Experimental Evaluation of the Wall Effect on Liquid Distribution in Trickle Beds

NÉSTOR JAVIER MARIANI; OSVALDO MIGUEL MARTÍNEZ; GUILLERMO FERNANDO BARRETO

Rio das Pedras, Rio de Janeiro, Brasil.

Congreso; II Mercosur Congress on Chemical Engineering, IV Mercosur Congress on Process System Engineering; 2005

UFRJ, UERJ, IME, UFRRJ, UNS, UNL, SCMC, Petrobras, Oxiteno.

The purpose of this work is to investigate the radial distribution of the liquid flow in a packed bed column with cocurrent downflow of water and air at low aspect ratios. To this end, an experimental device consisting in an acrylic column with different removable sections (to allow different bed heights) and an annular collector at the bed exit was set up. The experimental method is based on collecting the liquid in the annular region from the wall up to a particle radius separately from the liquid flowing in the core region. Glass spherical particles of two different sizes were used; thus, two aspect ratios (tube to particle diameter ratio, a) arise, 4.3 and 7.8. Experiments covered 300 different settings resulting from varying gas and liquid flow rates (restricted to trickle regime), bed length and aspect ratio. Each experimental condition (fixed gas and liquid flowrates, bed length and aspect ratio) was replicated with different packing structures obtained by liquid fluidization of the bed. The wall to core liquid superficial velocity ratio, R, was analysed. For a=4.3 the observed values of R varied strongly as the bed was repacked; therefore the configuration of the particles, as stochastically arises when the bed is repacked, exerts a very high impact on the liquid distribution. On the contrary, for a=7.8 there was little effect of bed repacking on R and a definite trend was found for the effect of liquid flow rate. The effect of gas flow rate on R was negligible, irrespective of the aspect ratio a.