MONITORING TECHNIQUE OF SOLID FLOW STATE IN PNEUMATIC CONVEYING OF POWDER MATERIALS

The pneumatic conveying is a useful technique which is used to provide powder materials such as fine coals, ores or fluxes to the metallurgical furnaces. The present paper describes the monitoring technique to distinguish between the two flow regimes of solid particles; the dispersive and the sliding flows in the reverse T-type tube junction where alumina particles fall vertically and are conveyed by a horizontal nitrogen flow. The flow regimes of the alumina particles were monitored by means of two kinds of indexes; the pressure difference fluctuation of the gas in the tube and the acoustic effect on the tube wall. For this purpose, two pressure transducers were equipped to the tube and two acceleration pick up sensors were touched directly on the outer surface of the tube. In the range of Froud number greater than 8, the pressure index is significantly large for the dispersive flow, while small for the sliding flow. In the range of Froud number less than 8, the acoustic index is, in contrast to the above, significantly large for the sliding flow, while small for the dispersive flow. The simultaneous application of both indexes will increase the monitoring reliability.