External Wetting Efficiency in a Three-Phase Fixed Bed Loaded with Porous and Non-Porous Packings

Abstract

Films and rivulets are the two basic forms of dynamic liquid in a three-phase fixed bed (trickle bed), which determines the wetting efficiency of the catalyst. This paper is devoted to the conflicting wetting performance observed between non-porous glass beads and porous alumina pellets, and a parallel zone model is applied to resolve the complex liquid flow texture. This shows that in the case of glass beads, the wetting efficiencies of the catalyst along with the liquid flow rate in increasing and decreasing branches are different, especially when the gas flow rate is low. In comparison, there is almost no wetting difference for the alumina pellets with respect to liquid flow rate increasing or decreasing. The dynamic liquid is significantly more uniformly distributed over the cross-section in the Al2O3 bed than in the glass one.

Evaluation of Time-on-Stream Deactivation Models with Effectiveness Factors for Industrial Feedstock Hydrotreating in Bench-Scale Tests

“…Incomplete wetting and the formation of stagnant liquid zones at particles are associated with a decrease in the catalyst effectiveness factor. − To add a wettability effect, Dudukovic proposed the concept of approximating the global effectiveness factor (η o ), considering a weight-averaged function of wetting efficiency and particle effectiveness . Particle shapes (sphere, cylinder, trilobe, and tetralobe) and pore structures (pore diameter and porosity) are equally important for improving internal diffusion limitations on HDT reactions. , To simplify the estimation of η in the HDT, it is possible to focus only on the solid phase (catalyst particle), neglecting liquid and gas phases.…”