Anti-carbon deposition waste heat boiler

Abstract

The utility model relates to the field of petrochemical engineering equipment, and discloses a carbon deposition prevention waste heat boiler. In order to achieve the purpose, the carbon deposition prevention waste heat boiler comprises a shell, a left side pipe box, a shell pass barrel and a right side pipe box, the left side pipe box, the shell pass barrel and the right side pipe box are sequentially arranged in the shell, and the shell pass barrel is connected with the left side pipe box and the right side pipe box through flexible pipe plates. A heat exchange pipe assembly is further arranged in the shell and comprises a heat exchange pipe and a false pipe inserted into the tail of the heat exchange pipe, the left side pipe box and the right side pipe box are communicated through the heat exchange pipe, and a fluid inlet and a fluid outlet are formed in the shell pass barrel. The anti-carbon-deposition waste heat boiler can remarkably improve the heat transfer coefficient of the tail of the heat exchanger, prevents carbon deposition and blockage of the heat exchange tube, and enables equipment to operate stably.

Description

Technical Field

[0001] The utility model relates to the field of petrochemical equipment, in particular to a carbon deposition-proof waste heat boiler. Background Art

[0002] In petrochemical plants, waste heat recovery equipment is often used, such as waste heat boilers for flue gas waste heat recovery, reforming gas waste heat boilers for cooling reforming gas in reforming furnaces, and waste heat boilers at the outlet of heavy oil gasification furnaces. For this type of equipment, since the temperature of flue gas / conversion gas is very high, generally between 600 and 1200°C, conventional shell and tube heat exchangers can no longer adapt to such harsh conditions. Flexible tube sheet heat exchangers are usually used to solve problems such as thermal expansion and thermal stress. Generally, flue gas / conversion gas flows through the tube side, and water flows through the shell side. When the temperature of flue gas / conversion gas is relatively high, the flow rate decreases at the end of the heat exchanger due to the decrease in the temperature of the flue gas / conversion gas, resulting in a decrease in the heat exchange efficiency of the heat exchanger. When the conversion gas carries ash, if the flow rate of the conversion gas is too small, carbon deposition on the tube wall is easy to occur, causing a rapid decrease in heat exchange efficiency, and in severe cases, it may cause blockage of the heat exchange tube. Utility Model Content

[0003] The purpose of the utility model is to overcome the problem in the prior art that when heat is recovered from the conversion gas with ash, carbon deposition causes the heat exchange efficiency to drop rapidly, and in severe cases, the heat exchange tubes may be blocked. The utility model provides a waste heat boiler with anti-carbon deposition, which can significantly improve the heat transfer coefficient at the tail of the heat exchanger, prevent carbon deposition and blockage of the heat exchange tubes, and ensure stable operation of the equipment.

[0004] In order to achieve the above-mentioned purpose, the utility model provides an anti-carbon deposition waste heat boiler, including a shell and a left-side pipe box, a shell-side cylinder and a right-side pipe box which are sequentially arranged inside the shell, and the shell-side cylinder is connected to the left-side pipe box and the right-side pipe box through flexible tube sheets respectively; a heat exchange tube assembly is also arranged inside the shell, and the heat exchange tube assembly includes a heat exchange tube and a dummy tube inserted at the tail of the heat exchange tube, the left-side pipe box and the right-side pipe box are connected through the heat exchange tube, and a fluid inlet and outlet are opened on the shell-side cylinder.

[0005] The process of the first fluid passing through the carbon deposition prevention waste heat boiler is as follows: the first fluid enters the left pipe box, passes through the heat exchange tube assembly in the shell cylinder, and is discharged from the right pipe box. The shell cylinder is provided with an inlet and an outlet for the second fluid. The second fluid enters the shell cylinder through the inlet for heat exchange and is discharged through the outlet, thereby completing the heat exchange between the two fluids.

[0006] When the first fluid flows through the heat exchange tube inside the shell cylinder, compared with the first fluid without heat exchange, the changes in various parameters during the same period of time are as follows: when the first fluid is continuously transported at high pressure, the temperature of the first fluid in the heat exchange tube remains unchanged. When the first fluid in the heat exchange tube continuously exchanges heat with the second fluid outside the heat exchange tube, the temperature of the first fluid in the heat exchange tube will gradually decrease, causing the volume of the first fluid to gradually decrease, thereby causing its flow rate to gradually decrease. When the flow rate of the first fluid in the heat exchange tube drops to a certain level, the ash in the first fluid will precipitate on the inner wall of the heat exchange tube to form carbon deposits, thereby greatly affecting the heat exchange efficiency. When the carbon deposits are serious, they may even block the heat exchange tubes.

[0007] A dummy tube is inserted into the tail of the heat exchange tube of the anti-carbon deposit waste heat boiler of the utility model, so that in the area where the original flow velocity drops to a certain level, when the first fluid flows through the heat exchange tube inserted with the dummy tube, the effective flow cross-sectional area of ​​the first fluid is reduced, thereby increasing the flow velocity of the first fluid. When the flow velocity of the first fluid is increased to a certain speed, the ash will be carried away by the particles in the first fluid and will not be precipitated into carbon deposits on the inner wall of the heat exchange tube, thereby avoiding the influence on the heat exchange efficiency of the two fluids and the blockage of the equipment.

[0008] Preferably, a dummy tube plate is provided in the right tube box, and the dummy tube plate is fixedly connected to the dummy tube.

[0009] The dummy tube extends out of the heat exchange tube as the first embodiment of the dummy tube setting. In order to allow the dummy tube to be better inserted into the tail of the heat exchange tube, a dummy tube tube sheet is provided in the right tube box. The dummy tube extends out of the heat exchange tube area and extends to the dummy tube tube sheet and is fixedly connected to the dummy tube tube sheet. The dummy tube tube sheet provides installation support for the dummy tube.

[0010] Preferably, the dummy tube is completely inside the heat exchange tube, and the heat exchange tube is fixedly connected to the dummy tube.

[0011] The second embodiment of the dummy tube arrangement is that the dummy tube is completely inside the heat exchange tube. The dummy tube extends inside the heat exchange tube to the end of the heat exchange tube and is fixedly connected to the heat exchange tube. This structure is simpler.

[0012] Preferably, the dummy tube is composed of sections with different diameters, and the diameter of the dummy tube in the heat exchange tube gradually increases in the direction of the rear end of the heat exchange tube.

[0013] The dummy tube can be set as a section with the same diameter, or it can be composed of sections with different diameters, depending on the actual working conditions. In the embodiment where the dummy tube is composed of tubes with different diameters, the diameter of the dummy tube in the heat exchange tube gradually increases. The principle is the same as above. Due to heat exchange, the flow rate of the first fluid flowing through the dummy tube section will gradually decrease. Therefore, in order to keep the flow rate of the first fluid above a certain flow rate, it is necessary to further reduce the effective flow cross-sectional area of ​​the heat exchange tube to increase the flow rate of the first fluid, thereby avoiding ash precipitation.

[0014] Preferably, the false tube comprises a head, a first section and an expanded diameter section in sequence, and the head is a conical structure.

[0015] As a preferred embodiment of the dummy pipe structure, the dummy pipe is provided with two sections, a first section and an expanded diameter section, and the head is provided with a conical structure to reduce the reverse effect of the dummy pipe on the flow velocity.

[0016] Preferably, the first section and the diameter-enlarging section are smoothly arranged.

[0017] In order to further reduce the reverse effect of the structure of the dummy tube itself on the flow velocity of the first fluid, the first section and the expanded diameter section are smoothed.

[0018] Preferably, the dummy tube plate is detachably connected to the right tube box.

[0019] The dummy tube plate is detachably connected to the right side tube box, which is convenient for installation and removal of the dummy tubes connected to the dummy tube plate.

[0020] Preferably, an equipment flange is provided on the right pipe box.

[0021] The equipment flange is set on the right pipe box to further provide conditions for the replacement of the dummy pipe. When the equipment load changes and the length and diameter of the dummy pipe need to be adjusted, or when the equipment needs to be repaired, the equipment flange can be opened, the dummy pipe tube sheet and the entire structure of the dummy pipe can be taken out of the equipment, and replaced with the required dummy pipe size before installation. Due to the equipment flange and the detachable dummy pipe tube sheet, the flow rate of the first fluid can be kept above the flow rate that prevents ash from settling under different working conditions.

[0022] Through the above technical scheme, the anti-carbon deposition waste heat boiler of the utility model changes the effective flow cross-sectional area of ​​the fluid in the heat exchange tube and increases the flow rate of the fluid by arranging a dummy tube in the heat exchange tube. The increase in the fluid flow rate can, on the one hand, increase the heat transfer coefficient at the tail of the heat exchanger and reduce the total heat exchange area, thereby reducing the length of the heat exchange tube; the increase in the flow rate of the fluid in the heat exchange tube can, on the other hand, keep the flow rate of the fluid above the target flow rate, thereby preventing carbon deposition and blockage in the heat exchange tube and improving the stable operation and life cycle of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of a waste heat boiler to prevent carbon deposition;

[0024] Figure 2 It is a structural schematic diagram of the AA section of the carbon deposition prevention waste heat boiler;

[0025] Figure 3 is a schematic diagram of the structure of a heat exchange tube assembly;

[0026] Figure 4It is a structural diagram of the pseudo tube.

[0027] Description of Reference Numerals

[0028] 1. Shell; 11. Left side tube box; 12. Left side flexible tube sheet; 13. Right side flexible tube sheet; 14. Right side tube box; 15. Shell side cylinder; 2. Heat exchange tube assembly; 21. Heat exchange tube; 22. Dummy tube; 221. Head; 222. First section; 223. Expanded diameter section; 3. Dummy tube and tube sheet; 4. First fluid flow direction; 5. Second fluid flow direction; N1. First inlet; N2. Second inlet; N3. First outlet; N4. Second outlet. DETAILED DESCRIPTION

[0029] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0030] In the present utility model, unless otherwise specified, directional words such as "up, down, left, right, inside, outside, far, near, front" generally refer to the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present utility model and simplifying the description, and therefore cannot be understood as limitations on the present utility model.

[0031] like Figure 1 and Figure 3 The figure shows an anti-carbon deposition waste heat boiler, comprising a shell 1 and a left-side pipe box 11, a shell-side cylinder 15 and a right-side pipe box 14 which are sequentially arranged inside the shell 1, and the shell-side cylinder 15 is connected to the left-side pipe box 11 and the right-side pipe box 14 through flexible tube sheets respectively; a heat exchange tube assembly 2 is also arranged inside the shell 1, and the heat exchange tube assembly 2 comprises a heat exchange tube 21 and a dummy tube 22 inserted into the tail of the heat exchange tube 21, the left-side pipe box 11 and the right-side pipe box 14 are connected through the heat exchange tube 21, and a fluid inlet and outlet are opened on the shell-side cylinder 15.

[0032] It should be noted that if Figure 1 As shown, the carbon deposition prevention waste heat boiler is a heat exchanger for two fluids. The process of the first fluid passing through the carbon deposition prevention waste heat boiler is that the first fluid enters the left pipe box 11, passes through the heat exchange tube assembly 2 in the shell cylinder 15, and is discharged from the right pipe box 14. The flow direction of the first fluid 4 is as shown in FIG. Figure 1 The shell side cylinder 15 is provided with an inlet and an outlet for the second fluid. The second fluid enters the shell side cylinder 15 through the inlet (N1, N2) and is discharged through the outlet (N3, N4) after heat exchange. The flow direction of the second fluid 5 is as shown in FIG. Figure 1 As shown, heat exchange between the two fluids is completed.

[0033] When the first fluid flows through the heat exchange tube inside the shell cylinder 15, compared with the first fluid that does not undergo heat exchange, the changes in various parameters during the same period of time are as follows: when the first fluid is continuously transported at high temperature and high pressure, there is no pressure difference in the pressure of the first fluid in the heat exchange tube. When the first fluid in the heat exchange tube continuously exchanges heat with the second fluid outside the heat exchange tube, the temperature of the first fluid in the heat exchange tube 21 will gradually decrease, causing the volume of the first fluid to gradually decrease, thereby causing its flow rate to gradually decrease. When the flow rate of the first fluid in the heat exchange tube drops to a certain level, the ash in the first fluid will precipitate on the inner wall of the heat exchange tube 21 to form carbon deposits, thereby forming a heat insulation layer, which greatly affects the heat exchange efficiency. When the carbon deposits are serious, they may even block the heat exchange tube 21.

[0034] The tail of the heat exchange tube 21 of the anti-carbon deposition waste heat boiler of the utility model is inserted into a dummy tube 22, so that when the first fluid flows through the area of ​​the heat exchange tube 21 where the dummy tube 22 is inserted, the effective flow cross-sectional area of ​​the first fluid is reduced, thereby increasing the flow rate of the first fluid. When the flow rate of the first fluid is increased to a certain level, the ash will be carried away by the particulate matter in the first fluid and will not be precipitated into a carbon deposition layer on the inner wall of the heat exchange tube 21, thereby avoiding the influence on the heat exchange efficiency of the two fluids and the blockage of the equipment.

[0035] Specifically, Figure 1 As shown, the left side pipe box 11 is connected to the left side of the shell side cylinder 15 through the left side flexible tube sheet 12, and the right side of the shell side cylinder 15 is connected to the right side pipe box 14 through the right side flexible tube sheet 13. The shell side cylinder 15 is provided with a heat exchange tube 21 that passes through the left side pipe box 11 and the right side pipe box 14. Figure 3 As shown, the left side pipe box 11, the heat exchange tube 21 and the right side pipe box 14 form a flow path for the first fluid. Figure 1 As shown, the shell-side cylinder 15 is provided with an inlet and an outlet for the second fluid on its circumference. The first fluid flows into the shell-side cylinder 15 outside the heat exchange tube 21 through the first outlet N1 and the second inlet N2, and is transported out from the first outlet N3 and the second outlet N4 after heat exchange with the first fluid in the heat exchange tube 21.

[0036] like Figure 3 As shown, the dummy tube 22 is inserted from the tail end of the heat exchange tube 21 . The dummy tube 22 can be connected to the heat exchange tube 21 , or can extend out of the heat exchange tube 21 to be connected to the right side tube box 14 .

[0037] Furthermore, a dummy tube sheet 3 is provided in the right tube box 14 , and the dummy tube sheet 3 is fixedly connected to the dummy tube 22 .

[0038] The dummy tube 22 extends out of the heat exchange tube 21 and is connected to the right tube box 14, which is the first embodiment of the dummy tube 22 structure. This structure enables the dummy tube 22 to be better inserted into the tail of the heat exchange tube 21. Figure 1 As shown, a dummy tube sheet 3 is provided in the right tube box 14, the dummy tube 22 extends out of the heat exchange tube 21 area and extends to the dummy tube sheet 3, and the dummy tube 22 is fixedly connected to the dummy tube sheet 3, and the fixed connection can be welding, or can be integrally formed, or can be threaded connection, as long as the dummy tube 22 and the dummy tube sheet 3 can be stably connected. The dummy tube sheet 3 provides stable support for the dummy tube 22 to be in the heat exchange tube 21.

[0039] Furthermore, the dummy tube 22 is completely located inside the heat exchange tube 21 , and the heat exchange tube 21 is fixedly connected to the dummy tube 22 .

[0040] The second embodiment of the dummy tube 22 structure is that the dummy tube 22 is completely inside the heat exchange tube 21 and is fixedly connected to the heat exchange tube 21. The dummy tube 22 extends inside the heat exchange tube 21 to the right end of the heat exchange tube 21 and is fixedly connected to the heat exchange tube 21. The fixed connection can be that the dummy tube 22 and the heat exchange tube 21 are integrally formed, or the dummy tube 22 and the heat exchange tube 21 are stably connected by a connector. The connector can be a cross-shaped, cross-shaped or triangular bracket that can suspend the dummy tube 22 in the heat exchange tube 21. The heat exchange tube assembly 2 composed of the dummy tube 22 and the heat exchange tube 21 has a simpler structure and is suitable for fluids with similar physical and chemical properties.

[0041] Furthermore, the dummy tube 22 is composed of sections with different diameters, and the diameter of the dummy tube 22 in the heat exchange tube 21 gradually increases along the direction of the rear end of the heat exchange tube 21 .

[0042] The dummy tube 22 can be set as a section with the same diameter, or it can be composed of sections with different diameters, depending on the actual working conditions. In the embodiment where the dummy tube 22 is composed of tubes with different diameters, the diameter of the dummy tube 22 in the heat exchange tube 21 gradually increases. The principle is the same as above. Due to heat exchange, the flow rate of the first fluid flowing through the dummy tube 22 section will gradually decrease as the temperature decreases. Therefore, in order to keep the flow rate of the first fluid above a certain flow rate, it is necessary to further reduce the effective flow cross-sectional area of ​​the heat exchange tube 21 to increase the flow rate of the first fluid, thereby avoiding ash precipitation.

[0043] Furthermore, the false tube 22 includes a head 221, a first section 222 and an expanded diameter section 223 in sequence, and the head 221 is a conical structure.

[0044] As a preferred embodiment of the structure of the dummy tube 22, the dummy tube 22 is provided with two sections, namely a first section 222 and an enlarged diameter section 223. Figure 4 As shown, the head 221 is configured as a conical structure to reduce the reverse effect of the dummy tube 22 on the flow rate of the first fluid.

[0045] Furthermore, the first section 222 and the diameter-enlarging section 223 are smoothly arranged.

[0046] In order to further reduce the reverse effect of the structure of the dummy tube 22 on the flow velocity of the first fluid, the connection between the first section 222 and the enlarged diameter section 223 is smoothed.

[0047] Furthermore, the dummy tube sheet 3 is detachably connected to the right tube box 14 .

[0048] like Figure 1 As shown, the dummy tube sheet 3 is detachably connected to the right tube box 14, which facilitates the installation and removal of the dummy tube 22 connected to the dummy tube sheet 3. Figure 2 As shown, the cross-sectional view of the dummy tube 22 and the dummy tube sheet 3 shows that a plurality of dummy tubes 22 are fixedly connected to the dummy tube sheet 3, and threaded holes are provided on the dummy tube sheet 3, so that the dummy tube sheet 3 and the right side tube box 14 can be threadedly connected, making the overall structure of the dummy tube 22 and the dummy tube sheet 3 easy to install and disassemble.

[0049] Furthermore, an equipment flange 7 is provided on the right pipe box 14 .

[0050] The right pipe box 14 is provided with an equipment flange 7, which further provides conditions for replacing the dummy pipe 22. When the equipment load changes and the length and diameter of the dummy pipe 22 need to be adjusted, or when the equipment needs to be repaired, the equipment flange 7 can be opened, the right pipe box 14 can be disassembled, and the entire structure of the dummy pipe sheet 3 and the dummy pipe 22 can be taken out from the right pipe box 14, replaced with the required size of the dummy pipe 22, and then installed. Due to the provision of the equipment flange 7 and the detachable dummy pipe sheet 3, the flow rate of the first fluid can be ensured to be maintained above the flow rate that prevents ash from settling under different load conditions.

[0051] Embodiment 1:

[0052] The second fluid is water. Shell-side water enters from the first inlet N1 and the second inlet N2. After heat exchange, saturated water vapor is discharged from the first outlet N3 and the second outlet N4.

[0053] The first fluid is synthesis gas, the synthesis gas temperature T≈1150℃, and the designed flow rate V a =50m / s, the critical value of the flow rate of ash and carbon deposition V≈30m / s;

[0054] like Figure 3 , Figure 4 As shown, at the inlet of point A of the heat exchange tube 21, the synthesis gas temperature T≈1150°C and the flow velocity Va=50m / s;

[0055] When the synthesis gas flows to point B, the flow rate decreases due to the decrease in temperature. The flow rate V b ≈30m / s;

[0056] At this time, the first section 222 of the dummy tube 22 is placed starting from point B, the effective flow cross-sectional area of ​​the heat exchange tube 21 is reduced, and the synthesis gas flow rate is further increased to 50 m / s.

[0057] Similarly, when the synthesis gas continues to flow to point C, the temperature continues to decrease and the flow rate also decreases. At this time, V c ≈30m / s, at this time, the dummy tube 22 is set as the expansion section 223 from point C, further reducing the effective flow cross-sectional area of ​​the heat exchange tube 21, thereby increasing the flow rate of the synthesis gas, so that the synthesis gas can still maintain a flow rate higher than the critical flow rate V≈30m / s of carbon deposition when it flows from point C to point D at the outlet of the heat exchange tube 21.

[0058] It can be seen that, by setting the dummy tube 22, it can be ensured that the flow rate of the synthesis gas flow inside the heat exchange tube 21 is greater than the critical flow rate of carbon deposition during the entire flow process, and it can be ensured that the ash of the synthesis gas will not adhere to the inner wall of the heat exchange tube. At the same time, due to the addition of the dummy tube 22, the flow rate of the synthesis gas is increased at the tail of the heat exchange tube 21. Since the heat transfer coefficient in the tube is related to the flow rate of the synthesis gas, increasing the flow rate can greatly increase the heat transfer coefficient in the heat exchange tube, that is, increase the total heat transfer coefficient of the entire heat exchanger. Compared with the heat exchange tube 21 without the dummy tube 22 inside, the total heat exchange area of ​​the heat exchanger can be reduced, thereby reducing the length of the heat exchange tube 21 and reducing the weight of the equipment.

[0059] Briefly, the dimension parameters of the dummy tube 22, the diameter d1 of the first section 222, the diameter d2 of the enlarged diameter section 223, the length L1 of the first section 222, and the length L2 of the enlarged diameter section 223 should be obtained through calculation according to different process gas parameters.

[0060] It should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present utility model will not further describe various possible combinations.

[0061] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A waste heat boiler with carbon deposition prevention, characterized in that: The invention comprises a shell (1) and a left pipe box (11), a shell-side cylinder (15) and a right pipe box (14) which are sequentially arranged inside the shell (1), and the shell-side cylinder (15) is connected to the left pipe box (11) and the right pipe box (14) respectively through flexible tube sheets; a heat exchange tube assembly (2) is also arranged inside the shell (1), and the heat exchange tube assembly (2) comprises a heat exchange tube (21) and a dummy tube (22) inserted into the tail of the heat exchange tube (21); the left pipe box (11) and the right pipe box (14) are connected through the heat exchange tube (21), and a fluid inlet and outlet are opened on the shell-side cylinder (15).

2. The anti-carbon deposition waste heat boiler according to claim 1, characterized in that: A dummy tube plate (3) is arranged in the right tube box (14), and the dummy tube plate (3) is fixedly connected to the dummy tube (22).

3. The anti-carbon deposition waste heat boiler according to claim 1, characterized in that: The dummy tube (22) is completely located inside the heat exchange tube (21), and the heat exchange tube (21) is fixedly connected to the dummy tube (22).

4. The anti-carbon deposition waste heat boiler according to claim 2 or 3, characterized in that: The dummy tube (22) is composed of sections with different diameters, and the diameter of the dummy tube (22) located in the heat exchange tube (21) gradually increases in the direction of the rear end of the heat exchange tube (21).

5. The anti-carbon deposition waste heat boiler according to claim 4, characterized in that: The false tube (22) comprises a head (221), a first section (222) and an expanded diameter section (223) in sequence, and the head (221) is a conical structure.

6. The anti-carbon deposition waste heat boiler according to claim 5, characterized in that: The first section (222) and the diameter-enlarging section (223) are arranged smoothly.

7. The anti-carbon deposition waste heat boiler according to claim 2, characterized in that: The dummy tube plate (3) is detachably connected to the right side tube box (14).

8. The anti-carbon deposition waste heat boiler according to claim 7, characterized in that: The right pipe box (14) is provided with an equipment flange (7).

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