Device for recovering tail gas of vacuum pump at top of high-boiling-point mixed solution rectifying tower

Abstract

The utility model discloses a device for recovering tail gas of a vacuum pump at the top of a high-boiling-point mixed solution rectifying tower and belongs to the technical field of tail gas treatment. The device comprises a discharge tank and a condenser, wherein a distributor is arranged at the top in the discharge tank; the discharge tank is of a horizontal column structure with two oval sides, the bottom of the discharge tank is connected with the circulating absorption pump, an outlet of the circulating absorption pump is connected with an inlet of the distributor at the top of the discharge tank and the rectifying tower, the distributor comprises a distribution pipeline, and spray heads are uniformly arranged in the horizontal direction and the vertical direction of the distribution pipeline; the top of the discharge tank is connected with a condenser, and a liquid inlet and a gas outlet of the condenser are both connected with the top of the discharge tank to form a circulating system. According to the device provided by the utility model, the tail gas of the vacuum pump is comprehensively and efficiently recovered after being collected to the discharge groove, so that the pollution of the tail gas to the environment is avoided, and the production energy consumption is reduced.

Description

Technical Field

[0001] The utility model relates to a device for recovering the tail gas of a vacuum pump at the top of a rectification tower for high-boiling mixed solutions, belonging to the technical field of tail gas treatment. Background Technique

[0002] In the rectification separation process of high-boiling mixed solutions, a vacuum pump is generally used to pump negative pressure to reduce the boiling points of the mixtures. At the same time, the tail gas of the vacuum pump is discharged into the air after adsorption or absorption. During this process, if the organic substances in the tail gas cannot be completely absorbed, it will cause environmental pollution and increase production consumption.

[0003] Zhu Chao et al. (Zhu Chao, Bai Yan, Discussion on the Process Design of Vacuum Pumping Systems, Petrochemical Design, 2022, 39(1), 4-7) discussed the process design problems of the vacuum pumping system supporting the vacuum rectification of hydrocarbon systems, such as its pumping volume, pressure control, and safe and environmental protection discharge of vacuum tail gas, and proposed reasonable and feasible solutions for optimizing the process design of the vacuum pumping system; however, no design or improvement was made on the device for recovering the tail gas of this vacuum pump. Content of the Utility Model

[0004] In order to overcome the above deficiencies, the utility model provides a device for recovering the tail gas of a vacuum pump at the top of a rectification tower for high-boiling mixed solutions, which is applicable to the system for recovering, separating, and purifying the tail gas of a vacuum pump at the top of a rectification tower for high-boiling mixed solutions. By collecting and absorbing the tail gas of the vacuum pump and recycling and treating the absorbed organic liquid, environmental pollution can be reduced and production consumption can be decreased.

[0005] The technical solution adopted by the utility model is as follows:

[0006] A device for recovering the tail gas of a vacuum pump at the top of a rectification tower for high-boiling mixed solutions includes a discharge tank and a condenser. A distributor is provided at the top inside the discharge tank; the discharge tank is a horizontal cylindrical structure with two elliptical sides at both ends, and the bottom is connected to a circulating absorption pump. The outlet of the circulating absorption pump is connected to the inlet of the distributor at the top of the discharge tank and the rectification tower. The distributor includes a distribution pipeline, and spray nozzles are evenly arranged in the horizontal and vertical directions of the distribution pipeline; a condenser is connected to the top of the discharge tank, and the liquid inlet and gas outlet of the condenser are both connected to the top of the discharge tank to form a circulating system.

[0007] The structure of the above distributor is as follows: sector-shaped spray nozzles are evenly arranged in the horizontal direction of the distribution pipeline; conical spray nozzles are evenly arranged in the vertical direction of the distribution pipeline; the combined setting method of the two types of spray nozzles is beneficial to the uniform distribution of the absorption liquid, making the absorption process more uniform and efficient.

[0008] Further, the aperture of the fan-shaped nozzle is 0.4 - 5.0 mm, and the spraying angle is 30° - 120°; the aperture of the conical nozzle is 0.4 - 15 mm; the spacing between the fan-shaped nozzles is 0.1 - 1.5 m, and the spacing between the conical nozzles is 0.5 - 2 m.

[0009] A solvent inlet and a vacuum pump tail gas inlet are provided at the top of the discharge tank. A remote pressure gauge for the discharge tank is connected to the top plate, and a remote liquid level gauge for the discharge tank is connected to the side of the discharge tank.

[0010] The solvent can be desalted water, which is used as an absorption liquid to absorb organic substances.

[0011] Further, a gas outlet is provided at the upper part of the condenser to discharge the non-condensable gas during the condensation process.

[0012] The non-condensable gas outlet of the condenser leads to a non-condensable gas adsorption tower. Activated carbon packing is provided in the adsorption tower. The adsorption towers are in a one-use-one-backup mode. The liquid phase flows by gravity from the bottom outlet of the adsorption tower to the discharge tank, and the gas phase is discharged at high altitude. When the discharged organic gas exceeds the emission standard, the adsorption tower is switched.

[0013] The operation process of the above device is as follows: About 1 / 3 of the absorption liquid is filled in the discharge tank, and the absorption liquid needs to be miscible with the vacuum pump tail gas. The vacuum pump tail gas is collected into the discharge tank and initially absorbed by the solvent in the discharge tank. The solution absorbing the organic substances is returned to the discharge tank through the circulating absorption pump for circulation. The circulation port of the discharge tank is connected to the inlet of the distributor, and the circulating liquid uniformly contacts the gas phase in the tank reversely through the distributor, so that the vacuum pump tail gas is secondarily absorbed. The liquid phase of the discharge tank is finally sent to the distillation column through the circulating absorption pump for separation and recovery, and the gas phase returns to the discharge tank after being condensed by the condenser. During the continuous circulation process, a part of the liquid of the circulating absorption pump at the bottom of the discharge tank circulates to the liquid distributor at the top of the discharge tank, and the other part leads to the distillation column; specifically: As the absorption liquid in the discharge tank continuously absorbs organic substances, the liquid level of the discharge tank continues to rise. When the liquid level of the discharge tank rises to 1 / 2 - 2 / 3 of the liquid level of the discharge tank, or the pressure of the discharge tank reaches 20 kPa (either of the above conditions is satisfied), open the valve of the circulating absorption pump to the distillation column, and all are sent to the distillation column, and then add the absorption liquid again to 1 / 3 of the liquid level of the discharge tank.

[0014] For the device provided by the present utility model, the organic substances in the tail gas are fully absorbed, including: ① Since the solvent filled in the discharge tank is miscible with the vacuum pump tail gas, a part of the vacuum pump tail gas is absorbed; ② When the circulating absorption pump in the discharge tank circulates by itself, the solvent can uniformly contact the vacuum pump tail gas reversely through the distributor in the tank, so that the vacuum pump tail gas is secondarily absorbed; ③ After the gas phase in the tank is condensed by the condenser, the condensate is recovered to the discharge tank, so that the vacuum pump tail gas is absorbed for the third time.

[0015] The vacuum pump tail gas recovery device for organic substances provided by the utility model has the following beneficial effects: After the vacuum pump tail gas is collected into the discharge tank, part of the tail gas is absorbed by the solvent in the tank. When the liquid in the tank circulates through the distributor, secondary recovery is carried out. The gas phase is condensed by the cooler, which is equivalent to tertiary recovery. The collected condensate is sent to the distillation column for separation and recovery through the condenser, discharge tank, circulating absorption pump, and distillation column loop. This not only avoids environmental pollution caused by the tail gas but also reduces production energy consumption.

[0016] The following further describes the present utility model with reference to the drawings and embodiments. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of the present utility model.

[0018] Figure 2 It is the three - view drawing of the distributor at the top of the discharge tank.

[0019] In the figure: 1 is the discharge tank, 2 is the solvent inlet, 3 is the vacuum pump tail gas inlet, 4 is the remote pressure gauge of the discharge tank, 5 is the condenser, 6 is the remote liquid level gauge of the discharge tank, 7 is the distributor, 8 - 1 is the first adsorption tower, 8 - 2 is the second adsorption tower, 9 is the circulating absorption pump, 10 is the distillation column, 11 is the circulating water supply, 12 is the circulating water return, 13 is the sector nozzle, 14 is the conical nozzle, 15 is the distributor inlet, and 16 is the distribution pipeline. Specific Embodiments Embodiment

[0020] As Figures 1 - 2 shown, a device for recovering the vacuum pump tail gas at the top of the distillation column of a high - boiling - point mixed solution includes a discharge tank 1 and a condenser 5. A distributor 7 is provided at the inner top of the discharge tank 1; the discharge tank 1 is a horizontal cylindrical structure with two - side elliptical shapes, and the bottom is connected to a circulating absorption pump 9. The outlet of the circulating absorption pump 9 is respectively connected to the distributor inlet 15 at the top of the discharge tank and the distillation column 10. The distributor 7 includes a distribution pipeline 16, and nozzles are uniformly arranged in the horizontal and vertical directions of the distribution pipeline 16; a condenser 5 is connected to the top of the discharge tank 1, and the liquid inlet and gas outlet of the condenser 5 are both connected to the top of the discharge tank, forming a circulating system.

[0021] The structure of the above - mentioned distributor is as follows: Sector nozzles 13 are uniformly arranged in the horizontal direction of the distribution pipeline 16; conical nozzles 14 are uniformly arranged in the vertical direction of the distribution pipeline; the combined setting method of the two types of nozzles is beneficial to the uniform distribution of the mixed liquid, making the absorption process more uniform and efficient. Further, the aperture of the sector nozzle is 0.4 - 5.0 mm, and the spraying range angle is 30° - 120°; the aperture of the conical nozzle is 0.4 - 15 mm; the spacing of the sector nozzles is 0.1 - 1.5 m, and the spacing of the conical nozzles is 0.5 - 2 m.

[0022] At the top of the discharge tank 1, there are a solvent inlet 2 and a vacuum pump tail gas inlet 3. A remote pressure gauge 4 for the discharge tank is connected to the top plate, and a remote liquid level gauge 6 for the discharge tank is connected to the side of the discharge tank.

[0023] The solvent inlet is the absorption liquid inlet.

[0024] The non-condensable gas outlet of the condenser leads to the non-condensable gas adsorption tower. The adsorption tower is filled with activated carbon packing. The adsorption tower has one in use and one in reserve, namely the first adsorption tower 8-1 and the second adsorption tower 8-2. The liquid phase flows by gravity from the bottom outlet of the adsorption tower to the discharge tank, and the gas phase is discharged into the air at high altitude. When the discharged organic gas exceeds the emission standard, the adsorption tower is switched.

[0025] The process of tail gas recovery of the present utility model is as follows: When the solvent in the discharge tank is in a self-circulation state, the vacuum pump tail gas is sent into the discharge tank. The solvent continuously absorbs the organic matter in the vacuum pump tail gas through self-circulation. The solvent (absorption liquid) continuously absorbs the organic matter, causing the liquid level of the discharge tank to rise continuously. When the liquid level of the discharge tank rises to a certain extent, it is sent to the distillation column through the circulating absorption pump. The gas phase forms condensate after condensation and returns to the discharge tank, and the non-condensable gas is sent to the adsorption tower. This device enables the organic matter in the tail gas to be fully absorbed, including: ① Since the solvent in the discharge tank is miscible with the vacuum pump tail gas, a part of the vacuum pump tail gas is absorbed; ② When the circulating absorption pump in the discharge tank is in self-circulation, the solvent can be evenly in reverse contact with the vacuum pump tail gas through the distributor in the tank, so that the vacuum pump tail gas is absorbed for the second time; ③ After the gas phase in the tank is condensed by the condenser, the condensate is recovered to the discharge tank, so that the vacuum pump tail gas is absorbed for the third time.

[0026] The specific operation process of the present utility model is illustrated by the following embodiments:

[0027] A certain company uses the indirect method of urea and methanol to produce DMC devices. Propylene glycol and methanol, as raw materials, need to be recycled to the system for reuse. The vacuum pumps at the top of the propylene glycol distillation column and the vacuum pumps at the top of the propylene glycol product tower distillation column discharge tail gas, which contains organic matters such as propylene glycol and methanol. The discharged tail gas without recovery has an adverse impact on the working environment of the operators and pollutes the surrounding environment, and the production consumption is relatively large. In this embodiment, desalted water is selected as the absorption liquid to absorb organic matters such as propylene glycol and methanol. The device provided by the present utility model is used to treat the above tail gas, and the operation steps are as follows:

[0028] (1) Open the desalted water pipeline at the top of the discharge tank and inject 1 / 3 of the desalted water to 1 / 3 of the liquid level of the discharge tank;

[0029] (2) Open the valve of the circulating cooling water inlet 11 of the condenser at the top of the discharge tank;

[0030] (3)Open the valves of the vacuum pump at the top of the propylene glycol rectification tower and the valve for discharging the tail gas from the vacuum pump at the top of the propylene glycol product rectification tower to the discharge tank.

[0031] (4)Open the bottom outlet valve of the discharge tank and the inlet valve of the circulating absorption pump.

[0032] (5)Start the circulating absorption pump of the discharge tank to make the discharge tank in a self-circulating state.

[0033] (6)Start the vacuum pump to send the vacuum pump tail gas into the discharge tank; the tail gas flow rate is 18 m 3 / h;

[0034] (7)After the system is put into operation, observe the liquid level and pressure of the discharge tank. When the liquid level rises to 1 / 2 of the liquid level height of the discharge tank or the pressure reaches 20 kPa, start the circulating absorption pump of the discharge tank and send it to the propylene glycol rectification tower.

[0035] During the above process of absorbing tail gas, the technical parameters of each component should meet the following requirements:

[0036] ①Before the vacuum pump tail gas enters the discharge tank, ensure that the solvent liquid level in the discharge tank is 1 / 3.

[0037] ②Before the vacuum pump tail gas enters the discharge tank, ensure that the solvent contained in the discharge tank is in a self-circulating state.

[0038] ③Before the vacuum pump tail gas enters the discharge tank, check that the valve for the circulating cooling water inlet of the condenser is open and the vent valve is open.

[0039] ④During operation, it is necessary to observe the remote pressure gauge and liquid level gauge of the discharge tank. When the pressure reaches 20 kPa or the liquid level rises to 1 / 2, open the valve of the circulating absorption pump to the rectification tower and send the material in the tank to the rectification tower for recovery.

[0040] ⑤After the material in the tank is sent to the rectification tower, replenish the solvent in a timely manner according to the remaining liquid level.

[0041] After trial use, it is found that the pungent smell in the on-site operation environment is reduced compared with before, the daily recovery amount of methanol and propylene glycol is significantly increased, and the production consumption is reduced.

Claims

1. An apparatus for recovering the tail gas of a vacuum pump at the top of a rectification column for a high-boiling-point mixed solution, characterized in that: It includes a discharge tank and a condenser. A distributor is provided at the top inside the discharge tank. The discharge tank is a horizontal cylindrical structure with oval shapes on both sides, and its bottom is connected to a circulating absorption pump. The outlet of the circulating absorption pump is connected to the inlet of the distributor at the top of the discharge tank and a rectification column. The distributor includes a distribution pipeline, and spray nozzles are evenly arranged in the horizontal and vertical directions of the distribution pipeline. A condenser is connected to the top of the discharge tank, and the liquid inlet and gas outlet of the condenser are both connected to the top of the discharge tank, forming a circulating system.

2. The device for recovering the tail gas of the vacuum pump at the top of the rectification tower for high-boiling mixed solution according to claim 1, characterized in that: The structure of the distributor is as follows: sector spray nozzles are evenly arranged in the horizontal direction of the distribution pipeline; conical spray nozzles are evenly arranged in the vertical direction of the distribution pipeline.

3. The device for recovering the tail gas of the vacuum pump at the top of the rectification column for high-boiling mixed solution according to claim 2, characterized in that: The aperture of the sector spray nozzle is 0.4 - 5.0 mm, and the spraying angle is 30° - 120°; the aperture of the conical spray nozzle is 0.4 - 15 mm.

4. The device for recovering the tail gas of the vacuum pump at the top of the rectification column for high-boiling mixed solution according to claim 2, wherein: The spacing of the sector spray nozzles is 0.1 - 1.5 m, and the spacing of the conical spray nozzles is 0.5 - 2 m.

5. The device for recovering the tail gas of the vacuum pump at the top of the rectification column for high-boiling mixed solution according to claim 1, characterized in that: A solvent inlet and a vacuum pump tail gas inlet are provided at the top of the discharge tank. A remote pressure gauge for the discharge tank is connected to the top plate, and a remote liquid level gauge for the discharge tank is connected to the side of the discharge tank.

6. The device for recovering the tail gas of the vacuum pump at the top of the rectification column for high-boiling mixed solution according to claim 1, characterized in that: A gas outlet is provided at the upper part of the condenser to discharge the non-condensable gas during the condensation process.

7. The device for recovering the tail gas of the vacuum pump at the top of the rectification column for high-boiling mixed solution according to claim 1, characterized in that: The non-condensable gas outlet of the condenser is connected to an adsorption tower. Activated carbon packing is provided in the adsorption tower. The adsorption towers are in a one-use-one-backup mode. The liquid phase flows by gravity from the bottom outlet of the adsorption tower to the discharge tank, and the gas phase is discharged into the air at a high altitude. When the discharged organic gas exceeds the emission standard, the adsorption tower is switched.

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