Coalescence air flotation oil removal device

Abstract

The utility model belongs to the technical field of sewage treatment, and particularly relates to a coalescence air floatation oil removal device for oil and gas field wastewater treatment, which is characterized in that a cyclone sand remover, an oil particle coalescence layer, a micro air floatation device, an oil discharge device and a water discharge pipe are sequentially arranged in a shell from bottom to top, and an exhaust device is arranged at the upper part of one side of the shell; a sewage inlet pipe is arranged on the lower portion of one side of the shell and connected to the feeding end of the cyclone desander. Oily sewage passes through the cyclone sand remover to remove large-particle-size silt, then passes through the oil particle coalescence layer, tiny oil particles gradually form an oil film on the surface of a coalescence material, after the oil film reaches a certain thickness, the oil film is deformed into large oil droplets which are sufficient to be separated and rise from a water phase, and then oil drops and suspended flocs in the oily sewage are removed through the micro air flotation device. Finally, floating oil enters the oil discharging device to be discharged, the oil-removed sewage is discharged through the water discharging pipe, oil-water separation is completed, the oil removal purpose is achieved, the oil removal effect is better, the sewage treatment effect is improved, and the water quality of produced water is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of sewage treatment, and particularly relates to a coalescing air flotation oil removal device for oil and gas field wastewater treatment. Background Technique

[0002] A large amount of produced water is generated during the oil and gas field exploitation process. The produced water is a multiphase system integrating suspended solids, oil, dissolved gas, and dissolved salts, which is extracted from the formation together with crude oil and undergoes primary processing processes such as crude oil demulsification and separation. The impurities in the produced water mainly include suspended solids, colloidal particles, dispersed oil, floating oil, emulsified oil, dissolved substances, etc. If these sewage waters are discharged without being deeply treated, it will have a great impact on the surrounding environment, etc. After the oilfield produced water is treated, it can be reused in water injection exploitation, which is the so-called "produced water reinjection". Produced water reinjection can effectively reduce the demand for fresh water in oil and gas field exploitation and is of great significance for saving water resources.

[0003] The polymer flooding oil recovery technology is one of the important technologies to improve the oil recovery rate during the tertiary oil recovery process in oilfields. However, while polymer flooding improves the oil recovery rate, it also generates a large amount of polymer flooding produced water. Compared with traditional produced water, the polymer flooding produced water has a higher oil and suspended solid content and is more difficult to treat. Direct reinjection will cause formation plugging, damage to the core, an increase in injection pressure, and a decrease in the oil recovery rate.

[0004] During the produced water reinjection process, its water quality should meet the relevant requirements of "Water Quality Index and Analysis Method for Water Injection in Clastic Rock Reservoirs" SY / T5329 - 2012. Therefore, it is necessary to remove suspended solids, floating oil, and emulsified oil in the produced water. Currently, physical and chemical methods are mainly used to remove suspended solids and oil substances in wastewater. Common treatment processes include coagulation, filtration, air flotation, and their combined processes. Typical treatment processes are coagulation + filtration, air flotation + filtration, and hydrocyclone + filtration. Coagulation refers to adding chemical agents to wastewater to aggregate colloidal particles and tiny suspended solids in the wastewater into large particles, and then the process of precipitation removal rate from the wastewater. Air flotation is to form highly dispersed tiny bubbles in water, adhere to solid or liquid particles with hydrophobic groups in the wastewater to form a water - gas - particle three - phase mixed system. After the particles adhere to the bubbles, flocs with an apparent density less than that of water float to the water surface to form a floating scum layer, which is scraped off, thereby realizing the solid - liquid or liquid - liquid separation process. Coagulation precipitation mainly removes suspended solids in the produced water, and the air flotation process has a good removal effect on both suspended solids and floating oil in the produced water.

[0005] Although the traditional coagulation - flotation process can significantly remove suspended solids and floating oil in produced water, it requires a large amount of chemical agents to be added, resulting in a high treatment cost. At the same time, the removal effect of emulsified oil in produced water is poor. In addition, the quality of produced water in oil and gas fields is complex, with a high polymer content. The coagulation - flotation process has a poor removal effect on organic matter in wastewater. The produced water containing polymers has a certain viscosity, and the coagulation and flotation effects are poor. Currently, there is still a lack of efficient and low - cost treatment devices for produced water containing polymers in oil and gas fields. Summary of the Utility Model

[0006] In view of the above deficiencies in the prior art, the present utility model provides a coalescence - flotation oil removal device with better oil removal effect, improved sewage treatment effect, and enhanced quality of produced water.

[0007] A coalescence - flotation oil removal device described in the present utility model includes a housing and support legs located at the bottom of the housing. Inside the housing, a hydrocyclone desander, an oil particle coalescence layer, a micro - flotation device, an oil drainage device, and a drain pipe are arranged in sequence from bottom to top. An exhaust device is provided at the upper part of one side of the housing, and a sewage inlet pipe is provided at the lower part of one side of the housing. The sewage inlet pipe is connected to the feed end of the hydrocyclone desander.

[0008] The sand discharge port of the hydrocyclone desander extends to the outer bottom of the housing.

[0009] The oil particle coalescence layer is composed of a fixed bed of PE plastic regular material and a moving bed of lipophilic granular filler.

[0010] The lower fixed bed of the oil particle coalescence layer is composed of PE plastic regular material, and the upper moving bed is composed of granular lipophilic and hydrophobic materials.

[0011] The micro - flotation device includes a pressure - dissolved air tank located on one side of the housing and a cylinder body arranged on the top of the oil particle coalescence layer. The pressure - dissolved air tank is respectively connected to an air compressor and a water pump, and the dissolved air outlet of the pressure - dissolved air tank is located inside the cylinder body.

[0012] The quality of the flotation effect mainly depends on the effect of recycled water dissolved air and release. The micro - flotation device adopts high - efficiency and energy - saving dissolved air and release equipment, so that the compressed air of the air compressor and the recycled water pressurized by the water pump after treatment are fully mixed and dissolved in the pressure - dissolved air tank to form dissolved air water. The working pressure of the dissolved air tank is generally 2 - 3.5 kg / cm2. The oily sewage enters the flotation pool formed inside the cylinder body. The dissolved air water in the pressure - dissolved air tank is suddenly decompressed through a dissolved air release device (located below the dissolved air outlet) below the dissolved air outlet, so that a large number of micro - bubbles are released from the air dissolved in the water due to sudden decompression. The micro - bubbles encounter larger oil droplets and suspended solids in the oily sewage during the rising process. The micro - bubbles attach to the oil droplets and suspended solids, making them float up quickly. In this way, all the treated oil droplets and suspended solids in the oily sewage enter the oil drainage device. The clear water enters the drain pipe.

[0013] The described oil drainage device has a convex structure. The highest point is the overflow weir, and the lowest point is provided with an oil drainage port that extends to the outside of the housing.

[0014] A filtering structure is provided at the inner bottom of the described drain pipe.

[0015] A demisting device is arranged inside the described exhaust device.

[0016] The beneficial effects of the present utility model are as follows:

[0017] The present utility model is provided with a hydrocyclone desander, an oil particle coalescence layer, a micro flotation device, an oil drainage device and a drain pipe. The oily sewage first passes through the hydrocyclone desander to remove large particle size sediment, and then passes through the oil particle coalescence layer. Tiny oil particles gradually form an oil film on the surface of the coalescence material. After the oil film reaches a certain thickness, it deforms into larger oil beads large enough to separate and rise from the water phase. Subsequently, the oil droplets and suspended flocs in the oily sewage are removed through the micro flotation device. Finally, the floating oil enters the oil drainage device and is discharged, and the deoiled sewage is discharged through the drain pipe to complete the oil-water separation and achieve the purpose of oil removal. The oil removal effect is better, the sewage treatment effect is improved, and the quality of the produced water is enhanced. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of the present utility model.

[0019] In the figure: 1. Housing; 2. Support legs; 3. Hydrocyclone desander; 4. Oil particle coalescence layer; 5. Micro flotation device; 6. Oil drainage device; 7. Drain pipe; 8. Exhaust device; 9. Sewage inlet pipe; 10. Sand discharge port; 11. Pressure dissolution air tank; 12. Cylinder body; 13. Air compressor; 14. Water pump; 15. Overflow weir; 16. Oil drainage port. Detailed Embodiments

[0020] The following further describes the embodiments of the present utility model in conjunction with the drawings:

[0021] As Figure 1 shown, a coalescence flotation oil removal device includes a housing 1 and support legs 2 located at the bottom of the housing 1. Inside the housing 1, a hydrocyclone desander 3, an oil particle coalescence layer 4, a micro flotation device 5, an oil drainage device 6 and a drain pipe 7 are sequentially arranged from bottom to top. An exhaust device 8 is provided at the upper part of one side of the housing 1, and a sewage inlet pipe 9 is provided at the lower part of one side of the housing 1. The sewage inlet pipe 9 is connected to the feeding end of the hydrocyclone desander 3.

[0022] The sand discharge port 10 of the hydrocyclone desander 3 extends to the outer bottom of the housing 1.

[0023] The oil particle coalescence layer 4 is composed of a fixed bed of PE plastic regular material and a moving bed of lipophilic granular filler.

[0024] The lower fixed bed of the oil particle coalescence layer is composed of regular PE plastic materials, and the upper moving bed is composed of granular oil-loving and hydrophobic materials.

[0025] The micro-aeration flotation device 5 includes a pressure dissolved air tank 11 located on one side of the housing 1 and a cylinder 12 arranged on the top of the oil particle coalescence layer 4. The pressure dissolved air tank 11 is respectively connected to an air compressor 13 and a water pump 14, and the dissolved air outlet of the pressure dissolved air tank 11 is located inside the cylinder 12.

[0026] The oil drainage device 6 is of a convex structure, with the highest point being the overflow weir 15 and the lowest point being provided with an oil drainage port 16, and the oil drainage port 16 extends to the outside of the housing 1.

[0027] The inner bottom of the drain pipe 7 is provided with a filtering structure.

[0028] A demisting device is arranged inside the exhaust device 8.

[0029] The working process is as follows:

[0030] The oily sewage enters the hydrocyclone desander 3 through the sewage inlet pipe 9. According to the principles of centrifugal sedimentation and density difference, when the water flow enters the device tangentially from the desander inlet under a certain pressure, a strong rotational movement will be generated. Due to the different densities of sand and water, under the action of centrifugal force, centripetal buoyancy, and fluid drag force, the oily sewage with a lower density rises to the oil particle coalescence layer 4, and the sand with a higher density settles to the bottom and is discharged through the sand discharge port 10, thereby removing large-particle-size sediment in the produced water.

[0031] The oily sewage enters the oil particle coalescence layer 4, which is composed of a fixed bed of regular PE plastic materials and a moving bed of oil-loving granular fillers. The coalescence separation part utilizes the characteristic that the surface affinities of oil and water for the coalescence material surface are very different. When the oily sewage flows through the fixed bed filler of regular PE plastic materials, the tiny oil particles are adsorbed on the surface or pores of the coalescence material. As the number of adsorbed oil particles increases, the tiny oil particles gradually form an oil film on the surface of the coalescence material. After the oil film reaches a certain thickness, it deforms into larger oil beads that are large enough to separate and rise from the water phase. When the remaining tiny oil particles pass through the moving bed of oil-loving granular fillers, the granular fillers continuously move and collide to make the tiny oil droplets aggregate into larger oil beads and separate and rise from the water phase.

[0032] The minimum particle size of the emulsified oil beads that the oil particle coalescence layer 4 can perform coalescence treatment on is 5 - 10 μm. The larger the oil bead particle size, the greater the interfacial tension between the oil and water phases, which is more conducive to agglomeration; increasing the content of inorganic salts in the oily water can increase the surface tension, while the increase in the alkalinity and the increase in surface active substances of the oily wastewater will hinder the coalescence of the emulsified oil beads.

[0033] When the oily wastewater continues to flow upward through the micro-air flotation device 5, the oil droplets quickly adsorb and combine with the micro-bubbles and rapidly rise, facilitating the separation of oil and water. At the same time, it plays a role in solid-liquid separation, and can reduce COD, BOD, chromaticity, etc.

[0034] The micro-air flotation device 5 is equipped with a pressure dissolved air tank 11. The micro-bubbles in the dissolved air water generated by the pressure dissolved air tank 11 adhere to the larger oil droplets and suspended solids in the oily sewage. The oil droplets and suspended solids rise to the water surface with the micro-bubbles, forming floating oil and floating scum, so as to remove the oil droplets and suspended flocs in the oily sewage.

[0035] The floating oil enters the oil discharge device 6. When a certain thickness of oil layer accumulates at the upper end of the device, the oil layer is automatically discharged from the overflow weir 15 through the oil discharge port 16 under the action of buoyancy.

[0036] The deoiled sewage is discharged through the drain pipe 7 to complete the separation of oil and water and achieve the purpose of oil removal.

[0037] In addition, the micro-bubbles in the water body float to the surface and will contain a large amount of water vapor after bursting. The mist is removed through the mist removal device, and after reducing the moisture content, it is released into the atmosphere through the exhaust device 8.

Claims

1. A coalescence flotation oil removal device, comprising a housing (1) and a support leg (2) located at the bottom of the housing (1), characterized in that: A cyclone desander (3), an oil particle agglomeration layer (4), a micro-floatation device (5), an oil discharge device (6) and a drainage pipe (7) are sequentially arranged in the shell (1) from bottom to top. An exhaust device (8) is arranged at an upper portion of one side of the shell (1). A sewage inlet pipe (9) is arranged at a lower portion of one side of the shell (1). The sewage inlet pipe (9) is connected to a feed end of the cyclone desander (3).

2. A coalescence flotation oil removal device according to claim 1, characterized in that: The sand discharge port (10) of the cyclone sand remover (3) extends to the outer bottom of the housing (1).

3. A coalescence flotation oil removal device according to claim 1, characterized in that: The oil particle agglomeration layer (4) is composed of a fixed bed of PE plastic structured material and a moving bed of oleophilic granular filler.

4. A coalescence flotation oil removal device according to claim 3, characterized in that: The fixed bed is composed of PE plastic regular material, and the particle size of the oleophilic granular filler moving bed material is 3-5 mm.

5. A coalescence flotation oil removal device according to claim 1, characterized in that: The micro-air flotation device (5) comprises a pressure-dissolving gas tank (11) located on one side of the housing (1) and a cylinder (12) arranged on the top of the oil particle aggregation layer (4); the pressure-dissolving gas tank (11) is respectively connected to an air compressor (13) and a water pump (14); and the dissolved gas outlet of the pressure-dissolving gas tank (11) is located in the cylinder (12).

6. A coalescence flotation oil removal device according to claim 1, characterized in that: The oil discharge device (6) is a raised structure, the highest point of which is an overflow weir (15), and the lowest point is provided with an oil discharge port (16), which extends to the outside of the housing (1).

7. A coalescence flotation oil removal device according to claim 1, characterized in that: The inner bottom of the drainage pipe (7) is provided with a filtering structure.

8. A coalescence flotation oil removal device according to claim 1, characterized in that: The exhaust device (8) is provided with a demisting device.

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