Discrete Element Modelling and Simulation of Vibratory Screens

Licentiate thesis, 2018

In Sweden about 85 million tonnes aggregate is used for road, railway and concrete every year. Crushing is the main process for producing the aggregate material in different fractions. The crushing process is divided into two sub-processes; comminution and separation. The vibratory screen is one of the separation machines used to make a final separation to produce the products based on a grade or a size range. In an industry where logistics play an important role, the transport of unnecessary materials can be costly and it therefore becomes critical to screen these materials before transporting them. Industrial vibratory screens are costly and also have a substantial effect on the quality of the final product. Therefore, selecting the correct vibratory screen from the beginning for the crushing plant results in a better return on investment and better quality products.

The main hypothesis of this research is to find the screen model and to understand the screening process in different conditions such as different particle size distribution (PSD) and different feed rate. The first step towards achieving the screening model is to understand the influence of different machine parameters and material properties in screening performance. Some of these parameters have been studied in this research such as motion type, the material of the screen deck and the aperture shape. Discreet Element Method (DEM) has been used to study those parameters with the idea that by using DEM simulation the interaction of particle to particle and particle to geometry can be studied in a way which is difficult to attain by real experiments.

The study results show some of these factors have a larger influence on screening such as a effect of motion type for different slope of deck. The elliptical motion is more efficient compared to linear motion. And also, the aperture shape in different parts of the screen deck has a different effect based on single layer material or multiple layer material in the feeding point. The result of this research needs further investigation in order to study the effect of interaction between different factors before achieving the complete screen model.