T. Penner, J. Meyer, A. Dittler

Separation and Purification Technology, 2020, 248, 117074, https://doi.org/10.1016/j.seppur.2020.117074

Coalescence filters in applications with high separation efficiency requirements, such as compressed air preparation, usually consist of several layers of nonwoven glass fiber media wrapped around a cylindrical metal support grid. The design of this grid has a crucial effect on gas flow inside the filter and therefore on droplet deposition and liquid transport inside the medium. Experimental studies were carried out with flat filter elements in combination seven different downstream support grids to investigate the impact of the grids on operating behavior of the filters in oil mist filtration. The grids differed in flow-through fraction, perforation size and distance and were used in combination with either oleophilic or oleophobic filter media. It was found that the choice of the grid affects liquid transport mechanisms in the media, especially the film formation on the filter rear side of oleophilic filters, thus affecting total pressure loss in quasi-steady state, while impact was less significant for oleophobic media. Separation efficiency was not significantly affected by the choice of grid, while entrainment depended on film coverage of the filter rear side and open area fraction of the grid.