A new liquid distribution factor and local mass transfer coefficient in a random packed bed

Abstract

Liquid distribution and local mass transfer in a packed bed of 25.4 mm metallic Pall rings were investigated. The liquid collecting method and electrochemical technique were used to measure local liquid flow rates and local mass transfer coefficients, respectively. Measurements were carried out at various radial and axial positions in the bed at varied liquid flow rates with three different liquid distributor designs: single point (SLD), cross (CLD), and ladder type (LLD) distributors. A new liquid-distribution factor for the liquid flow pattern in a packed bed was proposed and used for evaluation of liquid distribution in the bed. Liquid distribution and the local mass transfer coefficient for SLD were more sensitive to the bed height than those for CLD and LLD, as expected. Liquid redistribution was observed at x / D (the ratio of the packing height to the tower diameter) level of 4.9. The effect of the inlet liquid flow rate on local mass transfer was found to be significant for all liquid distributors. Local mass transfer coefficient increased with the inlet liquid flow rate. A correlation of the overall mass transfer with the particle Reynolds number was also developed taking into account the volume segments of different radial and axial regions in the bed. The mass transfer coefficient, in terms of the Sherwood number, was found to be proportional to the Reynolds number to a power of 0.26 for CLD and 0.44 for SLD.