JP4787796B2 - Air separation method and apparatus - Google Patents

Description

  The present invention relates to an air separation method and apparatus, and more particularly to an air separation method and apparatus for collecting oxygen and nitrogen as products by low-temperature distillation of compressed, purified, and cooled raw material air.

  In order to produce nitrogen, oxygen and the like by low-temperature distillation of air, a method using a double rectification column comprising a high-pressure column and a low-pressure column is the most common method. In order to suppress the power consumption when performing air separation and reduce the manufacturing cost, it is effective to reduce the power consumption of the raw air compressor, that is, to lower the discharge pressure of the raw air compressor. . However, the method using a double rectification column has a process restriction that requires the heat exchanger to evaporate the liquefied oxygen in the low pressure column with the nitrogen gas in the high pressure column, so the discharge pressure of the raw air compressor is greatly increased. It cannot be reduced.

  As a method for reducing the power consumption of the raw air compressor, there is known a method for producing oxygen using a medium pressure distillation column operated at an intermediate pressure in addition to a high pressure distillation column and a low pressure distillation column. In this method, a part of the raw material air is supplied to a medium pressure distillation column and separated into nitrogen gas and oxygen-enriched liquefied air, and nitrogen gas and oxygen-enriched liquefied air are separated by a condenser at the top of the intermediate pressure distillation column. Is heated to produce a reflux liquid of a medium pressure distillation column and a reflux liquid of a low pressure distillation column. Therefore, the pressure of the intermediate pressure distillation column can be operated at a lower pressure than the high pressure distillation column in which nitrogen gas and liquefied oxygen exchange heat, and a part of the power consumption of the compressor can be reduced (for example, patents). Reference 1).

As a method for further reducing the power consumption of the raw material air compressor, a method for producing oxygen and nitrogen using a heat exchange type distiller having an air distillation passage and an oxygen distillation passage formed so as to be able to exchange heat with each other is disclosed. Has been. In the method using a heat exchange type distiller, the raw material air is distilled in the air distillation passage of the heat exchange type distiller to separate into nitrogen concentrate and oxygen-enriched liquefied air, and the nitrogen concentrate is separated in a high purity nitrogen tower. Further distillation is performed to separate high pure nitrogen and low pure liquefied nitrogen, and the oxygen-enriched liquefied air and low pure liquefied nitrogen obtained in the heat exchange type distillation apparatus are distilled in a distillation column to obtain high pure nitrogen and crude liquefied oxygen. The crude liquefied oxygen is distilled in the oxygen distillation passage of the heat exchange type still to obtain liquefied oxygen. By efficiently exchanging heat and distilling with a heat exchange type distiller, the pressure of the raw material air can be greatly reduced, and the power consumption of the raw material air compressor is further reduced compared to the method using the medium pressure distillation column. (For example, refer to Patent Document 2).
U.S. Pat. No. 4,254,629 JP 2006-349319 A

  However, in the method described in Patent Document 2, the amount of medium-pressure nitrogen gas is significantly smaller than that described in Patent Document 1, so that the product nitrogen has a high pressure, for example, 1.0 MPa (absolute pressure, the same applies hereinafter). .)), The nitrogen compressor must compress a certain amount of low-pressure nitrogen gas, which increases the power consumption of the nitrogen compressor and effectively reduces the overall power consumption. There was a problem that I could not.

  Accordingly, an object of the present invention is to provide an air separation method and apparatus using a heat exchange type distiller that can reduce the overall power consumption even when high pressure nitrogen is required.

  In order to achieve the above object, the air separation method of the present invention is the air separation method in which the raw material air is subjected to cryogenic liquefaction separation to collect product oxygen and product nitrogen, and the first raw material air is distilled in an intermediate pressure distillation column. A first separation step of separating the first intermediate pressure nitrogen gas enriched with the nitrogen component and the first intermediate pressure oxygen enriched liquefied air enriched with the oxygen component, the first intermediate pressure nitrogen gas and the first The first intermediate pressure nitrogen gas is obtained by condensing and liquefying the first intermediate pressure nitrogen gas by exchanging heat with the intermediate pressure oxygen enriched liquefied air in the first intermediate pressure condenser, and at the same time the first intermediate pressure oxygen enrichment. A first heat exchange step for evaporating the liquefied liquefied gas to obtain a first medium-pressure oxygen-enriched air, and introducing the second raw material air into the air distillation passage of the heat exchange-type distiller. Distilling while cooling by exchanging heat with the fluid in the exchangeable oxygen distillation passage A second separation step of separating the second raw material air into a second medium-pressure nitrogen gas enriched with a nitrogen component and a second medium-pressure oxygen-enriched liquefied air enriched with an oxygen component; and the first raw material air And the third raw material air having a pressure higher than that of the second raw material air is distilled in a high-pressure distillation column to separate high-pressure nitrogen gas enriched with nitrogen components and high-pressure oxygen-enriched liquefied air enriched with oxygen components. The nitrogen component was concentrated by distilling the first intermediate-pressure oxygen-enriched air, the second intermediate-pressure oxygen-enriched liquefied air, and the high-pressure oxygen-enriched liquefied air in a low-pressure distillation column. A fourth separation step for separating the low-pressure nitrogen gas and the first low-pressure oxygen-enriched liquefied air enriched with the oxygen component, and introducing the first low-pressure oxygen-enriched liquefied air into the oxygen distillation passage of the heat exchange-type distiller; And heat exchange with the fluid in the air distillation passage A fifth separation step of separating the first liquefied oxygen enriched with oxygen components and the first low-pressure oxygen-enriched air enriched with nitrogen components by distillation, and the high-pressure nitrogen gas and the first liquefied oxygen Heat exchange with a high pressure condenser to condense and liquefy the high pressure nitrogen gas to obtain high pressure liquefied nitrogen and at the same time to evaporate and gasify at least a part of the first liquefied oxygen to obtain oxygen gas. A first liquid feeding step for introducing a part of the high pressure liquefied nitrogen into the intermediate pressure distillation column, a first gas feeding step for introducing the second medium pressure nitrogen gas into the intermediate pressure distillation column, and the low pressure A first product recovery step for deriving nitrogen gas as product low-pressure nitrogen gas after heat recovery; a second product recovery step for deriving oxygen gas as product oxygen gas after heat recovery; and a portion of the first medium-pressure nitrogen gas After the heat recovery, the product medium pressure nitrogen gas And a third product recovery step derived as follows.

  Furthermore, in the air separation method of the present invention, the air distillation passage of the heat exchange type distiller is divided into an air condensing unit and an air distilling unit, and the second separation step is performed by condensing the second raw material air. A sixth separation step in which the liquid is partially liquefied by heat exchange with the fluid in the oxygen distillation passage and cooled to be separated into vapor-phase nitrogen-enriched air and liquid-phase second medium-pressure oxygen-enriched liquefied air; The second medium-pressure nitrogen gas and the second medium-pressure nitrogen gas in which the nitrogen component is concentrated by performing heat exchange with the fluid in the oxygen distillation passage in the air distillation section and distilling the nitrogen-enriched air while cooling. It can be carried out in the seventh separation step of separating into the third medium pressure oxygen-enriched liquefied air having a lower nitrogen concentration. In addition, the second intermediate-pressure nitrogen gas and the first low-pressure oxygen-enriched liquefied air are subjected to heat exchange in a second intermediate-pressure condenser to condense and liquefy the second intermediate-pressure nitrogen gas to obtain a second intermediate pressure. A third heat exchange step for obtaining liquefied nitrogen and evaporating gas at least a part of the first low-pressure oxygen-enriched liquefied air to obtain a second low-pressure oxygen-enriched liquefied air; and The 2nd liquid feeding process introduce | transduced into the said low pressure distillation column can also be performed.

  Moreover, the air separation device of the present invention is a first air in which nitrogen components are concentrated by distilling the first raw material air in an air separation device that collects product oxygen and product nitrogen by cryogenic liquefaction separation of the raw material air. A medium pressure distillation column that separates pressurized nitrogen gas and first intermediate pressure oxygen-enriched liquefied air enriched with oxygen components, and heats the first intermediate pressure nitrogen gas and the first intermediate pressure oxygen-enriched liquefied air. By exchanging, the first intermediate pressure nitrogen gas is condensed and liquefied to obtain the first intermediate pressure liquefied nitrogen, and at the same time, the first intermediate pressure oxygen enriched liquefied air is evaporated and gasified to form the first intermediate pressure oxygen enriched air. A first intermediate pressure condenser, an air distillation passage, and an oxygen distillation passage disposed in the air distillation passage so as to be capable of exchanging heat, and the second raw material air introduced into the air distillation passage is subjected to the oxygen distillation. Cooled by heat exchange with the first low-pressure oxygen-enriched liquefied air introduced into the passage The second raw material air is separated into the second medium-pressure nitrogen gas enriched with the nitrogen component and the second medium-pressure oxygen-enriched liquefied air enriched with the oxygen component by distilling while being distilled. A heat exchange distiller that separates the liquefied liquefied air into a first liquefied oxygen enriched with oxygen components and a first low-pressure oxygen enriched air enriched with nitrogen components, the first feed air and the second feed air A high-pressure distillation column that separates high-pressure nitrogen gas enriched with nitrogen components and high-pressure oxygen-enriched liquefied air enriched with oxygen components by distilling the third raw material air having a higher pressure than the first raw material air; The low-pressure nitrogen gas enriched with the nitrogen component and the first low-pressure oxygen enriched with the oxygen component by distilling the oxygen-enriched air, the second medium-pressure oxygen-enriched liquefied air, and the high-pressure oxygen-enriched liquefied air Low pressure distillation separated into enriched liquefied air And by exchanging heat between the high-pressure nitrogen gas and the first liquefied oxygen, the high-pressure nitrogen gas is condensed and liquefied to obtain high-pressure liquefied nitrogen, and at the same time, at least a part of the first liquefied oxygen is evaporated and gasified. A high-pressure condenser for obtaining oxygen gas, a first liquid feed passage for introducing a part of the high-pressure liquefied nitrogen into the intermediate-pressure distillation column, and a first feed for introducing the second medium-pressure nitrogen gas into the intermediate-pressure distillation column. A gas path, a first product recovery path for deriving the low-pressure nitrogen gas as a product low-pressure nitrogen gas after heat recovery, a second product recovery path for deriving the oxygen gas as a product oxygen gas after heat recovery, and the first medium A third product recovery path is provided for extracting a part of the pressurized nitrogen gas as product intermediate-pressure nitrogen gas after heat recovery.

  Further, in the air separation device of the present invention, the air distillation passage of the heat exchange type distiller causes the second raw material air to exchange heat with the first low-pressure oxygen-enriched liquefied air introduced into the oxygen distillation passage. The air condensing part that is partially liquefied by cooling and separated into nitrogen-rich air in the gas phase and second medium-pressure oxygen-enriched liquefied air in the liquid phase, and introduces the nitrogen-enriched air into the oxygen distillation passage The second low-pressure oxygen gas enriched liquefied air and the second medium-pressure nitrogen gas in which the nitrogen component is concentrated by distillation while cooling and the third low-pressure nitrogen gas is lower than the second medium-pressure nitrogen gas. It can divide | segment into the air distillation part isolate | separated into medium pressure oxygen enriched liquefied air. Further, the second intermediate pressure nitrogen gas and the first low pressure oxygen-enriched liquefied air are subjected to heat exchange to condense and liquefy the second intermediate pressure nitrogen gas to obtain second intermediate pressure liquefied nitrogen. 1. A second intermediate pressure condenser that evaporates and gasifies at least part of the low-pressure oxygen-enriched liquefied air to obtain a second low-pressure oxygen-enriched liquefied air, and the second intermediate-pressure liquefied nitrogen is introduced into the low-pressure distillation column. A second liquid feeding path can also be provided.

  According to the present invention, the amount of medium-pressure nitrogen gas recovered can be increased while reducing the power consumption of the raw air compressor by using a heat exchange-type distiller, so that nitrogen when high-pressure nitrogen gas is required can be increased. The overall power consumption including the compressor can be reduced.

  FIG. 1 is a system diagram showing a first embodiment of an air separation device for carrying out the air separation method of the present invention.

  The air separation device 10 includes an air compressor 1 that compresses the raw material air RA, an air precooler 2 that removes the compression heat of the compressed raw material air, and impurities (moisture, dioxide dioxide) in the raw material air that has passed through the air precooler 2. A purifier 3 that removes carbon, etc., a first main heat exchanger 4 that cools the raw air that has passed through the purifier 3, and a medium pressure distillation that distills a portion of the raw air that has passed through the first main heat exchanger 4. A column 5, a first medium pressure condenser 6 that condenses the distillate taken out from the upper part through the medium pressure distillation column 5, and a heat exchange type distiller that distills the remainder of the raw material air that has passed through the main heat exchanger 4. 7, a first gas-liquid separator 8 that gas-liquid separates the gas-liquid mixture extracted from the heat-exchange distiller 7, and a secondary that secondarily compresses part of the raw material air compressed by the air compressor 1 An air compressor 9, a second main heat exchanger 11 that cools the raw air compressed by the secondary air compressor 9, and From the high-pressure distillation column 12 that distills the raw air that has passed through the main heat exchanger 11, the high-pressure condenser 13 that condenses the distillate taken out from the upper part through the high-pressure distillation column 12, and the middle pressure distillation column 5 The distillate taken out, the liquid taken out from the liquid phase part of the first gas-liquid separator 8, the fluid evaporated in the first intermediate pressure condenser 6, and the distillate taken out from the lower part of the high-pressure distillation column 12. A low-pressure distillation column 14 for further distilling the liquid, a supercooler 15 for supercooling the fluid introduced into the low-pressure distillation column 14, and an expansion turbine 16 and a blower 17 for obtaining the cooling required for the operation of the apparatus. The device and the path through which the low-temperature fluid flows are housed in the cold storage tank 18.

  The heat exchange-type distiller 7 includes an air distillation passage 71 and an oxygen distillation passage 72 disposed in the air distillation passage 71 so as to be capable of exchanging heat. In this embodiment, the air distillation passage 71 is provided. Is divided into an air condensing unit 73 and an air distillation unit 74. A plate fin type heat exchanger can be used for the heat exchange type distiller 7, and a separate device in which the air condensing unit 73 and the air distilling unit 74 are divided can be used.

  The raw material air RA is compressed to a predetermined pressure by the air compressor 1 and cooled to room temperature by the air precooler 2, and then impurities such as moisture and carbon dioxide in the raw material air are adsorbed and removed by the purifier 3. The raw material air in the path L0 purified by the purifier 3 is second-compressed by the secondary air compressor 9 into the first raw material air and the second raw material air flowing through the path L1, and converted into the third raw material air. It is branched into a flow. The raw material air in the path L1 is cooled to near the dew point in the first main heat exchanger 4 by heat exchange with a low-temperature fluid such as the first product low-pressure nitrogen gas GN1 and the product intermediate-pressure nitrogen gas MGN, and then the first air in the path L2 The first raw material air is branched into the first raw material air and the second raw material air in the path L <b> 3, and the first raw material air in the path L <b> 2 is introduced into the lower part of the intermediate pressure distillation column 5.

  In the medium pressure distillation column 5, the first raw material air introduced into the lower part of the column and the second medium pressure nitrogen introduced from the upper part of the air distillation part 74 of the air distillation passage 71 and introduced into the middle part of the tower via the path L4. In the process, the nitrogen component is concentrated in the gas phase, the oxygen component is concentrated in the liquid phase, the first intermediate pressure nitrogen gas is added to the upper part of the intermediate pressure distillation column 5, and the 1 Medium pressure oxygen-enriched liquefied air is separated (first separation step). A part of the first intermediate pressure nitrogen gas obtained at the upper part of the intermediate pressure distillation column 5 is introduced into the first intermediate pressure condenser 6 and led out from the lower part of the intermediate pressure distillation column 5 to the path L5 to be a supercooler. 15, the first intermediate pressure oxygen-enriched air is generated by evaporating and gasifying at least a part of the first intermediate-pressure oxygen-enriched liquefied air that has been cooled down through 15 and depressurized by the pressure reducing valve V5. Is condensed and liquefied to become the first medium pressure liquefied nitrogen, and a part thereof becomes the reflux liquid of the medium pressure distillation column 5 (first heat exchange step).

  The remainder of the first medium pressure liquefied nitrogen condensed and liquefied by the first medium pressure condenser 6 is cooled by the subcooler 15 via the path L6, and after being depressurized by the pressure reducing valve V1 via the path L7, Introduced at the top. Further, the second intermediate pressure liquefied nitrogen is led out from the middle part of the intermediate pressure distillation column 5 to the path L13, and after being depressurized by the pressure reducing valve V2 through the supercooler 15 and the path L14, is introduced into the middle part of the low pressure distillation column 14. The Further, the remainder of the first medium-pressure nitrogen gas obtained in the upper part of the medium-pressure distillation column 5 is led to the path L32 and is recovered by the first main heat exchanger 4 as the product medium-pressure nitrogen gas MGN. Recovered (third product recovery step). The product medium-pressure nitrogen gas MGN is compressed by the nitrogen compressor 20 as necessary to become a product high-pressure nitrogen gas HGN.

  The second raw material air branched into the path L3 is introduced into the air condensing unit 73 of the heat exchange type distiller 7, and in the process of descending the air condensing unit 73, the fluid in the oxygen distillation passage 72 (first low pressure) Heat-exchanged with oxygen-enriched liquefied air), cooled and partially condensed, led out to the path L8 in the gas-liquid two-phase state from the lower part of the air condensing unit 73, and in the first gas-liquid separator 8 the liquid phase part The second medium-pressure oxygen-enriched liquefied air and the gas-phase nitrogen-enriched air are gas-liquid separated (sixth separation step).

  The second medium-pressure oxygen-enriched liquefied air is led out to the path L9 from the lower part of the first gas-liquid separator 8, and then a part thereof is introduced into the lower part of the intermediate-pressure distillation column 5, and the remaining second medium-pressure oxygen The enriched liquefied air is introduced into the middle of the low-pressure distillation column 14 after being depressurized by the pressure reducing valve V3 via the supercooler 15 and the path L10. The nitrogen-enriched air is introduced into the lower portion of the air distillation section 74 via the path L11 and exchanges heat with the first low-pressure oxygen-enriched liquefied air in the oxygen distillation passage 72 in the process of rising in the air distillation section 74. Then, it is distilled while being cooled, so that the nitrogen component is concentrated in the gas phase and the oxygen component is concentrated in the liquid phase (seventh separation step).

  The second medium-pressure nitrogen gas obtained at the upper part of the air distillation unit 74 is introduced into the middle part of the medium-pressure distillation column 5 through the path L4 as described above (first gas feeding step). The third medium-pressure oxygen-enriched liquefied air obtained at the lower part of the air distillation section 74 is led to the path L12 and introduced into the first gas-liquid separator 8.

  The third raw material air is further pressurized by the secondary air compressor 9 and then introduced into the second main heat exchanger 11 via the path L15, and the low temperature of the second product low-pressure nitrogen gas GN2, product oxygen gas GO, etc. It is cooled to near the dew point by exchanging heat with the fluid, and introduced into the high-pressure distillation column 12 via the path L16. The third raw material air is distilled in the high-pressure distillation column 12, and in the process, the nitrogen component is concentrated in the gas phase, the oxygen component is concentrated in the liquid phase, and high-pressure nitrogen gas is formed in the upper portion of the high-pressure distillation column 12. The high-pressure oxygen-enriched liquefied air is separated at the lower part (third separation step).

  The high-pressure nitrogen gas obtained in the upper part of the high-pressure distillation column 12 is introduced into the high-pressure condenser 13, performs heat exchange with the first liquefied oxygen led out from the lower part of the oxygen distillation passage 72, and at least one of the first liquefied oxygens. The portion is vaporized to produce oxygen gas, which is condensed into liquefied nitrogen to become high-pressure liquefied nitrogen, and a part thereof becomes the reflux liquid of the high-pressure distillation column 12. The remainder of the high-pressure liquefied nitrogen is reduced in pressure by the pressure reducing valve V6 via the path L17 and then introduced into the upper portion of the intermediate pressure distillation column 5 and becomes the reflux liquid of the intermediate pressure distillation column 5 (first liquid feeding step).

  The high-pressure oxygen-enriched liquefied air obtained at the lower portion of the high-pressure distillation column 12 is led to the path L18, and after being depressurized by the pressure reducing valve V4 via the supercooler 15 and the path L19, is introduced into the middle portion of the low-pressure distillation column 14. The

  A part of the third raw material air secondarily compressed by the secondary air compressor 9 is branched into the path L20 as turbine air, introduced into the blower 17 and further pressurized, and then the first main heat exchanger 4 and After being cooled by the second main heat exchanger 11, it is adiabatically expanded by the expansion turbine 16 to generate the necessary cold in the air separation device 10. The expanded turbine air is introduced into the middle of the low-pressure distillation column 14 via a path L21.

  In the low pressure distillation column 14, the first medium pressure liquefied nitrogen from the path L7, the second medium pressure liquefied nitrogen from the path L14, the second medium pressure oxygen enriched liquefied air from the path L10, and the high pressure from the path L19. The oxygen-enriched liquefied air, the first medium-pressure oxygen-enriched air from the path L5, and the turbine air from the path L21 are distilled, and in the process, the nitrogen component is concentrated in the gas phase, and in the liquid phase Then, the oxygen component is concentrated, the low-pressure nitrogen gas is separated in the upper part of the low-pressure distillation column 14, and the first low-pressure oxygen-enriched liquefied air is separated in the lower part (fourth separation step).

  The low-pressure nitrogen gas concentrated in the upper part of the low-pressure distillation column 14 is led out to the path L22 and branched from the path L23 to the path L24 and the path L25 via the supercooler 15. The low-pressure nitrogen gas branched into the path L24 is introduced into the first main heat exchanger 4 and recovered, and then recovered as the first product low-pressure nitrogen gas GN1. The low-pressure nitrogen gas branched into the path L25 is the second After being introduced into the main heat exchanger 11 and heat recovered, it is recovered as the second product low-pressure nitrogen gas GN2 (first product recovery step).

  Further, from the lower part of the low-pressure distillation column 14, the first low-pressure oxygen-enriched liquefied air is led out to the path L 26 and is introduced into the oxygen distillation path 72 of the heat exchange type distiller 7. The first low-pressure oxygen-enriched liquefied air is distilled while being heated by exchanging heat with the nitrogen-enriched air in the air distillation unit 74 and the second source air in the air condensing unit 73 in the process of descending the oxygen distillation passage 72. In the process, the nitrogen component is concentrated in the gas phase, the oxygen component is concentrated in the liquid phase, the first low-pressure oxygen-enriched air is concentrated in the upper part of the oxygen evaporation passage 72, and the first liquefied oxygen is concentrated in the lower part. (Fifth separation step).

  The first low-pressure oxygen-enriched air is led out from the upper part of the oxygen distillation passage 72 to the path L27 and introduced into the lower part of the low-pressure distillation column 14, and the first liquefied oxygen is led out from the lower part of the oxygen distillation passage 72 to the path L28. It is introduced into the condenser 13.

  The first liquefied oxygen introduced into the high-pressure condenser 13 condenses and liquefies the high-pressure nitrogen gas to generate high-pressure liquefied nitrogen, which is vaporized into oxygen gas (second heat exchange step). This oxygen gas is led out to the path L29, and is recovered as product oxygen gas GO after being recovered by the second main heat exchanger 11 (second product recovery step). Further, the second liquefied oxygen that has not evaporated in the high-pressure condenser 13 is led out to the path L30 and recovered as product liquefied oxygen LO.

  In the air separation apparatus configured as described above, even when high-pressure nitrogen is produced in addition to oxygen, heat exchange between the air distillation passage 71 and the oxygen distillation passage 72 of the heat exchange-type distiller 7 is efficiently performed. This makes it possible to increase the maximum recovery amount of medium-pressure nitrogen while reducing the discharge pressure of the air compressor 1.

  In the present embodiment, the gas distillation passage 71 is divided into the air condensing unit 73 and the air distillation unit 74, but the same effect can be obtained even if there is only one air distillation passage. In this case, the second raw material air branched into the path L3 is introduced into the air distillation passage 71 of the heat exchange-type distiller 7, and exchanges heat with the first low-pressure oxygen-enriched liquefied air in the oxygen distillation passage 72, The upper second intermediate pressure nitrogen gas and the lower second intermediate pressure oxygen-enriched liquefied air are separated (second separation step). When the air distillation passage is not divided in this way, the first gas-liquid separator 8 is not necessary.

  Moreover, although the main heat exchanger is divided | segmented into the 1st main heat exchanger 4 and the 2nd main heat exchanger 11, one heat exchanger can also be used as a main heat exchanger. When the third raw material air is boosted by the blower 17, the blower 17 is coaxial with the expansion turbine 16, and the blower 17 is driven by using the power obtained when the expansion turbine 16 adiabatically expands the turbine air. However, the power of the expansion turbine 16 can also be used as a drive source for other equipment. Moreover, cold generation by the expansion turbine can be replaced by supplying a low-temperature fluid such as liquefied oxygen or liquefied nitrogen from the outside.

  FIG. 2 is a system diagram showing a second embodiment of the air separation device of the present invention. In the following description, the same components as those of the air separation device shown in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, the air condensing passage 71 of the heat exchange type distiller 7 is not divided into an air condensing part and an air distilling part, but is one, and is led out from the first main heat exchanger 4 and branched to the path L3. The second raw material air thus introduced is introduced into the lower portion of the air distillation passage 71. From the upper part of the air distillation passage 71, the second medium-pressure nitrogen gas is led out and introduced into the second medium-pressure condenser 19, and the first low-pressure oxygen-enriched liquefaction led out from the lower part of the low-pressure distillation column 14 to the path L26. It exchanges heat with air, and the entire amount is condensed and liquefied to become second intermediate pressure liquefied nitrogen, which is led out to the path L13, depressurized by the pressure reducing valve V2 via the supercooler 15 and path L14, and then placed in the middle of the low pressure distillation column 14 Introduced (third heat exchange step and second liquid feeding step).

  The first low-pressure oxygen-enriched liquefied air partially evaporated in the second intermediate-pressure condenser 19 is introduced into the second gas-liquid separator 21, and the second gas-phase second low-pressure oxygen-enriched air and the liquid phase second Separated into low pressure oxygen enriched liquefied air. The second low-pressure oxygen-enriched air is introduced into the lower part of the low-pressure distillation column 14 via the path L33, and the second low-pressure oxygen-enriched liquefied air is supplied to the upper part of the oxygen distillation passage 72 via the path L31. At this time, a part of the first low-pressure oxygen-enriched liquefied air led to the path L26 may be supplied to the upper part of the oxygen distillation passage 72.

  The air separation device shown in the present embodiment needs to add a second intermediate pressure condenser 19 and the like as compared with the air separation device shown in the first embodiment, but the heat exchange type distiller 7 and the intermediate pressure distillation. The applicable range of equipment used for the tower 5 and the like can be expanded. That is, in the first embodiment shown in FIG. 1, the first raw material air and the second raw material air are branched from the same path L1 and introduced into the intermediate pressure distillation column 5 and the heat exchange distiller 7 at the same pressure, respectively. Is done.

  At this time, when an apparatus having a sufficiently large pressure loss as compared with the heat exchange type distiller 7 such as a plate column is used for the medium pressure distillation column 5, the pressure at the upper part of the air distillation passage 71 is set to the medium pressure distillation column 5. Since the pressure is sufficiently higher than the middle pressure, a necessary valve differential pressure can be secured by the pressure reducing valve V7 in the path L4, and the flow rate of the second medium-pressure nitrogen gas flowing in the path L4 can be controlled.

  However, when a packing with a small pressure loss or the like is used for the intermediate pressure distillation column 5 or a device with a large pressure loss is used for the heat exchange type distiller 7, the required valve differential pressure is secured by the pressure reducing valve V7. It becomes impossible to control the flow rate. Therefore, the second intermediate pressure nitrogen gas is condensed by the second intermediate pressure condenser 19, and the liquefied second intermediate pressure liquefied nitrogen is liquefied by the second intermediate pressure condenser 19 without going through the intermediate pressure distillation column 5. By forming so as to be directly introduced into the low-pressure distillation column 14 from the path L13 and the path L14 via the pressure reducing valve V2, a packing having a small pressure loss or the like is used for the intermediate-pressure distillation column 5, or the heat exchange type distiller 7 In addition, the problem of the valve differential pressure when using a device having a large pressure loss can be solved, and the application range of devices such as the medium pressure distillation column 5 and the heat exchange type distillation device 7 can be expanded.

  Here, the operation and effect of the first embodiment apparatus will be described by comparing the process using the first embodiment apparatus shown in FIG. 1 with the conventional process described in Patent Document 1 shown in FIG. In addition, the system diagram of the air separation device shown in FIG. 3 is a device in which the device system diagram described in Patent Document 1 is matched to the system diagram of the first example device in order to facilitate comparison with the first embodiment device. It is arranged. Further, in the air separation device shown in FIG. 3, the same components as those of the air separation device shown in the first embodiment are denoted by the reference numerals added with 100, and detailed description thereof is omitted.

  A conventional apparatus 100 (hereinafter referred to as a first conventional apparatus) 100 shown in FIG. 3 includes an intermediate pressure distillation column 105, a low pressure distillation column 114, a high pressure distillation column 112, an intermediate pressure condenser 106, and a high pressure condenser. 113, the first raw material air having a relatively low pressure (for example, 0.3 MPa) is separated into medium-pressure nitrogen gas and medium-pressure oxygen-enriched liquefied air in the medium-pressure distillation column 105, for comparison. Second raw material air having a high pressure (for example, 0.5 MPa) is separated into high-pressure nitrogen gas and high-pressure oxygen-enriched liquefied air in the high-pressure distillation column 112, and the medium-pressure oxygen-enriched liquefied air and the high-pressure oxygen-enriched liquefied air Air is separated into low-pressure nitrogen gas and liquefied oxygen in the low-pressure distillation column 114.

  The low-pressure nitrogen gas derived from the upper part of the low-pressure distillation column 114 is recovered as a product low-pressure nitrogen gas GN after heat recovery, and the oxygen gas derived from the lower part of the low-pressure distillation column 114 is recovered as a product oxygen gas GO after heat recovery. Collected. A part of the medium-pressure nitrogen gas led out from the upper part of the medium-pressure distillation column 105 is recovered as product medium-pressure nitrogen gas MGN after heat recovery. The role of the high-pressure condenser 113 in the first conventional apparatus 100 is to produce a product by evaporating and gasifying the liquefied oxygen at the lower part of the low-pressure distillation column 114 by heat exchange with the high-pressure nitrogen gas at the upper part of the high-pressure distillation column 112. The oxygen gas is generated, and at the same time, the rising gas necessary for distillation in the low pressure distillation column 114 is generated. Accordingly, the third raw material air having a relatively high pressure supplies only the amount necessary for heat exchange in the high-pressure condenser 113.

  On the other hand, the role of the high-pressure condenser 13 in the apparatus (hereinafter referred to as the present embodiment apparatus) 10 shown in FIG. 1 is the first liquefied oxygen flowing from the oxygen distillation passage 72 of the heat exchange type distiller 7. The gas is vaporized to produce oxygen gas as a product, and the amount of the third raw material air at a relatively high pressure (for example, 0.5 MPa) does not produce rising gas as compared with the first conventional apparatus. It can be reduced by minutes. The raw material air for generating the rising gas in the oxygen distillation passage 72 is the second raw material air introduced into the heat exchange type distiller 7, which is efficiently exchanged by the heat exchange type distiller 7. , And can be supplied at a relatively low pressure (for example, 0.3 MPa) comparable to the first raw material air. Therefore, compared with the first conventional example apparatus 100, the present embodiment apparatus 10 can reduce the flow rate of the third raw material air having a relatively high pressure, so that the processing amount of the secondary air compressor 9 is reduced. Power consumption can be reduced.

  Next, the process of the first embodiment apparatus is compared with the process of the conventional air separation apparatus (hereinafter referred to as a second conventional apparatus) described in Patent Document 2 shown in FIG. The effects of the example apparatus will be described. In the second conventional apparatus shown in FIG. 4, the same constituent elements as those of the air separation apparatus shown in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The second conventional example apparatus 200 shown in FIG. 4 includes a heat exchange distiller 207, a low pressure distillation column 214, a nitrogen distillation column 205, a nitrogen condenser 206, and an oxygen evaporator 213 as main components. . The first raw material air having a relatively low pressure is converted into the second medium-pressure nitrogen gas and the medium-pressure oxygen-enriched liquefied air by the air condensing unit 273 and the air distillation unit 274 constituting the air distillation passage of the heat exchange type distiller 207. The separated second raw material air having a relatively high pressure exchanges heat with liquefied oxygen derived from the lower portion of the oxygen distillation passage 272 in the oxygen evaporator 213 to become high-pressure liquefied air, and is derived from the upper portion of the air distillation section 274. The second medium-pressure nitrogen gas is separated into the first medium-pressure nitrogen gas and the second liquefied nitrogen by distillation in the nitrogen distillation column 205, and the medium-pressure oxygen-enriched liquefied air, the high-pressure liquefied air, and the second liquefied air The liquefied nitrogen is separated into low pressure nitrogen gas and low pressure oxygen enriched liquefied air by distillation in the low pressure distillation column 214, and the low pressure oxygen enriched liquefied air is converted into low pressure oxygen enriched air and liquefied oxygen in the oxygen distillation passage 272. Separated The liquefied oxygen is the second feed air exchanges heat with oxygen evaporator 213, the oxygen gas and vaporized.

  The low-pressure nitrogen gas derived from the upper portion of the low-pressure distillation column 214 is recovered as product low-pressure nitrogen gas GN after heat recovery, and the oxygen gas derived from the oxygen evaporator 213 is recovered as product oxygen gas GO after heat recovery, Part of the medium-pressure nitrogen gas derived from the upper part of the nitrogen distillation column 205 is recovered as product medium-pressure nitrogen gas MGN after heat recovery.

  In the nitrogen distillation column 205 in the second conventional apparatus 200, since there is no sufficient margin in the amount of the reflux liquid, only a small amount of the product intermediate pressure nitrogen gas MGN can be recovered from the upper part. On the other hand, in the present embodiment apparatus 10 of FIG. 1, the liquefied nitrogen separated from the third raw material air having a relatively high pressure is supplied to the upper part of the intermediate pressure distillation column 5 via the path L17. Therefore, it is possible to recover a large amount of product intermediate pressure nitrogen gas MGN as compared with the second conventional apparatus 200.

  Next, an air separation method using the apparatus of the present embodiment shown in FIG. 1 will be described with specific numerical values. First, the product conditions were such that the oxygen concentration of the product oxygen gas was 95% or more, the pressure was 0.12 MPa, the oxygen concentration of the product nitrogen gas was 1 ppm or less, and the pressure was 1.0 MPa.

  The raw material air compressed to 0.36 MPa by the air compressor 1 is precooled and purified, and then branched into two systems. The raw material air cooled to the vicinity of the dew point in the first main heat exchanger 4 is further branched into a first raw material air and a second raw material air. The first raw material air is introduced into the medium pressure distillation column 5 and separated into a first medium pressure nitrogen gas having an oxygen concentration of 1 ppm and a medium pressure first oxygen enriched liquefied air having an oxygen concentration of 40.8%. In the air condensing unit 73 and the air distillation unit 74 of the heat exchange distiller 7, the second raw material air is a second medium pressure nitrogen gas having an oxygen concentration of 1.6% and a second medium pressure oxygen having an oxygen concentration of 36.0%. Separated into enriched liquefied air.

  The third raw material air branched after compression, precooling, and purification is pressurized to 0.53 MPa by the secondary air compressor 9, cooled to near the dew point by the second main heat exchanger 11, and introduced into the high pressure distillation column 12. And high pressure nitrogen gas having an oxygen concentration of 4.9 ppm and high pressure oxygen-enriched liquefied air having an oxygen concentration of 40.0%. Part of the third raw material air is compressed as turbine air by the blower 17, cooled by the second main heat exchanger 11, expanded by the expansion turbine 16, and introduced into the low-pressure distillation column 14.

  In the low-pressure distillation column 14, the second intermediate-pressure liquefied nitrogen having an oxygen concentration of 2.9% derived from the middle portion of the intermediate-pressure distillation column 5 and the oxygen concentration 40.8% evaporated by the first intermediate-pressure condenser 6 are used. 1 medium-pressure oxygen-enriched air, the turbine air, the second medium-pressure oxygen-enriched liquefied air, and the high-pressure oxygen-enriched liquefied air are distilled and low-pressure nitrogen gas and oxygen having an oxygen concentration of 0.5% It is separated into first low-pressure oxygen-enriched liquefied air having a concentration of 76.1%. The first low-pressure oxygen-enriched liquefied air is introduced into the oxygen distillation passage 72 and separated into first low-pressure oxygen-enriched air having an oxygen concentration of 50.9% and first liquefied oxygen having an oxygen concentration of 95.0%. . The first liquefied oxygen is heat-exchanged with the high-pressure nitrogen gas in the high-pressure condenser 13 to become oxygen gas having an oxygen concentration of 95.0%.

  The low-pressure nitrogen gas is recovered as a first product low-pressure nitrogen gas GN1 and a second product low-pressure nitrogen gas GN2 having an oxygen concentration of 0.5% after heat recovery, and a part of the first medium-pressure nitrogen gas is heated. After recovery, it is recovered as medium-pressure nitrogen gas MGN with an oxygen concentration of 1 ppm, and the oxygen gas is recovered as product oxygen gas GO with an oxygen concentration of 95.0% after heat recovery. The medium-pressure nitrogen gas MGN is compressed to 1.0 MPa by a nitrogen compressor to become product nitrogen gas HGN.

Table 1 shows the process value of each path when the flow rate of the raw material air is 100.

Further, in order to evaluate the power performance, the power consumption of the cases shown in Table 1 was compared with both the conventional devices 100 and 200. The results are shown in Table 2. The product oxygen gas had a flow rate of 22 and a pressure of 0.12 MPa, and the product nitrogen gas had a flow rate of 19 and a pressure of 1.0 MPa. The product nitrogen gas HGN was produced by compressing medium pressure nitrogen gas MGN derived from the cold storage tank to 1.0 MPa with a nitrogen compressor, and the power of the nitrogen compressor was also compared. In the conventional apparatus 200, since the product intermediate pressure nitrogen gas MGN can be recovered only at the flow rate 6, the shortage flow rate 13 is to compress the product low pressure nitrogen gas GN to 1.0 MPa to produce the product nitrogen gas HGN. .

  From the results shown in Table 2, it can be seen that the power consumption of this embodiment apparatus can be reduced by about 5% for the first conventional apparatus 100 and about 3% for the second conventional apparatus 200. In addition, since the amount of raw material air introduced into the heat exchange type distiller is smaller than that of the second conventional example apparatus 200 in this embodiment, the size of the heat exchange distiller can be reduced by about 40%. By reducing the size of the heat exchange type distiller, which has a complicated structure and is relatively expensive as compared with the distillation column, the cost of the entire apparatus can be expected to be reduced.

  In addition, about product nitrogen gas, it is possible to extract | collect a product nitrogen gas of higher purity or low purity, and can anticipate the effect of power reduction etc. to the same extent. The same applies to the second embodiment shown in FIG.

1 is a system diagram showing a first embodiment of an air separation device for carrying out an air separation method of the present invention. It is a systematic diagram which shows the 2nd example of an air separation apparatus for enforcing the air separation method of this invention. It is a systematic diagram which shows one structural example of the conventional air separation apparatus. It is a systematic diagram which shows the other structural example of the conventional air separation apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Air compressor, 2 ... Air precooler, 3 ... Purifier, 4 ... 1st main heat exchanger, 5 ... Medium pressure distillation tower, 6 ... 1st intermediate pressure condenser, 7 ... Heat exchange type distiller, DESCRIPTION OF SYMBOLS 8 ... 1st gas-liquid separator, 9 ... Secondary air compressor, 10 ... Air separation apparatus, 11 ... 2nd main heat exchanger, 12 ... High pressure distillation tower, 13 ... High pressure condenser, 14 ... Low pressure distillation tower, DESCRIPTION OF SYMBOLS 15 ... Supercooler, 16 ... Expansion turbine, 17 ... Blower, 18 ... Cold storage tank, 19 ... 2nd intermediate pressure condenser, 20 ... Nitrogen compressor, 21 ... 2nd gas-liquid separator, 71 ... Air distillation passage, 72 ... oxygen distillation passage, 73 ... air condensing part, 74 ... air distillation part

Claims (6)

  In an air separation method for collecting product oxygen and product nitrogen by cryogenic liquefaction separation of raw material air, first intermediate pressure nitrogen gas and oxygen in which nitrogen components are concentrated by distillation of the first raw material air in an intermediate pressure distillation column A first separation step of separating the first medium pressure oxygen-enriched liquefied air in which the components are concentrated; and the first medium-pressure nitrogen gas and the first medium-pressure oxygen-enriched liquefied air. The first intermediate pressure nitrogen gas is condensed and liquefied by exchanging heat to obtain the first intermediate pressure liquefied nitrogen, and at the same time, the first intermediate pressure oxygen enriched liquefied air is evaporated and gasified to obtain the first intermediate pressure oxygen enrichment. A first heat exchange step for obtaining liquefied air, and a second raw material air is introduced into an air distillation passage of a heat exchange type distiller, and heat exchange is performed with a fluid in an oxygen distillation passage disposed in the air distillation passage so as to be able to exchange heat. The second raw material air is concentrated with the nitrogen component by distilling while cooling. A second separation step for separating the medium-pressure nitrogen gas and the second medium-pressure oxygen-enriched liquefied air enriched with oxygen components; and the third material air having a pressure higher than that of the first material air and the second material air. A high-pressure nitrogen gas enriched in nitrogen components and a high-pressure oxygen-enriched liquefied air enriched in oxygen components by distilling in a high-pressure distillation column, and the first medium-pressure oxygen-enriched air And the second medium-pressure oxygen-enriched liquefied air and the high-pressure oxygen-enriched liquefied air in a low-pressure distillation column to concentrate a low-pressure nitrogen gas enriched with a nitrogen component and a first low-pressure oxygen enriched oxygen component. A fourth separation step for separating the liquefied liquefied air, and the first low-pressure oxygen-enriched liquefied air is introduced into the oxygen distillation passage of the heat exchange-type distiller, and is heated by exchanging heat with the fluid of the air distillation passage. The oxygen component was concentrated by distillation while A fifth separation step of separating the fluorinated oxygen and the first low-pressure oxygen-enriched air enriched with a nitrogen component; and the high-pressure nitrogen by heat-exchanging the high-pressure nitrogen gas and the first liquefied oxygen in a high-pressure condenser. A second heat exchange step of condensing and liquefying gas to obtain high-pressure liquefied nitrogen and at the same time evaporating and gasifying at least a part of the first liquefied oxygen to obtain oxygen gas; and a part of the high-pressure liquefied nitrogen to the intermediate pressure A first liquid feeding step for introducing into the distillation column; a first gas feeding step for introducing the second medium pressure nitrogen gas into the medium pressure distillation column; and the low pressure nitrogen gas is derived as product low pressure nitrogen gas after heat recovery. A first product recovery step, a second product recovery step of deriving the oxygen gas as product oxygen gas after heat recovery, and a second product recovery step of deriving a part of the first intermediate pressure nitrogen gas as product intermediate pressure nitrogen gas after heat recovery. 3 product recovery process Air separation method.   The air distillation passage of the heat exchange type distiller is divided into an air condensing part and an air distilling part, and the second separation step is performed by using the air condensing part for the second raw material air and the fluid and heat of the oxygen distillation passage. A sixth separation step of partial liquefaction by exchanging and cooling to separate the gas-phase nitrogen-enriched air and liquid-phase second medium-pressure oxygen-enriched liquefied air; The second intermediate pressure nitrogen gas in which the nitrogen component is concentrated by performing heat exchange with the fluid in the oxygen distillation passage in the section and distilling while cooling, and the third intermediate pressure oxygen having a lower nitrogen concentration than the second intermediate pressure nitrogen gas The air separation method according to claim 1, wherein the air separation method is performed in a seventh separation step of separating into enriched liquefied air.   The second intermediate-pressure nitrogen gas and the first low-pressure oxygen-enriched liquefied air are subjected to heat exchange in a second intermediate-pressure condenser to condense and liquefy the second intermediate-pressure nitrogen gas, thereby generating second intermediate-pressure liquefied nitrogen. And at the same time, a third heat exchange step of evaporating and gasifying at least a part of the first low-pressure oxygen-enriched liquefied air to obtain a second low-pressure oxygen-enriched liquefied air; and The air separation method according to claim 1, further comprising a second liquid feeding step to be introduced into the tower.   In an air separation device that collects product oxygen and product nitrogen by cryogenic liquefaction separation of raw material air, the first medium-pressure nitrogen gas and oxygen component concentrated by distilling the first raw material air were concentrated The first intermediate pressure nitrogen is obtained by exchanging heat between the intermediate pressure distillation column separating the first intermediate pressure oxygen enriched liquefied air, the first intermediate pressure nitrogen gas and the first intermediate pressure oxygen enriched liquefied air. A first intermediate pressure condenser for condensing and liquefying gas to obtain first intermediate pressure liquefied nitrogen and simultaneously evaporating and gasifying the first intermediate pressure oxygen enriched liquefied air to obtain first intermediate pressure oxygen enriched air; A first low-pressure oxygen-rich gas having an air distillation passage and an oxygen distillation passage disposed in the air distillation passage so as to be capable of exchanging heat, and the second raw material air introduced into the air distillation passage is introduced into the oxygen distillation passage. The first solution is obtained by performing heat exchange with liquefied air and distilling while cooling. The raw material air is separated into a second medium pressure nitrogen gas enriched with nitrogen components and a second medium pressure oxygen enriched liquefied air enriched with oxygen components, and at the same time, the first low pressure oxygen enriched liquefied air is concentrated with oxygen components. A heat exchange-type distiller that separates the first liquefied oxygen and the first low-pressure oxygen-enriched air enriched with a nitrogen component, and a third raw material having a pressure higher than that of the first raw material air and the second raw material air A high-pressure distillation column that separates high-pressure nitrogen gas enriched with nitrogen components and high-pressure oxygen-enriched liquefied air enriched with oxygen components by distilling air, the first medium-pressure oxygen-enriched air, and the second By distilling the medium pressure oxygen-enriched liquefied air and the high-pressure oxygen-enriched liquefied air, the low-pressure nitrogen gas enriched with nitrogen components and the first low-pressure oxygen-enriched liquefied air enriched with oxygen components are separated. A low-pressure distillation column, the high-pressure nitrogen gas, and the first A high-pressure condenser for condensing and liquefying the high-pressure nitrogen gas by heat exchange with liquefied oxygen to obtain high-pressure liquefied nitrogen and at the same time evaporating and gasifying at least a part of the first liquefied oxygen to obtain oxygen gas; and A first liquid feed path for introducing a part of the high pressure liquefied nitrogen into the intermediate pressure distillation tower, a first gas feed path for introducing the second intermediate pressure nitrogen gas into the intermediate pressure distillation tower, and the low pressure nitrogen gas as heat. A first product recovery path for deriving as product low-pressure nitrogen gas after recovery, a second product recovery path for deriving the oxygen gas as product oxygen gas after heat recovery, and a portion of the first intermediate-pressure nitrogen gas after heat recovery An air separation device comprising a third product recovery path that is led out as product intermediate pressure nitrogen gas.   The air distillation passage of the heat exchange-type distiller is partially liquefied by cooling the second raw material air by heat exchange with the first low-pressure oxygen-enriched liquefied air introduced into the oxygen distillation passage. An air condensing section that separates into a phase nitrogen enriched air and a liquid phase second medium pressure oxygen enriched liquefied air; and the first low pressure oxygen enriched liquefied gas introduced into the oxygen distillation passage. Separation into a second medium-pressure nitrogen gas enriched with nitrogen components and a third medium-pressure oxygen-enriched liquefied air having a nitrogen concentration lower than that of the second medium-pressure nitrogen gas by performing heat exchange with air and distillation while cooling. The air separation device according to claim 4, wherein the air separation device is divided into an air distillation section.   The second medium-pressure nitrogen gas and the first low-pressure oxygen-enriched liquefied air are heat-exchanged to condense and liquefy the second medium-pressure nitrogen gas to obtain second medium-pressure liquefied nitrogen, and at the same time, the first low-pressure nitrogen gas A second intermediate pressure condenser for evaporating and gasifying at least part of the oxygen-enriched liquefied air to obtain a second low-pressure oxygen-enriched liquefied air; and a second intermediate-pressure liquefied nitrogen introduced into the low-pressure distillation column. The air separation device according to claim 4, further comprising a liquid feeding path.

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