KR20040054561A - Sterilization method and sterilization device - Google Patents

Abstract

PURPOSE: Provided is a sterilizing method for certainly sterilizing or inactivating a microorganism included in the gas or liquid flowing at high speed, by generating a pulse streamer electricity discharge in the gas nearby both electrodes by applying high voltage in pulse waveform between the electricity discharging electrode and the corresponding electrode. CONSTITUTION: The sterilizing method sterilizes or inactivates an microorganism existing in an electricity discharging area by generating a streamer discharge of electricity nearby both electrodes by applying a high voltage in a pulse waveform between the electricity discharge electrode and a corresponding electrode. The sterilizer comprises an electricity discharging electrode(3), a corresponding electrode(4), and a high voltage application unit for applying the high voltage in a pulse waveform to generate a streamer discharge of electricity. The high voltage application unit is controlled more than once by a frequency to generate the streamer discharge of electricity within the time when the gas or liquid passes an electricity discharging area(5) at a predetermined speed.

Description

Sterilization Method and Sterilizer {STERILIZATION METHOD AND STERILIZATION DEVICE}

The present invention relates to a sterilization method and a sterilization apparatus for killing or inactivating microorganisms.

Conventionally, active particles such as ions and ozone are used to reproduce microorganisms present in objects related to food, such as food and cooking products, or on surfaces of objects with which microorganisms are a problem in public health, and in spaces storing these objects. A method of preventing is known.

For example, Japanese Patent Application Laid-Open No. Hei 9-108313 discloses a gas containing air, such as air, in an ionizing chamber to control discharge current when generating ions and ozone to contain a predetermined low concentration of ozone and high concentration of ions. A microbial propagation prevention method and apparatus for preventing the propagation of microorganisms by synergistic effect of ozone and ions by generating an ionizing gas and injecting the generated ionizing gas into an object in the ionization chamber or a space communicating with the object is disclosed. .

However, the microbial propagation prevention method and apparatus up to now have the effect of applying the microorganisms present on the surface of the object or the storage space as described above to the apparatus to which gas flows very quickly. In many cases, microorganisms pass through without being damaged. For this reason, it has become a problem to reliably kill or inactivate the gas flowing through at high speed and the microorganisms in the liquid.

1 is a cross-sectional view showing a schematic configuration of a sterilizing apparatus of one embodiment of the present invention;

2 is a cross-sectional view showing the sterilization apparatus of FIG. 1 from another direction;

3 is a high voltage waveform diagram of a first example applied in the sterilization apparatus of FIG.

4 is a high voltage waveform diagram of a second example applied in the sterilization apparatus of FIG.

5 is a high voltage waveform diagram of a third example applied in the sterilization apparatus of FIG.

6 is a high voltage waveform diagram of a fourth example applied in the sterilization apparatus of FIG.

7 is a high voltage waveform diagram of a fifth example applied in the sterilization apparatus of FIG. 1;

8 is a waveform diagram of a high voltage used when testing the sterilization effect of the sterilization apparatus of the present invention.

In order to solve the above problems, the sterilization method of the present invention by applying a high voltage of the pulse waveform between the discharge electrode and the counter electrode to generate a streamer discharge in the vicinity of both electrodes, killing or inactivating microorganisms present in the discharge region Characterized in that.

Moreover, the sterilizing apparatus of this invention is characterized by including the discharge electrode and the counter electrode, and high voltage application means which applies the high voltage of the pulse waveform which generate | occur | produces a streamer discharge between these electrodes.

According to such a sterilization method and a sterilizer, microorganisms can be killed or inactivated by electrons, ions or radicals scattering at high speed in the streamer discharge region, potential difference, and the like.

Preferably, the high voltage applying means is controlled at a frequency for generating streamer discharge at least once within the passage time of the gas or liquid passing through the discharge region formed near the discharge electrode and the counter electrode at a predetermined speed. As a result, all microorganisms contained in the gas and the liquid encounter the streamer discharge at least once while passing near the discharge electrode and the counter electrode, and are reliably killed or inactivated.

Preferably, the high voltage applying means is configured to apply a high voltage having a minimum pulse width. More preferably, it is configured to apply a high voltage having a minimum pulse width of 1 μsec or less. As a result, it is possible to increase the voltage in an instant, to rapidly scatter a large amount of electrons, to shorten the voltage application time, and to reduce the generation of ozone harmful to the human body.

Further, preferably, the high voltage applying means is configured to apply a high voltage of negative pulse waveform. As a result, negative ions can be generated, and clean air containing negative ions can be supplied.

Best Mode for Carrying Out the Invention Embodiments of the present invention will now be described in detail with reference to the drawings. Although gas, such as air, is demonstrated here, liquids, such as water, can also be processed similarly.

1 and 2, the sterilization unit 1 is disposed in a flow path of a gas such as air, and a wire-shaped discharge electrode 3 is disposed in a plurality of stages inside the casing 2, The flat counter electrodes 4 are arranged in parallel between the discharge electrodes 3, and the discharge regions 5 formed between the discharge electrodes 3 and the counter electrodes 4 are continuously connected to each other. It occupies an area larger than the passage area 6 of the air flow formed by the inlet port and the outlet port (not shown) opened in (2). 7 indicates an upstream air flow flowing into the airflow passage region 6, and 8 indicates a downstream airflow flowing out of the airflow passage region 6. The discharge electrode 3 can be used without any limitation as long as it is an electrode that causes discharge, such as a metal needle.

The high voltage applying device 9 has a positive electrode 10 connected to the discharge electrode 3, a negative electrode 11 (or earth 11) connected to the counter electrode 4, and the discharge electrode 3. And a high voltage of a pulse waveform capable of generating streamer discharge between the counter electrode and the counter electrode 4. As the high voltage applying device 9, for example, a switching means such as an insulated gate bipolar transistor (IGBT) is arranged in a double voltage circuit to generate a predetermined pulse waveform and a high frequency voltage, and to boost the voltage to a high voltage transformer. An electronic circuit or the like is used. However, as long as a high voltage of a predetermined pulse waveform and frequency can be applied, the present invention can be used without being limited thereto.

Hereinafter, the operation in the above configuration will be described.

By applying a high voltage of a predetermined pulse waveform between the discharge electrode 3 and the counter electrode 4 by the high voltage applying device 9, streamer discharge (hereinafter referred to as pulse streamer discharge) is applied to the discharge region 5. Generate.

The pulse streamer discharge generating mechanism is characterized in that ionization of the heavy molecules occurs in front of the electrons emitted from the discharge electrode 3 so that the electrons are released like an avalanche, and this electron avalanche is the next new electron. As it causes an avalanche, an avalanche gradually rises and coalesces and progresses at high speed, and most of the discharge current is caused by electrons.

At that time, since there is a remarkable electric field concentration near the discharge electrode 3 between the discharge electrode 3 and the counter electrode 4, an avalanche is generated when the applied high voltage is large enough to cause a large amount of ions and photons. Is produced.

At that time, since the wire-shaped discharge electrode 3 is a positive electrode, a large amount of photons are emitted in all directions in the vicinity of the discharge electrode 3, and the emitted photons are absorbed by the neutrons in the vicinity. The ionization is generated, and a large number of avalanches in the direction toward the discharge electrode 3 are generated, and at the same time, plasma columns are formed among the cations produced.

At the front edge of the plasma column, cations toward the counter electrode 4 (that is, a negative electrode or an electrode connected to the earth) are concentrated at a high density, and in addition to the electric field concentration, the space charge of these cations and the space charge of the group of avalanche groups are concentrated. Since a particularly strong electric field is formed between them, light emission of the front edge of the plasma column is further promoted.

Since such pulse streamer discharge occurs in the discharge region 5, when microorganisms are contained in the upstream current 7 flowing into the discharge region 5, a large amount of electrons and the like are scattered at high speed in the discharge region 5. Scattering particles, i.e., electrons emitted from the discharge electrode 3; gas molecules (heavy component molecules), electrons, cations, radicals and the like derived therefrom, potential differences, etc., to destroy proteins such as outer walls of microorganisms, RNA is damaged and microorganisms are killed or inactivated.

The high voltage to be applied is a high voltage capable of generating pulse streamer discharge, and also depends on the size of the gap between the discharge electrode 3 and the counter electrode 4, but for example, the discharge electrode 3 and the counter electrode ( When the gap of 4) is about 10 mm, a pulse waveform high voltage of about 7 mA or more is required when the gap is about 8 mm. This is a voltage value higher than the voltage of the pulse waveform generally applied for dust collection in an air conditioner or the like.

In order to reliably kill or inactivate microorganisms, the relationship between the velocity of the air stream passing through the discharge region 5 and the pulse frequency of the high voltage is important. At least once during the passage of the microorganisms in the air stream (in other words, any one point in the air stream) through the discharge region 5, a high frequency frequency capable of generating a pulse streamer discharge is required.

For example, in the case of an air conditioner, since the speed of the air flow passing through the indoor unit is 1 m / s, when the width of the discharge area 5 in the passage direction of the air flow is about 10 mm, the microorganisms in the air flow discharge at about 10 msec. Pass through area 5. Therefore, by applying a high voltage of about 100 kW, the microorganisms passing through the discharge region 5 can be encountered once in a pulse streamer discharge.

In order to reliably kill or inactivate microorganisms passing through the discharge region 5, a high voltage of the above-mentioned frequency, about several hundreds to several tens of times, that is, several hundreds to several thousand Hz, may be applied. Conversely, by applying such a high voltage of high frequency, even when the airflow passes through the discharge region 5 at a very high speed, microorganisms in the airflow can be reliably killed or inactivated. Such a high frequency is not essential when the microorganisms present in the surface or the storage space of the object are not microorganisms in the air stream.

In addition, by making the pulse width the minimum pulse width, it is possible to increase the voltage in an instant, thereby rapidly dissipating a larger amount of electrons in the discharge region 5, and shortening the voltage application time, which is harmful to human body. It is possible to reduce the occurrence of. A pulse width as small as possible is preferable, but a high sterilization effect is obtained by using a few microseconds or less, especially 1 microsecond or less.

In addition, by applying a high voltage of a negative pulse waveform, it is possible to generate negative ions in the discharge region 5, and to provide an atmosphere in which clean air containing negative ions as the downstream current 8 can be supplied and relaxed. Done.

The high voltage waveforms that can be used are shown in FIGS.

Fig. 3 shows (first example) of a pulse waveform which is a sine wave or a vibration waveform. In this (first example), the first pulse, the second pulse having a lower peak voltage than that, and the third pulse having a lower peak voltage than that are repeated.

4 shows (second example) of pulse waveforms. This (second example) has only negative pulse waveforms and does not have negative components. The pulse width voltage value is the same as that of (First example).

5 shows (third example) of pulse waveforms. This (third example) does not have a positive component only by a negative pulse waveform. The pulse width voltage value is the same as that of (First example).

6 shows a (fourth example) of the pulse waveform. In this (fourth example), only a single positive pulse waveform having a minimum pulse width is repeated and has no negative component.

7 shows a fifth example of the pulse waveform. In the fifth example, only a single negative pulse waveform having a minimum pulse width is repeated and does not have a positive component.

In these (first example) to (fiveth example), the rise of the voltage waveform gradually moves away from the reference earth potential and approaches the positive or negative peak, and the drop gradually approaches the reference earth potential from the positive or negative peak. Although it was a pulse wave of the shape, compared with (1st case)-(5th case), the rise of the voltage waveform is closer to the positive or negative peak at the reference earth potential more quickly, and the falling is the reference of the positive or negative peak at the positive or negative peak. The same effect can be expected in the case of the rectangular pulse waveform which is quickly approached by the earth potential.

(evaluation)

The sterilization effect of the sterilization apparatus of the present invention was evaluated by the fixed exposure test and the one pass test using the following high voltage pulse conditions. In each test, the voids were almost unchanged before and after treatment, and it was confirmed that the survival rate was 100%.

(High voltage pulse condition)

A) voltage; 5 Hz, frequency; 2 Hz (pps), pulse width; 1 μsec

B) voltage; 8 Hz, frequency; 2 Hz (pps), pulse width; 1 μsec

C) voltage; 8 Hz, frequency; 2 Hz (pps), pulse width; 20 μsec

The waveforms of the conditions A, B, and C are as shown in parts (a), (b) and (c) of FIG. 8, respectively, and are the same pulse waveforms as in FIG.

(Fixed exposure test)

The same sterilization unit (thickness 40 mm) as shown in Figs. 1 and 2 is installed in a container (180 x 80 x 40 mm), and the microbial sample is sequentially placed in the gap (10 mm) between the discharge electrode and the counter electrode of the sterilization unit. Was set, and it exposed to the high voltage of each high voltage pulse condition mentioned above for 30 second. Each microbial sample was obtained by isolating each of the commercial Bacillus suspensions with an acrylic sample chip (8 x 8) in an equal amount and naturally drying. The Bacillus bacteria of each microbial sample after the high voltage pulse treatment were recovered in Tween 80 and incubated equally in agar medium (37 ° C., 24 h) to count colonies. The count value obtained from the microbial sample after the treatment under the high voltage pulse conditions A to C was divided by the count value obtained from the blank to obtain a survival rate (%). The results are shown in Table 1.

Condition Output voltage frequency Pulse width Survival rate A 5㎸ 2 pp (pps) 1 μsec 103 (%) B 8㎸ 2 pp (pps) 1 μsec 38 (%) C 8㎸ 2 pp (pps) 20 μsec 66 (%)

(One pass examination)

The same sterilization unit (40 mm in thickness) as shown in Figs. 1 and 2 is installed during the flow path in the container (180 x 80 x 600 mm) with a fan, and the air flows through the container at about 1 m / s. In the vicinity, black mold as a test microorganism is scattered with a brush and contained in the air, and the air from the upstream side (before treatment) and downstream side (after treatment) of the sterilization unit is applied by applying a high voltage under each of the above high voltage pulse conditions. Black mold was collected on the agar medium placed in the air sampler. The collected black mold was incubated in agar medium (25 ° C., 168 h) to count the number of colonies. The value obtained from the sample before the treatment was divided by the value obtained from the sample after the treatment to obtain a survival rate (%). The results are shown in Table 2. The test is not conducted under conditions A), which were ineffective in the fixed exposure test.

Condition Output voltage frequency Pulse width Survival rate A 5㎸ 2 ㎑ (pps) 1 μsec - B 8㎸ 2 ㎑ (pps) 1 μsec 41 (%) C 8㎸ 2 pp (pps) 20 μsec 94 (%)

In Table 1 and Table 2, the sterilization effect could not be obtained at the output voltage of 5 ,, whereas the sterilization effect was obtained at the output voltage of 8 ,, and the smaller pulse width is used for the sterilization if the output voltage is constant (8 ㎸). It can be seen that the effect is great.

As described above, according to the present invention, a pulse streamer discharge is generated in a gas near both electrodes by applying a pulse waveform high voltage between the discharge electrode and the counter electrode, thereby killing and inactivating microorganisms contained in the gas. have.

Claims (6)

A sterilization method characterized by killing or inactivating microorganisms present in the discharge region by generating a streamer discharge in the vicinity of both electrodes by applying a pulse waveform high voltage between the discharge electrode and the counter electrode. A sterilizing apparatus comprising: a discharge electrode 3 and a counter electrode 4; and a high voltage applying means 9 for applying a high voltage of a pulse waveform for generating streamer discharge between the electrodes 3, 4; . 3. The high voltage applying means (9) according to claim 2, wherein the high voltage applying means (9) is used at least once within the passage time of the gas or liquid passing through the discharge region (5) formed near the discharge electrode (3) and the counter electrode (4) at a predetermined speed. Sterilizing apparatus, characterized in that controlled to the frequency of generating the streamer discharge. The sterilizing apparatus according to claim 2 or 3, wherein the high voltage applying means (9) is configured to apply a high voltage having a minimum pulse width. The sterilizing apparatus according to claim 2 or 3, wherein the high voltage applying means (9) is configured to apply a high voltage having a minimum pulse width of 1 mu sec or less. The sterilizing apparatus according to claim 2, wherein the high voltage applying means (9) is configured to apply a high voltage of a negative pulse waveform.