EP0754259A1

EP0754259A1 - Refiner component

Info

Publication number: EP0754259A1
Application number: EP95916728A
Authority: EP
Inventors: Yves Garnier; Guy Caucal
Original assignee: ARTE
Current assignee: ARTE
Priority date: 1994-04-08
Filing date: 1995-04-07
Publication date: 1997-01-22
Anticipated expiration: 2015-04-07
Also published as: DE69504490D1; ATE170578T1; JPH10506686A; FR2718469B1; WO1995027822A1; AU2311395A; FI108868B; FI964013A; EP0754259B1; DE69504490T2; US5836525A; FI964013A0; FR2718469A1

Abstract

A 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/or refining method using at least one such component are also disclosed.

Description

REFINER TRIM

The invention relates to a filling for a pulp refiner such as a pulp refiner, a refiner comprising at least one such filling, a process for preparing this filling and a refining process in which at least one such filling is used. .

STATE OF THE ART

π is known to carry out the refining of pulps such as paper pulps by passing through a refiner. Pulp refiners are equipped with 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 generally include one or more rotors and one or more stators, each consisting of a support disc on which is mounted another disc called a refining disc, the role of which is both to protect the support disc from erosion by the raw material to be refined and to participate in the refining of the latter.

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

The refining discs, as illustrated by FIGS. 1 and 2, generally have a fixing face 1 on the refiner and a working face 2 comprising an alternation of grooves 3 and projections called blades 4. The active surface 5 of these blades 4 gradually wears out during refining, so that the refiner must be periodically stopped and the refining discs replaced.

Currently used as refining discs, either discs which have a complete annular shape and which are cast in one piece, as a torus-shaped element (Figure 1), or discs, illustrated in Figure 3, composed of several segments 6 and which together form a ring. The conical refiners generally comprise a rotor 7 shown in Figures 4, and 5 of conical or frustoconical shape, and a stator 8, shown in Figures 6 and 7, also of conical or frustoconical shape. Cones or trunks of refined cone 9 and Î.0 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 trunks of refined cone 9,10 can be composed , respectively, of segments 13,14. They have an alternation of 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 rotor of the refiner, at the top of the cone or truncated cone constituting the rotor and comes out at the base of this same cone or truncated cone . Since the refining discs or cones must resist wear, they are generally made of a metal or a metal alloy having a high hardness. In order to improve the efficiency of the refining of paper pulp carried out using such metal discs or cones, the research currently carried out relates to the modification of the geometry of their working face and to the nature of the metal or the metal alloy.

Thus, international application No. WO 90/04673 proposes a process for manufacturing fiber pulp in which a starting material containing lignocellulose is defibrated and fibrillized between the blades of two grinding discs facing each other, and according to which, to improve refining, the blades were tilted at an angle of 5 to 30 degrees relative to 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.

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

Indeed, during refining using metal discs, there occurs between the rotor disc and the stator disc, shocks during which metal particles are torn from the disc blades. It follows that the active surface 5 of the blades

4 becomes very irregular and reduces the fibrillation of the paper fibers, which reduces the quality of the refining.

In addition, due to the fact that the metal discs wear out quickly, the quality of the refined paste is not constant over time and the refiner stops required. to replace worn discs with new metal discs, are common. Worn discs cannot be regenerated, so they must be discarded.

There is therefore, in the prior art, no possibility of refining which makes it possible to obtain a high and constant quality of the refined pulp, and which reduces the frequency of stops of the refiner necessary for changing the refining discs. There is also no refining disc having a high resistance to wear, a regenerable character with an acceptable regeneration cost.

SUMMARY OF THE INVENTION

The applicant, by carrying out its research in a new direction, has succeeded in developing a lining which overcomes the drawbacks linked to the metal discs of the state of the art. This lining has a fixing face on the refiner, a working face, at least one core of a rigid material, covered by a coating of a wear-resistant material, so that at least the active surface of the lining is formed by all or part of the outer surface of said coating and is distinguished from the linings of the prior art in that said coating consists of a superposition of thin layers or lamellae. Such a lining has a higher wear resistance than the linings known up to now.

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

In addition, it can, once the coating has been worn, be regenerated again by applying a new coating.

Furthermore, when it is used in a refiner, the refined paste obtained has, for the same specific power consumed, an average length of fibers and a whiteness greater than that of the pasta obtained in a refiner provided with fillings according to the state. of technique. There is also a reduction in noise during refining and greater stability of the air gap (distance between the rotor and the stator) of the refiner, which results in greater regularity in the properties of the refined dough.

Other advantages provided by the lining according to the invention and its implementation will appear on reading the detailed description which follows, as well as on examining FIGS. 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 along the 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 prior art, respectively in front view in cross section along the axis B-B and in right view.

Figures 6 and 7 schematically represent a conical refiner stator with refining cones according to the state of the art, respectively in front view in cross section along the 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 lining of Figures 8 and 9 in bottom view in section along D-D.

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

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 lining according to the invention.

Figures 19 and 20 schematically show a seventh variant of the lining according to the invention, respectively in front view and in bottom view in section along the axis GG. Figure 21 shows schematically in section, an eighth variant of the lining according to the invention. FIG. 22 schematically represents in perspective a packing according to the invention intended to be mounted on a conical refiner rotor block.

Figure 23 shows schematically in perspective a packing according to the invention intended to be mounted on a stator block of 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 the discs according to the prior art.

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

FIG. 27 represents another curve of weighted length of the fibers of a pulp 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 filling according to the invention are, respectively, the face intended to be fixed against the disc or cone support 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 to be used 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 lining: this is the case, in particular, when the working face is flat. The active surface 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 always consists of all or part of the external 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 of the coating therefore always includes at least the active surface of the lining. In other words, the active surface is always constituted by the material resistant to wear and tear of the coating. On the other hand, the extent of the external surface of the coating may not be limited to the active surface of the lining.

As a general rule, but this is not an obligation, the coating is only present on the working face which it therefore occupies at least in part. This coating is preferably continuous and of uniform thickness over the entire active surface. Its 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 packing is made is a material having mechanical properties, in particular of resistance to compression, allowing it not to break, when the rotor and the stator are brought closer to each other , and not to tear off and be carried away by the flow of the raw material being refined. It may be a metal, a metal alloy, cast iron, a plastic material having good mechanical characteristics, in particular sufficient shear strength, such as so-called "high performance" plastics, among which polyamides 4-6 may be mentioned, imide polyamides, or technical polymers such as polyamide 6-6. The rigid material can also be a composite material such as epoxy / carbon fibers, epoxy / glass fibers, or vinyl ester / carbon fibers. It goes without saying that the choice of rigid material is also a function of its resistance to the method chosen for applying 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 recovery metal or metal alloy or a plastic material produced from recycled polymers having the mechanical characteristics mentioned above. Indeed, unlike the seals of the prior art which must necessarily be manufactured with metals having a high resistance to wear such as steel or cast iron, the seals according to the invention can comprise a core made of '' a material little resistant to wear, because the core does not have an active surface and is 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 coating, a material which is not very resilient but having a high hardness. The lining obtained is then not very 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, Cr3C2- NiCr, WC-Ni and WC-NiCr, a ceramic such as alumina (A12O3), chromium oxide (Cr2θ3), titanium oxide (TiO 2), ^zirconia (Z1O2) oxide zirconium and yttrium (Zrθ2 Y2θ3), yttrium, barium and copper oxide (YjBa2Cu3θ7) or silica (Siθ2), a mineral such as apatite, a carbide such as tungsten carbide, of titanium, boron or silicon, or an adamantine carbon.

One can also provide that the coating is a mixture of these materials, or a superposition of layers made up of different materials chosen from these materials.

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

It is preferable to use a porous coating. This improves the characteristics of the refined dough. By porous coating is meant a coating whose ratio of total pore volume / total volume of the coating is between 2% and 50%, preferably between 10% and 30%. The Applicant was, in fact, surprised to discover that it is possible to use for the coating a material having a high porosity, because generally, when one seeks to increase the resistance to wear of an element, one coating it with a layer of material having the lowest possible porosity.

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

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

It turns out to be advantageous to use as a coating a material having good tribological characteristics and / or a high abrasiveness with respect to the material to be refined.

The coating may include a second material disposed between the wear-resistant material and the core, so as to cover the latter and protect it against 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, the core is made of a metal or an oxidizable alloy.

Said second material is preferably in the form of a thin layer, of thickness between approximately 20 and approximately 200 microns (micrometers μm) and preferably between approximately 50 and approximately 100 microns, preferably extending at least over all the working face. The choice of this second material depends on the physico-chemical conditions under which the lining will be required to work. Said second material can be, for example, a nickel and chromium oxide. It turned out that the alloy composed of nickel, chromium, aluminum and yttrium (NiCrAlY), gave excellent protection against corrosion phenomena.

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

When the lining according to the invention is intended to be mounted on a conical refiner, it may have a shape of a cone or of a truncated cone or a shape of a segment of a cone or of a truncated cone, such as those illustrated in FIGS. 22 and 23.

The lining according to the invention as illustrated in FIGS. 8 and 9, comprises a core 15 made of a rigid material comprising a fixing face 16 on the refiner and a working face 17 at least essentially planar. As the working face 17 of the lining is planar, the active surface 18 of the lining 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. Thus, the fibrillation action of the dough is only carried out 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 two thin layers or lamellae 21 arranged one on top of the other, preferably at least essentially parallel. These strips 21 allow a more uniform wear of the coating 20 and thus contribute to the constancy of the refining conditions. Preferably, the number of strips 21 is as high as possible that the technique used to produce the coating makes it possible to produce. 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 the stator. The slats give the coating a special wear capacity which allows the linings 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 the air gap is reduced, it happens that contacts occur, in certain places, between two facing discs. If the coating is made of a single thick layer, it is very often torn off. On the other hand, if the coating consists of lamellae, only the surface lamellae situated at the places where the contacts have occurred are torn off and the refining can then be carried out between the remaining lamellae of each of the discs.

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

- a low impact wear 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 grooves 23 alternating 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 rectangular section like those which one meets on the refining discs of the trade. They are present in the coating 25 which extends over the entire working face 22. The active surface of the lining is then the sum of the surfaces of all the vertices 26 of the blades 24. The area of the active surface is therefore less to the area of the working face 22. The geometry of the blades 24 and grooves 23 can be chosen as a function of the specific type of treatment which it is desired to subject to the material to be refined. 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 tops 30 of the blades 31. It is, in this case, preferable for 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 have the advantage of having good corrosion resistance.

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 working face 35. The coating 34 preferably matches all the shapes of the core 33. It is therefore disposed both on the tops 36 of the blades 37 and in their bottoms 38.

Its thickness is preferably uniform on all the vertices 36.

The coating 34 can also be composed of several parts each made of a different material. Thus, it is possible to cover the tops 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 materials having a high resistance to wear and / or good tribological properties such as alumina and said second material is chosen from materials having high abrasiveness such as carbide tungsten and / or high corrosion resistance.

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 as to produce one or more constrictions and to disturb the circulation of the dough by creating micro-vortices to the interior of 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 quality of the refining is then improved.

The exact shape of said obstacles 39 does not matter as long as they make it possible to cause a turbulent flow of the dough, π then follows an increase in the 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 one opposite the other, respectively on the walls 41 and 42 of the grooves 40. The obstacles located on the wall 41 can also be offset from those located on the wall 42.

The obstacles are preferably made of the same material as the covering 43 with which they are integral. Since the covering 43 covers the entire working face 44 according to this fifth variant, the obstacles 39 are therefore placed both in the grooves 40 and on the covering 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 tops 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 follows preferably 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 lining according to the invention, in which the grooves 56 have an almost circular section. Such linings thus have a high active surface (constituted by the sum of the surfaces of the tops 57 covered by the coating 58), while having grooves 56 which can contain a large volume of dough during refining.

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

When the lining according to the invention has grooves, it can be envisaged for these grooves a variable depth. The latter may, for example, be weak at one end (for example, the periphery for an annular lining), and increase, preferably regularly, to become significant at the other end (the center, for an annular seal), or vice versa. The choice between an increase in depth towards one end, or an increase towards the other end, 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 make or provide, in the coating and on its external surface, notches of shallow depth relative to the thickness of the coating, so as to create edges and thus give an abrasive character or increase the character coating abrasive.

Figures 22 and 23 show seals according to the invention intended to be implemented respectively on the rotor and on the stator of a conical refiner. 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 a known manner, to the rotor block or to the stator block of a refiner. This is why they may include one or more holes (not shown), passing through the core and possibly the coating by connecting the working face to the fixing face, and intended for the passage of fixing screws on the rotor block or the refiner stator block.

Preparation of fillings according to the invention:

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

The recovery is carried out according to any process making it possible 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 deposition by induction plasma, or the CVD (Chemical Vapor Deposition) plasma deposition process. The core is preferably provided with grooves which can be made by machining in a flat core, or else provided during the molding of the core, in the case in particular where it turns out to be more economical to manufacture the latter by molding. The core may advantageously be a disc or a segment of a commercial refining disc, or a cone, a truncated cone or a segment of a cone or truncated cone of commercial refining. Then preferably apply the coating of wear-resistant material so that all forms of the disc, disc segment, cone, truncated cone or segment of cone or truncated cone of commerce are retained.

It goes without saying that the coating can completely cover the core, that is to say both its working face as its fixing face or its side faces.

There is thus a lining according to the invention which leads to better refining than the disc, disc segment, cone, truncated cone or segment of cone or truncated cone of commerce. The lining according to the invention thus obtained also has better wear resistance than the disc, disc segment, cone, truncated cone or segment of cone or truncated cone of commerce. In addition, it 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 control 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 deposition process. Indeed, one thus obtains, when the core has grooves, a continuous coating and of uniform thickness and conforming well to all the shapes of the working face. In addition, since the grains forming the starting material have at least partially melted during the passage through the flame, the coating obtained is in a continuous, uniform form and of relatively high density.

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

Furthermore, the Applicant has noted, during its tests, that despite the significant forces occurring during refining, the coating deposited by the plasma process was not torn off.

In addition, the plasma deposition process proves to be particularly advantageous for producing a coating composed of a superposition or stacking of thin layers or lamellae. In fact, this method makes it possible to deposit the coating in several passes, each time depositing a very small amount of the wear-resistant material, so as to obtain a coating consisting of a superposition of thin layers or lamellae. . Such a coating then wears uniformly and has a surface having the 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 the implementation of the plasma deposition process is that a sophisticated and expensive material can be used as a coating, because this process makes it possible to deposit thin layers of material, therefore a small amount of material, which does not not result in a significant increase in the cost of the lining.

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

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

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

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

Use of fittings according to the invention;

The lining according to the invention is fixed in a known manner, for example by means of screws, to 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 stable refining conditions and maintaining the quality of the refined dough over time.

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

The packing according to the invention can be fixed on the rotor block or on the stator block 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 linings of equal or different dimensions on the rotor block or on the stator block, in particular, if it is desired to cover the entire working face of the rotor or stator and only the dimensions of one packing are insufficient to allow it to occupy by itself the entire 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 seals 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 with one or more seals according to the invention, so that the entire active surface of the refiner is made up of the material wear resistant. This gives a flow of the dough to be refined having maximum turbulence and optimal refining.

The linings according to the invention can be used for 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 prove to be particularly effective when the paper 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, as regards the cutting of the fibers (less cutting phenomena), than the linings of the prior art. It is therefore advantageous to use them in the paper recycling industry. In fact, because they can be used to refine old paper, that is to say improve its quality, they make it possible to reduce the content of long (new) fibers in recycled paper. In addition, they improve the dispersion of "stickies", the impurities of the paper, which makes it possible to obtain a paper comprising fewer dark spots. Thus, thanks to the linings according to the invention, a reduction in the cost of recycling is obtained.

Furthermore, the linings according to the invention can be used to carry out refining operations on disc refiners which have hitherto been practically possible only on conical refiners, more particularly on wide angle conical refiners. Such refining operations are those necessary for the preparation of special papers such as cigarette papers, tracing papers, etc., that is to say papers obtained from pulp of high Shopper-Riegler degree. (greater than 60 degrees). Furthermore, the linings according to the invention can also be used for the defibration of any cellulosic material, such as wood waste, of 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 state of the art and with 4 linings according to the invention. The discs according to the state of the art were 16 inch diameter crowns marketed by the company Black-Clawson, made of so-called "Ni-hard" cast iron having 10 sectors, blade tops of a width of about 5 , 5 mm, and grooves parallel to each other inside each sector, inclined by about 20 ° to the radius, of rectangular cross section, about 5.0 mm in width and about 6.0 mm depth. 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 (microns) of alumina / titanium oxide 97/3 (AI2O3 97% -Tiθ2 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 (half theoretically) of the raw material is refined between 2 refining discs from a first set and the other part between 2 refining discs from a second set. The raw material was introduced in the center of the refining discs. The refined dough stood out from the periphery of the discs.

The refiner was equipped with a 140 kW engine. The nominal pulp circulation rate was 30 to 40 m ^ / h, the maximum flow being 60 m ^ / h. The raw material had a concentration of 3% and consisted of so-called chemical pulp from softwoods of origin. Scandinavian. FIG. 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 the fibers as a function of their length is indicated above the curve.

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:

-Ε.T. ' designates the farms 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.

LRQ is the breaking length calculated from the breaking force with joined jaws while LRQ is the breaking length according to AFNOR Q03004.

The column '° SR' indicates the Schopper-Riegler degree of the refined dough.

TABLE A

TABLE B

TABLE C

Id time 100 I bursting LR Elongation at refining (mN. M ² / g) (kPa. M ² / g) (rn) rupture

(mn) NFQC 13-011 NFQC 13-053 NFQC 13-004 (%)

E.T. INV. E.T. INV. E.T. INV. E.T. INV.

0 1151 1151 2.59 2.59 3549 3549 3.05 3.05

5 1,131 1,368 3.51 3.85 4,923 5,397 3,715 3.3

10 1,046 1,438 3.97 4.71 5,638 6,669 3.99 3.69

15,875 1,210 4.09 5.43 6,202 7,662 3.97 3.74

20,830,962 4.33 5.35 6,830 7,873 4.2 3.79

25,853 5.65 8,796 3.72 TABLE D

It therefore appears from the results of these tables that the hydration and the fibrillation of the pulp take place without a notable phenomenon of fiber cutting being observed.

FIG. 25 represents the weighted length curve of the fibers and of the elements making up the dough after refining for 20 minutes with the discs according to the prior art, and with a useful power of 40 kW. The average fiber length was 1.55 mm.

FIG. 26 represents the weighted length curve of the fibers and of the elements making up the dough after refining for 20 minutes with the fillings according to the invention, also with a power of 40 kW. The average fiber length was 2.66 mm.

FIG. 27 represents the weighted length curve of the fibers and of the elements making up 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 make it possible to obtain a reduction in the fiber cutting phenomenon and a reduction in the production of fines.

Mechanical tests carried out in a comparative manner on paper sheets 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 on average about 15 to 20% higher than that of the paper obtained with the discs of the prior art. A superiority of around 30% was even obtained when the useful power applied was 60 kW. In this regard, it should be noted that when using discs according to the state of the art, it is impossible to apply such a high useful power under the specific operating conditions of the installation used to test the fittings according to the invention.

Surprisingly, it has also been observed that the tear index increases at the start of refining with the linings according to the invention while, as a general rule, the tear index of the formulas decreases from the start of the refining operation. with discs according to the state of the art.

Other tests carried out by the applicant on industrial installations have made it possible to observe, when using the linings according to the invention, a reduction of 10 to 15% of the no-load power of the refiner compared to the power required with state-of-the-art cast iron fittings. By idle power is meant 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 it was provided with the linings according to the invention, was much less noisy than when it included the cast iron linings of the prior art.

Obviously, the invention is in no way limited by the features which have just been specified or by the details of the figures and of the tests presented to illustrate it. A number of modifications can be made to the shapes of the particular fittings which have been described by way of illustration and to their constituent elements without thereby departing from the scope of the invention. The latter therefore includes all the means constituting technical equivalents of the means described as well as their combination.

Claims

1. Trim for refiner comprising a fixing face (16) on the refiner and a working face (17,22), and comprising at least one core (15,28,33,50,51) made of a rigid material, covered by a coating (19,20,25) made of a wear-resistant material in such a way that at least the active surface (18) of the lining is formed by all or part of the external surface of said coating (19 , 20,25), characterized in that said coating (19,20,25) consists of a superposition of thin layers or lamellae (21).

2. A fitting according to claim 1, characterized in that the thickness of said thin layers or lamellae (21) is between 0.003 and 0.100 mm and preferably between 0.005 and 0.025 mm.

3. A lining according to any one of the preceding claims, characterized in that said coating (19,20,25) is porous.

4. A lining according to claim 3, characterized in that the porosity of said coating (19,20,25) increases from the core (15,28,33,50,51) towards said active surface (18).

5. Filling according to any one of the preceding claims, characterized in that said working face (17,22) is provided with at least one groove (23,40,46) intended to facilitate the flow of the dough to refine.

6. A fitting according to claim 5, characterized in that said one or more grooves (23,40,46) are present in said core (15,28,33,50,51).

7. Trim according to any one of the preceding claims, characterized in that said coating (19,20,25) covers all of said working face (17,22).

8. Armature according to any one of claims 5 to 7, characterized in that at least one obstacle (39,45,55) intended to disturb the passage of the dough, is disposed in at least one of said grooves (23, 40.46).

9. A fitting according to any one of the preceding claims, characterized in that said rigid material is chosen from the group consisting of metals, metal alloys, cast iron, and plastic materials.

10. Trim according to any one of the preceding claims, characterized in that said wear-resistant material is chosen from the group consisting of pure metals, metal alloys, pseudo-alloys, cermets, ceramics, minerals and their mixtures.

11. Trim 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.

12. Disc or conical refiner, characterized in that it is provided with at least one lining according to any one of claims 1 to 11.

13. A method of preparing a lining according to any one of claims 1 to 11, characterized in that at least partially covers a core (15,28,33,50,51) in a rigid material to using a wear-resistant coating (19,20,25) in such a way that at least the active surface (18) of the lining consists of all or part of the outer surface of said coating (19 , 20.25).

14. Method according to claim 13, characterized in that the coating (19,20,25) is applied by a method of removal by plasma spraying.

15. Process for refining dough, characterized in that at least one filling according to one of claims 1 to 11 is used, during the refining of the dough.

16. Use of a filling according to any one of claims 1 to 11 for the refining of a paper pulp.

17. Use of a filling according to any one of claims 1 to 11 for the defibration of cellulosic materials.