CN114957025B - Method for recovering glycine from waste liquid in glycocyamine production - Google Patents
Method for recovering glycine from waste liquid in glycocyamine production Download PDFInfo
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- C07C227/38—Separation; Purification; Stabilisation; Use of additives
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C227/00—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton
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Abstract
The application relates to the field of industrial wastewater treatment and recovery, and particularly discloses a method for recovering glycine from waste liquid generated in glycocyamine production, which comprises the following steps: (1) concentrating: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution; the pressure of the reduced pressure evaporation environment is 0.05-0.2atm, the temperature of the reduced pressure evaporation is 40-90 ℃, and when the solid content in the waste liquid reaches 40-60 wt%, the concentration is stopped to obtain concentrated solution; (2) crystallization: adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing until complete layering; (3) solid-liquid separation: and centrifuging, filtering with a filter membrane, vacuumizing and filtering the upper-layer material obtained after standing, washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine product. The method has the advantage that the raw materials in the production waste liquid can be efficiently recovered.
Description
Technical Field
The application relates to the field of industrial wastewater recovery, in particular to a method for recovering glycine from waste liquid in glycocyamine production.
Background
The common production process of guanidinoacetic acid is to take water as a reaction medium, take aminoacetic acid and cyanamide as raw materials, and carry out reaction under alkaline conditions, wherein the reaction is carried out with a small amount of side reaction while synthesizing the guanidinoacetic acid, and the side reaction is accompanied with the generation of by-products which are inevitably generated, and the by-products mainly comprise cyanamide polymers such as dicyandiamide and melamine. In order to ensure higher product quality and reaction efficiency, the proportion of aminoacetic acid, namely glycine, is increased in the reaction raw materials to reduce the occurrence of side reactions. Therefore, a large amount of glycine exists in the waste liquid in the production process, and a large amount of glycine is still wasted even through the mother liquid recycling process and other processes.
Disclosure of Invention
In order to reduce the situation that the production cost is high due to serious glycine waste in the current production process, the application provides a method for recovering glycine from glycocyamine production waste liquid
The application provides a method for recovering glycine from waste liquid in glycocyamine production, which adopts the following technical scheme:
a method for recovering glycine from waste liquid generated in production of glycocyamine comprises the following steps:
(1) And (3) concentrating: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.05-0.2atm, the temperature of the reduced pressure evaporation is 40-90 ℃, and when the solid content in the waste liquid reaches 40-60 wt%, the concentration is stopped to obtain concentrated solution;
(2) And (3) crystallization: adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing;
(3) Solid-liquid separation: and filtering the material after standing, washing with a crystallizing agent to filter out solids, and drying the obtained product to obtain the glycine product.
Preferably, when the solid content in the concentrated solution in the step (1) reaches 45-55 wt%, the concentration is stopped.
Preferably, the method is characterized in that: the crystallizing agent is selected from methanol, ethanol, ethylene glycol, isopropanol and glycerol.
Preferably, it is characterized in that: the crystallizing agent is ethanol.
Preferably, the volume ratio of the crystallization agent to the concentrated solution in the step (2) is 0.8-1.2:1.
preferably, the volume ratio of the crystallization agent to the concentrated solution in the step (2) is 1.
In the technical scheme, the volume ratio of the crystallizing agent to the concentrated solution is adjusted, so that the crystallization of the glycine in the crystallizing agent is promoted, the solubility of the glycine is reduced, and the yield of the glycine is improved. Meanwhile, other impurities in the concentrated solution can be dissolved by the crystallizing agent, so that the purity of the glycine is improved.
Preferably, in step (2), the temperature of the concentrated solution is kept between 40 and 50 ℃, the crystallizing agent is added, and the concentrated solution is controlled to crystallize at the temperature of between 35 and 45 ℃.
Preferably, the crystallization rate of glycine is decreased by adjusting the temperature at which the concentrated solution is crystallized, and the filtration method in step (3) is any one selected from the group consisting of membrane separation, centrifugal separation, vacuum separation under reduced pressure, and pressure separation.
Preferably, the method for recovering the glycine from the waste liquid generated in the production of the glycocyamine further comprises the following steps:
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3) and recovering the crystallizing agent.
The rectification temperature of the method for recovering the glycine from the waste liquid generated in the production of the glycocyamine is 55-200 ℃.
In summary, the present application has the following beneficial effects:
1. because this application is through concentrating the waste liquid, crystallization, filtration treatment to the glycine in the glycocyamine production waste liquid has been retrieved to the glycine yield of retrieving is high, and purity is high, but recycles and carries out the reproduction in the glycocyamine.
Drawings
FIG. 1 is a flow chart of a method provided herein;
FIG. 2 is a photomicrograph of the recovered glycine and food grade glycine of example 3 of the present application;
FIG. 3 is a liquid chromatogram of glycine recovered in example 3 of the present application together with food grade glycine.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples.
The method uses the waste liquid from the production of glycocyamine as a treatment raw material, takes 10 batches of waste liquid from the normal production of glycocyamine, and measures the content of each component in the waste liquid, wherein the measurement result is as follows:
TABLE 1 contents of the components in the waste liquid
Therefore, main impurities of the glycine recovered from the waste liquid produced in the production of the glycocyamine are glycocyamine, cyanamide, dicyandiamide and melamine. Therefore, a treatment means is required to separate glycine from the above impurities. Thus recovering glycine.
Example 1
A method for recovering glycine from waste liquid in glycocyamine production comprises the following steps:
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 40wt%, the concentration is stopped to obtain concentrated solution; condensing and collecting the evaporated gas to obtain condensate;
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallization agent is ethanol, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing the product by using a crystallizing agent to filter out a solid, and drying the product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 78 +/-1 ℃ during rectification, recovering a crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
Example 2
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 45wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallizing agent is ethanol, and the volume ratio of the crystallizing agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 78 +/-1 ℃ during rectification, recovering the crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
Example 3
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain a concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallization agent is ethanol, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 78 +/-1 ℃ during rectification, recovering the crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
Example 4
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 55wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallization agent is ethanol, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 78 +/-1 ℃ during rectification, recovering a crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
Example 5
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 60wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, fully mixing the concentrated solution and the crystallizing agent, stopping stirring, and standing for crystallization;
the crystallization agent is ethanol, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 78 +/-1 ℃ during rectification, recovering a crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
Example 6
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain a concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallization agent is methanol, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 65 +/-1 ℃, recovering a crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
Example 7
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, fully mixing the concentrated solution and the crystallizing agent, stopping stirring, and standing for crystallization;
the crystallization agent is glycol, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing the product by using a crystallizing agent to filter out a solid, and drying the product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 197 +/-1 ℃, recovering the crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
The effluent component contains glycol and water, and the water in the water part does not affect the reuse of the glycol, so that the obtained distillate with the temperature of less than 197 +/-1 ℃ can be directly recycled for the next waste liquid treatment.
Example 8
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, fully mixing the concentrated solution and the crystallizing agent, stopping stirring, and standing for crystallization;
the crystallizing agent is isopropanol, and the volume ratio of the crystallizing agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 82 +/-1 ℃, recovering a crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
Example 9
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallization agent is n-hexane, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3) to obtain a distillate temperature of 69 +/-1 ℃, recovering a crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
Example 10
(1) And (3) concentrating: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, fully mixing the concentrated solution and the crystallizing agent, stopping stirring, and standing for crystallization;
the crystallization agent is cyclohexane, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 81 +/-1 ℃, recovering a crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
Example 11
(1) And (3) concentrating: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallization agent is N, N-dimethylformamide, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing the product by using a crystallizing agent to filter out a solid, and drying the product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 153 +/-1 ℃, recovering a crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
The distillate contains N, N-dimethylformamide and water, and the existence of the water does not influence the reuse of the N, N-dimethylformamide as a crystallizing agent in the next waste liquid treatment, so that the obtained distillate with the temperature of less than 153 +/-1 ℃ can be directly reused in the next waste liquid treatment.
Example 12
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain a concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallization agent is ethanol, and the volume ratio of the crystallization agent to the concentrated solution is 0.8;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 78 +/-1 ℃ during rectification, recovering a crystallizing agent, stopping distillation after 90% of liquid is rectified, and treating the residual liquid at the bottom of the kettle as solid waste after the residual liquid is cooled.
Example 13
(1) And (3) concentrating: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, fully mixing the concentrated solution and the crystallizing agent, stopping stirring, and standing for crystallization;
the crystallization agent is ethanol, and the volume ratio of the crystallization agent to the concentrated solution is 1.2;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 78 +/-1 ℃ during rectification, recovering the crystallizing agent, and cooling the residual liquid at the bottom of the kettle to be treated as solid waste.
Comparative example 1
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 35wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallization agent is ethanol, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing the product by using a crystallizing agent to filter out a solid, and drying the product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 78 +/-1 ℃ during rectification, and recovering the crystallizing agent.
Comparative example 2
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 65wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, fully mixing the concentrated solution and the crystallizing agent, stopping stirring, and standing for crystallization;
the crystallization agent is ethanol, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 78 +/-1 ℃ during rectification, and recovering the crystallizing agent.
Comparative example 3
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain a concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallization agent is ethyl acetate, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 77 +/-1 ℃ during rectification, and recovering the crystallizing agent.
Comparative example 4
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallizing agent is acetone, and the volume ratio of the crystallizing agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing the product by using a crystallizing agent to filter out a solid, and drying the product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 56.5 +/-1 ℃ during rectification, and recovering the crystallizing agent.
Comparative example 5
(1) And (3) concentrating: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, fully mixing the concentrated solution and the crystallizing agent, stopping stirring, and standing for crystallization;
the crystallization agent is N, N-dimethylacetamide, and the volume ratio of the crystallization agent to the concentrated solution is 1;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 166 +/-1 ℃ during rectification, and recovering the crystallizing agent.
The distillate contains N, N-dimethylacetamide and water, and the existence of water does not influence the reuse of the N, N-dimethylacetamide as a crystallizing agent in the next waste liquid treatment, so that the obtained distillate with the temperature of 166 +/-1 ℃ can be directly reused in the next waste liquid treatment.
Comparative example 6
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, fully mixing the concentrated solution and the crystallizing agent, stopping stirring, and standing for crystallization;
the crystallizing agent is ethanol, and the volume ratio of the crystallizing agent to the concentrated solution is 0.5;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 78 +/-1 ℃ during rectification, and recovering the crystallizing agent.
Comparative example 7
(1) Concentration: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.1atm, the temperature of the reduced pressure evaporation is 80 ℃, and when the solid content in the waste liquid reaches 50wt%, the concentration is stopped to obtain concentrated solution; the evaporated gas is condensed and collected to obtain condensate
(2) And (3) crystallization: cooling the concentrated solution to 40 ℃, adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing for crystallization;
the crystallizing agent is ethanol, and the volume ratio of the crystallizing agent to the concentrated solution is 1.5;
(3) Solid-liquid separation: and (3) filtering the product obtained in the step (2), washing with a crystallizing agent to filter out a solid, and drying the obtained product to obtain the glycine.
The crystallization temperature was maintained at 40 ℃. + -. 3 ℃.
(4) And (3) rectification: and (4) rectifying the filtrate obtained in the step (3), wherein the distillation temperature is 78 +/-1 ℃ during rectification, and recovering the crystallizing agent.
Examples 1-13, comparative examples 1-7, the parameters varied and the glycine yield purity obtained is shown in table 2.
Table 2, examples 1-13, comparative examples 1-7, part of the parameter variations and the yield purity of the glycine obtained
Referring to examples 1 to 5 and comparative examples 1 and 2 in Table 2, it can be seen that the yield of glycine gradually increased with the increase of the solid content in the concentrate, but when the solid content is more than 50wt%, the purity of the obtained glycine was lowered. When the solid content is more than 65, the yield of the obtained glycine is more than 100%, probably because a part of impurities is doped in the glycine, thereby causing a decrease in the purity of the glycine and an increase in the yield.
Referring to examples 3 and 6 to 11, it can be seen that methanol, ethanol, ethylene glycol, isopropanol, N-hexane, cyclohexane and N, N-dimethylformamide can promote the crystallization agent of glycine, and simultaneously, the yield of the obtained glycine is not less than 64.12%, and the purity is not less than 98.25. Wherein, when ethanol is selected as a crystallizing agent, the yield of the glycine can reach 86.92 percent, and the purity can reach 99.85 percent.
Referring to examples 3, 11 and 12 and comparative examples 6 and 7, it can be seen that the dosage ratio of the crystallizing agent to the concentrated solution affects the purity and yield of the glycine product, and when the ratio of the crystallizing agent to the concentrated solution is 0.8-1.2, the purity and yield of the glycine obtained are both excellent, and meet the requirements of recycling normal production. When the ratio of the crystallizing agent to the concentrated solution is reduced, the purity of the glycine is reduced, and when the ratio of the crystallizing agent to the concentrated solution is more than 1.2, the yield of the glycine is affected, so that waste is generated.
Confirmation of the treatment product
As shown in FIG. 2, the glycine crystals obtained in example 3 and the food grade glycine crystals were simultaneously placed under a microscope for observation and comparison.
Microscopic observation shows that the purity of the recovered glycine crystal is high, and the crystal form is consistent with that of food-grade glycine.
As shown in fig. 3, the liquid chromatography analysis of the glycine crystals obtained in example 3 and the food grade glycine crystals showed that the recovered glycine and the food grade glycine were consistent in peak profile and separation time.
By combining the above judgments, the recovered substance was glycine.
Application example, recycling effect of condensate and glycine
(1) 180.17g of glycine obtained in the step (3) of example 3, 280.27g of cyanamide (effective content is 30%) and 6g of sodium hydroxide are weighed;
(2) Heating in water bath, adding 475ml of condensate recovered in the step (1) in the embodiment 3 into a four-neck flask, heating to 80 ℃, adding glycine, stirring for 3-4 minutes, adding sodium hydroxide, and washing a beaker by using 25ml of condensate;
(3) After the temperature rises to about 85 ℃, dropwise adding cyanamide, finishing dropwise adding within about 3 hours, and controlling the temperature to be 86-88 ℃;
(4) After the cyanamide is dripped, continuously preserving the heat for 2 hours, and maintaining the temperature at 86-88 ℃;
(5) After the heat preservation is finished, closing the water bath, and continuing stirring to naturally cool the material to 30 ℃;
(6) And (3) carrying out vacuum filtration on the materials, collecting filter residues, drying at 80 ℃, weighing the samples and inspecting.
Weighing, and testing to obtain 210.03g of glycocyamine with the yield of 89.67%; the purity of the glycocyamine is 98.92 percent. The product yield and purity both meet the requirements of normal production.
It will be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principles of the present invention, and the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.
Claims (8)
1. A method for recovering glycine from waste liquid generated in production of glycocyamine is characterized in that: the method comprises the following steps:
(1) And (3) concentrating: carrying out reduced pressure evaporation on the glycocyamine waste liquid to obtain a concentrated solution;
the pressure of the reduced pressure evaporation environment is 0.05-0.2atm, the temperature of the reduced pressure evaporation is 40-90 ℃, and when the solid content in the waste liquid reaches 40-60 wt%, the concentration is stopped to obtain concentrated solution;
(2) And (3) crystallization: adding a crystallizing agent into the concentrated solution, stirring simultaneously, stopping stirring after the concentrated solution and the crystallizing agent are fully mixed, and standing;
the crystallizing agent is selected from methanol, ethanol, ethylene glycol and isopropanol;
the volume ratio of the crystallization agent to the concentrated solution is 0.8-1.2:1;
(3) Solid-liquid separation: and filtering the material after standing, washing with a crystallizing agent to filter out solids, and drying the obtained product to obtain the glycine product.
2. The method for recovering glycine from waste liquid in the production of glycocyamine according to claim 1, which is characterized in that: and (2) stopping concentration when the solid content in the concentrated solution in the step (1) reaches 45-55 wt%.
3. The method for recovering glycine from waste liquid in glycocyamine production and the application thereof according to claim 1 are characterized in that: the crystallizing agent is ethanol.
4. The method for recovering glycine from waste liquid in the production of glycocyamine according to claim 1, which is characterized in that: and (3) the volume ratio of the crystallization agent to the concentrated solution in the step (2) is 1.
5. The method for recovering glycine from the waste liquid in the production of glycocyamine according to claim 1 or 3, which is characterized in that: in the step (2), the temperature of the concentrated solution is kept between 40 and 50 ℃, a crystallizing agent is added, and the concentrated solution is controlled to crystallize at the temperature of between 35 and 45 ℃.
6. The method for recovering glycine from waste liquid in glycocyamine production according to claim 1, characterized in that: the filtration mode in the step (3) is any one of membrane separation, centrifugal separation, vacuum decompression separation or pressurization separation.
7. The method for recovering glycine from waste liquid in the production of glycocyamine according to claim 1, which is characterized in that: further comprising the steps of: (4) rectification: and (4) rectifying the filtrate obtained in the step (3) and recovering the crystallizing agent.
8. The method for recovering glycine from waste liquid in glycocyamine production according to claim 7, characterized in that: the rectification temperature is 55-200 ℃.
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