CFD-DEM modeling of strongly polydisperse particulate systems

Evolution and Physical Characteristics of a Raceway Based on a Transient Eulerian Multiphase Flow Model

In industrial processes, a semi-cavity area formed by airflow wherein the particles circulate is called a “raceway”. In a blast furnace, the role of the raceway is particularly important. To understand and predict the evolution and physical characteristics of the raceway, a three-dimensional transient Eulerian multiphase flow model in a packed particle bed was developed. In the model, it was assumed that the gas and solid (particle) phases constitute an interpenetrating continuum. The gas-phase turbulence was described as a k–ε dispersed model. The gas-phase stress was considered in terms of the effective viscosity of the gas. The solid-phase constitutive relationship was expressed in terms of solid stress. It was found that the evolution process of the raceway can be divided into three stages: (1) rapid expansion, (2) slow contraction, and (3) gradual stabilization. When the blast velocity was increased from 150 m/s to 300 m/s, the surface area of the raceway increased from 0.194 m2 to 1.644 m2. The depth and height of the raceway increased considerably with velocity, while the width slightly increased.

Study on Parameters of a New Gas-Water Spray in Ore Pass Dedusting Based on Experiment and Numerical Simulation

To solve the problem of ore unloading dust in ore pass crosscuts, the atomization characteristics of a new gas-water spray and the effect of the ore discharge airflow on the spray effect were studied by experiments, and the installation position of the spray nozzle in the crosscut was determined by numerical simulation. The results show that when the gas-water flow ratio is 100-150, the atomization effect is the best. In this situation, the droplet size can be less than 28 μm. The impact airflow induced by ore unloading has a great influence on the size of the spray droplets, and the dust-collecting ability of the spray is negatively correlated with the impinging airflow. The best location for the spray is 5 m away from the wellhead. At this position, the impact airflow is less than 1.5 m/s, which can ensure that the total dustfall rate of the gas-water spray is 67% and that of the respiratory dust is 34%.

Predicting the performance of pressure filtration processes by coupling computational fluid dynamics and discrete element methods

To obtain a fundamental understanding of the various factors affecting pressure filtration performance, we developed a coupled computational fluid dynamics (CFD) and discrete element method (DEM) model for simulating the effect of solvent flow through the solid particle cake. The model was validated using data collected by filtering mixtures of spherical glass beads and deionized water through a dead-end cell over a range of applied pressures. Numerical experiments were performed to study the effects of particle properties, liquid properties and operating conditions on filtration performance. The model predicted that the filtrate flow rate could be strongly affected by the mean size of the particles, the presence of small particles (i.e. fines) in the particle distribution, the viscosity of the liquid, and particle deformation leading to cake compression. Our study demonstrated that CFD-DEM modeling is a powerful approach for understanding cake filtration processes and predicting filtration performance.