JPH0322990A - Process for producing oxygen from carbon dioxide in gas - Google Patents

Abstract

PURPOSE:To produce oxygen in a closed space such as a submarine at a low cost by separating and recovering CO2 in a gas by membraneseparation, adsorption separation, ion exchange separation, etc., and supplying the CO2 to a reactor composed of a plant growing in a culture liquid to effect photosynthesis. CONSTITUTION:A gas 1 such as air rich in carbon dioxide is pretreated with a pretreatment part 2 composed of a coarse filter, etc., to remove dust, etc., and passed through a separation module 3 comprising a membrane-separation, adsorption separation under varying pressure and/or separation with ion exchange material to separate carbon dioxide. The separated carbon dioxide is stored in a carbon dioxide storage tank 4 and supplied to a reactor 8 filled with a plant (e.g. chlorella) growing in a culture liquid to effect the photosynthesis and produce oxygen. The produced oxygen is stored in an oxygen storage tank 7 and supplied, as necessary, as an oxygen-supplying gas 8 to obtain the objective oxygen.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of obtaining oxygen from carbon dioxide in a gas, and particularly a method of separating and recovering carbon dioxide in the air and biochemically obtaining oxygen. Regarding.

The method of the present invention is useful for removing and recovering carbon dioxide from the air and producing oxygen in closed spaces such as underground spaces, spaces in ocean development, spaces in the space industry, and inside submarines, and for air purification in homes and hospitals. It can also be used for producing oxygen in various industries.

[Conventional technology]

First, we will discuss the removal and recovery of atmospheric carbon dioxide and the production of oxygen in a closed space.

The use of underground space as a closed space is expected to become even more important in the future from the perspective of effective land use, and its development is currently underway.

On the other hand, in underground spaces, the challenge is how to effectively purify carbon dioxide (hereinafter referred to as C02) (hereinafter referred to as C02) generated by human activities (air purification).

Current air purification technology usually monitors the CO2 concentration in the air, and prevents the concentration from reaching a certain level by cleaning air that contains high concentrations of CD in the air above the ground. Instead, clean air is introduced from the ground.

This method releases high concentrations of CD2 into the surface atmosphere, so
Increasing the level of CO2a in the ground atmosphere, and in cases where the introduced air is not clean (for example, in urban areas, especially in the summer, the introduced air is polluted due to "so-called air pollution"), the air should be purified. This was an issue that needed to be done.

In particular, in recent years, global environmental problems due to emitted CD■ have become increasingly serious, and CO, released due to human activities, is said to be the main cause of global warming and is attracting attention as a new environmentally destructive substance. As a result, CD2 emissions into the atmosphere are being reviewed.

In addition, COi generated by human activities in ocean development and closed spaces such as submarines is absorbed and removed using chemicals, and the oxygen (hereinafter referred to as 0) required to sustain human life is obtained by electrolysis of seawater. . Here, waste is a byproduct (secondary pollution)
Because of the high energy cost and the high cost of CO2, the treatment of CO2 and the method of obtaining 02 have been issues.

[Problem to be solved by the invention]

As described above, emitted CO2 has recently been attracting attention as a pollutant, especially for global environmental problems, but conventional treatment methods have various problems, and it is difficult to achieve a satisfactory level of emitted CO2.
There was no way to use it.

Therefore, an object of the present invention is to provide a method for effectively recovering CD2 released into a gas and economically obtaining oxygen from it.

[Means to solve the problem]

In order to achieve the above object, the present invention separates and recovers carbon dioxide in gas by one or more methods selected from membrane separation method, pressure fluctuation type adsorption separation method, or separation method using ion exchanger. This is a method for obtaining oxygen from carbon dioxide in a gas, which is characterized by supplying the recovered carbon dioxide to a reactor made of plants growing in a culture solution and obtaining oxygen through photosynthesis or reaction.

Next, the present invention will be explained in detail.

FIG. 1 is an example of a process diagram for removing and recovering CO2 from the air in an underground space and producing oxygen.

Here, the separation and recovery of CD2 is performed using a membrane separation method, and the conversion of CO2 to 02 is performed using microalgae.

In the underground space (not shown), the 02 in the air becomes C02 due to human activities and the operation of equipment, and the CO. The concentration is increasing (1 degree of CO2 in the surface atmosphere = 300~4
50 ppm).

In FIG. 1, 1 is 2 released in the underground space. 0 0 0~5. 0 0 0 ppm CO
The discharged air contains 2.

The released air 1 is subjected to a pretreatment section 2 including a rough filter, etc., where dust and the like are removed, and then introduced into the membrane module 3 .

In the membrane module 3, CO2 in the emitted air 1 is separated from 0, and nitrogen, and becomes highly concentrated [:Di (CO2-enriched air)], which is stored in a storage tank 4.

CO, depleted air (CD. concentration 300-400p
PM ) 5 is recycled to underground space and normally used as atmospheric air.

Membrane module 3 is a discharge air CD. Any material can be used as long as it has the function of concentrating CO2 to a high concentration of CO2.

The membrane material here may be any material as long as it has the above-mentioned functions, and the following materials can be suitably used in terms of normal effects and workability of the membrane module.

Polyethylene, polystyrene, polyimide, polysulfone, polyethersulfone, polycarbonate, polyphenylene oxide, polyvinyl acetate, polysiloxane such as polydimethylsiloxane, ethyl cellulose, cellulose acetate, ethylene-vinyl acetate co-11i
Coalescing, ethylene-vinyl alcohol copolymer These can be used alone or in combination of two or more.

In the membrane module 3, these membrane materials can be processed into an appropriate shape and used in combination (in multiple stages).

In the wooden example, the polyimide material is made into hollow fibers and used in a multi-stage combination. ooo~5. 0 0 0
ppm CO2 is concentrated to 60-80% CO.

High concentration CD stored in storage tank 4. (CO2-enriched air) is a photosynthesis a IJ actor 6 consisting of microalgae.
will be introduced in The C02 is converted into B by a photosynthetic reaction in the photosynthesis or reactor 6, and is stored in the storage tank 7.

The reaction here is shown below.

6CO2 + 12LO + 688Kcal →C
The aHIJa+ 6H20 + 602 photocombinant reactor 6 is filled with photocombinant organisms, and 02 is produced by the above reaction. Any photosynthetic organism may be used as long as it produces 02 through photosynthesis, and it is particularly preferable that it satisfies the following conditions.

(1) High concentration CD2 can be used efficiently.

(2) High photosynthesis activity (large production capacity) (3) Does not produce harmful or odorous substances.

(4) Can grow within the reactor.

Plants that usually grow in a culture solution, especially cultured plant cells,
Microalgae such as cyanobacteria can be suitably used because they satisfy the above conditions.

As microalgae, green algae such as chlorella, spirulina, and Dunaliella, and cyanobacteria can be used.

Since the plants in the reactor proliferate, it is convenient if the plants themselves can be used for food. Examples of this are chlorella, spirulina, and dunariella.

This example uses chlorella.

As mentioned above, in Koai 11ii IJ actor 6, 70
~80% 02 is obtained and stored in a storage tank 7, after which it is appropriately used as a supply gas 8 to combustion equipment and water treatment equipment in underground space.

The light source used for photosynthesis or reaction may be any light source that allows plants growing in the culture solution to photosynthesize, and may vary depending on the type of plant used, field of application, equipment structure, scale, effectiveness, economical efficiency, etc. You can choose as appropriate.

Examples include sunlight, white light, and fluorescence.

Next, a pressure fluctuation adsorption separation method will be described as a method for separating and recovering low concentration CD2.

A PSA method (pressure swing adsorption method) is known as a pressure fluctuation adsorption separation method. The PSA method is a method in which the adsorbed material is adsorbed onto the adsorbent under high pressure, and then the adsorbed material is desorbed from the adsorbent by lowering the adsorption pressure, and the adsorbed material and non-adsorbed material are separated. .

In this PSA method, a plurality of adsorption towers filled with adsorbent are usually installed, and the series of operations of pressurization → adsorption → regeneration is repeated in each adsorption tower to continuously perform separation simulation as a whole device. I am trying to make it possible.

This will be explained with reference to FIG. Figure 2 is a basic process diagram of PSA, where At is an adsorption tower and B is a PSA process. reveals a regeneration tower. CO2 1
,0 0 0 ~5. The underground vent air containing 0 00 ppm is brought to high pressure by an air supply (not shown). High-pressure air 10 made high-pressure by an air supply device
passes through the valve v1, and CD2 in the air is adsorbed in the adsorption tower ^, and CO and depleted air are obtained from the outlet 20, recycled to the underground space 40, and used.

A portion 30 of the CO2-depleted air at the outlet 20 is sent to the regeneration tower B.
1 and used for regeneration, high concentration CO2 (CD, enriched air) is obtained from outlet 50 and stored in a storage tank (not shown) through valve v2.

Any pressure fluctuation type adsorption separation method can be applied as long as it can obtain a high concentration of CO from the CO2 in the released air.

As for the adsorption separation method, in addition to the method in this example in which CO2 is selectively adsorbed on an adsorbent and a high concentration of CD is obtained through regeneration (desorption), a method in which air is adsorbed can also be applied.

The former is usually used because of the performance of the adsorbent and the simplicity of the device. Examples of such adsorbents include zeolite, hydrotalcite, clathracil, and molecular sieve, and these can be used alone or in combination of two or more.

As a method of pressure swing, adsorption at high pressure as in this example,
In addition to near-atmospheric pressure regeneration (desorption), for example, there is a method in which adsorption is carried out at about atmospheric pressure and regeneration (desorption) is performed in a vacuum.

Further, in an adsorption tower, a moisture absorbent is usually filled at the entrance of the adsorption tower to protect the adsorbent (prevent performance deterioration, etc.).

Any moisture absorbent may be used as long as it can remove moisture present in the supplied air, and can be appropriately determined depending on the type of absorbent, the amount of moisture in the air, etc. Usually, synthetic zeolite, activated alumina, molecular sieve, etc. are used.

Adsorption separation methods, adsorbents, and moisture absorbers depend on the application field, equipment structure,
It can be selected and used as appropriate depending on scale, effectiveness, economic efficiency, etc.

Next, low concentration CD. A separation method using an ion exchanger as a separation and recovery method will be explained.

The ion exchanger collects released CD2 from the air stream and regenerates it (
Any material that can obtain a high concentration of CO2 by desorption of CO, can be used. For example, an ion exchanger supported by an appropriate method on a rod-shaped, granular, filter-shaped, net-shaped, woven or fibrous polymer support is used, and these can be appropriately manufactured by well-known methods. can.

Supports include polymers of aliphatic unsaturated hydrocarbons such as polyethylene, polybrobylene, polybutylene, and polybutene, polymers of aromatic hydrocarbons such as polystyrene and poly-α-methylstyrene, and alicyclic polymers such as polyvinylcyclohexane. Polymers of hydrocarbons, or copolymers of these hydrocarbons, polytetrafluoroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymers, tetrafluoroethylene-hexafluoropropylene copolymers , a fluorine-containing unsaturated hydrocarbon polymer such as vinylidene fluoride-propylene hexafluoride copolymer, or a copolymer thereof.

It is also possible to use matte, polyvinyl alcohol, polyamide, polyester, acrylic polymer, polyurethane, cellulose, cellulose acetate, wool, silk, cotton or mixtures thereof.

The shape of these supports is preferably such that the contact area with the gas flow is large and the resistance is low, and porous supports are usually used as appropriate. For example, suitable thin film-like cloths, filters, preferably net-like textiles, fibers, etc. may be used.

The porosity of the porous support is 10 to 95%, preferably 50 to 95%.
It is 85%. The shape, thickness, and porosity of the porous support can be appropriately determined depending on the shape of the device, the materials used, the structure, the expected effects, etc.

The ion exchanger that can be used in the present invention is not particularly limited, and various ion exchangers can be used.

For example, exchangers containing anion exchange groups such as hydroxyl groups, carbonate groups, bicarbonate groups, l-class to tertiary amino groups, quaternary ammonium groups, sulfonium groups, phosphonium groups, or cation and anion exchange groups. Polymerized or condensed type homogeneous or heterogeneous ion exchangers containing .

Among these, an exchanger containing a hydroxyl group-containing anion exchange group (anion exchanger) is preferred because of its performance and relatively easy production.

The method for supporting the ion exchanger on the support is not particularly limited, and may be carried out by any known method.

For example, the support is irradiated with ultraviolet rays or ionizing radiation such as alpha, beta, or gamma rays, or treated with an oxidizing agent such as oxygen, ozone, chlorosulfonic acid, hydrogen peroxide, penzoyl peroxide, peracetic acid, or the like; There is a method of carrying an ion exchanger by grafting an ion exchanger after performing two or more of these treatments.

As an example, a filter-like polypropylene as a support is treated with ozone, and then immersed in a solution containing 60% and 40% of hydroxystyrene monomer and isobrene, respectively.
A filter-like anion exchanger (anion exchange filter) can be obtained by heating to a temperature of 35° C. to perform a graft polymerization reaction, and then performing quaternary amination after the reaction.

To recover CD from the ion exchanger that has adsorbed CO, a well-known regeneration method for ion exchangers can be applied.

For example, in the case of a hydroxyl group-containing ion exchanger, this can be achieved by using an appropriate concentration of alkali, such as sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, or aqueous ammonia.

The method for separating and collecting CL and the selection of plants can be made appropriately depending on the field of application, equipment structure, scale, effectiveness, economic efficiency, etc.

For example, when selecting a CO2 separation/recovery method, the normal membrane separation method uses low to medium concentration CTo, the pressure fluctuation type adsorption separation method uses medium concentration CO2, and the separation method using an ion exchanger uses low concentration CTo.
They can be suitably applied to fields where D2 is released.

In addition, when selecting a plant, it is important that it has high photosynthetic activity (high growth activity) and easy maintenance in closed spaces, and it is even more advantageous if the plant itself is edible. Therefore, microalgae such as cyanobacteria, such as chlorella, are preferably used.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited thereto.

Example-1 Air containing 23,000 ppm of CD generated in an underground space was separated and concentrated using a membrane module made of polyimide material, and 60% CO, (100 liters of remaining air was obtained.ico
2 was supplied to a photosynthesis aU actor using chlorella.

Reactor size: 80l Light source: sunlight result After 2 hours, the gas in the reactor was 80% 02.

〔Effect of the invention〕

According to the present invention, the following effects are achieved.

1. CL can be separated by membrane separation method, pressure fluctuation type adsorption separation method, or separation method using ion exchanger. By supplying this highly concentrated CO to plants growing in a culture solution, (1) the released CD2 was converted to 0, and the CO2 could be effectively utilized.

■Environmental pollution due to released CDs has disappeared.

■ Particularly in underground spaces, spaces in ocean development, spaces in the space industry, and spaces inside submarines, a cycle of CO and D is created, eliminating the fear of air pollution and secondary pollution.

As the plant in 2.1, an edible (food) product is used and at the same time an edible (food) product is obtained, killing two birds with one stone. This is particularly effective in the above-mentioned closed space.

3. When the obtained 0, is supplied to a person's living space, a "pleasant feeling" can be obtained, which is meaningful.

[Brief explanation of drawings]

Figure 1 is a process diagram showing an example of the method of the present invention, and Figure 2 is a P
A basic process diagram of the SA method is shown. 1-CO. Concentrated air, 2... Pretreatment section, 3.
・Membrane module, 4・・CL storage tank, 5...C
O2-depleted air, 6... photocombination or reactor 7.
02 storage tank, 8・02 supply gas, island... adsorption tower, B1... regeneration tower, 10... CO2 high content high pressure air, v1 to v4, valve, 20... CO2 depleted air, 30 gas, 40...recycled gas, ・High concentration ['L gas, regeneration 50 ・Figure L

Claims (1)

[Claims] 1. Separate and recover carbon dioxide in a gas by one or more methods selected from a membrane separation method, a pressure fluctuation adsorption separation method, or a separation method using an ion exchanger, and collect the recovered carbon dioxide. is supplied to a reactor consisting of a plant growing in a culture solution,
A method of obtaining oxygen from carbon dioxide in a gas, which is characterized by obtaining oxygen through a photosynthetic reaction. 2. The membrane material used in the membrane separation method is polyethylene, polystyrene, polyimide, polysulfone, polyethersulfone, polycarbonate, polyphenylene oxide, polyvinyl acetate, polyorganosiloxane, ethyl cellulose, cellulose acetate, ethylene-vinyl acetate copolymer, or The method for obtaining oxygen from carbon dioxide in a gas according to claim 1, which comprises at least one type selected from ethylene-vinyl alcohol copolymers. 3. The method for obtaining oxygen from carbon dioxide in a gas according to claim 1, wherein the adsorbent used in the pressure fluctuation type adsorption separation method comprises one or more selected from zeolite, hydrotalcite, clathrasil, or molecular sieve. 4. The method for obtaining oxygen from carbon dioxide in a gas according to claim 1, wherein the ion exchanger used in the separation method using an ion exchanger is an anion exchanger. 5. The method for obtaining oxygen from carbon dioxide in a gas according to claim 1, wherein the plants growing in the culture solution are cultured plant cells and/or microalgae. 6. The method for obtaining oxygen from carbon dioxide in a gas according to claim 5, wherein the microalgae consists of one or more selected from chlorella, spirulina, and Dunaliella.