A CASE-STUDY OF PARTICLE MIXING IN A PLOWSHARES MIXER USING POSITRON EMISSION PARTICLE TRACKING

The motion of individual granular particles has been experimentally ob served in a horizontal batch ploughshare mixer. A technique called Pos itron Emission Particle Tracking has been used to locate a radio trace r particle with time. A quantitative picture has been constructed to d etermine when a particle moves between inter-plough regions within the mixer. Results are presented for a single case of 12.5% fill (volume basis) of rice where the ploughs rotate at 2 Hz. Particles were found to displace with a regular oscillatory magnitude of 9-14 mm due to the motion of the ploughs. However, larger distances of travel were far l ess frequent. The position of the particle relative to the blade has b een determined when the particle crosses the plane in which the blade rotates. Frequency distributions of the lead or lag angle between the tracer and blade show the influence of adjacent blades and indicate th e importance of the axial separation distance and angle between plough blades. The techniques presented here permit characterisation of the internal flows and development of a knowledge of the influence of mach ine design and operating parameters critical to mixing. (C) 1998 Elsev ier Science B.V.