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. , in
particular, is directed to simple system and continuous process of manufacture
Sponge Iron from Iron Ore fines using a tunnel kiln 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 save energy and also reduces 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.
Indian Patent no. 206196 discloses 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 900-1180cC, 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
The basic object of the present invention is thus directed to provide a simple and
cost effective system and method for continuous production of sponge iron from
iron ore fines in the form of green pellets and yet avoiding the cost-extensive
and complex process of induration/ Heating of Green Pellets of Iron Ore as is
conventionally done to make it suitable for charging in the Rotary Kilns.

Another object of the present invention is directed to a system and method for
continuous production of sponge iron from iron ore fines obtained in the form of
pellets/briquettes which would be convenient to operate/use and can be carried
out in remote locations for wide scale cost effective manufacture of Sponge Iron
to meet the present day growing demands of sponge iron in the Steel Industry.
A further object of the present invention is to provide a system and method for
continuous production of sponge iron in tunnel kiln involving Iron Ore fines i.e
less than 5 mm size obtained in the form of green pellets/ briquettes which would
be relatively cheaper than Iron Ore lumps.
Another object of the present invention is directed to providing a system and
method for continuous production of sponge iron from iron ore fines obtained in
the form of pellets which would be compatible to generate sponge iron involving
very simple and less expensive equipments which would be user friendly.
A still further object of the present invention is directed to providing a system and
method for continuous production of sponge iron involving composite
pellets/briquettes prepared from iron ore fines for better yield or improving
Metallic Iron in the Sponge Iron at a lesser cost and energy efficiency.
A still further object of the present invention is directed to providing a system and
method for continuous production of sponge iron from iron ore obtained in the
form of pellets and involving Tunnel kiln technology which would be relatively
cheaper and environmental friendly as compared to the Rotary Kiln based
manufacturing of sponge Iron from pellets.
A still further object of the present invention is directed to provide for a system
and the method for continuous production of sponge iron from iron ore fines
involving composite pellets/briquettes which would be simple and cost effective
and at the same time workable to produce sponge iron from both Hematite
(Fe2O3) and Magnetite (Fe3O4) based iron ore sources.
Another object of the present invention is to provide for a system and method for
continuous production of sponge iron from iron ore involving composite
pellets/briquettes 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 the form of
composite pellets/briquettes involving less risk by way of smaller charge and also
adapted for generation of sponge iron from low cost iron ore 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 and
waste 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 from iron ore fines involving composite
pellets/briquettes which would yield greater realization value in terms of
conversion of cost effective 0-5 mm size Iron ore fines as compared to 5-18 mm
size of Iron Ore.
A further object of the present invention is directed to a method of generation of
sponge iron from iron ore in composite pellet/ briquette form which would further
enable the 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.
An yet further object of the invention is directed to a system and method for
continuous production of Sponge Iron involving composite pellets/briquettes
which would enable advantageous utilization of cost effective labour in lieu of
capital and cost extensive power consumption in remote locations having scarcity
of power and skilled manpower.
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 with mix
of iron ore in the form of green composite pellets/briquettes and reductant in
desired proportions ;
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 pellet/briquettes and reductant in said heat transferable crucible/ containers
at temperature sufficient to effect reduction of iron ore pellets 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 pellets/ briquettes.
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 green pellets/briquettes of iron ore in
generation of sponge iron without the need for indurations/heating of the soft
pellet before being introduced in the furnace. Such a system thus favours in
making the sponge iron much simpler and cost-effective and avoiding the
complex induration process of green pellets usually followed in the art. The
process of indurating green pellets is not only capital intensive but energy
consuming as the temperature for pellet making needs to be raised to 1000-
1100 deg.
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
up toabout 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.
Preferably, the system includes heat transferable crucibles comprising of silicon
carbide crucibles. Advantageously, the said silicon carbide crucibles have
required heat transfer property and a life of about 100-150 heat cycles.
In accordance with another aspect of the invention , the system includes said
means for transfer the said loaded crucibles through the tunnel kiln zones

comprising tracks running through the tunnel on which the crucible loaded
car/vehicles are carried through the tunnel zones.
Also, in the above system the burner ports are preferably 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.
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.
According to a further aspect of the invention, the system comprises at the
discharge end screen for screening purposes and magnetic separator to separate
said ash from the sponge iron pellets/briquettes.
According to another aspect of the invention there is provided a method for
production of sponge iron from iron ore involving the system as above
comprising the steps of
(i) providing the iron ore in the form of pellets/briquettes alongwith said
reductant in desired proportions;
(ii) manually loading of mix of the said iron ore in the form of pellets/briquettes
adapted to favour the reduction in said system in combination with reducer coal
and limestone in heat transferable Crucible/container .
(iii) after filling of the formed pellets /briquettes in crucible/containers, these
filled crucible/containers are loaded on said means on cars/ trolleys for transfer
of the said loaded crucibles through the tunnel kiln zones wherein the said
formed pellets/briquettes are subjected to simple steps of pre-heating,
reduction and cooling whereby the thus formed pellets/briquettes 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;
(iv) unloading of reduced mix , screening and separating ash in magnetic
separator to finally obtain the sponge iron.
In accordance with a preferred aspect of the invention in the above method the
provision of said iron ore in the form of pellets/briquettes adapted to favour the
reduction in said system in combination with reducer coal and limestone in heat
transferable Crucible/container in proper ratio comprise providing simply green

soft pellets/briquettes of iron ore which can be directly loaded for reduction
process free of any cost-extensive hardening and wherein in said tunnel kiln pre-
heating zone the green pellets/briquettes get suitably formed to favour the
subsequent reduction in the reduction zone.
According to yet another preferred aspect the method comprises the steps of
(i) grinding and preparing iron ore fines and reductant into said green
pellets/briquettes using disc pelletizer/ Briquetting Machine.
(ii) mixing reducer coal and lime stones as per requirement and transferring to
loading section;
(iii) loading of Iron ore green pellets/briquettes and mix of reducer coal and
limestone in Silicon Crucible in proper ratio.
(iv) loading of the filled crucibles on cars which are pushed preferably on rails
inside the furnace with the help of hydraulic pusher;
(v) pre-heating of the filled crucible in preheating zone of the tunnel kiln to drive
away moisture from the mix;
(vi) thereafter the loaded and thus pre- heated pellet/briquettes 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;
(vii) cooling the crucibles contained the reduced ore in cooling zone for the
cooling of reduced material i.e Sponge Iron in Pellets/briquettes form.
(viii) unloading of reduced product in crucible on the screen at discharge end for
screening purpose and separating ash in magnetic separator.
In the above method , said green pellets comprise iron ore fines with reducer
coal/ carbon and are obtained in a pelletiser and the pellets thus are further
mixed with some coal fines and then filled in the silicon carbide crucible such as
to favour production of sponge iron with inherent carbon.
Advantageously, the present process for generation of sponge iron from soft
pellet/briquette of iron ore and coal/carbon combination leads to the sponge iron
with inherent carbon is desirable for melting in the induction furnaces and
electric arc furnaces because of inherent carbon which reduces the requirement
of Pig Iron or Calcifined Pet coke.
The reducer coal used in the pellet process comprises 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.

Advantageously, 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.
Also, after screening process, the ash is carried out on one conveyor and
spherical Sponge Iron Pellets/ Briquettes 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 objects and advantages of the present invention is described hereunder 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 system illustrating the
different zones inside the kiln which benefit the advantageous involvement of
green pellet/briquettes in the sponge iron generation in accordance with the
present invention.
Figure 2: is the schematic illustration of the silicon carbide crucible/saggers in
which the iron ore fines formed as green pellets /briquettes along with redundant
can be advantageously charged inside the Tunnel Kiln on trolleys for desired pre-
heating followed by reduction reaction to produce Sponge Iron.
Figure 3: is the flow diagram showing the detailed steps involved in the reduction
of composite iron ore green pellets inside Tunnel Kiln system in accordance with
the present invention.
Figure 4: is the schematic arrangement of loading iron ore fines with reductant
coal fine in the form of green pellets inside the silicon carbide crucibles for
charging inside the Tunnel Kiln.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention is thus directed to providing a system and method for
continuous process production of sponge iron from iron ore fines obtained in the
form of pellets/briquettes by reduction process inside Tunnel Kiln in a simple and
cost effective manner.In particular, the system of the invention enables carrying
out a simple method of direct reduction of iron ore wherein mixed charge of iron
ore fines in the form of composite green pellets and reductant coal fines along
with other ingredients like limestone / dolomite etc. following a process of pre-
heating in the presence of a reductant inside the Kiln and thereafter subjected to
reduction ensuring compact and atmospheric oxygen / air free contact of said iron
ore and reductant in said crucibles in the kiln at a defined temperature range
sufficient to thereby effect the reduction of composite pellets to sponge iron.
Reference is first invited to the accompanying Figure 1 that illustrates a
schematic diagram of an embodiment of the Tunnel Kiln system provided for
implementation of the process according to the invention and in particular
providing for the possible beneficial use of iron ore in pellet/briquette form
without the require induration favouring generation of sponge iron. The Tunnel
Kiln with the defined temperature based zones for pre heating, reduction and
cooling according to the invention can be of variety of 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 45 hrs. in the temperature range preferably of 850°C to 1150°C. The iron
ore green pellets and redundant coal fine are packed inside siliconcarbide
crucibles of selective sizes as composite green pellet for carrying out reduction
reaction in tunnel kiln to produce sponge iron.
Accompanying Figure 2 shows the siliconcarbide crucibles /containers for loading
of composite pellets for reducing in tunnel kiln. Such crucibles are preferably
Designed depending on the dimensions and the tunnel kiln and raw materials
required.
The construction of the furnace is very simple 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 pellets/
briquettes of desired quality.
According to the present invention, Direct Reduced Iron (DRI) is produced
involving Tunnel Furnace Technology, with 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 composite pellets
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 for
the purposes of the invention and its desired end objectives 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 provided 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.

The method of producing sponge iron from iron ore in pellet/briquette form
involving the Tunnel Furnace system based advancement according to the
invention thus comprises the following three basic stages :
a. Preparation of Material and Loading in Furnace
b. Heating Process
c. Unloading and screening of Sponge Iron Pellets/ Briquettes.
Accompanying Figure 3 illustrates the flow diagram showing the different steps
involved in the process of producing sponge iron by reduction of composite
pellets of iron ore fines alongwith reducer coal fines along with limestone powder.
a. Preparation of raw material and Loading in Furnace:
This is the first step of Tunnel Furnace system employed according to the
invention. In this step, the raw material is prepared and mixed. Iron ore fines
and high fixed carbon coal of less than 10mm will be discharged from bin and
grinded to size of 100-200 microns and some moisture and appropriate binding
material is added and made into Green Iron Ore Pellets/Briquettes using a disc
pelletizer/ Briquetting Machine.
In this step soft green pellets of iron ore are obtained alongwith reductant which
selectively and advantageously avoids the complex hardening of pellets and
assist in advantageous direct reduction in the system according to the present
invention. Coal involves the size fraction of -0.1 mm to - 200 mesh. Size of
limestone is also preferably 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.
Thereafter the Green Iron Ore pellets are mixed with the coal and Limestone
powder and loaded inside the silicon crucible. 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 the composite
pellets inside the silicon carbide crucibles prior to charging in tunnel furnace/kiln.
The process of loading and preparation of composite pellets thus comprises the
following steps:

1. Iron Ore fines is mixed with reductant carbon/coal.
2. Some moisture is added to the mix and is sent to a disc pelletizer for making
green pellets with the help of a binder.
3. The green pellets from the disc pelletizer are further mixed with some coal
fines in a certain proportion and then filled in the silicon carbide saggar/ crucible.
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 get Sponge Iron Pellets/
Briquettes. 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 composite green pellet
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:


After completing these reactions and at the end of reduction process, the
Sponge Iron Pellets/ Briquettes product 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 Pellets/ Briquettes:
After completion of cooling process, Sponge Iron Pellets/ Briquettes 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 spherical
Sponge Iron Pellets/ Briquettes 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 Pellets/ Briquettes 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 pellets/briquettes from
Iron Ore Fines and Coal Fines involving Tunnel Kiln/Furnace system 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 in Tunnel Kiln system involving iron ore
green pellets and mix of coal fines and limestone, in a simple and cost effective
manner to suit financing capabilities of small scale sector avoiding the need for
indurating the green pellets at the expense of extra energy thus meeting the
large scale present day demand of sponge iron 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 and waste in generation of sponge iron. 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 small 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 with mix
of iron ore in the form of green pellets/briquettes and reductant in desired
proportions ;
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 pellet/briquettes and reductant in said heat transferable crucible/ containers
at temperature sufficient to effect reduction of iron ore pellets 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.
2. A system as claimed in claim 1, wherein said tunnel kiln is designed in length
breadth and height to meet the reqirement 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 pellets/briquettes.
9. A method for production of sponge iron from composite iron ore pellets/
briquettes involving the system as claimed in anyone of claims 1 to 8 comprising
the steps of
(i) providing the iron ore in the form of pellets/briquettes alongwith reductant;
(ii) loading of mix of the said iron ore in the form of pellets/briquettes adapted
to favour the reduction in said system in combination with reductant including
selectively reducer coal and limestone in heat transferable Crucible/container .
(iii) after filling of the formed pellets /briquettes in crucible/containers, these
filled crucible/containers are carried on said means for transfer the said loaded
crucibles through the tunnel kiln zones wherein the said formed pellets/briquettes
are subjected to simple steps of pre-heating , reduction and cooling whereby
the thus formed pellets/briquettes 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;
(iv) unloading of reduced mix , screening and separating ash in magnetic
separator to finally obtain the sponge iron.
10.A method as claimed in claim 9 wherein the said iron ore in the form of
pellets/briquettes adapted to favour the reduction in said system in combination
with reducer coal and limestone in heat transferable Crucible/container
comprise green soft iron ore pellets/briquettes which can be directly loaded for
reduction process free of any cost-extensive hardening wherein in said tunnel kiln
system pre-heating zone the green pellets/briquettes get suitably pre-heated to
favour the subsequent reduction in the reduction zone.

11. A method as claimed in anyone of claims 9 or 10 comprising the steps of
(i) grinding and preparing iron ore fines and reductant into said green
pellets/briquettes using disc pelletizer/ Briquetting Machine.
(ii) mixing reducer coal and lime stones as per requirement and transferring to
loading section;
(iii) loading of Iron ore green pellets/briquettes and mix of reducer coal and
limestone in Silicon Crucible in proper ratio.
(iv) loading of the filled crucibles on cars which are pushed preferably on rails
inside the furnace;
(v) pre-heating of the pellet/briquette filled crucible in preheating zone of the
tunnel kiln to drive away moisture from the mix;
(vi) thereafter the loaded and thus pre- heated pellet/briquettes 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;
(vii) cooling the crucibles contained the reduced ore in cooling zone for the
cooling of reduced material i.e Sponge Iron in Pellets/briquettes form.
(viii) unloading of reduced product in crucible on the screen at discharge end for
screening purpose and separating ash in magnetic separator.
12. A method as claimed in anyone of claims 9 or 10 wherein said green pellets
comprise iron ore fines with reducer coal/ carbon and are obtained in a pelletiser
and the pellets thus are further mixed with some coal fines and then filled in the
silicon carbide crucible such as to favour production of sponge iron with inherent
carbon.
13. A method as claimed in anyone of claims 9 to 11, wherein said reducer coal
comprise of size fraction is -0.1 mm to - 200 mesh and size of limestone being
also same as the reducer coal.
14. 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.
15. 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.
16. A method as claimed in anyone of claims 9 to 14, wherein after screening
process, the ash is carried out on one conveyor and spherical Sponge Iron
Pellets/ Briquettes on another conveyor.
17. A method as claimed in anyone of claims 9 to 15, 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. Sponge iron with inherent coke produced by the process as claimed in anyone
of claims 9 to 16 comprising:
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 composite iron ore
pellets and a method of producing the same substantially as hereindescribed with
reference to the accompanying drawings.

A system and continuous process of manufacturing of Sponge Iron from iron ore
fines as composite Pellets 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 manner adapted to be used even in remote locations with
scarcity or even no power supply. The iron ore in the form of composite pellets
and adapted for reduction alongwith reductant such as coal or coke fines and
limestone are packed in siliconcarbide crucibles/containers/saggars and heated in
said kiln so as to ensure compact and atmospheric oxygen/air free contact of said
iron ore and reductant in said containers in the kiln at temperature range of 850-
1150°C sufficient to thereby effect the reduction of iron ore to sponge iron in the
form of pellets/briquettes without induration/ Heating of Pellets of Iron Ore saving
energy and reducing the cost of production.