Shutdown method of hydroisomerization device taking Fischer-Tropsch wax as raw material

Abstract

The invention relates to the technical field of Fischer-Tropsch wax hydroisomerization, in particular to a shutdown method of a hydroisomerization device taking Fischer-Tropsch wax as a raw material, which comprises the following steps: reducing the outlet temperature of a heating furnace, and repeating the operation for cooling; adjusting a discharge line of the reaction system to a shutdown circulation line, and circulating the isomerized product back into the raw material tank and discharging the isomerized product together with the raw oil; stopping feeding to the distillation tower, reducing temperature and pressure, and replacing and purging the distillation tower with nitrogen; reducing the temperature of the reactor and the pressure of the reaction system to required requirements; adjusting until the flushing oil tank is discharged, flushing the reaction system, replacing oil in the reaction system, and cleaning the reaction system; a compressor unit is stopped, and the system starts to release pressure and return oil; after the pressure is released, nitrogen is introduced, and water, electricity and gas sources are closed after a replacement and purging reaction system is qualified. The device is easy to operate, convenient and easy to implement, the safety of personnel and equipment is guaranteed, meanwhile, the device is thoroughly purged and cleaned, blockage of the next starting equipment and pipelines is prevented, and powerful guarantee is provided for smooth starting of the device again.

Description

Technical Field

[0001] The invention relates to the technical field of Fischer-Tropsch wax hydroisomerization, in particular to a shutdown method for a hydroisomerization device using Fischer-Tropsch wax as a raw material. Background Art

[0002] Fischer-Tropsch wax is a methylene polymer, an alkane polymer synthesized from hydrocarbon-based synthesis gas or natural gas. It mainly relies on high-quality and cheap raw materials from coal chemical industry for iron-based or cobalt-based synthesis, and has a more obvious price advantage over crude oil wax.

[0003] In the coal-to-liquids process, wax oil products accounting for about 20% to 40% of the total weight of the product are produced. At present, most domestic coal-to-liquids companies sell this part of wax oil directly as industrial wax after simple distillation and cutting, which is used in the fields of medicine, rubber, food packaging and automobiles. However, the sulfur, nitrogen and aromatic content of Fischer-Tropsch wax is extremely low, and the composition is generally normal alkanes from C8 to C90, which is a high-quality hydrogenation raw material for further production of high-value-added lubricant base oil.

[0004] Hydroisomerization unit using Fischer-Tropsch wax as raw material (process flow chart as follows Figure 1 (as shown) is a process in which, under the action of catalyst and hydrogen, under certain reaction temperature and pressure conditions, the crude oil molecules undergo a series of complex reactions such as cracking, isomerization, cyclization, hydrogenolysis, etc. during the hydrogenation reaction, which ultimately makes the raw material molecules smaller and the product lighter.

[0005] The key dangerous parts of the hydroisomerization unit using Fischer-Tropsch wax as raw material include: heating furnace and reactor, high-pressure separator area and high-pressure air cooling area, hydrogenation compressor room and fractionation tower. The main equipment involved include: hydrogenation reactor, high-pressure heat exchanger, high-pressure air cooling and separator, heating furnace and various compressors. The working conditions of these equipment determine the dangerous factors in their production and the preventive measures that should be taken. Especially during the shutdown process of the Fischer-Tropsch wax hydroisomerization unit, strict requirements are placed on the de-oiling, cooling and cleaning of the unit. Whether the equipment and pipelines of the unit are thoroughly cleaned will be the key to determining whether the unit can be started smoothly next time.

[0006] Therefore, it is necessary to develop a shutdown method for a Fischer-Tropsch wax hydroisomerization unit to achieve rapid, efficient and smooth shutdown, shorten shutdown time and reduce production costs. Summary of the invention

[0007] The present invention provides a shutdown method for a hydroisomerization unit using Fischer-Tropsch wax as raw material, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problems that the oil withdrawal, cooling and cleaning are difficult to meet the requirements during the shutdown process of the existing Fischer-Tropsch wax hydroisomerization unit, and incomplete cleaning will lead to difficulties in the next start-up operation.

[0008] The technical solution of the present invention is achieved by the following measures: A shutdown method for a hydroisomerization unit using Fischer-Tropsch wax as a raw material is carried out according to the following steps: The first step is to lower the outlet temperature of the heating furnace, confirm that the temperature of the hydroisomerization reactor and the hydrofining reactor has been lowered, stabilize for one hour, and continue to lower the temperature, and repeat the cooling operation; The second step is to adjust the discharge line of the reaction system to the shutdown circulation line, and the isomerized product is circulated back to the raw material tank and enters and exits together with the raw material oil; The third step is to stop feeding the distillation tower. After the distillation tower collects all the products, the temperature and pressure are lowered, and the distillation tower is purged with nitrogen. The fourth step is to reduce the temperature and reaction system pressure of the hydroisomerization reactor and the hydrofining reactor to the required requirements; The fifth step is to adjust the raw material tank to the flushing oil tank for discharge, and start to feed flushing oil into the reaction system to flush and replace the oil in the reaction system. After the oil replacement in the reaction system is completed, start to clean the reaction system. After the cleaning is qualified, stop the flushing oil pump; Step 6: Stop the compressor, and the system starts to release pressure and drain oil; The seventh step is to introduce nitrogen after the pressure of the reaction system is released. After the reaction system is replaced and purged and qualified, the water, electricity and gas sources are turned off to complete the shutdown of the hydroisomerization unit using Fischer-Tropsch wax as raw material.

[0009] The following are further optimizations and / or improvements to the above technical solutions: In the first step, the outlet temperature of the heating furnace is reduced at a rate of 20°C / h, and the temperatures of the hydroisomerization reactor and the hydrofining reactor are reduced at a rate of 10°C / h to 15°C / h.

[0010] In the third step, the temperature of the distillation tower is reduced to 20°C to 100°C, and the pressure of the distillation tower is reduced to 0 MPa.

[0011] In the fourth step, the temperature of the hydroisomerization reactor and the hydrofining reactor is reduced from 400°C to 200°C, and the pressure of the reaction system is reduced to 4MPa.

[0012] In the fifth step, the reaction system cleaning time is 23 to 25 hours, and the flushing oil pump is stopped when the system temperature drops to 90°C to 100°C.

[0013] In the sixth step above, when stopping the compressor, stop the new hydrogen compressor first, and when the system pressure of the device drops to about 2MPa, stop the circulating hydrogen compressor.

[0014] In the seventh step, after the reaction system is qualified, the reaction system pressure is maintained at 0.5 MPa.

[0015] The invention is simple to operate, convenient and easy to implement, and ensures the safety of personnel and equipment. At the same time, the device equipment is purged and cleaned thoroughly to prevent the equipment and pipelines from being blocked when the device is started next time, thus providing a strong guarantee for the smooth start-up of the device again. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Attached Figure 1 This is a schematic diagram of the process flow of the hydroisomerization unit using Fischer-Tropsch wax as raw material in Example 1 of the present invention. DETAILED DESCRIPTION

[0017] The present invention is not limited by the following embodiments, and specific implementation methods can be determined according to the technical scheme of the present invention and actual conditions. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all known and commonly used chemical reagents and chemicals in the prior art.

[0018] The present invention will be further described below in conjunction with embodiments: Example 1: Figure 1 As shown, the shutdown method of the hydroisomerization unit using Fischer-Tropsch wax as raw material is carried out according to the following steps: The first step is to lower the outlet temperature of the heating furnace, confirm that the temperature of the hydroisomerization reactor and the hydrofining reactor has been lowered, stabilize for one hour, and continue to lower the temperature, and repeat the cooling operation; The second step is to adjust the discharge line of the reaction system to the shutdown circulation line, and the materials obtained by the reaction are circulated back to the raw material tank and discharged together with the raw material oil; The third step is to stop feeding the distillation tower. After the distillation tower collects all the products, the temperature and pressure are lowered, and the distillation tower is purged with nitrogen. The fourth step is to reduce the temperature and reaction system pressure of the hydroisomerization reactor and the hydrofining reactor to the required requirements; The fifth step is to adjust the raw material tank to the flushing oil tank for discharge, and start to feed flushing oil into the reaction system to flush and replace the oil in the reaction system. After the oil replacement in the reaction system is completed, start to clean the reaction system. After the cleaning is qualified, stop the flushing oil pump; Step 6: Stop the compressor unit, and the system starts to release pressure and drain oil; The seventh step is to introduce nitrogen after the pressure of the reaction system is released. After the reaction system is replaced and purged and qualified, the water, electricity and gas sources are turned off to complete the shutdown of the hydroisomerization unit using Fischer-Tropsch wax as raw material.

[0019] like Figure 1 As shown, in the present invention, the hydroisomerization device using Fischer-Tropsch wax as raw material comprises: a raw material tank, a reaction system and a distillation tower, and the reaction system comprises a heating furnace, a hydroisomerization reactor, a hydrorefining reactor, a cooler, a cold high-pressure separator, a cold low-pressure separator and a distillation tower.

[0020] The discharge process of the reaction system includes: the raw oil transported from the raw material tank is heated by a heating furnace, and then passes through a hydroisomerization reactor, a hydrorefining reactor, a cooler, a cold high-pressure separator, and a cold low-pressure separator in sequence to obtain an isomerized product (i.e., the material obtained by the reaction in the second step).

[0021] During normal production, when the reaction system is discharged, the isomerized product obtained from the reaction system is sent to the distillation tower (for downstream stripping separation) through the discharge line of the reaction system. In the second step of the shutdown operation of the present invention, it is necessary to stop sending the isomerized product obtained from the reaction system to the distillation tower and adjust it to return to the raw material tank through the shutdown circulation line for circulation cooling.

[0022] The reaction system discharge line: the raw oil passes through the raw material tank → hydroisomerization reactor → hydrofining reactor → cooler → cold high-pressure separator → cold low-pressure separator → distillation tower in sequence; The shutdown circulation line: the raw oil (including the isomerized product obtained by the reaction system) passes through the raw material tank → hydrogenation isomerization reactor → hydrogenation refining reactor → cooler → cold high-pressure separator → cold low-pressure separator → raw material tank in sequence.

[0023] Example 2: As an optimization of the above example, in the first step, the outlet temperature of the heating furnace is reduced at a rate of 20°C / h, and the temperatures of the hydroisomerization reactor and the hydrotreating reactor are both reduced at a rate of 10°C / h to 15°C / h.

[0024] Example 3: As an optimization of the above example, in the third step, the distillation tower is cooled to a temperature of 20°C to 100°C, and the distillation tower is depressurized to a pressure of 0 MPa.

[0025] During the shutdown process of the hydroisomerization unit using Fischer-Tropsch wax as raw material, strict requirements are placed on the de-oiling, cooling and cleaning of the unit, because whether the equipment and pipelines of the unit are thoroughly cleaned will be the key to whether the unit can be successfully started next time. Therefore, the present invention strictly reduces the temperature of the hydroisomerization reactor and the hydrofining reactor as required, such as the outlet temperature of the heating furnace is reduced at a rate of 20°C / h, and the temperature of the hydroisomerization reactor and the hydrofining reactor are both reduced at a rate of 10°C / h to 15°C / h, to prevent the system from cooling too fast to accelerate the corrosion and damage of the equipment and pipelines, and the cooling duration is too long, which will affect the production plan.

[0026] Example 4: As an optimization of the above example, in the fourth step, the temperature of the hydroisomerization reactor and the hydrofining reactor is reduced from 400°C to 200°C, and the pressure of the reaction system is reduced to 4MPa.

[0027] Example 5: As an optimization of the above example, in the fifth step, the reaction system cleaning time is 23h to 25h, and the flushing oil pump is stopped when the system temperature drops to 90°C to 100°C.

[0028] Embodiment 6: As an optimization of the above embodiment, in the sixth step, when stopping the compressor unit, it includes: first stopping the new hydrogen compressor, and when the pressure of the reaction system drops to about 2MPa, then stopping the circulating hydrogen compressor.

[0029] According to the needs, the compressor unit includes a new hydrogen compressor and a circulating hydrogen compressor, and both are public equipment known in the art. In the hydroisomerization production using Fischer-Tropsch wax as raw material, the hydrogen raw material will be compressed by the new hydrogen compressor and sent to the reaction system for hydrogenation, and the hydrogen recovered in the reaction system will be recovered and compressed by the circulating hydrogen compressor and reused.

[0030] Example 7: As an optimization of the above example, in the seventh step, after the reaction system is qualified, the reaction system pressure is maintained at 0.5 MPa.

[0031] Example 8: Figure 1 As shown, the shutdown method of the hydroisomerization unit using Fischer-Tropsch wax as raw material is carried out according to the following steps: In the first step, the outlet temperature of the heating furnace is reduced at a rate of 20°C / h to confirm that the temperature of the hydroisomerization reactor and the hydrofining reactor drops below 200°C, and then the temperature is continued to decrease after stabilization for one hour, and the operation is repeated to decrease the temperature to below 100°C; The second step is to adjust the discharge line of the reaction system to the shutdown circulation line, and the isomerized product is circulated back to the raw material tank and enters and exits together with the raw material oil; The third step is to stop feeding the distillation tower. After the distillation tower collects all the products, the temperature and pressure are lowered, and the distillation tower is purged with nitrogen. The fourth step is to reduce the temperature of the hydroisomerization reactor and the hydrofining reactor and the pressure of the reaction system to the required requirements, that is, the temperature of the hydroisomerization reactor and the hydrofining reactor is reduced from 400°C to 200°C, and the pressure of the reaction system is reduced to 4MPa; The fifth step is to adjust the raw material tank to the flushing oil tank for discharge, and start to feed flushing oil into the reaction system to flush and replace the oil in the reaction system. After the oil replacement in the reaction system is completed, start to clean the reaction system. After the cleaning is qualified, stop the flushing oil pump; Step 6: Stop the compressor unit, and the system starts to release pressure and drain oil; The seventh step is to introduce nitrogen after the pressure of the reaction system is released. After replacement and purging for 6 hours, place a clean white cloth in front of the discharge port. The purge gas discharged from each low point is clean and has a large volume. Observe that there is no oil stain on the white cloth. After confirming that the reaction system is purged and cleaned up to standard, turn off the water, electricity and gas sources to complete the shutdown of the hydroisomerization unit using Fischer-Tropsch wax as raw material.

[0032] The original shutdown method of the device takes 3 days, but after using the shutdown method of the present invention, the shutdown of the hydroisomerization device using Fischer-Tropsch wax as raw material can be completed in 2 days. Therefore, the shutdown method of the hydroisomerization device using Fischer-Tropsch wax as raw material of the present invention is shorter in time, clean in purge, and completely replaced than the traditional method, and can efficiently ensure that the pipeline is unobstructed when the next start-up is started.

[0033] In summary, the present invention is simple to operate, convenient and easy to implement, and ensures the safety of personnel and equipment. At the same time, the device equipment is purged and cleaned thoroughly to prevent equipment and pipeline blockage when the device is started next time, providing a strong guarantee for the smooth start-up of the device again.

[0034] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A shutdown method for a hydroisomerization unit using Fischer-Tropsch wax as a raw material, characterized in that Follow the steps below: The first step is to lower the outlet temperature of the heating furnace, confirm that the temperature of the hydroisomerization reactor and the hydrofining reactor has been lowered, stabilize for one hour, and continue to lower the temperature, and repeat the cooling operation; The second step is to adjust the discharge line of the reaction system to the shutdown circulation line, and the isomerized product is circulated back to the raw material tank and enters and exits together with the raw material oil; The third step is to stop feeding the distillation tower. After the distillation tower collects all the products, the temperature and pressure are lowered, and the distillation tower is purged with nitrogen. The fourth step is to reduce the temperature and reaction system pressure of the hydroisomerization reactor and the hydrofining reactor to the required requirements; The fifth step is to adjust the raw material tank to the flushing oil tank for discharge, and start to feed flushing oil into the reaction system to flush and replace the oil in the reaction system. After the oil replacement in the reaction system is completed, start to clean the reaction system. After the cleaning is qualified, stop the flushing oil pump; Step 6: Stop the compressor, and the system starts to release pressure and drain oil; The seventh step is to introduce nitrogen after the pressure of the reaction system is released. After the reaction system is replaced and purged and qualified, the water, electricity and gas sources are turned off to complete the shutdown of the hydroisomerization unit using Fischer-Tropsch wax as raw material.

2. The shutdown method of the hydroisomerization unit using Fischer-Tropsch wax as raw material according to claim 1, characterized in that In the first step, the outlet temperature of the heating furnace is reduced at a rate of 20°C / h, and the temperatures of the hydroisomerization reactor and the hydrofinishing reactor are both reduced at a rate of 10°C / h to 15°C / h.

3. The shutdown method of the hydroisomerization unit using Fischer-Tropsch wax as raw material according to claim 1 or 2, characterized in that In the third step, the distillation tower is cooled to a temperature of 20°C to 100°C, and the distillation tower is depressurized to a pressure of 0 MPa.

4. The shutdown method of the hydroisomerization unit using Fischer-Tropsch wax as raw material according to claim 1 or 2, characterized in that In the fourth step, the temperature of the hydroisomerization reactor and the hydrofining reactor is reduced from 400°C to 200°C, and the pressure of the reaction system is reduced to 4MPa.

5. The shutdown method of the hydroisomerization unit using Fischer-Tropsch wax as raw material according to claim 3, characterized in that In the fourth step, the temperature of the hydroisomerization reactor and the hydrofining reactor is reduced from 400°C to 200°C, and the pressure of the reaction system is reduced to 4MPa.

6. The shutdown method of a hydroisomerization unit using Fischer-Tropsch wax as a raw material according to claim 1, 2 or 5, characterized in that In the fifth step, the reaction system is cleaned for 23 to 25 hours, and the flushing oil pump is stopped when the system temperature drops to 90°C to 100°C.

7. The shutdown method of a hydroisomerization unit using Fischer-Tropsch wax as a raw material according to claim 3, characterized in that In the fifth step, the reaction system is cleaned for 23 to 25 hours, and the flushing oil pump is stopped when the system temperature drops to 90°C to 100°C.

8. The shutdown method of a hydroisomerization unit using Fischer-Tropsch wax as a raw material according to claim 4, characterized in that In the fifth step, the reaction system is cleaned for 23 to 25 hours, and the flushing oil pump is stopped when the system temperature drops to 90°C to 100°C.

9. The shutdown method of a hydroisomerization unit using Fischer-Tropsch wax as a raw material according to claim 1, 2, 5, 7 or 8, characterized in that In the sixth step, when stopping the compressor, stop the new hydrogen compressor first, and when the system pressure of the device drops to about 2MPa, stop the circulating hydrogen compressor.

10. The shutdown method of a hydroisomerization unit using Fischer-Tropsch wax as a raw material according to claim 9, characterized in that In the seventh step, after the reaction system is qualified, the reaction system pressure is maintained at 0.5MPa.

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