Higher fluctuation in properties of limestone extracted from various deposits/benches
withsuitable mining requires proper blending of these materials to ensure quality
of cement. Stockpile homogenization systems equalize the variation of chemical
and physical properties of the raw materials and converts low quality raw material
in to uniform mixture of required quality material to produce the high quality of cement.
Lime stone is a main ingredient for producing the Portland Cement. The limestone
of sizes 1200 to 2000mm (Depending upon the type of mining equipment) from
the mines crushed in the limestone crusher to size 50 to 70mm will be transported
to its storage facility through belt conveyors. The crushed limestone is stacked in
the stockpiles with the help of stacker. In a stockpile, limestone is stacked and sub
sequently reclaimed from storage facility. Generally, a conventional pile can per
form the following functions:
- BUFFERING / DISTRIBUTING is the function of providing sufficient reserve of
limestone to guarantee a continuous operation of the plant under all normal
circumstances. The stockpile acts as a buffer between continuous and
discontinuous operation of a mine. - COMPOSING / BLENDING is the integration of number of raw materials with
different chemical and/or physical characteristics in such proportions that
a completed pile represents the requisite composition. - HOMOGENIZING is the function of a systematic transformation of the input
flow of the pile into the output flow, so that the fluctuations of a property in
the flow are minimum. The aim in the homogenizing / blending operation is to
narrow down the standard deviationof this normal distribution.
The limestone stockpile is made by a stacker in as many thin layers of identical volume
as possible. As a result of this large number of layers, varying material properties
in superposed layers are offset by the cutting process (Chevron method) of
machines in operation. The law of continuity tells us that each cross-section of the
stockpile contains the same amount of material and this fact is the essential
prerequisite for a good homogenization effect. The number of layers are determined
by the cross section of the pile, the handling capacity and traveling speed of the
stacking machine.
3.1 Type of Stockpiles
3.1.1 Longitudinal/Linear stockpiles
In this system, the stacker with slewing or without slewing mechanism stacks
the limestone longitudinally along the stockpile. The stacker and reclaimer are moving
on different rail track at different speeds. The bridge type reclaimer consisting of
harrow mechanism is used for the better homogenization.
The plant consists of at least two stockpiles, one being stacked and other being
re claimed. On an average one stockpile is half-full and the other one half empty;