ethylene unit coke cleaning tank coke powder separation system

Abstract

This utility model relates to a coke powder separation system in a coke removal tank of an ethylene plant. The system includes a coke removal tank comprising a main coke removal tank and a secondary water tank arranged sequentially. The main coke removal tank and the secondary water tank are separated by an overflow plate device. The overflow plate device includes an overflow plate at the bottom and a gate plate located above the overflow plate and movable up and down relative to the overflow plate. The gate plate adjusts the opening of the overflow opening between the two tanks as its position relative to the overflow plate changes. The system also includes a filter device located adjacent to the gate plate and downstream of the overflow opening. The advantage is that it effectively separates coke powder, thereby reducing blockage of the downstream drainage pipe.

Description

Technical Field

[0001] This utility model relates to the field of coking technology for ethylene plants, and in particular to a coke powder separation system for a coking tank in an ethylene plant. Background Technology

[0002] In ethylene plants employing a pre-ethane removal and pre-hydrogenation process, the cracking furnace is often a CBL-R type. In this process, the feedstock reacts in the tubular cracking furnace at a high temperature of 840–860°C to generate various component cracked gases. The hydrocarbon thermal cracking process involves both primary and secondary reactions. The secondary reaction further reacts the lower hydrocarbons such as ethylene and propylene generated in the primary reaction, ultimately leading to coking or carbon formation.

[0003] During the coking process in the pyrolysis furnace, the coking gas from the furnace passes through the main coking valve and proceeds to the coking tank. The coking tank utilizes a cyclone separator and is equipped with three cooling water lines: the upper cooling water controls the temperature of the coking gas, the middle cooling water is used to collect small coke particles during coking, and the bottom cooling water is used to regulate the temperature of the wastewater discharged from the coking tank. The wastewater from the bottom enters the coking tank, where it settles naturally, leaving the coke particles at the bottom. The wastewater is then discharged into the wastewater system through an overflow outlet. Ideally, in this coking process, the coke particles aggregate and settle, with water at the top and coke at the bottom of the coking tank, and a large amount of coke remaining in the coking tank through overflow. However, in actual use, the coke powder particles carried out by the coking gas are too fine to be settled quickly by adding a large amount of water in the middle of the coking tank. During the coking process, the water volume is large, and the coke powder in the coking cleaning tank is in a water-coke powder mixed state. The fine coke powder floats on the top of the coking cleaning water. The overflow weir structure of the coking cleaning tank alone cannot effectively separate them, and the coke powder is easily carried to the sewage system in large quantities, causing blockage. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide a coke powder separation system for the coke cleaning tank of an ethylene plant that can effectively separate coke powder and thus reduce the blockage of the downstream drain pipe, in light of the current state of the technology.

[0005] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: a coke powder separation system for a coke cleaning tank in an ethylene plant, including a coke cleaning tank, wherein the coke cleaning tank includes a main coke cleaning tank and a secondary water tank arranged in sequence, the main coke cleaning tank and the secondary water tank are separated by an overflow plate device, the overflow plate device includes an overflow plate located at the bottom and a gate plate located above the overflow plate and capable of moving up and down relative to the overflow plate, the gate plate adjusts the opening degree of the overflow opening between the two as its position relative to the overflow plate changes;

[0006] It also includes a filter device located adjacent to the gate and downstream of the overflow opening.

[0007] After long-term use, the filter device is prone to clogging by coke powder and requires frequent cleaning or replacement. Considering the difficulty of maintaining a fixed filter device, the filter device is installed on the gate plate in a detachable manner.

[0008] The aforementioned "detachable method" can be understood as the filter device being installed through mechanical connection structures such as bolts, clips, or slide rails, and can be disassembled without damaging the main equipment (e.g., the filter frame is embedded in the gate slide groove and can be unlocked and removed by the handle).

[0009] The aforementioned detachable design facilitates disassembly, cleaning, or replacement of the filter screen, reducing downtime; it also eliminates the need to empty the descaling tank to maintain the filtration device, reducing labor costs.

[0010] As an improvement, the filtration device includes a filter plate, a filter screen assembly disposed on the side of the filter plate opposite to the gate, and a wire mesh pressure plate for pressing the filter screen assembly onto the filter plate. Pressing the filter screen assembly onto the filter plate with the wire mesh pressure plate effectively prevents filter screen deformation or detachment; the filter plate acts as a supporting frame, and the filter screen assembly can be replaced independently, extending the overall lifespan.

[0011] Considering that single-mesh filters are easily clogged by fine coke dust or unable to intercept ultrafine particles, the filter assembly includes a main filter in the center and auxiliary filters on both sides of the main filter. The main filter has a larger mesh size than the auxiliary filters. The auxiliary filters (lower mesh size) intercept larger coke dust first, effectively reducing the load on the main filter, while the main filter (higher mesh size) can be used to intercept residual ultrafine particles. Furthermore, this layered interception prevents premature clogging of the main filter, reduces maintenance frequency, and extends the cleaning cycle.

[0012] To facilitate the lifting operation of the filter device, the filter device also includes a frame plate arranged at the outer periphery of the filter plate. The frame plate has a groove in which the outer periphery of the filter plate is embedded, and a sealing gasket is provided between the outer periphery of the filter plate and the inner wall of the groove.

[0013] To facilitate cleaning of the filter assembly, an isolation gap is provided between the gate and the filter device;

[0014] It also includes a steam purging line, the steam outlet of which faces the isolation gap. Specifically, the narrow gap between the gate and the filter device can be 2-20 cm, preferably 5 cm, to avoid direct contact between the two and to provide a passage for steam purging. Steam purging can backwash the filter device to help restore its filtration capacity.

[0015] Considering that the secondary water tank still contains trace amounts of suspended coke powder after overflow, the secondary water tank is equipped with a sewage pipe outlet for sewage discharge, and the bottom of the secondary water tank is constructed with a settling depression area that is recessed from the bottom of the sewage pipe outlet.

[0016] The aforementioned "sedimentation depression" can refer to a trough-like structure with a localized depression at the bottom of the secondary water tank, used to collect sediment (e.g., the sedimentation depression can be a conical hopper or a rectangular trough, with the sewage pipe opening higher than its lowest point). The sedimentation depression in the secondary water tank allows gravity to further settle residual coke powder.

[0017] As an improvement, the height between the bottom wall of the settling depression and the sewage pipe is set within the range of 3-10cm. This 3-10cm depth balances the sedimentation space and water flow velocity, ensuring effective settling and preventing sludge from being discharged through the sewage pipe with the water flow.

[0018] Compared with existing technologies, the advantages of this invention are as follows: This invention adds a filter device downstream of the overflow outlet of the coke removal tank, adjacent to the gate. This filter device can directly and effectively intercept a large amount of fine coke carried in the overflow water of the main coke removal tank, preventing it from directly entering the secondary water tank and subsequent sewage system, thus fundamentally solving the key problem of fine coke powder clogging the sewer pipes. The main coke removal tank and the secondary water tank are designed in series and isolated by an overflow plate device. The main coke removal tank performs preliminary sedimentation (treating larger particles and some fine powder), while the secondary water tank provides secondary sedimentation space, further extending the residence time of the coke-containing water flow, promoting the sedimentation of finer coke powder, and improving the overall separation efficiency. The liftable gate can block floating coke. By adjusting the height of the gate to change the overflow opening, the overflow speed can be precisely controlled, ensuring the reliability of blocking floating coke and facilitating stable sedimentation in the main coke removal tank and the secondary water tank, reducing the amount of coke carried in the overflow. The entire system (overflow plate, gate, and filter) has a relatively simple structure, making it easy to modify or integrate with existing coke removal tanks. Modification costs are low, and maintenance is convenient (e.g., cleaning or replacing the filter). This utility model's coke powder separation system for ethylene plant coke removal tanks effectively separates coke powder from water, reducing the cost of a single coke removal cycle to 37.5% of the original level. Statistics show that the current operating coke removal volume per cycle is approximately 8.5 tons, with an average operating cycle of 3 months for the pyrolysis furnace, resulting in 4 cycles of coke removal per year, saving approximately 34 tons of solid waste. Simultaneously, it reduces the frequency of manual cleaning of the coke removal tank, decreasing the number of times a single tank needs cleaning from 4 times a year to 1-2 times a year, significantly reducing the workload for operators due to blocked downstream drain pipes. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the coke powder separation system in the coke cleaning tank according to an embodiment of the present invention;

[0020] Figure 2This is a partial structural schematic diagram of the coke powder separation system in the coke cleaning tank according to an embodiment of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0022] In the specification and claims of this utility model, terms indicating direction, such as "front," "rear," "upper," "lower," "left," "right," "side," "top," and "bottom," are used to describe various exemplary structural parts and elements of this utility model. However, the use of these terms is merely for the purpose of explanation and is based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in this utility model can be arranged in different orientations, these terms indicating direction are for illustrative purposes only and should not be regarded as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

[0023] Figures 1-2 This invention illustrates a coke powder separation system for a coke removal tank in an ethylene plant. The system includes a coke removal tank, which can be cast in concrete and consists of a main coke removal tank 11 and a secondary water tank 12 connected in series. The main coke removal tank 11 and the secondary water tank 12 are separated by an overflow plate device.

[0024] The overflow plate device includes a fixedly installed overflow plate 21 (which may be made of plastic or metal) and a liftable gate 22, which is located above the overflow plate 21. When the bottom of the gate 22 is raised (by manual or electric drive) to a set distance above the overflow plate 21, an overflow opening 20 is formed.

[0025] Along the direction of sewage overflow flow (e.g.) Figure 1 As shown by the horizontal solid arrow in the diagram, a detachable filter device 30 is installed 50mm downstream of the gate 22 (near the secondary water tank 12). This filter device 30 can be connected to the gate 22 via a sliding rail buckle (or other sliding limit structure). For example, a vertical T-slot can be provided on the side of the gate 22, and the frame of the filter device 30 can be embedded in the slot and locked by rotating the handle. To disassemble, simply rotate the handle in the opposite direction to pull it out as a whole.

[0026] The filter device 30 includes a filter plate 31 made of perforated steel plate, a filter screen assembly 32, a wire mesh pressing plate 33 for fixing the filter screen assembly 32, and a frame plate 34 arranged at the outer periphery of the filter plate 31. The frame plate 34 has a groove into which the outer periphery of the filter plate 31 is embedded, and a sealing gasket 35 is provided between the outer periphery of the filter plate 31 and the inner wall of the groove. The bottom frame plate 34 has a baffle of about 350mm downward, replacing the original overflow weir. The wire mesh pressing plate 33 can be used to tightly press the filter screen onto the surface of the filter plate 31 facing away from the gate plate 22 by bolts. The filter screen assembly 32 adopts a multi-layer filter configuration. Specifically, the filter screen assembly 32 adopts a three-layer structure: a 2-mesh auxiliary filter screen 322 is installed on the side facing the gate plate 22 (as a support filter screen, which can achieve primary interception), a 40-mesh main filter screen 321 (fine interception) is in the middle, and a 2-mesh auxiliary filter screen 322 (also as a support filter screen) is set on the other side of the gate plate 22. The detachable filter assembly 32 is formed by three layers of filter screens sandwiched together, with support filter screens on both sides and a working filter screen on the inside. Another important purpose of setting the auxiliary filter screen 322 as a support filter screen is to strengthen the overall strength of the filter assembly 32 and prevent breakage due to the large pressure difference across the main filter screen 321.

[0027] In this embodiment, a 50mm isolation gap 36 is reserved between the gate 22 and the filter device 30. A corresponding steam pipe is welded along the downstream side of the gate 22, and the steam pipe is connected to the steam purging pipeline 41. Steam nozzles with a diameter of 2mm can be installed on the steam pipe at 100mm intervals, and the axis of the nozzles is inclined at a certain angle to the filter screen. The operator can use the steam manual valve of the service station to purge the coke powder attached to the filter screen assembly 32 online.

[0028] In this embodiment, the secondary water tank 12 has a rectangular settling depression 122 at its bottom. The main descaling tank 11 is sloped at a certain angle, with a 3cm drop, and its bottom is higher than that of the secondary water tank 12, thus improving the problem of water accumulation at the bottom. The secondary water tank 12 has a sewage pipe outlet 121, the bottom of which is 50mm higher than the bottom wall of the settling depression 122.

[0029] This embodiment can add handles to the gate 22 and filter device 30, and set up a coke tank suspension pulley to hook the gate 22 and filter screen handles. The bottom opening of the gate 22 can be adjusted by operating the pulley. Coke powder enters the main coke cleaning tank 11 from the coke drop port of the cyclone separator 42. Because the coke powder particles carried out by the coking gas are too fine, they cannot be aggregated and settled in a short time by adding a large amount of water in the middle of the coking tank. During coking, the water volume is large, and the coke powder in the main coke cleaning tank 11 is in a water-coke powder mixed state. The mixed water-coke powder in the main coke cleaning tank 11 enters water through the bottom opening of the gate 22, which effectively controls most of the floating coke from entering between the gate 22 and the filter device 30. The overflow part is filtered through the filter screen assembly 32 and enters the secondary water tank 12. After natural settling in the settling depression 122 before the sewage pipe outlet 121, the secondary overflowing coke cleaning water is discharged from the sewage pipe outlet 121. In this embodiment, the coke powder separation system in the coke removal tank has been improved from the original single overflow method to a method of valve plate blocking floating coke - overflow - filtration - re-sedimentation - re-overflow filtration entering the sewage system, which effectively solves the problem that the coke removal water contains both floating coke and settled coke.

[0030] This invention adds a filter device 30 downstream of the overflow outlet of the coke removal tank, adjacent to the gate 22. This filter device 30 can directly and effectively intercept a large amount of fine coke carried in the overflow water of the main coke removal tank 11, preventing it from directly entering the secondary water tank 12 and subsequent sewage system, thus fundamentally solving the key problem of fine coke powder clogging the sewer pipe. The main coke removal tank 11 and the secondary water tank 12 are designed in series and isolated by an overflow plate device. The main coke removal tank 11 performs preliminary sedimentation (treating larger particles and some fine powder), while the secondary water tank 12 provides secondary sedimentation space, further extending the residence time of the coke-containing water flow, promoting the sedimentation of finer coke powder, and improving the overall separation efficiency. The liftable gate 22 can block floating coke. By adjusting the height of the gate 22 to change the opening of the overflow opening 20, the overflow speed can be precisely controlled, ensuring the reliability of blocking floating coke and facilitating the stable sedimentation of the main coke removal tank 11 and the secondary water tank 12, reducing the amount of coke carried in the overflow. The entire system (overflow plate 21, gate 22, filter device 30) has a relatively simple structure, making it easy to modify or integrate with existing coke removal tanks. Modification costs are low, and maintenance and operation are convenient (e.g., cleaning or replacing filter device 30). This utility model's coke powder separation system for ethylene plant coke removal tanks effectively separates coke powder from water, reducing the cost of a single coke removal cycle to 37.5% of the original level. Statistics show that the current operating coke removal volume per cycle is approximately 8.5 tons, the average operating cycle of the pyrolysis furnace is 3 months, and there are a total of 4 coke removal cycles per year, saving approximately 34 tons of solid waste. Simultaneously, it reduces the number of times the coke removal tank needs manual cleaning, from 4 times per year to 1-2 times per year for a single tank, significantly reducing the workload for operators due to blocked downstream drain pipes.

Claims

1. A coke powder separation system for a coke removal tank in an ethylene plant, comprising a coke removal tank, wherein the coke removal tank includes a main coke removal tank (11) and a secondary water tank (12) arranged sequentially, the main coke removal tank (11) and the secondary water tank (12) being isolated by an overflow plate device, characterized in that: The overflow plate device includes an overflow plate (21) located at the bottom and a gate (22) located above the overflow plate (21) and capable of moving up and down relative to the overflow plate (21). The gate (22) adjusts the opening of the overflow opening (20) between the two as its position relative to the overflow plate (21) changes. It also includes a filter device (30) disposed adjacent to the gate (22) and located downstream of the overflow opening (20).

2. The coke powder separation system for the coke cleaning tank of an ethylene plant according to claim 1, characterized in that: The filter device (30) is detachably mounted on the gate (22).

3. The coke powder separation system for the coke cleaning tank of an ethylene plant according to claim 2, characterized in that: The filtration device (30) includes a filter plate (31), a filter screen assembly (32) arranged on the side of the filter plate (31) away from the gate (22), and a wire mesh pressure plate (33) for pressing the filter screen assembly (32) onto the filter plate (31).

4. The coke powder separation system for the coke cleaning tank of an ethylene plant according to claim 3, characterized in that: The filter assembly (32) includes a main filter (321) located in the middle and auxiliary filters (322) located on the front and rear sides of the main filter (321). The mesh count of the main filter (321) is greater than that of the auxiliary filters (322).

5. The coke powder separation system for the coke cleaning tank of an ethylene plant according to claim 3, characterized in that: The filter device (30) further includes a frame plate (34) arranged at the outer periphery of the filter plate (31), the frame plate (34) having a groove into which the outer periphery of the filter plate (31) is embedded, and a sealing gasket (35) is provided between the outer periphery of the filter plate (31) and the inner wall of the groove.

6. The coke powder separation system for the coke cleaning tank of an ethylene plant according to any one of claims 1 to 5, characterized in that: There is an isolation gap (36) between the gate (22) and the filter device (30); It also includes a steam purging line (41) with its steam outlet facing the isolation gap (36).

7. The coke powder separation system for the coke cleaning tank of an ethylene plant according to any one of claims 1 to 5, characterized in that: The secondary water tank (12) is provided with a sewage outlet (121) for sewage discharge, and the bottom of the secondary water tank (12) is constructed with a settling depression area (122) that is recessed from the bottom of the sewage outlet (121).

8. The coke powder separation system for the coke cleaning tank of an ethylene plant according to claim 7, characterized in that: The height between the bottom wall of the settling depression (122) and the sewage pipe ranges from 3 to 10 cm.

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