FIELD OF THE INVENTION
The present invention relates to a methodology to describe the shape of the burden
material heap in a bell less top blast furnace. This invention is based on extensive
experimentation and theoretical analysis. This invention is a tool to control the blast
furnace burden distribution leading to improved blast furnace performance.
BACKGROUND OF THE INVENTION
The term Burden Distribution is used to denote radial ore/coke distribution, shape of
profile formed and particle size distribution in upper part of blast furnace. On the stock
level, coke, sinter and iron ore lumps are not dumped as a mixture - alternative layers
of coke and metallics (mixture of sinter and iron ore lumps) are formed. The shape and
thickness of these layered material dictates the permeability distribution within the
furnace, which in turn influence the ascending gas distribution. In order to maximize
utilization of the chemical potential and thermal potential of the ascending gas,
permeability of the material bed should be optimum in order to maximize the solid-gas
interaction. Desired permeability can be achieved by designing burden distribution.
Therefore, it becomes necessary to predict the burden distribution for given operating
parameters. Experiments in commercial furnaces are done followed by model formation
to predict the shape of the layers of the materials for different charging sequence.
The Japanese Patent JP2009097048, from KOBE STEEL LTD., discloses a method for
estimating the distribution of a layer thickness of charged materials in a blast furnace
and an instrument use for this method. An estimation line of "n" slots is derived by
computing coefficient of continuous function where V is natural number. An
estimation profile is calculated, when volume of space introduced into estimation
profiles is equal to volume of nth time slot. The estimation line of second time slot is
corrected so that the line of wn" slots is located in downward direction of estimation line
of "n*" time slot. The thickness distribution of charging material of "n*" time slot from
furnace centre to side wall is estimated along radial direction.
The Japanese Patent JP2009242906 from KOBE STEEL LTD. discloses a method for
operating blast furnace. The method involves estimation of a coke layer and an ore
layer on the surface of a layer in a blast furnace. The ratio between ore layer thickness
and coke layer thickness is measured using a predetermined sounding mechanism. The
ratio of mass of ore with respect to the mass of the coke in the furnace is determined
at predetermined time. The ratio between thickness ratio of ore layer and coke layer
with respect to mass ratio of ore and coke is set to predetermined value.
The Japanese Patent JP59157207, from NIPPON STEEL CORP., discloses a method for
measuring burden in blast furnace. The method involves measuring the kind and the
thickness of the material layer in the blast furnace using a magnetising type
magnetism sensor. The height difference and the time difference between two peaks
which appears in the detection waves of the material changing part are detected by
the magnetism sensor. From the differences, the mixing ratio and the layer thickness
of the material changing part are found.
The prior art methods to define the heap shape in the blast furnace burden distribution,
in contrast, acquire the input from a measurement probe inserted into the furnace or
have too many tuning parameters and hence valid for a specific furnace.
OBJECT OF THE INVENTION
It is therefore the object of the invention to propose a methodology to determine the
configuration of a heap in blast furnace burden distribution formed because of charging
from a bell-less charging system.
This invention proposes a process to control the blast furnace burden distribution
leading to improved furnace performance.
SUMMARY OF THE INVENTION
Accordingly, there is provided a process to control the blast furnace burden distribution
in order to improve furnace performance.
The invention in a first aspect proposes a methodology to determine the configuration
of a material heap for blast furnace burden distribution. The invention shows that there
is existence of relationship between different parameters of concerned mathematical
expression, which is required to define the configuration of the heap. The invention
establishes that the shape of a heap is independent of the geometry of the furnace but
can be influenced only by material property.
The current invention proposes method that eliminates the use of specific instruments,
which measure profile at the stocklevel. Further, it is established through large number
of experiments that the heap configuration is only function of material properties,
therefore if the material is know very few tuning parameters are sufficient to predict the
heap configuration.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention can now be described in detail with the help of the figure of the
accompanying drawing in which:
Figure 1 - shows a schematic of the blast furnace burden distribution system
Figure 2- shows the definition of height of the heap (A) formed by the new burden
material
DETAILED DESCRIPTION OF THE INVENTION
As shown in figure 1, a blast furnace equipped with bell-less charging system having
distributing chute rotating about the centre of the furnace and distributes the material
along the circumferential direction on the stock level of the furnace (figure 1). The
inclination angle (angle between the chute and vertical) of the chute can be changed to
shift the impact point of the material in radial direction on the stock level. In a typical
charging, when one hopper of material is dumped, the chute rotates about the centre
of the furnace as well as changes the inclination angles to distribute the material on the
stock level of the furnace. The shape of the layer formed is dependent of the material
landing position on the stock level, amount and type of material and shape of the initial
surface on which the material is poured.
The landing position of the material on the stock level can be estimated from various
known models.
Experiments at different scales and at different models show that the shape of a heap
can be defined by a normal distribution curve-

Where, y is the height of the heap at r radial location. B is the location of the peak. In
this equation 3 unknowns A, B and C are there. These unknowns are evaluated to
define the heap shape. B is always at the outer stream of the trajectory. So from the
trajectory information B can be evaluated. For evaluation of A and C, two relationships
are required. Experiments at different scales and different furnaces show that A and C
are related for the heaps in the blast furnace. The relationships are as follows:
For metallics (consists of sinter, iron ore and flux)
A=mC+d
where m varies from 0.85 to 1 and d varies from -10 to -50.
For coke
A=nC+e
where as range of n is from 0.95-1.05 and range of e is -5 to +5.
Other relationship required to evaluate A and C is the conservation of mass.
This relationship does not depend on the geometry of the furnace and A and C is only
function of material type.
The effect of initial surface can be taken care of by initially defining A in an estimated
location, and then. W needs to be calculated from where the new heap surface touches
the initial surface as shown in figure 2.
WE CLAIM
1. A process to control the blast furnace burden distribution to improve
performance of the furnace, characterized by comprising the step of:
- defining a shape of a heap of burden in terms of a normal distribution curve -

where, y is the height of the heap at r radial location, B is a location of the peak,
and being associated with an outer stream of the trajectory, calculated from the
trajectory information, and applying two device relationships to determine 'A',
and' C':-
for metallics (consists of sinter, iron ore and flux) :-
A=mC+d,
for coke
A=nC+e, and
for conservation of mass:-
based on decided charging sequence.
2. The process as claimed in claim 1, wherein the determination is independent of
the geometry of the furnace, and applicable to blast furnaces of different
geometry.
3. The process as claimed in claim 1, wherein for metallics (consists of sinter, iron
ore and flux), m can vary from 0.85 to 1, and d can vary from -10 to -50 and for
coke n is from 0.95-1.05 and e can vary from -5 to +5 and wherein 'A' should be
more than zero.
4. The process as claimed in claim 1, wherein the process is adaptable even where
the heap is formed by distributing the material on the existing surface inside
the furnace.
5. The method claimed in claim 1 can be used in control system of distributing
material, process control.

The present invention relates to a process to control the blast furnace burden
distribution to improve performance of the furnace, characterized by comprising the
step of defining a shape of a heap of burden in terms of a normal distribution curve -

where, y is the height of the heap at r radial location, B is a location of the peak, and
being associated with an outer stream of the trajectory, calculated from the trajectory
information, and applying two device relationships to determine 'A', and 'C':-
for metallics (consists of sinter, iron ore and flux) :-
A=mC+d,
for coke
A=nC+e, and
for conservation of mass:-
based on decided charging sequence.