JP3176109B2 - Airflow dust removal method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing dust from an air flow, and more particularly to a method for removing dust from an air flow in a clean room in a semiconductor factory, an integrated circuit factory, a pharmaceutical factory and the like.

[0002]

2. Description of the Related Art Although there has been an interest in making the working environment dust-free, especially in recent LSIs, the line size of a pattern has been reduced to the order of submicrons (10 ^-6 m or less), and fabrication has become difficult. In order to prevent the characteristics and reliability of the device from being adversely affected by the contamination during the process, there is a great problem of making the working environment dust-free. Generally equipped with a clean room,
The structure is such that the clean air passed through the filter is supplied to the laminar flow from the ceiling, discharged from the floor, and the cleanliness in the clean room is maintained at a desired level or higher. For example,
Clean air is circulated 167 times / h through a clean room with an indoor area of 5,400 m ² and a ceiling height of 3 m.
It is configured to keep. Therefore, the amount of air to be processed reaches 45,000 m ³ / min. By the way, the cleanliness is 0.5 μm in diameter contained in one cubic foot of air.
It is represented by the number of dusts described above.

[0003]

However, in order to obtain clean air of a cleanliness class 10 in the clean room, a filter must be mounted on a pre-filter (collection rate: 20).
%), An intermediate filter (collection rate: 60%) and a high-efficiency filter (collection rate: 99.97%) in three stages.
It requires 1,100 kWh of blowing power. Furthermore,
As described above, the line width of the pattern is on the order of submicron, and dust having a diameter of 0.5 μm or less as a reference for cleanliness is also a problem. It can be said that it is almost impossible to remove dust simply by adding filters.

[0004] In view of the drawbacks of the prior art, the present invention provides
It is an object of the present invention to provide a method of removing an air stream that can be more completely removed with good energy efficiency.

[0005]

Means for Solving the Problems The invention described in claim 1 is an embodiment of the present invention.
The cooled air stream is humidified and compressed, and then
The wet compressed air stream is cooled and then is inflated characterized in that performing the dust removal by condensation by quenching to below the dew point, the invention is as claimed in claim 2, wherein, in addition to the first aspect of the invention
The pre-cooling is performed by the cooling airflow after the dust removal. Accordingly, the present invention compresses and humidifies the pre-cooled air stream, then expands after cooling, and condenses by cooling rapidly below the dew point. Since the dew condensation is carried out using dust as a core, the dust can be removed by discharging the dust to the outside together with the drain. Preferably, the humidification is performed during the compression step. Further, if the pre-cooling is performed by the cooling air flow after the dust removal, it is preferable in terms of thermal economy compared with the case where a heat source is obtained outside the air flow system.

[0006]

According to the technical means, the pre-cooled air stream is humidified and compressed, and then the humidified compressed air stream is cooled .
In order to rapidly cool the temperature of the air flow below the dew point by performing cooling and expansion in order, the water vapor in the air flow is discharged out of the system together with the drain at the discharge port of the expander in order to condense with dust as nuclei. Thus, dust can be removed.

[0007] Furthermore, the compressed air stream having a high temperature is
Before expansion into a low-temperature air flow by expansion, heat is radiated outside the system by a heat exchanger to cool the air flow. At this time, if the humidification is performed so that the relative humidity of the high-temperature compressed air flow becomes 100%, the temperature is reduced by the heat exchanger, and the saturated steam pressure is also reduced. Also at the heat exchanger outlet side, dust can be removed by discharging to the outside of the system together with the drain. At this time, the concentration of dust particles per unit volume of the air flow is increased by an amount corresponding to the compressed air flow, so that the dust removing effect can be improved.

Further, since the humidifier is humidified during the compression step, the humidifier is humidified to a high-temperature compressed air flow which has a high temperature due to the compression and also has a high saturated steam pressure. Thus, the amount of moisture that can be contained per unit air volume, that is, the humidification amount can be increased. That is,
The amount of dew condensation in the expansion step following the compression step also increases in accordance with the humidification amount, so that the dust removing effect can be improved, which is more preferable.

Further, if humidification is achieved by water injection during the compression step, the compressed air is cooled by water having a relatively low temperature as compared with the high-temperature compressed air, and by an amount corresponding to the latent heat of vaporization of the injected water. Can be. Therefore, the power for compression can be reduced by the lower temperature.

[0010] Generally, it is said that a screw type compressor is more efficient than a reciprocating type compressor. However, if the humidification is performed in the screw type compressor, the efficiency should be further improved. Can be. That is, when compression is performed by a screw compressor, water is injected into the compressor to seal the gap formed between the rotors and between the rotor and the casing with water. Compression efficiency can be increased.

[0011] A preliminary cooling before compressing the air flow, if allowed to reduce the enthalpy of the air flow, the amount of heat released out of the system that follows the compression stroke becomes smaller,
The capacity of the radiator can be reduced. Furthermore, also in the expansion step, it is possible to cool to a lower temperature by an amount corresponding to the above-mentioned reduced enthalpy, so that the saturated steam pressure is also reduced by the lowered temperature, so that a large amount of drain can be obtained, which is preferable. Further, if the pre-cooling is performed by the cooling air flow after the dust removal, it is preferable in terms of thermal economy compared with the case where a heat source is obtained outside the air flow system.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Not just.

FIG. 1 is a system diagram showing a method for removing dust from an air flow according to an embodiment of the present invention. Reference numeral 10 denotes a clean room in which the concentration of dust is a problem. The contaminated air is conducted to the heat exchanger 13 via the grid and the ducts 40 and 41. The ceiling duct 18
The space between the floor and the floor 11 constitutes a workplace as a so-called clean space.

In the middle of the ducts 40 and 41, a duct 48
Outside air is introduced through the heat exchanger 13 together with the circulating air.
Cooled within. Reference numeral 12 denotes an outside air intake device. The outside air taken in from the intake port 28 is washed and humidified by clean water circulating in the outside air intake device 12 by the pump 30, and is circulated through the duct 48. Merges into the duct 41. However, the physical properties of the circulating air in the duct 41 are not much different from the air in the clean room 10 because the amount of outside air taken in is small. That is, the duct 4
The physical properties of the circulating air in 1 were as follows: temperature 24 ° C., relative humidity RH: 40%, absolute humidity per unit dry air x: 0.0075
kg / kg ', 1ata. It is.

Cooling and circulating air after dust removal described later is also introduced into the heat exchanger 13 through a duct 46. Therefore, in the heat exchanger 13, the cold air (46)
Heat exchange is performed with the circulating air (41) after intake,
The cooled circulating air passes through the duct 42 through the compressor 14.
Will be introduced. The intake circulating air after heat exchange (42)
Physical properties change to 13.6 ° C. and RH: 76.6%.
Also, 20 is that the circulating air (41) is cooled and dewed,
The drain is discharged outside the circulating air system. In the present example, the relative humidity happens to be less than 100%, so there is no condensation and, therefore, the amount of drain is zero.

In the compressor 14, the circulating air (4
2) is 2ata. Compressed. The compressor 14
Are driven by a motor M, and the motor M is also directly connected to an expander 17 described later, which contributes to energy saving. During the compression step, the pure water in the pure water storage tank 31 is pressurized by the pump 32 and supplied into the compressor 14. Therefore, the circulating air (42) is humidified thereby, and the physical properties are as follows: temperature: 40.49 ° C., RH: 100%,
x: 0.02403 kg / kg '. The circulated air thus pressurized and humidified passes through the duct 43 through the heat exchanger 16.
Will be introduced.

In the heat exchanger 16, the circulating air (43) is cooled by cooling water circulating between the heat exchanger 16 and the cooling tower 33 by a pump 34, followed by a pipe 44 and a drain. It is introduced into the expander 17 via the separator 21 and the pipe 45. In addition, 22 is the drain separator 2
In 1, the drain is discharged outside the circulating air system.
In the heat exchanger 16, the circulating air (43)
To be cooled to 8.43 ° C., an absolute humidity x: 0.02146 kg / kg ′ corresponding to the saturated steam pressure at this temperature;
Absolute humidity x of the circulating air (43): 0.02403 kg / k
The difference X from g ′: 0.00257 kg / kg ′ is discharged as drain 22.

In the expander 17, a pressure of 2 at.
Of circulating air (45) is 1 data. And is introduced into the heat exchanger 13 through the drain separator 23 and the duct 46. As described above, the work due to the expansion is returned to the compressor 14 via the directly connected motor M. In addition,
Reference numeral 24 denotes a drain discharged from the drain separator 23 outside the circulating air system. The circulating air after expansion (4
6) drops to a temperature of 9.57, and therefore an absolute humidity x corresponding to the saturated water vapor pressure at this temperature x: 0.0073 kg /
kg 'and the absolute humidity x of the circulating air (45): 0.0214
A difference X from 6 kg / kg ′: 0.01416 kg / kg ′ is discharged as drain 24.

The circulating air (46) introduced into the heat exchanger 13 exchanges heat with the circulating air (41) and is sent to the clean room 10 through the duct 47 as described above. The physical properties of the circulating air (47) are temperature
20 ° C., RH: 51%, x: 0.0073 kg / kg ′.

As described above, the circulating air that has come into contact with the heat exchangers 13 and 16 is rapidly cooled, and is subjected to adiabatic expansion in the expander 17 to lower the temperature of the circulating air itself.
Of the water vapor contained in the circulating air, only the amount exceeding the saturated water vapor pressure at the cooled temperature is condensed and formed as fog and water droplets. At this time, as described above, since it is easier for water vapor to condense with dust contained in the circulating air as nuclei, the mist and water droplets are discharged outside the system as a drain, thereby achieving dust removal and purification of the circulating air. it can. In this embodiment, the amount X of the drains 20, 22 and 24 is set to 1 k of circulating dry air.
It reaches 0.01673 kg per g '.

[0021]

According to the present invention, as described above, the pre-cooling
After pressurizing and humidifying the air flow, it is expanded and quenched to a temperature below the dew point to condense and remove dust. Therefore, it is possible to provide a method of removing the air flow that can completely remove dust with good energy efficiency. Things become possible. In addition, since the dust is removed together with the wastewater, the dust collection rate does not deteriorate over time, as in the case of the conventional filter system. Can be eliminated. In a clean room in an integrated circuit factory, air conditioning equipment is indispensable even in the conventional filter system, and a pure water system is also an essential equipment. Equipment based on the invention can be introduced.

[Brief description of the drawings]

FIG. 1 is a system diagram illustrating a method for removing dust from an air flow according to an embodiment of the present invention.

Continuation of the front page (56) References JP-A-52-111874 (JP, A) JP-A-63-221822 (JP, A) JP-A-61-61609 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) B01D 47/00-47/18 B01D 50/00-51/10

Claims (3)

(57) [Claims] 1. A method for humidifying a pre-cooled air stream and applying a pressure
A method for removing dust by removing air by condensing, cooling the humidified and compressed air stream, and then expanding and rapidly cooling the air stream to a temperature below the dew point to form dew. 2. Pre-cooled air flow is humidified and pressurized.
And then cooling the humidified compressed air stream, and then
Expand and quench below the dew point to condense and remove dust
And performing the preliminary cooling with the cooling airflow after the dust removal. 3. The step of compressing the pre-cooled air flow.
3. The method according to claim 1 , wherein the humidification is performed in the inside.
The dust removal method of the air flow described. [0001]