FLUIDIZATION OF A MULTI-SIZED GROUP-B SAND AT REDUCED PRESSURE

The fluidized bed pyrolysis of oil sand produces a spent sand which co ntains 1-2 wt.% carbonaceous residue. The rapid bitumen pyrolysis reac tions indicate that the fluidized bed inventory is essentially spent s and. This spent sand has been shown to be a Group B sand according to the classification scheme of Geldart. A multi-sized Group B sand was s moothly fluidized with air by reducing the pressure above the surface of the bed to less than the pressure at the inlet of the distributor. Beds of sand with heights up to four times the reactor diameter were t aken from the slugging regime to smooth fluidization by changing the e ffective distributor pressure drop while the reactor was operating at reduced pressure above the bed. The characteristics of reactor pressur e drop versus superficial gas velocity were determined for the multi-s ized particles under reduced pressure and compared to the fluidization behavior of multi-sized particles in the more common positive gas pre ssure systems. The shapes of fluidizing and defluidizing curves caused by pulling air from the reactor top were similar but not the same as curves obtained at atmospheric pressure by pushing air through the dis tributor. An 'interpreted' minimum fluidization velocity definition fo r multi-sized particles fluidized at reduced pressures is proposed and shown to be consistent with predictive correlations.