Particle-scale modelling of raceway dynamics in a blast furnace using a smoothing method

Abstract

The lateral high-speed gas injection into a packed bed, forming a raceway cavity, has been commonly practised in chemical engineering applications such as ironmaking blast furnaces whereas the high Reynolds number gas flow and narrow orifice cannot be well resolved by the traditional unresolved CFD-DEM approach using low-resolution grids. In this work, a smoothing method is developed, in which the quantities are transferred between discrete particles and the continuum phase in a grid-independence fashion via solving an isotropic diffusion equation. The model is validated using two cases, i.e., sedimentation of one single particle in a rectangular box and gas-solid hydrodynamics in a spout fluidised bed. Then, the unresolved CFD-DEM approach with the smoothing method is applied to simulate raceway dynamics. The simulation results indicate that the smoothing method allowing high-resolution girds satisfactorily captures a plume-like raceway. The boundary and volume of the cavity are proposed as two criteria to determine the raceway profile quantitatively. The volume of the cavity is 3.03 × 10−3 m3, 3.91 × 10−3 m3, 4.49 × 10−3 m3 with three different inlet gas velocities of 210 m/s, 230 m/s, and 250 m/s, respectively. Higher inlet gas velocity needs a shorter time to establish an equilibrium state.