Bulk solid powder classification

After determining the relevant physical properties (i.e., particle size, solids particle density and bulk density), the next step is to evaluate some of the existing techniques of powder classification. 

The classification system introduced by Carr [29,30] was used to evaluate the flow properties of the sorbitol powders. In Carr s system, a flowable powder is defined as free flowing and will tend to flow steadily and consistently. This is to be contrasted with a floodable powder, which will exhibit an unstable, discontinuous, and gushing type of flow. The parameters in Carr s system include the angle of repose, angle of spatula, compressibility, cohesion, and dispersibility. Based on these parameters, flowability and floodability indices are calculated to determine the handling properties of bulk solids. 

Ortega-Rivas, E. and Svarovsky, L., Centrifugal air classification as a tool for narrowing the spread of particle size distributions of powders . Bulk Solids Handling, Vol. 14, No. 4, 811 13 (October/December 1994) also in Processing Part I, Trans Tech Publications, ISBN 0 87849 121 X, Qaiisthal-Zellerfeld, 193-195 (2000)... 

Sodium borohydride is available as a 12% solution in caustic soda and in solid form either as powder or pellets (3). The predominant form produced is the solution, the DOT shipping classification for which is corrosive liquid. Forms of packaging are 18.9-L pails, 208.2-L drums, and either tank truck or tank car for bulk shipments. 1991 pricing for the solution form was 40.34/kg of borohydride contained. Solid sodium borohydride, a white powder packaged in polyethylene bags in metal containers, was priced at 48.39/kg. 

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