Multifunctional pretreatment device and pretreatment method for complex waste liquid in oil and gas fields

Abstract

The present invention provides a multifunctional pretreatment device and a pretreatment method for complex waste liquid in oil and gas fields. The multifunctional pretreatment device for complex waste liquid in oil and gas fields has a waste liquid incoming water pipeline connected to a pipeline mixer through a lift pump. The pipeline mixer is sequentially connected to a gas-adding flocculation device and a strengthened flocculation separation device through pipelines. The first and second chemical dosing devices are respectively connected to the input and output ends of the pipeline mixer through the first and second chemical dosing pipelines, and are respectively connected to the first and second reaction chambers of the strengthened flocculation separation device through the third and fourth chemical dosing pipelines. The third chemical dosing device is communicated with the first reaction chamber through the fifth chemical dosing pipeline. Valves are provided on each chemical dosing pipeline. The gas-adding flocculation device performs microbubble gel breaking, aeration oxidation, flocculation and sedimentation treatment on the waste liquid. The strengthened flocculation separation device performs dissolved air flotation, floating oil collection, chemical oxidation, chemical dosing clarification, flocculation, inclined plate sedimentation and floating oil collection again on the waste liquid and then discharges it. Accordingly, the technological process can be optimized to meet the disposal requirements of waste liquids with different properties.

Description

Technical Field

[0001] The present invention relates to the field of complex waste liquid treatment in oil and gas fields, and in particular to a multifunctional pretreatment device and a pretreatment method for complex waste liquid in oil and gas fields. Background Art

[0002] With the gradual deepening of oilfield development, the components of the produced waste liquid are becoming more and more complex and its properties are becoming more and more variable, making it increasingly difficult to achieve up-to-standard treatment of the waste liquid. In addition, due to different formation fracturing conditions, the components of the fracturing fluid for each well are different, which also poses challenges to the adaptability of the produced water treatment process to different water qualities. In addition, major oilfields have gradually increased the development intensity of remote small blocks. However, due to the remote geographical location of remote small blocks, the produced water volume is small, and the produced water is mostly intermittent and non-continuous. If it is transported or piped to a centralized treatment station, the treatment cost will be high. In view of the above situation, if a single pretreatment technology is adopted, different pretreatment methods need to be selected according to the properties of different waste liquids (including produced water). However, a single pretreatment method usually cannot meet the treatment requirements of complex waste liquids and cannot achieve good treatment effects. Therefore, different pretreatment processes need to be combined according to the properties of different waste liquids to form a combined process. Combining the combined process flow widely adopted in the current oilfield waste liquid treatment process, such as gravity oil removal, coagulation sedimentation, dissolved air flotation, filtration, etc., not only has a long process flow, making the process device large in scale and difficult to be skid-mounted, but also has poor applicability to the treatment of refractory waste liquids, the effluent effect is not ideal, and its applicability to the treatment of scattered waste liquids in remote small blocks is poor. If the dosage of the medicament is increased to ensure the effluent water quality, it will inevitably cause an increase in the dosage of the medicament and the amount of sludge generated, thus increasing the operation and disposal costs.

[0003] In addition, referring to the related technologies for treating oilfield waste liquid, the patent document with the application number 201620765032.5 discloses an oil and gas field wastewater platform treatment system, which is successively connected to a flowback well site, a buffer tank, a fracturing flowback liquid treatment system, and a reused water temporary storage tank. The fracturing flowback liquid treatment system includes an oxidation tank, a hardness removal tank, a flocculation and sedimentation device, a media filter, and a sludge treatment device in sequence. However, the process flow of this device is too complex, resulting in a large device scale, a large investment in operating costs, and it cannot be skid-mounted, making it unsuitable for treating scattered waste liquid in remote small blocks. The patent document with the application number 201310120660.9 discloses an oil and gas field wastewater treatment device and its treatment method, which utilizes waste heat resources, directly contacts the wastewater heating system through an efficient floating bed, evaporates the wastewater into water vapor by counter-current contact with air, and then condenses it into purified water. The separated effective components can be reused after being highly concentrated. However, this technology requires waste heat resources, and it is difficult to meet the conditions at general waste liquid disposal sites. Therefore, although the device scale of this technology is small and the waste liquid treatment efficiency is high, it is difficult to be popularized and applied at general waste liquid disposal sites. The patent document with the application number 201520937062.5 discloses a mobile skid-mounted oil and gas field wastewater treatment device, which is provided with a flotation chamber, a filtration chamber, and a disinfection chamber. The oily substances in the wastewater are removed through the flotation chamber, and the filtration chamber also has a good effect on removing suspended solids. Although the device scale of this device is small, it can be skid-mounted and has a large cost advantage, but the adaptability of this device to waste liquid with poor water quality is not good.

[0004] Therefore, designing a pretreatment device and treatment method that can achieve multiple pretreatment functions to meet the disposal processes of waste liquids with different properties, can be flexibly adjusted according to the variability of waste liquid properties, has a small device scale, and can be used for treating scattered waste liquid in remote small blocks has become one of the urgent problems to be solved in this field. Summary of the Invention

[0005] The technical problem to be solved by this technical solution is how to provide a high-efficiency treatment device and treatment method that can meet the disposal processes of waste liquids with different properties, has a compact internal structure of the device, a small overall device scale, and can realize a process series flow of multi-stage dosing coagulation, microbubble demulsification, multi-stage oxidation, dissolved air flotation, sedimentation, and dosing clarification to implement functions of removing solid suspended solids, demulsifying, removing oil, and degrading different waste liquids.

[0006] To solve the above technical problems, the present technical solution provides a multifunctional pretreatment device for complex waste liquid in oil and gas fields, which includes: a lift pump, a pipeline mixer, an air-adding flocculation device, a strengthened flocculation separation device, a first chemical dosing device, a second chemical dosing device and a third chemical dosing device; wherein, the waste liquid incoming pipeline is connected to the pump-in end of the lift pump, the pump-out end of the lift pump is connected to the input end of the pipeline mixer through a pipeline, the output end of the pipeline mixer is connected to the water inlet end of the air-adding flocculation device through a pipeline, the water outlet end of the air-adding flocculation device is connected to the water inlet end of the strengthened flocculation separation device through a pipeline, the water outlet end of the strengthened flocculation separation device is connected to the drain pipe, the first chemical dosing device is connected to the pipeline at the input end of the pipeline mixer through a first chemical dosing pipeline and a valve is arranged on the first chemical dosing pipeline, the second chemical dosing device is connected to the pipeline at the output end of the pipeline mixer through a second chemical dosing pipeline and a valve is arranged on the second chemical dosing pipeline, the first chemical dosing device is also communicated with the first reaction chamber of the strengthened flocculation separation device through a third chemical dosing pipeline and a valve is arranged on the third chemical dosing pipeline, the second chemical dosing device is also communicated with the second reaction chamber of the strengthened flocculation separation device through a fourth chemical dosing pipeline and a valve is arranged on the fourth chemical dosing pipeline, the third chemical dosing device is communicated with the first reaction chamber of the strengthened flocculation separation device through a fifth chemical dosing pipeline and a valve is arranged on the fifth chemical dosing pipeline; the air-adding flocculation device can carry out microbubble degumming, aeration oxidation, flocculation and sedimentation treatment on the waste liquid conveyed into it and then convey it into the strengthened flocculation separation device through a pipeline, and the strengthened flocculation separation device can carry out dissolved air flotation, floating oil collection, chemical oxidation, chemical dosing clarification, flocculation, inclined plate sedimentation and floating oil collection again on the waste liquid conveyed into it and then discharge it through the drain pipe. Accordingly, through the series application of the air-adding flocculation device and the strengthened flocculation separation device, the overall structure of the pretreatment device can be optimized, thereby reducing the overall scale of the pretreatment device and ensuring the efficient operation of the waste liquid treatment process; in addition, by controlling the valves on each chemical dosing pipeline, the pretreatment device can realize the process of multi-stage chemical dosing coagulation, multi-stage oxidation and chemical dosing clarification to meet the disposal needs of waste liquids with different properties.

[0007] As another implementation of the present technical solution, the aerated flocculation device includes: an outer cylinder, a treatment liquid discharge pipe, an inner cylinder, a bubble liquid inlet pipe, a water inlet ring pipe, at least one bubble generator pipeline, and a sludge discharge pipe; wherein, the outer cylinder is in a capsule shape and is vertically arranged. An exhaust hole communicating with the outside is provided at the upper end of the outer cylinder. A through hole is provided at the central position of the lower end of the outer cylinder, and at least one treatment liquid outlet is provided around the through hole. The at least one treatment liquid outlet is connected to the treatment liquid discharge pipe; the inner cylinder is coaxial with the outer cylinder and is fixedly connected between the outer side surface of the inner cylinder and the inner side surface of the outer cylinder by several support rods, so that the inner cylinder is arranged inside the outer cylinder, and there is a spacing between the outer side surface of the inner cylinder and the inner side surface of the outer cylinder, thereby forming a sedimentation space; the inner cylinder includes a cylindrical section, a waist-constricted section, and a funnel section from top to bottom. The upper end of the cylindrical section is an open mouth. A double-layered diversion structure is provided at intervals on the inner side surface of the cylindrical section. The diversion structure is composed of several diverters with an isosceles triangle cross-section evenly spaced on the inner side surface of the cylindrical section. The two isosceles sides of the cross-section of the diverter are in a concave arc shape, and the diverters of the upper-layer diversion structure are staggered from the diverters of the lower-layer diversion structure. The waist-constricted section is combined with the lower end of the cylindrical section, and the diameter of the middle part of the waist-constricted section is smaller than the diameters of its upper and lower ends. The funnel section is combined with the lower end of the waist-constricted section, and the diameter of the funnel section gradually decreases from top to bottom. A through hole is provided at the lower end of the funnel section corresponding to the position of the through hole. The bubble liquid inlet pipe passes through and is hermetically combined with the through hole, and the upper end of the bubble liquid inlet pipe is communicated with the through hole. The lower end of the bubble liquid inlet pipe is located outside the through hole and is closed; the water inlet ring pipe is fixedly arranged in a ring shape on the upper part of the outer side surface of the outer cylinder, and a water inlet hole is provided on the water inlet ring pipe to connect to the output end of the pipeline mixer through a pipeline. At least one waste liquid output port is also provided on the water inlet ring pipe. At least one waste liquid input port is provided on the bubble liquid inlet pipe corresponding to the at least one waste liquid output port. At least one bubble generator pipeline is connected between the at least one waste liquid output port and the at least one waste liquid input port, and a bubble generator is arranged on the bubble generator pipeline; a slag discharge port is also provided at the bottom of the bubble liquid inlet pipe, and the slag discharge port is connected to the sludge discharge pipe. In this way, the internal structure of the aerated flocculation device is compact, the waste liquid treatment efficiency is high, and the waste liquid transported into it can be subjected to microbubble degumming, aeration oxidation, swirl and eddy current flocculation, and sedimentation processes.

[0008] As another implementation of the present technical solution, the enhanced flocculation separation device includes, from its water inlet end to its water outlet end: a contact chamber, two oil residue chambers, a separation chamber, a first mixing chamber, a first reaction chamber, a second mixing chamber, a second reaction chamber, an inclined plate sedimentation chamber, and a clear water chamber; the contact chamber is connected to the waste liquid inlet pipe, the two oil residue chambers are respectively arranged on both sides of the contact chamber, the separation chamber is arranged on the other side of the contact chamber relative to the waste liquid inlet pipe, and the separation chamber is separated from the contact chamber and the two oil residue chambers by a partition plate inclined upward toward the separation chamber. A first oil collection trough is installed at a position above the contact chamber and at the same height as the upper end of the partition plate. The two ends of the first oil collection trough communicate with the upper parts of the two oil residue chambers respectively. The waste liquid overflows from the contact chamber into the separation chamber. A first sludge hopper is formed at the bottom of the separation chamber, and a sludge discharge pipe is installed on the first sludge hopper. The first mixing chamber, the first reaction chamber, and the second mixing chamber are arranged side by side on the other side of the separation chamber relative to the partition plate, and the separation chamber is communicated with the first mixing chamber through a flow channel. The first mixing chamber is communicated with the first reaction chamber through a flow channel. The first reaction chamber is communicated with the second mixing chamber through a flow channel. And stirring devices are installed in both the first mixing chamber and the second mixing chamber. The second reaction chamber is arranged on the other side of the first mixing chamber, the first reaction chamber, and the second mixing chamber arranged side by side, and the second reaction chamber is communicated with the second mixing chamber through a flow channel. A second sludge hopper is formed at the bottom of the second reaction chamber, and a sludge discharge pipe is installed on the second sludge hopper. The inclined plate sedimentation chamber is arranged on the other side of the second reaction chamber, and the second reaction chamber is communicated with the inclined plate sedimentation chamber through a flow channel. A second oil collection trough is installed above the inclined plate sedimentation chamber. The clear water chamber is arranged on the other side of the inclined plate sedimentation chamber. The waste liquid overflows from the inclined plate sedimentation chamber into the clear water chamber. The clear water chamber is connected to a drain pipe. The third and fifth chemical addition pipelines are both connected to the first reaction chamber, and the fourth chemical addition pipeline is connected to the second reaction chamber. In this way, the internal structure of the enhanced flocculation separation device is compact, the waste liquid treatment efficiency is high, and the waste liquid transported into it can be subjected to processes such as floating oil collection, chemical oxidation, chemical addition clarification, flocculation, inclined plate sedimentation, and floating oil collection again.

[0009] As another implementation of the present technical solution, sampling ports are provided on both the waste liquid incoming water pipeline, the waste liquid inlet pipe, and the drain pipe, and a reflux pipe is connected to the clear water chamber. The reflux pipe is connected to the reflux port of the contact chamber through a dissolved air pump. In this way, according to the compliance situation of the treated waste liquid detected, the waste liquid that does not meet the discharge standard can be re-refluxed to the contact chamber through the reflux pipe and the dissolved air pump for repeated enhanced flocculation separation treatment, and at the same time, dissolved air flotation treatment can also be carried out on the waste liquid.

[0010] As another implementation of the present technical solution, the first chemical addition device is a coagulant chemical addition device, the second chemical addition device is a flocculant chemical addition device, and the third chemical addition device is a sodium hypochlorite chemical addition device.

[0011] As another implementation of the present technical solution, a first branch bypass is connected to the pipeline between the pump outlet of the lift pump and the inlet of the pipeline mixer. A second branch bypass is connected to the pipeline between the outlet of the pipeline mixer and the inlet of the aerated flocculation device. A third branch bypass is connected to the pipeline between the outlet of the aerated flocculation device and the inlet of the enhanced flocculation separation device. Valves are provided on the first, second, and third branch bypasses, and the first, second, and third branch bypasses communicate with each other. In this way, the process of the multifunctional pretreatment device for complex waste liquid in oil and gas fields can be transcended. According to the composition and properties of the waste liquid, the treatment of the waste liquid can be selected to start from the pipeline mixer, the aerated flocculation device, or the enhanced flocculation separation device by controlling the valves on the first, second, and third branch bypasses. In addition, the process transcendence can also facilitate the maintenance and repair of the pipeline mixer, the aerated flocculation device, and related pipeline devices.

[0012] As another implementation of the present technical solution, the lift pump, the pipeline mixer, the aerated flocculation device, the enhanced flocculation separation device, the first chemical dosing device, the second chemical dosing device, the third chemical dosing device, and the connecting pipelines are skid-mounted. In this way, it is convenient for the transportation of the multifunctional pretreatment device for complex waste liquid in oil and gas fields, so as to be applicable to the on-site treatment of scattered waste liquid in remote blocks.

[0013] To solve the above technical problems, the present technical solution also provides a pretreatment method for complex waste liquid in oil and gas fields. The method steps include:

[0014] Chemical dosing and mixing step: The waste liquid is added with a coagulant by the first chemical dosing device and then enters the pipeline mixer for mixing.

[0015] Chemical dosing and pre-flocculation step: The mixed waste liquid is output from the pipeline mixer and a flocculant is added by the second chemical dosing device.

[0016] Aerated flocculation step: The waste liquid enters the aerated flocculation device. In the microbubble generation and cavitation oxidation zone, air is injected into the waste liquid by the bubble generator to carry out microbubble demulsification and aeration oxidation reaction. Then the waste liquid sequentially enters the swirl flocculation reaction zone and the eddy flocculation reaction zone from bottom to top for flocculation reaction, and the precipitate generated by flocculation is discharged through the sludge discharge pipe. Then the waste liquid enters the sedimentation zone for sedimentation, and the sedimented waste liquid is output from the treated liquid discharge pipe of the aerated flocculation device.

[0017] Enhanced flocculation separation step: The waste liquid enters the enhanced flocculation separation device. In the contact area, the floating oil on the upper layer of the waste liquid is collected for the first time using an oil collection tank. Then the waste liquid overflows into the separation area for sedimentation, and the sediment produced by the sedimentation is discharged through the sludge discharge pipe. Then the waste liquid enters the first mixing area, the first reaction area, and the second mixing area in sequence through the flow channel. Stirring devices are provided in both the first and second mixing areas to stir the waste liquid. In the first reaction area, sodium hypochlorite is added to the waste liquid by the third dosing device for chemical oxidation reaction, and at the same time, a coagulant is added to the waste liquid by the first dosing device for clarification reaction. Then the waste liquid enters the second reaction area from the second mixing area through the flow channel, and a flocculant is added to the waste liquid by the second dosing device for flocculation reaction, and the sediment produced by the flocculation is discharged through the sludge discharge pipe. Then the waste liquid enters the inclined plate sedimentation area through the flow channel for inclined plate sedimentation, and at the same time, the floating oil on the upper layer of the waste liquid is collected for the second time using an oil collection tank in the inclined plate sedimentation area. Then the waste liquid overflows into the clear water area.

[0018] Pre-treated waste liquid discharge step: The clear water area is connected with a drain pipe to discharge the pre-treated waste liquid.

[0019] Accordingly, this pre-treatment method can achieve the processes of multi-stage dosing coagulation, microbubble demulsification, flocculation, multi-stage oxidation, sedimentation, and dosing clarification, which not only optimizes the waste liquid treatment process, but also ensures the high efficiency of waste liquid treatment, and can meet the disposal requirements of waste liquids with different properties.

[0020] As another implementation of this technical solution, a reflux enhanced flocculation separation step is also added before the pre-treated waste liquid discharge step: A sampling port is provided at the drain pipe of the clear water area. When the waste liquid detected from the sampling port does not meet the standard, the waste liquid in the clear water area is refluxed to the contact area through the reflux pipe and the dissolved air pump for dissolved air flotation reaction and the enhanced flocculation separation step is performed again until the waste liquid detected from the sampling port meets the standard and then the pre-treated waste liquid discharge step is performed. In this way, the efficiency of waste liquid treatment can be improved through the dissolved air flotation reaction, and the repeated implementation of the enhanced flocculation separation step can ensure that the waste liquid meets the discharge standard when discharged.

[0021] As another implementation of this technical solution, a waste liquid treatment process bypass step is additionally provided before the chemical addition and mixing step: sampling ports are provided on both the waste liquid incoming pipeline and the treated liquid discharge pipe of the air flocculation device, and branched bypass pipelines with valves are respectively connected to the waste liquid incoming pipeline, the pipeline at the water inlet end of the air flocculation device, and the treated liquid discharge pipe, and the branched bypass pipelines communicate with each other. By detecting the compliance of the waste liquid from each sampling port, the valves on each branched bypass pipeline are closed or opened, so as to select to start the pretreatment operation of the complex waste liquid in the oil and gas field from any one of the chemical addition and mixing step, the air flocculation step, or the enhanced flocculation separation step. In this way, depending on the composition and properties of the waste liquid, the starting point of the treatment step can be selected, thereby simplifying the treatment process and saving energy consumption; in addition, the process bypass can also facilitate the maintenance and repair of the pipeline mixer, the air flocculation device, and related pipeline devices. Brief Description of the Drawings

[0022] Figure 1 Schematic diagram of an embodiment of the multifunctional pretreatment device for complex waste liquid in the oil and gas field of the present invention;

[0023] Figure 2 Side sectional view of the air flocculation device in the present invention;

[0024] Figure 3 Side sectional view of the enhanced flocculation separation device in the present invention;

[0025] Figure 4 Top view of the enhanced flocculation separation device in the present invention;

[0026] Figure 5 Schematic diagram of another embodiment of the multifunctional pretreatment device for complex waste liquid in the oil and gas field of the present invention.

[0027] Symbol description in the drawings:

[0028] 1 Waste liquid inlet pipeline; 2 Lift pump; 3 Pipeline mixer; 4 Aeration flocculation device; 41 Outer cylinder; 411 Exhaust hole; 412 Through port; 413 Treated liquid outlet; 414 Treated liquid discharge pipe; 415 Support rod; 42 Inner cylinder; 421 Cylindrical section; 4211 Open end; 4212 Flow guide device; 422 Waist shrinking section; 423 Funnel section; 424 Through hole; 43 Bubble liquid inlet pipe; 431 Sludge discharge pipe; 44 Water inlet ring pipe; 441 Water inlet hole; 45 Bubble generator pipeline; 451 Bubble generator; 5 Enhanced flocculation separation device; 51 Waste liquid inlet pipe; 52 Contact chamber; 521 Partition board; 522 First oil collection tank; 523 Oil sludge chamber; 53 Separation chamber; 531 First sludge hopper; 532 Sludge discharge pipe; 54 First mixing chamber; 541 Stirring device; 55 First reaction chamber; 56 Second mixing chamber; 561 Stirring device; 57 Second reaction chamber; 571 Second sludge hopper; 572 Sludge discharge pipe; 58 Inclined plate sedimentation chamber; 581 Second oil collection tank; 59 Clear water chamber; 591 Return pipe; 592 Dissolved air pump; 6 First chemical dosing device; 61 First chemical dosing pipeline; 62 Third chemical dosing pipeline; 7 Second chemical dosing device; 71 Second chemical dosing pipeline; 72 Fourth chemical dosing pipeline; 8 Third chemical dosing device; 81 Fifth chemical dosing pipeline; 9 Valve; 10 Drain pipe; 11 Sampling port; 12 First branch bypass; 13 Second branch bypass; 14 Third branch bypass. Detailed implementation mode

[0029] The detailed description and technical content of the present invention are described below in conjunction with the drawings. However, the attached drawings are only for reference and illustration purposes and are not used to limit the present invention.

[0030] As Figure 1As shown in the figure, it is a schematic diagram of an embodiment of the multifunctional pretreatment device for complex waste liquid in oil and gas fields of the present invention. The multifunctional pretreatment device for complex waste liquid in oil and gas fields includes: a lift pump 2, a pipeline mixer 3, an air-added flocculation device 4, a strengthened flocculation separation device 5, a first chemical dosing device 6, a second chemical dosing device 7, and a third chemical dosing device 8. Among them, the waste liquid incoming pipeline 1 is connected to the pump-in end of the lift pump 2, the pump-out end of the lift pump 2 is connected to the input end of the pipeline mixer 3 through a pipeline, the output end of the pipeline mixer 3 is connected to the water inlet end of the air-added flocculation device 4 through a pipeline, the water outlet end of the air-added flocculation device 4 is connected to the water inlet end of the strengthened flocculation separation device 5 through a pipeline, and the water outlet end of the strengthened flocculation separation device 5 is connected to the drain pipe 10. The first chemical dosing device 6 is connected to the pipeline at the input end of the pipeline mixer 3 through a first chemical dosing pipeline 61, and a valve 9 is provided on the first chemical dosing pipeline 61. The second chemical dosing device 7 is connected to the pipeline at the output end of the pipeline mixer 3 through a second chemical dosing pipeline 71, and a valve 9 is provided on the second chemical dosing pipeline 71. The first chemical dosing device 6 is also communicated with the first reaction chamber 55 of the strengthened flocculation separation device 5 through a third chemical dosing pipeline 62 (combined with Figure 4 as shown), and a valve 9 is provided on the third chemical dosing pipeline 62. The second chemical dosing device 7 is also communicated with the second reaction chamber 57 of the strengthened flocculation separation device 5 through a fourth chemical dosing pipeline 72 (combined with Figure 4 as shown), and a valve 9 is provided on the fourth chemical dosing pipeline 72. The third chemical dosing device 8 is communicated with the first reaction chamber 55 of the strengthened flocculation separation device 5 through a fifth chemical dosing pipeline 81, and a valve 9 is provided on the fifth chemical dosing pipeline 81. The air-added flocculation device 4 can perform microbubble degumming, aeration oxidation, flocculation, and sedimentation treatment on the waste liquid transported into it, and then transport it into the strengthened flocculation separation device 5 through a pipeline. The strengthened flocculation separation device 5 can perform dissolved air flotation, floating oil collection, chemical oxidation, chemical dosing clarification, flocculation, inclined plate sedimentation, and floating oil collection again on the waste liquid transported into it, and then discharge it through the drain pipe 10.

[0031] Specifically, as Figure 2As shown in the figure, in this embodiment, the aerated flocculation device 4 includes: an outer cylinder 41, a treatment liquid discharge pipe 414, an inner cylinder 42, a bubble liquid inlet pipe 43, a water inlet ring pipe 44, at least one bubble generator pipeline 45, and a sludge discharge pipe 431. Among them, the outer cylinder 41 is in a capsule shape and is vertically arranged. An exhaust hole 411 communicating with the outside is provided at the upper end of the outer cylinder 41. A through hole 412 is provided at the central position of the lower end of the outer cylinder 41, and at least one treatment liquid outlet 413 is provided around the through hole 412. The at least one treatment liquid outlet 413 is connected to the treatment liquid discharge pipe 414. The inner cylinder 42 is coaxial with the outer cylinder 41 and is fixedly connected between the outer side of the inner cylinder 42 and the inner side of the outer cylinder 41 by several support rods 415, so that the inner cylinder 42 is arranged inside the outer cylinder 41, and there is a gap between the outer side of the inner cylinder 42 and the inner side of the outer cylinder 41 to form a sedimentation space. The inner cylinder 42 includes a cylindrical section 421, a waist-reducing section 422, and a funnel section 423 from top to bottom. Among them, the upper end of the cylindrical section 421 is an open mouth 4211. A double-layered flow guiding structure is arranged at intervals on the inner side of the cylindrical section 421. The flow guiding structure is composed of several flow guides 4212 with an isosceles triangle cross-section evenly spaced on the inner side of the cylindrical section 421. The two isosceles sides of the cross-section of the flow guide 4212 are in a concave arc shape, and the flow guides 4212 of the upper-layer flow guiding structure are staggered with the flow guides 4212 of the lower-layer flow guiding structure; the waist-reducing section 422 is combined with the lower end of the cylindrical section 421, and the diameter of the middle part of the waist-reducing section 422 is smaller than the diameters of its upper and lower ends; the funnel section 423 is combined with the lower end of the waist-reducing section 422, and the diameter of the funnel section 423 gradually decreases from top to bottom. A through hole 424 is provided at the lower end of the funnel section 423 corresponding to the position of the through hole 412. The bubble liquid inlet pipe 43 is hermetically combined through the through hole 412, and the upper end of the bubble liquid inlet pipe 43 is communicated with the through hole 424. The lower end of the bubble liquid inlet pipe 43 is located outside the through hole 412 and is closed. The water inlet ring pipe 44 is annularly fixed on the upper part of the outer side of the outer cylinder 41, and a water inlet hole 441 is provided on the water inlet ring pipe 44 to connect to the output end of the pipeline mixer through a pipeline. At least one waste liquid output port (not shown in the figure) is also provided on the water inlet ring pipe 44. At least one waste liquid input port (not shown in the figure) is provided on the bubble liquid inlet pipe 43 corresponding to the at least one waste liquid output port. At least one bubble generator pipeline 45 is connected between the at least one waste liquid output port and the at least one waste liquid input port, and a bubble generator 451 is provided on the bubble generator pipeline 45. A slag discharge port (not shown in the figure) is also provided at the bottom of the bubble liquid inlet pipe 43, and the slag discharge port is connected to the sludge discharge pipe 431.Through the above structure, the waste liquid enters the water inlet ring pipe 44 through the water inlet hole 441 and is injected into the funnel section 423 at the lower part of the inner cylinder 42 through at least one bubble generator pipeline 45. During this process, the bubble generator 451 in the bubble generator pipeline 45 introduces external air into the pipeline for microbubble generation to break the glue of the waste liquid with microbubbles and carry out aeration oxidation. The waste liquid entering the funnel section 423 undergoes swirl flocculation under the action of the liquid flow direction. After the liquid flow is stabilized by the waist shrinking section 422, the waste liquid enters the cylindrical section 421 and undergoes vortex flocculation through the double-layer diversion structure inside it. The sediment generated by the swirl and vortex flocculation is discharged through the slag discharge port at the bottom of the bubble liquid inlet pipe 43. The flocculated waste liquid overflows through the open mouth 4211 at the upper part of the cylindrical section 421 to the sedimentation space formed between the inner and outer cylinders 42 and 41 for sedimentation. At the same time, the gas released from the waste liquid is discharged through the exhaust hole 411. The waste liquid after sedimentation is input into the next treatment device through the treatment liquid outlet 413 and the treatment liquid discharge pipe 414. In this way, the internal structure of the aerated flocculation device is compact, the waste liquid treatment efficiency is high, and the waste liquid transported into it can be subjected to microbubble glue breaking, aeration oxidation, swirl and vortex flocculation, and sedimentation processes.

[0032] As Figure 1 , 3As shown in FIGS. 3 and 4, in this embodiment, the enhanced flocculation separation device 5 includes, from its water inlet end to its water outlet end: a contact chamber 52, two oil sludge chambers 523, a separation chamber 53, a first mixing chamber 54, a first reaction chamber 55, a second mixing chamber 56, a second reaction chamber 57, an inclined plate sedimentation chamber 58 and a clear water chamber 59. Among them, the contact chamber 52 is connected to the waste liquid inlet pipe 51. The two oil sludge chambers 523 are respectively arranged on both sides of the contact chamber 52. The separation chamber 53 is arranged on the other side of the contact chamber 52 relative to the waste liquid inlet pipe 51. And the separation chamber 53 is separated from the contact chamber 52 and the two oil sludge chambers 523 by a partition plate 521 that is inclined upward toward the separation chamber 53. At a position above the contact chamber 52 and at the same height as the upper end of the partition plate 521, a first oil collection tank 522 is installed. The two ends of the first oil collection tank 522 communicate with the upper parts of the two oil sludge chambers 523 respectively. The waste liquid overflows from the contact chamber 52 into the separation chamber 53. A first sludge hopper 531 is formed at the bottom of the separation chamber 53, and a sludge discharge pipe 532 is installed on the first sludge hopper 531. The first mixing chamber 54, the first reaction chamber 55 and the second mixing chamber 56 are arranged side by side on the other side of the separation chamber 53 relative to the partition plate 521. And the separation chamber 53 is communicated with the first mixing chamber 54 through a flow channel (not shown in the figure). The first mixing chamber 54 is communicated with the first reaction chamber 55 through a flow channel. The first reaction chamber 55 is communicated with the second mixing chamber 56 through a flow channel. And stirring devices 541 and 561 are installed in both the first mixing chamber 54 and the second mixing chamber 56. The second reaction chamber 57 is arranged on the other side of the first mixing chamber 54, the first reaction chamber 55 and the second mixing chamber 56 arranged side by side. And the second reaction chamber 57 is communicated with the second mixing chamber 56 through a flow channel. A second sludge hopper 571 is formed at the bottom of the second reaction chamber 57, and a sludge discharge pipe 572 is installed on the second sludge hopper 571. The inclined plate sedimentation chamber 58 is arranged on the other side of the second reaction chamber 57. And the second reaction chamber 57 is communicated with the inclined plate sedimentation chamber 58 through a flow channel. A second oil collection tank 581 is installed above the inclined plate sedimentation chamber 58. The clear water chamber 59 is arranged on the other side of the inclined plate sedimentation chamber 58. The waste liquid overflows from the inclined plate sedimentation chamber 58 into the clear water chamber 59. The clear water chamber 59 is connected to the drain pipe 10. The third and fifth chemical addition pipelines 62 and 81 are both connected to the first reaction chamber 55, and the fourth chemical addition pipeline 72 is connected to the second reaction chamber 57.Through the above structure, the waste liquid enters the contact chamber 52 through the waste liquid inlet pipe 51 and flows to the separation chamber 53 by overflow. During this overflow process, the floating oil on the upper layer of the waste liquid is collected by the first oil collection tank 522 and discharged into the oil residue chambers 523 on both sides of the contact chamber 52. The waste liquid settles in the separation chamber 53, and the settled sediment accumulates in the first sludge hopper 531 and is discharged through the sludge discharge pipe 532 by hydrostatic pressure. After that, the waste liquid enters the first mixing chamber 54, the first reaction chamber 55 and the second mixing chamber 56 in sequence through the flow channel. In the first and second mixing chambers 54 and 56, the waste liquid can be fully stirred by the stirring devices 541 and 561 to improve the effect of related reactions. In the first reaction chamber 55, chemicals are added to the waste liquid by the first and third chemical dosing devices 6 and 8 to carry out chemical oxidation and clarification reactions. After the waste liquid is dosed and stirred, it enters the second reaction chamber 57 through the flow channel, and chemicals are added to the waste liquid by the second chemical dosing device 7 to carry out flocculation treatment. The sediment generated by flocculation accumulates in the second sludge hopper 571 and is discharged through the sludge discharge pipe 572 by hydrostatic pressure. At the same time, the waste liquid also enters the inclined plate sedimentation chamber 58 for sedimentation, and the settled sediment also accumulates in the second sludge hopper 571 and is discharged through the sludge discharge pipe 572. After that, the waste liquid overflows from the inclined plate sedimentation chamber 58 into the clear water chamber 59 and is discharged through the drain pipe 10. In this way, the internal structure of the enhanced flocculation separation device is compact, and the waste liquid treatment efficiency is high. The waste liquid transported into it can be subjected to floating oil collection, chemical oxidation, chemical dosing clarification, flocculation, inclined plate sedimentation and re-floating oil collection processes.

[0033] In addition, as shown in Figure 1 Sampling ports 11 can be provided on the waste liquid incoming pipeline 1, the waste liquid inlet pipe 51 and the drain pipe 10 to detect the composition and properties of the waste liquid at each treatment stage. And a reflux pipe 591 can be connected to the clear water chamber 59. The reflux pipe 591 is connected to the reflux port (not shown in the figure) of the contact chamber 52 through a dissolved air pump 592. In this way, according to the compliance of the treated waste liquid detected, the waste liquid that does not meet the discharge standard can be re-circulated to the contact chamber through the reflux pipe and the dissolved air pump for repeated enhanced flocculation separation treatment, and at the same time, dissolved air flotation treatment can also be carried out on the waste liquid.

[0034] In this embodiment, the first chemical dosing device can be a coagulant dosing device, the second chemical dosing device can be a flocculant dosing device, and the third chemical dosing device can be a sodium hypochlorite dosing device.

[0035] As Figure 5As shown, in another embodiment of the multifunctional pretreatment device for complex waste liquid in the oil and gas field of the present invention, a first branch bypass 12 may be connected to the pipeline between the pump outlet of the lift pump 2 and the input end of the pipeline mixer 3, a second branch bypass 13 may be connected to the pipeline between the output end of the pipeline mixer 3 and the water inlet end of the air-added flocculation device 4, and a third branch bypass 14 may be connected to the pipeline between the water outlet end of the air-added flocculation device 4 and the water inlet end of the enhanced flocculation separation device 5. Valves 9 are provided on the first, second, and third branch bypasses 12, 13, and 14, and the first, second, and third branch bypasses 12, 13, and 14 communicate with each other. In this way, the process bypass of the multifunctional pretreatment device for complex waste liquid in the oil and gas field can be realized. According to the composition and properties of the waste liquid, the treatment of the waste liquid can be started from the pipeline mixer, the air-added flocculation device, or the enhanced flocculation separation device by controlling the valves on the first, second, and third branch bypasses. In addition, the process bypass can also facilitate the maintenance and repair of the pipeline mixer, the air-added flocculation device, and related pipeline devices.

[0036] The lift pump, pipeline mixer, air-added flocculation device, enhanced flocculation separation device, first chemical dosing device, second chemical dosing device, third chemical dosing device, and connecting pipelines in the multifunctional pretreatment device for complex waste liquid in the oil and gas field of the present invention can be skid-mounted (not shown in the figure), which is convenient for the transportation of the device and thus suitable for the on-site treatment of scattered waste liquid in remote blocks.

[0037] Combined with the above pretreatment device, the present invention also provides a pretreatment method for complex waste liquid in the oil and gas field. The steps of the pretreatment method include:

[0038] Chemical dosing and mixing step: The waste liquid is added with a coagulant by the first chemical dosing device and then enters the pipeline mixer for mixing.

[0039] Chemical dosing and pre-flocculation step: The mixed waste liquid is output from the pipeline mixer and the second chemical dosing device adds a flocculant.

[0040] Air-added flocculation step: The waste liquid enters the air-added flocculation device. In the microbubble generation and cavitation oxidation zone, the bubble generator injects air into the waste liquid to carry out microbubble demulsification and aeration oxidation reactions. Then the waste liquid sequentially enters the cyclone flocculation reaction zone and the eddy current flocculation reaction zone from bottom to top for flocculation reactions, and the precipitates generated by flocculation are discharged through the sludge discharge pipe. Then the waste liquid enters the sedimentation zone for sedimentation, and the waste liquid after sedimentation is output from the treated liquid discharge pipe of the air-added flocculation device.

[0041] Enhanced flocculation separation step: The waste liquid enters the enhanced flocculation separation device. In the contact area, the floating oil on the upper layer of the waste liquid is collected for the first time using an oil collection tank. Then the waste liquid overflows into the separation area for sedimentation, and the sediment generated by the sedimentation is discharged through the sludge discharge pipe. After that, the waste liquid enters the first mixing area, the first reaction area, and the second mixing area in sequence through the flow channel. Stirring devices are provided in both the first and second mixing areas to stir the waste liquid. In the first reaction area, sodium hypochlorite is added to the waste liquid by the third dosing device for chemical oxidation reaction, and at the same time, a coagulant is added to the waste liquid by the first dosing device for clarification reaction. Then the waste liquid enters the second reaction area from the second mixing area through the flow channel, and a flocculant is added to the waste liquid by the second dosing device for flocculation reaction, and the sediment generated by the flocculation is discharged through the sludge discharge pipe. Then the waste liquid enters the inclined plate sedimentation area through the flow channel for inclined plate sedimentation, and at the same time, the floating oil on the upper layer of the waste liquid is collected for the second time using an oil collection tank in the inclined plate sedimentation area. Then the waste liquid overflows into the clear water area.

[0042] Pre-treatment waste liquid discharge step: The clear water area is connected with a drain pipe to discharge the pre-treated waste liquid.

[0043] Accordingly, this pre-treatment method can achieve the processes of multi-stage dosing coagulation, microbubble demulsification, flocculation, multi-stage oxidation, sedimentation, and dosing clarification. It not only optimizes the waste liquid treatment process, but also ensures the high efficiency of waste liquid treatment and can meet the disposal requirements of waste liquids with different properties.

[0044] In the above pre-treatment method, a reflux enhanced flocculation separation step can also be added before the pre-treatment waste liquid discharge step: A sampling port is provided at the drain pipe of the clear water area. When the waste liquid detected from the sampling port does not meet the standard, the waste liquid in the clear water area is refluxed to the contact area through the reflux pipe and the dissolved air pump for dissolved air flotation reaction and the enhanced flocculation separation step is performed again until the waste liquid detected from the sampling port meets the standard and then the pre-treatment waste liquid discharge step is performed. In this way, the efficiency of waste liquid treatment can be improved through the dissolved air flotation reaction, and the repeated implementation of the enhanced flocculation separation step can ensure that the waste liquid meets the discharge standard when discharged.

[0045] In the above pretreatment method, a waste liquid treatment process bypass step can be additionally set before the chemical addition and mixing step: sampling ports are provided on both the waste liquid incoming water pipeline and the treated liquid discharge pipe of the air flocculation device, and branch bypass pipelines with valves are respectively connected to the waste liquid incoming water pipeline, the pipeline at the water inlet end of the air flocculation device, and the treated liquid discharge pipe, and the branch bypass pipelines communicate with each other. By detecting the compliance of the waste liquid from each sampling port, the valves on each branch bypass pipeline are closed or opened, so as to select to start the pretreatment operation of the complex waste liquid in the oil and gas field from any one of the chemical addition and mixing step, the air flocculation step, or the enhanced flocculation separation step. In this way, the starting point of the treatment step can be selected according to the composition and properties of the waste liquid, thereby simplifying the treatment process and saving energy consumption; in addition, the process bypass can also facilitate the maintenance and repair of the pipe mixer, the air flocculation device, and related pipeline devices.

[0046] By serially applying the air flocculation device and the enhanced flocculation separation device, the present invention can optimize the overall structure of the pretreatment device, thereby reducing the overall scale of the pretreatment device and ensuring the efficient operation of the waste liquid treatment process; in addition, by controlling the valves on each chemical addition pipeline, the pretreatment device can realize the process technologies of multi-stage chemical addition and coagulation, multi-stage oxidation, and chemical addition clarification to meet the disposal requirements of waste liquids with different properties.

[0047] The above are only the preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Equivalent changes made by using the patent concept of the present invention shall fall within the patent protection scope of the present invention.

Claims

1. A multi-functional pretreatment device for oil and gas field waste liquid, Characterized in that, Comprising: Lifting pump, pipeline mixer, aerated flocculation device, enhanced flocculation separation device, first chemical dosing device, second chemical dosing device and third chemical dosing device; the waste liquid incoming water pipeline is connected to the pump inlet end of the lifting pump, the pump outlet end of the lifting pump is connected to the input end of the pipeline mixer through a pipeline, the output end of the pipeline mixer is connected to the water inlet end of the aerated flocculation device through a pipeline, the water outlet end of the aerated flocculation device is connected to the water inlet end of the enhanced flocculation separation device through a waste liquid inlet pipeline, the water outlet end of the enhanced flocculation separation device is connected to a drain pipe, and the enhanced flocculation separation device includes, from its water inlet end to its water outlet end: a contact chamber, two oil sludge chambers, a separation chamber, a first mixing chamber, a first reaction chamber, a second mixing chamber, a second reaction chamber, an inclined plate sedimentation chamber and a clear water chamber; the contact chamber is connected to the waste liquid inlet pipeline, the two oil sludge chambers are respectively arranged on both sides of the contact chamber, the separation chamber is arranged on the other side of the contact chamber relative to the waste liquid inlet pipeline, and the separation chamber is separated from the contact chamber and the two oil sludge chambers by a partition plate inclined upward toward the separation chamber at the upper end, and a first oil collecting tank is installed at a position above the contact chamber and at the same height as the upper end of the partition plate, and both ends of the first oil collecting tank communicate with the upper parts of the two oil sludge chambers respectively, the waste liquid overflows from the contact chamber into the separation chamber, a first sludge hopper is formed at the bottom of the separation chamber, and a sludge discharge pipe is installed on the first sludge hopper, the first mixing chamber, the first reaction chamber and the second mixing chamber are arranged side by side on the other side of the separation chamber relative to the partition plate, and the separation chamber is communicated with the first mixing chamber through a flow channel, the first mixing chamber is communicated with the first reaction chamber through a flow channel, the first reaction chamber is communicated with the second mixing chamber through a flow channel, and stirring devices are installed in both the first mixing chamber and the second mixing chamber, the second reaction chamber is arranged on the other side of the first mixing chamber, the first reaction chamber and the second mixing chamber arranged side by side, and the second reaction chamber is communicated with the second mixing chamber through a flow channel, a second sludge hopper is formed at the bottom of the second reaction chamber, and a sludge discharge pipe is installed on the second sludge hopper, the inclined plate sedimentation chamber is arranged on the other side of the second reaction chamber, and the second reaction chamber is communicated with the inclined plate sedimentation chamber through a flow channel, a second oil collecting tank is installed above the inclined plate sedimentation chamber, the clear water chamber is arranged on the other side of the inclined plate sedimentation chamber, and the waste liquid overflows from the inclined plate sedimentation chamber into the clear water chamber, and the clear water chamber is connected to the drain pipe;The first chemical dosing device is connected to the pipeline at the input end of the pipeline mixer through a first chemical dosing pipeline, and a valve is provided on the first chemical dosing pipeline. The second chemical dosing device is connected to the pipeline at the output end of the pipeline mixer through a second chemical dosing pipeline, and a valve is provided on the second chemical dosing pipeline. The first chemical dosing device is also connected to the first reaction chamber of the enhanced flocculation separation device through a third chemical dosing pipeline, and a valve is provided on the third chemical dosing pipeline. The second chemical dosing device is also connected to the second reaction chamber of the enhanced flocculation separation device through a fourth chemical dosing pipeline, and a valve is provided on the fourth chemical dosing pipeline. The third chemical dosing device is connected to the first reaction chamber of the enhanced flocculation separation device through a fifth chemical dosing pipeline, and a valve is provided on the fifth chemical dosing pipeline. A sampling port is provided on the drain pipe, and a reflux pipe is connected to the clear water chamber. The reflux pipe is connected to the reflux port of the contact chamber through a dissolved air pump. The first chemical dosing device is a coagulant dosing device, the second chemical dosing device is a flocculant dosing device, and the third chemical dosing device is a sodium hypochlorite dosing device. Among them, the aerated flocculation device performs microbubble degumming, aeration oxidation, flocculation and sedimentation treatment on the waste liquid transported into it, and then transports it into the enhanced flocculation separation device through a pipeline. The enhanced flocculation separation device performs dissolved air flotation, floating oil collection, chemical oxidation, chemical dosing clarification, flocculation, inclined plate sedimentation and floating oil collection again on the waste liquid transported into it, and then discharges it through the drain pipe.

2. The multi-functional pretreatment device for oil and gas field waste liquid according to claim 1, Characterized in that, The aerated flocculation device includes: an outer cylinder, a treatment liquid discharge pipe, an inner cylinder, a bubble liquid inlet pipe, a water inlet ring pipe, at least one bubble generator pipeline and a sludge discharge pipe; the outer cylinder is in a capsule shape and is arranged vertically, an exhaust hole communicating with the outside is opened at the upper end of the outer cylinder, a through hole is opened at the central position of the lower end of the outer cylinder, and at least one treatment liquid outlet is opened around the through hole, and the at least one treatment liquid outlet is connected to the treatment liquid discharge pipe; the inner cylinder and the outer cylinder are coaxial, and the inner cylinder is fixedly connected between the outer side surface of the inner cylinder and the inner side surface of the outer cylinder by several support rods so that the inner cylinder is arranged inside the outer cylinder, and there is a gap between the outer side surface of the inner cylinder and the inner side surface of the outer cylinder; the inner cylinder includes a cylindrical section, a waist shrinking section and a funnel section from top to bottom, the upper end of the cylindrical section is an open mouth, a double-layer flow guiding structure is arranged at intervals on the inner side surface of the cylindrical section, the flow guiding structure is composed of several flow guiding devices with an isosceles triangle cross section evenly spaced on the inner side surface of the cylindrical section, and the two isosceles sides of the cross section of the flow guiding device are in an inward concave arc shape, and the flow guiding devices of the upper layer flow guiding structure are staggered with the flow guiding devices of the lower layer flow guiding structure, the waist shrinking section is combined with the lower end of the cylindrical section, and the diameter of the middle part of the waist shrinking section is smaller than the diameters of its upper and lower ends, the funnel section is combined with the lower end of the waist shrinking section, and the diameter of the funnel section gradually decreases from top to bottom, a through hole is opened at the lower end of the funnel section corresponding to the position of the through hole, the bubble liquid inlet pipe is penetrated and hermetically combined with the through hole, and the upper end of the bubble liquid inlet pipe is communicated with the through hole, the lower end of the bubble liquid inlet pipe is located outside the through hole and is closed; the water inlet ring pipe is fixedly arranged around the upper part of the outer side surface of the outer cylinder, and a water inlet hole is opened on the water inlet ring pipe to connect the output end of the pipeline mixer through a pipeline, at least one waste liquid output port is also opened on the water inlet ring pipe, at least one waste liquid input port is opened on the bubble liquid inlet pipe corresponding to the at least one waste liquid output port, and at least one bubble generator pipeline is arranged between the at least one waste liquid output port and the at least one waste liquid input port, and a bubble generator is arranged on the bubble generator pipeline; a slag discharge port is also opened at the bottom of the bubble liquid inlet pipe, and the slag discharge port is connected to the sludge discharge pipe.

3. The multi-functional pretreatment device for oil and gas field waste liquid according to claim 1, Characterized in that, Sampling ports are arranged on both the waste liquid incoming water pipeline and the waste liquid inlet pipe.

4. The multi-functional pretreatment device for oil and gas field waste liquid according to claim 1, Characterized in that, A first branch bypass is connected to the pipeline between the pump outlet of the lift pump and the inlet of the pipeline mixer. A second branch bypass is connected to the pipeline between the outlet of the pipeline mixer and the inlet of the air-added flocculation device. A third branch bypass is connected to the pipeline between the outlet of the air-added flocculation device and the inlet of the enhanced flocculation separation device. Valves are provided on the first branch bypass, the second branch bypass and the third branch bypass, and the first branch bypass, the second branch bypass and the third branch bypass are communicated with each other.

5. The multifunctional pretreatment device for oil and gas field waste liquid according to claim 1, characterized in that the lift pump, the pipeline mixer, the air-added flocculation device, the enhanced flocculation separation device, the first chemical dosing device, the second chemical dosing device, the third chemical dosing device and the connecting pipelines are skid-mounted.

6. A pretreatment method for oil and gas field waste liquid using the multifunctional pretreatment device for oil and gas field waste liquid according to claim 1, characterized in that the steps include: Chemical dosing and mixing step: The waste liquid is added with a coagulant by the first chemical dosing device and then enters the pipeline mixer for mixing; Chemical dosing and pre-flocculation step: The mixed waste liquid is output from the pipeline mixer and a flocculant is added to the waste liquid by the second chemical dosing device; Air-added flocculation step: The waste liquid enters the air-added flocculation device, and air is injected into the waste liquid by a bubble generator in the microbubble generation and cavitation oxidation zone to perform microbubble demulsification and aeration oxidation reactions; then the waste liquid sequentially enters the swirl flocculation reaction zone and the eddy flocculation reaction zone from bottom to top for flocculation reactions, and the precipitates generated by flocculation are discharged through the sludge discharge pipe; then the waste liquid enters the sedimentation zone for sedimentation, and the waste liquid after sedimentation is output from the treated liquid discharge pipe of the air-added flocculation device; Enhanced flocculation and separation step: The waste liquid enters the enhanced flocculation separation device, and the floating oil on the upper layer of the waste liquid is collected for the first time by an oil collection tank in the contact zone; then the waste liquid overflows into the separation zone for sedimentation, and the precipitates generated by sedimentation are discharged through the sludge discharge pipe; Then the waste liquid sequentially enters the first mixing zone, the first reaction zone and the second mixing zone through the flow channel. Stirring devices are provided in both the first and second mixing zones to stir the waste liquid. In the first reaction zone, sodium hypochlorite is added to the waste liquid by the third chemical dosing device for chemical oxidation reaction, and at the same time, a coagulant is added to the waste liquid by the first chemical dosing device for clarification reaction; then the waste liquid enters the second reaction zone from the second mixing zone through the flow channel, and a flocculant is added to the waste liquid by the second chemical dosing device for flocculation reaction, and the precipitates generated by flocculation are discharged through the sludge discharge pipe; Then the waste liquid enters the inclined plate sedimentation zone through the flow channel for inclined plate sedimentation, and at the same time, the floating oil on the upper layer of the waste liquid is collected for the second time by an oil collection tank in the inclined plate sedimentation zone; then the waste liquid overflows into the clear water zone; Return enhanced flocculation separation step: In the return enhanced flocculation separation step, a sampling port is provided at the drain pipe of the clear water area. When the waste liquid detected from the sampling port does not meet the standard, the waste liquid in the clear water area is returned to the contact area through the return pipe and the dissolved air pump for dissolved air flotation and the enhanced flocculation separation step is performed again until the waste liquid detected from the sampling port meets the standard and then the pre-treated waste liquid discharge step is performed; Pre-treated waste liquid discharge step: The clear water area is connected with a drain pipe to discharge the pre-treated waste liquid.

7. The pre-treatment method for oil and gas field waste liquid according to claim 6, characterized in that, a waste liquid treatment process bypass step is added before the chemical addition and mixing step. In the waste liquid treatment process bypass step, sampling ports are provided on both the waste liquid incoming pipeline and the treated liquid discharge pipe of the air addition and flocculation device, and branched bypass pipelines with valves are respectively connected to the waste liquid incoming pipeline, the pipeline at the inlet end of the air addition and flocculation device and the treated liquid discharge pipe, and the branched bypass pipelines communicate with each other. By the compliance of the waste liquid detected from each sampling port, the valves on each branched bypass pipeline are closed or opened, so as to select to start the pre-treatment operation of the oil and gas field waste liquid from any one of the chemical addition and mixing step, the air addition and flocculation step or the enhanced flocculation separation step.

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