HIGH-PURITY OXYGEN PRODUCTION METHOD, AND AIR SEPARATION DEVICE FOR PRODUCING HIGH-PURITY OXYGEN

Abstract

An air separation device comprises: a main heat exchanger; a nitrogen rectification column; a nitrogen condensers disposed in a top portion of the nitrogen rectification column; a high-purity oxygen rectification column; and an oxygen evaporator disposed in a bottom portion of the high-purity oxygen rectification column. An oxygen-containing fluid discharged from an intermediate stage of the nitrogen rectification column is rectified in the high-purity oxygen rectification column and is concentrated in the bottom portion of the high-purity oxygen rectification column.

Claims

1. A method for producing high purity oxygen, comprising steps: introducing a feed air cooled by a main heat exchanger to a lower section of a first nitrogen rectification column; introducing an oxygen-enriched liquid derived from a bottom portion of the first nitrogen rectification column into a rectification section of a second nitrogen rectification column; separating the feed air into a nitrogen-enriched component and an oxygen-enriched component in the first nitrogen rectification column and the second nitrogen rectification column; condensing a first vapor stream from the first nitrogen rectification column in a first nitrogen condenser; condensing a second vapor stream from the second nitrogen rectification column in a second nitrogen condenser; introducing an oxygen-containing fluid derived from the rectification section of the second nitrogen rectification column into a high-purity oxygen rectification column and producing high-purity product oxygen by using an oxygen evaporator; and using gas removed from a bottom portion of the second nitrogen rectification column as a heat medium for the oxygen evaporator which evaporates liquefied oxygen, and returning the gas to the second nitrogen condenser.

2. The method for producing high purity oxygen as claimed in claim 1, further comprising the steps of: compressing part of the feed air by a compressor; cooling the compressed part of the feed air in a main heat exchanger; expanding the feed air by a expansion turbine; and introducing the feed air into the second nitrogen rectification column.

3. The method for producing high purity oxygen as claimed in claim 1, further comprising expanding in a turbine a vapor formed by vaporizing liquid in the second condenser.

4. The method for producing high purity oxygen as claimed in claim 1, further comprising pressuring nitrogen condensed in the second condenser in a pump and then sending the pressurised condensed nitrogen to the top of the first nitrogen rectification column.

5. The method for producing high purity oxygen as claimed in claim 1, wherein the oxygen-containing fluid derived from the rectification section of the second nitrogen rectification column is introduced into the high-purity oxygen rectification column as the sole feed for the high-purity oxygen rectification column.

6. An air separation apparatus for producing high purity oxygen, comprising: a main heat exchanger a first nitrogen rectification column a second nitrogen rectification column a first nitrogen condenser a second nitrogen condenser a high purity oxygen rectification column a n oxygen evaporator a first conduit configured to introduce feed air cooled by a main heat exchanger to a lower section of a first nitrogen rectification column in order to separate the feed air into a nitrogen-enriched component and an oxygen-enriched component in the first nitrogen rectification column; a second conduit configured to introduce oxygen-enriched liquid derived from the bottom of the first nitrogen rectification column into a rectification section of a second nitrogen rectification column in order to separate the oxygen enriched liquid into a nitrogen-enriched component and an oxygen-enriched component in the second nitrogen rectification column; a third conduit configured send a nitrogen enriched vapor stream from the first nitrogen rectification column to the first nitrogen condenser; a fourth conduit configured to send a nitrogen enriched vapor stream from the second nitrogen rectification column to the second nitrogen condenser; a fifth conduit configured to send an oxygen-containing fluid derived from the rectification section of the second nitrogen rectification column into the high-purity oxygen rectification column and producing high-purity product oxygen at the bottom of the high purity oxygen rectification column; and a sixth conduit configured to send gas removed from the bottom of the second nitrogen rectification column as a heat medium for the oxygen evaporator which evaporates liquefied oxygen, and returning the gas condensed in the oxygen evaporator to the second nitrogen condenser.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0071] 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:

[0072] FIG. 1 is a drawing illustrating an air separation device according to embodiment 1;

[0073] FIG. 2 is a drawing illustrating an air separation device according to embodiment 2;

[0074] FIG. 3 is a drawing illustrating an air separation device according to embodiment 3;

[0075] FIG. 4 is a drawing illustrating an air separation device according to embodiment 4.

DETAILED DESCRIPTION OF THE INVENTION

[0076] 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.

Embodiment 1

[0077] The first air separation device A1 of embodiment 1 will be described with reference to FIG. 1.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] The high-purity oxygen rectification column 5 includes a bottom portion 51, a rectification portion 52, and a top portion 53.

[0088] 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.

[0089] 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.

[0090] 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.

Embodiment 2

[0091] The second air separation device A2 of embodiment 2 will be described with reference to FIG. 2. The same reference numerals as those in embodiment 1 have the same functions, and therefore descriptions thereof may be omitted.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

Embodiment 3

[0097] The third air separation device A3 of embodiment 3 will be described with reference to FIG. 3. The same reference numerals as those in embodiments 1 and 2 have the same functions, and therefore descriptions thereof may be omitted.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

Embodiment 4

[0108] The fourth air separation device A4 of embodiment 4 will be described with reference to FIG. 4. The same reference numerals as those in embodiments 2 and 3 have the same functions, and therefore descriptions thereof may be omitted.

[0109] 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.

[0110] The compressor 911 compresses a portion of the feed air.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

Example

[0116] The results of a physical simulation of the air separation device of embodiment 2 are presented. Feed air (1000 Nm.sup.3/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.

[0117] Nitrogen gas (531 Nm.sup.3/h, 10.0 barA), oxygen-enriched liquid (789 Nm.sup.3/h, oxygen 40.8%), and oxygen-containing fluid (120 Nm.sup.3/h, oxygen 20.2%) were discharged from the first nitrogen rectification column.

[0118] 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 Nm.sup.3/h, 5.95 barA), and was then supplied to the first nitrogen rectification column 2.

[0119] Oxygen-enriched liquid (349 Nm.sup.3/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.

[0120] A portion of the vaporised oxygen-enriched liquid (78.9 Nm.sup.3/h, 4.7 barA) was condensed by the oxygen evaporator 6 and resupplied to the first nitrogen condenser 3.

[0121] The oxygen rectification column 5 was operated at 1.5 barA, and high-purity oxygen (10.6 Nm.sup.3/h, 100%) collected in the bottom portion 51.

[0122] 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.

[0123] 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 Nm.sup.3/h, when feed air was used in the oxygen evaporator 6, 1027 Nm.sup.3/h of feed air was required.

[0124] 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.

[0125] 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.

OTHER EMBODIMENTS

[0126] (1) Although not explicitly stated, pressure regulating devices and flow rate control devices, etc. may be installed in each pipeline in order to regulate pressure and regulate flow rate. [0127] (2) Although not explicitly stated, control valves and gate valves, etc. may be installed in each line. [0128] (3) Although not explicitly stated, pressure regulating devices and temperature measuring devices, etc. may be installed in each column in order to regulate pressure and regulate temperature.

[0129] 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.

[0130] The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

Listing of Elements

[0135] 1 heat exchanger, [0136] 2 nitrogen rectification column, [0137] 3 nitrogen condenser, [0138] 5 oxygen rectification column, [0139] 6 oxygen evaporator, [0140] 91 compressor, [0141] 92 expansion turbine