EP4058177A1

EP4058177A1 - Process fluid filtration device

Info

Publication number: EP4058177A1
Application number: EP20807900.4A
Authority: EP
Inventors: Enrico Bellio; Luca BERTON
Original assignee: PIOVAN SpA
Current assignee: PIOVAN SpA
Priority date: 2019-11-13
Filing date: 2020-11-10
Publication date: 2022-09-21
Also published as: IT201900021123A1; WO2021094922A1

Abstract

A filtration device for heated process air used in an apparatus for the dehumidification of plastics in granules is disclosed, with a filter medium of tubular shape that is crossed by the air radially from the outside towards the inside and which comprises an outlet end through which the filtered gas can exit in an axial direction, a bottom placed at the outlet end of the filtered gas and at least one ring-shaped seal placed on an edge of the bottom to define an annular sealing zone against a seal seat, in which the seal is made of a silicone material by means of an injection overmoulding performed directly on the bottom.

Description

Process Fluid Filtration Device

Background of the invention [0001] The invention concerns a filtration device for a process fluid, in particular a process fluid comprising a dehumidifying gas (for example heated air) used in a dehumidification apparatus.

[0002] The invention also concerns a dehumidification apparatus comprising a filtration device for a process fluid and a manufacturing method for a filtration device for a process fluid.

[0003] Specifically, but not exclusively, the invention can be used to control the cleanliness of the air of a dehumidification apparatus, in particular for a dehumidification apparatus of incoherent plastics, that is in granular and/or micro granular and/or powdery and/or in the form of flakes, globules, pellets, particles, fragments or similar. The dehumidification apparatus can be configured, in particular, to feed at least one user machine, in particular a machine for treating and transforming plastics, for example a plant for extruding plastics and subsequently molding by injection and/or blowing and/or compression.

[0004] It is known, in the plastics molding field, to associate a dehumidification apparatus with at least one user machine, for example an injection press, to dehumidify the plastics by means of a process fluid before feeding the plastics to the user machine. The process fluid allows proper dehumidification, since it comes into direct contact with the surface or mass of the incoherent plastics to extract moisture from the plastics.

[0005] The plastics (resin in granules) are generally contained in a drying/dehumidification hopper with a generally upper material loading mouth and a generally lower discharge mouth. In the dehumidification process, the process fluid (heated air) is introduced from below into the hopper and then, after extracting the moisture from the material contained in the hopper, it is evacuated through at least one upper outlet of the hopper.

[0006] It is known that, during the dehumidification process, a certain amount of dust is generated, due to various factors such as, in particular, the thermal action of heating, the passage of the process fluid through the material, the descent of the incoherent material from the loading mouth to the unloading mouth of the hopper, etc. This amount of dust is generally expressed in ppm per kg of incoherent material processed (1 ppm = 1 mg/kg). [0007] It is also known that the incoherent material processed can have a greater or lesser capacity to generate dust, or to shatter, during the various stages of the process, due to various factors, for example the shape and/or size of the granules, and/or the type of production process, and/or the chemical composition of the resin, and/or the mechanical characteristics (for example hardness) of the resin, etc.

[0008] One of the problems present today in resin transformation plants is the need for continuous and scheduled maintenance of the plants in order to guarantee the continuity of the production process.

[0009] It is therefore essential to preserve and protect the operating components of the dehumidification system in order to minimize downtime for ordinary or extraordinary maintenance. For this purpose it is known to provide filtration systems for the dust present in the process fluid. In particular, the use of suitable materials for dust filtration made of paper and/or polyester and/or microfibers is known. The choice of the most suitable filter material may depend on various factors such as, for example, the type of substance from which the dust is formed, the size of the dust particles, the operating temperature and/or installation of the filter, etc. The known filters are characterized by an abbreviation (for example: G4, F7, F8, F9, H13, H14) which identifies the filtering capacity or the degree of filtration, in particular the ability to retain dust particles greater than a certain size.

[0010] A problem of the prior art is to design a filtering system suitable for the specific situation of use. Consider, in particular, that not all polymeric resins generate dust with the same characteristics, in particular with the same granulometry or dimensions of the powder, or with the same abrasive capacity; for example, a polymer loaded with glass fiber can release particles which, due to their high abrasive capacity, can quickly deteriorate a filter surface. Furthermore, the wear of the filtering surface may depend on the speed with which the fluid with dust particles crosses the filtering surface, due to the impact of the particles.

[0011] Another problem is the assembly or repositioning of the filter in its seat, due to the presence of contact surfaces that are not perfectly adherent, or due to the depression that is generated inside the housing of the filter. It is possible, in fact, that the filter undergoes such a deformation that a perfect seal on the seat is no longer obtained, allowing the unwanted passage of dust particles..

[0012] The size of the dust particles can be comprised, for example, between 2 pm and 20 pm. In general, the risk of giving rise to interstices or cracks of this order of magnitude, not visible to the naked eye, is very high. [0013] Another drawback is related to the cleaning of the filter before its reuse. In this regard, the use of a cleaning system is known that removes the dust accumulated on the filtering surface by means of compressed or vacuum jets. This cleaning method involves considerable mechanical stress on the filter surface, with the risk of reducing, in some cases, its work life.

[0014] Another limit of the prior art is the relative difficulty in recovering or ordering spare parts of the filtering system. Very often, in fact, the identification of the filter and the interpretation of its identification data is not easy and, in some cases, it can be extremely difficult to determine the appropriate degree of filtering. This limit is amplified in certain sectors due to regulatory restrictions, such as the medical and/or food sector, or due to the fact that a large amount of dust is generated in specific situations of use.

[0015] US 2014/373494 A1 discloses the features of the preamble of claim 1. Summary of the invention

[0016] An aim of the invention is to obviate one or more of the aforementioned limitations and drawbacks of the prior art.

[0017] An aim of the invention is to provide an alternative solution to the problem of effectively filtering the dust in a process fluid used in an apparatus for the dehumidification of incoherent plastics.

[0018] An advantage is to protect the components of a dehumidification apparatus for incoherent plastics by filtration of the process fluid.

[0019] An advantage is to effectively and accurately retain solid particles larger than or equal to a desired degree of filtration.

[0020] An advantage is to provide a filtration device that allows to reduce maintenance interventions and/or to reduce the risk of damage to the device even in the presence of high temperatures.

[0021] An advantage is to make available a filtration device with a relatively high filtration efficiency.

[0022] An advantage is to provide a filtration device which is constructively simple and economical.

[0023] These aims and advantages and others are achieved by a filtration device and/or a dehumidification apparatus and/or a manufacturing method according to one or more of the claims set out below.

[0024] In one example, a filtration device for a process gas comprises a tubular- shaped filter medium that is traversed by the gas radially from the outside to the inside and which includes an outlet end through which the filtered gas can exit in an axial direction, with a bottom which is arranged at the outlet end of the filtered gas and which is provided with at least one ring-shaped seal arranged on an edge of the bottom to define an annular sealing zone against a seal seat, in which the seal is made of a silicone material by means of an overmoulding performed directly on the bottom.

[0025] The tubular- shaped filter medium may comprise, in particular, a straight cross- section of cylindrical shape, although it is possible to provide a straight cross-section with other shapes, such as for example a multi-lobed (tri-lobed), elliptical, polygonal (square) shape with rounded comers, etc. The choice of the shape of the section of the tubular filter medium may depend, in particular, on the sector of use of the filter, the crossing speed of the gas to be filtered, the pressure or depression generated in the filtering surface, etc..

Brief description of the drawings [0026] The invention can be better understood and implemented with reference to the attached drawings which illustrate some non-limiting examples of implementation, in which:

Figure 1 is a side view of an example of a filtration device made in accordance with the present invention;

Figure 2 is a perspective view of the bottom of the filtering device of Figure 1 ;

Figure 3 is a plan view from behind of the bottom of Figure 2;

Figure 4 is the section IV-IV of Figure 3;

Figure 5 is a partial section of the filter medium of the filtration device of Figure 1 ;

Figure 6 is a perspective view of the filtration device of Figure 1.

Detailed description

[0027] With reference to the above-mentioned figures, number 1 indicates as a whole a filtration device for gas, in particular for air. The filtration device 1 may be used, in particular, for the filtration of a process fluid, for example a process fluid comprising a dehumidifying gas (for example heated air) used in a dehumidification apparatus. The filtration device may be used, in particular, to control the cleanliness of the air of a dehumidification apparatus, in particular for a dehumidification apparatus of incoherent plastics, i.e. resin in granular and/or micro-granular form and/or in form of dust, flakes, globules, pellets, particles, fragments or similar.

[0028] The filtration device 1 may comprise, in particular, at least one filter cartridge. The filter cartridge may include, in particular, an external structure in filtering material (filter medium) to retain solid particles in the radial direction and an internal duct that allows the filtered air to exit axially.

[0029] The filter cartridge may comprise, in particular, a filter medium 2 of tubular shape (for example of cylindrical shape, although it is possible to provide other tubular shapes) which is crossed by the gas radially from the outside towards the inside (see arrows in Figure 5).

[0030] The filter medium 2 may comprise, in particular, at least one external surface 3 for retaining dust. The filter medium 2 may comprise, in particular, at least one internal surface 4 which defines an internal space of filtered gas. The filter medium 2 may include, in particular, at least one outlet end 5 through which the filtered gas can exit in an axial direction.

[0031] The filter medium 2 may comprise, in particular, a pleated filtering surface so as to increase the surface and/or reduce the initial pressure drop and/or allow a good accumulation of dust.

[0032] The filtering medium 2 may comprise, in particular, a filtering surface with at least two layers made of different materials, in which a first layer 6 is more external than a second layer 7 (see Figure 5).

[0033] The first layer 6 may comprise, in particular, a cellulose-based filter material (for example paper for air filters). The first layer 6 may comprise, in particular, a polyester and/or polypropylene filter material.

[0034] The second layer 7 may be, in particular, made of a nanofiber-based material (where it is possible that nanofibers in this description means, in particular, fibers having a diameter of the order of 100 nanometers). The second layer 7 may be made, in particular, of a material based on carbon nanofibers and/or ceramic nanofibers and/or cellulose nanofibers.

[0035] The first layer 6 may be, in particular, the outermost layer of the surface of the filter medium 2. The second layer 7 may be, in particular, the innermost layer of the surface of the filter medium 2. In other examples, not illustrated, the surface of the filter medium 2 may comprise one or more further layers, for example further layers interposed between the first layer 6 and the second layer 7.

[0036] The filter cartridge may include, in particular, at least one bottom 8 arranged at the outlet end 5 of the tubular filter medium 2 and provided with at least one outlet 9 for the filtered gas. The bottom 8 may comprise, in particular, a disk- shaped element with a central hole. The bottom 8 may be made, in particular, of stainless steel.

[0037] The filter cartridge may comprise, in particular, at least one annular- shaped seal 10 arranged on the bottom 8 around an edge of the outlet opening 9 of the filtered gas to define an annular sealing zone against a seal seat. The seal 10 arranged at the head of the cartridge is configured to generate adherence and/or a sealing seal.

[0038] The seal 10 may be made, in particular, of a polymeric material. The seal 10 may be obtained, in particular, by overmoulding (for example by injection and/or compression and/or die-casting of plastics) carried out directly on the bottom 8. The polymeric material of the seal 10 may comprise, in particular, a silicone-based material. The seal 10 may be made, in particular, of a material suitable for the food sector, for example a silicone material with FDA (Food & Drug Administration) approval characteristics.

[0039] The seal 10 may comprise, in particular, at least one main body 11 with at least two or more discrete protuberances 12 arranged at intervals between them. The seal 10 may comprise, in particular, at least one main body 11 with at least one continuous protuberance 13 in the shape of a closed ring.

[0040] The continuous closed-loop protuberance 13 may be, in particular, more internal than the discrete protuberances 12 spaced apart. The continuous closed-loop protuberance 13 and the discrete protuberances 12 at intervals may be, in particular, coplanar with each other. The continuous closed-loop protuberance 13 and the interspersed discrete protuberances 12 may protrude from the main body 11, in particular, with dimensions which, measured in an axial direction (i.e. heights, or thicknesses, or depths of the protuberances), are equal to each other.

[0041] The continuous closed-loop protuberance 13 may develop, in particular, along a first circumference. The interspersed discrete protuberances 12 may develop, in particular, along a second circumference. The first circumference and the second circumference may be, in particular, concentric. In particular, the first circumference may have a smaller diameter than the second circumference. The first circumference may be, in particular, more internal than the second circumference.

[0042] The main body 11 may be, in particular, of an annular (closed) shape. The main body 11 may include, in particular, a fixing portion which is fixed on a front surface of the bottom 8. This fixing may take place, in particular, by hot overmoulding the seal 10 on the bottom 8, with consequent joining or welding of the polymeric material of the seal 10 on the bottom 8.

[0043] The fixing portion could be, in particular, inserted in a seat obtained on the bottom 8. The main body 11 may include, in particular, at least one projecting portion which projects axially from the bottom 8.

[0044] The main body 11 and the protuberances 12 and 13 emerging from the main body 11 may be made, in particular, in a single body made of plastics.

[0045] The main body 11 may exhibit, in particular, at least one external sealing front surface (orthogonal to the axis of the cartridge) from which the spaced apart discrete protuberances 12 and/or the closed ring continuous protuberance 13 emerge axially.

[0046] The two or more discrete protuberances 12 may be, in particular, extended longitudinally in a circumferential direction and may be arranged, in particular, at a circumferential distance from each other. The number of discrete protuberances 12 may be, for example, at least six, or at least eight, or at least ten, or at least twelve, or at least fourteen, or at least sixteen. In the specific example illustrated, the seal 10 comprises seventeen discrete protuberances 12.

[0047] Each discrete protuberance 12 may be, in particular, extended in length in the form of an arc of circumference. The various discrete protuberances 12 may be, in particular, of the same shape. The discrete protuberances 12 may be, in particular, equidistant from each other in the circumferential direction.

[0048] The filtration device 1 may comprise, in particular, at least one basket 14 for containing the filtering medium 2. The basket 14 may comprise, in particular, at least one containment mesh structure. The basket 14 may be made, in particular, of stainless steel. The basket 14 may act, in particular, as a stiffening structure. The basket 14 may act, in particular, as a protective structure, for example to protect the filter medium 2, against accidental knocks or impacts due to ordinary and extraordinary maintenance and/or cleaning operations.

[0049] The filtration device 1 may comprise, in particular, at least one identification element 15 readable by an electronic reader and fixed to the filtration device 1 (for example mounted on a further closing bottom axially opposite to the bottom 8). The identification element 15 may contain, in particular, data relating to the filtration device 1 which may include at least the degree of filtration, that is the ability of the filtration device to retain dust of a certain particle size. The data relating to the filtration device 1 contained in the identification element 15 may include, in particular, the product code and/or the production batch number and/or the date of manufacture and/or the date of installation, etc. [0050] The identification element 15 may include, in particular, a graphic code, for example a two-dimensional bar code (QR code) readable by a bar code reader. The identification element 15 may include, in particular, an RFID tag configured to receive and provide information on the degree of maintenance of the filtration device and readable by a fixed or portable RFID reader.

[0051] The characteristic of forming the seal 10 by overmoulding of polymeric material, directly above the bottom 8 of the filter cartridge, allows to considerably reduce the risk of leakage of dust particles and the degradation of the seal caused by the presence of adhesives or glues. The overmoulding may comprise, in particular, a hot molding of plastics, for example by injection and/or by compression and/or by die casting. The hot overmoulding of the polymeric material of the seal 10 on the bottom 8 determines, in particular, a permanent fixing or welding of the seal, with a continuity of the material and a particularly strong and durable joint.

[0052] The particular configuration of the seal 10, provided with outermost interspersed discrete protuberances 12, which are circumferentially extended and/or which are arranged circumferentially spaced apart, together with one innermost closed ring continuous protuberance 13, allows an effective adherence and a sealing with respect to any surface, thanks to the presence of the various protuberances 12 and 13 whose shape and arrangement allows an optimal deformation of the seal 10. In particular, the interspersed discrete protuberances 12 allow a good deformability also if the material of the seal 10 has a certain hardness. In the plastic materials sector it is standard to use the Shore hardness scale (ASTM D2240-00 standard), while for softer rubbers or plastics the Shore A hardness scale is used. A seal that is too soft (Shore index less than 10) could permanently deform over time under the action of the combination of temperature and compression. A seal that is too hard (Shore index greater than 30) could prevent proper deformation, adhesion and sealing of the seal.

[0053] As mentioned, it is possible to use a filter medium comprising at least two layers of different materials, in particular a first layer 6 outermost (for example with a degree of filtration lower than the second layer 7) and a second layer 7 innermost (for example with a degree of filtration higher than the first layer 6).

[0054] The first layer 6 may be used in direct contact with the “polluted” air flow and therefore with the dust contained in the air. The second layer 7 may be made with a material derived from nanofibers with high filtration capacity. The first layer 6 may be, in particular, ecological and washable. The first layer 6 may have, in particular, a higher flame retardancy degree than the second layer 7.

[0055] The solution with at least two different layers allows greater ease and effectiveness of maintenance, since, for example, it is possible to wash the first more resistant layer 6 by means of a fluid which removes the dust without mechanically stressing the second more filtering layer 7.

[0056] The filtration device 1 comprises adhesive means (in particular for gluing the filter medium 2 to the bottom 8 and/or to the further bottom) environmentally friendly and certified for the medical and/or food sector, for example according to the regulations FDA approved and/or FDA member.

[0057] The use of an identification element, which may be, for example, an identification element 15 readable by an electronic reader, allows, in particular, to facilitate the operations of replacement or recovery of spare parts and/or monitoring the degree of maintenance of the filtration device 1.

[0058] The filtration device 1 may be used, in particular, in an apparatus for dehumidifying incoherent plastic material. The dehumidification apparatus may include, in particular, at least one hopper to contain the plastic material. The dehumidification apparatus may include, in particular, means for generating a flow of a process gas (heated air) in the hopper. The dehumidification apparatus may include, in particular, at least one filtration device 1 configured to filter the process gas.

[0059] The filtration device 1 may be manufactured with a method which comprises the steps of providing the filter medium 2 with a tubular shape and providing the bottom 8 which will then be intended to be arranged at the outlet end 5 of the filtered air of the filter cartridge.

[0060] The manufacturing method may comprise, in particular, the step of forming the seal 10 in polymeric material with an annular shape on the bottom 8 around the edge of the outlet opening 9, by means of overmoulding (in particular hot) of the seal 10 directly above the bottom 8.

[0061] Overmoulding (in particular by injection of plastics) may include, in particular, the step of defining a forming cavity which is delimited at least in part by the area of the bottom 8 where the seal 10 is to be applied and molded and the step of introducing the plastics (by injection) into the forming cavity. In other embodiments, it is possible to provide that the seal 10 is formed by compression molding a dose of plastics (for example an annular dose) directly on the bottom 8 of the filtration device 1.

[0062] The manufacturing method may include, in particular, the step of assembling the filtration device 1, for example by joining the bottom 8, provided with the overmoulded seal 10, with the filter medium 2 (for example by means of bonding).

[0063] The filtration device 1 is particularly versatile and therefore suitable and adaptable for various situations of use such as, for example, use in environments with high temperatures (in particular for a dehumidification apparatus of incoherent plastics), and/or in the production and/or treatment of medical applications, and/or in the production and/or treatment of applications for food use.

Claims

1. Gas filtration device (1), said device comprising at least one filtration cartridge which in turn comprises: a filtering medium (2) of tubular shape which is traversed by the gas radially from the outside towards the inside and which comprises at least one outer surface (3) for retaining dust, at least one inner surface (4) which defines an internal space of filtered gas and at least one outlet end (5) through which the filtered gas can exit in an axial direction; a bottom (8) arranged at said outlet end (5) and provided with at least one outlet opening (9) of the filtered gas; at least one seal (10) of annular shape arranged on said bottom (8) around an edge of said outlet opening (9) to define an annular sealing area against a sealing seat, wherein said at least one seal (10) comprises a main body (11), two or more discrete protuberances (12) and at least one continuous protuberance (13), said main body ( 11) being of annular shape with at least one portion that protrudes axially from said bottom (8) and from which said two or more discrete protuberances (12) and said continuous protuberance (13) emerge, said continuous protuberance (13) being longitudinally extended in the form of a closed ring, said two or more discrete protuberances (12) being arranged in an annular arrangement and being spaced apart from one another along said annular arrangement; characterized in that said continuous protuberance (13) is arranged more internal than said annular arrangement.

2. Device according to claim 1, wherein said main body (11), said two or more discrete protuberances (12) and said at least one continuous protuberance (13) are made of a polymeric material and are obtained by overmolding performed directly over said bottom (8).

3. Device according to claim 2, wherein said main body (11), said two or more discrete protuberances (12) and said at least one continuous protuberance (13) are made of the same polymeric material.

4. Device according to claim 3, wherein said polymeric material comprises a material based on silicones.

5. Device according to any one of the preceding claims, wherein said main body (11), said two or more discrete protuberances (12) and said at least one continuous protuberance (13) are made of the same polymeric material are obtained by hot overmolding of plastics, in particular injection overmolding.

6. Device according to any one of the preceding claims, wherein said two or more discrete protuberances (12) and said at least one continuous protuberance (13) protrude from said main body (11) with dimensions which, measured in said axial direction, are equal to each other.

7. Device according to any one of the preceding claims, wherein said two or more discrete protuberances (12) and said at least one continuous protuberance (13) are coplanar with each other.

8. Device according to any one of the preceding claims, wherein said continuous protuberance (13) is spaced in a radial direction from said two or more discrete protuberances (12).

9. Device according to any one of the preceding claims, wherein said main body (11), said two or more discrete protuberances (12) and said at least one continuous protuberance (13) are made in a single body.

10. Device according to any one of the preceding claims, wherein the number of said two or more discrete protuberances (12) is at least six, or at least eight, or at least ten, or at least twelve, or at least fourteen, or at least sixteen.

11. Device according to any one of the preceding claims, wherein each of said two or more discrete protuberances (12) comprises a segment extending in length in the form of an arc of circumference and/or wherein said two or more discrete protuberances (12) are of the same shape and/or wherein said two or more discrete protuberances (12) are equidistant from one another.

12. Gas filtration device (1), in particular according to any one of the preceding claims, said device comprising at least one filtering cartridge which in turn comprises a filtering medium (2) of tubular shape which is traversed by the gas radially from the outside toward the inside and which comprises at least one outer surface (3) for retaining dust, at least one inner surface (4) which defines an internal space of filtered gas, and at least one outlet end (5) through which the filtered gas can exit in an axial direction, said filtering medium (2) comprising at least one filtering surface with at least two layers made of different materials, wherein a first layer (6) is more external than a second layer (7), characterized in that said second layer (7) is made of a nanofiber-based material.

13. Device according to claim 12, wherein said second layer (7) is made of a material based on carbon nano fibers.

14. Device according to claim 12 or 13, wherein said second layer (7) is made of a material based on ceramic nanofibers.

15. Device according to any one of claims 12 to 14, wherein said second layer (7) is made of a material based on cellulose nanofibers.

16. Device according to any one of claims 12 to 15, wherein said first layer (6) is made of a cellulose-based material.

17. Device according to any one of claims 12 to 16, wherein said second layer (7) is the innermost layer of said filtering surface.

18. Device according to any one of claims 12 to 17, wherein said first layer (6) is the outermost layer of said filtering surface.

19. Device according to any one of claims 12 to 18, wherein said first layer (6) has a higher flame retardancy degree than said second layer (7).

20. Device according to any one of the preceding claims, comprising at least one identifying element (15) readable by an electronic reader and fixed to said device, said identifying element (15) containing data relating to the filtration device (1) which include at least the degree filtration, i.e. the ability of the filtration device to retain the powder of a certain particle size; said identifying element (15) comprising, in particular, a graphic code and/or an RFID tag configured to receive and provide information on the degree of maintenance of the filtration device (1).

21. Apparatus for dehumidifying incoherent plastics, comprising at least one hopper for containing the plastics, means for generating a flow of a process gas in said hopper, and at least one filtration device for the process gas, characterized in that the filtration device (1) is made according to any one of the preceding claims.

22. Method for manufacturing a gas filtration device, in particular a filtration device according to any one of claims 1 to 20, said method comprising the steps of: providing a filtering medium (2) of tubular shape which comprises at least one outer surface (3) for retaining dust, at least one inner surface (4) which defines an internal space of filtered gas and at least one outlet end (5) through which the filtered gas can exit in an axial direction; providing a bottom (8) to be arranged in said outlet end (5) and provided with at least one outlet opening (9) of the filtered gas; arranging at least one annular seal (10) of a polymeric material on said bottom (8) around an edge of said outlet opening (9) to define an annular sealing area; in particular, providing protection means (14) with a mesh structure to protect said filtering medium (2); characterized in that said step of arranging comprises overmolding said seal (10) directly over said bottom (8).