A work done approach on analyzing the effects of densification parameters on tapered screw extruders

Densification is the process of compacting bulk material to increase its physical and energy density. One way of densification is by using screw extruders. Yet, sufficient theoretical studies have not been carried out on the densification parameters for a tapered screw. In this study, a mathematical model for investigating the effect of the operational parameters on a tapered screw has been studied by analyzing the work balance on the plug along the tapered screw channel. By using the taper angle, screw pitch, and barrel friction coefficients as control variables, a mathematical model for the pressure gradient, volumetric throughput, and output density was established. The velocity profile of the plug along the screw channel was measured to determine the volumetric throughput. The final model for the pressure gradient along the axial length of the screw has been approximated by Runge-Kutta fourth order approximation model in the python programing environment. From the results, an increase in screw length, screw taper angle, and barrel friction coefficient has been attributed to an increase in compaction pressure. This parameter has also changed for a 0 0 tapper angle, which is primarily due to centrifugal, gravity, and frictional forces acting on the plug. Further investigation into the volumetric throughput and output density has the same effect. According to the analysis, the optimum taper angle has been identified to be between 3 0 and 5 0 , which yields the optimum output density without compromising the combustion property of the compacted biomass.