A method for reducing pressure drop in a conversion hydrogenation reactor for low temperature fischer-tropsch synthesis oil

Abstract

This invention belongs to the field of low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation bed pressure difference technology, and discloses a method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor, comprising the following steps: (1) The system gradually reduces the fresh feed rate until the feed is cut off, the hydrogenation reaction system and the first fractionation system form a large circulation, and the isomerization cracking reaction system and the second fractionation system form a large circulation. (2) The hydrogenation reaction system in step (1) is flushed with crude liquid wax No. 2. (3) The isomerization cracking system in step (1) is flushed with crude liquid wax No. 2. (4) After the flushing of crude liquid wax No. 2 in steps (2) and (3) is completed, the hydrogenation reaction system and the isomerization cracking system are switched to large circulation. (5) The system in step (4) is switched to fresh feed, the load is gradually increased, and qualified products are produced. The method of this invention can effectively reduce the pressure difference of the reactor bed and extend the reactor operating cycle.

Description

Technical Field

[0001] This invention belongs to the technical field of pressure difference in low-temperature Fischer-Tropsch synthesis oil conversion hydrotreating bed, and relates to a method for reducing the pressure difference in a low-temperature Fischer-Tropsch synthesis oil conversion hydrotreating reactor, particularly a method for reducing the pressure difference in a low-temperature Fischer-Tropsch synthesis hydrotreating reactor and extending the operating cycle of the unit. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Since the industrial era, the main energy sources upon which human civilization has developed and the economy has prospered have been coal, oil, and natural gas. Among them, coal is used as a raw material to gasify syngas, and through Fischer-Tropsch synthesis, it can be efficiently converted into clean liquid fuels. Fischer-Tropsch synthesis uses iron-based catalysts, and during the slurry bed reaction, paraffin wax and high- and low-temperature condensates carry some of the iron-based catalysts.

[0004] In the current coal-to-oil industry, low-temperature Fischer-Tropsch synthesis mostly involves hydrogenating the crude Fischer-Tropsch product, followed by hydrocracking and fractionation to obtain liquefied petroleum gas, crude liquid wax No. 2, naphtha, and other products. As the reactor's operating cycle lengthens, the pressure differential gradually increases.

[0005] Therefore, it is crucial to find a new method to reduce the pressure drop in the Fischer-Tropsch synthesis hydrogenation reactor.

[0006] The paper "A Brief Analysis of the Causes of Increased Pressure Difference in Hydrogenation Reactors and Discussion on Countermeasures" discloses methods such as skimming, refining of feedstock oil, and staged loading of catalysts, but the problems of low processing efficiency and insignificant improvement effects still exist. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a method for reducing the bed pressure differential in a low-temperature Fischer-Tropsch synthesis hydrogenation reactor, thereby improving the operating cycle of a coal-to-oil hydrogenation unit.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A first aspect of the present invention provides a method for reducing the pressure differential in a low-temperature Fischer-Tropsch synthesis oil conversion hydrotreating reactor, comprising:

[0010] Gradually reduce the feed rate until the feed is cut off. The hydrogenation reaction system and the first fractionation system form a large cycle, and the isomerization cracking reaction system and the second fractionation system form a large cycle.

[0011] The hydrogenation reaction system was flushed with a crude liquid wax.

[0012] The isomerization cracking reaction system is flushed with crude liquid wax.

[0013] After flushing, the hydrogenation reaction system and the isomerization cracking system are switched to large circulation.

[0014] Restart feeding, gradually increase the load, and produce qualified products.

[0015] It should be noted that the hydrogenation system of the present invention is divided into hydrogenation and cracking. The hydrogenation reaction system and the first fractionation system constitute a cycle system, and the isomerization cracking reaction system and the second fractionation system constitute a cycle system.

[0016] In some implementations, during the large-scale circulation of the hydrogenation reaction system and the first fractionation system, the feed temperature of the hydrogenation reaction system is gradually increased to 300-305°C, while the feed temperature of the isomerization cracking reaction system is gradually decreased to 360-365°C.

[0017] In some embodiments, during the flushing process of the hydrogenation reaction system using crude liquid wax, the temperature of the cracking reactor is reduced to 340-345°C.

[0018] In some embodiments, during the switching of the isomerization cracking reaction system to crude liquid wax for rinsing, the hydrogenation system is switched to self-circulation.

[0019] In some embodiments, the light crude liquid wax is recycled from a fractionation tower via a stripping tower and an external air cooler into a raw material paraffin tank.

[0020] In some implementations, #1 soft wax enters the intermediate tank area from the fractionation tower via the stripping tower reboiler, the fractionation tower feed heat exchanger, the stabilizer tower reboiler, and the soft wax air cooler.

[0021] In some implementations, the heavy crude liquid wax is stripped from the stripping tower, sent to an external air cooler, and then enters the No. 2 soft wax buffer tank.

[0022] In some embodiments, the No. 2 soft wax is fed from the fractionation tower through the stripping tower reboiler, the fractionation tower feed heat exchanger, the stabilizer tower reboiler, and the soft wax air cooler into the intermediate tank area.

[0023] More specifically, including:

[0024] (1) The system gradually reduces the amount of fresh feed until the feed is cut off. The hydrogenation reaction system and the first fractionation system form a large loop, and the isomerization cracking reaction system and the second fractionation system form a large loop. The feed temperature of the hydrogenation reaction system is gradually increased to 300℃, and the feed temperature of the isomerization cracking reaction system is gradually decreased to 360℃.

[0025] (2) The hydrogenation reaction system in step (1) was flushed with crude liquid wax No. 2, and the temperature of the cracking reactor was reduced to 340°C.

[0026] (3) The crude liquid wax No. 2 of the isomerization cracking system in step (1) is rinsed, and the hydrogenation reaction system is changed to self-circulation;

[0027] (4) The system crude liquid wax No. 2 was rinsed and the hydrogenation reaction system and the isomerization cracking system were changed to large circulation.

[0028] Preferably, in step (1), the feed temperature of the hydrogenation reaction system is gradually increased to 300°C, while the temperature of the isomerization cracking reaction system is gradually decreased to 360°C.

[0029] Preferably, in step (2), the temperature of the cracking reactor is reduced to 340°C.

[0030] Preferably, the hydrogenation reaction system in step (3) is modified to be self-circulating.

[0031] Preferably, in step (4), the system crude liquid wax No. 2 is rinsed and the hydrogenation reaction system and the isomerization cracking system are recirculated.

[0032] Preferably, in step (5), the system gradually increases the load after fresh feed is introduced, and finally produces qualified products.

[0033] A second aspect of the present invention provides a low-temperature Fischer-Tropsch synthesis oil conversion hydrotreating and isomerization cracking system, comprising: a hydrorefining reactor, a fractionation tower, and a cracking reactor;

[0034] The raw material condensate tank and the raw material paraffin tank are respectively connected to the hydrogenation protection reactor, which is connected in sequence to the hydrogenation refining reactor, the high-precision tank, the low-precision tank, the flash tank, and the fractionation tower.

[0035] The crude liquid wax feed tank is connected in sequence to the soft wax buffer tank, the cracking reactor, the high-precision tank, the low-precision tank, the flash tank, and the fractionation tower.

[0036] In some embodiments, the fractionation tower is sequentially connected to a stripping tower, an external air cooler, and a raw material paraffin tank or a soft wax buffer tank.

[0037] In some embodiments, the fractionation tower is also sequentially connected to a stripping tower reboiler, a fractionation tower feed heat exchanger, a stabilizer tower reboiler, a wax air cooler, and an intermediate tank area.

[0038] Beneficial effects of the present invention

[0039] (1) The present invention utilizes the cleaning coarse liquid wax No. 2 for rinsing, which can effectively reduce the pressure difference of the reactor bed and extend the reactor operation cycle.

[0040] (2) The crude liquid wax No. 2 used for rinsing in this invention is crude liquid wax No. 2 produced by this device, which saves costs.

[0041] (3) The method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0042] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0043] Figure 1 This is a block diagram of the process flow of the crude liquid wax No. 2 rinsing process in the low-temperature Fischer-Tropsch synthesis stable hydrogenation reactor according to an embodiment of the present invention.

[0044] Figure 2 This is a schematic diagram of a low-temperature Fischer-Tropsch synthesis stable hydrogenation reactor according to an embodiment of the present invention; wherein, 151V001A: feed condensate tank, 151V001B: feed paraffin tank, 151R001: first hydrogenation protection reactor, 151R002: second hydrogenation refining reactor, 151V002: first high-precision fraction tank, 151V003: first low-precision fraction tank, 151V004: second high-precision fraction tank, 151V005: second low-precision fraction tank. Sub-tanks, 151V011: Flash tank, 151T001: Fractionating tower, 151T002: Stripping tower, 151AE004: No. 2 external air cooler for crude liquid wax, 151E007: Stripping tower reboiler, 151E003: Fractionating tower feed heat exchanger, 150E006B: Stabilizer reboiler, 151AE005: No. 1 soft wax air cooler, 151F001: Heating furnace, TC: Thermometer, PC: Pressure gauge.

[0045] Figure 3 This is a block diagram of the process flow for rinsing crude liquid wax No. 2 in a low-temperature Fischer-Tropsch synthesis isomerization cracking reactor according to an embodiment of the present invention.

[0046] Figure 4 This is a schematic diagram of a low-temperature Fischer-Tropsch synthesis isomerization cracking reactor according to an embodiment of the present invention, wherein: 152R001: isomerization cracking reactor; 152V002: first high-fraction tank; 152V003: first low-fraction tank; 152V004: second high-fraction tank; 152V005: second low-fraction tank; 152V018: flash tank; 152T001: fractionation tower; 152T002: stripping tower; 152AE004: No. 2 external air cooler for crude liquid wax; 152V001: No. 2 soft wax buffer tank; 152E014: stripping tower reboiler; 152E003: fractionation tower feed heat exchanger; 152E012: naphtha stabilizer reboiler; 152AE006: No. 2 soft wax air cooler; TC: thermometer; PC: pressure gauge. Detailed Implementation

[0047] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0048] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0049] In the following embodiments, unless otherwise specified, the settings and operation of each device can be conventionally selected and configured by those skilled in the art based on common industry knowledge.

[0050] Example 1

[0051] Step (1): The feed rate of the hydrogenation system was reduced from 110t / h to 80t / h, and the hydrogen-to-oil ratio was maintained at 300 during this period. After the system was changed to feed No. 2 crude liquid wax (80t / h), the pressure difference was observed. Then the hydrogen-to-oil ratio was gradually increased and the pressure difference was observed (i.e., the hydrogen-to-oil ratio is normally controlled at 350, and the maximum increase during flushing is 600). Every half hour, No. 1 soft wax was taken to observe the solid content (samples were retained for solid content analysis).

[0052] Step (2): Draw crude liquid wax No. 2 to the unit area. Send crude liquid wax No. 2 from the entire plant tank area to the degassing pump in the intermediate tank area, and then send it to the raw material condensate tank / raw material paraffin tank (tank 151V001A / B) using the degassing pump. Switch the reaction feed to crude liquid wax No. 2, reduce the circulation rate to 80t / h, and flush the crude liquid wax No. 2 in the stable hydrogenation reactor system. Circulate all of No. 1 soft wax and No. 2 soft wax to the No. 2 soft wax buffer tank 152V001, and change the light crude liquid wax No. 2 to the raw material condensate tank (151V001A) for circulation.

[0053] Step (3): Reactor temperature control. Raise the inlet temperature of the hydrogenation protection reactor (151R001) to 300℃.

[0054] Step (4): Temperature control of the distillation tower. The hydrogenation distillation tower (151T001) is cooled down at a rate of ≤25℃ / h until it reaches about 280℃. The crude liquid wax No. 2 is only supplied to the three high-pressure pumps and high-temperature pumps for flushing. After the crude liquid wax No. 2 is flushed for 1 hour, the No. 1 soft wax is sent to the "Degassed High and Low Temperature Condensate No. 1 Storage Tank" (i.e., the intermediate tank area sludge tank) through the start-up light sludge oil process.

[0055] Step (5): Reflux the top of the hydrofraction tower 151T001 and take a sample to observe its solid content. If the sample turns black, replacement is necessary. If establishing reflux at the top of the tower is difficult, supplement with some light naphtha via the start-up gasoline line.

[0056] After switching to crude liquid wax No. 2 feed in step (6), the flushing time of crude liquid wax No. 2 can be appropriately extended according to the reactor pressure difference and the condition of each sample. When the color of No. 1 soft wax becomes clear, the flushing of crude liquid wax No. 2 in the hydrogenation reactor is completed, and No. 1 soft wax is circulated to the raw material paraffin tank (151V001B). The crude liquid wax No. 2 in the tank area is changed to No. 2 soft wax buffer tank (152V001).

[0057] Step (7): Reduce the feed rate of the isomerization cracking system from 110 t / h to 80 t / h, maintaining the hydrogen-to-oil ratio at 700. After switching to crude liquid wax No. 2 feed (80 t / h), observe the pressure difference change, and then gradually increase the hydrogen-to-oil ratio to observe the pressure difference change (i.e., the hydrogen-to-oil ratio is normally controlled at 850, and the maximum increase during flushing is 1300). Observe the pressure difference of the cracking reactor. If the pressure difference of the first bed rises too quickly after flushing with crude liquid wax No. 2, immediately stop flushing with crude liquid wax No. 2. After feeding crude liquid wax No. 2, observe the pressure difference change, and then increase the hydrogen-to-oil ratio to observe the pressure difference change. Take samples of No. 2 soft wax every half hour to observe the solid content (retain samples for solid content analysis). Increase the temperature of No. 2 soft wax to 130℃ in the intermediate tank area. The switching conditions for externally discharging to Paraffin No. 1 tank and Degassing No. 1 tank are determined based on the freezing point of soft wax No. 2 and the flash evaporation of the top breather valve of Paraffin No. 1 tank. (That is, the switching is based on the amount of breather at the top of the storage tank. As the flushing time increases, the amount of light oil in the system increases and is sent to Paraffin No. 1 tank, and the exhaust from the top breather valve increases, thus switching to Degassing No. 1 tank. Those skilled in the art can make conventional selections based on actual working conditions, and this invention does not impose any special limitations on this.)

[0058] Step (8) After the hydrogenation reaction system starts cutting the coarse liquid wax No. 2, the inlet temperature of the isomerization cracking reactor (152R001) is reduced to 360°C;

[0059] When the liquid level in the cracking fractionation system rises due to the cooling of the cracking reactor in step (9), some heavy oil can be thrown to paraffin tank #1 (external equipment of the system) through the No. 2 soft wax external throwing process.

[0060] Step (10) When No. 1 soft wax begins to be thrown out separately, the cracking system begins to circulate (i.e., the product after the raw material of 152V001 is cooled by the air coolers 152AE004 and 152AE006 of the reactor and the fractionation tower enters 152V001 again), No. 2 soft wax and No. 2 heavy crude liquid wax are circulated to No. 2 soft wax buffer tank (152V001);

[0061] After switching the feed of crude liquid wax No. 2 to the hydrogenation reaction system in step (11), the isomerization cracking reactor begins to cool down until it reaches 340°C. The crude liquid wax No. 2 in the tank area is then changed to the No. 2 soft wax buffer tank (152V001).

[0062] Step (12) 2# soft wax is first thrown out to “degassed high and low temperature condensate 1# tank”, and crude liquid wax 2# is circulated to 2# soft wax buffer tank 152V001.

[0063] Step (13) The absorption and analysis system is operated according to normal indicators. If the naphtha is not qualified due to insufficient heat in the reboiler at the bottom of the tower, the naphtha is transferred to the intermediate tank area.

[0064] Actual production data shows that the total system pressure differential decreased by 0.2 MPa after flushing. After operation, it takes about 45-50 days for the system pressure differential to rise back to the pressure before flushing.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of reducing pressure differential across a hydroconversion reactor for low temperature Fischer-Tropsch derived oil, characterised in that, include: Gradually reduce the feed rate until the feed is cut off. The hydrogenation reaction system and the first fractionation system form a large cycle, and the isomerization cracking reaction system and the second fractionation system form a large cycle. The hydrogenation reaction system was flushed with a crude liquid wax. The isomerization cracking reaction system is flushed with crude liquid wax. After flushing, the hydrogenation reaction system and the isomerization cracking system are switched to large circulation. Restart feeding, gradually increase the load, and produce qualified products; During the large-scale circulation of the hydrogenation reaction system and the first fractionation system, the feed temperature of the hydrogenation reaction system is gradually increased to 300-305℃, while the feed temperature of the isomerization cracking reaction system is gradually decreased to 360-365℃. During the process of switching crude liquid wax for rinsing in the hydrogenation reaction system, the temperature of the cracking reactor is reduced to 340-345℃.

2. The method of reducing pressure drop in a hydroconversion reactor of a low temperature Fischer-Tropsch derived oil according to claim 1, wherein, During the process of switching crude liquid wax for rinsing in the heterogeneous cracking reaction system, the hydrogenation system is switched to self-circulation.

3. The method for reducing the pressure differential in a low-temperature Fischer-Tropsch synthesis oil conversion hydrotreating reactor as described in claim 1, characterized in that, Light, crude liquid wax is distilled from the fractionation tower, then stripped from the stripping tower, and sent to an external air cooler before entering the raw material paraffin tank for recycling.

4. The method for reducing the pressure differential in a low-temperature Fischer-Tropsch synthesis oil conversion hydrotreating reactor as described in claim 1, characterized in that, #1 soft wax enters the intermediate tank area from the fractionation tower via the stripping tower reboiler, the fractionation tower feed heat exchanger, the stabilizer tower reboiler, and the soft wax air cooler.

5. The method for reducing the pressure differential in a low-temperature Fischer-Tropsch synthesis oil conversion hydrotreating reactor as described in claim 1, characterized in that, The heavy crude liquid wax is sent from the stripping tower, external air cooler, and into the No. 2 soft wax buffer tank.

6. The method for reducing the pressure differential in a low-temperature Fischer-Tropsch synthesis oil conversion hydrotreating reactor as described in claim 1, characterized in that, #2 soft wax enters the intermediate tank area from the fractionation tower via the stripping tower reboiler, the fractionation tower feed heat exchanger, the stabilizer tower reboiler, and the soft wax air cooler.

7. A low-temperature Fischer-Tropsch synthetic oil conversion hydrocracking system, employing the method for reducing the pressure differential of the low-temperature Fischer-Tropsch synthetic oil conversion hydrocracking reactor as described in any one of claims 1-6, characterized in that, include: Hydrorefining reactor, fractionation tower, cracking reactor; The raw material condensate tank and the raw material paraffin tank are respectively connected to the hydrogenation protection reactor, which is connected in sequence to the hydrogenation refining reactor, the high-precision tank, the low-precision tank, the flash tank, and the fractionation tower. The crude liquid wax feed tank is connected in sequence to the soft wax buffer tank, the cracking reactor, the high-precision tank, the low-precision tank, the flash tank, and the fractionation tower.

8. The low-temperature Fischer-Tropsch synthesis oil conversion hydrocracking system as described in claim 7, characterized in that, The fractionation tower is connected in sequence to the stripping tower, the external air cooler, and the raw material paraffin tank or soft wax buffer tank. Alternatively, the fractionation tower may also be connected in sequence to the stripping tower reboiler, the fractionation tower feed heat exchanger, the stabilizer tower reboiler, the soft wax air cooler, and the intermediate tank area.

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