CN115894322A - Method and system for treating caprolactam crystallization mother liquor - Google Patents
Method and system for treating caprolactam crystallization mother liquor Download PDFInfo
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- CN115894322A CN115894322A CN202211743362.0A CN202211743362A CN115894322A CN 115894322 A CN115894322 A CN 115894322A CN 202211743362 A CN202211743362 A CN 202211743362A CN 115894322 A CN115894322 A CN 115894322A
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Abstract
A treatment method and a device of caprolactam crystallization mother liquor, the method comprises alkali washing, water back extraction, concentration and benzene extraction; alkali washing, namely mixing caustic soda and mother liquor containing impurities, a solvent and caprolactam, which is obtained by performing solid-liquid separation on the crystal slurry, discharging an alkaline inorganic phase, and allowing a mixed solution after the alkali washing to enter the next step; performing water back extraction, performing back extraction on the mixed solution after alkaline washing by using water, discharging the solution containing impurities, and performing the next step on the extraction residual phase; concentrating, namely concentrating the residual phase after extraction, and carrying out next step on the concentrated liquid; benzene extraction, namely extracting the concentrated liquid by using benzene to extract caprolactam; the impurities in the caprolactam crystallization mother liquor are separated from the caprolactam through the steps. The system consists of an alkaline washing tower, a water back extraction tower, a liquid concentration tower and a benzene extraction tower. The invention has the advantage of providing a guarantee measure for the development of a process route for refining caprolactam crystallization.
Description
Technical Field
The invention relates to the technical field of production of treatment of crystallization mother liquor generated in crystal separation in an industrial purification process, in particular to a process method for impurity removal treatment of mother liquor obtained after crystallization and crystal separation of caprolactam in a solvent and recovery of caprolactam in the mother liquor.
Background
In the existing caprolactam industrial production process, the refining of crude caprolactam usually adopts the technical scheme that: after the rearrangement reaction solution containing sulfuric acid and obtained after the Beckmann rearrangement reaction of cyclohexanone oxime is neutralized by ammonia water to separate crystal ammonium sulfate, crude caprolactam solution (amide oil) containing impurities and water of about 25-30% is subjected to benzene extraction, water back extraction, ion exchange, hydrogenation, dehydration and distillation to obtain the finished product caprolactam. The whole process does not relate to a process technology of caprolactam crystallization, and does not relate to a treatment technology of mother liquor in the process of caprolactam crystallization. The invention is in developing the crystallization technical process of caprolactam which takes cyclohexane or toluene or benzene or the composition of cyclohexane or toluene or benzene as solvent, after crystallization, purification and separation of caprolactam crystal, crystallization mother liquor also contains saturated caprolactam and a large amount of enriched impurities, and caprolactam recovery, refining and impurity removal treatment must be carried out on the crystallization mother liquor. The technology is a method for removing impurities from crystallization mother liquor and recovering and refining caprolactam in the crystallization mother liquor.
Disclosure of Invention
The invention provides a method and a system for refining and removing impurities and simultaneously recovering caprolactam in crystallization mother liquor generated in a caprolactam refining process, and provides a guarantee measure for opening up a process route for crystallizing and refining caprolactam. In the crystallization process of caprolactam containing impurities, the impurities are enriched in crystallization mother liquor, and the impurities in the mother liquor and caprolactam are not effectively separated, so that the crystallization system is collapsed or the product yield is reduced.
The technical scheme for realizing the aim of the invention is as follows: a method for treating caprolactam crystallization mother liquor comprises alkali washing, water back extraction, concentration and benzene extraction;
the alkali washing is to mix caustic soda and mother liquor containing impurities, solvent and caprolactam obtained by solid-liquid separation of crystal slurry, discharge alkaline inorganic phase, and enter the next step after the alkali washing;
performing water back extraction, namely performing back extraction on the mixed solution after alkaline washing by using water, discharging the solution containing impurities, and performing the next step on the extraction residual phase;
the concentration is carried out, the extraction residual phase is concentrated, and the concentrated liquid enters the next step;
the benzene extraction is to extract the concentrated liquid by using benzene to extract caprolactam; the impurities in the caprolactam crystallization mother liquor are separated from the caprolactam through the steps.
Further, the method also comprises acid washing, wherein the acid washing is carried out before the alkali washing;
and in the acid washing, sulfuric acid is mixed with mother liquor containing impurities, a solvent and caprolactam, which is obtained by carrying out solid-liquid separation on crystal slurry, an acidic inorganic phase is discharged, and the mixed liquid after the acid washing enters the next step.
Further, in the alkali washing step, the concentration of the caustic soda is 3-50%.
Further, in the acid washing step, the concentration of sulfuric acid is 3 to 98 percent.
Further, the acidic inorganic phase discharged from the acid washing step is mixed with the alkaline inorganic phase discharged from the alkaline washing step for neutralization.
Further, the impurity-containing solution discharged in the water back-extraction step is refined, impurities are discharged, and the refined liquid is subjected to benzene extraction.
Furthermore, in the concentration step, the aqueous solution of caprolactam is 5-50% of water.
A processing system of caprolactam crystallization mother liquor comprises an acid washing tower, an alkaline washing tower, a water back extraction tower, a liquid concentration tower and a benzene extraction tower;
sulfuric acid liquid is introduced into the acid washing tower, and caustic soda liquid is introduced into the alkaline washing tower;
the mixed liquid discharge pipe after acid cleaning of the acid cleaning tower is communicated with the alkaline cleaning tower, the acidic organic phase is discharged from the acid cleaning tower, the mixed liquid discharge pipe after alkaline cleaning of the alkaline cleaning tower is communicated with the water back-extraction tower, and the alkaline organic phase is discharged from the alkaline cleaning tower;
and the residual phase extracted by the water stripping tower is input into the liquid concentration tower for concentration, the extract phase is discharged out of the water stripping tower, and the liquid concentrated by the liquid concentration tower is input into the benzene extraction tower for benzene extraction.
A processing system of caprolactam crystallization mother liquor comprises an alkaline washing tower, a water back extraction tower, a liquid concentration tower and a benzene extraction tower;
caustic soda liquid is introduced into the caustic tower;
a mixed liquid discharge pipe after alkaline washing of the alkaline washing tower is communicated with the water back-extraction tower, and an alkaline organic phase is discharged from the alkaline washing tower;
and the residual phase extracted by the water stripping tower is input into the liquid concentration tower for concentration, the extract phase is discharged out of the water stripping tower, and the liquid concentrated by the liquid concentration tower is input into the benzene extraction tower for benzene extraction.
The invention has the advantages that: compared with the existing acid washing process, the method adopts alkali washing or alkali washing plus acid washing, the alkali washing is carried out firstly, the separation efficiency is better, and the separation efficiency is improved by 5-10% in comparison; the consumption index has larger reduction amplitude.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
FIG. 2 is a preferred flow diagram of the process of the present invention.
Fig. 3 is a block diagram of the system of the present invention.
Fig. 4 is a block diagram of another system of the present invention.
As shown in the figure, the system comprises an acid washing tower 1, a caustic washing tower 2, a water back extraction tower 3, a liquid concentration tower 4 and a benzene extraction tower 5.
Detailed Description
Referring to fig. 1, a treatment method of caprolactam crystallization mother liquor comprises alkali washing, water back extraction, concentration and benzene extraction;
the alkali washing comprises the steps of mixing caustic soda and mother liquor containing impurities, a solvent and caprolactam, wherein the mother liquor is obtained by carrying out solid-liquid separation on crystal slurry, discharging an alkaline inorganic phase, feeding the mixed liquor after the alkali washing into the next step, discharging the alkaline inorganic phase, and then incinerating or recycling the alkaline inorganic phase, preferably, in the alkali washing step, the concentration of the caustic soda is 3-50%, and the adding amount per hour is 0.3-0.8 time of the inflow amount of the mother liquor;
performing water back extraction, namely performing back extraction on the mixed solution after alkali washing by using water, discharging an impurity-containing solution, allowing an extraction residual phase to enter the next step, refining the impurity-containing solution by using a solvent after discharging, incinerating or recycling the impurity-containing solution after discharging, and allowing the solution to enter a benzene extraction unit for benzene extraction;
concentrating the extraction residual phase, and feeding the concentrated liquid into the next step, preferably, the caprolactam water solution is 5-50% of water;
the benzene extraction is to extract the concentrated liquid by using benzene to extract caprolactam;
the impurities in the caprolactam crystallization mother liquor are separated from the caprolactam through the steps.
Compared with the traditional acid flow process, the method has the characteristics of high treatment efficiency and stability, the data of a newly-built pilot test system for treating 100 tons of caprolactam crystallization mother liquor per day is compared with the data of a traditional system for treating 350 tons of caprolactam crude oil per day in the following table 1, and the data of the newly-built pilot test system for treating the caprolactam crystallization mother liquor is compared with the data of the traditional caprolactam extraction treatment system:
the compression time of the new process component (1) is 8-10% of that of the conventional water back extraction, because only alkali washing is carried out without acid washing, the impurity content is higher, but the comprehensive treatment effect is particularly obvious, particularly, the treatment speed is accelerated, and the capacity of the whole system is greatly improved.
Referring to fig. 2, a treatment method of caprolactam crystallization mother liquor comprises acid washing, alkali washing, water back extraction, concentration and benzene extraction;
the acid cleaning is to mix sulfuric acid with mother liquor containing impurities, solvent and caprolactam obtained by solid-liquid separation of crystal slurry, discharge acidic inorganic phase, and then the mixed liquor enters the next step, preferably, the concentration of the sulfuric acid is 3-98%, and the adding amount per hour is 0.3-0.8 times of the inflow amount of the mother liquor;
in the alkali washing, caustic soda and mother liquor containing impurities, a solvent and caprolactam, which is obtained by solid-liquid separation of crystal slurry, are mixed, an alkaline inorganic phase is discharged, the mixed liquor after alkali washing enters the next step, the alkaline inorganic phase and an acidic inorganic phase are neutralized and then are burned or recycled, preferably, in the alkali washing step, the caustic soda concentration is 3-50%, and the injection amount per hour is 0.3-0.8 time of the inflow amount of the mother liquor;
the water back extraction is carried out, the mixed solution after the alkali washing is back extracted by water, the solution containing impurities is discharged, the extraction residual phase enters the next step, the solution containing impurities is refined by a solvent after being discharged, the impurity phase is burned or recycled, and the solution enters a benzene extraction unit for benzene extraction;
concentrating the extraction residual phase, and feeding the concentrated liquid into the next step, preferably, the caprolactam water solution is 5-50% of water;
the benzene extraction is to extract the concentrated liquid by using benzene to extract caprolactam;
the impurities in the caprolactam crystallization mother liquor are separated from the caprolactam through the steps.
Compared with the traditional acid flow process, the method has the characteristics of high treatment efficiency and stability, the data of a newly-built pilot test system for treating 100 tons of caprolactam crystallization mother liquor per day is compared with the data of a traditional system for treating 350 tons of caprolactam crystallization mother liquor per day in the following table 1, and compared with the traditional caprolactam crystallization mother liquor treatment system, the pilot test system for treating the newly-built caprolactam crystallization mother liquor is additionally provided with an alkali washing step after the original acid washing:
compared with the new process component (1), the new process component (2) increases an acid washing step, the impurity content reaches the standard of conventional water back extraction, but the comprehensive reaction time is only accelerated by 5-6%.
Compared with the traditional treatment process, the two methods have the advantages that the alkali washing step is added, the treatment speed of the whole process is higher through alkali washing, the compression time is about 5-10%, and the recovery rate of caprolactam is improved to more than 94.5%.
As shown in fig. 3, a processing system of caprolactam crystallization mother liquor consists of an acid washing tower 1, an alkali washing tower 2, a water back extraction tower 3, a liquid concentration tower 4 and a benzene extraction tower 5;
sulfuric acid liquid is introduced into the acid washing tower 1, and caustic soda liquid is introduced into the alkaline washing tower 2;
the mixed liquid discharge pipe after acid cleaning of the acid cleaning tower 1 is communicated with the alkaline cleaning tower 2, the acidic organic phase is discharged from the acid cleaning tower 1, the mixed liquid discharge pipe after alkaline cleaning of the alkaline cleaning tower 2 is communicated with the water back-extraction tower 3, and the alkaline organic phase is discharged from the alkaline cleaning tower 2;
and the extraction residual phase taken by the water back extraction tower 3 is input into the liquid concentration tower 4 for concentration, the extraction phase is discharged out of the water back extraction tower 3, and the liquid concentrated by the liquid concentration tower 4 is input into the benzene extraction tower 5 for benzene extraction.
As shown in fig. 4, a treatment system of caprolactam crystallization mother liquor consists of an alkaline washing tower 2, a water back extraction tower 3, a liquid concentration tower 4 and a benzene extraction tower 5;
caustic soda liquid is introduced into the caustic tower 2;
the mixed liquid discharge pipe after alkaline washing of the alkaline washing tower 2 is communicated with the water back extraction tower 3, and an alkaline organic phase is discharged out of the alkaline washing tower 2;
and the extraction residual phase taken by the water stripping tower 3 is input into the liquid concentration tower 4 for concentration, the extraction phase is discharged out of the water stripping tower 3, and the liquid concentrated by the liquid concentration tower 4 is input into the benzene extraction tower 3 for benzene extraction.
Claims (9)
1. A processing method of caprolactam crystallization mother liquor is characterized in that: the method comprises alkali washing, water back extraction, concentration and benzene extraction;
the alkali washing is to mix caustic soda and mother liquor containing impurities, solvent and caprolactam obtained by solid-liquid separation of crystal slurry, discharge alkaline inorganic phase, and enter the next step after the alkali washing;
performing water back extraction, namely performing back extraction on the mixed solution after alkaline washing by using water, discharging the solution containing impurities, and performing the next step on the extraction residual phase;
the concentration is carried out, the extraction residual phase is concentrated, and the concentrated liquid enters the next step;
the benzene extraction is to extract the concentrated liquid by using benzene to extract caprolactam;
the impurities in the caprolactam crystallization mother liquor are separated from the caprolactam through the steps.
2. The method for processing caprolactam crystallization mother liquor according to claim 1, which is characterized in that: the method also comprises acid washing, wherein the acid washing is carried out before the alkali washing;
and in the acid washing, sulfuric acid is mixed with mother liquor containing impurities, a solvent and caprolactam, which is obtained by carrying out solid-liquid separation on the crystal slurry, an acidic inorganic phase is discharged, and the mixed liquid after the acid washing enters the next step.
3. The method for processing caprolactam crystallization mother liquor according to claim 1, which is characterized in that: in the alkali washing step, the concentration of caustic soda is 3-50%.
4. The method for processing caprolactam crystallization mother liquor as claimed in claim 2, which is characterized in that: in the acid washing step, the concentration of sulfuric acid is 3-98%.
5. The method for processing caprolactam crystallization mother liquor as claimed in claim 2, which is characterized in that: and mixing the acidic inorganic phase discharged in the acid washing step with the alkaline inorganic phase discharged in the alkaline washing step for neutralization.
6. A process according to claim 1 or 2, characterized in that: and refining the impurity-containing solution discharged in the water back-extraction step, discharging impurities, and performing benzene extraction on the refined liquid.
7. A process according to claim 1 or 2, characterized in that: in the concentration step, the water content of the caprolactam aqueous solution is 5 to 50 percent.
8. A processing system of caprolactam crystallization mother liquor is characterized in that: the system consists of an acid washing tower, an alkali washing tower, a water back extraction tower, a liquid concentration tower and a benzene extraction tower;
sulfuric acid liquid is introduced into the acid washing tower, and caustic soda liquid is introduced into the alkaline washing tower;
the mixed liquid discharge pipe after acid washing of the acid washing tower is communicated with the alkaline washing tower, the acidic organic phase is discharged from the acid washing tower, the mixed liquid discharge pipe after alkaline washing of the alkaline washing tower is communicated with the water back-extraction tower, and the alkaline organic phase is discharged from the alkaline washing tower;
and the residual phase extracted by the water stripping tower is input into the liquid concentration tower for concentration, the extract phase is discharged out of the water stripping tower, and the liquid concentrated by the liquid concentration tower is input into the benzene extraction tower for benzene extraction.
9. A processing system of caprolactam crystallization mother liquor is characterized in that: the system consists of an alkaline washing tower, a water back-extraction tower, a liquid concentration tower and a benzene extraction tower;
caustic soda liquid is introduced into the caustic tower;
a mixed liquid discharge pipe after alkaline washing of the alkaline washing tower is communicated with the water back-extraction tower, and an alkaline organic phase is discharged from the alkaline washing tower;
and the residual phase extracted by the water stripping tower is input into the liquid concentration tower for concentration, the extract phase is discharged out of the water stripping tower, and the liquid concentrated by the liquid concentration tower is input into the benzene extraction tower for benzene extraction.
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