Hydrodynamic characteristics of three-phase fixed bed reactors: comparison between cocurrent upflow and downflow operation modes

M. C. CASSANELLO; O. M. MARTINEZ; A.L. CUKIERMAN

Cambridge

Congreso; II International Conference on Gas-Liquid And Gas-Liquid-Solid Reactor Engineering; 1995

INSTITUTION OF CHEMICAL ENGINEERS

In three-phase fixed-bed reactors, three operation modes depending upon the relative orientation of the liquid and gas flow may be distinguished: cocurrent downflow (trickle-beds), cocurrent upflow (upf low reactors) and countercurrent. Although the downf low operation is the most widely employed, the other modes present some advantages under certain conditions. Hydrodynamic and transport characteristics usually affect the behaviour of three-phase fixed bed reactors. Therefore, to analyze and compare the performance of the different operation modes, particularly between the cocurrent downflow and upflow ones, reliable hydrodynamic and transport parameters are necessary. Although numerous studies on these parameters have been published, the scatter of data is significant. Hence, it is of interest to obtain parameters in the same experimental system by applying the same technique, in order to carry out reliable comparisons of the parameters values for each operation mode and to analyze the effect of geometrical and operating variables on them. The aim of the present work is the comparison of two importanthydrodynamic parameters, the holdup and axial dispersion of the liquid phase, for the cocurrent downflow and upflow operation modes. Experimental results for the upflow mode are analyzed and compared with others determined earlier for the downflow one. The set of results was obtained in the same equigment by applying in both cases a stimulus-response technique.Experiments were performed in order to determine the effect of the liquid and gas flow rates, geometrical characteristics of the particles and physical properties of the liquid phase on theparameters. The set of results was compared with others reported in the literature. Finally, correlations of the parameters for each operation mode are presented and their goodness to fit theexperimental results is examined .