Air flotation separation oil removal device

Abstract

The utility model discloses an air flotation separation oil removal device which comprises a wastewater tank, a micro-scale bubble generator, an oil removal reaction tank, an ozonized gas transmission device and an oil scraper, the wastewater pool is connected with the micro-scale bubble generator, the micro-scale bubble generator is respectively connected with the ozonized gas transmission device and the oil removal reaction pool, oily wastewater and ozonized gas are mixed in the micro-scale bubble generator and then are discharged into the oil removal reaction pool, and the oil removal reaction pool is provided with an oil scraper for removing oil. The utility model provides an air flotation separation oil removal device capable of generating micro-scale bubbles at low cost and a process system for efficiently and synergistically removing organic impurities, so as to meet the requirement of up-to-standard discharge of wastewater and improve the capability and level of treating oil-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of water-oil separation, and more specifically to an air flotation separation and oil removal device. Background Technology

[0002] This section provides only background information relevant to this disclosure and is not necessarily prior art.

[0003] Most industrial sectors, including petrochemicals, oil refining, steel, mining, food processing, and pharmaceuticals, generate large amounts of oily wastewater, causing severe damage to the water environment and seriously threatening public drinking water safety. Oily wastewater generally has a complex composition, with oily substances mainly existing in the form of vegetable oil, mineral oil, animal oil, petroleum derivatives, and other hydrocarbons. It also contains bacteria and other organic pollutants, making treatment extremely difficult. Utilizing appropriate technologies to separate oil from water in this type of wastewater is of great significance for its treatment and also provides a prerequisite for subsequent oil resource recovery.

[0004] Oily substances can be classified into floating oil, dispersed oil, emulsified oil, and dissolved oil based on their physical state and droplet size. Generally, the smaller the oil droplets in wastewater, the more stable the wastewater mixture, and the more difficult it is to separate the oil from the water. Furthermore, surfactants in wastewater can reduce the surface tension at the oil-water interface, further increasing the difficulty of oil-water separation. Traditional oil-water separation technologies include gravity separation, adsorption separation, flotation separation, and membrane separation. Gravity separation utilizes the density difference between oil and water, achieving separation through static stratification. It is suitable for removing floating oil, has a simple structure but requires a large area, has low processing capacity, and is difficult to directly treat to meet emission standards. Adsorption separation uses porous, hydrophobic, and oleophilic adsorbents to adhere oil to them, thus removing it. Commonly used adsorbents include coal ash, slag, and nutshells, but regeneration after use is difficult. Flotation separation utilizes the collision and adhesion between air bubbles and oil droplets, which then float and converge to remove the oil. This method has high removal efficiency and strong stability, but consumes more energy and requires a larger area. Membrane separation utilizes the poor permeability of oil and water on a membrane to achieve oil-water separation. This method is simple to operate and has low energy consumption, but it requires a large initial investment, and the subsequent cleaning and replacement costs of the membrane are also high. Most of the aforementioned oil removal processes are effective at separating floating oil and dispersed oil wastewater with larger oil droplets, but they are less effective at separating wastewater containing dissolved or emulsified oil. Currently, pre-demulsification can be performed by applying an electric field and adding chemical agents to improve oil-water separation efficiency, but these methods are complex to operate, have high energy consumption, and may cause secondary pollution.

[0005] Currently, dissolved air flotation (DAF) separation technology is commonly used in industrial wastewater oil removal processes, with the DAF machine being the core equipment. Depending on the properties of the oily substances in the wastewater and the actual removal requirements, DAF machines are categorized into dissolved air flotation (DAF), high-efficiency shallow DAF, vortex DAF, horizontal flow DAF, and shallow DAF. However, because the flotation bubbles acting on the oil have a large diameter and are difficult to distribute evenly, it is challenging to achieve separation of dissolved or emulsified oil from the wastewater. Furthermore, existing DAF machines suffer from drawbacks such as low gas production efficiency, discontinuous dissolved gas release, complex processes, high operational requirements, high compressor noise, and high power consumption.

[0006] Current consensus holds that smaller bubbles have a larger specific surface area, resulting in more thorough gas-liquid contact, slower rising speed in the liquid, and longer residence time, ultimately significantly improving the oil-water separation efficiency of wastewater. Furthermore, smaller bubbles, upon bursting, cause a dramatic change due to the disappearance of the gas-liquid interface, releasing the accumulated chemical energy at the interface and generating a large number of hydroxyl radicals. These radicals possess extremely high redox potentials and can synergistically degrade oily substances and other organic impurities that are difficult to remove by flotation, ensuring that the wastewater ultimately meets discharge standards. Therefore, the smaller the diameter of the flotation bubbles acting on oil, the more beneficial it is for the separation and flotation removal of various oily substances in wastewater. Developing devices capable of generating even smaller bubbles is one of the important directions in the research of efficient oil removal processes for wastewater. Summary of the Invention

[0007] This invention addresses the problems and shortcomings of existing air flotation separation oil removal devices and processes by providing an air flotation separation oil removal device.

[0008] The device includes a wastewater tank, a microscale bubble generator, an oil removal reaction tank, an ozonated gas transmission device, and an oil skimmer. The wastewater tank is connected to the microscale bubble generator, which is connected to both the ozonated gas transmission device and the oil removal reaction tank. Oily wastewater and ozonated gas are mixed in the microscale bubble generator and then discharged into the oil removal reaction tank, which is equipped with an oil skimmer to remove oil.

[0009] Oily wastewater stored in a wastewater tank is pumped into a microscale bubble generator. Ozone gas produced by the ozone generator is stored in a gas buffer tank and connected to the gas inlet of the microscale bubble generator via pipeline. After passing through the microscale bubble generator, the oily wastewater and ozone gas are thoroughly mixed and reacted, then discharged from the wastewater outlet and piped into the oil removal reaction tank. The microscale ozone bubbles adsorb and react with the oil in the wastewater, slowly rising to the surface of the tank liquid, where they are periodically removed by an oil skimmer located at the top of the tank. The wastewater after oil-water separation is discharged from the wastewater outlet at the bottom of the tank and pumped into subsequent advanced wastewater treatment processes to meet final discharge standards.

[0010] Oily wastewater in the wastewater pond can first undergo a simple gravity oil removal process to remove floating oil and dispersed oil with larger oil droplets, thereby reducing the processing load of the high-efficiency oil-water separation device system described in this patent and reducing operating costs.

[0011] Furthermore, the microscale bubble generator includes a converging section and a expanding section, and the structure of the microscale bubble generator is similar to a Venturi tube; a gas inlet is provided at the connection between the converging section and the expanding section, and the gas inlet is connected to an ozone gas transmission device; a wastewater inlet is provided at the end of the converging section away from the connection, and the wastewater inlet is connected to a wastewater tank; a gas-containing wastewater outlet is provided at the end of the expanding section away from the connection, and the gas-containing wastewater outlet is connected to an oil removal reaction tank; and a spiral shearing element is provided inside the expanding section.

[0012] The overall length of the venturi tube is 0.5-1.5 meters, the ratio of the length of the converging section to the length of the expanding section is 1:2 to 1:3, and the inlet diameter is 50-150 mm.

[0013] The water-gas mixing ratio is adjustable, with a gas-liquid volume ratio of 1:10 to 1:30.

[0014] Oily wastewater is pressurized by a transfer pump and enters through the wastewater inlet. The wastewater flows at high speed in the converging section, forming a low-pressure zone. The low-pressure zone draws in gas stored in the gas buffer tank through the gas inlet. After preliminary mixing of gas and liquid at the throat, it enters the diffuser section, where the speed decreases and the pressure increases, before being discharged from the gas-containing wastewater outlet.

[0015] Furthermore, the spiral shearing component is sized to fit the expanding section of the microscale bubble generator. The spiral shearing component is a variable-diameter spiral blade structure that matches the taper of the expanding section, with staggered wedge-shaped micro-teeth embedded on its surface. A double-spiral flow channel design enables efficient shearing and microbubble generation.

[0016] The spiral shear component is made of metal and is used for remixing after the initial gas-liquid mixing. Its spiral shape alters the fluid flow path, increasing turbulence and resulting in more thorough and uniform gas-liquid mixing. During the flow path alteration process, the shear component breaks larger bubbles into smaller, even micro-sized, bubbles, enhancing the subsequent oil removal effect on wastewater.

[0017] Furthermore, the ozonated gas transmission device includes a gas buffer tank and an ozone generator. The ozone generator is connected to the gas buffer tank, and the gas buffer tank is connected to a microscale bubble generator. The gas buffer tank stores a certain concentration of ozonated gas, with the ozone concentration controlled between 2% and 10%, which can be flexibly adjusted according to the COD and oil content of the influent wastewater. For the preparation of ozonated gas, an air-source ozone generator is preferred to reduce operating costs. The gas buffer tank and the gas inlet are connected only by a pipeline. Utilizing the structural characteristics of the microscale bubble generator, a negative pressure environment is created near the gas inlet, automatically drawing in the ozonated gas from the gas buffer tank.

[0018] Furthermore, the oil removal reaction tank is connected to a tail gas destruction device, which is mainly used to decompose and destroy the residual ozone in the tail gas that has not been fully reacted, so as to avoid damage to the atmospheric environment.

[0019] Furthermore, the oil removal reaction tank is a closed structure to prevent leakage of residual ozonated gas.

[0020] Furthermore, a stirrer is installed in the wastewater tank to keep the wastewater homogeneous.

[0021] Oily wastewater, after passing through a microscale bubble generator, forms a gas-liquid mixture rich in microscale ozonated bubbles. The ozonated bubble particle size is in the micro-nano scale, ranging from 0.1 μm to 10 μm. This gas-liquid mixture then enters the oil removal reaction tank via a distribution pipeline. Inside the tank, the microscale bubbles fully adsorb and aggregate with the oily substances in the wastewater, resulting in a significant separation and removal of dissolved oil and emulsified oil that are difficult to separate using conventional air flotation machines. Due to the micro-nano scale of the bubbles, their residence time in the reaction tank is longer, leading to better oil-carrying and flotation effects. Furthermore, unlike the air used in conventional air flotation machines, this invention uses ozonated gas, which, in addition to the oil-carrying and flotation effect caused by density differences, also has an oxidative degradation effect on the organic matter contained in the wastewater. Ozone, under the action of a catalyst or by breaking down, easily forms a large number of hydroxyl radicals with a high oxidation potential of 2.8V, which can better oxidize and degrade dissolved oil and other organic pollutants in the wastewater.

[0022] Oily substances carried by micro-scale bubbles float to the surface of the liquid in the pool and continuously accumulate. They are then scraped off periodically by an oil skimmer installed above the pool. The start-up cycle is reasonably selected based on the oil content of the feed wastewater, and the operating speed is generally 3 to 5 m / min.

[0023] Furthermore, the device includes a separation and purification section. This section separates and purifies oily substances with simple compositions and high recovery value, thereby realizing the resource utilization of these oily substances.

[0024] The oil removal reaction tank has a wastewater outlet pipeline at its bottom side, where the oil and water in the outlet wastewater have been thoroughly separated, and the oil content in the wastewater meets the discharge standards. The effluent can be further connected to a subsequent wastewater treatment unit for the treatment of other pollutants in the wastewater. Typically, even after oil removal, wastewater still contains excessive levels of COD and ammonia nitrogen, requiring a biological treatment unit to further reduce the COD and ammonia nitrogen content to within the discharge limits. The high-efficiency oil-water separation process system and device described in this patent can be considered as a pre-ozone conditioning of the biological treatment unit, enhancing the degradation and removal efficiency of pollutants such as COD by the biological treatment unit, and further reducing the operating costs of treating oily wastewater to meet standards.

[0025] The system features a simple process, a basic structure, reliable operation, low energy consumption, high oil-water separation efficiency, and simultaneous removal of organic impurities from wastewater, providing favorable conditions for subsequent wastewater discharge to meet standards.

[0026] To address the problems and shortcomings of existing air flotation separation oil removal processes and devices, a low-cost air flotation separation oil removal device that generates microscale bubbles and efficiently and synergistically removes organic impurities is invented to meet the requirements for wastewater discharge compliance and improve the capacity and level of oily wastewater treatment. Attached Figure Description

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0028] Figure 1 This is a flow chart of a high-efficiency oil-water separation process system.

[0029] Figure 2 This is a schematic diagram of a microscale bubble generator. Detailed Implementation

[0030] The technical solution and apparatus of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] The reference numerals in the attached figures are as follows: 1-Wastewater tank; 2-Transfer pump; 3-Microscale bubble generator; 31-Wastewater inlet; 32-Gas intake; 33-Gas-containing wastewater outlet; 34-Spiral shear component; 4-Oil removal reaction tank; 5-Wastewater outlet; 6-Gas buffer tank; 7-Ozone generator; 8-Tail gas destruction device; 9-Oil skimmer.

[0032] An oil refinery generates wastewater with an oil content of 500–800 mg / L, of which floating oil particles larger than 100 μm account for approximately 60% of the total oil content, and the COD content is 600–700 mg / L. This wastewater is treated using the high-efficiency oil-water separation process system and device described in this patent.

[0033] like Figure 1-2 As shown, the wastewater, after pretreatment in a gravity oil removal section, has an oil content of 200–300 mg / L, with most of the floating oil removed and stored in wastewater tank 1. A stirrer is installed in wastewater tank 1 to maintain the homogeneity of the wastewater. The wastewater is then pumped into a microscale bubble generator 3 via a transfer pump 2.

[0034] An air-source ozone generator 7 produces ozonated gas with an ozone concentration of approximately 8%. The generated ozonated gas is then transported via pipeline to a gas buffer tank 6 to maintain a slightly positive pressure operating condition within the tank. A pipeline is installed at the tank outlet to connect to the gas inlet 32 ​​of a microscale bubble generator.

[0035] Wastewater, pressurized by a transfer pump, enters the wastewater inlet of the microscale bubble generator. The fluid flows through a converging channel, where the velocity increases and the pressure decreases, creating a minimum negative pressure region near the gas inlet 32. Therefore, the ozonated gas from the gas buffer tank is drawn in, and the gas and liquid mix. The gas-liquid mixture continues into a diverging channel, where the velocity decreases and the pressure increases, exiting from the gas-containing wastewater outlet 33. Within the diverging channel, a helical shearing element 34 is installed to cut large bubbles into microscale bubbles while simultaneously increasing the turbulence during the fluid's flow. The microscale bubbles further mix and react thoroughly with the liquid.

[0036] The gas-liquid mixture enters the oil removal reaction tank 4 through a pipeline via the gas-containing wastewater outlet 33. It flows in from the bottom of the tank through a liquid distribution system. Micro-scale bubbles rise under buoyancy, reacting with oil and organic matter in the wastewater to undergo oxidation and degradation. Simultaneously, they adhere to smaller oil droplets in the wastewater, eventually floating to the surface and accumulating to form oil sludge, which is periodically scraped off by an oil skimmer at the top of the tank. After the ozonation bubbles rise and burst, the unreacted ozone in the exhaust gas is transported through the exhaust pipe to the exhaust gas destruction device 8 for ozone catalytic degradation, reducing the impact of exhaust gas ozone on the atmospheric environment.

[0037] Because the ozonation bubbles are at the micro-nano scale, they have a longer residence time in the oil removal reaction tank 4, generally 20-40 minutes, allowing for prolonged interaction with oily substances and organic matter. Therefore, the wastewater discharged from wastewater outlet 5 undergoes thorough oil-water separation, with an oil content of less than 1 mg / L. After oil-water separation, the wastewater enters the biological treatment system using the A2O process, ultimately achieving a COD content of less than 30 mg / L in the effluent, meeting the discharge standards.

[0038] This utility model provides a concept and method for an air flotation separation oil removal device. There are many methods and approaches to implement this technical solution; the above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this utility model, and these improvements and modifications should also be considered within the scope of protection of this utility model. All components not explicitly stated in this embodiment can be implemented using existing technology.

Claims

1. An oil removal device by air floatation separation, characterized by comprising: The device comprises a wastewater pool (1), a micro-scale bubble generator (3), an oil removal reaction pool (4), an ozone gas transmission device and an oil skimmer (9); the wastewater pool (1) is connected with the micro-scale bubble generator (3), the micro-scale bubble generator (3) is connected with the ozone gas transmission device and the oil removal reaction pool (4) respectively, the oil-containing wastewater is mixed with the ozone gas in the micro-scale bubble generator (3) and then discharged into the oil removal reaction pool (4), and the oil removal reaction pool (4) is provided with the oil skimmer (9) for removing oil.

2. The device according to claim 1, wherein The micro-scale bubble generator (3) comprises a converging section and a diverging section, a gas suction inlet (32) is arranged at the connection between the converging section and the diverging section, the gas suction inlet (32) is connected with the ozone gas transmission device, a wastewater inlet (31) is arranged at the end of the converging section away from the connection, the wastewater inlet (31) is connected with the wastewater pool (1), a gas-containing wastewater outlet (33) is arranged at the end of the diverging section away from the connection, the gas-containing wastewater outlet (33) is connected with the oil removal reaction pool (4), and a spiral shear element (34) is arranged in the diverging section.

3. The device according to claim 2, wherein The spiral shear element (34) is sized to fit the diverging section of the micro-scale bubble generator (3).

4. The device according to claim 1, wherein The ozone gas transmission device comprises a gas buffer tank (6) and an ozone generator (7), the ozone generator (7) is connected with the gas buffer tank (6), and the gas buffer tank (6) is connected with the micro-scale bubble generator (3).

5. The device according to claim 1, wherein The oil removal reaction pool (4) is connected with a tail gas destruction device (8).

6. The device according to claim 5, wherein The oil removal reaction pool (4) has a closed structure.

7. The device according to claim 1, wherein A delivery pump (2) is arranged at the connection between the wastewater pool (1) and the micro-scale bubble generator (3).

8. The device according to claim 7, wherein The wastewater pool (1) is provided with a stirrer.

9. The device according to claim 1, wherein The device is provided with a separation and purification section.

10. The device according to claim 1, wherein The ozone gas concentration is 2% to 10%.

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