Insight into the Mesoscale Slug Characteristics in the Dense Horizontal Pneumatic Conveying Process

Slug behavior in dense pneumatic conveying affects system stability and efficiency, which raises the urgent need for an in-depth understanding of this phenomenon. This investigation employs computational fluid dynamics coupled with a discrete element method to comprehensively analyze the behavior and properties of slugs and particles within a horizontal dense-phase pneumatic conveying system. Based on the validated model, this study explores slug velocity, volume, particle trajectory, dispersion, and other properties under diverse operating conditions, examining their characteristics and variation patterns. The findings indicate that the superficial gas velocity is a key factor affecting the efficiency of pneumatic conveying. As the superficial gas velocity increases from 8 to 12 m/s, a 53.60% increase in the slug velocity and a 70.12% decrease in the volume are observed at the midpoint of the pipe. Higher particle flow rate significantly increases the slug velocity while reducing the frequency and volume. The particle-scale information has an obvious effect on slug behavior. The lower density of particles makes them more easily caught and discarded by the slugs. Consequently, the maximum dispersion and displacement of foamed polypropylene (FPP) particles reach 1.64 m²/s and 0.30 m, respectively, whereas those of ceramic particles are only 0.71 m²/s and 0.13 m. These findings provide a valuable basis for optimizing the horizontal dense-phase pneumatic conveying system through an in-depth analysis of the slug.