A treatment system and method for tar-containing wastewater

Abstract

This invention discloses a treatment system and method for tar-containing wastewater, belonging to the field of water treatment. It includes: a coarse particle separation unit, consisting of an inner tank and an outer tank, with the inner tank placed inside the outer tank and its lower end penetrating through the outer tank; the inner tank is used for sedimentation oil removal, and the outer tank is used for coalescence oil removal; and a demulsification filtration unit, whose inlet is connected to the outlet of the outer tank after coalescence oil removal, for secondary coalescence oil removal while simultaneously performing demulsification oil removal. The treatment method includes a coarse particle separation step and a demulsification separation step. This invention can enhance the oil-water separation efficiency of tar-containing wastewater, achieving excellent separation effect of tar-containing wastewater at a lower ultrasonic demulsification frequency, ensuring stable wastewater quality after oil removal, creating favorable conditions for subsequent treatment, and providing an oil removal device and method for oily wastewater that is beneficial for the long-term stable operation of wastewater treatment systems.

Description

Technical Field

[0001] This invention pertains to water treatment processes, and more specifically, relates to a treatment system and method for tar-containing wastewater. Background Technology

[0002] Coal pyrolysis wastewater contains complex components such as tar, petroleum hydrocarbons, and phenols. Compared to oily wastewater from petrochemical plants, coal pyrolysis wastewater contains tar, which is sticky, contains asphaltenes, and is prone to solidification at low temperatures. This makes the treatment of tar-containing wastewater difficult: residual tar clogs the treatment device, tar-coated agglomerates reduce the efficiency of the oil separator, and oil blocks the respiration and metabolism of microorganisms.

[0003] A search revealed a Chinese patent application (application number 202011163336.1, publication date May 13, 2022) disclosing a method for removing oil from high-concentration oily wastewater. This method includes a hydrocyclone separator, an ultrasonic demulsifying reactor, and a corrugated oil removal device arranged sequentially. The ultrasonic demulsifying reactor is equipped with an ultrasonic transducer and an ultrasonic generator. A particle size analyzer is installed at the inlet of the ultrasonic demulsifying reactor, and a separation detector and a return pipeline are connected to the inlet of the ultrasonic demulsifying reactor at the outlet. Oil-water separation is achieved through a combination of hydrocyclone oil removal, ultrasonic demulsification, and sedimentation oil removal. However, this method has several drawbacks. First, it is only suitable for petrochemical oily wastewater. Treating tar-containing wastewater presents several problems: in the hydrocyclone separator, the hydrocyclone tubes are small, and long-term operation can lead to tar adhesion and blockage of the tube walls; furthermore, the density difference of tar-containing wastewater is small, resulting in poor centrifugation efficiency. Second, the device is complex and requires a large overall space. Summary of the Invention

[0004] 1. The problem to be solved

[0005] One of the objectives of this invention is to provide a treatment system for tar-containing wastewater, which aims to enhance the oil-water separation efficiency of tar-containing wastewater.

[0006] Another objective of this invention is to provide a method for treating tar-containing wastewater, achieving excellent separation of tar-containing wastewater at a lower ultrasonic demulsification frequency, ensuring stable wastewater quality after oil removal, creating favorable conditions for subsequent treatment, and providing an oil removal device and method for the long-term stable operation of wastewater treatment systems.

[0007] 2. Technical Solution

[0008] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0009] According to the purpose of this invention, a first aspect of the invention provides a treatment system for tar-containing wastewater, comprising:

[0010] The coarse particle separation unit consists of an inner tank and an outer tank, with the inner tank placed inside the outer tank and its lower end penetrating through the outer tank; the inner tank is used for sedimentation oil removal, and the outer tank is used for coalescence oil removal.

[0011] The demulsification and filtration unit has its inlet connected to the outlet of the outer tank after coalescence and oil removal, and is used for secondary coalescence and oil removal while simultaneously performing demulsification and oil removal.

[0012] When using the above technical solution, given the viscous and difficult-to-treat nature of tar in tar-containing wastewater, direct demulsification treatment is prone to clogging. In this application, the oil is first coarsened and then separated. At the same time, the oil particles in the discharged wastewater are smaller and then enter the demulsification separation treatment. By adopting a combination of coalescence oil removal and demulsification oil removal, tar-containing wastewater can be effectively treated.

[0013] As one possible implementation, in the coarse-grain separation unit:

[0014] The inner tank includes a flow guiding zone, an inclined plate separation zone, a settling zone, an oil sludge collection zone, and an oil-water separation zone. The flow guiding zone extends into the inner tank from top to bottom. The inclined plate separation zone is located between the outer wall of the flow guiding zone and the inner wall of the inner tank, forming a channel inclined to the inner wall of the inner tank. The settling zone is located below the flow guiding zone and the inclined plate separation zone. The oil sludge collection zone is located at the lower end of the inner tank. The oil-water separation zone is located in the upper part of the inner and outer tanks, above the inclined plate separation zone.

[0015] A coalescing plate separation zone is provided in the outer tank, which is located between the outer tank and the inner tank and below the oil-water separation zone.

[0016] As one possible implementation, the inclined plate separation zone is filled with inclined plate filler.

[0017] As one possible implementation, the demulsification filter unit includes a horizontal housing, inside which a coalescing filter element is installed, and an ultrasonic generator is wound around the outside of the housing at the location of the coalescing filter element; an oil collection bag is connected above the housing.

[0018] When the above technical solution is adopted, the tar-containing wastewater is first separated into coarse particles through a combination of sedimentation and coalescence oil removal in the coarse particle separation unit. The wastewater is then coarsened for the first oil-water separation. It enters the sedimentation zone in the inner tank from the guide zone. In the sedimentation zone, medium and light oils with a lower density than water float to the inclined plate separation zone. Although the inclined channel on the inner wall of the inner tank sacrifices some volume compared to the vertical channel, it can prolong the residence time in the inclined plate separation zone. In the inclined plate separation zone, oil, particulate matter, and water are separated more rapidly. As the heavy oil with a higher density than water in the sedimentation zone sinks to the oil sludge collection zone, it is discharged. The medium and light oils that float to the surface after passing through the inclined plate separation zone enter the oil-water separation zone and remain on top. The wastewater enters the outer tank through the opening at the top of the inner tank. After being coarsened by the coalescing plate separation zone, the oil in the wastewater is coarsened and floats upward. The wastewater then flows down to the outlet at the bottom of the outer tank and enters the demulsification filtration unit. The demulsification filtration unit uses a combination of coalescence oil removal and ultrasonic demulsification to perform a second oil-water separation and oil removal for fine-particle-size oily wastewater, achieving effective oil-water separation of tar-containing wastewater.

[0019] As one possible implementation, a baffle plate and an oil collection trough are provided in the oil-water separation zone. The lower end of the baffle plate is close to the opening of the inner tank, and wastewater is discharged from the opening of the inner tank and flows out from the lower end of the baffle plate through the action of the baffle plate. The oil collection trough is fixed around the upper end of the inner wall of the outer tank, and heavy oil and light oil pass over the upper end of the baffle plate and enter the oil collection trough.

[0020] As one possible implementation, a water collection unit is provided below the coalescing plate separation zone. The water collection unit is connected to the outlet below the outer tank and is used to discharge the wastewater at the bottom of the outer tank to the demulsification and filtration unit. The water collection unit includes a water collection ring pipe and a water collection hood. The water collection ring pipe is arranged around the inner wall of the outer tank, and several water collection hoods are arranged around the inner diameter of the water collection ring pipe and are connected to the water collection ring pipe.

[0021] As one possible implementation, the water collection hood includes at least one flared opening, preferably two flared openings connected in series to the water collection ring pipe. Through the suction effect, the water collection hood causes the oily substances to be further reduced in size and collected into the water collection ring pipe after being impacted by the flared opening. On the other hand, the flared opening facilitates uniform water collection and avoids flow deviation.

[0022] As one possible implementation, the water collection ring pipe is preferably a polygonal pipe, which facilitates stable fixation to the outer tank under suction.

[0023] As a possible implementation, to facilitate disassembly and cleaning, an oil scraping unit is also installed in the sludge collection area. The oil scraping unit includes an oil sludge collecting hopper and an oil sludge discharging hopper. The inner diameter of the oil sludge collecting hopper gradually decreases from top to bottom, which is conducive to the deposition of heavy oil, including asphaltenes, oil-adhered inorganic particles, etc. The oil sludge discharging hopper is a vertically arranged cylindrical tube of equal diameter, which uses gravity to discharge the heavy oil downwards.

[0024] As one possible implementation, the oil scraping unit also includes an oil scraper and a drive motor. That is, the oil scraper and the drive motor are installed in the oil sludge collection hopper. The drive motor is electrically connected to the oil scraper and drives the oil scraper to rotate around its center, thereby scraping away the accumulated oil on the inner wall of the oil sludge collection hopper.

[0025] As one possible implementation, the oil scraping unit also includes a heat tracing coil, which is wound around the outer wall of the oil sludge hopper to heat the oil and prevent it from hardening and clogging the outlet of the oil sludge hopper.

[0026] As one possible implementation, the inner tank and the outer tank are connected by a leveling pipe. Before starting the system, the valve on the leveling pipe is opened to ensure that the inner and outer tanks are level, so as to avoid generating an excessive internal and external pressure difference and to avoid damaging the outer tank. After the water surface is level, the valve on the leveling pipe is closed, and then the oil-water separation process is carried out.

[0027] A second aspect of the present invention provides a method for treating tar-containing wastewater, wherein the above-mentioned treatment system is used to treat the tar-containing wastewater, and the treatment method comprises the following steps:

[0028] S1. Coarse particle separation process: The tar-containing wastewater enters the coarse particle separation unit from the guide zone. Through the combination of sedimentation oil removal and coalescence oil removal, the coarse oil particles in the tar-containing wastewater are removed, and the wastewater containing fine-particle oil is discharged.

[0029] S2, Demulsification and Separation Process: The wastewater containing fine-particle oil discharged in step S1 is fed into the demulsification and filtration unit. The wastewater containing fine-particle oil is further degreased by a combination of coalescence oil removal and ultrasonic demulsification.

[0030] As one possible implementation, before the coarse particle separation step S1, ultrasonic demulsification treatment with a frequency of P0 is used on the tar-containing wastewater; after the coarse particle separation step S1, in the demulsification separation step S2, the frequency of ultrasonic demulsification is P, and P = (0.95~0.98)P0. Using the above technical solution, after the coarse particle separation step of this application, coarse oil particles are removed, and the oil particle size in the wastewater is reduced. This can lower the frequency of ultrasonic demulsification, reduce process difficulty, and is suitable for large-scale wastewater treatment.

[0031] 3. Beneficial effects

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] This invention provides a tar-containing wastewater treatment system that can simultaneously perform sedimentation oil removal, inclined plate oil removal, and coalescence oil removal functions within a settling tank-sized device, significantly reducing the equipment's footprint and material consumption. Specifically, the coarse particle separation unit, designed to address the clogging issues of heavy oil contamination, independently handles the removal of heavy oil and particulate matter, employing a simple structure and large internal space for easy maintenance. The demulsification filtration unit, connected independently to the coarse particle separation unit, allows for the use of more diverse structures and materials depending on water quality and treatment requirements. Under the combined action of ultrasound, the collision frequency of fine-diameter emulsified oil particles in the wastewater increases, greatly accelerating the coarsening process. Simultaneously, it allows the oil film to quickly detach from the surface of the coalescing filter element, preventing oil from passing through the filter element and improving treatment efficiency.

[0034] The complete treatment device and method of this invention are more adaptable to wastewater containing complex oily sludge and have a wider operating load range. They solve the problem of frequent equipment clogging and reduce equipment maintenance and consumable replacement. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of the processing system provided in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the internal structure of the processing system provided in an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of the oil scraping unit in the processing system provided in an embodiment of the present invention;

[0038] Figure 4 This is a top view of the coarse particle separation unit in the processing system provided in an embodiment of the present invention;

[0039] Figure 5 This is a top view of the water collection unit in the processing system provided in an embodiment of the present invention;

[0040] In the picture:

[0041] 1. Coarse particle separation unit; 11. Inner tank; 111. Guide zone; 112. Inclined plate separation zone; 113. Settling zone; 114. Oil sludge collection zone; 1141. Oil sludge collection hopper; 1142. Oil sludge discharge hopper; 1143. Oil sludge scraper; 1144. Drive motor; 1145. Heating coil; 115. Oil-water separation zone; 116. Baffle plate; 12. Outer tank; 121. Coalescing plate separation zone; 122. Water collection unit; 1221. Water collection ring pipe; 1222. Water collection hood; 123. Oil collection trough; 13. Leveling pipe; 2. Demulsification filtration unit; 21. Coalescing filter element; 22. Ultrasonic generator; 23. Oil collection bag; 3. Water inlet pipe; 4. Oil sludge discharge pipe; 5. Connecting pipe; 6. Oil discharge pipe; 7. Water outlet pipe. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments.

[0043] Example

[0044] This embodiment provides a treatment system for tar-containing wastewater, such as... Figure 1 As shown, the system includes a coarse particle separation unit 1 and a demulsification and filtration unit 2 arranged in sequence. The tar-containing wastewater enters the coarse particle separation unit 1 through the inlet pipe 3 for sedimentation and oil removal combined with coalescence and oil removal treatment. Then, it is transferred to the demulsification and filtration unit 2 through the connecting pipe 5 for secondary coalescence and oil removal while simultaneously demulsifying and removing oil.

[0045] Specifically, such as Figure 2 As shown, the coarse particle separation unit 1 consists of an inner tank 11 and an outer tank 12. The inner tank 11 is placed inside the outer tank 12, and the lower end of the inner tank 11 extends through the outer tank 12. The inner tank 11 is used for sedimentation and oil removal, and the outer tank 12 is used for coalescence and oil removal.

[0046] The inner tank 11 includes a flow guiding zone 111, an inclined plate separation zone 112, a settling zone 113, an oil sludge collection zone 114, and an oil-water separation zone 115.

[0047] The flow guide zone 111 is a flow guide tube that extends from top to bottom into the inner tank 11.

[0048] The inclined plate separation zone 112 is located between the outer wall of the guide zone 111 and the inner wall of the inner tank 11. The inclined plate separation zone 112 is filled with inclined plate packing to form a channel inclined to the inner wall of the inner tank 11, so as to prolong the residence time of wastewater.

[0049] Settling zone 113 is located below flow guiding zone 111 and inclined plate separation zone 112.

[0050] The sludge collection area 114 is located at the lower end of the inner tank 11; for ease of collection, the sludge collection area 114 has an inner diameter that gradually decreases from top to bottom, and heavy oil tends to deposit in the inclined sludge collection area 114; for ease of disassembly and cleaning, such as Figure 3As shown, an oil scraping unit is also installed in the sludge collection area 114. The oil scraping unit includes an oil sludge collection hopper 1141 and an oil sludge discharge hopper 1142. The inner diameter of the oil sludge collection hopper 1141 gradually decreases from top to bottom and is set to fit the oil sludge collection area 114, which is conducive to the deposition of heavy oil. The oil sludge discharge hopper 1142 is a cylindrical vertically set with a constant diameter, and uses gravity to discharge the heavy oil downward. In order to prevent heavy oil from caking, the oil scraping unit also includes an oil scraper 1143 and a drive motor 1144. That is, the oil scraper 1143 and the drive motor 1144 are installed in conjunction in the oil sludge collection hopper 1141. The drive motor 1144 is electrically connected to the oil scraper 1143, which drives the oil scraper 1143 to rotate around its center, thereby scraping away the oil accumulated on the inner wall of the oil sludge collection hopper 1141. To prevent oil from hardening, the oil scraping unit also includes a heat tracing coil 1145, which is wrapped around the outer wall of the oil sludge hopper 1142 to heat the oil and prevent it from hardening and clogging the outlet of the oil sludge hopper 1142. The outlet of the oil sludge hopper 1142 is connected to the oil sludge pipe 4.

[0051] The oil-water separation zone 115 is located in the upper part of the inner tank 11 and the outer tank 12, that is, above the inclined plate separation zone 112. To improve separation efficiency, a baffle plate 116 and an oil collection trough 123 are installed in the oil-water separation zone 115. The lower end of the baffle plate 116 is close to the opening of the inner tank 11. Wastewater is discharged from the opening of the inner tank 11 and flows out from the lower end of the baffle plate 116 through its action. Figure 4 As shown, the oil collection trough 123 is fixed around the upper end of the inner wall of the outer tank 12. Heavy oil and light oil pass over the upper end of the baffle plate 116 and enter the oil collection trough 123. The oil drain pipe 6 is connected to the oil collection trough 123 to drain the oil in the oil collection trough 123.

[0052] A coalescing plate separation zone 121 is provided in the outer tank 12. The coalescing plate separation zone 121 is located between the outer tank 12 and the inner tank 11 and below the oil-water separation zone 115. The coalescing plate separation zone 121 is filled with coalescing filler, such as metal wire mesh or materials with molecular adsorption force, to coarse oil particles and float them upward. Under the action of the coalescing plate separation zone 121, the coarse oil droplets are accelerated to separate and collect upward, while the wastewater flows downward into the lower part of the outer tank.

[0053] like Figure 5As shown, a water collection unit 122 is provided below the coalescing plate separation zone 121. The water collection unit 122 is connected to the outlet below the outer tank 12 and is used to discharge the wastewater at the bottom of the outer tank 12 to the demulsification filter unit 2. The water collection unit 122 includes a water collection ring pipe 1221 and a water collection hood 1222. The water collection ring pipe 1221 is a polygonal pipe that surrounds the inner wall of the outer tank 12. Several water collection hoods 1222 are arranged around the inner diameter of the water collection ring pipe 1221 and are connected to the water collection ring pipe 1221. Each branch water collection hood 1222 includes at least one flared opening. In this embodiment, it is preferred that the water collection hood 1222 includes two flared openings connected in series to the water collection ring pipe 1221. The water collection hood 1222 uses suction to, on the one hand, cause the oily substances to be further reduced in particle size and collected into the water collection ring pipe 1221 after being impacted by the flared openings; on the other hand, the flared openings facilitate uniform water collection and avoid flow deviation.

[0054] The inner tank 11 and the outer tank 12 are connected by a leveling pipe 13. Before starting the system, open the valve on the leveling pipe 13 to ensure that the inner tank 11 and the outer tank 12 are level, so as to avoid generating an excessive internal and external pressure difference and to avoid damaging the outer tank. After the water surface is level, close the valve on the leveling pipe 13 and then carry out the oil-water separation process.

[0055] like Figure 2 As shown, the demulsification filter unit 2 includes a horizontal housing, with coalescing filter elements 21 arranged horizontally and evenly inside the housing. The inlet end of the coalescing filter element 21 is connected to the connecting pipe 5, and the outlet end of the coalescing filter element 21 is connected to the outlet pipe 7. An ultrasonic generator 22 is evenly wound around the outside of the housing at the location of the coalescing filter element 21. An oil collection bag 23 is located above the housing at the location of the coalescing filter element 21 and is connected to it.

[0056] In this embodiment, the treatment method for tar-containing wastewater using the above-mentioned treatment system comprises the following steps:

[0057] S1. Coarse particle separation process: Tar-containing wastewater (total oil content 2500~3000mg / L, tar content ≥40%) enters coarse particle separation unit 1 through guide zone 111. Coarse particle separation unit 1 is filled with water. Through sedimentation oil removal combined with coalescence oil removal, coarse oil particles in the tar-containing wastewater are removed, and wastewater containing fine-particle oil is discharged.

[0058] The tar-containing wastewater enters the guide zone 111 through the inlet pipe 3, and then enters the sedimentation zone 113 and the inclined plate separation zone 112. In the inclined plate separation zone 112, oil, particulate matter and water are separated at an accelerated rate. The heavy oil and inorganic particles in the wastewater are separated in the sedimentation zone 113 and flow downward into the oil sludge collection zone 114.

[0059] Medium and light oils in the wastewater are initially separated upwards in the oil-water separation zone 115. The wastewater flows out of the inner tank 11 through the wastewater baffle 116 and enters the outer tank 12, passing downwards through the coalescing plate separation zone 121. Under the action of the coalescing plate separation zone 121, the coarse oil droplets are accelerated to separate and collect upwards, while the wastewater containing fine-particle oil flows downwards into the lower part of the outer tank 12.

[0060] S2, Demulsification and Separation Process: The wastewater containing fine-particle oil discharged in step S1 enters the demulsification and filtration unit 2, where the wastewater containing fine-particle oil is further degreased through a combination of coalescence oil removal and ultrasonic demulsification.

[0061] Wastewater containing fine-particle oil in the lower part of the outer tank 12 is evenly collected by the water collection unit 122 and enters the demulsification and filtration unit 2 through the connecting pipe 5. The demulsification and filtration unit 2 is also filled with water, and the coalescing filter element 21 is immersed in water. Oily substances cannot pass through the coalescing filter element 21. With the help of the ultrasonic generator 22, the emulsion is demulsified. The emulsified oil adheres to the surface of the coalescing filter element 21, increases in size due to collision, and then detaches and enters the oil collection bag 23. The wastewater is discharged through the coalescing filter element 21 and enters the outlet pipe 7. The total oil content in the wastewater discharged from the outlet pipe 7 is less than 150 mg / L, and the tar content is 3~7%. In the prior art, before the coarse particle separation process in step S1, ultrasonic demulsification treatment with a frequency of 20 kHz is used for tar-containing wastewater. In this embodiment, after the coarse particle separation process in step S1, the frequency of the ultrasonic generator 22 in the demulsification separation process in step S2 can be further reduced. In this embodiment, the frequency of the ultrasonic generator 22 is set to 19 kHz.

[0062] It should be noted that after a certain period of time, the medium and light oils accumulate to a certain oil layer thickness in the oil collection bag 23 at the top of the coarse particle separation unit 1 or the top of the demulsification and filtration unit 2. The water flow rate is adjusted to raise the liquid level to the oil discharge height of the oil collection tank 123, so that the oil enters the oil discharge pipe 6 and is discharged from the system.

[0063] Heavy oil and particulate matter mixed sludge accumulate in the sludge collection area 114. The sludge adhering to the wall of the sludge collection hopper 1141 is pushed into the bottom of the sludge discharge hopper 1142 by the sludge scraper 1143 and discharged from the system through the sludge inlet and outlet pipe 4.

[0064] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A treatment system for tar-containing wastewater, characterized in that: include: The coarse particle separation unit (1) consists of an inner tank (11) and an outer tank (12). The inner tank (11) is placed inside the outer tank (12), and the lower end of the inner tank (11) penetrates through the outer tank (12). The inner tank (11) is used for sedimentation oil removal, and the outer tank (12) is used for coalescence oil removal. The demulsification filter unit (2) has its inlet connected to the outlet of the outer tank (12) after coalescence and oil removal, and is used for secondary coalescence and oil removal while performing demulsification and oil removal. The demulsification filter unit (2) includes a horizontal shell, and a coalescence filter element (21) is installed inside the shell. An ultrasonic generator (22) is wrapped around the outside of the shell where the coalescence filter element (21) is located. An oil collection bag (23) is connected above the shell.

2. The tar-containing wastewater treatment system according to claim 1, characterized in that: In the coarse particle separation unit (1): The inner tank (11) includes a flow guiding area (111), an inclined plate separation area (112), a settling area (113), an oil sludge collection area (114), and an oil-water separation area (115). The flow guiding area (111) extends into the inner tank (11) from top to bottom. The inclined plate separation area (112) is located between the outer wall of the flow guiding area (111) and the inner wall of the inner tank (11), forming a channel inclined to the inner wall of the inner tank (11). The settling area (113) is located below the flow guiding area (111) and the inclined plate separation area (112). The oil sludge collection area (114) is located at the lower end of the inner tank (11). The oil-water separation area (115) is located in the upper part of the inner tank (11) and the outer tank (12). A coalescing plate separation zone (121) is provided in the outer tank (12), the coalescing plate separation zone (121) is located between the outer tank (12) and the inner tank (11), and is located below the oil-water separation zone (115).

3. The tar-containing wastewater treatment system according to claim 2, characterized in that: The inclined plate separation zone (112) is filled with inclined plate packing; the coalescing plate separation zone (121) is filled with coalescing packing.

4. The tar-containing wastewater treatment system according to claim 2, characterized in that: The oil-water separation zone (115) is provided with a baffle plate (116) and an oil collection trough (123). The lower end of the baffle plate (116) is close to the opening of the inner tank (11); the oil collection trough (123) is fixed around the upper end of the inner wall of the outer tank (12).

5. The tar-containing wastewater treatment system according to claim 2, characterized in that: A water collection unit (122) is provided below the coalescing plate separation area (121). The water collection unit (122) is connected to the outlet below the outer tank (12) and is used to discharge the wastewater at the bottom of the outer tank (12) to the demulsification filter unit (2). The water collection unit (122) includes a water collection ring pipe (1221) and a water collection cover (1222). The water collection ring pipe (1221) is arranged around the inner wall of the outer tank (12). Several water collection covers (1222) are arranged around the inner diameter of the water collection ring pipe (1221) and are connected to the water collection ring pipe (1221). The water collection cover (1222) includes at least one flared opening.

6. The tar-containing wastewater treatment system according to claim 5, characterized in that: The water collection cover (1222) has two flared openings connected in series to the water collection ring pipe (1221).

7. The tar-containing wastewater treatment system according to claim 2, characterized in that: The sludge collection area (114) is also equipped with an oil scraping unit, which includes an oil sludge collection hopper (1141) and an oil sludge discharge hopper (1142). The inner diameter of the oil sludge collection hopper (1141) gradually decreases from top to bottom. The oil sludge discharge hopper (1142) is a cylindrical vertically arranged hopper of equal diameter.

8. The tar-containing wastewater treatment system according to claim 7, characterized in that: The oil scraping unit also includes an oil scraper (1143) and a drive motor (1144). The oil scraper (1143) is installed inside the oil sludge hopper (1141), and the drive motor (1144) is electrically connected to the oil scraper (1143), driving the oil scraper (1143) to rotate around its center, used to scrape away the accumulated oil on the inner wall of the oil sludge hopper (1141); or, The oil scraping unit also includes an oil scraper (1143), a drive motor (1144), and a heat tracing coil (1145). The oil scraper (1143) is installed inside the oil sludge collection hopper (1141). The drive motor (1144) is electrically connected to the oil scraper (1143) and drives the oil scraper (1143) to rotate around its center to scrape off the accumulated oil on the inner wall of the oil sludge collection hopper (1141). The heat tracing coil (1145) is wound around the outer wall of the oil discharge sludge hopper (1142).

9. A method for treating tar-containing wastewater, characterized in that: To treat tar-containing wastewater using the treatment system according to any one of claims 1 to 8, the treatment method steps are as follows: S1. Coarse particle separation process: The tar-containing wastewater enters the coarse particle separation unit (1), and the coarse oil particles in the tar-containing wastewater are removed by sedimentation oil removal combined with coalescence oil removal, and the wastewater containing fine-particle oil is discharged. S2, Demulsification and Separation Process: The wastewater containing fine-particle-size oil discharged in step S1 is fed into the demulsification and filtration unit (2). The wastewater containing fine-particle-size oil is further degreased by coalescence oil removal combined with ultrasonic demulsification.

10. A method for treating tar-containing wastewater according to claim 9, characterized in that: Before the coarse particle separation process in step S1, ultrasonic demulsification treatment with a frequency of P0 is used on the tar-containing wastewater; after the coarse particle separation process in step S1, in the demulsification separation process in step S2, the frequency of ultrasonic demulsification is P, and P=(0.95~0.98)P0.

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