Static mixers: Effective means for intensifying mass transfer limited reactions

The potential of using screen-type static mixers to intensify mass transfer limited multiphase-reactions was investigated using a case of diesel desulfurization. Two reactor designs were assessed at different superficial velocities and operating temperatures. By focusing energy dissipation within a very narrow distance in the regions adjacent to the screen, it was possible to generate local energy dissipation rates as high as 40,000 W/kg while maintaining the specific energy consumption rates below 0.2 kWh/t of liquid processed.Depending on the operating temperature, up to 15,400-fold reduction in the residence time needed to react 95% of the sulfur present in the diesel can be achieved by replacing a standard mixing tank agitated by a Rushton-type impeller with a screen-type static mixer. About 97% of this can be credited to the higher inter-phase mass transfer achievable in screen-type static mixers, while the remaining 3% can be attributed to the higher average mass transfer driving force encountered under the plug flow conditions prevalent in this contactor. The relatively uniform flow conditions encountered across the pipe diameter minimized the formation of difficult-to-separate liquid–liquid dispersions with the ensuing dispersion separating within 20 s.