JP2009095729A - Method of condensing oxygen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of condensing oxygen capable of practically condensing oxygen by keeping the effect of leakage to a minimum with an oxygen separating apparatus having leakage from a gas supplying side to a gas permeating side. <P>SOLUTION: The method of condensing oxygen uses an oxygen separating apparatus which is driven by pressure with a separating membrane composed of an oxide ion-conductive oxide and has leakage from a gas supplying side to a gas permeating side wherein the pressure is higher than a normal pressure and lower than 0.5 MPa, an oxygen containing gas (A) of the gas supplying side has an oxygen concentration of 25-95%, and the pressure of the gas permeating side is a normal pressure. A gas (C) obtained by further separating oxygen from a gas (B) discharged without permeating through the separating membrane from the gas supplying side is supplied to the gas supplying side of the oxygen separating apparatus to recycle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oxygen concentrating method using an oxygen separator having a leak from a gas supply side to a gas permeation side, which is a pressure-driven system using a separation membrane made of an oxide ion conductive oxide.

Oxygen separation technology using oxide-ion-conducting oxides utilizes the phenomenon of moving through oxides in the form of oxide ions at high temperatures.
One is a power drive system. As disclosed in Patent Document 1 as a representative technique, an oxide is formed from a cathode side to an anode side by forming a positive electrode and a negative electrode with an oxide ion conductive oxide sandwiched between them. It moves as current in the form of ions. In this case, the ease of transmission of oxide ions is almost determined by the “oxide ion conductivity” which is one of the physical properties of the oxide.

  This method does not need to create an environment with different oxygen partial pressures as in the pressure driven method described below, and oxygen can be transported from the low oxygen partial pressure side to the high oxygen partial pressure side using electric power. It is also called a pump. However, it is difficult to recover the energy required for high temperatures, and the power required for oxygen production is in principle the same as electrolysis of water, so it is economical except where a small amount of oxygen with relatively high purity is required. This is an oxygen production method that is difficult to achieve.

  Another method is a pressure drive method. This is based on a phenomenon in which two types of gases having different oxygen partial pressures are sequestered to move through the oxide in the form of oxide ions from the high oxygen partial pressure side to the low oxygen partial pressure side. In order to maintain the balance of charges accompanying the movement of oxide ions, among oxide ion conductive oxides, oxides called mixed conductive oxides having both electron conductivity are used. That is, in order to compensate for the charge balance accompanying the movement of oxide ions by the movement of electrons, the permeation of oxygen is maintained without an external circuit.

  In this case as well, the ease of permeation of the oxide ions is an index based on the oxide ion conductivity of the material oxide. That is, the higher this value, the easier it is for the oxide ions to permeate. Therefore, various material designs and material preparation methods for increasing the oxide ion conductivity have been developed.

On the other hand, not only in terms of material development, but also in actual separation, oxide ions can be easily transmitted by the following device. That is,
(B) Increasing the oxygen partial pressure ratio that is the driving force for oxygen separation (b) Increasing the separation temperature (c) Decreasing the transmission distance (thinning the film)

  Increasing the oxygen partial pressure ratio can be achieved, for example, by increasing the pressure of the oxygen-containing mixed gas (such as air), reducing the pressure on the separation side, or a combination thereof. However, when the pressure on the separation side is reduced, it is difficult to recover the energy required for pressure reduction.For example, as disclosed in Patent Document 2, the oxygen-containing mixed gas side is increased in pressure for practical use. Energy is recovered by driving the gas turbine with the gas fluid discharged without contributing.

  The high separation temperature is based on the phenomenon that the oxide ion conductivity itself is a function of temperature and increases as the temperature rises. In addition, the oxygen separation rate increases in proportion to the absolute temperature. . However, since the metal material to be used is limited in the high temperature range, a temperature range of 700 ° C. to 950 ° C. is usually selected.

  If the permeation distance is reduced (thinning), the separation speed is inversely proportional to the film thickness as long as the transmission rate is controlled by the movement of oxide ions. For example, by halving the film thickness, the separation speed is doubled. can do. However, the thinning increases the frequency of occurrence of defects that allow gas molecules other than oxygen to pass through, leading to a decrease in the purity of the separated oxygen. Further, when the surface reaction controls the oxygen permeation, the oxygen permeation rate cannot be increased even if the surface reaction is reduced. Therefore, it is necessary to take a means for activating the surface reaction.

  The oxygen separation technique using oxide ion permeable oxide is a technique for obtaining oxygen on a principle completely different from oxygen PSA (Pressure Swing Adsorption) and the deep cold separation, which are conventional oxygen production methods. Its greatest feature is that, in principle, only oxygen can permeate, so that high-purity oxygen can be produced, and inexpensive oxygen production is possible, and development is underway all over the world.

  On the other hand, in the oxygen separation device using oxide ion permeable oxide, the oxygen separation pressure side that is a normal pressure, for example, the pressure of air is increased to about 2 MPa in order to increase the oxygen partial pressure ratio that is the driving force of oxygen separation. A large differential pressure is generated between For this reason, the purity of the separated oxygen is greatly reduced by the presence of a very slight leak path. Therefore, the current situation is that the development is focused on the formation of a defect-free thin film and the provision of high-temperature gas sealability at the joint between the member holding the separation membrane. For example, in Patent Document 3, a separation membrane with a small amount of gas leakage other than oxygen has been developed.

  On the other hand, in Patent Document 4, the development of a sealing method that does not cause gas leakage in an oxygen production apparatus using an oxide ion permeable oxide as a separation membrane has been made. However, at present, no oxygen-separation device that does not leak at all, such as a defect-free separation membrane or a gas seal that does not leak, has been developed. Not reached.

Japanese Patent Laid-Open No. 10-180031 JP 09-000858 A JP-A-2005-116478 JP 2004-323334 A

  As described above, in an oxygen separation apparatus using an oxide ion permeable oxide as described above, it is impossible to avoid a leak path, which is unavoidable in forming an oxygen separation film, and a leak due to imperfectness in high-temperature gas sealability.

  In view of the above-described current problems, the present invention uses an oxygen separation device having a leak from a gas supply side to a gas permeation side using a pressure-driven system with a separation membrane made of an oxide ion conductive oxide. An object of the present invention is to provide an oxygen concentration method capable of performing practical oxygen concentration while minimizing the influence of leakage.

The gist of the present invention for solving the above-mentioned problems is as follows.
(1) Uses an oxygen separation device with a leak from the gas supply side to the gas permeation side using a pressure-driven system with a separation membrane made of oxide ion conductive oxide, and has a pressure exceeding 0.5 MPa and exceeding normal pressure An oxygen concentrating method characterized in that an oxygen-containing gas (A) having an oxygen concentration of 25 to 95% is set as the gas supply side, and the gas permeation side is set at normal pressure.

(2) The oxygen concentration method according to (1), wherein the oxygen-containing gas (A) supplied to the gas supply side is obtained using a separation membrane made of the oxide ion conductive oxide. .

(3) Use a pressure-driven oxygen separation device with a separation membrane made of oxide ion-conducting oxide and leak from the gas supply side to the gas permeation side. The oxygen-containing gas (A) having an oxygen concentration of 25 to 95% is used as the gas supply side, and the oxygen is concentrated at the gas permeation side as normal pressure.
A gas (C) obtained by further separating oxygen from the gas (B) discharged without passing through the separation membrane from the gas supply side is supplied to the gas supply side of the oxygen separation device and recycled. Oxygen enrichment method.

(4) The oxygen concentration according to (1) or (3), wherein the leak is 1 × 10 ⁻⁶ to 1 × 10 ⁻⁸ Nm ³ · s ⁻¹ · m ⁻² · kPa ⁻¹ Method.

(5) A separation method in which oxygen is further separated from the gas (B) discharged without passing through the separation membrane from the gas supply side to obtain the gas (C) by adsorption and desorption. (2) The oxygen concentration method according to (3).

(6) The oxygen concentration method according to (1) or (3), wherein the oxide ion conductive oxide is a cubic perovskite type.

  According to the present invention, since the pressure difference before and after the separation can be small, the influence of leakage from the gas supply side to the gas permeation side in the oxygen separation device is minimized, and high-purity oxygen separation is possible in principle. Production of high-purity oxygen using a separation membrane that has been said but could not be put into practical use is realized by the oxygen concentration method of the present invention. Furthermore, since the formation yield of the separation membrane and the formation yield at the junction where high-temperature gas sealability is required are greatly improved, it is possible to produce inexpensive high-purity oxygen.

In order to permeate through the separation membrane with high selectivity in the form of oxide ions from the gas supply side to the gas permeation side maintained at normal pressure, oxygen of the oxygen-containing gas (A) supplied to the gas supply side The partial pressure must be 0.1 MPa or more. When trying to permeate oxide ions from the oxygen-containing gas (A) having a low pressure exceeding 0.5 MPa and exceeding the normal pressure of the present invention, if normal air (oxygen concentration 20.6%) is used, The oxygen partial pressure of the oxygen-containing gas (A) is as follows.
That is, 0.206 × 0.5 = 0.103 (MPa), and the driving force for transmission is virtually equal. Therefore, in order to obtain a practical driving force for transmission, the oxygen-containing gas (A) needs an oxygen concentration of 25% or more. On the other hand, if the oxygen concentration exceeds 95%, the oxygen concentration is already high, so that the effect of oxygen concentration is small and not practical. Therefore, as the oxygen-containing gas (A), so-called oxygen-enriched air having an oxygen concentration of 25% or higher or low-purity oxygen having an oxygen concentration of 95% or lower is used.

Preferred embodiments of the present invention will be described below with reference to the drawings.
In FIG. 1, a separation membrane made of an oxide ion permeable oxide is used, and oxygen is concentrated by permeating through the separation membrane with high selectivity in the form of oxide ions using low purity oxygen gas as a raw material. Specific method is shown. Here, a cylindrical tube closed on one side is illustrated as the shape of the separation membrane, but this may be other shapes such as a flat plate.

A plurality of oxygen separation tubes 104 are placed in the oxygen separation device main body 101 so as to isolate the space 102 and the space 103. The oxygen separation tube 104 has a structure in which an ultrathin film is formed on the porous support tube, and has a strength for maintaining a pressure difference generated between the space 102 and the space 103 in the porous support tube portion. The actual oxygen separation is performed at the thin film portion. The thicknesses of the porous support tube and the thin film are appropriately selected from the following viewpoints. The porous support tube needs to have a certain thickness or more in consideration of the pressure difference to be maintained. On the other hand, if the thickness is too large, a ventilation resistance is generated, and the oxygen permeation rate (permeation of oxide ions, O ₂ gas) The speed converted as the permeation of light) decreases. Generally, it is selected in the range of 0.5 mm to 10 mm. The thin film is more advantageous in increasing the oxygen permeation rate, but if it becomes too thin, the impurity gas tends to enter through the defect and a large amount of impurity gas enters. It is selected in the following range.

  Since a plurality of oxygen separation tubes 104 are placed in the oxygen separation device main body 101 so as to separate the space 102 and the space 103, in addition to gas leakage by the separation tube main body, a location for holding the separation tube (not shown) There is a possibility of leakage at the junction.

  Low-purity oxygen, for example, 93% oxygen is supplied from 106, and after the pressure is increased by the compression unit 112 of the gas turbine 111 (in this case, the temperature is slightly increased by adiabatic compression) In particular, the fuel introduced from 107 is combusted in the combustor 108 and heated to a predetermined temperature (for example, 900 ° C.). The exhaust gas from the oxygen separation device 101 is partly transferred to the low-purity oxygen gas, which is a raw material, by the heat exchanger 109, and then required to drive the expansion turbine 113 in the gas turbine 111 by the combustor 110. The temperature is raised to the temperature.

On the other hand, the concentrated oxygen is recovered from the discharge port 105 through the oxygen separation pipe 104.
As described above, the combustor 108 is preferably directly heated by combustion as described above, but an electric heating means can also be used. Also, a direct heating method, a burner method that emits a flame, or a catalytic combustor using a catalyst that promotes oxidation of fuel may be used.

Here, using an oxygen separation / concentration apparatus with a separation membrane made of oxide ion conductive oxide, oxygen concentration obtained from the conventional high-pressure oxygen-containing gas and oxygen concentration from the low-pressure oxygen-containing gas of the present invention Compare the oxygen purity of the gases. Consider the case where air is used as the former example and 93% low-purity oxygen gas is used as the oxygen-containing gas as the latter example. As a prerequisite, the oxygen permeation performance (speed) of the separation membrane is 1.5 × 10 ⁻³ Nm ³ · s ⁻¹ · m ⁻² (however, the driving force of oxygen permeation: inlet side oxygen partial pressure / outlet side oxygen partial pressure = 0.18 MPa / 0.1 MPa) and then, to the total leakage rate of the separation tube and joining portions (per unit area) and ^{8 × 10 -8 Nm 3 · s} -1 · m -2 · kPa -1.
Nm ³ in the above unit represents the gas volume in the standard state (0 ° C., 1 atm = 101.325 kPa), and will be similarly expressed thereafter.

When using air as the raw material : Assuming that 21% oxygen has dropped to 18% by the combustor, oxygen partial pressure
To reach 0.18MPa, it is necessary to increase the total pressure to 1MPa. The differential pressure is 0.9MPa (900kPa).
The leak rate is 8 × 10 ^-8 Nm ³ · s ^-1 · m ^-2 · kPa ^-1 × 900 kPa = 7.2 × 10 ^-5 Nm ³ · s ^-1 · m ^-2 , and 18% of the leak rate is Since oxygen is contained, the separated oxygen purity is as follows.
Separation oxygen purity = (1.5 x 10 ^-3 +7.2 x 10 ^-5 x 0.18) / (1.5 x 10 ^-3 +7.2 x 10 ^-5 ) = 96.24%

When 93% oxygen is used as a raw material : If 93% oxygen is reduced to 90% by the combustor, the total pressure may be increased to 0.2 MPa in order to achieve an oxygen partial pressure of 0.18 MPa. The differential pressure is 0.1MPa (100kPa).
The leak rate is 8 × 10 ^-8 Nm ³ · s ^-1 · m ^-2 · kPa ^-1 × 100kPa = 8 × 10 ^-6 Nm ³ · s ^-1 · m ^-2 , and 90% of the leak rate is 90% Since oxygen is contained, the separated oxygen purity is as follows.
Separation oxygen purity = (1.5 x 10 ^{-3 +8} x 10 ^-6 x 0.9) / (1.5 x 10 ^-3 +8 x 10 ^-6 ) = 99.95%

In this way, even if an extremely small leak amount of 8 × 10 ^-8 Nm ³ · s ^-1 · m ^-2 · kPa ^-1 can be achieved, an oxygen separator with a leak uses air on the gas supply side to 1 MPa. When the pressure is increased to a high pressure, the purity of the obtained oxygen remains at about 96%. On the other hand, when 93% low-purity oxygen is used, the pressure can be increased to 0.2 MPa, so that highly efficient oxygen concentration is possible, and 99.95% high-purity oxygen is obtained.

  Since low purity oxygen of about 93% can be produced at low cost using a pressure swing adsorption method or the like, the oxygen concentration method according to the present invention can also be used as a high purity oxygen production method. Furthermore, when high purity up to 99.95% is not required, the leak resistance required for the thin film is alleviated, so further thinning is possible, leading to a significant improvement in the separation rate (oxygen concentration treatment amount) and oxygen. This can contribute to reduction of the concentration cost.

  The leak in the present invention is a permeation of gas other than oxygen gas that occurs from the gas supply side to the gas permeation side in the oxygen separation device, and is a total leak in the oxygen separation device. As described above, the cause of the leak is mainly a leak due to an oxygen separation membrane defect or the like, or a leak due to imperfect gas sealability, but also includes a leak due to other causes.

In the oxygen concentration method of the present invention, the total gas leak amount in the oxygen separator is set to the following range. That is, it can be suitably used in the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻⁸ Nm ³ · s ⁻¹ · m ⁻² · kPa ⁻¹ . If the amount of leak increases beyond this range, the oxygen purity due to concentration cannot be secured at a level of 99%, and it may be difficult to enjoy the economic benefits of operating the above-mentioned pressure swing adsorption method in two stages. is there. Further, if a conventional separation membrane manufacturing technique and bonding technique are used, the amount of gas leak can be suppressed to 1 × 10 ⁻⁶ Nm ³ · s ⁻¹ · m ⁻² · kPa ⁻¹ or less.

  On the other hand, if it is attempted to reduce the amount of leakage beyond the above range, advanced technology that has not yet been established at the separation membrane and the junction part is necessary, which inevitably leads to a decrease in yield and substantially secures economic efficiency. It may disappear. If it is technically possible, high-purity oxygen can be separated by using the conventional technology that separates oxygen under a large differential pressure condition, which may reduce the merit of the oxygen concentration method of the present invention. is there.

  A further desirable embodiment of the present invention is an oxygen separation apparatus having the above-described leak, using low-purity oxygen obtained by using a separation membrane made of an oxide ion-permeable oxide as the oxygen-containing gas (A) of the present invention. The gas is supplied to the gas supply side. At this time, low-purity oxygen obtained by the separation membrane may be once stored in a gas holder, and then supplied as an oxygen-containing gas (A) to the gas supply side of the oxygen separator, but the apparatus illustrated in FIG. 2 is used. As a result, heat loss and energy loss accompanying compression can be minimized.

  First, a plurality of oxygen separation tubes 204 are placed in the first oxygen separation device main body 201 so as to isolate the space 202 and the space 203. Air as a raw material is supplied from 211, and after being pressurized by the compression unit 217 of the gas turbine 216 (in this case, the temperature is slightly increased by adiabatic compression), the temperature is further increased by the heat exchanger 214 and finally introduced from 212. The fuel is combusted in the combustor 213 and heated to a predetermined temperature (for example, 900 ° C.). The exhaust gas from the first oxygen separation device 201 is partly transferred to the raw material air by the heat exchanger 214, and then required to drive the expansion turbine 218 in the gas turbine 216 by the combustor 215. The temperature is raised to the temperature.

  On the other hand, since the exhaust gas of the second oxygen separation device main body 206 is held at a low pressure (for example, 0.2 MPa) by the pressure regulating valve 220, the low-purity oxygen 205 obtained through the oxygen separation pipe 204 is not cooled. Then, it is sent to the second oxygen separator main body 206 while maintaining a pressure equal to or higher than the normal pressure which is substantially equal to this.

In the second oxygen separation device main body 206, a plurality of oxygen separation tubes 209 are placed so as to isolate the space 207 and the space 208, and concentrated high-purity oxygen 210 is obtained. The normal pressure exhaust gas from the pressure regulating valve 220 is cooled by the heat exchanger 214 and then discharged.
Here, the oxygen concentration of the concentrated oxygen obtained by this method is calculated. Assuming that the separation condition in the first oxygen separation device main body 201 is inlet side oxygen partial pressure (gas supply side) / outlet side oxygen partial pressure (gas permeation side) = 0.36 MPa / 0.2 MPa, the driving force for permeation is the above example. Therefore, the oxygen permeability (speed) of the separation membrane is 1.5 × 10 ⁻³ Nm ³ · s ⁻¹ · m ⁻² . The total leak rate (per unit area) of the separation pipe and the junction is 8 × 10 ⁻⁸ Nm ³ · s ⁻¹ · m ⁻² · kPa ⁻¹ as described above.

Assuming that the air 211 as a raw material has an oxygen concentration reduced to 18% by the combustor, the total pressure is increased to 2 MPa in order to reach an oxygen partial pressure of 0.36 MPa. The differential pressure is 1.8MPa (1800kPa).
The leak rate is 8 × 10 ^-8 Nm ³ · s ^-1 · m ^-2 · kPa ^-1 × 1800 kPa = 1.44 × 10 ^-4 Nm ³ · s ^-1 · m ^-2 , and 18% of the leak amount is Since oxygen is contained, the separated oxygen purity is as follows.
Separation oxygen purity = (1.5 x 10 ^-3 +1.44 x 10 ^-4 x 0.18) / (1.5 x 10 ^-3 +1.44 x 10 ^-4 ) = 92.8%

Assuming that the separation condition of the second oxygen separation device main body 206 is inlet side oxygen partial pressure (gas supply side) / outlet side oxygen partial pressure (gas permeation side) = 0.18 MPa / 0.1 MPa, the concentration of the low-purity oxygen 205 is 92.8. Since the oxygen partial pressure is 0.18 MPa, the total pressure is increased to 0.194 MPa. The differential pressure is as follows. That is, 0.094 MPa (94 kPa).
The leak rate is 8 × 10 ^-8 Nm ³ · s ^-1 · m ^-2 · kPa ^-1 × 94 kPa = 7.52 × 10 ^-6 Nm ³ · s ^-1 · m ^-2 , and 92.8% of the leak rate is 92.8% Since oxygen is contained, the separated oxygen purity is as follows.
Separation oxygen purity = (1.5 x 10 ^-3 +7.52 x 10 ^-6 x 0.928) / (1.5 x 10 ^-3 +7.52 x 10 ^-6 ) = 99.96%
As a result, it is possible to obtain highly concentrated oxygen.

  Another preferred embodiment of the present invention uses an oxygen separation device that leaks from the gas supply side to the gas permeation side using a pressure-driven system with a separation membrane made of oxide ion conductive oxide, and exceeds normal pressure. Oxygen-containing gas (A) having a pressure of less than 0.5 MPa and having an oxygen concentration of 25 to 95% is used as the gas supply side, oxygen concentration is performed with the gas permeation side as normal pressure, and the gas supply side passes through the separation membrane This is an oxygen concentration method in which a gas (C) obtained by further separating oxygen from the discharged gas (B) is supplied to the gas supply side of the oxygen separator and recycled.

  When oxygen is concentrated from the above-mentioned 90% low-purity oxygen raw material, a large amount of oxygen is also present in the gas fluid discharged without being separated. The amount of residual oxygen varies depending on the supply amount and separation rate of the low-purity oxygen gas that is the raw material. For example, when separating and concentrating 50% of the oxygen present in the raw material (with an oxygen recovery rate of 50%) ), A gas fluid having an oxygen concentration of about 82% is discharged. If an attempt is made to further increase the oxygen recovery rate, the oxygen partial pressure on the raw material side decreases, so that the driving force for separation becomes difficult to work, so the oxygen separation rate decreases and the efficiency deteriorates. In order to prevent a decrease in efficiency, it is efficient to reduce the oxygen recovery rate to, for example, less than 50%, separate oxygen from the exhausted gas fluid by another means, and return to the original system.

  As means for separating and recovering oxygen from the gas (B) discharged without passing through the separation membrane from the oxygen separation device, those utilizing the phenomenon of adsorption / desorption of oxygen gas are suitably used. Specifically, the generally known pressure swing type PSA or temperature swing type TSA can be raised.

  FIG. 3 shows a specific example of this. In the oxygen separation device main body 301, a plurality of oxygen separation tubes 304 are placed so as to separate the space 302 and the space 303. The space 302 is pressurized to a certain pressure by adjusting the compressor 307 and the pressure regulating valve 313, and high-purity oxygen 305 concentrated by separation is obtained. After the gas fluid that does not contribute to the separation is cooled by the heat exchanger 308, oxygen is adsorbed by the PSA device 311. At this time, air 312 having a pressure corresponding to the space 302 is replenished from the outside. While the adsorption is in progress, gases other than oxygen that are not adsorbed are discharged to the outside using the discharge valve 314. When the adsorption is completed, the pressure regulating valve 313 is opened, and about 93% low-purity oxygen is sent to the compressor 307. After the pressure is increased by the compressor 307 (in this case, the temperature is slightly increased by adiabatic compression), the temperature is further increased by the heat exchanger 308, and finally the fuel introduced from 309 is combusted in the combustor 310 to a predetermined temperature (for example, The temperature is raised to 900 ° C.

  The lower diagram in FIG. 3 conceptually shows a series of processes for producing high-purity oxygen, and will be described below in order. Process A is a process in which the compressor 307 is operated while the pressure regulating valve 313 is closed, whereby the pressure in the space 302 is increased and the adsorption proceeds in the PSA device 311. In the process B, the compressor 307 is stopped while the pressure regulating valve 313 is closed, so that the pressure in the space 302 slightly decreases with the separation in the oxygen separation device, but the adsorption further proceeds in the PSA device 311. . Process C is a process in which the adsorbed oxygen is sent to the compressor 307 and the pressure in the space 302 is lowered by opening the pressure regulating valve 313. At this time, the oxygen partial pressure relationship between the space 302 and the space 303 is reversed, but the check valve 315 prevents oxygen from flowing back from the space 303 to the space 302.

Oxide ion permeable oxides used for oxygen separation include bismuth oxide-based, ceria-based, zirconia-based, perovskite-type oxides, pyrochlore-type oxides, etc., which have an oxide ion of 10 ⁻² Scm ⁻¹ or more at 850 ° C. An oxide having conductivity is preferably used. Among them, a substantially cubic perovskite oxide having a high oxide ion conductivity is most preferably used. Here, the term “substantially” means that even a perovskite oxide that is approximately cubic crystal is actually limited to a cubic perovskite oxide because the crystal structure is actually slightly distorted. It is not.

Example 1
Using the system excluding the gas turbine in the oxygen separator exemplified in FIG. 1, the case where air was used as a raw material and the case where low purity oxygen was used were compared. The total membrane area of the separation tubes (10 tubes) used in the test was 0.2 m ² , and the average leakage rate of the 10 separation tubes was 5 × 10 ⁻⁸ Nm ³ · s ⁻¹ · m ⁻² · kPa ^−1. It was. When this was fixed in the oxygen separator, a slight leak occurred at the junction, and the total leak rate at room temperature is as follows.
That is, it was found to be 1.6 × 10 ⁻⁸ Nm ³ · s ⁻¹ · kPa ⁻¹ (8 × 10 ⁻⁸ Nm ³ · s ⁻¹ · m ⁻² · kPa ⁻¹ per separation membrane area). .

When the concentration of oxygen separated from air pressurized to 1 MPa was evaluated by gas chromatography, it was found to be 96.2%. On the other hand, it was confirmed that the oxygen concentration separated from the pressure of 0.2 MPa using 93% low-purity oxygen (remaining nitrogen mixed gas) was 99.9% or more.
While it is generally said that separation of high-purity oxygen is a major advantage of solid electrolyte oxides, it is actually necessary to take extremely advanced measures against low leakage to achieve high purity. It was confirmed that oxygen concentration was easily performed and high-purity oxygen production could be realized.

(Example 2)
The same test as in Example 1 was performed using a separation tube having a high leak rate. The total area of the oxygen separator used was 0.2 m ² and the average leak rate was 1.9 × 10 ⁻⁶ Nm ³ · s ⁻¹ · m ⁻² · kPa ⁻¹ . When this was fixed in the oxygen separator, the total leak rate including the junction leak was 4 × 10 ⁻⁷ Nm ³ · s ⁻¹ · kPa ⁻¹ (2 × 10 per separation membrane area). ^-6 Nm ³ · s ^-1 · m ^-2 · kPa ^-1 ).

As a result of the oxygen separation test, it was confirmed that the oxygen concentration separated from the 0.2 MPa 93% low-purity oxygen (remaining nitrogen mixed gas) was 98.8%. The purity remained below 99%.
An oxygen separation tube exhibiting a leak of about 1.9 × 10 ^-6 Nm ³ · s ^-1 · m ^-2 · kPa ^-1 is relatively easy to manufacture, and the leak rate at the joint is larger than that of Example 1. Considering that bonding can be performed with a high probability at this level, it can be said that the oxygen concentration method according to the present invention is sufficiently effective.

It is a figure which shows the specific example of the oxygen separation apparatus combined with the gas turbine in this invention. It is a figure which shows the specific example of the oxygen concentration method which supplied the low purity oxygen obtained by the separation membrane which consists of an oxide ion permeable oxide in this invention to the gas supply side as oxygen-containing gas (A). A specific example of a method for supplying and recycling a gas (C) obtained by separating oxygen from a gas (B) discharged without separation in the present invention to the gas supply side of the oxygen separator, and a process for operating the same FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Oxygen separator main body 102 Space between oxygen separator outer surface and oxygen separator main body 103 Space between oxygen separator inner surface and oxygen separator main body 104 Oxygen separator pipe 105 Concentrated high purity oxygen 106 Low purity oxygen 107 Fuel 108 Combustor 109 Heat Exchanger 110 Combustor 111 Gas Turbine 112 Compressor 113 Expansion Turbine 114 Exhaust Port 201 First Oxygen Separator Main Body 202 Space between Oxygen Separation Pipe Outer Surface and First Oxygen Separator Main Body 203 Oxygen Separation Space 204 between tube inner surface and first oxygen separator main body 204 Oxygen separator pipe 205 Low-purity oxygen 206 Second oxygen separator main body 207 Space 208 between oxygen separator outer surface and second oxygen separator main body Space 209 between the inner surface of the pipe and the second oxygen separation device main body Oxygen separation pipe 210 Concentrated high-purity oxygen 211 Source air 212 Fuel 2 3 combustor 214 heat exchanger 215 combustor 216 gas turbine 217 compressing section 218 expansion turbine 219 outlet 220 pressure regulating valve 221 separated gas discharged without (B)
301 Oxygen Separator Main Body 302 Space between Oxygen Separation Pipe Outer Surface and Oxygen Separator Main Body 303 Space between Oxygen Separation Pipe Inner Surface and Oxygen Separator Main Body 304 Oxygen Separation Pipe 305 Concentrated High Purity Oxygen 306 Adsorption / Desorption Phenomenon Low purity oxygen 307 separated by the compressor 308 heat exchanger 309 fuel 310 combustor 311 PSA device 312 air 313 pressure regulating valve 314 discharge valve 315 check valve

Claims (6)

  Using an oxygen separator with a leak from the gas supply side to the gas permeation side using a separation membrane made of oxide ion conductive oxide and having a pressure from the gas supply side to the gas permeation side. An oxygen concentrating method, wherein an oxygen-containing gas (A) having a concentration of 25 to 95% is used as the gas supply side, and the gas permeation side is set to normal pressure.   The oxygen concentration method according to claim 1, wherein the oxygen-containing gas (A) supplied to the gas supply side is obtained using a separation membrane made of the oxide ion conductive oxide. Using an oxygen separator with a leak from the gas supply side to the gas permeation side using a separation membrane made of oxide ion conductive oxide and having a pressure from the gas supply side to the gas permeation side. Oxygen-containing gas (A) having a concentration of 25 to 95% is used as the gas supply side, oxygen concentration is performed using the gas permeation side as normal pressure,
A gas (C) obtained by further separating oxygen from the gas (B) discharged without passing through the separation membrane from the gas supply side is supplied to the gas supply side of the oxygen separator and recycled. To concentrate oxygen. 4. The oxygen concentration method according to claim 1, wherein the leak is 1 × 10 ⁻⁶ to 1 × 10 ⁻⁸ Nm ³ · s ⁻¹ · m ⁻² · kPa ⁻¹ .   The means for obtaining a gas (C) obtained by further separating oxygen from the gas (B) discharged without passing through the separation membrane from the gas supply side is a separation method performed by adsorption and desorption. The oxygen concentration method according to claim 3.   4. The oxygen concentration method according to claim 1, wherein the oxide ion conductive oxide is a cubic perovskite type.

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