Particle settling velocity slurry column

Provided the particle settling velocities vt are known, this equation allows the calculation of )e,s Usually, experiments at non-zero liquid rates are used to evaluate t , and )e,s separately. A similar concentration profile might occur in practice if slurry column reactors are operated close to the conditions given by the minimum suspension criterium. In this case, reactor calculations should take the solids concentration profiles into account. A recommended correlation for the solids dispersion coefficient for small particles is given by Kato et al. [15] ... 

It is desirable to measure the fluidization behavior of the particular solids in the column, ideally in actual mother liquors. A typical set of curves is shown in Fig. 1 l-22a. Each particle size is a relatively monosized sieve fraction. The x-intercept of each curve is the terminal settling velocity (slurry concentration 0 gm/liter), but it is more accurate to measure the tenninal settling velocity separately with a stopwatch and a graduated cylinder. Such a data set is shown in Fig. ll-22b. 

In the design of upflow, three phase bubble column reactors, it is important that the catalyst remains well distributed throughout the bed, or reactor space time yields will suffer. The solid concentration profiles of 2.5, 50 and 100 ym silica and iron oxide particles in water and organic solutions were measured in a 12.7 cm ID bubble column to determine what conditions gave satisfactory solids suspension. These results were compared against the theoretical mean solid settling velocity and the sedimentation diffusion models. Discrepancies between the data and models are discussed. The implications for the design of the reactors for the slurry phase Fischer-Tropsch synthesis are reviewed. 

In practice, however, the liquid velocity relative to fixed particles, Uf, is not very useful. Instead, the velocity of settling relative to the walls of an apparatus, Uf - u, is of practical importance. The volume of the solid phase moving downward should be equal to that of liquid moving upward. This means that volume rates of these phases must be equal. Consider a column of slurry having a unit cross section and imagine the liquid and solid phases to have a well defined interface. The column of solid phase will have a base 1 - e, and the liquid column phase will have a base e. Hence, the volumetric rate of the solid column will be (1 - e)u, and that of the liquid column will be (Uf - u)e. Because these flowrates are equal to each other, we obtain... 

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