EP0754259B1 - Refiner filling - Google Patents

Abstract

PCT No. PCT/FR95/00452 Sec. 371 Date Jan. 31, 1997 Sec. 102(e) Date Jan. 31, 1997 PCT Filed Apr. 7, 1995 PCT Pub. No. WO95/27822 PCT Pub. Date Oct. 19, 1995A component for a pulp refiner such as a paper pulp refiner. The component comprises an attachment surface (16) for attachment to the refiner, a working surface (17, 22), and at least one core (15, 28, 33, 50, 51) made of rigid material and provided with a wear resistant coating (19, 20, 25) so that at least the useful surface area (18) of the component at least partially consists of the outer surface of the coating (19, 20, 25). Said component is characterised in that said coating (19, 20, 25) consists of a stack of thin layers or strips (21). A refiner including at least one such component, a method for preparing said component and a fiberising and for refining method using at least one such component are also disclosed.

Description

The invention relates to a filling for a dough refiner such as a refiner. pulp, a refiner comprising at least one such filling, a process for preparation of this filling and a refining process in which we use minus such a garnish.

STATE OF THE ART

It is known to refine pulps such as paper pulps by passage in a refiner. Pulp refiners have a rotor and a stator between which the raw material is defibrated and fibrillated. There are two main categories of refiners: disc refiners and conical refiners.

Disc refiners typically include one or more rotors and a or several stators each consisting of a support disc on which is mounted a another disc called a refining disc, the role of which is both to protect the disk supporting erosion by the raw material to be refined and participating in refining of the latter.

During refining, the raw material can be introduced through the center of at least one of the refining discs, in the space between the two refining discs and flow towards their periphery. It can also be introduced at the level of the periphery of the discs and come out through the center of the discs. During one or the other of these circulations, the dough undergoes a treatment which modifies significantly the physical properties of the fibers in the pulp and then allows the paper made from treated pulp to possess the characteristics necessary for use for which it is intended.

The refining discs, as illustrated in FIGS. 1 and 2, include generally a fixing face 1 on the refiner and a working face 2 comprising an alternation of grooves 3 and projections called blades 4. The surface active 5 of these blades 4 gradually wears out during refining, so that periodically shut down the refiner and replace the refining discs.

Currently used as refining discs, discs which have a complete annular shape and which are cast in one piece, as a torus-shaped element (FIG. 1), ie disks, illustrated in FIG. 3, composed of several segments 6 and which together form a ring.

Conical refiners generally include a rotor 7 represented on Figures 4, and 5 of conical or frustoconical shape, and a stator 8, shown in the Figures 6 and 7, also conical or frustoconical. Cones or trunks of refining cone 9 and 10 are mounted, respectively, on the outer surface 11 of the rotor 7 and on the inner surface 12 of the stator 8. These cones or truncated cones of 9,10 refining can be composed, respectively, of 13,14 segments. They have alternating grooves and blades (not shown) and they play the same role as the refining discs mentioned above.

During refining in a conical refiner, the raw material is introduced between the stator and the refiner's rotor, at the top of the cone or trunk cone constituting the rotor and comes out at the base of this same cone or trunk of cone.

Since the refining discs or cones must be resistant to wear, they generally consist of a metal or a metal alloy having a high hardness.

In order to improve the efficiency of the refining of paper pulp using such discs or metal cones, research currently carried out on the modification of the geometry of their working face and on the nature of the metal or metallic alloy.

Thus, international application No. WO 90/04673 proposes a method of fiber pulp manufacturing in which a starting material containing lignocellulose is defibrated and fibrillized between the blades of two grinding discs facing, and according to which, to improve refining, the blades have been tilted angle of 5 to 30 degrees from the radius of the discs on which these blades are located.

However, this process does not yet sufficiently improve the quality of the dough obtained.

German patent application No. DE-A-1 621 703 proposes a seal metal for refiner at least the active surface of which is covered by a coating in wear-resistant material.

During its research, the plaintiff found that the quality of the refining was limited by the nature of the material of the discs, that is to say by the metal or metal alloy, and that to improve the refining of the dough, it would interesting to be able to get rid of the use of metallic active surfaces.

Indeed, during refining using metal discs, it occurs between the rotor disc and the stator disc, shocks during which particles of metal are torn from the disc blades. It follows that the active surface 5 of blades 4 becomes very irregular and reduces the fibrillation of the paper fibers, which decreases the quality of refining.

In addition, because the metal discs wear out quickly, the quality of the refined dough is not constant over time and the refiner's stops, necessary to replace worn discs with new metal discs, are frequent. Worn discs cannot be regenerated, so they must be thrown away.

There is therefore no prior art refining possibility which provides a high and constant quality of refined dough, which decreases the frequency of refiner stops required to change the discs refining. There is also no refining disc with resistance high in wear, a regenerable character with an acceptable regeneration cost.

Patent application EP-A-0634522 belongs to the state of the art referred to Article 53 (4) EPC which is not taken into account for the assessment of the activity inventive.

Patent application EP-A-0634522 relates to a defibration plate or paper pulp refining, comprising a grinding surface having ribs separated by grooves.

The body of the plate is made of a first material such as stainless steel or cast iron, ensuring the general mechanical strength of the plate in use. The upper part of the ribs is made of a layer of abrasion-resistant material comprising grains of hard abrasion-resistant material bonded in an alloy metallic whose melting and weldability characteristics are suitable for laser reloading on the first material forming the plate body. The ribs are successively recharged by scanning a laser beam and a spray nozzle, in one or more passes.

SUMMARY OF THE INVENTION

The plaintiff, in carrying out its research in a new direction, has succeeded in developing a packing which overcomes the drawbacks associated with state of the art metal discs. This trim has a face of attachment to the refiner, a working face, at least one core of a material rigid, covered by a coating of a wear-resistant material, such so that at least the active surface of the lining is made up of all or part of the exterior surface of said coating and is distinguished from the linings of the state of the technique in that said coating is porous and consists of a superposition of layers thin or strips.

Such a lining has a higher wear resistance than the linings known so far.

In addition, it may include a core made of a rigid material little expensive, such as a recovery material.

In addition, it can, once the coating is worn, be regenerated again by application of a new coating.

Furthermore, when it is used in a refiner, the refined dough obtained has, for the same specific power consumed, a length average fiber and whiteness superior to that of pasta obtained in a refiner provided with fittings according to the state of the art. We also observe reduced noise during refining and greater air gap stability (distance between rotor and stator) of the refiner, which results in greater regularity in the properties of the refined dough.

Other advantages provided by the filling according to the invention and its implementation work will appear on reading the detailed description which follows, as well as on examining the Figures 8 to 27, given simply by way of illustration.

SUMMARY DESCRIPTION OF THE FIGURES

Figures 1 and 2 schematically represent a refining disc according to the state of the art, respectively in front view and in side view in section according to axis A-A.

FIG. 3 schematically represents a second refining disc according to the state of the art.

Figures 4 and 5 schematically represent a conical refiner rotor equipped with refining cones according to the state of the art, respectively with a view to face in cross section along axis B-B and in right view.

Figures 6 and 7 schematically represent a conical refiner stator exhausted from refining cones according to the state of the art, respectively with a view to face in cross section along axis C-C, and in left view.

Figures 8 and 9 show a packing according to the invention, respectively in front view and in bottom view.

Figure 10 shows schematically in section, the packing of Figures 8 and 9 in bottom view in section according to D-D.

Figures 11 and 12 schematically represent a first variant of the lining according to the invention, respectively in front view and in bottom view in section along the E-E axis.

Figure 13 shows schematically in section, a second variant of the lining according to the invention.

Figure 14 shows schematically in section, a third variant of the lining according to the invention.

Figures 15 and 16 schematically represent a fourth variant of the lining according to the invention, respectively in front view and in bottom view in section along the axis F-F.

Figure 17 shows schematically in section, a fifth variant of the lining according to the invention.

Figure 18 shows schematically in section, a sixth variant of the packing according to the invention.

Figures 19 and 20 schematically represent a seventh variant of the lining according to the invention, respectively in front view and in bottom view in section along the axis G-G.

Figure 21 shows schematically in section, an eighth variant of the lining according to the invention.

Figure 22 shows schematically in perspective a lining according to the invention intended to be mounted on a conical refiner rotor block.

Figure 23 shows schematically in perspective a lining according to the invention intended to be mounted on a stator block of a conical refiner.

FIG. 24 represents the weighted length curve of the fibers of a raw material before refining.

FIG. 25 represents the weighted length curve of the fibers of a pulp obtained after refining with discs according to the state of the art.

FIG. 26 represents the weighted length curve of the fibers of a pulp obtained after refining with fillings according to the invention.

Figure 27 shows another weighted fiber length curve a paste obtained after refining with fillings according to the invention.

For the sake of clarity, Figures 9, 10, 12, 13, 14, 16, 17, 18, 20 and 21 although representing sections, have not been hatched.

DETAILED DESCRIPTION OF THE INVENTION

The fixing face and the working face of a gasket according to the invention are, respectively, the side intended to be fixed against the disc or support cone of the refiner, and the face intervening directly during the refining of the dough.

These faces are preferably parallel when the lining is intended to be used on a disc refiner, and concentric when the lining is intended for be implemented on a conical refiner.

By active surface is meant in the description of the invention, only the surface of the filling furthest from the fixing face and against which the dough will be refined (fibrillated). The active surface can occupy the entire working face of the packing: this is the case, in particular, when the working face is flat. The surface active can also represent only part of the working face, for example, when the latter has places, such as grooves, where the dough is not fibrillated.

The active surface of a lining according to the invention is always constituted by all or part of the exterior surface of the coating.

By exterior surface of the coating is meant the surface which is opposite to the surface of the coating in contact with the core. According to the invention, the outer surface coating therefore always includes at least the active surface of the lining. In in other words, the active surface is always constituted by the material resistant to wear and tear of the coating. However, the extent of the exterior surface of the coating may not be limited to the active surface of the lining.

As a rule, but this is not an obligation, the coating is not present only on the working face which it therefore occupies at least in part. This coating is preferably continuous and of uniform thickness at the level of the entire active surface. His thickness is generally between 0.1 and 2 mm, preferably between 0.5 and 0.8 mm.

The rigid material from which the core of the lining is made is a material having mechanical properties, in particular of compressive strength, allowing it not to break, when the rotor and the stator are close to each other, and do not tear off and be carried away by the flow of raw material during refining. It can be a metal, a metal alloy, cast iron, a plastic material having good mechanical properties, including shear strength sufficient, such as so-called "high performance" plastics, which may be mentioned polyamides 4-6, polyamide imides, or technical polymers such as polyamide 6-6. The rigid material can also be a composite material such as epoxy / carbon fiber, epoxy / glass fiber, or vinyl ester / fiber carbon. It goes without saying that the choice of rigid material also depends on its resistance to the process chosen to apply the coating.

An advantage of the lining according to the invention is that the rigid material can be an inexpensive recovery material such as a metal or metal alloy recovery or a plastic material made from recycled polymers having the mechanical characteristics mentioned above. Indeed, unlike the fittings of the state of the art which must be made of metals with high resistance to wear such as steel or cast iron, the linings according to the invention may comprise a core made up of a material which is not very resistant to wear, because the core does not have an active surface and has not intended to resist wear.

In addition, it is possible to choose as rigid material, a material having a high resilience (impact resistance) and as a coating, a poorly resilient material but with high hardness. The filling obtained is then little fragile while being very efficient.

The wear-resistant material constituting the coating is preferably a different material from that of which the core is made. It must be able to adhere to the latter in a sufficiently firm manner so as not to be torn off and carried away by the flow of raw material during refining. It can be a pure metal such as molybdenum (Mo), nickel (Ni), aluminum (Al), copper (Cu), tantalum (Ta) or titanium (Ti), a metal alloy such as nickel-chromium (NiCr), nickel-chromium-aluminum-yttrium (NiCrAlY), nickel-chromium-iron-boron-silicon (NiCrFeBSi), nickel-aluminum (NiAl) or copper-aluminum (CuAl), a pseudo-alloy such as aluminum-molybdenum (Al-Mo) or copper-tungsten (Cu-W), a cermet such as WC-Co, Cr ₃ C ₂ -NiCr, WC-Ni or WC-NiCr, a ceramic such as alumina (Al ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), titanium oxide (TiO ₂ ), zirconia (ZrO ₂ ), oxide zirconium and yttrium (ZrO ₂ / Y ₂ O ₃ ), yttrium, barium and copper oxide (Y ₁ Ba ₂ Cu ₃ O7) or silica (SiO ₂ ), a mineral such as l apatite, a carbide such as tungsten carbide, titanium, boron or silicon, or an adamantine carbon.

It can also be provided that the coating is a mixture of these materials, or a superposition of layers made up of different materials chosen among these materials.

Preferably, a ceramic is used as coating, in particular alumina.

According to the invention, a porous coating is used. We thus improve the characteristics of the refined dough. Porous coating means a coating with a ratio of total pore volume to total coating volume between 2% and 50%, preferably between 10% and 30%.

The plaintiff was, indeed, surprised to discover that it is possible to use for the coating a material having a high porosity, because generally, when we seek to increase the resistance to wear of an element, we coat it with a layer of a material with the lowest possible porosity.

It is further desirable that the porosity increases from the surface of the coating in contact with the core up to the active surface. Such a porosity gradient allows both good adhesion of the coating to the core and better refining paste. The porosity can thus be zero in contact with the core and close to 50% at level of the active surface.

The porosity is advantageously of the open type. Indeed, this seems cause a capillary effect with respect to the water contained in the dough being refining and beneficially modifying the circulation of the dough and its refining.

It is advantageous to use as a coating a material having good tribological characteristics and / or high abrasiveness towards the material to refine.

The coating may include a second material disposed between the material wear-resistant and core, so as to cover it and protect it from corrosion by the raw material to be refined which could pass through the coating, if this coating is porous. This is particularly advantageous when, for example example, the core is made of a metal or an oxidizable alloy.

Said second material is preferably in the form of a layer thin, between about 20 and about 200 microns thick (micrometers µm) and preferably between about 50 and about 100 microns, ranging from preferably at least on the entire working face. The choice of this second material depends on the physico-chemical conditions under which the packing will be brought to to work. Said second material can be, for example, an oxide of nickel and chromium. It turned out that the alloy composed of nickel, chromium, aluminum and yttrium (NiCrAlY), provided excellent protection against the phenomena of corrosion.

When the packing according to the invention is intended to be used in a disc refiner, it can have the shape of a ring or a washer like the refining rings or washers of the state of the art represented by FIG. 1, or the shape of a disc segment like segments 6 in Figure 3.

When the packing according to the invention is intended to be mounted on a conical refiner, it can have a cone or truncated cone shape or a shape of segment of cone or truncated cone, like those illustrated by the figures 22 and 23.

The lining according to the invention as illustrated in FIGS. 8 and 9, comprises a core 15 of a rigid material comprising a fixing face 16 on the refiner and a working face 17 at least essentially flat.

As the working face 17 of the lining is flat, the active surface 18 of the seal extends over the entire working face 17.

A coating 19 made of a wear-resistant material covers said core 15, so that at least the entire active surface 18 of the lining is made of wear-resistant material. So the fibrillation action of the dough is only performed on the wear-resistant material and not on the core 15.

As can be seen in FIG. 10, the coating 20 consists of at least at least two thin layers or lamellae 21 arranged one on top of the other, preferably, at least essentially parallel. These strips 21 allow more uniform wear of the coating 20 and thus contribute to the constancy of the refining conditions. Preferably, the number of lamellae 21 is the highest possible that the technique used to achieve the coating allows to achieve. Of tests have shown that when the coating consists of only one layer, it could be easily torn off when the rotor was brought closer to stator. The slats give the coating a special wear capacity which allows the toppings to adapt to the refiner. In the case of a disc refiner, for example, the discs are never in practice perfectly parallel. It follows that when we reduce the air gap, it happens- that contacts occur, to some places, between two facing discs. If the coating is made in one thick layer, it is very often torn off. However, if the coating is consisting of lamellae, only the superficial lamellae located at the places where products the contacts are torn off and refining can then take place between remaining strips from each of the discs.

• une résistance à l'usure élevée vis-à-vis de la pâte à raffiner, due à la nature du matériau constituant le revêtement, ce qui permet une usure lente et une utilisation de la garniture pendant de longues durées et
• une résistance à l'usure par choc faible qui permet de nombreux arrêts et redémarrages sans arrachement du revêtement.

Thus, the linings according to the invention can exhibit two types of wear resistance:

• a high wear resistance with respect to the dough to be refined, due to the nature of the material constituting the coating, which allows slow wear and use of the filling for long periods of time and
• low impact resistance which allows many stops and restarts without tearing off the coating.

According to a first advantageous variant represented by FIGS. 11 and 12, the working face 22 of the lining is provided with one or more alternating grooves 23 with one or more blades 24.

Said grooves 23 are intended to facilitate the flow of the dough. They can be of any section. They can in particular have a section rectangular like those found on the refining discs of the trade. They are present in the coating 25 which extends over the entire face of work 22. The active surface of the lining is then the sum of the surfaces of all vertices 26 of the blades 24. The area of the active surface is therefore less than the area of the working face 22. The geometry of the blades 24 and grooves 23 can be chosen by depending on the type of specific treatment you want to subject the material to refine. The geometry / material pair of said coating 25 can be optimized for each specific treatment of the material to be refined.

According to a second advantageous variant represented by FIG. 13, the grooves 27 are present in the core 28 and the coating 29 covers only the vertices 30 of the blades 31. In this case, it is preferable that the rigid material constituting the core 28 is a material having a fairly good resistance to wear, such as "Ni-hard" type cast iron or chrome steels. The latter also the advantage of having good resistance to corrosion.

According to a third advantageous variant represented by FIG. 14, the grooves 32 are present in the core 33 and the coating 34 occupies the entire face of work 35. The covering 34 preferably matches all the shapes of the core 33. It is therefore placed both on the vertices 36 of the blades 37 and on their bottoms 38. Its thickness is preferably uniform on all the vertices 36.

The coating 34 can also be composed of several parts made up each of a different material. Thus, it is possible to cover the vertices 36 of a first material and the bottoms 38 and the walls of the grooves 32 of a second material. Advantageously, said first material is then chosen from among the materials with high wear resistance and / or good properties tribological materials such as alumina and said second material is chosen from materials with high abrasiveness such as tungsten carbide and / or resistance high corrosion.

According to a fourth advantageous variant represented by FIGS. 15 and 16, one or more obstacles 39 are arranged in one or more grooves 40, so to achieve one or more throttles and to disturb the circulation of the dough by creating micro-vortexes inside the grooves 40, which has the effect of forcing the material to be refined to pass between the active surfaces of the rotor and the stator. The refining quality is then improved.

The exact form of the said obstacles 39 matters little since they make it possible to cause turbulent flow of the dough. It then follows a increased residence time of the dough between the rotor and the stator of the refiner, which improves the efficiency of refining and therefore the quality of the dough obtained.

Said obstacles 39 can be arranged randomly or in groups of two and located opposite one another, respectively on the walls 41 and 42 of the grooves 40. The obstacles located on the wall 41 can also be offset with respect to to those located on the wall 42.

Obstacles are preferably made of the same material as the coating 43 with which they are integral.

The covering 43 covering the entire working face 44 according to this fifth variant, the obstacles 39 are therefore arranged both in the grooves 40 and on the coating 43.

When the coating 43 comprises a first material for the active surface and a second material in the grooves 40, the obstacles 39 are preferably made of said second material.

According to a fifth advantageous variant represented by FIG. 17, the obstacles 45 are arranged in the bottoms or on the walls of the grooves 46. As the covering 47 covers only the vertices 48 of the blades 49, the obstacles 45 are therefore in contact and adhere to the core 50. They can also be part of the core 50 and therefore be made of the same material as this core 50.

According to a sixth advantageous variant represented by FIG. 18, the core 51 is provided with grooves 52. The covering 53 covers the entire working face 54. The obstacles 55 are therefore fixed against the covering 53 or form part of the latter which preferably follows all the shapes of the core 51 and preferably has a uniform thickness over the entire working face 54.

Figures 19 and 20 show a seventh advantageous variant of the packing according to the invention, in which the grooves 56 have a quasi-circular section. Such fittings thus have a high active surface (constituted by the sum of the surfaces of the vertices 57 covered by the coating 58), while having grooves 56 which may contain a large volume of dough during the refining.

FIG. 21 represents an eighth advantageous variant of the lining according to the invention, in which the coating 59 covers the entire working face and the grooves 60 have a dovetail shape, which is another way to achieve a high active surface while having grooves 60 in volume important.

When the lining according to the invention has grooves, it can be envisaged for these grooves a variable depth. The latter can, for example, be weak at one end (for example, the periphery for a trim annular), and increase, preferably regularly, to become important in level of the other end (the center, for an annular packing), or vice versa. The choice between increasing the depth towards one end, or increase towards the other of the extremities, will then depend on the characteristics of operation of the refiner, in particular, the direction imposed on the circulation of the dough in the refiner.

It may be advantageous to practice or plan, in the coating and on its outer surface, notches of small depth compared to the thickness of the coating, so as to create edges and thus give a character abrasive or increase the abrasiveness of the coating.

Figures 22 and 23 show fittings according to the invention intended for be implemented respectively on the rotor and on the stator of a refiner conical. During the operation of the latter, the raw material is fibrillated between the coatings 61 and 62 of the linings which are pressed against each other.

The packing according to the invention and its variants are intended to be fixed, in known manner, on the rotor block or on the stator block of a refiner. That is why they may include one or more holes (not shown), passing through the core and optionally the covering by connecting the working face to the fixing face, and intended for the passage of fixing screws on the rotor block or the stator block of the refiner.

Preparation of fillings according to the invention:

The linings according to the invention can advantageously be prepared for starting from a core of a rigid material which is covered at least partially with using a wear-resistant coating, in such a way that at least the surface active lining is formed by all or part of the outer surface of said coating.

The recovery is carried out according to any process allowing to deposit a hard coating on a substrate, such as, for example, the process called "laser-cladding", the process of plasma deposition by thermal spraying, the process of Induction plasma deposition, or the C.V.D. Vapor Deposition). The core is preferably provided with grooves which can be practiced by machining in a flat core, or else provided during the molding of the core, especially in the case where it is more economical to manufacture the latter by molding.

The core can advantageously be a disc or a disc segment of commercial refining, or a cone, truncated cone or segment of a cone or trade refined cone trunk. Then preferably apply the coating of wear-resistant material so that all forms of the disc, disc segment, cone, trunk of cone or segment of cone or trunk of cone of commerce are kept.

It goes without saying that the coating can completely cover the core, i.e. its working face as well as its fixing face or its lateral faces.

There is thus a packing according to the invention which leads to better refining as the disc, disc segment, cone, truncated cone or cone segment or commercial cone trunk. The packing according to the invention thus obtained has also better wear resistance than disc, disc segment, cone, commercial cone or cone or cone segment. In addition, she can be regenerated once worn.

Furthermore, when the coating is present in the grooves (first, third, fourth, sixth and eighth variants), and if this coating is abrasive, the turbulent nature of the flow is increased, which results in better maintenance of the dough film between the rotor and the stator of the refiner, for better refining and better management of the entire refining operation.

It is preferable to provide the core with the coating of wear-resistant material by implementing the so-called plasma removal process. Indeed, we obtain thus, when the core has grooves, a continuous coating of uniform thickness and fitting well to all forms of the working face. In addition, like grains forming the starting material have at least partially melted when passing through flame, the coating obtained is in a continuous, uniform form and relatively high density.

This also avoids the difficult and costly machining of projections in the wear-resistant material.

Furthermore, the plaintiff noted, during its tests, that despite the significant forces involved in refining, the coating deposited by the process plasma was not removed.

In addition, the plasma deposition process proves to be particularly advantageous to make a coating composed of a superposition or stack of layers thin or strips. In fact, this process makes it possible to deposit the coating in several passes, each time depositing a very small amount of the material resistant to wear, so as to obtain a coating consisting of a superposition of thin layers or coverslips. Such a coating then wears uniformly and has a surface with maximum flatness throughout its wear.

The thickness of the slats can thus be between 0.003 and 0.100 mm. It is preferably between 0.005 and 0.025 mm.

Another advantage of implementing the plasma deposition process is that can use a sophisticated and expensive material as a coating because this process allows to deposit thin layers of material, so a small amount of material, which does not lead to a significant increase in the cost price of the garnish.

Yet another advantage of the plasma deposition process is that the deposition of coating can be done precisely. This process therefore lends itself well to production of fittings according to the invention such as, for example, those corresponding to the second, fourth, fifth, sixth, seventh or the eighth variant.

The starting material for the implementation of the plasma process presents generally a particle size between about 10 and about 80 microns (µm) and preferably between about 30 and about 40 microns (µm).

The obstacles shown in FIGS. 16, 17 and 18 can be arranged by the plasma process.

To obtain a gasket whose working face includes blades and grooves and of which only the tops of the blades are covered with coating, it is possible to obstruct the grooves with covers, to deposit the coating on said tops and then remove the covers. The walls of the grooves are then devoid of coating.

Use of fittings according to the invention:

The packing according to the invention is fixed in a known manner, for example to the screw means, on the rotor block or the stator block of the refiner.

The Applicant has noticed that the implementation of the linings according to the invention makes it possible to keep a constant air gap during refining even when the refining power is very high, which has the advantage of leading to a stable refining conditions and maintaining the quality of the refined dough in time.

In addition, the refined dough has a whiteness greater than that obtained with the linings according to the state of the art.

The lining according to the invention can be fixed on the rotor block or on the block stator of the refiner. Preferably, it covers the entire working face of the rotor block or the stator block. Thus, the entire active surface of the block has a coating of wear-resistant material.

Of course, it is possible to have several trims of dimensions equal or different on the rotor block or on the stator block, in particular, if we wishes to cover the entire working face of the rotor or stator and that the dimensions a single trim are insufficient to allow it to occupy on its own all the working face of the rotor block or the stator block.

It is preferable to provide both the rotor and the stator of the refiner with one or more several fittings according to the invention. It is even more preferable to cover the entire working face of the rotor block and the entire working face of the stator block of one or several linings according to the invention, so that the entire active surface of the refiner is made of wear-resistant material. We then obtain a flow of the dough to be refined having maximum turbulence and refining optimal.

The linings according to the invention can be used with a view to defibering and / or refining any material composed of fibers, such as pulp, and in particular, paper pulp whose dry matter concentration is less than 60% and preferably less than 25%. They are particularly revealed effective when the pulp to be refined is an aqueous suspension whose concentration is between 3 and 8%.

The linings according to the invention make it possible to obtain better results, in regarding the cutting of fibers (less cutting phenomena), than state of the art fittings. It is therefore advantageous to use them in the paper recycling industry. Because they can be used to refine old paper, that is to say improve its quality, they make possible a reduction in the content of long (new) fibers in recycled paper. Of more, they improve the dispersion of "stickies", the impurities of the paper, which produces paper with fewer dark spots. So we get, thanks to the linings according to the invention, a lowering of the cost of recycling.

In addition, the fittings according to the invention can be used to produce on disc refiners refining operations that were previously practically possible only on conical refiners, more particularly on wide angle conical refiners. Such refining operations are those necessary for the preparation of special paper such as cigarette papers, tracing papers, etc ..., i.e. papers obtained from degree pulp High Shopper-Riegler (over 60 degrees).

Furthermore, the linings according to the invention can also be used for the defibration of any cellulosic material, such as wood waste, so-called "annual" plants (bagasse, sorghum, alfa, ...).

Comparative tests

The refining of a paper pulp was carried out under the same conditions, with 4 metal discs according to the prior art and with 4 fillings according to the invention. The discs according to the state of the art were 40.64 cm (16 inch) diameter crowns marketed by the company Black-Clawson, made of "Ni-hard" cast iron having 10 sectors, tops of blades of a width of about 5.5 mm, and grooves parallel to each other within each sector, inclined by about 20 ° with respect to the radius, of rectangular cross section, about 5.0 mm in width and d '' about 6.0 mm deep. The linings according to the invention were linings prepared by the plasma spraying deposition process, covering with a uniform or approximately uniform thickness of approximately 500 μ (microns) of alumina / titanium oxide 97/3 (Al ₂ O ₃ 97% -TiO ₂ 3%) the entire working face of crowns identical to those described above. The coating consisted of a superposition of 25 thin layers 20 μm thick each. The porosity was of the open type and equal to 20% (measured according to the alcohol penetration test).

The refiner used was the Twin Midjet refiner marketed by the company Black-Clawson, comprising 4 support discs and working in duo-flow, that is to say that the 4 support discs are arranged parallel to each other and a part (theoretically half) of the raw material is refined between 2 refining discs of a first game and the other part between 2 refining discs of a second game. The introduction of the raw material was done in the center of the refining discs. The refined paste stood out from the periphery of the discs.

The refiner was equipped with a 140 kW engine.

The nominal circulation rate of the pulp was 30 to 40 m ³ / h, the maximum flow being 60 m ³ / h.

The raw material had a concentration of 3% and consisted of Scandinavian softwood chemical pulp. Figure 24 represents the weighted length curve of the fibers and of the elements making up the raw material. The average fiber length measured by an optical sensor was 2.49 mm. The mass percentage of fibers as a function of their length is indicated above the curve.

• 'E.T.' désigne les formettes obtenues à partir de pâte raffinée dans un raffineur muni de 4 disques du commerce,
• 'INV.' désigne les formettes obtenues à partir de pâte raffinée dans un raffineur muni de 4 garnitures selon l'invention.

The superiority of the fillings according to the invention is evaluated through measurements carried out on paper sheets prepared from refined pulp. The results of these measurements are grouped in the following Tables A, B, C, and D in which:

• 'ET' designates the formettes obtained from refined dough in a refiner fitted with 4 commercial discs,
• 'INV.' denotes the formettes obtained from refined dough in a refiner provided with 4 fillings according to the invention.

The measurements were carried out according to the French standards indicated in the tables, in an atmosphere conditioned at 65% RH and at 20 ° C.

LR ₀ is the breaking length calculated from the breaking force with adjoining jaws while LR is the breaking length according to AFNOR Q03004 standard.

The column '° SR' indicates the Schopper-Riegler degree of the refined dough. Refining time (min) Weight (g / m ² ) NFQ03 -019 Thickness (µm) NFQ03 -016 ° SR NFQ50 -003 AND INV. AND INV. AND INV. 0 67.4 67.4 121 121 15 15 5 64 72.6 105 126 23 22 10 63.5 74 99 119 39 35 15 64 73.6 95 108 52 54 20 66 74 92 101 66 71 25 72 90.4 79 Refining time (min) Whiteness (%) NFQ03 -038 Corrected opacity (in% at 70g / m ² ) NFQ03 406 AND INV. AND INV. 0 83.8 83.8 76.3 76.3 5 81.1 82.1 75.9 75 10 79.4 81.7 75.8 75.3 15 77.3 81 76.1 71.7 20 74.6 80 75.6 69.7 25 78.4 66.7 Refining time (min) Id 100 (mN.m ² / g) NFQ03 -011 I burst (kPa.m ² / g) NFQ03 -053 LR (m) -004 NFQ03 Elongation at break (%) AND INV. AND INV. AND INV. AND INV. 0 1151 1151 2.59 2.59 3549 3549 3.05 3.05 5 1131 1368 3.51 3.85 4923 5397 3,715 3.3 10 1046 1438 3.97 4.71 5638 6669 3.99 3.69 15 875 1210 4.09 5.43 6202 7662 3.97 3.74 20 830 962 4.33 5.35 6830 7873 4.2 3.79 25 853 5.65 8796 3.72 Refining time (min) Permeability [cm ³ / (m ² .Pa s)] NFQ03 -061 LR ₀ sec (m) NFQ03 -056 LR ₀ hum. (m) NFQ03 -056 AND INV. AND INV. AND INV. 0 82.4 82.4 11171 11171 10480 10480 5 29.5 21.5 11767 11485 10418 9547 10 14.7 5 11800 11966 9369 9754 15 4.16 1.26 11988 11755 9189 9547 20 2 0.25 11190 12040 8090 8554 25 0.07 11560 8164

It therefore appears from the results of these tables that the hydration and fibrillation of the dough takes place without a notable cutting phenomenon being observed fibers.

Figure 25 shows the weighted length curve of fibers and components of the dough after refining for 20 minutes with the discs according to the state of the art, and with a useful power of 40 kW. The average length of fibers was 1.55 mm.

Figure 26 shows the weighted length curve of fibers and components of the dough after refining for 20 minutes with the fillings according to the invention, also with a power of 40 kW. The average length of fibers was 2.66 mm.

Figure 27 shows the weighted length curve of fibers and components of the dough after refining for 25 minutes with the fillings according to the invention, with a power of 60 kW. The average fiber length was 2.18 mm.

These curves clearly show that the linings according to the invention allow a reduction in the fiber cutting phenomenon and a decrease in the production of fines.

Mechanical tests carried out in a comparative manner on paper made from refined pulp show that the breaking length and the burst index of the paper obtained with the linings according to the invention are in about 15 to 20% higher on average than the paper obtained with the state of the art. A superiority of around 30% has even been obtained when the applied useful power was 60 kW. In this regard, it should be noted that during of the implementation of discs according to the state of the art, it is impossible to apply such a high power output under the specific conditions of operation of the installation used to test the linings according to the invention.

Surprisingly, we also noticed that the tear index increases at the start of refining with the fillings according to the invention while in good standing general the tear index of the formettes decreases from the start of the operation of refining with discs according to the state of the art.

Other tests carried out by the applicant on industrial installations, allowed to observe when using the linings according to the invention, a 10 to 15% reduction in the no-load power of the refiner compared to the power necessary with state-of-the-art cast iron fittings. By power at empty, we mean here the mechanical and hydraulic power used to circulate the dough through the refiner.

In addition, the Applicant has noted with satisfaction that the refiner when fitted with the fittings according to the invention, was much less noisy only when it included the cast iron fittings of the state of the art.

Claims (18)

1. A pulp refiner filling, comprising a face (16) for securing to [the] a refiner and a working face (17, 22) comprising an active surface and including at least one core (15, 28, 33, 50, 51) made of a rigid material covered by a coating made of a wear-resistant material in such a way that at least the active surface (18) of the filling is comprised of all or a portion of the external surface of the said coating (19, 20, 25), characterized in that the said coating (19, 20, 25) is porous and is comprised of an overlay of thin layers or lamellae (21).
2. Filling according to Claim 1, characterized in that the thickness of the said thin layers or lamellae (21) is between 0.003 and 0.100 mm and preferably between 0.005 and 0.025 mm.
3. Filling according to either of the preceding claims, characterized in that the ratio-total volume of the pore/total volume of the coating-is between 2% and 50%.
4. Filling according to claim 3, characterized in that the ratio-total volume of the pore /total volume of the coating-is between 10% and 30%.
5. Filling according to Claim 1,3 or 4, characterized in that the porosity of the said coating (19, 20, 25) increases from the core (15, 28, 33, 50, 51) towards the said active surface (18).
6. Filling according to any one of the preceding claims, characterized in that the said working face (17, 22) is provided with at least one groove (23, 40, 46) intended to facilitate the flow of the pulp to be refined.
7. Filling according to Claim 6, characterized in that the said groove or grooves (23, 40, 46) are present in the said core (15, 28, 33, 50, 51).
8. Filling according to any one of the preceding claims, characterized in that the said coating (19, 20, 25) covers the whole said working face (17, 22).
9. Filling according to claims 6 to 8 characterized in that at least one obstacle (39, 45, 55) intended to perturb the flow of the pulp is placed in at least one of the said grooves (23, 40, 46).
10. Filling according to any one of the preceding claims, characterized in that the said rigid material is chosen from the group consisting of metals, metal alloys, cast iron and plastics.
11. filling according to any one of the preceding claims, characterized in that the said wear-resistant material is chosen from the group consisting of pure metals, metal alloys, pseudoalloys, cermets, ceramics, minerals and mixtures thereof.
12. Filling according to any one of the preceding claims, characterized in that the thickness of the coating is between 0.1 and 2 mm, preferably between 0.5 and 0.8 mm.
13. Disc or conical refiner characterized in that it is fitted with at least one Filling according to any one of Claims 1 to 12.
14. Process for the preparation of a Filling according to any one of Claims 1 to 12, comprising a core (15, 28, 33, 50, 51) made of a rigid material at least partially covered with the aid of a porous wear-resistant coating (19, 20, 25) in such a way that at least the active surface (18) of the Filling consists of all or a portion of the external surface of the said coating (19, 20, 25), which is performed in a number of runs so as to obtain a coating (19,20,25) consisting of an overlay of thin layers or lamellae (21).
15. Process according to Claim 14, characterized in that the coating (19, 20, 25) is applied by a plasma spraying deposition process.
16. Process for refining pulp, characterized in that at least one Filling according to one of Claims 1 to 12 is used during the refining of the pulp.
17. Process according to Claims 16, in which the pulp to be refined is a paper pulp.
18. Use of a Filling according to any one of Claims 1 to 12 for defibring cellulosic matter.

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