KR102499960B1 - Sterilizing System for Powder products by low-temperature plasma - Google Patents

Abstract

An object of the present invention is to provide a novel food sterilization method and apparatus capable of maintaining nutrients and quality inherent in food while safely and effectively sterilizing edible powder.
In accordance with the above object, a dielectric barrier discharge (DBD) low temperature plasma powder food sterilization system capable of sterilizing powder at a 99.9% sterilization rate in a low temperature process of 50 ° C. or less is provided.

Description

Powder sterilization system using low-temperature plasma {Sterilizing System for Powder products by low-temperature plasma}

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

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

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. It inactivates microorganisms and their enzymes to prevent spoilage of food, so the storage period can be increased. However, there is a problem in that heat-resistant materials cannot be used in the heat sterilization process. In addition, since it is performed at high temperature, it causes changes in taste, scent, color, texture, shape, and ingredients, making it difficult to preserve the unique food quality. has the disadvantage of not being able to achieve the expected sterilization rate, making it difficult to apply to the process.

That is, in the conventional sterilization method, powdered food is sterilized by heating and processed and stored. This method inactivates microorganisms and their enzymes through high-temperature treatment, thereby preventing deterioration of food and increasing the storage period. However, since the heat sterilization process mainly proceeds at 100° C. or higher, there is a problem in that materials that are weak to heat cannot be used. In addition, since it is made at a 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 that it cannot achieve the target sterilization rate for sterilization of powdered foods.

In order to solve these problems, a lot of research on non-heat sterilization methods has been conducted, and among various methods, radiation, ultraviolet rays, and low-temperature plasma sterilization methods (Refer to Patent Registration No. 10-1571238, etc.) are attracting attention as a promising technology that can be applied. and is being applied in various ways in the food manufacturing process. Radiation methods using gamma rays, X-rays, and electron beams use high-energy waves to ionize and destroy 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 genetic modification of food may occur.

In addition, the ultraviolet irradiation method is a method of sterilizing powdered foods by emitting short-wavelength electromagnetic waves in the region of about 180 nm to 310 nm . Most of the energy of ultraviolet rays is absorbed on the surface of powdered foods, so it is difficult to penetrate more than 1 mm, so microorganisms present on the surface of the powder There is a downside to only sterilization.

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

The low-temperature plasma method is widely used for surface treatment of metal and non-metal materials and is widely applied to manufacturing processes such as bio industry, display, semiconductor, 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 energy of plasma electrons is 0.7 eV ~ 2.5 eV, and the plasma density is about 10 ¹² ~ 10 ¹⁴ / cm ^3. Mostly chemical reactions take place. Oxygen and nitrogen in the air are chemically generated by the discharge in the air, and various kinds of active species (OH, H ₂ O ₂ , O radical, N radical, NO, NO ₂ , O ₃ , etc.) and ultraviolet rays, Visible light, electromagnetic waves, and electric fields are generated. Plasma, which has various physical and chemical properties, is a gaseous state and can sterilize more than 99.9% of microorganisms (E. It is a safe way to effectively sterilize the powder.

Accordingly, the present invention provides a low-temperature atmospheric plasma sterilization method to hygienically produce health food, baby food for children, and senior-friendly nutritional food. 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 is provided.

The present invention controls the dielectric of the electrode and the position and thickness of the powder 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. Provided is a pasteurization system in which the transfer speed is controlled.

That is, the present invention,

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 facing the first metal electrode and grounded;

a dielectric powder having a dielectric constant ε2 placed on the second metal electrode and having a thickness d2; and

A power source 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 sterilizing power of the dielectric powder, the dielectric thickness d1 is made thinner than d0 or d2, and the dielectric constant ε1 is greater than ε2,

Provided is a powder sterilization system characterized in that the powder is sterilized by low-temperature plasma sterilization by generating dielectric barrier discharge plasma between the first metal electrode and the second metal electrode with the power source.

In the above, to reduce the power consumed in the dielectric d1 to 2% or less, ε1 is set to 5 or more, and d1 is set to 50 to 150 μm.

In the above, the powder sterilization system is characterized in that 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 to provide 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 is introduced into the descending part, a dielectric barrier covering a metal electrode under the circulating belt with a dielectric material It provides a powder sterilization system characterized in that the discharge plasma source is installed.

In the above, the powder sterilization system is characterized in that 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 leading to storage of the powder is installed at one end of the belt, and the plasma sterilized powder flows into the descending part along the belt,

The descending part,

Exterior walls containing metal to be grounded;

a dielectric covering a metal inside the outer wall;

Including; one or more surface electrodes fixed to the dielectric in an inclined manner;

It provides a powder sterilization system, characterized in that additional sterilization treatment for the powder 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 discharge gas or cooling water flow, a foreign matter removal filter at the fluid inlet, and a harmful gas adsorption filter at the fluid outlet.

chamber;

a screw mechanism for conveying powder including a rotary shaft disposed in the chamber and a screw attached to the rotary shaft;

Activated gas pass-through membranes installed on the top and bottom of the screw mechanism;

plasma sources for dielectric barrier discharge disposed above and below the screw mechanism and above and below the active gas passage layer, respectively; and

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

The powder transported 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 pass-through membrane,

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

In the above, a plurality of RF coils are arranged near the porous portion, and power is applied to the RF coils with an RF power source, so that the electrons of the plasma increase the density of the plasma by cyclone movement along the magnetic field in the chamber. sterilization system is provided.

In the above, a descending part leading to storage of powder is installed at one end of the screw mechanism, and the plasma sterilized powder flows into the descending part by riding the screw mechanism,

The descending part,

Exterior walls containing metal to be grounded;

a dielectric covering a metal inside the outer wall;

Including; one or more surface electrodes fixed to the dielectric in an inclined manner;

It provides a powder sterilization system, characterized in that additional sterilization treatment for the powder by generating a plasma discharge between the surface electrode and the outer wall.

columnar chamber;

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

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

a DBD plasma source that is arranged inside the columnar chamber and performs low-temperature plasma treatment on the flowing powder;

a gas exhaust filter disposed below the columnar chamber; and

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

In the above, the low-temperature plasma sterilization treatment time for the powder provides a powder sterilization system, characterized in that 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, and senior-friendly nutritional food. It is possible to achieve 99.9% sterilization by applying dielectric barrier discharge (DBD) low-temperature plasma that can sterilize powdered foods in a low-temperature process of 50 ° C or less, while maintaining the unique characteristics of powder due to low-temperature sterilization.

Active species such as OH radicals, O radicals, N radicals, H ₂ O ₂ , and O ₃ generated in atmospheric pressure DBD plasma capable of large-area stable discharge, and electrons, ultraviolet rays, visible rays, and electromagnetic waves are generated. 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 diffusing and infiltrating 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 a plasma powder sterilizer of the present invention.
2 is a graph showing the sterilization rate of bacteria contained in the powder versus 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 configuration diagram showing another embodiment of a belt type sterilizer.
5 is a configuration diagram showing that a screw is applied to the low-temperature plasma powder sterilizer according to the present invention.
6 is a configuration diagram showing an embodiment of another powder sterilization device of the present invention.
7 is a table and a graph showing the sterilization test results 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 portion, which is composed of an electrode portion having a SiOx dielectric, an electrode portion having a powder dielectric, and an air gap therebetween.

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

Through physical analysis of the electrode and powder arrangement structure, the voltage is calculated in the gap between the electrodes of the DBD plasma generator , 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 gap air.

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

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

C1, C0, C2 represent the capacitance, and Q represents the amount of charge, and it is displayed as follows.

The area S to which the voltage is applied, the thicknesses d1, d0, and d2 were tested to be 70μm, 3mm, and 3mm, respectively, and when the dielectric constants ε1, ε0, and ε2 were 5, 1, and 2.2, respectively, the applied voltage ratio was 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 of the 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 to 2% or less.

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

As such, since the discharge voltage in the air is increased by adjusting the thickness and dielectric constant of the dielectric 20 covering the electrode disposed on the powder, the discharge power is increased to generate a large amount of active species, thereby increasing the sterilization rate against microorganisms. .

On the other hand, Figure 2 shows the sterilization rate of bacteria contained in the powder with respect to the plasma irradiation time. Using this, the feed rate of the powder is determined in the powder sterilizers of FIGS. 3, 4, and 5.

No and Nt are the number of CFU (Colony Forming Units) after initial and plasma irradiation time t, respectively. For powdered foods A, B, and C containing bacteria, powdered food C shows the highest microbial sterilization rate with respect to plasma irradiation time. In the manufacturing process of powdered food, the bacterial sterilization rate (Nt /No) is less than 0.001, 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 must be sterilized to be below the red dotted line. Therefore, the plasma irradiation time for A, B, and C powdered foods should be 6 minutes or more, 3 minutes or more, and 1.5 minutes or more. Based on this, the traveling speed of the belt and screw for sterilization of powdered food is determined in FIGS. 3, 4, and 5.

The embodiment of FIG. 3 is described.

Embodiment 1 (FIG. 3) is a low-temperature plasma powder sterilization system 100 for sterilizing a large amount of powdered food such as health food, baby food for children, and nutritional food for the elderly.

In the powder sterilization chamber 50 in which the powder input hopper 40 is installed, the height of the powder 60 food on the belt 70 is uniform within 1 to 5 mm, preferably within 3 mm, and the belt 70 of the powder sterilization chamber Use to transfer at a uniform speed. The conveyed powder passes over the belt 70 and is grounded by trapezoidal or square dielectric barrier discharge (DBD) sources (electrode 10, dielectric 20, insulator 30) installed at regular intervals on the belt 70 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 trapezoidal or quadrangular protruding shape at predetermined intervals.

In this embodiment, the metal electrode 10 of the DBD source is an Ag electrode of the printing method of 0.1 mm to 1.5 mm, the thickness of the dielectric 20 of the DBD is 70 μm to 100 μm, and the dielectric constant is SiOx of 5 or more, and the dielectric 20 The power consumed in was within 2% of the total. The back surface of the electrode 10 is covered with an insulator 30 .

In the above, the distance d0 between the electrode 10 and the powder must 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 to generate sufficient active species (OH, NO, O) from high plasma density. , N, H ₂ O ₂ , O _{3 ,} etc.), electrons, and visible ultraviolet rays are generated to diffuse into the food powder to sterilize microorganisms.

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

The thickness of the edible powder 60 is within about 3 mm and has a permittivity of about 1.5 to 3.5. The powder 60 on the belt 70 is transported while being sterilized, and the microorganisms attached to the surface of the belt on the other side (the part of the belt after the powder is poured into the storage box) are transferred to 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 within 2 mm so that microorganisms on the surface are sterilized with a sufficiently high concentration of active species of plasma. On the other hand, plasma sterilization is also performed in the descending part (A) where the sterilized powder on the belt descends from the powder outlet to the storage box.

That is, as shown in the enlarged view of part A, sterilization is performed with low-temperature plasma once again.

The outer wall of the outlet portion is made of a metal ground 110, the inside is covered with a dielectric 20, and the surface electrode 120 (or an open-type tubular electrode or a curved electrode) is attached to the electrode fixing part 130. ) (applying a fixing member or welding) to the dielectric 20, and a plurality of surface electrodes are arranged in a zigzag manner with gaps between them. While being sterilized by the plasma generated from the surface electrodes, the powder reaches the storage box while flowing along the surface electrodes through the gaps between the surface electrodes. This will be described in more detail below.

The width of the belt 70 is 10 cm to 100 cm, and the moving speed of the belt is adjusted to have a sterilizing power of Log (Nt/No) = -3 or more. As described above, the sterilizing power and the conveying speed can be adjusted for each powder (type).

Since discharge occurs at the top and bottom of the metal belt to sterilize microorganisms, sterilization of powder spread in thin thickness is very effective.

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

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

In addition, as shown in FIG. 4, the plasma irradiation time can be lengthened when the powder moves along the belt by continuously installing the DBD discharge system horizontally along the belt. That is, the electrode 10, the dielectric 20, and the insulator 30 are configured to be continuously spread horizontally so that continuous plasma treatment occurs on the powder.

In order to absorb heat generated from the DBD discharge system, a cooling plate cooled by cooling water or a fan is installed on the DBD metal electrode to lower the temperature of the DBD electrode. The moving speed of the belt is adjusted to Nt/No=0.001 or less to have 99.9% or more sterilizing power. On the other hand, when the sterilized powder on the belt descends to the powder outlet, it is sterilized with low-temperature plasma once again, as shown 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 through the inlet of the chamber 50 to be placed on the screw surface. In the screw mechanism, a screw 150 is formed on a rotation shaft 155. A screw edge support is provided so that the powder can be sufficiently placed on the screw surface, and the powder is moved according to the rotational motion of the screw. A linear dielectric barrier discharge (DBD) plasma source (electrode 10, dielectric 20) is installed at 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 fragmentary metal electrodes vertically or radially arranged on a long dielectric 20 . However, the plasma source is not limited thereto, and may be configured with various shapes of electrodes and dielectrics.

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 pass-through membrane 140 is installed around the DBD plasma so that the active gas diffuses into the powder placed on the screw and prevents the powder from entering the DBD plasma system.

The periphery 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 create an air curtain, so that powder and active species gases are introduced into the outer wall. to avoid being released.

In addition, an RF (Radio Frequency) coil 160 is installed around the porous wall 170 to increase the density of the plasma by cyclone movement of electrons of the plasma along the magnetic field in the chamber.

The frequency of the RF power supply is 0.1 to 50 MHz, and the power is 0.1 to 1000 kW. Since the coil temperature rises due to the power applied to the RF coil 160, the temperature of the RF coil is lowered by flowing cooling water. Active species (NOx, OH radicals, O radicals, H ₂ O ₂ , O _{3 ,} etc.) of the high-density plasma generated by the RF coil diffuse into the powder and sterilize microorganisms. Discharge can be generated using air, and a large amount of NOx active species can be generated using reactive gases including N ₂ and O ₂ and/or inert gases such as Ar and He.

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

On the other hand, when the sterilized powder descends to the powder discharge port, it is sterilized with low-temperature plasma once again, as shown in the enlarged portion A (as shown in the enlarged view of portion A in FIG. 3).

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

In addition, the plasma densification by the RF coil 160 and the RF power source may also be applied to the belt transfer embodiment of 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 and maintain the unique characteristics such as flavor of the powder.

On the other hand, the edible powder can also be used for skin or hair care, and 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.

A powder flow guide plate 210 is arranged along the length of the chamber 200 in a zigzag manner inside the columnar chamber 200 where the powder input hopper 40 is installed at the top. The powder flow guide plate 210 extends obliquely from the inner wall of the chamber 200 toward the inner space, but is installed at a distance from the opposite inner wall. Arrange the falling point of the powder falling from the first powder flow guide plate to be 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 the second powder flow guide plate, and the length of the chamber Arrange a suitable number of powder flow guide plates.

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 length of the columnar chamber, and the powder is sterilized by plasma while passing through this place. 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 collection tray 41 placed thereunder. The gas exhaust filter 220 is a filter for removing gas such as ozone (O3).

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

The experimental results are shown in FIG. 7, and the time at which 99.9% or more of bacteria in the air are sterilized in atmospheric pressure plasma is shown graphically.

In the above embodiment, when powder is injected into the upper part of the columnar chamber 200, the time it takes to come out of the powder collecting tray 41 at the lower end is about 1 second. The concentration of ozone by the DBD low-temperature plasma source inside the chamber 200 was approximately 0.33 ppm (including H ₂ O ₂ , NO _{2 ,} etc.), and as shown in the graph, the treatment was repeated 16 times, that is, at 0.33 ppm for 16 seconds. When treated, more than 99.9% of bacteria were killed. For efficient processing, the chamber length can be designed to be long.

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

On the other hand, the specific numerical values presented in the above embodiments and experimental examples are illustrative and can be modified as needed, and those skilled in the art to which the present invention pertains can make other specific figures without changing the technical spirit or essential features of the present invention. It will be appreciated that it can be implemented in the form. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. The scope of the present invention is indicated by the following claims rather than the detailed description above, 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 part (130)
Activated gas pass-through membrane (140)
screw(150)
Rotation Axis(155)
RF Coil(160)
Porous wall (170)
Columnar chamber (200)
Powder flow guide plate (210)
Powder collection stand (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 facing the first metal electrode and grounded;
a dielectric powder having a dielectric constant ε2 placed on the second metal electrode and having a thickness d2; and
A power source for applying a voltage between the first metal electrode and the second metal electrode;
The power source causes dielectric barrier discharge plasma between the first metal electrode and the second metal electrode to sterilize the powder by low-temperature plasma sterilization,
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,
V1 : V0 : V2 = d1/ ε1 : d0/ε0 : d2/ ε2 (V1: Voltage across the dielectric of the first electrode, V0: Voltage across the air, V2: Voltage across the powder, ε0: Permittivity of air=1) Powder sterilization, characterized in that the dielectric thickness d1 is made thinner than d0 or d2, and the dielectric constant ε1 is greater than ε2, so that the voltage V1 applied to the dielectric d1 is lowered and the discharge voltage V0 in the air is increased. system. The powder sterilization system according to claim 1, characterized in that ε1 is set to 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 transferred relative to the first metal electrode, and the transfer speed is adjusted to maintain a plasma irradiation time required to achieve a sterilization rate of 99.9%. The powder sterilization system according to claim 3, wherein the second metal electrode is configured in the form of a circulating belt and transfers the powder placed on the belt at a predetermined speed. The method of claim 4, wherein a metal electrode is covered with a dielectric material under the lower surface of the circulating belt to sterilize the belt surface while the belt moves along the lower surface for circulation after the powder placed on the circulating belt is introduced into the descending portion. Powder sterilization system, characterized in that the dielectric barrier discharge plasma source is installed. The method of claim 1, wherein the powder is sterilized while being transferred relative to the first metal electrode, and the sterilization power is greater than Log (Nt/No) = -3 at a transfer rate to maintain a plasma irradiation time required to achieve a sterilization rate of 99.9%. A powder sterilization system characterized by being adjusted to have (No, Nt are the number of CFU (Colony Forming Unit) after the initial plasma irradiation time t, respectively). The method of claim 4, wherein a descending part leading to storage of the powder is installed at one end of the belt, and the plasma sterilized powder is introduced into the descending part along the belt,
The descending part,
Exterior walls containing metal to be grounded;
a dielectric covering a metal inside the outer wall;
Including; one or more surface electrodes fixed to the dielectric in an inclined manner;
Powder sterilization system, characterized in that for 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 a chamber,
The powder sterilization system, characterized in that the chamber includes a fluid inlet and a fluid outlet for discharge gas or cooling water flow, a foreign matter removal filter at the fluid inlet, and a harmful gas adsorption filter at the fluid outlet. chamber;
a screw mechanism for conveying powder including a rotary shaft disposed in the chamber and a screw attached to the rotary shaft;
Activated gas pass-through membranes installed on the top and bottom of the screw mechanism;
plasma sources for dielectric barrier discharge disposed above and below the screw mechanism and above and below the active gas passage layer, respectively;
Porous parts included in the upper and lower surfaces of the chamber; and
An RF coil arranged near the porous portion; including,
The powder transported 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 pass-through membrane,
By supplying gas from the outside of the chamber, the air flow flowing into the porous part prevents powder and active species from flowing out to the outer wall of the chamber,
Powder sterilization system, characterized in that by applying power to the RF coil with an RF power source, the electrons of the plasma increase the density of the plasma by cyclone movement along the magnetic field in the chamber.
delete 10. The method of claim 9, wherein a descending part leading to storage of the powder is installed at one end of the screw mechanism, and the plasma sterilized powder flows into the descending part by riding the screw mechanism,
The descending part,
Exterior walls containing metal to be grounded;
a dielectric covering a metal inside the outer wall;
Including; one or more surface electrodes fixed to the dielectric in an inclined manner;
Powder sterilization system, characterized in that for additional sterilization treatment for the powder by generating a plasma discharge between the surface electrode and the outer wall. delete The powder sterilization system according to any one of claims 1 to 7, 9 and 11, wherein the low-temperature plasma sterilization treatment time for the powder is 15 seconds or more.

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