Effects of aggregation on the kinetic properties of particles in fluidised bed granulation

• Aggregation decreases the bed pressure but enhances mixing.
• Aggregation increases the momentum and kinetic energy of the particles.
• Aggregation mainly takes place in the middle of the bed.
• Particles in the top of the bed have the largest probability to aggregate.

Aggregation in particulate flow affects not only the size but also the pressure, momentum, kinetic energy, mixing and aggregation efficiency of the particles. This paper demonstrates such effects using a kinetic theory of aggregation to study a gas fluidised bed granulation system with a comparison to that of the process without aggregation. The aggregation system showed a decreasing bed pressure and an increasing total momentum and kinetic energy of the particles over time. A continual mixing of the particles between regions from top to bottom of the bed was observed while for the non-aggregation system, after the fluidisation has fully developed, hardly any mixing of the particles between those regions was seen. It was found that the aggregation of particles mainly took place in the middle of the bed while in the top and bottom of the bed, aggregation had a smaller proportion and segregation showed to dominate. The calculated collision success factor suggests that the particles in the top of the bed have the largest probability to aggregate.

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