DEM simulations of tote blenders for enhanced axial mixing efficiency

The mixing performance of a multi-bladed tote blender is investigated using a graphics processing unit-based discrete element method program.The positioning,dimensions,and applicability of the baffles are systematically studied according to the axial mixing efficiency.The results indicate that the novel inclined multi-bladed baffles can break the symmetrical axial granular flow and introduce a more efficient convective flow into the granular mixing in the axial direction of the tote blender.Owing to the joint effects of convective mixing and asymmetrical granular flow,the axial mixing efficiency is increased by a factor of nearly 20.More importantly,the novel baffle placement approach exhibits excellent applicability to different operating conditions,particle shapes,and blender sizes.Additionally,the inclined baffles can prevent the segregation caused by shape discrepancies and improve the mixing homogeneity in the steady state.The novel baffle design is promising for applications in more complex industrial blenders for achieving a high axial mixing efficiency.

Axial gas mixing in conical spouted beds with high density particles

Conical spouted beds operating with high-density particles(ρp>2500 kg/m^(3))have recently gained attention because of their potential use as nuclear fuel coaters for next-generation nuclear reactors.In the literature,the number of axial gas mixing studies in conical and conical-cylindrical spouted beds is very limited and all axial mixing studies were carried out with relatively light particles(ρp≤2500 kg/m^(3)).Therefore,the objective of this study was to generate experimental data that can be used to explain the gas axial mixing behavior in conical spouted beds operating with both low-and high-density particles.Experiments were conducted in two(γ=30°,60°)conical spouted beds with three different types of particles:zirconia(ρp=6050 kg/m^(3)),zirconia toughened alumina(ρp=3700 kg/m^(3))and glass beads(ρp=2460 kg/m^(3)).In order to be able to compare experimental data obtained at different conditions,a 1-D convection-diffusion gas mixing model originally developed by San Joséet al.(1995)was implemented to determine the axial dispersion coefficients.The results show that the axial dispersion coefficients range between m^(2)/s and m^(2)/s,increase with superficial gas velocity and are higher than the corresponding dispersion coefficients of fixed beds,lower than the dispersion coefficients of fluidized beds and in the same range with the cylindrical spouted beds reported in the literature.The corresponding Peclet numbers were in the range of 0.6–7.8 for all operating conditions and slightly higher Peclet numbers were obtained with glass beads indicating the relative importance of gas convective transport over gas dispersion for light particles compared to heavy particles.