Incipient condition of hang-up in a long standpipe-hopper system for Geldart-D powders

The incipient condition of hang-up for three Geldart-D powders has been exp erimentally studied in a 21 m long standpipe hopper system. Experimental re sults show that the pressure gradient for hang-up to occur is independent o f the materials height in the hopper and the diameter of orifice and equals to (dp(w)/dl)(s) which can be predicted by Eq. (7). While the correspondin g gas velocity in the standpipe equals to the incipient fluidized velocity of particles at the high pressure and can be predicted by Kwauk's equation.