RU2176550C2 - Percussion grinding method - Google Patents

Abstract

FIELD: mining industry. SUBSTANCE: method involves dividing basic material into two flows; providing percussion pulse destruction of material by transmitting single flow of kinematic energy of working tool to lumps and percussion collision against particles of other flow according to the "lump-against-lump" principle in case of intersection of flow movement paths. Basic material is divided into two flows by holding portion of destructible material on surface of auxiliary working tool rotating in opposite direction by centrifugal force. Growth of percussion load is achieved by increasing relative circumferential rotational speed of working tools during transfer of material to other stage and providing contrary straight percussions in perpendicular direction. Working surfaces of baffle plates of auxiliary working tool are oriented perpendicular to tangent to working tool circle. Surface layer of material is shifted downward in rolling mode by gravitational force resultant and by centrifugal forces along adjacent guiding surface with angle of inclination to vertical plane being less than 45 deg. Method is useful for disintegration of rocks and ores. EFFECT: increased efficiency and improved quality of ground material. 4 dwg

Description

 The invention relates to the field of disintegration, processing of rocks and ores and is intended for use in industries processing solid minerals.

 The well-known "Method of impact crushing", where the kinetic energy is transmitted to the source material due to centrifugal forces, and the destruction occurs from impact collisions of particles on a fixed wall [1].

 The main disadvantage of this method is the low efficiency of one-sided impacts for the destruction of the material, which greatly limits their application in practice (used for crushing and grinding very fragile materials).

 The closest solution in technical essence to the claimed one is the crushing method implemented in the Varinac Rotofactor crushers, where the source material is divided into two streams, one is given a centrifugal force impulse by the working body on a horizontal plane, the other a vertical movement (drop) through some delay device (pocket), where the destruction occurs due to shock collision "piece on piece" at the intersection of the trajectories of the flows [2]. The lack of crushing efficiency in this way is caused by oblique rather than direct impacts of pieces of rock flying from a rotating accelerating working body, with pieces located in a holding device (pocket).

 The essence of the invention consists in a crushing method, comprising dividing the source material into two streams and destroying the material with a shock pulse by communicating to the pieces of one stream of kinetic energy of a rotating working body and impact collision with particles of another stream according to the "piece by piece" principle at the intersection of their trajectories, characterized in that the division of the source material into two streams is carried out by holding a portion of the material to be destroyed on the surface of the oppositely rotating additional of the working body by centrifugal force, and the increase in shock load is achieved by increasing the relative peripheral speeds of rotation of the working bodies during the transition of the material to another step and providing counter straight strokes along the normal, while the working planes of the reflecting surfaces of the additional working body are oriented normal to the tangent to the circle the working body, and the movement of the surface layer of the material down in the rolling mode occurs due to the resulting gravity and centrifugal forces along an adjacent guide plane with an angle of inclination to the vertical less than 45 degrees. A comparative analysis of the proposed solution with an analogue shows that in the claimed invention, the efficiency of crushing increases significantly due to the kinetic energy of the pieces of both streams and the provision of opposite counter impacts of the pieces rotating by the opposing working bodies and the constant increase of the shock pulse when the material being destroyed is transferred to the next stages of the working bodies.

 Compared with the technical solution adopted by the prototype in the claimed invention, the formation of intersecting flows is created by installing an additional rotating working body, the surface of which provides a mode of holding and gradual rolling of the material. A significant increase in the impact load on the pieces of the starting material is achieved due to the stepwise increase in the relative speed of rotation of the working bodies and the provision of direct counter impacts to the destructible pieces.

 Thus, the claimed device meets the criterion of "inventive step".

 The essence of the method of impact crushing is illustrated by graphic material. In FIG. 1. shows a kinematic diagram of crushing pieces of rock, in FIG. 2 shows a diagram of the forces acting on a piece of material on the surface of an additional working member, FIG. Figure 3 gives a graphical solution of the system of equations for calculating the zones of behavior of a particle of material on an adjacent guide plane in the form of a dependence of the speed of rotation of the working body on the angle of inclination of the guide surface, and Figure 4 shows the movement of the material in the working chamber and its movement to subsequent stages.

 At the beginning of the process (Fig. 1), pieces of material (1) are fed in one stream to the central part (2) of a rotating working body, due to friction on its surface, the pieces are held on it, acquire kinetic energy, move to the edge of the working body (3) and fly out tangent to the separation point (3). Upon reaching the working surface of the counter-rotating additional working body (4), the pieces of rock experience a direct counter impact on the reflective plane A and undergo disintegration, the crushed particles of the piece are thrown towards the inclined guide of the adjacent plane B (point 5) and are held on it, gradually moving down along the direction of T. 7. Part of the disintegrated mass remains on the surface A (points 6) and gradually slides toward the junction of the two planes A and B in the direction of T. 8. In this case, particles that have fallen on the surface of an additional working body are repeatedly subjected to "bombardment" of again and again incoming pieces from the side of the main working body.

 An important part of the crushing process described above is the creation of an optimal “rolling” mode of crushed material along an inclined guide plane B, since the crushing efficiency of the rock is directly dependent on the angular rotation speed (ω) of the additional working body. In other words, at low speeds, the desired increase in the degree of crushing is not achieved, and at high speeds, the probability of accumulation of crushed particles on the surface of an additional working body increases, which can lead to a loss in the productivity of the process.

 Consider a simplified model of the behavior of a particle on a rotating surface. The radius of rotation R, the angular velocity ω, α is the angle of inclination of the surface from the vertical. The coefficient of friction of the rock on steel will be considered equal to 0.1.

The following forces act in the particle-surface system (Fig. 2)
(1) F _cb = mω ² R is the centrifugal force acting on the particle;
(2) mg - particle gravity;
(3) F _n = F _cb cos α is the force of the normal pressure of the particle on the surface due to centrifugal force;
(4) F _omp = mg sin α is the component of gravity that repels the particle from the surface,
(5) F _ramp1 = F _CB sin α is the force that rolls the particle over the surface due to (centrifugal force;
(6) F _ram2 = mg cos α - component of gravity, rolling the particle from the surface;
(7) F _Tr = F _N - F _neg ) k _Tr - the friction force.

Выразив все силы их проекциями на оси ОХ и OY, перейдем на скалярную форму и составим уравнения равновесия:
mω $\genfrac{}{}{0ex}{}{\text{2}}{\text{1}}$ Rcosα = mgsinα (9)

Производя сокращение m и перестановку находим

Графическое решение данной системы уравнений показано на фиг. 3. На графике четко выделяются три зоны: зона закрепления (удержания) частиц за счет центробежных сил, зона свободного падения, где центробежные силы недостаточны для удержания частиц, и зона скатывания, т.е. зона неустойчивого равновесия, при котором частицы сползают вниз по наклонной поверхности.The equilibrium of a particle on a rotating plane will be observed provided:

Having expressed all the forces with their projections on the axes OX and OY, we pass to the scalar shape and compose the equilibrium equations:
mω $\genfrac{}{}{0ex}{}{\text{2}}{\text{1}}$ Rcosα = mgsinα (9)

Producing the contraction m and the permutation, we find

A graphical solution to this system of equations is shown in FIG. 3. Three zones are clearly distinguished on the graph: the zone of fastening (retention) of particles due to centrifugal forces, the zone of free fall, where centrifugal forces are insufficient to hold the particles, and the rolling zone, that is an unstable equilibrium zone in which particles slide down an inclined surface.

 On the graph, this region lies at angles less than 45 degrees, and the rolling speed depends on the angular velocity of rotation of the additional working body.

The multiplicity of impact on the source material and its sequential buildup is illustrated in Fig 4. The source material through the loading hole evenly enters the accelerating plane 4 of the main working body 1, made in the form of a concave recess, divided into sectors by radial ribs 3, where it acquires the necessary linear speed and fan is scattered on the inner surface of the additional working body 2, rotating opposite to the main one. Particles flying from the edge of the surface of the booster stage experience normal shocks with reflective surface 5 and are destroyed. Subsequently, the crushed material is divided into two streams: A is the material that is held on the working surface of the additional working body and gradually slides along the guide of the inclined surface to the next step, and B, consisting of particles thrown back along the path B ₁ onto the accelerating surface steps, and part along the path B ₂ falls to the next step and in the future, the crushing process is repeated. The number of steps is selected depending on the strength of the crushed material. The energy level communicated to the material depends on the linear velocity, i.e. from the peripheral speed of rotation of the working bodies ω and ω _in . The degree of increase in impact energy from one stage to another is determined by the ratio of the sums of linear velocities of particles in the last and first stages.

где V_b(Rn) - окружная скорость рабочей поверхности n ступени дополнительного (верхнего) рабочего органа;
V_{(r n)} - окружная скорость кромки и ступени рабочей поверхности (нижнего) рабочего органа;
V_b(R1) - окружная скорость рабочей поверхности 1 ступени дополнительного (верхнего) рабочего органа;
V_(r1) - окружная скорость кромки 1 ступени рабочей поверхности (нижнего) рабочего органа.

where V _{b (Rn)} is the peripheral speed of the working surface n of the step of the additional (upper) working body;
V _{(r n)} is the peripheral speed of the edge and step of the working surface (lower) of the working body;
V _{b (R1)} is the peripheral speed of the working surface of the 1st stage of the additional (upper) working body;
V _(r1) is the peripheral speed of the edge of the 1st stage of the working surface (lower) of the working body.

 Thus, the destruction process occurs stepwise, with an increase in the impact energy during the transition of the material to another stage; in each stage, multiple collisions of the material with each other and with the working surface of the working bodies occur, which significantly increases the crushing efficiency.

List of references
1. Handbook of ore dressing. / Preparatory processes. Ed. O.S. Bogdanova. M .: Nedra, 1972. - S.119 /
2. Barmac-Rubdbrecher. Aufbereifings-Techic-1987. TVN 11-S. 41-47.

Claims (1)

 The crushing method, including dividing the source material into two streams and destroying the material with a shock pulse by communicating to the pieces of one stream of kinetic energy of a rotating working body and impact collision with particles of another stream according to the principle "piece by piece" when crossing their trajectories, characterized in that the division the source material into two streams is produced by holding a portion of the material to be destroyed on the surface of the oppositely rotating additional working body by centrifugal force, and The impact load is achieved by increasing the relative peripheral speed of rotation of the working bodies during the transition of the material to another level and ensuring counter straight lines along the normal to the impacts, while the working planes of the reflecting surfaces of the additional working body are oriented normal to the tangent to the circumference of the working body, and the movement of the surface layer material down in the rolling mode occurs due to the resulting gravity and centrifugal forces along an adjacent guide plane with an angle of inclination and to the vertical less than 45 degrees.

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