Method for treating coking oily wastewater

Abstract

The present application discloses a coking oily sewage treatment method, which overcomes the problems of many treatment procedures and long process in the prior art. The method comprises three steps of 1) loading coke, 2) filtering and 3) flushing, wherein the step 1) is that the water containing coke powder is sequentially passed through the one-way anti-mixing hole plate, the coke layer partition plate and the Johnson net at the bottom of the oily sewage treatment tank from top to bottom in the oily sewage treatment tank, the coke powder is intercepted on the Johnson net, and the step is stopped after the coke powder layer with a thickness of more than 300 mm is formed on the Johnson net; the step 2) is that the oily sewage is sequentially passed through the one-way anti-mixing hole plate, the coke layer partition plate and the coke powder layer formed in the step 1) in the oily sewage treatment tank, the oil in the oily sewage is attached to the surface of the coke particles in the coke powder layer, and the step is stopped after the coke powder layer is gradually accumulated to a certain thickness; and the step 3) is that the flushing water is used to backwash the coke powder layer formed in the step 2), and the coke powder water solution in the coke powder layer is flushed out by the upper flushing water and the lateral flushing water, and the step is stopped after the flushing is completed.

Description

Technical Field

[0001] This invention belongs to the field of coking, and specifically relates to a method for treating oily wastewater from coking. Background Technology

[0002] Delayed coking is an important residual oil processing step in petroleum refining. After being heated to approximately 500°C in a heat exchanger and coking furnace, the feedstock enters a coking tower for thermal cracking and condensation reactions, generating oil and gas as well as solid coke. The oil and gas produced by the thermal cracking reaction enter a fractionation tower via the oil and gas pipeline at the top of the coking tower, where they are separated into rich gas and fractions such as naphtha, diesel, and wax oil. The solid coke settles inside the coking tower and is periodically removed and deposited into a coke pool.

[0003] Wastewater from delayed coking units mostly contains oil and coke powder, especially the wastewater from the top of the vent tower, which has a high oil content, is severely emulsified, and carries coke powder, making oil-water separation difficult. Even after gravity settling, the oil content of the wastewater often fails to meet standards, making it unsuitable for downstream acid stripping units or wastewater treatment plants. Wastewater treatment from the top of the coking vent tower is one of the technical challenges of this unit.

[0004] The conventional method for degreasing oily wastewater is static settling. Static settling requires large storage tanks, and for heavily emulsified wastewater, a long settling time is necessary. If degreasing is ineffective, a demulsifier needs to be injected to promote oil-water separation and accelerate the dehydration process. These methods are costly, inefficient, and require the introduction of a third medium, the demulsifier, which may generate additional pollution.

[0005] Another commonly used method for removing oil from oily wastewater is the coalescence method. The coalescence method encompasses the coalescence and corresponding sedimentation processes, primarily treating emulsified oil in water. This method utilizes the significant difference in affinity between oil and water for the coalescing material. Oil droplets are captured by the coalescing material and retained on its surface and within its pores, forming an oil film. When the oil film reaches a certain thickness, it detaches under the influence of hydraulic and buoyancy, breaking down into larger oil droplets. These larger droplets then easily settle and separate from the water. However, the wastewater at the top of the venting tower carries a large amount of coke powder, which can easily clog the coalescing material. Therefore, this method is not suitable for treating oily wastewater containing solid particles.

[0006] Chinese patent ZL201520308628.8 discloses a system for treating oily wastewater from delayed coking in petroleum refining, including a homogenizing buffer tank, a coke powder filter, a rapid filter, an oil-water separator, and a treated water storage tank. The oil-water separator is a two-stage system, consisting of a GOS-A oil-water separator and a GOS-B oil-water separator. This technology offers fast separation speed, short separation time, and high separation accuracy. The separated oil is of high quality with low water content, allowing for oil recovery and reuse. However, this system requires the integration of multiple treatment methods such as filtration, coalescence, and sedimentation to treat the coking oily wastewater to the required standards. Therefore, it involves numerous treatment steps, a long process, and a large number of pieces of equipment, resulting in high complexity. Summary of the Invention

[0007] The purpose of this invention is to provide a method for treating oily wastewater from coking plants, which utilizes the coke produced in the coking unit to remove oil and coke powder from the wastewater, overcoming the problems of multiple processing steps and long processes in the existing technology.

[0008] To achieve the above objectives, the present invention provides a method for treating oily wastewater from coking plants, characterized by comprising the following steps:

[0009] 1) Loading coke

[0010] Water containing coke powder in the coking unit enters the oily wastewater treatment tank from the top. Inside the tank, it passes sequentially from top to bottom through a one-way anti-mixing perforated plate, a coke layer baffle, and a Johnson screen at the bottom of the oily wastewater treatment tank. The coke powder is trapped on the Johnson screen, while the water flows out through the bottom outlet of the oily wastewater treatment tank and then returns to the coking unit or other devices. After a coke powder layer with a thickness of 300 mm or more, preferably 300 to 1000 mm, is formed on the Johnson screen, this step is stopped, and step 2) is performed. The water containing coke powder in the coking unit has a coke powder volume content of 5% or more, usually 5% to 30%, preferably 10% to 25%.

[0011] 2) Filtration

[0012] Oily wastewater in the coking unit enters the oily wastewater treatment tank from the top. Inside the tank, it passes sequentially through a one-way anti-mixing perforated plate, a coke layer baffle, and the coke powder layer formed in step 1). After passing through the coke powder layer, the water flows out from the bottom outlet of the oily wastewater treatment tank and is sent to the downstream acidic water stripping unit or other units. The oil in the oily wastewater adheres to the surface of the coke particles in the coke powder layer, thus removing the oil from the water. After a period of operation, the coke powder layer gradually accumulates to a certain thickness, usually near the bottom of the coke layer baffle, and can no longer receive coke powder carried by the oily wastewater; or the coke powder layer has adsorbed a lot of oily wastewater, and the pressure difference of the oily wastewater through the coke powder layer increases to a certain value, usually ≤150 kPa, preferably 20-200 kPa. At this point, this step is stopped, and step 3) is performed.

[0013] 3) Rinse

[0014] Rinse water enters the oily wastewater treatment tank from the bottom in reverse to backwash the coke powder layer formed in step 2) and loosen it. At the same time, upper rinse water enters the oily wastewater treatment tank from the top to prevent the coke powder from moving upward. Lateral rinse water enters the oily wastewater treatment tank from the side rinse port to wash away the coke powder water solution of the coke powder layer and discharge it to the coke pool or other device through the coke discharge port on the side of the tank. After rinsing is completed, this step is stopped.

[0015] 4) After rinsing in step 3), repeat steps 1) → 2) → 3) in a continuous cycle.

[0016] The unidirectional anti-mixing perforated plate in steps 1) and 2) is one layer or multiple layers.

[0017] The present invention provides a method for treating oily wastewater from coking plants, the further technical feature of which is that: in step 1), the water containing coke powder in the coking unit is cooled and then enters an oil-water separator for preliminary separation, and after being pressurized, it is sent to an oily wastewater treatment tank.

[0018] The present invention discloses a method for treating oily wastewater from coking plants, further characterized in that: in step 1), the water containing coke powder in the coking unit is typically a mixture of one or more of the following: coke pool, cold coke water tank, coke slurry tank (Triplelan closed coke removal technology), dehydration chamber, and collection tank (S-CCHS closed coke removal technology); in step 2), the oily wastewater in the coking unit is typically from the three-phase separator at the top of the venting tower and / or the three-phase separator at the top of the fractionation tower.

[0019] The present invention provides a method for treating coking oily wastewater, the further technical feature of which is that: in step 2), water flows out from the bottom outlet of the oily wastewater treatment tank after passing through the coke powder layer, and is then filtered by a filter and sent to a downstream acidic water stripping unit or other devices.

[0020] The present invention provides a method for treating oily wastewater from coking plants, wherein the coke layer partition is located 500-1200 mm above the Johnson mesh.

[0021] The present invention discloses a method for treating oily wastewater from coking plants, further characterized in that: the unidirectional anti-mixing perforated plate is a flat plate with holes on its surface, the perforation rate being 5-25%, preferably 10-20%, and the diameter of the holes being 10-15 mm; the coke layer partition plate is a flat plate with holes on its surface, the perforation rate being 5-25%, preferably 10-20%, and the diameter of the holes being 5-8 mm.

[0022] The present invention discloses a method for treating oily wastewater from coking plants, further characterized in that: there are at least two flushing ports on the side of the tank, preferably two to four, wherein at least one is located above and adjacent to the Johnson mesh, and at least one is located below and adjacent to the coke layer partition; there are at least four coke discharge ports on the side of the tank, preferably four to six, wherein at least one is located above and adjacent to the Johnson mesh, at least one is located below and adjacent to the coke layer partition, at least one is located above and adjacent to the coke layer partition, and at least one is located above and adjacent to the uppermost unidirectional anti-mixing perforated plate.

[0023] This invention discloses a method for treating oily wastewater from coking plants. A further technical feature is that the method includes 1-5 layers of unidirectional anti-mixing orifice plates. When more than 2 layers are used, the distance between adjacent unidirectional anti-mixing orifice plates is 0.5-2m, preferably 1-2m. The function of the unidirectional anti-mixing orifice plates is to prevent backflow and mixing of the fluid medium within the oily wastewater treatment tank, making the liquid flow more stable and closer to plug flow.

[0024] This invention is mainly used for coking wastewater treatment, and is especially suitable for the treatment of oily and coke powder-containing wastewater from the top of coking gas blowing towers (contact cooling towers).

[0025] Advantages of this invention compared to existing technologies: This invention provides a method for treating oily wastewater from coking plants. It utilizes coke, a byproduct of coking, to form a filter layer. By setting up Johnson screens, unidirectional anti-mixing perforated plates, side flushing ports, and side coke discharge ports on the tank, the method achieves the purpose of removing oil and coke powder from coking wastewater through a three-step cyclical operation of coke loading, filtration, and flushing. This allows the wastewater to meet discharge standards or be sent to downstream plants and wastewater treatment plants.

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this does not limit the scope of the invention. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the process of applying the coking oily wastewater treatment method of the present invention to a coking unit.

[0028] The reference numerals in the figure are:

[0029] 1-Oil-containing wastewater treatment tank; 2-Johnson screen; 3-One-way anti-mixing orifice plate; 4-Top inlet; 5-Bottom outlet; 6-Side flushing port; 7-Side coke discharge port; 8-Coke powder water inlet pipeline; 9-Oil-containing wastewater inlet pipeline; 10-Upper flushing water pipeline; 11-Side flushing water pipeline; 12-Bottom flushing water pipeline; 13-Side coke discharge water pipeline; 14-Coke powder water outlet pipeline; 15-Oil-containing wastewater outlet pipeline;

[0030] 21-Coke powder water inlet valve; 22-Coke powder water outlet valve; 23-Oil-containing wastewater inlet valve; 24-Oil-containing wastewater outlet valve; 25-Bottom flushing water inlet valve; 26-Side flushing water inlet valve; 27-Coke discharge water outlet valve; 28-Upper flushing water inlet valve; 29-Coke bed partition;

[0031] 31-Oil-water separator at the top of the venting tower; 32-Sewage pump at the top of the venting tower; 33-Filter; 34-Coke pit; 35-Slurry pump; 36-Pipeline at the top of the venting tower. Detailed Implementation

[0032] Figure 1 The tank shown has two side flushing ports: one located above and adjacent to the Johnson mesh, and the other located below and adjacent to the coke layer partition.

[0033] Figure 1 The tank shown has four coke discharge ports on its side. One port is located above and adjacent to the Johnson mesh, the second port is located below and adjacent to the coke layer partition, the third port is located above and adjacent to the coke layer partition, and the fourth port is located above and adjacent to the topmost one-way anti-mixing perforated plate.

[0034] like Figure 1 As shown, all valves are closed before the device is put into operation. It includes an oily wastewater treatment tank 1. The tank 1 has a top inlet 4 and a bottom outlet 5. Side flushing ports 6 are located at different heights along the vertical direction on the sides. On the opposite side, coke discharge ports 7 are located at different heights along the vertical direction on the other side. A Johnson screen 2 is installed at the bottom of the tank 1, and a coke layer baffle 29 is installed above the Johnson screen 2. A one-way anti-mixing perforated plate 3 is installed between the top end cap of the oily wastewater treatment tank 1 and the coke layer baffle 29. An oily wastewater inlet pipeline 9 connects to the top inlet 4 and is equipped with an oily wastewater inlet valve 23. Coke powder water enters... The feed line 8 is connected to the top inlet 4 of the tank or merges with the oily wastewater feed line 9 before connecting to the top inlet 4 of the tank. The coke powder water feed line 8 is equipped with a coke powder water feed valve 21. The upper flushing water line 10 is connected to the top inlet 4 of the tank or merges with the oily wastewater feed line 9 before connecting to the top inlet 4 of the tank. The upper flushing water line 10 is equipped with an upper flushing water feed valve 28. The bottom flushing water line 12 is connected to the bottom outlet 5 of the tank. The bottom flushing water line 12 is equipped with a bottom flushing water feed valve 25. The coke powder water discharge line 14 and the oily wastewater discharge line 15 are respectively connected to the bottom outlet 5 of the tank. The coke powder water discharge line 14 and the oily wastewater discharge line 15 are respectively equipped with a coke powder water discharge valve 22 and an oily wastewater discharge valve 24.

[0035] The method for treating oily wastewater from coking plants, when applied to coking units, includes the following steps:

[0036] 1) Loading coke

[0037] Open the coke powder water inlet valve 21 and the coke powder water outlet valve 22. The coke powder-containing water from the coke pit 34 is pressurized by the slurry pump 35, and then enters the oily wastewater treatment tank 1 through the coke powder water inlet pipeline 8 at the top inlet 4. Inside the tank, it passes from top to bottom through the one-way anti-mixing perforated plate 3, the coke layer baffle 29, and the Johnson screen 2 at the bottom of the oily wastewater treatment tank. When passing through the Johnson screen 2 at the bottom of the oily wastewater treatment tank 1, the coke powder is intercepted on the Johnson screen 2, gradually forming a coke powder layer of a certain thickness, while the water passes through... The bottom outlet 5 flows out from the coke powder water discharge pipeline 14 and then returns to the coke pool 34 or other devices in the coking unit. After the coke powder layer formed on the Johnson screen 2 is 300 mm or more, preferably 300 to 1000 mm thick, the coke powder water inlet valve 21 and the coke powder water outlet valve 22 are closed, this step is stopped, and step 2) is carried out. The coke powder water contains 5% or more of coke powder by volume, usually preferably 5% to 30% by volume, and more preferably 10% to 25% by volume.

[0038] 2) Filtration

[0039] Open the oily wastewater inlet valve 23 and the oily wastewater outlet valve 24. The oily wastewater separated by the oil-water separator 31 at the top of the venting tower is pressurized by the wastewater pump 32 at the top of the venting tower, and then enters the oily wastewater treatment tank 1 through the oily wastewater inlet pipeline 9 at the tank top inlet 4. Inside the tank, the wastewater passes from top to bottom through the one-way anti-mixing perforated plate 1, the coke layer partition 29, and the coke powder layer formed in step 1). Due to the bridging between coke particles in the coke powder layer to form microchannels and the presence of micropores in the coke powder structure, water can flow smoothly through the channels or pores, while the oil in the water tends to adhere to the surface of the coke particles, thus achieving the removal of oil from the water. In addition, the filter layer can intercept or filter out the coke powder carried in the oily wastewater. After passing through the coke powder layer formed in step 1) in the oily wastewater treatment tank 1, the water comes out from the oily wastewater discharge pipeline 15 through the bottom outlet 5 of the tank. After being filtered by the filter 33, it is sent to the downstream acidic water stripping unit or other units. The oil in the oily wastewater adheres to the surface of the coke particles in the coke powder layer, thereby removing the oil from the water. After running for a period of time, the coke powder layer gradually accumulates to a certain thickness, usually below the coke layer partition, and can no longer receive the coke powder carried by the oily wastewater; or the coke powder layer has adsorbed a lot of sludge oil, and the pressure difference of the oily wastewater through the coke powder layer increases to a certain value, usually ≤150kPa, preferably 20-200kPa. At this time, it is necessary to flush and replace the coke layer. Close the oily wastewater inlet valve 23 and the oily wastewater outlet valve 24, stop this step, and proceed to step 3).

[0040] 3) Rinse

[0041] First, open the bottom flushing water inlet valve 25. The flushing water enters the oily wastewater treatment tank 1 in reverse through the bottom flushing water pipeline 12 to backwash the coke powder layer formed in step 2) and loosen it. Then, open the side flushing water inlet valve 26, the coke discharge water outlet valve 27, and the upper flushing water inlet valve 28. The upper flushing water enters the oily wastewater treatment tank 1 through the upper flushing water pipeline 10 to prevent the coke powder from moving upward. The side flushing water enters the oily wastewater treatment tank 1 through the side flushing water pipeline 11 and the side flushing port 6 to wash away the coke powder water solution from the coke powder layer. The water is then discharged to the coke pool or other devices through the side coke discharge port 7 and the coke discharge water pipeline 13. After flushing, close the bottom flushing water inlet valve 25, the side flushing water inlet valve 26, the coke discharge water outlet valve 27, and the upper flushing water inlet valve 28 to stop this step.

[0042] 4) After rinsing in step 3), repeat steps 1)→2)→3) above, and so on.

[0043] The unidirectional anti-mixing perforated plate in steps 1) and 2) is one layer or multiple layers, as shown in the figure, which is two layers.

[0044] In step 1), the water containing coke powder in the coking unit is usually a mixture of one or more of the following: coke pool, cold coke water tank, coke slurry pool (triplan closed coke removal technology), dehydration chamber, and water collection tank (S-CCHS closed coke removal technology); in step 2), the oily wastewater in the coking unit is usually from the three-phase separator at the top of the venting tower and / or the three-phase separator at the top of the fractionation tower.

[0045] The coke layer partition is located 500-1200 mm above the Johnson web.

[0046] The unidirectional anti-mixing perforated plate is a flat plate with holes on its surface, the perforation rate being 5-25%, preferably 10-20%, and the diameter of the holes being 10-15 mm. The coke layer partition plate is a flat plate with holes on its surface, the perforation rate being 5-25%, preferably 10-20%, and the diameter of the holes being 5-8 mm.

Claims

1. A method for treating oily wastewater from coking plants, characterized in that... Includes the following steps: 1) Loading coke Water containing coke powder in the coking unit enters the oily wastewater treatment tank from the top. Inside the tank, it passes sequentially from top to bottom through a one-way anti-mixing perforated plate, a coke layer baffle, and a Johnson screen at the bottom of the oily wastewater treatment tank. The coke powder is trapped on the Johnson screen, while the water flows out through the bottom outlet of the oily wastewater treatment tank and then returns to the coking unit or other devices. After a coke powder layer with a thickness of 300 mm or more, preferably 300 to 1000 mm, is formed on the Johnson screen, this step is stopped, and step 2) is performed. The water containing coke powder in the coking unit has a coke powder volume content of 5% or more. 2) Filtration Oily wastewater in the coking unit enters the oily wastewater treatment tank from the top. Inside the tank, it passes sequentially through a one-way anti-mixing perforated plate, a coke layer baffle, and the coke powder layer formed in step 1). After passing through the coke powder layer, the water flows out from the bottom outlet of the oily wastewater treatment tank and is sent to the downstream acidic water stripping unit or other units. The oil in the oily wastewater adheres to the surface of the coke particles in the coke powder layer, thus removing the oil from the water. After a period of operation, the coke powder layer gradually accumulates to a certain thickness and can no longer receive the coke powder carried by the oily wastewater; or the coke powder layer has adsorbed a lot of oily wastewater, and the pressure difference of the oily wastewater through the coke powder layer increases to ≤150kPa. At this time, this step is stopped, and step 3) is performed. 3) Rinse The flushing water enters the oily wastewater treatment tank from the bottom in reverse to backwash the coke powder layer formed in step 2) and loosen the coke powder layer. At the same time, the upper flushing water enters the oily wastewater treatment tank from the top, and the side flushing water enters the oily wastewater treatment tank from the side flushing port to wash away the coke powder water solution of the coke powder layer and discharge it to the coke pool or other device through the coke discharge port on the side of the tank. After the flushing is completed, this step is stopped. 4) After rinsing in step 3), repeat steps 1) → 2) → 3) in a continuous cycle. The unidirectional anti-mixing perforated plate in steps 1) and 2) is one layer or multiple layers.

2. The method for treating oily wastewater from coking plants according to claim 1, characterized in that: In step 1), the water containing coke powder in the coking unit is cooled and then enters an oil-water separator for preliminary separation. After being pressurized, it is sent to an oily wastewater treatment tank.

3. The method for treating oily wastewater from coking plants according to claim 1, characterized in that: In step 1), the water containing coke powder in the coking unit usually comes from the coke pool, cold coke water tank, coke slurry pool, dehydration chamber or water collection tank; in step 2), the oily wastewater in the coking unit usually comes from the three-phase separator at the top of the venting tower or the three-phase separator at the top of the fractionation tower.

4. The method for treating oily wastewater from coking plants according to claim 1, characterized in that: In step 2), the water flows out from the bottom outlet of the oily wastewater treatment tank after passing through the coke powder layer, and is then filtered by a filter and sent to the downstream acidic water stripping unit or other units.

5. The method for treating oily wastewater from coking plants according to claim 1, characterized in that: The coke layer partition is located 500-1200 mm above the Johnson web.

6. The method for treating oily wastewater from coking plants according to claim 1, characterized in that: The unidirectional anti-mixing perforated plate is a flat plate with holes on its surface, the perforation rate being 5-25%, preferably 10-20%, and the diameter of the holes being 10-15mm; the coke layer partition plate is a flat plate with holes on its surface, the perforation rate being 5-25%, preferably 10-20%, and the diameter of the holes being 5-8mm.

7. The method for treating oily wastewater from coking plants according to claim 1, characterized in that: The tank side has at least two flushing ports, at least one of which is located above and adjacent to the Johnson mesh, and at least one is located below and adjacent to the coke layer partition; the tank side has at least four coke discharge ports, at least one of which is located above and adjacent to the Johnson mesh, at least one of which is located below and adjacent to the coke layer partition, at least one of which is located above and adjacent to the coke layer partition, and at least one of which is located above and adjacent to the uppermost unidirectional anti-mixing perforated plate.

8. The method for treating oily wastewater from coking plants according to claim 7, characterized in that: The tank side has 2-4 flushing ports; the tank side has 4-6 coke discharge ports.

9. A method for treating oily wastewater from coking plants according to claim 1, characterized in that: The unidirectional anti-mixing orifice plates consist of 1-5 layers. When more than 2 layers are installed, the distance between adjacent unidirectional anti-mixing orifice plates is 0.5-2m, preferably 1-2m. The function of the unidirectional anti-mixing orifice plates is to prevent backflow and mixing of the fluid medium in the oily wastewater treatment tank, making the liquid flow more stable and closer to plunger flow.

10. A method for treating oily wastewater from coking plants according to claim 1, characterized in that: In step 1), the water containing coke powder in the coking unit has a coke powder volume content of 5% to 30%, preferably 10% to 25%; in step 2), the oily wastewater increases to 20-200 kPa through the coke powder layer pressure difference, at which point this step is stopped and step 3 is performed.

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