Chin.J.Chem.Eng. ›› 2018, Vol. 26 ›› Issue (5): 1022-1030.doi: 10.1016/j.cjche.2017.12.002

• Separation Science and Engineering • Previous Articles     Next Articles

Experimental and simulation study of nylon 6 solid-liquid extraction process

Chunxi Qin1, Jie Tang1, Fenglei Bi1, Zhenhao Xi1,2, Ling Zhao1,2   

  1. 1 Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China;
    2 State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
  • Received:2017-06-16 Revised:2017-11-23 Online:2018-05-28 Published:2018-06-29
  • Contact: Ling Zhao,E-mail
  • Supported by:

    Supported by the National Key Research and Development Program of China (2016YFB0302701), the Shanghai Rising-Star Program (16QB140130) and the 111 Project (B08021).

Abstract: The solid-liquid extraction process of nylon 6 to eliminate small molecules, i.e., caprolactam (CL), cyclic dimers (CD) and cyclic trimers (CT), is investigated in detail by both batch extraction experiments and numerical simulations. In the batch extraction experiments, due to the small molecules attaching to the polymeric surface, the basic physical mechanism shifts from surface diffusion to internal diffusion as the extraction proceeded. The experimental data are well reproduced by a diffusion model consisting of two distinct steps, characterized as surface diffusion and internal diffusion. Furthermore, based on the established mass transfer mechanism and diffusion model of the two distinct steps, the equilibrium constants and internal diffusion coefficients of CL, CD and CT are acquired. An industrial countercurrent extraction tower is further simulated. It is found that the extraction efficiency of CL can be significantly improved by increasing the temperature at the bottom portion of the tower. The elimination of CD, which can be greatly promoted by a high-concentration CL-water solution, is controlled by mass transfer resistance, whereas the removal of CL is mainly affected by the equilibrium.

Key words: Solid-liquid extraction, Equilibrium, Diffusion, Numerical simulation