Patent ID: 7700767

Claim:
A system for purifying an aqueous solution of crude caprolactam, comprising a filtration zone (A) having a filtration apparatus for filtering an aqueous solution of crude caprolactam to remove ionic impurities therein, so as to obtain caprolactam-containing filtrate, wherein the filtration apparatus is an ion-exchange apparatus set; an inspection unit (B) for judging whether the filtrate from the filtration zone (A) meets preset inspection standards; a purification zone (C) for receiving the filtrate meeting the preset inspection standards, and concentrating and purifying the filtrate to thereby form a final caprolactam product, wherein the purification zone (C) comprises: (C 1 ) a vaporization apparatus for concentrating the filtrate not meeting the preset inspection standards: (C 2 ) a buffer apparatus for receiving the concentrated filtrate containing a high concentration of caprolactam from the vaporization apparatus (C 1 ); and; (C 3 ) a distillation apparatus for distillating the concentrated filtrate containing a high concentration of caprolactam to form the final caprolactam product; and a first temporary storage tank(D) for receiving the filtrate not meeting the preset inspection standards, which is then mixed with the aqueous solution of crude caprolactam and delivered back to the filtration zone (A).