Flow properties of three fuel powders

Flow and physical properties were measured for three fuel powders: sawdust, brown coal and hard coal. Besides physical properties, e.g., particle size, bulk density and moisture content, flowability was investigated using the standard shear testing technique of the Jenike shear cell. Flow functions of the three powders used for characterization of bulk flow and design of hoppers were determined, and then compared and discussed. The flow functions of the three powders are located in different regions: while brown coal and hard coal were classified respectively as easy flowing and cohesive material, sawdust was found in regions varying from cohesive to easy flowing at low consolidation stress. The measured effective angle of internal friction and angle of wall friction were 55° and 31.4° for sawdust; 36.2° and 26° for brown coal; and 43.3° and 27.8° for hard coal. Using the measured powder flow properties, Jenike's procedure was then followed to estimate and compare the critical hopper dimensions for mass flow of the three powders.

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► The flow properties and powder physical properties were measured for three fuel powders.
► The flow functions of the three powders are located in different regions.
► Both particle size and moisture content significantly affect the flow properties.
► Applying Jenike's mathematical analysis for designing a hopper shows that this can occasionally produce unexpected value for the hopper opening size.