(22g) Response of a Rotating Drum Instrument (GDR) to Powders From Different Geldart Groups

An instrument consisting of a rotating drum mounted on a framework that acts on a load cell, enables powder motion and flow to be tracked by monitoring the load cell signal. This instrument is also known as a GDR and has successfully been used to predict flow/no flow in standard test funnels used in the pharmaceutical industry for powders believed to be mainly Geldart Group A. In this paper we present data, from different sources, on a variety of different powders described as having different cohesiveness, and also on a small data set of powders chosen to come from each of the four Geldart Groups. Plots of the variance of load cell signal against drum speed are distinctly different for the different Geldart Groups, and this observation is supported by distinctive differences in their associated power spectral density plots. This approach to powder flow assessment may thus have application in assessment of the fluidization behaviour using small material samples, for materials that are difficult to fluidize, or that have extreme or unusual shapes.