Modeling of Classification Process in a Continuous Trommel Screen
Mechanical classification of bulk materials is quite widely used in various industries. Modeling of the process is complicated due to the fact that in a continuous mode the bulk material moves not only in axial, but also in longitudinal section of the classifier. To describe the classification process, deterministic and stochastic models can be used. When modeling the process of mixing-separation in a continuous drum classifier it is impossible to consider the process which takes place in the fixed circulation contour. It is necessary to take into account the material movement along the axis of the drum, and also the reduction in the area occupied by the material in the cross-section of the trommel screen. The process of movement in the continuous drum classifier can be presented as discrete in space and time. Thereby the process of mixing-separation can be considered similar to the periodic one, but the transition to each successive section along the length of the classifier must take into consideration changes in configuration of the circulation contour associated with a decrease in the area occupied by the material in the cross-section of the drum. To describe the process of mixing taking place simultaneously with the process of classification, the mechanism that determines the sequence of phases for a three-component mixture can be used. While describing the mechanism of separating small and product fractions from the mixture composition, constant coefficients defining the intensity of separation of these particles from the mixture are used. The presented mathematical description of the process considers both the mechanism of components segregation and the mechanism of separating the mixture into individual fractions. Options of practical use of the mathematical description for designing new equipment and optimizing the operating one are presented in the conclusion.