Vibrating screens are commonly used in the process industries for size segregation of polydisperse particle mixtures. Given the wide range of applications, such screens are available in a variety of designs. Multiple deck screens are used for the grading of the primary mixture into different groups according to size.
The primary function of a screen is to pass the fine particles through the screen surface. For any granular material subject to vibration, the fines naturally sink to the bottom while larger particles float to the top.
This phenomenon of stratification results in an efficient exposure of fines to the screen surface, and hence enhances the screening process. The vibratory motion, the surface slope angle as well as the geometrical parameters determine the effectiveness of the screen for a particular task.
The operation details of a vibrating screen can be illustrated by a simplified numerical simulation using DEM. We consider a single deck screen, modelled by a 800 mm square section with periodic boundary conditions assumed on each of its four lateral sides. The screen is comprised of a 2D array of 40 mm square holes, and is vibrated at an angle of 24o, a frequency of 3 Hz and an amplitude of 5.4 mm. An initial population of 4,000 particles with diameters between 10 and 60 mm was loaded above the screen.