Method and device for producing nitrogen
The method addresses the inefficiencies in producing high-purity oxygen and argon at low nitrogen pressures by employing advanced separation and condensation processes, achieving efficient gas production with reduced raw air and power usage.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NIPPON SANSO CORP
- Filing Date
- 2025-11-19
- Publication Date
- 2026-06-18
AI Technical Summary
Existing nitrogen production apparatuses face challenges in efficiently producing high-purity oxygen and argon simultaneously when nitrogen gas pressure is relatively low (e.g., 9 barA or less), leading to decreased argon production and increased raw air and power consumption.
A method involving multiple separation and condensation steps to separate and liquefy nitrogen, oxygen, and argon from low-temperature raw air, utilizing rectification columns and condensers to produce high-purity gases efficiently, with nitrogen gas being reused as a raw material in subsequent steps.
The method allows for efficient generation of high-purity oxygen and argon while producing nitrogen gas at low pressure, reducing raw air requirements and power consumption.
Smart Images
Figure JP2025040458_18062026_PF_FP_ABST
Abstract
Description
Nitrogen production method and apparatus 【0001】 The present invention relates to a nitrogen production method and a nitrogen production apparatus. 【0002】 In recent years, in nitrogen production apparatuses for semiconductor factories, there has been an increasing number of cases where, in addition to a large amount of nitrogen gas, a small amount of high-purity oxygen and argon are required. 【0003】 The nitrogen production apparatus disclosed in Patent Document 1 can simultaneously co-produce high-purity oxygen and argon while generating nitrogen gas. However, when the pressure of the product nitrogen gas is relatively low (for example, when it is 9 barA or less), there is a problem that the amount of product argon decreases. Also, when trying to collect a product argon amount above a certain level, there is a problem that the amount of raw air significantly increases and the power consumption increases. 【0004】 Japanese Patent No. 7329714 【0005】 An object of the present invention is to provide a nitrogen production method and apparatus that can efficiently generate high-purity oxygen and argon simultaneously while generating nitrogen gas with a relatively low pressure (for example, 9 barA or less). 【0006】To solve the above problems, the present invention provides the following means: [1] A first separation step of distilling low-temperature raw air obtained by cooling raw air containing oxygen, nitrogen, and argon to separate it into high-pressure nitrogen gas and high-pressure liquefied air; a first condensation step of exchanging heat between the high-pressure nitrogen gas and medium-pressure liquefied air obtained by depressurizing the high-pressure liquefied air to liquefy the high-pressure nitrogen gas and vaporize the medium-pressure liquefied air to produce medium-pressure air; a second separation step of distilling the medium-pressure air to separate it into medium-pressure nitrogen gas and medium-pressure liquefied air; a second condensation step of exchanging heat between the medium-pressure nitrogen gas and low-pressure liquefied air obtained by depressurizing the medium-pressure liquefied air to liquefy the medium-pressure nitrogen gas and vaporize the low-pressure liquefied air to produce low-pressure air; A method for producing nitrogen, comprising: an oxygen separation step of distilling a portion of the high-pressure liquefied air produced in the first rectification column or a portion of the medium-pressure liquefied air produced in the second separation step to separate it into low-pressure air, liquefied oxygen, and argon-enriched oxygen gas; an oxygen evaporation step of vaporizing the liquefied oxygen to produce oxygen gas; an argon separation step of distilling the argon-enriched oxygen gas produced in the oxygen separation step to separate it into argon gas and argon-enriched liquefied oxygen; an argon condensation step of indirectly exchanging heat between the argon gas and the high-pressure liquefied nitrogen or the medium-pressure liquefied nitrogen to liquefy the argon gas and produce liquefied argon, and vaporizing the high-pressure liquefied nitrogen or the medium-pressure liquefied nitrogen to produce nitrogen gas; a product nitrogen release step of releasing a portion of the high-pressure nitrogen gas as a product; a product oxygen release step of releasing a portion of the oxygen gas or the liquefied oxygen as a product; and a product argon release step of releasing a portion of the argon gas or the liquefied argon as a product. [2] The nitrogen production method according to [1], characterized in that it includes a nitrogen gas supply step of supplying the nitrogen gas generated in the argon condensation step as part of the raw materials for the second separation step. [3] The nitrogen production method according to [1], characterized in that the nitrogen gas generated in the argon condensation step is liquefied together with the medium-pressure nitrogen gas in the second condensation step to produce medium-pressure liquid nitrogen.[4] A first rectification column that distills low-temperature raw air obtained by cooling raw air containing oxygen, nitrogen, and argon to separate it into high-pressure nitrogen gas and high-pressure liquefied air; a first condenser that heat exchanges the high-pressure nitrogen gas with medium-pressure liquefied air obtained by reducing the pressure of the high-pressure liquefied air to liquefy the high-pressure nitrogen gas and vaporize the medium-pressure liquefied air to produce medium-pressure air; a second rectification column that distills the medium-pressure air to separate it into medium-pressure nitrogen gas and medium-pressure liquefied air; a second condenser that heat exchanges the medium-pressure nitrogen gas with low-pressure liquefied air obtained by reducing the pressure of the medium-pressure liquefied air to liquefy the medium-pressure nitrogen gas and vaporize the low-pressure liquefied air to produce low-pressure air; A nitrogen production apparatus comprising: an oxygen tower that distills a portion of the high-pressure liquefied air produced in the first rectification tower or a portion of the medium-pressure liquefied air produced in the second rectification tower to separate it into low-pressure air, liquefied oxygen, and argon-enriched oxygen gas; an oxygen evaporator that vaporizes the liquefied oxygen to produce oxygen gas; an argon tower that distills the argon-enriched oxygen gas produced in the oxygen tower to separate it into argon gas and argon-enriched liquefied oxygen; an argon condenser that heat-exchanges the argon gas with the high-pressure liquefied nitrogen or the medium-pressure liquefied nitrogen to liquefy the argon gas and produce liquefied argon, and vaporizes the high-pressure liquefied nitrogen or the medium-pressure liquefied nitrogen to produce nitrogen gas; a product nitrogen outlet line that discharges a portion of the high-pressure nitrogen gas as a product; a product oxygen outlet line that discharges a portion of the oxygen gas or the liquefied oxygen as a product; and a product argon outlet line that discharges a portion of the argon gas or the liquefied argon as a product. [5] The nitrogen production apparatus according to [4], characterized in that it includes a nitrogen gas supply line for supplying the nitrogen gas produced in the argon condenser as part of the raw material for the second rectification column. [6] The nitrogen production apparatus according to [4], characterized in that the nitrogen gas produced in the argon condenser is liquefied together with the intermediate pressure nitrogen gas in the second condenser to produce intermediate pressure liquid nitrogen. 【0007】According to the present invention, it is possible to efficiently generate high-purity oxygen and argon simultaneously while producing nitrogen gas at a relatively low pressure (for example, 9 barA or less). 【0008】 This figure shows a nitrogen production apparatus according to the first embodiment of the present invention. This figure shows a conventional nitrogen production apparatus. 【0009】 [First Embodiment] <Nitrogen Production Apparatus> The nitrogen production apparatus 1 of the first embodiment of the present invention will be described with reference to the drawings. Figure 1 is a schematic diagram of the nitrogen production apparatus 1 of the first embodiment to which the nitrogen production method of the present invention is applied. In the following description, high pressure, medium pressure, low pressure, high temperature, and low temperature refer to the relative pressure and temperature differences in each embodiment and do not specify a pressure range or temperature range. Furthermore, air and liquefied air are mixed fluids containing at least oxygen, nitrogen, and argon, with an oxygen concentration in the range of 5% to 70%, nitrogen gas and liquefied nitrogen are mixed fluids with a nitrogen concentration of 95% or more, oxygen gas and liquefied oxygen are mixed fluids with an oxygen concentration of 70% or more, and argon gas or liquefied argon are mixed fluids with an argon concentration of 90% or more. 【0010】 As shown in Figure 1, the nitrogen production apparatus 1 of this embodiment includes an air compressor 2, an air precooler 3, an air purifier 4, a main heat exchanger 5, a first rectification column 6, a first condenser 7, a second rectification column 8, a second condenser 9, an expansion turbine 10, an oxygen column 11, an oxygen evaporator 12, a liquefied nitrogen pump 13, an argon column 14, an argon condenser 15, a liquefied oxygen pump 16, a product nitrogen outlet line L19, product oxygen outlet lines L20 and L21, and a product argon outlet line L29. 【0011】 The air compressor 2, air precooler 3, and air purifier 4 are devices that compress, precool, and purify raw air containing oxygen, nitrogen, and argon. The main heat exchanger 5 is a device that performs heat exchange between the introduced fluids and discharges the fluid after heat exchange. 【0012】The first rectification column 6 is a rectification column that separates low-temperature raw material air B into high-pressure nitrogen gas C and high-pressure liquefied air D by low-temperature distillation. The first condenser 7 indirectly exchanges heat between high-pressure nitrogen gas C and medium-pressure liquefied air E obtained by reducing the pressure of high-pressure liquefied air D. The first condenser 7 is a device that liquefies high-pressure nitrogen gas C to produce high-pressure liquefied nitrogen G and vaporizes medium-pressure liquefied air E to produce medium-pressure air F. 【0013】 The second rectification column 8 is a rectification column that separates medium-pressure air F into medium-pressure nitrogen gas H and medium-pressure liquefied air I by low-temperature distillation. The second condenser 8 indirectly exchanges heat between the medium-pressure nitrogen gas H and the low-pressure liquefied air J obtained by reducing the pressure of the medium-pressure liquefied air I. The second condenser 9 is a device that liquefies the medium-pressure nitrogen gas H to produce medium-pressure liquefied nitrogen L, and vaporizes the low-pressure liquefied air J to produce low-pressure air K. 【0014】 The expansion turbine 10 is a device that adiabatically expands the introduced gas. 【0015】 The oxygen column 11 is a distillation column that separates a portion of the high-pressure liquefied air D produced in the first distillation column 6, or a portion of the medium-pressure liquefied air I produced in the second distillation column 8, into low-pressure air R, liquefied oxygen M, and argon-enriched oxygen gas N by low-temperature distillation. The oxygen evaporator 12 is a device that vaporizes a portion of the liquefied oxygen M to produce oxygen gas P. 【0016】 The argon column 14 is a rectification column that separates argon gas S and argon-enriched liquefied oxygen T by low-temperature distillation of argon-enriched oxygen gas N produced in the oxygen column 11. The argon condenser 15 indirectly exchanges heat between argon gas S and medium-pressure liquefied nitrogen O or pressurized liquefied nitrogen Q obtained by increasing the pressure of medium-pressure liquefied nitrogen O. The argon condenser 15 is a device that liquefies argon gas S to produce liquefied argon V, and vaporizes medium-pressure liquefied nitrogen O or pressurized liquefied nitrogen Q obtained by increasing the pressure of medium-pressure liquefied nitrogen O to produce nitrogen gas U. 【0017】 The liquefied nitrogen pump 13 is a device that increases the pressure of the medium-pressure liquefied nitrogen O discharged from the second rectification column 8 or the medium-pressure liquefied nitrogen L liquefied in the second condenser 9. The liquefied oxygen pump 16 is a device that increases the pressure of the liquefied oxygen M introduced from the oxygen column 11. 【0018】 Next, the pipelines connecting each of the above-mentioned devices will be described. Line L1 is a pipeline (path) that introduces raw material air (AIR) A, containing oxygen, nitrogen, and argon introduced from the atmosphere, to the lower part of the first rectification column 6 via the air compressor 2, air precooler 3, air purifier 4, and main heat exchanger 5. The raw material air A is cooled in the main heat exchanger 5 to become low-temperature raw material air B. Line L2 is a pipeline connected to the bottom of the first rectification column 6 and branches into lines L3 and L15. Lines L2 and L15 are pipelines that lead the high-pressure liquefied air D discharged from the first rectification column 6 to the lower part of the second rectification column 8. In addition, since a valve (pressure reducing valve) V5 is provided in the middle of line L15, the high-pressure liquefied air D becomes medium-pressure liquefied air E. Lines L2 and L3 are pipelines that introduce high-pressure liquefied air D from the first rectification column 6 to the first condenser 7. A valve V1 (pressure reducing valve) is installed in the middle of line L3. 【0019】 Line L4 is a pipeline that introduces high-pressure nitrogen gas C from the top of the first rectification column 6 to the first condenser 7. Line L5 is a pipeline that introduces high-pressure liquefied nitrogen G from the first condenser 7 to the top of the first rectification column 6. Line L6 is a pipeline that introduces high-pressure nitrogen gas C from the top of the first rectification column 6 to the oxygen tower evaporator 12. A valve V3 is installed in the middle of line L6. Line L19 is a pipeline that branches off from line L6 and leads high-pressure nitrogen gas C from the first rectification column 6 to the main heat exchanger 5, supplying product nitrogen gas GN to the outside of the system. Line L7 is a pipeline that introduces medium-pressure air F from the first condenser 7 to the bottom of the second rectification column 8. 【0020】Line L9 leads to the bottom of the second rectification column 8, supplying medium-pressure liquefied air I, which is then connected to valve V6. The medium-pressure liquefied air I is converted to low-pressure liquefied air J by valve (pressure reducing valve) V6. Line L10 is a pipeline that introduces low-pressure liquefied air J from valve V6 to the second condenser 9. Line L11 is a pipeline that introduces medium-pressure nitrogen gas H from the top of the second rectification column 8 to the second condenser 9. Line L12 is a pipeline that introduces medium-pressure liquefied nitrogen L from the second condenser 9 to the top of the second rectification column 8. Line L22 is a pipeline that introduces medium-pressure liquefied air I from the middle of the second rectification column 8 to the top of the oxygen column 11. Valve V4 is provided in the middle of line L22. Line L31 is a pipeline that branches off from line L7 and introduces a portion of the medium-pressure air F to the main heat exchanger 5. A portion of the heated medium-pressure air F introduced into the main heat exchanger 5 undergoes adiabatic expansion in the expansion turbine 10 and is introduced into line L14. Line L14 is a pipeline that discharges the low-pressure air, which has undergone adiabatic expansion in the expansion turbine 10, to the outside of the system. Line L13 is a pipeline that leads out low-pressure air K from the second condenser 9. The low-pressure air K merges with line L14 and is discharged as exhaust gas WG to the outside of the system through the main heat exchanger 5. Line L16 is a pipeline that leads out low-pressure air R from the top of the oxygen tower 11. The low-pressure air R merges with line L14 and is discharged as exhaust gas WG to the outside of the system through the main heat exchanger 5. Line L17 is a pipeline that leads out high-pressure liquefied nitrogen X from the oxygen tower evaporator 12 and introduces it to the top of the second rectification tower 8 via valve V7. Line L20 is a pipeline that takes liquefied oxygen M from the bottom of the oxygen tower 11, pressurizes it with a liquefied oxygen pump 16, vaporizes it in the main heat exchanger 5, and recovers it as product high-pressure oxygen gas HPGO. The liquefied oxygen M is pressurized into liquefied oxygen Y by the liquefied oxygen pump 16, vaporizes it through the main heat exchanger 5, and is discharged outside the system as product high-pressure oxygen gas HPGO. Line L21 is a pipeline that takes oxygen gas P from the bottom or middle of the oxygen tower 11, heats it in the main heat exchanger 5, and recovers it as product oxygen gas GO. 【0021】Line L23 is a pipeline that introduces argon-enriched oxygen gas N from the middle section of the oxygen tower 11 to the bottom of the argon tower 14. Line L24 is a pipeline that introduces argon-enriched liquefied oxygen T from the bottom of the argon tower 14 to the middle section of the oxygen tower 11. Line L25 is a pipeline that introduces argon gas S from the top of the argon tower 14 to the argon condenser 15. Line L26 is a pipeline that leads out medium-pressure liquefied nitrogen O from the top of the second rectification column 8 and is connected to the liquefied nitrogen pump 13. Line L18 is a pipeline that introduces pressurized liquefied nitrogen Q from the liquefied nitrogen pump 13 to the argon condenser 15 via valve V8. Line L27 is a pipeline that introduces pressurized liquefied nitrogen Q from the liquefied nitrogen pump 13 to the first rectification column 7. Line L28 is a pipeline that introduces liquefied argon V from the argon condenser 15 to the upper part of the argon column 14. Line L29 is a pipeline that branches off from line L28 and leads the liquefied argon V from the argon condenser 15 out of the system as the product liquefied argon LAR. 【0022】 Line L30 is the path through which nitrogen gas U, vaporized in the argon condenser, is introduced into the second condenser 9. 【0023】 <Nitrogen Production Method> Next, a nitrogen production method using the nitrogen production apparatus 1 of this embodiment will be described with reference to Figure 1. In the nitrogen production method of this embodiment, various product gases and product liquefied gases are produced from raw material air AIR. 【0024】 First, raw material air A containing oxygen, nitrogen, and argon, introduced from the atmosphere into line L1, is compressed by air compressor 2, pre-cooled by air pre-cooler 3, purified by air purifier 4, and cooled by main heat exchanger 5 to obtain low-temperature raw material air B. 【0025】 [First Separation Process] In the first separation process, low-temperature raw material air B is supplied to the lower part of the first rectification column 6 and separated into high-pressure nitrogen gas C and high-pressure liquefied air D by low-temperature distillation. 【0026】[First Condensation Process] In the first condensation process, medium-pressure liquefied air E, which is drawn out from the bottom of the first rectification column 6 and depressurized by valve V1, and high-pressure nitrogen gas C, which is drawn out from the upper part of the first rectification column 6, are indirectly heat-exchanged in the first condenser 7. This vaporizes the medium-pressure liquefied air E to produce medium-pressure air F, and liquefies the high-pressure nitrogen gas C to produce high-pressure liquefied nitrogen G. The high-pressure liquefied nitrogen G is introduced into the upper part of the first rectification column 6 from line L5 and becomes the reflux liquid of the first rectification column 6. 【0027】 [Product Nitrogen Derivation Process] In the product nitrogen departure process, a portion of the high-pressure nitrogen gas C that is discharged from the top of the first rectification column 6 to line L6 is branched to the product nitrogen departure line L19, where it is heated to room temperature in the main heat exchanger 5 and then recovered as product nitrogen gas GN. 【0028】 [Second Separation Process] A portion of the medium-pressure air F from line L7 is supplied to the bottom of the second rectification column 8 and separated into medium-pressure nitrogen gas H and medium-pressure liquefied air I by low-temperature distillation. A portion of the high-pressure liquefied air D led from the bottom of the first rectification column 6 to line L2 is branched to line L15, and the medium-pressure liquefied air E obtained by depressurizing with valve V5 is supplied to the lower part of the second rectification column 8. A portion of the high-pressure liquefied air D descending through the first rectification column 6 is withdrawn to the high-pressure liquefied air side cut line L8, depressurized with valve V2, and supplied to the middle section of the second rectification column 8, where it is used as part of the raw material for the second separation process (high-pressure liquefied air side cut process). 【0029】 A portion of the medium-pressure air F is branched from line L7 to line L31 and introduced into the main heat exchanger 5. After being heated in the main heat exchanger 5, it is adiabatically expanded in the expansion turbine 10 to generate the cold necessary for the operation of the device. The fluid obtained by adiabatically expanding in the expansion turbine 10 is introduced into the main heat exchanger 5 from line L14. After being heated to room temperature in the main heat exchanger 5, it is recovered as waste gas WG and used for regeneration of the air purifier 4, etc. 【0030】[Second Condensation Process] In the second condensation process, the medium-pressure liquefied air I, which is led from the bottom of the second rectification column 8 to line L9, is depressurized by valve V6 to obtain low-pressure liquefied air J, which is led to line L10, and the medium-pressure nitrogen gas H, which is led from the top of the second rectification column 8 to line L11, are indirectly heat-exchanged in the second condenser 9. This vaporizes the low-pressure liquefied air J to produce low-pressure air K, and liquefies the medium-pressure nitrogen gas H to produce medium-pressure liquefied nitrogen L. The medium-pressure liquefied nitrogen L is introduced into the upper part of the second rectification column 8 from line L12 and becomes the reflux liquid of the second rectification column 8. 【0031】 Low-pressure air K is introduced from line L13 to line L14, then into the main heat exchanger 5, where it is heated to room temperature before being recovered as waste gas WG and used for regeneration of the air purifier 4, etc. 【0032】 A portion of the medium-pressure liquefied air I descending through the second rectification column 8 is withdrawn via the medium-pressure liquefied air side cut line L22, depressurized by valve V4, and then supplied to the top of the oxygen column 11, where it is used as the raw material for the oxygen separation process (medium-pressure liquefied air side cut process). 【0033】 [Oxygen Separation Process] In the oxygen separation process, medium-pressure liquefied air I discharged from the bottom of the second rectification column 8, or medium-pressure liquefied air I supplied via the medium-pressure liquefied air side-cut process, is subjected to low-temperature distillation to separate it into low-pressure air R, liquefied oxygen M, and argon-enriched oxygen gas N. At this time, instead of medium-pressure liquefied air I, high-pressure liquefied air D discharged from the bottom of the first rectification column 6, or high-pressure liquefied air D supplied via the high-pressure liquefied air side-cut process, can also be subjected to low-temperature distillation to separate it into low-pressure air R, liquefied oxygen M, and argon-enriched oxygen gas N. 【0034】 Low-pressure air R is led from the top of the oxygen tower 11 to line L16, introduced into line L14, and the fluid is introduced from line L14 to the main heat exchanger 5. After being heated to room temperature in the main heat exchanger 5, it is recovered as waste gas WG and used for regeneration of the air purifier 4, etc. 【0035】[Oxygen Evaporation Process] In the oxygen evaporation process, high-pressure nitrogen gas C is led from the top of the first rectification column 6 to line L4 and then branched to line L6, and supplied to the oxygen evaporator 12 at the bottom of the oxygen column 11 via valve V3. The supplied high-pressure nitrogen gas C and the liquefied oxygen M located at the bottom of the oxygen column 11 are then indirectly heat-exchanged in the oxygen evaporator 12, liquefying the high-pressure nitrogen gas C to produce high-pressure liquefied nitrogen X, and vaporizing the liquefied oxygen M to produce oxygen gas P. 【0036】 The high-pressure liquid nitrogen X liquefied in the oxygen evaporator 12 is led to line L17 and supplied to the top or upper part of the second rectification column 8 via valve V7. 【0037】 [Product Oxygen Derivation Process] In the product oxygen derivation process, liquefied oxygen M that did not vaporize in the oxygen evaporator 12 is led to the product oxygen derivation line L20, where it is pressurized by the liquefied oxygen pump 16 to produce pressurized liquefied oxygen Y. The pressurized liquefied oxygen Y is vaporized in the main heat exchanger 5 and heated to room temperature before being recovered as product high-pressure oxygen gas HPGO. Oxygen gas P that has vaporized in the oxygen evaporator 12 and is rising through the oxygen tower 11 is led from the oxygen tower 11 to the product oxygen derivation line L21, where it is heated to room temperature in the main heat exchanger 5 before being recovered as product oxygen gas GO. 【0038】 Low-pressure air R, which is led from the top of the oxygen tower 11 to line L16, is merged with line L14 at the outlet of the expansion turbine 10, heated to room temperature in the main heat exchanger 5, and then recovered as waste gas WG. At this time, it is also possible to recover the waste gas WG after heating to room temperature in the main heat exchanger 5 without merging it with line L14. 【0039】 [Argon Separation Process] In the argon separation process, argon-enriched oxygen gas N is withdrawn from the middle section of the oxygen tower 11 via line L23 and supplied to the bottom of the argon tower 14, where it is separated into argon gas S and argon-enriched liquefied oxygen T by low-temperature distillation. The argon-enriched liquefied oxygen T is withdrawn from the bottom of the argon tower 14 via line L24 and supplied to the middle section of the oxygen tower 11. 【0040】[Argon Condensation Process] In the argon condensation process, medium-pressure liquefied nitrogen O is introduced from the top of the second rectification column 8 into line L26, pressurized by a liquefied nitrogen pump to produce pressurized liquefied nitrogen Q, and supplied to the argon condenser 15 from line L18 via valve V8. At this time, medium-pressure liquefied nitrogen L can also be supplied to the argon condenser 15 instead of pressurized liquefied nitrogen Q. In addition, argon gas S is introduced from the top of the argon column 14 into line L25 and supplied to the argon condenser 15. Then, the pressurized liquefied nitrogen Q is indirectly heat-exchanged in the argon condenser 15 to liquefy the argon gas S to produce liquefied argon V, and the pressurized liquefied nitrogen Q is vaporized to produce nitrogen gas U. The liquefied argon V is introduced into the upper part of the argon column 14 from line L28 and becomes the reflux liquid of the argon column 14. 【0041】 [Nitrogen Gas Supply Process] In the nitrogen gas supply process, nitrogen gas U vaporized in the argon condenser 15 is introduced from line L30 to the second rectification column 8 and used as part of the raw material for the second separation process. Alternatively, the nitrogen gas U vaporized in the argon condenser 15 can be liquefied in the second condenser 9 together with the medium-pressure nitrogen gas generated in the second rectification column 8. Since the nitrogen gas U vaporized in the argon condenser 15 is also used in the second separation process and the second condensation process, the amount of raw material air A can be reduced. 【0042】 [Product Argon Derivation Process] A portion of the liquefied argon V is branched from line L28 to product argon derivation line L29 and recovered as product liquefied argon LAR. 【0043】 When the product liquefied argon LAR or product high-pressure oxygen gas HPGO is not needed, or when it is necessary to shut down the oxygen tower 11 or argon tower 14 due to trouble or other reasons, the supply of medium-pressure liquefied air I supplied to the oxygen tower 11 via the medium-pressure liquefied air side cut line L15 can be stopped while continuing to collect product nitrogen gas GN. In this case, valves V4 and V7 are closed, and valve V7 is closed to stop the flow of high-pressure liquefied nitrogen X discharged from line L17. 【0044】As described above, according to the nitrogen production method using the nitrogen production apparatus 1 of the present embodiment, nitrogen gas with a relatively low pressure (for example, 9 barA or less) can be generated, and at the same time, high-purity oxygen and argon can be efficiently generated. 【0045】 As described above, the present invention has been described based on the above-described embodiment examples, but the present invention is not limited to the above-described embodiment examples. It can be implemented in various aspects without departing from the gist thereof. For example, the following modifications are possible. 【0046】 The line L27 that leads out the medium-pressure liquefied nitrogen O from the second rectification column 8, pressurizes it with the liquefied nitrogen pump 13, and supplies it to the first rectification column can be deleted. Instead, the medium-pressure nitrogen gas H can be led out from the second rectification column 8, heated to room temperature in the main heat exchanger, and recovered as the product nitrogen gas GN. 【0047】 As described above, the present invention has been described based on the embodiments, but the present invention is not limited to the above embodiments and can be variously modified. 【0048】 Hereinafter, the present invention will be described in detail using examples and comparative examples. As an example, a simulation of the nitrogen production apparatus 1 of the present invention shown in FIG. 1 was performed, and as a comparative example, a simulation of the conventional nitrogen production apparatus shown in FIG. 2 was performed. The conventional nitrogen production apparatus shown in FIG. 2 uses, as the fluid vaporized by the argon condenser 15, the fluid obtained by depressurizing the medium-pressure liquefied air led out from the middle or lower part of the second rectification column 8 with the valve V8, as disclosed in Reference 1, which is different from the example of the present invention shown in FIG. 1. The results of calculations under the conditions of setting the flow rate of the product nitrogen gas GN (oxygen concentration 10 ppb or less, pressure 9 barA) to 35, and simultaneously recovering the high-pressure product high-purity oxygen gas HPGO (nitrogen concentration 10 ppb or less, argon concentration 10 ppb or less, pressure 9.5 barA) at a flow rate of 1.2 and the product liquefied argon LAR (oxygen concentration 1.5% or less, nitrogen concentration 0.5% or less) at a flow rate of 0.2 are shown in the following table. 【0049】 【0050】These simulation results confirmed that in the comparative example, the amount of raw material air required to satisfy all of the above product flow rates was a flow rate of 100. In contrast, in the example, the amount of raw material air required to satisfy all of the above product flow rates was a flow rate of 85. Furthermore, it was confirmed that the power consumption was 100 in the comparative example, while it was 85 in the present invention. 【0051】 As is clear from the above results, the nitrogen production method and nitrogen production apparatus of this embodiment can recover a large amount of product nitrogen gas at a relatively low pressure (e.g., 9 bar A or less) (e.g., 40% or more of the air volume) while simultaneously recovering a small amount of product oxygen and a small amount of product argon, thereby increasing the argon recovery rate. Furthermore, it was confirmed that the nitrogen production method and nitrogen production apparatus of this embodiment can reduce the amount of raw air required to recover product argon and reduce power consumption. 【0052】 1...Nitrogen production equipment, 2...Air compressor, 3...Air precooler, 4...Air purifier, 5...Main heat exchanger, 6...First rectification column, 7...First condenser, 8...Second rectification column, 9...Second condenser, 10...Expansion turbine, 11...Oxygen tower, 12...Oxygen evaporator, 13...Liquid nitrogen pump, 14...Argon tower, 15...Argon condenser, 16...Liquid oxygen pump, A...Raw material air, B...Low temperature raw material air, C...High-pressure nitrogen gas, D...High-pressure liquefied air E...Medium-pressure liquefied air, F...Medium-pressure air, G...High-pressure liquefied nitrogen, H...Medium-pressure nitrogen gas, I...Medium-pressure liquefied air, J...Low-pressure liquefied air, K...Low-pressure air, L...Medium-pressure liquefied nitrogen, M...Liquid oxygen, N...Argon-enriched oxygen gas, O...Medium-pressure liquefied nitrogen, P...Oxygen gas, Q...Pressurized liquefied nitrogen, R...Low-pressure air, S...Argon gas, T...Argon-enriched liquefied oxygen, U...Nitrogen gas, V...Liquid argon, X...High-pressure liquefied nitrogen, Y...Pressurized liquefied oxygen
Claims
1. A first separation step in which low-temperature raw air obtained by cooling raw air containing oxygen, nitrogen, and argon is distilled to separate it into high-pressure nitrogen gas and high-pressure liquefied air; a first condensation step in which the high-pressure nitrogen gas and medium-pressure liquefied air obtained by depressurizing the high-pressure liquefied air are subjected to heat exchange to liquefy the high-pressure nitrogen gas to produce high-pressure liquefied nitrogen and vaporize the medium-pressure liquefied air to produce medium-pressure air; a second separation step in which the medium-pressure air is distilled to separate it into medium-pressure nitrogen gas and medium-pressure liquefied air; a second condensation step in which the medium-pressure nitrogen gas and low-pressure liquefied air obtained by depressurizing the medium-pressure liquefied air are subjected to heat exchange to liquefy the medium-pressure nitrogen gas to produce medium-pressure liquefied nitrogen and vaporize the low-pressure liquefied air to produce low-pressure air; An oxygen separation step in which a portion of the high-pressure liquefied air produced in the first rectification column, or a portion of the medium-pressure liquefied air produced in the second separation step, is distilled to separate it into low-pressure air, liquefied oxygen, and argon-enriched oxygen gas; an oxygen evaporation step in which the liquefied oxygen is vaporized to produce oxygen gas; an argon separation step in which the argon-enriched oxygen gas produced in the oxygen separation step is distilled to separate it into argon gas and argon-enriched liquefied oxygen; an argon condensation step in which the argon gas and the high-pressure liquefied nitrogen or the medium-pressure liquefied nitrogen are indirectly heat-exchanged to liquefy the argon gas to produce liquefied argon, and the high-pressure liquefied nitrogen or the medium-pressure liquefied nitrogen is vaporized to produce nitrogen gas; a product nitrogen discharge step in which a portion of the high-pressure nitrogen gas is discharged as a product; and a product oxygen discharge step in which a portion of the oxygen gas or the liquefied oxygen is discharged as a product. A method for producing nitrogen, characterized by comprising a product argon extraction step of extracting the argon gas or a portion of the liquefied argon as a product.
2. The nitrogen production method according to claim 1, characterized in that it includes a nitrogen gas supply step of supplying the nitrogen gas generated in the argon condensation step as part of the raw materials for the second separation step.
3. The nitrogen production method according to claim 1, characterized in that the nitrogen gas generated in the argon condensation step is liquefied together with the medium-pressure nitrogen gas in a second condensation step to produce medium-pressure liquid nitrogen.
4. A first rectification column that distills low-temperature raw air obtained by cooling raw air containing oxygen, nitrogen, and argon to separate it into high-pressure nitrogen gas and high-pressure liquefied air; a first condenser that heat exchanges the high-pressure nitrogen gas with medium-pressure liquefied air obtained by reducing the pressure of the high-pressure liquefied air to liquefy the high-pressure nitrogen gas and vaporize the medium-pressure liquefied air to produce medium-pressure air; a second rectification column that distills the medium-pressure air to separate it into medium-pressure nitrogen gas and medium-pressure liquefied air; a second condenser that heat exchanges the medium-pressure nitrogen gas with low-pressure liquefied air obtained by reducing the pressure of the medium-pressure liquefied air to liquefy the medium-pressure nitrogen gas and vaporize the low-pressure liquefied air to produce low-pressure air; A nitrogen production apparatus comprising: an oxygen tower that distills a portion of the high-pressure liquefied air produced in the first rectification tower or a portion of the medium-pressure liquefied air produced in the second rectification tower to separate it into low-pressure air, liquefied oxygen, and argon-enriched oxygen gas; an oxygen evaporator that vaporizes the liquefied oxygen to produce oxygen gas; an argon tower that distills the argon-enriched oxygen gas produced in the oxygen tower to separate it into argon gas and argon-enriched liquefied oxygen; an argon condenser that heat-exchanges the argon gas with the high-pressure liquefied nitrogen or the medium-pressure liquefied nitrogen to liquefy the argon gas and produce liquefied argon, and vaporizes the high-pressure liquefied nitrogen or the medium-pressure liquefied nitrogen to produce nitrogen gas; a product nitrogen outlet line that discharges a portion of the high-pressure nitrogen gas as a product; a product oxygen outlet line that discharges a portion of the oxygen gas or the liquefied oxygen as a product; and a product argon outlet line that discharges a portion of the argon gas or the liquefied argon as a product.
5. The nitrogen production apparatus according to claim 4, characterized in that it includes a nitrogen gas supply line for supplying nitrogen gas generated in the argon condenser as part of the raw material for the second rectification column.
6. The nitrogen production apparatus according to claim 4, characterized in that the nitrogen gas generated in the argon condenser is liquefied together with the intermediate-pressure nitrogen gas in a second condenser to produce intermediate-pressure liquid nitrogen.