CN111875542A - Refining method of caprolactam extraction liquid - Google Patents
Refining method of caprolactam extraction liquid Download PDFInfo
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- CN111875542A CN111875542A CN202010631753.8A CN202010631753A CN111875542A CN 111875542 A CN111875542 A CN 111875542A CN 202010631753 A CN202010631753 A CN 202010631753A CN 111875542 A CN111875542 A CN 111875542A
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- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D223/00—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom
- C07D223/02—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings
- C07D223/06—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
- C07D201/16—Separation or purification
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Abstract
The invention relates to a refining method of caprolactam extract, and the traditional caprolactam refining process is that crude caprolactam water solution neutralized by ammonia water is subjected to benzene extraction and back extraction to obtain caprolactam water solution with lower conductivity (generally less than 30 mus/cm). At present, most caprolactam manufacturers adopt a neutralization crystallization process for saving energy and reducing consumption, the re-discharged liquid of a reaction unit directly reacts with gaseous ammonia to be separated to obtain a crude caprolactam water solution, and then benzene extraction and back extraction are carried out. Inorganic salts and free acid in the crude caprolactam obtained by neutralization crystallization are high, the extraction effect and the product quality are seriously influenced, equipment is corroded, and the conductivity of the caprolactam water solution after back extraction is high. The process of the invention sequentially carries out water washing, alkali washing and water washing on the benzene extract of caprolactam and then carries out back extraction, can effectively remove inorganic salts and free acid in the caprolactam extract and improve the quality of caprolactam products.
Description
Technical Field
The invention belongs to the technical field of refining of caprolactam extraction liquid, and particularly relates to a refining system and a refining method of caprolactam extraction liquid.
Background
The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.
The traditional caprolactam refining process is that the caprolactam water solution with lower conductivity (generally less than 30 mus/cm) is obtained after benzene extraction and back extraction of the crude caprolactam water solution neutralized by ammonia water. At present, most caprolactam manufacturers adopt a neutralization crystallization process for saving energy and reducing consumption, the re-discharged liquid of a reaction unit directly reacts with gaseous ammonia to be separated to obtain a crude caprolactam water solution, and then benzene extraction and back extraction are carried out. Inorganic salts and free acid in the crude caprolactam obtained by neutralization crystallization are high, the extraction effect and the product quality are seriously influenced, equipment is corroded, and the conductivity of the caprolactam water solution after back extraction is high.
Disclosure of Invention
In view of the above-mentioned technical background, the present invention aims to provide an optimized caprolactam extraction process, wherein the steps of water washing and separation are added before the alkali washing, so that the inorganic salts and free acids in the caprolactam extraction liquid can be effectively removed, and the quality of the caprolactam product is improved.
Based on the technical effects, the invention provides a refining method of caprolactam extraction liquid, which comprises the following steps: the benzene extraction liquid of the caprolactam is firstly washed by primary water, then washed by an alkali solution and washed by secondary water in sequence, and then back extraction is carried out.
In the existing caprolactam extraction process, crude caprolactam obtained by neutralization crystallization needs to be refined by benzene extraction and back extraction, and after neutralization crystallization, inorganic salts carried in the crude caprolactam are more and enter an aqueous solution with caprolactam, so that the product quality is influenced.
The invention discovers that a water washing step is added before alkaline washing, inorganic salt components in the benzene extraction liquid can be removed in advance by using a small amount of water, and the inorganic salt impurities are effectively removed by naturally separating the benzene extraction liquid under the hydrophilic adsorption effect of the ceramic filler of the water washing tower, so that the conductivity of the caprolactam water solution is reduced (about 15 mu s/cm), and the product quality is improved.
The refining method provided by the invention has the advantages that the designed capacity can be used within 10-30 ten thousand tons, and the application range is wide; the operation is completely automated, the continuous operability is strong, and the system is safe and stable.
The beneficial effects of one or more technical schemes are as follows:
the refining method provided by the invention effectively reduces the conductivity of the caprolactam water solution and improves the quality of caprolactam. In addition, the method can effectively reduce the acidity of the extraction system, reduce the corrosion to equipment, and has the advantages of high automation degree, strong operability, large load elasticity and stable operation when being applied to actual production.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
FIG. 1 is a process flow diagram of the refining process of caprolactam extract as described in example 1.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
As described in the background of the invention, in order to solve the above technical problems, the present invention provides a refining method of caprolactam extraction.
In a first aspect of the invention, a caprolactam extraction liquid refining method is provided, which comprises the following steps: the benzene extraction liquid of the caprolactam is firstly washed by primary water, then washed by an alkali solution and washed by secondary water in sequence, and then back extraction is carried out.
Preferably, the first and/or second washing water is recovered water including but not limited to soft water, purified water or other industrial production; the washing water needs to have low content of impurities such as inorganic salts and the like so as to prevent the impurities from entering caprolactam to form new impurities.
In some embodiments with better effects, the evaporated condensate in the system can be used in addition to the desalted water, so that the caprolactam refining effect is met, and the desalted water can be reduced to save resources.
Preferably, the benzene extract of caprolactam is derived from: and adding benzene into the crude caprolactam solution obtained by the neutralization crystallizer to obtain a benzene extract of the caprolactam.
Further preferably, the ratio of caprolactam to benzene in the extract is 15-25: 75-85; in a more preferred technical scheme, the ratio of caprolactam to benzene in the extract liquid is 20: 80.
Preferably, the first water washing is to add a small amount of water to the benzene extraction liquid of the caprolactam, and the volume of the water accounts for 0.8-1.2% of the benzene extraction liquid of the caprolactam.
Further preferably, the first water washing step is as follows: and mixing the benzene extract of the caprolactam with washing water under the action of a pump, and feeding the mixture into a water washing tower to separate the washing water and the benzene extract part of the caprolactam.
Further preferably, the washing tower is provided with ceramic packing; in a more preferable scheme, a baffle device is further arranged in the water washing tower.
According to the invention, the ceramic filler is adopted in the washing tower, and due to the hydrophilicity of the ceramic, when the solution flows through the filler, the water dispersed in the caprolactam benzene extract can be well converged, so that the water is concentrated at the bottom of the washing tower and is separated from the caprolactam benzene extract.
Because the specific gravity of water is larger than that of benzene solution, after the water is separated by the water washing tower, the caprolactam benzene extract liquor at the upper layer enters the next link, and washing water is collected at the lower layer and is discharged through a pipeline and the like.
Preferably, the alkali solution washing is performed with an alkali solution having a concentration of 1 wt%.
Preferably, the alkali washing and the second water washing are carried out in an alkali washing-water washing combined tower, and the combined tower is provided with a pH meter.
Preferably, the caprolactam benzene extraction liquid after the first water washing enters an alkaline washing-water washing composite tower, and the amount of the added alkaline solution is adjusted by a pH meter until the solution is neutral; the dosage of the water of the second water washing is adjusted according to the content of the added alkali, and the more added alkali means that more salt is generated in the solution system, and the washing water needs to be properly added to remove the soluble salt.
Preferably, the back extraction is to add process evaporation condensate to a benzene extraction liquid of caprolactam to extract the caprolactam into a water phase, and the ratio of the addition evaporation condensate to the extraction liquid is about 1: 2.5.
In order to make the technical solutions of the present invention more clearly understood by those skilled in the art, the technical solutions of the present invention will be described in detail below with reference to specific embodiments.
Example 1
In this embodiment, a method for refining caprolactam extract is provided. As shown in FIG. 1, the crude caprolactam product from the neutralization crystallizer is combined with benzene in a caprolactam extraction column to produce a benzene extract of caprolactam.
The benzene extract of caprolactam was mixed with desalted water, which was 1% of the volume of the benzene extract of caprolactam, by means of a feed pump and fed to a water wash column. And after the benzene extraction liquid of the caprolactam is mixed with desalted water, the benzene extraction liquid enters the tower from the top of the water washing tower, the water washing tower is internally provided with a ceramic filler, when the mixed solution flows down from the top through the filler, the desalted water in the mixed system dissolves out the salt in the caprolactam, and the salt and the benzene solvent are gradually separated and gathered together under the adsorption action of the ceramic.
Layering the caprolactam benzene extraction liquid and desalted water below the washing tower due to specific gravity, wherein a baffle plate which is arranged perpendicular to the bottom of the washing tower is arranged at the bottom of the washing tower and plays a role in overflowing; the solution that flows through the filler concentrates on one side of baffle, and the opposite side has the pipeline that leads to next device, along with liquid constantly leaves, and the benzene solution of caprolactam constantly increases, when the liquid level is higher than the baffle, overflows to the baffle opposite side to get into next processing link.
And (3) feeding the caprolactam benzene extract after the first water washing into an alkaline washing-water washing composite tower, wherein the alkaline washing-water washing composite tower is provided with a pH meter for detecting the pH of the solution in the tower and controlling the addition amount of alkali until the solution in the alkaline washing-water washing composite tower is adjusted to be neutral, and the concentration of the alkali solution is 1 wt%. And the second water washing adopts desalted water, the dosage is determined according to the dosage of the salt produced after the alkali washing and the conductivity of the solution in the stripping tower, and the more the content of the salt produced after the alkali washing is, the more the dosage of the desalted water is needed. After the second washing, refined extract liquid discharged from the top of the alkali washing-water washing composite tower enters a stripping tower, and the wash liquid flows out of the bottom of the tower and returns to the caprolactam extraction tower.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for refining caprolactam extraction liquid, which is characterized by comprising the following steps: the benzene extraction liquid of the caprolactam is firstly washed by primary water, then washed by an alkali solution and washed by secondary water in sequence, and then back extraction is carried out.
2. The method for refining caprolactam extraction according to claim 1, wherein the first and/or second washing water is selected from the group consisting of, but not limited to, soft water, purified water, and evaporative condensate within the system; preferably, desalted water is used.
3. The process for refining a caprolactam extract according to claim 1, wherein the benzene extract of caprolactam is derived from: and adding benzene into the crude caprolactam solution obtained by the neutralization crystallizer to obtain a benzene extract of the caprolactam.
4. The method for refining caprolactam extract according to claim 1, wherein the ratio of the crude caprolactam aqueous solution to benzene is 15-25: 75-85; preferably, the ratio of caprolactam to benzene in the benzene extract is 20: 80.
5. The method for refining caprolactam extraction solution according to claim 1, wherein the first washing comprises adding a small amount of water to the benzene extraction solution of caprolactam, and the volume of the water is 0.8-1.2% of the benzene extraction solution of caprolactam.
6. The process for refining a caprolactam extract according to claim 1, wherein the first washing step comprises: and mixing the benzene extract of the caprolactam with washing water under the action of a pump, and feeding the mixture into a water washing tower to separate the washing water and the benzene extract part of the caprolactam.
7. The method for refining caprolactam extraction as claimed in claim 6, wherein the water scrubber contains a ceramic filler; preferably, the water washing tower is also provided with a baffle device.
8. The method for refining caprolactam extract according to claim 1, wherein the washing with the alkali solution is performed with an alkali solution having a concentration of 1 wt%.
9. The method for refining caprolactam extraction liquid according to claim 1, wherein the alkali washing and the second water washing are performed in an alkali washing-water washing combined tower, and the combined tower is provided with a pH meter;
preferably, the caprolactam benzene extraction liquid after the first washing enters an alkaline washing-water washing composite tower, and the amount of the added alkaline solution is adjusted by a pH meter until the solution is neutral; the dosage of the water for the second time of washing is adjusted according to the content of the added alkali.
10. The method for refining caprolactam extraction liquid according to claim 1, wherein the back extraction is to add process evaporation condensate to a benzene extraction liquid of caprolactam to extract the caprolactam into a water phase, and the ratio of the addition evaporation condensate to the extraction liquid is about 1: 2.5.
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| CN202010631753.8A CN111875542A (en) | 2020-07-03 | 2020-07-03 | Refining method of caprolactam extraction liquid |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115253380A (en) * | 2022-08-19 | 2022-11-01 | 清元智能科技研究院(湖北)有限公司 | Caprolactam extraction system and method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115253380A (en) * | 2022-08-19 | 2022-11-01 | 清元智能科技研究院(湖北)有限公司 | Caprolactam extraction system and method |
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