The present disclosure relates to a sintering process, more particularly, the
present disclosure relates to a flame stabilizing wind box structure for
providing a symmetrical flame front in sintering process.
BACKGROUND OF THE INVENTION
Sintering is a process of compacting and forming a solid mass of material by
heat or pressure without melting it to the point of liquefaction. Iron ore
sintering involves the application of heat to a blended mix of ores, fluxes and
coke breeze. Iron ore fines are pre-mixed with solid fuel and fluxes and are
subjected to heating for agglomeration. The top layer of the mix is ignited,
and then suction is applied to ensure continuous heating. The process
causes the partial melting of the mixture. On cooling, the solidified melt
provides the bonding phases required to form strong sinter. The amount of
melt formed is dependent on the thermal conditions in the bed, which is
affected by the flame front and the rate at which melt can be generated
from the sinter mix. Flame front is the velocity at which the heat/flame
travels through the bed when suction is applied.
In iron ore sintering, the properties of the flame front are critical as they
determine the heat imparted to the particulate bed and, hence, the strength
of the formed sinter. The temperature and the velocity at which the flame
front descends down the bed are critical to the sintering process. Post-
ignition airflow rate is a strong function of the pre-ignition airflow rate and
the flow resistance of the flame front. There is also strong dependence of
flame front resistance on gas flow velocity, flame front temperature and

applied suction. Maintaining the right thermal profile and interface between
the flame front and the ore blend is important. Hence a stabilized and
uniform flame front is required.
PRIOR ART:
CN203259486 (U) describes an improved sinter pot test device, which
belongs to the technical field of sinter pot test equipment and is used for a
sinter pot test in a metallurgical laboratory. According to the technical
scheme, a thermocouple is mounted in an igniter; another thermocouple is
mounted on a position above an air bellow and near a pot body of a sinter
pot; two layers of sinter pot grates are mounted in the pot body of the sinter
pot; a plurality of thermocouples are mounted on the body wall of the pot
body of the sinter pot; the front ends of the thermocouples are respectively
inserted into sintering materials; a primary mixer is provided with a
horizontal regulating device and a vertical regulating device; a spray gun is
used for spraying water in an atomization mode under the pressure of an air
compressor at a slantly-downward angle of 45 degrees in the horizontal
direction; the igniter is provided with an automatic igniter positioning device.
The sinter pot can be used for imitating the sinter pot test at various
material layers, controlling the ignition temperature and the final sintering
temperature and detecting the temperature of a burning layer. With the
additional arrangement of the water spray gun, the bonding of mixed
materials on the barrel wall of the mixer is reduced, so that the mixed
materials are accurate and reliable in moisture. By utilizing the automatic
igniter positioning device, the igniter can be aligned with a pot opening of
the sinter pot accurately, so that the accuracy and the comparison of the test
are improved.

Now, reference may be made to the following prior arts discussing state of
the art techniques.
OBJECTS OF THE INVENTION
The objective of the present invention is to provide a flame stabilizing wind
box to be used in sintering process to achieve a stable, uniform, and
symmetrical flame front.
Another objective is to enhance the equipment capability in the sintering
process by which the different blends of raw materials can be tested in the
existing setup.
Another objective is to reduce unsymmetrical thermal profile (asymmetrical
heating and cooling rates) in the sintering process due to test repeatability,
and further enhance lifespan of the setup.
SUMMARY OF THE INVENTION
The present disclosure relates to a flame stabilizing wind box (400) for a
sintering process. The wind box (400) includes a frusto-conical portion (402)
defining a first height (H1), a wide end (404) having first diameter (D1), and
a narrow end (406) having second diameter (D2); a cylindrical portion (408)
having a second height (H2), the cylindrical portion (408) being extending
from the wide end (404) of the frusto-conical portion (402); a box shaped
sinter pot (410) coupled to the cylindrical portion (408), the sinter pot (410)

being open from top (412) and defines a space (414) for receiving a sinter
mix; and a suction outlet (416) defining a third height (H3), the suction
outlet (416) extending coaxially from the narrow end (406) of the frusto-
conical portion (402), wherein wind is being sucked from the suction outlet
(416) for creating a symmetrical flame front.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from
the ensuing description when read in conjunction with the accompanying
drawings of the exemplary embodiments and wherein:
Figure 1 shows: An asymmetric flame front (between lines 102 and 104)
as visualized in a transparent pot associated with
conventional designed wind box.
Figure 2 shows: A simulation output corresponding to an asymmetrical
air circulation in existing wind box design setup.
Figure 3 shows: A simulation output corresponding to Non-uniform
velocity contours in the conventional designed wind box.
Figure 4 shows: A flame stabilizing wind box (400) for a sintering process
in accordance with an embodiment of the present
disclosure.
Figure 5a-c shows: Simulation results for the flame stabilizing wind box
(400) of Fig. 4.
Figure 6 shows: A symmetrical flame front in portion (602) as achieved
through the flame stabilizing wind box (400) of Fig. 4.

The figures depict embodiments of the present subject matter for the
purposes of illustration only. A person skilled in the art will easily recognize
from the following description that alternative embodiments of the structures
and methods illustrated herein may be employed without departing from the
principles of the disclosure described herein.
DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING
DRAWINGS
The present invention, now be described more specifically with reference to
the following specification.
It should be noted that the description and figures merely illustrate the
principles of the present subject matter. It should be appreciated by those
skilled in the art that conception and specific embodiment disclosed may be
readily utilized as a basis for modifying or designing other structures for
carrying out the same purposes of the present subject matter. It should also
be appreciated by those skilled in the art that by devising various
arrangements that, although not explicitly described or shown herein,
embody the principles of the present subject matter and are included within
its spirit and scope. Furthermore, all examples recited herein are principally
intended expressly to be for pedagogical purposes to aid the reader in
understanding the principles of the present subject matter and the concepts
contributed by the inventor(s) to furthering the art, and are to be construed
as being without limitation to such specifically recited examples and
conditions. The novel features which are believed to be characteristic of the
present subject matter, both as to its organization and method of operation,

together with further objects and advantages will be better understood from
the following description when considered in connection with the
accompanying figures.
These and other advantages of the present subject matter would be
described in greater detail with reference to the following figures. It should
be noted that the description merely illustrates the principles of the present
subject matter. It will thus be appreciated that those skilled in the art will be
able to devise various arrangements that, although not explicitly described
herein, embody the principles of the present subject matter and are included
within its scope.
In conventional wind box designs employed with sintering processes, velocity
across cross section of sinter bed is not symmetric as suction is applied from
one side of the wind box. Due to this, asymmetric velocity causes uneven
flame front movement during sintering tests or processes.
Computational fluid dynamics (CFD) methodology is employed for achieving
simulation of air flow through the sinter pot and conventional wind box. It
has been observed for the existing wind box designs that, the flow at the
inlet and outlet sections of the domain is turbulent. The porous media model
in FLUENT incorporates a momentum sink for flow resistance in governing
momentum equations. The flow through the sinter bed is laminar and is
characterized in the model by inertial and viscous loss coefficients in the flow
(Y) direction. The bed is impermeable in other directions, which is modeled
using loss coefficients whose values are three orders of magnitude higher
than in the (Y) direction. The porous media model assumes that the porosity

is isotropic and it can vary with space and time. Ergun equation defines the
pressure drop per unit length across the packed bed including both the
viscous and inertial loss coefficients given as:

The viscous loss coefficient (1/K) in (Y)-direction is given by:

The inertial loss coefficient (c) in (Y)-direction is given by:

Fig. 1, shows an asymmetric flame front (between lines 102 and 104) as
visualized in a transparent pot associated with conventional designed wind
box. Fig. 2, shows a simulation output corresponding to an asymmetrical air
circulation in existing wind box design setup. As shown in Fig.2, large
volumes (202) of recirculation zones are evident in the conventional
designed wind box. Fig. 3, shows another simulation output corresponding to
Non-uniform velocity contours at various planes in the sinter bed and the
wind box in the conventional sintering process employing the conventional
designed wind box.
Referring to Figs. 1, 2, and 3, the flow simulation of the existing wind box
provides the air flow prediction. It can be concluded that the recirculation
zone (202) extends in the wind box till the suction pipe which may cause an
asymmetrical flame front in the sinter bed. Also, it can be observed that the

air flow in the wind box near the suction pipe is diverted towards the bottom
end due to the presence of the recirculation zone (202) with high velocities
in the range of 3 m/s to 6.2 m/s. High velocity gradients are also observed in
the rectangular wind box used in the old design of sintering.
Fig. 4 illustrates a flame stabilizing wind box (400) for a sintering process in
accordance with an embodiment of the present disclosure. In an
embodiment, the flame stabilizing wind box (400) includes a frusto-conical
portion (402). The frusto-conical portion (402) defines a first height (H1), a
wide end (404) having first diameter (D1), and a narrow end (406) having
second diameter (D2).
The frusto-conical portion (400) further includes a cylindrical portion (408).
The cylindrical portion (408) includes a second height (H2) and extends from
the wide end (404) of the frusto-conical portion (402). In an embodiment, a
diameter of the cylindrical portion (408) is substantially similar to the first
diameter (D1). In an embodiment, the cylindrical portion (408) may be
secured to the frusto-conical portion (402) using state of the art joining
techniques such as welding, bonding, or the like. In an alternative
embodiment, the cylindrical portion (408) and the frusto-conical portion
(402) may be a single unit manufactured by state of the art manufacturing
techniques like casting, forging, extrusion, or the like.
The flame stabilizing wind box (400) further includes a box shaped sinter pot
(410) coupled to the cylindrical portion (408). The sinter pot (410) is open
from top (412) and defines a space (414) for receiving a sinter mix.

The flame stabilizing wind box (400) further includes a suction outlet (416).
The suction outlet (416) extends coaxially from the narrow end (406) of the
frusto-conical portion (402). In an embodiment, a diameter of the suction
outlet (416) is substantially similar to the second diameter (D2). In an
embodiment, the suction outlet (416) being extending from the narrow end
(406) of the frusto-conical portion (402), defines an aperture angle (α) in a
clockwise axis between the suction outlet (416) and the frusto-conical
portion (402). In an embodiment, the aperture angle (α) is in the range of
60 – 80 degrees.
The suction outlet (416) further includes a right-angle bend (418) extending
beyond the third height (H3). The right-angle bend (418) is defined by a
radius (R). In an embodiment, the radius (R) is in the range of 25 – 35 cm.
In an embodiment, wind is sucked from the suction outlet (416) for creating
a symmetrical flame front. In an example, a suction motor is utilized for
suction of wind from the suction outlet (416). The symmetrical flame front is
created by using the wind box (400) defining a column for airflow flowing
through the suction outlet (416), and generating suction with the help of the
suction motor. The column for air flow requires providing uniform suction,
without creating a back air flow zone.
Referring to Fig. 4, a ratio between the first height (H1), the second height
(H2), and the third height (H3) of the flame stabilizing wind box (400) is 1-
2:1.2-2.3:1.4-5. In an example, the first height (H1) is in the range of 35 –
50 cm, the second height (H2) is in the range of 30 – 40 cm, and the third
height (H3) is in the range of 35 – 45 cm. Further, the first diameter (D1) is
in the range of 60 – 70 cm, and the second diameter (D2) is in the range of

200mm. In an embodiment, the frusto-conical portion (402), the cylindrical
portion (408), and the suction outlet (416) of flame stabilizing wind box
(400) are made of steel, for example, mild steel, stainless steel, or the like.
Alternatively, the flame stabilizing wind box (400) may be made up of any
suitable material, capable of sustaining high temperatures of around 400
degrees, known to a person skilled in the art. Further in an embodiment, the
flame stabilizing wind box (400) is welded to a support structure (not shown)
to maintain the position and load.
The first height (H1), the second height (H2), the third height (H3), the first
diameter (D1), and the radius (R) are the parameters playing a significant
role in determining recirculation and pressure drop in the flame stabilizing
wind box (400). Velocity distribution and related simulation for new design of
the flame stabilizing wind box (400) is evaluated using Computational fluid
dynamics (CFD) modelling to arrive at the optimum values of R, D1, H1, H2,
and H3.
Simulation results for the flame stabilizing wind box (400) are now provided
with reference to Figs. 5a, 5b, and 5c. Fig. 5a illustrates symmetrical velocity
profiles across cross sections of the sinter pot (410), the cylindrical portion
(408), the frusto-conical portion (402), and the suction outlet (416). It is also
observed, as shown in Fig. 5b, that the air flow is symmetrical w.r.t the axis
of the wind box (400) for the total length. Also, the small recirculation zone
near the walls is suppressed in the frusto-conical portion (402) well before
the suction outlet (416). The velocity of the recirculating flow in the
cylindrical portion (408) near the suction outlet (416) is very less and in the
range of 0.5 m/s to 3 m/s, which indicates that the air flow in the wind box

(400) is subjected to a low turbulence intensity. This results in the uniform
velocity across sinter bed cross section and also a stable, uniform, and
symmetrical flame front is achieved as shown in Fig. 5c, and in portion 602
of Fig. 6.
The following specification provides data corresponding to an experimental
analysis conducted on the flame stabilizing wind box (400) to evaluate
optimum design parameters. Table 1 below dimensions provided to the wind
box (400).

It has been observed from the aforementioned experimental analysis
that, at low bend radius (R) of 18 cm and least first height (H1) of 20 cm,
the recirculation zone volume is high as shown in Fig. 4, 5, and 6.
Reducing the first diameter (D1) decreases the recirculation in the wind
box (400) as shown in Fig. 6 leading to high air velocities and less
pressure drop. This decreases the flow velocity through the sinter pot
(410) and results in less flame front velocity. After various simulations,

the design with the minimal turbulence and air recirculation was observed
with Case 2 in Table 1. The volume of the recirculation zone caused due
to low pressure created near to the bend (418) was reduced by
increasing the radius (R) of the bend (418).
It is to be noted that the present invention is susceptible to modifications,
adaptations and changes by those skilled in the art. Such variant
embodiments employing the concepts and features of this invention are
intended to be within the scope of the present invention, which is further
set forth under the following claims.

WE CLAIM :
1. A flame stabilizing wind box (400) for a sintering process, the wind
box (400) comprising:
a frusto-conical portion (402) defining a first height (H1), a wide
end (404) having first diameter (D1), and a narrow end (406)
having second diameter (D2);
a cylindrical portion (408) having a second height (H2), the
cylindrical portion being extending from the wide end (404) of the
frusto-conical portion (402);
a box shaped sinter pot (410) coupled to the cylindrical portion
(408), the sinter pot (410) being open from top (412) and defines
a space (414) for receiving a sinter mix; and
a suction outlet (416) defining a third height (H3), the suction
outlet (416) extending coaxially from the narrow end (406) of the
frusto-conical portion (402),
wherein wind is being sucked from the suction outlet (416) for
creating a symmetrical flame front.
2. The flame stabilizing wind box (400) as claimed in claim 1, wherein
a ratio between the first height (H1), the second height (H2), and
the third height (H3) is 1-2:1.2-2.3:1.4-5.

3. The flame stabilizing wind box (400) as claimed in claim 1, wherein
the frusto-conical portion (402), the cylindrical portion (408), and
the suction outlet (416) are made of mild steel.
4. The flame stabilizing wind box (400) as claimed in claim 1, wherein
the frusto-conical portion (402) and the suction outlet (416)
defines an aperture angle (α) between them, the aperture angle
(α) being in the range 60-80 degrees.
5. The flame stabilizing wind box (400) as claimed in claim 1, wherein
the suction outlet (416) includes a right-angle bend (418)
extending beyond the third height (H3), the right-angle bend (418)
being defined by a radius (R) in the range of 25 – 35 cm.
6. The flame stabilizing wind box (400) as claimed in claim 1, wherein
the wind is sucked from the suction outlet (416) by a suction
motor.
7. The flame stabilizing wind box (400) as claimed in claim 1, wherein
the first height (H1) is in the range of 35 – 50 cm.
8. The flame stabilizing wind box (400) as claimed in claim 1, wherein
the second height (H2) is in the range of 30 – 40 cm.

9. The flame stabilizing wind box (400) as claimed in claim 1, wherein
the third height (H3) is in the range of 35 – 45 cm.
10. The flame stabilizing wind box (400) as claimed in claim 1, wherein
the first diameter (D1) is in the range of 60 – 70 cm, and the
second diameter (D2) is in the range of 200 mm.