阅读说明：本技术 一种合成氨驰放气中氢氨回收系统及其工艺方法 (System and process method for recovering hydrogen and ammonia in synthetic ammonia purge gas ) 是由 范庆虎 于 2021-09-30 设计创作，主要内容包括：本发明提供一种合成氨驰放气中氢氨回收系统及其工艺方法,属于驰放气回收领域,其中回收系统包括高压放空富氢气回收装置、预冷换热器、深冷换热器、低温分离器、一级分离器、二级分离器；高压放空富氢气回收装置包括洗氨塔、游离水分离器、预热器和膜分离器,预冷换热器的进气端口还连通中压放空富氨气和闪蒸汽,预冷换热器的出口连接深冷换热器和一级分离器,深冷换热器的出口连接至低温分离器和二级分离器；低温分离器的液相出口连接至深冷换热器；工艺方法包括高压放空富氢气洗涤脱氨脱氢；中压放空富氨气脱氨；闪蒸汽脱氨；针对不同压力的驰放气,回收生产高纯氢气、液氨和燃料气,减少合成氨驰放气的排放,回收了氢、氨甲烷。(The invention provides a system and a process method for recovering hydrogen and ammonia in synthetic ammonia purge gas, belonging to the field of purge gas recovery, wherein the recovery system comprises a high-pressure purge hydrogen-rich gas recovery device, a precooling heat exchanger, a cryogenic heat exchanger, a low-temperature separator, a primary separator and a secondary separator; the high-pressure emptying hydrogen-rich gas recovery device comprises an ammonia washing tower, a free water separator, a preheater and a membrane separator, wherein a gas inlet port of the precooling heat exchanger is also communicated with medium-pressure emptying ammonia-rich gas and flash steam, an outlet of the precooling heat exchanger is connected with a cryogenic heat exchanger and a primary separator, and an outlet of the cryogenic heat exchanger is connected with a low-temperature separator and a secondary separator; the liquid phase outlet of the low-temperature separator is connected to the cryogenic heat exchanger; the process method comprises the steps of high-pressure emptying hydrogen-rich gas, washing, deamination and dehydrogenation; the rich ammonia gas is discharged at medium pressure to be deaminated; flash steam deamination; aiming at purge gases with different pressures, high-purity hydrogen, liquid ammonia and fuel gas are recovered and produced, the discharge of the purge gas of synthetic ammonia is reduced, and hydrogen and aminomethane are recovered.)

1. A hydrogen-ammonia recovery system in synthetic ammonia purge gas is characterized by comprising a high-pressure emptying hydrogen-rich gas recovery device, a precooling heat exchanger (7), a cryogenic heat exchanger (8), a low-temperature separator (11), a primary separator (9) and a secondary separator (12);

the high-pressure emptying hydrogen-rich gas recovery device comprises an ammonia washing tower (1), a free water separator (2), a preheater (3) and a membrane separator (4), wherein a gas inlet of the ammonia washing tower (1) is communicated to high-pressure emptying hydrogen-rich gas; a gas phase outlet of the ammonia washing tower (1) is sequentially communicated with a free water separator (2), a preheater (3) and a membrane separator (4), and a non-permeable gas outlet of the membrane separation is communicated with the precooling heat exchanger (7); the air inlet port of the precooling heat exchanger (7) is also communicated with medium-pressure emptying rich ammonia gas and flash steam, the outlet of the precooling heat exchanger (7) is respectively connected with a cryogenic heat exchanger (8) and a primary separator (9), and the outlet of the cryogenic heat exchanger (8) is respectively connected with a low-temperature separator (11) and a secondary separator (12); and a liquid phase outlet of the low-temperature separator (11) is connected to the cryogenic heat exchanger (8).

2. A system for recovering hydrogen and ammonia from synthesis ammonia purge gas as defined in claim 1, wherein: the system for recovering the hydrogen and the ammonia in the synthetic ammonia purge gas also comprises a low-temperature turboexpander (14), a high-temperature turboexpander (13), a primary cooler (15) and a secondary cooler (16); the expansion end gas phase outlet of the low-temperature turboexpander (14) and the expansion end gas inlet of the copious cooling heat exchanger (8), the precooling heat exchanger (7) and the high-temperature turboexpander (13) are connected in sequence after the gas phase outlet of the secondary separator (12) is converged, and the expansion end gas phase outlet of the high-temperature turboexpander (13) is communicated with the precooling heat exchanger (7), the high-temperature turboexpander (13) supercharging end, the primary cooler (15), the low-temperature turboexpander (14) and the secondary cooler (16) in sequence.

3. A system for recovering hydrogen and ammonia from synthesis ammonia purge gas as defined in claim 1, wherein: the lower inlet of the ammonia washing tower (1) is communicated with high-pressure air-release hydrogen-rich gas, the upper inlet of the ammonia washing tower (1) is provided with a desalting water tank (5) and a booster water pump (6), the lower outlet of the ammonia washing tower (1) is provided with a throttle valve, and the upper outlet of the ammonia washing tower (1) is communicated to the free water separator (2).

4. A system for recovering hydrogen and ammonia from synthesis ammonia purge gas as defined in claim 2, wherein: the precooling heat exchanger (7) comprises a first precooling channel, a third precooling channel and a fourth precooling channel; the cryogenic heat exchanger (8) comprises a first cryogenic channel, a third cryogenic channel, a fourth cryogenic channel and a fifth cryogenic channel; the inlet end of the first precooling channel is communicated with a non-permeable gas outlet and a medium-pressure air-release rich ammonia gas of the membrane separator (4), the outlet end of the first precooling channel is communicated with a first deep cooling channel and a low-temperature separator (11) in sequence, and a liquid phase outlet and a gas phase outlet of the low-temperature separator (11) are respectively and correspondingly connected with the third deep cooling channel and the fourth deep cooling channel.

5. The system for recovering hydrogen and ammonia from synthesis ammonia purge gas as defined in claim 4, wherein: the exit end of fourth cryrogenic passageway is connected to the expansion end of low temperature turbo expander (14), the expansion end gaseous phase export of low temperature turbo expander (14) communicate fifth cryrogenic passageway and fourth precooling passageway in proper order, the exit end of fourth precooling passageway communicates to the expansion end of high temperature turbo expander (13), the entry end of the expansion end gaseous phase exit linkage third precooling passageway of high temperature turbo expander (13), the exit end of third precooling passageway is connected to the pressure boost end of high temperature turbo expander (13).

6. The system for recovering hydrogen and ammonia from synthesis ammonia purge gas as defined in claim 5, wherein: the precooling heat exchanger (7) further comprises a second precooling channel, and the cryogenic heat exchanger (8) further comprises a second cryogenic channel; the entry end intercommunication flash distillation gas of second precooling passageway, the exit end intercommunication primary separator (9) of second precooling passageway, the gaseous phase export of primary separator (9) communicates the entry end of the cryogenic passageway of second, and the exit end of the cryogenic passageway of second is connected to secondary separator (12), the liquid phase exit linkage of secondary separator (12) the third is cryogenic passageway, the gaseous phase export of secondary separator (12) with be connected to after the confluence of the expansion end gaseous phase export of low temperature turbo expander (14) the fifth is cryogenic passageway.

7. The system for recovering hydrogen and ammonia from synthesis ammonia purge gas as defined in claim 4, wherein: the system for recovering the hydrogen and the ammonia in the synthetic ammonia purge gas further comprises a liquid ammonia buffer tank (10) and a liquid ammonia storage tank, wherein the liquid ammonia buffer tank (10) is communicated with the liquid ammonia storage tank through a liquid ammonia pump; and the liquid ammonia buffer tank (10) is simultaneously connected with the liquid phase outlet of the primary separator (9) and the third cryogenic channel.

8. A process method for recovering hydrogen and ammonia in synthetic ammonia purge gas, which adopts the system for recovering hydrogen and ammonia in synthetic ammonia purge gas as claimed in any one of claims 1 to 7, and is characterized in that: the method comprises the following steps:

s1: washing, deamination and dehydrogenation of high-pressure vented hydrogen-rich gas; introducing high-pressure desalted water into the high-pressure vented hydrogen-rich gas for deamination treatment to obtain an ammonia water product and first-stage hydrogen-rich gas; sequentially carrying out free water separation, heating treatment and membrane filtration on the first-stage hydrogen-rich gas to obtain a high-purity hydrogen product and non-permeable gas;

s2: the rich ammonia gas is discharged at medium pressure to be deaminated; sequentially cooling and low-temperature separating the medium-pressure vented ammonia-rich gas to obtain a liquid ammonia product and a first refrigerating gas;

s3: flash steam deamination; and the flash steam is sequentially subjected to condensation treatment and primary separation treatment to obtain a liquid nitrogen product and an intermediate gas product, and the intermediate gas product is subjected to secondary separation to obtain a liquid nitrogen product and a second refrigerating gas.

9. The process method for recovering hydrogen and ammonia from the synthetic ammonia purge gas as claimed in claim 8, wherein the process method comprises the following steps: the high-pressure desalted water is desalted water treated by pressure of more than 10 Mpa.

10. The process method for recovering hydrogen and ammonia from the synthetic ammonia purge gas as claimed in claim 8, wherein the process method comprises the following steps: and the first refrigerating gas in the step S2 is subjected to primary temperature reduction and then mixed with the second refrigerating gas in the step S3, and then primary refrigeration, secondary temperature reduction, secondary refrigeration and pressurization cooling treatment are sequentially performed.

Technical Field

The invention relates to a purge gas recovery technology, in particular to a system and a process method for recovering hydrogen and ammonia in a synthetic ammonia purge gas.

Background

In the ammonia synthesis process, in order to avoid the influence of harmful impurities such as argon, methane and the like on the synthesis catalyst, a large amount of purge gas with different pressures needs to be continuously discharged at different process nodes, for example, high-pressure purge rich hydrogen is arranged at the rear end of a cold-exchange heat exchanger, the pressure is generally 15MPa, wherein the hydrogen content is 65%, the methane content is 10%, the nitrogen content is 19%, the argon content is 2.4%, and the ammonia content is 3.6%; and (3) setting medium-pressure emptying on a liquid ammonia flash tank, wherein the pressure is generally 5.0MPa, and the medium-pressure emptying comprises 52% of hydrogen, 15% of methane, 17% of nitrogen, 3% of argon and 13% of ammonia. Meanwhile, a liquid ammonia storage tank is used as low-temperature equipment, and a large amount of flash evaporation gas is continuously volatilized, wherein the content of hydrogen is 32.8%, the content of methane is 15.8%, the content of nitrogen is 11.5%, the content of argon is 2.4%, and the content of ammonia is 37.5%.

The existing ammonia purge gas is usually directly discharged or combusted, however, substances such as hydrogen, ammonia, methane and the like contained in the waste gas are directly discharged or combusted to generate air pollutants, so that serious environmental pollution is caused, and energy is wasted.

Disclosure of Invention

In view of the above-mentioned disadvantages of the prior art, the present invention aims to provide a system and a process for recovering hydrogen and ammonia from purge gas of synthetic ammonia, which can recover and produce high-purity hydrogen, liquid ammonia and fuel gas, reduce the discharge of purge gas of synthetic ammonia, and recover valuable resources such as hydrogen, ammonia and methane.

In order to achieve the above objects and other related objects, the present invention provides a system for recovering hydrogen and ammonia from synthesis ammonia purge gas, which is characterized in that the system for recovering hydrogen and ammonia from synthesis ammonia purge gas comprises a high-pressure purge hydrogen-rich gas recovery device, a precooling heat exchanger, a cryogenic heat exchanger, a low-temperature separator, a first-stage separator and a second-stage separator;

the high-pressure emptying hydrogen-rich gas recovery device comprises an ammonia washing tower, a free water separator, a preheater and a membrane separator, wherein an air inlet of the ammonia washing tower is communicated with the high-pressure emptying hydrogen-rich gas; a gas phase outlet of the ammonia washing tower is sequentially communicated with a free water separator, a preheater and a membrane separator, and a non-permeable gas outlet of the membrane separator is communicated with the precooling heat exchanger; the air inlet port of the precooling heat exchanger is also communicated with medium-pressure emptying rich ammonia gas and flash steam, the outlet of the precooling heat exchanger is respectively connected with a cryogenic heat exchanger and a primary separator, and the outlet of the cryogenic heat exchanger is respectively connected with a low-temperature separator and a secondary separator; and a liquid phase outlet of the low-temperature separator is connected to the cryogenic heat exchanger.

In an embodiment of the present invention, the system for recovering hydrogen and ammonia from the synthetic ammonia purge gas further comprises a low temperature turboexpander, a high temperature turboexpander, a primary cooler and a secondary cooler; the gas phase outlet of the expansion end of the low-temperature turbo expander is converged with the gas phase outlet of the secondary separator and then is sequentially connected with the gas inlets of the cryogenic heat exchanger, the precooling heat exchanger and the high-temperature turbo expander, and the gas phase outlet of the expansion end of the high-temperature turbo expander is sequentially communicated with the precooling heat exchanger, the pressurization end of the high-temperature turbo expander, the primary cooler, the low-temperature turbo expander and the secondary cooler.

In an embodiment of the invention, a lower inlet of the ammonia scrubber is communicated with the high-pressure vented rich hydrogen gas, an upper inlet of the ammonia scrubber is provided with a desalted water tank and a pressurized water pump, a lower outlet of the ammonia scrubber is provided with a throttle valve, and an upper outlet of the ammonia scrubber is communicated with the free water separator.

In an embodiment of the present invention, the precooling heat exchanger includes a first precooling channel, a third precooling channel and a fourth precooling channel; the cryogenic heat exchanger comprises a first cryogenic channel, a third cryogenic channel, a fourth cryogenic channel and a fifth cryogenic channel; the inlet end of the first precooling channel is communicated with a non-permeable gas outlet and a medium-pressure air-release ammonia-rich gas of the membrane separator, the outlet end of the first precooling channel is sequentially communicated with a first copious cooling channel and a low-temperature separator, and a liquid phase outlet and a gas phase outlet of the low-temperature separator are respectively and correspondingly connected with the third copious cooling channel and the fourth copious cooling channel.

Furthermore, the exit end of the fourth deep cooling channel is connected to the expansion end of the low-temperature turboexpander, the expansion end gas phase outlet of the low-temperature turboexpander is sequentially communicated with a fifth deep cooling channel and a fourth precooling channel, the exit end of the fourth precooling channel is communicated to the expansion end of the high-temperature turboexpander, the expansion end gas phase outlet of the high-temperature turboexpander is connected with the inlet end of a third precooling channel, and the exit end of the third precooling channel is connected to the supercharging end of the high-temperature turboexpander.

Further, the precooling heat exchanger further comprises a second precooling channel, and the cryogenic heat exchanger further comprises a second cryogenic channel; the entry end intercommunication flash distillation gas of second precooling passageway, the exit end intercommunication primary separator of second precooling passageway, the gaseous phase export of primary separator communicates the entry end of the cryogenic passageway of second, and the exit end of the cryogenic passageway of second is connected to secondary separator, secondary separator's liquid phase exit linkage the third is cryogenic passageway, secondary separator's gaseous phase export with be connected to after the inflation end gaseous phase export confluence of low temperature turbo expander the fifth is cryogenic passageway.

In an embodiment of the present invention, the system for recovering hydrogen and ammonia from the purge gas of synthetic ammonia further includes a liquid ammonia buffer tank and a liquid ammonia storage tank, wherein the liquid ammonia buffer tank is communicated with the liquid ammonia storage tank through a liquid ammonia pump; and the liquid ammonia buffer tank is simultaneously connected with the liquid phase outlet of the primary separator and the third cryogenic channel.

Meanwhile, the invention also provides a process method for recovering hydrogen and ammonia in the synthetic ammonia purge gas, which comprises the technical characteristics of the system for recovering hydrogen and ammonia in the synthetic ammonia purge gas, and is characterized in that: the method comprises the following steps:

s1: washing, deamination and dehydrogenation of high-pressure vented hydrogen-rich gas; introducing high-pressure desalted water into the high-pressure vented hydrogen-rich gas for deamination treatment to obtain an ammonia water product and first-stage hydrogen-rich gas; sequentially carrying out free water separation, heating treatment and membrane filtration on the first-stage hydrogen-rich gas to obtain a high-purity hydrogen product and non-permeable gas;

s2: the rich ammonia gas is discharged at medium pressure to be deaminated; sequentially cooling and low-temperature separating the medium-pressure vented ammonia-rich gas to obtain a liquid ammonia product and a first refrigerating gas;

s3: flash steam deamination; and the flash steam is sequentially subjected to condensation treatment and primary separation treatment to obtain a liquid nitrogen product and an intermediate gas product, and the intermediate gas product is subjected to secondary separation to obtain a liquid nitrogen product and a second refrigerating gas.

In an embodiment of the present invention, the high pressure desalted water is desalted water treated by a pressure of 10Mpa or more.

In an embodiment of the invention, the first refrigeration gas in the step S2 is subjected to primary cooling and then mixed with the second refrigeration gas in the step S3, and then the primary refrigeration, the secondary cooling, the secondary refrigeration and the pressure boost cooling process are sequentially performed.

As mentioned above, the system and the process method for recovering hydrogen and ammonia in the synthetic ammonia purge gas have the following beneficial effects:

the invention carries out targeted treatment on the purge gas with different pressures, carries out dehydrogenation and deamination treatment on the high-pressure vented hydrogen-rich gas, carries out deamination recovery treatment on the medium-pressure vented ammonia-rich gas and the liquid ammonia flash gas evaporated by the liquid ammonia storage tank, reduces the discharge of the synthetic ammonia purge gas, recovers hydrogen and ammonia, and simultaneously recovers valuable resources such as methane and the like in the purge gas with different pressures, thereby being more environment-friendly.

Drawings

FIG. 1 is a schematic system flow diagram of a system for recovering hydrogen and ammonia from syngas purge gas as disclosed in the embodiments of the present invention.

Description of the element reference numerals

1-ammonia washing tower; 2-free water separator; 3-a preheater; 4-a membrane separator; 5-a desalted water tank; 6-a booster water pump; 7-precooling a heat exchanger; 8-cryogenic heat exchanger; 9-a first-stage separator; 10-liquid ammonia buffer tank; 11-a cryogenic separator; 12-a secondary separator; 13-a high temperature turboexpander; 14-a low temperature turboexpander; 15-primary cooler; 16-secondary cooler.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

Please refer to fig. 1. It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions under which the present invention can be implemented, so that the present invention has no technical significance, and any structural modification, ratio relationship change, or size adjustment should still fall within the scope of the present invention without affecting the efficacy and the achievable purpose of the present invention. In addition, the terms "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for clarity of description, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not to be construed as a scope of the present invention.

Referring to fig. 1, the present invention provides a system for recovering hydrogen and ammonia from synthesis ammonia purge gas, which is characterized in that the system for recovering hydrogen and ammonia from synthesis ammonia purge gas comprises a high-pressure purge hydrogen-rich gas recovery device, a precooling heat exchanger 7, a cryogenic heat exchanger 8, a low-temperature separator 11, a primary separator 9 and a secondary separator 12;

the high-pressure emptying hydrogen-rich gas recovery device comprises an ammonia washing tower 1, a free water separator 2, a preheater 3 and a membrane separator 4, wherein an air inlet of the ammonia washing tower 1 is communicated with high-pressure emptying hydrogen-rich gas; a gas phase outlet of the ammonia washing tower 1 is sequentially communicated with a free water separator 2, a preheater 3 and a membrane separator 4, and a non-permeable gas outlet of the membrane separator is communicated with a precooling heat exchanger 7; the air inlet port of the precooling heat exchanger 7 is also communicated with medium-pressure emptying rich ammonia gas and flash steam, the outlet of the precooling heat exchanger 7 is respectively connected with a cryogenic heat exchanger 8 and a primary separator 9, and the outlet of the cryogenic heat exchanger 8 is respectively connected with a low-temperature separator 11 and a secondary separator 12; the liquid phase outlet of the cryogenic separator 11 is connected to the cryogenic heat exchanger 8.

The lower end of the membrane separator 4 is a permeable gas outlet, and the upper end is a non-permeable gas outlet; the permeating gas is a hydrogen product, and the non-permeating gas is a methane-rich gas; the precooling heat exchanger 7 is a four-stream channel heat exchanger, the first two-stream channel is an upper inlet and a lower outlet, and the third four-stream channel is a lower inlet and an upper outlet; the cryogenic heat exchanger 8 is a five-flow channel heat exchanger, the first two flow channels are an upper inlet and a lower outlet, and the third four five flow channels are a lower inlet and an upper outlet.

Further, the system for recovering hydrogen and ammonia in the synthetic ammonia purge gas also comprises a low-temperature turbo expander 14, a high-temperature turbo expander 13, a primary cooler 15 and a secondary cooler 16; an expansion end gas phase outlet of the low-temperature turbo expander 14 and a gas phase outlet of the second-stage separator 12 are converged and then sequentially connected with a cryogenic heat exchanger 8, a precooling heat exchanger 7 and an expansion end gas inlet of the high-temperature turbo expander 13, and an expansion end gas phase outlet of the high-temperature turbo expander 13 is sequentially communicated with the precooling heat exchanger 7, a high-temperature turbo expander 13 pressurization end, a first-stage cooler 15, the low-temperature turbo expander 14 and a second-stage cooler 16.

Further, the lower inlet of the ammonia washing tower 1 is communicated with high-pressure air-release hydrogen-rich gas, the upper inlet of the ammonia washing tower 1 is provided with a desalting water tank 5 and a booster water pump 6, the lower outlet of the ammonia washing tower 1 is provided with a throttle valve, and the upper outlet of the ammonia washing tower 1 is communicated to the free water separator 2.

Further, the precooling heat exchanger 7 comprises a first precooling channel, a third precooling channel and a fourth precooling channel; the cryogenic heat exchanger 8 comprises a first cryogenic channel, a third cryogenic channel, a fourth cryogenic channel and a fifth cryogenic channel; the inlet end of the first precooling channel is communicated with a non-permeable gas outlet of the membrane separator 4 and the medium-pressure air-bleed rich ammonia gas, the outlet end of the first precooling channel is sequentially communicated with the first cryogenic channel and the low-temperature separator 11, and a liquid phase outlet and a gas phase outlet of the low-temperature separator 11 are respectively and correspondingly connected with the third cryogenic channel and the fourth cryogenic channel.

Furthermore, the outlet end of the fourth cryogenic channel is connected to the expansion end of the low-temperature turbo expander 14, the gas phase outlet of the expansion end of the low-temperature turbo expander 14 is sequentially communicated with the fifth cryogenic channel and the fourth precooling channel, the outlet end of the fourth precooling channel is communicated to the expansion end of the high-temperature turbo expander 13, the gas phase outlet of the expansion end of the high-temperature turbo expander 13 is connected to the inlet end of the third precooling channel, and the outlet end of the third precooling channel is connected to the supercharging end of the high-temperature turbo expander 13.

Further, the precooling heat exchanger 7 also comprises a second precooling channel, and the cryogenic heat exchanger 8 also comprises a second cryogenic channel; the inlet end of the second precooling channel is communicated with flash vapor, the outlet end of the second precooling channel is communicated with the first-stage separator 9, the gas phase outlet of the first-stage separator 9 is communicated with the inlet end of the second cryogenic channel, the outlet end of the second cryogenic channel is connected to the second-stage separator 12, the liquid phase outlet of the second-stage separator 12 is connected to the third cryogenic channel, and the gas phase outlet of the second-stage separator 12 is connected to the fifth cryogenic channel after being converged with the gas phase outlet of the expansion end of the low-temperature turbo expander 14.

Further, the system for recovering the hydrogen and the ammonia in the synthetic ammonia purge gas also comprises a liquid ammonia buffer tank and a liquid ammonia storage tank, wherein the liquid ammonia buffer tank is communicated with the liquid ammonia storage tank through a liquid ammonia pump; the liquid ammonia buffer tank is simultaneously connected with the liquid phase outlet of the first-stage separator 9 and the third cryogenic channel.

When the device is used, the gas separated by the low-temperature separator 11 is reheated by the cryogenic heat exchanger 8 and then enters the expansion end of the low-temperature booster turboexpander for expansion refrigeration, and the expanded gas is mixed with the gas separated by the secondary separator 12 and then enters the cryogenic heat exchanger 8 and the precooling heat exchanger 7 to provide cold energy for condensation of medium-pressure purge gas and flash steam; the reheated gas enters an expansion end of a high-temperature turbine expander 13 for expansion refrigeration, then enters a precooling heat exchanger 7 to provide cold energy for precooling of medium-pressure purge gas and flash gas, the reheated gas sequentially passes through a pressurization end of the high-temperature turbine expander 13, a primary cooler 15, a pressurization end of a low-temperature turbine expander 14 and a secondary cooler 16, and the purge gas after pressurization cooling is rich in methane and is used as fuel gas.

The parameters of each device in this example are described as follows:

the pressure of the high-pressure emptying hydrogen-rich gas is 14-15 MPa, the pressure of the ammonia washing tower 1, the water separator, the preheater 3 and the membrane separator 4 is controlled at 12-14MP, and the preheating temperature is controlled at 50-60 ℃; the ammonia content in the top gas of the ammonia scrubber 1 is controlled to be 10 ppm; the pressure of the medium-pressure discharged ammonia-rich gas is 4.5-5.0MPa, the pressure of the flash evaporation gas of the liquid ammonia is 1.5-1.6MPa, the low-temperature outlet temperature of the precooling heat exchanger 7 is controlled at-8 ℃, and the low-temperature outlet temperature of the cryogenic heat exchanger 8 is controlled at-60 ℃; the gas pressure at the outlet of the expansion end of the low-temperature turbo expander 14 is 0.6-1.0 MPa; the gas pressure at the outlet of the expansion end of the high-temperature turbo expander 13 is 0.2-0.3 Mpa; the pressure at the outlet of the liquid ammonia pump is 2.6 MPa.

Meanwhile, the invention also provides a process method for recovering hydrogen and ammonia in the synthetic ammonia purge gas, which comprises the technical characteristics of the system for recovering hydrogen and ammonia in the synthetic ammonia purge gas, and is characterized in that: the method comprises the following steps:

s1: washing, deamination and dehydrogenation of high-pressure vented hydrogen-rich gas; introducing high-pressure desalted water into the high-pressure vented hydrogen-rich gas for deamination treatment to obtain an ammonia water product and first-stage hydrogen-rich gas; sequentially carrying out free water separation, heating treatment and membrane filtration on the first-stage hydrogen-rich gas to obtain a high-purity hydrogen product and non-permeable gas;

s2: the rich ammonia gas is discharged at medium pressure to be deaminated; sequentially cooling and low-temperature separating the medium-pressure vented ammonia-rich gas to obtain a liquid ammonia product and a first refrigerating gas;

s3: flash steam deamination; and the flash steam is sequentially subjected to condensation treatment and primary separation treatment to obtain a liquid nitrogen product and an intermediate gas product, and the intermediate gas product is subjected to secondary separation to obtain a liquid nitrogen product and a second refrigerating gas.

Further, the high-pressure desalted water is desalted water treated by pressure of more than 10 Mpa.

Further, the first refrigerant gas in the step S2 is subjected to primary cooling and then mixed with the second refrigerant gas in the step S3, and then primary cooling, secondary cooling, and supercharging cooling processing are sequentially performed.

In conclusion, the invention carries out targeted treatment on the purge gas with different pressures, carries out dehydrogenation and deamination treatment on the high-pressure vented hydrogen-rich gas, carries out deamination recovery treatment on the medium-pressure vented ammonia-rich gas and the liquid ammonia flash gas evaporated by the liquid ammonia storage tank, reduces the discharge of the synthetic ammonia purge gas, recovers hydrogen and ammonia, and simultaneously recovers valuable resources such as methane and the like in the purge gas with different pressures, thereby being more environment-friendly. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.