HK40006469A - Tangential flow separation element incorporating flexuous channels - Google Patents

Description

Tangential flow separation element comprising a curved channel

Technical Field

The present invention relates to the technical field of cross-flow separation elements for separating a fluid medium to be treated into a filtrate and a retentate, these cross-flow separation elements being commonly referred to as filtration membranes.

More precisely, the invention relates to a new channel shape for such a separation element, which can increase the flow of filtrate and/or for reducing the energy consumption of the installation using such a separation element.

The invention also provides a method of manufacturing such a cross-flow separation element by an additive technique.

Background

Separation processes using membranes are used in a variety of industries, particularly in the context of producing drinking water (potable water) and treating industrial effluents, as well as in the chemical, petrochemical, pharmaceutical, agricultural product industries, and biotechnology fields.

The membrane constitutes a selective barrier which, under the action of the transport force, allows certain components of the fluid medium to be treated to pass through or to be prevented. The size of these components relative to the size of the pores in the membrane causes them to pass or be blocked, and the membrane thus resembles a filter. Depending on the pore size, these techniques are called "microfiltration", "ultrafiltration", or "nanofiltration".

There are films with different textures and textures. In general, the membrane is built on a porous support (carrier) which provides mechanical strength to the membrane and determines the total filtration surface area of the membrane by defining the number and morphology of the channels. In particular, layers called "separation layers", "filtration layers", "separation layers", "active layers" or "skin" separate on the inner walls of these channels. During separation, the transport of the filtered fluid takes place through the separation layer, and subsequently the fluid is spread out by the porous texture of the support so as to travel towards the peripheral surface of the porous support. The portion of the fluid used for treatment that has passed through the separation layer and porous support is referred to as "permeate" or "filtrate" which is recovered by a collection chamber surrounding the membrane. The remaining portion is called "retentate" and it is re-injected into the fluid to be treated upstream of the membrane, typically via a circulation loop.

In the conventional manner, when the support is made of ceramic material, the support is initially manufactured in the desired shape by extrusion (extrusion), and then sintered at a temperature and for a time sufficient to ensure the desired robustness, while retaining the desired open and interconnected porous texture in the resulting ceramic. The method is limited to obtaining one or more linear channels within which one or more separation layers are deposited and sintered. The support body is conventionally tubular with one or more rectilinear channels arranged parallel to the central axis of the support body. Typically, the inner surface of the channel is smooth and free of any irregularities.

However, it has been observed that filtration membranes made of supports having such a shape are subject to problems of clogging or "fouling" and therefore exhibit limited performance in terms of throughput. In particular, small particles and macromolecules may be adsorbed on the surface of the separation layer or may deposit thereon to form gels or deposits, and they may even penetrate into the pores and block some of the pores.

All membrane separations with filter elements, in particular cross-flow separations, rely on the principle of selective transport, the efficiency of which depends on the selectivity of the membrane (active layer) and the permeability (flow) of the filter element as a whole (support + active layer). The selectivity and permeability are not solely determined by the characteristics of the active layer and its support, since selectivity and permeability are reduced or limited by concentration polarization, precipitation and/or plugging phenomena caused by blocked pores.

Concentration polarization occurs when macromolecules present in the liquid to be treated become concentrated at the membrane/solution interface during the filtration operation, where the macromolecules exert an osmotic back pressure opposite to the separation force, or scatter back to the centre of the liquid to be treated under the influence of fick's law. The cause of this concentration polarization phenomenon is that residual components are accumulated in the vicinity of the membrane by permeation of the solvent.

Fluid resistance other than that of the membrane can also occur when the concentration of particles on the membrane surface increases sufficiently to cause the appearance of a condensed phase in the form of a gel or a viscous deposit.

When particles having a size less than or equal to the size of the pores invade, the pores become clogged, thereby reducing the filtration surface area.

Clogging and its reversibility or irreversibility are complex phenomena and depend on the filter element and in particular on the separation layer, as well as on the liquid used for the treatment and the operating parameters.

Clogging is a major obstacle to the economic attractiveness of filtration, since, when dimensioning the filtration installation, it results in an increase in the surface area of the installation to meet the volume requirements to be treated, and also specific technical measures, such as cleaning cycles using detergents or periodic backflushing, have to be implemented to prevent later clogging.

In the prior art, the following proposals have been made for a number of technical solutions: the reduction of clogging is sought by creating turbulent conditions within the channels of the filter element to increase the flow of filtrate.

In a first type of solution, channels in tubular filter elements have been proposed to receive spirals or helices to create turbulence or turbulence, as taught in patent US 3648754 or publication "Reduction of membrane formation using a magnetic band for cross-flow filtration" (School of Chemical Engineering, University resins Malaysia-2003, a.l. ahmad, a.maridas, m.m. d.zurkali). The screw inserted into the channel is a separate fitting that needs to be held in place (usually at the entrance to the channel). Inserting such a screw into each channel and fastening it to the inlet of each channel becomes difficult to achieve. Furthermore, the diameter of the helix is suitably smaller than the diameter of the channel to enable the helix to be inserted (into the channel) and, if necessary, also to allow the helix to be extracted. Thus, the gap remains unchanged, allowing the helix to "float" and vibrate freely in the channel and cause friction with the active layer, thereby irreversibly damaging the active layer. In addition, the presence of the gap results in lateral leakage, which can short-circuit the helical flow of fluid, thereby reducing the effectiveness of the screw.

Another type of solution consists in forming notches or projections in or on the inner wall of the channel, so as to interfere with the fluid medium in the vicinity of the filtering surface, thereby limiting the accumulation and clogging of substances. Patent EP 0813445 proposes to make each channel comprise in its wall one, two or three initial helical grooves having a cross section of about 25% of the total section of the channel. Application FR 2736843 teaches to make a porous tube with a single channel, the walls of which have notches, while the peripheral wall of the support is smooth. For this purpose, the perforated tube is shaped by means of an extrusion die comprising cylindrical pins arranged on its axis, the outlet pins or matrix of the die being mounted so as to rotate and having a non-circular cross-section.

Forming grooves or notches in the inner surface of the channel does not cause all the fluid medium to follow a helical path, limiting the advantages of this solution. Furthermore, the technique for manufacturing such a separating element is limited to certain types of recesses, mainly recesses that are continuous from one end of the separating element to the other, and do not cause any variation in the through-going part of the channel. Furthermore, it cannot be converted to the manufacture of a separation element having a plurality of internal channels. However, as multi-channel separation elements are used to increase the filtration surface area and thus improve performance, there is an increasing need for multi-channel separation elements.

For the same purpose, patent application FR 3024665 proposes a cross-flow separation element for separating a fluid medium to be treated into a filtrate and a retentate. The element comprises a one-piece rigid porous support having at least one channel for flowing a fluid medium therethrough for treatment between an inlet and an outlet. The porous support has an outer surface for recovering filtrate that has passed through the support.

This document proposes to make obstacles to the flow of liquid to be filtered on the inner walls of the channel, these obstacles presenting continuity of material and a porous texture with a support. According to patent application FR3024664, at least one channel has obstacles, in particular in the form of a spiral, arranged on the inner wall of the support body. These obstacles obstruct or impede the flow of the fluid, which must be bypassed in order to generate turbulence that helps reduce clogging, but nevertheless have the major drawback of simultaneously generating inactive zones with a velocity of almost zero immediately downstream of each obstacle.

Another type of solution involves creating Dean vortices (Dean vortices) to reduce clogging and increase permeate flow in organic ultrafiltration membranes. Thus, the publication "Developing length hs in zero and logical tubes with Dean vortices flow" (Engineering Applications of computerized Fluid Mechanics, vol.3, No.1, pp.123-134(2009), f.springer, e.carretier, d.veyret, p.moulin) gives a theoretical treatment of numerical simulation of Dean vortex appearance and velocity increase that locally induces helically curved organic hollow fibers of circular cross-section, while still having the major drawback that the diameter of said circular cross-section is limited to a maximum of 2 millimeters (mm). In addition, the technique for bending organic fibers as described in this publication causes a dependency between the pitch (pitch) and the number of turns (turns).

Disclosure of Invention

In this context, the invention proposes to provide novel rigid filter elements presenting a single-channel or multi-channel structure and the shape of the above-mentioned channel structure being adapted to increase the filtrate flow and to reduce the energy consumption in the installation using such separation elements.

In order to achieve this object, the invention provides a cross-flow separation element for separating a fluid medium to be treated into filtrate and retentate, said separation element comprising a one-piece rigid porous support having arranged within its volume at least one channel for flowing the fluid medium to be treated between an inlet for the fluid medium to be treated and an outlet for the retentate, the one-piece rigid porous support having an outer surface for recovering filtrate that has passed through said support. According to the invention, at least one channel presents a curved flow volume between an inlet and an outlet, the curved flow volume being defined by a sweep of a generator plane section along a curvilinear path around a reference axis, and the reference axis not intersecting said generator plane section and being contained within the volume of the porous support.

The separating element further comprises one and/or more of the following additional features:

the curved flow volume of at least one channel is defined over only a portion of its length between the inlet and the outlet or over its entire length from its inlet to its outlet;

-a one-piece rigid porous support body having a plurality of flow channels for a fluid medium, which flow channels are arranged within said support body;

at least one channel has a generator cross-section of constant or variable area;

at least one channel has a generator cross-section of constant or variable shape;

-the generator cross-section of at least one channel is spaced from the reference axis by a constant distance;

-the generator cross-section of at least one channel is spaced from the reference axis by a variable distance;

-the reference axis is tangent to the generator section of the at least one channel;

-a series of multiple channels presenting generating element cross-sections spaced from the reference axis by a distance R suitable for ensuring their separation from each other by a separating partition;

the generating element section of at least one channel follows a path resulting from a translation motion in a constant or variable direction combined with a rotation motion around a reference axis with a constant or variable pitch in a left-handed or right-handed direction over at least a portion taken between the inlet and the outlet;

-the path has a pitch p in the range of 0.1mm to 250mm and the distance between the curvilinear path and the reference axis is in the range of 0.1mm to 100 mm;

-the generating element cross-section of the at least one channel taken over at least a portion between the inlet and the outlet follows a helical path;

-the generating element section of at least one channel taken over a limited portion from the inlet to the outlet follows a path resulting from a translational movement parallel to the reference axis;

at least one channel has a generator cross-section extending perpendicular to or parallel to the reference axis;

-the porous support is made of a material selected from the group consisting of: organic materials such as polyamides, polyetherketones, polystyrenes, aluminides, polyphenylsulfones, fluorinated thermoplastic elastomers, polypropylenes, polyethylenes, epoxies, acrylates, acrylonitrile butadiene, styrenes, polymethylmethacrylate, polycarbonate, nylon, polyetherimide, acrylonitrile styrene acrylate, polylactic acid, polyvinyl chloride, and mixtures thereof; inorganic materials such as alumina, titania, zirconia, aluminum titanate, aluminum nitride, titanium nitride, boron nitride, silicon nitride, sialon, graphitic carbon, silicon carbide, tungsten carbide, and mixtures thereof; metallic materials such as aluminum, aluminum alloys, cobalt and chromium alloys, nickel and chromium alloys, steel and stainless steel, titanium alloys, copper and tin alloys, copper, tin and aluminum alloys, copper and zinc alloys, and mixtures thereof;

-the cross-flow separation element comprises a porous support and at least one separation layer deposited continuously on the inner wall of each channel, each separation layer being made of a ceramic selected from the group consisting of alumina, titania, zirconia, aluminum titanate, aluminum nitride, titanium nitride, boron nitride, silicon nitride, sialon, graphitic carbon, silicon carbide, tungsten carbide and mixtures thereof, titanium nitride, aluminum nitride, boron nitride, silicon carbide, optionally mixed with another ceramic material;

-the channels have a hydraulic diameter in the range of 0.5mm to 20 mm;

-each channel has a constant or variable hydraulic diameter;

-the average pore size of the support is in the range of 4 micrometers (μm) to 100 μm;

the average pore diameter corresponds to the d50 value of the volume distribution, wherein 50% of the total volume of the pores corresponds to the volume of pores with a diameter smaller than the d50 value, the volume distribution being obtained by means of a pressure pump, for example using ISO standard 15901-1: 2005, et seq.

The invention also provides a novel method of manufacturing a cross-flow separation element, wherein a support is made by forming superposed individual layers, which are successively bonded to each other so as to gradually grow the three-dimensional shape of the support, at least one curved channel according to the invention being arranged within the three-dimensional shape of the support.

In addition, the method of the invention comprises the manufacture of the support by additive techniques, wherein, by using computer-aided design software, the shape of the support is subdivided into slices, which are made one after the other in the form of single layers successively superimposed and glued together, by repeating the following two steps: depositing a bed of powder material for forming a support, the bed being continuous, uniform and of constant thickness and covering, over the height of the layer, an area larger than the section of the porous body to be formed; consolidating a portion of the deposited material in a localized manner according to the pattern determined for each layer so as to form individual layers; these two steps are repeated in such a way as to ensure that the individual layers formed in this way adhere simultaneously to the previously formed layers at each repetition, thus causing the shape of the support to grow gradually.

Drawings

Other various features will appear from the following description with reference to the accompanying drawings, which show, by way of non-limiting example, embodiments of the invention.

Fig. 1A is an end view showing a first embodiment of a separating element according to the invention.

Fig. 1B is a perspective view of the separating element shown in fig. 1A.

FIG. 1C is a longitudinal cross-section of the separating element on line C-C of FIG. 1A.

FIG. 1D is a perspective view illustrating a path for constructing a tortuous path disposed in the separation element shown in FIG. 1B.

Fig. 2A shows how a curved flow volume is configured for the channel of the separation element according to the invention.

FIG. 2B is a perspective view of a curved flow volume according to the present invention, showing various possible shapes of embodiments labeled F1 through F5 and described elsewhere.

Figure 3A shows an example of a curved flow volume according to the invention constructed to contain a plane inclined at 90 deg. to the reference axis for generating a flat section of the volume.

Fig. 3B shows a curved flow volume according to the present invention obtained using the construction technique shown in fig. 3A.

Fig. 4A shows an example of constructing a curved flow volume according to the present invention, wherein the plane containing the cross-section for creating the volume also contains the reference axis.

Fig. 4B shows a curved flow volume according to the present invention, which is obtained by the construction technique shown in fig. 4A.

Fig. 5A shows a more general example of the configuration of a curved flow volume according to the invention, in which the plane containing the resulting flat section has an inclination angle with respect to the reference axis between 0 ° and 90 ° (the boundaries are excluded).

FIG. 5B illustrates a curved flow volume according to the present invention obtained using the construction technique shown in FIG. 5A.

Fig. 6 is a perspective view showing an example of manufacturing a curved flow volume according to the present invention, wherein the distance between the production plane cross-section and the reference axis is such that the reference axis is tangent to the production plane cross-section.

Fig. 7 is a perspective view showing an example of manufacturing a curved flow volume according to the present invention, wherein a change in distance between the flat section and the reference axis is produced.

FIG. 8 is a perspective view showing one example of making a curved flow volume according to the present invention where the distance between the resulting flat section and the reference axis, which is curvilinear, is constant while the pitch is also constant.

Fig. 9A is a perspective view showing an example of making a curved flow volume according to the present invention in which a left-handed path is connected to a right-handed path by a straight path parallel to a reference axis.

Fig. 9B is a cross-sectional view illustrating a curved flow volume embodiment according to fig. 9A.

FIG. 10A is a perspective view showing one embodiment of a curved flow volume according to the present invention in which the shape of the resulting cross-section is varied.

Fig. 10B is a view of a longitudinal cross-sectional plane containing a reference axis, illustrating an embodiment of a curved flow volume according to fig. 10A.

FIG. 11A is a perspective view illustrating one embodiment of a curved flow volume according to the present invention in which a change in area of the cross-section is produced.

Fig. 11B is a view of a longitudinal cross-sectional plane containing a reference axis, illustrating an embodiment of a curved flow volume according to fig. 11A.

Fig. 12A is a perspective view showing a portion of a curved flow volume according to the present invention in which segments of the left-handed path directly alternate with segments of the right-handed path.

Fig. 12B is a perspective view illustrating an embodiment of a curved flow volume according to fig. 12A.

Fig. 13A is an end view of a support body provided with a pair of channels according to the present invention.

Fig. 13B is a perspective view illustrating the support body having a pair of channels as shown in fig. 13A according to the present invention.

Fig. 13C is a longitudinal cross-sectional view of the support body on line C-C of fig. 13A.

Fig. 13D is a perspective view showing curved flow volumes V1 and V2, respectively, for each of the two channels shown in fig. 13A-13C, in accordance with the present invention.

Fig. 13E is a perspective view showing paths H1 and H2, respectively, for the curved flow volumes V1 and V2 for each of the two channels shown in fig. 13A-13D, in accordance with the present invention.

Fig. 14A is an end view of a support provided with seven repetitions of pairs of channels, each pair of channels corresponding to fig. 13A to 13E.

Fig. 14B is a perspective view illustrating a curved flow volume according to the present invention as shown in fig. 13A-13E repeated seven times within a single support.

Fig. 15A is an end view of a support body provided with twenty-three channels made up of three types of channels.

Fig. 15B is a longitudinal section of the support body on line B-B of fig. 15A.

Fig. 15C is a perspective view illustrating the flow volume of the central passage shown in fig. 15A.

FIG. 15D is a perspective view illustrating a curved flow volume for one of the six channels belonging to the middle category according to the present invention.

FIG. 15E is a perspective view showing a curved flow volume for six channels belonging to the middle class and surrounding a central channel according to the present invention.

Fig. 15F is a perspective view showing a curved flow volume for one of sixteen channels belonging to the peripheral category, in accordance with the present invention.

Fig. 15G is a perspective view showing a curved flow volume for one of the sixteen peripheral channels surrounding the middle class of channels according to the present invention.

Figure 15H is a perspective view showing the tortuous flow volumes for twenty-two channels as shown in figures 15D through 15G surrounding a central channel in accordance with the present invention within a single support body.

Detailed Description

First, some definitions of terms used in the context of the present invention are given below.

The term "average particle size" is used to indicate the d50 value of the volume distribution (capacity distribution) in which 50% of the total volume of the particles corresponds to the volume of particles having a diameter smaller than this d50 value. The volume distribution is a curve (analytical function) representing the particle volume frequency as a function of the particle diameter. This d50 value corresponds to the median value that divides the area under the frequency curve obtained by laser diffraction particle size measurement into two equal parts, which is the reference technique used to measure average particle size in the context of the present invention. For techniques to measure d50, specific reference may be made to the following:

ISO standard 13320: 2009, for laser particle size measurement techniques;

ISO standard 14488: 2007, techniques for sampling the powder analyzed; and

ISO standard 14887: 2000 for reproducibly dispersing a powder sample in a liquid prior to measurement by laser particle size measurement.

The term "average pore diameter" is used to indicate the d50 value of the volume distribution, wherein 50% of the total volume of pores corresponds to the volume of pores having a diameter smaller than this d50 value. The volume distribution is a curve (analytical function) representing the pore volume frequency as a function of the diameter of the pores. This d50 value corresponds to the median value that divides the area under the frequency curve, obtained by mercury intrusion for an average diameter of the order of a few nanometers (nm), into two equal parts, or by adsorption of gases, in particular of N, for smaller pore sizes₂(to obtain a frequency curve), both techniques being used as references in the context of the present invention for measuring the average pore size.

In particular, the techniques described below may be used:

ISO Standard 15901-1: 2005, techniques for measurement by mercury intrusion; and

ISO Standard 15901-2: 2006 and 15901-3: 2007, relates to gas adsorption measurement techniques.

The present invention proposes a cross-flow separation element for separating a fluid medium to be treated into filtrate and retentate, comprising a porous single piece support provided with one or more shaped channels selected for flow along a curved, meandering and advantageously spiral path for a major part or for all of the fluid to be filtered, any remaining fluid possibly flowing in one or more non-curved channels.

One or more flow channels for the fluid to be filtered are arranged in the porous support. Each of these flow channels has an inlet and an outlet. Typically, the inlet of the flow channel is placed at one end of the support body, which end serves as an inlet area for the fluid medium to be treated; and an outlet is placed at the other end of the support body, serving as an outlet area for the retentate.

In such a separating element, the body constituting the support body exhibits a porous texture. This porous texture is characterized by an average pore size derived from the distribution of pores measured by pressure pump porosimetry. Typically, the average pore size of the porous support is in the range of 4 μm to 100 μm.

The porous texture of the support is open and forms an array of interconnected pores, such that fluid filtered through the filtering separation layer can pass through the porous support and be recovered at the periphery. In practice, the permeability of the support body to water is measured in order to specify the fluid resistance of the support body. Specifically, in porous media, the steady flow of incompressible viscous fluid is governed by Darcy's Law. The velocity of the fluid (permeate) in the pores is proportional to the pressure gradient and inversely proportional to the dynamic viscosity of the fluid, which is related to a characteristic parameter called "permeability" which can be measured by applying the french standard NF X45101, 12 months 1996.

Thus, the permeate is recovered from the peripheral surface of the porous support. The walls of the channels are continuously covered by at least one filter separation layer for filtering the fluid medium for treatment. By definition, the average pore size of the filtration separation layer must be smaller than the average pore size of the support. The separation layer defines a surface of the cross-flow separation element which is in contact with and along which the fluid for treatment flows.

The thickness of the filtration separation layer is usually in the range of 1 μm to 100 μm. Of course, in order to achieve its separation function, and to serve as an active layer, the average pore diameter of each separation layer is smaller than that of the support. Typically, the average pore size of the filtration separation layer is at least 3 times, preferably at least 5 times smaller than the average pore size of the support.

The concept of microfiltration, ultrafiltration and nanofiltration separation layers is well known to the person skilled in the art. It is generally believed that:

-the mean pore size of the microfiltration separation layer is in the range of 0.1 μm to 10 μm;

-the mean pore size of the ultrafiltration separation layer is in the range of 10nm to 0.1 μm; and

-the nanofiltration separation layer has an average pore size in the range of 0.5nm to 10 nm.

Such a microfiltration or ultrafiltration layer, called "active" layer, can be deposited directly on the porous support, or on an intermediate layer having a smaller average pore size, which is itself deposited directly on the porous support.

For example, the separation layer may be composed of a ceramic selected from oxides, nitrides, carbides or other ceramic materials and mixtures thereof, in particular from titanium oxide, alumina, zirconia or mixtures thereof, titanium nitride, aluminum nitride, boron nitride, silicon carbide, possibly mixed with other ceramic materials.

For example, the separation layer may also be composed of one or more polymers such as Polyacrylonitrile (PAN), Polystyrene (PS), Polystyrene Sulfonate (PSs), Polyethersulfone (PES), polyvinylidene fluoride (PVDF), cellulose acetate, or other polymers.

Fig. 1A to 1D show a first embodiment of a cross-flow separation element 1 according to the invention, comprising a porous support 2 which is made in an elongated shape, such that the porous support is of the so-called "straight" type. The porous support 2 shown in fig. 1A to 1D has a circular right cross section and thus has a cylindrical outer surface 3, however the right cross section may be arbitrary or polygonal. In a preferred embodiment of a feature of the invention, the outer or peripheral surface 3 of the support body presents a constant profile. In other words, the outer surface 3 does not present any surface irregularities, except due to the inherent surface roughness of the material and due to the forming method used. Thus, the outer surface 3 does not have any deformations or indentations.

The porous support 2 comprises at least one flow channel and, in general, a plurality of flow channels 4i for the passage of the fluid medium (the symbol i is used in a general way to indicate some characteristic of the support and this symbol may take the value 1, 2, 3 … … according to the number of characteristics described in the examples), each flow channel being arranged within the porous support 2.

In the first embodiment shown in fig. 1A to 1D, the porous support 2 has a single channel 4₁Whereas in the second embodiment shown in fig. 13A it has two channels 4₁And 4₂. In the third embodiment shown in fig. 14A, the porous support 2 has fourteen channels, while in the fourth embodiment shown in fig. 15A, the porous support 2 has twenty-three channels arranged in three types of channels 4₁、4₂And 4₃In (1).

Each channel 4i corresponds to a region of the porous support 2 which does not comprise porous material and is delimited internally thereof by a wall 5, the wall 5 having a surface covered by at least one separation layer for contact with the fluid medium to be treated flowing inside the channel. A portion of the fluid medium passes through the separation layer deposited on the walls 5 of the porous support 2 so that a corresponding amount of fluid being treated (referred to as "permeate") flows through the outer surface 3 of the porous support. The fluid medium to be treated flows in the channel between the inlet 6 and the outlet 7 in the flow direction indicated by the arrow f. The inlet 6 is located at one end of the porous support and the outlet 7 is located at the other end of the porous support.

According to the invention, the porous support 2 comprises at least one channel 4i, the shape of which is adapted to increase the throughput of filtrate. The shape is in fact defined as follows: each channel 4i presents, between the inlet 6 and the outlet 7, at least one curved flow volume Vi, defined by a sweep of a generator section Si, lying in a plane P called "reference" plane, along a curvilinear path Hi around a reference axis Ai. Furthermore, the reference axis Ai does not intersect said generator section Si and is contained within the volume of the porous support body 2.

It is to be understood that the channel 4i according to the invention has at least one meandering flow volume Vi as described above. Of course, this curved flow volume Vi corresponds to a region of the porous support 2 that does not comprise any porous material, and this region is defined by a plurality of walls of the channel. It should be observed that the porous support 2 presents a varying thickness in a plane P lying between its outer surface 3 and the walls 5 of the channel taken.

Such a curved flow volume Vi according to the invention is defined between the inlet 6 and the outlet 7. This curved flow volume Vi may be present only over a small part of the length of the channel taken between the inlet 6 and the outlet 7, or over the entire length of the channel taken between its inlet and its outlet. Of course, the porous support 2 may comprise at least one flow channel of the fluid medium to be treated, which flow channel does not comprise the meandering flow volume Vi according to the invention.

The general principle of constructing a meandering channel exhibiting a flow volume Vi according to the invention is particularly clearly illustrated in fig. 2A. The general principle for constructing a curved channel consists in making the plane generator section Si follow a curved path Hi, which is constructed between the two ends of the flow volume Vi by the movement of a point M belonging to the plane generator section and located at a distance R from the reference axis Ai. The point M performs a rotational movement around the reference axis Ai and the point M simultaneously performs a translational movement along the reference axis. The rotation may be constant or variable. Likewise, the translational movement may be constant or variable. The distance R may also be constant or variable. The point M is any point of the generator section Si located in the reference plane P. Thus, the curved path Hi of the flow volume Vi does impart a channel bending property, at least over the length of the flow volume.

As can be seen from the above description, the curved flow volume Vi of the channel can exhibit a very wide variety of geometric features. As shown in fig. 2B, the reference axis Ai may be linear and/or curved without any cusps. The reference axis Ai may be linear along all or a portion of the length of the curved flow volume Vi. Likewise, the reference axis Ai may be curved over all or a portion of the length of the curved flow volume Vi. This reference axis Ai does not intersect the generator section Si, i.e. it is always located outside the curved flow volume Vi. The reference axis Ai may therefore be tangent to the generator section Si or it may be spaced therefrom by a determined distance, which may be variable or constant.

Since the tortuous channels must be contained within the volume of the porous support 2, the following results occur: the curvilinear path Hi and the reference axis Ai themselves must be contained within the volume of the porous support 2.

The curved path Hi may exhibit a wide variety of geometric features depending on the value of the distance R and the simultaneous movement in terms of rotation and translation.

The form of the curved channel depends on the reference axis Ai, on the curved path Hi, but also on the dimensions and shape of the generating element section Si and on the position of the generating element section Si with respect to the curved path Hi and with respect to the reference axis Ai. More precisely, fig. 3A and 3B show a situation in which the circular section Si contained in a plane perpendicular to the rectilinear reference axis Ai follows a helical path Hi around the reference axis Ai. In this example, a reference plane P containing the circular section Si is perpendicular to the rectilinear reference axis Ai. Combining the rotation of the circular section Si about the rectilinear reference axis Ai with the translational movement of the circular section Si along the rectilinear reference axis Ai, it is possible to obtain a curved channel for which the resulting helical geometry is known by means of the terms "solomon" column or "maltose" column. Fig. 3A and 3B show, by way of illustration only, two circular cross-sections S1 and S2, each contained in a respective plane P1, P2 perpendicular to the rectilinear reference axis Ai.

Fig. 4A and 4B show a case in which the circular section Si is contained in a reference plane also containing a rectilinear reference axis Ai, the circular section Si following a helical path Hi around the reference axis Ai. In this example, a reference plane P containing the circular section Si is parallel to the rectilinear reference axis Ai. Rotating the circular section Si around the rectilinear reference axis Ai while also moving the circular section Si along the rectilinear reference axis Ai serves to obtain a curved channel, the resulting spiral ladder being called a "scan of Saint-Gilles". Fig. 4A and 4B show, purely by way of illustration, two circular cross sections S1 and S2, each contained in a respective plane P1, P2 parallel to the rectilinear reference axis Ai.

Fig. 5A and 5B show a more general intermediate case in which the circular section Si contained in a plane exhibits an angle of inclination comprised between 0 ° and 90 ° with respect to a rectilinear reference axis Ai which follows a helical path Hi around the reference axis Ai. Rotating the circular section Si around the rectilinear reference axis Ai while translating the circular section Si along the rectilinear reference axis Ai serves to obtain a curved channel, the resulting coil geometry being called "serpentine". Typically the geometry obtained when winding the tube on a cylinder. Fig. 5A and 5B show, purely by way of illustration, two circular sections S1 and S2, each contained in a respective plane P1, P2 inclined with respect to a rectilinear reference axis Ai.

The following table 1 summarizes the characteristics of these three examples:

in general, the pitch p or the rotation value of the generator section Si about the reference axis Ai can take different values. For a spiral path Hi, the rotation value of the generating element section Si around the reference axis Ai is equal to a multiple of 2 pi radians (for a spiral with multiple spirals) or equal to a fraction of 2 pi radians (for a spiral with a number of spirals less than one).

As can be seen from fig. 3A-3B, 4A-4B and 5A-5B, the curved paths Hi shown in these three examples have a constant pitch value p. Of course, the curved path Hi may have a variable pitch value p, since it depends on the values of the rotational and translational movements.

The curved path Hi has a pitch p that is constant over all or part of the length of the curved flow volume Vi or has a pitch p that is variable along all or part of the length of the curved flow volume Vi.

In fig. 2B, section F2 specifically shows the case of a non-variable pitch p, while section F3 specifically shows the case of a variable pitch p.

It should be observed that fig. 2B illustrates various other parameters involved in defining a curved channel in accordance with the present invention. Thus, section F4 particularly shows the alternation between left and right turns separated by the straight channel portion Tr, and section F5 particularly shows the case of a section Si with variable morphology, while section F1 particularly shows the case of a variable distance R.

The reference axis Ai may be separated from the curved path Hi by a distance R that is not variable over all or part of the length of the curved flow volume Vi (fig. 3A-3B, 4A-4B and 5A-5B), or a distance that varies over all or part of the length of the curved flow volume Vi, as shown in fig. 7, wherein the distance R varies regularly, however it may naturally also vary in an irregular manner. In this example, the channel follows a spiral-to-spiral path.

It should be recalled that the distance R may be such that the reference axis Ai is tangent to the generator section Si. Although in the example shown in fig. 1A to 1D the reference axis Ai is spaced apart from the generator section S1, it is conceivable that the generator section S1 is tangential to the reference axis a1, which reference axis a1 is also the longitudinal symmetry axis of the porous support, as shown in the example of fig. 6.

It should be observed that fig. 6 shows a particular case in which the plane containing the flat section Si (in this example a triangle) for generating the volume is inclined by 90 ° (in this example one of the vertices of the triangle) with respect to the tangential reference axis Ai to said triangle generating primitive flat section. This figure shows the case in which the triangular flat section Si contained in a plane Pi perpendicular to the rectilinear reference axis Ai follows a helical path Hi around the reference axis Ai tangent to the triangular generator flat section. The rotation of the triangular section around the rectilinear reference axis Ai (which in this example is in contact at a point) is combined with the movement of this triangular section Si translated along the rectilinear reference axis Ai for obtaining a curved channel exhibiting a geometry known as an "archimedean spiral". It should be observed that the curved channel acquires a geometry also known as an "archimedean spiral" in the special case in which the plane containing the flat section for generating the volume is parallel to the reference axis Ai tangent to said generating element flat section at one or more points, and in the more general case in which the plane containing the flat section for generating the volume is inclined at any angle with respect to the reference axis Ai tangent to said generating element flat section at one point.

When the pitch p and the distance R are simultaneously constant, the curved path Hi is called a spiral (fig. 3B, 4B, 5B). The curved path Hi may spiral around the reference axis Ai in a counter-clockwise direction (right-hand) and/or in the opposite direction (left-hand) over all or part of the length of the curved flow volume Vi. Thus, the curved path Hi may be established in a single direction, or it may alternate along two opposite directions which may be selected as segments of the same or different lengths.

In the example shown in fig. 8, the generator section follows, in the direction of the right-hand, a helical path Hi with a constant pitch p around the curvilinear reference axis Ai.

In the example shown in fig. 9A-9B, the left-handed path H1 is connected to the right-handed path H2 by a straight path Tr parallel to the reference axis Ai, whereas in the example shown in fig. 10A and 10B, the path H1 is left-handed and is directly connected to the left-handed path H2.

Advantageously, for example, the curvilinear path Hi alternates between right and left turns over sections that may have the same length (fig. 12A-12B).

The generator cross-section Si of the curved flow volume Vi may assume any kind of contour.

The morphology or shape of the generator cross-section Si may be constant along all or a portion of the length of the curved flow volume Vi, or the morphology or shape of the generator cross-section may vary along all or a portion of the length of the curved flow volume Vi. As non-limiting examples, the morphology of the generator cross-section Si for this flow volume may be polygonal, circular, semicircular or elliptical. Fig. 10A to 10B show the change in the form of the generator section Si.

The area of the generator section Si may be constant along all or part of the length of the curved flow volume Vi, or the area of the generator section may vary along all or part of the length of the curved flow volume Vi. Fig. 11A to 11B show the case where the area of the generator cross section Si changes.

The characteristics of the example curved volumes shown in the above figures are summarized in table 2 below:

the following description gives a preferred but non-limiting example of a porous support 2 comprising channels 4i with a curved flow volume Vi according to the invention.

In the example shown in fig. 1A to 1D, the generator section S1 is a portion of a disc, and the reference axis a1 is a straight line coinciding with the longitudinal axis of symmetry of the porous support. The curvilinear support H1 is helical, i.e. the distance R between the curvilinear path H1 and the reference axis a1 is constant, and therefore the helical pitch p is also constant. The reference axis a1 does not pass through the generator section S1, and in the example shown, the generator section S1 is located at a distance from the axis. Of course, the generator section S1 may be tangent to the reference axis a 1.

Channel 4₁Along only a part of the length of the channel, between the inlet 6 and the outlet 7 of the channel. As can be seen more clearly in fig. 1B, the curved flow volume V1 of the channel is arranged over a length L of the porous support 2, which is shorter than the total length of the porous support.

According to an advantageous embodiment feature, the generator section S1, taken over a limited portion with respect to the inlet 6 and the outlet 7, follows a path resulting from a translational movement parallel to the reference axis a 1. From the inlet 6 and the outlet 7, the channel 4₁Thus having respective linear inlet and outlet flow volumes Ve and Vs parallel to the reference axis a1 and communicating with the curved flow volume V1 of the channel. Thus, between its inlet 6 and outlet 7, the channel 4₁Having an inlet flow volume Ve, a curved flow volume V1 and an outlet flow volume Vs.

In the example shown in fig. 13A to 13E, the porous support body 2 has a tubular shape and a circular cross section, and it includes two channels 4₁And 4₂. These two channels present generator sections S1 and S2, which are separated from each other by a separating partition 11. These generator sections S1 and S2 exhibit the same shape as the disk portions having the same area.

Each channel 4₁And 4₂A curved flow volume V1, V2 is present extending along a helical curved path H1, H2, which spirals around a reference axis a1, a 2. The curvilinear paths H1, H2, which exhibit the same constant pitch, are parallel to each other. The reference axes a1 and a2 coincide along a common straight line (advantageously corresponding to the longitudinal symmetry axis of the porous support). Each curvilinear path H1, H2 is spaced from the reference axis a1, a2 by the same constant distance R, such that the channels extend symmetrically with respect to the common reference axis and nest with one another.

In the example shown in fig. 13A to 13E, the two channels have parallel paths, but it will be clear that a series of multiple (more than two) channels can be provided in which the paths are parallel or not actually parallel. If not parallel, these channels naturally also present generating element sections spaced from the reference axis Ai by a distance R suitable for ensuring their separation from each other by the separating partition 11.

In a similar manner to the embodiment shown in fig. 1A to 1D, the curved flow volumes V1, V2 of the channel extend between the inlet 6 and the outlet 7 of the channel over only a small portion of the length of the channel. Thus, each channel 4₁And 4₂The inlet flow volume Ve, which presents a straight path from its inlet 6 to its outlet 7, the curved flow volumes V1, V2 and the outlet flow volume Vs of the straight path, respectively, it being understood that in the present invention no particular flow direction is used and that the inlet and outlet can be interchanged as well.

In the example shown in fig. 13A to 13E, the porous support 2 has two channels 4₁And 4₂However, it is clear that the porous support may have a larger number of channels arranged optionally symmetrically around an optional common reference axis, the channels being separated from each other by a separating partition.

It should be observed that the channel 4₁And 4₂Can be replicated as in the example shown in fig. 14A and 14B, wherein the porous support 2 has a series of seven structures, each structure comprising two channels 4₁And 4₂As depicted in fig. 13A-13E. In the embodiment shown in fig. 14A and 14B, the porous support 2 thus has fourteen channels, but it is obviously possible to provide a porous support with some other number of channels.

In the embodiment shown in fig. 15A to 15H, the porous support 2 has twenty-three channels 4, which are subdivided into three categories, the three categories of channels being arranged concentrically from the centre to the periphery of the porous support. In this embodiment, the porous support 2 is tubular and circular in cross-section, and in a first class it has a central channel 4₁The central channel being rectilinear and having a longitudinal symmetry axis A1 of the porous support 2A center. The central passage 4₁With a flow volume V1 according to the invention (fig. 15C) having no bending properties.

In a second category, called the intermediate category, the porous support 2 has a series of six channels 4₂These channels are arranged in a ring centered on the longitudinal symmetry axis a1 of the porous support 2. Channel 4₂The generator section S2 having the same shape and area is presented. In this example, each generator section S2 exhibits a non-circular general shape. Each channel 4₂A curved flow volume V2 is present extending along a helical curved path H2 of constant pitch and constant distance R, the curved path H2 spiralling about a reference axis corresponding to the longitudinal axis of symmetry a1 (fig. 15D).

Each curved flow volume V2 is located around the central passage 4₁At a certain distance. As shown in FIG. 15E, the channel group 4 in the middle category₂Along a helical curvilinear path H2 having the same pitch and the same distance R, around a reference axis corresponding to the longitudinal axis of symmetry a 1. Six channels 4₂Extend symmetrically with respect to the common reference axis a1 and they nest with each other.

In a manner similar to the embodiment shown in fig. 1A-1D, the curved flow volume V2 of the channel extends between the inlet 6 and the outlet 7 of the channel over only a portion of the length of the channel. Thus, each channel 4 in the intermediate category₂Between its inlet 6 and its outlet 7 an inlet flow volume Ve following a straight path, a curved flow volume V2 and an outlet flow volume Vs following a straight path are present.

In a third category, known as "peripheral", the porous support 2 has a series of sixteen channels 4₃These channels are arranged centered on the longitudinal symmetry axis a1 of the porous support 2 and surround the annular channels 4 of the second class₂A ring extending concentrically. Channels 4 in this third category₃The generator section S3 is presented with the same shape and area. In this example, each generator section S3 is generally in the shape of an isosceles trapezoid. Each channel 4₃Exhibits a curved flow extending along a helical path H3Volume V3, and the curved path H3 spirals about a reference axis corresponding to the longitudinal axis of symmetry a1 (fig. 15F). Each curved flow volume V3 is located in a channel 4 of the second type₂A distance around. As can be seen in FIG. 15G, the third category of channels 4₃Extends along a helical curved path H3 having the same pitch and radius of gyration relative to a reference axis corresponding to the longitudinal axis of symmetry a 1. Sixteen channels 4₃Extend symmetrically with respect to the common reference axis a1 and they nest with each other.

In a similar manner to the example shown in fig. 1A to 1D, the curved flow volume V3 of each channel extends over only a portion of the channel length between the inlet 6 and the outlet 7 of the channel. Thus, each channel 4 in the peripheral category₃Between its inlet 6 and its outlet 7 an inlet flow volume Ve following a straight path, a curved flow volume V3 and an outlet flow volume Vs following a straight path are present, respectively.

FIG. 15H shows a porous support 2 in which three classes of channels 4 are arranged₁、4₂And 4₃And exhibits a curved flow volume as shown in fig. 15C to 15G. Of course, the invention may be practiced with a porous support having some other number of channels distributed in some other number of categories.

Numerical simulations of the Computational Fluid Dynamics (CFD) type applied to the embodiment shown in fig. 13A to 13E have given the following results in terms of performance and energy consumption when compared to straight channels having the same hydraulic diameter. These are simulation results obtained using a digital model built on the basis of experimental measurements obtained by flowing red wine as the fluid for treatment in a single rectilinear circular channel with a transmembrane pressure of 1.5 bar and a cutoff threshold of 0.2 μm.

In Table 3 below, the permeate volume flow volume Qp (cubic meters per hour (m))³H)) and the volumetric flow volume Qa (m) to which the fluid for treatment is supplied³The ratio Qp/Qa between/h) is expressed in%, for the same transmembrane pressure (TMP) and the same cut-off thresholdThe value (μm) reveals the intrinsic performance of the curved channel compared to a straight channel with the same hydraulic diameter (Dh).

Energy efficiency of a filtration unit, wherein a filter element with this type of tortuous channels itself extracts cubic meters (m) of permeate per kilojoule of energy³KJ) to flow the fluid for treatment in the channel. The average velocities in the respective channels (in meters per second (m/s)) are given by indication in table 3.

For the example of spiral curved channels as shown in fig. 1A to 1D, the results given in the table indicate that, compared to a filter element with straight channels of the same hydraulic diameter:

the intrinsic performance of the filter element is multiplied by 17 and its energy efficiency by 5 when the helix pitch is 24mm compared to a filter element with straight channels; and

the intrinsic performance of the filter element is multiplied by 26 and its energy efficiency by 8 when the helix pitch is 12 mm.

According to an advantageous feature of the invention, the curved channel 4i according to the invention can present a value of pitch p independent of the value of distance R between the curvilinear path H1 and the reference axis a 1. Thus, a meandering channel can be produced having a small value of the pitch p together with a small value of the distance R. Typically, a meandering channel may be provided having a pitch p in the range of 1mm to 250mm and a distance R in the range of 0.1mm to 100 mm. Furthermore, according to an advantageous feature, the curved channel of the invention exhibits a hydraulic diameter in the range 0.5mm to 20 mm. It should be recalled that the hydraulic diameter Dh is such that Dh is 4A/P, where a is the area of the flow cross-section of the channel and P is the wetted perimeter of this cross-section.

Advantageously, each channel has a hydraulic diameter which may be constant or variable.

In the context of the present invention, the porous support 2 or indeed the entire cross-flow separation element is manufactured using additive techniques. The method of the invention consists in making the three-dimensional structure of the support by forming superposed single layers, which are successively bonded to each other so as to cause the three-dimensional structure of the support to grow gradually.

Said technique has the advantage, compared to the prior art, of manufacturing the support body in a single production step that does not require the use of tools or machining, thus enabling a greater range of support shapes to be obtained and enabling the shape and size of the obstacles in the channel to be varied.

When using solid materials such as powder, the thickness of the powder bed, and thus the thickness of each successive consolidated layer, is relatively small, so that it can be bonded to the underlying layer by the application of energy or by spraying a liquid. In particular, the thickness of the deposited powder is in the range 20 μm to 200 μm, which is a function of the addition technique that has been selected.

The binary sequence is repeated layer by layer to enable the desired three-dimensional shape to be built up. The pattern of merging may vary from one layer to another. The desired three-dimensional shape is grown along the selected growth direction.

The particle size of the deposited powder is one of the factors that determines the minimum thickness of each powder bed, and the particle size also determines the average pore size that is ultimately obtained. In particular, a powder comprising the material constituting the support, for example, a metal oxide powder, or a powder for one of its precursors, is used. For example, the deposited powder may exhibit an average particle size of about 35 μm in order to obtain an average pore size of about 10 μm in the ceramic support.

The applicant has observed that by adjusting various parameters, such as the material chosen and, for a given material, the average particle size of the powders used, and, for a given material and particle size, the thickness of the powder bed repeated layer by layer, and by adjusting the settings of the various parameters specific to the technique chosen for the purpose of consolidation, it is possible to obtain and control an interconnected residual pore texture within the consolidated monolithic material. The remaining porous texture is the result of sintering or controlled binder bonding of the powder particles, leaving interconnected voids between the particles.

When using an energy beam, the main parameters that can work are its focal point, i.e. the beam diameter where it hits the powder bed, the speed at which the powder bed is scanned by the photon or electron beam, or indeed the amount of overlap between the surfaces hit by the energy beam when building a layer.

When using liquid spraying, the main parameters that can work are the weight of the droplets, their frequency, the speed of scanning the powder bed by the "jet" of droplets, or indeed the amount of overlap between the passages.

The applicant has also observed that by adjusting the various parameters described above, it is possible to adjust the distribution of pore sizes and, for each given population of pores, to control the number of pores and their tortuosity.

Once the powder has agglomerated in the selected area, the particles of non-agglomerated powder material are removed by any suitable technique and this operation is facilitated by the initial flowability of the powder used. It is possible to use air-flow techniques (suction) or water-flow techniques, or indeed to use vibrations, in order to remove the last traces of powder remaining in the curved channels or on the walls of the shapes already made.

The final consolidation and final state of the porous texture of the filter is generally obtained by one or more subsequent heat treatments set to suitably eliminate the binding (debinding) and/or sintering of the material. The temperature selected for such final sintering depends on the nature of the inorganic material used and the average size of the powder particles used.

The support or indeed the entire cross-flow separation element as a whole is thus built up layer by layer. For this purpose, upstream and by using computer-aided design software, the three-dimensional structure of the support body or of the cross-flow separation element to be manufactured is subdivided into slices. Therefore, the virtual three-dimensional object to be fabricated is subdivided into two-dimensional slices of very small thickness. These thin slices are then made one after the other in the form of superimposed individual layers, and they are glued to each other in order to grow the desired three-dimensional shape gradually.

This three-dimensional structure is manufactured in the following way:

-by repeating the steps of:

preparing a bed of solid material (organic or inorganic powder) or of liquid material (organic precursor or liquid in which the powder (which may be organic or inorganic) is dispersed), which forms a porous support, the bed having a constant thickness and occupying, at the height of the layer, an area greater than the cross-section of the porous support; and

consolidating a portion of the material in a localized manner according to the determined pattern of each layer, so as to form a single layer, while bonding the resulting monolayer to the preceding layer;

-either by melting an organic or inorganic powder projected into the laser beam and forming a continuous bead of material in a predetermined pattern per layer;

or by melting a strand of hot-melt solid precursor continuously or discontinuously (drop-wise). When the precursor is a hot melt organic polymer used alone, the support is of organic nature and can be immediately used to deposit a layer of organic nature. When the precursor is a mixture of a hot-melt organic polymer and a ceramic or metallic inorganic powder, the support is inorganic once the polymer used as binder has been eliminated and the particles of inorganic powder have been sintered.

In general, in the first case, the material used is a solid or a liquid, and the individual layers are consolidated by applying energy or by spraying the liquid in fine droplets. The local delivery of energy can be done with a directed beam (LED or laser) or a directed beam of electrons, or indeed with any energy source that can be focused and scanned on the powder bed in a pattern that is consistent with CAD selection. The interaction between the energy and the material then leads to sintering, or to melting and solidification of the material, or indeed to photopolymerization or photocuring of the material, depending on its nature and on the nature of the energy source used.

The liquid can be delivered in a localized manner to the powder bed using micro-droplets produced by a piezoelectric system, which can optionally be charged and guided in an electromagnetic field. The liquid is then a binder for the agent for activating the binder that has been added to the ceramic powder.

With the addition technique as envisaged in the context of the present invention, it is possible to obtain firstly an improvement in terms of throughput and reliability, and secondly a great variation in terms of the shapes and relief portions that may be selected for the support body and that may be formed in one or more channels within the support body, compared to the prior art.

In the context of the present invention, various additive techniques may be used in order to design a three-dimensional shape, for example: selective Laser Sintering (SLS) or Selective Laser Melting (SLM); 3D printing or adhesive jetting; lithographic-based ceramic manufacturing (LCM); fused deposition modeling (FDP); and/or a stereolithography apparatus (SLA).

In the context of the present invention, a separation element (often referred to as a filter membrane) is provided for separating a fluid medium by cross-flow filtration. Such a separating element comprises a porous support made of a material which may be organic or inorganic.

For the organic porous support, the following organic materials may be chosen, given as non-limiting examples: polyamides, polyetherketones, polystyrenes, aluminides, polyphenylsulfones, fluorinated thermoplastic elastomers, polypropylenes, polyethylenes, epoxies, acrylates, acrylonitrile butadiene, styrene, polymethyl methacrylate, polycarbonate, nylon, polyetherimide, acrylonitrile styrene acrylate, polylactic acid, polyvinyl chloride, and mixtures thereof.

For non-metallic (ceramic) inorganic porous supports, the following inorganic materials may be selected, given as non-limiting examples: alumina, titania, zirconia, aluminum titanate, aluminum nitride, titanium nitride, boron nitride, silicon nitride, sialon, graphitic carbon, silicon carbide, tungsten carbide, and mixtures thereof.

For metallic (metals and alloys) inorganic porous supports, the following metallic materials can be chosen, given as non-limiting examples: aluminum, aluminum alloys, cobalt and chromium alloys, nickel and chromium alloys, steel and stainless steel, titanium alloys, copper and tin alloys, copper, tin and aluminum alloys, copper and zinc alloys, and mixtures thereof.

Claims (25)

1. A cross-flow separation element for separating a fluid medium to be treated into a filtrate and a retentate, the separation element comprising a single-piece rigid porous support (2) arranged with at least one channel (4i) within its volume for flowing the fluid medium to be treated between an inlet (6) for the fluid medium to be treated and an outlet (7) for the retentate, the single-piece rigid porous support having an outer surface (3) for recovering the filtrate that has passed through the support, characterized in that at least one channel (4i) presents a curved flow volume (Vi) between the inlet and the outlet, the curved flow volume being defined by sweeping a generator flat section (Si) along a curved path (Hi) around a reference axis (Ai), and said reference axis (Ai) does not intersect said generator section (Si) and is contained within the volume of said porous support.

2. The cross-flow separation element according to claim 1, characterized in that the curved flow volume (Vi) of at least one channel (4i) is defined over only a part of its length between the inlet and the outlet or over its entire length from its inlet to its outlet.

3. The cross-flow separation element according to claim 1, characterized in that the single-piece rigid porous support (2) has a plurality of flow channels (4i) for the fluid medium, which flow channels are arranged within the support.

4. Cross flow separation element according to claim 2, characterized in that the single piece rigid porous support (2) has a plurality of flow channels (4i) for the fluid medium, which flow channels are arranged within the support.

5. The cross-flow separation element according to any of claims 1 to 4, characterized in that at least one channel (4) has a generator cross-section (Si) of constant or variable area.

6. The cross-flow separation element according to any of claims 1 to 4, characterized in that at least one channel (4i) has a constant or variable shape of generator cross-section (Si).

7. The cross-flow separation element according to any of claims 1 to 4, characterized in that the generating element cross-section of at least one channel (4i) is spaced from the reference axis (Ai) by a constant distance.

8. The cross-flow separation element according to claim 7, characterized in that the generating element cross-section of at least one channel (4i) is spaced from the reference axis (Ai) by a variable distance.

9. The cross-flow separation element according to any one of claims 1 to 4, characterized in that the reference axis (Ai) is tangent to the generating element cross-section of at least one channel (4 i).

10. The cross-flow separation element according to any one of claims 1 to 4, characterized in that it comprises at least one series of a plurality of channels presenting a generating element cross-section spaced from the reference axis (Ai) by a distance (R) suitable for ensuring that the plurality of channels are separated from each other by a separation baffle (11).

11. The cross-flow separation element according to any of claims 1 to 4, characterized in that the generating element section (Si) of at least one channel (4i) follows a path resulting from a translational motion in constant or variable direction combined with a rotational motion around the reference axis (Ai) over at least a portion taken between the inlet and the outlet in constant or variable pitch (p) in left-hand or right-hand direction.

12. Cross-flow separation element according to claim 11, characterized in that the path has a pitch (p) in the range of 0.1mm to 250mm and the distance (R) between the curvilinear path (H1) and the reference axis (a1) is in the range of 0.1mm to 100 mm.

13. The cross-flow separation element according to any of claims 1 to 4, characterized in that the generating element cross-section (Si) of at least one channel (4i) taken over at least a portion between the inlet and the outlet follows a spiral path (Hi).

14. The cross-flow separation element according to any of claims 1 to 4, characterized in that the generator section (Si) of at least one channel (4i) taken over a limited portion from the inlet (6) to the outlet (7) follows a path (Hi) resulting from a translational movement parallel to the reference axis.

15. The cross-flow separation element according to any of claims 1 to 4, characterized in that at least one channel (4i) has a generator cross-section (Si) extending perpendicular to or parallel to the reference axis.

16. The cross-flow separation element according to any of claims 1 to 4, characterized in that the porous support (2) is made of a material selected from organic materials, inorganic materials, metallic materials, the organic materials being selected from polyamides, polyetherketones, polystyrenes, aluminides, polyphenylsulfones, fluorinated thermoplastic elastomers, polypropylene, polyethylene, epoxy resins, acrylates, acrylonitrile butadiene, styrene, polymethyl methacrylate, polycarbonate, nylon, polyetherimide, acrylonitrile styrene acrylate, polylactic acid, polyvinyl chloride and mixtures thereof; the inorganic material is selected from: alumina, titania, zirconia, aluminum titanate, aluminum nitride, titanium nitride, boron nitride, silicon nitride, sialon, graphitic carbon, silicon carbide, tungsten carbide, and mixtures thereof; the metal material is selected from: aluminum, aluminum alloys, cobalt and chromium alloys, nickel and chromium alloys, steel and stainless steel, titanium alloys, copper and tin and aluminum alloys, copper and zinc alloys, and mixtures thereof.

17. A cross-flow separation element according to any of claims 1 to 4, characterized in that it comprises a porous support body (2) and at least one separation layer deposited successively on the inner wall of each channel (4i), each separation layer being made of a ceramic selected from the following materials: oxides, nitrides, carbides and other ceramic materials and mixtures thereof.

18. The cross-flow separation element of claim 17 wherein each separation layer is made of a ceramic selected from the group consisting of: alumina, titania, zirconia, or mixtures thereof, titanium nitride, aluminum nitride, boron nitride, silicon carbide, or mixed with another ceramic material.

19. The cross-flow separation element according to any of claims 1 to 4, characterized in that the channels (4i) have a hydraulic diameter in the range of 0.5mm to 20 mm.

20. The cross-flow separation element according to any of claims 1 to 4, characterized in that each channel (4i) has a constant or variable hydraulic diameter.

21. A cross-flow separation element according to any of claims 1 to 4, characterized in that the average pore size of the support body (2) is in the range of 4 to 100 μm.

22. The cross-flow separation element of claim 21 wherein the average pore size corresponds to a d50 value of the volume distribution at which 50% of the total volume of the pores corresponds to the volume of pores having a diameter less than a d50 value, the volume distribution being obtained by mercury intrusion.

23. A lateral flow separation element according to claim 22, wherein the volume distribution is determined using ISO standard 15901-1: 2005, respectively.

24. A method of manufacturing a cross-flow separation element according to any of claims 1 to 23, wherein the support is made by forming a stack of individual layers which are successively glued to each other in order to gradually grow the three-dimensional shape of the support, the at least one channel (4i) being arranged within the three-dimensional shape of the support.

25. The method according to claim 24, characterized in that it comprises manufacturing the support by additive techniques, wherein the shape of the support is subdivided, by using computer-aided design software, into slices made one after the other in the form of a plurality of single layers successively superimposed and glued together, by repeating the following two steps: depositing a bed of powder material for forming the support, said bed being continuous, uniform and of constant thickness and covering, at the height of the layer, an area larger than the section to be formed of the porous support; consolidating a portion of the deposited material in a localized manner according to the pattern determined for each layer so as to form said single layer; these two steps are repeated in such a way that: ensuring that at each repetition, the single layer thus formed adheres simultaneously to the previously formed layer, thus allowing the shape of the support to grow gradually.