Method for removing new pollutants through hydrodynamic cavitation of assisted enhanced mass transfer high-speed multiphase flow

Abstract

The invention relates to the technical field of water treatment, in particular to a method for removing new pollutants through hydrodynamic cavitation of auxiliary enhanced mass transfer high-speed multiphase flow. The method comprises the following steps: pumping pretreated wastewater containing new pollutants to an inlet of a reverse shearing mechanism, and generating initial-stage fluid with high-energy-density hydroxyl radicals by utilizing cavitation; the initial-section fluid is conveyed into the connecting pipeline and is fully disturbed and mixed with the fluid sprayed by the Venturi tube to generate high-speed multi-phase middle-section fluid; the middle-section fluid is conveyed to an inlet of a forward rotation shearing mechanism, and a tail-section fluid with a large number of hydroxyl free radicals which are evenly distributed is generated through cavitation; and the target pollutant concentration of the tail-section fluid is detected, and the steps are repeated or multiple stages of cavitation generation assemblies are added until the target pollutant concentration is smaller than or equal to a preset concentration value. Therefore, the hydrodynamic cavitation effect can be improved, the energy density of free radicals at an outlet is increased, and the mass transfer effect between pollutants and free radicals in wastewater is improved.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, in particular to a method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with auxiliary enhanced mass transfer. Background Art

[0002] With the rapid development of industry and the increasing frequency of human activities, the problem of new pollutants in wastewater has become increasingly prominent. New pollutants usually include perfluorinated or polyfluorinated compounds, microplastics, endocrine disruptors, drugs and personal care products. These new pollutants are characterized by a wide variety, wide sources, low environmental concentrations but great harm. In the past, wastewater treatment mainly focused on the removal of conventional pollutants such as chemical oxygen demand, ammonia nitrogen, total phosphorus, etc. However, the emergence of new pollutants poses a potential threat to the environment and human health. They may interfere with the endocrine system of organisms and affect reproductive development; they are bioaccumulative and can be transmitted in the food chain; they may even cause serious diseases such as cancer.

[0003] The treatment methods for new pollutants in wastewater are mainly divided into four categories: advanced oxidation technology, adsorption technology, membrane separation technology and biological treatment technology. Adsorption technology represented by activated carbon adsorption and ion exchange resin and membrane separation technology represented by reverse osmosis and nanofiltration only enrich new pollutants, and the adsorbed material or concentrate still needs further treatment. There are many types of new pollutants in wastewater, and biological treatment technology requires the screening of efficient and multifunctional degradation strains. In addition, many pollutants in wastewater are often highly toxic, and the adaptability and stability of microorganisms need to be improved. Advanced oxidation technology oxidizes and degrades new pollutants by producing strong oxidizing active species. It has strong oxidation ability and fast reaction speed. However, for low-concentration and high-stability new pollutants in wastewater, low-cost and high-efficiency advanced oxidation technology still needs to be further developed.

[0004] Hydrodynamic cavitation is an advanced oxidation technology. Its principle is to use pressure drop to release the gas dissolved in the fluid to produce a large number of cavitation bubbles. When the cavitation bubbles flow with the fluid to the high-pressure area, their volume will shrink sharply until they collapse, and local high temperature and high pressure will be generated in the extremely small space around them. Water molecules will be cracked into free radicals such as OH under the extreme environment of high temperature and high pressure, thus causing a series of oxidation reactions.

[0005] The hydraulic cavitation methods for wastewater treatment in the prior art are mostly based on venturi tubes or orifice plates, which have low cavitation intensity, small flow rate and poor reaction effect. Summary of the invention

[0006] The objects of the present invention include, for example, providing a method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with auxiliary enhanced mass transfer, which can improve the hydraulic cavitation effect, increase the outlet free radical energy density, and enhance the mass transfer effect between pollutants and free radicals in wastewater.

[0007] The embodiments of the present invention can be implemented as follows:

[0008] In a first aspect, the present invention provides a method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with auxiliary mass transfer enhancement. The method is based on a cavitation generating device, wherein the cavitation generating device comprises a multi-stage cavitation generating assembly arranged in series, wherein the cavitation generating assembly of each stage comprises a reverse shearing mechanism, a connecting pipe, and a forward shearing mechanism connected in sequence, wherein the connecting pipe is provided with a venturi tube arranged in an array; and the method comprises at least the following steps:

[0009] The pretreated wastewater containing new pollutants is pumped to the inlet of the reverse shear mechanism, and the wastewater is accelerated and pressurized by the reverse shear mechanism to form a high-speed multiphase flow, and cavitation occurs at the outlet of the reverse shear mechanism to generate a primary fluid with high energy density hydroxyl free radicals;

[0010] The initial stage fluid is transported to a connecting pipe having an array of venturi tubes, and is fully disturbed and mixed with the venturi tube jet fluid to generate a high-speed multiphase middle stage fluid;

[0011] The middle-stage fluid is transported to the inlet of the forward-rotating shear mechanism, the middle-stage fluid is further pressurized by the forward-rotating shear mechanism, and cavitation occurs at the outlet of the forward-rotating shear mechanism to generate a final-stage fluid having a large amount of evenly distributed hydroxyl radicals;

[0012] Detect the target pollutant concentration of the final fluid; when the target pollutant concentration is greater than a preset concentration value, repeat the above steps or add a multi-stage cavitation generating component until the target pollutant concentration is less than or equal to the preset concentration value.

[0013] In an alternative embodiment, the hydrodynamic cavitation effect is evaluated by the following formula:

[0014]

[0015] In the formula, C v is the dimensionless hydraulic cavitation number, P 2 is the fully restored downstream pressure, P v is the vapor pressure of the wastewater to be treated, v 0 is the velocity at the outlet of the cavitation structure, and ρ is the density of the wastewater to be treated;

[0016] Hydrodynamic cavitation number C v When the value is less than 1, cavitation will occur, C v The smaller it is, the better the cavitation effect is and the more cavitation bubbles are generated; C v The value is 0.1-0.3.

[0017] In an alternative embodiment, v 0It is regulated by the pumping flow rate and the rotation speed and number of stages of the cavitation generating structure;

[0018] P 2 Regulated by the inlet pressure of the cavitation generating structure and the diameter of the connecting pipe;

[0019] P v The amount of dissolved gas in the wastewater to be treated is regulated by changing the amount of dissolved gas in the wastewater to be treated by injecting fluid through a venturi tube;

[0020] Thus achieving C v Optimal value.

[0021] In an optional embodiment, the reverse shearing mechanism is a rotational contraction structure, the wastewater flows into the reverse shearing mechanism radially, and is ejected along the axial outlet after rotational contraction to generate hydroxyl radicals with high energy density.

[0022] In an optional embodiment, the forward shearing mechanism is a rotary diffusion structure, the wastewater flows into the forward shearing mechanism along the axial direction, and rotates and diffuses radially around the rotary acceleration port to generate a large amount of evenly distributed hydroxyl radicals.

[0023] In an optional embodiment, the total injection flow rate of the plurality of venturi tubes is 5%-10% of the wastewater flow rate in the connecting pipe;

[0024] The flow rate of the jet port of the venturi tube is 0.6-0.8 times the flow rate of the wastewater in the connecting pipe;

[0025] The angle between the injection direction of the venturi tube and the flow direction of the wastewater is 10-60°.

[0026] In an optional embodiment, in the connecting pipe, the fluid sprayed into the connecting pipe by the venturi tube may be at least one of a liquid, a gas or a mixture;

[0027] The liquid sprayed by the venturi tube includes circulating water and process water treated by the method;

[0028] The gas sprayed by the venturi tube includes any oxidizing gas such as air, oxygen, and ozone;

[0029] The mixture sprayed by the venturi tube includes any combination of the above-mentioned liquid and gas.

[0030] In an optional embodiment, a fluid flow is arranged in the inner wall of the connecting pipe upstream of the venturi tube;

[0031] After the wastewater flows through the vortex body, a vortex is formed, which can enhance the disturbance degree of the wastewater and increase the collision effect with the fluid sprayed by the venturi tube.

[0032] In an optional embodiment, in a multi-stage cavitation generating assembly, a forward shearing mechanism of the cavitation generating assembly is connected to a reverse shearing mechanism via a matching pipe; a plurality of venturi tubes are arranged in an array in the matching pipe.

[0033] In an optional embodiment, the cavitation generating device also includes a liquid storage tank, an inlet pipe, an outlet pipe, a bypass pipe, a bypass regulating valve and a pressure pump; the liquid storage tank is connected to the inlet of the multi-stage cavitation generating assembly through the inlet pipe, and the outlet of the multi-stage cavitation generating assembly is connected to the liquid storage tank through the outlet pipe; the pressure pump is arranged on the inlet pipe; the inlet of the bypass pipe is connected to the inlet pipe, the outlet of the bypass pipe is connected to the liquid storage tank, and the bypass regulating valve is arranged on the bypass pipe.

[0034] The beneficial effects of the embodiments of the present invention include, for example:

[0035] The method of removing new pollutants by hydraulic cavitation of high-speed multiphase flow with auxiliary enhanced mass transfer in this scheme is based on the characteristics of low concentration and strong stability of new pollutants in wastewater. The pretreated wastewater is pressurized and pumped into the inlet of the reverse shear mechanism. The wastewater containing new pollutants is accelerated and pressurized in the reverse shear mechanism to form a high-speed gas-liquid multiphase flow. Cavitation occurs at the outlet of the reverse shear mechanism and in the connecting pipe due to the pressure reduction to generate hydroxyl radicals with high energy density distribution, which are used for the removal of low-concentration new pollutants. Venturi tubes are arranged in the intermediate pipe array, and the Venturi effect is used to spray fluid into the intermediate pipe. The fluid sprayed at the outlet of the Venturi tube collides with the main fluid in the intermediate pipe to increase the mass transfer rate of free radicals and new pollutants in the wastewater, thereby achieving effective removal of low-concentration new pollutants in the wastewater, increasing the amount of gas dissolved in the wastewater, and improving the cavitation effect of the subsequent forward shear mechanism. Subsequently, the high-speed multiphase flow in the connecting pipe enters the forward shear mechanism, and a large number of evenly distributed hydroxyl radicals are formed at the diffusion outlet of the forward shear mechanism, which are used to remove conventional organic matter in the wastewater, and realize the coordinated treatment of multiple pollutants in the wastewater containing new pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 It is a structural schematic diagram of a cavitation generating device according to an embodiment of the present invention;

[0038] Figure 2 is the hydroxyl radical distribution diagram of Example 1 of the present invention;

[0039] Figure 3 This is the hydroxyl radical distribution diagram of Example 2 of the present invention;

[0040] Figure 4 The velocity field, mass transfer rate field, and cavitation rate distribution diagram of Example 3 of the present invention;

[0041] Figure 5 This is a distribution diagram of the eddy flow field formed by the wastewater flowing around the fluid in the intermediate pipe of Example 4 of the present invention;

[0042] Figure 6 The velocity field and pressure field distribution diagram of the wastewater flowing through the intermediate pipe of Example 5 of the present invention is generated by the vortex formed by the fluid flowing around the fluid and the collision with the fluid injected by the venturi tube;

[0043] Figure 7 This is a velocity field distribution diagram when no fluid flow and venturi tube are installed in the middle pipeline of comparative example 1 of the present invention.

[0044] Icons: 1-reverse shear mechanism; 2-reverse shear mechanism outlet pressure gauge; 3-flow body; 4-Venturi tube; 5-intermediate pipeline pressure gauge; 6-forward shear mechanism inlet pressure gauge; 7-forward shear mechanism; 8-forward shear mechanism outlet pressure gauge; 9-liquid storage tank; 10-boosting pump; 11-reverse shear mechanism inlet pressure gauge; 12-bypass regulating valve. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0046] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0048] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear to indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0049] In addition, the terms “first”, “second”, etc., if used, are merely used to distinguish between the descriptions and should not be understood as indicating or implying relative importance.

[0050] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0051] Please refer to Figure 1 This embodiment provides a method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with auxiliary mass transfer enhancement. The method is based on a cavitation generating device, which includes a multi-stage cavitation generating assembly arranged in series. Each stage of the cavitation generating assembly includes a reverse shearing mechanism 1, a connecting pipe, and a forward shearing mechanism 7 connected in sequence. The connecting pipe is provided with an array-arranged venturi tube 4. The method includes at least the following steps:

[0052] The pretreated wastewater containing new pollutants is pumped to the inlet of the reverse shear mechanism 1, and the wastewater is accelerated and pressurized by the reverse shear mechanism 1 to form a high-speed multiphase flow, and cavitation occurs at the outlet of the reverse shear mechanism 1 to generate an initial fluid with high energy density hydroxyl free radicals;

[0053] The initial stage fluid is transported to a connecting pipe having an array of venturi tubes 4, and is fully disturbed and mixed with the venturi tube jet fluid to generate a high-speed multiphase middle stage fluid, which is then output from the outlet of the connecting pipe;

[0054] The middle-stage fluid is transported to the inlet of the forward-rotating shear mechanism 7, and the forward-rotating shear mechanism 7 is used to further pressurize the middle-stage fluid, and cavitation occurs at the outlet of the forward-rotating shear mechanism 7 to generate a final-stage fluid having a large amount of evenly distributed hydroxyl radicals;

[0055] Detect the target pollutant concentration of the final fluid; when the target pollutant concentration is greater than the preset concentration value, repeat the above steps or add multiple cavitation generating components until the target pollutant concentration is less than or equal to the preset concentration value.

[0056] It should be noted that in the middle pipe, the venturi tubes 4 arranged in an array around the middle pipe are used to spray fluid into the wastewater containing new pollutants to be treated by using the venturi effect, and the fluid at the outlet of the venturi tube 4 collides and mixes with the high-speed wastewater in the connecting pipe, increasing the degree of disturbance of the wastewater, improving the mass transfer rate, and increasing the amount of air dissolved, so as to enhance the cavitation effect and the pollutant removal efficiency. In this way, the decontamination effect is guaranteed.

[0057] The forward shearing mechanism 7 further pressurizes the gas-liquid mixed high-speed wastewater, and cavitation occurs at the outlet to generate a large number of evenly distributed hydroxyl radicals to remove various organic matter. The reverse shearing mechanism 1 and the forward shearing mechanism 7 cooperate to complete the decontamination operation in a timely and efficient manner.

[0058] from Figure 1 It can also be seen that in an optional embodiment, the cavitation generating device also includes a liquid storage tank 9, an inlet pipe, an outlet pipe, a bypass pipe, a bypass regulating valve 12 and a pressure pump 10; the liquid storage tank 9 is connected to the inlet of the multi-stage cavitation generating assembly through the inlet pipe, and the outlet of the multi-stage cavitation generating assembly is connected to the liquid storage tank 9 through the outlet pipe; the pressure pump 10 is arranged on the inlet pipe; the inlet of the bypass pipe is connected to the inlet pipe, the outlet of the bypass pipe is connected to the liquid storage tank 9, and the bypass regulating valve 12 is arranged on the bypass pipe.

[0059] Furthermore, the cavitation generating device also includes a reverse shear mechanism outlet pressure gauge 2, an intermediate pipeline pressure gauge 5, a forward shear mechanism inlet pressure gauge 6, a forward shear mechanism outlet pressure gauge 8 and a reverse shear mechanism inlet pressure gauge 11.

[0060] The outlet pressure gauge 2 of the reverse shearing mechanism is arranged on the end of the intermediate pipeline close to the reverse shearing mechanism 1, and the intermediate pipeline pressure gauge 5 is arranged on the intermediate pipeline; the inlet pressure gauge 6 of the forward shearing mechanism is arranged on the end of the intermediate pipeline close to the forward shearing mechanism 7, the inlet pressure gauge 11 of the reverse shearing mechanism is arranged on the inlet pipe, and the outlet pressure gauge 8 of the forward shearing mechanism is arranged on the outlet pipe.

[0061] In an optional embodiment, in a multi-stage cavitation generating assembly, the forward shearing mechanism 7 of a cavitation generating assembly is connected to the reverse shearing mechanism 1 through a matching pipe; a plurality of venturi tubes 4 are arranged in an array in the matching pipe. It should be noted that, optionally, the matching pipe and the connecting pipe have the same structure, and the venturi tubes arranged in an array are also the same, which is only used to distinguish the internal pipe of the cavitation generating assembly from the pipe connecting the adjacent cavitation generating assemblies.

[0062] In an alternative embodiment, the hydrodynamic cavitation effect is evaluated by the following formula:

[0063]

[0064] In the formula, C vis the dimensionless hydraulic cavitation number, P 2 is the fully restored downstream pressure, P v is the vapor pressure of the wastewater to be treated, v 0 is the velocity at the outlet of the cavitation generating structure (the cavitation generating structure here refers to the forward cavitation mechanism 7 or the reverse cavitation mechanism 1, the same below, no further description is given), ρ is the density of the wastewater to be treated;

[0065] Hydrodynamic cavitation number C v When the value is less than 1, cavitation will occur, C v The smaller it is, the better the cavitation effect is and the more cavitation bubbles are generated; C v The value is 0.1-0.3.

[0066] It should be noted that in order to ensure the number of cavitations generated and the strength of cavitation collapse and to avoid blockage caused by super cavitation, C v The value is 0.1-0.3. By adjusting the corresponding parameters, the hydraulic cavitation effect can be guaranteed, thereby ensuring the decontamination effect.

[0067] Furthermore, 0 It is regulated by the pumping flow rate (i.e., the pumping flow rate of the booster pump 10, the same below, no further details) and the rotation speed and number of stages of the cavitation generating structure (i.e., the number of shear wheel groups in the forward cavitation mechanism 7 and the reverse cavitation mechanism 1, the same below, no further details); P 2 Adjusted by the inlet pressure of the cavitation generating structure and the diameter of the connecting pipe; P v The venturi tube 4 injects fluid to change the amount of gas dissolved in the wastewater to be treated; thereby achieving C v Optimal value.

[0068] In an optional embodiment, the reverse shearing mechanism 1 is a rotational contraction structure, and the wastewater flows into the reverse shearing mechanism 1 radially, and is ejected along the axial outlet after rotational contraction to generate hydroxyl radicals with high energy density.

[0069] In an optional embodiment, the forward shearing mechanism 7 is a rotating diffusion structure, and the wastewater flows into the forward shearing mechanism 7 along the axial direction, and rotates and diffuses radially around the rotating acceleration port to generate a large amount of evenly distributed hydroxyl radicals.

[0070] In an optional embodiment, the total injection flow rate of the multiple venturi tubes 4 is 5%-10% of the wastewater flow rate in the connecting pipeline;

[0071] The flow rate of the jet port of the venturi tube 4 is 0.6-0.8 times the flow rate of the wastewater in the connecting pipe;

[0072] The angle between the injection direction of the venturi tube 4 and the flow direction of the wastewater is 10-60°.

[0073] In an optional embodiment, in the connecting pipe, the fluid sprayed by the venturi tube 4 into the connecting pipe may be at least one of a liquid, a gas or a mixture; the type and flow rate of the fluid sprayed in each venturi tube 4 may be different;

[0074] The liquid sprayed by the venturi tube 4 includes the circulating water and process water treated by the method;

[0075] The gas ejected by the venturi tube 4 includes any oxidizing gas such as air, oxygen, or ozone;

[0076] The mixture sprayed by the venturi tube 4 includes any combination of the above-mentioned liquid and gas.

[0077] from Figure 1 It can also be seen that in an optional embodiment, a flow body 3 is arranged upstream of the venturi tube 4 in the inner wall of the connecting pipe; after the wastewater flows through the flow body 3, a vortex is formed, which can enhance the disturbance degree of the wastewater and increase the collision effect with the fluid sprayed by the venturi tube 4.

[0078] Furthermore, the above-mentioned reverse shear mechanism 1, the fluid flow 3, the venturi tube 4 and the forward shear mechanism 7 constitute a set of Venturi effect assisted cavitation generating structural components. When considering shortening the processing time or improving the processing effect, the number of series-connected components can be increased. When multiple sets of Venturi effect assisted cavitation generating structural components are arranged in series, the outlet of the forward shear mechanism 7 of the previous stage is connected to the inlet of the reverse shear mechanism 1 of the next stage, and the intermediate pipeline between the two stages of components is also arranged with the venturi tube 4 in an array.

[0079] Example 1

[0080] Using a method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with assisted mass transfer enhancement provided in a specific embodiment, ANSYS software was used to perform fluid mechanics simulation on the distribution of hydroxyl radicals at the outlet of the reverse shear mechanism 1. The results are as follows: Figure 2 As shown. It can be seen that the maximum volume fraction of hydroxyl radicals at the outlet of the reverse shear mechanism 1 is about 8.4%, but the radicals are concentrated and have a higher energy density, which can be used to remove new pollutants with low concentration and strong stability in wastewater.

[0081] Example 2

[0082] Other conditions are the same as those in Example 1. The ANSYS software is used to perform fluid dynamics simulation on the hydroxyl radical distribution at the outlet of the forward shear mechanism 7. The results are as follows: Figure 3 It can be seen that the maximum volume fraction of hydroxyl radicals at the outlet of the forward shear mechanism 7 is about 27.3%, the amount of hydroxyl radicals generated is large and evenly distributed, and can be used to remove difficult conventional organic pollutants.

[0083] Example 3

[0084] The conditions are the same as those in Example 2. The outlet velocity field, mass transfer rate field and cavitation rate distribution of the forward shear mechanism 7 are as follows: Figure 4 It can be seen that the maximum cavitation rate at the outlet of the forward shear mechanism 7 reaches 81.06%, and the average cavitation rate is 24.81%, which is significantly higher than the cavitation rate reported in the prior art. In addition, there is a strong mass transfer rate region at the diffusion outlet, which is conducive to the reaction between the hydroxyl radicals generated by cavitation and various organic substances.

[0085] Example 4

[0086] Other conditions are the same as those in Example 1. When the high-speed wastewater at the outlet of the reverse shearing mechanism 1 flows through the fluid 3 in the intermediate pipe, the flow field changes as follows: Figure 5 As shown. Downstream of the fluid 3, the high-speed wastewater in the middle pipe generates obvious vortices, which increases the disturbance degree of the fluid. When the venturi tube 4 is used to spray the fluid, the fluid at the outlet of the venturi tube 4 will collide with the vortex of the main fluid in the middle pipe, increasing the mixing effect, improving the mass transfer rate between free radicals and pollutants, and increasing the amount of gas dissolved in the wastewater to be treated, thereby improving the cavitation effect of the subsequent forward shear mechanism 7.

[0087] Example 5

[0088] The other conditions are the same as those in Example 4. The fluid injected by the venturi tube 4 is the circulating water, the injection amount is 10% of the wastewater flow rate, the flow rate is 0.8 of the wastewater flow rate, the injection direction and the wastewater flow direction have an angle of 30°, and the high-speed wastewater at the outlet of the reverse shear mechanism 1 flows around the fluid 3 in the middle pipe and collides with the fluid injected by the venturi tube 4. The velocity cloud diagram and pressure cloud diagram of the mixed fluid in the pipe are as follows: Figure 6 As shown. From the velocity cloud map, it can be seen that the vortex formed after the wastewater flows through the body 3 collides with the fluid sprayed obliquely into the middle pipe by the Venturi tube 4, and mixing occurs downstream. From the pressure cloud map, it can be seen that after the fluid sprayed by the Venturi tube 4 collides with the high-speed wastewater, the energy is dissipated downstream to generate a low-pressure area, and the pressure drop contributes to the occurrence of cavitation. In general, the vortex formed after the wastewater flows through the body 3 collides with the fluid sprayed by the Venturi tube 4 to achieve a good mixing effect.

[0089] Comparative Example 1

[0090] Other conditions are the same as those in Example 5. The intermediate pipeline is not equipped with the flow body 3 and the venturi tube 4. The flow field distribution of the wastewater to be treated from the outlet of the reverse shearing mechanism 1 to the intermediate pipeline is as follows: Figure 7 As shown, the flow velocity of the wastewater to be treated gradually decreases from the outlet of the reverse shear mechanism 1 to the middle pipe, and the flow field distribution is continuous without obvious disturbance. Under this working condition, the mass transfer rate between free radicals and pollutants in the wastewater is low, and the cavitation effect is poor.

[0091] In summary, the embodiments of the present invention provide a method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with enhanced mass transfer, which has at least the following advantages:

[0092] (1) The present invention proposes a method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with auxiliary enhanced mass transfer, which utilizes the Venturi effect to spray fluid into wastewater and collide with the high-speed wastewater in the middle pipe at the outlet of the reverse shear mechanism 1, thereby enhancing the disturbance degree of the wastewater, increasing the mass transfer rate, improving the removal effect of new pollutants, and increasing the amount of gas dissolved, so as to enhance the cavitation effect of the subsequent forward shear mechanism 7.

[0093] (2) The contraction form of the reverse shear mechanism 1 is utilized to form high-energy-density hydroxyl radicals to remove new pollutants with strong stability and low concentration. The diffusion outlet of the forward shear mechanism 7 is coordinated to form a large number of evenly distributed hydroxyl radicals to remove the interference of conventional high-difficulty organic matter, thereby achieving coordinated and efficient treatment of wastewater containing low-concentration new pollutants with a large treatment flux.

[0094] (3) By utilizing the array-arranged Venturi tubes 4, the wastewater in the middle pipe can be sprayed and collided with each other by using various fluids such as air, oxygen, ozone, circulating treated water, treated process water, etc., with different combinations, flow rates, and flow velocities, to achieve the purpose of enhancing mass transfer by the Venturi effect. This method is flexible, simple, convenient, and easy to adjust.

[0095] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with enhanced mass transfer, the method is based on a cavitation generating device, the cavitation generating device comprises a multi-stage cavitation generating assembly arranged in series, each stage of the cavitation generating assembly comprises a reverse shear mechanism (1), a connecting pipe, and a forward shear mechanism (7) connected in sequence, the connecting pipe is provided with an array-arranged venturi tube (4); characterized in that At least the following steps are included: The pre-treated wastewater containing new pollutants is pumped to the inlet of the reverse shear mechanism (1), and the wastewater is accelerated and pressurized by the reverse shear mechanism (1) to form a high-speed multiphase flow, and cavitation occurs at the outlet of the reverse shear mechanism (1) to generate a primary fluid with high energy density hydroxyl free radicals; The initial stage fluid is transported to a connecting pipe having an array of venturi tubes (4), and is fully disturbed and mixed with the fluid ejected by the venturi tubes (4) to generate a high-speed multiphase middle stage fluid; The middle-stage fluid is transported to the inlet of the forward-rotating shear mechanism (7), the forward-rotating shear mechanism (7) is used to further pressurize the middle-stage fluid, and cavitation occurs at the outlet of the forward-rotating shear mechanism (7) to generate a final-stage fluid having a large amount of evenly distributed hydroxyl radicals; detecting a target pollutant concentration of the final fluid; When the target pollutant concentration is greater than the preset concentration value, the above steps are repeated or multiple cavitation generating components are added until the target pollutant concentration is less than or equal to the preset concentration value.

2. The method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with assisted mass transfer enhancement according to claim 1, characterized in that: The hydrodynamic cavitation effect is evaluated by the following formula: In the formula, C v is the dimensionless hydraulic cavitation number, P2 is the fully restored downstream pressure, P v is the vapor pressure of the wastewater to be treated, v0 is the velocity at the outlet of the cavitation structure, and ρ is the density of the wastewater to be treated; Hydrodynamic cavitation number C v When the value is less than 1, cavitation will occur, C v The smaller it is, the better the cavitation effect is and the more cavitation bubbles are generated; C v The value is 0.1-0.

3.

3. The method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with assisted mass transfer enhancement according to claim 2, characterized in that: v0 is adjusted by the pumping flow rate and the speed and number of stages of the cavitation generating structure; P2 is adjusted by the inlet pressure of the cavitation generating structure and the diameter of the connecting pipe; P v The amount of dissolved gas in the wastewater to be treated is regulated by injecting fluid through the venturi tube (4); Thus achieving C v Optimal value.

4. The method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with assisted mass transfer enhancement according to claim 1, characterized in that: The reverse shearing mechanism (1) is a rotational contraction structure. Wastewater flows into the reverse shearing mechanism (1) in a radial direction and is ejected along an axial outlet after rotational contraction, thereby generating hydroxyl radicals with high energy density.

5. The method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with assisted mass transfer enhancement according to claim 1, characterized in that: The forward shearing mechanism (7) is a rotational diffusion structure. Wastewater flows into the forward shearing mechanism (7) along the axial direction and rotates and diffuses radially around the rotational acceleration port to generate a large amount of evenly distributed hydroxyl radicals.

6. The method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with assisted mass transfer enhancement according to claim 1, characterized in that: The total injection flow rate of the plurality of venturi tubes (4) is 5%-10% of the wastewater flow rate in the connecting pipeline; The flow rate of the jet outlet of the venturi tube (4) is 0.6-0.8 times the flow rate of the wastewater in the connecting pipe; The angle between the injection direction of the Venturi tube (4) and the flow direction of the wastewater is 10-60°.

7. The method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with assisted mass transfer enhancement according to claim 6, characterized in that: In the connecting pipe, the fluid sprayed into the connecting pipe by the venturi tube (4) may be at least one of a liquid, a gas or a mixture; The liquid sprayed by the venturi tube (4) includes circulating water and process water treated by the method; The gas ejected by the venturi tube (4) includes any oxidizing gas such as air, oxygen and ozone; The mixture sprayed by the venturi tube (4) includes any combination of the above-mentioned liquid and gas.

8. The method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with assisted mass transfer enhancement according to claim 1, characterized in that: A fluid flow (3) is arranged in the inner wall of the connecting pipe upstream of the venturi tube (4); After the wastewater flows through the vortex body (3), a vortex is formed, which can enhance the disturbance degree of the wastewater and increase the collision effect with the fluid sprayed by the venturi tube (4).

9. The method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with assisted mass transfer enhancement according to claim 1, characterized in that: In a multi-stage cavitation generating assembly, a forward shearing mechanism (7) of the cavitation generating assembly is connected to a reverse shearing mechanism (1) via an intermediate pipe; a plurality of venturi tubes (4) are arranged in an array in the intermediate pipe.

10. The method for removing new pollutants by hydraulic cavitation of high-speed multiphase flow with assisted mass transfer enhancement according to claim 9, characterized in that: The cavitation generating device further comprises a liquid storage tank (9), an inlet pipe, an outlet pipe, a bypass pipe, a bypass regulating valve (12) and a pressure pump (10); the liquid storage tank (9) is connected to the inlet of the multi-stage cavitation generating assembly via the inlet pipe, and the outlet of the multi-stage cavitation generating assembly is connected to the liquid storage tank (9) via the outlet pipe; the pressure pump (10) is arranged on the inlet pipe; the inlet of the bypass pipe is connected to the inlet pipe, the outlet of the bypass pipe is connected to the liquid storage tank (9), and the bypass regulating valve (12) is arranged on the bypass pipe.

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