JP2019188311A - Plasma sterilization water generation device - Google Patents

Abstract

To provide a plasma sterilization water generation device generating plasma sterilization water with high sterilization effect.SOLUTION: A plasma sterilization water generation device includes: a decompression chamber 1; a box-shaped water tank 2 disposed inside the decompression chamber 1 and storing water to be treated; a pair of electrodes 3 disposed inside the decompression chamber 1; and an electric power source 5 applying AC voltage to the pair of electrodes 3. The pair of electrodes 3 includes: a flat plate-shaped electrode 3a provided so as to be positioned above a water surface of water to be treated stored in the water tank 2; a dielectric substance 4 provided on a lower surface side of the flat plate-shaped electrode 3a and facing the water surface of the water to be treated stored in the water tank 2 via space; and a grounding electrode 3b provided so as to be positioned in the water to be treated stored in the water tank 2. To the decompression chamber 1, a decompression pump 1 decompressing air phase atmosphere so that an inside of the decompression chamber 1 becomes super low vacuum is connected.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a plasma sterilizing water generating device that generates plasma sterilizing water, which is used, for example, for sterilization of a vaporizing humidifier of an outside air processing air conditioner.

  In recent years, energy consumption has been greatly reduced by applying a vaporizing humidification method that saves energy compared to general steam humidification methods to outdoor air processing air conditioners (external air conditioners) used in factories in the electronics industry. Has succeeded in reducing. The demand for energy saving is also increasing for facilities having biological clean rooms such as pharmaceutical manufacturing. Therefore, it is desired to perform humidification by a vaporizing humidification method even in a biological clean room.

  In the vaporizing humidification method, humidification is performed by natural transpiration by impregnating humidifying feed water into the element part of the vaporizing humidifier and allowing air-conditioned air to pass through. Therefore, since the element part is constantly in a wet state, an environment in which microorganisms can easily propagate is obtained. In addition, it is known that the propagation of microorganisms causes a bad odor. Particularly in biological clean rooms, contamination control by microorganisms is very important, and the vaporization humidification method is not widespread due to the concern. Therefore, it was necessary to develop an effective sterilization method for the vaporizing humidifier of the external air conditioner.

  As a sterilization method, there is a method in which a chemical solution or functional water having a sterilizing power is used as water supply dripped into a vaporizing humidifier. Electrolyzed water, ozone water, or the like is used as functional water having sterilizing power. However, for example, when ozone water is used, problems such as odor due to residual components and corrosion of peripheral members have occurred. A method for sterilizing a vaporizing humidifier using an ultraviolet lamp has also been proposed. However, since the sterilization range is limited to the ultraviolet irradiation range, it is not suitable for performing a wide range of sterilization.

  In addition, microwave irradiation to vaporizing humidifiers and supply of silver ions to humidified water supply have been proposed. However, the microwave irradiation apparatus is expensive and the system becomes complicated. In addition, in order to supply silver ions, concentration control is required, and the life of an electrode which is a supply source of silver ions has been a problem.

  In response to such a background, in recent years, a sterilization method using discharge plasma has been proposed as a sterilization method without using a chemical solution or the like. In this method, sterilization is performed by using highly reactive chemically active species or ion oxidizing power generated by discharge plasma. A high bactericidal effect can be obtained only by electric energy, and since there is no persistence like a method using a chemical solution, it is applied in various fields.

JP 1999-187872 A JP 2001-252665 A

  As for sterilization using plasma, there is a method in which corona discharge is generated using an electrode and sterilization is performed using generated radicals. However, since the lifetime of radicals is short and the sterilization range is limited, it is not suitable for sterilizing the vaporizing humidifier of the external air conditioner. In addition, a method has been proposed in which a high voltage pulse is applied between electrodes in the water to be treated, and the water to be treated is subjected to dielectric breakdown, and the water to be treated is sterilized by generated radicals and shock waves. When sterilization is performed using the water to be treated, it is necessary to remove the vaporizing humidifier from the external conditioner and put it into the water tank to be treated, which increases the work load. That is, a sterilization method using plasma suitable for sterilization of a vaporizing humidifier of an external air conditioner has not been proposed yet, and its development is eagerly desired.

  The present invention has been proposed to solve the above-described problems of the prior art. An object of the present invention is to provide a plasma sterilizing water generator that generates plasma sterilizing water having a high sterilizing effect.

In order to achieve the above object, the plasma sterilizing water generator of the present invention has the following characteristics.
(1) A decompression chamber, a box-shaped water tank that is disposed inside the decompression chamber and stores water to be treated, a pair of electrodes disposed inside the decompression chamber, and an AC voltage applied to the pair of electrodes A pair of electrodes, a flat electrode provided so as to be positioned above the surface of the water to be treated stored in the water tank, and a lower surface side of the flat electrode. A dielectric that faces the surface of the water to be treated stored in the water tank via a space, and a grounding electrode that is provided so as to be located in the water to be treated stored in the water tank, The decompression chamber is connected to a decompression pump that decompresses the gas phase atmosphere so that the interior of the decompression chamber is at a very low vacuum.

(2) The power source may be configured to input power of 10 Wh or more per liter of the water to be treated.

(3) A water supply pipe for supplying pure water may be connected to the water tank.

(4) The sterilization target to which the plasma sterilizing water generated by the plasma sterilizing water generator is supplied is a vaporizing humidifier of an external air conditioner, and the water supply pipe is connected to the vaporizing humidifier in the external air conditioner. You may be connected to the humidification water supply piping which supplies pure water as dripping water.

(5) The sterilization target to which the plasma sterilization water generated by the plasma sterilization water generator is supplied is a vaporizing humidifier of an external air conditioner, and plasma sterilization water is supplied to the water tank with respect to the sterilization target A supply pipe may be connected, and the supply pipe may be connected to a humidification water supply pipe that supplies pure water as dripped water to the vaporizing humidifier in the external controller.

(6) The water tank may be made of metal and connected to the ground to form the ground electrode.

(7) The water tank may be provided with a stirring device that stirs the water to be treated stored in the water tank.

(8) The water tank may be provided with a cooling device for cooling the water to be treated, and the water to be treated during the plasma treatment may be cooled to 10 ° C. or lower.

(9) The water tank may be provided with a cooling device for cooling the water to be treated, and the generated plasma sterilizing water may be cooled to 7 ° C. or lower.

(10) The space between the dielectric and the surface of the water to be treated stored in the water tank may be 5 mm or more and 10 mm or less.

(11) A space of 50 mm or more may be provided between the inner wall surface of the water tank and the side surface of the flat electrode.

  ADVANTAGE OF THE INVENTION According to this invention, the plasma sterilization water production | generation apparatus which produces | generates the plasma sterilization water which has a high sterilization effect can be provided.

It is a block diagram which shows an example of the plasma sterilization water production | generation apparatus concerning 1st Embodiment. It is the elements on larger scale which show an example of the plasma sterilization water production | generation apparatus concerning 1st Embodiment. It is a flowchart which shows the production | generation process of plasma disinfection water. It is a graph which shows the sterilization effect of the plasma sterilization water which the plasma sterilization water production | generation apparatus concerning 1st Embodiment produced | generated. It is a graph which shows the sterilization effect of the plasma sterilization water which the plasma sterilization water production | generation apparatus concerning 1st Embodiment produced | generated, and the sterilization effect of electrolyzed water. It is a graph which shows the sterilization effect of the plasma sterilization water produced | generated in the state which cooled the to-be-processed water. It is a graph which shows the sterilization effect of the plasma sterilization water produced | generated in the state which made the input electric energy 10Wh / L. It is a graph which shows the sterilization effect of the plasma sterilization water produced | generated in the state which set input electric energy to 20 Wh / L. It is a graph which shows the sterilization effect of the plasma sterilization water produced | generated in the state which used input electric energy as 20 Wh / L or 17 Wh / L. It is a graph which shows the sterilization effect of the plasma sterilization water produced | generated using 2 L of to-be-processed water of normal temperature. It is a graph which shows the sterilization effect of the plasma sterilization water produced | generated using 2 L of to-be-processed water cooled to 2 degreeC. It is a graph which shows the sterilization effect of the plasma sterilization water produced | generated in the state which varied the cooling temperature of to-be-processed water, and input electric energy. (A) is the graph which plotted the storage temperature of plasma sterilization water, and the duration of the sterilization effect. (B) is a graph showing the result of calculating the storage temperature at which the bactericidal effect lasts 30 minutes or more. (A) is a graph which shows the storage time and sterilization effect in case the processing temperature and storage temperature of plasma sterilization water are 10 degreeC. (B) is a graph which shows the storage time and sterilization effect in case the processing temperature and storage temperature of plasma sterilization water are 7 degreeC.

[First Embodiment]
[1. overall structure]
(Outline of device configuration)
Embodiments of a plasma sterilizing water generator according to the present invention will be described with reference to the drawings.
The plasma sterilizing water generator A is a device that generates plasma sterilizing water to be supplied to the sterilization target. Plasma sterilized water is water in which radicals generated by performing plasma discharge on water to be treated are dissolved. The object to be sterilized is sterilized by the sterilizing power that these radicals have.

  In the present embodiment, a vaporizer humidifier of an external air conditioner is assumed as an example of a sterilization target. The plasma sterilizing water generator A is installed on the outside of the air conditioner or on the side, for example. The plasma sterilizing water generator A is connected to a vaporizing humidifier of an external air conditioner via a plasma sterilizing water supply pipe. The plasma sterilizing water generator A has a decompression chamber 1, a water tank 2, a pair of electrodes 3, a dielectric 4, and a power source 5. Hereinafter, each configuration will be described in detail with reference to FIG.

(Decompression chamber)
The decompression chamber 1 is a vacuum container having a pressure resistant structure made of metal or resin. An exhaust duct E having a decompression pump 1a and a valve 1b is connected to the decompression chamber 1. The exhaust duct E is a duct for discharging the gas inside the decompression chamber 1. The decompression pump 1 a is a pump for sucking and discharging the gas inside the decompression chamber 1. The valve 1b is a valve for adjusting the exhaust amount when the gas inside the decompression chamber 1 is exhausted. The decompression pump 1a and the valve 1b are connected to a control device (not shown), and the flow rate of the decompression pump 1a and the opening degree of the valve 1b are controlled by a control signal from the control device.

  Specifically, the decompression pump 1 a decompresses the gas phase atmosphere of the decompression chamber 1. Due to the decompression of the gas phase atmosphere by the decompression pump 1a, the applied voltage required for generating the dielectric barrier discharge is reduced. Here, the decompression pump 1a only needs to be able to exhaust the gas inside the decompression chamber 1 so that the dielectric strength of air is reduced to some extent and an extremely low vacuum state in which plasma can easily progress is achieved.

  The ultra-low vacuum indicates a state where the degree of decompression is 50 kPa (abs) or less, more preferably about 50 kpa (abs) to 30 kPa (abs) when the power supply voltage is 20 kV / cm. By setting the decompression chamber 1 to an extremely low vacuum, the applied voltage required for discharge can be reduced by about 50%. For example, when the decompression chamber 1 is at atmospheric pressure and an applied voltage of 30 kVpp is required, the necessary applied voltage is 14 kVpp by setting the decompression chamber 1 to an extremely low vacuum of 30 kPa (abs).

  The decompression chamber 1 only needs to have an extremely low vacuum inside, and since the water tank 2 is disposed inside the decompression chamber 1, the gas phase volume of the decompression chamber 1 is relatively small. Therefore, even if a relatively inexpensive pump having an ultimate pressure of about 20 kPa (abs) to 30 kPa (abs) and an exhaust speed of about 10 L / min is used as the decompression pump 1a, the decompression chamber 1 is brought into an extremely low vacuum state. be able to. Even if it is a relatively inexpensive and compact pump with a commercially available price of about several tens of thousands of yen, it is possible to set the gas phase volume of several tens of liters to an extremely vacuum state in a few minutes.

(Aquarium)
The water tank 2 is a metal or resin tank that is disposed inside the decompression chamber 1 and stores treated water. The water tank 2 is a box-shaped member having an opening on the upper surface. The water tank 2 has a size that can store, for example, 5 L of water to be treated. What is necessary is just to determine the storage amount of to-be-processed water in consideration of the electrode structure by a pair of electrode 3 and the dielectric material 4 mentioned later, the power supply capacity of the power supply 5, etc. When the amount of treated water stored is too large for the electrode configuration and power capacity used, plasma sterilized water having sufficient sterilizing power cannot be obtained. This embodiment demonstrates as an example the structure which can give sufficient sterilization power with respect to 5 L of to-be-processed water.

  A water supply pipe S having a valve 2 a is connected to the water tank 2. The water supply pipe S is a pipe for introducing a liquid to be treated water into the water tank 2. The valve 2a is a valve for adjusting the amount of liquid introduced. The valve 2a is connected to a control device (not shown), and the opening degree of the valve 2b is controlled by a control signal from the control device. Water to be treated such as pure water or tap water is supplied to the water tank 2 from the water supply pipe S. As treated water supplied to the water tank 2, pure water is preferably used. This is because the sterilizing power of the generated plasma sterilizing water is improved.

  When an external air conditioner to be sterilized is used in a biological clean room, pure water is generally supplied to the vaporizing humidifier of the external air conditioner as dripped water. Therefore, you may connect the water supply pipe S of the water tank 2 via the valve | bulb to the humidification water supply piping which supplies dripping water with respect to a vaporization type humidifier in an external air conditioner. By switching this valve, pure water is supplied to the vaporizing humidifier during normal operation of the external air conditioner, and pure water is supplied to the water tank 2 after the operation of the external air conditioner is completed. That is, pure water used in the external air conditioner can be supplied to the water tank 2 as water to be treated. This configuration is preferable because it is not necessary to secure a pure water supply line for the plasma sterilizing water generator A.

A supply pipe D having a valve 2b and a liquid feed pump 2c is connected to the water tank 2.
The supply pipe D is a pipe for supplying plasma sterilized water to the sterilization target. The supply pipe D may be connected to the humidification water supply pipe of the external air conditioner via a valve, for example. By switching this valve, dripping water is supplied to the vaporizing humidifier during normal operation of the external air conditioner, and plasma sterilizing water is supplied to the vaporizing humidifier after the operation of the external air conditioner is completed. When the humidifying water supply pipe of the external air conditioner is used, the plasma sterilizing water is supplied to the vaporizing humidifier through a humidifying dropping header that drops dripping water onto the vaporizing humidifier. However, the supply pipe D may be connected to a vaporizing humidifier that is a sterilization target and provided with a dedicated supply header without being connected to the humidifying water supply pipe of the external air conditioner.

  The valve 2b is a valve for adjusting the supply amount when supplying the plasma sterilizing water to the sterilization target. The liquid feed pump 2c is a pump for adjusting the flow rate of the supplied plasma sterilizing water. The valve 2b and the liquid feed pump 2c are connected to a control device (not shown), and the opening degree of the valve 2b and the flow rate of the liquid feed pump 2c are controlled by a control signal from the control device.

  The faster the supply speed of the plasma sterilizing water, the shorter the time for the sterilization process. However, when the humidifier water supply pipe and humidifying drip header of the external air conditioner are used to send the plasma sterilizing water, the flow rate of the liquid feed pump is limited by the pipe resistance of the humidifying water supply pipe and the dampening drip header. become. In that case, the opening degree of the valve 2b and the flow rate of the liquid feed pump 2c are controlled so that the maximum flow rate is within the limits of the pipe resistance of the humidification water supply pipe and the dampening drip header.

  Furthermore, you may provide the stirring apparatus which stirs to-be-processed water when there are many amounts of to-be-processed water and the water depth is 100 mm or more. Usually, since the surface of the water to be treated is shaken by the dielectric barrier discharge, it can be said that the dielectric barrier discharge has a stirring function. However, when the water depth is deep, stirring may be insufficient only by shaking due to discharge. Therefore, it is preferable to provide a propeller or the like in the water tank 2 so as to be located in the stored treated water.

  Moreover, plasma sterilization water is produced | generated in the water surface which is the vicinity of the electrode 3a mentioned later. On the other hand, as shown in FIG. 2, the plasma sterilizing water supply pipe D is often provided on the lower side of the water tank 2 due to the system configuration. Therefore, by providing a stirring device inside the water tank 2, the sterilizing power of the plasma sterilizing water supplied to the sterilization target may be kept constant.

  Furthermore, it is good also as a structure which provides a cooling device in the water tank 2 and cools to-be-processed water. When the temperature of the water to be treated rises due to plasma discharge, the sterilizing factor may be decomposed and the sterilizing effect may be reduced. In particular, when plasma treatment is performed on 2L or more of water to be treated, a rise in the temperature of the water to be treated during or after the treatment appears significantly. In addition, the temperature of the water to be treated may increase even under 2L of water to be treated due to the influence of the plasma discharge conditions of the plasma sterilizing water generator A and the temperature when the device is used. In such a case, by cooling the water to be treated, the sterilizing power of the generated plasma sterilizing water is increased by suppressing the decomposition of the sterilizing factor.

  The water to be treated is preferably cooled not only during the plasma discharge but also when storing the plasma sterilizing water generated in the plasma treatment. By cooling the water to be treated after the plasma treatment, the sterilizing power of the plasma sterilizing water can be maintained for a long time. By setting the cooling temperature of the water to be treated by the cooling mechanism to 10 ° C. or less, plasma sterilizing water having strong sterilizing power is generated. Moreover, in order to maintain the sterilizing effect of the plasma sterilizing water after the generation for a longer time, the storage temperature of the plasma sterilizing water is preferably set to 7 ° C. or less.

  From the above, it is preferable to use a chiller having a capacity of about 700 W that can cool 5 to 10 L of treated water to 10 ° C. or less in about 10 to 15 minutes. Attached to this chiller, by installing a heat exchanger for metal tubes in the water tank 2, the water to be treated in the water tank 2 can be cooled. The heat exchanger for the metal tube of the cooling mechanism may also be used as the following ground electrode 3b.

(A pair of electrodes and dielectric)
Inside the decompression chamber 1, an electrode 3a corresponding to a pair of electrodes 3 and a ground electrode 3b are arranged so as to face each other. A dielectric 4 is provided between the electrode 3a and the ground electrode 3b.

  The electrode 3a is a flat electrode and is made of metal. As the metal, for example, nickel, various stainless steels, aluminum, or copper can be used as a metal having corrosion resistance. In addition, Kovar may be used because of compatibility with glass which is an example of the dielectric 4. The size of the electrode 3a in the horizontal direction is smaller than the opening of the water tank 2 and is large enough to fit inside the water tank. That is, the area of the plane of the electrode 3a is approximately the same as the area of the water surface. Thereby, a planar dielectric barrier discharge having an area comparable to the area of the water surface is generated.

  The flat electrode 3a is preferably a disk shape or a quadrangular shape with rounded corners. By adopting a shape having no corners, electrolytic concentration on the edge portion and progress of spark discharge are prevented. From the above, the electrode 3a can be formed into a disk shape of, for example, φ150 mm. Note that heat generated by application of an AC voltage is conducted to the metal portion of the electrode 3a. Therefore, a heat sink made of metal may be installed on the upper surface of the electrode 3a to promote heat dissipation.

  The electrode 3 a is disposed on the upper side of the water tank 2. Specifically, as shown in FIG. 2, the electrode 3 a is provided so as to be positioned above the surface of the water to be treated when the water to be treated is supplied in the water tank 2 so as to be full. That is, a space is generated between the surface of the water to be treated and the electrode a.

  In the present embodiment, the lower surface side of the electrode 3 a is covered with the dielectric 4. Therefore, the dielectric 4 faces the surface of the water to be treated stored in the water tank 2 through the space. Therefore, the space between the electrode 3a and the water surface of the water to be treated actually means the space between the dielectric 4 and the water surface of the water to be treated.

  The narrower the space between the dielectric 4 and the water surface of the water to be treated, the easier it is to discharge because the resistance becomes lower. However, the plasma sterilizing water generator A may be placed in a place where fine shaking occurs, such as an upper part of an external air conditioner. Therefore, there is a possibility that the dielectric 4 and the water to be treated come into contact with the water to be treated due to vibration or the like. Therefore, it is preferable that the space between the dielectric 4 and the water surface of the water to be treated is 5 mm or more and 10 mm or less. In particular, it was confirmed that, by setting the space to 8 mm, it is possible to discharge with an appropriate applied voltage and to prevent the dielectric 4 from contacting the water to be treated.

  The dielectric 4 preferably has a relatively large dielectric constant (εr), a small dielectric loss tangent (tan δ), and a good dielectric strength (KV / mm). However, when a ferroelectric material typified by barium titanate having a relative dielectric constant exceeding several thousand is used, there is a possibility that heat generated by the dielectric effect due to application of an AC voltage reaches a high temperature. In that case, it is preferable to provide a heat dissipation mechanism such as a heat sink in the electrode 3a to dissipate heat. As for the thickness of the dielectric 4, the thinner one is easier to discharge. However, it is necessary to consider the balance between the applied voltage of the power source 5 described later and the dielectric strength of the dielectric 4. The thickness of the dielectric 4 is determined in consideration of durability and mechanical strength as the electrode 3a.

  Considering the above conditions, the dielectric 4 is made of glass (εr: 3 to 10, tan δ: 0.003), polyethylene (εr: 2 to 2.5, tan δ: to 0.0005), polypropylene ( εr: 2 to 2.3, tan δ: to 0.0005), polytetrafluoroethylene (εr: 2.0, tan δ: to 0.0002), alumite (oxalic acid alumite; εr: 6 to 10, tan δ: to 0 .001) or silicon nitride (εr: 7 to 8, tan δ: 0.0005) or the like can be used. For example, a glass plate or ceramic plate having a thickness of about 2 to 3 mm is used so that the dielectric 4 has sufficient strength, and a metal layer of about 50 μm can be deposited thereon as the electrode 3a. For example, nickel or titanium may be used as the metal to be deposited. In particular, glass and nickel are compatible with each other and can be uniformly deposited so as not to cause holes or the like in the nickel layer. It is also possible to weld to Kovar using Kovar sealing glass as the dielectric.

  The grounding electrode 3 b is disposed on the lower side of the water tank 2. In the example of FIG. 1, the water tank 2 is formed of resin, and the ground electrode 3 b is provided at a position where it is submerged in the water to be treated stored in the water tank 2. The discharge current of the dielectric barrier discharge is configured to flow to the ground electrode 3b through the water to be treated.

  The material of the ground electrode 3b may be a metal, and its shape can be freely changed. However, it is configured so that the discharge current of the dielectric barrier discharge can be reliably guided to the ground. As will be described later, it has become clear from experiments that the water to be treated has a pH of about 3 due to the influence of nitric acid generated by plasma. Therefore, when the ground electrode 3b is submerged in the non-treated water of the water tank 2, for example, stainless steel may be used as a metal that is excellent in corrosion resistance in water and relatively resistant to nitric acid.

  In addition, when the water tank 2 is formed of metal, the water tank 2 may be provided with the function of the ground electrode 3b by connecting the water tank 2 to the ground. That is, the ground electrode 3b disposed in the water to be treated 2 includes the water tank 2 itself. However, when the water tank 2 is made of metal, when the inner wall surface of the water tank 2 exposed to the gas phase side from the water surface of the water to be treated becomes extremely close to the electrode 3a, a spark discharge is generated toward the inner wall surface of the water tank 2. It is possible to do.

  Therefore, as shown in FIG. 2, a predetermined distance may be secured between the side surface of the electrode 3 a and the inner wall surface of the water tank 2. This distance varies depending on the voltage applied to the electrode 3a, the thickness of the dielectric 4, and the atmospheric pressure of the decompression chamber 1, but considering that the air insulation is 30 kV per cm, spark discharge is ensured by securing 50 mm or more. Can be prevented. Moreover, you may carry out insulation coating of the part exposed to the gaseous phase of the inner wall face of the water tank 2 using the resin coating 2d.

(Power supply)
The power source 5 is a high-voltage power source that applies an AC voltage for generating a dielectric barrier discharge to the pair of electrodes 3. As the power source 5, an AC alternating frequency of several kHz to several tens of kHz, an applied voltage of about 10 kV _0-p (2 to 3 kV / cm) at maximum, and a power source capacity of about 500 VA can be used. The power source 5 may be appropriately selected in consideration of the capacity of the water to be treated and the like, when the voltage application time is 30 minutes or less, and the power source capable of obtaining the peak of the sterilizing power of the plasma sterilizing water. The power source 5 is provided outside the decompression chamber 1 and is connected to the electrode 3a.

The circuit configuration of the power supply, a sine wave of several kHz~ tens kHz, a triangular wave, a pulse wave, 10 kV _0-p may be one (2 to 3 kV / cm) of about AC voltage can be generated. The higher the applied voltage is, the higher the processing efficiency is. However, since the gas phase portion in the decompression chamber 1 is decompressed to an extremely low vacuum of 50 kPa or less, an applied voltage of about 10 kV _0-p (2 to 3 kV / cm). Can develop the plasma.

  Here, the power supply 5 is configured to supply power of 10 Wh or more, more preferably 20 Wh or more, to 1 L of water to be treated. For example, 20 Wh of electric power can be supplied to 1 L of water to be treated by treating 3 L of water to be treated at 180 W for 20 minutes. In addition, when the same electric energy is input, even if the electric power and the input time are different, the same sterilizing effect can be obtained if the total input electric energy is the same. In the plasma sterilizing water generating apparatus A of the present embodiment, plasma treated water having a sterilizing effect is generated when electric power of 10 Wh / L or more is input. The sterilization effect of the generated plasma sterilizing water is improved by setting the electric power to be input to 20 Wh / L or more. The input power can be monitored by installing a power meter in the power system.

[2. Sterilization water generation process]
The plasma sterilizing water generator A having the above-described configuration generates plasma sterilizing water through the following steps as shown in FIG.
(1) To-be-processed water supply process to water tank 2 (2) Depressurization process of decompression chamber 1 (3) Plasma treatment process by dielectric barrier discharge (4) Atmospheric pressure release process of decompression chamber 1 (5) Supply of plasma sterilization water Process

  The vaporization type humidifier which is a sterilization target in the present embodiment is a humidifier that humidifies gas by blowing air to an element portion such as a humidified filter. This humidifying filter absorbs about 5 to 15 L of liquid. A typical external air conditioner is often provided with two humidifying filters. Therefore, in the following sterilizing water generation step, a configuration and conditions suitable for generating 30 L of plasma sterilizing water are described as an example.

  In addition, it is assumed that sterilization of the vaporizing humidifier with plasma sterilizing water is performed at night or the like after the operation of the external air compressor. Therefore, the 30 L plasma sterilizing water does not necessarily have to be generated at one time. The plasma sterilized water may be generated several times by dividing into several L and supplied to the vaporizing humidifier each time. In the following description, the processing step of generating 30 L of plasma sterilizing water by generating 5 L of plasma sterilizing water six times will be described in detail.

  The power supply capacity necessary for generating 5 L of plasma sterilizing water is a power supply capacity of 500 VA to 1000 VA. In addition, a disk-shaped electrode 3a having a diameter of about 150 mm is used, and the dielectric 4 is preferably made of glass. The thickness of the glass that is the dielectric 4 was set to 2 to 3 mm in consideration of the electrode capacity, and had sufficient strength.

(Processed water supply process)
In the to-be-treated water supply step, 5 L of pure water as the to-be-treated water is supplied to the water tank 2. That is, the valve 2a of the water tank 2 is opened by a control signal from the control device. By opening the valve 2a, pure water is supplied to the water tank 2 via the water supply pipe S of the water tank 2 connected to the humidifying water supply pipe of the external air conditioner. Here, when 5 L of pure water is supplied to the water tank 2, the valve 2a is returned to the closed state by a control signal from the control device.

(Decompression step)
In the depressurization step, the gas inside the depressurization chamber 1 is exhausted to make the depressurized state. That is, the valve 1b of the decompression chamber 1 is opened by a control signal from the control device. When the valve 1b is opened, the decompression pump 1a is operated by a control signal from the control device. The decompression pump 1a sucks and discharges the gas inside the decompression chamber 1 until the decompression chamber 1 is in an extremely low vacuum state. Here, extremely low vacuum means a state where the degree of decompression is 50 kPa or less. After the decompression chamber 1 is in an extremely low vacuum state, the control device stops the decompression pump 1a and closes the valve 1b.

(Plasma treatment process)
In the plasma processing step, plasma is generated by dielectric barrier discharge in a space between the electrode 3a covered with the dielectric 4 and the surface of the water to be treated. That is, when a high voltage from the power source 5 is applied to the electrode 3 a, plasma is generated in the space between the water surface of the water to be treated and the dielectric 4. Since the water to be treated is electrically connected to the ground electrode 3 b, plasma is generated in the space between the water surface of the water to be treated and the dielectric 4. Since the radicals are generated in the water to be treated by the plasma generated in the gas phase, plasma sterilized water can be obtained.

(Atmospheric pressure release process)
In the atmospheric pressure release process, the reduced pressure in the reduced pressure chamber 1 is released to the atmospheric pressure. That is, the valve 1b of the decompression chamber 1 is opened by a control signal from the control device.

(Plasma sterilizing water supply process)
In the plasma sterilizing water supply step, the generated plasma sterilizing water is supplied to the vaporizing humidifier of the external air conditioner. That is, the valve 2b of the water tank 2 is opened by a control signal from the control device. When the valve 2b is opened, the liquid feed pump 2c is operated by a control signal from the control device. The liquid feed pump 2c sucks and discharges the plasma sterilizing water inside the water tank 2 until 5 L of plasma sterilizing water stored in the water tank 2 is discharged. Since the plasma sterilizing water supply pipe D is connected to the humidifying water supply pipe of the external air conditioner, the plasma sterilizing water discharged from the water tank 2 is supplied to the vaporizing humidifier of the external air conditioner. Sterilize. And when all the plasma sterilization water inside the water tank 2 is discharged, the valve 2b is returned to the closed state by the control signal from the control device.

  By repeating the plasma sterilizing water generation process as described above six times, a total of 30 L of plasma sterilizing water is generated and supplied to the vaporizing humidifier of the external air conditioner. In addition, the drain pan is provided in the lower part of the vaporization type humidifier of an external air conditioner. Therefore, the plasma sterilizing water dripped from the vaporizing humidifier is discharged to the outside of the external air conditioner through this drain pan. Although the pH of the plasma sterilizing water is low, the plasma sterilizing water is sufficiently diluted with pure water supplied to the vaporizing humidifier during normal operation.

[3. About the sterilization principle of plasma sterilization water]
Below, the principle which the plasma sterilization water which the plasma sterilization water production | generation apparatus of this embodiment produced | generated sterilizes the sterilization object is demonstrated.

First, representative examples of radicals generated by a plasma gas phase, hydroxyl radicals (OH ·) and the superoxide anion radicals (O 2 _- ^·), include the hydroperoxy radicals (HOO ·). These radicals are dissolved and diffused in the plasma sterilizing water to exert sterilizing power. According to research so far, hydroxy radicals (OH.) Having a high sterilizing power have a very short life and hardly diffuse into the liquid to be sterilized. On the other hand, the superoxide anion radical (O ₂ ^−. ) Can exist in water for several seconds, and as shown in the formula (1), it reacts with hydrogen ions (H ⁺ ) in the liquid to give hydroperoxy having extremely high bactericidal activity. A radical (HOO.) Is formed. And it is supposed that the bacteria in a liquid are sterilized by this hydroperoxy radical (HOO *).
[O ₂ ⁻ ·] + [H ⁺ ] ⇔ [HOO ·] (1)

  The acid dissociation constant of this equilibrium reaction is pKa 4.8. Therefore, in the state where the pH in the liquid is lower than 4.8, the reaction of the formula (1) proceeds to the right, and the hydroperoxy radical (HOO) increases. Therefore, in the conventional plasma sterilizing water generating apparatus, plasma sterilizing water having a desired sterilizing power is obtained by adjusting the pH of the liquid to 4.8 or less in advance.

  Also in the plasma sterilized water obtained in the present embodiment, it is considered that radicals generated by the gas-phase dielectric barrier discharge are dissolved and diffused in the water to be treated to obtain sterilizing power. The bactericidal factor seems to be hydroperoxy radical (HOO). Here, in the plasma sterilizing water generating apparatus A of the present embodiment, the nitrogen content contained in the gas phase is oxidized by the dielectric barrier discharge acting on the gas phase inside the decompression chamber 1, and finally the water is treated. It has been confirmed that it dissolves as nitric acid. Therefore, as shown in Table 1, it was confirmed from experimental data that the pH was automatically lowered to around 3.

As is clear from Table 1, the plasma sterilized water subjected to dielectric barrier discharge for 30 minutes in the plasma sterilized water generator A contains 500 ppm or more of nitric acid, and the pH drops to around 3.1. Was. From the above measurement results, in the plasma sterilizing water generator A of the present embodiment, the pH of the water to be treated is 4.8 or less, so that a high sterilizing effect can be obtained without taking a procedure for adjusting the pH in advance. can do.

Next, in a conventional research, pernitric acid (peroxynitric acid: HOONO ₂ ) is shown as a supply source of hydroperoxy radical (HOO.) Having a high bactericidal power. Chemistry over nitric synthesized by such (HOONO _2), as shown in equation (2), hydrogen ions ^(H +) in the liquid, superoxide anion radicals _{(O 2} ^- ·), nitrogen dioxide (NO ₂ ·) are to be generated, etc., resulting superoxide anion radicals (O 2 _- ^·), when sterilizing power generates a high hydroperoxy radicals germicidal under strongly acidic conditions (HOO ·) is obtained Has been.
[HOON ₂ ] ⇔ [H ⁺ ] + [O ₂ ⁻ ·] + [NO ₂ ·] (2)

The production mechanism of pernitric acid (HOONO ₂ ) is as shown in equations (3) to (5). That is, nitrous acid (HNO ₂ ) and hydrogen peroxide (H ₂ O ₂ ) react to produce peroxynitrite (HOONO). Then, it reacts with hydrogen ions (H ⁺ ) under acidic conditions to generate nitronium ions (NO ₂ ⁺ ) and water (H ² O). Furthermore, a reaction in which nitronium ion (NO ₂ ⁺ ) reacts with hydrogen peroxide (H ₂ O ₂ ) to produce pernitric acid (HOONO ₂ ) and hydrogen ion (H ⁺ ) proceeds under strong acidity. ing.
[HNO ₂ ] + [H ₂ O ₂ ] → [HOONO] (3)
[HOONO] + [H ⁺ ] ⇔ [NO ₂ ⁺ ] + [H ² O] (4)
[NO ₂ ⁺ ] + [H ₂ O ₂ ] ⇔ [HOONO ₂ ] + [H ⁺ ] (5)

Here, in general, various reaction products are generated in the discharge field of the atmospheric pressure plasma, and it is reported that hydrogen peroxide (H ₂ O ₂ ) and nitrous acid (HNO ₂ ) are included in the reaction product. Yes. As described in Table 1 above, in the plasma sterilized water generated by the plasma sterilized water generating apparatus A of the present embodiment, it is confirmed that hydrogen peroxide (H ₂ O ₂ ) and nitric acid (HNO ₃ ) are contained. . Accordingly, dielectric barrier discharge acts on the water to be treated, thereby generating nitrous acid (HNO ₂ ) and hydrogen peroxide (H ₂ O ₂ ), which are precursors of pernitric acid (HOONO ₂ ). By the formation of the precursor is believed that excessive nitrate (HOONO ₂₎ is generated in the water to be treated.

As described above, the pH of the plasma sterilizing water generated by the plasma sterilizing water generating apparatus A is under a strong acidity around 3.1. Accordingly, pernitric acid (HOONO ₂ ) is generated by nitrous acid (HNO ₂ ) and hydrogen peroxide (H ₂ O ₂ ) by dielectric barrier discharge, and is dissolved in the water to be treated. These substances are considered to be a source of hydroperoxy radical (HOO) having high bactericidal activity.

[4. Experiment]
(1) Experiment using room-temperature plasma sterilization water The results of verifying the sterilization effect of the plasma sterilization water generated by the plasma sterilization water generator A of the present embodiment are shown below. The plasma sterilizing water used in the experiment was generated using 1 L of pure water at room temperature (about 25 ° C.) as the water to be treated. The degree of decompression of the decompression chamber 1 is 50 kPa (abs), a dielectric barrier discharge is generated by a sine wave generated at an alternating frequency of the power source 5 of 20 kHz and an applied voltage of 10 kV _0-p (18 kV _p-p ). . The voltage application time, that is, the plasma generation time was 30 minutes.

The experiment was performed by preparing four ampoules obtained by collecting 1 mL of an Escherichia coli (ATCC 13706) suspension adjusted to a concentration of about 10 ⁸ CFU / mL. Of ampoule, a pure water to one was added to diluted 10-fold 9 mL, was used as a control sample at a concentration of about ¹⁰ 8 CFU / mL. To the remaining 3 ampoules, 9 mL of plasma sterilized water was added and diluted 10 times to obtain a test specimen. For the test specimens, each test specimen was prepared using three types of plasma sterilized water: plasma sterilized water immediately after generation, plasma sterilized water 30 minutes after generation, and plasma sterilized water 60 minutes after generation. After culturing the control specimen and three kinds of test specimens, the number of colonies was counted.

  The results of counting the number of colonies are shown in FIG. As shown in FIG. 4, the number of viable bacteria in the test sample using the plasma sterilized water immediately after the plasma treatment is reduced by 6 digits or more compared to the control sample, and the plasma sterilized water immediately after the generation has a strong sterilizing power. I understand that. Moreover, in the test sample using plasma sterilized water 30 minutes after the plasma treatment, the number of viable bacteria was reduced by 5 digits or more compared to the control sample, and it had a sufficiently high sterilizing power. On the other hand, in the test specimen using plasma sterilized water 60 minutes after the plasma treatment, it can be seen that the sterilizing power is reduced as compared with the other two types of plasma sterilized water.

  From the above results, it was confirmed that the sterilizing effect of the normal temperature plasma sterilized water generated by the plasma sterilized water generating apparatus A of the present embodiment continues for about 30 minutes after the plasma treatment is completed.

(2) Experiment about the sterilization effect of plasma sterilization water The sterilization effect of the plasma sterilization water which the plasma sterilization water production | generation apparatus A of this embodiment produced | generated and the sterilization effect of the commercially available electrolytic water used for a sterilization use were compared. The electrolyzed water used as a comparison object is also used for sterilization of the vaporizing humidifier of the external air conditioner, and is slightly acidic hypochlorous acid water (HCLO) around pH 6. The plasma sterilizing water used in the following experiments was generated using 500 mL of pure water. The conditions of the decompression chamber 1 are the same as those in the experiment (1). The voltage application time, that is, the plasma generation time was 10 minutes.

  The experimental method is the same as the above two experiments, and 1 mL of E. coli (ATCC 13706) suspension was used as a control sample, 9 mL of pure water, and as a test sample, plasma sterilized water generated by the plasma sterilized water generator A of the present embodiment. 9 mL and the comparative sample were each diluted 10 times with 9 mL of electrolyzed water (slightly acidic hypochlorous acid water). These three specimens were cultured and the number of colonies was counted.

  From FIG. 5, the viable cell counts of the test sample and the comparative sample decreased by 6 digits or more compared to the control sample, and reached the detection limit. Thus, the plasma sterilized water generated by the plasma sterilized water generator A of the present embodiment is equivalent to a commercially available electrolyzed water (slightly acidic hypochlorous acid water) used for sterilization of a vaporizing humidifier. Proven to have a bactericidal effect.

(3) Experiment using low-temperature treated water Plasma sterilized water produced using treated water at room temperature (about 25 ° C) and plasma sterilized produced using treated water in a cooled state (about 5 ° C) The sterilizing power of water was compared. The plasma sterilizing water used in the experiment was generated using 500 mL of pure water. The conditions of the decompression chamber 1 are the same as those in the experiment (1). The voltage application time, that is, the plasma generation time was 10 minutes.

The experiment was performed by preparing eight ampoules obtained by collecting 1 mL of an Escherichia coli (ATCC 13706) suspension adjusted to a concentration of about 10 ⁸ CFU / mL. The control sample was prepared in the same manner as (1) above. The same sample was prepared with cooled pure water and used as a control sample when cooled. In addition, 9 mL of plasma sterilized water was added to the three ampoules and diluted 10 times to obtain test specimens. For the test specimens, each test specimen was prepared using three types of plasma sterilized water: plasma sterilized water immediately after generation, plasma sterilized water 30 minutes after generation, and plasma sterilized water 60 minutes after generation. Further, three ampoules were prepared with various plasma sterilized water produced by cooling the same one, and used as test specimens when cooled. After culturing 2 types of control samples and 6 types of test samples, the number of colonies was counted.

  The results of counting the number of colonies are shown in FIG. In FIG. 6, the result when the to-be-processed water was normal temperature and the case where it cooled is shown side by side. First, plasma sterilization water produced using normal water to be treated has a high sterilization power for about 30 minutes after the plasma treatment, but after 60 minutes, the sterilization effect was significantly reduced. On the other hand, in the plasma sterilized water generated using the water to be treated cooled to about 5 ° C., the bacteria were reduced by 5 digits or more with respect to the control specimen even after 60 minutes had passed after the plasma treatment.

  As above-mentioned, pernitric acid is contained in the plasma sterilization water which the plasma sterilization water production | generation apparatus A produces | generates as a sterilization factor. Since this pernitric acid disappears as the temperature rises, it is considered that the sterilization factor could be extended by cooling the water to be treated. From the above results, it was found that the sustainability of the sterilizing effect of the generated plasma sterilizing water can be improved by performing the plasma treatment while keeping the water temperature of the water to be treated low.

(4) Experiment on input electric energy for water to be treated A result of verifying the relationship between the electric energy input by the plasma sterilizing water generator A of the present embodiment and the sterilizing effect of the generated plasma sterilizing water is shown below. The plasma sterilizing water used in the first experiment was generated using 4 L of pure water cooled as water to be treated. The conditions of the decompression chamber 1 are the same as those in the experiment (1). And the power supply 5 applied 240-w electric power with respect to the to-be-processed water 4L for 10 minutes. That is, the input power amount in the first experiment is 10 Wh / L.

The experiment was performed by preparing 10 ampoules obtained by collecting 1 mL of an E. coli (ATCC 13706) suspension adjusted to a concentration of about 10 ⁸ CFU / mL. Half of the 5 ampoules were added 9 mL of pure water and diluted 10-fold to obtain a control sample having a concentration of about 10 ⁸ CFU / mL. To the remaining 5 ampoules, 9 mL of plasma sterilized water was added and diluted 10 times to obtain a test specimen. About the test specimen, each test specimen was created using plasma sterilized water immediately after generation. After culturing the control sample and the test sample, the number of colonies was counted.

  The results of counting the number of colonies are shown in FIG. FIG. 7 shows that although there are variations in the bactericidal effect, the number of viable bacteria of 3 to 6 digits is reduced and has a bactericidal power. From the above results, the plasma sterilizing water having sterilizing power can be generated by setting the power source 5 of the plasma sterilizing water generating apparatus A of the present embodiment to a power of 10 Wh to the treated water 1L. It was confirmed that there was.

  Next, a second experiment was performed by increasing the amount of power input by the power source 5. The plasma sterilizing water used in the second experiment was generated using 3 L of pure water cooled as water to be treated. The conditions of the decompression chamber 1 are the same as those in the experiment (1). The power source 5 applied 180 W of power to the treated water 3L for 20 minutes. That is, the input power amount in the second experiment is 20 Wh / L.

The experiment was performed by preparing 14 ampoules obtained by collecting 1 mL of an E. coli (ATCC 13706) suspension adjusted to a concentration of about 10 ⁸ CFU / mL. Half of the seven ampoules were diluted 10-fold by adding 9 mL of pure water to serve as a control sample having a concentration of about 10 ⁸ CFU / mL. To the remaining 7 ampoules, 9 mL of plasma sterilized water was added and diluted 10-fold to prepare test specimens. About the test specimen, each test specimen was created using plasma sterilized water immediately after generation. After culturing the control sample and the test sample, the number of colonies was counted.

  The results of counting the number of colonies are shown in FIG. From FIG. 8, it can be seen that in the second experiment, viable bacteria are reduced by 6 orders of magnitude or more in almost all specimens except one, and has a very high bactericidal power. From the above results, the power source 5 of the plasma sterilizing water generating apparatus A of the present embodiment is configured to apply 20 Wh of power to 1 L of water to be treated, so that plasma sterilizing water having higher sterilizing power can be reliably obtained. It was confirmed that it can be generated.

(5) Examination of the amount of electric power supplied to the water to be treated The electric power supplied by the power source 5 of the plasma sterilizing water generating apparatus A of the present embodiment and the influence on the generated plasma sterilizing water were examined. Specifically, as plasma sterilizing water A, sterilizing water in which 180 W of power was applied for 20 minutes to 3 L of pure water cooled as water to be treated was prepared. The amount of power input to the plasma sterilizing water A is 20 Wh / L. Moreover, as the plasma sterilizing water B, sterilizing water was prepared by applying 400 W of power for 10 minutes to 4 L of pure water cooled as water to be treated. The amount of power input to the plasma sterilizing water B is 17 Wh / L.

The experiment was performed by preparing 10 ampoules obtained by collecting 1 mL of an E. coli (ATCC 13706) suspension adjusted to a concentration of about 10 ⁸ CFU / mL. Five ampoules were added 10 mL of pure water and diluted 10-fold to obtain a control sample having a concentration of about 10 ⁸ CFU / mL. Among the remaining ampoules, 9 mL of plasma sterilized water A was added to three ampoules and diluted 10 times to obtain test specimens. In addition, 9 mL of plasma sterilized water B was added to the two ampoules and diluted 10 times to obtain test specimens. About the test specimen, each test specimen was created using plasma sterilized water immediately after generation. After culturing the control sample and the test sample, the number of colonies was counted.

  The results of counting the number of colonies are shown in FIG. From FIG. 9, it can be seen that in both cases where the plasma sterilizing water A and the plasma sterilizing water B are used, viable bacteria are reduced by 6 digits or more and have a very high sterilizing power. . That is, it was confirmed that plasma sterilizing water having sterilizing power based on the total amount of electric power can be generated even when the electric power and the input time are different if almost the same amount of electric power is applied.

(6) Experiment on amount of water to be treated and water temperature As the experiment described in (1) above, when the amount of water to be treated is 1 L or less, plasma sterilizing water having sterilizing power even if plasma treatment is performed at room temperature It was possible to generate Therefore, in this experiment, the sterilizing power of room temperature plasma sterilized water generated by increasing the temperature of the treated water to 2 L of normal water (about 25 ° C.) was verified.

  The conditions of the decompression chamber 1 are the same as those in the experiment (1). First, the power source 5 applied 180 W electric power for 20 minutes to 2 L of normal water to be treated was designated as room temperature plasma sterilizing water C. Next, the power source 5 applied 180 W electric power for 30 minutes to 2 L of normal water to be treated was designated as room temperature plasma sterilizing water D.

The experiment was performed by preparing five ampoules obtained by collecting 1 mL of an Escherichia coli (ATCC 13706) suspension adjusted to a concentration of about 10 ⁸ CFU / mL. The control sample was prepared in the same manner as (1) above. The remaining four ampoules were each diluted 10-fold by adding 9 mL of plasma sterilized water C and D that was allowed to stand for 1 minute after generation, and 9 mL of plasma sterilized water C and D that was allowed to stand for 30 minutes after generation, did. After culturing the control sample and the test sample, the number of colonies was counted.

  The results of counting the number of colonies are shown in FIG. In FIG. 10, the number of colonies of the control specimen is indicated by a dotted line at the top of the graph. As shown in FIG. 10, neither the plasma sterilized water C nor the plasma sterilized water D had sufficient sterilizing power regardless of the standing time. In addition, even if plasma sterilization water was produced | generated by making input electric energy into 330Wx20 minutes and 330Wx30 minutes with respect to 2L of to-be-processed water, the bactericidal effect was not able to be acquired. This result was thought to be caused by the need to increase the plasma power when the amount of water to be treated increased, and the water temperature after treatment being increased. In the said experiment, although the temperature of the to-be-processed water before a plasma process start was about 20 degreeC, the temperature of the to-be-processed water after a process was 30-40 degreeC. It was expected that the bactericidal factor was decomposed and the bactericidal effect was lost due to the rise in water temperature due to plasma discharge.

  Therefore, the same experiment was performed by cooling 2 L of pure water to 2 ° C. during the plasma treatment step. First, what the power supply 5 applied 180-watt electric power with respect to the to-be-processed water for 10 minutes was used as the plasma sterilization water E of normal temperature. Next, a power source 5 that applied 180 W of power to the water to be treated for 20 minutes was used as plasma sterilizing water F at room temperature. Finally, the power source 5 applied 180 W of power to the water to be treated for 30 minutes was designated as plasma sterilized water G at room temperature.

The experiment was performed by preparing 13 ampoules obtained by collecting 1 mL of an Escherichia coli (ATCC 13706) suspension adjusted to a concentration of about 10 ⁸ CFU / mL. The control sample was prepared in the same manner as (1) above. Of the remaining 12 ampoules, 9 mL of plasma sterilized water E, which was allowed to stand for 1 minute after generation, was added to the ampules and diluted 10-fold to prepare test specimens. To the other two ampoules, 9 mL of plasma sterilized water F, which was allowed to stand for 1 minute after generation, was added and diluted 10-fold to prepare test specimens. In addition, 9 mL of plasma sterilized water G that was allowed to stand for 1 minute after the production was added to the other two ampoules and diluted 10 times to obtain test specimens. Further, for the remaining six amplifiers, test specimens were similarly prepared using plasma sterilized waters E, F, and G that were allowed to stand for 30 minutes after generation. After culturing the control sample and the test sample, the number of colonies was counted.

  The results of counting the number of colonies are shown in FIG. From FIG. 11, in the plasma sterilized water that was allowed to stand for 1 minute after generation, viable bacteria were reduced by 5 digits or more, and a sufficient sterilizing effect was obtained. In particular, in the plasma sterilizing waters F and G in which the power input amount is 30 Wh / L or more, it was found that viable bacteria decreased by 6 digits or more, and plasma sterilizing water having a strong sterilizing effect was obtained. When the water to be treated was 2 L or more, it was confirmed that the plasma sterilizing water having a sterilizing effect could be generated by cooling the water to be treated.

  Moreover, the sterilization effect was not acquired in the plasma sterilization water left still for 30 minutes after production | generation from FIG. In this experiment, since the water to be treated was cooled only during the plasma treatment, the temperature of the plasma sterilizing water increased during the standing and the sterilizing factor was considered to be decomposed.

(7) Experiment on cooling temperature and input electric energy In the plasma sterilizing water generating apparatus A of the present embodiment, the cooling temperature by the cooling mechanism and the influence of the input electric energy on the generated plasma sterilizing water were examined. The conditions of the decompression chamber 1 are the same as those in the experiment (1). The plasma sterilizing water H was obtained by applying a power of 180 W for 10 minutes to 3 L of water to be treated cooled to 2 ° C. The plasma sterilized water I was obtained by applying a power of 180 W for 20 minutes to 3 L of water to be treated cooled to 2 ° C. The plasma sterilized water J was obtained by applying a power of 180 W for 30 minutes to 3 L of water to be treated cooled to 2 ° C.

  The power source 5 was plasma sterilized water K obtained by applying 180 W of power to 3 L of water to be treated cooled to 10 ° C. for 10 minutes. The power source 5 was plasma sterilized water L obtained by applying 180 W of power to 3 L of water to be treated cooled to 10 ° C. for 20 minutes. The plasma sterilizing water M was obtained by applying 180 W of power to the treated water 3L cooled to 10 ° C. for 30 minutes.

The experiment was performed by preparing seven ampoules obtained by collecting 1 mL of an Escherichia coli (ATCC 13706) suspension adjusted to a concentration of about 10 ⁸ CFU / mL. The control sample was prepared in the same manner as (1) above. To the remaining 6 ampoules, 9 mL each of plasma sterilizing water H and K with a discharge time of 10 minutes, plasma sterilizing waters I and L with a discharge time of 20 minutes, and plasma sterilizing waters J and M with a discharge time of 30 minutes were added. The test specimen was diluted 10 times. About the test specimen, each test specimen was created using plasma sterilized water immediately after generation. After culturing the control sample and the test sample, the number of colonies was counted.

  The results of counting the number of colonies are shown in FIG. In FIG. 12, the number of colonies of the control sample is indicated by a dotted line at the top of the graph. From FIG. 12, comparing the plasma sterilized water H and G in which the power input was 15 Wh / L, the plasma sterilized water H in which the water to be treated was cooled to 2 ° C. showed a decrease in viable bacteria by 5 digits or more. The bactericidal effect was obtained. On the other hand, in the plasma sterilizing water K in which the water to be treated was cooled to 10 degrees, a sufficient sterilizing effect was not obtained.

  On the other hand, in the plasma sterilized waters I, L, J, and M in which the power input amount is 20 Wh / L or more, viable bacteria are reduced by 6 digits or more regardless of the cooling temperature, and an excellent sterilizing effect is obtained. It was. From the above results, it was confirmed that the cooling temperature is preferably lower than 10 ° C. Moreover, it turned out that the plasma sterilization water with high sterilization power can be produced | generated by making electric power input amount into 20 Wh / L.

(8) Experiment on storage temperature of plasma sterilization water From the experiment of (6) above, it was found that even if the plasma treatment was performed after cooling, the sterilization effect was reduced when left standing for 30 minutes. Therefore, the storage temperature of plasma sterilizing water was further examined. FIG. 13A shows the results of measuring the duration of the sterilizing effect of plasma sterilizing water with the same plasma sterilizing water at storage temperatures of 5 ° C., 12 ° C., 14 ° C., and 20 ° C. From this result, it was found that the lower the cooling temperature, the longer the duration of the bactericidal effect.

  From the result of FIG. 13 (a), the graph of FIG. 13 (b) was created, and the relationship between the duration of the sterilization effect and the storage temperature was determined. In order to maintain the sterilization effect for 30 minutes, it was cooled to 7 ° C. or lower. I found it necessary to do. The plasma sterilization water generated by the plasma sterilization water generator A needs to maintain a certain degree of sterilization effect in consideration of the supply speed to the sterilization target. It turned out that it can be set as the structure which considered supply time by making the storage temperature of plasma disinfection water into 7 degrees C or less.

(9) Experiment on cooling temperature and storage temperature during plasma treatment From the experiment of (7) above, it was found that the cooling temperature during plasma treatment is preferably 10 ° C. or less. Moreover, it turned out that it is preferable that the storage temperature of the produced | generated plasma disinfection water shall be 7 degrees C or less from the experiment of said (8). In order to make the cooling energy common at the time of generation and storage, the processing temperature and the storage temperature were made common at 10 ° C. and 7 ° C. and verified.

  FIG. 14A is a graph showing the relationship between the storage time and the bactericidal effect when the processing temperature and the storage temperature are both 10 ° C. FIG. 14 (a) shows that under the conditions of 10 ° C. treatment and 10 ° C. storage, although there is a high sterilization effect after the plasma treatment, there is also a variation and the sterilization effect is weakened with time. Moreover, FIG.14 (b) is a graph which shows the relationship between storage time and a bactericidal effect when processing temperature and storage temperature are both 7 degreeC. From FIG. 14 (b), under the conditions of 7 ° C. treatment and 7 ° C. storage, even after 30 minutes have passed immediately after the plasma treatment, the number of viable bacteria has decreased by 6 digits or more, and the sterilizing effect of the plasma sterilizing water is high. It was found to be sustained. From the above, it has been confirmed that when the processing temperature and the storage temperature are made common, it is preferable that the cooling temperature of both is preferably 7 ° C. or less based on the storage temperature.

[5. Effect]
The effects of the plasma sterilizing water generator of the present embodiment as described above are as follows.
(1) A decompression chamber 1, a box-shaped water tank 2 that is disposed inside the decompression chamber 1 and stores water to be treated, a pair of electrodes 3 disposed inside the decompression chamber 1, and a pair of electrodes 3 A pair of electrodes 3, a flat electrode 3 a provided so as to be positioned above the surface of the water to be treated stored in the water tank 2, and a flat electrode The dielectric 4 provided on the lower surface side of 3a and facing the water surface of the water to be treated stored in the water tank 2 through the space, and the ground electrode provided to be located in the water to be treated stored in the water tank 2 The decompression chamber 1 is connected to a decompression pump 1a that decompresses the gas phase atmosphere so that the interior of the decompression chamber 1 is at a very low vacuum.

  With the above configuration, it is possible to generate plasma by dielectric barrier discharge in the space between the electrode 3a covered with the dielectric 4 and the surface of the water to be treated. Since the radicals are generated in the water to be treated by the plasma generated in the gas phase, plasma sterilized water having a high sterilizing effect can be obtained.

  Further, the decompression pump 1a decompresses the gas phase atmosphere in the decompression chamber 1, so that the applied voltage required for generating the dielectric barrier discharge is lowered. The decompression of the gas phase atmosphere only requires that the decompression chamber 1 be in an extremely low vacuum state, so that the decompression chamber 1 can be brought into an extremely low vacuum state even if a relatively inexpensive pump is used.

(2) The power source 5 is configured to input power of 10 Wh or more per 1 L of water to be treated.

  By making the input power of the power source 5 10 Wh / L, plasma sterilized water having a sterilizing effect can be obtained. Even if the input power and the input time are different, plasma sterilizing water having the same sterilizing effect can be obtained if the total input power amount is the same. Therefore, the sterilizing effect of the obtained plasma sterilizing water can be controlled by the input power.

(3) A water supply pipe S for supplying pure water is connected to the water tank 2.

  By using pure water as the water to be treated, the sterilizing effect of the generated plasma sterilizing water can be enhanced.

(4) The sterilization target to which the plasma sterilizing water generated by the plasma sterilizing water generating apparatus A is supplied is a vaporizing humidifier of an external air conditioner, and a water supply pipe S is supplied with pure water to the vaporizing humidifier in the external air conditioner. Is connected to a humidified water supply pipe for supplying water as dripping water.

  By connecting the water supply pipe S to the humidified water supply pipe, pure water used in the external air conditioner can be supplied to the water tank 2 as water to be treated. Therefore, since it is not necessary to secure a pure water supply line for the plasma sterilizing water generator A, it is possible to provide a plasma sterilizing water generator A having a simpler structure.

(5) The sterilization target to which the plasma sterilization water generated by the plasma sterilization water generator A is supplied is a vaporizer-type humidifier of an external air conditioner, and plasma sterilization water is supplied to the water tank 2 for the sterilization target. The supply piping D is connected, and the supply piping D is connected to the humidification water supply piping which supplies pure water as dripping water to the vaporization type humidifier in an external air conditioner. Plasma sterilizing water generator.

  By connecting the supply pipe D to the humidifying water supply pipe, the plasma sterilizing water can be supplied to the vaporizing humidifier which is the sterilizing water by using the configuration on the external controller side including the humidifying dripping header. Since it is not necessary to provide a plasma sterilizing water supply pipe on the external air conditioner side, it is possible to provide a plasma sterilizing water generating apparatus having a simpler structure.

(6) The water tank 2 is made of metal and connected to the ground to form the ground electrode 3b.

  With the configuration described above, it is not necessary to separately provide the ground electrode 3b in the water tank 2. Therefore, it is possible to provide a plasma sterilizing water generating device having a cheaper and simple structure.

(7) The water tank 2 is provided with a stirring device so as to be located in the water to be treated stored in the water tank 2.

  By providing a stirring device inside the water tank 2, even when the amount of water to be treated is large and the water depth is deep, dielectric barrier discharge can be performed on the entire water to be treated. Therefore, plasma sterilized water having a high sterilizing effect can be generated. Moreover, the sterilization power of the plasma sterilization water supplied to the sterilization target can be kept constant.

(8) The water tank 2 is provided with a cooling device for cooling the water to be treated, and cools the water to be treated during the plasma treatment to 10 ° C. or less.

  By cooling the water to be treated during plasma treatment to 10 ° C. or less by the cooling device, plasma sterilized water having a strong sterilizing power can be generated.

(9) The water tank 2 is provided with a cooling device for cooling the water to be treated, and cools the generated plasma sterilized water to 7 ° C. or less.

  By cooling the plasma sterilizing water after generation to 7 ° C. or less by the cooling device and storing it, it becomes possible to maintain the sterilizing effect of the plasma sterilizing water for a long time.

(10) The space between the dielectric 4 and the water surface of the water to be treated stored in the water tank 2 is not less than 5 mm and not more than 10 mm.

  By setting the space between the dielectric 4 and the water to be treated to be 5 mm or more and 10 mm or less, it is possible to discharge with an appropriate applied voltage. Moreover, it is prevented that the dielectric material 4 and to-be-processed water contact by vibration etc.

(11) A space of 50 mm or more is provided between the inner wall surface of the water tank 2 and the side surface of the flat electrode 3a.

  When the water tank 2 is made of metal, when the inner wall surface of the water tank 2 exposed to the gas phase side from the surface of the water to be treated is extremely close to the electrode 3a, a spark discharge is generated toward the inner wall surface of the water tank 2. It is possible to do. Spark discharge can be prevented by ensuring a space of 50 mm or more between the inner wall surface of the water tank 2 and the side surface of the flat electrode 3a.

[Other embodiments]
(1) In the above embodiment, the water tank 2 is provided with a cooling device for cooling the water to be treated. However, cold water for air conditioning (usually about 7 ° C.) used as a refrigerant for the cooling coil of the external air conditioner may be used as the water to be treated. That is, the water supply pipe S of the water tank 2 can be connected to the air conditioning cold water supply pipe of the external air conditioner. By reducing the water temperature at the start of the plasma treatment, the water temperature of the plasma sterilizing water can be kept low. Therefore, the sterilizing power of the generated plasma sterilizing water can be maintained for a long time.

(2) The control of the plasma sterilizing water generator A using the input power amount described in the above embodiment may be configured such that the control device calculates and controls the voltage application time based on the amount of water to be treated and the power. good. In the above embodiment, it is assumed that the control device is built in the plasma sterilizing water generating device A, but an external control device may be connected to the plasma sterilizing water generating device A. The control device can be realized by controlling the computer with a predetermined program or by a dedicated electronic circuit. In addition, it can also be set as the structure which a user inputs the amount of to-be-processed water, input electric energy, and voltage application time.

(3) When the sterilization target is a vaporizer type humidifier for an external air conditioner, the vaporization type humidifier may be dried after the air conditioner operation of the external air conditioner is stopped. Plasma sterilizing water generated by the plasma sterilizing water generating device can easily penetrate into the humidifying element portion, and the sterilizing effect by the plasma sterilizing water can be improved.

(4) In the above embodiment, the sterilization target is described as a vaporizing humidifier of an external air conditioner, but the sterilization target is not limited to this. For example, the present invention can be applied to a household vaporizing humidifier, an air purifier with a household vaporizing humidification function, and the like. These devices often have a structure in which a part of the vaporizing humidifying element (filter medium, filter) is always in contact with the water in the humidifying water storage part or while rotating. Therefore, by causing dielectric barrier discharge to act on the water in the humidifying reservoir, sterilization of the humidifying water and the vaporizing humidifier element (filter material, filter) impregnated with the humidifying water can be performed. It becomes possible.

A Plasma disinfection water generator 1 Decompression chamber E Exhaust duct 1a Decompression pump 1b Valve 2 Water tank S Water supply pipe 2a Valve D Supply pipe 2b Valve 2c Liquid feed pump 3a Electrode 3b Ground electrode 4 Dielectric 5 Power supply

Claims (11)

A vacuum chamber;
A box-shaped water tank that is disposed inside the decompression chamber and stores treated water;
A pair of electrodes disposed within the vacuum chamber;
A power source for applying an alternating voltage to the pair of electrodes,
The pair of electrodes includes:
A plate-like electrode provided to be located above the surface of the water to be treated stored in the water tank;
A dielectric that is provided on the lower surface side of the plate-like electrode and faces the surface of the water to be treated stored in the water tank via a space;
A grounding electrode provided to be located in the water to be treated stored in the water tank,
A plasma sterilizing water generating apparatus, wherein a decompression pump for decompressing a gas phase atmosphere is connected to the decompression chamber so that the interior of the decompression chamber becomes an extremely low vacuum.   The plasma sterilizing water generating device according to claim 1, wherein the power source is configured to input a power of 10 Wh or more per 1 L of the water to be treated.   The plasma sterilizing water generator according to claim 1 or 2, wherein a water supply pipe for supplying pure water is connected to the water tank. The sterilization target to which the plasma sterilization water generated by the plasma sterilization water generator is supplied is a vaporizer type humidifier of an external air conditioner,
The plasma sterilizing water generating device according to claim 3, wherein the water supply pipe is connected to a humidifying water supply pipe for supplying pure water as dropped water to the vaporizing humidifier in the external air conditioner. The sterilization target to which the plasma sterilization water generated by the plasma sterilization water generator is supplied is a vaporizer type humidifier of an external air conditioner,
A supply pipe for supplying plasma sterilized water to the sterilization target is connected to the water tank,
The plasma sterilizing water generator according to any one of claims 1 to 4, wherein the supply pipe is connected to a humidification water supply pipe that supplies pure water as dripped water to the vaporizing humidifier in the external air conditioner. .   The plasma sterilizing water generating device according to any one of claims 1 to 5, wherein the water tank is made of metal and is grounded to become the ground electrode.   The plasma sterilizing water generator according to any one of claims 1 to 6, wherein the water tank is provided with a stirring device for stirring the water to be treated stored in the water tank.   The plasma sterilizing water generator according to any one of claims 1 to 7, wherein the water tank is provided with a cooling device for cooling the water to be treated, and the water to be treated during the plasma treatment is cooled to 10 ° C or lower.   The plasma sterilizing water generator according to any one of claims 1 to 8, wherein the water tank is provided with a cooling device for cooling the water to be treated, and the generated plasma sterilizing water is cooled to 7 ° C or lower.   The plasma sterilizing water generator according to any one of claims 1 to 9, wherein a space between the dielectric and the surface of the water to be treated stored in the water tank is 5 mm or more and 10 mm or less.   The plasma sterilizing water generator according to any one of claims 1 to 10, wherein a space of 50 mm or more is provided between an inner wall surface of the water tank and a side surface of the flat electrode.