Determination of bed voidage using water substitution and 3D magnetic resonance imaging, bed density and pressure drop in packed-bed reactors

Using a water substitution method to determine bed voidage, an independent relationship between bed height and bed voidage was observed for the trilob e (virgin and crushed) and cylindrical alumina supports. Typical bed voidag e values of 0.49-0.51 (virgin trilobe). 0.46-0.52 (crushed trilobe) and 0.2 8-0.31 (cylindrical) were observed within 0.1 and 0.19 m i.d. columns. Howe ver, bed voidage values were approximately 6% larger in the 0.05 m i.d. col umn and could be attributed to a greater extent of wall zone voidage. Dense packing of the columns in all cases resulted in a decrease in bed voidage which had significant effects on bed density and column pressure drop, in a ddition to the water substitution measurements of bed voidage, three-dimens ional magnetic resonance imaging (MRI) data were used in conjunction with d igital image analysis techniques to obtain one-dimensional radial profiles of voidage from comparable alumina catalyst support material. Similar resul ts and trends in voidage values between the water substitution method and t hose obtained from MRI data are evident. In all cases, the analysis of the MRI data yields voidage values that are consistently higher than those obta ined from water substitution measurements. (C) 2001 Elsevier Science Ltd. A ll rights reserved.