Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
  • B01D63/06—Tubular membrane modules
  • B01D63/066—Tubular membrane modules with a porous block having membrane coated passages
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/10—Supported membranes; Membrane supports
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2311/00—Details relating to membrane separation process operations and control
  • B01D2311/16—Flow or flux control
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2325/00—Details relating to properties of membranes
  • B01D2325/20—Specific permeability or cut-off range

Definitions

• the present invention relates to a porous support for tangential filtration and its method of preparation.
• the invention relates in particular to such a porous support made of sintered ceramic, sintered glass, sintered metal or carbon material, pierced with one or more longitudinal and parallel channels, and whose surface of said channels is covered with one or more filtering layers.
• a sintered or organic ceramic material in which circulates a liquid to be purified or concentrated, or in general a fluid to be treated.
• the porous support assembly and filter layer is referred to below as the membrane.
• the fluid to be treated arrives through an inlet chamber at an inlet end of the porous support or block (macro), flows in the channels to an outlet end, to an outlet chamber ; a fraction of liquid to be treated or permeate passes radially through the layer and the macroporous support, before being collected in the permeate-side outlet chamber.
• the liquid to be treated circulates along the channel or channels, and this flow induces a pressure drop between the inlet and the outlet of said channels.
• This pressure drop depends on a set of parameters such as, for example, the speed of the liquid to be treated or purified in the channel, the viscosity of said liquid, as well as the hydraulic diameter of the channel.
• This decreasing variation in the pressure of the liquid to be treated along the channel or channels modifies the transverse flow of the permeate which passes through the filtering layer and then the macroporous body.
• transverse pressure drop which is the difference between the pressure of a point of the channel and the pressure of the permeate chamber, according to the direction of circulation of the liquid in the channel or channels.
• This decrease can affect the performance of the filtration device, for example by reducing the permeate flow, or by modifying for example the retention threshold, and also, by establishing different filtration regimes along the channel or channels.
• the inlet pressure in the channels is 3.8 bar
• the outlet pressure of the channels is 2 bar
• the pressure in the chamber of permeate outlet is constant, for example 1.5 bar.
• the transverse pressure drop varies along the membrane from 2.3 to 0.5 bar.
• US Pat. No. 4,105,547 discloses a tangential filtration device using an auxiliary compensation system for the longitudinal pressure drop.
• Said ancillary system consists in that the outer surface of the support on the permeate side is swept by the permeate which circulates in the same direction as the liquid to be treated so as to create in the permeate chamber a longitudinal pressure drop such as the loss. Transverse load remains approximately constant along the filter.
• Patent EP-A-0 333 753 describes an embodiment of this device that makes it possible to compensate for this variation in transverse pressure drop induced by the circulation of a liquid inside one or more channels.
• said system consists in that a permeate circulation is established on the outer surface of a tubular membrane, a porous support pierced with a channel or a porous block also pierced one or more channels.
• Such filtering media may be assembled individually or in a bundle in a housing where the permeate chamber is filled with filler bodies such as beads or granules which induce a longitudinal flow resistance of the permeate which is likely to counterbalance the variation of longitudinal pressure drop induced by the circulation of the liquid to be treated in the channel or channels covered with a filter layer.
• EP-A-0 870 534 describes a macroporous support having a permeability gradient in the direction of flow of the fluid to be treated.
• This macroporous support preferably has a mean porosity gradient on the belt in the direction of flow of the fluid to be treated, the average porosity increasing in said direction of flow.
• Document FR-A-2,846,255 describes a membrane for the tangential filtration of a fluid to be treated, said membrane comprising a porous support delimiting at least one circulation channel for the fluid to be treated flowing in a given direction between an inlet and an outlet, the inner surface of the porous support delimiting the channel being covered by at least one separation layer for the fluid to be treated, a fraction called permeate passing through the separation layer and the porous support.
• the support has a variable partial blockage extending from the inner surface of the support on which the separation layer is deposited, said clogging creating, on a wafer of the support of given constant thickness extending from the inner surface of the support, a mean porosity gradient, according to the direction of circulation of the fluid to be treated, the minimum mean porosity being located at the inlet and the maximum mean porosity at the outlet.
• FR-A-2797198 discloses a membrane for the tangential filtration of a fluid to be treated, said membrane comprising an inorganic rigid porous support delimiting at least one circulation channel for the fluid to be treated circulating in a given direction, the channel surface being covered by at least one separating layer of the fluid to be treated, in a fraction called permeate passing through the layer and the support.
• the separation layer has a thickness gradient decreasing in the direction of flow of the fluid to be treated.
• the object of the invention is to provide a simpler preparation filtration support.
• the invention relates to a porous support for tangential filtration with a coating surrounding the outer surface of the support, the coating having one or more fluid discharge ports through the outer surface.
• the coating has several lumens along the support, the interval between two lumens decreases in the direction of flow of the fluid to be treated.
• the lights have a surface that increases in the direction of flow of the fluid to be treated.
• the light or lights have a shape chosen from the group comprising rings concentric with the longitudinal axis of the support, a spiral around the longitudinal axis, holes of geometric shape defined or indefinite.
• the coating material is selected from a group consisting of a porous material, a polymer, a polymer blend, or a plastic sheath.
• the invention also relates to a membrane comprising a support as defined above in association with a filtration layer.
• the invention also relates to a module comprising one or more supports or membranes as defined above.
• the invention also relates to a method of preparing a support as defined above, in which the outer surface of the support is surrounded by a coating and in which lights are made through the coating.
• the outer surface is surrounded by coating of the support.
• the outer surface of the support is partially masked by masks during the coating, the masks then being removed.
• the support is immersed in a half-length coating solution.
• the outer surface is surrounded by coating by an inking roller system or by spraying.
• the outer surface is surrounded by thermoforming of the coating.
• the coating is pierced.
• the invention also relates to the use of a membrane as defined above for tangential filtration.
• FIG. for tangential filtration Figure 2 is a side view of the support of Figure 1; Figures 3 and 4 of the graphs with reference to Example 1; Figures 5 to 9 of the membrane configurations and graphs with reference to Example 2.
• the invention relates to a porous support for tangential filtration with a coating surrounding the outer surface of the support; the coating has one or more fluid discharge ports through the outer surface.
• the coating provided with light makes it possible to create preferential passage zones for the fluid in the support towards the outside. This makes it possible to create a pressure in the support so as to create a transmembrane pressure in a simpler way.
• Figure 1 shows a support 10 for tangential filtration.
• the support 10 shown is elongated along the axis 1 1.
• the support may be about one meter long.
• the support has a tubular shape.
• the support may have a circular cross section; the outer diameter of the support may be 10 or 25 mm, for example.
• the support 10 may also comprise a transverse cross section of another shape, such as polygonal.
• the support 10 is bounded outwards by an outer surface 12.
• the support 10 is pierced by one or more channels 14a, 14b, 14c ... of passage of the fluid to be treated.
• the channels may have identical geometry and equivalent hydraulic diameter or variable sizes.
• the channel or channels are optionally covered with a filter layer, the support and the layer forming a membrane.
• the filtration layer is intended to be in contact with the fluid to be treated.
• the filtration layer is characterized by a retention threshold or cutoff threshold; this threshold is relative to the size of the filtered molecules in the fluid to be treated.
• the direction of the flow of the fluid to be treated is indicated by arrows, so as to define an inlet end 16 and an outlet end 18 of the support 10.
• the fluid to be treated is separated between the permeate which flows to through the support in a direction transverse to the longitudinal axis and the retentate which continues its flow along the channels.
• the transverse pressure drop is defined so as to obtain a filtration regime compatible with the nature of the liquid to be treated. It is therefore adapted in advance to the flow velocity in the channel or channels of the fluid to be treated, and to the viscosity characteristics and the filtration rate of said fluid.
• the support 10 further comprises a coating or envelope 20 surrounding the outer surface 12 of the support 10.
• the coating is integral with the support which allows to place the support equipped with the coating in a conventional module without adaptation of the module.
• the coating only partially surrounds the outer surface, in that the entire outer surface 12 is not surrounded by the coating 20. Areas of the outer surface 12 are left free.
• the fluid flowing radially in the support 10 may flow out of the support by these zones, in particular to the permeate chamber.
• the coating 20 partially surrounds the outer surface, the coating thus has one or more fluid discharge ports 22 through the outer surface.
• the coating In the presence of the coating it is possible to channel the flow of permeate within the support towards the lights; this allows to create a pressure on the side of the filter layer facing the support. This avoids an excessive pressure difference on either side of the filter layer, this pressure difference may be detrimental to the quality of the filtration. This pressure difference is also detrimental to maintaining the retention threshold (or cutoff threshold), and therefore detrimental to the integrity of the layer. It is thus possible to obtain high fluxes while having a separation power adapted and stable over time.
• the lights 22 are distributed along the support evenly or not.
• the shape, number and arrangement of the lumens 22 are such that higher filtration performance is obtained than that obtained on an uncoated substrate.
• the disposition, the shape and the number of lights are also chosen according to the size of the molecules of the fluid to be treated and the clogging power of the fluid to be treated (depending on whether water or milk is treated, for example).
• the slots 22 may for example be holes on part of the circumference of the support or be in the form of rings centered on the axis 11 of the support.
• the lights are ring-shaped, which ensures a simplicity of preparation of the support.
• the ring-shaped lights make it possible to maintain the symmetry of the support; at the height of the rings, in cross section of the support, the pressure in the support is substantially the same.
• the lights may also be one or more spirals wound around the longitudinal axis of the support; the pitch of the spiral or spirals can be adjusted to adjust the passage of the permeate.
• the lights may be geometrically defined holes such as circular, square or triangular holes, or indefinitely shaped holes. The holes can be arranged in rings along the support or in the form of a spiral.
• the lumens 22 are evenly distributed along the support being spaced apart from the same gap constituted by the coating 20.
• the interval between two lumens decreases in the direction of flow of the fluid to be treated.
• the interval between two lumens can decrease continuously from one end to the other of the support in the support; alternatively, the interval between two lumens may decrease in steps from one end to the other of the support.
• the bearings may be regular or not.
• the interval considered is between two neighboring lights. By neighboring lights is meant two consecutive lights, angularly offset or not along the support.
• the advantage of the decreasing interval is that the pressure within the support is better controlled. Indeed, by decreasing the gap between the lights in the direction of flow of the fluid, it is possible to reduce the pressure in the support because the fluid flowing transversely is removed more easily out of the support. Thus, since the pressure in the channels decreases in the direction of flow, it is possible to control the transmembrane pressure because it is also possible to reduce the pressure in the support; the transmembrane pressure can even be constant along the support by placing the lights on the outer surface so as to create the same pressure gradient in the support and in the channel. It is thus possible to maintain the permeate flow rate and maintain the cutoff threshold of the filtration layer.
• the same effects and benefits can be obtained by keeping the interval between lights along the support but increasing the surface of the lights in the direction of flow of the fluid to be treated. These effects and benefits can be further enhanced by combining the variation of the gap and the variation of the surface of the lights.
• the coating 20 may be sealed in that the coating 20 does not pass the fraction of the fluid flowing radially in the support; the coating 20 does not allow the permeate to pass through it.
• the coating is impermeable to permeate. In FIG. 1, the fluid flowing radially in the support 10 can not access the permeate chamber through the coating 20.
• the material retained for the coating is chosen to allow retention of the permeate.
• the coating 20 may be a polymer or a mixture of PTFE and Xylene type polymers; it may be an AS48 reference polymer solution from SAPPI.
• the coating 20 may also be a plastic sheath.
• the coating 20 may be porous.
• the coating then has a cutoff threshold which is greater than the cutoff threshold of the filtration layer.
• the fluid flowing radially in the support is able to be discharged through the porous coating, the fluid preferably flows to the fluid discharge ports. This creates a pressure within the support.
• the advantage is that the coating 20 may be stronger than before; in particular, the coating 20 may be more resistant to cleaning solutions of the membrane.
• the material used for the coating 20 may be for example the type of material used for the filter layer on the inner surface of the channels.
• FIG. 2 shows an exemplary embodiment of the support 10.
• the support 10 has an inlet end 16 and an outlet end 18.
• the support 10 is for example of a porosity of 0.1 ⁇ m and may comprise 19 channels.
• the support comprises the outer surface 12 surrounded by the coating 20.
• the coating 20 delimits the slots 22.
• nine envelope sections 20 are delimited and separated by a light 22.
• the sections 1 to 7 have a similar dimension for example 15 cm long, the section 8 has a smaller dimension, for example 11 cm long, and the section 9 has an even smaller dimension, for example 3 cm long.
• the lights 22 are for example 1 mm long. In this example, the lights have an identical surface, but are separated by an interval that decreases in steps in the direction of flow. Of course, these dimensions are given as an example; this type of arrangement will be adjusted according to the membrane and the application.
• the support may be prepared by a preparation process during which the outer surface of the support 12 is surrounded by the coating 20 and in which lights are created through the coating.
• the advantage of the method is that it is simple and thus easily allows to create a pressure within the support.
• the deposition of the coating is simpler than in the prior art where it is necessary to modify the porosity of the support itself. In this case, it is sufficient to deposit the coating on the outer surface of the support.
• the coating can surround the outer surface by thermoforming. It is then a question of placing the support in a sheath and of thermoforming the sheath over the entire length of the support and then to pierce lights in the sheath.
• the lights 22 are for example obtained by masking the outer surface 12 by an outer sheath or with the aid of rubber bracelets, the sheath making it possible to obtain lights of larger size.
• the bracelets are threaded along the support at the desired locations of the lights. This has the advantage of being easy to handle.
• the support 10 carrying the masks is dipped in a coating solution.
• the advantage of this way of proceeding is that the most hardened support parts are a soaking time closer than the soaking time of the less soaked support parts. This makes it possible to obtain a more homogeneous coating of the support, in particular for a manual operation.
• the soaking time is for example at most 4 seconds, preferably 2 seconds.
• the coated support can be initially dried at room temperature for a few hours and then dried at 340 ° C for 24 hours.
• the ends of this support can be plugged.
• the supports or membranes as described above can be placed in a module.
• the supports or membranes are in communication with a permeate chamber for collecting the permeate discharged by the supports or membranes.
• the module comprises an installation for circulating the fluid to be treated in the various supports or membranes.
• the transmembrane pressure is regulated at the level of the supports or membranes themselves; the advantage is that the module is of a simple construction. It can even have supports or membranes in existing modules, without special adaptation.
• the coating can be applied by any method of coating (or coating) of the spray type or inking rollers. These processes are automated, resulting in a more homogeneous coating.
• Figure 3 shows the passage of serum proteins and shows a comparison of the membranes.
• the curve KB37WM1M2 is the curve obtained with a support provided with a coating.
• the curve KWM2 is the curve obtained with a standard support. Note the coated support allows better recovery of "serum" proteins.
• Figure 4 shows the retention of caseins and a comparison of membranes. At this stage, the comparative measurements were made by measuring turbidity (permeate staining).
• the supports of KBT M1, KBT M3 (27 channels) and KW M2 (19 channels) are not coated and the KB37 curve WM1M2 is a coated carrier. It can be seen that the support provided with the coating makes it possible to have less "caseous" cheese proteins in the permeate. With both figures 3 and 4 it can be seen that a better selectivity is obtained with the support provided with a coating.
• transmembrane pressure on permeate flow and retention is performed. During these tests, the transmembrane pressures will be gradually increased in increments (+0.2 bar increase with stabilization for 15 minutes). The flux measurements are made by compensated weighing of the density of the product, individually per module. Protein analyzes are performed in a standard way by the dairy industry. The raw material is pasteurized skim milk received cold (4 0 C) and will be heated for testing at 50 ° C. The test is started with the permeate compartment full of water to have a good control of transmembrane pressure.
• the membranes 12 are covered with a coating 20.
• the coating 20 comprises slots 22 in the form of rings arranged along the length and centered on the axis 11.
• the slots 22 are 1 mm in the direction of flow.
• the lights 22 delimit and separate sections.
• Configuration 2 has nine sections. The first seven sections are 147 mm long, the eighth section is 109 mm and the last section is 32 mm long.
• Configuration 3 has seventeen sections. The first section is 147 mm long, the next twelve sections are 73 mm long, the next two sections are 54 mm long and the last two sections are 20 mm and 11 mm long respectively.
• Configuration 4 has thirteen sections. The first five sections are 147 mm long, the four sections Following are 73 mm, the next two sections are 54 mm long, and the last two sections are 20 mm and 11 mm long respectively.
• Figures 6 and 7 show results on 0.8 ⁇ -type cut-off membranes.
• Figure 6 shows the observed flux results.
• Figure 6 shows the variation of the flux (overall performance of the membrane) as a function of the transmembrane pressure.
• the treated material is skimmed milk with a volume concentration factor of 1.
• FIG. 7 shows the evolution of the protein rejection rate as a function of the transmembrane pressure on a 0.8 ⁇ membrane. Observed values are below the 5% threshold. An increase in transmembrane pressure does not result in an increase in protein retention, which is suitable for application.
• FIGS. 8 and 9 show the results on a 0.1 ⁇ cutoff membrane.
• the membranes tested are a native membrane (without coating 20), a membrane according to configuration 2 above and a membrane according to configuration 3 above.
• Figure 8 shows the variation of the flux (overall performance of the membrane) as a function of the transmembrane pressure.
• the treated material is skimmed milk with a volume concentration factor of 1.
• the membrane according to configuration 2 is tested twice.
• FIG. 9 shows the evolution of the rate of protein rejection as a function of the transmembrane pressure on a membrane of 0.1 ⁇ m.
• Figure 9 shows a 90% acceptable threshold in bold lines. Although the flow rate (flux) of the membranes provided with a coating is lower than the flow rate of the native membrane without coating, the values of the protein rejection rate are only acceptable on the membranes provided with the coating 20.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Separation Using Semi-Permeable Membranes (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=38704793

Family Applications (1)

Country Status (5)

Families Citing this family (2)

Family Cites Families (5)

• 2007
  • 2007-03-26 FR FR0702169A patent/FR2914197B1/fr not_active Expired - Fee Related
• 2008
  • 2008-03-26 CN CN200880017642A patent/CN101687146A/zh active Pending
  • 2008-03-26 WO PCT/FR2008/000413 patent/WO2008132357A1/fr active Application Filing
  • 2008-03-26 EP EP08787856A patent/EP2136907A1/de not_active Withdrawn
• 2009
  • 2009-11-23 US US12/623,630 patent/US20100133191A1/en not_active Abandoned

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events