AIR SEPARATION UNIT

Abstract

An air separation unit including: a main heat exchanger, a medium-pressure rectification column, a low-pressure rectification column, a crude argon column, a nitrogen condenser, a crude argon condenser, an oxygen turbine, a nitrogen compressor, and a nitrogen turbine. The nitrogen turbine expands nitrogen gas supplied from the nitrogen compressor. The air separation unit includes an inlet temperature of the oxygen turbine is lower than an inlet temperature of the nitrogen turbine.

Claims

1: An air separation unit comprising: a main heat exchanger comprising feed air introduced from a warm end thereof and drawn from a cold end thereof; a medium-pressure rectification column into configured to introduce the feed air drawn from the main heat exchanger; a nitrogen condenser into configured to introduce a vapour stream from the medium-pressure rectification column, the vapour stream being condensed and drawn out as a reflux liquid; a low-pressure rectification column into configured to introduce an oxygen-rich liquid drawn from the medium-pressure rectification column; an oxygen turbine for expanding and cooling an oxygen-rich gas drawn from the nitrogen condenser, after the oxygen-rich gas has undergone heat exchange in the main heat exchanger; and a nitrogen turbine for expanding nitrogen gas drawn from the low-pressure rectification column, after said nitrogen gas has undergone heat exchange at least in the main heat exchanger, been compressed to a predetermined pressure and cooled, and once again cooled in the main heat exchanger, wherein, an inlet temperature of the oxygen turbine is lower than an inlet temperature of the nitrogen turbine.

2: The air separation unit according to claim 1, further comprising a crude argon column into configured to introduce an oxygen-containing fluid drawn from the low-pressure rectification column; and a crude argon condenser into configured to introduce a vapour stream from the crude argon column, the vapour stream being condensed and drawn out as a reflux liquid.

3: The air separation unit according to claim 1, further comprising: a nitrogen gas pipeline configured to draw nitrogen gas from the low-pressure rectification column and extracts nitrogen gas at least via the main heat exchanger; a nitrogen gas branch pipeline configured to branch the nitrogen gas pipeline downstream from the main heat exchanger, configured to introduce the nitrogen gas from the warm end of the main heat exchanger, configured to draw out out nitrogen gas from an intermediate portion, the nitrogen gas then being expanded by the nitrogen turbine and merged into the nitrogen gas pipeline or extracted as nitrogen gas once again via the main heat exchanger; a bypass line configured to branch from the nitrogen gas branch pipeline, configured to bypasds the main heat exchanger so that nitrogen gas is not introduced therein, and configured to merge with the nitrogen gas branch pipeline; and a regulating valve for regulating an amount of nitrogen gas circulating through the bypass line.

4: The air separation unit according to claim 1, comprising: a nitrogen gas pipeline configured to draw nitrogen gas from the low-pressure rectification column and configured to extract nitrogen gas at least via the main heat exchanger; a nitrogen gas branch pipeline configured to branch from the nitrogen gas pipeline downstream from the main heat exchanger, configured to introduce the nitrogen gas from the warm end of the main heat exchanger, configured to draw out nitrogen gas from an intermediate portion, the nitrogen gas then being expanded by the nitrogen turbine and merged into the nitrogen gas pipeline or extracted as nitrogen gas once again via the main heat exchanger; a nitrogen booster which is provided in the nitrogen gas branch pipeline and configured to boost the pressure of the nitrogen gas to a predetermined pressure; and a second cooling unit configured to cool the nitrogen gas pressure-boosted by the nitrogen booster.

5: The air separation unit according to claim 3, further comprising a recycling nitrogen line configured to branch from the nitrogen gas branch pipeline inside the main heat exchanger, configured to draw nitrogen gas out from the cold end of the main heat exchanger, and configured to introduce nitrogen gas into the medium-pressure rectification column.

6: The air separation unit according to claim 3, further comprising: a second nitrogen booster which is provided in the nitrogen gas branch pipeline and configured to boost the pressure of the nitrogen gas to a predetermined pressure; and a second cooling unit which is provided in the nitrogen gas branch pipeline and configured to cool the nitrogen gas pressure-boosted by the second nitrogen booster.

7: The air separation unit according to claim 1, further comprising a sub-cooler which is configured to accept an oxygen-rich liquid drawn from the medium-pressure rectification column introduced from a warm end and drawn from a cold end.

Description

BRIEF DESCRIPTION OF THE FIGURES

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

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

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

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

[0076] FIG. 5 is a drawing illustrating an air separation unit according to embodiment 5.

[0077] FIG. 6 is a drawing illustrating an air separation unit according to embodiment 6.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the Invention

[0078] Several embodiments of the present disclosure will be described below. 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 constituents described below are necessarily essential to the present disclosure. Upstream and downstream are based on a flow direction of a fluid (liquid or gas).

(Embodiment 1)

[0079] A first air separation unit A1 according to embodiment 1 will be described with the aid of FIG. 1.

[0080] The first air separation unit A1 comprises: a main heat exchanger (1), a medium-pressure rectification column (2), a low-pressure rectification column (4), a crude argon column (5), a nitrogen condenser (3), a crude argon condenser (6), an oxygen turbine (9), a nitrogen compressor (10), and a nitrogen turbine (8).

[0081] The main heat exchanger 1 cools feed air introduced from a warm end and discharges the feed air from a cold end thereof. The cooled feed air is introduced into the medium-pressure rectification column 2 via a feed air pipeline L1.

[0082] The medium-pressure rectification column 2 comprises a bottom 21, a rectification portion 22, and a top 23. The feed air pipeline L1 is connected to the bottom 21.

[0083] Oxygen-rich liquid that collects in the bottom 21 is delivered via a nitrogen-rich liquid pipeline L21 to a rectification portion 42 of the low-pressure rectification column 4 after undergoing heat exchange in a sub-cooler 7. A portion of the oxygen-rich liquid following heat exchange in the sub-cooler 7 is introduced into a refrigerant storage portion 61 of the crude argon condenser 6.

[0084] A portion of the liquid nitrogen in the top 23 is delivered via a liquid nitrogen pipeline L23 to a top 43 of the low-pressure rectification column 4 after undergoing heat exchange in the sub-cooler 7. A liquid nitrogen branch pipeline L231 is a line which branches from the liquid nitrogen pipeline L23 downstream from the sub-cooler 7, and extracts liquid nitrogen.

[0085] The nitrogen condenser 3 is provided above the top 23 of the medium-pressure rectification column 2. A portion of the nitrogen gas (vapour stream) drawn from the top 23 of the medium-pressure rectification column 2 is introduced into the nitrogen condenser 3 via a reflux pipeline and is cooled (condensed) and liquefied by means of heat exchange with oxygen-rich liquid constituting a refrigerant. The liquid nitrogen which has been liquefied is returned to the top 23 of the medium-pressure rectification column 2 as a reflux liquid.

[0086] A liquid nitrogen extraction line L31 is a line for extracting, as liquid oxygen (LOX), the refrigerant (oxygen-rich liquid) from the refrigerant storage portion 32 of the nitrogen condenser 3.

[0087] The low-pressure rectification column 4 comprises a rectification portion 42 and a top 43. The bottom thereof may also serve as the refrigerant storage portion 32 of the nitrogen condenser 3.

[0088] An oxygen-containing fluid drawn from the rectification portion 42 of the low-pressure rectification column 4 is introduced into the bottom 51 of the crude argon column 5 via the oxygen-containing fluid pipeline L421.

[0089] The crude argon column 5 comprises a bottom 51, a rectification portion 52, and a top 53.

[0090] A crude argon column-bottom fluid pipeline L51 is a line for drawing a bottom fluid from the bottom 51 of the crude argon column 5, and introducing the bottom fluid below a draw-out position of the oxygen-containing fluid pipeline L421 in the rectification portion 42 of the low-pressure rectification column 4.

[0091] The argon extraction line L53 is a line for drawing a vapour stream or reflux liquid (crude argon-containing fluid) from the upper portion of the crude argon column 5.

[0092] The vapour stream from the upper portion of the crude argon column 5 is introduced into the crude argon condenser 6 where it is condensed and drawn out as a reflux liquid.

[0093] The crude argon condenser pipeline L62 is a line for drawing the upper vapour phase in the refrigerant storage portion 62 of the crude argon condenser 6, and introducing same into the rectification portion 42 of the low-pressure rectification column 4 above the oxygen-rich liquid pipeline L21.

[0094] The oxygen-rich liquid drawn from the bottom 21 of the medium-pressure rectification column 2 is introduced from the warm end of the sub-cooler 7 and drawn from the cold end thereof. Furthermore, the vapour stream drawn from the upper portion 23 of the medium-pressure rectification column 2 is introduced from the warm end of the sub-cooler 7 and drawn from the cold end thereof. Furthermore, nitrogen gas drawn from the top 43 of the low-pressure rectification column 4 is introduced from the cold end of the sub-cooler 7 and drawn from the warm end thereof.

[0095] The oxygen turbine 9 expands and cools the oxygen gas drawn from the gas phase in the refrigerant storage portion 32 of the nitrogen condenser 3, after the oxygen gas has undergone heat exchange in the main heat exchanger 1.

[0096] An oxygen extraction line L32 is a line which draws oxygen from an upper gas phase in the refrigerant storage portion 32 of the nitrogen condenser 3, introduces the oxygen at an intermediate stage of the main-heat exchanger 1 where the oxygen is warmed and then drawn out and expanded by the oxygen turbine 9, the oxygen then being once again introduced from the cold end of the main heat exchanger 1 and drawn from the warm end thereof, and extracted as product oxygen gas.

[0097] The nitrogen turbine 8 expands the nitrogen gas drawn from the top 43 of the low-pressure rectification column 4, after said nitrogen gas has undergone heat exchange in the sub-cooler 7 and the main heat exchanger 1, been compressed to a predetermined pressure in the nitrogen compressor 10, cooled in the cooling unit 11, and once again cooled in the main heat exchanger 1.

[0098] The nitrogen gas drawn out from the top 43 of the low-pressure rectification column 4 is extracted as low-pressure nitrogen gas via the nitrogen gas pipeline L43 and via the sub-cooler 7 and the main heat exchanger 1.

[0099] The nitrogen compressor 10 and the cooling unit 11 are provided in the nitrogen gas pipeline L43, downstream from the warm end of the main heat exchanger 1.

[0100] The nitrogen gas branch pipeline L431 is a line which branches from the nitrogen gas pipeline L43 downstream from the cooling unit 11, once again introduces the nitrogen gas from the warm end of the main heat exchanger 1, draws out nitrogen gas from an intermediate portion, the nitrogen gas then being expanded by the nitrogen turbine 8 and merged into the nitrogen gas pipeline L43.

[0101] In order to make the inlet temperature of the oxygen turbine 9 lower than the inlet temperature of the nitrogen turbine 8 in this embodiment 1, the temperature of a gas drawn from a first intermediate portion 1a of the main heat exchanger 1 and delivered to the oxygen turbine 9 is lower than the temperature of a gas drawn from a second intermediate portion 1b of the main heat exchanger 1 and delivered to the nitrogen turbine 8. For example, a position (first intermediate portion 1a) of an extraction nozzle of a pipe connected to the oxygen turbine 9 from the main heat exchanger 1 is disposed on the low temperature side of a position (second intermediate portion 1b) of an extraction nozzle of a pipe connected to the nitrogen turbine 8.

(Embodiment 2)

[0102] An air separation unit A2 according to embodiment 2 will be described with the aid of FIG. 2. Reference numerals the same as those in embodiment 1 have the same functions, and therefore descriptions thereof may be omitted. The air separation unit A2 comprises a bypass pipeline L431a, a regulating valve V1, and a temperature measuring unit 12.

[0103] The bypass line L431a is a line which is provided in order to regulate the heat balance in the main heat exchanger 1, branching from the nitrogen gas branch pipeline L431, bypassing the main heat exchanger 1 so that nitrogen gas is not introduced therein, and merging with the nitrogen gas branch pipeline L431.

[0104] The temperature measuring unit 12 measures the temperature of the nitrogen gas introduced into the nitrogen turbine 8. In this embodiment, the temperature measuring unit 12 is provided in a line downstream from a merging point of the bypass line L431a and the nitrogen gas branch pipeline L431.

[0105] The regulating valve V1 regulates the amount of nitrogen gas circulating through the bypass line L431a so that the temperature measured by the temperature measuring unit 12 is higher than the inlet temperature of the oxygen turbine 9 (a temperature value from a thermometer which is installed but not depicted).

[0106] The bypass line L431a is provided from the nitrogen gas pipe at the warm end of the main heat exchanger 1 to a nitrogen turbine inlet pipe, and is configured to be capable of regulating the temperature so that the inlet temperature of the nitrogen turbine 8 is higher than the inlet temperature of the oxygen turbine 9.

(Embodiment 3)

[0107] An air separation unit A3 according to embodiment 3 will be described with the aid of FIG. 3. Reference numerals the same as those in embodiment 1 have the same functions, and therefore descriptions thereof may be omitted. The air separation unit A3 comprises a nitrogen booster 14 and a cooling unit 15.

[0108] The nitrogen booster 14 is provided in the nitrogen gas branch pipeline L431 upstream from the main heat exchanger 1, and boosts the pressure of the nitrogen gas to a predetermined pressure.

[0109] The second cooling unit 15 cools the nitrogen gas pressure-boosted by the nitrogen booster 14 to a predetermined temperature.

[0110] An expansion turbine 81 expands the nitrogen gas which has been cooled by the second cooling unit 15, once again introduced from the warm end of the main heat exchanger 1, and drawn from an intermediate stage thereof.

(Embodiment 4)

[0111] An air separation unit A4 according to embodiment 4 will be described with the aid of FIG. 4. Reference numerals the same as those in embodiment 3 have the same functions, and therefore descriptions thereof may be omitted. The air separation unit A4 comprises a recycling nitrogen line L431b.

[0112] The recycling nitrogen line L431b is a line which branches from the nitrogen gas branch pipeline L431 inside the main heat exchanger 1, draws nitrogen gas out from the cold end of the main heat exchanger 1, and serves to introduce nitrogen gas into the rectification portion 22 or the upper portion 23 of the medium-pressure rectification column 2.

[0113] A valve V2 is provided in the recycling nitrogen line L431b to regulate the start of introduction, stopping, and the introduction amount of the recycling nitrogen gas.

(Embodiment 5)

[0114] An air separation unit A5 according to embodiment 5 will be described with the aid of FIG. 5. Reference numerals the same as those in embodiment 4 have the same functions, and therefore descriptions thereof may be omitted. The air separation unit A5 comprises a second nitrogen booster 17 and a second cooling unit 18.

[0115] The second nitrogen booster 17 is provided in the nitrogen gas branch pipeline L431 upstream from the first nitrogen booster 14, and boosts the pressure of the nitrogen gas to a predetermined pressure.

[0116] The second cooling unit 18 is provided in the nitrogen gas branch pipeline L431 upstream from the first nitrogen booster 14 and downstream from the second nitrogen booster 17, and cools the nitrogen gas pressure-boosted by the second nitrogen booster 17 to a predetermined temperature.

[0117] The second nitrogen booster 17 is driven by means of the oxygen turbine 9.

(Embodiment 6)

[0118] An air separation unit A6 according to embodiment 6 will be described with the aid of FIG. 6. Reference numerals the same as those in embodiment 1 have the same functions, and therefore descriptions thereof may be omitted. The air separation unit A6 is configured without the crude argon column or the crude argon condenser.

[0119] The oxygen pipeline L31 is a pipeline which introduces oxygen into the cold end of the sub-cooler 7 and draws oxygen from the warm end thereof.

(Example)

[0120] The results of a physical simulation of the air separation unit according to embodiment 3 will be presented.

[0121] Feed air at a temperature of 20.0 C., a pressure of 9.4 barA, and a flow rate of 1000 Nm.sup.3/h is introduced from the warm end of the main heat exchanger, cooled to 163 C., and then introduced into the medium-pressure rectification column.

[0122] The medium-pressure rectification column comprises the nitrogen condenser at the top, and although the nitrogen gas at the top is condensed and returned to the medium-pressure rectification column top, a 424 Nm.sup.3/h portion of the liquid nitrogen is drawn out and cooled to 184 C. in the sub-cooler, and supplied to the top of the low-pressure rectification column. An oxygen-rich liquid having an oxygen concentration of 36.4% is drawn at 576 Nm.sup.3/h from the bottom of the medium-pressure rectification column and cooled to 170 C. in the sub-cooler, after which it is introduced at an intermediate stage of the low-pressure rectification column or the low-temperature side of the crude argon condenser.

[0123] Low-pressure nitrogen gas is drawn at 781 Nm.sup.3/h from the top of the low-pressure rectification column, and drawn out at 18 C. and 2.4 barA through the sub-cooler and the main heat exchanger. Oxygen gas having an oxygen concentration of 99% is drawn at 211 Nm.sup.3/h from the bottom of the low-pressure rectification column, heated to 126 C. in the main heat exchanger, and then expanded from 2.5 barA to 1.28 barA by the oxygen turbine. At this time, the oxygen turbine outputs 1.7 kW of work to the outside, and the oxygen gas is cooled to 149 C. The oxygen gas is reintroduced into the main heat exchanger where it is heated and then drawn from the warm end of the main heat exchanger.

[0124] A gas comprising 10% argon and 90% oxygen is introduced at 299 Nm.sup.3/h to the bottom of the crude argon column where it is rectified, and argon is drawn from the column top at 8 Nm.sup.3/h. 291 Nm.sup.3/h of liquid is returned to the low-pressure rectification column from the bottom of the crude argon column.

[0125] Under these conditions, the cold required to liquefy 8 Nm.sup.3/h corresponding to approximately 1% of the low-pressure nitrogen gas in order to produce liquid nitrogen is 1.1 KW, corresponding to 65% of the amount of cold generated by the oxygen turbine. In order to generate this cold, nitrogen gas at 20 C., 10 barA and 75 Nm.sup.3/h is cooled to 119 C., expanded to 2.6 barA by the nitrogen turbine, and cooled to 164 C. This is then merged with low-pressure nitrogen gas supplied from the sub-cooler and is introduced into the main heat exchanger. The nitrogen turbine is capable of generating the cold required for this liquefaction, and therefore enables the heat balance in the air separation unit to be maintained even if liquid nitrogen is drawn out.

[0126] In the configurations of the embodiments above, the inlet temperature of the oxygen turbine is 126 C. while the inlet temperature of the nitrogen turbine is 119 C., thereby enabling gas to be drawn at a temperature 7 C. higher. In the turbine cycle, the amount of work provided to the outside can be increased when the gas is expanded at a higher temperature, but it may no longer be possible to supply the cold required for gas cooling in a low-temperature region. In this embodiment, when additional cold is required by the nitrogen turbine in order to liquefy the product gas, etc. while the base load of cold is supplied by the oxygen turbine, the cold can be efficiently generated using the synergistic effect with the oxygen turbine by expanding the nitrogen gas at a higher temperature than the oxygen turbine inlet temperature.

[0127] This configuration does not employ feed air or medium-pressure nitrogen which contribute to the vapour stream in the medium-pressure rectification column, so the yields of product nitrogen and product argon are unaffected. For example, when feed air is used as a cold source, around 7% of the feed air is expanded by the expansion turbine in order to generate cold, which means that it no longer contributes to rectification, and this affects the yield of nitrogen or argon by around 7%, so this embodiment also has the marked advantage of eliminating such an effect.

(Other Embodiments)

[0128] (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.

[0129] (2) Although not explicitly stated, control valves and gate valves, etc. may be installed in each line.

[0130] (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.

[0131] 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.

[0132] The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

[0133] 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 is defined herein as necessarily encompassing the more limited transitional terms consisting essentially of and consisting of; comprising may therefore be replaced by consisting essentially of or consisting of and remain within the expressly defined scope of comprising.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.

KEY TO SYMBOLS

[0138] 1 . . . Main heat exchanger, 2 . . . Medium-pressure rectification column, 3 . . . Nitrogen condenser, 4 . . . Low-pressure rectification column, 5 . . . Crude argon column, 6 . . . Crude argon condenser, 8 . . . Nitrogen turbine, 9 . . . Oxygen turbine, 10 . . . Nitrogen compressor, 11 . . . Cooling unit