Filter separators are available in horizontal and vertical orientations, with horizontal the most common. Fig. 7-24 shows a horizontal filter separator. This type of separator is often used for solids and liquid removal in relatively low liquid loading applications. A filter separator is a two-stage device. Gas enters the inlet nozzle and passes through the filter section, where solid particles are filtered from the gas stream and liquid particles are coalesced into larger droplets. Any free liquids are also removed in the first section. The coalesced droplets pass through the filter riser tubes and are carried into the second section of the separator, where a final mist extraction element removes these droplets from the gas stream. Flow through the filter elements is from an outside-to-inside direction. A pressure drop of 1-2 psi is normal in a clean filter separator. If solids are present, it will normally be necessary to replace the filter elements at regular intervals. A 10 psi pressure drop criteria is often used for filter changeout. Removal of the filters is achieved via a quick-opening closure.
The second stage of a filter separator contains a mist extraction device. As for a conventional separator this may be a mesh pad, vane pack or multicyclone bundle. The same issues regarding mist extractor selection criteria, sizing, etc. apply as discussed previously. Mesh pads and vane pack are most commonly utilized.
The design of filter separators is proprietary and a manufacturer should be consulted for specific sizing and recommendations.