A steady-state model for trickle-bed reactors was developed, primarily concerning hydroprocessing of light oil feedstocks containing volatile compounds. The case of a homogeneous plug flow fixed bed reactor with axial dispersion was considered. Catalyst particles were assumed to be isothermal and isoconcentrational. Mass balances, overall two-phase flow momentum balance and phase energy balances were written in detail. Hydrodynamic flow of the two phases and specifically the flow regime under which the bed was operated, the liquid holdup, the wetting efficiency of the solid particles, the two-phase flow pressure drop and the gas-liquid and liquid-solid interfacial areas were all predicted using carefully selected industrial engineering correlations. In addition. all necessary thermophysical properties, such as phase densities, viscosities, conductivities, diffusivities, interfacial tension. latent heats of vaporization, specific heats, and molar partial enthalpies were continuously calculated as functions of the system pressure, temperature and phase composition. A suitable numerical package was developed for this kind of calculations. Phase equilibrium was calculated with the aid of the same package and the non-ideal phase behavior was taken into account. as well. Mass transfer rates were calculated by the effective diffusivity method. Compared to a set of experimental data taken from the operation of a pilot scale hydrodesulfurization plant, excellent agreement was found. A user-friendly interface was developed to facilitate the use of the numerical package. (C) 2003 Elsevier Science B.V. All rights reserved.