Title of Invention	A PROCESS OF MAKING STEEL USING 60% TO 100% HOT METAL IN TWIN-SHELL ELECTRIC ARC FURNACE
Abstract	A process of making steel with hot metal in twin shell electric arc furnace, characterizes charging 60 % to 100 % hot metal in said furnace which is modified by reducing the refractory safety lining thickness, reducing the thickness of Dry Hearth Ramming Mass, wherein the process steps comprises; (a) Killing of hot metal with injection of coke through consumable door lance/supersonic lance with compressed gas and/or air, which conveys coke particles into the bath through the lance (b) Charging of 140 - 220 tons hot metal into the furnace preferably obtained from blast furnace by using the hot metal ladle and Hot metal launder; (c) De-siliconisation by oxygen (99% purity) blowing through top lance at blow rate in the range 150 to 200 Nm3/min and continuously charging lime in the furnace in order to maintain basicity in between 2.5-3; (d) Deslagging of silicon enriched acidicrslag at the end of the above step of de-siliconisation, through the slag door of the furnace.; (e) Decarburisation and dephosphorisation by oxygen (99% purity) blowing at 150 to 200 Nm3/min through top lance and charging lime continuously to maintain basicity in between 2.5-3; (f) Deslagging of (phosphorous enriched slag through the slag door of the furnace; .'(g) Taking sample for chemical analysis & slag analysis and measuring in the temperature range of 1580°C - 1640°C through an immersion lance with the disposable thermocouples; (h) Tapping of liquid steel into the ladle;

Title of Invention

A PROCESS OF MAKING STEEL USING 60% TO 100% HOT METAL IN TWIN-SHELL ELECTRIC ARC FURNACE

Abstract

A process of making steel with hot metal in twin shell electric arc furnace, characterizes charging 60 % to 100 % hot metal in said furnace which is modified by reducing the refractory safety lining thickness, reducing the thickness of Dry Hearth Ramming Mass, wherein the process steps comprises; (a) Killing of hot metal with injection of coke through consumable door lance/supersonic lance with compressed gas and/or air, which conveys coke particles into the bath through the lance (b) Charging of 140 - 220 tons hot metal into the furnace preferably obtained from blast furnace by using the hot metal ladle and Hot metal launder; (c) De-siliconisation by oxygen (99% purity) blowing through top lance at blow rate in the range 150 to 200 Nm3/min and continuously charging lime in the furnace in order to maintain basicity in between 2.5-3; (d) Deslagging of silicon enriched acidicrslag at the end of the above step of de-siliconisation, through the slag door of the furnace.; (e) Decarburisation and dephosphorisation by oxygen (99% purity) blowing at 150 to 200 Nm3/min through top lance and charging lime continuously to maintain basicity in between 2.5-3; (f) Deslagging of (phosphorous enriched slag through the slag door of the furnace; .'(g) Taking sample for chemical analysis & slag analysis and measuring in the temperature range of 1580°C - 1640°C through an immersion lance with the disposable thermocouples; (h) Tapping of liquid steel into the ladle;

Full Text	FORM 2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION (See Section 10) "A PROCESS OF MAKING STEEL USING 60% to 100% HOT METAL IN TWIN-SHELL ELECTRIC ARC FURNACE" Ispat Industries Limited, a Company incorporated under the Companies Act, 1956 and having its office at Casablanca, Plot No. 45, Sector-11, CBD, Belapur, Navi Mumbai-400 614,MaharashtraState,India The following specification particularly describes the nature of this invention and the manner in which it is to be performed. The following specification particularly describes and ascertain the nature of this invention and the manner in which it is to be performed This invention relates to process of making steel using 60% to 100% hot metal in twin-shell electric arc furnace. More particularly this invention relates 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. DEFINITIONS OF VARIOUS TERMS USED IN THE FOLLOWING DESCRIPTION ARE AS FOLLOWS:- 1. Hot Metal: This is a product from Blast Furnace technically termed as molten pig iron or Hot Metal. This is transferred from Blast Furnace to steel melt shop at an approximate temperature of 1450°C through a vessel called as Torpedo car. This is one of a raw material for steel melt shop. The composition is in the approximate range of Carbon: 4.5 -5.0%, Manganese: 0,1 -0.4%, Silicon: 0.3 -1.2%, Sulphur: 0.05% max, Phosphorus: 0.08% max. Titanium: 0.06%max. Balance will be Iron, Fe. 2. Direct Reduced Iron: This is a product from Sponge Iron Plant termed as sponge iron or DRI. Transferred to steel melt shop through conveyor system. The typical composition is: Fe (Total): 93%, SiO2: 1.9%, Carbon: 1.8 %, A12O3: 0.6 % max, Phosphorous: 0.040% max, CaO:0.5% max, MgO: 0.3 % max,.Sulphur : 0.01 % max, Other oxides 1.85%). This is used as coolant during the process. 3. Hot Heel: This is the leftover liquid steel in the furnace after tapping the heat from the furnace. Approximate Quantity of 20 -35 tons will-remain after every batch. This is a process requirement to avoid slag carry over into the ladle at the time of tapping along with steel, which affects the steel quality during refining at secondary metallurgy-stage. 4. Coke : This is a de-oxidiser which is used for the deoxidation of hot heel leftover after tapping the liquid steel. Coke reacts with the dissolved oxygen present in steel and FeO present in slag. This is perfected to avoid any violent reaction during hot metal pouring into EAF. Coke is injected through a consumable or non-consumable supersonic lance 5. Lime: This is used as a flux during the process, to remove all impurities material like oxides and silicates generated. Depending on the raw material composition, quantity of lime to be added is decided. The approximate composition of lime is CaO: 90% minimum, Si02: 1.5% maximum, LOI: 3% max, MgO: 2% maximum, Al2O3: 1.5% maximum. 6. Dolomite: This is also used as a flux to maintain MgO in EAF Slag to reduce furnace refractory erosion. MgO is to be maintained in the range of 8 -10% in slag which is obtained from dolomite. The basic composition of Dolomite is CaO: 50-55%, MgO:30-35%, LOI:4% max, R203:3% max. 7. Liquid Steel: This is the product from furnace, which is further refined in ladle down the line. Liquid steel is super heated up to 1620°C for down stream processing. The melting point of steel is 1539°C. The liquid steel is tapped through a tap hole of 180mm diameter after the end of the heat. The typical composition by weight percent of elements are: Carbon: 0.03%, Managanese:0.15%, Sulphur:0.015%, Phosphorous: 0.010%, Si: 0.03%. However the composition varies depending on end applications. 8. Slag: Slag is a byproduct of furnace, which contains various oxide mixtures. The typical composition of slag is CaO:30-35%, Mgo:8-10%, SiO2:10-15%, FeO:20-25%, A1203: 3%. Slag being lighter in weight floats on top of metal during process. This is drained out of the furnace through slag door from time to time and constant basicity is maintained. 9. Basicity: This is a ratio of basic oxides to acidic oxide (CaO / Si02) present in slag. This ratio is maintained at 2.5 to 3.0, to remove the silicates and oxides during process. EXISTING STEEL MAKING PROCESSES/METHODS KNOWN IN THE PRIOR ART ARE AS FOLLOWS:- 1. Open hearth process: The furnace is refractory lined shallow vessel, heated by either liquid or gaseous fuels using heat regeneration principle. Charge is molten pig iron and scrap. The scrap is heated to near its melting point and molten pig iron from blast furnace is poured into it. The charge may contain iron ore and limestone. Refining is done by oxygen blowing enabling the process autogenous. This process takes a long time affecting the productivity. 2. Converter process: This furnace is having a solid refractory lined bottom with height to diameter (H/D) ratio greater than 1.5. This is a basic oxygen process using oxygen blowing from top. The scrap is used as a coolant. The energy source is from exothermic chemical reactions. The heat is generated by the carbon and oxygen reaction releasing carbon monoxide gas which is called exothermic reaction. The Direct Reduced Iron is not used in this type of furnace. There is no flexibility of charge-mix like that in Electric Arc Furnace. 3. Electric Arc Furnace Process: The energy source in this process is Electrical Energy. The advantage in this method is flexibility of using charge-mix like Direct Reduced Iron, scrap and Hot Metal. The vessel is shallow with two split shells: refractory lined bottom shell and water cooled upper shell. There are two types of Electric Arc Furnaces : AC type & DC type. The high cost of electric energy makes'this process.costly. Hence efforts are made to maximize hot metal in Electric Arc Furnace to reduce cost of production. In the conventional process, Direct Reduced Iron and Hot metal are mixed in the ratio of 40% and 60%. Method of operation of Conventional Process The conventipnal process is called 'ConArc' process.-The philosophy of this concept is to operate two processes i.e., 'Converter' and 'Arc' simultaneously in two alternate shells. This process uses Hot Metal upto 60% and balance Direct Reduced Iron to synchronize the twin-shell operation. When one shell is in blowing mode the other shell will be arcing mode. The furnace capacity to hold the charge is 210 ton. The sequence of operation in thexonventional process is as follows: 1. Furnace preparation: This involves tapping of previous heat, Tap hole filling, furnace repair, if necessary. 2. Killing of hot heel: This process of de-oxidation is carried out through feeding of Aluminum or Ferro Aluminium or Ferro Silicon -or Ferro Manganese from the top. 3. Charging: Hot metal charging upto 60%, through launder from the slag door. The desired quantity of hot metal supplied from Blast Furnace is poured into hot metal ladle. The entire hot metal is poured into the furnace in single pouring before blowing starts. 4. Converter process: Oxygen blowing through the top lance to blow down the Carbon, Silicon, Manganese & de-phosphorisation. 5. Flushing out silicious slag through slag door 6. Roof swiveling and switchover from top lance to arcing mode 7. Arcing process: Meltdown the balance 40% Direct Reduced Iron with Electric Arc. Direct Reduced Iron is fed from the top through conveyer system in the controlled feed-rate. 8. Superheat the total melt to tapping temperature using Electric Energy 9. Check chemistry & temperature as per tapping conditions 10. Tap the liquid steel to ladle retaining 15% of liquid steel called hot heel, in the furnace A typical blowing & arcing profile is given in Table -A The typical activity chart of the conventional process is shown in Table - B hereto. Disadvantages of conventional Process: The basic disadvantages of this process are: 1. Hot metal can be used upto a maximum of 60% only. The furnace volume is a limitation and there is a loss of liquid metal through slag door during deslagging. This means there is a loss of liquid metal yield and hence cost of production is high. 2. Usage of Electric Energy: In this process, charge-mix is 60% hot metal and balance 40% is Direct Reduced Iron. Electric arcing is done to melt the Direct Reduced Iron in the Arcing process. Hence this process consumes costly electrical energy increasing the liquid steel cost. 73. Improper hot heel killing leading to violent reaction and equipment damage: The -killing of hot heel is done through materials like Aluminium or Ferro Aluminium or Ferro Silicon or Ferro Manganese, which are fed from top. The top layer of hot heel being slag, these materials react partially with FeO present in slag and partially react with dissolved oxygen present in liquid steel. This results in inhomogeneous and incomplete reaction. Hence the dissolved oxygen in liquid steel and unreacted FeO present in slag react with carbon in hot metal as soon as hot metal pouring starts. This has led to violent reaction followed by explosion leading to equipment damage frequently. 4. Usage of costlier materials for Hot heel killing: The killing was done through costlier materials like Aluminum or Ferro Aluminium or Ferro Silicon or Ferro Manganese. 5.'Heavy reaction during arcing'cycle resulting in unsafe operation : After the end of blowing and before charging of Direct Reduced Iron for arcing cycle, due to soft blowing and over-oxidation of the bath, there is a tendency of boiling. The high percentage of FeO in slag & carbon in liquid steel will react when slag layer is broken during start of arcing. 6. Increased cost of production due to higher consumption of: a. Power b. Electrode c. Carburiser d. Refractory e. De-oxidisers for hot heel killing 7. Production delays due to Electrode gantry breakdown 8. Higher maintenance cost of Electrode gantry & water cooled cables:- The Improved Process :- The main object of this invention is to obviate the above mentioned drawbacks and limitations of the conventional steel making processes using electric arc furnace and to provide an improved processes/methods of making steel by using twin-shell electric arc furnace in which use of 60% to 100% hot metal is now made possible and Direct Reduced Iron is used just to utilise the excess heat generated during oxygen blowing. Another object of this invention is to provide a process of making steel by using twin-shell electric arc furnace, wherein 100% hot metal is used as the feed stock to the electric arc furnace. A-further object of this invention is to provide a process of making steel by using twin-shell electric arc furnace, wherein the oxygen is blown through top lance and/or door lance. A further object of this invention is to provide a process of making steel by using twin- shell electric arc furnace, wherein killing of hot heel is done with injection of coke through consumable door lance or side lance using compressed air as carrier gas instead of using Aluminum or Ferro Aluminium or Ferro Silicon or Ferro Manganese from the top as in case of prior art process which is very costly in comparison to coke injection of this invention. of using Aluminum or Ferro Aluminium or Ferro Silicon or Ferro Manganese from the top as in case of prior art process which is very costly in comparison to coke injection of this invention. Accordingly this invention provides: A process of making steel with hot metal in twin shell electric arc furnace, characterizes charging 60 % to 100 % hot metal in said furnace which is modified by reducing the refractory safety lining thickness, reducing the thickness of Dry Hearth Ramming Mass, wherein the process steps comprises; a) Killing of hot metal with injection of coke through consumable door lance/supersonic lance with compressed gas and/or air, which conveys coke particles into the bath through the lance b) Charging of 140 - 220 tons of hot metal into the furnace preferably obtained from blast furnace by using the hot metal ladle and hot metal launder; c) De-siliconisation by oxygen (99% purity) blowing through top lance at blow rate in the range 150 - 200 Nm3/min and continuously charging lime in the furnace in order to maintain basicity ratio in between 2.5-3; d) Deslagging of silicon enriched acidic slag at the end of the above step of de- siliconisation, through the slag door of the furnace; e) Decarburisation and dephosphorisation by oxygen (99% purity) blowing at 150 to 200 Nm3/min through toplance and charging lime continuously to maintain basicity ratio in between 2.5-3; f) Deslagging of phosphorous enriched slag through the slag door of the furnace.; g) Taking sample for chemical analysis & slag analysis and measuring in the temperature range of 1580 °C - 1640 °C through an immersion lance with the disposable thermocouples.; h) Tapping of liquid steel into the ladle. THE VARIOUS STEPS OF A PROCESS OF MAKING STEEL USING 60% to 100% HOT METAL IN TWIN-SHELL ELECTRIC ARC FURNACE IS AS UNDER:- 1. Killing of hot heel remained from previous heat: This is done with injection of coke through consumable door lance or side lance using compressed air as carrier gas. The said lance is dipped into the hot heel and the coke is injected at a flow rate of 50 Kg/min so as to escaping the gas produced out of the furnace and eliminating any violent reaction.In the conventional method this is done with costlier Aluminium or ferro alloys like Ferro- Silicon, Ferro Aluminium, Ferro Manganese. This was fed from the top and the reaction was inhomogeneous and incomplete, resulting in violent reaction. Moreover, the products being oxides, remain in the furnace and higher basicity had to be maintained under this condition. Hot heel killing is done in two methods: 1) The said consumable door lance used for injecting the coke for killing of hot heel is mounted on lance manipulator. 2) The injection of coke for killing of hot heel is carried out by the lance inserted through the upper shell of the furnace in order to perform hot heel killing simultaneously with the hot-metal pouring. 2. Quality of Raw material used a. Direct Reduced Iron Fe (Total) : 93 % min Carbon : 1.8% Si02 : 1.9% max. A1203 : 0.6% max Phosphorous : 0.040 % max CaO :0.5% max MgO :-0.3%max Sulphur : 0.010% max Miscellaneous oxides : 1.85% max b. Hot Metal Carbon : 5.-0 % max Manganese : 0.3 % max Silicon : 1.0 % max Sulphur : 0.050% max Phosphorous : 0.080 % max Iron(Fe) : 93.57% min 3. Charging of Hot Metal into the furnace: Hot metal from Blast Furnace is supplied through a vessel called Torpedo. The required quantity is poured into hot metal ladle in the pit. The hot metal from hot metal ladle is transferred to the furnace through an intermediate vessel called hot metal launder, in order to have a controlled pouring. Hot metal launder is preheated before pouring the hot metal. Hot metal charged into the furnace varies preferably in between 60 % to 90%. There are two methods of pouring the hot metal. 1) 60 % to 90% charge of hot metal is carried out in a single charge in the beginning 'itself, before blowing starts followed by single blowing. 2) Charge of 60 % to 90% hot metal is split-into two, 60% of hot metal being first poured in the beginning and blown with the oxygen.and after the end of the first blowing the remaining hot metal is poured into the furnace followed by second blowing. The different methods followed at Ispat's case are given separately as Examples in point no.5., 4. Furnace shell volume: This is a limitation of conventional process. Before adopting the inventive process, the furnace volume is increased. The lower shell of the furnace is modified to accommodate the increased hot metal quantity. The thickness of the safety lining, dry hearth ramming mass is decreased resulting in increase of furnace volume by 18.22%: 5. De-Siliconisation: Oxygen blowing through-top lance at 200 Nm3/min for de-Siliconisation. Lime to be charged continuously to maintain Basicity 2.5 - 3.0. 6. Deslagging: After the end of de-siliconisation, the silicon-enriched slag being acidic in nature is flushed out of the furnace through slag-door 7. Decarburisation and dephosphorisation: Oxygen blowing is done for idecarburisation and dephosphorisation at 200 Nm3/min. Lime is charged continuously to maintain Basicity of 2.5 - 3.0 8. Addition of coolant: During the decarburisation, excess heat energy is generated. Hot metal charge being 60% to 90% and the balance is completed by feeding Direct Reduced Iron into the liquid pool, of the hot meal, which melts by utilizing the excess heat energy generated during the decarburisation and thereby reduced energy cost for melting the said Direct Reduced Iron. The hot metal in charge is with balance quantity as Direct Reduced Iron-which is fed to the liquid pool The Direct Reduced Iron add to the quantity of liquid metal with out any energy cost for melting and acts as a coolant to safeguard the refractory of the furnace from high - temperature to increase the life of refractory and maintaining the temperature of the Liquid metal 1590°C to 1600 °C. 9. Deslagging: Total de-slagging is done for the removal of phosphorous enriched slag. This operation is done without furnace stoppage 10. Sampling : Sample is taken for chemical analysis & slag analysis during the process 11. Temperature measurement: The temperature is measured through an immersion lance with the disposable thermocouples during the process. 12. Tapping: After the confirmation of the tapping conditions like chemistry & temperature and after the end of blowing, top lance is swung back with its roof cover to its parking position. Liquid steel is tapped into the preheated ladle. There is no usage of Electrical Energy. The invention will now be described with respect to the accompanying drawings, wherein: Fig. 1 : Cross section of twin-shell Con Arc Furnace (Conventional) Fig. 2/1: Cross section of Conarc Furnace (Conventional) with Hot heel killing arrangement from the top. Fig. 2/2: Cross section of Conarc Furnace (invented) with Hot heel killing arrangement through slag door. Fig. 3/1: Top view of Conarc Furnace (Conventional) with Hot heel killing arrangement from the top. Fig. 3/2: Top view of Conarc Furnace (invented) with Hot heel killing arrangement through slag door. Fig. 4/1: Cross section of Conarc Furnace under conventional blowing practice. Fig. 4/2: Cross section of Conarc Furnace with invented blowing practice. Fig 1 is cross section of twin-shell (1,2) Conarc furnace comprising Top lance(3) for oxygen blowing, roof(4), refractory lined bottom shell(5),slag door(6) for removal of slag, electrode column(7) for supplying electrical energy. Fig 2/1 is cross section of Conarc Furnace with hot heel killing arrangement through material feeding chute (8) from the top in the conventional mode Fig 2/2 is cross section of Conarc Furnace with hot heel killing arrangement through slag door (6) comprising of coke injection lance (9), coke injection unit (10) and carrier gas unit (11). Fig 3/1 is the top view of Conarc Furnace showing the hot heel killing arrangement through material feeding chute (8) from the top in the conventional mode Fig :3/2 is the top view of Conarc Furnace showing the invented hot heel killing arrangement through slag door (6) comprising of coke injection lance (9), coke injection unit (10) and carrier gas unit (11). Fig 4/1 is the cross section of Conarc furnace in the conventional blowing practice showing the top lance (3) for oxygen blowing. Fig 4/2 is the cross section of Conarc furnace in the invented process showing the top lance (3) as well as the door lance arrangement mounted on oxygen lance manipulator (12), which comprises of oxygen lancing pipe (13) and oxygen hose (14). The oxygen is blown inside the liquid metal (15). ADVANTAGES OF PROCESS OF MAKING STEEL USING 60% to 90% HOT METAL-IN TWIN-SHELL ELECTRIC ARC FURNACE This invention provides the use of hot metal up to 90%. Hot heel killing is done with cheaper material and with safe operation and the cost of production is reduced as described below: 1. Cost reduction due to usage of cheaper coke breeze for hot heel killing: In the. patented process a new innovative method of hot heel killing through coke breeze resulted in. considerable cost reduction by replacing costlier materials like Aluminium, Ferro Silicon, Ferro Manganese or Ferro Aluminium. The cost comparison is given below: SI. No Material Unit consumption kg/tls Unit cost Rs. Cost/ ton Rs. Saving Rs/tls 1 Coke Breeze 2.5 3.50 8.00 163.00-8.00 = 155.00 2 Aluminium 2.0 81.50 163.00 ^Hence there is a cost saving of Rs. 155 per ton of liquid steel produced. The only modification done was replacement of existing oxygen lance mounted on oxygen lance manipulator with coke injector lance. 2. Zero Electrical Energy consumption: In the case of 60-90% Hot Metal, arcing is not required, alternatively oxygen is used with lower cost, for blowing down insignificant elements like Carbon, Manganese, Silicon and Phosphorous. It has been established fact that with an increase.in Hot Metal Ratio (HMR) by 1%, power consumption is reduced by 6kWh per ton of liquid steel (tls) produced. Each unit (kWh) costs Rs.4.00. Hence below matrix shows the savings in Patent Process: Hot Metal Ratio (%) Direct Reduced Iron (%) Energy consumption (kWh/ tls) Reduction in consumption (kWh) Cost benefit (Rs/ tls) 50 50 300 0 0 60 40 240 60 4 x 60 = 240 70 30 180 60 4 x 60 = 240 80 20 120 60 4 x 60 = 240 90 10 0 60 4 x 120 = 480 Hence ultimate effect is reduction in cost of production. 3. Melting of Direct Reduced Iron without Energy consumption: Additional benefit is that during blowing Direct Reduced Iron is used as a coolant to compensate the excessive heat generated during blowing. 4. Zero Electrode consumption: Since electrical energy is not consumed in this process hence electrode consumption is nil, resulting in cost reduction. Inventory of this material is not required. 5. Reduced Carburiser consumption: Carburiser is used to form foamy slag during arcing for melting DRI in conventional process to protect the refractory lining from radiation. This is not required in 60 - 90% Hot metal operation. 6. Saving in Refractory consumption: Refractory erosion is a big constraint in conventional process which is overcome by this new process, since arcing is not required in the inventive process, shell life is increased much more.-. Frequency of furnace repair has drastically come down, resulting in cost reduction. 7. Safe operation In this new process, no any abnormality or violent reaction is observed. The process is very safe and tested with different methods. Examples The four different charging methods and blowing techniques developed according to this invention are given for an example as under: Method 1: Charging of Hot Metal in two-batches with top oxygen blowing in first blow followed by door lance in second blow. 1. Blowing profile is annexed as Table -Chereto Method of operation 1. Set-up time is the furnace preparation time which involves the following activities: -a) Tapping of the previous heat: 5 mins b) EBT filling : 5 mins c) Gunning & Fettling : 6 mins d) Killing of hot heel : 6 mins e) Pouring of hot metal : 8 mins Total : 30 mins During hot heel killing, lime & dolomite is fed at 200 k-g/min for 2.5 mins. 2. Heat-size :200± 2 MT 3. Charge Qty. : 230.MT (Hot metal + chiller DRI) a. Hot heel :20-25 MT b. Hot Metal (IBatch) : 140 MT c. Hot Metal (II Batch) : 65 MT d. Chiller DRI : 25 MT 4. Slag Basicity and Flux addition quantity during Hot metal blowing operation: a. Basicity of 2.5 - 3.0 is to be maintained. b. Addition of flux quantity as per the Table below. 5. Blowing^through Top lance (40 mins): a. Start oxygen blowingat an absolute lance height of 1060 cm at 200 Nm3/min for 40 mins. b. During this period, lime is to fed at 100 kg/min for 35 mins. Dolomite is to be fed at lOOkg/min for 15 mins. c. DRI is used as coolant at 500kg/min after 25 mins of blowing (temp, will be 1590 -1600°C) of blowing for 5 mins. Subsequently DRI is to be fed at 750 kg/min for ' 10 mins. depending on the temperature rise. d. Sample to be drawn after 4000Nm3 blow of oxygen. e. End of first blow after 40 mins of blowing time. 6. Place the launder in position & pour the II batch of 65ton hot metal. This takes 5 mins. 7. Blowing through door lance (54 mins) a. After 75 minutes of process, start door blowing at 100 Nm3/min. through consumable door lance for 54 mins. b.DRI to be fed at 500kg/min for 4 mins after 3 mins. of door blowing till 82 mins c. Sample to be drawn after 3000Nm3 blow of oxygen d. Start lime at 100 kg/min for 32.5 mins after 80th min of the.process. e. Dolo to be fed at 1 OOkg/min after 85 mins of the process for 10 mins f. DRI to be fed at 750kg/min for 4 mins after 82 mins. of process g. During de-carburisation period, minimum slag volume to be maintained h. Check %C & %P within the range and aim bath temperature at 1620 ± 10°C i. At 128th min. of process, celoxis to be taken to judge the oxygen and carbon level 8. Blow end & tapping at 129th min. under the following conditions: a. Temperature : 1620 ± 10 °C b. Carbon : 0.03%-0.04% c. Dissolved oxygen : 700 - 900 ppm 9. Total oxygen consumption during a) Top blowing : 6400 Nm3 b) Door blowing : 5400 Nm3 Total: 11800 Nm3 Method 2: Charging of HM in two batches with top oxygen blowing in Blow I and II blow with top lance followed by door lance 1. Blowing profile : is annexed as Table -D hereto 2. Method of operation 1. Set-up time is the furnace-preparation time, which-involves the following activities: a) Tapping of the previous heat: 5 mins b) EBT filling : 5 mins c) Gunning & Fettling : 6 mins d) Killing of hot heel : 6 mins e) Pouring of hot metal : 8 mins Total : 30 mins During hot heel killing, lime & dolomite is fed at 200 kg/min for 2.5 mins. 2. Heat-size :200± 2MT 3. Charge Qty. : 230 ± 2 MT (Hot metal + chiller DRI) a. Hot heel :20-25 MT b. Hot Metal (I Batch) : 140 MT c. Hot Metal (II Batch) : 65 MT d. Chiller DRI : 25 MT 4. Slag Basicity and Flux addition quantity during Hot metal blowing operation: a. Basicity of 2.5 - 3.0 is to be maintained. 5. Blowing through Top lance (40 mins): a. Start oxygen blowing at an absolute lance height of 1060 cm at 200 Nm3/min for '40 mins. b. During this period, lime is to fed at 100 kg/min for 35 mins. Dolomite is to be fed at 100kg/min for 15 mins. c. DRI is used as coolant at 500kg/min after 25 mins of blowing (temp. will be 1590-1600°C) of blowing for 5 mins. Subsequently DRI is to be fed at 750 kg/min for 10 mins. depending on the temperature rise. d. Sample to be drawn after 4000Nm3 blow of oxygen. e. End of first blow after 40 mins of blowing time. 6. Place the launder in position & pour the II batch of 65ton hot metal. This takes 5 mins. 7. Blowing through Top lance (15 mins) a. After 75 minutes of process, start door blowing at 160 Nm3/min. through consumable top lance for 15 mins. b. DRI to be fed at 500kg/min for 4 mins after 78mins till 82 mins c. Start lime at 100 kg/min for 10 mins after 80 min of the process. d. Dolo to be fed at lOOkg/min after 85 mins of the process for 5 mins e. DRI to be fed at 750kg/min for 4 mins after 82 mins. of process Blowing through Door lance (30 mins) a. Start door blowing at 100Nm3/min for30 mins after 90mins of the process. b. Continue lime from top blowing period, at 100 kg/min for 22.5 mins of door blowing c. Continue dolo from top blowing period, at 100 kg/min for 5 mins of door blowing d. Check %C & %P within the range and aim bath temperature at 1620 ± 10°C e. At 118th min. of process, celox is to be taken to judge the oxygen and carbon level 8. Blow end & tapping at 120 min. under the following conditions: a) Temperature : 1620 ± 10 °C b. Carbon : 0.03'% - 0.:04% c. Dissolved oxygen : 700 - 900 ppm 9. Total oxygen consumption during a) Top blowing I : 6400 Nm3 b) Top blowing II : 2400 Nm3 c) Door blowing :3000 Nm3 Total: 11800 Nm3 Method 3: Gharging of entire HM in two ladles consecutively, single blowing with top Oxygen lance 1. Blowing profile is annexed as Table -E hereto 2. Method of operation 1 Set-up-time is the furnace preparation time which involves the following activities: a) Tapping of the previous heat: 5 mins b)EBT filling : 5 mins c) Gunning & Fettling : 6 mins d) Killing of hot heel : 6 mins e) Pouring of hot metal I : 8 mins f) Pouring of hot metal II : 5 mins Total : 35 mins During hot heel killing, lime & dolomite is fed @ 200 kg/min for 2.5 mins. 2. Heat-size : 200 ± 2 MT 3. Charge Qty. : 230 ± 2 MT (Hot metal + chiller DRI) a. Hot heel :20-25 MT b. Hot Metal (I Batch) : 140 MT c. Hot Metal (II Batch) : 65 MT d. Chiller DRI : 25 MT 4. Slag Basicity and Flux addition quantity during Hot metal blowing operation: a. Basicity of 2.5 - 3.0 is to be maintained. b. Addition of flux quantity as per the Table below. 5. Single blowing through Top lance (75 mins): a. Start oxygen blowing at an absolute lance height of 1050 cm at 200 Nm3/min for 15 mins. b. During this period, lime is to fed at 200 kg/min for 15 mins. from 38th min. till 53 mins. of the process c. Decrease the absolute -lance height to 1000 cm & continue blowing at 200 Nm3/min for 60 mins. d. DRI is used .as coolant at 500kg/min for 50 mins after 53 mins of process of blowing till 103 mins. e. During this period, lime is to fed at 500 kg/min for 50 mins. from 54th min. of the process till 104 min. f. Dolo is to be fed at 100 kg/min from 75th min to 95th min for 20 mins. g. Sample to be drawn after 4000Nm3 blow of oxygen. f.. Check'%C & %P within the range and aim bath temperature at 1620 ± 10°C g. At 108th min. of process, celox is to-be taken to judge the oxygen and carbon level 6. Blow end & tapping at 1 10th min under the following conditions: a. Temperature : 1620 ± 10 °C b. Carbon : 0.03%-0.04% c. Dissolved oxygen : 700 - 900 ppm 7. Total oxygen consumption during blowing : 12000 Nm3 Method 4: Charging of entire HM in two ladles consecutively, first blowing with top oxygen lance followed by door lance 1. Blowing profile is annexed as Table-F hereto 2. Method of operation 1. Set-up time is the furnace preparation time which involves the following activities: a) Tapping of the previous heat: 5 mins b)-EBT filling : 5 mins c) Gunning & Fettling : 6 mins d) Killing of hot heel : 6 mins - e) Pouring of hot metal I : 8 mins f) Pouring of hot metal I : 5 mins -Total : 35 mins During hot heel killing, lime & dolomite is fed at 200 kg/min for 2.5 mins. 2. Heat-size :200 ± 2 MT 3. Charge Qty. : 230 ± 2 MT ( Hot metal + chiller DRI) a. Hot heel : 20-25 MT b. Hot Metal (I Batch) : 140 MT c. Hot Metal (II Batch) : 65 MT d. Chiller DRI : 25 MT 4. Slag Basicity and Flux addition quantity during Hot metal blowing operation: a) Basicity of 2.5 - 3.0 is to be maintained. b) Addition of flux quantity as per the Table below. 5. Blowing through Top lance (69 mins): a. Start oxygen blowing at an absolute lance height of 1060 cm at 200 Nm3/min for 15 mins. Subsequently decrease absolute lance height to 10.00 cm and continue blowing at 200 Nm3/rriin for 44 mins. till 104 mins.of process. b. During this period, lime is to fed at 200 kg/min for 15 mins. Continue lime feeding at l00kg/min for 50 mins. till 103 mins. of process. c. Dolomite is to be fed at 100kg/min for 2.0 mins. from 75th min to 95 mins. of process. d. DRI is used as coolant at 500kg/min for 50 mins. from 52nd min to 102 min. e. Sample to be drawn after 4000Nm3 blow of oxygen. f. End of first-blow after 104 mins of process through top lance 6. Blowing through door lance (10 mins) a. After 104 minutes of process, start door blowing at 100 Nm3/min. through consumable door lance for 10 mins. till 114th min. b. Check %C & %P within the range and aim bath temperature at 1620 ± 10°C c. At 112th min. of process, celox is to be taken to judge the oxygen and carbon level 7. Blow end & tapping at 114th min. under the following conditions: a. Temperature : 1620 ± 10 °C b. Carbon :0.03%-0.04% c. Dissolved oxygen: 700 - 900 ppm 8. Total oxygen consumption during a) Top blowing : 11000 Nm3 b) Door blowing : 1000 Nm3 Total : 12000 Nm3 WECLAIM 1) A process of making steel with hot metal in twin shell electric arc furnace, characterizes charging 60 % to 100 % hot metal in said furnace which is modified by reducing the refractory safety lining thickness, reducing the thickness of Dry Hearth Ramming Mass, wherein the process steps comprises; (a) Killing of hot metal with injection of coke through consumable door lance/supersonic lance with compressed gas and/or air, which conveys coke particles into the bath through the lance (b) Charging of 140 - 220 tons hot metal into the furnace preferably obtained from blast furnace by using the hot metal ladle and Hot metal launder; (c) De-siliconisation by oxygen (99% purity) blowing through top lance at blow rate in the range 150 to 200 Nm3/min and continuously charging lime in the furnace in order to maintain basicity in between 2.5-3; (d) Deslagging of silicon enriched acidicrslag at the end of the above step of de-siliconisation, through the slag door of the furnace.; (e) Decarburisation and dephosphorisation by oxygen (99% purity) blowing at 150 to 200 Nm3/min through top lance and charging lime continuously to maintain basicity in between 2.5-3; (f) Deslagging of (phosphorous enriched slag through the slag door of the furnace; .'(g) Taking sample for chemical analysis & slag analysis and measuring in the temperature range of 1580°C - 1640°C through an immersion lance with the disposable thermocouples; (h) Tapping of liquid steel into the ladle; 2) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claim 1, wherein the said lance used in killing of hot heekis dipped into the hot heel and the coke.is injected at a flow-rate of 50 Kg/min. 3) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claims 1 & 2, wherein the said consumable door lance used for injecting the coke for killing of hot heel is mounted on lance manipulator. 4) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claims 1 & 2, wherein the injection of coke for killing of hot heel is carried out by the lance inserted through the upper shell of the furnace in order to perform hot heel killing simultaneously with the hot metal pouring. 5) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claims 1, wherein the said hot metal charged into the furnace varies preferably in between 60 % to 90%. 6) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claim 5, wherein the said 60 % to 90% charge of hot metal is carried out in a single charge in the beginning itself, before blowing starts followed by single blowing. 7) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claim 5, wherein the said charge of 60 % to 90% hotmetal is split into two, 60% of hot metal being first poured in the beginning and blown with the oxygen and after the end of the first blowing the remaining hot metal is poured into the furnace followed by second blowing. 8) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claim 5, wherein the case of hot meal charge being 60% to 90% and the balance is completed by feeding Direct Reduced Iron into the liquid pool of the hot meal, which melts by utilizing the excess heat energy generated during the redecarburisation.and thereby reduced energy cost for melting the said Direct Reduced Iron. 9) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claim 8, wherein the said Direct Reduced Iron add to the quantity of liquid metal with out any energy cost for melting and acts as a coolant to safeguard the refractory of the furnace from high temperature to increase the life of refractory and maintaining the temperature of the Liquid metal 1590° C to 1600 °C. 10) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claim 1, wherein hot metal launder is pre-heated before pouring the hot metal 11) A process of making steel with hot metal in twin shell electric arc furnace as claimed in any of the preceding claims, wherein the said-oxygen blowing rate for de-siliconisation, de-carburisation and de-phosphorisation is 200 Nm3 per minute. 12) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claim 1, wherein the said lance is dipped into the hot heel and the coke is injected at a flow rate of 50 Kg/min so as to escaping the gas produced out of the furnace and eliminating any violent reaction. 13) A process of making steel with hot metal in twin shell electric arc furnace as claimed in any of the preceding claims, wherein hot metal consists of Carbon 5.0 % max, Manganese 0.3 % max, Silicon 1.0 % max, Sulphur 0.050% max, Phosphorous 0.080 % max & Iron (Fe) 93.57% min. 14) A process of making steel with hot metal in twin shell electric arc furnace as 'Claimed in any of the preceding claims, wherein the said Direct Reduced Iron consists Fe (Total) 93 % min, Carbon 1.8 %, Si02 1.9 % max, A1203 0.6 % max, Phosphorous 0.040 % max, CaO 0.5% max, MgO 0.3 % max, Sulphur 0.010 % max & Miscellaneous oxides 1.85% max. 15. An improved process of making steel using 60% to 90% hot metal in electric arc furnace as claimed in any of the preceding claims, wherein the said electric arc furnace is used for carrying out the process of this invention is having a higher height to diameter (H/D) ratio (increased by about 10-15%), higher furnace volume (increased by about 15-20% ) and lesser refractory thickness (reduced by 18-22%). 16. An improved process of making steel using 60% to 90% hot metal in electric arc furnace of making steel using 60 % to 90% of hot metal in electric arc furnace substantially as herien described and illustrated in the Examples/ Methods 1-4. Dated this 7th day of November, 2001 (Bharat S. Shah) Duly Constituted Attorney

Full Text

FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See Section 10)
"A PROCESS OF MAKING STEEL USING 60% to 100% HOT METAL IN TWIN-SHELL ELECTRIC ARC FURNACE"
Ispat Industries Limited, a Company incorporated under the Companies Act, 1956 and having its office at Casablanca, Plot No. 45, Sector-11, CBD, Belapur, Navi Mumbai-400
614,MaharashtraState,India

The following specification particularly describes the
nature of this invention and the manner in
which it is to be performed.

The following specification particularly describes and ascertain the nature of this invention and the manner in which it is to be performed
This invention relates to process of making steel using 60% to 100% hot metal in twin-shell electric arc furnace.
More particularly this invention relates 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.
DEFINITIONS OF VARIOUS TERMS USED IN THE FOLLOWING DESCRIPTION
ARE AS FOLLOWS:-
1. Hot Metal: This is a product from Blast Furnace technically termed as molten pig iron or Hot Metal. This is transferred from Blast Furnace to steel melt shop at an approximate temperature of 1450°C through a vessel called as Torpedo car. This is one of a raw material for steel melt shop. The composition is in the approximate range of Carbon: 4.5 -5.0%, Manganese: 0,1 -0.4%, Silicon: 0.3 -1.2%, Sulphur: 0.05% max, Phosphorus: 0.08% max. Titanium: 0.06%max. Balance will be Iron, Fe.
2. Direct Reduced Iron: This is a product from Sponge Iron Plant termed as sponge iron or DRI. Transferred to steel melt shop through conveyor system. The typical composition is: Fe (Total): 93%, SiO2: 1.9%, Carbon: 1.8 %, A12O3: 0.6 % max, Phosphorous: 0.040% max, CaO:0.5% max, MgO: 0.3 % max,.Sulphur : 0.01 % max, Other oxides 1.85%). This is used as coolant during the process.
3. Hot Heel: This is the leftover liquid steel in the furnace after tapping the heat from the furnace. Approximate Quantity of 20 -35 tons will-remain after every batch. This is a process requirement to avoid slag carry over into the ladle at the time of tapping along with steel, which affects the steel quality during refining at secondary metallurgy-stage.
4. Coke : This is a de-oxidiser which is used for the deoxidation of hot heel leftover after tapping the liquid steel. Coke reacts with the dissolved oxygen present in steel and FeO present in slag. This is perfected to avoid any violent reaction during hot metal pouring into EAF. Coke is injected through a consumable or non-consumable supersonic lance
5. Lime: This is used as a flux during the process, to remove all impurities material like oxides and silicates generated. Depending on the raw material composition, quantity of lime to be added is decided. The approximate composition of lime is CaO: 90% minimum, Si02: 1.5% maximum, LOI: 3% max, MgO: 2% maximum, Al2O3: 1.5% maximum.

6. Dolomite: This is also used as a flux to maintain MgO in EAF Slag to reduce furnace refractory erosion. MgO is to be maintained in the range of 8 -10% in slag which is obtained from dolomite. The basic composition of Dolomite is CaO: 50-55%, MgO:30-35%, LOI:4% max, R203:3% max.
7. Liquid Steel: This is the product from furnace, which is further refined in ladle down the line. Liquid steel is super heated up to 1620°C for down stream processing. The melting point of steel is 1539°C. The liquid steel is tapped through a tap hole of 180mm diameter after the end of the heat. The typical composition by weight percent of elements are: Carbon: 0.03%, Managanese:0.15%, Sulphur:0.015%, Phosphorous: 0.010%, Si: 0.03%. However the composition varies depending on end applications.
8. Slag: Slag is a byproduct of furnace, which contains various oxide mixtures. The typical composition of slag is CaO:30-35%, Mgo:8-10%, SiO2:10-15%, FeO:20-25%, A1203: 3%. Slag being lighter in weight floats on top of metal during process. This is drained out of the furnace through slag door from time to time and constant basicity is maintained.
9. Basicity: This is a ratio of basic oxides to acidic oxide (CaO / Si02) present in slag. This ratio is maintained at 2.5 to 3.0, to remove the silicates and oxides during process.
EXISTING STEEL MAKING PROCESSES/METHODS KNOWN IN THE PRIOR
ART ARE AS FOLLOWS:-
1. Open hearth process: The furnace is refractory lined shallow vessel, heated by either liquid or gaseous fuels using heat regeneration principle. Charge is molten pig iron and scrap. The scrap is heated to near its melting point and molten pig iron from blast furnace is poured into it. The charge may contain iron ore and limestone. Refining is done by oxygen blowing enabling the process autogenous. This process takes a long time affecting the productivity.
2. Converter process: This furnace is having a solid refractory lined bottom with height to diameter (H/D) ratio greater than 1.5. This is a basic oxygen process using oxygen blowing from top. The scrap is used as a coolant. The energy source is from exothermic chemical reactions. The heat is generated by the carbon and oxygen reaction releasing carbon monoxide gas which is called exothermic reaction. The Direct Reduced Iron is not used in this type of furnace. There is no flexibility of charge-mix like that in Electric Arc Furnace.
3. Electric Arc Furnace Process: The energy source in this process is Electrical Energy. The advantage in this method is flexibility of using charge-mix like Direct Reduced Iron, scrap and Hot Metal. The vessel is shallow with two split shells: refractory lined bottom shell and water cooled upper shell. There are two types of Electric Arc Furnaces : AC

type & DC type. The high cost of electric energy makes'this process.costly. Hence efforts are made to maximize hot metal in Electric Arc Furnace to reduce cost of production. In the conventional process, Direct Reduced Iron and Hot metal are mixed in the ratio of 40% and 60%.
Method of operation of Conventional Process
The conventipnal process is called 'ConArc' process.-The philosophy of this concept is to operate two processes i.e., 'Converter' and 'Arc' simultaneously in two alternate shells. This process uses Hot Metal upto 60% and balance Direct Reduced Iron to synchronize the twin-shell operation. When one shell is in blowing mode the other shell will be arcing mode. The furnace capacity to hold the charge is 210 ton.
The sequence of operation in thexonventional process is as follows:
1. Furnace preparation: This involves tapping of previous heat, Tap hole filling, furnace repair, if necessary.
2. Killing of hot heel: This process of de-oxidation is carried out through feeding of Aluminum or Ferro Aluminium or Ferro Silicon -or Ferro Manganese from the top.
3. Charging: Hot metal charging upto 60%, through launder from the slag door. The desired quantity of hot metal supplied from Blast Furnace is poured into hot metal ladle. The entire hot metal is poured into the furnace in single pouring before blowing starts.
4. Converter process: Oxygen blowing through the top lance to blow down the Carbon, Silicon, Manganese & de-phosphorisation.
5. Flushing out silicious slag through slag door
6. Roof swiveling and switchover from top lance to arcing mode
7. Arcing process: Meltdown the balance 40% Direct Reduced Iron with Electric Arc. Direct Reduced Iron is fed from the top through conveyer system in the controlled feed-rate.
8. Superheat the total melt to tapping temperature using Electric Energy 9. Check chemistry & temperature as per tapping conditions
10. Tap the liquid steel to ladle retaining 15% of liquid steel called hot heel, in the furnace
A typical blowing & arcing profile is given in Table -A

The typical activity chart of the conventional process is shown in Table - B hereto.

Disadvantages of conventional Process:
The basic disadvantages of this process are:
1. Hot metal can be used upto a maximum of 60% only. The furnace volume is a
limitation and there is a loss of liquid metal through slag door during deslagging. This
means there is a loss of liquid metal yield and hence cost of production is high.
2. Usage of Electric Energy: In this process, charge-mix is 60% hot metal and balance
40% is Direct Reduced Iron. Electric arcing is done to melt the Direct Reduced Iron in
the Arcing process. Hence this process consumes costly electrical energy increasing the
liquid steel cost.
73. Improper hot heel killing leading to violent reaction and equipment damage: The -killing of hot heel is done through materials like Aluminium or Ferro Aluminium or Ferro Silicon or Ferro Manganese, which are fed from top. The top layer of hot heel being slag, these materials react partially with FeO present in slag and partially react with dissolved oxygen present in liquid steel. This results in inhomogeneous and incomplete reaction. Hence the dissolved oxygen in liquid steel and unreacted FeO present in slag react with carbon in hot metal as soon as hot metal pouring starts. This has led to violent reaction followed by explosion leading to equipment damage frequently.

4. Usage of costlier materials for Hot heel killing: The killing was done through costlier materials like Aluminum or Ferro Aluminium or Ferro Silicon or Ferro Manganese.
5.'Heavy reaction during arcing'cycle resulting in unsafe operation : After the end of blowing and before charging of Direct Reduced Iron for arcing cycle, due to soft blowing and over-oxidation of the bath, there is a tendency of boiling. The high percentage of FeO in slag & carbon in liquid steel will react when slag layer is broken during start of arcing.
6. Increased cost of production due to higher consumption of:
a. Power
b. Electrode
c. Carburiser
d. Refractory
e. De-oxidisers for hot heel killing
7. Production delays due to Electrode gantry breakdown
8. Higher maintenance cost of Electrode gantry & water cooled cables:-
The Improved Process :-
The main object of this invention is to obviate the above mentioned drawbacks and limitations of the conventional steel making processes using electric arc furnace and to provide an improved processes/methods of making steel by using twin-shell electric arc furnace in which use of 60% to 100% hot metal is now made possible and Direct Reduced Iron is used just to utilise the excess heat generated during oxygen blowing.
Another object of this invention is to provide a process of making steel by using twin-shell electric arc furnace, wherein 100% hot metal is used as the feed stock to the electric arc furnace.
A-further object of this invention is to provide a process of making steel by using twin-shell electric arc furnace, wherein the oxygen is blown through top lance and/or door lance.
A further object of this invention is to provide a process of making steel by using twin- shell electric arc furnace, wherein killing of hot heel is done with injection of coke through consumable door lance or side lance using compressed air as carrier gas instead of using Aluminum or Ferro Aluminium or Ferro Silicon or Ferro Manganese from the
top as in case of prior art process which is very costly in comparison to coke injection of
this invention.

of using Aluminum or Ferro Aluminium or Ferro Silicon or Ferro Manganese from the top as in case of prior art process which is very costly in comparison to coke injection of this invention.
Accordingly this invention provides:
A process of making steel with hot metal in twin shell electric arc furnace, characterizes charging 60 % to 100 % hot metal in said furnace which is modified by reducing the refractory safety lining thickness, reducing the thickness of Dry Hearth Ramming Mass, wherein the process steps comprises;
a) Killing of hot metal with injection of coke through consumable door lance/supersonic lance with compressed gas and/or air, which conveys coke particles into the bath through the lance
b) Charging of 140 - 220 tons of hot metal into the furnace preferably obtained from blast furnace by using the hot metal ladle and hot metal launder;
c) De-siliconisation by oxygen (99% purity) blowing through top lance at blow rate in the range 150 - 200 Nm3/min and continuously charging lime in the furnace in order to maintain basicity ratio in between 2.5-3;
d) Deslagging of silicon enriched acidic slag at the end of the above step of de-
siliconisation, through the slag door of the furnace;
e) Decarburisation and dephosphorisation by oxygen (99% purity) blowing at 150 to 200 Nm3/min through toplance and charging lime continuously to maintain basicity ratio in between 2.5-3;
f) Deslagging of phosphorous enriched slag through the slag door of the furnace.;
g) Taking sample for chemical analysis & slag analysis and measuring in the temperature range of 1580 °C - 1640 °C through an immersion lance with the disposable thermocouples.;
h) Tapping of liquid steel into the ladle.
THE VARIOUS STEPS OF A PROCESS OF MAKING STEEL USING 60% to 100% HOT METAL IN TWIN-SHELL ELECTRIC ARC FURNACE IS AS UNDER:-
1. Killing of hot heel remained from previous heat: This is done with injection of coke through consumable door lance or side lance using compressed air as carrier gas. The said lance is dipped into the hot heel and the coke is injected at a flow rate of 50 Kg/min

so as to escaping the gas produced out of the furnace and eliminating any violent reaction.In the conventional method this is done with costlier Aluminium or ferro alloys like Ferro- Silicon, Ferro Aluminium, Ferro Manganese. This was fed from the top and the reaction was inhomogeneous and incomplete, resulting in violent reaction. Moreover, the products being oxides, remain in the furnace and higher basicity had to be maintained under this condition.
Hot heel killing is done in two methods:
1) The said consumable door lance used for injecting the coke for killing of hot heel is mounted on lance manipulator.
2) The injection of coke for killing of hot heel is carried out by the lance inserted through the upper shell of the furnace in order to perform hot heel killing simultaneously with the hot-metal pouring.
2. Quality of Raw material used
a. Direct Reduced Iron
Fe (Total) : 93 % min
Carbon : 1.8%
Si02 : 1.9% max. A1203 : 0.6% max Phosphorous : 0.040 % max CaO :0.5% max MgO :-0.3%max
Sulphur : 0.010% max
Miscellaneous oxides : 1.85% max
b. Hot Metal
Carbon : 5.-0 % max
Manganese : 0.3 % max Silicon : 1.0 % max Sulphur : 0.050% max
Phosphorous : 0.080 % max
Iron(Fe) : 93.57% min
3. Charging of Hot Metal into the furnace: Hot metal from Blast Furnace is supplied
through a vessel called Torpedo. The required quantity is poured into hot metal ladle in
the pit. The hot metal from hot metal ladle is transferred to the furnace through an

intermediate vessel called hot metal launder, in order to have a controlled pouring. Hot metal launder is preheated before pouring the hot metal.
Hot metal charged into the furnace varies preferably in between 60 % to 90%. There are two methods of pouring the hot metal.
1) 60 % to 90% charge of hot metal is carried out in a single charge in the beginning
'itself, before blowing starts followed by single blowing.
2) Charge of 60 % to 90% hot metal is split-into two, 60% of hot metal being first
poured in the beginning and blown with the oxygen.and after the end of the first blowing the remaining hot metal is poured into the furnace followed by second blowing.
The different methods followed at Ispat's case are given separately as Examples in point no.5.,
4. Furnace shell volume: This is a limitation of conventional process. Before adopting the inventive process, the furnace volume is increased. The lower shell of the furnace is modified to accommodate the increased hot metal quantity. The thickness of the safety lining, dry hearth ramming mass is decreased resulting in increase of furnace volume by 18.22%:
5. De-Siliconisation: Oxygen blowing through-top lance at 200 Nm3/min for de-Siliconisation. Lime to be charged continuously to maintain Basicity 2.5 - 3.0.
6. Deslagging: After the end of de-siliconisation, the silicon-enriched slag being acidic in nature is flushed out of the furnace through slag-door
7. Decarburisation and dephosphorisation: Oxygen blowing is done for idecarburisation and dephosphorisation at 200 Nm3/min. Lime is charged continuously to maintain Basicity of 2.5 - 3.0
8. Addition of coolant: During the decarburisation, excess heat energy is generated. Hot metal charge being 60% to 90% and the balance is completed by feeding Direct Reduced Iron into the liquid pool, of the hot meal, which melts by utilizing the excess heat energy generated during the decarburisation and thereby reduced energy cost for melting the said Direct Reduced Iron. The hot metal in charge is with balance quantity as Direct Reduced Iron-which is fed to the liquid pool
The Direct Reduced Iron add to the quantity of liquid metal with out any energy cost for melting and acts as a coolant to safeguard the refractory of the furnace from high - temperature to increase the life of refractory and maintaining the temperature of the
Liquid metal 1590°C to 1600 °C.
9. Deslagging: Total de-slagging is done for the removal of phosphorous enriched slag.
This operation is done without furnace stoppage
10. Sampling : Sample is taken for chemical analysis & slag analysis during the process

11. Temperature measurement: The temperature is measured through an immersion lance with the disposable thermocouples during the process.
12. Tapping: After the confirmation of the tapping conditions like chemistry & temperature and after the end of blowing, top lance is swung back with its roof cover to its parking position. Liquid steel is tapped into the preheated ladle. There is no usage of Electrical Energy.
The invention will now be described with respect to the accompanying drawings, wherein:
Fig. 1 : Cross section of twin-shell Con Arc Furnace (Conventional)
Fig. 2/1: Cross section of Conarc Furnace (Conventional) with Hot heel killing arrangement from the top.
Fig. 2/2: Cross section of Conarc Furnace (invented) with Hot heel killing arrangement through slag door.
Fig. 3/1: Top view of Conarc Furnace (Conventional) with Hot heel killing arrangement from the top.
Fig. 3/2: Top view of Conarc Furnace (invented) with Hot heel killing arrangement through slag door.
Fig. 4/1: Cross section of Conarc Furnace under conventional blowing practice.
Fig. 4/2: Cross section of Conarc Furnace with invented blowing practice.
Fig 1 is cross section of twin-shell (1,2) Conarc furnace comprising Top lance(3) for oxygen blowing, roof(4), refractory lined bottom shell(5),slag door(6) for removal of slag, electrode column(7) for supplying electrical energy.
Fig 2/1 is cross section of Conarc Furnace with hot heel killing arrangement through material feeding chute (8) from the top in the conventional mode
Fig 2/2 is cross section of Conarc Furnace with hot heel killing arrangement through slag door (6) comprising of coke injection lance (9), coke injection unit (10) and carrier gas unit (11).
Fig 3/1 is the top view of Conarc Furnace showing the hot heel killing arrangement through material feeding chute (8) from the top in the conventional mode

Fig :3/2 is the top view of Conarc Furnace showing the invented hot heel killing arrangement through slag door (6) comprising of coke injection lance (9), coke injection unit (10) and carrier gas unit (11).
Fig 4/1 is the cross section of Conarc furnace in the conventional blowing practice showing the top lance (3) for oxygen blowing.
Fig 4/2 is the cross section of Conarc furnace in the invented process showing the top lance (3) as well as the door lance arrangement mounted on oxygen lance manipulator (12), which comprises of oxygen lancing pipe (13) and oxygen hose (14). The oxygen is blown inside the liquid metal (15).
ADVANTAGES OF PROCESS OF MAKING STEEL USING 60% to 90% HOT METAL-IN TWIN-SHELL ELECTRIC ARC FURNACE
This invention provides the use of hot metal up to 90%. Hot heel killing is done with cheaper material and with safe operation and the cost of production is reduced as described below:
1. Cost reduction due to usage of cheaper coke breeze for hot heel killing:
In the. patented process a new innovative method of hot heel killing through coke breeze resulted in. considerable cost reduction by replacing costlier materials like Aluminium, Ferro Silicon, Ferro Manganese or Ferro Aluminium. The cost comparison is given below:

SI.
No Material Unit
consumption
kg/tls Unit cost Rs. Cost/ ton Rs. Saving Rs/tls
1 Coke Breeze 2.5 3.50 8.00 163.00-8.00 = 155.00
2 Aluminium 2.0 81.50 163.00
^Hence there is a cost saving of Rs. 155 per ton of liquid steel produced. The only modification done was replacement of existing oxygen lance mounted on oxygen lance manipulator with coke injector lance.
2. Zero Electrical Energy consumption:
In the case of 60-90% Hot Metal, arcing is not required, alternatively oxygen is used with lower cost, for blowing down insignificant elements like Carbon, Manganese, Silicon and Phosphorous. It has been established fact that with an increase.in Hot Metal Ratio (HMR) by 1%, power consumption is reduced by 6kWh per ton of liquid steel (tls) produced. Each unit (kWh) costs Rs.4.00. Hence below matrix shows the savings in Patent Process:

Hot
Metal
Ratio
(%) Direct
Reduced
Iron
(%) Energy consumption (kWh/ tls) Reduction in consumption
(kWh) Cost benefit (Rs/ tls)
50 50 300 0 0
60 40 240 60 4 x 60 = 240
70 30 180 60 4 x 60 = 240
80 20 120 60 4 x 60 = 240
90 10 0 60 4 x 120 = 480
Hence ultimate effect is reduction in cost of production.
3. Melting of Direct Reduced Iron without Energy consumption:
Additional benefit is that during blowing Direct Reduced Iron is used as a coolant to compensate the excessive heat generated during blowing.
4. Zero Electrode consumption:
Since electrical energy is not consumed in this process hence electrode consumption is nil, resulting in cost reduction. Inventory of this material is not required.
5. Reduced Carburiser consumption:
Carburiser is used to form foamy slag during arcing for melting DRI in conventional process to protect the refractory lining from radiation. This is not required in 60 - 90% Hot metal operation.
6. Saving in Refractory consumption:
Refractory erosion is a big constraint in conventional process which is overcome by this new process, since arcing is not required in the inventive process, shell life is increased much more.-. Frequency of furnace repair has drastically come down, resulting in cost reduction.
7. Safe operation
In this new process, no any abnormality or violent reaction is observed. The process is very safe and tested with different methods.
Examples
The four different charging methods and blowing techniques developed according to this invention are given for an example as under:

Method 1:
Charging of Hot Metal in two-batches with top oxygen blowing in first blow followed by door lance in second blow.
1. Blowing profile
is annexed as Table -Chereto

Method of operation
1. Set-up time is the furnace preparation time which involves the following activities:
-a) Tapping of the previous heat: 5 mins
b) EBT filling : 5 mins
c) Gunning & Fettling : 6 mins
d) Killing of hot heel : 6 mins
e) Pouring of hot metal : 8 mins Total : 30 mins
During hot heel killing, lime & dolomite is fed at 200 k-g/min for 2.5 mins.
2. Heat-size :200± 2 MT
3. Charge Qty. : 230.MT (Hot metal + chiller DRI)
a. Hot heel :20-25 MT
b. Hot Metal (IBatch) : 140 MT
c. Hot Metal (II Batch) : 65 MT
d. Chiller DRI : 25 MT
4. Slag Basicity and Flux addition quantity during Hot metal blowing operation:
a. Basicity of 2.5 - 3.0 is to be maintained.
b. Addition of flux quantity as per the Table below.

5. Blowing^through Top lance (40 mins):
a. Start oxygen blowingat an absolute lance height of 1060 cm at 200 Nm3/min for
40 mins.
b. During this period, lime is to fed at 100 kg/min for 35 mins. Dolomite is to be fed
at lOOkg/min for 15 mins.
c. DRI is used as coolant at 500kg/min after 25 mins of blowing (temp, will be 1590
-1600°C) of blowing for 5 mins. Subsequently DRI is to be fed at 750 kg/min for
' 10 mins. depending on the temperature rise.
d. Sample to be drawn after 4000Nm3 blow of oxygen.
e. End of first blow after 40 mins of blowing time.
6. Place the launder in position & pour the II batch of 65ton hot metal. This takes 5 mins.
7. Blowing through door lance (54 mins)
a. After 75 minutes of process, start door blowing at 100 Nm3/min. through
consumable door lance for 54 mins. b.DRI to be fed at 500kg/min for 4 mins after 3 mins. of door blowing till 82 mins
c. Sample to be drawn after 3000Nm3 blow of oxygen
d. Start lime at 100 kg/min for 32.5 mins after 80th min of the.process.
e. Dolo to be fed at 1 OOkg/min after 85 mins of the process for 10 mins
f. DRI to be fed at 750kg/min for 4 mins after 82 mins. of process
g. During de-carburisation period, minimum slag volume to be maintained
h. Check %C & %P within the range and aim bath temperature at 1620 ± 10°C
i. At 128th min. of process, celoxis to be taken to judge the oxygen and carbon level
8. Blow end & tapping at 129th min. under the following conditions:
a. Temperature : 1620 ± 10 °C
b. Carbon : 0.03%-0.04%
c. Dissolved oxygen : 700 - 900 ppm
9. Total oxygen consumption during
a) Top blowing : 6400 Nm3
b) Door blowing : 5400 Nm3

Total: 11800 Nm3
Method 2:
Charging of HM in two batches with top oxygen blowing in Blow I and II blow with top lance followed by door lance
1. Blowing profile : is annexed as Table -D hereto
2. Method of operation
1. Set-up time is the furnace-preparation time, which-involves the following activities:
a) Tapping of the previous heat: 5 mins
b) EBT filling : 5 mins
c) Gunning & Fettling : 6 mins
d) Killing of hot heel : 6 mins
e) Pouring of hot metal : 8 mins Total : 30 mins
During hot heel killing, lime & dolomite is fed at 200 kg/min for 2.5 mins.
2. Heat-size :200± 2MT
3. Charge Qty. : 230 ± 2 MT (Hot metal + chiller DRI)
a. Hot heel :20-25 MT
b. Hot Metal (I Batch) : 140 MT
c. Hot Metal (II Batch) : 65 MT
d. Chiller DRI : 25 MT
4. Slag Basicity and Flux addition quantity during Hot metal blowing operation:
a. Basicity of 2.5 - 3.0 is to be maintained.

5. Blowing through Top lance (40 mins):
a. Start oxygen blowing at an absolute lance height of 1060 cm at 200 Nm3/min for
'40 mins.
b. During this period, lime is to fed at 100 kg/min for 35 mins. Dolomite is to be fed
at 100kg/min for 15 mins.
c. DRI is used as coolant at 500kg/min after 25 mins of blowing (temp. will be
1590-1600°C) of blowing for 5 mins. Subsequently DRI is to be fed at 750
kg/min for 10 mins. depending on the temperature rise.
d. Sample to be drawn after 4000Nm3 blow of oxygen.
e. End of first blow after 40 mins of blowing time.
6. Place the launder in position & pour the II batch of 65ton hot metal. This takes 5 mins.
7. Blowing through Top lance (15 mins)
a. After 75 minutes of process, start door blowing at 160 Nm3/min. through
consumable top lance for 15 mins.
b. DRI to be fed at 500kg/min for 4 mins after 78mins till 82 mins
c. Start lime at 100 kg/min for 10 mins after 80 min of the process.
d. Dolo to be fed at lOOkg/min after 85 mins of the process for 5 mins
e. DRI to be fed at 750kg/min for 4 mins after 82 mins. of process
Blowing through Door lance (30 mins)
a. Start door blowing at 100Nm3/min for30 mins after 90mins of the process.
b. Continue lime from top blowing period, at 100 kg/min for 22.5 mins of door
blowing
c. Continue dolo from top blowing period, at 100 kg/min for 5 mins of door blowing
d. Check %C & %P within the range and aim bath temperature at 1620 ± 10°C
e. At 118th min. of process, celox is to be taken to judge the oxygen and carbon level

8. Blow end & tapping at 120 min. under the following conditions:
a) Temperature : 1620 ± 10 °C
b. Carbon : 0.03'% - 0.:04%
c. Dissolved oxygen : 700 - 900 ppm
9. Total oxygen consumption during
a) Top blowing I : 6400 Nm3
b) Top blowing II : 2400 Nm3 c) Door blowing :3000 Nm3
Total: 11800 Nm3
Method 3:
Gharging of entire HM in two ladles consecutively, single blowing with top Oxygen lance
1. Blowing profile
is annexed as Table -E hereto

2. Method of operation
1 Set-up-time is the furnace preparation time which involves the following activities:
a) Tapping of the previous heat: 5 mins b)EBT filling : 5 mins
c) Gunning & Fettling : 6 mins
d) Killing of hot heel : 6 mins
e) Pouring of hot metal I : 8 mins
f) Pouring of hot metal II : 5 mins
Total : 35 mins
During hot heel killing, lime & dolomite is fed @ 200 kg/min for 2.5 mins.
2. Heat-size : 200 ± 2 MT
3. Charge Qty. : 230 ± 2 MT (Hot metal + chiller DRI)
a. Hot heel :20-25 MT
b. Hot Metal (I Batch) : 140 MT
c. Hot Metal (II Batch) : 65 MT
d. Chiller DRI : 25 MT
4. Slag Basicity and Flux addition quantity during Hot metal blowing operation:
a. Basicity of 2.5 - 3.0 is to be maintained.
b. Addition of flux quantity as per the Table below.

5. Single blowing through Top lance (75 mins):
a. Start oxygen blowing at an absolute lance height of 1050 cm at 200 Nm3/min for
15 mins.
b. During this period, lime is to fed at 200 kg/min for 15 mins. from 38th min. till 53
mins. of the process
c. Decrease the absolute -lance height to 1000 cm & continue blowing at 200
Nm3/min for 60 mins.
d. DRI is used .as coolant at 500kg/min for 50 mins after 53 mins of process of
blowing till 103 mins.
e. During this period, lime is to fed at 500 kg/min for 50 mins. from 54th min. of the
process till 104 min.
f. Dolo is to be fed at 100 kg/min from 75th min to 95th min for 20 mins.
g. Sample to be drawn after 4000Nm3 blow of oxygen.
f.. Check'%C & %P within the range and aim bath temperature at 1620 ± 10°C
g. At 108th min. of process, celox is to-be taken to judge the oxygen and carbon level
6. Blow end & tapping at 1 10th min under the following conditions:
a. Temperature : 1620 ± 10 °C
b. Carbon : 0.03%-0.04%
c. Dissolved oxygen : 700 - 900 ppm
7. Total oxygen consumption during blowing : 12000 Nm3
Method 4:
Charging of entire HM in two ladles consecutively, first blowing with top oxygen lance followed by door lance
1. Blowing profile
is annexed as Table-F hereto

2. Method of operation
1. Set-up time is the furnace preparation time which involves the following
activities:
a) Tapping of the previous heat: 5 mins b)-EBT filling : 5 mins
c) Gunning & Fettling : 6 mins
d) Killing of hot heel : 6 mins
- e) Pouring of hot metal I : 8 mins f) Pouring of hot metal I : 5 mins -Total : 35 mins
During hot heel killing, lime & dolomite is fed at 200 kg/min for 2.5 mins.
2. Heat-size :200 ± 2 MT
3. Charge Qty. : 230 ± 2 MT ( Hot metal + chiller DRI)
a. Hot heel : 20-25 MT
b. Hot Metal (I Batch) : 140 MT
c. Hot Metal (II Batch) : 65 MT
d. Chiller DRI : 25 MT
4. Slag Basicity and Flux addition quantity during Hot metal blowing operation: a) Basicity of 2.5 - 3.0 is to be maintained.
b) Addition of flux quantity as per the Table below.

5. Blowing through Top lance (69 mins):
a. Start oxygen blowing at an absolute lance height of 1060 cm at 200 Nm3/min for
15 mins. Subsequently decrease absolute lance height to 10.00 cm and continue
blowing at 200 Nm3/rriin for 44 mins. till 104 mins.of process.
b. During this period, lime is to fed at 200 kg/min for 15 mins. Continue lime
feeding at l00kg/min for 50 mins. till 103 mins. of process.
c. Dolomite is to be fed at 100kg/min for 2.0 mins. from 75th min to 95 mins. of
process.
d. DRI is used as coolant at 500kg/min for 50 mins. from 52nd min to 102 min.
e. Sample to be drawn after 4000Nm3 blow of oxygen.
f. End of first-blow after 104 mins of process through top lance
6. Blowing through door lance (10 mins)
a. After 104 minutes of process, start door blowing at 100 Nm3/min. through
consumable door lance for 10 mins. till 114th min.
b. Check %C & %P within the range and aim bath temperature at 1620 ± 10°C
c. At 112th min. of process, celox is to be taken to judge the oxygen and carbon level
7. Blow end & tapping at 114th min. under the following conditions:
a. Temperature : 1620 ± 10 °C
b. Carbon :0.03%-0.04%
c. Dissolved oxygen: 700 - 900 ppm
8. Total oxygen consumption during
a) Top blowing : 11000 Nm3
b) Door blowing : 1000 Nm3
Total : 12000 Nm3

WECLAIM
1) A process of making steel with hot metal in twin shell electric arc furnace, characterizes charging 60 % to 100 % hot metal in said furnace which is modified by reducing the refractory safety lining thickness, reducing the thickness of Dry Hearth Ramming Mass, wherein the process steps comprises;
(a) Killing of hot metal with injection of coke through consumable door
lance/supersonic lance with compressed gas and/or air, which conveys
coke particles into the bath through the lance
(b) Charging of 140 - 220 tons hot metal into the furnace preferably obtained from blast furnace by using the hot metal ladle and Hot metal launder;
(c) De-siliconisation by oxygen (99% purity) blowing through top lance at blow rate in the range 150 to 200 Nm3/min and continuously charging lime in the furnace in order to maintain basicity in between 2.5-3;
(d) Deslagging of silicon enriched acidicrslag at the end of the above step of de-siliconisation, through the slag door of the furnace.;
(e) Decarburisation and dephosphorisation by oxygen (99% purity) blowing at 150 to 200 Nm3/min through top lance and charging lime continuously to maintain basicity in between 2.5-3;
(f) Deslagging of (phosphorous enriched slag through the slag door of the furnace;
.'(g) Taking sample for chemical analysis & slag analysis and measuring in the temperature range of 1580°C - 1640°C through an immersion lance with the disposable thermocouples;
(h) Tapping of liquid steel into the ladle;

2) A process of making steel with hot metal in twin shell electric arc furnace as
claimed in claim 1, wherein the said lance used in killing of hot heekis dipped into the
hot heel and the coke.is injected at a flow-rate of 50 Kg/min.
3) A process of making steel with hot metal in twin shell electric arc furnace as
claimed in claims 1 & 2, wherein the said consumable door lance used for
injecting the coke for killing of hot heel is mounted on lance manipulator.
4) A process of making steel with hot metal in twin shell electric arc furnace as
claimed in claims 1 & 2, wherein the injection of coke for killing of hot heel is
carried out by the lance inserted through the upper shell of the furnace in order to
perform hot heel killing simultaneously with the hot metal pouring.
5) A process of making steel with hot metal in twin shell electric arc furnace as
claimed in claims 1, wherein the said hot metal charged into the furnace varies
preferably in between 60 % to 90%.
6) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claim 5, wherein the said 60 % to 90% charge of hot metal is carried out in a single charge in the beginning itself, before blowing starts followed by single blowing.
7) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claim 5, wherein the said charge of 60 % to 90% hotmetal is split into two, 60% of hot metal being first poured in the beginning and blown with the oxygen and after the end of the first blowing the remaining hot metal is poured into the furnace followed by second blowing.
8) A process of making steel with hot metal in twin shell electric arc furnace as
claimed in claim 5, wherein the case of hot meal charge being 60% to 90% and
the balance is completed by feeding Direct Reduced Iron into the liquid pool of
the hot meal, which melts by utilizing the excess heat energy generated during the
redecarburisation.and thereby reduced energy cost for melting the said Direct
Reduced Iron.

9) A process of making steel with hot metal in twin shell electric arc furnace as
claimed in claim 8, wherein the said Direct Reduced Iron add to the quantity of
liquid metal with out any energy cost for melting and acts as a coolant to
safeguard the refractory of the furnace from high temperature to increase the life
of refractory and maintaining the temperature of the Liquid metal 1590° C to 1600
°C.
10) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claim 1, wherein hot metal launder is pre-heated before pouring the hot metal
11) A process of making steel with hot metal in twin shell electric arc furnace as claimed in any of the preceding claims, wherein the said-oxygen blowing rate for
de-siliconisation, de-carburisation and de-phosphorisation is 200 Nm3 per minute.
12) A process of making steel with hot metal in twin shell electric arc furnace as claimed in claim 1, wherein the said lance is dipped into the hot heel and the coke is injected at a flow rate of 50 Kg/min so as to escaping the gas produced out of the furnace and eliminating any violent reaction.
13) A process of making steel with hot metal in twin shell electric arc furnace as
claimed in any of the preceding claims, wherein hot metal consists of Carbon 5.0
% max, Manganese 0.3 % max, Silicon 1.0 % max, Sulphur 0.050% max,
Phosphorous 0.080 % max & Iron (Fe) 93.57% min.
14) A process of making steel with hot metal in twin shell electric arc furnace as
'Claimed in any of the preceding claims, wherein the said Direct Reduced Iron
consists Fe (Total) 93 % min, Carbon 1.8 %, Si02 1.9 % max, A1203 0.6 % max,
Phosphorous 0.040 % max, CaO 0.5% max, MgO 0.3 % max, Sulphur 0.010 %
max & Miscellaneous oxides 1.85% max.

15. An improved process of making steel using 60% to 90% hot metal in electric arc furnace as claimed in any of the preceding claims, wherein the said electric arc furnace is used for carrying out the process of this invention is having a higher height to diameter (H/D) ratio (increased by about 10-15%), higher furnace volume (increased by about 15-20% ) and lesser refractory thickness (reduced by 18-22%).
16. An improved process of making steel using 60% to 90% hot metal in electric arc furnace of making steel using 60 % to 90% of hot metal in electric arc furnace substantially as herien described and illustrated in the Examples/ Methods 1-4.
Dated this 7th day of November, 2001
(Bharat S. Shah)
Duly Constituted Attorney

Documents:

1069-mum-2001-cancelled pages(1-12-2004).pdf

1069-mum-2001-claims(granted)-(1-12-2004).doc

1069-mum-2001-claims(granted)-(1-12-2004).pdf

1069-mum-2001-correspondence(10-12-2004).pdf

1069-mum-2001-correspondence(ipo)-(28-2-2007).pdf

1069-mum-2001-form 1(1-12-2004).pdf

1069-mum-2001-form 1(10-12-2004).pdf

1069-mum-2001-form 1(7-11-2001).pdf

1069-mum-2001-form 19(5-9-2003).pdf

1069-mum-2001-form 2(granted)-(1-12-2004).doc

1069-mum-2001-form 2(granted)-(1-12-2004).pdf

1069-mum-2001-form 26(2-11-2001).pdf

1069-mum-2001-form 3(7-11-2001).pdf

1069-mum-2001-form 5(7-11-2001).pdf

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Patent Number

204622

Indian Patent Application Number

1069/MUM/2001

PG Journal Number

24/2007

Publication Date

15-Jun-2007

Grant Date

28-Feb-2007

Date of Filing

07-Nov-2001

Name of Patentee

ISPAT INDUSTRIES LIMITED

Applicant Address

CASABLANCA, PLOT NO. 45, SECTOR-11, CBD, BELAPUR, NAVI MUMBAI - 400 614, MAHARASHTRA, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	MR. MISRA ATUL KUMAR	FLAT NO. 201, DEV DRASHTI, PLOT NO. 26, MATHERAN ROAD, SECTOR - 12, NEW PANVEL, RAIGAD DISTRICT, MAHARASHTRA, INDIA.

PCT International Classification Number

A41C 1/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA