Local Mass Transfer in a Packed Bed: Experiments and Model

Liquid-to-packing local mass-transfer coefficients (LMTC) were measured in a 0.3 m diameter column with a bed height of 5.5 times the column diameter using the limiting-current technique. Several electrodes were placed at various radial and axial positions (packing heights) in the bed. Measurements were conducted at various liquid flow rates with two different liquid distributor designs: multipoint (MPLD) and single-point (SPLD) distributors. For shallow beds, mass-transfer variation with radial location and liquid flow rate using MPLD was less than that for SPLD. However, for larger bed depths, the local mass-transfer coefficient became less dependent on liquid flow rate with both liquid distributors. A mathematical model for the LMTC in a packed bed was also developed, taking into account the axial and radial positions in the bed. The model predicts the LMTC well with the root-mean-square errors (RMS) of predicted and measured values of 0.07 and 0.08 for the multipoint and single-point liquid distributors, respectively.