Multilayer filter media
A filter media is disclosed for removing particles from an air stream. The filter media, in an embodiment, includes a porous membrane layer and a pre-filter layer including a downstream surface and an upstream surface. The pre-filter layer is arranged with the downstream surface adjacent an upstream side of the porous membrane layer. The pre-filter layer includes a wet laid composite media having a mixture of glass fibers and synthetic fibers. A method for using the filter media in a gas turbine is also disclosed.
1. Multilayer filter media for removing particles from an air stream, said filter media comprising:
a porous membrane layer; and
a pre-filter layer including
a downstream surface and an upstream surface, the downstream surface being adjacent an upstream side of the porous membrane layer and wherein said pre-filter layer comprises a wet laid composite media including a mixture of glass fibers and synthetic fibers, and
wherein a first ratio of a first amount of synthetic fibers in a first plane parallel to said downstream surface to a first total amount of fibers in the first plane decreases from the downstream surface of the pre-filter layer towards the upstream surface of said pre-filter layer.
2. Multilayer filter media according to claim 1 , wherein the porous membrane layer is laminated to the pre-filter layer.
3. Multilayer filter media according to claim 1 , wherein a supporting layer is laminated to a downstream side of the porous membrane layer.
4. Multilayer filter media according to claim 1 , wherein a majority of the fibers at the downstream surface of the pre-filter layer are synthetic fibers.
5. Multilayer filter media according to claim 1 , wherein a second ratio of the amount of synthetic fibers at the downstream surface of the pre-filter layer to the total amount of fibers at the downstream surface of the pre-filter layer is larger than 0.7.
6. Multilayer filter media according to claim 1 , wherein a second ratio of the amount of synthetic fibers at the upstream surface of the pre-filter layer to the total amount of fibers at the upstream surface of the pre-filter layer is larger than 0.5.
7. Multilayer filter media according to claim 1 , wherein, in a second plane parallel to said downstream surface, the second plane being centrally positioned between the downstream surface and the upstream surface of the pre-filter layer, a second ratio of the amount of synthetic fibers to a second total amount of fibers in the second plane is less than 0.5 and a ratio of an amount of glass fibers to the second total amount of fibers is larger than 0.5.
8. Multilayer filter media according to claim 1 , wherein the glass fibers of the pre-filter layer have diameters between 0.01 μm and 50 μm.
9. Multilayer filter media according to claim 1 , wherein the synthetic fibers of the pre-filter layer have diameters between 0.01 μm and 50 μm.
10. Multilayer filter media according to claim 1 , wherein the pre-filter layer is not electrostatically charged.
11. Multilayer filter media according to claim 1 , wherein the porous membrane layer comprises an ePTFE-membrane.
12. Multilayer filter media according to claim 1 , wherein the porous membrane layer comprises an Ultra High Molecular Weight Polyethylene-membrane.
13. Multilayer filter media according to claim 1 , wherein the porous membrane layer comprises a membrane of spun bound polymer fibers.
14. Multilayer filter media according to claim 8 , wherein the glass fibers of the pre-filter layer have diameters between 0.1 μm and 0.5 μm.
15. Multilayer filter media according to claim 9 , wherein the synthetic fibers of the pre-filter layer have diameters between 0.5 μm and 50 μm.
16. Multilayer filter media according to claim 1 , wherein the first ratio of the first amount of synthetic fibers in a first plane parallel to said downstream surface to the first total amount of fibers in the first plane is lower than a second ratio of a second amount of synthetic fibers in a second plane parallel to the downstream surface to a second total amount of fibers in the second plane and is lower than a third ratio of a third amount of synthetic fibers in a third plane parallel to the downstream surface to a third total amount of fibers in the third plane, the second ratio being lower than the third ratio.
17. Multilayer filter media according to claim 1 , wherein a first content of glass fibers increases from the downstream surface toward the upstream surface and a second content of synthetic fibers decreases from the downstream surface toward the upstream surface.