CN1764813A - Air separator - Google Patents

Abstract

The present invention provides an air separator oxygen gas capable of producing oxygen gas in an energy-saving manner, thereby remarkable downsizing can be realized. The air separator includes an air compressor (1) for taking in air from the outside and compressing it, first adsorption towers (2,3) for concentrating oxygen gas that is contained in the air compressed by the air compressor (1), an oxygen/air compressor (11) for further compressing oxygen-rich compressed air (X) passed through the first adsorption towers (2,3), a main heat exchanger (21) for cooling oxygen-rich compressed air (Y) passed through the oxygen/air compressor (11), and a high-pressure rectification tower (23) and a low-pressure rectification tower (28) for taking out oxygen gas by separating the oxygen-rich compressed air (Y) passed through the main heat exchanger (21) so as to be cooled to a low temperature by utilizing differences in boiling points of elemental gases.

Description

air separation unit

technical field

The present invention relates to an air separation device capable of energy-saving production of oxygen and capable of remarkably downsizing the device.

Background technique

Generally, nitrogen (GN ₂ ), oxygen (GO ₂ ), argon (Ar) etc. are produced through the following process as shown in Figure 6: use air as raw material to compress it with air compressor 61, and then introduce it into the adsorption tower 62, absorb and remove water (H ₂ O), carbon dioxide (CO ₂ ) and hydrocarbon gas (C _n M _m ) in the compressed air, and then pass through the main heat exchanger (not shown) in the cold box 63 Exchange heat with refrigerant, cool to ultra-low temperature, and then cryogenically separate in a rectification tower (not shown), produce product gas (nitrogen, oxygen, etc.), pass it through the above-mentioned main heat exchanger to raise its temperature to around room temperature. In addition, the exhaust gas discharged from the cold box 63 is used for regeneration of the adsorption tower 62 (see, for example, JP-A-8-261644). In FIG. 6, 64 is a regeneration/exhaust heater.

In such an air separation plant, an air compressor 61 with a discharge pressure of about 5 kg/cm ² G [0.5 MPaG (gauge pressure)] is usually used as the air compressor 61 , but when the air compressor 61 is to be used to manufacture 10000 m ³ / When h (standard) oxygen, the amount of air it needs, because the composition ratio (volume %) of each component gas of air is oxygen 20.9%: nitrogen 78.1%: argon 0.9%, therefore when making the recovery efficiency of oxygen be 97% When using air volume = (10000÷0.209)÷0.97 to calculate theoretically, an air volume of about 50000m ³ /h (standard) is necessary. For this reason, it is necessary to use the adsorption tower 62, the main heat exchanger, the rectification tower, etc. corresponding to the above-mentioned necessary air volume, and the whole apparatus becomes large. In addition, when producing 10000 m ³ /h (standard) of oxygen, the necessary compression power of the air compressor 61 (this compression power is usually obtained by multiplying the value of the above-mentioned necessary air volume by about 0.09) is about 4500 kW, Since the driving power of the regeneration/exhaust heater 64 of the adsorption tower 62 is about 500 kW, a large power of about 5000 kW in total is required, and huge energy is required for the production of oxygen.

The present invention has been made in view of such facts, and its object is to provide an air separation device capable of energy-saving production of oxygen and capable of greatly reducing the size of the cryogenic separation mechanism (cold box (cold box) and its internal equipment).

Contents of the invention

In order to achieve the above object, the air separation device of the present invention adopts the following structure, which comprises: an air compression device that obtains air from the outside and compresses it at a low pressure; an oxygen concentration device that concentrates oxygen in the compressed air compressed by the air compression device; device; an oxygen air compressing device for further compressing the compressed air X containing high-concentration oxygen passing through the oxygen concentrator; a heat exchanger for cooling the compressed air Y containing high-concentration oxygen passing through the oxygen concentrating device; A rectification tower for extracting oxygen by separating the compressed air Y containing high concentration of oxygen cooled to a low temperature by using the difference in boiling point of each component gas.

That is, the air separation device of the present invention uses an air compression device to compress the raw air to a low pressure, and is connected to the air compression device to install an oxygen concentrator for concentrating the oxygen in the compressed air, so as to increase the oxygen concentration in the raw air. It is supplied to the rectification column through an oxygen air compression device and a heat exchanger. Therefore, when producing the same amount of oxygen, etc., energy can be greatly saved, and by greatly reducing the flow rate of each device after the oxygen concentrator, they can be reduced in size to less than half of the past. As a result, significant miniaturization of the entire device can be achieved. Here, the above-mentioned low pressure means that it is lower than the compression pressure caused by the oxygen air compressor, and generally refers to 1/3 or less, preferably 1/5 or less, more preferably 1/10 or less of the compression pressure of the oxygen air compressor.

In addition, when the above-mentioned oxygen concentrator is used as an adsorption tower containing an adsorbent for absorbing nitrogen in the compressed air, and the purpose is to use the above-mentioned adsorbent to remove impurities such as moisture in the compressed air, through the action of the adsorbent of the above-mentioned adsorption tower, It can concentrate the oxygen in the compressed air and remove the moisture in the compressed air, so the object compressed by the oxygen air compression device connected to the oxygen enrichment device becomes drier and can reduce the compression power even more.

In addition, when a removal device for removing impurities in the compressed air Y containing high concentration of oxygen is installed between the oxygen air compressor and the heat exchanger, it is possible to remove hydrocarbons and moisture remaining in a small amount in the compressed air Y containing high concentration of oxygen , _NOx, etc., as raw material air can also use poor quality air such as air along the coast (a lot of sodium ions) or air along roads (a lot of car exhaust).

In addition, when a part of the compressed air compressed by the air compressing device is directly supplied to the introduction path that introduces the compressed air X containing high-concentration oxygen passing through the oxygen concentrator into the oxygen air compressing device without passing through the oxygen concentrating device, in the above-mentioned In the introduction path, a part of the compressed air that is directly supplied to the above-mentioned introduction path after passing through the air compression device, and a part of the compressed air that is passed through the air compression device and then introduced into the oxygen concentrator, where it becomes compressed air X containing high-concentration oxygen, is then supplied to the above-mentioned introduction. The remaining part of the compressed air in the path merges, thereby reducing the oxygen concentration in the compressed air X containing high-concentration oxygen. Therefore, when it is desired to reduce the amount of oxygen production, by adjusting the amount of compressed air directly supplied to the above-mentioned introduction path, to be able to cope.

A brief description of the drawings

Fig. 1 is a block diagram showing an embodiment of the air separation plant of the present invention.

Fig. 2 is a block diagram showing another embodiment of the air separation plant of the present invention.

Fig. 3 is a structural diagram showing still another embodiment of the air separation plant of the present invention.

Fig. 4 is a structural diagram showing still another embodiment of the air separation plant of the present invention.

Fig. 5 is a structural diagram showing still another embodiment of the air separation plant of the present invention.

FIG. 6 is a configuration diagram showing a conventional example.

Best way to implement the invention

Figure 1 shows an embodiment of the air separation plant of the present invention. In the figure, 1 is an air compressor (air compression device) that collects and compresses the atmosphere, and its discharge pressure is set to a low pressure of about 0.1 kg/cm ² G [0.01 MPaG (gauge pressure)]. 1a is the first delivery pipe for sending the compressed air passing through the air compressor 1 to the first adsorption towers 2 and 3 . The first adsorption towers (oxygen concentrators) 2 and 3 are filled with an adsorbent such as silica gel on the upstream side and a molecular sieve adsorbent developed by the present inventors (AW0203 manufactured by Ea Uo-ta Co., Ltd.) on the downstream side. The first adsorption towers 2 and 3 are operated by alternately switching between adsorption and regeneration in pairs of two. In this embodiment, the composition ratio (volume %) of each component gas in the low-pressure compressed air passing through the air compressor 1 is made such as Oxygen 50%: nitrogen 47.5%: argon 2.5%, the concentration of oxygen in the compressed air is concentrated from 20.9% by volume to 50% by volume. The first adsorption towers 2 and 3 absorb and remove water (H ₂ O), carbon dioxide (CO ₂ ) and hydrocarbon gas (C _n H _m ) in the compressed air through the action of the adsorbent while concentrating. 4 is a vacuum pump for the regeneration and exhaust of the first adsorption towers 2 and 3, and 4a is a first discharge pipe, which discharges the waste gas adsorbed by the adsorbents of the first adsorption towers 2 and 3 to the atmosphere and regenerates the adsorbents. Like this, by the 1st adsorption tower 2,3 and the pipeline that band switching valve 6a, 6b, 8a, 8b thereof and the system that vacuum pump 4 constitute, become VSA (vacuum rotary adsorption) membrane separation, one the 1st adsorption tower 2 (3 ) during the adsorption operation, the other first adsorption tower 3(2) is regenerated by the vacuum suction of the vacuum pump 4. Between above-mentioned air compressor 1 and the 1st adsorption tower 2,3, be provided with the water separator (not shown) that removes the moisture in the compressed air that is compressed by air compressor 1, and be provided with according to occasion will pass through this Compressed air cooled flon cooler (not shown) for the water separator. In addition, in this embodiment, the above-mentioned system becomes VSA, but membrane separation of PSA (Pressure Swing Adsorption), TSA (Temperature Swing Adsorption) may also be used. In the figure, 6a, 6b, 7a, 7b, 8a, and 8b are on-off valves for making the first adsorption towers 2, 3 alternately perform adsorption and regeneration operations.

11 is a small oxygen air compressor that further compresses the compressed air X containing high-concentration oxygen that has passed through the first adsorption towers 2 and 3 (in order to make the circulating gas less than 1/2 of the conventional one, the small size of 1/2 or less ie enough) [Oxygen Air Compression Unit]. In this embodiment, as the above-mentioned oxygen air compressor 11, a small oxygen air compressor (oil-free centrifugal compressor: discharge pressure 5 kg/cm ² G [0.5 MPaG (Table pressure)] around the oxygen air compressor). The oxygen air compressor 11 is a mechanism without oil or the like in order to prevent an explosion when the compressed air X containing high-concentration oxygen is further compressed. 11a is a second delivery pipe for sending the compressed air Y containing high-concentration oxygen passing through the oxygen air compressor 11 to the second adsorption towers 12 and 13 . 12, 13 Small-sized second adsorption towers in a set of two that are filled with adsorbents such as commercially available molecular sieves and alternately perform adsorption and regeneration (small size of 1/2 or less of conventional adsorption towers) , play the role of adsorbing and removing trace residual water, carbon dioxide, C _n M _m and NO _x in the compressed air Y containing high-concentration oxygen further compressed by the oxygen air compressor 11. 14 is the second discharge pipe, which plays the role of discharging the exhaust gas that has completed the regeneration function in the second adsorption towers 12 and 13 to the atmosphere. The system constituted by the second adsorption towers 12, 13 and their pipelines with on-off valves 16a, 16b, 19a, 19b is called TSA. In the figure, 16a, 16b, 17a, 17b, 18a, 18b, 19a, 19b are on-off valves for making the second adsorption towers 12, 13 alternately perform adsorption and regeneration operation.

21 is the main heat exchanger, including fin type, etc., which cools the compressed air Y containing high-concentration oxygen that has absorbed and removed trace amounts of water and carbon dioxide through the second adsorption towers 12 and 13 to an ultra-low temperature. This main heat exchanger 21 is also reduced in size to about 1/2 or less, since it is 1/2 of the throughput of the circulating gas in the past. Reference numeral 22 is a supply pipe for sending the compressed air Y containing high-concentration oxygen cooled to an ultralow temperature by the main heat exchanger 21 to the lower part of the high-pressure rectification column 23 . This high-pressure rectification column (tray or packed column) 23 has a capacity of 1/2 or less because the gas flowing therein is reduced to 1/2 or less than conventional ones, and the capacity is also reduced to 1/2 or less in size. In the high-pressure rectification column 23, among the high-concentration oxygen-containing compressed air Y sent from the supply pipe 22, liquid-type high-concentration oxygen-containing liquid air 24 accumulates at the bottom, and nitrogen gas rises to the upper part. Part of the nitrogen gas rising to the upper part is introduced into the condenser (condenser) 30 at the lower part of the low-pressure rectification column 28 through the first reflux pipe 31 , and the rest becomes the driving gas of the expansion turbine 37 through the nitrogen gas extraction pipe 26 . And, the nitrogen gas introduced into the condenser 30 is liquefied there to become liquid nitrogen, returns to the upper part of the high-pressure rectification tower 23 as a reflux liquid through the second reflux pipe 32, and flows downward in the high-pressure rectification tower 23. , convectively contact with the gas-type high-concentration oxygen-containing compressed air Y rising from below, and liquefy the high-boiling-point component gas (oxygen gas) of the high-concentration oxygen-containing compressed air Y to flow downward. Therefore, the liquid-type high-concentration oxygen-containing liquid air 24 accumulated at the bottom is further enriched in oxygen, and the low-boiling point component gas (nitrogen gas) rises to the upper part of the high-pressure rectification column 23 . The nitrogen gas taken out from the nitrogen gas take-out pipe 26 is sent to the main heat exchanger 21, and after cooling the compressed air passing through the main heat exchanger 21, it is supplied to the expansion turbine 37 through the first connecting pipe 26a, as described above. , becomes the driving source of the expansion turbine 37 to generate cold. 38 is a bypass passage with an on-off valve 38a. That is, the nitrogen gas introduced into the expansion turbine 37 through the nitrogen gas extraction pipe 26 and the first connecting pipe 26a with the on-off valve 26b expands inside, and by performing thermodynamic external work, it becomes significantly low temperature, thereby generating the necessary cold for the device. In this state, it enters the main heat exchanger 21 through the second connecting pipe 37a, where it exchanges heat with the raw material air, and gives the generated cold to the raw material air, which itself becomes normal temperature, and most of it is discharged as exhaust gas through The pipe 37b is discharged, and a part becomes regeneration gas of the adsorbent of the second adsorption towers 12 and 13 via the branch pipe 40 . The role of this branch pipe 40 is to supply the introduced nitrogen gas to the first pipe 42 with a heater 41 or the second pipe 43 without a heater. 42 or the nitrogen gas in the second pipe 43 is supplied to the second adsorption towers 12 and 13 as adsorbent regeneration gas.

28 is the low-pressure rectification tower (tray type or packed column type) that is arranged on the top of the high-pressure rectification tower 23, and the liquid air 24 that is accumulated in the bottom of the high-pressure rectification tower 23 and contains high-concentration oxygen passes through the belt expansion valve 29a The feeding tube 29 is sent in. A condenser 30 is provided at the bottom of the low-pressure rectification column 28 , and a part of the nitrogen gas taken out from the high-pressure rectification column 23 is introduced there through a first reflux pipe 31 . This nitrogen gas acts to heat the liquid oxygen (LO ₂ : purity of about 99.7% by volume) 34 stored at the bottom of the low-pressure rectification tower 28 to vaporize the liquid oxygen 34, and itself is cooled by the coldness of the liquid oxygen 34. A part of the liquefied liquid is refluxed to the upper part of the high-pressure rectification column 23 through the second reflux pipe 32 provided with the flow rate adjustment valve 32a as described above, and becomes a reflux liquid. In addition, the remaining part of the above-mentioned liquid nitrogen 34 is introduced into the upper part of the low-pressure rectification tower 28 through the branch pipe 33 with a flow regulating valve 33a, and becomes a reflux liquid, which flows downward in the low-pressure rectification tower 28, and plays a role of gas-liquid separation. 35 is a product oxygen extraction pipe extending from the lower side of the low-pressure rectification tower 28, and its function is to take out vaporized high-purity oxygen from the liquid oxygen 34 accumulated at the bottom of the low-pressure rectification tower 28, and guide it to the main Inside the heat exchanger 21, it exchanges heat with the compressed air Y containing high-concentration oxygen, turns it to normal temperature, and sends it out of the apparatus as product oxygen. 36 is the product nitrogen take-out pipe that extends from the top of the low-pressure rectification tower 28, and the effect that plays is: take out the nitrogen that rises to the top of the low-pressure rectification tower 28, send in the main heat exchanger 21, make containing high-concentration oxygen While cooling the compressed air Y, it heats itself up to normal temperature, and sends it out of the device as product nitrogen. In the figure, 39 is a cold box, and heat insulating materials (not shown) such as perlite used for low-temperature heat insulation are stuffed inside. In this embodiment, the lines of the first adsorption towers 2 and 3 concentrate oxygen by nitrogen adsorption, but oxygen adsorbed and concentrated by the adsorbent may be taken out by using an adsorbent that absorbs oxygen.

Using this device, nitrogen and oxygen can be produced as follows. That is, first, the outside air is obtained from the air compressor (air compression device) 1, and the air is compressed at a low pressure here, and the moisture in the compressed air is removed by a water separator (not shown), and in this state, it is sent into In the first adsorption towers (oxygen concentrators) 2 and 3, nitrogen, moisture, carbon dioxide and hydrocarbons (C _n H _m ) in the compressed air are adsorbed and removed. Accordingly, the oxygen in the compressed air is concentrated. This is the greatest feature of the present invention. Then, the compressed air X containing high-concentration oxygen that has passed through the first adsorption towers 2 and 3 is introduced into the oxygen air compressor (oxygen air compressor) 11, and the compressed air X containing high-concentration oxygen is further compressed by the oxygen air compressor 11. The compressed air X is sent into the second adsorption towers 12 and 13 after forming the compressed air Y containing high concentration oxygen, and the water, carbon dioxide and NO _x etc. in the compressed air Y containing high concentration oxygen are adsorbed and removed. Then, the high-concentration oxygen-containing compressed air Y from which water, carbon dioxide, and _NOx have been adsorbed and removed is fed into the main heat exchanger 21, cooled to an ultra-low temperature, and introduced into the lower part of the high-pressure rectification column 23 in this state. Next, in the high-pressure rectification tower 23, the compressed air Y containing high-concentration oxygen is brought into countercurrent contact with the reflux liquid produced in the low-pressure rectification tower 28, and the compressed air is rectified. (The boiling point of oxygen at atmospheric pressure is -183°C, and the boiling point of nitrogen under the same conditions is -196°C), and the high boiling point component oxygen in the compressed air Y containing high concentration of oxygen is liquefied to turn nitrogen into a gas. The nitrogen gas is taken out from the nitrogen take-out pipe 26, sent to the main exchanger 21, supplied to the expansion turbine 37, and after generating cold here, most of it is discharged to the outside of the device, and a part is used as the second adsorption tower 12,13. regeneration gas.

In addition, the nitrogen accumulated in the upper part of the low-pressure rectification column 28 is taken out from the product nitrogen gas extraction pipe 36, sent to the main heat exchanger 21, and after the temperature is raised to around normal temperature, it is sent out of the device as product nitrogen gas. On the other hand, the liquid air 24 containing high-concentration oxygen in the form of liquid stored at the bottom of the high-pressure rectification tower 23 is sent to the low-pressure rectification tower 28 through the delivery pipe 29, and is stored as liquid oxygen 34 from which nitrogen has been vaporized. The bottom of the low-pressure rectification column 28 is vaporized by heat exchange with nitrogen passing through the condenser 30 at the bottom of the low-pressure rectification column 28 . The vaporized oxygen is taken out from the product oxygen take-out pipe 35, sent to the main heat exchanger 21, heated up to around normal temperature, and then sent out of the apparatus as product oxygen. This gives the products oxygen and nitrogen.

In the above embodiment, the concentration of oxygen in the compressed air is concentrated from 20.9% by volume to about 50% by volume through the first adsorption towers 2 and 3, so the amount of air necessary to produce 10,000m ³ /h (standard) of oxygen , when the recovery efficiency of oxygen is 97%, it is theoretically calculated with air volume = (10000÷0.500)÷0.97, which is about 20600m ³ /h (standard) air volume, which is reduced to 41% of the conventional one described at the beginning about. Furthermore, the compression power of the oxygen air compressor 11 necessary to produce 10,000 m ³ /h (standard) of oxygen is reduced to about 2,000 kW, and it is estimated that the compression power of the oxygen air compressor 1 becomes about 300 kW, and the driving power of the vacuum pump 4 changes. It is about 900kW, and the electric power of the electric heater 41 becomes about 200kW, so the total is 3400kW, which is reduced to about 70% of the past. Therefore, energy saving of more than 30% can be realized.

In addition, in this embodiment, following the air compressor 1 that compresses the raw air, the first adsorption towers 2 and 3 that condense the oxygen in the compressed air are installed to increase the oxygen concentration in the raw air, and pass it through oxygen air. The compressor 11 and the main heat exchanger 21 are supplied to the high-pressure distillation column 23 and the low-pressure distillation column 28 . Therefore, by realizing a significant reduction in the flow rate of each device after the oxygen-air compressor 11, the main heat exchanger 21, the two rectification towers 23, 28, etc., they can be downsized to less than half of the previous ones, and as a result, it is possible to achieve Significant miniaturization of the entire device.

For example, when producing 70,000m ³ /h (standard) of oxygen, in the past, the diameter of the high-pressure rectification tower 23 was 7m (calculated by our company), and there was no transportation device to assemble it at the factory and transport it to the site. It is assembled on site, but in the present embodiment, when the same amount of oxygen is produced, since the gas flowing through the rectification tower becomes 1/2 or less, the diameter of the rectification tower can be made about 4.2m. Therefore, it becomes possible to assemble it at a factory and transport it to a site, and labor can be greatly saved.

Figure 2 shows another embodiment of the air separation plant of the present invention. In this embodiment, the second adsorption towers 12 and 13 are omitted. That is, omit the pipeline of the 2nd adsorption tower 12,13, the 2nd discharge pipe 14, band switch valve 16a, 16b, 17a, 17b, 18a, 18b, 19a, 19b, branch pipe 40 and the 1st-3rd Tubes 42-44. Other parts are the same as those in the above-mentioned embodiment, and the same parts are given the same symbols. In this embodiment, by installing the device in a place where clean air is used as raw air, the same effects as those of the above-described embodiment are obtained, and the device can be simplified and downsized.

Figure 3 shows yet another embodiment of the air separation plant of the present invention. In this embodiment, except in the embodiment shown in FIG. 2 , instead of the expansion turbine 37, a liquid oxygen storage tank (not shown) for supplying liquid oxygen (LO ₂ ) from an oil tank truck or the like outside the plant is used, and the Except that liquid oxygen is used as the cold source, the others are basically the same as the device shown in Fig. 2 . In the figure, 47 is an introduction pipe for introducing liquid oxygen from the liquid oxygen storage tank as a cooling source to the lower part of the low-pressure rectification column 28, and the liquid oxygen introduced from the introduction pipe 47 flows downward to the lower part of the low-pressure distillation column 28. the bottom, and joins the liquid oxygen 34 accumulated at the bottom. 48 is a discharge pipe extending from the low-pressure rectification tower 28, and its function is to take out the nitrogen (waste GN ₂ ) accumulated on the upper part of the tray (or packed column) 28a of the low-pressure rectification tower 28, and introduce it into the subcooling A device 49 guides the waste nitrogen gas passing through the subcooler 49 into the main heat exchanger 21, cools the compressed air Y containing high concentration of oxygen, and discharges it to the outside. The supercooler 49 passes through the liquid air 24 containing high-concentration oxygen in the supply pipe 29, the liquid nitrogen (reflux liquid) in the branch pipe 33, the product nitrogen gas in the product nitrogen gas extraction pipe 36, and the discharge pipe 48. The waste nitrogen in the pipe 29 plays the role of cooling the liquid air 24 containing high concentration oxygen in the feed pipe 29. 50 is a liquid oxygen take-out pipe extending from the bottom of the low-pressure rectification tower 28, and its function is to take out the liquid oxygen accumulated at the bottom of the low-pressure rectification tower 28, guide it into the main heat exchanger 21, and make the liquid oxygen containing high The oxygen-concentrated compressed air Y is heated up to normal temperature while being cooled, and introduced into the product oxygen take-out pipe 35 as product oxygen. 51 is the product nitrogen compressor that is arranged on the product nitrogen take-out pipe 36, and its function is to boost the pressure of the product nitrogen passing through the product nitrogen take-out pipe 36 to a specified pressure. 52 is the first product oxygen compressor installed on the product oxygen take-out pipe 35, and its function is to increase the pressure of the product oxygen passing through the product oxygen take-out pipe 35 to a specified pressure, and supply it to the low-pressure product oxygen take-out pipe 53 in. 54 is the 2nd product oxygen compressor, and the effect that plays is: the product oxygen that has passed through the 1st product oxygen compressor 52 is further boosted, and is supplied to the high pressure product oxygen take-out pipe 55. In this embodiment, the top surface of the high-pressure distillation column 23 and the bottom surface of the low-pressure distillation column 28 provided above the high-pressure distillation column 23 are integrated and formed of the same material. In the figure, 36 a is a pipe for supplying the product nitrogen gas passing through the product nitrogen gas extraction pipe 36 to the discharge pipe 48 . 39A is a cold box which is filled with heat insulating materials such as perlite and vacuum-sucked inside. The other parts are the same as those in the embodiment shown in FIG. 2, and the same symbols are attached to the same parts.

Using this device, nitrogen and oxygen can be produced as follows. That is, like the embodiment shown in FIG. 2 , external air is obtained from an air compressor (air compressing device) 1, and the air is compressed at a low pressure here, and the compressed air is removed by a water separator (not shown). In this state, the moisture is sent to the first adsorption tower (oxygen concentrator) 2, 3 to adsorb and remove nitrogen, moisture, carbon dioxide and hydrocarbon gas (C _n H _m ) in the compressed air. Accordingly, the oxygen in the compressed air is concentrated. Then, the compressed air X containing high-concentration oxygen that has passed through the first adsorption towers 2 and 3 is introduced into the oxygen air compressor (oxygen air compressor) 11, and the compressed air X containing high-concentration oxygen is further compressed by the oxygen air compressor 11. Compress air X to form compressed air Y containing high concentration of oxygen. Then, the compressed air Y containing high-concentration oxygen is fed into the main heat exchanger 21, cooled to an ultra-low temperature, and introduced into the lower part of the high-pressure rectification column 23 in this state. Next, in the high-pressure rectification tower 23, the compressed air Y containing high-concentration oxygen is brought into countercurrent contact with the reflux liquid produced in the low-pressure rectification tower 28, and the compressed air is rectified, utilizing the difference in boiling points between nitrogen and oxygen ( The boiling point of oxygen at atmospheric pressure is -183°C, and the boiling point of nitrogen is -196°C under the same conditions), the high boiling point component oxygen in the compressed air Y containing high concentration of oxygen is liquefied, and nitrogen becomes a gas.

In addition, the nitrogen gas accumulated in the upper part of the low-pressure rectification column 28 is taken out from the product nitrogen gas extraction pipe 36, sent to the subcooler (heat exchanger) 49, introduced into the main heat exchanger 21, and in the main heat exchanger 21 After raising the temperature to near normal temperature, it is sent out of the device as product nitrogen. On the other hand, the liquid air 24 containing high-concentration oxygen accumulated at the bottom of the high-pressure rectification column 23 is sent into the subcooler 49 with the delivery pipe 29, and the gas-liquid mixed state that is cooled here contains high-concentration oxygen. The liquid air 24 of oxygen is sent in the low-pressure rectification tower 28, and the liquid oxygen 34 that has removed nitrogen as vaporization is accumulated in the bottom of the low-pressure rectification tower 28, makes it and the condenser 30 at the bottom of the low-pressure rectification tower 28 The nitrogen passing through the medium is exchanged with heat to make it gasify. The vaporized oxygen is taken out from the product oxygen take-out pipe 35, sent to the main heat exchanger 21, and after it is heated to near normal temperature, the product oxygen passed through the first product oxygen compressor 52 is sent out by the low-pressure product oxygen take-out pipe 53. To the outside of the device, the product oxygen passed through the second product oxygen compressor 54 is sent out of the device through the high-pressure product oxygen extraction pipe 55 . This gives product oxygen and product nitrogen.

As described above, also in this embodiment, the same operations and effects as those in the embodiment of FIG. 2 are obtained.

Figure 4 shows yet another embodiment of the air separation plant of the present invention. In this embodiment, instead of the expansion turbine 37 in the embodiment shown in FIG. 2 , a liquid nitrogen storage tank (not shown) for supplying liquid nitrogen (LN ₂ ) from an oil tanker outside the plant or the like is used, and Except that the liquid nitrogen is used as a cooling source, the other is basically the same as the device shown in FIG. 2 . That is, 47a is an introduction pipe for introducing liquid nitrogen from a liquid nitrogen storage tank as a cold source to the upper part of the high-pressure rectification column 23, and the liquid nitrogen introduced from the introduction pipe 47a is absorbed by the condenser at the lower part of the low-pressure distillation column 28. Part of the liquefied liquid nitrogen at 30 is introduced into the upper part of the high-pressure rectification column 23 . The other parts are the same as those in the embodiment shown in FIG. 2, and the same symbols are attached to the same parts.

Figure 5 shows yet another embodiment of the air separation plant of the present invention. This embodiment is that in the embodiment shown in Fig. 1, the compressed air that will pass through air compressor 1 is sent to the 1st delivery pipe 1a of the 1st adsorption tower 2,3, and the 1st delivery pipe 1a that has passed through the 1st adsorption tower The compressed air X containing high-concentration oxygen of 2 and 3 is introduced into the inlet pipe 57 of the oxygen air compressor 11 (the symbol 57 is not added in FIG. 1 ) and communicates with the communication pipe 58 with the on-off valve (or flow regulating valve) 58a. And, open the above-mentioned on-off valve 58a, a part of the compressed air that has passed through the air compressor 1 and the water separator (not shown in the figure) is sent directly (that is, without passing through the first adsorption towers 2 and 3) through the above-mentioned communication pipe 58. into the introduction pipe 57, while the remaining part is sent into the introduction pipe 57 through the first adsorption tower 2, 3, and the introduction pipe 57 is used to merge the two, and the compressed air that is introduced into the introduction pipe 57 through the communication pipe 58 Part of the air dilutes the oxygen concentration of the rest of the compressed air introduced into the introduction pipe 57 via the first adsorption towers 2 and 3 . The other parts are the same as those in the embodiment shown in FIG. 1, and the same symbols are assigned to the same parts. This embodiment also obtains the same actions and effects as those of the embodiment shown in FIG. 1 . Furthermore, the concentration of oxygen in the compressed air supplied to the lower part of the high-pressure rectification column 23 becomes low, and the amount of product oxygen can be reduced. Therefore, when you want to reduce the oxygen content of the product, you can respond accordingly. Such a communication pipe 58 with an on-off valve 58a can also be used in the embodiments shown in FIGS. 2-4 .

Claims (4)

1. An air separation device, characterized in that, possesses: an air compressing device that obtains air from the outside and compresses it at a low pressure; an oxygen concentrating device that will adopt the oxygen concentration in the compressed air compressed by the air compressing device; Oxygen air compressing device containing compressed air X containing high-concentration oxygen passing through the oxygen concentrator; a heat exchanger for cooling compressed air Y containing high-concentrated oxygen passing through the oxygen concentrating device; cooling through the heat exchanger to A rectification tower that separates low-temperature compressed air Y containing high-concentration oxygen by using the difference in boiling point of each component gas to extract oxygen. 2. The air separation plant according to claim 1, wherein said oxygen concentrator is used as an adsorption tower for accommodating an adsorbent for absorbing nitrogen in compressed air, and is intended to remove impurities such as moisture in compressed air with said adsorbent. 3. The air separation unit according to claim 1 or 2, wherein a removal device for removing impurities in the compressed air Y containing high-concentration oxygen is arranged between the oxygen air compression unit and the heat exchanger. 4. The air separation plant according to any one of claims 1-3, wherein the compressed air X containing high-concentration oxygen that has passed through the oxygen concentrator is imported into the oxygen air compressor without going through the oxygen concentrator. The introduction path directly supplies a part of the compressed air compressed by the air compression device.

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