Transport behavior of shredded tobacco particles with different aspect ratios in pneumatic conveying using CFD-CGDEM

Particle aspect ratio is an important geometric parameter; however, its role in pneumatic conveying remains insufficiently understood. This study employed the bonded particle model (BPM) to construct shredded tobacco particles with 11 different aspect ratios, and simulated the industrial-scale pneumatic conveying process using the coarse-grained Computational Fluid Dynamics-Discrete Element Method (CFD-CGDEM). Particle conveying behavior in straight pipes, horizontal elbows, and vertical elbows was analyzed. The degree of radial mixing was quantitatively characterized by the Lacey mixing index ( M ). Simulation results revealed that particle aspect ratio influenced conveying characteristics through particle–fluid interactions and flow-induced motion characteristics. In straight pipes, particles with high aspect ratio were more likely to accumulate near pipe walls due to gravity ( M < 0.1). In elbows, these particles showed stronger radial migration driven by curvature-induced flow and secondary flow, but the mixing uniformity was still low. When gas velocity was 18–27 m/s, the average particle velocity decreased approximately linearly as the aspect ratio increased. Under stable conveying conditions (21–27 m/s), the average residence time increased correspondingly. At higher gas velocities, the influence of gas flow on particle transport behavior became more significant, and the above correlations gradually weakened. The simulation results were validated by industrial-scale experiments under three gas velocity conditions (21, 24, and 27 m/s), with relative deviations in average residence time all below 5%. This study clarifies how particle aspect ratio affects pneumatic conveying, and provides a basis for optimizing the conveying of flexible elongated particles.