FIELD OF THE INVENTION
The present invention relates to a system and continuous process of
manufacturing of Sponge Iron(DRI) from iron ore fines below 10mm size and, in
particular, is directed to simple system and continuous process of manufacture
Sponge Iron from Iron Ore fines using a tunnel kiln in selective shapes including
preferably hollow cylindrical shape involving low capital cost and yet suitable for
utilizing both Hematite (Fe2O3) Iron Ore as well as Magnetite (Fe3O4) Iron Ore and
even from iron ore fines of less than 5 mm, apart from the usual sponge grade
iron ore of 5-18mm sizes used in the traditional rotary kiln furnaces.
Advantageously, the system and the method according to the present invention is
clean, energy efficient and environment friendly while adapted to be used even in
remote locations with scarcity or even no power supply. The system and process
is adapted to favour generation of such sponge iron in the form of hollow cylinder
which would be energy efficient and also reduce the cost of production. The
Sponge Iron produced by the process is also preferred for melting in the induction
and electric arc furnaces because of inherent carbon which reduces the
requirement of Pig Iron or Calcifined Pet coke.
BACKGROUND ART
Sponge Iron is basically Direct Reduced Iron (DRI) and is the product obtained
from direct reduction of Iron Ore. Usually, in the reduction process the Oxygen in
the Iron Ore is eliminated leaving void space and the whole mass becomes
porous and spongy. Sponge Iron is widely applicable in the Steel Industry as an
important raw material for steel making via the Electric Arc Furnace (EAF) and
the Induction Furnace (IF) routes substituting and supplementing the charge of
iron and steel scrap.
Presently there are two main technologies for producing Sponge Iron (i) Gas
based and (ii) Coal based.
The gas-based method involves several alternative technologies and any
generalization of the gas based method is not possible. In one such process
popularly known as "Midrex process", the gas based system adopts a continuous,
moving bed process which converts Iron Oxide (Lump/pellets) into Direct

Reduced Iron (DRI) at elevated pressure and predetermined temperature under
the reducing action of a mixture of hydrogen and carbon monoxide (CO) gas
produced by natural gas / steam reforming.
IN 191425 discloses a process for producing Sponge Iron from particulate iron
oxide containing ore characterized by the steps of reducing the iron oxide
containing ore to Sponge Iron in a reduction zone by reacting the iron oxide
containing material with a reducing gas, withdrawing the gas formed during
reduction from the reduction zone as a top gas, subjecting the top gas to CO2
purification thereby forming a CO2 containing off gas and purified top gas, mixing
the CO2 containing off gas and a purified top gas and burning it, supplying the
thermal energy produced by the CO2 containing off gas to a consumer and
recovering the sponge iron obtained in the first step from the reduction zone.
In the coal based method of producing Sponge Iron the same involves reducing
iron ore (lump/pellets) with carbonaceous material like coal or lignite. The
reduction process is carried out in a shaft furnace or rotary furnace at stipulated
temperature in the range of 850°C-1050°C. The reduced iron from the furnace is
cooled and the cold product after being discharged is next subjected to product
separation and handling. Magnetic separators are used to separate the magnetic
component from the non-magnetic ingredients.
US 4,362,554 disclosed a method and apparatus for manufacturing sponge iron
by the continuous reduction of iron oxides in a shaft utilizing recirculation gases.
Reaction gas is removed from the shaft furnace, substantially cleaned of all CO2
and H2O, and then divided into at least two flow portions one of which is passed
to a gas generator comprising a plasma burner. A reducing agent such as pit coal
is injected together with an oxidant into the hot gas from the plasma burner so as
to form a gas mixture comprised primarily of CO and H2, which gas mixture is
then mixed with the other flow portion of the cleaned reaction gas in such
proportion that the temperature of the resulting reduction gas is suitable for the
reduction of iron oxides in the shaft furnace.
IN191759 discloses a device for producing Sponge Iron from lumps of Iron Oxide
in a reduction shaft comprising using a hot dust containing an Carbon
Monoxide(CO) rich reduction gas, the reduction is produced in a gas generator by
partial oxidation of solid carbon containing material and introduced via a plurality
of lateral reduction gas inlets arranged at the same level on the circumference of

the reduction shaft, into the reduction shaft at the lower end of the reduction
zone and iron oxide lumps are entered in the upper area of the reduction shaft
and its lower end discharged as Sponge iron characterized in that below the level
of lateral gas inlets are provided additional reduction gas inlets in the form of at
least one channel which is over its length downwardly opened and extends from
the outside into the radially central area of the reduction shaft.
US4469509 discloses operation of the rotary kiln provided at its charging end
with a central burner, solid reducing agents having a high content of volatile
constituents are used and the charge and the gas atmosphere are conducted in
cocurrent streams. To avoid a high heat load per unit of volume in the heating-up
zone and yet to increase the heating-up rate, a solid carbonaceous reducing
agent having a high content of volatile constituents is charged together with the
iron oxide-containing material into the charging end of the rotary kiln, oxygen-
containing gases are blown through nozzle blocks into the free gas space and into
the charge in the heating-up zone, and oxygen-containing gases are blown
through nozzle blocks into the free kiln space in the reducing zone.
WO 02/064844 Al discloses a method for producing sponge iron wherein iron
oxide is reduced through heating together with a solid reducing agent to form
sponge iron, characterized in that a mixed powder of a hematite powder and an
iron ore powder or a mixed powder of hematite powder and a mill scale powder is
used as iron oxide and the hematite powder has a specific surface area of 2.0
m2/g or more and is used in an amount of 5 to 45mass % based on the total
amount of the iron oxide.
Swedish Pat. No. 73 04 322-5, describes about directly gassifying coal in solid
form using a plasma generator. This process essentially requires that the supply
of coal must be extremely accurately adjusted and for some grades of coal there
are problems in handling the ash. Moreover, the gas produced has a hydrogen
content which is lower than the ideal for reduction purposes.
The drawbacks with the above known coal based methods of producing sponge
iron are primarily the extremely high investment cost and also the exceptionally
high energy consumption or the limitations in charge characteristics for effective
reduction of the ore.
In particular the rotary furnace method involves pit coal together with the ore to
be reduced, in an inclined rotary furnace. Such rotary furnace involving coal

based system of manufacture of Sponge Iron from Iron Ore is complex and cost
extensive and essential involves lot of power consumption by way of achieving
the rotary motion of the kiln in the continuous process of reduction of the Ore.
Moreover, apart from being capital intensive such coal based method/system
involving the rotary kiln is essentially also complex to install involving huge
installation space and skilled manpower to handle and use. One of the biggest
limitations of the process is that it cannot use Iron ore fines unless agglomerated
and made into pellets.
Granted Patent no. 206196 of the Applicants disclosed a system and method for
batch production of sponge iron from iron ore in a cost effective manner wherein
vertically aligned saggers/containers with ceramic lining filled with a charge
containing iron ore fines mixed with redundant coal dust, graphite and charcoal,
along with dolomite or lime stone, sodium nitrate and potassium carbonate is
subjected to a firing cycle from 17-32 hours in conventional coal fired down draft
or up draft kiln, at a temperature range of 900-1180°C, thereby reducing the iron
ore in absence of atmospheric air/oxygen to produce sponge iron which is
unloaded at a unloading platform by unloading saggers starting from top towards
bottom under gravity. The sponge iron obtained is allowed to cool for 10-50 hrs
and subjected to magnetic separation and screening to separate ash and unburnt
coal dust. This method of producing sponge iron is cost effective but is not
continuous operation type, thus low productivity, not energy efficient and
generates air pollution.
There has been thus a continued need in the art to cater to the increasing
demands for sponge iron in the steel industry to look for alternative methods and
system of manufacture of sponge iron on continuous basis which could avoid the
complexities and capital intensive approach by way of some simple and cost
effective system/technique, ensure shortened reduction cycle and improved
metallization in the DRI output, suitable for installation in remote locations with
scarcity or even no power sources/supply while ensuring higher productivity and
desired quality.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to providing a simple and cost
effective system and method for manufacture of sponge iron from iron ore fines

in Tunnel Kiln on continuous basis in selective shapes including a desired hollow
cylindrical form.
A further object of the present invention is directed to a system and method for
continuous production of sponge iron in selective shapes including hollow
cylindrical shape from iron ore fines which would be convenient to operate/use in
remote locations for wide scale cost effective manufacture of Sponge Iron to meet
the quality as well as quantity requirements.
A further object of the present invention is to provide a system and method for
continuous production of sponge iron in selective shapes including hollow
cylindrical shape in Tunnel Kiln by making use of Iron Ore fines of less than 5 mm
size which is relatively cheaper than lumps and can not be used in producing
Sponge Iron in the Rotary Kiln method.
A still further object of the present invention is directed to providing a system and
method for producing sponge iron in selective shapes including hollow cylindrical
shape from iron ore fines in Tunnel Kiln wherein ore fines can be directly filled in
crucible/container along with coal fines and limestone fines in a desired manner
for charging in tunnel kiln without needing any pre processing.
A still further object of the present invention is directed to providing a system and
method for producing sponge iron in selective shapes including hollow cylindrical
shape from iron ore fines in a Tunnel Kiln which is relatively cheaper and
environment friendly as compared to the rotary Kiln based process for
Manufacturing Sponge Iron.
A still further object of the present invention is directed to provide for a system
and method for continuous production of sponge iron in selective shapes including
hollow cylindrical shape form from iron ore in tunnel kiln which would be simple
and cost effective and at the same time workable to produce sponge iron from
both the iron ore sources Hematite (Fe2O3) and Magnetite (Fe3O4).
Another object of the present invention is to provide for a system and method for
continuous process production of sponge in selective shapes including hollow
cylindrical shape from iron ore using Tunnel Kiln, which can be adopted by the

small scale industry with low investments and favour advantageous use of cost
effective kilns such as low cost Tunnel Kiln using a coal gasifier technology.
Yet another object of the present invention is to provide for the much required
system and process for continuous production of sponge iron in selective shapes
including hollow cylindrical shape from iron ore fines in Tunnel Kiln involving
continuous charge and also adapted for generation of sponge iron from low cost
iron ore fines such as those available in sizes of 0-5 mm which are cheaper than
the usual expensive sponge grade iron ore of 5-18 mm size, thereby favoring the
use of iron ore fines gainfully in generation of sponge iron.
A still further object of the present invention is directed to a system and method
for continuous production of sponge iron in selective shapes including hollow
cylindrical shape from iron ore fines using Tunnel Kiln, which would yield greater
realization value in terms of conversion of cost effective Iron ore fines.
An yet further object of the invention is directed to a system and method for
continuous production of Sponge Iron in selective shapes including hollow
cylindrical shape from iron ore fines in Tunnel Kiln, which would enable
advantageous utilization of cost effective labour in lieu of costly equipments
adapted for operation in remote locations having scarcity of power and skilled
manpower.
Yet another object of the present invention is directed to provide a system and
method for continuous production of Sponge Iron in selective shapes including
hollow cylindrical shape from iron ore fines using Tunnel Kiln, which can be
carried out in remote locations involving low power or less consumption of power.
A further object of the present invention is directed to a method of generation of
shaped sponge iron having inherent carbon from iron ore fines which would
further enable the shaped Sponge Iron production which would be preferred for
melting in the induction furnaces because of inherent carbon which reduces the
requirement of Pig Iron or Calcifined Pet coke.
A still further object of the present invention is directed to provide for a system
and method for manufacture of sponge iron in selective shapes including hollow
cylindrical shape using Tunnel Kiln, which would be environment friendly and less
polluting.

SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a
system for continuous production of sponge iron from iron ore comprising,
a tunnel kiln comprising a pre-heating zone with heating means to maintain a
temperature in the range of 100°C to 600°C , reduction zone having heating
means to maintain a temperature in the range of 850° to 1200°C and cooling
zone adapted to maintain a temperature of upto 100-200°C ;
a plurality of heat transferable crucibles/ containers adapted to be filled
selectively with iron ore fines and/or redundant such as to generate said
selective hollow cylindrical form of sponge iron;
means to transfer the said loaded heat transferable crucibles/ containers through
the said tunnel kiln zones the pre-heating zone , reduction zone and cooling zone
for desired duration to ensure atmospheric oxygen/air free contact of said iron
ore fines and/or reductant in said heat transferable crucible/ containers at
temperature sufficient to effect reduction of iron ore to sponge iron while exiting
from kiln on a continuous basis; and
magnetic separator and screen to separate ash and unburnt carbon from sponge
iron of selective hollow cylindrical form.
In the above system the length of the tunnel kiln Is adjusted to meet the
production capacity of the unit. The tunnel Kiln could be as small as 25meters to
approx 220 meters with production capacity ranging from 5 MT Per Day to about
350 MT per day. Several tunnel kilns could be added in order to enhance capacity
as and when required.
Importantly, the above system of the invention which comprises of the tunnel kiln
having three zones comprising a preheating zone, a reduction zone and a cooling
zone with selective temperature control in the respective zones is adapted to
enable for the first time utilization of iron ore fines in generation of shaped
sponge iron. Such a system thus favours in making the shaped sponge iron is
much simpler and cost-effective.

The system of the invention includes heat transferable crucibles preferably
comprising silicon carbide crucibles.The said silicon carbide crucibles are found to
have required heat transfer property and a life of about 100-150 heat cycles.
In the above system of the invention, the said means for transfer the said
loaded crucibles through the tunnel kiln zones comprises tracks running
through the tunnel on which the crucible loaded car/vehicles are carried through
the tunnel zones.
Also, in the system of the invention , the burner ports are on the wall of the two
sides along the length direction of tunnel kiln and the fuel used in burners can be
producer gas or Furnace oil.
In the above system, the pre heating zone has a stack at the starting of the zone
which draws hot air through suction thereby supplying heat in the pre heating
zone from the heating zone to the pre heating zone for maintaining the
temperature requirement and thus optimum utilisation of energy.
Also in the above system there is provided at the discharge end screen for
screening purposes and magnetic separator to separate said ash from the sponge
iron produced.
In accordance with another aspect of the invention there is provided a method for
production of shaped sponge iron from composite iron ore involving the system
as above comprising the steps of
(i) providing the iron ore fines and said reductant;
(iii) selectively loading of the said iron ore and/or reducer coal in heat
transferable Crucible/container such as to generate desired shaped form of
sponge iron.
(iv) after loading of materials in crucible/containers, these filled
crucible/containers are loaded on trolley/cars for transfer of the said loaded
crucibles through the tunnel kiln zones the pre-heating zone , reduction zone and
cooling zone wherein the selectively loaded said iron ore and/or reducer coal are
(a) first pre-heated in said pre-heating zone in the temperature range of 100°C to
600°C (b) subjected to reduction in the reduction zone having a temperature in
the range of 850° to 1150°C and finally (c ) cooled in said cooling zone having a
temperature upto 100-200°C when at the discharge end of the tunnel;

(viii) unloading of thus reduced mix , screening and separating ash in magnetic
separator to finally obtain the sponge iron in selective shaped form.
According to a preferred aspect there is provided the method wherein for
producing the hollow cylindrical shaped sponge iron product the step of
selectively loading of the said iron ore and/or reducer coal in heat transferable
crucible/container comprises :
(a) providing (i) mix of iron ore fines and reductant preferably including coal
and limestone ;
(b)loading the said mix of iron ore fines with said reductant therebetween an
inner core of the coal with limestone and an outer layer of the coal with limestone
within said crucible in concentric circles.
According to a further aspect the method of the invention comprises the steps
of
(i) grinding and preparing iron ore fines and/or coal with limestone;
(ii) loading in said crucibles the said mix of iron ore fines with said reductant
therebetween an inner core of the coal with limestone and an outer layer of the
coal with limestone within said crucible in concentric circles;
(iii) loading of the thus filled crucibles on cars which are pushed preferably on
rails inside the furnace with the help of hydraulic pusher;
(iv) pre-heating of the filled crucible in preheating zone of the tunnel kiln to drive
away moisture from the mix;
(v) thereafter the loaded and thus pre- heated filled crucibles are allowed to
pass through the reduction zone in the temperature range of 850-1150 °C for
desired duration to remove all the oxides from the charge and generate the
selective hollow cylinder shaped sponge iron;
(vi) cooling the crucibles containing the shaped reduced ore in cooling zone for
the cooling of reduced material i.e Sponge Iron in hollow cylindrical form,
(viii) unloading of reduced product in crucible on the screen at discharge end for
screening purpose and separating ash in magnetic separator to finally obtain the
hollow cylindrical shaped sponge iron.
In the above method the said reducer coal preferably involves the size fraction
-0.1 mm to - 200 mesh and size of limestone is also same as the reducer coal.
Also according to an aspect in the above method the said filled crucibles are
pre-heated from 100°C to max 600°C to reduce the moisture of the material as

well as increase the temperature of the filled material to get faster reduction of
filled crucibles in next step.
In said cooling zone the temperature is reduced up to 200°C by air blowing just
to cool the crucibles such that by the time the crucible car leaves the tunnel
furnace it reaches 150 °C and is allowed for further cooling in bay beside the
furnace with a small covered shed with a vent connected to it.
After screening process, the ash is carried out on one conveyor and
shaped/hollow cylindrical shaped Sponge Iron on another conveyor.
At discharge and feed end, a moving trolley with rails is used to position the car
for feeding and removing it at discharge end.
The object and advantages of the present invention is described in greater details
with reference to the following accompanying non limiting illustrative drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is the schematic illustration of the Tunnel Kiln showing the different
zones inside the kiln wherein iron ore fines loaded in ceramic crucibles, are
reduced to produce Sponge iron in presence of redundant in a continuous
process.
Figure 2: is the schematic illustration of the siliconcarbide crucible/saggers in
which the iron or fines along with redundant anthracite and limestone is
selectively charged inside for desired reduction reaction to produce shaped
Sponge Iron in tunnel kiln.
Figure 3: is the flow diagram showing the detailed steps involved in the reduction
of iron ore fines filled in crucible in the form of concentric hollow cylinders for
reduction to sponge iron in Tunnel Kiln according to the process of the present
invention.
Figure 4: is the schematic arrangement of loading iron ore fines with reductant
coal fine and limestone fines in the form of concentric hollow cylinders inside the
siliconcarbide crucibles for charging inside the Tunnel Kiln on moving trolleys/car
on track.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
As discussed hereinbefore ,the present invention is directed to providing a system
and method for continuous process production of sponge iron in shaped form
from iron ore fines by reduction process inside Tunnel Kiln in a simple and cost
effective manner.
Reference is first invited to the accompanying Figure 1 that illustrates a
schematic diagram of the Tunnel Kiln for implementation of the process according
to the invention. Any Tunnel Kiln of conventional design such as coal fired Tunnel
kiln, Tunnel chamber kilns, oil fired or gas fired tunnel kiln and shuttle kilns can
be involved to carry out the iron ore reduction process to produce sponge iron on
continuous basis. The kiln should be adapted for firing cycles of 32 to 35 hrs. in
the temperature range preferably of 850°C to 1150°C. The iron ore and
redundant coal fine is packed inside siliconcarbide crucibles of selective sizes as
hollow cylinder for carrying out reduction reaction in tunnel kiln to produce
sponge iron. Accompanying Figure 2 shows the siliconcarbide crucibles
/containers used for the selective loading of iron ore fines along with coal and
lime stone for obtaining desired sponge iron of desired shape from the iron ore
fines reduced in tunnel kiln. Such crucibles are of selective sizes to accommodate
iron ore fines with coal fine and lime for carrying out reduction reaction in tunnel
kiln to produce hollow cylinder shaped sponge iron.
The construction of the furnace is very simple and can be and the length can be
designed to meet the Production Capacity. The special structure of long narrow
tunnel furnace makes it reliable for working. The life of tunnel furnace is
substantially long under the operating reduction temperature.
At discharge and feed end, a moving trolley with rails is provided to position the
car for feeding crucible/saggar with charge and removing sponge iron at
discharge end. Alongside the Tunnel furnace, one rail is there to bring Silicon
crucible car to unloading station and carry further empty car to filled crucible
station and then bringing to feed end for getting transferred by trolley to feed
filled crucible in the furnace.
The iron ore reduction process as of the present invention is carried out inside
the high speed reducing furnace. Suitable stable temperature and reduction time

of the furnace are the key Important aspects for producing Sponge Iron of
desired quality in the shape of hollow cylinders.
According to the present invention, Direct Reduced Iron (DRI) is produced with
the help of Tunnel Furnace system to produce shaped Sponge preferably the
hollow cylinder shaped sponge iron. Significant technological improvement and
innovation is effected in establishing a steady and reliable process to ensure
desired quality and yield. The method of reducing iron ore fines inside enclosed
crucible in the reducing furnace favour increased concentration and pressure of
the reducing ambience. This process uses HMI to control the temperature.
Reducing ambience is easy to control. So it is easy to maintain desired process
parameters to achieve steady and consistent product quality.
It is clearly apparent from the accompanying Figure 1 that the Tunnel Kiln is
divided into the following zones based on temperature range and functions served
- Preheating zone, Reducing Zone, Cooling zone, in between the entry and exit
openings of the tunnel.
Burner port is on the wall of the two sides along the length direction. Producer
gas or Furnace oil is used as fuel. To adjust the gas consumption by heating
curve of the furnace, the temperature inside the furnace should be controlled
within the specific limits. The normal temperature of the furnace's top is 950-
1180°C. For long narrow tunnel furnace, saggars/crucibles are put into the
furnace in succession, through preheating, reducing, heat preservation and slow-
cooling. The temperature and time of roasting is also easy to achieve. So tunnel
kiln process is easy to control.
Tunnel Furnace system involved in the process basically comprises the following
three processes:
a. Preparation of Material and Loading in Furnace
b. Heating Process
c. Unloading and screening of Sponge Iron hollow cylinders.
Accompanying Figure 3 illustrates the flow diagram showing the different steps
involved in the process of producing hollow cylindrical shaped sponge iron by
reduction of iron ore fines mixed with reducer coal fines/anthracite along with
limestone powder filled selectively in silicon crucible.

a. Preparation of raw material and Loading in Furnace:
This is the first step of Tunnel Furnace technology employed according to the
invention. In this step, the raw material is prepared and mixed. Coal should be of
80 fixed carbons (12% max ash) and the size fraction is -0.1 mm to - 200 mesh.
Size of limestone is same as that of the reducer coal. Reducer Coal and
Limestone with proper ratio are transferred from the bins through conveyor for
homogeneous mixing where mixing of Reducer Coal and limestone takes place.
After mixing, material is transferred to drying zone to reduce the moisture. With
the drying process, moisture will get reduced. Side by side Iron ore is discharged
from a separate bin.
Filling of the crucible with charge of iron ore fines and the reducer mix is carried
out following the steps of:
1. Iron Ore fines is mixed with reductant as desired.
2. For the purpose of generating the preferred shape of hollow cylindrical shaped
sponge iron , loading in crucibles is carried out in concentric circles wherein the
said mix of iron ore fines with said reductant is selectively done therebetween
an inner core of the coal with limestone and an outer layer of the coal with
limestone within said crucible in concentric circles thus defining a hollow
cylindrical shape of iron ore fines.
3. The Containers/ crucibles are then placed on the trolley and hydraulically
pushed inside the feed side of the Tunnel Kiln for reduction process.
These loaded crucibles are placed on a car which is on rail track and then moved
to the feed end of the tunnel kiln. Accompanying Figure 4 shows the
arrangement of loading of iron ore fines with redundants in the form of hollow
cylindrical shape inside the silicon carbide crucibles prior to charging in tunnel
furnace/kiln to generate the sponge iron of hollow cylindrical shape.
The above process can be done manually as well as mechanically.
The Containers/ crucibles are then placed on the trolley and hydraulically pushed
inside the feed side of the Tunnel Kiln for reduction process.

b. Heating Process:
This step is the main part of the reduction process to obtain Sponge Iron in the
form of hollow cylinders. Tunnel furnace is divided into three zones to complete
reduction process of iron ore.
• Preheating Zone:
After the entering of iron ore and reducer filled crucibles in furnace,
preheating zone begins and heating process starts taking place. In this
zone, the filled crucible are pre-heated in the temperature range from
100°C to max 600°C to reduce the moisture of the iron ore and reducer
materials. In this zone, temperature of the filled material is increased to
get faster reduction of filled crucibles in the next step.
• Reduction Zone:
After preheating process, Filled crucibles enter in reduction zone.
Temperature reaches in the range from 850°C to 1150°C. Reduction
Process means that reduction of the oxides. When the crucibles are
heated then iron ore which is filled in crucible get reduced with the
burning of coal. Reduction reactions are as given below:
2C + O2 -» 2CO
3 Fe2O3(s) + CO (g) -+ 2 Fe304(s) + CO2 (g)
Fe3O4(s) + CO (g) - 3 FeO(s) + CO2 (g)
FeO(s) + CO (g) — Fe(s) + CO2 (g)
a) Fe2O3 (Hematite)
b) Fe3O4 (Magnetite)
c) FeO (Wustite)
d) Fe (Pure Iron)
After completing these reactions and at the end of reduction process, the
Sponge Iron product of hollow cylindrical form is obtained.
The present process ensures high metallization. When the content of the
iron in the refined ore powder is more than 63%, the analysis of the
products is C>0.04%, S<0.01%, P<0.02%, SiO2<3%, MFe>80%,
TFe>86%.

• Cooling Zone:
Cooling zone is the third stage of Tunnel Furnace Technology. After
completion of reduction process, Crucibles with sponge iron products enter
in cooling zone, where the temperature is reduced up to 200°C. Cooling
zone is just to cool the crucible containing the products.
A blower is there at cooling zone which delivers air required to cool
crucibles and the air from blower is pre heated in the cooling Zone while
coming in contact with the hot crucibles and this hot air is used for
combustion of fuel at reducing zone to heat the furnace. The fuel used is
producer gas or Furnace oil, burnt through the burners mounted
selectively on side walls of the tunnel kiln. The hot off-gas is made to flow
through the preheating zone of furnace before they escape through a
chimney near the charging end of kiln.
By the time the crucible car leaves the tunnel furnace it is at 150 °C and it
is allowed for cooling in bay beside the furnace with a small covered shed
so that nobody touches it and there is a vent connected to it.
c. Unloading and Screening of Sponge Iron hollow cylinders;
After completion of cooling process, Sponge Iron hollow cylinders are ready to
leave the Tunnel Furnace. After further step of magnetic separation and
screening, unburnt carbon and ash will be separated from sponge iron product.
After screening process, the ash comes out on one conveyor and hollow
cylindrical shaped Sponge Iron on another conveyor. The separated sponge iron
product are transferred to covered product shed.
The system and method for continuous production of sponge iron using tunnel
kiln according to the present invention thus involve simple process steps as well
as simple equipments for producing Sponge Iron of hollow cylindrical shape using
iron ore fines and coal fines. The system comprises equipments like Tunnel Klin,
Trolley, Transition Car, Fans, Temperature Meter, Chimney and other simple
devices. The special structure of long narrow tunnel furnace makes it reliable for
working with longer furnace life under the reduction temperature. The process of

reducing the iron oxide in tunnel furnace involves chemical reactions under high
temperature. The reducing material is mainly CO2 and iron. There are no water
pollution and noise pollution and insignificant air pollution. The process is thus
environment friendly as compared to conventional rotary kiln based operations
for similar purposes existing in the art.
The system and method for production of sponge iron of hollow cylindrical shape
from Iron Ore Fines and Coal Fines using Tunnel Kiln/Furnace thus ensure a fast,
economic process with reliable quality of end product and has the potential for
wide scale application and use because of the following advantages over the
conventional Rotary Kiln based technology/process,
1) Low Project Cost.
2) Low Maintenace.
3) Longer furnace time as no accretion, so no shut-down process.
4) Low Labour requirement.
5) High metallization.
6) Utilization of Iron Ore Fines directly without any processing.
7) Low land requirement.
8) Easy Operation, no high skill requirement of technical team.
9) Higher Shelf life; as the Bulk density is High, so no reaction with water
resulting in no backward reaction (as in the case of Rotary Kiln).
It is thus possible by way of the above disclosed system and method of
continuous production of sponge iron from iron ore fines in Tunnel Kilns, in a
simple and cost effective manner to suit financing capabilities of small scale
sector in an energy efficient manner, replacing costly and complex rotary kiln
based reduction system. The system can be provided in remote locations where
there is scarcity or even no availability of power to meet the present day growing
demands of sponge iron in the Steel Industry. Importantly, the system is
workable to produce sponge iron from both the iron ore sources Hematite (Fe2O3)
and Magnetite (Fe3O4) and even favour utilization of iron ore fines which is
otherwise wasted. Importantly, the system and method for manufacture of
sponge iron is energy efficient and environment friendly, making the process and
system widely acceptable as cost effective alternative technology to medium scale
sponge iron producers.

We Claim:
1. A system for continuous production of sponge iron from iron ore comprising,
a tunnel kiln comprising a pre-heating zone with heating means to maintain a
temperature in the range of 100°C to 600°C , reduction zone having heating
means to maintain a temperature in the range of 850° to 1150°C and cooling
zone adapted to maintain a temperature of upto 100-200°C ;
a plurality of heat transferable crucibles/ containers adapted to be filled
selectively with iron ore fines and/or redundant such as to generate said
selective hollow cylindrical form of sponge iron;
means to transfer the said loaded heat transferable crucibles/ containers through
the said tunnel kiln zones the pre-heating zone , reduction zone and cooling zone
for desired duration to ensure atmospheric oxygen/air free contact of said iron
ore fines and/or reductant in said heat transferable crucible/ containers at
temperature sufficient to effect reduction of iron ore to sponge iron while exiting
from kiln on a continuous basis; and
magnetic separator and screen to separate ash and unburnt carbon from sponge
iron of selective hollow cylindrical form.
2. A system as claimed in claim 1 wherein said tunnel kiln is designed in length
breadth and height to meet the requirement of production capacity.
3. A system as claimed in anyone of claims 1 to 2 wherein said heat transferable
crucibles comprise silicon carbide crucibles.
4. A system as claimed in claim 3 wherein said silicon carbide crucibles have
required heat transfer property and a life of about 100-150 heats.
5. A system as claimed in anyone of claims 1 to 4 wherein said means for
transfer the said loaded crucibles through the tunnel kiln zones comprises
tracks running through the tunnel on which the crucible loaded car/vehicles are
carried through the tunnel zones.

6. A system as claimed in anyone of claims 1 to 5, wherein burner ports are on
the wall of the two sides along the length direction of tunnel kiln and the fuel
used in burners is producer gas or Furnace oil.
7. A system as claimed in anyone of claims 1 to 6, wherein an air blower is
provided at cooling zone so that the air is so that hot air is drawn from heating
zone to pre heating zone and is used for combustion of fuel to heat the furnace.
8. A system as claimed in anyone of claims 1 to 7 comprising at the discharge
end screen for screening purposes and magnetic separator to separate said ash
from the sponge iron produced.
9. A method for production of sponge iron from iron ore fines involving the
system as claimed in anyone of claims 1 to 8 comprising the steps of
(i) providing the iron ore fines and said reductant in desired proportions;
(iii) selectively loading of the said iron ore and/or reducer coal in heat
transferable Crucible/container such as to generate the selective hollow
cylindrical form of sponge iron.
(iv) after loading of materials in crucible/containers, these filled
crucible/containers are loaded on trolley means/cars for transfer the said loaded
crucibles through the tunnel kiln zones the pre-heating zone , reduction zone and
cooling zone wherein the selectively loaded said iron ore and/or reducer coal are
(a) first pre-heated in said pre-heating zone in the temperature range of 100°C to
600°C (b) subjected to reduction in the reduction zone having a temperature in
the range of 850° to 1150°C and finally (c ) cooled in said cooling zone having a
temperature upto 200°C
(viii) unloading of thus reduced mix , screening and separating ash in magnetic
separator to finally obtain the sponge iron in selective hollow cylindrical form.
10.A method as claimed in claim 9 wherein for producing the hollow cylindrical
shaped sponge iron product the step of selectively loading of the said iron ore
and/or reducer coal in heat transferable crucible/container comprises :
(a) providing (i) mix of iron ore fines and reductant preferably including coal
and limestone ;
(b)loading the said mix of iron ore fines with said reductant therebetween an
inner core of the coal with limestone and an outer layer of the coal with limestone
within said crucible in concentric circles.
11. A method as claimed in anyone of claims 9 or 10 comprising the steps of

(i) grinding and preparing iron ore fines and/or coal with limestone;
(ii) loading in said crucibles the said mix of iron ore fines with said reductant
therebetween an inner core of the coal with limestone and an outer layer of the
coal with limestone within said crucible in concentric circles;
(iii) loading of the thus filled crucibles on cars which are pushed preferably on
rails inside the furnace with the help of hydraulic pusher;
(iv) pre-heating of the filled crucible in preheating zone of the tunnel kiln to drive
away moisture from the mix;
(v) thereafter the loaded and thus pre- heated filled crucibles are allowed to
pass through the reduction zone in the temperature range of 850-1150 °C for
desired duration to remove all the oxides from the charge and generate the
selective hollow cylinder shaped sponge iron;
(vi) cooling the crucibles containing the shaped reduced ore in cooling zone for
the cooling of reduced material i.e Sponge Iron in hollow cylindrical form,
(viii) unloading of reduced product in crucible on the screen at discharge end for
screening purpose and separating ash in magnetic separator to finally obtain the
hollow cylindrical shaped sponge iron.
12. A method as claimed in anyone of claims 9 to 11, wherein said reducer coal
comprise of 80 fixed carbons (12% max ash) and the size fraction is -0.1 mm to
- 200 mesh and size of limestone is also same as the reducer coal.
13. A method as claimed in anyone of claims 9 to 12 wherein said filled crucibles
are pre-heated from 100°C to max 600°C to reduce the moisture of the material
as well as increase the temperature of the filled material to get faster reduction
of filled crucibles in next step.
14. A method as claimed in anyone of claims 9 to 13 wherein in said cooling
zone the temperature is reduced up to 200°C by air blowing just to cool the
crucibles such that by the time the crucible car leaves the tunnel furnace it
reaches 150 °C and is allowed for further cooling in bay beside the furnace with a
small covered shed with a vent connected to it.
15. A method as claimed in anyone of claims 9 to 14, wherein after screening
process, the ash is carried out on one conveyor and hollow cylindrical shaped
Sponge Iron on another conveyor.
16. A method as claimed in anyone of claims 9 to 14 wherein said iron ore fines
with reducer coal/ carbon disposed therebetween the outer and inner concentric

layers of the reductant in the silicon carbide crucible favour production of shaped
sponge iron with inherent carbon.
17. A method as claimed in anyone of claims 9 to 16, wherein at discharge and
feed end, a moving trolley with rails is used to position the car for feeding and
removing it at discharge end.
18. Shaped sponge iron with inherent coke produced by the process as claimed in
anyone of claims 9 to 17 comprising:
Hollow cylindrical shaped sponge iron :with Fe(Metalic) 79 to 83% by wt.
Carbon: 0.5 to 1 % by wt.
19. A system for continuous production of sponge iron from iron ore fines and a
method producing the same substantially as hereindescribed with reference to the
accompanying drawings.

A system and method for continuous production of Sponge Iron from iron ore
fines in a Tunnel Kiln is disclosed. The system and process of manufacture of
Sponge Iron from Iron Ore is cost effective, energy efficient and environment
friendly adapted to be used even in remote locations with scarcity or even no
power supply. The iron ore fines are packed in siliconcarbide crucible/saggers to
generate shape preferably hollow cylindrical shape and adapted for reduction
alongwith surrounding cover of reductant such as coal or coke fines/ limestone
and heated in tunnel kiln so as to ensure compact and atmospheric oxygen/air
free contact of said iron ore and reductant in said containers inside the kiln at a
temperature range of 850-1150°C sufficient to thereby effect the reduction of iron
ore to sponge iron in the form of hollow cylinders, with reduced energy
consumption and reducing the cost of production.