This paper presents a new type of spinning disk reactor configuration for gas−liquid operations. It combines the features of a classical spinning disk with a liquid film on the rotor [e.g., Aoune, A.; Ramshaw, C. Int. J. Heat Mass Transfer
1999, 42, 2543−2556] and those of a rotor−stator spinning disk unit with a single gas inlet in the bottom stator [Meeuwse, M.; van der Schaaf, J.; Kuster, B. F. M.; Schouten, J. C. Chem. Eng. Sci.
2010, 65 (1), 466−471]. In this new configuration, gas and liquid are cofed through an inlet in the top stator. It is shown that gas−liquid mass transfer mainly takes place in the dispersed region between the rotor and the bottom stator. k
GL
a
GL
V
R in this region is up to a factor of 6 larger than in the region with the liquid film on the rotor. Simulation of gas desorption from a saturated liquid shows that the gas−liquid mass transfer in this cofed configuration is considerably improved in comparison to the separate reactors, at similar operating conditions. The new reactor has also a higher potential for scaling up: gas and liquid can be cofed from one rotor−stator unit to another without the need for redistribution of the gas.
The scale up of a rotor-stator spinning disc reactor by stacking single stage rotorstator units in series is demonstrated. The gas-liquid mass transfer per stage is equal to the mass transfer in a single stage spinning disc reactor. The pressure drop per stage increases with increasing rotational disc speed and liquid flow rate. The pressure drop is more than a factor 2 higher for gas-liquid flow than for liquid flow only, and is up to 0.64 bar at 459 rad s À1 . The high mass and heat transfer coefficients in the (multistage) rotor-stator spinning disc reactor make it especially suitable for reactions with dangerous reactants, highly exothermic reactions and reactions where selectivity issues can be solved by high mass transfer rates. Additionally, the multistage rotor-stator spinning disc reactor mimics plug flow behavior, which is beneficial for most processes.
The heterogeneously catalyzed oxidation of glucose is performed in a rotor−stator spinning disk reactor. One side of the rotor is coated with a Pt/C and Nafion catalytic layer, resulting in a liquid−solid interfacial area of 274 mi
2 mR
−3. At the lowest rotational disk speed, 26 rad s−1, the reaction is liquid−solid mass transfer limited; at the highest rotational disk speed, 180 rad s−1, the intrinsic kinetics are rate determining. The experimental overall reaction rates are fitted with a resistances in series model, with the activation energy, pre-exponential factor, and volumetric liquid−solid mass transfer coefficient as parameters. The volumetric liquid−solid mass transfer coefficient, k
LS
a
LS, increases from 0.02 to 0.22 mL
3 mR
−3 s−1 for a rotational disk speed of 26 to 157 rad s−1. These values are high in comparison to conventional reactors, like packed beds, in spite of the low liquid−solid interfacial area used in this study. The values of the liquid−solid mass transfer coefficient k
LS are 1 order of magnitude higher compared to values reported for packed beds. The Sherwood number for the liquid−solid mass transfer in the rotor−stator spinning disk reactor depends on the Reynolds number to the power 2 in the range 1 × 105 < Re < 7 × 105. In this range, the transition of laminar flow to turbulent flow takes place, resulting in a change of the mass transfer mechanism.
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