Shell-and-tube coal tar cooler based on falling film theory

Abstract

This invention discloses a shell-and-tube coal tar pitch cooler based on falling film theory, comprising a cylinder with a first container flange and a second container flange at its upper and lower ends. The first container flange connects to an upper tube box, which is welded with a first end cap and a coal tar pitch inlet. The second container flange connects to a lower tube box, which is welded with a second end cap and has inner tube cooling medium inlets welded to both sides. The second end cap has a coal tar pitch outlet. The outer wall of the cylinder has a shell-side cooling medium outlet and a shell-side cooling medium inlet. Tube sheets a and b are fixed to the inner wall of the cylinder, with multiple heat exchange tubes arranged between them. A distributor is located inside the first end cap and connected to the heat exchange tubes. In this cooler, the coal tar pitch flows through the annular gap between the outer and inner heat exchange tubes in a liquid film form from top to bottom, simultaneously cooling the coal tar pitch on both sides. Compared to existing coolers, this results in higher heat transfer efficiency, more uniform coal tar pitch temperature, lower pressure drop, and less clogging.

Description

Technical Field

[0001] This invention belongs to the technical field of heat exchange equipment, specifically relating to a shell-and-tube coal tar cooler based on falling film theory. Background Technology

[0002] With the depletion of petroleum resources, coal tar hydrogenation technology is increasingly demonstrating its importance in the production of automotive fuel oil. There are three main types of coal tar hydrogenation technology: fixed-bed hydrogenation, suspended-bed hydrogenation, and fluidized-bed hydrogenation. Suspended-bed hydrogenation technology involves passing a highly dispersed fine-particle catalyst along with coal tar and hydrogen through a reactor. The catalyst is suspended in the coal tar, forming a three-phase bed of gas, liquid, and solid. The contact between hydrogen, coal tar, and catalyst is relatively sufficient, resulting in a process that is simple, with high conversion and demetallization rates, and high light oil yield. It also exhibits good adaptability to coal tar feedstocks with high sulfur content, high viscosity, and high residual carbon. Furthermore, the coal tar suspended-bed hydrogenation reactor has a low pressure drop, high operational flexibility, long operating cycle, and lower investment and operating costs. Therefore, coal tar suspended-bed hydrogenation technology has a promising future in coal tar hydrogenation treatment.

[0003] In the coal tar suspension bed hydrogenation technology, the residual coal tar pitch (300℃) after the hydrogenation reaction needs to be cooled to 150-200℃ through a heat exchanger, then extruded into a pitch molding machine to form columnar pitch, and then transported into a water tank to exchange heat with cooling water to further cool to below 60℃, before being loaded and transported or participating in other reactions.

[0004] In the industrial sector, coal tar coolers mainly include spiral plate heat exchangers and shell-and-tube heat exchangers. Spiral plate heat exchangers generally exchange heat between coal tar and tar, offering advantages such as high heat transfer efficiency, effective recovery of low-temperature heat energy, low metal consumption, and the ability to flexibly combine multiple units. However, they have poor pressure resistance, are difficult to maintain, and are prone to clogging due to the rapid solidification of coal tar at the inlet. Currently, the shell-and-tube heat exchangers used for coal tar cooling are mainly U-tube heat exchangers, with coal tar flowing through the shell side and the cooling medium flowing through the tube side. They offer advantages such as good thermal compensation performance and strong pressure resistance. However, when coal tar flows in the shell side, its high viscosity, poor fluidity, and poor thermal conductivity not only lead to low heat transfer efficiency but also cause uneven coal tar temperature, affecting heat transfer. Furthermore, the flow of coal tar around the baffles in the shell side creates large dead zones and back-mixing, resulting in large pressure drops and easy accumulation of coal tar, clogging the heat exchanger. Therefore, the development and practical application of suspended bed hydrogenation technology urgently require the research and development of a new type of shell-and-tube heat exchanger with high heat transfer efficiency, uniform coal tar temperature, low pressure drop, and low clogging resistance for cooling coal tar. Summary of the Invention

[0005] The purpose of this invention is to provide a shell-and-tube coal tar cooler based on falling film theory, which solves the problems of low heat transfer efficiency, uneven coal tar temperature, large pressure drop and easy clogging in existing shell-and-tube heat exchangers for coal tar cooling.

[0006] The technical solution adopted in this invention is a shell-and-tube coal tar pitch cooler based on falling film theory, comprising a cylinder, with a first container flange and a second container flange respectively provided at the upper and lower ends of the cylinder. The first container flange is connected to an upper tube box, and a first end cap is welded to the upper end of the upper tube box, with a coal tar pitch inlet welded to the upper end of the first end cap. The second container flange is connected to a lower tube box, and a second end cap is welded to the lower end of the lower tube box, with inner tube cooling medium inlets welded to both sides of the lower tube box. Tube sheets c are also provided inside the two inner tube cooling medium inlets. A coal tar pitch outlet is welded to the lower end of the second end cap. Shell-side cooling medium outlet and shell-side cooling medium inlet are respectively provided on the upper and lower sides of the outer wall of the cylinder. Tube sheets a and b are fixed at the top and bottom of the inner wall of the cylinder, respectively. Multiple heat exchange tubes are arranged between tube sheets a and b. A distributor is provided inside the first end cap, and the distributor is connected to the heat exchange tubes.

[0007] The invention is further characterized in that,

[0008] The distributor includes a main pipe, multiple branch pipes, and a cap a; the upper end of the main pipe is fixedly connected to the coal tar pitch inlet, and the lower end is fixedly connected to the cap a; the multiple branch pipes are fixedly connected to the main pipe in a circumferential array layer by layer; the outermost branch pipe is located at the top of the main pipe, and the innermost branch pipe is located at the bottom of the main pipe.

[0009] The heat exchange tube includes an outer heat exchange tube, which is a spiral grooved tube. An inner heat exchange tube is installed inside the outer heat exchange tube. The upper and lower ends of the outer heat exchange tube pass through the tube sheet holes on tube sheet a and tube sheet b, respectively, and are fixedly connected to tube sheet a and tube sheet b by welding. The outlets of the branch pipes on the distributor correspond one-to-one with the tube sheet holes on tube sheet a and tube sheet b, and the ends of the branch pipes are connected to the upper ends of the outer heat exchange tubes.

[0010] Multiple support rods are arranged vertically between the heat exchange outer tube and the heat exchange inner tube. One end of the support rod is fixedly connected to the outer wall of the heat exchange inner tube, and the other end is fixedly connected to the inner wall of the heat exchange outer tube. A cover b is provided at the upper end of the heat exchange inner tube. The lower end of the heat exchange inner tube passes through the tube sheet b and extends into the lower tube box. The ends of the heat exchange inner tube extend into the inner tube cooling medium inlet and pass through the round hole on the tube sheet c.

[0011] An exhaust pipe is connected to the upper end of the inner heat exchange tube along the outer wall, and the exhaust pipe extends out of the outer heat exchange tube.

[0012] The cylinder is also equipped with a set of spiral baffles, and the heat exchange tubes all pass through the round holes on the spiral baffles.

[0013] Both tube sheet a and tube sheet b have multiple tube sheet holes arranged in a concentric circle pattern.

[0014] The beneficial effects of this invention are:

[0015] (1) The cooler of the present invention is developed based on the falling film theory. The coal tar pitch flows through the tube side and the cooling medium flows through the shell side. The coal tar pitch flows from top to bottom in the annular gap between the inner and outer tubes of the heat exchanger in the form of a liquid film, which effectively solves the problem of low heat transfer efficiency of the heat exchanger caused by the high viscosity, poor fluidity and poor thermal conductivity of the coal tar pitch itself.

[0016] (2) The cooler of the present invention has a heat exchange tube with a shell-and-tube structure. The inner tube carries the cooling medium, and the annular gap between the outer tube and the inner tube carries coal tar pitch. The coal tar pitch can be cooled by the cooling medium in the inner tube and by the cooling medium in the shell side. Compared with single-sided cooling, double-sided cooling can further improve the heat transfer efficiency of the cooler and effectively solve the problem of uneven temperature during the cooling process of coal tar pitch.

[0017] (3) In the cooler of the present invention, the coal tar pitch flows through the annular gap between the heat exchange outer tube and the inner tube, and flows from top to bottom in the form of a liquid film. Compared with the traditional shell-and-tube heat exchanger, the coal tar pitch flows through the shell side, there is no dead zone, no back mixing, small pressure drop, and it is not easy to be blocked.

[0018] (4) The cooler of the present invention uses spiral groove tubes for heat exchange outer tubes and spiral baffles for shell side, which can further enhance heat transfer and improve heat transfer efficiency.

[0019] (5) The cooler of the present invention includes a coal tar pitch distributor. The present invention changes the “hole” on the traditional shower head type distributor to a “branch pipe”, which overcomes the defect of easy clogging. At the same time, the “branch pipes” on the distributor are connected to the main pipe in a circumferential array layer by layer. The outermost branch pipe is located at the upper part of the main pipe and the innermost branch pipe is located at the lower part of the main pipe, which ensures that the coal tar pitch can enter the annular gap between the heat exchange outer tube and the inner tube at the same time quickly and accurately to form a continuous liquid film, thus solving the problem of uniform distribution of coal tar pitch in the application of falling film theory.

[0020] (6) This invention applies the falling film theory to coal tar cooling equipment and adopts double-sided cooling, which is not only of great significance for promoting the practical application of coal tar suspension bed hydrogenation technology, but also provides ideas, references and guidance for the research and development of high viscosity fluid cooling equipment. Attached Figure Description

[0021] Figure 1 This is a schematic diagram (I) of the shell-and-tube coal tar cooler based on the falling film theory of the present invention;

[0022] Figure 2 This is a schematic diagram (II) of the shell-and-tube coal tar cooler based on the falling film theory of the present invention;

[0023] Figure 3This is a schematic diagram of the internal structure of the shell-and-tube coal tar cooler based on the falling film theory of this invention.

[0024] Figure 4 This is a structural diagram of tube sheet a and tube sheet b in the shell-and-tube coal tar pitch cooler based on falling film theory of the present invention;

[0025] Figure 5 This is a connection diagram of the heat exchange outer tube and tube sheet a in the shell-and-tube coal tar pitch cooler based on the falling film theory of this invention;

[0026] Figure 6 This is a connection diagram of the inner and outer heat exchange tubes in the shell-and-tube coal tar pitch cooler based on the falling film theory of this invention.

[0027] Figure 7 This is a connection diagram of the heat exchange inner tube and the exhaust pipe in the shell-and-tube coal tar pitch cooler based on the falling film theory of this invention.

[0028] Figure 8 This is a structural diagram of the coal tar distributor in the shell-and-tube coal tar cooler based on the falling film theory of this invention.

[0029] In the diagram, 1. Shell, 2. First container flange, 3. Second container flange, 4. First bolt, 5. First nut, 6. Upper tube box, 7. First end cap, 8. Second bolt, 9. Second nut, 10. Lower tube box, 11. Second end cap, 12. Coal tar pitch inlet, 13. Coal tar pitch outlet, 14. Shell-side cooling medium inlet, 15. Shell-side cooling medium outlet, 16. Inner tube cooling medium inlet, 17. Main pipe, 18. Branch pipe, 19. Cover a, 20. Distributor, 21. Tube sheet a, 22. Spiral baffle plate, 23. Heat exchanger outer tube, 24. Heat exchanger inner tube, 25. Cover b, 26. Tube sheet b, 27. Tube sheet c, 28. Tube sheet orifice, 29. Exhaust pipe, 30. Support rod. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0031] This invention relates to a shell-and-tube coal tar cooler based on falling film theory, such as... Figure 1 As shown, the device includes a cylindrical body 1, with a first container flange 2 and a second container flange 3 respectively installed at the upper and lower ends of the cylindrical body 1. The first container flange 2 is connected to an upper pipe box 6 by several first bolts 4 and first nuts 5. A first end cap 7 is welded to the upper end of the upper pipe box 6, and a coal tar pitch inlet 12 is welded to the upper end of the first end cap 7. The second container flange 3 is connected to a lower pipe box 10 by several second bolts 8 and second nuts 9. A second end cap 11 is welded to the lower end of the lower pipe box 10, and a coal tar pitch outlet 13 is welded to the lower end of the second end cap 11.

[0032] like Figure 2As shown, shell-side cooling medium outlet 15 and shell-side cooling medium inlet 14 are respectively provided on the upper and lower sides of the outer wall of the cylinder 1; the shell-side cooling medium outlet 15 and shell-side cooling medium inlet 14 are located on both sides of the cylinder 1; inner tube cooling medium inlet 16 is welded on both sides of the lower tube box 10; tube sheet c27 is also provided inside the two inner tube cooling medium inlets 16.

[0033] like Figure 3 and Figure 8 As shown, a distributor 20 is provided inside the first end cap 7. The distributor 20 includes a main pipe 17, multiple branch pipes 18, and a cover a19. The upper end of the main pipe 17 is fixedly connected to the coal tar pitch inlet 12, and the lower end is fixedly connected to the cover a19. The multiple branch pipes 18 are fixedly connected to the main pipe 17 in a circumferential array, with the outermost branch pipe 18 located above the main pipe 17 and the innermost branch pipe 18 located below the main pipe 17.

[0034] like Figure 3 and Figure 4 As shown, tube sheet a 21 and tube sheet b 26 are fixed at the top and bottom of the inner wall of the cylinder 1, respectively. Multiple tube sheet holes 28 are arranged in concentric circles on both tube sheet a 21 and tube sheet b 26; the pipe openings of the branch pipe 18 correspond one-to-one with the tube sheet holes 28 on tube sheet a 21 and tube sheet b 26.

[0035] Multiple heat exchange tubes are arranged between tube sheet a 21 and tube sheet b 26, such as Figure 5 , Figure 6 and Figure 7 As shown, the heat exchange tube includes an outer heat exchange tube 23, which is a spiral groove tube. An inner heat exchange tube 24 is installed inside the outer heat exchange tube 23. The upper and lower ends of the outer heat exchange tube 23 are welded to tube sheet a 21 and tube sheet b 26, respectively, and the outer heat exchange tube 23 passes through the tube sheet hole 28. The end of the branch pipe 18 is connected to the upper end of the outer heat exchange tube 23.

[0036] Multiple support rods 30 are arranged vertically between the heat exchange outer tube 23 and the heat exchange inner tube 24. One end of the support rod 30 is fixedly connected to the outer wall of the heat exchange inner tube 24, and the other end is fixedly connected to the inner wall of the heat exchange outer tube 23, which serves to fix the heat exchange inner tube 24. A cover b25 is provided at the upper end of the heat exchange inner tube 24. An exhaust pipe 29 is connected to the upper end of the heat exchange inner tube 24 along the outer wall. The exhaust pipe 29 extends out of the heat exchange outer tube 23. The lower end of the heat exchange inner tube 24 passes through the tube sheet b26 and extends into the lower tube box 10. The ends of the heat exchange inner tube 24 extend into the inner tube cooling medium inlet 16 and pass through the round hole on the tube sheet c27.

[0037] Inside the cylinder 1, there is also a set of spiral baffles 22 with circular holes. The heat exchange tubes 23 inside the cylinder 1 all pass through the circular holes on the spiral baffles 22.

[0038] The spiral baffle 22 adopts the spiral baffle published in the Journal of Chemical Engineering of Chinese Universities in August 2015 by Wen Jian of Xi'an Jiaotong University.

[0039] The present invention relates to a shell-and-tube coal tar pitch cooler based on falling film theory, the specific working principle of which is as follows:

[0040] It has three fluid flow paths: one hot fluid flow path and two cold fluid flow paths, which cool the coal tar pitch through two-way convective heat transfer.

[0041] The first flow path of the hot fluid, namely coal tar pitch, is as follows: the coal tar pitch enters the distributor 20 through the coal tar pitch inlet 12, flows evenly into the heat exchange outer tube 23 through the branch pipe 18, and then flows downward in the form of a liquid film along the annular gap between the heat exchange outer tube 23 and the heat exchange inner tube 24 under the action of gravity and pressure; during the downward flow of the coal tar pitch, heat exchange occurs on one side through the tube wall of the heat exchange outer tube 23 with the shell-side cooling medium, and on the other side through the tube wall of the heat exchange inner tube 24 with the inner tube cooling medium, i.e., double-sided cooling is performed; after the heat exchange is completed, it flows into the lower tube box 10 through the tube sheet b26, and after collecting in the lower tube box 10, it flows out through the coal tar pitch outlet 13;

[0042] The first cold fluid flow path, namely the shell-side cooling medium flow path, is as follows: the cooling medium in the shell side enters the interior of the shell body 1 through the shell-side cooling medium inlet 14 and flows spirally from bottom to top along the spiral baffle 22. During the flow process, the shell-side cooling medium absorbs the heat from the coal tar pitch transferred from the tube wall of the heat exchange outer tube 23, undergoes a phase change, changes from liquid to gas, and finally flows out through the shell-side cooling medium outlet 15.

[0043] The second cold fluid flow path, namely the heat exchange inner tube cooling medium flow path, is as follows: the inner tube cooling medium enters the heat exchange inner tube 24 through the inner tube cooling medium inlet 16 on both sides of the lower tube box 10, and flows from bottom to top inside the heat exchange inner tube 24; during the flow process, the inner tube cooling medium absorbs the heat of coal tar pitch transferred from the tube wall of the heat exchange inner tube 24, and undergoes a phase change, changing from liquid to gas, and is discharged into the shell side from the exhaust pipe 29 at the upper end of the heat exchange inner tube 24, and flows out through the shell side cooling medium outlet 15 with the shell side fluid.

Claims

1. A shell-and-tube coal-tar cooler based on the falling-film theory, characterized in that, The application relates to a coal-tar pitch heat exchanger, which comprises a cylinder (1), a first container flange (2) and a second container flange (3) arranged at the upper and lower ends of the cylinder (1) respectively, an upper pipe box (6) connected to the first container flange (2), a first head (7) welded to the upper end of the upper pipe box (6), a coal-tar pitch inlet (12) welded to the upper end of the first head (7), a lower pipe box (10) connected to the second container flange (3), a second head (11) welded to the lower end of the lower pipe box (10), inner pipe cooling medium inlets (16) welded to the two sides of the lower pipe box (10), pipe plate c (27) arranged in the inner pipe cooling medium inlets (16), a coal-tar pitch outlet (13) welded to the lower end of the second head (11), a shell-side cooling medium outlet (15) and a shell-side cooling medium inlet (14) arranged on the outer wall of the cylinder (1) respectively, pipe plate a (21) and pipe plate b (26) fixed to the top and bottom of the inner wall of the cylinder (1) respectively, a plurality of heat exchange pipes arranged between the pipe plate a (21) and the pipe plate b (26), and a distributor (20) arranged in the first head (7) and connected with the heat exchange pipes.

2. The shell-and-tube coal-tar pitch cooler based on the falling-film theory according to claim 1, characterized in that The distributor (20) comprises a main pipe (17), a plurality of branch pipes (18) and a cover a (19), the upper end of the main pipe (17) is fixedly connected with the coal-tar pitch inlet (12), the lower end of the main pipe (17) is fixedly connected with the cover a (19), the plurality of branch pipes (18) are arranged and fixedly connected on the main pipe (17) in a circular array form layer by layer from top to bottom, the outermost branch pipes (18) are located on the upper part of the main pipe (17), and the innermost branch pipes (18) are located on the lower part of the main pipe (17).

3. The shell-and-tube coal-tar pitch cooler based on the falling-film theory according to claim 2, characterized in that The heat exchange pipe comprises a heat exchange outer pipe (23), the heat exchange outer pipe (23) is a spiral groove pipe, a heat exchange inner pipe (24) is arranged in the heat exchange outer pipe (23), the upper and lower ends of the heat exchange outer pipe (23) are welded to the pipe plate a (21) and the pipe plate b (26) respectively, and the heat exchange outer pipe (23) penetrates through the pipe plate holes (28); the end of the branch pipe (18) is connected with the upper end of the heat exchange outer pipe (23), and the pipe opening of the branch pipe (18) corresponds to the pipe plate holes (28) on the pipe plate a (21) and the pipe plate b (26) one by one.

4. The shell-and-tube coal-tar pitch cooler based on the falling-film theory according to claim 3, characterized in that A plurality of support rods (30) are arranged between the heat exchange outer pipe (23) and the heat exchange inner pipe (24) in a top-down mode, one end of the support rod (30) is fixedly connected with the outer side wall of the heat exchange inner pipe (24), the other end of the support rod (30) is fixedly connected with the inner wall of the heat exchange outer pipe (23), the upper end of the heat exchange inner pipe (24) is provided with the cover b (25), the lower end of the heat exchange inner pipe (24) penetrates through the pipe plate b (26) and extends into the lower pipe box (10), and the end of the heat exchange inner pipe (24) extends into the inner pipe cooling medium inlet (16) respectively and penetrates through the round holes on the pipe plate c (27).

5. The shell-and-tube coal-tar pitch cooler based on the falling-film theory according to claim 3, characterized in that, The upper end of the heat exchange inner pipe (24) is connected with an exhaust pipe (29) along the outer side wall, and the exhaust pipe (29) extends out of the heat exchange outer pipe (23).

6. The shell-and-tube coal-tar pitch cooler based on the falling-film theory according to claim 3, characterized in that A group of spiral ladder type helical baffles (22) are arranged in the cylinder (1), and the heat exchange outer pipe (23) penetrates through the round holes on the spiral ladder type helical baffles (22).

7. The shell-and-tube coal-tar pitch cooler based on the falling film theory according to claim 1, characterized in that The tube plate a (21) and the tube plate b (26) are both provided with a plurality of tube plate holes (28) in the form of concentric circles.

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