KR20220026712A - Sterilizing System for Powder products by low-temperature plasma - Google Patents

Abstract

The present invention is to provide a novel food sterilization method and apparatus which can safely and effectively sterilize edible powder while maintaining nutrients inherent in food and quality thereof. To this end, provided is a dielectric barrier discharge (DBD) low-temperature plasma powder food sterilization system capable of sterilizing powder in a low temperature process of 50℃ or less at a sterilization rate of 99.9%.

Description

Powder sterilization system using low-temperature plasma

The present invention relates to food sterilization technology, and more particularly, to a powder food sterilization system using low-temperature plasma.

In the process of manufacturing food, deterioration may occur due to the inflow of bacteria by equipment, air, tools, and workers. Sterilization technology to prevent spoilage is an important key food manufacturing process that can increase the added autonomy of powdered food. In particular, the production of powdered foods such as baby food for children, elderly-friendly nutritional food, and various health foods is increasing in various countries around the world as human civilization develops and interest in health increases. In addition, when spices such as red pepper powder, pepper powder, curry powder, and powdered foods such as coffee, green tea, and black tea are contaminated with various pathogens, serious problems occur. Most of these powdered foods require mass pasteurization, and the domestic and international market is worth tens of trillions of dollars.

The method of sterilizing bacteria contained in food or powdered food at a high temperature of 100°C or higher is the most widely used method. However, there is a problem in that heat-sensitive materials cannot be used in the heat sterilization process. In addition, since it is made at high temperature, it causes changes in taste, aroma, color, texture, shape, and ingredients, making it difficult to preserve the unique food quality. is difficult to apply to the process because it has the disadvantage that it cannot achieve the expected sterilization rate.

That is, in the conventional sterilization method, powdered food is sterilized by heating and processed and stored. This method inactivates microorganisms and enzymes possessed by high-temperature treatment to prevent spoilage of food and increase storage period. However, since the heat sterilization process is mainly performed at 100° C. or higher, there is a problem in that a material weak to heat cannot be used. In addition, since it is made at high temperature, it is difficult to preserve the inherent quality of food, such as taste, aroma, color, texture, shape, and component change. On the other hand, the cold sterilization method performed at a low temperature of 50° C. or less has a disadvantage in that the sterilization rate targeted for sterilization of powdered foods cannot be achieved.

In order to solve this problem, a lot of research on non-heat sterilization has been made, and among various methods, radiation, ultraviolet, and low-temperature plasma sterilization methods (refer to Patent Registration No. 10-1571238, etc.) and has been applied in various ways in the food manufacturing process. In the radiation method using gamma rays, X-rays and electron beams, high-energy waves are emitted to ionize and destroy the organic components of microorganisms contained in food, thereby killing microorganisms. The radiation method costs a lot of installation costs such as professional manpower and safety facilities, and there is a problem that food can be genetically modified.

In addition , the ultraviolet irradiation method sterilizes powdered food by electromagnetic wave radiation of a short wavelength in the range of about 180 nm to 310 nm. However, there is a downside to sterilization.

It is an object of the present invention to provide a novel food sterilization method and apparatus capable of safely and effectively sterilizing edible powder while maintaining the inherent nutrients and quality of food.

The low-temperature plasma method is widely used for surface treatment of metal and non-metal materials, and is widely applied in the manufacturing process of bio-industry, displays, semiconductors, and electronic products. Low-temperature plasma generated at atmospheric pressure uses a dielectric to control the current, and the price of the generator is low, the average electron energy of plasma is 0.7 eV ~ 2.5 eV, and the plasma density is about 10 ¹² ~ 10 ¹⁴ / cm ³ Mostly chemical reactions take place. Various types of active species (OH, H ₂ O ₂ , O radicals, N radicals, NO, NO ₂ , O ₃ etc.) and ultraviolet rays, Visible light, electromagnetic waves, and electric fields are generated. Plasma with various physical and chemical properties is a gaseous state that can sterilize more than 99.9% of microorganisms (E. It is a safe way to effectively sterilize powder.

Accordingly, the present invention provides a low-temperature atmospheric pressure plasma sterilization method to hygienically produce health food, baby food for children, elderly-friendly nutritional food, and the like. Disclosed is a dielectric barrier discharge (DBD) low-temperature plasma powder food sterilization system capable of sterilizing powdered food in a low-temperature process of 50° C. or less.

The present invention controls the position and thickness of the dielectric and powder of the electrode so that the applied power can produce the maximum power consumption for the powder in the structure of the dielectric barrier discharge plasma source, and the powder is applied to the dielectric barrier discharge source for 99.9% sterilization power To provide a pasteurization system with controlled transport speed.

That is, the present invention is

a first metal electrode;

a dielectric having a thickness d1 and a dielectric constant ε1 covering the first metal electrode;

a second metal electrode spaced apart from the lower surface of the dielectric and disposed to face the first metal electrode and grounded;

a dielectric powder having a dielectric constant ?2 placed on the second metal electrode to a thickness d2; and

a power supply for applying a voltage between the first metal electrode and the second metal electrode;

maintaining a distance d0 between the lower surface of the dielectric and the upper surface of the dielectric powder;

In order to increase the sterilization power of the dielectric powder, the dielectric thickness d1 is made thinner than the d0 or d2, and the dielectric constant ε1 is larger than ε2,

It provides a powder sterilization system, characterized in that the power supply generates a dielectric barrier discharge plasma between the first metal electrode and the second metal electrode to sterilize the powder by low-temperature plasma sterilization.

In the above, it provides a powder sterilization system, characterized in that ε1 is 5 or more and d1 is 50 to 150 μm so as to lower the power consumed in the dielectric d1 to 2% or less.

In the above, the powder is sterilized while being transferred relative to the first metal electrode, and the transfer speed is adjusted to maintain the plasma irradiation time required to achieve a sterilization rate of 99.9%.

In the above, the second metal electrode is configured in the form of a circulating belt, and provides a powder sterilization system, characterized in that the powder placed on the belt is transferred at a predetermined speed.

In the above, in order to sterilize the belt surface while the belt moves along the lower surface for circulation after the powder placed on the circulating belt flows into the descending part, a dielectric barrier covering the metal electrode with a dielectric under the circulating belt lower surface It provides a powder sterilization system, characterized in that the discharge plasma source is installed.

In the above, the powder is sterilized while being transferred relative to the first metal electrode, and the transfer speed is adjusted to maintain the plasma irradiation time required to achieve a sterilization rate of 99.9%.

In the above, a descending part for guiding the powder into storage at one end of the belt is installed so that the plasma sterilized powder flows into the descending part on the belt,

The lower part,

Exterior walls containing earthed metal;

a dielectric covering the metal inside the outer wall;

Including; at least one surface electrode fixed to the dielectric while forming an inclination;

It provides a powder sterilization system, characterized in that the powder is additionally sterilized by generating a plasma discharge between the surface electrode and the outer wall.

The powder sterilization system is disposed in the chamber,

The chamber includes a fluid inlet and a fluid outlet for discharging gas or coolant flow, a foreign material removal filter at the fluid inlet, and a harmful gas adsorption filter at the fluid outlet.

chamber;

a screw mechanism for transferring powder comprising a rotation shaft disposed in the chamber and a screw attached to the rotation shaft;

an active gas passing membrane installed on the upper and lower portions of the screw mechanism;

a plasma source for dielectric barrier discharge disposed above and below the screw mechanism and above and below the active gas passing film; and

Including; porous portion included in the upper and lower surfaces of the chamber;

The powder transferred by the screw mechanism is sterilized by the dielectric barrier discharge plasma, and the active gas penetrates and diffuses into the powder through the active gas passage membrane,

Provided is a powder sterilization system, characterized in that by supplying gas from the outside of the chamber, the airflow flowing into the porous part is prevented from flowing out of the powder and the active species to the outer wall of the chamber.

In the above, by arranging a plurality of RF coils near the porous part, and applying power to the RF coil with an RF power source, the plasma electrons in the chamber increase the density of the plasma by cyclonic motion along the magnetic field. A sterilization system is provided.

In the above, a descending part for guiding the powder into storage at one end of the screw mechanism is installed so that the plasma sterilized powder flows into the descending part by riding the screw mechanism,

The lower part,

Exterior walls containing earthed metal;

a dielectric covering the metal inside the outer wall;

Including; at least one surface electrode fixed to the dielectric while forming an inclination;

It provides a powder sterilization system, characterized in that the powder is additionally sterilized by generating a plasma discharge between the surface electrode and the outer wall.

column chamber;

a powder input hopper placed on the top of the columnar chamber;

a plurality of powder flow guide plates arranged in a zigzag manner from the top to the bottom inside the columnar chamber, maintaining gaps with each other;

a DBD plasma source arranged in the columnar chamber and performing low-temperature plasma treatment on the flowing powder;

a gas exhaust filter disposed under the columnar chamber; and

It provides a powder sterilization system, characterized in that the powder is subjected to low-temperature plasma sterilization, including; a powder collecting pedestal disposed at the lower end of the columnar chamber to collect and discharge sterilized powder.

In the above, it provides a powder sterilization system, characterized in that the low-temperature plasma sterilization treatment time for the powder is carried out for 15 seconds or more.

The low-temperature atmospheric pressure plasma sterilization method of the present invention makes it possible to hygienically produce health food, baby food for children, nutritional food for the elderly, and the like. By applying a dielectric barrier discharge (DBD) low-temperature plasma that can sterilize powdered food in a low-temperature process below 50°C, 99.9% sterilization is achieved while maintaining the unique properties of the powder due to low-temperature sterilization.

It generates active species such as OH radicals, O radicals, N radicals, H ₂ O ₂ , and O ₃ generated from atmospheric pressure DBD plasma capable of large-area stable discharge, as well as electrons, ultraviolet rays, visible rays, and electromagnetic waves. It is possible to implement a low-temperature plasma food sterilization system for mass production that can effectively sterilize harmful microorganisms in large quantities by spreading and penetrating these plasma active species and physical factors into food powder.

1 is a cross-sectional view for explaining the configuration of a dielectric barrier plasma source to be applied to the plasma powder sterilizer of the present invention.
2 is a graph showing the bacterial sterilization rate contained in the powder compared to the low-temperature plasma sterilization time.
3 is a block diagram of a belt-type sterilizer as an embodiment of a low-temperature plasma powder sterilizer according to the present invention.
4 is a block diagram showing another embodiment of the belt-type sterilizer.
5 is a configuration diagram showing the application of a screw to the low-temperature plasma powder sterilizer according to the present invention.
6 is a block diagram showing an embodiment of another powder sterilizer of the present invention.
7 is a table and graph showing the results of the sterilization test of the powder sterilizer of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 shows a DBD plasma electrode part and is composed of an electrode part having a SiOx dielectric, an electrode part having a powder dielectric, and an air gap therebetween.

That is, in the plasma generating structure in which DBD plasma is generated between powdered food, a pair of first and second metal electrodes 10 are spaced apart from each other to face each other, and a dielectric powder is placed on the lower second (ground) electrode and the electrode By applying a voltage to both ends to generate dielectric barrier discharge plasma, the powder is treated with plasma. A dielectric covering the electrode is disposed on the electrode 10 disposed on the powder. The dielectric material can be made of various ceramic materials and polymer materials other than SiOx.

The voltage is calculated in the gap between the electrodes of the DBD plasma generator through physical analysis of the electrode and powder arrangement structure, and when a high frequency voltage is applied, the resistance impedance of the circuit is the same, so a high sterilization rate can be obtained with high power. Power is converted from the voltage and current applied to the DBD electrode.

In the plasma sterilization system structure of FIG. 1, the voltage applied to the air gap is calculated from the following equation applied to the SiOx dielectric, the powder dielectric, and the air gap.

V = V1 + V0 + V2, (V1: voltage applied to the first electrode dielectric, V0: voltage applied to air, V2: voltage applied to powder)

In the above, V1 : V0 : V2 = Q/C1 : Q/C2 : Q/C3 is expressed.

C1, C0, and C2 are capacitance and Q is the amount of charge, and is expressed as follows.

The area S to which the voltage is applied and the thicknesses d1, d0, and d2 were tested at 70 μm, 3 mm, and 3 mm, respectively, and when the dielectric constants ε1, ε0, and ε2 were 5, 1, and 2.2, respectively, the applied voltage ratio is as follows.

C1 = ε1 S / d1, C0 = ε0 S / d0, C2 = ε2 S / d2,

Therefore, V1 : V0 : V2 = d1/ ε1 : do/ε0 : d2/ ε2 = 1% : 68% : 31%.

That is, when a voltage of 15 kV (Vp) is applied, the voltage applied to the air is 10.2 kV, the voltage applied to the SiOx dielectric 20 on the electrode side is 0.2 kV, and the voltage applied to the dielectric powder 60 is about 4.6 kV. . Since the dielectric constant and thickness of the powder are constant, ε1 is high and d1 is small in order to lower the applied power of the electrode dielectric 20 part to 2% or less.

In this embodiment, the dielectric constant ε1 is 5 or more, and the thickness d1 thereof is 50 to 150 μm, preferably 70 μm to 100 μm.

In this way, by adjusting the thickness and dielectric constant of the dielectric 20 covering the electrode disposed on the powder, the discharge voltage in the air is increased, so the discharge power is increased to generate a large amount of active species, thereby increasing the sterilization rate for microorganisms. .

On the other hand, Figure 2 shows the bacterial sterilization rate contained in the powder with respect to the plasma irradiation time. By using this, the transfer speed of the powder is determined in the powder sterilizer of FIGS. 3, 4, and 5 .

No, Nt is the number of CFU (Colony Forming Unit) after initial and plasma irradiation time t, respectively. It shows that powdered food C showed the highest sterilization rate of microorganisms with respect to plasma irradiation time for powdered foods A, B, and C containing bacteria. In the manufacturing process of powdered food, the bacterial sterilization rate (Nt /No) is 0.001 or less, and a bacterial sterilization rate of 99.9% or more is generally required. It is indicated by the red dotted line Log (Nt/No)=-3 in FIG. 2 .

That is, since Nt/No = 10 ^-3 , the plasma powder food should be sterilized so that it is below the red dotted line. Therefore, plasma irradiation time for A, B, and C powder food should be 6 minutes or more, 3 minutes or more, and 1.5 minutes or more. Based on this, the speed of the belt and the screw for sterilizing powdered food is determined in FIGS. 3, 4, and 5 .

The embodiment of Fig. 3 will be described.

Example 1 (FIG. 3) is a low-temperature plasma powder sterilization system 100 for sterilizing powdered foods such as health food, baby food for children, and elderly-friendly nutritional food in large quantities.

In the powder sterilization chamber 50 installed with the powder input hopper 40, the height of the powder 60 food on the belt 70 is uniformly 1 to 5 mm, preferably, within 3 mm, and the belt 70 of the powder sterilization chamber is used to feed at a uniform speed. The transferred powder passes over the belt 70 and the belt 70 is grounded by a trapezoidal or rectangular dielectric barrier discharge (DBD) source (electrode 10, dielectric 20, insulator 30) installed at regular intervals. and discharge, and active species generated at this time penetrate into the powder to sterilize microorganisms. In the above, the electrode 10 may have a shape protruding in a trapezoidal or quadrangular shape with a predetermined interval therebetween.

In this embodiment, the metal electrode 10 of the DBD source is an Ag electrode of 0.1 mm to 1.5 mm printing method, and the dielectric 20 of the DBD is made of SiOx having a thickness of 70 μm to 100 μm and a dielectric constant of 5 or more. The power consumption was set to less than 2% of the total. The rear surface of the electrode 10 is covered with an insulator 30 .

In the above, the distance d0 between the electrode 10 and the powder should be greater than d1, and in this embodiment, by setting d0 to 3 mm or more, a high voltage is applied between the air gaps and sufficient active species (OH, NO, O , N, H ₂ O ₂ , O ₃ etc.) and electrons, ultraviolet and visible light are generated and diffused into the food powder to sterilize microorganisms.

The belt 70 is made of a metal material such as Cu, Al, Ti, and is connected to the ground. The belt is composed of a circulation type, both ends are driven by rollers to put the powder on the upper surface of the belt, and when the powder supplied from one end of the belt reaches the other end, it flows into the lower part toward the storage box, and the empty belt part is the bottom of the roller The powder is loaded when it reaches the end again and becomes an ascending section.

The thickness of the edible powder 60 is within about 3 mm and has a dielectric constant of about 1.5 to 3.5. The powder 60 on the belt 70 is transferred while being sterilized, and the microorganisms attached to the surface of the opposite belt (the belt part after pouring the powder into the storage box) are in the plasma of the DBD source 15 configured under the belt. sterilized by The distance between the lower belt and the electrode of the DBD source 15 is less than 2 mm, so that the microorganisms on the surface are sterilized with a sufficiently high concentration of plasma active species. On the other hand, plasma sterilization is also made in the descending part (A) in which the powder sterilized on the belt descends from the powder outlet to the storage box.

That is, as in the enlarged view of part A, it is sterilized with low-temperature plasma once again.

The outer wall of the outlet portion is made of a metal ground 110 portion, the inside thereof is covered with a dielectric 20, and the surface electrode 120 (or may be an open tubular electrode or a curved electrode) is attached to the electrode fixing portion 130 ) (applied by a fixing member or welding) to the dielectric 20, and a plurality of surface electrodes are arranged in a zigzag manner with a gap between them. The powder is sterilized by the plasma generated from the cotton electrodes and flows through the gaps between the cotton electrodes and flows along the cotton electrodes to reach the storage box. This will be described later in more detail.

The width of the belt 70 is 10 cm to 100 cm, and the movement speed of the belt is adjusted to have a sterilizing power of Log (Nt/No)=-3 or more. As described above, the sterilization power and feed rate can be adjusted for individual powders (types).

Discharge is generated from the top and bottom of the metal belt to sterilize microorganisms, so sterilization of powder spread in a thin thickness is very effective.

In addition, a dust removal filter 80 is installed at the fluid inlet port for injecting gas/water of the powder food chamber to remove foreign substances such as dust in the air and clean air is injected, inert gas of Ar or He or O ₂ , N The sterilization rate can be increased by injecting a reactive gas of ₂ , etc. to generate a large amount of NOx gas inside the powder sterilization chamber. Noxious gas such as ozone generated by the discharge in the powder sterilization chamber 50 is adsorbed and removed by the noxious gas adsorption filter 90 installed at the fluid outlet.

In order to increase the sterilization rate of the powder when the powder placed on the belt 70 moves horizontally while sterilization is completed with DBD plasma and falls vertically, the powder descending portion may have a structure similar to that of the enlarged part A. The outer wall of the powder drop box uses a conductor such as Cu, Al, Ti, etc., and the inner wall is coated with about 0.07 mm to 0.1 mm dielectric (eg, SiOx). By installing a metal plate inclined at an angle θ with respect to the inner wall of the vertical drop box, DBD discharge is caused by the voltage applied between the metal ground 110 and the metal plate electrode 120 on the outer wall of the descending part to additionally sterilize the falling powder. The angle formed by the metal plate of FIG. 3 with the metal grounding of the outer wall is inclined to about 20deg ~ 80deg, so that it is possible to control the falling time of the powder.

In addition, as shown in Fig. 4, the DBD discharge system can be continuously installed horizontally along the belt to lengthen the plasma irradiation time when the powder moves along the belt. That is, the electrode 10 , the dielectric 20 , and the insulator 30 are continuously spread horizontally so that the powder is continuously subjected to plasma treatment.

In order to absorb the heat generated by the DBD discharge system, a cooling plate cooled with cooling water or a fan can be installed on the DBD metal electrode to lower the temperature of the DBD electrode. The movement speed of the belt is adjusted to have a sterilization power of 99.9% or more by setting Nt/No=0.001 or less. Meanwhile, when the sterilized powder on the belt descends to the powder outlet, it is sterilized with low-temperature plasma once again as in the enlarged part A. The configuration of part A is the same as in FIG. 3 .

5 is a modified embodiment of sterilizing microorganisms while moving the powder using a screw mechanism. The powder is injected into the inlet of the chamber 50 and placed on the screw surface. In the screw mechanism, a screw 150 is formed on a rotation shaft 155 . A screw edge holder is provided so that the powder can be sufficiently placed on the screw surface, and the powder moves according to the rotational motion of the screw. A straight dielectric barrier discharge (DBD) plasma source (electrode 10, dielectric 20) is installed on the top of the screw to generate plasma, and a voltage is applied to the upper and lower metal electrodes 10 of the DBD source dielectric to generate plasma. do. The DBD source includes a plurality of pieces of metal electrodes arranged vertically or radially on a long dielectric 20 . However, the plasma source is not limited thereto, and may be configured by forming electrodes and dielectrics in various shapes.

The dielectric constant of the dielectric 20 of the DBD plasma discharge system is 5 to 10, the thickness is 50 μm to 200 μm, the applied frequency is 1 kHz to 100 kHz, and the voltage is 1 kV to 100 kV. An active gas passing film 140 is installed around the DBD plasma so that the active gas is diffused into the powder placed on the screw, and the powder is prevented from flowing into the DBD plasma system.

The perimeter of the powder food sterilizer chamber 50 is a porous wall 170, and gas (Ar, N ₂ , O ₂ ) or air is injected from the outside to make an air curtain, so that the powder and active species gas are separated from the external wall to prevent it from being released.

In addition, an RF (high frequency) coil 160 is installed around the porous wall 170 so that electrons of the plasma in the chamber increase the density of the plasma by cyclonic motion along the magnetic field.

The frequency of RF power is 0.1 ~ 50MHz, and the power is 0.1 ~ 1000kW. Since the coil temperature rises due to the power applied to the RF coil 160, cooling water is flowed to lower the temperature of the RF coil. Active species of high-density plasma (NOx, OH radical, O radical, H ₂ O ₂ , O ₃ , etc.) generated by the RF coil diffuse into the powder and sterilize microorganisms. A discharge may be generated using air, and a large amount of NOx active species may be generated using a reactive gas including N ₂ , O ₂ and/or an inert gas such as Ar or He.

Powdered food that has been sterilized is discharged through the outlet. The screw movement speed is adjusted so that the bacterial sterilization rate is 99.9% or more.

On the other hand, when the sterilized powder descends to the powder outlet, it is sterilized with low-temperature plasma once again like the enlarged part A (same as the enlarged view of part A in FIG. 3).

In the above, if the DBD plasma systems 10 and 20 and the plasma by the RF coil 160 are used at the same time, there is a possibility of interference of the internal electric field, so they are used respectively. For example, it can be driven alternately in time division.

In addition, the plasma densification by the RF coil 160 and the RF power source may be applied together to the embodiment of the belt transfer according to FIGS. 3 and 4 .

In this way, while sterilizing the powder at a high sterilization rate of 99.9% or more, it is possible to maintain the low temperature to maintain the intrinsic properties such as the flavor of the powder.

On the other hand, the edible powder may be used for skin or hair care, and even in this case, the edible powder low-temperature plasma sterilization system described in the above embodiment may be applied as it is.

6 shows another embodiment of the present invention.

The powder flow guide plate 210 is arranged along the length of the chamber 200 in a zigzag manner inside the columnar chamber 200 in which the powder input hopper 40 is installed at the top. The powder flow guide plate 210 is installed while extending obliquely from the inner wall of the chamber 200 toward the inner space and spaced apart from the opposite inner wall. It is arranged so that the falling point of the powder falling from the first powder guide plate is the upper end of the second powder flow guide plate so that the powder flowing along the first powder flow guide plate can go down on the second powder flow guide plate, and the chamber length Arrange the appropriate number of powder flow guide plates for

The powder flows toward the bottom of the chamber in a zigzag manner along the powder flow guide plate 210, and the DBD source 15 is installed in the middle of the columnar chamber length, and the powder is sterilized by plasma while passing through it. The low-temperature plasma sterilized powder passes through the gas exhaust filter 220 installed at the bottom of the chamber 200, and is collected and discharged through the powder collecting pedestal 41 placed thereunder. The gas exhaust filter 220 is a filter for removing gases such as ozone (O3).

In this example, the low-temperature plasma sterilization system was used to sterilize wheat flour (barley: 26%, brown rice: 24%, non-glutinous rice: 24%, black rice: 12.5%, black beans: 3%, others: 10.5%). . The columnar chamber 200 was a paper cylinder (satisfied with a porous wall) manufactured for experiments, and had a length of 1,150 mm and a diameter of 100 mm.

The experimental results are recorded in FIG. 7, and the time at which more than 99.9% of airborne bacteria are sterilized in atmospheric pressure plasma is shown as a graph.

In the above embodiment, when powdered powder is injected into the upper part of the columnar chamber 200, the time taken to exit the powder collecting pedestal 41 at the lower end is about 1 second. The concentration of ozone by the DBD low-temperature plasma source in the chamber 200 was approximately 0.33 ppm (including H ₂ O ₂ , NO ₂ , etc.), and as shown in the graph, 16 repeated treatments, that is, 0.33 ppm for 16 seconds When treated, more than 99.9% of bacteria were sterilized. The length of the chamber can be designed for efficient processing.

Therefore, the powder is almost completely sterilized by low-temperature plasma treatment for about 15 to 30 seconds.

On the other hand, the specific numerical values presented in the above embodiments and experimental examples are exemplary and can be modified as needed, and those skilled in the art to which the present invention pertains will appreciate that the present invention does not change the technical spirit or essential features of the present invention. It will be understood that it may be implemented in the form. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. do.

electrode (10)
DBD Source(15)
Dielectric (20)
Insulator (30)
Powder input hopper (40)
Powder Sterilization System (100)
chamber (50)
Powder(60)
Belt(70)
filter(80)
Adsorption filter (90)
Ground(110)
cotton electrode 120
Electrode fixing unit 130
Activated gas pass-through membrane (140)
screw(150)
rotation shaft (155)
RF Coil(160)
porous wall (170)
column chamber (200)
Powder flow guide plate (210)
Powder collection pedestal (41)
gas exhaust filter (220)

Claims (13)

a first metal electrode;
a dielectric having a thickness d1 and a dielectric constant ε1 covering the first metal electrode;
a second metal electrode spaced apart from the lower surface of the dielectric and disposed to face the first metal electrode and grounded;
a dielectric powder having a dielectric constant ?2 placed on the second metal electrode to a thickness d2; and
a power supply for applying a voltage between the first metal electrode and the second metal electrode;
maintaining a distance d0 between the lower surface of the dielectric and the upper surface of the dielectric powder;
In order to increase the sterilization power of the dielectric powder, the dielectric thickness d1 is made thinner than the d0 or d2, and the dielectric constant ε1 is larger than ε2,
A powder sterilization system, characterized in that the power supply generates a dielectric barrier discharge plasma between the first metal electrode and the second metal electrode to sterilize the powder by low-temperature plasma sterilization. The powder sterilization system according to claim 1, wherein ε1 is 5 or more and d1 is set to 50 to 150 μm so as to lower the power consumed in the dielectric d1 to 2% or less. The powder sterilization system according to claim 1, wherein the powder is sterilized while being transported relative to the first metal electrode, and the transport speed is controlled to maintain the plasma irradiation time required to achieve a sterilization rate of 99.9%. [4] The powder sterilization system according to claim 3, wherein the second metal electrode is configured in the form of a circulating belt, and the powder placed on the belt is transferred at a predetermined speed. 5. The method of claim 4, wherein after the powder placed on the circulating belt flows into the lower part, a metal electrode is covered with a dielectric under the circulating belt to sterilize the belt surface while the belt moves along the lower surface for circulation. Powder sterilization system, characterized in that the dielectric barrier discharge plasma source is installed. The powder sterilization system according to claim 1, wherein the powder is sterilized while being transported relative to the first metal electrode, and the transport speed is controlled to maintain a plasma irradiation time required to achieve a sterilization rate of 99.9%. [Claim 5] The method of claim 4, wherein a lowering part for guiding the powder into storage is installed at one end of the belt so that the plasma sterilized powder flows into the lowering part by riding the belt,
The lower part,
Exterior walls containing earthed metal;
a dielectric covering the metal inside the outer wall;
Including; at least one surface electrode fixed to the dielectric while forming an inclination;
Powder sterilization system, characterized in that the additional sterilization treatment for the powder by generating a plasma discharge between the surface electrode and the outer wall. The powder sterilization system of any one of claims 1 to 7 is disposed in the chamber,
The chamber includes a fluid inlet and a fluid outlet for discharge gas or coolant flow, a foreign material removal filter at the fluid inlet, and a harmful gas adsorption filter at the fluid outlet. chamber;
a screw mechanism for transferring powder comprising a rotation shaft disposed in the chamber and a screw attached to the rotation shaft;
an active gas passing membrane installed on the upper and lower portions of the screw mechanism;
a plasma source for dielectric barrier discharge disposed above and below the screw mechanism and above and below the active gas passing film; and
Including; porous portion included in the upper and lower surfaces of the chamber;
The powder transferred by the screw mechanism is sterilized by the dielectric barrier discharge plasma, and the active gas penetrates and diffuses into the powder through the active gas passage membrane,
A powder sterilization system, characterized in that by supplying gas from the outside of the chamber, the airflow flowing into the porous part is prevented from flowing out of the powder and active species to the outer wall of the chamber. [Claim 10] The method of claim 9, wherein a plurality of RF coils are arranged near the porous part, and power is applied to the RF coil with an RF power source to increase the density of the plasma by cyclone motion along the magnetic field inside the chamber. powder sterilization system. [10] The method of claim 9, wherein a descending part for guiding the powder into a storage box is installed at one end of the screw mechanism so that the plasma sterilized powder flows into the descending part by riding the screw mechanism,
The lower part,
Exterior walls containing earthed metal;
a dielectric covering the metal inside the outer wall;
Including; at least one surface electrode fixed to the dielectric while forming an inclination;
Powder sterilization system, characterized in that the additional sterilization treatment for the powder by generating a plasma discharge between the surface electrode and the outer wall. column chamber;
a powder input hopper placed on the top of the columnar chamber;
a plurality of powder flow guide plates arranged in a zigzag manner from the top to the bottom inside the columnar chamber, maintaining gaps with each other;
a DBD plasma source arranged in the columnar chamber and performing low-temperature plasma treatment on the flowing powder;
a gas exhaust filter disposed under the columnar chamber; and
A powder sterilization system, comprising: a powder collecting pedestal disposed at the lower end of the columnar chamber to collect and discharge sterilized powder; 13. The powder sterilization system according to any one of claims 1 to 7 and 9 to 12, wherein the low-temperature plasma sterilization treatment time for the powder is 15 seconds or more.

Images