EP0045705A1 - Method and apparatus for separating suspensions of solid particles in a liquid, particularly for treating fibrous suspensions in the paper-making industry - Google Patents

Abstract

A process for fractionating a suspension of solid particles in a liquid, of the type wherein said suspension is made to pass through a filtering screen, characterized in that said suspension is directed in a direction parallel to the longitudinal axis of an elastically deforming, flexible, perforated sleeve forming a filtering screen, and in that a sequence of high and low pressures is continuously created within this sleeve and travels at least predominantly opposite the direction of the suspension flow. The invention also applies to equipment.

Description

The invention relates to a method and a device for the fractionation of suspensions of solid particles in a liquid; it relates more particularly, but not specifically, to a method and a device for treating fibrous suspensions in the paper industry.

In the following description, the invention will be more particularly described in its preferred application to the paper industry.

In stationery, it is well known to try to recover the fibers in the suspensions rejected in the sewers. However, the low concentration of these suspensions, which is of the order of 0.2 and 1 g of solids per liter, requires treating very large quantities of water.

However, the hitherto known methods which make it possible to economically treat very large quantities of suspensions at low concentration do not make it possible simultaneously to carry out the fractionation of the solid phase contained in the effluents in order to recover the recoverable part thereof.

It is possible, for example to decant or "float" the effluents before discharging them, which makes it possible to purify the water, but does not make it possible to selectively recover the fibers from the thickened suspension which is then entirely rejected at the discharge.

We thus lose significant quantities of raw materials which, moreover, become more and more expensive.

In US Patent 3,833,468, it has been suggested to purify suspensions by means of an inclined screen formed by a curved and rigid grid. This solution, which is suitable for retaining large impurities, such as sticks and gravel, is however not effective in selectively recovering the fibers because, in the long run, the grids are blocked by said fibers which have the annoying tendency to be planted perpendicular to the filtering grid.

In British Patent 485,553, an apparatus has been described for the filtration of paper pulps formed by a rectilinear series of sieves with inclined rigid slots through which the suspension to be purified and in which the filtrate of each sieve is collected in separate chambers where a diaphragm applies pressure pulses to it. Thus, the unclogging is carried out by a back and forth of the filtrate through the sieve, which risks on the one hand to reintroduce part of the "fines" and water in the suspension to be treated and on the other hand, is insufficient to disrupt the fibrous mattress retained by the sieve.

In the German patent 366,127 _t was associated with a horizontal sieve with slotted fins arranged in the filtrate collection chamber and, rotating in the direction of flow of the suspension to be married. In addition to the drawbacks mentioned above, this device suitable for extracting fiber agglomerates does not make it possible to economically split more individual fibers by the very fact of the slit sieve, namely low flow rates and significant fiber losses, therefore unsuitability the treatment of very diluted suspensions.

In French patent 1,145,263, a process for draining fine grain products with a high water content has been described, in which the filter cloth is subjected to mechanical vibrations. These vibrations of the fabric allow liquid particle release, but are unfortunately inadequate to désorga _- nise the formed cake, which moreover is not sought. As a result, this technique cannot be used effectively for the fractionation of a fibrous suspension.

• - soit, parce qu'ils se colmatent en cours de traitement,
• - soit, qu'ils ne permettent pas d'obtenir une séparation sélective de la fraction fibreuse.

In other words, the purifying devices known and operated to date cannot be suitable:

• - either, because they clog up during treatment,
• - Or, that they do not make it possible to obtain a selective separation of the fibrous fraction.

The object of the invention is a method and a device for the selective separation of a fraction of the solid particles in a liquid suspension which is rapid, economical, even at high flow rates and low concentration.

The invention also relates to a method and a device particularly suitable for the treatment of fibrous paper mill suspensions and especially for solids concentrations of between 0.2 and 2 g per liter.

More specifically, the invention is suitable for the treatment of paper mill effluents, upstream of the purification station, a treatment in which it is sought to selectively recover the recoverable fibers.

This process for the separation of solid particles in a liquid suspension, of the type in which said suspension is passed through a filtering sieve

features:

• - in that said suspension is directed in a direction parallel to the longitudinal axis of a perforated, flexible, elastically deformable sleeve, forming a filter screen,
• _- And in that, continuously, one creates inside this sleeve a succession of pressures and depressions which moves against the current relative to the direction of the flow of the suspension.

• - le manchon est en un matériau textile.tel qu'une toile tissée ajourée dont la maille est de préférence rectangulaire, la plus petite dimension de ce rectangle étant disposée dans le sens du flux, afin de favoriser le passage des "fines" et la rétention des fibres ;
• - on crée la succession de pressions et de dépressions en déformant la section du manchon et en propageant cette déformation le long d'une génératrice dudit manchon et ce, à contre courant du flux de la suspension ;
• - on crée cette succession de pressions et de dépressions en déplaçant un corps mobile à l'intérieur du manchon à contre courant par rapport au flux de la suspension.

According to particular embodiments:

• - the sleeve is made of a textile material such as an openwork woven fabric, the mesh of which is preferably rectangular, the smallest dimension of this rectangle being arranged in the direction of flow, in order to favor the passage of the "fines" and the fiber retention;
• - we create a succession of pressures and depressions sions by deforming the section of the sleeve and propagating this deformation along a generator of said sleeve and this, against the flow of the suspension;
• - This succession of pressures and depressions is created by moving a movable body inside the sleeve against the current with respect to the flow of the suspension.

• - un conduit d'amenée de la suspension liquide à traiter, ,
• - un élément filtrant,
• - un organe d'extraction du filtrat,
• - un organe pour la récupération de la fraction solide concentrée,

se caractérise en ce que ledit élément filtrant se compose :

• - d'un manchon fixe perforé, souple élastiquement déformable, de forme générale tronconique, connecté à son extrémité la plus large au conduit d'amenée et à son extrémité la plus étroite à l'organe de récupération,
• - d'un moyen apte à diriger le courant de suspension à traiter dans l'axe longitudinal dudit manchon,
• - d'un moyen apte à créer l'intérieur du manchon une succession de pressions et de dépressions qui se déplace. continuellement à contre courant du flux de ladite suspension.

The invention also relates to a device for the separation of solid particles in a liquid suspension. This device of the type comprising:

• - a supply line for the liquid suspension to be treated,,
• - a filter element,
• - an organ for extracting the filtrate,
• - an organ for the recovery of the concentrated solid fraction,

is characterized in that said filter element consists of:

• - a fixed perforated, flexible, elastically deformable sleeve, of generally frustoconical shape, connected at its widest end to the supply duct and at its narrowest end to the recovery member,
• a means capable of directing the suspension current to be treated in the longitudinal axis of said sleeve,
• - A means capable of creating the interior of the sleeve a succession of pressures and depressions which moves. continuously against the flow of said suspension.

• - le manchon est en un tissu filtrant souple dont les mailles sont, comme déjà dit, avantageusement rectangulaires ;
• - ce manchon est orientable et inclinable, notamment par rapport au moyen destiné à créer la succession de pressions et de dépressions, afin de pouvoir augmenter la déformation dudit manchon ;
• - l'axe du conduit d'amenée de la suspension à épurer est généralement confondu avec l'axe longitudinal du manchon ;
• - le moyen apte à créer à l'intérieur du manchon déformable une succession de pressions et de dépressions est formé par une spirale rigide hélicoïdale rotative qui s'appuie transversalement en permanence contre ledit manchon et le déforme, le point de contact entre ladite spirale et la paroi filtrante du manchon se déplaçant en sens inverse de l'écoulement du flux de la suspension ;
• - le pas de cette spirale est inférieur à la longueur du manchon ;
• - le moyen apte à créer à l'intérieur du manchon une succession de pressions et de dépressions est formé par un corps mobile situé à l'intérieur dudit manchon ayant un mouvement longitudinal alternatif, ledit corps mobile présentant son coefficient de pénétration maximum lorsqu'il se déplace à contre courant du flux de la suspension et son coefficient de pénétration minimum lorsqu'il revient dans l'autre sens.

In practice :

• - The sleeve is made of a flexible filtering fabric whose meshes are, as already said, advantageously rectangular;
• - This sleeve is orientable and tiltable, in particular relative to the means intended to create the succession of pressures and depressions, in order to be able to increase the deformation of said sleeve;
• - The axis of the supply line of the suspension to be purified is generally coincident with the longitudinal axis of the sleeve;
• the means capable of creating a succession of pressures and depressions inside the deformable sleeve is formed by a rigid rotating helical spiral which permanently leans transversely against said sleeve and deforms it, the point of contact between said spiral and the filter wall of the sleeve moving in the opposite direction to the flow of the suspension flow;
• - The pitch of this spiral is less than the length of the sleeve;
• the means able to create inside the sleeve a succession of pressures and depressions is formed by a mobile body situated inside said sleeve having a reciprocating longitudinal movement, said mobile body having its maximum penetration coefficient when it moves against the flow of the suspension and its minimum penetration coefficient when it returns in the other direction.

Advantageously, the means able to create inside the deformable sleeve a succession of pressures and depressions is formed by an endless belt moving in the opposite direction to the flow of the suspension flow and having rigid bars spaced along of said belt, part of said bars resting transversely and in turn on the flexible sleeve by deforming it. These rigid bars can have various shapes and sections. Likewise, they can be mounted idly on their axis.

In practice, the purification device can have several parallel sleeves and a single means capable of creating inside these sleeves a succession of pressures and depressions which then acts simultaneously on said sleeves.

Similarly, the device can also include in the sleeve of the auxiliary introduction means for the suspension, these means, such as supply conduits, being substantially directed in the direction of the flow of the suspension, in order to compensate for the gradual fall in speeds resulting from the reduction in flow at as the filtrate is evacuated. This also makes it possible to carry out an additional purification of the fibrous fraction to be recovered.

The operation of this device can be explained as follows.

When (see FIG. 1) a fibrous suspension (2) is sent in a flexible filter sleeve (1), for example in a woven fabric, in the longitudinal direction of said sleeve (1) (direction indicated by arrow A), at the level of the wall (1), the elementary fibers (3) of said suspension are preferably oriented in this direction A.

When (see FIG. 2) a rigid member (4) which moves against the current in the direction indicated by arrow B is applied to this flexible sleeve (1), this rigid member (4) first exerts on the sleeve (1) deformation. In parallel, upstream of this member (4) (area indicated by reference 5), the suspension (2) is filtered and the fibers (3) form a fibrous mat (6) on the wall of the sleeve. If the fibers (3) were allowed to continuously deposit on the mattress (6), this mattress would in turn play the role of filtering media, thus opposing the passage of liquid and "fines" through the wall of the sleeve.

But, when the member (4), which advances against the current, encounters the mattress (6), this mattress then destroys and peels off from the wall in the area (7).

Downstream of the member (4) (see FIG. 3), between the unstuck mattress (7) and the fabric (1), a depression (8) is formed which in turn detaches the remainder (7) of the mattress (6) and puts the fibers back into the suspension in (9).

This suspension is then accelerated by the vortex created by the movement of the member (4) along the sleeve (1).

Thus, a series of pressures and depressions moving in the opposite direction to the flow of the flow of the suspension to be treated is indeed created, the pressure being exerted upstream with respect to the flow, that is to say in the zone (5), while the depression is exerted downstream, that is to say in zone (8).

• - l'utilisation d'un manchon perforé souple élastiquement déformable, ce qui permet de remettre.efficacement les fibres en suspension lors de l'application de la succession de pressions-dépressions ;
• - le déplacement de la suspension par rapport au manchon, ce qui favorise la mobilité des fibres et leur orientation longitudinale dans la couche limite de cisaillement ;
• - la déformation du manchon par application d'une succession de pressions-dépressions ;
• - le déplacement continu de cette succession de pressions-dépressions :
  • . par rapport à la surface du manchon, ce qui conduit à un décolmatage uniforme et continu,
  • . par rapport à l'écoulement de la suspension et principalement en sens inverse de cet écoulement, ce qui, d'une part, augmente l'amplitude des pulsations de pression et_.d'autre part favorise le retour dans la suspension des fibres partiellement engagées dans les mailles du manchon.

In other words, the invention relates to a method and a fractionation device which is particularly effective for suspensions with low solids concentration, using the combination of four. characteristics

• - The use of an elastically deformable flexible perforated sleeve, which makes it possible to effectively put fibers back in suspension during the application of the succession of pressure-depressions;
• - The displacement of the suspension relative to the sleeve, which promotes the mobility of the fibers and their longitudinal orientation in the shear boundary layer;
• - deformation of the sleeve by application of a succession of pressure-depressions;
• - the continuous displacement of this succession of pressure-depressions:
  • . relative to the surface of the sleeve, which leads to a uniform and continuous unclogging,
  • . relative to the flow of the suspension and mainly in the opposite direction to this flow, which, on the one hand, increases the amplitude of the pressure pulses and _. on the other hand promotes the return in the suspension of the fibers partially engaged in the stitches of the sleeve.

More precisely, it is the mattress at the start of training, the return of which to the suspension is favored. Indeed, the return in the suspension of the fibers partially engaged in the stitches of the sleeve is due to the speed of the fluid relative to the fabric of the sleeve which creates a boundary layer in which the fine elements can flow through the fabric, while the fibers, one end of which is in front of a mesh generally have the other end in a layer of the fluid further from the fabric and thus the speed with respect to the sleeve is significantly greater than the speed of "crossing" of the fluid through the sleeve; this thus promotes the return of the fibers in the suspension.

In practice, as we know, when the fibrous mat (6) is formed at the inlet of the sleeve (1), it initially contains not only fibers (recoverable materials) but also 'fines' (mineral fillers, fragments of fibers and other materials that are not very valuable) which are "trapped" in the structure of said mattress during its formation and can therefore no longer migrate to the filtering wall.

By deforming the sleeve (1) thanks to the translational movement of the member (4) against the flow of the suspension, the fibrous mat (6) is released and it is detached from the wall, which releases the "fines "and allows them to be entrained with the liquid through the filter cloth.

In a way, an unclogging of the filter cloth and a self-cleaning of the fibrous mat are simultaneously carried out without the introduction of additional water into the system.

Thus, as one advances along the generatrix of the sleeve (1), the fibrous mat (6) is more and more concentrated in fibers.

Because the flow of the suspension (2) is directed in the longitudinal direction of the sleeve (1) at the boundary layer, the fibers (3) are preferably arranged in this fibrous mat (6) parallel to the longitudinal axis and therefore will not tend to get stuck in the web, which limits the tendency to clogging.

On the other hand, the preferential orientation of the fibers in the longitudinal direction allows the use of fabrics with larger mesh, which promotes both a better selectivity of the separation (easier evacuation of the "fines") and a more high speed of treatment (higher filtration speed).

The filtration effect is also promoted by the displacement of the member (4) in contact with the wall OUTSIDE _- higher of the sleeve (1), which windscreen "runoff drop which precludes filtration.

In addition, by its very shape, the sleeve has neither a blind spot nor a stagnation zone.

The manner in which the invention can be implemented and the advantages which result therefrom will emerge more clearly from the following description and from the exemplary embodiments, with the support of the appended figures, the whole being given by way of non-limiting indication.

As said, Figures 1 to 3 illustrate a summary explanation of the phenomena in question.

Figures 4 and 5 schematically show a first device for implementing the invention, respectively seen in front section (Figure 4) and seen in longitudinal section (Figure 5). Figure (6) shows a detail of this device seen from above.

Figures 7 and 8 show two other embodiments of the invention.

Figures 9 and 10 show respectively in longitudinal and cross section a preferred device of the invention.

FIG. 11 is a schematic summary view of an improved installation implementing this method.

Figures 4, 5 and 6 show a first device in which the succession of pressures and depressions is caused by deformation of the section of the filter sleeve from the outside and in which this deformation is propagated along a generator of the sleeve and this, in the opposite direction to the flow of the flow suspension.

• - d'un conduit d'amenée (10) pour la suspension liquide à traiter ;
• - d'un manchon (11), par exemple en toile de polyester souple, à maille rectangulaire de dimensions courantes pour cet usage en pàpèterie ; grâce à deux plaques de serrage (12) et des écrous (13), cette toile prend la forme générale d'un corps cylindrique tronconique ;
• - de deux supports réglables (14) et (15) grâce auxquels on peut faire varier l'inclinaison de cette toile (11) ;
• - d'un tube rigide (16) spiralé en hélice et raccordé par des rayons (17) à un axe longitudinal (18), entraîné en rotation par le jeu d'une poulie (19), d'une courroie (20), d'une seconde poulie (21) et d'un moteur (22) ; l'axe (18) est sensiblement parallèle à l'axe longitudinal du manchon (11) ;
• - d'un montant vertical (23) sur lequel se déplace le porte-manchon (24), ce qui permet ainsi de régler la distance entre le manchon (11) et l'hélice (16) et en d'autres termes, la pression de cette hélice (16) sur le manchon (11), mais également l'inclinaison de ce manchon (11) par rapport à cette hélice (16) ;
• - d'un bac de récupération (25) ;
• - d'une goulotte (26) pour l'évacuation du filtrat, c'est-à-dire de l'eau filtrée et des "fines" ;
• - d'un organe (27) pour récupérer la fraction concentrée disposée à l'extrémité basse du manchon (11) ; ce peut être par exemple un plan incliné, avantageusement filtrant relié à une goulotte de récupération.

Referring to these Figures 4 to 6, the device consists of:

• - a supply conduit (10) for the liquid suspension to be treated;
• - A sleeve (11), for example made of flexible polyester fabric, with rectangular mesh of common dimensions for this use in baking; thanks to two clamping plates (12) and nuts (13), this fabric takes the general form of a frustoconical cylindrical body;
• - two adjustable supports (14) and (15) by which the inclination of this fabric (11) can be varied;
• - a rigid tube (16) spiraled into a helix and connected by spokes (17) to a longitudinal axis (18), driven in rotation by the play of a pulley (19), a belt (20), a second pulley (21) and a motor (22); the axis (18) is substantially parallel to the longitudinal axis of the sleeve (11);
• - a vertical upright (23) on which the sleeve holder (24) moves, which thus makes it possible to adjust the distance between the sleeve (11) and the propeller (16) and in other words, the pressure of this propeller (16) on the sleeve (11), but also the inclination of this sleeve (11) relative to this propeller (16);
• - a recovery tank (25);
• - A chute (26) for the evacuation of the filtrate, that is to say filtered water and "fines";
• - a member (27) for recovering the concentrated fraction disposed at the lower end of the sleeve (11); it may for example be an inclined plane, advantageously filtering, connected to a recovery chute.

Figure 6 shows seen from above a detail (deformed to facilitate understanding) of the sleeve (11) fixed by the nuts (14) on the clamping plates (12) on the outer side and resting on the inner side on a support (28) tapered in the direction of flow A. In this way, this tapered shape gives the sleeve (11) a generally frustoconical shape which tapers in the direction of flow and this, in order to compensate for the gradual fall in speeds resulting from the decrease in the flow rate as the evacuation of the filtrate ..

The inclination of the entire system also helps to maintain the speed of the flow by taking advantage of gravity to reduce the effect of the pressure drop.

FIG. 7 represents a variant of the equipment of FIG. 4 in which the external spiral propeller (16) has been replaced by a movable body (30) secured to a longitudinal shaft (31) parallel to the longitudinal axis of the sleeve (11); this longitudinal shaft (31) is driven in an alternating back and forth movement by one. suitable means and is placed inside the sleeve (11). This movable body (30) can have very varied shapes (plane, ovoid shape, etc.) and it must be sufficiently spaced from the edges of the sleeve, so as not to scrape the fibrous mattress (6) and not to substantially interfere with the flow of the suspension.

Upstream of the movable body (30), pressure is exerted, which promotes filtration. Just downstream, therefore behind this movable body (30), a vacuum is created which tends to deform in (33) the flexible sleeve (11). As before, there is therefore a succession of pressures and depressions which promotes the effectiveness of the treatment, as shown above.

It goes without saying that in the case where the sleeve (11) is rigid, there would then be only a succession of pressures and depressions and no deformation. In a particular embodiment, when the movable body (30) returns in the upstream-downstream direction, that is to say in the direction of flow of the flow of the suspension, so as not to disturb the flow of the suspension, the downstream walls (34) of the movable body (30) are then deformed to reduce the coefficient of penetration. One can for example give the movable body (30) the general shape of an umbrella which one would open when one moves in the upstream-downstream direction.

It is also possible to mount on the longitudinal shaft (31) a series of movable bodies (30) suitably spaced from one another.

Figure 8 illustrates another embodiment with a flexible sleeve (11) and deformation from the outside. Here, the deformation is caused by a set of successive parallel rollers (40) spaced along an endless belt (42) driven in continuous rotation by two synchronized drive pulleys (43) and (44). These rollers are mounted idly around the axis (41) in order to reduce the friction on the sleeve (11) and thus reduce the wear of this fabric (11) and the energy consumption. This forms a succession of pressures and depressions inside the sleeve thanks to these rollers moving in the opposite direction to the flow of the suspension flow, only part of said rollers being supported transversely and in turn on the flexible sleeve by deforming it.

Figures 9 and 10 show respectively in longitudinal section and in cross section a preferred device according to the invention. This device essentially comprises a frame (50) mounted on casters (51) which receives a motor (52) which, via a variator (53) drives a pulley '(54). This motor pulley (54) drives an endless chain (55) which passes over two other return pulleys (56) and (57) carried by the cross-member (58). This horizontal crosspiece (58) also has a tensioning chain guide (59). The chain (55) carries rigid cylindrical bars (60) regularly spaced, so that there is always at least one point of contact between a bar (60) and the deformable sleeve (11).

On the top of the frame (50), adjustable supports (61) hold a plate in height and laterally (62) which, seen from above, has from left to right a generally tapered shape in order to give the sleeve (11) a generally frustoconical shape. This assembly (62) is connected to the flexible perforated sleeve (11) produced as previously in a stationery fabric. The upstream end (63) of this fabric (11) is connected, when the time comes, to the conduit (10) for supplying the suspension to be purified, while its downstream end (64) opens into a box (65) where we will recover the concentrated fibers (similar to 27). (66) designates a conduit through which the filtrate will be discharged (similar to the chute 26).

Example 1:

• - manchon (11) en toile tissée de crin polyester de 320µm de diamètre,
• - maille de la toile du manchon (11) : 250 x 600/Am
• - longueur du manchon (11) : 100 cm
• - diamètre de l'hélice (16) : 100 cm
• - pas de l'hélice (16) : 80 cm
• - vitesse de rotation de l'hélice (16) : 200 tours/ minute.

A device is produced in accordance with FIGS. 4 to 6 having the following general characteristics;

• - sleeve (11) made of woven polyester horsehair fabric, 320 µm in diameter,
• - mesh of the sleeve fabric (11): 250 x 600 / Am
• - sleeve length (11): 100 cm
• - propeller diameter (16): 100 cm
• - propeller pitch (16): 80 cm
• - propeller rotation speed (16): 200 revolutions / minute.

• - concentration en matières solides de la suspension amenée en (10) : 0,45 g/litre
• - débit de la suspension : 12,6 m3/heure
• - taux de cendres avant traitement : 17 %.

A suspension collected just downstream of a paper machine is treated in this device, before being discharged into the river. This suspension, which essentially contains long fibers and "fines", is treated under the following conditions:

• - concentration of solids in the suspension supplied in (10): 0.45 g / liter
• - suspension flow: 12.6 m3 / hour
• - ash rate before treatment: 17%.

After treatment, a filtrate (in 26) is obtained having an average concentration of solid matter (the values indicated are obtained by the average of 20 measurements) of 0.11 g / liter, while the fibrous fraction accepted in (27) has an average concentration of 7.5 g / liter. The fibrous yield is approximately 75%.

Example 2:

• - concentration en matières solides : 1,22 g/litre,
• - taux de cendres 58 %.

Example 1 is repeated with another suspension more loaded with mineral matter (stationery sludge containing a high proportion of very short fibers) having the following characteristics:

• - solids concentration: 1.22 g / liter,
• - ash rate 58%.

• - concentration en matières solides : 4,1 g/litre,
• - taux de cendres : 16 %,
• - rendement fibreux : 28 %. Filtrat recueilli en (26) :
• - concentration en matières solides : 1,0 g/litre,
• - taux de cendres : 62,6 %

The following results are obtained (fibrous fraction accepted in 27)

• - solids concentration: 4.1 g / liter,
• - ash rate: 16%,
• - fibrous yield: 28%. Filtrate collected in (26):
• - solids concentration: 1.0 g / liter,
• - ash rate: 62.6%

Example 3:

Example 2 is repeated with a mud having a solids concentration of 1 g / liter, an ash rate of 45% and a drip index of 75 ° SR (Schopper-Riegler degrees).

• - en (27) des acceptés (concentration en matières solides 15 g/litre - taux de cendres : 20 % - rendement fibreux : 70 % - indice d'égouttage : 20° SR),
• _- en (26) des refusés (concentration en matières solides : 0,7 g/litre - taux de cendres : 77 % - rendement fibreux : 30 %).

After treatment, we obtain:

• - in (27) accepted (concentration of solid matter 15 g / liter - ash rate: 20% - fibrous yield: 70% - drip index: 20 ° SR),
• _- in (26) refusals (solids concentration: 0.7 g / liter - ash rate: 77% - fiber yield: 30%).

Example 4:

• - acceptés (concentration en matières solides : 9,5 g/litre - taux de cendres : 7 % - rendement fibreux : 42 %),
• - refusés (concentration en matières solides : 0,77 g/litre - taux de cendres : 58 %).

By way of comparison, the same mud is used as in Example 3 in a purifier with rigid curved grids of the trade of the type of that described in the preamble. The following results are obtained:

• - accepted (solids concentration: 9.5 g / liter - ash rate: 7% - fiber yield: 42%),
• - refused (solids concentration: 0.77 g / liter - ash rate: 58%).

Example 5:

• 3 manchons (11) en parallèle semblables à celui de l'exemple 1 longueur : 200 cm
• . diamètre moyen de ces manchons : 9 cm
• . conicité de la plaque (62) à l'entrée côté 63 : 12 cm à la sortie côté 64 : 8 cm
• . barres cylindriques (60) diamètre : 3 cm espacement : 80 cm
• . longueur de la chaîne (50) : 480 cm
• . vitesse de translation des barres 60 : 200 m/min.

A device is used in accordance with FIGS. 9 and 10 having the following general characteristics:

• 3 sleeves (11) in parallel similar to that of Example 1 length: 200 cm
• . average diameter of these sleeves: 9 cm
• . taper of the plate (62) at the inlet on side 63: 12 cm at the outlet on side 64: 8 cm
• . cylindrical bars (60) diameter: 3 cm spacing: 80 cm
• . chain length (50): 480 cm
• . bar translation speed 60: 200 m / min.

Using this device, the same suspension is treated as in Example 1. The same results are obtained substantially, but with a flow rate of the order of 80m ³ / h.

Example 6:

• - une tubulure d'amenée (70) de la suspension à épurer ;
• - une vanne (71) et un organe de prélèvement d'échantillon (72) ;
• - une caisse de répartition (73) d'où partent trois conduits séparés (74) présentant chacun une vanne manuelle (75), des rotules (76) et (77), connecté au conduit d'amenée (10) placé juste en amont du manchon (11) ; on a donc trois manchons filtrants parallèles ;
• - une chaîne (55) avec ses barres rectilignes (60) ;
• - de cette même caisse (73) partent également trois autres conduits auxiliaires (78) qui débouchent dans chacun des trois manchons (11) en aval de (10) par des injecteurs (79) dirigés vers l'aval du manchon (11) ; on peut avoir un ou plusieurs injecteurs dans le même manchon (11) ;
• - un conduit (80) pour l'évacuation vers l'égout du filtrat et un by-pass (81) connecté à ce même égout.

The device shown in FIG. 11 is used, which essentially comprises:

• - a supply tube (70) of the suspension to be purified;
• - a valve (71) and a sample collection member (72);
• - a distribution box (73) from which three separate conduits (74) leave each having a manual valve (75), ball joints (76) and (77), connected to the supply conduit (10) placed just upstream the sleeve (11); there are therefore three parallel filter sleeves;
• - A chain (55) with its rectilinear bars (60);
• - From this same box (73) also leave three other auxiliary conduits (78) which open into each of the three sleeves (11) downstream of (10) by injectors (79) directed downstream of the sleeve (11); it is possible to have one or more injectors in the same sleeve (11);
• - A conduit (80) for the evacuation to the sewer of the filtrate and a by-pass (81) connected to this same sewer.

These auxiliary suspension feeds improve industrial operating safety by promoting unclogging and purification.

It goes without saying, taking into account the principle of fractionation implemented by the invention, that it may happen that some large impurities are retained with the concentrated fibrous fraction. This is not very annoying, on the one hand because, if the manufacturing circuits are well designed, the large impurities are eliminated almost entirely upstream of the paper machine, on the other hand, because at the concentration reached, the elimination of these impurities, if it turns out to be necessary, would not pose any problem.

• - la possibilité de traiter de gros débits par unité de surface filtrante de l'ordre de 150 m³/heure par 2 m
• - la faible consommation d'énergie;
• - le faible encombrement de l'appareil et son coût réduit;
• - la possibilité de mettre plusieurs manchons soit en parallèle, soit en série associés à un seul élément de déformation;
• - la possibilité de réaliser un effet d'égouttage- essuyage de la toile pour empêcher la formation de la goutte de ruissellement qui s'oppose à la filtration;
• - bref, la possibilité de réaliser, dans des conditions économiques la récupération des fibres valorisables dans des suspensions que jusqu'alors on rejetait en totalité.

The invention has many advantages over the techniques used to date. We can cite :

• - the possibility of treating large flows per unit of filtering surface of the order of 150 m ³ / hour per 2 m
• - low energy consumption;
• - the small size of the device and its reduced cost;
• - The possibility of putting several sleeves either in parallel or in series associated with a single deformation element;
• - The possibility of achieving a dripping-wiping effect of the fabric to prevent the formation of the drop of runoff which opposes filtration;
• - in short, the possibility of carrying out, under economic conditions, the recovery of recoverable fibers in suspensions which until then had been rejected entirely.

• - la filtration d'effluents urbains ou industriels;
• - le traitement de minerais ou d'aliments;
• - le traitement d'effluents de papèterie;
• - le fractionnement de suspensions de pâtes vierges, de vieux papiers de récupération et notamment dans le cas des opérations de désencrage.

This technique can therefore be used successfully for selective purification-filtration in all processes using particle size phenomena. We can cite :

• - filtration of urban or industrial effluents;
• - the processing of minerals or food;
• - the treatment of paper mill effluents;
• - the fractionation of suspensions of virgin pulp, of old recovery paper and in particular in the case of deinking operations.

In stationery, the device is preferably placed on the final sewer, just before the treatment plant or at specific points in the production line.

Claims (12)

1 / Process for the fractionation of suspension of solid particles in a liquid, of the type in which said suspension is passed through a filtering sieve, characterized: - in that said suspension is directed in a direction parallel to the longitudinal axis of a flexible perforated sleeve, elastically deformable, forming a filter screen, - And in that, continuously, there is created inside this sleeve a succession of pressures and depressions which moves at least mainly against the current relative to the direction of flow of the flow of the suspension. 2 / A method according to claim 1, characterized in that one creates the succession of pressures and depressions by deforming the section of the sleeve, and by propagating this deformation along a generatrix of said sleeve and this, in the opposite direction to flow of suspension flow. 3 / A method according to claim 1, characterized in that one creates the succession of pressures and depressions by moving a movable body inside the sleeve mainly against the current with respect to the flow of the suspension. 4 / Device for the fractionation of suspensions of solid particles in a liquid comprising: - a supply pipe (10) for the liquid suspension to be treated, - a filter element (11), - a member for extracting the filtrate (26-66), - a member (27-65) for the recovery of the fraction of concentrated solid particles, characterized in that said filter element consists of: - a flexible flexible, elastically deformable fixed sleeve (11) of generally frustoconical shape, connected at its widest end to the supply duct (10) and at its other end which is closest to the recovery member (27-65), a means capable of directing the suspension current to be treated in the longitudinal axis of said sleeve, - A means.suitable to create inside the sleeve a succession of pressures and depressions which continuously moves against the flow of said suspension. 5 / Device according to claim 4, characterized in that the entire device is orientable and tiltable at will in a vertical plane. 6 / Device according to claims 4 and 5, characterized in that the sleeve is orientable relative to the means intended to create the succession of pressures and depressions. 7 / Device according to one of claims 4 to 6, characterized in that the axis of the supply conduit of the suspension to be treated is coincident with the longitudinal axis of the sleeve. 8 / Device according to one of claims 4 to 7, characterized in that the means capable of creating inside the deformable sleeve (11) a succession of pressures and depressions is formed by a rigid helical spiral (16) rotatable , which permanently leans transversely against the external wall of said sleeve (11) and deforms it, the direction of translation of the point of contact between said spiral (16) and the sleeve (11) being opposite to the direction of flow suspension. 9 / Device according to one of claims 4 to 7, characterized in that the means capable of creating inside the deformable sleeve (11) a succession of pressures and depressions is formed by an endless belt (42-45 ), moving in the opposite direction to the flow direction of the suspension flow and having rigid parallel bars (40-60) spaced along said belt, part of said bars (40-60) being supported dirty on the outer wall of said flexible sleeve (11) by deforming it. ₁ 0 / Device according to one of claims 4 to 7, characterized in that the means capable of creating inside the sleeve (11) a succession of pressures and depressions is formed by a movable body (34) located at inside and on the longitudinal axis of said sleeve (11), having a reciprocating longitudinal movement, said movable body (34) having its maximum penetration coefficient when it moves against the flow of the suspension and its coefficient of minimum penetration when it returns the other way. 11 / Device according to one of claims 4 to ₁ 0, characterized in that it has several sleeves ( ₁₁ ) parallel associated with a single means capable of creating inside said sleeves a succession of pressures and depressions (11 ). 12 / Device according to one of claims 4 to 11, characterized in that it comprises auxiliary suspension supply lines (78) arranged in the sleeve (11) downstream of the main supply line (10) and directed substantially along the axis of the sleeve (11).

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