Silo flow-pattern diagnosis using the tracer method

The storage silo of a sugar refinery was designed by its manufacturer for a plug-flow pattern of sugar ingots in order to ensure effective drying of the sugar introduced at the top of the silo. Because of the excessive moisture content of the extracted ingots, the quality of flow within the silo was called into question. The silo flow-pattern was thus studied by introducing sugar lumps as a tracer at the top of the silo filled with ingots. The tracer weight percentage was measured at the outlet. Results show that the silo flow-pattern is not of the plug-flow type in its whole volume: after formation of a crater, only the central volume flows, while the outer residual volume remains motionless. The tracer test also enabled the detection of preferential flow patterns. The tracer method was found to be quite useful as a diagnosis method for such a device in normal functioning. (C) 2008 Elsevier Ltd. All rights reserved.