RU2117514C1 - Cone-shaped porous filter element and filter components - Google Patents

Abstract

FIELD: filtration technics. SUBSTANCE: filter element has external supporting structure that serves as radial support for filter element. External structure together with element are wrapped by at least one layer of sheet material. Element may be manufactured either from glass fibers or from a filter material, which is originally shaped as flat sheet and folded in the manufacturing operation. Fibers may be of boron-silicate glass. Element may contain internal cone-shaped support and internal sheet material layer. Filter assembly comprises filter in casing with inlet device tightly communicating with internal space of filter. Casing encloses several conical filter elements each having upper end cap; lower settler; and tube plate between intake and discharge devices. There are uprights placed in the holes of tube plate, their upper ends supporting filter elements. EFFECT: enabled slower flow of medium to eliminate recurring loss of drops. 7 cl, 7 dwg

Description

 The invention relates to coagulation, in particular, to an improved filter element that can be used in almost any coagulating filter. More specifically, the present invention relates to a conical shaped coagulating porous filter element and a filter assembly used to separate liquid droplets from gases or other liquids.

 The need to separate liquid droplets from gases or other liquids has been around for a long time. As a rule, liquids found in air and gas flows are lubricating oils, water, salt water, acids, alkalis, hydrocarbons, waste liquids, glycols and amines. Usually the liquid is present in the form of tiny droplets or aerosols. The size distribution of aerosols mainly depends on the surface tension of contaminants in the liquid and the method of their formation. With a decrease in surface tension, the size of the aerosol decreases accordingly. This is because the cohesive forces of intermolecular interaction (the forces that attract surface aerosol molecules inside to reduce the surface area with respect to volume) are the weakest.

 It has been established that over 50% of all oil aerosols by weight have a diameter of less than 1 μm. Due to the same surface tension, the same can be said about glycols, amines and hydrocarbons. Conventional filtration and / or separation equipment, such as precipitation or settling chambers, wire mesh separators (based on particle removal or collision), centrifugal or paddle (mechanical) separators and filters with a glass or cellulose filter medium for rough cleaning are only effective at a particle size of 1 μm, and they do not remove essentially widespread aerosols and particles smaller than 1 μm. To remove these contaminants that create a problem, it is necessary to use highly efficient coalescence filters.

 All known coalescence filters and coalescence elements of the type to which the present invention relates have a tubular or cylindrical configuration and are used to filter the inlet or outlet stream. Although predominantly using a filter, separation is carried out from the effluent, a certain advantage is also achieved by separating the incoming stream to separate liquid droplets and aerosols from gases or to coagulate immiscible liquid phases.

 When this is usually used coagulating elements attached inside the pressure vessel or located in it to form a device with a coagulating filter. The continuous phase of a gas or liquid contains dispersed droplets of liquid aerosol, and this phase is sometimes called the discontinuous phase. The mixture enters the device through the inlet connection and then passes into the coagulating element. When the fluid passes through the filter medium of the coagulating element, liquid droplets come in contact with the fibers of the filter medium and are removed from the fluid stream. Inside this medium, the drops merge with other drops and increase in size, appearing on the surface of the element, are located downstream, in the form of large drops that can be separated by gravity from the fluid of a continuous phase. If the density of the droplets exceeds the density of the fluid, for example, oil droplets in the air, then these droplets will settle under the action of gravity to the bottom of the filter assembly in countercurrent with the air flow up. If the density of the droplets is less than the density of the fluid, for example, drops of oil in water, then the droplets will rise up the node in countercurrent flow with the water flow down.

 The size, density of the droplets, viscosity and density of the fluid will determine how soon the droplet settles or rises in the filter assembly. During the design of the coagulating filter, it is advisable to maximize the flow rate of the liquid through the device, however, without reducing the separation efficiency, in order to reduce the filter housing size for a given current speed and, therefore, reduce production costs.

 However, the known cylindrical coagulating elements create significant limiting factors in the design of filter housings. The cylindrical configuration of the coagulating elements forms a constant annular space between the elements and the housing wall. Thus, even with a uniform distribution of the flow through the surface of the coagulating element, the peripheral speed will increase linearly from the lower to the upper part of the element.

 With a cylindrical design of the element, the peripheral speed will be different at all points along the axial length of the element. For example, when droplets of oil are separated from the gas, the gas will flow up after it leaves the element, and the liquid droplets will settle down. There will be no flow at the bottom of the element, so the peripheral speed will be zero. At the top of the element, all gases will go up. The peripheral speed will be 100% of the flow divided by the open cross-sectional area (the area between the element and the vessel wall). Similarly, at a point in the middle of the element, the peripheral speed will be 50% of the total flow divided by the open cross-sectional area. It is necessary to take measures to avoid exceeding the peripheral speed, as this may cause re-trapping of the droplets.

 The pressure drop that is created by the passage of gas to the open end of the element is a function of the internal diameter of the element. The inner diameter of the cylindrical elements is limited by the diameter of the housing, the wall thickness of the element and the size of the annular space. In order to prevent liquid particles from being re-captured, it is necessary to maintain a sufficiently low peripheral speed. The smaller the inner diameter, the higher the pressure drop for a given flow rate.

 To reduce the peripheral speed in order to prevent re-trapping of liquid droplets, a substantially conical coagulating filter has been developed in which the open area between the housing wall and the filter element increases in the direction of flow.

 The only known patent that discloses a conical coagulating element is US Pat. No. 2,823,760, issued to S.K. Anderson, entitled "Water separator". After careful study of the Anderson patent, only external resemblance was revealed. Anderson's patent deals with maintaining constant pressure. It does not disclose a coagulating filter for cleaning the incoming stream, but in reality a centrifugal coagulator based on the use of centrifugal force, as well as at a steady flow rate to separate the merged droplets from the main phase fluid. Thus, it is intended for another purpose and does not solve problems in the field of coagulating filter.

 Known porous filter element of a conical shape made of randomly oriented fibers, through which the flow flows from inside to outside and having upper and lower annular sealing surfaces (application Germany N 2904830, B01 D 45/04, 1980).

 Also known is a filter assembly comprising a housing with an inlet and outlet device, conical filter elements with upper end caps, a tube sheet with several holes that is located between the inlet and outlet devices, a lower settler located below the inlet device (PNR patent N 15440, B 01 D 29/32, 1982).

 However, the indicated element and filter assembly are used in the processes of wire impact separation and, therefore, cannot be applied and do not solve problems in the field of coagulation.

 The aim of the present invention is to provide a porous filter element with a conical shape of a coagulating filter and a filter assembly providing a lower peripheral speed than cylindrical elements with similar flow characteristics in a tank of the same size.

 An object of the present invention is to provide an element and a coalescence filter assembly in which the peripheral speed remains substantially constant at all points along the axial length of the element.

 An object of the present invention is also to provide a coagulating element and a coagulating filter assembly in which the peripheral speed can be reduced when the flow moves from the lower part to the upper part of the filter element.

 In addition, the aim of the invention is to provide an element and a coagulating filter assembly providing a lower overall pressure drop in the coalescing filter assembly.

 The goals are achieved by a porous filter element of a conical shape made of randomly oriented fibers, through which the flow flows from the inside out and having an upper and lower annular sealing surfaces, which, according to the invention, has an external supporting structure, the strength of which is sufficient to serve radial support of the porous filter element, and the inner diameter of which is equal to or slightly less than the outer diameter of the porous filter element, to which is completely supported by this structure, in addition, the outer supporting structure together with the porous filter element is wrapped in at least one layer of sheet material.

 Preferably, the fibers are glass fibers and at least one layer of thin sheet material is wound around the porous filter element, which adheres tightly to it.

 Preferably, the element is made of filter material, which in the initial state is in the form of a flat sheet and the filter material is folded during manufacture.

 The fibers may be borosilicate glass fibers.

 Preferably, the element also has an internal support structure of a conical shape and an inner layer of sheet material wound on an internal support structure.

 The set goals are also achieved by a filter assembly comprising a filter installed in the housing with an input device tightly communicating with the internal cavity of the filter, and an exhaust device communicating with the atmosphere in which according to the invention the filter is made as described above, namely, has an internal supporting structure of a conical shape and the inner layer of sheet material wound on the inner supporting structure.

 In addition, these goals are achieved by a filter assembly comprising a filter housing with an inlet and outlet device, several conical filter elements installed in the housing and having upper end caps, a lower sump located below the inlet device, and a tube sheet with several holes that is located between inlet and outlet devices, which according to the invention is equipped with several risers, hermetically connected to the holes of the tube sheet and having at their upper ends The sealing surfaces filled with them at the same time, on which conical filter elements are installed, the sealing of which is carried out by the sealing surfaces of the risers and the upper end caps, the upper sump located above the tube sheet and the upper drainage communicating with the upper sump.

 Preferably, the filter assembly is provided with a lower sump located underneath the inlet and lower drainage in communication with the lower sump.

 The conical porous filter element (conical element) of the coagulating filter can be used in virtually any coagulating filter, depending on the application for separating liquid droplets from gases or other liquids. The conical configuration allows lower primary fluid velocities to be applied in the zone located between the outer surface of the coagulating elements and the inner wall of the filter assembly, thus eliminating the re-entrainment of the merged liquid droplets back into the air stream.

 In a specific embodiment of the present invention, the conical element is located in the housing of a conventional T-type filter, with its small end communicating with the entrance to the filter housing to separate the oil from air. The same conical filter element can be used in a filter housing with many elements, in which the flow enters through the bottom or a wide part of the element. In both embodiments, the flow passes from inlet to outlet, and the peripheral speed between the filter elements and the wall of the filter housing will be substantially constant. Depending on the specific application, other configurations can be used, since the smallest end of the conical (filter is directed towards the direction of flow of the primary phase. The medium used in the filter element can be formed under vacuum, while it can be in the form of layers or a roll, and the conical the coagulating element in accordance with the present invention can be used to separate liquids from a gas or liquid from another liquid.

 In FIG. 1 is a schematic view of a known coagulating element installed in a cylindrical filter housing; in FIG. 2 is a schematic view of a conical coagulating filter in accordance with the present invention installed in a cylindrical filter housing; in FIG. 3 is a perspective view, partially in section, of a T-type filter assembly showing a conical coagulating filter in accordance with the present invention between end caps in a cylindrical body; in FIG. 4 is a view in vertical projection, partially in section, of a highly efficient coagulating filter consisting of many elements; in FIG. 5 is a sectional view, in the direction of the arrows, in the plane of section 5-5 of FIG. 4; in FIG. 6 is a sectional view of a filter element having an external support structure according to the invention and in which this structure, together with the porous filter element, is wrapped in at least one layer of sheet material; in FIG. 7 is a sectional view of another embodiment of an element having an internal support structure of a conical shape and an inner layer of sheet material wound on an internal support structure.

 Obviously, the invention is not limited to structural details and the arrangement of the parts shown in the drawings, since other variations and other methods of carrying out the invention are possible within the scope of the invention. It should also be clear that the phraseology and terminology used herein are intended only to describe and not limit the invention.

As noted above, when designing a coagulating filter, it is advisable to maximize the flow rate in the device in order to reduce the size of the casing required for a given flow rate and the manufacturing cost of the device without reducing the separation efficiency. To achieve this, three factors are important:
1. Surface speed through the filter medium.

 2. The peripheral velocity of the continuous phase fluid.

 3. The pressure drop in the coagulating filter.

 The effect of the surface speed on the filter will be controlled due to the fact that when the surface speed increases, the filter efficiency decreases. In addition, a high surface speed will also cause high pressure drops in the filter medium and element.

 When dispersed droplets are captured by the fibers of the filter medium, the speed with which they move towards the surface directed downstream is a function of the drag force of the continuous phase passing through the medium on the droplets. When the drag force generated by the droplet exceeds the cohesive strength of the droplet with the fiber, the droplet will be carried away by the fluid. The drag force is a function of the surface tension at the interface between the droplet and the fiber.

 Another factor in the design of coagulating filters is the formation of as large droplets as possible so that they can settle (or rise) and not be carried away repeatedly by the fluid stream. When the surface velocity of the continuous liquid increases, the drag force also increases. The increased drag force is capable of moving small droplets of fibers. After the fluid passes through the coagulating filter element, it flows between the outer surface of the element and the inner wall of the vessel. The speed with which the fluid flows inside the annular space between the element and the housing wall is called the peripheral speed. If the peripheral velocity of the fluid exceeds the rate of deposition of the droplets, the droplet will not settle and will remain trapped in the fluid.

 In addition, it is advisable to reduce the pressure drop in the filter assembly. The pressure drop or pressure loss is mainly caused by restricting the flow through the filter medium and restricting the flow through the open end of the element as the fluid flows inside the element. The pressure drop in the filter assembly is the sum of the pressure drops in the housing and the coagulating element. The pressure drop in an element depends on the permeability of the fluid and the surface area. The pressure drop in the housing is mainly caused by the restriction of the connections at the inlet and outlet and the hole or restriction inside the element. When creating a conical coagulating filter element, the filter designer will need to consider these factors.

The peripheral speed can be expressed as V _a = Q / A _x , where V _a is the peripheral speed, Q is the flow velocity, A is the annular space between the filter elements. Please note that this formula is approximate. As a result of developing a filter element in which the speed will be constant along the linear length of the filter, a filter having a slightly parabolic shape will be obtained. Although this design option is within the scope of the invention, however, it is not preferred.

 After the designer has determined all of the mentioned parameters, it is possible to produce conical coagulating filter elements in accordance with the present invention in a similar manner to the known coagulating filters. Such coagulating filters may have one or more support cores, supporting layers, end caps and elastomeric seals. The medium can be made in a seamless tube by applying a vacuum to the inside of the porous mandrel and immersing the mandrel in a suspension of fibers of various compositions, as described in US Pat. Nos. 4,836,931 (Spearman) and 4,052,316 (Berger). You can also make a conical filter from the medium in a flat sheet form and roll it several times around the central core, similar to the devices shown in U.S. Patent Nos. 3802160 (Flotz), 4157968 (Kronsbein) or 3708965 (Dominik).

 The medium can be made in a flat sheet form and rolled several times around a cylindrical mandrel impregnated with a resinous binder for stiffness, after which the mandrel is removed, as shown in US Pat. Nos. 4,060,554, 4,102,785 (Head) and 4,367,675 (Perotta).

 The filter medium can also be placed in the form of corrugations. Corrugation is well known in the art.

The advantages of a coagulating conical element are obvious when comparing it with conventional cylindrical coagulating elements. The following examples compare two sizes of cylindrical elements (2.75 '' outer diameter • 30 '' long and 6 '' outer diameter • 36 '' long) (69.8 mm • 762 mm and 152.4 mm • 914 mm, respectively ) with conical coagulating elements, which are installed in the filter housing with the same inner diameter as the corresponding cylindrical element. In both examples, the fluid used is natural gas at a pressure of 1000 psi and a temperature of 60 F (16.11 ^o C).

 Example 1. With a given filter diameter, the improved conical coagulating filter element provides a lower peripheral speed and lower pressure drop than conventional cylindrical elements. In example 1, conical elements are compared with cylindrical elements at the same flow rate passing through the compared elements. The dimensions of the conical element are used, providing approximately the same surface area of the compared elements so that the pressure drop across the filter medium is the same.

 The parameters and results of the comparison are shown below, namely, the effect of using a conical shape element on the peripheral speed and pressure drop.

 In both cases, the conical element provides a lower peripheral speed than the cylindrical element (6.13 compared to 10 and 5.83 compared to 10) at the same flow rate and surface velocity. In addition, the pressure drop in the end cap (inner diameter of the base) is much lower (0.03 compared to 0.24 and 0.02 compared to 0.10).

 Example 2. The advantage of an improved coagulating filter element is the ability to pass more gas in a filter housing of a given diameter. In Example 2, the length of the conical element is increased to obtain a larger surface area compared to a cylindrical element to pass more gas through the medium at the same pressure drop (associated with surface speed) and peripheral speed in the housing.

 Below are the parameters and results of the comparison.

In both cases, the conical element provides a higher flow rate than the cylindrical element at the same peripheral speed (45 compared to 27.6 and 157 compared to 91.5). Furthermore, the pressure drop at the end (the inner diameter of the base) is substantially lower (0.08 lb / ⁱⁿ² compared to 0.24 and 0.06 lb / in ² compared to 0.1).

In FIG. 1 is a schematic view of a typical known filter design in which a hollow cylindrical filter element 20 is located inside the cylindrical body 21. The filtered liquid or gas is introduced through the inlet 22, and it extends from the inner cavity of the filter outward and moves between the filter element 20 and the cylindrical body 21 until it comes out of the filter housing. Since the peripheral speed V _a can be expressed as the quotient of dividing the flow Q by the area A between the filter element 20 and the filter housing 21, when the flow increases from 0% on the lower part of the filter element 20 to 100% on the upper side of the filter element (the area is constant ), the speed should increase. As already discussed, if the speed becomes too high, the merged liquid droplets, which usually move towards the bottom of the filter element 20, will be carried away by the air flow, and the efficiency will decrease.

 In FIG. 2 shows a schematic conical coagulating element 25 in accordance with the present invention mounted in a similar filter housing 21. The feed stream enters through the inlet 22 and moves up. As the area between the filter element 25 and the filter housing 21 increases, due to the correct design of the filter, the peripheral speed can be kept constant or reduced so that it depends on the specific parameters chosen by the filter designer.

 In FIG. 3 shows a typical T-type filter assembly 30. The filter assembly has a T-head 35 known in the art with an inlet 36 including a central opening 37. The filter head also has an outlet 38 in communication with the annular cavity 39. Together, the inlet 36 and the outlet 38 constitute filtered fluid inlet means inside the filter assembly. At the lower end of the head 35 there is a threaded portion 40 to which a retaining ring 41 can be attached by thread. The ring 41 holds the filter housing 42 having a lip 43 which is pressed against the sealing ring 45 located in the corresponding groove 46 in the head 35. It can be seen that the head 35, the retaining ring 41 and the sealing ring in combination form a sealed inner cavity 46. The inlet device 36 and the outlet device 38 are sealingly in communication with the inner cavity 46. In the center of the filter head 35 is located but means 47 for holding the filter, which is contained in the sealed inner cavity 46.

 A conical filter element 50 having a lower end 50A and an upper end 50B is sealed between an end cap 51, which is secured to the holding means 47 by a threaded connection, and an annular sealing surface 48 located around the central hole 37. In this embodiment, the annular the sealing surface 48 is integral with the filter head 35 and replaces the upper end cap, sometimes used in the T-type filter housing.

 Thus, the conical filter element 50 has its ends 50A and 50B substantially closed between a pair of closing elements, in this case an annular sealing surface 48 and an end cap 51, and is installed inside the corresponding filter housing having an input device that is tightly connected to the internal cavity filter, and exhaust device in communication with the atmosphere.

 In FIG. 4 and FIG. 5 shows a highly efficient coagulating filter assembly consisting of a plurality of elements, for example, a filter assembly made by the applicant but modified to accommodate a conical coagulating filter element in accordance with the present invention. In this embodiment, the multi-element filter assembly 60 has a filter housing 61 with an inlet 62 and an exhaust device 63. Between the inlet 62 and the exhaust device 63, there is a tube grill 64 having a plurality of openings hermetically connected to risers 65 having integral parts 65A of end caps on which a plurality of elongated conical filter elements 67 are mounted. As indicated, depending on various design considerations, the elongated conical filter elements 67 may be true cones having a rounded apex (not shown), or they may have, as shown, upper and lower sealing surfaces (67A, 67B) and can be sealed between the sealing surfaces 65A of the risers and the end cap assembly 68 held in place by the holding rod 69.

 Large contaminants and liquid unburned fuel passing through the inlet 62 are collected in the lower sump 72 and flow through the lower drain pipe 73. The remaining liquid aerosols are separated from the gas stream and flow away from the stream using coagulating elements 67. If necessary, the contents of the upper the sump is discharged through the upper downpipe 71.

 In FIG. 6 shows a filter element 80 with a filter material 81 of a conical shape. The cone-shaped filter material 81 is enclosed in a support shell 82, which can be any suitable sheet material. The supporting shell 82 is placed inside the outer supporting frame 83. The diameter of the external supporting frame is equal to or slightly less than the diameter of the supporting shell 82 together with the filter material 81 located therein.

 In FIG. 7 shows another design of the filter, which is similar to the filter shown in FIG. 6, and differs from it by the presence of an internal supporting frame and an internal supporting shell. The filter shown in Fig. 7 has an inner supporting frame 85 located inside the inner supporting shell 84, which can be made of any suitable sheet material. The inner support shell 84 is located inside the cone-shaped filter material 81. The filter material 81 is placed in the outer support shell 82, which in turn is placed in the outer support frame 83. The dimensions of all filter elements are such that the filter assembled from them has an upper annular sealing surface 86 and the lower annular sealing surface 87.

 Thus, the present invention describes a new conical coagulating filter element and various filter assemblies that can be used in conventional filters to achieve their improved performance.

Claims (9)

 1. A porous filter element of a conical shape made of randomly oriented fibers through which the flow flows from inside to outside and which has an upper and lower annular sealing surface, characterized in that it has an external supporting structure, the strength of which is sufficient to serve radial support of the porous filter element and the inner diameter of which is equal to or slightly less than the outer diameter of the porous filter element, which is completely based on this the structure and the outer supporting structure together with the porous filter element are wrapped in at least one layer of sheet material.  2. The element according to claim 1, characterized in that the fibers are glass fibers and at least one layer of thin sheet material that wraps tightly around it is wound around the porous filter element.  3. The element according to claim 1, characterized in that it is made of a filter material, which in the initial state has the form of a flat sheet.  4. The element according to claim 3. characterized in that the filter material is folded during manufacture.  5. An element according to any one of claims 1 to 3, characterized in that the fibers are borosilicate glass fibers.  6. The item according to any one of paragraphs. 1 to 5, characterized by the presence of an internal supporting structure of a conical shape and an inner layer of sheet material wound on an internal supporting structure.  7. A filter assembly comprising a filter installed in a housing with an input device tightly communicating with the internal cavity of the filter and an exhaust device communicating with the atmosphere, characterized in that the filter is made according to claim 6.  8. A filter assembly comprising a filter housing with inlet and outlet devices, several conical filter elements installed in the housing and having upper end caps, a lower settler located below the inlet device, and a tube sheet with several holes that is located between the inlet and outlet devices , characterized in that it is equipped with several risers, hermetically connected to the holes of the tube sheet and having at their upper ends made with them for one sealing on top spine on which it is installed conical filter elements, which seal is accomplished sealing surfaces and risers upper end caps, an upper sump located above the tube sheet and the upper drainage in communication with the upper sump.  9. The node of claim 8, characterized in that it is equipped with a lower sump located under the inlet device and the lower drainage in communication with the lower sump.

Images