Hydrodynamic characterization of a trickle bed air biofilter

This paper reports the effect of superficial liquid mass flow rate and bed void fraction on the pressure drop, dynamic liquid hold-up, mean liquid residence time and biofilm wetting, in a co-current down-flow xylene-removing trickle bed air biofilter (TBAB). The gas-liquid pressure drop increased with liquid mass flow rate and it also increased with diminishing bed void fraction, the effect being larger at bed void fraction of 0.41. Dynamic liquid hold-up was higher with increasing liquid mass flow rate, and showed a maximum when the bed void fraction was 0.69. The same pattern was observed for the mean liquid residence time and the wetting efficiency. Liquid residence time distribution curves indicate stagnant regions, channeling, and recirculation within the TBAB, whose effects were larger at a bed void fraction of 0.41. A maximum elimination capacity of 30 g/m3 h, with 78% removal efficiency, was reached when the bed void fraction was 0.8 and the liquid mass rate 14.1 kg/m2 s. An average minimum elimination capacity of 6 g/m3 h was observed at a bed void fraction of 0.41. Xylene isomers were preferentially removed in the order of o > m > p.