EP0359682B1 - Device for selectively separating particles in a fluid, in particular for purifying fibrous paper-making suspensions - Google Patents

Abstract

PCT No. PCT/FR89/00458 Sec. 371 Date Apr. 30, 1990 Sec. 102(e) Date Apr. 30, 1990 PCT Filed Sep. 12, 1989 PCT Pub. No. WO90/02839 PCT Pub. Date Mar. 22, 1990.A device for separating particles in a liquid in which a paper suspension is to be cleaned and supplied to a chamber of revolution (1) rotating about an axis (2). Movable deviators (7, 8) precede the fixed outlets (9, 10) to intercept most of the through-put of the suspension in the region of the periphery of the chamber (1), then deviate it towards the longitudinal axis of rotation (2) so as to recover most of the kinetic energy of rotation. The outlets (7, 8, 9, 10) are situated at the opposite end to that of chamber (1) from the supply (5, 6) and are arranged at the periphery of this chamber (1). A diabolo-shaped central body of revolution (11) is arranged inside the chamber, along the longitudinal axis of rotation (2) for rotation about its axis and with a radial run-off (12) in the vicinity of its smallest cross-section connected to an axial outlet duct (13).

Description

The invention relates to a device for the selective separation of particles in a liquid, in particular in a suspension. The invention is particularly suitable for the paper industry, in particular for the purification of particulate suspensions, such as for example fibrous suspensions. The invention may however find other applications in classification or fractionation techniques by centrifugation, in the recovery of immiscible liquids of different densities, etc.

There are currently in the paper industry a large number of devices intended for the purification or classification of fibrous suspensions.

• des moyens fixes d'amenée de la suspension, disposés selon l'axe longitudinal de ladite enceinte de révolution, prolongés par des moyens mobiles de déviation du courant de suspension vers la périphérie de l'enceinte ;
• des moyens pour entraîner ladite enceinte en rotation autour de son axe longitudinal ;
• des moyens fixes de sortie de la suspension épurée et des différentes fractions séparées, disposés selon l'axe longitudinal de ladite enceinte précédés par des moyens mobiles de déviation et dans lesquels le moyen de sortie des composants les plus légers est disposé sur l'axe longitudinal de rotation (2) du même côté que les moyens d'amenée,
  qui se caractérise :
• en ce que les moyens mobiles de déviation précédant les moyens fixes de sortie captent la plus grande partie du débit de la suspension au niveau de la périphérie de l'enceinte, puis la dévient vers l'axe longitudinal de rotation, de manière à récupérer la majeure partie de l'énergie cinétique de rotation ;
• et en ce que les moyens principaux de sortie sont situés à l'extrémité opposée de celle de l'enceinte comportant les moyens d'amenée, et sont disposés à la périphérie de cette enceinte, de manière à disposer d'une importante zone centrale de centrifugation.

In document EP-B-0037 347 of the Applicant (corresponding to US-A-4,443,331), a free vortex device has been proposed, in which the suspension to be purified is brought into a chamber of revolution rotating around its axis, of the type comprising:

• fixed means for supplying the suspension, arranged along the longitudinal axis of said enclosure of revolution, extended by movable means for deflecting the suspension current towards the periphery of the enclosure;
• means for driving said enclosure in rotation about its longitudinal axis;
• fixed means for leaving the purified suspension and the various separate fractions, arranged along the longitudinal axis of said enclosure preceded by mobile deflection means and in which the means for leaving the lightest components is arranged on the longitudinal axis of rotation (2) on the same side as the supply means,
  which is characterized:
• in that the movable deflection means preceding the fixed outlet means capture most of the flow of the suspension at the periphery of the enclosure, then deflects it towards the longitudinal axis of rotation, so as to recover the most of the kinetic energy of rotation;
• and in that the main outlet means are situated at the opposite end from that of the enclosure comprising the supply means, and are arranged at the periphery of this enclosure, so as to have a large central area of centrifugation.

This device gives excellent results in terms of efficiency, rejection rate and energy consumption, in particular for productions of less than about three hundred cubic meters per hour in diluted paste (concentration of the order from 1 %). To effectively process higher productions, that is to say flows greater than 300 cubic meters per hour in diluted paste, it becomes necessary to increase the volume of the device, and therefore its diameter. There are then various drawbacks on these large devices with high purification capacity depending on their conditions of use.

Thus, if working with diluted paste, we first of all witness an increase in pressure losses at the bearings and the inlet-outlet heads, as well as in the peripheral purification zone, and this made the need to maintain sufficient agitation with a high flow rate. In addition, still in diluted paste, it becomes necessary, due to the larger diameter, to increase the outlet counterpressure, to extract the rejects picked up in the axis of the central area of the vortex, or to capture them at the periphery. of this zone: an air nucleus is formed along the axis of the device which, having no fixed geometry, moves inside the suspension, and generates vibrations throughout the body of the device.

If you work in more concentrated dough (up to about three (3)%, the problems that arise are different. First of all, by the effect of centrifugal force, the dough tends to accumulate against the walls, which also gives rise to risks of vibrations due to unbalance, and of clogging of the apparatus, by very concentrated paste. In addition, to individualize the movement of the fibers, it is necessary to maintain a degree of high agitation, and for this a large difference in peripheral-wall flow velocities, resulting in high pressure losses. In addition, the flow control at the periphery of the vortex, by the geometry of the heads, and that of the body of the device essentially for small diameters, is quite delicate and poses problems of homogeneity of flow which can be detrimental to the quality of the purification and which lead to risks of deposits.

Document US-A-2,748,668 describes an apparatus intended for purifying paper pulp comprising a fixed external enclosure, in which a rotary central body with fins is disposed. This device is mainly intended to purify heavy contaminants. In this way, the dough is collected in the center with the light fraction. The general divergent shape of the central body prevents the exit of the light components which then accumulate at the entry because of their tendency to migrate radially towards the axis.

The present invention overcomes these drawbacks.

It relates to an improved device of the type described in document EP-B-0037 347, in which the flow control in the peripheral purification zone is improved and the evacuation of light rejects in the central zone is favored. vortex, even for high flow rates, while ensuring stable operation of the device.

The invention also relates to an improved device of the type in question as claimed in claim 1, making it possible to purify high quantities of pasta of the order of five hundred cubic meters per hour (500 m3 / h) and more .

In other words, the invention consists in providing in the device described in document EP-B-0037 347 of the Applicant, a single rigid central body of generally tapered and convergent shape inside the enclosure, which occupies degressive part of the interval between the supply and exit means, associated with a scooping means arranged in the vicinity of its smallest section and intended to extract the light fraction from the suspension.

The scoop system arranged in the central body of revolution of the device converts the residual energy of the vortex (dynamic and static pressure) into static pressure. This avoids back pressure on the outlet side and therefore allows the inlet pressure to be reduced by the same amount, thus resulting in appreciable energy savings.

• l'intervalle entre la paroi interne de l'enceinte et la paroi du corps central croit progressivement de l'entrée vers la sortie ;
• l'enceinte a une forme générale interne cylindrique et le corps central caractéristique a une forme de diabolo ;
• le corps central en forme de diabolo comprend trois portions distinctes, respectivement :
  • . une première portion tronconique, effilée vers la sortie ;
  • . une seconde portion cylindrique reliée à la première portion, comportant en périphérie des orifices associés aux moyens d'écopage ;
  • . une troisième portion également tronconique, mais de conicité inverse à la première portion, reliée à la seconde portion cylindrique et comportant un conduit axial associé aux moyens d'écopage, destiné à extraire lafraction légère ;
• les moyens d'écopage sont constitués par des ailettes radiales associées aux orifices périphériques de la seconde portion cylindrique ;
• les extrémités d'entrée et de sortie du corps central sont solidaires de l'enceinte de révolution, et sont entraînées en rotation par un moteur unique à la même vitesse que la vitesse de rotation de ladite enceinte ;
• le corps central est entraîné en rotation à une vitesse différente de celle de l'enceinte, mais est solidaire des têtes d'entrée et/ou de sortie de l'enceinte ; dans ce cas, avantageusement le corps central présente en périphérie des ailettes disposées le long d'une génératrice.

Advantageously:

• the interval between the internal wall of the enclosure and the wall of the central body increases progressively from the entry to the exit;
• the enclosure has a generally cylindrical internal shape and the characteristic central body has a diabolo shape;
• the diabolo-shaped central body has three distinct portions, respectively:
  • . a first frustoconical portion, tapered towards the exit;
  • . a second cylindrical portion connected to the first portion, comprising at the periphery orifices associated with the scooping means;
  • . a third portion also frustoconical, but of opposite conicity to the first portion, connected to the second cylindrical portion and comprising an axial duct associated with the scooping means, intended to extract the light fraction;
• the scooping means are constituted by radial fins associated with the peripheral orifices of the second cylindrical portion;
• the inlet and outlet ends of the central body are integral with the enclosure of revolution, and are driven in rotation by a single motor at the same speed as the speed of rotation of said enclosure;
• the central body is rotated at a speed different from that of the enclosure, but is integral with the inlet and / or outlet heads of the enclosure; in this case, advantageously the central body has, at the periphery, fins arranged along a generator.

In the field of centrifuges, or centrifugal decanters, it has long been known to have inside the rotor a central body substantially of revolution and of shape similar to the general internal shape of the rotor. This shape delimits a flow space of substantially constant thickness in order to avoid any agitation unfavorable for the settling of the suspension. This central body generally comprises scraping or scooping elements of the heavy particles decanted against the internal wall of the rotor, in order to bring them close to the axis and to extract them from the device (see for example FR-A- 1,450,895 (US correspondent US-A-3,467,304); US-A-4,332,350 or GB-A-1,366,170). On the other hand, in the device of the invention, the central body is necessarily of a different shape from the internal wall of the enclosure, in particular at the level of the scooping devices, so as to bring it back to the vicinity of the central body and to extract from the axis no longer the heavy particles, but the light fraction of the suspension.

Thus, for the extraction of light fractions, the state of the art dissuaded from using a central body.

In other words, the invention consists, for this new application and in order to achieve the objective of extracting the light fraction, to define a particular and specific shape of central body with respect to the internal wall of the enclosure, namely converging and positioning the scooping point on this central body at the point of smallest section.

If the central body is integral with the rotary enclosure of the apparatus, the apparatus is in this case particularly suitable for the field of fine purification in diluted paste, because the presence of the central body makes it possible to better channel the flow, in particular at the outlet of the injection channels of the inlet head. In fact, the parasitic recirculation flows, as well as the radial variations in the angular speed of the dough, are reduced, which makes the flow more uniform, with in particular a more homogeneous state of agitation.

On the other hand, if the central body is driven in rotation separately from the rotary body of the device, but jointly with the inlet and / or outlet heads of the suspension, the device is then perfectly suited for purifying suspensions more concentrated. Indeed, the improvement of the control of the flow in the external peripheral zone is ensured not only by the presence of the central body, but also by the choice of its differential speed of rotation, which makes it possible to re-train the dough in rotation, in order to keep the suspension at the optimum degree of agitation. In practice, the differential in speed of rotation of the central body is chosen in accordance with the difference in speed of the suspension relative to the wall at the level of the injection zone, according to the characteristics of the supply head.

The enclosure, the supply means, the mobile deflection means, the output means, the rotation drive means are produced in a known manner, in particular according to the teachings of document EP-B-0037 347 referred to in the preamble , for example stainless steel.

• une forme cônique convergente à partir des têtes d'amenée et de sortie de la suspension (diabolo) permet une bonne évacuation des refus légers, en favorisant le déplacement des composants légers vers la zone d'extraction qui peut se situer à tous niveaux entre les têtes, et en particulier vers la tête de sortie, lorsque celle-ci comporte le tube axial d'évacuation des refus légers ;
• le diamètre de l'écope, disposé au point de plus faible section du diabolo, doit être suffisamment grand pour éviter la formation du noyau d'air et pour récupérer la pression résiduelle nécessaire à l'extraction de la fraction légère, mais il doit être également sensiblement inférieur au diamètre interne de l'enceinte, pour éviter l'extraction simultanée de particules lourdes ;
• le diamètre du corps central au niveau des têtes d'amenée et de sortie doit être assez important, afin de bien contrôler l'écoulement dans la zone périphérique d'épuration, et plus particulièrement au niveau de la tête d'amenée, afin de mieux canaliser les écoulements parasites ; dans le cas où le corps central est entraîné en rotation séparément du corps de l'appareil, ce corps central peut avantageusement être équipé d'éléments de réentraînement de la suspension, tels des ailettes radiales disposées longitudinalement à sa surface, et se rapprochant plus ou moins de la paroi selon le cisaillement, et donc l'état d'agitation souhaité.

The converging central body has the following characteristics:

• a conical shape converging from the heads of inlet and outlet of the suspension (diabolo) allows a good evacuation of the light refusals, by favoring the displacement of the light components towards the extraction zone which can be located at all levels between the heads, and in particular towards the outlet head, when the latter comprises the axial tube for evacuating light rejects;
• the diameter of the scoop, arranged at the point of smallest section of the diabolo, must be large enough to avoid the formation of the air core and to recover the residual pressure necessary for the extraction of the light fraction, but it must be also substantially smaller than the internal diameter of the enclosure, to avoid the simultaneous extraction of heavy particles;
• the diameter of the central body at the level of the inlet and outlet heads must be fairly large, in order to properly control the flow in the peripheral purification zone, and more particularly at the level of the inlet head, in order to better channel parasitic flows; in the case where the central body is rotated separately from the body of the device, this central body can advantageously be equipped with elements for re-driving the suspension, such as radial fins arranged longitudinally on its surface, and is approximating the wall more or less depending on the shear, and therefore the desired state of agitation.

For technical and mechanical reasons, the internal wall of the enclosure is cylindrical. One could possibly use a general slightly frustoconical shape, provided that, as already said, the distance between the walls of the enclosure and the central body, increases regularly from the entrance to the scooping device. This slightly frustoconical arrangement however induces an additional construction cost which is not essential.

The manner in which the invention can be implemented and the advantages which result therefrom will emerge more clearly from the exemplary embodiments in support of the appended figures.

Figure 1 shows schematically in longitudinal section an apparatus in which the characteristic central body is integral with the enclosure of the apparatus.

Figure 2 shows schematically in longitudinal section an apparatus where the central body is adapted to be driven in rotation separately from the enclosure of the apparatus.

Figure 3 shows schematically in longitudinal section a preferred embodiment of the invention, while Figure 4 illustrates in cross section a detail of Figure 3 (scooping) along the axis IV-IV '.

• d'une enceinte creuse (1) cylindrique intérieurement et extérieurement entraînée en rotation autour de son axe longitudinal (2), par des moyens connus, non représentés (moteur) ;
• de paliers (3) et (4), associés à des joints d'étanchéité classiques (20-24), permettant à l'enceinte (1) de tourner sur son axe (2) ;
• d'une tubulure (5) formant moyen fixe d'amenée de la suspension à épurer et débouchant par l'intermédiaire d'un raccord tournant en tête de l'enceinte (1), dans un conduit d'amenée (6) formant moyen mobile de déviation ;
• en face des moyens d'entrée (5,6) et à l'opposé de l'enceinte (1), des moyens de sortie formés également par deux conduits fixes (9,10) formant des moyens fixes de sortie, reliés, grâce à des raccords tournants, respectivement au conduit (7) le plus près de la périphérie de sortie, pour l'extraction des particules les plus lourdes, et au conduit concentrique (8) de sortie, pour l'extraction de la fraction intermédiaire ;
• d'un corps central (11) caractéristique rigide de révolution en forme de diabolo aligné sur l'axe longitudinal (2), fixé à l'enceinte (1) par des moyens étanches non représentés ; ce corps central (11) comporte une écope (12), située dans la section la plus faible du diabolo, destinée à recueillir la fraction la plus légère de la suspension le plus près de l'axe de rotation (2) ; de la sorte, la distance D (figure 3) entre la paroi interne cylindrique de l'enceinte (1) et la paroi (51) du diabolo (11,30) croît régulièrement de l'entrée (5,6) vers la sortie (7,8) ;
• d'un conduit de sortie (13) de la suspension épurée, situé dans le prolongement aval de l'écope (12) et dans l'axe longitudinal (2) de l'enceinte (1), pour éliminer la fraction la plus légère de la suspension collectée par l'écope (12).

Referring to Figure 1, the purification device consists of:

• an internally and externally cylindrical hollow enclosure (1) rotated about its longitudinal axis (2), by known means, not shown (motor);
• bearings (3) and (4), associated with conventional seals (20-24), allowing the enclosure (1) to rotate on its axis (2);
• a tube (5) forming a fixed means for supplying the suspension to be purified and opening out via a rotary connection at the top of the enclosure (1), in a supply conduit (6) forming a means diversion mobile;
• opposite the inlet means (5,6) and opposite the enclosure (1), outlet means also formed by two fixed conduits (9,10) forming fixed outlet means, connected by to rotary connections, respectively to the duct (7) closest to the outlet periphery, for the extraction of the heaviest particles, and to the concentric outlet duct (8), for the extraction of the intermediate fraction;
• a central body (11) rigid characteristic of revolution in the form of a diabolo aligned on the longitudinal axis (2), fixed to the enclosure (1) by sealed means not shown; this central body (11) comprises a scoop (12), located in the weakest section of the diabolo, intended to collect the lightest fraction of the suspension closest to the axis of rotation (2); in this way, the distance D (FIG. 3) between the cylindrical internal wall of the enclosure (1) and the wall (51) of the diabolo (11.30) increases regularly from the inlet (5.6) to the outlet (7.8);
• an outlet duct (13) for the purified suspension, located in the downstream extension of the scoop (12) and in the longitudinal axis (2) of the enclosure (1), to eliminate the lightest fraction of the suspension collected by the scoop (12).

It is therefore an improved purifier of the type described in the aforementioned document EP-B-0037 347, having a cylindrical enclosure (1), in which a single central body in the form of a diabolo (11) with scoop is provided. (12) in the weakest section, which makes it possible to promote the evacuation of light rejects, to reduce the pressures necessary for the proper functioning of the purifier, to avoid vibration problems and to improve the homogeneity of suspension.

On the device of FIG. 2, the central body (11) and the inlet (6) and outlet (7) means constitute an integral assembly driven in rotation separately from the enclosure. As in FIG. 1, the fixed means (5) and (8) are respectively connected to the mobile means (6) and (10) by tight connections (20-24) and (22-23), and the central body has a form of diabolo. This diabolo (11) is also equipped at the periphery with fins (14,15) for driving the suspension to be purified, arranged along generators and equidistant from each other. Bearings (16,17) associated with conventional seals (23,24) allow the central diabolo (11) to rotate around the longitudinal axis (2) at an appropriate speed. The scoop (12) formed in the central body forms a movable means for leaving the light fraction and is extended downstream by a discharge duct (13) disposed along the axis (2). A scoop (18) formed in the outlet head (19) allows the heaviest fraction to be extracted in the peripheral zone (7) by forming the movable means for leaving this heavy fraction. This scoop (18) is extended downstream by an outlet duct (25) arranged along the longitudinal axis (2). Movable means (26) for supplying an auxiliary dilution fluid are provided along the outlet head (19) secured to the central diabolo (11) and are connected, by means of sealed connections (21-22), to fixed means (27) for supplying the auxiliary dilution fluid. It is important that the characteristic scoop (12) is placed in the vicinity of the weakest section of the converging central body (11) and preferably on this point, to properly recover the entire light fraction.

The introduction of washing water minimizes, in the case of paper pulps, the fiber losses which tend to concentrate towards the wall, with heavy contaminants.

In the advantageous embodiment of the device of FIG. 2, the continuous evacuation assembly (18,25) of heavy rejects is associated with devices (26,27) for continuous injection of washing water which put take advantage of the space (26) located between the outlet head (19) linked to the central body (11) in diabolo and the outlet flange of the enclosure (1) of the device. In a simplified form, the same devices (18,25) can be used alternately for the discontinuous injection of washing water from the heavy fraction and for the discontinuous extraction of the heavy contaminants, the extraction phase being advantageously very short. relative to the washing phase, in order to minimize the heavy refusal losses.

• une première portion (30) tronconique, effilée vers la sortie (7), occupant plus de la moitié de la distance entre l'entrée (6) et la sortie (7) ; pour des commodités de fabrication et de montage, cette portion tronconique (30) est fixée à sa partie large (31) à la tête d'alimentation (32) de forme cylindrique et comportant les canaux obliques d'injection de la pâte à papier ; ainsi, la distance D entre la paroi interne (50) de l'enceinte (1) et la paroi (51) du corps central (30) croit régulièrement de l'entrée (6) vers la sortie (7) ;
• une seconde portion cylindrique (33) emmanchée (34) à l'extrémité effilée de la première portion (30), pour définir une zone de moindre section, présentant en périphérie des orifices (35,36,37) et dont la paroi interne (38) (voir figure 4) comporte des ailettes (40,41,42) radiales ; l'ensemble orifices (35-37), ailettes (40-42) forme un ensemble d'écopage analogue à (12) ; de la sorte, comme précédemment (12), l'écopage est effectué au point bas du corps central (30) ;
• une troisième portion tronconique (45), mais de conicité inverse à (30), solidaire en (46) de la portion cylindrique (33) et qui comporte un conduit axial (47) analogue à (13), associé à l'ensemble d'écopage (35-37, 40-42), destiné à extraire la fraction légère de la suspension.

Figure 3 shows schematically in longitudinal section a device particularly suitable for the purification of paper suspensions. The internal washing wall of the enclosure (1) is cylindrical. The characteristic converging central body (11) in the shape of a diabolo, includes:

• a first frustoconical portion (30), tapered towards the outlet (7), occupying more than half the distance between the inlet (6) and the outlet (7); for manufacturing and mounting convenience, this frustoconical portion (30) is fixed at its wide part (31) to the supply head (32) of cylindrical shape and comprising oblique channels for injecting paper pulp; thus, the distance D between the internal wall (50) of the enclosure (1) and the wall (51) of the central body (30) increases regularly from the inlet (6) towards the outlet (7);
• a second cylindrical portion (33) fitted (34) at the tapered end of the first portion (30), to define an area of smaller section, having orifices (35,36,37) at the periphery and whose internal wall ( 38) (see FIG. 4) comprises radial fins (40,41,42); the set of orifices (35-37), fins (40-42) form a scooping assembly similar to (12); in this way, as before (12), the scooping is carried out at the low point of the central body (30);
• a third frustoconical portion (45), but of opposite taper to (30), integral at (46) with the cylindrical portion (33) and which comprises an axial duct (47) similar to (13), associated with the assembly d scooping (35-37, 40-42), intended to extract the light fraction from the suspension.

In a practical embodiment, the cylindrical enclosure (1) has an internal diameter of 0.75 m for a length of 2.5 m. The inlet cylindrical portion (32) has a diameter of 0.62 m for a length of 0.2 m. The first frustoconical inlet portion (30) has a length of 1.7 m for a diameter which gradually decreases from 0.6 to 0.36 m. The cylindrical scooping section (33) has a length of 0.2 m for a diameter of 0.36 m. The third frustoconical outlet portion (45) has a length of 0.4 m with a diameter which increases from 0.45 to 0.55 m. Finally, the orifices (35,36) have a diameter of 0.05 m and the axial duct (47) a diameter of 0.05 m.

Such a purifying device, according to Figures 3 and 4, can treat flow rates of the order of five hundred cubic meters per hour (500 m3 / h) and more. In the case where the suspension treated is a pulp suspension, the fiber concentration of which is of the order of 0 to 3%, preferably of the order of 1.5%, the effectiveness of this purifier is between 90 and 99%, with a fiber loss rate of less than 0.5%. In addition, the energy consumption is considerably reduced compared to that of an installation comprising two usual purifiers in parallel (21 kw against 2 x 17 kw), a saving to which must be added a saving of pumping energy of 12 kw, for a total of 21 kw against 46 kw for a nominal flow of 450 m3 / hour. This considerable reduction is due to the increase in capacity of the device and the fact that it is no longer necessary to provide back pressure at the outlet of the device.

Furthermore, due to the presence of the central body of revolution, in particular in diabolo, which prevents the formation of the air core and due to the general symmetry of the device in rotation, harmful vibrations are eliminated.

• la possibilité d'augmenter le diamètre de l'enceinte, c'est-à-dire son volume, donc la production de matières traitées et, à efficacité équivalente, la productivité spécifique ;
• pour la même quantité de matière traitée, la possibilité de diminuer l'incidence de l'investissement;
• la diminution de la consommation d'énergie, par réduction des puissances spécifiques d'entraînement de l'appareil et de pompage, du fait de la diminution de la contrepression ;
• la réduction notable des vibrations néfastes, ce qui améliore la durée de vie des éléments mécaniques (roulements, garnitures, joints...).

The separator device of the invention has many advantages over those known to date, in particular that described in document EP-B-0037347 of the Applicant referred to in the preamble. We can cite :

• the possibility of increasing the diameter of the enclosure, that is to say its volume, therefore the production of treated materials and, at equivalent efficiency, the specific productivity;
• for the same quantity of material treated, the possibility of reducing the impact of the investment;
• the reduction in energy consumption, by reduction of the specific drive powers of the apparatus and of pumping, due to the reduction of the back pressure;
• the significant reduction of harmful vibrations, which improves the service life of mechanical elements (bearings, seals, seals ...).

In this way, this device can be successfully used for the treatment and purification of various suspensions, such as for example suspensions of various paper pulps, waste water or polluted water, water-petroleum suspensions, etc.

Claims (8)

1. A device for separating particles in a liquid, in which the suspension to be cleaned is supplied to a chamber of revolution (1) rotating about a longitudinal axis (2), of the type comprising:

- fixed means (5) for supplying the suspension, arranged along the longitudinal axis (2) of the chamber of revolution (1), extended by movable means (6) for deviating the suspension current towards the periphery of the chamber (1);

- means for driving said chamber (1) in rotation about its longitudinal axis (2);

- fixed means (9,10) for discharging the cleaned suspension and the different separated fractions, arranged along the longitudinal axis (2) of said chamber (1), preceded by movable deviating means (7,8) and in which the means (13) for discharging (13) the lightest components is arranged on the longitudinal axis of rotation (2), either on the side where the suspension to be cleaned is admitted or on the side where the cleaned suspension is discharged ; and in which :

. the movable deviating means (7,8) preceding the fixed outlet means (9,10) intercept most of the throughput of the suspension in the region of the periphery of the chamber (1), then deviate it towards the longitudinal axis of rotation (2) so as to recover most of the kinetic energy of rotation;

. the outlet means (7,8,9,10) are situated at the opposite end to that of the chamber (1) comprising the supply means (5,6) and are arranged at the periphery of this chamber (1);

. a central body (11) of revolution is arranged inside the chamber, along the longitudinal axis of rotation (2) of this chamber (1), between the fixed means (5,6) supplying the suspension and the means (7-10) discharging said cleaned suspension,

characterized in that :

- said central body of revolution (11) has a general shape, which, from the inlet means (5,6), converges towards the outlet means (7-10);

- and comprises a run-off means (12,33-42) arranged in the vicinity of the smallest cross-section of said central body of revolution (11), connected to an axial outlet duct (13,47).

2. The device as claimed in claim 1, wherein the gap D between the inner wall (50) of the chamber (1) and the wall (51) of the central body (11,30) increases gradually from the inlet (5, 6) towards the run-off zone (12,33).

3. The device as claimed in claim 2, wherein the chamber (1) is cylindrical and wherein the central body of revolution (11) has a general diabolo shape.

4. The device as claimed in claim 3, wherein the diabolo-shaped central body of revolution (11) comprises three distinct portions, namely:

- a first frustoconical portion (30), tapered towards the outlet (7);

- a second cylindrical portion (33) connected to the first portion (30), having at the periphery orifices (35-37) associated with the run-off means (40-42);

- a third portion (45), also frustoconical, but with a conicity which is opposite to that of the first portion (30), connected to the second cylindrical portion (33) and having an axial duct (47) associated with the run-off means and intended to extract the light fraction.

5. The device as claimed in claim 4, wherein the run-off means consist of radial fins (40-42) associated with the peripheral orifices (35-37) of the second cylindrical portion (33) and connected to the axial duct (47).

6. The device as claimed in one of claims 1 to 4, wherein the inlet and outlet ends of the central convergent body (11) are integral with the chamber (1) and are driven in rotation by a single motor at the same speed as the speed of rotation of said chamber (1).

7. The device as claimed in one of claims 1 to 4, wherein the central convergent body (11) is driven in rotation at a speed which is different from that of the chamber (1), but is integral with the inlet (6) and/or outlet (7, 8) ends of the chamber (1).

8. The device as claimed in claim 7, wherein the diabolo-shaped central body (11) has at the periphery fins (14) which are equidistant and arranged along a generatrix.

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