Numerical study on flow behavior of ultrafine powders in conical spouted bed with coarse particles

Numerical Study on the Gas-Solid Flow in a Spouted Bed Installed with a Controllable Nozzle and a Swirling Flow Generator

The swirling flow technology is adopted on a nozzle of the spouted bed in order to enhance the radial movement of the particles. The hydrodynamic characteristics in a spouted bed with a swirling flow generator installed on the nozzle are numerically investigated based on the two-fluid model (TFM). The traditional spouted bed and spouted bed with an integral swirling blade nozzle (ISBN) are simulated and analyzed. Numerical results show that the dead zone at the cone region of the annulus can be effectively eliminated by using the ISBN. The maximum decrease in particle concentration near the cone region is 72%, and the ISBN structure can significantly improve the comprehensive fluidization degree of the spouted bed when γ equals 86°. The turbulent kinetic energy of gas can be significantly increased by the swirling flow along the radial direction in the spouted bed, especially in the spout region. Also, the swirling flow can promote the radial velocity and granular temperature of the particles in the spouted bed, which is helpful to the radial mixing of particles and gas phase between the central spout and the annulus in the spouted bed. There exists a value of ξ (equals 0.526), which brings the greatest elimination effect of the flow dead zone in the annulus of the limited spouted bed space, and the overall fluidization of the spouted bed has the best performance when ξ = 0.316.

Simulation of Particle Mixing and Separation in Multi-Component Fluidized Bed Using Eulerian-Eulerian Method: A Review

In practical engineering applications, the mixing and separation behavior of multi-component particles is importance to the fluidized bed operation. The development of many practical processes is inseparable from the knowledge of particle mixing and separation, such as material processing of ash-soluble coal gasification, multi-phase flow in boilers, and petrochemical catalytic processes. In recent years, due to the obvious advantages of the Eulerian–Eulerian model, many researchers at home and abroad have used it to study the mixing and separation behavior of particles. The paper reviews the use of Eulerian–Eulerian model to study the mixing and separation of multi-component particles in fluidized beds. The Eulerian–Eulerian model describes the gas-phase and each of the individual particles as continuums. The mechanism of particle mixing and separation, the influence of different factors on the particle mixing and separation including differences in particle size and density, the differences in apparent air velocity, the differences in model factors are discussed. Finally, an outlook for the use of Eulerian–Eulerian model to study the mixing and separation behavior of three component particles and related research on the drag model between particles.

CFD Simulation and Optimization of Mixing Behaviors in a Spouted Bed with a Longitudinal Vortex

The radial mixing characteristics of gas and solid phases in a cylindrical spouted bed with a pair of longitudinal vortex generators (LVGs) are numerically studied by a two-fluid model. The influence of the distance between the centers of two spheres (L) and the shape of LVGs on hydrodynamics in a spouted bed are discussed. The results show that the value of the coefficient of variation (CV) of the particle concentration can be significantly reduced by the longitudinal vortex produced in spouted beds. The particle concentration near the spout decreases first and then increases with the increase of L. When the shape of LVGs is cylindrical, a maximum increase of 188 % for particle volume fraction is found near the spout region of the spouted bed. The strengthening effect on particles' velocity achieves the best in annulus of the spouted bed, and CV of the particle concentration in the spouted bed reaches its minimum value with a pair of cylindrical LVGs.