Equipment for synchronously removing petroleum, suspended solids and COD (Chemical Oxygen Demand) in electro-desalting sewage

Abstract

The utility model discloses equipment for synchronously removing petroleum, suspended solids and COD (Chemical Oxygen Demand) in electro-desalting sewage, which relates to the field of refinery sewage treatment and comprises a crude oil electro-desalting tank, a primary heat exchanger, a floating oil rapid separation tank, a deep synergistic separation tank and a secondary heat exchanger, an outlet of the primary heat exchanger is connected with a sewage inlet of the oil slick rapid separation tank, a sewage outlet of the oil slick rapid separation tank is connected with a sewage inlet of the deep synergy separation tank, a sewage outlet of the deep synergy separation tank is connected with an inlet of the secondary heat exchanger, and an outlet of the secondary heat exchanger is connected with a sewage treatment plant. The device disclosed by the utility model realizes synchronous removal of petroleum, suspended matters and COD (Chemical Oxygen Demand) in electro-desalting production sewage, avoids the situation that a sewage treatment plant is impacted due to high contents of the petroleum, the suspended matters and the COD, and has the effects of high removal efficiency, low energy consumption and reduction of treatment cost.

Description

Technical Field

[0001] This utility model relates to the field of refinery wastewater treatment, and more specifically, it relates to a device for the simultaneous removal of petroleum, suspended solids and COD from electro-desalinated wastewater. Background Technology

[0002] Electrostatic desalting (ESD) units are indispensable equipment in oil refineries, and their operational efficiency plays a crucial role in the long-term, safe, and stable operation of refining processes. The main function of crude oil ESD is to remove inorganic salts and water from crude oil. This is achieved by adding a certain amount of demulsifier and water, dissolving the salt in the water at a specific temperature, and then separating the oil and water under the influence of an electric field, thus achieving the purpose of crude oil desalting and dehydration.

[0003] However, electrostatic desalination units often face a series of problems during operation. The effectiveness of crude oil electrostatic desalination is mainly measured by indicators such as the salt content, water content, and oil content in the wastewater after desalination. However, due to factors such as deterioration of raw material properties, changes in process operating conditions, unit fluctuations, and backwashing, electrostatic desalination wastewater often exhibits high and fluctuating concentrations of oil and suspended solids, which severely impacts downstream wastewater treatment units such as flotation and biological treatment. In particular, as the properties of crude oil deteriorate, controlling the salt content and oil content in the wastewater becomes increasingly difficult, and these problems become more pronounced.

[0004] The existing treatment process for wastewater from electrostatic desalination (ESD) production is as follows: After being discharged from the ESD tank, the wastewater first undergoes two stages of heat exchange for cooling, then enters a collection tank. After being buffered in the collection tank, it is pumped into an oil separator for oil removal. The oil-separated wastewater enters a regulating tank for settling, and then is sent to an air flotation treatment unit. After air flotation, it enters a biological treatment unit. The two-stage heat exchange cooling process involves: firstly, the ESD wastewater generated during crude oil desalination undergoes a heat exchange to cool to 70-80℃, followed by a second heat exchange to cool to 40-50℃. Finally, the wastewater after both heat exchange cooling stages is sent to a wastewater treatment plant for further treatment. The first-stage and second-stage heat exchange cooling processes are carried out in the first-stage and second-stage heat exchangers, respectively.

[0005] However, in the existing electrostatic desalination wastewater treatment process, the high oil content and suspended solids in the desalinated wastewater cause blockages and low heat exchange efficiency in the primary and secondary heat exchangers. Furthermore, the wastewater with high oil content, suspended solids, and COD, after being sent to the wastewater treatment plant, severely impacts the flotation and biological treatment units, resulting in the wastewater treatment failing to meet standards. In addition, the large amount of sludge generated during the treatment process is disposed of as hazardous waste along with the scum, which not only cannot be recycled but also causes serious waste of resources.

[0006] And in the existing treatment process, because the electric desalting wastewater contains a large amount of emulsified oil and small solid particles when emulsified, the small oil beads are easily surrounded by surfactants and hydrophobic solid particles to form a stable state suspended in water. This state of oil is difficult to separate from the wastewater by gravity separation method, which results in low separation efficiency of the oil separation tank and the adjusting tank, and therefore the removal effect of emulsified oil and high concentration suspended solids is limited, resulting in low separation efficiency and affecting the normal operation of the downstream biochemical device.

[0007] In order to solve these problems, a number of patents and technologies have been proposed at home and abroad:

[0008] For example, a Chinese utility model with patent authorization publication number CN2205202210U discloses a device for removing oil and sand from electric desalting drainage, which uses a cyclone to separate the sand and oil from the electric desalting wastewater.

[0009] For example, a Chinese invention patent with patent publication number CN118062961A discloses an electric desalting wastewater treatment device and method, which uses a centrifugal air flotation method to remove oil and suspended solids from the electric desalting wastewater.

[0010] For example, a Chinese utility model patent with patent authorization publication number CN214936479U discloses a new type of atmospheric and vacuum electric desalting wastewater deep oil-water separation equipment, which uses a wastewater pump, a container device, a particle size-based high-efficiency separation device, a non-fiber particle oil removal device, a waste oil mixer and a wastewater mixer to treat the electric desalting wastewater.

[0011] For example, a Chinese utility model patent with patent authorization publication number CN208136008U discloses an atmospheric electric desalting wastewater pretreatment device, which uses coke to adsorb salts, oil-soluble COD, sulfides, ammonia nitrogen and phenols in the electric desalting wastewater.

[0012] For example, a Chinese utility model patent with patent authorization publication number CN207129989U discloses an electric desalting wastewater treatment device, which uses a ceramic membrane filtration system to remove suspended solids, oil content, volatile phenol and COD from the electric desalting wastewater.

[0013] For example, a Chinese invention patent with patent publication number CN106745991A discloses an electric desalting wastewater pretreatment oil removal system and method, which uses air energy flocculation and air flotation to treat electric desalting wastewater containing different concentrations of emulsified oil and COD.

[0014] For example, a Chinese invention patent with patent publication number CN105621517A discloses a device and method for treating oil-containing wastewater based on a single-tank two-stage cyclone air flotation device, which uses a single-tank two-stage air flotation to achieve compact and efficient separation of oil and water.

[0015] A kind of electric desalting sewage oil removal equipment and method are disclosed in a Chinese patent with patent publication number CN105000695A, which utilizes sedimentation oil-water separator and cyclone gas floatation device to remove oil and sand.

[0016] A kind of heavy crude oil processing process electric desalting sewage oil removal method is disclosed in a Chinese patent with patent publication number CN104944619A, which utilizes cyclone separator to remove solid and utilizes coalescer to break emulsion coalescence and oil-water separation.

[0017] The above patents mainly utilize cyclone, gas floatation, filtration and adsorption, including utilizing cyclone, centrifugal gas floatation, particle size grading high-efficiency separation, oil removal of anisotropic fiber particles, ceramic membrane filtration system, gas energy flocculation and gas floatation, single-tank two-stage cyclone gas floatation and sedimentation oil-water separator and cyclone gas floatation device to remove oil, sand and suspended solids. However, these technologies have poor complex working condition adaptability, high energy consumption and short running period in actual application.

[0018] Therefore, it is necessary to develop and apply more adaptive electric desalting sewage oil, suspended solids and COD synchronous removal equipment. Utility model content

[0019] In view of this problem in actual application, the utility model aims at providing a kind of electric desalting sewage oil, suspended solids and COD synchronous removal equipment, which has higher removal efficiency for oil, suspended solids and COD, to prevent the downstream sewage device of sewage treatment plant from being impacted, reduce the labor intensity of operating personnel, at the same time, the waste oil resources entrained in electric desalting sewage are recycled and utilized to avoid resource waste, improve the economic and clean operation level of the device, and the specific scheme is as follows:

[0020] A kind of electric desalting sewage oil, suspended solids and COD synchronous removal equipment, including crude oil electric desalting tank, primary heat exchanger, floating oil rapid separation tank, depth collaborative separation tank, secondary heat exchanger, wherein:

[0021] The sewage outlet of the crude oil electric desalting tank is connected to the inlet of the primary heat exchanger, the outlet of the primary heat exchanger is connected to the sewage inlet of the floating oil rapid separation tank, the sewage outlet of the floating oil rapid separation tank is connected to the sewage inlet of the depth collaborative separation tank, the sewage outlet of the depth collaborative separation tank is connected to the inlet of the secondary heat exchanger, and the outlet of the secondary heat exchanger is connected to the sewage treatment plant.

[0022] Further, the system further comprises a waste oil heat exchanger, a mixer and a waste oil dehydration tank, wherein: the waste oil outlet of the floating oil quick separation tank and the waste oil outlet of the deep collaborative separation tank are connected to the inlet of the waste oil heat exchanger, the outlet of the waste oil heat exchanger is connected to the inlet of the mixer, the outlet of the mixer is connected to the inlet of the waste oil dehydration tank, and the waste oil outlet of the waste oil dehydration tank is connected to the floating oil separation tank and the waste water outlet is connected to the waste water tank.

[0023] Further, the floating oil quick separation tank comprises a horizontal floating oil quick separation tank body and a self-adapting cyclone separation core unit, a sand removal unit, a rectifying unit, a quick separation unit and a corrugated quick settling unit which are sequentially arranged in the tank body along the axial direction of the tank body.

[0024] Further, the self-adapting cyclone separation core unit is composed of a main pipe and a secondary pipe combined column-cone cyclone separation pipe.

[0025] Further, the sand removal unit is composed of multiple layers of sand removal plates which are uniformly and obliquely arranged along the axial direction of the floating oil quick separation tank body.

[0026] Further, the rectifying unit is composed of multiple layers of rectifying plates which are uniformly and horizontally arranged along the axial direction of the floating oil quick separation tank body.

[0027] Further, the quick separation unit is composed of multiple layers of quick separation plates which are uniformly and vertically arranged along the axial direction of the floating oil separation tank body, and each quick separation plate is arranged in parallel to each other.

[0028] Further, the corrugated quick settling unit is composed of multiple layers of corrugated plates which are uniformly and parallelly arranged along the axial direction of the floating oil separation tank body, and small holes are formed at the wave crests and wave troughs of the corrugated plates.

[0029] Further, the deep collaborative separation tank comprises a horizontal deep collaborative separation tank body and a suspended matter filtration unit and a fiber coagulation extraction separation unit which are sequentially arranged in the tank body along the axial direction of the tank body.

[0030] Further, the suspended matter filtration unit is arranged by using a particle mixed filter core with different surface interface properties.

[0031] Further, the fiber coagulation extraction separation unit is woven by using fibers with different surface interface properties.

[0032] Further, the waste oil dehydration tank is installed with a heterogeneous fiber coalescence demulsification unit and a wave-based quick separation unit.

[0033] Further, the backwash water outlet of the deep cooperative separation tank and the sewage outlet of the waste oil dehydration tank are both communicated to the sewage inlet of the sewage tank, the waste oil outlet of the sewage tank is connected to the waste oil inlet of the waste oil heat exchanger through a waste oil pump, and the sewage outlet of the sewage tank is connected to the sewage inlet of the floating oil separation tank through a sewage pump.

[0034] Further, the floating oil rapid separation tank, the deep cooperative separation tank and the waste oil dehydration tank are all provided with an oil-water interface level meter.

[0035] Further, the device is arranged close to the electric desalting device or in a sewage treatment plant, and the device is wholly closed.

[0036] Compared with the prior art, the device has the following beneficial effects:

[0037] The device provided by the utility model realizes synchronous removal of petroleum, suspended matter and COD in electric desalting sewage, avoids the impact of high petroleum, suspended matter and COD content on the sewage treatment plant, and can also recycle and utilize the separated waste oil.

[0038] The device has a short treatment process, high removal efficiency and high automation degree, is a completely closed structure, does not produce VOD gas diffusion to the surrounding atmosphere compared with the traditional open air flotation treatment, achieves pollution-free treatment, has low energy consumption in the treatment process, saves treatment cost, has high waste oil recycling efficiency, and realizes efficient recycling. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is a device connection schematic diagram of the petroleum, suspended matter and COD synchronous removal process of electric desalting sewage in the utility model embodiment.

[0040] Figure 2 It is a structure schematic diagram of the floating oil rapid separation tank in the utility model embodiment.

[0041] Figure 3 It is a structure schematic diagram of the deep cooperative separation tank in the utility model embodiment.

[0042] Figure 4 It is a structure schematic diagram of the waste oil dehydration tank in the utility model embodiment.

[0043] Reference signs: 100, crude oil electric desalting tank;

[0044] 200, primary heat exchanger;

[0045] 300, floating oil rapid separation tank; 301, first sewage inlet; 302, first partition plate; 303, self-adaptive cyclone separation core unit; 304, desanding unit; 305, rectifying unit; 306, rapid separation unit; 307, corrugated rapid settling unit; 308, contaminated oil collection bag; 309, first oil-water interface meter; 310, first contaminated oil outlet; 311, communication pipe; 312, floating oil rapid separation tank body; 313, first sewage outlet;

[0046] 400, deep collaborative separation tank; 401, second sewage inlet; 402, second partition plate; 403, suspended matter filtering unit; 404, second oil-water interface meter; 405, second contaminated oil outlet; 406, fiber coagulation extraction separation unit; 407, third oil-water interface meter; 408, third contaminated oil outlet; 409, deep collaborative separation tank body; 410, second sewage outlet;

[0047] 500, contaminated oil heat exchanger;

[0048] 600, mixer;

[0049] 700, contaminated oil dewatering tank; 701, contaminated oil inlet; 702, dissimilar fiber coalescence demulsification unit; 703, corrugated rapid separation unit; 704, fourth contaminated oil outlet; 705, contaminated oil coalescence dewatering tank body; 706, third sewage outlet; 707, fourth oil-water interface meter;

[0050] 800, two-stage heat exchanger. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments.

[0052] Embodiment 1

[0053] This embodiment gives a kind of equipment for simultaneously removing oil, suspended matter and COD in electric desalting sewage, as shown in Fig. 1. Figure 1As shown, the system comprises a crude oil electric desalting tank 100, a primary heat exchanger 200, a floating oil rapid separation tank 300, a deep synergistic separation tank 400, a waste oil heat exchanger 500, a mixer 600, a waste oil dehydration tank 700, and a secondary heat exchanger 800. The waste water outlet of the crude oil electric desalting tank 100 is connected to the inlet of the primary heat exchanger 200. The outlet of the primary heat exchanger 200 is connected to the first waste water inlet 301 of the floating oil rapid separation tank 300. The first waste water outlet 313 of the floating oil rapid separation tank 300 is connected to the second waste water inlet 401 of the deep synergistic separation tank 400. The second waste water outlet 410 of the deep synergistic separation tank 400 is connected to the inlet of the secondary heat exchanger 800. The outlet of the secondary heat exchanger 800 is connected to a waste water treatment plant. The first waste oil outlet 310 of the floating oil rapid separation tank 300 and the second waste oil outlet 405 and the third waste oil outlet 408 of the deep synergistic separation tank 400 are all connected to the inlet of the waste oil heat exchanger 500. The outlet of the waste oil heat exchanger 500 is connected to the inlet of the mixer 600. The outlet of the mixer 600 is connected to the inlet of the waste oil dehydration tank 700. The fourth waste oil outlet 704 of the waste oil dehydration tank 700 is connected to a floating oil separation tank. The third waste water outlet 706 of the waste oil dehydration tank 700 is connected to a waste water tank (not shown in the figure).

[0054] More specifically, as shown in the figure, the floating oil rapid separation tank 300 comprises a horizontal floating oil rapid separation tank body 312 and, installed in the tank body and arranged along the axial direction of the tank body in sequence, an adaptive cyclone separation core unit 303, a sand removal unit 304, a rectifying unit 305, a rapid separation unit 306, and a corrugated rapid settling unit 307. Figure 2

[0055] One side of the floating oil rapid separation tank body 312 is provided with a first waste water inlet 301. The inside of the tank body is provided with a first partition plate 302. The first partition plate 302 and the tank body enclose a space. The waste water inlet is in communication with the space. The adaptive cyclone separation core unit 303 is arranged on the top of the first partition plate 302. The sand removal unit 304, the rectifying unit 305, and the rapid separation unit 306 are sequentially adjacent to and spaced apart from the adaptive cyclone separation core unit 303. The corrugated rapid settling unit 307 is spaced apart from the sand removal unit 304, the rectifying unit 305, and the rapid separation unit 306. The top of the floating oil rapid separation tank body 312 and the rear end of the corrugated rapid settling unit 307 are connected through a communication pipe 311 to a waste oil collection bag 308. The top of the waste oil collection bag 308 is provided with a first waste oil outlet 310. The bottom of the tank body and the rear end of the corrugated rapid settling unit 307 are provided with a first waste water outlet 313.

[0056] ​The adaptive cyclone separation core unit 303 is composed of a column-cone type cyclone separation pipe combined by a main pipe and a secondary pipe, preferably a structure combined by a central main pipe and three secondary pipes. A self-adaptive multi-phase integrated separation device disclosed in Patent No. CN 112387013B can be used. The liquid oil in the electric desalting wastewater and the suspended solids adhered to the liquid oil are separated by cyclone.

[0057] The desanding unit 304 is composed of desanding plates arranged in multiple layers along the tank body 312 of the floating oil rapid separation tank in a uniform and inclined manner, and the inclination angle is preferably 55-60°. The suspended solids and other pollutants in the electric desalting wastewater are removed by the multiple layers of desanding plates.

[0058] The rectifying unit 305 is composed of rectifying plates arranged in multiple layers along the tank body 312 of the floating oil rapid separation tank in a uniform and horizontal manner, and each rectifying plate is arranged in parallel with each other, and the parallel plate spacing is preferably 15-20 mm. The rectifying plates effectively weaken the cyclone speed, so that the suspended solids are more easily precipitated.

[0059] The rapid separation unit 306 is composed of rapid separation plates arranged in multiple layers along the tank body of the floating oil separation tank in a uniform and vertical manner, and each rapid separation plate is arranged in parallel with each other, and the plate spacing is preferably 15-0 mm. The floating oil in the wastewater is rapidly separated out by the rapid separation plates.

[0060] The corrugated rapid settling unit 307 is composed of corrugated plates arranged in multiple layers along the tank body of the floating oil separation tank in a uniform and parallel manner, and small holes are opened at the wave crests and troughs of the corrugated plates, and the small hole diameter is preferably 3-5 mm. The corrugated plates achieve rapid settling of the suspended solids in the wastewater.

[0061] More specifically, as shown in Figure 3 The depth collaborative separation tank 400 includes a horizontal depth collaborative separation tank body 409 and a suspended solids filtering unit 403 and a fiber coagulation extraction separation unit 406 installed in the tank body and arranged in sequence along the tank body.

[0062] One side of the depth collaborative separation tank body 409 is provided with a second wastewater inlet 401, and the inside of the tank body is provided with a second partition plate 402, which forms a convex space (not shown in the figure) with the tank body. The suspended solids filtering unit 403 is located at one side of the top of the convex space close to the inlet end, and the fiber coagulation extraction separation unit 406 is located at one side of the top of the convex space close to the outlet end. The second oil outlet 405 is located above the middle position of the convex space at the top of the depth collaborative separation tank body 409, so that the second oil outlet 405 is located at the middle position of the suspended solids filtering unit 403 and the fiber coagulation extraction separation unit 406. The third oil outlet 408 is provided at the top of the tank body at the rear end of the convex space, and the second wastewater outlet 410 is provided at the bottom of the tank body at the rear end of the convex space.

[0063] The suspended matter filtering unit 403 is arranged by using a mixed filter core with different surface interface properties, preferably PTFE, 316L stainless steel and quartz sand; the suspended matter filtering unit 403 is used for intercepting the suspended solid particles in the oily sewage.

[0064] The fiber coagulation extraction separation unit 406 is woven by fibers with different surface interface properties, preferably PTFE and 316L stainless steel fibers. The fiber coagulation extraction separation unit 406 is used for realizing efficient separation of oil, suspended matter and COD.

[0065] More specifically, as shown in Figure 4 The oil dewatering tank 700 includes an oil dewatering tank body 705 and a heterogeneous fiber coagulation demulsification unit 702 and a Botten rapid separation unit 306 arranged along the inside axis of the oil dewatering tank body 705 in sequence.

[0066] One side of the oil dewatering tank body 705 is provided with an oil inlet 701, the top of the oil dewatering tank body 705 and the rear end of the Botten rapid separation unit 306 are provided with a fourth oil outlet 704, and the bottom of the tank body and the rear end of the Botten rapid separation unit 306 are provided with a third sewage outlet 706.

[0067] The heterogeneous fiber coagulation demulsification unit 702 is used for destroying the stable emulsification state between oil droplets and water droplets in the oily sewage by the coagulation effect of the heterogeneous fibers, so as to realize oil-water separation.

[0068] The Botten rapid separation unit 306 separates the water and impurities in the oil to obtain relatively pure oil products.

[0069] The oil dewatering tank 700 can use the existing coagulation dewatering device to coagulate and dewater the sewage, such as the modular combined high-efficiency separation device disclosed in the patent with the publication number CN103706149B. Therefore, the specific structure of the heterogeneous fiber coagulation demulsification unit and the Botten rapid separation unit will not be described here.

[0070] In addition, the floating oil rapid separation tank 300, the deep collaborative separation tank 400 and the oily water dehydration tank 700 are all provided with automatic oil-water interface monitoring and automatic oil and water discharge functions. Specifically, in the floating oil rapid separation tank 300: a first oil-water interface meter 309 is arranged between the oily water collection bag 308 and the floating oil rapid separation tank body 312; in the deep collaborative separation tank 400: a second oil-water interface meter 404 and a third oil-water interface meter 407 are arranged between the deep collaborative separation tank body 409 and the second oily water outlet 405 and the third oily water outlet 408 respectively; in the oily water dehydration tank 700: a fourth oil-water interface meter 707 is arranged between the oily water dehydration tank body 705 and the third oily water outlet 706. The automatic oil and water discharge function can be realized by using an oil pump and a water pump (not shown in the figure).

[0071] More specifically, the deep collaborative separation tank 400 is also provided with a backwashing water outlet (not shown in the figure), and the backwashing water outlet of the deep collaborative separation tank 400 and the oily water outlet of the oily water dehydration tank 700 are both connected to the oily water inlet of the oily water tank (not shown in the figure) to be used for the settlement separation or air floatation separation of the backwashing water and the oily water produced in the coalescence dehydration process.

[0072] The oily water outlet of the oily water tank is connected to the oily water inlet 701 of the oily water heat exchanger 500 through an oily water pump, and the oily water outlet of the oily water tank is connected to the oily water inlet of the floating oil separation tank (not shown in the figure) through an oily water pump.

[0073] In addition, the electric desalting oily water petroleum, suspended solids and COD synchronous removal equipment can be arranged near the electric desalting device or in the oily water treatment plant; and the equipment adopts an integrated closed equipment, so that the treatment medium is not in contact with the atmosphere throughout the process, and VOC gas diffusion into the surrounding atmosphere is avoided, so that the effect of pollution-free treatment process is achieved.

[0074] Based on the given electric desalting oily water petroleum, suspended solids and COD synchronous removal equipment, an electric desalting oily water petroleum, suspended solids and COD synchronous removal process is also given in the embodiment.

[0075] The electric desalting oily water refers to the oily water discharged from the electric desalting tank 100, which contains 2000-200000 mg / L of petroleum, 500-50000 mg / L of suspended solids and 1000-50000 mg / L of COD.

[0076] The electric desalting oily water petroleum, suspended solids and COD synchronous removal process comprises the following steps:

[0077] Step 1) One-time heat exchange cooling: the electric desalting oily water generated from the electric desalting process in the electric desalting tank 100 is cooled to 70℃ after one-time heat exchange in the primary heat exchanger 200;

[0078] Step 2) Floating oil rapid separation: The electric desalted sewage after once heat exchange and temperature reduction enters the floating oil rapid separation tank 300 to remove floating oil through the floating oil rapid separation process, to obtain primary waste oil and electric desalted sewage after removal of waste oil, the floating oil is oil droplet particle size above 50 μm, and the floating oil separation tank has a separation efficiency of more than 98 wt% for floating oil;

[0079] Step 3) Deep synergistic separation: The electric desalted sewage after removal of floating oil enters the deep synergistic separation tank 400 to simultaneously deeply remove suspended solids, petroleum and COD through the deep synergistic separation process, to obtain secondary waste oil and purified electric desalted sewage, the suspended solids content in the water out of the deep synergistic separation tank 400 is reduced to less than 50 m / L, the petroleum content is reduced to less than 100 mg / L, and the COD removal efficiency is more than 60%;

[0080] Step 4) Secondary heat exchange and temperature reduction: The electric desalted sewage after purification through the deep synergistic separation is sent to the secondary heat exchanger 800 to reduce the temperature to 40℃ after secondary heat exchange, and then sent to the sewage treatment plant.

[0081] In the process, in the deep synergistic separation process, the process further includes: backwashing the suspended solids filtration unit 403 of the deep synergistic separation tank 400, and the backwashing interval is not less than 7 days.

[0082] Since the process in the embodiment removes petroleum, suspended solids and COD in the electric desalted sewage through the deep synergistic separation process, the sewage after removal is cleaner, and the problem of heat exchange efficiency reduction due to blockage in the secondary heat exchange and temperature reduction process is avoided, so that the heat exchange efficiency can be maintained at more than 90% for a long period.

[0083] More specifically, the process further includes resource recycling of waste oil: the primary waste oil and the secondary waste oil obtained by separation are sent to the waste oil heat exchanger 500 to heat to 85-95℃ through heat exchange, then added with 50-500 mg / L of demulsifier in the mixer 600, and then sent to the waste oil dewatering tank 700 for dewatering to reduce the water content to less than 1 wt%, and the dewatered waste oil and sewage are obtained. Among them: the dewatered waste oil is pumped to the floating oil separation tank, and after deep dewatering, it is recycled for resource utilization, and the resource utilization rate of waste oil is more than 90%; the discharged sewage is pumped to the sewage tank for separation.

[0084] More specifically, the process of the application further includes: the sewage discharged from the waste oil dewatering tank 700 and the suspended solids-containing sewage backwashed from the deep synergistic separation tank 400 are sent to the sewage tank for sedimentation separation, and the floating sludge and bottom mud obtained by separation are treated to remove the mud and suspended solids in the electric desalted sewage from the sewage treatment system.

[0085] The suspended solid-containing sewage washed out by the deep cooperative separation tank 400 and the oil-containing sewage separated by the waste oil dewatering tank 700 are sent to a sewage tank for sewage settlement. After settlement, the sewage tank has waste oil at the upper part and sewage at the lower part, and also has scum and sludge. The waste oil at the upper part of the sewage tank is pumped to the waste oil heat exchanger 500 for heat exchange, temperature rising, chemical addition, demulsification and coalescence dewatering again. The sewage at the lower part of the sewage tank is pumped to the floating oil separation tank for floating oil separation and deep cooperative separation again. The scum and sludge of the sewage tank are cleaned regularly.

[0086] It should be further understood that the process can also use air floatation separation, which will not be described herein.

[0087] More specifically, the pressure loss of the electric desalting sewage in the process of once heat exchange, temperature reduction, floating oil rapid separation and deep cooperative separation is less than 0.2 MPa. Since the treatment process of the embodiment uses a pure physical method, the pressure loss of the equipment in the process is small, and the pump needs less or no pressure boosting. Compared with air floatation, the process does not need to consume electric energy by air blower, so that the treatment process of the embodiment has low energy consumption.

[0088] In general, the whole equipment process avoids the impact on the sewage treatment plant caused by high oil content, suspended solids and COD content, and the separated waste oil is dewatered deeply and then recycled and utilized as resources. The process has the effects of completely closed treatment, low energy consumption and high resource recycling efficiency of waste oil.

[0089] Comparative Example

[0090] The existing treatment process of the electric desalting production sewage of a certain refinery is as follows: the electric desalting sewage is discharged from the electric desalting tank, first passes through two-stage heat exchange and temperature reduction, then enters a buffer tank, is pumped into an oil separation tank for oil removal after passing through the buffer tank, the oil-separated sewage enters a conditioning tank for standing, and then is sent to an air floatation treatment device.

[0091] The refinery finds through actual use that, since the electric desalting sewage contains a large amount of emulsified oil and small solid particles when emulsified, the small oil beads are easily surrounded by surfactants and hydrophobic solid particles to form a stable state and suspended in water. This kind of oil is difficult to separate from the sewage by gravity separation method, which causes the separation efficiency of the oil separation tank and the conditioning tank to be very low, and seriously affects the normal operation of the downstream biochemical device.

[0092] The treatment of the electric desalting production sewage is carried out by the process of the comparative example and the process of Example 1 under the same conditions, and the treatment results of the two processes are compared. The comparison results are shown in Table 1.

[0093] Table 1

[0094]

[0095] As can be seen from Table 1, through actual application comparison, under the same inlet conditions, the process of Example 1 can treat electric desalting wastewater until meeting the biochemical system conditions under smaller land area, lower energy consumption, shorter time, lower treatment cost and higher automation degree, and no dangerous waste and VOC etc. are generated in the treatment process, and the oil recovery efficiency is improved, and the oil resource is maximized recovered.

[0096] The preferred embodiments of the present application have been described above, the protection scope of the present application is not limited to the above-mentioned embodiments, any technical solutions falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled in the art, some improvements and refinements without departing from the principles of the present application, these improvements and refinements shall also be considered as the protection scope of the present application.

Claims

1. An electric desalting wastewater petroleum, suspended matter and COD synchronous removal equipment, characterized in that, The device comprises a crude oil electric desalting tank, a first heat exchanger, a floating oil rapid separation tank, a deep collaborative separation tank, and a second heat exchanger. The sewage outlet of the crude oil electric desalting tank is connected to the inlet of the first heat exchanger, the outlet of the first heat exchanger is connected to the sewage inlet of the floating oil rapid separation tank, the sewage outlet of the floating oil rapid separation tank is connected to the sewage inlet of the deep collaborative separation tank, the sewage outlet of the deep collaborative separation tank is connected to the inlet of the second heat exchanger, and the outlet of the second heat exchanger is connected to a sewage treatment plant.

2. The electric desalting wastewater oil, suspended matter and COD synchronous removal equipment according to claim 1, characterized in that, The device further comprises a waste oil heat exchanger, a mixer, and a waste oil dehydration tank, wherein the waste oil outlet of the floating oil rapid separation tank and the waste oil outlet of the deep collaborative separation tank are both connected to the inlet of the waste oil heat exchanger, the outlet of the waste oil heat exchanger is connected to the inlet of the mixer, the outlet of the mixer is connected to the inlet of the waste oil dehydration tank, the waste oil outlet of the waste oil dehydration tank is connected to a floating oil separation tank, and the sewage outlet is connected to a sewage tank.

3. The electric desalting wastewater oil, suspended matter and COD synchronous removal equipment according to claim 1, characterized in that, The floating oil rapid separation tank comprises a horizontal floating oil rapid separation tank body and, installed in the tank body and arranged along the axial direction of the tank body, a self-adapting cyclone separation core unit, a desanding unit, a rectifying unit, a rapid separation unit, and a corrugated rapid settling unit.

4. The electric desalting wastewater oil, suspended matter and COD synchronous removal equipment according to claim 3, characterized in that, The self-adapting cyclone separation core unit is composed of a main pipe and a vice pipe combined column-cone cyclone separation pipe. The desanding unit is composed of multiple layers of desanding plates that are uniformly and obliquely arranged along the axial direction of the floating oil rapid separation tank body. The rectifying unit is composed of multiple layers of rectifying plates that are uniformly and horizontally arranged along the axial direction of the floating oil rapid separation tank body. The rapid separation unit is composed of multiple layers of rapid separation plates that are uniformly and vertically arranged along the axial direction of the floating oil separation tank body, and each rapid separation plate is arranged in parallel to each other. The corrugated rapid settling unit is composed of multiple layers of corrugated plates that are uniformly and parallelly arranged along the axial direction of the floating oil separation tank body, and small holes are formed at the wave crests and wave troughs of the corrugated plates.

5. The electric desalting wastewater oil, suspended matter and COD synchronous removal equipment according to claim 1, characterized in that, The deep collaborative separation tank comprises a horizontal deep collaborative separation tank body and, installed in the tank body and arranged along the axial direction of the tank body, a suspended solids filtration unit and a fiber coagulation extraction separation unit.

6. The electric desalting wastewater oil, suspended matter and COD synchronous removal equipment according to claim 5, characterized in that, The suspended solids filtration unit is arranged by using a mixed filter core with different surface interface properties. The fiber coagulation extraction separation unit is woven by using fibers with different surface interface properties.

7. The electric desalting wastewater oil, suspended matter and COD synchronous removal equipment according to claim 2, characterized in that, The waste oil dehydration tank is installed with a heterogeneous fiber coalescence demulsification unit and a wave-based rapid separation unit.

8. The electric desalting wastewater oil, suspended matter and COD synchronous removal equipment according to claim 2, characterized in that, The backwash water outlet of the deep collaborative separation tank and the sewage outlet of the waste oil dehydration tank are both connected to the sewage inlet of a sewage tank, the waste oil outlet of the sewage tank is connected to the waste oil inlet of the waste oil heat exchanger through a waste oil pump, and the sewage outlet of the sewage tank is connected to the sewage inlet of the floating oil separation tank through a sewage pump.

9. The electric desalting wastewater oil, suspended matter and COD synchronous removal equipment according to claim 1, characterized in that, Oil-water interface level gauges are arranged in the floating oil rapid separation tank, the deep collaborative separation tank, and the waste oil dehydration tank.

10. The electric desalting wastewater oil, suspended matter and COD synchronous removal equipment according to claim 1, characterized in that, The device is arranged close to an electric desalting device or in a sewage treatment plant, and the whole device is arranged in a sealed manner.

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