Rapid treatment method and device for oily sewage in oilfields

Abstract

The present invention relates to a method and device for rapidly treating oily wastewater in an oilfield, and belongs to the technical field of oily wastewater treatment. The method and device include a crude oil storage tank, a wastewater storage tank, an inclined plate oil skid, a solid-liquid separation skid, a dissolved air flotation skid, and a sludge dewatering skid. The inclined plate oil skid has a raw material inlet, and its sand and water outlet pipeline is connected to the solid-liquid separation skid. The solid-liquid separation skid is provided with a mud and sand outlet. The upper crude oil outlet pipeline of the inclined plate oil skid is connected to the crude oil storage tank, the wastewater outlet pipeline of the inclined plate oil skid is connected to the wastewater storage tank, and the outlet of the wastewater storage tank is connected to the dissolved air flotation skid. The scum outlet of the dissolved air flotation skid is connected to the sludge dewatering skid, and a clean water outlet is provided at the bottom. This technology uses an inclined plate oil skid to treat early-stage wastewater, reducing the requirements for the oil content and suspended solids content of the raw water; the terminal automatically discharges low-water dry mud, reducing or eliminating the transportation cost of wastewater sludge; the online conditioning process has a high degree of automation; crude oil recovery is completed in one step, and the processing cost is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of oily wastewater treatment, and in particular relates to a method and device for quickly treating oilfield oily wastewater. Background Art

[0002] In oilfield surface production processes, produced water treatment systems are large in scale, complex in process flow, and challenging to operate and manage. Several significant issues exist in wastewater treatment, and many challenges remain to be addressed. For example, water quality compliance in some oilfields needs to be further improved, sterilization effectiveness is poor, and produced water discharge pressure is high.

[0003] Due to varying crude oil production locations and production processes, the quality of oilfield wastewater varies significantly. In China, treatment methods primarily include physical, chemical, physicochemical, and biological treatment, tailored to the specific characteristics of oilfield wastewater. Walnut shell filtration technology is the most widely used method for treating oily wastewater. Walnut shell filters are a type of separation device developed based on the principles of filtration and separation. They utilize oil-resistant filter media—special walnut shells—as their filter medium. They utilize the large surface area, strong adsorption capacity, and high pollutant interception capacity of walnut shells to remove oil and suspended solids from water. This device offers both automatic and manual control modes. During filtration, water flows from top to bottom through a water distributor, filter media layer, and water collector to complete filtration. During backwashing, an agitator rotates the filter media, allowing water to flow from bottom to top, thoroughly cleaning and regenerating the filter media. However, the disadvantages of walnut shell filtration technology are: the water inlet process requirements of the walnut shell filter are relatively strict, requiring the raw water oil content to be less than 100 mg / l and the suspended solids content to be less than 50 mg / l, so a coagulation and flocculation sedimentation process should be added before the sewage enters the filter tank; the replacement of the filter material is labor-intensive and produces secondary pollution; the backwash sewage is discharged into the sedimentation tank, which will cause secondary pollution; the cleaning of the sedimentation tank and the sedimentation tank (about once a year) requires a lot of manpower costs and will cause secondary pollution; the high-water content sludge after manual cleaning is transported to the designated oil field sludge treatment station for treatment, which will incur high treatment costs, and the sewage treated at the sludge treatment station is again transported to the sewage treatment station for treatment, so some sulfide impurities are viciously circulated in the oil field ground treatment process system; there is no complete process plan, and there is no effective means to separate the mud and sand and crude oil in the waste liquid, which affects the long-term operation of the equipment. Summary of the Invention

[0004] The present invention addresses the above-mentioned deficiencies in the prior art and provides a method and device for rapidly treating oilfield oily wastewater.

[0005] The oilfield oily wastewater rapid treatment device of the present invention comprises a crude oil storage tank and a wastewater storage tank, and also comprises an inclined plate oil collection skid, a solid-liquid separation skid, a dissolved air flotation skid and a sludge dewatering skid. The inclined plate oil collection skid is provided with a raw material inlet, and its sand and water outlet pipeline is connected to the solid-liquid separation skid. The solid-liquid separation skid is provided with a mud and sand discharge outlet. The upper crude oil outlet pipeline of the inclined plate oil collection skid is connected to the crude oil storage tank, the wastewater outlet pipeline of the inclined plate oil collection skid is connected to the wastewater storage tank, the outlet of the wastewater storage tank is connected to the dissolved air flotation skid, the scum outlet of the dissolved air flotation skid is connected to the sludge dewatering skid, and a clean water discharge outlet is provided at the bottom. Dewatered water cake is discharged from the skid bottom of the sludge dewatering skid.

[0006] As a further improvement of the present invention, the inclined plate oil collecting skid is divided into a control room, a slow flow chamber and a crude oil collection chamber from left to right by partitions, and a sand and water output pump, a crude oil output pump and a sewage output pump are provided in the control room; a raw material inlet is provided on the upper left side of the slow flow chamber, and an oil collecting assembly to the crude oil collection chamber is provided on the right side, and downwardly inclined inclined plates are provided from right to left at the bottom of the crude oil collection chamber and the slow flow chamber, and the inclination angle is 3 to 8 degrees. One or more sedimentation inclined plates are fixed at intervals on the inner walls of the box on both sides of the slow flow chamber, and the lower part of the sedimentation inclined plate is provided with a sewage output pipeline in the slow flow chamber and a crude oil output pipeline of the crude oil collection chamber. The sewage output pipeline enters the sewage storage tank through the sewage outlet via the sewage output pump, and the crude oil output pipeline enters the crude oil storage tank through the crude oil outlet via the crude oil output pump. The sand and water outlet at the bottom left side of the slow flow chamber enters the solid-liquid separation skid through the sand and water outlet I via the sand and water output pump.

[0007] As a further improvement of the present invention, a sand retaining plate is fixed on the inclined plate at the rear section of the slow flow chamber, the crude oil output pipeline passes through the sand retaining plate, and a sewage pipe is provided at the bottom of the slow flow chamber, which passes through the sand retaining plate, and its inlet is placed on the right side of the sand retaining plate, and its outlet enters the solid-liquid separation skid through the sand and water output pump and the sand and water outlet I.

[0008] As a further improvement of the present invention, the outlet of the sewage output pump is also connected to a fine sand collection flushing pipe, a sand discharge backwashing pipe and a sand flushing and stirring pipe respectively; the fine sand collection flushing pipe is an L-shaped pipe, which is placed at the lower part of the sedimentation inclined plate, and a bent pipe is longitudinally placed on the left side of the bottom sand retaining plate of the slow flow chamber, and a nozzle is provided on the bent pipe; the outlet of the sand discharge backwashing pipe is connected to the sand and water outlet pipeline; the sand flushing and stirring pipe is longitudinally placed above the left side of the slow flow chamber, and a sprinkler head is provided on it; and a crude oil tank sewage inlet is provided on the slow flow chamber.

[0009] As a further improvement of the present invention, an oil collection spray pump is also provided in the control room, an oil collection spray inlet pipe is provided above the slow flow chamber and is connected to the oil collection spray pump pipeline, the outlet of the oil collection spray pump is connected to the oil collection spray outlet nozzle, the oil collection spray outlet nozzle is longitudinally located above the left side of the slow flow chamber, and a nozzle is provided on it.

[0010] As a further improvement of the present invention, the liquid inlet I on the crude oil storage tank is connected to the crude oil outlet of the inclined plate oil skid, and its sewage outlet is connected to the sewage inlet of the crude oil tank on the inclined plate oil skid; a crude oil outlet is provided on the tank body, an electric heater is provided inside, and a self-circulating heating pipeline is provided inside to connect to the circulation pump.

[0011] As a further improvement of the present invention, the solid-liquid separation skid is provided with a separation inclined bucket fixed in a box body, a sand-water separator is installed in the separation inclined bucket, the liquid inlet pipe of the separation skid is connected to the sand-water outlet I of the inclined plate oil collecting skid, the liquid outlet of the liquid inlet pipe is placed above the separation inclined bucket through a cyclone, a sewage overflow port is provided on the separation inclined bucket, and the sand-water separator has a sand discharge outlet.

[0012] As a further improvement of the present invention, a dissolved air flotation skid is provided with a partition I in the box body to separate it into a reaction chamber and a separation chamber. The sewage outlet pipeline of the sewage storage tank enters the reaction chamber through the liquid inlet II, the liquid inlet pump, and the liquid inlet pipeline. A releaser is provided at the bottom of the front section of the reaction chamber and the separation chamber. The releaser is connected to the outlet of the dissolved air tank through a pipeline. A scum collection device is provided at the top of the separation chamber and a scum box is provided at the tail end; a clean water outlet of the separation chamber is provided at the bottom of the scum box, and the clean water is discharged to the high-pressure pump room through the clean water outlet by the clean water pump. The inlet of the scum box is provided with a downward-inclined scum plate, and the bottom outlet pipeline of the scum box is discharged to the sludge dewatering skid through the scum outlet via the scum pump.

[0013] As a further improvement of the present invention, the sludge dewatering skid includes a scum mixing box, a scum liquid inlet is provided on the scum mixing box, the scum outlet is connected to the scum liquid inlet pipeline, the scum mixing box is provided with a stirring device and a built-in heater, the bottom liquid outlet pipeline is connected to the liquid outlet pump, the water outlet of the liquid outlet pump is discharged to the slow flow chamber through the outlet pipe, and the sludge outlet pipeline is connected to the screw machine, and the screw machine is provided with a liquid outlet and a mud discharge outlet.

[0014] The method for rapidly treating oilfield oily wastewater of the present invention comprises the following steps:

[0015] 1. Solid-liquid separation

[0016] Oily wastewater is poured into the inlet of the inclined plate oil skid. After sufficient diffusion by the settling inclined plate, the solid mud and sand in it settle to the bottom of the skid and are discharged. The floating crude oil in the liquid phase is collected by a scraper and sent to the crude oil storage tank, and the wastewater in the middle layer is collected and discharged to the wastewater storage tank. The bottom temperature of the inclined plate oil skid is 0-8℃, the liquid phase temperature is 50-80℃, the inclination angle of the settling inclined plate is 30-60°, and the number of plates is 2-8.

[0017] 2. Flotation purification of sewage

[0018] The sewage is added with flocculants, coagulants and oxidants through a dissolved air flotation skid, which adheres the fine impurities in the sewage into suspended masses, which are then removed by a chain scraper to produce purified water;

[0019] 3. Sludge dewatering

[0020] The sludge after solid-liquid separation is pressure filtered using a plate and frame filter to form a mud cake for discharge, and the filtered sewage is returned to the dissolved air flotation skid.

[0021] The method and device for rapidly treating oily wastewater in an oilfield of the present invention utilizes an inclined plate oil skid to treat early-stage wastewater, thereby reducing requirements for the oil content and suspended solids content of raw water and extending its applicability. The method eliminates the need for filter media replacement, thereby reducing labor intensity. The terminal automatically discharges low-water-content dry mud, thereby reducing or eliminating wastewater sludge transportation costs and preventing secondary pollution. The method utilizes an online conditioning process with a high degree of automation. Crude oil can be recovered in one step, thereby improving economic efficiency. Furthermore, the method reduces treatment costs, achieves standard-compliant treatment in one step, and avoids the vicious cycle of sulfide impurities within the oilfield surface treatment process system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The process flow chart of the method for rapidly treating oilfield oily wastewater of the present invention is as follows;

[0023] Figure 2 Longitudinal section of the inclined plate skid;

[0024] Figure 3 yes Figure 2 A top view of

[0025] Figure 4 It is a longitudinal cross-section of a crude oil storage tank;

[0026] Figure 5 yes Figure 4 A top view of

[0027] Figure 6 Longitudinal cross-section of the solid-liquid separation skid;

[0028] Figure 7 yes Figure 6 A top view of

[0029] Figure 8 is a longitudinal cross-section of a dissolved air flotation sled;

[0030] Figure 9 yes Figure 8 A top view of

[0031] Figure 10 It is a longitudinal cross-section of the sludge dewatering skid;

[0032] Figure 11 yes Figure 10 Top view of . DETAILED DESCRIPTION

[0033] The method and device for rapidly treating oilfield oily wastewater of the present invention will be further described below with reference to the accompanying drawings.

[0034] The oilfield oily wastewater rapid treatment device of the present invention comprises a crude oil storage tank 1 and a wastewater storage tank 2. Figure 1 As shown, the system further includes an inclined plate oil collection skid 3, a solid-liquid separation skid 4, a dissolved air flotation skid 5 and a sludge dewatering skid 6. The inclined plate oil collection skid 3 is provided with a raw material inlet 7, and its sand and water outlet pipeline is connected to the solid-liquid separation skid 4. The solid-liquid separation skid 4 is provided with a mud and sand discharge outlet. The upper crude oil outlet pipeline of the inclined plate oil collection skid 3 is connected to the crude oil storage tank 1, the sewage outlet pipeline of the inclined plate oil collection skid 3 is connected to the sewage storage tank 2, the outlet of the sewage storage tank 2 is connected to the dissolved air flotation skid 5, the scum outlet of the dissolved air flotation skid 5 is connected to the sludge dewatering skid 6, and a clean water discharge outlet is provided at the bottom. Dewatered water cake is discharged from the bottom of the sludge dewatering skid 6.

[0035] The inclined plate oil collecting skid 3 is divided into a control chamber 9, a slow flow chamber 10 and a crude oil collecting chamber 11 from left to right by a partition 8. Figure 2 、 Figure 3 As shown, the control room 9 is provided with a sand and water output pump 12, a crude oil output pump 13, a sewage output pump 14 and an oil collection spray pump 15; heaters are installed in the slow flow chamber 10 and the crude oil collection chamber 11, and an operation hole is opened on the upper part of the slow flow chamber 10.

[0036] A raw material inlet 7 is provided at the upper left side of the slow flow chamber 10, and an oil collection assembly 30 is provided on the right side to the crude oil collection chamber 11. A downwardly inclined inclined plate 16 is provided from right to left at the bottom of the crude oil collection chamber 11 and the slow flow chamber 10, with an inclination angle of 3 to 8 degrees. One or more sedimentation inclined plates 17 are fixed at intervals on the inner walls of the box on both sides of the slow flow chamber 10. There is a certain gap between the sedimentation inclined plates 17 and the bottom wall. The lower part of the sedimentation inclined plates 17 is provided with a sewage output pipeline 18 in the slow flow chamber 10, a crude oil output pipeline 19 of the crude oil collection chamber 11, and a sewage pipe 75 and a fine sand collection flushing pipe 25.

[0037] A sand retaining plate 24 is fixed on the inclined plate 16 of the rear section of the slow flow chamber 10, and the sewage output pipeline 18 and the fine sand collection flushing pipe 25 are located in front of the sand retaining plate 24. The crude oil output pipeline 19 and the sewage pipe 75 pass through the sand retaining plate 24, and the crude oil output pipeline 19 is connected to the bottom outlet of the crude oil collection chamber 11; the sewage in the slow flow chamber 10 enters from the sewage output pipeline 18 through the sewage output pump 14 and enters the sewage storage tank 2 through the sewage outlet 20; the crude oil output pipeline 19 enters the crude oil storage tank 1 through the crude oil outlet 21 through the crude oil output pump 13. At the same time, the output pipe of the crude oil output pump 13 A sewage outlet is also provided on the line, which is used to extract the sewage from the bottom of the crude oil collection chamber 11 and transport it to the slow flow chamber, and then control the upper crude oil through the crude oil output pipeline and the crude oil outlet 21 into the crude oil storage tank 1; since the bottom of the slow flow chamber 10 is an inclined plate structure, materials with a higher specific gravity of sand and gravel are accumulated on the left side. Therefore, a sand and water outlet 22 is provided at the bottom of the left side, and the sand and water output pump 12 enters the solid-liquid separation skid 4 through the sand and water outlet I 23. At the same time, the outlet of the sewage pipe 75 is also connected to the sand and water output pump 12 and enters the solid-liquid separation skid 4 through the sand and water outlet I 23.

[0038] In order to facilitate the flow of upper dirty oil, an oil collection spray inlet pipe 31 is provided above the slow flow chamber 10 to suck the sewage in the slow flow chamber and connect it to the oil collection spray pump 15 pipeline. The outlet of the oil collection spray pump 15 is connected to the oil collection spray outlet nozzle 32. The oil collection spray outlet nozzle 32 is longitudinally located above the left side of the slow flow chamber 10 and is provided with a nozzle to spray the sucked sewage above the liquid surface to promote its flow.

[0039] The outlet of the sewage output pump 14 in this device is also connected to a fine sand collection flushing pipe 25, a sand discharge backwashing pipe 26 and a sand flushing and stirring pipe 27 respectively; the fine sand collection flushing pipe 25 is an L-shaped pipe, placed at the lower part of the sedimentation inclined plate 17, and a bent pipe is longitudinally placed on the left side of the sand retaining plate 24 at the bottom of the slow flow chamber 10, and a nozzle 28 is provided on the bent pipe to facilitate flushing the fine sand retained at the bottom of the inclined plate to the outlet 22 on the left; the outlet of the sand discharge backwashing pipe 26 is connected to the sand and water outlet 22 pipeline, and it will be flushed open when the sand and water outlet 22 pipeline is blocked; the sand flushing and stirring pipe 27 is longitudinally placed above the left side of the slow flow chamber 10, and is provided with a sprinkler head on it, which is used to stir the sand and gravel accumulated at the sand and water outlet 22 to enhance fluidity and facilitate output; a crude oil tank sewage inlet 29 is provided on the slow flow chamber 10.

[0040] During treatment, the wastewater is discharged from the tank truck through the raw material inlet 7 into the oil collecting skid 3, and flows through the 4 sedimentation inclined plates inside. The block impurities, large particles and sediment in the liquid are deposited at the bottom of the skid and sent to the solid-liquid separation skid 4 through the sand and water output pump 12. The crude oil floating on the liquid surface is cleaned and collected by the chain scraper and transported to the crude oil storage tank 1 by the centrifugal pump. The wastewater is temporarily transferred to the liquid collecting tank at the rear end of the device through overflow, and finally pumped into the 500m 3Intermediate sewage storage tank for storage.

[0041] Electric heaters and liquid level gauges are installed in the slow flow chamber 10 and the crude oil collection chamber 11 to ensure that the temperature inside the skid is always 0-8°C in winter and the upper crude oil recovery temperature is 50-80°C, realizing automatic temperature control. The liquid level gauge is linked with the centrifugal pump for automatic control and is equipped with an ultra-high liquid level early warning system.

[0042] like Figure 4 、 Figure 5 As shown, crude oil storage tank 1 stores crude oil collected by the sloping plate skid 3. Its liquid inlet I 33 is connected to the crude oil outlet 21 of the sloping plate skid 3, and its wastewater outlet 34 is connected to the crude oil tank wastewater inlet 29 on the sloping plate skid 3. A crude oil outlet 35 is located on the tank body, equipped with an electric heater 36 to enhance flow. A self-circulating heating line 37 connected to a circulating pump 38 ensures uniform heating. After separation, the crude oil in the incoming liquid is collected and stored in a 50m³ crude oil storage tank. Crude oil enters from the top and exits from the bottom. A water cut-off return line is installed at the bottom of the tank, and wastewater at the bottom is diverted back to the sloping plate skid. An internal electric heater (with adjustable temperature) ensures a constant tank temperature of 20-80°C in winter.

[0043] like Figure 6 、 Figure 7 As shown, the solid-liquid separation skid 4 stores the sand and water discharged from the sand and water outlet 22 and the sewage pipe 75 of the inclined plate oil skid 3. The solid-liquid separation skid 4 houses a separation hopper 39 within a housing. Inside this hopper is a sand and water separator 40, along with a heater and thermostat. Its liquid inlet pipe 41 is connected to the sand and water outlet 123 of the inclined plate oil skid 3. The liquid outlet of the liquid inlet pipe 41 is located above the separation hopper 39 via a cyclone 42. The separation hopper 39 is equipped with a sewage overflow port 43, which discharges sewage into the buffer chamber of the inclined plate oil skid 3. A sand outlet 44 is located in the sand and water separator 40. Sediment and sewage are separated using the principle of inclined plate sedimentation. The settled sediment is dewatered by a variable-pitch slit screen screw dewaterer and discharged to a sludge trough outside the device. The separated sewage is then transferred back to the inclined plate oil skid. An electric heater is installed inside the device to ensure that the temperature inside the skid is always between 0 and 8 degrees Celsius in winter. The device is temperature-controlled, and the liquid level gauge is linked to the centrifugal pump for automatic control, and is equipped with an over-high liquid level warning system.

[0044] like Figure 8 、 Figure 9As shown, the oil is discharged from the inclined plate skid 3 through the sewage storage tank 2 into the dissolved air flotation skid 5. The dissolved air flotation skid 5 is provided with a partition I 45 in the box body to separate it into a reaction chamber 46 and a separation chamber 47. The bottom wall I 76 of the reaction chamber 46 and the bottom wall II 77 of the separation chamber 47 are both inclined bottoms. The inclination angle of the bottom wall I 76 is 15 to 20 degrees, and the inclination angle of the bottom wall II 77 is 3 to 10 degrees. The sewage outlet pipeline from sewage storage tank 2 enters reaction chamber 46 through liquid inlet II 48, liquid inlet pump 49, and liquid inlet pipeline 50. A releaser 51 is installed at the bottom of both reaction chamber 46 and separation chamber 47, connected to the outlet of vapor dissolving tank 52 via pipeline 60. A scum collection device 55 is installed at the top of separation chamber 47, and a scum tank 56 is installed at the rear end. A clean water outlet 54 for separation chamber 47 is located at the bottom of scum tank 56. Clean water is discharged to high-pressure pump room 63 through clean water outlet 62 via clean water pump 61. A downward-sloping scum plate 57 is installed at the inlet of scum tank 56. The bottom outlet pipeline of scum tank 56 is discharged through scum pump 58 and scum outlet 59 to sludge dewatering skid 6. The inlet pipeline of vapor dissolving tank 52 is connected to clean water outlet 54 via air dissolving pump 53. A dosing device 64 is installed on liquid inlet pipeline 50, connected to dosing tank 65 via a pipeline. A backup liquid inlet 66 is provided on the liquid inlet pipeline 50. The wastewater is purified by a dissolved air flotation skid. Flocculants, coagulants, gel breakers, and degradation agents are added to clump fine impurities and suspended solids in the wastewater. Simultaneously, nano-scale microbubbles released by the dissolved air rise to the liquid surface, entrapping the clumped impurities and rapidly separating them. A chain scraper then collects the scum on the liquid surface into a scum tank, where it is finally pumped to the sludge dewatering skid using a centrifugal pump.

[0045] like Figure 10 、 Figure 11 As shown, the scum outlet 59 of the dissolved air flotation skid 5 is connected to the scum liquid inlet 67 and enters the scum mixing tank 68 of the sludge dewatering skid 6. The scum mixing tank 68 is equipped with a stirring device 69, a dosing device, and a built-in heater 70. Its bottom liquid outlet 71 is connected to a liquid pump 72. The water outlet of the liquid pump 72 is discharged into the sewage storage tank 2 through an outlet pipe 73. The sludge outlet pipeline is connected to a screw conveyor 74, which is equipped with a liquid outlet and a sludge discharge port. The scum collected in the dissolved air flotation skid is treated with flocculants and coagulants online, and the sludge is dewatered by the screw conveyor. The dewatered cake is discharged, and the filtrate is returned to the dissolved air flotation skid.

[0046] The method for rapidly treating oilfield oily wastewater of the present invention comprises the following steps:

[0047] 1. Solid-liquid separation

[0048] Oily wastewater is poured into the inlet of the inclined plate oil skid. After sufficient diffusion by the settling inclined plate, the solid mud and sand in it settle to the bottom of the skid and are discharged. The floating crude oil in the liquid phase is collected by a scraper and sent to the crude oil storage tank, and the wastewater in the middle layer is collected and discharged to the wastewater storage tank. The bottom temperature of the inclined plate oil skid is 0-8℃, the liquid phase temperature is 50-80℃, the inclination angle of the settling inclined plate is 30-60°, and the number of plates is 2-8.

[0049] 2. Flotation purification of sewage

[0050] The sewage is added with flocculants, coagulants and oxidants through a dissolved air flotation skid, which adheres the fine impurities in the sewage into suspended masses, which are then removed by a chain scraper to produce purified water;

[0051] 3. Sludge dewatering

[0052] The sludge after solid-liquid separation is pressure filtered using a plate and frame filter to form a mud cake for discharge, and the filtered sewage is returned to the dissolved air flotation skid.

[0053] A complete set of 30m 3 / h processing capacity of oilfield comprehensive waste liquid skid-mounted treatment device:

[0054] Site conditions:

[0055] Location: Comprehensive Waste Liquid Deep Injection Station of Daqing Oilfield Production Plant No. 6

[0056] Source of raw materials: Well washing fluid and workover fluid from the Sixth Oil Production Plant Operation Team

[0057] Production trial period: November 21, 2019 to December 30, 2019

[0058] Heating source: 150kw electric heater

[0059] Clean water source: 0.15Mpa tap water

[0060] Compressed air source: 0.7Mpa dry air (provided by on-site air compressor)

[0061] Power source: 380V, 50HZ (provided by on-site 400Kw transformer)

[0062] Oilfield waste liquid treatment production test process:

[0063] 1. Tankers for oilfield waste liquid (10-20m3 of liquid per tanker) 3 The unloading pipe (around) is used to discharge the liquid to the unloading port of the inclined plate oil skid, and the daily unloading volume is 150-200m 3 about;

[0064] 2. The interior of the inclined plate skid is designed with a sedimentation separation system with a plate grid. Through the grid interception and sedimentation, the block impurities and mud and sand in the incoming liquid are deposited at the bottom of the skid, and the crude oil floats on the liquid surface and gathers. After separation, the sewage enters the 300-500m 3 Storage tanks;

[0065] 3. After the unloading work is completed, the impurities deposited on the bottom of the skid are transported to the solid-liquid separation skid through the mud pump (3-5 minutes);

[0066] 4. After the unloading work is completed, the crude oil floating on the liquid surface is statically heated by two underwater electric heaters (10-20kw) to a temperature of (40-60°C), then cleaned by a chain scraper and collected into the crude oil tank of the inclined plate oil skid. After secondary heating (50-80°C), it is transported to the crude oil storage tank by a crude oil centrifugal pump;

[0067] 5. The wastewater is purified by a dissolved air flotation skid. Flocculants (0.01-0.05%), coagulants (0.5-2%), and oxidants (0.5-1%) are added to clump fine impurities and suspended solids in the wastewater. Nano-scale microbubbles released by the dissolved air rise to the liquid surface, enveloping the clumped impurities and causing them to float and separate. A chain scraper collects the scum on the liquid surface into a scum tank, and finally, a centrifugal pump transports it to the sludge dewatering skid, where the qualified water is transported out.

[0068] 6. The wastewater containing mud and sand pumped from the inclined plate oil skid is separated from the wastewater by the inclined plate sedimentation principle in the solid-liquid separation skid. The wastewater is then dehydrated by the variable pitch slit screen spiral dewatering machine and the mud and sand are discharged. The wastewater is pumped into the inclined plate oil skid.

[0069] 7. The crude oil collected from the inclined plate skid is collected uniformly to 50m 3 Crude oil is stored in tanks, with crude oil entering from the top and exiting from the bottom. An electric heater is installed at the bottom of the tank for heating and dehydration (electric heater power is 30-50kw, dehydration temperature is 60-90℃). Water is cut off at the bottom of the tank regularly, and the cut water flows back to the inclined plate oil skid.

[0070] 8. The scum from the dissolved air flotation skid is added with flocculants (0.01-0.05%) and coagulants (0.5-2%) in the sludge dewatering skid, and then the sludge dewatering screw machine is used to dehydrate the material. The dehydrated cake is discharged and the filtrate is returned to the dissolved air flotation skid. The sludge dewatering skid is equipped with a 20-30m3 stirring 3 The tank will start running when it is full.

[0071] Test results:

[0072] From November 21 to December 30, 2019, over 7,000 cubic meters of wastewater were treated. The water content of the treated mud was less than 70%; the water content of the mud and sand separated by the variable-pitch slotted mesh screw dehydrator was less than 80%; the water content of the collected crude oil was less than 10%; the oil content in the treated water was less than 20 mg / l (the standard for treating polymer-containing wastewater in oilfields is 20 mg / l); and the suspended solids content in the water was less than 20 mg / l. Tests showed that the treatment results exceeded the expected standards.

Claims

1. A rapid treatment device for oily wastewater in an oil field, comprising a crude oil storage tank (1) and a wastewater storage tank (2), characterized in that The system also includes an inclined plate oil collecting skid (3), a solid-liquid separation skid (4), a dissolved air flotation skid (5) and a sludge dewatering skid (6). The inclined plate oil collecting skid (3) has a raw material inlet (7), and its sand and water outlet pipeline is connected to the solid-liquid separation skid (4). The solid-liquid separation skid (4) is provided with a mud and sand outlet. The upper crude oil outlet pipeline of the inclined plate oil collecting skid (3) is connected to the crude oil storage tank (1). The sewage outlet pipeline of the inclined plate oil collecting skid (3) is connected to the sewage storage tank (2). The outlet of the sewage storage tank (2) is connected to the dissolved air flotation skid (5). The scum outlet of the dissolved air flotation skid (5) is connected to the sludge dewatering skid (6). A clean water outlet is provided at the bottom. The dewatered cake is discharged from the skid bottom of the sludge dewatering skid (6). The inclined plate oil collecting skid (3) is a partition (8) used to divide the box body into a control room (9), a slow flow room (10) and a crude oil collection room (11) from left to right. The control room (9) is provided with a sand and water output pump (12), a crude oil output pump (13) and a sewage output pump (14); a raw material inlet (7) is provided on the upper left side of the slow flow room (10), and an oil collecting assembly (30) is provided on the right side to the crude oil collection room (11). A downwardly inclined inclined plate (16) is provided at the bottom of the crude oil collection room (11) and the slow flow room (10) from right to left, and its inclination angle is 3 to 8 degrees. The inner wall of the box on both sides of the slow flow room (10) is provided with a plurality of inclined plates (16). More than one settling inclined plate (17) is fixed at the upper interval. A sewage output pipeline (18) in the slow flow chamber (10) and a crude oil output pipeline (19) of the crude oil collection chamber (11) are provided at the lower portion of the settling inclined plate (17). The sewage output pipeline (18) enters the sewage storage tank (2) through the sewage outlet (20) via the sewage output pump (14), and the crude oil output pipeline (19) enters the crude oil storage tank (1) through the crude oil outlet (21) via the crude oil output pump (13). The sand and water outlet (22) at the bottom left of the slow flow chamber (10) enters the solid-liquid separation skid (4) through the sand and water outlet pump (12) and the sand and water outlet I (23). The outlet of the sewage output pump (14) is also connected to a fine sand collection flushing pipe (25), a sand discharge backwashing pipe (26) and a sand flushing and stirring pipe (27), respectively; the fine sand collection flushing pipe (25) is an L-shaped pipe, placed at the lower part of the sedimentation inclined plate (17), and a bent pipe is longitudinally placed on the left side of the bottom sand retaining plate (24) of the slow flow chamber (10), and a nozzle (28) is provided on the bent pipe; the outlet of the sand discharge backwashing pipe (26) is connected to the sand and water outlet (22) pipeline; the sand flushing and stirring pipe (27) is longitudinally placed above the left side of the slow flow chamber (10), and a sprinkler head is provided on it; and a crude oil tank sewage inlet (29) is provided on the slow flow chamber (10).

2. The oilfield oily wastewater rapid treatment device as claimed in claim 1, characterized in that A sand retaining plate (24) is fixed on the inclined plate (16) at the rear section of the slow flow chamber (10), and the crude oil output pipeline (19) passes through the sand retaining plate (24). A sewage pipe (75) is provided at the bottom of the slow flow chamber (10) and passes through the sand retaining plate (24), and its inlet is located on the right side of the sand retaining plate (24), and its outlet enters the solid-liquid separation skid (4) through the sand and water output pump (12) and the sand and water outlet I (23).

3. The oilfield oily wastewater rapid treatment device according to claim 1, characterized in that An oil collecting spray pump (15) is also provided in the control room (9). An oil collecting spray inlet pipe (31) is provided above the slow flow chamber (10) and is connected to the oil collecting spray pump (15) pipeline. The outlet of the oil collecting spray pump (15) is connected to the oil collecting spray outlet nozzle (32). The oil collecting spray outlet nozzle (32) is longitudinally located above the left side of the slow flow chamber (10) and is provided with a nozzle.

4. The oilfield oily wastewater rapid treatment device according to claim 1, characterized in that The liquid inlet I (33) on the crude oil storage tank (1) is connected to the crude oil outlet (21) of the inclined plate oil skid (3), and the sewage outlet (34) of the crude oil storage tank (1) is connected to the crude oil tank sewage inlet (29) on the inclined plate oil skid (3); a crude oil outlet (35) is provided on the crude oil storage tank (1), an electric heater (36) is provided inside the crude oil storage tank (1), and a self-circulating heating pipeline (37) is provided inside the crude oil storage tank (1) and is connected to a circulation pump (38).

5. The oilfield oily wastewater rapid treatment device according to claim 1, characterized in that The solid-liquid separation skid (4) is a box in which a separation slanted bucket (39) is fixed. A sand-water separator (40) is installed in the separation slanted bucket (39). The liquid inlet pipe (41) of the solid-liquid separation skid (4) is connected to the sand-water outlet I (23) of the inclined plate oil collecting skid (3). The liquid outlet of the liquid inlet pipe (41) is placed above the separation slanted bucket (39) through a cyclone (42). The separation slanted bucket (39) is provided with a sewage overflow port (43). The sand-water separator (40) has a sand discharge outlet (44).

6. The oilfield oily wastewater rapid treatment device according to claim 1, characterized in that The dissolved air flotation skid (5) is provided with a partition plate I (45) in the box body to separate it into a reaction chamber (46) and a separation chamber (47). The sewage outlet pipe of the sewage storage tank (2) enters the reaction chamber (46) through the liquid inlet II (48), the liquid inlet pump (49), and the liquid inlet pipe (50). A releaser (51) is provided at the bottom of the front section of the reaction chamber (46) and the separation chamber (47). The releaser (51) is connected to the outlet of the dissolved air tank (52) through a pipe (60). 47) is provided with a scum collecting device (55) at the top and a scum box (56) at the tail end; a clean water outlet (54) of the separation chamber (47) is provided at the bottom of the scum box (56); clean water is discharged to the high-pressure pump room (63) through the clean water outlet (62) via the clean water pump (61); a downward-inclined scum receiving plate (57) is provided at the inlet of the scum box (56); the bottom outlet pipeline of the scum box (56) is discharged to the sludge dewatering skid (6) through the scum outlet (59) via the scum pump (58).

7. The oilfield oily wastewater rapid treatment device according to claim 6, characterized in that The sludge dewatering skid (6) includes a sludge mixing box (68), a sludge liquid inlet (67) is provided on the sludge mixing box (68), a sludge outlet (59) is connected to the sludge liquid inlet (67) through a pipeline, a stirring device (69) and a built-in heater (70) are provided on the sludge mixing box (68), a bottom liquid outlet (71) is connected to a liquid outlet pump (72) through a pipeline, a water outlet of the liquid outlet pump (72) is discharged to a slow flow chamber (10) through an outlet (73) pipe, and a sludge outlet pipeline is connected to a screw conveyor (74), and the screw conveyor (74) is provided with a liquid outlet and a sludge outlet.

8. A method for treating oilfield oily wastewater using the rapid treatment device of claim 1, characterized in that The steps include: (1) Solid-liquid separation The oily wastewater is poured into the inlet of the inclined plate oil skid. After being fully diffused by the settling inclined plate, the solid mud and sand in it are settled to the bottom of the skid and discharged; The floating crude oil in the liquid phase is collected by a scraper and sent to the crude oil storage tank, while the sewage in the middle layer is collected and discharged to the sewage storage tank. In winter, the bottom temperature of the inclined plate skid is 0-8°C, the liquid phase temperature is 50-80°C, the inclination angle of the settling inclined plate is 30-60°, and the number of plates is 2-8. (2) Flotation purification of sewage The sewage is added with flocculants, coagulants and oxidants through a dissolved air flotation skid, which adheres the fine impurities in the sewage into suspended masses, which are then removed by a chain scraper to produce purified water; (3) Sludge dewatering The sludge after solid-liquid separation is pressure filtered using a plate and frame filter to form a mud cake for discharge, and the filtered sewage is returned to the dissolved air flotation skid.

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