FIELD OF THE INVENTION
This invention relates to a process for producing iron ore sinter with low
reduction degradation index (RDI).
BACKGROUND OF INVENTION
Iron ore sinter is the agglomerate produced from ore fines, fluxes, coke fines
and other in -process solid wastes generated in an integrated steel plant. In
recent years, sinter has earned the status of most preferred charge material
for blast furnaces. Indian blast furnaces use 50-70% sinter in burden due to
high RDI.
The reduction degradation index (RDI) is an important property of sinter,
which is a measure of its amount of degradation under a reducing
atmosphere at 600-800°C as exist in the upper stack region of a blast
furnace, Thus , blast furnace sinter burden cannot be increased unless
impro vem ent of RDI is m ade.
Control of RDI is one of the most challenging tasks before a sinter maker,
because of its interdependence on chemical as well as micro structural

properties of sinter. Under Indian conditions the task becomes doubly
difficult due to high Al2O3 content, led by an unfavourable Al2O3/SiO2 ratio
in most Indian ores. Moreover, the existing blast furnaces do not allow high
driving rate. Thus residual time of sinter in upper stack region is longer,
putting more emphasis to have low RDI in sinter.
OBJECT OF THE INVENTION
One object of the present invention is to propose a process control of
important parameter/s in a sinter plant to control RDI of agglomerate
produced from ore fines, fluxes , coke fines and other in-process solid
wastes generated in an integrated steel plant.
Another object of this invention is to propose a process to produce sinter of
improved RDI using Indian iron ore fines and thereby maximizing the
productivity of Indian blast furnaces.

One more object of this invention is to propose a process to produce sinter
with lower standard deviation of RDI value the production plant, so that the
operation at blast furnace can be improved further.
Further object and advantages of this invention will be more apparent from
ensuing description.
At the outset of the description it is to be understood that the ensuing
description is only illustrative of a particular form of the process of the
invention.
However, such a particular form is only an exemplary embodiment and
without intending to imply any limitation on the scope of this invention.
Accordingly, the description is to be understood as an exemplary
embodiment and reading of this invention is not intended to be taken
restrictively.

DESCRIPTION OF THE INVENTION
According to the present invention there is provided a process for producing if
iron ore sinter with low reduction degradation index (RDI). The sinter
agglomerate is produced from ore fines, fluxes, coke fines and other in-
process solid wastes generated in an integrated steel plant.
The reduction degradation index (RDI) of the sinter is controlled by
controlling wind box temperature below the sinter strand such that the
following criterion is fulfilled.
To maintain Maximum Wind Box Temperature (also called the burn through
temperature) above 3Q0°C to achieve RDI value below 28 under steady state
of plant operation. Here steady state means the plant should run without
interruption for at least 4 hours, during which 3 increments of sinter sample is
collected,

Trial at sinter plant Tata Steel during a period of 54 days has resulted in
sinter with RDI less than 28 by maintaining windbox temperature of 300-
3200C.
A drop in average RDI by both magnitude and standard deviation has been
observed during this trial run of the plant. The result has been illustrated in
the table given below to substantiate the claim made by the inventors.

1. A process for producing iron ere sinter with low reduction degradation
(RDI) by controlling the wind box temperature below the sinter stand
through changing in trimming Coke breeze \n continuous mode so that
the maximum wind box temperature is attainable in the range of 300-
320°C.
2. The process as claimed in claim 1 wherein a maximum wind box
temperature is attainable in the range of 300-320°C, the RDI value
achieved in range of 27-28.
3. The process as claimed in claim 1 and 2 wherein with a maximum wind
box temperature in the range of 300-320°C, a tower standard
deviation of RDI value 0.5-1.0 is achieved.

The present invention provides a process for producing iron ore sinter
from ore fines, fluxes, coke fines other in-process solid wastes generated
in an integrated steel plant, with low reduction degradation index (RDI)
by controlling the wind box temperature below the sinter strand, so that
the maximum wind box temperature is equal to or greater than 300°C so
that an RDI value of less than 28 can be achieved.