ABSTRACT
Selection of the carrier particle for an FBBR is an important consideration because it has several influences, as we will see shortly. One important consideration is the stability of the bed to fluctuations in flow rate; that is, to fluctuations in superficial velocity. If the expanded bed height is overly sensitive to such fluctuations, small variations in flow rate might carry particles out in the effluent, thereby destroying the bed. Figure 18.4 illustrates how carrier particle size and density affect bed height over the range of superficial velocities commonly encountered.28 The curves were obtained by simulation and the conditions employed are indicated in the figure. Those curves illustrate that the stability of a bed increases with increasing carrier particle size and density. Common silica sand has a density of around 2.65 g/cm3, which provides reasonable stability over a broad range of superficial velocities.
