JPS63111923A - Dehumidifier for air - Google Patents

Abstract

PURPOSE:To miniaturize the titled apparatus and to decrease the installation cost and the operation cost by providing a feed path wherein one part of dehumidified air fed from one chamber of a module consisting of two chambers is fed to the other chamber therethrough and also interposing a reducing valve to the feed path. CONSTITUTION:A feed path 4 wherein one part of dehumidified air fed from one chamber is fed to the other chamber therethrough is provided. A reducing valve 6 is provided to this feed path 4 in order that both one chamber A of a module 2 and the other chamber B thereof are prevented from being made to pressure equalization by communicating one chamber A with the other chamber B therethrough. The pressure difference between the chamber A and the other chamber B in a vessel can always be kept at constant value by means of this reducing valve 6. Further a flow rate control valve 5 for controlling the moisture content of dehumidified air by controlling the amount of dehumidified air fed to the other chamber B may be provided to the feed path 4. This flow rate control valve 5 may be provided to either side of the upstream or downstream sides of the reducing valve 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air dehumidifying device using a moisture permeable membrane.

(Prior Art) As a conventional method for dehumidifying air, a method has generally been used in which air is brought into contact with a hygroscopic solid such as silica gel or quicklime, or a hygroscopic liquid such as concentrated sulfur, lithium chloride, etc. However, the above method However, there is a limit to the hygroscopicity of the solids and liquids used, making it impossible to dehumidify continuously.

Recently, a dehumidifying device using membrane separation has been proposed as an energy-saving process that solves the above-mentioned problems of the conventional technology (Japanese Patent Laid-Open Nos. 53-97246, 53-129440, 53
-145343, 54-6345, 54-13
No. 653, No. 54-15349, No. 54-15267
No. 9 etc.). These dehumidifiers supply pressurized air to one chamber of a module containing a permeable membrane, which is separated by a membrane, or reduce the pressure in the other chamber, or a combination of both. is operated to increase the water vapor partial pressure difference. In addition, sweep air is circulated to release the moisture that has passed through the membrane to the outside of the system, thereby creating a concentration gradient.

(Problem to be solved by the invention) However, in conventional dehumidification devices using membrane separation, one chamber is pressurized to a high degree or the other chamber is pressurized to a high degree in order to increase the water vapor partial pressure difference between the membranes. This is necessary, leading to an increase in the size of the pressurizing device and depressurizing device, and an accompanying increase in equipment costs and operating costs.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a dehumidifying device that eliminates the above-mentioned problems of conventional devices.

(Means for Solving the Problems) The device of the present invention supplies air to one chamber of a module partitioned into two chambers by a moisture-permeable membrane, and reduces the pressure in the other chamber, thereby allowing air to flow between the compartments. A device that dehumidifies air by transferring moisture in the air to another chamber through a moisture permeable membrane using a water vapor partial pressure difference of , and supplies a portion of the dehumidified air from one chamber to the other chamber This is an air dehumidifying device characterized in that a flow rate regulating valve and a pressure reducing valve are interposed in the supply passage.

(Function) The present invention supplies dehumidified air from one chamber to the other chamber, which is depressurized through a pressure reducing valve and has a very low steam partial pressure. Since the supplied air is dehumidified, the water vapor partial pressure difference between the two characters is reduced,
The water vapor partial pressure of air can be made sufficiently small.

(Example) Next, one embodiment of the device of the present invention will be described with reference to the drawings.

As shown in Figure 1s1, the device of the present invention includes a module 2 that is partitioned into two chambers (A) and (B) by a moisture permeable membrane 1, and a vacuum pump 3 that reduces the pressure in the permeation chamber (B) of the module. and part of the dehumidified air from one chamber (A) to the other chamber (B).
It is composed of a supply path 4 with a pressure reducing valve 6 interposed therebetween.

As the moisture-permeable membrane housed in the module 2, a membrane having a selective separation layer made of a polymer having dehumidifying performance whose water vapor permeability coefficient (PH20) is larger than the air permeability coefficient (Pair) can be used. Further, the separation coefficient α (=PHzO/Pa1r), which is the ratio of PH20 to Pa1rO, is 5 or more, preferably 100 or more. Since the water vapor partial pressure difference obtained between the moisture permeable membranes is smaller than the partial pressure difference of air (regarded as a mixture of nitrogen and oxygen), the dehumidification efficiency will not be good unless α is large.

As such a polymer, a polymer having a certain degree of hydrophilicity is preferable, such as cellulose, cellulose acetate, ethyl cellulose, carboxymethyl cellulose,
Cellulose-based products such as hydroxycellulose and ethylhydroxyethylcellulose, partially saponified or fully saponified polyvinyl alcohols, ethylene-vinyl alcohol copolymers, and polyvinyl copolymers of vinyl alcohol and monomers having carboxylic acid groups such as maleic anhydride and itaconic acid. Alcohol-based and poly(meth)acrylic acid,
It is preferable to use an acrylic polymer such as polyacrylamide, polyacrylonitrile, or a copolymer of a monomer having a sulfonic acid group and an acrylic monomer as the selective separation layer.

The membrane structure may be one having a uniform dense structure such as a dialysis membrane, but a membrane with an asymmetric structure having a dense layer only on the surface is usually preferably used because it can reduce the thickness of the selective separation layer. Furthermore, a composite membrane structure in which the selective separation layer and the support layer supporting and reinforcing the selective separation layer are made of different polymers is more preferably used because a more suitable polymer can be used as the selective separation layer and the separation I/Q can be made thinner. In this case, polysulfone, polyimide, polyethylene, polypropylene,
Polymer porous membranes such as polyphenylene sulfide,
On the surface of inorganic porous membranes such as ceramics.

An ultra-thin film of polymer having the above dehumidifying performance is formed.

The ultrathin film is 5 μm or less, usually 1 μm or less.

The shape of the membrane may be either hollow fiber or flat membrane.
A hollow fiber shape is preferably used from the viewpoint of membrane packing density and pressure resistance.

When supplying air into the hollow fibers, the diameter of the hollow fibers is preferably 0.1 to 2.0 g in consideration of pressure loss. On the other hand, it is suitable to ensure the effective length of the hollow fibers to be 0.3 m or more in order to ensure a predetermined dehumidification performance.

As the vacuum pump 3, a general-purpose water ring type vacuum pump with a vacuum degree of 30 to 30 Q torr can be used.

The air to be dehumidified may be in a pressurized state or in a normal pressure state, but normal pressure air is usually used.

In the present invention, a supply path 4 is provided for supplying part of the dehumidified air from one chamber to the other chamber. This supply path connects one chamber (A) and the other chamber (A) of the module through the supply path.
It is absolutely necessary to provide a pressure reducing valve 6 in order to prevent B) from reaching an equal pressure in the communication 1-1. The pressure reducing valve can always keep the pressure difference between one chamber (A) and the other chamber (B) constant in the container. A flow control valve 5 may be provided to adjust the moisture content of the dehumidified air by adjusting the amount of air. The flow control valve may be provided either upstream or downstream of the pressure reducing valve. Usually, it is preferable to provide it downstream of the pressure reducing valve because it makes it easy to adjust the flow rate.

Example 1 Polysulfone porous hollow fiber (outer diameter/inner diameter = 1500 μm
After pouring a 1% by weight aqueous solution of polyvinyl alcohol onto the inner surface of the film (/1000 μm), the liquid was drained and the film was dried with hot air at 100°C. The permeability Q-it rate of the obtained hollow fiber composite membrane (polyvinyl alcohol film thickness 0.27 μm) was 1t6x10'N
od -cm/d -5eC- (zHf/).

A hollow fiber composite membrane module having a membrane area of 0.2- was manufactured using the polysulfone hollow fiber composite membrane.

Using this module, a dehumidification test was conducted according to the system diagram shown in FIG. Supply 1ONd/H of air to be dehumidified to the inside of the hollow fiber membrane, reduce the pressure of 1Nd/H of the dehumidified nitrogen gas that comes out from the outlet with a pressure reducing valve, and supply it to the other chamber (B) of the container. Then, the outside of the hollow fiber membrane was washed away. The room (B)
The vacuum level was maintained at 35 torr using a vacuum pump.

When the steady state was reached, we measured the temperature and humidity at the air inlet and dehumidifying air outlet of the device, and found that the temperature at the inlet was 30°C.
, relative humidity 70%, pressure atmospheric pressure, outlet temperature 30°C, relative temperature 30%, pressure atmospheric pressure.

Comparative Example 1 A test similar to Example 1 was conducted using pressurized air. 30 N, f/H of air to be dehumidified was supplied into the hollow fiber membrane, and INd/H of the dehumidified air coming out of the outlet was reduced in pressure with a pressure reducing valve and supplied to the other chamber (B) of the module.

The chamber (B) was maintained at a vacuum level of 35 torr using a vacuum pump. Air inlet section when steady state is reached.

When we measured the temperature, humidity, and pressure at the outlet of the dehumidified air, we found that the inlet temperature was 30°C and the relative humidity was 100%.

Pressure 5 kg/ciG, outlet temperature 30°C, atmospheric compatibility
The dew point was -46°C and the pressure was 5°C/IG.

Next, the supply of dehumidified air to chamber (B) was stopped and only the X empty pump was operated to supply the same amount of air into the module, and the X empty pump maintained chamber (B) at l torr. However, the atmospheric pressure equivalent dew point of the dehumidified air was only Fi-30°C. Furthermore, when the vacuum pump was stopped and dehumidified air was supplied to chamber (B) and the same amount of air was supplied into the module, 6N+1//H of dehumidified air was supplied to chamber (B) (dehumidified air was not supplied for the first time in 7 The dew point converted to atmospheric pressure was -40℃,
In this case, four membrane modules had to be arranged in series.

Furthermore, the same test as in Example 1 was conducted with the pressure reducing valve interposed in the supply path removed. In this case chamber (B)
Due to the dehumidified air supplied with K, the water vapor partial pressure difference between chambers (A) and (B) in the module became small, and dehumidification could not be performed.

(Effects of the Invention) As described above, the device of the present invention can sufficiently dehumidify i11'2 air, and furthermore, it is a device that is extremely useful in practice, as it achieves miniaturization and reductions in equipment and operating costs.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram showing the configuration of the apparatus of the present invention.

Claims (1)

[Claims] By supplying air to one chamber of the module, which is divided into two chambers by a moisture permeable membrane, and reducing the pressure in the other chamber, moisture in the air is drawn through the moisture permeable membrane due to the water vapor partial pressure difference between the two chambers. A device for dehumidifying air by moving it to another chamber, which is provided with a supply path for supplying a portion of the dehumidified air from one chamber to the other chamber, and a pressure reducing valve is interposed in the supply path. An air dehumidifier characterized by: