Recycling device for circulating caprolactam

Abstract

The utility model provides a recycling device of circulating caprolactam, which comprises a residual liquid tank, the residual liquid tank is sequentially communicated with a concentration preparation mixer and a preparation tank through a pipeline via a residual liquid delivery pump, and the preparation tank is communicated with a pH adjusting mixer through a pipeline. The pH adjusting mixer is sequentially communicated with the membrane filter and the preparation tank through a pipeline via the hexane water circulating pump, the membrane filter is sequentially communicated with the hexane water buffer tank, the hexane water delivery pump and the circulating extraction tower through a pipeline, and the residual liquid tank is communicated with a distillation residual liquid pipeline, a flash distillation branch pipeline and a light component removal tower fraction pipeline. According to the caprolactam-benzene extraction device, caprolactam with poor quality, such as distillation tower raffinate, light component removal tower fractions and flash distillation fractions, and a water phase of an alkaline washing tower are mixed according to a ratio, the mixture is adjusted to hexane water with a proper pH value and concentration, mechanical impurities such as oligomers are removed through a high-precision membrane filter, and then the hexane water and refined benzene are extracted, so that a qualified caprolactam-benzene solution is prepared; a large amount of circulation of distillation tower raffinate, light component removal tower fractions, flash distillation fractions and the like is avoided, the load of an extracted tower is reduced, the system operation efficiency is improved, and the production cost is reduced.

Description

Technical Field

[0001] This utility model belongs to the field of chemical industry and relates to a device for recycling caprolactam, specifically a device for recovering residual liquid from a distillation column. Background Technology

[0002] In current caprolactam production processes both domestically and internationally, the residual liquid from the distillation tower is mixed with the condensate from the steam jet pump and then sent to the ammonium sulfate unit to regenerate crude oil, resulting in the recycling of caprolactam. Similarly, the aqueous phase from the benzene stripping tower, after water washing and alkali washing, contains a large amount of caprolactam, which is also stripped of benzene and then sent back to the flow rate, resulting in significant energy and material consumption and increasing production costs. Summary of the Invention

[0003] This invention provides a device for recycling caprolactam, which reduces the load on the caprolactam extraction tower, improves system operating efficiency, and reduces production costs.

[0004] The technical solution of this utility model is,

[0005] A device for recycling caprolactam includes a residual liquid tank, which is connected in sequence to a concentration mixing unit and a preparation tank via a residual liquid transfer pump. The preparation tank is connected in sequence to a pH adjusting mixer via a pipeline. The pH adjusting mixer is connected in sequence to a membrane filter and the preparation tank via a caprolactam circulation pump via a pipeline. The membrane filter is connected in sequence to a caprolactam buffer tank, a caprolactam transfer pump, and a circulating extraction tower via a pipeline. The residual liquid tank is connected to a distillation residual liquid pipeline, a flash distillation fraction pipeline, and a light distillation fraction pipeline.

[0006] Preferably, the bottom of the circulating extraction tower is connected to the raffinate phase to bottom liquid stripping tower pipeline via a raffinate transfer pump, and the top outlet of the circulating extraction tower is connected to the benzene to benzene tank pipeline.

[0007] Preferably, the concentration mixing unit is also connected to the water in the alkali washing tower via a pipeline; the pipeline is equipped with a flow meter and a regulating valve to stabilize the flow rate to the mixer.

[0008] Preferably, the concentration preparation mixer and the pH adjustment mixer are static mixers.

[0009] Preferably, the pH adjusting mixer is connected to a dilute sulfuric acid pipeline; the dilute sulfuric acid pipeline is equipped with a regulating valve and a flow meter.

[0010] Preferably, a pH meter is installed at the outlet of the sulfuric acid circulating pump; the pH value is controlled by a regulating valve on the dilute sulfuric acid pipeline and should be controlled between 4 and 7.

[0011] Preferably, a membrane filter is installed on the outlet pipe of the water circulation pump; the membrane filter is a cross-flow membrane filter, and the membrane material is not limited to ceramic and metal, but preferably its filtration accuracy should be less than 50 nanometers; the membrane filter is equipped with a regulating valve at the clear liquid outlet to control the liquid level of the preparation tank and to transport the clear liquid to the water buffer tank.

[0012] Preferably, the circulating extraction tower is a packed tower, and the packing type is preferably Pall rings made of 316L material.

[0013] Preferably, the bottom of the circulating extraction tower is provided with a benzene pipeline, which is equipped with a regulating valve and a flow meter and the hexane water at the outlet of the hexane water transfer pump.

[0014] Preferably, the feed to the top of the circulating extraction tower comes from the outlet pipeline of the self-water conveying pump and is equipped with a regulating valve and a flow meter; the extract phase at the top of the circulating extraction tower goes to the phenylene-to-phenylene tank via the extraction phenylene-to-phenylene tank pipeline 18.

[0015] This invention involves mixing caprolactam (of lower quality) from distillation column residue, light column fraction, and flash distillate with the aqueous phase from an alkaline washing column in a specific ratio, adjusting the pH and concentration to a suitable level, and then passing the mixture through a high-precision membrane filter to remove mechanical impurities such as oligomers before extraction with refined benzene to obtain a qualified caprolactam-benzene solution. This process avoids the excessive recycling of distillation column residue, light column fraction, and flash distillate, reduces the load on the caprolactam extraction column, improves system operating efficiency, and lowers production costs.

[0016] This utility model has the following beneficial effects:

[0017] 1) Reduce the load on the extraction tower; 2) Improve the extraction efficiency of the extraction tower; 3) Reduce production costs. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the system structure of this utility model.

[0019] In the diagram: 1. Residual liquid tank; 2. Residual liquid transfer pump; 3. Concentration preparation mixer; 4. Preparation tank; 5. pH adjustment mixer; 6. Hexane circulating pump; 7. Membrane filter; 8. Hexane buffer tank; 9. Hexane transfer pump; 10. Circulating extraction tower; 11. Raffinate transfer pump; 12. Distillation residual liquid pipeline; 13. Flash distillation fraction pipeline; 14. Light precipitate removal tower fraction pipeline; 15. Alkali washing tower aqueous phase pipeline; 16. Dilute sulfuric acid pipeline; 17. Raffinate phase stripping tower pipeline; 18. Benzene extraction tank pipeline; 19. Refined benzene pipeline. Detailed Implementation

[0020] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0021] Example 1

[0022] A device for recycling caprolactam includes a residual liquid tank 1. The residual liquid tank 1 is connected in sequence to a concentration mixing unit 3 and a preparation tank 4 via a residual liquid transfer pump 2 through a pipeline. The preparation tank 4 is connected to a pH adjusting mixer 5 via a pipeline. The pH adjusting mixer 5 is connected in sequence to a membrane filter 7 and the preparation tank 4 via a caprolactam circulation pump 6 through a pipeline. The membrane filter 7 is connected in sequence to a caprolactam buffer tank 8, a caprolactam transfer pump 9, and a circulating extraction tower 10 via a pipeline. The residual liquid tank 1 is connected to a distillation residual liquid pipeline 12, a flash distillation fractionation pipeline 13, and a light distillation fractionation pipeline 14.

[0023] Preferably, the bottom of the circulating extraction tower 10 is connected to the raffinate phase to bottom liquid stripping tower pipeline 17 via the raffinate transfer pump 11, and the top outlet of the circulating extraction tower 10 is connected to the benzene to benzene tank pipeline 18.

[0024] Preferably, the concentration mixing unit 3 is also connected to the water phase 15 of the alkali washing tower via a pipeline; a flow meter and a regulating valve are installed on the pipeline to stabilize the flow rate to the mixer.

[0025] Preferably, the concentration mixing mixer 3 and the pH adjusting mixer 5 are static mixers.

[0026] Preferably, the pH adjusting mixer 5 is connected to the dilute sulfuric acid pipeline 16; the dilute sulfuric acid pipeline 16 is equipped with a regulating valve and a flow meter.

[0027] Preferably, a pH meter is installed at the outlet of the sulfuric acid circulating pump 6; the pH value is controlled by a regulating valve on the dilute sulfuric acid pipeline 16 and should be controlled between 4 and 7.

[0028] Preferably, a membrane filter 7 is installed on the outlet pipe of the water circulation pump 6; the membrane filter 7 is a cross-flow membrane filter, and the membrane material is not limited to ceramic and metal, preferably its filtration accuracy should be less than 50 nanometers; the membrane filter 7 is equipped with a regulating valve at the clear liquid outlet to control the liquid level of the preparation tank 4 and to transport the clear liquid to the water buffer tank 8.

[0029] Preferably, the circulating extraction tower 10 is a packed tower, and the packing type is preferably Pall rings made of 316L material.

[0030] Preferably, the bottom of the circulating extraction tower 10 is provided with a benzene pipeline 19, which is equipped with a regulating valve and a flow meter and the hexane water at the outlet of the hexane water transfer pump 9.

[0031] Preferably, the feed at the top of the circulating extraction tower 10 comes from the outlet pipeline of the self-water conveying pump 9 and is equipped with a regulating valve and a flow meter; the extract phase at the top of the circulating extraction tower 10 goes to the benzene tank via the benzene-to-benzene tank pipeline 18.

[0032] The caprolactam production unit of Example 1 was used, with an annual output of 500,000 tons, a cyclohexanone feed rate of 56 t / h, and a total load of 114 m³ for the hexanoextraction tower. 3 / h, distillation column feed 69m 3 / h, the output distillate flow rate is 63t / h, and the residual liquid flow rate is 6t / h.

[0033] The distillation residue was mixed with the aqueous phase after washing with benzoyl hexane and alkali at a volume ratio of 1 to 1.5:1 to obtain an aqueous solution of benzoyl hexane with a concentration of about 70%.

[0034] The 70% aqueous solution was adjusted to pH 5 with dilute sulfuric acid and filtered to remove mechanical impurities and oligomers.

[0035] After adjusting the temperature of the aqueous solution to 45-50℃, it was mixed with refined benzene at a volume ratio of 1:2.9 to obtain a 20% caprolactam-benzene solution. Its E... 290nm The absorbance is approximately between 0.3 and 0.4.

[0036] The total load of the extraction tower is 114m 3 / h decreased to 107m 3 / h;

[0037] Subsequently, the light distillate and flash distillate were gradually added to the distillation residue, and the load of the extractor was eventually reduced to 95 m³. 3 / h;

[0038] As the amount of caprolactam returning to the ammonium sulfate unit decreased, the color of the ammonium sulfate crystals noticeably faded from yellow and gradually decreased to colorless.

[0039] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A device for recycling caprolactam, comprising a residual liquid tank (1), characterized in that: The residual liquid tank (1) is connected in sequence to the concentration mixing mixer (3) and the preparation tank (4) via a pipeline through the residual liquid transfer pump (2). The preparation tank (4) is connected in sequence to the pH adjusting mixer (5) via a pipeline. The pH adjusting mixer (5) is connected in sequence to the membrane filter (7) and the preparation tank (4) via a water circulation pump (6) via a pipeline. The membrane filter (7) is connected in sequence to the water buffer tank (8), the water transfer pump (9), and the circulating extraction tower (10) via a pipeline. The residual liquid tank (1) is connected to the distillation residual liquid pipeline (12), the flash distillation fraction pipeline (13), and the light distillation column fraction pipeline (14).

2. The device for recycling caprolactam according to claim 1, characterized in that: The bottom of the circulating extraction tower (10) is connected to the raffinate phase to bottom liquid stripping tower pipeline (17) via the raffinate transfer pump (11), and the top outlet of the circulating extraction tower (10) is connected to the benzoyl to benzoyl extracting tank pipeline (18).

3. The device for recycling caprolactam according to claim 1, characterized in that: The concentration mixing unit (3) is also connected to the water phase (15) of the alkaline washing tower via a pipeline.

4. The recycling device for caprolactam according to claim 1, characterized in that: The concentration mixing mixer (3) and pH adjusting mixer (5) are static mixers.

5. The device for recycling caprolactam according to claim 1, characterized in that: The pH adjusting mixer (5) is connected to the dilute sulfuric acid pipeline (16).

6. The recycling device for caprolactam according to claim 1, characterized in that: A pH meter is installed at the outlet of the water circulation pump (6).

7. The device for recycling caprolactam according to claim 1, characterized in that: A membrane filter (7) is installed on the outlet pipe of the water circulation pump (6); the membrane filter (7) is a cross-flow membrane filter, and the filtration accuracy of the membrane filter (7) is less than 50 nanometers; the clear liquid outlet of the membrane filter (7) is equipped with a regulating valve to control the liquid level of the preparation tank (4) and to transport the clear liquid to the water buffer tank (8).

8. The recycling device for caprolactam according to claim 1, characterized in that: The circulating extraction tower (10) is a packed tower.

9. The device for recycling caprolactam according to claim 1, characterized in that: The bottom of the circulating extraction tower (10) is equipped with a benzene pipeline (19).

10. The recycling device for caprolactam according to claim 1, characterized in that: The top feed of the circulating extraction tower (10) comes from the outlet pipeline of the water transfer pump (9) and is equipped with a regulating valve and a flow meter; the extract phase at the top of the circulating extraction tower (10) goes to the phenylene tank through the extraction phenylene to phenylene tank pipeline (18).

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