Preparation process of bubble mixed type medium-expansion gel foam

Abstract

The invention discloses a preparation process of bubble mixed type medium-expansion gel foam. Firstly, gas is injected into solutions of a component A system and a component B system to generate foams, molecules of a cross-linking agent and a thickening agent are promoted to be distributed in a foam liquid film, then the two foams are mixed, the cross-linking agent and the thickening agent in the liquid film are promoted to be subjected to a cross-linking reaction, and medium-expansion gel foams are generated in a gas-liquid-bubble sequential mixing mode. According to the method, the interfacial area of the crosslinking reaction of the crosslinking agent and the thickening agent is increased through bubble mixing, the crosslinking reaction activity is improved by more than 3 times, the dosage of the crosslinking agent is reduced by more than 50%, the problems of uneven liquid-liquid and gas-liquid mixing and the like caused by relatively high viscosity of a gel foam system solution are avoided, and the formed gel foam is continuous in jet flow and high in stability. The produced gel foam has better performance, the maximum foaming multiple exceeds 20 times, and the 25% drainage time is longer than 48 hours.

Description

Technical Field

[0001] The invention relates to the technical field of foam fire extinguishing, and in particular to a preparation process of a bubble mixing type medium-multiple gel foam. Background Art

[0002] Gel foam is a highly stable foam based on a cross-linking reaction between a thickener and a cross-linking agent. Different from the single-component foam fire extinguishing agent used in the fire protection field, gel foam is produced by a mixed gas of an A / B two-component system solution, in which the A component system mainly includes a foaming agent, a cross-linking agent, etc., and the B component system mainly includes a thickener. During the foaming process, the thickener and the cross-linking agent are fully mixed, and a three-dimensional network structure polymer gel that is firm and not easy to break is formed through cross-linking, thereby enhancing the liquid film strength and foam viscosity of the gel foam. Due to the long liquid separation time and high foam viscosity, gel foam has the advantages of high water retention, good adhesion, strong coverage and good thermal stability. After being applied to the surface of solid and liquid combustibles, it can effectively inhibit the volatilization of liquid vapor, prevent the combustibles from rekindling or being ignited, and prevent the fire from further expanding.

[0003] CN 113750413A, CN 113750414A, CN 117225223A, CN 117442908A, CN 117797427A, etc. mix gel foam liquid A and liquid B to form a two-component foam system solution, and then introduce gas through the foam generating chamber to promote the mixing of the solution and air to produce gel foam, that is, a "liquid-liquid-gas-liquid" sequential mixing method is adopted. CN103570375A, CN 105344040A, CN 117982830A, etc. add a thickener to form gel foam after the foam is formed. The common technical solution adopted by the above patent applications is to promote a more uniform cross-linking reaction and a more complete gas-liquid mixing by strengthening the liquid-liquid, gas-liquid or bubble-liquid mixing technology.

[0004] However, for thickener solutions with high viscosity (viscosity higher than 3000cp under the condition of rotor 3 at 60rpm), the above method still has problems such as uneven liquid-liquid and gas-liquid mixing, resulting in discontinuous gel foam jets. In particular, high-viscosity gel foam solutions have poor foaming performance and the foam expansion multiple is low, usually around 4 times. For example, Shi Quanlin of China University of Mining and Technology pointed out in the paper "Research on the Theory and Characteristics of Colloidal Foam for Preventing and Controlling Coal Spontaneous Combustion" that when the thickener concentration is 8g / L, the foam expansion multiple is only about 1.2 times. Therefore, it is necessary to provide a new gel foam generation method and device. Summary of the invention

[0005] In order to solve the technical problem of poor foaming performance of a high-viscosity gel foam solution system, the present invention provides a bubble mixing type medium-multiple gel foam preparation process.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present invention is as follows: a bubble mixing type medium-multiple gel foam preparation process, firstly, air is injected into the A component system and the B component system solution respectively to generate foam, so as to promote the distribution of cross-linking agent and thickener molecules in the foam liquid film, and then the two foams are mixed to promote the cross-linking reaction between the cross-linking agent and the thickener in the liquid film, and the medium-multiple gel foam is generated by the "gas-liquid-bubble" mixing method.

[0007] The specific steps include:

[0008] (1) Mix the foam fire extinguishing agent, the cross-linking agent and water according to the usage ratio to prepare the component A system solution;

[0009] (2) Mix the foam fire extinguishing agent, thickener and water according to the usage ratio to prepare the component B system solution;

[0010] (3) injecting air into the A component system solution and the B component system solution to generate foam;

[0011] (4) The two foams are mixed to produce gel foam.

[0012] Preferably, the volume flow ratio of the A component system solution to air in step (1) is selected in the range of 1:4 to 1:35.

[0013] Preferably, the volume flow ratio of the B component system solution to air in step (2) is selected in the range of 1:4 to 1:10.

[0014] Preferably, the volume flow ratio of the A component system solution to the B component system solution is selected in the range of 2:1 to 1:2.

[0015] Preferably, the foam fire extinguishing agent in step (1) and step (2) is one of a Class A foam fire extinguishing agent and an aqueous film-forming foam fire extinguishing agent.

[0016] Preferably, the crosslinking agent in step (1) is one or more of borax, organic boron crosslinking agent, and organic titanium crosslinking agent; and the mass concentration of the crosslinking agent in the A component system solution is 1%.

[0017] Preferably, the thickener in step (2) is one or more of guar gum, carboxymethyl hydroxypropyl guar gum, and hydroxypropyl guar gum; and the mass concentration of the thickener in the B component system solution is 1%.

[0018] Furthermore, the present invention also provides a bubble mixing type medium-multiple gel foam generating device for the above-mentioned preparation process, the device comprising a component A solution storage tank, a centrifugal pump, a first gas-liquid mixer, a first one-way valve, a component B solution storage tank, a gear pump, a second gas-liquid mixer, a second one-way valve, an air supply device, a first three-way valve, a first pressure regulating valve, a second pressure regulating valve, a second three-way valve, and a bubble mixer; the component A solution storage tank, the centrifugal pump, the first gas-liquid mixer, and the first one-way valve are connected in sequence through a pipeline; the component B solution storage tank, the gear pump, the second gas-liquid mixer, and the second one-way valve are connected in sequence through a pipeline; the air supply device is connected to the first pressure regulating valve and the second pressure regulating valve respectively through the first three-way valve; the first pressure regulating valve is connected to the air inlet of the first gas-liquid mixer through a pipeline, and the second pressure regulating valve is connected to the air inlet of the second gas-liquid mixer through a pipeline; the first one-way valve and the second one-way valve are respectively connected to the feed end of the bubble mixer through the second three-way valve.

[0019] Preferably, the first gas-liquid mixer has the same structure as the second gas-liquid mixer; the first gas-liquid mixer comprises a feed chamber and a mixing chamber which are interconnected, an atomizing nozzle is arranged on the central axis of the feed chamber inlet, the atomizing nozzle is connected to the feed port, and an air inlet is arranged on the side wall of the feed chamber to form a vertical cross-injection pattern in which the jet direction of the atomizing nozzle and the injection direction of the gas are perpendicular; a plurality of screens are installed at equal intervals inside the mixing chamber.

[0020] Preferably, a plurality of screen meshes 2 are installed at equal intervals inside the bubble mixer, and the aperture of the screen mesh 2 is smaller than that of the screen mesh 1.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention designs a new gel foam generation method, injects gas into the A / B two-component system solution to form foam, causes the crosslinking agent and the thickener to be distributed in the liquid film, and then increases the interface area of ​​the crosslinking reaction of the crosslinking agent and the thickener through bubble mixing, the crosslinking reaction activity is increased by more than 3 times, the amount of crosslinking agent is reduced by more than 50%, and the problems of uneven liquid-liquid and gas-liquid mixing caused by the high viscosity of the gel foam system solution are avoided. The formed gel foam jet is continuous, the generated gel foam performance is better, the maximum foaming multiple exceeds 20 times, and the 25% liquid separation time is greater than 48h.

[0023] 2. The present invention adopts a component A solution storage tank and a centrifugal pump to supply a certain volume flow rate of component A solution to the first gas-liquid mixer; a nozzle and a screen are arranged inside the first gas-liquid mixer to fully mix the gas and the component A solution to produce a target multiple of compressed air foam, and at the same time promote the cross-linking agent to be evenly distributed in the foam liquid film; a component B solution storage tank and a gear pump are used to supply a certain volume flow rate of component B solution to the second gas-liquid mixer; a nozzle and a screen are arranged inside the second gas-liquid mixer to mix the gas and the component B solution to improve the distribution of the thickener in the foam liquid film; an air supply device, a first three-way valve and a pressure regulating valve are used to supply a certain volume flow rate of gas to the mixer; a one-way valve prevents foam backflow, which causes the cross-linking agent and the thickener to react and block the pipeline; the second three-way valve is used to collect the two foams and realize preliminary mixing of the two foams; the bubble mixer can promote further mixing of the two foams, realize sufficient cross-linking reaction of the cross-linking agent and the thickener, and at the same time produce a target multiple of gel foam. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a bubble mixing gel foam generating device of the present invention;

[0025] Figure 2 is a schematic diagram of a gas-liquid mixer;

[0026] Figure 3 Schematic diagram of a bubble mixer.

[0027] In the figure, 1, A component solution storage tank; 2, centrifugal pump; 3, first gas-liquid mixer; 301, feed port; 302, air inlet; 303, atomizing nozzle; 304, feed chamber; 305, mixing chamber; 306, screen one; 4, first pressure regulating valve; 5, B component solution storage tank; 6, gear pump; 7, second gas-liquid mixer; 8, second pressure regulating valve; 9, air supply device; 10, first three-way valve; 11, first one-way valve; 12, second one-way valve; 13, second three-way valve; 14, bubble mixer; 1401, feed end; 1401, screen two. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Example 1

[0030] like Figure 1As shown, this embodiment provides a bubble mixing gel foam generating device, including a component A solution storage tank 1, a centrifugal pump 2, a first gas-liquid mixer 3, a first one-way valve 11, a component B solution storage tank 5, a gear pump 6, a second gas-liquid mixer 7, a second one-way valve 12, an air supply device 9, a first three-way connection 10, a first pressure regulating valve 4, a second pressure regulating valve 8, a second three-way connection 13, and a bubble mixer 14; the component A solution storage tank 1, the centrifugal pump 2, the first gas-liquid mixer 3, and the first one-way valve 11 are sequentially connected through pipelines; the component B solution storage tank 5, a gear pump 6, a second gas-liquid mixer 7, a second one-way valve 12, an air supply device 9, a first three-way connection 10, a first pressure regulating valve 4, a second pressure regulating valve 8, a second three-way connection 13, and a bubble mixer 14; the component A solution storage tank 1, the centrifugal pump 2, the first gas-liquid mixer 3, and the first one-way valve 11 are sequentially connected through pipelines; The liquid separation storage tank 5, the gear pump 6, the second gas-liquid mixer 7, and the second one-way valve 12 are connected in sequence through pipelines; the air supply device 9 is connected to the first pressure regulating valve 4 and the second pressure regulating valve 8 respectively through the first three-way valve 10; the first pressure regulating valve 4 is connected to the air inlet 302 of the first gas-liquid mixer 3 through a pipeline, and the second pressure regulating valve 8 is connected to the air inlet of the second gas-liquid mixer 7 through a pipeline; the first one-way valve 11 and the second one-way valve 12 are connected to the feed end 1401 of the bubble mixer 14 respectively through the second three-way valve 13.

[0031] like Figure 2 As shown, in this embodiment, the first gas-liquid mixer 3 includes a feed chamber 304 and a mixing chamber 305 that are interconnected. The atomizing nozzle 303 is arranged at the central axis of the inlet of the feed chamber 304. The atomizing nozzle 303 is connected to the feed port 301. The gas inlet 302 is arranged on the side wall of the feed chamber 304 to form a vertical cross-spraying shape in which the jet direction of the atomizing nozzle 303 and the spray direction of the gas are perpendicular to each other; a plurality of screens 306 are installed at equal intervals inside the mixing chamber 305. The aperture of the screen 306 is 40 mesh to 100 mesh. In the first gas-liquid mixer 3, the A component solution is mixed with the gas and then foamed through the screen 306, so that the cross-linking agent is evenly distributed in the foam liquid film.

[0032] The second gas-liquid mixer 7 has the same structure as the first gas-liquid mixer 3. In the second gas-liquid mixer 7, the B component solution is mixed with the gas and then foamed through the screen 306, so that the thickener is evenly distributed in the foam liquid film.

[0033] like Figure 3 As shown, in this embodiment, a plurality of screens 1402 are installed at equal intervals inside the bubble mixer 14. The aperture of the screen 1402 is 200 mesh to 1000 mesh. In the bubble mixer 14, the two foams are mixed and passed through the screen 1402, which promotes the crosslinking reaction between the crosslinking agent and the thickener in the liquid film to obtain gel foam.

[0034] In addition, the gas supply device 9 of the present invention can be a nitrogen generator or an air compressor, the nitrogen generator outputs nitrogen, and the air compressor outputs compressed air. This embodiment uses an air compressor.

[0035] The present invention adopts a component A solution storage tank 1 and a centrifugal pump 2, which are used to supply a certain volume flow rate of component A solution to a first gas-liquid mixer 3; an atomizing nozzle 303 and a screen 306 are arranged inside the first gas-liquid mixer 3, which are used to fully mix the gas and the component A solution to produce a target multiple of compressed air foam, and at the same time, promote the uniform distribution of the cross-linking agent in the foam liquid film; a component B solution storage tank 5 and a gear pump 6 are used to supply a certain volume flow rate of component B solution to a second gas-liquid mixer 7; an atomizing nozzle 303 and a screen 306 are arranged inside the second gas-liquid mixer 7 The net 1 306 is used to mix the gas and the B component solution to improve the distribution of the thickener in the foam liquid film; the gas supply device 9, the first tee 10 and the two pressure regulating valves are used to supply a certain volume flow of gas into the gas mixer; the one-way valve prevents the foam from flowing back and causing the cross-linking agent and the thickener to react and block the pipeline; the second tee 13 is used to collect the two foams and achieve preliminary mixing of the two foams; the bubble mixer 14 can promote further mixing of the two foams to achieve a full cross-linking reaction between the cross-linking agent and the thickener, and at the same time produce a target multiple of gel foam.

[0036] The method for producing bubble-mixing gel foam using the above device comprises the following steps: in a component A solution storage tank 1, a class A foam fire extinguishing agent and borax are mixed with water at a mass concentration of 1% to prepare a component A system solution; in a component B solution storage tank 5, a class A foam fire extinguishing agent and guar gum are mixed with water at a mass concentration of 1% to prepare a component B system solution; starting a centrifugal pump 2, a gear pump 6 and a gas supply device 9, setting the volume flow of the component A system solution and the component B system solution to 5.7 L / min, adjusting the first pressure regulating valve 4 and the second pressure regulating valve 8, respectively injecting gas into the first gas-liquid mixer 3 and the second gas-liquid mixer 7, the gas volume flow rate is 100 L / min, and collecting the gel foam sprayed from the outlet of the bubble mixer 14. According to the standard test method of GB 15308-2006 "Foam Fire Extinguishing Agent", the foam expansion multiple and 25% liquid separation time are tested, and the test results are shown in Table 1.

[0037] In terms of gel time determination, there is currently no method for determining the gel time of gel foam due to differences between gel foam and gel in terms of strength and morphology. Therefore, the experiment refers to Sydansk's GSC (Gel Strength Codes) visual code method to determine the gel time of gel foam. When the gel foam strength reaches level D - medium flow gel, that is, when the foam appears in a tongue-shaped morphology, the recorded time is the gel time.

[0038] Table 1 Visual code method gel characteristics

[0039]

[0040] Example 2-11

[0041] In this embodiment, the composition of the component A system and the component B system are the same as those in Example 1, and the difference from Example 1 is the volume flow rate of the component A system solution and the component B system solution and the volume flow rate of the gas injected into the first gas-liquid mixer and the second gas-liquid mixer, and the working parameters and test results are shown in Table 2. From the test results, it can be seen that the gel foam multiple produced by the present invention is adjustable between 4 and 17 times, the 25% liquid separation time is up to more than 60 hours, and under the action of the borax crosslinking agent, the foam containing the borax crosslinking agent and the foam containing guar gum are rapidly crosslinked to form a gel foam, and the crosslinking time is within 30 seconds.

[0042] Table 2 Gel foam foaming test results

[0043]

[0044] Comparative Examples 1-3

[0045] In order to compare the advantages of the production method of the present invention, the existing gel foam "liquid-liquid first, then gas-liquid" mixing method is adopted for foaming. The compositions of the A component system solution and the B component system solution are the same as those in the above-mentioned embodiments 1-11. The working parameters of the foaming process are shown in Table 3 below. The maximum foaming multiple of the gel foam measured by this method does not exceed 3 times, which is significantly lower than the foam foaming multiple of the present invention, and the foam jet state is discontinuous.

[0046] Table 3 Gel foam foaming test results

[0047]

[0048] Example 12

[0049] The difference between this embodiment and embodiment 1 is that the types of crosslinking agent and thickener used are different, and the other operation steps and working parameters are the same as those of embodiment 1. Among them, the crosslinking agent is an organic boron crosslinking agent, and the thickener is carboxymethyl hydroxypropyl guar gum, and the addition amount is 1% by mass concentration. The test results are shown in Table 4.

[0050] Examples 13-22

[0051] The bubble mixing gel foam generation method in this embodiment is different from that in embodiment 12 in terms of the volume flow rate of the A component system solution and the B component system solution, and the volume flow rate of the gas injected into the first gas-liquid mixer 3 and the second gas-liquid mixer 7, and the test results are shown in Table 4. From the test results, it can be seen that the gel foam multiples generated in embodiments 12-22 are adjustable between 4-23 times, the 25% liquid separation time is greater than 48 hours, the cross-linking time is 2 minutes, and the foam jet state is continuous.

[0052] Table 4 Gel foam foaming test results

[0053]

[0054]

[0055] Comparative Examples 4-6

[0056] In order to compare the advantages of the production method of the present invention, the existing gel foam "liquid-liquid first, then gas-liquid" mixing method is adopted for foaming. Except that the amount of cross-linking agent is increased to 2% by mass concentration, the compositions of the A component system solution and the B component system solution are the same as those in Examples 12-22. The working parameters of the foaming process are shown in Table 5 below. The foaming multiple of the gel foam measured in this method is significantly lower than that of the foaming method of the present invention, the maximum foaming multiple does not exceed 7 times, the foam jet state is discontinuous, and under the condition that the amount of cross-linking agent is doubled, the foam cross-linking time is as long as 15 minutes, and the 25% liquid separation time is less than 48 hours.

[0057] Table 5 Gel foam foaming test results

[0058]

[0059] Embodiment 23

[0060] The difference between this embodiment and embodiment 1 is that the types of foam fire extinguishing agent, cross-linking agent and thickener used are different, and the other operation steps and working parameters are the same as those of embodiment 1. Among them, the foam fire extinguishing agent is an aqueous film-forming foam fire extinguishing agent, and the addition amount is 3% by mass concentration; the cross-linking agent is an organic titanium cross-linking agent, and the thickener is hydroxypropyl guar gum, and the addition amount of both is 1% by mass concentration. The test results are shown in Table 6.

[0061] Examples 24-33

[0062] The bubble mixing gel foam generation method in this embodiment is different from that in embodiment 23 in the volume flow rate of the A component system solution and the B component system solution, and the volume flow rate of the air injected into the first gas-liquid mixer 3 and the second gas-liquid mixer 7, and the test results are shown in Table 6. From the test results, it can be seen that the gel foam multiples generated in embodiments 23-33 are adjustable between 5-23 times, the 25% liquid separation time is greater than 48 hours, the cross-linking time is 2 minutes, and the foam jet state is continuous.

[0063] Table 6 Gel foam foaming test results

[0064]

[0065] Comparative Examples 7-9

[0066] In order to compare the advantages of the production method of the present invention, the existing gel foam "liquid-liquid first, then gas-liquid" mixing method was adopted for foaming. Except that the amount of cross-linking agent was increased to 2% by mass concentration, the compositions of the A component system solution and the B component system solution were the same as those in Examples 29-39. The working parameters of the foaming process are shown in Table 7 below. The foaming multiple of the gel foam measured in this method was significantly lower than that of the foaming method of the present invention, the maximum foaming multiple did not exceed 7 times, the foam jet state was discontinuous, and under the condition that the amount of cross-linking agent was doubled, the foam cross-linking time was as long as 15 minutes, and the 25% liquid separation time was less than 48 hours.

[0067] Table 7 Gel foam foaming test results

[0068]

[0069] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent substitution and improvement made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A process for preparing a bubble-mixing medium-multiple gel foam, characterized in that: The following steps are involved: (1) Mixing a foam fire extinguishing agent and a cross-linking agent with water according to a usage ratio to obtain a component A system solution; (2) Mixing the foam fire extinguishing agent and the thickener with water according to the usage ratio to obtain a component B system solution; (3) injecting air into the A component system solution and the B component system solution to generate foam; (4) The two foams are mixed to produce gel foam.

2. A bubble mixing type medium multiple gel foam preparation process according to claim 1, characterized in that: The volume flow ratio of the A component system solution to air is selected in the range of 1:4 to 1:

35.

3. The process for preparing a bubble-mixing medium-multiple gel foam according to claim 1, characterized in that: The volume flow ratio of the B component system solution to air is selected in the range of 1:4 to 1:

10.

4. The process for preparing a bubble-mixing medium-multiple gel foam according to claim 1, characterized in that: The volume flow ratio of the A component system solution to the B component system solution is selected in the range of 2:1 to 1:

2.

5. The process for preparing a bubble-mixing medium-multiple gel foam according to claim 1, characterized in that: The foam fire extinguishing agent described in step (1) and step (2) is one of Class A foam fire extinguishing agent and water film-forming foam fire extinguishing agent.

6. The process for preparing a bubble-mixing medium-multiple gel foam according to claim 1, characterized in that: The crosslinking agent in step (1) is one or more of borax, organic boron crosslinking agent, and organic titanium crosslinking agent; and the mass concentration of the crosslinking agent in the A component system solution is 1%.

7. The process for preparing a bubble-mixing medium-multiple gel foam according to claim 1, characterized in that: The thickener in step (2) is one or more of guar gum, carboxymethyl hydroxypropyl guar gum, and hydroxypropyl guar gum; the mass concentration of the thickener in the B component system solution is 1%.

8. A process for preparing a bubble-mixing medium-multiple gel foam according to any one of claims 1 to 7, characterized in that: The preparation process adopts a bubble mixing gel foam generating device, which includes a component A solution storage tank, a centrifugal pump, a first gas-liquid mixer, a first one-way valve, a component B solution storage tank, a gear pump, a second gas-liquid mixer, a second one-way valve, an air supply device, a first three-way connection, a first pressure regulating valve, a second pressure regulating valve, a second three-way connection, and a bubble mixer; the component A solution storage tank, the centrifugal pump, the first gas-liquid mixer, and the first one-way valve are connected in sequence through a pipeline; the component B solution storage tank, the gear pump, the second gas-liquid mixer, and the second one-way valve are connected in sequence through a pipeline; the air supply device is connected to the first pressure regulating valve and the second pressure regulating valve respectively through the first three-way connection; the first pressure regulating valve is connected to the air inlet of the first gas-liquid mixer through a pipeline, and the second pressure regulating valve is connected to the air inlet of the second gas-liquid mixer through a pipeline; the first one-way valve and the second one-way valve are respectively connected to the feed end of the bubble mixer through the second three-way connection.

9. A bubble mixing type medium multiple gel foam preparation process according to claim 8, characterized in that: The first gas-liquid mixer has the same structure as the second gas-liquid mixer; the first gas-liquid mixer comprises a feed chamber and a mixing chamber which are interconnected, an atomizing nozzle is arranged on the central axis of the feed chamber inlet, the atomizing nozzle is connected with the feed port, an air inlet is arranged on the side wall of the feed chamber to form a vertical cross-injection pattern in which the jet direction of the atomizing nozzle and the injection direction of the gas are perpendicular; a plurality of screens are installed at equal intervals inside the mixing chamber.

10. A bubble mixing type medium multiple gel foam preparation process according to claim 9, characterized in that: A plurality of screen meshes 2 are installed at equal intervals inside the bubble mixer, and the aperture of the screen mesh 2 is smaller than that of the screen mesh 1.

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