Modeling the discharge characteristics of rectangular flights in a flighted rotary drum

Rotary drums equipped with longitudinal flights are essentially used to dry granular material to handle high throughputs. The design of the flights is the crucial task that influences the distribution of the material over the dryer cross section. A mathematical model for the flighted rotating drum that determines the holdup and the cascading rate of the particles discharging from the flight surface is developed. Experiments were performed with a drum of 500 mm in diameter and 150 mm in length, which is furnished with 12 flights around the inner shell of the drum. The model predictions depicted that the carrying capacity of the flight increases with increasing the flight length ratio, but the discharge rate decreases during the initial discharge. Bulk movement of the material has been observed into the airborne phase of the drum during the final discharge at higher flight length ratios. The validation of the model was carried out with different profiles of the flight by varying the tangential length. It is proved from the experiments that increase in flight length ratio increases the material distribution over the drum cross section. The experimental results were observed to be in good agreement with the model predictions.