FIELD OF APPLICATION
The present invention relates to a process for producing high strength briquettes
from high grade chromite concentrates and fines.
BACKGROUND OF THE INVENTION
The chromite ore is an indispensable raw material for iron-chromium alloy
making. This in turn is used for producing alloy steels. Naturally occurring Indian
chromite ores are mostly powdery in nature. On beneficiation of available low
grade ores also results finer size 9-1 mm concentrates. As such these fines
cannot be used in conventional AC furnaces.
A need therefore existed for agglomeration of these fines for use In iron-
chromium alloy making in a conventional submerged electric arc furnace (SAF).
SUMMARY OF THE INVENTION:
The main object of the present Invention therefore is to provide a
process of agglomeration (briqueting, pelletlzatlon and sintering) of
high grade chromlte concentrates and fines for use in submerged arc
furnaces for production of Iron-chromium alloy.
On technical and economic considerations, brlquettlng method is
more promising form of agglomerate if strength is ensured.
Another object of the present Invention Is to produce high strength
(greater than 50 Kg/cm2) water resistant and thermally stable
briquettes for use In submerged electric arc furnace conditions.
The present Invention thus provides a process for producing high
strength briquettes from high grade chromlte concentrates and fines
comprising the steps of taking a known quantity and quality of high grade
chromite fines; mixing said chromite fines with an optimized quantity of binder to
provide a compression strength; compressing the mixture into a desired shape;
curing the briquettes naturally for about 24 hours; heat -hardening the naturally
cured briquettes in a furnace to an identified temperature; and cooling the
briquettes to room temperature.
DETAILED DESCRIPTION
In the present invention for producing high strength briquettes, the materials
used are high grade chromite concentrates and fines with
Cr/Fe ratio : 2.6-3.2
Cr2O3Wt% : 46-54
Particle : Below 0.5 mm with a average particle size of 100 microns size
Moisture : 10% wt
The chromite fines are mixed with an optimized quantity of a binder which can
provide the required compression strength. The binder used in the present
invention for briquetting is inorganic plastic clay.
The mixture is then compressed into briquettes. The shape of the compressed
mixture is dependent upon the die used. Cylindrical briquettes of 2540 mm
diameter/height are produced by using universal compression testing machine.
In a pilot scale rolled briquettes is used to produce briquettes (50X30X25 mm).
These briquettes are naturally used for about 24 hours. After this, the briquettes
are heat hardened to identified temperature by introducing these naturally cures
briquettes in a furnace for an hour and the furnace cooled to room temperature.
The preferred prcx:ess conditions are as follows :
Binder quantity, % : 6-8
Green briquettes curing time, hrs : 24
Compress load, tons : 2-4
Heat hardening temperature, °C : 700-900°C
Under the above process conditions, it Is possible to produce
briquettes with high compressive strength (> 50 leg/cm2), water
resistant, and thermally stable properties. The briquettes can be
used as 100% feed in submerged arc furnace.
WE CLAIM
1. A process for producing high strength Chromite briquettes from high
grade chromite concentrates and fines comprising the steps mixing
chromite concentrates and fines containing Cr/Fe ratio -2.6 - 3.2, Cr2O3 in
weight % 46-52, particle size <0.5 mm with an average particle size of
100 microns and moisture 10% in weight with 6-8 % weight in organic
plastic clay;
- compressing the resulted mix in die of a universal compression testing
machine to produce green briquettes of predetermined diameter and
height;
- curing the green briquettes naturally for about 24 hours;
- heat hardening the cured briquettes on heating in a furnace at 700-900°C
for an hour;
- followed by cooling to room temperature.
2. The process of producing high strength chromite briquettes as claimed in
claim 1, wherein a compression load of 2 to 4 tons is used during
compression of the mixture.
3. The process of producing high strength chromite briquettes, wherein
optionally the green briquettes formed after compression is rolled to
produce pillow briquettes of size 50X30x25 mm before being heat
hardened.
4. High strength water resistant and thermally stable chromite briquettes
produced by the steps according to claim 1 with compressive strength >
50kg/cm2, which can be used as 100% feed in submerged are furnace for
producing Ferro chromium alloy.

This invention relates to a process for producing high strength Chromite
briquettes from high grade chromite concentrates and fines comprising the steps
mixing chromite concentrates and fines containing Cr/Fe ratio -2.6 - 3.2, Cr2O3 in
weight % 46-52, particle size <0.5 mm with an average particle size of 100
microns and moisture 10% in weight with 6-8 % weight in organic plastic clay;
compressing the resulted mix in die of a universal compression testing machine
to produce green briquettes of predetermined diameter and height; curing the
green briquettes naturally for about 24 hours; heat hardening the cured
briquettes on heating in a furnace at 700-900°C for an hour; followed by cooling
to room temperature.