Effects of the surface roughness on the separation efficiency of oil–gas mixture impingement on the vertical wall

Abstract

This paper investigated the effect of the surface roughness (0.3 μm, 1.1 μm, 2.5 μm, and 4.5 μm) on the oil–gas separation efficiency. Through spraying the oil–gas mixture onto the vertical wall, the droplets impingement in inertial separators was imitated. The impact separation efficiency on a wall was calculated by comparing the volume of the collected oil flowing down from the wall with the volume of the impinging oil. Experiments were conducted three different impingement conditions. The impinging velocity and droplets size distributions on the impingement surface were characterized by the Malvern particle size analyzer and the particle image velocimetry (PIV) technique, respectively. The droplets impinging velocities varied in the range of 3−5 m/s, and the Sauter mean diameter was observed around 40 μm. The collecting process can be divided into the initial stage and the steady stage according to the film flow state. It was found that the surface roughness has both advantages and disadvantages effect on the film flow. These two opposite effects are of different importance at different roughness levels. Under the studied impingement conditions, the separation efficiency was all above 80%, and the surface of the middle roughness (1.1–2.5 μm) performed better than the smoothest 0.3 μm surface and the roughest 4.5 μm surface.