JPH0849968A - Air liquefaction separating method and apparatus - Google Patents

Abstract

PURPOSE:To improve the argon yield without affecting the yields and the composition of a product sampled from an upper column. CONSTITUTION:A liquid at a lower part of the argon column 51 is heated with a reboiler 52 using a stock argon gas led out of an upper column 8 as heating source to make an ascending gas while the stock argon cooled to be liquefied with the reboiler 52 is decompressed with an expansion valve 54. Then, it is introduced into the medium stage of the argon column 51 as descending liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for air liquefaction separation, and more specifically, to liquefaction rectification separation of air to obtain oxygen
The present invention relates to a method and apparatus for separating and collecting air components such as nitrogen and argon, and more particularly to a method and apparatus configuration for improving argon yield.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventional air liquefaction separation apparatus. Approximately 6 kgf / cm ² abs with a compressor
The raw material air that has been compressed into water and removed of water and carbon dioxide is cooled to near the dew point and introduced from the conduit 1 to the lower column 2 of the double rectification column. This raw material air is separated into liquefied air rich in liquefied nitrogen, nitrogen gas and oxygen by the rectification action in the lower tower 2. Liquefied nitrogen in the upper part of the lower column is introduced as a reflux liquid into the upper part of the upper part of the upper column 8 of the double rectification column through the conduit 3, the subcooler 4, the conduit 5, the expansion valve 6 and the conduit 7. Further, the nitrogen gas is led to the conduit 9 from the upper part of the lower tower 2 and sent to a main heat exchanger and an expansion turbine (not shown) to be used for obtaining refrigeration for cooling the device.

The oxygen-rich liquefied air led out from the bottom of the lower tower 2 to the conduit 10 is cooled by the supercooler 11 and then partly branched to pass through the conduit 12, the expansion valve 13 and the conduit 14. After being introduced into the argon condenser 15 to provide cold by partially gasifying, it is introduced into the middle stage of the upper tower 8 through the conduit 16. On the other hand, another branched liquefied air is introduced into the upper middle part of the upper tower 8 through the conduit 26, the expansion valve 27, and the conduit 28.

In the upper tower 8, the conduits 7, 28, 16, 21
The liquids respectively introduced by are lowered in the upper tower, and almost all of the liquid is vaporized in the main condenser 17 to rise in the upper tower. Fractionation proceeds by the descending liquid and the rising gas, and oxygen, argon, and nitrogen are separated. As a result, nitrogen gas is discharged from the upper part of the upper tower, waste gas is discharged from the lower part of the dozen stages, and oxygen gas is discharged from the lower part.

Raw material argon gas is discharged from the lower middle part of the upper tower 8 and passes through a conduit 18 to make the argon tower 19
Will be introduced to. The raw material argon gas introduced into the argon tower 19 rises in the tower and is liquefied in the argon condenser 15, and a part of the raw material argon gas is used as liquid or gaseous crude argon in the conduit 20.
And the remaining liquid descends in the tower. The liquid descending in the argon column is returned from the lower part of the column through the conduit 21 to the lower part of the middle part of the upper column 8.

The nitrogen gas led from the top of the upper tower 8 to the conduit 22 passes through the subcooler 4 and the subcooler 11 and is sent to the main heat exchanger where it is heated to room temperature. Further, the waste gas led from the upper tower 8 to the conduit 23 passes through the subcoolers 4 and 11 similarly to the nitrogen gas, and is heated to room temperature by the main heat exchanger. Further, from the lower part of the upper tower 8, oxygen gas is led out by a conduit 24 and liquefied oxygen is led out by a conduit 25.

[0007]

Conventionally, the upper tower 8 and the argon tower 1 in the air liquefaction separation apparatus as described above are used.
Numerous methods have been proposed to improve the rectification state of 9 to improve the argon yield. For example, the argon yield can be improved by increasing the amount of raw material argon gas introduced into the argon column 19 from the upper column 8 through the conduit 18. However, in this case, the rectification conditions of the upper column 8 were changed due to changes in the state of the liquefied air at the outlet of the argon condenser 15 and the other product yields and compositions were affected.

Therefore, an object of the present invention is to provide an air liquefaction separation method and apparatus capable of improving the argon yield without affecting the yield and composition of the product collected from the upper column.

[0009]

In order to achieve the above-mentioned object, the air liquefaction separation method of the present invention is a liquefaction rectification separation of raw material air by an air liquefaction separation apparatus equipped with a double rectification column and an argon column. In the method of collecting oxygen, nitrogen, argon, etc., the raw material argon gas derived from the upper middle stage lower part of the double rectification column is introduced into the reboiler installed in the lower part of the argon column, and the liquid in the lower part of the argon column is After liquefying by heat exchange, it is characterized in that it is depressurized and introduced into the middle stage of the argon column, and further, it is introduced as a cooling source into a condenser installed in the upper part of the argon column, and liquefied air is discharged. Is adjusted according to the required temperature difference of the condenser, and the argon column is a packed column filled with a regular packing material or an irregular packing material.

Further, in the air liquefaction separation apparatus of the present invention, a reboiler is installed in the lower part of the argon column, and a route for introducing the raw material argon gas derived from the upper middle stage of the double rectification column into the reboiler, The reboiler is provided with a path for introducing raw material argon, which has been liquefied by exchanging heat with the liquid in the lower part of the argon column, into the middle stage of the argon column after decompressing it with an expansion valve.

[0011]

[Operation] By installing a reboiler using the raw material argon gas as a heating source in the lower part of the argon column, and lowering the operating pressure of the argon column to a pressure at which the required temperature difference between the raw material argon gas and the liquid in the lower part of the argon column is obtained, A reboiler using the raw material argon gas as a heating source heats the liquid in the lower part of the argon tower to produce rising gas, and the raw material argon cooled and liquefied by the reboiler is introduced as a descending liquid into the middle stage of the argon column. As a result, the rectification conditions are improved by increasing the descending liquid in the argon column, and the yield of argon is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail based on an embodiment shown in FIG. The same elements as those of the conventional apparatus shown in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the air liquefaction / separation apparatus shown in FIG. 1, a reboiler 52 is installed in the lower part of an argon tower 51, and a raw material argon gas derived from the lower middle part of the upper tower 8 is introduced into the reboiler 52 and the reboiler 52. A conduit 55 is provided in which the raw material argon, which has been cooled by exchanging heat with the liquid in the lower part of the argon tower in 52 and liquefied, is decompressed by an expansion valve 54 and introduced into the middle stage of the argon tower 51.

The lower pressure of the argon tower 51 is the reboiler 5
The temperature difference between the raw material argon gas introduced into 2 and the liquid at the bottom of the argon column is determined so as to be the temperature difference required for the operation of the reboiler 52, and the reboiler is passed from the lower middle stage of the upper tower 8 via the conduit 53. The raw material argon gas introduced into 52 is cooled and liquefied by heat exchange with the liquid in the lower part of the tower, introduced into the middle stage of the argon tower 51 through the expansion valve 54 and the conduit 55, and becomes the descending liquid of the argon tower 51. . On the other hand, the liquid at the bottom of the argon tower 51 is heated and vaporized by heat exchange with the raw material argon gas in the reboiler 52, and becomes ascending gas in the argon tower 51. The gas that has risen to the top of the argon column 51 is liquefied in the argon condenser 57, a part of which is taken out from the conduit 56 as liquid or gaseous crude argon, and the remaining liquid becomes a reflux liquid that descends in the column, Conduit 55
It joins with the liquid introduced from, and is returned from the bottom of the tower to the lower middle part of the upper tower 8 via the conduit 58.

The liquefied air led from the bottom of the lower tower 2 to the conduit 10 is supercooled by the subcooler 11 and then branched through the conduit 12 into the conduit 61 and the conduit 62. The liquefied air branched into the conduit 61 is decompressed by the expansion valve 63 and then introduced into the argon condenser 57. This liquefied air exchanges heat with the argon gas in the upper part of the argon tower, a part of which is vaporized and led to the conduit 64, and the rest is led to the conduit 65 having the valve 66 while being in a liquid state. In the state, or before they enter the upper tower 8, they are merged and introduced into the middle stage of the upper tower 8 in a mixed state of gas and liquid. On the other hand, the liquefied air branched to the conduit 62 is supplied to the expansion valve 67.
After being expanded and decompressed with, the gas is introduced into the upper middle part of the upper tower 8 through the conduit 68.

In the present invention, the reboiler 52 is installed in the lower part of the argon tower 51. However, a temperature difference is required so that the raw material argon gas is liquefied in the reboiler 52 and the liquid at the bottom of the tower is evaporated. Therefore, the operating pressure of the argon tower 51 is
It needs to be lower than before. On the other hand, in the argon condenser 57, since the operating pressure of the argon column 51 becomes low, it becomes difficult to secure a temperature difference for liquefying the argon gas in the upper part of the column.

Therefore, in the argon condenser 57, the top of the argon column 51 is adjusted so that the temperature difference between the liquefied air at the condenser outlet and the argon gas in the upper part of the argon column becomes the temperature difference required for the operation of the condenser. It is necessary to adjust the operating pressure or adjust the amount of liquefied air introduced into the argon condenser 57 through the conduit 61 and discharged through the conduit 65.

In other words, the argon column 51 has a lower pressure for obtaining the temperature difference required for the operation of the lower reboiler 52 and an upper pressure for obtaining the temperature difference required for the operation of the upper argon condenser 57. The operating pressure is determined. At this time, if a packed column in which the argon column 51 is filled with a regular packing material or an irregular packing material with a small pressure loss is used, the pressure loss is small, so that the upper part of the tower is sufficient. The pressure may be such that a temperature difference can be obtained. On the other hand, when a conventional tray is used for the argon column 51, the pressure in the upper part of the column becomes low due to the large pressure loss, and the temperature difference required for the operation of the argon condenser 57 cannot be obtained. By increasing the amount of liquefied air introduced into the condenser 57 via the conduit 61 and the amount of liquefied air discharged from the condenser 57 via the conduit 65 to a greater extent than in the conventional case, the required temperature difference in the argon condenser 57 can be obtained. For example, the amount of liquefied air introduced from the conduit 61 to the argon condenser 57 and the amount of liquefied air discharged from the argon condenser 57 to the conduit 65 are increased, and the amount of gas discharged from the conduit 64 and the liquid discharged from the conduit 65 are increased. By changing the ratio with the amount of the oxygen concentration in the argon condenser 57, the oxygen concentrations of the liquid phase and the gas phase in the argon condenser 57 are reduced, which lowers the vapor-liquid equilibrium temperature and can increase the temperature difference.

In such an apparatus configuration, the raw material argon gas derived from the lower middle part of the upper tower 8 is introduced into the reboiler 52 installed in the lower part of the argon tower 51, and heat-exchanged with the liquid at the bottom of the argon tower to generate the bottom of the tower. Liquid is evaporated and the raw material argon gas is liquefied, and then decompressed by the expansion valve 54 and introduced into the middle stage of the argon column 51, so that the amount of liquid descending downward from the raw material argon introduction part in the middle stage of the argon column is smaller than in the conventional case. It is possible to improve the rectification conditions in this part, improve the separation efficiency of argon, and increase the argon yield.

Next, in the apparatus of the embodiment and the apparatus of the prior art, the amount of raw material air introduced from the conduit 1 is 1 respectively.
Table 1 shows the result of simulating the conditions under which the maximum amount of argon can be collected at 00000 Nm ³ / h. The configurations other than the argon column were the same, and the argon column 51 in the example apparatus was a packed column packed with a regular packing material.

[0021]

[Table 1]

From these results, it is understood that the argon yield (the amount of collected argon / the amount of argon in the raw material air) can be improved by about 3.5% as compared with the conventional case. Further, in Table 1, although the flow rate of the raw material argon gas is slightly different, it has almost no influence on the sampling amount and purity of nitrogen gas, oxygen gas, and liquefied oxygen collected from the upper tower 8. Furthermore, by using a packing material with a small pressure loss for the argon tower 51, the temperature of the liquefied air at the outlet of the argon condenser remains approximately the same as that of the conventional apparatus, and 1.1 ° C. is set in the argon condenser 57. In the reboiler 52, a temperature difference of 1.5 ° C could be obtained.

[0023]

As described above, according to the present invention,
Since the reboiler using the raw material argon gas as a heating source heats the liquid in the lower part of the argon tower to make an ascending gas, the raw material argon cooled and liquefied by the reboiler is introduced into the middle part of the argon column as a descending liquid. The rectification conditions of the argon column are improved by increasing the amount of the descending liquid below, and the argon yield can be improved with almost no influence on the operation of the upper column and the like. Further, the amount of liquefied air introduced into the argon condenser and the amount of liquefied air discharged from the argon condenser are adjusted, or the argon column is filled with a regular packing material or an irregular packing material having a small pressure loss. The required temperature difference in the reboiler and argon condenser can be easily obtained by using a column, or a combination of both.

[Brief description of drawings]

FIG. 1 is a system diagram of an air liquefaction separation apparatus showing an embodiment of the present invention.

FIG. 2 is a system diagram showing an example of a conventional air liquefaction separation device.

[Explanation of symbols]

2 ... Lower tower, 8 ... Upper tower, 51 ... Argon tower, 52 ... Reboiler, 54, 63, 67 ... Expansion valve, 57 ... Argon condenser

Claims (4)

[Claims] 1. An air liquefaction / separation device equipped with a double rectification column and an argon column is used to liquefy and rectify the raw material air to separate oxygen,
In the method of collecting nitrogen, argon, etc., the raw material argon gas derived from the upper middle stage lower part of the double rectification column is
An air liquefaction separation method, which comprises introducing into a reboiler installed in the lower part of the argon column, heat-exchanging with the liquid in the lower part of the argon column to liquefy, and then reducing the pressure and introducing the solution into the middle stage of the argon column. 2. The air according to claim 1, wherein the amount of liquefied air introduced into and discharged from a condenser installed above the argon column is adjusted according to the temperature difference of the condenser. Liquefaction separation method. 3. The air liquefaction separation method according to claim 1, wherein the argon column is a packed column filled with a regular packing material or an irregular packing material. 4. An air liquefaction / separation apparatus equipped with a double rectification column and an argon column, wherein a reboiler is installed in the lower part of the argon column, and a raw material argon gas derived from the lower middle part of the upper column of the double rectification column is supplied. A route for introducing the reboiler and a route for decompressing the raw material argon gas liquefied by heat exchange with the liquid in the lower part of the argon column in the reboiler and introducing it into the middle stage of the argon column. Air liquefaction separation device.