A PHENOMENOLOGICAL STUDY OF A BATCH MIXER USING A POSITRON CAMERA

Particulate motion within a Lodige mixer has been analysed using a refinement of the nuclear imaging technique, positron emission tomography. The detailed tracking of a single, in this case large, radioactive tracer particle has revealed information on the detailed flow behaviour in the mixer, by determining not only axial, radial and angular locations but also axial, radial and angular velocity distributions. The mixer had a five litre mixing bowl containing tow ploughshare blades and two end scraper blades mounted upon a horizontal mixing shaft rotating at a fixed frequency of 4Hz. Three active mixing regions separated by boundaries coinciding with the axial positions of the ploughshare blades were found, and residence time distributions in these regions of the mixer determined. Assessment was performed for eight powder fill proportions ranging from 7% to 70% by volume; the results show a great influence of detailed mixer geometry on behaviour. This application of the positron emission particle tracking technique demonstrates its potential for powder mixing studies.