Particle Motion in Rotary Screen

Abstract

Rotary screens are an important unit operation in materials processing. Much of their design has been empirical. Herein, a mathematical model is developed with three major components: particle rise on the screen, particle trajectory through the air, and screening of the particle while in contact with the screen. All were implemented on a computer using numerical methods, allowing use of the original theoretical expressions with simplifications for solvability. Particle rise incorporates friction; particle trajectory incorporates drag. The screening element makes use of an entirely new probabilistic theory that differs from previous work by immediately considering the depth of the bed. Results show very good predictive capabilities. Analysis shows the delicate nature of rotational velocity, the significance of drag on the particles in terms of particle density and airflow in the trommel, and the importance of the coefficient of friction.