Abstract:
Two downflow operational modes with different hydrodynamic states were
compared to upflow operation. Various gas limited conditions (γ = 15 - 60) were
employed. The downflow mode with the higher wetting efficiency consistently
outperformed the downflow mode with the lower wetting efficiency. Both the
downflow modes outperformed the upflow mode at high gas mass fluxes and
underachieved against upflow at lower gas mass fluxes. The results stand in
contradiction to the theory on direct gas-solid mass transfer under trickle flow
conditions. The switching behavior of the upflow mode performance was attributed
to hydrodynamic regime shifts, hinting that the perceived ‘poor’ performance of
upflow reactors under gas limited conditions might be linked to slugging in
laboratory scale reactors.
