JP3986905B2 - Clean air supply system and operation method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a clean air supply system and an operation method thereof.
[0002]
[Prior art]
For example, in a semiconductor device manufacturing process, contamination with gaseous impurities in a clean room has become a problem as the degree of integration increases. Further, it is known that a natural oxide film is formed on a wafer when moisture is contained in the air supplied to the manufacturing process. Therefore, recently, it has been proposed to use so-called chemical-free dry air having almost no gaseous impurities.
[0003]
From this point of view, for example, Japanese Patent Application Laid-Open No. 2001-38137 proposes a clean air purification system using a dry dehumidifier. In this prior art, in a method for producing clean air having a gaseous impurity concentration of 1 ppb or less, a rotary type for dehumidifying the treated air by passing the treated air through a rotatable rotor having silica gel or metal silicate. Adsorbers were connected in series, and the treated air was dehumidified and cleaned.
[0004]
[Problems to be solved by the invention]
By the way, in the system described above, if the air components exiting the rotor contain particulate components from the adsorbent, in order to prevent these particulate components from entering the target chamber, such as a ULPA filter or a HEPA filter on the downstream side. Use high-performance filters.
[0005]
However, the above-described high-performance filter may generate gaseous organic substances from the adhesive used when the filter medium of the filter is bonded to the frame and the packing used for sealing the frame and the exterior panel of the filter.
[0006]
In order to prevent the generation of organic substances from the adhesive and packing of the filter as described above, for example, as disclosed in JP-A-9-220425, the entire filter is exposed to high-temperature air in advance to remove the organic substance from the adhesive and packing. It has been proposed to perform a heat treatment called "baking" to remove.
[0007]
However, even if it is baked in advance, the packing material may be damaged during transportation and storage, or after installation, the filter medium will adsorb organic components due to contact with the surrounding air. There is a risk of detachment and outflow to the load side. In such a case, if the operation is continued as it is, it is possible to expel organic substances from these adhesives and packings. However, in that case, it takes a long time until the so-called start-up time until the actual operation becomes possible. It is not preferable.
In addition, since moisture adheres to the surface of the high-performance filter, it is necessary to remove the moisture at the time of start-up. However, even if it is baked by exposure to high-temperature air in advance, the moisture remains in the filter medium during transportation and storage. The effect is hardly expected from the point of shortening the rise time.
[0008]
The present invention has been made in view of the above points, and a clean air supply system in which a high-performance filter is incorporated into a system as it is without being previously baked, can be baked in the system, and has a short rise time. The purpose is to provide a driving method and to solve the problems.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the clean air supply system of the present invention is a clean air supply system that supplies organic substances or moisture in the processing air with a rotary adsorber provided with an adsorbent in the rotor, and then supplies it to the target chamber. A high-performance filter is installed downstream of the rotary adsorption device, and a heater is installed in the air flow path between the rotary adsorption device and the high-performance filter, and is heated by the heater. It is characterized in that it can be introduced into the high performance filter without actively cooling the air.
[0010]
Since the present invention has the above-described configuration, even if it is an existing general-purpose high-performance filter, it can be used without being baked in advance and incorporated into the system as it is, by heating the processing air with the heater. , High-temperature air can be passed through the high-performance filter, which can be baked to desorb gaseous organic impurities from adhesives, sealing materials, packing, etc. . In addition, moisture adhering to the surface of the high-performance filter can be removed at the same time. Therefore, the start-up time can be shortened compared with the conventional case.
In addition to moisture and gaseous organic impurities from the high-performance filter, it exists at the downstream of the heater, for example, the duct connecting the heater and the high-performance filter, the joint of the duct from the high-performance filter to the inlet of the target space, and the joint It is also possible to remove packings, sealing materials, and organic substances contained in damper grease.
[0011]
A return flow path for returning the air that has passed through the high performance filter to the inlet side of the rotary adsorption device is provided, and the air that has passed through the high performance filter flows to the target chamber or the return flow path side. For example, when the organic matter is detached, it can be prevented from flowing into the target chamber by flowing it to the return channel side, and when the generation of organic matter is no longer observed. It can flow to the target room side, and can prevent the organic matter from flowing into the target room itself.
[0012]
If an air washer for treating the outside air is provided on the upstream side of the rotary adsorption device, the air after the outside air is treated by the air washer can be introduced into the rotary adsorption device as the treatment air for treatment. By treating the outside air with an air washer beforehand, inorganic and organic pollutant gases are reduced. This makes it possible to supply air with higher cleanliness to the target chamber. According to the experiments by the inventors, the inorganic gas component was able to be reduced to about 1/10 of the conventional one. In addition, since the temperature and humidity conditions of the inlet air of the rotary adsorber are stable, the dew point temperature of the supplied clean air is also stable.
In simple terms, in winter, the primary treated outdoor air humidified with an air washer is dehumidified by a rotary adsorber, which increases energy consumption, but ultimately, low enthalpy clean air is supplied to the target room. Therefore, there is not much loss when considering the entire purification system in the target room.
[0013]
When multiple stages of rotors are connected in series in the rotary adsorption device, a cooler is installed only at the processing zone inlet side of the first stage rotor, and no cooler is installed after the second stage. Therefore, the processing air system and the regeneration system for each rotor in the rotary adsorption device are provided with only one blower for each of the rotary adsorption devices in order to simplify the entire system. May be.
[0014]
When this type of conventional rotary adsorption device is used with multiple rotors connected to each other, a single cooler is installed on the inlet side of the processing zone in each rotor, and each rotor is also installed in the processing air system and the regeneration system. A blower was installed every time. As a result, the installation area was enlarged and the equipment costs were soaring. In this regard, according to the present invention, both the installation area and the equipment cost can be reduced by 20% compared to the conventional case.
[0015]
When operating the clean air supply system of the present invention, at the start of operation, the heater is operated and all the air that has passed through the high-performance filter is flowed to the return flow path side, and after a predetermined time has elapsed, the heater is stopped. In addition, all the air that has passed through the high-performance filter may be allowed to flow toward the target chamber.
Thereby, for example, while the organic substance is detached, the organic substance can be prevented from flowing into the target chamber, and the organic substance can be detached from the high-performance filter by performing a process that takes a predetermined time thereafter. Then, by letting it flow to the target room side after a lapse of a predetermined time, it is possible to automatically switch between the organic matter detachment process and the supply of clean air to the target room. Yes. In addition, the use of a heater can be suppressed to less than necessary, and energy consumption can be reduced.
[0016]
In such a case, as a criterion for flowing to the target room side, the concentration of impurities in the air passing through the high-performance filter or the dew point temperature is measured, and the heater is turned on after the concentration or dew point temperature falls below a predetermined value. You may make it stop and switch to the target room side. In this case, it is only necessary to use the minimum necessary heater, and the time to flow to the return flow path side can be suppressed to the minimum necessary, and the start-up time can be further shortened.
[0017]
Furthermore, as described above, instead of flowing the entire amount of air that has passed through the high-performance filter immediately after the start of operation to the return flow path side, as described in claim 7, first, a connection portion on the upstream side of the return flow path is firstly provided. A separate exhaust duct will be provided. The heater is operated and the high-performance filter is operated until a predetermined time elapses after the start of operation or until the concentration of impurities or dew point temperature in the air that has passed through the high-performance filter after the start of operation falls below a predetermined value. All the air that has passed through is exhausted through the exhaust duct. After that, all the air that has passed through the high-performance filter flows to the return flow path side, and after that, after a predetermined time has elapsed, or the concentration of impurities or dew point temperature in the air that has passed through the high-performance filter has become below a predetermined value. Later, the heater may be stopped and all the air that has passed through the high-performance filter may flow to the target chamber side.
In this way, it is possible to prevent impurities having a high concentration from flowing into the return channel at the beginning of operation and contaminating the return channel.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a system of a clean air supply system according to the present embodiment. This system manufactures clean air having an ultra-low dew point of −80 ° C. or lower, for example, a storage for semiconductor wafers. S is configured as a system to supply to S.
[0019]
The outside air OA as the raw material air is first subjected to primary processing by the air washers 1 and 1 functioning as an outside air conditioner and then guided to the processing system duct 3 by the processing fan 2. By such primary treatment, 80% or more of gaseous inorganic impurities and some gaseous organic impurities in the outside air OA are removed. In this embodiment, there are two external air introduction systems, and an air washer 1 is installed in each.
[0020]
The processing air guided to the processing system duct 3 is first cooled and dehumidified by the cooler 4. The cooled and dehumidified air then passes through the treatment area 11a of the rotor 11 of the first stage rotary adsorption device 10 and is dehumidified.
[0021]
As shown in FIG. 2, the first-stage rotary adsorption device 10 has a configuration in which chambers 12 and 13 are disposed on both end surfaces of a rotating rotor 11. Each chamber 12, 13 has three partition plates 14, 14, 14 radially arranged therein, and divides the space in the chambers 12, 13 into three. Correspondingly, on the end surface of the rotor 11, three air passage areas of a processing area 11 a, a regeneration area 11 b and a purge area 11 c are arranged in the order of the rotation direction of the rotor 11 indicated by the thin arrows in FIG. 2. 14 is partitioned. A processing outlet 12a, a regeneration inlet 12b, and a purge outlet 12c for connecting to a duct or the like are formed on the outer end face of the chamber 12 so as to correspond to these areas. A processing inlet 13a, a regeneration outlet 13b, and a purge inlet 13c are also formed on the outer end surface of the chamber 13 corresponding to the three areas.
[0022]
The rotor 11 is made by impregnating a base material with a slight amount of Al (aluminum) or Zn (zinc) added to silica gel. That is, for example, a fine fiber of a honeycomb-like fiber paper or ceramic fired body is impregnated with a metal silicate mixed mainly with silica gel with Al (aluminum) and Zn (zinc), and the metal silicate is put around the fiber. A tightly attached one can be used. The thickness of the rotor 11 is 400 mm, and the rotation speed of the rotor 11 is set to 4 rotations / hour.
[0023]
The air that has passed through the treatment zone 11a of the rotor 11 of the first stage rotary adsorption device 10 has been dehumidified to a dew point temperature of, for example, −50 ° C., but a part thereof is returned to the purge zone 11c. On the other hand, the air that has passed through the processing area 11a of the rotor 11 of the first stage rotary adsorption device 10 is sent to the cooler 6 by the processing fan 5, cooled by the cooler 6, and then the second stage rotary adsorption. It is guided to the treatment area 21a of the rotor 21 of the apparatus 20 and is subjected to dehumidification.
[0024]
The second-stage rotary adsorption device 20 includes rotary adsorption devices 21 and 31 having basically the same configuration as the first-stage rotary adsorption device 10. In other words, the end face of the rotor 22 of the first stage rotary adsorption device 21 in the rotary adsorption device 20 is divided into three air passage zones of the processing zone 22a, the regeneration zone 22b, and the purge zone 22c in the order of rotation of the rotor 22. The air that has passed through the treatment area 22a of the rotor 22 of the first stage rotary adsorption device 21 is dehumidified to, for example, air with a low dew point of −80 ° C.
[0025]
A part of the air that has passed through the processing zone 22a of the first stage rotor 22 in the rotary adsorption device 20 is returned to the purge zone 22c. On the other hand, the remaining air is directly introduced into the processing area 32a of the rotor 3 of the next-stage rotary adsorption device 32 in the second-stage rotary adsorption device 20.
[0026]
The rotary adsorption device 31 at the next stage in the rotary adsorption device 20 basically has the same configuration as the rotary adsorption device 10 at the first stage as described above. That is, the end face of the rotor 32 at the next stage in the rotary adsorption device 20 is divided into three air passage areas, a treatment area 32a, a regeneration area 32b, and a purge area 32c, in the order of rotation of the rotor 32. The rotor 32 is a second stage rotor in the rotary adsorption device 20, and the air that has passed through the treatment area 32a is dehumidified to an ultra-low dew point with a dew point temperature of −110 ° C., for example. To be processed.
[0027]
A part of the air that has passed through the treatment area 32a of the rotor 32 in the rotary adsorption device 31 is returned to the purge area 32c. On the other hand, a part of the remaining air is further diverted and sent to a regenerative heater 51 which will be described later, and the remaining air passes through an electric heater 41 and is then cleaned by removing particles and the like by a ULPA filter 42 and then stored. The storage S is supplied as an air supply SA.
Here, no cooling means is provided in the duct (clean air flow passage) downstream from the electric heater 41, that is, from the outlet of the electric heater 41 to the storage S that is the target space. Therefore, apart from the natural temperature drop, the air temperature in the duct is equal to the temperature of the electric heater 41.
[0028]
Next, the purge and regeneration system of the above system will be described. A part of the processing air diverted immediately before the electric heater 41 is sent to the regeneration heater 51, for example, heated to 120 ° C., and then sent to the regeneration section 32 b of the rotor 32 for use in the regeneration processing of the rotor 32. Is done. The air that has exited the regeneration zone 32b is mixed with the air that has been subjected to the purge process of the rotor 32 in the previous purge zone 32c, sent to the regeneration heater 52, and heated to 120 ° C., for example.
[0029]
The air heated by the regeneration heater 52 is sent to the regeneration zone 22b of the rotor 22 and used for the regeneration process of the rotor 22. The air exiting the regeneration zone 22b is mixed with the air subjected to the purge process of the rotor 22 in the previous purge zone 22c, and further the rotor 11 in the purge zone 11c of the rotor 11 of the rotary adsorption device 10 in the first stage. The air supplied to the purge process is also mixed and sent to the regenerative heater 54 by the processing fan 53. In the regenerative heater 54, the temperature of the inflowing air is increased to 120 ° C., for example.
[0030]
The air heated by the regeneration heater 54 is sent to the regeneration zone 11b of the rotor 11 and used for the regeneration process of the rotor 11. The air exiting the regeneration zone 22b is exhausted to the outside by the exhaust fan 55 as exhaust EA. Is done.
[0031]
A return duct 61 as a return flow path is provided between the downstream side of the ULPA filter 42 and the processing system duct 3 between the upstream side of the processing fan 2 and the downstream side of the air washer. . In FIG. 1, D1 to D15 are air dampers (having at least an opening / closing function, and the opening degree can be controlled by receiving a signal if necessary), and the air dampers D1 and D2 located at both ends of the return duct 61 are operated. Thus, it is possible to switch whether the air that has passed through the ULPA filter 42 is sent to the target chamber S side or the return duct 61 side.
[0032]
The processing fans 2, 5, the regeneration fan 53, and the exhaust fan 55 are all capable of inverter control based on the amount of air flowing through the duct and the temperature. Also, in the system of FIG. 1, what is indicated by “「 ”is a dew point measuring port. T1 to T7 are temperature detectors.
[0033]
The main air flow of the clean air supply system according to the present embodiment is illustrated in FIG. In FIG. 3, the flow of air that exits the purge area of each rotor is omitted.
[0034]
The clean air supply system according to the present embodiment is configured as described above. After the ULPA filter 42 is newly incorporated in the system, first, a baking operation for desorbing organic substances from the ULPA filter 42 is performed. Is made. At this time, the air dampers D1 and D2 are opened, and the air damper D15 is closed. In addition, the electric heater 41 is in an operating state. In this state, when the air primarily processed by the air washer 1 is processed by the rotary adsorption devices 10, 21, and 31, the electric heater 41 passes through the processing area 32a of the rotor 32 in the rotary adsorption device 31 at the final stage. For example, it is heated to 50 to 60 ° C. The air heated up to such a temperature passes through the ULPA filter 42 as it is without being actively cooled, flows through the return duct 61 and returns to the upstream side of the processing fan 2.
The above-described electric heater 41-target space is also applied to the return duct 61, that is, a duct that branches downstream from the electric heater 41 and returns a part of the heated air to a merging portion of the primary treated air introduction duct 3 to be described later. As with the duct between the entrances, no cooling means are provided.
[0035]
By this baking operation, the organic gas component is desorbed from the sealing material or adhesive of the ULPA filter 42. The desorbed organic gas component is returned to the upstream side of the first-stage rotor 11, but since there are many organic gas components at this stage, the organic substance desorbed from the ULPA filter 42 causes the rotor 11 to move away from the rotor 11. There is no degradation in performance. In addition, since the ultra-low dew point and high-temperature air is supplied to the ULPA filter 42, the moisture adhering to the ULPA filter 42 evaporates quickly as soon as the organic gas component is released.
[0036]
During the baking operation, the supply of primary processed air from the air washer 1 is not stopped, and the air supplied from the air washer 1 is reduced by reducing the amount of air returned by the return duct 61 and the air dampers D3 and D9. Reduce the amount. This is because, in the present embodiment, a part of the processing air is used for purge and regeneration of the rotor and exhausted, so that the shortage is compensated.
[0037]
Then, after a predetermined time, for example 48 hours, has elapsed since the start of such baking operation, steady operation is started. That is, the air dampers D1 and D2 are closed and the air damper D15 is opened. Further, the electric heater 41 is in a stopped state. As a result, the air that has passed through the treatment area 32a of the rotor 32 in the rotary adsorption device 31 at the final stage is supplied to the storage S after the particle components are removed by the ULPA filter 42.
[0038]
According to the above clean air supply system, the gaseous organic impurities can be removed from the ULPA filter 42 by baking the ULPA filter 42 incorporated in the system. At the same time, moisture in the ULPA filter 42 can be removed.
[0039]
Then, after the predetermined time has elapsed, since the dry air with high cleanliness from which gaseous impurities have been removed to a high level can be immediately supplied to the storage S, the conventional desorption operation by spontaneous release of gaseous organic impurities can be performed. In comparison, the startup time can be reduced to about half. Moreover, since the gaseous organic impurities do not flow into the storage S during the baking operation, there is no contamination in the storage S due to the operation of the system.
[0040]
In addition, since the ULPA filter 42 can be baked in the system, it is not necessary to pay extra attention to the installation, transportation, packaging, and the like of the ULPA filter 42 than in the past.
[0041]
Furthermore, since the air after the primary treatment by the air washer 1 is used as the treatment air, the inorganic gas component, particularly the soluble inorganic gas component can be largely removed in advance, and the inorganic gas component, It is possible to supply the storage S with air with extremely high cleanliness from which organic gas components have been significantly removed.
[0042]
Furthermore, the second stage rotary adsorption removal device 20 is , Although the rotors 22 and 32 are connected in series in multiple stages, the rotary adsorption / removal device 20 as a whole If you look, only one cooler 6 and one processing fan 5 Since it is not provided, both the installation area and the equipment cost can be reduced by 20% compared to the conventional case.
[0043]
In the above embodiment, since the ULPA filter 42 is used as a high performance filter, the heating temperature by the electric heater 41 is 50 to 60 ° C. However, a metal filter can be used instead of the ULPA filter 42. In this case, the heating temperature by the electric heater 41 may be set to 200 ° C., for example. In short, it may be heated to the heat resistant temperature of the filter by the electric heater 41 and supplied to the filter. Of course, instead of the electric heater, various heaters such as a hot water heater or a steam heater can be used.
[0044]
In the baking operation, since the high-temperature air is returned to the upstream side by the return duct 61, a load is applied to the coolers 4 and 6. Since some of the impurities are condensed and removed together with moisture, there is an advantage in terms of removing gaseous organic substances.
[0045]
Furthermore, in the above embodiment, when switching from the baking operation to the steady operation, the switching is performed after the elapse of a predetermined time on the basis of the time. However, for example, the concentration of a specific organic impurity is set on the downstream side of the ULPA filter 42. A sensor to be measured may be installed, and the baking operation may be switched to the steady operation when the detection result from the sensor falls below a predetermined threshold value. Alternatively, the dew point temperature may be measured by installing a sensor or a device for measuring the dew point temperature, and the operation may be switched to the steady operation when the temperature is lower than the predetermined dew point temperature. As a result, unnecessary baking operation time can be reduced, and startup time can be shortened.
[0046]
In the above embodiment, an electric heater is used as a heater (heating means). However, when a steam heater is already installed in a factory or the like, it is advantageous in terms of cost if a steam coil is used. Although an air washer was used as an external air conditioner, if a unit with a built-in air washer and a heat exchanger and filter for air heating and air cooling was used, the subsequent cooling coil processing load was reduced, and the control system Will also improve. At this time, if the cooling coil in the external air conditioner is installed upstream by the air washer, the air guided to the air washer becomes low temperature, and the growth of bacteria and algae in the air washer water tank is suppressed.
[0047]
Furthermore, a separate exhaust duct (not shown) may be provided at the connection portion between the processing system duct 3 and the return duct 61. If this exhaust duct is provided, for example, until a predetermined time elapses after the start of operation, or until the concentration of impurities in the air passing through the high-performance filter or the dew point temperature becomes a predetermined value or less after the start of operation, the electric heater 41 And the entire amount of air that has passed through the ULPA filter 42 is exhausted through the exhaust duct, and then the amount of air that has passed through the ULPA filter 42 is allowed to flow to the return duct 61. Thereafter, after a predetermined time has elapsed, or the ULPA filter 42 After the impurity concentration or dew point temperature in the air that has passed through the temperature has become equal to or lower than a predetermined value, the electric heater 41 is stopped and the operation that allows the air that has passed through the ULPA filter 42 to flow to the storage S side is possible. Become.
[0048]
When starting up the system, there is a high possibility that high-concentration impurities will be generated. Therefore, by stopping the flow to the return duct 61 immediately after the start of operation and forcibly exhausting through the exhaust duct as described above, the high-concentration impurities can be discharged out of the system. It is possible to prevent the return duct 61 from being contaminated during operation. Thereafter, as described above, the flow may be made to flow to the storage S side after a predetermined time has elapsed since the flow started to the return duct 61, or when the impurity concentration or the dew point temperature becomes a predetermined value or less. The switching of the air that has passed through the ULPA filter 42 to the exhaust duct, the return duct 61, and the storage S can be easily performed by, for example, providing an air damper in the exhaust duct and switching each damper.
[0049]
【The invention's effect】
According to the present invention, even if the high-performance filter is incorporated in the system as it is without baking in advance, the baking process can be performed in the system. In addition, the system startup time can be shortened. Furthermore, if a return channel is provided, the organic substance itself can be prevented from flowing into the target chamber during the organic substance desorption process. If an air washer is used, the inorganic gas component can be reduced to about 1/10 of the conventional one. Both the installation area and equipment cost can be reduced by 20% compared to the prior art.
[0050]
Furthermore, according to the operation method of the system of the present invention, it is possible to automatically switch between the organic substance desorption process and the supply of clean air to the target chamber, so that efficient operation as a whole can be performed. In addition, it is possible to reduce energy consumption by minimizing the use of heaters.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of a configuration of a clean air supply system according to an embodiment of the present invention.
2 is a perspective view of a rotor portion of a first-stage dry-type dehumidifier used in the clean air supply system of FIG. 1. FIG.
FIG. 3 is an explanatory diagram showing main air flows in the clean air supply system according to the embodiment of the present invention.
[Explanation of symbols]
1 Air washer
3 Processing system duct
10 Drying dehumidifier (first stage)
11 Rotor
11a treatment area
11b Regeneration area
11c Purge area
20 Drying dehumidifier (second stage)
22 Rotor
32 rotor
41 Electric heater
42 ULPA filter
61 Return duct
D1-D15 damper
S vault

Claims (7)

A clean air supply system for removing organic matter or moisture in the processing air with a rotary adsorber provided with an adsorbent in the rotor and then supplying it to the target chamber. And installing
A heater is installed in the air flow path between the rotary adsorption device and the high performance filter,
A clean air supply system characterized in that the air heated by the heater can be introduced into the high performance filter without being actively cooled. A return flow path for returning the air that has passed through the high-performance filter to the inlet side of the rotary adsorption device;
The clean air supply system according to claim 1, wherein the air after passing through the high-performance filter can be switched to flow to the target chamber or the return flow path side. The clean air supply system according to claim 1 or 2, further comprising an air washer for treating outside air upstream of the rotary adsorption device. In the rotary adsorption device, when multiple stages of rotors are connected in series,
A cooler is installed only at the processing zone inlet side of the first stage rotor, and no cooler is installed after the second stage.
The processing air system and the regeneration system for each rotor in the rotary adsorption device are provided with only one blower for each of the rotary adsorption devices as a whole. Or the clean air supply system according to 3. A method for operating the clean air supply system according to claim 2,
At the start of operation, the heater is operated and all the air that has passed through the high-performance filter flows to the return flow path side.
A method of operating a clean air supply system, characterized in that after a predetermined time has elapsed, the heater is stopped and all the air that has passed through the high-performance filter is allowed to flow toward the target chamber. A method for operating the clean air supply system according to claim 2,
At the start of operation, the heater is operated and all the air that has passed through the high-performance filter flows to the return flow path side.
After the impurity concentration or dew point temperature in the air that has passed through the high performance filter has become a predetermined value or less, the heater is stopped and the air that has passed through the high performance filter is allowed to flow to the target chamber side. A method of operating a clean air supply system. A method for operating the clean air supply system according to claim 2,
Furthermore, a separate exhaust duct is provided at the upstream connection portion of the return flow path,
The heater is operated and passed through the high-performance filter until a predetermined time has elapsed after the start of operation or until the concentration of impurities in the air or dew point temperature that has passed through the high-performance filter after the start of operation is below a predetermined value. The exhausted air is exhausted through the exhaust duct,
After that, all the air that has passed through the high performance filter is allowed to flow to the return flow path side, and after a predetermined time has elapsed, or after the impurity concentration or dew point temperature in the air that has passed through the high performance filter has fallen below a predetermined value. Is a method for operating a clean air supply system, wherein the heater is stopped and all the air that has passed through the high-performance filter is allowed to flow toward the target chamber.

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