Hardness attrition factor

Table 5.20 shows the relationship between hardness, time and bake temperature. A lower attrition factor indicates a harder powder. 

Table 5.20. Relationship Between Particle Hardness (Attrition Factor), Time, and Bake Temperature ...

Much effort has been made by catalyst manufacturers to improve catalyst atttition resistance and thus reduce the formation of fines (see Catalysts, supported). In the 10-year petiod from 1980 to 1990, most catalyst manufacturers improved the atttition resistance of their catalyst by a factor of at least 3—4. This improvement was achieved even though the catalyst zeoHte content duting this petiod was continually increasing, a factor that makes achieving catalyst hardness more difficult. As an example of the type of atttition improvement that has been achieved, the catalyst atttition index, which is directiy related to catalyst loss rate in a laboratory attrition test, decreased from 1.0 to 0.35 for one constant catalyst grade during 1989—1990 (37). 

Compression and compaction parameters such as density, porosity, stress, and strain are introduced. Furthermore, other factors of importance in stress measurement of powder beds in different situations such as compression, tension, shearing, and impact are explained. The fluidity of food powders is a controversial topic in food powder characterization and of top relevance in the food industry. Concepts such as compressibility and other flowability indicators are important for understanding the effects of compression phenomena during storage, production, and handling. Food powder strength concepts such as hardness relate to other concepts like attrition, which are a common occurrence in compaction processes. 

A related property, which is also an important factor, is the ability of the individual coal particles to retain their initial size during handling and processing. In fluidized-bed processes, attrition and decrepitation of the feed coal may result in unacceptable tines carryover losses. For processes that must withstand high temperatures and blast velocities, only hard and resistant coals are satisfactory feed materials. In addition, the fusibility and caking characteristics are properties of importance to moving bed or fluidized-bed processes. 

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