WO2006049272A1

WO2006049272A1 - Process and apparatus for nitrogen production

Info

Publication number: WO2006049272A1
Application number: PCT/JP2005/020340
Authority: WO
Inventors: Makoto Irisawa; Toshiyuki Nojima; Takashi Tatsumi
Original assignee: Taiyo Nippon Sanso Corporation
Priority date: 2004-11-08
Filing date: 2005-11-07
Publication date: 2006-05-11
Also published as: CN101048637A; KR100859916B1; CN100529622C; KR20070083808A; TWI326350B; US20080264101A1; TW200617336A; JP2006132854A; JP4515225B2

Abstract

A process and apparatus for producing nitrogen by which product nitrogen can be efficiently supplied. The nitrogen production process comprises: a first separation step in which feed air is distilled at a low temperature; a first indirect heat exchange step in which a first nitrogen gas and a first oxygen-enriched liquefied fluid which have been separated in the first separation step are subjected to indirect heat exchange to obtain a first liquefied nitrogen and a first oxygen-enriched gas fluid; a second separation step in which the first oxygen-enriched gas fluid is distilled at a low temperature; a second indirect heat exchange step in which a second nitrogen gas and a second oxygen-enriched liquefied fluid which have been separated in the second separation step are subjected to indirect heat exchange to obtain a second liquefied nitrogen and a second oxygen-enriched gas fluid; a cold generation step in which the second oxygen-enriched gas fluid is adiabatically expanded to generate cold; a first product recovery step in which part of the first nitrogen gas is discharged as a first product nitrogen gas; and a second product recovery step in which part of the second nitrogen gas is discharged as a second product nitrogen gas after the cold is recovered.

Description

Specification

Nitrogen production method and apparatus

Technical field

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for producing nitrogen, and more particularly, a method and apparatus for separating and refining raw material air by a cryogenic liquefaction separation method to collect nitrogen, particularly in a pressure range of 0.6 to 1. It relates to the most suitable nitrogen production method and equipment for collecting product nitrogen of about IMPa (absolute pressure, the same shall apply hereinafter).

Background art

[0002] Air liquefaction separation by a cryogenic liquefaction separation method is often used for industrial production of nitrogen, and various methods and equipment are used to improve the power unit of product nitrogen gas and expand the range of weight loss. Has been proposed. For example, by using the first rectification column and the second rectification column that have different operating pressures, the power unit of product nitrogen can be reduced, and the amount of product nitrogen reduced can be increased. An apparatus has been proposed (see, for example, Patent Document 1) o Patent Document 1: Japanese Patent Application Laid-Open No. 2003-156284.

Disclosure of the invention

Problems to be solved by the invention

[0003] However, further improvements are required for the power unit of product nitrogen. In particular, since product nitrogen with a pressure of about 0.6 to 1. IMPa is in great demand, development of a method and apparatus that can be efficiently produced is desired. For example, the two-column nitrogen production apparatus described in JP-A-2003-156284 expands a part of the first oxygen-enriched gas fluid extracted from the first rectifying column and evaporated in the first condenser. Since it is introduced into the turbine to generate cold, the throughput of the second fractionator is small. In addition, in the case of a small-scale nitrogen production system, there was still room for improvement, for example, because the throughput of the expansion turbine was reduced, and the range of expansion turbine models was narrowed.

[0004] The present invention is capable of efficiently and economically supplying product nitrogen having a pressure range of about 0.6 to 1. IMPa using a two-column type nitrogen production apparatus, and facilitates optimal configuration of equipment. The purpose is to provide a nitrogen production method and a nitrogen production apparatus that can be selected. Means for solving the problem

[0005] The first aspect of the nitrogen production method for collecting product nitrogen by cryogenic liquefaction separation of the raw material air of the present invention is to compress the raw material air that has been compressed, purified, and cooled to a pressure of 0.8 MPa or more and 1. IMPa or less. A first separation step in which the first nitrogen gas and the first oxygen-enriched liquid fluid are separated by low-temperature distillation at an indirect heat exchange between the first nitrogen gas and the first oxygen-enriched liquid fluid; A first indirect heat exchange step of condensing the first nitrogen gas to obtain first liquefied nitrogen and at the same time evaporating the first oxygen-enriched liquefied fluid to obtain a first oxygen-enriched gas fluid; and A second separation step of separating the gas fluid into a second nitrogen gas and a second oxygen-enriched liquefied fluid by low-temperature distillation at a pressure of 0.4 MPa or more and lower pressure than the first separation step; Nitrogen gas and the second oxygen-enriched liquid fluid are indirectly heat exchanged to condense the second nitrogen gas to obtain the second liquid nitrogen, and at the same time, the second acid A second indirect heat exchange step of evaporating the enriched liquefied fluid to obtain a second oxygen-enriched gas fluid; and A first product recovery step for deriving a part of the first nitrogen gas as a first product nitrogen gas after cold recovery; and a part of the second nitrogen gas as a second product nitrogen gas after cold recovery Including the second product recovery process to be derived!

[0006] A second aspect of the nitrogen production method of the present invention is that the compressed, purified, and cooled raw material air is subjected to low temperature distillation at a pressure of 0.6 MPa or more and 1. IMPa or less to produce first nitrogen gas and first oxygen. A first separation step of separating the enriched liquid into a first fluid; indirect heat exchange between the first nitrogen gas and the first oxygen-enriched liquefied fluid to condense the first nitrogen gas to form a first liquid A first indirect heat exchange step of obtaining a first oxygen-enriched gas fluid by evaporating the first oxygen-enriched liquefied fluid at the same time as obtaining nitrogen; and said first oxygen-enriched gas fluid at 0.3 MPa or more, and A second separation step of separating into a second nitrogen gas and a second oxygen-enriched liquefied fluid by low-temperature distillation at a lower pressure than the first separation step; the second nitrogen gas and the second oxygen-enriched liquid The second nitrogen gas is condensed by indirect heat exchange with the fluid to obtain the second liquid nitrogen, and at the same time, the second oxygen-enriched liquid fluid is evaporated to produce the second oxygen-enriched gas stream. A second indirect heat exchange step for obtaining a cold; a cold generation step for generating cold necessary for operation by adiabatically expanding a part of the raw material air; and a raw material air that has undergone the cold generation step in the second separation step An air introduction step for introducing into the intermediate stage; a first product recovery step for deriving a part of the first nitrogen gas as a first product nitrogen gas after cold recovery; and the second A second product recovery step of extracting a part of the nitrogen gas as a second product nitrogen gas after cold recovery. Further, the first and second aspects of the nitrogen production method may include a step of compressing the second product nitrogen gas.

[0007] A first aspect of the nitrogen production apparatus for collecting product nitrogen by cryogenic liquefaction separation of raw material air of the present invention is a nitrogen production apparatus for collecting product nitrogen by cryogenic liquefaction separation of raw material air. The nitrogen production equipment is: low-temperature distillation of compressed, refined, and cooled raw material air at a pressure of 0.8 MPa or higher, 1. IMPa or lower, and the first nitrogen gas at the top of the tower and the first oxygen-enriched liquid at the bottom of the tower. A first rectifying column that is separated into a fluid; a heat exchange between the first nitrogen gas and the first oxygen-enriched liquefied fluid to condense the first nitrogen gas to form a first liquid nitrogen A first condenser for evaporating the first oxygen-enriched liquefied fluid to obtain a first oxygen-enriched gas fluid; and the first oxygen-enriched gas fluid at 0.4 MPa or more and the first oxygen-enriched gas fluid A second rectifying column that is subjected to low-temperature distillation at a pressure lower than that of the rectifying column and rectifying and separating the second nitrogen gas at the top of the column and the second oxygen-enriched liquefied fluid at the bottom of the column; Gas and the second oxygen-enriched liquefied fluid are indirectly heat-exchanged to condense the second nitrogen gas to obtain second liquefied nitrogen, and at the same time, the second oxygen-enriched liquefied fluid is evaporated to produce the second oxygen-enriched gas. A second condenser that obtains fluid; an expansion turbine that adiabatically expands the second oxygen-enriched gas fluid to generate the cold necessary to operate the apparatus; and first product after cold recovery of part of the first nitrogen gas A first product recovery path that leads out as nitrogen gas; and a second product recovery path that leads out part of the second nitrogen gas as second product nitrogen gas after cold recovery.

[0008] A second aspect of the nitrogen production apparatus of the present invention is the first nitrogen gas at the top of the tower by low-temperature distillation of the compressed, purified and cooled raw material air at a pressure of 0.6 MPa or more and 1. IMPa or less. A first rectifying column that is separated into a first oxygen-enriched liquefied fluid at the bottom of the column; the first nitrogen gas and the first oxygen-enriched liquid fluid are indirectly heat-exchanged to produce a first nitrogen gas A first condenser for condensing to obtain a first liquid-nitrogen and simultaneously evaporating a first oxygen-enriched liquefied fluid to obtain a first oxygen-enriched gas fluid; and A second rectifying column that is 3 MPa or more and is subjected to low-temperature distillation at a pressure lower than that of the first rectifying column to separate a rectified fraction into a second nitrogen gas at the top of the column and a second oxygen-enriched liquefied fluid at the bottom of the column. The second nitrogen gas and the second oxygen-enriched liquefied fluid are indirectly heat exchanged to condense the second nitrogen gas to obtain a second liquid nitrogen, and at the same time a second oxygen-enriched liquid fluid The A second condenser that evaporates to obtain a second oxygen-enriched gas fluid; an expansion turbine that adiabatically expands part of the raw material air to generate cold necessary for operation of the apparatus; and a raw material that passes through the expansion turbine An air introduction path for introducing air into the intermediate stage of the second rectification column; a first product recovery path for extracting a portion of the first nitrogen gas as a first product nitrogen gas after cold recovery; and A second product recovery route for extracting a part of the nitrogen gas as a second product nitrogen gas after cold recovery.

[0009] The first and second aspects of the nitrogen production apparatus may include a nitrogen compressor that performs a compression step of the second product nitrogen gas, and the second rectification column is provided from outside the apparatus. A liquid nitrogen introducing path for introducing liquefied nitrogen can be provided. The invention's effect

[0010] In the first aspect of the nitrogen production method and the nitrogen production apparatus according to the present invention, as a fluid to be introduced into the expansion turbine that performs the cold generation process, the second vapor that has evaporated in the second condenser that performs the second indirect heat exchange step. 2Oxygen-enriched gas fluid is used. Therefore, almost the entire amount of the first oxygen-enriched gas fluid that does not need to be branched and introduced into the expansion turbine is introduced into the second rectification column. The amount of product nitrogen collected from the second rectification column can be increased because the throughput of the second rectification column is higher than before.

[0011] In a second aspect of the nitrogen production method and nitrogen production apparatus according to the present invention, a part of the compressed, refined, and cooled raw material air is branched into an expansion turbine that performs a cold generation step, and adiabatic expansion is performed. After generating the cold necessary for the operation of the equipment, it is introduced into the intermediate stage of the second rectification column. Therefore, the required amount of cold can be efficiently obtained, the throughput of the second rectification column can be increased, and the amount of product nitrogen collected from the second rectification column can be increased.

[0012] Furthermore, by installing a nitrogen compressor to compress the second product nitrogen gas, the pressure of the second product nitrogen gas can be made the same as that of the first product nitrogen gas and supplied to the user. . In addition, by introducing liquid-nitrogen as an external force of the apparatus, it is not necessary to introduce a part of the first oxygen-enriched liquid-fluid to the second rectifying column for cold replenishment, and further, the treatment of the expansion turbine. It can also reduce or reduce the reasoning.

Brief Description of Drawings FIG. 1 is a system diagram of a nitrogen production apparatus showing a first embodiment (low pressure turbine process) of the present invention.

FIG. 2 is a system diagram of a nitrogen production apparatus showing a second embodiment (air turbine process) of the present invention.

FIG. 3 is a system diagram of a nitrogen production apparatus related to a conventional medium pressure turbine process used for comparison with the present invention.

FIG. 4 is a system diagram showing an example of a nitrogen production apparatus related to a conventional low-pressure process using one rectification column.

[FIG. 5] A diagram showing a power unit for each product pressure in the low pressure type process, the low pressure turbine process, and the air turbine process.

[FIG. 6] A diagram showing a range of product pressure and product flow rate advantageous for the low-pressure turbine process and the air turbine process.

Explanation of symbols

[0014] 11 ··· First fractionator, 12 ··· First condenser, 13 ··· Second fractionator, ·················· Second condenser, 15… low pressure expansion turbine, 16… main heat 17 ... pressure reducing valve, 18 ... nitrogen compressor, 19 ... pressure reducing valve, 20 ... pressure reducing valve, 32 ... raw material air inflow path, 35 ... first product recovery path, 43 ... second product recovery path, 72 ... Air turbine, 73 ... Air introduction path, 74 ... Oxygen-enriched liquefied fluid introduction path, 85 ... Medium pressure expansion turbine

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a first embodiment of the present invention and is a system diagram of a nitrogen production apparatus to which a first aspect of the nitrogen production method and the nitrogen production apparatus is applied.

[0016] The nitrogen production apparatus shown in the present embodiment is a low-temperature distillation of compressed, purified, and cooled raw material air at a pressure of 0.8 MPa or more and 1. IMPa or less, and the first nitrogen gas at the top of the tower and the bottom of the tower A first rectifying column 11 that separates into a first oxygen-enriched liquefied fluid, and the first nitrogen gas and the first oxygen-enriched liquid fluid are indirectly heat exchanged to condense the first nitrogen gas. The first condenser 12 for obtaining the first oxygen-enriched gas fluid by evaporating the first oxygen-enriched liquefied fluid at the same time as obtaining the first liquid nitrogen, and the first oxygen-enriched gas fluid is reduced to 0. 4 MPa or more and low-temperature distillation at a pressure lower than that of the first rectifying column 11 to refine the second nitrogen gas at the top of the column and the second oxygen-enriched liquefied fluid at the bottom of the column. When the second rectifying column 13 for fractional separation and the second nitrogen gas and the second oxygen-enriched liquefied fluid are subjected to an indirect heat exchange to condense the second nitrogen gas to obtain a second liquid nitrogen. At the same time, the second condenser 14 that evaporates the second oxygen-enriched fluid to obtain the second oxygen-enriched gas fluid, and the second oxygen-enriched gas fluid is adiabatically expanded to generate the cold necessary for the operation of the device. Expansion turbine (hereinafter referred to as a low pressure expansion turbine) 15.

[0017] The compressed and refined raw material air flows into the main heat exchanger 16 from the path 31, and is cooled to a predetermined temperature by exchanging heat with product nitrogen gas and waste gas in the main heat exchanger 16. The cooled raw material air is introduced into the lower part of the first rectifying column 11 through the raw material air inflow path 32, and nitrogen gas (first nitrogen) in the upper part of the column is obtained by low-temperature distillation in the first rectifying column 11. Gas) and the oxygen-enriched liquefied fluid (first oxygen-enriched liquefied fluid) at the bottom of the column (first separation step). Part of the first nitrogen gas extracted from the top of the tower to the path 33 is branched to the path 34, exchanges heat with the raw material air in the main heat exchanger 16, and is recovered as cold. It is derived from the recovery path 35 as the first product nitrogen gas (first product recovery process). The remaining first nitrogen gas is introduced into the first condenser 12 through the path 36.

[0018] The first oxygen-enriched liquefied fluid is extracted to the lower force path 37 of the first rectifying column 11, and is reduced by the pressure reducing valve 17 to a pressure at which the first nitrogen gas can be liquefied. And introduced into the first condenser 12 from the path 38. The first oxygen-enriched liquid fluid and the first nitrogen gas undergo indirect heat exchange in the first condenser 12, and the first nitrogen gas condenses and becomes liquid nitrogen (first liquid nitrogen). At the same time, the first oxygen-enriched liquid fluid evaporates to become an oxygen-enriched gas fluid (first oxygen-enriched gas fluid) (first indirect heat exchange step). The first liquefied nitrogen is introduced into the upper part of the first rectifying column 11 through the path 39 to become a reflux liquid.

The first oxygen-enriched gas fluid evaporated in the first condenser 12 is introduced into the lower part of the second rectifying column 13 through the path 40 and is subjected to low-temperature distillation in the second rectifying column 13. The gas is separated into nitrogen gas (second nitrogen gas) at the top of the tower and oxygen-enriched liquefied fluid (second oxygen-enriched liquefied fluid) at the bottom of the tower (second separation step). Part of the second nitrogen gas extracted from the tower top force into the path 41 is also branched into the path 42 to exchange heat with the raw material air in the main heat exchange. The second product nitrogen gas is derived from the route 43 (second product recovery step), compressed to a predetermined pressure by the nitrogen compressor 18, and sent to the user from the route 44 (compression step). o) The remaining second nitrogen gas is introduced into the second condenser 14 through the path 45.

[0020] The second oxygen-enriched liquefied fluid is withdrawn into the lower force path 46 of the second rectifying column 13, branched from the path 37 to the path 47, and is reduced by the pressure reducing valve 19 with the second oxygen-enriched liquid. After the first oxygen-enriched liquid, which has been reduced to the pressure of the fluid, is combined with the fluid, the pressure is reduced to a pressure at which the second nitrogen gas can be liquefied by the pressure reducing valve 20, It is introduced into the condenser 14. In the second condenser 14, the mixed fluid of the first oxygen-enriched liquid and the second oxygen-enriched liquid and the second nitrogen gas exchange heat indirectly, and the second nitrogen gas is condensed. At the same time, liquid nitrogen (second liquid nitrogen) is formed, and at the same time, the mixed fluid is evaporated to become oxygen-enriched gas fluid (second oxygen-enriched gas fluid) (second indirect heat exchange step). The second liquefied nitrogen is introduced into the upper part of the second rectifying column 13 through the path 49 and becomes a reflux liquid.

[0021] The second oxygen-enriched gas fluid led out from the second condenser 14 to the path 50 is branched into a path 51 and a path 52, and most of the fluid is introduced into the main heat exchange through the path 52. The temperature is raised to an intermediate temperature, extracted to path 53, and introduced into low-pressure expansion turbine 15. The remaining part of the path 51 is decompressed by the valve 21. The second oxygen-enriched gas fluid that has generated the cold necessary for the operation of the apparatus by adiabatic expansion in the low-pressure expansion turbine 15 (the cold generation process) passes through the path 54 and branches to the path 51 to be a valve. The second oxygen-enriched gas fluid depressurized in 21 is merged, and after recovering cold by main heat exchange, it is led out as waste gas from path 55. Part of this waste gas is used to regenerate the adsorber, which purifies the raw air.

[0022] The first oxygen-enriched liquefied fluid branched into the path 47 is branched in a small amount for the purpose of cold replenishment of the second rectification column 13, and most of the first oxygen-enriched liquefied fluid. The fluid is introduced into the first condenser 12. The first oxygen-enriched liquid fluid branched into this path 47 may be introduced into the middle stage of the second rectification column 13. In addition, for the purpose of adjusting the pressure in the second rectification column 13, a part of the first oxygen-enriched gas fluid flowing through the path 40 may be flowed to the path 50 through the control valve. The first oxygen-enriched gas fluid flowing from 40 to the path 50 is small, and most of the first oxygen-enriched gas fluid is introduced into the second fractionator 13. Therefore, all or most of the first oxygen-enriched liquid fluid separated in the first rectification column 11 evaporates in the first condenser 12 to become the first oxygen-enriched gas fluid. All or most of the enriched gas fluid is introduced into the second fractionator 13. [0023] The second product nitrogen gas is compressed by the nitrogen compressor 18 and is usually brought to the same pressure as the first product nitrogen gas led out from the first product recovery path 35, but depends on the situation of the user. Any pressure can be selected at the same time, and the second product recovery path 43 can be supplied at the same pressure without installing the nitrogen compressor 18. It is also possible to install a compressor that compresses the first product nitrogen gas as needed.

[0024] The low-pressure expansion turbine 15 can also be introduced with the entire amount of the second oxygen-enriched gas fluid passing through the path 50, and the first liquid in the path 39 can be utilized by utilizing the increased coldness due to the increased processing amount. Nitrogen and a part of the second liquid nitrogen in channel 49 can be collected as product liquid nitrogen.

[0025] Further, the operating pressure of the rectifying columns 11 and 13 is determined by the pressure of the waste gas taken out from the path 55. That is, the second oxygen-enriched gas fluid (waste gas) derived from the low-pressure expansion turbine 15 is recovered by cooling with the main heat exchanger 16 and then used for regeneration of the adsorber. The second oxygen-enriched gas fluid in path 54 in the air must have a pressure that can be released to the atmosphere after regeneration of the adsorber, including pressure loss in the main heat exchanger 16 etc.

Furthermore, in order to generate the amount of cold necessary for the operation of the apparatus in the low-pressure expansion turbine 15, it is necessary to ensure a predetermined expansion ratio in the low-pressure expansion turbine 15, so the low-pressure expansion turbine 15 The pressure of the second oxygen-enriched gas fluid in the passage 53 at the inlet of the pipe should be about 0.16 MPa or more.

[0027] Further, in the second condenser 14, the second oxygen-enriched liquid fluid and the second nitrogen gas are indirectly heat-exchanged, and the second nitrogen gas is liquefied to produce the second oxygen-enriched liquid. It is necessary to evaporate the fluid. Therefore, if the minimum pressure of the second oxygen-enriched gas fluid is about 0.16 MPa, the pressure at the top of the second rectifying column 13, which is the pressure of the second nitrogen gas, will be about 0.4 MPa or more. Must be set.

[0028] Furthermore, when the pressure at the top of the second rectifying column 13 is about 0.4 MPa or more, the pressure in the second rectifying column 13 is changed to the first nitrogen in the first condenser 12 as described above. Because it is the pressure of the first oxygen-enriched gas fluid that indirectly exchanges heat with the gas, the pressure at the top of the first rectification column 11 that is the pressure of the first nitrogen gas is set to about 0.8 MPa or more. There is a need.

That is, the operating pressure of the first rectifying column 11 must be set to 0.8 MPa or more, The operating pressure of the rectifying column 13 is 0.4 MPa or more, and the necessary power to receive the first oxygen-enriched gas fluid. The operating pressure of the rectifying column 13 must be set lower than the operating pressure of the first rectifying column 11.

FIG. 2 shows a second embodiment of the present invention, and is a system diagram of a nitrogen production apparatus to which the second aspect of the nitrogen production method and the nitrogen production apparatus is applied. In the following description, the same components as those in the nitrogen production apparatus shown in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[0031] The nitrogen production apparatus shown in the present embodiment has a main heat exchanger that is compressed and refined and branches a part of the raw material air that has flowed into the main heat exchanger 16 from the path 31 to the path 71 at an intermediate temperature. After being extracted from 16 and introduced into an expansion turbine (hereinafter referred to as an air turbine) 72 using a part of the raw material air, it is adiabatically expanded to generate cold (chill generation process), and then passed through an air introduction path 73. Then, it is introduced into the intermediate stage of the second rectification column 13 (air introduction process). In addition, a part of the first oxygen-enriched liquid soot fluid branched from the path 37 to the path 47 and depressurized by the pressure reducing valve 19 passes through the oxygen-enriched liquefied fluid introduction path 74 to the middle of the second rectifying column 13. It is introduced as a cold source in the stage.

[0032] It should be noted that the ratio of the raw material air branched into the air turbine 72 is a force that can be appropriately set according to the required amount of cold, turbine efficiency, etc. Usually, a range of 10 to 20% is appropriate. The connection position of the air introduction path 73 and the oxygen-enriched liquefied fluid introduction path 74 to the second rectification column 13 can be arbitrarily set according to the design conditions, but is usually set to the same position.

[0033] Most of the raw material air flowing into the main heat exchanger from the path 31 is cooled to a predetermined temperature, and then introduced into the lower part of the first rectifying column 11 through the path 32. A part of the first nitrogen gas separated by low-temperature distillation in the first rectification column 11 is led out as the first product nitrogen gas, and the first liquid is recovered by indirect heat exchange in the first condenser 12. Nitrogen and first oxygen-enriched gas fluid are obtained.

The raw material air branched into the path 71 and introduced into the air turbine 72, and adiabatically expanded by the air turbine 72 and then led out to the air introduction path 73 rises to the intermediate stage of the second rectification column 13. Introduced as ascending gas, along with first oxygen-enriched gas fluid from path 40, first oxygen-enriched liquid fluid from oxygen-enriched liquefied fluid inlet path 74, and second liquid-nitrogen from path 49 low temperature It is distilled and separated into nitrogen gas (second nitrogen gas) at the top of the column and oxygen-enriched liquefied fluid (second oxygen-enriched liquefied fluid) at the bottom of the column. Part of the second nitrogen gas passes through the path 42, the main heat exchanger 16, and the path 43, and is led out as the second product nitrogen gas. The second oxygen-enriched gas fluid evaporated by indirect heat exchange in the second condenser 14 and led to the path 50 is recovered as cold by the main heat exchanger 16 and then led out as waste gas from the path 55. .

In the present embodiment, the second oxygen-enriched gas fluid (waste gas) evaporated by the second condenser 14 and led to the path 50 passes through the main heat exchanger 16 without passing through the expansion turbine. Since it is exhausted through and then used only for regeneration of the adsorber, it is not necessary to consider the expansion in the expansion turbine as in the first embodiment, so that it is derived from the second condenser 14. The pressure can be about atmospheric pressure. In order to liquefy the second nitrogen gas with the second oxygen-enriched liquid near the atmospheric pressure, it is necessary to set the pressure at the top of the second rectifying column 13 to about 0.3 MPa or more. Since the pressure of the second rectification column 13 is the pressure of the first oxygen-enriched gas fluid that indirectly exchanges heat with the first nitrogen gas in the first condenser 12 as described above, the pressure of the first nitrogen gas The pressure at the top of the first rectification column 11, which is the pressure, must be set to about 0.6 MPa or more.

[0036] In both embodiments, the second rectifying column is introduced by introducing a part of the first oxygen-enriched liquid soot extracted from the first rectifying column 11 into the path 46 or the second rectifying column. If the cold necessary for the operation of 13 is covered, but other cold supply means can be used as the cold source, for example, liquid nitrogen from the outside of the equipment should be introduced into the second rectification column 13. This makes it possible to introduce the entire amount of the first oxygen-enriched liquid-fluid into the second rectification column, and further reduce the throughput of the expansion turbine. Can be improved. The introduction of a cold source such as liquefied nitrogen from the outside of the apparatus can be appropriately selected according to the operation state of the apparatus and the required amount of cold, and liquid nitrogen or the like is introduced into the first rectification column 11. But ヽ.

[0037] Next, a result of comparison between the nitrogen production apparatus having the configuration shown in the both embodiments and a conventional nitrogen production apparatus will be described. FIG. 3 shows a system diagram of a conventional two-column nitrogen production apparatus used for comparison, in which the pressure of the fluid introduced into the expansion turbine is the second oxygen-enriched gas shown in the first embodiment. Since the pressure is intermediate between the pressure of the fluid and the pressure of a part of the raw air shown in the second embodiment, the first embodiment is hereinafter referred to as a low-pressure turbine process, Two examples will be referred to as an air turbine process and a conventional example as an intermediate pressure turbine process. In FIG. 3, the same components as those in the nitrogen production apparatus shown in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[0038] The low pressure turbine process of the first embodiment and the conventional intermediate pressure turbine process are different in the fluid introduced into the expansion turbine. That is, the first oxygen-enriched gas fluid is not used in the low-pressure turbine process, and most of the second oxygen-enriched gas fluid derived from the second condenser 14 to the path 50 is introduced to the low-pressure expansion turbine 15 from the path 53. On the other hand, in the medium pressure turbine process, as shown in FIG. 3, a part of the first oxygen-enriched gas fluid evaporated in the first condenser 12 is branched from the path 40 to the path 81 and extracted. Further, a part thereof is branched into a path 82, and the remaining part is introduced into the main heat exchanger from the path 83, extracted into the path 84 at an intermediate temperature, and introduced into the expansion turbine (medium pressure expansion turbine) 85.

[0039] In addition, most of the first oxygen-enriched gas fluid in the path 40 is introduced into the lower part of the second rectification column 13 through the path 40a. Therefore, the amount of the first oxygen-enriched gas fluid introduced into the second rectification column in the intermediate pressure turbine process is reduced by the amount branched into the path 81 compared to the low pressure turbine process.

[0040] The first oxygen-enriched gas fluid adiabatically expanded by the intermediate-pressure expansion turbine 85 and led to the path 86 is the second oxygen-enriched gas fluid decompressed by the pressure-reducing valve 87 from the path 50 and the decompression of the path 82. The first oxygen-enriched gas fluid depressurized by the valve 88 is merged, and cold heat is recovered by the main heat exchanger 16, and then is discharged as waste gas from the path 55.

[0041] Flow rate of each fluid flowing through main paths A to M when the low pressure turbine process of the first embodiment and the air turbine process of the second embodiment and the conventional intermediate pressure turbine process are operated under substantially the same pressure conditions. (Relative values), pressure, and oxygen concentration are shown in Table 1 (first example: low-pressure turbine process), Table 2 (second example: air turbine process), and Table 3 (conventional equipment: medium-pressure turbine process). Shown respectively.

[0042] As shown in Figs. 1 to 3, reference signs A to M shown in the tables are reference feed air for path 31 and reference sign B is feed air for the first rectification column introduced in path 32. C is the first product nitrogen gas in the first product recovery path 35, code D is the first oxygen-enriched liquefied fluid derived from the first rectification column in path 37, and code E is the branched first oxygen-enriched liquid in path 47 Fluid, sign F is the first condenser in path 38 Introduced first oxygen-enriched liquefied fluid, symbol G is the second rectifying column introduced first rectifier in channel 40 or 40a, symbol H is second product nitrogen gas in symbol second product recovery channel 43, symbol I Is the compressed second product nitrogen gas in path 44, J is the second condenser-derived second oxygen-enriched gas fluid in path 50, and K is the second oxygen-enriched gas fluid in path 53 in the low-pressure turbine process, air In the turbine process, the feed air in path 71, and in the intermediate pressure turbine process, the first oxygen-enriched gas fluid in path 84, both of which are the expansion turbine introduction fluid, symbol L is the second in path 51 in the low pressure turbine process. Oxygen-enriched gas fluid, source air in path 73 for air turbine process, first oxygen-enriched gas fluid in path 82 for medium-pressure turbine process, sign M is exhausted second oxygen-enriched gas fluid in path 55 (waste gas ).

[table 1]

[Table 2]

[Table 3] Symbol ABCDEFG Flow rate [-] 100 100 40 60 L ² 58 50

Pressure [MPa] 0.98 0.97 0.94 0.97 0.97 0.51 0.51

Oxygen concentration 21% 21 ¾ 0.1 ppm 35% 35% 35% 35%

Symbol H I J K and M

Flow rate [-] 19 19 33 7 1 41

Pressure [MPa] 0.49 0.94 0.19 0.50 0.13 0.12

Oxygen concentration 0.1 ppm 0.1 ppm 55% 35% 35% 51%

[0043] First, in Tables 1 and 3, since the first rectification column 11 has the same pressure, the yield of nitrogen is also the same. The first product nitrogen gas ( In C), the flow force is 0 in both cases. Similarly, the flow rate of the first oxygen-enriched liquefied fluid (D) derived from the first rectification column 11 is 60, respectively.

[0044] However, in the intermediate pressure turbine process, a part of the first oxygen-enriched gas fluid led out from the first condenser 12 to the path 40 is branched toward the intermediate pressure expansion turbine 85, so that the path 81 The first oxygen-enriched gas fluid (G) introduced into the second rectification column 13 is reduced by the flow rate (7 + 1 = 8) of the first oxygen-enriched gas fluid (K + L) branched to The flow rate is 50. On the other hand, in the low-pressure turbine process, most of the first oxygen-enriched gas fluid led out from the first condenser 12 to the path 40 is introduced into the second rectification column 13, so the flow rate is 58. .

[0045] Therefore, the flow rate of the second product nitrogen gas (H) obtained from the second rectification column 13 is different and the flow rate of the intermediate pressure turbine process is 19, whereas the flow rate of the low pressure turbine process is 2 2. Increased in number. From this, the total flow rate of product nitrogen in the medium-pressure turbine process is 59 with raw air at a flow rate of 100, whereas the total flow rate of product nitrogen is increased to 62 in the low-pressure turbine process.

[0046] Further, comparing Table 2 and Table 3, in the air turbine process, part of the raw air is branched to the air turbine, so the first product nitrogen gas (C) obtained from the first rectification column 11 is On the other hand, the flow rate is reduced to 33 in the air turbine process compared to 40 in the medium pressure turbine process.

[0047] However, in the air turbine process, the raw air and oxygen-enriched liquid derived from the expansion turbine from the air introduction path 73 are connected to the second rectifying column 13 only by the first oxygen-enriched gas fluid from the path 40. Since the first oxygen-enriched liquid fluid from the fluid introduction path 74 is introduced, the second The flow rate of the second product nitrogen gas (H) obtained from the rectification column 13 is greatly increased. The flow rate of the intermediate pressure turbine process is 19, whereas the flow rate is increased to 30 in the air turbine process. Therefore, the total flow rate of product nitrogen is increased to 59 for the medium pressure turbine process and 63 for the air turbine process.

[0048] Table 4 shows the results of calculating the power consumption in each of the above processes.

[Table 4]

[0049] From Table 4, it can be seen that the power unit is improved by about 4% in the low-pressure turbine process and the air turbine process compared to the conventional medium-pressure turbine process. Here, it is assumed that each rectification column is a tray-type rectification column. However, each rectification column is a regular-packed rectification column that is generally used. A distillation column or the like can be used, and even if these are used, substantially the same effect can be obtained.

FIG. 4 is a system diagram showing an example of a nitrogen production apparatus employing a conventional low-pressure process using one rectification column. This nitrogen production apparatus operates the rectifying column 91 at a low pressure of about 0.5 MPa, compresses the obtained product nitrogen gas to a required pressure with a nitrogen compressor 92, and supplies raw air (not shown). This is a method of realizing a low unit by reducing the compressor power and simultaneously improving the yield of the rectification column, and has been widely practiced. The explanation of each part of the device and the flow of each gas and liquid in Fig. 4 are well known in the past. Will not be described.

[0051] FIG. 5 shows the power unit for each product pressure in the low-pressure type process and the low-pressure turbine process and the air turbine process described above. From Fig. 5, it can be seen that the product pressure of the low-pressure turbine process and the air turbine process is smaller on the low-pressure side than the product pressure of 1.1 MPa. It can be seen that the force unit becomes smaller.

[0052] This is because in the low-pressure turbine process and the air turbine process, as the product pressure is increased, the pressure in the first rectification column 11 and the second rectification column 13 is increased, and the pressure of the waste gas is also increased. . Therefore, the percentage of waste gas energy that cannot be effectively utilized simply by being decompressed and exhausted increases, so increasing the product nitrogen pressure gradually increases waste and reduces the basic unit. On the other hand, in the low pressure type process, the power of the nitrogen compressor 92 simply increases.

[0053] From this result, in the product nitrogen pressure, that is, in the low-pressure turbine process and the air turbine process, the top force of the first rectification column 11 is also extracted and is derived from the first product recovery path 35. The pressure of the product nitrogen gas is 1. Both the limit that IMPa can expect the effects of the present invention is the limit. When sending product nitrogen to the user at a pressure exceeding this, the conventional low pressure process is more advantageous. Become.

[0054] Table 5 shows the specifications of the expansion turbine in the low-pressure turbine process and the air turbine process, which are compared in the case where the same level of product nitrogen is collected.

[Table 5]

In this example, the volume flow rate of both is about 10 times different (= 172Z16). This is because the low-pressure expansion turbine process has a low expansion ratio due to the low inlet pressure of the expansion turbine, and it is necessary to process a relatively large amount of fluid in order to obtain a predetermined cold. . This volumetric flow rate has a significant effect on the mechanical specifications (dimensions) of the expansion turbine.

[0056] The expansion turbine used in these processes is a general-purpose general-purpose expansion turbine. When the volume flow rate is extremely small, it may be difficult to adopt a general-purpose product. Conversely, even when the volumetric flow rate is extremely high, it may be difficult to adopt general-purpose products, or it may be necessary to install multiple expansion turbines!

[0057] However, when the low-pressure turbine process is adopted in a relatively small-scale nitrogen production apparatus, the processing flow rate of the expansion turbine increases with respect to the scale of the apparatus, and it does not become extremely small. Can be adopted. Conversely, when the air turbine process is adopted in a medium and large-scale nitrogen production apparatus, the processing flow rate of the expansion turbine can be reduced for the scale of the apparatus. Can be adopted.

[0058] Fig. 6 shows the ranges of product pressure and product flow rate that are advantageous for the low-pressure turbine process and the air turbine process in consideration of this point. However, since the treatment flow rate of the expansion turbine varies depending on whether or not the product liquefied nitrogen is collected and the equipment is kept cool, the selection of the low-pressure turbine process and the air turbine process is determined in consideration of various conditions. It is desirable to do so. However, qualitatively, a low-pressure turbine process is advantageous in the case of small-scale nitrogen production equipment with a product nitrogen flow rate of several thousand Nm3Zh or less, and a medium to large scale with a product nitrogen flow rate of several thousand Nm3Zh to tens of thousands Nm3Zh. In the case of nitrogen production equipment, the air turbine process seems to be advantageous.

Claims

The scope of the claims

[1] A nitrogen production method for collecting product nitrogen by subjecting raw material air to cryogenic liquefaction separation;

A first separation step in which the compressed, refined, and cooled raw material air is subjected to low-temperature distillation at a pressure of 0.8 MPa or more and 1. IMPa or less and separated into a first nitrogen gas and a first oxygen-enriched liquefied fluid;

The first nitrogen gas and the first oxygen-enriched liquid fluid are indirectly heat exchanged to condense the first nitrogen gas to obtain first liquefied nitrogen, and at the same time evaporate the first oxygen-enriched liquefied fluid. A first indirect heat exchange step to obtain a first oxygen-enriched gas fluid;

A second separator that separates the first oxygen-enriched gas fluid into a second nitrogen gas and a second oxygen-enriched liquefied fluid by low-temperature distillation at a pressure of 0.4 MPa or more and lower pressure than the first separation step. About;

The second nitrogen gas and the second oxygen-enriched liquid fluid are indirectly heat exchanged to condense the second nitrogen gas to obtain second liquefied nitrogen, and at the same time evaporate the second oxygen-enriched liquefied fluid. A second indirect heat exchange step to obtain a second oxygen-enriched gas fluid;

A cold generating step of generating cold necessary for operation by adiabatic expansion of the second oxygen-enriched gas fluid;

A first product recovery step of deriving a part of the first nitrogen gas as a first product nitrogen gas after cold recovery;

A second product recovery step of extracting a part of the second nitrogen gas as a second product nitrogen gas after cold recovery;

A method for producing nitrogen.

[2] A nitrogen production method for collecting product nitrogen by cryogenic liquefaction separation of raw material air;

A first separation step in which the compressed, refined and cooled raw material air is subjected to low-temperature distillation at a pressure of 0.6 MPa or more and 1. IMPa or less and separated into a first nitrogen gas and a first oxygen-enriched liquefied fluid;

The first nitrogen gas and the first oxygen-enriched liquid fluid are indirectly heat exchanged to condense the first nitrogen gas to obtain first liquefied nitrogen, and at the same time evaporate the first oxygen-enriched liquefied fluid. A first indirect heat exchange step to obtain a first oxygen-enriched gas fluid; A second separator that separates the first oxygen-enriched gas fluid into a second nitrogen gas and a second oxygen-enriched liquefied fluid by low-temperature distillation at a pressure of 0.3 MPa or more and lower than the pressure in the first separation step. About;

Generating a cold necessary for operation by adiabatic expansion of a part of the raw material air;

An air introduction step of introducing the raw material air having passed through the cold generation step into an intermediate stage of the second separation step;

A method for producing nitrogen.

[3] The method for producing nitrogen according to claim 1 or 2, further comprising a step of compressing the second product nitrogen gas.

[4] Nitrogen production equipment that collects product nitrogen by cryogenic liquefaction separation of raw material air;

Compressed, refined, and cooled feed air is 0.8 MPa or higher and 1. IMPa or lower pressure is distilled at a low temperature to separate the first nitrogen gas at the top of the tower and the first oxygen-enriched liquefied fluid at the bottom of the tower. A rectifying tower;

The first nitrogen gas and the first oxygen-enriched liquid fluid are indirectly heat exchanged to condense the first nitrogen gas to obtain first liquefied nitrogen, and at the same time evaporate the first oxygen-enriched liquefied fluid. A first condenser to obtain a first oxygen-enriched gas fluid;

The first oxygen-enriched gas fluid is subjected to low-temperature distillation at a pressure of 0.4 MPa or more and lower pressure than the first rectification column, and the second nitrogen gas at the top of the column and the second oxygen-enriched liquefied fluid at the bottom of the column And a second rectifying column that separates The second nitrogen gas and the second oxygen-enriched liquid fluid are indirectly heat exchanged to condense the second nitrogen gas to obtain second liquefied nitrogen, and at the same time evaporate the second oxygen-enriched liquefied fluid. A second condenser to obtain a second oxygen-enriched gas fluid;

An expansion turbine that adiabatically expands the second oxygen-enriched gas fluid to generate the cold necessary to operate the device;

A first product recovery path for deriving a part of the first nitrogen gas as a first product nitrogen gas after cold recovery;

A second product recovery path for extracting a portion of the second nitrogen gas as a second product nitrogen gas after cold recovery;

Nitrogen production equipment.

Nitrogen production equipment that collects product nitrogen by cryogenic liquefaction separation of raw material air;

The compressed, refined, and cooled raw air is distilled at a low temperature of 0.6 MPa or higher, 1. IMPa or lower, and separated into the first nitrogen gas at the top of the tower and the first oxygen-enriched liquefied fluid at the bottom of the tower. A rectifying tower;

The first oxygen-enriched gas fluid is cryogenically distilled at a pressure of 0.3 MPa or higher and lower than the pressure of the first rectification column, and the second nitrogen gas at the top of the column and the second oxygen-enriched liquefied fluid at the bottom of the column And a second rectifying column that separates

The second nitrogen gas and the second oxygen-enriched liquid fluid are indirectly heat exchanged to condense the second nitrogen gas to obtain second liquefied nitrogen, and at the same time evaporate the second oxygen-enriched liquefied fluid. A second condenser to obtain a second oxygen-enriched gas fluid;

An expansion turbine that adiabatically expands a part of the raw material air to generate cold necessary for operation of the apparatus;

An air introduction path for introducing the raw air passed through the expansion turbine into an intermediate stage of the second rectification column; A first product recovery path for deriving a part of the first nitrogen gas as a first product nitrogen gas after cold recovery;

Nitrogen production equipment.

6. The nitrogen production apparatus according to claim 4 or 5, further comprising a nitrogen compressor that compresses the second product nitrogen gas.

7. The nitrogen production apparatus according to claim 4 or 5, wherein the second rectification column is provided with a liquefied nitrogen introduction path for introducing liquefied nitrogen from outside the apparatus.