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.
Generally unloading
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
apertures.
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 [1].
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 [1].
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.
Literature:
1.Анистратов Ю.И., Жабин Н.И.,
Мисник Ю.М. Теория и практика бункеризации склонной к слеживанию горной массы.-
М.: Наука, 1999 г.