OA16860A - Device for reducing friction between sealing plates of filtration units and its use in a filtration process - Google Patents

Abstract

Device for reducing friction between sealing plates of filtration units and its use in a filtration process The present invention relates to a device and a method for reducing the friction between two plates (4, 5) d 'a filtration unit, driven in relative rotation by being subjected to axial pressing forces, said plates being carried respectively, by the longitudinal end of a drum (1) integral with a rotary shaft (3) mounted on a bearing (6) and having internal collectors (11) and the opposite end of a box (2) locked in rotation and supported by said shaft, characterized in that it comprises at least one traction system (8) acting on the casing (2) by exerting a force intended to at least partially compensate for the axial forces pressing the plate (5) against the plate (4) to reduce the friction while ensuring the maintenance of a sealed mutual contact.

Description

Device for reducing friction between sealing plates of filtration units and its use in a filtration process

The present invention relates to a device for reducing friction between sealing plates of filtration units and its use in a filtration process.

The present invention relates more particularly to a device for adjusting the contact pressure between two surfaces materialized respectively by a first plate carried by one of the longitudinal ends of a rotating drum and a second plate carried by the opposite end. a non-deformable fixed box blocked in rotation.

Such an arrangement is found, in particular, in certain installations for liquid-solid separation under vacuum or under pressure. These installations generally include a large drum (diameter sometimes greater than 2m), containing internal collectors and connected at the periphery to filtering sectors forming once discs have been assembled. This drum is rotated by a motorized shaft mounted on bearings and rotating at speeds up to more than 5 revolutions per minute. According to a variant of the installation, the drum does not carry discs and the filtration is carried out directly on the surface of said drum.

During a rotation of the drum which corresponds to an elementary separation operation, the collectors are successively placed under vacuum (usually -0.5 bar relative)

I during the filtration and spinning phases, then under pressure (commonly +0.2 bar relative) during the separation phase of the cakes of solid matter which have accumulated on the sectors.

Thus, in this type of industrial installation, the rotary drum is equipped at one of its ends with a so-called wear plate provided with orifices communicating, through openings made on a facing plate called distribution, successively during the separation cycle, with a suction circuit and a blower circuit connected to the fixed casing.

More precisely, the flat faces of the two plates are in contact to ensure the sealing of the system and, during the rotation of the drum, the orifices of the wear plate pass successively in front of the openings of the distribution plate.

Due, in particular, to the vacuum generated by the suction circuit in the fixed box and the internal collectors of the drum during the filtration phase, the wear and distribution plates are subjected to a pressing force leading to them being applied one by one. against the other and to establish a contact pressure ensuring a peripheral and central sealing but generating a significant friction between the surfaces of the facing plates.

This pressing force is a function of the ratio between the pressing surface and the pressed surface which is in this range of the order of 3 to 4, it being understood that the surfaces in contact of the plates are mainly the solid parts at the periphery and in the center to ensure

The sealing of the system with the outside, as well as the solid parts between the orifices and the openings.

In the context of pressure filtration, the filtration system is placed in a pressurized enclosure.

The pressure difference between the outside and the inside of the assembly formed by the box and the drum can be up to 20 times greater than that of the vacuum system. The contact pressure between the plates will therefore be increased proportionally.

The evolution of filtration needs and in particular the demand from manufacturers for greater treatment capacities, leads, on the one hand, to an increase in the sizes of solid-liquid separation installations and therefore in the diameter of the plates, and on the other hand, to improve productivity, the rotational speeds tend to increase. From the description of the system, it is clear that the greater the dimensions, the speed of rotation and the vacuum level, the greater the friction between the plates and, consequently, the faster their wear.

In addition, the greater the friction between the plates, the greater the torque and the power required to drive the drum, which poses energy problems.

Typically, if the vacuum level in the manifold during vacuum filtration is about -0.5 bar relative, the contact pressure will reach at least 1.2 bar. In the case of pressure filtration, the air pressure around the casing and the drum may be greater than * I ¹ relative bars, the pressure inside the casing and the drum being equal to atmospheric pressure, the contact pressure will then reach more than 18 bars.

The object of the present invention is to solve these technical problems satisfactorily and effectively by proposing a solution making it possible to reduce the contact pressure between the plates without breaking the seal of their connection.

This object is achieved according to the invention by means of a device characterized in that it comprises at least one traction system acting on the box by exerting a force in the direction opposite to the pressing force due to the vacuum of the plate. distribution on the wear plate, thereby reducing the contact pressure between the surfaces of the plates and consequently the friction while ensuring the maintenance of a sealed mutual contact.

Thanks to the traction system, the device of the invention thus makes it possible to at least partially compensate for the axial forces pressing the two plates against each other.

According to an advantageous characteristic, said traction system is controlled by the pressure difference between the inside and the outside of the assembly formed by the drum and the box.

Advantageously, said box comprises lateral conduits equipped with flexible end pieces for connection to the suction and blowing circuits in order to avoid uncontrolled stresses on the box.

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According to yet another characteristic, said box is provided with a central sleeve mounted around said rotary shaft and, on the other hand, means for locking in rotation.

According to one variant, said traction system is mounted to bear on the fixed bearing supporting said rotary shaft or on a fixed frame.

According to another variant, said traction system comprises at least one pneumatic cylinder capable of producing forces in the opposite direction to said axial forces.

In this case, for a vacuum filter, said actuator is mounted coaxially in the extension of said rotary shaft and applies a force to a ribbed central plate ensuring the connection with tie rods connected to the box and parallel to said shaft.

Preferably, said box can slide on said rotary shaft to allow bearing contact of the distribution plate on the wear plate, regardless of the loss of thickness of said wear plate during operation.

The device of the invention makes it possible to offer precise adjustment of the contact pressure between the plates and thus to reduce the friction forces to a minimum. This results in less wear of the box plate.

The regulation and the stability of the contact pressure between the plates can be ensured by the device * 1 "of the invention thanks to the slaving of the force exerted by the traction system on the box to the pressure difference between the interior and exterior of the assembly formed by the drum and the box, where appropriate, by associating therewith reduction members such as lever arms.

According to an advantageous characteristic, this control is carried out for filtration under vacuum or under pressure by placing the chambers of the jack, or of the jacks if there are several, of the traction system with the interior air, by means of conduits. and outside the assembly formed by the drum and the box. The force supplied by the jack will then be proportional to the pressure difference.

The use of the device of the invention in the context of a liquid-solid separation process, in particular in controlled operating mode, allows an optimum increase in the size and the capacity of the industrial filtration units without the need for Additional maintenance problems appear at the level of the moving elements and while controlling the drive torques.

The invention will be better understood on reading the description which follows, accompanied by the drawings in which;

Figure 1 shows an exploded perspective view of an embodiment of the device of the invention on a vacuum disc filter with a wave actuator operating under pressure.

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Figure 2 shows a perspective view of the embodiment of Figure 1 in the assembled position.

Figure 3 shows a side sectional view of the embodiment of Figures 1 and 2.

FIG. 4 represents a perspective view of another embodiment of the device of the invention making it possible to control precisely and without a measuring instrument the force exerted by the traction system at the vacuum level of a disc filter under empty.

Figure 5 shows a perspective view of a side section of the embodiment of Figure 4.

FIG. 6 represents a schematic view of the embodiment of the device of the invention on a pressurized disc filter, the traction system of which comprises three pneumatic cylinders of small diameter.

FIG. 7 represents a schematic view of a variant of the embodiment of FIG. 6 with a single pneumatic cylinder of small diameter exerting the same tensile force on the box by means of a lever arm.

The device of the invention as shown in the various figures is intended for adjusting the contact pressure between two surfaces carried respectively by a rotary drum 1 (partially shown in the figures) and a box 2 mounted in the longitudinal extension of the drum. 1.

The housing 2 is locked in rotation while retaining the possibility of sliding along the motor shaft 3.

The motor shaft 3 is integral with the drum 1, being fixed here to a central hub 13.

The drum 1 carries, in this embodiment, discs formed of filtering sectors 7 connected to the drum 1 by pipes 10. Only two filtering sectors 7 have been shown in FIGS. 1, 2 and 4.

The interior volume of the drum 1 is split into multiple compartments forming the collectors 11 which are intended to recover the filtrate.

The collectors are here separated by radial internal partitions 12.

During the filtration phase of the separation cycle, the collectors 11 are placed under negative pressure then, conversely, during the unclogging phase of the sectors 7, the collectors are placed under overpressure to take off the cakes of solid matter which have been deposited previously. . This cycle is generally implemented during a complete revolution of drum 1.

At one of the longitudinal ends of the collectors 11 of the drum 1 is positioned a so-called wear cylindrical plate 4 (because it is liable to lose thickness and therefore to be replaced), the thickness of which is here a few centimeters. The plate 4 rests on the field of the partitions 12 and is fixed in a removable manner on a flange 14 itself carried by the periphery of the drum 1.

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The plate 4 is provided with orifices 40 formed on its surface and positioned opposite each collector 11 as illustrated in FIG. 1.

The box 2 comprises a central sleeve 21 mounted coaxially on the motor shaft 3 which supports it.

The box is immobilized by means for locking in rotation (for example of the stopper type, not shown), it is provided that the sleeve 21 can nevertheless slide along the shaft 3 over a stroke of the order of a few centimeters.

The box 2 receives, on its side wall facing the drum 1, an attached cylindrical plate 5 called distribution because placing the manifolds 11 of the shaft in communication alternately with circuits in depression and in overpressure with respect to the pressure prevailing at the exterior of the assembly formed by the box 2 and the drum 1.

The rods 62, linked to the bearing 6 by spring strips, push on the box 2 to pre-apply the plate 5 against the plate 4 before the start of the filtration process.

The plate 5 is provided with apertures 50. In the case of vacuum filtration, FIG. 1 to 5, these apertures 50 are the outlets of the suction and blowing circuits (not shown) intended to establish respectively and successively a depression and overpressure in the manifolds 11 of the drum.

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The box 2 further comprises lateral conduits 20 capable of being fitted with flexible end pieces (not shown) for connection to the suction and blowing circuits and opening into the two chambers sharing the internal volume of the box 2 and communicating, via the openings 50 of the plate 5 and the orifices 40 of the plate 4, with the collectors 11 of the drum 1.

For the variant of pressurized filtration, shown in Figures 6 and 7, the suction circuit described above is replaced by a circuit for bringing the interior to atmospheric pressure of the assembly formed by the drum 1 and the box. 2, ensuring the pressure difference with the compressed air of a pressurized enclosure 9.

During the filtration phase, under the effect of the pressure difference between the inside and the outside of the assembly formed by the box 2 and the drum 1, the plate 5 and the box 2, free to slide on shaft, are subjected to axial pressing forces directed towards the plate 4 and the rotating drum opposite.

These forces, the intensity of which is proportional to the pressure difference between the inside and the outside of the assembly formed by the box and the drum, cause the fixed plate 5 to press and be sealed against the rotating plate 4. This results in a high friction between the plates 5 and 4, itself proportional to the contact pressure and therefore to the pressure difference.

To reduce this friction, the invention provides for the use of at least one traction system acting on the non-deformable box 2, and therefore on the distribution plate 5 by exerting a force intended to at least partially compensate for the axial forces which press the distribution plate 5 on the wear plate 4. The traction system thus reduces the contact pressure between the plates and therefore the friction while ensuring the maintenance of a sealed mutual contact.

In the case of vacuum filtration, Figures 1 to 5, the traction system is mounted on the bearing 6 of the motor shaft 3 supported by the fixed frame 61.

The traction system 8 shown in Figures 1 to 3 comprises at least one cylinder 83 here pneumatic or, according to another variant, a hydraulic cylinder or a spring, capable of producing forces in the opposite direction to the forces pressing the distribution plate. 5 on the wear plate 4.

In Figures 1 to 3, the cylinder 83 is mounted on the bearing 6 coaxially in the extension of the rotary shaft 3 and applies a force to a ribbed central plate 81 ensuring the connection with tie rods 82 parallel to the shaft. 3 and whose ends are connected to the outer side wall of the box 2 locally reinforced by gussets 22, as shown in Figures 2 and 3.

Preferably, the force exerted by the jack 83 is controlled at the level of prevailing in the internal volume of the box 2 and of the collectors 11 of the drum 1 so as to obtain an automatic, fine and optimal adjustment of the contact pressure between the plates. regardless of the variations in the vacuum level caused by changes in vacuum circuit conditions.

According to a variant shown in FIGS. 4 and 5, it is sought to obtain a servo-control which is perfectly proportional to the operating vacuum level of the force exerted by the jack 83. For this, the chamber 87 of the pneumatic jack 83, shown in FIG. 5, is placed in communication with the interior of the box 2 by means of a duct 87A. The piston of the jack 83, subjected to the operating vacuum, pulls on the lever arms 85 in a manner proportional to said vacuum. The force supplied by the jack 83 is transmitted by the lever arm 85 to the tie rods 82, which makes it possible to exert a traction, continuously slaved to vacuum, on the box 2 and therefore on the plate 5.

Said lever arms 85 are linked to the piston of the cylinder 83 by the sliding pivot links 85B and to the tie rods 82 by the pivot links 85A. The force transmitted by the lever depends on the position of the sliding pivot link 85C between the lever arm 85 and the support column of the lever 84. By adjusting the position of the support column of the lever 84 carried by the base 86 of the jack 83, itself mounted on the bearing 6, the tensile force exerted on the box 2 and therefore on the plate 5 can be adjusted.

The effect of the lever arms 85 multiplies the force supplied by the jack 83 sufficiently to compensate for the action of the vacuum on the plate 5 with a jack 83 of small size relative to the size of the box 2.

According to another variant, shown in Figures 6 and

7, the filtration is carried out under pressure and the force exerted by the traction system 8 is controlled, precisely and without a measuring instrument, to the pressure difference 5 between the inside and the outside of the assembly formed by the box 2 and drum 1. The filter comprises the same elements 1 to 7 as the vacuum filters described above but is enclosed in a pressurized chamber 9.

In the cases shown in Figures 6 and 7, the chambers 87 of the pneumatic cylinders 83 are placed in communication on the one hand with the compressed air of the pressurized enclosure 9 through the ducts 87A and on the other hand 15 with the air at atmospheric pressure outside the enclosure 9 through the ducts 87B. In this way, the force provided by the jacks 83 will be continuously proportional to the pressure difference between the outside and the inside of the assembly formed by the box 2 and the drum 1.

For reasons of space, several jacks 83 of small dimensions, relative to the box 2, will generally be required, as shown in FIG. 6 where the traction system comprises three jacks 83. In FIG. 6, the jacks 83 are linked. to the wall of the pressurized chamber 9 and their pistons are connected to the tie rods 82.

In this case, the three pneumatic cylinders 83 will be of the same size and subjected to the same pressure difference, they will therefore provide an identical tensile force which will make it possible to compensate for the axial pressing forces "

I * pressing the distribution plate 5 against the wear plate 4.

According to another configuration of the traction system shown in FIG. 7, a single pneumatic cylinder 83 of small dimensions relative to the box 2, will provide, by pushing on a lever arm 85 at the level of the pivot link 85B, the traction force necessary on the pivot link 85A of the lever arm 85 with the tie rods 82 to compensate for the pressing forces applying the distribution plate 5 to the wear plate 4.

In this configuration, the adjustment of the position of the support of the sliding pivot link 85C will make it possible to adjust the force exerted by the traction system on the box 2.

Claims (10)

Device for reducing friction between two plates {4, 5) of a filtration unit, driven in relative rotation by being subjected to axial pressing forces, said plates being carried respectively, by the longitudinal end of a drum (1) integral with a rotating shaft (3) mounted on a bearing (6) and having internal collectors (11) and the opposite end of a box (2) locked in rotation and supported by said shaft, characterized in that it comprises at least one traction system ( 8) acting on the casing (2) by exerting a force intended to at least partially compensate for the axial forces pressing the plate (5) against the plate (4) to reduce the friction while ensuring the maintenance of a sealed mutual contact. 2. Device according to claim 1, characterized in that said plates (4, 5) are provided respectively, for one, orifices (40) for communication with the collectors (11) of the drum (1) and, for the other, of slots (50) corresponding to the suction and blowing circuits intended to establish a depression / overpressure in the manifolds (11) of the drum (1) by relative to the external pressure at drum (1). 3. Device according to claim 2, characterized in what he understands means enslavement the effort provided by said system of traction (8) at the pressure difference between the inside and the outside of the assembly formed by the box (2) and the drum (1). . R ' 4. Device according to one of the preceding claims, characterized in that said box (2) comprises lateral conduits (20) equipped with flexible end fittings for connection to the suction and blowing circuits. 5. Device according to one of the preceding claims, characterized in that said box (2) is provided, on the one hand, with a central sleeve (21) which can slide around said rotary shaft (3) and, on the other hand share of means of 6. previous, traction (8) locking in rotation. Device according to one of the claims characterized in that said comprises at least one jack (83) capable of producing a force transmitted to (82) with a view to being exerted on said casing of the tire system of the tie rods (2) in the opposite direction to said axial pressing forces. 7. Device according to one of the preceding claims, characterized in that the traction system (8) is mounted on the bearing (6) of said rotary shaft (3). 8. Device according to claims 6 and 7, characterized in that said cylinder (83) is mounted coaxially in the extension of said rotary shaft (3) and exerts a force on a ribbed central plate (81) ensuring the connection with the tie rods (82) parallel to said shaft, the end is connected to said box (2). 9. Device according to one of claims 6 or 7, characterized in that it comprises lever arms (85) intended to transmit the force supplied by the jack (83) of the traction system (8) to the tie rods ( 82) in order to minimize the diameter of the cylinder (83). 10. Use of the device according to one of claims 6, 7 or 9 for vacuum filtration, J 4 1 'characterized in that a chamber (87) of the pneumatic cylinder (83) of said traction system (8) is placed in communication with the casing (2) under vacuum through a duct (87A), control precisely and continuously 5 the force provided by the cylinder (83) at the vacuum level inside the box (2). 11. Use of the device according to one of claims 6 or 9 for pressurized filtration, characterized in that the chamber (87) of the pneumatic cylinder or cylinders (83) of the traction system (8) are placed in communication, on the one hand, with the compressed air of a pressurized enclosure (9) through ducts (87A) and, on the other hand, with the air at atmospheric pressure outside said enclosure (9) ) through conduits (87B) precisely and continuously slaving the force supplied by the jacks (83) to the pressure prevailing inside said enclosure (9).