Title of Invention

A DEVICE FOR INTRODUCING STIRRING GAS INTO A TOP-AND-BOTTOM BLOWN CONVERTER TO ACHIEVE DESIRED MIXING DURING THE PROCESS OF STEEL MAKING

Abstract The present invention discloses a device adaptable for introducing a stirring gas into the molten metal in the top-and-bottom blown converters in steel-works. In the present arrangement, the bottom tuyeres (Tl, T2) are placed on two imaginary circles (2,3) concentric with the vessel bottom (1). Four tuyeres (Tl) are placed on one circle (2) and another four tuyeres (T2) on other circle (3) in a manner such that the angles (Al or A2) between the adjacent lines (AL1, AI2) joining each tuyere (Tl, T2) to a center (4) of the vessel bottom (1) are equal or unequal. Such an arrangement of tuyeres ensured good distribution of energy within the bath that consequently gives better mixing. An equal or unequal amount of the stirring gas flows through the each tuyere.
Full Text 2
FIELD OF INVENTION
The present invention relates to an arrangement of plurality of tuyeres at the
bottom of top-and-bottom-blown converter vessel used for steelmaking in steel
works. More particularly, the present invention relates to a device for introducing
stirring gas into a top-and-bottom blown converter to achieve a desired mixing
during the process of steel making.
BACKGROUND OF THE INVENTION
A top-and-bottom blown converter vessel (henceforth referred as vessel) is used
for steelmaking. A reactive gas is injected into the molten metal bath (henceforth
referred as bath) through a top lance to refine the metal into steel. An inert gas,
for example, nitrogen or argon in blown into the bath to agitate the bath from a
plurality of tuyeres arranged at the vessel bottom. The injected gas thus provides
mixing in the bath to bring about homogenization of temperature and
concentration. A good and fast mixing dictates the refining efficiency of the
process. It has been known through several studies that the arrangement of
bottom tuyeres affects mixing in the bath.

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According to prior art, a number of tuyeres are generally placed on a circle
perimeter placed equidistantly from adjacent tuyeres. More number of tuyers is
required for good mixing as the capacity of the vessel increases. Placing more
number of tuyeres on a circle reduces the distance between two adjacent
tuyeres, in turn; increase the possibility of undesired plume interaction. Placing
the tuyeres on a single circle, ignores the rest of the area available thus result in
poorer mixing.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device for introducing
stirring gas into a top-and-bottom blown converter to achieve a during the
process of steel making.
Another object of the invention is to propose a device for introducing stirring gas
into a top-and-bottom converter, which achieves improved and faster mixing in a
process of steekmaking.
A still another object of the invention is to propose a device for introducing
stirring gas into a top-and-bottom converter, which is capable of achieving
optimum distribution of energy in the converter.

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SUMMARY OF THE INVENTION
Accordingly, the present invention proposes a device for introducing stirring gas
into a top-and-bottom blown converter to achieve a desired mixing during the
process of steel making.
In the present arrangement, bottom tuyeres are placed on two imaginary circles
concentric with the vessel bottom. Four tuyeres are placed on one circle and
another four tuyeres on other circle in a manner such that the angles between
the adjacent lines joining each tuyeres to a center of the vessel bottom are
equal. Such an arrangement of tuyeres ensures good distribution of energy
within the bath that consequently gives better mixing. An equal or unequal
amount of the stirring gas flows through the each tuyere.
The stirring gas can be an inert gas, such as nitrogen or argon, or an argon
mixture, i.e. argon containing a little oxygen and containing no other gas except
as traces.
According to a particular characteristic of the invention, the angle between the
adjacent lines joining each tuyere to the center of the vessel bottom may change
alternately like 60°-30° or 65°-25° so that the cumulative angle is 90°. Such an
arrangement of tuyers brings asymmetry into the stirring system and thus adds
towards the better mixing.

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According to another characteristic of the invention, the flow rate of stirring gas
through the tuyeres placed on two circles is different. Hence a differential flow
pattern is followed i.e. the tuyeres on one circle have different stirring gas flow
rate as compared to the tuyeres on the other circle. The examples of a ratio of
flow through tuyeres placed on one circle to the tuyeres placed on the other
circle can be 2:3 or 3:7.
The inventive concept is to distribute the tuyeres on multiple circles; here two
conconcentric circles has been proposed. As the capacity of the vessel increases,
the diameter is also expected to increase, consequently the vessel bottom area
available also increases, and as a result more area is available at the vessel
bottom.
Accordingly, a device has been proposed which provide improved and faster
mixing than that of the conventional arrangement of plurality of tuyeres placed
on a single circle concentric with the vessel bottom.
The concept behind proposing such a configuration is to cover more bath area
for energy input i.e. a better distribution of energy into the bath. The diameter of
each of the two circles can have any value less than that of the vessel bottom.
Taking as an example here, an arrangement can be made with two circles having
diameter of 50% and 60% of vessel bottom diameter.

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BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above and other objects, features and advantages of the present invention
will be more fully understood by reading the following description in conjuction
with accompanying drawings.
Fig. 1 is the schematic of the vessel bottom mounted with the device according
to one embodiment of the invention.
Fig. 2 is the schematic of the vessel bottom mounted with the device according
to another embodiment.
Fig. 3 is the graph showing the result achieved by adapting the device as shown
in the fig. 1 in comparison to the prior art device where eight tuyeres are placed
on single circle having diameter of 58% of diameter of the vessel bottom.
Fig. 4 is the graph showing the results achieved by adapting the device as shown
in the Fig. 2 in comparison to the prior art device where eight tuyeres are placed
on a single circle having diameter of 58% of diameter of the vessel bottom.

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Fig. 5. is the graph showing the results achieved by adapting the device as
shown in fig. 2 in comparison to the device of prior art where eight tuyeres are
placed on a single circle having diameter of 58% of diameter of the vessel
bottom.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF
THE INVENTION
As shown in Fig 1, the angle between the adjacent lines is equal. Plurality of
tuyeres are placed on vessel bottom (1). Here eight tuyeres (T1, T2) are shown
distributed on two circles (2,3). The angle (A1) between adjacent lines (AL1)
each tuyere (T1, T2) to the center (4) of the vessel (v) is equal, each 45°.
As shown in Fig. 2, the angle between the adjacent lines (AL2) changes
alternatively. Plurality of tuyeres (T1, T2) are placed on vessel bottom (1). Here
eight tuyeres are shown distributed on two circles (2, 3). The angle (A2)
between the adjacent lines (AL2) joining each tuyere (T1, T2) and the center (4)
of the vessel (V) is changing alternately to a° and 90-a°, where a° is less
than 90°.

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In the present invention, eight tuyers are placed over two concentric circles (2,3)
having same center (4) as that of the vessel bottom (1). The details of the
bottom arrangement are shown in Figs. 1 & 2. Basically 8 tuyeres (T1,T2 )are
rearranged on two imaginary circles for example, circle (2) and circle (3) having
different diameters, with four tuyeres (T1 or T2) placed on each. Four tuyeres
(T1) are placed on the circle (2) in a manner such that the distance between any
two adjacent tuyeres (T1) is equal. Similarly four other tuyers (T2) are placed on
another circle (3). If imaginary lines can be joined from each tuyere (T1, T2) to
the vessel bottom center (4), the angle (A1 or A2) between adjacent lines (AL1 or
AL2) can be equal or change alternately between two angles (A1 or A2) summing
to 90°.
As shown in Fig. 1, the tuyeres are placed on two circle (2,3) having diameter of
50% and 66% of diameter of the vessel bottom (1). An equal flow is injected
through each tuyere (T1, T2). The flow rate shown in the graph is the total flow
rate injected through all the tuyeres (T1, T2). Mixing time for the each specified
bottom flow rate is shown. (which Figure is being discussed.)
An equal flow is injected through each tuyere (T1, T2). The flow rate shown in
the graph is the total flow rate injected through all the tuyere (T1,/ T2). Mixing
time for the each specified bottom flow rate is shown, (which Figure is being
discussed.)

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As further shown in Fig - 2, the tuyeres are placed on two circles (2,3) having
diameter of 50% and 58% of diameter of the vessel bottom (1). Two different
bottom gas flow rate is injected from the tuyeres (T1, T2) placed on the two
circles (2,3). One bottom gas flow rate is injected through the tuyeres (T1)
placed on one circle (2) and another bottom gas flow rate through the tuyeres
(T2) placed on another circle (3). Ratio of the gas flow rate in circle (2) to circle
(3) is 3:7. The flow rate shown in the graph is the total flow rate injected
through all the tuyeres. Mixing time for the each specified bottom flow rate is
shown. . (which Figure is being discussed.)
The dimension of the tuyeres can be suitably designed as per the flow rate
required through tuyeres depending upon the converter capacity.
The stirring gas delivery into the bath can of two type. The flow rate through
each tuyere can be equal or unequal.
To enable the invention to be fully understood, the bottom tuyere configuration
and there use will be described herein after by way of non-limiting examples.
Water modeling of the mixing in the actual converter is presented here as an
example to described the invention.

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Simulation of mixing in actual converter can be done in a 1/6th scaled-down
water model. Mixing in the vessel depends upon the fluid flow. To bring similarly
in the fluid flow the dynamic and kinematic forces can be scaled down properly.
The model is equipped with top and bottom blowing arrangements as in case of
actual converter. The model has bottom of size of 724 millimeters diameter. The
two circles are placed at 50% and 66% of the bottom diameter i.e. have
diameter of 362 millimeters and 478 millimeters respectively. The eight tuyere of
size of 1 millimeter are paced on the two circles as shown in Fig. 1. Water is
filled upto the level generally used in the steel converter. Gas is blown onto the
bath at an appropriately scaled-down flow rate from top lance as in the actual
converter. From bottom of the vessel through tuyeres gas is blown into the bath
at an appropriately scaled-down flow rate. From bottom a range of stirring gas
flow rate is used like 20, 30, and 50 liters/minute. Mixing time is evaluated by a
reliable method for each set of experiments. To demonstrate the effectiveness of
the present invention, the total flow rate is distributed equally through all the
tuyeres. Fig. 3 compares the mixing time of the present invention with the earlier
used bottom tuyeres configuration of using one circle at 58% of bottom vessel.
As per another characteristic where tuyeres are separated by alternate angles of
65° and 25° on two circles. Here again equal flow is distributed among all the
tuyeres. Fig. 4 compares the mixing time of the present configuration with the
one that uses bottom tuyeres placed on one circle of diameter of 58% of bottom
vessel.

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A differential flow is applied on the two circles. Here total flow was divided into
ratio 3:7. Here more flow i.e. 7x was kept at outer circle while lesser flow of 3x
was kept at inner circle. Though it can be otherwise also i.e. 7x on inner circle
and 3x on outer circle. 7x floe rate was distributed equally among all the tuyeres
placed on the inner circle. Fig. 5 compares the mixing time of the present
configuration with the one that uses bottom tuyeres placed on one placed on
one circle of diameter of 58% of bottom vessel.
It will be understood that the type of bottom blowing through the device in
accordance with present invention has many advantages, some of which it
shares with other type of arrangement presently used in the steel works, and
others which are special to the present invention.
1. The arrangement of bottom tuyeres in accordance with present invention
ensures greater volume of molten metal is affected by stirring through
bottom gas ensuring efficient mixing in the bath.
2. Interaction of the adjacent plumes is reduced in comparison with if
tuyeres are placed on single circle. Consequently, the tuyere wear is also
expected to come down.
3. Another advantage of this invention is an improvement in the life of the
bottom tuyeres wherein the two different flow rates are used through the
two circles. If a total flow rate of 10Nm3/min is to be introduced through
tuyeres, it is divided in a ratio of 3:7 with one part introduced through the

12
tuyeres placed on one circle and other part through the tuyeres placed on
other circle. Then the flow through circle (2) will be 3 Nm3/min and
through circle (3) will be 7 Nm3/min or vice-versa.
4. Another advantage of the invention is saving in amount of the blowing
gas. Lesser amount of the blowing gas will be required for the same
degree of mixing efficiency as in case of all the tuyeres placed on a single
circle than that of the tuyeres arrangement as per the present invention.

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WE CLAIM
1. A device for introducing stirring gas into a top-and-bottom blown
converter to achieve desired mixing during the process of steel making,
the device comprising:
- a first plurality of tuyers (T1) disposed on a first imaginary circle (2)
having a center (4) common to that of a bottom (1) of the furnace
vessel (V), the distance between each of said first plurality of
tuyers (T1) being equal;
- a second plurality of tuyers (T2) disposed on a second imaginary
circle (3) concentric to the first imaginary circle (2) including the
vessel bottom (1), the distance between each of said second
plurality of tuyers (T2) being equal, characterized in that the angles
(A1, A2) between the adjacent lines (AL1, AL2) joining each of the
tuyers (T1, T2) to the center (4) of the vessel bottom (1) is equal,
and in that the number of the first plurality of tuyers (T1) is equal
to that of the second plurality of tuyers (T2).
2. A device for introducing stirring gas into a top-and-bottom blown
converter to achieve desired mixing during the process of steel making,
characterized in that the angles (A1, A2) between the adjacent lines (AL1,

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AL2) joining each of the tuyers (T1, T2) to the center (4) of the vessel
bottom (1) alternately changes between said angles (A1, A2) summing to
90°, and in that the number of the first plurality of tuyers (T1) equal to
that of the second plurality of tuyers (T2).
3. The device as claimed in claim 1 or 2, wherein bottom gas at an equal
flow-rate is injected through the first and second plurality of tuyers (T1,
T2).
4. The device as claimed in claim 1 or 2, wherein bottom gas at two different
flow-rate is injected through the first and second plurality of tuyers (T1,
T2).
5. The device as claimed in any of the preceding claims, wherein the
diameter of the first and second imaginary circles (2,3) is any value less
than the diameter of the vessel bottom (1).
6. The device as claimed in any of the preceding claims, wherein a ratio of
gas flow through the first and second plurality of tuyers (T1, T2) is
unequal.

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7. A device for introducing stirring gas into a top-and-bottom blown
converter to achieve desired mixing during the process of steel making, as
substantially described and illustrated herein with reference to the
accompanying drawings.

The present invention discloses a device adaptable for introducing a stirring gas
into the molten metal in the top-and-bottom blown converters in steel- works. In
the present arrangement, the bottom tuyeres (Tl, T2) are placed on two
imaginary circles (2,3) concentric with the vessel bottom (1). Four tuyeres (Tl)
are placed on one circle (2) and another four tuyeres (T2) on other circle (3) in a
manner such that the angles (Al or A2) between the adjacent lines (AL1, AI2)
joining each tuyere (Tl, T2) to a center (4) of the vessel bottom (1) are equal or
unequal. Such an arrangement of tuyeres ensured good distribution of energy
within the bath that consequently gives better mixing. An equal or unequal
amount of the stirring gas flows through the each tuyere.

Documents:

01087-kol-2007-abstract.pdf

01087-kol-2007-claims.pdf

01087-kol-2007-correspondence others 1.1.pdf

01087-kol-2007-correspondence others 1.2.pdf

01087-kol-2007-correspondence others.pdf

01087-kol-2007-description complete.pdf

01087-kol-2007-drawings.pdf

01087-kol-2007-form 1 1.1.pdf

01087-kol-2007-form 1.pdf

01087-kol-2007-form 18.pdf

01087-kol-2007-form 2.pdf

01087-kol-2007-form 3.pdf

01087-kol-2007-gpa.pdf

1087-KOL-2007-(14-08-2012)-CORRESPONDENCE.pdf

1087-KOL-2007-(20-04-2012)-ABSTRACT.pdf

1087-KOL-2007-(20-04-2012)-AMANDED CLAIMS.pdf

1087-KOL-2007-(20-04-2012)-DESCRIPTION (COMPLETE).pdf

1087-KOL-2007-(20-04-2012)-DRAWINGS.pdf

1087-KOL-2007-(20-04-2012)-EXAMINATION REPORT REPLY RECEIVED.pdf

1087-KOL-2007-(20-04-2012)-FORM-1.pdf

1087-KOL-2007-(20-04-2012)-FORM-2.pdf

1087-KOL-2007-(20-04-2012)-FORM-3.pdf

1087-KOL-2007-(20-04-2012)-OTHERS.pdf

1087-KOL-2007-(28-05-2012)-AMANDED CLAIMS.pdf

1087-KOL-2007-(28-05-2012)-CORRESPONDENCE.pdf

1087-KOL-2007-CORRESPONDENCE.pdf

abstract-01087-kol-2007.jpg


Patent Number 254302
Indian Patent Application Number 1087/KOL/2007
PG Journal Number 42/2012
Publication Date 19-Oct-2012
Grant Date 17-Oct-2012
Date of Filing 06-Aug-2007
Name of Patentee TATA STEEL LIMITED
Applicant Address JAMSHEDPUR
Inventors:
# Inventor's Name Inventor's Address
1 VIKAS SINGH TATA STEEL LIMITED, JAMSHEDPUR 831001
2 JYOTI KUMAR TATA STEEL LIMITED, JAMSHEDPUR 831001
3 SURYA NARAYAN LENKA TATA STEEL LIMITED, JAMSHEDPUR 831001
PCT International Classification Number C21C 5/32; C21C 5/46
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA