This invention relates generally to mist eliminators and more particularly to a compact fiber bed mist eliminator having high removal efficiency and low pressure drop without re-entrainment.
Undesired liquid aerosol and/or particulate entrainment in a gas flow is a common problem that can be addressed by placing a fiber bed in the flow that is selected to capture the liquid or particulate while permitting the gas to flow through. Considerations in the filtering out of aerosols, entrained liquids and/or particulates include the efficacy of the fiber bed in removing the airborne entrained material, and the energy required to move the flow stream through the fiber bed to achieve separation. The energy consumed is reflected by the pressure drop across the fiber bed (i.e., between the upstream and downstream sides of the fiber bed). In addition to requiring energy, the back pressure may be highly detrimental to the operation of the machinery generating the flow stream. The smaller the area of the fiber bed the flow stream must be forced through, the more the pressure drop and hence the greater to back pressure to upstream equipment. Moreover, while a thicker fiber bed provides greater collection efficiencies, this will also produce a greater pressure drop. Thinner fiber beds can fail to provide adequate removal of aerosols from the flow stream, especially when the mass mean particle size is submicron.
In one aspect of the present invention, a mist eliminator for use in separating aerosols from a gas flow generally comprises a container having an inlet at an inlet end of the container and an outlet at an outlet end of the container. Filter panels each include a fiber mat having fibrous filter material formed by fine fibers. The fiber mat has pleats extending lengthwise of the filter panels. The filter panels are disposed in the container so that the filter mats of adjacent filter panels are spaced apart. The filter panels define flow channels between adjacent filter panels and flow channels between filter panels and adjacent walls of the container. Some of the flow channels define inlet flow channels in fluid communication with the inlet and blocked at the outlet end of the container to prevent gas flow from exiting the inlet flow channel to the outlet and some of the flow channels define outlet flow channels in fluid communication with the outlet and blocked at the inlet end of the container to prevent gas flow entering the container through the inlet from entering the outlet flow channels. Thus, the gas flow enters the container, passes into the inlet flow channels and thence laterally with respect to the inlet flow direction through one of the filter panels into the outlet flow channels for passage to the outlet of the container.
In another aspect of the present invention, a mist eliminator for use in separating aerosols from a gas flow generally comprises a container as set forth in the preceding paragraph. Filter panels each include a pleated fiber mat having fibrous filter material. The filter panels are disposed in the container so that the filter mats of adjacent filter panels are spaced apart. The filter panels define flow channels. At least one of the flow channels defines an inlet flow channel in fluid communication with the inlet and blocked at the outlet end of the container to prevent gas flow from exiting the inlet flow channel to the outlet and at least one of the flow channels defines an outlet flow channel in fluid communication with the outlet and blocked at the inlet end of the container to prevent gas flow entering the container through the inlet from entering the outlet flow channel. Thus, the gas flow enters the container, passes laterally with respect to the inlet flow direction through at least one of the filter panels into the outlet flow channel for passage to the outlet of the container.
Other objects and features will be in part apparent and in part pointed out hereinafter.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
Referring now to the drawings and in particular to
The housing 3 contains four filter panels (indicated generally at 31, 33, 35 and 37) each comprising a rectangular frame 39 supporting a pleated fiber mat 41 between opposite panel face screens 43 (see,
The interior of the housing 3 is constructed to mount the filter panels 31-37 in spaced relation from each other. The filter panels 31-37 are rectangular in shape and arranged so that their lengths extend along the height of the housing 3 (which is the greatest dimension of the housing). Referring to
The gasket 45 on the filter panel 35 (see,
Gas flow entering the housing 3 into a plenum 73 between the bottom wall 15 and the standoff plate 49 pass is divided into three flow streams. One flow stream passes through the inlet slot 51 in the standoff plate 49 into the flow channel 65 between the central filter panels 33, 35, as indicated by arrows 75. As there is no exit from the flow channel 65 at the top wall 17, the gas flow stream is split and forced laterally as indicated by arrows 77 through the central filter panels 33, 35 which filter the aerosol (e.g., oil) from the gas flow, and into the flow channels 63, 67 in fluid communication with the outlet slots 25. The other two streams flow through the recesses 53, 55 in the standoff plate 49 between the left and right filter panels 31, 37 and the left and right walls 7, 9 (respectively) of the housing 3, as indicated by arrows 79 and 81. The streams 79, 81 entering the flow channels 61, 69 between the left and right filter panels 31, 37 and the corresponding left and right walls 7, 9 are similarly blocked by the sealed connections of the filter panels with the top plate 17. Gas is forced to flow inward through the fiber mats 41 of the filter panels 31, 37 as indicated by arrows 83, 85 so that the aerosol can be filtered. The lateral flows 83, 85 enter the flow channels 63, 67 connected to the outlet slots 25. The pleat velocity (i.e., the velocity of the fluid across the thickness of the fiber mat 41) is relatively low.
In one example, turbine lube oil bearing exhaust is routed by the inflow pipe 23 to the mist eliminator 1. In this example, the size of the housing 3 was 14 inches (36 cm) wide by 14 inches (36 cm) deep by 36 inches (91 cm) tall. The total exposed surface area of the fiber mats 41 of the filter panels 31, 33, 35, 37 available for aerosol collection was 154 ft2 (14 m2). The pressure drop across the mist eliminator 1 was less than 0.5″ we (125 Pa) at a flow rate of about 50 ft3/min (0.02 m3/min) The removal efficiency of the mist eliminator 1 was 99.5%. based on inlet mist loading of about 500 mg/m3. It is anticipated that the emissions would be no more than about 1 to 2 ppmw turbine oil mist. More generally, the ratio of an area of the filter panels available to filter the gas flow to a volume of the container is preferably about 20 ft2/ft3 (66 m2/m3) to about 36 ft2/ft3 (118 m2/m3).
When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “up”, “down”, “inner”, “outer” and other orientational terms is made for convenience, but does not require any particular orientation of the components.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
This application claims the benefit of U.S. Provisional Application Ser. No. 61/109,447, filed Oct. 29, 2008, the entire contents of which are incorporated herein by reference.
The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of U.S. Navy Prime Contract N00024-04-C-2118 awarded by the Department of Defense.
Number | Date | Country | |
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61109447 | Oct 2008 | US |