Shift catalyst passivation system and method for an adiabatic fixed bed

Abstract

This invention discloses a passivation system and method for a thermocouple in an adiabatic fixed bed. The system includes a first shift converter, with a first low-pressure nitrogen gas introduced at its inlet; an ammonia scrubbing tower inlet connected to the outlet of the first shift converter; a second circulating fan inlet connected to the outlet of the ammonia scrubbing tower, and its outlet connected to the inlet of a circulating nitrogen heater, the outlet of which is connected to the inlet of the first shift converter. By adjusting the circulating nitrogen heater, the temperature of the second low-pressure nitrogen gas can be adjusted, making the inlet temperature of the first shift converter adjustable and using less nitrogen to complete the passivation reaction. The second circulating fan ensures a more uniform temperature distribution within the first shift converter, preventing overheating during catalyst unloading.

Description

Technical Field

[0001] This invention relates to the field of methanol technology in coal chemical industry, and in particular to a passivation system and method for a shift catalyst in an adiabatic fixed bed. Background Technology

[0002] Whether it's coal-water slurry gasification or pulverized coal gasification, the crude syngas produced mainly consists of carbon monoxide, hydrogen, carbon dioxide, hydrogen sulfide, and methane. It generally needs to undergo a shift reaction to adjust the hydrogen-to-carbon ratio before being sent to downstream units to produce different chemicals, such as methanol. In the shift process, depending on the requirements of subsequent processes, one, two, or three shift reactors are typically installed to achieve the shift reaction of carbon monoxide in the crude syngas, yielding shift gas with hydrogen as the main component. The shift catalyst is generally a wide-temperature, sulfur-resistant cobalt-molybdenum catalyst, with the active components being sulfided cobalt and molybdenum. Due to its high activity, it reacts violently upon contact with air, releasing a large amount of heat and causing a rapid temperature rise, posing a fire and explosion hazard. Therefore, the shift catalyst needs to be passivated before shutdown and unloading.

[0003] During passivation, the highly active cobalt-molybdenum catalyst undergoes an oxidation reaction upon contact with air, releasing a large amount of heat and causing the bed temperature to rise rapidly, even exceeding 500°C. This rapid temperature increase adversely affects equipment operation. At this point, it is necessary to reduce the amount of air supplied and increase the amount of nitrogen used to reduce the oxygen concentration and thus lower the reaction rate, making the bed temperature controllable. The passivation process is lengthy and consumes a large amount of nitrogen. To conserve nitrogen, a cyclic passivation method is generally used. During cyclic passivation, a certain flow rate of air is maintained. If a rapid temperature rise is observed, even if the air supply is stopped, the system still contains a large amount of oxygen, which can still cause the bed temperature to rise rapidly. Therefore, controlling the bed temperature to prevent a rapid increase becomes a key challenge in the cyclic passivation process of cobalt-molybdenum catalysts. To reduce the pressure drop in the bed of the first converter, most first converters adopt axial-radial converters. The nitrogen flow rate used for passivation is relatively small, which makes it easy for the flow to be biased during the passivation process. This makes the upper part easy to passivate, while the bottom catalyst is not completely passivated, resulting in uneven passivation. When unloading, there is still a problem of oxidation and heat generation after contact with air. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] In view of this, the present invention provides a passivation system and method for a thermally adiabatic fixed bed catalyst, wherein the passivation system can adjust the temperature of the second low-pressure nitrogen by adjusting the circulating nitrogen heater, making the inlet temperature of the first converter adjustable, accelerating the passivation in the first converter, using less nitrogen to complete the passivation reaction, and avoiding easy flow deviation during the passivation process; the setting of the second circulating fan can make the temperature distribution in the first converter more uniform, avoiding the problem of overheating during unloading.

[0006] Specifically, the following technical solutions are included: An embodiment of a first aspect of the present invention provides a shift catalyst passivation system in an adiabatic fixed bed, the shift catalyst passivation system comprising: A first converter furnace, wherein a first low-pressure nitrogen gas is introduced into the inlet of the first converter furnace; An ammonia washing tower, the inlet of which is connected to the outlet of the first converter; The second circulating fan has its inlet connected to the outlet of the ammonia washing tower, its outlet connected to the inlet of the circulating nitrogen heater, and its outlet connected to the inlet of the first converter. The second circulating fan and the circulating nitrogen heater are also connected to a second low-pressure nitrogen and compressed air.

[0007] Optionally, the shift catalyst passivation system further includes: The first cooler has its inlet connected to the outlet of the first converter, its outlet connected to the inlet of the first circulating fan, and the outlet of the first circulating fan connected to the inlet of the first converter.

[0008] Optionally, the shift catalyst passivation system further includes a low-pressure steam superheater, a low-pressure waste boiler, a first separator, a low-pressure waste boiler, a second separator, a second cooler, and a third cooler, which are sequentially arranged between the outlet of the first shift furnace and the ammonia washing tower, and the low-pressure waste boiler is fed by a low-pressure boiler.

[0009] Optionally, the shift catalyst passivation system further includes a second shift furnace connected in series with the first shift furnace; The shift catalyst passivation system also includes a second shift furnace and a third shift furnace connected in series with the first shift furnace.

[0010] Optionally, when the first converter is connected in series with the second converter, the inlet of the second converter is connected to the outlet of the first converter, and the outlet of the second converter is connected to the inlet of the low-pressure waste boiler. The inlet of the second converter is also connected to the outlet of the circulating nitrogen heater.

[0011] Optionally, a medium-pressure steam superheater, a low-pressure steam superheater, and a medium-pressure waste boiler are sequentially provided between the first converter and the second converter.

[0012] Optionally, the low-pressure boiler feedwater passes through the low-pressure waste boiler and exchanges heat with the shift gas of the second shift furnace to generate low-pressure steam. The low-pressure steam enters the low-pressure steam superheater and is then superheated with the shift gas of the medium-pressure steam superheater to become low-pressure hot steam, which is then sent to the low-pressure steam pipeline network. Medium-pressure boiler feedwater enters the medium-pressure waste boiler and exchanges heat with the shift gas entering the low-pressure steam superheater to generate medium-pressure steam. The medium-pressure steam enters the medium-pressure steam superheater and is superheated with the shift gas of the first shift furnace to become medium-pressure superheated steam 17, which is then sent to the medium-pressure steam pipeline network.

[0013] Optionally, when the shift catalyst passivation system further includes a second shift furnace and a third shift furnace connected in series with the first shift furnace, the third shift furnace is disposed between the first separator and the low-pressure waste boiler, and the inlet of the third shift furnace is also connected to the outlet of the circulating nitrogen heater.

[0014] A second aspect of the present invention provides a method for passivating a shift catalyst in an adiabatic fixed bed, utilizing the aforementioned shift catalyst passivation system. The method includes the following steps: Nitrogen gas is supplied to the first converter by a first low-pressure nitrogen gas set at the inlet of the first converter. The second low-pressure nitrogen gas is used to replenish the nitrogen gas in the first converter furnace through a circulating nitrogen heater; The temperature of the second low-pressure nitrogen is adjusted based on the temperature of the superheated steam in the circulating nitrogen heater. Based on the changing temperature of the second low-pressure nitrogen, the temperature at the inlet of the first shift furnace is adjusted to achieve passivation of the shift catalyst.

[0015] Optionally, after the passivation of the shift catalyst is completed, the shift catalyst passivation method further includes system cooling, which includes the following steps: Turn off the circulating nitrogen heater and turn on the second circulating fan; Increase the amount of low-pressure nitrogen entering the first converter to reduce the bed temperature of the first converter; The second circulating fan is turned off, and compressed air or second low-pressure nitrogen is introduced to lower the bed temperature of the first converter to room temperature for unloading.

[0016] The present invention provides an adiabatic fixed-bed catalyst passivation system and method. The passivation system includes a first low-pressure nitrogen gas directly introduced into a first converter to achieve basic passivation of the catalyst within the first converter. Through the sequential connection of the first converter, ammonia washing tower, second circulating fan, and circulating nitrogen heater, the second low-pressure nitrogen gas between the second circulating fan and the circulating nitrogen heater is recycled, saving nitrogen consumption and operating costs. During the circulation of the first and second low-pressure nitrogen gases, the circulating nitrogen heater adjusts the internal steam temperature, making the bed inlet temperature of the second circulating nitrogen gas in the first converter adjustable, accelerating passivation within the first converter and preventing flow deviation during passivation. The second circulating fan ensures a more uniform temperature distribution within the first converter, preventing the catalyst from overheating upon contact with air during unloading.

[0017] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a shift catalyst passivation system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a shift catalyst passivation system according to another embodiment of the present invention; Figure 3 This is a schematic diagram of a shift catalyst passivation system according to yet another embodiment of the present invention.

[0020] in, Figures 1 to 3 The correspondence between the reference numerals and component names in the attached drawings is as follows: 1. Crude syngas, 2. First low-pressure nitrogen, 3. Second low-pressure nitrogen, 4. Compressed air, 9. Preheater, 10. First converter, 11. First cooler, 12. First circulating fan, 13. Medium-pressure steam superheater, 14. Low-pressure steam superheater, 15. Medium-pressure waste boiler, 15-1. Medium-pressure waste boiler feed line, 16. Medium-pressure boiler feedwater, 17. Medium-pressure superheated steam, 20. Second converter, 30. Low-pressure waste boiler, 31. Low-pressure boiler feedwater, 32. Low-pressure superheated steam, 40. First separator, 41. First condensate, 45. Third converter, 50. Low-pressure waste boiler, 60. Second separator, 61. Second condensate, 62. Second cooler, 63. Second cooler, 70. Ammonia scrubbing tower, 71. Third condensate, 72. Ammonia scrubbing converter gas, 73. Nitrogen vent, 74. Second circulating fan, 75. Circulating nitrogen heater. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Before providing a further detailed description of the embodiments of the present invention, the directional terms used in the embodiments of the present invention, such as "upper part", "lower part" and "side part", are not intended to limit the scope of protection of the present invention.

[0023] To make the technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0024] Figure 1 This is a schematic diagram of a catalyst passivation system according to an embodiment of the present invention.

[0025] like Figure 1 As shown, one embodiment of the present invention provides a shift catalyst passivation system in an adiabatic fixed bed, the shift catalyst passivation system further comprising: First converter 10, first low-pressure nitrogen gas 2 is introduced into the inlet of the first converter 10; Ammonia washing tower 70, the inlet of which is connected to the outlet of the first converter 10; The inlet of the second circulating fan 74 is connected to the outlet of the ammonia washing tower 70, the outlet of the second circulating fan 74 is connected to the inlet of the circulating nitrogen heater 75, and the outlet of the circulating nitrogen heater 75 is connected to the inlet of the first converter 10. The second circulating fan 74 and the circulating nitrogen heater 75 are also connected to a second low-pressure nitrogen 3 and a compressed air 4.

[0026] The catalyst passivation system includes a first low-pressure nitrogen gas 2 directly introduced into the first converter 10 to achieve basic passivation of the catalyst within the converter 10. Through the sequential connection of the first converter 10, ammonia washing tower 70, second circulating fan 74, and circulating nitrogen heater 75, the second low-pressure nitrogen gas 3 between the second circulating fan 74 and the circulating nitrogen heater 75 is circulated, saving nitrogen consumption and operating costs. During the circulation of the first low-pressure nitrogen gas 2 and the second low-pressure nitrogen gas 3, the circulating nitrogen heater 75 adjusts the internal steam temperature, making the bed inlet temperature of the second circulating nitrogen gas in the first converter 10 adjustable, accelerating passivation within the converter 10 and preventing flow deviation during passivation. The second circulating fan 74 ensures a more uniform temperature distribution within the first converter 10, preventing the catalyst from overheating upon contact with air during unloading.

[0027] It should be noted that a circulating nitrogen heater 75 is provided during the passivation process, which can be heated with steam at 4.1 MPa (G) and a temperature of 380°C to 430°C. The bed inlet temperature of the first converter 10 is adjustable within the range of 150°C to 300°C. Alternatively, the circulating nitrogen heater 75 can also be heated with steam at 1.1 MPa (G) and a temperature of 280°C to 320°C. The bed inlet temperature of the first converter 10 is adjustable within the range of 150°C to 250°C.

[0028] It is understandable that the preheater 9 is located between the crude syngas 1 and the inlet of the first converter 10. The outlet of the first converter 10 is connected to the inlet of the preheater 9. The preheater 9 preheats the crude syngas entering the first converter 10, which helps the subsequent process. This step is unrelated to passivation and will not be described in detail.

[0029] In one feasible implementation, the catalyst passivation system further includes: The first cooler 11 has its inlet connected to the outlet of the first converter 10, its outlet connected to the inlet of the first circulating fan 12, and its outlet connected to the inlet of the first converter 10.

[0030] The first converter 10 is equipped with a first cooler 11 and a first circulating fan 12 at its outlet. The outlet of the first circulating fan 12 is reconnected to the inlet of the first converter 10. By adjusting the flow rates of the first cooler 11, the first low-pressure nitrogen 2, and the second low-pressure nitrogen 3, the bed temperature of the first converter 10 can be suppressed from rising too quickly. At the same time, the nitrogen discharged from the outlet of the first converter 10 and the small amount of unreacted oxygen therein are sent back into the first converter 10 by turning on the first circulating fan 12, so that the small amount of oxygen is further utilized, the passivation time of the conversion catalyst is shortened, and the efficiency is improved.

[0031] It should be noted that the first converter 10 is usually an axial-radial converter, equipped with a first cooler 11 and a first circulating fan 12 to increase the flow rate of circulating nitrogen. This makes the temperature distribution inside the first converter 10 more uniform, so that the converter catalyst at the bottom of the first converter 10 can also be fully passivated, avoiding the problem of the converter catalyst still being exposed to air and generating heat when unloading.

[0032] In one feasible implementation, the catalyst passivation system further includes a low-pressure steam superheater 14, a low-pressure waste boiler 30, a first separator 40, a low-pressure waste boiler 50, a second separator 60, a second cooler 62, and a third cooler 63, which are sequentially arranged between the outlet of the first converter 10 and the ammonia washing tower 70. The low-pressure waste boiler 30 is fed by a low-pressure boiler feedwater 31.

[0033] During normal production, the process is as follows: the shift gas from the first shift reactor 10 passes through the low-pressure steam superheater 14 and enters the low-pressure waste boiler 30. The low-pressure waste boiler 30 then enters the first separator 40, and the first condensate 41 produced by the first separator 40 is sent to the condensate system for recycling. The shift gas in the first separator 40 passes through the low-pressure waste boiler 50 and then enters the second separator 60. The second condensate 61 produced by the second separator 60 is sent to the condensate system for recycling. The shift gas in the second separator 60 is cooled by the second cooler 62 and the third cooler 63 and then enters the ammonia washing tower 70. The third condensate 71 produced by the ammonia washing tower 70 is sent to the condensate recovery system for utilization. The ammonia washing shift gas 72 produced by the ammonia washing tower 70 is sent to the downstream acid gas removal unit for methanol synthesis. During passivation, the first low-pressure nitrogen 2 and the second low-pressure nitrogen 3 are added to the passivation system. At least one medium-low pressure nitrogen can be selected. Excess nitrogen in the shift catalyst passivation system is discharged through the exhaust port of the ammonia washing tower 70 to balance the pressure of the shift catalyst passivation system.

[0034] It should be noted that the low-pressure boiler feedwater 31 passes through the low-pressure waste boiler 30 and exchanges heat with the heat generated during the passivation process. The resulting saturated steam passes through the low-pressure steam superheater 14 to form low-pressure superheated steam 32, which is then sent to the low-pressure steam network. The first separator 40 and the second separator 60 can separate the small amount of water carried out by nitrogen from the conversion catalyst during the passivation process. The third cooler 63 is used to achieve heat classification, allowing subsequent gases and / or liquids to be cooled to ambient temperature for easy subsequent utilization and use. The low-pressure boiler feedwater 31 passes through the low-pressure waste boiler 30 and exchanges heat with the heat generated during the passivation process. The resulting saturated steam passes through the low-pressure steam superheater 14 to form low-pressure superheated steam 32, which is then sent to the low-pressure steam network.

[0035] In one feasible embodiment, the shift catalyst passivation system further includes a plurality of second shift furnaces 20 connected in series with the first shift furnace 10; or The shift catalyst passivation system also includes a second shift furnace 20 and a third shift furnace 45 connected in series with the first shift furnace 10.

[0036] It should be noted that the second converter 20 can be passivated in series with the first converter 10, or in parallel. Specifically, a portion of the nitrogen from the circulating nitrogen heater 75 can be introduced to the inlet of the second converter 20, allowing for more flexible passivation methods. In series passivation, nitrogen and compressed air are used to passivate the first converter 10 first, followed by passivation of the catalyst in the second converter 10. Because the first converter 10 consumes a large amount of oxygen from the compressed air during catalytic passivation, its catalyst passivation time is shortened. However, the oxygen concentration at the inlet of the second converter 20 is lower, resulting in a lower bed temperature and a longer passivation time. In parallel passivation, nitrogen and compressed air are simultaneously introduced into both the first and second converters. Due to the higher oxygen concentration at the inlet of the second converter 20, its catalyst passivation time can be shortened. During passivation, because the first converter 10 has a larger catalyst loading, series passivation is initially used, with parallel passivation possible later.

[0037] Understandably, a second converter 20 can be set up, connected in series or parallel with the first converter 10. Similarly, the bed inlet temperature of the second converter 20 can be adjusted by the circulating nitrogen heater 75 to suppress the bed temperature of the second converter 20 from rising too quickly, thus ensuring the reliability and safety of the catalyst passivation system. At the same time, the second circulating fan 74 can make the distribution of catalysts in each converter more uniform, avoiding the problem of overheating during unloading.

[0038] Figure 2 This is a schematic diagram of a shift catalyst passivation system according to another embodiment of the present invention.

[0039] In one feasible implementation, as shown in Figure 2, when the first converter 10 is connected in series with the second converter 20, the inlet of the second converter 20 is connected to the outlet of the first converter 10, and the outlet of the second converter 20 is connected to the inlet of the low-pressure waste boiler 30. The inlet of the second converter 20 is also connected to the outlet of the circulating nitrogen heater 75.

[0040] The inlet of the second converter 20 is connected in series with the circulating nitrogen heater 75 and the second circulating fan 74. This is the same as adjusting the bed inlet temperature of the first converter 10. By adjusting the steam temperature inside the circulating nitrogen heater 75, the bed inlet temperature of the second circulating nitrogen in the second converter 20 is adjustable, which accelerates the catalyst passivation in the second converter 20 and avoids easy flow deviation during the passivation process.

[0041] It should be noted that, due to the use of the first circulating fan 12, the oxygen in the circulating nitrogen at the outlet of the first converter 10 can be further utilized, thereby reducing the oxygen content entering the second converter 20. This is beneficial for adjusting the bed temperature of the second converter 20 during the initial and middle stages of passivation.

[0042] Furthermore, by adjusting the opening degree of the medium-pressure waste heat boiler auxiliary line 15-1 before the second converter 20, the temperature and circulating nitrogen flow rate are adjusted to suppress the excessively rapid rise in the bed temperature of the second converter 20, ensuring the stability and safety of the catalyst passivation system. The inlet of the medium-pressure waste heat boiler auxiliary line 15-1 is located between the outlet of the low-pressure steam superheater 14 and the inlet of the medium-pressure waste heat boiler 15, and the outlet of the medium-pressure waste heat boiler auxiliary line 15-1 is connected between the outlet of the medium-pressure waste heat boiler 15 and the inlet of the second converter 20. In one feasible implementation, a medium-pressure steam superheater 13, a low-pressure steam superheater 14, and a medium-pressure waste boiler 15 are sequentially provided between the first converter 10 and the first second converter 20.

[0043] Among them, the low-pressure boiler feedwater 31 passes through the low-pressure waste boiler 30 and exchanges heat with the change gas of the second change furnace 20 to generate low-pressure steam. The low-pressure steam enters the low-pressure steam superheater 14 and then is superheated with the change gas of the medium-pressure steam superheater 13 to become low-pressure hot steam and is sent to the low-pressure steam pipeline network. Medium-pressure boiler feedwater 16 enters medium-pressure waste boiler 15 and exchanges heat with the shift gas entering low-pressure steam superheater 14 to generate medium-pressure steam. The medium-pressure steam enters medium-pressure steam superheater 13 and is superheated with the shift gas of first shift furnace 10 to become medium-pressure superheated steam 17, which is then sent to medium-pressure steam pipeline network.

[0044] Specifically, taking a first converter 10 and a second converter 20 connected in series as an example, the following explanation is provided. The crude syngas 1, after passing through preheater 9, and the converted gas from the outlet of the first converter 10, after passing through preheater 9, enter the first converter 10 together. After contacting the conversion catalyst in the first converter 10 and undergoing a conversion reaction, it sequentially passes through a medium-pressure steam superheater 13, a low-pressure steam superheater 14, and a medium-pressure waste boiler 15 before entering the second converter 20. In the second converter 20, it contacts the conversion catalyst and undergoes a conversion reaction. After passing through the low-pressure waste boiler 30, it enters the first separator 40. The first condensate 41 produced in the first separator 40 is sent to the condensate system for recycling. The converted gas in the first separator 40 passes through the low-pressure waste boiler 50 and enters the second separator 60. The second condensate 61 produced in the second separator 60 is sent to the condensate system for recycling. The shifted gas in the second separator 60 is cooled by the second cooler 62 and then enters the ammonia washing tower 70. The third condensate 71 produced in the ammonia washing tower 70 is sent to the condensate system for recycling, and the ammonia washing shifted gas 72 in the ammonia washing tower 70 is sent to downstream units. The low-pressure boiler feedwater 31 generates low-pressure steam after heat exchange with the shifted gas in the low-pressure waste boiler 30. The low-pressure steam is superheated by the low-pressure steam superheater 14 and the medium-pressure steam superheater 13, becoming low-pressure superheated steam 32, which is sent to the low-pressure steam network. The medium-pressure steam superheater 13 superheats the shifted gas from the first converter 10, becoming medium-pressure superheated steam 17, which is sent to the medium-pressure steam network. The medium-pressure saturated steam from the medium-pressure waste boiler 15 enters the medium-pressure steam superheater 13 and is connected to the medium-pressure network.

[0045] The system includes a first low-pressure nitrogen gas 2 before entering the first converter 10. This nitrogen gas is used to replace the passivation system during shutdown or startup. When unloading the catalyst during shutdown, passivation is required. A first cooler 11 and a first circulating fan 12 are installed at the outlet of the first converter 10, with the outlet of the first circulating fan 12 connected to the inlet of the first converter 10. A second circulating fan 74 and a circulating nitrogen heater 75 are installed at the outlet of the ammonia scrubbing tower 70. A second low-pressure nitrogen gas 3 is supplied at the inlet of the circulating nitrogen heater 75 for replenishment. Excess nitrogen is discharged through a nitrogen outlet 73 to balance the pressure of the catalyst passivation system. When the catalyst passivation system requires additional nitrogen for passivation, this can be achieved by supplying either the first low-pressure nitrogen gas 2 before the first converter 10 or the second low-pressure nitrogen gas 3 before the circulating nitrogen heater 75. The circulating nitrogen heater 75 is equipped with superheated steam at 4.1 MPa (G) and a temperature ranging from 380°C to 430°C to adjust the temperature of the circulating nitrogen. During passivation, the inlet temperature of the first converter 10 is gradually increased by adjusting the 4.1 MPa (G) steam flow rate and the circulating nitrogen flow rate of the circulating nitrogen heater 75, achieving an adjustable inlet temperature within the range of 300°C. Alternatively, the circulating nitrogen heater 75 can use superheated steam at 1.1 MPa (G) and a temperature ranging from 280°C to 320°C, and the inlet temperature of the first converter 10 is gradually increased by adjusting the steam flow rate and the circulating nitrogen flow rate, achieving an adjustable inlet temperature within the range of 250°C. The outlet of the circulating nitrogen heater 75 is also connected to the inlet of the second converter 20. During the passivation process of the second converter 20, the inlet temperature of the second converter 20 is gradually increased by adjusting the 4.1 MPa (G) steam flow rate of the circulating nitrogen heater 75, achieving an adjustable inlet temperature within the range of 320°C. A medium-pressure waste boiler 15 is provided in front of the second converter 20. The medium-pressure waste boiler 15 is provided with a medium-pressure waste boiler auxiliary line 15-1. The inlet temperature of the second converter 20 can be further increased or decreased by adjusting the opening of the auxiliary line 15-1.

[0046] It should be noted that when cooling is required after passivation, the circulating nitrogen heater 75 is shut down. The circulating nitrogen entering the first converter 10 is increased using the second circulating air and the first circulating fan 12, thus lowering the bed temperature of the first converter 10. Similarly, the circulating nitrogen in the second converter 20 is increased using the second circulating fan 74, further lowering the bed temperature of the second converter 20. Finally, the second circulating fan 74 and the first circulating fan 12 are shut down, and compressed air 4 or second low-pressure nitrogen 3 (first low-pressure nitrogen 2) is introduced, allowing both the first converter 10 and the second converter 20 to cool to room temperature, facilitating unloading.

[0047] Figure 3 This is a schematic diagram of a shift catalyst passivation system according to yet another embodiment of the present invention.

[0048] In one feasible implementation, such as Figure 3 As shown, when the catalyst passivation system also includes a second converter 20 and a third converter 45 connected in series with the first converter 10, the third converter 45 is located between the first separator 40 and the low-pressure waste boiler 50, and the inlet of the third converter 45 is also connected to the outlet of the circulating nitrogen heater 75.

[0049] The 1.1 MPa (G) circulating nitrogen superheater 75 allows for adjustable inlet temperatures of both the second converter 20 and the third converter 45 within a range of 250°C. When multiple converters are connected in series, the third converter 45 is further regulated by a low-pressure waste heat boiler 30 connected to the second converter 20. Other principles are as described above and will not be repeated here.

[0050] One embodiment of the present invention provides a method for passivating a shift catalyst in an adiabatic fixed bed. Utilizing the aforementioned shift catalyst passivation system, the method includes the following steps: Nitrogen gas is supplied to the first converter furnace by using a first low-pressure nitrogen gas set at the inlet of the first converter furnace. The second low-pressure nitrogen gas is used to replenish the nitrogen gas in the first converter furnace through a circulating nitrogen heater; The temperature of the second low-pressure nitrogen is adjusted based on the temperature of the superheated steam in the circulating nitrogen heater. Based on the changing temperature of the second low-pressure nitrogen gas, the temperature at the inlet of the first shift furnace is adjusted to achieve passivation of the shift catalyst.

[0051] A first low-pressure nitrogen gas 2 is introduced before entering the first converter 10 to purge the catalyst passivation system during shutdown or startup. Passivation of the catalyst is required during shutdown and catalyst unloading. A first cooler 11 and a first circulating fan 12 are installed at the outlet of the first converter 10, with the outlet of the first circulating fan 12 connected to the inlet of the first converter 10. A second circulating fan 74 and a circulating nitrogen heater 75 are installed at the outlet of the ammonia scrubbing tower 70. A second low-pressure nitrogen gas 3 is supplied at the inlet of the circulating nitrogen heater 75 for replenishment. Excess nitrogen is discharged through a nitrogen outlet 73 to balance the pressure of the catalyst passivation system. When the catalyst passivation system requires nitrogen replenishment, it can be achieved through the first low-pressure nitrogen gas 2 before the first converter 10 or the second low-pressure nitrogen gas 3 before the circulating nitrogen heater 75. The circulating nitrogen heater 75 is equipped with superheated steam at 4.1 MPa (G) and a temperature of 380°C to 430°C to adjust the temperature of the circulating nitrogen. During the passivation process, the inlet temperature of the first converter 10 is gradually increased by adjusting the 4.1 MPa (G) steam flow rate and the circulating nitrogen flow rate of the circulating nitrogen heater 75, achieving an adjustable inlet temperature of the first converter 10 within a range of 300°C. Alternatively, the circulating nitrogen heater 75 can use superheated steam at 1.1 MPa (G) and a temperature of 280°C to 320°C, and the inlet temperature of the first converter 10 can be gradually increased by adjusting the steam flow rate and the circulating nitrogen flow rate, achieving an adjustable inlet temperature of the first converter 10 within a range of 250°C.

[0052] In one feasible implementation, after the passivation of the shift catalyst is completed, the shift catalyst passivation method further includes system cooling, which includes the following steps: Turn off the circulating nitrogen heater and turn on the second circulating fan; Increase the amount of low-pressure nitrogen entering the first converter to reduce the bed temperature of the first converter; Turn off the second circulating fan and introduce compressed air or second low-pressure nitrogen to lower the bed temperature of the first converter to room temperature for unloading.

[0053] When passivation is complete and cooling is required, the circulating nitrogen heater 75 is shut down. The circulating nitrogen entering the first converter furnace 10 is increased by relying on the second circulating air and the first circulating fan 12, thereby lowering the bed temperature of the first converter furnace 10. Finally, the second circulating fan 74 and the first circulating fan 12 are shut down, and compressed air 4 or second low-pressure nitrogen 3 (first low-pressure nitrogen 2) is introduced, allowing the first converter furnace 10 to cool to room temperature, facilitating unloading.

[0054] Example 1 This embodiment uses a first converter 10 connected in series with a second converter 20 as an example for specific explanation.

[0055] When the converters are shut down, the bed temperatures of the first converter 10 and the second converter 20 are reduced to 180°C using first and second nitrogen gases. The nitrogen circulation rate is 20,000 Nm³ / h to 40,000 Nm³ / h. At this time, compressed air is introduced at a rate of 200 Nm³ / h to 1,000 Nm³ / h, and the oxygen concentration in the compressed air 4 at the inlet of the first converter 10 is measured to be 0.1% to 1%. As the compressed air 4 is continuously introduced, the oxygen concentration increases continuously. The converter catalyst reacts with the compressed air 4, and the temperature inside the first converter 10 rises rapidly, with the bed temperature increasing to 250°C to 400°C. At this point, the flow rate of compressed air 4 is reduced to lower the oxygen concentration and slow down the intensity of the reaction inside the first converter 10. The circulation rate of the second low-pressure nitrogen 3 is increased so that the heat generated during the passivation process is continuously carried away by the nitrogen. In the initial passivation stage, the circulating nitrogen gas from the outlet of the first converter 10 is cooled to 30°C to 50°C by the first cooler 11 and then enters the first circulating fan 12. The first circulating fan 12 is adjusted to maintain a low circulating nitrogen flow rate (2000 Nm³ / h to 15000 Nm³ / h) for circulation. Returning to the inlet of the first converter 10 lowers the inlet temperature, thereby adjusting the bed temperature. It should be noted that in the initial passivation stage, the circulating nitrogen heater 75 does not need to be supplied with 4.1 MPa (G) steam. The catalyst in the first converter 10 has high activity and can undergo a passivation reaction upon encountering oxygen in the compressed air, releasing heat.

[0056] After the bed temperature stabilized, the inlet temperature of the first converter 10 was gradually increased to 250°C for deep passivation by increasing the steam flow rate of the circulating nitrogen heater 75 to 4.1 MPa (G). As the inlet temperature of the first converter 10 increased, the heat generated by the passivation reaction increased, causing the bed temperature to rise rapidly. Then, the compressed air flow rate 4 was reduced, the circulation rate of the first circulating fan 12 was increased to 40,000 Nm³ / h, and some circulating nitrogen and oxygen were released to reduce the oxygen concentration in the catalyst passivation system, thereby lowering the bed temperature of the first converter 10. The bed temperature of the first converter 10 reached a maximum of 450°C before decreasing. The first converter 10 is an axial-radial converter. Due to the significant increase in the circulating nitrogen flow, the catalyst passivation was more uniform during the passivation process, and the catalyst at the bottom was also effectively passivated. When the oxygen concentration in the circulating nitrogen at the inlet of the first converter 10 reaches 16% to 21%, and the oxygen concentration in the circulating nitrogen at the outlet of the first converter 10 is consistent with the oxygen concentration in the circulating nitrogen at the inlet of the first converter 10, the catalyst passivation process of the first converter 10 is completed.

[0057] During the passivation process, the shift catalyst in the first shift converter 10 comes into contact with oxygen, reducing the oxygen concentration. Then, after passing through the first circulating fan 12, the oxygen concentration entering the second shift converter 20 is further reduced, which is beneficial for regulating the bed temperature within the second shift converter 20. In the initial stage of passivation, the inlet temperature of the second shift converter 20 is maintained at 180℃ by adjusting the opening of the medium-pressure waste boiler 15 and its auxiliary line 15-1. To facilitate the adjustment of the inlet temperature of the second shift converter 20, the pressure of the medium-pressure waste boiler 15 is maintained below 0.5 MPa (G), and the liquid level in the medium-pressure waste boiler 15 is maintained at a normal level through the medium-pressure boiler feedwater 16. The catalyst in the second converter 20 undergoes a passivation reaction upon contact with oxygen. Due to the oxygen concentration in the circulating nitrogen entering the second converter 20, the oxygen concentration in the second converter 20 is reduced after being returned to the first converter 10 by the first circulating fan 12 for further reaction. The catalyst in the second converter 20 has high activity and releases a large amount of heat upon encountering oxygen, causing the bed temperature to rise to 300°C before decreasing. To prevent the temperature from rising too quickly, the flow rate of compressed air 4 is reduced, and the opening of the medium-pressure waste heat boiler 15-1 is closed. The medium-pressure waste heat boiler 15 is used to reduce the inlet temperature of the second converter 20, thereby lowering the bed temperature of the second converter 20. As the passivation process proceeds, it is necessary to adjust the opening of the medium-pressure waste boiler branch line 15-1 of the medium-pressure waste boiler 15 or the inlet pipeline of the second converter 20 via the circulating nitrogen heater 75, so that the inlet temperature of the second converter 20 gradually increases to 250°C. At this time, due to the increase in inlet temperature, the catalyst in the second converter 20 comes into contact with oxygen and reacts. After the temperature rises, the activity of the conversion catalyst is higher, and the reaction rate further increases, causing the bed temperature of the second converter 20 to rise to 300°C to 380°C. By significantly reducing the flow rate of compressed air 4 and closing the opening of the medium-pressure waste boiler branch line 15-1 of the medium-pressure waste boiler 15, the inlet temperature of the second converter 20 is reduced by the medium-pressure waste boiler 15 and some circulating nitrogen and oxygen are released, thereby causing the bed temperature of the second converter 20 to decrease. When the oxygen concentration in the circulating nitrogen at the inlet of the second converter 20 reaches 16% to 21%, and the oxygen concentration in the circulating nitrogen at the outlet of the second converter 20 is consistent with the oxygen concentration at the inlet of the second converter 20, the catalyst passivation process of the second converter 20 is complete. During passivation, the circulating nitrogen is introduced through the second low-pressure nitrogen 3. The second converter 20 can also be connected to the preheater 9 to increase the inlet temperature of the second converter; this is not involved in the passivation process and will not be described in detail.

[0058] After passivation, the shift catalyst in the first shift furnace 10 and the second shift furnace 20 is unloaded. After the unloaded shift catalyst is placed for three to five days, it still maintains the ambient temperature and there is no slow temperature rise, indicating that the passivation process is relatively thorough (if the shift catalyst is not completely passivated, it will still passivate and cause the temperature to rise when it encounters air during the unloading process).

[0059] Example 2 Unlike Example 1, a third converter 45 is provided after the second converter 20, and the third converter 45 is located between the second separator 40 and the low-pressure waste boiler 50. The third converter 45 is an adiabatic axial converter, and the outlet of the circulating nitrogen heater 75 is also connected to the inlet of the third converter 45. The inlet temperature of the third converter 45 is regulated by the low-pressure waste boiler 30 and the circulating nitrogen heater 75 to the inlet of the third converter 45. The temperature change of the bed in the first converter 10 and the second converter 20 during the passivation process is the same as in Example 1, and only the third converter 45 will be described here. The inlet temperature of the third converter 45 is regulated to 180°C by passing through the second cooler 62 and the third cooler 63 and then through the circulating nitrogen heater 75 to the inlet of the third converter 45. After circulating nitrogen passes through the first converter 10 and the second converter 20, the oxygen concentration in the circulating nitrogen further decreases, and the catalyst in the third converter 45 begins to passivate. As the passivation process in the first and second converters progresses, the oxygen concentration accumulated in the second converter 20 gradually increases with the continuous circulation of the passivation process. Therefore, the oxygen concentration in the circulating nitrogen entering the third converter 45 also continuously increases. After the catalyst in the third converter 45 reacts with the oxygen, the bed temperature continuously increases. The bed temperature in the third converter 45 is rapidly increased by reducing the amount of compressed air 4 introduced, opening the second and third coolers 62 and 63 before the circulating nitrogen enters the circulating nitrogen heater 75 to the third converter, and releasing circulating nitrogen and oxygen. The temperature can rise to 180°C to 250°C. When the inlet temperature of the third converter 45 gradually increases to 250°C, the bed temperature rises to 250°C to 350°C. When the oxygen concentration in the circulating nitrogen at the inlet of the third converter 45 reaches 16% to 21%, and the oxygen concentration in the circulating nitrogen at the outlet of the third converter 45 is consistent with the oxygen concentration in the circulating nitrogen at the inlet of the third converter 45, the catalyst passivation process of the third converter 45 is completed.

[0060] After passivation, the catalysts in the first converter 10, the second converter 20, and the third converter 45 were unloaded. After 3-5 days, the temperatures of the catalysts in the first converter 10, the second converter 20, and the third converter 45 remained at ambient temperature, and no slow temperature rise occurred.

[0061] In this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "a plurality" refers to two or more unless otherwise expressly defined.

[0062] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. The invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A passivation system for a shift catalyst in an adiabatic fixed bed, characterized in that, The shift catalyst passivation system includes: A first converter furnace, wherein a first low-pressure nitrogen gas is introduced into the inlet of the first converter furnace; An ammonia washing tower, the inlet of which is connected to the outlet of the first converter; The second circulating fan has its inlet connected to the outlet of the ammonia washing tower, its outlet connected to the inlet of the circulating nitrogen heater, and its outlet connected to the inlet of the first converter. The second circulating fan and the circulating nitrogen heater are also connected to a second low-pressure nitrogen and compressed air.

2. The adiabatic fixed-bed shift catalyst passivation system according to claim 1, characterized in that, The shift catalyst passivation system further includes: The first cooler has its inlet connected to the outlet of the first converter, its outlet connected to the inlet of the first circulating fan, and the outlet of the first circulating fan connected to the inlet of the first converter.

3. The adiabatic fixed-bed shift catalyst passivation system according to claim 2, characterized in that, The catalyst passivation system further includes a low-pressure steam superheater, a low-pressure waste boiler, a first separator, a low-pressure waste boiler, a second separator, a second cooler, and a third cooler, which are sequentially arranged between the outlet of the first converter and the ammonia washing tower. The low-pressure waste boiler is fed by a low-pressure boiler.

4. The adiabatic fixed-bed shift catalyst passivation system according to claim 3, characterized in that, The shift catalyst passivation system further includes a second shift furnace connected in series with the first shift furnace; or The shift catalyst passivation system also includes a second shift furnace and a third shift furnace connected in series with the first shift furnace.

5. The adiabatic fixed-bed shift catalyst passivation system according to claim 4, characterized in that, When the first converter is connected in series with the second converter, the inlet of the second converter is connected to the outlet of the first converter, and the outlet of the second converter is connected to the inlet of the low-pressure waste boiler. The inlet of the second converter is also connected to the outlet of the circulating nitrogen heater.

6. The adiabatic fixed-bed shift catalyst passivation system according to claim 5, characterized in that, A medium-pressure steam superheater, a low-pressure steam superheater, and a medium-pressure waste boiler are sequentially provided between the first converter and the second converter.

7. The adiabatic fixed-bed shift catalyst passivation system according to claim 6, characterized in that, The low-pressure boiler feedwater passes through the low-pressure waste boiler and exchanges heat with the shift gas of the second shift furnace to generate low-pressure steam. The low-pressure steam enters the low-pressure steam superheater and is then superheated with the shift gas of the medium-pressure steam superheater to become low-pressure hot steam, which is then sent to the low-pressure steam pipeline network. Medium-pressure boiler feedwater enters the medium-pressure waste boiler and exchanges heat with the shift gas entering the low-pressure steam superheater to generate medium-pressure steam. The medium-pressure steam enters the medium-pressure steam superheater and is superheated with the shift gas of the first shift furnace to become medium-pressure superheated steam, which is then sent to the medium-pressure steam pipeline network.

8. The adiabatic fixed-bed shift catalyst passivation system according to claim 7, characterized in that, When the catalyst passivation system further includes a second and a third converter connected in series with the first converter, the third converter is located between the first separator and the low-pressure waste boiler, and the inlet of the third converter is also connected to the outlet of the circulating nitrogen heater.

9. A method for passivating a shift catalyst in an adiabatic fixed bed, utilizing the shift catalyst passivation system according to any one of claims 1 to 8, characterized in that, The catalyst passivation method includes the following steps: Nitrogen gas is supplied to the first converter by a first low-pressure nitrogen gas set at the inlet of the first converter. The second low-pressure nitrogen gas is used to replenish the nitrogen gas in the first converter furnace through a circulating nitrogen heater; The temperature of the second low-pressure nitrogen is adjusted based on the temperature of the superheated steam in the circulating nitrogen heater. Based on the changing temperature of the second low-pressure nitrogen, the temperature at the inlet of the first shift furnace is adjusted to achieve passivation of the shift catalyst.

10. The method for passivating a shift catalyst in an adiabatic fixed bed according to claim 9, characterized in that, After the passivation of the shift catalyst is completed, the shift catalyst passivation method further includes system cooling, which includes the following steps: Turn off the circulating nitrogen heater and turn on the second circulating fan; Increase the amount of low-pressure nitrogen entering the first converter to reduce the bed temperature of the first converter; The second circulating fan is turned off, and compressed air or second low-pressure nitrogen is introduced to lower the bed temperature of the first converter to room temperature for unloading.

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