is provided with a plugging plate 8. The plugging plate 8 is provided with a bottom flow hole 9. The side wall of the tubular member is provided with a side flow hole 10. The total flow area of ​​the side flow holes 10 is greater than the total flow area of ​​the bottom flow holes 9. Water or ethylbenzene first flows through the liquid distributor 4 to preliminarily distribute the medium to the entire lower tube box 1. The mixed medium enters the heat exchange tube group from bottom to top under the action of the pressure in the tube box. Before entering each heat exchange tube 6, it is mixed again by the secondary mixer 5 arranged at the inlet end of each heat exchange tube to form a water / ethylbenzene azeotrope, which enters the heat exchange tube and evaporates under heat.

[0024] There is one bottom flow hole 9 and at least two side flow holes 10, which are arranged in an upper and lower manner in the same vertical area of ​​the tubular wall. By adjusting the aperture diameter of the bottom flow hole 9 and the aperture diameter and number of the side flow holes 10, a difference in the total flow area of ​​the two is achieved.

[0025] The principle of the secondary mixer to improve the mixing effect: the flow area of ​​the bottom flow hole 9 and the side flow hole 10 is much smaller than the inner area of ​​the heat exchange tube. The bottom flow hole 9 is arranged along the axial direction of the heat exchange tube, and the side flow hole 10 is arranged along the radial direction of the heat exchange tube, so that the mixed fluid enters the heat exchange tube along the axial and radial directions of the heat exchange tube. The axial fluid and the radial fluid impact each other in the heat exchange tube, disrupting the original mixed components of the mixture, forming secondary mixing, and achieving the purpose of uniform distribution. A small flow area is conducive to increasing the axial and radial flow velocity of the mixed fluid entering the heat exchange tube, wherein the axial flow area is smaller than the radial flow area, so that the local axial flow velocity is greater than the radial flow velocity, and multiple mixing is formed at the inlet of the heat exchange tube, which is conducive to the uniform mixing of the fluid in the heat exchange tube. Too small a flow area will seriously increase the fluid resistance of the tube. Therefore, when actually processing and manufacturing a specific heat exchanger, it is necessary to first perform fluid simulation, experimental verification and detailed calculation to select the appropriate data size to achieve a relative balance between fluid resistance and mixing degree.

[0026] When installing the secondary mixer, the side flow holes 10 are arranged radially toward the center 13 of the tube sheet, such as Figure 4 As shown. Due to the limitation of the tube box cylinder, the fluid that enters the tube box for the first time will form a centripetal force, causing the first mixed fluid to form annular flow and radial flow toward the center of the tube sheet. The radial flow holes of this patent are arranged toward the center of the tube sheet, which can avoid the influence of the annular flow and radial flow in the tube box on the flow rate of the fluid entering the heat exchange tube, making the flow rate and flow rate of the fluid entering each heat exchange tube more uniform, which is more conducive to the secondary uniform mixing of the first mixed fluid.

[0027] The preferred embodiment is that the tubular member is a round tube, and the connection between the tubular member and the heat exchange tube 6 is plug-in. The outer diameter of the tubular member is 0-2 mm larger than the inner diameter of the heat exchange tube 6. The upper part of the tubular member is cut and the diameter is reduced to form a step 11. An inclined cone 12 is processed at the end of the step 11 so that the tubular member can be inserted into the heat exchange tube 6. Since the end diameter of the inclined cone is larger than the outer diameter of the heat exchange tube, the circumferential wall between the step 11 and the inclined cone 12 forms an interference fit with the heat exchange tube 6. Figure 3 , 5 The step 11 can be further welded to the contact seam of the heat exchange tube 6, as shown in FIG. Figure 5 shown.

[0028] Another more simplified connection method is to connect the tubular member and the heat exchange tube 6 by welding. The tubular member and the heat exchange tube 6 are of the same size, the outer edge of the tube mouth is chamfered, and the alignment is welded, such as Figure 6 shown.

[0029] like Figure 7 As shown, the liquid distributor 4 is a pipe arrangement type, comprising a main distribution pipe 14 and a liquid distribution pipe 15. The main distribution pipe 14 is horizontally placed in the middle of the lower pipe box 1, one end of which is connected to the pipe opening of the horizontal feed port 2 extending into the lower pipe box 1, and the other end is fixed to the bracket 17 on the inner wall of the pipe box. The liquid distribution pipes 15 are distributed on both sides of the main distribution pipe 14. The length of the liquid distribution pipes 15 is adapted according to the distance between the inner wall of the lower pipe box 1 and the liquid distribution pipes 15 (when the inner wall is circular, it presents a pattern of the longest in the middle and the length decreasing toward both sides). The diameter of the liquid distribution pipe 15 is smaller than that of the main distribution pipe 14. The liquid distribution pipes 15 and the main distribution pipe 14 are provided with a certain number and diameter of liquid distribution holes 16. The number and diameter of the liquid distribution pipes 15 are determined according to the flow rate of the inlet medium. The liquid from the horizontal feed port 2 enters the main distribution pipe 14, which distributes the liquid to each liquid distribution pipe 15. The liquid distribution holes 16 on the liquid distribution pipe 15 distribute the liquid into the lower pipe box 1, so that the medium is preliminarily mixed with another group of media that have entered the lower pipe box 1.

[0030] The liquid distribution pipe 15 and the main distribution pipe 14 can be connected by welding or by a detachable connection, such as a flange plus bolt connection.

[0031] The liquid distribution pipe 15 with a long length can be placed on the cross bar 18 in order to have a fulcrum for support. The two ends of the cross bar 18 are fixed to the brackets 17 on the inner wall of the pipe box, and the liquid distribution pipe 15 and the cross bar 18 are connected and fastened by U-bolts 19. With the cross bar 18, the liquid distribution pipe 15 can be supported at two places, the flange end and the cross bar contact point, avoiding the problem of excessive force on the flange connection caused by only the flange end being connected.

Claims

1. A feed mixing distributor for an ethylbenzene / styrene tower top heat recovery heat exchanger, the structure of the tower top heat recovery heat exchanger is a vertical tube-in-tube fixed tube sheet heat exchanger, the shell side medium is the feed from the ethylbenzene / styrene separation tower, the tube side medium is a mixture of water and ethylbenzene, the lower tube box (1) of the tower top heat recovery heat exchanger is provided with a horizontal feed inlet (2) and a bottom feed inlet (3), water and ethylbenzene enter the lower tube box (1) from the horizontal feed inlet (2) or the bottom feed inlet (3), respectively, and the characteristics are as follows: The horizontal feed port (2) is connected to a liquid distributor (4), and a secondary mixer (5) is provided above the liquid distributor (4). The secondary mixer (5) comprises a plurality of hollow tubular members, each of which is connected to a heat exchange tube (6) at its upper end and provided with a plugging plate (8) at its lower end, the plugging plate (8) being provided with a bottom flow hole (9), and a side flow hole (10) being provided on a side wall of the tubular member, wherein the total flow area of ​​the side flow holes (10) is greater than the total flow area of ​​the bottom flow holes (9).

2. The ethylbenzene / styrene tower top heat recovery heat exchanger feed mixing distributor according to claim 1, characterized in that the bottom There is one flow hole (9), and there are more than two side flow holes (10), which are arranged in an upper and lower arrangement in the same vertical area of ​​the wall of the tubular member. By adjusting the diameter of the bottom flow hole (9) and the diameter and number of the side flow holes (10), a difference in the total flow area of ​​the two is achieved.

3. The feed mixing distributor for the ethylbenzene / styrene tower top heat recovery heat exchanger according to claim 1, characterized in that The side flow holes (10) face the center of the tube sheet (13).

4. The feed mixing distributor for the ethylbenzene / styrene tower top heat recovery heat exchanger according to claim 1, characterized in that The tubular member is a round tube. The connection between the tubular member and the heat exchange tube (6) is plug-in. The outer diameter of the tubular member is 0-2 mm larger than the inner diameter of the heat exchange tube (6). A step (11) is machined on the upper part of the tubular member. An inclined cone (12) is machined at the end of the step (11). The circumferential wall between the step (11) and the inclined cone (12) is interference-fitted with the heat exchange tube (6).

5. The feed mixing distributor for the ethylbenzene / styrene tower top heat recovery heat exchanger according to claim 4, characterized in that The step (11) is further welded to the contact seam of the heat exchange tube (6).

6. The feed mixing distributor for the ethylbenzene / styrene tower top heat recovery heat exchanger according to claim 1, characterized in that The connection between the tubular member and the heat exchange tube (6) is welding; the tubular member and the heat exchange tube (6) are tubes of the same size, the outer edges of the tube openings are chamfered, and the tubes are aligned and welded.

7. The feed mixing distributor for the ethylbenzene / styrene tower top heat recovery heat exchanger according to claim 1, characterized in that The liquid distributor (4) is of a pipe arrangement type, comprising a main distribution pipe (14) and a liquid distribution pipe (15). The main distribution pipe (14) is horizontally placed in the middle of the lower pipe box (1), one end of which is connected to a pipe opening of a horizontal feed port (2) extending into the lower pipe box (1), and the other end is fixed to a bracket (17) on the inner wall of the pipe box. The liquid distribution pipes (15) are distributed on both sides of the main distribution pipe (14). The length of the liquid distribution pipes (15) is adapted to be set according to the distance between the inner wall of the lower pipe box (1) and the liquid distribution pipes (15). The diameter of the liquid distribution pipes (15) is smaller than that of the main distribution pipes (14). Liquid distribution holes (16) of a certain number and diameter are provided on the liquid distribution pipes (15) and the main distribution pipes (14).

8. The feed mixing distributor for the ethylbenzene / styrene tower top heat recovery heat exchanger according to claim 1, characterized in that The liquid distribution pipe (15) and the main distribution pipe (14) are connected by welding or in a detachable manner.

9. The feed mixing distributor for the ethylbenzene / styrene tower top heat recovery heat exchanger according to claim 1, characterized in that The liquid distribution pipe (15) with a longer length is placed on the cross bar (18), and both ends of the cross bar (18) are fixed to the brackets (17) on the inner wall of the pipe box. The liquid distribution pipe (15) and the cross bar (18) are connected and fastened by U-bolts (19).

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