There are several non-invasive techniques used to study the hydrodynamic characteristics of gas-solid fluidised bed reactors. In this study a two phase, gas-solid fluidised bed consisting of air and a linear low-density polyethylene (LLDPE) resin was examined. The polyethylene sample was composed of irregular, non-monosized particles ranging in size from 165 to 1500 μ m. The experimental techniques used were digital fluoroscopy and pressure fluctuations. This study presents a comparison of the two-phase system experimental results and two-dimensional CFD simulation results. CFD packages FLUENT and MFIX were used.