JP4401999B2 - Air separation method and air separation device - Google Patents

Description

  The present invention relates to an air separation method and an air separation device, and in particular, an air separation method and an air separation device for collecting medium pressure product nitrogen gas and medium pressure product oxygen gas by cryogenic liquefaction separation of raw material air. It is about.

  Conventionally, as a method for industrially producing oxygen and nitrogen, generally, a method for producing by low temperature distillation using air as a raw material using a double rectification column (deep cold separation method) and an apparatus used therefor (Air separation device) is known.

  For example, in Patent Document 1, a typical air separation device that collects oxygen gas and nitrogen gas as products is described as a conventional example. This typical air separation apparatus includes a high pressure column having an operating pressure of about 0.6 MPa (6 bar) (hereinafter, absolute pressure unless otherwise specified) and a low pressure column of about 0.14 MPa (1.4 bar). The high pressure column and the low pressure column are thermally coupled.

  A main condenser is installed to liquefy the nitrogen gas at the top of the high-pressure column and vaporize liquid oxygen at the bottom of the low-pressure column, ensuring a temperature difference between the nitrogen gas and liquid oxygen necessary for heat exchange. In order to do this, the above-mentioned operating pressures of the high pressure column 0.6 MPa and the low pressure column 0.14 MPa are required.

  In this air separation apparatus, product oxygen gas is collected from the bottom of the low-pressure tower, and the collection pressure is as low as about 0.14 MPa. Therefore, the product is often used after being increased to a medium pressure by some method. . In order to collect such a medium-pressure product gas, the following method can be considered.

  (1) In order to collect medium-pressure product oxygen gas, there is a method of increasing the pressure of low-pressure oxygen gas generated by the air separation device. This is a method in which a product gas compressor is installed separately from the air separation device, for example, product oxygen gas collected from the air separation device is introduced into the oxygen gas compressor as necessary, and the pressure is increased to a predetermined pressure. (For example, see Patent Document 1). In Patent Document 1, product oxygen gas and product nitrogen gas collected from an air separation device at a low pressure are introduced into respective compressors to increase the pressure to a predetermined pressure.

  This method has the advantage that there are few operational restrictions because each compressor is completely independent of the air separation device. However, the oxygen gas compressor is expensive because it has a special specification compared to an air compressor or the like, and there is a problem that there are many points to be noted in daily maintenance and operation management.

  (2) There is also a method (high pressure rectification method) in which the operating pressure of the entire air separation device is increased according to the pressure required for the product gas. For example, in Non-Patent Document 1, in order to collect product nitrogen gas from a low-pressure column at a medium pressure, a high-pressure column having an operating pressure of about 0.95 MPa (9.5 bar), about 0.35 MPa (3.5 bar), respectively. An example of an air separation device consisting of a low-pressure column is described.

  In the high-pressure rectification method, the operating pressure of the high-pressure column needs to be set higher in accordance with the operating pressure of the low-pressure column. Therefore, the operating pressure of the entire air separation device increases and the power unit of the product increases. There is. For example, in the conventional double rectification column, every time the low pressure column operating pressure is set higher by 0.01 MPa (0.1 bar) in order to ensure the temperature difference in the main condenser, the high pressure column operating pressure is set to 0.025 to It was necessary to increase the pressure by about 0.03 MPa (0.25 to 0.30 bar).

  In addition, fluid other than oxygen gas from the low-pressure column, such as exhaust gas, is also taken out at a higher pressure than that of a normal air separation device, but this exhaust gas is simply decompressed and used for regeneration of the pretreatment adsorber. Therefore, there is a problem that the pressure energy is wasted.

  Patent Document 2 proposes an example of a high-pressure rectification method in which the discharge pressure of the raw material air compressor is 0.7 to 1.7 MPa (7 to 17 bar gauge pressure). In this high-pressure rectification system, a part of the pressure energy is recovered by introducing a part of the pressurized exhaust nitrogen gas taken out from the low-pressure column into the expansion turbine. There was still a problem of loss of pressure energy.

  (3) Further, there is a method (internal pressurization process) in which liquid oxygen of 0.14 MPa (1.4 bar) collected from a low pressure column is compressed to a predetermined pressure using a pump in a liquid state. For example, Patent Document 3 proposes an example of an internal boosting process. According to this, after increasing the pressure of liquid oxygen to about 0.531 MPa (5.31 bar) with a liquid acid pump, the temperature is raised with a main heat exchanger and collected as medium pressure product oxygen gas. In this internal pressurization process, as a heating source for vaporizing pressurized liquid oxygen, for example, part of the raw material air needs to be pressurized to about 1 MPa (10 bar) with a compressor and introduced into the main heat exchanger. .

A device adopting this internal boosting process has many achievements, and is not a special device but a generally adopted device. There is also a merit that increasing the pressure of liquid oxygen with a liquid acid pump has less power than the method (1). However, since not only a liquid acid pump but also a raw material air booster is required, there is a problem that a plurality of rotating machines constituting the air separation device are required and the control becomes complicated.
JP 7-270064 A JP 2004-85032 A JP-A-7-174460 BA Hands, Cryogenic Engineering, Academic Press, 1986, p. 402-404

  As described above, in the methods (1) to (3) for collecting the medium-pressure product gas, the power of the product due to the high cost of the oxygen gas compressor and the high operating pressure of the high-pressure tower. There was a problem that the basic unit was increased, the number of rotating machines was increased and the control was complicated by using a liquid acid pump and a raw material air booster.

  In view of the above-mentioned problems of the prior art, the present invention is easy to control with a simple configuration without using an oxygen gas compressor or a liquid acid pump, reduces the product power consumption, and reduces the medium pressure product nitrogen gas. It is an object of the present invention to provide an air separation method and an air separation device that can collect oxygen and medium-pressure product oxygen gas.

To solve this problem,
The invention according to claim 1 is an air separation method in which raw material air is subjected to cryogenic liquefaction separation to collect medium pressure product nitrogen gas and medium pressure product oxygen gas. A first separation step of separating the nitrogen gas fluid at the top of the tower and the first oxygen-enriched liquefied fluid at the bottom of the tower, and introducing the first oxygen-enriched liquefied fluid into the auxiliary tower, A second separation step for separating an air composition fluid having substantially the same oxygen composition as air; a second oxygen-enriched liquefied fluid at the bottom of the column; a part of the nitrogen gas fluid; and the second oxygen-enriched liquefied product A first indirect heat exchange step of indirect heat exchange with a fluid to condense the nitrogen gas fluid into liquefied nitrogen and simultaneously evaporate the second oxygen enriched liquefied fluid into a second oxygen enriched gas fluid. A portion of the second oxygen-enriched gas fluid is introduced into the low pressure column, A third separation step for separating the enriched gas fluid into liquefied oxygen at the bottom of the column; a compression step for boosting the air composition fluid having the same oxygen composition as air; and the boosted oxygen composition being substantially air. The same air composition fluid and the liquefied oxygen are indirectly heat exchanged to condense the air composition fluid having the same oxygen composition as the air into a liquefied air composition fluid, and at the same time evaporate the liquefied oxygen. A second indirect heat exchanging step for converting the oxygen gas fluid into a product, a product nitrogen gas recovering step for deriving the remainder of the nitrogen gas fluid as the medium-pressure product nitrogen gas after heat recovery, and the oxygen gas fluid after heat recovery. A product oxygen gas recovery step derived as the medium pressure product oxygen gas.

  The invention according to claim 2 is the air separation method according to claim 1, wherein liquefied gas is introduced from outside the system to replenish the coldness necessary for the apparatus.

  The invention according to claim 3 is an air separation device (70) for extracting a medium-pressure product nitrogen gas and a medium-pressure product oxygen gas by subjecting the raw material air to a cryogenic liquefaction separation, wherein the raw material air is compressed and purified. The main heat exchanger (3) for cooling the raw material air by heat exchange with the product gas, and the raw material air cooled by the main heat exchanger (3) are introduced into the lower part of the high-pressure tower (5). A line (4), a high-pressure column (5) for separating the raw air into a nitrogen gas fluid and a first oxygen-enriched liquefied fluid, and the first oxygen-enriched liquefaction at the lower portion of the high-pressure column (5) A pipe (14) for introducing a fluid into the upper part of the auxiliary tower (7), and the first oxygen-enriched liquefied fluid, an air composition fluid having substantially the same oxygen composition as air, and a second oxygen-enriched liquefied fluid A part of the nitrogen gas fluid led out from the upper part of the auxiliary tower (7) and the high pressure tower (5) separated into a condenser ( 2) a condenser (12) provided in the lower part of the auxiliary tower (7) for indirect heat exchange between the pipe (11) to be introduced and a part of the nitrogen gas fluid and the second oxygen-enriched liquefied fluid. ), And the nitrogen gas fluid is indirectly heat exchanged into the liquefied nitrogen by the condenser (12), and then the pipe (13) introduced into the upper portion of the high pressure column (5), and the second oxygen-enriched liquefaction. Lines (15, 18) for introducing a part of the second oxygen-enriched gas fluid obtained by evaporating the fluid by indirect heat exchange into the low-pressure column (20), and the second oxygen-enriched gas fluid, A low-pressure column (20) that separates into three oxygen-enriched gas fluid and liquefied oxygen, and a part of the air composition fluid that is derived from the upper part of the auxiliary column (7) and that has substantially the same oxygen composition as air, Pipe lines (17, 31) to be introduced into the booster (51) and an air composition fluid in which the oxygen composition is substantially the same as air An air pressure booster (51) to be pressurized, and a pipe (32) for introducing an air composition fluid having the same oxygen composition as that of the air boosted by the air pressure booster (51) into the evaporator (21), A vaporizer (21) provided at the lower portion of the low-pressure column (20) for indirectly heat-exchanging the liquefied oxygen with an air composition fluid having the same oxygen composition as that of air, and the oxygen composition is substantially the same. A pipe line (33) for introducing a liquefied air composition fluid obtained by indirect heat exchange of an air composition fluid that is the same as air into the upper portion of the low-pressure tower (20), and the remainder of the nitrogen gas fluid are used as the high-pressure tower. (5) A pipe (6) that is led out from the upper part and collected as the medium-pressure product nitrogen gas, and a pipe that leads out the oxygen gas fluid from the lower part of the low-pressure column (20) and collects it as the medium-pressure product oxygen gas An air separation device characterized by providing a passage (19) is there.

  The invention according to claim 4 is the air separation device according to claim 3, further comprising a liquefied gas introduction pipe (45) for introducing liquefied gas from outside the air separation device (70).

  According to the air separation method and the air separation apparatus of the present invention, since the high pressure column (5) and the low pressure column (20) are not directly thermally coupled, the operating pressure of the low pressure column (20) can be increased. It is not necessary to increase the operating pressure of the high-pressure tower (5) as much as before. As a result, the operating pressure of the high-pressure tower (5) can be made lower than that of the conventional apparatus, and the product power consumption can be reduced.

  Further, since the high-pressure column (5) and the low-pressure column (20) are not directly thermally coupled, the operating pressure of the low-pressure column (20) can be increased without using an oxygen gas compressor or a liquid acid pump. The medium-pressure product oxygen gas can be sampled with a simple configuration and a simple control.

  Hereinafter, an example of a system diagram of an air separation device according to an embodiment of the present invention will be shown in the drawings and described in detail.

  FIG. 1 is a system diagram of an air separation device (70) according to the present embodiment. The air separation device (70) of the present embodiment includes a main heat exchanger (3), a feed air introduction line (4), a high-pressure tower (5), a product nitrogen gas collection line (6), and an auxiliary A tower (7), a condenser (12), a nitrogen gas fluid introduction line (11) to the condenser, a liquefied nitrogen introduction line (13) to the high pressure tower, and a first oxygen rich to the auxiliary tower Liquefied liquefied fluid introduction line (14), low pressure column (20), evaporator (21), second oxygen-enriched gas fluid introduction line (15, 18) to the low pressure column, and air booster (51), the air composition fluid introduction line (17, 31) to the air booster, the product oxygen gas collection line (19), the expansion turbine (40), and the second oxygen enrichment to the expansion turbine Gas fluid, third oxygen-enriched gas fluid introduction line (30, 24, 26), air composition fluid introduction line (32) to the evaporator, and liquefied air set to the low pressure column Fluid inlet conduit (33), and since the liquefied gas introduction pipe line from the outside of the air separation unit (45) is schematically configured.

  First, the raw material air sucked from the atmosphere is pressurized to a predetermined pressure by the raw material air compressor (1), cooled by the cooler (8), and then introduced into the adsorption tower (2, 2). In the adsorption tower (2, 2), impurities such as moisture and carbon dioxide in the raw material air are removed. The raw material air from which impurities have been removed is introduced into the main heat exchanger (3).

  The raw air cooled to the vicinity of the liquefaction point in the main heat exchanger (3) is introduced from the raw air introduction pipe (4) to the lower part of the high-pressure tower (5). In the high-pressure column (5), the auxiliary column (7) and the low-pressure column (20) described later, a rectification stage (shelf), a regular filler, an irregular filler, or the like is provided.

  The raw material air introduced into the high pressure column (5) makes countercurrent contact with the liquefied nitrogen as the descending liquid while rising in the high pressure column (5), and the composition of the low boiling point component is increased by distillation. ) Separated into a nitrogen gas fluid at the top and a first oxygen-enriched liquefied fluid having an oxygen concentration of about 35% at the bottom of the high pressure column (5).

  The nitrogen gas fluid generated at the top of the high-pressure tower (5) is led out from the upper part of the high-pressure tower (5), and partly passes through the product nitrogen gas collection line (6) and is heated in the main heat exchanger (3). It is collected, heated to room temperature, and collected as medium-pressure product nitrogen gas.

  The remainder of the nitrogen gas fluid generated at the top of the high-pressure tower (5) is introduced into the condenser (12) provided at the lower part of the auxiliary tower (7) through the nitrogen gas fluid introduction line (11). In the condenser (12), indirect heat exchange is performed between the nitrogen gas fluid and a second oxygen-enriched liquefied fluid generated at the bottom of the auxiliary tower (7) described later, and the nitrogen gas fluid is condensed to liquefied nitrogen. And the second oxygen-enriched liquefied fluid evaporates into a second oxygen-enriched gas fluid.

  This liquefied nitrogen is introduced into the upper portion of the high-pressure column (5) as a reflux liquid through the liquefied nitrogen introduction pipe (13). In the high-pressure column (5), this liquefied nitrogen descends in the high-pressure column (5) as a descending liquid and makes countercurrent contact with the raw material air that is the ascending gas, and the composition of high-boiling components increases accordingly. A first oxygen-enriched liquefied fluid is produced at the bottom of the column (5).

  The first oxygen-enriched liquefied fluid produced at the bottom of the high-pressure tower (5) is led out from the pipe (14) and passes through the supercooler (9) and the pressure reducing valve (10) as an auxiliary tower ( 7) Introduced at the top.

  In the auxiliary column (7), countercurrent contact occurs between the first oxygen-enriched liquefied fluid that is the reflux liquid and the second oxygen-enriched gas fluid that rises in the auxiliary column (7) described later, and as a result of distillation, A fluid (air composition fluid) having almost the same oxygen composition as air is generated at the top of the auxiliary tower (7), and a second oxygen-enriched liquefied fluid having an oxygen concentration of about 48% is generated at the bottom of the auxiliary tower (7). To do.

  The second oxygen-enriched liquefied fluid is indirectly heat exchanged with the nitrogen gas fluid in the condenser (12) provided at the lower part of the auxiliary tower (7), and evaporated to become the second oxygen-enriched gas fluid. (7) Go up inside.

  A part of the second oxygen-enriched gas fluid is bisected after being led out from the pipe (15), and most of the second oxygen-enriched gas fluid is supplied from the second oxygen-enriched gas fluid introduction pipe (18) to the low pressure column (20). To be introduced.

  The air composition fluid generated at the top of the auxiliary tower (7) is led out from the pipe (17) and divided into two after passing through the subcooler (9). The pressure is raised to room temperature via the exchanger (50) and then introduced into the air pressure booster (51). Thereafter, the pressure is increased by the air pressure booster (51), and then cooled by passing through the cooler (52) and the heat exchanger (50), from the air composition fluid introduction pipe (32), and the lower part of the low pressure column (20) Is introduced into the evaporator (21) provided as a heating source.

  The remainder of the air composition fluid passes through the valve (27) and the discharge pipe (29), exchanges heat with the raw air in the main heat exchanger (3), and is then discharged as the exhaust gas 1.

  In the evaporator (21) provided at the lower part of the low-pressure column (20), indirect heat exchange is performed between the pressurized air composition fluid and liquefied oxygen generated at the bottom of the low-pressure column (20), which will be described later. The fluid condenses into a liquefied air composition fluid and the liquefied oxygen evaporates into an oxygen gas fluid.

  The liquefied air composition fluid is led out from the pipe (33) and is introduced into the upper portion of the low-pressure column (20) as a reflux liquid via the supercooler (22) and the pressure reducing valve (23).

  In the low pressure column (20), the liquefied air composition fluid which is the reflux liquid introduced into the upper portion, the second oxygen-enriched gas fluid introduced from the pipe line (18), and the oxygen rising in the low pressure column (20). Countercurrent contact with the gas fluid occurs, and as a result of distillation, a third oxygen-enriched gas fluid is present at the top of the low pressure column (20), and liquefied oxygen having an oxygen concentration of about 95% is present at the bottom of the low pressure column (20). Generate.

  Part of the oxygen gas fluid generated by indirect heat exchange in the evaporator (21) passes through the product oxygen gas collection line (19) provided at the lower part of the low pressure column (20), and passes through the main heat exchanger (3 ), The temperature is raised to room temperature and collected as medium-pressure product oxygen gas.

  The third oxygen-enriched gas fluid produced at the top of the low pressure column (20) is led out from the line (30). This third oxygen-enriched gas fluid merges with the remainder of the second oxygen-enriched gas fluid led out from the pipe (15) below the auxiliary tower (7) in the pipe (24). The second oxygen-enriched gas fluid and the third oxygen-enriched gas fluid pass through the supercooler (22) and the main heat exchanger (3), and partly from the pipe (26) to the expansion turbine (40 ) To generate the cold required for the air separation device (70). Thereafter, the pipe (28) joins the discharge pipe (29) and is discharged as the exhaust gas 1.

  The remainder of the second oxygen-enriched gas fluid and the third oxygen-enriched gas fluid is discharged as exhaust gas 2 from the discharge line (25).

  In addition, a part or all of the cold necessary for the air separation device (70) may be replenished with cold by introducing a liquefied gas from outside the air separation device (70). In the present embodiment, a liquefied gas introduction line (45) is provided on the upper portion of the low-pressure column (20), and liquid air, liquid nitrogen, or liquid oxygen can be supplied therefrom. The liquefied gas introduction line (45) may be provided in the high-pressure column (5), the auxiliary column (7), the low-pressure column (20), a pipe introduced into these columns, or the like. When all of the cooling required for the air separation device (70) is performed by introducing liquefied gas from the outside of the air separation device (70), the expansion turbine (40) is unnecessary. In that case, the fluid in the conduit (24) can be discharged from the conduit (25).

  In addition, if necessary, pipes (60, 61) may be provided at the lower part of the auxiliary tower (7) and the low-pressure tower (20) to take out the liquid oxygen for safety.

  In the present embodiment, the main heat exchanger (3) and the heat exchanger (50) are provided separately, but these heat exchangers may be integrated or divided for each fluid. Good.

  Next, it will be described in the present embodiment that it is not necessary to increase the operating pressure of the high-pressure tower (5) as much as in the past.

  In this air separation device (70), an auxiliary tower (7) is provided, and the second oxygen-enriched liquefied fluid produced at the bottom of the auxiliary tower (7) is used as an auxiliary to liquefy the nitrogen gas at the top of the high-pressure tower (5). The air composition fluid generated at the top of the tower (7) is characterized in that it is used for evaporation of liquefied oxygen at the bottom of the low pressure tower (5).

  For example, if the pressure required for the product oxygen gas is 0.3 MPa (3 bar), the operating pressure of the auxiliary tower (7) is also about 0.3 MPa, and the second oxygen-enriched liquefaction produced at the bottom of the auxiliary tower (7). The saturation temperature of the fluid will be about 97K. If the temperature difference required for the condenser (12) for heat exchange between the nitrogen gas and the second oxygen-enriched liquefied fluid is 2K, the temperature required for the nitrogen gas fluid at the top of the high pressure column (5) is about 99K, and the operating pressure required for the high pressure column (5) is 0.69 MPa (6.9 bar).

  On the other hand, in the conventional air separation apparatus described in FIG. 1 of Patent Document 1, for example, liquefied oxygen having an oxygen concentration of about 95% is generated at the bottom of the low-pressure column. The saturation temperature of this liquefied oxygen at 0.3 MPa (3 bar) is about 102K. Therefore, in the condenser (41) shown in FIG. 1 of Patent Document 1, if the temperature difference required for heat exchange between the oxygen fluid and the nitrogen fluid is 2K, the temperature required for the nitrogen gas fluid at the top of the high-pressure tower is: About 104K. As a result, the operating pressure required for the high-pressure column shown in Patent Document 1 is 0.99 MPa (9.9 bar).

  That is, when 0.3 MPa product oxygen gas is required, the discharge pressure of the raw material air compressor (1) can be reduced by about 0.3 MPa (= 0.99 MPa−0.69 MPa) by using the present invention. And the power consumption of the product can be reduced.

  Moreover, after taking out an air composition fluid from a pipe line (17) using an auxiliary tower (7), and compressing this with an air booster (51), it is to the evaporator (21) below a low pressure tower (20). Is introduced from the pipe (32). By using the auxiliary tower (7), since it is the air composition fluid that is taken out, a normal air compressor can be used as the air booster (51) without using a special oxygen gas compressor. Costs and maintenance effort can be reduced.

Moreover, using an air composition fluid as a heating source for the evaporator (21) at the lower part of the low-pressure column (20) is advantageous in terms of process.
If the operating pressure of the low pressure column (20) is 0.3 MPa (3 bar), the saturation temperature of the oxygen fluid at the bottom of the low pressure column is about 102K. If the temperature difference required for the evaporator (21) is 2K, the saturation temperature required for the heating source of the evaporator (21) is about 104K. When an air composition fluid is used as a heating source of the evaporator (21), the pressure needs to be about 0.85 MPa from the saturation temperature.

  On the other hand, when nitrogen gas is used as the heating source of the evaporator (21), the operating pressure needs to be about 0.99 MPa from the saturation temperature. That is, by using “air composition fluid” as the heating source of the evaporator (21), the discharge pressure of the air booster (51) can be reduced, and a general air compressor as a booster can be used. Benefits that can be adopted.

  In the present specification, the “air composition fluid” means a fluid that can be used by a general air compressor for compression. Therefore, it is not limited to the meaning that the composition completely coincides with the normal atmospheric composition. In particular, the oxygen composition may vary somewhat depending on the compressor manufacturer and model number employed.

  Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited to the following examples.

[Example 1]
Nitrogen gas and oxygen gas were produced using the air separation device (70) shown in FIG. The raw material air 3630Nm ³ / h from which dust and the like have been removed by a filter (not shown) is compressed to about 0.73 MPa (7.3 bar) by the raw material air compressor (1), and then the moisture is absorbed by the adsorber (2, 2). Removed carbon dioxide. It was cooled to near the dew point with the main heat exchanger (3) and introduced into the lower part of the high-pressure tower (5).

From the upper part of the high-pressure column (5), 0.69 MPa (6.9 bar) of product nitrogen gas 1450 Nm ³ / h was taken out, heated to room temperature with the main heat exchanger (3), and then collected as product nitrogen gas.

A first oxygen-enriched liquefied fluid 2180 Nm ³ / h having an oxygen concentration of about 35% is taken out from the bottom of the high-pressure tower (5), cooled by a supercooler (9), and then supplied to the upper part of the auxiliary tower (11) as a reflux liquid. did.

The auxiliary tower (11) is operated at about 0.3 MPa (3 bar), and the first oxygen-enriched liquefied fluid 2180 Nm ³ / h, which is the reflux liquid, is supplied, and the oxygen composition at the top of the auxiliary tower (7) is substantially equal to air. The same air composition fluid 1160 Nm ³ / h and a second oxygen-enriched liquefied fluid 1020 Nm ³ / h having an oxygen concentration of about 48% at the bottom of the auxiliary tower (7) were separated.

  The air composition fluid was taken out from the pipe line (17), heated to room temperature with a heat exchanger (50), and then pressurized to about 0.85 MPa (8.5 bar) with an air pressure booster (51). The pressurized air composition fluid was cooled again by the heat exchanger (50) and introduced into the evaporator (21) at the lower part of the low-pressure column (20).

The low pressure column (20) is operated at about 0.3 MPa (3 bar), an oxygen gas of 465 Nm ³ / h with an oxygen concentration of about 0.3 MPa (3 bar) is extracted from the lower portion of the low pressure column (20), and the main heat exchanger After raising the temperature in (3), it was collected as product oxygen gas.

  Further, the third oxygen-enriched gas fluid is taken out from the top of the low-pressure column (20) and introduced into the expansion turbine (40) together with a part of the second oxygen-enriched gas fluid from the lower portion of the auxiliary column (7). The coldness required for the air separation device (70) was generated.

  From the above results, according to the air separation method and the air separation apparatus of the present invention, it is confirmed that the medium pressure product nitrogen gas and the medium pressure product oxygen gas can be sampled and the operating pressure of the high pressure column (5) can be lowered than before. It was done.

It is a systematic diagram of the air separation device concerning an embodiment of the invention.

Explanation of symbols

3 Main heat exchanger 4 Raw material air introduction line 5 High pressure column 6 Product nitrogen gas sampling line 7 Auxiliary tower 11 Nitrogen gas fluid introduction line to condenser 12 Condenser 13 Liquid nitrogen introduction line to high pressure column 14 Auxiliary First oxygen-enriched liquefied fluid introduction line to the tower 15, 18 Second oxygen-enriched gas fluid introduction line to the low-pressure tower 17, 31 Air composition fluid introduction line to the air booster 19 Product oxygen gas sampling pipe Route 20 Low-pressure tower 21 Evaporator 32 Air composition fluid introduction line to the evaporator 33 Liquefied air composition fluid introduction line to the low-pressure tower 45 Liquefied gas introduction line from the outside of the air separation device 51 Air booster 70 Air Separation device

Claims (4)

In the air separation method in which raw material air is liquefied and separated to collect medium pressure product nitrogen gas and medium pressure product oxygen gas,
A first separation step of introducing the compressed, purified, and cooled raw material air into a high-pressure tower and separating it into a nitrogen gas fluid at the top of the tower and a first oxygen-enriched liquefied fluid at the bottom of the tower;
A second separation step of introducing the first oxygen-enriched liquefied fluid into the auxiliary tower and separating it into an air composition fluid whose oxygen composition at the top of the tower is substantially the same as air and a second oxygen-enriched liquefied fluid at the bottom of the tower When,
A part of the nitrogen gas fluid and the second oxygen-enriched liquefied fluid are indirectly heat exchanged to condense the nitrogen gas fluid into liquefied nitrogen, and at the same time evaporate the second oxygen-enriched liquefied fluid. A first indirect heat exchange step into a second oxygen-enriched gas fluid;
A third separation step of introducing a part of the second oxygen-enriched gas fluid into the low-pressure column and separating it into a third oxygen-enriched gas fluid at the upper part of the tower and liquefied oxygen at the lower part of the tower;
A compression step of pressurizing an air composition fluid whose oxygen composition is substantially the same as air;
An indirect heat exchange is performed between the air composition fluid whose oxygen composition is substantially the same as air and the liquefied oxygen, and the air composition fluid whose oxygen composition is substantially the same as air is condensed to a liquefied air composition fluid. And at the same time, a second indirect heat exchange step of evaporating the liquefied oxygen into an oxygen gas fluid;
A product nitrogen gas recovery step of deriving the remainder of the nitrogen gas fluid as the medium pressure product nitrogen gas after heat recovery;
And a product oxygen gas recovery step of deriving the oxygen gas fluid as the medium pressure product oxygen gas after heat recovery.   The air separation method according to claim 1, wherein liquefied gas is introduced from outside the system to replenish the coldness necessary for the apparatus. An air separation device (70) for cryogenic liquefaction separation of raw material air to collect medium pressure product nitrogen gas and medium pressure product oxygen gas,
A main heat exchanger (3) for heat-exchanging the compressed and purified raw material air and product gas to cool the raw material air;
A conduit (4) for introducing the raw material air cooled in the main heat exchanger (3) into the lower portion of the high-pressure tower (5);
A high pressure column (5) for separating the raw material air into a nitrogen gas fluid and a first oxygen-enriched liquefied fluid;
A line (14) for introducing the first oxygen-enriched liquefied fluid at the lower part of the high-pressure tower (5) to the upper part of the auxiliary tower (7);
An auxiliary tower (7) for separating the first oxygen-enriched liquefied fluid into an air composition fluid having an oxygen composition substantially the same as air and a second oxygen-enriched liquefied fluid;
A pipe line (11) for introducing a part of the nitrogen gas fluid derived from the upper part of the high-pressure column (5) into a condenser (12);
A condenser (12) provided at a lower portion of the auxiliary tower (7) for indirectly heat-exchanging a part of the nitrogen gas fluid and the second oxygen-enriched liquefied fluid;
After this nitrogen gas fluid is indirectly heat exchanged in the condenser (12) to liquefied nitrogen, a pipe line (13) introduced into the upper part of the high-pressure tower (5),
Lines (15, 18) for introducing a part of the second oxygen-enriched gas fluid obtained by evaporating the second oxygen-enriched liquefied fluid by indirect heat exchange into the low-pressure column (20);
A low pressure column (20) for separating the second oxygen-enriched gas fluid into a third oxygen-enriched gas fluid and liquefied oxygen;
Pipes (17, 31) for introducing an air composition fluid derived from the upper part of the auxiliary tower (7) and having the same oxygen composition as that of air into an air booster (51);
An air booster (51) for boosting an air composition fluid whose oxygen composition is substantially the same as air;
A pipe line (32) for introducing an air composition fluid having the oxygen composition boosted by the air pressure booster (51) substantially the same as air into the evaporator (21);
A vaporizer (21) provided at the lower part of the low-pressure column (20) for indirectly heat-exchanging the liquefied oxygen with an air composition fluid having the same oxygen composition as that of air;
A conduit (33) for introducing a liquefied air composition fluid obtained by indirect heat exchange of an air composition fluid having substantially the same oxygen composition as air into the upper portion of the low pressure column (20);
A conduit (6) for extracting the remainder of the nitrogen gas fluid from the upper part of the high-pressure tower (5) and collecting it as the medium-pressure product nitrogen gas;
An air separation apparatus comprising: a pipe line (19) for extracting an oxygen gas fluid from a lower part of the low pressure column (20) and collecting the oxygen gas fluid as the medium pressure product oxygen gas. The air separation device according to claim 3, further comprising a liquefied gas introduction pipe (45) for introducing liquefied gas from outside the air separation device (70).

Images