JPH0425021B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a sterilization method, and particularly to a method of air sterilization or surface sterilization using ozone. BACKGROUND OF THE INVENTION In recent years, with the development of medical technology, opportunities for cross-infection among patients are increasing due to the movement of personnel and equipment in medical facilities. Especially in hospital waiting rooms, there are many opportunities for cross-infection due to visiting patients. For this reason, many medical facilities have installed sterile air conditioning equipment as a measure to prevent infection. A sterile environment is also required in the food industry, and bio-clean rooms are being actively adopted, especially in factories producing sterile packs and long-life foods. Most conventional air sterilization methods are based on air filters. In this method, the air to be treated is passed through a filter to collect dust and microorganisms, and clean, sterile air is blown into the clean room. This method increases the blowing power due to the pressure loss of the filter, requires filter maintenance, or if the filter is not properly maintained, there is a risk that the duct will become contaminated and air containing bacteria will be sent into the clean room. There are some problems. Ozone sterilization is being considered as an alternative to the air filter method (for example,
No. 115593). It is known that ozone has a bactericidal effect. Ozone is suitable as an air disinfectant because it decomposes into harmless oxygen. However, ozone remains in the sterile air obtained by ozone sterilization. Ozone is harmful to the human body even at low concentrations, and the ozone concentration in the workplace is usually reduced to 0.1ppm.
It is said that the following must be done. For this reason, residual ozone in sterile air must be decomposed. Natural decomposition methods and thermal decomposition methods are known as ozone decomposition methods. Ozone itself is chemically unstable and decomposes into oxygen if left untreated, but the half-life of ozone at room temperature is approximately 16 hours, which is quite a long time, so natural decomposition methods have little industrial applicability. In the pyrolysis method, not only does the operating cost required for heating increase, but also the air after pyrolysis must be cooled to room temperature. For this reason, it is difficult to employ the pyrolysis method in air conditioning systems. The applicant of the present application disclosed an ozone decomposition method using microwaves in Japanese Patent Application No. 8275/1982. Although this method overcomes the drawbacks of conventional ozonolysis methods, it has problems such as low energy efficiency and high equipment cost. The second problem in applying the ozone sterilization method to air conditioning systems is that the sterilization rate is slow.
Although it depends on the ozone concentration, the contact time between ozone and air generally requires several hours or more. For this reason, it has been difficult to apply the conventional ozone sterilization method to air conditioning systems that must sterilize a large amount of air. Purpose of the Invention The present invention is a novel ozone sterilization method that overcomes the drawbacks of the prior art, and provides an ozone sterilization method that decomposes ozone more easily and quickly than before, and that dramatically increases the sterilization speed of ozone. With the goal. Key Points of the Invention Ozone itself is unstable, and when external energy is applied, it releases active oxygen and decomposes into oxygen. The present inventors discovered that when ozone-containing air was discharged, ozone instantly decomposed into oxygen. At this time, they discovered that microorganisms in the air were also sterilized at the same time, leading to the completion of the present invention. Embodiments Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic system diagram showing a preferred embodiment of the present invention, which is composed of an ozone generation zone 1, a mixing zone 2, a discharge zone 3, and a work space 4. In this method, air in the work space 4 is drawn out by a blower B and supplied to the mixing zone 2, where ozone generated from the ozone generation zone 1 and air are mixed. The ozone-mixed air is sent to the discharge zone 3, where the ozone is decomposed into oxygen, and the resulting sterile air is circulated to the work space 4, thereby creating a sterile atmosphere in the work space 4. The work space 4 may be any space that requires a sterile atmosphere, such as a bio-clean room such as an operating room, a waiting room of a hospital, a building of a food manufacturing factory, or a pharmaceutical factory. In the method shown in FIG. 1, it is possible to create a sterile atmosphere in the work space 4 without containing ozone, so it is possible to create a sterile atmosphere in a space where people are present, such as an operating room or a hospital waiting room. It can be done. Air drawn from work space 4 is mixed into zone 2
where it is mixed with ozone. The ozone generation zone 1 can be a conventional ozone generator, for example a silent discharge ozone generator or an ozone cylinder. The ozone concentration in mixing zone 2 is a number
It may range from ppm to several thousand ppm and is not particularly limited. Although the ozone mixed air may be allowed to remain in the mixing zone 2 for a certain period of time to sterilize the air to some extent,
As will be described later, the synergistic effect of ozone and active oxygen in the discharge zone 3 produces a remarkable sterilizing effect, so it is possible to make the residence time in the mixing zone 2 very short, for example by injecting ozone into the piping. can. The ozone mixed air flowing out from the mixing zone 2 is introduced into the discharge zone 3, where the ozone mixed air is discharged. As the discharge type, corona discharge, arc discharge, glow discharge, etc. can be adopted. It is also possible to use creeping discharge. FIG. 2 is a schematic perspective view of a discharge device suitable for use in the discharge zone of the present invention. In this device, parallel linear electrodes 22 fixed by an insulating support 21 are arranged as shown in the figure, and a high DC voltage is applied between the electrodes. When an ozone-containing fluid is passed between the electrodes, the ozone is decomposed by corona discharge and a fluid with a reduced ozone concentration is obtained. Although the material of the linear electrode 22 is not particularly limited, tungsten can be suitably used. The distance between the electrodes is determined by various factors such as the flow rate of the fluid to be treated and the discharge voltage, and is, for example, several centimeters to several tens of centimeters. FIG. 3 is a schematic perspective view showing another aspect of the discharge device. In this device, linear electrodes 32 are placed at equal intervals before or after plate electrodes 31 arranged in parallel. In this case, it is preferable that the linear electrode 32 is a negative electrode. Electrons generated by the discharge decompose or ionize ozone, and the ionized ozone molecules are collected on the plate-shaped electrode, making it possible to effectively decompose ozone. As a result of intensive study by the present inventors regarding the discharge conditions, it was found that a discharge power of 1.0 W·hr/m ³ per unit aeration amount of the fluid to be treated is sufficient.
The upper limit of the discharge power is not particularly limited, but will be limited to some extent from an economic standpoint. A particularly preferable discharge power is 500 W·hr/m ³ or less. The present invention can be preferably carried out at a discharge power of 5,000 to 25,000 volts. In the above explanation, the case where one discharge device is used in the discharge band is exemplified, but as a modified example, two discharge devices are used.
One or more discharge devices can be incorporated into the discharge zone of the present invention. For example, when the amount of ozone added is large, that is, when the ozone concentration in the fluid to be treated is high, such as several thousand ppm, the ozone is decomposed by the first discharge device (e.g. creeping discharge device) and the ozone concentration is significantly reduced ( Sterilization is also carried out at the same time), and a subsequent second discharge device can further decompose ozone to reduce the ozone concentration to 0.1 ppm or less. It is also possible to incorporate the ozone generation zone 1 into the processing line. That is, air containing microorganisms is introduced into a conventional ozonizer and silently discharged to generate ozone at a desired concentration, and then discharged in the discharge zone according to the present invention under the above-mentioned discharge conditions to decompose the ozone and Sterilization treatment is also performed. In Figure 1, the fluid to be sterilized is placed in the working space 4.
However, other outside air is discharged from discharge zone 3.
The present invention can also adopt a so-called non-circulation method in which sterilized air is introduced into the work space 4 and supplied to the work space 4. In addition to air, an inert gas such as nitrogen can also be used as the gas to be treated. FIG. 4 is a schematic system diagram showing another embodiment of the present invention. This method can effectively sterilize germs adhering to the wall surface of the work space 4, and the germs adhering to the surface of the operating table 5 or other articles installed in the work space 4. Ozone is introduced into the work space 4 from the ozone generation zone 1, left for several hours to complete surface sterilization, and then the ozone-containing air in the work space is pulled out by the blower B and sent to the discharge zone 3, where the ozone is converted to oxygen. After being disassembled, it is circulated to the work space 4. Conventionally, formalin has been mainly used in this type of surface sterilization, but the formalin sterilization method has had problems such as formalin remaining on the surface of the article and treatment of the residual formalin. In the method of the present invention, ozone is completely decomposed into oxygen and no ozone remains. Surprisingly, the present inventors have discovered that when air containing ozone is discharged, ozone decomposes into oxygen and germs in the air are almost completely killed. Conventionally, when air sterilization was performed using ozone alone, it was necessary to mix the air and ozone and hold it for several hours in order to achieve sufficient sterilization, and the residual ozone in the resulting sterile air had to be decomposed and removed. It didn't happen. It has been found that, according to the method of the present invention, the seemingly contradictory effects of ozone decomposition and sterilization occur simultaneously and in a very short time. Complete air sterilization can be achieved by subjecting ozone-containing air to electrical discharge treatment even for a short time, for example, a residence time of several seconds, when ozone alone cannot be expected to have any sterilizing effect. The ozone decomposition and sterilization mechanism according to the present invention is considered as follows. When air containing ozone is discharged, the electrons generated react with the highly reactive ozone. O ₃ +e→O ₂ +(O)...(1) Active oxygen (O) obtained from equation (1) has an extremely short lifespan, but is very active and quickly reacts with other ozone to form oxygen. Become. O ₃ + (O) → 2O ₂ ...(2) Equation (1) is considered to be the rate-determining step in the ozone decomposition reaction, and in the present invention, it is believed that the reaction of equation (1) will proceed rapidly due to discharge treatment. It will be done. In addition, active oxygen (O) exhibits a strong oxidizing effect and more easily combines with carbon and hydrogen of organic matter, oxidizing and decomposing the organic matter into carbon monoxide, carbon dioxide, and water vapor. If we replace the organic matter with bacteria in the air, it is thought that the bacteria in the air react with some of the active oxygen generated by the decomposition of ozone, are oxidized and decomposed, and die. It is thought that in the method of the present invention, active oxygen rapidly increases due to the discharge treatment, and the sterilization rate is dramatically accelerated. Example 1 The bactericidal effect of the present invention was studied. FIG. 5 shows the experimental apparatus used in this example. Ten
Dried yeast (Saccharomyces
Formosensis) (number of viable bacteria: 2.3 x 10 ⁸ ) was placed on the plate. As shown in the figure, an acrylic pipe 53 was fixed to the top of the shear plate 52, and tungsten wire electrodes 54 were horizontally arranged within the pipe at intervals of 2 cm. Ozone is sealed in the container 51 to increase the ozone concentration.
It was set to 25ppm. Blower B circulates ozone-containing air while applying DC 12KV to the electrodes to generate 33W.
Discharge treatment was performed for 3 minutes at a discharge power of hr/m ³ . After the treatment, the number of viable bacteria in the shell was measured, and the sterilization rate was 93%. On the other hand, the sterilization rate when no discharge treatment was performed was 17%. Example 2 The ozone decomposition effect by the method of the present invention was studied. The device used in this example consists of a discharge device consisting of four plate-shaped electrodes arranged in parallel and three linear electrodes located upstream thereof, and a discharge device composed of four plate-shaped electrodes arranged in parallel and three linear electrodes arranged in parallel. This is an arrangement in which electric field forming devices consisting of electrodes are arranged in series. In the first discharge device, the plate electrode was grounded and a negative DC voltage was applied to the linear electrode. In the second discharge device, a positive DC voltage was alternately applied to the plate electrodes. Ozone-containing air was flowed in from the linear electrode side, and the ozone concentration in the air flowing out from the electrolytic formation device was measured. The results are shown in Table 1.

[Table] This example shows that ozone decomposition is possible even at low discharge energy of 0.46 W·hr/m ³ . Furthermore, when ozone decomposition is performed by arranging three of the devices used in this example in series, the ozone concentration can be reduced.
The power consumption can be reduced from 60ppm to 90ppm, and this power consumption is extremely low at 1.38W・hr/ ^m3 . Example 3 Air with an ozone concentration of 1300 ppm was poured at 16.7 to 33.4 mm between cylindrical creeping discharge electrodes (60 mm x 335 mm, glass core: 40 mm x 335 mm, discharge space volume 0.53).
The ozone decomposition rate was determined by inflowing at a flow rate of /min. The results are shown in Table 2 below.

[Table] Effects of the present invention According to the present invention, ozone can be decomposed and sterilized in an extremely short time by electric discharge treatment. In particular, it is possible to perform ozone decomposition and sterilization simultaneously in less than 1/10 the processing time compared to the microwave irradiation method of the previous application.
Furthermore, in terms of device structure, a discharge device is much simpler than a microwave irradiation device and can be manufactured at a lower cost. Furthermore, compared to conventional pyrolysis methods, the method of the present invention does not require a cooling step after treatment.
As described above, the method of the present invention can create a sterile atmosphere in a space where people are present, such as an operating room or a hospital waiting room, by using ozone.

[Brief explanation of drawings]

1 and 4 are schematic diagrams showing preferred embodiments of the method of the present invention. 2 and 3 are schematic perspective views showing preferred embodiments of the discharge device used in the method of the present invention. FIG. 5 is a schematic structural diagram of the experimental apparatus used in Example 1. 1...Ozone generation band, 2...Mixing band, 3...
...Discharge zone, 4... Working space, 21... Insulating support, 22... Linear electrode, 31... Plate electrode, 51
... Container, 52 ... Schare, 54 ... Tungsten wire electrode.

Claims (1)

[Claims] 1. A sterilization method using ozone, characterized in that ozone decomposition and sterilization are performed simultaneously by subjecting a gas containing ozone and microorganisms to electrical discharge treatment. 2. The method according to claim 1, wherein the discharge treatment is performed with a discharge power of 1.0 W·hr/m ³ or more. 3. The method according to claim 1 or 2, wherein the gas is air. 4 Ozone concentration in the air is 10ppm to 5000ppm
A method according to claim 3 within the scope of.