JPS6096509A - Method for improving recovery in o2-production apparatus - Google Patents

Abstract

PURPOSE:To improve the yield of separated and recovered O2 in the process comprising the supply of air alternately to a pair of adsorption columns packed with N2- adsorbent, by carrying out the desorption of N2 from the N2-adsorbent under reduced pressure. CONSTITUTION:Sodium faujasite whuch is a zeolite mineral represented by Na-X is packed as the N2-adsorbent 9, 9' in a pair of N2-adsorption columns 8, 8'. Air 1 is compressed with a compressor 2, cleaned by passing through the column 4 for removing moisture and CO2, cooled with the refrigerator 20, and supplied to the bottom of the N2-adsorption column 8. The N2 in the air is adsorbed to the N2-adsorbent 9, and the remaining gas having high O2 content is discharged from the top valve 10 and charged in the O2-gas reservior 13. The N2-adsorption column 8' containing the N2- adsorbent 9' saturated with adsorbed N2 is evacuated with the vacuum pump 18 to effect the desorption of the adsorbed N2 and the regeneration of the adsorbent 9'. The regenerated adsorption column 8 is used in place of the column 8. In contrast with conventional process, the desorption of N2 from the N2 adsorbent is carried out without using a part of the separated O2 in the present process, and accordingly, the yield of the recovered O2 gas can be improved.

Description

Detailed Description of the Invention: 0□ using a N2 adsorbent that selectively adsorbs N2 from gas, and 02 from a mixed gas containing N2 as the main component.

The present invention relates to a method for separating N2.

O2 adsorption separation method from air using N2 adsorbent has the advantage that the equipment is small and simple and requires almost no maintenance, which is close to unmanned operation.
In recent years, the number of users has been increasing as a small to medium-sized device of about ooN/02/h. # Replacement of transporting and using liquid oxygen produced by cold separation equipment is underway.

Let me give an overview of the typical devices.

The equipment consists of an air compressor, two or more N2 adsorption towers, and in some cases a vacuum pump. In this device. When compressed air is sent to one tower, the filled N
N2 in the air is adsorbed and removed by the 2 adsorbent, and the remaining high pressure O2 flows out to the rear of the adsorption tower and is recovered. On the other hand, in other towers, the adsorbed N2 is released under reduced pressure conditions (sometimes a part of product 02 is flowed in a countercurrent, or a vacuum pump is used to forcefully release N2).
(There are also methods for removing the .). Repeat this process alternately to continuously separate o and N2.

A typical N2 adsorbent packed in the above adsorption tower is a 60-70% Ca exchanger of Na-A type barrier olide, which was put into practical use by Union Carbide. It selectively adsorbs N2 from the N2 component mixed gas, and co-adsorption of 02 under air conditions is estimated to be 10% or less of N2 adsorption.

02 due to this adsorption. As mentioned above, N2 separation equipment is advantageous in small and medium-sized areas, but in order to produce o2 of INr/0.75
~I Kwh is required, and the power consumption is larger than 0.45 Kwh of 02, which is produced by a large-capacity cryogenic separation method. Also, there is little merit of scale for increasing equipment capacity.

3.000 Nu? It is said that in the region of -02/h or higher, it cannot be mixed in the cryogenic separation method.

Therefore, various methods can be considered to improve these drawbacks, but when describing the improvement methods in connection with the present invention, the following problems usually occur.

First, in order to reduce power consumption, it is possible to lower the blowing pressure and perform the adsorption operation at low pressure, but since the amount of N2 adsorption decreases almost in proportion to the pressure, the &lik of the device increases significantly. Next, in order to increase the amount of adsorption, it is possible to perform the adsorption operation under low temperature conditions, but in this case, although the amount of N2 adsorbed increases, the adsorption/desorption rate will decrease significantly, so even if the column length is the same, The O2A degree of the product is actually lower than that at room temperature. Furthermore, as the temperature decreases, the amount of 02 co-adsorbed during N2 adsorption increases, so the power consumption rate gradually increases.

Therefore, the present inventors have already developed a high-performance 02. In the process of conducting intensive research and experiments on N2 separation methods.

Sodium fauziasite, a mineral represented by Na-X type zeolite, increases the amount of N2 adsorption under low temperature and low pressure adsorption conditions, and can maintain the N2 adsorption rate within a practical range, making it an excellent choice for N2 adsorption. He discovered that 7 had a small decrease in the viscosity, and had already filed a patent application for an invention based on this.
Filed as No. 626@ Below, an embodiment of the invention disclosed in Japanese Patent Application No. 58-54626 will be described with reference to FIG.

1.05 to 3 ata in compressor 2 through population side line l
The pressurized air enters the dehumidifying and dehumidifying CO2 tower 4 through the flow path 3, and becomes extremely clean pressurized air. A valve 5 installed downstream of the flow path 3' is open.

Clean pressurized air enters adsorption tower 8 through channel 6 and valve 7 which is open. The pressurized air that has entered the adsorption tower 8 has N2 adsorbed and removed by the N2 adsorbent 9, and the 02 concentration increases as it moves toward the rear. After this, the pressurized air is released into the open valve 10.
11, 12 and the product 02 tank 13 inserted between the valves 11 and 12, the product 02 is recovered. −
A part of the ten thousand products 02 is depressurized by the pressure reducing valve 15 located in the middle of the flow path 14, and passed through the open valve 10' to the adsorption tower 8'.
The adsorption tower 8' is depressurized and drawn by the vacuum pump 18 connected through the open valve 16 and the flow path 17, so that the adsorption tower 8' is injected with the product 02 in the opposite direction to the air flow.
A part of the adsorbent flows under negative pressure, and the N2 adsorbed on the adsorbent 9' in the adsorption tower 8' is easily released and the adsorbent 9' is regenerated in a short time. When the N2 absorbent 9 of the adsorption tower 8 is saturated, and on the other hand, N2 is released from the N2 adsorbent 9' of the adsorption tower 8' and regeneration is completed, the flow path 6 for artificial air is switched to 6', and as described above. By performing these methods alternately, product 02 can be continuously recovered. In addition, the clean pressurized air line 3' at the inlet and the disconnection N
A heat exchanger 19 is used to exchange heat between the gas lines 17 containing 02 as the main component, and a heat exchanger 22 is also used to exchange heat between the product 02 line 21 and the flow path 3'. There is.

Also, since a compression refrigerator 20 is installed in the flow path 3',
Very efficiently the adsorption columns 8 and 8' are cooled and set to low temperature conditions. In addition, when switching the adsorption tower, it is not only necessary to simply switch from flow path 6 to 6' (or vice versa), but also to prevent inlet air from blowing through due to pressure increase immediately after switching.

In order to minimize the release of the pressurized air remaining at the rear of the adsorption tower and the pressurized air at the front, valves 1G and 15.
10' is fully opened and a portion of the remaining 02 at the rear of the adsorption tower 8 immediately after adsorption is transferred to the adsorption tower 8' immediately after regeneration.

At this time, the pressure in the adsorption tower 8 is Pa(ata), the pressure in the adsorption tower 8' is P+(ata);E), equal pressure t(D
The pressure fJ becomes approximately ".+P-' (ata)2. After this, the adsorption tower 8', which has reached approximately - (ata), opens the valve 10.11' to equalize the pressure of the product O2 tank 13 and the adsorption tower. , and the adsorption tower 8' is not filled with even higher pressure 02.The pressure p2 (ata) at the time of pressure equalization with product 02 tank 13
is the dead valley density of the adsorption tower 8.8' (the volume of the space not occupied by the adsorbent in the adsorption tower) is V + (Z), the volume of the product O2 tank is Vz (t), and the Product o2 tank 13
Assuming that the pressure of po(ata) and K are approximately equal, it becomes equal, and P+(ata) when simply switching the column is p.

Compared to the rapid pressure increase to (ata), Pl
(ata), 2(ata), P2(ata),
' Since the pressure is gradually increased with PG (ata), it prevents air from blowing through when increasing the pressure, while reducing the residual 0+ in the desorption process.
Measures are being taken to minimize the flow of high-pressure air out of the system.

Air separation was carried out using the air separation apparatus shown in FIG. 1 using the operating method described below. The operating specifications of the device are shown in Table 1.

However, the pressure swing method shown in FIG.
In the N2 adsorption separation method, a portion of the product oxygen is always used for regeneration. This lowered the yield of product 02 oxygen and increased the power consumption of the vacuum pump 18.

The inventors of the present invention believe that measures to improve this power consumption are one of the major issues to be solved, and as a result of experiments and studies in each building, it is possible to easily open the pressure reducing valve fully and simply desorb the N2 in the adsorption tower using a vacuum pump. I have found that it is possible to play it. Therefore, the power consumption of the vacuum pump is reduced by about 10%.

It was decided that the product recovery rate would improve by about 10%.

In other words, 1 the present invention refers to at least two adsorption towers filled with the mineral name sodium faujasite represented by Na-X, at a temperature F below room temperature, a mixed gas containing oxygen and nitrogen as main components. The nitrogen contained in the mixed gas is selectively adsorbed by flowing into an adsorption tower at a pressure of 13 aLa or higher than atmospheric pressure.

High-purity oxygen or oxygen-enriched gas is discharged from the outlet of the adsorption tower, while the adsorption tower adsorbing nitrogen is heated to a concentration of 0.008 ata or more.
5 ata Hereinafter, the method of the present invention will be explained in detail with reference to Examples.

EXAMPLE In order to demonstrate the effectiveness of the present invention, an attempt was made to separate Na-X, etc. from the air using an air separation apparatus shown in FIG. 2 using an IJ umfaujasite-based N2 adsorbent.

The details of the implementation will be explained below based on FIG.

1.05 to 3 at compressor 2 through inlet side line 1
The pressurized air enters the dehumidifying and dehumidifying CO2 tower 4 through the flow path 3, and becomes extremely clean pressurized air. A valve 5 installed downstream of the flow path 3' is open.

Clean pressurized air enters adsorption tower 8 through channel 6 and valve 7 which is open. The pressurized air that has entered the adsorption tower 8 has N2 absorbed and removed by the N2 adsorbent 9, and the 02 concentration increases as it moves toward the rear. After this, the pressurized air is supplied to the valve 10 in the open state,
11.12 and the product 02 is pushed between the valves 11 and 12 and is recovered as product 02 through N3.

Next, when the N2 adsorbent 9 of the adsorption tower 8 becomes saturated and, on the other hand, N2 is released from the N2 adsorption agent 9' of the adsorption tower 8' and regeneration is completed, the flow path 6 for one person L1 air is switched to 6'.

By performing the methods described so far alternately, product 02 can be continuously recovered. Note that a heat exchanger 19 is installed between the clean pressurized air line 3' and the gas line 170 whose main component is separated N2, allowing heat exchange between the product 02 line 21.
A heat exchanger 22 also allows heat exchange between the flow path 3' and the flow path 3'. Further, since a compression type refrigerator 20 is installed in the flow path 3', the adsorption towers 8 and 8' are extremely efficiently cooled and set to a low temperature condition. In addition, when switching the adsorption tower, simply switch from channel 6 to channel 6' (or vice versa).

Air separation was performed using the air separation apparatus shown in Part 2 using the following operating method. The operating specifications of the device are shown in Table 2.

Table 2 Adsorption device specifications 02.0 from air under the operating conditions shown in Table 2. N2 was separated.

The conventional example shown in Figure 1 and Table 1, and the conventional example shown in Figure 2 and Table 1.
Experimental results with one embodiment of the present invention shown in the table are summarized in FIG. 3 and below. The following aE3 diagram shows the pressure swing type 02 from air using a sequential sodium faujasite adsorbent (hereinafter referred to as -FNa-X), the conventional product of N2 adsorption separation, the case of o2 recirculation, and the case of this product o2 recirculation. The main improvements for air separation in the case of vacuum regeneration without air separation will be explained.

Figure 3 is a graph showing the relationship between adsorption pressure and power consumption. In Figure 3, the horizontal axis is adsorption pressure po ata
, FU 'l1ll & Yospxm/h is the power consumption (暉) required to manufacture 02. Na- as an adsorbent
X and Ca2/3-Na1/3 A, temperature 2
0'C.

When the adsorption tower pressure is changed from 15 to 4.5 ata with the desorption pressure P l-'0.2 ata and the column cavity velocity U = 0.8 cWV'a e C (outlet regulation). In the figure, which is a study of power consumption, the ○ marks are for products without O2 recirculation, and the ■ marks are for products with O2 recirculation.As can be seen from Figure 3, product O2 recirculation iR It can be seen that the adsorbent can be regenerated without any problem even if it is regenerated under vacuum without any problems.In the figure, the data of the conventional adsorbent is C a 2/3-Na 1/3-A
Product 02 Power consumption without recirculation is marked O.
I wrote it down. This is because Na-X is not used in the conventional air separation method using the 142 adsorbent, which has been put into practical use, and no previous literature has shown that this adsorbent does not require product 02 recirculation. It can be said that this is a completely new fact since it is not mentioned in the previous article.

Next, the adsorption pressure P o is the region where the above effectiveness holds true.
= 1.5 a ta , cylinder speed W IJ = 0.8CI
The operating conditions were set to IL/see, temperature zO ℃, and Ca 2/3 Na 1/3-A, Na-X were used as adsorbents.
For each, the desorption pressure p+ was changed from O1 to 0.5ata, and for Na-X, the power consumption was measured with and without product 02 recirculation, and the results are shown in FIG. FIG. 4 is a graph showing the relationship between desorption pressure and power consumption.

In Figure 4, the horizontal axis shows the desorption pressure pl (ata), and the vertical axis shows the power consumption during production (CINm/h). The mark is for product 02 with recirculation.The mark is C8 E-Nal/
3-A also shows the conventional example in the case where product 02 is not recirculated. 02 production power consumption by cryogenic separation method is 0.45 to 0.6 tiles h/Ny? 02, and the power consumption rate for separation with the current equipment using N2 adsorbent is 0.7
By setting the lower limit near KW h /N m' Oz and from Figure 4, as a practical source pressure, in relation to the desorption pressure, the N2 selectivity of the adsorbent increases as the regeneration pressure is lowered. , the power consumption of the vacuum pump increases inversely by 0.2, so the power consumption is 9=F a t when the desorption pressure is
It is minimum near a, so 0.08 ata to 0.5 att
It is the area of 'l! preferably 01 to 0.3 at
It seems to be near a.

Next, the adsorption tower was brought to a cooling condition and adsorption separation under low temperature conditions was attempted. This can be achieved by setting the temperature to low temperature.
This is because the breakthrough zone during adsorption is generally reduced, leading to a reduction in the size of the device and an increase in separation efficiency.

Other operating conditions were set to adsorption pressure 1.5 ata, -A raw pressure 0.2 ata, and cavity speed U = 0.8/sea, and the temperature was gradually lowered from room temperature to low temperature.
The power unit at the time of manufacture was determined. FIG. 5 is a graph showing the relationship between operating temperature and power consumption rate. In Figure 5, the horizontal axis is the temperature, the vertical axis is the power consumption, and the ○ mark is the Na-X product 0.
2 If there is recirculation, I! The mark I is for product 02 without recirculation, and the mark is Ca2/3Me-1LNa1/3
- The case where product 02 of A is not recirculated is shown. As shown in Figure 5, Ca 2/3-Na 1/3-A
In the case of Na-X, the power consumption rate actually increased as the temperature decreased, whereas in the case of Na-X, the power consumption rate continued to decrease as the temperature decreased. Also, the efficiency decreases constantly due to the lack of product 02 recirculation.

The power unit consumption of Na-X in the region up to -60°C was investigated, and no particular problems were found regarding adsorption and separation of air. Furthermore, according to the isobaric data of Na-X in the first-order subsystem, -1
Its effectiveness is not lost even at temperatures around 0°C. However, temperatures lower than this are not preferable because the co-adsorption of 02 during Na adsorption cannot be ignored. Regarding the cooling means, there are no particular problems in this temperature range, and the cooling technology of cryogenic separators can be commonly used.

Significant improvement in performance of Na-X and Ca2 in low temperature range
The incompatibility of /3-N a 1/3-A is also reflected in the 02 concentration at the outlet of the adsorption column. Figure 6 shows temperature and adsorption tower outlet 02
This is a graph showing the relationship with the concentration. In Figure 9, the horizontal axis is the eddy current. The vertical axis is the concentration of the adsorption tower outlet 02, and the circle indicates the Na-X product 02.
Regarding C without circulation, c mark is Ca, )-Nal/3-A
The case of product 02 without recirculation is shown. The operating conditions are: adsorption pressure P o = 1.5 a ta , desorption pressure p + = Q2a ta , cylinder speed [U = = 0.4
~o, 8 cm/sec, temperature was lowered to low F, and adsorption separation was performed.

The axis line in FIG. 6 shows the case where U=0.8 crn/see. As can be seen from Figure 6, Ca2/3-N
In a1/3-A, 02d11 degrees at the adsorption tower outlet hardly increases even in the low temperature range, whereas in Na-X, 02g1Jt increases rapidly as the temperature decreases. Furthermore, when the cylinder speed is 04crn78ec and the temperature is -30℃, the 02 concentration is the theoretical upper limit for air separation by the N2 adsorbent.
The concentration exceeded 945% (residual gas argon) and reached 96%. This has led to a new method for producing high-purity 02 that can also remove argon by using Na-X in this temperature range. Furthermore, the fact that the N2 adsorption performance has been improved on the low-temperature side means that the problem of lowering the temperature inside the column due to scale-up is considerably alleviated.

What has been described above is mainly related to power costs and 02 purity, but next we will discuss items related to initial equipment costs. The operating conditions in FIG. 6, namely adsorption pressure P o = l,
5 a t a , desorption pressure p + = 0.2 a t
FIG. 7 shows the amount of adsorbent required to produce 02 INm/hour at a cylinder velocity [U=0.8 cIn//sec c. Figure 7 is a graph showing the relationship between temperature and the amount of adsorbent mentioned above. In Figure 9, the horizontal axis is temperature and the vertical axis is lN per hour as described above
The adsorbent weight [~] required to produce 02 of m' is the O
The markings indicate the case without Ca 2/3-Na 1/3-A product 02 recirculation. As can be seen from Figure 7, Ca2/3-Na1/3-A can save only about 10% of the adsorbent weight at room temperature even at low temperatures, while Na-X can save 45% at -30°C. It is highly effective because it can save a considerable amount of ql, which can be used to reduce the amount of adsorbent that accounts for a considerable portion of the equipment cost. As described in detail above, according to the present invention, mineral-based sodium faujasite represented by Na-X is used, the adsorption process pressure is 3 ata or less, and the desorption process pressure is 0.08 to 0. If the pressure swing adsorption separation of a mixed gas, such as air, is carried out under a pressure range of 5 at a and without recirculating the product 02 and using a temperature range below room temperature, it is possible to conventionally produce I Nm' of 02 per hour. The power unit required to do this is 045-0.6K using the cryogenic separation method
The current adsorption separation process, which requires 0.7KW or more, can be reduced to around 0.4KW, and the amount of adsorbent used can also be reduced to 55% of the current adsorbent method.

Since the regeneration process is still performed without recycling product 02, the power consumption of the vacuum pump is reduced by about 10%.
Furthermore, the product recovery rate is expected to improve by about 10%.

As explained in detail above, 1. The present invention proposes a method for separating oxygen and nitrogen from a mixed gas that requires less power consumption and less adsorbent than conventional adsorbent methods, and is very useful industrially. It is something.

[Brief explanation of drawings]

FIG. 1 is an illustration of an air separation device used to carry out the conventional separation method, FIG. 2 is an illustration of an air separation device used to carry out the separation method of the present invention, and FIG. 3 is an illustration of an air separation device used to carry out the separation method of the present invention. Graph showing the relationship between pressure and power consumption. Figure 4 is a graph showing the relationship between desorption pressure and power consumption. Figure 5 is a graph showing the relationship between temperature and power consumption. Figure 6 is temperature. FIG. FIG. 7 is a graph showing the relationship between temperature and adsorbent required to produce INm-Q2/h. 2... Compressor, 4... Dehumidification and COm tower, 8... Adsorption tower. 13...Product 02 tank, 1B...Vacuum pop, 2
0...Compression refrigerator. Figure 2 Figure 3 Adsorption pressure P0rofa) De-nJE force Pf (ata) 50th 60th bubble seat r'c) Figure 7, dp41 匈子'S? One Temperature of Leather r'cJ Continued from page 1 @ Inventor Fuku 1) No. 1-1 Uramachi, Nagasaki Heavy Artillery, Mitsubishi Heavy Industries, Ltd. Nagasaki Research Institute Procedural Amendment (Voluntary) Incident of May 7, 1980 Indication 1982 Patent Application No. 204408 Name of the invention 02 Relationship with the case of a person who amends a method for improving the recovery rate of manufacturing equipment Patent applicant address Marunouchi, Chiyoda-ku, Tokyo-', l'D 5 & 1 Title h. (620) Mitsubishi Heavy Industries Co., Ltd. Agent 111' Subject of domain amendment 1, "Valve 16" in Line 14 of Specification No. 5jj is amended to "Valve 16'". λ Change “Remaining 01” on page 7, line 15 of the detailed description to “Remaining”
and correct it. 3. “On the other hand, adsorption tower 8
'...can be recovered. ” is corrected as follows. Meanwhile, with respect to the adsorption tower 8', the valve 10' is closed, the valve 16' is opened, the adsorption tower 8' is brought to a reduced pressure by the vacuum pump 18, and N2 is separated from the N2 adsorbent 9' and flows into the flow path 17. The high concentration 02 remaining at the rear of the adsorption tower 8 is discharged to the outside of the thread by the vacuum pump 18, and the regeneration is completed.Then, when the valves 7, 7' and 11 are closed and the valves jO and 10' are opened, the high concentration 02 remaining at the rear of the adsorption tower 8 is removed. It is transferred to adsorption tower 8' under reduced pressure and recovered. At this time, the pressures of towers 8 and 8' are approximately equal to #1. After that, the inlet air flow path is switched from 6 to 6', and the By performing the methods alternately, product 02 can be recovered continuously.'' 4. Insert the following sentence between lines 15 and 16 on page 11 of the specification. [No, as mentioned earlier, it goes without saying that there is no need to branch part of product 02 and purge the adsorption tower in the regeneration process. 1 5 Specification-1 11th work 1i Correct "2nd" in line 16 to "Fig. 2". 6. Figure 1 shall be amended as shown in Figure 1 of the attached drawings. 7. Correct 1!21”?l as shown in Figure 2 of the attached drawings.

Claims (1)

[Claims] In at least two adsorption towers filled with the mineral name sodium faujasite represented by Na - Nitrogen contained in the mixed gas is selectively adsorbed by flowing into an adsorption tower, and high-purity oxygen or oxygen-enriched gas is discharged from the outlet of the adsorption tower, while the adsorption tower that has adsorbed nitrogen is heated to a concentration of 0.08 ata or more. .5a
A method for improving the recovery rate of a 0□ manufacturing device, characterized in that the product is depressurized and regenerated without being recirculated below ta.