JPH11118352A - Manufacture of low purity oxygen, and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently recover the low purity oxygen gas at high pressure by using the expansion work generated in the first expansion process to expand the compressed air from a power generating equipment to the pressure corresponding to the operation pressure of a high pressure tower as the power to compress the fluid to make an effective use of the pressure energy. SOLUTION: The compressed air as a part of the raw air received from a power generating equipment G is expanded to the pressure capable of efficiently separating oxygen from nitrogen in a multiple distillation tower 13 by a power recovery turbine 2. The raw air is separated into oxygen and nitrogen through lower temperature distillation by the multiple distillation tower 13 comprising a high pressure tower 10, a main condenser 11 and a low pressure tower 12. The expansion work generated through expansion of the compressed air in the power recovery turbine 2 is used as the compression power of the rest of the raw air (the atmospheric air A). According to this constitution the compression power can be reduced without reducing the yield of the product oxygen, and the power consumption unit can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing low-purity oxygen, and more particularly, to a method in which compressed air from a power generation facility is used as raw air, and purified and cooled raw air is introduced into a double distillation column. The present invention relates to a method and an apparatus for producing low-purity oxygen, in which low-purity oxygen (99% O ₂ or less) is mainly recovered as a product by distillation and separation under a relatively high pressure.

[0002]

2. Description of the Related Art In recent years, low-purity oxygen has been used in integrated coal gasification combined cycle power generation equipment and heavy residue gasification power generation equipment, and further demand is expected in the future. I have. Since these facilities consume a large amount of oxygen, it is desired to reduce the production cost of oxygen in particular.

In these power generation facilities, in order to reduce the production cost of low-purity oxygen, part or all of the raw air introduced into a low-temperature air distillation apparatus for producing low-purity oxygen is supplied to a combustion gas turbine of the power generation facility. A method using compressed air from a connected air compressor has been proposed. At this time, since the pressure of the compressed air supplied from the power generation equipment is higher than that of the raw material air used in a general low-temperature air distillation apparatus, it is necessary to effectively use this relatively high pressure.

[0004] As a method of effectively using the compressed air having a high pressure, a conventional method is employed in which distillation separation is performed at a pressure higher than that of a normal low-temperature air distillation apparatus, and a product gas such as a low-purity oxygen gas is recovered at a high pressure. A method in which product gas is directly sent to the consuming equipment at the pressure recovered from the cryogenic air distillation unit without recompressing the product gas, or a part of the compressed air is further pressurized to reduce product oxygen. A method of using a liquid derived from a liquefied oxygen pump that compresses in a liquid state as a heat source for vaporizing the liquid has been proposed.

[0005] Here, the pressure of the compressed air generated in the power generation equipment is, for example, coaxial with the combustion gas turbine in the case of generating electricity by introducing the combustion gas of 1300 ° C burned in the combustor into the combustion gas turbine. The discharge pressure of the air compressor connected above is about 15 kg / cm ² G. Also, a method of introducing the combustion gas into the combustion gas turbine at 1500 ° C. has been studied. In this case, the pressure of the compressed air is about 3
The pressure is further increased to 0 kg / cm ² G. These pressures
This is considerably higher than the pressure (about 5 to 6 kg / cm ² G) of the raw air used in the ordinary low-temperature air distillation apparatus.

[0006] When such high pressure (about 15 kg / cm ² G or more) air is introduced into a low-temperature air distillation column to perform distillation, the value of the relative volatility of nitrogen with respect to oxygen is lower than that in a normal low pressure distillation method. Is reduced, the effect of separating oxygen and nitrogen is reduced, the flow rate of liquefied nitrogen extracted from the high-pressure column is reduced, and the reflux liquid in the upper part of the low-pressure column becomes insufficient. In addition, the operating pressure of the low pressure column also becomes higher (about 5 kg / cm ² G) in accordance with the operating pressure of the high pressure column, and similarly, the effect of separating oxygen and nitrogen is reduced. In addition, the unit consumption is greatly deteriorated with a decrease in the recovery rate.

[0007] Therefore, in the method of distillation under high pressure (high pressure distillation), in order to ensure the product recovery rate, the descending liquid (reflux liquid) in the upper part of the distillation column is required as compared with the method of distillation under low pressure (low pressure distillation). ) And the rising gas (hereinafter L /
However, the conventional process cannot sufficiently increase the L / V ratio, and cannot sufficiently improve the product recovery rate and the power consumption rate. .

Accordingly, the present invention is capable of efficiently recovering low-purity oxygen gas at a relatively high pressure by effectively utilizing the pressure energy of high-pressure compressed air from a power generation facility,
It is an object of the present invention to provide a method and an apparatus for producing low-purity oxygen that can improve the product recovery rate and reduce the power consumption.

[0009]

According to a first aspect of the present invention, there is provided a method for producing low-purity oxygen, wherein raw air is subjected to low-temperature distillation in a double distillation apparatus having a high-pressure column and a low-pressure column. By the method of producing a low-purity oxygen that separates and recovers at least a low-purity oxygen as a product,
An air compression step of compressing the atmosphere to a pressure corresponding to the operating pressure of the high-pressure tower, and receiving compressed air having a pressure higher than the operating pressure of the high-pressure tower from a power generation facility to a pressure corresponding to the operating pressure of the high-pressure tower. A first expansion step of expanding, a raw air mixing step of mixing the air that has passed through the air compression step and the compressed air that has passed through the first expansion step to obtain raw air, and a raw air that has passed through the raw air mixing step. A step of pre-cooling, a step of purifying by removing impurities such as moisture and carbon dioxide from the pre-cooled raw air, a step of branching the purified raw air into a first raw air and a second raw air, After cooling the first raw material air by heat exchange with the fluid obtained by the low-temperature distillation, introducing the high-pressure raw material air into the high-pressure column, and pressurizing the branched second raw material air, and then obtaining the same by the low-temperature distillation Flow After cooling by heat exchange with, a second expansion step of expanding to the operating pressure of the low pressure column, and a step of introducing the second raw material air that has passed through the second expansion step to the low pressure column as low pressure raw material air, A step of separating high-pressure raw air and low-pressure raw air into oxygen and nitrogen by low-temperature distillation, and after extracting the oxygen and nitrogen separated in the low-pressure tower from the low-pressure tower and raising the temperature by heat exchange with the raw air, A product recovery step of recovering at least the oxygen as product oxygen gas, and the expansion work generated in the first expansion step, as at least a part of power for compressing a fluid other than compressed air received from the power generation facility. It is characterized by using.

Further, in the above-mentioned first structure, the expansion work generated in the first expansion step is used as power for the air compression step or power for compressing product gas in the product recovery step. Features.

A second structure of the method of the present invention is to produce low-purity oxygen by separating and recovering at least low-purity oxygen as a product by low-temperature distillation of raw air in a double distillation apparatus having a high-pressure column and a low-pressure column. In the method, a step of receiving compressed air having a pressure higher than the operating pressure of the high-pressure column from a power generation facility to make at least a part of the raw air, a step of pre-cooling the raw air, and a step of removing water or carbon dioxide from the pre-cooled raw air. A step of purifying by removing impurities such as, a step of branching the purified raw air into a first raw air and a second raw air, and expanding the branched first raw air to the operating pressure of the high-pressure column. And introducing into the high-pressure column, and cooling the branched second raw material air by heat exchange with a fluid obtained by low-temperature distillation, then reducing the pressure to the operating pressure of the high-pressure column and introducing it to the high-pressure column. A step of separating the introduced raw material air into oxygen and nitrogen by low-temperature distillation in a double distillation column, and extracting the oxygen and nitrogen separated in the double distillation column and raising the temperature by heat exchange with the raw material air. After the heating, including a product recovery step of recovering at least the oxygen as product oxygen gas, the expansion work generated in the expansion step of the first raw material air, compressing the fluid other than the compressed air received from the power generation equipment It is characterized in that it is used as at least a part of the driving power.

Further, in the above-mentioned second configuration, the step of recovering the product oxygen gas is performed by extracting and compressing liquefied oxygen at the bottom of the low-pressure column, and then vaporizing it by heat exchange with the raw material air. It is characterized by
The step of branching the raw air into the first raw air and the second raw air is performed in the course of cooling by heat exchange with the fluid obtained by the low-temperature distillation. In addition, expansion work generated when expanding the first raw material air is used as power for compressing product gas extracted from the low-pressure column in the product recovery step. Further, after increasing the pressure of at least one of the high-pressure nitrogen gas extracted from the high-pressure column and the low-pressure nitrogen gas extracted from the low-pressure column, the mixture is cooled by heat exchange with a fluid obtained by low-temperature distillation, and then the high-pressure nitrogen is cooled. Liquefied by heat exchange with the bottom liquid of the column, and introduced into at least one of the high-pressure column and the low-pressure column, and as the power for increasing the pressure of the nitrogen gas, the first raw material air is expanded. It is characterized by utilizing expansion work generated at the time.

[0013] The apparatus for producing low-purity oxygen of the present invention comprises:
As a first configuration, in a low-purity oxygen producing apparatus that separates and recovers at least low-purity oxygen as a product by distilling raw air at a low temperature in a double distillation facility having a high-pressure tower and a low-pressure tower, An air compressor that compresses to a pressure corresponding to the operating pressure, and a power recovery turbine that receives compressed air having a pressure higher than the operating pressure of the high-pressure tower from a power generation facility and expands the compressed air to a pressure corresponding to the operating pressure of the high-pressure tower. A mixing path for mixing the raw air compressed by the air compressor and the compressed air expanded by the power recovery turbine to obtain raw air, a pre-cooling device for pre-cooling the raw air derived from the mixing path, Purification equipment for purifying by removing impurities such as moisture and carbon dioxide from the purified raw air, and a branch path for branching the purified raw air into a first raw air and a second raw air, A main heat exchanger for exchanging the branched first raw material air with a fluid obtained by low-temperature distillation, and a high-pressure raw air introduction path for introducing the first raw air derived from the main heat exchanger to the high-pressure column, A booster for boosting the second raw material air branched in the branch path; a cold generation turbine for introducing the second raw material air derived from the booster after cooling it in the main heat exchanger and expanding the turbine; A low-pressure feed air introduction path for introducing the second feed air derived from the generation turbine to the low-pressure tower, and oxygen by low-temperature distillation of the feed air introduced from the high-pressure feed air introduction path and the low-pressure feed air introduction path. A double distillation column consisting of a high-pressure column, a main condenser and a low-pressure column which separates into nitrogen, and oxygen and nitrogen separated in the low-pressure column of the double distillation column are extracted and heated by the main heat exchanger. acid And a product recovery path for recovering the product as product oxygen gas, and the power recovery turbine is coaxially connected to a compressor that compresses a fluid other than compressed air received from the power generation facility. Features.

A second configuration of the apparatus of the present invention is a method for producing low-purity oxygen by separating and recovering at least low-purity oxygen as a product by distilling raw air at a low temperature in a double distillation facility having a high-pressure column and a low-pressure column. In the apparatus, a compressed air supply / demand path for receiving compressed air at a pressure higher than the operating pressure of the high-pressure tower as at least a part of the raw material air from the power generation equipment, a precooling equipment for precooling the raw air, and a raw air derived from the precooling equipment A purification equipment for removing impurities such as moisture and carbon dioxide from the purification equipment, a branch path for branching the raw material air derived from the purification equipment into a first raw material air and a second raw material air, and a branched first raw material air. A power recovery turbine that expands to the operating pressure of the high pressure tower, a first raw material air introduction path for introducing the first raw material air derived from the power recovery turbine into the high pressure tower, A main heat exchanger that cools the second raw material air branched in the path by heat exchange with a fluid obtained by low-temperature distillation, and after the second raw material air led out of the main heat exchanger is depressurized through a pressure reducing valve, A second raw material air introduction path to be introduced into the high pressure tower, and a high pressure column for separating the raw material air introduced from the first raw material air introduction path and the second raw material air introduction path into oxygen and nitrogen by low-temperature distillation. A double distillation column consisting of a main condenser and a low-pressure column, and a product recovery system in which oxygen and nitrogen separated in the double distillation column are extracted and heated by the main heat exchanger, and at least the oxygen is recovered as product oxygen gas. And a power recovery turbine, wherein the power recovery turbine is provided so as to be coaxially connected to a compressor that compresses a fluid other than compressed air from a power generation facility that is received via the compressed air supply and demand path. It is a symptom.

Further, in the above-mentioned second configuration, a branch path for branching into the first raw material air and the second raw material air is provided in the main heat exchanger, and the power recovery turbine supplies low-temperature raw material air. The low-temperature turbine to be introduced is characterized in that a low-temperature compressor that compresses a low-temperature fluid is connected coaxially with the low-temperature power recovery turbine. Also, a path for extracting high-pressure nitrogen gas from the upper part of the high-pressure column, a high-pressure circulating booster for increasing the pressure of the high-pressure nitrogen gas extracted to the path, and a pressurized nitrogen gas pressurized by the high-pressure circulator A high-pressure nitrogen circulation system comprising a condenser / reboiler which liquefies by exchanging heat with the bottom liquid and a path for introducing liquefied nitrogen liquefied by the condenser / reboiler into the high-pressure column, or a low-pressure nitrogen gas from the upper part of the low-pressure column , A low-pressure circulating pressurizer for pressurizing the low-pressure nitrogen gas discharged to the path, and a nitrogen condensate for liquefying by heat-exchanging the pressurized nitrogen gas pressurized by the low-pressure circulating press with the bottom liquid of the high-pressure column. A low-pressure nitrogen circulation system comprising a vessel and a path for introducing liquefied nitrogen liquefied by the nitrogen condenser into the low-pressure column. Further, the apparatus of the present invention is characterized in that at least one of the low-pressure column and the high-pressure column is a packed distillation column.

[0016]

FIG. 1 is a system diagram showing a first embodiment of a low-purity oxygen producing apparatus according to the present invention. The low-purity oxygen production apparatus S includes, as main components, an air compressor 1 for compressing the atmosphere A, which is a part of the raw air, and a power recovery turbine 2 for expanding the compressed air received from the power generation equipment G.
And a pre-cooling facility 3 for pre-cooling the raw material air in which the air derived from the air compressor 1 and the power recovery turbine 2 are merged.
And a purification equipment 4 for removing impurities such as water and carbon dioxide contained in the pre-cooled raw air to purify the raw air, and a main heat exchanger for cooling the purified raw air with a fluid obtained by low-temperature distillation. 5, a booster 6 that boosts a part of the raw air derived from the purification facility 4, a cooler 7 that cools the raw air (pressurized air) boosted by the booster 6, and a cooler 7 that is derived. Pre-cooler 8 for exchanging heat between the pressurized air thus obtained and the raw air introduced into the booster 6, a cold-generation turbine 9 for adiabatically expanding the pressurized air derived from the air pre-cooler 8, -Pressure column 10, which separates into nitrogen and nitrogen,
A double distillation column 13 composed of a main condenser 11 and a low pressure column 12,
Subcooler 1 for cooling the reflux liquid introduced into low pressure column 12
4, 15 are provided. Among these constituent devices, the device having a low temperature is housed in a cold storage tank to constitute a low-temperature distillation facility C. Further, the air compressor 1 and the power recovery turbine 2, and the booster 6 and the cold generation turbine 9 are provided coaxially and connected to each other.

Next, the air compressor 1 and the power generation equipment G are supplied with substantially equal amounts of raw material air (atmosphere and compressed air) to the low-purity oxygen producing apparatus S configured as described above to reduce the product quality. The method of the present invention will be described based on a process for producing pure oxygen gas.

50900 Nm ³ taken from the atmosphere
/ H of raw material air is 12.5kgf / c by the air compressor 1.
m ² abs. And is introduced into the path 20 through the path 21 and introduced from the power generation facility G through the path 21.
5 kgf / cm ² abs. , 51700 Nm ³ / h compressed air is introduced into the power recovery turbine 2, where the compressed air having the same pressure as the discharge pressure of the air compressor 1 is discharged.
2.5 kgf / cm ² abs. To the path 22. The raw material air led out to the two paths 20 and 22 merges in the mixing path 23, becomes 102600 Nm ³ / h of raw material air, and is introduced into the precooling facility 3.

The raw material air cooled to a required temperature in the precooling facility 3 is purified by adsorbing and removing impurities such as water and carbon dioxide contained in the refining facility 4, and then passes through a path 24 to a branch path 25. It branches into a first raw material air in a path 26 and a second raw material air in a path 27. 9980 branched to route 26
The first raw material air of 0 Nm ³ / h is introduced into the main heat exchanger 5 and exchanges heat with a low-temperature fluid derived from the double distillation column 13 to be cooled to a substantially dew-point temperature. Air is introduced into the lower part of the high-pressure column 10 from the air introduction path 28.

On the other hand, the 2800N branched to the path 27
m ³ / h of the second raw material air is introduced into the booster 6 through the air precooler 8 and the path 29, where the pressure of 19 kgf /
cm ² abs. After cooling to 17 ° C. through the cooler 7 and the air precooler 8, it is further cooled through the path 30 and the main heat exchanger 5, and introduced into the cold-generation turbine 9 from the path 31. Is done. The second raw material air introduced into the cold generation turbine 9 is 3.8 kgf / cm ²
abs. The adiabatic expansion causes cold to occur, resulting in low-pressure raw air, which is introduced into the low-pressure tower 12 through the low-pressure raw air introduction path 32.

The high-pressure feed air introduced into the high-pressure column 10 is
By ascending in the tower and coming into gas-liquid contact with the descending liquid flowing down in the tower, it is separated into nitrogen gas at the top of the tower and oxygen-enriched liquefied air at the bottom of the tower. The oxygen-enriched liquefied air extracted from the passage 33 at the bottom of the tower is cooled to a supercooled state by exchanging heat with low-temperature nitrogen in the subcooler 14, passes through the passage 34, and is reduced by the pressure reducing valve 35 to 3.8 kgf / cm. ² abs. After the pressure is reduced to
From 6, it is introduced into the middle part of the low pressure column 12 as a reflux liquid.

On the other hand, the nitrogen gas separated at the top of the high-pressure column 10 is introduced into the main condenser 11 through a path 37, and exchanges heat with liquefied oxygen at the bottom of the low-pressure column 12 to vaporize the liquefied oxygen. As the rising gas in the low pressure column 12 is generated, it is liquefied and led to the passage 38, and is returned to the top of the high pressure column 10 as a reflux liquid. Route 3 branches from Route 38
9 liquefied nitrogen 42000Nm ³ / h
Is cooled to a supercooled state by exchanging heat with low-temperature nitrogen in the subcooler 15, passes through a path 40 and is reduced by a pressure reducing valve 41 to 3.7 kgf.
/ Cm ² abs. After being reduced to a pressure, the liquid is introduced into the upper part of the low-pressure column 12 from the passage 42 as a reflux liquid.

In the low-pressure column 12, the reflux liquid supplied from the paths 36 and 42 and the ascending gas composed of the oxygen gas vaporized in the main condenser 11 and the low-pressure raw material air supplied from the path 32 are vapor-liquid. Upon contact, further distillation is performed, and oxygen is separated at the bottom of the column and nitrogen is separated at the top of the column.

Of the oxygen separated at the lower part of the low pressure column 12,
The oxygen gas of 2300 Nm ³ / h is extracted from the path 43 constituting the product oxygen recovery path, and the temperature is increased by cooling the raw material air in the main heat exchanger 5 so that the pressure is 3.7 kgf / h.
cm ² abs. 95% pure from path 44 at 13 ° C
Of the product oxygen gas GO.

The nitrogen gas 80300 Nm ³ / h separated at the top of the low-pressure column 12 is extracted from a path 45 constituting a product nitrogen recovery path, and is refluxed and liquefied from the upper part of the high-pressure column 10 by a subcooler 15. The temperature of the nitrogen is further increased by successively cooling the nitrogen and the oxygen-enriched liquefied air from the bottom of the high-pressure column 10 in the subcooler 14 through a path 46, and further increased by a path 47.
And the temperature was increased by cooling the raw material air in the main heat exchanger 5 to a pressure of 3.6 kgf / cm ² abs. , At a temperature of 13 ° C., from the path 48 as product nitrogen gas GN.

In this embodiment, the oxygen recovery rate (the ratio of the amount of pure oxygen in product oxygen to the amount of oxygen in the raw air) is 9
The raw material air (atmosphere A) to be compressed by the air compressor 1 is 12.5 kgf / cm ² abs.
Approximately 15% of the power required for compression to the maximum was compensated by the expansion work generated in the power recovery turbine 2.

As shown in the present embodiment, the compressed air as a part of the raw material air received from the power generation equipment G can be efficiently separated into oxygen and nitrogen in the double distillation column 13 by the power recovery turbine 2. By expanding to a pressure and using the expansion work generated by the expansion as the compression power of the remaining raw material air (atmosphere A), the compression power can be reduced without lowering the yield of product oxygen. . Therefore, the power consumption can be improved.

Further, in this embodiment, the case where the expansion work of the compressed air received from the power generation equipment G is used as the compression power of the remaining raw material air is shown, but this expansion work is used to recover the product oxygen gas. One or both of the product nitrogen gas in the route 48 for recovering the product oxygen gas and the product nitrogen gas in the route 44 can be used as power for compressing the product nitrogen gas.

Further, by using a packed distillation column using a packing having a smaller pressure loss than a sieve tray as a gas-liquid contacting means for one or both of the high pressure column 10 and the low pressure column 12, the double distillation column When the pressure of the raw material air supplied to 13 is the same, the product can be extracted at a higher pressure than when the sieve tray is used, and the power for compressing the product gas can be reduced.

FIG. 2 is a system diagram showing a second embodiment of the present invention. The same components as those in the low-purity oxygen production apparatus of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this low-purity oxygen production apparatus, raw air consisting of compressed air received from the power generation equipment G and air compressed to the same pressure as the compressed air by the air compressor 51 is converted into an intermediate temperature by the main heat exchanger 5. After cooling to a low temperature, a part thereof is expanded in a low-temperature state by a low-temperature power recovery turbine 52, and the expansion work due to the expansion is led out from the high-pressure column 10 of the double distillation column 13 to the path 37 and branched to the path 53. The nitrogen gas pressurized by the high-pressure circulating nitrogen pressurizer 54 is used as the power of the high-pressure circulating nitrogen pressurizer 54 that pressurizes a part of the high-pressure nitrogen gas, and the nitrogen gas pressurized by the high-pressure circulating nitrogen pressurizer 54 is supplied to the tower It is formed such that it is liquefied by heat exchange with the bottom liquid and then introduced as a reflux liquid into the upper part of the high-pressure column 10 via the pressure reducing valve 56. Further, in the present embodiment, a liquid product (liquefied oxygen) can be recovered in addition to the gas product.

That is, the power recovery turbine 52 expands the low-temperature raw material air branched out from the central part of the main heat exchanger 5 to the operating pressure of the high-pressure tower 10. And is used for the compression power of a high-pressure circulating nitrogen booster 54 connected to the compressor.

Next, a substantially equal amount of raw material air is supplied from the air compressor 51 and the power generation equipment G to the low-purity oxygen production equipment S configured as described above, and a process for producing low-purity oxygen of the product is performed. The method of the present invention will be described based on this.

51,000 Nm taken from atmosphere A
³ / h of raw air is supplied to the air compressor 51 at a pressure of the same pressure as the compressed air received from the power generation equipment G via the path 21.
5 kgf / cm ² abs. And is derived to the path 20, and 51700Nm ^{3 /} h, 30.5k from the path 21
gf / cm ² abs. With the compressed air in the mixing path 23 to obtain 102700 Nm ³ / h of raw material air. The high-pressure raw material air is cooled in the pre-cooling equipment 3, purified in the purification equipment 4, and then guided to the main heat exchanger 5 through the passage 24.

During the cooling of the raw air introduced into the main heat exchanger 5, the first raw air of the path 58 and the path 59 are branched by a branch path 57 provided at an intermediate portion of the main heat exchanger 5.
The first raw material air of 66100 Nm ³ / h branched to one path 58 and 15 kgf / cm ² abs. After expanding to
It is introduced into the high-pressure column 10 from the first raw material air introduction path 60. The remaining 36600 branched to the other route 59
The Nm ³ / h second raw material air passes through the raw material air passage of the main heat exchanger 5 and is further cooled, liquefied in its entirety and led to the second raw material air introduction path 61.
gf / cm ² abs. After the pressure is reduced, the pressure is introduced into the high-pressure column 10 through the path 63.

The oxygen-enriched liquefied air led from the bottom of the high-pressure tower 10 to the path 33 is subcooled by the subcooler 14 and passes through the path 34, the pressure reducing valve 35, and the path 36. Is introduced as a reflux liquid into the middle part. On the other hand, high pressure tower 1
The nitrogen gas separated at the upper part of the zero gas is led out to a path 37 and branches into a path 37a and the path 53, and the nitrogen gas branched into the path 37a is liquefied in the main condenser 11 and a path 38 Most of which is returned to the top of the high pressure column 10 as reflux. The remaining 50500 Nm ³ / h of liquefied nitrogen branched from the path 38 to the path 39 is supplied to the subcooler 1
After being supercooled in 5, a path 40 toward the low pressure column 12;
The liquefied nitrogen of 49100 Nm ³ / h branched to the liquefied nitrogen extraction path 64 and branched to the path 40 passes through the pressure reducing valve 41 and the path 42 and is introduced as a reflux liquid to the top of the low-pressure column 12. Also, the 1400N branched to the liquefied nitrogen extraction path 64
The liquefied nitrogen LN of m ³ / h is taken out of the system for controlling the temperature of the low-temperature distillation facility C.

On the other hand, the nitrogen gas of 61600 Nm ³ / h extracted from the high-pressure tower 10 to the path 37 and branched to the path 53 is guided to the high-pressure circulating nitrogen booster 54 to remove the bottom liquid of the high-pressure tower 10. Of the pressure that can be liquefied by heat exchange
3 kgf / cm ² abs. Is boosted. The pressurized nitrogen gas is introduced into the main heat exchanger 5 through a path 65 and cooled, and is guided through a path 66 to a condenser / reboiler 55 at the bottom of the high-pressure column. In this condenser / reboiler 55, the heat exchange between the pressurized nitrogen gas and the oxygen-enriched liquefied air at the bottom of the high-pressure tower 10 causes the oxygen-enriched liquefied air to evaporate and the nitrogen gas to be entirely liquefied and vaporized. The oxygen-enriched air rises in the high-pressure column 10, and the liquefied nitrogen is led out to a path 67, depressurized by the pressure reducing valve 56, and then introduced as a reflux liquid to the top of the high-pressure column 10 through a path 68. .

Of the oxygen separated at the bottom of the low pressure column 12, 2
The liquefied oxygen of 2300 Nm ³ / h is extracted to a passage 69 forming a product oxygen recovery passage, and is supplied to a liquefied oxygen pump 70 at 14 kgf / cm ² abs. After being compressed to
The raw material air is led to the main heat exchanger 5 where it is vaporized and heated by cooling the raw material air, and has a pressure of 14 kgf / cm ² a.
bs. , A temperature of 13 ° C. and a purity of 95% as product oxygen gas GO.

On the other hand, 790 separated at the top of the low pressure column 12
After the nitrogen gas of 00 Nm ³ / h is extracted to the path 45 constituting the product nitrogen recovery path, the supercooler 1
5, through the path 46, the subcooler 14, and the path 47, and the temperature is increased in the main heat exchanger 5, and the pressure is 4.7 kgf / cm ² abs. , At a temperature of 13 ° C. as a product nitrogen gas GN.

In the present embodiment, as the raw material air necessary for low-temperature distillation, a case where raw air introduced from the atmosphere and compressed by the air compressor 51 and compressed air received from the power generation equipment G are mixed in substantially equal amounts. Although shown, the compressed air received from the power generation equipment G without the air compressor 51 can be the total amount of the raw air required for the low-temperature distillation equipment C.

As described above, according to the present invention, since the high-pressure raw material air is directly supplied to the low-temperature distillation facility C, the supplied raw-material air is obtained by distillation rather than the enthalpy brought into the low-temperature distillation facility C. However, the enthalpy brought out from the low-temperature distillation facility C is larger. Therefore, a cold generation turbine is not required, and the liquid product can be collected. In the present embodiment, the case where liquefied nitrogen is extracted as a product for cooling control has been described.However, instead of or simultaneously with liquefied nitrogen, the product liquefied oxygen LO may be extracted from the path 73 indicated by a broken line. it can. In addition, it is also possible to control the cooling by adjusting the hot end temperature difference of the main heat exchanger 5 without extracting the liquid product. In this case, the size of the main heat exchanger 5 can be reduced.

In this embodiment, the power recovery turbine 5
The expansion work due to the expansion of the high-pressure raw material air generated in Step 2
This expansion work is converted into the power for raising the pressure of the high-pressure circulating nitrogen gas in the high-pressure circulating nitrogen booster 54 and the heat generated by the pressurization because the pressure is used as the power for raising the pressure of the nitrogen gas in the high-pressure circulating nitrogen booster 54. Have been. Since the boosted heat generated at this time is not taken out of the system, the power recovery turbine 52 does not substantially generate cooling, and functions as power recovery.

Further, as described above, a part of the high-pressure nitrogen gas separated at the top of the high-pressure column 10 is branched without being introduced into the main condenser 11 and pressurized, and the pressurized nitrogen gas is supplied to the condenser / reboiler 55. After liquefaction, the liquid was introduced as a reflux liquid at the top of the high-pressure column 10.
Is improved, and the amount of reflux liquefied nitrogen liquefied in the main condenser 11 to the low-pressure column 12 branched to the path 39 can be increased.
Can be increased, and the product oxygen recovery rate can be 98.5% despite the high operating pressure of the double distillation column 13.

Further, in the present embodiment, the liquefied oxygen pump 7 is provided in the product oxygen recovery path for extracting liquefied oxygen from the low-pressure column 12.
Although the case where 0 is provided is shown, the product oxygen gas can be directly extracted from the low pressure column 12 without providing the liquefied oxygen pump 70. In addition, a part of the nitrogen gas extracted from the high-pressure tower 10 is branched into a path 74 shown by a broken line, heated in the main heat exchanger 5, and can be collected as a high-pressure product nitrogen gas MN from a path 75.

The power recovery turbine 52 introduces low-temperature first raw material air which is being cooled in the main heat exchanger 5, and the high-pressure circulating nitrogen booster 54 introduces low-temperature nitrogen gas from the high-pressure tower 10. It is equipment of low temperature specification that expands or compresses at low temperature, and when expanding or compressing at such low temperature,
The device can be downsized as compared with the case where the process is performed at room temperature.

The first raw material air introduced into the power recovery turbine 52 is supplied to the main heat exchanger 5
It is possible to branch out at an arbitrary position up to the cold end of, for example, a branch path is provided in a path 24 from the refining facility 4 to the main heat exchanger 5, and a first branch of the temperature near normal temperature is provided. Feed air can be introduced into the power recovery turbine 52.
The expansion work generated in the power recovery turbine 52 is used not only for the compression power of the low-pressure high-pressure circulating nitrogen booster 54 but also in accordance with the specification temperature of the power recovery turbine 52.
It can also be used as a compression power for a high-pressure circulating nitrogen booster operated near normal temperature, a product gas compressor for compressing low-temperature or normal-temperature products, or a liquefied oxygen pump for compressing liquid products.

FIG. 3 is a system diagram showing a third embodiment of the present invention, wherein the same components as those in the first and second embodiments are denoted by the same reference numerals. This embodiment is different from the second embodiment in that the high-pressure nitrogen circulation system is replaced with a low-pressure tower 1.
2 shows an example in which a low-pressure nitrogen circulation system is provided in which a part of the low-pressure nitrogen gas derived from 2 is pressurized and liquefied and circulated to the low-pressure tower 12.

That is, the path 45 from the top of the low pressure tower 12
And a part of the low-pressure nitrogen gas flowing to the main heat exchanger 5 through the subcooler 15, the path 46, the subcooler 14, and the path 47 is branched into a path 80, and the branched low-pressure nitrogen is used as power. The pressure of the pressurized nitrogen gas is increased by a low-pressure circulating nitrogen booster 81 utilizing the expansion work of the compressed air in the recovery turbine 52, and the increased nitrogen gas is supplied to a path 82, a main heat exchanger 5, a path 83, a subcooler 14, and a path 8
4. Cooling is sequentially performed through the subcooler 15, and further liquefied by heat exchange with the bottom liquid (oxygen-enriched liquefied air) of the high-pressure tower 10 from the pressure reducing valve 35a through the nitrogen condenser 85, and then the pressure reducing valve 86 And a low-pressure nitrogen circulation system for circulating the low-pressure nitrogen through the passages 87 and 42 to the low-pressure tower 12 is provided.

The power recovery turbine 52 expands the low-temperature and high-pressure first raw material air branched to the path 58 in the middle part of the main heat exchanger 5 to the operating pressure of the high-pressure tower 10 as in the second embodiment. The expansion work by the expansion is used for the compression power of a low-pressure circulating nitrogen booster 81 provided coaxially and connected. In addition, low pressure circulating nitrogen booster 8
1 is to raise the pressure of the low-pressure nitrogen gas extracted from the low-pressure column 12 to a pressure at which it is liquefied by heat exchange with the column bottom liquid extracted from the bottom of the high-pressure column 10 and reduced in the nitrogen condenser 85. The pressurized nitrogen gas is liquefied in a nitrogen condenser 85, then reduced in pressure to the operation pressure of the low-pressure column 12, and circulated as a reflux liquid into the upper part of the low-pressure column 12.

Next, a process for supplying substantially equal amounts of raw material air from the air compressor 51 and the power generation facility G to the low-purity oxygen production equipment S thus configured to produce low-purity oxygen of the product. The method of the present invention will be described based on FIG.

51,000 Nm ³ taken from the atmosphere
/ H of the raw material air having the same pressure as the compressed air received from the power generation equipment G via the path 21 by the air compressor 51.
5 kgf / cm ² abs. 51700 from the power generation facility G, which is compressed to
Nm ^{3 /} h, 30.5 kgf / cm ² abs. 102700 by mixing with the compressed air of
Nm ³ / h of raw material air, cooled by the pre-cooling equipment 3,
Next, water, carbon dioxide, and the like are removed in the refining facility 4 and guided to the main heat exchanger 5.

The raw air introduced into the main heat exchanger 5 is branched into a first raw air in a path 58 and a second raw air in a path 59 through a branch path 57 in the course of cooling. The 56500 Nm ³ / h first raw material air branched to the path 58 is supplied to the power recovery turbine 52 at 15 kgf / cm ² abs. After that, it is introduced into the lower part of the high-pressure column 10 from the first raw material air introduction path 60. 46200 branched to the route 59
The second raw material air of Nm ³ / h is cooled and liquefied as it is in the main heat exchanger 5, is led out to the second raw material air introduction path 61, and is depressurized by the pressure reducing valve 62.
Introduced at the bottom.

The oxygen-enriched liquefied air led from the bottom of the high-pressure column 10 to the path 33 is supercooled by the subcooler 14 and led to the path 34, and after being depressurized by the pressure reducing valve 35a, the nitrogen Is introduced into the vessel 85. The oxygen-enriched liquefied air that has exchanged heat with the pressurized nitrogen gas flowing through the low-pressure nitrogen circulation system in the nitrogen condenser 85 is introduced as a reflux liquid into the center of the low-pressure column 12 through the path 36a.

The nitrogen gas led from the upper part of the high-pressure column 10 to the path 37 is liquefied in the main condenser 11 and led to the path 38, and most of the nitrogen gas is returned to the top of the high-pressure tower 10 as a reflux liquid. A part of liquefied nitrogen 32,800 Nm ³ / h branches to the path 39 and is supercooled by the supercooler 15, and then a part of liquefied nitrogen (LN) 1300 Nm ³ / h branches to the path 64 to control the cooling. The remaining 31500 Nm ³ / h of liquefied nitrogen which was taken out of the system and branched to the path 40 was supplied to the pressure reducing valve 41 at 4.9 kgf / cm ² abs. After being decompressed to
The solution is introduced into the top of the low-pressure column 12 as a reflux liquid through a path 42.

The liquefied oxygen of 22300 Nm ³ / h extracted from the bottom of the low-pressure column 12 to the passage 69 was supplied to the liquefied oxygen pump 70 at 14 kgf / cm ² abs. And introduced into the main heat exchanger 5 through the passage 71 to evaporate and raise the temperature, and the pressure is 14 kgf / cm ² abs. , A temperature of 13 ° C. and a purity of 95% as product oxygen gas GO.

The nitrogen gas of 120400 Nm ³ / h separated at the top of the low-pressure column 12 and extracted to the path 45 passes through the subcooler 15, the path 46, the subcooler 14, and the path 47.
Here, the flow branches into a path 47a that is recovered as product nitrogen gas GN and a path 80 that goes to the low-pressure nitrogen circulation system. 79100Nm ³ /
h nitrogen gas is heated in the main heat exchanger 5 and has a pressure of 4.7 k.
gf / cm ² abs. , Product nitrogen gas GN at 13 ° C
From the path 48.

On the other hand, 41000 Nm branched to the path 80
The nitrogen gas of ³ / h is led to the low-pressure circulating nitrogen booster 81, and is a pressure that can be liquefied by the nitrogen condenser 85, that is, 7.5 kg.
f / cm ² abs. Is boosted. The pressurized nitrogen gas is introduced into the main heat exchanger 5 from the path 82 and cooled,
Subsequently, it is further cooled through a path 83, a subcooler 14, a path 84, and a subcooler 15, and is further cooled through a path 88 to the nitrogen condenser 85.
Will be introduced. The pressurized nitrogen gas introduced into the nitrogen condenser 85 is entirely liquefied by heat exchange with oxygen-enriched liquefied air from the bottom of the high-pressure column 10, is led out to a path 89, and is depressurized by a pressure reducing valve 86. After passing through the passage 87, it joins the passage 42 through which the reflux liquefied nitrogen flows from the upper part of the high-pressure column, and is introduced as a reflux liquid at the top of the low-pressure column 12.

As described above, the low-pressure nitrogen gas extracted from the low-pressure column 12 is pressurized, the pressurized nitrogen gas is liquefied in the nitrogen condenser 85, and then introduced into the top of the low-pressure column 12 as a reflux liquid. The L / V ratio at the top of the low-pressure column 12 is improved, and the recovery rate of product oxygen can be increased to 98.5% despite the high operating pressure of the double distillation column 13.

In this embodiment, similarly to the second embodiment shown in FIG. 2, the compressed air received from the power generation equipment G can be the entire amount of the raw air required for low-temperature distillation.
In addition, as a product, a part of the nitrogen gas extracted from the high-pressure tower 10 to the path 37 can be collected as a high-pressure product nitrogen gas MN via the path 90, the main heat exchanger 5, and the path 91, and the cold generation can occur. Since a liquid product can be recovered without a turbine, a part of the liquefied oxygen extracted from the lower part of the low-pressure column 12 to the path 69 is transferred from the path 73 to the product liquefied oxygen LO.
It can also be collected as. Conversely, instead of recovering the liquid product in this way, as described above, the main heat exchanger 5
By controlling the temperature difference between the hot end and the cold end, the main heat exchanger 5 may be downsized. Further, when recovering the product oxygen gas, the liquefied oxygen pump 7
Without providing 0, the product oxygen gas may be directly extracted from the low pressure column 12.

The expansion work generated in the power recovery turbine 52 can be used as compression power for various fluids. By using a packed distillation column as the distillation column, the product recovery pressure can be increased. And the like are the same as those in the above embodiments, and the same operation and effect can be obtained.

In each embodiment, when nitrogen gas is unnecessary, it may be released to the atmosphere without being recovered as a product, and may be used for other purposes, for example, as a cooling source for precooling equipment. Part of the nitrogen gas is also used for regenerating purification equipment. Further, in the second and third embodiments, it is also possible to use a part of the liquefied nitrogen circulated as a reflux liquid from each circulation system to the low-pressure column or the high-pressure column as a reflux liquid for another column, Can be extracted out of the system. Further, both circulation systems can be provided in parallel.

[0062]

As described above, according to the present invention,
The pressure of the compressed air received from the power generation equipment can be effectively used, and the recovery rate of the product low-purity oxygen gas can be improved and the power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a first embodiment of a low-purity oxygen production apparatus of the present invention.

FIG. 2 is a system diagram showing a second embodiment of the low-purity oxygen production apparatus of the present invention.

FIG. 3 is a system diagram showing a third embodiment of the low-purity oxygen production apparatus of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Air compressor, 2 ... Power recovery turbine, 3 ... Pre-cooling equipment, 4 ... Refining equipment, 5 ... Main heat exchanger, 6 ... Booster, 7 ...
Cooler, 8 ... Air pre-cooler, 9 ... Cold generation turbine, 10
... high-pressure column, 11 ... main condenser, 12 ... low-pressure column, 13 ... double distillation column, 14, 15 ... subcooler, 23 ... mixing path, 25 ...
Branch path, 28 high-pressure raw material air introduction path, 32 low-pressure raw material air introduction path, 35 pressure reducing valve, 41 pressure reducing valve, 51 ...
Air compressor, 52: power recovery turbine, 54: high pressure circulating nitrogen booster, 55: condenser / reboiler, 56: pressure reducing valve, 57: branch path, 60: first raw material air introduction path, 6
DESCRIPTION OF SYMBOLS 1 ... Second raw material air introduction path, 62 ... Pressure reducing valve, 64 ... Liquefied nitrogen extraction path, 70 ... Liquefied oxygen pump, 81 ... Low pressure circulating nitrogen booster, 85 ... Nitrogen condenser, 86 ... Pressure reducing valve, A ... Atmosphere, C: low-temperature distillation equipment, G: power generation equipment, S: low-purity oxygen production equipment, GN: product nitrogen gas, GO: product oxygen gas,
LN: liquefied nitrogen, LO: product liquefied oxygen, MN: high pressure product nitrogen gas

Claims (16)

[Claims] 1. A low-purity oxygen production method for separating and recovering at least low-purity oxygen as a product by subjecting raw air to low-temperature distillation in a double distillation apparatus having a high-pressure tower and a low-pressure tower, wherein the air is treated by operating the high-pressure tower. An air compression step of compressing to a pressure corresponding to the pressure, and a first expansion step of receiving compressed air having a pressure higher than the operating pressure of the high-pressure tower from a power generation facility and expanding the compressed air to a pressure corresponding to the operating pressure of the high-pressure tower. A raw air mixing step of mixing the air that has passed through the air compression step and the compressed air that has passed through the first expansion step to obtain raw air, and a step of pre-cooling the raw air that has passed through the raw air mixing step, A step of purifying by removing impurities such as moisture and carbon dioxide from the raw material air; a step of branching the purified raw material air into a first raw material air and a second raw material air; After cooling by heat exchange with the fluid obtained by low-temperature distillation, a step of introducing the high-pressure raw material air into the high-pressure column, and pressurized the branched second raw material air, and then the fluid obtained by low-temperature distillation A second expansion step of expanding to an operating pressure of the low-pressure column after cooling by heat exchange of the low-pressure column, a step of introducing the second raw material air having passed through the second expansion step as the low-pressure raw material air into the low-pressure column, A step of separating the raw air and the low-pressure raw air into oxygen and nitrogen by low-temperature distillation, and extracting the oxygen and nitrogen separated in the low-pressure tower from the low-pressure tower and raising the temperature by heat exchange with the raw air, A product recovery step of recovering the oxygen as product oxygen gas, and the expansion work generated in the first expansion step, the power of compressing fluid other than compressed air received from the power generation equipment. Low purity oxygen production method characterized by utilizing as least part. 2. The method for producing low-purity oxygen according to claim 1, wherein the expansion work generated in the first expansion step is used as power for the air compression step. 3. The method for producing low-purity oxygen according to claim 1, wherein the expansion work generated in the first expansion step is used as power for compressing product gas in the product recovery step. 4. A method for producing low-purity oxygen by separating and recovering at least low-purity oxygen as a product by subjecting raw air to low-temperature distillation in a double distillation apparatus having a high-pressure column and a low-pressure column, wherein the operating pressure of the high-pressure column is reduced. A step of receiving high-pressure compressed air from a power generation facility to form at least a part of the raw air, a step of pre-cooling the raw air, and a step of purifying by removing impurities such as moisture and carbon dioxide from the pre-cooled raw air. And, a step of branching the purified raw material air into a first raw material air and a second raw material air, and a step of expanding the branched first raw material air to the operating pressure of the high pressure column and introducing it to the high pressure column, After cooling the branched second raw material air by heat exchange with a fluid obtained by low-temperature distillation, reducing the pressure to the operating pressure of the high-pressure column and introducing the raw material air into the high-pressure column, A step of separating into oxygen and nitrogen by low-temperature distillation in a double distillation column, and extracting the oxygen and nitrogen separated in the double distillation column and raising the temperature by heat exchange with the raw material air; Including a product recovery step of recovering as gas, and using expansion work generated in the expansion step of the first raw material air as at least a part of power for compressing a fluid other than compressed air received from the power generation facility. A method for producing low-purity oxygen, characterized in that: 5. The method according to claim 4, wherein the step of recovering the product oxygen gas is performed by extracting liquefied oxygen at the bottom of the low-pressure column, compressing the liquefied oxygen, and vaporizing the liquefied oxygen by heat exchange with the raw material air. Method for producing low-purity oxygen. 6. The step of branching the source air into a first source air and a second source air is performed in the middle of a step of cooling by heat exchange with a fluid obtained by the low-temperature distillation. The method for producing low-purity oxygen according to claim 4. 7. The method according to claim 4, wherein expansion work generated when expanding the first raw material air is used as power for compressing a product gas extracted from a low-pressure column in the product recovery step. A method for producing low-purity oxygen. 8. After increasing the pressure of at least one of the high-pressure nitrogen gas extracted from the high-pressure column and the low-pressure nitrogen gas extracted from the low-pressure column, the mixture is cooled by heat exchange with a fluid obtained by low-temperature distillation, The method for producing low-purity oxygen according to claim 4, wherein the liquid is liquefied by heat exchange with the bottom liquid of the high-pressure column, and is introduced into at least one of the high-pressure column and the low-pressure column. 9. The method for producing low-purity oxygen according to claim 8, wherein expansion work generated when expanding the first raw material air is used as power for increasing the pressure of the nitrogen gas. 10. A low-purity oxygen producing apparatus for separating and recovering at least low-purity oxygen as a product by subjecting raw material air to low-temperature distillation in a double distillation apparatus having a high-pressure column and a low-pressure column, An air compressor that compresses to a pressure corresponding to the pressure, a power recovery turbine that receives compressed air having a pressure higher than the operating pressure of the high-pressure tower from a power generation facility and expands the compressed air to a pressure corresponding to the operating pressure of the high-pressure tower, A mixing path for mixing the raw air compressed by the air compressor and the compressed air expanded by the power recovery turbine to obtain raw air, a pre-cooling facility for pre-cooling the raw air derived from the mixing path, A purifying facility for purifying by removing impurities such as moisture and carbon dioxide from the raw air, a branch path for branching the purified raw air into a first raw air and a second raw air, and a branch. A main heat exchanger for exchanging the first raw material air with the fluid obtained by the low-temperature distillation, and a high-pressure raw air introduction path for introducing the first raw air derived from the main heat exchanger into the high-pressure column, A booster that boosts the second raw material air branched in the branch path; a cold generating turbine that cools the second raw material air derived from the booster in the main heat exchanger and then introduces and expands the cold; Oxygen and nitrogen by low-temperature distillation of the low-pressure raw air introduction path for introducing the second raw air derived from the turbine into the low-pressure tower, and low-temperature raw air introduced from the high-pressure raw air introduction path and the low-pressure raw air introduction path. A double distillation column comprising a high-pressure column, a main condenser and a low-pressure column, and oxygen and nitrogen separated in the low-pressure column of the double distillation column are extracted and heated by the main heat exchanger. To A product recovery path for recovering as product oxygen gas, and the power recovery turbine is provided coaxially connected to a compressor that compresses a fluid other than compressed air received from the power generation equipment. Low-purity oxygen production equipment. 11. A low-purity oxygen producing apparatus for separating and recovering at least low-purity oxygen as a product by subjecting raw air to low-temperature distillation in a double distillation facility having a high-pressure tower and a low-pressure tower, A compressed air supply / reception path for receiving compressed air at a pressure higher than the operating pressure as at least a part of the raw air, a precooling facility for precooling the raw air, and removing impurities such as moisture and carbon dioxide from the raw air derived from the precooling equipment. Refining equipment for refining, and a branch path for branching the raw material air derived from the refining facility into a first raw air and a second raw air, and a power for expanding the branched first raw air to the operating pressure of the high-pressure column. A recovery turbine, a first raw material air introduction path for introducing the first raw material air derived from the power recovery turbine to the high-pressure tower, and a second raw material air branched on the branch path. A main heat exchanger that cools by heat exchange with a fluid obtained by low-temperature distillation, and a second raw material that is introduced into the high-pressure column after the second raw material air derived from the main heat exchanger is depressurized through a pressure reducing valve. An air introduction path, a high-pressure column, a main condenser, and a low-pressure column for separating the raw air introduced from the first raw air introduction path and the second raw air introduction path into oxygen and nitrogen by low-temperature distillation. A double distillation column, and a product recovery path for extracting oxygen and nitrogen separated in the double distillation column, heating the temperature by the main heat exchanger, and recovering at least the oxygen as product oxygen gas, and An apparatus for producing low-purity oxygen, wherein a turbine is provided coaxially with a compressor that compresses a fluid other than compressed air from a power generation facility that is received through the compressed air supply and demand path. 12. A low-temperature specification turbine in which a branch path for branching into the first raw material air and the second raw material air is provided in the main heat exchanger, and the power recovery turbine introduces low-temperature raw material air. The low-purity oxygen producing apparatus according to claim 11, wherein: 13. The apparatus for producing low-purity oxygen according to claim 12, wherein a low-temperature specification compressor for compressing a low-temperature fluid is connected coaxially with said low-temperature specification power recovery turbine. 14. A path for extracting high-pressure nitrogen gas from the upper part of the high-pressure column, a high-pressure circulating booster for increasing the pressure of the high-pressure nitrogen gas extracted to the path, and a high-pressure circulating pressure booster for increasing the pressure of the high-pressure nitrogen gas. A high-pressure nitrogen circulation system comprising a condenser / reboiler that liquefies by exchanging heat with the bottom liquid of the column and a path for introducing liquefied nitrogen liquefied by the condenser / reboiler into the high-pressure column. Item 12. An apparatus for producing low-purity oxygen according to Item 11. 15. A path for extracting low-pressure nitrogen gas from the upper part of the low-pressure column, a low-pressure circulating booster for increasing the pressure of the low-pressure nitrogen gas extracted to the path, and a high-pressure nitrogen gas pressurized by the low-pressure circulating pressure booster. A low-pressure nitrogen circulation system comprising a nitrogen condenser that liquefies by exchanging heat with the bottom liquid of the column and a path for introducing liquefied nitrogen liquefied by the nitrogen condenser into the low-pressure column. Item 12. An apparatus for producing low-purity oxygen according to Item 11. 16. The apparatus for producing low-purity oxygen according to claim 10, wherein at least one of the low-pressure column and the high-pressure column is a packed distillation column.