FIELD OF THE INVENTION
The present invention relates to a process of increasing productivity/yield of sintering
machine and improving quality of sinter product and apparatus/system to carryout such
process. More particularly, the process is directed to faster iron ore sintering process that
would improve sinter quality in terms of sinter strength, reduction degradation index (RDI)
decreased from existing 33.1 to 23.3, increased air filtration velocity due to increased
permeability, increased heat capacity of ambient air by preferred injection of steam at
selective pressure and quantity at selective location along the bed length, preferably
humidity adjusted to about 80gm/Nm3 and the injection region is about 3/4th of the length
of bed from the charging end, decrease in iron fines in sinter product. Importantly, the
present process will also help in reducing the coke rate in iron-ore sintering process,
reducing the carbon monoxide emission in sinter exhaust gases and reduction in exhauster
power consumption by about 5%. The present process and system thereof is thus adapted
to carry out the sintering to improve quality with reduced RDI and higher reducibility of
sinter in a faster way, having wide industrial application in steel plants.
BACKGROUND ART
The process of sintering is essentially carried out in the steel industry for converting iron ore
fines to lumps or briquettes such as to favour feeding to BF operation as the main iron
bearing charge. In the sintering plant, iron sintering is carried out on a moving conveyor
bed on which mixed ingredients comprising iron ore fines, coke fines, limestone fines and
various iron and flux bearing materials like flue dust, slag etc. commonly known as the
sinter mix are charged at one end of the moving bed. The top layer of the sinter mix on the
moving bed is ignited by gas burners installed at suitable locations. Ambient air required for
the combustion of sinter mix, is sucked in through the sinter bed from top into the wind
boxes, installed below the bed, by the operation of an exhauster fan. The variable factors
that influence the productivity of the sintering machine are the rate of airflow through the
sinter bed (m3/min) and the heat capacities of the gas and sinter mix. The rate of airflow is
not uniform through out the length of the bed. It is ideally low ranging between 50-70% of
the sinter machine length.
Conventionally, to increase the sinter machine productivity, under grate suction is increased
introducing an exhauster of higher suction capacity and providing better sealing for
gases/air leakage. This results in higher volumetric flow rate of air through the moving bed
2

for sintering. An alternative method of increasing productivity of sintering machine, the
heat capacity of the air is effectively increased by injecting steam through the bed in the
50-70% range of the machine bed length, such that the vertical sintering speed of mix
across the depth of bed is also increased as the exchange of heat between the mix and the
humidified air is more.
The airflow rate usually need not be lowest between 50-70% of the machine length. It will
depend on the position along the sinter bed at which the burn raise point is achieved.
Generally, it is in the region of where the wind box temperature is around 100°C. This is
possibly occurring in the 60-80% of the sinter machine bed length. The pressure at which
the steam is required to be injected and the quantity of steam required to be controlled
depending on the humidity in the ambient air.
In our co-pending application for Patent no. 188/KOL/2006 dated 07.03.2006 entitled "A
process for sintering iron ore adapted for faster sintering and higher productivity" there is
disclosed a process for improving quality of sinter and productivity of the sintering plant.
While such co-pending application did disclose the possible increasing of the heat capacity of
the air during sintering by humidification of air by steam injection, there has been the
continuing need in the art to improve efficiency of sintering and making sintering faster and
cost-effective.
In particular, there has been a need to develop a sintering process which would provide
desired quality and productivity of sinter product in the sintering machine/plant, by effecting
higher under grate air suction and steam injection at selective location at desired pressure
and quantity to increase the heat capacity of combustion air on one hand and at the same
time reduce the carbon monoxide emission (of CO) in exhaust gases and thereby reducing
the power consumption of exhauster, on the other hand. The present invention is a
technical advancement over the prior art in a sense that it is directed to a process to
improve the sinter quality in terms of higher strength and RDI for better utilization of the
sinter product in the subsequent BF operation and also in reducing the coke rate in iron-ore
sintering process, favoring improved reducibility of the resulting sinter.
3

OBJECTS OF THE INVENTION:
The basic object of the present invention is therefore directed to a faster process for iron
ore sintering for improving productivity and quality of sinter and a system/apparatus to
carry out such process, by selective injection of steam through sinter mix along with
ambient air at preferred location sucked through sinter bed to increase heat capacity of
moisturized air and thereby improving the vertical speed of sintering improving the
productivity, yield and quality of sinter produced in sintering machine.
A further object of the present invention is directed to a faster process of sintering for
improving the productivity and quality of sinter produced in sintering machine, achieving
increased air filtration velocity by about 20% due to increased bed permeability.
A further object of the present invention is directed to a faster process of sintering for
improving the productivity and quality of sinter produced in sintering machine, wherein said
steam injection is carried out at selective pressure and controlled quantity to ensure
characteristics of the resulting sinter in terms of improved strength or reduction in
Reduction Degradation Index (RDI) and wherein the steam spray is adapted to be stopped
with the stoppage of machine.
A further object of the present invention is directed to a faster process of sintering for
improving the productivity and quality of sinter produced in sintering machine, wherein a
steam trap is provided in the line to collect and eliminate the condensate from the steam.
A still further object of the present invention is directed to a faster process of sintering for
improving the productivity and quality of sinter, wherein the process is capable to achieve
significant decrease in sinter fines ranging about 5-7% in the final sinter product, favoring
increased yield of sintered ore.
A further object of the present invention is directed to a faster process of improving the
productivity and quality of sinter produced in sintering machine, wherein said steam
injection with controlled humidity and quantity, is carried out at a region of sinter bed where
the burn raise point temperature is achieved and the air filtration velocity is minimum and
thus favoring controlling the width of the hot zone, increasing the heat exchange rate
4

between the humidified air and the sinter mix and more advantageously, increasing the
vertical sintering speed.
A further object of the present invention is directed to a process of faster iron ore sintering
directed to significant decrease in coke breeze consumption by 5-10% and an increase in
tumbler index ranging from 65 points to 80 points.
A further object of the present invention is directed to a sintering process and apparatus
and system thereof to carry out such process so that coking rate of iron ore sintering
process is reduced resulting in higher reducibility of the sinter with reduced Reduction
Degradation Index (RDI) from 33.1 to 23.3 of sinter, to achieve higher yield in BF operation.
A still further object of the present invention is directed to a process of iron ore sintering
and an apparatus/system for carrying out such process wherein the complete combustion of
coke is achieved the carbon monoxide emission in sinter exhaust gases is reduced and also
reduction in the exhauster power consumption is achieved.
A still further object of the present invention is directed to a process of iron ore sintering
and an apparatus/system for carrying out such process wherein the temperature of the
exhaust gas is increased to about 120°C, which increases the efficiency of exhauster motor
and facilitate reducing exhauster motor power consumption by about 5%.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a process for faster sintering of
iron ore comprising:
controlling steam spraying over sinter bed and stopping such spraying with the stoppage of
the machine;
said controlled spraying covering the regions where the air filtration velocity is minimum;
removing the condensate from the steam in the steam line; and
5

regulating the pressure and flow of steam and in the process controlling the heat capacity of
the ambient air sucked through the bed in the region where the air velocity is minimum and
favour heat transfer between sinter mix and air and complete faster sintering.
A further aspect of the present invention directed to a process for faster sintering of iron ore
wherein the steam spraying is automatically stopped with the stoppage of the machine.
A still further aspect of the present invention directed to a process for faster sintering of iron
ore wherein the humidification of air by steam injection is carried out in the location where
air filtration is minimum.
A still further aspect of the present invention directed to a process for faster sintering of iron
ore wherein a mixture of steam and air is sucked through the bed whereby the humidity of
air can be adjusted up to 80gm/Nm3.
A still further aspect of the present invention directed to a process for faster sintering of iron
ore wherein the quantity of steam to be mixed with air is selectively done based on the
humidity of the ambient air.
A still further aspect of the present invention directed to a process for faster sintering of iron
ore wherein the steam injection is done in the region where the burn raise point
temperature is achieved which is around 3/4th length of the machine.
A still further aspect of the present invention directed to a process for faster sintering of iron
ore wherein the temperature of the wind main exhaust gas is increased to around 120°C
6

which in turn increases the efficiency of exhauster motor and facilitates reduction in
exhauster motor power consumption.
According to a further aspect of the present invention directed to an apparatus for faster
sintering of iron ore comprising:
means for providing steam spray over sinter bed adapted to get automatically stopped with
the stoppage of machine;
selectively angled preferably 90° wide angle spray nozzles in staggered manner covering the
region where the air filtration velocity is minimum;
steam trap in the line to remove the condensate from the steam in the steam line; and
valve means in the stream line adapted to regulate the pressure and flow of steam as
required.
A still further aspect of the present invention directed to an apparatus for faster sintering of
iron ore comprising globe valve to regulate the flow rate of steam spray and selective set of
headers adapted to regulate/stop the steam spray;
pressure reducing valves installed before the solenoid valve in the long header such as to
reduce the pressure of the incoming steam to desired level.
A still further aspect of the present invention directed to an apparatus for faster sintering of
iron ore comprising solenoid valve means is provided to control the steam spraying which is
7

interlocked with the sinter machine drive such that the steam spray is automatically stopped
with the stoppage of the machine.
A still further aspect of the present invention directed to an apparatus for faster sintering of
iron ore comprising a long header connecting the existing source of steam supply to the
main header and wherein the main header is insulated and laid parallel to the sinter
machine which is adapted to provide steam to plurality of feeders.
The present invention and its objects and advantages are described in further details with
reference to the following non-limiting illustrative figure/embodiment.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1: is the illustration of the schematic arrangement of the system and its different
equipments/apparatus for carrying out the process of sintering directed to improved
productivity and quality according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference is first invited to accompanying Figure 1, that illustrates the system/apparatus
comprising steam injection/spray at controlled pressure and in controlled quantity as of the
present invention to achieve desired improved quality and productivity of sinter following
the process according to the present invention. The steam manifold of the system
comprises two different sizes of seamless pipe viz 40 NB and 25 NB(1) in three different
sets. The 40 NB pipe is the main feeder catering to two 25 NB pipes in the first and second
set of transverse pipes of 25 NB and three in the third set, on which the spray nozzles are
mounted on suitable position and spacing for desired controlled steam disposal/spray on
sinter bed. The feeder pipe of NB 40 size is provided with ball valve (9) to facilitate
regulating the steam spray. Steam spray through specific set of header may be regulated/
stopped as necessary for process to achieve objective of improved productivity and quality
through faster vertical speed of sintering. A steel work fabricated structure (2) is provided
for enough rigidity adequate to support the spray pipes of 25 NB size, to prevent them from
sagging over the hot sinter bed. Similar, steel structural support (3) is provided also for the
8

spray headers. These supports are fixed over sinter machine floor suitably, so that the
assembly and dismantling may be carried out easily as and when required during the
maintenance work. The main header line (4) of 50 NB size pipe is laid parallel to the sinter
machine bed. It provides steam to the three feeders of 40 NB size (1) The main steam
header (4) is insulated (12) with adequate insulating material layer to prevent heat loss.
The long header of 50 NB, which is laid on the sinter machine floor, provides steam to the
main header (4). The long header is also insulated (12) to prevent heat losses. The long
header connects the existing source of steam supply to the main header. A solenoid valve is
put in the long header (5) line, which is functionally interlocked with sinter machine drive.
This facilitates in automatically stopping the steam supply for spray in case the sinter
machine is stopped for any reason. This unique novel feature prevents- (i) unnecessary
spray of steam over sinter bed, (ii) excessive moisture addition in a localized place on sinter
mix due to stoppage of the machine, (iii) requirement of additional manpower in case
manual stopping of steam spray was to be done when machine is stopped.
On the long header (5) line, a pressure-reducing valve (7) is also installed before solenoid
valve to reduce the pressure of incoming steam to desired level. This facility avoids
excessive pressure and possible erosion of the top layer of the sinter bed as a result of this.
The long header receives steam also through a globe valve (8) in a row with the pressure
reducing valve (7), which is capable of controlling/regulating the flow of steam in the main
header (4) and subsequently in the downstream headers. Further, there are three numbers
Ball valves are provided on the 40 NB feeder pipe and one number globe valve is provided
on the 50 NB long header line. As the ball valves control the spray of steam in individual
specific set of header, the total number of ball valves depend on the number of spray
headers. The ball valve in the long header has been provided to shut off the steam supply in
the long header manually, from the steam source. A pressure gauge (10) is provided in the
long header line to measure the steam pressure in the line. It is located after the pressure
reducing valve. A thermal insulation (12) layer, comprising slag wool and refractory of
selective length tied with wiremesh, is provided on the steam header lines long header,
main header and connecting headers. No insulation is provided in the spray headers as
these are having nozzles fixed on to it. A control cable (13) is provided for interconnecting
the solenoid valve (6) with auxiliary contact of the sinter machine drive. A steam trap (14)
has been provided on the main header line to remove the condensate from the steam line.
Details at 'X' and 'Y' shows the structural support to the steam headers and sprayers pipes
9

with accessories, provided at either side of the conveyor carrying the sinter mix/bed,
transferred to the foundation on the floor through a base plate (15).
The system as described above is adapted to execute the process of improving the
productivity and the quality of the sinter in sintering machine. The advantageous faster
sintering by preferred steam injection at selective locations on the sinter bed is achieved by
providing Steam spray Nozzles over the sinter bed during the sinter process and the
spraying is operatively stopped as soon as the sinter machine is stopped. The nozzles
provided over the sinter bed are 90° wide angle spray nozzle, located in a staggered manner
to cover the entire region of sinter bed where the air filtration velocity is minimum and the
burn raise point temperature is achieved and the heat exchange between the humidified air
and the sinter mix is maximized such that the vertical speed of sintering is increased. This
region starts from about 3/4th of the length of bed of the sintering machine from the
charging end. The steam spraying at controlled pressure and quantity flow rate provides
optimum improvement in the heat capacity of the humidified air that carries up to
80gm/Nm3 moisture, said control being effected in the system operatively by the set of
valves on the header lines. The present process of sintering iron ore thus the quantity of
steam to be mixed with air suck in through the sinter bed can be adjusted during the
various seasons of a year depending upon the humidity of the ambient air.
In the present process of iron ore sintering the width of the hot zone is reduced by better
heat exchange because of the higher heat capacity of the mixture of air and steam.
Importantly, this increases the vertical sintering speed. The process further achieves
reduced coke rate in sintering and there by improving the reducibility of the sintered ore.
The release of heat energy due to Boudward reaction involved and also due to dissociation
of the water/moisture molecule in to H+ and OH- radical that helps in providing the heat for
agglomeration process in sintering.
The present process of sintering also facilitate complete combustion of coke whereby
reduction in carbon monoxide emission in exhaust gases for sintering is achieved. Further
the rise in exhaust gas temperature to about 120°C increases the efficiency of the exhauster
motor and facilitate reduction in exhauster motor power consumption.
10

The process according to the present invention directed to faster sintering, higher
productivity of the sintering machine and improved quality of sinter, thus comprising the
steps of:
(i) providing mixed ingredients on moving conveyor bed at the charging end,
comprising iron ore fines, coke fines, limestone fines and various iron and flux
bearing materials like flue dust, slag etc. in selective proportion known as the
sinter mix;
(ii) top layer of the sinter mix on the moving bed is ignited by gas burners installed
at suitable locations in preferred numbers;
(iii) Ambient air required for the combustion of sinter mix, is sucked in through the
sinter bed from top into the wind boxes installed below the bed, by the operation
of an exhauster fan.
(iv) increase of volumetric air flow rate through the sinter bed and increasing the
heat capacity of the air during sintering by selective humidification of air by
steam injecting, preferably through nozzles, at a pressure range of 1 to 2 kg/cm2
and at flow rate of up to 0.5 t/hr, by operation of a set of valves in a piping
manifold, to obtain improved heat exchange in selective location on sinter bed,
preferably at 50% to 70% length of the machine from the charging side, such
that the hot zone(>600°C) width extension is restricted and the vertical speed of
sintering is increased.
(v) providing solenoid valve based control means for steam spray over sinter bed
adapted to get automatically stopped with the stoppage of machine and therebv
preventing excess moistening of sinter mix when the machine is stopped;
(vi) The nozzles provided over the sinter bed are 90° wide angle spray nozzle, located
in a staggered manner to cover the entire region of sinter bed where the air
filtration velocity is minimum and the burn raise point temperature is achieved;
(vii) to remove the condensate from the steam in the steam line by a steam trap
installed in the line;
(viii) The steam spraying at controlled pressure and flow rate providing optimum
improvement in the heat capacity of the humidified air that carries up to
80gm/Nm3 moisture, said control being effected in the system operatively by the
set of valves on the header lines, the amount depending on the moisture content
of ambient air, ensuring desired strength and RDI based improved quality of
sinter product.
11

(ix) The process further achieves reduced coke rate in sintering and there by
improving the reducibility of the sintered ore.
(x) The present process further release heat energy due to Boudward reaction
involved and also due to dissociation of the water/moisture molecule in to H+ and
OH" radical that helps in providing the heat for agglomeration process in
sintering,
(xi) The present process ensure complete combustion of coke whereby reduced
carbon monoxide (CO) emission in exhaust gases during sintering is achieved,
(xii) Due to the rise in exhaust gas temperature to about 120°C, the efficiency of the
exhauster motor increases and facilitate reduction in exhauster motor power
consumption.
It is thus possible by way of this invention to obtain sinter of higher strength, lower RDI and
improved reducibility produced at a faster rate and lesser power consumption and thus
improving overall productivity of the sintering plant.
12

WE CLAIM:
1. A process for faster sintering of iron ore comprising:
controlling steam spraying over sinter bed and stopping such spraying with the
stoppage of the machine;
said controlled spraying covering the regions where the air filtration velocity is
minimum;
removing the condensate from the steam in the steam line; and
regulating the pressure and flow of steam and in the process controlling the heat
capacity of the ambient air sucked through the bed in the region where the air velocity is
minimum and favour heat transfer between sinter mix and air and complete faster
sintering.
2. A process for faster sintering of iron ore as claimed in claim 1 wherein the steam
spraying is automatically stooped with the stoppage of the machine.
3. A process for faster sintering of iron ore as claimed in anyone of claims 1 or 2 wherein
the humidification of air by steam injection is carried out in the location where air
filtration is minimum.
4. A process for faster sintering of iron ore as claimed in anyone of claims 1 to 3 wherein
a mixture of steam and air is sucked through the bed whereby the humidity of air can be
adjusted up to 80gm/Nm3.
13

5. A process for faster sintering of iron ore as claimed in anyone of claims 1 to 4 wherein
the quantity of steam to be mixed with air is selectively done based on the humidity of
the ambient air.
6. A process for faster sintering of iron ore as claimed in anyone of claims 1 to 5 wherein
the steam injection is done in the region where the burn raise point temperature is
achieved which is around 3/4th length of the machine.
7. A process for faster sintering of iron ore as claimed in anyone of claims 1 to 6 wherein
the temperature of the wind main exhaust gas is increased to around 120°C which in
turn increases the efficiency of exhauster motor and facilitates reduction in exhauster
motor power consumption.
8. An apparatus for faster sintering of iron ore comprising:
means for providing steam spray over sinter bed adapted to get automatically stopped
with the stoppage of machine;
selectively angled preferably 90° wide angle spray nozzles in staggered manner covering
the region where the air filtration velocity is minimum;
steam trap in the line to remove the condensate from the steam in the steam line; and
valve means in the stream line adapted to regulate the pressure and flow of steam as
required.
14

9. An apparatus for faster sintering of iron ore as claimed in claim 8 comprising globe
valve to regulate the flow rate of steam spray and selective set of headers adapted to
regulate/stop the steam spray;
pressure reducing valves installed before the solenoid valve in the long header such as
to reduce the pressure of the incoming steam to desired level.
15
10. An apparatus for faster sintering of iron ore as claimed in anyone of claims 8 or 9
comprising solenoid valve means is provided to control the steam spraying which is
interlocked with the sinter machine drive such that the steam spray is automatically
stopped with the stoppage of the machine.
11. An apparatus for faster sintering of iron ore as claimed in anyone of claims 8 to 10
comprising a long header connecting the existing source of steam supply to the main
header and wherein the main header is insulated and laid parallel to the sinter machine
which is adapted to provide steam to plurality of feeders.
12. An apparatus for faster sintering of iron ore substantially as here in described and
illustrated with reference to the accompanying figures.

A faster process of sintering and improving quality of sinter product and a system
apparatus/ to carryout such process. More particularly, the process is directed to faster iron
ore sintering process that would improve sinter quality in terms of sinter strength, reduction
degradation index (RDI) decreased from existing 33.1 to 23.3, increased air filtration
velocity due to increased permeability, increased heat capacity of ambient air by preferred
injection of steam at selective pressure and controlled quantity over desired region of bed
length, humidity adjusted to about 80gm/Nm3, decrease in sinter fines in sinter product.
Importantly, the process and apparatus is adapted to reduce the coke rate and the carbon
monoxide emission in sinter exhaust gases and also reducing exhauster power consumption
by about 5%. A solenoid valve interlocking with sinter machine drive , stops steam supply
when the machine is stopped. The present process and system thereof to carry out the
process, is therefore adapted to improve quality with reduced RDI and higher reducibility of
sinter in a faster way, having wide industrial application in steel plants.