Nitrogen production method and apparatus
The described method and apparatus address the inefficiencies in nitrogen production by employing multi-step separation and condensation processes to produce high-purity oxygen and argon efficiently at low pressures, minimizing raw air and power consumption.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- NIPPON SANSO CORP
- Filing Date
- 2024-12-10
- Publication Date
- 2026-06-22
AI Technical Summary
Existing nitrogen production apparatuses face challenges in efficiently producing high-purity oxygen and argon while generating nitrogen gas at relatively low pressures (e.g., 9 barA or less), leading to increased raw air consumption and power consumption when attempting to collect a significant amount of argon.
A method and apparatus involving multiple separation and condensation steps, including low-temperature distillation and heat exchange processes, to separate and condense nitrogen, oxygen, and argon gases, with integrated rectification columns and condensers to optimize gas production and recovery.
The method and apparatus enable efficient production of high-purity oxygen and argon simultaneously with nitrogen gas at low pressures, reducing raw air requirements and power consumption.
Smart Images
Figure 2026100904000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a nitrogen production method and a nitrogen production apparatus.
Background Art
[0002] In recent years, in nitrogen production apparatuses for semiconductor factories, cases where a small amount of high-purity oxygen and argon are required in addition to a large amount of nitrogen gas have been increasing.
[0003] The nitrogen production apparatus disclosed in Patent Document 1 can produce high-purity oxygen and argon simultaneously while producing nitrogen gas. However, when the pressure of the product nitrogen gas is relatively low (for example, 9 barA or less), there is a problem that the amount of product argon decreases. Further, when trying to collect a product argon amount above a certain level, there is a problem that the amount of raw air increases significantly and the power consumption increases.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] An object of the present invention is to provide a nitrogen production method and apparatus capable of efficiently producing high-purity oxygen and argon while producing nitrogen gas with a relatively low pressure (for example, 9 barA or less).
Means for Solving the Problems
[0006] To solve the above problems, the present invention provides the following means. [1] A first separation step of distilling the low-temperature raw air obtained by cooling the raw air containing oxygen, nitrogen, and argon to separate it into high-pressure nitrogen gas and high-pressure liquefied air; A first condensation step involves heat exchange between the high-pressure nitrogen gas and the medium-pressure liquefied air obtained by reducing the pressure of the high-pressure liquefied air, thereby liquefying the high-pressure nitrogen gas to produce high-pressure liquefied nitrogen and vaporizing the medium-pressure liquefied air to produce medium-pressure air. A second separation step involves distilling the aforementioned medium-pressure air to separate it into medium-pressure nitrogen gas and medium-pressure liquefied air. A second condensation step involves heat exchange between the aforementioned medium-pressure nitrogen gas and low-pressure liquefied air obtained by reducing the pressure of the aforementioned medium-pressure liquefied air, thereby liquefying the medium-pressure nitrogen gas to produce medium-pressure liquefied nitrogen and vaporizing the low-pressure liquefied air to produce low-pressure air. An oxygen separation step is performed by distilling a portion of the high-pressure liquefied air generated in the first rectification column, or a portion of the medium-pressure liquefied air generated in the second separation step, to separate it into low-pressure air, liquefied oxygen, and argon-enriched oxygen gas. An oxygen evaporation step is performed to vaporize the aforementioned liquid oxygen to produce oxygen gas, An argon separation step is performed by distilling the argon-enriched oxygen gas generated in the oxygen separation step to separate it into argon gas and argon-enriched liquefied oxygen. An argon condensation step is performed by indirect heat exchange between the argon gas and the high-pressure liquid nitrogen or the medium-pressure liquid nitrogen to liquefy the argon gas and produce liquid argon, and by vaporizing the high-pressure liquid nitrogen or the medium-pressure liquid nitrogen to produce nitrogen gas. A product nitrogen extraction process for extracting a portion of the aforementioned high-pressure nitrogen gas as a product, A product oxygen extraction process for extracting the oxygen gas or a portion of the liquid oxygen 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 [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] A method for producing nitrogen 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 a second condensation step to produce medium-pressure liquid nitrogen. [4] A first rectification column that distills low-temperature raw material air obtained by cooling raw material air containing oxygen, nitrogen, and argon to separate it into high-pressure nitrogen gas and high-pressure liquefied air, A first condenser that exchanges heat between the high-pressure nitrogen gas and the medium-pressure liquefied air obtained by reducing the pressure of the high-pressure liquefied air, thereby liquefying the high-pressure nitrogen gas to produce high-pressure liquefied nitrogen and vaporizing the medium-pressure liquefied air to produce medium-pressure air, A second rectification column distills the aforementioned medium-pressure air to separate it into medium-pressure nitrogen gas and medium-pressure liquefied air, A second condenser that exchanges heat between the aforementioned medium-pressure nitrogen gas and low-pressure liquefied air obtained by reducing the pressure of the aforementioned medium-pressure liquefied air, thereby liquefying the medium-pressure nitrogen gas to produce medium-pressure liquefied nitrogen and vaporizing the low-pressure liquefied air to produce low-pressure air, An oxygen column that distills 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 rectification column, to separate it into low-pressure air, liquefied oxygen, and argon-enriched oxygen gas. An oxygen evaporator that vaporizes the aforementioned liquid oxygen to produce oxygen gas, An argon column that distills the argon-enriched oxygen gas generated in the oxygen column to separate it into argon gas and argon-enriched liquid oxygen, An argon condenser that exchanges heat between the argon gas and the high-pressure liquid nitrogen or the medium-pressure liquid nitrogen to liquefy the argon gas and produce liquid argon, and vaporizes the high-pressure liquid nitrogen or the medium-pressure liquid nitrogen to produce nitrogen gas, A product nitrogen discharge line that discharges a portion of the aforementioned high-pressure nitrogen gas as a product, A product oxygen outlet line that outputs the oxygen gas or a portion of the liquid oxygen as a product, A nitrogen production apparatus characterized by including a product argon outlet line for discharging the argon gas or a portion of 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 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 [4], characterized in that the nitrogen gas produced in the argon condenser is liquefied together with the medium-pressure nitrogen gas in a second condenser to produce medium-pressure liquid nitrogen. [Effects of the Invention]
[0007] According to the present invention, it is possible to efficiently generate nitrogen gas at a relatively low pressure (for example, 9 bar A or less) while simultaneously producing high-purity oxygen and argon. [Brief explanation of the drawing]
[0008] [Figure 1] This figure shows a nitrogen production apparatus according to the first embodiment of the present invention. [Figure 2] This is a diagram showing a conventional nitrogen production apparatus. [Modes for carrying out the invention]
[0009] [First Embodiment] <Nitrogen production equipment> A nitrogen production apparatus 1 according to the first embodiment of the present invention will be described with reference to the drawings. Figure 1 is a schematic diagram of a nitrogen production apparatus 1 of a 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 pressure ranges or temperature ranges. 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 Fig. 1, the nitrogen production apparatus 1 of this embodiment includes an air compressor 2, an air pre-cooler 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, the air pre-cooler 3, and the air purifier 4 are devices for compressing, pre-cooling, and purifying raw air containing oxygen, nitrogen, and argon. The main heat exchanger 5 is a device that performs heat exchange between introduced fluids and导出 the fluids after heat exchange.
[0012] The first rectification column 6 is a rectification column that performs low-temperature distillation on low-temperature raw air B and separates it into high-pressure nitrogen gas C and high-pressure liquefied air D. The first condenser 7 indirectly heat-exchanges the medium-pressure liquefied air E obtained by depressurizing the high-pressure nitrogen gas C and the high-pressure liquefied air D. The first condenser 7 is a device that liquefies the high-pressure nitrogen gas C to generate high-pressure liquefied nitrogen G and vaporizes the medium-pressure liquefied air E to generate medium-pressure air F.
[0013] The second rectification column 8 is a rectification column that performs low-temperature distillation on medium-pressure air F and separates it into medium-pressure nitrogen gas H and medium-pressure liquefied air I. The second condenser 8 indirectly heat-exchanges the low-pressure liquefied air J obtained by depressurizing the medium-pressure nitrogen gas H and the medium-pressure liquefied air I. The second condenser 9 is a device that liquefies the medium-pressure nitrogen gas H to generate medium-pressure liquefied nitrogen L and vaporizes the low-pressure liquefied air J to generate 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 the argon-enriched oxygen gas N produced in the oxygen column 11 into argon gas S and argon-enriched liquefied oxygen T by low-temperature distillation. The argon condenser 15 indirectly exchanges heat between argon gas S and high-pressure liquid nitrogen or medium-pressure liquid nitrogen O. The argon condenser 15 is a device that liquefies argon gas S to produce liquid argon V, and vaporizes pressurized liquid nitrogen Q or medium-pressure liquid 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 tower 11.
[0018] Next, we will describe the conduits that connect each of the devices mentioned above. Line L1 is a pipeline (path) that introduces raw material air (AIR) A, containing oxygen, nitrogen, and argon introduced from the atmosphere, into 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. 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 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 installed in 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 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 upper part 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 along 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 lower part 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 the 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 upper part of the oxygen column 11. A valve V4 is installed along line L22. Line L31 is a pipeline that branches off from line L7 and introduces a portion of the intermediate-pressure air F to the main heat exchanger 5. A portion of the heated intermediate-pressure air F introduced to the main heat exchanger 5 undergoes adiabatic expansion in the expansion turbine 10 and is then introduced to line L14. Line L14 is a pipeline that discharges the low-pressure air that has undergone adiabatic expansion in the expansion turbine 10 to the outside of the system. Line L13 is a pipeline that leads low-pressure air K from the second condenser 9. The low-pressure air K merges with line L14 and is discharged outside the system as exhaust gas WG through the main heat exchanger 5. Line L16 is a pipeline that leads to the low-pressure air R at the top of the oxygen tower 11. The low-pressure air R merges with line L14 and is discharged outside the system as exhaust gas WG after passing through the main heat exchanger 5. Line L17 is a pipeline that leads high-pressure liquid nitrogen X from the oxygen tower evaporator 12 and introduces it to the top of the second rectification column 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 then 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 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 extracts oxygen gas P from the lower or middle section of the oxygen tower 11, heats it in the main heat exchanger 5, and then 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 into the argon condenser 15. Line L26 is a pipeline that leads to the extraction of medium-pressure liquefied nitrogen O from the upper part of the second rectification column 8 and is connected to the liquefied nitrogen pump 13. Line L18 is a pipeline that introduces pressurized liquid nitrogen Q from the liquid 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 top of the argon column 14. Line L29 is a pipeline that branches off from line L28 and leads out liquefied argon V from the argon condenser 15 to the outside of the system as the product liquefied argon LAR.
[0022] Line L30 is the pathway for introducing nitrogen gas U, vaporized in the argon condenser, into the second condenser 9.
[0023] <Methods for producing nitrogen> Next, with reference to Figure 1, a nitrogen production method using the nitrogen production apparatus 1 of this embodiment will be described. In the nitrogen production method of this embodiment, various product gases and product liquefied gases are produced from raw material air.
[0024] First, raw material air A, containing oxygen, nitrogen, and argon, is introduced into line L1 from the atmosphere, 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 step] In the first separation step, the 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 Condensing Process] In the first condensation step, the medium-pressure liquefied air E, which is drawn out from the bottom of the first rectification column 6 and depressurized by valve V1, and the high-pressure nitrogen gas C, which is drawn out from the top 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. High-pressure liquefied nitrogen G is introduced from line L5 to the top of the first rectification column 6 and becomes the reflux liquid of the first rectification column 6.
[0027] [Product Nitrogen Extraction Process] In the product nitrogen discharge process, a portion of the high-pressure nitrogen gas C discharged from the top of the first rectification column 6 to line L6 is branched to the product nitrogen discharge 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 step] A portion of the medium-pressure air F from line L7 is supplied to the bottom of the second rectification column 8, where it is subjected to low-temperature distillation to separate it into medium-pressure nitrogen gas H and medium-pressure liquefied air I. A portion of the high-pressure liquefied air D, which is 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 it 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 extracted to the high-pressure liquefied air side cut line L8, depressurized by valve V2, and then 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 undergoes adiabatic expansion in the expansion turbine 10 to generate the cold necessary for the operation of the device. The fluid obtained from the adiabatic expansion in the expansion turbine 10 is introduced into the main heat exchanger 5 from line L14, heated to room temperature in the main heat exchanger 5, and then recovered as waste gas WG, which is used for regeneration of the air purifier 4, etc.
[0030] [Second Condensing 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. Medium-pressure liquefied nitrogen L is introduced from line L12 to the top of the second rectification column 8 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, as it descends 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 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 separated into low-pressure air R, liquefied oxygen M, and argon-enriched oxygen gas N by low-temperature distillation.
[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 extraction process] In the product oxygen extraction process, liquefied oxygen M that did not vaporize in the oxygen evaporator 12 is extracted to the product oxygen extraction line L20, where it is pressurized by the liquefied oxygen pump 16 to produce pressurized liquefied oxygen Y. The pressurized liquefied oxygen Y is then vaporized in the main heat exchanger 5, heated to room temperature, and recovered as product high-pressure oxygen gas (HPGO). The oxygen gas P, which is vaporized in the oxygen evaporator 12 and rises through the oxygen tower 11, is discharged from the oxygen tower 11 to the product oxygen outlet line L21, where it is heated to room temperature in the main heat exchanger 5 and then 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. Alternatively, the air can be heated to room temperature in the main heat exchanger 5 and then recovered as waste gas WG without merging it with line L14.
[0039] [Argon separation process] In the argon separation process, argon-enriched oxygen gas N is extracted from the middle section of the oxygen column 11 via line L23 and supplied to the bottom of the argon column 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 drawn out from the bottom of the argon column 14 into line L24 and supplied to the middle section of the oxygen column 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, where it is pressurized by a liquefied nitrogen pump to produce pressurized liquefied nitrogen Q, which is then supplied to the argon condenser 15 via valve V8 through line L18. 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 argon gas S and produce liquefied argon V, while the pressurized liquefied nitrogen Q is vaporized to produce nitrogen gas U. Liquefied argon V is introduced from line L28 to the top of the argon column 14 and becomes the reflux liquid in the argon column 14.
[0041] [Nitrogen gas supply process] In the nitrogen gas supply process, the 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 and second condensation processes, 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 output 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, the nitrogen production method using the nitrogen production apparatus 1 of this embodiment makes it possible to efficiently produce high-purity oxygen and argon at the same time while generating nitrogen gas at a relatively low pressure (for example, 9 bar A or less).
[0045] Although the present invention has been described above based on the above embodiments, the present invention is not limited to the above embodiments. It can be implemented in various forms without departing from the spirit of the invention, and for example, the following modifications are also possible.
[0046] Alternatively, the line L27 that extracts medium-pressure liquefied nitrogen O from the second rectification column 8, pressurizes it with a liquefied nitrogen pump 13, and supplies it to the first rectification column can be removed. In this case, medium-pressure nitrogen gas H can be extracted from the second rectification column 8, heated to room temperature in the main heat exchanger, and recovered as product nitrogen gas GN.
[0047] Although the present invention has been described above based on embodiments, the present invention is not limited to the above embodiments and can be modified in various ways. [Examples]
[0048] The present invention will be described in detail below using examples and comparative examples. As an example, a simulation of the nitrogen production apparatus 1 of the present invention shown in Figure 1 was performed, and as a comparative example, a simulation of a conventional nitrogen production apparatus shown in Figure 2 was performed. The following table shows the results of calculations performed under the conditions of recovering product nitrogen gas GN (oxygen concentration 10 ppb or less, pressure 9 barA) at a flow rate of 35, and simultaneously recovering 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 product liquefied argon LAR (oxygen concentration 1.5% or less, nitrogen concentration 0.5% or less) at a flow rate of 0.2.
[0049] [Table 1]
[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 85 for the present invention compared to 100 for the comparative example.
[0051] As is clear from the above results, the nitrogen production method and nitrogen production apparatus of the present invention can increase the argon recovery rate when recovering 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 amount of air) while simultaneously recovering a small amount of product oxygen and a small amount of product argon. Furthermore, it has been confirmed that the nitrogen production method and nitrogen production apparatus of the present invention can reduce the amount of raw air required when recovering the amount of argon product, and also reduce power consumption. [Explanation of Symbols]
[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 air, B...Low-temperature raw 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 S, I...Medium-pressure liquefied air, J...Low-pressure liquefied air, K...Low-pressure air, L...Medium-pressure liquefied nitrogen, M...Liquefied 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...Liquefied argon, X...High-pressure liquefied nitrogen, Y...Pressurized liquefied oxygen
Claims
1. A first separation step involves cooling raw material air containing oxygen, nitrogen, and argon to obtain low-temperature raw material air, which is then distilled to separate it into high-pressure nitrogen gas and high-pressure liquefied air. A first condensation step involves heat exchange between the high-pressure nitrogen gas and the medium-pressure liquefied air obtained by reducing the pressure of the high-pressure liquefied air, thereby liquefying the high-pressure nitrogen gas to produce high-pressure liquefied nitrogen and vaporizing the medium-pressure liquefied air to produce medium-pressure air. A second separation step involves distilling the aforementioned medium-pressure air to separate it into medium-pressure nitrogen gas and medium-pressure liquefied air. A second condensation step involves heat exchange between the aforementioned medium-pressure nitrogen gas and low-pressure liquefied air obtained by reducing the pressure of the aforementioned medium-pressure liquefied air, thereby liquefying the medium-pressure nitrogen gas to produce medium-pressure liquefied nitrogen and vaporizing the low-pressure liquefied air to produce low-pressure air. An oxygen separation step is performed by distilling a portion of the high-pressure liquefied air generated in the first rectification column, or a portion of the medium-pressure liquefied air generated in the second separation step, to separate it into low-pressure air, liquefied oxygen, and argon-enriched oxygen gas. An oxygen evaporation step is performed to vaporize the aforementioned liquid oxygen to produce oxygen gas, An argon separation step is performed by distilling the argon-enriched oxygen gas generated in the oxygen separation step to separate it into argon gas and argon-enriched liquefied oxygen. An argon condensation step is performed by indirect heat exchange between the argon gas and the high-pressure liquid nitrogen or the medium-pressure liquid nitrogen to liquefy the argon gas and produce liquid argon, and by vaporizing the high-pressure liquid nitrogen or the medium-pressure liquid nitrogen to produce nitrogen gas. A product nitrogen extraction process for extracting a portion of the aforementioned high-pressure nitrogen gas as a product, A product oxygen extraction process for extracting the oxygen gas or a portion of the liquid oxygen 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 separates low-temperature raw material air obtained by cooling raw material air containing oxygen, nitrogen, and argon into high-pressure nitrogen gas and high-pressure liquefied air by distillation. A first condenser that exchanges heat between the high-pressure nitrogen gas and the medium-pressure liquefied air obtained by reducing the pressure of the high-pressure liquefied air, thereby liquefying the high-pressure nitrogen gas to produce high-pressure liquefied nitrogen and vaporizing the medium-pressure liquefied air to produce medium-pressure air, A second rectification column that distills the aforementioned medium-pressure air to separate it into medium-pressure nitrogen gas and medium-pressure liquefied air, A second condenser that exchanges heat between the aforementioned medium-pressure nitrogen gas and low-pressure liquefied air obtained by reducing the pressure of the aforementioned medium-pressure liquefied air, thereby liquefying the medium-pressure nitrogen gas to produce medium-pressure liquefied nitrogen and vaporizing the low-pressure liquefied air to produce low-pressure air, An oxygen tower that distills 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 rectification column, to separate it into low-pressure air, liquefied oxygen, and argon-enriched oxygen gas. An oxygen evaporator that vaporizes the aforementioned liquid oxygen to produce oxygen gas, An argon column is used to distill the argon-enriched oxygen gas generated in the oxygen column to separate it into argon gas and argon-enriched liquid oxygen. An argon condenser that exchanges heat between the argon gas and the high-pressure liquid nitrogen or the medium-pressure liquid nitrogen to liquefy the argon gas and produce liquid argon, and vaporizes the high-pressure liquid nitrogen or the medium-pressure liquid nitrogen to produce nitrogen gas, A product nitrogen discharge line that discharges a portion of the aforementioned high-pressure nitrogen gas as a product, A product oxygen outlet line that outputs the oxygen gas or a portion of the liquid oxygen as a product, A nitrogen production apparatus comprising a product argon outlet line for discharging the argon gas or a portion of 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 medium-pressure nitrogen gas in a second condenser to produce medium-pressure liquid nitrogen.