A new design method for multiphase reactors combining field synergy theory with process intensification strategy: Application to downer reactor for coal pyrolysis

Optimizing multiphase reactor design is crucial in chemical engineering. This study introduces a new approach that combines field synergy with process intensification for optimizing reactor design, and apply it to the design of a downer for low-rank coal pyrolysis. The core design parameters of downer with swirling blade nozzle(DSBN), including blade number(N), height(H), angle($\theta$$\theta$), and number of turns(T) were optimized. Results indicate that the optimized DSBN achieves a more uniform coal temperature, which is 65.735 K higher than in a conventional side nozzle downer(CSND). The global reaction rate in DSBN is 13.36 % higher than in CSND. This improvement is attributed to the enhanced synergistic effect between physical fields in the DSBN. The optimal parameter settings for energy efficiency and overall performance are N = 8, $\theta$$\theta$=90°, H = 100 mm, T = 0.125. Sensitivity analysis indicates H significantly impacts resistance and heat transfer, while $\theta$$\theta$ most affects comprehensive performance.