Abstract:
Densification is the process of compacting bulk material to increase its physical and energy density. One way of densifica tion is by using screw extruders. Yet, sufficient theoretical studies have not been carried out on the densification para meters 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 pres sure 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 00 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 identi fied to be between 30 and 50, which yields the optimum output density without compromising the combustion property
of the compacted biomass.
