Thoenes-Kramers correlation

It is desired to double the capacity of the existing plant by processing twice the feed of reactant A while maintaining the same fractional conversion of A to B in the reactor. How much larger a reactor, in terms of catalyst weight, would be required if all other operating variables are held constant You may use the Thoenes-Kramers correlation for mass transfer coefficients in a packed bed. Describe the effects of the flow rate, temperature, particle size at conversion. 

To calculate the external mass transfer coefficient, the Thoenes—Kramers correlation is used. 

This correlation can be well represented in the range of Reynolds numbers covered by the experiments by an expression of the Thoenes-Kramers form. It is... 

The mass transfer coefficient can be calculated from the appropriate correlation, such as that of Thoenes-Kramers, for the flow conditions through the bed. When Equation (12-62) is satisfied, no concentration gradients exist between the bulk gas and external surface of the catalyst pellet. 

To learn the effect of flow rate and temperature on conversion, we need to know how these parameters affect the mass transfer coefficient. That is, we must determine the correlation for the mass transfer coefficient for the particular geometry and flow field. For flow through a packed bed, the correlation given by Thoenes and Kramers for 0.25 < cj) < 0.5, 40 < Re < 4000, and 1< Sc < 4000 is... 

This type of plot has been used widely to correlate experimental mass-transfer data. De Acetis and Thodos have summarized the data available up to 1960 in a single rve of vs Reynolds number, as shown in Fig. 10-2. For spherical pellets /)sis the diameter for other shapes dp can be taken as the diameter of a sphere with the same external area. Other investigations and correlations of mass-transfer datg include those of Carberry, Yeh, Bradshaw and Bennett, and Thoenes and Kramers. ... 

---