Title of Invention	" A PROCESS FOR PRODUCING PIG IRON AND SPHEROIDAL GRAPHITE IRON INGOTS FROM BLUE DUST USING A PLASMA FURNACE"
Abstract	A process comprising the steps: (a) selecting blue dust of required composition and a carbonaceous reductant; (b) feeding the blue dust and reductant with a varying proportion of CaO and MgO into a Linde type plasma furnace, such as herein described; (c) smelting the charge in the fttrnace operating under conditions, such as herein described; (d) pouring the solten charge from the furnace into magnesia coated graphite moulds; (e) feeding a charge of pig lron ingots, carbon in the form of a kind of carbonised lignite called LECO and a magnesium alloy of iron, such as herein described, into the furnace and re-melting the charge under the said operating conditions; (f) homogenelztogthe melt by stirring the same with a graphite rod with further addition of the said magesium alloy to the melt, as required; (g) pouring the melt into magnesia coated graphite moulds in which a given quantity of the said magnesium alloy is spread beforehand. Reference: Figures 1 and 2 of the accompanying drawings.

Title of Invention

" A PROCESS FOR PRODUCING PIG IRON AND SPHEROIDAL GRAPHITE IRON INGOTS FROM BLUE DUST USING A PLASMA FURNACE"

Abstract

A process comprising the steps: (a) selecting blue dust of required composition and a carbonaceous reductant; (b) feeding the blue dust and reductant with a varying proportion of CaO and MgO into a Linde type plasma furnace, such as herein described; (c) smelting the charge in the fttrnace operating under conditions, such as herein described; (d) pouring the solten charge from the furnace into magnesia coated graphite moulds; (e) feeding a charge of pig lron ingots, carbon in the form of a kind of carbonised lignite called LECO and a magnesium alloy of iron, such as herein described, into the furnace and re-melting the charge under the said operating conditions; (f) homogenelztogthe melt by stirring the same with a graphite rod with further addition of the said magesium alloy to the melt, as required; (g) pouring the melt into magnesia coated graphite moulds in which a given quantity of the said magnesium alloy is spread beforehand. Reference: Figures 1 and 2 of the accompanying drawings.

Full Text	The present invention relates to a process for producing pig iron and spheroidal graphite iron ingots from blue dust uaing a plasaa furnace. Blue dust is a powdery ore which is available plentifully in India and contains irt>n oxide (Fe205) to the extent of about 989% aloqg with less than 196 of oxides like SiOp and Al2O3 The presence of sulphur (S) and phosphorus (P) which are treated as" critical impurities of iron is negligibly small in blue dust, namely, less than 0,0696 for S and less than 0.049( for P, Inspite of the abovementioned advantageous featxires, blue dust is not at present directly usable for production of pig iron in a blast furxxace without its prior sintering or pelletizirig at an additional cost which makes its use uneconomic so lorjg as lumpy iron ores are available at a relatively low cost in India. There is therefore a need for providing an economically viable process for producing ingots of pig iron and spheroidal graphite (SG) iron, directly from blue dust, without prior sintering or pelletising thereof. The object of the p:resent invention is to provide an economically viable process for producing value-added products like pig iron and SG (spheroidal graphite) iron ingots directly from blxie dust without sintering or pelletising thereof, in a plasma furnace constructed for the purpose. The invented process comprises the following main steps : (a) selection of blue dust and other Ingredients for use as raw materials; (b) constniction of a Linde type plasma furnace to be used; (c) smelting of blue dust in the plasma furnace to produce pig iron ingots; and (d) production of SG iron ingots from pig iron by nodularization of the graphite content of pig ircaa in magnesium vapour. The blue dust of composition as given in Table I is selected as raw material, which contains (by weight):98.5% Fe2O3,1.05% SiO2, 0.40% AI2O3, 0.035% S and 0.025% P. Because of the negligibly small contents of both S and P, the blue dust selected is considered to be ideally suitable for producing SG iron having an allowable S content limit of 0.14% and P content limit of 0.04%. The distribution of particle size in the selected blue dust is presented in Table II which shows that the content of fine Particles of size below 53 micron is relatively high i.e. 35.88%. The carbonaceous reductant selected for use in the process is the Dankuni char of relatively high fixed carbon content i.e. 55% by weight and low sulphur content i.e. 0.2A% by weight, which is produced by low temperature carbonisation of coal. Besides blue dust and Dankuni char, CaO and MgO powders are added to the charge for adjusting basicity of the slag produced during smelting of the charge in a plasma furnace. The Linde type plasma furnace constructed is capable of being operated in both 'transferred' and 'non-transferred' modes, although the smelting of raw materials in the process was carried out entirely in the 'transferred' mode with a view to attaining an increased thermal efficiency of the furnace. The hearth of the plasma furnace is a magnesia-lined graphite crucible provided with a bubble alumina insulation. Two graphite electrodes are provided in vertical configuration, one above the other, for forming the plasma,between their adjacent ends inside the crucible,!.e. a matter (usually ga^) in an ionised state containing almost equal number of positive and negative charges. The remaining ends of both the electrodes are cooled by circulating water through the copper holders thereof. The upper electrode has an axial bore through which Argon gas is introduced into the arc zone inside the crucible. The lower electrode is held stationary while the upper electrode is movable In the vertical direction by means of a rack and pinion arrangement. The exhaust gases produced in the crucible are allowed to escape thiough an outlet provided for the purpose. The two electr The charge of blue dust and Dankunl char is smelted in the plasma furnace for producing pig iron through reduction of FCgOj into Fe in presence of 25% excess carbon ovex^ the stoichiometric requirement, following the reaction PegOj + 3C - 2Fe + 3C0. Basicity of the slag,namely, the ratio of (CaO + MgO) to (Si02 + AlgO,), is vaxied between 1 and 2, by adding CaO and MgO to the charge. The pig iron produced is converted into ingots of required sizes by casting in moulds, which are re-melted in the plasma furnace with additicm of extra carbon, magnesium alloy of iron and ccaaverted into SG iron by nodularizing the graphites present in the pig iron in presence of magnesium vapour and cast into ingots of required sizes in moulds. The invention is described fully and particularly, without restricting its scope in any manner, with reference to the accompanying drawings in which - Figure 1 is a sectional elevation of the Llnde type plasma furnace ccmstructed and used in the process; and Figure 2 is a flow diagram showing the main steps followed in the process. Referring to Pig. 1, the Linde type plasma furnace constructed for use in the invented process comprises graphite crucible 3 having magnesia lining 2; bubble alumina insulation A; M.S. casing 5; tap hole 6 for discharge of molten metal; alumina bush7ApBp.ower graphite electrode 8 with copper holder 15A:, water inlet 9A and water outlet 10A; outlet 11 for exhaust gases; graphite sleeve 12 for upper graphite electrode 13 provided with copper holder 15B, water inlet 9B and water outlet 10B, axial bore 1A for the entry of plasma forming gas 16 into the crucible, insulation 17, and rack and pinion arrangement 18 for moving the upper graphite electrode downward and upward as required; and hopper 19 for feeding the charge of raw materials into the crucible. The plasma 1 is formed inside the crucible of the furnace betwe^i the adjacent ends of the two graphite electrodes. The typical operating, parameters of the furnace are' : (i ) Plasma generating gas - Argon. (ii) Flow rate of Plasma generating gas - 0.7 to ?.1 litre/ minute. (iii) D.C. Power supply - 20 to 80 volts, 100-550 Amperes. (iv) Power consumption - upto 35 KW. (v) Arc length of plasma - 2-7 cm. (vi) Temperature Attained - 10,000 to 15,000°C. Referring to Fig. 2 the main steps followed in sequence in the process ares (a) feeding the charge of blue dust, Dankuni char and varying weight of CaO and MgO for adjusting basicity, of the slag produced into graphite crucible of the plasma furnace (Fig. 1.) thixsugh hopper 19; (b) smelting the charge in the graphite crucible at a temperature of 10,000 to 15,000°C; (c) discharging the pig iron through tap hole 6 of the plasma furnace into moulds to produce pig iron ingot; (d) re-charging the pig iron ingots into the graphite crucible of the plasma furnace through hopper 19; (e) re-melting the pig iron ingots charged into the graphite czucSbLLe at a pjasma tamper at ure of 10,000 to 15,000°C; (f) homogenaizirig the re-melted pig iron in the graphite crucible with addition of a magnesium alloy of iron; (g) discharging the melt from the graphite crucible into moal.ds through tap hole 6; and (h) removing the SG iron ingots from the mould. Experiments are performed with the composition of the charge of blue dust Dankuni char and vailing weight of CaO and MgO added for adjustment of the slag basicity. A typical-composition of the charge having slag basicity adjusted to 1.5 is presented in Table III. The charge of weight 500 - 750g/2000g is fed Into the graphite crucible of the plasma furnace while keeping the adjacent ends of the upper and lower graphite electrodes 8 and 13 at a separation of less than imm inside the charge. The plasEca forming Argon gas 16 is then allowed to flow into the graphite crucible through the bore 1A in the upper electrode 13. An arc is struck between the adjacent ends of the two electrodes by switching on the electric power supply to the electrodes. The separation between the adjacent ends of the electrodes is then quickljr increased to 2 to 3 mm and kept in this state for about 2 minutes for preheating the charge materials. The upper electrode.13 is.then slowly moved upward' by means of the rack and pinion arrangement 18 to set arc length at 2 to 7 cm. The current flowing through the two •l««trodt« IC thftn iacraased to tlOe Xevel required for smelting the charge materials, Tlrie typical conditions for carrying out the smelting operation are :- (i) Power supply : 20-80V DC, 1OO-550A. (ii) Arc length : 2-7 cm. (iii) Flow rate of Argon gas : 0.7 - 2 litre/minute, (iv) plasma temperature : 10,000 to 15,000^C. (v) diameter of graphite electrodes used : 2.5 cm. (vi) diameter of bore in the upper electrode : 5 mm, (vii) smelting duration (a) for charge weight 5O0-750g ; 20 to 30 minutes. (b) for charge weight 2 kg : 60 to 70 minutes. (viii) Power consumption : 7 KVH per Kg of pig iron produced. On completion of the smelting operation, the molten charge is poured into magnesia coated graphite moulds to produce cylindrical pig iron ingots of weight 200- 250g each for charge weight of 500-750g gud of weight 850g for charge weight of 2000g, Pig iron ingots obtained at slag basicity varying from 1,0 to 1.8 are analysed for their chemical composition and found to be deficient in their Si content. A charge comprising pig iron ingot - A55g, carbon (LEGO) - 23g and Mg alloy containing Fe-51%, Si-^0%, Mg-996 -15g is fed into the same plasma furnace and re-melted therein for 15 minutes under the remad.ning conditions same as followed for the smelting operation. After homogenelsing the melt in the furnace for 2 to 3 minutes, 10 g of the said Mg alloy is added to the melt in the form of lumps of size 2-3 mm with stirring of the melt by means of a graphite rod. The melt is then qiiickly poured into magnesia coated graphite moulds in which 5 g of the Said Mg alloy is spread beforehand. Mg vapour diffuses throughout the melt during solidification of the same in the moulds. The flaky graphite present in pig iron is iiiodularised by Mg vapour to produce SG iron Ingots of the required composition. The chemical composition and percentage yield of the pig iron ingots produced at different slag basicity and the chemical composition of the SG iron ingots produced are given in Tables IV and V respectively. From Table IV it is noted that the yield of pig iron increases from 83 to 97% with increase in the slag basicity from 1.0 to 1.8 but decreases to 88% with further increase in the slag basicity from 1.8 to 2.0, Considering the yield and content of S and P, the pig iron ingots produced at the slag basicity 1,5 appears to be of the optimum quality for the production of SG iron ingots. In respect of the mechanical properties, such as, hardness, ultimate tensile strength, elOTigation at break and machinability also, the SG iron ingots produced at slag basicity 1.5 appears to be the best. The advantages of the invented process are :- 1. The estimated cost of production of SG iron from blue dust is lower in comparision the production in the Blast furnace process. 2. The production rate is A to 6 times faster in comparison with the Blast furnace process. 3. The size of the furnace used is smaller than that of the Blast furnace of equivalent production capacity. A. The heat loss of the furnace is less compare! with the Blast furnace. (Table Removed) …….1 to 5 We Claim :- 1. A process for producing pig ix»on and spheroidal graphite iron ingots from blue dust using a plasma fUrnace, without prior sinterlng/pelletising of the blue dust characterised in that the steps followed are: (a) selecting blue dust of composition (by % weight): Fe2O3 - 98.1 to 98.9, SiO2 - 0.9 to 1.2, Al2O3 - 0.2 to 0.6, S - 0.01 to 0.06 and P - 0.01 to 0.04 and a carbonaceous reductant like Dankuni char containing 54.7% by weight of fixed carbon; (b) feeding a charge of the blue dust and reductant with a varying proportion of CaO and MgO for adjusting the basicity of the slag to be produced, into a Linde type plasma furnace, such as herein described; (c) smelting the charge in the furnace operating under conditions, such as herein described; (d) pouring the molten charge from the furnace into magnesia coated graphite moulds to produce pig iron ingots of weight 200-250 g/850 g, and compositions, (by % weight): C-3.602, Si-0.94, S-0.0093 and P-0.0292; (e) feeding a charge of pig iron ingots, carbon in the form of a kind of carbonised lignite called LSOO and a magnesixam alloy of iron, such as herein described, into the furnace and re-melting the charge under the same operating conditions as in step (c); (f) homogeniixing the melt by stirring the same with a graphite rod with further addition of the said magnesium alloy to the melt, as required; (g) pouring the melt into magnesia coated graphite moulds in which a gi-ven quantity of the said magnesium alloy is spread beforehand; and (h) removing the SG iron ingots of composition (by % weight): C-3.25, P-0.035, S-0.028, S1-2.30, Mg-0.03 and Fe from the moulds. 2. The process as claimed in claim 1, wherein the blue dust contains 35.88?6 by weight of particles of size smaller than 53 micron. 3. The process as claimed in claim 1, wherein the operating conditions of the Linde type plasma furnace used are: plasma temperature - 10,000 to 15,000°C, arc length of plasma -2 to 7 cm, D.C. voltage suppply - 20 to 80 V, current supply -100 to 330 amperes and flow-rate of Argon gas supply - 0.7 to 2.1 litre/minute. 4. The process as claimed in claim 1, wherein the composition of the charge is : blue dust - 373g, Dankuni char -181.15g, CaO - 88.774g and MgO - 17.755g.

Full Text

The present invention relates to a process for producing pig iron and spheroidal graphite iron ingots from blue dust uaing a plasaa furnace.
Blue dust is a powdery ore which is available plentifully in India and contains irt>n oxide (Fe205) to the extent of about 989% aloqg with less than 196 of oxides like SiOp and Al2O3 The presence of sulphur (S) and phosphorus (P) which are treated as" critical impurities of iron is negligibly small in blue dust, namely, less than 0,0696 for S and less than 0.049( for P, Inspite of the abovementioned advantageous featxires, blue dust is not at present directly usable for production of pig iron in a blast furxxace without its prior sintering or pelletizirig at an additional cost which makes its use uneconomic so lorjg as lumpy iron ores are available at a relatively low cost in India.
There is therefore a need for providing an economically viable process for producing ingots of pig iron and spheroidal graphite (SG) iron, directly from blue dust, without prior sintering or pelletising thereof.
The object of the p:resent invention is to provide an economically viable process for producing value-added products like pig iron and SG (spheroidal graphite) iron ingots directly from blxie dust without sintering or pelletising thereof, in a plasma furnace constructed for the purpose.
The invented process comprises the following main steps :
(a) selection of blue dust and other Ingredients for use as raw materials;
(b) constniction of a Linde type plasma furnace to be used;
(c) smelting of blue dust in the plasma furnace to produce pig iron ingots; and
(d) production of SG iron ingots from pig iron by nodularization of the graphite content of pig ircaa in magnesium vapour.
The blue dust of composition as given in Table I is selected as raw material, which contains (by weight):98.5% Fe2O3,1.05% SiO2, 0.40% AI2O3, 0.035% S and 0.025% P. Because of the negligibly small contents of both S and P, the blue dust selected is considered to be ideally suitable for producing SG iron having an allowable S content limit of 0.14% and P content limit of 0.04%.
The distribution of particle size in the selected blue dust is presented in Table II which shows that the content of fine Particles of size below 53 micron is relatively high i.e. 35.88%.
The carbonaceous reductant selected for use in the process is the Dankuni char of relatively high fixed carbon content i.e. 55% by weight and low sulphur content i.e. 0.2A% by weight, which is produced by low temperature carbonisation of coal.
Besides blue dust and Dankuni char, CaO and MgO powders are added to the charge for adjusting basicity of the slag produced during smelting of the charge in a plasma furnace.
The Linde type plasma furnace constructed is capable of being operated in both 'transferred' and 'non-transferred' modes, although the smelting of raw materials in the process was carried out entirely in the 'transferred' mode with a view
to attaining an increased thermal efficiency of the furnace. The hearth of the plasma furnace is a magnesia-lined graphite crucible provided with a bubble alumina insulation. Two graphite electrodes are provided in vertical configuration, one above the other, for forming the plasma,between their adjacent ends inside the crucible,!.e. a matter (usually ga^) in an ionised state containing almost equal number of positive and negative charges. The remaining ends of both the electrodes are cooled by circulating water through the copper holders thereof. The upper electrode has an axial bore through which Argon gas is introduced into the arc zone inside the crucible. The lower electrode is held stationary while the upper electrode is movable In the vertical direction by means of a rack and pinion arrangement. The exhaust gases produced in the crucible are allowed to escape thi*ough an outlet provided for the purpose. The two electr The charge of blue dust and Dankunl char is smelted in the plasma furnace for producing pig iron through reduction of FCgOj into Fe in presence of 25% excess carbon ovex^ the stoichiometric requirement, following the reaction
PegOj + 3C - 2Fe + 3C0. Basicity of the slag,namely, the ratio of (CaO + MgO) to (Si02 + AlgO,), is vaxied between 1 and 2, by adding CaO and MgO to the charge.
The pig iron produced is converted into ingots of required sizes by casting in moulds, which are re-melted in the plasma furnace with additicm of extra carbon, magnesium alloy of iron and ccaaverted into SG iron by nodularizing the graphites present in the pig iron in presence of magnesium vapour and cast into ingots of required sizes in moulds.
The invention is described fully and particularly, without restricting its scope in any manner, with reference to the accompanying drawings in which -
Figure 1 is a sectional elevation of the Llnde type plasma furnace ccmstructed and used in the process; and
Figure 2 is a flow diagram showing the main steps followed in the process.
Referring to Pig. 1, the Linde type plasma furnace constructed for use in the invented process comprises graphite crucible 3 having magnesia lining 2; bubble alumina insulation A; M.S. casing 5; tap hole 6 for discharge of molten metal; alumina bush7ApBp.ower graphite electrode 8 with copper holder 15A:, water inlet 9A and water outlet 10A; outlet 11 for exhaust gases; graphite sleeve 12 for upper graphite electrode 13 provided with copper holder 15B, water inlet 9B and water outlet 10B, axial bore 1A for the entry of plasma forming gas 16 into the crucible, insulation 17, and rack and pinion arrangement 18 for moving the upper graphite electrode downward and upward as required; and hopper 19 for feeding the charge of raw materials into the crucible. The plasma 1 is formed inside the crucible of the furnace betwe^i the adjacent ends of the two graphite electrodes.
The typical operating, parameters of the furnace are' :
(i ) Plasma generating gas - Argon.
(ii) Flow rate of Plasma generating gas - 0.7 to ?.1 litre/
minute.
(iii) D.C. Power supply - 20 to 80 volts, 100-550 Amperes.
(iv) Power consumption - upto 35 KW.
(v) Arc length of plasma - 2-7 cm.
(vi) Temperature Attained - 10,000 to 15,000°C.
Referring to Fig. 2 the main steps followed in sequence in the process ares (a) feeding the charge of blue dust, Dankuni char and varying weight of CaO and MgO for adjusting basicity, of the slag produced into graphite crucible of the plasma furnace (Fig. 1.) thixsugh hopper 19; (b) smelting the charge in the graphite crucible at a temperature of 10,000 to 15,000°C; (c) discharging the pig iron through tap hole 6 of the plasma furnace into moulds to produce pig iron ingot*; (d) re-charging the pig iron ingots into the graphite crucible of the plasma furnace through hopper 19; (e) re-melting the pig iron ingots charged into the graphite czucSbLLe at a pjasma tamper at ure of 10,000 to 15,000°C; (f) homogenaizirig the re-melted pig iron in the graphite crucible with addition of a magnesium alloy of iron; (g) discharging the melt from the graphite crucible into moal.ds through tap hole 6; and (h) removing the SG iron ingots from the mould.
Experiments are performed with the composition of the charge of blue dust Dankuni char and vailing weight of CaO and MgO added for adjustment of the slag basicity. A typical-composition of the charge having slag basicity adjusted to 1.5
is presented in Table III.
The charge of weight 500 - 750g/2000g is fed Into the graphite crucible of the plasma furnace while keeping the adjacent ends of the upper and lower graphite electrodes 8 and 13 at a separation of less than imm inside the charge. The plasEca forming Argon gas 16 is then allowed to flow into the graphite crucible through the bore 1A in the upper electrode 13. An arc is struck between the adjacent ends of the two electrodes by switching on the electric power supply to the electrodes. The separation between the adjacent ends of the electrodes is then quickljr increased to 2 to 3 mm and kept in this state for about 2 minutes for preheating the charge materials. The upper electrode.13 is.then slowly moved upward' by means of the rack and pinion arrangement 18 to set arc length at 2 to 7 cm. The current flowing through the two
•l««trodt« IC thftn iacraased to tlOe Xevel required for smelting
the charge materials, Tlrie typical conditions for carrying out the smelting operation are :-
(i) Power supply : 20-80V DC, 1OO-550A. (ii) Arc length : 2-7 cm. (iii) Flow rate of Argon gas : 0.7 - 2 litre/minute, (iv) plasma temperature : 10,000 to 15,000^C.
(v) diameter of graphite electrodes used : 2.5 cm. (vi) diameter of bore in the upper electrode : 5 mm,
(vii) smelting duration
(a) for charge weight 5O0-750g ; 20 to 30 minutes.
(b) for charge weight 2 kg : 60 to 70 minutes.
(viii) Power consumption : 7 KVH per Kg of pig iron
produced.
On completion of the smelting operation, the molten charge is poured into magnesia coated graphite moulds to produce cylindrical pig iron ingots of weight 200- 250g each for charge weight of 500-750g gud of weight 850g for charge weight of 2000g,
Pig iron ingots obtained at slag basicity varying from 1,0 to 1.8 are analysed for their chemical composition and found to be deficient in their Si content.
A charge comprising pig iron ingot - A55g, carbon (LEGO) - 23g and Mg alloy containing Fe-51%, Si-^0%, Mg-996 -15g is fed into the same plasma furnace and re-melted therein for 15 minutes under the remad.ning conditions same as followed for the smelting operation.
After homogenelsing the melt in the furnace for 2 to 3 minutes, 10 g of the said Mg alloy is added to the melt in the form of lumps of size 2-3 mm with stirring of the melt by means of a graphite rod.
The melt is then qiiickly poured into magnesia coated graphite moulds in which 5 g of the Said Mg alloy is spread beforehand. Mg vapour diffuses throughout the melt during solidification of the same in the moulds. The flaky graphite present in pig iron is iiiodularised by Mg vapour to produce SG iron Ingots of the required composition.
The chemical composition and percentage yield of the pig iron ingots produced at different slag basicity and the chemical composition of the SG iron ingots produced are given in Tables IV and V respectively.
From Table IV it is noted that the yield of pig iron increases from 83 to 97% with increase in the slag basicity from 1.0 to 1.8 but decreases to 88% with further increase in the slag basicity from 1.8 to 2.0, Considering the yield and content of S and P, the pig iron ingots produced at the slag basicity 1,5 appears to be of the optimum quality for the production of SG iron ingots.
In respect of the mechanical properties, such as, hardness, ultimate tensile strength, elOTigation at break and machinability also, the SG iron ingots produced at slag basicity 1.5 appears to be the best.
The advantages of the invented process are :-
1. The estimated cost of production of SG iron from blue dust is lower in comparision the production in the Blast furnace process.
2. The production rate is A to 6 times faster in comparison with the Blast furnace process.
3. The size of the furnace used is smaller than that of the Blast furnace of equivalent production capacity.
A. The heat loss of the furnace is less compare! with the Blast furnace.
(Table Removed) …….1 to 5

We Claim :-
1. A process for producing pig ix»on and spheroidal graphite iron ingots from blue dust using a plasma fUrnace, without prior sinterlng/pelletising of the blue dust characterised in that the steps followed are: (a) selecting blue dust of composition (by % weight): Fe2O3 - 98.1 to 98.9, SiO2 - 0.9 to 1.2, Al2O3 - 0.2 to 0.6, S - 0.01 to 0.06 and P - 0.01 to 0.04 and a carbonaceous reductant like Dankuni char containing 54.7% by weight of fixed carbon; (b) feeding a charge of the blue dust and reductant with a varying proportion of CaO and MgO for adjusting the basicity of the slag to be produced, into a Linde type plasma furnace, such as herein described; (c) smelting the charge in the furnace operating under conditions, such as herein described; (d) pouring the molten charge from the furnace into magnesia coated graphite moulds to produce pig iron ingots of weight 200-250 g/850 g, and compositions, (by % weight): C-3.602, Si-0.94, S-0.0093 and P-0.0292; (e) feeding a charge of pig iron ingots, carbon in the form of a kind of carbonised lignite called LSOO and a magnesixam alloy of iron, such as herein described, into the furnace and re-melting the charge under the same operating conditions as in step (c); (f) homogeniixing the melt by stirring the same with a graphite rod with further addition of the said magnesium alloy to the melt, as required; (g) pouring the melt into magnesia coated graphite moulds in which a gi-ven quantity of the said magnesium alloy is spread beforehand; and (h) removing the SG iron ingots of composition (by % weight): C-3.25, P-0.035, S-0.028, S1-2.30, Mg-0.03 and Fe from the moulds.
2. The process as claimed in claim 1, wherein the blue dust contains 35.88?6 by weight of particles of size smaller than 53 micron.
3. The process as claimed in claim 1, wherein the operating conditions of the Linde type plasma furnace used are: plasma temperature - 10,000 to 15,000°C, arc length of plasma -2 to 7 cm, D.C. voltage suppply - 20 to 80 V, current supply -100 to 330 amperes and flow-rate of Argon gas supply - 0.7 to 2.1 litre/minute.
4. The process as claimed in claim 1, wherein the composition of the charge is : blue dust - 373g, Dankuni char -181.15g, CaO - 88.774g and MgO - 17.755g.

Documents:

891-del-1997-abstract.pdf

891-del-1997-claims.pdf

891-del-1997-complete specifiction (granted).pdf

891-del-1997-correspondence-others.pdf

891-del-1997-correspondence-po.pdf

891-del-1997-description (complete).pdf

891-del-1997-form-1.pdf

891-del-1997-form-19.pdf

891-del-1997-form-2.pdf

891-del-1997-gpa.pdf

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Patent Number

232439

Indian Patent Application Number

891/DEL/1997

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

17-Mar-2009

Date of Filing

08-Apr-1997

Name of Patentee

STEEL AUTHORITY OF INDIA LTD

Applicant Address

ISPAT BHAWAN, LODI ROAD, NEW DELHI-110003, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	SWAPAN KUMAR MUKHERJEE	RDCIS/SAIL, RANCHI 834002, INDIA
2	ALOK KUMAR STSANGI	RDCIS/SAIL, RANCHI 834002, INDIA
3	NARMADESHWAR PRASAD	RDCIS/SAIL, RANCHI 834002, INDIA
4	BIJAN BIHARI NAYAK	RRL, BHUBANESWAR-751013, INDIA
5	BISHNU CHARANARABINDA MOHANTY	RRL, BHUBANESWAR-751013, INDIA
6	KRUSHNA CHANDRA DAS	RRL, BHUBANESWAR-751013, INDIA

PCT International Classification Number

C21C 3/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA