A multi-process wastewater treatment method and complete system

Abstract

The application discloses a kind of multi-flow wastewater treatment method and complete system, and the processing method includes the following steps: solid-containing waste liquid is entered into the broken glue coagulation device, reagent is added by dosing device, and mixed liquor is formed after reaction;Mixed liquor is transported to processing mechanism, and different processes are used for waste liquid treatment according to the solid content of mixed liquor, to obtain first liquid;First liquid is transported to multi-stage filtering device for multi-stage filtering, to obtain second liquid;Second liquid is transported to fine filtering device for fine filtering, to obtain treated water.The application uses a set of device, combines three process flows, and the processing object covers high solid content waste drilling mud, high solid content mud supernatant, low solid content treatment waste liquid and low solid content produced water, which can meet the waste liquid treatment requirements of each stage of oilfield site at one time, reduce the investment, relocation and other costs of waste liquid treatment device at each stage, and improve work efficiency.

Description

[0001] This application claims priority to the application with the application number "202211526421.9" and the invention name "A multi-process wastewater treatment method and complete system" filed in the China Patent Office on November 30, 2022, the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application belongs to the technical field of oilfield wastewater treatment, and particularly relates to a multi-process wastewater treatment method and complete system. BACKGROUND

[0003] A large amount of operation waste liquid will be generated in the development process and later production of unconventional oil and gas fields. If it is not disposed in time and in a standard manner, it will bring a lot of environmental problems. At the same time, a large amount of clean water is needed to prepare fracturing fluid or to inject back into the formation to balance the formation pressure, whether in the process of hydraulic fracturing or in the later development of oil and gas wells. If the appropriate treatment technology and equipment are selected to dispose of a large amount of operation waste liquid in a standard manner, and the clean water after treatment is used to prepare fracturing fluid or to inject back into the formation to achieve resource utilization, it not only can reduce the discharge of sewage and save clean water, but also has important significance for reducing the environmental risk of unconventional oil and gas development and realizing green and sustainable development.

[0004] A large amount of drilling waste mud, drilling and workover waste liquid, and reservoir reconstruction waste liquid such as fracturing flowback liquid and acidizing liquid generated by various reservoir stimulation measures in new and old oil areas have become an environmental problem for oil and gas field enterprises. Due to the complex composition of these waste liquid pollutants, containing a large amount of organic matter and various additives, it has the treatment difficulties of high emulsified oil content, high small particle suspended matter content, and high viscosity, and is relatively difficult to treat. Domestic and foreign scholars have carried out more research on this. The main difficulty of the research work is the complex diversity of wastewater quality. The quality of no one kind of wastewater is constant, especially for the wastewater generated by different operation methods of oil and gas fields, the difference between the qualities of the wastewater is more obvious. At present, there are complete sets of devices that can meet the treatment of a single type of waste liquid, such as drilling waste mud generated in the drilling stage, which is collected and disposed by the while-drilling and no-falling-to-the-ground integrated skid-mounted equipment, drilling and workover waste liquid, which is disposed by the drilling and workover waste water treatment equipment, and fracturing flowback liquid, which is disposed by the reservoir reconstruction special waste liquid treatment skid-mounted product. However, there is no mature complete set of devices that can meet the treatment needs of complex waste liquid.

[0005] In addition to the complex and variable quality of waste liquid, the operation site will also generate mixed waste liquid with higher solid content than waste liquid, such as waste drilling mud, mud supernatant, and other measure waste liquid with low solid content, such as fracturing flowback liquid, acidizing waste liquid, and workover waste water, as well as produced water with low solid content. The solid content of waste liquid varies greatly.

[0006] The formed waste liquid treatment technology and equipment currently use conventional oil field waste liquid treatment equipment to treat the waste mud or mixed waste liquid with high solid content, and the flocculation treatment produces a large amount of flocculation, and the equipment is prone to blockage, resulting in shutdown or failure, so it is necessary to solve the problem of treating high solid content waste liquid by waste liquid treatment equipment, and form a comprehensive integrated oil field waste liquid treatment device that can use various waste liquid properties.

[0007] From the technical point of view, the oil field operation site urgently needs a waste liquid treatment equipment that can adapt to the large change of solid content in the liquid. From the oil and gas field enterprise management and drilling site operation point of view, a set of equipment with wide adaptability has the advantages of reducing investment cost caused by frequent replacement of treatment equipment, shortening construction period, and reducing coordination management workload. SUMMARY

[0008] In view of the above problems, the application discloses a multi-process waste water treatment method, comprising the following steps:

[0009] The solid-containing waste liquid to be treated enters the gel-breaking and coagulation device, and the reagent is added by the reagent adding device, and the mixed liquid is formed after reaction;

[0010] The mixed liquid is transported to the treatment mechanism, different processes are adopted for waste liquid treatment according to the solid content of the mixed liquid, and the first liquid is obtained;

[0011] The first liquid is transported to the multi-stage filtration device for multi-stage filtration, and the second liquid is obtained;

[0012] The second liquid is transported to the fine filtration device for fine filtration, and the treated water is obtained.

[0013] Further, the solid-containing waste liquid to be treated is a first waste liquid, a second waste liquid and a third waste liquid;

[0014] 1%≤ solid content of the first waste liquid≤10%;

[0015] 0.2%≤ solid content of the second waste liquid<1%;

[0016] The solid content of the third waste liquid is less than 0.2%.

[0017] Further, the waste liquid treatment is a first waste liquid treatment, a second waste liquid treatment and a third waste liquid treatment;

[0018] The specific process of the first waste liquid treatment is as follows:

[0019] The mixed liquid is transported to the solid-liquid separation device through the pipeline for solid-liquid separation treatment, the separated solid phase is transported to the solid phase collection tank, and the liquid phase is transported to the air floatation residue removal device through the pipeline for residue removal treatment, and the first liquid is obtained;

[0020] The floating sludge collected by the air floatation slag removal device enters the sludge concentration device, the bottom sludge of the sludge concentration device enters the sludge drying machine of the solid-liquid separation device for disposal, and the supernatant of the sludge concentration device overflows back to the gel breaking and coagulation device.

[0021] Further, the specific process of the second waste liquid treatment is as follows:

[0022] The mixed liquid is transported to the sludge concentration device through a pipeline for concentration treatment, the supernatant of the sludge concentration device overflows back to the gel breaking and coagulation device; the settled sludge at the bottom of the tank in the sludge concentration device enters the solid-liquid separation device for solid-liquid separation treatment, and the liquid phase obtained by the solid-liquid separation treatment is transported to the air floatation slag removal device for slag removal treatment to obtain a first liquid.

[0023] The floating sludge collected by the air floatation slag removal device enters the sludge concentration device.

[0024] Further, the specific process of the third waste liquid treatment is as follows:

[0025] The mixed liquid is transported to the air floatation slag removal device through a pipeline for slag removal treatment to obtain a first liquid, the removed sludge is discharged into the sludge concentration device for concentration treatment, the supernatant overflows into the gel breaking and coagulation device, the settled sludge enters the solid-liquid separation device for solid-liquid separation treatment, and the liquid phase obtained by the solid-liquid separation treatment is transported to the gel breaking and coagulation device.

[0026] A multi-process wastewater treatment complete system, comprising: a gel breaking and coagulation device, a dosing device, a treatment mechanism, a multi-stage filtration device, a fine filtration device, and a first bypass pipeline;

[0027] The gel breaking and coagulation device is connected with the dosing device and the treatment mechanism respectively;

[0028] The treatment mechanism is connected with the multi-stage filtration device;

[0029] The multi-stage filtration device is connected with the fine filtration device and the first bypass pipeline respectively;

[0030] The treatment mechanism adopts different treatment processes according to instructions.

[0031] Further, the treatment mechanism comprises a sludge concentration device, a solid-liquid separation device, an air floatation slag removal device, and a second bypass pipeline;

[0032] The solid-liquid separation device is connected with the gel breaking and coagulation device and the air floatation slag removal device respectively;

[0033] The air floatation slag removal device is connected with the sludge concentration device, the multi-stage filtration device, and the second bypass pipeline respectively;

[0034] The sludge concentration device is connected with the gel breaking and coagulation device and the solid-liquid separation device respectively.

[0035] Further, the processing mechanism comprises a sludge concentration device, a solid-liquid separation device, a floatation residue removal device and a second bypass pipeline.

[0036] The sludge concentration device is connected with the gel breaking and coagulation device and the solid-liquid separation device respectively.

[0037] The solid-liquid separation device is connected with the floatation residue removal device.

[0038] The floatation residue removal device is connected with the sludge concentration device, the multi-stage filtration device and the second bypass pipeline respectively.

[0039] Further, the processing mechanism comprises a sludge concentration device, a solid-liquid separation device, a floatation residue removal device and a second bypass pipeline.

[0040] The floatation residue removal device is connected with the gel breaking and coagulation device, the sludge concentration device, the multi-stage filtration device and the second bypass pipeline respectively.

[0041] The sludge concentration device is connected with the gel breaking and coagulation device and the solid-liquid separation device respectively.

[0042] The solid-liquid separation device is connected with the gel breaking and coagulation device.

[0043] Further, the solid-liquid separation device comprises a solid-liquid separator.

[0044] The solid-liquid separator is a centrifuge or a sludge drying machine.

[0045] The sludge drying machine is a plate-frame filter press or a stacked screw machine.

[0046] Further, the solid-liquid separation device comprises a solid-liquid separator.

[0047] The solid-liquid separator is a spin dryer or a sludge drying machine.

[0048] The sludge drying machine is a plate-frame filter press or a stacked screw machine.

[0049] Compared with the prior art, the embodiment of the present application has at least the following advantages: the present application adopts a set of device, combines three process flows, and makes the processing object of the device cover the waste drilling mud with high solid content, the mud supernatant with relatively high solid content, the fracturing flowback fluid / acidification waste liquid / well washing and repairing waste water and the produced water with relatively low solid content, so that the waste liquid treatment requirements of each stage of the oilfield site are met at one time, the investment, relocation and other costs of the waste liquid treatment devices of each stage are reduced, the cost is saved, and the work efficiency is improved.

[0050] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 A schematic diagram of the layout of a multi-process wastewater treatment system according to an embodiment of the present invention is shown. Figure 1 ;

[0053] Figure 2 A schematic diagram of the layout of a multi-process wastewater treatment system according to an embodiment of the present invention is shown. Figure 2 ;

[0054] Figure 3 A schematic diagram of the layout of a multi-process wastewater treatment system according to an embodiment of the present invention is shown. Figure 3 ;

[0055] Figure 4 A schematic diagram of a gel-breaking coagulation device according to an embodiment of the present invention is shown;

[0056] Figure 5 A schematic diagram of a dosing device according to an embodiment of the present invention is shown;

[0057] Figure 6 A schematic diagram of a sludge thickening apparatus according to an embodiment of the present invention is shown;

[0058] Figure 7 A schematic diagram of a solid-liquid separation apparatus according to an embodiment of the present invention is shown;

[0059] Figure 8 A schematic diagram of an air flotation slag removal device according to an embodiment of the present invention is shown;

[0060] Figure 9 A schematic diagram of a multi-stage filtration device according to an embodiment of the present invention is shown;

[0061] Figure 10 A schematic diagram of a fine filtration device according to an embodiment of the present invention is shown;

[0062] Figure 11A schematic diagram of the treatment process of a multi-process wastewater treatment system according to an embodiment of the present invention is shown. Figure 1 ;

[0063] Figure 12 A schematic diagram of the treatment process of a multi-process wastewater treatment system according to an embodiment of the present invention is shown. Figure 2 ;

[0064] Figure 13 A schematic diagram of the treatment process of a multi-process wastewater treatment system according to an embodiment of the present invention is shown. Figure 3 .

[0065] Attached reference numerals: 1. De-gelling and coagulation device; 2. Dosing device; 3. Sludge thickening device; 4. Solid-liquid separation device; 5. Air flotation sludge removal device; 6. Multi-stage filtration device; 7. Fine filtration device. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] The present invention proposes a multi-process wastewater treatment system, comprising: a decoction and coagulation device 1, a dosing device 2, a treatment mechanism, a multi-stage filtration device 6, a fine filtration device 7, and a first bypass pipeline;

[0068] The gelling and coagulation device 1 is connected to the dosing device 2 and the processing mechanism, respectively.

[0069] The processing mechanism is connected to the multi-stage filtration device 6;

[0070] The multi-stage filtration device 6 is connected to the fine filtration device 7 and the first bypass pipeline, respectively.

[0071] Each unit is an independent skid-mounted unit with its own function, integrating all the equipment required to achieve that function. Once fixed in place, each unit remains stationary; process flow switching is achieved through pipeline switching. An example of the layout of a multi-process wastewater treatment system is shown below. Figure 1As shown, the layout is not unique, but process flow switching can be achieved through pipeline switching. Various units are connected via quick-connect pipes and flanges, with the flanges being electrically operated valves for automatic control. Different treatment processes exist for different objects, mainly divided into three processes. These processes are switched by setting the program and activating or deactivating the electric valves. The optimal treated water quality can achieve suspended solids ≤2mg / L, oil content ≤1mg / L, and boron ion ≤5mg / L, meeting the requirements for reinjection into the formation or remixing fracturing fluid after oilfield wastewater treatment.

[0072] The treatment facility can employ different treatment processes according to instructions to perform primary, secondary, or tertiary wastewater treatment operations. Instructions are issued by the operators to the treatment facility based on the solids content of the mixture, selecting the appropriate wastewater treatment process.

[0073] In some embodiments, such as Figure 1 As shown, for the first waste liquid (drilling waste mud) with high solid content, the treatment mechanism includes a sludge thickening device 3, a solid-liquid separation device 4, an air flotation slag removal device 5, and a second bypass pipeline.

[0074] The solid-liquid separation device 4 is connected to the gel breaking and coagulation device 1 and the air flotation slag removal device 5, respectively.

[0075] The air flotation sludge removal device 5 is connected to the sludge thickening device 3, the multi-stage filtration device 6, and the second bypass pipeline, respectively.

[0076] The sludge thickening device 3 is connected to the gel breaking and coagulation device 1 and the solid-liquid separation device 4, respectively.

[0077] In some embodiments, such as Figure 2 As shown, for the second waste liquid (sludge supernatant, sludge filtrate) with a high solid content, the treatment mechanism includes a sludge thickening device 3, a solid-liquid separation device 4, an air flotation slag removal device 5, and a second bypass pipeline.

[0078] The sludge thickening device 3 is connected to the gel breaking and coagulation device 1 and the solid-liquid separation device 4, respectively.

[0079] The solid-liquid separation device 4 is connected to the air flotation slag removal device 5;

[0080] The air flotation sludge removal device 5 is connected to the sludge thickening device 3, the multi-stage filtration device 6, and the second bypass pipeline, respectively.

[0081] In some embodiments, such as Figure 3 As shown, for the third type of waste liquid (various types of waste liquid) with low solid content, the treatment unit includes a sludge thickening device 3, a solid-liquid separation device 4, an air flotation sludge removal device 5, and a second bypass pipeline.

[0082] The air flotation sludge removal device 5 is connected to the gel breaking and coagulation device 1, the sludge thickening device 3, the multi-stage filtration device 6, and the second bypass pipeline, respectively.

[0083] The sludge thickening device 3 is connected to the gel breaking and coagulation device 1 and the solid-liquid separation device 4, respectively.

[0084] The solid-liquid separation device 4 is connected to the gel breaking and coagulation device 1.

[0085] In some embodiments, such as Figure 4 As shown, the degumming and coagulation device 1 includes a quick-connect inlet, a quick-connect outlet, a degumming and coagulation tank, a pipeline mixer and dosing coil, a slurry pump, a centrifugal pump, a stirrer, a flow meter and a control cabinet; the above components are integrated in an independent skid, and its function is to degumme and destabilize the waste liquid and to allow the suspended matter after degumming to undergo a coagulation reaction.

[0086] The quick-connect inlet, feed pump, pipeline mixer and dosing coil, and breaker coagulant tank are connected sequentially via pipelines. The breaker coagulant tank is equipped with multiple agitators. The other end of the breaker coagulant tank is connected via pipelines to a centrifugal pump and a slurry pump, which are respectively connected to the quick-connect outlet. Flow meters are installed on the inlet and outlet pipelines. The breaker coagulant device 1 also includes multiple thermometers, level gauges, solenoid valves, and other components, all of which are electrically connected to the control cabinet. The breaker coagulant tank, pipeline mixer and dosing coil, slurry pump, centrifugal pump, and agitators are all electrically connected to the control cabinet.

[0087] After the waste liquid enters the feed pump through the quick-connect inlet, it passes through the pipeline mixer and dosing coil. The reagent from the dosing device 2 enters the waste liquid through the dosing coil and is fully mixed in the pipeline mixer. Then it enters the de-gelling and coagulation tank, where it is stirred. Under the full stirring of the agitator, a de-gelling and coagulation reaction occurs, and the fine suspended solids and residual petroleum substances in the waste liquid aggregate to form fine flocs. After the reaction is completed, a mixture containing flocs is formed. The mixture with a low solids content (floc volume accounts for less than 20% of the total liquid volume) is transported to the air flotation sludge removal device 5 by a centrifugal pump; the mixture with a high solids content is transported to the sludge thickening device 3 or the solid-liquid separation device 4 by a slurry pump. The mixture with a floc volume accounting for 20%-50% of the total liquid volume goes to the sludge thickening device 3, and the mixture with a floc volume accounting for more than 50% of the total liquid volume goes to the solid-liquid separation device 4. The entire coagulation and depolymerization unit 1 is automatically operated through interlocking between the level gauge and the feed pump, and between the level gauge and the centrifugal pump or slurry pump. The flow meter and control cabinet are not shown in the diagram.

[0088] In some embodiments, such as Figure 5As shown, the dosing device 2 includes 4-10 dosing tanks, each of which has a clean water inlet pipeline (not shown in the figure), a bladed agitator (blades not shown in the figure), a level gauge (not shown in the figure), a dosing pump, pipelines from the pump to each dosing point, and a control cabinet.

[0089] Multiple dosing tanks are spaced apart. Each tank is equipped with a mixer on top and a clean water inlet pipe on its side wall. A level gauge is mounted on the outer side wall of each tank. The tanks are connected to a dosing pump via piping, and the pump is connected to the corresponding equipment via piping. A control cabinet is electrically connected to the dosing tanks, mixer, level gauge, and dosing pump, and controls these components.

[0090] Different reagents can be poured directly into the corresponding dosing tank from the top opening. The level gauge is interlocked with the water inlet valve of the clean water pipeline and the dosing pump. It can provide dissolution and temporary storage of reagents such as desiccant, pH adjuster, coagulant, flocculant, and flotation agent, and is used for the addition of various reagents to meet the dosing requirements of each process unit.

[0091] The dosing device 2 supplies reagents to the de-gelling and coagulation device 1, the air flotation and slag removal device 5, and the solid-liquid separation device 4, respectively. For example, a dosing tank storing pH adjuster is connected to the de-gelling and coagulation device 1 via a pipeline. A dosing tank storing de-gelling agent is connected to the de-gelling and coagulation device 1 via a pipeline. A dosing tank storing coagulant is connected to the de-gelling and coagulation device 1 via a pipeline. A dosing tank storing flocculant is connected to the solid-liquid separation device 4 via a pipeline. A dosing tank storing flotation agent is directly connected to the air flotation and slag removal device 5 via a pipeline. Reagent tanks storing other reagents are set up according to actual conditions and connected to the corresponding devices via pipelines, which will not be elaborated here.

[0092] In some embodiments, such as Figure 6 As shown, the sludge thickening device 3 includes a quick-connect inlet, a quick-connect outlet, a thickening tank, a stirrer, a screw pump, and a control cabinet;

[0093] The concentration tank has a quick-connect inlet at the top, an agitator inside, and a screw pump at the bottom, connected to the quick-connect outlet. The control cabinet is electrically connected to the concentration tank, agitator, and screw pump, and controls these components.

[0094] The mixed liquor enters the sludge thickening tank through the top inlet. The tank contains an agitator; the need for agitation and the agitation rate are determined based on the solids content of the mixed liquor. Sometimes, agitation is used to prevent excessive sediment buildup at the bottom, which can clog the bottom outlet. A high-level overflow pipe is located at a position opposite or at a 90° angle to the top inlet; when the liquid level in the tank reaches this height, it overflows through the overflow pipe. A quick-connect outlet and a screw pump are located at the bottom of the tank to transport the thickened sludge to the next unit.

[0095] The main function of the sludge thickening device 3 is to use gravity settling to separate the solid and liquid in the tank. The bottom of the tank contains the thickened sludge, which enters the solid-liquid separation skid; the top of the tank contains the supernatant after sedimentation, which overflows to other devices.

[0096] A stirrer is installed inside the sludge thickening tank. The stirrer should be activated when necessary to thoroughly mix the sludge and prevent clogging. The sludge at the bottom is pumped into a centrifuge for dewatering via a screw pump. Sludge thickener must be added to the centrifuge via a pipeline mixer before entering the centrifuge. The screw pump should have variable frequency drive functionality.

[0097] In some embodiments, such as Figure 7 As shown, the solid-liquid separation device 4 includes a quick-connect inlet, a pipeline mixer and dosing coil, a solid-liquid separator, a sludge tank, a sewage tank, a sludge pump, a sewage pump, and a control cabinet.

[0098] The quick-connect inlet, pipeline mixer and dosing coil, centrifuge, pipeline mixer and dosing coil, sludge dryer, and quick-connect outlet are connected sequentially via pipelines. A sludge tank and a wastewater tank are placed at the bottom of the solid-liquid separator for easy collection of sludge and wastewater. The wastewater tank contains a wastewater pump, and the sludge tank contains a sludge pump. The control cabinet is electrically connected to the pipeline mixer and dosing coil, solid-liquid separator, sludge tank, wastewater tank, sludge pump, and wastewater pump, and controls these components.

[0099] The solid-liquid separator can be used alone or in series with either a centrifuge or a sludge dryer. A centrifuge can be replaced with a spin dryer. A plate and frame filter press or a screw press can be used as the sludge dryer. The centrifuge includes an automatic chemical dissolving and dosing device (not shown in the diagram), which automatically dissolves and adds chemicals based on the amount and properties of the incoming sludge.

[0100] The solid phase separated by the centrifuge (spin dryer) is high-moisture sludge, while the solid phase separated by the sludge dryer is low-moisture sludge. When the centrifuge (spin dryer) or sludge dryer is used alone, the solid phase (high-moisture sludge or low-moisture sludge) produced by the solid-liquid separation device 4 can be directly stored in the solid phase collection tank for subsequent external transportation and comprehensive utilization. When the centrifuge (spin dryer) and sludge dryer are used in series, the high-moisture sludge separated by the centrifuge (spin dryer) first enters the sludge tank of the solid-liquid separation device 4, and is then transported to the sludge dryer by a sludge pump. The low-moisture sludge produced after processing by the sludge dryer is temporarily stored in the solid phase collection tank for subsequent external transportation and comprehensive utilization.

[0101] Centrifuges (spin dryers) and sludge dryers each have multiple feed sources. The centrifuge (spin dryer) can be fed from the depolymerizing and coagulating unit 1 and the sludge thickening unit 3; the sludge dryer can be fed from the sludge tank of the solid-liquid separation unit 4 and the sludge thickening unit 3. The sludge dryer's inlet pipeline has a pipe mixer and a dosing coil, allowing for chemical dosing based on sludge properties. Flow meters are installed on both the inlet and outlet pipelines, and the control cabinet is located in a suitable position within the skid. Corresponding flow meters, thermometers, and level gauges are also included. The system includes quick-connect inlets, quick-connect outlets, and various other auxiliary equipment such as solenoid valves. The comprehensive utilization of solids in the solid phase collection tank includes paving roads, filling well sites, and incinerating in cement kilns.

[0102] In some embodiments, such as Figure 8 As shown, the air flotation slag removal device 5 consists of a quick-connect inlet, an air flotation tank, a dissolved air tank, a dissolved air water pump, a dissolved air release nozzle, a slag scraper, a centrifugal pump, a quick-connect outlet, instruments, process pipes, valves, and a control cabinet.

[0103] The dissolved air tank and dissolved air pump are connected. Clean water from the dissolved air tank is mixed with gas by the pump and then sprayed out into the flotation tank through the dissolved air release nozzle. A quick-connect inlet is connected to the flotation tank and is located near the dissolved air release nozzle. The sludge scraper is located at the top of the flotation tank and can contact the liquid surface. A centrifugal pump and a quick-connect outlet are located at the rear of the flotation tank. Flow meters are installed on the inlet and outlet pipelines. The control cabinet is located in a suitable position within the skid. The control cabinet is electrically connected to the flotation tank, dissolved air tank, dissolved air pump, dissolved air release nozzle, sludge scraper, centrifugal pump, instruments, and valves, and controls these components.

[0104] The mixed liquid enters the dissolved air flotation tank. A large number of microbubbles are released from the dissolved air release nozzle at the bottom of the tank. The mixed liquid is fully mixed with dissolved air water in the release zone and then enters the separation zone. The microbubbles in the dissolved air water lift the suspended solids to the surface of the liquid and are collected by a scraper to the sludge collection zone. Then, it is discharged into the sludge thickening tank by a screw pump for further treatment. The clear water after removing the suspended solids enters the clear water zone of the dissolved air flotation sludge removal device 5 and enters the next process for further treatment.

[0105] In some embodiments, such as Figure 9 As shown, the multi-stage filtration device 6 includes a quick-connect inlet, a primary filter tank (two tanks in parallel), a secondary filter tank (two tanks in parallel), a filter pump, a quick-connect outlet, a control cabinet, and a backwash pump.

[0106] The quick-connect inlet, filter pump, primary filter tank, and secondary filter tank are connected sequentially; the primary filter tank, secondary filter tank, backwash pump, and quick-connect outlet are connected sequentially. The quick-connect inlet, backwash pump, and quick-connect outlet are connected sequentially via pipelines, and the filtration and backwashing process is controlled by electric valves. Flow meters, pressure sensors, and other components are installed on the inlet and outlet pipelines, respectively. The control cabinet is located in a suitable position within the skid and is electrically connected to the filter pump, backwash pump, valves, and instruments within the skid to control them and achieve automatic control.

[0107] The multi-stage filtration unit 6 consists of two fully automatic filter tanks, with an effluent specification of suspended solids (mg / L) ≤10. The multi-stage filtration unit 6 is mainly used to filter the incoming water from the air flotation and sludge removal unit 5, further reducing suspended solids and petroleum hydrocarbons in the water. The gradation of the filter media is determined by the manufacturer, but the long-term stable operation of the filtration unit must be ensured. The filter material of the multi-stage filtration unit 6 can be common filter materials such as quartz sand, ceramics, and fiber bundles.

[0108] The clean water from the clear water zone of the flotation and sludge removal device 5 is pumped into the multi-stage filtration device 6. Suspended solids and some oxidized residues in the water are trapped on the surface of the filter media. The filtered water then enters the next treatment device. When the amount of contaminants trapped on the surface of the filter media reaches the backwash set value, the equipment starts automatic backwashing.

[0109] In some embodiments, such as Figure 10 As shown, the fine filtration device 7 includes a quick-connect inlet, filter I, filter II, filter pump, backwash pump, quick-connect outlet, and control cabinet;

[0110] The quick-connect outlet, filter pump, filter I, and filter II are connected in sequence; filter I, filter II, backwash pump, and quick-connect outlet are connected in series; the quick-connect inlet, backwash pump, and quick-connect outlet are connected in sequence via pipelines. The control cabinet is electrically connected to filter I, filter II, filter pump, and backwash pump, and controls the above components.

[0111] The fine filtration unit 7 consists of filter I (fiber filtration or other equivalent filtration) and filter II (boron-removing resin filtration). A centrifugal pump sequentially pumps the filtered water from the purified water tank into filters I and II of the fine filtration unit 7. After filtration, the water enters the purified water tank for further preparation and reuse. When the surface contaminant concentration of the filter media reaches the backwash setpoint, the equipment begins automatic backwashing; the backwash water uses water from the purified water tank. Effluent specifications: suspended solids ≤ 2 mg / L, oil content ≤ 1 mg / L, boron ions ≤ 5 mg / L.

[0112] Based on the above-described multi-process wastewater treatment system, embodiments of the present invention also provide a multi-process wastewater treatment method, comprising the following steps:

[0113] The solid waste liquid to be treated enters the gel breaking and coagulation device 1, and the reagent is added by the dosing device 2. After the reaction, a mixed liquid is formed.

[0114] The mixture is transported to the treatment unit, where different processes are used to treat the waste liquid according to the different solid content of the mixture, to obtain the first liquid. Among them, the operators determine the solid content of the mixture and then select different waste liquid treatment processes and issue different waste liquid treatment instructions to the treatment unit.

[0115] The first liquid is sent to the multi-stage filtration device 6 for multi-stage filtration to obtain the second liquid;

[0116] The second liquid is conveyed to the fine filtration device 7 for fine filtration to obtain treated water.

[0117] The solid waste liquids to be treated are classified as the first waste liquid, the second waste liquid, and the third waste liquid;

[0118] The solid content of the first waste liquid is 1% ≤ 10%; for example, the first waste liquid is drilling waste mud, etc.

[0119] The solid content of the second waste liquid is 0.2% ≤ 1%; for example, the second waste liquid is mud supernatant, mud filtrate, mixed waste liquid, etc.

[0120] The solids content of the third waste liquid is <0.2%. For example, the third waste liquid is various types of waste liquid such as fracturing flowback fluid, acidizing waste liquid, and well cleaning and repair wastewater.

[0121] Waste liquid treatment is divided into first waste liquid treatment, second waste liquid treatment and third waste liquid treatment.

[0122] like Figure 11 As shown, the first waste liquid treatment mainly targets drilling waste mud with high solids content (1% ≤ solids content ≤ 10%), and the specific process is as follows:

[0123] Drilling waste mud enters the de-gelling and coagulation unit 1, where a dosing device 2 adds a de-gelling agent and a coagulant. The waste liquid undergoes a de-gelling and coagulation reaction in the de-gelling and coagulation tank, forming a mixture containing a large amount of flocculent material (flocculent volume accounting for more than 50% of the total liquid volume). The mixture is then transported via pipeline to the solid-liquid separation unit 4, where it first undergoes preliminary centrifugation and dewatering. The separated sludge with higher water content is either transported to a solid phase collection tank or further processed in a sludge dryer. The low-water-content sludge after treatment in the sludge dryer is transported to the solid phase collection tank. The waste liquid from the centrifuge and sludge dryer is temporarily stored in a water tank before entering the air flotation and sludge removal unit 5. After further removal of suspended solids in the air flotation and sludge removal unit 5, the effluent (first liquid) from the air flotation and sludge removal unit 5 can be directly transported, or it can be transported after entering a multi-stage filtration unit 6, or it can be transported after sequentially passing through a multi-stage filtration unit 6 and a fine filtration unit 7, achieving the reinjection / reuse criteria. The scum collected by the flotation sludge removal device 5 enters the sludge thickening device 3, the bottom sludge of the sludge thickening device 3 enters the sludge drying machine of the solid-liquid separation device 4 for disposal, and the supernatant of the sludge thickening device 3 overflows back to the depolymerization and coagulation device 1.

[0124] Drilling waste mud has a high solids content. After the depolymerization and flocculation reaction, it produces a large amount of flocs. If it enters the air flotation slag removal unit 5 directly, it will produce a large amount of scum, exceeding the processing capacity of the air flotation slag removal unit 5 and causing equipment blockage. The mixed liquid containing a large amount of flocs enters the solid-liquid separation unit 4. After solid-liquid separation, the solids content in the liquid phase is reduced, which reduces the load on the subsequent air flotation slag removal unit 5 and ensures the normal operation of the air flotation slag removal unit 5.

[0125] like Figure 12 As shown, the second waste liquid treatment mainly targets the mud supernatant and mud filtrate with high solid content (0.2% ≤ solid content < 1%). The specific process is as follows:

[0126] The supernatant and filtrate from the sludge enter the de-gelling and coagulation device 1, where the waste liquid undergoes a de-gelling and coagulation reaction to form a mixed liquid containing flocculants (the floc volume accounts for 20%-50% of the total liquid volume). The mixed liquid is then transported via pipeline to the sludge thickening device 3 (sludge thickening tank). The sludge settled at the bottom of the tank enters the solid-liquid separation device 4 for solid-liquid separation treatment. The solid-liquid separator can be either a centrifuge or a sludge dryer used individually, or both can be used in series. The solid phase separated by the solid-liquid separation device 4 is transported to a solid phase collection tank, while the liquid phase enters the air flotation and sludge removal device 5. After further removing suspended solids from the waste liquid, the effluent (first liquid) from the air flotation and sludge removal device 5 sequentially enters the multi-stage filtration device 6 and the fine filtration device 7 to meet the reinjection / reuse criteria. The multi-stage filtration device 6 and the fine filtration device 7 can also be bypassed. The scum collected by the flotation sludge removal device 5 enters the sludge thickening device 3, the bottom sludge of the sludge thickening device 3 enters the solid-liquid separation device 4, and the clear liquid on top of the sludge thickening device 3 overflows to the debinding and coagulation device 1. The dosing device 2 supplies chemicals to the debinding and coagulation device 1, the flotation sludge removal device 5, and the solid-liquid separation device 4 respectively.

[0127] Because the mud supernatant and mud filtrate are relatively clear liquids after sedimentation and filtration on site, they contain a certain amount of suspended matter. However, the suspended matter content and particle size are small, and the flocs formed by flocculation are relatively loose and not easy to settle. Therefore, the mixed liquid containing flocs from the de-gelling and coagulation device 1 enters the sludge thickening tank. After gravity settling, the sludge at the bottom of the tank is separated into solid and liquid, and the supernatant at the top of the tank goes to the de-gelling and coagulation device 1, which also reduces the operating load of the air flotation sludge removal device 5.

[0128] like Figure 13 As shown, the third wastewater treatment mainly targets various types of wastewater from fracturing flowback fluid, acidizing wastewater, and well cleaning wastewater with low solid content (solid content < 0.2%). The specific process is as follows:

[0129] The waste liquid from the treatment process enters the de-gelling and coagulation device 1, where it undergoes a de-gelling and coagulation reaction to form a mixed liquid containing flocculents (the volume of flocculents accounts for less than 20% of the total liquid volume). The mixed liquid is then transported via pipeline to the air flotation and sludge removal device 5 for sludge removal. The numerous microbubbles generated by the air flotation and sludge removal device 5 lift the suspended solids to the liquid surface, where they are removed by a scraper. The sludge removed by the scraper is then pumped into the sludge thickening device 3 via a screw pump. The sludge settled at the bottom of the sludge thickening tank enters the solid-liquid separation device 4 for solid-liquid separation. The solid-liquid separator can be either a centrifuge or a sludge dryer used individually, or both can be used in series. The solid phase separated by the solid-liquid separation device 4 is transported to a solid phase collection tank, while the separated liquid phase enters the coagulation and de-gelling device 1. The clear liquid overflowing from the top of the sludge thickening device 3 returns to the coagulation and de-gelling device 1. The clear water (first liquid) after the suspended solids are removed in the air flotation and sludge removal device 5 sequentially enters the multi-stage filtration device 6 and the fine filtration device 7 to meet the reinjection / reuse standards. The multi-stage filtration device 6 and the fine filtration device 7 can also be bypassed. The dosing device 2 supplies chemicals to the de-gelling and coagulation device 1, the air flotation and slag removal device 5, and the solid-liquid separation device 4, respectively.

[0130] Because the waste liquid is diverse in type and complex in composition, containing a large amount of organic matter and various additives, with high emulsified oil content, high content of small particulate suspended solids, and high viscosity, it is difficult to completely break down the gel in one go. Therefore, the supernatant of the sludge thickening device 3 and the liquid separated from the solid-liquid are returned to the gel breaking and coagulation device 1 for secondary gel breaking to improve the gel breaking efficiency and improve the air flotation slag removal effect.

[0131] The present invention proposes a multi-process wastewater treatment method and complete system that combines three process flows. This allows the device to treat waste drilling mud with high solids content, mud supernatant with high solids content, fracturing flowback fluid / acidification waste fluid / well cleaning waste water with low solids content, and produced water with low solids content. This method can meet the wastewater treatment needs of oilfields at all stages in one go, reduce investment and relocation costs of wastewater treatment equipment at each stage, save costs, and improve work efficiency.

[0132] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-process wastewater treatment method, characterized in that, Includes the following steps: The solid waste liquid to be treated enters the gel breaking and coagulation device (1), and the reagent is added by the dosing device (2). After the reaction, a mixture is formed. The mixture is transported to the treatment unit, where different processes are used to treat the waste liquid according to the different solid content of the mixture, to obtain the first liquid; the process flow is switched by pipeline switching. The first liquid is sent to a multi-stage filtration device (6) for multi-stage filtration to obtain the second liquid; The second liquid is conveyed to the fine filtration device (7) for fine filtration to obtain treated water; The solid-containing waste liquid to be treated is the first waste liquid, the second waste liquid, and the third waste liquid; The solid content of the first waste liquid is ≤10%; The solid content of the second waste liquid is 0.2% ≤ 1%; The solid content of the third waste liquid is <0.2%; The specific process for treating the first waste liquid is as follows: The mixture is transported via pipeline to the solid-liquid separation device (4) for solid-liquid separation treatment. The separated solid phase is transported to the solid phase collection tank, and the liquid phase is transported via pipeline to the air flotation slag removal device (5) for slag removal treatment to obtain the first liquid. The scum collected by the flotation sludge removal device (5) enters the sludge thickening device (3), the bottom sludge of the sludge thickening device (3) enters the sludge drying machine of the solid-liquid separation device (4) for disposal, and the supernatant of the sludge thickening device (3) overflows back to the debinding coagulation device (1). The specific process for the second waste liquid treatment is as follows: The mixed liquid is transported to the sludge thickening device (3) via pipeline for thickening treatment. The supernatant of the sludge thickening device (3) overflows back to the debinding coagulation device (1). The sludge settled at the bottom of the tank in the sludge thickening device (3) enters the solid-liquid separation device (4) for solid-liquid separation treatment. The liquid phase obtained from the solid-liquid separation treatment is transported to the air flotation slag removal device (5) for slag removal treatment to obtain the first liquid. The scum collected by the air flotation sludge removal device (5) enters the sludge thickening device (3). The specific process for treating the third waste liquid is as follows: The mixed liquid is transported through pipeline to the air flotation sludge removal device (5) for sludge removal treatment to obtain the first liquid. The removed sludge is discharged into the sludge thickening device (3) for thickening treatment. The supernatant overflows into the debinding coagulation device (1). The settled sludge enters the solid-liquid separation device (4) for solid-liquid separation treatment. The liquid phase obtained from the solid-liquid separation treatment is transported to the debinding coagulation device (1).

2. A multi-process wastewater treatment system for performing the multi-process wastewater treatment method according to claim 1, characterized in that, include: The equipment includes a gel breaking coagulation device (1), a dosing device (2), a processing mechanism, a multi-stage filtration device (6), a fine filtration device (7), and a first bypass pipeline; The gelling and coagulation device (1) is connected to the dosing device (2) and the processing mechanism respectively; The processing mechanism is connected to the multi-stage filtration device (6); The multi-stage filtration device (6) is connected to the fine filtration device (7) and the first bypass pipeline, respectively; The treatment unit adopts different treatment processes according to instructions to perform first waste liquid treatment, second waste liquid treatment, or third waste liquid treatment operations; among them, the process flow is switched through pipeline switching process; The solid content of the first waste liquid is ≤10%; The solid content of the second waste liquid is 0.2% ≤ 1%; The solid content of the third waste liquid is <0.2%.

3. The multi-process wastewater treatment system according to claim 2, characterized in that, The processing unit includes a sludge thickening device (3), a solid-liquid separation device (4), an air flotation slag removal device (5), and a second bypass pipeline. The solid-liquid separation device (4) is connected to the gel breaking and coagulation device (1) and the air flotation slag removal device (5) respectively; The air flotation sludge removal device (5) is connected to the sludge thickening device (3), the multi-stage filtration device (6), and the second bypass pipeline, respectively. The sludge thickening device (3) is connected to the gel breaking and coagulation device (1) and the solid-liquid separation device (4) respectively.

4. The multi-process wastewater treatment system according to claim 2, characterized in that, The processing unit includes a sludge thickening device (3), a solid-liquid separation device (4), an air flotation slag removal device (5), and a second bypass pipeline. The sludge thickening device (3) is connected to the depolymerization and coagulation device (1) and the solid-liquid separation device (4) respectively; The solid-liquid separation device (4) is connected to the air flotation slag removal device (5); The air flotation sludge removal device (5) is connected to the sludge thickening device (3), the multi-stage filtration device (6), and the second bypass pipeline, respectively.

5. The multi-process wastewater treatment system according to claim 2, characterized in that, The processing unit includes a sludge thickening device (3), a solid-liquid separation device (4), an air flotation slag removal device (5), and a second bypass pipeline. The air flotation sludge removal device (5) is connected to the gel breaking and coagulation device (1), the sludge thickening device (3), the multi-stage filtration device (6), and the second bypass pipeline, respectively. The sludge thickening device (3) is connected to the depolymerization and coagulation device (1) and the solid-liquid separation device (4) respectively; The solid-liquid separation device (4) is connected to the gel breaking and coagulation device (1).

6. The multi-process wastewater treatment system according to any one of claims 3-5, characterized in that, The solid-liquid separation device (4) includes a solid-liquid separator; The solid-liquid separator is a centrifuge or a sludge dryer; The sludge drying machine is either a plate and frame filter press or a screw press.

7. The multi-process wastewater treatment system according to claim 6, characterized in that, The solid-liquid separator is a spin dryer.

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