High-oil-content sewage treatment system and method

Abstract

The invention relates to the technical field of oilfield produced water purification, in particular to a high-oil-content sewage treatment system and method. The high-oil-content sewage treatment system comprises an oil-water separation module and a sewage treatment module, according to the high-oil-content sewage treatment system provided by the invention, oil-water separation is firstly realized through the oil-water separation module, then flocculation separation of residual oil stains and pollutants is realized through the sewage treatment module, and pollutants such as organic matters and nitrogen in sewage are degraded through electrocatalytic oxidation, so that harmless treatment of the sewage is realized.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield produced water purification, and in particular to a system and method for treating high-oil-content sewage. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Oilfield oily wastewater has a large volume, complex composition, is difficult to degrade, and has a wide range of pollution. In particular, the large-scale application of tertiary oil recovery technology in oilfields has produced a large amount of highly emulsified, highly viscous, and highly oily wastewater, which has increased the difficulty of oilfield wastewater treatment. The oil in this type of wastewater has a variety of distribution forms, including floating oil, dispersed oil, emulsified oil, etc. Large-sized oil droplets are relatively easy to remove in conventional separation, while small-sized oil droplets require other technologies to achieve effective separation. In addition to oil substances, highly oily wastewater also contains a large amount of organic matter and nitrogen pollutants that are difficult to degrade. If oily wastewater is discharged directly, it will cause serious environmental pollution and have adverse effects on humans, animals, plants, and ecosystems. For the treatment of this type of wastewater, a single treatment method cannot fully adapt to the removal of all pollutants. The existing wastewater treatment technologies mostly use a single flocculation technology or oxidation technology to achieve oil-water separation and organic matter degradation. At the same time, the flocculation process will add flocculants and other chemical agents to the water body. This treatment technology will increase the treatment cost and cause secondary pollution to the water body. Therefore, the research on efficient and clean oilfield wastewater treatment technology has become a new direction for oilfield development and ecological environmental protection. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a system and method for treating high-oil-content wastewater.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] The first aspect of the present invention provides a high oil content wastewater treatment system, comprising:

[0007] Oil-water separation module and sewage treatment module;

[0008] The oil-water separation module includes a first oil-water separation unit and a second oil-water separation unit; the first oil-water separation unit includes a solid-liquid separation tank, the solid-liquid separation tank includes a first outlet and a second outlet, the first outlet is connected to the crude oil dehydrator; the second oil-water separation unit includes a coalescing separator, the coalescing separator is connected to the crude oil dehydrator; the coalescing separator is connected to the second outlet;

[0009] The sewage treatment module includes a flocculation separation unit and an electrocatalytic oxidation unit;

[0010] The coalescence separator is sequentially connected to a flocculation separation unit and an electrocatalytic oxidation unit.

[0011] The second aspect of the present invention provides a method for treating high-oil content wastewater, comprising:

[0012] Separate the oil and water from the highly oily wastewater, and collect the oil and the wastewater after oil separation;

[0013] The wastewater after oil separation is subjected to electrolytic flocculation, the flocculants are separated by magnetic separation, and then the effluent from the separated flocculants is subjected to electrocatalytic oxidation treatment.

[0014] The beneficial effects of the present invention are:

[0015] The high-oil-content sewage treatment system provided by the present invention first realizes the separation of oil and water through the oil-water separation module, removes a large amount of floating oil and dispersed oil in the sewage, and then passes through the sewage treatment module to realize the flocculation separation of the remaining oil and pollutants, and then electrocatalytically oxidizes and degrades organic matter, nitrogen and other pollutants in the sewage to achieve harmless treatment of the sewage. Specifically: the high-oil-content sewage first enters the solid-liquid separation tank of the first oil-water separation unit for solid-liquid separation, and a large amount of floating oil, sewage containing a small amount of floating oil, and solid impurities such as mud and sand will be separated in the solid-liquid separation tank; the floating oil enters the crude oil dehydrator, and the sewage containing a small amount of floating oil enters the second oil-water separation unit for water-oil separation again, and solid impurities such as mud and sand enter the sewage pipeline. The second oil-water separation unit will separate and produce a small amount of floating oil and a large amount of sewage, of which a small amount of floating oil will also enter the crude oil dehydrator, where the floating oil will be dehydrated. After dehydration, a large amount of crude oil with low water content can be recycled and processed, and the remaining sewage will enter the flocculation separation unit together with the sewage separated from the second oil-water separation unit for electroflocculation, which will form large-size floccules with small-size emulsified oil and further remove them through the magnetic separator. The sewage after flocculation separation enters the electrocatalytic oxidation unit for harmless treatment. This multi-level separation design significantly improves the effect of sewage treatment, especially the removal of emulsified oil and other pollutants with a particle size of micrometers that still exist after agglomeration and separation, solving the problem that traditional sewage treatment technology cannot be deeply treated in the treatment of high-oil sewage.

[0016] (2) The present invention can remove most of the suspended oil samples through two oil-water separation treatments, reduce the high oil content in the water body, reduce the burden of subsequent flocculation, separation, and oxidation treatment, and prevent the subsequent electrode plates from being attached with a large amount of pollutants to produce passivation, thereby ensuring the normal electrochemical reaction. The sewage after sedimentation enters the flocculation separation and catalytic oxidation unit, and the small-particle emulsified oil, organic pollutants, and nitrogen pollutants in the sewage are efficiently separated, which can achieve thorough separation and treatment compared to a single treatment technology.

[0017] (3) Compared with previous sewage treatment technologies, the present invention adopts a modular design and includes solid-liquid separation, coagulation separation, electro-flocculation, magnetic separation and electrocatalytic oxidation modules. Each module is independent but interconnected, and the combination mode can be flexibly adjusted according to the different oil content and pollution characteristics of the sewage to meet different treatment needs. For example, when treating sewage with a high oil content, the working time of coagulation separation can be increased. For sewage with a high organic content, the treatment time of electrocatalytic oxidation can be extended or the treatment can be circulated again. The entire treatment process will treat oil droplets of different particle size ranges step by step, gradually reduce the oil content and pollutant content in the sewage, and multiple processes work together to establish good conditions for subsequent treatment; no chemical agents are added during the entire separation and treatment process, and the method of combining physical separation with electrocatalytic oxidation is used to reduce secondary pollution to the water body and achieve the goal of green and environmentally friendly sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0019] Figure 1 It is a structural schematic diagram of the high-oil-content wastewater treatment system of the present invention, wherein 1 is a solid-liquid separation tank, 2-1 is a first centrifugal pump, 2-2 is a second centrifugal pump, 3 is a heater, 4 is a coalescing separator, 5 is a sedimentation tank, 6 is a crude oil dehydrator, 7 is an electrolytic cell, 8 is a magnetic separator, 9 is an electrocatalytic oxidation tank, 10-1, 10-2, 10-3, 10-4, 10-5, 10-6, 10-7, 10-8, 10-9, 10-10 are all flow valves, 11-1 is a first sewage valve, 11-2 is a second sewage valve, 11-3 is a third sewage valve, 12 is a spoiler, 12-1 is a water pipeline, and 12-2 is a spiral blade;

[0020] Figure 2 It is a schematic diagram of the structure of the spoiler, wherein 12-1 is a water pipe and 12-2 is a spiral blade. DETAILED DESCRIPTION

[0021] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0022] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0023] A first typical embodiment of the present invention provides a high oil content wastewater treatment system, comprising:

[0024] Oil-water separation module and sewage treatment module;

[0025] The oil-water separation module includes a first oil-water separation unit and a second oil-water separation unit; the first oil-water separation unit includes a solid-liquid separation tank, the solid-liquid separation tank includes a first outlet and a second outlet, the first outlet is connected to the crude oil dehydrator; the second oil-water separation unit includes a coalescing separator, the coalescing separator is connected to the crude oil dehydrator; the coalescing separator is connected to the second outlet;

[0026] The sewage treatment module comprises a flocculation separation unit and an electrocatalytic oxidation unit; the coalescence separator is sequentially connected to the flocculation separation unit and the electrocatalytic oxidation unit.

[0027] In one or more embodiments, the solid-liquid separation tank further includes a third outlet, and the third outlet is connected to a sewage pipeline.

[0028] In one or more embodiments, the second outlet of the solid-liquid separation tank is connected to the inlet of the heater, and the outlet of the heater is connected to the inlet of the coalescing separator.

[0029] In one or more embodiments, the outlet of the coalescing separator is connected to the inlet of the settling tank.

[0030] Preferably, the settling tank comprises a fourth outlet and a fifth outlet, the fourth outlet is connected to the crude oil dehydrator, and the fifth outlet is connected to the spoiler.

[0031] Further preferably, the disruptor is connected to a flocculation separation unit.

[0032] Further preferably, the crude oil dehydrator comprises a sixth outlet, and the sixth outlet is connected to the spoiler.

[0033] Further preferably, the spoiler is a spiral spoiler, and the spiral spoiler comprises a water pipeline, and the inner wall of the water pipeline is provided with spiral blades along the length direction of the water pipeline.

[0034] In one or more embodiments, the flocculation separation unit includes an electrolytic cell and a magnetic separator connected in sequence.

[0035] Preferably, the anode material of the electrolytic cell is an iron-aluminum alloy.

[0036] In one or more embodiments, the electrocatalytic oxidation unit includes an electrocatalytic oxidation tank; and the electrocatalytic oxidation unit is connected to the second oil-water separation unit.

[0037] A second typical embodiment of the present invention provides a method for treating high-oil-content wastewater, comprising:

[0038] Separate the oil and water from the highly oily wastewater, and collect the oil and the wastewater after oil separation;

[0039] The wastewater after oil separation is subjected to electrolytic flocculation, the flocculants are separated by magnetic separation, and then the effluent from the separated flocculants is subjected to electrocatalytic oxidation treatment.

[0040] In one or more embodiments, the collected oil is recovered and reprocessed.

[0041] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0042] Example 1

[0043] refer to Figure 1 , a high oil content sewage treatment system, comprising:

[0044] Oil-water separation module and sewage treatment module;

[0045] The oil-water separation module includes a first oil-water separation unit and a second oil-water separation unit; the first oil-water separation unit includes a solid-liquid separation tank 1, the solid-liquid separation tank 1 includes a first outlet and a second outlet, the first outlet is connected to the crude oil dehydrator 6 through a first centrifugal pump 2-1; the second oil-water separation unit includes a coalescing separator 4, the coalescing separator 4 is connected to the crude oil dehydrator 6; the coalescing separator 4 is connected to the second outlet;

[0046] The sewage treatment module includes a flocculation separation unit and an electrocatalytic oxidation unit;

[0047] The coalescence separator 4 is sequentially connected to the flocculation separation unit and the electrocatalytic oxidation unit.

[0048] The solid-liquid separation tank 1 also includes a third outlet, which is connected to the sewage pipeline. The highly oily sewage first enters the solid-liquid separation tank of the first oil-water separation unit for solid-liquid separation, and a large amount of floating oil, sewage containing a small amount of floating oil, and solid impurities such as mud and sand will be separated from the solid-liquid separation tank; the floating oil enters the crude oil dehydrator through the first outlet, and the sewage containing a small amount of floating oil enters the second oil-water separation unit through the second outlet for water-oil separation again, and solid impurities such as mud and sand enter the sewage pipeline through the third outlet.

[0049] In the second oil-water separation unit, the second outlet of the solid-liquid separation tank 1 is connected to the inlet of the heater 3 through the second centrifugal pump 2-2, and the outlet of the heater 3 is connected to the inlet of the coalescing separator 4. The outlet of the coalescing separator 4 is connected to the inlet of the settling tank 5. The settling tank 5 includes a fourth outlet, a fifth outlet and a seventh outlet, the fourth outlet is connected to the crude oil dehydrator 6, the fifth outlet is connected to the spoiler 12, and the seventh outlet is connected to the sewage pipe; the spoiler is connected to the flocculation separation unit. The crude oil dehydrator 6 includes a sixth outlet and an eighth outlet, the sixth outlet is connected to the spoiler, and the eighth outlet is connected to the sewage pipe.

[0050] The wastewater containing a small amount of floating oil discharged from the second outlet of the first oil-water separation unit enters the second oil-water separation unit for water-oil separation again. Among them, the wastewater is first heated by the heater 3. The viscosity of the heated wastewater and the stability of the emulsion are reduced, and the dispersed oil can be effectively removed in the subsequent coalescence separation process. The heated wastewater enters the coalescence separator 4. The filler in the packing layer of the coalescence separator 4 is made of oleophilic and hydrophobic materials. When the oil droplets in the wastewater approach the oleophilic and hydrophobic materials, they will adhere to these materials. The oil droplets in the subsequent wastewater will also adhere to them or collide with the oil droplets on them to form large particle oil droplets. When the oil droplets grow large enough, they will detach from the material surface under the action of the fluid drag force and flow out of the coalescence separator 4. The coalescence separation technology belongs to the physical separation technology, which can coalesce the oil droplets with smaller particle size in the wastewater after the floating oil is removed into oil droplets with larger particle size, and then continue to remove the small particle oil droplets in part of the wastewater through sedimentation separation. At the same time, this treatment method will not cause pollution to the environment. The sewage generated in the coalescing separator 4 enters the settling tank 5 for sedimentation separation. After coalescing separation, the oil droplets coalesce and settle on the upper layer of the sewage to form a high-water floating oil layer and a small amount of solid impurities such as silt. The floating oil will enter the crude oil dehydrator 6 through the fourth outlet, and the remaining sewage enters the spoiler 12 through the fifth outlet. A small amount of solid impurities such as silt is connected to the sewage pipe through the seventh outlet. In the crude oil dehydrator 6, the crude oil is efficiently dehydrated by electric dehydration. A large amount of crude oil with low water content after dehydration can be recycled and processed to prevent the waste of petroleum resources. The dehydrated sewage enters the spoiler through the sixth outlet. The traditional oil-water separation technology has a poor treatment effect on highly emulsified sewage, especially when the emulsion stability in the sewage is high, it is difficult to completely separate it by conventional physical or chemical methods. The above-mentioned multi-stage separation design significantly improves the effect of oil-water separation, especially when there is still dispersed oil in the water body after the sewage is simply removed from the floating oil, which solves the problem of incomplete separation of traditional technology in the treatment of high-oil sewage.

[0051] refer to Figure 2 : is a schematic diagram of the structure of the spoiler 12. In this embodiment, the spoiler 12 is a spiral spoiler, which includes a water pipe 12-1, and the inner wall of the water pipe is provided with spiral blades 12-2 along the length direction of the water pipe. The sewage discharged from the crude oil dehydrator 6 through the sixth outlet collides and mixes with the sewage discharged from the settling tank 5 through the fifth outlet. At the same time, under the action of the spiral spoiler, the turbulence of the sewage is increased, so that the sewage entering the electrolytic cell can be better flocculated.

[0052] The flocculation separation unit includes an electrolytic cell 7 and a magnetic separator 8 connected in sequence, and the magnetic separator 8 is connected to the sewage pipe. The anode material of the electrolytic cell 7 is an iron-aluminum alloy. The anode material is dissolved during the electrolysis process to produce corresponding metal ions, which further react with the hydroxide produced by water electrolysis to form hydroxyl compounds. The hydroxyl compounds condense and precipitate with suspended matter, oils and other substances in the wastewater to achieve the purpose of purifying the wastewater. At the same time, in the process of oil field development, there will be a certain amount of chloride ions, which can produce CLO during the electrolytic treatment process. - In the subsequent electrocatalytic oxidation process, it can catalytically oxidize some of the oxides in the wastewater into water, carbon dioxide and non-toxic small molecular organic matter, thereby improving the removal rate of COD in the wastewater. At the same time, the hydroxyl compound and the suspended matter, emulsified oil and other substances in the wastewater condense and precipitate to form magnetic floccules. When the sewage enters the magnetic separator 8, the magnetic field applied by the magnetic separator causes the magnetic floccules to be subjected to magnetic force and then separated, thereby improving the overall separation effect. The separated solids enter the sewage pipe. Compared with other magnetic separation treatment methods, magnetic powder is added to the water body during the magnetic separation process, and the floccules are inoculated with magnets by using a mixer. This method not only has a small processing capacity, but also may cause insufficient stirring during the inoculation of magnetic powder and floccules, and the magnetic powder cannot be completely recovered later; the spoiler is used to make the sewage have sufficient turbulence intensity during the process of entering the electrolytic cell, ensuring that the water body is fully mixed during the "electro-inoculation" process without any dead corners, and at the same time solving the problem that the processing capacity is not restricted by the stirring equipment.

[0053] The electrocatalytic oxidation unit includes an electrocatalytic oxidation tank 9; the electrocatalytic oxidation tank 9 is connected to the sewage pipe, and the electrocatalytic oxidation tank 9 is connected to the second centrifugal pump 2-2. The electrocatalytic oxidation treatment utilizes the catalytic activity of the anode and the precipitated oxidizing groups or free radicals to directly oxidize and degrade organic matter, nitrogen and other pollutants in the water to achieve harmless treatment of sewage. When the treated sewage meets the discharge standards, it can be discharged. However, when the treated sewage cannot meet the discharge standards, the sewage in the electrocatalytic oxidation tank 9 continues to enter the second oil-water separation unit for subsequent treatment. The solid waste generated in the electrocatalytic oxidation tank 9 enters the sewage pipe.

[0054] In view of the problem that traditional sewage treatment systems often lack modular design and cannot flexibly adjust the operating parameters of different modules, resulting in poor adaptability to different types of sewage, this method adopts modular design to make each separation and treatment unit independently adjustable, and flexibly adjust the operating parameters according to different sewage characteristics, thereby improving the adaptability and flexibility of the system. This system not only removes large oil droplets through conventional multi-stage oil-water separation, but also introduces the synergistic effect of electro-flocculation, magnetic separation and electrocatalytic oxidation; in most existing sewage treatment systems, flocculants are often used for flocculation, followed by adding magnetic powder for stirring and then magnetic separation, and flocculation and oxidation are usually carried out separately. The present invention combines different processes closely to achieve one-time treatment of suspended oil droplets, difficult-to-degrade organic matter and nitrogen, thereby improving the overall treatment efficiency.

[0055] In order to better regulate the flow of sewage in the entire system, flow valves are provided between the first outlet and the first centrifugal pump 2-1 (10-1), between the second outlet and the second centrifugal pump 2-2 (10-2), between the heater 3 and the coalescing separator 4 (10-3), between the coalescing separator 4 and the settling tank 5 (10-4), between the fourth outlet and the crude oil dehydrator 6 (10-5), between the fifth outlet and the spoiler 12 (10-6), between the sixth outlet and the spoiler 12 (10-7), between the electrolytic cell 7 and the magnetic separator 8 (10-8), between the magnetic separator 8 and the electrocatalytic oxidation tank 9 (10-9), and between the electrocatalytic oxidation tank 9 and the sewage pipe (10-10).

[0056] In order to better discharge sewage, a first sewage valve (11-1) is provided between the magnetic separator 8 and the sewage pipe, a second sewage valve (11-2) is provided between the eighth outlet and the sewage pipe, and a third sewage valve (11-3) is provided between the seventh outlet and the sewage pipe.

[0057] Example 2

[0058] A method for treating high-oil-containing wastewater, comprising:

[0059] Separate the oil and water from the highly oily wastewater, and collect the oil and the wastewater after oil separation;

[0060] The wastewater after oil separation is subjected to electrolytic flocculation, the flocculants are separated by magnetic separation, and then the wastewater from which the flocculants are separated is subjected to electrocatalytic oxidation treatment.

[0061] Specific:

[0062] (1) Highly oily wastewater first enters the solid-liquid separation tank 1 of the first oil-water separation unit for solid-liquid separation. A large amount of floating oil, wastewater containing a small amount of floating oil, and solid impurities such as mud and sand will be separated from the solid-liquid separation tank 1; the floating oil enters the crude oil dehydrator through the first outlet, the wastewater containing a small amount of floating oil enters the second oil-water separation unit through the second outlet for water-oil separation again, and solid impurities such as mud and sand enter the sewage pipeline through the third outlet.

[0063] The wastewater containing a small amount of floating oil discharged from the second outlet of the first oil-water separation unit enters the second oil-water separation unit for water-oil separation again. Among them, the wastewater is first heated by the heater 3. The viscosity of the heated wastewater and the stability of the emulsion are reduced, and the dispersed oil can be effectively removed in the subsequent coagulation and separation process. The heated wastewater enters the coagulation separator 4, and the oil droplets with smaller particle sizes in the wastewater are agglomerated into oil droplets with larger particle sizes. The wastewater generated in the coagulation separator 4 enters the sedimentation tank 5 for sedimentation separation. After coagulation and separation, the oil droplets are agglomerated and settled on the upper layer of the wastewater to form a high-water floating oil layer and a small amount of solid impurities such as silt. The floating oil will enter the crude oil dehydrator 6 through the fourth outlet, and the remaining wastewater enters the spoiler 12 through the fifth outlet. A small amount of solid impurities such as silt are connected to the sewage pipe through the seventh outlet. In the crude oil dehydrator 6, a large amount of floating oil separated from the solid-liquid separation tank 1 and a small amount of floating oil produced in the coalescing separator 4 are dehydrated by electric dehydration to achieve efficient dehydration of crude oil. A large amount of crude oil with low water content after dehydration can be recycled and reprocessed to prevent waste of oil resources. The dehydrated sewage enters the spoiler 12 through the sixth outlet. The sewage discharged from the crude oil dehydrator 6 through the sixth outlet and the sewage discharged from the settling tank 5 through the fifth outlet collide and mix in the spoiler 12 and enter the sewage treatment module.

[0064] (2) The sewage enters the electrolytic cell 7 for electrolysis and preliminary oxidation of pollutants in the sewage, and then enters the magnetic separator 8 for separation. The separated solids enter the sewage pipe. The flocculated sewage finally enters the electrocatalytic oxidation tank 9 for electrocatalytic oxidation. The electrocatalytic oxidation unit can deeply degrade difficult-to-degrade organic matter and nitrogen pollutants through the generated oxidizing groups, significantly improving the treatment effect of sewage and achieving harmless treatment of sewage. When the treated sewage meets the discharge standards, it can be discharged. However, when the treated sewage cannot meet the discharge standards, the sewage in the electrocatalytic oxidation tank 9 continues to enter the second oil-water separation unit for subsequent treatment.

[0065] Example 3

[0066] (1) The sewage entering the treatment system first enters the solid-liquid separation tank 1 of the first oil-water separation unit for gravity sedimentation, and then solid-liquid separation is performed. At the same time, a floating oil layer is formed on the upper layer. According to the Stokes sedimentation equation Under the action of gravity, the sedimentation rate of large particles of sediment in the tank can reach more than 5cm / min, so they will quickly reach the bottom of the tank to achieve solid-liquid separation. At the same time, the floating speed of oil droplets with large particle size will reach more than 2cm / min. Within 15 to 25 minutes, oil and water can also quickly achieve preliminary separation. Therefore, a large amount of floating oil, a small amount of floating oil wastewater, and solid impurities such as sediment will be separated from the solid-liquid separation tank 1; the floating oil enters the crude oil dehydrator through the first outlet, the wastewater containing a small amount of floating oil enters the second oil-water separation unit through the second outlet for water-oil separation again, and the solid impurities such as sediment enter the sewage pipeline through the third outlet.

[0067] (2) The wastewater containing a small amount of floating oil discharged from the second outlet of the first oil-water separation unit enters the second oil-water separation unit for water-oil separation again. The wastewater is first heated to 45-55°C by heater 3, and then the wastewater is heated to 45-55°C according to the formula As the temperature rises, the interfacial tension of the emulsion will decrease, and the stability will decrease, which can enhance the coalescence effect when the oil droplets collide with each other, making the oil droplets easier to float and separate, thereby strengthening the subsequent coalescence separation. Similarly, the viscosity of the sewage after heating is reduced, which is beneficial to the subsequent treatment. The sewage enters the coalescence separator 4. In the coalescence separator, the flow rate is controlled at 0.01m / s to 0.02m / s. After 35 to 50 minutes of coalescence separation, the oil droplets with smaller particle sizes in the sewage coalesce into oil droplets with larger particle sizes. The sewage generated in the coalescence separator 4 enters the sedimentation tank 5 for sedimentation separation. After coalescence separation, the oil droplets coalesce and settle on the upper layer of the sewage to form a high-water floating oil layer and a small amount of solid impurities such as silt. The floating oil will enter the crude oil dehydrator 6 through the fourth outlet, and the remaining sewage enters the spoiler 12 through the fifth outlet. A small amount of solid impurities such as silt are connected to the sewage pipe through the seventh outlet. In the crude oil dehydrator 6, a large amount of floating oil separated from the solid-liquid separation tank 1 and a small amount of floating oil produced in the coalescing separator 4 are dehydrated by electric dehydration to achieve efficient dehydration of crude oil. A large amount of crude oil with low water content after dehydration can be recycled and reprocessed to prevent waste of oil resources. The dehydrated sewage enters the spoiler 12 through the sixth outlet. The sewage discharged from the crude oil dehydrator 6 through the sixth outlet and the sewage discharged from the settling tank 5 through the fifth outlet collide and mix in the spoiler 12 and enter the sewage treatment module.

[0068] (3) The sewage enters the electrolytic cell 7 for electrolysis, and the current density in the electrolytic cell is in the range of 10 to 100 A / m 2 The reaction time is 45 to 60 minutes. The previous oil-water separation removes some pollutants and reduces the degree of pollution. The current density of flocculation is set to 40A / m 2If the pollution level is high, the current density can be increased. During the electrocoagulation process, the iron or aluminum metal on the anode electrode loses electrons to generate metal ions. These metal ions combine with hydroxide in the electrolyte to generate highly active flocculating groups Fe(OH)2 - and Al(OH)3 - These groups have strong adsorption capacity and can capture suspended particles and colloidal substances in sewage through the grid structure, thereby achieving efficient flocculation and pollutant removal; on the cathode, water molecules are reduced to generate hydrogen (H2), and the generated bubbles can assist flocculation and promote the floating of pollutants. After flocculation in the electrolytic cell, the floccules enter the magnetic separator 8 for separation. The magnetic separator uses electromagnetic equipment with a power supply current of 1 to 20A. In order to meet the treatment of different magnetic floccules, the magnetic field strength is set in the range of 5 to 100T. The high gradient magnetic field can remove tiny floccules within 5 to 50μm, and the separated solids enter the sewage pipe. Compared with other magnetic separation treatment methods, magnetic powder is added to the water body during the magnetic separation process, and the flocculants are inoculated with magnets using a mixer. This method not only has a small processing capacity, but also may lead to insufficient stirring during the inoculation of magnetic powder and flocculants, and the magnetic powder cannot be completely recovered later. The spoiler is used to ensure that the sewage has sufficient turbulence intensity when entering the electrolytic cell, ensuring that the water body is fully mixed during the "electro-inoculation" process without any dead corners, while solving the problem that the processing capacity is not restricted by the stirring equipment.

[0069] (4) The separated sewage finally enters the electrocatalytic oxidation tank 9 for electrocatalytic oxidation. The current density in the electrocatalytic oxidation tank is adjusted in the range of 100 to 800 A / m 2 The reaction time is 35 to 50 minutes. The anode is a ruthenium-iridium-coated titanium (Ru-Ir / Ti) electrode with strong corrosion resistance to ensure efficient electrochemical reaction and corrosion resistance. At the anode, water molecules (H2O) are electrolyzed to generate hydroxyl radicals (·OH) with strong oxidizing properties. This free radical can quickly oxidize organic pollutants and decompose them into carbon dioxide (CO2) and water (H2O). The reaction is as follows: H2O→·OH+H + +e - , NH3+·OH→N2+H2O / R+·OH→CO2+H2O; similarly, chloride ions are affected by the electric field and are oxidized to generate hypochlorous acid (HClO) and hypochlorite ions (ClO-), Cl - +H2O→HClO+H + +2e - , and then acts as a strong oxidant to degrade organic matter and ammonia nitrogen substances, R+HClO→CO2+H2O+Cl - , NH3+HClO→NH2Cl+H2O, NH2Cl+HClO→N2+H2O+Cl -This series of reactions can be used to oxidize and degrade organic matter, nitrogen and other pollutants in the water, thus achieving harmless treatment of sewage. The previous treatment can reduce impurities in sewage, so that strong oxidants such as hydroxyl radicals (·OH) and hypochlorous acid (HClO) generated during the electrocatalytic oxidation process can act more concentratedly on difficult-to-degrade soluble organic matter and ammonia nitrogen. The concentrated action of the oxidant improves its utilization efficiency, making the removal effect of COD and ammonia nitrogen more significant.

[0070] In this embodiment, the sewage entering the treatment system has an initial oil content of 1500 mg / L, a suspended solid content of 180 mg / L, and an ammonia nitrogen content of 50 mg / L. It first enters the solid-liquid separation tank 1 of the first oil-water separation unit for gravity sedimentation for 20 minutes. The floating oil enters the crude oil dehydrator through the first outlet. The sewage is first heated to 50°C by the heater 3 and then enters the coalescing separator 4. The oil content of the sewage at the inlet is 600 mg / L and the suspended solid content is 60 mg / L. In the coalescing separator, the sewage flow rate is 0.02 m / s. After 40 minutes of coalescing separation, it enters the sedimentation tank. The floating oil in the tank enters the crude oil dehydrator 6 through the fourth outlet. The sewage in the tank enters the spoiler 12 through the fifth outlet and mixes with the sewage from the crude oil dehydrator 6, and then enters the electrolytic cell 7 for electrolysis. The initial oil content at the inlet is 200 mg / L, the suspended solid content is 25 mg / L, and the ammonia nitrogen content is 45 mg / L. At the same time, the current density in the electrolytic cell is in the range of 40 A / m 2 , reaction time 50min. After flocculation in the electrolytic cell, the floccules enter the magnetic separator 8 for separation. The magnetic field strength is set to 20T. The high gradient magnetic field can remove the floccules with small particle size. The separated sewage finally enters the electrocatalytic oxidation tank 9 for electrocatalytic oxidation. At this time, the oil content at the inlet is reduced to 20mg / L, the suspended matter content is 10mg / L, and the ammonia nitrogen content is 40mg / L. The current density adjustment range in the electrocatalytic oxidation tank is 600A / m 2 , the reaction time is 40min. The final treatment effect is shown in the following table:

[0071] Table 1 Treatment effect of each pollutant

[0072]

[0073] Table 2 Detection of other substances before and after sewage treatment

[0074] Detection Initial Value Final Value PH 7.6 7.1 Mineralization (mg / L) 4500 2300 COD(mg / L) 1120 50 Cl(mg / L) 1500 1200 <![CDATA[SO4(mg / L)]]> 300 150 <![CDATA[Ca 2+ (mg / L)]]> 250 100 <![CDATA[Mg 2+ (mg / L)]]> 100 55 Fe(mg / L) 5 0.3

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high oil content wastewater treatment system, characterized in that: include: Oil-water separation module and sewage treatment module; Wherein, the oil-water separation module includes a first oil-water separation unit and a second oil-water separation unit; The first oil-water separation unit comprises a solid-liquid separation tank, the solid-liquid separation tank comprises a first outlet and a second outlet, the first outlet is connected to the crude oil dehydrator; the second oil-water separation unit comprises a coalescing separator, the coalescing separator is connected to the crude oil dehydrator; the coalescing separator is connected to the second outlet; The sewage treatment module includes a flocculation separation unit and an electrocatalytic oxidation unit; The coalescence separator is sequentially connected to a flocculation separation unit and an electrocatalytic oxidation unit.

2. The high oil content wastewater treatment system according to claim 1, characterized in that: The solid-liquid separation tank further comprises a third outlet, and the third outlet is connected to a sewage discharge pipeline; Alternatively, the second outlet of the solid-liquid separation tank is connected to the inlet of the heater, and the outlet of the heater is connected to the inlet of the coalescing separator.

3. The high oil content wastewater treatment system according to claim 1, characterized in that: The outlet of the coalescing separator is connected to the inlet of the settling tank; The settling tank comprises a fourth outlet and a fifth outlet, the fourth outlet is connected to the crude oil dehydrator, and the fifth outlet is connected to the spoiler.

4. The high oil content wastewater treatment system according to claim 3, characterized in that: The flow disruptor is connected to the flocculation separation unit.

5. The high oil content wastewater treatment system according to claim 3, characterized in that: The crude oil dehydrator comprises a sixth outlet, and the sixth outlet is connected to the spoiler.

6. The high oil content wastewater treatment system according to claim 3, characterized in that: The spoiler is a spiral spoiler, which comprises a water pipeline, and the inner wall of the water pipeline is provided with spiral blades along the length direction of the water pipeline.

7. The high oil content wastewater treatment system according to claim 1, characterized in that: The flocculation separation unit comprises an electrolytic cell and a magnetic separator connected in sequence; The anode material of the electrolytic cell is an iron-aluminum alloy.

8. The high oil content wastewater treatment system according to claim 1, characterized in that: The electrocatalytic oxidation unit comprises an electrocatalytic oxidation tank; the electrocatalytic oxidation unit is connected to the second oil-water separation unit.

9. A method for treating high-oil wastewater, characterized in that: include: Separate the oil and water from the highly oily wastewater, and collect the oil and the wastewater after oil separation; The wastewater after oil separation is subjected to electrolytic flocculation, the flocculants are separated by magnetic separation, and then the effluent from the separated flocculants is subjected to electrocatalytic oxidation treatment.

10. The method for treating high-oil-content wastewater according to claim 9, characterized in that: The collected oil is recycled and processed.

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