On-line monitoring of the residence time distribution along a kneading block of a twin-screw extruder

• Published in: Polymer testing 2004-12, Vol.23 (8), p.925-937
• Main Authors: Carneiro, O.S., Covas, J.A., Ferreira, J.A., Cerqueira, M.F.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Extrusion; Flow visualisation; Fluorescent tracer; On-line RTD; Partial RTD; Physicochemistry of polymers; Polymer industry, paints, wood; Technology of polymers
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/j.polymertesting.2004.05.001

An on-line Residence Time Distribution (RTD) measuring set-up that enables the characterisation of twin screw extruders at short axial increments is presented. It uses the light emission of a fluorescent tracer (perylene) to generate concentration versus time curves, which are then used to determine the usual RTD parameters, delay time, mean residence time and variance. The system is initially mounted on a rectangular die coupled to a single screw extruder, on-line and off-line measurements being directly contrasted. Then, the optical probe is positioned at several points along the axis of a modular co-rotating twin screw extruder, on-line and off-line data being again compared. Having gained confidence in the measuring technique, an experimental unit utilizing a transparent barrel is used to characterize the evolution of RTD along a kneading block of a twin screw extruder.