JP2019162070A - Gas plasma sterilization equipment - Google Patents

Abstract

To provide sterilization equipment that can sequentially sterilize a large quantity of seeds in an open space, when sterilizing the seeds by using plasma without using pesticide and water.SOLUTION: Sterilization equipment includes: a gas plasma generator 3 including at least one pair of electrodes 3b, 3b in a gas flow path 3a where the gas g serving as a plasma source flows through, generating gas plasma by applying AC voltage between the pair of electrodes 3b, 3b, and discharging the generated gas plasma from an exit out of gas flow path 3a to the air to form a continuation movement area Z of the gas plasma toward the exit out outward; and holding means 2 for holding seeds 1 in the continuation movement area Z of this gas plasma generator 3. The gas plasma is applied from different directions to the seeds 1 held by the holding means 2, and thereby sterilization is performed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a gas plasma sterilization facility for sterilizing particulate matter using a gas plasma generator.

As an example of this type of sterilization equipment, the technique described in Patent Document 1 can be cited.
The technique disclosed in this document generates plasma according to the type and characteristics of granular or powdery sterilization target (specifically, seeds), and can suppress ill effects to perform sterilization stably and reliably. An object of the present invention is to provide a plasma sterilization apparatus that can be downsized and can be sterilized even in batch processing.

As described in paragraph [0009], this plasma sterilization apparatus targets agricultural product seeds. As the problem, as described in the following paragraphs, in the case of this type of sterilization target, since the sterilization characteristics may be different, the mounting unit 1 made of a conductive material for mounting the sterilization target object 100 and The power supply switching unit 2 for switching the one electrode 10 and the mounting unit 1 to the power source unit 12 and the ground switching unit 3 for switching the one electrode 10, the other electrode 11 and the mounting unit 1 to the grounding unit 13. By providing, different sterilization objects (agricultural seeds) are sterilized well.
This plasma sterilization apparatus is configured in a sterilization container 14, and it is necessary to put in and out a sterilization target (for example, seeds of agricultural products) on the mounting portion 1 provided in the container 14. Therefore, it is not suitable for an application in which a large amount of seeds is continuously processed.

JP 2017-86705 A

When the seeds of agricultural products are to be sterilized, it is necessary to continuously and stably treat a relatively large amount of seeds even when sequentially sterilized.
Furthermore, in comparison with conventional sterilization methods, it is not preferable to use agricultural chemicals or water because of environmental problems.

  In view of this situation, the main problem of the present invention is that sterilization capable of sequentially sterilizing a large number of seeds in an open space when using plasma to sterilize seeds without using agricultural chemicals, water, or the like. It is in providing facilities.

The first characteristic configuration of the present invention is:
At least a pair of electrodes are provided in a gas flow path through which a gas serving as a plasma source flows, and an alternating voltage is applied between the pair of electrodes to generate a gas plasma between the pair of electrodes. A gas plasma generator that discharges into the atmosphere from the outlet of the gas flow path and forms a continuous movement region of the gas plasma toward the outside of the outlet;
Holding means for holding seeds in the continuous movement region of the gas plasma generator,
The seeds held by the holding means are configured to be able to irradiate the gas plasma from different directions.

  According to this characteristic configuration, the gas plasma generator forms a gas plasma continuous movement region in the atmospheric environment outside the outlet of the gas flow path. In the gas plasma generator used in the present invention, the gas plasma generated between at least a pair of electrodes is discharged from the outlet in a form where the gas plasma is conveyed to the gas flow flowing through the gas flow path, and continues as plasma while moving. Continue.

  The holding means holds the seed in this continuous movement area. As a result, the seed can be sterilized well by the gas plasma irradiated to the seed. This treatment can be carried out sequentially and sequentially because seeds can be conveyed and held in the continuous movement region of the gas plasma in an open space in the atmosphere.

  Although it is the irradiation form, since the form which irradiates from several directions is taken in this invention, it can irradiate gas plasma by the form which covers the outer surface of a seed without excess and deficiency, and can perform sufficient sterilization.

The second characteristic configuration of the present invention is:
Comprising at least a pair of the gas plasma generators arranged so that the outlets of the gas flow paths face each other;
The seed is held in at least one pair of the continuous movement regions that are opposed to each other and are generated by the at least one pair of the gas plasma generators while being held by the holding means.

  According to this characteristic configuration, at least a pair of gas plasma generators are provided and are opposed to each other. Therefore, at least both front and back surfaces are irradiated with gas plasma with the irradiation direction of one gas plasma generator as the front side and the other as the back side. And can be sterilized.

The third characteristic configuration of the present invention is:
The holding means is composed of a conveyor device having holes through which the gas plasma can move through the conveyor surface in a state where the seeds are distributed and held on the conveyor surface,
The conveyor device is located between the gas plasma generators arranged to face each other, and the conveyor device is in a stop state where the conveyor surface is stopped and serves as the holding means.

  According to this characteristic configuration, a pair of gas plasma generators are provided across the conveyor surface of the conveyor device that serves as the holding means, and in a stopped state in which the conveyor surface stops, the gas plasma is generated through the holes provided in the conveyor surface. Can be sterilized by irradiating gas plasma from the front side and the back side of the conveyor surface.

The fourth characteristic configuration of the present invention is:
It is the point provided with the attitude | position change means which changes the attitude | position of the said seed hold | maintained in the area where the said gas plasma continues.

According to this characteristic configuration, by providing the seed posture changing means, it is possible to sterilize by irradiating gas plasma from various (plural) directions.
In this configuration, since the posture change of the seed is realized, the irradiation direction of the gas plasma can be set to one specific direction, for example, and the number of gas plasma generators can be limited.

The fifth characteristic configuration of the present invention is:
The posture changing means is one or both of a posture changing mechanism that changes the posture by applying an air flow to the seeds dispersed on the conveyor surface of the conveyor device and a vibration mechanism that vibrates the conveyor surface. In the point.

  According to this feature configuration, the posture can be changed satisfactorily by changing one or both of applying an air flow to the seed and vibrating the conveyor surface in changing the posture of the seed.

The sixth characteristic configuration of the present invention is:
The holding means comprises a conveyor device;
The conveyor surface of the conveyor device is configured as a transmissive conveyor surface that allows airflow to pass through in a form capable of holding the seeds,
The outlet of the gas flow path of the gas plasma generator is located on one side of the conveyor surface, and has a blowing means for supplying the airflow from the back side of the conveyor surface.

  According to this characteristic configuration, while the seed is held on the conveyor surface, the gas plasma is irradiated from one side thereof, and while changing the posture of the seed by flowing an air flow from the opposite side which is the back side of this direction The seed can be irradiated with gas plasma from a plurality of directions to perform sterilization well.

The seventh characteristic configuration of the present invention is:
A plurality of gas plasma generators having the same gas plasma emission direction are distributed and arranged,
The seed is moved across the gas plasma continuous movement regions of the plurality of gas plasma generators arranged in a distributed manner and is sterilized in the plurality of continuous movement regions.

  According to this characteristic configuration, it is possible to perform continuous processing by sequentially moving the seeds in the continuous moving region of the plurality of gas plasmas and changing the irradiation position on the seeds and the generation source of the gas plasma. Here, for example, when it is detected that the seed is located immediately below the gas plasma generation device, the movement may be temporarily stopped to increase the irradiation time.

The eighth feature of the present invention is
The holding means is composed of a conveyor device that moves the seeds in a state of being distributed and held on the conveyor surface,
The dispersed arrangement direction of the plurality of gas plasma generators is in the direction of conveyance of the conveyor device.

  According to this characteristic configuration, since the conveying direction of the conveyor device and the dispersed arrangement direction of the gas plasma generator coincide with each other, the seed sterilization process can be performed in a form in which the conveyor device is conveyed.

External view of gas plasma sterilization facility according to the first embodiment Side view explanatory drawing of the gas plasma sterilization equipment shown in FIG. Configuration diagram of gas plasma generator Diagram showing AC voltage and current applied to each electrode External view of gas plasma sterilization facility according to the second embodiment Side view explanatory drawing of the gas plasma sterilization equipment shown in FIG. External view of gas plasma sterilization facility according to the third embodiment Diagram showing the sterilization effect of gas plasma

Embodiments of the present invention will be described with reference to the drawings.
1. First Embodiment FIG. 1 shows an appearance of a gas plasma sterilization facility 100 according to this embodiment, and FIG. These figures are simplified for easy understanding of the present embodiment.
As can be seen from this figure, the gas plasma sterilization equipment 100 includes a conveyor device 2 in which a large number of seeds 1 to be sterilized are dispersed and conveyed, and the identification of the conveying direction D of the conveyor device 2 is specified. A plurality (six in the illustrated example) of gas plasma generators 3 are provided at the position. The gas plasma generator 3 is disposed in pairs in the vertical direction with the conveyor surface 2a on which the seeds 1 are held (see FIG. 2).

<Gas plasma generator>
A specific configuration of the gas plasma generator 3 is shown in FIG.
The gas plasma generator 3 includes at least a pair of electrodes 3b in a gas flow path 3a through which a gas g serving as a plasma source flows, and an AC voltage is applied between the pair of electrodes 3b so that a gas plasma is generated between the pair of electrodes 3b. Is generated. The generated gas plasma is discharged into the atmosphere from the outlet out of the gas flow path 3a, and forms a continuous movement region Z of the gas plasma toward the outside of the outlet out.
As will be described later, the gas flow path 3a is formed in a straight pipe 3c made of an insulating material, and includes a voltage applying device 3d that applies an AC voltage to each electrode 3b fixed in the straight pipe 3c. .

  As shown in FIGS. 1 to 3, by using the gas plasma generator 3, the gas plasma continuous movement region Z extending in the longitudinal direction is formed from the outlet out of the gas flow path 3 a. As can be seen from the drawing, the continuous movement region Z is tapered, and the plasma concentration decreases toward the tip.

  The above is the outline of the gas plasma generation apparatus 3 employed in the gas plasma sterilization facility 100, which will be described in more detail below.

A gas g serving as a plasma source is supplied to the gas gas flow path 3a. The gas g is not particularly limited, and is a polyatomic gas such as a monoatomic gas such as helium or argon, such as oxygen or carbon dioxide. , Nitrogen, hydrogen, and other mixed gas, such as air, mixed gas related to any combination of the above monoatomic molecules and polyatomic molecules, and the like.

  Regarding the supply of the gas g to the gas flow path 3a, a mass flow controller MFC is provided upstream of the gas flow path 3a to control the supply pressure and supply amount of the gas g to the gas flow path 3a.

Gas Channel The gas channel 3a is formed in a straight pipe 3c made of an insulating material (for example, glass or ceramic), and a gas g is supplied from the inlet in.
The length of the gas flow path 3a only needs to be long enough to arrange at least the pair of electrodes 3b. However, by increasing the length of the straight pipe 3c, the time required for the gas g to pass between the electrodes 3b increases, and the amount of energy applied increases. The length of the gas flow path 3a is about 10 cm at the maximum.

  On the other hand, in the present invention, in order to sterilize the seed 1 in the gas plasma continuous movement region Z formed outside the outlet out of the straight pipe 3c, the electrode on the outlet side located on the lower side in FIGS. The length from 3b to the outlet out is limited.

  The inner diameter of the gas flow path 3a is preferably 1 mm or more. The upper limit value is about 4 mm, for example.

Examples of the material of the strip electrode constituting the electrode 3b include metals such as copper, silver, nickel, aluminum, and stainless steel, conductive metal oxides, and organic conductive materials such as carbon.

The structure is basically a pair of strip electrodes arranged in an annular shape along the inner periphery of the straight pipe 3c.
As can be seen from FIG. 3, both the electrodes 3b are spaced apart by a predetermined length (20 mm in the present embodiment) in the longitudinal direction of the gas flow path 3a. On the other hand, the length of the survival movement area Z is secured to about 40 mm.

(Voltage application device)
The voltage application device 3d applies an alternating voltage (preferably an alternating voltage of a sinusoidal voltage that changes at a constant period) between the pair of strip electrodes 3b, and causes glow discharge in the straight tube 3c under atmospheric pressure. It is a means to make. The voltage application device 3d shown in the figure includes an AC power supply unit 3d1 and a voltage adjustment unit 3d2 that can apply an AC voltage in a predetermined voltage range for the electrode 3b positioned on the inlet in side in the straight pipe 3c. Yes. On the other hand, the electrode 3b positioned on the outlet out side in the straight pipe 3c includes a voltage maintaining unit 3d3 that maintains the electrode 3b at a predetermined voltage, and has resistance to current flowing between the electrodes 3b. The resistance portion 3d4 is provided. In this structure, electric shock is generated from the inlet in side to the outlet out side.
Synchronization between the AC power supply unit 3d1 and the voltage maintaining unit 3d3 was performed by the synchronization control device C3.

  When using the voltage application device 3d, for example, the maximum voltage and / or frequency is increased in the initial stage of operation to satisfy certain conditions (for example, when a certain period of time has elapsed or glow discharge has been confirmed). In this state, the voltage and / or frequency is decreased sequentially to continuously maintain the generation of gas plasma.

Sine-wave AC voltage Voltage If the maximum voltage of the sine-wave AC voltage is too high, it may cause arc discharge from glow discharge and damage the straight tube 3c and the like, and if it is too low, glow discharge may not occur. If the applied voltage is too high, creeping discharge may occur between the adjacent strip electrodes 3b on the outer periphery of the straight tube 3c. Therefore, the maximum voltage between the electrodes 2b is preferably 5 to 25 kVp-p, and more preferably 5 to 15 kVp-p.

Frequency The frequency of the applied voltage is not particularly limited, and can be applied from a low frequency of several kHz to a high frequency of several tens of kHz or MHz. However, insulation becomes more difficult as the frequency increases. Therefore, the frequency is preferably 5 kHz to 5 MHz, more preferably 5 kHz to 1 MHz, and particularly preferably 10 to 30 kHz. FIG. 4 is an example of a timing chart when a sinusoidal AC voltage is applied between a pair of strip electrodes.

Sterilization treatment in a gas plasma sterilization facility In the present invention, it is necessary that at least a part of the surface of the seed 1 to be sterilized is present in the continuous movement region Z.
Therefore, as shown in FIGS. 1 and 2, the gas plasma sterilization equipment 100 includes at least a pair of gas plasma generators 3 arranged so that the outlets out of the gas flow paths 3 a face each other, and the conveyor surface of the conveyor device 2. In a state in which the seed 1 is held on the seed 2a, the seed 1 is located in the continuous moving region Z of at least one pair of gas plasmas that are generated by at least one pair of gas plasma generators 3, and the gas plasma moves up and down the seed 1 Irradiated from both sides and sterilized. In the drawing, only the tip of the survival moving area Z is shown as being in contact with the seed 1, but this is for facilitating understanding of the irradiation form of the gas plasma irradiated from a plurality of directions. Z has a certain spread and wraps around the surface of the seed 1 (the same applies to FIGS. 2, 5, 6, and 7).
In this way, as shown in FIG. 3, the length of the continuous movement area Z is secured to about 40 mm.

In this gas plasma sterilization equipment 100, since a plurality of gas plasma generation devices 3 are arranged in a direction crossing the transport direction D of the conveyor device 2, it is necessary to irradiate the sterilization-treated seeds 1 with gas plasma for a certain period of time. There is.
Therefore, a holding portion 2b provided with a pair of protruding guides 2bg for holding the seed 1 is provided on the conveyor surface 2a, and the seed 1 held by the holding portion 2b is positioned at the lower and upper portions of the gas plasma generator 3. The conveyor device 2 is stopped at the phase to be performed. And the seed 1 is hold | maintained in the continuous movement area | region Z of gas plasma for the predetermined time. Therefore, at least the holding portion 2b is provided with a plurality of holes 2c penetrating the conveyor surface 2a in the front and back direction. In order to prevent the seed 1 from falling, the hole 2c has a diameter that does not cause the seed 1 to fall.
Therefore, in 1st Embodiment, it becomes a sequential process accompanied by the driving | operation stop of the conveyor apparatus 2. FIG.

  As described above, in the gas plasma sterilization facility 100, the conveyor device 2 serves as a holding unit that holds the seed 1 in the continuous movement region Z of the gas plasma generation device 3, and the seeds that are held by the holding unit. 1, the seed 1 can be sterilized by irradiating gas plasma from different directions.

2. Second Embodiment FIG. 5 shows an appearance of a gas plasma sterilization facility 101 according to this embodiment, and FIG. 6 shows a side view explanatory view. As is clear from the comparison with the first embodiment, the gas plasma generator rows 30 arranged in a row orthogonal to the transport direction D of the conveyor device 2 in the first embodiment are A plurality of rows (30 rows in the illustrated example) are arranged in the transport direction D. That is, a plurality of gas plasma generators 30 are distributed along the transport direction D.
By arranging in this way, in the first embodiment, the sterilization of the seeds 1 that had to be performed with the stop of the conveyor device 2 is performed in a continuously operated state without stopping the conveyor device 2. Can do.
In this embodiment, the holes 2c are provided uniformly over the entire conveyor surface 2a.

3. Third Embodiment A gas plasma sterilization facility 103 according to this embodiment is shown in FIG.
In the gas plasma sterilization facilities 100 and 101 according to the first and second embodiments, a number of holes 2c through which gas plasma can be transmitted are formed on the conveyor surface 2a of the conveyor device 2, and these holes 2c are formed into gas plasma. With the seed 1 sandwiched in at least a pair of gas plasma continuous moving regions Z (a surviving moving region Z generated on the upper side and a surviving moving region Z generated on the lower side) generated opposite to each other. The seed 1 was sterilized from at least two directions.

  Further, in the second embodiment, the gas plasma generators 3 are arranged in the transport direction D of the conveyor device 2 and passed through the gas plasma continuous movement region Z a plurality of times (multiple times of gas plasma irradiation).

However, the structure in which the gas plasma generators 3 are arranged to face each other increases the size and size of the equipment itself.
Therefore, in the third embodiment, the gas plasma generator 3 is arranged only on one side (for example, the upper side) of the conveyor surface 2a of the conveyor device 2 so as to change the posture of the seed 1.
In this 3rd Embodiment, the gas plasma generator group 300 located above the conveyor apparatus 2 is also arrange | positioned also in the conveyance direction D of the conveyor apparatus 2 similarly to 2nd Embodiment. Therefore, continuous processing is possible.

  In this embodiment, instead of disposing the gas plasma generating device 3 so as to face each other, posture changing means for changing the posture of the seed 1 in the continuous movement region Z of the gas plasma is provided. Specifically, as the posture changing means, a blower mechanism 400 is provided as an example of a posture changing mechanism that changes the posture by applying an air flow W to the seeds 1 dispersed on the conveyor surface 2a of the conveyor device 2. By doing in this way, changing the posture in the continuous movement region Z of the gas plasma of the seed 1 by the air flow W, changing the irradiation part of the gas plasma, and performing effective sterilization by irradiating from different directions Can do.

  Instead of adopting such a configuration, as shown by a broken line in FIG. 7, a permeable type conveyor surface that allows airflow to pass in a form in which the conveyor surface 2 a of the conveyor device 2 is maintained on the conveyor surface 2 a. (For example, a perforated plate), the gas plasma generator 3 is positioned on the outlet out side of the gas flow path 3a, and the air flow W is directed to the back surface of the conveyor surface 2a (with respect to the arrangement side of the gas plasma generator 3). It is good also as a structure provided with the ventilation mechanism 401 supplied from the back of the conveyor surface 2a.

  Thus, without changing the posture by the airflow W, a vibration mechanism (not shown) that vibrates the conveyor surface may be provided, and the posture changing means may be used.

Hereinafter, in order to confirm the effectiveness of the present invention, the tests conducted by the inventors will be described.
The operating conditions of the gas plasma generator 3 are listed below. Irradiation was performed in one direction from above the seed 1.

Gas type: Helium gas Gas flow rate: 5 liters / min
Voltage between electrodes: 11.0 kVp-p
Interelectrode current: 5.3 mAp-p
AC frequency: 27.0 kHz
Input electric energy: 2.6 W (estimated from current-voltage characteristics)

  FIG. 4 shows the interelectrode voltage and interelectrode current when the gas plasma generator 3 is operated under these conditions. A ripple appears in the current, but it is understood that a ripple appears in relation to the generation of the helium plasma. The interelectrode voltage is indicated by a solid line, and the interelectrode current is indicated by a dotted line.

Results FIGS. 8A and 8B show the test results.
The figure (a) is a result of Escherichia coli, and (b) is a result of Staphylococcus aureus.
In these figures, the vertical axis represents the “viable count per seed weight (CFU / g-DRY-Seed)”, and the horizontal axis represents “gas plasma irradiation time (min)”.

result,
The sterilization property can be improved by increasing the gas plasma irradiation time (sterilization treatment time).
Even with single-sided treatment, about 90-99% sterilization was possible with 10 minutes of treatment regardless of the bacterial species.

[Another embodiment]
(1) In the above-described embodiment, the electrode 3b has a strip shape and is provided around the gas flow path 3a. However, for example, the number of electrodes may be increased.

1 Seed 2 Conveyor device (holding means)
2a Conveyor surface 3 Gas plasma generator 3a Gas flow path
3b Electrode 100 Gas plasma sterilization equipment 300 Gas plasma generator group 400 Blower mechanism (attitude change means)
401 Blower mechanism (attitude change means)
W Air flow Z Gas plasma continuous moving region g Gas out outlet

Claims (8)

At least a pair of electrodes are provided in a gas flow path through which a gas serving as a plasma source flows, and an alternating voltage is applied between the pair of electrodes to generate a gas plasma between the pair of electrodes. A gas plasma generator that discharges into the atmosphere from the outlet of the gas flow path and forms a continuous movement region of the gas plasma toward the outside of the outlet;
Holding means for holding seeds in the continuous movement region of the gas plasma generator,
The gas plasma sterilization equipment comprised so that the said gas plasma can be irradiated to the said seed hold | maintained by the said holding means from a different direction. Comprising at least a pair of the gas plasma generators arranged so that the outlets of the gas flow paths face each other;
2. The gas plasma sterilization facility according to claim 1, wherein seeds are held in at least one pair of the continuous movement regions that are opposed to each other and are generated by the at least one pair of gas plasma generators while being held by the holding unit. The holding means is composed of a conveyor device having holes through which the gas plasma can move through the conveyor surface in a state where the seeds are distributed and held on the conveyor surface,
The gas plasma sterilization equipment according to claim 2, wherein the conveyor device is located between the gas plasma generators arranged to face each other and serves as the holding means in a stopped state in which the conveyor surface stops.   The gas plasma sterilization equipment according to claim 1, further comprising posture changing means for changing the posture of the seed held in the region where the gas plasma continues to move.   The posture changing means is one or both of a posture changing mechanism that changes the posture by applying an air flow to the seeds dispersed on the conveyor surface of the conveyor device and a vibration mechanism that vibrates the conveyor surface. The gas plasma sterilization equipment according to claim 4. The holding means comprises a conveyor device;
It is configured as a transmission type conveyor surface that allows airflow to pass through in a form that can hold the seed on the surface of the conveyor device,
The blower means for supplying the gas plasma generator from the back side of the conveyor surface to the arrangement side of the gas plasma generator while the conveyor surface is positioned on the outlet side of the gas flow path The gas plasma sterilization equipment according to claim 4 provided with. A plurality of gas plasma generators having the same gas plasma emission direction are distributed and arranged,
7. The seed according to claim 1, wherein the seeds move between the continuous movement regions of the gas plasma of the plurality of gas plasma generators arranged in a distributed manner and are sterilized in the plurality of the continuous movement regions. Gas plasma sterilization equipment. The holding means is composed of a conveyor device that moves the seeds in a state of being distributed and held on the conveyor surface,
The gas plasma sterilization facility according to claim 7, wherein a dispersed arrangement direction of the plurality of gas plasma generation devices is a conveyance direction of the conveyor device.

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