Solids mixing in a three phase fluidized bed containing spherically shaped-porous solid particles

Solids mixing a 3 phase fluidized bed containing 1.8 mm nominal diameter porous spherically shaped solids was studied using a batch type tracer technique. High speed photography was used to determine concentration time traces of color code solid tracer in a region near the wall of a 2 in. i.d. fluidization tube, located at a vertical elevation about 7 in. above the distributor. An add mixture of water and gaseous nitrogen at room temperature and essentially ambient pressure was used to fluidize a spherically shaped, nickel molybdate on alumina solid phase throughout this study. An empirical steady state mixing time was defined in order to characterize top to bottom of bed solids mixing. This mixing index was in turn correlated with superficial liquid velocity, superficial gas velocity, and an axial characteristic dimension.