Xiaoping Chen

Numerical simulations of a 120 t/d sludge fluidized bed incinerator were performed using Computational Particle Fluid Dynamics (CPFD) method. The effects of secondary air on temperature distribution, gas distribution and pollutant emissions were investigated. The results show that the secondary air with a tangential arrangement significantly enhance flow field disturbance in the furnace compared with the original opposed arrangement. This can increase temperature and temperature distribution uniformity in the dilute phase region. The tangential arrangement facilitates vortex formation within the furnace, thereby accelerating gas-solid mixing and enhancing O₂ concentration uniformity in radial sections. Compared with the opposed arrangement, the tangential arrangement can promote the oxidation of CO and SO₂ while enabling effective reductive removal of NO. The computational results demonstrate that under the tangential arrangement, CO emissions at the furnace outlet decrease by 96.44%, with simultaneous reductions of 6.80% for NO and 53.42% for SO₂, indicating significant improvements in comprehensive pollutant emissions control.

Understanding wet particle collisions involving droplets is essential for optimizing industrial processes. This study employs interface-resolved simulations combining the volume of fluid model, surface tension model, particle motion model, and overset grids to analyze particle–droplet interactions. Key phenomena investigated include particle motion, droplet spreading, successive particle collisions, and liquid bridge stretching. In symmetric systems, particle dynamics and droplet interactions show consistent patterns. The peak droplet spreading area increases with higher initial velocities and larger droplet sizes. Conversely, it decreases with greater liquid viscosity. Rotational velocity increases with higher collision velocity, lower viscosity, smaller droplet size, and is strongly influenced by collision angle, exhibiting trends similar to normal relative velocity. Increased initial collision velocity amplifies capillary and viscous forces, leading to greater energy dissipation. Force–displacement analysis confirms alignment between kinetic energy dissipation components and total energy loss. Moreover, larger droplets significantly enhance energy dissipation and reduce energy gain effects. Higher liquid viscosity further strengthens liquid bridge forces. These findings highlight the complex interactions involved in droplet-mediated particle collisions within multi-particle systems.

In industrial-scale powder storage facilities, abnormal stress distribution on silo walls can lead to severe safety accidents, including structural deformation and collapses. The powder weight distribution in three-dimensional flat-bottomed silos was studied from the force chain network rearrangement of the micro-mechanism to the wall stress distribution of the macro-behavior. The effects of particle size, silo diameter, and powder type were considered using the discrete element method. At a constant filling height-to-diameter ratio (Hfilling/D), increasing particle size slightly raises the bottom load-bearing percentage, while maintaining a constant filling height significantly increases this percentage as silo diameter increases. The size effect notably affects load-bearing distribution and pressure accumulation on the silo wall. The bottom effect weakens the sidewall load-bearing capacity near the bottom. The average particle–wall friction coefficient in static packing is lower than the predefined value, indicating insufficient wall friction mobilization. Shallow silos primarily support powder weight from the bottom. As Hfilling/D increases, strong force chains develop, enhancing force transmission and uniformity, while enhancing the sidewall load-bearing capacity.