JP4587428B2 - Deaerator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid processing apparatus and processing method for degassing and / or degassing a liquid.
[0002]
[Prior art]
As a method for reducing the concentration of dissolved gas dissolved in a liquid, for example, so-called vacuum degassing, heating degassing, ultrasonic degassing, or bubbling a gas other than oxygen / nitrogen that depressurizes the inside of a packed tower or a spray tower. A method, a method using centrifugation, a method of applying pressure, a method of adding an antifoaming agent, and the like are known. Among them, the membrane-type vacuum degassing method, in which the liquid is passed through one of the membranes through which gas does not permeate and the other side is depressurized, is small in size, easy to handle, and highly degassed. And is widely used for degassing and / or defoaming liquids used for analysis, cleaning, and production in various fields such as chemicals, food, medicine, and semiconductors.
[0003]
As a vacuum pump used for decompression of vacuum deaeration, an oil rotary vacuum pump, a water ring vacuum pump, a roots blower vacuum pump, a diaphragm vacuum pump, a scroll vacuum pump, and the like are known. Japanese Patent Laid-Open No. 06-273797 describes a diaphragm vacuum pump, and Japanese Patent Laid-Open No. 09-45615 describes a water ring vacuum pump.
[0004]
[Problems to be solved by the invention]
There is a solvent-based cleaning agent that needs to be degassed. However, when conventional technology is applied to flammable liquids such as IPA (isopropyl alcohol), a flammable explosion occurs due to a short-circuit of a vacuum pump contact point where the drive source is electric. There was a risk of doing. As a countermeasure, a method using an explosion-proof vacuum pump that can be used even in an atmosphere of flammable gas can be considered, but the pump becomes a large-sized one equipped with a large capacity motor, which increases the weight and shape of the entire deaeration device. It was difficult to handle, took up a lot of space, and required a lot of construction and maintenance costs.
[0005]
In addition, there is a method to connect the deaeration piping of the deaeration device to a vacuum pump at another location in the factory and depressurize the deaeration device. However, the piping length to the vacuum pump is long and complicated, and costs high. . Furthermore, in order to avoid a reduction in suction capacity due to an increase in piping resistance, it is necessary to increase the piping diameter to reduce piping resistance, or to select a vacuum pump with a high exhaust speed, which increases the size of the equipment Cost was necessary. Furthermore, there is a case where the exhaust capacity is reduced due to a pipe leak or the like, and a great maintenance cost of the pipe is necessary.
[0006]
Further, when an oil rotary vacuum pump is used, an oil mist trap is required because oil mist is generated during exhaust. In addition, there is a problem of oil deterioration due to reaction with the cleaning agent and oil emulsification due to moisture suction, and it is necessary to provide an oil / water separator separately from the vacuum pump, which requires a lot of cost for installation and maintenance There's a problem.
[0007]
Moreover, when using a water ring vacuum pump, there exists a problem that a vacuum capability is low compared with another pump, and also water temperature management is required. Further, when toxic gases or liquids other than water vapor and water are sucked, it is necessary to perform a sealed circulation of the sealed water because they are dissolved in the sealed water and the sealed water cannot be drained as it is. Further, when the sealed water is drained, a separation device for components dissolved in the sealed water is required, and there is a problem that the installation and maintenance of the device requires a great deal of cost.
[0008]
Also, when degassing by membrane vacuum degassing, if the pressure is reduced at a pressure lower than the saturated vapor pressure of the liquid, vaporization of the liquid is promoted and a large amount of liquid vapor is discharged out of the system. There is also, and it becomes easy to flow into the pump which decompresses. When iron, aluminum, or NBR (nitrile butadiene rubber) is used as the material of the vacuum pump, there is a problem in that the vacuum pump may break down due to corrosion caused by contact with the sucked solvent or water inside the pump. .
[0009]
The present invention has been made in view of such problems, and can be used in a flammable gas atmosphere, and does not cause corrosion even in a corrosive gas atmosphere, and supplies a deaeration device with low maintenance cost. For the purpose.
[0010]
[Means for Solving the Problems]
That is, the gist of the present invention is a deaeration device for treating a liquid using a membrane and a gas-driven vacuum pump , wherein the deaeration device houses the membrane and the vacuum pump and has a through-hole. A deaerator having a configuration in which the driving gas exhausted from the vacuum pump is once exhausted into the casing and then exhausted to the outside of the casing through the through hole .
[0011]
The member in contact with the liquid to be treated of the vacuum pump is made of at least one material of tetrafluororesin, fluororubber, stainless steel, or at least one surface of tetrafluororesin coating, Ni plating, cation painting When the treatment is performed, the durability is excellent and preferable.
It is preferable that the vacuum pump is a reciprocating type or a rotary type because the pressure reducing process can be efficiently performed .
It is preferable that the membrane comprises a three-layer hollow fiber membrane in which both sides of a non-porous membrane are sandwiched between porous support layers because efficient degassing is possible.
A casing containing the membrane and the vacuum pump and having a through-hole is provided, and driving air exhausted from the vacuum pump is once exhausted into the casing, and then exhausted outside the casing through the through-hole. This is preferable because the solvent does not enter the apparatus when the solvent is deaerated.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The deaeration device of the present invention will be described below with reference to the drawings.
FIG. 1 is a flow diagram showing an example of a deaeration device of the present invention, and FIGS. 2 and 3 are cross-sectional views showing an embodiment of a deaeration membrane used in the present invention.
In FIG. 1, the liquid is introduced from the liquid introduction port 6 of the degassing device 1, degassed by the degassing membrane 2, and led out from the liquid outlet port 7.
[0013]
Here, the decompression means shown in FIG. 1 may be any means that can depressurize the pressure on the gas phase side of the membrane below the pressure on the liquid phase side of the membrane, but an electrical contact that generates an electric spark. It is necessary to use a fluid-driven vacuum pump that does not have any gas, and by using the degassing device of the present invention, degassing can be performed in a flammable atmosphere.
[0014]
The fluid-driven vacuum pump in the present invention refers to a pump that uses a fluid as a driving force for decompressing, and refers to a pump, diaphragm, screw, or the like that moves or rotates with the force of liquid or gas.
Of course, it can be used as long as it is similar to these and can be depressurized, and examples thereof include a depressurizing means using a flow of liquid or gas such as a water flow aspirator or a venturi tube.
[0015]
The operation method of the fluid-driven vacuum pump is not particularly limited, but a reciprocating type or a rotary type is preferably used. Here, the reciprocating method is a method of reducing the pressure by reciprocating, for example, a piston method or a diaphragm method. Further, the rotary type is a method of reducing the pressure by a rotational motion, and for example, a scroll method and a screw method are applicable.
[0016]
As the driving fluid, gas is preferable, and it is not necessary to prepare the liquid in the tank in advance, and it is not necessary to install the drainage pipe and drain the liquid as compared with the case of liquid such as water. Further, among the gases, air is ubiquitous and is particularly preferable since it is excellent in handleability, and can be easily supplied from the atmosphere using a compressor or the like, and can be exhausted directly to the atmosphere. Therefore, it is preferable to use an air-driven vacuum pump in the deaeration device of the present invention.
[0017]
As the type of pump, it is preferable to use a so-called dry type vacuum pump such as a piston type vacuum pump, a diaphragm type vacuum pump, a scroll type vacuum pump, a screw type vacuum pump, etc. Problems such as countermeasures against mist, deterioration of pump oil and emulsification, or temperature control of sealed water and water quality management of sealed water when using a water-sealed vacuum pump are eliminated, and maintenance costs can be reduced.
[0018]
The form of the membrane used in the present invention is not necessarily limited, and a flat membrane, a hollow fiber membrane, a tubular membrane or the like can be used, but the membrane area per unit volume can be increased, and the device can be easily made compact. The form of a hollow fiber membrane is more preferable.
The hollow fiber membrane used in the present invention is preferably a hollow fiber membrane having an inner diameter of 50 to 500 μm and a film thickness of 10 to 150 μm. If the inner diameter is smaller than this range, the pressure loss becomes too large when liquid is passed through the hollow fiber membrane, and if larger, the efficiency of defoaming and degassing decreases. Further, if the film thickness is thinner than this range, the mechanical strength is lowered, and the hollow fiber membrane is vibrated due to fluctuations in pressure, and the hollow fiber membrane is likely to be damaged. Defoaming efficiency decreases.
[0019]
The structure of the hollow fiber membrane is more preferably a composite hollow fiber membrane having a three-layer structure in which a porous layer is disposed on both sides of a non-porous layer. When such a composite hollow fiber membrane is used, it is difficult for the liquid to come into direct contact with the non-porous layer, so that the non-porous layer is not easily affected by the liquid, and the liquid can be degassed and degassed efficiently.
As the composite hollow fiber membrane, when a composite hollow fiber membrane having a non-porous layer thickness of 0.3 to 3 μm and a porous layer thickness of 5 to 100 μm is used, the mechanical strength is high and the removal is achieved. It is possible to improve the gas permeation amount when performing gas and defoaming.
[0020]
Examples of the polymer constituting the non-porous layer of the composite hollow fiber membrane include polydimethylsiloxane, silicon rubber-based polymers such as a copolymer of silicon and polycarbonate, poly (4-methylpentene-1), and low density polyethylene. Examples include polyolefin polymers such as fluorine-containing polymers such as perfluoroalkyl polymers, cellulose polymers such as ethyl cellulose, polyphenylene oxide, poly (4-vinylpyridine), urethane polymers, and copolymers of these polymer materials. Or a blend polymer etc. can also be used.
[0021]
Among these, as a material for the non-porous layer that can efficiently perform degassing and defoaming of a liquid, a material composed of a urethane-based polymer, a styrene-based thermoplastic elastomer, and a polyolefin is preferable. In particular, a combination of a styrenic thermoplastic elastomer and a polyolefin is preferable because it has excellent durability against chemicals, and even when it comes into contact with chemicals, the material is not damaged or the performance is not easily lowered.
[0022]
Specific materials for the styrene-based thermoplastic elastomer include styrene / butadiene copolymer, styrene / ethylene-butylene copolymer, styrene / isoprene copolymer, styrene / ethylene-propylene copolymer, and the like. Can be mentioned. These polymers and elastomers may be used alone or in combination of a plurality of materials.
[0023]
Polymer materials constituting the porous layer of the composite hollow fiber membrane include polyolefin polymers such as polyethylene, polypropylene, poly (3-methylbutene-1), poly (4-methylpentene-1), polyvinylidene fluoride, polytetra Fluoropolymers such as fluoroethylene, polymers such as polystyrene, polyetheretherketone, and polyetherketone can be used.
The combination of the polymer material constituting the non-porous layer and the polymer material constituting the porous layer is not particularly limited, and different types of polymers or the same kind of polymers may be used.
[0024]
When using a hollow fiber membrane, a liquid may be passed through the hollow portion of the hollow fiber membrane and the outside of the hollow fiber membrane may be decompressed, or a liquid may be passed through the outside of the hollow fiber membrane and the hollow portion may be decompressed. Either can be adopted. FIG. 2 shows an example of a hollow fiber membrane module when a liquid is passed through the hollow fiber membrane. While maintaining the open state of both ends of the hollow fiber membrane 3 , the liquid flowing side and the decompressed side on the fixing member 4 Is hermetically sealed.
FIG. 3 is an example of a hollow fiber membrane module when liquid is passed outside the hollow fiber membrane, and is the same as the configuration of FIG. 2 except that the liquid inlet 6 and the liquid outlet 7 are provided in the container 5 (case) . is there. However, the decompression ports 8 do not necessarily have to exist at both ends, and the decompression can be performed from only one side. In this case, it is preferable that the end portion of the hollow fiber that is not decompressed is closed.
[0025]
When the liquid vapor used has a property of permeating the membrane, the lower limit of the degree of vacuum is preferably about the vapor pressure of the liquid. When the degree of decompression is lower than the vapor pressure of the liquid, the vapor of the liquid can easily pass through the membrane and be guided to the vacuum pump, which may cause a reduction in the performance of the vacuum pump. Therefore, although not shown in FIG. 1, it is preferable to provide a trap between the hollow fiber membrane module 2 and the vacuum pump 9. Even in a normal state, a very small amount of liquid may ooze out from the degassing module 2 to the vacuum pump side, and dew condensation may occur in the vacuum pipe. This is a preferable method because it is possible to prevent liquid from flowing into the interior of the container.
[0026]
When degassing a corrosive liquid such as a solvent, using a vacuum pump made of a material such as iron, aluminum or NBR (nitrile butadiene rubber) will cause corrosion inside the pump and cause failure. A member made of at least one of tetrafluororesin, fluorine rubber, and stainless steel is used as a member that comes into contact with the deaeration liquid of the vacuum pump 9 or a surface of the member that comes into contact with the deaeration liquid of the vacuum pump is made of 4 It is preferable to perform at least one surface treatment such as coating of a fluorinated resin, Ni plating, or cationic coating. Moreover, it is not limited to this, It is preferable to select the material according to properties, such as the corrosivity of the liquid deaerated.
[0027]
The liquid feeding means is not shown in the figure, but is not particularly limited to the arrangement and method of the liquid feeding means. For example, from a liquid tank and a liquid feeding pump installed separately from the deaeration device. The sent non-processed liquid is introduced into the liquid inlet 6 of the deaerator, and the deaerated liquid deaerated by the deaerator is supplied from the liquid outlet 7 to a supply destination such as an ultrasonic cleaning tank via a pipe. There is a way to supply. In addition, there is a method of circulating a liquid between a liquid tank and a deaeration device using a circulation pump.
[0028]
Moreover, in the deaeration device of the present invention, it is preferable to provide a gate valve 11 and a leak valve 12 between the hollow fiber membrane module 2 and the vacuum pump 9. When performing deaeration operation, the hollow valve membrane module 2 and the vacuum pump 9 are communicated by opening the gate valve 11 and closing the leak valve 12, and pressure reduction inside the hollow fiber membrane module is performed. Here, the gate valve 11 and the leak valve 12 are preferably manually operated or air driven, and there is no risk of flammable explosion when using an electrically driven valve. The type of valve is not particularly limited, and for example, a ball valve, a diaphragm valve, or a needle valve can be used.
In the deaeration device of the present invention, it is preferable to open the leak valve 12 before starting the vacuum pump so that the atmosphere is introduced to bring the suction side of the vacuum pump to atmospheric pressure, and the suction side of the vacuum pump is in a negative pressure state. The starting power can be reduced as compared with the case where starting is performed from the beginning, and a small vacuum pump with a small power can be selected. In addition, it is preferable to provide a filter 13 in front of the leak valve 12, so that damage caused by dust flowing into the hollow fiber membrane module or the vacuum pump can be prevented.
[0029]
The deaeration device 1 of the present invention accommodates the membrane 2 and the vacuum pump 9, is provided with a casing 18 having a through-hole 17, is supplied from the driving air inlet 14 to the vacuum pump 9, and is exhausted from the driving air outlet 15. It is preferable that the air is once exhausted into the casing 18 and then exhausted to the outside of the casing 18 through the through-hole 17. With such a configuration, when the degassing device 1 is installed and operated in a vapor atmosphere such as a solvent, it is possible to prevent the solvent vapor from flowing into the device. Since the number of contact times can be greatly reduced, the lifetime of various components inside the apparatus can be extended, and maintenance and the like can be reduced.
For the same reason, it is preferable that the gas or the mixture of gas and liquid sucked and discharged by the vacuum pump is directly discharged out of the apparatus from the degassing gas discharge port 16 using a pipe.
In addition, it is preferable to use the through-hole 17 as a through-hole for releasing internal pressure by driving air discharged from an air-driven vacuum pump in terms of simplifying the structure of the deaeration device. Further, the through-hole 17 has an effect of releasing internal heat storage due to heat generated by a vacuum pump or the like.
[0030]
Hereinafter, the present invention will be specifically described based on examples.
<Example 1>
A deaeration device was manufactured based on the configuration shown in the flowchart of FIG. The vacuum pump used an air-driven diaphragm type and did not use any electrical components. In addition, a stainless steel casing is used, and a through-hole is provided in the casing. The exhaust is once exhausted from the driving unit of the air-driven vacuum pump into the casing and then exhausted from the through-hole to the outside of the casing. Further, the gas discharged from the vacuum pump or a mixture of the gas and the liquid is provided with a degassing gas discharge port so as to be discharged directly from the casing through the degassing gas discharge port.
The hollow fiber membrane module uses a three-layer structure hollow fiber membrane (MHF200TL, manufactured by Mitsubishi Rayon Co., Ltd.) having an inner diameter of 200 μm and an outer diameter of 254 μm (film thickness of 27 μm). A hollow fiber membrane module having a membrane area of 0.64 m ² was manufactured and used.
[0031]
The manufactured degassing apparatus was installed indoors, and an aqueous solution of 88% ethanol was degassed continuously for 48 hours. At this time, the flow rate of the liquid was 300 ml / min, and the dissolved oxygen removal rate was measured from the dissolved oxygen concentration before degassing and the dissolved oxygen concentration after degassing. In addition, the vapor concentration of ethanol in the vicinity of the apparatus was measured at intervals of 10 minutes using a Gastec GV-100S manufactured by Gastec and a detector tube for ethanol. The temperature of the liquid was 25 ° C.
[0032]
As a result, the dissolved oxygen removal rate was always 80% or more, and it was confirmed that stable operation was possible.
Moreover, the ethanol vapor concentration inside the apparatus measured by inserting the detection tube into the apparatus through the through-hole always showed 0% from the start to the end of the operation. On the other hand, the ethanol vapor concentration measured at the degassing gas outlet was about 5% on average due to the ethanol vapor contained in the exhaust of the vacuum pump.
In the observation after the end of the operation, wetting by ethanol or water was not observed inside the apparatus, and the state in which the constituent members were corroded was not recognized.
As described above, it can be confirmed that operation can be performed while preventing contact with corrosive gas inside the device by purging the inside of the device using air exhausted from the drive part of the air driven vacuum pump and always filling it with new air. It was.
[0033]
<Example 2>
A deaeration process was performed in the same manner as in Example 1 except that no casing was provided.
As a result, the dissolved oxygen removal rate was always 80% or more, and it was confirmed that stable operation was possible.
The ethanol vapor concentration in the vicinity of the vacuum pump gradually increased as the ethanol vapor contained in the exhaust of the vacuum pump diffused, and showed 4.4% after 10 hours. Although the ethanol vapor concentration at the outlet showed about 5%, it was an air-driven vacuum pump, so there was no concern of flammable explosion.
Moreover, in the observation after the end of the operation, wetting by ethanol or water was recognized inside the apparatus, and corrosion due to wetting was observed in a part of the constituent members.
As described above, it was confirmed that operation could be performed stably even in an atmosphere of flammable gas by using an air-driven vacuum pump, except for corrosion of the constituent members.
[0034]
【The invention's effect】
As described above, since the deaeration apparatus of the present invention uses a fluid-driven vacuum pump, the apparatus can be used in a flammable gas atmosphere.
In addition, by purging the inside of the casing using air exhausted from the drive part of the air-driven vacuum pump and always filling it with fresh air, the number of contact with corrosive gas can be greatly reduced. Corrosion and failure are unlikely to occur and maintenance costs can be reduced.
Moreover, since the apparatus can be reduced in size, it can be installed in the vicinity of the supply destination apparatus to greatly reduce the piping construction cost and the maintenance cost.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an example of a deaeration device of the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of a hollow fiber membrane module used in the present invention.
FIG. 3 is a cross-sectional view showing one embodiment of a hollow fiber membrane module used in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Deaeration device 2 Hollow fiber membrane module 3 Hollow fiber membrane 4 Fixing member 5 Container 6 Liquid inlet 7 Liquid outlet 8 Depressurizer 9 Vacuum pump 10 Pressure gauge 11 Gate valve 12 Leak valve 13 Filter 14 Drive air inlet 15 Drive Air outlet 16 Degassing gas discharge port 17 Through port 18 Casing

Claims (6)

In a deaeration device for treating a liquid using a membrane and a gas-driven vacuum pump , the deaeration device accommodates the membrane and the vacuum pump and has a casing having a through hole, and is exhausted from the vacuum pump. A degassing apparatus comprising a configuration in which the driving gas is once exhausted into the casing and then exhausted to the outside of the casing through the through hole . The deaeration apparatus according to claim 1, wherein the member of the vacuum pump that comes into contact with the liquid to be treated is made of at least one material of tetrafluororesin, fluororubber, and stainless steel. The deaeration according to claim 1, wherein the surface of the member in contact with the liquid to be treated of the vacuum pump is subjected to at least one surface treatment of tetrafluororesin coating, Ni plating, or cationic coating. apparatus.   The deaeration device according to claim 1, wherein the vacuum pump is a reciprocating type or a rotary type. The deaeration device according to claim 1, wherein the membrane is a hollow fiber membrane. The deaerator according to claim 5, wherein the hollow fiber membrane is a three-layer hollow fiber membrane in which both sides of a non-porous membrane are sandwiched between porous support layers.

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