Distillation apparatus for NMP

A distillation apparatus configured for NMP distillation such that a spent NMP comprising light-boiling components and high-boiling components as impurities is purified, the apparatus comprising:

• a raw material tank configured to store spent NMP as a liquid to be treated;
• a distillation column configured such that liquid to be treated, which is supplied from the raw material tank, is subjected to distillation to obtain a purified high-purity NMP;
• and
• a product tank configured to store the high-purity NMP obtained in the distillation column,
• wherein the distillation column is a side-cut distillation column comprising:
• a top portion configured such that the liquid to be treated is separated into a high-concentration NMP having a concentration of not less than 99% by weight and water comprising light-boiling components;
• a bottom portion configured such that the liquid to be treated is separated into the high-purity NMP having a concentration of not less than 99.9% by weight and the high-concentration NMP comprising high-boiling components;
• a mid-stage portion configured such that the high-purity NMP is withdrawn as a side-cut vapor;
• a condenser, at a rear stage of the distillation column, configured to condense the high-purity NMP withdrawn as a side-cut vapor;
• a flow controller configured to regulate an amount of a liquid of the high-purity NMP withdrawn from the condenser to the product tank on the basis of a height of a liquid level in the bottom portion of the distillation column;
• and
• a flow path configured to withdraw the side-cut vapor which extends up to the condenser and is connected to the mid-stage portion of the distillation column,
• wherein an inner circumferential portion of the distillation column comprises a liquid guard cover of an open-bottomed box shape at a connecting position thereof to the flow path for withdrawing the side-cut vapor, and
• wherein the liquid guard cover is configured to prevent liquid from entering into the flow path.