JPH05200229A - Method and device for generating oxygen - Google Patents

Abstract

PURPOSE: To generate oxygen with a lightweight and low energy consumption generator by supplying air to one side surface of a mixed mode conductor material wall of a ceramic membrane apparatus, establishing a pressure gradient with high pressure at the wall and heating the wall. CONSTITUTION: In an apparatus of the mixed mode (electronic/ionic) conductor material in a form of membrane or thin wall, by exposing the first surface A to oxygen having higher partial pressure than an oxygen partial pressure at the opposite surface B, a reaction occurs at the surface A to reduce an oxygen molecule O2 to two oxygen ions. An oxygen ion O<2-> crosses the wall by the pressure gradient between the high partial pressure of oxygen at surface A and the high partial pressure of oxygen at surface B. Simultaneously a reverse flow of electron e<-> occurs from the surface B to the surface A forming the oxygen ions into an oxygen molecule. By heating the wall at the same time, the oxygen diffuses through the wall. Thus it is possible to generate high purity oxygen without impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen generation system, and more particularly to a system for generating oxygen by an air separation process.

[0002]

2. Description of the Related Art Small-scale oxygen production systems used in many conventional air separations are designed to absorb pressure fluctuations [pr
essure swing adsorption (PSA) technology or membrane technology. Modern airborne oxygen generation systems rely on the PSA method, which uses zeolite molecular sieves to separate oxygen from air. According to this, there are at least two zeolite beds, which require continuous cycles of on-stream oxygen production and off-stream purging. The disadvantage of such a system is that it requires the introduction of feed air into the bed, valve actuation to control the flow of oxygen-rich gas and nitrogen-rich purge gas, which creates moving parts that can cause wear and malfunction. Is what you need. The limitation of such a system is that the theoretical maximum concentration of oxygen produced is 95%, unless additional measures are taken to remove argon and other trace gases. This is also unacceptable in terms of cost, weight and size, especially in aircraft. In practice, even in the most efficient system, 9
It is difficult to obtain a product gas having an oxygen concentration of 3% or more.

Current membrane technology generally uses polymeric membranes and separates based on molecular size and diffusion rate through the membrane. Although such membranes are widely used for the separation of nitrogen from air, their limited selectivity makes it uneconomical to obtain product gases above about 40-50% oxygen concentration. ..

A number of ceramic materials are known, for example yttria-stabilized zirconia, which is the so-called oxygen ionic conductor. At high temperatures, such materials become electrically conductive due to the mobility of oxygen ions within the crystal lattice and can be used as oxygen sensors or pump-type generators; however, this material is only conductive for oxygen ions. Therefore, an external electric circuit for electric conduction is required. This requires a large amount of current, power, which is not suitable for aircraft and other systems, such as systems that produce oxygen for medical purposes.

Other ceramic materials are known that show conductivity when mixed electronically and with oxygen ions. This membrane can maintain a continuous flow of oxygen ions without the need for an external electrical circuit as shown in FIG. A similar mechanism with the peroxide ion O ₂ ⁻ is also possible. Oxygen flow is directly dependent on the logarithm of the oxygen partial pressure, inversely related to absolute temperature, and either by the ionic or electronic conductivity of the material or by the surface reaction rate at which molecular oxygen dissociates into its ionic species. Is also limited.

It is an object of the present invention to provide a method for producing oxygen of substantially 100% of respirable quality by an air separation process using a mixed mode conductor.
Another object of the present invention is substantially 100 of breathable quality for use in aircraft and other breathing applications.
% Oxygen is provided.

[0007]

The present invention therefore provides a method of generating oxygen by air separation which comprises the following steps. Air is delivered over one surface of a mixed-mode conductor material wall of a ceramic membrane device; the pressure gradient across the wall by exposing the one surface to a higher oxygen partial pressure than the opposite surface. From the side exposed to high pressure to the side exposed to low pressure at a temperature such that oxygen ions diffuse through the wall and electron conduction occurs in the opposite direction. Heat; and collect oxygen product at the low pressure side surface of the wall.

The oxygen diffusion process is based on the partial pressure of oxygen (PPO
₂ ) Dependent on the ratio (where PPO ₂ =% O ₂ × pressure).
In order to get 100% pure oxygen from air, a pressure ratio of the order of 5: 1 is required to start the process, in practice a 10: 1 pressure ratio is only 2: 1 PPO. _It only gives a ratio of ₂ . Therefore, in order to increase the efficiency of oxygen generation, it is desirable to supply high-pressure air to one side of the wall using a compressor or the like and reduce the pressure on the opposite surface using a vacuum pump or the like. A particular advantage of the mixed-mode conductor arrangement is that hot air can be supplied, and preferably by supplying hot air to the high pressure side, the wall can be heated to a temperature suitable for oxygen diffusion. Is.

The method of the present invention is practiced in a ceramic membrane device comprising the following constructions: a ceramic wall made of mixed mode conductor material; an inlet for supplying air to a passage on one side of the wall; the opposite of the wall. Outlet for taking oxygen from the side passage;
Means for creating a pressure gradient through the wall; means for heating the wall to a temperature at which oxygen ions diffuse across the wall from the air inlet side to the oxygen outlet side; and nitrogen and other trace gases to the wall air Vent means to escape from the entrance side passage.

If desired, a compressor for pressurizing the feed air may be provided to create a pressure gradient across the wall. Alternatively or in addition, negative pressure may be applied to the outlet, for example with a vacuum pump. Although it may be heated electrically, other sources of thermal energy are preferred for this purpose as they require a power source. For one, thermal energy is supplied by supplying air to the inlet at a temperature suitable for heating the wall. A suitable source of hot air is obtained by withdrawing high pressure air from the compressor stage of a gas turbine engine. Alternatively, or in addition, thermal energy may install the device in a hot body, such as the outlet of a gas turbine engine.

The device according to the invention is particularly useful in combination with a gas turbine engine. It is itself suitable as an oxygen generator on board an aircraft powered by one or more gas turbine engines. This is, in particular, substantially 10 of breathable quality.
It can be stored at high pressure for emergency use when 0% oxygen is generated and the inside of the cabin is depressurized. Since this equipment can supply air at high temperature, PS
It is even more advantageous for use in aircraft compared to the A system. At higher temperatures, the PSA process is less efficient, so the air exiting the engine must be cooled by passing it through a heat exchanger before being fed to the zeolite molecular sieves.

[0012] Therefore, in another aspect of the present invention, there is provided an on-board oxygen generator characterized by the following: connected to an outlet for discharging hot, high-pressure air from a compressor of an aircraft gas turbine engine. A ceramic membrane device having an inlet for supplying air from the inlet to a passage on one side of a mixed mode conductor ceramic wall such that in operation there is a pressure gradient across the wall and the temperature of the wall is oxygen. The temperature is raised to a temperature such that the ions diffuse through the wall into the opposite passage; an outlet that collects oxygen from the opposite wall passage. Further, the apparatus of the present invention is advantageously used in combination with a small gas turbine engine to provide an oxygen generator that can be breathed by a patient in a hospital.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. FIG. 1 shows the conductivity of ions and electrons when the mixed mode conductor film is exposed to oxygen having a high partial pressure on one side and oxygen having a low partial pressure on the other side. Figure 2
1 is a diagrammatic view of an apparatus according to one aspect of the invention. FIG. 3 is a diagrammatic view of an apparatus according to another aspect of the invention. FIG. 4 is a diagram illustrating an aspect of the present invention in which air is supplied from a compressor stage of a gas turbine engine. FIG. 5: is a figure which shows another aspect.

If formed into a film or a thin wall,
Mixed-mode (electronic / ionic) conductor materials such as perovskite type oxides (La _1-x Sr _X CO _1-Y Fe _Y
O _{3- δ} ), bismuth erbia and bismuth terbia are 50
If heated to above 0 ° C. and the first surface A is exposed to oxygen at a partial pressure higher than the oxygen partial pressure of the opposite surface B (see FIG. 1), the reaction takes place at surface A, Oxygen molecule O ₂
Is reduced to two oxygen ions: O2 + 4e → 2O ^2-

Due to the high oxygen partial pressure of surface A and the low oxygen partial pressure of surface B, the pressure gradient across the wall results in oxygen ions O
^2- flows across the wall from surface A to surface B (ionic conductivity). At the same time, a reverse flow of electrons e ⁻ from surface B to surface A occurs (electron conductivity). On the surface B, the opposite reaction takes place and the oxygen ions become oxygen molecules: 2O ^2- → O ₂ + 4e ⁻

Effective ceramic membranes that separate oxygen from air can be prepared as follows: i. La _1-x Sr _X CO _1-Y Fe _Y O _3-δ type perovskite type oxide, where δ is the stoichiometric difference. An example of this type of perovskite is La _0.2 Sr _0.8 CO
_{It is 0.5} Fe _0.5 O _3-δ . ii. A nickel / cobalt perovskite type oxide having a composition of La _0.5 Sr _0.5 CO _0.5 Ni _0.2 O _3-δ type. iii. (Bi ₂ O ₃ ) _1-X (Er ₂ O ₃ ) _X type bismuth erbia. iV. (Bi ₂ O ₃ ) _1-X (Tb ₂ O ₃ ) _X type bismuth terbia.

In order to minimize the energy required to heat the membrane wall, the temperature should be kept as low as possible; however, oxygen flow also affects the diffusion properties of the material,
It also depends on the pressure gradient across the wall and the reaction at the surface. The wall should be as thin as possible, as the temperature increases with wall thickness in order to produce an equal amount of oxygen flow across the membrane wall made from the same material.
Ideally, the strength is 150 to 200 μm while maintaining the strength enough to endure in the operating environment.

Referring to FIG. 2, an apparatus 10 for producing substantially 100% oxygen product breathable by air separation is a wall made of mixed mode conductors (not shown in FIG. 2). ) Is included in the ceramic film assembly 11. The membrane assembly 11 can have a honeycomb extruded structure with alternating passages closed on opposite sides, just as used in catalytic converters. The flow of oxygen through this material is driven by a pressure gradient across the walls that separate the passages, which pressure gradient
From the inlet 13 with one open end 12 of the membrane assembly
Is provided by the air supply to. The membrane assembly is connected to a thermal energy source 15, which is an electric heat or other heating body, and is heated to at least 500 ° C. At this temperature oxygen diffusion through the isolation wall takes place, allowing the collection of oxygen products at the open end 16 opposite the assembly 11. The open end of this passage is connected to an outlet 17 through which the oxygen produced is transferred to the end user or high pressure store (not shown). The passages to the end 16 are perforated with each other and communicate with each other and a vent outlet 18 for removing nitrogen and other residual gases.

The apparatus shown in FIG. 3 is similar to that of FIG. 2, but the pressure gradient across the wall of the passage is provided by the negative pressure in the passage leading to the oxygen outlet duct 17. This negative pressure is generated by a vacuum pump 19 provided in the outlet duct 17, in which case the compressor in the inlet duct 13 is omitted. Although not shown, a compressor may be provided in the inlet duct and a vacuum pump may be provided in the oxygen outlet duct if the weight does not matter so much.

Referring to FIG. 4, a ceramic membrane device 30 according to another aspect of oxygen production by air separation is connected to a hot, high pressure air outlet from a compressor 31 of a gas turbine engine 32. The supply air enters the inlet 33 at one end of the device and flows from there to the passage 34. The passage 34 communicates with a vent gas plenum 35 and a vent gas passage 36. The passage 34 is formed by the membrane wall 37 and the passage 38.
And 38 has a closed end at the inlet 33 and communicates with the oxygen gas outlet 39 at the other open end.
Membrane wall 37 is made of a ceramic mixed mode conductor material which, when heated to about 500 ° C. or higher in hot air, causes oxygen ions to diffuse across the wall, the flow of oxygen ions causing a pressure gradient. Driven by, and a flow of electrons occurs in the opposite direction. Oxygen in passage 38 is outlet 3
9 and from there through outlet passage 40 to a reservoir or end user (not shown).

The device 30 may be manufactured by extrusion extrusion molding of ceramic, or may be manufactured from ceramic parts. If, as mentioned above, the ceramic wall is thin enough and strong enough to withstand the environment in which the device is operated, it is sufficient to heat it below the temperature of the air supplied by the engine compressor. No external device for heating the is required. If that is not possible, external heating energy, for example electric heating means, is required, first heating the device to operating temperature and then maintaining this temperature with hot feed air.

The device of the present invention is particularly useful as an oxygen generator for an aircraft. The device is a unit fitted to one or more gas turbine engines and oxygen is transferred to the aircraft storage tanks. This is particularly advantageous as it utilizes the hot air available from the engine's compressor and, if necessary, the heat from the engine exhaust to heat the system. By law, such a device requires one of the crew to constantly breathe oxygen when flying at altitudes above 12000 m in order to protect against the effects of altitude effects from sudden decompression in the cabin, Also used for on-board oxygen generation of aircraft carrying passengers when systems are in place to provide oxygen for passengers and crew to breathe until the aircraft descends to a safe altitude of 3000m. can do.

However, the device is not limited to aircraft oxygen generators, and within the scope of the invention, it may be used on a small gas turbine engine on the ground to generate oxygen for hospital or other purposes. It can also be provided as an attached device. The particular advantage of this device is that it can provide substantially 100% oxygen free of contaminants, has few moving parts and is not affected by external temperature. In addition, the aircraft system is light in weight and requires a small installation space.

An apparatus 50 according to another embodiment of the present invention shown in FIG.
Is a ceramic membrane assembly 5 for separating oxygen from air.
When 1 is heated by electric heat 52, electric power consumption is reduced. The membrane assembly and heating elements are placed in an insulating space 53 and power is supplied externally (not shown). The pressurized air is supplied to the membrane assembly 51 from an external source (not shown) from the passage 55 to the inlet 54. The passage 55 is connected upstream to the outlet 56 of the heat exchanger 57. In this manner, the heat exchanger is of the counterflow type and feed air enters from the source of pressurized air via passageway 59 through inlet 58. Oxygen from the outlet 62 opposite the membrane assembly inlet 54 enters the passage 60 of the heat exchanger 57. The oxygen, which has cooled through the heat exchanger, is passed to a reservoir (not shown) or to the end user through passage 6
Enter after 3 In a similar manner, nitrogen and other residual gases enter the outlet 62 through passage 64 into the other passage 65 of the heat exchanger 57 and vent to the vent passage 66.

Since the membrane assembly 51 needs to be heated to about 500 ° C., the produced oxygen gas and the nitrogen / residual gas mixture come out at a temperature higher than the air supplied from the passage 59. Since the supply air is preheated by the heat exchange of these gases with the supply air by the heat exchanger, the supply air assists in maintaining the temperature of the membrane assembly after the start-up of the device and the heating element 52. The power of can be reduced.

[0026]

Since the present invention is configured as described above, it is a device that has almost no moving parts and is not affected by external temperature.
Since it can provide substantially 100% oxygen free from impurities, it is useful as an oxygen generator onboard an aircraft or as an oxygen generator in a hospital or the like.

[Brief description of drawings]

FIG. 1 shows the ionic and electronic conductivities of a mixed-mode conductor film when one surface is exposed to high partial pressure oxygen and the other surface is exposed to low partial pressure oxygen.

FIG. 2 is a diagrammatic view of an apparatus according to one aspect of the invention.

FIG. 3 is a diagrammatic view of an apparatus according to another aspect of the invention.

FIG. 4 illustrates an aspect of the invention in which air from a compressor stage of a gas turbine engine is provided.

FIG. 5 shows still another embodiment.

[Explanation of symbols]

 10 Device 11 Membrane Assembly 13 Inlet 14 Compressor 15 Thermal Energy Source 17 Oxygen Outlet 18 Vent Gas Outlet 19 Vacuum Pump 30 Ceramic Membrane Device 32 Turbine Engine 36 Vent Gas Passage 37 Membrane Wall 40 Oxygen Outlet 51 Membrane Assembly 57 Heat Exchanger 59 Air Supply Passage 63 Oxygen outlet passage 66 Vent gas passage

Claims (10)

[Claims] 1. A method of generating oxygen by air separation comprising the steps of: delivering air onto one surface of a mixed mode conductor material wall of a ceramic membrane device; one surface opposite the other surface. By exposing it to a higher oxygen partial pressure than
Create a pressure gradient across the wall; such that oxygen ions diffuse through the wall from the side exposed to high pressure to the side exposed to low pressure, causing electron conduction in the opposite direction The wall is heated to temperature; and oxygen products are collected on the low pressure side surface of the wall. 2. A ceramic membrane device for generating oxygen by air separation, including: a ceramic wall made of mixed mode conductor material; an inlet for supplying air to a passage on one side of the wall; An outlet for removing oxygen from the passage opposite the wall; a means for creating a pressure gradient through the wall; a means for heating the wall to a temperature such that oxygen ions diffuse across the wall from the air inlet side to the oxygen outlet side; and Venting means for escaping nitrogen and other trace gases from the passageway on the air inlet side of the wall. 3. A compressor is provided at the entrance for pressurizing the air supplied to one passage of the wall,
The device according to claim 2. 4. Apparatus according to claim 2, wherein a vacuum pump is provided at the outlet for creating a negative pressure in the passage opposite the wall. 5. A device according to claim 2, comprising electrothermal heating means for supplying thermal energy for heating the wall. 6. The mixed mode conductor material is La _1-x Sr _x CO.
The device of claim 2 containing a perovskite type oxide in the form of _1-Y Fe _Y O _3-δ . 7. The device of claim 2, wherein the mixed mode conductor material is bismuth erbia or bismuth terbia. 8. The device according to claim 2, wherein an attachment is provided as an attachment to the heating element device. 9. The apparatus according to claim 2, wherein the apparatus is provided with a heat exchanger for reheating the feed air in such a way that it heat exchanges with the oxygen and / or nitrogen leaving the device. 10. An oxygen generator mounted on an aircraft characterized by the following: a ceramic membrane device having an inlet connected to an outlet for discharging high temperature, high pressure air from a compressor of a gas turbine engine of the aircraft; There is a passage supplying air to the passage on one side of the mixed-mode conductor ceramic wall, so that in operation there is a pressure gradient across the wall, the temperature of the wall being such that oxygen ions pass through the wall to the passage on the opposite side. The temperature is raised to such a temperature that it diffuses; an outlet that collects oxygen from the passage in the opposite wall.