Технические науки/ 4.Транспорт
Togizbaeva B., Kenesbek A.
The Karaganda state technical university
Research of parametres of bunkers at storage of smally split up ore
One of problems at a choice of bunkers for a loose material are their rational design data and the sizes of final apertures. Obvious communication with physicomechanical properties of mountain weight and parametres of heat-sink capacity leads to necessity of research of conditions of the expiration of a loose material at an unloading on a feeder.
qualities of final apertures of bunkers are characterised by their throughput, influencing duration of unloading, size of an angle of slope of
lateral walls of the bunker, and also conformity of the sizes of heat-sink capacities to parametres of their final
By working out of bunkers following basic questions are considered:
- A choice of the form and the sizes of final apertures;
- A choice of angles of slope of walls and edges of bunkers;
- Definition of throughput of the mountain-transport equipment.
The choice of the rational sizes and the form of final apertures has the important practical value for maintenance of necessary throughput of unloading bunkers and the unloading mechanism.
In particular at the insufficient sizes of final apertures because of arch- formation mountain weight throughput of bunkers that leads to increase in duration and labour input of discharging decreases. The excessive increase in the sizes of final apertures causes increases in pressure of a loose material at tape feeders and unjustified increase in their weight and complication of a design of the mountain-transport equipment.
In turn the form of a final aperture along with a bunker design directly influences character of the expiration of mountain weight. At the expiration in movement there is "column" of a loose material in a zone of a final aperture, and on its periphery «stagnant zones» are formed so-called. The free surface of a loose material at the free expiration represents a cone along forming, which particle of mountain weight move to the central zone. The continuous expiration at which in movement there is all ore weight which is in the bunker is preferable. At the continuous expiration speed of a loose material on an exit from an aperture practically does not depend on height of "column" of ore weight in the bunker and is connected, basically with the form and the sizes of a final aperture.
Available recommendations for choice final apertures are ambiguous, however operating experience of the mountain-transport equipment testifies to efficiency of slot-hole apertures.
Loadings from the accumulated mountain weight are considered in settlement schemes by means of two components, namely horizontal pressure put on vertical and inclined walls of the bunker and the distributed vertical loading from weight of the loose material, put on a bottom and inclined walls of bunkers.
The greatest pressure upon walls of bunkers is rendered by the bulk cargoes close on properties to a liquid: for example, strongly aerated bulk cargoes, the loose material containing a considerable quantity of a moisture, and also the ore weight which is in a condition of such intensive vibrations that the constancy of pressure upon walls is broken.
Pressure from loose bodies on vertical and inclined planes according to formulas of building mechanics differs from hydrostatic pressure as in loose bodies there is the factor of an internal friction different from an internal friction in liquids and gases, besides there is a friction between a wall and cargo and discontinuity of the appendix of loading - of emptiness between elements of cargo and other factors. Pressure upon walls and a bottom of bunkers that more than is less internally a friction of a loose body. The factor of an internal friction considerably fluctuates for the same material and its size strongly depends on porosity of a loose material, humidity, granuly structure and many other factors. From the form of the expiration of mountain weight and from sequence of its filling and an unloading pressure upon walls and a bunker bottom considerably changes.
It is established that pressure upon bunker walls on perimetre at one level in the course of loading and unloading non-uniformly: pressure is maximum in the final period of loading and in an initial stage of unloading of the bunker and exceeds on (40-100) % average size of pressure at a condition of rest of mountain weight.
Excess of settlement pressure at loading of mountain weight is connected with presence of additional pressure of air compressed between particles of a loose material. During endurance the compressed air leaves a material and its pressure reduces to zero. During the initial moment of unloading non-uniform movement of mountain weight in the bunker, sharp movement of all column of a loose material is observed, pressure upon walls fluctuates in considerable limits. After formation of a column and the channel of the expiration of a loose material from the bunker unloading process is stabilised, and pressure upon walls becomes more uniform.
As the basic criteria of quality by optimisation new iron bunker system the weight and adaptability to manufacture of a design have been chosen. For restrictions the bunker geometry, parametres of durability of system are taken.
Bunkers, hydraulic radiuses of final apertures at which more than radius arch –formation apertures, should provide the steady expiration of mountain weight. For the continuous and uniform expiration of mountain weight, except the sizes, it is necessary to choose also rational angles of slope of walls and edges of bunkers to horizon .
The basic condition of normal unloading is excess of angles of slope of walls of the bunker over a corner of a natural slope of a loose material.
It is necessary to notice that effective the form of a surface of walls of bunkers is not the plane, and the surface bent on a hyperbolic curve. We will consider the bunkers which walls are established under a constant angle of slope to horizon.
Usually at designing of bunkers the angle of slope of walls is accepted slightly more than settlement size since it is necessary to consider increase in factor of a friction as a result of corrosion of walls of bunkers and sticking to them of the rests of a loose material .
For the purpose of improvement of the expiration of mountain weight it is necessary, that angles of slope of edges of the bunkers formed by adjacent walls, also exceeded a corner of a friction of a material about walls.
1.Анистратов Ю.И., Жабин Н.И., Мисник Ю.М. Теория и практика бункеризации склонной к слеживанию горной массы.- М.: Наука, 1999 г.