Numerical Simulation of Roughness Effects Inside a Brick-lined Cyclone Separator

Abstract

An industrial cyclone used for separating dust from a hot gas mixture was studied by means of numerical simulation. Because of the high gas temperatures (about 1075 K), the inner surfaces of the cyclone separator and the inlet pipe must be lined with refractory bricks, causing high wall roughness. The virtual wall model was used to simulate this roughness, and a new model extension accounting for joints between the bricks is proposed and validated experimentally. As the cyclone inlet mass load was relatively low (0.01 kg/kg), the Eulerian-Lagrangian approach was used for the simulations. The continuous phase conservation equations were solved in the Eulerian reference frame on a fixed grid, whereas the discrete phase properties were determined by computing particle trajectories through the computational domain in a Lagrangian reference frame. Besides inlet particle diameters ranging from 1 μm to 100 μm, different particle materials with varying particle densities had to be considered. The measurements and the Muschelknautz analytical model were compared to the numerical simulations regarding pressure loss, particle spectra at the outlet, and the fractional separation efficiency. The Muschelknautz model exhibited some difficulties with the kind of wall roughness considered here (especially joints between bricks). Moreover, this method was not designed to handle multiple different particle densities simultaneously. Nevertheless, comparisons show good agreement between numerical simulations, measurements and theoretical predictions.