Solid foam packings for multiphase reactors: Modelling of liquid holdup and mass transfer

In this paper, experimental and modeling results are presented of the liquid holdup and gas–liquid mass transfer characteristics of solid foam packings. Experiments were done in a semi-2D transparent bubble column with solid foam packings of aluminum in the range of 5–40 pores per inch (ppi). The relative permeability model described by Saez and Carbonell (1985) is used to describe the liquid holdup data for solid foam packings of 5, 20 and 40 ppi. The investigated system variables are the superficial gas and liquid velocities, using counter-current flow with maximum gas velocities and liquid velocities of 0.8 m s-1 and 0.03 m s-1, respectively. The relative permeability model is able to describe the liquid holdup in the low liquid holdup or trickle flow regime as well as in the high liquid holdup regime, which resembles flow in a packed bubble column. Gas-to-liquid mass transfer is modelled using the penetration theory. Mass transfer coefficients up to 6 s-1 are predicted; these high values are largely due to the high specific surface area of the solid foam packings.