Acetonitrile continuous negative pressure distillation extraction technology

Abstract

The invention relates to an acetonitrile continuous negative pressure distillation extraction technology. The technology comprises preheating crude acetonitrile to a temperature of 70-80 DEG C, feeding the crude acetonitrile into a dehydrating tower, carrying out rectification separation, thoroughly removing ammonium sulfate in the crude acetonitrile at the tower bottom, simultaneously separating a part of water, feeding acetonitrile with content of 70% or more from the tower top into an extraction and rectification tower, simultaneously adding glycol with water content of 0.2% into the extraction and rectification tower, carrying out extraction water-removal purification, congealing acetonitrile with a concentration of 99% from the extraction and rectification tower top through an external condenser of the extraction and rectification tower, storing the acetonitrile in an acetonitrile receiving tank for finished product storage, feeding hydrous ethylene glycol from the tower bottom into an ethylene glycol dehydrating tower, carrying out deep dehydration, returning the ethylene glycol with water content less than 0.2% obtained by the ethylene glycol dehydrating tower to the extraction and rectification tower, and carrying out circular extraction and rectification. The technology has the advantages of energy saving, cost saving, stable processes, operation easiness and high purification degree.

Description

technical field [0001] The invention relates to a distillation extraction process, which belongs to the field of acetonitrile purification, in particular to an acetonitrile continuous negative pressure distillation extraction process. Background technique [0002] In the process of producing acetonitrile, the crude acetonitrile synthesized by "glacial acetic acid + liquid ammonia" contains 52% acetonitrile, 47% water, 1% ammonium sulfate and a small amount of acetone, propionitrile, tar, etc.; in order to obtain more than 99% For pure acetonitrile, the crude acetonitrile synthesized needs to be purified. In the process of purifying acetonitrile, the crude acetonitrile is dehydrated to obtain a high-concentration acetonitrile with a water content of 30%; Add the extractive distillation tower after 80°C, and heat the anhydrous ethylene glycol to 180°C and add it into the extractive distillation tower, and perform heat exchange and water exchange in the extractive distillation ...

AI Technical Summary

Problems solved by technology

[0002] In the process of producing acetonitrile, the crude acetonitrile synthesized by "glacial acetic acid + liquid ammonia" contains 52% acetonitrile, 47% water, 1% ammonium sulfate and a small amount of acetone, propionitrile, tar, etc.; in order to obtain more than 99% For pure acetonitrile, the crude acetonitrile synthesized needs to be purified. In the process of purifying acetonitrile, the crude acetonitrile is dehydrated to obtain a high-concentration acetonitrile with a water content of 30%; Add the extractive distillation tower after 80°C, and heat the anhydrous ethylene glycol to 180°C and add it into the extractive distillation tower, and perform heat exchange and water exchange in the extractive distillation tower, and the water with high concentration of acetonitrile is drawn into the extractive distillation tower Anhydrous ethylene glycol is taken away, and high-concentration acetonitrile absorbs the heat of anhydrous ethylene glycol and then vaporizes into pure acetonitrile. The obtained pure acetonitrile goes out from the top of the extraction and rectification column and is cooled to a liquid state by a condenser before entering the acetonitrile receiving tank. After the water is obtained from ethylene glycol, it goes out from the bottom of the extractive distillation tower, and is recycled after being distilled and dehydrated in the glycol dehydration tower; however, such acetonitrile extractive distillation process requires high-concentration acetonitrile containing 30% water to be heated to 80°C Adding to the extractive distillation tower, anhydrous ethylene glycol needs to be heated to 180°C and then added to the extractive distillation tower. This process consumes a lot of energy, which will inevitably cause serious energy waste and economic losses for the production enterprise.