A microwave catalytic oxidation water treatment method and treatment device

Abstract

The present invention relates to a microwave catalytic oxidation water treatment method and treatment device, belonging to the technical field of sewage treatment. The treatment device of the present invention comprises a mixing tank, an oxidation tank, a solid-liquid separator, a microwave reaction tank, a metal shell covered outside the microwave reaction tank, and a microwave generating device. A stirring device is arranged inside the microwave reaction tank; a vacuum pump provides vacuum for the microwave reaction tank, and the microwave generating device provides a stable and uniform microwave field for the wastewater reaction; the sewage is catalytically oxidized under microwave and vacuum conditions. The present invention can shorten the catalytic oxidation reaction time and reduce the catalytic oxidation reaction temperature, greatly improving the efficiency of microwave sewage treatment, and the treatment temperature only needs to be controlled at 30-40°C, solving the technical problem that the catalyst needs to be at high temperature to exert a better catalytic effect.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a microwave catalytic oxidation water treatment method and a treatment device. Background Art

[0002] The main pollutants in wastewater include organic matter, ammonia nitrogen, total nitrogen, total phosphorus, heavy metals, etc. Organic matter is of various types and complex structure, which is very harmful to water bodies. If it is discharged directly without treatment, it will consume the dissolved oxygen in the water, resulting in hypoxia in the water. At the same time, corruption and fermentation will occur, causing bacteria to grow, deteriorating water quality, destroying water bodies, and thus endangering aquatic life. Organic pollutants in industrial water will also reduce the quality of products.

[0003] In the current sewage treatment technology, the commonly used methods for removing organic matter are: biological treatment, adsorption, membrane separation technology, chemical oxidation and advanced oxidation. The chemical oxidation method is to add oxidants such as ozone and H2O2 to cause organic matter to undergo oxidation reaction, and convert inorganic pollutants into harmless substances. The chemical oxidation method has a significant effect in removing difficult-to-degrade organic matter and toxic substances, but it has disadvantages such as slow reaction rate, incomplete reaction and low reaction efficiency. The reaction rate can be accelerated and the energy required for the reaction can be reduced by adding a catalyst. However, the catalytic reaction is affected by temperature, pressure, substance concentration, etc. The catalyst shows a better catalytic oxidation effect under high temperature environmental conditions. The use of traditional heating methods has problems such as high energy consumption, slow heating rate, long treatment cycle and high treatment cost.

[0004] Studies have shown that using chemical oxidation to treat sewage under microwave conditions, using microwaves to act on catalysts and their carriers to create active sites on the surface of the porous carrier, can accelerate the catalytic oxidation reaction and improve the sewage treatment effect. However, in order to ensure the efficiency of the catalyst, this method still requires a higher temperature, and there are problems such as uneven microwave fields and excessive energy consumption. Summary of the invention

[0005] In view of the shortcomings of the existing chemical oxidation technology, the present invention proposes a microwave catalytic oxidation water treatment method and equipment. By improving the microwave reaction equipment and using vacuum conditions, the catalytic oxidation reaction time is shortened and the catalytic oxidation reaction temperature is reduced, which greatly improves the efficiency of microwave sewage treatment. The treatment temperature only needs to be controlled at 30-40°C, solving the technical problem that the catalyst needs to be at high temperature to exert a better catalytic effect.

[0006] To achieve the above-mentioned purpose, the present invention provides a microwave catalytic oxidation water treatment method and a microwave catalytic oxidation water treatment device.

[0007] The microwave catalytic oxidation water treatment method is as follows: adding a catalyst and an oxidant to the wastewater, carrying out a microwave reaction in a microwave water treatment device, controlling the microwave reaction temperature to 30-40°C, and the reaction pressure to -90--70KPa; the catalyst is adsorbed on a carrier for use, the catalyst is FeSO4, MnO2 or NiO2, and the carrier is activated carbon, SiC or diatomaceous earth;

[0008] The microwave water treatment device comprises a microwave reaction tank, a metal shell covering the outside of the microwave reaction tank, a microwave generating device and a vacuum pump; the tank body of the microwave reaction tank is made of plastic material and is equipped with a stirring device; the microwave generating device forms a uniform and controllable microwave field in the microwave water treatment device, and the vacuum pump provides vacuum reaction conditions for the microwave reaction tank.

[0009] Furthermore, the aspect ratio of the microwave reaction tank is 2:1 to 4:1.

[0010] Furthermore, the amount of oxidant, carrier and oxidant was controlled according to the COD content in the wastewater. The mass ratio of catalyst to COD in the wastewater was (1-3):1, the mass ratio of carrier to COD in the wastewater was (4-5):1, the mass ratio of oxidant to COD in the wastewater was (5-8):1, and the microwave intensity was 0.6-1.2 W / cm 2 , the microwave reaction time is 10 to 15 minutes.

[0011] Furthermore, the microwave catalytic oxidation water treatment method comprises the following steps:

[0012] (1) mixing wastewater and a powdered carrier loaded with a catalyst in a mixer;

[0013] (2) adding an oxidant to the wastewater;

[0014] (3) Microwave reaction of wastewater;

[0015] (4) Adding flocculation and liquid-solid separation to wastewater;

[0016] (5) The supernatant produced by liquid-solid separation is returned to step (2), and the solid portion is returned to step (1) after drying;

[0017] (6) After solid-liquid separation, the clean water is reused or discharged in compliance with the discharge standards.

[0018] Furthermore, the wastewater stays in the mixing tank of step (1) for 10 to 30 minutes; and the mixing time with the oxidant in step (2) is 10 to 30 minutes.

[0019] The microwave catalytic oxidation water treatment device comprises a mixing tank, an oxidation tank, microwave water treatment equipment and a solid-liquid separator; the microwave water treatment equipment comprises a microwave reaction tank, a metal shell covered outside the microwave reaction tank, a microwave generator, a waveguide tube and a vacuum pump; the microwave reaction tank is made of plastic; one end of the waveguide tube is connected to the microwave generator and the other end is connected to the metal shell, and the waveguide tube is made of metal; a stirring device is arranged in the microwave reaction tank; the vacuum pump is connected to the microwave reaction tank shell through a vacuum tube; the mixing tank and the oxidation tank are connected through a pipeline; the oxidation tank and the microwave reaction tank are connected through a water inlet pump and a pipeline; the microwave reaction tank and the solid-liquid separator are connected through a pipeline; a carrier loaded with a catalyst is added into the mixing tank; and the oxidation tank is equipped with an oxygen generator or an oxidant adding device.

[0020] Furthermore, the microwave reaction tank is provided with a liquid level meter and a temperature sensor.

[0021] Furthermore, the microwave water treatment equipment also includes a condensate circulation pump; the condensate circulation pump draws water from the condensate tank through the condensate circulation pipe to cool the radiator of the microwave generator.

[0022] Furthermore, the solid-liquid separator is a tank structure, which is provided with a central tube and a stirring device; the stirring device is arranged in the central tube; a filtering filler layer is provided between the central tube and the outer tube, and a cofferdam is provided on the inner wall of the outer tube, and its clean water outlet is opened in the cofferdam area; the water inlet of the microwave reaction tank and the solid-liquid separator is connected to the central tube.

[0023] Furthermore, a buffer tank is provided between the microwave water treatment equipment and the solid-liquid separator.

[0024] Beneficial effects of the present invention:

[0025] The water treatment device of the present invention can realize microwave oxidation reaction under vacuum conditions, reduce the COD catalytic oxidation decomposition temperature, shorten the catalytic oxidation time, and improve the catalytic oxidation decomposition efficiency of COD in sewage. Moreover, the treatment temperature only needs to be controlled at 30-40°C, which solves the technical problem that the catalyst needs to be at high temperature to exert a better catalytic effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a wastewater treatment process flow chart of the present invention;

[0027] Figure 2 It is a diagram of a wastewater treatment device of the present invention;

[0028] In the figure, 1 is a mixing tank, 2 is an agitator, 3 is a catalyst and its carrier, 4 is an oxidation tank, 5 is an oxidant generator, 6 is a water inlet pump, 7 is a metal shell, 8 is a microwave generator, 9 is a waveguide, 10 is a microwave catalytic oxidation reactor, 11 is an exhaust device, 12 is a liquid level meter, 13 is a temperature sensor, 14 is a condensate circulation pump, 15 is a condenser, 16 is a solid-liquid separator, 17 is a vacuum pump, 18 is an aeration pipe, 19 is a central tube, 20 is a filter packing layer, and 21 is a cofferdam. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0030] In order to more clearly illustrate the present invention, it is described in detail through the following examples.

[0031] Example 1

[0032] A microwave catalytic oxidation water treatment device comprises a mixing tank 1, an oxidation tank 4, microwave water treatment equipment and a solid-liquid separator 16.

[0033] The microwave water treatment equipment comprises a microwave reaction tank 10, a rectangular metal shell 7 covering the outside of the microwave reaction tank, a microwave generator 8, a waveguide 9, a vacuum pump 17 and a condensed water circulation pump 14. The waveguide 9 is connected between the microwave generator 8 and the metal shell 7, and the metal shell plays a role in preventing microwave leakage. The tank body of the microwave reaction tank 10 is made of plastic material, which allows microwaves to pass through.

[0034] The microwaves emitted by the microwave generator 8 are transmitted to the microwave reaction tank 10 through the waveguide 9. The rectangular metal shell 7 reflects the microwaves multiple times to form a high-frequency electromagnetic field, which continuously oscillates within the metal shell 7 to form a high-energy microwave resonance zone, providing a stable and uniform microwave field for the wastewater reaction and enhancing the efficiency of the microwave oxidation reaction in the microwave reaction tank 10.

[0035] As a preferred solution, the height-to-diameter ratio of the microwave reaction tank 10 is designed to be 2:1 to 4:1. Under this height-to-diameter ratio, wastewater flows into the reaction tank from the upper part and flows out from the lower part. The larger the height-to-diameter ratio, the longer the path through which the wastewater flows, the more fully the microwave radiation energy is absorbed, the better the mass transfer effect, the more thorough the reaction, and the higher the treatment efficiency.

[0036] Since microwaves have poor penetration into liquids (less than 5 cm), a stirring device is provided in the microwave reaction tank 10 so that the wastewater can evenly absorb microwave radiation energy, react more fully, and allow the microwave energy to act on the wastewater more effectively.

[0037] The vacuum pump 17 is connected to the metal shell 7 through a vacuum tube to provide the required vacuum field for the microwave reaction. The vacuum degree during the reaction process is controlled to be -90 to -70 KPa.

[0038] The mixing tank 1 and the oxidation tank 4 are connected through a pipeline; the oxidation tank 4 and the microwave reaction tank 10 are connected through a water inlet pump 6 and a pipeline, and the microwave reaction tank 10 and the solid-liquid separator 16 are connected through a pipeline.

[0039] The carrier 3 carrying the catalyst is added into the mixing tank 1; the oxidation tank 4 is equipped with an oxidant generator 5 or an oxidant (hydrogen peroxide) adding device, the oxidant generator 5 can be an oxygen generator or an ozone generator, and the oxidant generator 5 is equipped with an aeration pipe 18, and oxygen or ozone is provided to the oxidation tank 4 through the oxidant generator 5 and the aeration pipe 18.

[0040] A liquid level meter 12 and a temperature sensor 13 are provided in the microwave reaction tank 10 for detecting the temperature and liquid level of the microwave reaction.

[0041] The microwave generator 8 is equipped with a condensate circulation pump 14 and a condensate circulation pipe 15 for cooling the microwave generator 8 .

[0042] The solid-liquid separator 16 is a tank structure, which is provided with a central tube 19 and a stirring device 2; the stirring device 2 is arranged in the central tube 19; a filtering packing layer 20 is provided between the central tube 19 and the outer tube, and a cofferdam 21 is provided on the inner wall of the outer tube, and its clean water outlet is opened in the cofferdam area; the water inlet of the microwave reaction tank 10 and the solid-liquid separator 16 is connected to the central tube 19.

[0043] As an alternative, a buffer tank is provided between the microwave water treatment equipment and the solid-liquid separator 16 .

[0044] Example 2

[0045] A microwave catalytic oxidation water treatment method, using the equipment described in Example 1 to treat wastewater, comprises the following steps:

[0046] (1) Mixing the wastewater and the catalyst-loaded powdered carrier in a mixing tank 1, and allowing the wastewater to stay in the mixing tank 1 for 10 to 15 minutes by controlling the water inlet and outlet, so that the wastewater and the catalyst-loaded carrier are fully and evenly mixed in the mixing tank 1.

[0047] The catalyst uses FeSO4, MnO2 or NiO2. These transition metal elements are cheap, biocompatible, highly catalytic and stable. The carrier is powdered activated carbon, SiC or diatomaceous earth. These three carriers have good microwave absorption performance and a sponge-like porous structure on the surface. They have good adsorption performance and can absorb organic matter, pigments, odors and some metal ions in wastewater. The carrier has good stability and will not cause secondary pollution.

[0048] (2) The wastewater is sent to the oxidation tank 4, and the wastewater continuously flows in and out of the oxidation tank 4. The wastewater is kept in the oxidation tank 4 for 10 to 15 minutes by controlling the water volume of the water inlet and outlet, so that the wastewater, the powder carrier and the oxidant are fully contacted and evenly mixed in the oxidation tank 4.

[0049] The oxidant of the present invention can be O2, O3, air or H2O2. These oxidants have strong oxidizing properties, are green and environmentally friendly, and will not cause secondary pollution. Oxygen has a high electronegativity, and by providing sufficient oxygen molecules, the rate and efficiency of the oxidation reaction can be increased.

[0050] (3) The wastewater is pumped into the microwave water treatment equipment through the water inlet pump for chemical reaction under microwave conditions.

[0051] In the microwave water treatment equipment, organic pollutants in wastewater react with catalysts and oxidants quickly and efficiently under microwave radiation, and catalytic oxidation reactions also proceed vigorously on carriers with adsorption, condensation and strong wave absorption functions. Microwaves can drive reactions that cannot occur under traditional heating methods, making chemical oxidation reactions faster and more efficient.

[0052] Finally, the organic pollutants in the wastewater are decomposed into harmless inorganic substances such as H2O and CO2 during the catalytic oxidation process of microwave radiation. The inventors have found through a large number of experimental studies that microwave reaction under vacuum conditions can produce obvious microwave non-thermal effects, allowing the oxidation reaction to proceed rapidly at 30-40°C, greatly shortening the reaction time and reducing energy consumption.

[0053] (4) PAM (anionic polyacrylamide) is added to the effluent of the microwave reactor and enters the solid-liquid separator for flocculation reaction to form flocs, and then liquid-solid separation is performed. The powdered carrier of the present invention can also play a flocculation role, and only one flocculant needs to be added. The water temperature has a great influence on the flocculation effect of the flocculant, and 20-30°C is most suitable. Too high a temperature will make the formed flocs small, increase the moisture content of the sludge, and make it difficult to handle. Too low a water temperature will affect the flocculation effect and prolong the flocculation time. The present invention uses microwave reaction under vacuum conditions, which not only improves the efficiency of microwave reaction, but also reduces the active temperature of the catalyst, so that the temperature of the wastewater after microwave oxidation reaction is closer to the optimal flocculation temperature.

[0054] Although the present invention reduces the reaction temperature of sewage by microwave oxidation reaction under vacuum conditions, actual tests have shown that when PAM flocculant is used for flocculation, the water temperature after microwave reaction will affect the flocculation effect. Therefore, a buffer tank (underground tank) is provided between the microwave water treatment equipment and the solid-liquid separator 16. The sewage is transferred through the buffer tank and then sent to the solid-liquid separator 16, which can reduce the sewage temperature to 20-30°C, obtain better flocculation and sedimentation effect, reduce the amount of flocculant used and improve the solid-liquid separation effect.

[0055] The wastewater first enters the central tube 19, and a stirring device 2 is provided on the upper part of the central tube 19. PAM is added from the upper hole of the central tube 19 for coagulation reaction. After the reaction is completed, larger flocs are formed and sink to the bottom of the pool to form sludge, which is finally discharged into the sludge pool. The supernatant is discharged from the upper outlet of the solid-liquid separator, and the solid-liquid separation is completed.

[0056] (5) The supernatant produced by liquid-solid separation is returned to step (2), and the solid portion is returned to step (1) after drying.

[0057] (6) After solid-liquid separation, the clean water is reused or discharged in compliance with the discharge standards.

[0058] The separated sludge is mainly inorganic sludge that has been sterilized by microwave radiation, so it can be driven into a dryer for drying and then partially returned to the mixing tank for recycling as a catalyst carrier.

[0059] Production Application:

[0060] Application Example 1

[0061] The treatment process of Example 2 was adopted, the catalyst used was FeSO4, the carrier used was powdered activated carbon, and the oxidant was H2O2. The amount of catalyst, carrier and COD in the sewage was in the following relationship: 1 kg of catalyst, 2.5 kg of catalyst carrier and 5 kg of oxidant were used for every 1 kg of CODcr. The microwave intensity was controlled to be 0.85 W / cm 2 , the vacuum degree is -80KPa, and the reaction temperature is 35℃.

[0062] Start the microwave water treatment system and continuously feed water. Sampling begins at 40 minutes after startup. Samples are taken every 10 minutes to detect the COD value of the effluent. The COD removal rate of the microwave water treatment system changes over time. The data are as follows:

[0063] Table 1 Microwave reaction time and COD removal under vacuum conditions

[0064]

[0065] Application Example 2

[0066] Under the same conditions as in Application Example 1, the vacuum pump was turned off to allow the reaction to proceed at normal pressure. Sampling was also started at the 40th minute of the reaction and was performed every 10 minutes. The relationship between microwave reaction time and COD removal rate was investigated as shown in the following table:

[0067] Table 2 Microwave reaction time and COD removal under normal pressure

[0068]

[0069] Application Example 3

[0070] Under the same conditions of catalyst, oxidant and microwave intensity as those in Application Example 1, the vacuum pump was turned off and the reaction temperature was raised to 50°C, so that the microwave reaction was carried out under normal pressure and high temperature. Sampling was also started at the 40th minute of the reaction, and samples were taken every 10 minutes. The relationship between microwave reaction time and COD removal rate was investigated as shown in the following table:

[0071] Table 3 Microwave reaction time and COD removal under normal pressure

[0072]

[0073] From the data in the above table, it can be seen that the organic matter removal rate is significantly improved by increasing the temperature of the microwave reaction, but the microwave reaction under low temperature and vacuum conditions still achieves a good removal effect on the organic matter removal rate. The microwave reaction under vacuum conditions of the present invention is not only that the vacuum conditions reduce the microwave reaction temperature, but the vacuum conditions may strengthen the non-thermal effect of the microwave, and the non-thermal effect can still enhance the efficiency of microwave catalytic oxidation.

[0074] It should be noted that the method and device of the present invention are mainly used for treating organic wastewater with a CODcr concentration of less than 2000 mg / L and using a physical and chemical treatment process. However, it is also applicable to the following situations as pretreatment or deep treatment.

[0075] (1) CODcr concentration is 2000-10000 mg / L, but the conventional anaerobic reactor has poor treatment effect, or the water temperature is low and the pretreatment efficiency of biochemical treatment is low.

[0076] (2) When the nutrient ratio in sewage is unbalanced and an external carbon source is needed, the carbon-nitrogen ratio can be increased, the amount of carbon source added can be saved, and the efficiency of biochemical treatment can be improved.

[0077] (3) After conventional biochemical treatment, the CODcr concentration is 100-500 mg / L, which cannot meet the discharge standards. In the case where difficult-to-biodegrade pollutants still exist in the water, it is suitable for deep treatment of biochemical treatment effluent to improve biodegradability, remove residual pollutants, and disinfect and sterilize.

[0078] (4) Pretreatment of biodegradable organic wastewater with a B / C ratio less than 0.3 can improve biodegradability and remove organic pollutants.

[0079] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A microwave catalytic oxidation water treatment method, characterized in that: Adding a catalyst and an oxidant to the wastewater, performing a microwave reaction in a microwave water treatment device, controlling the microwave reaction temperature to 30-40°C, and the reaction pressure to -90--70KPa; the catalyst is adsorbed on a carrier for use, the catalyst is FeSO4, MnO2 or NiO2, and the carrier is activated carbon, SiC or diatomaceous earth; The amount of catalyst and oxidant is controlled by the COD content in the wastewater. The mass ratio of catalyst to COD in the wastewater is 1-3:1, the mass ratio of oxidant to COD in the wastewater is 5-8:1, and the microwave intensity is 0.6-1.2W / cm 2 , microwave reaction time is 10~15min; The microwave water treatment equipment comprises a microwave reaction tank, a metal shell covering the outside of the microwave reaction tank, a microwave generating device and a vacuum pump; the tank body of the microwave reaction tank is made of plastic material and is equipped with a stirring device; the microwave generating device forms a uniform and controllable microwave field in the microwave water treatment equipment, and the vacuum pump provides vacuum reaction conditions for the microwave reaction tank.

2. The processing method according to claim 1, characterized in that: The microwave reaction tank has a height-to-diameter ratio of 2:1 to 4:

1.

3. The microwave catalytic oxidation water treatment method according to claim 1, characterized in that: The oxidant is O2, O3, air or H2O2.

4. The microwave catalytic oxidation water treatment method according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Mixing the wastewater and the catalyst-loaded powder carrier in a mixing tank; (2) Adding oxidants to wastewater; (3) Microwave reaction of wastewater; (4) Add flocculants to wastewater to separate liquid and solid; (5) The supernatant produced by liquid-solid separation is returned to step (2), and the solid portion is returned to step (1) after being dried; (6) After solid-liquid separation, the clean water is reused or discharged in compliance with the discharge standards.

5. The microwave catalytic oxidation water treatment method according to claim 4, characterized in that: The wastewater stays in the mixing tank of step (1) for 10 to 30 minutes; the mixing time with the oxidant in step (2) is 10 to 30 minutes.

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