CN115839600A - Cryogenic air separation device - Google Patents
Cryogenic air separation device Download PDFInfo
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- CN115839600A CN115839600A CN202310147318.1A CN202310147318A CN115839600A CN 115839600 A CN115839600 A CN 115839600A CN 202310147318 A CN202310147318 A CN 202310147318A CN 115839600 A CN115839600 A CN 115839600A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
- F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
- F25J3/04078—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression
- F25J3/04084—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression of nitrogen
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
- F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
- F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
- F25J3/04193—Division of the main heat exchange line in consecutive sections having different functions
- F25J3/042—Division of the main heat exchange line in consecutive sections having different functions having an intermediate feed connection
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
- F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
- F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
- F25J3/0429—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of feed air, e.g. used as waste or product air or expanded into an auxiliary column
- F25J3/04296—Claude expansion, i.e. expanded into the main or high pressure column
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
- F25J3/0446—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the heat generated by mixing two different phases
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
- F25J3/04642—Recovering noble gases from air
- F25J3/04648—Recovering noble gases from air argon
- F25J3/04654—Producing crude argon in a crude argon column
- F25J3/04666—Producing crude argon in a crude argon column as a parallel working rectification column of the low pressure column in a dual pressure main column system
- F25J3/04672—Producing crude argon in a crude argon column as a parallel working rectification column of the low pressure column in a dual pressure main column system having a top condenser
- F25J3/04678—Producing crude argon in a crude argon column as a parallel working rectification column of the low pressure column in a dual pressure main column system having a top condenser cooled by oxygen enriched liquid from high pressure column bottoms
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
- F25J3/04642—Recovering noble gases from air
- F25J3/04648—Recovering noble gases from air argon
- F25J3/04721—Producing pure argon, e.g. recovered from a crude argon column
- F25J3/04727—Producing pure argon, e.g. recovered from a crude argon column using an auxiliary pure argon column for nitrogen rejection
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/04—Processes or apparatus using separation by rectification in a dual pressure main column system
- F25J2200/06—Processes or apparatus using separation by rectification in a dual pressure main column system in a classical double column flow-sheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
- F25J2235/50—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being oxygen
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2245/00—Processes or apparatus involving steps for recycling of process streams
- F25J2245/42—Processes or apparatus involving steps for recycling of process streams the recycled stream being nitrogen
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- General Engineering & Computer Science (AREA)
- Separation By Low-Temperature Treatments (AREA)
Abstract
The application provides a cryogenic air separation device which comprises a main tower and a mixing tower, wherein a main condensation evaporator of the main tower is provided with a liquid oxygen outlet, the liquid oxygen outlet is provided with a first liquid oxygen branch communicated with the mixing tower, a lower tower of the main tower is provided with a liquid nitrogen outlet, the liquid nitrogen outlet is provided with a first liquid nitrogen branch communicated with the mixing tower, so that part of liquid oxygen and liquid nitrogen are extracted from the main tower and sent into the mixing tower; the tower bottom of the mixing tower is provided with a reboiler to heat and vaporize the mixed liquid at the tower bottom, so that an oxygen-enriched product with pressure of 80-98% is obtained at the tower top. The cryogenic air separation device can directly produce the pressurized oxygen-enriched product in the cold box, the working pressure of the mixing tower is obtained by pressurizing the pressurized oxygen-enriched product by the liquid oxygen pump, an oxygen compressor is not required to be arranged outside, the total cost of the device is reduced, and the fire hazard is avoided; meanwhile, the medium on the evaporation side of the reboiler is oxygen-enriched liquid, so that carbon hydrogen is not easy to accumulate, and oxygen-enriched evaporation is safer under the same carbon hydrogen content.
Description
Technical Field
The application relates to the technical field of high-purity oxygen preparation, in particular to a cryogenic air separation device.
Background
The air separation device separates oxygen, nitrogen, argon and other gases in the air from the air by a cryogenic method according to the principle that different components in the air have different boiling points; the non-ferrous metal smelting industry also has the demand of oxygen-enriched air separation, but the conventional cryogenic air separation can not directly produce pressurized (2-6 bar) oxygen-enriched products in a cold box of a cryogenic air separation device while producing pure oxygen and liquid argon, and pressurized air needs to be doped in the pure oxygen products outside the cold box, so that the pure oxygen and the liquid argon are mixed to achieve the required oxygen-enriched purity (80% -98%), but the energy consumption of the whole process route is higher; the existing oxygen-enriched air separation device can directly output pressurized oxygen-enriched products from the cold box, but pure oxygen and liquid argon products cannot be extracted simultaneously due to the particularity of the oxygen-enriched air separation device.
Disclosure of Invention
The invention aims to provide a cryogenic air separation device, which can directly produce oxygen enriched with pressure in a cold box and reduce the energy consumption of the device.
The invention provides a cryogenic air separation device, which comprises a main tower and a mixing tower, wherein the main tower is provided with a first mixing tower; the main tower comprises an upper tower, a lower tower and a main condensation evaporator arranged between the upper tower and the lower tower; the bottom of the main condensation evaporator is provided with a liquid oxygen outlet, the liquid oxygen outlet is used for extracting liquid oxygen, the liquid oxygen outlet is provided with a first liquid oxygen branch, the first liquid oxygen branch is communicated with a feed inlet of the mixing tower, and a liquid oxygen pump is arranged on the first liquid oxygen branch; a liquid nitrogen outlet is formed in the top of the lower tower and used for extracting liquid nitrogen, a first liquid nitrogen branch is formed in the liquid nitrogen outlet and communicated with a feeding hole of the mixing tower; the tower bottom of mixing column is equipped with the reboiler, the top of mixing column is equipped with the oxygen-enriched product export, the tower bottom of mixing column is equipped with the oxygen-enriched liquid export, the oxygen-enriched liquid export with the oxygen-enriched liquid backward flow mouth of last tower bottom is linked together.
Further, the cryogenic air separation plant also comprises a mixing tower heat exchanger; the mixing tower heat exchanger comprises a cold flow channel, the first liquid oxygen branch and the first liquid nitrogen branch are respectively communicated with an inlet of the cold flow channel, an outlet of the cold flow channel is communicated with a feed inlet of the mixing tower, and the mixing tower heat exchanger is used for heating the liquid oxygen and the liquid nitrogen flowing through the cold flow channel to a preset temperature.
Furthermore, the cryogenic air separation plant also comprises a main heat exchanger and a subcooler; the outlet of the oxygen-enriched product is communicated with the oxygen-enriched channel of the main heat exchanger, and the outlet of the oxygen-enriched channel of the main heat exchanger is communicated with the pressurized oxygen-enriched product conveying pipeline; the top of the upper tower is provided with a low-pressure nitrogen outlet which is sequentially communicated with a low-pressure nitrogen channel of the subcooler and a low-pressure nitrogen channel of the main heat exchanger, and the low-pressure nitrogen channel of the main heat exchanger is communicated with a low-pressure nitrogen product conveying pipeline; a waste nitrogen outlet is formed in the top of the upper tower and communicated with a waste nitrogen channel of the subcooler, and a first nitrogen branch and a second nitrogen branch are formed in the outlet of the waste nitrogen channel of the subcooler; the first nitrogen branch is communicated with a first waste nitrogen channel of the main heat exchanger and then is communicated with a waste nitrogen conveying pipeline; and the second nitrogen branch is communicated with a second waste nitrogen channel of the main heat exchanger and then is used for being communicated with a waste nitrogen conveying pipeline for regeneration of the purification system.
Further, the cryogenic air separation plant also comprises a feeding unit, wherein the feeding unit comprises an air compressor, a precooling system, a purification system, an air supercharger and an expansion machine; the air compressor, the precooling system and the purifying system are sequentially connected, and a first air branch and a second air branch are arranged at an outlet of the purifying system; the first air branch is sequentially connected with a first air channel of the main heat exchanger and a raw material feeding hole of the lower tower; the second air branch is communicated with the air supercharger and is connected to the pressurization end of the expansion machine through the final stage outlet of the air supercharger; a third air branch and a fourth air branch are arranged at an outlet of the pressurizing end, and the third air branch is sequentially connected with a second air channel of the main heat exchanger, a first throttling valve and a raw material feeding hole of the lower tower; and the fourth air branch is sequentially connected with a third air channel of the main heat exchanger, an expansion end of the expansion machine, a fourth air channel of the main heat exchanger and a raw material feeding port of the lower tower.
Further, the air supercharger is provided with a middle pumping port; and the middle pumping port is sequentially connected with a fifth air channel of the main heat exchanger, the reboiler, a heat flow channel of the mixing tower heat exchanger and the raw material feeding port of the lower tower.
Furthermore, a liquid oxygen outlet of the main condensation evaporator is divided into two paths, wherein one path is the first liquid oxygen branch, and the other path is the second liquid oxygen branch; the second liquid oxygen branch is communicated with a liquid oxygen channel of the subcooler, and an outlet of the liquid oxygen channel is communicated with a liquid oxygen product conveying pipeline.
Further, the cryogenic air separation plant also comprises a liquid nitrogen gas-liquid separator; liquid nitrogen outlets at the top of the lower tower are divided into three paths, namely the first liquid nitrogen branch, the second liquid nitrogen branch and the third liquid nitrogen branch in sequence; the second liquid nitrogen branch is sequentially connected with a liquid nitrogen channel of the subcooler, a second throttling valve and an inlet of the liquid nitrogen gas-liquid separator; the bottom of the liquid nitrogen-gas separator is provided with a liquid nitrogen product outlet which is communicated with a liquid nitrogen product conveying pipeline, the top of the liquid nitrogen-gas separator is provided with a flash evaporation nitrogen gas outlet, and the flash evaporation nitrogen gas outlet is communicated with a nitrogen gas reflux port of the upper tower; the third liquid nitrogen branch is communicated with a liquid nitrogen channel of the main heat exchanger through a liquid nitrogen pump, and an outlet of the liquid nitrogen channel of the main heat exchanger is communicated with a nitrogen product conveying pipeline.
Further, the cryogenic air separation plant also comprises a crude argon column and a fine argon column; an argon fraction outlet is formed in the middle of the upper tower and is sequentially communicated with the crude argon tower and the fine argon tower; the thick argon tower with the tower bottom of smart argon tower is equipped with liquid argon export respectively, the liquid argon export of thick argon tower through thick argon delivery pump with the thick argon backward flow mouth of last tower is linked together, the liquid argon export of smart argon tower is used for being linked together with liquid argon product transfer passage.
Further, a crude argon condenser is arranged at the top of the crude argon tower; a pure argon evaporator is arranged at the bottom of the fine argon tower, and a pure argon condenser is arranged at the top of the fine argon tower; the bottom of the lower tower is provided with an oxygen-enriched liquid air outlet, and the oxygen-enriched liquid air outlet is divided into two paths after being sequentially communicated with the subcooler and the pure argon evaporator: one path is communicated with the upper tower through the pure argon condenser, and the other path is communicated with the upper tower through the crude argon condenser.
Furthermore, the middle part of the lower tower is provided with a liquid-air outlet, the liquid-air outlet is sequentially communicated with the liquid-air channel of the subcooler and the liquid-air return port of the upper tower, and a throttle valve is arranged on a pipeline between the liquid-air channel of the subcooler and the liquid-air return port of the upper tower.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a cryogenic air separation plant, which comprises a main tower and a mixing tower, wherein the main tower is core equipment of the cryogenic air separation plant and comprises an upper tower, a lower tower and a main condensation evaporator, the main condensation evaporator is arranged between the upper tower and the lower tower, the lower tower is provided with a raw material feeding hole, and raw material air can enter the lower tower through the raw material feeding hole to be rectified so as to separate various components, such as liquid oxygen, liquid nitrogen and argon fractions; the main tower is provided with a liquid oxygen outlet for extracting liquid oxygen from the main tower and a liquid nitrogen outlet for extracting liquid nitrogen, the liquid oxygen outlet is arranged at the bottom of the main condensation evaporator, the liquid oxygen outlet is provided with a first liquid oxygen branch, the first liquid oxygen branch is used for being communicated with a feed inlet of the mixing tower, and the first liquid oxygen branch is provided with a liquid oxygen pump so as to pump partial liquid oxygen from the main tower and send the partial liquid oxygen into the mixing tower after being pressurized by the liquid oxygen pump; the liquid nitrogen outlet is arranged at the top of the lower tower and is provided with a first liquid nitrogen branch which is communicated with the feed inlet of the mixing tower so as to extract part of liquid nitrogen from the main tower and feed the liquid nitrogen into the mixing tower; the tower bottom of the mixing tower is provided with a reboiler, the mixed liquid of liquid oxygen and liquid nitrogen falls into the bottom of the mixing tower through a filler in the mixing tower and is heated and vaporized by the reboiler, so that an oxygen-enriched product with pressure ranging from 80% to 98% is obtained on the tower top of the mixing tower, the working pressure of the mixing tower is the pressure required by the oxygen-enriched product, and the oxygen-enriched product with pressure can be pumped out through an oxygen-enriched product outlet in the top of the mixing tower.
The cryogenic air separation device innovatively introduces a pure liquid oxygen and pure liquid nitrogen mixing tower process route, and can directly produce oxygen-enriched products with pressure in a cold box on the basis of maintaining a conventional cryogenic air separation argon extraction system; meanwhile, the working pressure of the mixing tower is pressurized to the required pressure by a liquid oxygen pump, and the working pressure of the mixing tower is the pressure required by the pressurized oxygen-enriched product, an oxygen compressor is not required to be arranged outside, the total cost of the device is reduced, and the fire hazard caused by the adoption of an oxygen turbine compressor is avoided; meanwhile, as the medium on the evaporation side of the reboiler is oxygen-enriched liquid, compared with a pure liquid oxygen environment under the same pressure, the hydrocarbon is less prone to accumulation, and in an impure oxygen environment, the oxygen-enriched evaporation is safer under the same hydrocarbon content.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic structural diagram of a cryogenic air separation plant provided in an embodiment of the present invention.
Reference numerals are as follows:
the method comprises the following steps of 1-an air compressor, 2-a precooling system, 3-a purifying system, 4-an air supercharger, 5-an expander, 6-a main heat exchanger, 7-a mixing tower, 8-a reboiler, 9-a subcooler, 10-a main tower, 11-a main condensing evaporator, 12-an upper tower, 13-a lower tower, 14-a crude argon tower, 15-a fine argon tower, 16-a pure argon evaporator, 17-a crude argon condenser and 18-a pure argon condenser.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention.
The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention.
All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
A cryogenic air separation plant according to some embodiments of the present application is described below with reference to fig. 1.
The application provides a cryogenic air separation plant, as shown in figure 1, which comprises a feed unit, a main heat exchanger 6, a main column 10, a mixing column 7, a subcooler 9, a crude argon column 14 and a fine argon column 15.
The main tower 10 is a core device of a cryogenic air separation plant, and comprises an upper tower 12, a lower tower 13 and a main condensation evaporator 11, wherein the main condensation evaporator 11 is arranged between the upper tower 12 and the lower tower 13, the lower tower 13 is provided with a raw material feed inlet, and raw material air can enter the lower tower 13 through the raw material feed inlet to be rectified after being processed by a feed unit and cooled by the main heat exchanger 6 so as to separate various components, such as liquid oxygen, liquid nitrogen and argon fractions.
The feeding unit comprises an air compressor 1, a precooling system 2, a purifying system 3, an air supercharger 4 and an expander 5, the air compressor 1 is communicated with a raw material air conveying pipeline, an outlet of the air compressor 1 is sequentially connected with the precooling system 2 and the purifying system 3, and raw material air is sequentially precooled and purified by the precooling system 2 and the purifying system 3 after being compressed by the air compressor 1.
Raw materials air is divided into two routes after the purification, and purification system 3's export is equipped with first air branch and second air branch promptly: the first air branch is sequentially communicated with a first air channel of the main heat exchanger 6 and a raw material feeding port of the lower tower 13, so that air in the first air branch enters the lower tower 13 after being cooled by the main heat exchanger 6; the second air branch communicates with the air supercharger 4 and is connected to the supercharging end of the expander 5 via the final outlet of the air supercharger 4.
The outlet of the pressurizing end of the expansion machine 5 is also divided into two paths, namely a third air branch and a fourth air branch, wherein the third air branch is sequentially communicated with a second air channel of the main heat exchanger 6, a first throttling valve and a raw material feeding port of the lower tower 13, so that the pressurized raw material air is cooled by the main heat exchanger 6 and then throttled to enter the lower tower 13; the fourth air branch is sequentially communicated with a third air channel of the main heat exchanger 6, the expansion end of the expansion machine 5, a fourth air channel of the main heat exchanger 6 and a raw material feed inlet of the lower tower 13, so that the pressurized raw material air is cooled to a certain temperature by the main heat exchanger 6, then flows out of the main heat exchanger 6 and enters the collision expansion end, and is further cooled to a preset temperature close to the saturation temperature by the main heat exchanger 6 after being expanded and then enters the lower tower 13.
The air supercharger 4 is also provided with a middle pumping port which is sequentially communicated with a fifth air channel of the main heat exchanger 6, a reboiler 8 at the bottom of the mixing tower 7, a heat flow channel of the heat exchanger and a raw material inlet of the lower tower 13 through pipelines; the medium pumped air from the air-air supercharger 4 is cooled by the main heat exchanger 6 and then enters the reboiler 8 at the bottom of the mixing tower 7 as a heat source, the kettle liquid (the mixed liquid of liquid oxygen and liquid nitrogen) at the bottom of the mixing tower 7 is heated and vaporized, the kettle liquid is discharged from the reboiler 8 and then enters the hot flow channel of the mixing tower heat exchanger, exchanges heat with the liquid oxygen and the liquid nitrogen in the cold flow channel of the mixing tower heat exchanger, and finally enters the lower tower 13.
The main column 10 is provided with a liquid oxygen outlet for extracting liquid oxygen from the main column 10, a liquid nitrogen outlet for extracting liquid nitrogen, and an argon fraction outlet for extracting an argon fraction.
Wherein the liquid oxygen outlet is arranged at the bottom of the main condensation evaporator 11 of the main tower 10, and the liquid oxygen outlet is divided into two paths, i.e. the liquid oxygen outlet is provided with a first liquid oxygen branch and a second liquid oxygen branch.
The first liquid oxygen branch is used for being communicated with a feed inlet of the mixing tower 7 so as to extract partial liquid oxygen from the main tower 10 and feed the partial liquid oxygen into the mixing tower 7 to participate in the preparation of the oxygen-enriched product under pressure.
The second liquid oxygen branch is firstly communicated with the liquid oxygen channel of the subcooler 9 and then communicated to an external liquid oxygen product conveying pipeline, so that the liquid oxygen on the branch is subcooled and then sent out of the cold box as a liquid oxygen product through the liquid oxygen product conveying pipeline, for example, sent into a liquid oxygen storage tank for storage through the liquid oxygen product pipeline.
The liquid nitrogen outlet is arranged at the top of the lower tower 13 and divided into three paths, namely a first liquid nitrogen branch, a second liquid nitrogen branch and a third liquid nitrogen branch in sequence.
The first liquid nitrogen branch is used for being communicated with a feed inlet of the mixing tower 7 so as to extract part of liquid nitrogen from the main tower 10 and feed the liquid nitrogen into the mixing tower 7 to participate in preparation of the pressurized oxygen-enriched product together with the liquid oxygen from the first liquid oxygen branch.
The second liquid nitrogen branch is sequentially communicated with a liquid nitrogen channel of the subcooler 9, the second throttle valve and an inlet of the liquid nitrogen-gas liquid separator, so that liquid nitrogen in the branch is sent into the liquid nitrogen-gas liquid separator through the subcooled back throttle of the subcooler 9 for gas-liquid separation.
The bottom of the liquid nitrogen gas-liquid separator is provided with a liquid nitrogen product outlet for extracting a liquid nitrogen product, and the liquid nitrogen product outlet is communicated with a liquid nitrogen product conveying pipeline so as to convey the liquid nitrogen product out of the cold box; the top of the liquid nitrogen separator is provided with a flash evaporation nitrogen outlet which is communicated with a nitrogen reflux opening at the top of the upper tower 12 so as to send the flash evaporation nitrogen to the top of the upper tower 12.
And the third nitrogen branch is communicated with a liquid nitrogen channel of the main heat exchanger 6 through a liquid nitrogen pump, and an outlet of the liquid nitrogen channel is communicated with a nitrogen product conveying pipeline, so that the liquid nitrogen of the branch is pressurized by the liquid nitrogen pump, then is heated and vaporized by the main heat exchanger 6 to serve as product nitrogen, and is sent out of the cold box through the nitrogen product conveying pipeline.
In the preparation of the pressurized oxygen-enriched product, specifically, the cryogenic air separation plant further comprises a mixing tower heat exchanger which comprises a hot flow channel and a cold flow channel capable of performing heat exchange, as described above, the extracted air in the incoming air supercharger 4 flows through the main heat exchanger 6, the reboiler 8 at the bottom of the mixing tower 7, the hot flow channel and then flows into the lower tower 13 in sequence, and in the mixing tower heat exchanger, the extracted air is used as a heat source to heat the fluid flowing through the cold flow channel.
The first liquid oxygen branch is provided with a liquid oxygen pump, and the first liquid oxygen branch and the first liquid nitrogen branch are respectively communicated with the inlet of the cold flow channel; the outlet of the cold flow channel is communicated with the feed inlet of the mixing tower 7, so that part of the liquid oxygen extracted from the bottom of the main condensation evaporator 11 is pressurized by a liquid oxygen pump and then mixed with the liquid nitrogen from the top of the lower tower 13, and the mixture is heated by an independent heat exchanger (namely, a mixing tower heat exchanger) to be reheated to a slightly supercooled preset temperature and then fed into the mixing tower 7.
The working pressure of the mixing tower 7 is pressurized to the required pressure by a liquid oxygen pump, the mixed liquid of liquid oxygen and liquid nitrogen falls into the bottom of the mixing tower 7 through the packing in the mixing tower 7 and is heated and vaporized by a reboiler 8 at the bottom of the mixing tower 7 (as mentioned above, the heat of the reboiler 8 is provided by the air pumped by the incoming air supercharger 4), so that 80 to 98 percent of oxygen-enriched product is obtained at the top of the mixing tower 7, the working pressure of the mixing tower 7 is the required pressure of the oxygen-enriched product, and the oxygen-enriched product under pressure can be pumped out through an oxygen-enriched product outlet at the top of the mixing tower 7.
Preferably, an oxygen-enriched product outlet at the top of the mixing tower 7 is communicated with an oxygen-enriched channel of the main heat exchanger 6, and an outlet of the oxygen-enriched channel is communicated with a pressurized oxygen-enriched product conveying pipeline, so that the pressurized oxygen-enriched product is heated and reheated to a predetermined temperature through the main heat exchanger 6 and then is sent out of the cooling box through the pressurized oxygen-enriched product conveying pipeline.
Preferably, the bottom of the mixing tower 7 is provided with an oxygen-rich liquid outlet, the bottom of the upper tower 12 is provided with an oxygen-rich liquid reflux port, and the oxygen-rich liquid outlet is communicated with the oxygen-rich liquid reflux port, so that a small part of oxygen-rich liquid can be extracted from the bottom of the mixing tower 7 and recycled to the upper tower 12, and the risk of accumulation of hydrocarbon is reduced.
In the embodiment of the present application, preferably, the top of the upper tower 12 is further provided with a low-pressure nitrogen outlet, the low-pressure nitrogen outlet is used for extracting low-pressure nitrogen from the top of the upper tower 12, the low-pressure nitrogen outlet is sequentially communicated with a low-pressure nitrogen channel of the subcooler 9 and a low-pressure nitrogen channel of the main heat exchanger 6, an outlet of the low-pressure nitrogen channel is used for being communicated with a low-pressure nitrogen product conveying pipeline, and the extracted low-pressure nitrogen is reheated by the chiller 9 and the main heat exchanger 6 and then is sent out of the cold box as a low-pressure nitrogen product through the low-pressure nitrogen product conveying pipeline.
In this embodiment, preferably, the top of the upper tower 12 is provided with a waste nitrogen outlet, the waste nitrogen outlet is communicated with the waste nitrogen channel of the subcooler 9, and the outlet of the waste nitrogen channel of the subcooler 9 is provided with a first nitrogen branch and a second nitrogen branch; the first nitrogen branch is communicated with a first waste nitrogen channel of the main heat exchanger 6 and then communicated with a waste nitrogen conveying pipeline; and the second nitrogen branch is communicated with a second waste nitrogen channel of the main heat exchanger 6 and then is used for being communicated with a waste nitrogen conveying pipeline for regeneration of the purification system. The waste nitrogen extracted from the upper tower 12 is heated and reheated by the subcooler 9 and the main heat exchanger 6, the waste nitrogen is divided into two paths, one path of the waste nitrogen is sent out of the cold box through a waste nitrogen conveying pipeline, the other path of the waste nitrogen is used for molecular sieve regeneration of the purification system 3, and the waste nitrogen is sent out of the cold box through a waste nitrogen conveying pipeline for purification system regeneration.
In this embodiment, preferably, the middle part of the lower tower 13 is provided with a liquid-air outlet, the upper tower 12 is provided with a liquid-air return port, and the liquid-air outlet of the lower tower 13 is sequentially communicated with the liquid-air channel of the subcooler 9, the throttle valve and the liquid-air return port of the upper tower 12 through a pipeline; so that liquid air can be extracted from the lower tower 13 through a liquid air outlet of the lower tower 13, and the extracted liquid air is throttled to enter the upper tower 12 after being supercooled by the cooler 9.
In this embodiment, an oxygen extraction opening is preferably reserved at the bottom of the upper tower 12.
In this embodiment, preferably, the cryogenic air separation plant further comprises a crude argon column 14 and a fine argon column 15, wherein an argon fraction outlet is arranged in the middle of the upper column 12, and the argon fraction outlet is communicated with the crude argon column 14 and the fine argon column 15 in sequence; specifically, the argon fraction outlet of the upper column 12 is communicated with the argon fraction inlet of the crude argon column 14, and the crude argon outlet of the crude argon column 14 is communicated with the crude argon inlet of the fine argon column 15, so that the argon fraction extracted from the upper column 12 sequentially enters the crude argon column 14 and the fine argon column 15 for purification, crude liquid argon is obtained at the bottom of the crude argon column 14, and pure liquid argon is obtained at the bottom of the fine argon column 15.
The bottom of the crude argon tower 14 is provided with a liquid argon outlet, and the liquid argon outlet of the crude argon tower 14 is communicated with the crude argon reflux port of the upper tower 12 through a crude argon delivery pump, so that the crude liquid argon at the bottom of the crude argon tower 14 can flow back to the upper tower 12 through the crude argon delivery pump.
The bottom of the fine argon tower 15 is also provided with a liquid argon outlet, and the liquid argon outlet of the fine argon tower 15 is communicated with the liquid argon storage tank through a liquid argon product conveying channel, so that pure liquid argon at the bottom of the fine argon tower 15 can be sent into the liquid argon storage tank as a liquid argon product to be collected.
In this embodiment, preferably, the top of the crude argon column 14 is provided with a crude argon condenser 17, the bottom of the fine argon column 15 is provided with a pure argon condenser 18, and the bottom of the fine argon column 15 is provided with a pure argon evaporator 16; the bottom of the lower tower 13 is provided with an oxygen-enriched liquid air, and the bottom of the lower tower 13 is provided with an oxygen-enriched liquid air outlet so as to be capable of extracting the oxygen-enriched liquid air from the bottom of the lower tower 13; the oxygen-enriched liquid air outlet is sequentially communicated with an oxygen-enriched liquid air channel of the subcooler 9 and a pure argon evaporator 16 at the bottom of the fine argon tower 15, so that the oxygen-enriched liquid air at the bottom of the lower tower 13 is subcooled by the subcooler 9 and flows into the pure argon evaporator 16 at the bottom of the fine argon tower 15.
The outlet of the pure argon evaporator 16 is divided into two paths, wherein one path is communicated with the pure argon condenser 18 and the upper tower 12 in sequence, and the other path is communicated with the crude argon condenser 17 and the upper tower 12 in sequence; the oxygen-enriched liquid air from the pure argon evaporator 16 is divided into two paths, wherein one path flows into the pure argon condenser 18 to provide a cold source for the pure argon condenser 18, and enters the upper tower 12 after being evaporated; the other path flows into the crude argon condenser 17 to provide a cold source for the crude argon condenser 17 and enters the upper column 12 after evaporation.
The cryogenic air separation device innovatively introduces a pure liquid oxygen and pure liquid nitrogen mixing tower process route, and can directly produce pressurized oxygen-enriched products in a cold box and high-extraction-rate by-product liquid argon products on the basis of maintaining a conventional cryogenic air separation and argon extraction system.
Meanwhile, the working pressure of the mixing tower is pressurized to the required pressure by the liquid oxygen pump, and the working pressure of the mixing tower is the pressure required by the pressurized oxygen-enriched product, an oxygen compressor is not required to be arranged outside, the total cost of the device is reduced, and the fire hazard caused by the adoption of an oxygen turbine compressor is avoided.
Meanwhile, the reboiler of the mixing tower utilizes the middle pumped air as a heat source, and the medium on the evaporation side of the reboiler is oxygen-enriched liquid, so that the saturation temperature of the reboiler is lower than that of pure liquid oxygen, and the pressure of the corresponding required middle pumped air is lower, thereby saving energy and reducing consumption to a certain extent.
Meanwhile, as the medium on the evaporation side of the reboiler is oxygen-enriched liquid, compared with a pure liquid oxygen environment under the same pressure, the carbon hydrogen is less prone to accumulation, and in an impure oxygen environment, the oxygen-enriched evaporation is safer under the same carbon hydrogen content.
Meanwhile, after being pressurized by the liquid oxygen pump, the liquid oxygen is firstly reset to a saturated state by the independently arranged mixing tower heat exchanger and then enters the mixing tower, so that the enthalpy value required by unit liquid oxygen vaporization is reduced, and the quantity of the medium pumped air used as a heat source is reduced as much as possible.
Meanwhile, after the intermediate pumped air is condensed into liquid air by a reboiler of the mixing tower, the liquid air is cooled to saturation temperature after exchanging heat with pressurized liquid oxygen by an independent mixing tower heat exchanger, so that the gasification rate of the liquid air after entering the lower tower after throttling is greatly reduced, the liquefied high-pressure liquid air required by the main heat exchanger is reduced, the quantity of the positive flow air directly entering the bottom of the lower tower is increased, the heat exchange temperature difference of the main heat exchanger is optimized, and the rectification efficiency of the whole cold box is improved.
Simultaneously, compare in conventional oxygen-enriched air separation plant, pure liquid oxygen still can be produced to the upper column of cryrogenic air separation plant of this application to the middle and lower section in upper column can take out the argon fraction, with the liquid argon product that obtains high extraction rate, satisfies peripheral high-value market demand.
Meanwhile, because the oxygen-enriched product is directly compressed in the cold box for heat exchange and rewarming, the whole heat exchange temperature field is distributed more uniformly, even if the device has a slightly large liquid amount, single expansion refrigeration can be adopted, the expanded air enters the main heat exchanger for further cooling and then enters the lower tower, and compared with the condition that the expanded air directly enters the lower tower, the device has the advantages of small whole heat exchange loss, low energy consumption and higher device extraction rate; compared with the conventional high-low temperature expansion, the single expansion of the application has low cost and lower failure rate.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A cryogenic air separation plant is characterized by comprising a main tower and a mixing tower;
the main tower comprises an upper tower, a lower tower and a main condensation evaporator arranged between the upper tower and the lower tower;
the bottom of the main condensation evaporator is provided with a liquid oxygen outlet, the liquid oxygen outlet is used for extracting liquid oxygen, the liquid oxygen outlet is provided with a first liquid oxygen branch, the first liquid oxygen branch is communicated with a feed inlet of the mixing tower, and a liquid oxygen pump is arranged on the first liquid oxygen branch;
a liquid nitrogen outlet is formed in the top of the lower tower and used for extracting liquid nitrogen, a first liquid nitrogen branch is formed in the liquid nitrogen outlet and communicated with a feeding hole of the mixing tower;
the tower bottom of mixing column is equipped with the reboiler, the top of mixing column is equipped with the oxygen-enriched product export, the tower bottom of mixing column is equipped with the oxygen-enriched liquid export, the oxygen-enriched liquid export with the oxygen-enriched liquid backward flow mouth of last tower bottom is linked together.
2. The cryogenic air separation plant according to claim 1, further comprising a mixing column heat exchanger;
the mixing tower heat exchanger comprises a cold flow channel, the first liquid oxygen branch and the first liquid nitrogen branch are respectively communicated with an inlet of the cold flow channel, an outlet of the cold flow channel is communicated with a feed inlet of the mixing tower, and the mixing tower heat exchanger is used for heating the liquid oxygen and the liquid nitrogen flowing through the cold flow channel to a preset temperature.
3. The cryogenic air separation plant of claim 2, further comprising a main heat exchanger and a subcooler;
the outlet of the oxygen-enriched product is communicated with the oxygen-enriched channel of the main heat exchanger, and the outlet of the oxygen-enriched channel of the main heat exchanger is communicated with the pressurized oxygen-enriched product conveying pipeline;
the top of the upper tower is provided with a low-pressure nitrogen outlet which is sequentially communicated with a low-pressure nitrogen channel of the subcooler and a low-pressure nitrogen channel of the main heat exchanger, and the low-pressure nitrogen channel of the main heat exchanger is communicated with a low-pressure nitrogen product conveying pipeline;
a waste nitrogen outlet is formed in the top of the upper tower and communicated with a waste nitrogen channel of the subcooler, and a first nitrogen branch and a second nitrogen branch are formed in an outlet of the waste nitrogen channel of the subcooler;
the first nitrogen branch is communicated with a first waste nitrogen channel of the main heat exchanger and then is communicated with a waste nitrogen conveying pipeline; and the second nitrogen branch is communicated with a second waste nitrogen channel of the main heat exchanger and then is used for being communicated with a waste nitrogen conveying pipeline for regeneration of the purification system.
4. The cryogenic air separation plant of claim 3, further comprising a feed unit comprising an air compressor, a pre-cooling system, a purification system, an air booster, and an expander;
the air compressor, the precooling system and the purifying system are sequentially connected, and a first air branch and a second air branch are arranged at an outlet of the purifying system;
the first air branch is sequentially connected with a first air channel of the main heat exchanger and a raw material feeding hole of the lower tower; the second air branch is communicated with the air supercharger and is connected to the pressurization end of the expansion machine through the final stage outlet of the air supercharger;
a third air branch and a fourth air branch are arranged at an outlet of the pressurizing end, and the third air branch is sequentially connected with a second air channel of the main heat exchanger, a first throttling valve and a raw material feeding hole of the lower tower;
and the fourth air branch is sequentially connected with the third air channel of the main heat exchanger, the expansion end of the expansion machine, the fourth air channel of the main heat exchanger and the raw material feed inlet of the lower tower.
5. The cryogenic air separation plant according to claim 4, wherein the air booster is provided with a central suction port;
and the middle pumping port is sequentially connected with a fifth air channel of the main heat exchanger, the reboiler, a heat flow channel of the mixing tower heat exchanger and the raw material feeding port of the lower tower.
6. The cryogenic air separation plant according to claim 4, wherein the liquid oxygen outlet of the main condensing evaporator is divided into two paths, wherein one path is the first liquid oxygen branch and the other path is the second liquid oxygen branch;
the second liquid oxygen branch is communicated with a liquid oxygen channel of the subcooler, and an outlet of the liquid oxygen channel is communicated with a liquid oxygen product conveying pipeline.
7. The cryogenic air separation plant according to claim 4, further comprising a liquid nitrogen gas liquid separator;
liquid nitrogen outlets at the top of the lower tower are divided into three paths, namely a first liquid nitrogen branch, a second liquid nitrogen branch and a third liquid nitrogen branch in sequence;
the second liquid nitrogen branch is sequentially connected with a liquid nitrogen channel of the subcooler, a second throttling valve and an inlet of the liquid nitrogen gas-liquid separator; the bottom of the liquid nitrogen-gas separator is provided with a liquid nitrogen product outlet which is communicated with a liquid nitrogen product conveying pipeline, the top of the liquid nitrogen-gas separator is provided with a flash evaporation nitrogen gas outlet, and the flash evaporation nitrogen gas outlet is communicated with a nitrogen gas reflux port of the upper tower;
the third liquid nitrogen branch is communicated with a liquid nitrogen channel of the main heat exchanger through a liquid nitrogen pump, and an outlet of the liquid nitrogen channel of the main heat exchanger is communicated with a nitrogen product conveying pipeline.
8. The cryogenic air separation plant of claim 3 further comprising a crude argon column and a fine argon column;
an argon fraction outlet is formed in the middle of the upper tower and is sequentially communicated with the crude argon tower and the fine argon tower;
the crude argon tower with the tower bottom of smart argon tower is equipped with the liquid argon export respectively, the liquid argon export of crude argon tower pass through crude argon delivery pump with the crude argon backward flow mouth of last tower is linked together, the liquid argon export of smart argon tower is used for being linked together with liquid argon product transfer passage.
9. The cryogenic air separation plant according to claim 8, wherein a crude argon condenser is provided at the top of the crude argon column;
a pure argon evaporator is arranged at the bottom of the fine argon tower, and a pure argon condenser is arranged at the top of the fine argon tower;
the bottom of the lower tower is provided with an oxygen-enriched liquid air outlet, and the oxygen-enriched liquid air outlet is divided into two paths after being sequentially communicated with the subcooler and the pure argon evaporator:
one path is communicated with the upper tower through the pure argon condenser, and the other path is communicated with the upper tower through the crude argon condenser.
10. The cryogenic air separation plant according to claim 3, wherein a liquid-air outlet is arranged in the middle of the lower tower, the liquid-air outlet is sequentially communicated with the liquid-air channel of the subcooler and the liquid-air return port of the upper tower, and a throttle valve is arranged on a pipeline between the liquid-air channel of the subcooler and the liquid-air return port of the upper tower.
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