A caprolactam refining tail gas treatment device and method

Abstract

The application discloses a caprolactam refining tail gas treatment device and method, and relates to the technical field of chemical equipment. The device comprises an amide oil storage tank for buffering and storing absorption liquid. An ammonium sulfate device for conveying the absorption liquid is arranged at the upper end of the amide oil storage tank. The liquid outlet end of the amide oil storage tank is in communication with the liquid inlet end of an amide oil conveying pump. The amide oil conveying pump is connected with a tail gas absorption tower for absorbing tail gas. The liquid inlet position of the tail gas absorption tower is arranged at the left upper side. In the caprolactam tail gas treatment design, the tail gas absorption tower is added. Meanwhile, the amide oil from the ammonium sulfate device is used to countercurrently absorb the tail gas at the top of the extraction tower, the tail gas of the washing tower, the tail gas at the top of the back extraction tower, the tail gas of the benzene stripping system and the tail gas of the benzene distillation, so that the benzene in the tail gas is recovered, the benzene content in the tail gas is reduced, which is far lower than the benzene content in the tail gas in the prior art, and the tail gas treatment amount of the caprolactam device to the flare is reduced.

Description

Technical Field

[0001] This invention relates to the field of chemical equipment technology, specifically to a device and method for treating tail gas from caprolactam refining. Background Technology

[0002] Caprolactam is an important chemical raw material, mainly used in the production of polyamide chips, which are further processed into fibers, engineering plastics, etc. With the development of downstream industries, the quality requirements for caprolactam are becoming increasingly stringent, leading to a greater demand for more efficient caprolactam refining technologies. The main refining processes for caprolactam are: extraction, alkali washing, back-extraction, stripping, ion exchange, hydrogenation, triple-effect evaporation, removal of light and heavy impurities, and removal of heavy impurities. In the extraction process, benzene is used as the extractant to extract caprolactam from an aqueous caprolactam solution, while inorganic impurities such as ammonium sulfate and water-soluble impurities remain in the aqueous phase. Back-extraction extracts caprolactam from the benzene into water to form a water-soluble solution, while impurities easily soluble in benzene remain in the benzene and are separated from the caprolactam. In the caprolactam refining process, benzene-containing tail gas is generated at the top of the columns during extraction, alkali washing, back-extraction, stripping, and benzene distillation. Benzene is a highly toxic solvent, making the treatment of this tail gas crucial. Most existing designs either separate the benzene-containing tail gas from each column in a tail gas buffer tank and then pipe it to a factory flare for incineration, or use disposable adsorbents such as activated carbon granules / activated carbon fibers / molecular sieves for adsorption before venting. However, these designs have two drawbacks: firstly, the solvent benzene is not fully recovered, increasing benzene loss; secondly, the adsorbents used are disposable, resulting in high replacement costs. Therefore, designing a more efficient method and apparatus for treating benzene-containing tail gas in the caprolactam refining process is both necessary and meaningful. Summary of the Invention

[0003] The purpose of this invention is to provide a device and method for treating exhaust gas from caprolactam refining, so as to solve the problems in the prior art.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A caprolactam refining tail gas treatment device includes an amide oil storage tank for buffering absorbent. An ammonium sulfate device for conveying the absorbent is located at the upper end of the amide oil storage tank. The outlet of the amide oil storage tank is connected to the inlet of an amide oil conveying pump. The amide oil conveying pump is connected to a tail gas absorption tower for absorbing tail gas. The inlet of the tail gas absorption tower is located on the upper left side. The tail gas absorption tower contains a mixing component to improve the contact effect between the absorbent and the tail gas. A device for conveying tail gas is connected to the outside of the tail gas absorption tower below the mixing component. The gas supply components include a bottom drain position of the tail gas absorption tower connected to a bottom solution discharge pump, a bottom solution discharge pump connected to an extraction unit, an exhaust end of the top of the tail gas absorption tower connected to a tail gas buffer tank, a benzene residue tank for conveying residual leaves at the bottom of the tail gas buffer tank, an exhaust port at the top of the tail gas buffer tank connected to the exhaust end of a tail gas extraction pump, an exhaust end of the tail gas extraction pump connected to a tail gas separator, and an exhaust end of the tail gas separator connected to a flare tube gallery for incinerating tail gas.

[0006] Based on the above technical solutions, the present invention also provides the following optional technical solutions:

[0007] In one alternative: the surface of the exhaust gas absorption tower where the mixing component is located is provided with a movable door.

[0008] In one alternative: the mixing component includes at least one rotating disk rotatably disposed on the inner wall of the exhaust gas absorption tower, the rotating disk having a plurality of mounting holes, each mounting hole having a flow-slowing structure fitted therein, and the lower end of the rotating disk being connected to a rotating component for driving its rotation.

[0009] In one alternative: the rotating component includes a water storage tray disposed below the rotating disk, the middle position of the water storage tray is connected to the middle position of the bottom of the rotating disk by a central rod, and multiple drain side pipes are provided on the outer side of the central rod, each drain side pipe being set at an acute angle to the cross-section of the water storage tray, and the projection of the mounting hole falling on the water storage tray.

[0010] In one alternative: the slow-flow structure includes a loading frame for filling porous blocks, the outer side of the loading frame being slidably disposed with mounting holes, the bottom of the loading frame having vent holes, and the upper end of the porous block having a retaining ring that presses against the top of the rotating disk.

[0011] In one alternative: the porous block is a porous stone or a stainless steel porous block.

[0012] In one alternative: each mounting hole has a filter structure at its lower end, which forms a liquid film structure when liquid falls on it.

[0013] In one alternative: the exhaust gas absorption tower is provided with at least one side rod on its side, and the upper side of the side rod is provided with a scraper brush that contacts the lower end face of the rotating disk.

[0014] In one alternative: the gas supply components include the tail gas pipe of the extraction tower, the tail gas pipe of the washing tower, the tail gas pipe of the back-extraction tower, the tail gas pipe of the benzene stripping system, and the tail gas pipe of the benzene distillation tower, and each tail gas pipe is equipped with a throttling valve.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] This invention adds a tail gas absorption tower to the caprolactam tail gas treatment design. At the same time, it uses amide oil from the ammonium sulfate unit to countercurrently absorb the tail gas from the top of the extraction tower, the washing tower, the top of the back-extraction tower, the benzene stripping system, and the benzene distillation tail gas to recover benzene from the tail gas, reducing the benzene content in the tail gas to a level far lower than that in the prior art, thus reducing the amount of tail gas to be treated in the caprolactam unit to the flare. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the rotating disk structure of the present invention.

[0019] Figure 3 This is a schematic diagram of the water storage tray structure of the present invention.

[0020] Figure label annotations: 1 Ammonium sulfate unit, 2 Amide oil storage tank, 3 Amide oil transfer pump, 4 Tail gas absorption tower, 5 Tower bottom solution discharge pump, 6 Tail gas buffer tank, 7 Hexane extraction unit, 8 Tail gas extraction pump, 9 Benzene residue tank, 10 Tail gas separator, 11 Hexane extraction tower tail gas pipe, 12 Scrubber tower tail gas pipe, 13 Back-extraction tower tail gas pipe, 14 Benzene stripping system tail gas, 15 Benzene distillation tower tail gas pipe, 16 Plant area flare pipe gallery;

[0021] 20 Rotary disc, 21 Snap ring, 22 Perforated block, 23 Loading frame, 24 Scraper brush, 25 Side rod, 26 Center rod, 27 Water storage pan, 28 Drainage side pipe. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] In one embodiment, such as Figures 1-3As shown, a caprolactam refining tail gas treatment device includes an amide oil storage tank 2 for buffering the absorbent. An ammonium sulfate device 1 for conveying the absorbent is located at the upper end of the amide oil storage tank 2. The outlet of the amide oil storage tank 2 is connected to the inlet of an amide oil transfer pump 3. The amide oil transfer pump 3 is connected to a tail gas absorption tower 4 for absorbing the tail gas. The inlet of the tail gas absorption tower 4 is located on the upper left side. The tail gas absorption tower 4 contains a mixing component to improve the contact effect between the absorbent and the tail gas. The mixing component ensures sufficient contact between the liquid and gas, thus absorbing the toxic substances in the tail gas and ensuring the absorption effect. A gas supply component for conveying the tail gas is connected to the outside of the tail gas absorption tower 4 below the mixing component. The bottom of the tail gas absorption tower 4 is connected to the bottom solution discharge pump 5. The outlet of the bottom solution discharge pump 5 is connected to the extraction unit 7. The exhaust end of the top of the tail gas absorption tower 4 is connected to the tail gas buffer tank 6 for buffering. The bottom of the tail gas buffer tank 6 is provided with a benzene residue tank 9 for conveying residual leaves. The exhaust port at the top of the tail gas buffer tank 6 is connected to the exhaust end of the tail gas extraction pump 8. The exhaust end of the tail gas extraction pump 8 is connected to the tail gas separator 10. The exhaust end of the tail gas separator 10 is connected to the flare tube corridor 16 of the plant area for tail gas incineration treatment. This application ensures the absorption effect of toxic substances in the tail gas by first treating the tail gas through the tail gas absorption tower 4 and fully contacting the absorbent liquid with the tail gas through the mixing component.

[0024] The surface of the exhaust gas absorption tower 4, where the mixing component is located, is provided with an movable door, which facilitates the cleaning of the mixing part in the later stage and ensures the efficient absorption effect of the product.

[0025] The mixing component includes at least one rotating disk 20 rotatably disposed on the inner wall of the exhaust gas absorption tower 4. The rotating disk 20 has several mounting holes, and each mounting hole is fitted with a slow-flow structure. The lower end of the rotating disk 20 is connected to a rotating component for driving its rotation. In this way, the slow-flow structure can be used to divide the downward flowing liquid, thereby fully contacting the upward flowing gas, thus improving the absorption effect of toxic substances in the exhaust gas.

[0026] The rotating component includes a water storage tray 27 disposed below the rotating disk 20. The middle position of the water storage tray 27 is connected to the middle position of the bottom of the rotating disk 20 via a central rod 26. Multiple drain side pipes 28 are provided on the outer side of the central rod 26. Each drain side pipe 28 is set at an acute angle to the cross-section of the water storage tray 27. The projection of the mounting hole falls on the water storage tray 27, so that the water storage tray 27 collects liquid from top to bottom. When the liquid is discharged along the drain side pipes 28, it generates a reaction force, thereby causing the rotating disk 20 to rotate. Under the action of centrifugal force, the liquid slides down the slow flow structure more slowly and disturbs the gas-liquid mixing, which helps to fully absorb toxic substances in the gas.

[0027] The slow-flow structure includes a loading frame 23 for filling the porous block 22. The loading frame 23 is slidably disposed with the mounting hole on the outside. Ventilation holes are distributed at the bottom of the loading frame 23. The upper end of the porous block 22 is provided with a retaining ring 21 that presses against the top of the rotating disk 20. Here, the porous block 22 is a porous stone.

[0028] Each mounting hole has a filter structure at the bottom. When liquid falls on it, the filter structure forms a liquid film structure, which helps to mix it thoroughly with the gas.

[0029] The exhaust gas absorption tower 4 is provided with at least one side rod 24 on its side. The upper side of the side rod 24 is provided with a scraping brush 24 that contacts the lower end face of the rotating disk 20. This allows for scraping of the filter structure, preventing blockage at the lower end of the rotating disk 20.

[0030] The gas supply components here include the tail gas pipe 11 of the extraction tower, the tail gas pipe 12 of the washing tower, the tail gas pipe 13 of the back-extraction tower, the tail gas pipe 14 of the benzene stripping system, and the tail gas pipe 15 of the benzene distillation tower. This allows for the treatment of benzene-containing tail gas at the top of the towers during the extraction, alkaline washing, back-extraction, stripping, and benzene distillation processes in the caprolactam refining process, thereby reducing environmental pollution.

[0031] The above embodiments disclose a caprolactam refining tail gas treatment device and method. In actual use, the absorbent is fed into the amide oil storage tank 2 along the ammonium sulfate device 1, and then the absorbent is fed from top to bottom into the tail gas absorption tower 4 through the amide oil transfer pump 3. The tail gas is fed from bottom to top into the tail gas absorption tower 4 through the gas supply component. The gas and liquid are fully mixed by the mixing component, which greatly reduces the content of toxic benzene in the tail gas. Subsequently, the absorbent in the tail gas absorption tower 4 is sent to the caprolactam extraction unit 7 through the tower bottom solution discharge pump 5. The treated tail gas enters the tail gas buffer tank 6. The waste liquid remaining in the tail gas buffer tank 6 will enter the benzene residue tank 9. Then, under the action of the tail gas extraction pump 8, the treated tail gas enters the tail gas separator 10, and then enters the plant flare tube corridor 16 from the exhaust end of the tail gas separator 10. This method of reducing the benzene content in the tail gas in advance can reduce the intensity of flame treatment and further reduce the final pollution to the environment.

[0032] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A caprolactam refining tail gas treatment device, comprising an amide oil storage tank (2) for buffering an absorption liquid, an ammonium sulfate device (1) for delivering the absorption liquid being arranged at the upper end of the amide oil storage tank (2), a liquid outlet end of the amide oil storage tank (2) being in communication with a liquid inlet end of an amide oil delivery pump (3), the amide oil delivery pump (3) being connected to a tail gas absorption tower (4) for absorbing tail gas, a liquid inlet position of the tail gas absorption tower (4) being arranged at the left upper side, characterized in that, The tail gas absorption tower (4) is internally provided with a mixing component for improving the contact effect of the absorption liquid and the tail gas, the outside of the tail gas absorption tower (4) below the mixing component is connected with a gas supply component for conveying the tail gas, the liquid discharge position of the bottom of the tail gas absorption tower (4) is connected with a tower kettle solution discharge pump (5), the liquid outlet end of the tower kettle solution discharge pump (5) is connected with a hexane extraction unit (7), the exhaust end of the top of the tail gas absorption tower (4) is connected with a tail gas buffer tank (6) for buffering, the bottom of the tail gas buffer tank (6) is provided with a benzene residual liquid tank (9) for conveying residual leaves, the exhaust port of the upper end of the tail gas buffer tank (6) is in communication with the exhaust end of a tail gas extraction pump (8), the exhaust end of the tail gas extraction pump (8) is connected with a tail gas separation tank (10), and the exhaust end of the tail gas separation tank (10) is connected with a plant flare pipe gallery (16) for burning the tail gas. The mixing component comprises at least one rotating disc (20) rotatably arranged on the inner wall of the tail gas absorption tower (4), a plurality of mounting holes are formed in the rotating disc (20), and a buffer flow structure is arranged in each mounting hole. The side surface of the tail gas absorption tower (4) is provided with at least one side rod (24), and the upper side of the side rod (24) is provided with a scraping brush (24) in contact with the lower end surface of the rotating disc (20).

2. The caprolactam refining off-gas treatment device according to claim 1, characterized in that, The surface of the tail gas absorption tower (4) where the mixing component is located is provided with a movable door.

3. The caprolactam refining off-gas treatment device according to claim 1, characterized in that, The rotating component comprises a water storage disc (27) arranged below the rotating disc (20), the middle position of the water storage disc (27) is connected with the middle position of the bottom of the rotating disc (20) through a center rod (26), the outer side of the center rod (26) is provided with a plurality of liquid discharge side pipes (28), each liquid discharge side pipe (28) is arranged at an acute angle with the section of the water storage disc (27), and the projection of the mounting hole falls on the water storage disc (27).

4. The caprolactam refining off-gas treatment device according to claim 1, characterized by The buffer flow structure comprises a charging frame (23) for charging a porous block (22), the charging frame (23) is slidably arranged outside the mounting hole, the bottom of the charging frame (23) is provided with a plurality of air permeable holes, and the upper end of the porous block (22) is provided with a snap ring (21) in abutting contact with the top of the rotating disc (20).

5. The caprolactam purification off-gas treatment device according to claim 4, characterized by The porous block (22) is a porous stone or a stainless steel porous block.

6. The caprolactam refining off-gas treatment device according to claim 1, characterized in that, Each mounting hole is provided with a filter screen structure at the lower end, and the filter screen structure forms a liquid film structure when liquid falls thereon.

7. The caprolactam refining off-gas treatment device according to claim 1, characterized by The gas supply component comprises a hexane extraction tower tail gas pipe (11), a washing tower tail gas pipe (12), a stripping tower tail gas pipe (13), a benzene stripping system tail gas pipe (14) and a benzene distillation tower tail gas pipe (15), and a throttle valve is arranged on each corresponding tail gas pipe.

8. A process for treating the caprolactam purification off-gas in the apparatus according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: Step one: the absorption liquid is sent into the amide oil storage tank (2) along the ammonium sulfate device (1), then the absorption liquid is sent into the tail gas absorption tower (4) from top to bottom through the amide oil conveying pump (3), the tail gas is sent into the tail gas absorption tower (4) from bottom to top through the gas supply component, and the gas and the liquid are fully mixed through the mixing component, so that the content of the toxic substance benzene in the tail gas is greatly reduced. Step two: the absorption liquid in the tail gas absorption tower (4) is sent into the hexane extraction unit (7) through the tower kettle solution discharge pump (5), the treated tail gas enters the tail gas buffer tank (6), the residual waste liquid in the tail gas buffer tank (6) enters the benzene residual liquid tank (9), and then under the action of the tail gas extraction pump (8), the treated tail gas enters the tail gas separation tank (10), and then enters the plant flare pipe corridor (16) from the exhaust end of the tail gas separation tank (10).

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