CN-121990946-A - Recovery method of acetonitrile-containing waste liquid

Abstract

The application discloses a recovery method of acetonitrile-containing waste liquid, which relates to the technical field of separation and purification and comprises the following continuous processes of concentration rectification, two-stage light removal, extraction rectification and solvent recovery, and purifying the waste liquid containing water, ethanol and methanol step by step to obtain the recyclable acetonitrile. The process includes concentrating at low temperature to recover most acetonitrile, eliminating light components in two light component eliminating towers, extracting and rectifying with composite extractant compounded with glycol, 1, 2-propylene glycol and dimethyl carbonate in certain proportion, breaking acetonitrile-water azeotropy with polarity difference, eliminating trace amount of water and organic impurity deeply, and decompression distilling and dewatering of the extractant in subsequent solvent recovering towers for reuse. The recovery method adopts the optimized matching of the reflux ratio and the number of the tower plates, and can realize the effects of low energy consumption and high yield under mild conditions.

Inventors

• LIU WEI
• QIU LIJING
• ZHOU YIWEN

Assignees

• 江苏电科环保有限公司

Dates

Publication Date

20260508

Application Date

20260127

Claims (10)

1. 1. The recovery method of the acetonitrile-containing waste liquid is characterized by comprising the following steps: s1, pumping acetonitrile-containing waste liquid into a concentration rectifying tower at the temperature of 80-105 ℃ to obtain concentrated liquid; s2, pumping the liquid concentrated in the step S1 into a first light component removal tower, wherein the temperature is 75-82 ℃ to obtain a first light component removal liquid; S3, pumping the first light component removing liquid in the step S2 into a second light component removing tower at the temperature of 62-68 ℃ to obtain second light component removing liquid; S4, pumping the light component removed in the step S3 into an extraction rectifying tower, adding an extractant at the temperature of 70-90 ℃ to obtain an extract; S5, pumping the extract liquid obtained in the step S4 into a light component removal rectifying tower to obtain purified acetonitrile; s6, recycling the extraction extractant for recycling.
2. 2. The method for recovering acetonitrile-containing waste liquid according to claim 1, wherein the extractant is one or more of ethylene glycol, 1, 2-propylene glycol, dimethyl carbonate and isopropanol.
3. 3. The method for recovering acetonitrile-containing waste liquid according to claim 2, wherein the extractant is a mixture of ethylene glycol, 1, 2-propylene glycol and dimethyl carbonate.
4. 4. The method for recycling acetonitrile-containing waste liquid according to claim 3, wherein the extractant is a mixture of ethylene glycol, 1, 2-propylene glycol and dimethyl carbonate according to a mass ratio of (5-6): 3-4): 1.
5. 5. The method for recycling acetonitrile-containing waste liquid according to claim 1, wherein the mass ratio of the second light component removing liquid to the extractant is 1 (1-4).
6. 6. The method for recovering acetonitrile-containing waste liquid according to claim 1, wherein the theoretical plate number of the extraction rectifying tower is 42-46, the second light component removing liquid is 38-42 in the feeding position of the extraction rectifying tower, and the extracting agent is 3-4 in the feeding position of the extraction rectifying tower.
7. 7. The method for recovering acetonitrile-containing waste liquid according to claim 1, wherein the pressure of the extractive distillation column is 0.4-0.5atm and the reflux ratio is 1.5-2.5.
8. 8. The method for recovering acetonitrile-containing waste liquid according to claim 1, wherein the top temperature of the extractive distillation column is 62-66 ℃ and the bottom temperature is 120-130 ℃.
9. 9. The method for recovering acetonitrile-containing waste liquid according to claim 1, wherein the reflux ratio of the first light component removal tower is 1.0-1.6, and the reflux ratio of the second light component removal tower is 1.4-2.2.
10. 10. The method for recovering acetonitrile-containing waste liquid according to claim 1, wherein the acetonitrile waste liquid contains 60 to 80wt% of water, 10 to 20wt% of acetonitrile, 3 to 10wt% of ethanol, and the balance of methanol.

Description

Recovery method of acetonitrile-containing waste liquid Technical Field The application relates to the technical field of separation and purification, in particular to a recovery method of acetonitrile-containing waste liquid. Background In the production and processing process in the field of biological medicine, acetonitrile is used as an organic solvent with excellent performance, and is widely applied to a plurality of key links such as medicine synthesis, natural product extraction, finished product purification and the like by virtue of good solubility and chemical stability, so that the acetonitrile becomes an indispensable basic material in biological medicine production. However, after the actual production operation is finished, a large amount of acetonitrile waste liquid is generated, and the waste liquid contains complex components, besides main acetonitrile and water, various complex organic matters including raw materials and auxiliary materials which are not completely reacted, byproducts generated in the reaction process, degradation products generated in the medicine storage or reaction process and the like. If the acetonitrile waste liquid is directly discarded without treatment, the acetonitrile waste liquid not only can cause serious waste of acetonitrile which is a valuable resource and increase the production cost of biological medicine enterprises, but also can cause serious pollution to surrounding water, soil and atmospheric environment and destroy ecological balance, and meanwhile, the development concept of national environmental protection and resource recycling is not met, so that the efficient and feasible acetonitrile waste liquid recovery process is developed, the recycling of acetonitrile resources is realized, the environmental pollution is reduced, and the method has important economic value and environmental protection significance for sustainable development of the biological medicine industry. At present, a plurality of process methods are developed for separating and purifying acetonitrile and water in the industry, and different methods have characteristics and have respective limitations. The pressure-variable rectifying method breaks an azeotropic system formed by acetonitrile and water by changing the pressure of the system, so that the acetonitrile and the water are separated, but the method needs to consume a large amount of energy, has higher running cost and is not beneficial to large-scale popularization and application. The constant boiling rectification method needs to add a third component into the waste liquid as an entrainer to break the original azeotropic balance, but the defect is that the addition of the entrainer possibly introduces new impurities to influence the purity of the recovered acetonitrile, and then, additional processes are added to remove the impurities, thereby increasing the complexity of the production flow. The salting-out method is relatively simple to operate, does not need to be input by complex equipment, but has the problems that salts are difficult to recycle and secondary pollution is easy to cause, and the environmental protection treatment pressure is increased after long-term use. The dehydrating agent dehydration method has higher separation efficiency, can rapidly realize the separation of acetonitrile and water, but has higher cost, and part of dehydrating agent has corrosiveness, and has higher subsequent treatment difficulty, thus limiting the application of the dehydrating agent in mass production. The extraction and rectification method can effectively separate acetonitrile and water by virtue of good selectivity, but the core is that the selection of the extractant is that the proper extractant not only needs to have good separation effect, but also needs to be convenient for recycling, otherwise, the process cost is increased, and the screening and recycling of the high-quality extractant are always key problems facing the process. The adsorption method and the ion exchange method are simple and convenient to operate, the equipment investment is small, and the method is suitable for small-scale acetonitrile waste liquid treatment, but the adsorbents and the ion exchange resins used by the two methods are difficult to regenerate, new pollutants can be generated in the regeneration process, and the operation cost and the environmental protection burden of enterprises can be increased after long-term use. The membrane separation method is used as a novel separation technology, has the advantages of energy conservation, environmental protection, high separation efficiency, no secondary pollution and the like, accords with the development trend of green chemical industry, is limited by the performance of membrane materials, has shorter solvent resistance, stability and service life, has higher preparation cost, and is difficult to meet the requirement of large-scale acetonitrile waste liquid recovery in the field of bio