High-efficiency and energy-saving caprolactam recovery technology

Abstract

The invention relates to an aqueous caprolactam solution concentration method. The method comprises steps as follows: 1), extract water is preheated through a heat exchanger by the aid of a pump I, and enters an evaporation pipe through a top inlet of a single-effect falling-film evaporator; 2), the extract water is distributed by an in-tower liquid distributor, is distributed in a heat exchange pipe in a film-like mode and is subjected to thin film evaporation through steam heating outside the pipe when entering a pipe cavity by the aid of gravity flow, and the extract water and secondary steam in the pipe flow down to the bottom of an effect body and enter a single-effect separation tank for liquid-steam separation; 3), a concentrated solution at the bottom of the effect body and the bottom of the separation tank is sent to the top of a two-effect falling-film evaporator through a pump II, and the concentrated solution of the two-effect falling-film evaporator is subjected to liquid-steam separation through a pump III, a pump IV and a two-effect separation tank; 4), the concentrated solution is sucked by a pump V from the bottom of the effect body and sent into the top of a three-effect falling-film evaporator for circulating concentration, and the technological requirement is met.

Description

technical field [0001] The invention relates to a high-efficiency and energy-saving caprolactam aqueous solution concentration process, which adopts a process route combining falling film evaporation with mechanical steam and compressor heating technical background [0002] The polymerization reaction of nylon 6 is an equilibrium reaction, and about 8% to 10% of monomer caprolactam and cyclic oligomers will inevitably be produced during production. These cyclic oligomers, especially cyclic dimers, will affect the polymerization process. Serious hazards are caused. In actual production, about 1:1 deionized water is used to extract and wash the polymerized nylon 6 slices. After extraction, the deionized water becomes extracted water containing about 10% caprolactam and oligomers. Concentrate and recycle. [0003] The traditional caprolactam water concentration process is generally a three-effect evaporation process. In the production process, 1.0MPa(G) steam is required as a ...

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Problems solved by technology

[0003] The traditional caprolactam water concentration process is generally a three-effect evaporation process. In the production process, 1.0MPa(G) steam is required as a heat source to directly heat the caprolactam aqueous solution. The secondary steam produced by the last effect evaporation concentration is usually cooled due to its low heat enthalpy. After the water is cooled, it is discharged, and the energy consumption is large, and the operation cost is high

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