Synthetic ammonia tail gas treatment system

Abstract

The utility model relates to the technical field of tail gas treatment, in particular to a synthetic ammonia tail gas treatment system. The system comprises a conveying unit used for receiving and conveying synthetic ammonia tail gas to the system, a heat exchange unit used for cooling the synthetic ammonia tail gas conveyed by the conveying unit, a dehydrogenation unit used for removing a hydrogen component in the synthetic ammonia tail gas, a demethanation unit used for removing a methane component in the synthetic ammonia tail gas, and a heat exchange unit used for cooling the synthetic ammonia tail gas conveyed by the demethanation unit. The argon removal unit is used for removing an argon component in the synthesis ammonia tail gas; and the supercooling unit is used for cooling a system product. The utility model aims to solve the problems of poor recovery effect, high energy consumption and high cost of the synthetic ammonia tail gas in the prior art, and can fully extract and recycle hydrogen, methane and argon in the synthetic ammonia emptying tail gas, thereby not only improving the economic benefit, but also reducing the emptying pollution, and realizing both economic development and environmental protection.

Description

Technical Field

[0001] The present application relates to the technical field of tail gas treatment, and in particular to a synthetic ammonia tail gas treatment system. Background Art

[0002] Synthetic ammonia is an important chemical product. Currently, the Haber-Bost process is usually used in industry to produce ammonia, which is to react nitrogen and hydrogen in the presence of a catalyst to produce ammonia. In industrial production, in order to increase the yield of synthetic ammonia, nitrogen and hydrogen need to react under high temperature and high pressure conditions. This production-promoting method results in unreacted nitrogen and hydrogen still existing in the reaction system when the reaction reaches equilibrium, and is finally discharged as tail gas.

[0003] The main component of synthetic ammonia tail gas is nitrogen, and there are also some hydrogen, methane and argon. Based on economic and environmental considerations, synthetic ammonia tail gas is usually recovered. At present, the means of recovering synthetic ammonia tail gas mainly include adsorption, membrane separation, chemical absorption and catalytic conversion, but these methods have problems such as poor recovery effect, high energy consumption and high cost. Utility Model Content

[0004] In order to solve the above-mentioned problems of the prior art, the utility model provides a synthetic ammonia tail gas treatment system, which solves the problems of poor synthetic ammonia tail gas recovery effect, high energy consumption and high cost in the prior art, and can fully extract and recycle the hydrogen, methane and argon in the synthetic ammonia tail gas at relatively low energy consumption, which not only improves the economic benefits, but also reduces the venting pollution, taking into account both economic development and environmental protection.

[0005] The utility model provides a synthetic ammonia tail gas treatment system, comprising:

[0006] A delivery unit, the delivery unit is used to receive and deliver synthetic ammonia tail gas to the system;

[0007] A heat exchange unit, the heat exchange unit is used to cool the synthetic ammonia tail gas transported by the transport unit;

[0008] A dehydrogenation unit, which is used to remove hydrogen components from the synthetic ammonia tail gas, and includes a dehydrogenation tower, a first dehydrogenation condensation evaporator, a second dehydrogenation condensation evaporator and a dehydrogenation reboiler;

[0009] A demethanization unit, which is used to remove methane components from synthetic ammonia tail gas, and comprises a demethanization tower, a demethanization condenser evaporator and a demethanization reboiler;

[0010] A de-argon unit, which is used to remove argon components from synthetic ammonia tail gas, and comprises a pure argon tower and a supplementary flow channel thereof;

[0011] A subcooling unit, the subcooling unit is used to cool the system product, and the subcooling unit is operably connected to the dehydrogenation unit, the demethanization unit and the deargonization unit respectively;

[0012] The dehydrogenation unit is configured to receive the synthetic ammonia tail gas cooled by the heat exchange unit in the dehydrogenation tower, and to generate a first nitrogen-rich waste stream to be returned to and / or released to the bottom of the dehydrogenation tower by means of the dehydrogenation reboiler, and to generate a dehydrogenation tower top distillate stream to be sequentially directed to the first dehydrogenation condensation evaporator and the second dehydrogenation condensation evaporator;

[0013] The first dehydrogenation condenser-evaporator is configured to condense the dehydrogenation column overhead stream by relying on a cold source from the pure argon column and produce a first nitrogen-rich reflux stream that is returned to or released into the dehydrogenation column, and produce a first hydrogen-rich product stream that is directed to the second dehydrogenation condenser-evaporator;

[0014] The second dehydrogenation condensation evaporator is configured to condense the first hydrogen-rich product stream by relying on the cold source from the heat exchange unit, and generate a second nitrogen-rich reflux stream returned to or released into the dehydrogenation column, and generate a second hydrogen-rich product stream directed to the subcooling unit;

[0015] wherein the demethanizer unit is configured to receive the first nitrogen-rich waste stream from the bottom of the dehydrogenation tower in the demethanizer, and to generate a methane-rich product stream returned to / or released to the bottom of the demethanizer by means of the demethanizer reboiler, and to generate a demethanizer overhead stream directed to the demethanizer condenser evaporator;

[0016] The demethanizer condenser evaporator is configured to condense the demethanizer overhead stream by relying on the cold source from the heat exchange unit and through indirect heat exchange with the first nitrogen-rich waste stream from the dehydrogenation unit and the methane-rich product stream from the demethanizer unit, and to return or release a portion of the condensed demethanizer overhead stream to the demethanizer as a third nitrogen-rich reflux stream, and another portion is directed to the deargon removal unit as a second nitrogen-rich waste stream;

[0017] wherein the deargon unit is configured to receive the second nitrogen-rich waste stream from the top of the demethanizer in the pure argon column, and to generate a crude nitrogen stream at the top of the pure argon column and a first pure argon stream at the bottom of the pure argon column, respectively;

[0018] The deargonation unit is further configured to receive liquid nitrogen reflux liquid from the heat exchange unit in the supplementary flow channel at the top of the pure argon column and mix it with the crude nitrogen flow to generate a nitrogen product flow returned to the top of the pure argon column and to generate a second pure argon flow released to the bottom of the pure argon column, the first pure argon flow and the second pure argon flow together serving as a liquid argon product flow.

[0019] Further, the delivery unit includes a circulating nitrogen compressor, the circulating nitrogen compressor being configured to receive an incoming nitrogen flow and generate a compressed nitrogen flow;

[0020] wherein the compressed nitrogen flow is split into a first portion of the compressed nitrogen flow and a second portion of the compressed nitrogen flow;

[0021] The first part of the compressed nitrogen flow and the second part of the compressed nitrogen flow are respectively used as heat sources and / or cold sources and after being supercooled by the supercooling unit and reheated by the heat exchange unit, they are merged again and received and compressed by the circulating nitrogen compressor for the next cycle.

[0022] Furthermore, the delivery unit further includes a booster compressor, which is configured to further compress the first part of the compressed nitrogen flow and guide it to the heat exchange unit for cooling.

[0023] Furthermore, the delivery unit also includes a high-temperature turbine expander, a low-temperature turbine expander and a gas-liquid separator;

[0024] The high temperature turbine expander is configured to receive a first portion of the cooled compressed nitrogen gas flow and expand it endothermically to form a first nitrogen-liquid nitrogen mixed flow;

[0025] The gas-liquid separator is configured to receive the first nitrogen-liquid nitrogen mixed flow and separate it into a first nitrogen mixed flow and a first liquid nitrogen mixed flow; the first nitrogen mixed flow is guided to the subcooling unit and the heat exchange unit for reheating;

[0026] The low-temperature turbine expander is configured to receive the reheated first nitrogen mixed flow and endothermally expand it to form a second nitrogen mixed flow. The second nitrogen mixed flow is guided to the subcooling unit and the heat exchange unit for reheating and then received and compressed by the circulating nitrogen compressor for the next cycle.

[0027] Furthermore, the first liquid nitrogen mixed flow is guided by the gas-liquid separator to the demethanization condensation evaporator as a cold source.

[0028] Further, the delivery unit is further configured to cool the second part of the compressed nitrogen gas flow, and direct its split flow to the dehydrogenation reboiler and the demethanization reboiler as a heat source to be condensed and then merged again;

[0029] The subcooling unit is also configured to subcool the second part of the condensed compressed nitrogen gas flow and then divert it again, and guide it to the top of the pure argon tower as the liquid nitrogen reflux liquid, to the demethanization condenser evaporator as a cold source, and to the second dehydrogenation condenser evaporator as a cold source.

[0030] Further, the second dehydrogenation condenser evaporator is further configured to condense the first hydrogen-rich product stream via indirect heat exchange with the first nitrogen-rich waste stream from the dehydrogenation unit and the methane-rich product stream from the demethanization unit.

[0031] Further, the demethanizer condenser evaporator is further configured to condense the demethanizer overhead stream via indirect heat exchange with the first nitrogen-rich waste stream from the dehydrogenation unit and the methane-rich product stream from the demethanizer unit.

[0032] Furthermore, the second hydrogen-rich product flows through the supercooling unit and the heat exchange unit and is then reheated and sent to a product storage tank.

[0033] Furthermore, the methane-rich product flow at the bottom of the demethanizer is pressurized by a cryogenic liquid pump and then reheated by the heat exchange unit before being sent to the gas user.

[0034] Beneficial effects:

[0035] It can be seen from the above technical scheme that the technical scheme of the utility model provides a synthetic ammonia tail gas treatment system, which forms a three-tower distillation by utilizing a dehydrogenation unit, a demethanization unit and a deargonization unit to remove hydrogen, methane and argon components in the synthetic ammonia tail gas respectively, and obtain nitrogen-hydrogen mixed gas, liquefied natural gas, liquid argon and gas nitrogen and other products, while recovering useful gases, reducing flammable and explosive components and hydrocarbons in the vented gas, thereby reducing environmental pollution; at the same time, the products between the distillation towers are fully utilized for heat exchange through the supercooling unit, while ensuring the hydrogen recovery rate, the circulation volume of the nitrogen compressor is reduced, effectively reducing energy consumption, improving resource utilization, and realizing efficient, economical and environmentally friendly recovery of synthetic ammonia tail gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0037] Figure 1 A schematic diagram of the structure of a synthetic ammonia tail gas treatment system provided in an embodiment of the present application.

[0038] Figure 2 Another structural schematic diagram of the synthetic ammonia tail gas treatment system provided in the embodiment of the present application

[0039] In the figure, the meanings of the reference numerals are as follows:

[0040] Delivery unit 1, circulating nitrogen compressor 101, booster compressor 102, high temperature turbine expander 103, low temperature turbine expander 104, gas-liquid separator 105;

[0041] Heat exchange unit 2: heat exchanger 201;

[0042] Dehydrogenation unit 3, dehydrogenation tower 301, first dehydrogenation condensation evaporator 302, second dehydrogenation condensation evaporator 303, dehydrogenation reboiler 304;

[0043] Demethanization unit 4, demethanization tower 401, demethanization condenser evaporator 402, demethanization reboiler 403, first cryogenic liquid pump 404;

[0044] Deargon unit 5, pure argon tower 501, supplementary flow channel 502, second cryogenic liquid pump 503;

[0045] Subcooling unit 6. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0047] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0048] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0049] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0050] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the various specific processes and material examples provided by the present application, but those of ordinary skill in the art can appreciate the application of other processes and / or the use of other materials.

[0051] The embodiment of the utility model provides a synthetic ammonia tail gas treatment system, which forms a three-tower distillation system, which reduces the flammable and explosive components and hydrocarbons in the vented gas while recovering useful gas, reduces environmental pollution, and realizes efficient, economical and environmentally friendly recovery of synthetic ammonia tail gas. Figure 1 The synthetic ammonia tail gas treatment system is mainly composed of a conveying unit 1, a heat exchange unit 2, a dehydrogenation unit 3, a demethanization unit 4, a deargon removal unit 5 and a supercooling unit 6.

[0052] The delivery unit 1 is used to receive and deliver synthetic ammonia tail gas to the system.

[0053] The heat exchange unit 2 is used to cool the synthetic ammonia tail gas transported by the transport unit 1 .

[0054] Reference Figure 2 The heat exchange unit 2 may be a heat exchanger 201, which realizes the temperature change between different media by transferring heat. Specifically, different types of heat exchangers may be selected according to the scale of production, such as a shell and tube heat exchanger, a plate heat exchanger, etc.

[0055] The dehydrogenation unit 3 is used to remove hydrogen components from the synthetic ammonia tail gas. The dehydrogenation unit 3 includes a dehydrogenation tower 301 , a first dehydrogenation condensation evaporator 302 , a second dehydrogenation condensation evaporator 303 and a dehydrogenation reboiler 304 .

[0056] The demethanization unit 4 is used to remove the methane component in the synthetic ammonia tail gas, and the demethanization unit 4 includes a demethanization tower 401 , a demethanization condenser evaporator 402 and a demethanization reboiler 403 .

[0057] The de-argon unit 5 is used to remove the argon component in the synthetic ammonia tail gas. The de-argon unit 5 includes a pure argon tower 501 and a supplementary flow channel 502 thereof.

[0058] The subcooling unit 6 is used to cool the system product, and the subcooling unit 6 is operably connected to the dehydrogenation unit 3, the demethanization unit 4 and the deargonization unit 5 respectively.

[0059] Wherein, the dehydrogenation unit 3 is configured to receive the synthetic ammonia tail gas from the heat exchange unit 2 after being cooled in the dehydrogenation tower 301, and rely on the dehydrogenation reboiler 304 to generate a first nitrogen-rich waste stream returned to and / or released to the bottom of the dehydrogenation tower 301, and generate a top distillate stream of the dehydrogenation tower 301 which is sequentially guided to the first dehydrogenation condensation evaporator 302 and the second dehydrogenation condensation evaporator 303.

[0060] The first dehydrogenation condensation evaporator 302 is configured to condense the top distillate stream of the dehydrogenation tower 301 by relying on the cold source from the pure argon tower 501, and generate a first nitrogen-rich reflux stream returned to or released into the dehydrogenation tower 301, and generate a first hydrogen-rich product stream directed to the second dehydrogenation condensation evaporator 303.

[0061] The second dehydrogenation condensation evaporator 303 is configured to condense the first hydrogen-rich product stream by relying on the cold source from the heat exchange unit 2, and generate a second nitrogen-rich reflux stream returned to or released into the dehydrogenation tower 301, and generate a second hydrogen-rich product stream directed to the supercooling unit 6.

[0062] The demethanizer unit 4 is configured to receive the first nitrogen-rich waste stream from the bottom of the dehydrogenation tower 301 in the demethanizer 401, and to generate a methane-rich product stream returned to / or released to the bottom of the demethanizer 401 by means of the demethanizer reboiler 403, and to generate a top distillate stream of the demethanizer 401 directed to the demethanizer condenser evaporator 402.

[0063] The demethanizer condenser evaporator 402 is configured to condense the top distillate stream of the demethanizer 401 by relying on the cold source from the heat exchange unit 2 and through indirect heat exchange with the first nitrogen-rich waste stream from the dehydrogenation unit 3 and the methane-rich product stream from the demethanizer 4, and to return or release a portion of the condensed top distillate stream of the demethanizer 401 to the demethanizer 401 as a third nitrogen-rich reflux stream, and to direct another portion to the deargon removal unit 5 as a second nitrogen-rich waste stream.

[0064] The deargon unit 5 is configured to receive the second nitrogen-rich waste stream from the top of the demethanizer 401 in the pure argon tower 501 , and to generate a crude nitrogen stream at the top of the pure argon tower 501 and a first pure argon stream at the bottom of the pure argon tower 501 .

[0065] The deargonation unit 5 is further configured to receive the liquid nitrogen reflux liquid from the heat exchange unit 2 in the supplementary flow channel 502 at the top of the pure argon tower 501 and mix it with the crude nitrogen flow to generate a nitrogen product flow returned to the top of the pure argon tower 501, and to generate a second pure argon flow released to the bottom of the pure argon tower 501, and the first pure argon flow and the second pure argon flow together serve as a liquid argon product flow.

[0066] The following is a further description of the recovery process of synthetic ammonia tail gas in combination with each unit in the above structure:

[0067] First, the raw gas (i.e., synthetic ammonia tail gas) at about 1.6 MPa is cooled by heat exchange with the reflux gas in the heat exchanger 201 and then enters the dehydrogenation tower 301 .

[0068] At the bottom of the dehydrogenation tower 301, the nitrogen and hydrogen components in the feed gas absorb heat through the dehydrogenation reboiler 304 and rise to the top of the dehydrogenation tower 301. At this time, the first nitrogen-rich waste stream is obtained at the bottom of the dehydrogenation tower 301, and the rising nitrogen and hydrogen components are used as the top distillate stream of the dehydrogenation tower 301 and exchange heat with the liquid argon at the bottom of the pure argon tower 501 in the first dehydrogenation condensation evaporator 302 at the top of the tower.

[0069] After heat exchange, part of the nitrogen in the top distillate stream of the dehydrogenation tower 301 is condensed, and the condensed nitrogen component is released into the dehydrogenation tower 301 as a first nitrogen-rich reflux stream, and part of the nitrogen and hydrogen components in the top distillate stream of the dehydrogenation tower 301 enter the second dehydrogenation condensation evaporator 303 as a first hydrogen-rich product stream to exchange heat with low-pressure liquid nitrogen.

[0070] After heat exchange, part of the nitrogen in the first hydrogen-rich product flow is condensed, and the condensed nitrogen component is released into the dehydrogenation tower 301 as a second nitrogen-rich reflux flow, and the remaining uncondensed part (hydrogen content of about 70%) in the first hydrogen-rich product flow is recycled as a second hydrogen-rich product flow through the subcooling unit 6 and the heat exchange unit 2 for reheating and exiting the cold box.

[0071] Secondly, the first nitrogen-rich waste flow at the bottom of the dehydrogenation tower 301 enters the demethanization unit 4 after throttling and pressure reduction.

[0072] At the bottom of the demethanizer 401, the nitrogen and argon components in the first nitrogen-rich waste stream absorb heat through the demethanizer reboiler 403 and rise to the top of the demethanizer 401. At this time, a methane-rich product stream is obtained at the bottom of the demethanizer 401. The methane-rich product stream can be used as liquefied natural gas (LNG) and pressurized by the first cryogenic liquid pump 404 to enter the heat exchange unit 2 for vaporization, reheating and cold recovery, and then exit the cold box and be sent to the gas user for recycling. The rising nitrogen and argon components are used as the top distillate stream of the demethanizer 401 and exchange heat with the liquid nitrogen from the heat exchange unit 2 in the demethanizer condenser evaporator 402 at the top of the tower.

[0073] After heat exchange, the top distillate stream of the demethanizer 401 is condensed, and a portion of the condensed liquid is released into the demethanizer 401 as a third nitrogen-rich reflux stream, and the other portion enters the deargon unit 5 as a second nitrogen-rich waste stream.

[0074] Finally, the second nitrogen-rich waste stream enters the pure argon column 501 as a feedstock.

[0075] In the middle of the pure argon tower 501, the nitrogen component and a small amount of argon component in the second nitrogen-rich waste stream (nitrogen-argon mixed liquid) rise to the top of the pure argon tower 501, and the argon component refluxes to the top of the pure argon tower 501. At this time, the top and bottom of the pure argon tower 501 respectively obtain a crude nitrogen stream and a first pure argon stream.

[0076] Subsequently, a stream of liquid nitrogen is sprayed into the pure argon tower 501 through the supplementary flow channel 502 at the top thereof. The supplementary liquid nitrogen serves as a reflux liquid to wash the argon component in the second nitrogen-rich waste stream and the crude nitrogen stream as a second pure argon stream to the bottom of the pure argon tower 501.

[0077] A gaseous nitrogen product stream is obtained at the top of the pure argon tower 501, and a liquid argon product stream formed by mixing the first pure argon stream and the second pure argon stream is obtained at the bottom of the tower. Figure 2 The liquid argon product stream can be pressurized by the second cryogenic liquid pump 503 and sent to the product storage tank for recycling.

[0078] In the above process, the dehydrogenation tower 301, the demethanization tower 401 and the pure argon tower 501 cooperate with each other to perform three-tower distillation on the synthetic ammonia tail gas, so as to effectively recover the components such as hydrogen, nitrogen and argon in the synthetic ammonia tail gas, and finally obtain the second hydrogen-rich product stream, the methane-rich product stream and the liquid argon product stream for recycling.

[0079] In the three-tower distillation, the transport unit 1, the heat exchange unit 2 and the subcooling unit 6 need to coordinately provide the heat source and cold source required for distillation to the top and bottom of the dehydrogenation tower 301, the demethanization tower 401 and the pure argon tower 501. Figure 2 In this embodiment, the delivery unit 1 includes a circulating nitrogen compressor 101 , a high-temperature turbine expander 103 , a low-temperature turbine expander 104 and a gas-liquid separator 105 .

[0080] The circulating nitrogen compressor 101 is used to receive a nitrogen gas flow and compress it to obtain a compressed nitrogen gas flow, and the compressed nitrogen gas flow is further divided into a first part and a second part; wherein the first part of the compressed nitrogen gas flow and the second part of the compressed nitrogen gas flow are respectively used as a heat source and / or a cold source in the three-tower distillation, and then are combined again after being supercooled by the supercooling unit 6 and reheated by the heat exchange unit 2, and are finally received and compressed by the circulating nitrogen compressor 101 and carry out the next cycle.

[0081] After receiving the first part of the cooled compressed nitrogen flow, the high temperature turbine expander 103 makes it expand by endothermic absorption to form a first nitrogen-liquid nitrogen mixed flow. The first nitrogen-liquid nitrogen mixed flow is separated by the gas-liquid separator 105 to form a first nitrogen mixed flow and a second nitrogen mixed flow.

[0082] Among them, the first nitrogen mixed flow is guided to the subcooling unit 6 and the heat exchange unit 2 for reheating, and the first nitrogen mixed flow after reheating enters the low-temperature turbine expander 104, absorbs heat and expands to form a second nitrogen mixed flow, and the second nitrogen mixed flow is finally transported by the pipeline network to the subcooling unit 6 and the heat exchange unit 2 for reheating, and finally is received and compressed by the circulating nitrogen compressor 101 as a nitrogen flow and performs the next cycle.

[0083] In some embodiments, the first liquid nitrogen mixed flow can be guided by the gas-liquid separator 105 to pass through a throttle valve and then be sent to the demethanizing condenser evaporator 402 to be used as a cold source.

[0084] In some embodiments, the conveying unit 1 also includes a booster compressor 102, which can be coaxially dragged by the high-temperature turbine expander 103 and the low-temperature turbine expander 104, and is used to cooperate with the circulating nitrogen compressor 101 to further compress the first part of the compressed nitrogen flow and guide it to the heat exchange unit 2 for cooling.

[0085] In some embodiments, the delivery unit 1 can also be used to cool the compressed nitrogen gas flow and then split it. Of the two split compressed nitrogen gas flows, one is the first part of the compressed nitrogen gas flow sent to the high-temperature turbine expander 103 mentioned above, and the other is further split as the second part of the compressed nitrogen gas flow and sent to the dehydrogenation reboiler 304 and the demethanization reboiler 403, and finally condensed as a heat source and then merged again.

[0086] After the second part of the compressed nitrogen gas flow after condensation and re-merging is supercooled by the supercooling unit 6, it will be split into three streams again, one of which flows to the pure argon tower 501 and serves as the liquid nitrogen reflux liquid at the top of the tower, one stream is used as a cold source in the demethanization condensation evaporator 402, and the other stream is used as a cold source in the second dehydrogenation condensation evaporator 303. Finally, after the second part of the compressed nitrogen gas flow used as a cold source is reheated to room temperature by the supercooling unit 6 and the heat exchange unit 2, a part of it is sent to the circulating nitrogen compressor 101 as a nitrogen gas flow for the next cycle, and the other part is recovered as a nitrogen product for use by downstream users.

[0087] In some embodiments, in addition to relying on the cold source delivered from the circulating nitrogen compressor 101 to condense the first hydrogen-rich product stream, the second dehydrogenation condensation evaporator 303 can also condense the first hydrogen-rich product stream via indirect heat exchange with the first nitrogen-rich waste stream from the dehydrogenation unit 3 and the methane-rich product stream from the demethanization unit 4, thereby reducing the circulation volume of the circulating nitrogen compressor 101 while ensuring the hydrogen recovery rate, effectively reducing system energy consumption and reducing production costs.

[0088] Similar to the configuration of the second dehydrogenation condenser evaporator 303, in some embodiments, the demethanizer condenser evaporator 402 is also configured to condense the top distillate flow of the demethanizer 401 via indirect heat exchange with the first nitrogen-rich waste flow from the dehydrogenation unit 3 and the methane-rich product flow from the demethanizer unit 4, which also effectively reduces the system energy consumption.

[0089] In summary, the utility model forms a three-tower distillation by utilizing a dehydrogenation unit, a demethanization unit and a deargonization unit, thereby removing hydrogen, methane and argon components in the synthetic ammonia tail gas respectively, obtaining nitrogen-hydrogen mixed gas, liquefied natural gas, liquid argon and gaseous nitrogen and other products, reducing flammable and explosive components and hydrocarbons in the vented gas while recovering useful gases, thereby reducing environmental pollution; at the same time, the subcooling unit fully utilizes the products between the distillation towers for heat exchange, reducing the circulation volume of the nitrogen compressor while ensuring the hydrogen recovery rate, effectively reducing energy consumption, improving resource utilization, and realizing efficient, economical and environmentally friendly recovery of synthetic ammonia tail gas.

[0090] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0091] The above is a detailed introduction to a synthetic ammonia tail gas treatment system provided in an embodiment of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solution and its core idea of ​​the present application. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A synthetic ammonia tail gas treatment system, characterized in that: include: A delivery unit, the delivery unit is used to receive and deliver synthetic ammonia tail gas to the system; A heat exchange unit, the heat exchange unit is used to cool the synthetic ammonia tail gas transported by the transport unit; A dehydrogenation unit, which is used to remove hydrogen components from the synthetic ammonia tail gas, and includes a dehydrogenation tower, a first dehydrogenation condensation evaporator, a second dehydrogenation condensation evaporator and a dehydrogenation reboiler; A demethanization unit, which is used to remove methane components from synthetic ammonia tail gas, and comprises a demethanization tower, a demethanization condenser evaporator and a demethanization reboiler; A de-argon unit, which is used to remove argon components from synthetic ammonia tail gas, and comprises a pure argon tower and a supplementary flow channel thereof; A subcooling unit, the subcooling unit is used to cool the system product, and the subcooling unit is operably connected to the dehydrogenation unit, the demethanization unit and the deargonization unit respectively; The dehydrogenation unit is configured to receive the synthetic ammonia tail gas cooled by the heat exchange unit in the dehydrogenation tower, and to generate a first nitrogen-rich waste stream to be returned to and / or released to the bottom of the dehydrogenation tower by means of the dehydrogenation reboiler, and to generate a dehydrogenation tower top distillate stream to be sequentially directed to the first dehydrogenation condensation evaporator and the second dehydrogenation condensation evaporator; The first dehydrogenation condenser-evaporator is configured to condense the dehydrogenation column overhead stream by relying on a cold source from the pure argon column and produce a first nitrogen-rich reflux stream that is returned to or released into the dehydrogenation column, and produce a first hydrogen-rich product stream that is directed to the second dehydrogenation condenser-evaporator; The second dehydrogenation condensation evaporator is configured to condense the first hydrogen-rich product stream by relying on the cold source from the heat exchange unit, and generate a second nitrogen-rich reflux stream returned to or released into the dehydrogenation column, and generate a second hydrogen-rich product stream directed to the subcooling unit; wherein the demethanizer unit is configured to receive the first nitrogen-rich waste stream from the bottom of the dehydrogenation tower in the demethanizer, and to generate a methane-rich product stream returned to / or released to the bottom of the demethanizer by means of the demethanizer reboiler, and to generate a demethanizer overhead stream directed to the demethanizer condenser evaporator; The demethanizer condenser evaporator is configured to condense the demethanizer overhead stream by relying on the cold source from the heat exchange unit and through indirect heat exchange with the first nitrogen-rich waste stream from the dehydrogenation unit and the methane-rich product stream from the demethanizer unit, and to return or release a portion of the condensed demethanizer overhead stream to the demethanizer as a third nitrogen-rich reflux stream, and another portion is directed to the deargon removal unit as a second nitrogen-rich waste stream; wherein the deargon unit is configured to receive the second nitrogen-rich waste stream from the top of the demethanizer in the pure argon column, and to generate a crude nitrogen stream at the top of the pure argon column and a first pure argon stream at the bottom of the pure argon column, respectively; The deargonation unit is further configured to receive liquid nitrogen reflux liquid from the heat exchange unit in the supplementary flow channel at the top of the pure argon column and mix it with the crude nitrogen flow to generate a nitrogen product flow returned to the top of the pure argon column and to generate a second pure argon flow released to the bottom of the pure argon column, the first pure argon flow and the second pure argon flow together serving as a liquid argon product flow.

2. The synthetic ammonia tail gas treatment system according to claim 1, characterized in that: The delivery unit includes a circulating nitrogen compressor configured to receive an incoming nitrogen flow and produce a compressed nitrogen flow; wherein the compressed nitrogen flow is split into a first portion of the compressed nitrogen flow and a second portion of the compressed nitrogen flow; The first part of the compressed nitrogen flow and the second part of the compressed nitrogen flow are respectively used as heat sources and / or cold sources and after being supercooled by the supercooling unit and reheated by the heat exchange unit, they are merged again and received and compressed by the circulating nitrogen compressor for the next cycle.

3. The synthetic ammonia tail gas treatment system according to claim 2, characterized in that: The delivery unit further includes a booster compressor configured to further compress the first portion of the compressed nitrogen flow and direct it to the heat exchange unit to be cooled.

4. The synthetic ammonia tail gas treatment system according to claim 2, characterized in that: The delivery unit also includes a high-temperature turbine expander, a low-temperature turbine expander and a gas-liquid separator; The high temperature turbine expander is configured to receive a first portion of the cooled compressed nitrogen gas flow and expand it endothermically to form a first nitrogen-liquid nitrogen mixed flow; The gas-liquid separator is configured to receive the first nitrogen-liquid nitrogen mixed flow and separate it into a first nitrogen mixed flow and a first liquid nitrogen mixed flow; the first nitrogen mixed flow is guided to the subcooling unit and the heat exchange unit for reheating; The low-temperature turbine expander is configured to receive the reheated first nitrogen mixed flow and endothermally expand it to form a second nitrogen mixed flow. The second nitrogen mixed flow is guided to the subcooling unit and the heat exchange unit for reheating and then received and compressed by the circulating nitrogen compressor for the next cycle.

5. The synthetic ammonia tail gas treatment system according to claim 4, characterized in that: The first liquid nitrogen mixed flow is guided by the gas-liquid separator to the demethanization condensation evaporator as a cold source.

6. The synthetic ammonia tail gas treatment system according to claim 2, characterized in that: The delivery unit is further configured to cool the second part of the compressed nitrogen gas flow and direct the second part of the compressed nitrogen gas flow to the dehydrogenation reboiler and the demethanization reboiler as a heat source to be condensed and then merged again; The subcooling unit is also configured to subcool the second part of the condensed compressed nitrogen gas flow and then divert it again, and guide it to the top of the pure argon tower as the liquid nitrogen reflux liquid, to the demethanization condenser evaporator as a cold source, and to the second dehydrogenation condenser evaporator as a cold source.

7. The synthetic ammonia tail gas treatment system according to claim 1, characterized in that: The second dehydrogenation condenser evaporator is further configured to condense the first hydrogen-rich product stream via indirect heat exchange with the first nitrogen-rich waste stream from the dehydrogenation unit and the methane-rich product stream from the demethanization unit.

8. The synthetic ammonia tail gas treatment system according to claim 1, characterized in that: The demethanizer condenser-evaporator is further configured to condense the demethanizer overhead stream via indirect heat exchange with the first nitrogen-rich waste stream from the dehydrogenation unit and the methane-rich product stream from the demethanizer unit.

9. The synthetic ammonia tail gas treatment system according to claim 1, characterized in that: The second hydrogen-rich product flows through the subcooling unit and the heat exchange unit for reheating and is then sent to the product storage tank.

10. The synthetic ammonia tail gas treatment system according to claim 1, characterized in that: The methane-rich product at the bottom of the demethanizer is pressurized by a first cryogenic liquid pump and then reheated by the heat exchange unit before being sent to the gas user.

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