JP2019163897A - Manufacturing method for product nitrogen gas and product argon gas, and manufacturing device therefor - Google Patents

Abstract

A method for producing high-purity nitrogen and argon with high energy efficiency by utilizing the cooling of an oxygen-containing gas and an apparatus used for the method are provided. A first rectification column 2 into which raw air is introduced, a second rectification column 5 into which product nitrogen gas is derived, a third rectification column 6 into which product argon gas is derived, Product nitrogen gas comprising: a first condenser 3 configured to exchange heat between the gas stored at the top of the rectifying column 2 and the liquid stored at the bottom of the second rectifying column 5 In the product argon production apparatus 100, the intermediate gas containing nitrogen is led out from the intermediate part of the second rectifying column 5 and merged with the condenser gas discharged from the first condenser 3. The combined gas is expanded and cooled by the expansion turbine 8 to use the cold. [Selection] Figure 1

Description

  The present invention relates to a method and an apparatus for producing nitrogen and argon for producing nitrogen gas and producing argon.

In a method for producing nitrogen gas by a nitrogen production apparatus using a cryogenic separation method, there is a method for improving energy efficiency by using a gas containing oxygen derived from a condenser part of a rectifying column as a cold source. It has been proposed (for example, Patent Document 1). In patent document 1, the fluid derived | led-out from the intermediate part of a rectification column is introduce | transduced into a main heat exchanger, and is utilized as a cold source by making heat exchange with raw material air. A method is disclosed in which the fluid after being used as the cold source is expanded and cooled by an expansion turbine, introduced again into the main heat exchanger, and the cold is further utilized.
A method for producing nitrogen, argon and oxygen by an air separation device using a cryogenic separation method is known. Since the boiling points of oxygen and argon are close to each other, it is necessary to perform rectification to separate oxygen and argon when producing argon. In this process, high-purity oxygen is also produced. It is common (for example, patent document 2).

U.S. Pat. No. 4,222,756 JP-A-8-61844

In order to improve energy efficiency, the method of using oxygen-containing gas derived from the condenser part of the rectifying column, disclosed in Patent Document 1, as a cold source is used as a method for producing not only nitrogen but also argon. It was difficult to apply. In addition, in the method disclosed in Patent Document 1, nitrogen can be produced, but the production of argon is not mentioned.
However, in recent years, there is an increasing demand for taking out not only nitrogen but also argon.

  In view of the above circumstances, an object of the present invention is to provide a method for producing high-purity nitrogen and argon with high energy efficiency by utilizing the cooling of an oxygen-containing gas, and an apparatus used in the method. To do.

(Invention 1)
The production method of product nitrogen gas and product argon gas according to the present invention is as follows:
A cooling step in which the raw air from which predetermined impurities are removed is cooled;
A raw air introduction step in which the raw air cooled in the pre-cooling step is introduced into the first fractionator;
A first oxygen-enriched liquid introduction step in which the oxygen-enriched liquid derived from the bottom of the first rectifying column is introduced into the second rectifying column;
A second oxygen-enriched liquid introducing step in which at least a part of the oxygen-enriched liquid derived from the bottom of the first rectifying column is introduced into a second condenser disposed in the third rectifying column;
Introducing a nitrogen-containing liquid condensed in the first rectifying column into the upper part of the second rectifying column as a reflux liquid; and
The intermediate gas derived from the intermediate part of the second rectification tower, the gas stored at the top of the first rectification tower and the liquid stored at the bottom of the second rectification tower are heated. An expansion step in which at least a portion of the gas mixture with the condenser gas derived from the first condenser configured to be exchanged is expanded to generate cold;
An argon-containing gas introduction step in which an argon-containing gas derived from the lower part of the second rectification column is introduced into the third rectification column;
A product nitrogen gas derivation step in which product nitrogen gas is derived from the top of the second rectification column;
A product argon deriving step in which product argon is derived from an intermediate portion of the second rectification column.

  The first rectification column has an operating pressure higher than that of the second rectification column, and can separate the raw material air into an oxygen-enriched liquid and nitrogen gas. In the second rectification column, a gas containing argon and oxygen is produced and supplied to the third rectification column. Product argon is produced in the third rectification column.

  First, the raw material air that has been compressed and from which predetermined impurities have been removed is cooled by a cooling process in the main heat exchanger to become low-temperature raw material air. The raw air is introduced into the first rectification column in the raw air introduction step. The raw air introduced into the first rectifying column comes into contact with liquid nitrogen condensed at the top of the first rectifying column, is rectified, and is separated into an oxygen-enriched liquid and nitrogen gas.

The oxygen-enriched liquid stored in the lower part of the first rectifying column is supplied to a predetermined position of the second rectifying column in the first oxygen-enriched liquid introducing step. The oxygen-enriched liquid supplied to the second rectification column is a raw material for product nitrogen and product argon, and is also used as a refrigerant in the second rectification column.
At least a part of the oxygen-enriched liquid stored in the lower part of the first rectifying column is placed in the third rectifying column in the second oxygen-enriched liquid introducing step before being supplied to the second rectifying column. To the second condenser. The introduced oxygen-enriched liquid is used as a refrigerant for condensing argon in the second condenser.
The oxygen-enriched liquid vaporized in the second condenser is led out from the third rectifying column and then supplied as a refrigerant to a predetermined position of the second rectifying column.
The oxygen-enriched liquid stored in the lower part of the first rectification column is divided and partly supplied to the second rectification column, and the part not supplied to the second rectification column is supplied to the second condenser. It is also possible to supply all of the oxygen-enriched liquid to the second condenser and then to the second rectification column. Even when the oxygen-enriched liquid is diverted and a part is supplied to the second rectification column without going through the second condenser, the oxygen-enriched liquid after going through the second condenser is also Since it is supplied to the second rectifying column, the whole amount of the oxygen-enriched liquid is finally supplied to the second rectifying column.

The nitrogen-containing liquid condensed in the first rectifying column is introduced as a reflux liquid into the upper part of the second rectifying column in the nitrogen-containing liquid introducing step.
The condenser of the first rectifying column is configured to exchange heat between the gas stored at the top of the first rectifying column and the liquid stored at the bottom of the second rectifying column. A condenser gas is derived from the condenser. The gas condensed in the condenser is supplied as a reflux liquid to the first rectification column, and the liquid vaporized in the condenser is supplied as a condenser gas to the second rectification column. Since the argon-containing gas is derived from the lower part of the second rectification column, the main component of the condenser gas is oxygen. This is because in order to produce argon by cryogenic separation, it is necessary to concentrate and recover almost all oxygen to high purity. Otherwise, since argon has a boiling point very close to that of oxygen, argon easily flows out into the oxygen stream and cannot be recovered. Therefore, the condenser gas derived from the lower part of the second rectification column is almost 100% pure oxygen gas.

  For this reason, when it is going to utilize the cold of condenser gas in a main heat exchanger, it is necessary to use piping of the special material which can endure use of oxygen gas. Furthermore, when the condenser gas after using cold in the main heat exchanger is expanded and cooled, and the cold is further used in the main heat exchanger, an expansion turbine made of a special material that can withstand the use of oxygen gas is used. Must be used. Similarly, when the condenser gas is introduced directly into the expansion turbine without going through the main heat exchanger and is expanded and cooled by the expansion turbine, a special expansion turbine capable of supporting high-concentration oxygen must be used as well. . Examples of the special material include materials such as duralumin, but are difficult to obtain and expensive.

  Therefore, in the present invention, the intermediate part gas derived from the intermediate part of the second rectification column is merged with the condenser gas, and then the cold is discharged, expanded and cooled, and further the cold is generated. Since the intermediate portion gas contains a large amount of nitrogen gas, the oxygen concentration contained in the gas can be reduced if mixed with the condenser gas. This makes it possible to use ordinary piping and expansion turbines that do not use special materials that can withstand the use of oxygen gas. Expansion turbines and pipes that do not use special materials have the advantage of being readily available and inexpensive. The oxygen concentration in the gas introduced into the expansion turbine can also be reduced by mixing product nitrogen gas with the condenser gas instead of the intermediate gas, but this reduces the amount of product nitrogen gas. So undesirable.

  When the oxygen-enriched liquid is introduced from the bottom of the first rectifying column to the second rectifying column, the oxygen-enriched liquid before being introduced into the second rectifying column is cooled via the subcooler. Also good. This is because a decrease in the rectification efficiency can be suppressed by vaporizing a large amount of the oxygen-enriched liquid inside the second rectification column, and the rectification efficiency is further improved. In the subcooler, the fluid passing through the oxygen-enriched liquid outlet pipe and the nitrogen-containing liquid inlet pipe is cooled by heat exchange with the product nitrogen gas passing through the product nitrogen gas outlet pipe.

  In the present invention, it is possible to use the cooling of oxygen gas for cooling the raw material air. By introducing the condenser gas mainly composed of oxygen into the main heat exchanger together with the intermediate part gas, after using the cold of the condenser gas and the intermediate part gas, it is further expanded and cooled to use the cold. Can do. Therefore, especially for applications that require nitrogen and argon but do not require oxygen gas, the production of energy-efficient product nitrogen gas and product argon is possible due to the use of oxygen refrigeration, which is not necessary as a gas product. It becomes possible to provide a method.

By the way, in the second rectification column, the nitrogen-containing gas comes into contact with the liquid nitrogen supplied to the upper part of the second rectification column while being raised inside the second rectification column, and is rectified. In this step, part of argon and oxygen entrained in the nitrogen-containing gas also rises in the second rectification column. Since the accompanying argon and oxygen are mixed in the product nitrogen gas, the purity of the product nitrogen gas is reduced. In order to completely separate the oxygen-nitrogen argon component and produce high-purity product nitrogen gas, it may be possible to install many distillation stages. The complete rectification separation requires very precise adjustment of operation control, and it becomes difficult to operate the apparatus stably in response to load fluctuations such as the supply amount of raw material air.
In the present invention, the amount of argon and oxygen rising inside the second rectification column can be reduced by deriving the intermediate gas containing nitrogen from the intermediate part of the second rectification column. As a result, the amount of argon and oxygen contained in the product nitrogen gas is reduced, and the purity of the product nitrogen gas can be increased without installing a large number of distillation stages.

(Invention 2)
The apparatus for producing product nitrogen gas and product argon gas (100; 101; 102; 103) according to the present invention comprises:
A main heat exchanger (1) for cooling the raw air from which predetermined impurities have been removed;
A first rectifying column (2) into which the cooled raw air is introduced;
A second rectification column (5) from which product nitrogen gas is derived;
A third rectification column (6) from which product argon is derived;
A first condenser (3) configured to exchange heat between the gas stored at the top of the first rectifying column and the liquid stored at the bottom of the second rectifying column;
A nitrogen-containing liquid introduction pipe (11) for introducing at least part of the nitrogen-containing liquid condensed in the first condenser (3) into the second rectification column as a reflux liquid;
An argon-containing gas introduction pipe (17) for introducing an argon-containing gas into the third rectification column from the lower part of the second rectification column;
An argon-containing liquid outlet pipe (19) for introducing an argon-containing liquid into the second rectifying tower from the bottom of the third rectifying tower;
A condenser gas outlet pipe (14) for leading condenser gas from the gas phase part of the first condenser (3);
An intermediate gas outlet pipe (15) for extracting intermediate gas from the intermediate part of the second rectification column;
An expansion turbine (8) for expanding and cooling a mixed gas of the condenser gas and the intermediate part gas;
A product nitrogen gas outlet pipe (16) for extracting the product nitrogen gas from the second rectification column;
A product argon outlet pipe (18) for extracting the product argon from an intermediate part of the third rectifying column.
In addition, the code | symbol described in this specification in parentheses shows one Embodiment, Comprising: It is not restricted to this.

When the intermediate gas outlet pipe (15) in the present invention is not provided, the oxygen concentration in the condenser gas led out from the condenser gas outlet pipe (14) becomes extremely high (for example, 99% or more). This is because, in order to produce argon gas, a gas containing argon is led out from the second rectification column (5) through the argon-containing gas introduction pipe (17).
In the present invention, the intermediate portion gas outlet pipe (15) is provided, and the oxygen concentration is reduced by joining the intermediate portion gas containing nitrogen to the condenser gas containing high concentration oxygen (for example, 70). % To 97%). Therefore, it is not necessary to use a special material (for example, duralumin) that can be used for oxygen gas in the expansion turbine (8). Therefore, there is an advantage that the piping and the expansion turbine are easily available and the price is low.
The mixed gas of the condenser gas and the intermediate gas is introduced into the expansion turbine (8) and is cooled by expansion. The cold generated thereby is introduced into the main heat exchanger (1) and used for heat exchange with the raw air.
Before being introduced into the expansion turbine (8), a mixed gas of condenser gas and intermediate gas may be introduced into the main heat exchanger (1). In this case, the mixed gas of the condenser gas and the intermediate part gas performs heat exchange with the raw material air in the main heat exchanger (1), thereby releasing the cold. Further, after releasing the cold, it is introduced into the expansion turbine (8) and expanded and cooled. The expanded and cooled gas is again introduced into the main heat exchanger (1), and the cold is used for heat exchange with the raw material air.
As described above, since the cooling of oxygen-containing gas is used, product nitrogen gas and product argon gas can be produced with high energy efficiency, particularly in applications that do not require oxygen as the product gas.

  Furthermore, in the present invention, by providing the intermediate gas outlet pipe (15), the argon rising in the second rectification column (5) accompanied by the nitrogen gas rising in the second rectification column (5) and It becomes possible to reduce the amount of oxygen. For this reason, there exists an effect that the purity of the product nitrogen gas obtained from the tower | column top part of a 2nd fractionator (5) becomes high.

(Invention 3)
In the apparatus for producing product nitrogen gas and product argon gas according to the above invention,
An oxygen-enriched solution outlet pipe (21) for allowing the oxygen-enriched solution stored at the bottom of the first rectifying column to be derived from the bottom of the first rectifying column;
A second oxygen-enriched liquid introduction pipe (introducing the oxygen-enriched liquid led out from the oxygen-enriched liquid lead-out pipe (21) into the second condenser (7) disposed in the third rectifying column. 13)
A third oxygen-enriched liquid introduction pipe (22) for introducing the oxygen-enriched liquid led out from the second condenser into the second rectification column may be further provided.

(Invention 4)
In the invention 3, the third oxygen-enriched liquid introduction pipe (22) introduces a gaseous oxygen-enriched liquid from the gas phase part of the second condenser (7) into the second rectification column (5). May be.

  The oxygen-enriched liquid is introduced into the second rectification column (5) as a refrigerant and as a raw material for product nitrogen and product argon. However, part or all of the oxygen-enriched liquid may be introduced into the second condenser (7) and returned to the second rectification column (5) after using the cooling of the oxygen-enriched liquid. In this case, the oxygen-enriched liquid vaporized in the second condenser (7) exists in the gaseous state at the upper part of the second condenser (7), and the third oxygen stretched from the upper part of the second condenser (7). It is returned to the second rectification column (5) by the enrichment liquid introduction pipe (22).

(Invention 5)
The apparatus for producing product nitrogen gas and product argon gas according to the invention described above,
A fourth rectifying column (9) disposed at the top of the second condenser;
A fourth rectifying tower top gas introduction pipe (23) for introducing the fourth rectifying tower top gas taken out from the top of the fourth rectifying tower into the second rectifying tower; May be.
The third oxygen-enriched liquid introduction pipe introduces a liquid oxygen-enriched liquid from the liquid phase part of the second condenser into the second rectifying column.
The oxygen-enriched liquid stored at the bottom of the first rectifying column is introduced into the second condenser via the gas phase of the fourth rectifying column.

  By providing the fourth rectifying column (9), the argon contained in the oxygen-enriched liquid is further concentrated inside the fourth rectifying column (9) and supplied to the second rectifying column (5). Is possible. Therefore, the separation load in the second rectification column (5) can be reduced, the rectification efficiency can be improved, and the argon recovery rate can also be improved.

(Invention 6)
In the apparatus for producing product nitrogen gas and product argon gas according to the above invention,
A fourth rectifying column (9) disposed at an upper part of the second condenser, and at least a part of the oxygen-enriched liquid stored at the bottom of the first rectifying column, It is also possible to further include a first oxygen-enriched liquid introducing pipe (12) introduced into

(Invention 7)
In the apparatus for producing product nitrogen gas and product argon gas according to the above invention, a mixed gas of the condenser gas and the intermediate gas is introduced into the compression turbine (8). The mixed gas includes the condenser gas taken out directly from the gas phase part of the first condenser (3), and the intermediate part gas taken out directly from the intermediate part of the second rectifying column (5). The mixed gas may be used.

  After the mixed gas of the condenser gas and the intermediate gas is further cooled by the expansion turbine (8), the cold can be used in the main heat exchanger (1). Energy efficiency can be improved by effectively using the coldness of the mixed gas.

(Invention 8)
Further, the mixed gas is a mixture of the condenser gas taken out directly from the gas phase part of the first condenser and the intermediate part gas taken out directly from the intermediate part of the second rectifying column. It may be a mixed gas passed through the main heat exchanger.

  The mixed gas of the condenser gas and the intermediate gas is introduced into the main heat exchanger (1) before being introduced into the expansion turbine (8), the cold is used, and further, expansion cooling is performed by the expansion turbine (8). Then, the cold can be used in the main heat exchanger (1). Energy efficiency can be improved by effectively using the coldness of the mixed gas.

(Invention 9)
In the apparatus for producing product nitrogen gas and product argon gas according to the above invention, at least one of the nitrogen-containing liquid pipe (11) and the oxygen-enriched liquid lead-out pipe (21), and the product nitrogen gas lead-out pipe, However, you may comprise so that a subcooler (4) may be routed.

  The nitrogen-containing liquid and / or the oxygen-enriched liquid is cooled by performing heat exchange with the product nitrogen gas having a low temperature via the subcooler (4). As a result, the nitrogen-containing liquid and / or the oxygen-enriched liquid introduced into the second rectifying column (5) is vaporized in a large amount inside the second rectifying column (5) to reduce the rectifying efficiency. It becomes possible to suppress.

(Invention 10)
In the apparatus for producing product nitrogen gas and product argon gas according to the above invention, the intermediate part gas outlet pipe is connected to the condenser gas outlet pipe at the first junction (25) after being introduced into the subcooler. Also good. The first junction (25) is a stage after the subcooler and a stage before the expansion turbine.

By introducing the intermediate part gas into the subcooler (4), the cold of the intermediate part gas is used for cooling the oxygen-enriched liquid and / or the nitrogen-containing liquid, so that the energy efficiency can be further improved.

(Invention 11)
In the apparatus for producing product nitrogen gas and product argon gas according to the above invention, an intermediate part of the second rectifying column is attached to the second rectifying column (5) side of the nitrogen-containing liquid introduction pipe (11). It may be below the position and above the attachment position on the second fractionator (5) side of the first oxygen-enriched liquid introduction pipe (12).

  By attaching the intermediate part gas outlet pipe (15) below the nitrogen-containing liquid introduction pipe (11) and above the first oxygen-enriched liquid introduction pipe (12), the purity of the product nitrogen gas It is possible to control the oxygen concentration in the gas introduced into the expansion turbine (8) to a predetermined concentration or less (for example, 97% or less) while maintaining a high value.

(Invention 12)
In the apparatus for producing product nitrogen gas and product argon gas according to the above invention,
The ratio of the derived flow rate of the intermediate part gas derived from the intermediate part gas outlet line (15) to the derived flow rate of the condenser gas derived from the condenser gas outlet line (14) is 0.03 or more and 2 or less. Also good. The ratio of the outlet flow of the intermediate gas to the outlet flow of the condenser gas may be preferably 0.25 or more and 0.5 or less.

  By setting the above flow ratio, the temperature is maintained while maintaining the oxygen concentration contained in the mixed gas of the condenser gas and the intermediate gas introduced into the main heat exchanger (1) at 70% or more and 97% or less. It becomes possible to control to −185 ° C. or more and −165 ° C. or less.

  In the apparatus for producing product nitrogen gas and product argon gas according to the above invention, the oxygen concentration in the gas introduced into the expansion turbine (8) may be 70% or more and 97 or less. By setting the oxygen concentration to 70% or more and 97 or less, the expansion turbine (8) made of an inexpensive material (for example, stainless steel) can be applied.

  According to the product nitrogen gas and product argon production apparatus described above, it is possible to achieve high energy efficiency by utilizing the coldness of the condenser gas and intermediate gas containing oxygen without reducing the argon recovery rate. Product nitrogen gas and product argon can be produced. Moreover, when using cold, it becomes possible to use piping and an expansion turbine using a general raw material (for example, stainless steel), without using a special member durable to oxygen gas. In addition, it is possible to produce a high-purity product nitrogen gas having a low oxygen and argon content.

It is a figure which shows the structural example of the manufacturing apparatus of product nitrogen gas and product argon of Embodiment 1. FIG. It is a figure which shows the structural example of the manufacturing apparatus of product nitrogen gas and product argon of Embodiment 2. FIG. It is a figure which shows the structural example of the manufacturing apparatus of product nitrogen gas and product argon of Embodiment 3. It is a figure which shows the structural example of the manufacturing apparatus of product nitrogen gas and product argon of Embodiment 4.

  Several embodiments of the present invention will be described below. Embodiment described below demonstrates an example of this invention. The present invention is not limited to the following embodiments, and includes various modified embodiments that are implemented within a range that does not change the gist of the present invention. Note that not all of the configurations described below are essential configurations of the present invention.

  The flow of the nitrogen production method according to the present invention will be described.

(Cooling process)
A cooling process is a process of cooling raw material air in a heat exchanger. The raw material air introduced into the main heat exchanger has undergone a compression step of compressing the raw material air taken from outside by one or a plurality of compressors, and a removal step of removing predetermined impurities from the compressed raw material air. Source air may be used. The method for removing impurities in the removing step is not particularly limited, and may be performed by a known method such as adsorption or cooling. The impurities to be removed are not particularly limited, and may be carbon dioxide gas, moisture, or the like that causes the heat exchanger or the like to be blocked.
The compression step may include a cooling step for cooling the compressed raw material air. In the case where the raw material air is compressed by a plurality of compressors, a plurality of cooling steps for cooling the raw material air compressed by the respective compressors may be included.

In the cooling process, the raw air is cooled by exchanging heat with at least one of the product nitrogen gas, the condenser gas, and the intermediate part gas described later.
In the production apparatus 100 for product nitrogen gas and product argon gas shown in FIG. 1, a cooling process is performed in the main heat exchanger 1.

(Raw material air introduction process)
The raw material air introduction step is a step in which the raw material air cooled in the cooling step is introduced into the first rectification column. The raw air may be expanded and cooled before introducing the first rectification column. The raw material air may be expanded and cooled by an expansion valve. The temperature of the raw air introduced into the first rectification column is, for example, in the range of −170 ° C. to −155 ° C., and the pressure is, for example, in the range of 7.0 barA to 15 barA.
The raw air introduced into the first rectification column in the raw air introduction step is separated into an oxygen-enriched liquid and nitrogen gas. The oxygen-enriched liquid is stored at the bottom of the first rectifying column, and the nitrogen gas is condensed into liquid nitrogen by a condenser arranged at the upper part of the first rectifying column.

(First oxygen-enriched liquid introduction process)
The first oxygen-enriched liquid introducing step is a step of introducing the oxygen-enriched liquid stored at the bottom of the first rectifying column into the second rectifying column. A part or all of the oxygen-enriched liquid may be introduced into the second condenser of the third rectification column before being introduced into the second rectification column. The temperature of the oxygen-enriched liquid introduced into the second rectification column is, for example, −175 ° C. or more and −160 ° C. or less, and the gas rising the second rectification column while descending the second rectification column It contacts and is stored by the condensation part arrange | positioned between a 1st rectification tower and a 2nd rectification tower.
The oxygen-enriched liquid derived from the bottom of the first rectifying column may be cooled by passing through the subcooler before being introduced into the second rectifying column, but may not be passed through the subcooler. .

(Second oxygen-enriched liquid introduction process)
In the second oxygen-enriched liquid introducing step, part or all of the oxygen-enriched liquid stored at the bottom of the first rectification column (for example, 10% or more of the oxygen-enriched liquid stored at the bottom of the tower is 100% In the third rectification column. The oxygen-enriched liquid introduced into the third rectification column exchanges heat with argon gas in the condensing part arranged at the upper part of the third rectification column. The vaporized oxygen-enriched liquid led out from the upper part of the condensing part arranged at the upper part of the third rectifying column is returned to the second rectifying column.
Here, the vaporized oxygen-enriched liquid comes into contact with the liquid descending from the upper part of the second rectifying column and is rectified.

(Nitrogen-containing liquid introduction process)
The nitrogen-containing liquid introduction step is a step of introducing liquid nitrogen obtained by being condensed in the first condenser as a reflux liquid into the upper part of the second rectification column. The first condenser is configured to exchange heat between the gas stored at the top of the first rectifying column and the liquid stored at the bottom of the second rectifying column. The temperature of the nitrogen-containing liquid introduced into the second rectification column is, for example, −192 ° C. or higher and −175 ° C. or lower.
The acid-nitrogen-containing liquid led out from the first condenser may be cooled by passing through the subcooler before being introduced into the second rectification column, but may not be passed through the subcooler.

(Argon-containing gas introduction process)
The argon-containing gas introduction step is a step in which the argon-containing gas derived from the lower part of the second rectification column is introduced into the third rectification column. The argon-containing gas introduced into the third rectification column is separated into oxygen-enriched argon-containing liquid and product argon by rectification.

(Product argon gas derivation process)
The product argon gas deriving step is a step of deriving the product argon gas obtained in the third rectifying column from the third rectifying column. The purity of the product argon gas is, for example, 99.9% or more.

(Product nitrogen gas derivation process)
The product nitrogen gas deriving step is a step of deriving product nitrogen gas from the top of the second rectification column. The purity of the product nitrogen gas is, for example, 99.9999% or more. The temperature of the product nitrogen gas derived from the top of the second rectification column may be, for example, -192 ° C or more and -175 ° C or less, and the product nitrogen gas contains oxygen-enriched liquid and / or liquid nitrogen in the subcooler. Although it may cool, a subcooler does not need to be provided. The product nitrogen gas is further introduced into the main heat exchanger from the cold end side, and after the heat exchange with the raw material air, it is led out from the warm end side. The temperature of the product nitrogen gas derived from the main heat exchanger may be 0 ° C. or higher, for example.

(Expansion process)
The expansion process is a process in which the mixed gas of the condenser gas and the intermediate part gas is expanded and cooled after releasing the cold in the main heat exchanger, and the expanded and cooled gas releases the cold again in the main heat exchanger. The mixed gas of the condenser gas and the intermediate gas is introduced to the cold end side of the main heat exchanger at a temperature of, for example, −185 ° C. or more and −165 ° C. or less. Therefore, cold is released by performing heat exchange with the raw air, and the temperature of the mixed gas becomes, for example, −120 ° C. or more and −80 ° C. or less. The mixed gas is expanded and cooled by an expansion turbine, and the temperature thereof becomes, for example, −140 ° C. or higher and −100 ° C. or lower, and is again introduced to the cold end side of the main heat exchanger. Here, the mixed gas performs heat exchange with the raw material air, and after releasing cold, it is released from the warm end side of the main heat exchanger.
The oxygen concentration of the condenser gas is, for example, 99% or more, but the oxygen concentration is reduced to, for example, 70% or more and 97% or less by mixing with the intermediate gas.

(Embodiment 1)
The apparatus for producing product nitrogen gas and product argon of Embodiment 1 will be described with reference to FIG.
The apparatus 100 for producing product nitrogen gas and product argon according to Embodiment 1 includes a main heat exchanger 1, a first rectifying column 2, a second rectifying column 5, a third rectifying column 6, and a nitrogen-containing product. Liquid inlet pipe 11, first oxygen enriched liquid inlet pipe 12, second oxygen enriched liquid inlet pipe 13, condenser gas outlet pipe 14, intermediate gas outlet pipe 15, expansion turbine 8, and product A nitrogen gas outlet pipe 16, an argon-containing gas inlet pipe 17, and a product argon outlet pipe 18 are provided.

  The production apparatus 100 for product nitrogen gas and product argon gas is an apparatus for producing nitrogen gas and argon gas by cryogenic separation, and is an apparatus that does not need to produce oxygen gas used as product gas.

The main heat exchanger 1 is a heat exchanger that cools raw material air. Before being introduced into the main heat exchanger, the raw air, for example, the raw air amount is 1000 Nm ³ / h) is compressed by a compressor (not shown) to remove predetermined impurities. The predetermined impurity is not particularly limited, and may be carbon dioxide gas, moisture, or the like that causes a heat exchanger or the like to be blocked.
Inside the main heat exchanger 1, the raw material air exchanges heat with at least one of the product nitrogen gas, the condenser gas, and the intermediate part gas described later. Thereby, raw material air is cooled to the vicinity of the liquefaction point. The temperature of the raw material air is, for example, 20 ° C. when the main heat exchanger 1 is introduced, and is cooled by the main heat exchanger 1 from −170 ° C. to −155 ° C., for example.

  In the first rectifying tower 2, the raw air cooled by the main heat exchanger 1 is introduced and rectified. The number of theoretical plates of the first rectifying column 2 is 30 to 80, and can be 50, for example. The operating pressure range of the first rectification column 2 is 7 barA to 15 barA, and the operating pressure can be 9 barA, for example.

  In the second rectification column 5, product nitrogen gas is taken from the top of the column. The number of theoretical plates of the second rectification column 5 is 40 to 120, and can be 80, for example. The operating pressure range of the second rectifying column 5 is 1.5 barA to 6 barA, and the operating pressure can be, for example, 2.5 barA.

  In the third rectification column 6, product argon gas is taken out. The number of theoretical plates of the third rectifying column 6 is 100 to 300, and can be 180, for example. The operating pressure range of the third rectifying column 6 is 1.5 barA to 6 barA, and the operating pressure can be, for example, 2.5 barA.

The first condenser 3 is arranged so as to exchange heat between the gas stored at the top of the first rectifying column and the liquid stored at the bottom of the second rectifying column. In the first rectifying tower 2, the raw air is separated into an oxygen-enriched liquid and nitrogen gas, and the oxygen-enriched liquid is stored at the bottom of the first rectifying tower 2. In the first condenser 3, the separated nitrogen gas is condensed into liquid nitrogen. By descending the inside of the second rectifying column 5 disposed on the first condenser 3, an oxygen-enriched liquid described later is used as a refrigerant for the first condenser 3.
At least a part of the liquid nitrogen obtained by condensing in the first condenser 3 (for example, 10% or more 97% of the liquid nitrogen condensed in the first condenser 3) passes through the nitrogen-containing liquid introduction pipe 11. It is introduced into the upper part of the two rectifying column 5 as a reflux liquid. The upper part of the second rectifying column 5 is above the uppermost stage of the rectifying part inside the second rectifying column 5, for example, when the number of theoretical plates of the second rectifying column 5 is 80. , Above the 80th stage.
The second rectifying column 2 may be disposed above the first condenser 3, but may be disposed in the lateral direction.

  The oxygen-enriched liquid stored at the bottom of the first rectifying tower 2 is led out from the bottom of the first rectifying tower through the oxygen-enriched liquid outlet pipe 21. A part or all of this oxygen-enriched liquid (for example, 10% or more and 100% or less of the oxygen-enriched liquid stored at the bottom of the column) passes through the first oxygen-enriched liquid introduction pipe 12 to the second rectification. Of the oxygen-enriched liquid introduced into the tower 5 and stored at the bottom of the first rectifying tower 2, the portion that is not introduced into the second rectifying tower 5 passes through the second oxygen-enriched liquid introducing pipe 13. It is introduced into the third rectifying column 6.

The attachment position of the first oxygen-enriched liquid introduction pipe 12 on the second rectification tower 5 side is below the nitrogen-containing liquid introduction pipe 11 and an intermediate part gas outlet pipe 15 described later.
The attachment position of the nitrogen-containing liquid introduction pipe 11 on the second rectification tower 5 side is, for example, above the position filled with the rectification filler in the second rectification tower. The attachment position of the first oxygen-enriched liquid introduction pipe 12 on the second rectifying column 5 side is, for example, higher than 2/4 of the height of the second rectifying column and lower than 3/4. Also good.
In the case of calculating the number of theoretical plates, the mounting position of the first oxygen-enriched liquid introduction pipe 12 on the second rectifying column 5 side corresponds to, for example, the number of plates obtained by multiplying the previous number of stages by 0.5 or more and 0.7 or less. It is a position to do. Specifically, when the number of theoretical plates of the second rectifying column 5 is 80, it is above the 40th plate (80 × 0.5 = 40) and the 56th plate (80 × 0. 7 = 56).
The second oxygen-enriched liquid introduction pipe 13 is arranged so that the oxygen-enriched liquid is introduced into the second condenser arranged above the third rectifying column 6. The oxygen-enriched liquid that has passed through the second oxygen-enriched liquid introduction pipe 13 is used as a refrigerant in the second condenser 7 in order to condense the argon gas that rises inside the third fractionator 6. The oxygen-enriched liquid vaporized in the second condenser 7 may be discharged from the second condenser 7 and then merged into the first oxygen-enriched liquid introduction pipe 12 and introduced into the second rectifying column 5.

  The condenser gas outlet pipe 14 is configured to exchange heat between the gas stored at the top of the first rectifying column 2 and the liquid stored at the bottom of the second rectifying column 5. This is a pipe for leading out the condenser gas discharged from the vessel 3. The oxygen concentration in the condenser gas is, for example, 99.9% or more.

The intermediate part gas outlet pipe 15 is a pipe for extracting the intermediate part gas from the intermediate part of the second fractionator 5. The intermediate gas outlet pipe 15 is located below the attachment position of the nitrogen-containing liquid introduction pipe 11 on the second rectification tower side, and on the second rectification tower side of the first oxygen-enriched liquid introduction pipe 12. Above the mounting position. When the number of theoretical plates of the second rectifying column 5 is 80, the attachment position of the intermediate gas outlet pipe 15 is, for example, a position of 56 or more and 79 or less. The nitrogen concentration in the intermediate gas is, for example, not less than 80% and not more than 99%.
The condenser gas outlet pipe 14 and the intermediate part gas outlet pipe 15 merge at the front stage of the main heat exchanger 1, where the strike condenser gas is mixed in the intermediate part. The oxygen concentration in the mixed gas is, for example, 70% or more and 97% or less.
The ratio of the outlet flow of the intermediate gas to the outlet flow of the condenser gas may be 0.1 or more and 2 or less, and preferably 0.2 or more and 0.5 or less.

  The expansion turbine 8 exchanges the mixed gas of the intermediate gas and the condenser gas after releasing the cold by performing heat exchange with the raw material air inside the main heat exchanger 1 via the main heat exchanger 1. It is an expansion turbine that is expanded and cooled. The temperature of the mixed gas of the intermediate part gas and the condenser gas when initially introduced into the main heat exchanger is, for example, −185 ° C. or more and −165 ° C. or less. The temperature before being introduced into is, for example, −120 ° C. or more and −80 ° C. or less. This mixed gas is expanded and cooled by the expansion turbine 8 to a temperature of −140 ° C. or higher and −100 ° C. or lower, for example. The expanded and cooled mixed gas is again introduced into the main heat exchanger 1 and discharged from the main heat exchanger 1 after releasing cold by performing heat exchange with the raw material air.

  The product nitrogen gas outlet pipe 16 is a pipe for leading the product nitrogen gas from the top of the second rectifying column 5. The temperature of the derived product nitrogen gas is, for example, in the range of −192 ° C. or more and −175 ° C. or less, and may be supplied as nitrogen gas as it is, but is introduced into the main heat exchanger 1 to exchange heat with the raw material air. By performing, the cold may be released and supplied, for example, as nitrogen gas having a temperature of 0 ° C. or higher and 20 ° C. or lower. Furthermore, heat exchange may be performed in the subcooler 4 before the main heat exchanger 1 is introduced.

Inside the subcooler 4, the nitrogen-containing liquid and the oxygen-enriched liquid and the product nitrogen gas exchange heat. That is, in the subcooler 4, the nitrogen-containing liquid and the oxygen-enriched liquid are cooled using the coldness of the product nitrogen gas.
By cooling the nitrogen-containing liquid and the oxygen-enriched liquid, the nitrogen-containing liquid and the oxygen-enriched liquid are vaporized in a large amount inside the second rectifying column 5 to reduce the rectifying efficiency of the second rectifying column 5. Although the phenomenon can be suppressed, the subcooler need not be installed.

  When the subcooler 4 is not installed, the nitrogen-containing liquid condensed in the first condenser 3 is directly introduced into the upper part of the second rectifying column 5 through the nitrogen-containing liquid introduction pipe 11. Similarly, the oxygen-enriched liquid derived from the bottom of the first rectifying column 2 via the oxygen-enriched liquid deriving pipe 21 is directly introduced into the intermediate part of the second rectifying column 5. The product nitrogen gas derived from the top of the second rectifying column 4 via the product nitrogen gas deriving pipe 16 is directly introduced into the main heat exchanger 1, and after using the cold of the product nitrogen gas, the main heat exchange is performed. Discharged from the vessel 1.

  The argon-containing gas introduction pipe 17 is a pipe that introduces an argon-containing gas into the third rectification tower 6 from the lower part of the second rectification tower 5. The attachment position of the argon-containing gas introduction pipe 17 on the second rectification tower 5 side is below the first oxygen-enriched liquid introduction pipe 12, for example, when the number of theoretical plates of the second rectification tower 5 is 80. The position is 20 to 40 steps.

  The argon-containing gas introduced into the third rectifying column 6 is separated into an oxygen-enriched argon-containing liquid and product argon gas by rectification. The product argon gas is led out from the product argon gas outlet pipe 18. On the other hand, the oxygen-enriched argon-containing liquid stored at the bottom of the third rectifying column 6 is introduced into the second rectifying column 5 via the argon-containing liquid outlet pipe 19. The position of the argon-containing liquid outlet pipe 19 is lower than the product argon gas outlet pipe 18.

(Embodiment 2)
The production apparatus 101 for product nitrogen gas and product argon of Embodiment 2 will be described with reference to FIG. Elements having the same reference numerals as those in the apparatus for producing product nitrogen gas and product argon of the first embodiment have the same functions, and thus description thereof is omitted.
In the second embodiment, the intermediate part gas is introduced into the subcooler 4 via the intermediate part gas outlet pipe 152. In the subcooler 4, the intermediate gas is mixed with the condenser gas after the temperature is raised to about -170 ° C.
As a result, the oxygen-enriched liquid and / or the nitrogen-containing liquid can be further cooled, and the rectification efficiency in the second and third rectification columns can be improved.

The intermediate gas outlet pipe 152 is connected to the condenser gas outlet pipe 14 at the first junction 25 via the subcooler 4. The first confluence is located after the subcooler 4 and before the expansion turbine 8. When the mixed gas of the intermediate part gas and the condenser gas before being introduced into the expansion turbine is introduced into the main heat exchanger 1, the first junction point is the rear stage of the subcooler 4, Located in the front stage of the heat exchanger 1.
At the first junction point 25, the intermediate gas and the condenser gas are mixed to generate a mixed gas. Since the oxygen concentration in the mixed gas is, for example, 70% or more and 97% or less, it is not necessary to use a special expansion turbine that can cope with high concentration oxygen.

(Embodiment 3)
The product nitrogen gas and product argon production apparatus 102 of Embodiment 3 will be described with reference to FIG. Elements having the same reference numerals as those in the production apparatus for product nitrogen gas and product argon of Embodiment 1 or Embodiment 2 have the same functions, and thus the description thereof is omitted.
A fourth rectifying column 9 for rectifying the oxygen-enriched liquid evaporated in the second condenser may be disposed above the second condenser disposed in the third rectifying column 6. The oxygen-enriched liquid vaporized in the second condenser is separated into the oxygen-enriched liquid and the nitrogen-enriched gas in the fourth rectifying column 9. Here, the nitrogen-enriched gas is taken out from the top of the fourth rectifying column 9, that is, from the top of the third rectifying column 6, and passes through the first oxygen-enriched liquid introduction pipe 121 on the gas phase side. It is introduced into the second rectification tower. On the other hand, the oxygen-enriched liquid in the fourth rectifying column 9 is stored in the second condenser 7 and is transferred to the second rectifying column via the first oxygen-enriched liquid introducing pipe 122 on the liquid phase side. be introduced. In this way, the oxygen-enriched liquid separated into the gas phase and the liquid phase in the fourth rectifying column 9 is introduced into the second rectifying column 5 to improve the rectifying efficiency of the second rectifying column. It becomes possible to make it.

In the third embodiment, the oxygen-enriched liquid stored at the bottom of the first rectifying tower 2 is led out from the first rectifying tower 2 by the oxygen-enriched liquid outlet pipe 21. Subsequently, the oxygen-enriched liquid is introduced into the upper part of the fourth rectifying column 9 from the second oxygen-enriched liquid introducing pipe 133 and is introduced into the second condenser 7 via the fourth rectifying tower 9.
The oxygen-enriched liquid that passes through the oxygen-enriched liquid outlet pipe may be introduced into the subcooler 4 or may not be introduced.

(Another embodiment)
As another embodiment, the intermediate part gas outlet pipe 15 in the third embodiment may be configured to pass through the subcooler 4.

(Embodiment 4)
The production apparatus 103 for product nitrogen gas and product argon of Embodiment 4 will be described with reference to FIG. Elements having the same reference numerals as those in the apparatus for producing product nitrogen gas and product argon of Embodiments 1 to 32 have the same functions, and thus description thereof is omitted.
In the first to third embodiments, the first condenser 3 is disposed on the first rectifying column 2, and the second rectifying column 5 is disposed on the first condenser 3. However, when piled up in this way, the total height of the rectifying column becomes very high, and construction and installation may become difficult. Therefore, in the fourth embodiment, a portion (illustrated by 541) corresponding to the upper portion of the second rectifying column is arranged beside the first rectifying column 2 and the first condenser 3.

In Embodiment 4, the second rectification column is composed of two sections, a section indicated by 542 and a section indicated by 541 in FIG. Gas is supplied from the top of the second section 542 to the bottom of the first section 541 of the second rectification tower through the pipe 41. On the other hand, the fluid is supplied to the tower top of the second section 542 from the tower bottom of the first section 541 via the pipe 42 and the reflux liquid pump 30.
The intermediate part gas outlet pipe 154 guides the intermediate part gas from the intermediate part of the upper part 541 of the second rectification column, and merges with the condenser gas outlet pipe 14.

  Similarly, the fourth rectifying column 9 is divided into two sections as required, and the upper portion of the fourth rectifying column can be arranged in the lateral direction of the third rectifying column 6 and the second condenser 7. It is.

(Example 1)
Using the nitrogen production apparatus 100 according to the first embodiment (shown in FIG. 2), when air having 75.6 wt% nitrogen as a raw material and having a temperature of 20 ° C. and a pressure of 9.0 barA is used at 1295 kg / hr. The pressure (barA), temperature (° C.), flow rate (kg / h), etc. in each part were verified by simulation.

(result)
The raw material air pressure taken from outside is increased from 1.013 barA to 9.0 barA by a raw material air compressor (not shown).
Thereafter, the raw material air from which carbon dioxide and moisture have been removed in the removing section is introduced into the main heat exchanger 1. The temperature of the raw material air at the time of introduction of the main heat exchanger 1 is 20 ° C.
The temperature of the raw material air derived from the main heat exchanger 1 is −160 ° C. The raw air is introduced into the first rectification column 2 and rectified. The operating pressure of the first rectification column 2 is 8.8 barA. The first rectifying column 2 has 50 theoretical plates.
10% by weight of the oxygen-enriched liquid stored at the bottom of the first rectifying column 2 passes through the first oxygen-enriched liquid introducing pipe 12 at a temperature of −180 ° C. Introduced at the position of the theoretical stage 50. Of the oxygen-enriched liquid stored at the bottom of the first rectifying tower 2, the portion that has not been introduced into the second rectifying tower 5 passes through the second oxygen-enriched liquid introducing pipe 13 and has a temperature of −180. It introduce | transduces into the 2nd condenser of the 3rd rectification tower 6 at ° C.
The nitrogen gas separated in the upper part of the first rectifying column is condensed in the first condenser 3 to generate liquid nitrogen. 40% by weight of the obtained nitrogen is introduced into the upper part of the second fractionator 5 at a temperature of −190 ° C. via the nitrogen-containing liquid introduction pipe 11. The introduction position is above the position of 80 theoretical plates. From the upper part of the first condenser disposed between the first rectifying column 2 and the second rectifying column 5, a condenser gas containing 99% by weight of oxygen gas is discharged from the condenser gas outlet pipe 14. The
From the intermediate part of the second rectification column 5, the intermediate part gas is discharged via the intermediate part gas outlet pipe 15. The composition of the intermediate gas is 85 wt% nitrogen, 13 wt% oxygen, and 2 wt% argon. The attachment position of the intermediate part gas outlet pipe 15 is a position having 55 theoretical plates.
The intermediate part gas and the condenser gas are mixed to form a mixed gas, which is introduced into the main heat exchanger 1 at a temperature of −170 ° C. and releases cold. The oxygen concentration of the mixed gas is 84%. Thereafter, the mixed gas led out from the main heat exchanger 1 is introduced into the expansion turbine 8 at −110 ° C., is expanded and cooled, and is introduced into the main heat exchanger 1 again at a temperature of −130 ° C. Thereafter, heat exchange with the raw material air is performed inside the main heat exchanger 1 to release cold, and the heat is discharged from the main heat exchanger 1.
From the top of the second rectifying column 5, product nitrogen gas (purity is 99.99 wt%) having a temperature of −185 ° C. is led out via the product nitrogen gas outlet pipe 16. The temperature of the product nitrogen gas is raised to −170 ° C. by heat exchange in the subcooler 4, and then cold is further released in the main heat exchanger 1 to become product nitrogen gas at 15 ° C. The purity of the product nitrogen gas was 99.99% by weight, the argon content was 10 ppm, and the oxygen content was 100 ppb.
Argon-containing gas (argon concentration is 10% by weight) is introduced into the third rectification column 6 from the lower part of the second rectification column 5 via the argon-containing gas introduction pipe 17 and rectified. The operating pressure of the third rectification column 6 is 2.5 barA, and the number of theoretical plates is 200. A product argon outlet pipe 18 is arranged at the lower part of the second condenser, and product argon with a purity of 99.9% by weight is led out.
The oxygen-enriched argon-containing liquid stored at the bottom of the third rectifying column 6 is returned to the second rectifying column 5 via the argon-containing liquid outlet pipe 19. The argon-containing liquid contains 92% by weight oxygen and 8% by weight argon.
The vaporized oxygen-enriched liquid is discharged from the upper part of the second condenser 7 disposed at the upper part of the third rectifying column 6 and joins the first oxygen-enriched liquid introducing pipe 12 to be the second rectifying column. 5 is introduced.

  With the above configuration, product nitrogen gas (935 kg / hr) having a temperature of 20 ° C. and a pressure of 2.2 barA and product argon (14 kg / hr) having a temperature of −175 ° C. and a pressure of 2.3 barA could be obtained. The energy required for the production of product nitrogen gas and product argon is 110 kW, and since the cold of the intermediate part gas and the condenser gas could be used effectively, product nitrogen gas and product argon gas could be produced with energy efficiency. I can say that. Further, in the production, not a special material that can withstand the use of oxygen gas, but a commonly used expansion turbine could be used. Furthermore, by providing the intermediate part gas outlet pipe 15, the argon and oxygen concentrations in the product nitrogen gas could be reduced, and a high purity product nitrogen gas could be obtained.

1. 1. Main heat exchanger First rectification tower 3. First condenser 4. 4. Sub cooler Second rectification tower 6. Third rectification tower 7. Second condenser 8. Expansion turbine 9. Fourth rectifying tower 11. 11. Nitrogen-containing liquid introduction pipe First oxygen-enriched liquid introduction pipe 13. Second oxygen-enriched liquid introduction pipe 14. Condenser gas outlet piping 15. Middle gas outlet piping 16. Product nitrogen gas outlet piping 17. Argon-containing gas introduction pipe 18. Product argon outlet piping 19. 20. Argon-containing liquid outlet pipe 21. Oxygen-enriched liquid outlet pipe 22. Third oxygen-enriched liquid introduction pipe 23. Fourth rectification tower top gas introduction pipe
25. First confluence 100. Product nitrogen gas and product argon production equipment

(Invention 1)
The production method of product nitrogen gas and product argon gas according to the present invention is as follows:
A cooling step in which the raw air from which predetermined impurities are removed is cooled;
A raw air introduction step in which the raw air cooled in the cooling step is introduced into the first fractionator;
A first oxygen-enriched liquid introduction step in which the oxygen-enriched liquid derived from the bottom of the first rectifying column is introduced into the second rectifying column;
A second oxygen-enriched liquid introducing step in which at least a part of the oxygen-enriched liquid derived from the bottom of the first rectifying column is introduced into a second condenser disposed in the third rectifying column;
And nitrogen containing liquid introducing step of introducing a flowing liquid changing the nitrogen-containing liquid which has been condensed in the first condenser to the second rectification column top,
The intermediate gas derived from the intermediate part of the second rectification tower, the gas stored at the top of the first rectification tower and the liquid stored at the bottom of the second rectification tower are heated. Expansion after at least part of the gas mixture with the condenser gas derived from the first condenser configured to be exchanged releases the cold by performing heat exchange with the raw air in the main heat exchanger Expansion step , generating cold and releasing further cold by being reintroduced into the main heat exchanger ;
An argon-containing gas introduction step in which an argon-containing gas derived from the lower part of the second rectification column is introduced into the third rectification column;
A product nitrogen gas derivation step in which product nitrogen gas is derived from the top of the second rectification column;
A product argon deriving step in which product argon is derived from an intermediate portion of the third rectifying column.

Nitrogen-containing liquid that has been condensed in the first rectification column, the nitrogen-containing liquid introducing step is introduced as the flowing liquid instead of the second rectification column top.
The condenser of the first rectifying column is configured to exchange heat between the gas stored at the top of the first rectifying column and the liquid stored at the bottom of the second rectifying column. A condenser gas is derived from the condenser. The gas condensed in the condenser is supplied as a reflux liquid to the first rectification column, and the liquid vaporized in the condenser is supplied as a condenser gas to the second rectification column. Since the argon-containing gas is derived from the lower part of the second rectification column, the main component of the condenser gas is oxygen. This is because in order to produce argon by cryogenic separation, it is necessary to concentrate and recover almost all oxygen to high purity. Otherwise, since argon has a boiling point very close to that of oxygen, argon easily flows out into the oxygen stream and cannot be recovered. Therefore, the condenser gas derived from the lower part of the second rectification column is almost 100% pure oxygen gas.

(Invention 2)
The apparatus for producing product nitrogen gas and product argon gas (100; 101; 102; 103) according to the present invention comprises:
A main heat exchanger (1) for cooling the raw air from which predetermined impurities have been removed;
A first rectifying column (2) into which the cooled raw air is introduced;
A second rectification column (5) from which product nitrogen gas is derived;
A third rectification column (6) from which product argon is derived;
A first condenser (3) configured to exchange heat between the gas stored at the top of the first rectifying column and the liquid stored at the bottom of the second rectifying column;
At least a portion as the changing the flow through a nitrogen-containing liquid introducing pipe for introducing into the second rectification column nitrogen-containing liquid which has been condensed (11) in said first condenser (3),
An argon-containing gas introduction pipe (17) for introducing an argon-containing gas into the third rectification column from the lower part of the second rectification column;
An argon-containing liquid outlet pipe (19) for introducing an argon-containing liquid into the second rectifying tower from the bottom of the third rectifying tower;
A condenser gas outlet pipe (14) for leading condenser gas from the gas phase part of the first condenser (3);
An intermediate gas outlet pipe (15) for extracting intermediate gas from the intermediate part of the second rectification column;
An expansion turbine (8) for expanding and cooling the mixed gas of the condenser gas and the intermediate gas after passing through the main heat exchanger (1) ;
Piping for introducing the gas cooled and expanded in the expansion turbine (8) into the main heat exchanger (1);
A product nitrogen gas outlet pipe (16) for extracting the product nitrogen gas from the second rectification column;
A product argon outlet pipe (18) for extracting the product argon from an intermediate part of the third rectifying column.
In addition, the code | symbol described in this specification in parentheses shows one Embodiment, Comprising: It is not restricted to this.

(Nitrogen-containing liquid introduction process)
The nitrogen-containing liquid introduction step is a step of introducing liquid nitrogen obtained by being condensed in the first condenser as a reflux liquid into the upper part of the second rectification column. The first condenser is configured to exchange heat between the gas stored at the top of the first rectifying column and the liquid stored at the bottom of the second rectifying column. The temperature of the nitrogen-containing liquid introduced into the second rectification column is, for example, −192 ° C. or higher and −175 ° C. or lower.
The nitrogen-containing liquid led out from the first condenser may be cooled by passing through the subcooler before being introduced into the second rectification column, but may not be passed through the subcooler.

(Expansion process)
The expansion process is a process in which the mixed gas of the condenser gas and the intermediate part gas is expanded and cooled after releasing the cold in the main heat exchanger, and the expanded and cooled gas releases the cold again in the main heat exchanger. . The mixed gas of the condenser gas and the intermediate gas is introduced to the cold end side of the main heat exchanger at a temperature of, for example, −185 ° C. or more and −165 ° C. or less. Therefore, cold is released by performing heat exchange with the raw air, and the temperature of the mixed gas becomes, for example, −120 ° C. or more and −80 ° C. or less. The mixed gas is expanded and cooled by an expansion turbine, and the temperature thereof becomes, for example, −140 ° C. or higher and −100 ° C. or lower, and is again introduced to the cold end side of the main heat exchanger. Here, the mixed gas performs heat exchange with the raw material air, and after releasing cold, it is released from the warm end side of the main heat exchanger.
The oxygen concentration of the condenser gas is, for example, 99% or more, but the oxygen concentration is reduced to, for example, 70% or more and 97% or less by mixing with the intermediate gas.

In Embodiment 4, the second rectification column is composed of two sections, a section indicated by 542 and a section indicated by 541 in FIG. Gas is supplied from the top of the second section 542 to the bottom of the first section 541 of the second rectification tower through the pipe 41. On the other hand, the top of the second section 542, from the bottom of first section 541, through the pipe 42 and instead flowing liquid pump 30, fluid is supplied.
The intermediate part gas outlet pipe 154 guides the intermediate part gas from the intermediate part of the upper part 541 of the second rectification column, and merges with the condenser gas outlet pipe 14.

Claims (12)

A cooling step in which the raw air from which predetermined impurities are removed is cooled;
A raw air introduction step in which the raw air cooled in the pre-cooling step is introduced into the first fractionator;
A first oxygen-enriched liquid introduction step in which the oxygen-enriched liquid derived from the bottom of the first rectifying column is introduced into the second rectifying column;
A second oxygen-enriched liquid introducing step in which at least a part of the oxygen-enriched liquid derived from the bottom of the first rectifying column is introduced into a second condenser disposed in the third rectifying column;
Introducing a nitrogen-containing liquid condensed in the first rectifying column into the upper part of the second rectifying column as a reflux liquid; and
The intermediate gas derived from the intermediate part of the second rectification tower, the gas stored at the top of the first rectification tower and the liquid stored at the bottom of the second rectification tower are heated. Condenser configured to be exchanged At least part of the mixed gas with the condenser gas derived from the condenser located between the first rectifying column and the second rectifying column is expanded and cooled. Generating an expansion step;
An argon-containing gas introduction step in which an argon-containing gas derived from the lower part of the second rectification column is introduced into the third rectification column;
A product nitrogen gas derivation step in which product nitrogen gas is derived from the top of the second rectification column;
A product nitrogen gas and a product argon production method, comprising: a product argon deriving step in which product argon is derived from an intermediate part of the second rectification column. A main heat exchanger for cooling the raw air from which predetermined impurities have been removed;
A first rectifying column into which the cooled raw air is introduced;
A second rectification column from which product nitrogen gas is derived;
A third rectification column from which product argon is derived;
A first condenser configured to exchange heat between the gas stored at the top of the first rectifying column and the liquid stored at the bottom of the second rectifying column;
A nitrogen-containing liquid introduction pipe for introducing at least part of the nitrogen-containing liquid condensed in the first condenser into the second rectification column as a reflux liquid;
From the lower part of the second rectification tower, an argon-containing gas introduction pipe for introducing an argon-containing gas into the third rectification tower,
From the bottom of the third rectifying tower, an argon-containing liquid outlet pipe for introducing an argon-containing liquid into the second rectifying tower,
A condenser gas outlet pipe for extracting the condenser gas from the gas phase portion of the first condenser;
An intermediate part gas outlet pipe for extracting intermediate part gas from the intermediate part of the second fractionator;
An expansion turbine for expanding and cooling a mixed gas of the condenser gas and the intermediate gas;
A product nitrogen gas outlet pipe for extracting the product nitrogen gas from the second fractionator;
A product argon outlet pipe for letting out the product argon from an intermediate part of the third rectifying column;
An apparatus for producing product nitrogen gas and product argon. An oxygen-enriched liquid lead-out pipe for deriving the oxygen-enriched liquid stored in the tower bottom of the first rectifying tower from the tower bottom of the first rectifying tower;
A second oxygen-enriched liquid introduction pipe for introducing the oxygen-enriched liquid derived from the oxygen-enriched liquid outlet pipe into a second condenser disposed in the third rectification column;
A third oxygen-enriched liquid introduction pipe for introducing the oxygen-enriched liquid derived from the second condenser into the second rectification column;
The apparatus for producing product nitrogen gas and product argon according to claim 2.   4. The product nitrogen gas and product according to claim 3, wherein the third oxygen-enriched liquid introduction pipe introduces a gaseous oxygen-enriched liquid from the gas phase part of the second condenser into the second rectification column. Argon production equipment. A fourth rectifying column disposed at the top of the second condenser;
A fourth rectifying tower top gas introduction pipe for introducing the fourth rectifying tower top gas taken from the top of the fourth rectifying tower into the second rectifying tower; and
The third oxygen-enriched liquid introduction pipe introduces a liquid oxygen-enriched liquid from the liquid phase part of the second condenser into the second rectification column,
The oxygen-enriched liquid stored at the bottom of the first rectifying column is introduced into the second condenser via the gas phase of the fourth rectifying column. 3. Product nitrogen gas and product argon production apparatus according to 3.   The first oxygen-enriched liquid introduction pipe for introducing at least a part of the oxygen-enriched liquid stored at the bottom of the first rectifying column into the second rectifying column. Item 6. The apparatus for producing product nitrogen gas and product argon according to any one of items 5.   The mixed gas is a mixed gas of the condenser gas taken out directly from the gas phase part of the first condenser and the intermediate part gas taken out directly from the intermediate part of the second rectifying column. The apparatus for producing product nitrogen gas and product argon according to any one of claims 2 to 6.   The mixed gas is a mixture of the condenser gas taken out directly from the gas phase part of the first condenser and the intermediate part gas taken out directly from the intermediate part of the second rectification column. The apparatus for producing product nitrogen gas and product argon according to any one of claims 2 to 6, which is a mixed gas that has passed through a main heat exchanger.   The product according to any one of claims 2 to 8, wherein at least one of the nitrogen-containing liquid pipe and the oxygen-enriched liquid outlet pipe and the product nitrogen gas outlet pipe pass through a subcooler. Nitrogen gas and product argon production equipment.   The intermediate gas outlet pipe is connected to the condenser gas outlet pipe at a first junction after being introduced into the subcooler, and the first junction is a stage subsequent to the subcooler and a stage upstream of the expansion turbine. The apparatus for producing product nitrogen gas and product argon according to claim 9.   The intermediate portion of the second rectification column is below the attachment position on the second rectification column side of the nitrogen-containing liquid introduction pipe, and the second rectification tower of the first oxygen-enriched liquid introduction pipe. The apparatus for producing product nitrogen gas and product argon according to any one of claims 2 to 10, which is above a mounting position on a distillation column side.   The ratio of the derived flow rate of the intermediate part gas derived from the intermediate part gas outlet pipe to the derived flow rate of the condenser gas derived from the condenser gas outlet pipe is 0.03 or more and 2 or less. The apparatus for producing product nitrogen gas and product argon according to any one of claims 2 to 11.

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