Research And Application Of Caprolactam-containing Wastewater Recovery With Centrifugal Extraction Technology

Caprolactam (CPL) is raw material to polymerize Nylon6 and engineering plastics. During the refine procedure of CPL production, a large amout of CPL-containing wastewater is produced, and the average mass concentration of CPL is about 2%. The discharge of CPL-containing wastewater causes a big loss of products.To deal with the problem above, a new extraction technology which is called as centrifugal extraction is proposed to reclaim CPL from the wastewater. In this paper, a cold mold experiment was conduted with (?)50mm annular centrifugal extractor. Effects of different operation conditions and geometry dimentions on the mass transfer efficiency and separation performance were studied. Results show that the highest mass transfer efficiency is 99.8% and the maximum separation capacity can reach 109L/min when the phase entrainment is under 0.5%. Furthermore, CFD simulation was used to study the mechanism of mass transfer in the annulus. The same operation conditions and geometry dimentions as the experimental device were simulated by the software Fluent 6.3.26. The ruslts are consistent with the experiment.Depend on 200,000 tons/y production project of CPL,(?)350mm annular centrifugal extractor was used to build the industrial equipment. Under nomal conditions, the recovery efficiency can reach to 75.3% and the concentration of CPL can be reduced to below 0.7% when the phase entrainment is under 0.5%, which is siginifigent to ecomomic and environment protection.