Title of Invention	ROTATIONAL FLOW STRATEGY THROUGH BOTTOM TUYERES IN TOP AND BOTTOM BLOWN CONVERTER FOR IMPROVED MIXING EFFICIENCY
Abstract	This invention relates to a method of imparting rotational flow of stirring gas through the tuyeres at the bottom of a top-and-bottom-blown converter vessel to achieve enhanced mixing in the bath. The method comprises dividing the total number of tuyeres into multiple groups and imparting a flow of the stirring gas through the groups in an ascending ratio, the total flow rate being kept constant; and imparting a rotation to each flow through the tuyeres at a step size of either an angle between two consecutive tuyeres (θ) or a multiple of n in either clockwise, anticlockwise or a combination of both.

Title of Invention

ROTATIONAL FLOW STRATEGY THROUGH BOTTOM TUYERES IN TOP AND BOTTOM BLOWN CONVERTER FOR IMPROVED MIXING EFFICIENCY

Abstract

This invention relates to a method of imparting rotational flow of stirring gas through the tuyeres at the bottom of a top-and-bottom-blown converter vessel to achieve enhanced mixing in the bath. The method comprises dividing the total number of tuyeres into multiple groups and imparting a flow of the stirring gas through the groups in an ascending ratio, the total flow rate being kept constant; and imparting a rotation to each flow through the tuyeres at a step size of either an angle between two consecutive tuyeres (θ) or a multiple of n in either clockwise, anticlockwise or a combination of both.

Full Text	FILED OF INVENTION The present invention relates to a method of imparting rotational flow of stirring gas through the tuyeres at the bottom of top-and-bottom-blown converter vessel to achieve an enhanced mixing in the bath. BACKGROUD OF INVENTION A top-and-bottom blown converter vessel (henceforth referred to as vessel) 's 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, generally nitrogen or argon is 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 the mixing in the bath. Generally, a number of tuyeres are placed on a circle perimeter placed equi- distantly from adjacent tuyeres. An equal amount of gas is injected through each tuyere. This creates distinct zone of mixing by creating a symmetry plane between the two adjacent tuyeres. Mixing in the bath is delayed by this mechanism. To enhance the mixing, the zone corresponding to each tuyere should be delayed to interact with each other. OBJECT OF INVENTION It is therefore the object of the invention to propose a method of imparting rotational flow of stirring gas through the tuyeres at the bottom of top-anc- bottom-blown converter vessel to achieve an enhanced mixing in the bath. SUMMARY OF INVENTION According to the invention, to achieve an enhanced mixing in the top-and-bottom blown converter vessel, the number of tuyeres and its placement on a particular pitch circle diameter remains undisturbed. It is basically the flow rate which is distributed and rotated by means of which each tuyere experience a different level of flow rates making a pulsating kind of flow through the tuyeres with respect to time. A methodology of flow distribution and its rotation both clockwise and anticlockwise with varying rotation steps is devised that provides improved and faster mixing than that of the conventional constant flow rate through each tuyere. Such a flow - distribution improves the mixing through pulsation and changing flow positions which in turn creates a driving force for energy dissipation in the bulk fluid i.e. a better distribution of energy into the bath. The rotation is imparted to each flow through tuyeres at a step size of either an angle between two consecutive tuyeres (0) or a multiple of n (where n = 1,2,3,4) in either clockwise, anticlockwise or a combination of both. Taking as an example here, an arrangement can be made with a rotation step with an alternating clockwise and anticlockwise rotation. Thus, the subject of the present invention constitutes a method of injecting a rotational flow through the bottom tuyeres via the bottom of a top-and-bottom blown converter used for steelmaking. In the present invention, the total number of tuyeres is divided into sets of tuyeres clubbed together with a flow through them in an ascending ratio. The total flow rate through the bottom tuyeres is kept constant. Such a of flow rate distribution is termed as distributed flow with an ascending flow rate from one set to another. This primarily helps in better distribution of energy within the bath by providing an energy gradient in the bulk phase that consequently gives better mixing. An unequal amount of the stirring gas flows through each of the tuyeres in the group. Furthermore, the distributed flow through the set of tuyeres gets rotated as a function of time and step size. 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 obtaining no other gas except as traces. According to a particular characteristic of the invention, the step size between the adjacent time steps may change. The step size can always be a different combination of the above mentioned steps. Such an arrangement of rotation brings asymmetry into the stirring system and thus adds towards better mixing. According to another characteristic of the invention, the clockwise and anticlockwise combination which brings about an imaginary impeller kind of situation as practiced in chemical reactor for better mixing. This method is very effective in creating a direction for the energy to dissipate and get distributed and homogeniozed throughout the vessel, and in turn improving the mixing efficiency of the bath. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The above and other objects and features of the present invention will be more fully understood by reading the following description in conjunction with accompanying drawings. Fig. 1 - is the schematic of a converter vessel bottom with tuyeres on a pitch circle diameter according to the present invention. Fig. 2 - shows positions 9-11 of tuyeres 1-8 during a typical rotation of the converter vessel according to the invention. DETAILED DESCRIPTION OF THE INVENTION In the present innovative method the total flow is distributed among a sets of tuyeres clubbed from the total number of tuyeres. To make it understandable, an example is illustrated. A set of total 8 number of tuyeres as shown in Fig. 1 have been divided into 3 groups (3+2+3). The flow through the groups would be in an increasing order. However, the total flow through all of them remains constant. Rotation imparted with a rotation step size, rotation direction and rotation number. A typical rotation step can be either 45°, 90°, 135° and 180° between two consecutive tuyeres. Rotation direction can be chosen either clockwise, anticlockwise or a combination of the both. The switching of the rotation can be determined by a time interval termed as the rotation number. It will be understood that the type of bottom blowing through the tuyeres arrangement is 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 flow rate through bottom tuyeres in accordance with present invention ensures a better distribution of energy ensuring efficient mixing in the bath. 2. The intensity of fluid flow shear on tuyeres is reduced as a result of rotational strategy. Consequently, life of the bottom tuyeres improves as the tuyeres wear is expected to come down. 3. Another advantage of the invention is saving in amount of the blowing gas. Lesser amount of the blowing gas would be required for the same degree of mixing efficiency as per the present invention than in case of where equal amount of gas flow through all the tuyeres. The dimension of the tuyeres can be suitably designed as per the flow rate required through tuyeres depending upon the converter capacity. WE CALIM 1. A method of imparting rotational flow of stirring gas through the tuyeres at the bottom of a top-and-bottom-blown converter vessel to achieve enhanced mixing in the bath, comprising the steps of: - dividing the total number of tuyeres into multiple groups and imparting a flow of the stirring gas through the groups in an ascending ratio, the total flow rate being kept constant; - imparting a rotation to each flow through the tuyeres at a step size of either an angle between two consecutive tuyeres (0) or a multiple of n in either clockwise, anticlockwise or a combination of both. 2. The method as claimed in claim 1, wherein the step size is variable. 3. The method as claimed in claim 1 or 2, wherein the rotation generates asymmetry into the stirring process to add improved mixing. 4. The method as claimed in any of the preceding claims, wherein the clockwise and anticlockwise combination of rotation creates a direction for the energy to dissipate and get distributed and homogeniozed throughout the vessel to improve the mixing efficiency of the bath. 5. A method of imparting rotational flow of stirring gas through the tuyeres at the bottom of a top-and-bottom-blown converter vessel to achieve enhanced mixing in the bath, as substantially described and illustrated herein with reference to the accompanying drawings. This invention relates to a method of imparting rotational flow of stirring gas through the tuyeres at the bottom of a top-and-bottom-blown converter vessel to achieve enhanced mixing in the bath. The method comprises dividing the total number of tuyeres into multiple groups and imparting a flow of the stirring gas through the groups in an ascending ratio, the total flow rate being kept constant; and imparting a rotation to each flow through the tuyeres at a step size of either an angle between two consecutive tuyeres (θ) or a multiple of n in either clockwise, anticlockwise or a combination of both.

Full Text

FILED OF INVENTION
The present invention relates to a method of imparting rotational flow of stirring
gas through the tuyeres at the bottom of top-and-bottom-blown converter vessel
to achieve an enhanced mixing in the bath.
BACKGROUD OF INVENTION
A top-and-bottom blown converter vessel (henceforth referred to as vessel) 's
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, generally nitrogen or argon is 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 the mixing in the bath.
Generally, a number of tuyeres are placed on a circle perimeter placed equi-
distantly from adjacent tuyeres. An equal amount of gas is injected through each
tuyere. This creates distinct zone of mixing by creating a symmetry plane
between the two adjacent tuyeres. Mixing in the bath is delayed by this
mechanism. To enhance the mixing, the zone corresponding to each tuyere
should be delayed to interact with each other.

OBJECT OF INVENTION
It is therefore the object of the invention to propose a method of imparting
rotational flow of stirring gas through the tuyeres at the bottom of top-anc-
bottom-blown converter vessel to achieve an enhanced mixing in the bath.
SUMMARY OF INVENTION
According to the invention, to achieve an enhanced mixing in the top-and-bottom
blown converter vessel, the number of tuyeres and its placement on a particular
pitch circle diameter remains undisturbed. It is basically the flow rate which is
distributed and rotated by means of which each tuyere experience a different
level of flow rates making a pulsating kind of flow through the tuyeres with
respect to time. A methodology of flow distribution and its rotation both
clockwise and anticlockwise with varying rotation steps is devised that provides
improved and faster mixing than that of the conventional constant flow rate
through each tuyere.
Such a flow - distribution improves the mixing through pulsation and changing
flow positions which in turn creates a driving force for energy dissipation in the
bulk fluid i.e. a better distribution of energy into the bath. The rotation is
imparted to each flow through tuyeres at a step size of either an angle between
two consecutive tuyeres (0) or a multiple of n (where n = 1,2,3,4) in either
clockwise, anticlockwise or a combination of both. Taking as an example here, an
arrangement can be made with a rotation step with an alternating clockwise and
anticlockwise rotation.

Thus, the subject of the present invention constitutes a method of injecting a
rotational flow through the bottom tuyeres via the bottom of a top-and-bottom
blown converter used for steelmaking. In the present invention, the total number
of tuyeres is divided into sets of tuyeres clubbed together with a flow through
them in an ascending ratio. The total flow rate through the bottom tuyeres is
kept constant. Such a of flow rate distribution is termed as distributed flow with
an ascending flow rate from one set to another. This primarily helps in better
distribution of energy within the bath by providing an energy gradient in the bulk
phase that consequently gives better mixing. An unequal amount of the stirring
gas flows through each of the tuyeres in the group. Furthermore, the distributed
flow through the set of tuyeres gets rotated as a function of time and step size.
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 obtaining no other gas except
as traces.
According to a particular characteristic of the invention, the step size between
the adjacent time steps may change. The step size can always be a different
combination of the above mentioned steps. Such an arrangement of rotation
brings asymmetry into the stirring system and thus adds towards better mixing.
According to another characteristic of the invention, the clockwise and
anticlockwise combination which brings about an imaginary impeller kind of
situation as practiced in chemical reactor for better mixing. This method is very
effective in creating a direction for the energy to dissipate and get distributed

and homogeniozed throughout the vessel, and in turn improving the mixing
efficiency of the bath.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above and other objects and features of the present invention will be more
fully understood by reading the following description in conjunction with
accompanying drawings.
Fig. 1 - is the schematic of a converter vessel bottom with tuyeres on a pitch
circle diameter according to the present invention.
Fig. 2 - shows positions 9-11 of tuyeres 1-8 during a typical rotation of the
converter vessel according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
In the present innovative method the total flow is distributed among a sets of
tuyeres clubbed from the total number of tuyeres. To make it understandable, an
example is illustrated. A set of total 8 number of tuyeres as shown in Fig. 1 have
been divided into 3 groups (3+2+3). The flow through the groups would be in
an increasing order. However, the total flow through all of them remains
constant. Rotation imparted with a rotation step size, rotation direction and
rotation number. A typical rotation step can be either 45°, 90°, 135° and 180°
between two consecutive tuyeres. Rotation direction can be chosen either

clockwise, anticlockwise or a combination of the both. The switching of the
rotation can be determined by a time interval termed as the rotation number.
It will be understood that the type of bottom blowing through the tuyeres
arrangement is 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 flow rate through bottom tuyeres in accordance with
present invention ensures a better distribution of energy ensuring efficient
mixing in the bath.
2. The intensity of fluid flow shear on tuyeres is reduced as a result of
rotational strategy. Consequently, life of the bottom tuyeres improves as
the tuyeres wear is expected to come down.
3. Another advantage of the invention is saving in amount of the blowing
gas. Lesser amount of the blowing gas would be required for the same
degree of mixing efficiency as per the present invention than in case of
where equal amount of gas flow through all the tuyeres.
The dimension of the tuyeres can be suitably designed as per the flow rate
required through tuyeres depending upon the converter capacity.

WE CALIM
1. A method of imparting rotational flow of stirring gas through the tuyeres
at the bottom of a top-and-bottom-blown converter vessel to achieve
enhanced mixing in the bath, comprising the steps of:
- dividing the total number of tuyeres into multiple groups and
imparting a flow of the stirring gas through the groups in an
ascending ratio, the total flow rate being kept constant;
- imparting a rotation to each flow through the tuyeres at a step size
of either an angle between two consecutive tuyeres (0) or a
multiple of n in either clockwise, anticlockwise or a combination of
both.

2. The method as claimed in claim 1, wherein the step size is variable.
3. The method as claimed in claim 1 or 2, wherein the rotation generates
asymmetry into the stirring process to add improved mixing.
4. The method as claimed in any of the preceding claims, wherein the
clockwise and anticlockwise combination of rotation creates a direction for
the energy to dissipate and get distributed and homogeniozed throughout
the vessel to improve the mixing efficiency of the bath.

5. A method of imparting rotational flow of stirring gas through the tuyeres
at the bottom of a top-and-bottom-blown converter vessel to achieve
enhanced mixing in the bath, as substantially described and illustrated
herein with reference to the accompanying drawings.

This invention relates to a method of imparting rotational flow of stirring gas
through the tuyeres at the bottom of a top-and-bottom-blown converter vessel
to achieve enhanced mixing in the bath. The method comprises dividing the total
number of tuyeres into multiple groups and imparting a flow of the stirring gas
through the groups in an ascending ratio, the total flow rate being kept constant;
and imparting a rotation to each flow through the tuyeres at a step size of either
an angle between two consecutive tuyeres (θ) or a multiple of n in either
clockwise, anticlockwise or a combination of both.

Documents:

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Patent Number

272224

Indian Patent Application Number

1499/KOL/2008

PG Journal Number

14/2016

Publication Date

01-Apr-2016

Grant Date

22-Mar-2016

Date of Filing

01-Sep-2008

Name of Patentee

TATA STEEL LIMITED

Applicant Address

RESEARCH AND DEVELOPMENT AND SCIENTIFIC SERVICES DIVISION, JAMSHEDPUR

Inventors:

#	Inventor's Name	Inventor's Address
1	SURYA NARAYAN LENKA	C/O RESEARCH & DEVELOPMENT DEPARTMENT, TATA STEEL, JAMSHEDPUR-831001
2	VIKAS SINGH	C/O RESEARCH & DEVELOPMENT DEPARTMENT, TATA STEEL, JAMSHEDPUR-831001

PCT International Classification Number

B01F5/02; B01F5/06

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA