JPH07110762B2 - Method for producing high concentration oxygen - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing high concentration oxygen by using a pressure swing method (hereinafter referred to as PSA) using air as a raw material.

[0002]

2. Description of the Related Art A method for obtaining oxygen by PSA method using air as a raw material is the conventional method of using a zeolite molecular sieve having a pore size centered at 5Å with two or more adsorption columns. Oxygen concentration of up to 95% was obtained by adsorbing at a pressure higher than atmospheric pressure and desorbing and regenerating at a pressure lower than atmospheric pressure.

Zeolite molecular sieves having a pore size centered on 5Å have the property of preferentially adsorbing nitrogen over oxygen and argon, and the oxygen concentration in the air is 20.9%.
Even if the argon concentration of 0.9% was concentrated up to about 5 times and nitrogen was completely adsorbed and removed, oxygen could not be concentrated to more than about 95% because argon was present at a concentration of about 5%. In fact, no method has so far been known for obtaining oxygen having a concentration of 95% or more by PSA.

[0004]

Means for Solving the Problems The inventors of the present invention considered that it is possible to further increase the oxygen concentration by removing this argon, and the applicant of the present application filed Japanese Patent Application Laid-Open No. 59-92907. Publication "Production Method of High Concentration Argon"
The present invention has been achieved as a result of extensive studies on a method for producing high-concentration oxygen of 95% or more by applying the method described in 1.

That is, oxygen containing argon obtained by PSA (hereinafter referred to as a first-stage apparatus) using zeolite molecular sieve is introduced into an adsorption tower filled with carbon molecular sieve having a pore size centered at 3 to 4Å. Then, by performing PSA in the three-column type second-stage device, oxygen is preferentially adsorbed to the carbon molecular sieve,
It was possible to separate and remove argon as a non-adsorbed gas.

Since carbon molecular sieve has a property of diffusing oxygen into pores faster than nitrogen and argon in a short time of 1 to 2 minutes, oxygen is preferentially adsorbed by utilizing this difference in adsorption rate, By desorbing this, a high concentration of oxygen could be recovered. As a result, we succeeded in obtaining high concentration oxygen of 95% or more, and even 99% or more.

An object of the present invention is to provide a method for industrially producing highly concentrated oxygen, the gist of which is:
First-stage adsorption device packed with zeolite molecular sieves
Pressure swing using air as the raw material.
Non-adsorbing, containing oxygen and argon as main components
Get the gas and fill it with carbon molecular sieves
To the second stage adsorption device and perform a pressure swing.
To separate and remove argon and nitrogen as non-adsorbed gas.
In the method of producing high concentration oxygen by desorbing the deposited oxygen
The second-stage adsorption device is a three-column type, and two of them are
The main component is the oxygen generated from the first stage adsorption device.
Gas is passed in series, and then the acid on the upstream side of the two towers
Desorption is carried out in a tower that has saturated adsorption of elements, and the gas at the initial stage of desorption is
While recovering in the raw material gas introduced into the two-stage adsorption device,
Characterized by acquiring gas in the late stage of desorption as high-concentration oxygen
And a method for producing high-concentration oxygen . In addition, oxygen recovery
For the purpose of increasing the rate, install a third stage adsorption device
Good.

Since the conventional PSA method can only obtain oxygen at a maximum concentration of 95%, it is impossible to apply all the oxygen obtained by PSA to the industrial field where liquid oxygen is used. Now, by simply obtaining high-concentration oxygen from the air only with PSA, it becomes possible to generate and use high-concentration oxygen corresponding to liquid oxygen at a low cost, at a necessary place, and at a necessary time.

The first-stage PSA apparatus filled with zeolite molecular sieves is a conventional method, that is, the PSA apparatus filled with carbon molecular sieves operated at an adsorption pressure of not less than atmospheric pressure and not more than 1 kg / cm ² G is the second stage. It is composed of a third stage, and has respective steps of adsorption-equalizing pressure-pressurization-desorption, the adsorption pressure is 0.3 to 10 kg / cm ² G, preferably 1 to 3 kg / cm ² G, and the desorption pressure is atmospheric pressure. It is economically advantageous to reduce the pressure at 400 torr or less, more preferably 200 torr or less, from the viewpoint of the size and recovery rate of the device and the amount of power consumption.

The present invention has been added to the first and second stage adsorption devices.
And about the whole equipment that has the third stage adsorption device,
As described above, the 3rd stage adsorption device recovers oxygen as described above.
This is a device that is appropriately installed to improve the rate. Table 1 shows the second-stage sequence, Table 2 shows the third-stage sequence, and FIG.
Shows the flow combining the first stage, the second stage and the third stage. In this flow, the second stage device is a 3-tower type, and the third stage device is 2
Although a tower type apparatus is shown, the number of adsorption towers can be appropriately changed. However, in terms of the cost of the apparatus, the ease of operation, and the stabilization of product purity, good results are often obtained when the second-stage apparatus is a three-column type and the third-stage apparatus is a two-column type.

[0011]

[Table 1]

[0012]

[Table 2]

In FIG. 1, first, existing PSA is performed by using air as a raw material in a first-stage device filled with a zeolite molecular sieve to obtain a gas having an oxygen concentration of 93% or more as a non-adsorbed gas.

About 3 kg / cm ^{2 of} this gas is compressed by the compressor A.
Pressurize to G, valve 1, valve 13, valve 9, valve 1 of the second stage device
2 is introduced in series into the tower I and the tower III to adsorb oxygen so that the oxygen concentration is about 80% and the oxygen is discharged to the receiver D.

The oxygen already adsorbed in the column II is circulated to the inlet of the compressor A after the pressure is stabilized in the buffer tank F through the valve 5 and the valve 17 for about 5 seconds in the initial stage of desorption.
This is because in the initial stage of desorption, the desorption gas concentration is almost equal to the source gas concentration and 99% high concentration oxygen cannot be obtained. In the latter half of desorption, it takes about 55 seconds to use vacuum pump B for about 1
After decompression regeneration to a pressure of 50 Torr, the desorbed high concentration oxygen of 99% or more is stored in the receiver E through the valve 16.

Next, the column I after the two adsorption steps and the column II after the desorption step are valve 4, valve 5, valve 13, and valve 1.
The pressure is equalized through 4 to recover the raw material gas. In accordance with the above steps, the second-stage apparatus repeats the steps shown in Table 1 with about 3 minutes as one cycle.

The third-stage apparatus has a gas concentration of about 80% introduced from the second-stage apparatus and the rest is nitrogen and argon. A gas having a pressure of 1.5 to 2.0 kg / cm ² G is supplied to the valve 18 and the valve. 24
After adsorbing oxygen in the tower I through the
It is discharged to the receiver H as the gas.

Before the desorption, the oxygen adsorbed in the tower I is pressure-equalized with the tower III which has completed the desorption process through the valves 22 and 23 to collect the raw material gas. Then, the tower I enters the desorption process through the valve 20, oxygen of about 93% concentration is desorbed by the vacuum pump C and stored in the buffer tank G, and then circulated to the inlet of the compressor A of the second stage device and recovered. To be done.
The column III subjected to pressure equalization is pressurized by the gas introduced through the valve 19 and then enters the adsorption step.

According to the above steps, the third stage apparatus repeats the steps shown in Table 2 with one cycle of about 2 minutes. The second-stage device , which is a feature of the present invention, and the third-stage device connected to the second-stage device will be further described. The second-stage device is a device for recovering high-concentration oxygen as a desorption gas. This is to circulate the desorbed oxygen in the raw material gas of the second stage apparatus in order to increase the yield of oxygen, whereby the oxygen introduced from the first stage apparatus can be obtained with a recovery rate of 80% or more.

The characteristic of the sequence of the second-stage apparatus shown in Table 1 is that the raw material gas is passed through the two adsorption towers in series at the time of adsorption and then oxygen is present at the upstream side of the two towers at the time of desorption. The purpose is to select the saturated adsorption column and regenerate it under reduced pressure to desorb and collect high-concentration oxygen. In this case, before desorption, the pressure in the column after the desorption process is equalized and the gas in the column is recovered. afterwards,
Although desorption is started by decompressing and starting desorption, since the desorption gas at the initial stage of desorption is close to the composition of the source gas, it can be circulated as a part of the source gas, and the gas desorbed in the latter stage can be obtained as high concentration oxygen.

In order to omit the vacuum pumps B and C shown in FIG. 1, the adsorption pressure of the second and third stage devices is set to 3 kg / c.
and Sosaku in the range of m ² G or more up to 10kg / cm ² G, it is also possible to perform the PSA desorption pressure during decompression reproduced as about atmospheric pressure, 3 kg of the discharge pressure of the compressor A in which case the / Cm ² G or more to a maximum of 10 kg / cm ² G and the suction pressure must be kept at atmospheric pressure or less. Therefore, the selection should be made according to the condition of the device.

[0022]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 Using air as a raw material, the adsorption pressure was set to 50 in a three-column type first stage apparatus.
Oxygen gas of 93.3% concentration obtained by performing PSA with 0 mmH ₂ O desorption pressure of 150 Torr, carbon having a pore diameter centered on 3Å to 4Å manufactured by Bergbau in West Germany in 200 mmφ × 1100 mmH as an adsorption tower. A three-column type second-stage device filled with molecular sieves was pressurized to 3.0 kg / cm ² G with a compressor, and adsorption 1-
58 seconds, hold (process that does nothing) -2 seconds, adsorption 2
-58 seconds, pressure equalization-2 seconds, desorption-58 seconds, pressure equalization-2 seconds (1
PSA was performed in a sequence of 3 minutes in total cycle).

At this time, the adsorption pressure is 2.6 kg / cm ² G
Desorption pressure is 160 Torr and compressor inlet gas volume is 2
2.8 Nm ³ / H, oxygen concentration 93.3%, the amount of gas sent from the second stage device to the third stage device is 6.1 Nm ³ / H,
Oxygen concentration is 79.2%, desorption gas amount to be a product as high concentration oxygen is 20.0 Nm ³ / H, oxygen concentration is 99.3%
Met. In this case, the desorption gas at the initial stage of desorption was circulated to the compressor inlet for only 5 seconds.

Furthermore, as a third stage device, a two-column type 125 m
PSA was carried out by filling an adsorption tower of mφ × 1100 mmH with the same carbon molecular sieve manufactured by Bergbau GmbH of West Germany as in the second-stage apparatus. The sequence at this time is adsorption-5
5 seconds, pressure equalization-1.5 seconds, desorption-58.5 seconds, pressure equalization-1.
5 seconds, pressurization-3.5 seconds (total of 2 minutes per cycle), adsorption pressure is 0.9 kg / cm ² G, desorption pressure is 150 Torr, and exhaust gas amount of the third stage device is 2.8 Nm ³ / The H 2 oxygen concentration was 50%. The desorbed gas circulated to the compressor inlet of the second stage device.

From the above results, a high concentration of oxygen of 99.3% was obtained with a recovery rate of 93.4%. The recovery rate of high-concentration oxygen when the third-stage device was not provided was calculated to be 77.3%.

Example 2 The same 93.3% concentration oxygen gas generated from the first-stage device of Example 1 was pressurized to 6.5 kg / cm ² G with a compressor, and the same 200 mmφ × 1100 mmH as in Example 1 was applied. Adsorption 1-58 seconds, hold (no process) -2 seconds, adsorption 2-58 seconds, pressure equalization-2 seconds, desorption-58 seconds, pressure equalization-2 seconds as a second stage device with three adsorption towers. (1 cycle total 3
Min) sequence was used for PSA.

In this case, the adsorption pressure is 6.3 kg / cm ²
The desorption pressure was G, and the desorption pressure was almost atmospheric pressure without providing a vacuum pump. Compressor inlet gas amount is 23.6 Nm ³ / H, oxygen concentration is 93.3%, gas amount sent from the second stage device to the third stage device is 18.8 Nm ³ / H, oxygen concentration is 80.6%,
The amount of desorption gas that becomes a product as high-concentration oxygen is 18.4 Nm.
^{The 3} / H oxygen concentration was 99.2%. The desorption gas at the initial stage of desorption was circulated to the compressor inlet for 6 seconds.

Further, as a third stage device, as in Example 1, 1
25mmφ × 1100mmH adsorption tower with 2 tower type P
SA was performed. At this time, the sequence was adsorption-55 seconds, pressure equalization-1.5 seconds, desorption-58.5 seconds, pressure equalization-1.5 seconds, pressurization-3.5 seconds (1 cycle total 2 minutes). Was 5.8 kg / cm ² G, and the desorption pressure was atmospheric pressure without a vacuum pump. The exhaust gas volume of the third stage device is 5.2 Nm ³
/ H oxygen concentration was 71.2%. The desorption gas circulated to the inlet of the second stage device. From the above results, a high concentration of oxygen of 99.2% was obtained with a recovery rate of 83.9% smaller than that in Example 1.

[0030]

According to the production method of the present invention, a high concentration of oxygen can be produced industrially advantageously.

[Brief description of drawings]

FIG. 1 is a first stage and a second stage showing an embodiment of the present invention.
It is a flow sheet comprising a stage and a third stage adsorption device.

Claims (3)

[Claims] 1. A first stage adsorption device filled with a zeolite molecular sieve is used to perform a pressure swing using air as a raw material to obtain a non-adsorbed gas containing oxygen as a main component and containing argon and nitrogen, which is then treated with a carbon molecular sieve. It led to the second stage adsorption device packed, by performing pressure swing separating and removing argon and nitrogen as the non-adsorbed gas, a process for the preparation of highly concentrated oxygen to desorb the adsorbed oxygen, the second stage adsorption The device is a three tower type
And, after passing through a gas mainly composed of the oxygen generated from the first stage adsorption device 2 tower of its series, the second column
Of the above , desorption is performed in a column that has saturatedly adsorbed oxygen on the upstream side, and the gas at the initial stage of desorption is recovered in the raw material gas that is introduced into the second-stage adsorption device and the gas at the latter stage of desorption is obtained as high-concentration oxygen. A characteristic method for producing high-concentration oxygen. 2. The adsorption pressure of the second stage device is 0.3 to 10 kg.
The method according to claim 1, which is / cm ² G. 3. The method of claim 1 wherein the desorption pressure is below atmospheric pressure.