CFD modeling and simulation of expanded polystyrene pyrolysis in a fluidized bed reactor

Abstract This study presents a multiphase CFD model, predicated upon the Eulerian–Eulerian framework integrated with the granular kinetic theory, to study expanded polystyrene (EPS) pyrolysis in a fluidized-bed reactor under stable fluidization conditions. The proposed model was validated against experimental data from the literature. Subsequently, the fluidization characteristics and overall gas-particle flow patterns; the temperature profiles and heat-transfer rates; as well as the product distributions and pyrolysis reaction progression within a fluidized-bed reactor were studied in detail, both qualitatively and quantitatively. To deepen the analysis, a comprehensive parametric study was conducted, analyzing the influence of operating temperature, inlet superficial gas velocity, bed particle size, and initial bed height on the yields and compositions of pyrolysis products. The simulation results indicate that operating temperature has the greatest influence on product distribution. For the main product classes, as operating temperature increases, the yield of condensable volatiles diminishes, whereas the yield of non-condensable volatiles rises. Regarding specific products, the yield of styrene – often the target product in EPS pyrolysis – exhibits a non-monotonic trend, initially rising with temperature, reaching a maximum of 61.64 wt% at 600 °C, and then decreasing at higher temperatures. In contrast, inlet superficial gas velocity, bed particle size, and initial bed height are found to have a limited impact on product yields.