Hydrogen peroxide gas generator and hydrogen peroxide gas generation method

Abstract

To provide a hydrogen peroxide gas generator and a hydrogen peroxide gas generation method capable of supplying hydrogen peroxide gas with a higher concentration.SOLUTION: The generator comprises a mixture of sodium percarbonate and an acidic solid acid or salt, a heating device 3 for heating the mixture, and gas supply means for supplying gas to the mixture. The heating device 3 heats the mixture, and the gas is caused to pass through the mixture via the gas supply means. The acidic solid acid or salt is a solid acid or salt which is acidic when dissolved in water. A solid acid or salt which is acidic when dissolved in water is citric acid.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a hydrogen peroxide gas generating device and a method for generating hydrogen peroxide gas. [Background technology]

[0002] In recent years, hydrogen peroxide (H ) has been used to sterilize clean rooms and other target spaces, instead of formaldehyde, which is considered to be harmful to the human body due to its acute toxicity and carcinogenicity. 2 O 2 ) gas is now being used. 2 O 2 ) Gas is 2H 2 O 2 →2H 2 O+O 2 As shown in the chemical formula, hydrogen peroxide decomposes to eventually become oxygen and water, and no harmful substances are produced. For this reason, hydrogen peroxide gas is used to sterilize small spaces such as clean rooms, indoors, draft chambers, isolators, RABS (Restricted Access Barrier Systems), safety cabinets, and bus boxes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-288647 A [Non-patent literature]

[0004] [Non-Patent Document 1] Takeshi Wada, Nobuyoshi Koga, “Kinetics and Mechanism of the Thermal Decomposition of Sodium Percarbonate: Role of the Surface Product Layer”, THE JOURNAL OF PHYSICAL CHEMISTRY A, 2013, pp. 1880-1889 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, hydrogen peroxide solution is used to generate hydrogen peroxide gas. Hydrogen peroxide solution is usually sold commercially as a 35 wt% aqueous solution, so when it is used for sterilization, hydrogen peroxide gas and water vapor are generated, increasing the humidity in the target room. This causes the water vapor to condense on the walls, etc., causing corrosion of the structural materials of clean rooms, etc. In order to deal with this problem, conventionally, special filters have been used to remove moisture from hydrogen peroxide gas, or dehumidifiers with cooling coils have been installed to dehumidify the target space. This has led to larger systems and higher costs.

[0006] Sodium percarbonate is also known as a substance that contains hydrogen peroxide. Sodium percarbonate is blended in detergents and the like, and dissociates into hydrogen peroxide and sodium carbonate in an aqueous solution. It is possible to release hydrogen peroxide in the gas phase by heating sodium percarbonate. However, the hydrogen peroxide released by heating is immediately decomposed into water and oxygen, so it was not possible to obtain hydrogen peroxide gas from sodium percarbonate.

[0007] The present invention has been proposed to solve the above-mentioned problems. An object of the present invention is to provide a hydrogen peroxide gas generating device and a hydrogen peroxide gas generating method that can supply hydrogen peroxide gas at a higher concentration. [Means for solving the problem]

[0008] The inventors believed that the weakly basic nature of the water film that is generated when sodium percarbonate is heated prevents an increase in the concentration of hydrogen peroxide gas. Therefore, they conducted extensive research to determine whether a high concentration of hydrogen peroxide gas could be obtained by mixing a substance that would cause the pH of the water film to become acidic. As a result, they discovered that a higher concentration of hydrogen peroxide gas could be generated by mixing an acidic solid acid or salt with sodium percarbonate.

[0009] (1) A method for producing a gas-dispersing apparatus comprising: a mixture of sodium percarbonate and an acidic solid acid or salt; a heating device for heating the mixture; and a gas supplying means for supplying a gas to the mixture, wherein the heating device heats the mixture and the gas is passed through the mixture via the gas supplying means.

[0010] (2) The acidic solid acid or salt may be a solid acid or salt that exhibits acidity when dissolved in water.

[0011] (3) The solid acid or salt that exhibits acidity when dissolved in water may be citric acid.

[0012] (4) The citric acid may be citric acid monohydrate, and the mixture may contain the sodium percarbonate and the citric acid monohydrate in a molar ratio of 1:0.5 to 1:3.

[0013] (5) The heating device may heat the mixture so that the temperature of a mixture heating portion of the heating device is 60° C. or higher and 120° C. or lower.

[0014] (6) The heating device may heat the mixture so that the temperature of a mixture heating portion of the heating device is 80° C. or higher and 100° C. or lower.

[0015] (7) The mixture may be a mixture of powdered sodium percarbonate and powdered citric acid.

[0016] Each of the above aspects can also be understood as a method for generating hydrogen peroxide gas. Effect of the Invention

[0017] According to the present invention, it is possible to provide a hydrogen peroxide gas generating device and a hydrogen peroxide gas generating method capable of supplying hydrogen peroxide gas at a higher concentration. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 shows examples of the configuration of a hydrogen peroxide gas generator according to the present invention, where (a) shows an example of the configuration when the hydrogen peroxide gas generator is connected to a target space, and (b) shows an example of the configuration when the hydrogen peroxide gas generator is placed within the target space. [Diagram 2] 1 is a configuration diagram showing a hydrogen peroxide gas generation device according to a first embodiment. [Diagram 3] FIG. 1 shows examples of the configuration of a heating part, where (a) shows a double-tube structure, (b) shows a flask structure, and (c) shows a cylindrical or rectangular parallelepiped structure. [Figure 4] 1 is a flowchart showing a process for generating hydrogen peroxide gas. [Diagram 5] 1 shows an example of the configuration of a one-pass experimental system used to measure hydrogen peroxide gas. [Figure 6] 1 is a graph showing the concentration of hydrogen peroxide gas when sodium percarbonate alone and a mixture of sodium percarbonate and citric acid monohydrate are heated. [Figure 7] 1 is a graph showing the concentration of hydrogen peroxide gas when a mixture of sodium percarbonate and citric acid monohydrate is heated while varying the humidity of the gas being aerated. [Figure 8] 1 is a graph showing the hydrogen peroxide gas concentration when a mixture having different molar ratios of sodium percarbonate and citric acid monohydrate is heated. [Figure 9] 1 is a graph showing the concentration of hydrogen peroxide gas when a mixture of sodium percarbonate and citric acid monohydrate is heated at different heating temperatures in a molar ratio of 1:2. [Figure 10] FIG. 4 is a configuration diagram showing a hydrogen peroxide gas generation device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] [First embodiment] [1. Configuration] A hydrogen peroxide gas generator G according to a first embodiment of the present invention will be described in detail with reference to the drawings. The hydrogen peroxide gas generator G of this embodiment can be configured to be connected to a target space S, as shown in FIG. 1(a). That is, it is configured to supply hydrogen peroxide gas to the target space S from outside the target space S. Also, as shown in FIG. 1(b), the hydrogen peroxide gas generator G may be disposed within the target space S. When the hydrogen peroxide gas generator G is connected to the target space S as shown in FIG. 1(a), the hydrogen peroxide gas generator G includes a gas supply path A, a heating unit 1, and a hydrogen peroxide gas supply path H, as shown in FIG. 2.

[0020] (mixture) First, the mixture placed in the heating unit 1 will be described in detail. As described later, the heating unit 1 includes a container 2 that contains sodium percarbonate. Sodium percarbonate is contained in the container 2 as a mixture containing a solid acid or a salt. The solid acid or salt is an acidic solid acid or salt. In addition, as the acidic solid acid or salt, a solid acid or salt that is acidic when dissolved in water may be used. Examples of solid acids or salts that are acidic when dissolved in water include citric acid, sodium sulfite, hydrogen sulfite, sodium hydrogen sulfate, and chlorate. Among these, citric acid is superior in that it is highly safe and inexpensive. Citric acid may be a hydrate such as citric acid monohydrate, or anhydrous citric acid.

[0021] The mixture may be a powdered mixture of sodium percarbonate and an acidic solid acid or salt. After mixing sodium percarbonate and an acidic solid acid or salt, the mixture may be processed into a thin sheet having a thickness of several mm. The mixture may be prepared on-site where the hydrogen peroxide gas generator G is used. Alternatively, a mixture prepared in advance at a different location may be used. When prepared at a different location, it is recommended that the mixture be opened on-site from a sealed container or bag.

[0022] The reason for mixing an acidic solid acid or salt with sodium percarbonate is to shift the pH of the water surrounding the sodium percarbonate to the acidic side in the hydrogen peroxide generation process. When hydrogen peroxide gas is generated by heating sodium percarbonate alone, the following process is thought to take place. (1) When heated, sodium percarbonate decomposes into sodium carbonate and hydrogen peroxide. (2) Some of the hydrogen peroxide decomposes into water, forming a water film on the surface of the sodium percarbonate. (3) Hydrogen peroxide dissolves from sodium percarbonate into the water film (3) Water evaporates when heated. (4) Hydrogen peroxide gas is generated

[0023] The inventors considered that in the above (2), the weak basicity of the water film hinders an increase in the concentration of hydrogen peroxide gas generated. Therefore, they investigated a method of mixing a substance that makes the pH of the water film acidic. As a result, the inventors established a method of generating hydrogen peroxide gas at a higher concentration by mixing an acidic solid acid or salt with sodium percarbonate. As the acidic solid acid or salt, a solid acid or salt that dissolves in water and exhibits acidity can be used.

[0024] When citric acid monohydrate is used as a solid acid or salt that dissolves in water and exhibits acidity, in the above (1), citric acid monohydrate becomes water and citric acid. Citric acid has deliquescence, so water is adsorbed onto the surface of citric acid. The solubility of citric acid in water is 73 g / 100 mL at 20°C, but the amount of dissolution increases because the mixture is heated. In the above (2), the water film formed on the surface of sodium percarbonate and the liquid film on the surface of citric acid are considered to be united. The pH of the united water film and liquid film is acidic due to the influence of citric acid, so it is presumed that hydrogen peroxide exists stably.

[0025] For reference, the pH of a 5% aqueous solution of a mixture of sodium percarbonate and citric acid monohydrate is shown below. Molar ratio 1:0.5 pH 6.8 Molar ratio 1:1 pH 5.0 Molar ratio 1:2 pH 3.7 Molar ratio 1:3 pH 3.3

[0026] When a mixture of sodium percarbonate and citric acid monohydrate was heated, the generation of bubbles was confirmed by visual observation. The gas released from these bubbles was CO. 2 It has been confirmed through experiments that sodium percarbonate contains CO. When sodium percarbonate is heated alone, no bubbles are generated, so the specific reaction is unknown. However, by mixing it with citric acid monohydrate, hydrogen peroxide and CO are present on the combined sodium percarbonate water film and citric acid monohydrate liquid film. 2 , H 2 O, and O 2 is presumed to exist.

[0027] And CO 2 When bubbles containing hydrogen peroxide are generated, the bubble surface expands, reducing the pressure inside the bubble, which is thought to release hydrogen peroxide as gas. Therefore, when the bubbles burst, the hydrogen peroxide gas and H 2It is highly likely that the release of O is promoted. The above is one of the speculations on the mechanism of hydrogen peroxide gas generation when a mixture of sodium percarbonate and citric acid monohydrate is heated. However, we believe that the release of hydrogen peroxide gas due to azeotropy and salting out effect is also an important generation process of hydrogen peroxide gas.

[0028] When citric acid is used as the solid acid or salt that dissolves in water and shows acidity, for example, commercially available granular sodium percarbonate and powdered citric acid may be ground to a particle size of about several tens of μm and then mixed. By using the ground sodium percarbonate and citric acid, the efficiency of generating hydrogen peroxide gas increases. As the granular sodium percarbonate, particles having a particle size of about 100 μm to about 1.5 mm can be used. As the granular sodium percarbonate, a commercially available reagent may be used as it is. As the powdered sodium percarbonate, a powder having a particle size of about 0.1 μm to several hundreds of μm can be used.

[0029] When citric acid monohydrate is used as citric acid, the molar ratio of sodium percarbonate to citric acid monohydrate is preferably 1:0.5 to 1:3. That is, when sodium percarbonate is 0.5g, the range of citric acid monohydrate is 0.3345g to 2.007g. By setting the molar ratio in this range, it is possible to confirm the generation of high-concentration hydrogen peroxide gas. More preferably, the molar ratio of sodium percarbonate to citric acid monohydrate is 1:1 to 1:2. By setting the molar ratio in this range, it is possible to stably supply high-concentration hydrogen peroxide gas. From the experimental results described later, it has been revealed that when the molar ratio of sodium percarbonate to citric acid monohydrate is 1:2, high-concentration hydrogen peroxide gas can be supplied for a long time. Therefore, it is considered that the molar ratio of sodium percarbonate to citric acid monohydrate is optimal at 1:2.

[0030] (Gas supply line) The gas supply path A is a duct that supplies gas to the heating unit 1. In the gas supply path A, from the upstream side of the gas flow, a ventilation means a1, a check valve a2, a flow control mechanism a3, and a flow path switching device a4 are arranged. The ventilation means a1 is arranged or connected to the end of the gas supply path A on the most upstream side of the gas flow. The heating unit 1 is connected to the end of the gas supply path A on the most downstream side of the gas flow.

[0031] The ventilation means a1 is a means for introducing the gas supplied to the heating unit 1 side into the gas supply path A. As the ventilation means a1, a blower such as a fan or a blower or an air pump can be used. One of the reasons for supplying gas to the heating unit 1 is to push the hydrogen peroxide gas generated from the sodium percarbonate toward the target space S by the supplied gas.

[0032] A compressor can also be used as the ventilation means a1. When a compressor is used as the ventilation means a1, even if the hydrogen peroxide gas generator G is placed inside the target space S, the compressor is placed outside the target space S and connected to the gas supply path A via a pipe. This is a configuration for compressing gas that does not contain hydrogen peroxide gas. With such a configuration, the amount of gas in the target space S increases, and it becomes necessary to discharge the increased amount of gas in the target space S to the outside. Since the gas in the target space S contains hydrogen peroxide gas, the hydrogen peroxide gas is decomposed by a hydrogen peroxide gas decomposition device before the gas is discharged to the outside of the target space S. The hydrogen peroxide gas decomposition device may be provided with a ventilation means such as a fan.

[0033] The gas supplied to the heating section 1 has an absolute humidity of 0.176 g / m 3 ~16.0g / m 3 The gas can be less than 0.176 g / m 3is the absolute humidity when the atmospheric pressure dew point of the dryer-equipped compressor air is -40°C. In other words, the gas supplied to the heating unit 1 may be dry air that does not contain water vapor, or moist air that contains water vapor. In addition, a humidifier may be provided in the gas supply path A to increase the absolute humidity of the indoor air, and humidified air obtained by humidifying the indoor air to the above absolute humidity may be used.

[0034] Experiments described later have shown that within the above absolute humidity range, hydrogen peroxide gas can be generated while preventing an increase in humidity, regardless of whether dry air, moist air, or humidified air is used. It has also been pointed out that supplying moist air or humidified air may contribute to the generation time.

[0035] Also, the ventilation means a1 may be configured to include an oil mist separator for removing oil, if necessary. Furthermore, a filter for removing dust, bacteria, and organic matter may be installed. That is, in order to satisfy the gas conditions required for the target space S such as a biological clean room, a dryer, a separator, a filter, etc. can be appropriately installed in the gas supply path A as the ventilation means a1.

[0036] The check valve a2 is a valve for preventing the gas supplied to the gas supply path A from flowing backward. The check valve a2 has a structure that automatically closes if the gas supplied to the gas supply path A attempts to flow in the reverse direction. A control device (not shown) is connected to the check valve a2, and the opening degree of the check valve a2 is adjusted by a control signal from this control device. The control device closes the check valve a2 when the operation of the hydrogen peroxide gas generator G is finished.

[0037] In addition to the check valve a2, a pressure reducing valve may be disposed in the gas supply path A. The pressure reducing valve is a valve for reducing the pressure of the gas supplied to the gas supply path A and keeping the pressure constant after reduction. A control device (not shown) is connected to the pressure reducing valve, and the opening degree of the pressure reducing valve is adjusted by a control signal from the control device.

[0038] The flow rate control mechanism a3 is a mechanism for controlling the flow rate of the gas supplied to the gas supply path A. The flow rate control mechanism a3 may include a flow meter as a measuring device for measuring the flow rate of the gas supplied to the gas supply path A. The measurement results of the flow meter can be displayed so that a user of the hydrogen peroxide gas generator G can visually confirm them. The flow rate of the gas may be determined taking into consideration the volume of the target space S, the concentration of the hydrogen peroxide gas, the sterilization time, etc.

[0039] The flow rate control mechanism a3 may include a control device for a flow meter. The flow rate of the gas may be automatically determined when the user inputs the volume of the target space S, the concentration of hydrogen peroxide gas, and the sterilization time into the control device. The flow rate control mechanism a3 may be configured so that the user can manually adjust the flow rate of the gas supplied to the gas supply path A by checking the value of the flow meter. However, the flow rate can also be adjusted to a desired value by providing a valve in the gas supply path A and adjusting the opening of this valve with the control device.

[0040] The flow path switching device a4 is a valve for switching the gas supplied to the gas supply path A to multiple flow paths. In the example of FIG. 2, the hydrogen peroxide gas generator G is equipped with multiple heating units 1. Therefore, the flow path switching device a4 is configured to switch the flow paths so that the gas supplied to the gas supply path A can be supplied to each of the multiple heating units 1. The timing of flow path switching by the flow path switching device a4 can be configured to be programmed or controlled by a control device in advance, so that the flow paths are switched and the heating units 1 corresponding to these flow paths perform heating.

[0041] In addition, it is preferable to maintain the hydrogen peroxide gas in the target space S at a certain concentration for a certain period of time. Therefore, when there are multiple systems, it is preferable to configure the flow path switching device a4 to switch the flow path at predetermined time intervals, and the heating unit 1 corresponding to the switched flow path performs heating. For example, when there are multiple flow paths (three or more), they can be switched one by one in order, and the heating unit 1 corresponding to the switched flow path can be controlled to perform heating. Note that when a single heating unit 1 is provided, the flow path switching device a4 may not be disposed in the gas supply path A.

[0042] (heating part) The heating unit 1 is a component for heating sodium percarbonate. There may be a single heating unit 1, or as shown in the example of FIG. 2, a configuration in which a plurality of heating units 1 are connected to the gas supply path A may be adopted. In FIG. 2, the heating unit 1 has two paths, but there may be three or more paths. Since the amounts of sodium percarbonate and citric acid required for sterilization vary depending on the volume of the target space S, it is sufficient to provide the required number of heating units 1 in consideration of the volume of the target space S.

[0043] The heating section 1 includes a container 2 that contains the mixture and a heating device 3 that heats the container 2. The heating section 1 may also include a housing that contains the container 2 and the heating device 3. An example of the configuration of the heating section 1 is shown in Figures 3(a) to (c).

[0044] (container) The container 2 is a member that contains a mixture of sodium percarbonate and an acidic solid acid or salt. The example of FIG. 3(a) illustrates a configuration in which the mixture is placed in a container 2 with a double tube structure. The example of FIG. 3(b) illustrates a configuration in which the mixture is placed in a container 2 with a flask structure. The example of FIG. 3(c) illustrates a configuration in which the mixture is placed in a cylindrical or rectangular container 2. For example, the container 2 can be made of glass or metal. As the metal, it is preferable to use a metal that is corrosion-resistant against hydrogen peroxide gas. For example, the container 2 may be made of a metal such as aluminum, aluminum alloy, stainless steel, tantalum, or zirconium with a purity of 99.5% or more.

[0045] The mixture of sodium percarbonate and an acidic solid acid or salt is placed on the inner bottom surface of the container 2. However, other arrangements may be adopted, such as filling a cartridge or the like with the mixture or placing the mixture on the inner surface of the container 2.

[0046] 3(a) to 3(c), a gas supply line A and a hydrogen peroxide gas supply line H are connected to container 2. Specifically, gas supply line A and hydrogen peroxide gas supply line H are connected to an opening of a glass or metal container via a tube connector. Gas supply line A and hydrogen peroxide gas supply line H may be connected to the same opening via a tube connector having multiple flow paths, or multiple openings may be provided in container 2 and each may be connected to a different opening via a tube connector.

[0047] Container 2 is configured to be removable from hydrogen peroxide gas generator G, and can be replaced after hydrogen peroxide gas is generated. Also, a configuration may be adopted in which multiple heating units 1 are installed depending on the amount of hydrogen peroxide gas generated. The bottom area and height of container 2 may be configured so that the mixture in container 2 is uniformly heated when heated by heating device 3 as described below.

[0048] (heating device) The heating device 3 is a device for heating the container 2. When a mixture of sodium percarbonate and an acidic solid acid or salt is placed on the inner bottom surface of the container 2, the heating device 3 is preferably provided so as to heat the outer bottom surface of the container 2. For example, a thin sheet-like planar heating element that generates heat by passing electricity through a metal foil may be used as the heating device 3. When it is necessary to heat the outer surface of the container 2, a conductor may be used as the heating device 3. As the conductor for heating the container 2, it is preferable to use a conductor with high electrical conductivity, such as an aluminum wire or a copper wire. Nichrome wire and Kanthal wire may also be used.

[0049] The heating element and conductor of the heating device 3 are adjusted in terms of the heating area of ​​the heating element, the cross-sectional area of ​​the conductor, the winding length, etc., in consideration of the resistance of the container 2 so that the container 2 can be heated to the desired temperature by the current supplied from the power supply transformer. Note that a hot plate may be used as the planar heating element, or a water bath, oil bath, sand bath, etc. may be used in accordance with the shape and material of the container 2.

[0050] The heating device 3 may be connected to a control device (not shown). The container 2 is heated by a conductor so that the sodium percarbonate in the container 2 reaches a desired temperature according to a control signal from the control device. Specifically, it is preferable to heat the container 2 by setting the temperature of the mixture heating portion of the heating device 3 to 60°C or more and 120°C or less. The mixture heating portion of the heating device 3 means a portion of the heating device 3 that contacts the mixture and heats the mixture. The mixture heating portion of the heating device 3 may be in direct contact with the mixture, or may be in contact with the mixture via the container 2. For example, when a planar heating element is used as the heating device 3, the mixture may be heated by setting the temperature of the surface that contacts the mixture to 60°C or more and 120°C or less. By heating the sodium percarbonate by the heating device 3 in such a temperature range, hydrogen peroxide gas is efficiently generated while suppressing an increase in humidity.

[0051] While hydrogen peroxide has a strong bond to sodium carbonate, when it is heated to 50°C or higher, hydrogen peroxide decomposes while detaching. In other words, the efficiency of hydrogen peroxide gas generation is low below 50°C. Heating sodium percarbonate at a higher temperature tends to improve the efficiency of hydrogen peroxide gas generation. Therefore, by heating the mixture with the heating device 3 so that the mixture heating portion of the heating device 3 is in the temperature range of 60°C to 120°C, the generation of hydrogen peroxide gas can be confirmed.

[0052] More preferably, the temperature of the mixture heating portion of the heating device 3 is set to 80° C. or higher and 100° C. or lower to heat the container 2. Setting the temperature at 80° C. or higher stabilizes the generation of hydrogen peroxide gas. Setting the temperature at 100° C. or lower prevents a decrease in the concentration of the generated hydrogen peroxide gas.

[0053] In the hydrogen peroxide gas generation process, the heating device 3 may heat the container 2 continuously, or may be configured to heat the container 2 intermittently taking into account the relative water saturation. In addition, the actual heating temperature of the heating device 3 and the temperature of the mixture in the container 2 differ due to the influence of the shape and material of the container 2. For this reason, it is preferable that the heating device 3 sets the temperature of the mixture heating portion of the heating device 3 to 60°C or higher and 120°C or lower, although the heating temperature may include an error of about ±5°C depending on the actual device configuration.

[0054] (Hydrogen peroxide gas supply line) The hydrogen peroxide gas supply path H is a duct that supplies hydrogen peroxide gas to the target space S. The end of the hydrogen peroxide gas supply path H opposite the end connected to the container 2 is installed within the target space S. The gas supplied to the container 2 via the gas supply path A sweeps up the hydrogen peroxide gas immediately after it is desorbed within the container 2, and is supplied to the target space S via the hydrogen peroxide gas supply path H together with the hydrogen peroxide gas.

[0055] In the above configuration, a temperature sensor may be provided near container 2, heating device 3, or hydrogen peroxide gas supply path H. The temperature sensor is preferably connected to a control device, and the control device controls heating device 3 so that container 2 and hydrogen peroxide gas supply path H do not exceed a predetermined temperature. By controlling the components that serve as the path for hydrogen peroxide gas to be kept at a predetermined temperature or lower, the hydrogen peroxide gas is prevented from decomposing into water and oxygen.

[0056] The hydrogen peroxide gas generator G may also include a humidity sensor and a hydrogen peroxide concentration sensor. These sensors may also be connected to a control device, and the control device may calculate the relative saturation level based on the measured humidity and hydrogen peroxide concentration, and if it determines that the relative saturation level may exceed 100%, it may perform control such as turning off the power to the heating device 3 or stopping the ventilation means a1.

[0057] [2. Hydrogen peroxide gas generation process] The hydrogen peroxide gas generator G having the above-mentioned configuration generates hydrogen peroxide gas through the following steps as shown in FIG. (1) Heating process of container 2 (2) Gas supply process to vessel 2

[0058] (Heating process) In the heating step, the container 2 is heated by the heating device 3 in the heating section 1 of the hydrogen peroxide gas generator G. That is, in response to a control signal from the control device, the heating device 3 heats the container 2 so that the mixture heating portion of the heating device 3 is at 60°C or higher and 120°C or lower. By heating the container 2, the mixture of sodium percarbonate and acidic solid or salt placed in the container 2 is heated, and hydrogen peroxide gas is generated. The gas supplying step is also started at the same time as the heating step starts.

[0059] (Gas supply process) In the gas supply step, gas is supplied to the container 2. That is, in response to a control signal from the control device, the check valve a2 is opened and the ventilation means a1 is operated to supply gas to the gas supply path A. The gas supplied to the gas supply path A is sent to the heating unit 1 via the flow rate control mechanism a3 and the flow path switching device a4.

[0060] The gas supplied to heating unit 1 travels through container 2 toward hydrogen peroxide gas supply path H. In the process, the gas sweeps up the hydrogen peroxide gas generated from sodium percarbonate. That is, the hydrogen peroxide gas generated from sodium percarbonate is constantly drawn toward hydrogen peroxide gas supply path H by the gas.

[0061] The gas containing hydrogen peroxide gas reaches the outlet side of container 2 and flows directly into hydrogen peroxide gas supply path H. The hydrogen peroxide gas is then supplied to target space S via hydrogen peroxide gas supply path H. Container 2 is heated and gas is supplied to container 2 for a predetermined time so that sufficient hydrogen peroxide gas is supplied to sterilize target space S.

[0062] [3. Experiment] The hydrogen peroxide gas generated by the hydrogen peroxide gas generator G of this embodiment was verified below. In each experiment, unless otherwise specified, hydrogen peroxide gas was generated and measured using the same experimental equipment and conditions.

[0063] (Experimental equipment) Hydrogen peroxide gas was generated and measured using the one-pass experimental equipment shown in Figure 5. The names of the pieces of equipment indicated by numbers in the figure are as follows: (1) Clean Air (2)Flowmeter (3) Porous PTFE tube + ultrapure water (humidity control) (4) Gas mixer (5) Hot plate (6) Hydrogen peroxide gas detector (electrochemical type) Among the above-mentioned equipment, the gas supplied to the container was adjusted to a desired relative humidity using (2) to (3). In addition, the container was placed on the hot plate (5), and the mixture of sodium percarbonate and citric acid monohydrate was heated to a predetermined temperature.

[0064] (Verification of the effect of mixing citric acid) To confirm the effect of mixing sodium percarbonate with citric acid, 0.5g of sodium percarbonate (SPC) alone and a mixture of 0.5g of sodium percarbonate (SPC) and 0.669g of citric acid monohydrate (CA) were used for verification. Gas with a relative humidity of 40% was passed through the container at a flow rate of 1L / min. The temperature of the surface of the hot plate where the mixture was heated was 120°C. Figure 6 shows a graph plotting the measured hydrogen peroxide gas concentration.

[0065] As is clear from the graph in Figure 6, by mixing sodium percarbonate with citric acid monohydrate, both the generation efficiency and concentration are significantly improved. The generation efficiency of sodium percarbonate alone was 3%, while the generation efficiency of the mixture was 35.5%. In addition, when examining the peak concentration of hydrogen peroxide gas, the peak of sodium percarbonate alone was 76 ppm, while the peak of the mixture was 660 ppm.

[0066] (Verification of the gas to be vented) The gas passed through the container was a mixture of 0.5g of sodium percarbonate (SPC) and 0.669g of citric acid monohydrate (CA). Gases with relative humidity of 0% (less than 10ppm), 20%, 30%, and 40% were passed through the container at a flow rate of 1L / min. The temperature of the surface of the hot plate where the mixture was heated was 100°C. Figure 7 shows a graph plotting the measured hydrogen peroxide gas concentration.

[0067] As is clear from the graph in Figure 7, when gases with relative humidity between 0 and 40% were passed through, hydrogen peroxide gas was generated at high concentrations. The generation efficiency was 29.52% at a relative humidity of 0%, 29.55% at a relative humidity of 20%, 27.47% at a relative humidity of 30%, and 22.53% at a relative humidity of 40%. Although it cannot be said that there is a significant difference in the generation efficiency depending on the relative humidity of the gas being passed through, it was found that the generation efficiency of dry air was high.

[0068] On the other hand, it was found that the time required for hydrogen peroxide gas generation increases as the relative humidity of the gas being aerated increases. Since hydrogen peroxide gas can be generated at high concentrations in dry air, moist air, or humidified air, it is conceivable to select the humidity of the gas being aerated according to the desired generation time.

[0069] (Consideration of mixing ratio) To study the mixing ratio of sodium percarbonate and citric acid monohydrate, we used sodium percarbonate and citric acid monohydrate mixed at different molar ratios. 0.5 g of sodium percarbonate was mixed with citric acid monohydrate at molar ratios of CA / SPC=0.1, CA / SPC=0.5, CA / SPC=1, CA / SPC=2, and CA / SPC=3. The flow rate of the gas ventilated into the container was 1 L / min. The surface temperature of the hot plate heating the mixture was 100°C. Figure 8 shows a graph plotting the measured hydrogen peroxide gas concentrations.

[0070] As is clear from FIG. 7, when CA / SPC=0.1, the peak concentration of hydrogen peroxide gas was very low at 30 ppm, and the generation efficiency was also 1.5%. This is thought to be because the amount of citric acid monohydrate mixed was small, and the pH of the water film around the sodium percarbonate was not sufficiently shifted to the acidic side. When CA / SPC=0.5, the peak concentration of hydrogen peroxide gas was high at 576 ppm, but the generation time was short, and the generation efficiency was 13.5%. This is thought to be because the citric acid monohydrate was consumed before the measurement time of 40 minutes had elapsed.

[0071] With CA / SPC=1, the hydrogen peroxide gas peak concentration was high at 609 ppm, and the generation efficiency was 26.4%, which was a good result. With CA / SPC=2, the hydrogen peroxide gas peak concentration was high at 622 ppm, the generation time was the longest, and the generation efficiency was the best at 43.7%. With CA / SPC=3, the hydrogen peroxide gas peak concentration was high at 624 ppm, and the generation efficiency was good at 23.1%. However, there was some fluctuation in the concentration immediately after hydrogen peroxide gas generation, and the generation of hydrogen peroxide gas was somewhat unstable.

[0072] From the above results, it was revealed that high concentration hydrogen peroxide gas can be generated by setting the molar ratio of sodium percarbonate to citric acid monohydrate to 1:0.5 to 1:3. Within this molar ratio range, even if the ratio of sodium percarbonate to citric acid monohydrate was changed, there was no significant change in the peak concentration of hydrogen peroxide gas. However, by increasing the amount of citric acid monohydrate, the time for hydrogen peroxide gas generation was extended.

[0073] Therefore, it can be said that high-concentration hydrogen peroxide gas can be stably supplied by setting the molar ratio of sodium percarbonate to citric acid monohydrate at 1:1 to 1:2. It was also revealed that when the molar ratio of sodium percarbonate to citric acid monohydrate is 1:2, high-concentration hydrogen peroxide gas can be supplied for a long period of time.

[0074] (Consideration of heating temperature) The heating temperature of the mixture was examined using a mixture of 0.5g of sodium percarbonate (SPC) and 1.338g of citric acid monohydrate (CA) (molar ratio 1:2). Gas with a relative humidity of 40% was passed through the container at a flow rate of 1L / min. The temperatures of the surface of the hot plate where the mixture was heated were set to 60°C, 80°C, 100°C, and 120°C for the experiments. Figure 9 shows a graph plotting the measured hydrogen peroxide gas concentrations. Note that the temperature of the surface of the hot plate where the mixture was heated will be referred to as the heating temperature below.

[0075] As is clear from Figure 9, when sodium percarbonate and citric acid monohydrate are mixed in a molar ratio of 1:2, it was confirmed that high concentrations of hydrogen peroxide gas are generated at heating temperatures of 80°C, 100°C, and 120°C. In addition, at a heating temperature of 60°C, although the peak concentration of hydrogen peroxide gas is reduced by half compared to the other temperatures, it was confirmed that hydrogen peroxide gas can be supplied stably at a relatively high concentration for a long period of time. The generation efficiency at a heating temperature of 60°C was 46.7%.

[0076] It was confirmed that high-concentration hydrogen peroxide gas could be generated stably and continuously at a heating temperature of 80°C. The generation efficiency at a heating temperature of 80°C was 45.2%. Additionally, at a heating temperature of 100°C, the highest concentration of hydrogen peroxide gas was generated stably, but it can be seen that the generation time was shorter compared to a heating temperature of 80°C. The generation efficiency at a heating temperature of 100°C was 41.5%.

[0077] It was also confirmed that at a heating temperature of 120°C, a high concentration of hydrogen peroxide gas was generated, but the concentration peak and generation time were shorter than those at a heating temperature of 80°C. The generation efficiency at a heating temperature of 120°C was 37.2%.

[0078] From the above results, it was confirmed that when sodium percarbonate and citric acid monohydrate are mixed in a molar ratio of 1:2, high-concentration hydrogen peroxide gas can be generated at a heating temperature range of 60 to 120°C. Among these, a heating temperature of 80°C was the most favorable condition.

[0079] From the above experiments, it became clear that the concentration and generation time of hydrogen peroxide gas generated change depending on the mixing ratio of sodium percarbonate and citric acid monohydrate and the heating temperature. The generated concentration and generation time can be appropriately selected taking into consideration the target space S to be sterilized and the sterilization conditions, but it became clear that high concentration hydrogen peroxide gas can be generated by heating so that the temperature of the mixture heating part of the heating device 3 is 60°C or higher and 120°C or lower, more preferably 80°C or higher and 100°C or lower.

[0080] [4. Effects] The effects of the hydrogen peroxide gas generator G of this embodiment as described above are as follows. (1) The apparatus comprises two containers each containing a mixture of sodium percarbonate and an acidic solid acid or salt, a heating device 3 for heating the container 2, a gas supply means connected to the container 2 for supplying gas to the container 2, and a hydrogen peroxide gas supply path H connected to the container 2 for supplying hydrogen peroxide gas to a target space S, and the heating device 3 heats the container 2 while ventilating the gas into the container 2 via the gas supply means.

[0081] By heating the container 2 containing a mixture of sodium percarbonate and an acidic solid acid or salt, it is possible to generate high-concentration hydrogen peroxide gas for a long period of time compared to heating sodium percarbonate alone. As described above, this is achieved by making the hydrogen peroxide generation environment acidic due to the acidic solid acid or salt. In addition, by passing air through the container 2, hydrogen peroxide gas can be efficiently extracted. As a result, hydrogen peroxide gas at a higher concentration can be stably supplied.

[0082] In addition, it is possible to obtain hydrogen peroxide gas with lower humidity than when hydrogen peroxide gas is generated from an aqueous hydrogen peroxide solution. Specifically, when hydrogen peroxide gas is generated from an aqueous hydrogen peroxide solution, a large amount of moisture is generated immediately after generation, but in the case of a mixture, the initial generation of moisture can be suppressed. Although an aqueous hydrogen peroxide solution is dangerous to transport, sodium percarbonate and an acidic solid acid or salt are solid and highly safe, and therefore can be transported at low cost.

[0083] (2) An acidic solid acid or salt is a solid acid or salt that exhibits acidity when dissolved in water.

[0084] In the hydrogen peroxide generation process, a water film is formed on the surface of the sodium percarbonate. By using a solid acid or salt that dissolves in water and exhibits acidity, it is possible to more effectively shift this water film from a weakly basic state to an acidic state. Therefore, by passing air through the container 2, hydrogen peroxide gas can be efficiently extracted. As a result, hydrogen peroxide gas of a higher concentration can be stably supplied.

[0085] (3) The solid acid or salt that dissolves in water and exhibits acidity is citric acid.

[0086] Citric acid is an excellent solid acid that dissolves in water and exhibits acidity, because it is highly safe and inexpensive. It has been confirmed that a mixture of sodium percarbonate and citric acid can be used to generate high-concentration hydrogen peroxide gas for a long period of time. It has also been confirmed that bubbles are generated when a mixture of sodium percarbonate and citric acid is heated. Another advantage of using citric acid is that the bubbles are likely to promote the release of hydrogen peroxide gas.

[0087] (4) The citric acid is citric acid monohydrate, and the mixture contains sodium percarbonate and citric acid monohydrate in a molar ratio of 1:0.5 to 1:3.

[0088] By setting the molar ratio of sodium percarbonate to citric acid monohydrate in this range in the mixture, it is possible to confirm the generation of high-concentration hydrogen peroxide gas.

[0089] (5) Heating device 3 heats container 2 so that the temperature of the mixture heating portion of heating device 3 is 60°C or higher and 120°C or lower.

[0090] By setting the temperature of the mixture heating portion of heating device 3 to 60° C. or higher and 120° C. or lower, it is possible to generate hydrogen peroxide gas while suppressing an increase in humidity and maintaining the efficiency of hydrogen peroxide gas generation.

[0091] (6) Heating device 3 heats container 2 so that the temperature of the mixture heating portion of heating device 3 is 80°C or higher and 100°C or lower.

[0092] By setting the temperature of the mixture heating portion of the heating device 3 to 80° C. or higher and 100° C. or lower, it becomes possible to generate hydrogen peroxide gas at a higher concentration for a relatively long period of time.

[0093] (7) The mixture contains powdered sodium percarbonate and powdered citric acid.

[0094] By using powdered sodium percarbonate and powdered citric acid, it is possible to obtain hydrogen peroxide gas with a higher concentration.

[0095] [Other embodiments] In the above embodiment, the hydrogen peroxide gas generator G has been described as generating hydrogen peroxide gas for sterilizing the walls and the surfaces of devices installed in the target space S, such as a biological clean room. However, the hydrogen peroxide gas generated by the hydrogen peroxide gas generator G may be used for purposes other than sterilization. For example, the hydrogen peroxide gas generated by the hydrogen peroxide gas generator G in the above embodiment can also be used for air purification, deodorization, decomposition of pollutants, and the like.

[0096] When hydrogen peroxide gas generator G is placed in target space S as in FIG. 1(b), a configuration may be adopted in which heating device 3, on the upper part of which a mixture of sodium percarbonate and an acidic solid acid or salt is placed, is placed in target space S as shown in FIG. 10. Enclosure 2a is placed on heating device 3 so as to rise from the periphery of heating device 3. Enclosure 2a plays a role in preventing the mixture from scattering. In this way, a configuration may be adopted in which heating device 3 directly heats the mixture without using container 2. In that case, it is preferable to use a mixture processed into a sheet shape to prevent scattering.

[0097] 1(b), a fan or the like may be disposed in the target space S as ventilation means a1 to agitate the gas in the target space S and supply the gas to the hydrogen peroxide gas generator G. When the hydrogen peroxide gas generator G is provided in the target space S, the gas supply path A and the hydrogen peroxide gas supply path H do not need to be configured as tangible objects such as ducts. However, even in the example of FIG. 1(a), gas is supplied to the container 2 by the ventilation means a1, and this flow path may be regarded as the gas supply path A. Furthermore, the flow path through which the hydrogen peroxide gas generated from the container 2 fills the target space S may be regarded as the hydrogen peroxide gas supply path H. [Explanation of symbols]

[0098] S: Target space G: Hydrogen peroxide gas generator H: Hydrogen peroxide gas supply line A: Gas supply line a1: Ventilation means A2: Check valve A3: Flow control mechanism a4: Flow path switching device 1: Heating part 2: Container 2a: Enclosure 3: Heating device

Claims

1. A mixture of sodium percarbonate and an acidic solid acid or salt; A heating device for heating the mixture; A gas supply means for supplying a gas to the mixture; having A hydrogen peroxide gas generating apparatus, wherein the heating device heats the mixture and the gas is supplied to the mixture via the gas supply means.

2. 2. The hydrogen peroxide gas generator according to claim 1, wherein the acidic solid acid or salt is a solid acid or salt that exhibits acidity when dissolved in water.

3. 3. The hydrogen peroxide gas generator according to claim 2, wherein the solid acid or salt that dissolves in water and exhibits acidity is citric acid.

4. the citric acid is citric acid monohydrate, 3. The hydrogen peroxide gas generator according to claim 2, wherein the mixture contains the sodium percarbonate and the citric acid monohydrate in a molar ratio of 1:0.5 to 1:

3.

5. 3. The hydrogen peroxide gas generator according to claim 1, wherein the heating device heats the mixture so that the temperature of a portion of the heating device that heats the mixture is 60° C. or higher and 120° C. or lower.

6. 3. The hydrogen peroxide gas generator according to claim 1, wherein the heating device heats the mixture so that the temperature of the mixture heating portion of the heating device is 80° C. or higher and 100° C. or lower.

7. 4. The hydrogen peroxide gas generator according to claim 3, wherein the mixture is a mixture of powdered sodium percarbonate and powdered citric acid.

8. a heating step of heating a mixture of sodium percarbonate and an acidic solid acid or salt to generate hydrogen peroxide gas; a gas supplying step of supplying the gas toward the hydrogen peroxide gas so that the hydrogen peroxide gas flows toward a target space.

9. 9. The hydrogen peroxide gas generator according to claim 8, wherein the acidic solid acid or salt is a solid acid or salt that exhibits acidity when dissolved in water.

10. 10. The method for generating hydrogen peroxide gas according to claim 9, wherein the solid acid or salt that exhibits acidity when dissolved in water is citric acid.

11. 10. The method for generating hydrogen peroxide gas according to claim 8, wherein the heating step is a step of heating the mixture so that the temperature of a mixture heating portion of a heating device for heating the mixture is 60°C or higher and 120°C or lower.

12. 10. The method for generating hydrogen peroxide gas according to claim 8, wherein the heating step is a step of heating the mixture so that the temperature of a mixture heating portion of a heating device for heating the mixture is 80° C. or higher and 100° C. or lower.

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