Slurry reactors Sherwood number

Figure 13. Sherwood number for liquid-solid mass transfer in sparged stirred tank slurry reactors (adapted from Asai et al. [119]).

If a transport parameter rc — CS/CL is defined, where Cs is the concentration of C at the catalyst surface, then Peterson134 showed that for gas-solid reactions t)c < rc, where c is the catalyst effectiveness factor for C. For three-phase slurry reactors, Reuther and Puri145 showed that rc could be less than t)C if the reaction order with respect to C is less than unity, the reaction occurs in the liquid phase, and the catalyst is finely divided. The effective diffusivity in the pores of the catalyst particle is considerably less if the pores are filled with liquid than if they are filled with gas. For finely divided catalyst, the Sherwood number for the liquid-solid mass-transfer coefficient based on catalyst particle diameter is two. 

Pg pressure inside the gas plug pi pressure in the liquid at the interface AP pressure drop q volumetric flow rate r radial coordinate reaction rate Tc radius at chaimel comer Ri principal radius of curvature Ri principal radius of curvature Re Reynolds number S selectivity Sc Schmidt number Sh Sherwood number SR slurry reactor STYv space lime yield t time... 

For slurry reactors several correlations were proposed in the literature, which relate the dimensionless Sherwood number to the Reynolds and Schmidt numbers. Data collected by Temkin for various slurry reactors (Kinetika i kataliz, 28 (1977) 493) show that the Sherwood number can be described by the following equation... 

The liquid—solid and gas—liquid mass transfer coefficients can be estimated by the approach discussed in detail in Chapter 10, which is based on the correlation between Sherwood number and Reynolds and Schmidt numbers. The critical issue in the calculation of the Reynolds number is the energy dissipated, which, in many cases, can be much lower than the energy imposed by the stirrer of a slurry reactor. 

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