JPS5857211B2 - An improved method for industrially and continuously producing high-concentration oxygen from air - Google Patents

Description

Detailed Description of the Invention: Japanese Patent Publication No. 47-50996 discloses a first method filled with an adsorbent whose adsorption capacity for nitrogen is larger than that for oxygen.
The column is connected in series with a second column filled with an adsorbent whose adsorption capacity for components in the air that would degrade the adsorption capacity in the first column is greater than the adsorption capacity for nitrogen or oxygen, with a valve that can be opened and closed, When the first and second columns are depressurized and exhausted from the exhaust port provided on the end face of the second column that is not connected to the first column, substantially most of the gas desorbed from the first column is transferred to the second column. A gas having an oxygen concentration higher than the desired concentration is introduced into the first column and then the second column from the end face of the first column which is not connected to the second column, and the inside of both columns is used for adsorption operation. Feedback operation to maintain almost the same pressure, and adsorption operation to feed ordinary air as it is from the same end face as the exhaust port during the desorption operation and at the same time collect high concentration oxygen from the same end face as the oxygen inlet during the feedback operation. The operations are repeated in the above order, and if the components that degrade the first column break through from the second column during the adsorption operation in the main operation, a sub-operation is performed to heat and regenerate the second column. A method for producing oxygen with a higher concentration than crude air, which is characterized by its characteristics, is explained.

In this known method, a method is described in which three units of unit equipment consisting of a combination of the fourth column and the second column are operated in parallel when the method is to be operated continuously on an industrial scale.

The present inventor has previously improved the method of using the 3-unit device, simplified the operation, and improved the efficiency of the device. An improved method that can be operated in the unit's second column was discovered, and the present invention was completed.

That is, according to the present invention, it is possible to efficiently produce highly concentrated oxygen of desired purity by using ordinary air containing moisture, carbon dioxide, etc. as a raw material without any pretreatment in the apparatus of the present invention. I can do it.

The present invention (FIG. 1) will be explained below with reference to the accompanying drawings.

FIG. 1 explains the present invention, and shows a first column 1 of a first unit, which is a nitrogen adsorption column for oxygen separation, and a first column 1 of a second unit, which is a nitrogen adsorption column for oxygen separation.
A column 2, a first column 3 of the third unit, a second column 4 of the first unit, which is two adsorption columns (hereinafter referred to as pretreatment columns) for removing moisture and carbon dioxide, and a second column of the second unit. It consists of 2 towers and 5 towers.

Adsorption towers 1, 2, and 3 are filled with commonly used adsorbents such as molecular sieves 5A and 13X, which have a high selective adsorption power for nitrogen. It is preferable to use a suitable adsorbent.

In the pretreatment towers 4 and 5, adsorbents capable of adsorbing moisture, carbon dioxide, etc., such as silica gel and alumina, can be used in addition to the adsorbents used in the adsorption towers 1, 2, and 3.

Although not shown, each of the pretreatment towers 4 and 5 can be provided with a heating device known per se, so that the inside of the tower can be heated if necessary.

At the beginning of operation, the vacuum pump 25 is passed through the tube 24.
The first column 1 of the first unit and the second column 4 of the first unit are evacuated, and the components adhering to the adsorbent and the walls of the adsorption system are evacuated and removed (hereinafter referred to as desorption operation).

The valves 26 and 27 are check valves through which gas passes only in the direction of the arrow.

At this time, valves 6 and 9°15 are closed, and valves 12.18.21-
1.22-2゜When 23-1 is opened, desorption gas flows from both the path from the end face of the column 1 connected to the column 4 and the path passing through the valve 12 from the other end face, both of which are passed through the column 4. and is exhausted.

Therefore, the evacuation time is very short compared to known methods.

The degree of vacuum varies from 1/2 to 1/2 depending on the concentration of oxygen to be obtained.
It is appropriate to set the pressure to about 1/1.00 atm.

The higher the degree of vacuum at this time, the more pure oxygen can be absorbed.

Next, valve 18 and valve 12 are closed, valve 6 is opened, and highly purified dry oxygen is introduced into the system from high concentration oxygen gas reservoir 28 (hereinafter referred to as feedback operation).

This pure oxygen is supplied from another oxygen source only for the first operation, but the oxygen obtained by the method of the invention can be used from the next operation.

The oxygen supply pressure required for this feedback operation differs depending on whether the next adsorption operation is performed based on normal pressure or pressurization, but if it is performed based on normal pressure, the pressure in the system will decrease. (g) Supply until the pressure reaches atmospheric pressure, or if the pressure is based on the pressurized state, supply until the pressure reaches that pressure.

In the present invention, the start of this feedback operation in the first column 1 of the first unit means that at the same time the valve 9 opens and the third
The adsorption tower 3 of the unit first tower 3 during the adsorption operation to be explained later.
The concentrated oxygen, which may be discharged, is introduced into a part of column 1 via valve 9 and the serial connection of columns 1 and 4.

Therefore, compared to the known method, the time required for feedback is halved, and the amount of product oxygen flowing back from the high-concentration oxygen gas reservoir 28 consumed for feedback is also approximately halved, so according to the method of the present invention, Compared to known methods, the efficiency of operation and equipment is significantly increased.

At the same time as valve 9 opens, valves 212° 23-2, 22-1
is opened, the pretreatment column 4 (the second column of the first unit) performs an adsorption operation, and the pretreatment column 5 (the second column of the second unit) performs a desorption operation.

In this way, even after the feedback operation of the present invention is completed, the introduction of gas from the pull column 3 is stopped and the high concentration oxygen gas in the column 1 is driven out. 6 and then collected as a product at 28.

This expulsion operation is the first half of the adsorption operation. The nitrogen concentration in the gas at the outlet end of the adsorption tower 1 is the same as the gas used for feedback for a while, but as the adsorption operation continues, the nitrogen concentration suddenly increases after a certain time. Eventually, g becomes the same as the air composition (hereinafter, the point where the nitrogen concentration suddenly changes like this will be referred to as the nitrogen breakthrough point,
Also, the curve showing the relationship between the gas outflow amount and the nitrogen concentration at the outlet end is called a breakthrough curve).

Therefore, in the present invention, which aims to keep the nitrogen concentration in the product gas low, valves 9 and 6 are closed just before the nitrogen breakthrough point, valves 15 and 10.7 are opened, and a conduit 29 is connected to the floor 30. of air, that is, air still containing carbon dioxide gas and moisture, is introduced into the column 5, and the high concentration oxygen gas coming out of the column 1 passes through the valve 10 and enters the first column 2 of the second unit. , valve 7
After that, it is discharged as a product to the high concentration oxygen gas reservoir 28 (
Column 1 is the second half of the adsorption operation).

At this time, valve 21-1.22-2.23i is opened,
Column 4 is used for desorption operation, and column 5 is used for adsorption operation.

At this time, the first column 2 of the second unit corresponds to the feedback operation, and functions in exactly the same way as the feedback operation and expulsion operation described in the first column 1 of the first unit.

When the column 1 switches from the first half of the adsorption operation to the second half, the first column 3 of the third unit switches from the second half of adsorption to desorption.

That is, while valve 8 is closed, valves 14 and 20 are opened, valve 17 is closed (valve 11.9 is already closed), and pipe 24 is closed.
This is a desorption operation in which a vacuum is drawn from the first unit.
It functions exactly the same as the desorption operation described for tower 1.

Just before the nitrogen in the product from valve 7 breaks through, column 1 finishes the second half of adsorption, valves 6 and 9 are closed and valves 10 and 15 are closed.
is closed, valves 12 and 18 are opened to begin the desorption operation, and one cycle of the first column 1 of the first unit is completed.

At this time, the valves 22-1, 21-2 and 23-2 are opened, and the column 4 becomes an adsorption operation and the column 5 becomes a desorption operation.

Note that even when the first cycle of the tower 1 is completed, the 1.5 cycle of the tower 4 is completed, and when the second cycle of the tower 1 is completed, the third cycle of the tower 4 is completed, and the first cycle is started for the first time in this construction. Both tower 1 and tower 2 will return to their initial state.

Note that the pipe 31 is a pipe for taking out high concentration oxygen gas, which is a product gas.

As explained above, in the present invention, by simply reducing the number of pretreatment towers by one unit to two units and adding three three-way valves, it is possible to achieve a greater effect than the known method. Since the treatment tower is operated for 1.5 cycles, there is also the great effect that the pretreatment tower is sufficiently regenerated (desorbed).

The above-mentioned breakthrough point can be detected while monitoring the nitrogen concentration in the gas using an ordinary oxygen concentration meter, but it is possible to detect the rapid temperature rise as the breakthrough point is passed by utilizing the heat generated by the adsorbent due to nitrogen adsorption. This can also be done by detecting with a thermocouple, thermistor, etc.

Also, if you test in advance under certain operating conditions and know the time until breakthrough, you can operate under time conditions.

Further, the detection position of the breakthrough point may be at the gas outlet end, or may be located at a position somewhat closer to the gas inlet than the outlet end.

In order to further clarify the method of the present invention, the open and closed states of the valve are shown.

Valve 6 to 20, valve 211 to 23 in the order shown in Table 1 below.
-2 opens and closes each unit device A, B.

Oxygen can be continuously produced by performing adsorption, feedback, and desorption operations sequentially in each operation cycle from the first operation cycle to the sixth operation cycle shown in Table 1.

Regarding the pretreatment tower (second tower), the 4th column of the first tower →
Since this is a method in which adsorption and desorption are repeated every 5th, 6th → 1st, 2nd → 3rd, in Table 1, there is a discontinuity between 3rd and 4th valves (valves 21-1 to 23). You can understand this by paying attention to the opening and closing of -2).

This is displayed continuously when the first tower reaches the 12th operation cycle, but is omitted in this article.

It is advisable to switch the valves during the "first half of adsorption" operation, when the oxygen concentration near the first column is decreasing and nitrogen is about to break through.

If the adsorbent capacity, adsorption rate, adsorption pressure, adsorption temperature, flow rate of air flow, etc. are constant, the switching timing for each cycle can be determined at approximately constant intervals. Alternatively, if the gas concentration at the outlet end of the three towers and the temporal relationship are determined in advance empirically, it is possible to easily switch to the next cycle at regular intervals.

In addition, when the adsorption conditions are not constant or the air feeding speed is not constant, place the above-mentioned appropriate breakthrough detector at an appropriate position in the tower in advance and perform the following at the time indicated by the detector. It is most desirable to switch to a cycle.

That is, switching from the second cycle to the third cycle, from the fourth cycle to the fifth cycle, and from the sixth cycle to the first cycle in Table 1 is performed at the gas outlet of adsorption tower 2, 3, or 1, respectively. It is only necessary to switch when the nitrogen concentration in the gas at the end increases even slightly than the desired value.

In the above-mentioned adsorption operation, for example, the first column (adsorption column) 1 of the first unit is compared with the second column (pretreatment column) 4 of the first unit.
So, unless the capacity is extremely small, the feed air is mainly composed of nitrogen, and the adsorption capacity of commonly used adsorbents for moisture and carbon dioxide is significantly greater than that for nitrogen. Before the adsorption capacity for moisture and carbon dioxide reaches saturation, column 1 passes the breakthrough point for nitrogen, and furthermore, even if column 1 is transferred to the latter half of the adsorption operation, and even after the adsorption operation is completed, column 4 remains saturated. You can also prevent it from reaching .

In other words, even if air is fed into column 4 until the adsorption operation in column 1 is completed, if the amount of adsorbent in column 4 is kept above a certain value compared to the amount of adsorbent in column 1, the incoming air All of the carbon dioxide gas and moisture contained therein are adsorbed into the column 4, and no moisture or carbon dioxide gas can enter the column 1.

However, in the present invention, column 4 switches before column 1 switches from adsorption to desorption, and this cycle ratio is 1:1.
5, the adsorbent in the pretreatment tower is reduced to 1/1 of that in the above case.
Another great feature is that it can be reduced to 1.5.

Next, in the desorption operation, the valves 21-1 and 23-1 are opened, and the gas mainly composed of dry nitrogen in the first column is exhausted.
During this time, the moisture and carbon dioxide in the tower 4 are also desorbed.

Next, a feedback operation is performed using the oxygen obtained by the adsorption operation, and at this time, the oxygen gas is
At the same time as flowing in the direction of the column, e.g. from valve 9 to column 3
The highly concentrated oxygen obtained in step 1 flows in, which simultaneously flows in the direction of the first column until the pressure inside the first column reaches normal pressure.

At the start of this feedback operation, column 4 has already been switched to perform adsorption (decarbonization and dehydration), and the dry, clean air from column 4 is sent to column 1, which is the "second half of the adsorption operation." Supplied.

Therefore, in the conventional method, if such operations are repeated for a long time, moisture and carbon dioxide gas gradually accumulate in the column 4, and the adsorption capacity is eventually lost.

In order to prepare for such cases, the conventional method uses multiple pretreatment towers (for example, 6) to allow desorption and regeneration of each pretreatment tower while switching to these. However, in the present invention, this is not necessary at all (it is sufficient to replace a part with a new one at the time of regular inspection approximately once a year).

As mentioned above, in known methods, desorption is performed exclusively in the first step.
Whereas it is done from the end of the tower that connects to the second tower,
In the present invention, since desorption is performed from both end faces of the first column, the desorption time can also be reduced to about 1/2.

Furthermore, since the desorbed gas from the first column contains neither moisture nor carbon dioxide, the second column can significantly recover its performance through this desorption operation and its life is extended.

Furthermore, the present invention also has the following effects.

In other words, a tower consisting of 3 units of adsorption tower and 2 units of pretreatment tower is installed, and in the feedback operation, the previously collected product is fed back with high-concentration oxygen gas, and at the same time, the high-concentration gas discharged during the adsorption operation is fed back. By introducing oxygen gas between the first column and the second column (the part connected in series), the pressure of the first column is adjusted to the adsorption pressure, which cooperates with the original feedback operation, and after the feedback is completed. In addition to introducing the above-mentioned discharged high-concentration oxygen as an expulsion operation, it is possible to subsequently introduce moderate-concentration oxygen gas (the first half of the adsorption operation), thereby extending the time of the adsorption operation. In addition, the operation time for the desorption operation is shortened by exhausting air from both ends of the first column as described above, and in addition to shortening the operation time, the number of valve switching times is significantly reduced compared to the conventional method. was completed.

Furthermore, according to the present invention, the amount of high-concentration oxygen gas from the collected product that is fed back to the first column for feedback operation can be halved, and the efficiency of the device can be doubled. Moreover, it has the great effect of requiring only two units of pretreatment towers with relatively small internal volumes to be installed.

In the above-mentioned oxygen separation method by adsorption, the nitrogen adsorption tower is filled with an adsorbent that has a different adsorption capacity for nitrogen and oxygen, and the pretreatment tower is filled with air that degrades the ability of the adsorbent packed in the nitrogen adsorption tower. As already mentioned, it is sufficient to fill the container with an adsorbent that can adsorb and remove the components.

As such adsorbents, molecular sieves 5A and 13X, which are a type of synthetic zeolite, are suitable for the former.
It is known that these synthetic zeolites, alumina, silica gel, etc. are suitable for the latter.

The inventors of the present invention have discovered that oxygen gas of even higher purity can be produced at a higher yield by using the following substances instead of these known substances.

That is, it is a kind of tuff mainly composed of SiO2, A1□03 and H2O, with 1 to 10% by weight of alkali metal and alkaline earth metal oxides, and the X as shown in Table 2 or Table 3 below. It is preferable to use an adsorbent obtained by pulverizing a naturally produced inorganic substance having a line diffraction pattern to an appropriate particle size, heating the resulting material to 350 to 700°C, particularly 400 to 650°C, and dehydrating it.

One of the basic features of the invention is as follows.

That is, FIG. 2 shows the direction of gas flow, and 32 indicates a first column, and 33 indicates a second column, which are connected in a straight line for convenience.

``A'' in ``A'' indicates the flow in the first half of the adsorption operation, ``B'' indicates the flow in the second half of the adsorption operation, ``a'' and ``b'' in the opening indicate the gas flow during the desorption operation, and ``A'' in C indicates the gas flow from the product gas reservoir during the feedback operation. , b is the gas flow from the pre-bath (the tower performing the latter half of the adsorption operation) during the feedback operation, C is the flow of the raw air after desorption, and C' is the dehydration-cleaned gas flow. This shows the flow of air, which is similar to the flow shown in b of A.

As will be seen, in the first column, the gas flow direction A for the adsorption operation and a part of the gas flow direction port for the desorption operation are in the same direction, and the gas flow direction A for the adsorption operation and the gas flow direction for the feedback operation are in the same direction. The gas flow direction for the desorption operation and the gas flow direction for the feedback operation are completely opposite directions, and this feature has the various effects described above. It can be said that it is producing.

The high concentration oxygen gas reservoir 28 shown in FIG. 1 is generally made of a flexible material or a rigid material such as metal.

Among these, flexible tanks allow gas to be taken in and out at a constant pressure, making it possible to have a large effective volume.However, since organic films are generally used, moisture and carbon dioxide gas easily permeate through flexible tanks, which causes problems during feedback operations. Not only does it become a nuisance, but it also causes corrosion of the materials of towers, tanks, piping, etc.

On the other hand, with resin tanks made of steel, the permeation of moisture and carbon dioxide is reduced, but the pressure changes are large when loading and unloading.
In order to reduce this, it is necessary to have the characteristics of a buffer tank, and therefore the tank must be very large.

Therefore, it is proposed that the gas reservoir 28 of the present invention be constructed in the same way as an adsorption tower, by filling a resin tank with an adsorbent such as zeolite.

In this way, since zeolite is an adsorbent that has the property of adsorbing oxygen in addition to nitrogen, the inflowing oxygen gas is adsorbed by the adsorbent, and the amount of oxygen adsorbed is more than 5 times the space occupied by the adsorbent under normal pressure. , and the higher the pressure, the larger the amount of adsorption becomes.

This increases the effective capacity of the tank, which not only has the advantage that the tank itself can be very small, but also has the advantage that there is very little pressure change when gas is put in and taken out.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram showing one embodiment of the method of the present invention, and FIG. 2 is a flow diagram showing the direction of gas flow during each operation of adsorption, desorption, and feedback in the method of the present invention. 3 indicates an adsorption operation, 3 indicates an adsorption operation, 3 indicates a feedback operation, 32 indicates a first column, and 33 indicates a second column. 1.2, 3: Nitrogen adsorption tower (first tower); 4, 5: Pretreatment tower (second tower); 6 to 20. 21-1 to 23-2: Valve; 24
: Vacuum outlet; 25: Vacuum pump; 26, 27: Check valve; 28: Product high concentration oxygen gas reservoir: 29: Raw material air inlet; 30 Two raw material air blowers; 31: Product high concentration oxygen Gas outlet.

Claims (1)

[Scope of Claims] 1. A first column filled with an adsorbent whose adsorption capacity for nitrogen is higher than that for oxygen, and an adsorption capacity for components present in the air that would degrade the adsorption capacity in the first column. The first column of the second column is connected in series with a second column filled with an adsorbent having a larger adsorption capacity for nitrogen or oxygen.
The first and second towers are depressurized and exhausted from exhaust ports provided on the end faces that are not connected to the tower, and the gas desorbed from the first tower passes through both end faces of the first tower and then into the second tower. a desorption operation carried out by passing through the first column, introducing a gas having an oxygen concentration higher than the desired concentration from the end face of the first column that is not connected to the second column,
Feedback operation to make the pressure inside the first column almost the same as during adsorption operation, normal air is fed as it is from the same end face as the exhaust port during desorption operation, and at the same time, the same end face as the oxygen inlet during feedback operation. The two main operations are the adsorption operation for deriving high concentration oxygen from
The units are arranged in parallel, and the highly concentrated oxygen derived during the adsorption operation of the first column of the first unit is transferred to the first column of the second unit almost simultaneously with the start of the feedback operation of the first column of the second unit, which has completed the desorption operation. The second
The high-concentration oxygen gas in the first column of the unit is expelled from the end face that is not connected to the second column, and the high-concentration oxygen gas is collected as a product and stored in a high-concentration oxygen gas reservoir. Further, at or before the time when the oxygen concentration in the product gas falls below a predetermined concentration, the first column of the first unit is switched from adsorption operation to desorption operation, and the first column of the second unit is switched from expulsion operation. The first column of the third unit, which has completed the adsorption operation, is switched to the feedback operation and the subsequent expulsion operation, and the second column of the first unit and the second column of the second unit are switched as described above. Sometimes there are two desorption and adsorption operations.
A method for industrially continuously producing high-concentration oxygen from air, characterized by switching so that only operations are performed alternately. 2. Claim 1, characterized in that the high-concentration oxygen gas reservoir of the product is made of a material that does not permeate moisture and carbon dioxide gas, and the gas reservoir is filled with an adsorbent that has at least the ability to adsorb oxygen. The method described in section.