Multi-impeller system

DT. Air-aqueous KjCO /KHCOj Air-water, glass beads, multi-impeller system... 

Multi-impeller system hollow half-elliptical blade dispersing turbine below two up-pumping wide blade hydrofoils, identified as HEDT -r 2WHU. Air-hot water (temperature 355°K), polypropylene particles... 

Gas-dispersing disc turbine with concave halfelliptical blades (HEDT) at bottom with two up-pumping (WHU) wide blade hydrofoils above. Air-water (hot and cold) containing 90 pm glass beads Pg 2500 kg/m. Solid loading 3-21 vol.% Bao et al. (2008b) Air-water (hot and cold). Multi-impeller system. 

Three-phase multi-impeller systems with six-blade DT and 45° PTD spaced at a distance equal to the vessel diameter (Dutta and Pangarkar 1996) ... 

In view of (2), the gas-inducing impeller has to be necessarily located closer to the top liquid level (Section 3.4.2.4.3 and Figure 3.3 Praxair liquid oxidation reactor). For three-phase reactions involving a solid catalyst, a multi-impeller system is required. This is because a single impeller used to induce the gas is not capable of suspending the solid settled at the bottom. Further, because of the poor gas dispersion by the top gas-inducing impeller, the second lower impeller has to also perform this duty of gas dispersion in the lower part of the reactor. 

Figure 2.5 Possible technological solutions to bioprocess problems a) Fed-batch culture b) Continuous product removal (eg dialysis, vacuum fermentation, solvent extraction, ion exchange etc) c) Two-phase system combined with extractive fermentation (liquid-impelled loop reactor) d) Continuous culture, internal multi-stage reactor e) Continuous culture, dual-stream multi-stage reactor f) Continuous culture with biomass feedback (cell recycling). (See text for further details).

Dutta NN, Pangarkar VG. (1995a) Critical impeller speed for solid suspension in multi-impeUer agitated contactors. Solid-liquid system. Chem. Eng. Commun., 137 135-146. 

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