JPS63158114A - Gas separation method - Google Patents

Abstract

PURPOSE:To improve separation rate by causing a material to be separated to be selectively charged into a mixed gas through ionization treatment, attracted to the direction of an attractive electrode provided near a gas separation membrane by means of electrostatic force, and thereby increasing the density of a material to be separated near the membrane. CONSTITUTION:A supply air passes between electrodes 21, 23 via a filter 13, and O2 is selectively ionized among other gases near a discharging electrode 21 by a corona discharge generated between both electrodes 21, 23. Next, the air is supplied to a gas separation membrane 18 and attracted by the electrostatic force to an attractive grounding electrode 19, thus increasing the O2 concentration in the neighborhood of the surface of a gas separation membrane 17. O2 permeates the gas separation membrane 17 selectively, and a gas separation rate is increased because of a high O2 concentration near the membrane.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of separating gases using a gas separation membrane, and particularly to a method of separating gases by subjecting a mixed gas to ionization treatment.

Disaster! The method of separating a specific gas in a mixed gas using a gas separation membrane has a simple device structure, and its use is increasing dramatically as the performance of separation membranes improves (Magazine ``
Kagaku Instruments J, September 1985 issue, pp. 112-117).

This membrane separation method utilizes the difference in the membrane permeation rate of each gas component in a mixed gas, and uses a non-porous membrane in which the gas dissolves and diffuses, and a porous membrane in which the gas is passed through by Knudsen flow. Porous membranes are known.

FIG. 6 is an explanatory diagram of a conventional gas separation system. When air (mixed gas), which is a mixture of nitrogen molecules 41 and oxygen molecules 43, is brought into contact with the gas separation membrane 17, the oxygen molecules 43, which are the substance to be separated, selectively pass through the gas separation membrane 17,
Oxygen-enriched air (oxygen-enriched gas) with a high oxygen concentration can be obtained.

The permeation rate of a gas separation membrane, that is, the separation rate of a substance to be separated, is determined by the difficulty of movement of the substance in the membrane (diffusivity) and the extent to which the substance to be separated (oxygen molecules) exists on the surface of the membrane (
determined by solubility).

The former depends on the physical properties of the gas separation membrane. In order to improve solubility, it is necessary to increase the supply of the substance to be separated to the membrane surface. Since the substances to be separated are uniformly present in the mixed gas to be processed, it is necessary to increase the supply rate of the gas to be processed in order to increase the supply of the substances to be separated to the membrane surface. becomes. However, if the gas velocity is increased too much, it will lead to destruction of the membrane, so there is a natural limit to this.

The inventor of the present invention selectively ionizes a substance to be separated in a mixed gas by causing a corona discharge between a ground electrode and a discharge electrode provided in the vicinity of a gas separation membrane. proposed to increase the concentration of the substance to be separated in the vicinity of the separation membrane by drawing it to the ground electrode (patent application filed by the same applicant on December 9, 1985 titled "Title of the invention: Gas separation method"), No. FIG. 5 shows the gas separation method of the present invention, in which oxygen is selectively permeated from the supply air introduced through the filter 13 through the gas separation membrane 17, and oxygen-enriched air is recovered. A voltage is applied between the screen-shaped discharge ground electrode 21 and the discharge electrode 23 provided near the gas separation membrane 17, causing discharge (corona discharge), whereby oxygen in the air is selectively charged. However, they are attracted to the discharge ground electrode 21 by electrostatic attraction, and the concentration of oxygen gas molecules near the air separation membrane 17 is increased.

According to this method, the concentration of the substance to be separated on the surface of the gas separation membrane can be relatively increased, and the separation speed of the gas separation membrane can be improved.

However, this method causes the following problems.

(2) Insulating means between the discharge electrode 23 and the discharge ground electrode 21 is required.

(2) Since it is necessary to maintain a constant distance between the two electrodes (at worst, they must not come into contact with each other), it is necessary to ensure that the installation accuracy of the gas separation membrane 17 and the electrodes 21 and 23 is sufficiently high. Therefore, it becomes difficult to increase the size of the gas separation membrane 17, and it also becomes difficult to increase the degree of membrane filling by narrowing the interval between the gas separation membranes 17.

■ In order to meet the above requirements (■) and (■), costs will increase.

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas separation method that improves the separation rate using a gas separation membrane, and that is simplified and can be easily made dense or compact.

Monthly income in m The gas separation method of the present invention is a separation method in which a mixture to be treated is brought into contact with a gas separation membrane, and a substance to be separated in the mixed gas is selectively permeated through the gas separation membrane to be separated. The mixed gas is passed through an ionization treatment means to perform ionization treatment to selectively charge the separation target substance, and the charged separation target substance is attracted by electrostatic attraction toward a suction electrode provided near the gas separation line, and the gas is Separation' is characterized by increasing the concentration of the substance to be separated near the membrane.

11 Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The gas separation method of the present invention can be carried out using an apparatus equipped with a gas separation membrane provided with a suction electrode for charged gas molecules in the vicinity, and an ionization means provided upstream of the gas separation membrane. FIG. 1 is an explanatory diagram showing an example of the basic configuration of such a system. Supply air (mixed gas to be treated) is sent by a blower 11 to a membrane module 15 via a filter 13. The membrane module 15 is partitioned by a gas separation membrane 17 to form a supply chamber 31 and a recovery chamber 33. The recovery chamber 33 is depressurized by a vacuum pump 35, and the supply chamber 31 and recovery chamber 33 are separated from each other. A pressure difference is set. When air is sent to the supply chamber 31, oxygen selectively permeates through the gas separation membrane 17 and enters the recovery chamber, where it is recovered as oxygen-enriched air via the filter 37.

In the present invention, in the gas separation system as shown in FIG. 1, a ground electrode for sucking charged gas is further provided in the vicinity of the gas separation membrane 17, and an ionization processing means is provided upstream of this gas separation zone. It is being FIG. 2 is an explanatory diagram showing an example of electrostatic separation by providing a discharge device upstream of the gas separation membrane as an ionization treatment means, and FIG. 3 is an explanatory diagram schematically showing the vicinity of the gas separation membrane 17. It is.

A discharge electrode 21 and a discharge ground electrode 2 are provided before the gas separation membrane 17.
3 is provided to form a charging zone 22, and a screen-shaped suction ground electrode 19 is provided near the gas separation membrane 17 to form a gas separation zone 18.

When a voltage is applied between the electrodes 21 and 23, both electrodes 21°2
3, corona discharge occurs and the gas near the discharge electrode 21 is ionized. At this time, ionization does not occur uniformly for various gases, but as is well known in the field of electrical discharge technology, substances that have a large electron affinity and tend to become negative ions are selectively ionized.For example, oxygen In the case of air, which is a mixed gas of nitrogen and nitrogen, nitrogen is hardly ionized and oxygen is selectively ionized. Air containing selectively ionized and negatively charged oxygen molecules is supplied to gas separation zone 18 .

It is attracted to the suction ground electrode 19 by Coulomb force (electrostatic force), and the oxygen concentration near the surface of the gas separation membrane 17 can be dramatically increased, thereby making it possible to significantly improve the separation speed.

Furthermore, in the configuration shown in FIG. 5, since a voltage is applied to the discharge electrode 23 and the discharge ground electrode 21, it is necessary to maintain a constant electrode spacing. Therefore, the spacing between the gas separation membranes 17 must be kept constant (for example, In contrast, in the configuration of the present invention shown in FIG. 2, the gas separation membrane 17
The interval between can be reduced. In the configuration shown in FIG. 5, if the electrodes 21 and 23 come into contact, voltage cannot be applied and the entire function stops, whereas in the configuration shown in FIG. Even if there is, it will only block the supply air passage in that part and will not stop the entire function.

Charged electric molecules such as oxygen ions are mobile and can move toward the suction ground electrode 19 even when no electric field is applied. Also.

An electric field can also be applied by applying a bias voltage to the attraction ground electrode 19.

Furthermore, in the configurations shown in FIGS. 2 and 3, by providing the screen-shaped suction ground electrode 19 on the front surface of the gas separation membrane 17, foreign substances entrained in the gas to be treated are removed from the gas separation membrane. collision can be effectively prevented, and the lifespan of the gas separation membrane can be improved.

FIG. 4 shows another configuration used in the present invention, which is the same as FIG. 2 except that an ion beam source 25 is provided in the charging zone 22 as an ionization means. An ion beam is emitted from the ion beam source 25 to selectively ionize oxygen in the supplied air, which is then sent to the gas separation zone 18 .

In the above explanation, we have explained the separation (concentration) of oxygen from the air, but it is also possible to separate gases other than oxygen.
Differences in electron affinity between various gas components make it possible to concentrate specific gas components near the surface of the separation membrane. With the conventional technology, it is impossible to increase the concentration of the substance to be separated on the membrane surface to a level higher than the concentration of the mixture gas to be treated. Therefore, if an attempt is made to increase the supply of the target substance to be separated to the membrane surface, it becomes inevitable to increase the supply rate of the mixed gas to be treated, which may lead to destruction of the membrane. On the other hand, according to the method of the present invention, the membrane surface concentration of the substance to be separated can be made equal to or higher than the component ratio, so that the gas separation rate is improved.

According to the present invention, the mixed gas to be treated is subjected to ionization treatment in the first stage, and the substance to be treated is selectively ionized by utilizing the difference in electron affinity of each component in the mixed gas. By charging the substance with electricity and drawing it toward the gas separation membrane through electrostatic attraction with the suction electrode for the charged substance to be separated, which is provided near the gas separation membrane, the concentration of the substance to be separated on the surface of the gas separation membrane is increased. , the separation speed of the gas separation membrane can be improved.

Furthermore, since there is no need to apply a voltage to the suction electrode provided near the gas separation membrane, there is no need for electrodes or insulating means that require precision, and it is possible to significantly reduce costs. Furthermore, since the gap between the gas separation membranes can be reduced, the entire device can be made more compact or more dense.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are explanatory diagrams showing the gas separation method of the present invention. FIG. 4 is an explanatory diagram showing another embodiment of the present invention. FIG. 5 is an explanatory diagram showing a gas separation method of a comparative example. FIG. 6 is an explanatory diagram showing the principle of a gas separation membrane. 11...Blower 15...Membrane module 1
7... Gas separation membrane 19... Suction ground electrode 21
...Discharge electrode 25...Ion beam source 35
...Decompression pump patent applicant Sumitomo Heavy Industries, Ltd. Figure 1 Figure 2 Exhaust air (empty air) Figure 3 II air Figure 6 Exhaust air

Claims (1)

[Claims] 1. In a gas separation method in which a mixed gas is brought into contact with a gas separation membrane and the substance to be separated in the mixed gas is selectively permeated through the gas separation membrane to be separated, the mixed gas is passed through an ionization treatment means to undergo ionization treatment. selectively charges the substance to be separated, and the charged substance to be separated is attracted by electrostatic attraction toward a suction electrode provided near the gas separation membrane, thereby increasing the concentration of the substance to be separated near the gas separation membrane. Characteristic gas separation method.