Spraying device and spraying method

Abstract

The spray device includes a mist generating unit and a plasma activating unit. The plasma activation unit includes a tube made of a dielectric material, an external electrode provided on an outer surface of the tube made of the dielectric material, an internal electrode provided on an inner surface of the tube made of the dielectric material, and a high-frequency power source that applies a high-frequency voltage to the external electrode and the internal electrode. The positions of the outer electrode and the inner electrode in the axial direction of the dielectric material tube are configured so as not to overlap or only partially overlap. The spray device is configured such that the mist fed from the mist generation unit to one end of the dielectric material tube passes through the dielectric material tube, is activated by plasma, and is discharged from the other side of the dielectric material tube.

Description

Technical Field

[0001] The invention relates to a spray device and a spray method. Background Art

[0002] A spray device and a spray method have been developed that generate peroxynitrous acid (HOONO) having a bactericidal ability by activating mist plasma generated from a liquid containing water as a main component (for example, Patent Document 1). Figure 7 A plasma activation unit of a spray device as a plasma mist generator is disclosed. The plasma activation unit is configured to activate mist plasma containing tiny droplets and air supplied to the inside of a tube by applying a high-frequency voltage between a rod-shaped internal electrode arranged inside a tube and an external electrode arranged outside the tube to generate peroxynitrous acid (HOONO).

[0003] However, the generation rate of peroxynitrous acid (HOONO) generated in the plasma activation section is not sufficient.

[0004] Therefore, there is a need for a spraying device and a spraying method that can generate peroxynitrous acid (HOONO) at a sufficiently high generation rate.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent document: WO2014 / 145570 Summary of the invention

[0008] Problems to be solved by the invention

[0009] An object of the present invention is to provide a spray device and a spray method capable of generating peroxynitrous acid (HOONO) at a sufficiently high generation rate.

[0010] Means for solving problems

[0011] A spray device according to a first aspect of the present invention comprises a mist generating unit and a plasma activating unit. The plasma activating unit comprises a tube of a dielectric material, an external electrode provided on the outer surface of the tube of the dielectric material, an internal electrode provided on the inner surface of the tube of the dielectric material, and a high-frequency power supply for applying a high-frequency voltage to the external electrode and the internal electrode, wherein the positions of the external electrode and the internal electrode in the axial direction of the tube of the dielectric material are configured not to overlap or only partially overlap, and the spray device is configured such that the mist sent from the mist generating unit to one end of the tube of the dielectric material is plasma activated after passing through the tube of the dielectric material and is sent out from the other side of the tube of the dielectric material.

[0012] The plasma activation section of the spray device according to the present embodiment can reduce the mist adhering to the inner surface of the tube of the dielectric material, and can release more plasma-activated mist, compared with the plasma activation section of the conventional structure. In addition, the plasma activation section of the spray device according to the present embodiment can generate active species required for the generation of peroxynitrous acid (HOONO) having various functions such as sterilization, virus killing, and deodorization at an appropriate ratio, so that the generation rate of peroxynitrous acid (HOONO) can be increased compared with the plasma activation section of the conventional structure.

[0013] The spray device according to the first embodiment of the first aspect of the present invention is configured such that the outer electrode and the inner electrode partially overlap in the axial direction of the tube of the dielectric material.

[0014] According to the present embodiment, since the two electrodes are configured so that their axial positions partially overlap, discharge between the two electrodes is easily generated.

[0015] In the spray device according to the second embodiment of the first aspect of the present invention, the frequency of the high-frequency power source is in the range of 1 kHz to 100 kHz, and the peak-to-peak value of the voltage is in the range of 1 kilovolt to 30 kilovolt.

[0016] In the spray device according to the third embodiment of the first aspect of the present invention, the mist generating section is configured to generate liquid droplets having a diameter of 0.5 μm to 30 μm.

[0017] In the spray device according to a fourth embodiment of the first aspect of the present invention, the diameter of the tube of the dielectric material is in the range of 0.5 mm to 20 mm.

[0018] In the spray device according to a fifth embodiment of the first aspect of the present invention, the internal electrode is a tube inside the tube of the dielectric material.

[0019] The spray method according to the second aspect of the present invention generates plasma-activated mist from a liquid containing water as a main component using the above-mentioned spray device.

[0020] According to the spray method of this embodiment, compared with the spray method using the plasma activation part of the conventional structure, the mist adhering to the inner surface of the tube of the dielectric material can be reduced, and more plasma-activated mist can be released. In addition, according to the spray method of this embodiment, the active species required for the generation of peroxynitrous acid (HOONO) with bactericidal ability can be generated at an appropriate ratio, so compared with the spray method using the plasma activation part of the conventional structure, the generation rate of peroxynitrous acid (HOONO) with bactericidal ability can be increased.

[0021] In the spray method according to the first embodiment of the second aspect of the present invention, the liquid is an aqueous solution containing nitrous acid or nitrite ions.

[0022] According to the present embodiment, the generation rate of peroxynitrous acid (HOONO) having a bactericidal ability can be increased compared to the case where the liquid is water.

[0023] In the spray method according to the second embodiment of the second aspect of the present invention, the liquid contains sodium nitrite, and the molar concentration of the sodium nitrite is in the range of 1 micromole to 100 millimoles. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram showing a spray device according to one embodiment of the present invention.

[0025] Figure 2 This is a diagram showing an example of the structure of the plasma activation portion according to the present embodiment.

[0026] Figure 3 This is a diagram showing an example of the structure of a conventional plasma activation unit.

[0027] Figure 4 It is shown Figure 2 The plasma activation part and Figure 3 Graph of the mist emission amount of the plasma activation portion of the volume DBD structure shown.

[0028] Figure 5 This is a diagram showing the structure of a plasma activation portion of a surface DBD structure used for measuring the generation rate of peroxynitrous acid (HOONO).

[0029] Figure 6 It is a graph showing the generation rate of peroxynitrous acid (HOONO) in the plasma activation part of the surface DBD structure and the plasma activation part of the volume DBD structure.

[0030] Figure 7 It is a graph showing the concentrations of hydrogen peroxide, nitrous acid, nitrate ions, and nitrite ions generated by the plasma activated portion of the surface DBD structure.

[0031] Figure 8 Graphs showing the concentrations of hydrogen peroxide, nitrous acid, nitrate ions, and nitrite ions generated by the plasma activation portion of the volume DBD structure.

[0032] Fig. 9 Shown on an enlarged scale Figure 7 The concentration of nitrite and Figure 8 Graph of the concentration of nitrite.

[0033] Fig.10This is a graph showing the concentrations of hydrogen peroxide, nitrous acid, nitrate ions, and nitrite ions generated by the plasma activated portion of the surface DBD structure when an aqueous solution of sodium nitrite is used.

[0034] Fig.11 This is a graph showing the generation rate of peroxynitrous acid (HOONO) in the plasma activation portion of the surface DBD structure when an aqueous solution of sodium nitrite is used.

[0035] Fig.12 This is a graph showing the change over time of the concentration of active species obtained by simulation when the concentration of sodium nitrite in the aqueous solution is 1200 micromolar.

[0036] Fig.13 This is a graph showing the change over time of the concentration of active species obtained by simulation when the concentration of sodium nitrite in the aqueous solution is 2000 micromolar.

[0037] Fig.14 This is a graph showing the change over time of the concentration of peroxynitrous acid (HOONO) obtained by simulation when the concentration of sodium nitrite in the aqueous solution is 1200 micromolar and 2000 micromolar. DETAILED DESCRIPTION

[0038] Figure 1 : is a diagram showing a spray device according to an embodiment of the present invention. The spray device as a plasma mist generator includes a mist generating unit 100 and a plasma activation unit 200. The mist generating unit 100 can atomize a liquid mainly composed of water stored in a tank by an ultrasonic vibrator. The ultrasonic vibrator is, for example, an ultrasonic humidification unit NB-80E-01-H of TDK Corporation. The diameter of the mist droplets is 0.5 micrometers to 30 micrometers. The plasma activation unit 200 is tubular and includes a tubular external electrode 220 disposed on the outside of the tube 210, a tubular internal electrode 230 disposed on the inside of the tube 210, and a high-frequency power supply 240. The tubular internal electrode 230 protrudes from the upper end of the tube 210. The material of the tube 210 is a dielectric. The high-frequency power supply 240 is connected in a manner that a high-frequency voltage is applied between the external electrode 220 and the internal electrode 230. The terminal of the high-frequency power supply 240 connected to the internal electrode 230 is grounded. Generally, the frequency of the high frequency power source 240 is in the range of 1 kHz to 100 kHz, preferably in the range of 5 kHz to 30 kHz. The peak-to-peak value of the voltage of the high frequency power source 240 is in the range of 1 kilovolt to 30 kilovolt.

[0039] The mist generated by the mist generating unit 100 is Figure 1The lower end of the tube 210 shown is fed into the plasma activation part 200. The flow rate of the mist is preferably in the range of 0.01 microliters / second (μL / s) to 1000 microliters / second (μL / s). By applying a high-frequency voltage between the external electrode 220 and the internal electrode 230 using the high-frequency power supply 240, the mist is plasma-activated and discharged as plasma-activated mist 300 from the front end of the tubular internal electrode 230 protruding from the upper end of the tube 210.

[0040] Figure 2 : is a diagram showing an example of the structure of the plasma activation part 200 of the present embodiment. The axial length of the tube 210 is 34 mm, the tube diameter is 3.9 mm, and the wall thickness of the tube is 0.7 mm. Generally, the diameter of the tube of the dielectric material is preferably in the range of 2 mm to 10 mm. The material of the tube 210 is quartz glass. In this example, the external electrode 220 arranged on the outside of the tube 210 is a conductive copper foil tape covering the outer periphery of the tube 210. The width (axial length) of the conductive copper foil tape is 20 mm and the thickness is 0.7 mm. The position of the upper end of the external electrode 220 is 12 mm lower than the position of the upper end of the tube 210. In this example, the tubular internal electrode 230 arranged inside the tube 210 is a stainless steel tube. The axial length of the stainless steel tube is 20 mm, the outer diameter is 2.41 mm, and the wall thickness is 0.21 mm. The length of the axial overlapping portion of the external electrode 220 and the internal electrode 230 is 3 mm. The inner electrode 230 protrudes from the upper end of the tube 210, and the axial length of the protruding portion is 5 mm. In this example, below the lower end of the inner electrode 230, a portion of the region where the outer electrode 2210 exists on the outer surface of the tube 210 and is adjacent to the lower end generates plasma-activated mist 300 along the inner surface of the tube 210.

[0041] Usually, the outer electrode and the inner electrode are arranged at different positions in the axial direction of the tube. In order to facilitate discharge between the two electrodes, it is preferable that the positions of the two electrodes in the axial direction of the tube 210 partially overlap.

[0042] Figure 3 1 is a diagram showing an example of the structure of a conventional plasma activation section. The dimensions and materials of the tube 210 and the tubular external electrode 220 provided outside the tube 210 are the same as those of the above-mentioned example. The upper end of the external electrode 220 is located 12 mm below the upper end of the tube 210. The internal electrode 235 is in the shape of a rod, the length of the rod is 100 mm, and the diameter of the rod is 0.9 mm. The material of the internal electrode 235 is tungsten. The internal electrode 235 is arranged at the position of the central axis of the tube 210. In the conventional plasma activation section, the mist 300 activated by plasma is generated in the space inside the tube 210, in the region where the axial positions of the external electrode 220 and the internal electrode 235 overlap.

[0043] Figure 2and Figure 3 The plasma activation part shown forms plasma through dielectric barrier discharge. Figure 2 The structure of the plasma activation part 200 of the present invention is called a surface dielectric barrier discharge structure (surface DBD structure). Figure 3 The structure of the plasma activation portion shown is called a volume dielectric barrier discharge structure (volume DBD structure).

[0044] Figure 4 It is shown Figure 2 The plasma activation part and Figure 3 A graph of the mist emission amount of the plasma activation portion of the volume DBD structure shown in FIG. 2 is shown. The frequency of the high-frequency power supply 240 is 9 kHz, and the peak-to-peak value of the voltage is 18 kV. The mist emission amount is measured by allowing the mist emitted from the plasma activation portion to adhere to a glass plate. The mist emission amount of the plasma activation portion of the surface DBD structure is about 1.7 microliters / second (μL / s), and the mist emission amount of the plasma activation portion of the volume DBD structure is about 0.5 microliters / second (μL / s). The reason why the mist emission amount of the plasma activation portion of the surface DBD structure is greater than the mist emission amount of the plasma activation portion of the volume DBD structure is presumably that, in the volume DBD structure, the strong electric field required for plasma generation is applied to the entire area of ​​the tube cross section, and the charged mist is easily attached to the wall surface. Therefore, from the viewpoint of the mist emission amount, the plasma activation portion of the surface DBD structure of the present invention is more preferred than the plasma activation portion of the conventional volume DBD structure.

[0045] Next, the sterilization ability of plasma-activated mist is described. It is known that peroxynitrous acid (HOONO) has sterilization ability, and there is a clear correlation between its sterilization ability and the generation rate of peroxynitrous acid (HOONO). It is known that peroxynitrous acid (HOONO) can be continuously produced from hydrogen peroxide and nitrous acid, and hydrogen peroxide and nitrous acid can be produced by activating mist plasma, which is tiny droplets of water flying in the air.

[0046] Therefore, the generation rates of peroxynitrous acid (HOONO) in the plasma activated portion of the surface DBD structure and the plasma activated portion of the volume DBD structure were measured.

[0047] Figure 5: This is a diagram showing the structure of the plasma activation portion of the surface DBD structure used in the determination of the generation rate of peroxynitrous acid (HOONO). The axial length of the tube 210 is 34 mm, the tube diameter is 3.9 mm, and the wall thickness is 0.7 mm. The material of the tube 210 is quartz glass. In this example, the external electrode 220 arranged on the outside of the tube 210 is a conductive copper foil tape. The width (axial length) of the conductive copper foil tape is 20 mm and the thickness is 0.7 mm. The position of the upper end of the external electrode 220 is 12 mm lower than the position of the upper end of the tube 210. In this example, the tubular internal electrode 230 arranged inside the tube 210 is a stainless steel tube. The axial length of the stainless steel tube is 18.5 mm, the outer diameter is 2.41 mm, and the wall thickness is 0.21 mm. The length of the axial overlapping portion of the external electrode 220 and the internal electrode 230 is 1.5 mm. The inner electrode 230 protrudes from the upper end of the tube 210, and the axial length of the protruding portion is 5 mm. In this example, below the lower end of the inner electrode 230, a portion of the region where the outer electrode 2210 exists on the outer surface of the tube 210 and is adjacent to the lower end generates plasma-activated mist 300 along the inner surface of the tube 210.

[0048] The plasma activation part of the volume DBD structure used in the measurement of the generation rate of peroxynitrous acid (HOONO) is as follows: Figure 3 shown.

[0049] Figure 6 It is a graph showing the generation rate of peroxynitrous acid (HOONO) in the plasma activation part of the surface DBD structure and the plasma activation part of the volume DBD structure. Figure 6 The horizontal axis represents the peak-to-peak value of the voltage applied between the two electrodes. The unit of voltage is kilovolts. Figure 6 The vertical axis represents the generation rate of peroxynitrous acid (HOONO). The unit of the generation rate of peroxynitrous acid (HOONO) is micromole / second (μM / s). The mole represented by M is the number of moles per liter. The method for measuring the generation rate of peroxynitrous acid (HOONO) is described below.

[0050] according to Figure 6 , the generation rate of peroxynitrous acid (HOONO) in the plasma activated portion of the surface DBD structure when the peak-to-peak voltage is 18 kV is about 3 micromoles / second (μM / s), while the generation rate of peroxynitrous acid (HOONO) in the plasma activated portion of the volume DBD structure when the peak-to-peak voltage is 18 kV is zero. Therefore, from the viewpoint of the generation rate of peroxynitrous acid (HOONO), the plasma activated portion of the surface DBD structure of the present invention is more preferred than the plasma activated portion of the conventional volume DBD structure.

[0051] Peroxynitrous acid (HOONO) is produced according to the following reaction formula (1).

[0052] [Number 1]

[0053] H2O2+HNO2+H+→HOONO+H2O+H + (1)

[0054] The active species on the left side of reaction equation (1), namely hydrogen peroxide, nitrous acid and hydrogen ions

[0055] [Number 2]

[0056] H +

[0057] It is generated by plasma-activated mist and remains for a long time, continuously generating peroxynitrous acid (HOONO). The half-life of peroxynitrous acid (HOONO) is typically about 1 second, and it is decomposed into nitrate ions.

[0058] [Number 3]

[0059]

[0060] and nitrite ions

[0061] [Number 4]

[0062]

[0063] Continue to generate hydrogen peroxide

[0064] [Number 5]

[0065] H2O2

[0066] Until it dries up.

[0067] Figure 7 It is a graph showing the concentrations of hydrogen peroxide, nitrate ions, nitrous acid, and nitrite ions generated by the plasma activated portion of the surface DBD structure. Figure 7 The horizontal axis represents the peak-to-peak value of the voltage applied between the two electrodes. The unit of voltage is kilovolts. Figure 7 The vertical axis represents the concentration of active species. The unit of concentration is millimole. The concentration of active species is determined by measuring droplets recovered from mist using a glass plate or the like using an absorptiometry quantitative method using an ultra-micro cuvette.

[0068] Figure 8 Graphs showing the concentrations of hydrogen peroxide, nitrate ions, nitrous acid, and nitrite ions generated by the plasma activation portion of the volume DBD structure. Figure 8 The horizontal axis represents the peak-to-peak value of the voltage applied between the two electrodes. The unit of voltage is kilovolts. Figure 8The vertical axis represents the concentration of active species. The unit of concentration is millimole. It should be noted that Figure 8 The scale of the vertical axis is Figure 7 The scale range of the vertical axis is large.

[0069] Compare Figure 7 and Figure 8 , Figure 8 When the peak-to-peak voltage is 18 kV, the concentration of hydrogen peroxide is about 6 mmol. Figure 7 When the peak-to-peak voltage is 18 kV, the concentration of hydrogen peroxide is about 1.3 mmol. That is, Figure 8 The concentration of hydrogen peroxide in the case of the bulk DBD structure is Figure 7 The concentration of hydrogen peroxide in the case of the surface DBD structure is about 5 times higher.

[0070] Fig. 9 Shown on an enlarged scale Figure 7 The concentration of nitrite and Figure 8 Graph of the concentration of nitrite. Fig. 9 The horizontal axis represents the peak-to-peak value of the voltage applied between the two electrodes. The unit of voltage is kilovolts. Fig. 9 The vertical axis represents the concentration of nitrite. The unit of concentration is micromolar. Fig. 9 , when the peak-to-peak voltage is 18 kV, the concentration of nitrous acid generated by the plasma activated portion of the surface DBD structure is about 170 micromolar, while when the peak-to-peak voltage is 18 kV, the concentration of nitrous acid generated by the plasma activated portion of the volume DBD structure is zero. It should be noted that the detection limit of the concentration of nitrous acid is 10 micromolar, so the concentration of nitrous acid generated by the plasma activated portion of the DBD structure is less than 10 micromolar.

[0071] according to Figures 6 to 9 From the results shown, it can be inferred that in order to increase the generation rate of peroxynitrous acid (HOONO), it is important that the active species and hydrogen ions on the left side of reaction formula (1) are generated at an appropriate ratio (ideally, equal amounts of each), and in particular, the concentration of nitrous acid has a great influence on the generation rate of peroxynitrous acid (HOONO). It is inferred that in the case of the plasma activated portion of the conventional volume DBD structure, the concentration of hydrogen peroxide is high compared to the case of the plasma activated portion of the surface DBD structure, but the concentration of nitrous acid is less than the detection limit, so the generation rate of peroxynitrous acid (HOONO) is also reduced.

[0072] Next, considering that the concentration of nitrous acid has a great influence on the generation rate of peroxynitrous acid (HOONO), in the case of the plasma activated portion of the surface DBD structure, an attempt was made to increase the concentration of the generated nitrous acid by using an aqueous solution of sodium nitrite instead of water to produce mist.

[0073] Fig.10 This is a graph showing the concentrations of hydrogen peroxide, nitrous acid, nitrate ions, and nitrite ions generated by the plasma activated portion of the surface DBD structure when an aqueous solution of sodium nitrite is used. Fig.10 The horizontal axis represents the concentration of sodium nitrite in the aqueous solution. The unit of concentration is micromolar. Fig.10 The vertical axis represents the concentration of active species. The unit of concentration is millimolar. The peak-to-peak value of the voltage applied between the two electrodes is 16.3 kV.

[0074] Fig.11 This is a graph showing the generation rate of peroxynitrous acid (HOONO) in the plasma activation portion of the surface DBD structure when an aqueous solution of sodium nitrite is used. Fig.11 The horizontal axis represents the concentration of sodium nitrite in the aqueous solution. The unit of concentration is micromolar. Fig.11 The vertical axis represents the generation rate of peroxynitrous acid (HOONO). The unit of the generation rate is micromole / second (μM / s).

[0075] The method for calculating the generation rate of peroxynitrous acid (HOONO) is described below. Based on the reaction formula (1), the generation rate of peroxynitrous acid (HOONO) is represented by the following formula (2).

[0076] [Number 6]

[0077]

[0078] k is a reaction rate constant, and the following values ​​were used.

[0079] [Number 7]

[0080] k = 9.6 × 10 3 (M -2 s -1 )

[0081] The value of the concentration of the active species measured by the above method is substituted into the formula (2) to determine the generation rate of peroxynitrous acid (HOONO).

[0082] Figure 6 The reason why the generation rate of peroxynitrous acid (HOONO) in the plasma activated portion of the DBD structure shown is zero is that the concentration of nitrous acid generated in the plasma activated portion of the DBD structure is less than the detection limit and is zero.

[0083] according to Fig.11 The rate of generation of peroxynitrous acid (HOONO) increases with the concentration of sodium nitrite in the aqueous solution. In practice, the concentration of sodium nitrite in the aqueous solution is preferably in the range of 1 micromolar to 100 millimolar.

[0084] Next, the time-dependent changes in the concentrations of active species and peroxynitrous acid (HOONO) are estimated by simulation. The simulation is a zero-order chemical reaction simulation, and the time-dependent changes in the concentrations of active species and peroxynitrous acid (HOONO) are obtained by an implicit method using the Newton-Raphson method using multiple nonequilibrium reaction equations and equilibrium reaction equations related to the reaction.

[0085] Fig.12 This is a graph showing the change over time of the concentration of active species obtained by simulation when the concentration of sodium nitrite in the aqueous solution is 1200 micromolar. Fig.12 The horizontal axis represents time. The unit of time is seconds. Fig.12 The vertical axis represents the concentration of active species. The unit of concentration is micromolar. As the initial value of the concentration of active species, use Fig.10 Data shown.

[0086] Fig.13 This is a graph showing the change over time of the concentration of active species obtained by simulation when the concentration of sodium nitrite in the aqueous solution is 2000 micromolar. Fig.13 The horizontal axis represents time. The unit of time is seconds. Fig.13 The vertical axis represents the concentration of active species. The unit of concentration is micromolar. As the initial value of the concentration of active species, use Fig.10 Data shown.

[0087] Fig.14 This is a graph showing the change over time of the concentration of peroxynitrous acid (HOONO) obtained by simulation when the concentration of sodium nitrite in the aqueous solution is 1200 micromolar and 2000 micromolar. Fig.14 The horizontal axis represents time. The unit of time is seconds. Fig.14 The vertical axis represents the concentration of peroxynitrous acid (HOONO). The unit of concentration is micromolar.

[0088] according to Fig.14, when the concentration of sodium nitrite in the aqueous solution is 1200 micromolar and when the concentration of sodium nitrite in the aqueous solution is 2000 micromolar, the concentration of peroxynitrous acid (HOONO) is maintained at more than 300 seconds and more than 0.5 micromolar. In addition, regarding the initial value of the concentration of peroxynitrous acid (HOONO), the concentration of sodium nitrite in the aqueous solution is 1200 micromolar, which is greater than the concentration of sodium nitrite in the aqueous solution is 2000 micromolar. On the other hand, regarding the reduction rate of the concentration of peroxynitrous acid (HOONO), the concentration of sodium nitrite in the aqueous solution is 1200 micromolar, which is also greater than the concentration of sodium nitrite in the aqueous solution is 2000 micromolar. When the concentration of sodium nitrite in the aqueous solution is 1200 micromolar, the initial value of the concentration of peroxynitrous acid (HOONO) is large, so it is more suitable for uses such as hand disinfectants. When the concentration of sodium nitrite is 2000 micromolar, the concentration of peroxynitrous acid (HOONO) is maintained for a relatively long time, so it is more suitable for uses such as indoor spraying.

[0089] In the above embodiment, sodium nitrite is added to the liquid used to generate mist in order to increase the concentration of peroxynitrous acid (HOONO). Generally, the concentration of peroxynitrous acid (HOONO) can be increased by adding nitrous acid or nitrite ions to the liquid used to generate mist.

Claims

1. A spray device comprising a mist generating unit and a plasma activating unit, wherein: The plasma activation section includes a tube of dielectric material, an external electrode arranged on the outer surface of the tube of dielectric material, an internal electrode arranged on the inner surface of the tube of dielectric material, and a high-frequency power supply for applying a high-frequency voltage to the external electrode and the internal electrode. The axial positions of the tube of dielectric material of the external electrode and the internal electrode are configured to be non-overlapping or only partially overlapping. The spray device is configured so that the mist sent from the mist generating section to one end of the tube of dielectric material is plasma activated after passing through the tube of dielectric material and is sent out from the other side of the tube of dielectric material. 2 . The spray device according to claim 1 , wherein the outer electrode and the inner electrode are configured so that their positions in the axial direction of the dielectric material tube only partially overlap.

3. The spray device according to claim 1, wherein: The frequency of the high frequency power source is in the range of 1 kHz to 100 kHz, and the peak-to-peak value of the voltage is in the range of 1 kilovolt to 30 kilovolt.

4. The spray device according to claim 1, wherein the mist generating unit generates droplets having a diameter of 0.5 micrometers to 30 micrometers.

5. The spray device according to claim 1, wherein: The diameter of the tube of dielectric material is in the range of 0.5 mm to 20 mm.

6. The spray device according to claim 1, wherein: The inner electrode is a tube inside the tube of dielectric material.

7. A spraying method, comprising generating plasma-activated mist from a liquid containing water as a main component by using the spraying device according to claim 1.

8. The spraying method according to claim 7, wherein: The liquid is an aqueous solution containing nitrous acid or nitrite ions.

9. The spraying method according to claim 8, wherein: The liquid contains sodium nitrite, and the molar concentration of the sodium nitrite ranges from 1 micromolar to 100 millimolar.

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