System for recycling heavy oil in cyclohexanone production

Abstract

The utility model provides a system for recycling heavy oil in cyclohexanone production, the system comprises a heavy oil coalescer, a heavy oil separator and the like, DMAC is added into heavy oil, so that the relative volatility of methylcyclopentane and cyclohexanol in the heavy oil can be improved, rectification separation of cyclohexanol is facilitated, cyclohexanol is convenient to recycle, the utilization rate of cyclohexanol is improved, and the enterprise cost is reduced. The pressure in the heavy oil separator can be reduced by using the two parallel vacuum pumps and the two parallel compressors, so that the boiling point of heavy oil in the heavy oil separator is reduced, and rectification separation is facilitated; and meanwhile, the use amount of 1.2 MPa live steam is also saved. The mixed steam compressed by the compressor is introduced into the second reboiler or the third reboiler according to different temperatures of the mixed steam, so that heat is provided for the heavy oil separator, meanwhile, the energy of the secondary steam is reasonably utilized, and the use amount of 1.2 MPa live steam is further saved.

Description

Technical Field

[0001] This utility model belongs to the field of heavy oil recovery technology, and relates to a system for recovering and utilizing heavy oil in the production of cyclohexanone. Background Technology

[0002] Cyclohexanone is a colorless and transparent liquid that is mainly used in industry as a raw material and solvent for organic synthesis. It is an important organic chemical raw material.

[0003] During the production of cyclohexanone, a large amount of heavy oil is collected from the alcohol tower and transported to the heavy oil storage tanks in the tank farm at a rate of 30 kg / h. The heavy oil contains, by mass percentage, 35% methylcyclopentane and 64% cyclohexanol, with the remaining 1% consisting of cyclohexane and cyclohexanone. Since cyclohexanol is an important chemical product, it can be recovered from the heavy oil to improve its utilization rate. However, existing conventional distillation units struggle to completely separate cyclohexanol from the heavy oil, and the separation process is energy-intensive. Therefore, this portion of cyclohexanol is sold off along with the methylcyclopentane as part of the heavy oil, resulting in a significant waste of resources from the earlier stages of the process. Utility Model Content

[0004] The purpose of this invention is to provide a system for recovering and utilizing heavy oil in the production of cyclohexanone, in order to solve the problem that existing distillation units have difficulty recovering cyclohexanol from heavy oil.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This application provides a system for recovering heavy oil in cyclohexanone production, including a heavy oil coalescer and a heavy oil separator connected in series, the heavy oil separator also being connected to a live steam pipe; a second reboiler is provided at the bottom of the heavy oil separator, and a third reboiler is provided in the upper middle part of the heavy oil separator; a vacuum pump, a first buffer tank, and a compressor are connected in sequence at the top of the heavy oil separator, the compressor being connected to the second reboiler and the third reboiler respectively; the first buffer tank is also connected to a second buffer tank, and the second buffer tank is connected to the second reboiler and the third reboiler respectively; the second buffer tank is also connected to the heavy oil separator through a circulation pump.

[0007] Preferably, the bottom of the heavy oil separator is also provided with a first reboiler, which is connected to the live steam pipeline.

[0008] Preferably, the vacuum pump comprises two vacuum pumps connected in parallel.

[0009] Preferably, the heavy oil separator has 12 trays, and the third reboiler is located at the 6th tray.

[0010] Preferably, the temperature inside the heavy oil separator is 100-130℃ and the pressure is 88kPa.

[0011] Preferably, the compressor has a pressure of 0.5 MPa and a temperature of 150°C.

[0012] This utility model has the following beneficial effects:

[0013] (1) In the heavy oil coalescer, adding DMAC to the heavy oil can increase the relative volatility of methylcyclopentane and cyclohexanol in the heavy oil, which is conducive to the distillation and separation of cyclohexanol, facilitates the recovery of cyclohexanol, improves the utilization rate of cyclohexanol, and reduces enterprise costs.

[0014] (2) The use of two parallel vacuum pumps and compressors can reduce the pressure inside the heavy oil separator, thereby reducing the boiling point of the heavy oil in the heavy oil separator and facilitating distillation separation; at the same time, it also saves 1.2 MPa of live steam.

[0015] (3) The mixed steam after being compressed by the compressor is fed into the second or third reboiler according to its temperature, so as to provide heat to the heavy oil separator and realize the rational use of secondary steam energy, further saving the amount of 1.2MPa live steam. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the system for recovering and utilizing heavy oil in the production of cyclohexanone provided in an embodiment of this application;

[0017] Symbolic representation:

[0018] 1-Heavy oil coalescer, 2-Heavy oil separator, 3-Live steam pipe, 4-Second reboiler, 5-Third reboiler, 6-Vacuum pump, 7-First buffer tank, 8-Compressor, 9-Second buffer tank, 10-Circulation pump, 11-First reboiler. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] This application provides a system for recovering and utilizing heavy oil in cyclohexanone production. The system includes a heavy oil coalescer 1 and a heavy oil separator 2 connected in series, as shown in the attached figure. Figure 1As shown. The heavy oil coalescer 1 is a component that mixes the heavy oil produced in the cyclohexanone production process with DMAC (N,N-Dimethylacetamide). The addition of DMAC increases the relative volatility of methylcyclopentane and cyclohexanol in the heavy oil, which is beneficial for the distillation and separation of cyclohexanol, and thus facilitates the recovery of cyclohexanol. In the embodiments of this application, the feed ratio of heavy oil to DMAC is 1:(1.5-1.72).

[0021] The heavy oil separator 2 is a component for the rectification of heavy oil and DMAC. The heavy oil separator 2 is also connected to a live steam pipe 3, through which live steam at a pressure of 1.2 MPa is introduced. The heavy oil mixed with DMAC and the 1.2 MPa live steam enter the heavy oil separator 2, facilitating the rectification and separation of cyclohexanol. In this embodiment, the feed ratio of 1.2 MPa live steam to heavy oil is 1:(1.3-1.5). More preferably, the feed ratio of 1.2 MPa live steam to heavy oil is 1:1.36 to control the rational utilization of live steam and reduce costs.

[0022] To heat the heavy oil separator 2, a first reboiler 11 is provided at the bottom of the heavy oil separator 2, which is connected to the live steam pipe 3. Heat exchange is achieved by introducing 1.2 MPa live steam into the first reboiler 11, thereby heating the heavy oil separator 2 and facilitating the distillation and separation of heavy oil.

[0023] The top of the heavy oil separator 2 is sequentially connected to a vacuum pump 6, a first buffer tank 7, and a compressor 8, with the first buffer tank 7 also connected to a second buffer tank 9. The vacuum pump 6 can reduce the pressure inside the heavy oil separator 2 to 88 kPa, thereby lowering the boiling point of the heavy oil inside the separator 2 and facilitating distillation separation. In this embodiment, the internal temperature of the heavy oil separator 2 is 100-130°C. At this temperature and lower vacuum pressure, gaseous cyclohexanol can be separated from the heavy oil, saving 1.2 MPa of live steam. In this embodiment, the vacuum pump 6 includes two vacuum pumps connected in parallel. Smaller vacuum pumps can be selected to save on operating costs and civil engineering investment costs.

[0024] Under the pressure reduction action of vacuum pump 6, the gaseous cyclohexanol and the generated secondary vapor form mixed vapor, which is then discharged from the top of heavy oil separator 2 and temporarily stored in first buffer tank 7. Part of the mixed vapor in first buffer tank 7 is fed into second buffer tank 9, and the other part of the mixed vapor is fed into compressor 8 for compression processing.

[0025] The heavy oil separator 2 has a second reboiler 4 at its bottom and a third reboiler 5 in its upper middle part. The compressor 8 is connected to both the second reboiler 4 and the third reboiler 5, and the second buffer tank 9 is also connected to both the second reboiler 4 and the third reboiler 5. The second buffer tank 9 is also connected to the heavy oil separator 2 via a circulation pump 10.

[0026] Compressor 8 pressurizes and heats the mixed steam to conserve heat from the gaseous cyclohexanol discharged by vacuum pump 6, and then discharges the pressurized and heated mixed steam into the second reboiler 4 or the third reboiler 5, thereby facilitating the supply of heat to the heavy oil separator 2 and improving the utilization rate of steam heat. In this embodiment, the compressor 8 has a pressure of 0.5 MPa, a temperature of 150°C, and a discharge capacity of 3000 m³ / s. 3 .

[0027] When the temperature of the pressurized and heated mixed steam reaches 115-125℃, the compressor 8 discharges the mixed steam into the second reboiler 4 to heat the heavy oil separator 2 at the bottom, reducing the consumption of 1.2MPa live steam. When the temperature of the pressurized and heated mixed steam reaches 88-92℃, the compressor 8 discharges the mixed steam into the third reboiler 5 to heat the heavy oil separator 2 in the upper middle part, reasonably saving the consumption of 1.2MPa live steam.

[0028] The mixed steam, after heat exchange in the second reboiler 4 or the third reboiler 5, is discharged into the second buffer tank 9. The content of gaseous cyclohexanol in the second buffer tank 9 is tested. If the content exceeds 75%, it is discharged and directly reused in the unit. If the content does not exceed 75%, it is pumped through the circulating pump 10 into the heavy oil separator 2 for further separation and purification. Cases where the gaseous cyclohexanol content does not exceed 75% are mostly due to substandard wastewater generated during initial start-up or during periods of unstable production.

[0029] In this embodiment, the heavy oil separator 2 is a packed tower. To better separate the components in the heavy oil, the packed tower is designed with a large height margin, and the height of the packed tower is set to 70m. In addition, to save a small amount of steel and civil engineering investment, the diameter of the packed tower is set to 500mm. The heavy oil separator 2 has 12 trays, and the third reboiler 5 is located at the 6th tray.

[0030] Based on the above-mentioned system for recovering and utilizing heavy oil in cyclohexanone production, the workflow of this system includes:

[0031] S01: After heavy oil and DMAC are mixed in the heavy oil coalescer 1, they enter the heavy oil separator 2 with the live steam. Under the action of vacuum pump 6, they are subjected to vacuum distillation. Mixed steam is obtained at the top of the column, and methylcyclopentane is obtained at the bottom of the column.

[0032] S02: The mixed steam is compressed by the compressor 8 and then enters the second reboiler 4 or the third reboiler 5. After heat exchange, it enters the second buffer tank 9.

[0033] S03: Detect the cyclohexanol content in the second buffer tank 9. If the content exceeds 75%, it is discharged; if it does not exceed 75%, it is re-entered into the heavy oil separator 2 via the circulation pump 10.

[0034] The technical solution of this utility model will be further explained and described below through specific embodiments.

[0035] Example 1

[0036] This application provides a system for recovering and utilizing heavy oil in the production of cyclohexanone. The usage process of this system includes:

[0037] S101: Heavy oil in the heavy oil storage tank is mixed with DMAC at a feed ratio of 1:1.5 in the heavy oil coalescer 1, and then fed into the heavy oil separator 2. When the liquid level in the heavy oil separator 2 reaches the preset level, live steam at a pressure of 1.2 MPa is slowly introduced into the heavy oil separator 2 through the live steam pipe 3 at a feed ratio of 1:1.36, while the vacuum pump 6 is turned on to ensure that the pressure inside the heavy oil separator 2 is 88 kPa. Under the conditions of 88 kPa and 120°C, the heavy oil is distilled under reduced pressure in the heavy oil separator 2. A mixed vapor of gaseous cyclohexanol and secondary steam is obtained at the top of the column, and methylcyclopentane is obtained at the bottom. The mixed vapor is fed into the first buffer tank 7, and part of the mixed vapor in the first buffer tank 7 is pressurized and heated in the compressor 8, while the other part of the mixed vapor is fed into the second buffer tank 9. The methylcyclopentane is stored and then sold.

[0038] S102: Start compressor 8 to pressurize and heat the mixed steam at a pressure of 0.5 MPa and a temperature of 150°C. When the temperature of the pressurized and heated mixed steam reaches 120°C, compressor 8 discharges the mixed steam into the second reboiler 4. When the temperature of the pressurized and heated mixed steam reaches 90°C, compressor 8 discharges the mixed steam into the third reboiler 5. The mixed steam after heat exchange in the second reboiler 4 or the third reboiler 5 is discharged into the second buffer tank 9.

[0039] S103: Check the content of gaseous cyclohexanol in the second buffer tank 9. If the content of gaseous cyclohexanol exceeds 75%, it is discharged and directly enters the unit for use. If the content of gaseous cyclohexanol does not exceed 75%, it is passed into the heavy oil separator 2 through the circulation pump 10 for re-separation and purification.

[0040] Example 2

[0041] This application provides a system for recovering and utilizing heavy oil in the production of cyclohexanone. The usage process of this system includes:

[0042] S201: Heavy oil in the heavy oil storage tank is mixed with DMAC at a feed ratio of 1:1.72 in the heavy oil coalescer 1, and then fed into the heavy oil separator 2. When the liquid level in the heavy oil separator 2 reaches the preset level, live steam at a pressure of 1.2 MPa is slowly introduced into the heavy oil separator 2 through the live steam pipe 3 at a feed ratio of 1:1.3 to live steam. At the same time, the vacuum pump 6 is turned on to ensure that the pressure inside the heavy oil separator 2 is 88 kPa. Under the conditions of 88 kPa and 130°C, the heavy oil is distilled under reduced pressure in the heavy oil separator 2. A mixed vapor of gaseous cyclohexanol and secondary steam is obtained at the top of the column, and methylcyclopentane is obtained at the bottom of the column. The mixed vapor is fed into the first buffer tank 7, and part of the mixed vapor in the first buffer tank 7 is pressurized and heated in the compressor 8, while the other part of the mixed vapor is fed into the second buffer tank 9. The methylcyclopentane is stored and then sold.

[0043] S202: Start compressor 8 to pressurize and heat the mixed steam at a pressure of 0.5 MPa and a temperature of 150°C. When the temperature of the pressurized and heated mixed steam reaches 125°C, compressor 8 discharges the mixed steam into the second reboiler 4. When the temperature of the pressurized and heated mixed steam reaches 88°C, compressor 8 discharges the mixed steam into the third reboiler 5. The mixed steam after heat exchange in the second reboiler 4 or the third reboiler 5 is discharged into the second buffer tank 9.

[0044] S203: Check the content of gaseous cyclohexanol in the second buffer tank 9. If the content of gaseous cyclohexanol exceeds 75%, it is discharged and directly enters the unit for use. If the content of gaseous cyclohexanol does not exceed 75%, it is passed into the heavy oil separator 2 through the circulation pump 10 for re-separation and purification.

[0045] Example 3

[0046] This application provides a system for recovering and utilizing heavy oil in the production of cyclohexanone. The usage process of this system includes:

[0047] S301: Heavy oil in the heavy oil storage tank is mixed with DMAC at a feed ratio of 1:1.6 in heavy oil coalescer 1, and then fed into heavy oil separator 2. When the liquid level in heavy oil separator 2 reaches the preset level, live steam at a pressure of 1.2 MPa is slowly introduced into heavy oil separator 2 through live steam pipe 3 at a feed ratio of 1:1.5 to live steam. At the same time, vacuum pump 6 is turned on to ensure that the pressure inside heavy oil separator 2 is 88 kPa. Under the conditions of pressure of 88 kPa and temperature of 100°C, heavy oil is distilled under reduced pressure in heavy oil separator 2. A mixed vapor of gaseous cyclohexanol and secondary steam is obtained at the top of the column, and methylcyclopentane is obtained at the bottom of the column. The mixed vapor is fed into the first buffer tank 7, and part of the mixed vapor in the first buffer tank 7 is pressurized and heated in compressor 8, while the other part of the mixed vapor is fed into the second buffer tank 9. Methylcyclopentane is stored and then sold.

[0048] S302: Start compressor 8 to pressurize and heat the mixed steam at a pressure of 0.5 MPa and a temperature of 150°C. When the temperature of the pressurized and heated mixed steam reaches 115°C, compressor 8 discharges the mixed steam into the second reboiler 4. When the temperature of the pressurized and heated mixed steam reaches 92°C, compressor 8 discharges the mixed steam into the third reboiler 5. The mixed steam after heat exchange in the second reboiler 4 or the third reboiler 5 is discharged into the second buffer tank 9.

[0049] S303: Check the content of gaseous cyclohexanol in the second buffer tank 9. If the content of gaseous cyclohexanol exceeds 75%, it is discharged and directly enters the unit for use. If the content of gaseous cyclohexanol does not exceed 75%, it is passed into the heavy oil separator 2 through the circulation pump 10 for re-separation and purification.

[0050] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A system for recycling heavy oil in cyclohexanone production, characterized by, The heavy oil separator includes a connected heavy oil coalescer (1) and a heavy oil separator (2), the heavy oil separator (2) is also connected to a live steam pipe (3); the bottom of the heavy oil separator (2) is provided with a second reboiler (4), and the upper middle part of the heavy oil separator (2) is provided with a third reboiler (5); the top of the heavy oil separator (2) is connected in sequence to a vacuum pump (6), a first buffer tank (7) and a compressor (8), the compressor (8) is connected to the second reboiler (4) and the third reboiler (5) respectively; the first buffer tank (7) is also connected to a second buffer tank (9), and the second buffer tank (9) is connected to the second reboiler (4) and the third reboiler (5) respectively; the second buffer tank (9) is also connected to the heavy oil separator (2) through a circulation pump (10).

2. The system for recycling heavy oil in cyclohexanone production according to claim 1, characterized by, The bottom of the heavy oil separator (2) is also provided with a first reboiler (11), which is connected to the live steam pipe (3).

3. The system for recycling heavy oil in cyclohexanone production according to claim 1, characterized by, The vacuum pump (6) comprises two vacuum pumps connected in parallel.

4. The system for recycling heavy oil in cyclohexanone production according to claim 1, characterized by, The heavy oil separator (2) is equipped with 12 trays, and the third reboiler (5) is located at the 6th tray.

5. The system for recycling heavy oil in cyclohexanone production according to claim 1, characterized by, The temperature inside the heavy oil separator (2) is 100-130℃ and the pressure is 88kPa.

6. The system for recycling heavy oil in cyclohexanone production according to claim 1, characterized by, The compressor (8) has a pressure of 0.5 MPa and a temperature of 150 °C.

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