Sewage treatment equipment and method for oil field thickened oil produced water

Abstract

The invention discloses sewage treatment equipment and method for oil field thickened oil produced water. The equipment comprises pretreatment equipment, main body equipment, dissolved gas supply equipment and a water outlet pump. Main body equipment comprises barrel equipment, and a flotation cyclone used for achieving the functions of dissolved air flotation and cyclone separation at the same time, separating out large-particle suspended solids through centrifugal force difference and achieving floating of oil drops through microbubble adsorption surfaces is sequentially arranged on the inner portion of the barrel equipment from top to bottom. The coalescence filler layer is made of oleophylic and hydrophobic core-shell structure fibers, and emulsified oil is promoted to polymerize and break emulsion through surface energy difference; and the inclined plate sedimentation device adopts an inclined tube labyrinth surrounding structure, performs deep sedimentation by utilizing a laminar flow principle, and further removes oil drops formed after coalescence.

Description

TECHNICAL FIELD

[0001] The present application relates to a sewage treatment method and equipment, in particular to a sewage treatment equipment and method specially used for oilfield heavy oil produced water. BACKGROUND

[0002] With the increase of the oil well exploitation years, the water content in the crude oil is higher and higher, and the water quantity of the crude oil is also larger. In addition to containing oil, the sewage may also carry mud and various viscosity reducers, making the sewage treatment process more complex. The main goal of sewage treatment is to treat the wastewater containing various pollutants into clean water meeting the discharge standard. At the same time, with the development of the tertiary oil recovery in the oilfield, the emergence of the oilfield polymer injection and the ternary drive development, the oilfield sewage becomes more and more complex and more and more difficult to treat. Specifically, the oilfield heavy oil sewage has the following characteristics: the water temperature is high, the oil in the water mainly exists in the form of suspended oil, emulsified oil and dissolved oil, contains a large amount of oil, heavy metals and organic matter and other pollutants, the oil emulsification is serious, and the oil and water densities are close. Therefore, the sewage treatment process needs to face the challenges including the removal of oil, the treatment of heavy metals, the degradation of organic matter and the efficient treatment of a large amount of sewage, and needs to reduce the production of secondary pollutants and avoid the addition of chemical agents or less addition of chemical agents. More specifically, with the change of the exploitation and development method, the water content is greatly increased in the current steam flooding exploitation, and the clean water quantity required by the steam flooding is also correspondingly increased. Therefore, the steam flooding method is used to exploit more heavy oil sewage after the long-term exploitation in the oilfield, and the produced heavy oil sewage has the following characteristics: (1) The density difference between oil and water is small, and the oil particles can be suspended in water for a long time; (2) The oil in the heavy oil sewage exists in the form of emulsion, which is difficult to separate; (3) The heavy oil sewage has high viscosity, especially at low water temperature; (4) The heavy oil sewage has more impurities, in addition to its own colloid asphalt, it also carries more mud sand, and various viscosity reducers are often added in the development process, making the composition of the heavy oil sewage more complex; (5) The heavy oil sewage has high temperature, in order to reduce the viscosity of the crude oil, the temperature is often increased to 70-80℃ in the development process of the heavy oil, while the transportation temperature of the thin oil is about 50℃; the above characteristics of the heavy oil sewage determine the particularity and complexity of the heavy oil sewage treatment technology.

[0003] Therefore, how to provide a method for effectively solving the problems faced by the steam flooding exploitation on the basis of the existing sewage treatment is urgent to be solved. SUMMARY

[0004] The present application aims to provide a sewage treatment equipment and method for oilfield heavy oil produced water, which is specially used for steam flooding type oilfield produced water, especially for treating steam flooding type oilfield heavy oil sewage, high-polymer-containing sewage, high-sulfur-containing sewage and high-iron-containing sewage.

[0005] The sewage treatment equipment for oilfield heavy oil produced water in the present application integrates the functions of pretreatment, air floatation separation, coalescence enhancement, ultrasonic cleaning and solid-liquid separation, and can effectively solve the above technical problems through reasonable distribution and combination, and has the advantages of high efficiency, simple operation and long-term effect.

[0006] The sewage treatment equipment for oilfield heavy oil produced water in the present application comprises a pretreatment equipment, a main equipment, a dissolved gas supply equipment and a water outlet pump, the main equipment comprises a barrel equipment, and an upper floatation cyclone, a middle coalescence filler layer and a lower inclined plate settling device are sequentially arranged in the barrel equipment. The floatation cyclone is used for realizing the functions of dissolved gas floatation and cyclone separation, and separating large particle suspended matters by using centrifugal force difference, and realizing oil droplet floating by using micro-bubble adsorption surface; The coalescence filler layer adopts oil-wet hydrophobic core-shell structure fiber, and promotes emulsified oil polymerization and demulsification by surface energy difference; The inclined plate settling device adopts inclined pipe labyrinth surrounding structure, and uses laminar flow principle for deep sedimentation to further remove oil droplets formed after coalescence.

[0007] Preferably, an ultrasonic scrubbing device and a cleaning solid-liquid separation device are arranged above the floatation cyclone in the barrel equipment, and the ultrasonic scrubbing device and the cleaning solid-liquid separation device both extend out of the top of the barrel equipment; a scrubbing pump and a backwashing air blower are additionally arranged outside the barrel equipment; The inlet of the scrubbing pump is connected with the outlet of the coalescence filler of the main equipment through a pipeline; The outlet of the scrubbing pump is connected with the liquid inlet of the ultrasonic scrubbing device, and is also connected with the inlet of the coalescence filler of the main equipment; The outlet of the ultrasonic scrubbing device is connected with the inlet of the cleaning solid-liquid separation device; The outlet of the backwashing air blower is connected with the backwashing gas inlet of the main equipment.

[0008] Preferably, the pretreatment equipment is a tubular reactor, which is connected with the tangential liquid inlet of the floatation cyclone in the main equipment through a pipeline; The dissolved gas supply equipment comprises an inclined pipe type dissolved gas tank and a dissolved gas pump, the outlet of the inclined pipe type dissolved gas tank is connected with the tangential liquid inlet of the floatation cyclone in the main equipment through a pipeline, and is also connected with the phase-cut inlet of the main equipment; The outlet of the dissolved gas pump is connected with the liquid inlet pipe of the inclined pipe type dissolved gas tank through a pipeline.

[0009] Preferably, the flow directions of the liquid entering the tangential inlet and the liquid entering the tangential inlet are opposite to each other.

[0010] Preferably, the flotation hydrocyclone includes a straight cylindrical section and a conical section that can rotate relatively independently. The flotation hydrocyclone is fixedly installed in the middle part of the cylindrical equipment via a tubular flotation hydrocyclone support, and is connected to the underflow sludge outlet at the bottom of the cylindrical equipment via the flotation hydrocyclone support. The tangential feeder is provided on the outer periphery of the straight cylindrical section. The tangential feeder goes around the bottom of the straight cylindrical section of the flotation hydrocyclone and then connects to the inner cylinder of the flotation hydrocyclone.

[0011] Preferably, the inlet of the tangential feeder connected to the inner cylinder of the flotation cyclone is irregularly shaped.

[0012] Preferably, the inclined plate settling device includes an inclined plate settling device support and a stainless steel inclined tube. The inclined plate settling device support is a stainless steel frame, including a main frame and a limiting slot. The limiting slot is used to fix the stainless steel inclined tube. The stainless steel inclined tube is a V-shaped folded inclined plate installation.

[0013] The wastewater treatment method of the oilfield heavy oil produced water treatment equipment in this invention operates according to the following steps: The wastewater temperature was controlled between 70 and 90°C, and the pH value was adjusted to 6.5 to 8.0 within the tubular reactor. The dissolved air pump draws 20% to 30% of clean water from the outlet of the main equipment and enters the inclined tube dissolved air tank to mix with compressed air. The resulting dissolved air water enters the treatment tank of the main equipment through the tangential inlet. Wastewater and dissolved air water in the main process tubular reactor are mixed at a volume ratio of 1:0.2~0.3 and then enter the flotation hydrocyclone inside the main equipment. A swirling field with a centrifugal intensity of 200~400G is formed in the flotation hydrocyclone to carry out solid-liquid separation and liquid-liquid separation, separating the liquid into three layers. The oil droplets in the upper layer enter the oil collection device, the sludge in the bottom layer is directly discharged, and the middle layer is the liquid after dissolved air flotation-cyclone separation. After dissolved air flotation-cyclone separation, the liquid passes through a coalescing packing layer. In the coalescing packing layer, the fine oil droplets in the liquid after dissolved air flotation-cyclone separation aggregate on the surface of the packing and grow to more than 50μm. The coalesced oil phase floats to the oil collection device, and the clear water flows out evenly to the inclined plate settling device. The inclined plate settling device utilizes a V-shaped folded inclined plate to form a two-way upward floating channel. Oil droplets collide and coalesce at the angle between the inclined plates, and after the droplet size increases, they quickly float to the oil collection device.

[0014] Preferably, in step 4), the coalescing packing layer is filled above the filter plate with oleophilic modified polypropylene packing with a specific surface area ≥ 500 m² / m³, the particle size of the packing is in the range of 1.2–2.5 mm, and the filling height is 0.8–1.0 m.

[0015] Preferably, the present invention adds a step of periodically performing intelligent cleaning and regeneration of the coalesced packing layer within the main equipment. This step, through a multi-stage gradient cleaning process, restores the flux of the coalesced packing to 98%. The specific cleaning steps are as follows: 1) Dissolved gas water is directly introduced into the coalescing packing layer by the dissolved gas supply equipment. The gas-water mixing fluidization technology is used to increase the shear force of the packing layer and use dissolved gas water to wash away the oil droplets that can be peeled off from the surface of the packing particles. 2) Simultaneously start the backwash fan and ventilate through the backwash inlet for 5-10 minutes. Distribute the air through the air distribution pipe to loosen the coalesced packing layer. The flushing intensity is 3L / (m²·s). 3) The wash pump is used to suck out the packing in the coalesced packing layer. The mechanical strength of the wash pump impeller is used to mechanically wash away the more stubborn contaminants and transfer some of the packing into the ultrasonic wash device. 4) By combining mechanical stirring with ultrasonic technology, the cavitation, acceleration and direct flow of ultrasonic waves in the liquid are used to directly and indirectly affect the liquid and dirt, thereby dispersing, emulsifying and peeling off the dirt layer to achieve the purpose of cleaning.

[0016] The wastewater treatment equipment for heavy oil produced water in this invention adopts full automatic control. It uses principles such as cyclone, flotation, sedimentation, coalescence, filtration, and ultrasonic cleaning to achieve a series of processes including solid-liquid separation, oil coalescence demulsification, coalescence filtration, backwashing of coalescence packing, and regeneration of heavy oil wastewater. This removes emulsified oil and suspended solids from the water, reduces the input of chemical agents, reduces the production of secondary pollutants, reduces labor workload, improves wastewater treatment efficiency, and solves problems such as severely substandard water quality after treatment, insufficient resistance to shock loads and treatment effect, and high operation and management costs.

[0017] Compared with the prior art, the present invention has the following advantages: The pretreatment process is complete and simple, and can be directly combined with the main equipment. It can replace the existing pretreatment and coarse filtration processes for heavy oil wastewater in oil fields, effectively removing oil and suspended solids from the wastewater, and has a good effect on removing asphaltene oil contained in the wastewater.

[0018] The contamination of the packing material generated during the wastewater treatment process was completely regenerated, ensuring that the effluent quality of heavy oily wastewater consistently meets standards and reducing the difficulty of water quality affecting subsequent processes.

[0019] The equipment of this invention is simple, requires no chemical addition, has low operating costs, produces no secondary pollution, and is highly intelligent. It only uses electricity during operation and does not require chemical addition. It is not only green and environmentally friendly, safe and pollution-free, but also has good treatment effect, low engineering investment and operating costs, and is easy to manage. It can be widely used for the removal of asphalt-like oils and suspended solids from heavy oil wastewater in oil fields. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural schematic diagram of the wastewater treatment equipment for produced water from heavy oil fields in this invention.

[0021] Figure 2 This is a top view schematic diagram of the wastewater treatment equipment for produced water from heavy oil fields in this invention.

[0022] Figure 3 This is a three-dimensional structural diagram of the main equipment in this invention.

[0023] Figure 4 This is a cross-sectional structural diagram of the main body of the present invention.

[0024] Figure 5 This is a side view of the flotation cyclone in this invention.

[0025] Figure 6 This is a three-dimensional structural diagram of the flotation cyclone in this invention.

[0026] Figure 7 This is a three-dimensional structural diagram of the inclined plate settling device support in this invention.

[0027] Explanation of some drawing numbers: 1. Tubular reactor, 2. Main equipment, 3. Inclined tube dissolved gas tank, 4. Dissolved gas pump, 5. Effluent pump, 6. Scrubbing pump, 7. Backwash fan, 8. Cleaning solid-liquid separation device, 9. Wastewater collection tank, 10. Cleaning water and wastewater discharge outlet, 11. Tangential inlet, 12. Underflow conduit, 13. Tangential liquid inlet, 14. Coalescing packing layer, 15. Filter cap, 16. Exhaust and liquid discharge outlet, 17. Manhole, 18. Underflow sludge discharge outlet, 19. 20. Mixer, 21. Ultrasonic generator, 22. Ultrasonic scrubbing device, 23. Oil collection device, 24. Top oil outlet, 25. Liquid inlet and conduit, 26. Flotation hydrocyclone, 27. Coalescing packing outlet, 28. Coalescing packing inlet, 29. Filter plate, 30. Backwash air inlet, 31. Inclined plate settling device, 32. Inclined plate settling device support, 33. Flotation hydrocyclone support, 34. Sludge removal device, 35. Common water outlet. Detailed Implementation

[0028] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, but this should not be construed as limiting the scope of the invention.

[0029] like Figure 1 and Figure 2 As shown, the wastewater treatment equipment for produced water from heavy oil fields in this invention includes pretreatment equipment, main equipment 2, inclined tube dissolved air tank 3, dissolved air pump 4, effluent pump 5, scrubbing pump 6, and backwash fan 7. Details are as follows: The pretreatment equipment is a tubular reactor 1. A demulsifier can be pre-added at the inlet of the tubular reactor 1. Turbulence is created by the spiral guide vanes inside the tubular reactor 1, achieving rapid mixing of the agent and wastewater. Under normal conditions, the mixing time is ≤30 seconds. The wastewater temperature is controlled at 70~90℃ and the pH value is adjusted to 6.5~8.0 inside the tubular reactor 1 to optimize the demulsification effect.

[0030] like Figure 3 and Figure 4 As shown, the main equipment 2 includes a cylindrical equipment 40, and inside the cylindrical equipment 40, from top to bottom, are arranged the following: Ultrasonic scrubbing device 21: Utilizing mechanical stirring combined with ultrasonic technology, specifically, under the action of mechanical stirring, the cavitation effect, acceleration effect, and direct flow effect generated by ultrasonic waves propagating in the liquid are used to directly and indirectly act on the liquid and dirt, causing the dirt layer to be dispersed, emulsified, and peeled off. It can efficiently remove dirt such as grease, oil stains, dust, particles, oxides, and biofilms from the surface and crevices of objects. This allows for thorough cleaning of the oleophilic and hydrophobic core-shell structure fibers in the coalesced filler layer, achieving the purpose of reuse.

[0031] Flotation hydrocyclone 25 (also known as hydrocyclone separation and air flotation device): It is used to simultaneously realize dissolved air flotation and hydrocyclone separation functions. It uses the difference in centrifugal force to separate large suspended particles, and at the same time uses microbubbles to adsorb the surface to achieve oil droplet flotation. Cohesive filler layer 14: It adopts oleophilic and hydrophobic core-shell structured fibers, which promote the polymerization of emulsified oil and demulsify through surface energy difference; Inclined plate settling device 30: It adopts an inclined tube labyrinth surrounding structure and utilizes the laminar flow principle for deep sedimentation to further remove the oil droplets formed after coalescence, thereby further improving the oil removal effect without adding oil-water separation equipment in the next stage.

[0032] like Figure 1 and Figure 2As shown, the inclined tube dissolved air tank 3, dissolved air pump 4, effluent pump 5, scrubbing pump 6, and coalescing packing backwash fan 7 are rationally arranged and fixed around the main equipment 2. This allows the main equipment 2 to be fully automated, integrating principles such as cyclone, flotation, sedimentation, coalescence, filtration, and ultrasound. After reasonable coordination and control, it can achieve a series of operations such as solid-liquid separation of heavy oil wastewater, oil coalescence demulsification, coalescence filtration, coalescing packing backwashing, and regeneration. It effectively removes emulsified oil and suspended solids from the water, reduces the input of chemical agents, reduces the production of secondary pollutants, reduces labor workload, and improves wastewater treatment efficiency. It effectively solves problems such as severely substandard water quality after treatment, insufficient resistance to shock loads and treatment effect, and high operation and management costs.

[0033] Specifically: the tubular reactor 1 is connected to the tangential inlet 13 of the main equipment 2 via a pipeline; the outlet of the inclined tube dissolved gas tank 3 is connected to the tangential inlet 13 of the main equipment 2 via a pipeline, and is also connected to the tangential inlet 11 of the main equipment 2; the outlet of the dissolved gas pump 4 is connected to the inlet of the inclined tube dissolved gas tank 3 via a pipeline, and the inlet of the dissolved gas pump 4 is connected to the common outlet 34 of the main equipment 2; the inlet of the water pump 5 is connected to the common outlet 34 of the main equipment 2; the inlet of the scrubbing pump 6 is connected to the outlet 26 of the coalescing packing of the main equipment 2, and the outlet conduit 24 of the scrubbing pump 6 is connected to the inlet of the ultrasonic scrubbing device 21 installed inside the main equipment 2, while the outlet of the scrubbing pump 6 is connected to the inlet 27 of the coalescing packing; the outlet of the backwash fan 7 is connected to the backwash air inlet 29 of the main equipment 2.

[0034] like Figure 3 and Figure 4 As shown, the inner top of the cylindrical equipment 40 is also provided with a circular oil collection device 22, which is connected to the top oil discharge port 23, and can periodically discharge the collected oil.

[0035] A manhole 17 and a sludge discharge device 33 are provided at the bottom of the cylindrical equipment 40. The sludge discharge device 33 is connected to the bottom flow sludge discharge outlet 18 provided on the wall of the cylindrical equipment 40. It is used to periodically clean the sludge (solid) discharged from the bottom of the flotation hydrocyclone 25 as well as the sludge generated by the coalescing packing layer 14 and the inclined plate settling device 30.

[0036] The flotation hydrocyclone 25 is fixedly installed in the middle of the cylindrical equipment 40, forming a treatment tank 41 outside the flotation hydrocyclone 25 and inside the cylindrical equipment 40.

[0037] like Figure 5 and Figure 6As shown, the flotation hydrocyclone 25 includes a straight cylindrical section 42 and a conical section 43 that can rotate relatively independently. The flotation hydrocyclone 25 is fixedly installed via a tubular flotation hydrocyclone support 32, and is connected to the underflow sludge discharge outlet 18 at the bottom of the cylindrical device 40 via the flotation hydrocyclone support 32, for discharging the sludge generated in the straight cylindrical section 42 and the conical section 43. The top of the straight cylindrical section 43 is provided with a trumpet-shaped extension tube 44, and a tangential feeder 13 is provided on the outer periphery of the straight cylindrical section 42. One end of the tangential feeder 13 goes around the bottom of the straight cylindrical section 42 of the flotation hydrocyclone 25 and then connects to the inner cylinder of the flotation hydrocyclone 25. The inlet of the tangential feeder 13 connecting to the inner cylinder of the flotation hydrocyclone 25 is irregularly shaped, such as... Figure 6 As shown, the irregularly shaped inlet 45 can disperse the flow rate of liquid entering the inner cylinder and accelerate the mixing of dissolved air water and sewage. The conical side surface of the conical section 43 preferably forms an angle of 80 degrees with the horizontal plane, and the other end of the tangential liquid inlet 13 extends out of the side wall of the cylinder equipment 40 after passing through the treatment tank 41.

[0038] The tangential feeder 13, extending from the sidewall of the flotation hydrocyclone 25, connects to both the tubular reactor 1 and the inclined tube dissolved air tank 3. Wastewater from the main process of the tubular reactor 1 is mixed with dissolved air water generated in the inclined tube dissolved air tank 3 at a volume ratio of 1:0.2~0.3 and then enters the tangential feeder 13. The mixture then flows tangentially into the flotation hydrocyclone 25 at a velocity of 4~6 m / s, forming a swirling field with a centrifugal intensity of 200~400G. Specifically, oily wastewater, under high pressure, enters the hydrocyclone's straight section 42 and conical section 43 through the irregular inlet 45 of the tangential feeder 13. Within the straight section 42, the swirling flow generates a high-speed centrifugal force field, creating a strong swirling motion. Within the conical section 43, the rotational speed further increases, generating a centrifugal force hundreds or even thousands of times stronger than gravity. Utilizing the difference in specific gravity between solids and liquids in wastewater, and relying on flotation force for dissolved air flotation-cyclone separation, solid-liquid and liquid-liquid separation are achieved. The separated material forms three layers: heavier solids settle to the bottom, lighter oil droplets rise to the top of the liquid layer, and the oil droplets and suspended solids aggregate towards the center under centrifugal force. The middle layer is the liquid from the dissolved air flotation-cyclone separation, located at 1 / 3 to 2 / 3 of its height above the bottom of the flotation cyclone separator 25. Finally, the continuously entering and separated water layer lifts the liquid into the treatment tank 41. Simultaneously, the oil droplets and suspended solids at the top are further lifted into the oil collection device 22 (oil collection efficiency ≥95%), and discharged into the sludge tank through the top oil outlet 23. The sludge generated in the flotation cyclone separator 25 is introduced into the sludge thickening tank through the bottom sludge outlet 18, minimizing the amount of solids entering the next step.

[0039] Because the wastewater entering the flotation hydrocyclone 25 contains dissolved air water, under centrifugal force, the bubbles are rapidly dispersed throughout the cyclone space, accelerating the selective collision and oil formation of particles and bubbles. As the particles move towards the wall of the flotation hydrocyclone 25 in the centrifugal field, they collide with radially inward-moving bubbles in the opposite direction. Hydrophobic particles easily adhere to the bubbles, forming oily bubbles. Centrifugal force can significantly increase the relative velocity and collision probability between particles and bubbles, solving the problem of slow flotation kinetics for fine particles. Because the density of the oily bubbles is less than that of liquids, under the action of centripetal buoyancy, they overcome centrifugal force and aggregate towards the low-pressure air core region at the center of the hydrocyclone, forming a foam phase rich in the target oily wastewater. The oily bubbles aggregated in the center diffuse out through the top opening and enter the oil slurry tank under the action of buoyancy. Particles containing heavy metals and impurities are pushed towards the wall by centrifugal force and discharged downwards along the cone from the sludge discharge port, thus adapting to the problems faced in steam-driven mining.

[0040] After being treated by dissolved air flotation-cyclone separation in flotation hydrocyclone 25, the liquid directly enters treatment tank 41 and flows through coalescing packing layer 14 and inclined plate settling device 30 in sequence by gravity. Finally, the clear water is output from common outlet 34 by water pump 5.

[0041] The coalescing packing layer 14 includes a filter plate 28 that is sealed and fixed to the inner wall of the cylindrical device 40, filter caps 15 evenly distributed on the filter plate 28, and oleophilic modified polypropylene packing (specific surface area ≥ 500 m² / m³) filled above the filter plate 28. The particle size range of the packing is 1.2–2.5 mm, and the optimal filling height is 0.8–1.0 m. After dissolved air flotation-cyclone separation, the liquid passes through the coalescing packing layer 14, and the fine oil droplets (particle size < 20 μm) aggregate on the surface of the packing and grow to more than 50 μm. After coalescence, the oil phase floats to the oil collection device 22, and the clean water flows out evenly through the water collection and distribution filter cap 15. Preferably, the packing adopts a non-uniform particle size distribution, coarser at the bottom and finer at the top; density 1.08 g / cm³, which can better filter out clean water and evenly distribute the water flow through the bottom filter cap 15.

[0042] like Figure 4 and Figure 7As shown, an inclined plate settling device 30 is installed below the coalescing packing layer 14. The inclined plate settling device 30 includes an inclined plate settling device support 31 and a stainless steel inclined tube. The inclined plate settling device support 31 is a stainless steel frame, including a Lego-style main frame and a limiting slot fixed on the main frame. The limiting slot is used to fix the stainless steel inclined tube installed on the inclined plate settling device support 31. The stainless steel inclined tube is a folded inclined plate, i.e., a V-shaped inclined plate. To enhance oil removal, the distance between two adjacent inclined plates is 50mm or 80mm, and they are installed at a 60° angle. The surface load is controlled at 5~8m³ / (m²·h). With the help of the V-shaped structure to form a bidirectional floating channel, oil droplets collide and coalesce at the angle of the inclined plates (coalescing effect), and after the particle size increases, they quickly float to the top. The 90° folded angle area forms a static oil collection space, which avoids the oil layer being disturbed and broken by the water flow. The shallow pool effect is multiplied. The V-shaped structure divides the water flow into multiple independent settling units with short settling distances, which can effectively enhance the separation of sludge and oil and optimize the upward path of oil droplets.

[0043] Preferably, the inclined plate sedimentation device 30 divides the inclined plate sedimentation device support 31 into 12 groups, which has the advantages of small gaps between installations, flexible disassembly, and easier water and air distribution.

[0044] Dissolved air pump 4 draws clean water from common outlet 34 to prepare dissolved air water. Specifically, dissolved air pump 4 draws 20%~30% clean water from common outlet 34 of cylindrical equipment 40, mixes it with compressed air (pressure 0.65MPa) in inclined tube dissolved air tank 13. The inclined tube dissolved air tank 13 is installed at an inclination angle of 15°, and the residence time of dissolved air water in the inclined tube dissolved air tank 13 is ≥15 seconds, generating microbubbles with a diameter of 10~30μm. Thus, this invention, by utilizing the interaction between inclined tube dissolved air tank 3 and flotation hydrocyclone 25, combined with static dissolved air and dynamic cyclone separation, can effectively improve the removal rate of micron-level oil droplets. At the same time, the dissolved air water generated by inclined tube dissolved air tank 3 can enter the treatment tank 41 of main equipment 2 through tangential inlet 11 for further dissolved air flotation treatment of the liquid after dissolved air flotation-cyclone separation. The direction of rotation of the dissolved air water entering the main equipment 2 from the tangential inlet 11 is opposite to the direction of rotation of the dissolved air water entering the flotation hydrocyclone 25 from the tangential feeder 13. For example, one enters clockwise and the other counterclockwise, further increasing the selective collision and oiling of particles and bubbles. The tangential inlet 11 is set higher than the tangential feeder 13 in the main equipment 2, which can avoid the collision of the water entering the tangential inlet 11 and the water entering the tangential feeder 13 during rotational convection, thus avoiding disturbance of the upward flow and having a counteracting effect; at the same time, it can also play a secondary relay role, supporting large particulate pollutants whose upward force has been exhausted.

[0045] An ultrasonic scrubbing device 21 is located above the flotation hydrocyclone 25 and in the middle of the annular oil collection device 22. The ultrasonic scrubbing device 21 includes a cleaning chamber 46, a mixer 19, and an ultrasonic generator 20. The top of the cleaning chamber 46 extends beyond the upper surface of the cylindrical device 41. The mixer 19 and the ultrasonic generator 20 are fixedly installed on the top of the cleaning chamber 46. A cleaning solid-liquid separation device 8 and a wastewater collection tank 9 are fixedly installed on the side of the cleaning chamber 46, with the wastewater collection tank 9 located near the cleaning solid-liquid separation device 8. The cleaning chamber 46 has an inlet and a conduit 24 extending outside the cylindrical device 40. The outlet of the cleaning chamber 46 is connected to the inlet of the cleaning solid-liquid separation device 8, and the wastewater outlet of the cleaning solid-liquid separation device 8 is connected to the wastewater collection tank 9, and the wastewater is discharged from the main equipment through the cleaning water wastewater discharge port 10 on the side wall of the wastewater collection tank 9. The underflow port of the cleaning solid-liquid separation device 8 extends through the underflow conduit 12 to a height of 500 mm above the coalescing packing layer 14, such as... Figure 4 As shown.

[0046] The inlet of the scrubbing pump 6 is connected to the coalescing packing outlet 26 of the main equipment 2 through a pipeline. The outlet of the scrubbing pump 6 is connected to the liquid inlet and conduit 24 and coalescing packing inlet 27 of the main equipment 2, respectively. The outlet of the backwash fan 7 is connected to the backwash air inlet 29 of the main equipment 2.

[0047] When the pressure differential of the coalescing packing reaches 30 kPa, the backwash fan 7 is started to ventilate through the backwash inlet 29 for 5-10 minutes, and the air is distributed by the air distribution pipe to loosen the packing in the coalescing packing layer 14. The flushing intensity is 3 L / (m²·s). The scrubbing pump 6 draws coalescing packing from the coalescing packing outlet 26 of the cylindrical equipment 40. Using the centrifugal force of the scrubbing pump 6, the packing is pre-scrubbed in the scrubbing pump 6. Then, a portion is pumped into the treatment tank 41 through the coalescing packing inlet 27, with a flushing intensity of 5 L / (m²·s), so that the coalescing packing is fluidized in the treatment tank 41. A portion enters the cleaning chamber 46, where the ultrasonic generator 20 performs ultrasonic cleaning and regeneration while the mixer 19 mechanically stirs the packing. That is, the ultrasonic scrubbing device 21 is started simultaneously with the mixer 19. The ultrasonic generator 20 emits ultrasonic waves with a frequency of 40 kHz and a power density of 0.5 W / cm² for 10-15 minutes, using the cavitation effect to remove oil and dirt from the surface of the packing. The mixer 19 operates at a speed of 100-200 rpm to assist in agitation and enhance the cleaning effect. This invention utilizes ultrasonic-mechanical synergistic cleaning; the cavitation effect of the ultrasonic generator 20, combined with the mechanical stirring, thoroughly removes oil and grime from the surface of the coalesced packing material, extending its service life. Through modular intelligent backwashing, and by controlling the timing of the backwash fan 7, the scrubbing pump 6, and the sludge discharge system, automatic cleaning without shutdown is achieved, ensuring continuous system operation.

[0048] After the gas backwashing stops, the exhaust and liquid discharge ports 16 of the main equipment 2 between the coalescing packing layer 14 and the inclined plate settling device 30 will periodically discharge to prevent gas accumulation.

[0049] The device in this invention operates in the following manner: 1. Wastewater Input: Heavy oil produced water is pumped to tubular reactor 1. A demulsifier (if applicable) is added at the inlet of tubular reactor 1. Turbulence is created by the spiral guide vanes inside the reactor, achieving rapid mixing of the agent and wastewater (mixing time ≤ 30 seconds). The wastewater temperature is controlled at 70~90℃ (if the raw water temperature is insufficient, a heat exchanger can be added), and the pH is adjusted to 6.5~8.0 to optimize the demulsification effect.

[0050] 2. Dissolved air water preparation: Dissolved air pump 4 draws 20%~30% clean water from the common outlet 34 of the main equipment 2 and enters the inclined tube type dissolved air tank 3. After mixing with compressed air (pressure 0.65MPa), dissolved air water is formed. The dissolved air water enters the main equipment 2 through the tangential inlet 11.

[0051] 3. The main process wastewater in the tubular reactor 1 and the dissolved air water generated by the inclined tube dissolved air tank 3 enter the flotation hydrocyclone 25 at a volume ratio of 1:0.25. The water enters the flotation hydrocyclone 25 tangentially at a flow rate of 4~6m / s through the tangential feeder 13, forming a swirling field with a centrifugal intensity of 200~400G, completing the dissolved air flotation-swirling separation stage. Oil droplets and suspended solids gather towards the center under the action of centrifugal force. The floating oil enters the oil collection device, and the sludge is introduced into the sludge thickening tank through the bottom sludge discharge outlet 18.

[0052] 4. After dissolved air flotation-cyclone separation, the liquid (flotated water) enters the coalescing packing layer 14. The fine oil droplets (particle size <20μm) in the liquid after dissolved air flotation-cyclone separation coalesce on the surface of the packing and grow to more than 50μm. After coalescence, the oil phase floats to the oil collection device 22, and the clean water flows out evenly through the water collection and distribution filter cap 15.

[0053] 5. The water is collected and distributed through the filter cap 15 and then enters the inclined plate sedimentation device 30 for further separation of the residual oil phase, with the surface load controlled at 5~8 m³ / (m²·h).

[0054] 6. The treated clean water is output from the common outlet 34 of the main equipment 2 by the water pump 5. 70% to 80% of it is recycled for oilfield water injection or external discharge, and the remaining 20% ​​to 30% is used as a dissolved air water source for recycling.

[0055] The wastewater treatment equipment for produced water from heavy oil fields in this invention needs to be cleaned regularly during operation. The specific cleaning process is as follows: When the pressure differential of the coalescing packing reaches 30 kPa, the backwash fan 7 is started to ventilate through the backwash inlet 29 for 5-10 minutes. The air is distributed through the air distribution pipe to loosen the packing layer, with a flushing intensity of 3 L / (m²·s). The scrubbing pump 6 extracts the coalescing packing from the coalescing packing outlet 26 of the main equipment 2. Using the centrifugal force of the scrubbing pump 6, the packing is pre-scrubbed in the scrubbing pump 6. Then, a portion is pumped in through the coalescing packing inlet 27 and sprayed through the nozzle to flush the packing, with a flushing intensity of 5 L / (m²·s). This fluidizes the coalescing packing in the treatment tank 41, while a portion enters the ultrasonic scrubbing device 21 for ultrasonic cleaning and regeneration.

[0056] Wastewater generated from cleaning the coalescing packing enters the cleaning solid-liquid separation device 8 from the outlet of the ultrasonic scrubbing device 21. After separation, the underflow (solid content ≥15%) is discharged back into the main equipment 2 through the underflow conduit 12. The underflow outlet of the cleaning solid-liquid separation device 8 extends through the underflow conduit 12 to a height of 500mm above the coalescing packing layer 14. The supernatant returns to the wastewater collection tank 9 and is discharged into the wastewater pool for further treatment. The backwashing and regeneration water consumption rate is <3%.

[0057] After the equipment of this invention was put into use at the Liaohe Oilfield heavy oil wastewater treatment station, it achieved very good results. The specific experimental data recorded are as follows: On November 22, 2024, the daily water treatment volume was 11m³. 3 Backwash water consumption: 0.35m³ 3 On November 28th, the daily water treatment volume was 20.29 m³. 3 Backwash water consumption: 0.37m³ 3 On November 30th, the daily water treatment volume was 16.15 m³. 3 Backwash water consumption: 0.48m³ 3 On December 8th, the daily water treatment volume was 18.87 m³. 3 Backwash water consumption: 0.42m³ 3 .

[0058] In summary, this invention provides dissolved air pump and inclined tube dissolved air tank to supply dissolved air water to the equipment. The water used for dissolved air is filtered water to ensure the dissolved air volume. This invention also adds a scrubbing pump and a backwash fan, and uses an ultrasonic scrubbing device to periodically transfer the coalescing packing to the ultrasonic scrubbing device for thorough cleaning, ensuring the restoration and regeneration of the coalescing packing.

Claims

1. A wastewater treatment device for produced water from heavy oil fields, comprising pretreatment equipment, main equipment, dissolved air supply equipment, and effluent pump, characterized in that, The main equipment includes a cylindrical device, inside which are arranged in a top-middle-bottom order: Flotation hydrocyclone: ​​It is used to simultaneously achieve dissolved air flotation and cyclone separation. It separates large suspended particles by utilizing the difference in centrifugal force, and at the same time uses microbubbles to adsorb the surface and achieve oil droplet flotation. The coalescing filler layer uses oleophilic and hydrophobic core-shell structured fibers, which promote the polymerization of emulsified oil and effectively demulsify it through surface energy differences; Inclined plate sedimentation device: It adopts an inclined tube labyrinth structure and uses the laminar flow principle to perform deep sedimentation, further removing the oil droplets formed after coalescence.

2. The wastewater treatment equipment for produced water from heavy oil fields according to claim 1, characterized in that, An ultrasonic scrubbing device and a cleaning solid-liquid separation device are provided inside the cylindrical equipment above the flotation hydrocyclone, and both the ultrasonic scrubbing device and the cleaning solid-liquid separation device extend beyond the top of the cylindrical equipment; a scrubbing pump and a backwash fan are added outside the cylindrical equipment. The inlet of the scrubbing pump is connected to the outlet of the coalescing packing of the main equipment via a pipeline; The outlet of the scrubbing pump is connected to the inlet of the ultrasonic scrubbing device, and also to the inlet of the coalescing packing of the main equipment; The outlet of the ultrasonic scrubbing device is connected to the inlet of the cleaning solid-liquid separation device. The outlet of the backwash fan is connected to the backwash air inlet of the main equipment.

3. The wastewater treatment equipment for produced water from heavy oil fields according to claim 2, characterized in that, The pretreatment equipment is a tubular reactor, which is connected to the tangential feeder of the flotation hydrocyclone in the main equipment via a pipeline; The dissolved gas supply equipment includes an inclined tube dissolved gas tank and a dissolved gas pump. The outlet of the inclined tube dissolved gas tank is connected to the tangential liquid inlet of the flotation cyclone in the main equipment through a pipeline, and is also connected to the tangential inlet of the main equipment. The outlet of the dissolved gas pump is connected to the inlet of the inclined tube dissolved gas tank via a pipeline.

4. The wastewater treatment equipment for produced water from heavy oil fields according to claim 3, characterized in that, The flow directions of the liquid entering the tangential inlet and the liquid entering the tangential inlet are opposite to each other.

5. The wastewater treatment equipment for produced water from heavy oil fields according to claim 3, characterized in that, The flotation hydrocyclone includes a straight cylindrical section and a conical section that can rotate relatively independently. The flotation hydrocyclone is fixedly installed in the middle part of the cylindrical equipment via a tubular flotation hydrocyclone support, and is connected to the underflow sludge outlet at the bottom of the cylindrical equipment via the flotation hydrocyclone support. The tangential feeder is provided on the outer periphery of the straight cylindrical section. The tangential feeder goes around the bottom of the straight cylindrical section of the flotation hydrocyclone and then connects to the inner cylinder of the flotation hydrocyclone.

6. The wastewater treatment equipment for produced water from heavy oil fields according to claim 5, characterized in that, The inlet of the tangential feeder connected to the inner cylinder of the flotation hydrocyclone has an irregular shape.

7. The wastewater treatment equipment for produced water from heavy oil fields according to claim 5, characterized in that, The inclined plate settling device includes an inclined plate settling device support and a stainless steel inclined tube. The inclined plate settling device support is a stainless steel frame, including a main frame and a limiting slot. The limiting slot is used to fix the stainless steel inclined tube. The stainless steel inclined tube is a V-shaped folded inclined plate installation.

8. A method for treating wastewater from produced water of heavy oil fields as described in any one of claims 1-7, characterized in that, Follow these steps: The wastewater temperature was controlled between 70 and 90°C, and the pH value was adjusted to 6.5 to 8.0 within the tubular reactor. The dissolved air pump draws 20% to 30% of clean water from the outlet of the main equipment and enters the inclined tube dissolved air tank to mix with compressed air. The resulting dissolved air water enters the treatment tank of the main equipment through the tangential inlet. Wastewater and dissolved air water in the main process tubular reactor are mixed at a volume ratio of 1:0.2~0.3 and then enter the flotation hydrocyclone inside the main equipment. A swirling field with a centrifugal intensity of 200~400G is formed in the flotation hydrocyclone to carry out solid-liquid separation and liquid-liquid separation, separating the liquid into three layers. The oil droplets in the upper layer enter the oil collection device, the sludge in the bottom layer is directly discharged, and the middle layer is the liquid after dissolved air flotation-cyclone separation. After dissolved air flotation-cyclone separation, the liquid passes through a coalescing packing layer. In the coalescing packing layer, the fine oil droplets in the liquid after dissolved air flotation-cyclone separation aggregate on the surface of the packing and grow to more than 50μm. The coalesced oil phase floats to the oil collection device, and the clear water flows out evenly to the inclined plate settling device. The inclined plate settling device utilizes a V-shaped folded inclined plate to form a two-way upward floating channel. Oil droplets collide and coalesce at the angle between the inclined plates, and after the droplet size increases, they quickly float to the oil collection device.

9. The wastewater treatment method for produced water from heavy oil fields according to claim 8, characterized in that, In step 4), the coalescing packing layer is filled above the filter plate with oleophilic modified polypropylene packing with a specific surface area ≥500m² / m³, the particle size range of the packing is 1.2–2.5mm, and the filling height is 0.8–1.0m.

10. The wastewater treatment method for produced water from heavy oil fields according to claim 8, characterized in that, An additional step is added to the regular intelligent cleaning and regeneration of the coalesced packing layer within the main equipment. This step, through a multi-stage gradient cleaning process, restores the coalesced packing flux to 98%. The specific cleaning steps are as follows: 1) Dissolved gas water is directly introduced into the coalescing packing layer by the dissolved gas supply equipment. The gas-water mixing fluidization technology is used to increase the shear force of the packing layer and use dissolved gas water to wash away the oil droplets that can be peeled off from the surface of the packing particles. 2) Simultaneously start the backwash fan and ventilate through the backwash inlet for 5-10 minutes. Distribute the air through the air distribution pipe to loosen the coalesced packing layer. The flushing intensity is 3L / (m²·s). 3) The wash pump is used to suck out the packing in the coalesced packing layer. The mechanical strength of the wash pump impeller is used to mechanically wash away the more stubborn contaminants and transfer some of the packing into the ultrasonic wash device. 4) By combining mechanical stirring with ultrasonic technology, the cavitation, acceleration and direct flow effects of ultrasonic waves in the liquid are used to directly and indirectly affect the liquid and dirt, thereby dispersing, emulsifying and peeling off the dirt layer to achieve the purpose of cleaning.

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