Cracking tail oil heat recovery system of slurry bed residual oil hydrogenation device
By optimizing the heat exchange system network structure of the slurry bed residue oil hydrotreating unit, using cracked tail oil as the heating medium, and introducing a tail oil cold feed preheater, the problems of low tail oil heat utilization and safety hazards were solved, achieving efficient heat recovery and safe production.
Patent Information
- Application Number
- CN202520173247.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-26
- Publication Date
- 2026-03-03
- Estimated Expiration
- 2035-01-26
AI Technical Summary
The existing slurry bed wax oil hydrocracking unit has a long heat exchange system and an unreasonable network structure, resulting in low tail oil heat utilization rate, increased steam consumption, safety hazards, and resource waste.
The heat exchange system network structure was optimized by introducing an isopentane bottom heat exchanger and a tail oil cold feed preheater. Cracking tail oil was used as the heating medium to reduce steam usage and improve the operational safety of the heat exchanger. The tail oil cold feed preheater was used to replace the tail oil air cooling to reduce the risk of temperature difference.
It improves the efficiency of heat recovery from tail oil, reduces processing costs, reduces steam usage, eliminates safety hazards of heat exchangers, avoids water hammer problems, and optimizes the safety and economy of the system.
Smart Images
Figure CN223963462U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of cracking tail oil recovery technology, and in particular to a heat recovery system for cracking tail oil in a slurry bed residue oil hydrotreating unit. Background Technology
[0002] The slurry bed wax oil cracking unit has a complex process. With increasingly stringent requirements for energy consumption and environmental protection in petrochemical plants, how to tap the potential of existing mature processes to reduce energy consumption and improve economic efficiency is an important issue facing petrochemical plant designers.
[0003] The cracking tail oil produced by slurry-bed wax oil hydrocracking units needs to be recovered. However, existing technologies for cracking tail oil heat recovery involve long processes and complex heat exchange networks, with process flows such as... Figure 1 As shown, the 310°C high-temperature tail oil from the bottom of the fractionation tower is cooled to 230°C by the jet fuel tower bottom heat exchanger, and then cooled to 170°C by the butane removal tower bottom heat exchanger. It is then divided into two paths: one path is returned to the buffer tank before the heater for recycling, and the other path is cooled to 95°C by the low-temperature hot water heat exchanger, and then cooled to 60°C by the tail oil air cooler before exiting the unit. The utilization rate of the tail oil heat is low, and the temperature control of the tail oil exiting the unit varies greatly.
[0004] In other heat exchange systems of the slurry bed wax oil hydrocracking unit, such as the heat exchange process between the bottom pumice of the isopentane tower and low-pressure steam, the heat exchange medium is low-pressure steam at 0.5 MPa and a temperature of 177°C. The steam is de-cooled and depressurized by deoxygenated water before going to the heat exchanger for heat exchange. The bottom liquid of the isopentane tower (pumice component) is heated through the heat exchanger circulation to remove isopentane from the pumice. Then, it is pumped out of the unit at a temperature of 103°C and a flow rate of 95 t / h. The steam loss is about 30 t / h. Due to the large heat exchange area, the steam and liquid form two phases. The flow rate and temperature in the heat exchanger tube bundle change greatly and irregularly, which causes great damage to the heat exchanger tube bundle. Heat exchanger leakage failures often occur, which bring the risk of shutdown to the normal operation of the isopentane tower.
[0005] For example, in the cold feed heat exchange process, the mixed wax oil from the raw material tank area has a flow rate of 120t / h and a temperature of 60℃. After being dehydrated by the coalescer, it is sent to the cold feed / steam heat exchanger for heating. The heat exchange steam comes from a low pressure of 0.5 MPa and has a steam temperature of 177℃. After being de-heated and depressurized by deoxygenated water, it goes to the heat exchanger to heat the raw material, raising the temperature from 60℃ to 150℃. After being mixed with the hot feed, it enters the backwash filter to remove impurities. Due to the low temperature of the cold feed and the high temperature of the steam, the heat exchange temperature rise is large, and water hammer problems often occur in the condensate pipeline, causing severe pipeline vibration and affecting safe production.
[0006] In summary, the heat exchange system of the existing slurry bed wax oil hydrocracking unit has a long process and an unreasonable network structure, resulting in low heat utilization rate of tail oil, additional steam consumption and operating costs of tail oil air cooling, waste of resources, and potential safety hazards in production.
[0007] Therefore, it is necessary to propose a heat recovery system for cracking tail oil in a slurry bed residue hydrotreating unit to overcome the shortcomings of existing technologies. Utility Model Content
[0008] The purpose of this invention is to solve the problems in the prior art and provide a heat recovery system for cracking tail oil in a slurry bed residue hydrotreating unit.
[0009] The technical solution of this utility model is:
[0010] A heat recovery system for cracking tail oil in a slurry bed residue hydrotreating unit includes a fractionation tower. A bottom pump is installed at the bottom of the fractionation tower. The outlet of the bottom pump is connected in series with a jet fuel tower bottom heat exchanger, a butane removal tower bottom heat exchanger, an isopentane tower bottom heat exchanger, and a tail oil cold feed preheater. The isopentane tower bottom heat exchanger is connected to the butane removal tower heat exchanger tail oil outlet pipe through the isopentane tower heat exchanger tail oil inlet pipe. The isopentane tower bottom heat exchanger is connected to the cold feed preheater tail oil inlet pipe through the isopentane tower heat exchanger tail oil outlet pipe. The cold feed preheater tail oil inlet pipe is installed on the tail oil cold feed preheater. A tail oil discharge pipe is installed on the tail oil cold feed preheater.
[0011] Preferably, a first bypass pipe is provided between the tail oil outlet pipe of the butane tower heat exchanger and the tail oil outlet pipe of the isopentane tower heat exchanger, and a first bypass regulating valve is provided on the first bypass pipe.
[0012] Preferably, a first tail oil return pipeline is connected in parallel to the tail oil inlet pipeline of the cold feed preheater, and a first return regulating valve is installed on the first tail oil return pipeline.
[0013] Preferably, the isopentane bottom heat exchanger is connected to the isopentane tower via a bottom liquid inlet pipe and a bottom liquid outlet pipe, and the isopentane tower is equipped with an isopentane bottom pump.
[0014] Preferably, a second bypass pipe is provided between the tail oil inlet pipe and the tail oil discharge pipe of the cold feed preheater, and a second bypass regulating valve is provided on the second bypass pipe. The second tail oil return pipe is connected to the first tail oil return pipe.
[0015] Preferably, the tail oil cold feed preheater is equipped with a cold feed inlet pipe and a cold feed outlet pipe, with two cold feed inlet pipes connected in parallel, and a feed regulating valve is installed on the cold feed inlet pipe.
[0016] Preferably, a second tail oil return pipeline is provided on the pipeline between the bottom heat exchanger of the butane tower and the bottom heat exchanger of the isopentane tower, and a second return regulating valve is provided on the second tail oil return pipeline.
[0017] Preferably, a third bypass pipeline is provided between the fractionation tower and the bottom pump of the fractionation tower, and a third bypass regulating valve is provided on the third bypass pipeline; a fourth bypass pipeline is connected in parallel to the heat exchanger at the bottom of the jet fuel tower, and a fourth bypass regulating valve is provided on the fourth bypass pipeline; a fifth bypass pipeline is connected in parallel to the heat exchanger at the bottom of the butane removal tower, and a fifth bypass regulating valve is provided on the fifth bypass pipeline.
[0018] Compared with the prior art, the beneficial effects of this utility model are:
[0019] This invention optimizes the heat exchange system network structure of cracking tail oil and changes the heat exchange method by introducing an isopentane bottom heat exchanger and a tail oil cold feed preheater into the tail oil heat exchange system. This achieves efficient heat recovery from the tail oil. By changing the heating medium of the isopentane bottom heat exchanger from steam to cracking tail oil, the amount of steam used is reduced, processing costs are lowered, and steam leakage in the isopentane bottom heat exchanger is prevented, eliminating safety hazards. The tail oil air cooler is replaced with a tail oil cold feed preheater. By using the tail oil as the heat exchange medium in the tail oil cold feed preheater, the investment in tail oil air cooling equipment is reduced, the cold feed temperature is increased, the temperature difference between the cold feed inlet and outlet is reduced when using steam heat exchange, and the water hammer hazard that often occurs with steam heat exchange is eliminated. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the structure of this utility model;
[0021] Figure 2 This is a flow chart of the isopentane bottom heat exchanger of this utility model;
[0022] Figure 3 This is a flow chart of the tail oil cold feed preheater of this utility model;
[0023] Figure 4 This is a flow chart of the existing tail oil recovery process;
[0024] Figure 5 This is a process flow diagram of an existing isopentane tower heat exchange system;
[0025] Figure 6 This is a process flow diagram of a cold feed heat exchange system for raw materials in the existing technology.
[0026] The components include: 1. Fractionating tower; 2. Fractionating tower bottom pump; 3. Aviation kerosene tower bottom heat exchanger; 4. Butane stripper bottom heat exchanger; 5. Isopentane tower bottom heat exchanger; 6. Tail oil cold feed preheater; 7. Isopentane tower heat exchanger tail oil inlet pipeline; 8. Butane stripper heat exchanger tail oil outlet pipeline; 9. Isopentane tower heat exchanger tail oil outlet pipeline; 10. Cold feed preheater tail oil inlet pipeline; 11. Tail oil discharge pipeline; 12. First bypass pipeline; 13. First bypass regulating valve; 14. First tail oil return pipeline; 15. First return regulating valve. 16. Isopentane tower; 17. Bottom liquid inlet pipe; 18. Bottom liquid outlet pipe; 19. Isopentane tower bottom pump; 20. Second bypass pipe; 21. Second bypass regulating valve; 22. Cold feed inlet pipe; 23. Cold feed outlet pipe; 24. Feed regulating valve; 25. Second tail oil return pipe; 26. Second return regulating valve; 27. Third bypass pipe; 28. Third bypass regulating valve; 29. Fourth bypass pipe; 30. Fourth bypass regulating valve; 31. Fifth bypass pipe; 32. Fifth bypass regulating valve. Detailed Implementation
[0027] To make the technical means, technical features, utility model purpose and technical effects of this utility model easier to understand, the present utility model will be further described below with reference to specific illustrations.
[0028] like Figures 1-3 As shown, a slurry-bed residue hydrotreating unit cracking tail oil heat recovery system is connected to a fractionation tower 1. A fractionation tower bottom pump 2 is installed at the bottom of the fractionation tower 1. A jet fuel bottom heat exchanger 3, a butane removal bottom heat exchanger 4, an isopentane bottom heat exchanger 5, and a tail oil cold feed preheater 6 are connected in series at the outlet end of the fractionation tower bottom pump 2. The fractionation tower bottom pump 2 is used to pressurize and transport the tail oil at the bottom of the fractionation tower 1. The tail oil flows sequentially through the jet fuel bottom heat exchanger 3 and the butane removal bottom heat exchanger 4. The tail oil is discharged into the designated unit after being discharged from the bottom heat exchanger 5 of the isopentane tower and the tail oil cold feed preheater 6. This allows the tail oil to serve as the heating medium for the bottom heat exchanger 5 of the isopentane tower, reducing the amount of steam used, preventing steam leakage from the bottom heat exchanger 5 of the isopentane tower, eliminating safety hazards, and reducing processing costs. In the tail oil cold feed preheater 6, the tail oil and cold feed exchange heat, increasing the temperature of the cold feed, reducing the temperature difference between the inlet and outlet of the tail oil cold feed preheater 6, and eliminating the safety hazard of water hammer from condensate.
[0029] like Figures 1-3As shown, after heat exchange in the bottom heat exchanger 4 of the butane tower, the tail oil is transported to the bottom heat exchanger 5 of the isopentane tower through the tail oil outlet pipe 8 connected to the bottom heat exchanger 4. The bottom heat exchanger 5 is connected to the isopentane tower tail oil inlet pipe 7, the isopentane tower tail oil outlet pipe 9, the bottom liquid inlet pipe 17, and the bottom liquid outlet pipe 18. The tail oil circulates within the bottom heat exchanger 5 through the tail oil inlet pipe 7 and the tail oil outlet pipe 9. The bottom heat exchanger 5 is connected to the isopentane tower through the bottom liquid inlet pipe 17 and the bottom liquid outlet pipe 18. The connection of the isopentane tower 16 enables the circulation of the bottom liquid in the isopentane tower 16 within the isopentane tower bottom heat exchanger 5. During the circulation process, heat exchange occurs with the tail oil, raising its temperature. After removing isopentane from the light stone in the bottom liquid, it is transported outward by the isopentane tower bottom pump 19 connected to the isopentane tower 16. A first bypass pipe 12 connects the tail oil outlet pipe 8 of the butane tower heat exchanger and the tail oil outlet pipe 9 of the isopentane tower heat exchanger. A first bypass regulating valve 13 is installed on the first bypass pipe 12. The flow rate of the tail oil entering the isopentane tower bottom heat exchanger 5 is adjusted by the opening degree of the first bypass regulating valve 13, thereby controlling the temperature at the outlet end of the isopentane tower bottom heat exchanger 5.
[0030] The tail oil after heat exchange with the isopentane tower bottom heat exchanger 5 is divided into two paths. One path is sent to the tail oil cold feed preheater 6 through the tail oil inlet pipeline 10, which is connected to the tail oil outlet pipeline 9 of the isopentane tower heat exchanger. The other path is returned to the preheater buffer tank (not shown in the figure) for recycling through the first tail oil return pipeline 14 connected in parallel to the tail oil inlet pipeline 10 of the cold feed preheater. A first return regulating valve 15 is installed on the first tail oil return pipeline 14 to realize the opening and closing of the first tail oil return pipeline 14 and to regulate the flow rate.
[0031] like Figures 1-3As shown, the tail oil enters the cold feed preheater 6 through the tail oil inlet pipe 10. The cold feed preheater 6 is also connected to a tail oil discharge pipe 11, a cold feed inlet pipe 22, and a cold feed outlet pipe 23. The tail oil circulates within the cold feed preheater 6 through the tail oil inlet pipe 10 and the tail oil discharge pipe 11. The tank farm cold feed circulates within the cold feed preheater 6 through the cold feed inlet pipe 22 and the cold feed outlet pipe 23. During the circulation process, the tank farm cold feed exchanges heat with the circulating tail oil, increasing its temperature. The cold feed inlet pipe 22... Two are installed in parallel to achieve redundant backup of the feed and avoid system shutdown due to failure. A feed regulating valve 24 is installed on the cold feed feed pipeline 22. The feed regulating valve 24 is used to control the opening and closing of the cold feed feed pipeline 22 and regulate the flow. A second bypass pipeline 20 is connected between the tail oil inlet pipeline 10 and the tail oil discharge pipeline 11 of the cold feed preheater. A second bypass regulating valve 21 is installed on the second bypass pipeline 20. By adjusting the opening of the second bypass regulating valve 21, the flow of tail oil into the tail oil cold feed preheater 6 is adjusted, thereby controlling the outlet temperature of the tail oil cold feed preheater 6.
[0032] like Figures 1-3 As shown, a second tail oil return pipeline 25 is connected between the bottom heat exchanger 4 of the butane tower and the bottom heat exchanger 5 of the isopentane tower. The second tail oil return pipeline 25 is connected to the first tail oil return pipeline 14. The tail oil flowing out of the bottom heat exchanger 4 of the butane tower is divided into two paths. One path enters the bottom heat exchanger 5 of the isopentane tower, and the other path merges with the first tail oil return pipeline 14 and returns to the buffer tank in front of the heater for recycling. A second return regulating valve 26 is installed on the second tail oil return pipeline 25. The second return regulating valve 26 controls the opening and closing of the second tail oil return pipeline 25 and realizes the flow rate regulation.
[0033] like Figures 1-3 As shown, a third bypass pipe 27 is connected between the outlet of fractionation tower 1 and the bottom pump 2 of fractionation tower. A third bypass regulating valve 28 is installed on the third bypass pipe 27. By opening the third bypass regulating valve 28, the tail oil can flow by gravity through the third bypass pipe 27. A fourth bypass pipe 29 is connected in parallel to the jet fuel tower bottom heat exchanger 3. A fourth bypass regulating valve 30 is installed on the fourth bypass pipe 29. A fifth bypass pipe 31 is connected in parallel to the butane stripper bottom heat exchanger 4. A fifth bypass regulating valve 32 is installed on the fifth bypass pipe 31. By adjusting the opening of the fourth bypass regulating valve 30 and the fifth bypass regulating valve 32, the flow rate of tail oil entering the jet fuel tower bottom heat exchanger 3 and the butane stripper bottom heat exchanger 4 is adjusted respectively, thereby achieving temperature control of the tail oil at the outlet end of the jet fuel tower bottom heat exchanger 3 and the butane stripper bottom heat exchanger 4.
[0034] In this embodiment, the tail oil temperature at the bottom of fractionation tower 1 is 310℃, and the flow rate is 200t / h. The bottom pump 2 of the fractionation tower is started to extract and pressurize the tail oil from fractionation tower 1, and then transport it to the jet fuel tower bottom heat exchanger 3. After heat exchange in the jet fuel tower bottom heat exchanger 3, the tail oil temperature drops to 230℃, and the flow rate is 200t / h. The tail oil after heat exchange with the jet fuel tower bottom heat exchanger 3 enters the butane removal tower bottom heat exchanger 4, where it undergoes heat exchange at a temperature of 170℃ and a flow rate of 200t / h. The tail oil after heat exchange with the butane removal tower bottom heat exchanger 4 is divided into two paths: one path enters the isopentane tower bottom heat exchanger 5 through the isopentane tower heat exchanger tail oil inlet pipe 7, and the other path returns to the preheater buffer tank for recycling through the second tail oil return pipe 25. The tail oil entering the bottom heat exchanger 5 of the isopentane tower exchanges heat with the bottom liquid (light stone component) of the isopentane tower 16. The bottom liquid is circulated and heated by the bottom pump 19 of the isopentane tower, with a circulation rate of about 95 t / h. The bottom liquid needs to be heated from 103℃ to 105℃ to remove isopentane from the light stone. The total heat exchange enthalpy is about 132244 MJ / kg. The flow rate of the tail oil at 170℃ is only 70 t / h, which greatly meets the heat exchange requirements of the bottom liquid in the isopentane tower 16. The temperature of the tail oil after heat exchange in the bottom heat exchanger 5 of the isopentane tower is 105℃. The tail oil is divided into two paths. One path enters the tail oil cold feed preheater 6, and the other path returns to the buffer tank in front of the heater through the first tail oil return pipeline 14 for recycling.
[0035] The cold feed rate from the tank area entering the tail oil cold feed preheater 6 through the cold feed pipeline 22 is approximately 120 t / h at a temperature of 60°C, while the tail oil flow rate is approximately 70 t / h at a temperature of 105°C. Heat exchange occurs within the tail oil cold feed preheater 6, preheating the cold feed. According to material heat balance calculations, the temperature of the cold feed can rise to 86°C after being heated by the tail oil cold feed preheater 6, while the tail oil temperature can drop from 105°C to 60°C. Through the two-phase material heat exchange within the tail oil cold feed preheater 6, the investment and construction costs of a tail oil air cooler and its daily operation and maintenance costs can be saved. At the same time, the temperature control of the tail oil discharge pipeline 11 is more stable than that of the tail oil air cooler.
[0036] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of this utility model. All equivalent changes and modifications made in accordance with the scope of the claims of this utility model should fall within the technical scope of this utility model.
Claims
1. A heat recovery system for cracking tail oil in a slurry bed residue hydrotreating unit, comprising a fractionating tower (1), wherein a bottom pump (2) is provided at the bottom of the fractionating tower (1), characterized in that: The outlet end of the fractionation tower bottom pump (2) is connected in series with a jet fuel tower bottom heat exchanger (3), a butane de-butane tower bottom heat exchanger (4), an isopentane tower bottom heat exchanger (5), and a tail oil cold feed preheater (6). The isopentane tower bottom heat exchanger (5) is connected to the butane de-butane tower heat exchanger tail oil outlet pipe (8) through the isopentane tower heat exchanger tail oil inlet pipe (7). The isopentane tower bottom heat exchanger (5) is connected to the cold feed preheater tail oil inlet pipe (10) through the isopentane tower heat exchanger tail oil outlet pipe (9). The cold feed preheater tail oil inlet pipe (10) is installed on the tail oil cold feed preheater (6). The tail oil cold feed preheater (6) is provided with a tail oil discharge pipe (11).
2. The slurry bed residue hydrotreating unit cracking tail oil heat recovery system according to claim 1, characterized in that: A first bypass pipe (12) is provided between the tail oil outlet pipe (8) of the butane tower heat exchanger and the tail oil outlet pipe (9) of the isopentane tower heat exchanger, and a first bypass regulating valve (13) is provided on the first bypass pipe (12).
3. The slurry bed residue hydrotreating unit cracking tail oil heat recovery system according to claim 1, characterized in that: The cold feed preheater tail oil inlet pipeline (10) is connected in parallel with a first tail oil return pipeline (14), and a first return regulating valve (15) is provided on the first tail oil return pipeline (14).
4. The slurry bed residue hydrotreating unit cracking tail oil heat recovery system according to claim 1, characterized in that: The isopentane bottom heat exchanger (5) is connected to the isopentane tower (16) through the bottom liquid inlet pipe (17) and the bottom liquid outlet pipe (18), and the isopentane tower (16) is equipped with an isopentane bottom pump (19).
5. The slurry bed residue hydrotreating unit cracking tail oil heat recovery system according to claim 1, characterized in that: A second bypass pipe (20) is provided between the tail oil inlet pipe (10) of the cold feed preheater and the tail oil discharge pipe (11), and a second bypass regulating valve (21) is provided on the second bypass pipe (20).
6. The slurry bed residue hydrotreating unit cracking tail oil heat recovery system according to claim 1, characterized in that: The tail oil cold feed preheater (6) is equipped with a cold feed inlet pipe (22) and a cold feed outlet pipe (23). The cold feed inlet pipe (22) is configured as two in parallel, and a feed regulating valve (24) is provided on the cold feed inlet pipe (22).
7. The slurry bed residue hydrotreating unit cracking tail oil heat recovery system according to claim 3, characterized in that: A second tail oil return pipeline (25) is provided on the pipeline between the bottom heat exchanger (4) of the butane tower and the bottom heat exchanger (5) of the isopentane tower. A second return regulating valve (26) is provided on the second tail oil return pipeline (25). The second tail oil return pipeline (25) is connected to the first tail oil return pipeline (14).
8. The slurry bed residue hydrotreating unit cracking tail oil heat recovery system according to claim 1, characterized in that: A third bypass pipe (27) is provided between the fractionation tower (1) and the bottom pump (2) of the fractionation tower. A third bypass regulating valve (28) is provided on the third bypass pipe (27). A fourth bypass pipe (29) is connected in parallel to the bottom heat exchanger (3) of the jet fuel tower. A fourth bypass regulating valve (30) is provided on the fourth bypass pipe (29). A fifth bypass pipe (31) is connected in parallel to the bottom heat exchanger (4) of the butane removal tower. A fifth bypass regulating valve (32) is provided on the fifth bypass pipe (31).