Multiphase Fluid Dynamics in a Vertical Pyrolysis Reactor Using Computational Fluid Dynamics

This study employs Computational Fluid Dynamics (CFD) to investigate the nitrogen gas flow patterns, feedstock particle size, turbulence zones, and the distribution of the solid volume fraction in a vertical pyrolysis reactor. By employing the Eulerian multiphase model and a transient solver, the analysis allows the investigation of whether the feedstock particle size is appropriate for maintaining good mixing and identifying potential turbulence zones during the feedstock loading stage. The results highlighted the critical importance of feedstock particle size and nitrogen gas velocity in maintaining adequate mixing. Using a time-averaged profile, feedstock with a 0.55 mm diameter and a bulk density of 536 kg/m3, combined with a continuous nitrogen gas supply at 0.485 m/s, resulted in significant bed expansion, twice the initial height. This ensures that the biomass feedstock particles do not settle at the bottom of the reactor, thus facilitating uniform heat transfer, which affects yield efficiency. The velocity of the feedstock with nitrogen gas peaked at 0.98 m/s. At 25% loading capacity, the solid-phase volume fraction decreases from 0.6 to a range of 0.1 to 0.3, indicating efficient mixing and heat transfer. It was observed that the proper nitrogen gas velocity also promotes uniform heating, enhancing the process’s overall performance.