Real-time monitoring of bulk density in a rotating drum batch mixer for dry particulate solids

摘要

Two techniques for monitoring the progress of a batch mixing operation in a rotating drum in real time have been described. A bulk density sensor was mounted on the internal wall of the drum, and periodically sampled the bed of solids, to provide a measurement of bulk density once each revolution. The experiments were carried out with silica sand and an ironsand tracer, in a 1 meter diameter drum at a bed fill level of 20%, turning at 1.47 rpm. Results were well fitted by a Fickian diffusion model. The other approach utilised an acoustic probe which returned a signal proportional to particle size, again mounted at the drum wall, so that the bed was periodically sampled in the same way as for bulk density. The material was soap powder and the tracer was silica sand; the method clearly demonstrated the changes in mean size arising from the addition of the fine sand tracer, but considerable banding of the components was observed, and the results exhibited considerable scatter. Both sensors were battery powered and in both cases data were digitised and transmitted from the drum to a computer by FM telemetry.