WO2003045564A1

WO2003045564A1 - Grinding body for revolving mills

Info

Publication number: WO2003045564A1
Application number: PCT/BR2002/000166
Authority: WO
Inventors: Ivan José DOS SANTOS; Joaquim Donizetti Donda
Original assignee: Samarco Mineração S/A
Priority date: 2001-11-28
Filing date: 2002-11-27
Publication date: 2003-06-05
Also published as: BR0105527A; AU2002347231A1; BR0105527C1; BRPI0105527B1; BR0105527F1

Abstract

The invention relates to grinding bodies for revolving-mills having the shape of a truncated cone having spherical caps on the smaller base, with variants as to the geometric configuration.

Description

Title: "GRINDING BODY FOR REVOLVING MILLS"

The present invention relates to grinding bodies designed to be inserted into revolving mills used for reducing grain size of ores and concentrates, with a view to conform the grain size to the subsequent concentrating, pumping and pelletizing processes. Background of the invention

Ball mills usually refer to horizontal rotary cylinders, used for grinding ores particles. The objective of grinding is to alter the grain size of mineral particles, reducing their size to a desired standard. These mills are provided with pieces called grinding bodies, and about 40% of their internal volume is filled by the grinding bodies. A sectioned ball mill is shown in the figure 1 of the drawings.

The mills may be manufactured either in small dimensions for laboratories and plants that process small masses, or in large dimensions, which may reach 6m in diameter, 10m in length, their total weight reaching

800 tons (machine + charge of grinding bodies) for use in plants that process large masses of materials.

By virtue of the rotation movement of the mill, the charge undergoes such a revolving movement, that the particles to be ground suffer the action of collision of the grinding bodies and break up. Such mills operate continuously, and the worn-out grinding bodies are replaced at determined intervals of time, so that the correct charge of grinding bodies inside the mill will be maintained. The worn-out grinding bodies are expelled from the mill by the flow of ground material itself, a fact that occurs when the grinding bodies reach diameters smaller than 15mm.

More than 95% of the grinding bodies used in this activity are balls (spheres) and cylpebs (truncated-cone shaped). Besides that, pebbles or pieces of the material to be ground itself may also be used.

The conventional techniques further present other types of mills that use balls and cylpebs, which are the tower-type vertical mills, vibratory horizontal mills or non-rotary carcass horizontal mills, with rotary axles provided with devices for revolving the charge. As it can be seen from the figure 2, the balls (grinding bodies) are spheres which may be manufactured from cast iron, cast steel or laminated steel, and further may have additional elements to form alloys, such as chromium, manganese, niobium, among others. For some special applica- tions, the grinding bodies may be manufactured from other materials.

Cylpebs, illustrated in the figure 3, may be manufactured from the same material of the balls, but they gain ground in application in the form of cast iron molded in chill molds, since this is the form which presents the lowest manufacture cost. Regarding the dimensions of the materials to be used in the grinding process, the size of the biggest particle to be ground, in most applications ranges from 12 to 0.074 mm from ball mills. In practice, for each particle size to be ground there is an ideal, more effective size for the grinding body. These bodies are manufactured with intervals of 1.27cm or 5mm. Usu- ally, the manufacture range ranges from 25mm to 120mm.

The grinding bodies of the prior art used in the grinding process have characteristics that are a function of the manufacturing process: one of the factors that raise the price of the balls that actuate as grinders is that the manufacture thereof requires sand molds. Cylpebs have the great advantage that they may be manufactured on molding belts, in chill molds, in a continuous way, so that the manufacture cost will drop. However, grinding efficiency of cylpebs is lower.

Since the capacity of a mill is a function of the efficiency of the grinding charge, the greater the efficiency of the grinding body, the larger the mass processed by the mill. In short, mills charged with balls have greater production capacity than those charged with cylpebs. Summary of the invention

In view of the above drawbacks faced by the professionals skilled in this activity, it is a object of the present invention to provide an improved grinding body which has a grinding efficiency similar to that of the balls, while presents lower manufacture costs, as those practiced in the production of the cylpebs. The above object is achieved by means of a grinding body which comprises a truncated cone having a spherical cap at one end thereof. Brief description of the drawings

Figure 1 shows a revolving ball mill unit with the grinding bodies arranged in its interior.

Figure 2 shows a grinding body in the ball format as those used in the prior art systems.

Figure 3 shows a further grinding body in the cylpeb format which is also largely used in the conventional grinding processes. Figure 4 shows the grinding body as provided by the present invention. Detailed description of the preferred embodiments

As it can be seen from the figure 4, the present invention may be carried out by means of a truncated cone comprising a spherical cap in its smaller base. The desired technical effect, that is, a grinding efficiency similar to that of the balls associated with a lower manufacturing cost, as in the case of the cylpebs, is achieved by means of the union of the two geometric formats, the sphere with a truncated cone.

Such grinding body that may be manufactured by the same manufacturing processes used for cylpebs, further presenting efficiency similar to that of balls, according to the data obtained from laboratory tests.

The technical efficiency of the invented bullet was proven during the tests carried out, and indicated in the following results: Type of grinding body Productivity for the 1300 kW mill Balls 650 t/h

Cylpebs 600 t/h

Bullets (invention) 645 t/h

As it can be seen from the output obtained by the grinding body of the invention, considering the manufacture cost and efficiency, it is noticed that the same involves novelty, inventive activity over the state of the art, besides the fact that it is passible of industrial application.

Tests carried out in mills of 30.48cm in diameter, 30.48cm in length, for an end product with 90% of passing in a 0.15mm mesh sieve.

Each format of a grinding body designed for employ in revolving mills should be tested in practice and provide results that are compared with each other, to increase more and more the operational output of the processing plant in altering the grain size of ores and concentrates. A preferred form of realization of the invention has been described. However, it should be noticed that such description is not limitative and does not reflect the scope of the invention, which shall be considered with basis on the appended claims.

Claims

1. Grinding body for revolving mills characterized in that it comprises a truncated cone having a spherical cap at one end thereof.

2. Grinding body according to claim 1 , wherein the spherical cap is provided on the smaller base of the cone.

3. Grinding body according to claim 1 or 2, wherein the size of the grinding body ranges from 25 mm to 120 mm.