WO2017049600A1

WO2017049600A1 - Multi-media filter with spiral flow element

Info

Publication number: WO2017049600A1
Application number: PCT/CN2015/090754
Authority: WO
Inventors: Chen Wang; Todd Alan Anderson; Su Lu; Hua Li; XueLian Gong
Original assignee: General Electric Company
Priority date: 2015-09-25
Filing date: 2015-09-25
Publication date: 2017-03-30
Also published as: TW201722544A

Abstract

A filter has a spiral flow (SF) membrane element (10) combined with a second filtration element (60). The second element (60) is preferably in the form of a hollow tube and the SF element (10) is located inside of the second element (60). Both elements are contained within a common housing (42). The housing (42) has an inlet (44) and a filtered water outlet (46), which are separated by the two elements in series. Examples are illustrated in which the pre-filter is a cartridge filter (such as a depth or surface filter), a packed bed and another spiral flow element. In a filtration process, feed water travels radially through two filtration elements in series. Essentially all of the water treated by the second element may also be treated by the SF element (10). The SF element (10) may separate the feed water into permeate and concentrate streams.

Description

MULTI-MEDIA FILTER WITH SPIRAL FLOW ELEMENT

FIELD

This invention relates to membrane separation, for example reverse osmosis or nanofiltration, and to spiral flow separators and to methods of making them.

BACKGROUND

Spiral flow and spiral wound membrane elements both use one or more flat sheet membranes wrapped, with feed and permeate spacers, in a spiral around a core. Once wrapped, the membrane and spacers form a generally cylindrical element with two circular ends. In a spiral wound membrane, feed water enters one circular end of the element and flows across the membrane parallel to the central axis of the cylinder. Permeate flows perpendicular to the central axis in a spiral towards the core and is exhausted from the core. Concentrate (also called retentate or brine) exhausts from the other circular end of the element. In a spiral flow element, feed water enters the element through the lateral side of the cylinder between the circular ends. Feed water and permeate both flow across the membrane perpendicular to the central axis in a spiral towards the core. Permeate and concentrate, if any, are both exhausted from the core.

International Publication Number WO 2010/044961, entitled Spirally Wound Membrane Separator Assembly, describes a spiral wound element. The element has a membrane stack assembly and a central core element. The membrane stack assembly comprises a feed carrier layer, a permeate carrier layer, and a membrane layer. The central core element comprises a concentrate exhaust conduit and a permeate exhaust conduit. The concentrate exhaust conduit and the permeate exhaust conduit are separated by a first portion of the membrane stack assembly. A second portion of the membrane stack assembly forms a multilayer membrane assembly disposed around the central core element. The feed carrier layer is in contact with the concentrate exhaust conduit and not in contact with the permeate exhaust conduit. The permeate carrier layer is in contact with the permeate exhaust conduit and not in contact with the concentrate exhaust conduit. The permeate carrier layer does not form an outer surface of the separator assembly.

In an example, the central core assembly is in the form of two porous half cylinders, one being the concentrate exhaust conduit and the other being the permeate exhaust conduit. These conduits are separated from each other by the membrane stack assembly, which is positioned with its permeate carrier layer against the permeate exhaust conduit and its feed carrier layer against the concentrate exhaust conduit. Parts of the membrane stack assembly extend outwards from the central core element in both directions before the element is wound up. In particular, the membrane layer and permeate carrier layer extend outwards from one side of the central core element and the feed carrier layer and the membrane layer extend outwards from the other side of the central core element. When the central core element is rotated, the membrane stack assembly is wound around the central core element such that the permeate carrier layer is wrapped around and in direct contact with the permeate exhaust conduit. The feed carrier layer is wrapped around and in direct contact with the exhaust conduit. The membrane stack assembly is sealed at the circular ends of the cylinder. Any edge of the permeate carrier layer that would otherwise be open to the lateral side of the cylinder is also sealed. Feed water can only enter the spiral from a feed carrier layer open to the lateral side of the cylinder.

International Publication Number WO 2010/044970, entitled Spirally Wound Membrane Separator Assembly, describes a similar spiral flow element. However, this element has two permeate exhaust conduits and no concentrate exhaust conduit.

International Publication Number WO 2012/166834, entitled Central Core Element for a Separator Assembly, describes another spiral flow element. In this element, the central core assembly comprises a permeate exhaust conduit located inside of a concentrate exhaust conduit. The membrane stack assembly is wrapped around the permeate exhaust conduit, passes through a gap in the concentrate exhaust conduit, and is then wrapped in a spiral around the concentrate exhaust conduit.

INTRODUCTION

This specification describes a filter in which a spiral flow (SF) element is combined with a second filtration element. Preferably, the second element is in the shape of a hollow tube and the SF element is located inside of the second element. Both elements are contained within a common housing. The housing has an inlet and a filtered water outlet, which are separated by the two elements in series. Examples are illustrated in which the pre-filter is a cartridge filter (such as a depth or surface filter) , a packed bed and a membrane filter, for example a spiral flow element with a different pore size.

This specification also describes a filtration process in which feed water travels radially through two filtration elements in series. One element, typically the downstream element, is a spiral flow element. Essentially all of the water treated by the upstream element may also be treated by the downstream element. The downstream element may separate the feed water into permeate and concentrate streams.

In conventional filtration systems, pre-filters may be located in separate units from membrane filtration elements. Combining multiple elements in one housing can reduce total system cost, complexity or footprint. Combining a spiral flow element with another radial flow element allows for a simple combined housing. For example, internal baffles are not required to redirect flow between the elements. The outer filter may also benefit from having an inner diameter large enough to accommodate the SF element. Surface area increases with diameter, while the ratio of outer diameter to inner diameter for a given filter thickness decreases with diameter. Either of these factors may make a large diameter outer filter desirable, but volume at the center of the housing might be wasted if it were not occupied by the SF element.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a drawing of a spiral flow (SF) element.

Figure 2 is a drawing of a composite filter having an SF element inside of a cartridge filter.

Figure 3 shows a process for assembling the filter of Figure 2.

Figure 4 shows the filter of Figure 2 in a housing.

Figure 5 is a drawing of another composite filter having an SF element inside of a packed bed.

Figure 6 shows a process for assembling the filter of Figure 5.

Figure 7 shows the filter of Figure 5 in a housing.

Figure 8 is a drawing of another composite filter having an SF element inside of another SF element.

Figure 9 shows a process for assembling the filter of Figure 8.

Figure 10 shows the filter of Figure 8 in a housing.

DETAILED DESCRIPTION

Figure 1 shows a spiral flow (SF) element 10. The SF element 10 has a membrane stack assembly 12 and a central core element 14. The membrane stack assembly 12 has a feed carrier layer, a permeate carrier layer, and a membrane layer. At least part of the membrane stack assembly 12 is wrapped around the central core element 14. The central core element 14 has a concentrate exhaust conduit 16 and a permeate exhaust conduit 18. The feed carrier layer is in contact with the concentrate exhaust conduit and not in contact with the permeate exhaust conduit. The permeate carrier layer is in contact with the permeate exhaust conduit and not in contact with the concentrate exhaust conduit. The permeate carrier layer is not in communication with the outer surface of the SF element 10. Alternatively, the central core element 14 might not have a concentrate exhaust conduit 16, and there may be two permeate exhaust conduits 18. The SF element 10 may be made as described in International Publication Number WO 2010/044961, International Publication Number WO 2010/044970, or International Publication Number WO 2012/166834, all of which are incorporated herein by reference.

The membrane stack assembly is configured to leave part of the feed carrier layer 26 exposed at the outer lateral side of the cylinder (or tube) formed by the membrane stack assembly 12. When in use, feed water 20 enters the SF element 10 from the outer lateral side of the SF element 10 and flows through the feed carrier layer 26 towards the central core element 14. The membrane layer within the membrane stack assembly 12 allows at least some of the feed water 20 to pass through the membrane layer to the permeate carrier layer. Permeate 24 travels through the permeate carrier layer and is exhausted from the central core element 14. Optionally, a portion of the feed water 20 may flow through the feed carrier layer 26 to the central core element 14 and be exhausted as concentrate 22.

Figure 2 shows a first composite filter 30. The first composite filter 30 has an SF element 12 located inside of a cartridge filter 32. The cartridge filter 32 may be made with any filtration media that can be provided or packaged in a freestanding tubular form. Examples of cartridge filters include depth filters such as melt blown filters, surface filters such as pleated filters, porous ceramic tubes and sintered tubes. Some cartridge filters include granular material, for example granular activated carbon. Cartridge filters are typically designed for use in dead end filtration wherein all of the feed water applied to the outside of the filter emerges from the inside of the filter.

The exemplary cartridge filter 32 shown in Figure 2 is made up of multiple filter layers 34, 36 and 38. Each

layer

34, 36 and 38 is made with one or more melt spun (also called melt blown) filaments. The size of solid particles retained in each

layer

34, 36, 38 decreases towards the inside of the cartridge filter 32. Alternatively, media types may be mixed. For example, a pleated filter may be used outside or inside of a depth filter. Alternatively, the cartridge filter 32 may have one, two, or more than three layers.

When in use, feed water 20 flows radially through the cartridge filter 32 and then flows through the SF element 12. Some of the solid particles in the feed water are retained and accumulate in the cartridge filter 32. When the cartridge filter 32 reaches its limit of accumulated solids it is removed. The removed cartridge filter 32 may be cleaned and returned to service, or disposed and replaced with a new cartridge filter 32.

Referring to Figure 3, the first composite filter 30 is made by inserting the SF element 12 inside of the cartridge filter 32. In the example shown, the

layers

34, 36, 38 are added to the SF element 12 individually. End caps, not shown, similar to end caps conventionally used with cartridge filters, are added to

layers

34, 36, 38. Preferably, the

layers

34, 36, 38 are pre-assembled into a cartridge filter 32, and optionally have ends caps attached, before being placed over the SF element 12. A small difference, for example 1-2 mm, between the outside diameter of the SF element 12 and the inside diameter of the cartridge filter 32 allows the cartridge filter 32 to slide over the SF element 12.

Figure 4 shows a filtration unit 40 having the first composite filter 30 inside of a housing 42. Feed water 20 enters the housing 42 through an inlet 44. The permeate exhaust conduit 18 is sealed, for example with O-rings not shown, to a permeate outlet 46 of the housing 42. The concentrate exhaust conduit 16 is sealed, for example with O-rings not shown, to a concentrate outlet 48 of the housing 42. End caps 50 at the ends of the cartridge filter 32 are sealed to the ends of the housing 42 by rubber rings 52. In an alternative construction, a protrusion from the housing 42 seals against a ring embedded in the end caps 50. Other methods typically used to seal the end of a cartridge filter to a housing may also be adapted. The end caps 50 force feed water to flow radially through the cartridge filter 32 and prevent feed water 20 from flowing into the ends of the cartridge filter 32. Seals at the ends of the SF element 12 prevent feed water 20 from bypassing to the central core element 14. The rubber rings 52 prevent feed water 20 from reaching the SF element 12 without flowing through the cartridge filter 32. Alternatively, end caps 50 can be sealed to the ends of the SF element 12 and rubber rings 52 omitted. However, this is not a preferred construction because it makes it more difficult to replace a cartridge filter 32 without replacing the SF element 12.

Figure 5 shows a second composite filter 60. The second composite filter 60 has a SF element 12 located inside of a packed bed filter 62. The packed bed filter 62 has many discrete pieces of media 64 that are packed in contact with each other but not bonded or otherwise attached to each other. The media 64 is typically granular, such as activated carbon granules. The media 64 may provide filtration for an appropriate size of particle, but it is not necessary for the media 64 to provide any significant filtration in a particular application. For example, activated carbon, zeolite or other sorption media 64 may be used primarily to provide sorption in an application where few, if any, particles in the feed water 20 are large enough to be filtered out by the media 64. In other examples, the media 64 provide chemical treatment, for example ion exchange using resin bead media 64, or provide biological treatment, for example by having a fixed biofilm supporting media 64. Mixtures of different types of media 64 may also be used.

The media 64 is held between an outer mesh 66 and an inner mesh 68. The outer mesh 66 and the inner mesh 68 are porous to permit feed water 20 to flow through them. However, the pores are small enough to retain the media 64. A top cap 72 and bottom cap 70 complete, in combination with the outer mesh 66 and inner mesh 68, a pre-treatment vessel 78 containing the media 64. In the example shown, the

caps

70, 72 also extend and seal (for example with a rubber ring not shown) to the central core element 14 or the ends of the SF element 12. The inner mesh 68 may be located, for example, 1-2 mm outside of the SF element 12. The outer mesh 66 may be located, for example, 3-5 cm outside of the SF element 12.

When in use, feed water 20 flows radially through the media 64 and then flows through the SF element 12. The

caps

70, 72 prevent the feed water 20 from flowing into the ends of the packed bed filter 62 and prevent the feed water 20 from by-passing the packed bed filter 62 on its way to the SF element 12. Some solid particles in the feed water may be retained and accumulate in the packed bed filter 62. When the packed bed filter 62 reaches its limit, for example of retained solids, sorption, ion exchange etc., the media 64 is removed and either cleaned (or otherwise regenerated) and returned to service, or disposed and replaced with new media 64.

Referring to Figure 6, the second composite filter 60 is made by assembling part of the pre-treatment vessel 78. Initially, the outer mesh 66 and inner mesh 68 are attached only to the bottom cap 70. The attachment may be by, for example, an adhesive, chemical or sonic welding, or a press, screwed or interference fit. The SF element 12 is placed inside of the pre-treatment vessel 80 with the central core element 14 passing through the bottom cap 70. The media 64 is added between the outer mesh 66 and the inner mesh 66, either before or after adding the SF element 12. The top cap 72 is added over the central core element 14 of the SF element 12 and the media 64 and attached to the inner mesh 68 and outer mesh 66. The top cap 72 may be attached as described for the bottom cap 70. Preferably at least one of the

caps

70, 72 is removable to allow the media 64 to be removed and replaced.

Figure 7 shows a filtration unit 80 having the second composite filter 60 inside of a housing 42. Feed water 20 enters the housing 42 through an inlet 44. The permeate exhaust conduit 18 is sealed, for example with O-rings not shown, to a permeate outlet 46 of the housing 42. The concentrate exhaust conduit 16 is sealed, for example with O-rings not shown, to a concentrate outlet 48 of the housing 42. Feed water 20 flows radially through the packed bed filter 62 and then through the SF element 12.

Figure 8 shows a third composite filter 90. The third composite filter 90 has a SF element 12 located inside of a membrane filter 92. The membrane filter 92 preferably has a larger pore size than the SF element 12. For example, the membrane filter 92 may be an ultrafiltration or microfiltration membrane.

The membrane in the membrane filter 92 is in the form of a flat sheet wrapped in a spiral around the SF element 12. The membrane filter 92 may have one or more membrane sheets. Additional layers, such as a feed carrier layer, permeate carrier layer or an impervious layer, are added as appropriate. In the example shown, an assembly 94 of a permeate carrier layer, membrane layer, feed carrier layer and an impervious layer (or second membrane layer) is wrapped around the SF element 12. The permeate carrier layer is in fluid communication with the SF element 12. The membrane layer and the impermeable layer are sealed together at their edges on the inner lateral side of the spiral, or a membrane sheet is folded around the feed carrier layer to produce two membrane layers with the fold in the inner lateral side of the spiral. The impermeable layer (or one of the membrane layers) is preferably shorter than the feed carrier layer so that some of the feed carrier layer is exposed on the outer lateral side of the spiral. The edges of the layers at the base and top of the spiral are sealed, for example with adhesive applied between the layers before the assembly 94 is wound around the SF element 12. The membrane layer separates a permeate carrier layer, which is in fluid communication with the SF element 12, from a feed carrier later, which is not in fluid communication with the SF element 12.

When in use, feed water 20 flows radially (and in a spiral) through the membrane filter 92 and then flows through the SF element 12. All of the feed water 20 reaching the SF element 12 passes through the membrane layer. Plates 96 prevent the feed water 20 from bypassing the membrane filter 92 on its way to the SF element 12. Optionally, the edges of the SF element 12 or the membrane filter 92 or both may be left unsealed at the base and top of their spirals when they are rolled up. In this case, the plates 96 are used to seal these edges. Alternatively, the edges of the SF element 12 and the membrane filter 92 at the base and top of their spirals may be sealed as these elements are rolled. In that case, the plates 96 are configured to seal the ends of the SF element 12 to the ends of the membrane filter 92. For example, the plates 96 may be compressed against the SF element 12 and the membrane filter 92 by screwing the plates 96 onto threads provided in the central core element 14. In this option, the membrane filter 92 is removable from the SF element 12.

Referring to Figure 9, the third composite filter 90 is made by wrapping the assembly 94 around the SF element 12. Optionally, the permeate carrier layer of the assembly 94 may extend into the SF element 12 in contact with the feed carrier layer of the SF element 12. The membrane stack assembly of the SF element 12 and the assembly 94 may be rolled around the central core element 14 in one continuous rolling step. Alternatively, the assembly 94 may be rolled around a previously rolled SF element 12. Preferably, a glue line 98 is added at lateral outside edge of the assembly 94. The glue line 98 is added on the side of the membrane layer in contact with the permeate carrier layer. When the assembly 94 is rolled up, the glue line 98 cures and seals the outside lateral edge of the permeate carrier layer. The plates 96 are added after the assembly 94 has been rolled.

Figure 10 shows a filtration unit 100 having the third composite filter 90 inside of a housing 42. Feed water 20 enters the housing 42 through an inlet 44. The permeate exhaust conduit 18 is sealed, for example with O-rings not shown, to a permeate outlet 46 of the housing 42. The concentrate exhaust conduit 16 is sealed, for example with O-rings not shown, to a concentrate outlet 48 of the housing 42. Feed water 20 flows radially (and in a spiral) through the membrane filter 92 and then radially (and in a spiral) through the SF element 12.

The examples shown in the Figures are intended to help provide an enabling disclosure of the invention but other composite filters may also be constructed. In the examples described above, the feed water flows radially inwards. However, alternative devices may be made in which the feed water flows radially outwards, for example starting from a central core element 14 and ending at the lateral side of a housing 42. In the examples described above, the SF element 12 is located inside of another filter. However, alternative devices may be made in which another filter is inside of the SF element 12, with feed water flowing radially inwards or radially outwards.

Claims

An apparatus comprising,

a spiral flow membrane filter element； and,

a second filtration element,

wherein the second filtration element is concentric with the spiral flow element and one is inside of the other.
The apparatus of claim 1 wherein the second filtration element is outside of the spiral flow element.
The apparatus of claim 1 or 2 wherein the second filtration element is selected from the group consisting of, a cartridge filter, a packed bed filter and a membrane filter.
The apparatus of claim 3 wherein the second filtration element is a cartridge filter.
The apparatus of claim 3 wherein the second filtration element is a packed bed filter.
The apparatus of claim 3 wherein the second filtration element is membrane filter.
The apparatus of claim 6 wherein the second filtration element is a spiral flow membrane filter.
The apparatus of any preceding claim wherein the second filtration element is removable from the spiral flow element.
The apparatus of any preceding claim wherein the spiral flow element and the second filtration element are contained within a common housing.
The apparatus of claim 9 wherein the housing has an inlet and a filtered water outlet, wherein the inlet and filtered water outlet are separated by the spiral flow element and the second filtration element in series.
A process comprising the steps of,

a) flowing feed water radially through a spiral flow element,

b) flowing the feed water radially between the spiral flow element and a second filtration element； and,

c) flowing the feed water radially though the second filtration element.
The process of claim 11 wherein step c) occurs upstream of step b) which occurs upstream of step a) .
The process of claim 11 or 12 wherein the feed water flows radially inwards in steps a) , b) and c) .
The process of any of claims 11 to 13 wherein essentially all of the water treated by the upstream element is also treated by the downstream element.
The process of any of claims 11 to 14 wherein the downstream element separates the feed water into permeate and concentrate streams.