FORM 2
THE PATENT ACT, 1970
(39 of 1970)
&
THE PATENTS RULES,2003
COMPLETE SPECIFICATION
(See section 10 and rule 13 )
A SYSTEM AND METHOD OF STEEL MAKING
INVOLVING
1 . TITLE OF INVENTION
ADVANCEMENTS IN ART
OF OXYGEN BLOWING IN CONARC FURNACE.
2 . APPLICANT(S)

Name Nationality Address
GEETAPURAM, DOLVI, TALUKA
JSW ISPAT MUMBAI PEN, DIST.
STEEL LIMITED
RAIGAD,
MAHARASHTRA-402107, INDIA
3. PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification particularly describes the
invention and the manner in which it is to performed

4. DESCRIPTION (Description shall start from next page.) FIELD OF THE INVENTION The present invention relates to development of advanced system of blowing involved in furnaces having the limitations of lower height-to-diameter ratio (typically 1:1) such as in CONARC furnace adapted to achieve operational benefits of LD convertor and in the process provide for operations involving such furnaces including the CONARC furnace leading to faster and efficient productivity. Importantly, the advancement is directed to several operational advantages including reducing the cycle time during blowing operation as well as reducing operations of jamming in furnaces having the limitations of lower height-to-diameter ratio (typically 1:1) such as in CONARC furnace, The advancement is also directed to achieve technical advance in the art of blowing in furnaces with the limitations of lower height-to-diameter ratio (typically 1:1) such as in CONARC furnace and provide for a method of refining of steel in such refining vessels such as CONARC furnace which would achieve higher efficiency and productivity inspite of the limitations of vessels constructions with lower height-to-diameter ratio (typically 1:1). Importantly the system of blowing and the blowing methodology attained thereby under the present advancement is further directed to facilitate the automatised slag coating and better shell life (both top and bottom shell) of such furnaces. The advancement would thus enable attaining for CONARC furnace productivity and yield, compatible with LD converter. BACKGROUND OF THE INVENTION High cycle time with use in EAF / CONARC is a bottleneck for determining the productivity of a steel plant. Various improvement have been done in the steel-making technology in past decades to decrease the cycle time as well as increase the flexibility of using various combination of raw material i.e. Hot metal or pig iron, Direct reduced iron (DRI), scrap, iron ore. US 5956365 discloses an electric arc furnace comprises a closed melting vessel and includes a roof through which metal to be molten is charged into the melting vessel. At least one electrode extends into the melting vessel and generates an electric arc and forms a molten metal bath. At least one oxygen lance can be extended into the melting vessel for injecting oxygen into the molten metal bath and create a reaction where the carbon monoxide is generated. Gas is exhausted from the melting vessel and the carbon monoxide gas concentration of the exhaust gas is measured. A post combustion chamber receives the exhaust gas and provides post combustion of the exhaust

gas. Post combustion oxygen is injected into the melting vessel in an amount sufficient to provide post combustion based on the amount of oxygen necessary for post combustion of the exhaust gas and the post combustion chamber. EP 0735146 A1 discusses an apparatus for producing molten pig iron by direct reduction of iron ore, comprising (i)a metallurgical vessel, in which with supply of coal and oxygen the iron ore undergoes a final reduction with production of a process gas and said process gas undergoes a partial post-combustion, and (ii) a melting cyclone in which the iron ore undergoes a pre-reduction and is melted. To improve the control of the thermal flows and to reduce maintenance, the vessel has (a)a top part, in which the partial post-combustion of said process gas takes place, in the form of a pressure-resistant hood having an interior wall comprising cooling water pipes, and (b)a bottom part for accommodating an iron bath having a slag layer in which said final reduction of said iron ore takes place, the bottom part having an internal refractory lining and means for water cooling the internal refractory lining. US7550108 B2 teaches the provision of a metallurgical vessel for iron and steel making including a bottom portion, a sidewall and a lance arrangement of at least two lances for supplying oxygen containing gas to the interior of the vessel in operation. Each lance includes an end portion for emitting oxygen containing gas. The lance arrangement is configured so as to achieve in operation a substantially downwardly directed flow of post-combusted gases at the side wall of the vessel and a substantially upwardly directed flow of post-combusted gases in the center of the vessel. In their granted IN 204622 the present Applicants have disclosed advancements relating to the steel making-process using-twin shell-electric arc furnace, in which feed stock comprises 60% to 100% hot metal and' oxygen is blown through top lance and/or door lance and in which Direct Reduced Iron (DRI) is used as a coolant for utilizing the excess heat generated during blowing and thereby provides a cost effective and safe method of making steel. It would be well known to the person in the related art that the metallurgical vessels on which advancements have been proposed under the above in terms of constructional features and intended function are completely different from the presently available CONARC (which is a new generation hybrid steel refining vessel comprising of features of convertor & electric arc furnace, hence derives its name, CONARC) process which is a recent development in this domain which offer significant advantages in terms of productivity

and flexibility of using different proportion of raw materials. It is thus found that in spite of advantage of flexibility of charge-mix such as by way of optimizations in processing parameters to improve charge mix, output quality and address other operational issues, furnace such as the CONARC furnace which usually have lower Height-to-diameter ratio (typically 1:1) as compared to LD Converters (typically 1.4-1.7) have some inherent disadvantages for making effective heat and process utilization which include: a)Less approach area of metal bath surface that is in direct contact with the oxygen jets leading to reduced rates of reaction in the bath hence lower efficiency of the blowing operation. b)Operational limitation on the oxygen flow rate from top lance of maximum 210 Nm3/min due to splash (leading to metallic jams), high refractory wear & other operational difficulties in case of higher flow rate. High skull formation needs arcing heat or physical removal in between. It also causes shell damage/ water leakage. c)Reduced penetration depth and blowing strength of the oxygen jet. d)A disadvantage of increasing oxygen flow rate is increased churning below lance area leading to high erosion of bottom refractory which is significant in case of CONARC because of lower bath height. e)Higher operation times, leading to loss in yield and higher refractory consumption. f)Higher Opening nitrogen at LF. Leading to higher nitrogen in product which is an inherent limitation of EAF & CONARC. g)The side walls always remain exposed to damages. More specifically, the existing CONARC furnace involves a single top lance along the central vertical axis which is used for injecting Oxygen through multiple orifices, as required for the refinement of hot metal. It is a standard practice worldwide to use similar position of the lance and all commercially available steel refining vessels use single lance design. As per the conventional oxygen blowing practice, this oxygen injection into the bath is usually done using a single Top Lance with a max flow rate of 210 Nm3/min. Operational limitation on the oxygen flow rate from top lance of maximum 210 Nm3/min due to splash leads to jamming, while higher flow rate leads to high refractory wear & other operational difficulties. High skull formation needs arcing heat or physical removal in between. It also causes shell damage/ water leakage. Thus because of the above such limitations while using 100% hot metal, higher operational efficiency of converter was desired, that could not be achieved with the existing limitations of CONARC furnace. There has been therefore a continuing need in the related field of steel production using CONARC furnace

to developing a system and method to reduce the cycle time, increase the service life of refractory lining, and improve furnace efficiency and productivity. OBJECTS OF THE INVENTION It is thus the basic object of the present invention to provide for advanced system of blowing involved in furnaces having the limitations of lower height-to-diameter ratio (typically 1:1) such as in CONARC furnace adapted to achieve operational benefits of LD convertor and in the process provide for operations involving such furnaces including the CONARC furnace leading to faster and efficient productivity Another object of the present advancement is directed to advancements to achieve technical advance in the art of effective blowing in furnaces having the limitations of lower height-to-diameter ratio (typically 1:1) such as in CONARC furnace and provide for a method of refining of steel in such refining vessels such as CONARC furnace and in the process achieve higher efficiency and productivity in spite of the limitations of vessels constructions with lower height-to-diameter ratio (typically 1:1). Yet further object of the present advancement is directed to system of blowing and the blowing methodology attained involving the same which would apart from improving efficiency and productivity would also facilitate the automatised slag coating and better shell life (both top and bottom shell) of such furnaces and thus enable attaining for CONARC furnace productivity and yield, compatible with LD converter. Another object is directed to system and a method for steel making involving such CONARC furnace adapted to substantially reduce the oxygen blowing time and the cycle time for furnace operation. A further object of the present invention is directed to providing a system and method of steel making involving advancements in art of oxygen blowing in CONARC furnace for steel making to achieve the operational benefits of LD converter in CONARC furnace. A still further object of the present invention is directed to advancements in system and method for oxygen blowing in CONARC furnace for steel making wherein higher volumetric oxygen flow rate can be achieved for desired faster processing time without increasing the flow rate through individual lance and thus avoiding churning at furnace bottom. A still further object of the present invention is directed to advancements in system and method for oxygen blowing in CONARC furnace for steel making directed to ensure protection of refractory lining on furnace wall and bottom with increased service life and reduced refractory consumption. Yet another object of the present invention is directed to

providing a system and method for oxygen blowing in CONARC furnace for steel making favouring reducing occurrence of Jamming in EAF operation. A still further object of the present invention is directed to providing a system and method for oxygen blowing in CONARC furnace for steel making enabling automatic slag coating on side wall and better Oxygen distribution leading to high shell life (both top shell & bottom shell). A still further object of the present invention is directed to providing a system and method for oxygen blowing in CONARC furnace favouring reduced opening nitrogen at LF, leading to lower nitrogen content in product. SUMMARY OF THE INVENTION The basic aspect of the present invention is directed to a system for oxygen blowing in furnaces having the limitations of lower height-to-diameter ratio (typically 1:1) such as in CONARC furnace for smooth blowing operation and better operational efficiency comprising providing oxygen blowing through plurality of lances disposed within the furnace from top preferably three lances spaced at equal circumferential gaps such that the impact area of the bath blowing is enhanced with controllable oxygen flow rate in individual lances based on desired ferrostatic pressure to avoid jamming and controllable cumulative flow rate of the plurality of lances favouring achieving faster and homogeneous reactions in the bath. A further aspect of the present invention is directed a system for oxygen blowing in furnaces comprising three identical vertical oxygen blowing lances disposed within the furnace from top spaced at equal circumferential gaps on a selective pitch circle diameter maintaining desired gap from furnace wall, each said lance adapted to flow oxygen at said desired rate to favour required slag-metal reaction and homogeneity with reduced oxygen blowing time and the cycle time avoiding splashing or jamming. A still further aspect of the present invention is directed to a system wherein said pitch circle diameter is maintained to the maximum extent possible in relation to furnace configuration such that the lances are closer to the furnace walls. According to an aspect of the invention directed to said system wherein said pitch circle diameter is preferably about 2647mm. A still further aspect of the present invention is directed to said system wherein said vertical oxygen blowing lances are spaced 120 degrees apart on said pitch circle diameter. Yet another aspect of the present invention is directed to said system wherein the gap between each said vertical lance from the furnace wall is maintained at preferably about 1871 mm so as to favour good coating of slag layer throughout the

furnace enhancing furnace life and reducing refractory consumption. A further aspect of the present invention is directed to said system comprising three number gantry lances spatially arranged at an angular distance of 120 degrees, disposed vertically suspended through the furnace delta from the furnace roof, oxygen and water-cooling arrangements for each lance provided, along with necessary visualization on the WinCC HMI screen . A still further aspect of the present invention is directed to a method for smooth blowing operation and better operational efficiency of oxygen blowing in furnaces having the limitations of lower height-to-diameter ratio (typically 1:1) such as in CONARC furnace using the system as described above comprising carrying out said oxygen blowing through plurality of lances disposed within the furnace from top preferably three lances spaced at equal circumferential gaps such that the impact area of the bath blowing is enhanced with controllable oxygen flow rate in individual lances based on desired ferrostatic pressure to avoid jamming and controllable cumulative flow rate of the plurality of lances favouring achieving faster and homogeneous reactions in the bath. A further aspect of the present invention is directed to said method comprising maximum flow rate through each lance maintained at 85 to 125 Nm3/min, preferably 100 Nm3/min, with the cumulative flow rate through all three lances at 255 to 375 Nm3/min, preferably 300 Nm3/min, without adversely affecting the refractory at furnace bottom. A still further aspect of the present invention is directed to said method wherein the gap between lance tip and the metal bath top layer is maintained at 800 to 1000 mm preferably 900 mm which is adjusted based on the basis of Oxygen flow rate in order to achieve sound blowing conditions so that the slag conditions are good avoiding bottom churning or splashes hard blowing, which affects the slag health. Besides, extensive churning will result in increased splashes. Yet another aspect of the present invention is directed to said method wherein the blowing time is maintained for 30 to 35 min preferably 30 min and cycle time is maintained at 55 to 60 preferably 60 min to thereby improving the furnace productivity and yield. A still further aspect of the present invention is directed to a method wherein lower Nitrogen ppm in the liquid steel is achieved due to lower nitrogen pickup due to lesser process time. Yet another aspect of the present invention is directed to said method involving increased use of Chiller is in the range of 28 to 33 preferably 30%, thus effectively reducing the energy demand of the furnace for arcing operation. A

further aspect of the present invention is directed to said method comprising generating slag layer coating during process of oxygen blowing involving said multiple lances. The objects and advantages of the present invention are described hereunder in greater details with reference to the following accompanying non limiting illustrative drawings. BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES Figure 1: shows the Top view of conventional CONARC furnace before modification showing three electrodes and one top lance. Figure 2: shows the Top view of CONARC furnace after modification showing lance system according to the present invention involving three top lances. Figure 3: showing the schematic sectional view of the general assembly drawing of the CONARC furnace showing the arrangement of lance system according to the present invention involving three gantry lances suspended from the furnace roof inside the furnace shell. Figure 4: showing the spatial arrangement of the triple top lance assembly in the CONARC furnace wherein the disposition of the three lances are finalized based on trial. DESCRIPTION OF THE INVENTION The present invention is directed to a lance system for oxygen blowing in CONARC furnace directed to reduce oxygen blow time and cycle time for steel production, improving productivity and yield in a cost effective manner. It is already described that the lower Height-to-diameter ratio (typically 1:1) of CONARC furnace as compared to LD Converters (typically 1.4-1.7) results in much less approach area of metal bath surface that is in direct contact with the oxygen jets leading to reduced rates of reaction in the bath hence lower efficiency of the blowing operation. One obvious approach would be to increase the flow rate of Oxygen, which leads to many operational difficulties and is found to be a non viable solution. Accompanying Figure 1 shows the Top view of conventional CONARC furnace before modification showing three electrodes and one top lance. The lance system according to the present invention distributes the Oxygen through multiple lances (3 in present invention) and ensures a uniformly distributed approach area without any increase in Oxygen flow rate of individual lance. Also, in earlier configuration a single central lance is situated at a greater distance from the walls and hence, it was not able to provide adequate slag layer coating to the refractory walls. In this novel approach, new location of lances, which are relatively closer to the walls, is able to provide a slag coating to the walls thus improving the refractory walls. Accompanying Figure 2 shows the Top view of CONARC furnace after modification

showing lance system according to the present invention involving three top lances. Accompanying Figure 3 is the schematic sectional front view of the general assembly of the CONARC furnace showing the arrangement of lance system according to the present invention involving three gantry lances suspended from the furnace roof inside the furnace shell. According to an embodiment of the present invention as illustrated in Figure 3, the lance system for CONARC furnace incorporates three number gantry lances(1), spatially arranged at an angular distance of 120 degrees, disposed vertically suspended through the furnace delta(3) from the furnace roof(4). The lances are held in position with the help of holding arm(2). Oxygen and water-cooling arrangements for each lance have been provided, along with necessary visualization on the WinCC HMI screen for its operation by the pulpit engineers. The use of three lances has facilitated blowing oxygen with a flow rate of 300 Nm3/min, which was earlier restricted to 210 Nm3/min in case of a conventional Single lance due to operational difficulties. The multiple lances and improved blowing practice help to achieve lower Nitrogen content in product compared to conventional process in CONARC. Moreover, improved life of refractory wall is achieved by means of a slag layer coating generated during process because of new location of lance in proximity to walls of furnace shell(5). Also, erosion of bottom shell is reduced because of reduced churning below the lance region. The maximum flow rate through each lance can be approx. 125 Nm3/min, with the cumulative flow rate through all three lances as 375 Nm3/min, without adversely affecting the refractory at bottom. The spatial arrangement of 3 lances cause better metal-slag reactions in the bath with improved oxygen efficiency as compared to single lance practice, keeping the total flow rate constant in the two cases. It is worthy to note here that with the use of 3 lances, the flow rate through each is lower compared to that in case of single lance (practised now), hence lesser splashing and hence less jamming of roof and elbow as contrast to the present system. With the increase in flow rate, reaction kinetics in the bath increases. Due to the limitations of applicants’ Gas Cleaning Plant (GCP), going beyond a combined flow rate of 375 Nm3/min resulted in increase of the GCP FD cooler inlet temperature to >500 oC, which if continuous can have adverse impact on the Bag filter and other components of GCP. With major modification in our GCP, higher flow-rates can be used. The number of lance to be used has been arrived at on the basis of the following considerations:- ?The relative location of the top lances

should not fall above the porous plugs’ position. ?Limitation on the cumulative flow rate (due to the GCP). ?Reduced oxygen flow rate per lance will result in metallurgical issues like soft blowing. As per prevalent furnace operating conditions, increasing beyond a cumulative flow rate of 375 Nm3/min results in an adverse impact on GCP parametes. Because of the inherent shape of the furnace, the arrangement of 2 lances will not allow fast steel bath mixing, thus less homogeneous steel bath temperature, resulting in inefficient blowing. Using 4 lances is not practical as per our furnace design. Technically, the individual flow rates will be around 94 Nm3/min, which will result in soft blowing. Also the fixed cost and variable cost due to maintenance of 4 lances will increase. The use of 3 lances is optimum for our furnace, with optimum flow-rate per lance and efficient blowing operation with enhanced O2 efficiency. Accompanying Figure 4 schematically shows the spatial arrangement of the triple top lance assembly in the CONARC furnace wherein the disposition of the three lances are finalized through conducting trials. The selective disposition of the three top lances are achieved based on the following considerations:- (1). The Pitch Circle Diameter (PCD) of the three lances should not be so less that the situation of lance tip puncture arises due to extensive splashes created near the impact area of the bath. Such a situation occurred in one of the trials which led to increasing the diameter to the maximum extent possible as per our existing furnace design. Also the loss in homogenity of the bath in terms of bath reactions and temperature is bound to take place. (2). Even the PCD can’t be kept too high (such that the lances are closer to the furnace walls), otherwise appropriate slag-metal reactions in the central area of the bath will not take place resulting in loss of homogenity again in this case. Thus by way of the present invention a lance system for CONARC furnace is provided which would ensure on one hand increased approach area of metal bath surface that is in direct contact with the oxygen jets leading to enhanced rates of reaction in the bath hence improved efficiency of the blowing operation and on the other hand overcomes operational limitation on the oxygen flow rate from top lance of maximum 210 Nm3/min to a level of 300 Nm3/min avoiding problems of splash (leading to metallic jams), high refractory wear & other operational difficulties in case of higher flow rate through single lance. The technological and techno-economic improvements achieved by the system and method of steel production according to the present invention are as follows:

1.Increase in charge-to-LM yield from 87.5 to >88%. 2.Increase in %Chiller from 19.5% to 30%. 3.Less Oxygen consumption per tonne of Hot metal (dropped from 60 Nm3/t to 48.6 Nm3/t). 4.Blowing time reduced from 54 mins to 30 mins. 5.Cycle time reduced from 100 mins to 60 mins. 6.Lower opening nitrogen at LF (reduced from 35-55 ppm to 24-33 ppm). 7.Improved life of side refractory walls by means of a good layer of slag coating resulting from proximity of lance. 8.Reduced erosion of bottom shell due to reduced churning below the lances. It is thus possible by way of the present invention to provide for an advanced system of blowing involved in furnaces having the limitations of lower height-to-diameter ratio (typically 1:1) such as in CONARC furnace adapted to achieve operational benefits of LD converter and in the process provide for operations involving such furnaces including the CONARC furnace leading to faster and efficient productivity, Advantageously , the system of blowing and the blowing methodology attained thereby under the present advancement is further directed to facilitate the automatised slag coating and better shell life (both top and bottom shell) of such furnaces. The advancement would thus enable attaining for CONARC furnace productivity and yield, compatible with LD converter.

5. CLAIMS (not applicable for provisional specification.) We Claim: 1. A system for oxygen blowing in furnaces having the limitations of lower height-to-diameter ratio (typically 1:1) such as in CONARC furnace for smooth blowing operation and better operational efficiency comprising providing oxygen blowing through plurality of lances disposed within the furnace from top preferably three lances spaced at equal circumferential gaps such that the impact area of the bath blowing is enhanced with controllable oxygen flow rate in individual lances based on desired ferrostatic pressure to avoid jamming and controllable cumulative flow rate of the plurality of lances favouring achieving faster and homogeneous reactions in the bath. 2.A system for oxygen blowing in furnaces as claimed in claim 1 comprising three identical vertical oxygen blowing lances disposed within the furnace from top spaced at equal circumferential gaps on a selective pitch circle diameter maintaining desired gap from furnace wall, each said lance adapted to flow oxygen at said desired rate to favour required slag-metal reaction and homogeneity with reduced oxygen blowing time and the cycle time avoiding splashing or jamming. 3.A system as claimed in anyone of claims 1 or 2 wherein said pitch circle diameter is maintained to the maximum extent possible in relation to furnace configuration such that the lances are closer to the furnace walls. 4. A system as claimed in anyone of claims 1 to 3 wherein said pitch circle diameter is preferably about 2647mm. 5. A system as claimed in anyone of claims 1 to 4 wherein said vertical oxygen blowing lances are spaced 120 degrees apart on said pitch circle diameter. 6. A system as claimed in anyone of claims 1 to 5 wherein the gap between each said vertical lance from the furnace wall is maintained at preferably about 1871 mm so as to favour good coating of slag layer throughout the furnace enhancing furnace life and reducing refractory consumption. 7. A system as claimed in anyone of claims 1 to 6 comprising three number gantry lances spatially arranged at an angular distance of 120 degrees, disposed vertically suspended through the furnace delta from the furnace roof, oxygen and water-cooling arrangements for each lance provided, along with necessary visualization on the WinCC HMI screen. 8.A method for smooth blowing operation and better operational efficiency of oxygen blowing in furnaces having the limitations of lower height-to-diameter ratio (typically 1:1) such as in CONARC furnace using the system as claimed in claims 1 to 7 comprising carrying out

said oxygen blowing through plurality of lances disposed within the furnace from top preferably three lances spaced at equal circumferential gaps such that the impact area of the bath blowing is enhanced with controllable oxygen flow rate in individual lances based on desired ferrostatic pressure to avoid jamming and controllable cumulative flow rate of the plurality of lances favouring achieving faster and homogeneous reactions in the bath. 9.A method as claimed in claim 8 comprising maximum flow rate through each lance maintained at 85 to 125 preferably 100 Nm3/min, with the cumulative flow rate through all three lances at 255 to 375 preferably 300 Nm3/min, without adversely affecting the refractory at furnace bottom. 10.A method as claimed in anyone of claims 8 or 9, wherein the gap between lance tip and the metal bath top layer is maintained at 800 to 1000 mm preferably 900 mm which is adjusted based on the basis of Oxygen flow rate in order to achieve sound blowing conditions so that the slag conditions are good avoiding bottom churning or splashes hard blowing, which affects the slag health. Besides, extensive churning will result in increased splashes. 11.A method as claimed in anyone of claims 8 to 10 wherein the blowing time is maintained for 30 to 35 min preferably 30 min and cycle time is maintained at 55 to 60min preferably 60 min to thereby improving the furnace productivity and yield. 12.A method as claimed in anyone of claims 7 to 10 wherein lower Nitrogen ppm in the liquid steel is achieved due to lower nitrogen pickup due to lesser process time. 13.A method as claimed in anyone of claims 7 to 11 involving increased use of Chiller is in the range of 28 to 33 preferably 30%, thus effectively reducing the energy demand of the furnace for arcing operation. 14.A method as claimed in anyone of claims 8 to 13 comprising generating slag layer coating during process of oxygen blowing involving said multiple lances. Dated this the 22nd day of November, 2013 Anjan Sen Of Anjan Sen & Associates (Applicants Agent)
6. DATE AND SIGNATURE (to be given at the end of last page of specification)