Numerical simulation of the liquid distribution in a trickle-bed reactor

Numerical simulations of the two-phase flow distribution in a trickle-bed reactor used for fuel hydrodesulfurization are reported. As a first step, the heat and mass transfer, as well as the chemical reactions, are not considered. The reactor has four packed-beds and a distribution tray above the catalytic beds equipped with cylindrical chimneys. The flow distribution at the outlet of the circular chimney predicted by the simulations is not axisymmetric because of the spatial distributions of the liquid and gas inlets in the chimney. This causes that the liquid entering the packed beds is distributed in three main streams. For the simulation of the two-phase flow in the packed beds, an Eulerian three-phase model that considers the particles of catalyst as a granular static phase has been used following the Holub single slit model for particle–fluid interaction to compute the liquid–solid and gas–solid drag coefficients. Numerical simulations of the dispersion of water–air flow in a column of glass beads using this model were initially carried out and results were found to be in reasonable agreement with numerical and experimental data available in the literature. The simulations consider the flow dispersion in the central region of the reactor bed as well as in the region close to the cylindrical lateral wall of the reactor. In both cases most of the liquid spreading takes place in the top part of the bed. The distributions of the liquid volume fraction do not change significatively as the depth of the bed is increased except in the third bed and at the interface of two beds with different porosity.