Device for improving hexane water concentration in caprolactam back extraction

Abstract

The utility model belongs to the technical field of caprolactam production, and particularly relates to a device for improving caprolactam back extraction hexane water concentration, which is characterized in that a hexane solution discharge port of a hexane extraction tower is connected with a hexane solution feed port of a hexane evaporation tower through a pipeline, and a hexane solution discharge port of the hexane evaporation tower is connected with a back extraction tower through a pipeline; a benzene steam pipeline is arranged at the top of the benzene-hexane evaporation tower, a hexane water pipeline is arranged at the bottom of the back extraction tower and is connected to the next working section, and a water inlet pipe and a liquid benzene pipeline are arranged at the middle upper part of the back extraction tower. The device has the beneficial effects that by increasing the concentration of the benzene-hexane solution, the concentration of hexane water can be increased during back extraction, so that the consumption of steam during evaporation of hexane water in a subsequent working section is reduced, the energy is saved, the productivity is improved, and meanwhile, the solvent benzene in the benzene-hexane solution is recovered and recycled.

Description

Technical Field

[0001] The utility model belongs to the technical field of caprolactam production, and particularly relates to a device for increasing the concentration of caprolactam in the back extraction of caprolactam aqueous solution. Background Art

[0002] Caprolactam is an important chemical raw material, mainly used for producing polyamide chips, which are further processed into fibers, engineering plastics, etc.

[0003] The main post-treatment processes of caprolactam production are: ion exchange, hydrogenation, evaporation, and rectification. Among them, in the evaporation process, the caprolactam aqueous solution is evaporated by steam to obtain a caprolactam aqueous solution with a caprolactam concentration of about 90%. Then, through negative pressure flash evaporation, a 99% caprolactam aqueous solution is obtained. Finally, through negative pressure distillation, pure caprolactam liquid is obtained.

[0004] In traditional production, the benzene-caprolactam solution for back extraction feed is about 20%. It is countercurrently extracted with demineralized water or process water to obtain a caprolactam aqueous solution with a caprolactam content of about 30%. In the subsequent evaporation section, a large amount of water needs to be evaporated to concentrate the 30% caprolactam aqueous solution to about 90% by using steam, which requires a large amount of steam consumption and high energy consumption. In order to reduce the steam consumption for caprolactam aqueous solution evaporation, the caprolactam in the benzene-caprolactam solution is concentrated. During back extraction, the concentration of caprolactam aqueous solution can be increased to about 40%, which can reduce evaporation consumption, save energy, and increase production capacity.

[0005] Therefore, it is necessary to provide a device for increasing the concentration of caprolactam in the back extraction of caprolactam aqueous solution to solve the above problem of high energy consumption. Summary of the Invention

[0006] Aiming at the problem that the above-mentioned caprolactam aqueous solution has too high steam consumption during evaporation in the subsequent section due to low concentration, the utility model provides a device for increasing the concentration of caprolactam in the back extraction of caprolactam aqueous solution. The technical solution is as follows: The benzene-caprolactam solution discharge port of the benzene-caprolactam extraction tower is connected to the benzene-caprolactam solution feed port of the benzene-caprolactam evaporation tower through a pipeline. The benzene-caprolactam solution discharge port of the benzene-caprolactam evaporation tower is connected to the back extraction tower through a pipeline. A benzene vapor pipeline is arranged at the top of the benzene-caprolactam evaporation tower. A caprolactam aqueous solution pipeline is arranged at the bottom of the back extraction tower, and the caprolactam aqueous solution pipeline is connected to the next section. A water inlet pipe and a liquid benzene pipeline are arranged in the upper-middle part of the back extraction tower.

[0007] The liquid benzene pipeline is connected to the liquid benzene storage tank through a liquid benzene transfer pump.

[0008] The benzene vapor pipeline is connected to a condenser, and the condenser is connected to the liquid benzene storage tank through a pipeline.

[0009] The liquid benzene storage tank is connected to the top of the benzene-caprolactam extraction tower through a pipeline.

[0010] As a preferred embodiment, the benzene-caprolactam content in the benzene-caprolactam solution obtained after extraction in the benzene-caprolactam extraction column is 18-22%.

[0011] As a preferred embodiment, the benzene-caprolactam content in the benzene-caprolactam solution obtained after evaporation in the benzene-caprolactam evaporation column is 30-35%.

[0012] As a preferred embodiment, the benzene-caprolactam distillation column is a sieve plate column or a packed column, and sieve plates or structured packings are installed inside.

[0013] As a preferred embodiment, the back-extraction column is a packed column, and a pulse device is further provided at the bottom.

[0014] As a preferred embodiment, the water in the water inlet pipe is demineralized water or process water.

[0015] The working principle of the present utility model: By the difference in solubility of caprolactam in water and benzene, the caprolactam in the benzene-caprolactam solution is back-extracted into water to obtain an aqueous caprolactam solution, and by increasing the caprolactam content in the benzene-caprolactam solution, the caprolactam content in the back-extracted aqueous caprolactam solution is increased.

[0016] The beneficial effects of the present utility model:

[0017] By increasing the concentration of the benzene-caprolactam solution, the concentration of the aqueous caprolactam can be increased during back-extraction, thereby reducing the consumption of steam during the evaporation of the aqueous caprolactam in the subsequent process section, saving energy, increasing production capacity, and at the same time recovering the solvent benzene in the benzene-caprolactam solution and recycling it. Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the device process of the present utility model.

[0019] In the figure: 1. Benzene-caprolactam extraction column; 2. Benzene-caprolactam evaporation column; 3. Back-extraction column; 4. Liquid benzene pipeline; 5. Water inlet pipe; 6. Aqueous caprolactam pipeline; 7. Liquid benzene transfer pump; 8. Condenser; 9. Liquid benzene storage tank. Detailed Embodiments

[0020] The following further describes the present utility model in detail according to the drawings and specific embodiments.

[0021] Embodiment 1

[0022] As Figure 1 shown, a device for increasing the concentration of the aqueous caprolactam in the back-extraction of caprolactam includes that the benzene-caprolactam solution outlet of the benzene-caprolactam extraction column 1 is connected to the benzene-caprolactam solution inlet of the benzene-caprolactam evaporation column 2 through a pipeline, the benzene-caprolactam solution outlet of the benzene-caprolactam evaporation column 2 is connected to the back-extraction column 3 through a pipeline, a benzene vapor pipeline 10 is provided at the top of the benzene-caprolactam evaporation column 2, an aqueous caprolactam pipeline 6 is provided at the bottom of the back-extraction column 3, the aqueous caprolactam pipeline 6 is connected to the next process section, and a water inlet pipe 5 and a liquid benzene pipeline 4 are provided in the upper middle part of the back-extraction column 3.

[0023] The described liquid benzene pipeline 4 is connected to the liquid benzene storage tank 9 through a liquid benzene transfer pump 7.

[0024] The described benzene vapor pipeline 10 is connected to a condenser 8, and the condenser 8 is connected to the liquid benzene storage tank 9 through a pipeline.

[0025] The described liquid benzene storage tank 9 is connected to the top of the benzene-caprolactam extraction tower 1 through a pipeline.

[0026] Further, the benzene-caprolactam content in the benzene-caprolactam solution obtained after extraction by the benzene-caprolactam extraction tower 1 is 18 - 22%.

[0027] Further, the benzene-caprolactam content in the benzene-caprolactam solution obtained after evaporation by the benzene-caprolactam evaporation tower 2 is 30 - 35%.

[0028] Further, the benzene-caprolactam distillation tower 2 is a packed tower, and structured packing is installed inside.

[0029] Further, the back-extraction tower 3 is a packed tower, and a pulse device is also provided at the bottom.

[0030] Further, the water in the water inlet pipe 5 is demineralized water.

[0031] The working process of this device is as follows: The benzene-caprolactam extraction tower 1 transports a benzene-caprolactam solution with a caprolactam content of 18 - 22% into the benzene-caprolactam evaporation tower 2 for concentration to obtain a benzene-caprolactam solution with a caprolactam content of 30 - 35%. The benzene-caprolactam evaporation tower 2 transports the benzene-caprolactam solution into the back-extraction tower 3 and generates benzene vapor. The benzene vapor enters the condenser 8 and is condensed into liquid benzene and transported into the liquid benzene storage tank 9. Then, the water inlet pipe 5 transports demineralized water into the back-extraction tower 3 for back-extraction to obtain an aqueous caprolactam solution with a caprolactam content of 35 - 42% and liquid benzene. The aqueous caprolactam solution is transported to the next evaporation section for evaporation. The liquid benzene is transported into the liquid benzene storage tank 9 through the liquid benzene transfer pump 7. The discharge port of the liquid benzene storage tank 9 is connected to the benzene-caprolactam extraction tower 1 for the recycling of liquid benzene.

Claims

1. A device for increasing the concentration of caprolactam stripping water, characterized in that: The invention comprises a benzene-hexyl solution outlet of a benzene-hexyl extraction tower (1) connected to a benzene-hexyl solution feed port of a benzene-hexyl evaporation tower (2) through a pipeline, a benzene-hexyl solution outlet of the benzene-hexyl evaporation tower (2) connected to a stripping tower (3) through a pipeline, a benzene vapor pipeline (10) is arranged at the top of the benzene-hexyl evaporation tower (2), a benzene water pipeline (6) is arranged at the bottom of the stripping tower (3), the benzene water pipeline (6) is connected to the next working section, and a water inlet pipe (5) and a liquid benzene pipeline (4) are arranged at the middle and upper part of the stripping tower (3).

2. A device for increasing the concentration of caprolactam stripping water according to claim 1, characterized in that: The liquid benzene pipeline (4) is connected to the liquid benzene temporary storage tank (9) via a liquid benzene transfer pump (7).

3. A device for increasing the concentration of caprolactam stripping water according to claim 1, characterized in that: The benzene vapor pipeline (10) is connected to the condenser (8), and the condenser (8) is connected to the liquid benzene temporary storage tank (9) through a pipeline.

4. A device for increasing the concentration of caprolactam stripping water according to claim 2 or 3, characterized in that: The liquid benzene temporary storage tank (9) is connected to the top of the benzene-hexyl extraction tower (1) via a pipeline.

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