ES2305117T3 - MOLTURATION OF MATERIAL IN PARTICLES. - Google Patents

Abstract

Apparatus (1) for grinding a suspension of a particulate solid material. The apparatus (1) comprises a grinding chamber (2), means (7, 8) for introducing a suspension of the particulate solid material into the grinding chamber (2) and an impeller (6) which is rotated and thereby agitates the particulate grinding medium and the suspension of particulate solid material in the grinding chamber (2). The impeller (6) has at least one blade (12), the said blade (12) having a leading face (14) in the direction of rotation (R) of the impeller (6), which leading face (14) is offset relative to a plane of rotation of the impeller (6). In a preferred embodiment, an upper edge of the said leading face (14) is the leading edge and a lower edge of the said leading face is the trailing edge of each blade (12), so that the impeller (6) acts to drive the material in the grinding chamber (2) downwards towards a base of the grinding chamber (2), thereby compresing the material in the grinding chamber (2). A baffle member (16) comprising an annular plate may be located in the grinding chamber (2) above the impeller (6) at a preset height, so that the material in the grinding chamber (2) is maintained in a compressed condition.

Description

Grinding of particulate material.

The present invention relates to the sector of the grinding, and particularly to an apparatus and a method for friction grinding particulate mineral materials.

It is well known how to grind a material particulate solid suspended in a liquid medium, such as a aqueous medium. The grinding of said material suspensions is known in the art as "wet" grinding and the name typical of a type of device used to perform said grinding is that of a stirred media mill or a mill of ultra-fine grinding

The U.S.A. number 4,108,385 gives know a colloid mill that has milling impellers Rotating in a bowl. Each blade of them can be disassemble and exchange individually.

Document DE 1248440 discloses an apparatus of grinding comprising a vessel, a stirrer impeller the contents of the container and a bulkhead to vary the volume of Work of the latter.

The applicant has currently created a mode improved to grind solid particulate materials which is more economically effective and more efficient energetically than the grinding apparatus of the technique Previous known.

According to a first aspect of the present invention, an apparatus for grinding a suspension is disclosed of a solid particulate material, said comprising apparatus:

a grinding chamber to contain a medium particle milling;

means to introduce the suspension of solid particulate material in the grinding chamber;

a rotating impeller to stir the means of particle grinding and suspension of solid material in particles in the grinding chamber, the impeller having the minus one blade, in which the blade or impeller blades are inclined relative to the plane of rotation of the impeller; Y

means for driving the impeller, for the purpose of make a suspension of a solid particulate material milled, the rotation plane being substantially horizontal of the impeller, and the impeller blade or vanes being inclined in relation to the impeller rotation plane for the purpose of driving down the material in the grinding chamber towards a base Of the same.

The impeller configuration arranged in the apparatus of the invention makes the suspension of particulate material introduced into the apparatus. The device of the invention consumes less energy during operation and achieves an improved level of grinding compared to prior art configurations.

According to another aspect of the present invention, discloses a method to grind a suspension of a material particulate solid in an apparatus as defined by the first aspect of the invention, said method comprising:

insert the medium into the grinding chamber particle milling and solid material suspension in particles; Y

shake the particle milling medium and the suspension of solid particulate material by rotation of the impeller, for the purpose of making a suspension of a solid material in ground particles.

Preferably, the impeller blade or vanes they have a front face in the direction of impeller rotation, and preferably an upper edge of said front face is the leading edge and a lower edge of said front face is the rear edge In this way, the impeller acts to propel towards down the material in the grinding chamber towards a base of the same, thereby compressing the material in the chamber of grinding

The impeller can comprise a centerpiece in the form of an annular body with a central opening that can be arranged on a rotating shaft, oriented so substantially vertical An upper end of the tree can be connected to drive means to rotatably drive the shaft and the impeller during the operation of the device. Be prefers that the impeller annular body can comprise a series of blades, radially protruding from the annular body each one of the blades and being preferably separated so equidistant from each other around an outer face of the body to annul, and being inclined each one of the blades in relation to the impeller rotation plane. In this specification, the "inclination" of a blade is defined as the angle between the blade of the blade (or the front face of the blade in the direction of impeller rotation) and the plane of rotation of the blades of the driving. The impeller can have an annular body and a series of blades that can be unitary, or, alternatively, the series of Blades can be fixedly secured to the annular body.

It is preferred that inclined blades have a tilt angle in the range from about 30º until about 60º. Optimally, the angle of inclination is approximately 45º, with which, during the use of the apparatus of the invention, advantageously elaborates a product of material in ground particles having the desired size properties of particle. It is also preferred that the plane of rotation of the impeller can be substantially perpendicular to a tree substantially vertically oriented swivel of the driving. Preferably, each blade of the blade series of the impeller has a substantially tilt angle equivalent; in other words, the string of each blade can have a substantially equivalent gradient. Preferred orientation of the inclined blades provides improved grinding of the suspension of particulate mineral material, to make a milled mineral product with the required particle size with a reduced energy input. Preferably, a front face (front) and / or a rear (rear) side of each blade can be substantially crushed (flat).

In an embodiment of the apparatus of the invention, The impeller may comprise an arrangement of one or more rows. Preferably, there are two, three or four rows to improve additionally the performance of the method of the invention. A double row impeller arranged in said apparatus can be called a double row impeller. Preferably, the double row impeller can be arranged to rotate in unison and the top row of the impeller can be separated upwards of the bottom row to maximize the grinding effect of the impeller in order to shred the suspension of particulate material introduced into the grinding chamber. Preferably, the upper row impeller blades may be inclined substantially at an angle of inclination equivalent to the blades of the bottom row impeller.

The prior art configurations known of "wet" grinding devices do not use a inclined impeller as defined by the present invention and, accordingly, said prior art configurations known do not provide the advantages described in the present memory In general, the effectiveness of a process of grinding can be attributed to the fineness of the processed product and to obtaining product with the desired particle size. A shredded product consisting mainly of particles with a particle size less than 2 µm is recognized in the art, in general, as a properly milled product. He milled particulate product, prepared by the method of invention, advantageously consists in a greater obtaining of particles with a particle size finer than that of a product milling that has been prepared by grinding apparatus of the known prior art. Preferably, at least 90% by weight of the milled particulate product comprises particles with a particle size less than 5 µm; and preferably at least 70% by weight of the milled product comprises particles with a particle size less than 2 µm.

In addition, the use of the apparatus of the invention equipped with an inclined impeller is more effective from the point of economical and more energy efficient view than that of milling apparatus of the prior art known. The apparatus of the invention consumes less energy during the operation and get an improved level of grinding if Compare with prior art settings. The amount of energy used by apparatus according to the invention when grind materials such as kaolin can be in the range from about 20 kWh / t to 150 kWh / t; optimally the Energy that is applied is from approximately 55 kWh / t to 150 kWh / t The amount of energy that is applied when ground Materials such as calcium carbonate is preferably up to 300 kWh / t

In tests carried out by the applicant, the use of an impeller that has blades with an inclination of 45º instead of pin-type vanes (cylindrical) in a conventional chamber wet grinding test decreased approximately at half the energy input to get a product milled in that 80% of the particles were less than 2 µm.

The use of an inclined impeller, as it has been described above, in the apparatus of the invention causes the load is better mixed, which results in grinding Improved suspension of material introduced into the apparatus. In this descriptive memory, the "load" is defined as the mixture of the particle milling medium and the suspension of solid particulate material contained in the grinding chamber of the apparatus, a term that is commonly known to experts in The technique. The applicant considers that such improved milling It is caused because the suspension of mineral material is ground relatively close to an inner face, or in the area thereof, from the wall of the grinding chamber. You can start the rotational grinding of the impeller at a speed suitable for fluidizing the milling medium (or the bed of the same) and have the grinding medium mixed with the suspension of material to be ground. One gear suitable rotary of the inclined impeller can be in the range from 50 rpm to 400 rpm.

A partition element can be arranged on the particle milling medium and the suspension of solid particulate material. The partition element can be formed by an annular partition wall plate with a central opening that can receive through it a rotating shaft oriented so substantially vertical The partition wall can be made of a plastic material, such as for example a material of polyurethane. More preferably, the partition element is of Rigid construction and can be made of steel. Said element may be lined with an antiwear component, such as a polyurethane lining or lining.

Preferably, the partition element is detachably attached to an inner face of the wall of the grinding chamber, or, alternatively, to an upper end of the same. Preferably, the partition element is in a plane that is substantially perpendicular to an axis of rotation of the impeller shaft Preferably, the partition element is located at a preset height above the load, so that during operation of the device, the partition element ensures that the load is in a relatively condition compressed Said position of the partition element optimizes the energy supplied to each unit volume of the load (by impeller rotation) maximizing, in this way, the grinding of the suspension of mineral material. The element of partition also serves to limit the distance that the load goes up on the inside of the wall of the grinding chamber.

In tests carried out by the applicant, the adding a partition element to a conventional chamber of wet grinding test decreases approximately 40% the energy input to get a milled product in which 80% of the particles are less than 2 µm.

The arrangement of a partition element in the apparatus of the invention further improves also the advantages techniques that can be achieved by the arrangement of an impeller inclined as described above. For example, it further improves the obtaining of particulate product milled with a fine particle size (ideally smaller than 2 um) and the amount of energy applied to the apparatus is further reduced, resulting in a particularly preferred embodiment of the invention.

The particulate grinding media that can be used, according to the method of the invention, can be of a natural or synthetic material. The grinding media can comprise balls, splinters or granules of any hard mineral, ceramic or metallic material; such materials may include, by example, alumina, zirconia, zirconium, silicate, silicate aluminum or mullite-rich material that is made by calcining kaolinitic clay at a temperature in the range from 1,300 ° C up to 1,800 ° C. Alternatively, they can be used in the method of invention natural sand particles with a suitable size of particle.

In general, the type of grinding media and the particle size thereof to be selected with in view of its use in the invention may be dependent on properties, such as, for example, particle size and chemical composition of the material feed suspension Inorganic to be ground. Preferably, the particle characterization such as, for example, size of particle and chemical composition of the suspension of feed of inorganic material to be ground. Preferably, the particulate grinding medium comprises particles having an average diameter in the range from 0.1 mm to 6.0 mm and, more preferably in the range from 0.2 mm up to 4.0 mm Preferably, the means (or means) of grinding can be present in an amount from 40% up to 70% by volume of the load; and more preferably in a amount of approximately 60% by volume of the load.

The suspension of solid particulate material to be shredded by the method of the invention can be of an inorganic material and preferably of a mineral material. He Mineral material can be used in the form presented naturally or with its chemically synthesized form. Sayings materials may include, for example calcium carbonate, a kaolin clay and any other suitable mineral material.

The inorganic particulate material may be preferably present in an amount from 10% to 85% by weight of the suspension; more preferably, the material inorganic may be present in an amount from 20% to 80% by weight of the suspension. Most preferably, the material inorganic may be present in an amount of approximately 30% to 75% by weight of the suspension.

The suspension of solid material to be crumble can be of a relatively high viscosity, in which case a dispersing agent can preferably be added to the suspension before shredding by the method of the invention. The dispersing agent can be, for example, a condensed phosphate water soluble, a water soluble salt of a polysilicic acid or a polyelectrolyte, for example a water soluble salt of an acid polyacrylic or a polymethacrylic acid that has a weight molecular number average not greater than 20,000. The amount of dispersing agent used would generally be in the range from 0.1 to 2.0% by weight, based on weight of the solid dry particulate material. The suspension can be enter the device's grinding chamber at a temperature in the range from 4 ° C to 100 ° C.

An embodiment of the invention by way of example only and with reference to the drawings that are accompanied, in which:

Figure 1 is a sectional view, in shape schematic, of an apparatus incorporating the invention, which is arranged to grind a suspension of a solid material in particles by a method that incorporates the invention.

Figure 2 is a perspective view, from the upper part of an inclined impeller for use in a apparatus incorporating the invention as illustrated, for example, in figure 1.

Referring to figure 1, a grinding apparatus generally designated by numeral reference (1), comprising a grinding chamber (2) that contains a mixture (3) of a particulate grinding medium and a suspension of a solid particulate material. A tree vertically oriented swivel (4) is suspended in the chamber grinding (3), with an upper end of the shaft being supported (4) above the grinding chamber. An engine (5) is connected to the tree by means of an adequate arrangement of wheels toothed A double tilt impeller (6), which has two rows (6a), (6b), is fixed to the tree (4). A conduit (7), which it has an entrance opening (8), it is arranged at the base of the grinding chamber (2) to supply the chamber (2) with a solid particle feed suspension which is It has to crumble. The inlet opening (8) is located in the center of the grinding chamber base (2) under one end free of the vertically oriented tree (4).

An annular partition plate (16), located in a preset height above the impeller (6), is set to a side wall (18) of the grinding chamber (2). The tree of drive (4) extends through an opening (20) in the partition wall plate (16).

Referring to figure 2, it is shown a row (6a, 6b) of the inclined impeller (6) for use in the apparatus of figure 1. The inclined impeller (6) comprises a annular body (11) with a central opening to arrange the impeller (6) in the shaft (4), and six blades (12) protruding radially of the annular body (11). Each blade (12) is inclined with an equivalent angle of approximately 45º in relation to plane of rotation of the impeller (6), so that a face front (14) of each blade in the direction of rotation (R) of the impeller is directed in one direction with a component towards down.

As the feed suspension gets supplies the grinding chamber (2), the shaft (4) and the inclined impeller (6) rotate to fluidize the means of particle grinding and make the medium to mix grinding with the suspension of solid particulate material, resulting in a milling of the solid suspension in particles

The action of the inclined blades (6) and the septum plate (16) combine to compress the suspension of Particle solid and improve grinding performance.

The crumbled solid suspension, which it comprises particles with a desired particle size, leaves the grinding chamber (2) through a mesh (9) and is transported along a conduit (10) to refine it additionally, if necessary.

The invention will be described below with Reference to the following example.

Example

A kaolin suspension was introduced which contained 30% by weight solids through the inlet duct (7) in a grinding apparatus of the type shown in Figure 1. Silica sand was used, present in an amount of 60% in volume, as the milling medium in the apparatus. The magnitude of the energy applied to the device was 75 kWh / t. The suspension shredded, obtained from the apparatus through the conduit (10), It was found to contain 92% by weight of particles with a size of particle less than 2 µm.

The previous experiment was also carried out. using conventional prior art apparatus and was obtained a milled kaolin suspension containing 88% by weight of particles with a particle size less than 2 µm.

These results show that it can be elaborated an improved suspension of crumbled product with one more size fine particle using the apparatus and method of the invention.

Claims (25)

1. Apparatus (1) for grinding a suspension of a solid particulate material, said apparatus comprising:

a camera of grinding (2) to contain a grinding medium in particles;

media (7, 8) to introduce the suspension of the solid particulate material into the grinding chamber (2);

a driver swivel (6) to stir the particulate grinding media and the suspension of solid particulate material in the chamber of grinding (2), the impeller (6) having at least one blade (12), in which the blade or blades (12) of the impeller (6) are inclined with relation to the plane of rotation of the impeller (6); Y

means (5) for driving the impeller (6), for the purpose of making a suspension of a molded particulate solid material, characterized in that said plane of rotation of the impeller (6) is substantially horizontal, and because the blade or blades (12) of the impeller (6) are inclined relative to the plane of rotation of the impeller (6) in order to propel the material in the grinding chamber (2) down towards a base of the grinding chamber (2).

2. Apparatus according to claim 1, characterized in that the impeller (6) comprises a central part (11), the vane or blades (12) of the impeller (6) projecting substantially at right angles from the central part (11). impeller rotation axis (6). 3. Apparatus according to claim 2, characterized in that the central part (11) comprises an annular body (11) with a central opening that receives a rotating drive shaft (4). 4. Apparatus according to claim 3, characterized in that the drive shaft (4) is fixed to the impeller (6) at one end and is connected to drive means (5) at its other end. 5. Apparatus according to any of claims 2 to 4, characterized in that the vanes (12) are integrally formed with the central part (11) of the impeller. 6. Apparatus according to any of the preceding claims, characterized in that the inclination of the blade or blades (12) relative to the plane of rotation of the impeller (6) is between 30 ° and 60 °. 7. Apparatus according to claim 6, characterized in that the inclination of the blade or blades (12) of the impeller (6) in relation to the plane of rotation of the impeller (6) is 45 °. Apparatus according to any of the preceding claims, characterized in that the impeller (6) has a series of blades (12), and each of the blades (12) is inclined substantially at the same angle in relation to the plane of rotation of the impeller (6). 9. Apparatus according to any of the preceding claims, characterized in that the impeller (6) comprises a series of blades (12) which are arranged in two or more rows (6a, 6b). 10. Apparatus according to claim 9, characterized in that the rows (6a, 6b) are located one above the other in a substantially vertical aligned stack. 11. Apparatus according to claim 10, characterized in that each row (6a, 6b) of blades is mounted on a respective centerpiece (11), the central parts being mounted on a common drive shaft (4). 12. Apparatus according to any of claims 9 to 11, characterized in that the blades (12) of respective rows (6a, 6b) of the impeller (6) are inclined at the same angle in relation to the plane of rotation of the impeller (6) . 13. Apparatus according to any of the preceding claims, characterized in that a partition element (16) is located in the grinding chamber (2) above the impeller (6). An apparatus according to claim 13, characterized in that the partition element (16) comprises a plate that is arranged in a plane that is substantially parallel to the plane of rotation of the impeller (6). 15. Apparatus according to claim 13 or 14, characterized in that the partition element (16) has a central opening (20) that receives a drive shaft (4) from the impeller. 16. Apparatus according to any of claims 13 to 15, characterized in that the partition element (16) is of rigid construction and is provided with an anti-wear component. 17. Apparatus according to claim 16, characterized in that the wear component comprises a lining or polyurethane coating element. 18. Apparatus according to any of claims 13 to 17, characterized in that the partition element (16) is detachably fixed to a wall (18) of the grinding chamber (2). 19. Apparatus according to any one of claims 13 to 18, characterized in that the partition element (16) is located at a preset height above the suspension of the solid particulate material in the grinding chamber (2). 20. Apparatus according to any of the preceding claims, characterized in that the means (5) for driving the impeller (6) are located above the grinding chamber (2). 21. Apparatus, according to any of the preceding claims, characterized in that a front face (14) of the blade or blades (12), in the direction of rotation of the impeller (6), is directed in a direction with a component facing down. 22. Method for milling a suspension of a solid particulate material in an apparatus (1), according to any of the preceding claims, characterized by the steps of:

enter in the grinding chamber (2) the particulate grinding medium and the suspension of solid particulate material; Y

shake the medium particle milling and solid material suspension in particles by impeller rotation (6), in order to produce a suspension of a molded particulate solid material.

23. Method according to claim 22, characterized in that the grinding medium comprises particles having an average diameter in the range from 0.1 mm to 6 mm. 24. Method according to claim 23, characterized in that the grinding medium has an average diameter in the range from 0.2 mm to 4 mm. 25. Method according to claim 23 or 24, characterized in that the grinding medium is present in an amount from 40% to 70% by volume of the material (3) introduced into the grinding chamber (2).