Modifying geld art classification for various cohesion forces

Fluidized beds (FB) have significant applications in various industries. Classical Geldart classification is used for a long time to classify materials to four groups, each behave differently in a fluidized bed. Geldart's classification is based on the relationship between the particle and fluid density difference and the particle diameter. The four groups show behavior related to the cohesion forces. Group C has very high cohesion forces to create channels or rising plugs. Group A has countable cohesion forces while particles behave as individuals to present a bed volume increase at fluidization. Groups B and D are big enough to have negligible cohesion forces show none of the above-fluidization starts as bubbling and slugging. However the classical Geldart classification is based on dry materials in which the major cohesion force is related to Van der Waals force. In this research the effect of other cohesion forces on the classification is examined. A number of materials were tested at various moisture contents to present cohesion forces by liquid bridges. By these tests materials originally classified in groups B or D behaved like groups C or A at various moisture contents. Further, experiments with liquid fluidization were conducted. In this case there are no liquid bridge forces and also the Van der Waals forces are negligible. Indeed, even materials originally classified to groups C or A are expected to behave like groups B or D. In this way, Geldart's classification can be modified to consider various cohesion forces.