Effect of capillary pressure force on local liquid distribution in a trickle bed

Accurate prediction of the local liquid volume fraction (epsilon(L)) distribution, an important process parameter that governs the performance of Trickle Bed Reactors (TBRs), is still a challenge. In the present work, Eulerian multi-fluid simulations of local epsilon(L) distribution were performed in a laboratory-scale pseudo-3D (rectangular) and cylindrical TBR and the predictions were compared with the Electrical Resistance Tomography (ERT) measurements of Singh et al. (2017). The effect of formulation of capillary pressure force ((F) over bar (C)) was investigated and it was found that -P-C Delta epsilon(L) definition of P-C preserved the functional relation between the capillary pressure (P-C) and epsilon(L), and that epsilon(L)Delta P-C definition of (F) over bar (C) reversed the same. Through the simulations performed for the pseudo-3D column, we showed that the alteration in the functional relation severely affects the ability of (F) over bar (C) = ELVPc definition to predict the effects of particle diameter, gas and liquid flow rates. It was elucidated that such an alteration underpredicts (F) over bar (C) and could necessitate the inclusion of additional dispersion forces for particles with small diameters. (F) over bar (C) implemented as -P-C Delta epsilon(L) provided satisfactory predictions of the steady-state local epsilon(L) distribution for the bed pre-wetted with the pseudo-Kan pre-wetting method. However, the P-C model required an empirical correction ([(d(P)/d(thr))(epsilon(S))(0.6)](-13.957)) to predict the steady-state local epsilon(L) distribution in the bed pre-wetted using the Levec method. While the modified (F) over bar (C) predicted the time-averaged local epsilon(L) distribution satisfactorily for different liquid flow rates and liquid distributor configurations, it was seen that further reduction in (F) over bar (C) was required to predict the dynamic liquid spreading behavior under synthetically created pulsing flow conditions. (C) 2018 Elsevier Ltd. All rights reserved.