FIELD OF THE INVENTION
The present invention generally relates to a process for production of highly
metallized directly reduced-iron (DRI) with low sulphur contents. More
particularly, the present invention relates to a process for production of highly
metallized direct reduced iron pellets from waste iron or slime and rejected coal
containing more than 50% ash.
BACKGROUND OF THE INVENTION
A number of gas and solid based processes for production of directly reduced
iron (DRI) are known in the art. All these gas based and solid based processes of
making DRI mostly requires iron oxide in the form of lump, fines, pellets or
composite pellets and reducing agents in the form of gas or solid to convert
these iron oxide into a metallic iron. It is interesting to note that, all the solid
based DRI processes require coking or non coking coal having less than 20% ash
as the reducing agent to convert iron oxide into a metallic iron. In contrast to the
requirement, the worldwide shortage of coking coal in particular a limited
reserves of coking coal with low ash contents especially, in India, forced the iron
and steel makers to find a way to use coking or non coking coal having high ash

content for iron and steel making. In addition to the limited reserve of coking
coal with low ash content, a huge quantity of coal gets rejected during
beneficiation and washing which interalia remains unutilized due to low carbon
and high ash content. Similarly, during beneficiation and washing of iron ore,
more than 30% slime is generated which remains unutilized. These iron ore
slimes and rejected coals are although stored in massive water ponds, however
they possess enormous problem for disposal and causes environmental hazards.
The beneficiation/safe disposal of iron ore slime and rejected coal or converting
the slime into a value added produce thus remains a challenging task for iron
and steel industry. It may be noted that none of the prior art processes is
capable to convert these waste iron ore slime and rejected coal containing more
than 50% ash in a value added product.
The non-patent literatures by J. Feinman et al (Direct Reduction and Smelting
Processes, Iron Making Volume, Chapter - 11, pp 741-780. The SISE Steel
Foundation 1999) and by All hasanbeigi et al (Ernest Orlando Lawrence Berklye
national Laboratory Report on "Emerging Energy - Efficiency and Carbon Dioxide
Emissions - Reduction Technologies for the Iron and Steel Industries:

January, 2013, p.26 - 44), discussed about the historical development of directly
reduced iron (DRI) making processes as well as emerging highly energy efficient
iron making technology respectively, such as Midrex, HYL, Purofer, Finmet,
Circored, Krupp-CODIR, SL/RN, DRC, OSIL, Fastmet, Technored, ITmk3, Coal
based HYL process, Coal based MIDREX etc.
US Patent No. 6,284,017 Bl discloses a production process of DRI using iron
oxide and solid reductant. In this prior-published invention, fine iron oxide and
powdered solid reductant is mixed and compacted into a sheet form using
rollers. These compacted sheets are charged in a reduction furnace at a
temperature of more than 1100°C for reduction. The directly reduced iron (DRI)
thus produced is further charged into a shaft furnace or in a bath smelting
furnace for melting at high thermal efficiency. However, the DRI produced by
this process, requires more reductant and suffers from the quality requirement
for steel which does not allow an economic use this DRI for steel making.
US Patent No. 6,036,744 teaches method and apparatus for production of DRI
using iron oxide and carbonaceous material. The iron oxide and a carbonaceous
reductant are compacted together and exposed to heat for reduction to obtain a

metallic iron. During the reduction, a shell composed of the metallic iron is
generated and grown on the surface of the surface of the compact including the
slag aggregates inside the shell. Further, heating is performed to melt the
reduced compact and subsequently, metallic iron is separated from the slag to
get a highly metallized iron. Although the metallic iron thus produced has high
metallization. However, this metallized iron finds very limited use for steel
making due to high process cost and lack of quality requirements of steel.
US Patent No. 5,849,063 discusses a process for production of DRI or pig iron
from industrial waste streams. The DRI or pig iron is produced from the electric
arc furnace (EAF) and blast furnace dust stream, involves magnetic separation or
floatation of iron containing material followed by briquetting and reduction in a
suitable furnace. The reduced iron obtained from the above process however
contains several other elements which do not allow economical use of produced
DRI in the steel making process.
US Patent No.8182575 B2 teaches utilization of iron ore dust generated in the
iron making process. The iron bearing materials are separated from the group of
raw material and dried . These iron bearing materials are mixed with known
reducing agents to get a mixture which is subjected to drying. Pulverizing of the

mixture is carried out to obtain 80% minus sieve to have a particle diameter of
70 µm to 500 µm; the mixture is kneaded after the moisture content of the
mixture is subjected to the kneading step to be agglomerated, and reducing the
agglomerates in a rotary hearth furnace to produce direct reduced iron (DRI).
The DRI thus produced contains very high gangue minerals due to mixing of
reducing agents with the iron bearing materials. Hence, this prior art
process/product did not find the market for production of iron and steel.
US Patent No. 3,443,931 teaches agglomeration of pulverized iron ore and
pulverized coal mixture, drying of the agglomerated mass, and pre-induration
between 872°C - 982°C temperature. The pellets are then subjected to reduction
through application of a radiant heat source between 1260°C to 1425°C yielding
reduced iron. The reduced iron obtained using the above mentioned process is
charged into an electric arc furnace as a source of metallic iron. This method,
however does not involve any low grade / lean iron ore fines and coal fine which
narrows the selection of source of raw material for making the iron. Moreover,
the pre-induration of agglomerates was carried to get optimum dry strength for
handling and processing including reduction at high temperature to get a DRI.
Thus, the process is a techno-economical process.

To overcome the problem of pre-induration at higher temperature a process for
production of metallized briquette is disclosed in US Patent No. 4,701,214, which
describes a method mixing iron oxide fines and coal fines with a known binder to
form a mixture which is agglomerated by palletizing to form pellets. These pellets
were charged into a rotary hearth furnace to get pre-reduced pellets and finally
melted in a smelting reduction furnace in presence of carbon to get a metallized
briquette. The smelting reduction of these pre-reduced pellets requires an
additional carbon and extra energy for reducing and smelting, making the
process a high energy consumption process.
US Patent No. 5, 637,133 discloses a process for manufacturing of sponge iron
with low sulphur content. In the particular process, a superposed layer of finely
divided iron oxide is deposited on a moving hearth and another layer made up of
a mixture of solid reducing agent and a desulphurizing agent. These charge mix
is heated externally above 900°C by using a burner, where the iron oxide is
reduced by carbon monoxide (CO) and the gaseous compound of sulphur is fixed
by desulphurizing agents yielding a solid cake of the sponge iron which is
separated from the residue of the reducing materials containing sulphuring
agent. The reduced solid cake contains huge quantity of impurities which
restricts the use of this sponge iron in an electric steel making.

Thus, the known process as discussed hereinabove, have several drawbacks
which can be summarized as under:-
(1) In all the above processes, high grade iron ore in form of fines, lumps and
agglomerates of iron ore and coal fines are used.
(2) The carbonaceous material used in prior art as a reducing agent for
production of directly reduced iron (DRI) contains high fixed carbon
(> 65%) and low ash (<20%).
(3) In all the processes, iron ore fines are agglomerated with carbonaceous
material leading to increased gangue content in the reduced iron yielding
poor metallization with high level of impurity.
(4) Increased gangue content in the directly iron (DRI) requires more fluxes
during melting, resulting in decrease in the rate of production.
(5) The DRI produced from the conventional routes pickup more sulphur and
other elements from the coal during reduction which disallows economical
use of the produced DRI for iron and steel making.

(6) All the known DRI processes require pre-indurated pellets (indurated at
1250 to 1350°C) for reduction which interalia require additional energy
and increases the process steps for production of the DRI.
(7) No process has been developed till date to utilize the waste iron ore slime
and rejected coal containing more than 50 % ash for production of the
DRI.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a process for
production of low sulphur directly reduced iron from waste iron ore and includes
rejected coal containing more than 50% ash which eliminates the drawbacks of
the prior art.
Another object of the present invention is to propose a process for production of
low sulphur directly reduced iron from waste iron ore and includes rejected coal
containing more than 50% ash which ensures use of the rejected coal for
complete reduction of the waste iron ore slime pellets to produce highly
metallized low sulphur reduced iron suitable for iron and steel making.

A still another object of the present invention is to propose a process for
production of low sulphur directly reduced iron from waste iron ore and includes
rejected coal containing more than 50% ash which avoids the sulphur pickup in
the produced DRI during reduction.
Yet another object of the present invention is to propose a process for
production of low sulphur directly reduced iron from waste iron ore and includes
rejected coal containing more than 50% ash which provides optimum size of the
iron ore slime pellets, for complete reduction of iron ore slime pellets.
Another object of the present invention is to propose a process for production of
low sulphur directly reduced iron from waste iron ore and includes rejected coal
containing more than 50% ash which reduces the pellets by utilizing only
optimum amount of rejected coal.
A further object of the present invention is to propose a process for production
of low sulphur directly reduced iron from waste iron ore and includes rejected
coal containing more than 50% ash in which an optimum reduction temperature
and reduction time is used to get highly metallized low sulphur reduced iron with
high cold crushing strength applicable for blast furnace and electric steel making
processes.

SUMMARY OF THE INVENTION
Accordingly, the present invention provides a process for the production of highly
metallized low sulphur directly reduce iron from waste iron ore slime and
rejected coal which comprises :
(i) Grinding and screening of waste iron ore slime to an optimum size
range between - 70 to - 200 mesh and palletizing to get pellets of
diameter ranging between 12 to 20 mm.
(ii) Optimizing the moisture content in the iron ore slime pellets (12 - 20)
mm size) by known method to get the green strength of the pellets
ranging between 8 to 15 N pellet without binder for safe handling and
further processing.
(iii) Grinding and screening of waste rejected coal in the size range
between - 70 to -200 mesh to be used as a reducing agent during
reduction.

(iv) Grinding and screening of the desulphurizing agent (dolomiter) in the
size ranges of - 70 - -200 mesh to be used as a desulphurizing agent
during reduction.
(v) Mixing of rejected coal and desulphurizing agent (dolomite) in the
weight ratio of 1:0.05 to 1:0 0.15.
(vi) Technique for arrangement of iron ore slime pellets in the static bed of
mixture of rejected coal and desulphurizing agents for reduction in the
weight ratio of 1:0.3 to 1:0.6.
(vii) Arrangements of crucible containing iron ore slime pellets in bed of
mixture of rejected coal and a desulphurizing agent for reduction in
the temperature range of 900°C to 1200°C for 1 to 6 hours reduction
time.
(viii) Removal and cooling of crucible containing reduced iron ore slime
pellets from reduction temperature to a temperature range of 600 to
500°C in the normal atmosphere (reducing atmospheres inside the
crucible) to avoid the re-oxidation of reduced iron ore slime pellets and
thereafter cooling to room temperature.

(ix) Separation of reduced iron ore slime pellets from the bed of residue
of mixing of rejected coal and a desulphurizing agent.
In one embodiment of the present invention, the waste iron ore fines used may
be iron ore slime or low grade iron ore fines collected from iron ore mines or iron
ore beneficiation / washing pond having a composition in the range of :
Fe :40 - 58%
LOI :4 - 11%
Si02 :8 - 15%
Al203 :4 - 8%
P :0.12-0.18%
S :0.006 - 0.01%
In still another embodiment of the present invention, the waste rejected coal or
other coal from coal mines or coal washery used in the process may have the
composition in range of :
Fixed carbon :25 - 35% Volatile Matter: 8 -15%
Moisture: 0.5-3% Ash :50-65%

In still another embodiment of the present invention, the size range of iron ore
slime pellets vary from 12 mm to 20 mm for reduction in the bed of a mixture of
rejected coal and desulphurizing agents or other carbonaceous materials.
Yet another embodiment of the present invention, the size, shape and materials
of the crucibles used in the process is selected according to the furnace design
and mode of heating source.
In a further embodiment of the present invention, reduction of iron ore slime
pellets is carried out in a temperature rang between 900°C to 1200°C in the bed
of said mixture of rejected coal and a desulphurizing agent.
In a still further embodiment of the present invention, reduction of the iron ore
slime pellets is carried out for a time period of 1 to 6 hours.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 - shows a schematic of reduction mechanism according to the
invention.

The produced highly metallized low sulphur DRI of the present invention can be
charged into electrical arc furnace, induction furnace, and basic oxygen furnace
without further processing for steel making as a substitute of scrap.
DETAIL DESCRIPTION OF THE INVENTION
The present invention is a process for reduction of waste iron ore slime pellets in
a bed of mixture of rejected coal and a desulphurizing agent to produce highly
metallized low sulphur reduced iron directly applicable in a blast furnace, electric
arc furnace, induction furnace and basic oxygen furnace for iron steel and steel
making. The following examples are given by way of illustration and should not
be construed to limit the scope of the invention.
EXAMPLE 1
75.1 grams iron ore slime pellets (12 - 20 mm diameter) of composition:
Fe 48.5 %, L0I:9.46 %, Si02:13%, Al203: 7.5%, P: 0.18%, S: 0.01% was kept in
the bed of mixture of rejected coal and a desulphurizing agent in a crucible and
reduced at 900°C for 1 - 6 hours in a reduction furnace. At the reduction

temperature, the gasification of rejected coal produced CO2 which immediately
reacted with the carbon present in the bed of rejected coal which gives rise to
Co. The CO thus generated is highly reducing in nature and reacted with iron ore
slime pellets (iron oxide) kept in bed of rejected coal to produce metallic iron.
The process of gasification and reduction is continued till the completion of
carbon for gasification or complete reduction of pellets. This process is not only
limited to the rejected coal but can be extended to the other carbon bearing
material such as low reactive coal, Jhama coal and middling coal etc. The
reduction mechanisms taking place during reduction are shown in Figure 1. The
details of reactions taking place the during the reduction step is illustrated
hereinbelow:


After reduction, the crucible is removed from the furnace and allowed to cool
from a reduction temperature to 500°C in normal atmosphere (reducing crucible
atmosphere) to avoid re-oxidation of the reduced pellets and thereafter
separated from the residue of the mixture of rejected coal and the desulphurizing
agent. The samples collected from different reduction time were analyzed for
their percentage reduction and found that up to 77.72 %, the reduction is
achieved at 900°C 4 fours reduction time. After 4 hours reduction, the complete
gasification of carbon occurs and further increase in reduction times leads to a
re-oxidation of the reduced pellets.
The percentage reduction achieved at 900°C for different reduction time is given
in the table 1.


EXAMPLE 2
24 sets of 100 grams iron ore slime pellets of compositions: Fe 55.94%, LOI:
4.96%, Si02: 9.14%, Al203 : 4.48%, P:0.172%, S: 0.008% was kept in the bed
of mixture of rejected coal and a desulphurizing agent in a crucible and each set
of crucible containing iron ore slime pellets were reduced in a reduction furnace
at 900°C, 1100°C, and 1200°C for 1 - 6 hours. After reduction of pellets,
crucibles were removed from the furnace at the interval of 1 hour and allowed to
cool from reduction temperature of 500°C in normal atmosphere and thereafter
separated from the residue of mixture of rejected coal and a desulphurizing
agent. The samples collected from different reduction temperature and time
were analyzed for their percentage reduction, cold crushing strength, %
shrinkage and density. The kinetic study of the reduced pellets were carried out
and it was found that, the 1100°C temperature and 3 hours reduction time was
the optimum temperature and time for the reduction of iron ore slime pellets in
the bed of mixture of rejected coal and a desulphurizing agent to get more than
98% reduction.

EXAMPLE 3
24 sets of iron ore slime pellets containing 100 grams of pellets in each set
(crucible) in the size range of 10 - 15 mm diameter and another 24 sets of sets
of iron ore slime pellets having diameter 16 - 15 mm size range were reduced in
the bed of mixture of rejected coal and a desulphurizing agent at 900°C to
1200°C for 1 - 6 hours. After reduction of pellets, crucibles were removed from
the furnace and analyzed for their properties such as percent reduction, percent
metallization, sulphur contents, cold crushing strength and swelling shrinkage
etc. It was observed that the pellets having size range between 10 15 mm
diameter have shown more percent reduction compared to the pellets having
size range between 16 - 20 mm diameter at lower reduction time (< 1 hr) at all
the reduction temperature (900°C to 1200°C). The further increase in reduction
time the present reduction of pellets having size range of 16 - 20 mm diameter
reveals more reduction compared to pellets having size range 10 15 mm
diameter up to 2 ½ hours reduction time. The further increase in the reduction
time (more than 3 hours) the percent reduction of the pellets achieved more
than 98 % in the all size range of the pellets.

EXAMPLE 4
The effects of sulphur pick up from the rejected coal into the reduced iron ore
slime pellets during reduction between 900°C to 1200°C for 1-6 hours has been
carried out by the addition of a desulphurizing agent in the rejected coal.
Moreover, particularly dolomite was chosen as a desulphurizing agent due to its
economically availability and efficiency to reacts with the gaseous compound to
form solid compound. At reduction temperature, during gasification of rejected
coal, the sulphur contents in the coal also formed the gaseous compound of
sulphur which immediately reacted with the desulphurizing agents and remains
in the bed of rejected coal. The addition of desulphurizing agent particularly
dolomite decreases the sulphur diffusion in the reduced iron ore pellets from
0.168% to 0.006%. The addition of dolomite in the rejects coal has been
optimized to get very low sulphur content which will influence the quality of steel
made from the DRI produced. The addition of the desulphurizing agents was not
only limited to dolomite but other low cost desulphurizing agents such as sodium
carbonate, calcium carbonate etc and like wise can be used as a reducing agent.
The major advantages of the present invention are given here:

1. A process for production of low sulphur Directly Reduced Iron (DRI)
utilizing waste iron ore slime and rejected coal.
2. Ability to utilize the waste or discarded slime or low grade iron ore fines or
likewise from mines heat or beneficiation plant or waste from iron and
steel plant up to -400 # mesh size with wide range of Fe content about
40-58%.
3. Ability to utilize waste or discarded carbonaceous material from coal
beneficiation plant or coal washery containing low carbon and high ash
(> 50 % ash) with wide range of size fraction.
4. Ability to get optimum green strength of pellets for handling and further
processing without any binder.
5. The process has ability to use air dried pellets without any pre-induration.
6. The process requires only little excess amount of rejected coal than the
stoichiometric carbon required for reduction compared to the existing
conventional process which requires 1:0.8 to 1:1 ore to coal ratio.

7. The process utilizes cheap and economically available desulphurizing
agents to avoid the sulphur pickup in the DRI during reduction.
8. The process has ability to produce DRI with as low as 0.006% sulphur.
9. The process requires only 1: 0.4 to 1: 0.6 ore to coal radio for complete
reduction.
10. The process has ability to avoid the re-oxidation of the reduced pellets
after reduction.
11. Ability to reduce iron ore slime pellets in the static bed of the rejected
coal.
12. The DRI produced have very low sulphur content which makes it suitable
to meet the quality requirement for production of all grade of steel.

WE CLAIM :
1. A process for production of low sulphur directly reduced iron from waste
iron ore and includes rejected coal containing more than 50% ash
comprising the steps of:
(i) grinding and screening waste iron ore slime to an optimum size range
between - 70 to - 200 mesh and pelletizing to get pellets of diameter
ranging between 12 to 20 mm;
(ii) optimizing moisture content in the iron ore slime pellets (12 - 20 mm
size) by a known method to obtain a green strength of the pellets
ranging between 8 to 15 N per pellet without any binder for safe
handling and further processing;
(iii) grinding and screening rejected coal in a size range between - 70
to -200 mesh in order to use as a reducing agent during the reduction;
(iv) grinding and screening a desulphurizing agent (dolomite) to size
ranges between - 70 to -200 mesh for application as a
desulphurization agent during the reduction;

(v) mixing the rejected coal and the desulphurizing agent (dolomite) in a
weight ratio of 1:0.05 to 1: 0.15;
(vi) locating the iron ore slime pellets in a static bed of the mixture of
rejected coal and the desulphurizing agents for reduction in a weight
ratio of 1: 0.3 to 1: 0.6; wherein a plurality of crucibles containing the
iron ore slimmer pellets in the bed of mixture of rejected coal and
desulphurizing agent is provided for reduction in a temperature range
of 900°C to 1200°C for a time period of 1 to 6 hours ;
(vii) removing and cooling the crucibles containing the reduced iron ore
slime pellets from said reduction temperature to a temperature range
of 600 to 500°C in an ambient atmosphere (reducing atmospheres
inside the crucible) to eliminate re-oxidation of the reduced iron ore
slime pellets including cooling of the pellets to room temperature; and
(viii) separating the reduced iron ore slime pellets from the bed of residue
of the mixture of rejected coal and desulphurizing agent.

2. A process as claimed in claim 1, wherein the waste iron ore slime
comprises a compositional range:
Fe : 40 - 58%
LOI : 4 - 11%
Si02 : 8 - 15%
Al203 :4 -8%
P : 0.12-0.18%
S : 0.006 - 0.01%
3. A process as claimed in claim 1 or 2, wherein the iron ore slime fines
comprises a size range between - 70 to -200 mesh.
4. A process as claimed in claim 1, wherein the iron ore slime pellets has a
size range between 12 to 20 mm.
5. A process as claimed in any of the preceding claims, wherein the iron ore
slime pellets comprise a green strength between 8 to 15 N per pellet.

6. A process as claimed in any of the preceding claims, wherein the waste
rejected coal comprises a following compositional range:
Fixed carbon : 25 - 35% Volatile Matter: 8 - 15%
Moisture: 0.5-3% Ash :50 - 65%.
7. A process as claimed in any of the preceding claims, wherein the
desulphurizing agent is a commercially available industrial grade dolomite
having following compositional range:
8. A process as claimed in any of the preceding claims, wherein the rejected
coal is mixed with dolomite in a weight ratio of 1:0.05 to 1:0.15.
9. A process as claimed in any of claims 1 to 8, wherein the
arrangement of iron ore slime pellets in the static bed of rejected coal
has a ratio of 1: 0.4 to 1: 0.8.

10. A process as claimed in any of claims 1 to 9, wherein reduction
temperature and time vary from 900°C to 1200°C and 1 to 6 hours
respectively.
11. A process as claimed in any of claims 1-8, wherein cooling of the crucible is
carried out in a temperature range of 600°C to 500°C to avoid re-oxidation
of reduced pellets.
12. A process as claimed in any of claims 1 to 9, wherein separation of the
reduced iron ore pellet from the residue of rejected coal and desulphurizing
agent is carried out below 500°C to room temperature depending upon the
requirement.

ABSTRACT

This invention relates to a process for the production of highly metallaized
directly reduced iron (DRI) with low sulphur contents from waste iron ore slime
and rejected coal containing more than 50% ash. The iron ore slime pellets of
12 - 20 mm were made by the conventional method of pelletizing, utilizing - 70
to -200 mesh size iron ore slime fines. The green iron ore slime pellets were
dried in the normal atmosphere and kept in the bed of mixture of rejected coal
and desulphurizing agent of size range between -50 to -200 in a crucible. The
pellets kept in the bed of rejected coal in a crucible were reduced between 900°C
to 1200°C for 1 - 6 hours to get highly metallized low sulphur directly reduced
iron via reduction. After reduction, crucible were removed from the furnace and
allowed to cool from reduction temperature to about 600°C to 500°C temperature
in the normal atmosphere maintaining reducing atmosphere inside the crucible to
avoid re-oxidation and then separated from the residue of rejected coal and
desulphurizing agent. Process parameters were optimized with respect to
reduction temperature, time, amount of desulphurizing agents and rejected coal
required for reduction to yield highly metallized low sulphur directly reduced iron
(DRI), suitable for iron and steel making. This invention is particularly useful for
converting mining waste, iron and steel plant wastes and low grade raw
materials such as low grade iron ore, fines, slime, coking or non coking coal
having low carbon high ash into a value added product.