EP1292394B1 - Tubular rotary mill liner - Google Patents

Abstract

The invention concerns a liner consisting of juxtaposed individual rings of lining plates forming the cover of the cylindrical housing of a rotary mill. The liner consists of a number of lining plates located at selected sites and configured in the form of deflectors ( 20, 30 ) comprising a fin ( 26, 36 ) arranged on edge on a base plate ( 22, 32 ) fixed to the housing and forming an angle less than 25° relative to a diametral plane of the mill.

Description

The present invention relates to a shield for a rotary tubular mill comprising a cylindrical shell for containing the material to be ground and a load of grinding machines, wherein the shield consists of rings of individual shielding plates juxtaposed.

The invention relates more particularly to grinders used for the grinding of cement (clinker) dry, coal, limestone and ores dry or wet. These grinders consist of a cylindrical metal shell rotating about its longitudinal axis and containing a grinding charge consisting of grinding apparatus, generally balls, but may also consist of cylpebs, boulpebs, etc., of varying sizes. The material to be ground is introduced on one side of the mill and, as it progresses towards the outlet, on the opposite side, it is crushed and milled between the grinding machines.

A conventional mill is generally divided, in the axial direction, by means of a dividing partition wall into two successive chambers. The first chamber in which the rough crushing of the material is carried out contains grinding balls generally having a diameter of between 60 mm and 90 mm. The second chamber, in which the fine grinding is carried out, contains grinding balls with a diameter generally between 15 mm and 60 mm. Next to these two-chamber mills there are also mills at one only chamber which contain grinding machines of different diameters and in different quantities according to the diameter.

In the second chambers of conventional mills or in single-chamber mills, it is well known that it is necessary to have self-leveling shields, that is to say shieldings which, during the rotation of the mill around their axis, automatically classify the grinding machines according to their size and more particularly the large grinding machines at the entrance of the grinding chamber and the smaller ones towards the exit of this same chamber, so that the weight and the size of the grinding machines decrease as the particle size of the material advancing in the grinding chamber decreases and becomes thinner. In this way, over the length of the grinding chamber, the size of the grinding machines is adapted to the particle size and fineness of the material to be grinded. This generally makes it possible to reduce the energy consumption per ton of ground material by 10 to 20%.

There are currently different types of self-healing shields. One of these has a sawtooth shape in the axial direction of the mill, that is to say that it consists of a succession of cone frustums along the length of the mill which converge towards the mill. outlet and have a slope directed towards the inlet of the grinding chamber. The plates forming these shields have a relatively high average thickness and are therefore quite heavy. This high thickness also leads to a loss of useful volume of the grinding chamber and, consequently, in some cases, an impossibility of absorbing all the available power of the grinding chamber. engine. These shieldings are, in addition, very sensitive to grains, that is to say when there is a certain accumulation of very hard grains (about 6 to 12 mm) in the areas where small grinding machines are located, the classification is very disturbed, up to the opposite classification, that is to say the return of small gear to the entrance and large gear to the exit.

In another type of shielding as described in the document BE 09301481 , the plates have corrugations which can be inclined at an angle of 15 to 30 ° with respect to the generatrix of the mill. The purpose of the inclination of these corrugations is to create a screw effect to act on the grinding load and the material to grind. Indeed, when the mill rotates, the large grinding gear is generally found, in the majority of the periphery of the grinding load and the purpose of the inclination of the corrugations is to push these grinding gear by screw effect to the input of the grinding chamber. In practice, the classification sought in this way is however very difficult and often random. The plates are also relatively heavy and the ranking effect decreases as the wear of the corrugations increases. These undulations can not be too pronounced, otherwise there is a discontinuous lift, that is to say, too important in which the outer layers of the grinding charge are raised up to the region of the top of the mill and fall back on the shielding instead of falling and rolling on the foot of the grinding load. These shields are, in practice, very little used.

In the document US 4211370 the plates have baffles having a spiral configuration. Nevertheless with this configuration the classification is also difficult and often random.

The object of the present invention is to provide a new shield for a tubular mill that eliminates or at least reduce the disadvantages of conventional shields, specifically a grinder with a lighter shield that allows to create a good ranking which is efficient and flexible to use.

To achieve this object, the present invention provides a tubular mill of the kind described in the preamble which is characterized in that a number of shielding plates located at selected locations are formed as baffles comprising a field-mounted vane. on a base plate attached to the shell and forming an angle less than 25 ° with respect to a diametral plane of the mill.

The side side of the fin on the front side, seen in the direction of rotation of the mill, is preferably bevelled, this bevel is provided on the side facing the mill inlet.

This beveled lateral side of the fin is, with respect to the direction of advancement of the material, set back from the opposite lateral side.

This inclination of the fins, which is preferably greater than 5 °, thus creates a propeller effect which promotes the progression of the material and contributes to the classification of grinding machinery.

The fin may form an integral part of the base plate and be made together therewith by casting.

The fin may also be a separate piece, integral with a base provided with a hole to be fixed to the ferrule of the mill. This base may have a frustoconical periphery which can penetrate into a complementary shape opening of a base plate. Thus, the attachment of the fin by its base is, at the same time, a fixation of the base plate to the ferrule.

• la figure 1 est une vue schématique en plan d'un premier mode de réalisation d'un déflecteur selon la présente invention ;
• la figure 2 est une vue de profil du même déflecteur vu suivant la flèche II sur la figure 1 ;
• les figures 3 à 6 illustrent schématiquement différentes configurations d'emplacement des déflecteurs sur la paroi intérieure de la virole ;
• la figure 7 montre schématiquement une vue en plan d'un second mode de réalisation d'un déflecteur ;
• la figure 8 montre une coupe transversale suivant le plan de coupe VIII-VIII sur la figure 7;
• la figure 9 montre une vue de profil d'une ailette avec son socle ;
• la figure 10 montre une vue en plan d'une pièce de remplissage ;
• la figure 11 montre une vue en coupe transversale à travers la pièce de la figure 10 et
• les figures 12 et 13 montrent des vues analogues à celles de la figure 3 d'un mode de réalisation avec une autre orientation des déflecteurs.

Other features and characteristics of the invention will emerge from the description of some embodiments, presented below, by way of illustration, with reference to the appended drawings in which:

• the figure 1 is a schematic plan view of a first embodiment of a deflector according to the present invention;
• the figure 2 is a profile view of the same deflector seen along arrow II on the figure 1 ;
• the Figures 3 to 6 schematically illustrate different configurations of location of the deflectors on the inner wall of the ferrule;
• the figure 7 schematically shows a plan view of a second embodiment of a deflector;
• the figure 8 shows a cross-section along the section plane VIII-VIII on the figure 7 ;
• the figure 9 shows a profile view of a fin with its base;
• the figure 10 shows a plan view of a filling piece;
• the figure 11 shows a cross-sectional view through the room of the figure 10 and
• the Figures 12 and 13 show similar views to those of the figure 3 of an embodiment with another orientation of the baffles.

In accordance with the present invention, a number of shield plates are formed as deflectors 20 as shown in FIGS. Figures 1 and 2 whose figure 1 is a bird's eye view of a deflector 20 while the figure 2 is a side view in the direction of the arrow It on the figure 1 which also represents the direction of rotation of the mill. Each deflector comprises a base plate 22 provided with a central hole 24 to be fixed on the inner wall of the mill shell.

On the plate 22 and forming an integral part thereof (by casting) in the embodiment of the Figures 1 and 2 there is a fin 26 which is erected from the field on the plate 22, preferably perpendicular to it. This fin 26 may have a thickness of between 25 and 50 mm and a height (radial relative to the mill) preferably between 100 and 350 mm.

According to an important characteristic of the invention, each fin 26 is inclined with respect to a diametral plane of the mill of an angle α less than 25 °, preferably between 5 ° and 25 ° according to the operating conditions of the mill and the nature of the grinding load and the material to be grinded.

The lateral side of the fin 26 which is on the front side, seen in the direction of rotation of the mill, is beveled, in the embodiment of the invention. Figures 1 and 2 , on the face of the fin 26 which is turned towards the entrance of the mill to form a more or less acute edge 28. This edge 28 facilitates penetration into the load and contributes to continuous lifting, that is to say prevents the projection of grinding gear on the shield.

The fins 26 will generally be made of very hard cast iron or steel if the working conditions of grinding are harder, for example when using grinding balls of 90 mm diameter. For fine grinding, with milder working conditions, the working side of these deflectors, that is to say the face turned towards the exit of the grinder (to the right on the figure 1 ), as well as the edge 28 can be made more resistant to abrasion wear by using "padding" (that is to say a mixture of metal and ceramic material). These areas can also be protected by very hard tungsten carbide welding beads, for example.

The figures 3 , 4 and 5 show, each, a part of the crusher of the mill in development and with different examples of placement of the deflectors. In each of these figures, the arrow R denotes the direction of rotation of the mill whereas the arrow D designates the direction of movement of the material to be ground. The plates designated A are conventional normal plates, while the plates designated B are plates designed in accordance with the present invention as baffles.

According to figure 3 each deflector B is adjacent to another deflector B at the two diametrically opposite corners to thereby define a complete or partial spiral around the inside of the ferrule.

The figure 4 shows a configuration similar to that of the figure 3 with the difference that between a deflector B and two adjacent deflectors of the same spiral is a longitudinal row of plates A without reflectors.

The figure 5 shows an example of a configuration similar to that of the figure 4 , but here each deflector B is separated from neighboring baffles of the same spiral by a diametral row of plate without baffles. It should be noted that, in this configuration, the axial spacing between two adjacent deflectors is greater than in the configurations of figures 3 and 4 .

In a full shield, the number of deflectors can vary between 5% and 15% of the total number of armor plates.

The figure 6 shows the complete development of a mill shell of 4 meters in diameter and 10 meters long. The baffles are spirally arranged in the mill according to the configuration of the figure 3 . In such a perforated mill DIN standard, there are 40 plates on the circumference and 40 plates on the length, a total of 1600 plates. If there are 10% deflectors, or 160 deflectors, they are arranged in four spirals of 40 plates each in the mill. These spirals are schematically represented on the figure 6 and numbered successively by 1, 2, 3 and 4.

It is, moreover, possible to change the distance between two adjacent spirals along the length of the mill. It is, for example, possible to bring the spirals closer to the exit of the mill, that is to say to provide more deflectors.

During the rotation of the mill, all these baffles penetrate the grinding load like the plow of a plow and their inclination relative to a diametral plane combines with the spiral-shaped configuration of the baffles pushes the grinding charge to the outlet of the crusher . This produces an inclination of the grinding charge with respect to the longitudinal axis of the mill which is of the order of 0.5 ° to 2 °.

The consequence is that the degree of filling measured at the inlet of the mill is a little lower than that measured at the outlet of the grinding chamber.

The larger grinding machines therefore roll faster than the smaller grinding machines on the foot of the grinding load, that is to say from the back of the grinder to its entrance. This process of classification of grinding bodies is very effective. It has, on the other hand, another great advantage because the degree of filling increases from the inlet to the outlet. It is known, in fact, that the best grinding efficiency is obtained when the voids between the grinding bodies (more or less 41%) are filled with material and that the material to grind, while advancing in the grinder, "swells" (c that is, its apparent density decreases). It is therefore advantageous to have a higher degree of filling at the outlet of the mill to optimize the grinding efficiency.

Another advantage is that the material to be ground is pushed more quickly through the mill and there is, thanks to these baffles, a better mixing between the grinding machinery and the material to be grinded.

As indicated above, the deflector shown on the Figures 1 and 2 is a monobloc piece made by casting. A embodiment with a composite baffle will be described below with reference to the following figures.

This composite deflector, generally designated by the reference 30 on the figure 7 , has a fin 36 comparable to the fin 26 of Figures 1 and 2 but provided, at its base, a base 34 which, in the embodiment shown, has a square shape. The base 34 and the fin 36 form a single piece that can be made by casting but separated from the base plate 32. This base plate has an opening 40 of complementary shape to that of the base 34 and forming a frame for receiving this one. this.

As shown by Figures 8 and 9 , the base 34 and the opening 40 of the base plate 32 have complementary frustoconical sections, so that when the base 34 is disposed in its housing of the base plate 32 and is fixed through its fixing hole 38, at the mill shell, the base plate 32 is held in place by the base 34 and no longer needs to be attached to the ferrule.

According to an advantageous embodiment, there are provided filling pieces 42 represented on the Figures 10 and 11 . These filling pieces 42 have exactly the same shape and the same section as the pedestals 34 shown on the Figures 7 to 9 but do not have fins 36. These parts make it possible to fill the openings 40 in the base plates 32 when it is desired to eliminate, as desired, certain deflectors 30 shown on the FIG. Figures 7 to 9 . It suffices, in fact, to unbolt the base 34, remove it with its fin 36, close the opening with the filling piece 42 and bolt it to the shell through its central opening 44.

It is also possible to provide a number of base plates with a filling piece 42, which makes it possible to transform, if necessary, a base plate into a baffle by replacing the filling piece 42 with a fin 36 and a base 34. It is thus possible to increase or decrease, at will, the number of deflectors and to change the internal configuration of the location of the deflectors.

The fins 26 and 36 shown in the various figures are suitable, because of their beveled edge 28, for a grinder rotating in the direction indicated on them. figures 1 and 3 to 5 . In a grinder rotating in the opposite direction, it is necessary to provide deflectors which are symmetrical with respect to those shown in the figures.

Tests in a small scale pilot plant have shown that for a DIN standard perforated mill (ie with plates of 314.16 mm arc length circumferentially and 250 mm long in length). axial direction of the mill), a satisfactory number of plates transformed into baffles is of the order of ± 10%.

1. a) à un faible de degré de remplissage (± 20%) du broyeur, le nombre de déflecteurs est plus grand quand la vitesse exprimée en pourcentage de la vitesse critique est faible. La vitesse critique est la vitesse de rotation du broyeur à laquelle se produit une centrifugation et cette vitesse est déterminée par la formule : $\frac{42,3}{\sqrt{\mathrm{D}}},$
   
   exprimée en nombre de tours par minute, D étant exprimé en mètres pour le diamètre du broyeur. Pour un broyeur perforé norme DIN, c'est-à-dire avec des plaques de 314,16 mm sur 250 mm, on obtient les valeurs suivantes :
   • de 55% à 65% Vcr (vitesse critique) : nombre de déflecteurs : environ 9% ;
   • de 65% à 75% Vcr : nombre de déflecteurs : environ 8% ;
   • de 75% à 85% Vcr : nombre de déflecteurs : environ 7%.
2. b) avec un degré de remplissage de ± 30%, on aura les valeurs suivantes:
   • de 55% à 65% Vcr : nombre de déflecteurs : environ 11% ;
   • de 65% à 75% Vcr : nombre de déflecteurs : environ 10% ;
   • de 75% à 85 % Ver : nombre de déflecteurs : environ 9%.
3. c) avec un degré de remplissage de ± 40%, on aura les valeurs suivantes :
   • de 55% à 65% Vcr : nombre de déflecteurs : environ 13% ;
   • de 65% à 75% Vcr : nombre de déflecteurs : environ 11% ;
   • de 75% à 85 % Vcr : nombre de déflecteurs : environ 10%.

This number may however vary with the operating conditions of the mill:

1. a) at a low degree of filling (± 20%) of the mill, the number of baffles is greater when the speed expressed as a percentage of the critical speed is low. The critical speed is the speed of rotation of the mill at which centrifugation occurs and this speed is determined by the formula: $\frac{42,3}{\sqrt{\mathrm{D}}},$
   
   expressed in revolutions per minute, where D is expressed in meters for the diameter of the mill. For a DIN standard perforated mill, that is to say with plates of 314.16 mm by 250 mm, the following values are obtained:
   • from 55% to 65% Vcr (critical speed): number of deflectors: about 9%;
   • from 65% to 75% Vcr: number of deflectors: about 8%;
   • from 75% to 85% Vcr: number of deflectors: about 7%.
2. (b) with a degree of filling of ± 30%, the following values shall be obtained:
   • from 55% to 65% Vcr: number of deflectors: about 11%;
   • from 65% to 75% Vcr: number of deflectors: about 10%;
   • from 75% to 85% Ver: number of deflectors: about 9%.
3. (c) with a degree of filling of ± 40%, the following values shall be obtained:
   • from 55% to 65% Vcr: number of deflectors: about 13%;
   • from 65% to 75% Vcr: number of deflectors: about 11%;
   • from 75% to 85% Vcr: number of deflectors: about 10%.

• pour des diamètres compris entre 1,5 et 2,5 m : ± 100 mm de hauteur,
• pour des diamètres compris entre 2,6 et 3,6 m : ± 200 mm de hauteur,
• pour des diamètres compris entre 3,7 et 4,8 m : ± 250 mm de hauteur,
• pour des diamètres compris entre 4,9 et 6,2 m : ± 300 mm de hauteur.

The height of the baffles depends essentially on the diameter of the mills. For exemple :

• for diameters between 1.5 and 2.5 m: ± 100 mm in height,
• for diameters between 2.6 and 3.6 m: ± 200 mm high,
• for diameters between 3.7 and 4.8 m: ± 250 mm high,
• for diameters between 4.9 and 6.2 m: ± 300 mm high.

It should be noted that, if the height of the baffles increases, their number may decrease.

Standard base plates generally have an average thickness of ± 40 mm, i.e. a standard DIN plate (314.16 x 250 mm) has a weight of the order of 24 kg. In the case of composite deflectors according to Figures 7 to 9 , the whole of a fin and a base weighs a maximum of 25 kg. Therefore, from the point of view of ergonomics and safety when fitting the shield, the deflectors proposed do not constitute a handicap.

• surface à blinder : 150,8 m² ;
• poids d'un blindage classant standard : 465 kg/m², soit un total de 70 122 kg ;
• poids d'un blindage selon l'invention avec 10% de déflecteurs : 350 kg/m², soit un total de 52 800 kg.

The invention also has the advantage of allowing a fairly significant gain in weight of the shielding per m ² . For a second grinding chamber 4.8 meters in diameter and 10 meters long, this is as follows:

• surface to be shielded: 150.8 m ² ;
• weight of standard screening: 465 kg / m ² , for a total of 70,122 kg;
• weight of a shield according to the invention with 10% deflectors: 350 kg / m ² , a total of 52,800 kg.

The comparison shows a weight reduction of almost 25%.

In the case where 15% of plates designed as deflectors should be provided, the weight per m ² would be 366 kg corresponding to a total weight of ± 55 200 kg, that is to say a decrease of the order of 20%. In the case of a standard classifying shield, one is sometimes faced with the problem that one can not absorb all the available power of the motor driving the crusher. This is due to the average thickness of these shields which reduces the useful internal volume of the mill.

• épaisseur moyenne d'un blindage classant standard : 87 mm ;
• épaisseur moyenne du nouveau blindage avec déflecteurs : 44 mm ;
• la puissance absorbée avec le blindage classant standard pour la deuxième chambre est de l'ordre de 3,256 KWh ;
• la puissance absorbée avec le nouveau blindage avec déflecteurs pour cette deuxième chambre est de l'ordre de 3,451 KWh, soit une augmentation de 6%.

In the case of a mill with a diameter of 4.8 meters and a useful length of 14.3 meters turning at 14.48 revolutions per minute (or 75% of the critical speed) with a degree of filling of 30% in grinding bodies and a useful length of 4.3 meters of the first chamber and 10 meters of the second chamber, we have the following values:

• average thickness of standard screening: 87 mm;
• average thickness of the new shield with deflectors: 44 mm;
• the power absorbed with the standard classifying shield for the second chamber is of the order of 3,256 KWh;
• the power absorbed with the new shield with deflectors for this second chamber is of the order of 3,451 KWh, an increase of 6%.

For the total crusher, that is to say the two chambers, we will have, when the second has standard classification plates, a total power of 4,754 KWh. On the other hand, when the second the chamber is equipped with the new shielding, the total power will be of the order of 4.949 KWh, a favorable difference of 4%, which translates into an increase of the flow of the order of 4%.

The Figures 12 and 13 show a part of the grinder shell, in development with an embodiment in which the deflectors of the plates B are oriented in the opposite direction of the embodiment of the preceding figures. If the fins are always inclined at an angle between 5 ° and 25 ° relative to a diametral plane, this inclination is, according to the Figures 12 and 13 , in the direction of the exit of the mill, that is to say that the lateral side of attack, seen in the direction of the rotation, which is also the beveled side, is this time closer to the exit of the grinder than the opposite side. The baffles are, moreover, bevelled on the face of the fin which is turned towards the exit of the mill and not on the opposite face as in the embodiment of the preceding figures. The mutual arrangement of the different deflectors B is, however, always made with the aim of obtaining a configuration in the form of a spiral whose inclination may, however, vary as shown by the comparison between the Figures 12 and 13 .

Tests with a grinder whose shield is designed according to the embodiment of the Figures 12 and 13 has revealed, surprisingly, that the classification effect of grinding gear is at least as effective as that achieved with the embodiment of the previous figures. It must therefore be concluded that, with regard to the classification effect, the configuration of the various spiral deflectors or The spin on the length of the mill is at least as important and decisive as the direction of inclination of the individual fins relative to a diametral plane of the mill.
The mutual disposition of the deflectors B in the embodiment of the figure 12 is the same as this of the figure 3 and the configurations of the spirals made are roughly the same.
In the embodiment of the figure 13 , the spiral is less steep than in that of the figure 12 . For this purpose, the deflectors B are associated in pairs in successive adjacent rings. However, to achieve a spiral configuration, the fins of two adjacent deflectors B of the same ring are disposed, one of the inlet side of the deflector and the other of the outlet side of the deflector.
It goes without saying that the deflectors of Figures 12 and 13 can be either monobloc castings as illustrated on the Figures 1 and 2 , or composite parts according to the Figures 7 to 11 . Similarly, the working side of the fins in the Figures 12 and 13 (which this time is the face turned towards the entrance of the mill) can be worked or include incrustations to increase its resistance.

Claims (13)

1. Lining for a rotary tubular grinding mill comprising a cylindrical shell intended to contain material to be ground and a load of grinding media, wherein the lining is constituted by rings of individual juxtaposed lining plates, wherein a given number of lining plates located at selected positions have the shape of deflectors (20, 30) comprising a fin (26, 36) raising edgewise on a base plate (22, 32) secured to the shell and forming an angle of less than 25° with respect to a diametric plane of the grinding mill, and wherein the positions of the deflectors (20, 30) are selected so that the assembly of the deflectors shows a configuration in the form of spirals.
2. Lining according to claim 1, characterized in that the fin (26, 36) of each deflector (20, 30) delimits an angle of between 5 and 25° with respect a diametric plane of the grinding mill.
3. Lining according to either of claims 1 or 2, characterized in that the lateral side of the fin (26, 36) located at the front side, as seen in the direction of rotation of the grinding mill, is chamfered so as to form a sharp edge (28), with the chamfering being provided on the side facing the inlet of the grinding mill.
4. Lining according to claim 3, characterized in that the chamfering is provided on the side of the fin facing the inlet of the grinding mill.
5. Lining according to any of claims 3 or 4, characterized in that the chamfered lateral side of the fin (26, 36) is, in the direction of the forward motion of the material to be ground, standing back with respect to the opposed lateral side.
6. Lining according to claim 3, characterized in that the chamfering is provided on the side of the fin facing the outlet of the grinding mill.
7. Lining according to any of claims 3 or 6, characterized in that the chamfered lateral side of the fin (26, 36) is, in the direction of the forward motion of the material to be ground, located in front of the opposed lateral side.
8. Lining according to any of claims 1 to 7, characterized in that the fin (26) is an integral part of the base plate (22) and is manufactured by casting at the same time as said base plate (22).
9. Lining according to any of claims 1 to 7, characterized in that the deflector (30) is a composite part comprising a fin (36) with a mounting base (34) that is received in an opening (40) of the base plate (32), said opening (40) having a complementary shape to that of the mounting base (34).
10. Lining according to claim 9, characterized in that the mounting base (34) and the opening (40) have truncated complementary shapes so that the base plate (32) is held in place by the mounting base (34) when the latter is bolted to the shell of the grinding mill.
11. Lining according to either of claims 9 or 10, characterized by filling parts (42) having the same shape as that one of a mounting base (34) of a fin (36) and being intended to replace the said part in a base plate (32).
12. Lining according to any of claims 1 to 11, characterized in that the working side of the fins (26, 36) as well as the edge (28) have ceramic incrustations to enhance the abrasion resistance.
13. Rotary tubular grinding mill comprising a lining according to any of claims 1 to 12.

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