JP2706157B2 - Dehumidification method for steam-containing gas - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for dehumidifying a steam-containing gas such as a corrosive gas or an industrial gas, for example, a liquefied petroleum gas.

[Conventional technology]

Conventionally, as a method for drying a water vapor-containing gas such as liquefied petroleum gas, a molecular sieve adsorption method, a freezing method, and the like have been generally used. However, these methods have problems that operability and safety are poor, and that the equipment becomes large and the equipment cost increases.

Then, in order to solve such a problem, a method for dehumidifying a water vapor-containing gas using a gas separation membrane, for example, the following method has been proposed.

(I) A method of dehumidifying a water vapor-containing gas by using an aromatic polyimide membrane as a gas separation membrane and flowing a dry gas through the gas-permeable side of the membrane (Japanese Patent Laid-Open No. 62-42723)
issue).

(Ii) A method of increasing the partial pressure difference of water vapor between the gas supply side and the gas permeation side of the gas separation membrane by reducing the gas permeation side of the gas separation membrane, and dehumidifying the water vapor-containing gas based on the partial pressure difference. (JP-A-54-152679).

All of these methods are excellent in operability and safety, unlike the molecular sieve adsorption method, the freezing method, and the like, and require only small equipment.

[Problems to be solved by the invention]

However, the method using the gas separation membrane as described above has the following problems.

That is, the method (i) has a problem that the effect of removing water vapor is not sufficient. Further, in the case of the method (ii), there is a problem that it is uneconomical to use a supplementary facility having a high operating cost such as a vacuum pump to reduce the pressure on the gas-permeable side of the gas separation membrane.

An object of the present invention is to provide a method for dehumidifying a steam-containing gas that can solve the above-mentioned problems of the various methods while taking advantage of the method for dehumidifying a steam-containing gas using a gas separation membrane.

[Means for solving the problem]

The method of the present invention provided for this purpose provides a method of dehumidifying a steam-containing gas using a gas separation device having a built-in gas separation membrane, wherein the steam-containing gas is passed through a drain separator and a heater. After reducing the humidity, the water vapor-containing gas is supplied to one side of the gas separation membrane in a pressurized state, and the gas is expanded in a state where compressed air is expanded to approximately atmospheric pressure after drying with an adsorbent. By supplying to the other side of the separation membrane, and flowing the water vapor-containing gas and the air in the countercurrent direction in the gas separation device, to allow the water vapor in the water vapor-containing gas to permeate through the gas separation membrane This is characterized in that the dehumidification is performed.

Further, when the steam-containing gas supplied to the gas separation device is a liquefied petroleum gas, a polyimide resin obtained by condensation polymerization of biphenyltetracarboxylic dianhydride and an aromatic diamine as a gas separation membrane of the gas separation device; Multiple layers in which a thin film having a dense structure made of a cellulose-based material, a polyvinyl-based material, or an acrylic-based material is formed on the surface of a base layer made of a perfluorosulfonic acid-based ion-exchange resin or a polyester- or polysulfone-based porous resin. Structure, and the transmission speed ratio between water vapor and propane
1000 or more, and the water vapor transmission rate is 1.0 × 10 ⁻³ Ncm ³ /
cm is ² · sec · cmHg or more, and an outer diameter of 0.1~1.0mm,
It is preferable to use a hollow fiber having a thickness of 10 to 100 μm.

(Operation)

According to the method of the present invention, the steam-containing gas supplied to one side of the gas separation membrane is in a pressurized state, but the compressed air supplied to the other side of the gas separation membrane reaches approximately atmospheric pressure after drying. Since the air is supplied in an expanded state as described above, the air is in a dry state and is in a reduced pressure state with respect to the water vapor-containing gas. As a result, the difference in the partial pressure of water vapor on both sides of the separation membrane becomes large. The water vapor in the water vapor-containing gas effectively permeates the gas separation membrane based on the partial pressure difference,
Therefore, dehumidification of the water vapor-containing gas is effectively performed. At this time, when the compressed air is supplied to the gas separation device, the compressed air is expanded after being dried by the adsorbent to be in a low temperature state. Therefore, the temperature on the secondary side of the gas separation membrane becomes higher, so that the moisture on the membrane surface is quickly evaporated, the concentration gradient is increased, the diffusion rate of the membrane can be increased, and the dehumidification ability can be increased. . Further, since relatively high-temperature dry air is supplied by drying with the adsorbent, the temperature difference between the primary gas and the secondary gas is reduced, and dew condensation due to the temperature difference can be more effectively prevented. Since both the primary side gas and the secondary side gas have relatively high temperatures, the temperature of the membrane itself is also relatively high, and the moisture permeation rate of the separation membrane is increased, so that the dehumidifying ability is further improved. Further, since the compressed air is dried with the adsorbent, the adsorption efficiency by the adsorbent is high and the drying efficiency is also excellent.

〔The invention's effect〕

Thus, according to the method of the present invention, dehumidification of a water vapor-containing gas is effectively performed. However, the method of the present invention does not require a vacuum pump or the like which was required in the conventional method of performing effective dehumidification using a gas separation membrane. In addition to being economical and solving the above-mentioned conventional problems, the problems of operability, safety, and equipment costs that have occurred in the conventional molecular sieve adsorption method, refrigeration method, etc.
Since the method of the present invention is essentially a method for dehumidifying a water vapor-containing gas using a gas separation membrane, the method does not occur similarly to the methods (i) and (ii).

In addition, when water is sufficiently infiltrated into the gas separation membrane in the gas separation device, the performance and strength are reduced. To prevent this, the water vapor-containing gas supplied to the gas separation device is prevented. Is supplied to a drain separator and a heater before the supply thereof, thereby lowering the relative humidity of the water vapor-containing gas. Further, when the water vapor-containing gas supplied to the gas separation device is a liquefied petroleum gas, a polyimide resin obtained by condensation polymerization of biphenyltetracarboxylic dianhydride and an aromatic diamine is used as a gas separation membrane of the gas separation device. A multi-layer structure in which a thin film having a dense structure made of a cellulose-based material, a polyvinyl-based material, or an acrylic-based material is formed on the surface of a base layer made of a fluorine-based ion-exchange resin of fluorosulfonic acid or a porous resin of polyester or polysulfone. , and the and the permeation rate ratio between steam and propane 1000 or more, a permeation rate of water vapor ^{1.0 × 10 -3 N · cm 3} / cm 2 · sec · cmHg or greater, the outer diameter
If a hollow fiber having a thickness of 0.1 to 1.0 mm and a thickness of 10 to 100 μm is used, the vapor separation performance of the gas separation membrane is extremely good, and the dehumidification of the liquefied petroleum gas is effectively performed. become.

〔Example〕

Hereinafter, the method of the present invention will be described with reference to FIG.

In the figure, (1) shows a gas separation device for drying liquefied petroleum gas. The gas separation device (1) is a gas separation membrane (2) having a large number of hollow fibers arranged in parallel. A structure in which the gas separation membrane (2) is built in the closed vessel (3) by fixing both ends to the center of the closed vessel (3) using an adhesive layer (4) made of epoxy resin or the like. It has become. The hollow fiber is made of a polyimide resin obtained by condensation polymerization of biphenyltetracarboxylic dianhydride and an aromatic diamine, a fluorinated ion exchange resin of perfluorosulfonic acid, or a porous resin of polyester or polysulfone. A multi-layer structure in which a thin film having a dense structure made of a cellulose-based material, a polyvinyl-based material, or an acrylic-based material is formed on the surface of a base layer made of and a permeation rate of ^{1.0 × 10 -3 N · cm 3} / cm 2 · sec · cmHg or more, an outer diameter of 0.1 to 1.0 mm, and a wall thickness 10~100μ
m is a hollow fiber. Further, the adhesive layer (4) has a space in the closed vessel (3) which is divided into a central space (3c) where the gas separation membrane (2) is present and a space (3a) on both sides where the membrane (2) is not present. , (3b), and also functions to seal between the spaces.

Both ends (3a) and (3b) on both sides of the space inside the closed container (3) divided into three by the adhesive layer (4), The liquefied petroleum gas is used as a gas separation pool which is stored before and after being subjected to gas separation by the gas separation membrane (2). However, the space (3a) as the gas separation pool before being subjected to the gas separation is used. Is connected to a liquefied petroleum gas supply pipe (7) for supplying liquefied petroleum gas to be dried in a pressurized state via a drain separator (5) and a heater (6). On the other hand, a liquefied petroleum gas delivery pipe (8) for sending dried liquefied petroleum gas from the gas separation device (1) communicates with the space (3b) as a gas separation pool after being subjected to the gas separation. It is connected. The liquefied petroleum gas is supplied by the liquefied petroleum gas supply pipe (7), and after the predetermined gas separation by the gas separation membrane (2) is performed, is sent out by the liquefied petroleum gas delivery pipe (8). It has become so.

In the remaining space (3c) in the closed container (3),
As described above, the gas separation membrane (2) in which a large number of hollow fibers are juxtaposed is present, but the liquefaction occurs outside the gas separation membrane (2) in the space (3c). Air supply pipe (9) at appropriate position on oil gas delivery pipe (8) side
Are connected to each other, and an air discharge pipe (10) is connected to the liquefied petroleum gas supply pipe (7) at a position symmetrical to the air supply pipe (9). Then, the air supplied to the space (3c) by the air supply pipe (9) flows in the space (3c) counter to the liquefied petroleum gas passing through the gas separation membrane (2). It circulates in the direction.

A valve (11) is interposed in the upstream part of the air supply pipe (9), and the upstream part is further branched into a plurality of parts. Each pipe has an adsorbent such as silica gel or alumina incorporated therein. Towers (12a) and (12b) and these adsorption towers (12a) and (12b)
, Four valves (V ₁ ) to (V ₄ ) for alternately supplying compressed air are interposed. And
The compressed air supplied through the air supply pipe (9) is dried by absorbing moisture in one of the adsorption towers (12a) or (12b), and then passes through a valve (11). The pressure is reduced to substantially the atmospheric pressure, and then the pressure is led to the gas separation device (1). Adsorption tower (12a),
When the compressed air is expanded to atmospheric pressure after drying with the adsorbent in (12b), the temperature becomes low, but the temperature is relatively high compared to the case of drying with a cooling drier. The secondary side temperature of (2) increases. As a result, it is possible to evaporate the water quickly to increase the diffusion speed of the gas separation membrane (2), to increase the dehumidifying ability, and to more effectively prevent dew condensation due to a temperature difference. In the upstream part of the air supply pipe (9) in which the adsorption towers (12a) and (12b) are interposed, air generated by a blower (13) and then heated by a heater (14) Is the adsorption tower (12a), (1
2b) is connected to a pipe that is fed into the pipe, and furthermore, in the middle of the pipe, the adsorption tower (12a),
(12b) 4 for selecting supplying hot air alternately valves _{(V 5) ~ (V 8} ) is being interposed against the heat wind the adsorption tower (12a), suitably into (12b) By alternately feeding, the adsorbent contained therein is appropriately regenerated.

When the method of the present invention is carried out using such an apparatus, the gas is supplied to one side of the gas separation membrane (2) composed of the hollow fiber, that is, the inside of the hollow fiber, via the supply pipe (7) and the space (3a). The liquefied petroleum gas as the steam-containing gas is in a pressurized state, but the compressed air supplied to the other side of the gas separation membrane (2), that is, to the outside of the hollow fiber, is passed through the adsorption tower (12). After being dried, the air is supplied in a state of being expanded to approximately atmospheric pressure by passing through the valve (11), so that the air is in a state of reduced moisture and is in a reduced pressure state. The difference in partial pressure of water vapor on both sides of the gas separation membrane (2) increases, and the water vapor in the liquefied petroleum gas effectively permeates through the gas separation membrane (2) based on the difference in partial pressure. Dehumidification is effectively performed. When the compressed air is supplied to the gas separation device (1), the compressed air is expanded by passing through the valve (11) to a relatively low temperature state. As a result of permeating through the membrane (2) at a high speed, the liquefied petroleum gas is effectively dehumidified.

In this embodiment, the gas separation device (1)
Is a liquefied petroleum gas supplied to the gas separator, so that the gas separation membrane (2) of the gas separation device is a polyimide resin obtained by polycondensation of biphenyltetracarboxylic dianhydride and aromatic diamine, perfluorosulfone A multi-layer structure in which a thin film having a dense structure made of a cellulose-based material, a polyvinyl-based material, or an acrylic-based material is formed on a surface of a base layer made of a fluorine-based ion-exchange resin of sulfonic acid or a porous resin of polyester or polysulfone. Yes, the transmission speed ratio between water vapor and propane is 1000 or more, and the water vapor transmission speed is 1.0 × 10 ^-3 Ncm ³ / cm ²
g or more, the outer diameter is 0.1 to 1.0 mm, and the wall thickness is 1
A hollow fiber having a diameter of 0 to 100 μm was used. this is,
This is because the gas separation membrane (2) has a very good performance of permeating water vapor in the liquefied petroleum gas, and effectively dehumidifies the liquefied petroleum gas.

In the case where the gas separation membrane (2) is used as in the present embodiment, if water is sufficiently infiltrated into the gas separation membrane (2), the performance and strength are reduced. In order to reduce the relative humidity of the steam-containing gas, the steam-containing gas supplied to the gas separator is supplied to a drain separator and a heater before the gas is supplied.

Further, it is preferable that the average temperature of the compressed air and the liquefied petroleum gas supplied to the gas separation device (1) be 40 ° C. or less. The reason is that under 40 ° C or lower conditions, hydrocarbon components in liquefied petroleum gas
Since the permeation rate in the gas separation membrane (2) is low, the hydrocarbon component hardly permeates the gas separation membrane (2) and remains as a non-permeate, while the water vapor passes through the gas separation membrane (2). This is because the liquefied petroleum gas is effectively dehumidified because of the effective permeation.

In this embodiment, since the air sent into the adsorption tower (12) is compressed air, the adsorption efficiency in the adsorption tower (12) is improved, and the necessary adsorption in the adsorption tower (12) is improved. The dosage can be reduced. The pressure of the compressed air is
The pressure is preferably set to 4 to 8 atm from economical conditions such as the operation cost of the air compressor and the cost of related equipment.

The method of the present invention can also be applied to the case of dehumidifying a steam-containing gas other than liquefied petroleum gas.

For example, as shown in FIG. 2, the present invention may be applied to a case where moisture in raw air is removed by an air separation device (A) which separates and manufactures oxygen, nitrogen and argon from raw air as products.

In this embodiment, a gas separation device (1) having the same structure as that of the above-described embodiment is used, and raw air is compressed by a compressor (1).
The pressurized state in 5) is supplied to the space (3a) of the gas separation device (1), and the dry raw material air sent out from the space (3b) of the gas separation device (1) is supplied to the air separation device (A). ), And the dry low-temperature waste gas generated during the production process in the air separation device (A) is supplied to the space (3c) of the gas separation device (1) via a valve (11). I have.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the method of the present invention is limited to the method implemented by using the apparatus having the structure shown in the attached drawings. is not.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an apparatus used in an embodiment of a method for dehumidifying a steam-containing gas according to the present invention, and FIG. 2 is a schematic configuration diagram showing another embodiment. (1) gas separation device (2) gas separation membrane
(5) ... drain separation device, (6) ... heater.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-241527 (JP, A) JP-A-63-209731 (JP, A) Real opening Sho-56-151604 (JP, U)

Claims (2)

(57) [Claims] 1. A method for dehumidifying a steam-containing gas using a gas separation device (1) having a built-in gas separation membrane (2), wherein said steam is passed through a drain separator (5) and a heater (6). After lowering the relative humidity of the contained gas, the steam-containing gas is supplied to one side of the gas separation membrane (2) in a pressurized state, and the compressed air is dried with an adsorbent so as to reach substantially atmospheric pressure. The gas separation membrane (2) is supplied to the other side in an expanded state, and the water vapor-containing gas and the air are allowed to flow in a countercurrent direction in the gas separation device (1), whereby the gas separation is performed. A method for dehumidifying a water vapor-containing gas, wherein the water vapor in the water vapor-containing gas is transmitted through the membrane (2) to perform the dehumidification. 2. The method according to claim 1, wherein the surface of the mother layer made of a polyimide resin obtained by polycondensation of biphenyltetracarboxylic dianhydride and an aromatic diamine, a fluorinated ion exchange resin of perfluorosulfonic acid, or a porous resin of polyester or polysulfone. , A multilayer structure in which a thin film having a dense structure made of a cellulose-based material, a polyvinyl-based material, or an acrylic-based material is formed, the transmission speed ratio between water vapor and propane is 1000 or more, and the water vapor transmission speed is 1.0 × 10 ^-3 Ncm
³ / cm ² · second · cmHg or more, a hollow fiber having an outer diameter of 0.1 to 1.0 mm and a wall thickness of 10 to 100 μm is used as the gas separation membrane (2), whereby The steam-containing gas according to claim 1, comprising a separating device (1), supplying liquefied petroleum gas as the steam-containing gas to the gas separating device (1), and dehumidifying the liquefied petroleum gas. Dehumidification method.