JPS6333632B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for extracting argon from an air separation device using an air liquefaction rectification method, and more specifically, it is aimed at stabilizing argon extraction during reduction operation of the air separation device. .

To collect argon using the air liquefaction rectification method, raw air is compressed and cooled, then separated into oxygen and nitrogen in a double rectification tower, and the oxygen with a high argon content is extracted for rectification and purification. is normal. A general example of separating and purifying argon from oxygen with a high argon concentration will be described with reference to FIG. Oxygen containing 5 to 15% argon and a trace amount of nitrogen is supplied to tube 1 from the upper column (not shown) of the double rectification column.
The cruder argon is sucked into the lower part of column 2. This suction gas is liquid air, which is a cooling source for reflux, and is supplied from the lower column (not shown) of the double rectification column through a pipe 3 and a valve 4 to a condenser 5 installed at the upper part of the crude argon column 2. As a result, the top tube 6
Crude argon gas (95-98 vol. % argon, 1-2 vol. % oxygen, 1-2 vol. % nitrogen) is discharged, and liquid oxygen is also discharged from the bottom pipe 7, which is returned to the upper column. Further, the liquid air supplied to the condenser 5 is introduced into the upper column via the pipe 8 after being vaporized. The crude argon led out from the pipe 6 is introduced into the heat exchanger 9, where it is heated to room temperature by exchanging heat with the return gas, and then pressurized to 1 to 2 kg/cm ² by the blower 10. After being
A sufficient amount of hydrogen is added from the hydrogen gas reservoir 11 to remove the oxygen contained in the crude argon gas through an oxygen and hydrogen reaction, and the hydrogen is sent to the catalyst cylinder 12.
The oxygen content in the crude argon gas introduced into the catalyst cylinder 12 reacts with added hydrogen to produce water, which is separated in a water separator 13 with a water cooler and further removed in a dryer 14. Ru. The crude argon gas from which oxygen has been removed in this way is sent to the heat exchanger 9,
After being cooled by heat exchange with the crude argon gas discharged from the crude argon column 2, it is introduced into the high purity argon column 16 through the pipe 15.

The high-purity argon column 16 is provided with a condenser 17 at the top and an evaporator 18 at the bottom.
In addition, liquid nitrogen is liquefied in the evaporator 18 and sent through the pipe 19, as well as pipe 20 from the lower column of the double rectification column.
Liquid nitrogen is supplied as a cooling source. In addition, a pipe 21 is connected to the evaporator 18 from the lower column.
Nitrogen gas is supplied as a heating source. The crude argon gas introduced into the high-purity argon column 16 rises while being purified, and passes through the condenser 17.
It is liquefied and flows down while being rectified in the column, and is vaporized in the evaporator 18 and subjected to rectification. As a result, high-purity argon is collected from the pipe 22, and nitrogen and excess hydrogen added for the purpose of removing oxygen are discharged from the pipe 23 as waste gas.

Argon is generally collected from an air separation device using the air liquefaction rectification method as described above.

By the way, in air separation equipment, oxygen and nitrogen are extracted as the main products, and argon is extracted as a by-product, so the air separation equipment is operated according to the demand for oxygen and nitrogen. It's normal. For example, when the demand for oxygen and nitrogen decreases, the air separation device is operated with a reduced amount of feed air supplied to the double rectification tower. As is clear from the graph shown in Figure 3, when the amount of raw air is reduced,
The yield of oxygen decreases with a gentle curve (see curve a in FIG. 3), whereas the yield of argon decreases with a steep curve (see curve b in FIG. 3). The reason why the amount of argon extracted rapidly decreases is that when the amount of feed air decreases, the operating pressure in the lower column and upper column of the double rectification column decreases, resulting in a decrease in the superficial column velocity and a decrease in rectification efficiency. This is because the flow rate and purity of the feed argon sucked into the crude argon column 2 from the upper column decreases, and as a result, the operability of the crude argon column 2 deteriorates. If the operability of the crude argon column 2 deteriorates,
As the oxygen content and nitrogen content in the crude argon gas drawn out from the crude argon column 2 increases, the amount of crude argon gas drawn out decreases, and therefore,
The heat exchanger 9, blower 10, catalyst cylinder 12, etc. are no longer able to perform their predetermined functions, and the amount of argon that can be collected is drastically reduced, and in some cases, it becomes virtually impossible to collect argon.

In this way, as the air separation equipment is operated at reduced capacity, the amount of argon that can be collected is drastically reduced, and in some cases, it becomes virtually impossible to collect argon, making it impossible to secure argon. The demand for argon will not be met.

The present invention was made in view of the above circumstances, and involves mixing part of the deoxidized argon gas introduced into the high-purity argon column with the crude argon gas derived from the crude argon column. By increasing the amount of crude argon gas while diluting the oxygen contained in the argon gas, the above-mentioned inconvenience during reduced operation of the air separation equipment was resolved, and by stabilizing argon extraction, it was possible to increase the yield. It is something. An embodiment of the present invention will be described below with reference to FIG. 2, where the same components as those shown in FIG.

The crude argon gas led out from the top of the crude argon column 2 through the pipe 6 contains part of the deoxidized crude argon gas introduced into the high purity argon column 16 before being introduced into the heat exchanger 9. are mixed through tube 30.
As a result, the oxygen contained in the crude argon gas is diluted, while the amount of crude argon gas increases. Therefore, it is no longer dangerous to add hydrogen gas and cause it to react in the catalyst cylinder 12, and the heat exchanger 9,
The blower 10, the catalyst cylinder 12, the water separator 13, and the dryer 14 each perform a predetermined function, so that the oxygen content in the crude argon gas discharged from the crude argon column 2 is sufficiently removed. The crude argon gas from which oxygen has been removed returns to the heat exchanger 9, where it is cooled by exchanging heat with the gas discharged from the crude argon column 2, and then passed through the pipe 15 to the high-purity argon column 16.
A portion of it is returned to the gas discharged from the crude argon column 2 through the pipe 30 as described above. The amount returned to the gas discharged from the crude argon column 2 is adjusted by a valve 31 provided in the pipe 30.

The deoxidized crude argon gas introduced into the high-purity argon column 16 is purified in the same manner as in the past, and is collected as high-purity argon through the pipe 22.

According to the above manufacturing method, the amount of oxygen contained in the crude argon gas derived from the crude argon column 2 increases while the amount of crude argon gas decreases due to the reduced operation of the air separation device. Also, since the deoxidized crude argon gas is mixed with the pipe 30 before being introduced into the heat exchanger 9, it is no longer dangerous to add hydrogen and cause a reaction in the catalyst cylinder 12, and the heat exchanger 9 etc. perform a predetermined function, and as shown by curve c in the graph of FIG. 3, the yield of argon is improved compared to the conventional case (curve b).

Further, according to the present invention, it is possible to shorten the time required to start collecting argon at the time of startup. That is, it takes a long time from starting the crude argon column 2 to stabilizing it, and normally the catalyst cylinder 12 cannot be used until a predetermined purity is reached. This is because the maximum oxygen content to be processed in the catalyst cylinder 12 is 3.5 vol%, and if it exceeds that, the catalyst carrier may deteriorate or it may become dangerous to add hydrogen and cause the reaction. . Therefore, by mixing the deoxidized crude argon gas with the crude argon derived from the crude argon column 2, the oxygen content is diluted, eliminating the danger in the catalyst cylinder 12, and starting the argon extraction operation. can be accelerated. Note that when the steady state is approached, the valve 31 may be gradually closed to reduce the amount of crude argon gas mixed after deoxidation.

In the above embodiment according to the present invention, the pipe 30 is provided between the pipe 6 and the pipe 15 to recycle the deoxidizing argon gas after being led out of the heat exchanger 9 to the crude argon gas before being introduced into the heat exchanger 9. However, the method of the present invention is not limited to this, and deoxidized argon gas before introduction of the heat exchanger 9 may be recycled to crude argon gas after exiting the heat exchanger 9 at room temperature. A similar effect can be obtained.

As explained above, the present invention has the feature that the above effects can be obtained simply by providing a line for recycling deoxidized argon gas into crude argon gas, so that it can be easily applied to existing equipment. Furthermore, in the case of a newly installed apparatus, by enlarging the heat exchanger 9, catalyst cylinder 12, etc. and making full use of the method of the present invention, it is possible to increase the amount of argon collected during the reduction operation.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing an example of conventional argon production, Fig. 2 is a process diagram showing an example of the present invention, and Fig. 3 shows the oxygen yield and argon yield as the amount of raw air is reduced. It is a graph. 2... Crude argon column, 11... Hydrogen gas reservoir, 1
6...High purity argon column, 6,15,30...tube,
31... Valve.

Claims (1)

[Claims] 1 Crude argon gas discharged from the crude argon column is passed through a heat exchanger to a deoxidation treatment step to remove the oxygen contained therein, and then introduced into a high-purity argon column via the heat exchanger for rectification and high-purity argon gas. In a method for producing argon in which pure argon is collected, a part of the deoxidized argon gas is mixed with the crude argon gas derived from the crude argon column to dilute the oxygen contained in the crude argon gas and to dilute the oxygen contained in the crude argon gas. A method for producing argon, characterized by increasing the amount of crude argon gas.