High-temperature co2 micro-nano bubble wastewater treatment system and method

Abstract

The application provides a high-temperature CO2 micro-nano bubble wastewater treatment system, which comprises a CO2 supply unit, a heating unit and a micro-nano bubble generating unit which are sequentially connected. The heating unit can heat the gas to 150-600 DEG C. The gas at least comprises CO2 gas provided by the CO2 supply unit. The micro-nano bubble generating unit comprises a gas injection structure and a Venturi structure. The Venturi structure comprises a water inlet section, a contraction section, a throat section, an expansion section, a mixing section, a diffusion section and a water outlet section which are sequentially arranged along the water flow direction. One end of the gas injection structure is communicated with the CO2 supply unit and the heating unit, and the other end of the gas injection structure is communicated with the throat section. The application also provides a method for treating wastewater by using the high-temperature CO2 micro-nano bubble wastewater treatment system. The method can utilize the interface heat inactivation and the CO2 chemical penetration synergistic reaction to rapidly inactivate microorganisms in the wastewater.

Description

Technical Field

[0001] This application relates to the field of water treatment and disinfection technology, and in particular to a high-temperature CO2 micro-nano bubble wastewater treatment system and method. Background Technology

[0002] With the acceleration of industrialization and the improvement of urbanization, wastewater discharge is increasing year by year. Because the bacteria, viruses, and other pathogenic microorganisms contained in wastewater pose a serious threat to the aquatic environment and human health, it is necessary to treat and disinfect the generated wastewater. Traditional water disinfection methods mainly include chlorination, ozone disinfection, ultraviolet disinfection, and thermal disinfection. Chlorination produces carcinogenic disinfection byproducts such as trihalomethanes; ozone disinfection equipment requires large investments and needs to be prepared on-site; ultraviolet light has limited penetration into water and lacks continuous disinfection capabilities; thermal disinfection raises the overall temperature of the water body through high temperatures, resulting in extremely high energy consumption and prohibitive operating costs.

[0003] In recent years, micro- and nanobubble technology has attracted widespread attention in the field of water treatment due to its large specific surface area, long residence time, and high mass transfer efficiency. However, most existing micro- and nanobubble technologies use room temperature air and rely only on the small amount of free radicals generated when the bubbles burst for limited sterilization, making it difficult to completely eliminate microorganisms in the water. Summary of the Invention

[0004] In view of this, the purpose of this application is to propose a high-temperature CO2 micro-nano bubble wastewater treatment system and method, which uses micro-nano bubbles formed by at least high-temperature CO2 gas to rapidly inactivate microorganisms in wastewater by utilizing the synergistic reaction of interfacial thermal inactivation and CO2 chemical osmosis.

[0005] To achieve the above objectives, this application provides a high-temperature CO2 micro / nano bubble wastewater treatment system, comprising a CO2 supply unit, a heating unit, and a micro / nano bubble generating unit connected in sequence. The heating unit is capable of heating the gas to 150-600°C, and the gas includes at least the CO2 gas supplied by the CO2 supply unit. The micro / nano bubble generating unit includes an injection structure and a Venturi structure. The Venturi structure includes an inlet section, a contraction section, a throat section, an expansion section, a mixing section, a diffusion section, and an outlet section arranged in sequence along the water flow direction. One end of the injection structure is connected to the CO2 supply unit and the heating unit, and the other end of the injection structure is connected to the throat section.

[0006] In one embodiment, the CO2 supply unit is used to supply CO2 accounting for 5%-100% of the total gas volume to the micro / nano bubble generating unit. When the percentage of CO2 gas supplied by the CO2 supply unit to the total gas volume is less than 100%, nitrogen and / or air are added as supplementary gases.

[0007] In one embodiment, the contraction angle of the contraction segment is 12-18°, the diameter of the throat segment is 8-20mm, and the expansion angle of the dilation segment is 8-12°.

[0008] In one embodiment, the micro / nano bubble generating unit further includes a shell sleeved on the outside of the Venturi structure, and an annular gas collecting cavity is formed between the outer walls of the contraction section, the throat section, and the expansion section and the inner wall of the shell; at least one gas distribution ring is provided on the wall of the throat section, and the gas distribution ring has an injection hole along the circumferential direction, with the axis of the injection hole forming an angle of 30-60° with the water flow direction in the throat section; the gas injection structure is connected to the throat section through the annular gas collecting cavity and the injection hole on the gas distribution ring.

[0009] In one embodiment, the inlet section includes an inlet grille and a submersible pump connected to each other. The inlet grille forms a streamlined horn-shaped inlet structure, and the grille has an aperture of 5-15 mm. The submersible pump is used to provide an inlet pressure of 0.1-0.6 MPa.

[0010] In one embodiment, the mixing section is 20-40 mm long, the inner wall of the mixing section is provided with micro-turbulence teeth, and / or the diffusion section includes a multi-stage metal cutting mesh and a spiral guide vane arranged sequentially in the cavity of the diffusion section. The cavity diameter of the diffusion section is 2-3 times larger than the outlet of the expansion section, and the mesh size of the multi-stage metal cutting mesh decreases sequentially along the water flow direction.

[0011] In one embodiment, the inlet section, the contraction section, the throat section, the expansion section, the mixing section, and the diffusion section are coaxially arranged along a first central axis, the outlet section has a second central axis, the first central axis and the second central axis are perpendicular to each other, and / or the outlet section includes a microporous metal diffusion plate located at the outlet, the pore size of the microporous metal diffusion plate being 0.5-2mm.

[0012] In one embodiment, the micro / nano bubble generating unit further includes a temperature monitoring device, which is installed at one or more of the throat section, the annular gas collecting chamber, and the water outlet section.

[0013] This application also provides a method for wastewater treatment using any of the high-temperature CO2 micro / nano bubble wastewater treatment systems described above, comprising the following steps: S1, CO2 gas is supplied using the CO2 supply unit; S2, using the heating unit to heat the gas to 150-600°C, wherein the gas includes at least the CO2 gas generated by the CO2 supply unit; S3, inject wastewater into the Venturi structure; S4, the heated gas is injected into the throat section through the gas injection structure, mixes with the wastewater in the throat section to form micro-nano bubbles, and flows sequentially through the expansion section, the mixing section, the diffusion section and the gas outlet section into the wastewater pool.

[0014] In one embodiment, the diameter of the micro-nanobubbles is 10-50 μm, and the density of the micro-nanobubbles is 1 × 10⁻⁶. 6 -1×10 8 The micro-nano bubbles have a transient thermal layer with a temperature of 70–150°C and a thickness of 40–200 nm.

[0015] As can be seen from the above description, the high-temperature CO2 micro / nano bubble wastewater treatment system and method provided in this application, according to the embodiments of the present invention, heats a gas containing at least CO2 to a high temperature of 150-600°C in the heating unit. The high-temperature gas containing at least CO2 enters the throat section of the Venturi structure through the gas injection structure and mixes with the wastewater therein to form micro / nano bubbles, which then flow sequentially through the expansion section, mixing section, diffusion section, and outlet section into the wastewater. The formed micro / nano bubbles have a transient thermal layer, and by utilizing the synergistic reaction of interfacial thermal inactivation and CO2 chemical osmosis, microorganisms in the wastewater, such as bacteria, viruses, and other pathogenic microorganisms, can be rapidly inactivated, achieving highly efficient sterilization at a relatively low water temperature, significantly reducing energy consumption compared to traditional thermal disinfection. Furthermore, the CO2 gas used for synergistic disinfection is non-toxic and non-corrosive, and does not produce toxic chemical byproducts after use, making it environmentally friendly. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this application or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the overall process and pipeline connection flow of the high-temperature CO2 micro-nano bubble wastewater treatment system of this application; Figure 2 This is an internal cross-sectional view of the micro / nano bubble generating unit of this application; Figure 3 This is a schematic diagram of the microscopic mechanism of the synergistic effect of interfacial thermal inactivation and CO2 chemical permeation of micro-nano bubbles in this application; Figure 4 This is a schematic diagram of the wastewater treatment method of this application.

[0018] The system includes: 100-High-temperature CO2 micro / nano bubble wastewater treatment system; 110-CO2 supply unit; 120-Heating unit; 130-Micro / nano bubble generating unit; 132-Injection structure; 1341-Inlet section; 13411-Inlet grille; 13412-Submersible pump; 1342-Contraction section; 1343-Throat section; 13431-Gas distribution ring; 1344-Expansion section; 1345-Mixing section; 13451-Micro turbulence teeth; 1346-Diffusion section; 13461-Multi-stage metal cutting mesh; 13462-Spiral guide vane; 1347-Outlet section; 13471-Microporous metal diffuser plate; 136-Shell; 1361-Annular gas collection chamber; 140-Micro / nano bubbles. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0020] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0021] Please refer to Figure 1 as well as Figure 2This application provides a high-temperature CO2 micro / nano bubble wastewater treatment system 100, which may include a CO2 supply unit 110, a heating unit 120, and a micro / nano bubble generating unit 130 connected in sequence. The heating unit 120 can heat the gas to 150-600℃, and the gas may include at least the CO2 gas supplied by the CO2 supply unit 110. The micro / nano bubble generating unit 130 may include an injection structure 132 and a Venturi structure. The Venturi structure may include an inlet section 1341, a contraction section 1342, a throat section 1343, an expansion section 1344, a mixing section 1345, a diffusion section 1346, and an outlet section 1347 arranged in sequence along the water flow direction. One end of the injection structure 132 is connected to the CO2 supply unit 110 and the heating unit 120, and the other end of the injection structure 132 is connected to the throat section 1343.

[0022] Please refer to Figure 3 CO2 molecules are highly water-soluble and can penetrate bacterial cell membranes and viral capsids, resulting in a significantly better sterilization effect than other gases such as N2 and O2. At low temperatures (18-100°C), CO2 molecules can penetrate viral capsids or bacterial membranes, destroying their structure through acidification or protein binding (e.g., MS2 is inactivated by 0.9-log / 10 minutes at 22°C). At high temperatures (>100°C), a transient thermal layer forms around micro- and nano-bubbles (e.g., at a gas supply temperature of 150°C, the transient thermal layer around the micro- and nano-bubbles is about 44 nm thick and about 70°C). Combined with thermal collisions and the chemical action of CO2, viruses (such as MS2) can be inactivated by 3-log in 3 minutes at 200°C.

[0023] The high-temperature CO2 micro / nano bubble wastewater treatment system 100 provided in this application heats a gas containing at least CO2 to a high temperature of 150-600℃ via a heating unit 120. This high-temperature CO2-containing gas enters the throat section 1343 of a Venturi structure through an injection structure 132, mixing with the wastewater therein to form micro / nano bubbles 140. These bubbles then flow sequentially through an expansion section 1344, a mixing section 1345, a diffusion section 1346, and an outlet section 1347 before entering the treated wastewater. The formed micro / nano bubbles 140 possess a transient thermal layer. Utilizing the synergistic reaction of interfacial thermal inactivation and CO2 chemical osmosis, they can rapidly inactivate microorganisms in the wastewater, such as bacteria and viruses, achieving highly efficient sterilization at relatively low water temperatures. Compared to traditional thermal disinfection, energy consumption is significantly reduced. Furthermore, the CO2 gas used for synergistic disinfection is non-toxic and non-corrosive, and does not produce toxic chemical byproducts after use, making it environmentally friendly.

[0024] Optionally, the CO2 supply unit 110 provides CO2, accounting for 5%-100% of the total gas volume, to the micro / nano bubble generating unit 130. That is, the gas entering the micro / nano bubble generating unit 130 can be pure CO2 or a mixture of CO2 and other gases. In other words, when the CO2 supplied by the CO2 supply unit 110 accounts for less than 100% of the total gas volume, nitrogen and / or air can be used as supplementary gases to be supplied to the micro / nano bubble generating unit 130 along with the CO2, reducing CO2 consumption while ensuring the inactivation effect. Specifically, the volume concentration of CO2 in the gas can be 5%, 10%, 15%, 20%, 40%, 50%, 60%, 80%, 100%, etc., while the volume concentration of air and / or nitrogen can be set sequentially to 95%, 90%, 85%, 80%, 60%, 50%, 40%, 20%, 0%, etc., depending on the actual conditions of the wastewater to be treated; these are not listed here.

[0025] Optionally, the CO2 supply unit 110 may include a CO2 gas source and a CO2 supply pipeline. In one embodiment, the CO2 supply pipeline may also be equipped with a gas flow meter, a proportional regulating valve, a high-temperature shut-off valve, and a high-temperature check valve, etc., to dynamically adjust the injected CO2 gas content according to the turbidity and microbial load of the wastewater to be treated, ensuring that the CO2 gas-to-water ratio is maintained within the optimal disinfection range. The CO2 supply pipeline can be made of 310S stainless steel or Inconel 600. The CO2 supply pipeline may also be covered with an insulation layer to reduce heat loss during transportation. The insulation layer can be 30-50mm thick, and the insulation layer material can be a combination of aluminum silicate fiber and aluminum foil reflective layer.

[0026] Optionally, the heating unit 120 can be set to different heating temperatures to heat the gas according to different water quality conditions and treatment requirements, thereby enabling the high-temperature CO2 micro-nano bubble wastewater treatment system 100 of this application to adapt to wastewater treatment in various environments and thus have a wider range of applications. The heating unit 120 heats the gas containing at least CO2 to a high temperature of 150-600℃. Specifically, the heating unit 120 can heat the gas to 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, 500℃, 600℃, etc.

[0027] Optionally, the inlet section 1341 may include an inlet grille 13411 and a submersible pump 13412 connected to each other. The inlet grille 13411 forms a streamlined, funnel-shaped inlet structure, which can effectively reduce head loss. The inlet grille 13411 can be made of 316 stainless steel, and the aperture of the inlet grille 13411 can be 5-15mm. The submersible pump 13412 can be used to provide an inlet pressure of 0.1-0.6 MPa to smoothly draw wastewater into the micro / nano bubble generating unit 130 and provide a certain pressure environment for the subsequent formation of micro / nano bubbles 140. The submersible pump 13412 can be a variable frequency high-temperature resistant submersible pump.

[0028] Optionally, the contraction angle of the contraction section 1342 can be 12-18°, such as 12°, 14°, 16°, 18°, etc. The throat section 1343 can be cylindrical, with a diameter of 8-20 mm, such as 8 mm, 10 mm, 13 mm, 16 mm, 20 mm, etc. The expansion angle of the expansion section 1344 can be 8-12°, such as 8°, 9°, 10°, 11°, 12°, etc.

[0029] Optionally, the micro / nano bubble generating unit 130 also includes a shell 136 fitted around the outside of the venturi structure. The shell 136 can be a hollow cylinder. The space formed between the outer walls of the contraction section 1342, the throat section 1343, and the expansion section 1344 and the inner wall of the shell 136 is an annular gas collecting cavity 1361. The shell 136 can be made of a high-temperature resistant and corrosion-resistant metal material, specifically including 304 stainless steel, 316L stainless steel, 310S stainless steel, or Inconel alloy, to ensure long-term stable operation under high-temperature conditions.

[0030] Optionally, at least one gas distribution ring 13431 may be provided on the wall of the throat section 1343. The gas distribution rings 13431 are spaced apart on the wall of the throat section 1343. Preferably, multiple gas distribution rings 13431 are spaced apart and distributed throughout the wall of the throat section 1343. Each gas distribution ring 13431 has 6-12 injection holes along its circumference, for example, 6, 8, 10, or 12 holes, with a diameter of 2-4 mm. The angle between the axis of the injection hole and the flow direction within the throat section 1343 is 30-60°, for example, 30°, 40°, 50°, or 60°. The direction of the injected gas is adjusted by changing the angle between the injection hole and the flow direction within the throat section 1343. The Venturi tube operates based on Bernoulli's principle. When high-pressure wastewater enters the contraction section 1342, the flow velocity increases sharply, forming a strong negative pressure zone in the throat section 1343. Under the combined effect of pressure difference and Venturi jet entrainment, the gas is forcefully drawn into the throat section 1343, which is more conducive to achieving gas flow shearing.

[0031] The gas injection structure 132 is connected to the throat section 1343 through the gas injection holes on the annular gas collecting chamber 1361 and the gas distribution ring 13431. In one embodiment, the housing 136 has an air inlet, and the gas injection structure 132 is connected to the air inlet, allowing heated gas to enter the annular gas collecting chamber 1361 through the air inlet. In another embodiment, the housing 136 has an air inlet, and the gas injection structure 132 may include a first section and a second section, located on opposite sides of the air inlet. Alternatively, the first section may be located outside the housing 136, and the second section inside the housing 136. In this embodiment, the airflow rate can be adjusted by changing the size of the opening in the second section.

[0032] Optionally, the length of the mixing section 1345 can be 20-40 mm, specifically 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, etc., providing ample space for gas-liquid heat exchange and primary bubble generation. The inner wall of the mixing section 1345 can be provided with micro-turbulence teeth 13451. These micro-turbulence teeth 13451 further enhance the mixing of bubbles and wastewater, resulting in more thorough heat exchange between gas and liquid. The height of the micro-turbulence teeth 13451 from the inner wall of the mixing section 1345 towards its central axis can be 2-6 cm. The number of micro-turbulence teeth 13451 can be 4-8, and they can be arranged in a staggered pattern on the inner wall of the mixing section 1345 to increase the turbulence effect.

[0033] Optionally, the diffuser section 1346 may include a multi-stage metal cutting mesh 13461 and spiral guide vanes 13462 sequentially disposed within the cavity of the diffuser section 1346. Optionally, the cavity diameter of the diffuser section 1346 is 2-3 times larger than the outlet of the expansion section 1344, and the length of the diffuser section 1346 can be 150-300 mm, specifically 150 mm, 200 mm, 250 mm, 300 mm, etc. The metal cutting mesh is arranged at intervals to form a multi-stage metal cutting mesh 13461. The number of metal cutting meshes can be 2-3 layers, and the interval between adjacent layers can be 2-4 cm, which can be the same or different. The mesh aperture of the multi-stage metal cutting mesh 13461 decreases sequentially along the flow direction. For example, when 3 layers of metal cutting mesh are provided, the mesh aperture of each layer along the flow direction can be 1.0 mm, 0.5 mm, and 0.2 mm respectively. As the micro-nano bubbles 140 pass through, they are repeatedly sheared and broken to a suitable size by the multi-level metal cutting mesh 13461, while the spiral guide vanes 13462 cause the fluid to swirl, using centrifugal force to fully mix the micro-nano bubbles 140 with the water, preventing the micro-nano bubbles 140 from merging and failing.

[0034] Optionally, the inlet section 1341, the contraction section 1342, the throat section 1343, the expansion section 1344, the mixing section 1345, and the diffusion section 1346 are coaxially arranged along a first central axis. The outlet section 1347 has a second central axis. The first and second central axes are perpendicular to each other, and this design allows micro-nano bubbles to float from the bottom up, further increasing the disinfection area during the water treatment process.

[0035] The optional outlet section 1347 includes a microporous metal diffuser plate 13471 located at the outlet. The pore size of the microporous metal diffuser plate 13471 can be 0.5-2 mm, and the microporous metal diffuser plate 13471 can be manufactured using a laser drilling process. Micro- and nano-bubbles 140 can be uniformly released from the microporous metal diffuser plate 13471 into the wastewater.

[0036] Optionally, the micro / nano bubble generating unit 130 also includes flow-through components. These components can be made of high-temperature resistant and corrosion-resistant metal materials, specifically including 304 stainless steel, 316L stainless steel, 310S stainless steel, or Inconel alloy, ensuring long-term stable operation under high-temperature conditions. Sealing elements can also be installed at the connections between the components of the micro / nano bubble generating unit 130. These seals can be made of high-temperature resistant flexible graphite spiral wound gaskets or polytetrafluoroethylene composite gaskets. The micro / nano bubble generating unit 130 has a simple structure and can be directly immersed in the wastewater to be treated. It is suitable for various wastewater treatment scenarios, especially for low-turbidity wastewater.

[0037] Optionally, the micro / nano bubble generating unit 130 may also include a cooling and protection structure. This cooling and protection structure may further include a cooling water jacket, a heat insulation layer, a temperature monitoring device, and a PLC control cabinet. The cooling water jacket may be located on the outer periphery of the micro / nano bubble generating unit 130. The heat insulation layer may be a ceramic fiber blanket with a thickness of 20-30 mm. The temperature monitoring device may be a K-type or S-type thermocouple, which may be installed at one or more of the following locations: the throat section 1343, the annular gas collecting chamber 1361, the outlet section, and below the liquid surface in the wastewater tank. The temperature measurement signal can be transmitted to the PLC control cabinet in real time to monitor the temperature of key components and adjust the high-temperature gas flow rate and cooling water circulation volume.

[0038] Optionally, the flow rate of wastewater treated by the micro / nano bubble generating unit 130 can be 2-20 m³ / h. 3The hydraulic retention time can be 5-30 minutes per hour. Using the micro-nano bubble generator unit 130 to generate CO2-containing micro-nano bubbles 140 for water treatment, the bacterial inactivation rate can reach over 99.99%, and the virus inactivation rate can reach over 99.9%. It is understandable that one or more micro-nano bubble generator units 130 can be used in actual operation. That is to say, depending on the actual water treatment volume required, one or more units can be operated in parallel.

[0039] Please refer to Figure 4 This application also provides a method for treating wastewater using any of the aforementioned high-temperature CO2 micro / nano bubble wastewater treatment systems 100, which may include the following steps: S1, CO2 gas is supplied using CO2 supply unit 110; S2, using heating unit 120 to heat the gas to 150-600°C, the gas including at least the CO2 gas generated by CO2 supply unit 110; S3, wastewater is injected into the Venturi structure; S4, the heated gas is injected into the throat section 1343 through the gas injection structure 132, and mixes with the wastewater in the throat section 1343 to form micro-nano bubbles 140, which then flow sequentially through the expansion section 1344, the mixing section 1345, the diffusion section 1346 and the outlet section 1347 into the wastewater pool.

[0040] Optionally, in step S4, the diameter of the formed micro / nanobubbles can be 10-50 μm, and the density of the micro / nanobubbles 140 can be 1×10⁻⁶. 6 -1×10 8 The micro-nano bubbles (140) have a small diameter and a large specific surface area, enabling rapid heat exchange between high-temperature gas and wastewater.

[0041] Optionally, in step S4, the micro / nanobubbles 140 have a transient thermal layer. The temperature of the transient thermal layer can be 70–150℃, specifically 70℃, 90℃, 100℃, 120℃, 130℃, 150℃, etc. The thickness of the transient thermal layer can be 40–200 nm, specifically 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, etc. The transient thermal layer of the micro / nanobubbles 140 can directly act on microorganisms, causing protein denaturation and nucleic acid damage, thus achieving microbial thermal inactivation. The bulk temperature of the wastewater only rises and remains at 45–55℃, achieving targeted utilization of thermal energy. Compared to heating the entire tank, this significantly reduces energy consumption. The treated wastewater can be directly discharged or reused without additional cooling. Simultaneously, CO2 molecules can penetrate microbial cell membranes or viral capsids, forming carbonic acid within the cell, lowering the intracellular pH, and disrupting enzyme systems and genetic material, achieving synergistic chemical inactivation. The localized high temperature and pressure generated when the bubbles burst, along with hydroxyl radicals, further enhance the bactericidal effect. The interfacial thermal inactivation of the transient thermal layer and the synergistic reaction of CO2 chemical osmosis significantly improve the efficiency against microorganisms in wastewater. It can be understood that the transient thermal layer is the bubble wall of the micro-nano bubbles 140 formed by the contact between the heated gas and the aqueous solution. The wastewater to be treated can be medical low-turbidity wastewater, municipal reclaimed water, food processing low-turbidity wastewater, aquaculture low-turbidity wastewater, etc.

[0042] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0043] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0044] Unless otherwise specified, all experimental materials used in the following examples were purchased from conventional biochemical reagent stores.

[0045] Example 1: Disinfection and treatment of low-turbidity wastewater from hospitals Background: Medical wastewater with low turbidity after biochemical treatment at a hospital contains high concentrations of pathogenic bacteria and MS2-like viruses and other pathogenic microorganisms. Traditional chlorination disinfection easily produces harmful byproducts, necessitating an efficient disinfection treatment method that avoids secondary chemical pollution.

[0046] Parameter settings: 1) Adjust the control panel and set the input gas to 100% pure CO2 gas by volume; 2) Temperature and Inlet Water: The heating unit 120 is set to an outlet temperature of 200℃; the inlet water is filtered through a 316L stainless steel inlet grille 13411 with a 10mm aperture, and then pressurized to 0.3MPa by a variable frequency high-temperature submersible pump 13412. The processing flow rate of the micro-nano bubble generating unit 130 is 10m³ / h.3 / h.

[0047] Operation Process and Results: High-temperature CO2 gas and wastewater are vigorously mixed at the throat of a venturi tube. After being refined by a multi-stage cutting mesh and spiral guide vanes 13462, a large number of micro-nano bubbles 140 with a diameter of 10-50 μm are generated. Within a 15-minute hydraulic retention time, relying on the transient high-temperature thermal layer formed on the bubble surface combined with the chemical action of CO2, MS2 virus inactivation can be achieved in just 3 minutes (3-log). The final effluent bacterial inactivation rate reaches over 99.99%, and the main water temperature is maintained at only 48℃, avoiding the enormous energy consumption of heating the entire water body.

[0048] Example 2: Disinfection and treatment of low-turbidity wastewater from recirculating aquaculture Background: The low-turbidity, slightly acidic wastewater discharged from a certain factory-scale recirculating aquaculture system (RAS) needs to inactivate aquatic pathogens and viruses in the water to prevent cross-infection, and the disinfection process must not leave any toxic residues in the aquatic environment.

[0049] Parameter settings: 1) Adjust the control panel to set the CO2 volume content in the mixed gas to 50%, with the remaining 50% being air as an auxiliary carrier gas; 2) Temperature and Inlet Water: The outlet temperature of the gas heating unit 120 is set at 150℃; the inlet water pressure of the submersible pump 13412 is controlled at 0.2MPa, with each unit operating continuously and the processing flow rate set at 20m³ / h. 3 / h.

[0050] Operation Process and Results: The micro-nano bubble generating unit 130 is completely submerged in the wastewater. As the micro-nano bubbles 140 rise, a transient high-temperature layer of 70-150°C forms on their surface, targeting microorganisms to achieve thermal denaturation. Simultaneously, CO2 molecules penetrate the bacterial membrane, acidifying and destroying its structure. Highly efficient disinfection is achieved within a 10-minute hydraulic retention time. The treated water temperature rise is minimal (maintained at around 45°C), and the entire process produces no toxic chemical byproducts such as trihalomethanes. After cooling, the water can be directly reused in aquaculture ponds.

[0051] Example 3: Deep disinfection treatment of municipal reclaimed water (secondary treated effluent) Background: The low-turbidity effluent from the secondary biological treatment of a municipal wastewater treatment plant needs to be deeply disinfected before it can be used as recycled water for urban greening and flushing. The daily treatment volume is large, and heat loss needs to be strictly controlled to ensure economic efficiency.

[0052] Parameter settings: 1) Set the CO2 volume content in the input mixed gas to 20%, and the remaining 80% to nitrogen auxiliary carrier gas; 2) Temperature and Inlet Water: The gas is intelligently heated to 300℃, and the gas pipeline is wrapped with a 50mm thick aluminum silicate fiber insulation layer and an aluminum foil reflective layer; the variable frequency submersible pump 13412 increases the inlet water pressure to 0.5MPa, with a processing flow rate of 15m³ / h. 3 / h.

[0053] Operation Process and Results: High-pressure wastewater enters the contraction section 1342 and is drawn into the throat section 1343, a high-pressure zone with a 300°C high-temperature mixed gas, through the injection hole. Through the coupling of bubble heat transfer kinetics and chemical reaction, pathogenic E. coli are completely inactivated within a short 5-minute hydraulic residence time. The PLC control cabinet dynamically adjusts the gas flow rate by receiving real-time temperature signals from K-type thermocouples, ensuring the gas-to-water ratio is maintained within the optimal disinfection range.

[0054] Example 4: Residue-free disinfection treatment of low-turbidity wastewater from food and beverage processing Background: Low-turbidity wastewater discharged from the cleaning section of a beverage processing plant. Because the food industry is extremely sensitive to chlorine disinfection residues, there is an urgent need for safe disinfection methods that leave no chemical residues and produce no harmful disinfection byproducts.

[0055] Parameter settings: 1) A high-concentration CO2 gas source is used, with the CO2 volume content in the input gas set to 80%; 2) Temperature and Inlet Water: The gas supply temperature is set at 250℃; the inlet water pressure is stabilized at 0.4MPa, and the single-unit processing flow rate is 5m³ / h. 3 / h, the hydraulic retention time is extended to 30 minutes to ensure absolute sterilization effect.

[0056] Operation Process and Effects: A large number of CO2 molecules penetrate the cell membranes of microorganisms, forming carbonic acid within the cells, lowering the pH value, and disrupting enzyme systems and genetic material. The localized high temperature and pressure generated when bubbles burst, along with hydroxyl free radicals, further enhance sterilization. The effluent bacterial inactivation rate remains consistently above 99.99%, and the water quality is pure with no chemical residues. The cooling water jacket and 20-30mm ceramic fiber insulation layer on the outside of the device ensure a safe external wall temperature, and the equipment integrates seamlessly with the existing factory piping network.

[0057] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this disclosure (including the claims) is limited to these examples; within the framework of this disclosure, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of this disclosure as described above, which are not provided in detail for the sake of brevity.

[0058] Although this disclosure has been described in conjunction with specific embodiments thereof, many substitutions, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description.

[0059] This disclosure is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A high-temperature CO2 micro / nano bubble wastewater treatment system, characterized in that, The device includes a CO2 supply unit, a heating unit, and a micro / nano bubble generating unit connected in sequence. The heating unit can heat the gas to 150-600°C. The gas includes at least the CO2 gas supplied by the CO2 supply unit. The micro / nano bubble generating unit includes an injection structure and a Venturi structure. The Venturi structure includes an inlet section, a contraction section, a throat section, an expansion section, a mixing section, a diffusion section, and an outlet section arranged in sequence along the water flow direction. One end of the injection structure is connected to the CO2 supply unit and the heating unit, and the other end of the injection structure is connected to the throat section.

2. The high-temperature CO2 micro-nano bubble wastewater treatment system according to claim 1, characterized in that, The CO2 supply unit is used to provide CO2, accounting for 5%-100% of the total gas volume, to the micro-nano bubble generating unit. When the percentage of CO2 gas provided by the CO2 supply unit to the total gas volume is less than 100%, nitrogen and / or air are added as supplementary gases.

3. The high-temperature CO2 micro-nano bubble wastewater treatment system according to claim 1, characterized in that, The contraction angle of the contraction section is 12-18°, the diameter of the throat section is 8-20mm, and the expansion angle of the expansion section is 8-12°.

4. The high-temperature CO2 micro-nano bubble wastewater treatment system according to claim 1, characterized in that, The micro / nano bubble generating unit also includes a shell sleeved on the outside of the Venturi structure. An annular gas collecting cavity is formed between the outer walls of the contraction section, the throat section, and the expansion section and the inner wall of the shell. At least one gas distribution ring is provided on the wall of the throat section. The gas distribution ring has an injection hole along the circumferential direction. The angle between the axis of the injection hole and the water flow direction in the throat section is 30-60°. The gas injection structure is connected to the throat section through the annular gas collecting cavity and the injection hole on the gas distribution ring.

5. The high-temperature CO2 micro-nano bubble wastewater treatment system according to claim 4, characterized in that, The micro-nano bubble generating unit also includes a temperature monitoring device, which is installed at one or more of the throat section, the annular gas collecting chamber, and the water outlet section.

6. The high-temperature CO2 micro-nano bubble wastewater treatment system according to claim 1, characterized in that, The inlet section includes an inlet grille and a submersible pump connected to each other. The inlet grille forms a streamlined trumpet-shaped inlet structure with a pore size of 5-15mm. The submersible pump is used to provide an inlet pressure of 0.1-0.6Mpa.

7. The high-temperature CO2 micro-nano bubble wastewater treatment system according to claim 1, characterized in that, The mixing section is 20-40 mm long, and the inner wall of the mixing section is provided with micro-turbulence teeth. The diffusion section includes a multi-stage metal cutting mesh and a spiral guide vane arranged sequentially in the cavity of the diffusion section. The cavity diameter of the diffusion section is 2-3 times larger than the outlet of the expansion section. The mesh size of the multi-stage metal cutting mesh decreases sequentially along the water flow direction.

8. The high-temperature CO2 micro-nano bubble wastewater treatment system according to claim 1, characterized in that, The inlet section, the contraction section, the throat section, the expansion section, the mixing section, and the diffusion section are coaxially arranged along a first central axis. The outlet section has a second central axis. The first central axis and the second central axis are perpendicular to each other. And / or the outlet section includes a microporous metal diffusion plate located at the outlet. The pore size of the microporous metal diffusion plate is 0.5-2mm.

9. A method for treating wastewater using the high-temperature CO2 micro / nano bubble wastewater treatment system as described in any one of claims 1-8, characterized in that, Includes the following steps: S1, CO2 gas is supplied using the CO2 supply unit; S2, using the heating unit to heat the gas to 150-600°C, wherein the gas includes at least the CO2 gas generated by the CO2 supply unit; S3, inject wastewater into the Venturi structure; S4, the heated gas is injected into the throat section through the gas injection structure, mixes with the wastewater in the throat section to form micro-nano bubbles, and flows sequentially through the expansion section, the mixing section, the diffusion section and the outlet section into the wastewater pool.

10. The method according to claim 9, characterized in that, The diameter of the micro-nano bubbles is 10-50 μm, and the density of the micro-nano bubbles is 1×10⁻⁶. 6 -1×10 8 The micro-nano bubbles have a transient thermal layer with a temperature of 70-150°C and a thickness of 40-200 nm.

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