RU2521709C2 - Semi-self-grinding of primarily ferromagnetic stock - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to grinding of ferromagnetics and can be used in processing of magnetite and sulphide ores containing magnetite, pyrrotine, that is, minerals with high magnetic susceptibility. This method consists in application of at least one electromagnetic system S configured in circuit "electromagnet-diametrically located electromagnet". At use of several electromagnetic systems S (at S>1), these are arranged in helical line with the shift over drum cylindrical surface. Said drum rotates at n=20D^-1/2, where n is mill drum rpm, D is drum diameter, m, drum electromagnets excite magnetic pulses there inside. Note here that at displacement of electromagnets from 0° making the origin of angular coordinates at intersection of horizontal diameter left end with the drum to 30-50° to ensure increase in fall speed of ferromagnetic lumps at acceleration a, to be summed with gravity acceleration g. Magnetic pulses in the drum are eliminated in sector from 30-50° to 70-110° to resume the motion of balls and stock grinding by abrasion and crushing. Magnetic pulses are excited in section from 70-110° to 180° to trap ferromagnetic stock to be lifted to 180°. Magnetic pulses in the drum are eliminated in sector from 180-0° to deliver stock by friction and inertia to coordinate 225-226°. Another portion of stock is accelerated by magnetic pulses in sector of electromagnets of 0° to 30-50°, electromagnets being transferred the mill right to left. Horizontal components h of acceleration make ferromagnetic lumps crush the stock at <90° and move over lining of the pole and stock layer formed earlier.

EFFECT: higher efficiency of grinding.

Description

The invention relates to the grinding of predominantly ferromagnetic materials and can be used in the processing of magnetite and sulfide ores containing magnetite, pyrrhotite - minerals with high magnetic susceptibility.

Known methods for the destruction of mineral raw materials by mechanical means with an efficiency of up to 1% [1]. The low value of the efficiency of the ore grinding process is due to the application of mechanical stresses and the propagation of brittle deformations in mineral aggregates in random directions, small mechanical loads of grinding media on raw materials [2] and the presence of mills (balls, rods, etc.) in the grinding feed, in which balls, for example in amounts up to 30%, do not participate in the process of destruction of raw materials [3].

There is also a method of self-grinding of ores in a drum mill using large pieces of ore as grinding bodies [4].

During self-grinding of ores, pieces from 25 to 75 mm in size are accumulated in the mill drum, which are large in order to be broken by a larger piece, and small for destruction of smaller pieces [5].

The method was developed during the implementation of project 12-P-5-1028 under the program of the Presidium of the Russian Academy of Sciences No. 34 "Forecast of technological development in the management of the quality of raw materials in the mining industries.

The addition of steel balls to the mill with a higher density than ore with a diameter of 100-150 mm in the amount of 10-15% of the drum volume transfers the ore self-grinding to semi-self-grinding mode and to the destruction of pieces with sizes from 25 to 75 mm by balls.

The dead zone of grinding media and ore is preserved in the modes of self-grinding and semi-self-grinding of ores.

To increase the efficiency of ball grinding of ores, the drum mill is equipped with an electromagnetic system S, consisting of two flat electromagnets mounted on the drum through 180 ° according to the scheme “electromagnet - diametrically distributed electromagnet” [6]. The cores of electromagnets are directed into the drum in the diametrical direction and placed under a non-magnetic lining [7]. Magnetic pulses, excited by current pulses in electromagnets, are used to control the circulation of balls in the mill (raising balls to the optimum height, eliminating the dead zone of balls, increasing the kinetic energy of the balls when they hit the raw materials). The destructive effects of deformations that occur upon impact and as a result of exposure to raw materials, such as magnetostriction of ferromagnetic minerals, are combined in time and space, which increases the grinding efficiency.

By technical nature, the closest to the invention is a method of magnetomechanical grinding of raw materials in a drum mill with steel balls. The mill contains one S. The cores of electromagnets are directed through the lining with a low value of magnetic susceptibility (χ ~ 10 ^-6 m ³ / kg or less) into the drum cavity [8]. The magnetic field S is also used to control the circulation of balls in the mill. Grinding is carried out, for example, by rotating the drum counterclockwise at a speed

$$n=\mathrm{twenty}{D}^{-\mathrm{one}/2}\left(\mathrm{one}\right)$$

where n is the number of revolutions per minute of the mill drum, D is the diameter of the drum, m [7].

When the electromagnet moves, for example, 1 from the left end of the horizontal diameter of the drum (0 ° is the beginning of the mill's angular coordinates) to the right (coordinate 180 °), two electric current pulses that generate two magnetic pulses are fed into the electromagnet winding. The first magnetic pulse with a duration equal to the time of movement of the electromagnet from 0 ° to a point with a coordinate of 30-50 ° attracts balls to the electromagnet, which fall on its pole with acceleration a and the formation of a ball of balls. The acceleration a is combined with the acceleration of gravity g. The value of a can significantly exceed g with increasing magnetic induction of the electromagnet.

Electromagnet 1 with a ball of balls is disconnected from the current source when the electromagnet moves in a sector with coordinates from 30-50 to 100-140 °. In this sector, the ball of balls breaks up into separate balls, the movement of balls and the destruction of the raw materials by abrasion and crushing methods [9], which are absent during grinding according to [6 and 7], are restored in it. At a point with a coordinate from 100 to 140 °, a second magnetic pulse is excited by the electromagnet 1, which raises the newly formed ball of balls to a point with a coordinate of 180 °, where the electromagnet is disconnected from the current source. By friction and inertia, the balls are delivered to the optimum height (~ 225 °), where they fall off its lining and fall into the drum. Balls during a fall are accelerated from 0 to a point with a coordinate of 30-50 ° by an electromagnet 2, which is moved from the right side of the mill to the left side by rotating the drum at a speed of [1].

Electromagnet 2 operates further in electromagnet 1 mode.

Magnetic pulses accelerating and raising balls are divided into a number of short ones [8] and magneto-pulsed processing of raw materials is used to soften it with magnetism effects [10-13] (magneto-induction — pronounced interaction of ferromagnets with a magnetic field, magnetostrictive and magnetocaloric — respectively, shape change and the size and temperature (7) of solids under the influence of a magnetic field, the Villari effects with the action opposite to magnetostriction, and Einstein-de Haas - the acquisition of a rotational moment by a ferromagnet the one relative to the direction of magnetization).

Restoring the grinding of raw materials by abrasion and crushing in a sector with coordinates from 30-50 ° to 100-140 ° [9] reduces the energy consumption for the operation of electromagnets to 44%. Periodic connection and disconnection of electromagnets intensifies the destruction of raw materials and reduces electricity costs by up to 22% with equal duration of disconnections and connections [8].

Lumps of balls, drawn alternately to the poles of electromagnets 1 and 2 and raised to a point with a coordinate of 180 °, increase the magnitude of the drum torque (M _B ), which requires an increase in engine power and energy consumption to overcome M _B. To reduce the mass of the balls attracted to the electromagnets and M _B , which is opposite to the rotational moment of the engine, several S are used, which are placed on the mill drum along a helical line with an angle shift θ [14]

$$\theta =k\left(0.95÷1.05\right)\pi /S-\mathrm{one,}\left(2\right)$$

where k is an odd integer.

The disadvantages of this method:

1. The magnetic energy of electromagnets is used inefficiently - one pole of each electromagnet is directed into the cavity of the mill drum.

2. From ferromagnetic pieces of raw materials that are ahead of non-magnetic pieces when electromagnets fall on poles, a tight lump is formed by magnetic attraction. In the lump, the destruction of raw materials predominates, mainly, by the energy-intensive crushing deformation, which increases the energy consumption for grinding [15].

The present invention solves the problem of increasing the grinding efficiency.

The technical result obtained by using the invention is to increase the grinding efficiency of ferromagnetic raw materials.

The specified technical result is achieved by the fact that in the semi-self-grinding method of predominantly ferromagnetic raw materials in a drum mill, which includes the use of at least one electromagnetic system S, formed according to the scheme "electromagnet - diametrically located electromagnet" with S placed along a helical line on the cylindrical surface of the drum at S > 1, the rotation of the drum, for example, counterclockwise at a speed of [1], the excitation in the drum of magnetic pulses by electromagnets when they move from 0 ° (beginning Glov mill coordinates - the intersection of the left end of the horizontal diameter of the drum) to 30-50 ° to increase the incident speed of ferromagnetic pieces acceleration a, which is summed with the earth's gravitational acceleration g, the elimination of the magnetic pulses in the drum sector coordinates of 30-50 ° to 70- 110 ° to restore the movement of raw materials in it and the process of grinding it by abrasion and crushing, excitation in the sector with coordinates from 70-110 ° to 180 ° of magnetic pulses designed to capture and raise ferromagnetic materials to 180 °, face magnetic pulses in the sector from 180 ° to 0 ° for the delivery of raw materials by friction and inertia to a height with a coordinate of 225-226 °, from which the next portion of the incident ferromagnetic raw materials is accelerated by magnetic pulses in the sector from 0 ° to 30-50 ° by electromagnets by rotating the drum from the right side of the mill to the left, the grinding efficiency of ferromagnetic raw materials is increased by converting its pieces, mainly of increased fineness, into intensive grinding and self-grinding grinding bodies, whose new properties (grinding fractionation of grains from 25 to 75 mm in size, intensive self-destruction of grinding bodies formed from raw materials) is ensured by several S located on the drum along a helical line with an angle shift θ = π / S, by increasing the kinetic energy of ferromagnetic grinding bodies falling on ore, to a value that generates deformations in raw materials and ferromagnetic grinding media that exceed the tensile strength of the ore by acting on the ore and ferromagnetic grinding media with the corresponding value in each S magnetic induction of U-shaped electromagnets whose poles sent to the mill drum, fixed along a generatrix of the drum and transversely to it at diametrically opposite electromagnets, with the accumulation of magnetic pulses between the poles of the electromagnets dumbbell aggregates of ferromagnetic materials, acquiring a fall during attraction it to poles horizontal component h acceleration (in addition to the a and g), under the influence of which ferromagnetic pieces hit the raw material at an angle <90 ° and move along the lining of the poles and the previously formed layer of the raw material with the destruction of the raw material by abrasion and energy-saving shear deformation, which in combination with the energy impact of grinding media and the effects of magnetism increase the grinding efficiency.

The novelty and originality of the proposed method:

1. Fixing in each system S poles of U-shaped electromagnets along and across the drum generates a mixture of “grinding bodies-pieces of raw materials” and dumbbell-shaped aggregates formed from raw materials in the phase of its rise to the optimum height, horizontal component h of acceleration (in addition to a and g) in the fall. Under the influence of h, which generates impacts of pieces on raw materials at an angle <90 °, attraction of ferromagnetic pieces to each other when they move along the lining of electromagnets and along a previously formed layer, the raw material is additionally affected by shear deformation, which increases the grinding efficiency.

2. The proposed method converts the process of self-grinding of ferromagnetic raw materials into semi-self-grinding without adding steel balls to the mill drum and gives the pieces of ferromagnetic raw materials a new quality - high grinding efficiency and intensive self-destruction of grinding media.

3. The proposed method eliminates the class of ore with a particle size of 25 to 75 mm, not crushed in known mills self-grinding. A class with a particle size of 25 to 75 mm goes into the category of crushed raw materials and self-grinding grinding bodies due to a significant increase in the kinetic energy E of the raw material by increasing its speed when v = ( a + g) t decreases due to acceleration a

$$E=m_{\mathrm{to}}{\left[\left(a+g\right)t\right]}^2/2\left(3\right)$$

where m _to - grinding media formed from pieces of ferromagnetic materials.

4. Raw materials in the magnetic field of the mill is divided by the magnitude of the magnetic susceptibility χ:

4.1. Ferromagnetic pieces are captured and accelerated by magnetic pulses.

Pieces of waste rock with a small value of χ are displaced in those parts of the mill where the grinding intensity is less, the safety of the pieces is greater, which increases the likelihood of non-magnetic minerals being separated into an independent product, for example, by an energy-saving screening operation.

Information sources

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2. Autogenous ore preparation in the processing of non-ferrous metal ores / V.P. Yashin. A.V. Bortnikov, V.D. Molodtsov et al. // Development of the theory of improvement of engineering and technology for preparing ores for enrichment. Sat scientific tr / Institute of Mechanobr. - L., 1982. - P. 41-48.

3. Muizemnek Yu.A., Gabov O.A., Egorov M.V. Tests of the ball mill model // Ore beneficiation. - 1961. - No. 5. - S. 39-42.

4. Handbook of ore dressing. Preparatory processes. M .: "bowels". - 1972, v. 1. - S. 327.

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8. Patent No. 2319546 Russian Federation, MKI ⁷ V02C 19/00. The method of magnetomechanical grinding of materials by ferromagnetic grinding media / F.F. Boriskov, D.F. Boriskov, V.A. Motovilov et al .; Applicant and patent holder: Institute of Electrophysics, Ural Branch of the Russian Academy of Sciences. - No. 2005134598/03, declared 2005, publ. 2008, Bull. No. 8.

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Claims (1)

The method of semi-self-grinding of predominantly ferromagnetic raw materials in a drum mill, including the use of at least one electromagnetic system S, formed according to the scheme "electromagnet - diametrically located electromagnet" with the electromagnetic system S placed along a helical line on the cylindrical surface of the drum with the number of electromagnetic systems S> 1, rotation of the drum, for example, counterclockwise at a speed n = 20D ^-1/2 , excitation of magnetic pulses in the drum by electromagnets when moving them from 0 ° - the beginning of the angular coordinates of the mill, the intersection of the left end of the horizontal diameter with the drum to 30 ° -50 ° to increase the speed of the falling ferromagnetic pieces by acceleration a , which is combined with the acceleration of gravity g, the elimination of magnetic pulses in the drum sector with coordinates from 30 ° -50 ° up to 70 ° -110 ° to restore the movement of raw materials in it and the process of grinding it by abrasion and crushing, excitation in the sector with coordinates from 70 ° -110 ° to 180 ° of magnetic pulses designed to capture and raise ferromagnetic cheese I to 180 °, the elimination of magnetic pulses in the sector from 180 ° to 0 ° for the delivery of raw materials by friction and inertia to a height with a coordinate of 225 ° -226 °, from which the next portion of the incident ferromagnetic material is accelerated by magnetic pulses in the sector from 0 ° to 30 ° -50 ° electromagnets moved by rotating the drum from the right side of the mill to the left, characterized in that the grinding efficiency of the ferromagnetic feedstock is increased by converting its pieces, mainly of increased fineness, into intensive grinding and self-grinding grinding m ate, whose new properties are grinding fractions with sizes from 25 mm to 75 mm, intensive self-destruction of grinding bodies formed from raw materials, is provided by several electromagnetic systems S located on the drum along a helical line with an angle shift θ = π / S, by increasing the kinetic energies of ferromagnetic grinding bodies incident on the ore to a value that generates deformations in raw materials and ferromagnetic grinding bodies that exceed the tensile strength of the ore by acting on the ore and ferromagnetic grinding bodies with the corresponding value in each electromagnetic system S of the magnetic induction of U-shaped electromagnets, the poles of which are directed to the mill drum, are fixed along the generatrix of the drum and across it at diametrically located electromagnets, with the accumulation of magnetic pulses between the poles of the electromagnets of dumbbell-shaped aggregates of ferromagnetic raw materials, which acquire when they fall to the h poles horizontal component of acceleration, in addition to a and g, which is influenced by the ferromagnetic pieces falling under hit the raw angular <90 ° and move along the pole and the lining layer previously formed raw material to the generation of shear energy saving deformation, which in conjunction with the energy impact milling bodies and magnetism improves grinding efficiency effects.