Method and device for refining caprolactam

Abstract

The invention relates to a method and a device for refining caprolactam. The device comprises a stripping tower, a hydrogenation tower, a triple-effect evaporator, a dehydration tank, a concentration buffer tank, a No. 1 climbing film evaporator, a No. 2 climbing film evaporator, an evaporation and condensation tank, a light component removal tower and a heavy component removal tower. Amide oil is subjected to caustification and extraction processes to remove most of byproducts, and a separated caprolactam water solution is subjected to benzene stripping, hydrogenation, triple-effect evaporation, concentration and dehydration processes and then enters the concentration buffer tank. Alkali is added into the buffer tank for performing alkali treatment, and the caprolactam water solution after alkali treatment enters the climbing film evaporators for climbing film evaporation. Residues after evaporation return into a crystallization device for treatment. The caprolactam water solution evaporated by climbing film evaporation enters the light component removal tower and the heavy component removal tower for rectification to obtain a caprolactam product. The climbing film evaporators are used for replacing thin film evaporators, and the alkali treatment process is performed in the concentration buffer tank in advance, so that the corrosion problem of the evaporators is solved; meanwhile, the alkali distillation process in an alkali tower is canceled, the process flow is simplified and the energy consumption and the production cost are reduced.

Description

technical field [0001] The invention belongs to the technical field of chemical production, and relates to a method and a device for refining caprolactam. Background technique [0002] Caprolactam refining is an important process for the production of caprolactam. The production process of caprolactam mainly includes benzene method and toluene method. Among them, the toluene process includes the oxidation of toluene to benzoic acid, the hydrogenation of benzoic acid to cyclohexane carboxylic acid, the amidation reaction of cyclohexane carboxylic acid and nitrosyl sulfuric acid to produce amidated products, neutralization crystallization, extraction and refining, etc. process. In these production processes, in addition to caprolactam, some by-products are also formed. The presence of impurities will affect the polymerization process of caprolactam, which is directly related to the quality of nylon 6 products, so it must be removed. Caprolactam refining is through caustic ...

AI Technical Summary

Problems solved by technology

During the three-effect evaporation, the ammonium salt is decomposed by heat, which makes the concentrated material acidic, which causes problems such as corrosion of subsequent process equipment. The heat exchangers of the main equipment, the rising film evaporator and the thin film evaporator, are severely corroded and the service life is shortened.

At the same time, due to the characteristics of the toluene refining process, the material refining process is long, and the material undergoes repeated distillations, which consumes a lot of energy and costs.

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