The gas-liquid contacting effects on liquid dispersion in pilot scale upflow hydrotreaters

A model for the estimation of the extent of the non-ideal liquid flow from RTD data at operating conditions in small-scale hydrotreaters has been developed accounting for the gas oil evaporation and gas-liquid mass transfer. Non-ideal flow is described by the axial dispersion model. Gas-liquid phase mass transport and equilibrium are considered by simulating the petroleum gas oil fraction with five pseudocomponents. Liquid holdup and axial dispersion coefficients for an upflow reactor are estimated by fitting the response curves after a step change of the tracer concentration at the inlet of a fixed bed operating at reaction conditions to the model predictions. The results obtained with the developed model are compared with those estimated by a simplified pseudohomogeneous model. It has been found that the model parameters estimated by the developed model are compatible with those determined with a mock up system of toluene and nitrogen at ambient conditions. (C) 2004 Elsevier Ltd. All rights reserved.