JP3756370B2 - Membrane air dryer that automatically adjusts the purge air flow rate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a membrane air dryer using a hollow fiber membrane, and more specifically to a membrane air dryer having a function of automatically adjusting a purge air flow rate according to an outlet air flow rate.
[0002]
[Prior art]
A large number of hollow fiber membranes are bundled and stored in the main body case, and high-humidity air is supplied to these hollow fiber membranes to dehumidify them, and a part of the dehumidified air is purged to discharge the separated moisture. In the membrane type air dryer configured to flow as air between the hollow fiber membranes, a part of the dry air is discharged as purge air to the atmosphere on the principle of dehumidification. Normally, this purge air is led out between the hollow fiber membranes through a fixed orifice built in the outlet side of the main body case, so it is constant corresponding to the pressure and corresponds to the air flow rate at the outlet. Thus, a predetermined dew point performance is obtained.
[0003]
However, depending on the application, there is a requirement to change the air flow rate at the outlet to multiple stages. In that case, if the above-mentioned fixed orifice is used, for example, even if no outlet air is flowing at all, pressure is applied. The purge air with a substantially constant flow rate is always discharged. Therefore, at least when the flow rate of the outlet air varies, a part of the purge air is wasted.
[0004]
More specifically, the membrane air dryer can obtain a predetermined dew point performance even if the purge air flow rate is reduced if the outlet air flow rate is small. Therefore, the outlet air flow rate is constant. For example, when the inlet air pressure is 0.7 MPa and the maximum outlet air flow rate is 1000 L / min (ANR) during full operation, 190 L / min (ANR) is required as the purge air flow rate. For the minimum outlet air flow rate of 300 L / min (ANR) during operation, a purge air amount of about 50 L / min (ANR) may be flowed. Therefore, it is desired that the purge air flow rate can be switched to a plurality of stages according to the outlet air flow rate.
[0005]
Japanese Patent Laid-Open No. 6-238119 discloses a system in which the purge air flow rate is made variable by selecting a plurality of fixed orifices (holes) provided on the outlet side with a manual rotary cock. However, since the flow rate is set manually, it is necessary to monitor and set the air flow rate at the outlet. Even if the waste of purge air can be eliminated, the operation is troublesome. For this reason, it is desirable to enable automatic adjustment.
[0006]
Japanese Patent Application Laid-Open No. 9-57043 and Japanese Patent Application Laid-Open No. 11-33338 also propose a method in which the purge air flow rate is automatically changed. These use a pressure-receiving plate that is displaced according to the flow rate of dry air, and the air flow rate can be adjusted by utilizing the change in pressure drop in the hollow fiber membrane that changes according to the flow rate of dry air. . However, since the pressure drop in the hollow fiber membrane is small, and the pressure drop also changes due to variations in the hollow fiber membrane inner diameter, if the change in the flow rate of the dry air is converted into the pressure plate displacement as it is, the operation is very It becomes unstable.
[0007]
[Problems to be solved by the invention]
The technical problem of the present invention is to provide a membrane air dryer in which the purge air flow rate of the membrane air dryer is automatically and stably changed in accordance with the outlet air flow rate so that the purge air is not consumed unnecessarily. There is to do.
A more specific technical problem of the present invention is that the difference in pressure drop of dehumidified air at different outlet air flow rates is utilized without using a sensor such as a flow switch, and the pressure drop is amplified by simple means. Another object of the present invention is to provide a membrane air dryer which can obtain a purge air flow rate corresponding to a dehumidified air flow rate with a reliable operation.
Another technical problem of the present invention, on the difference in pressure drop definitive during different outlet air flow - using a process valve to turn off, thereby a flow of second purge air passage on - off control Another object of the present invention is to provide a membrane air dryer which can obtain a required purge air flow rate.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the membrane-type air dryer of the present invention bundles and accommodates a large number of hollow fiber membranes in the main body case, supplies high-pressure air to these hollow fiber membranes, dehumidifies them, and In a membrane type air dryer in which a part of the dehumidified air is flowed to the low pressure side of the hollow fiber membrane as purge air for discharging moisture separated by the hollow fiber membrane, the part of the dehumidified air is sent to the low pressure side of the hollow fiber membrane A first orifice is provided in the first purge air flow path to be sent to the first purge air flow path, and a second purge air flow path for sending a part of the dehumidified air to the low pressure side of the hollow fiber membrane is provided in the dehumidified air flow path. In addition, a process valve and a second orifice that operate based on a differential pressure between a downstream side of the pressure drop amplification throttle and a high pressure side that supplies air to the hollow fiber membrane are provided.
[0009]
In the membrane air dryer, purge air having a flow rate corresponding to the minimum dehumidified air flow rate is flowed to the first purge air flow path through the first orifice, and the second orifice is passed through the first orifice. In general, the flow rate of purge air corresponding to the maximum dehumidified air flow rate is obtained by merging with the purge air to flow, but the purge air flow rate can be increased or decreased according to various conditions.
In the membrane air dryer according to the present invention, the first and second orifices are incorporated in the main body case, and the pressure drop amplification throttle and the process valve are formed separately from the main body case. In addition, the first and second orifices, the pressure drop amplifying restriction, and the process valve may be incorporated.
[0010]
In the membrane-type air dryer having the above configuration, high-humidity air supplied from the inlet of the main body case flows through a number of hollow fiber membranes, and while flowing therethrough, moisture is permeated and separated through the membrane to the outside low-pressure side, The moisture is carried out to the outside by purge air flowing between the hollow fiber membranes. On the other hand, the dehumidified compressed air is supplied to a required fluid device from the outlet of the main body case.
In this case, when the dehumidified air flow rate at the outlet of the main body case is fluctuated, the purge air is automatically adjusted to a flow rate at which at least a predetermined dew point performance can be obtained, and is unnecessary. Purge air is not consumed.
[0011]
That is, the dehumidified air at the outlet of the main body case is partly purged air and flows from the outlet directly to the low pressure side around the hollow fiber membrane through the first orifice in the first purge air flow path. The first orifice is set to flow purge air having a flow rate corresponding to the minimum dehumidified air flow rate. When the dehumidified air flow rate is small, the low-pressure side moisture of the hollow fiber membrane is purged only with the dehumidified air sent through the first purge air flow path.
[0012]
On the other hand, the second orifice in the second purge air flow path has the highest dehumidified air flow rate in the main body case by merging with the purge air that always flows through the first orifice when the purge air flows therethrough. The second purge air flow path is automatically opened / closed according to the dehumidified air flow rate provided at the outlet of the main body case. Cut off by a valve.
[0013]
The above process valve is operated by utilizing the pressure drop in the hollow fiber membrane, but since the pressure drop is generally relatively small and unstable, dehumidified air at the outlet side of the main body case. A pressure drop amplification throttle is provided in the flow path, and the process valve is operated stably based on the differential pressure between the downstream side of the pressure drop amplification throttle and the high pressure side supplying air to the hollow fiber membrane. .
Therefore, based on the reliable and stable operation of the process valve, the purge air corresponding to the flow path of the dehumidified air at the outlet of the main body case is passed through the second orifice in the second purge air flow path to the low pressure of the hollow fiber membrane. Can be sent to the side.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 conceptually shows the overall configuration (circuit configuration) of a membrane air dryer that can automatically adjust the purge air flow rate according to the present invention.
This membrane-type air dryer includes a dryer main body 1 in which a large number of hollow fiber membranes 3 (see FIGS . 2 and 3 ) are bundled and accommodated in a main body case 2, and the compressed air of the main body case 2 is contained in the hollow fiber membrane 3. High-pressure and high-humidity air (pressure P _A , flow rate Q ₁ ) is supplied from the inlet 4, and moisture is permeated and separated from the low-pressure side outside through the membrane while flowing through the numerous hollow fiber membranes 3 to dehumidify it. The dehumidified air (pressure P _B , flow rate Q ₀ ) is connected to the required fluid equipment through the outlet 5 of the dryer body 1.
[0015]
Further, when dehumidifying the high-humidity air, in order to discharge the moisture separated by the hollow fiber membrane 3, a part of the dehumidified air is hollowed out at a flow rate corresponding to the dehumidified air flow rate at the outlet 5. It is configured to flow as purge air around the yarn membrane 3 (low pressure side). The outline of the configuration is that a first orifice 11 is provided in the first purge air flow path 10 that sends a part of the dehumidified air at the outlet 5 to the periphery (low pressure side) of the hollow fiber membrane 3 and dehumidified. An air-operated process valve 21 is connected to the introduction portion 20a of the second purge air flow path 20 for sending a part of the air from the outlet 5 to the hollow fiber membrane 3 side, and further from the valve 21 to the hollow fiber membrane 3 The second orifice 22 is provided in the communicating portion 20b of the second purge air flow path 20 to reach the downstream side of the pressure drop amplification throttle 23 provided in the dehumidified air flow path. Based on the differential pressure between the pressure P _B introduced from the side through the communication passage 25 and the pressure P _A introduced through the communication passage 24 from the high pressure side of the inlet 4 for supplying air to the hollow fiber membrane 3 It is made to let you.
[0016]
That is, when the air flow rate at the inlet 4 in the main body case 2 is Q ₁ and the outlet air flow rate is Q ₀ , and the outlet air flow rate Q ₀ is the minimum, the purge air that passes through the first orifice 11 ( Only the flow rate Q ₂ ) is used for purging the moisture of the hollow fiber membrane 3, and the relationship of the air flow rate is Q ₁ = Q ₀ + Q ₂ (Q ₄ = Q ₂ ).
On the other hand, when the outlet air flow rate Q ₀ is the maximum, the process valve 21 is opened, so that purge air (flow rate Q ₂ ) passing through the first orifice 11 and purge air passing through the second orifice 22 (flow rate Q ₃ ) is used for purging moisture of the hollow fiber membrane 3, and the relationship of the air flow rate is Q ₁ = Q ₀ + Q ₂ + Q ₃ (Q ₄ = Q ₂ + Q ₃ ).
[0017]
The operation of the process valve 21, when the pressure P _A of the high pressure air at the inlet 4 of the body case 2 is constant, since the difference of pressure drop in the case of most and minimum outlet air flow rate is small, the By providing the pressure drop amplifying throttle 23, the difference in pressure drop is amplified. As a result, the difference between the inlet air pressure P _A and the outlet air pressure P _B introduced into the process valve 21 is amplified. Is switched on and off in a stable manner, and the purge air flow rate Q ₃ is flowed when it is in the open position.
In FIG. 1, reference numeral 6 is a pressure air source, and 7 is a pressure adjusting valve that compensates for a pressure drop caused by the pressure drop amplification throttle 23.
[0018]
2 to FIG. 4, the first and second orifices 11 and 22 are incorporated in the main body case 2 in the configuration of FIG. 1, and the pressure drop amplification throttle 23 and the process valve 21 are separated from the main body case 2. FIG. 5 and FIG. 6 show the first and second orifices 11 and 22 in the main body case 2 for pressure drop amplification. A specific configuration of the second embodiment in which the throttle 23 and the process valve 21 are incorporated is shown. The configuration and operation of these embodiments will be described below.
[0019]
In the first embodiment shown in FIGS. 2 to 4, the main body case 2 includes a cap 31 provided with an inlet 4 for high-pressure air to be dehumidified and an outlet 5 for dehumidified air, and a cylindrical case 32 integrally connected thereto. The inlet 4 communicates with a space in the center fitting wall 33 in the cap 31, and the outlet 5 communicates with a space outside the fitting wall 33. And in the said main body case 2, many hollow fiber membranes 3 which consist of a polymer permeable membrane are bundled and accommodated in the cylinder shape, and the hollow fiber membrane 3 bundled in the both ends of these hollow fiber membranes 3 is accommodated. The sealing members 35 and 36 are filled with each other in an airtight manner, and a shielding cylinder 37 is inserted into the bundle of the hollow fiber membranes 3 and the central portion of the sealing members 35 and 36, and an air guiding cylinder 38 is also provided around the periphery. The both ends of the shielding cylinder 37 and the air guide cylinder 38 are hermetically attached to the seal members 35 and 36.
[0020]
The hollow fiber membrane 3 is configured such that the end of the shielding cylinder 37 on the side of the upper seal member 35 is externally fitted to the fitting wall 33 and the air guide cylinder 38 is air-tightly inserted into the cap 31. 38 is fixed in the main body case 2 by airtightly fitting the end of the lower seal member 36 on the inner periphery of the cylindrical case 32, and the lower end of the cylindrical case 32 is between the seal member 36. It is closed by an end cover 40 with a space 39 interposed.
Therefore, the humid air supplied through the air inlet 4 of the cap 31 is guided to the space 39 at the other end of the hollow fiber membrane 3 through the shielding cylinder 37 and from there to the fitting wall 33 through the hollow fiber membrane 3. The water is permeated and separated during that time, and is dehumidified and sent from the outlet 5 to the required fluid equipment.
[0021]
On the other hand, the cap 31 is provided with a purge air flow passage 45 opened to the outside of the air guide cylinder 38. In addition, a seal member 46 that blocks the space between the air guide cylinder 38 and the cylindrical case 32 is interposed in the intermediate portion between the air guide cylinder 38 and the flow path 45 of the seal member 46 in the air guide cylinder 38. A plurality of ventilation holes 38 a and 38 b are formed on the side and the opposite side, respectively, and further, a ventilation hole 32 a that communicates with the outside is provided at the lower portion of the cylindrical case 32.
Accordingly, the purge air that flows between the cylindrical case 32 and the air guide cylinder 38 from the flow path 45 of the cap 31 passes through the air hole 38 a of the air guide cylinder 38 and between the air guide cylinder 38 and the shield cylinder 37. The water flowing between the hollow fiber membranes 3 is retained and the permeated and separated water is retained and flows into the cylindrical case 32 from the vent hole 38b of the air guide cylinder 38, and is discharged to the outside through the vent hole 32a of the cylindrical case 32. Is done.
[0022]
An orifice assembly 47 incorporating the first orifice 11 and the second orifice 22 is attached to the cap 31 constituting a part of the main body case 2. The first orifice 11 is disposed in the first purge air flow path 10 extending from the space outside the fitting wall 33 through the flow passage 45 to the periphery of the hollow fiber membrane 3, and the second orifice 22 is The purge valve 20 is disposed in the communication portion 20b of the purge air passage 20 extending from the output port of the process valve 21 to the flow passage 45. In addition, a pressure drop amplification throttle 23 is provided in the flow path that connects the space outside the fitting wall 33 to the outlet 5.
[0023]
The process valve 21 includes a valve body 50 integrated with a piston 52 urged in a valve closing direction by a spring 51 in the valve body by a shaft, and a pressure chamber on the side of the piston 52 that houses the spring 51. The dehumidified air pressure P _B on the outlet 5 side is piped through the communication path 25, and the air pressure P _A on the inlet 4 side is introduced into the pressure chamber on the opposite side of the piston 52 through the communication path 24. Further, the inlet 20a of the purge air channel 20 is provided at the input port of the valve chamber having the valve seat 54 opened and closed by the valve body 50, and the purge air channel 20 leading to the orifice assembly 47 is provided at the output port. The communication part 20b is connected.
[0024]
Thus, the process valve 21, the biasing force of the pressure P _B and the spring 51 to be introduced through the communicating path 25 from the downstream side of the pressure drop amplification throttle 23, the pressure P _A from the inlet 4 side is introduced through the communicating path 24 When the pressure is smaller than the urging force by the valve, the valve is opened, and purge air is introduced into the flow passage 45 through the second orifice 22.
Specifically, when the outlet air flow rate is minimum, the pressure drop due to the hollow fiber membrane 3 and the pressure drop amplifying throttle 23 becomes small, and the pressure P _B becomes a large value. the valve body 50 is closed, on the contrary, when the outlet air flow rate is most the pressure P _B for the pressure drop increases becomes a small value, to open the valve body 50 by the biasing force of the pressure P _a Become.
[0025]
In this way, a part of the dehumidified air on the outlet 5 side of the main body case 2, purge air having a flow rate corresponding to the minimum dehumidified air flow rate at the outlet 5 passes through the first orifice 11 and around the hollow fiber membrane 3. When the dehumidified air flow rate is low and flows to the low pressure side, the low pressure side moisture of the hollow fiber membrane is purged only by the dehumidified air sent through the first purge air flow path 10.
On the other hand, the second orifice 22 corresponds to the case where the flow rate of the dehumidified air is maximized due to the merge with the purge air that always flows through the first orifice 11 when the purge air flows through the process valve 21. The purge air flow is caused to flow, and the purge air flowing through the second orifice 22 is automatically controlled by the process valve 21 according to the dehumidified air flow rate at the outlet 5 of the main body case.
[0026]
In the first embodiment, the process valve 21 is mounted on the cap 31 of the main body case 2 and the process valve 21 and the main body case 2 are connected by necessary piping. In the second embodiment, first and second orifices 11 and 22, a pressure drop amplification throttle 23 and a process valve 21 are incorporated in the main body case 2. Therefore, there is no need to connect the process valve 21 and each part by piping, and a through hole corresponding to the piping is formed in the main body case 2, and the second orifice 22 is connected to the process valve by providing such passage. However, the other configurations and functions are not substantially different from those of the first embodiment.
Therefore, the same reference numerals are given to the same or corresponding parts as in the first embodiment in the drawing, and the detailed description thereof is omitted.
[0027]
【The invention's effect】
According to the membrane air dryer of the present invention described in detail above, the purge air flow rate can be automatically and stably changed according to the outlet air flow rate, and unnecessary consumption of purge air can be suppressed. In particular, without using a sensor such as a flow switch, the difference in pressure drop of the dehumidified air at different outlet air flow rates is utilized, and the pressure drop is amplified by simple means to achieve a dehumidified air flow rate with reliable operation. A corresponding purge air flow rate can be obtained.
[Brief description of the drawings]
FIG. 1 conceptually shows the overall configuration (circuit configuration) of a membrane air dryer that can automatically adjust the flow rate of purge air according to the present invention.
2 is a cross-sectional view of a first embodiment that embodies the configuration of FIG. 1;
FIG. 3 is a partially enlarged cross-sectional view taken along the line AA in FIG.
FIG. 4 is a plan view of the first embodiment.
FIG. 5 is a cross-sectional view of a second embodiment that embodies the configuration of FIG. 1;
6 is a partially enlarged cross-sectional view taken along the line BB in FIG.
[Explanation of symbols]
2 Body Case 3 Hollow Fiber Membrane 10 First Purge Air Channel 11 First Orifice 20 Second Purge Air Channel 23 Pressure Drop Amplifying Throttle 21 Process Valve 22 Second Orifice

Claims (4)

A large number of hollow fiber membranes are bundled and accommodated in the main body case, and high-pressure air is supplied to these hollow fiber membranes to dehumidify them, and moisture separated from the dehumidified air by the hollow fiber membranes is removed. In the membrane air dryer that flows to the low pressure side of the hollow fiber membrane as purge air for discharging,
Providing a first orifice in the first purge air flow path for sending a part of the dehumidified air to the low pressure side of the hollow fiber membrane;
Air is supplied to the second purge air flow path for sending a part of the dehumidified air to the low pressure side of the hollow fiber membrane, to the downstream side of the pressure drop amplification throttle provided in the dehumidified air flow path and to the hollow fiber membrane. A process valve and a second orifice are provided that operate based on a differential pressure between the high pressure side and
A membrane air dryer that automatically adjusts the purge air flow rate. The first orifice shall flow purge air at a flow rate corresponding to the minimum dehumidified air flow rate to the first purge air flow path,
The flow rate of purge air corresponding to the maximum dehumidified air flow rate is obtained by merging the second orifice with the purge air flowing through the first orifice.
The membrane air dryer for automatically adjusting the purge air flow rate according to claim 1. The first and second orifices were incorporated into the main body case, and the pressure drop amplification throttle and the process valve were formed separately from the main body case.
The membrane air dryer for automatically adjusting the purge air flow rate according to claim 1 or 2. The main body case incorporates first and second orifices, a pressure drop amplification throttle and a process valve.
The membrane air dryer for automatically adjusting the purge air flow rate according to claim 1 or 2.

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