Establishment and verification of a model for the movement of pulverized sweet sorghum stalks in a rotary drum bioreactor by discrete element method

Abstract The mixing of raw materials in a rotary drum bioreactor is important for advanced solid-state fermentation technology. However, the shape, size, and other properties of pulverized sweet sorghum stalk particles are more complicated than those of the spherical particles. In this study, a soft rod-shaped discrete particle model was established and verified to simulate the mixing behavior of sweet sorghum stalk particles in a rotary drum bioreactor. We were inspired by the particle shape and established a rod-shaped particle model by investigating the influence of the shape (length–diameter ratio) and size (diameter) on the particle packing (stack height and bed porosity). We used orthogonal simulations and extremum difference analysis to determine the main factors, optimum level, and groups of other parameters. Based on calibrated parameters, twelve sets of simulations of radial mixing in the drum were performed, and the results were compared with experiments conducted under identical operating conditions. The average relative error between the simulation and the experiment was 10.95%, which indicates that they agreed well and that the simulation could predict the mixing process well.