Effect of moisture on the performance of a gas cyclone

Traditional gas cyclones are effective in collecting fine but not ultrafine particles. A recent proposed technology, cloud-air-purifying (CAP) shows that by introducing moisture in the cyclone, the collection efficiency for ultrafine particles can be significantly enhanced. This paper presents a numerical study to understand the effect of moisture content on the collection efficiency of fine to ultrafine particles in a gas cyclone. The multiphase (air, vapour and particles) flow in the cyclone is simulated by computational fluid dynamics (CFD) by using Fluent software. The turbulence of air flow is modelled by the Reynolds Stress Model (RSM), and the particles are modelled by Lagrangian particle tracking (LPT) model. In addition, the particle growth due to the absorption of the moisture is modelled and implemented in Fluent simulations through the user defined function (UDF). The effect of moisture content on the performance of the cyclone is studied by a series of controlled numerical experiments. The results demonstrate that the particle collection efficiency increases with the increase of super-saturation rate. Ultrafine particles can be more effectively collected because of the increase in their sizes. Moreover, three different flow patterns of particles are identified in the cyclone, which can be related to the micromechanisms of the separations of different sized particles. These studies can help improve the understanding of CAP technology.