RU2181627C2 - Rattler - Google Patents

Abstract

FIELD: dry and wet grinding of ores. SUBSTANCE: proposed rattler has housing filled with ball-shaped and cubic blocks used as milling bodies. Size of block rib and rounding off of its sides are found from equation contained in description of invention. EFFECT: improved efficiency of grinding process. 3 dwg

Description

 The invention relates to a device for dry and wet grinding of minerals and can be used in the enrichment of raw materials in the metallurgical, mining and chemical industries, the production of building materials and components of cement production, as well as in coal, coke, refractory, energy and other industries.

 Known devices for grinding, containing a horizontally arranged cylindrical body filled with grinding media and rotating in bearings, end caps, loading and unloading devices and drive. (Handbook of ore dressing. Preparatory processes. / Edited by O. S. Bogdanov, V. A. Olevsky, 2nd ed. Revised and enlarged. - M .: Nedra, 1982. - 366 p. [1] )

 Closest to the technical nature of the claimed technical solution is a device for grinding, comprising a housing with a lining filled with grinding media, loading and unloading devices, a drive; disks are mounted obliquely inside the housing on a horizontal shaft, and the loading nozzle is offset relative to the vertical axis of the cross section of the housing in the direction of rotation of the disks. This allows you to increase the degree of filling of the body with grinding bodies, change the trajectory of their movement and increase the efficiency of the grinding process due to impact and abrasion (a.s. 1507443 USSR. Ball mill / IM Aleksyuk. - Publish. 15.09.89, Bul. 34 )

 Significant disadvantages of these devices are the low efficiency of the grinding process and the low resource of grinding media, due to the following reasons. The kinetic energy for grinding in these devices is created due to the mass of grinding media and their speeds determined by the movement, together with the body and falling from top to bottom inside it. Moreover, all the main parameters (impact speed, number of them, mass of grinding media), which determine the productivity and other technological parameters of grinding, are limited in disadvantageous ranges.

 These restrictions are mutually interconnected and fundamentally difficult to change: if you need to increase the performance of these devices usually increase their geometric dimensions. In this regard, the devices are characterized by low efficiency of the grinding process.

 Another significant drawback of these devices is the significant wear of grinding media.

 Depending on the purpose (grinding stage), the following types of grinding bodies of drum mills are used: rods, balls, tsilpepsy and others. The specific consumption of grinding media in processing plants reaches 3 kg per ton of ground ore; at the current scale of mineral processing in the world, about one million tons of steel is irretrievably lost annually.

 Rod and ball grinding loading are most widely used. The use of balls in the second and third stages of grinding causes an increased wear rate and, accordingly, a high specific consumption of steel (from 0.1 to 1.25 kg / t and from 0.061 to 0.5 kg / t when using rods [1, p. 304- 311]).

Ball wear rate is described by the equation
dG / dt = -kD ⁿ ,
where G is the gravity of the ball;
t is the duration of wear;
k is the coefficient of proportionality;
n is an exponent depending on the operating mode of the mill, the physical and mechanical properties of the balls and the abrasiveness of the ore (Andreev S.E., Perov V.P., Zverevich V.V. Crushing, grinding and screening of minerals - M .: Nedra, 1982. - 366 p. [2]).

 In the low-speed mode (cascading with rolling balls), the value of n is taken equal to 2, considering the wear rate proportional to the surface of the ball (according to Mertsell and Prentis). In the operating mode of the mill, leading to the flight of balls, the value of the exponent is in the range of 2.3-2.5 (according to Bond and Olevsky). In these cases, the proportional dependence of the wear rate of the surface of the balls is most convincing, since in the cascade mode all the balls are in contact with the crushed medium, and with the waterfall mode in the crushed medium there are from 54.8 to 70.8% of the ball load [2, p. 262]. Wear of falling balls occurs as a result of impact with the crushed medium and is significantly (almost 4 times) less than wear due to abrasion (Wahl N., Kantenwein G., Rzepka L., Hart - Zerkleinerung und Verschleis. - Aufbereitungs Technik, 1963, 2, v. 3, s. 47-58, 91-111 [3]).

Use as a characteristic wear bodies of various shapes specific surface _ud A grinding body - the ratio of the surface A to the volume V (mass) of the body:
And _beats = A / V.

Для куба с учетом описанной вокруг него сферы:
А_к=4,24/R (2)
С учетом опыта эксплуатации барабанных мельниц со стержневой загрузкой, показавшего, что износ стержней по торцевой поверхности незначителен, удельная поверхность А_с выразится в виде:
A_c=2/R (3)
и является наименьшей из всех применяемых видов мелющих тел.For a ball of radius R, the specific surface will be:

For a cube, taking into account the sphere described around it:
A _k = 4.24 / R (2)
Taking into account the operating experience of drum mills with core loading, which showed that the wear of the rods on the end surface is negligible, the specific surface A _with will be expressed as:
A _c = 2 / R (3)
and is the smallest of all used types of grinding media.

 The largest of the considered bodies, the number of elements through which the load is transferred to the crushed medium, is a cube (6 faces, 8 angles, 12 edges), the tetrahedron has 4 faces, 4 angles and 6 edges.

A _t = 9.02 / R (4)
The cube wear rate compared to the ball is lower than 5.33 / 4.24 = 1.26 by 26%; therefore, a grinding body made in the form of a cube is most suitable. The dimensions of the ribs are determined from the condition of free movement in combination with ball loading.

 The purpose of the invention is to increase the efficiency of the grinding process by increasing the resource of grinding media by improving the shape and composition of them, as well as the trajectory of their movement.

 In FIG. 1 shows a ball mill, section; in FIG. 2 - the trajectory of the combined grinding load; in FIG. 3 is a cross section of grinding media made in the form of cubes in ball mills.

 The drum mill consists of a horizontally arranged cylindrical body 1 with end caps 2 of the loading and unloading 3 ends, a discharge funnel 4, symmetrically located bearings 5, feeder 6, lining 7 and discharge grill 8. The mill body is filled with grinding media 9 and 10.

 Drum mill operates as follows. Before starting work, the housing 1 of the drum mill is loaded with grinding media, half of which is made in the form of balls, and the other half - in the form of cubes.

To ensure the ability to move individual layers of grinding media, the size "a" of the ribs is determined from the ratio
a = R _W -R _W ² / R _b
where R _W and R _b are the radii of the balls and the drum, respectively, R _b = D _b / 2 in FIG. 1.

 As studies have shown (Rotary crushers / V.A.Bauman, V.A. Streltsov, A.I. Kosarev et al. - M.: Mashinostroenie, 1973, 272 p.), The lowest wear rate with impact is the working bodies with with a radius of rounded sharp edges equal to R = 0.01a.

 The housing 1 is rotated in bearings 5, into the grinding space formed by the housing 1 and the end caps 2 and 3 by the feeder 6, a crushed material is supplied, which, as it is grinded, moves towards the discharge funnel 4, and the finished product passing through the slotted openings of the discharge grill 8, discharged from the mill.

 With existing forms of grinding bodies, characterized by a circular cross-section, the grinding bodies roll over the lining that rotates together with the body or the lower layers of the grinding bodies, and is characterized by cascading motion in the low-speed mode. The presence of grinding bodies with a square cross section ensures their movement with sliding friction and the transition to a regime that leads to the flight of grinding bodies (waterfall mode) at a lower number of revolutions.

 In the waterfall regime, both grinding and wear occur as a result of the impact of grinding bodies, and the grinding process is more efficient, while wear is much lower [2, 3]. In addition, an increase in the volume of grinding media provides an increase in their resource.

Claims (1)

A drum mill containing a housing partially filled with ball grinding media, end caps, lining, feeder, discharge funnel and bearings, characterized in that the other part of the grinding media is made in the form of cubes, the rib size of which is determined from the ratio
a = R _W -R _W ² / R _b
where R _W and R _b are the radii of the balls and drum, respectively
and the sharp edges are rounded with a radius of r = 0.01a.

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