Numerical analysis of chevron demisters with drainage hooks in optimizing separation performance

Abstract

Chevron demister is widely used in the industry program to remove the liquid droplets from gas flow. Design a demister with optimal separation performance (higher separation efficiency and lower pressure loss) is mainly concerned in the industry process. In this study, the separation performances of the four demisters (named as A, B, C, and D) are numerically evaluated and compared to find the ideal one. A combination of DPM, EWF model, and DRW model are used to simulate the motion of droplets in gas flow. Contours of velocity magnitude, pressure, particle tracks, and wall film thickness on vanes are obtained. Overall separation efficiency η, grade separation efficiency ηd and pressure loss ΔP are also discussed. It can be concluded that separation efficiency of type D is 17% higher than that of type A when inlet velocity v = 2 m/s, and becomes 3% higher when v = 10 m/s. Pressure loss increases 5178.2 Pa, 6278.2 Pa, 8621.1 Pa and 11,450.2 Pa for type A, B, C and D respectively when v increases from 2 m/s to 10 m/s. Large droplets are mainly captured at the first two stages, as the velocity increases, the liquid film expands backwards and can be observed at the last two stages. Compared to double hook, single hook induces higher separation efficiency as well as pressure loss. Splashing and film stripping are the main reason of re-entrainment. The ideal type of chevron demister is related to the specified situation with respect to its separation efficiency and pressure loss.