Method and device for the continuous return of extract water in the polyamide production process

摘要

Continuously recycling extract waters in polyamide production process comprises polymerizing, granulating and subsequently extracting the granules with water. The method comprises concentrating the extract water of at least one production line, subjecting the extract water as an extract water flow to re-polymerizator for degradation of cyclic oligomers, diluting the extract water as re-polymerization with at least an inflow and subsequently supplying as a mixed stream of the polymerization. Continuously recycling extract waters in polyamide production process comprises polymerizing, granulating and subsequently extracting the granules with water. The method comprises concentrating the extract water of at least one production line, subjecting the extract water as an extract water flow to re-polymerization for degradation of cyclic oligomers, diluting the extract water as re-polymerizate with at least an inflow, and subsequently supplying as a mixed stream of the polymerization. The temperature is adjusted to 220-280[deg] C, the water content is adjusted to 20-40 wt.% and the residence time is adjusted to 0.5-20 hours to maximize the oligomer degradation during the re-polymerization. The pressure formation is reduced by metering at least one inflow containing caprolactam for direct supply of the mixed stream in the production process of polyamide. An independent claim is also included for a device for continuously recycling the extract water in polyamide production process comprising (a) re-polymerizator for degradation of cyclic oligomers, (b) a premixer for mixing fresh lactum, optionally additives and mixed stream, (c) a bypass for recycling the circular flow, which is branched into the premixer and dosed at a feed point prior to the premixer, and (d) a pump, which is arranged in the bypass, for conveying the circular flow.