The present invention relates to an improved method of producing sponge
iron by reduction of iron ore fines by non-coking coal. More particularly, this
invention pertains to production of sponge iron from iron ore fines generated in
the course of mining as well as sizing for production of sponge iron, and
specifically in the course of removing oxygen from the iron ore fines through
fluidised bed route.
It is known that iron ore occurs in nature mainly as iron oxide which is a
chemical compound of iron and oxygen and the reducing agents generally used
for reduction of iron ores are hydrogen and carbon monoxide. The product
produced by the reduction of iron ores in the solid state is known as 'direct
reduced iron', commonly known as "sponge iron". The sponge iron is generally
produced by the reduction of iron ore lumps either in a rotary kiln or in a shaft
furnace.
Iron ores are first crushed to the size range +5 mm - 15 mm. and then fed
into rotary kiln for reduction. Crushing of iron ore produces a sizable amount of
-5 mm, function (iron ore fines). Iron ore of this size fraction cannot be effectively
utilized as they tend to fuse with the ash of coal and form rings (accretions) at
various places along the length of the kiln. These rings or accretions hinder the
passage of material and a reduction in productivity. These fines require costly
grinding and pelletization for making them suitable as a raw material for sponge
iron making. Moreover, the tumbling action of the rotary kiln prevents the usage
of pellets of low strength. Therefore, the usability of mined ore is considerably
low in a sponge iron manufacturing set-up.
Presently some methods have been developed for the reduction of iron ore
fines using fluidised beds. Current methods for reduction of iron ore fines by
coal fines into a gasifier from where the ore and coal mix is subsequently
transferred into a circulating fluidised bed reactor. This method is not sufficiently
effective due to high operating temperature required for gasification and
reduction as well as due to the low fusion temperature of composite coal ash and
reduced iron ore fines. Further, this method results in sticking of the composite
on the walls of the reactor. The problem becomes more acute in the case of coal
having higher ash content and lower ash fusion temperature.

It has also been reported that Lurgi Metallurgic GmbH, a German Company,
is in the process of developing a process called "CIRCOFER", but it is still to be
implemented on a commercial scale.
In order to overcome the problems enumerated above, the present invention
provides a method of reducing iron ore fines of 5 mm. size generated during the
course of mining as well as sizing during crushing. This improved method,
according to the invention leads to an effective yield of sponge iron per ton of
iron ore mined or used for sizing.
The present invention provides an improved method of producing sponge
iron by reduction of iron ore fines by non-coking coal, which comprises in
combination the steps of -
a) feeding iron ore fines and char into a circulating fluidized bed reactor
(stage-I) in a ratio of around 2 to 3 ;
by passing gas from the bubbling bed reactor (stage-II) as reducing-cum-
fiuidising medium to form fluidized partially reduced solids ;
c) allowing the fluidized partially reduced solids to flow from internal down-
comers of said circulating fluidized bed reactor to said bubbling bed reactor
wherein the bed is converted into semi-fluidised state by the hot gases
from a coal gasifier at a temperature less than around 900°C where
reduction continues till completion ;
d) cooling the sponge iron fines and char with water, and
e) subjecting the partially cooled mixture obtained from step (d) to continuous
separation by a hot magnetic separator to separate magnetic sponge iron
from non-magnetic materials.
The essential features of the improved method are as follows :
(i) separation of the coal gasifier and the fludised bed reactor into two separate
units and charging the iron ore fines into the fludised bed reactor so that
the coal ash and iron ore fines do not mix to form a low fusion mixture.
(ii) Reduction of the fluidised bed reactor operating temperature by generating and
utilizing a gaseous mixture of hydrogen and carbon monoxide as the reducing agent.
(iii) Conservation of energy by using a composite reactor comprising the twin stage
reduction reactor with internal down-comer for solid flow and the gasifier one above
the other.
(iv) Maximisation of crushing and sizing requirement of iron by using a fluid bed reactor
designed to accept iron ore fines of a wide size range.

(v) Regulation of inpu or oxygen at all stages of the reactors in order to supplement the
energy requirement at individual stages and maintain required temperature.
(vi) Prevention of re-oxidation of sponge iron by indirectly cooling the sponge iron
fines and char with water, removal of char fines by a hot magnetic separator and
hot briquetting the sponge iron fines in the absence of air.
Description of the invented method :
Iron ore fines and char in a precalculated ratio is fed into the circulating fludised
bed reactor (stage 1) where the gas from the bubbling bed (semi-fluidised) reactor (stage-
II) is used as a fluidised medium, the operating temperature maintained is - 800°C.
Fluidised partially reduced solids flow through the down-comers from said
circulating fluidised bed reactor to said bubbling bed reactor (stage-II) where the bed is
semi-fluidised by the hot gases from the gasifier when the temperature maintained is
- 900°C. and the reduction here is continued till it is complete. The reduced solids
continuously pass out at a regulated rate to a hot magnetic separator where char and

magnetics are separated and the hot gases from said bubbling bed reactor enter into said
circulating fludised bed reactor (stagc-I).
The reduction cum fluidization gas used in bubbling bed reactor (stage-II) is
generated in a gasifier where solid coal is gasified by recycled gas, which is also the
main'component of the fludising medium. Oxygen and steam are admitted to the
circulating fluid bed gasifier in order to facilitate both gasification and meet energy
requirement.
Gas Circulation
The exit gas from stage-I of the reactor is at a temperature of - 800°C. This gas is
passed through a hot heat exchanger to pre-heat the boosted recirculating gas to the
gasifier. The gas next goes to a preheating cyclone where it preheats the feed iron ore
fines and char. The exit gas from this cyclone then enters into a boiler and is considerably
cooled. The dust content of the gas is removed in a core separator and the clean gas is
subjected to scrubbing to partially remove CO2,SO2 The clean gas is then heated in the
hot heat exchange before being sent to the gasifier. The excess gas which is not utilized
in the circuit is flared out.
Throughout the description made above, the sign ' —' whenever used means less
than words or figures put before and the sign '+' means more than similarly.
We claim :
1. An improved method of producing sponge iron by reduction of iron ore
fines by non-coking coal, which comprises in combination the steps of:
a) feeding iron ore fines and char into a circulating fluidised bed reactor
(stage-I) in a ratio of around 2 to 3 ;
b) passing gas from the bubbling bed reactor (stage-II) as reducing-
cum-fludising medium to form fludized partially reduced solids ;
c) allowing the fluidized partially reduced solids to flow fom internal
down-comers of said circulating fluidized bed reactor to said bubbling
bed reactor wherein the bed is converted into semi-fluidised state
by the hot gases from a coal gasifier at a temperatue less than
around 900°C where reduction continues till completion ;
d) cooling the sponge iron fines and char with water, and
e) subjecting the partially cooled mixture obtained fom step (d) to
continuous separation by a hot magnetic separator to separate
magnetic sponge iron from non-magnetic mateials.
2. A method as claimed in Claim 1, wherein said reduction cum fluidisation
gas is generated in said gasifier where solid coal is gasified by the recycled
gas, the said gas being also the main component of the fluidising medium.
3. A method as claimed in Claims 1 and 2, wherein the exit gas from stage-I
of the reactor is at a temperature of less than around 800°C.
4. A method as claimed in Claims 1 to 3, wherein oxygen and steam are
admitted to said gasifier for facilitating gasification.
5. An improved method of producing sponge iron by reduction of iron ore
fines by non-coking coal, substantially as hereinbefore described and illustrated
in the accompanying drawings.

The invention relates to an improved method of producing sponge iron by reduction of
iron ore fines by non cooking coal. More particularly this invention pertains to production
of sponge iron from iron ore fines generated in course of mining as well as sizing for
production of sponge iron.