FIELD OF THE INVENTION
The present invention relates to a process for production of highly metallised
directly reduced iron (DRI) from iron ore slime and middling coal. More
particularly, the present invention relates to a process for production of highly
metallised directly reduced iron from waste iron ore slime and middling coal
containing 28 to 35% ash.
BACKGROUND OF THE INVENTION
The commercial method of DRI making utilizes good quality of raw materials
such as lump iron ore, iron ore fines, iron ore pellets, iron ore - coal composite
pellets and iron ore - coal agglomerates containing more than 58 % Fe and coal
or non coking coal containing less than 20 % ash as a reducing agent in the ratio
of 1:0.8 to 1:1.2. Further, the majority of coal based conventional processes
adopts shaft furnace or rotary kiln or SIVRN process or rotary hearth furnace for
making DRI which requires pre-indurated pellets and good quality reducing
agents to confirm the optimum reduction.
Slimes are generated during beneficiation of iron ore in the mines head as well
as while preparing burden whereas middling coal is by-product after third wash
of coal. Generally, these slime and middling coal are not suitable for iron and
steel making due to low iron content in iron ore slime and high ash content in
the middling coal.
US Patent No. 3,443,931, disclosed a DRI making process wherein, pulverized
iron ore and pulverized coal mixture are agglomerated, dried and pre-indurated
in a temperature range between 872°C to 982°C. The agglomerated pellets were
subjected to reduction through application of radiant heat source at 1260°C to

1425°C yielding reduction of iron. Initially, in mid 60's this reduced iron was used
as a blast furnace feed. In this process, pre-induration of agglomerates are
carried out to get optimum strength for handling and processing of material
besides the reduction of agglomerates at high temperature. However, this
method does not involve the use of low grade iron ore fines and coal fines which
narrow down the choice of raw material selection for iron making.
To overcome the problem of pre-induration and utilization of iron ore fines and
coal fines in 1990's, a process for production of metalized briquette was
described in US Patent No. 4,701,214 which disclosed the concept of briquetting
of iron ore fines and coal fines. In this process, iron oxide fines and coal fines
are mixed with a suitable binder to form a mixture and this mixture was
agglomerated by pelletizing or briquetting to form pellets. These pellets are
charged in a rotary hearth furnace to get pre-reduced pellets and finally melted
in a smelting furnace in presence of carbon to get the metalized briquette. This
smelting reduction of these pre-reduced pellets further requires additional
carbon/coal and energy for smelting.
U.S Patent No. 6, 284, 017 Bl teaches mixing of iron oxide fines and solid
reductant in the form powder and compacting into sheet using rollers. These
compacted sheets are charged into a reduction furnace at a temperature more
than 1100°C for reduction. This reduced sheets are further charged into a shaft
furnace or smelting furnace for melting with high thermal efficiency. However,
the smelting process requires an additional amount of reductant for reduction
and melting. The product obtained from this route also suffers from the quality
requirement which does not allow the process to be economically viable.
U.S Patent No. 5, 37, 133 discloses a process for production of sponge iron with
low sulphur content. In this process, a superposed layer of finely divided iron

oxide is deposited on a moving hearth including another layer of mixed solid
carbon and desulphurising agents. These charge mix is externally heated at a
minimum temperature of 900°C using a burner so that iron oxide is reduced by
carbon monoxide yielding a solid cake of sponge iron, which is separated from
the residue of reducing and desulphurization agents. The reduced iron cake thus
obtained contains huge quantity of impurities which restricts the use of sponge
iron in an electric furnace.
U.S Patent No. 6,379,426 B1 teaches, a method for pre-reduction of iron ore
fines in a bubbling fluidized bed reactor with instantaneously generated reducing
gases from non-coking coal, known as Circofer® process. In this process, coal
and ore are fed into two fluid beds. The first one is a circulating fluidized bed
where the coal is charred, and the ore is 50% metallized. The second
one is a bubbling fluidized bed where final reduction using char is achieved at a
temperature ~ 950°C. This 50% metallized product can be charged in to a
smelter and smelting reduction using char/coke to achieve final reduction. In this
process, the productivity is limited because of high retention time in the bubbling
fluidized bed and further smelting requires additional char/coal/coke which leads
to economical problem.
US Patent No. 8,182,575 B2 describes a process for production of DRI pellets
from dust generated during iron making process which includes converter dust,
blast furnace dust, mill scale and electric furnace dust and coal, coke fines and
granular carbons. Composite pellets are made utilizing these dust and reduced in
a rotary hearth furnace, also known as called FASTMET® process. The DRI
pellets thus produced have poor metallization.
In order to achieve high metallization the concept of iron nuggets was taught in
US Patent No. 6, 036,744 in year of 2000. In this process, iron oxide was

compacted with a carbonaceous reductant and subjected to reduction through
application of heat to yield metallic iron. The metallic iron shell is generated and
grown via reduction through application of heat in a temperature range of
1450°C to 1500°C. This method requires sufficient amount of heat to separate
the metallic iron from the slag leading to fusion of complete agglomerates.
US Patent No. 2009, 0175,753 A1 describes a method to produce metallic iron
nuggets through arranging a discrete portion of mixtures of reducing agent and
iron ore oxide at 1375°C to 1425°C resulting formation of intermediate iron or
iron nuggets.
US Patent No. 8,021,460 B2 teaches a method for producing metallic iron
nodules from coarse carbonaceous material and iron bearing material through
reduction at a fusion atmosphere of 1200 to 1450°C in a hearth furnace.
European Patent No. EP 2,189,546 Bl disclosed for production of DRI in hot-
molded, hot briquetted iron (HBI) at a temperature of 500°C to 800°C and
subsequent reduction in a carbon monoxide atmosphere at 1200°C to 1420°C in
a rotary hearth furnace. However, the process requires additional energy and
special equipments for hot briquetting.
The non-patent literature by H. Michishita and H. Tanaka and H. Ishikawa
(Kobelco Tech. Rev., No. 29, pp. 69-76, Dec. 2010 and, Archive of metallurgy
and materials, Vol. 53, pp. 541-545, 2008), discussed about coal-based rotary
hearth furnace (RHF) technologies such as FASTMET, FASTMELT and ITmk3.
These technologies are using carbon-ore composite pellets or briquettes were
agglomerated to produce DRI, liquid iron and iron nuggets respectively.
The non-patent literature by K.C. Woody and Henry P. Gaines, (Direct from

MIDREX, 2nd quarter, pp. 1-14, 2012) showed that DRI is produced apart from
RHF route using reformed natural gas-fired shaft furnace, also called MIDREX. In
this process, the feed material of iron oxide can be in the form of pellets or
lumps and the reductant are non-coking coal, CO, H2 and coke oven gases etc.
MIDREX has developed another process called MXCOL process, where, instead of
natural gas; syngas from coal (Midrex Technologies, Inc., MXCOL: A
breakthrough in coal-based direct reduction, pp. 1-4) was used as a combustion
medium in shaft furnace. The DRI produced other than the RHF route contains
high porosity and thus prone to re-oxidation.
Thus conventional processes so far developed as described above have several
draw backs such as:
(1) All the process utilizes high Fe and low gangue content iron oxide such as
lump iron ore, iron ore fines and ore-coal composite, pellets and
agglomerate for production of directly reduced iron.
(2) The reducing agents so far used for production of directly reduced iron
contains high fixed carbon (>65%) and low ash (<20%).
(3) Almost in all the processes, the iron ore fines are mixed or agglomerated
with reducing agent which leads to increased gangue content in the
directly reduced iron yielding poor metallization coupled with high level of
impurities.
(4) Thus the increased gangue/impurities contents in the directly reduced iron
requires more fluxing agent during melting resulting in decrease in the
rate of production.

(5) The DRI produced from conventional route including above mentioned
routes pickup more sulphur and other undesirable elements from the coal
during reduction which restricts the use of DRI for quality steel making.
(6) Almost all the processes of DRI making, requires pre-indurated pellets for
reduction which requires additional energy and heat source as well as
increased number of processing steps for production of the DRI.
(7) All the above processes, do not involve any low grade / lean iron ore or
iron ore fines or unutilized slimes and less reactive coke / coal fines such
as high ash middling coals or Jhama coal which narrow down the choice
of source of raw material for making iron.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a process for production of
highly metallised directly reduced iron (DRI) with low sulphur content from waste
or rejected iron ore slime and middling coal, which eliminates the disadvantages
of prior art.
Another object of the present invention is to propose a process for production of
highly metallised directly reduced iron (DRI) pellets utilizing waste middling coals
as a reduceing agent containing 24 - 38% ash.
A still another object of the present invention is to propose a process for
production of highly metallised directly reduced iron (DRI) pellets utilizing waste
middling coals as a reduceing agent containing 24 - 38% ash, in which optimum
moisture is required for making pellets from iron ore slime.

Yet another object of the present invention is to propose a process for
production of highly metallised directly reduced iron (DRI) pellets utilizing waste
middling coals as a reduceing agent containing 24 - 38% ash, which provides
optimum size of iron ore slime pellets for complete reduction with middling coal.
Another object of the present invention is to propose an arrangement for
locating iron ore slime pellet in bed of middling coal for reduction.
A still another object of the present invention is to a process for production of
highly metallised directly reduced iron (DRI) with low sulphur content from waste
or rejected iron ore slime and middling coal, in which optimum quantity of waste
middling coal required for complete reduction of iron ore slime pellets to produce
highly metalized directly reduced iron suitable for iron and steel making.
A further object of the present invention is to propose a process for production
of highly metallised directly reduced iron (DRI) with low sulphur content from
waste or rejected iron ore slime and middling coal, which requires an optimum
reduction temperature and time for conversion to highly metalized reduced iron
with high cold crushing strength suitable for blast furnace iron making and
electric steel making processes.
A still further object of the present invention is to propose a method of cooling of
reduced pellets in order to avoid the re-oxidation of the DRI pellets.
Yet further object of the present invention is to propose a process for production
of low sulphur directly reduced iron suitable for production of different grades of
steel.

SUMMARY OF THE INVENTION
Accordingly the present invention provides a process for production of highly
metallised DRI from low grade iron ore fines called slime, which are generated
during beneficiation of iron ore in the mines head and washing of the raw
material while preparing burden. This iron ore slime has low iron value and
cannot be used as a feed for blast furnace and hence gets rejected. In India,
about 10 million tons of iron ore slimes are getting generated every year and
remain unutilized in the washing pond leading to several problems of land filing,
disposal, environmental and loss of minerals.
Similarly, during beneficiation of coal, a large quantity of middling coal are
generated as a by product after 3rd wash of coal which is rejected due to high
ash content varying from 24 - 38% ash. This high percentage of ash in the
middling coal restricts its application in the field of iron and steel sectors.
However, it has been partially utilised in power plants, brick manufacturing,
cement plants, domestic fuels and remaining left for land filing. Moreover, the
projected requirement of coking coal in India is about 70 million tonnes with an
annual expected growth of 7.3% in the coming year of 2019 - 2020. Thus,
coking coal is imported, causing an economical disadvantage, as coking coal
prices have increased manifold in the recent years. Therefore, the present
invention herein discloses a process for production of highly metallised DRI
pellets utilizing waste iron ore slime and middling coal.
The inventors proposes a method to produce highly metallised DRI pellets
utilizing these waste iron ore slime and middling coal. The produced highly
metallised DRI pellets are much cheaper and superior than the DRI produced
from the conventional route and can be directly charged in to an Electrical Arc
Furnace, Induction Furnace, and Basic Oxygen Furnace for production of steel.

The process essentially comprises the steps of: -
- grinding and screening of waste iron ore slime to an optimum size range
between -70 to -200 mesh,
- pelletizing the grinded and screened waste iron ore slime to obtain pellets
in a diameter range of 12 to 20 mm,
- optimizing the moisture content in the iron ore slime pellets by known
method to achieve the green strength of the pellets ranging between 8 to
15 N per pellet without / with little addition of a binder for safe handling
and further processing,
- grinding and screening waste middling coal in size fraction of -70 to -200
mesh for mixing as a reducing agent during reduction,
- grinding and screening desulphurisation agent (dolomite) in the size range
of - 70 to -200 mesh for mixing during reduction,
- mixing the ground and screened middling coal and the desulphurizing
agent (dolomite) in a weight ratio of 1: 0.05 to 1: 0.15,
- locating a plurality of iron ore slime pellets in a static bed having the
mixture of middling coal and desulphurizing agent for reduction in a
weight ratio of 1: 0.3 to 1: 0.6,
- iron ore slime pellets are accommodated in crucibles for reduction in a
temperature range between 900 to 1200°C for 1 to 6 hours,

- removing and cooling of the reduced iron ore slime pellets from said
reduction temperature to a temperature between 600 to 500°C in the
crucibles to avoid the re-oxidation of the reduced iron ore slime pellets
and cooling thereafter to room temperature; and
- Separating the reduced iron ore slime pellets from the residue of the
mixture of middling coal and the desulphurizing agent.
In one embodiment of the present invention, the waste iron ore fines (slimes)
are collected either from iron ore mines or from steel plant waste and having a
composition in the range of:
Fe : 42 - 56 %
LOI :4-ll%
SiO2 : 8 - 15%
Al2O3 :4-8%
P : 0.12-0.18%
S : 0.006 - 0.01%
In another embodiment of the present invention the waste middling coal can be
selected from a group of coals consisting of coal for coal mines, coal washery,
mining waste, and steel plant waste having a composition in the range of:
Fixed carbon : 45 - 52% Volatile Matter: 15 - 24 %
Moisture : 0.5 - 2% Ash : 24 - 38%
In yet another embodiment of the present invention the desulphurising agent
may be commercially available industrial grade dolomite having the following

compositional range:
MgO : 30 - 42% CaO : 50 - 60%
SiO2 : 1-2% Al2O3 :2-4%
In still another embodiment of the present invention, the size range of iron ore
slime pellets may vary from 12 mm to 20 mm for reduction in the bed of
middling coal or other carbonaceous materials,
In another embodiment of the present invention, the size, shape and materials of
the crucible may vary according to furnace design and mode of heating.
In a further embodiment of the present invention, reduction of iron ore slime
pellets is carried out in temperature range from 900 to 1200°C in the bed of
middling 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 in a suitable
reduction furnace.
In an yet further embodiment of the present invention the reduced pellets are
cooled form 600 to 500°C in the bed of residue of middling coal and a
desulphurising agent, and separated separation by screening.
BRIEF DESCRIPTION F THE ACCOMPANYING DRAWING
Figure 1 - schematic of reduction mechanism of iron are slime pallets in bed
of middling coal during reduction step according to the invention.

DETAIL DESCRIPTION OF THE INVENTION
In accordance with the first and second object of the present invention, the
invention provides a method of DRI making utilizing waste iron ore slime and
waste middling coals for production of highly metalized directly reduced iron
which can be used without further processing in iron and steel industries.
The present invention is characterized by reduction of waste iron ore slime
pellets in the bed of mixture of waste middling coal and a desulphurizing agent
to produce highly metalized directly reduced iron suitable for blast furnace,
electric arc furnace, induction furnace and basic oxygen furnace for iron and
steel making. The following examples are given by way of illustration and should
not be construed to limit the scope of invention.
EXAMPLE -1
100 grams iron ore slime pellets (12 - 20 mm diameter) of composition: Fe: 52.4
%, LOI: 8.1 %, Si02:9.5%, AI203: 7.1%, P: 0.18%, S: 0.015% was reduced in
the bed of mixture of middling coal and a desulphurizing agent in a crucible at
900oC for 1 - 6 hours in a reduction furnace. At this temperature C02 is
produced during gasification of middling coal, which reacts with the carbon
present in the bed of middling coal gives rise to CO. The CO thus generated was
highly reducing in nature and reacted with iron ore slime pellets (iron oxide) kept
in bed of middling coal to produce metallic iron via reduction. The process of
gasification of middling coal and reduction of pellets will be continued till the
completion of carbon present in middling coal for gasification or complete
reduction of iron ore slime pellets. This process is not only limited to the middling
coal but also be extended to the other carbonaceous material such as low
reactive coal or Jhama coal or rejected coal or likewise. The mechanism of

reduction of iron ore slime pellets in bed of middling coal during reduction is
shown in figure 1 and illustrated hereinbelow :-

After reduction of iron ore slime pellets at 900°C, crucibles were removed from
the furnace at an interval of one hour and allowed to cool from reduction
temperature to 500°C in normal atmosphere (maintaining reducing atmosphere
inside the crucible) to avoid re-oxidation of the reduced pellets and thereafter
separated from the residue of mixture of middling coal and a desulphurizing
agent. The reduced iron ore slime pellets collected from different reduction time
were analysed for their percentage reduction and found that up to 78.7 %
reduction was achieved at 900°C for 4 hours reduction time. After 4 hours,
percent reduction of the pellets revealed decrease in percent reduction which
may be due to complete gasification of carbon in the bed of middling coal
leading to 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 composition: Fe: 55.94%, LOI:
4.96%, SiO2: 9.14%, Al2O3: 4.48%, P: 0.172%, S: 0.008% were kept in the bed
of mixture of middling coal and a desulphurizing agent in a crucible and reduced
in a reduction furnace at 900°C, 1000°C, 1100°C and 1200°C for 1 - 6 hours.
After reduction of pellets, crucibles were removed from the furnace at an interval
of 1 hour and allowed to cool from reduction temperature to 600°C in normal
atmosphere. After cooling, reduced iron ore slime pellets were separated from
the residue of mixture of middling coal and a desulphurizing agent. The samples
collected from different reduction temperature and time were analysed for their
properties such as percentage reduction, cold crushing strength, % shrinkage
and density. The kinetics of the reduced pellets was also carried out to optimize
the process parameter for production of highly metallised directly reduced iron.
It was observed that the middling coal have the tendency to form the solid cake
at higher temperature (more than 1150°C) which leads to the problem of
separation of reduced iron ore slime pellets from the residue of middling coal. It
was interesting to note that 1000°C reduction temperature and 3 to 4 hours
reduction time was found to be the optimum temperature and time for reduction
of iron ore slime pellets with middling coal to get more than 94 % 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 - 20 mm size range were reduced in
the bed of middling coal containing a desulphurizing agent at 900°C to 1200°C
for 1 - 6 hours. After reduction, crucibles were removed from the furnace and
analysed 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 ( < 2 hr) at 900°C to
1100°C. However the pellets reduced at 1200°C was difficult to separate from the
residue of middling coal due to formation of solid cakes of coal. Further increase
in reduction time (more than 2 hours) the percent reduction of the pellets
achieved more than 94 % in both size range of iron ore slime pellets.
EXAMPLE - 4
The effect of sulphur pick up in reduced iron ore slime pellets during reduction at
higher temperature (900°C to 1100°C) from middling coal has been explored by
addition of a desulphurizing agent in the middling coal. Moreover, industrial
dolomite was chosen as a desulphurizing agent due to its economically
availability and efficiency to reacts with the gaseous compound of sulphur to
form solid compound. During reduction, gasification of middling coal occurred,
consequently sulphur contents in the coal had also formed the gaseous
compound of sulphur which immediately reacted with the desulphurizing agent
to form the solid compound of sulphur which remain in the bed of middling coal.
The addition of desulphurizing agent thus decreased the sulphur diffusion in the
reduced iron ore pellets resulting decrease in the sulphur contents in the reduced

pellets from 0.16% to 0.008%. The addition of the desulphurizing agent 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 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 middling coal.
2. Ability to utilize the waste or discarded slime or low grade iron ore fines
or likewise from mines head or from beneficiation plant up to -200 mesh
size with wide range of Fe content (40 - 56% Fe).
3. Ability to utilize waste middling coal or discarded carbonaceous material
from coal beneficiation plant or coal washery containing low carbon and
high ash (24 to 38% ash) with a wide range of size fraction.
4. Ability to get optimum green strength of pellets for handling and further
processing without/with little use of binder.
5. Ability to use air dried pellets for reduction without pre-induration.
6. The process requires only little excess amount of middling coal than the
stoichiometric carbon required for reduction compared to the existing
conventional process which requires 1: 0.8 to 1: 1.1 ore to coal ratio.
7. The process utilizes cheep and economically available desulphurizing
agents to avoid the sulphur pickup in the DRI during reduction.
8. The process has ability to produce DRI with more than 94% reduction.

9. The process has ability to produce DRI with low sulphur of 0.008%.
10. The process requires only 1: 0.3 to 1: 0.6 ore to coal ratio for complete
reduction.
11. The process has ability to avoid the re-oxidation of the reduced pellets
after reduction.
12. Ability to reduce iron ore slime pellets in the static bed of the middling
coal.
13. The DRI produced have very low sulphur content which makes it suitable
to meet all quality requirements for production of different grade of steel.

WE CLAIM
1. A process for production of highly metallised directly reduced iron (DRI)
with low sulphur content from waste or rejected iron ore slime and
middling coal, comprising the steps of:-
(i) grinding and screening waste iron ore fines (slimes) to an optimum
size ranging between -70 to -200 mesh;
(ii) pelletizing the ground and screened waste iron ore slime to obtain
pellets of 12 to 20 mm diameter without or with addition of a
binder;
(iii) optimizing moisture content for making iron ore slime pellets by
known method to achieved a green strength of the pellets ranging
between 8 to 15N per pellet without / with addition of a binder for
safe handling and further processing;
(iv) grinding and screening waste middling coal in a size range of -70 to
-200 mesh to use as a reducing agent during reduction;
(v) grinding and screening desulphurisation agent (dolomite) to a size
range of -70 to -200 mesh to be used during reduction;
(vi) mixing the middling coal with desulphurizing agent (dolomite) in a
weight ratio of 1: 0.05 to 1: 0.15;
(vii) locating iron ore slime pellets in a static bed of middling coal for
reduction in a weight ratio of 1: 0.3 to 1: 0.6,
(viii) arranging a plurality of crucible containing said iron ore slime

pellets in the bed of middling coal for reduction in a temperature
range of 900 to 1100°C for a period of 1 to 6 hours;
(ix) removing and cooling the crucibles containing the reduced iron ore
slime pellets from said reduction temperature to a temperature
between 500 to 600°C in the crucibles (reducing atmospheres) to
avoid re-oxidation of the reduced iron ore slime pellets.
(x) separating the reduced iron ore slime pellets from the residue of
the bed of the middling coal.
2. A process as claimed in claim 1, wherein the waste iron ore slime
comprises a compositional range:
Fe : 42 - 56%
LOI : 4 - 11%
SiO2 : 8 - 15%
Al2O3 :4-8%
P : 0.12 -0.18%
S : 0.006 - 0.01%
3. A process as claimed in one of claims 1 or 2, wherein the iron ore slime
pellets have a size range between 12 to 20 mm.
4. A process as claimed in any of claims 1 or 3, wherein the waste middling
coal have the following compositional range:
Fixed carbon : 45 - 52% Volatile Matter: 15 - 24%
Moisture : 0.5 - 2% Ash : 24 - 38%

5. A process as claimed in any of claims 1 or 4, wherein the desulphurizing
agent is commercially available industrial grade dolomite with a
compositional range:
MgO : 30 - 42% CaO : 50 - 60%
SiO2 : 1 - 2% Al2O3 : 2 - 4%
6. A process as claimed any of in claims 1 or 5, wherein the middling coal is
mixed with dolomite have a weight ratio in the range of 1: 0.05 to 1:
0.15.
7. A process as claimed in any of claims 1 or 6 wherein the arrangement of
iron ore slime pellets in the static bed of middling coal has a weight ratio
in the range of 1: 0.3 to 1: 0.6.
8. A process as claimed in any of claims 1 or 7, wherein reduction
temperature and time vary from 900°C to 1100°C and 1 to 6 hours
respectively.
9. A process as claimed in any of claims 1 or 8, wherein cooling of the
crucibles is carried out in a temperature range of 500°C to 600°C to avoid
re-oxidation of the reduced pellets.
10. A process as claimed in any of claim 1 or 9, wherein separation of the
reduced iron ore pellets from residue of the middling coal and
desulphurising agent is carried out below 500°C to room temperature
depending upon the requirement.
11. A process for the production of highly metallised low sulphur directly
reduced iron (DRI) from waste iron ore slime and middling coal

substantially as herein described herein with reference to the examples
provided in the specification.

ABSTRACT

The invention relates to a process for production of highly metallised directly
reduced iron (DRI) with low sulphur content from waste or rejected iron ore slime and middling coal, comprising the steps of:-
(i) grinding and screening waste iron ore fines (slimes) to an optimum size ranging between -70 to -200 mesh;
(ii) pelletizing the ground and screened waste iron ore slime to obtain pellets of 12 to 20 mm diameter without or with addition of a binder;
(iii) optimizing moisture content for making iron ore slime pellets by known method to achieved a green strength of the pellets ranging
between 8 to 15N per pellet without/with addition of a binder for safe handling and further processing;
(iv) grinding and screening waste middling coal in a size range of -70 to-200 mesh to use as a reducing agent during reduction;
(v) grinding and screening desulphurisation agent (dolomite) to a size range of -70 to -200 mesh to be used during reduction;
(vi) mixing the middling coal with desulphurizing agent (dolomite) in a weight ratio of 1: 0.05 to 1: 0.15;
(vii) locating iron ore slime pellets in a static bed of middling coal for reduction in a weight ratio of 1: 0.3 to 1: 0.6,
(viii) arranging a plurality of crucible containing said iron ore slime pellets in the bed of middling coal for reduction in a temperature range of 900 to 1100°C for a period of 1 to 6 hours;
(ix) removing and cooling the crucibles containing the reduced iron ore slime pellets from said reduction temperature to a temperature
between 500 to 600°C in the crucibles (reducing atmospheres) to avoid re-oxidation of the reduced iron ore slime pellets.
(x) separating the reduced iron ore slime pellets from the residue of the bed of the middling coal.