Method for reducing pressure difference of low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor

Abstract

The invention belongs to the technical field of low-temperature Fischer-Tropsch synthesis oil product conversion hydrogenation bed pressure difference, and discloses a method for reducing low-temperature Fischer-Tropsch synthesis oil product conversion hydrogenation reactor pressure difference, which comprises the following steps: (1) a system gradually reduces fresh feeding amount until feeding is cut off, a hydrogenation reaction system and a first fractionation system form a large cycle, and a second fractionation system forms a small cycle; and the isomerization cracking reaction system and the second fractionation system form a large cycle. And (2) washing the hydrogenation reaction system in the step (1) by switching crude liquid wax No.2. And (3) introducing crude liquid wax No.2 to the isomerization cracking system in the step (1) for flushing. And (4) washing the crude liquid wax 2 in the step (2) and the step (3), and improving the hydrogenation reaction system and the isomerization cracking system to circulate. And (5) feeding the system in the step (4) to be fresh, gradually increasing the load, and producing qualified products. The method provided by the invention can effectively reduce the bed pressure difference of the reactor and prolong the operation cycle of the reactor.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation bed pressure difference, and relates to a method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor, and in particular to a method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis hydrogenation reactor and extending the operation cycle of the device. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Since the industrial age, the main energy sources for the development of human civilization and economic prosperity have been coal, oil and natural gas. Among them, coal is used as a raw material to gasify and obtain synthesis gas, which can be efficiently converted into clean liquid fuel by Fischer-Tropsch synthesis. Fischer-Tropsch synthesis uses iron-based catalysts. During the slurry bed reaction process, paraffin and high and low temperature condensates carry some iron-based catalysts.

[0004] In the current "coal-to-liquid" industry, most low-temperature Fischer-Tropsch processes still produce liquefied petroleum gas, crude liquid wax No. 2, naphtha and other products by hydrogenation saturation, hydrocracking and product fractionation. As the reactor operation cycle increases, the reactor pressure difference gradually increases.

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

[0006] The paper "A Brief Analysis of the Causes and Countermeasures for Increased Pressure Difference in Hydrogenation Reactors" discloses methods such as skimming, refining of crude oil, and graded loading of catalysts, but there are still problems such as low processing efficiency and unclear improvement effects. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a method for reducing the bed pressure difference of a low-temperature Fischer-Tropsch synthesis hydrogenation reactor, thereby increasing the operation cycle of a coal-to-liquid hydrogenation device.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] The first aspect of the present invention provides a method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor, comprising:

[0010] The feed amount is gradually reduced 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] Switching the hydrogenation reaction system to crude liquid wax for flushing;

[0012] Switching the crude liquid wax to the isomerization cracking reaction system for flushing;

[0013] After flushing is completed, the hydrogenation reaction system and isomerization cracking system are changed to larger 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, wherein the hydrogenation reaction system and the first fractionation system constitute a circulation system, and the isomerization cracking reaction system and the second fractionation system constitute a circulation system.

[0016] In some embodiments, during the large cycle 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, and the feed temperature of the isomerization cracking reaction system is gradually decreased to 360-365°C.

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

[0018] In some embodiments, when the isomerization cracking reaction system switches to the crude liquid wax for flushing, the hydrogenation system is changed to self-circulation.

[0019] In some embodiments, the light crude liquid wax is sent from a distillation tower to a stripping tower, an external air cooler, and then into a raw paraffin tank for recycling.

[0020] In some embodiments, 1# soft wax is discharged from the distillation tower through the stripping tower reboiler, the distillation tower feed heat exchanger, the stabilization tower reboiler, and the soft wax air cooler to enter the intermediate tank area.

[0021] In some embodiments, the heavy crude liquid wax is sent from the stripping tower to an external air cooler and enters the 2# soft wax buffer tank.

[0022] In some embodiments, the 2# soft wax is discharged from the distillation tower through the stripping tower reboiler, the distillation tower feed heat exchanger, the stabilization tower reboiler, and the soft wax air cooler to enter the intermediate tank area.

[0023] More specifically, they include:

[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 cycle, and the isomerization cracking reaction system and the second fractionation system form a large cycle. The feed temperature of the hydrogenation reaction system is gradually increased to 300°C, and the feed temperature of the isomerization cracking reaction system is gradually reduced to 360°C;

[0025] (2) The hydrogenation reaction system in step (1) is switched to crude liquid wax No. 2 for flushing, and the temperature of the cracking reactor is lowered to 340° C.;

[0026] (3) Flushing the crude liquid wax No. 2 introduced into the isomerization cracking system in step (1), and converting the hydrogenation reaction system into a self-circulating system;

[0027] (4) The flushing of the crude liquid wax No. 2 of the system is completed, and the hydrogenation reaction system and the isomerization cracking system are changed to a larger circulation.

[0028] Preferably, in step (1), the feed temperature of the hydrogenation reaction system is gradually increased to 300°C, and the feed 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 lowered to 340°C for operation.

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

[0031] Preferably, in step (4), after the flushing of the crude liquid wax No. 2 in the system is completed, the hydrogenation reaction system and the isomerization cracking system are changed to a larger circulation.

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

[0033] The second aspect of the present invention provides a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation and isomerization cracking system, comprising: a hydrofining 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, and the hydrogenation protection reactor is connected to the hydrofining reactor, the high separation tank, the low separation tank, the flash tank, and the fractionation tower in sequence;

[0035] The crude liquid wax raw material tank is connected with the soft wax buffer tank, the cracking reactor, the high separation tank, the low separation tank, the flash tank and the fractionation tower in sequence.

[0036] In some embodiments, the distillation tower is connected to the stripping tower, the external air cooler, the raw paraffin tank or the soft wax buffer tank in sequence.

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

[0038] Beneficial Effects of the Invention

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

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

[0041] (3) The method of the present invention is simple, practical and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

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

[0044] Figure 2 151V001A: raw material condensate tank, 151V001B: raw material paraffin tank, 151R001: first hydrogenation protection reactor, 151R002: second hydrogenation refining reactor, 151V003: first high separation tank, 151V004: second high separation tank, 151V005: second low separation tank, 151V006: second high separation tank, 151V007: second high separation tank, 151V008: second low separation tank, 151V009: second high separation tank, 151V010: second high separation tank, 151V011: second high separation tank, 151V012: second high separation tank, 151V013: second high separation tank, 151V014: second high separation tank, 151V015: second high separation tank, 151V016: second high separation tank, 151V017: second high separation tank, 151V018: second high separation tank, 151V019: second high separation tank, 151V020: first high separation tank, 151V021: first high separation tank, 151V022: first high separation tank, 151V023: first high separation tank, 151V024: second high separation tank, 151V025: second high separation tank, 151V026: second high separation tank, 151V027: second high separation tank, 151V028: second high separation tank, 151V029: second high separation tank, 151V030: second high separation tank, 151V031: second high separation tank, 151V032: first high separation tank, 151V033: first low separation tank, 151V034: second high separation Division tanks, 151V011: flash tank, 151T001: distillation tower, 151T002: stripping tower, 151AE004: No. 2 external air cooler for crude liquid wax, 151E007: stripping tower reboiler, 151E003: distillation tower feed heat exchanger, 150E006B: stabilization tower reboiler, 151AE005: 1# soft wax air cooler, 151F001: heating furnace, TC: thermometer, PC: pressure gauge.

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

[0046] Figure 4 152R001: isomerization cracking reactor, 152V002: first high separation tank, 152V003: first low separation tank, 152V004: second high separation tank, 152V005: second low separation tank, 152V018: flash tank, 152T001: fractionation tower, 152T002: stripping tower, 152AE004: No. 2 air cooler for crude liquid wax delivery, 152V001: No. 2 soft wax buffer tank, 152E014: stripping tower reboiler, 152E003: fractionation tower feed heat exchanger, 152E012: naphtha stabilization tower reboiler, 152AE006: No. 2 soft wax air cooler, TC: thermometer, PC: pressure gauge. DETAILED DESCRIPTION

[0047] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0048] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0049] In the following embodiments, the settings and operations of the devices not specifically described may be routinely selected and configured by those skilled in the art based on common knowledge in the industry.

[0050] Example 1

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

[0052] Step (2): Lead crude liquid wax No. 2 to the device area. Send crude liquid wax No. 2 from the tank area of ​​the whole plant to the degassing pump in the intermediate tank area, and use the degassing pump to send it to the raw material condensate tank / raw material paraffin tank (151V001A / B tank), switch the reaction feed to crude liquid wax No. 2, reduce the circulation volume to 80t / h, stabilize the hydrogenation reactor system to flush crude liquid wax No. 2, circulate all 1# soft wax and 2# soft wax to 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: The inlet temperature of the hydrogenation protection reactor (151R001) was raised to 300°C.

[0054] Step (4): Temperature control of the distillation tower. The hydrogenation distillation tower (151T001) is cooled at a rate of ≯25°C / h until the temperature drops to about 280°C. The crude liquid wax No. 2 is only used to flush the oil for three high-pressure pumps and high-temperature pumps. After the crude liquid wax No. 2 is flushed for 1 hour, the 1# soft wax is delivered to the "degassing high and low temperature condensate 1# storage tank" (i.e., the intermediate tank area dirty oil tank) through the start-up light dirty oil process.

[0055] Step (5) The top of the hydrogenation fractionation tower 151T001 is fully refluxed, and a sample is taken to observe the solid content of the sample. If the sample is black, it needs to be replaced. If the top reflux is difficult to establish, some light naphtha is supplemented by starting the gasoline line.

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

[0057] Step (7) The feed rate of the isomerization cracking system is reduced from 110 t / h to 80 t / h, and the hydrogen-oil ratio is maintained at 700. After the system changes to the crude liquid wax No. 2 feed (80 t / h), observe the pressure difference change, and then gradually increase the hydrogen-oil ratio to observe the pressure difference change (that is: the hydrogen-oil ratio is normally controlled at 850, and the maximum increase during flushing is 1300). Observe the pressure difference of the cracking reactor. After changing to the crude liquid wax No. 2 flushing, if the pressure difference of the first bed rises too fast, immediately stop flushing the crude liquid wax No. 2. Observe the pressure difference change after feeding the crude liquid wax No. 2, and then increase the hydrogen-oil ratio to observe the pressure difference change. Take 2# soft wax every half an hour to observe the solid content (keep samples for solid content analysis). Increase the 2# soft wax to be thrown out to the temperature index of the intermediate tank area of ​​130°C. The switching conditions for externally swinging to the paraffin tank #1 and the degassing tank #1 are determined based on the freezing point of the 2# soft wax and the flash evaporation volume of the breathing valve on the top of the paraffin tank #1 (i.e., switching is performed based on the breathing volume on the top of the storage tank. As the flushing time increases, the light oil in the system increases and is sent to the paraffin tank #1, and the exhaust gas from the top breathing valve increases, and the system switches to the degassing tank #1. Those skilled in the art can make conventional choices based on actual working conditions, and the present invention does not make any special limitation to this).

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

[0059] In step (9), when the liquid level of the cracking fractionation system rises due to the cooling of the cracking reactor, part of the heavy oil can be dumped into the paraffin 1# tank (system external equipment) through the 2# soft wax dumping process;

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

[0061] After the hydrogenation reaction system in step (11) switches to feed crude liquid wax No. 2, the isomerization cracking reactor begins to cool down until the temperature drops to 340°C, and the crude liquid wax No. 2 in the tank area is transferred to the 2# soft wax buffer tank (152V001).

[0062] Step (12) 2# soft wax begins to be dumped out to "degassed high and low temperature condensate tank 1#", and crude liquid wax 2# is circulated to 2# soft wax buffer tank 152V001.

[0063] In step (13), the absorption and analysis system is operated according to normal indicators. If the naphtha is unqualified due to insufficient heat in the bottom reboiler, the naphtha is transferred to the intermediate tank area.

[0064] The actual production situation shows that after flushing, the total pressure difference of the system is reduced by 0.2MPa on the original basis. After operation, it takes about 45-50 days for the system pressure difference to rise to the pressure before flushing again.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor, characterized in that: include: The feed amount is gradually reduced 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; Switching the hydrogenation reaction system to crude liquid wax for flushing; Switching the crude liquid wax to the isomerization cracking reaction system for flushing; After flushing is completed, the hydrogenation reaction system and isomerization cracking system are changed to larger circulation; Restart feeding, gradually increase the load, and produce qualified products.

2. The method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor according to claim 1, characterized in that: During the large cycle 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, and the feed temperature of the isomerization cracking reaction system is gradually reduced to 360-365°C.

3. The method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor according to claim 1, characterized in that: When the hydrogenation reaction system switches to the crude liquid wax for flushing, the temperature of the cracking reactor is reduced to 340-345° C. for operation.

4. The method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor according to claim 1, characterized in that: During the isomerization cracking reaction system switching to the crude liquid wax for flushing, the hydrogenation system is changed to self-circulation.

5. The method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor according to claim 1, characterized in that: The light crude liquid wax is sent from the fractionating tower to the stripping tower, and then to the external air cooler, and then enters the raw paraffin tank for recycling.

6. The method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor according to claim 1, characterized in that: 1# soft wax enters the intermediate tank area from the distillation tower through the stripping tower reboiler, distillation tower feed heat exchanger, stabilization tower reboiler, and soft wax air cooler.

7. The method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor according to claim 1, characterized in that: The heavy crude liquid wax is sent from the stripping tower to the external air cooler and enters the 2# soft wax buffer tank.

8. The method for reducing the pressure difference of a low-temperature Fischer-Tropsch synthesis oil conversion hydrogenation reactor according to claim 1, characterized in that: The 2# soft wax enters the intermediate tank area from the distillation tower through the stripping tower reboiler, the distillation tower feed heat exchanger, the stabilization tower reboiler, and the soft wax air cooler.

9. A low-temperature Fischer-Tropsch synthesis oil conversion hydrocracking system, characterized in that: include: Hydrotreating reactors, fractionating towers, cracking reactors; The raw material condensate tank and the raw material paraffin tank are respectively connected to the hydrogenation protection reactor, and the hydrogenation protection reactor is connected to the hydrofining reactor, the high separation tank, the low separation tank, the flash tank, and the fractionation tower in sequence; The crude liquid wax raw material tank is connected with the soft wax buffer tank, the cracking reactor, the high separation tank, the low separation tank, the flash tank and the fractionation tower in sequence.

10. The low-temperature Fischer-Tropsch synthesis oil conversion hydrocracking system according to claim 8, characterized in that: The fractionating tower is connected with the stripping tower, the external air cooler, the raw material paraffin tank or the soft wax buffer tank in sequence; Alternatively, the fractionation tower is also connected to a stripping tower reboiler, a fractionation tower feed heat exchanger, a stabilization tower reboiler, a soft wax air cooler, and an intermediate tank area in sequence.

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