JP4514970B2 - Impurity removal equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for removing impurities of soluble gas contained in the air, which is used in an outside air introduction system of a clean room .
[0002]
[Prior art]
This type of impurity removal apparatus is used in an outside air supply system of a clean room where high cleanliness is required, and is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-239224. The apparatus for removing gas impurities disclosed in the above publication is configured to absorb and remove soluble gas in the air by efficiently bringing gas-liquid contact between the air containing the soluble gas component and the absorbing liquid. . The absorbing liquid used here is generally pure water having a high cleanliness. However, the pH value of the absorbing solution varies depending on the component composition ratio of the soluble gas in the processing air, and the variation in pH further varies the gas removal rate. More specifically, the pH value depends on the component ratio (molar ratio) between the acidic gas component and the basic gas component. For example, when the acidic gas component increases, the pH value tends to be more acidic, and gradually the acidic gas component Removal performance decreases. Such a pH fluctuation phenomenon remarkably occurs when clean water (lower conductivity), for example, pure water, is used as makeup water.
[0003]
Japanese Patent Application Laid-Open No. 10-309432 discloses a countermeasure for the problem of pH value fluctuation when clean water such as pure water is used as makeup water. That is, the pH value of the circulating absorbent or the drainage of the absorbent is monitored, and (1) the amount of clean (fresh) absorbent is increased so that the pH value falls within a predetermined range. (2) pH It has been proposed to introduce means such as injecting an adjustment solution (an acidic solution or an alkaline solution) and (3) injecting a pH buffer solution.
[0004]
[Problems to be solved by the invention]
However, (1) the method of increasing the amount of clean absorption liquid is that, as long as clean water such as pure water is used as make-up water, a considerable amount of make-up water is needed to change the pH value of the circulating absorption liquid. When the pH value changes abruptly, it takes time to return to the control range (that is, the response speed is low), and there is room for improvement in the stable control of the removal performance.
[0005]
In addition, (2) pH adjustment solution injection, (3) pH buffer injection method has no problem in response speed and controllability, but most of chemical components added to pH adjustment solution and pH buffer solution are Because it is a substance to be removed from the air, there is a risk of contaminating the processing air depending on the injection volume. In such a system for injecting chemicals, maintenance such as replenishment and replacement of chemicals is indispensable every 1 to 3 months, and there is room for improvement when maintenance-free is required.
[0006]
The present invention has been made in view of the above points, and an object thereof is to provide an impurity removal apparatus which has good pH control responsiveness and is easy to handle and which is improved from the viewpoint of maintenance.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to claim 1, the soluble gas used in the outside air introduction system of a clean room is removed by gas-liquid contact with a clean absorbent in the chamber, and the absorbent An impurity removing apparatus having an absorption liquid circulation system for circulating and using a pH sensor for detecting the pH value of the absorption liquid in the circulation system and general water having a pH value of 6 to 8 A general water supply pipe for supplying the circulation system;
A water supply pipe for supplying clean absorption liquid to the circulation system, and a control device for controlling opening and closing of the valve of the general water supply pipe based on the detection result of the pH sensor, the detection result of the pH sensor However, if it is within the preset range, clean absorption liquid is replenished to the circulation system from the water supply pipe, and if the detection result of the pH sensor is outside the preset range, the control device An impurity removing device is provided in which general water is supplied to the circulation system from the general water supply pipe .
[0008]
In this way, the pH value of the absorbent in the circulatory system is controlled by replenishing general water separately, so it is possible to supply a large amount and immediately control it to a predetermined pH value, and the responsiveness Is good. General water here means tap water (tap water), industrial water (including water taken directly from rivers by industrial water, etc.), well water (well water), rain water or middle water (miscellaneous drainage) Water that has been simply purified. Therefore, it is easy to obtain and handle and has excellent maintenance.
[0009]
As described above, this type of impurity removal apparatus is often used in the outside air introduction system of a clean room. For example, when the concentration of acidic gas in the atmosphere near the facility having the clean room increases rapidly, Conventional technology cannot cope with it, and its control is difficult. For example, as the effects of SO ₂ gas eruption of Miyake Island, only acidic gas concentration at far from Miyake cases to rise 100 times the normal concentration it is actually happening.
[0010]
When general water is used as the absorbing liquid, the cleanliness of the absorbing liquid itself is lower than that of pure water, so downstream air may be contaminated by substances contained in the general water. However, considering the degree of influence on the production environment, as described above, for example, when the acid gas concentration is increased 100 times, such influence due to the use of general water is almost negligible. Therefore, the present invention has a remarkable effect especially when the concentration of pollutant gas in the atmosphere is temporarily increased.
[0011]
The impurity removal apparatus of the present invention can be used for outdoor air processing by itself, or can be incorporated into an outdoor air conditioner and used for external air processing, and is installed in an air circulation system to prepare for obstacles to production facilities. It can also be used as emergency equipment.
[0012]
The circulatory system of the absorbing liquid may have a storing part that collects and stores the absorbing liquid after being brought into gas-liquid contact in the chamber, and the pH sensor may be arranged in the storing part. The shape of the chamber may be a substantially box shape, for example. In this case, the upper part of the chamber has a blown-out port for processed air, the side part of the chamber has an inlet for treated air, and a mist or water droplet collecting part disposed at the upper part in the chamber. And a watering nozzle for spraying the absorbing liquid above the mist or water droplet collecting part, the processing air around the chamber is taken into the chamber and processed, and then sent out of the chamber as a vertical air flow. be able to. Here, the mist or water droplet collection unit means, for example, a device that collects mist or water droplets by the action of inertial collision or cooling condensation, and examples thereof include a collision plate, a cooling coil, an eliminator, and the like. It is also possible to employ a filler constituted by a three-dimensional network structure of lump or synthetic fiber.
[0013]
Further , if the configuration has a conductivity meter that measures the conductivity of the absorbent in the circulation system and a control device that controls the opening and closing of the valve of the water supply pipe based on the measurement result of the conductivity meter, Based on the soluble ion component of the absorbing liquid, it is possible to determine the necessity of replenishing a clean absorbing liquid, and it is possible to more appropriately replenish the absorbing liquid.
[0014]
The conductivity of the clean absorption liquid replenished through the water supply pipe is preferably less than 20 μS / cm, and the conductivity of general water replenished to the circulation system is 20 μS / cm or more, more preferably 100 μS / cm or more. Good.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described. FIG. 1 shows an outline of the configuration of an impurity removal apparatus 1 according to the first embodiment. It is a device for removing the soluble gas from the air and purifying it, and then supplying it to a clean space such as a clean room.
[0016]
The impurity removing apparatus 1 has an eliminator 3 disposed at right angles to the flow of processing air in a chamber 2 serving as a flow path for processing air. A water spray nozzle 4 is disposed on the upstream side of the eliminator 3 in the chamber 2. Below the chamber 2, a pit 5 is disposed as a storage portion having a length longer than the distance between the eliminator 3 and the water spray nozzle 4 in the direction along the air flow. Therefore, the absorbing liquid sprayed into the processing air from the water spray nozzle 4 collects impurities in the processing air, for example, soluble gas, by gas-liquid contact, collides with the eliminator 3 as it is, and is recovered by the eliminator 3. . Further, when the surface of the eliminator 3 is wetted with the sprayed absorption liquid mist and the processing air passes through the eliminator 3, impurities such as soluble gas are collected by the eliminator 3. The absorption liquid from the eliminator 3 that has collected the mist is stored in the pit 5. Mist and droplets are also stored in the pit 5 from the water spray nozzle 4.
[0017]
A drainage pipe 11 is connected to the bottom surface of the pit 5, and the absorbent stored in the pit 5 can be drained by the pump 12 as appropriate. An overflow pipe 13 is connected in the vicinity of the upper portion of the side wall of the pit 5 so that the absorbent stored in the pit 5 is discharged by the overflow pipe 13 before overflowing. The absorbing liquid discharged from the drain pipe 11 and the overflow pipe 13 may be cleaned and used again as the absorbing liquid.
[0018]
A water supply pipe 14 is connected to the pit 5, and a clean absorbent, for example, pure water is supplied into the pit 5 through the water supply pipe 14. A circulating water pipe 15 is provided between the bottom surface of the pit 5 and the water spray nozzle 4, and circulating water in the pit 5 pumped from the vicinity of the bottom surface of the pit 5 by the pump 16 is supplied to the water spray nozzle 4. Water is fed and sprayed into the process air. The sprayed absorption liquid flows along with the air flow to the downstream eliminator 3, and only the water droplets are captured by the eliminator 3 and returned to the pit 5. Therefore, in this case, the pit 5 and the circulating water pipe 15 constitute a circulating system.
[0019]
A general water supply pipe 17 is connected to the circulating water pipe 15. The general water supply pipe 17 is provided with an electromagnetic two-way valve 18, and the general water is supplied into the circulating water pipe 15 through the general water supply pipe 17 by opening and closing the two-way valve 18. The opening and closing of the two-way valve 18 is controlled by the control device 19.
[0020]
That is, a pH sensor 20 that detects the pH value of the circulating absorbent flowing from the pit 5 into the circulating water piping 15 is provided upstream of the connection portion of the circulating water piping 15 with the general water supply piping 17. The control device 19 controls the opening and closing of the two-way valve 18 based on the pH value of the circulating absorption liquid detected by the pH sensor 20. An example of control will be described later.
[0021]
An operation example of the impurity removal apparatus 1 according to the first embodiment having the above configuration will be described. First, in a normal time, the absorption circulating water is drained by a predetermined amount of water from the drain pipe 11, and the amount of drainage and the amount of evaporated water in the gas-liquid contact treatment are fed from the clean water feed pipe 14. The water in the pit 5 is sent to the water spray nozzle 4 by the pump 16 of the circulating water piping system and sprayed to the processing air. Return. The soluble gas in the processing air is absorbed and removed in the absorbing liquid by gas-liquid contact with the spray water and the wet surface of the eliminator 3 surface.
[0022]
Here, when the detection result of the pH sensor 20, that is, the pH value of the circulating water from the pit 5 is within the range of 5.0 to 7.5, clean makeup water is supplied from the water supply pipe 14 to a predetermined amount of water continuously. In this way, it is controlled by the control device 19. That is, when the pH value of the circulating water from the pit 5 is in the range of 5.0 to 7.5, the control device 19 controls the two-way valve 18 to be closed. When the impurity removal process proceeds and the ratio of the acidic and basic gas component concentrations in the processing air is significantly shifted, the pH value of the circulating water changes outside the set range.
[0023]
When the detection result of the pH sensor 20 is outside the set range (pH value is 5.0 to 7.5), the two-way valve 18 is opened under the control of the control device 19 and circulates from the general water supply pipe 17. General water is supplied to the water pipe 15. That is, general water is supplied to the circulating water system. If it does so, the pH value of circulating water will return gradually, and the pH value which is the said setting range will reach in the range of 5.0-7.5 eventually. When the pH sensor 20 detects that the circulating water from the pit 5 has reached the range, the control device 19 sends a control signal to the two-way valve 18, closes the two-way valve 18, and stops supplying general water. Is done.
[0024]
In the above embodiment, the general water is supplied from the suction side of the pump 16, and the amount of water supplied during the general water supply is close to the amount of spray water. When the amount of makeup water at this time is larger than the amount of drainage drained from the drainage pipe 11, the water is drained from the overflow pipe 13.
[0025]
Next, the results of experiments conducted by the inventors using the impurity removal apparatus 1 will be described. In the winter season when the acid gas component ratio increased, the outside air treatment was performed for 2 days using an impurity removal device. That is, outside air was used as the processing air. On the first day, the pH sensor 20 and the like were stopped, and the impurity removal process was performed for 6 hours without starting the control system by the control device 19. The sulfuric acid ion concentration and the ammonium ion concentration in the outside air were about 10 μg / m ³ and 1 μg / when it becomes m ^3, pH value of the circulating water was recorded for 4.5. At this time, the sulfate ion removal rate was 54%.
[0026]
On the next day, impurity removal treatment was performed for 6 hours in a state where the control system by the control device 19 could be started. While the ammonium ion concentration in the outside air was stable at 1 μg / m ³ as in the previous day, the sulfate ion concentration varied in the range of 8 to 13 μg / m ³ . The pH value of the circulating water varied in the range of 4.9 to 5.5. The pH value was 4.9, which was 0.1 lower than the control range. After the pH value of the circulating water became 5.0 or less, the general water began to be replenished, and from a few minutes until the pH value returned. This is because it takes about 10 minutes. The removal rate of sulfate ion was 69% when the lowest pH value was recorded. Thus, it was found that the pH control system by replenishing general water is effective in stabilizing the removal performance of the air impurity removal device.
[0027]
In the above embodiment, the pH control range is set to a pH value of 5.0 to 7.5, but it is of course possible to change this pH control range depending on the substance to be removed and the target value for removal performance. For example, when it is desired to always remove 70% or more of both acid gas and basic gas, it is desirable to set the pH control range to 5.5 to 7.0.
[0028]
In the above-described embodiment, city water (clean water) having a pH of 7.6 is used as general water for pH control. For this reason, when the pH value of the circulating water is biased toward the alkali side (7.5 or more), it cannot be controlled. However, the environment in which the impurity removal apparatus 1 is installed has a large amount of acid gas components, resulting in circulation from the pit 5. Although it has been known in advance that the water is largely biased to the acidic side but not to the alkaline side (pH 7.0 or higher), the pH value of the circulating water is within the range of 5.0 to 7.5 without any problem. Could be controlled.
[0029]
On the other hand, when there is a possibility that the pH value of the circulating water is biased to both the acidic side and the alkaline side, the pH value of the general water for pH control needs to be within the control range. On the other hand, when the circulating water from the pit 5 is biased only to the acidic side as in the experimental example, there is no problem even if the pH value of the general water for pH control exceeds the control value on the alkaline side. On the other hand, if it is biased only to the alkali side, there is no problem even if the pH value of the general water for pH control exceeds the control value on the acidic side. The pH control for general water, clean water, well water, industrial water (exclusive industrial water), rainwater, gray water (water to gray water and simple filtration), etc. can be utilized. Therefore, it is easy to obtain and handle, and the cost is low.
[0030]
The mounting location of the pH sensor 20 is in the circulating water pipe 15 in the first embodiment, but the pH value of the circulating water is measured in the pit 5 or the drain pipe 11. It can be anywhere you can.
[0031]
As a method for replenishing general water for pH control, in the first embodiment, water is supplied to the suction side of the pump 16 of the circulating water pipe 15, but the general water for pH control is directly supplied to the circulating water system. Or as long as it can supply water indirectly , what kind of water supply means may be performed.
[0032]
For example, in the impurity removing apparatus 21 according to the second embodiment shown in FIG. 2, the general water supply pipe 17 is piped into the pit 5 to supply water directly into the pit 5. Further, the detection part of the pH sensor 20 is also installed in the pit 5. In this impurity removing device 21, the water spray nozzle 4 is installed at the top of the eliminator 3 and sprayed directly from the water spray nozzle 4 to the eliminator 3 so that the surface of the eliminator 3 is always wet so that the eliminator 3 Collection and removal are carried out.
[0033]
In addition, in the impurity removing device 21 according to the second embodiment, a predetermined amount of clean absorption liquid replenishment and drainage are drained from the pit 5 by the drainage pump 12, and the amount of drainage and evaporation of circulating water at the time of gas-liquid contact. An amount of water is automatically supplied by the ball tap water supply valve 14a. As a normal water supply / drainage means, it is also possible to propose a method in which the amount of replenishment water is constant and the drainage is drained from the overflow pipe 13. This can be adopted in each embodiment of the present invention.
[0034]
As a method for supplying general water when the pH value exceeds the control range, a control system that implements until the pH value returns to the control range is adopted in each of the above embodiments. It is also possible to propose a water supply method that determines the time in advance. For example, once general water is supplied, it is stopped after 30 minutes of continuous water supply, and when the pH value after 30 minutes is not yet within the control range, water supply is started again and water is supplied continuously for 30 minutes. .
[0035]
Next, a third embodiment will be described with reference to FIG. In each of the above-described embodiments, the eliminator 3 is installed vertically in the chamber 2 and arranged so as to be perpendicular to the air flow of the processing air flowing horizontally in the chamber 2. In the impurity removing device 31 according to the embodiment, the impurity removing device 31 is horizontally installed at an upper portion in a substantially box-shaped chamber 32.
[0036]
That is, a blowout port 33 for blowing out processed air is formed in the upper part of the chamber 32, and a blower fan 34 is installed in the lower part thereof. An inlet 35 for taking in processing air is formed in the side portion of the chamber 32. The eliminator 3 is installed horizontally on the upstream side of the blower fan 34 in the chamber 32. A pit 5 is provided at the bottom of the chamber 32.
[0037]
The water supply pipe 14 is connected to the pit 5. A water intake pipe 36 is connected to the bottom of the pit 5. The intake pipe 36 diverges and one becomes the drain pipe 11, and the other is connected to the upper part of the chamber 32 as the circulating water pipe 15. A pump 37 is interposed on the upstream side of the branch point in the intake pipe 36. In the chamber 32, a water spray nozzle 38 is provided in the circulating water pipe 15. The water spray nozzle 38 is located between the eliminator 3 and the blower fan 34. The general water supply pipe 17 is connected to the intake pipe 36. The drain pipe 11 is provided with a valve V1, and the circulating water pipe 15 is provided with a valve V2. These valves V1 and V2 are mainly used for flow rate adjustment.
[0038]
The detection unit of the pH sensor 20 is disposed in the pit 5, and the detection result is sent to the control device 19. The control device 19 is provided in the general water supply pipe 17 based on the detection result. The opening and closing of the two-way valve 18 is controlled.
[0039]
According to the impurity removing device 31 according to the third embodiment having such a configuration, by the operation of the pump 37, the circulating water in the pit 5 flows through the circulating water pipe 15 through the intake pipe 36 and is supplied to the water spray nozzle 38. Is done. Then, water is sprayed from the watering nozzle 38 to the upper surface of the eliminator 3.
[0040]
When the blower fan 34 is activated, the processing air is taken into the chamber 32 from the introduction port 35 and is raised in the chamber 32 as a vertical air flow. At this time, clean water, for example pure water, is sprayed from the water spray nozzle 38 on the upper surface of the eliminator 3, so that the surface of the eliminator 3 is wet, and when the process air passes through the eliminator 3, By contact, impurities such as soluble gas components are collected and removed from the processing air.
[0041]
As in the first embodiment described above, when the pH value of the circulating water from the pit 5 falls outside the set range by the pH sensor 20, the two-way valve 18 is controlled by the control device 19 as in the first embodiment described above. The general water is supplied from the general water supply pipe 17 to the circulating water pipe 15 via the intake pipe 36. And if general water is supplied to this circulating water system, the pH value of circulating water will return gradually, and the pH value which is the said setting range will reach | attain the range of 5.0-7.5 before long. When the pH 20 sensor detects that the circulating water from the pit 5 has reached such a range, the control device 19 sends a control signal to the two-way valve 18 to close the two-way valve 18 and the supply of general water is stopped. The
[0042]
Next, an impurity removal apparatus according to a fourth embodiment will be described. As shown in FIG. 4, the impurity removing device 41 according to the fourth embodiment is further provided with a conductivity meter 42 in the pit 5 of the impurity removing device 1 according to the first embodiment. Based on the result, the control device 43 controls the two-way valve 44 provided in the water supply pipe 14. That is, as a method of supplying clean absorption liquid when the pH value of the circulating water in the pit 5 is within the control range, the conductivity of the circulating water is measured by the conductivity meter 42 and when the predetermined conductivity is exceeded. The control device 43 opens the two-way valve 44 to replenish clean absorbent.
[0043]
According to such a method, unlike those methods in which a constant amount of water is drained at all times, the conductivity of circulating water is measured, and when the conductivity exceeds a predetermined value, forced blow or forced water supply is used. It is possible to take A drainage pipe may be separately provided in the pit 5, and a solenoid valve may be provided in the drainage pipe so that the water supply pipe side is a ball tap water supply.
[0044]
【The invention's effect】
According to the present invention, when the soluble gas in the air is removed by gas-liquid contact with the absorbing liquid, the responsiveness of the pH control of the absorbing liquid to be circulated is good, and it is easy to handle and is easy to maintain. Also excellent. Therefore, stable removal performance can always be maintained even if the composition ratio of gas components in the processing air varies.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of a configuration of an impurity removal apparatus according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing an outline of a configuration of an impurity removal apparatus according to a second embodiment of the present invention.
FIG. 3 is an explanatory diagram showing an outline of a configuration of an impurity removing apparatus according to a third embodiment of the present invention.
FIG. 4 is an explanatory diagram showing an outline of a configuration of an impurity removal apparatus according to a fourth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Impurity removal apparatus 2 Chamber 3 Eliminator 4 Water spray nozzle 5 Pit 11 Drain piping 14 Water supply piping 15 Circulating water piping 16 Pump 17 General water replenishment pipe 18 Two-way valve 19 Controller 20 pH sensor

Claims (6)

Used in a clean room outside air introduction system, a soluble gas in the processing air is removed by gas-liquid contact with a clean absorption liquid in the chamber, and an absorption liquid circulation system for circulating the absorption liquid is used. An impurity removal device comprising:
A pH sensor for detecting the pH value of the absorbent in the circulation system;
a general water supply pipe for supplying general water having a pH value of 6 to 8 to the circulation system;
A water supply pipe for supplying clean absorption liquid to the circulation system;
A control device for controlling the opening and closing of the valve of the general water supply pipe based on the detection result of the pH sensor ,
If the detection result of the pH sensor is within a preset range, clean absorption liquid is replenished to the circulation system from the water supply pipe,
When the detection result of the pH sensor is outside a preset range, the controller removes general water from the general water supply pipe to the circulation system by the control device. The circulatory system has a storage part that collects and stores the absorption liquid after being brought into gas-liquid contact in the chamber, and the pH sensor is disposed in the storage part. 2. The impurity removal apparatus according to 1. The chamber is substantially box-shaped, has a treated air outlet at the top of the chamber, and has a processing air inlet at the side of the chamber,
A mist collector disposed in an upper portion of the chamber;
3. The impurity removing device according to claim 1, further comprising a watering nozzle that sprays the absorbing liquid above the mist collecting unit. A conductivity meter for measuring the conductivity of the absorbent in the circulation system;
4. The impurity removing device according to claim 1, further comprising: a control device that controls opening and closing of the valve of the water supply pipe based on a measurement result of the conductivity meter. 5. 5. The impurity removing apparatus according to claim 4, wherein the conductivity of the clean absorption liquid replenished through the water supply pipe is less than 20 [mu] S / cm. 6. The impurity removing apparatus according to claim 1, wherein the conductivity of the general water is 20 μS / cm or more.

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