FILTER MEDIA, FILTER AND FILTRATION MACHINE.

Abstract

The present invention relates to a filter medium for filtering condensate containing oily contaminants. The present invention also relates to a filter comprising the filter medium. The present invention also relates to a filtration machine comprising the filter medium.

Description

FILTER MEDIA, FILTER AND FILTRATION MACHINE Description of the Invention FIELD OF INVENTION This invention relates to filter media and more particularly, but not exclusively, to filter media for filtering the condensate of an air compressor. This invention also relates to a filtration machine and more particularly, but not exclusively, to a filtration machine for filtering the condensate of an air compressor. Such condensate is normally predominantly water, with the entrainment of some substances, including oil. BACKGROUND OF THE INVENTION It is known how to remove oil from condensate using filter media, typically by filtering the condensate through activated carbon. This removes the oil, but it is relatively expensive. The carbon media can become contaminated quickly when the condensate contains large amounts of oil. US patent 4,753,730 describes the use of oleophilic polypropylene fibers as a filter medium. Although the use of fine fibers, such as those suggested in US patent 4,753,730, maximizes the surface area available for contact with the condensate to be filtered, a problem with such fine fibers is that they clump together when subjected to heavy fluid flows or when immersed in the condensate (or filtrate). These clumped fibers reduce the flow of liquid through the filter medium. Therefore, such filter media cannot be densely packed in a filter housing, as this exacerbates the restriction of liquid flow. In US patent 4,753,730, the clumped fibers are cut into strands in an effort to improve liquid flow through the medium. After prolonged use of such a filter medium in this form, even if immersed in the liquid to be filtered, many of the tightly packed fine fibers will tend to remain dry and out of contact with the liquid as the liquid to be filtered flows through the flow paths of least resistance in the packed fibers. To improve filtration efficiency and aid fluid flow, it is desirable to wet the fine fiber media. However, typical wetting agents, when used with polypropylene fibers, have a detrimental effect. Detergent or other surfactants, for example, reduce the polypropylene's ability to discriminate between, for instance, oil and water, causing the media to adsorb both oil and water, thus reducing filtration efficiency. Document WO 2011 / 064561 Al described that the use of a mass of silica-based oleophilic fibers provides effective condensate filtration. Document WO 2011 / 064561 A1 described how silica-based oleophilic fibers, and in particular, but not exclusively, glass fibers, are effective at filtering oily contaminants from water. These fibers can be moistened with a detergent or other surfactant, for example, to further improve filtration efficiency and aid flow through the filter medium, or at least the passage of the filtrate, without the silica-based fibers losing their ability to discriminate between oily contaminants and water. Therefore, more oily contaminant is adsorbed, while more water in the condensate is allowed to flow through the medium. Because silica-based moistened fibers are much more efficient at filtering than, for example, polypropylene, it is possible to pack the silica-based fibers at a higher density in the outer casing. WO 2011 / 064561 A1 described a filter medium comprising silica-based fibers and, supported within the fiber mass, an anti-caking material, such as perlite particles. Although this anti-caking material may not actively participate in condensate filtration (perlite does not adsorb any significant amount of oily contaminant, if any), it can help prevent the fibers in the filter packing from obstructing the flow of liquid through the filter, which mechanically separates the fibers and maintains this separation in use. The present invention seeks to provide an improved filtering medium. SUMMARY OF THE INVENTION According to a first aspect of the present invention, a filter medium is provided for filtering condensate that includes water and oily contaminants, wherein the filter medium comprises: oleophilic silica-based fibers and an anti-caking material, wherein the anti-caking material consists of polystyrene beads from 0.5% by weight to 5.0% by weight. Preferably, wherein the polystyrene beads are present in a proportion of 1.0% to 3.0% by weight. More preferably, wherein the silica-based oleophilic fibers are glass wool fibers and / or silicate fibers and / or sodium silicate fibers. Advantageously, where: The polystyrene beads are entangled in the fibers; or, the polystyrene beads are in one, two, three, four or five separate layers, between two, three, four, five or six separate layers of fibers. Preferably, where the polystyrene beads are spherical and have a diameter of 1 mm to 10 mm. More preferably, in which the polystyrene beads have a diameter of 3 mm to 5 mm. Advantageously, where the silica-based oleophilic fibers are silicate fibers and / or sodium silicate fibers with a diameter of 1 to 10 pm. Preferably, where the silicate fibers and / or sodium silicate fibers have a diameter of 2 to 5 pm. More preferably, in which the filter medium has a compact density of 100 to 220 g / 1. Advantageously, where the filter medium has a compacted density of: 150 to 210 g / 1; or, 170 to 200 g / 1. Preferably, wherein the filter medium further comprises one, two, three or all of the following: Polypropylene fibers; Perlite; Water; and / or, Glycerin. More preferably, wherein the filter medium comprises: oleophilic silica-based fibers (optionally, glass wool fibers and / or silicate fibers and / or sodium silicate fibers) in a percentage of 70% to 80% by weight, and polystyrene beads from 0.5% to 5.0% by weight, the balance being one, two or three polypropylene fibers, water and / or glycerin. Advantageously, where the filter medium comprises: oleophilic silica-based fibers (optionally, glass wool fibers and / or silicate fibers and / or sodium silicate fibers) in a percentage of 70% to 80% by weight, polystyrene beads from 0.5% to 5.0% by weight, polypropylene fibers from 2.0% to 4.0% by weight, water from 1.0% to 20.5% by weight, and glycerin from 7.0% to 10.0% by weight; Optionally, the filter medium also includes unavoidable impurities. Preferably, wherein the filter medium comprises: silica-based oleophilic fibers (optionally, glass wool fibers and / or silicate fibers and / or sodium silicate fibers) in a percentage of 73% to 78% by weight, polystyrene beads from 1.0% to 3.0% by weight, polypropylene fibers from 2.0% to 3.0% by weight, water from 7.0% to 16.0% by weight, and glycerin from 8.0% to 9.0% by weight; Optionally, the filter medium also includes unavoidable impurities. According to another aspect of the present invention, a filter is provided comprising the filter medium described above. According to another aspect of the present invention, a filtration machine is provided comprising the filtering media described above, or the filter described above. According to another aspect of the present invention, a method is provided for removing oil from a condensate that includes water and oily contaminants, wherein the method comprises: pass the condensate through the filter media described above; or a filter described above; or, a filtration machine described above. Preferably, in which the condensate comprises water and oil, the oil present in the condensate: from 20 ppm to 2,000 ppm; or, from 50 ppm to 1,000 ppm; or, from 100 ppm to 500 ppm; or, from 150 ppm to 250 ppm. BRIEF DESCRIPTION OF THE FIGURES Examples of the invention are described below with reference to the accompanying figures. The accompanying figures illustrate various examples of systems, methods, and other aspects of the disclosure. A person skilled in the art will appreciate that the boundaries of the illustrated elements (e.g., boxes, groups of boxes, or other shapes) in the figures represent an example of the limitations. In some examples, one element may be designed as several elements, or several elements may be designed as a single element. In some examples, an element shown as an internal component of one element may be implemented as an external component in another, and vice versa. Furthermore, the elements may not be drawn to scale. Non-limiting and non-exhaustive descriptions are provided with reference to the following figures. The components in the figures are not necessarily to scale; rather, the emphasis is on illustrating the principles. Figure 1 is an illustrative view of a filtration machine according to one aspect of the invention. Figure 2 is an illustrative perspective view of the machine filter in Figure 1. Figure 3 is an illustrative cross-sectional side view of the filter in Figure 2. Figure 4 is a similar view to that in Figure 3 but of an alternative example. Figure 5 is an illustrative view of a filter from another example. Figure 6 is an illustrative view of an alternative filtration machine according to one aspect of the invention. Figure 7 is an illustrative cross-sectional view of the filter inside the filtration machine of Figure 6. DETAILED DESCRIPTION OF THE INVENTION Some examples of this disclosure will be discussed in detail below. The words comprising, having, containing, and including, and other forms thereof, are intended to be equivalent in meaning and open in the sense that an article or articles following any of these words are not meant to be an exhaustive list of such article or articles, nor are they intended to be limited to the article or articles listed. It should also be noted that as used herein and in the accompanying claims, the singular forms a, an, and the, she include plural references unless the context clearly indicates otherwise. Although any system and method similar to or equivalent to those described herein may be used in the practice or testing of examples in this disclosure, the preferred systems and methods are described herein. The examples in this disclosure will be described more fully below with reference to the accompanying figures, in which the same numbers represent similar elements throughout the figures, and in which examples are shown. However, the examples in the claims can be incorporated in many different ways and should not be construed as being limited to the examples given herein. The examples given herein are non-limiting and are simply examples among other possible examples. Definitions Some of the terms used to describe the present invention are set out below: Silica-based oleophilic fibers refer to fibers containing silica that adsorb and / or absorb oil. These fibers may be silicate fibers (sometimes called glass wool fibers and / or sodium silicate fibers) with a diameter of 1 to 10 µm or 2 to 5 µm. They may also be a plurality of silicate fibers with a packing density of 100 to 220 g / m³, 150 to 210 g / m³, or 170 to 200 g / m³. A non-limiting example of silica-based oleophilic fibers is SUPAFIL 40 glassblowing mineral wool sold by Knauf Insulation (EU index number 65 0-016-0 0-2). Fiber or fibers refers to a natural or synthetic substance that is significantly longer than it is wide (for example, with an aspect ratio (a ratio between the length of the fiber and the diameter) of 20 to 400; or 20 to 60; or 60 to 400). For example, fiber refers to a yarn or filament from which a textile or material is formed. Anti-caking material refers to a material present in the filter medium that acts to prevent the fibers from clumping together and obstructing the flow of liquid through the filter medium. Polystyrene beads refer to generally spherical beads made of polystyrene. Such beads are of the type used as filling for bean bags. The polystyrene beads used in the present invention may have a diameter of: 1 mm to 10 mm; or 1.5 mm to 7.5 mm; or 2 mm to 6 mm; or 3 mm to 5 mm. A non-limiting example of polystyrene beads are the expanded polystyrene beads sold by Springvale EPS Limited, which have a diameter of 3 mm to 5 mm. Perlite refers to an amorphous volcanic glass typically formed by the hydration of obsidian. Perlite is used in horticulture (as an additive and soil solids enhancer), as a lightweight filler (in roofing tiles and plasterboard), as a filter aid in the food industry, and as a spill absorbent. One non-exhaustive example of perlite is the expanded perlite sold by RS Minerals Ltd. Glycerin refers to the compound 1,2,3-propanetriol (CAS number 56-81-5). Glycerin is a colorless, odorless, viscous liquid. A non-limiting example of glycerin is the glycerin sold by Monarch Chemical Ltd. % by weight refers to the mass fraction, that is, the mass of a substance present in a mixture as a percentage of the total mass of the mixture. Condensate refers to the waste product of an industrial process that is predominantly water, with some entrained impurities, including oil. A common type of condensate comes from an air compressor during operation. Such condensate cannot be safely disposed of without removing the entrained oil. Unavoidable impurities refer to components present in a mixture that are generally inert and have no effect on the rest of the mixture. Unavoidable impurities are present in a mixture at: less than 2% by weight; or less than 1% by weight; or less than 0.5% by weight; or less than 0.1% by weight. Examples Filtration Machine of Figures 1, 2 and 3 With reference to Figures 1, 2, and 3, a filtration machine 10 has a main filter chamber 12 in which a filter 14 is provided. The filter 14 comprises filter media. The main filter chamber 12 is substantially cylindrical, and the filter 14 has a corresponding configuration, but the filter chamber 12 and / or the filter 14 could have another configuration as required. The filter 14 includes an external housing 15, and at an axial end, i.e., the upper end of the filter 14, the filter 14 includes an external seal 19 which, when the filter 14 is received in the chamber 12, provides a seal with an inner wall 16 of the main filter chamber 12. The filtration machine 10 also includes an inlet 17 to the main filter chamber 12 through which the condensate to be filtered enters the chamber 12 in a position located above the filter 14 in this example. Inlet 17 in this example receives condensate below a weir 18. Condensate from one or more air compressors (or refrigeration plants, etc.) with entrained oily contaminants is collected in an antechamber 9 of the weir device 18, to which it flows through a machine inlet 31. As the liquid accumulates in the antechamber 9, there will be some separation between the water component of the condensate and the oily contaminant, although some water will remain emulsified with the oily contaminant. When the liquid level in the antechamber 9 rises to that of an outlet weir 7, the lighter, floating oily contaminant (and said contaminant emulsified with water) will pass over the weir 7 and into a collector (not shown) for disposal. The condensate that does not pass from the weir device 18 over the weir 7, i.e., that is the predominantly water fraction, passes from a lower region of the antechamber 9 to the inlet 17 to the main filter chamber 12, which has the same height as the weir 7. The condensate entering the main filter chamber 12 through inlet 17 is forced to pass through filter 14 where it is filtered, and then to a main filter chamber outlet 24 below filter 14 in this example. The filtrate then passes in this example to the secondary filter chamber 20, flows through a carbon filter 21, and from the carbon filter 21 to a machine discharge outlet 22, which in this example is at the same level as weir 7, but could be at a lower level. If necessary, by filtering the condensate in both the main filter chamber 12 and the secondary filter chamber 20, the filtrate discharged at 22 is substantially cleaned of oily contaminants, and the goal is for it to be clean enough to safely discharge the filtrate into the environment. The outer housing 15 of the filter 14 in the main filter chamber 12 internally defines a filter interior. The housing 15 in this example has a generally flexible cylindrical side wall 25 made of fabric, woven, non-woven, or the like, and substantially rigid upper and lower end walls 27, 28, respectively. The upper and lower end walls 27, 28 have openings provided by perforations (or the openings may be integral with the upper and / or lower end walls 27, 28), and the flexible side wall 25 is provided with openings by needle perforation, for example, during fabric manufacturing. In another example, an alternative portion or the entire outer housing 15 may be rigid, semi-rigid, or flexible, or the side wall 25 may be rigid and one or both end walls 27, 28 flexible.In each case, the openings in the outer casing 15 in at least the upper end wall 27 provide passages through which condensate can pass into the filter, and the openings in the side wall 25 and the lower end wall 28 provide passages through which the filtered liquid can return to the filter. Depending on where and how the seal 19 is provided, if at all, it separates the condensate entering the main filter chamber 12 from the filtrate. Therefore, 10 different openings, other than those identified, may allow condensate / filtrate to pass into and out of the filter interior. For example, if the seal 19 were provided axially, partially along the side wall 25, the openings in the side wall 25 above the seal would allow condensate to pass into the filter interior, and the openings in the side wall 25 below the seal would allow the filtrate to exit the filter interior. Inside the filter 14, a filter medium is provided which, according to the invention, includes a mass of silica-based oleophilic fibers 29. In the examples shown in the figures, the silica-based oleophilic fibers 29 are short glass fibers 25; for example, the fibers are predominantly 20 mm or less in length. The silica-based oleophilic fibers are fine, with a diameter in the range of 1 to 10 µm; or, 2 to 5 µm; or, 5.0 µm to 10 µm; or, 5.0 µm to 8 µm; or, 5.0 µm to 5.5 µm, as required. The silica-based oleophilic fibers can be a plurality of silicate fibers with a packing density of: 100 to 220 g / L; or 150 to 210 g / L; or 170 to 200 g / L. When such fibers are kneaded (for example, pressed together), they produce glass wool. The fibers of silica-based oleophilic fibers 29 (e.g., glass wool) exhibit a particular affinity for oil and therefore when condensate comes into contact, e.g., passes through the filter medium, predominantly the oily contaminant is absorbed by the silica-based oleophilic fibers 29 and allowed to pass into the water component. Using these short silica-based fibers of this diameter allows for particularly efficient condensate filtration, as the oleophilic silica-based fibers collectively present a large surface area to the condensate. However, any other silica-based fiber with oleophilic properties can be used instead of glass wool, but silica-based fibers supplied as wool provide a particularly effective and economical solution. To improve filtration efficiency, the glass wool fibers can be pre-treated with a wetting agent, such as detergent or another surfactant, which has been shown to improve the adsorption of the oily contaminant, while allowing the passage of the water component of the condensate. Inside the filter 14, glass wool or other fiber filter media (e.g., silica-based oleophilic fibers 29) can be packed in the outer housing 15 at a density of 80 grams per liter to 200 grams per liter; or, alternatively, on the order of 140 grams per liter (plus or minus 10%). The mass of the filter media provides a substantial flow volume formed by the interstitial spaces between the silica-based oleophilic fibers 29 so as not to substantially obstruct the flow of liquid through the filter media, at least before the adsorption of a significant amount of the oily contaminant. Because the condensate flowing into the main filter chamber 12 tends not to be provided as a constant and sustained fluid flow, even from large-scale air compressors, i.e., the flow rate of the condensate to the filtration machine 10 tends not to be large, the condensate flowing through the filter 14 does not tend during use to compact the fibers at least to the point of obstructing the flow of liquid through the filter. However, in the example shown in Figures 1 to 3, embedded within the silica-based oleophilic fibers 29 (e.g., glass wool) are polystyrene beads 30. Thus, the silica-based oleophilic fibers 29 support the polystyrene beads 30 within their mass, and these beads 30 provide an anti-caking function. The polystyrene beads can have a diameter of: 1 mm to 10 mm; or 1.5 mm to 7.5 mm; or 2 mm to 6 mm; or 3 mm to 5 mm. A non-limiting example of polystyrene beads are the expanded polystyrene beads sold by Springvale EPS Limited, which have a diameter of 3 mm to 5 mm. While such anti-caking material (i.e., polystyrene beads 30) may not actively participate in condensate filtration, the polystyrene beads 30 help prevent fibers in the filter packing from obstructing the flow of liquid through the filter 14 by separating the silica-based oleophilic fibers 29 and maintaining this separation in use. In the example of Figures 1 to 3, the polystyrene beads 30 become entangled in the silica-based oleophilic fibers 29 of the filter medium by mixing with the silica-based oleophilic fibers 29 before packing the filter medium into the outer casing 15. In some examples, glycerin is added to the filter medium. Glycerin provides a temporary band (before contact with the condensate) to ensure that the polystyrene beads mix and remain entangled within the silica-based oleophilic fibers. Polystyrene beads are lighter than other materials within the filter medium. The glycerin ensures a uniform mixture and prevents the lighter materials from separating and settling on top of the heavier ones. Filtration Machine of Figure 4 15 Figure 4 illustrates a modification in which the glass wool or other silica-based oleophilic fibers 29 of the filter medium are arranged in discrete layers 29a, 29b, 29c, 29d in the outer casing 15 in four layers as indicated in the example 20, and between layers 29a-29d, polystyrene beads 30 are provided interposed between layers 29a-29d. Thus, polystyrene beads 30 can be embedded in the fibrous mass of silica-based oleophilic fibers 29, for example, when manufacturing the filter 14. However, if desired, the polystyrene bead particles 30 can be entangled in the silica-based oleophilic fibers 29 and interposed between the fiber layers. At least in the example illustrated in Figures 1 to 3, the openings in the side wall 15 and the upper and lower end walls 27, 28 of the outer casing that allow the flow of condensate / filtered liquid are all smaller than, or at least not substantially larger than, the polystyrene beads 30 particles; for example, the openings may be smaller than 10 mm but preferably smaller than 4.76 mm. This is to prevent the migration of the polystyrene beads 30 from the filter 14 through the openings. However, the polystyrene beads 30 will be retained mainly embedded in the silica-based oleophilic fibers 29. In the example in Figure 4, it can be seen that at least the lower end wall 28 of the housing is lined with an inner lining 35 that covers the openings in the lower end wall 28. In this example, the lining 35 is made of a felt-like material, so the fluid flow passages in the felt-like material 35 will be very small, at least smaller than the openings in the lower end wall 28. This lining 35 will provide additional protection to prevent the polystyrene beads 33 from the filter 14 from being washed through the openings in the lower end wall 28. In general, the outer housing 15 of the filter 14, or any part thereof, may include, over at least part of its extent, multiple layers, including an outer housing layer 15 with openings, and an inner or outer lining layer such as the felt-like material layer 35, with passages smaller than the openings in the outer housing layer 15. Figure 5 Filtration Machine In the example in Figure 5, the filter 14 has an outer housing 15 made of rigid or semi-rigid material that is impermeable to liquids. However, the filter 14 has an inlet at one end, indicated by 14a, to receive the condensate, and an outlet 14b at the opposite end for filtration. The filter 14 does not need to be housed in a filter chamber as in the previous examples. The filter 14 does not require a seal 19. Several additional modifications can be made without departing from the scope of the invention. Another filtration machine according to the invention does not need to have a weir device 18 to collect the condensate, but the condensate can enter directly into the main filter chamber 12 through an inlet 17 where a chamber 12 is provided, or directly into the filter through inlet 14a as in the example of Figure 5. In the examples in Figures 1 to 4, the main filter chamber 12 includes a cap 38 at its upper end, which, when closed as shown, seals the main filter chamber 12. When the cap 38 is removed or otherwise opened, the interior of the main filter chamber 12 can be accessed to allow the removal and replacement of filter 14 through the upper end of the main filter chamber 12 when filter 14 becomes clogged and / or saturated with oily contaminant. To facilitate this operation, the example assumes that filter 14 has a handle 13 at its upper end. In another example, filter 14 could be a floating filter that descends as more and more oily contaminant is adsorbed or absorbed. Silica-based oleophilic fibers (e.g., glass wool) are lightweight, even when packed at the density mentioned above. When the filter housing 15 is lightweight, filter 14 may float in the filter chamber 12, or at least float too easily, especially when new. Therefore, if required, ballast can be added to filter 14 to ensure it does not float, or at least floats to the desired level in filter chamber 12 when new. Although the silica-based oleophilic fibers 29, for example glass wool fiber, of the filter 14 described herein are a considerable improvement over other filter media such as polypropylene used in the context of air compressor condensate filtration, particularly when the filter 14 is new and first exposed to condensate, it may not be as efficient at filtering as it can become in due course as the filter medium becomes saturated. In another example from the examples in Figures 1 to 4, a secondary filter chamber 20 may not be provided, or at least it is not necessary to provide such a secondary filter chamber with a carbon filter 21, but some other means of further treating the intended filtered liquid may be provided, either inside or outside the filtration machine 10, to allow the filtered liquid to be cleaned to the point that it can be released into the environment. When a second filter is provided, it may be of the same type as the filter 14 according to the invention. In another example, the main filter chamber 12 does not need to be cylindrical; it can have a different configuration. In this case, filter 14 may need to be configured accordingly. In another example, in addition to silica-based fibers and polystyrene beads, the filter medium may include other constituents, such as other fibers that may or may not be oleophilic, to improve filtration efficiency. Filtration Machine of Figures 6 and 7 Figure 6 shows a filtration machine similar to a SEP 60 ST currently sold by Bowman Stor Ltd. With reference to Figures 6 and 7, a filtration machine 40 has a main filter chamber (not shown) in which a filter 46 is provided. The filter 46 includes an outer housing that fits inside the filtration machine 40. Filter 46 also includes an inlet 45 through which the condensate to be filtered enters the filter 46. The condensate entering filter 46 through inlet 45 passes through filter 46 where it is filtered and then exits through outlet 43. As shown in Figure 7, the filter 46 includes a depressurization vacuum 41 filled with a loose mixture of polypropylene fibers. The polypropylene fibers are packed tightly and retain the filter medium 42. In addition, the polypropylene fibers remove larger oil particles and other debris. Condensate passes through the depressurization vacuum 41 and into the filter medium 42. The filter medium 42 adsorbs and / or absorbs oil from the condensate. The filtered condensate exits the filter 46 through the outlet port 43 (via the outlet pipe shown in Figure 7). A filter medium 42 is provided within filter 46, which, according to the invention, includes a mass of silica-based oleophilic fibers and polystyrene beads. In the examples shown in Figures 6 and 7, the silica-based oleophilic fibers 29 are short glass fibers, for example, the fibers are predominantly 20 mm or less in length. The silica-based oleophilic fibers are fine, with a diameter in the range of 1 to 10 µm; or, 2 to 5 µm; or, 5.0 µm to 10 µm; or, 5.0 µm to 8 µm; or, 5.0 µm to 5.5 µm, as required. The silica-based oleophilic fibers can be a plurality of silicate fibers with a packing density of: 100 to 220 g / L; or 150 to 210 g / L. or 170 to 200 g / 1. When these fibers are kneaded (for example, pressed together) they provide a glass wool. The fibers of the glass wool mass show a particular affinity for oil and therefore when the condensate comes into contact, for example, passes through the filter medium 42, the oily contaminant is predominantly absorbed by the fibers, and the water component passes through the outlet port 43. Filter 46 includes an anti-siphon vent 44 to allow pressure release and ensure smooth flow of condensate through filter 46 and out through outlet port 43. Using these short silica-based fibers of this diameter allows for particularly efficient condensate filtration, as the fibers collectively present a large surface area to the condensate. However, any other silica-based fiber with oleophilic properties can be used instead of glass wool, but silica-based fibers supplied as wool provide a particularly effective and economical solution. To improve filtration efficiency, the glass wool fibers can be pre-treated with a wetting agent, such as detergent or another surfactant, which has been shown to improve the adsorption of the oily contaminant, while allowing the passage of the water component of the condensate. Inside filter 46, filter medium 42 can be packed at a density of 80 to 200 grams per liter; or, on the order of 140 grams per liter (±10%); or, on the order of 175 grams per liter (±10%). The mass of the filter medium provides a substantial flow volume formed by the interstitial spaces between the fibers so as not to substantially obstruct the flow of liquid through the filter medium, at least before the adsorption of a significant amount of the oily contaminant. Because the condensate flowing into filter 46 tends not to be supplied as a constant and sustained fluid flow, even from large-scale air compressors—that is, the flow rate of condensate to the filtration machine tends not to be large—the condensate flowing through filter 46 does not tend during use to compact the fibers at least to the point of obstructing the flow of liquid through the filter. In the example shown in Figures 6 and 7, polystyrene beads are embedded within the glass wool filter medium (inside filter medium 42). The fibers support the polystyrene beads within their mass, and the polystyrene beads provide an anti-caking function. The polystyrene beads can have a diameter of: 1 mm to 10 mm; 1.5 mm to 7.5 mm; 2 mm to 6 mm; or 3 mm to 5 mm. A non-exhaustive example of polystyrene beads is the expanded polystyrene sold by Springvale EPS Limited, which has a diameter of 3 mm to 5 mm. While such anti-caking material (i.e., polystyrene beads) may not actively participate in condensate filtration, the polystyrene beads help prevent fibers in the filter packing from obstructing the flow of liquid through filter 46 by separating the fibers and maintaining this separation in use. In the example of Figures 6 and 7, the polystyrene beads are entangled in the filter medium fibers, mixing with the fibers before packing the filter medium into filter 4 6 . In some examples, glycerin is added to the filter medium. Glycerin provides a temporary band (before contact with the condensate) to ensure that the polystyrene beads mix and remain entangled within the silica-based oleophilic fibers. Polystyrene beads are lighter than other materials within the filter medium. The glycerin ensures a uniform mixture and prevents the lighter materials from separating and settling on top of the heavier ones. Laboratory tests Five SEP 60 ST filtration machines, as currently sold by Bowman Stor Ltd., were modified to test different filter media. Referring to Figure 7, filter medium 42 was changed in these five examples. A standard SEP 60 ST (using Medium 2 from Table 1) was also used for comparison. Tests were carried out in the Bowman Stor Ltd. on-site laboratory (under confidential conditions) to examine the benefit of using a filter medium combined with polystyrene beads versus a filter medium combined with perlite. First, a manufactured condensate effluent of 200 ± 5 ppm was formed. Tests were performed to measure the time required to pass a condensate through a filter (with a given filter medium) and then how much condensate passed through the same filter bed during a period of 4 hours. Method A manufactured condensate effluent containing 200 ppm of used compressor oil was formed by pumping tap water through an in-line cutting mixer pump (a Silverson). 150L in this non-limiting example) at 1.2 L / h (i.e., tap water was dosed with oil at 2.4 ml / h). This mixed the oil with the water to form a manufactured condensate effluent (air compressor). Identical SEP 60 ST filtration machines were used for each filter media mixture. The filter medium (filter medium 42 in Figure 7) was filled with different filter media mixtures to the same total volume of 2.6 liters. The SEP 60 ST uses a filter medium combined with perlite as standard (i.e., Medium 2 listed in Table 1 below). In these tests, the six different filter media mixtures were filled into the lower section 5 (filter media 42 in Figure 7) of the filter, while the upper section (depressurization void 41 in Figure 7) was filled with polypropylene fragments (an industry standard of 80 mm to 125 mm, in 4 mm strips). In each case, the only difference was the filter medium comprising the 2.6 liters (filter medium 42 in Figure 7). Table 1: Filter Media Mixtures Component / % by weight Medium 1 Medium 2 Medium 3 Medium 4 Medium 5 Medium 6 Silicate Fibers 96.7 48.0 76.4 76.4 75.3 75.3 Polypropylene Fibers 3.3 1.6 2.6 2.6 2.6 2.6 Perlite None 34.0 None 1.4 2.5 None Water None 9.8 10.9 10.9 0.9 10.9 10.9 Glycerin None 0.6 8.7 8.7 8.7 8.7 Polystyrene Beads None None 1.4 None None 2.5 The components listed above were obtained as follows: Pounds of silicate (sodium silicate fibers): SUPAFIL 40 glassblowing mineral wool sold by Knauf Insulation (EU index number 650-016-00-2). Polypropylene fibers: FYBA 0001, a non-woven mat of randomly oriented polypropylene fibers having diameters of 4 to 10 pm, as sold by Fybagrate. Perlite: Expanded perlite sold by RS Minerals Ltd. Water: tap water. Glycerin: Glycerin sold by Monarch Chemical Ltd. Polystyrene beads: Expanded polystyrene beads with a diameter of 3 mm to 5 mm sold by Springvale EPS Ltd. The packed density of the Media in each case was: Media 1 173 g / 1; Media 2 200 g / 1; Media 3 200 g / 1; Media 4 180 g / 1; Media 5 180 g / 1; Media 6 170 g / 1. For each medium tested, the amount of each component present is given as a % by weight, within the 2.6 liters of medium used for each test. Table 2: Elapsed time and flow rate results for 4 hours Media 1 Media 2 Media 3 Media 4 Media 5 Media 6 Time 1.22.51 1.17.31 1.1^.43 l.30.1c 1.22.20 0.53.11 elapsed Hours Hours Hours Hours Hours Hours Flow rate of 4 2.5 3.2 3 .1 2.9 3. 35 hours 111 liters liters liters liters liters To calculate the residence time (as shown in Table 2), the manufactured condensate effluent containing 200 ppm of used compressor oil was passed through the filter at a flow rate of 1.2 liters per hour, at a pressure of 2.5 bar and 20°C. Each filter medium has a different residence time because its composition varies. The filters were filled from the top, so the manufactured condensate passed through the entire filter and then to the outlet. For this to occur, the entire section of the filter medium below the outlet (2.6 liters) had to become saturated. The shorter the residence time, the faster the manufactured condensate will pass through the medium. After recording the flow time, the condensate produced by the filter was passed through for an additional 4 hours. The 4-hour flow rate in Table 2 shows the volume of filtered condensate that passed through the filters after four hours. The higher the 4-hour flow rate, the more efficient the filter was during that 4-hour period at allowing the condensate to flow through. The filtered condensate, which had passed through the filter media in each case, was generally free of oil contamination. In other words, all the media adsorbed and / or absorbed the oil and generally yielded pure water as a result of the filtration. Conclusions Medium 1 did not allow the condensate to establish a substantial flow (it gave the lowest flow rate of 4 hours). This was expected because Medium 1 did not include anti-packing material. Medium 2 had a better 4-hour flow rate than Medium 1 and allowed more condensate to pass through the filter during the period. Medium 3 passed through the medium faster than Medium 1 but did not allow the same flow as Medium 2. This was also shown by the comparative 4-hour flow rates. However, Medium 2 had a substantially higher proportion of anti-caking material (34.0 wt% perlite in Medium 2 vs. 1.4 wt% polystyrene beads in Medium 3). Medium 3 provided more silicate fibers for the same volume (compared to Medium 2). This proportionally higher amount of silicate fibers in Medium 3 provided more relative surface area of ​​silicate fibers for adsorption and / or absorption of oily contaminants. Therefore, Medium 3 will have a longer shelf life than Medium 2 (before the medium needs to be replenished or replaced). Medium 4 and Medium 3 are comparable because Medium 4 has the same relative amount of perlite as Medium 3 has polystyrene beads. Surprisingly, Medium 3 provided a faster passage time and a higher 4-hour flow rate than Medium 4. Medium 5 and Medium 6 are comparable because Medium 5 has the same relative amount of perlite as Medium 6 has polystyrene beads. Surprisingly, Medium 6 provided a faster passage time and a higher flow rate of 4 hours than Medium 5. The results of comparative tests show that the use of an anti-caking material in filters helps the flow of condensate through the filter medium. Comparing combined media of perlite with the same percentage mix of combined media of polystyrene beads (Medium 3 vs. Medium 4; and Medium 5 vs. Medium 6) shows that polystyrene beads provide better passage time and flow rate for 4 hours. Surprisingly, the inclusion of polystyrene beads as an anti-caking material resulted in a faster passage time and a higher flow rate for 4 hours, without any loss of filtration efficiency. Therefore, the inclusion of polystyrene beads in the filter medium of the present invention surprisingly provides an improvement over at least the inclusion of perlite as an anti-caking material. The present inventors discovered that the anti-caking effect of the polystyrene beads was reduced to a negligible amount when the amount of polystyrene beads present in the medium was less than 0.5% by weight. The present inventors discovered that increasing the amount of polystyrene beads present in the medium to more than 5.0% by weight reduced the filtering capacity of the medium. When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps, or whole numbers are included. The terms should not be construed as excluding the presence of other features, steps, or components. The features disclosed in the preceding description, or the following claims, or the accompanying figures, expressed in their specific forms or in terms of a means of performing the disclosed function, or a method or process for achieving the disclosed result, as appropriate, separately, or in any combination of such features, may be used to carry out the invention in 5 various forms thereof. Although certain exemplary embodiments of the invention have been described, the scope of the appended claims is not intended to be limited solely to these embodiments. The claims should be interpreted literally, intentionally, and / or to encompass equivalents.

Claims

1. Filter medium for filtering condensate that includes water and oily contaminants, wherein the filter medium 5 comprises: silica-based oleophilic fibers and an anti-caking material, wherein the anti-caking material 10 is polystyrene beads from 0.5% by weight to 5.0% by weight.

2. The filter medium of claim 1, wherein the polystyrene beads are present from 1.0% by weight to 3.0% by weight.

3. The filter medium of claim 1 or claim 2, wherein the silica-based oleophilic fibers are glass wool fibers and / or silicate fibers and / or sodium silicate fibers.

4. The filter medium of any of claims 1 to 3, wherein: the polystyrene beads are entangled in the fibers; or, the polystyrene beads are in one, two, three, four or five separate layers, between two, three, four, five or six separate layers of fibers.

5. The filter medium of any one of claims 1 to 4, wherein the polystyrene beads are spherical and have a diameter of 1 mm to 10 mm.

6. The filter medium of claim 5 wherein the polystyrene beads have a diameter of 3 mm to 5 mm.

7. The filter medium of any one of claims 1 to 6, wherein the silica-based oleophilic fibers are silicate fibers and / or sodium silicate fibers with a diameter of 1 to 10 pm.

8. The filter medium of claim 7, wherein the silicate fibers and / or the sodium silicate fibers have a diameter of 2 to 5 pm.

9. The filter medium of any of claims 1 to 8, wherein the filter medium has a compact density of 100 to 220 g / 1.

10. The filter medium of claim 9, wherein the filter medium has a compacted density of: 150 to 210 g / 1; or, 170 to 200 g / 1.

11. The filter medium of any of claims 1 to 10, wherein the filter medium further comprises one, two, three or all of the following: Polypropylene fibers; Perlite; Water; and / or, Glycerin.

12. The filter medium of any of claims 1 to 11, wherein the filter medium comprises: silica-based oleophilic fibers (optionally, glass wool fibers and / or silicate fibers and / or sodium silicate fibers) in a percentage of 70% to 80% by weight, and polystyrene beads from 0.5% to 5.0% by weight, the balance being one, two or three polypropylene fibers, water and / or glycerin.

13. The filter medium of any of claims 1 to 12, wherein the filter medium comprises: silica-based oleophilic fibers (optionally, glass wool fibers and / or silicate fibers and / or sodium silicate fibers) in a percentage of 70% to 80% by weight, polystyrene beads from 0.5% to 5.0% by weight, polypropylene fibers from 2.0% to 4.0% by weight, water from 1.0% to 20.5% by weight, and glycerin from 7.0% to 10.0% by weight; optionally, the filter medium further comprises unavoidable impurities.

14. The filter medium of any of claims 1 to 13, wherein the filter medium comprises: silica-based oleophilic fibers (optionally, glass wool fibers and / or silicate fibers and / or sodium silicate fibers) in a percentage of 73% to 78% by weight, polystyrene beads from 1.0% to 3.0% by weight, polypropylene fibers from 2.0% to 3.0% by weight, water from 7.0% to 16.0% by weight, and glycerin from 8.0% to 9.0% by weight; optionally, the filter medium further comprises unavoidable impurities.

15. A filter comprising the filter medium of any of claims 1 to 14.

16. A filtration machine comprising the filter medium of any of claims 1 to 14, or the filter of claim 15.

17. A method for removing oil from a condensate that includes water and oily contaminants, wherein the method comprises: passing the condensate through the filter medium of any of claims 1 to 14; or a filter according to claim 15; or, a filtration machine according to claim 16.

18. The method of claim 17 wherein the condensate comprises water and oil, the oil present in the condensate being: from 20 ppm to 2,000 ppm; or, from 50 ppm to 1,000 ppm; or, from 100 ppm to 500 ppm; or, from 150 ppm to 250 ppm.