Attrition and Breakage

This section is concerned with those properties which determine particle breakage and attrition. The powder characteristics which play a role in this can be divided into three groups ... 

Resin consumption and cost. Resin deteriorates in use. Volume changes during adsorption and elution and mechanical wear cause breakage and attrition. Chemical poisoning and fouling cause gradual loss of adsorptive capacity. In three South African plants, useful resin life was estimated ([M3], p. 143) at from 19,000 to 27,000 volumes of solution treated per volume of resin. This represents about 3 years usage in normal service. 

The number of particles in a size class, class L to I + dl (Figure 9.6), will change with the (i) growth of smaller particles into this size class and with the growth of particles out of this size class, (2) generation of particles of this size by nucleation and agglomeration, (3) loss of particles due to breakage and attrition, and (4) influx of particles and as well as by product removal. 

Breakage and attrition really cover two separate phenomena ... 

A major quaUty feature of particles is their mechanical strength. This parameter depends mainly on the material properties but also, as discussed in Section 7.3.2, on the microstructure of the particles. Microscopic changes in the structure, porosity or surface properties of the granules occur under the influence of different process parameters and can lead to major changes in properties on a macroscopic scale, for example breakage and attrition resistance. 

The catch can also contain an error due to breakage and attrition, processes which are very difficult to trace. 

It is most important that the catalyst be strong enough to resist breakage and attrition. Fixed bed and tubular reactors are carefully filled with catalyst to ensure that the pellets or granules are not damaged and pack with a uniform density. 

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