This work presents a novel demister which combines the principle of a swirl or cyclone separator with the micro-impaction principle, i.e., inertial impaction on the micro-scale. The latter was already investigated by Kaiser (2020) for planar droplet-laden flows through woven wire meshes with weft and warp wires aligned perpendicularly and parallel to the flow direction, respectively.

Kaiser’s work showed, that separation performance of wire meshes can be significantly increased by a shallow inflow angle with respect to the wire-mesh plane, while at the same time only moderately increasing pressure drop across the mesh. The present work aims to synergetically combine the prescribed separation effect with that exploited in cyclone separators, i.e., centrifugal separation in swirling flows (Dwars and Mehring (2024)).

To that extend, numerical flow simulations were carried out for a 7.7 degree periodic sector of a cylindrical flow cell with prescribed swirl in the incoming axial flow, as shown in Figure 1 (left). The droplet-laden swirling gas stream is allowed to flow radially outward through a cylindrical square wire-mesh along the height of the flow cell. At its outer radius, the flow cell is limited by a wall diverting the flow in axial direction.

Simulations are based on the steady-state incompressible RANS equations with SST k-ω turbulence model (including curvature correction) and Lagrangian description of the disperse phase using a random-walk model for turbulent dispersion. Numerical solutions were computed using the - ANSYS Fluent Version 2022R1. A contour plot of the calculated velocity magnitude in a q=const. plane is shown in Figure 1 (right).

Numerical simulations show that, depending on flow cell geometry and operating parameters, low flow angles through the wire mesh can be maintained and the benefit of inertial droplet impaction can be preserved even at through-flow directions not aligned with weft or warp wires.

Experimental comparison of pressure drop and separation efficiency for a properly tuned modified separator geometry (consisting of the flow cell with an integrated swirler) and a unidirectional cyclone (with identical swirler-blading but different swirler-core and a downstream cylindrical section) were carried out. A white-light aerosol spectrometer (Palas WELAS digital 3000) was used to determine particle size distributions in the upstream and downstream flows. Information on the geometry of the two separators is summarized in Table 1. Experimental results for a mean axial inflow velocity of 16 m/s are illustrated in Figure 2. The cut size diameter x50 of the new separator is found to be 40% lower than that of the unidirectional cyclone, while at the same time yielding a pressure drop reduction of nearly 50%. In addition, the new mesh-type swirl separator is 50% shorter than the comparable typical axial flow cyclone design.