FIELD OF THE INVENTION

The present invention relates to preferentially segregating wet sinter mixture granules while
they are charged onto pallet car of sinter making machine. More particularly, the invention
relates to an improved method of charging wet granular sinter feed mixture onto a sinter
machine trolley or pallet cars in preferentially segregated manner such that larger granules
are layered at the bottom of the pallet cars and smaller particles at the top of the larger
granules that promote significant increase in permeability of the sinter bed, especially before
ignition.
BACKGROUND OF THE INVENTION
Iron ore sintering is a process in which a mixture of different raw material such as iron ore
fines, limestone, dolomite/pyroxenite, burnt lime, coke breeze and other metallurgical wastes
are agglomerated into larger and porous solid lump via melt formation at the particle interface
of different raw materials constituting the mixture. These large size agglomerates are then
crushed and sized as per the requirement of the blast furnace.
For industrial scale production of sinter, most common and widely used technology in
application is Dwight Lloyd straight grate sintering machine. In a plant consisted of this
technology, different raw material constituents are mixed and granulated in a balling drum or
a high intensity mixer. The wet granules, thus produced, are charged onto a trolley/
continuously moving pallet cars from the top. A bed of wet/moist granules is formed and top
layer of same is ignited in an ignition hood. Suction is applied at the bottom of the bed so that
the flame-front travels downward and in the process different constituents get
agglomerated/joined to each other. One factor which controls the speed at which the flame-
front travels downward (i.e. vertical sintering speed) is permeability of the wet granule sinter
bed especially permeability before ignition of the bed or pre-ignition sinter bed. Vertical
sintering speed governs the productivity of the sinter plants. To improve the permeability of
the of the pre-ignition sinter bed and in turn productivity of the sinter plants; different ways
and method have been tried to effectively segregate the coarser granules at bottom and finer
granules at top.

A device for segregating feed of sintering machine mixture, in the metallurgical industry is
described by Chen Shuci et al., in Patent No. CN2663896 (Y)
Jinlu Mou et al., in Patent No. CN101144118 (A), described a sintering process which can
promote increase in productivity by adding yield increasing agent during granulation step.
A supporting plate clean chute segregation distributor and segregation distributing device for
segregating wet granulated raw material and increasing productivity is reported by Kejian Liu
et. al., Patent No. CN102032790 (A).
Guanghui Li et al., described a method of distributing iron ore sinter feed mixture which can
promote particle size segregation, fuel segregation, magnetite particle segregation and
improvement in bed permeability in Patent No. CN102676797 (A)
An apparatus for improving air permeability of sintering layer to improve quality and
productivity of sinter produced by mounting a puff pipe on the lower part of a backward
inclined plate of a charging unit is reported by Byun Sang Geun et al., Patent No.
KR20020088119 (A).
The setbacks of the aforementioned inventions are fluctuations in the wet granules sinter bed
permeability, ineffectiveness in segregating wet granules onto pallet car, high maintenance
cost of the device/equipment etc. Furthermore, fluctuation or change in raw material such as
its chemical composition and particle size analysis or fluctuation in moisture added during
granulation have an effect on angle of repose of the mixture which in turn result in inefficient
segregation of large particle at bottom and smaller particle at top, thus resulting in
unprofitable permeability of the sinter bed, especially before ignition.
OBJECTS OF THE INVENTION
It is therefore an object of this invention to propose a method and a device of charging wet
sinter mixture granules onto pallet car of sinter making machine.
Another object of the invention is to propose a method and a device of charging wet sinter
mixture granules onto pallet car of sinter making machine, in which the wet sinter mixture
granules are preferentially segregated so that the coarse granules remain at the bottom and
small granules at the top of the mixture.

A still another object of the invention is to propose a method and a device of charging wet
sinter mixture granules onto pallet car of sinter making machine, which eliminates the
drawbacks such as fluctuation in sinter bed permeability, ineffective segregation of mixture,
and high maintenance cost of prior art.
A further object of the invention is to propose a device which can increase the air
permeability of the bed of sinter mixture on pallet car of sintering machine.
SUMMARY OF THE INVENTION
This invention relates to an improved method of charging wet granular sinter feed mixture
onto a sinter machine trolley or pallet cars in preferentially segregated manner such that
larger granules are layered at the bottom of the pallet cars and smaller particles at the top of
the larger granules that promote significant increase in permeability of the sinter bed,
especially before ignition.
According to the invention, there is also provided a device to increase the air permeability of
the bed of sinter mixture on pallet car of sintering machine, the device comprising a drum or
roll feeder with sieves or screen or more particularly, drum or roll feeder with roller screen to
distribute wet sinter mixture onto a trolley or pallet car of the sinter machine. This unique
arrangement increases the permeability of the sinter bed, especially before ignition, by
promoting segregation of large particles at bottom and small particles at top.
Accordingly, there is provided a device comprising a roll feeder/drum feeder, and an inclined
sieve in particular an inclined roller screen, optionally a vibration device attached, wherein an
increase in the gap between adjacent rolls of the roller screen in course of moving from upper
end to lower end, allows charging of layers of wet sinter mixture granules on the pallet car
such that the coarse particles are layered at the bottom and smaller particles are layered at top
of the pallet car.

DETAILED DESCRIPTION OF THE INVENTION
The configuration of the device is such that it can uniformly distribute wet or moist sinter
feed mixture granules onto the pallet cars of sinter machine, across the length and width of
pallet car in an efficiently segregated manner. For this, the roller screen is fixed below the
roll/drum feeder in a sloping position with a predefined angle, and a gap between the adjacent
rolls of the roller screen is maintained in an increasing order while moving from an upper end
of roller screen to its lower end, as shown in fig 1.
Figure-1 details: Part no. 1- feed mixture hopper, part no. 2- drum or roll feeder, part no. 3-
roller screen, part no. 4- pallet car of sinter machine, part no. 5- pre-ignition sinter bed, part
no. 6- wind box.
With reference to fig 1, wet sinter feed mixture granules or particles, filled in the feed
mixture hopper (1) are discharged onto the roller screen (3) with the help of the drum/roll
feeder (2). Thereafter, the roller screen (3), because of large gap between adjacent rolls at
lower end, release larger particles onto the pallet cars (4) from the lower end of the roller
screen. Smaller particles are discharged onto the pallet car from the upper end of the roller
screen. Intermediate size granules are released from the roller screen (3) onto the pallet car
from a middle part of the roller screen (3). As the car moves in forward direction, layers of
granules forms where larger granules remain at bottom and smaller at top side of the pallet
car, and in this way, a wet/moist sinter mixture granule bed (5) forms. When the suction is
applied from the bottom, through the wind box (6), air starts passing through the bed. With
sinter bed layer being of ideal structure i.e. larger particles in bottom layer and smaller
particles at top layer, the pre-ignition air permeability of the bed increases significantly as
compared to normal charging process.
It is also to be understood that the invention is not limited by the specific example and
embodiment described hereinabove, but includes such changes and modifications as may be
apparent to one skilled in the art. Therefore, the arrangement of drum feeder and roll screen
can be in any combination as per the requirement and interest of the operator of sinter
machine. One such additional arrangement is shown in fig 2. If the ore fines contain higher
percentage of coarser size particles then it is possible that they may not participates in
agglomeration process and will be layered onto hearth layer of sinter bed and at the end of

process comes out of the pallet car without getting sintered. Additional drum feeder and roller
screen combination, as shown in fig 2, will help in distributing coarser particle between
bottom layer and middle layer and thus helps them participate in sintering process. Also,
additional drum feeder and roller screen can work as standby combination of equipment
during scheduled maintenance work.
As shown in figure-1, the roll feeder (2) receives sinter feed mixture from the feed hopper
(1). As the roll feeder (2) rotates on its axis in anticlockwise direction, it distributes the
mixture uniformly across the width of the roller screen (3). The gaps between the adjacent
rolls of the roller screen (3) are in increasing order while moving from the upper end of the
roller screen to lower end. Individual roll rotates on its own axis in counter clockwise
direction and in that process, it releases the sinter feed mixture onto the pallet car through the
gaps between the adjacent roll.
Since the gaps between the adjacent roll is higher towards the lower end of the roller screen
and less at the upper end of it, therefore, the rollers screen releases larger granules from the
lower end and smaller particles from the upper end and in the process, a bed of sinter feed
mixture granules (5) forms on the pallet car having an ideal layered structure in which the
larger particles are layered at the bottom end and smaller particles are layered at the top side
of the pallet car (as shown in fig 1). With this type of bed structure, when suction is applied
from the bottom of the bed, air permeability of the bed increases significantly as compared to
normal charging.
Detailed schematic of the sintering process with present invention incorporated is shown in
figure 3. Present invention, as described in previous paragraphs, is shown in bold dash box in
figure 3. Raw material used in sintering process like ore fines, fluxes, solid fuel, waste by-
products etc. are conveyed from raw material storage yard to a proportioning unit (which can
be bedding and blending station or proportioning bins, depending on which technology is
available to and used by particular sinter plant). From the proportioning unit, raw materials
are conveyed to a mixing and granulation unit (which can be balling drum or high intensity
mixer, depending on which one is available to and used by particular sinter plant). Wet sinter
mixture granule, formed in said mixing and granulation unit, are then conveyed to a feeding

hopper. The feeding hopper releases the sinter mixture granules on top of a feeder/rolling
drum. Accordingly, the feeder rolls, when rotates, discharge the material on to the roller
screens, which is disposed below the feeder roll and is in a sloping position. As described in
the previous paragraphs that individual rolls of the roller screen rotates along their own axis
and the gaps between the adjacent rolls is smaller near the roll feeder (upper end of roller
screen) and larger near the bottom end . Therefore, the rollers screen releases large granules
at the bottom and smaller granules at the top and a bed of sinter mixture granules forms
which is preferentially segregated such that the large granules are layered at bottom and
smaller granules at the top. As the pallet car moves forward, the bed of wet sinter mixture
granules comes under ignition hood. Top layer of the bed is ignited under the ignition hood.
Further, during the movement of the pallet car in forward direction, by the action of suction
applied from the bottom of the bed, the flame front moves towards the bottom of the bed, and
in the process, the sinter mixture gets dried, fluxes gets calcinated, solid fuel gets ignited and
eventually all the constituent gets agglomerated to each other resulting in the formation of
large sinter cake. The downward movement of the flame front which is also known as vertical
sintering speed, governs by pre-ignition sinter bed permeability. By incorporation of present
invention, the pre-ignition sinter-bed permeability increases significantly because of ideally
layered structure of the sinter bed i.e. larger granules towards bottom and smaller toward top
side of pallet car. The sinter cake, thus formed, is discharged onto a sinter crusher in a
product receiving hopper during tilting of the pallet cars. The product sinter is then cooled in
coolers, screened and sized as per the plant specification and finally transported to blast
furnace units.
The method and device developed in this work, functioned suitably to segregate the wet
sinter feed mixture granules and to increase the pre-ignition sinter bed permeability. A case
study is provided below to establish the fact.
CASE STUDY:
To establish that raw material charging using roller screen segregates the raw material
mixture onto pallet car and promotes increase in the permeability of the wet/moist bed of raw
material sinter feed, a batch of raw material comprising iron ore fines 63.25 wt.%, limestone

fines, 12.7 wt. %, pyroxenite fines 1.04 wt.%, coke breeze 6 wt.% lime fines 2 wt.% and
sinter return fines 15 wt.% was mixed in a granulation drum for 15 minutes. Thereafter, water
was sprinkled on the dry mixture and granulation drum was allowed for rotation for
granulation to occur for 5 minutes in the same drum. Water added was 7.2 wt.% of the dry
mix.
The wet granules of the mixture, thus formed, were then charged uniformly above the upper
end of the roller screen. Roller screen was then powered on and vibration was also applied.
Materials passing through different pre-defined roll gaps were then collected separately. It
was found that mixture while moving from upper end to lower end segregated effectively i.e.
larger particles were collected below lower end and smaller particles below upper end of the
roller screen.
A pot grate sintering equipment was used to measure the pre-ignition permeability of the
sinter bed. A 50 mm high layer of 10-20 mm size sinter was placed at the bottom of pot as
hearth layer. Above that, layers of sinter feed mixture granules, collected from bottom of the
roller screen were manually layered in order that granules collected from lower end (bigger
size particles) were always placed below granules collected from upper end (smaller size
granules). Suction was then applied from the bottom of the pot sinter using blower fans.
Velocity of air passing through the bed of sinter feed mixture granules was measured and
permeability (i.e. pre-ignition permeability) of the bed was calculated. This pre-ignition
permeability was compared with the pre-ignition permeability of sinter bed when normal
charging of sinter mixture was done i.e. without any preferential segregation of the granules.
Table 1 provides the operating parameter and permeability data of normal charging and
segregated charging using method discussed in present invention.


Bed height: Total height of the pre-ignition sinter bed including hearth layer sinter
P: Suction pressure applied across the bed during velocity measurement
v: Velocity of the air passing through wet/moist granule sinter bed.
Permeability: Pre-ignition permeability of the wet/moist granule sinter bed calculated using
equation for Japanese Permeability unit given below.

Where,
P= Permeability in Japanese permeability unit
V= Air flow rate through sinter bed
A=Cross sectional area of the sinter pot
H= Height of the sinter bed
ΔP= Suction applied across the bed height
On comparing the permeability of the pre-ignition sinter bed, it is clearly visible from the
table 1 that, there is on an average a significant increase of 20.28 % in the permeability of the
pre-ignition sinter bed.

WE CLAIM:
1. An improved method of charging wet granular sinter feed mixture onto a sinter machine
trolley or pallet cars in preferentially segregated manner such that larger granules are layered
at the bottom of the pallet cars and smaller particles at the top of the larger granules that
promote significant increase in permeability of the sinter bed, especially before ignition,
wherein an increase of 15 to 20% increase in the permeability of the pre-ignition sinter bed is
achieved.
2. A device to segregate the sinter feed mixture granules on to pallet car of sinter machine,
comprising a roll feeder/drum feeder and an inclined sieve, in particular an inclined roller
screen, optionally a vibration device attached, wherein an increase in the gap between
adjacent rolls of the roller screen in course of moving from upper end to lower end, allows
charging of layers of wet sinter mixture granules on the pallet car such that the coarse
particles are layered at the bottom and smaller particles are layered at top of the pallet car.
3. The device as claimed in claim 2, wherein the sieve is disposed below the bottom of the
roll feeder.
4. The device as claimed in claim 2, wherein the sieve can be configured as a roller screen.
5. The device as claimed in claim 2 wherein angle of the roller screen or sieves is adjustable
between 0° to 90°.
6. The device as claimed in claim 2, wherein the roller screen features bigger openings at the
lower end as compared to that at the upper end.
7. The device as claimed in claim 2, wherein the gaps between the adjacent rolls of the roller
screen can be adjusted from 1 mm to 20 mm or more preferably 3.15 mm to 15 mm.

8. The device as claimed in claim 2, wherein a vibrating action can be provided to the roller
screen when the vibration device is activated.