Oil coalescing filter and filtering process

Claim 2

A filter for coalescing droplets of atomized oil in an airstream, comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the coalescing layer, said drainage layer receiving oil from the coalescing layer, impeding reentrainment of oil in an air flow leaving the filter, and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, the fluorocarbon serving to reduce an oil wetted area of the drainage layer, whereby there is a reduced tendency to oil re-contamination of the airstream.

Claim 3

A filter according to claim 1, wherein the oil coalescing layer and the second layer are in face to face contact either directly or through an intervening partly open mechanical support.

Claim 4

A filter according to claim 1 or 2, which is tubular and has a coalescing layer which fits within or has within it depending on the direction of flow a drainage sleeve, coalesced oil draining from the sleeve which is of a coarser porosity than the coalescing layer.

Claim 5

A filter according to claim 1 or 2, wherein the coalescing layer is fabricated or molded from an inorganic material and has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282.

Claim 6

A filter according to claim 4, wherein the coalescing layer is fabricated or molded from glass microfibers.

Claim 7

A filter according to claim 1, wherein the coalescing layer is of borosilicate glass microfibres and is formed from layers of sheet wrapped one around the other, formed from pleated sheet, made by moulding or vacuum forming.

Claim 8

A filter according to claim 1, wherein the drainage layer is of a polyester fabric.

Claim 9

A filter according to claim 7, wherein the fluorocarbon material is present in an amount of 1-5% by weight based on the weight of the polyester fabric.

Claim 10

A filter according to claim 1, wherein the drainage layer is of an open-pore plastics selected from the group consisting of polyester, polyethylene and polyurethane foam.

Claim 11

A process for removing an oil aerosol from an airstream by passing said airstream through a coalescing filter comprising the steps of: supplying an airstream containing atomized oil; passing said airstream through an oil coalescing layer of the filter, said oil coalescing layer comprising a microfibrous material which is not impregnated with a fluorocarbon; passing said airstream through a macroporous drainage layer of the filter, said drainage layer being downstream of said coalescing layer and comprising an oil drainage material which is impregnated with a fluorocarbon; and providing a flow path through the drainage layer for oil to flow by gravity from the filter.

Claim 12

A process for removing an oil aerosol from an airstream by passing said airstream through a coalescing filter comprising the steps of: supplying an airstream containing atomized oil; passing said airstream through an oil coalescing layer of the filter, said oil coalescing layer comprising a microfibrous material which is not impregnated with a fluorocarbon; passing said airstream through a macroporous drainage layer of the filter, said drainage layer being downstream of said coalescing layer and comprising an oil drainage material which is impregnated with a fluorocarbon; and providing a flow path through the drainage layer for oil to flow by gravity from the filter.

Claim 13

The process according to claim 10, further comprising the step of: impinging the airstream against a surface located upstream of said coalescing filter, so that a major proportion of the oil originally present in the airstream coalesces on said surface before the airstream enters the coalescing filter.

Claim 14

A process for removing oil from an airstream containing oil in the form of an aerosol comprising the steps of: passing said airstream through a filter in which droplets of atomized oil in the airstream coalesce, said filter comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the oil coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, the effect of the fluorocarbon material in the drainage layer being to reduce the proportion of the drainage layer that is wetted through and to reduce oil carry-over.

Claim 15

A process for removing oil from an airstream containing oil in the form of an aerosol comprising the steps of: passing said airstream through a filter in which droplets of atomized oil in the airstream coalesce, said filter comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the oil coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, the effect of the fluorocarbon material in the drainage layer being to reduce the proportion of the drainage layer that is wetted through and to reduce oil carry-over.

Claim 16

The process as claimed in claim 12, further comprising the step of supporting said filter with its axis generally horizontal.

Claim 17

A filter for coalescing droplets of atomized oil in an airstream, comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282, and wherein the drainage layer comprises a material having a pore size of a much coarser nature than the pore size of the coalescing layer.

Claim 18

A filter for coalescing droplets of atomized oil in an airstream, comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282, and wherein the drainage layer comprises a material having a pore size of a much coarser nature than the pore size of the coalescing layer.

Claim 19

A process for removing an oil aerosol from an airstream by passing said airstream through a coalescing filter comprising the steps of: supplying an airstream containing atomized oil; passing said airstream through an oil coalescing layer of the filter, said oil coalescing layer comprising a microfibrous material which is not impregnated with a fluorocarbon; passing said airstream through a macroporous drainage layer of the filter, said drainage layer being downstream of said coalescing layer and comprising an oil drainage material which is impregnated with a fluorocarbon; and providing a flow path through the drainage layer for oil to flow by gravity from the filter; wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282; and wherein said oil drainage material comprises a material having a pore size of a much coarser nature than the pore size of the coalescing layer.

Claim 20

A process for removing an oil aerosol from an airstream by passing said airstream through a coalescing filter comprising the steps of: supplying an airstream containing atomized oil; passing said airstream through an oil coalescing layer of the filter, said oil coalescing layer comprising a microfibrous material which is not impregnated with a fluorocarbon; passing said airstream through a macroporous drainage layer of the filter, said drainage layer being downstream of said coalescing layer and comprising an oil drainage material which is impregnated with a fluorocarbon; and providing a flow path through the drainage layer for oil to flow by gravity from the filter; wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282; and wherein said oil drainage material comprises a material having a pore size of a much coarser nature than the pore size of the coalescing layer.

Claim 21

A process for removing oil from an airstream containing oil in the form of an aerosol comprising the steps of: passing said airstream through a filter in which droplets of atomized oil in the airstream coalesce, said filter comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the oil coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, the effect of the fluorocarbon material in the drainage layer being to reduce the proportion of the drainage layer that is wetted through and to reduce oil carry-over, wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282, and wherein said drainage layer comprises a material having a pore size of a much coarser nature than the pore size of the coalescing layer.

Claim 22

A process for removing oil from an airstream containing oil in the form of an aerosol comprising the steps of: passing said airstream through a filter in which droplets of atomized oil in the airstream coalesce, said filter comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the oil coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, the effect of the fluorocarbon material in the drainage layer being to reduce the proportion of the drainage layer that is wetted through and to reduce oil carry-over, wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282, and wherein said drainage layer comprises a material having a pore size of a much coarser nature than the pore size of the coalescing layer.

Claim 23

A filter for coalescing droplets of atomized oil in a stream of gas, comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282, and wherein the drainage layer includes fibers having a diameter of 10-20 micrometers.

Claim 24

A filter for coalescing droplets of atomized oil in a stream of gas, comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282, and wherein the drainage layer includes fibers having a diameter of 10-20 micrometers.

Claim 25

A filter for coalescing droplets of atomized oil in a stream of gas, comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282, wherein the drainage layer is of an open-pore plastics selected from the group consisting of polyester, polyethylene and polyurethane foam, and wherein the foam has about 80 pores per inch.

Claim 26

A filter for coalescing droplets of atomized oil in a stream of gas, comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282, wherein the drainage layer is of an open-pore plastics selected from the group consisting of polyester, polyethylene and polyurethane foam, and wherein the foam has about 80 pores per inch.

Claim 27

A process for removing an oil aerosol from an airstream by passing said airstream through a coalescing filter comprising the steps of: supplying an airstream containing atomized oil; passing said airstream through an oil coalescing layer of the filter, said oil coalescing layer comprising a microfibrous material which is not impregnated with a fluorocarbon; passing said airstream through a macroporous drainage layer of the filter, said drainage layer being downstream of said coalescing layer and comprising an oil drainage material which is impregnated with a fluorocarbon; and providing a flow path through the drainage layer for oil to flow by gravity from the filter; wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282; and wherein said oil drainage material includes fibers having a fiber diameter of 10-20 micrometers.

Claim 28

A process for removing an oil aerosol from an airstream by passing said airstream through a coalescing filter comprising the steps of: supplying an airstream containing atomized oil; passing said airstream through an oil coalescing layer of the filter, said oil coalescing layer comprising a microfibrous material which is not impregnated with a fluorocarbon; passing said airstream through a macroporous drainage layer of the filter, said drainage layer being downstream of said coalescing layer and comprising an oil drainage material which is impregnated with a fluorocarbon; and providing a flow path through the drainage layer for oil to flow by gravity from the filter; wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282; and wherein said oil drainage material includes fibers having a fiber diameter of 10-20 micrometers.

Claim 29

A process for removing oil from an airstream containing oil in the form of an aerosol comprising the steps of: passing said airstream through a filter in which droplets of atomized oil in the airstream coalesce, said filter comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the oil coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, the effect of the fluorocarbon material in the drainage layer being to reduce the proportion of the drainage layer that is wetted through and to reduce oil carry-over, wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282, and wherein said drainage layer includes fibers having a fiber diameter of 10-20 micrometers.

Claim 30

A process for removing oil from an airstream containing oil in the form of an aerosol comprising the steps of: passing said airstream through a filter in which droplets of atomized oil in the airstream coalesce, said filter comprising an oil coalescing layer of a microfibrous material and a second layer of a macroporous oil drainage material located downstream of the oil coalescing layer, said drainage layer receiving oil from the coalescing layer and providing a path through the drainage layer for oil to flow by gravity from the filter, wherein the drainage layer but not the coalescing layer is impregnated with a low surface energy material which is a fluorocarbon, the effect of the fluorocarbon material in the drainage layer being to reduce the proportion of the drainage layer that is wetted through and to reduce oil carry-over, wherein the coalescing layer has a structure and pore size such that it will retain particles and droplets having a size from 0.01 to 10 microns with an efficiency of between 99.97 and 99.9999% when tested in accordance with Military Standard 282, and wherein said drainage layer includes fibers having a fiber diameter of 10-20 micrometers.