Flocculation of spin bath NMMO solution for removal of colloidal impurities in lyocell process

ABSTRACT

Evaluation of various flocculants, selection of suitable flocculant and optimization of process parameters for reduction of colloidal particles have been carried out for lyocell spin bath solution. Maximum turbidity reduction was achieved with polyacrylamide based flocculant. Experiments were carried out using lab jar tests and factorial design of experiment was applied to optimize the flocculation process parameters, i.e., flocculant dosage, mixing time and mixing speed. Operation at optimum conditions reduced turbidity by 80–90% and improved the downstream operation of ion-exchanger by 11%. Without flocculation treatment, surface fouling of ion-exchange resin was observed in Scanning Electron Microscopy.