Device for treating gas field produced water with oil content ranging from 500mgL to 30000mgL

Abstract

The utility model relates to a device for treating gas field produced water with the oil content ranging from 500mgL to 30000mgL, which comprises an air floatation unit, an air floatation circulating treatment unit and a water treatment unit, the air floatation unit comprises a plurality of stages of air floater units and an air floatation circulating treatment unit which are connected with each other, and an inlet of the air floatation circulating treatment unit is connected with the last stage of air floater unit; the homogenizing unit is connected with the last stage of air floatation unit in the multiple stages of air floatation units; the mechanical stirring unit is connected with the homogenizing unit; the first filtering unit is connected with the mechanical stirring unit; the electrolysis unit is connected with the first filtering unit; the COD removal unit is connected with the electrolysis unit; the second filtering unit is connected with the COD removal unit, the filtering mode of the first filtering unit is physical filtering, and the filtering mode of the second filtering unit is chemical reaction filtering; and the reverse osmosis membrane unit is connected with the second filtering unit.

Description

Technical Field

[0001] This utility model relates to the field of produced water treatment technology, and in particular to a gas field produced water treatment device for oil content in the range of 500 mg / L to 30000 mg / L. Background Technology

[0002] During gas well production, low acid flowback rates often result in residual acid fracturing fluid remaining in the formation. To increase well production and fully realize capacity, acid fracturing is typically used to modify the well network and develop reservoir fractures. During well production, residual formation fluid is carried to the surface with the gas and undergoes gas-liquid separation before entering subsequent processes. This fluid contains oil and bitumen-like impurities (injected fracturing fluid). To ensure the stable, full-capacity, and efficient operation of natural gas desulfurization units, it is necessary to treat and effectively utilize the produced water from the relevant oil and gas fields.

[0003] The related technology discloses a device for treating recycled waste emulsion. The process method includes, in sequence: a hardening step: adding a reagent to the produced water to remove scale-forming ions; an electrochemical oxidation step: electrolyzing the produced water, controlling the pH value of the influent between 8 and 9, using DC voltage for electrolysis to remove ammonia nitrogen and reduce COD; an iron-carbon micro-electrolysis step: passing the produced water through iron-carbon packing material, adding an acid to control the pH value of the influent between 5.5 and 6.0 to further remove ammonia nitrogen and reduce COD; and a reverse osmosis step: passing the produced water through a reverse osmosis membrane to further remove conductive ions and reduce COD, obtaining the treated effluent.

[0004] However, the process systems for resource utilization of produced water from oil and gas fields provided by related technologies have problems such as poor treatment effect and high treatment cost for produced water from high-content oil and gas fields, such as oil content of 500mg / L-30000mg / L. Utility Model Content

[0005] This invention provides a gas field produced water treatment device for oil content in the range of 500 mg / L to 30,000 mg / L. It can at least solve the problems of poor treatment effect and high treatment cost of the process system for resource utilization treatment of oil and gas field produced water provided by related technologies for low content, such as oil content of 500 mg / L to 30,000 mg / L in high oil field produced water.

[0006] The solution provided by this utility model is as follows:

[0007] A treatment device for produced water from gas fields with oil content ranging from 500 mg / L to 30000 mg / L, comprising:

[0008] The air flotation unit includes interconnected multi-stage air flotation sub-units and an air flotation circulation treatment unit. The inlet of the air flotation circulation treatment unit is connected to the last stage air flotation sub-unit, and the outlet of the air flotation circulation treatment unit is used to connect to a preset level air flotation sub-unit based on the oil content in the gas field produced water after treatment by the last stage air flotation sub-unit. The air flotation circulation treatment unit is used to detect when the oil content in the gas field produced water after treatment by the last stage air flotation unit is greater than a first preset content, and then perform a second air flotation treatment through the air flotation sub-unit. The operating pressure of the multi-stage air flotation units increases sequentially from the inlet to the outlet of the gas field produced water.

[0009] The homogenization unit is connected to the last stage air flotation unit in the multi-stage air flotation unit;

[0010] A mechanical stirring unit is connected to the homogenizing unit;

[0011] The first filtration unit is connected to the mechanical stirring unit;

[0012] The electrolysis unit is connected to the first filtering unit;

[0013] The COD removal unit is connected to the electrolysis unit;

[0014] The second filtration unit is connected to the COD removal unit, wherein the filtration method of the first filtration unit is physical filtration, and the filtration method of the second filtration unit is chemical reaction filtration.

[0015] The reverse osmosis membrane unit, connected to the second filtration unit, is used to remove impurities and salts from the produced water from the gas field.

[0016] In one optional embodiment, the air flotation circulation treatment unit includes a first oil stain detection unit and a first circulation treatment pipeline;

[0017] The first circulation processing pipeline is connected to the outlet of the last stage air flotation unit, and the other end is used to connect to the air flotation unit of a preset level according to the oil content in the gas field produced water after the last stage air flotation unit is processed.

[0018] The first oil stain detection unit is located at the outlet of the last stage air float unit.

[0019] In an optional embodiment, the air flotation circulation processing unit further includes a first control valve disposed on the first circulation processing pipeline.

[0020] In one optional embodiment, the air flotation subunit includes: a tank, an aerator, an air flotation tank, and a sludge scraping mechanism;

[0021] The aerator is located at the first end of the tank, and the air flotation tank is located at the second end of the tank.

[0022] The sludge scraping mechanism is located at the top of the tank, and the tank has an inlet at the first end and an outlet at the second end.

[0023] In one optional embodiment, the aerator produces bubbles with a diameter of 10 μm to 100 μm.

[0024] In one optional embodiment, the electrolysis unit includes a plurality of electrolysis sub-units connected in series and an electrolysis cycle processing unit;

[0025] The electrolysis cycle processing unit is connected to the outlet of the last electrolysis subunit. The electrolysis cycle processing unit is used to perform a second electrolysis process when the oil content is detected to be greater than the second preset content.

[0026] In one optional embodiment, the electrolytic circulation processing unit includes: a second oil stain detection unit and a second circulation processing pipeline;

[0027] One end of the second circulation processing pipeline is connected to the outlet of the last electrolysis subunit, and the inlet is connected to the inlet of the first electrolysis subunit;

[0028] The second oil stain detection unit is installed on the second circulation treatment pipeline.

[0029] In one optional embodiment, the electrolytic circulation processing unit further includes a second control valve disposed on the second circulation processing pipeline.

[0030] In one alternative embodiment, the first filter is a diamond filter and the second filter is a manganese sand filter.

[0031] In one alternative embodiment, it further includes: a demulsification unit and a sludge collection unit;

[0032] The demulsification unit is connected to the air flotation unit, and the demulsification unit is used to demulsify the produced water from the gas field.

[0033] The inlet of the wastewater collection unit is connected to the air flotation unit, and the outlet is connected to the homogenization unit.

[0034] Compared with existing technologies, the gas field produced water treatment device provided in this embodiment of the invention addresses the issue of relatively high oil content in the gas field produced water, which ranges from 500 mg / L to 30000 mg / L. By connecting multiple stages of air flotation sub-units and an air flotation circulation treatment unit, the oil content in the produced water can be significantly reduced. The air flotation circulation treatment unit connects its inlet to the final stage air flotation sub-unit, and its outlet can be connected to a preset level of air flotation sub-unit based on the oil content in the produced water after treatment by the final stage. In other words, this invention can detect the oil content in the produced water after treatment by the final stage air flotation unit through the air flotation circulation treatment unit. When the concentration exceeds a preset level, the produced water from the gas field is further treated using an air flotation unit to improve the treatment effect and facilitate subsequent treatment, reducing costs and increasing efficiency. The system then homogenizes the produced water using a homogenization unit, mechanically agitates it using a stirring unit to reduce calcium and magnesium ions, removes suspended solids of the first particle size using a first filtration unit, removes oil using an electrolysis unit, removes organic pollutants using a COD removal unit, removes suspended solids using a second filtration unit, and removes impurities and salts using a reverse osmosis membrane unit, ultimately achieving the target treatment effect. The device provided in this embodiment can treat produced water from high-oil-content gas fields (500 mg / L - 30000 mg / L), and compared to treating produced water without distinguishing oil content, it reduces treatment costs while improving efficiency and effectiveness. Attached Figure Description

[0035] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings.

[0036] Figure 1 This is a schematic diagram of the gas field produced water treatment device in an embodiment of this utility model.

[0037] Figure 2 This is a schematic diagram of the air float unit structure in an embodiment of this utility model.

[0038] Figure label:

[0039] 1-Air flotation unit, 2-Homogenization unit, 3-Mechanical stirring unit, 4-First filtration unit, 5-Electrolysis unit, 6-COD removal unit, 7-Second filtration unit, 8-Reverse osmosis membrane unit, 81-High-pressure membrane reverse osmosis unit, 82-Low-pressure membrane reverse osmosis unit, 9-Demulsification unit, 10-Wastewater collection unit, 11-First oil stain detection unit, 12-First circulation treatment pipeline, 13-First control valve, 14-Air flotation sub-unit, 141-Tank body, 142-Aerator, 143-Air flotation tank, 144-Sludge scraping mechanism, 15-Mechanical steam recompression unit, 41-Second oil stain detection unit, 42-Second circulation treatment pipeline, 43-Second control valve. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings.

[0041] Please see Figure 1 This utility model provides a gas field produced water treatment device for oil content in the range of 500 mg / L to 30000 mg / L, including: an air flotation unit 1, a homogenization unit 2, a mechanical stirring unit 3, a first filtration unit 4, an electrolysis unit 5, a COD removal unit 6, a second filtration unit 7, and a reverse osmosis membrane unit 8.

[0042] The air flotation unit 1 includes a multi-stage air flotation sub-unit 14 connected to an air flotation circulation treatment unit. The inlet of the air flotation circulation treatment unit is connected to the last stage air flotation sub-unit 14, and the outlet of the air flotation circulation treatment unit is used to connect to a preset level air flotation sub-unit 14 based on the oil content in the gas field produced water after treatment by the last stage air flotation sub-unit 14. The air flotation circulation treatment unit is used to detect when the oil content in the gas field produced water after treatment by the last stage air flotation sub-unit 14 is greater than a first preset content, and then perform air flotation treatment again through the air flotation sub-unit 14. The working pressure of the multi-stage air flotation unit 14 increases sequentially from the inlet to the outlet of the gas field produced water.

[0043] The homogenizing unit 2 is connected to the last stage air flotation sub-unit 14 in the multi-stage air flotation unit 1; the mechanical stirring unit 3 is connected to the homogenizing unit 2; the first filtration unit 4 is connected to the mechanical stirring unit 3; the electrolysis unit 5 is connected to the first filtration unit 4; the COD removal unit 6 is connected to the electrolysis unit 5; the second filtration unit 7 is connected to the COD removal unit 6, wherein the filtration method of the first filtration unit 4 is physical filtration, and the filtration method of the second filtration unit 7 is chemical reaction filtration; the reverse osmosis membrane unit 8 is connected to the second filtration unit 7 and is used to remove impurities and salts from the gas field produced water.

[0044] The gas field produced water treatment device provided in this embodiment of the invention addresses the issue of relatively high oil content in the gas field produced water, which ranges from 500 mg / L to 30000 mg / L. Therefore, by setting up interconnected multi-stage air flotation sub-units 14 and air flotation circulation treatment units, the oil content in the produced water can be significantly reduced through the multi-stage air flotation sub-units 14. The air flotation circulation treatment unit connects its inlet to the last stage air flotation sub-unit 14, and its outlet can be connected to a preset level air flotation sub-unit 14 based on the oil content in the produced water after treatment by the last stage air flotation sub-unit 14. In other words, this invention can detect the oil content in the produced water after treatment by the last stage air flotation sub-unit 14 through the air flotation circulation treatment unit. If the oil content is greater than the first stage air flotation sub-unit 14, the device can detect the oil content in the produced water. When the preset content is reached, the gas field produced water is further treated by the air flotation unit 14 to improve the treatment effect of the gas field produced water, and also to facilitate subsequent treatment of the gas field produced water, reduce the cost of subsequent treatment and improve the treatment efficiency; the gas field produced water is homogenized by the homogenization unit 2; the gas field produced water is mechanically stirred by the mechanical stirring unit 3 to reduce the calcium and magnesium ions in the gas field produced water; the first filtration unit 4 removes suspended solids of the first particle size in the gas field produced water; the electrolysis unit 5 removes oil from the gas field produced water; the COD removal unit 6 removes organic pollutants from the gas field produced water; the second filtration unit 7 removes suspended solids from the gas field produced water; and the reverse osmosis membrane unit 8 removes impurities and salts from the gas field produced water, so that the treated gas field produced water finally achieves the target treatment effect. The device provided in this embodiment can treat produced water from high-oil-content gas fields with oil content ranging from 500 mg / L to 30000 mg / L, achieving the technical requirement of oil content ≤1 mg / L. Compared to treating produced water from gas fields that does not differentiate between oil contents, it reduces treatment costs while improving treatment efficiency and effectiveness. It has broad application value in the oil and gas field development industry, specifically in the extraction of produced water from oil-containing gas fields.

[0045] For example, in this embodiment of the present invention, the first preset content can be 30 mg / L, that is, when the oil content in the gas field produced water is 30 mg / L, it indicates that the treatment of the gas field produced water by the flotation unit 1 meets the standard. If the oil content in the gas field produced water is greater than 30 mg / L, the gas field produced water needs to be further treated by the flotation circulation treatment unit.

[0046] The air flotation unit 14 of this embodiment generates microbubbles by introducing air into the water. Oil droplets and suspended particles adhere to these bubbles, and due to the buoyancy of the bubbles, these adhered particles float to the surface, forming a scum layer, thereby purifying the produced water from the gas field. Exemplarily, the air flotation unit 14 can be implemented using diffused air flotation, dissolved air flotation, or electrolytic air flotation. Diffuse air flotation refers to dispersing air into the produced water from the gas field through microporous aeration or shearing bubbles, forming a large number of microbubbles that cause oil droplets and suspended particles to float. Dissolved air flotation includes dissolved air vacuum flotation and pressurized dissolved air flotation. The former involves dissolving air in the produced water under vacuum conditions to precipitate microbubbles, while the latter involves dissolving air in the produced water under pressure conditions and then depressurizing to precipitate microbubbles. Electrolytic air flotation refers to generating hydrogen and oxygen bubbles through electrolysis, causing oil droplets and suspended particles to float. The air flotation unit 14 can adopt any of the above methods, and this embodiment of the invention does not limit this.

[0047] In this embodiment of the invention, the homogenization unit 2 can be a gas field water receiving tank. The produced water from the gas field is placed in the receiving tank, and homogenization is achieved through extensive aeration. This breaks down the gel in the produced water system, and microbubbles are used to remove petroleum contaminants and a large amount of suspended solids (SS) from the produced water. Homogenization of the gas field water removes suspended solids and colloidal substances, thereby improving water quality and reducing the impact on subsequent treatment processes. Through homogenization, the suspended solids content in the produced water can be effectively reduced, improving the transparency and stability of the wastewater and providing better conditions for subsequent treatment processes.

[0048] In this embodiment of the invention, mechanical stirring of the produced water from the gas field can promote mixing, improve mass transfer efficiency, prevent sedimentation, and promote chemical reactions. The mechanical stirring unit 3 stirs the produced water from the gas field by placing it into a mechanical stirring tank or other stirring container, thereby fully dispersing the gas, liquid, or solid particles in the produced water within the liquid, thus accelerating the heat and mass transfer process and improving processing efficiency.

[0049] In one optional embodiment, the first filtration unit 4 is a diamond abrasive filter. Filtering the gas field produced water using a diamond abrasive filter removes impurities and suspended solids: the diamond abrasive filter effectively removes particles, silt, and impurities from the water, ensuring the purity of the treated water and preventing equipment clogging and damage. The diamond abrasive filter reduces equipment wear and maintenance requirements, extending the equipment's lifespan. Cleaned gas field produced water improves the efficiency of the entire treatment unit, ensuring the smooth operation of the gas field produced water treatment process.

[0050] In one optional embodiment, the second filter is a manganese sand filter. The manganese sand filter can remove suspended solids, particulate matter, iron ions, and manganese ions from the gas field produced water, thereby improving the quality of the treated water and meeting treatment standards. Iron and manganese ions in the gas field produced water are removed by adsorption from the manganese sand after aeration oxidation. The oxidized iron and manganese ions form insoluble compounds, which are effectively removed by the adsorption and filtration of the manganese sand filter. Through adsorption and filtration, impurities in the water are effectively removed, ensuring the treatment quality of the gas field produced water.

[0051] Electrolysis unit 5 can be an electrolysis device. The role of the electrolysis device in gas field water treatment is to remove pollutants from the produced water of the gas field through the electrolysis process, mainly including heavy metal ions, organic matter and other harmful substances.

[0052] The specific steps involved in using electrolysis units for gas field water treatment include: Electrolytic oxidation: Pollutants in the produced water are removed through oxidation-reduction reactions generated during electrolysis. This step is typically carried out in an electrolytic cell, where the cathode is connected to the negative terminal of the power supply, and the anode is connected to the positive terminal. The anode acts as the oxidant, and the cathode acts as the reducing agent. Membrane system treatment: The produced water after electrolytic oxidation is treated through a membrane system to further remove residual pollutants. Evaporation treatment: Salt and other impurities in the produced water are removed through evaporation. Electron beam irradiation treatment: Finally, electron beam irradiation treatment ensures that the effluent meets discharge standards, achieving "zero discharge."

[0053] The role of COD removal unit 6 in gas field produced water treatment is to reduce the chemical oxygen demand (COD) in the produced water, thereby reducing organic pollution and ensuring that the treated water quality meets the reinjection or discharge standards, thus protecting the environment and ecosystem.

[0054] The COD removal unit 6 provided in this embodiment of the present invention uses chemical oxidation: chemical oxidants such as ozone, hydrogen peroxide or potassium permanganate are used to oxidize organic matter, which is suitable for treating water from gas fields with high sulfur content.

[0055] For example, ferrous ions (Fe) 2+ A chain reaction occurs between H₂O₂ and hydrogen peroxide (H₂O₂) to generate hydroxyl radicals (·OH) with strong oxidizing power. This reaction proceeds under acidic conditions, where H₂O₂ reacts with Fe. 2+ Under catalysis, it decomposes to produce ·OH, with an oxidation potential as high as 2.80V, second only to fluorine in oxidation ability. Hydroxyl radicals have strong electronegativity and addition reaction characteristics, enabling them to non-selectively oxidize most organic matter in produced water from gas fields and effectively degrade organic wastewater.

[0056] In this embodiment of the present invention, the reverse osmosis membrane unit 8 includes: a high-pressure membrane reverse osmosis unit 81 and a low-pressure membrane reverse osmosis unit 82; the inlet of the high-pressure membrane reverse osmosis unit 81 is connected to the second filtration unit 7, and the outlet is connected to the low-pressure membrane reverse osmosis unit 82.

[0057] The principle of reverse osmosis technology is to use a semi-permeable membrane that allows only the solvent (such as water) to pass through, but not the solute. By applying pressure higher than the osmotic pressure of the solution, the produced water from the gas field is forced to permeate through the reverse osmosis membrane with extremely small pores, thereby separating the solute from the solvent. This technology can remove not only various ions from the produced water from the gas field, but also larger particles, organic matter, colloids, viruses, bacteria, and suspended solids.

[0058] The role and pathway of high-pressure membrane reverse osmosis in gas field produced water treatment is mainly to remove impurities from the produced water through efficient filtration, including dissolved salts, heavy metals, organic pollutants, bacteria, and viruses, thereby producing pure water that meets high water quality standards. Reverse osmosis technology can remove more than 99% of impurities in water, including dissolved salts, heavy metals, organic pollutants, bacteria, and viruses. Therefore, water treated by reverse osmosis is extremely pure and suitable for various high-standard water quality requirements.

[0059] Low-pressure membrane reverse osmosis plays a crucial role in gas field produced water treatment by removing salts and impurities, reducing chemical oxygen demand (COD), and bringing the water quality up to reuse standards. This method is particularly important in treating produced water from sulfur-containing gas fields, where it can significantly improve the water's "green content," i.e., its environmental performance.

[0060] Low-pressure membrane reverse osmosis technology achieves its function through the following pathways: Electrolytic catalytic oxidation: First, electrolytic catalytic oxidation oxidizes and decomposes organic matter in the produced water from the gas field, reducing the chemical oxygen demand (COD). High and low pressure reverse osmosis technology: Next, high and low pressure reverse osmosis technology is used to remove salt and impurities from the produced water from the gas field. This step involves using ultra-low pressure reverse osmosis membranes, which operate at lower pressures and are suitable for produced water solutions from gas fields with low salinity. Post-biological treatment: Finally, post-biological treatment further removes organic matter and ammonia nitrogen from the produced water from the gas field, ensuring that the water quality meets reuse standards.

[0061] In one optional embodiment, the air flotation circulation treatment unit includes a first oil pollution detection unit 11 and a first circulation treatment pipeline 12; the first circulation treatment pipeline 12 is connected to the outlet of the last stage air flotation sub-unit 14, and the other end is used to connect to a preset level air flotation sub-unit 14 according to the oil content in the gas field produced water after the last stage air flotation sub-unit 14; the first oil pollution detection unit 11 is located at the outlet of the last stage air flotation unit 14.

[0062] The first oil stain detection unit 11 and the second oil stain detection unit 41 may include any one of an oil quality analyzer, an infrared spectrometer, a chromatograph, a mass spectrometer, or an oil film thickness gauge.

[0063] In an optional embodiment, the air flotation circulation processing unit further includes a first control valve 13, which is disposed on the first circulation processing pipeline 12.

[0064] This embodiment of the invention uses a first oil detection unit 11 to detect the oil content in the produced water from the gas field exiting the last-stage flotation unit 14. When the oil content is greater than a first preset content, such as 30 mg / L, the first control valve 13 is opened, and the produced water enters the flotation unit 14 through the first circulation treatment pipeline 12 for further flotation treatment. This continues until the oil content in the produced water at the outlet of the last-stage flotation unit 14 is less than the first preset content. Then, the first control valve 13 is closed, allowing the produced water to enter the homogenization unit 2 for homogenization treatment. In this way, produced water with high oil content (e.g., 500 mg / L - 30000 mg / L) can be treated efficiently, improving the treatment effect of the produced water.

[0065] Please see Figure 2 In one optional embodiment, the air flotation subunit 14 includes: a tank 141, an aerator 142, an air flotation tank 143, and a sludge scraping mechanism 144; the aerator 142 is disposed at the first end of the tank 141, and the air flotation tank 143 is disposed at the second end of the tank 141; the sludge scraping mechanism 144 is disposed at the top of the tank 141, and the first end of the tank 141 has an inlet and the second end has an outlet.

[0066] The air flotation unit 14 provided in this embodiment can be a vortex aerator. The vortex aerator can include: a tank 141, an aerator 142, an air flotation tank 143, and a sludge scraping mechanism 144. The working principle of the vortex aerator 142 is that the air diffuser impeller at the bottom of the aerator 142 directly injects "microbubbles" into the untreated gas field produced water. Under the combined action of the coagulant and flocculant added to the tank 141, the suspended matter undergoes physical flocculation and chemical flocculation, thereby forming large suspended matter flocs. Under the buoyancy of the bubble group, the "flocs" float to the surface of the liquid to form scum, which is collected through the air flotation tank 143 and separated from the gas field produced water by the sludge scraping mechanism 144.

[0067] In one alternative embodiment, the aerator 142 produces bubbles with a diameter of 10 μm to 100 μm.

[0068] In an optional embodiment, the electrolysis unit 5 includes multiple electrolysis sub-units connected in series and an electrolysis cycle processing unit; the electrolysis cycle processing unit is connected to the outlet of the last electrolysis sub-unit, and the electrolysis cycle processing unit is used to perform a second electrolysis treatment when the oil content is detected to be greater than a second preset content.

[0069] In this embodiment of the invention, the electrolysis unit 5 is used to remove organic pollutants from the produced water of the gas field. Through multiple electrolysis sub-units connected in series, the produced water of the gas field can be circulated multiple times to further reduce the oil content in the produced water of the gas field, thereby reducing the difficulty of subsequent COD treatment and reverse osmosis membrane treatment, and thus improving the treatment efficiency and effect.

[0070] In one optional embodiment, the electrolytic circulation processing unit includes: a second oil stain detection unit 41 and a second circulation processing pipeline 42; one end of the second circulation processing pipeline 42 is connected to the outlet of the last electrolytic subunit, and the inlet is connected to the inlet of the first electrolytic subunit; the second oil stain detection unit 41 is on the second circulation processing pipeline 42.

[0071] In an optional embodiment, the electrolytic circulation processing unit further includes a second control valve 43, which is disposed on the second circulation processing pipeline 42.

[0072] This embodiment of the invention uses a second oil detection unit 41 to detect the oil content in the produced water from the last electrolysis subunit. When the oil content exceeds a second preset limit, for example, 1 mg / L, the second control valve 43 is opened, and the produced water enters the electrolysis subunit through the second circulation pipeline 42 for further electrolysis. This continues until the oil content in the produced water from the last electrolysis subunit is less than 1 mg / L. Then, the second control valve 43 is closed, allowing the produced water to enter the homogenization unit 2 for homogenization. This allows for efficient treatment of produced water with high oil content (e.g., 500 mg / L - 30000 mg / L), improving the overall treatment effect.

[0073] In an optional embodiment, it further includes: a demulsification unit 9 and a wastewater collection unit 10; the demulsification unit 9 is connected to the flotation unit 1 and is used to demulsify the produced water from the gas field; the inlet of the wastewater collection unit 10 is connected to the flotation unit 1 and the outlet is connected to the homogenization unit 2.

[0074] The demulsification unit 9 of this embodiment can achieve efficient demulsification, sedimentation, and oil-water separation of produced water from gas fields, thereby increasing oil and gas production and reducing environmental pollution. For example, the demulsification unit 9 can employ a tubular electrocoagulation demulsification device that utilizes the special structure of the electrocoagulation reactor to promote the demulsification and coalescence of emulsified oil droplets through the interaction of the electrode plates and the acoustic field.

[0075] Example 1

[0076] For produced water from gas fields with high oil content (500mg / L-30000mg / L), a temporary storage tank (demulsification unit 9) was used as a receiving homogenization tank based on the actual site conditions. Chemicals were added to the receiving homogenization tank for demulsification, flocculation, and pre-oil removal via air flotation (reducing the oil content to 30mg / L). The wastewater was then discharged to a wastewater pond and pumped to the gas field water receiving tank for homogenization (homogenization unit 2) via a supernatant lift pump. A series of processes were then applied, including mechanical stirring to remove hardness, electrolytic oxidation to remove oil, advanced oxidation to remove COD, filtration to remove suspended solids, reverse osmosis for desalination, and MVR (mechanical vapor recompression unit 11) evaporation and concentration. The resulting treated water had an oil content ≤1mg / L, and the actual quality of the recycled water exceeded the requirements of the "Water Conservation and Emission Reduction Assessment Indicators and Recycled Water Quality Control Indicators for Refining and Chemical Enterprises" (Q / SH0104-2007). See Table 1 for details. Table 1 is a comparison table of the contents of various compounds in the gas field produced water before and after treatment provided in this embodiment. As can be seen from Table 1, all compounds in the treated gas field produced water meet the treatment standards.

[0077] Table 1

[0078]

[0079] The water quality after treatment using the device provided in this embodiment meets the requirements for makeup water quality of circulating cooling water system in the "Assessment Indicators for Water Conservation and Emission Reduction and Control Indicators for Reclaimed Water Quality of Refining and Chemical Enterprises" (Q / SH0104-2007), and its application in a series of desulfurization stations in the Sichuan West Gas Field is feasible.

[0080] Produced water from oil and gas fields is treated and reused after reinjection. Before treatment, it is hazardous waste costing 2,300 yuan per cubic meter. After treatment, each cubic meter of water produces 80% reclaimed water, 10% hazardous waste, 5% miscellaneous salts, and 5% mother liquor. The cost of reclaimed water is 40 yuan per cubic meter, miscellaneous salts are 145 yuan per cubic meter, mother liquor is 400 yuan per cubic meter, and purchased circulating water is 5 yuan per cubic meter. Therefore, each cubic meter of water reused can save 2,300 - (40*80% + 2,300*10% + 145*5% + 400*5% + 5) = 2,000 yuan. The economic benefits over the entire life cycle are considerable.

[0081] The device provided in this embodiment of the invention not only reduces the amount of hazardous waste after water treatment, but also "turns waste into treasure". It can treat (reduce the generation of) 200 cubic meters of hazardous waste per day * 330 days = 66,000 cubic meters per year, which has practical significance and promotion value for environmental protection.

[0082] Although the present invention has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A treatment device for produced water from gas fields with oil content ranging from 500 mg / L to 30000 mg / L, characterized in that, include: The air flotation unit includes interconnected multi-stage air flotation sub-units and an air flotation circulation treatment unit. The inlet of the air flotation circulation treatment unit is connected to the last stage air flotation sub-unit, and the outlet of the air flotation circulation treatment unit is used to connect to a preset level air flotation sub-unit based on the oil content in the gas field produced water after treatment by the last stage air flotation sub-unit. The air flotation circulation treatment unit is used to detect when the oil content in the gas field produced water after treatment by the last stage air flotation unit is greater than a first preset content, and then perform a second air flotation treatment through the air flotation sub-unit. The operating pressure of the multi-stage air flotation units increases sequentially from the inlet to the outlet of the gas field produced water. The homogenization unit is connected to the last stage air flotation unit in the multi-stage air flotation unit; A mechanical stirring unit is connected to the homogenizing unit; The first filtration unit is connected to the mechanical stirring unit; The electrolysis unit is connected to the first filtering unit; The COD removal unit is connected to the electrolysis unit; The second filtration unit is connected to the COD removal unit; The reverse osmosis membrane unit is connected to the second filtration unit.

2. The gas field produced water treatment device according to claim 1 for oil content in the range of 500 mg / L to 30000 mg / L, characterized in that, The air flotation circulation treatment unit includes a first oil pollution detection unit and a first circulation treatment pipeline; The first circulation processing pipeline is connected to the outlet of the last stage air flotation unit, and the other end is used to connect to the air flotation unit of a preset level according to the oil content in the gas field produced water after the last stage air flotation unit is processed. The first oil stain detection unit is located at the outlet of the last stage air float unit.

3. The gas field produced water treatment device according to claim 2 for oil content in the range of 500 mg / L to 30000 mg / L, characterized in that, The air flotation circulation treatment unit further includes a first control valve, which is installed on the first circulation treatment pipeline.

4. The gas field produced water treatment device according to claim 1 for oil content in the range of 500 mg / L to 30000 mg / L, characterized in that, The air flotation subunit includes: a tank, an aerator, an air flotation tank, and a sludge scraping mechanism; The aerator is located at the first end of the tank, and the air flotation tank is located at the second end of the tank. The sludge scraping mechanism is located at the top of the tank, and the tank has an inlet at the first end and an outlet at the second end.

5. The gas field produced water treatment device according to claim 4 for oil content in the range of 500 mg / L to 30000 mg / L, characterized in that, The aerator produces bubbles with a diameter of 10μm to 100μm.

6. The gas field produced water treatment device according to claim 1 for oil content in the range of 500 mg / L to 30000 mg / L, characterized in that, The electrolysis unit includes multiple electrolysis sub-units connected in series and an electrolysis cycle processing unit; The electrolysis cycle processing unit is connected to the outlet of the last electrolysis subunit. The electrolysis cycle processing unit is used to perform a second electrolysis process when the oil content is detected to be greater than the second preset content.

7. The gas field produced water treatment device according to claim 6 for oil content in the range of 500 mg / L to 30000 mg / L, characterized in that, The electrolytic circulation processing unit includes: a second oil stain detection unit and a second circulation processing pipeline; One end of the second circulation processing pipeline is connected to the outlet of the last electrolysis subunit, and the inlet is connected to the inlet of the first electrolysis subunit; The second oil stain detection unit is installed on the second circulation treatment pipeline.

8. The gas field produced water treatment device according to claim 7 for oil content in the range of 500 mg / L to 30000 mg / L, characterized in that, The electrolytic circulation processing unit further includes a second control valve, which is installed on the second circulation processing pipeline.

9. The gas field produced water treatment device according to claim 1 for oil content in the range of 500 mg / L to 30000 mg / L, characterized in that, The first filter is a diamond filter, and the second filter is a manganese sand filter.

10. The gas field produced water treatment device according to claim 1 for oil content in the range of 500 mg / L to 30000 mg / L, characterized in that, Also includes: Demulsification unit and sludge collection unit; The demulsification unit is connected to the air flotation unit, and the demulsification unit is used to demulsify the produced water from the gas field. The inlet of the wastewater collection unit is connected to the air flotation unit, and the outlet is connected to the homogenization unit.

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