In-Line Determination of the Bulk Density of Particulate Solids by Direct Weighing Methods

Bulk density is an important, often critical, property of many manufactured products, but direct determination is challenging to measure in real time during processing, because simultaneous measurements of both the mass and volume of the process material are required. Two approaches to direct measurement are considered here. First, a method previously developed, in which a free-flowing the test material flows continuously through a test cell is reviewed and its potential and limitations outlined. Secondly, a novel system in which a powder is collected and characterised using a moving cup which periodically fills and empties is described. Materials tested using the two methods include bread crumbs, plastic pellets, flour, icing sugar and agricultural peat. Measured densities were reproducible, and consistent with values obtained off-line.