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 |
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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. 3 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. 4 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. 5 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. 6 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. 7 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°. 8 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.) 9 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. 10 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. 11 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. 13 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, 14 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. 15 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. |
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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
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
Patent Number | 254302 | ||||||||||||
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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:
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PCT International Classification Number | C21C 5/32; C21C 5/46 | ||||||||||||
PCT International Application Number | N/A | ||||||||||||
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PCT Conventions:
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