JPS6257557A - Sterilizing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a sterilization method, and more particularly to a method of air sterilization or surface sterilization using ozone.

In recent years, with the development of medical technology, opportunities for cross-infection among patients are increasing in medical facilities due to the movement of personnel and equipment. 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 that manufacture sterile packed long-life foods.

Most of the conventional air sterilization methods are based on one type of air filter. 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 pressure loss in the filter, requires maintenance of the filter, 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.

An ozone sterilization method has been considered as an alternative to the single air filter method (for example, Japanese Patent Application Laid-open No. 115593/1983). 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. It is said that it must be kept below lppm. For this reason, residual ozone in sterile air must be decomposed. Natural decomposition methods, thermal decomposition methods, and the like are known as ozone decomposition methods. Ozone itself is chemically unstable and decomposes into oxygen if left alone, but the half-life of ozone at room temperature is approximately 16 hours, which is quite a long time, so natural decomposition methods have poor 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. Patent application filed earlier by the applicant in 1973
No. 9-8275 disclosed a microwave ozone decomposition method.

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 conventional ozone sterilization methods to air conditioning systems that require sterilization of large amounts of air.

The applicant of the present application has disclosed an ozone sterilization method that eliminates the drawbacks of the above-mentioned conventional techniques in Japanese Patent Application No. 59-98432. This method is characterized by instantaneous decomposition and sterilization of ozone by subjecting air containing ozone and microorganisms to electrical discharge treatment.

OBJECTS OF THE INVENTION The present invention is an improvement on the prior invention, and an object of the present invention is to provide a method for decomposing and sterilizing ozone in a more energy-saving manner than the prior invention.

Summary of the Invention The present invention involves adding ozone to a gas containing microorganisms; introducing the resulting ozone-containing gas into a discharge zone to form a plasma state; and passing this treated gas through a catalytic reaction zone at room temperature to remove ozone and microorganisms. This is a sterilization method consisting of the above steps to obtain a gas containing almost no gas.

Furthermore, the present invention performs surface sterilization by adding ozone to the working space; after surface sterilization, the ozone-containing gas in the working space is introduced into the discharge zone to form a plasma state; and the resulting treatment gas undergoes a catalytic reaction at room temperature. There is also provided a sterilization method comprising the steps of: passing the gas through the zone to obtain a gas substantially free of ozone; and circulating the ozone-free gas to the work space.

Preferred embodiments of the invention Preferred embodiments of the invention will now 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,
It consists of an ozone generation zone 1, a mixing zone 2, a discharge zone 3, a catalytic reaction zone 4, and a working space 5. In this method, air in the work space 5 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 active oxygen, and the resulting air is sent to the catalytic reaction zone 4, where residual ozone is decomposed and residual microorganisms are sterilized.

By circulating the obtained sterile air into the work space 5,
The work space 5 is made into a sterile atmosphere.

The work space 5 may be any space that requires a sterile atmosphere, such as a bioclean 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 5 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 the working space 5 is sent to the mixing 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. Mixing band 2
The ozone concentration within the tank may range from several ppm to several thousand ppm and is not particularly limited. Although the air may be sterilized to some extent by allowing the ozone-mixed air to remain in the mixing zone 2 for a certain period of time, as will be described later, the synergistic effect of ozone and active oxygen produces a sterilizing effect in the discharge zone 3. The residence time of ozone can be made very short, for example, by injecting ozone into the conduit.

The ozone mixed air flowing out of the mixing zone 2 is also introduced into the discharge zone 3, where the ozone mixed air is discharged. The discharge type may be corona discharge, arc discharge, or glow discharge, and preferably glow discharge. Glow discharge is a stable, self-sustaining discharge that changes from spark discharge to arc discharge. The discharge conditions are, for example, an electric field strength of several tens to tens of thousands of ports per centimeter, and a discharge current of several tens of ports per centimeter to several tens of ports per centimeter. The applied voltage is preferably a direct current negative voltage. discharge band 3
In this step, the gas is allowed to remain for a sufficient time to form plasma.

The required superficial velocity (SV) in the discharge zone is about 1000 to about 60,000 hr.

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, the insulating support 21
Parallel linear electrodes 22 fixed by 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.
For example, it is 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.

Still another discharge device that can be suitably used in the discharge zone 3 is shown in FIG. This discharge device includes application electrodes 41 to which a voltage is applied and which are arranged to face each other;
It consists of an intermediate electrode 42 located on a line connecting the discharge portions of both of the application electrodes 41 and placed between these electrodes at a distance from these electrodes. Four application electrodes 41 are arranged in parallel on the left and right sides of the electrode support frame 44, respectively. The application electrodes 41 located on the horizontal plane are arranged so that their tip ends face each other, and an intermediate electrode 42 is installed on the line connecting these tips, and the application electrode 41
1 and the intermediate electrode 42 as well as each intermediate electrode 42 are separated from each other by a predetermined interval.

The application electrode 41 is preferably a needle-shaped electrode, but a horizontal plate electrode or a rod-shaped electrode can also be used. For needle-like electrodes, the tip portions are arranged opposite to each other, for flat electrodes, the end portions are arranged opposite to each other, and for rod-like electrodes, the length directions are arranged opposite to each other.

As the material of the application electrode 41, conventionally known conductive materials such as iron, aluminum, and tungsten can be used.

Although various shapes and materials can be used for the intermediate electrode 42 as described above, a needle-shaped electrode is preferable. This intermediate electrode enables uniform discharge in each discharge gap. Here, the discharge gap length is a value obtained by subtracting the length of the intermediate electrode 42 from the length from the tip of the application electrode 41 on the left side to the tip of the application electrode 41 on the right side. That is,
The discharge gap length l is l=right+lt"1ls (in the formula, l, , l, and 13 each indicate the distance between the electrodes as shown in the figure). In the conventional device, the length between the two electrodes is The length corresponds to 1, but in the device according to the present invention, 1 is divided by interposing the intermediate electrode 42. In the figure, 1 is divided into three.

Generally speaking, if the number of intermediate electrodes located on the same horizontal line is n, then l is divided into n+1. 11゜1t-I
s may be equidistant or different.

However, the most stable and uniform discharge is formed when 11=ll=ls. The length of the intermediate electrode 42 can be selected as appropriate. It is preferable that the intermediate electrode 42 be movable left and right on the support frame 44 so that Att, At, and Is can be finely adjusted.

The gas treated by making it into a plasma state in the discharge zone 3 is introduced into the catalytic reaction zone 4, where residual ozone is decomposed and sterilized. Catalysts that can be used in the present invention include solid acid catalysts such as synthetic zeolites and silica-alumina catalysts, activated carbon, or supported metal catalysts such as lead, copper, zinc, and nickel. Solid acid catalysts are preferred, especially synthetic zeolite catalysts. The shape of the catalyst is not particularly limited, and may be spherical or pellet-shaped. The superficial velocity of the catalyst layer is not particularly limited, but is between 1000 and 100,000.
hr""", preferably io, ooo or ioo
,oo.

hr'''.The catalytic reaction can be conventionally carried out at normal pressure.

In FIG. 1, the fluid to be sterilized is drawn out from the working space 5, but the present invention also employs a so-called non-circulation method in which outside air is introduced into the mixing zone 2 and sterilized air is supplied to the working space 5. can. In addition to air, an inert gas such as nitrogen can also be used as the gas to be treated.

FIG. 5 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 5, and germs adhering to the surfaces of the operating table 6 or other objects installed in the work space 5. Ozone is introduced into the work space 5 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 5.

FIG. 6 is a schematic system diagram showing still another embodiment of the present invention. In the method shown in this figure, air in the working space 5 is first drawn out by a blower B, and ozone is added to this air from the ozone generation zone. The resulting ozone-containing air is sent through a bypass 7 to the workspace 5, where it is exposed to the walls of the workspace 5,
Sterilize surfaces such as ceilings and items. After the surface sterilization is completed, the bypass 7 is closed and the air in the working space 5 is sent to the discharge zone 3 and then to the catalytic reaction zone 4, and sterile air containing no ozone is circulated to the working space 5.

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 residual formalin. In the method of the present invention, ozone is completely decomposed into oxygen and no ozone remains.

Surprisingly, the inventors have found that when air containing ozone is passed through a discharge zone and then brought into contact with a catalyst, the ozone is decomposed 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. did not become. 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. That is, in the present invention, ozone-containing air is introduced into the discharge zone where it is discharged with low discharge power, so that ozone is partially decomposed (for example, ozone decomposition rate is 80%) and sterilization is also performed. Next, the air containing residual ozone and residual viable bacteria is sent to the catalytic reaction zone, where ozone is completely decomposed and completely sterilized.

The discharge power applied in the present invention is preferably about 60 times the power required to completely decompose ozone by discharge or less.

Function 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. 03+ e→0. + (0) ・・・・・・・・・
...(1) Active oxygen 0) obtained by formula (1) has an extremely short lifespan, but is very active and quickly reacts with other ozone to become oxygen.

03+ (0)→202 ・・・・・・・・・・・・
(2) In the ozone decomposition reaction, equation (1) is considered to be the rate-determining step, and in the present invention, the reaction of equation (1) is thought to proceed rapidly due to the discharge treatment.

In addition, active oxygen (0) exhibits a strong oxidizing effect and easily combines with carbon and hydrogen in organic matter, converting organic matter into carbon monoxide,
Oxidatively decomposes to carbon dioxide and water vapor. If we replace the organic matter with bacteria in the air, we can think 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.

By the way, as described above, in the present invention, the air flowing out from the discharge zone contains undecomposed ozone and viable bacteria. It is thought that when this air is passed through the catalytic reaction zone, the reaction of the above formula (2) occurs on the catalyst surface and ozone is decomposed into oxygen (02). It is also believed that residual viable bacterial cells are captured on the catalyst surface and oxidized and decomposed there by ozone or active oxygen.

Effects of the present invention According to the present invention, the discharge energy is 40% lower than that of the prior invention.
It can be reduced by more than Furthermore, since the catalytic reaction can be carried out at room temperature, the catalyst is less susceptible to deterioration and has the advantage of having a long catalyst life. Furthermore, since the catalyst used in the present invention is a non-noble metal catalyst such as zeolite, maintenance costs for the catalyst are low. Another advantage is that due to the action of the catalytic reaction zone, variations in the amount of ozone added do not affect the outflow air.

Number of viable bacteria 2 x 10'/cc (yeast: Saccharo
mycesformosensis + Bacillus subtilis:
Bacillus 5ubtilis) containing air 12
'm/h was processed by the method shown in FIG. The amount of ozone added was 10 ppm. In the discharge zone, a glow discharge was formed by applying an alternating current of -10 kV between the electrodes using the apparatus shown in FIG. The catalyst used was Molecular Sieves 3A. On the other hand, in a comparative example, the same procedure as above was carried out except that no catalyst was used.

The results are shown in the table below.

Table 1 Example 1 40 0 0 Example 2
28 0 4 Comparative example 4006

[Brief explanation of the drawing]

1, 5 and 6 are schematic diagrams showing preferred embodiments of the method of the present invention. FIG. 2, FIG. 3, and FIG. 4 are schematic perspective views showing preferred embodiments of the discharge device used in the method of the present invention. 1...Ozone generation band 2...Mixing band 3...
・Discharge zone 4...Catalytic reaction zone Patent applicant Shinryo Corporation (5 others) Collection 1I21 Base 3 designs 4 figures + 4 sides, 5 Procedures Amendment Document J/J1, 1985 Patent Director General Uga Michibu 1, Indication of the case Patent Application No. 197229 of 1985 2, Name of the invention Sterilization method 3, Relationship with the case by the person making the amendment Patent applicant address name Shinryo Corporation 4. Column 6 of the agent's specification [detailed description of the invention], contents of the amendment 1) "Air containing 12 m'/
Correct "h" to "a suspension of bacterial cells is sprayed into the air flowing at a wind speed of 12+++)/h." 2) "AC" on page 17, line 1013 of the specification is changed to "DC"
I am corrected. that's all

Claims (1)

[Claims] 1) Ozone is added to a gas containing microorganisms; the resulting ozone-containing gas is introduced into a discharge zone to form a plasma state; and the resulting treated gas is passed through a catalytic reaction zone at room temperature to form ozone and Obtaining a gas containing almost no microorganisms; A sterilization method consisting of each of the above steps. 2) The method of claim 1, wherein the gas is air. 3) The method according to claim 1, wherein 10 to 5000 ppm of ozone is added. 4) The method according to claim 1, wherein a glow discharge or a corona discharge is formed in the discharge zone. 5) The catalyst used in the catalytic reaction zone is zeolite;
The method of claim 1, wherein the method is selected from the group consisting of a silica-alumina catalyst; activated carbon; and a lead, zinc, copper or nickel supported catalyst. 6) Add ozone to the working space to perform surface sterilization; After surface sterilization, the ozone-containing gas in the working space is introduced into the discharge zone to form a plasma state; the resulting treatment gas is passed through the catalytic reaction zone at room temperature. A sterilization method comprising the steps described above: obtaining a gas containing almost no ozone; and circulating this ozone-free gas into the working space.