Patent Application
20250189218
This application claims the benefit of priority under 35 U.S.C. § 119 (a) and (b) to Japanese patent application No. JP2023-206377, filed Dec. 6, 2023, which is herein incorporated by reference in its entirety.
The present invention relates to a high-purity oxygen production method and an air separation device for producing high-purity oxygen.
As high-purity oxygen production methods in which components having a higher boiling point or a lower boiling point than oxygen are controlled to the order of ppm or less, there are known methods that employ cryogenic air separation. One such production method that can be cited is a method in which an oxygen-containing liquid or gas is discharged from a cryogenic air separation device, and high-purity oxygen is rectified (see, e.g., WO2018/219685).
In order to rectify high-purity oxygen, a step is required in which feedstock liquefied oxygen is heated to vaporise low boiling point components such as nitrogen and argon, and as a heat medium for this process, it is known to use an oxygen-enriched liquid (see, e.g., WO2018/219685), feed air (see e.g., WO2014/173496), recycled air (see e.g., Japanese Unexamined Patent Publication 2020-173041), and nitrogen gas (see e.g., U.S. Pat. No. 11,549,747).
If a process liquid such as an oxygen-enriched liquid is used as the heat medium, as in WO2018/219685, since the sensible heat of the process liquid is used to provide the latent heat of vaporisation of the liquefied oxygen, a large molar flow rate is required, while at the same time the amount of heat supplied is limited by process balance constraints, and as a result there is a problem in that the amount of high-purity oxygen that can be recovered remains small.
In the methods of WO2014/173496, JP2020-173041, and U.S. Pat. No. 11,549,747, the flow rate of the feed air, recycled air, or nitrogen gas used to vaporise the liquefied oxygen can be increased, so there are no constraints on the high-purity oxygen production capacity, but there is another problem in that the methods involve a gas compression process, and thus energy consumption is high.
The present disclosure provides a high-purity oxygen production method and an air separation device for producing high-purity oxygen, with which energy consumption is reduced even while a process gas is used as a heat medium for liquefied oxygen, so as to avoid high-purity oxygen production capacity constraints.
An air separation device (A1) of the present disclosure comprises: a main heat exchanger (1); one or more nitrogen rectification columns (2); nitrogen condensers (3) disposed in a top portion (23) of each of the nitrogen rectification columns (2); a high-purity oxygen rectification column (5); and an oxygen evaporator (6) disposed in a bottom portion (51) of the high-purity oxygen rectification column (5).
An oxygen-containing fluid discharged from an intermediate stage (22, 221, 222) of the nitrogen rectification column (2) is rectified in the high-purity oxygen rectification column (5) and is concentrated in the bottom portion (51) of the high-purity oxygen rectification column (5). As a result, the oxygen-containing fluid is concentrated and becomes high-purity oxygen. In addition, the high-purity oxygen is vaporised in the oxygen evaporator (6) by indirect heat exchange with oxygen-enriched gas vaporised in the nitrogen condenser (3), and is supplied as a vapour stream to a rectification portion (52) of the high-purity oxygen rectification column (5).
In the present disclosure, a fluid that is discharged from a rectification stage of the rectification column above an introduction point of the feed air, recycled air, or oxygen-enriched liquid and that is introduced into the high-purity oxygen rectification column (5) is referred to as oxygen-containing fluid, and a liquid discharged below the feed air introduction stage (for example, the bottom portion of the nitrogen rectification column) is referred to as oxygen-enriched liquid.
The oxygen-containing fluid may be a liquid or a gas-liquid mixture.
With this configuration, the nitrogen gas in the vapour stream is caused to exchange heat with the oxygen-enriched liquid in the nitrogen condenser, thereby vaporising the oxygen-enriched liquid to generate oxygen-enriched gas. The oxygen-enriched gas, which is utilised as a heat medium for the oxygen evaporator, has a pressure and composition sufficient to vaporise the rectified liquefied oxygen in the bottom portion of the high-purity oxygen rectification column using latent heat. In particular, since oxygen-enriched gas containing a large amount of oxygen can vaporise liquefied oxygen at a lower pressure than air or nitrogen, liquefied oxygen can be vaporised at the supply pressure from the nitrogen evaporator without the use of a compressor.
The oxygen-containing gas condensed (re-liquefied) in the oxygen evaporator (6) may be re-supplied to the nitrogen condenser (3).
With this configuration, recondensed oxygen enriched liquid obtained by condensing the oxygen enriched gas in the oxygen evaporator is re-supplied to a refrigerant side of the nitrogen condenser and vaporised through heat exchange with the vapour stream (nitrogen gas). The recondensed oxygen enriched liquid may be delivered to the nitrogen condenser (3) by means of a head pressure utilizing a height difference between the oxygen evaporator (6) and the nitrogen condenser (3).
If the oxygen evaporator (6) is disposed at a lower position than the nitrogen condenser (3), delivery may be effected using a pump.
The nitrogen rectification column (2) may include a rectification portion (22) for separating high boiling-point components (for example, methane) from the oxygen contained in the supplied feed air, and for discharging an oxygen-containing liquid from an upper stage thereof.
With this configuration, the high boiling-point components contained in the feed air are concentrated in the liquefied oxygen. The oxygen-containing liquid serving as the feedstock for the high-purity oxygen is obtained by discharging some reflux liquid from above the feed air introduction portion of the nitrogen rectification column (2) as the oxygen-containing liquid, the reflux liquid containing sufficient oxygen to serve as a feedstock for the high-purity oxygen while having high boiling-point components removed sufficiently. A rectification portion (221) is disposed midway between the feed air introduction portion and the oxygen-containing liquid discharge portion, and is configured such that high boiling-point components derived from the feed air are transferred into the liquefied oxygen by gas-liquid contact and are concentrated in the lower portion of the rectification column.
The rectification portion (22, 221, 222) may consist of rectification plates, structured packing, or random packing.
A first high-purity oxygen production method may include: a nitrogen-oxygen separation step in which feed air cooled in a main heat exchanger (1) is introduced into an introduction portion in a lower part of a nitrogen rectification column (2), and the feed air is separated in the nitrogen rectification column (2) into a nitrogen-enriched component (nitrogen-enriched fluid) and an oxygen-enriched component (oxygen-enriched fluid); a nitrogen condensation step in which a vapour stream (nitrogen-enriched gas) from the nitrogen rectification column (2) is condensed in a nitrogen condenser (3); an oxygen-enriched liquid circulation step in which oxygen-enriched liquid discharged from a bottom portion (21) of the nitrogen rectification column (2) is sent to a refrigerant side (31) of the nitrogen condenser (3); a waste gas extraction step in which gas discharged from a top portion (31) of the nitrogen condenser (3) is passed through a portion of the main heat exchanger (1), is then expanded and cooled in an expansion turbine (92), and is then passed through the main heat exchanger (1) again and is extracted as waste gas; a product nitrogen gas extraction step in which gas discharged from a top portion (23) of the nitrogen rectification column (2) is passed through the main heat exchanger (1) and is extracted as product nitrogen gas; a high-purity oxygen production step in which an oxygen-containing fluid discharged from an intermediate stage (221) of the rectification portion (22) of the nitrogen rectification column (2) is introduced into a top portion (53) of the high-purity oxygen rectification column (5), and an oxygen evaporator (6) provided in a bottom portion (51) is utilised to produce high-purity oxygen; and a heat medium utilisation step in which gas (oxygen-enriched gas) discharged from a top portion (31) of the nitrogen condenser (3) is utilised as a heat medium for the oxygen evaporator (6) which vaporises liquefied oxygen, and is returned to the refrigerant side or the top portion (31) of the nitrogen condenser (3).
The nitrogen-enriched component is a fluid, for example, including a gas, a liquid, or a gas-liquid two-phase flow.
The oxygen-enriched component is a fluid, for example, including a gas, a liquid, or a gas-liquid two-phase flow.
A second high-purity oxygen production method may include: a nitrogen-oxygen separation step in which feed air cooled in (partially cooled by being discharged from an intermediate part of) a main heat exchanger (1) is introduced into an introduction portion in a lower part of a nitrogen rectification column (2), and the feed air is separated in the nitrogen rectification column (2) into a nitrogen-enriched component (nitrogen-enriched fluid) and an oxygen-enriched component (oxygen-enriched fluid); a nitrogen condensation step in which a vapour stream (nitrogen-enriched gas) from the nitrogen rectification column (2) is condensed in first and second nitrogen condensers (3, 4); an oxygen-enriched liquid circulation step in which oxygen-enriched liquid discharged from a bottom portion (21) of the nitrogen rectification column (2) is passed through the main heat exchanger (1) and is then sent to a refrigerant side (41) of the second nitrogen condenser (4); a waste gas extraction step in which gas discharged from a top portion (31) of the first nitrogen condenser (3) is passed through a portion of the main heat exchanger (1), is then expanded and cooled in an expansion turbine (92), and is then passed through the main heat exchanger (1) again and is extracted as waste gas; a product nitrogen gas extraction step in which gas discharged from a top portion (23) of the nitrogen rectification column (2) is passed through the main heat exchanger (1) and is extracted as product nitrogen gas; a high-purity oxygen production step in which an oxygen-containing fluid discharged from an intermediate stage (221) of the rectification portion (22) of the nitrogen rectification column (2) is introduced into a top portion (53) of the high-purity oxygen rectification column (5), and an oxygen evaporator (6) provided in a bottom portion (51) is utilised to produce high-purity oxygen; a heat medium utilisation step in which gas (oxygen-enriched gas) discharged from the top portion (31) of the nitrogen condenser (3) is utilised as a heat medium for the oxygen evaporator (6) which vaporises liquefied oxygen, and is returned to the top portion (31) of the nitrogen condenser (3); and a recycled gas introduction step in which gas discharged from a top portion (41) of the second nitrogen condenser (4) is compressed by a compressor (91), is passed through the main heat exchanger (1), and is then introduced as recycled gas into a lower part of the nitrogen rectification column (2).
A third high-purity oxygen production method may include:
The first, second, third and fourth high-purity oxygen production methods may include: a waste gas extraction step in which gas discharged from the top portion (53) of the high-purity oxygen rectification column (5) is passed through the main heat exchanger (1) and is extracted as waste gas.
As used herein, “high-purity oxygen” is oxygen having a concentration of at least 99.99%.
A first air separation device (A1) of the present disclosure may comprise: a main heat exchanger (1) into which feed air is introduced; a nitrogen rectification column (2) having a rectification portion (22) or a bottom portion (21) into which the feed air that has been subjected to heat exchange in the main heat exchanger (1) is introduced; at least one nitrogen condenser (3) for condensing nitrogen-enriched gas discharged from a top (23) of the nitrogen rectification column (2); an expansion turbine (92) into which gas discharged from a top portion or a refrigerant phase (31) of the nitrogen condenser (3) is introduced after passing partially through the main heat exchanger (1); a high-purity oxygen rectification column (5) including a top portion (53) or a rectification portion (52) into which an oxygen-containing fluid (which may be in a gaseous or liquid state, or a mixed state of gas and liquid) discharged (at a position higher than the feed air introduction position) from the rectification portion (22) of the nitrogen rectification column (2); and an oxygen evaporator (6) disposed in a bottom portion (51) of the oxygen rectification column (5) to vaporise liquefied oxygen using gas discharged from a top portion (31) of the nitrogen condenser (3) as a heat medium.
The configuration may be such that the nitrogen gas utilised as the heat medium is returned to the top portion of the nitrogen condenser (3).
The high-purity oxygen production device (A1) may comprise:
The waste gas extraction pipeline (L31) and the waste gas extraction pipeline (L53) may merge together into either one thereof.
The heat medium pipeline (L311) may branch off from the product nitrogen gas extraction pipeline (L31).
Further, a second air separation device (A2) may use the nitrogen condenser (3) as a first nitrogen condenser (3), and may additionally comprise a second nitrogen condenser (4).
The second air separation device (A2) may comprise: an oxygen-enriched liquid pipeline (L211) through which oxygen-enriched liquid discharged from a bottom portion (21) of the nitrogen rectification column (2) is passed partially through the main heat exchanger (1) and is then introduced into the second nitrogen condenser (4); a compressor (91) into which gas discharged from a top portion (41) of the second nitrogen condenser (4) is introduced; and a recycled gas pipeline (L41) through which gas discharged from the top portion (41) of the second nitrogen condenser (4) is compressed by a compressor (91), is passed through the main heat exchanger (1), and is then introduced as recycled gas into the rectification portion (22) of the nitrogen rectification column (2).
Further, a third air separation device (A3) is provided with a second nitrogen rectification column (7) which is operated at a lower pressure than the first nitrogen rectification column (2).
Oxygen-enriched gas (vapour) generated in the first nitrogen condenser (3) and/or oxygen-enriched liquid discharged from the bottom portion (21) of the first nitrogen rectification column (2) may be introduced into the second nitrogen rectification column (7).
The third air separation device (A3) may comprise:
Further, a fourth air separation device (A4) may comprise: a compressor (911) for compressing a portion of the feed air, and an expansion turbine (921) for expanding compressed air that has been compressed by the compressor (911), introduced into the main heat exchanger (1), and discharged from an intermediate part thereof.
The fourth air separation device (A4) may comprise: a feed air branch pipeline (L11) which sends a portion of the feed air to the compressor (911) that compresses the feed air, sends the feed air compressed by the compressor (911) to the main heat exchanger (1) and discharges the same from an intermediate part thereof to the expansion turbine (921) to expand the feed air, and then sends the feed air to the rectification portion of the second nitrogen rectification column (7); a low-pressure nitrogen gas extraction pipeline (L732) through which gas discharged from a top portion (73) of the second nitrogen rectification column (7) is extracted as low-pressure nitrogen gas; and a waste gas extraction pipeline (L412) through which gas discharged from the top portion (41) of the second nitrogen condenser (4) is extracted as waste gas.
The air separation devices (A1, A2, A3, A4) may include: various measuring instruments such as flow rate measuring instruments, pressure measuring instruments, temperature measuring instruments, and liquid level measuring instruments; various valves such as control valves and gate valves; and piping that connects each element.
In certain embodiments of the present invention, energy consumption can be reduced even while using a process gas as a heat medium for liquefied oxygen, so as to avoid high-purity oxygen production capacity constraints.
Other features and advantages of the invention will be further disclosed in the description that follows, and in several embodiments provided as non-limiting examples in reference to the appended schematic drawings, in which:
Several embodiments of the present invention will now be described. The embodiments described below are given as an example of the present disclosure. The present disclosure is in no way limited by the following embodiments, and also includes a number of variants which are implemented within a scope that does not alter the gist of the present disclosure. It should be noted that not all the configurations described below are necessarily essential to the present disclosure. Upstream and downstream are based on a flow direction of a gas stream.
The first air separation device A1 of embodiment 1 will be described with reference to
The first air separation device A1 comprises a main heat exchanger 1, a nitrogen rectification column 2, a nitrogen condenser 3, an expansion turbine 92, a high-purity oxygen rectification column 5, and an oxygen evaporator 6.
The main heat exchanger 1 cools feed air introduced from a hot end and discharges the same from a cold end. The cooled feed air is introduced into the nitrogen rectification column 2 via a feed air pipeline LL.
The nitrogen rectification column 2 comprises a bottom portion 21, a rectification portion 22, and a top portion 23. The feed air pipeline L1 is connected to the bottom portion 21.
Oxygen-enriched liquid that collects in the bottom portion 21 is sent to a refrigerant phase 31 of the nitrogen condenser 3 via an oxygen-enriched liquid pipeline L21.
The nitrogen condenser 3 is provided above the top portion 23. A portion of nitrogen gas (vapour stream) discharged from the top 23 of the nitrogen rectification column 2 is introduced into the nitrogen condenser 3 via a reflux pipeline L231, and is cooled (condensed) through heat exchange with the oxygen-enriched liquid to form liquefied nitrogen. The liquefied nitrogen is returned to the top portion 23 of the nitrogen rectification column 2 as reflux liquid.
An oxygen-containing fluid is discharged from between intermediate portions 221, 222 of the rectification portion 22 of the nitrogen rectification column 2 via the oxygen-containing fluid pipeline L221 and is introduced into a top portion 53 of the high-purity oxygen rectification column 5.
Nitrogen gas discharged from the top portion 23 of the nitrogen rectification column 2 is sent via a product nitrogen gas extraction pipeline L23 to the main heat exchanger 1 and is extracted as product nitrogen gas.
Oxygen-enriched gas (oxygen-enriched liquid vapour) discharged from a top portion 31 of the nitrogen condenser 3 is introduced via a waste gas extraction pipeline L31 into the cold end of the main heat exchanger 1, is discharged from an intermediate part thereof, is then expanded and cooled in the expansion turbine 92, and is again sent to the main heat exchanger 1 and is extracted as waste gas.
A portion of the oxygen-enriched gas (oxygen-enriched liquid vapour) discharged from the top portion (refrigerant phase) 31 of the nitrogen condenser 3 is sent as a heat medium via a heat medium pipeline L311 to the oxygen evaporator 6, is re-liquefied, and is returned again to the top portion (refrigerant phase) 31 of the nitrogen condenser 3. The re-liquefied oxygen-enriched gas is supplied as a recycled oxygen-enriched liquid to the nitrogen condenser 3, as a refrigerant.
The high-purity oxygen rectification column 5 includes a bottom portion 51, a rectification portion 52, and a top portion 53.
Oxygen-containing liquid is introduced into the top portion 53 of the high-purity oxygen rectification column 5 and is rectified in the rectification portion 52, and liquefied oxygen collects in the bottom portion 51.
The oxygen evaporator 6 is provided in the bottom portion 51 of the high-purity oxygen rectification column 5. Liquid oxygen is converted into a vapour stream (oxygen gas) by the heat medium nitrogen gas in the oxygen evaporator 6, heat and material are exchanged in the rectification portion 52, and high-purity oxygen accumulates in the bottom portion 51. Gas discharged from the top portion 53 of the high-purity oxygen rectification column 5 passes through a pipeline L53 to merge with the waste gas extraction pipeline L31, is sent to the main heat exchanger 1, and is extracted as waste gas.
According to the air separation device A1 of the first embodiment, coldness necessary to maintain the heat balance of the air separation device can be supplied.
The second air separation device A2 of embodiment 2 will be described with reference to
The second air separation device A2 comprises the main heat exchanger 1, the nitrogen rectification column 2, a first nitrogen condenser 3, a second nitrogen condenser 4, a compressor 91, the expansion turbine 92, the high-purity oxygen rectification column 5, and the oxygen evaporator 6. Aspects of the configuration that differ from embodiment 1 will mainly be described.
The first nitrogen condenser 3 is disposed above the nitrogen rectification column 2, and the second nitrogen condenser 4 is disposed above the first nitrogen condenser 3. Some nitrogen gas (vapour stream) discharged from the top portion 23 of the nitrogen rectification column 2 is introduced into the first nitrogen condenser 3 via a first reflux pipeline L231, and is cooled (condensed) through heat exchange with the oxygen-enriched liquid to form liquefied nitrogen.
The liquefied nitrogen is returned to the top portion 23 of the nitrogen rectification column 2 as reflux liquid. Some nitrogen gas (vapour stream) discharged from the top portion 23 of the nitrogen rectification column 2 is introduced into the second nitrogen condenser 4 via a second reflux pipeline L232, and is cooled (condensed) through heat exchange with the oxygen-enriched liquid to form liquefied nitrogen. The liquefied nitrogen is returned to the top portion 23 of the nitrogen rectification column 2 as reflux liquid.
An oxygen-enriched liquid pipeline L211 is a pipeline through which oxygen-enriched liquid discharged from the bottom portion 21 of the nitrogen rectification column 2 is passed partially through the main heat exchanger 1 and is then introduced into the second nitrogen condenser 4. The oxygen-enriched liquid from the second nitrogen condenser 4 is sent as a refrigerant to the first nitrogen condenser 3.
The compressor 91 compresses gas discharged from a top portion 41 of the second nitrogen condenser 4. A recycled gas pipeline L41 is a pipeline through which gas is discharged from the top portion 41 of the second nitrogen condenser 4, is compressed by the compressor 91, is passed through the main heat exchanger 1, and is then introduced as recycled gas into the rectification portion 22 of the nitrogen rectification column 2.
The third air separation device A3 of embodiment 3 will be described with reference to
The third air separation device A3 comprises the main heat exchanger 1, a first nitrogen rectification column 2, a second nitrogen rectification column 7, the first nitrogen condenser 3, the second nitrogen condenser 4, the compressor 91, the expansion turbine 92, the high-purity oxygen rectification column 5, and the oxygen evaporator 6. Aspects of the configuration that differ from embodiment 2 will mainly be described.
Oxygen-enriched gas (vapour) generated in the first nitrogen condenser 3 and/or oxygen-enriched liquid discharged from the bottom portion 21 of the first nitrogen rectification column 2 are introduced into the second nitrogen rectification column 7.
An oxygen-enriched liquid pipeline L212 is a pipeline through which oxygen-enriched liquid discharged from the bottom portion 21 of the first nitrogen rectification column 2 is introduced into the main heat exchanger 1, is discharged from an intermediate stage thereof, and is then introduced between intermediate stages 721 and 722 of the rectification portion of the second nitrogen rectification column 7.
An oxygen-containing liquid pipeline L723 is a pipeline that introduces oxygen-containing fluid discharged from between intermediate stages 722, 723 of the rectification portion of the second nitrogen rectification column 7 into the top portion 53 of the high-purity oxygen rectification column 5.
The position at which the oxygen-containing fluid is discharged into the oxygen-containing fluid pipeline L723 is above the position at which the oxygen-enriched liquid from the oxygen-enriched liquid pipeline L212 is introduced.
A heat medium pipeline L711 is a pipeline through which gas (oxygen-enriched gas) discharged from below the lower-stage rectification portion 721 of the second nitrogen rectification column 7 is sent as a heat medium to the oxygen evaporator 6, is re-liquefied, and is sent to a refrigerant phase 41 of the second nitrogen condenser 4.
A recycled gas pipeline L722 is a pipeline through which gas is discharged from between the intermediate stages 721 and 722 of the rectification portion of the second nitrogen rectification column 7, is compressed by the compressor 91, is passed through a portion of the main heat exchanger 1, and is then introduced as recycled gas into the rectification portion 22 of the first nitrogen rectification column 2.
A waste gas extraction pipeline L411 is a pipeline through which gas discharged from the top portion 41 of the second nitrogen condenser 4 is passed partially through the main heat exchanger 1, is then sent to the expansion turbine 92 to be expanded and cooled, is again passed through the main heat exchanger 1, and is extracted as waste gas.
A vapour stream pipeline L731 is a pipeline through which a vapour stream that is discharged from a top portion 73 of the second nitrogen rectification column 7 and is sent to the second nitrogen condenser 4 is returned to the top portion 73 of the second nitrogen rectification column 7.
A pipeline L732 branches off from the vapour stream pipeline L731 downstream of the second nitrogen condenser 4 and feeds into the top portion 23 of the first nitrogen rectification column 2. A liquid transfer pump P1 is provided in the pipeline L732.
The fourth air separation device A4 of embodiment 4 will be described with reference to
The fourth air separation device A4 comprises the main heat exchanger 1, the first nitrogen rectification column 2, the second nitrogen rectification column 7, the first nitrogen condenser 3, the second nitrogen condenser 4, the compressor 911, the expansion turbine 921, the high-purity oxygen rectification column 5, and the oxygen evaporator 6. Aspects of the configuration that differ from embodiment 3 will mainly be described.
The compressor 911 compresses a portion of the feed air.
The expansion turbine 921 expands compressed air that has been compressed by the compressor 911, introduced into the main heat exchanger 1, and discharged from an intermediate part thereof.
A feed air branch pipeline L11 is a pipeline that branches off from the feed air pipeline L1 upstream of the main heat exchanger 1, sends a portion of the feed air to the compressor 911 that compresses the feed air, sends the feed air compressed by the compressor 911 to the main heat exchanger 1 and discharges the same from an intermediate part thereof to the expansion turbine 921 that expands the feed air, and then sends the feed air to the rectification portion of the second nitrogen rectification column 7.
A low-pressure nitrogen gas extraction pipeline L732 is a pipeline through which gas discharged from the top portion 73 of the second nitrogen rectification column 7 is extracted as low-pressure nitrogen gas.
A waste gas extraction pipeline L412 is a pipeline through which gas discharged from the top portion 41 of the second nitrogen condenser 4 is extracted as waste gas. The pipeline L53 merges with the waste gas extraction pipeline L412.
According to the fourth embodiment, coldness required for the heat balance is obtained by using the expansion turbine 921 to expand either a portion of the feed air or product nitrogen gas discharged from the first nitrogen rectification column 2 to the pressure of the second nitrogen rectification column 7. Motive power obtained by the expansion turbine 921 may be applied to the motive power of the compressor 911 that compresses the feed air. It should be noted that the same applies to embodiments 2 and 3.
The results of a physical simulation of the air separation device of embodiment 2 are presented. Feed air (1000 Nm3/h, 10.3 barA) was introduced into the hot end of the main heat exchanger, was cooled to −163° C., and was then introduced into the first nitrogen rectification column.
Nitrogen gas (531 Nm3/h, 10.0 barA), oxygen-enriched liquid (789 Nm3/h, oxygen 40.8%), and oxygen-containing fluid (120 Nm3/h, oxygen 20.2%) were discharged from the first nitrogen rectification column.
The oxygen-enriched liquid was supplied to the second nitrogen condenser 4, and was compressed by the recycled air compressor 91 as vaporised recycled air (440 Nm3/h, 5.95 barA), and was then supplied to the first nitrogen rectification column 2.
Oxygen-enriched liquid (349 Nm3/h, 53.2%) concentrated by the second nitrogen condenser 4 was supplied to the first nitrogen condenser 3 and vaporised. A portion of the vaporised oxygen-enriched liquid was supplied to the main heat exchanger 1, was heated and then discharged, was expanded and cooled in the expansion turbine 92, and then reintroduced into the main heat exchanger 1.
A portion of the vaporised oxygen-enriched liquid (78.9 Nm3/h, 4.7 barA) was condensed by the oxygen evaporator 6 and resupplied to the first nitrogen condenser 3.
The oxygen rectification column 5 was operated at 1.5 barA, and high-purity oxygen (10.6 Nm3/h, 100%) collected in the bottom portion 51.
A comparison will be made with a case in which feed air was used as the heat medium in the oxygen evaporator 6, as presented in Patent literature article 2.
In order to obtain the same nitrogen gas and high-purity oxygen liquid as in the above example (embodiment 2), whereas the amount of feed air required in the present example was 1000 Nm3/h, when feed air was used in the oxygen evaporator 6, 1027 Nm3/h of feed air was required.
This is because the heat medium used in the oxygen evaporator 6 in the present example has a higher oxygen concentration than the feed air, thus allowing condensation to occur at a lower pressure, and as a result reducing the compression energy required for the heat medium.
In addition, since it is not necessary to use the feed air as the heat medium, the amount of feed air that can be supplied to the first nitrogen rectification column 2 can be increased, also making it possible to improve the nitrogen gas recovery.
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.
The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.
“Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms “consisting essentially of” and “consisting of” unless otherwise indicated herein.
“Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.
Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.
Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-206377 | Dec 2023 | JP | national |
