KR20210017738A - Method and apparatus for producing high concentration hydrogen peroxide concentrated water by plasma - Google Patents

Abstract

The present invention relates to a method for producing high-concentration hydrogen peroxide-enriched water, comprising generation of a water surface plasma at an oscillating temperature of N_2 of 4900 K or less. More specifically, the present invention provides the method for producing the best hydrogen peroxide solution, which solves the problem that the concentration of hydrogen peroxide is rather lowered after a certain period of time during the production of hydrogen peroxide solution by conventional water surface plasma discharge.

Description

TECHNICAL FIELD [Method and apparatus for producing high concentration hydrogen peroxide concentrated water by plasma]

The present invention relates to a method and apparatus for generating plasma treated water (PTW) containing hydrogen peroxide (H ₂ O ₂ ) by water surface plasma. Preferably, the water surface plasma of the present invention may be a water surface plasma in which ac driving power is applied to a pin-to-water discharge system.

Hydrogen peroxide (H ₂ O ₂ ) is used in a variety of industries including sterilization and bleaching. However, the high concentration of H ₂ O ₂ supplied by chemical generation is recommended to occur in the field as necessary, as there is a risk of injury to the user.

Plasma can be a promising source for H ₂ O ₂ generation. The present invention has been developed based on the H ₂ O ₂ generation mechanism of a fin-to-water discharge system, which has high energy efficiency and a simple discharge system, among various plasma discharge methods such as UV, gliding arc, microwave, and RF.

In low-pressure-low-temperature plasma, chemical species are mainly controlled through EEDF (electron energy distribution function), but in normal-pressure-low-temperature plasma, it is controlled mainly through gas temperature.

The present invention aims to provide a method for producing a high-concentration PTW by water surface plasma, and it was found that the vibration temperature of nitrogen molecules may be a key parameter in the production of a high-concentration PTW. During PTW generation by water surface plasma, the concentration of H ₂ O ₂ was not saturated, but a specific phenomenon was found that decreased after 25-35 minutes after plasma treatment, and this phenomenon was found to be due to the vibration temperature of nitrogen molecules. It aims to provide a method and apparatus for producing hydrogen peroxide concentrated water based on high concentration PTW.

As an aspect, the present invention provides a method for producing high-concentration hydrogen peroxide concentrated water, comprising generating plasma on the water surface at a vibration temperature of N ₂ of 4900K or less.

In the present invention, the water surface plasma device refers to the registered Korean Patent Registration Nos. 10-1707441 and 10-1661135 of the present inventor, and is an apparatus for producing plasma-treated water by allowing a thin film water film to flow between two opposite electrodes. . Preferably, in this water surface plasma apparatus, water supplied to the water film and plasma-treated water are configured to circulate to form hydrogen peroxide at a high concentration.

The inventors of the present invention have confirmed a specific phenomenon in which the concentration of hydrogen peroxide decreases after a certain period of time when generating hydrogen peroxide water with such a water surface plasma device, and newly revealed that this decrease is related to the nitrogen oscillation temperature of the plasma. It was confirmed that the number of hydrogen peroxide decreased at a nitrogen vibration temperature of more than 4900K.

Accordingly, the present inventors claim that the nitrogen oscillation temperature of the plasma must be 4900K or less in order to generate a high concentration of hydrogen peroxide water by the water surface plasma.

In order to generate hydrogen peroxide water by plasma with a water surface plasma at a nitrogen oscillation temperature of 4900 K or less, the present invention prepares plasma treated water by plasma treatment of water with a water surface plasma apparatus, and the N of the plasma of the plasma treatment apparatus _It provides a method for producing a high-concentration hydrogen peroxide concentrated water comprising measuring the vibration temperature of ₂ and stopping the plasma treatment of the water surface when the vibration temperature of N ₂ is 4900K or higher.

The vibration temperature of N ₂ of the plasma can be determined by measuring by optical emission spectroscopy (OES).

As another aspect, the present invention provides an apparatus for producing a high-concentration hydrogen peroxide solution using plasma. The apparatus of the present invention comprises: a plasma generating unit generating plasma on a surface of water; A water tank for receiving the treated water treated with the water surface from the plasma generating unit; And a measuring unit for checking the vibration temperature of N ₂ of the plasma on the water surface.

The plasma generator may include: a first electrode body spaced apart on the surface of the water of the water tank; A second electrode body positioned on the outer or inner surface of the water tank, or in the water accommodated in the water tank; And a power supply for applying a voltage to the first electrode body and the second electrode body.

Preferably, the plasma generating unit comprises: a first electrode body having a water supply surface; A second electrode body positioned to be spaced apart from the water supply surface by a predetermined distance; And a power supply device for applying a voltage to the first electrode body and the second electrode body, wherein the hydrogen peroxide solution production device is in the form of a water film that can be spaced apart from the second electrode body on the water supply surface. A water film supply unit supplying water to flow and receive into the water tank; And a circulation unit circulating water from the water tank to the water film supply unit. Preferably, the first electrode body and the second electrode body are upright, the water film flows from the top to the bottom of the first electrode body, and the water tank holds the water film under the first electrode body. It is characterized by accommodation.

The measurement unit may be an optical emission spectroscopy (OES) that analyzes an emission signal from the plasma.

And a control unit for controlling power supply to the power supply device, wherein the control unit is configured to cut off the power supply when the vibration temperature of N ₂ measured by the measurement unit exceeds a predetermined value.

The vibration temperature of N ₂ is characterized in that the predetermined value is 4900K.

The apparatus of the present invention includes an outlet for discharging hydrogen peroxide water from the water tank; A water supply unit supplying additional water to the circulation unit; And a control unit for controlling the circulation unit, the water supply unit, and the discharge port, wherein the control unit opens the discharge port when the vibration temperature of N ₂ measured by the measurement unit is higher than a predetermined value, and the water supply unit It is characterized in that it is configured to supply additional water to the circulation unit through.

The present invention provides a method for producing the best hydrogen peroxide solution, which solves the problem of lowering the concentration of hydrogen peroxide after a certain period of time, when producing hydrogen peroxide solution by conventional water surface plasma discharge.

1 is a schematic diagram of an apparatus for a water surface plasma discharge system according to the present invention, in which an experiment of the present invention is performed.
2 shows the H ₂ O ₂ concentration versus time of PTW for plasma treatment conditions. Here, the short, medium and long electrode lengths are 34, 36 and 38 mm electrode lengths, respectively.
3 shows the vibration temperature of N2 versus time for plasma treatment conditions. The short, medium and long electrode lengths are 34, 36 and 38 mm electrode lengths, respectively.
4 shows a spectrum as a result of measuring the dynamics of a neutral species in a discharge gas containing H ₂ O ₂ using FTIR. Figure 4a is a representative IR spectrum in the range of 4000 ~ 500cm ^-1 , the H ₂ O ₂ signal can be identified by comparison with the H ₂ O signal, Figure 4b shows the H ₂ O ₂ signal band of ~ 3500 cm ^-1 It can be extracted from the measured signal. Figure 4c is a time-wavenumber contour plot of the measured spectrum. Figure 4d is a time-wavenumber contour plot of the extracted H ₂ O ₂ spectrum.
5 shows the time-resolved absorbance of H ₂ O ₂ FTIR for discharge conditions. The short, medium and long electrode lengths are 34, 36 and 38 mm electrode lengths, respectively.
6 shows the time-decomposition characteristics of PTW for discharge conditions. Figure 6a is the electrical conductivity, pH Figure 6b, Figure 6c is the temperature, Figure 6d is NO ₂ ^- density, and Figure 6e is NO ₃ ^- is the density. The short, medium and long electrode lengths are 34, 36 and 38 mm electrode lengths, respectively.
7 shows the average gas velocity in the plasma region versus the electrode length. The short, medium and long electrode lengths are 34, 36 and 38 mm electrode lengths, respectively.
Figure 8 shows the calculated species density and gas temperature of the plasma column against the discharge power density. FIG. 8A is 1.53e8 W/m ³ , FIG. 8B is 3.56e8 W/m ^3, and FIG. 8C is 7.13e8 W/m ³ .
9 is a diagram of the chemical species reaction path of the circulating water contact type discharge system.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Since the present invention can apply various changes and have various forms, specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific form of disclosure, it is to be understood as including all changes, equivalents, or substitutes included in the spirit and scope of the present invention. In describing each drawing, similar reference numerals have been used for similar elements.

The terms used in the present application are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the existence of features, steps, actions, components, parts, or a combination thereof described in the specification, but one or more other features or steps It is to be understood that it does not preclude the possibility of addition or presence of, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms as defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in this application. Does not.

The device of the discharging system of the present invention is illustrated in FIG. 1. The hydrogen peroxide solution production apparatus of the present invention comprises: a first electrode body 100 having an upright water supply surface 110; A second electrode body 200 positioned to be spaced apart from the water supply surface 110 by a predetermined distance; A power supply device (300) for applying voltage to the first electrode body (100) and the second electrode body (200); A water film supply unit 400 supplying water to the water supply surface to flow in the form of a water film spaced apart from the second electrode body; A water tank 600 accommodating the water film; A water surface plasma device for forming plasma between the second electrode body and the water film, including a circulation unit 700 for circulating water from the water tank 600 to the water film supply unit 400; And a measurement unit 800 (OES (optical emission spectroscopy)) for checking the vibration temperature of N ₂ of the plasma.

In the present invention, the present inventor analyzed the H ₂ O ₂ generation characteristics according to the plasma power density and the temperature of water in contact with the plasma. The plasma power density was varied according to the electrode length l, and the water temperature was controlled using a cooler as shown in FIG. 1.

At low discharge gas temperatures, the dominant reactive oxygen species (ROS) and reactive nitrogen species (RNS) increased with the gas temperature. In a temperature condition near room temperature, plasma-separated hydroxy (OH) and oxygen atoms (O) form H ₂ O ₂ by recombination. At high gas temperature conditions, H ₂ O ₂ production can be reduced because plasma chemistry is transferred to nitrogen species generation. Since nitrogen ions are formed in the discharge into the air, the concentration of H ₂ O ₂ may decrease due to the bonding between hydrogen peroxide and nitrogen ions, and nitric acid may be oxidized to nitric acid. In other words, the concentration of H ₂ O ₂ in PTW is the dissolution process of H ₂ O ₂ that occurs in the recombination of OH that occurs during separation of water vapor containing air discharge plasma, electron collision on the water surface, or plasma-generated ozone (O ₃ ) Will be decided in Therefore, H ₂ O ₂ containing PTW can be obtained at an appropriate concentration by controlling the plasma operation parameter.

The Pin-to-water plasma illustrated in FIG. 1 of the present invention was generated by applying 0.2 kW power driven at 14.3 kHz. The electrode lengths were 34 (short), 36 (medium) and 38 (long) mm to control the plasma power density. The cooler temperature was set to 0, 20, and 40 °C. During discharge, properties of PTW such as H ₂ O ₂ density, electrical conductivity, temperature and pH were monitored. Plasma-producing species were observed in gas and PTW using FT-IR (Frontier, PerkinElmer), IC (Dionex ICS-2100, Thermo) and UV-VIS spectrophotometer (DR 6000, Hach). Each measurement was repeated 3 times to confirm reproducibility.

The measured concentration of H ₂ O ₂ in PTW is shown in FIG. 2. Although there are slight differences depending on the experimental conditions, overall, the concentration of H ₂ O ₂ shows a steep increase in the initial 15 to 25 minutes during plasma discharge and decreases slowly for 35 to 45 minutes. The decrease in the H ₂ O ₂ concentration during plasma discharge means a change in the plasma chemical reaction. The difference in H ₂ O ₂ peak concentration for discharge conditions is the temperature of the PTW or the gap distance between the electrode and the PTW.

In order to understand the details of the H ₂ O ₂ concentration of PTW, it is necessary to understand the characteristics of the plasma and PTW at the same time because H ₂ O ₂ is generated in the plasma and transformed into PTW. The main reaction of H ₂ O, generation and loss in plasma is explained in Equation (1-6) below. The key reaction may be the reaction between the oscillatory excited N ₂ and the atom O in equation (4).

3 shows the vibration temperature of N ₂ for plasma discharge conditions. The temperature was measured from the OES signal. During plasma discharge, the temperature gradually increases from -3000 K to -5500 K. It was found that the gap distance had a greater effect on the temperature than the cooler temperature. The temperatures of the cooler temperatures are relatively similar to each other. The short and long intervals represent the highest and lowest temperatures, respectively.

However, the excitation T _vib of N ₂ is not directly connected to H ₂ O ₂ of PTW. Therefore, the present inventor measured the dynamics of neutral species in a discharge gas containing H ₂ O ₂ using FTIR. A typical spectrum is shown in Figure 4. Most of the signals in the spectrum are evaporated H ₂ O. The low intensity H ₂ O ₂ signal is shown in Fig. 4(a). The H ₂ O signal is relatively softer than the H ₂ O ₂ signal. By filtering the H ₂ O signal, the H ₂ O ₂ signal can be extracted as shown in FIG. 4(b). The time-resolved H ₂ O ₂ signal is shown in the contour diagram of Fig. 4(cd). The H ₂ O signal of 500-2000 cm ^-1 was not completely removed. The time-resolved H ₂ O ₂ intensity is deduced from the average intensity in the range 3250-3750 cm ^-1 .

The time-resolved average H ₂ O ₂ intensity for the discharge conditions is shown in FIG. 5. Similar to T _vib of FIG. 3, the gap distance caused a distinct difference in H ₂ O ₂ strength compared to the cooler temperature. The T _vib and H ₂ O ₂ intensities of FTIR showed a tendency to change after 30-40 minutes. It appears to be a change in plasma properties that causes this change. As the plasma increases the electrical conductivity of the PTW, the plasma properties change from a normal glow discharge to an abnormal glow discharge. Similar changes in PTW such as electrical conductivity, pH and temperature are confirmed as shown in Fig. 6(ac). Ions from the plasma dissolve in the PTW, increasing the electrical conductivity. H ions (H ⁺ ) reduce the pH. The PTW temperature gradually increases and reaches 40°C (Fig. 6(c)). The long flow path and relatively large plasma heating appear to be compared to the cooling capacity resulting in unsaturated PTW temperatures.

So, the present inventors confirmed the PTW temperature effect on the H ₂ O ₂ concentration. A 1.5mg/LH ₂ O ₂ solution was prepared by diluting H ₂ O ₂ in water and contained in two beakers. One beaker was kept at room temperature and the other was heated while measuring the H ₂ O ₂ concentration. When the heated H ₂ O ₂ solution temperature increased to 60°C, both solutions maintained the initial H ₂ O ₂ concentration almost constant. No significant difference was observed between the two solutions. Therefore, PTW temperature influence can be excluded.

The generation trend of NO ₂ ^- and NO ₃ ^- in the plasma column can be confirmed by liquid ion chromatography (IC/LC). The concentrations of NO and NO ₂ are presented in Fig. 6(de). It is noted that the NO and NO ₂ concentrations increase rapidly 25-35 minutes after plasma ignition. Steep NOx increase is of a H ₂ O ₂ concentration of the PTW peak, H ₂ O ₂ and the intensity of the plasma slope T _vib tendency of the N ₂ gyeongsa here. This means that the nonlinear H ₂ O ₂ concentration trend of PTW is due to the change in plasma characteristics.

The chemical reaction of H ₂ O ₂ production and loss in plasma columns was analyzed using a three-dimensional flow simulation using Fluent® v18.0 and a global model. 7 shows the average gas velocity in the plasma region versus the electrode length. Modified the model version of Sakiyama et al. Global models H ₂ O ₂ , HNO ₂ , HNO ₃ , NO and NO ₂ , OH 623 reactions and 53 concentrations are calculated. The existing model was improved by adding heat equations and gas flow rates. By adding the heat equation to the simple geometry, the gas temperature can be calculated with a given plasma power density instead of assuming a constant temperature. It was also possible to calculate the loss of chemical species by taking the gas flow into account. The orthogonal gas flow to the exhaust column reduces the dose of the species on the PTW.

8 shows the results for 1 hour of plasma discharge from the global model. Among the various species, the major species for H ₂ O ₂ and for the occurrence and loss species are presented. The model reflected the electrode length in the form of gas flow rate and plasma power density. The power density was assumed to be the measured plasma power divided by the plasma volume. The gas temperature is not saturated, but continues to increase for 1 hour of discharge. The gas temperature of the model represents the value inside the plasma column. As the power density increased from 1.5x10 ⁸ to 7.1x10 ⁸ W/m ³ , the maximum gas temperature increased from 525K to 710K. The calculated results well showed the nonlinear tendency of the H ₂ O ₂ density. That is, the H ₂ O ₂ density increases and gradually decreases after 10 seconds of discharge. As the temperature increases, the excited N ₂ (A) density increases. It consumes the ROS required to produce O ₃ and H ₂ O ₂ . Therefore, the NO and NO ₂ density increased.

Based on this result, the mechanism of H ₂ O ₂ generation in PTW in fin-to-water discharge can be expressed as shown in Fig. 9. First, the plasma is discharged between the metal pin electrode and the liquid electrode. Due to the low electrical conductivity of PTW, PTW acts as a current blocking dielectric. Thus, the gas temperature is kept close to room temperature. Therefore, the N ₂ (A) density is low. The atoms O and OH and H ₂ O ₂ which are rarely consumed by N ₂ (A) can be produced.

As the plasma discharge continues, the plasma current increases due to the electrical conductivity and surface tension of the PTW. Plasma produced dissolved ions in PTW. Since ions increase the electrical conductivity of PTW to several hundred μS/cm, PTW acts as a resistance rather than a dielectric, and plasma shows a resistive barrier discharge, not DBD. Ions also reduce the surface tension of PTW. In a fin-to-water discharge system, the water surface is transformed by an electric field from the electrode. PTW occurs towards the electrode and the height of the deformed surface increases as the surface tension decreases.

The increased plasma current accelerates the increase in T _vib of N ₂ (T). When T _vib reaches 4900K, the N ₂ (A) portion increases significantly and OH is consumed as NO. The plasma generated H ₂ O ₂ density is reduced. Since OH is produced from H ₂ O, most of the OH is produced on the PTW surface in contact with the plasma. OH is produced by evaporated H ₂ O adjacent to the water surface. Part of the plasma produced chemical species drifted by the air stream during diffusion, but drift seems to play an important role, mainly because of the H ₂ O ₂ generated at the liquid surface. Therefore, the gap distance between the pin and PTW is a controlling factor of power density.

Played a role. In the present invention, the cooler set temperature did not significantly change the PTW temperature due to the relatively long PTW path length compared to the cooling power.

We implemented H ₂ O ₂ containing PTW generation using pin-to-water discharge on a spoke-type electrode to find for application purposes the plasma operating parameters to generate PTW with an appropriate H ₂ O ₂ concentration. The mechanism of H ₂ O ₂ generation was confirmed by measurement and simulation of plasma and PTW properties. The H ₂ O ₂ concentration measured in PTW is nonlinear, i.e. a monotonic increase and peak density rather than saturation. The decrease in H ₂ O ₂ density during plasma treatment implies a change in plasma-producing species rather than H ₂ O ₂ decay because the lifetime of H ₂ O ₂ in the liquid is several days.

The plasma-generated species varied significantly with the gas temperature, particularly the oscillating excitation temperature of N2(A). Gas temperature is a key parameter of the H ₂ O ₂ concentration control knob. The gas temperature can be controlled using various factors such as power density, PTW temperature and discharge time. High H ₂ O ₂ concentrations can be obtained while T _vib is maintained below 4900 K. If the discharge system shows the unsaturated gas temperature before the H ₂ O ₂ density saturation, the discharge should be stopped when the H ₂ O ₂ concentration reaches the required value.

Claims (11)

Including the occurrence of water surface plasma at a vibration temperature of N ₂ of 4900K or less,
High-concentration hydrogen peroxide concentrated water production method. The method of claim 1,
Plasma treatment of water with a water surface plasma device to produce plasma treated water,
Measuring the vibration temperature of N ₂ of the plasma of the plasma processing apparatus,
Including that when the vibration temperature of the N ₂ is 4900K or more, stopping the water surface plasma treatment or starting to supply new water to the plasma treated water,
High-concentration hydrogen peroxide concentrated water production method. The method of claim 2,
The vibration temperature of N ₂ of the plasma is measured by OES (optical emission spectroscopy),
High-concentration hydrogen peroxide concentrated water production method. A plasma generator generating plasma on the surface of water;
A water tank for receiving the treated water treated with the water surface from the plasma generating unit; And
Including a measuring unit for checking the vibration temperature of N ₂ of the plasma on the water surface,
An apparatus for producing hydrogen peroxide water using water surface plasma. The method of claim 4,
The plasma generating unit,
A first electrode body spaced apart on the water surface of the water tank;
A second electrode body located on the outer or inner surface of the water tank, or located in water accommodated in the water tank; And
It characterized in that it comprises a power supply for applying a voltage to the first electrode body and the second electrode body,
An apparatus for producing hydrogen peroxide water using water surface plasma. The method of claim 4,
The plasma generating unit,
A first electrode body having a water supply surface;
A second electrode body positioned to be spaced apart from the water supply surface by a predetermined distance; And
Including a power supply for applying a voltage to the first electrode body and the second electrode body,
The hydrogen peroxide solution manufacturing apparatus includes: a water film supply unit supplying water to the water supply surface in a water film form that can be spaced apart from the second electrode body to be accommodated in the water tank; And
Including a circulation unit for circulating water from the water tank to the water film supply unit,
An apparatus for producing hydrogen peroxide water using water surface plasma. The method of claim 6,
The first electrode body and the second electrode body are erect,
The water film flows from the top to the bottom of the first electrode body,
The water tank is characterized in that accommodating the water film under the first electrode body,
An apparatus for producing hydrogen peroxide water using water surface plasma. The method of claim 4,
The measuring unit is characterized in that the OES (optical emission spectroscopy) for analyzing the light emission signal from the plasma,
An apparatus for producing hydrogen peroxide water using water surface plasma. The method of claim 4,
It includes a control unit for controlling the power supply of the power supply device,
The control unit is configured to cut off the power supply when the vibration temperature of N ₂ measured by the measurement unit exceeds a predetermined value,
An apparatus for producing hydrogen peroxide water using water surface plasma. The method of claim 9,
The vibration temperature of N ₂ characterized in that the predetermined value is 4900K,
An apparatus for producing hydrogen peroxide water using water surface plasma. The method of claim 6,
An outlet for discharging the hydrogen peroxide solution from the water tank;
A water supply unit supplying additional water to the circulation unit; And
And a control unit for controlling the circulation unit, the water supply unit, and the outlet,
The control unit is configured to open the outlet and supply additional water to the circulation unit through the water supply unit when the vibration temperature of N ₂ measured by the measurement unit is higher than a predetermined value,
An apparatus for producing hydrogen peroxide water using water surface plasma.

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