Size distribution inner feed

In addition to the normal feed particle size distribution that enters the cyclone, Muschelknautz and co-workers (Muschelknautz and Trefz, 1990,1991 Trefz, 1992) have modified their earlier cyclone model (or models) to include an inner feed or inner feed particle size distribution . The concept here is that, if the inlet solids loading exceeds the limit loading , some portion of the incoming feed solids will quickly separate out but those that don t will have a somewhat finer particle size than that feeding the cyclone. It is this... 

The entrance cut-point, xsom, establishes, or helps to establish, the inner feed particle size distribution which we will now compute. 

The functional form of this inner-feed particle size distribution cannot be rigorously computed at this time. Even so, it is reasonable to assume that it should resemble that of the particles entering the cyclone. Thus, if a Rosin-Rammler distribution described the feed size distribution, then the inner feed should have this same functional form. Many feeds can be represented by a distribution function that is identical in form to the grade-efficiency equation shown in Eq. (6.3.1) ... 

Independently of the equation selected to describe the inner-feed particle size distribution, all such equations can only be regarded as rough approximations to the true size distributions. Fortuitously, perhaps, in most practical situations wherein saltation or mass loading effects occur, the effect tends to dominate the overall collection process and so only a small portion of incoming solids ever report to the inner vortex. As a consequence, the overall collection efficiency is not highly sensitive to the choice of distribution function for the inner feed. If, however, one is only interested in the loss fraction, a difference in the total overall efficiency of 0.9992 and 0.9998, for example, can be significant since, in this case, the amount lost differs by a factor of 4. 

As shown above, we may now substitute Eq. (6.B.14) into Eq. (6.B.12) to obtain a rough estimate of the inner feed particle size distribution for the intermediate case where Eq. (6.B.13) applies. 

If Co < CoL, then there is no mass loading effect and the comparatively simple method for computing the cyclone s separation performance, as described in Sects. 13.5.1 and 13.5.2, applies. Conditions that may lead to this scenario include a low liquid loading, Co, a very fine feed drop size distribution, and a large inner vortex cut-point diameter, X50 ... 

When air classification is employed for ash beneficiation purposes, the mechanism is similar, but a high-performance cyclone is used. An example is shown in Fig. 8. Devices vary considerably in the feed arrangement used, but most employ some mechanism to effectively distribute the ash particles across the profile of the cyclone, such as a rotating cage or distribution plate. The velocity of the feed is controlled to produce the desired size separation whereby fine particles and most of the air migrate to the inner vortex while coarse ash exits the bottom. Air classifiers have been used for many years to control pozzolan fineness simply by removing coarse ash particles, particularly when LOI is not a problem. Air classification is usually not effective for reducing LOI, particularly if the carbon is fine. Some coarse carbon particles may be rejected with the coarse ash, but since the density of the carbon particles is lower than... 

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