MODELING THE RESIDENCE TIME DISTRIBUTION OF A NONINTERMESHING TWIN-SCREW EXTRUDER

The residence time distribution (RTD) of a counter-rotating non-interm eshing twin screw extruder has been studied by a radioactive tracer te chnique. RTDs were measured at both the die exit and at the first comp ounding zone of the extruder. The operating parameters investigated we re: screw speed, screw flight stagger, and barrel temperature. These p arameters have an effect on the mixing efficiency. The mixing efficien cy was characterized by fitting measured response data with models com prised of different combinations of ideal reactor elements. The empiri cal flow models tested were: plug flow and tanks-in-series (with and w ithout recirculation), plug flow and axial dispersion, and the Wolf-Re snick model. The fitted model parameters characterized the observed ch anges in the RTD due to the variation of the operating parameters.