High Density and Low Velocity Pneumatic Transportation of Powders and Granular Materials

Abstract

High density and low velocity pneumatic transportation of granules, the conveying state of which is like the state of moving bed, has been obtained using both a reciprocating feeder and an orifice attached at the exit of the tube. In this experiment the maximum velocity of a particle was 7.5cm/sec. The authors have named "Rod-like flow" for this state of pneumatic transportation and have discussed the pressure drop of gas and the flow rate of granules at the steady state. It has been concluded that the pressure drop is approximately expressed by Ergun's equation using the porosity εmf at the minimum fluidization. It is shown that the formula which expresses the flow rate of granules can be related to the effective superficial gas velocity u*=uf-umf (uf: superficial gas velocity, umf: superficial minimum fluidizing gas velocity) and the opening of the orifice attached at the exit of the tube. The empirical equation of flow rate has been obtained as follows.εup=α′{(De-2Dp)/Dp}n′(u*)n