Oily sewage treatment system

Abstract

The utility model relates to an oily sewage treatment system and belongs to the technical field of sewage treatment. The sewage treatment system comprises an oil-containing sewage storage device, an electric flocculation reaction device and a sedimentation device which are sequentially arranged in the flowing direction of oil-containing sewage, and the top of the electric flocculation reaction device is provided with a gas collecting hood which is used for sealing the electric flocculation reaction device and gathering air flotation foam. An air flotation foam outlet is formed in the air collecting hood; the oily sewage treatment system further comprises a gas-liquid separation device connected with the air flotation foam outlet and a gas storage device used for storing gas separated by the gas-liquid separation device. The oil-containing sewage treatment system can prevent hydrogen from escaping and gathering around the oil-containing sewage treatment system to cause explosion, improves the safety of oil-containing sewage electric flocculation treatment, is also beneficial to recycling of oil and hydrogen, and saves energy.

Description

Technical Field

[0001] The utility model relates to an oily sewage treatment system and belongs to the technical field of sewage treatment. Background Art

[0002] Nowadays, most of China's oil fields have entered the tertiary oil recovery stage. The tertiary produced water has the characteristics of high temperature, high mineralization, many bacteria and many residual chemicals. At the same time, polymers, such as the commonly used polyacrylamide, need to be added to the well during the tertiary oil recovery process, which will also cause the tertiary produced water to have high viscosity, strong emulsification, strong ability to condense solid particles, large resistance to the movement of oil droplets and solid particles, and high consumption of chemical adsorbents. At present, the commonly used methods in oily wastewater treatment technology include physical methods, chemical methods and biological methods, but these methods have the disadvantages of high energy consumption, high cost, complex equipment and difficult maintenance. Therefore, oily wastewater treatment requires the research and development of new technologies that are efficient, energy-saving, economical and safe.

[0003] Electroflocculation is an efficient and clean sewage treatment technology. The reaction principle of electroflocculation is that aluminum, iron and other metals are used as anodes. Under the action of direct current, the anode is dissolved to produce a large number of metal cations such as Al and Fe. These metal cations are hydrolyzed to generate hydroxides and polynuclear hydroxyl complexes with strong adsorption effects, which cause colloidal impurities and suspended impurities in the wastewater to condense and precipitate and separate. At the same time, the charged pollutant particles migrate in the electric field, and part of their charge is neutralized by the electrode to promote their destabilization and flocculation. When the wastewater is treated with electrolytic flocculation, it not only has a flocculation and precipitation effect on colloidal impurities and suspended impurities, but also can remove a variety of pollutants in the water due to the oxidation of the anode and the reduction of the cathode. As an efficient and clean sewage treatment technology, electroflocculation combines the advantages of chemical flocculation and electrochemical methods for sewage treatment, removes pollutants more thoroughly, and can remove inorganic pollutants and difficult-to-degrade organic pollutants that cannot be treated by ordinary methods. Therefore, it is also often used in the treatment of polymer-containing and oily sewage.

[0004] In the prior art, a Chinese invention patent application with application publication number CN111115923A and application publication date May 8, 2020 discloses an oily wastewater treatment system based on electrocoagulation technology, the system comprising a sewage pool for holding oily wastewater, the sewage pool being connected to the lower part of an electrocoagulation device through an inlet pipe, the upper part of the electrocoagulation device being connected to the lower part of a sedimentation tank through a discharge pipe, and a liquid outlet pipe being provided at the upper part of the sedimentation tank; the flocculation device comprising a reaction tank, a plurality of electrode plates arranged at intervals being provided in the reaction tank, the plurality of electrode plates being fixedly connected together through non-conductive connectors, the distance between two adjacent electrode plates being 1.8 cm, and the electrode plates being electrically connected to a DC power supply. When this system is used to treat oily wastewater, the oily wastewater is passed from the sewage pool into the electrocoagulation device for electrolysis. During the electrolysis process, the oily wastewater undergoes oil-water separation, and is separated into qualified water, floccules, and air-floating foam. The air-floating foam and a part of the floccules remain in the reaction tank, and the qualified water and another part of the floccules flow into the sedimentation tank through the discharge pipe. After the floccules settle in the sedimentation tank, the qualified water is discharged to the outside through the outlet pipe. The electrode plate spacing of this system is reasonably designed, which is conducive to accelerating the sedimentation movement of the floccules and the floating movement of the bubbles; the electrode plates can be connected together through connectors, which simplifies the replacement operation of the power connection device and the electrode plates, and improves work efficiency. However, the flotation foam in the reaction tank is mainly formed by the hydrogen and emulsified oil and other pollutants generated during the electrolysis of the oily wastewater, which float to the water surface. The reaction tank is open to the atmosphere. As the flotation foam remaining in the reaction tank continues to accumulate and burst, hydrogen continues to accumulate around the reaction tank. Since hydrogen is easy to burn or explode when it accumulates to a certain concentration, the above-mentioned oily wastewater treatment system has a high safety risk. Utility Model Content

[0005] The utility model aims to provide an oily sewage treatment system to solve the problem of low safety of the existing oily sewage treatment device based on the electric flocculation technology during use.

[0006] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0007] A system for treating oily wastewater comprises an oily wastewater storage device, an electric flocculation reaction device and a sedimentation device which are sequentially arranged in the flow direction of the oily wastewater, wherein a gas collecting hood for sealing the electric flocculation reaction device and collecting flotation foam is arranged on the top of the electric flocculation reaction device, and a flotation foam outlet is arranged on the gas collecting hood; the system for treating oily wastewater further comprises a gas-liquid separation device connected to the flotation foam outlet and a gas storage device for storing gas separated by the gas-liquid separation device.

[0008] Furthermore, the gas collecting hood is in a cone shape, and the flotation foam outlet is arranged at the top of the gas collecting hood.

[0009] Furthermore, a gas collecting hood for sealing the sedimentation device and collecting flotation foam is arranged on the top of the sedimentation device, and a flotation foam outlet is arranged on the gas collecting hood of the sedimentation device, and the flotation foam outlet on the sedimentation device is connected to the gas-liquid separation device.

[0010] Furthermore, the gas collecting hood of the sedimentation device is in a cone shape, and the flotation foam outlet is arranged at the top of the gas collecting hood.

[0011] Furthermore, the oily wastewater treatment system also includes an oil storage device, the oily wastewater storage device is provided with an oil outlet, and the oil outlet on the oily wastewater storage device and the liquid outlet on the gas-liquid separation device are both connected to the oil storage device.

[0012] Furthermore, a conical oil collecting hood for sealing the oily wastewater storage device and gathering the oil layer is provided on the top of the oily wastewater storage device; the oil outlet of the oily wastewater storage device is provided on the top of the oil collecting hood.

[0013] Furthermore, the electrode assembly of the electro-flocculation reaction device comprises two spiral electrode plates arranged at intervals, the two spiral electrode plates have a same spiral axis, and the spiral axis extends in the up-and-down direction of the electro-flocculation reaction device.

[0014] Furthermore, the electro-flocculation reaction device is equipped with a stirring mechanism for stirring the sewage flowing through the electrode assembly during the electro-flocculation reaction process, and the stirring mechanism is arranged below the electrode assembly.

[0015] Furthermore, the water outlet of the electric flocculation reaction device is arranged below the stirring mechanism.

[0016] Furthermore, the electric flocculation reaction device is equipped with an AC pulse power supply.

[0017] The oily wastewater treatment system of the utility model improves the existing technology, and a gas-liquid separation device is provided to perform gas-liquid separation on the flotation foam and hydrogen generated in the electric flocculation reaction device to obtain oil and hydrogen respectively, and then the hydrogen is collected, so that the hydrogen can be prevented from escaping and gathering around the oily wastewater treatment system to cause explosion, thereby improving the safety of the electric flocculation treatment of the oily wastewater, and also contributing to the recycling of oil and hydrogen, saving energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the oily wastewater treatment system of Example 1;

[0019] Figure 2 is a schematic diagram of an electrode assembly in the electrocoagulation reaction device in Example 1;

[0020] Among them, 1-oil-containing wastewater storage device, 101-wastewater inlet, 102-first valve, 103-boosting pump, 104-second valve, 105-liquid level window, 106-third valve, 107-fourth valve, 108-fifth valve; 2-electric flocculation reaction device, 201-liquid level window, 202-sixth valve, 203-seventh valve, 204-eighth valve, 205-detachable sealing door, 206-ninth valve, 207-electrode assembly; 3-sedimentation device, 301-liquid level window, 302-tenth valve, 30 3- detachable sealing door, 304- the eleventh valve, 305- the twelfth valve, 306- the booster pump, 307- the thirteenth valve, 308- the outlet pipe; 4- the gas storage tank, 401- the fourteenth valve, 402- the fifteenth valve, 403- the compressor; 5- the gas-liquid separation device, 501- the booster pump, 502- the liquid level window, 503- the sixteenth valve, 504- the seventeenth valve, 505- the eighteenth valve, 506- the nineteenth valve; 6- the oil storage tank, 601- the twentieth valve, 602- the twenty-first valve; 7- the distribution box. DETAILED DESCRIPTION

[0021] The technical solution of the utility model is further described below in conjunction with specific implementation methods.

[0022] Example 1

[0023] The oily wastewater treatment system of this embodiment is as follows: Figure 1 As shown, it includes an oily wastewater storage device 1, an electric flocculation reaction device 2, a sedimentation device 3, a gas-liquid separation device 5, a gas storage device 4, an oil storage device 6 and an AC pulse power supply matched with the electric flocculation reaction device 2. The alternating conversion of the positive and negative poles of the AC pulse power supply can eliminate the disadvantages of easy passivation, low efficiency and high energy consumption of DC flocculation, and has good purification effect and low processing cost. The AC pulse power supply is arranged in the distribution box 7.

[0024] The oily wastewater storage device 1 comprises a vertically arranged cylinder with a circular cross section, a conical cylindrical oil collecting hood sealedly connected to the upper end of the cylinder, and a conical cylindrical sewage collecting part arranged at the lower end of the cylinder, an oil outlet is arranged at the top of the oil collecting hood, a sludge outlet is arranged at the bottom of the sewage collecting part, an oily wastewater inlet and a water outlet are arranged on the cylinder, the oily wastewater inlet is located above the water outlet, the oil outlet of the oily wastewater storage device 1 is equipped with a third valve (check valve) 106, the water outlet is equipped with a fourth valve (water outlet valve) 107, the sludge outlet is equipped with a fifth valve (drain valve) 108, the oily wastewater inlet is connected to the water inlet pipe 101, and the water inlet pipe is sequentially equipped with a first valve 102, a booster pump 103, and a second valve (sewage inlet valve) 104 in the water flow direction. A liquid level window 105 is also arranged on the cylinder of the oily wastewater storage device 1.

[0025] The electro-flocculation reaction device 2 comprises a shell, an electrode assembly 207 and a stirring mechanism 208 arranged in the shell, the shell comprises a vertically arranged cylinder with a circular cross section, a conical cylindrical gas collecting hood sealedly connected to the upper end of the cylinder, and a conical cylindrical sewage collecting part arranged at the lower end of the cylinder, the top of the gas collecting hood is provided with an air flotation foam outlet, the bottom of the sewage collecting part is provided with a sewage outlet, the cylinder is provided with a water inlet and a water outlet, the water inlet is provided above the electrode assembly 207, and the water outlet is provided at the stirring mechanism 208. 8; the flotation foam outlet of the electric flocculation reaction device 2 is equipped with a ninth valve (one-way valve) 206, and the water inlet of the electric flocculation reaction device 2 is connected to the water outlet of the oily wastewater storage device 1; the water outlet of the electric flocculation reaction device 2 is equipped with a seventh valve (one-way valve) 203, and the sewage outlet of the electric flocculation reaction device 2 is equipped with an eighth valve (sewage valve) 204. The cylinder of the outer shell of the electric flocculation reaction device 2 is also provided with a liquid level window 201 and a detachable sealing door 205;

[0026] The electrode assembly 207 of the electrocoagulation reaction device 2 is as follows Figure 2 As shown, it includes two spiral electrode plates 810 arranged at intervals, and the two spiral electrode plates have the same spiral axis extending along the vertical direction of the electric flocculation reaction device 2, and one of the spiral electrode plates is completely overlapped with the other spiral electrode after rotating 180° around the spiral axis; the cross section and thickness of each electrode plate 810 are consistent. One of the electrode plates is connected to the live wire of the AC pulse power supply, and the other electrode plate is connected to the neutral wire of the AC pulse power supply. Compared with the traditional planar electrode plates, the electric flocculation reaction device of the electrode assembly has a reduced floor space under the condition of the same area of ​​electrode plates, thereby increasing the pole-water ratio, reducing the current density, and further reducing the overvoltage, improving the voltage efficiency, and increasing the volume of sewage flowing through per unit time, thereby improving the treatment efficiency and saving energy consumption. The spiral electrode plate 810 is made of aluminum material; the shell of the electric flocculation reaction device 2 is made of PVC material.

[0027] The stirring mechanism 208 is arranged below the electrode assembly 207. Turning on the stirring mechanism 208 during the electroflocculation process can enhance the flow of water between the electrode plates, eliminate dead water areas, make the electroflocculation more complete, break up and reorganize the flocs, accelerate the sedimentation of the flocs, improve the separation efficiency, and prevent the water outlet from being blocked.

[0028] The outer shell of the sedimentation device 3 includes a vertically arranged cylinder with a circular cross-section, a conical cylindrical air collecting hood sealed and connected to the upper end of the cylinder, and a conical cylindrical sewage collecting part arranged at the lower end of the cylinder. The top of the air collecting hood of the sedimentation device 3 is provided with an air flotation foam outlet, the bottom of the sewage collecting part is provided with a sewage outlet, and the cylinder is provided with a water inlet and a water outlet. The air flotation foam outlet of the sedimentation device 3 is equipped with a tenth valve (one-way valve) 302. The water inlet of the sedimentation device 3 is connected to the outlet of the electric flocculation reaction device 2. The water outlet is connected, and the sewage outlet of the sedimentation device 3 is equipped with an eleventh valve (sewage valve) 304. The water outlet of the sedimentation device 3 is connected to the water outlet pipe 308. The water outlet pipe 308 is provided with a twelfth valve 305, a booster pump 306 and a thirteenth valve 307. The twelfth valve 305 is located upstream of the booster pump 306, and the thirteenth valve 307 is located downstream of the booster pump 306. A liquid level window 301 and a detachable sealing door 303 are also provided on the cylinder of the outer shell of the sedimentation device 3.

[0029] The gas-liquid separation device 5 is specifically a gas-liquid separation tank, and is provided with a flotation foam inlet, a gas outlet, a liquid outlet and a sewage outlet. The flotation foam inlet of the gas-liquid separation device 5 is connected to the flotation foam outlet of the electric flocculation reaction device 2 and the flotation foam outlet of the sedimentation device 3, and the flotation foam inlet is equipped with a sixth valve (one-way valve) 202, the gas outlet of the gas-liquid separation device 5 is equipped with a sixteenth valve (outlet valve) 503, the sewage outlet of the gas-liquid separation device 5 is equipped with a seventeenth valve (sewage valve) 504, and a liquid level window 502 is also provided on the gas-liquid separation device 5.

[0030] The gas storage device 4 is specifically a gas storage tank, which is provided with an air inlet, an exhaust port and a liquid discharge port. The air inlet of the gas storage device 4 is connected to the gas outlet of the gas-liquid separation device 5 through a pipeline, and a compressor 403 is arranged on the connecting pipeline. The liquid discharge port of the gas storage device 4 is equipped with a fourteenth valve 401, and the exhaust port of the gas storage device 4 is equipped with a fifteenth valve (exhaust valve) 402.

[0031] The oil storage device 6 is specifically an oil storage tank, which is provided with a first liquid inlet, a second liquid inlet and a liquid discharge port, and the first liquid inlet of the oil storage device 6 is connected to the oil outlet of the oily wastewater storage device 1. The second liquid inlet of the oil storage device 6 is connected to the liquid outlet of the gas-liquid separation device 5 through a pipeline, and a booster pump 501 and an eighteenth valve 505 and a nineteenth valve 506 are provided on the connecting pipeline, wherein the eighteenth valve 505 is provided upstream of the booster pump 501, and the nineteenth valve 506 is provided downstream of the booster pump 501; the liquid discharge port of the oil storage device 6 is provided with a twentieth valve 601, and the oil storage device 6 is also provided with a twenty-first valve (pressure relief valve) 602.

[0032] In the process of treating oily wastewater using the oily wastewater treatment system of this embodiment, the one-way valve 106 and the pressure relief valve 602 are first opened, and then the second valve 104, the first valve 102 and the booster pump 103 are opened to inject oily wastewater into the oily wastewater storage device 1. After the oily wastewater enters the oily wastewater storage device 1, a part of the solid impurities and suspended matter are initially settled at the bottom of the oily wastewater storage device 1 and separated from the wastewater. Due to the difference in density between oil and water and the difficulty in dissolving each other, the oily wastewater undergoes oil-water separation during the settling process of the solid impurities and suspended matter to form an oil layer and a water layer (the oil layer is on the top and the water layer is on the bottom), and the sludge in the oily wastewater settles below the water layer during the oil-water separation process. When the oil in the oil layer begins to enter the oil storage device 6, the fifth valve (drain valve) 108, the fourth valve 107, the ninth valve (one-way valve) 206 and the sixth valve (one-way valve) 202, as well as the stirring mechanism of the electro-flocculation reaction device 2 are opened.

[0033] The oily wastewater entering the electric flocculation reaction device 2 from the oily wastewater storage device 1 undergoes electrolysis by the electrode assembly, and the impurities form flocs. The hydrogen produced by the reaction floats with pollutants such as emulsified oil in the water to form flotation foam, and the remaining oil floats to become floating oil and mixes into the flotation foam, while some flocculent impurities formed by the electric flocculation settle in the electric flocculation reaction device.

[0034] As the electric flocculation reaction proceeds, the flotation foam and the floating oil begin to enter the gas-liquid separation device 5 through the flotation foam outlet of the electric flocculation reaction device 2, and then the eighth valve (drain valve) 204, the seventh valve (check valve) 203, the tenth valve (check valve) 302, the compressor 402, the nineteenth valve 506, the eighteenth valve 505 and the boosting pump 501 are opened, and most of the flocculent impurities generated by the electric flocculation reaction enter the sedimentation device 3 with the sewage for sedimentation, thereby further separating the flocculent impurities from the clean water, while the hydrogen and oil remaining in the sewage float to form a mixture of flotation foam and floating oil during the sedimentation of the flocculent impurities. When the mixture of flotation foam and floating oil in the sedimentation device 3 begins to enter the gas-liquid separation device 5 through the tenth valve (check valve) 302, the thirteenth valve 307, the twelfth valve 305, the boosting pump 306 and the eleventh valve (drain valve) 304 are opened.

[0035] The floating foam and floating oil entering the gas-liquid separation device 5 are separated by gas and liquid, and the separated liquid enters the oil storage tank 6 through the pipeline through the 18th valve 505, the booster pump 501, and the 19th valve 506, and the separated gas enters the gas storage tank 4 through the pipeline through the 16th valve 503 and the compressor 403. The recovered oil products are discharged and transported through the pipeline through the 20th valve 601, and the recovered gas is discharged and transported through the pipeline through the 15th valve 402. The settled sludge is processed or reinjected through the pipeline through the sewage valve 5th valve 108, the 8th valve 204, the 11th valve 304, and the 17th valve 504, and the water remaining in the hydrogen is condensed in the gas storage device and then discharged through the 14th valve 401.

[0036] The changes of the liquid levels in the corresponding devices are observed through the liquid level windows 105 on the oily wastewater storage device 1, the liquid level window 201 on the electro-flocculation reaction device 2, the liquid level window 301 on the sedimentation device 3 and the liquid level window 502 on the gas-liquid separation device 5.

[0037] Example 2

[0038] The oily wastewater treatment system of this embodiment is different from the oily wastewater electro-flocculation reaction device of Embodiment 1 only in that the electro-flocculation reaction device 2 used in this embodiment is not provided with a stirring mechanism 208, so that the volume of the electro-flocculation reaction device can be reduced.

[0039] Example 3

[0040] The oily wastewater treatment system of this embodiment is different from the oily wastewater electric flocculation reaction device of Example 1 only in that the top of the cylinder of the oily wastewater storage device is open, and an overflow port is arranged at the edge, and the first liquid inlet of the oil storage device is connected to the overflow port of the oily wastewater storage device. During the oily wastewater treatment process, the floating oil layer in the oily wastewater storage device can enter the oil storage device through the overflow port.

Claims

1. An oily wastewater treatment system, comprising an oily wastewater storage device, an electric flocculation reaction device and a sedimentation device arranged in sequence in the flow direction of the oily wastewater, characterized in that: A gas collecting hood for sealing the electro-flocculation reaction device and gathering flotation foam is arranged on the top of the electro-flocculation reaction device, and a flotation foam outlet is arranged on the gas collecting hood; the oily wastewater treatment system also includes a gas-liquid separation device connected to the flotation foam outlet and a gas storage device for storing the gas separated by the gas-liquid separation device.

2. The oily wastewater treatment system according to claim 1, characterized in that: The gas collecting hood is in a cone shape, and the air flotation foam outlet is arranged at the top of the gas collecting hood.

3. The oily wastewater treatment system according to claim 1, characterized in that: The top of the sedimentation device is provided with a gas collecting hood for sealing the sedimentation device and collecting flotation foam. The gas collecting hood of the sedimentation device is provided with a flotation foam outlet, and the flotation foam outlet on the sedimentation device is connected to the gas-liquid separation device.

4. The oily wastewater treatment system according to claim 3 is characterized in that: The gas collecting hood of the sedimentation device is in a cone shape, and the air flotation foam outlet is arranged at the top of the gas collecting hood.

5. The oily wastewater treatment system according to claim 1 or 2, characterized in that: The oily wastewater treatment system also includes an oil storage device, which is provided with an oil outlet. The oil outlet on the oily wastewater storage device and the liquid outlet on the gas-liquid separation device are both connected to the oil storage device.

6. The oily wastewater treatment system according to claim 5, characterized in that: A conical oil collecting hood for sealing the oily wastewater storage device and gathering the oil layer is arranged on the top of the oily wastewater storage device; the oil outlet of the oily wastewater storage device is arranged on the top of the oil collecting hood.

7. The oily wastewater treatment system according to claim 1, characterized in that: The electrode assembly of the electro-flocculation reaction device comprises two spiral electrode plates arranged at intervals. The two spiral electrode plates have the same spiral axis, and the spiral axis extends in the up-and-down direction of the electro-flocculation reaction device.

8. The oily wastewater treatment system according to claim 7, characterized in that: The electro-flocculation reaction device is equipped with a stirring mechanism for stirring the sewage flowing through the electrode assembly during the electro-flocculation reaction process, and the stirring mechanism is arranged below the electrode assembly.

9. The oily wastewater treatment system according to claim 8, characterized in that: The water outlet of the electric flocculation reaction device is arranged below the stirring mechanism.

10. The oily wastewater treatment system according to claim 1 or 8, characterized in that: The electric flocculation reaction device is equipped with an AC pulse power supply.

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