JPH06277434A - Separation of oxygen gas - Google Patents

Abstract

PURPOSE:To enable oxygen gas to be separated efficiently by performing four steps such as adsorption, exhaust, recovery, and adsorption of cleaned exhaust gas on one hand, and four steps such as adsorption, exhaust, cleaning and recovery on the other hand sequentially and repeatedly, in a dual adsorption tower filled with a molecular sieve carbon. CONSTITUTION:Two adsorption towers 3, 3a with an inner volume ratio of 1:1 to 3:1 are filled with molecular sieve carbon to perform a pressure swing adsorption method. In this case, four steps such as adsorption, exhaust, recovery and the adsorption of cleaned exhaust gas are performed as a series of operations at an adsorption tower 3 of the primary side, and four steps such as adsorption, exhaust, cleaning and recovery likewise as a series of operations at an adsorption tower 3a. These operations are repeated in a sequential interlocked fashion. The gas discharged from the adsorption tower 3a which is in a cleaning process is introduced from one end of the adsorption tower 3 which is through with a recovery process and is allowed to be adsorbed into the adsorption tower. Thus it is possible to obtain oxygen gas of high concentration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating oxygen gas in air by utilizing the selective adsorption property of molecular sieving carbon.

[0002]

2. Description of the Related Art In recent years, a pressure swing adsorption method (hereinafter abbreviated as PSA method) has been developed and put into practical use as a technology for separating oxygen gas in air. This gas separation method using the PSA method separates gas by utilizing the selective adsorption property of the adsorbent, and the apparatus is smaller in size than the cryogenic separation method, and the operation is simple and on-site. It has features such as continuous unmanned operation.

Conventionally, when the oxygen gas in the air is separated by the PSA method, zeolite is used as an adsorbent, nitrogen gas is adsorbed and removed under pressure, and oxygen gas which is a non-adsorbed component is separated as a product gas. Although a method has been adopted, since zeolite is a hydrophilic material and has a strong water adsorption power, and the performance is significantly deteriorated when water is adsorbed, prior to PSA operation,
It has drawbacks such that the water content in the raw material gas must be sufficiently removed in advance, the equipment becomes complicated, and careful attention is required in maintenance.

In addition, 5A type and 13 which are usually used for oxygen production
In X-type zeolite, nitrogen is an adsorbing component and oxygen and argon are non-adsorbing components, so that separation of oxygen and argon is theoretically impossible. Therefore, in an oxygen generator that concentrates oxygen in the air, about 0.93% of the argon contained in the raw material air is concentrated together with oxygen, and the oxygen concentration can be increased only up to about 95%. Is currently limited. For this reason, in the case of obtaining a high concentration oxygen gas, a device for removing argon is newly required, and the oxygen gas refining cost becomes high.

On the other hand, molecular sieving carbon is a non-polar hydrophobic material and does not undergo extreme performance deterioration due to moisture, and oxygen is an adsorbing component and nitrogen and argon are non-adsorbing components. It is considered to be a material suitable for oxygen enrichment because it is possible in principle to extract only oxygen in high concentration from the feed air containing nitrogen and argon.

[0006]

The present inventors have completed the present invention as a new method for separating oxygen gas as a result of intensive research from the above viewpoint. The purpose of the present invention is to
It is to separate oxygen gas in the air at a high concentration easily and inexpensively.

[0007]

The above objects and advantages of the present invention are obtained by filling two adsorption towers A and B having an internal volume ratio of 1: 1 to 3: 1 with molecular sieving carbon to obtain a pressurized raw material. In the pressure swing adsorption method in which air is supplied and pressure and decompression are sequentially repeated in each adsorption tower to recover oxygen gas as an adsorbed component, in the adsorption tower A on the primary side 1) Supply raw material air to the adsorption tower Adsorbing step for adsorbing oxygen gas by continuing to supply the raw material air while maintaining the pressurization state, and further discharging the non-adsorbed components in the adsorption tower after the adsorption step,
Exhaust process for reducing pressure 3) Recovery process after decompressing the adsorption tower after the exhaust process to collect adsorbed oxygen gas and send it to the adsorption tower B on the secondary side 4) Washing adsorption tower A after completion of the recovery process In the process, the secondary side adsorption tower B is connected to the secondary side adsorption tower B, and a series of four steps of cleaning exhaust gas adsorption step for adsorbing oxygen gas is performed. Adsorption step of supplying the recovered gas of A to increase the pressure and continuing supply of the recovered gas while maintaining the pressurized state, and adsorbing oxygen gas 2) Discharging non-adsorbed components in the adsorption tower after the adsorption step is completed Exhaust process 3) Cleaning process in which a part of the product oxygen gas is introduced into the adsorption tower B after completion of the exhaust process for cleaning 4) Decompression of the adsorption tower after completion of the cleaning process and recovery of adsorbed oxygen gas A series of operations consisting of 4 steps are sequentially and continuously repeated in conjunction with each other. It is taken to continue the oxygen gas can be accomplished by a method of separating oxygen gas, wherein.

The molecular sieving carbon used in the present invention is coal,
It can be produced from coconut shell charcoal or various synthetic polymer materials. And these manufacturing methods, for example,
JP-B-49-37036, JP-B-52-1867, JP-B-52-47758, JP-A-59-45914, JP-A-SHO
It is disclosed in, for example, JP 61-6108 A, JP 62-59510 A, and the like.

The molecular sieving carbon applied to the method for separating oxygen gas of the present invention may be appropriately selected from known molecular sieving carbons. Particularly, the phenol resin fine powder described in Japanese Patent Application No. 63-57175, thermal More preferable results are obtained when the molecular sieving carbon produced by using the curable resin solution and the polymer binder as the main raw material is used as the filler. The molecular sieving carbon described in Japanese Patent Application No. 63-57175 has (A) a structure in which a large number of spherical carbon particles having a particle size of 0.8 to 120 μm are three-dimensionally irregularly overlapped and united. (B) There are continuous passages that run irregularly in three dimensions between the plurality of carbon particles. (C) Each of the plurality of carbon particles has a plurality of fine passages that communicate with the passages between the particles. A molecular sieving carbon having pores, and (D) having a carbon content of at least 85% by weight, the production method of which is: (a) thermosetting phenolic resin fine powder (b) Thermosetting Resin Solution Here, the thermosetting resin is a phenol resin or a melamine resin. And (c) Polymer binder The polymer binder is selected from polyvinyl alcohol and water-soluble or water-swellable cellulose derivatives. And a solution of the thermosetting resin (b) per 100 parts by weight of the thermosetting phenol resin fine powder (a).
Prepare a uniform mixture of 5 to 50 parts by weight (as solids) and 1 to 30 parts by weight of the polymeric binder (c), form the homogeneous mixture into granules, and add the granules to a non-oxidizing atmosphere. It is characterized in that it is heat-treated at a temperature in the range of 500 to 1100 ° C. to produce carbonized particles.

The molecular sieving carbon used in the present invention preferably has a pore diameter and a pore volume of micropores as a result of measurement by a molecular probe method described later, and a pore diameter distribution of 3 to 5Å. Most distributed in
The proportion of pores having a diameter of Å or more is 15% or less,
It is more preferably 10% or less, and most preferably 5% or less. Also, the pore volume is preferably 1 molecular sieve carbon.
It is 0.05 to 4.0 cc per g, and more preferably 0.08 to 0.
It is 3cc.

The molecular sieving carbon used in the present invention is
As a compositional characteristic, they usually have a carbon content of at least 85% by weight, preferably at least 90% by weight. The specific surface area of molecular sieving carbon is usually 5 to 600 cm ² / g as a value measured by the BET method by N ₂ adsorption,
Preferably 10 to 400 cm ² / g, more preferably 20 to 350 cm ² / g
It is a degree. This molecular sieving carbon has a diameter of 0.5-
It is provided in the form of a cylinder with a length of 5 mm and a length of 1 to 10 mm.
The packing density when the molecular sieving carbon used in the present invention is packed in an adsorption tower is usually 0.5 to 0.8 g / cm ³ , preferably 0.6 to 0.7.
It is 5 g / cm ³ .

The apparatus used for separating oxygen gas according to the present invention is
Two adsorption towers filled with molecular sieving carbon, a pressure supply device for sending raw material gas to the adsorption tower such as a blower and a compressor, a vacuum pump for desorbing / recovering adsorbed oxygen gas, and a server for storing oxygen. It is composed of a ditank, piping connecting these components, an automatic valve for controlling the gas flow and its control system, etc., and if necessary, a dehumidifier for the raw air, a flow controller and a gas concentration analyzer. Etc. may be attached.

The adsorption step of the adsorption tower A according to the present invention means that the raw material pressurized air is supplied from one end of the adsorption tower filled with molecular sieving carbon to increase the pressure, and the non-adsorption gas is supplied from the other end of the adsorption tower. It is a step of continuing to supply the raw material and adsorbing oxygen gas while maintaining a constant pressure inside the adsorption tower while discharging. The pressure in the adsorption tower in this adsorption step is usually 0.1 to 9.9.
It is kgf / cm2 · G.

Although the adsorption capacity of the adsorbent increases as the adsorption pressure increases, on the other hand, the higher the adsorption pressure, the higher the unit power consumption of the apparatus increases. Therefore, it is usually preferable to operate within the above range.
This pressure range is preferably 0.5-7.0 kgf / cm ² G,
Most preferably, it is 1.0 to 5.0 kgf / cm ² · G.

When the adsorption step is continued, the amount of oxygen gas adsorbed on the molecular sieving carbon gradually increases, and the oxygen concentration in the non-adsorbed gas discharged from the outlet of the other end of the adsorption tower gradually increases. The time required for the adsorption step is set in consideration of the adsorption capacity of the adsorbent, the pressure in the adsorption tower, the purity of the desired product gas, etc., but is usually 20 to 240 seconds, preferably 40 to 210 seconds, and most preferably 60 to 180 seconds.

The exhaust step of the adsorption tower A of the present invention is a step of discharging the non-adsorbed components remaining in the adsorption tower after the adsorption step. This evacuation step is performed by exposing the adsorption tower to the atmosphere. If the time required for the exhaust step is too short, the non-adsorbed components are insufficiently discharged, and if the time is too long, oxygen gas is also discharged, so that it is usually 1 to 30 seconds, preferably 2 to
25 seconds, most preferably 3 to 20 seconds.

The recovery step of the adsorption tower A of the present invention means to desorb the oxygen gas adsorbed on the molecular sieving carbon by depressurizing the inside of the adsorption tower A after the exhaust step with a vacuum pump or the like to make the adsorption tower on the secondary side. It is a process of sending to B. The degree of pressure reduction in the adsorption tower in this step is usually 200 torr or less, preferably 10 torr.
It is 0 torr or less, more preferably 50 torr or less. The time required for the recovery step is usually 10 to 240 seconds, preferably 20 to 210 seconds, more preferably 30 to 180 seconds.

The cleaning exhaust gas adsorption step of the present invention is a step in which the gas exhausted from the adsorption tower B in the cleaning step is introduced and adsorbed from one end of the adsorption tower A after the recovery step. Since the product oxygen gas is used for cleaning in the cleaning step of the adsorption tower B, the oxygen concentration of the gas discharged here is higher than that of the raw material air. Therefore, by introducing this exhaust gas into the adsorption tower A after the completion of the recovery step and adsorbing it to the molecular sieving carbon, the oxygen gas exhausted in the cleaning step can be recovered, and the oxygen gas Since the amount of adsorption becomes large, it is possible to recover high-concentration oxygen gas.

The time required for this cleaning exhaust gas adsorption step is
Usually, 25 to 150% of the time required for the adsorption step, preferably
40-125%, most preferably 60-100%.

The adsorption step of the adsorption tower B of the present invention means that the recovered gas recovered in the recovery step of the adsorption tower A on the primary side is adsorbed in the adsorption tower B.
Is a step of adsorbing oxygen gas while continuing to supply the recovered gas while maintaining the pressurized state. The time required for the adsorption process of the adsorption tower B is set to the same length as the recovery process of the adsorption tower A. The adsorption pressure of the adsorption tower B is determined by the ratio between the adsorption tower A and the adsorption tower B and the degree of pressure reduction in the adsorption tower A recovery process. When the internal volume ratio of the adsorption tower A and the adsorption tower B is smaller than the adsorption tower A: adsorption tower B = 1: 1 to 3: 1, the pressure in the adsorption step of the adsorption tower B does not rise sufficiently, and When it is large, the pressure of the adsorption tower B rises too much, and a large amount of oxygen gas is exhausted in the next exhaust step, and the recovery rate of oxygen gas decreases, which is not suitable.

The exhaust step of the adsorption tower B of the present invention is a step of discharging the non-adsorbed components remaining in the adsorption tower after the adsorption step. This evacuation step is performed by exposing the adsorption tower to the atmosphere. If the time required for the exhaust step is too short, the non-adsorbed components are insufficiently discharged, and if the time is too long, oxygen gas is also discharged, so that it is usually 1 to 30 seconds, preferably 2 to
25 seconds, most preferably 3 to 20 seconds.

The cleaning step of the present invention is a step in which a part of the product oxygen gas is supplied from one end of the adsorption tower after the end of the adsorption step and discharged from the other end. In this step, the mixed gas with a low oxygen concentration remaining in the adsorption tower is discharged from the inside of the tower,
Further, the oxygen partial pressure in the adsorption tower can be increased to desorb and discharge the nitrogen gas slightly adsorbed on the molecular sieving carbon to improve the concentration of the product oxygen gas in the recovery step. The supply pressure of the cleaning gas is usually not less than the atmospheric pressure and not more than the product gas extraction pressure, preferably 0.3 to 7.0 kg.
f / cm ² · G, more preferably 0.5 to 5.0 kgf
/ Cm ² · G. In addition, the supply amount of the cleaning gas increases with the increase in the product gas concentration, but if the amount is too large, the yield of the product gas decreases, so the amount of the product gas taken out from the surge tank is usually 10 to 150 vol.
%, Preferably 30 to 120%, more preferably 40
Is about 100 vol%.

The recovery step of the present invention is a step of decompressing the inside of the adsorption tower after the cleaning step with a vacuum pump to desorb the oxygen gas adsorbed on the molecular sieving carbon and recovering it in the surge tank. The degree of pressure reduction in the adsorption tower in this step is usually 200 torr or less, preferably 100 torr or less, and more preferably 50 torr or less. Also, the time required for the recovery process is
It is usually 20 to 240 seconds, preferably 40 to 210 seconds, more preferably 60 to 180 seconds.

In the present invention, in the PSA apparatus comprising the two adsorption towers filled with the above-mentioned molecular sieving carbon, the adsorption tower A has 1) adsorption step 2) exhaust step 3) recovery step
4) A series of operations consisting of four steps of the cleaning exhaust gas adsorption step is sequentially performed in the adsorption tower B by interlocking a series of operations consisting of four steps of 1) adsorption step 2) exhaust step 3) cleaning step 4) recovery step. Oxygen gas can be efficiently separated by continuously and repeatedly performing.

In the present invention, the product oxygen concentration is arbitrarily selected from the 20% to 90% range by appropriately setting the process time and setting the feed air supply amount, the product extraction amount, and the cleaning gas supply amount. be able to.

Hereinafter, the case of using the two-column PSA apparatus shown in FIG. 1 will be specifically described. In FIG. 1, each of the adsorption towers 3 and 3a is filled with molecular sieving carbon. In the adsorption step of the adsorption tower 3, the valves 8, 12, 13 are opened, and the air pressurized by the air compressor 1 is dehumidified by the dehumidifier 2
Then, the gas is supplied to the adsorption tower 3 through the valve 8 and the pipe 21. Then, while maintaining a predetermined pressurization state, the supply of the raw material air is continued and the oxygen gas in the air is adsorbed. During this time, gas mainly consisting of nitrogen gas is discharged through the pipe 23, the valve 12, the pipe 24, the valve 13 and the throttle valve 16.

When the adsorption tower 3 is in the adsorption step, the adsorption tower 3
a is in the recovery step. That is, the valve 18 is opened, and the oxygen gas adsorbed on the molecular sieving carbon in the adsorption tower 3a is recovered by the vacuum pump 5 and introduced into the surge tank 6 through the pipe 25 and the valve 18.

Immediately before the adsorption of oxygen gas on the molecular sieving carbon of the adsorption tower 3 is saturated, the valves 8 and 13 are closed and the adsorption step of the adsorption tower 3 is completed. Next, the valve 15 is opened (the valve 12 is kept open), and the adsorption tower 3 is exhausted. The non-adsorbed components in the adsorption tower 3 are the pipe 23, the valve 12, the pipe 24 and the valve 15.
Exhausted through the atmosphere. At this time, the adsorption tower 3a is still in the recovery step. When the exhaust step is completed, the adsorption tower 3 closes the valves 12 and 15 (closes the valve 18) and moves to the recovery step. That is, the valve 9 is opened, and the oxygen gas adsorbed on the molecular sieving carbon in the adsorption tower 3 is desorbed and collected by the vacuum pump 4 through the pipe 21 and the valve 9 and sent to the adsorption tower 3 a through the pipe 25. That is, at this time, the adsorption process is performed in the adsorption tower 3a.

When the recovery step of the adsorption tower 3 (adsorption step of the adsorption tower 3a) is completed, the valve 9 is closed. Then, in the adsorption tower 3a, the exhaust process is started. The valves 12a and 15 are opened and the non-adsorbed components in the adsorption tower 3a are pipe 23a Valve 12a Pipe 2
It is discharged through the four-valve 15. When the exhaust process of the adsorption tower 3a is completed, the valves 12a and 15 are closed.

Next, the adsorption tower 3 proceeds to the cleaning exhaust gas adsorption step, and the adsorption tower 3a proceeds to the cleaning step. I.e. valves 10, 11
a, 12, 14, 19 are opened, a part of the product oxygen gas is sent to the adsorption tower 3a through the throttle valve 20 valve 19,
Further, the exhaust gas from the adsorption tower 3a is fed to the pipe 23a and the valve 11
a, pipe 22, valve 10, pipe 21 through adsorption tower 3
Pipe 23, valve 12 pipe 24, valve 14,
Discharge through the throttle valve 17.

Cleaning of adsorption tower 3 Exhaust gas adsorption step, adsorption tower 3
When the washing step of a is completed, each valve is closed and one cycle is completed, and the adsorption tower 3 moves to the adsorption step again. By repeating these steps, oxygen gas can be separated from the air.

In the present invention, as described above, in the adsorption tower A, a series of operations consisting of 1) adsorption step 2) exhaust step 3) recovery step 4) cleaning exhaust gas adsorption step is performed in the adsorption tower B by 1). Adsorption step 2) Exhaust step 3) Washing step 4) Recovery step A series of operations, which are four steps, are interlocked with each other and sequentially and repeatedly performed to efficiently separate oxygen gas from the air. it can. Further, in the present invention, steps other than the above eight steps,
For example, after the adsorption step of the adsorption tower 3a, the adsorption tower 3a and the adsorption tower 3 are connected and the pressure equalization step of equalizing the pressures of both towers, or after the recovery step of the adsorption tower 3a, the product oxygen gas is fed to the adsorption tower 3a. Addition of a refluxing step for sending in is not limited at all.

[0033]

The oxygen gas separation method of the present invention has a wide range of oxygen concentration from the production of oxygen-enriched air in which the oxygen gas concentration is slightly higher than that of air to the production of high-concentration oxygen having an oxygen concentration of 95% or more. Since it can be used as a gas production device, its application range is wide.

For example, the oxygen-enriched air produced by the apparatus of the present invention can be used as an oxygen-enriched combustion gas for various combustion facilities, and a product gas having an oxygen concentration of about 30 to 45% can be used for various bioreactors. It can be used as oxygen enriched air. In addition, product oxygen gas with an oxygen concentration of 90 to 95% is used for aeration in medical treatment of wastewater, medical use, and other various applications.
It can be used as an inexpensive oxygen source. Furthermore, high-concentration oxygen of 98% or more can be utilized especially in fields requiring high temperatures such as welding and fusing. The oxygen gas obtained in the present invention can be used as a substitute for an oxygen cylinder for various uses other than the above-mentioned uses.

[0035]

[Measurement method] The pore diameter and volume of the micropores of the molecular sieving carbon used in the present invention are measured by a molecular probe method using a fully automatic gas adsorption measuring device (BELLSORP28) (manufactured by Bell Japan Ltd.). I did.

The measuring method is oxygen at 298 K (molecular size 2.8
Å), ethane (molecular diameter 4.0 Å), isobutane (molecular diameter 5.
(0 Å) The adsorption isotherm measurement results from 0 to 760 mmHg are organized by the Dubinin-Astakhov equations (1) and (2) to determine the characteristic energy E of adsorption and the micropore volume W0, and to determine the pore size distribution. Created a histogram.

W / W 0 = exp {-(A / E) n} (1) A = R · T · ln (P 0 / P) (2) where W: at equilibrium pressure P Adsorption amount W0: Ultimate adsorption amount (micropore volume) A: Adsorption potential E: Adsorption characteristic energy R: Gas constant T: Measurement temperature P0: Saturated vapor pressure P: Equilibrium pressure n: 2 or 3. Hereinafter, the present invention will be specifically described with reference to examples.

[0038]

Example 1 A 400-liter reaction vessel was charged with 300 kg of a mixed aqueous solution of hydrochloric acid 18% and formaldehyde 8%, and the temperature was set to 20 ° C. Then, add 9
12% of a phenol aqueous solution (20 ° C.) having a concentration of 90%, which was prepared by using 8% (2% is water) phenol and water.
g was added. After the addition, the mixture was stirred for 30 to 40 seconds, and the contents in the reaction vessel suddenly turned cloudy, at the same time, the stirring was stopped and the mixture was allowed to stand. When left to stand, the internal temperature gradually increased, the contents gradually turned pale pink, and after 30 minutes from becoming cloudy, a slurry-like or resinous product was observed.
After the above steps, the contents are continuously heated to 75 to 76 ° C for 3 minutes.
The temperature was raised in 9 minutes, and the temperature was maintained for 40 minutes while stirring. Next, this content is washed with water, and then neutralized with a 0.1% aqueous ammonia solution at 50 ° C. for 6 hours,
Then, it was washed with water, filtered, and stirred at 80 ° C. for 6 hours. As a result, a desired phenol resin powder having a spherical particle shape was obtained.

Next, 10 kg of the spherical phenol resin prepared by the above method was weighed, and 100 parts by weight of the spherical phenol resin powder was further mixed with a water-soluble melamine resin (Sumitex Resin, manufactured by Sumitomo Chemical Co., Ltd.). M-3, solid content 8
20% by weight of solid content, 4 parts by weight of polyvinyl alcohol having a degree of polymerization of 1700 and a saponification degree of 88%, 20 parts by weight of potato starch and 4 parts by weight of ethylene glycol were weighed. Of the above raw materials, use 2 parts of polyvinyl alcohol with warm water.
The mixture was dissolved to give a 0% by weight aqueous solution, and a water-soluble melamine resin, potato starch and ethylene glycol were added to this polyvinyl alcohol aqueous solution and mixed for 10 minutes with a kneader. Then add spherical phenol resin and add 10 more.
Mix for minutes.

A biaxial extrusion granulator (manufactured by Fuji Paudal Co., Ltd., Peretta Double, EXDF-100) was mixed with this mixed composition.
And a granule having an average particle diameter of 3 mmφ × 6 mmL was granulated. After heat-treating the granules at 80 ° C. for 24 hours, the granules were put into a rotary kiln having an effective size of 800 mmφ × 2000 mmL, and the temperature was raised to 60 ° C./hr in a nitrogen atmosphere.
Hold at 00 ° C for 1 hour, then cool in a furnace, average particle size 24
mmφ × 4 mm pellet-like molecular sieving carbon was obtained.

In order to evaluate the characteristics of this molecular sieving carbon, the adsorption amounts of nitrogen gas and oxygen gas were measured by the adsorption characteristic measuring device shown in FIG. In the figure, the sample chamber 4 (2
(00 ml), put 3 g of sample, close valves 11 and 8, open valves 2 and 3 for 30 minutes to degas, then close valves 2 and 3 to open valve 11 and degas for 30 minutes,
The valves 2 and 3 are closed, the valve 11 is opened, and the adjustment chamber 5 (20
Oxygen gas or nitrogen gas is fed into the chamber, and when the set pressure (6.00 kgf / cm ² · G) is reached, the valve 11 is closed, the valve is opened, and the change in internal pressure at a predetermined time is measured. The amount of nitrogen adsorbed was determined. 1 is a vacuum pump, 6 and 7 are pressure sensors, 9 is a recorder, 10 is a pressure gauge, 14 and 15 are gas regulators, 16 is a nitrogen cylinder, and 17 is an oxygen cylinder.

As a result of the measurement, the amount of adsorption per 1 g of this molecular sieving carbon was found to be 1.0 mg / nitrogen at 1 minute after the start of adsorption.
g (adsorption pressure 2.613 kgf / cm ² · G) 1 oxygen
9.5 mg / g (adsorption pressure 2.527 kgf / cm ² ·
G), the parallel adsorption amount is 21.3 mg / g for nitrogen (adsorption pressure 2.509 kgf / cm ² · G) and 22.8 mg / for oxygen.
It was g (adsorption pressure 2.504 kgf / cm ² · G).

This molecular sieving carbon is shown in FIG.
Adsorption tower of SA device (Adsorption tower 3 has an inner diameter of 53.5 mmφ x 1
200 L, adsorption tower 3a has an inner diameter of 53.5 mmφ × 800
L) was filled, and the operation cycle and operation time shown in Table 1 were operated.

[0044]

[Table 1]

At this time, the adsorption pressure in the adsorption tower 3 is 3 kg.
f / cm ² · G, the degree of decompression in each recovery step is 50 torr, the feed rate of raw material air is 5 NL / min, the product gas flow rate for cleaning is 0.15 NL / min (average flow rate in one cycle), and the column pressure is 0. It was set to 1 kgf / cm ² · G. Table 2 shows the amount of product oxygen gas taken out and the recovery rate obtained as a result. Here, the product oxygen gas recovery rate Y (%) was determined according to the following equation.

[0046]

[Equation 1]

[0047]

[Table 2]

According to this embodiment, the oxygen concentration is 50.3 to 86.
A product gas of 1% was obtained with a recovery rate of 20.6% to 50.4%, and especially in Experiment 9, the oxygen concentration was the best. Further, in Experiment 1, since the time of each step was short, the product oxygen concentration was low, and Experiment 8 was excellent in both concentration and recovery rate.

[0049]

Example 2 The molecular sieving carbon used in Example 1 is shown in FIG.
The adsorption tower of the two-tower PSA device shown in Fig.
3.5 mmφ x 1200 L, adsorption tower 3a has an inner diameter of 53.5
(mmφ × 800 L), and the influence of the degree of reduced pressure in each recovery step was examined. That is, as the operating conditions of the PSA apparatus, the degree of pressure reduction in each recovery step was set as shown in Table 3, and the other conditions were the same as the experiment number 8 of Example 1 and the experiment was conducted. Table 3 shows the amount, concentration, and recovery rate of the product oxygen gas obtained as a result.

[0050]

[Table 3]

According to this example, the lower the column pressure in the recovery step, the higher the product oxygen gas concentration and the higher the recovery rate. In particular, when the pressure was 100 torr or less, product oxygen having a concentration of 83% or more was obtained with a recovery rate of 42% or more.

[0052]

Example 3 The molecular sieving carbon used in Example 1 was used in the adsorption tower of the two-column PSA apparatus shown in FIG. 1 (the adsorption tower 3 has an inner diameter of 5).
3.5 mmφ x 1200 L, adsorption tower 3a has an inner diameter of 53.5
(mmφ × 800 L), the operating conditions of the PSA device are as shown in Table 4 for the cleaning gas, and the other conditions are those of Example 1.
The experiment was performed in the same manner as Experiment No. 8 of.

[0053]

[Table 4]

According to this embodiment, the higher the cleaning gas flow rate, the higher the product oxygen gas concentration. If the cleaning gas flow rate is 20% or more of the product oxygen gas removal amount, the product oxygen gas concentration is 80% or more. Became. On the other hand, in Experiment No. 15, since the cleaning gas flow rate is small, the product gas concentration is low,
In Experiment No. 20, since the cleaning gas flow rate was high, the product oxygen concentration was high, but the product withdrawal amount decreased and the recovery rate was low.

[0055]

Example 4 The molecular sieving carbon used in Example 1 is shown in FIG.
2 tower type PSA device shown in (The adsorption tower 3 has an inner diameter of 53.5 mm.
φ × 1600L, adsorption tower 3a has an inner diameter of 53.5 mm φ × 8
00L) and the operating conditions of the PSA apparatus were the experiments conducted at the operating cycle and time shown in Table 5.

[0056]

[Table 5]

At this time, the adsorption pressure in the adsorption tower 3 is 3 kg.
f / cm ² · G, the degree of decompression in each recovery step is 25 torr, the feed rate of raw material air is 6 NL / min, the product gas flow rate for cleaning is 0.2 NL / min, and the internal pressure of the column is 0.1 kgf / c.
m ² · G. Table 6 shows the amount of product oxygen gas taken out and the recovery rate obtained as a result.

[0058]

[Table 6]

In this embodiment, the oxygen concentration is 92.5-9.
A product gas of 9.9% was obtained with a recovery rate of 31.8 to 36.8%. In particular, in Experiment 23, a product oxygen gas having a very high concentration of 99.9% was obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a two-tower PSA device according to the present invention. 3,3a Adsorption tower 1 Air compressor 2 Dehumidifier 4,5 Vacuum pump 6 Surge tank 7 Flowmeter 8-15,18,19,11a, 12a Automatic valve 16,17,20 Throttle valve 21-25,23a Pipe

FIG. 2 is an explanatory diagram of an apparatus for measuring adsorption characteristics of molecular sieving carbon used in the present invention. 1 Vacuum pump 2,3,8,11,12,13 Valve 4 Sample chamber 5 Adjustment chamber 6,7 Pressure sensor-9 Recorder 10 Pressure gauge 14,15 Gas regulator

Claims (1)

[Claims] 1. Two adsorption towers A and B having an internal volume ratio of 1: 1 to 3: 1 are filled with molecular sieving carbon, pressurized raw material air is supplied, and each adsorption tower is sequentially pressurized. In the pressure swing adsorption method in which decompression is repeated to recover oxygen gas as an adsorbing component, in the adsorption tower A on the primary side, 1) feed air is supplied to the adsorption tower to raise the pressure, and the raw material while maintaining a pressurized state Adsorption step of continuing to supply air and adsorbing oxygen gas 2) Discharging non-adsorption components in the adsorption tower after the adsorption step is completed,
Exhaust process for reducing pressure 3) Recovery process after decompressing the adsorption tower after the exhaust process to collect adsorbed oxygen gas and send it to the adsorption tower B on the secondary side 4) Washing adsorption tower A after completion of the recovery process In the process, the secondary side adsorption tower B is connected to the secondary side adsorption tower B, and a series of four steps of cleaning exhaust gas adsorption step for adsorbing oxygen gas is performed. Adsorption step of supplying the recovered gas of A to increase the pressure and continuing supply of the recovered gas while maintaining the pressurized state, and adsorbing oxygen gas 2) Discharging non-adsorbed components in the adsorption tower after the adsorption step is completed Exhaust process 3) Cleaning process in which a part of the product oxygen gas is introduced into the adsorption tower B after completion of the exhaust process for cleaning 4) Decompression of the adsorption tower after completion of the cleaning process and recovery of adsorbed oxygen gas A series of operations consisting of 4 steps are sequentially and continuously repeated in conjunction with each other. The method of separating oxygen gas, characterized in that taken to continue the oxygen gas