A common approach to improve the efficiency of single screw extruders is an increase in screw speed. At higher screw speeds the solid conveying zone in single screw extruders becomes more important, especially if the hopper opening is not designed properly what can lead to an insufficiently filled screw channel. Consequently, the total extruder throughput can be limited by the solid conveying throughput, if the latter is smaller than the theoretically conveyable melt throughput. At high screw speeds the pellets inflow is additionally influenced by a so called circulation flow within the feeding opening. To investigate such effects the Discrete Element Method (DEM) becomes more and more important. This work deals with possibilities to validate DEM simulations in the field of single screw extruders’ solid conveying zone. Apart from detecting coefficients of friction, the representation of the pellets’ shape is crucial. On the basis of DEM simulations of the bulk density within the screw channel it is shown, that most of the common plastic pellets can be represented adequately by the combination of two spheres. Additionally, simulations of the feeding opening’s pellet flow during a solid conveying process are conducted and validated by comparisons to experimental studies. A quite good conformance results if the pellets are represented by several spheres as described above. Furthermore, the throughput of simulations and experiments is compared and also in this case there is good conformance. All mentioned solid conveying simulations are conducted without pressure built-up up to now. To get a first approach, how this can be regarded, simulations and experimental compression tests are conducted. By comparing the results a suitable DEM material model is suggested and advice for its parameterization is given.