The application provides a process for recovering purified -caprolactam from nylon 6-containing multi-component material which comprises the steps of a) providing a pre-concentrated nylon 6-containing material obtained by extraction, b) depolymerization, c) recovery, and d) purification that comprises extraction, back-extraction, distillation and crystallization.

Methods of cleaning an N-methyl-2-pyrrolidone (NMP) purification and recovery system having an NMP-containing chemical waste stream, a separation tower fluidically coupled with the chemical waste stream, a reflux drum fluidically coupled with an upper section of the separation tower, a reboiler fluidically coupled with a lower section of the separation tower, and a purified NMP stream fluidically coupled with the reboiler. The methods include injecting a cleaning solution into the reflux drum and the reboiler with an amount of the cleaning solution sufficient to at least substantially fill the reflux drum and the reboiler, the cleaning solution comprising a solvent having a primary amine and a hydroxyl group, circulating the cleaning solution through at least the separation tower, the reflux drum, the reboiler for a period of time to solubilize foulants contained within the system, and draining the cleaning solution having foulants solubilized therein from the system.

Methods of cleaning an N-methyl-2-pyrrolidone (NMP) purification and recovery system having an NMP-containing chemical waste stream, a separation tower fluidically coupled with the chemical waste stream, a reflux drum fluidically coupled with an upper section of the separation tower, a reboiler fluidically coupled with a lower section of the separation tower, and a purified NMP stream fluidically coupled with the reboiler. The methods include injecting a cleaning solution into the reflux drum and the reboiler with an amount of the cleaning solution sufficient to at least substantially fill the reflux drum and the reboiler, the cleaning solution comprising a solvent having a primary amine and a hydroxyl group, circulating the cleaning solution through at least the separation tower, the reflux drum, the reboiler for a period of time to solubilize foulants contained within the system, and draining the cleaning solution having foulants solubilized therein from the system.