Apparatus for large-scale production of plasma-activated liquid and its application in food sterilization

Abstract

The application discloses a device for large-scale preparation of plasma-activated liquid and application thereof in food sterilization. The device comprises a power supply, a gas supply system, a water tank and at least one mixed plasma reactor. The mixed plasma reactor is arranged in the water tank and comprises a medium pipe, a rod-shaped grounding electrode, a first high-voltage electrode and a second high-voltage electrode. The rod-shaped grounding electrode, the first high-voltage electrode and the second high-voltage electrode are fixed in the medium pipe. The first high-voltage electrode is a metal pipe and is sleeved outside the rod-shaped grounding electrode, and the rod-shaped grounding electrode is located at the center of the first high-voltage electrode. The inner surface of the first high-voltage electrode is provided with a dielectric layer. The second high-voltage electrode is arranged below the first high-voltage electrode and is sleeved outside the rod-shaped grounding electrode, and the rod-shaped grounding electrode is located at the center of the second high-voltage electrode. The application improves the types and concentrations of active components in the plasma-activated liquid, realizes high-level food sterilization application, has spectral antibacterial property, is simple in device, energy-saving and expandable, and can be applied to various food sterilization scenes.

Description

Technical Field

[0001] This invention relates to the field of non-thermal sterilization technology, and in particular to an apparatus for large-scale preparation of plasma-activated liquid and its application in food sterilization. Background Technology

[0002] Atmospheric pressure cryogenic plasma and its derivative form—plasma-activated solutions—possess strong bactericidal capabilities and hold promise as green agents for eliminating pathogens. Plasma-activated solutions are generated through the interaction of atmospheric pressure cryogenic plasma with a liquid medium, produced by direct plasma discharge in water or plasma discharge on the water surface. The biochemical activity of plasma-activated solutions is related to the concentration of highly reactive oxygen / nitrogen substances in the water, such as hydrogen peroxide, hydroxyl radicals, and pernitrite. The synergistic effect of these reactive substances and low pH plays a crucial role in oxidative stress in bacterial cells and damage to intracellular DNA.

[0003] However, there are still several technical problems in the process of plasma-activated solutions moving from the laboratory to industrial applications: (1) the preparation scale of plasma-activated solutions is small and the efficiency is low; (2) the plasma source required for the preparation method of plasma-activated solutions is large and the energy consumption is high; (3) the reactive substances generated by the interaction between plasma and water have poor loading and particle activity. Summary of the Invention

[0004] To overcome the aforementioned shortcomings and deficiencies of the prior art, the present invention aims to provide an apparatus for large-scale preparation of plasma activation liquid, which introduces two discharge schemes: dielectric barrier discharge and sliding arc discharge, thereby increasing the types and concentrations of active ingredients in the plasma activation liquid, enabling high-level food sterilization applications, exhibiting spectral antibacterial properties, effectively removing harmful bacteria from the surfaces of food, food packaging materials, and processing equipment, and the apparatus for large-scale preparation of plasma activation liquid is simple in structure, energy-saving, and scalable, making it suitable for various application scenarios.

[0005] Another object of the present invention is to provide the application of the above-mentioned apparatus for large-scale preparation of plasma-activated liquid in food sterilization.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention provides an apparatus for large-scale preparation of plasma activation liquid, comprising a power supply, a gas supply system, a water tank, and at least one mixed plasma reactor; the mixed plasma reactor is disposed inside the water tank;

[0008] The hybrid plasma reactor includes a dielectric tube, a rod-shaped grounding electrode, a first high-voltage electrode, and a second high-voltage electrode; the rod-shaped grounding electrode, the first high-voltage electrode, and the second high-voltage electrode are fixed inside the dielectric tube.

[0009] The first high-voltage electrode is a metal tube, which is sleeved on the outside of the rod-shaped grounding electrode, and the rod-shaped grounding electrode is located at the center of the first high-voltage electrode; the inner surface of the first high-voltage electrode is provided with a dielectric layer;

[0010] The second high-voltage electrode is located below the first high-voltage electrode and is sleeved on the outside of the rod-shaped grounding electrode, with the rod-shaped grounding electrode located at the center of the second high-voltage electrode;

[0011] The working gas in the gas supply system enters the medium tube from the air inlet at the top of the medium tube, generating dielectric barrier discharge plasma between the first high-voltage electrode and the rod-shaped grounding electrode; and generating sliding arc discharge plasma between the second high-voltage electrode and the rod-shaped grounding electrode; the dielectric barrier discharge plasma and the sliding arc discharge plasma form a mixed plasma and disperse it from the air outlet at the bottom of the medium tube into the liquid in the water tank to obtain plasma activation liquid.

[0012] Preferably, the working gas enters the medium tube at a flow rate of 5-15 L / min.

[0013] Preferably, the second high-voltage electrode has a spiral structure, with its radius increasing from top to bottom.

[0014] Preferably, the second high-voltage electrode is welded to the lower end of the first high-voltage electrode.

[0015] Preferably, the air outlet below the medium tube is provided with multiple microporous aerators; the microporous aerators are provided with Pall rings on the outside.

[0016] Preferably, the liquid in the water tank contains a surfactant; the mixed plasma forms bubbles with a particle size of 50nm-1μm in the liquid; the surfactant is fatty alcohol polyoxyethylene ether, polyethylene glycol fatty acid ester, or polyvinyl alcohol.

[0017] Preferably, the dielectric layer is borosilicate and covers the inner surface of the first high-voltage electrode.

[0018] Preferably, there are two mixed plasma reactors, one of which is connected to the positive terminal of a power source and the other is connected to the negative terminal of a power source.

[0019] Preferably, the apparatus for large-scale preparation of plasma activation liquid further includes a humidification device for humidifying the working gas. Preferably, the apparatus for large-scale preparation of plasma activation liquid also includes a solar plasma generator system, specifically including a foldable solar panel power generation system, a plasma power supply, and a high-voltage transformer, which can utilize the power supply or solar power to drive the hybrid plasma generation system.

[0020] Preferably, the outer layer of the dielectric tube is further provided with a heat sink, which is in close contact with the outer layer of the quartz dielectric tube.

[0021] Preferably, the grounding electrode lead of the apparatus for large-scale preparation of plasma activation liquid needs to be installed below the liquid surface, and can be installed at the bottom or side of the water tank or suspended in the water.

[0022] Preferably, the second high-voltage electrode can also employ other structures to form a sliding arc discharge jet mode, generating a sliding arc discharge through vortex airflow. Specifically, the sliding arc discharge jet mode utilizes a vortex airflow generator to create vortex motion in the plasma airflow inside the reactor, thereby generating a dynamic sliding arc discharge between the high-voltage electrode and the ground electrode. Through this sliding arc discharge jet mode, the hybrid plasma reactor can adapt to different water treatment needs and can flexibly adjust the plasma generation method without significantly altering the existing structure, achieving a more efficient water treatment effect.

[0023] Preferably, the plasma power source of the present invention can provide up to 10-80 kV (V p-p The system provides high-voltage pulses with a repetitive pulse frequency of 100-3000Hz. The gas supply system can provide working gas with a flow rate of 5-15L / min. Two discharge modes can be switched or coexisted through different voltage or gas flow ranges.

[0024] Preferably, the working gas can be a mixture of different gases or a single gas. The working gas is humidified by a water-washing gas source and then pumped into the mixed plasma generation system.

[0025] The present invention also provides the application of the above-mentioned apparatus for large-scale preparation of plasma-activated liquid in food sterilization. The plasma-activated liquid prepared by the apparatus is used to disinfect Escherichia coli, mold, Staphylococcus aureus, Salmonella, Listeria monocytogenes and Clostridium botulinum in food, food packaging and food processing equipment. The sterilization method includes at least one of rinsing, spraying, soaking, wiping, dripping and coating. The materials of the food packaging and food processing equipment include at least one of quartz, metal, glass, stainless steel, plastic and paper.

[0026] The method for large-scale preparation of plasma activation liquid based on the above-described apparatus includes the following processing steps:

[0027] S1: Pass the aqueous solution to be treated into the water tank and add surfactant to the aqueous solution;

[0028] S2: Turn on the gas supply system to introduce the humidified working gas into the mixed plasma reactor, and then turn on the solar plasma generator system. The mixed plasma activation gas is generated in the mixed plasma reactor at the same time.

[0029] S3: The mixed plasma reaches the microporous aerator at the bottom of the quartz tube medium tube with the airflow, and the mixed plasma activation gas forms ultra-fine nanobubbles through the micropores and disperses into the liquid flow.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] (1) The apparatus for large-scale preparation of plasma activated liquid of the present invention introduces two discharge schemes: dielectric barrier discharge and sliding arc discharge. The dielectric barrier discharge region focuses on generating highly loaded active oxygen substances, while the sliding arc discharge region focuses on generating highly active active nitrogen substances. Furthermore, the solubility of the mixed plasma active gas generated by the two is greatly improved in water, and a large number of high-valence nitrogen oxides that play a key role in sterilization are generated, thereby achieving high-level food sterilization applications and exhibiting spectral antibacterial properties.

[0032] (2) The apparatus for large-scale preparation of plasma activation liquid of the present invention implements a dual-reactor configuration (one connected to the positive terminal and the other connected to the negative terminal) in an AC loop, which greatly reduces the energy loss (unused micro-discharge) of the negative electrode in a single-reactor configuration and significantly improves the generation of high-valence nitrogen oxide species and energy efficiency.

[0033] (3) The apparatus for large-scale preparation of plasma-activated liquid of the present invention integrates plasma discharge with bubbles. By utilizing plasma bubble technology and bubble dynamics control (Pall ring) design, a large surface area is provided for gas-liquid interaction, and mass transfer and residence time are improved, greatly increasing the efficiency of plasma activation. In addition, the addition of surfactants improves the particle size of ultrafine bubbles, further improving the efficiency of plasma activation, thereby realizing the large-scale preparation of plasma-activated liquid.

[0034] (4) The device for large-scale preparation of plasma activation liquid of the present invention can switch or coexist with two discharge modes through different voltage or gas flow ranges, and can activate various different liquid media (deionized water, physiological saline, cell culture medium or artificial seawater), showing great potential applications in microbial disinfection in various scenarios (seawater aquaculture, medical treatment, cell and tissue engineering).

[0035] (5) In the apparatus for large-scale preparation of plasma activation liquid of the present invention, the solar plasma generator system has a hybrid power supply mode of solar energy and traditional power supply, which has the advantages of low carbon and environmental protection, economic and energy saving, and is suitable for areas with power shortage and field environment, especially in remote areas or emergency situations. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the apparatus for large-scale preparation of mixed plasma activation liquid according to the present invention.

[0037] Icons: 1. Water tank, 2. Solar plasma generator system, 3. Gas supply system, 4. Grounding electrode lead, 5-1. First mixed plasma reactor, 5-2. Second mixed plasma reactor, 6. Water inlet, 7. Water outlet, 8. Foldable solar panel power generation system, 9. Plasma power supply, 10. High-voltage transformer, 11. Gas source, 12. Air pump, 13. Mixing tank, 14. Flow controller, 15. Switch valve, 16. Second high-voltage electrode, 17. First high-voltage electrode, 18. Radiator, 19. Quartz dielectric tube, 20. Microporous aerator, 21. Pall ring, 22. Gas inlet, 23. Stainless steel rod grounding electrode.

[0038] Figure 2 A schematic diagram of the second high-voltage electrode, the first high-voltage electrode, and the stainless steel rod grounding electrode in the apparatus for preparing the mixed plasma activation liquid on a large scale according to the present invention.

[0039] Figure 3 The sterilization effect of different plasma activation liquid volumes (10L, 15L, 20L and 30L) on Escherichia coli in Example 1 of the present invention is shown.

[0040] Figure 4 This invention demonstrates the bactericidal effect of the mixed plasma activation liquid in Example 2 on various common foodborne pathogens (Escherichia coli, mold, Staphylococcus aureus, Salmonella, Listeria monocytogenes and Clostridium botulinum) on the surface of food.

[0041] Figure 5 This invention describes the bactericidal effect of the mixed plasma activating liquid in Example 3 on Escherichia coli on the surfaces of food packaging and processing equipment made of different materials (quartz, metal, glass, stainless steel, plastic, and paper).

[0042] Figure 6 This is a comparison chart of the concentrations of five typical gaseous reactants in the large-scale preparation equipment of the mixed plasma activation liquid in Examples 1 and 2 of the present invention, and in other comparative examples.

[0043] Figure 7The image shows a comparison of the bactericidal effects of the mixed plasma activating solutions prepared in Example 1, Comparative Examples 1-4, and Example 4 of this invention on Escherichia coli. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0045] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0046] The terms "including," "have," etc., used in this article are all open-ended, meaning they include but are not limited to.

[0047] Example 1

[0048] Please refer to Figures 1-2 The apparatus for large-scale preparation of plasma activation liquid of the present invention includes a water tank 1, a solar plasma generator system 2, a gas supply system 3, a grounding electrode lead 4, a mixed plasma reaction 5-1, and a mixed plasma reaction 5-2. The water tank 1 is used to hold the aqueous solution to be treated and is provided with a water inlet 6 and a water outlet 7. The solar plasma generator system 2 includes a foldable solar panel power generation system 8, a plasma power supply 9, and a high-voltage transformer 10, which can use the power supply or solar power to drive the mixed plasma generation system 5. The gas supply system 3 includes a gas source 11, a gas pump 12, a mixing tank 13, a flow controller 14, and a switching valve 15. The gas source 11 provides working gas, which enters the mixing tank 13 through a gas supply pipe, and then supplies working gas with a certain pressure and flow rate to the mixed plasma reaction 5-1 and the mixed plasma reaction 5-2 through the flow controller 14. The grounding electrode lead 4 needs to be installed below the liquid surface and can be installed at the bottom, side, or suspended in the water of the water tank.

[0049] Hybrid plasma reactors 5-1 and 5-2 have identical structures and are connected to the positive and negative electrodes of plasma power supply 9, respectively. The hybrid plasma reactor includes a quartz dielectric tube 19, a second high-voltage electrode 16, a first high-voltage electrode 17, a heat sink 18, a stainless steel rod grounding electrode 23, a microporous aerator 20, and a Pall ring 21. The second high-voltage electrode 16, the first high-voltage electrode 17, and the stainless steel rod grounding electrode 23 are fixed inside the quartz dielectric tube 19, with the second high-voltage electrode 16 welded to the lower end of the first high-voltage electrode 17. The first high-voltage electrode 17 is a metal tube fitted over the stainless steel rod grounding electrode 23, which is located at the center of the first high-voltage electrode 17. A dielectric layer, made of borosilicate, covers the inner surface of the first high-voltage electrode 17. The inner and outer layers of the quartz dielectric tube 19 are covered with insulators, and a gas inlet 22 is installed at the upper end. Multiple microporous aerators 20 are evenly distributed around the bottom of the quartz dielectric tube 19. Pall rings 21 can be placed outside the microporous aerators 20 as packing material. The heat sink 18 is tightly attached to the outer layer of the quartz dielectric tube 19 to ensure that the temperature generated by the plasma discharge does not affect the normal operation of the mixed plasma reactor.

[0050] The working gas enters the quartz dielectric tube through the inlet at the top, generating dielectric barrier discharge plasma between the first high-voltage electrode 17 and the stainless steel grounding electrode 23; and generating sliding arc discharge plasma between the second high-voltage electrode 16 and the stainless steel grounding electrode 23. The dielectric barrier discharge plasma and the sliding arc discharge plasma form a mixed plasma, which is dispersed into the water in the tank through the outlet at the bottom of the dielectric tube. The water can be deionized water, physiological saline, cell culture medium, or artificial seawater. A surfactant is added to the water, causing the plasma gas to form ultrafine nanobubbles in the surfactant-containing liquid. The ultrafine nanobubbles have a particle size of 50 nm to 1 μm. In this embodiment, the surfactant can be fatty alcohol polyoxyethylene ether (such as surfactant AI-600), polyethylene glycol fatty acid ester (such as the Tween series), polyvinyl alcohol (PVA), etc. These nonionic surfactants are chemically stable, have low pH sensitivity, and are suitable for various aquatic environments. In addition, these surfactants can significantly reduce surface tension and promote the formation of ultrafine nanobubbles.

[0051] In this embodiment, the working gas can be a mixture of different gases or a single gas. The working gas is humidified by a water-washing gas source and then pumped into the mixed plasma reaction 5-1 and the mixed plasma reaction 5-2.

[0052] In this embodiment, the plasma power source 9 is capable of providing up to 10-80 kV (Vp-p The gas supply system 3 provides working gas at a flow rate of 5-15 L / min, and the high-voltage pulse frequency is 100-3000 Hz. Different voltage or gas flow ranges allow for switching or coexistence of two discharge modes. Specifically, the voltage range for the single dielectric barrier discharge mode is 10-30 kV (V). p-p The frequency is 100-500Hz, and the gas flow rate is 5-10L / min; while the voltage range of the independent sliding arc discharge mode is 20-40kV (V). p-p The frequency is 500-3000Hz, and the gas flow rate is 10-15L / min. If both discharge modes need to coexist, the voltage can be controlled at 20-30kV (V). p-p The frequency is controlled at 300-1000Hz, and the gas flow rate is controlled at 8-12L / min.

[0053] Single Escherichia coli colonies were inoculated into Luria-Bertani broth containing 3% NaCl at 37°C and incubated at 37°C for 24 hours, resulting in a bacterial concentration of approximately 1.0 × 10⁻⁶. 8 CFU / mL. Take 10.0 mL of the cultured E. coli suspension, centrifuge at 5000 rpm for 10 min, and resuspend in pre-prepared aqueous solutions (10 L, 15 L, 20 L, and 30 L) to achieve a final concentration of 1.0 × 10⁻⁶ CFU / mL. 6 CFU / mL was used for subsequent water microbial disinfection experiments.

[0054] The prepared bacterial suspension was selected as the test water and treated using a device for large-scale preparation of plasma-activated solution. The treatment steps are as follows:

[0055] S1: Different volumes (10L, 15L, 20L and 30L) of the aqueous solution to be treated are introduced into the water tank through the water inlet, and surfactants are added to the aqueous solution to be treated;

[0056] S2: Turn on the air supply system and introduce humidified compressed air at a flow rate of 10L / min into the mixed plasma reactor. Then turn on the solar plasma generator system and generate mixed plasma for 1 minute in the first and second mixed plasma reactors under the conditions of discharge voltage of 30kV, excitation frequency of 1000Hz, and ultrafine nanobubble particle size of 150nm.

[0057] S3: The mixed plasma reaches the microporous aerator at the bottom of the quartz tube medium tube with the airflow, and the mixed plasma activation gas forms ultra-fine nanobubbles through the micropores and disperses into the liquid flow.

[0058] Bacterial colony counts were determined using the standard plating method. Figure 3It can be concluded that within a short discharge time (1 min), this equipment for large-scale preparation of mixed plasma activation fluid can efficiently generate effective mixed plasma activation fluid, thereby reducing E. coli colonies by at least 6 logarithmic orders. Furthermore, this equipment can improve the energy efficiency of mixed plasma activation fluid while increasing the liquid volume (from 10 L to 30 L). Even with an aqueous solution volume of 30 L, a mixed plasma activation fluid reducing E. coli colonies by 5.2 logarithmic orders can still be prepared within 1 min. This is because industrial applications require the production of larger quantities of effective plasma activation fluid while minimizing energy consumption.

[0059] Example 2

[0060] The apparatus for large-scale preparation of plasma-activated liquid in Example 1 was used to kill bacteria in food.

[0061] The preparation process of the mixed plasma activation solution is as follows:

[0062] S1: The aqueous solution to be treated is introduced into the water tank through the water inlet, and a surfactant is added to the aqueous solution to be treated;

[0063] S2: Turn on the air supply system and introduce humidified compressed air at a flow rate of 10L / min into the mixed plasma reactor. Then turn on the solar plasma generator system and generate mixed plasma in the first and second mixed plasma reactors at a discharge voltage of 50kV, an excitation frequency of 1000Hz, and an ultrafine nanobubble particle size of 150nm for 1min to obtain a mixed plasma activation liquid.

[0064] The mixed plasma activation solution prepared in this embodiment was applied by spraying onto colonies inoculated with different bacterial strains (bacterial concentration approximately 1.0 × 10⁻⁶). 6 On food surfaces (CFU / mL), the test results are as follows: Figure 4 As shown. (Through) Figure 4 It can be seen that the six most common foodborne pathogens in food sterilization applications—Escherichia coli, mold, Staphylococcus aureus, Salmonella, Listeria monocytogenes, and Clostridium botulinum—were completely inactivated. Furthermore, complete inactivation can be achieved by any of the methods of action (rinsing, spraying, soaking, wiping, dripping, and coating), which also means that this invention is adaptable to different food processing scenarios (such as large-scale production lines, small-scale manual operations, and retail packaging).

[0065] Example 3

[0066] The apparatus for large-scale preparation of plasma-activated liquid in Example 1 was used to kill bacteria in food.

[0067] The preparation process of the mixed plasma activation solution is as follows:

[0068] S1: The aqueous solution to be treated is introduced into the water tank through the water inlet, and a surfactant is added to the aqueous solution to be treated;

[0069] S2: Turn on the air supply system and introduce humidified compressed air at a flow rate of 10L / min into the mixed plasma reactor. Then turn on the solar plasma generator system and generate mixed plasma in the first and second mixed plasma reactors at a discharge voltage of 50kV, an excitation frequency of 1000Hz, and an ultrafine nanobubble particle size of 150nm for 1min to obtain a mixed plasma activation liquid.

[0070] The mixed plasma activation solution prepared in this embodiment was applied by spraying onto bacteria inoculated with Escherichia coli (bacterial concentration approximately 1.0 × 10⁻⁶). 6 Test results (CFU / mL) on the surfaces of different food packaging materials and processing equipment (quartz, metal, glass, stainless steel, plastic, and paper) are as follows: Figure 4 As shown. (Through) Figure 4 It can be seen that the six different materials used to sterilize E. coli on the surfaces of food packaging and processing equipment all achieved good sterilization efficiency. While the sterilization efficiency varied slightly among the materials due to differences in surface properties, reactivity, and interaction with plasma, overall, all met the sterilization requirements for food packaging materials and processing equipment surfaces.

[0071] Comparative Example 1

[0072] A 20L bacterial suspension was selected as the test water. The apparatus for preparing the mixed plasma activation solution was the same as in Example 1, except that the spiral electrode at the lower end of the high-voltage electrode of the mixed plasma reactor was removed, while maintaining a dual-reactor configuration within an AC circuit (one connected to the positive terminal and the other to the negative terminal). The bacterial suspension was treated with dielectric barrier discharge plasma for 1 minute at a discharge voltage of 30kV, an excitation frequency of 500Hz, and an ultrafine nanobubble particle size of 100nm, using compressed air at a flow rate of 5L / min as the working gas.

[0073] Comparative Example 2

[0074] A 20L bacterial suspension was selected as the test water. The apparatus for preparing the mixed plasma activation solution was the same as in Example 1, except that the first high-voltage electrode of the mixed plasma reactor was removed, while maintaining a dual-reactor configuration within an AC circuit (one connected to the positive terminal and the other to the negative terminal). The bacterial suspension was treated with sliding arc discharge plasma for 1 min at a discharge voltage of 40kV, an excitation frequency of 2000Hz, and an ultrafine nanobubble particle size of 200nm, using compressed air at a flow rate of 15L / min as the working gas.

[0075] Comparative Example 3

[0076] A 20L bacterial suspension was selected as the test water. Compared to Example 1, the apparatus for preparing the mixed plasma activation solution was modified by removing the spiral electrode at the lower end of the high-voltage electrode in the mixed plasma reactor and using a single mixed plasma reactor. This was achieved by connecting the negative electrode to the grounding electrode of the stainless steel rod in the plasma bubble reactor. The bacterial suspension was treated with dielectric barrier discharge plasma for 1 minute at a discharge voltage of 30kV, an excitation frequency of 500Hz, and an ultrafine nanobubble particle size of 100nm, using compressed air at a flow rate of 5L / min as the working gas.

[0077] Comparative Example 4

[0078] A 20L bacterial suspension was selected as the test water. The apparatus for preparing the mixed plasma activation solution was the same as in Example 1, except that the first high-voltage electrode of the mixed plasma reactor was removed, and a single plasma bubble reactor configuration was used. This was achieved by connecting the negative electrode to the grounding electrode of a stainless steel rod within the plasma bubble reactor. The bacterial suspension was treated with sliding arc discharge plasma for 1 minute at a discharge voltage of 40kV, an excitation frequency of 2000Hz, and an ultrafine nanobubble particle size of 200nm, using compressed air at a flow rate of 15L / min as the working gas.

[0079] Example 4

[0080] A 20L bacterial suspension was selected as the test water. The same large-scale preparation equipment for the mixed plasma activation solution as in Example 1 was used, except that the Pall ring in the mixed plasma generation system was removed. The bacterial suspension was treated with mixed plasma for 1 min under the conditions of a discharge voltage of 30kV, an excitation frequency of 1000Hz, an ultrafine nanobubble particle size of 150nm, and a flow rate of 10L / min using compressed air as the working gas.

[0081] Figure 6The concentrations of five typical gaseous reactants in the mixed plasma activation liquid prepared by the large-scale preparation equipment of the mixed plasma activation liquid in Examples 1 and 1-2 of this invention are shown. It is worth noting that O3, NO, and NO2 have very low solubility; therefore, neither the dielectric barrier discharge mode nor the sliding arc discharge mode of air plasma can effectively activate water. The Henry's law constant of NO2 is only 1.2 × 10⁻⁶. -4 MPa -1 The Henry's law coefficients for O3 and NO are even lower. In contrast, the main discharge product of the mixed plasma in Example 1 of this invention is high-valence NO. x (such as N2O5 and NO3), therefore their activation efficiency in water may be much higher. This is because high-valence nitrogen oxides are easily soluble in water through reaction absorption, and their oxidation reactivity is also higher than that of NO and NO2, which is positively correlated with the bactericidal effect.

[0082] Figure 7 The large-scale preparation equipment for the mixed plasma activation solution in Examples 1, 1-4, and 4 of the present invention was compared with other comparative examples to assess the inactivation efficiency of Escherichia coli. In comparison, the large-scale preparation equipment for the mixed plasma activation solution in Example 1 of the present invention exhibits better sterilization efficiency, and the implementation of a dual-reactor configuration results in lower energy consumption.

[0083] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An apparatus for large-scale preparation of plasma activation liquid, characterized in that, It includes a power supply, a gas supply system, a water tank, and at least one hybrid plasma reactor; the hybrid plasma reactor is located inside the water tank; The hybrid plasma reactor includes a dielectric tube, a rod-shaped grounding electrode, a first high-voltage electrode, and a second high-voltage electrode; the rod-shaped grounding electrode, the first high-voltage electrode, and the second high-voltage electrode are fixed inside the dielectric tube. The first high-voltage electrode is a metal tube, which is sleeved on the outside of the rod-shaped grounding electrode, and the rod-shaped grounding electrode is located at the center of the first high-voltage electrode; the inner surface of the first high-voltage electrode is provided with a dielectric layer; The second high-voltage electrode is located below the first high-voltage electrode and is sleeved on the outside of the rod-shaped grounding electrode, which is located at the center of the second high-voltage electrode. The second high-voltage electrode has a spiral structure, and its radius increases from top to bottom. The second high-voltage electrode is welded to the lower end of the first high-voltage electrode. The working gas in the gas supply system enters the medium tube from the air inlet at the top of the medium tube, generating dielectric barrier discharge plasma between the first high-voltage electrode and the rod-shaped grounding electrode. A sliding arc discharge plasma is generated between the second high-voltage electrode and the rod-shaped grounding electrode. The dielectric barrier discharge plasma and the sliding arc discharge plasma form a mixed plasma, which is dispersed from the outlet below the dielectric tube into the liquid in the water tank to obtain the plasma activation liquid.

2. The apparatus for large-scale preparation of plasma activation liquid according to claim 1, characterized in that, The working gas enters the medium tube at a flow rate of 5-15 L / min.

3. The apparatus for large-scale preparation of plasma activation liquid according to claim 1, characterized in that, The air outlet below the medium tube is equipped with multiple microporous aerators; the microporous aerators are equipped with Pall rings on their exterior.

4. The apparatus for large-scale preparation of plasma activation liquid according to claim 3, characterized in that, The liquid in the water tank contains a surfactant; the mixed plasma forms bubbles with a particle size of 50 nm-1 μm in the liquid; the surfactant is fatty alcohol polyoxyethylene ether, polyethylene glycol fatty acid ester or polyvinyl alcohol.

5. The apparatus for large-scale preparation of plasma activation liquid according to claim 1, characterized in that, The dielectric layer is borosilicate and covers the inner surface of the first high-voltage electrode.

6. The apparatus for large-scale preparation of plasma activation liquid according to claim 1, characterized in that, The hybrid plasma reactor consists of two units, one connected to the positive terminal of a power source and the other connected to the negative terminal.

7. The apparatus for large-scale preparation of plasma activation liquid according to claim 1, characterized in that, It also includes a humidification device for humidifying the working gas.

8. The application of the apparatus for large-scale preparation of plasma-activated liquid as described in claim 1 in food sterilization, characterized in that, The plasma activation liquid prepared by the aforementioned large-scale plasma activation liquid preparation device is used to disinfect Escherichia coli, mold, Staphylococcus aureus, Salmonella, Listeria monocytogenes and Clostridium botulinum in food, food packaging and food processing equipment; the disinfecting method includes at least one of rinsing, spraying, soaking, wiping, dripping and coating; the material of the food packaging and food processing equipment includes at least one of quartz, metal, glass, stainless steel, plastic and paper.

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