CN-121974838-A - Separation and recovery method for components in residual liquid in kettle in rectification section

CN121974838ACN 121974838 ACN121974838 ACN 121974838ACN-121974838-A

Abstract

The invention belongs to the technical field of chemical waste liquid recycling, and particularly discloses a separation and recovery method for each component in kettle residual liquid in a rectification section, which comprises the following steps that S1, an inorganic acid aqueous solution is added into the kettle residual liquid to obtain upper-layer liquid and lower-layer grease-like substances; S2, performing reduced pressure distillation on the lower-layer grease-like substance, then performing solvent-induced fractional crystallization treatment, sequentially separating out hydroxy fatty acid and amino-terminated fatty acid, S3, enabling upper-layer liquid to pass through a molecular sieve adsorption bed, and then steaming out in a reduced pressure distillation tower to obtain TMBDA, S4, introducing the rest materials after TMBDA removal into an extraction rectifying tower, extracting NEP from the top of the tower, S5, feeding tower bottom materials into a flash tank, and carrying out flash evaporation to obtain NMP. The method for separating and recovering each component in the residual liquid in the rectifying section kettle effectively separates and recovers all components from the residual liquid in the rectifying section kettle, has mild operation conditions and obvious economic and environmental benefits.

Inventors

TAN XUEJUN
LIANG BIN
HE GUOTAO
LI KAI
Zhao Kaichuan
ZHOU JUNBO
LI JIANSHE

Assignees

新迈奇材料股份有限公司

Dates

Publication Date: 20260505
Application Date: 20260320

Claims (10)

1. The separation and recovery method for each component in the residual liquid in the kettle of the rectification section is characterized by comprising the following steps: S1, acid precipitation and centrifugal separation, namely adding an inorganic acid aqueous solution into kettle residual liquid, regulating the pH value of the system to 2-4, stirring for reaction, standing for sedimentation, and naturally separating liquid or centrifuging to obtain upper-layer liquid and lower-layer grease-like substances; S2, separating a fatty acid mixture, namely performing reduced pressure distillation on the lower-layer grease-like substance obtained in the step S1 to obtain a crude fatty acid mixture, and then performing solvent-induced fractional crystallization treatment to sequentially separate out hydroxy fatty acid and amino-terminated fatty acid; s3, liquid dehydration and pre-separation, namely, distilling the upper layer liquid obtained in the step S1 in a reduced pressure distillation tower, adsorbing by a molecular sieve adsorption bed, and then distilling out in the reduced pressure distillation tower at a constant temperature, and rectifying to obtain TMBDA; S4, separating and purifying NMP and NEP, namely introducing the residual materials after TMBDA removal into an extraction rectifying tower, adding an extractant, heating for reaction, and extracting NEP from the tower top to obtain tower bottom materials of which the residual materials are NMP and ionic liquid; S5, recovering the solvent, namely sending the tower kettle material obtained in the step S4 into a flash tank or a thin film evaporator, performing high-temperature high-vacuum treatment to obtain NMP, and returning the ionic liquid to the extraction rectifying tower for recycling.
2. The method for separating and recovering components in kettle residual liquid in a rectification section according to claim 1, wherein in S1, the inorganic acid is dilute sulfuric acid with the concentration range of 10% -25% or dilute hydrochloric acid with the concentration range of 10% -15%, and the adding process of the inorganic acid is slowly performed under the cooling of ice water bath.
3. The method for separating and recovering components in kettle raffinate in a rectification section according to claim 1, wherein in S2, the solvent-induced fractional crystallization treatment is specifically: Adding an ethyl acetate-petroleum ether mixed solvent into the crude fatty acid mixture, standing, preferentially separating out the hydroxy fatty acid by controlling the cooling rate and the crystallization temperature, obtaining a hydroxy fatty acid product and a mother solution after solid-liquid separation, and further concentrating and crystallizing the mother solution to obtain the amino-terminated fatty acid.
4. The method for separating and recovering each component in kettle raffinate in a rectification section according to claim 3, wherein the ethyl acetate-petroleum ether mixed solvent is specifically: the volume ratio of the petroleum ether to the ethyl acetate is 1:0.8-1.2.
5. The separation and recovery method for each component in kettle residual liquid in a rectification section according to claim 3 is characterized by comprising the steps of firstly crystallizing and separating hydroxy fatty acid at 13-16 ℃, controlling the cooling rate to be 0.5-1.5 ℃ per minute, standing for 27-35 min, then crystallizing and separating amino fatty acid at-5~0 ℃ and controlling the cooling rate to be 0.4-1.0 ℃ per minute, and standing for 27-35 min.
6. A method for separating and recovering components in a rectifying section kettle raffinate according to claim 3, wherein the mass ratio of the crude fatty acid mixture to the ethyl acetate-petroleum ether mixed solvent is 1:10.
7. The method for separating and recovering components in kettle raffinate in a rectification section according to claim 1, wherein in the step S3, the control temperature is 118-130 ℃.
8. The separation and recovery method of components in kettle raffinate in a rectification section according to claim 1, wherein in S4, an extractant of the extraction rectification tower is 1-ethyl-3-methylimidazole tetrafluoroborate, and a feed mass ratio of the 1-ethyl-3-methylimidazole tetrafluoroborate to the residual materials after TMBDA removal is 1:0.65-2.
9. The method for separating and recovering components in kettle raffinate in a rectification section according to claim 1, wherein in S4, the control parameters of the heating reaction are specifically as follows: The temperature of the tower bottom is controlled to be 110-115 ℃, the temperature of the tower top is controlled to be 103-120 ℃, and the vacuum degree is not lower than-0.098 MPa.
10. The method for separating and recovering components in kettle raffinate in a rectification section according to claim 1, wherein in S5, the control parameters of the high-temperature high-vacuum treatment are specifically as follows: the temperature of the tower bottom is controlled to be 135-140 ℃, the temperature of the tower top is controlled to be 128-135 ℃, and the vacuum degree is not lower than-0.098 MPa.

Description

Separation and recovery method for components in residual liquid in kettle in rectification section Technical Field The invention relates to the technical field of chemical waste liquid recycling, in particular to a separation and recovery method for each component in kettle residual liquid in a rectification section. Background The rectifying section still residue is a complex multicomponent mixture generated in the chemical production process, namely a typical multicomponent mixture containing high boiling point solvent, surfactant and amine, and the typical composition of the rectification section still residue comprises N-methylpyrrolidone (NMP, 76.8%), N-ethylpyrrolidone (NEP, 6.1%), sodium amino-terminated fatty acid (6.1%), sodium hydroxy fatty acid (7%) and tetramethylbutanediamine (TMBDA, 4.0%). The NMP and NEP are polar aprotic solvents, have similar physical and chemical properties (high boiling point and close boiling point), consume a large amount of energy sources for conventional rectification separation, have low separation efficiency, are ionic surfactants, are extremely high in heat sensitivity and easy to decompose and coke after being heated, can block equipment and cannot realize separation through conventional rectification, and TMBDA is taken as organic amine, and can form azeotropes or interact with other components. In the prior art, the invention patent with publication number CN116650983B discloses a TDI distillation raffinate treatment technology, namely, recovery of a focused single component (TDI), and separation by high-temperature drying and quenching, which does not involve cooperative separation of multiple components (such as NMP, NEP, fatty acid salt and the like) and does not solve the problem of equipment coking caused by ionic surfactants. The invention patent application with publication No. CN120966553A discloses a cinnamon oil kettle residue recovery technology, which is only applicable to low-boiling point perfume components by adopting superheated steam distillation and physical crystallization, and cannot treat complex systems of high-boiling point organic solvents (such as NMP and NEP) and ionic compounds. Direct rectification is difficult to effectively separate all components, equipment scaling and product decomposition are easy to cause, and a method for economically, efficiently and highly-purity recycling all components from the complex mixture is lacked, so that the waste of kettle residual liquid resources is serious, and meanwhile, environmental protection pressure is brought. Therefore, there is an urgent need to develop an integrated process with low energy consumption, no product decomposition, no scaling of equipment, and thorough separation. Disclosure of Invention The invention aims to provide a separation and recovery method for each component in the residual liquid of the kettle in the rectification section, which effectively separates and recovers five components including NMP, NEP, sodium amino-terminated fatty acid, sodium hydroxy fatty acid and TMBDA from the residual liquid of the kettle in the rectification section, has mild operation conditions and has remarkable economic and environmental benefits. In order to achieve the purpose, the invention provides a separation and recovery method for each component in residual liquid in a rectification section kettle, which comprises the following steps: S1, acid precipitation and centrifugal separation, namely adding an inorganic acid aqueous solution into kettle residual liquid, regulating the pH value of the system to 2-4, stirring for reaction, standing for sedimentation, and naturally separating liquid or centrifuging to obtain upper-layer liquid and lower-layer grease-like substances; S2, separating a fatty acid mixture, namely performing reduced pressure distillation on the lower-layer grease-like substance obtained in the step S1 to obtain a crude fatty acid mixture, and then performing solvent-induced fractional crystallization treatment to sequentially separate out hydroxy fatty acid and amino-terminated fatty acid; s3, liquid dehydration and pre-separation, namely, distilling the upper layer liquid obtained in the step S1 in a reduced pressure distillation tower, adsorbing by a molecular sieve adsorption bed, and then distilling out in the reduced pressure distillation tower at a constant temperature, and rectifying to obtain TMBDA; S4, separating and purifying NMP and NEP, namely introducing the residual materials after TMBDA removal into an extraction rectifying tower, adding an extractant, heating for reaction, and extracting NEP from the tower top to obtain tower bottom materials of which the residual materials are NMP and ionic liquid; S5, recovering the solvent, namely sending the tower kettle material obtained in the step S4 into a flash tank or a thin film evaporator, performing high-temperature high-vacuum treatment to obtain NMP, and returning the ionic liquid to the extraction