Typical agglomerate strengths

53fL GRAPHITE POWDER WITH RESIN BINDER 26  

As indicated by eqn. (4) (Section 2.1), the main variables affecting the strength of an agglomerate, other than the bonding mechanism, are the void ratio and the size of the particles from which it is composed. A number of empirical relationships have been used to correlate the effects of these variables. For example, eqn. (18) has been used [39] to represent the crushing strength of compressed tablets of constant size. 

Equation (19) has been used [40] to correlate the compression strength of 

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Fig. 2.9. Typical compressive strengths of various spherical agglomerates formed by tumbling.

Compacting of specific materials can be facilitated with certain kinds of additives. Binders are additives that confer strength to the agglomerates, and lubricants reduce friction during the operation. Some additives may function both ways. A few of the hundreds of binders that have been tried or proposed are listed in Table 12.12. Lubricants include the liquids water, glycerine, and lubricating oils and typical solids are waxes, stearic acid, metallic stearates, starch, and talc. 

A typical example is shown in Figure 67. The tensile strength Ut of dry agglomerates, obtained after removal of the crust, is plotted versus the drying temperature The parameter is the liquid saturation before drying. This diagram was obtained using a nearly saturated salt (sodium chloride) solution and a narrowly sized limestone powder. 

For those reasons, strength" means many different things in industry. Typically, measurement of strength is based on a simulation of the stresses which a particular agglomerated product must withstand. Very few industrial methods for the determination of this property are standardized or even known. In a competitive environment it is of less interest to compare quality between rivals than to make sure internally that the product properties that are expected by the industrial or public consumer are maintained. Therefore, most measurements of strength are undertaken as quality assurance. A few will be described below as examples. 

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