EP1166876A1 - Lining for a rotary tubular mill - Google Patents

Abstract

The liner consists of rings made up of a series of adjoining plates (22), some of which are made in the form of deflectors (20) having angled fins (26) set at 5 - 25 degrees to the mill's diametrical plane. The fins measure between 25 and 50 mm ythick and100 - 350 mm high; their leading edges (28) are chamfered at an acute angle, and the deflector plates are positioned in the mill so that adjacent fins form spiral lines.

Description

The present invention relates to a shield for a tubular crusher rotary comprising a packed cylindrical ferrule intended to contain of the material to be ground and a charge of grinding material, in which the shielding consists of rings of individual shielding plates juxtaposed.

The invention relates more particularly to the shredders used for the dry grinding of cement (clinker), coal, limestone and dry or wet ores. These shredders consist of a metallic cylindrical shell rotating around its longitudinal axis and containing a grinding charge consisting of grinding media, generally balls, but can also be made of cylpebs, boulpebs, etc., of variable dimensions. The material to be ground is introduced on one side of the grinder and, as it progresses towards the outlet, on the opposite side, it is crushed and ground between the machines grinding.

A conventional mill is generally divided, in the direction axial, by means of a diametrical partition dividing into two chambers successive. The first room in which the crushing takes place coarse material contains grinding balls usually having a diameter between 60 mm and 90 mm. The second bedroom, in which fine grinding takes place, contains grinding balls with a diameter generally between 15 mm and 60 mm. Beside these two chamber mills also exist single mills single chamber that contain grinding gear of different diameters and in different quantities depending on the diameter.

In the second chambers of conventional mills or in single-chamber mills, it is well known that self-classifying shields, i.e. shields which, during rotation of the crusher around their axis, automatically classify the machines grinders according to their size and more particularly large machines grinders at the entrance to the grinding chamber and the smaller ones to the exit from this same room, this so that the weight and the size of the machines grinders decrease as the particle size of the material which advances in the grinding chamber decreases and becomes finer. Of this way, over the length of the grinding chamber, the dimension of grinding gear is adapted to the grain size and the fineness of the material to be ground. This generally reduces consumption energy per tonne of ground material from 10 to 20%.

There are currently different types of self-classifying shielding. One of these has a sawtooth shape in the axial direction of the crusher, i.e. it consists of a succession of truncated cones along the length of the mill which converge towards the outlet and present a slope towards the entrance to the grinding chamber. The plates forming these shields have a relatively high average thickness and are therefore quite heavy. This high thickness also results in a loss useful volume of the grinding chamber and therefore in in some cases, an impossibility of absorbing all the available power of the engine. These shields are, moreover, very sensitive to grains, that is to say when there is a certain accumulation of very hard grains (about 6 to 12 mm) in areas where small grinding devices are found, the classification is very disturbed, up to the reverse classification, that is to say the return of small devices to the entrance and large devices to the exit.

In another type of shielding as described in document BE 09301481, the plates have corrugations which can be tilted at an angle of 15 to 30 ° relative to the generator of the mill. The purpose of the inclination of these undulations is to create a screw effect to act on the grinding charge and the material to be ground. Indeed, when the crusher rotates, large grinding machines are generally found, in majority, at the periphery of the grinding load and the purpose of the inclination of the corrugations is to push these grinding machines by screw effect towards the entrance of the grinding chamber. In practice, the desired classification of this however is very difficult and often random. The plates are also relatively heavy and the ranking effect decreases as measurement of the progress of the wear of the corrugations. These ripples do not cannot be too pronounced, otherwise there is a discontinuous lifting, that is to say too important during which the outer layers of the grinding charge is noted up to the region of the summit of the grinder and fall back on the armor instead of falling and rolling on the foot of the crushing load. These shields are in practice very little used.

The object of the present invention is to provide a new shielding for a tubular mill which eliminates or, at least, reduces the disadvantages of conventional shielding, more specifically a grinder with lighter armor which creates a good ranking, which is effective and very flexible to use.

To achieve this objective, the present invention provides a grinder tubular of the kind described in the preamble which is characterized in that that a number of armor plates found in places selected consist of deflectors comprising a fin erected from the field on a base plate fixed to the ferrule and forming an angle less than 25 ° relative to a diametrical plane of the mill.

The lateral side of the fin located on the front side, viewed in the direction of rotation of the mill, is preferably beveled, this beveling being provided on the side facing the entrance to the mill.

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

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

The fin can form an integral part of the base plate and be made together with it by casting.

The fin can also be a separate piece, integral with a base provided with a hole so that it can be fixed to the shell of the mill. This base may have a frusto-conical periphery which may enter an opening complementary in shape to a base plate. So fixing the fin by its base constitutes, at the same time, a fixing of the plate basic 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 et
• la figure 11 montre une vue en coupe transversale à travers la pièce de la figure 10.

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:

• Figure 1 is a schematic plan view of a first embodiment of a deflector according to the present invention;
• Figure 2 is a side view of the same deflector seen along arrow II in Figure 1;
• Figures 3 to 6 schematically illustrate different configurations of location of the deflectors on the inner wall of the shell;
• Figure 7 schematically shows a plan view of a second embodiment of a deflector;
• Figure 8 shows a cross section along the section plane VIII-VIII in Figure 7;
• Figure 9 shows a side view of a fin with its base;
• FIG. 10 shows a plan view of a filling part and
• FIG. 11 shows a cross-sectional view through the part of FIG. 10.

In accordance with the present invention, a number of armor plates are formed in the form of deflectors 20 such as shown in Figures 1 and 2, Figure 1 is a bird's-eye view on a deflector 20 while FIG. 2 is a side view in the direction of arrow II in FIG. 1 which also represents the direction of rotation of the mill. Each deflector has a plate of base 22 provided with a central hole 24 to be fixed on the interior wall of the crusher shell.

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

According to an important characteristic of the invention, each fin 26 is inclined relative to a diametral plane of the mill at an angle α less than 25 °, preferably between 5 ° and 25 ° depending on the conditions of the grinder and the nature of the grinding load and the material to be ground.

The lateral side of the fin 26 which is on the front side, seen in the direction of rotation of the mill, is bevelled on the face of the fin 26 which is facing the grinder inlet to form a more or less edge acute 28. This edge 28 facilitates penetration into the load and contributes continuous lifting, i.e. prevents projection of gear shredding on the armor.

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

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

According to Figure 3, each deflector B is adjacent to another deflector B at the two diametrically opposite corners to thus define a full or partial spiral all around the inside of the shell.

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

Figure 5 shows an example of a configuration similar to that of Figure 4, but here each deflector B is separated from neighboring deflectors of the same spiral by a diametrical row of plate without deflectors. Note that, in this configuration, the axial spacing between two deflectors neighbors is larger 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.

Figure 6 shows the complete development of a shell of a grinder 4 meters in diameter and 10 meters long. The deflectors are arranged in a spiral in the grinder according to the configuration of the figure 3. In such a DIN standard perforated grinder, there are 40 plates on the circumference and 40 plates lengthwise, for a total of 1600 plates. If there are 10% deflectors, i.e. 160 deflectors, these are arranged in four spirals of 40 plates each in the grinder. These spirals are shown schematically in Figure 6 and numbered successively by 1, 2, 3 and 4.

During the rotation of the mill, all these deflectors penetrate into the crushing load like the ploughshare of a plow and their inclination by with respect to a diametrical plane, pushes the grinding charge towards the exit of the mill. This produces an inclination of the grinding load relative to 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 entrance of the crusher is a little lower than that measured at the exit of the chamber grinding.

Larger grinding machines therefore travel faster that the smallest grinding materials on the base of the grinding load, that is to say from the rear of the mill to its entrance. This classification process of crushing bodies is very effective. He also has another great advantage of the fact that the degree of filling increases from the entrance to the exit. We know, in fact, that the best grinding yield is obtained when the voids between the grinding bodies (more or less 41%) are filled with material and that the material to be ground, advancing in the grinder, "swells" (ie its apparent density decreases). There is therefore interest in having a higher degree of filling at the exit of the grinder to optimize the grinding yield.

Another advantage is that the material to be ground is pushed faster through the crusher and there is, thanks to these deflectors, better mixing between the grinding media and the material to be ground.

As indicated above, the deflector shown in the figures 1 and 2 is a single piece produced by casting. We will describe below, with reference to the following figures, an embodiment with a composite deflector.

This composite deflector, generally designated by the reference 30 in FIG. 7, has a fin 36 comparable to the fin 26 of Figures 1 and 2 but provided at its base with a base 34 which, in the mode of shown embodiment, has a square shape. The base 34 and the fin 36 form a single piece which can be produced by casting but separate from the base plate 32. This base plate has a opening 40 of shape complementary to that of the base 34 and forming a frame to receive it.

As shown in 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, to the ferrule of the crusher, the base plate 32 is held in place by the base 34 and no longer needs to be attached to the shell.

According to an advantageous embodiment, parts are provided filling 42 shown in Figures 10 and 11. These parts of filling 42 have exactly the same shape and the same section as the bases 34 shown in FIGS. 7 to 9 but are devoid of the fins 36. These parts make it possible to fill the openings 40 in the plates basic 32 when it is desired to remove, as desired, certain deflectors 30 shown in FIGS. 7 to 9. It suffices, in fact, to unbolt the base 34, to remove it with its fin 36, to fill the opening with the piece of filling 42 and bolt it to the ferrule through its opening central 44.

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

The fins 26 and 36 shown in the different figures do not due to their bevelled edge 28, are suitable only for a grinder turning in the direction shown in Figures 1 and 3 to 5. In a grinder turning in the opposite direction, it is necessary to provide deflectors which are symmetrical with respect to those shown in the figures.

Trials in a small scale pilot station have shown that, for a DIN standard perforated mill (i.e. with plates of 314.16 mm arc length in circumference and 250 mm of length in the axial direction of the mill), a satisfactory number of plates transformed into deflectors is of the order of ± 10%.

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 : 42,3 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%.

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 % Vcr : nombre de déflecteurs : environ 9%.

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 can however vary with the operating conditions of the mill:

a) at a low degree of filling (± 20%) of the mill, the number of deflectors 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: 42.3 D , expressed in number of revolutions per minute, D being 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: approximately 9%;
• from 65% to 75% Vcr: number of deflectors: approximately 8%;
• from 75% to 85% Vcr: number of deflectors: approximately 7%.

b) with a degree of filling of ± 30%, we will have the following values:

• from 55% to 65% Vcr: number of deflectors: approximately 11%;
• from 65% to 75% Vcr: number of deflectors: approximately 10%;
• from 75% to 85% Vcr: number of deflectors: approximately 9%.

c) with a degree of filling of ± 40%, we will have the following values:

• from 55% to 65% Vcr: number of deflectors: approximately 13%;
• from 65% to 75% Vcr: number of deflectors: approximately 11%;
• from 75% to 85% Vcr: number of deflectors: approximately 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 deflectors depends essentially on the diameter of the crushers. 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 in height,
• for diameters between 3.7 and 4.8 m: ± 250 mm in height,
• for diameters between 4, 9 and 6.2 m: ± 300 mm in height.

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

Standard base plates are usually thick average of ± 40 mm, i.e. a DIN standard plate (314.16 x 250 mm) has a weight of the order of 24 kg. In the case of deflectors composites according to Figures 7 to 9, the assembly of a fin and a base weighs a maximum of 25 kg. Therefore, from an ergonomic and security in mounting the shielding, the deflectors proposed do not constitute not 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 calculated as follows:

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

The comparison shows a decrease in weight 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, ie a decrease of around 20%. In the case of a standard class shielding, we are sometimes faced with the problem that we cannot absorb all the available power of the engine driving the crusher. This is due to the average thickness of these shields which reduces the useful interior 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 grinder 4.8 meters in diameter and 14.3 meters in useful length rotating at 14.48 revolutions per minute (i.e. 75% of the critical speed) with a degree of filling of 30% in grinding bodies and a useful length of 4.3 meters from the first chamber and 10 meters from the second chamber, we have the following values:

• average thickness of standard class armor: 87 mm;
• average thickness of the new shielding with deflectors: 44 mm;
• the power absorbed with the standard class shielding for the second chamber is of the order of 3.256 KWh;
• the power absorbed with the new shielding with deflectors for this second chamber is around 3,451 kWh, an increase of 6%.

For the total crusher, i.e. the two chambers, we will have, when the second has standard filing plates, a total power of 4.754 KWh. However, when the second room has new shielding, the total power will be around 4.949 KWh, a favorable difference of 4%, which results in an increase in throughput of around 4%.

Claims (10)

Shield for a rotary tubular crusher comprising a packed cylindrical shell intended to contain material to be ground and a load of crushing machines, in which the shield consists of rings of juxtaposed individual shield plates, characterized in that a certain number of armor plates located at selected locations are formed in the form of deflectors (20, 30) comprising a fin (26, 36) erected on the field on a base plate (22, 32) fixed to the ferrule and forming a angle less than 25 ° with respect to a diametral plane of the mill. Shielding according to claim 1, characterized in that the fin (26, 36) of each deflector (20, 30) forms an angle between 5 and 25 ° relative to a diametral plane of the mill. Shield according to one of claims 1 or 2, characterized in that the lateral side of the fin (26, 36) located on the front side, seen in the direction of rotation of the mill, is bevelled to form a sharp edge ( 28), the beveling being provided on the face facing the inlet of the mill. Shield according to any one of Claims 1 to 3, characterized in that the bevelled lateral side of the fin (26, 36) is set back with respect to the direction of advance of the material to be ground on the opposite side. Shield according to any one of claims 1 to 4, characterized in that the fin (26) forms an integral part of the base plate (22) and is produced together with the latter by casting. Shield according to any one of claims 1 to 4, characterized in that the deflector (30) is a composite part comprising a fin (36) with a base (34) which is engaged in an opening (40) of the plate base (32), said opening (40) having a shape complementary to that of the base (34). Shield according to claim 6, characterized in that the base (34) and the opening (40) have complementary frustoconical shapes so that the base plate (32) is held in place by the base (34) when this is bolted to the grinder shell. Shield according to one of claims 6 or 7, characterized by filling parts (42) having the same shape as that of a base (34) of a fin (36) and intended to replace the latter in a plate basic (32). Shielding according to any one of Claims 1 to 8, characterized in that the working face of the fins (26, 36) facing the outlet of the crusher as well as the edge (28) comprises ceramic inlays to increase the resistance to the 'abrasion. Rotary tubular mill comprising a screen according to one any of claims 1 to 9.

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