TITLE: A process for the production of highly metalized Directly Reduced Iron (DRI)
from waste iron ore fines.
FIELD OF INVENTION:
This invention relates to a process for the production of highly metalized Directly
Reduced Iron (DRI) from waste iron ore fines.
BACKGROUND OF THE INVENTION:
In the conventional method of directly reduced iron making process, iron ore / pellets
containing iron oxide are directly reduced in the temperature ranges between 900°C to
1200°C in presence of solid or gaseous reducing agents to obtain reduced iron. In
recent years, attempts have been made to produce directly reduced iron utilizing low
grade iron ore and coal. The technologies for production of directly reduced iron is
known in a number of ways and are already in practice, in which iron ore is subjected to
reduction through application of heat using coal as a reductant.
In recent years, several efforts have been made to develop a process for production of
directly reduced iron utilizing iron ore fine and coke / coal fine. Reference may be made
to US Patent No. 3,443,931 in which pulverized iron ore and pulverized coal mixture are
agglomerated and the agglomerated mass are dried and pre-indurated in the
temperature between 872°C to 982°C. The pellets are then subjected to reduction
through the application of radiant heat source at 1260°C to 1425°C yielding reduced
iron.
The reduced iron obtained using the above mentioned process is charged into the
electric arc furnace as a source of metallic iron. This method, however does not involve
the low grade / lean iron ore fines and coal fine which narrows the choice of source of
raw material for making iron. Moreover, pre-induration of the agglomerates to get
optimum dry strength for handing and processing and further reduction at higher
temperature in not techno-economic feasible process.

To overcome the problem of pre-induration at higher temperature a process for
production of metalized briquette is found in US Patent No. 4, 701,214 which describe a
method of mixing iron oxide fines and coal fine with a binder to form a mixture and
agglomerating the mixture by pelletizing to form pellets. These pellets were charged in
the rotary hearth furnace to get the pre-reduced pellets and finally melted in the
smelting furnace in presence of carbon to get the metalized briquette. The smelting
reduction of these pre-reduced pellets require addition carbon and energy for further
reduction and smelting leading to high coke/coal and energy consumption .
Another process is disclosed in US Patent No. 6, 036,744 to produce metallic iron. In
this process iron oxide is compacted with the carbonaceous reductant and subjected to
reduction through the application of heat to yield metallic iron. The metallic iron shell is
generated and grown via reduction through the application of heat to a temperature of
1450°C to 1500°C. This method must have to generate sufficient amount of heat to
separate the metallic iron from the slag leading to fusion of the complete agglomerates.
The advance method of utilizing iron agglomerates of iron oxide with coke to produce
reduced iron is disclosed in US Patent No. 6,602,320 B2 which describes
agglomeration of the raw material, having particle size less than 6 mm or particle size of
3 mm or more and less than 6 mm to grains pellets, thereafter drying and heat
reduction of pellets at 1200°C. Similar kind of work has been carried by M. KUMAR
et.al (M. Kumar, P. Mohapatra & S. K. Patel (2009): Studies on the reduction kinetics of
hematite iron ore pellets with non coking coals for sponge iron plants, Mineral
Processing and Extractive Metallurgy Review: An International Journal, 30:4, and 372-
392) in which hematite iron ore fines of -100, -16 +18, and -8 +10 mesh size were
mixed in different ratio and fired pellets were made and thereafter reduced between
850°C-1000°C temperatures range in the bed of coal. However in the above process
lean coals were used as a reducing agent but suffers from the requirement of rich iron
ore containing more than 64% Fe.
Further study on the direct reduction behaviors of iron ore pellets were carried out by
Deqing ZHU et al (Direct Reduction Behaviors of Composite Binder Magnetite Pellets in
Coal-based Grate-rotary Kiln Process Deqing ZHU, Vinicius MENDES, Tiejun CHUN,

Jian PAN, Qihou LI, Jian LI and Guanzhou QIU ISIJ International, Vol. 51 (2011), No. 2,
pp. 214-219) in which preheated pellets made of magnetite concentrate and composite
binder were directly reduced using non-coking coal as reductant in a tube furnace. The
reducibility of these pellets were observed to be good but again this process is suitable
for only high grade of iron ore containing more than 65% Fe.
The conventional processes so far developed as described above have several draw
backs such as:
(1) In all the processes high purity iron ore such as lump iron ore / iron ore
fines with less gangue content is used for the preparation of directly
reduced iron.
(2) The reducing agent so far used for the production of directly reduced is
containing high fixed carbon with low ash content.
(3) Almost in all process the reducing agents are agglomerated with the iron
ore leading to the increased gangue content in the reduced iron yielding
lower metallic yield.
(4) Increased gangue content in the directly reduced iron required more
fluxing agent during melting.
(5) All above processes does not involve the low grade / lean iron ore or iron
ore fines and less reactive coke / coal fine which narrow down the choice
of source of raw material for making iron.
OBJECTS OF THE INVENTION:
An object of the present invention is to propose a process for the production of directly
reduce iron from lean or waste iron ore fines and lean or waste coke or less reactive
coal.

Another object of the present invention is to provide optimum waste carbonaceous
material such as Jhama Coal for complete reduction of waste iron ore pellets such as
iron ore slime pellets to produce highly metalized reduced iron suitable for steel making.
Further object of the present invention is to provide optimum reduction temperature and
time to get highly metalized reduced iron with high cold crushing strength suitable for
blast furnace and electric steel making processes.
BRIEF DESCRIPTION OF THE INVENTION:
According to this invention there is provided a process for the production of highly
metallized Directly Reduced Iron (DRI) comprising:
subjecting the waste iron ore to the step of grinding;
pelletizing the grinded ore to form pellets;
removing the moisture content from the pellets to give strength to the pellets ranging
between 8 to 15 N;
grinding the waste carbonaceous materials to be used as a reducing agent;
mixing the pellets and grinded waste carbonaceous materials in a ratio ranging
between 2:1 to 10:7;
subjecting the pellets to the step of reduction, heating;
cooling the pellets in reducing atmosphere to avoid the reoxidation.
DETAILED DESCRIPTION OF THE INVENTION:
The present invention provides a process for the production of directly reduce iron from
lean or waste iron ore fines and lean or waste coke or less reactive coal which
comprises:
i) grinding the waste iron ore to an optimum size range between -70 to -200 mesh
and thereafter pelletizing to get pellets of diameter ranging between 12 to 16
mm,

ii) optimizing the moisture content in the pellets by known method to get the green
strength of the pellets ranging between 8 to 15N per pellet for safe handling and
further processing without binder,
iii) grinding of waste carbonaceous materials to particle size ranging between -70 to
-200 mesh to use as a reducing agent,
iv) taking pellets and grinded waste carbonaceous materials in the weight ratio
ranging between 2:1 to 10:7 and reducing the pellets in the bed of grinded waste
carbonaceous material in temperature range between 900°C to 1100°C for a
period of 2 to 8 hours,
v) cooling the pellets to temperature ranging between 500 to 600°C in reducing
atmosphere to avoid the reoxidation of the reduced pellets and cooling thereafter
to room temperature.
In an embodiment of the present invention the waste iron ore fines used may be
selected from steel plant waste or from iron ore mines and may have composition in
range of:
Fe :40 - 55 %
LOI : 4 - 11 %
Si02 :8-15%
Al2O3 :4-8%
P : 0.12-0.18%
S : 0.006-0.01%
In another embodiment of the present invention the waste carbonaceous materials may
be selected from steel plant waste or mining waste such as low reactive coals
/unutilized coal obtained from coal mines and may have composition in range of
Fixed carbon : 48 - 72% Volatile Matter: 8 - 15 %
Moisture : 0.5 - 2% Ash : 15 - 25%

Detailed reduction mechanism taking place during reduction of the present invention
are given below:

After reduction, the pellets were removed from the furnace and allowed to cool from
reduction temperature to 500 - 600°C in reducing atmosphere and thereafter allowed to
cool in normal atmosphere. The samples were collected from different reduction
temperature and sintering time was characterized for their properties.
The present invention resides in the reduction of waste iron ore fines in bed of waste
carbonaceous materials to produce highly metalized reduced iron suitable for blast
furnace and steel making. The following examples are given by way of illustration and
should not be construed to limit the scope of invention.
EXAMPLES:
EXAMPLE-1
70.19 grams iron ore pellets of composition: Fe: 40 %, LOI: 9%, SiO2: 13%, Al2O3: 7%,
P: 0.18%, S: 0.01% is kept in the bed of waste carbonaceous material and reduced at
900°C for 2 - 8 hrs. After reduction, the pellets were removed from the furnace and
allowed to cool from reduction temperature to 500°C in reducing atmosphere and

thereafter cooled in normal atmosphere. The samples collected from different reduction
temperature and sintering time were analysed for their percentage reduction and found
that up to 85% reduction were achieved at 900°C. The percentage reduction at 900°C
for different reduction temperature and time is given in the table 1.
Table: 1. Percentage reduction of pellets at 900°C for different reduction time.

EXAMPLE - 2
Three sets of 1.5 kg iron ore pellets of composition: Fe: 55 %, LOI: 11%, SiO2: 15%,
AI2O3: 8 %, P: 0.18%, S: 0.01% is kept in the bed of waste carbonaceous material and
each set of iron ore pellet were reduced at 900°C, 1000°C and 1100°C for 2 - 8 hrs. The
reduction temperature of the pellets were optimized and found that 1000°C temperature
is optimum reduction temperature for the pellets to get more than 99% reduction.
EXAMPLE - 3
100 grams dried pellets are kept in the bed of carbonaceous material such as Jhama
coal with 20, 30 and 40% excess carbonaceous material than the stiochiometrically
required for the reduction of the pellets according to the reaction (1) to investigate the
optimum carbonaceous material required for reduction.
Fe2O3+3C→2Fe + 3CO (1)
It is observed that the 45 grams carbonaceous material is optimum for complete
reduction of 100 grams iron ore pellets. Therefore it is investigated that 450 kg
carbonaceous material is optimum for reduction of one tone of iron ore pellets.

WE CLAIM:
1. A process for the production of highly metallized Directly Reduced Iron (DRI)
comprising:
subjecting the waste iron ore to the step of grinding;
pelletizing the grinded ore to form pellets;
removing the moisture content from the pellets to give strength to the pellets ranging
between 8 to 15 N;
grinding the waste carbonaceous materials to be used as a reducing agent;
mixing the pellets and grinded waste carbonaceous materials in a ratio ranging
between 2:1 to 10:7;
subjecting the pellets to the step of reduction, heating;
cooling the pellets in reducing atmosphere to avoid the reoxidation.
2. The process as claimed in claim 1 wherein the size of the grinded ore is in a range
between -70 to -200 mesh.
3. The process as claimed in claim 1, wherein the particle size of the reducing agent is -
70 to -200 mesh.

4. The process as claimed in claim 1, wherein the said pellets and the carbonaceous
material is heated at a temperature range between 900°C to 1100°C for a period of 2
to 8 hrs.
5. The process as claimed in claim 1, wherein the said pellets is cooled to a
temperature range between 500 to 600°C.