Analysis of Dust Dispersion Behavior and Influencing Factors for Powder Coatings in a 20 L Transparent Sphere

Dust dispersion is a critical determinant of the initiation and severity of dust explosions. This study investigates the dispersion dynamics of epoxy-polyester powder within a transparent 20 L spherical vessel using a custom eight-channel laser extinction system and CFD simulations. The dispersion process was characterized as a four-stage evolution: rapid injection, turbulent diffusion, stabilization, and sedimentation, with settling beginning after approximately 300 ms. Experimental results demonstrate that a dual-nozzle configuration markedly enhances spatial homogeneity compared to a single-nozzle setup, achieving a 61.3% reduction in the coefficient of variation and a 93.8% increase in peripheral concentration coverage. Furthermore, while increasing injection pressure (0.3-0.4 MPa) optimizes radial uniformity, it simultaneously introduces localized axial instabilities. Among the tested nozzle diameters (16 mm, 20 mm, and 32 mm), the 20 mm nozzle exhibited the optimal balance between jet momentum and volumetric coverage, yielding the most isotropic dust cloud. These findings provide essential quantitative benchmarks for the design of industrial powder coating systems and the enhancement of explosion risk assessment protocols.