Process for producing high-purity epsilon-caprolactam

A plant for producing high-purity ε-caprolactam, the plant comprises:

• an operation unit (2) for treating a reaction product obtained from a reaction that forms ε-caprolactam to produce a crude caprolactam;
• an operation unit (3) for subjecting the crude caprolactam to crystallization to produce a crystallization product and a crystallization mother liquor;
• an operation unit (4) for subjecting the crystallization mother liquor to crystallization to produce a crystal slurry;
• wherein the operation unit (4) comprises an equipment for subjecting the crystal slurry to countercurrent washing, the countercurrent washing equipment is provided with a dense phase bed of ε-caprolactam crystal and/or internal component(s) for forming the dense phase bed such as partition(s) or valve(s);
• an equipment for returning at leaat a part of the washed crystal slurry from the operation unit (4) to the operation unit (2) and/or the operation unit (3);
• wherein the countercurrent washing equipment is optionally provided with a dilute phase bed of ε-caprolactam crystal;
• wherein the amount of the dense phase bed of ε-caprolactam crystal is at least one, for example, 1, 2, 3, 4, 5 or 6;
• the amount of the dilute phase bed of ε-caprolactam crystal is 0 or at least one, for example 0, 1, 2, 3, 4, 5 or 6.