Cargo Fluidisation and Aeration in Fine Bulk Powders
Why fine powders behave as fluids when aerated: the mechanism, de-aeration and settling after loading, the free surface and stability window, and the cargoes it affects.
A fine powder entrains air as it is poured and can behave for a period as a fluid rather than a solid, which is a property engineered into cargoes such as smelter-grade alumina and cement so that they can be conveyed in airslides and dense phase lines ashore. The same property has a shipboard consequence that is easy to overlook, because a freshly loaded hold does not behave as the settled cargo it becomes.
The full article will cover the mechanism, the factors that govern how much air is entrained and how long it is retained, and the de-aeration and settling process that follows loading. It will cover the practical signs, including surface level change and ullage movement over the hours after a pour.
It will also cover the stability implication during that window, since an aerated cargo can present something closer to a free surface than a solid mass, and the interaction with trimming, where the Code’s own stated purpose for trimming includes minimising the air entering the cargo. The cargoes affected and those not affected will be identified.