Zero-discharge treatment system for fracturing flow-back fluid

Abstract

The utility model relates to the technical field of water treatment, in particular to a zero-discharge treatment system for fracturing flow-back fluid, which comprises pretreatment equipment, chemical oxidation treatment equipment, filtering equipment, salt separation equipment, high-power concentration equipment and evaporative crystallization equipment which are communicated in sequence, the salt separation equipment comprises an outlet I and an outlet II and is used for separating monovalent salt and divalent salt, the monovalent salt flows out through the outlet I, and the divalent salt flows out through the outlet II; the high-power concentration equipment comprises a reverse osmosis mechanism I and a reverse osmosis mechanism II, the evaporative crystallization equipment comprises an evaporator I and an evaporator II, the outlet I, the reverse osmosis mechanism I and the evaporator I are sequentially communicated, and the outlet II, the reverse osmosis mechanism II and the evaporator II are sequentially communicated; and the system also comprises a produced water collecting tank communicated with the high-power concentration equipment. The treatment degree is high, the quality of produced water is good, the salt content of the product is high, resource recycling of high-quality produced water and salt of the fracturing flow-back fluid is achieved, and the system is good in operation stability and high in reliability.

Description

TECHNICAL FIELD

[0001] The utility model relates to water treatment technical field especially relates to a fracturing flowback fluid's zero emission treatment system. BACKGROUND

[0002] Hydraulic fracturing is a technique used for the extraction of oil and gas reservoirs, by creating fractures in the formation to increase the flow path of oil and gas. During the fracturing process, high-pressure liquid (usually containing water, chemical additives and proppants) is injected downhole to create fractures in the formation. As the fractures are formed, proppants are injected into the fractures to keep the fractures open, allowing oil and gas to flow more easily into the well.

[0003] Fracturing flowback fluid refers to the liquid used for fracturing that returns to the surface from the well after the completion of the hydraulic fracturing process. This liquid usually contains a large amount of water, chemical additives, proppants (such as sand) and possibly formation fluids (such as crude oil, natural gas and formation water). Specifically, the main components of fracturing flowback fluid include guar gum, preservatives, gel breakers, petroleum and other various chemical additives, containing a large amount of suspended solids, salt and organic matter, high content of sand and particulate matter, high viscosity, high degree of emulsification, difficult to separate, difficult to handle.

[0004] Therefore, the treatment and disposal of fracturing flowback fluid is an important environmental issue, as these liquids may contain harmful chemicals and formation fluids, which can have an impact on the environment and public health if not properly handled.

[0005] Existing flowback fluid treatment technologies mostly use the process flow of "oxidation + coagulation sedimentation + filtration + membrane separation". These technologies mainly focus on the optimization of water treatment processes and the reduction of reagent consumption in some process sections. The existing flowback fluid treatment technology has the following disadvantages: (1) insufficient treatment depth: most technologies fail to achieve deep treatment of various impurities and pollutants in the flowback fluid, resulting in low water quality and product salt purity after treatment; (2) low degree of resource utilization: existing technologies fail to fully utilize the salt resources in the flowback fluid, resulting in resource waste. SUMMARY

[0006] In order to solve the above technical problems existing in the prior art, the utility model provides a fracturing flowback fluid zero emission treatment system.

[0007] The technical solution of the utility model to solve the above technical problems is as follows:

[0008] The utility model provides a kind of zero discharge treatment system of fracturing flowback fluid, including the pretreatment equipment, chemical oxidation treatment equipment, filter equipment, salt separation equipment, high multiple concentration equipment and evaporation crystallization equipment communicated sequentially;The salt separation equipment includes outlet one and outlet two, and the salt separation equipment is used to separate monovalent salt and divalent salt, and the monovalent salt flows out the salt separation equipment by outlet one, and the divalent salt flows out the salt separation equipment by outlet two;The high multiple concentration equipment includes reverse osmosis mechanism one and reverse osmosis mechanism two, and the evaporation crystallization equipment includes evaporator one and evaporator two, and outlet one, reverse osmosis mechanism one, evaporator one are sequentially communicated, and outlet two, reverse osmosis mechanism two, evaporator two are sequentially communicated;It further includes water production collection tank communicated with the high multiple concentration equipment.

[0009] By using the zero discharge treatment system of fracturing flowback fluid provided by the utility model, various impurities and pollutants in the fracturing flowback fluid are treated respectively and specifically or intensively by the multi-stage combined process of "pretreatment-chemical strengthening treatment-multistage filtration-salt separation-high multiple concentration-evaporation crystallization", the treatment degree is deep, the water quality of produced water is good, the product salt is high, high-quality produced water and salt resource recycling of fracturing flowback fluid are realized, and the system has good stability and high reliability.

[0010] On the basis of the above technical scheme, the utility model can also make the following technical improvements:

[0011] Further, the pretreatment equipment includes flocculation zone, coagulation aid zone, sludge settling zone and sludge treatment mechanism, the inlet of flocculation zone is connected with fracturing flowback fluid conveying pipeline, the outlet of flocculation zone is connected with the inlet of coagulation aid zone, the outlet of coagulation aid zone is connected with the inlet of sludge settling zone, and the outlet of sludge settling zone is connected with sludge treatment mechanism;Stirring mechanism is arranged in flocculation zone and coagulation aid zone.

[0012] Further, the pretreatment equipment further includes air flotation zone and sludge collection zone, the inlet of sludge zone is connected with air flotation zone, and the outlet of sludge zone is connected with sludge treatment mechanism;Air tank is connected with air flotation zone, aeration disc is arranged in air flotation zone, and mud scraper is arranged in the upper part of air flotation zone.

[0013] Further, compressed air or ozone is stored in the air tank.

[0014] The beneficial effects of the further technical scheme are that: through flocculation precipitation and air flotation treatment, the dispersed matter, colloid, turbidity, floating oil, and sediment sand in the fracturing flowback fluid are removed; specifically, by adding flocculants and coagulants in the flocculation zone and coagulation zone, the dispersed matter, colloid, turbidity, and the like in the fracturing flowback fluid are gathered into groups, the light components float on the upper layer of the water surface, and the heavy components settle at the bottom of the water; at the same time, the gathered particles can play a role in adsorbing and reducing inorganic and organic substances and oil; in this process, by adding hydrochloric acid or sulfuric acid and sodium hydroxide to adjust the pH, and adding lime and sodium carbonate to reduce the hardness of the water; on this basis, through the air flotation process, compressed air or ozone is pumped into the fracturing flowback fluid, and the compressed air / ozone forms micro-nano air bubbles or ozone bubbles through the aeration disc, which are wrapped on the outer wall of the oil and residual particles, so that the residual alunite with medium and low density floats on the surface of the upper layer of the liquid flow under the action of the air bubble buoyancy, and enters the sludge collection hopper in the sludge collection area under the action of the mud scraper, realizing oil-water separation, and the substances in the sludge collection area are transported to the sludge treatment mechanism through the pipeline.

[0015] Further, the chemical oxidation treatment equipment comprises a first oxidation tank, a second oxidation tank, and a third oxidation tank arranged in parallel in sequence, the first oxidation tank is an ozone oxidation tank, the second oxidation tank is an electrochemical oxidation tank, and the third oxidation tank is a Fenton or Fenton-like oxidation tank.

[0016] The beneficial effects of the further technical scheme are that: the dispersed matter, colloid, and oil in the pretreated fracturing flowback fluid are greatly reduced, but there are still dissolved macromolecular organic substances, which will cause serious pollution and blockage to the subsequent evaporation system if not treated, and will also affect the quality of the product salt; by using one or more of Fenton, Fenton-like, electrochemical catalytic oxidation, and ozone oxidation to break the glue and decompose the macromolecular organic substances, the dissolved macromolecular organic substances are broken, degraded, or even completely oxidized into CO2 and H2O, that is, the macromolecular organic substances are fragmented or completely decomposed, and the water viscosity is reduced; in this process, the COD value may not be significantly reduced, but the colority is significantly reduced, and the viscosity of the feed liquid is greatly reduced in the later evaporation process, which plays an important role in improving the reliability of the evaporation system and the quality of the product salt.

[0017] Further, the first oxidation tank is provided with a valve on the inlet pipeline and the outlet pipeline, the second oxidation tank is provided with a valve on the inlet pipeline and the outlet pipeline, and the third oxidation tank is provided with a valve on the inlet pipeline and the outlet pipeline; the chemical oxidation treatment device further comprises a first parallel pipeline and a second parallel pipeline, the first parallel pipeline is located between the first oxidation tank and the second oxidation tank, and the second parallel pipeline is located between the second oxidation tank and the third oxidation tank; the inlet and the outlet of the first oxidation tank are communicated with both ends of the first parallel pipeline through a first connecting pipeline, the inlet and the outlet of the second oxidation tank are communicated with both ends of the first parallel pipeline through a second connecting pipeline, the inlet and the outlet of the second oxidation tank are communicated with both ends of the second parallel pipeline through a third connecting pipeline, and the inlet and the outlet of the third oxidation tank are communicated with both ends of the second parallel pipeline through a fourth connecting pipeline; the first connecting pipeline, the second connecting pipeline, the third connecting pipeline and the fourth connecting pipeline are provided with valves.

[0018] The beneficial effects of the above further technical solutions are that by controlling the opening or closing of the valves arranged on each module and pipeline, the single oxidation technology of the incoming liquid, the free combination of any two oxidation technologies and three oxidation technologies can be realized, and the sequence of any oxidation technology can be controlled to meet the needs of different oxidation degrees.

[0019] Further, the filter device comprises one or a combination of several of a fine sand filtering mechanism, an activated carbon filtering mechanism, a security filtering mechanism and an ultrafiltration mechanism.

[0020] The beneficial effects of the above further technical solutions are that by using one or a combination of several of fine sand filtering, activated carbon filtering, security filtering and ultrafiltration (tubular ultrafiltration, submerged ultrafiltration and the like), the residual particles, oil, COD, colority and the like brought by the upstream can be removed step by step, thereby ensuring the stable operation of the subsequent salt separation and concentration section and evaporation section.

[0021] Fine sand filtering is a kind of media filter, which forms a sand bed as a filtering carrier by using homogeneous quartz sand (particle size of about 0.5-1.2 mm) to perform three-dimensional deep filtration, and mainly functions to intercept macromolecular solid particles and colloids in the incoming liquid to clarify the incoming liquid.

[0022] Activated carbon is a kind of adsorption material with rich microporous structure and high specific surface area, and activated carbon filtering mainly relies on the strong adsorption of activated carbon to remove various impurities in the incoming liquid, such as organic matter, heavy metals, colloids, residual chlorine, peculiar smell, pigment and the like through physical and chemical actions, thereby improving water quality.

[0023] The security filter is generally used as a precision filter before ultrafiltration, nanofiltration and reverse osmosis membrane, and its function is to intercept particles larger than 5 mu m in raw water.

[0024] Further, the reverse washing device is in communication with the filtration device, and the blowdown outlet of the filtration device is in communication with the inlet of the pretreatment device.

[0025] Further, the reverse washing device comprises a gas washing mechanism and a water washing mechanism.

[0026] The beneficial effects of the above further technical solutions are that the incoming liquid is controlled by a pump and a valve, enters and is discharged from the system in sequence through the water inlet and the water outlet, and is purified; when the pressure difference of the filtration device is higher than 0.5-0.7 bar, the reverse washing device is started to clean the filtration device; during the reverse washing, gas washing is firstly performed, under the action of the gas flow, the pollutants adhered to the sand particles are separated from the sand particles through friction, and then water washing is performed, the high-quality water from the system water tank enters the filter through the reverse washing port under the action of the pump, and the pollutants are returned to the inlet of the pretreatment section through the blowdown outlet; after the reverse washing is completed, the valve is cut off, and the filtration program is re-entered to perform the water quality purification process.

[0027] Further, the salt separation device is a nanofiltration mechanism.

[0028] The beneficial effects of the above further technical solutions are that nanofiltration (NF) is a pressure-driven membrane separation process between reverse osmosis and ultrafiltration, and the pore size of the nanofiltration membrane is about several nanometers; due to the unique screening and charge effects of NF, the NF has the effect of separating monovalent salt and divalent salt; through this process, the monovalent salt and the divalent salt in the incoming liquid are separated, and the subsequent concentration and evaporation crystallization of the two kinds of salt solutions are carried out; specifically, under the action of the pump, the liquid treated by the previous section enters the nanofiltration salt separation device, under the action of the nanofiltration membrane, the monovalent salt and the divalent salt in the liquid are separated, the monovalent salt solution (sodium chloride solution) is obtained on the water production side, and the divalent salt solution (calcium chloride solution) is obtained on the concentrated water side; the monovalent salt solution and the divalent salt solution enter reverse osmosis mechanism one and reverse osmosis mechanism two respectively for further treatment.

[0029] The beneficial effects of the above further technical solutions are that:

[0030] Compared with the prior art, the utility model has the following technical effects:

[0031] The zero-discharge treatment system of fracturing flowback fluid provided by the utility model, through the multi-section combined process of "pretreatment-chemical strengthening treatment-multistage filtration-salt separation-high multiple concentration-evaporation crystallization", various impurities and pollutants in the fracturing flowback fluid are treated respectively in pertinence or strengthening, the treatment degree is deep, the water quality of produced water is good, the product salt is high, high quality produced water and salt resource reuse of the fracturing flowback fluid are realized, and the system has good running stability and high reliability;

[0032] The produced water (sodium chloride part of monovalent salt) and the concentrated water (calcium chloride part of divalent salt) of the salt separation section enter respective high multiple concentration sections, and high multiple concentration and high quality produced water are realized through reverse osmosis technology.

[0033] Reverse osmosis (RO) is a membrane separation technology taking reverse osmosis membrane as medium and pressure as driving force, and is an application technology separating solute and solvent in solution through selective permeation membrane, and can intercept various dissolved salts except water molecules.

[0034] The water separated by the NF system enters reverse osmosis mechanism one and reverse osmosis mechanism two respectively, and is concentrated respectively, the RO system can efficiently intercept the salt in water, and the concentrated liquid of each respectively enters evaporator one and evaporator two, the produced water quality of each is good, and is collected to a produced water collecting tank.

[0035] The concentrated water after high multiple concentration is evaporated and crystallized to obtain sodium chloride and calcium chloride dihydrate crystalline salt, or is concentrated to obtain supersaturated crystalline state, the cost is only 20-25% of evaporation, and the running cost is reduced.

[0036] The concentration of the material liquid concentrated by the RO system is as high as 10-15%, after the evaporation system, the salt and water are completely separated, the salt is respectively sodium chloride and calcium sulfate dihydrate, and the water vapor is condensed to become clean water and is collected to the produced water collecting tank. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A schematic view of the zero-discharge treatment system of fracturing flowback fluid is shown.

[0038] Reference signs:

[0039] 1, pretreatment device; 2, chemical oxidation treatment device; 3, filtration device; 4, salt separation device; 5, high concentration device; 6, evaporation crystallization device; 7, reverse osmosis mechanism one; 8, reverse osmosis mechanism two; 9, evaporator one; 10, evaporator two; 11, water production collection tank one; 12, water production collection tank two; 13, flocculation zone; 14, coagulation aid zone; 15, sludge sedimentation zone; 16, sludge treatment mechanism; 17, stirring mechanism; 18, air flotation zone; 19, sludge collection zone; 20, aeration disc; 21, sludge scraper; 22, first oxidation tank; 23, second oxidation tank; 24, third oxidation tank; 25, first parallel pipeline; 26, second parallel pipeline; 27, valve; 28, backwashing device; 29, ultrafiltration mechanism. DETAILED DESCRIPTION

[0040] The implementation of the present application will be described by specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure. Although the description of the present application will be introduced together with the preferred embodiments, this does not mean that the features of the present application are limited to the embodiments. On the contrary, the purpose of introducing the present application with the embodiments is to cover other options or modifications that can be extended based on the claims of the present application. In order to provide a deep understanding of the present application, many specific details will be included in the following description. The present application can also be implemented without using these details. In addition, in order to avoid confusion or obscure the focus of the present application, some specific details will be omitted in the description. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0041] Reference Figure 1 A zero discharge treatment system for fracturing flowback fluid, comprising pretreatment device 1, chemical oxidation treatment device 2, filtration device 3, salt separation device 4, high concentration device 5 and evaporation crystallization device 6 connected in sequence; the salt separation device 4 comprises outlet one and outlet two, the salt separation device 4 is used for separating monovalent salt and divalent salt, the monovalent salt flows out of the salt separation device 4 through the outlet one, and the divalent salt flows out of the salt separation device 4 through the outlet two; the high concentration device 5 comprises reverse osmosis mechanism one 7 and reverse osmosis mechanism two 8, the evaporation crystallization device 6 comprises evaporator one 9 and evaporator two 10, the outlet one, the reverse osmosis mechanism one 7 and the evaporator one 9 are connected in sequence, the outlet two, the reverse osmosis mechanism two 8 and the evaporator two 10 are connected in sequence; further comprising a water production collection tank in communication with the high concentration device 5, the water production collection tank comprises water production collection tank one 11 and water production collection tank two 12, the water production collection tank one 11 is in communication with the water outlet of the reverse osmosis mechanism one 7, and the water production collection tank two 12 is in communication with the water outlet of the reverse osmosis mechanism two 8, for collecting high-quality water production.

[0042] Valves and pumps are arranged on the connecting pipes and water inlet pipes between the devices.

[0043] The pretreatment device 1 comprises a flocculation zone 13, a coagulation zone 14, a sludge sedimentation zone 15, a sludge treatment mechanism 16, a gas floatation zone 18 and a sludge collection zone 19, the inlet of the flocculation zone 13 is connected with a fracturing flowback fluid conveying pipeline, the outlet of the flocculation zone 13 is connected with the inlet of the coagulation zone 14, the outlet of the coagulation zone 14 is connected with the inlet of the sludge sedimentation zone 15, and the outlet of the sludge sedimentation zone 15 is connected with the sludge treatment mechanism 16; the flocculation zone 13 and the coagulation zone 14 are both provided with stirring mechanisms 17; the inlet of the sludge collection zone 19 is connected with the gas floatation zone 18, and the outlet of the sludge collection zone 19 is connected with the sludge treatment mechanism 16; the gas floatation zone 18 is connected with a gas storage tank, the gas storage tank stores compressed air or ozone, the gas floatation zone 18 is provided with an aeration disc 20, and the upper part of the gas floatation zone 18 is provided with a sludge scraper 21; the flocculation zone 13, the coagulation zone 14, the gas floatation zone 18 and the sludge collection zone 19 are separated by partitions.

[0044] In the flocculation zone 13, one or more of acid, alkali, flocculant and softening agent can be added through the dosing points A, B and C for adjusting the pH value of the incoming liquid, adding flocculant or softening agent, so that the dispersed substance, colloid, turbidity, COD and oil in the incoming liquid form fine particle or amorphous suspended solids (SS), or the water hardness is removed; in the coagulation zone 14, a coagulant is added through the dosing point D to agglomerate the fine SS in the flocculation zone 13 into large particle or amorphous alum flowers, which are separated in the sludge sedimentation zone 15 under the action of gravity, and a large amount of alum flowers are settled in the collection hopper and discharged from the lower end into the sludge treatment mechanism 16; in the gas floatation zone 18, the compressed air / ozone is converted into micro-nano air bubbles or ozone bubbles under the action of the aeration disc 20, the micro-nano air bubbles or ozone bubbles are wrapped on the outer wall of the residual alum flowers with medium or low density, the alum flowers wrapped by the bubbles float on the surface of the liquid flow under the action of the bubble buoyancy, and enter the sludge collection hopper of the sludge collection zone 19 under the action of the sludge scraper 21 and are conveyed to the sludge collection zone 19 through a pipeline.

[0045] The liquid treated by the air floatation zone 18 enters the next treatment equipment, i.e. the chemical oxidation treatment equipment 2, for further chemical strengthening treatment. The pretreated water dispersion, colloid and oil are greatly reduced, and there still exists dissolved macromolecular organic matter. If not treated, the dissolved macromolecular organic matter will bring about serious pollution blocking tendency to the subsequent evaporation system and will also affect the product salt quality. Through the chemical strengthening treatment, the dissolved macromolecular organic matter is mainly broken, degraded or even completely oxidized into CO2 and H2O by using Fenton, electro-catalytic oxidation, ozone and other processes. In this process, the COD value is not necessarily significantly reduced, but the colority is significantly reduced, and the viscosity of the feed liquid in the later evaporation process is greatly reduced, which plays an important role in improving the reliability of the evaporation system and improving the product salt quality.

[0046] Specifically, the chemical oxidation treatment equipment 2 comprises a first oxidation tank 22, a second oxidation tank 23 and a third oxidation tank 24 which are arranged in sequence and in parallel. The first oxidation tank 22 is an ozone oxidation tank, the second oxidation tank 23 is an electrochemical oxidation tank, and the third oxidation tank 24 is a Fenton or Fenton-like oxidation tank. Valves 27 are arranged on the inlet pipeline and the outlet pipeline of the first oxidation tank 22, the inlet pipeline and the outlet pipeline of the second oxidation tank 23 and the inlet pipeline and the outlet pipeline of the third oxidation tank 24. The chemical oxidation treatment equipment 2 further comprises a first parallel pipeline 25 and a second parallel pipeline 26. The first parallel pipeline 25 is located between the first oxidation tank 22 and the second oxidation tank 23, and the second parallel pipeline 26 is located between the second oxidation tank 23 and the third oxidation tank 24. The inlet and the outlet of the first oxidation tank 22 are communicated with both ends of the first parallel pipeline 25 through a first connecting pipeline, the inlet and the outlet of the second oxidation tank 23 are communicated with both ends of the first parallel pipeline 25 through a second connecting pipeline, the inlet and the outlet of the second oxidation tank 23 are communicated with both ends of the second parallel pipeline 26 through a third connecting pipeline, and the inlet and the outlet of the third oxidation tank 24 are communicated with both ends of the second parallel pipeline 26 through a fourth connecting pipeline. Valves 27 are arranged on the first connecting pipeline, the second connecting pipeline, the third connecting pipeline and the fourth connecting pipeline. By controlling the opening of the valves 27 arranged on each module and pipeline, the single oxidation technology, the free combination of any two oxidation technologies and three oxidation technologies of the incoming water can be realized, and the sequence of any oxidation technology can be controlled to meet the needs of different oxidation degrees.

[0047] The filter equipment 3 comprises any one of a fine sand filtering mechanism, an activated carbon filtering mechanism and a security filtering mechanism in series with the ultrafiltration mechanism 29. Specifically, the inlet of the filter equipment 3 is communicated with the outlet of the chemical oxidation treatment equipment 2, and the outlet of the filter equipment 3 is communicated with the inlet of the ultrafiltration mechanism 29.

[0048] Also included is a backwashing device 28, which is in communication with the filter device 3 and an ultrafiltration mechanism 29, the blowdown port of the filter device 3 is in communication with the inlet of the pretreatment device 1, returning the pollutants to the water inlet of the pretreatment device 1 through the blowdown port, the backwashing device 28 includes an air washing mechanism and a water washing mechanism. The incoming water is controlled by a pump and a valve, and sequentially enters and is discharged from the system through the water inlet and the water outlet to obtain purification; when the filter pressure difference is higher than 0.5-0.7 bar, the backwashing program is started, during backwashing, air washing is first performed, under the action of the air flow, the pollutants adhered to the sand particles are separated from the sand particles by friction, and then water washing is performed, the high-quality water from the system water tank enters the filter through the backwashing port under the action of the pump, and the pollutants are returned to the water inlet of the pretreatment device 1 through the blowdown port; after backwashing is completed, the valve is cut off to re-enter the filtration program to perform the water quality purification process. The air washing is performed by using compressed air or ozone, and the air used for air washing is from a gas storage tank.

[0049] Ultrafiltration is a process that uses the screening principle of an ultrafiltration membrane, takes the pressure difference on both sides of the membrane as the driving force, takes the ultrafiltration membrane as the filtration medium, and under a certain pressure, when the raw liquid flows through the membrane surface, the many small pores densely distributed on the surface of the ultrafiltration membrane only allow water and small molecules to pass through to become the permeate, and the substances with a volume greater than the pore diameter of the membrane surface in the raw liquid are retained on the inlet side of the membrane to become the concentrated liquid, so as to realize the purposes of purification, separation and concentration of the raw liquid. The ultrafiltration (UF) system adopts one or a combination of the processes of submerged ultrafiltration and tubular ultrafiltration. When normally operating, water quality purification is performed; when the pressure difference reaches higher than 0.5-0.7 bar, backwashing is performed, or backflushing is performed once every 15-20 minutes, the blowdown water is returned to the water inlet of the pretreatment device 1 through the blowdown pipeline; after backwashing is completed, the valve is cut off to re-enter the filtration program to perform the water quality purification process.

[0050] The desalination device 4 is a nanofiltration mechanism, under the action of a pump, the water treated in the previous stage is introduced into the nanofiltration NF desalination system, under the action of the nanofiltration membrane, the monovalent salt and the divalent salt in the water are separated, the monovalent salt sodium chloride solution is obtained on the water production side, and the divalent salt calcium chloride solution is obtained on the concentrated water side, the monovalent salt sodium chloride solution and the divalent salt calcium chloride solution are introduced into reverse osmosis mechanisms one 7 and two 8 respectively for further treatment, and the concentration of the two kinds of salt solutions is performed.

[0051] The reverse osmosis system can efficiently intercept the salt in water. The monovalent salt sodium chloride solution enters the reverse osmosis mechanism 7 to be concentrated, and forms monovalent salt concentrated solution and product water. The monovalent salt concentrated solution enters the evaporator 9 to be evaporated and crystallized, and obtains monovalent salt sodium chloride. The product water is collected into the product water collecting tank 11. The divalent salt calcium chloride solution enters the reverse osmosis mechanism 8 to be concentrated, and forms divalent salt concentrated solution and product water. The divalent salt concentrated solution enters the evaporator 2 10 to be evaporated and crystallized, and obtains divalent salt calcium chloride. The product water is collected into the product water collecting tank 2 12. The water quality after treatment and the product salt purity are high. The salt resources in the flowback fluid can be fully utilized, and the degree of resource utilization is high.

[0052] The above merely illustrates the preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A zero-discharge treatment system for fracturing flowback fluid, characterized in that, The system includes a pretreatment device, a chemical oxidation treatment device, a filtration device, a salt separation device, a high-concentration device, and an evaporation crystallization device connected in sequence. The salt separation device includes an outlet one and an outlet two, and is used to separate monovalent salts and divalent salts. The monovalent salts flow out of the salt separation device through outlet one, and the divalent salts flow out of the salt separation device through outlet two. The high-concentration device includes a reverse osmosis mechanism one and a reverse osmosis mechanism two. The evaporation crystallization device includes an evaporator one and an evaporator two. The outlet one, the reverse osmosis mechanism one, and the evaporator one are connected in sequence, and the outlet two, the reverse osmosis mechanism two, and the evaporator two are connected in sequence. The system also includes a product water collection tank connected to the high-concentration device.

2. The zero-discharge treatment system for fracturing flowback fluid according to claim 1, characterized in that, The pretreatment equipment includes a flocculation zone, a coagulation aid zone, a sludge settling zone, and a sludge treatment mechanism. The inlet of the flocculation zone is connected to the fracturing flowback fluid delivery pipeline, the outlet of the flocculation zone is connected to the inlet of the coagulation aid zone, the outlet of the coagulation aid zone is connected to the inlet of the sludge settling zone, and the outlet of the sludge settling zone is connected to the sludge treatment mechanism. Both the flocculation zone and the coagulation aid zone are equipped with a stirring mechanism.

3. The zero-discharge treatment system for fracturing flowback fluid according to claim 2, characterized in that, The pretreatment equipment also includes an air flotation zone and a sludge collection zone. The inlet of the sludge collection zone is connected to the air flotation zone, and the outlet of the sludge collection zone is connected to the sludge treatment mechanism. The air flotation zone is connected to a gas storage tank, and an aeration disc is provided in the air flotation zone. A sludge scraper is provided at the top of the air flotation zone.

4. The zero-discharge treatment system for fracturing flowback fluid according to claim 3, characterized in that, The gas storage tank contains compressed air or ozone.

5. The zero-discharge treatment system for fracturing flowback fluid according to claim 1, characterized in that, The chemical oxidation treatment equipment includes a first oxidation tank, a second oxidation tank, and a third oxidation tank arranged in parallel in sequence. The first oxidation tank is an ozone oxidation tank, the second oxidation tank is an electrochemical oxidation tank, and the third oxidation tank is a Fenton or Fenton-like oxidation tank.

6. The zero-discharge treatment system for fracturing flowback fluid according to claim 5, characterized in that, Valves are provided on the inlet and outlet pipes of the first oxidation tank, the inlet and outlet pipes of the second oxidation tank, and the inlet and outlet pipes of the third oxidation tank. The chemical oxidation treatment equipment also includes a first parallel pipe and a second parallel pipe. The first parallel pipe is located between the first oxidation tank and the second oxidation tank, and the second parallel pipe is located between the second oxidation tank and the third oxidation tank. The inlet and outlet of the first oxidation tank are connected to both ends of the first parallel pipe through a first connecting pipe. The inlet and outlet of the second oxidation tank are connected to both ends of the first parallel pipe through a second connecting pipe. The inlet and outlet of the second oxidation tank are connected to both ends of the second parallel pipe through a third connecting pipe. The inlet and outlet of the third oxidation tank are connected to both ends of the second parallel pipe through a fourth connecting pipe. Valves are provided on the first, second, third, and fourth connecting pipes.

7. The zero-discharge treatment system for fracturing flowback fluid according to claim 1, characterized in that, The filtration equipment includes one or a combination of several of the following: fine sand filtration mechanism, activated carbon filtration mechanism, security filtration mechanism, and ultrafiltration mechanism.

8. The zero-discharge treatment system for fracturing flowback fluid according to claim 1, characterized in that, It also includes a backwashing device, which is connected to the filtration device, and the drain outlet of the filtration device is connected to the inlet of the pretreatment device.

9. The zero-discharge treatment system for fracturing flowback fluid according to claim 8, characterized in that, The backwashing equipment includes an air washing mechanism and a water washing mechanism.

10. The zero-discharge treatment system for fracturing flowback fluid according to claim 1, characterized in that, The salt separation device is a nanofiltration mechanism.

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