JPH0822365B2 - Dehumidifier - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dehumidifying device for removing water in a compressed gas by using a polymer separation membrane.

[Prior Art] This type of dehumidifying device is disclosed in JP-A-62-42723. In this device, a large number of hollow fiber membranes made of polymer separation membranes are bundled and placed in a sealed container, and the inside of the sealed container is divided into a region inside the hollow fiber membrane and a region outside the hollow fiber membrane, The high-pressure steam mixed gas is supplied to the region outside the hollow fiber membrane, and the dehumidified gas is supplied into the hollow fiber membrane. Moisture in the steam mixed gas permeates into the hollow fiber membrane through the hollow fiber membrane, and the moisture permeated into the hollow fiber membrane is discharged to the outside of the sealed container together with the dehumidified gas (purge gas) flowing in the hollow fiber membrane. To be done. This polymer separation membrane system has various advantages such as continuous dehumidification, long life of the separation membrane, and non-movable structure without vibration.

[Problems to be Solved by the Invention] In the dehumidification method using a polymer separation membrane, not only the pressure difference between the high and low pressure regions with the polymer permeation membrane as a boundary, but also the water vapor partial pressure difference between the both regions is high. Influences the permeation separation efficiency of
The lower the humidity on the low pressure side, the higher the permeation separation effect. In order to increase the water vapor partial pressure difference between both pressure regions, the low pressure region side is dehumidified and purged with gas, but there is no difference in the water vapor partial pressures in both the high and low pressure regions at the start of supply of the high pressure steam mixed gas. Therefore, the necessary permeation separation action cannot be obtained at the initial stage of supplying the steam-mixed gas, and it takes time to obtain the required low dew point. Such a defect is particularly fatal when the steam mixed gas is intermittently supplied.

An object of the present invention is to provide a dehumidifying device capable of shortening the time until the required low dew point is obtained.

[Means for Solving the Problems] Therefore, in the present invention, a desiccant that adsorbs moisture on the passage of the dehumidified gas discharged from the membrane housing separated into the high pressure region and the low pressure region by the polymer separation membrane is provided. Intervene,
Part of the gas after adsorption dehumidification that has passed through the desiccant was supplied to the low-pressure region for purging.

[Operation] When high-pressure pre-dehumidification gas is supplied to the high-pressure region in the membrane housing, there is no difference in water vapor partial pressure between the high and low pressure regions, and the pre-dehumidification gas is osmotically separated based on the pressure difference between the high and low pressure regions. Be affected. Therefore, the dehumidification degree of the gas after dehumidification that has escaped to the outside of the membrane housing due to the permeation separation action is low at the initial stage of supplying the high-pressure dehumidification gas, but the dew point of the high-pressure gas that has been adsorbed and dehumidified through the desiccant has a dew point. Low compared to the high pressure gas immediately after passing. Part of the gas after the adsorption and dehumidification that has passed through the desiccant is supplied to the low pressure region, and the low pressure region is purged. Therefore, compared with the case where the gas after dehumidification immediately after passing through the membrane housing is used for purging, the degree of decrease in the water vapor partial pressure in the low pressure region is faster, and the dew point of the gas after dehumidification that has passed through the membrane housing is at the required level. Quickly declines to.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

The one chamber S ₁ of the intermediate pair of chamber S ₁ partitioned by the partition wall 1a of the unit, S ₂ of the housing 1 is accommodated a large number of hollow fiber membrane 2 made of a polymer separation membrane, both chambers S ₁ and S ₂ are bulkheads 1
It is connected by a passage 1b on the top of a. Both ends of the multiple hollow fiber membranes 2 are bundled by seal members 3 and 4, and the seal members 3 and 4 are closely fitted and fixed to the peripheral wall of the chamber S ₁ . The desiccant 5 is contained in the other chamber S ₂ and is sandwiched and held by a pair of holding plates 6 having a large number of through holes 6a. Caps 7 and 8 are tightly fitted to the openings of both chambers S ₁ and S ₂ , and a supply port 7a is provided through the cap 7 and a discharge port 8a is provided through the cap 8. There is.
The high-pressure dehumidifying gas is supplied through the supply pipe 9 to the supply port 7a.
Supplied through the hollow fiber membranes 2 and exits to the passage 1b. The high-pressure gas that has escaped to the passage 1b flows through the desiccant 5 and the discharge port 8a to the discharge pipe 10.

The housing 1 has a purge inlet hole 1c and a purge outlet hole 1d.
It is transparently provided so as to communicate with S ₁ , and the purge outlet 1d communicates with the atmosphere. The purge inlet 1c and the discharge pipe 10 are connected by a purge pipe 11, and the purge pipe 11
A flow rate adjusting valve 12 is interposed above.

The high-pressure pre-dehumidification gas supplied from the supply port 7a of the cap 7 into the housing 1 enters the hollow fiber membrane 2 and passes through the passage 1b.
Get out. The outer surface side of the hollow fiber membrane 2 communicates with the atmospheric pressure through the purge outlet 1d, and the chamber S ₁ is divided into a high pressure area inside the hollow fiber membrane 2 and a low pressure area outside the hollow fiber membrane 2. Moisture in the high-pressure gas passing through the hollow fiber membrane 2 permeates outside the membrane due to the difference between the high pressure on the inner surface side of the hollow fiber membrane 2 and the atmospheric pressure on the outer surface side of the hollow fiber membrane 2 and the partial pressure difference of water vapor inside and outside. The high-pressure dehumidified gas that has passed through the hollow fiber membrane 2 under the permeation separation action is in the passage 1b.
Flows into the chamber S ₂ through, go through the desiccant 5 in the chamber S _2. The dehumidified gas passing through the desiccant 5 is adsorbed by the desiccant 5, and is further dehumidified.

The flow rate control valve for the dehumidified gas that has passed through the desiccant 5 is 12
According to the degree of adjustment of the purge pipe 11 and flows into the low pressure region in the chamber S ₁ from the purge inlet 1c. Then, the outer surface of the hollow fiber membrane 2 is swept and the air comes out from the purge outlet 1d to the atmospheric region.

At the start of the supply of the pre-dehumidification gas, there is almost no difference in water vapor partial pressure between the high and low pressure regions in the chamber S ₁ , and therefore the permeation separation action of the hollow fiber membrane 2 is low. The degree of dew point decrease of the dehumidified gas that has passed through, that is, the degree of drying is low. The dehumidified gas having a low degree of dryness is adsorbed by passing through the desiccant 5, and the desiccated gas after passing through the desiccant 5 has a high degree of dryness. By using part of this highly dry gas after adsorption dehumidification as the purge gas, the partial pressure of water vapor on the low-pressure side can be reduced rapidly, and the amount of water vapor between the high and low pressure areas at the initial stage of supplying the gas before dehumidification can be reduced. The pressure difference quickly decreases. As a result, the dew point of the high-pressure gas that has passed through the hollow fiber membrane 2 is reduced to a desired value in a short time, and smooth dehumidification can be performed without lack of dew point even at the initial stage of supplying gas before dehumidification.

When the dew point of the gas after dehumidification that has passed through the hollow fiber membrane 2 becomes sufficiently low, the gas after dehumidification that has passed through the hollow fiber membrane 2 will start to remove the water adsorbed on the desiccant 5, and the gas supply before dehumidification will start. Sometimes the desiccant 5 is dried and regenerated. Therefore, the dehumidifying device is always in the best dehumidification starting state at the time of starting the supply of the pre-dehumidification gas, and even in the intermittent supply of the pre-dehumidification gas, continuous dehumidification without dew point shortage is performed.

Of course, the present invention is not limited to the above-mentioned embodiment, and for example, the housing of the hollow fiber membrane and the housing of the desiccant are separated, or the adsorption is performed only on the purge pipe 11 branched from the discharge pipe 10 in the above-mentioned embodiment. An embodiment in which the agent is interposed or the outside of the hollow fiber membrane is set to a high pressure region is also possible.

[Effects of the Invention] As described in detail above, the present invention provides a desiccant that adsorbs moisture on the passage of the dehumidified gas discharged from the membrane housing separated from the high pressure region and the low pressure region by the polymer separation membrane. Since a part of the adsorbed dehumidified gas that has passed through the desiccant is supplied to the low pressure region for purging, the dew point of the purge gas supplied to the low pressure region is promptly increased from the start of the supply of the pre-dehumidification gas. This results in an excellent effect that the partial pressure of water vapor in the low pressure region can be rapidly reduced and a dry gas having a low dew point can be obtained promptly after the supply of the gas before dehumidification is started.

[Brief description of drawings]

The drawings are vertical cross-sectional views showing an embodiment of the present invention. A housing 1 that serves as a membrane housing, a hollow fiber membrane 2, a desiccant 5, and a chamber S ₂ that serves as a passage for gas after dehumidification.

Claims (1)

[Claims] 1. A high-pressure gas before dehumidification is supplied from outside the membrane housing (1) along the membrane surface on the high-pressure region side into the membrane housing (1) separated by a polymer separation membrane into a high-pressure region and a low-pressure region. And discharge to the outside of the membrane housing (1),
In a dehumidifying device that supplies a part of the dehumidified gas discharged to the outside of the membrane housing (1) to the low-pressure region side to perform the purging of the low-pressure region side, the passage of the dehumidified gas discharged from the membrane housing (1) ( A desiccant (5) for adsorbing moisture is interposed on S ₂ ) and a part of the gas after adsorption dehumidification that has passed through the desiccant (5) is supplied to the low pressure region for purging. And dehumidifier.