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The Mechanics of Feeding Bulk Solids in a Rotary Dryer

Based on an industrial case study, the performance of a rotary dryer employed in a mineral processing plant was investigated. The loads on the rotating elements of the dryer are analyzed with a view to ascertaining possible causes of failure. The particular type of dryer comprises a steam-heated drying unit composed of a central hollow drum and a number of parallel sets of circular heating tubes attached to the drum via radial header tubes. The drying unit rotates inside a stationary vessel containing the moist mineral ore. Blades attached by welds to the outer circular heating tubes assist in the circulation and transport of the ore through the dryer. However, in the actual dryer, the blade angles were less than optimal for good feed of material through the drying unit, and their welded attachments were a source of high levels of concentrated stress. While the close spacing between parallel sets of circular heating tubes is beneficial for heat transfer for the drying process, the close spacing leads to material buildup problems impeding the material feed. Influence of the variation of blade angle on feeding performance was investigated, and the various loads acting on the tubes and blades were analyzed.