FORM 2
THE PATENTS ACT, 1970. (39 OF 1970)
COMPLETE SPECIFICATION [See sections 10 and Rule 13]
TITLE A New Process To Manufacture Direct Reduced Iron
(Sponge Iron), Hot (Liquid) Iron, Steel Out Of Formed Briquettes.
APPLICANT Agarwal Bajrang Lai
ADDRESS "Siddharth", Gita Nagar, Raipur, Chhattisgarh, INDIA.
Pin 492 001
NATIONALITY Indian
The following specification describes the nature of this invention and tile manner in which it is to be performed:
TITLE A New Process To Manufacture Direct Reduced Iron
(Sponge Iron), Hot (Liquid) Iron, Steel Out Of Formed Briquettes.

1. Field of Invention
The Invention relates to a new process to manufacture Direct Reduced Iron / Sponge Iron/ Pig Iron, and Steel out of formed briquettes made from iron bearing wastes/fines & carbonaceous materials.
2. Background of the Invention
Hot metal (liquid iron) is currently produced in blast furnaces, which is cast as pig iron for sale or processed in liquid state into steel. Small & medium scale steel making units, which produce steel in induction furnaces, use pig iron, steel scrap and / or sponge iron (DRI) for manufacturing steel. Pig iron is one of the costliest inputs in steel making through induction furnace route. The claimed invention attempts to address this issue. With the claimed invention, hot metal is produced in the induction furnace using iron bearing wastes / fines and coke fines. Subsequently, steel scrap and or DRI can be added to hot metal in the induction furnace to proceed to steel making phase.
Several inventions claim methods of manufacturing briquettes from iron bearing wastes / fines and their subsequent use for iron & steel making. But none of the inventions claim the process of making liquid iron and subsequently steel in the induction furnace without going through an intermediate reduction stage. The uniqueness of this invention is that no intermediate reduction stage in a separate equipment /process is suggested. According to this invention, briquettes are charged directly into the induction furnace along with electrically conductive materials. The reduction of iron oxides into iron takes place in the induction furnace itself with subsequent melting into liquid iron.
US patent No. 3941582 discloses a process for forming highly dense, metal briquettes of reduced size which are suitable for direct melting in an electric furnace. Briquettes,
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as per the claimed process, are formed by intermixing finely divided metal ore concentrates with finely divided carbonaceous reductant along with a thermosetting binder. These briquettes are heated in two stages, first between 350-550 oF and then in non-oxidizing atmosphere between 1900-2200oF. It is claimed that subsequent to these two heating steps, shrunken, highly dense metal mass is produced from briquettes, which may be directly melted in electric induction furnace. Our invention differs with this invention in the sense that in our invention no intermediate heating steps are suggested to convert briquettes into metal.
U. S. Patent No. 4731112 discloses a method of making a molten ferroalloy product in a melting furnace by charging a briquette consisting essentially of metallised iron, granulated alloying metal oxide, into a carbon source, such as coke breeze, to the melting furnace, burning solid carbonaceous material to reduce the alloying metal oxide to metallized form and to heat the drudge to form a molten ferroalloy product.
U.S. Patent no. 6126718 discloses a method of producing iron from a metal containing reducing material comprised of iron oxide compounded with metal reducing materials in a rotary hearth furnace. The reducible material is filled into horizontal trays, where said horizontal trays resemble Ice-trays. The filled horizontal trays are conveyed through a hearth furnace that is fired with a hot, reducing, mixture of gases. The reducible material, which contains iron oxide, is converted into iron.
US Patent No. 4529446 claims to produce cold briquettes from metal containing wastes with aqueous solution of ammonium polyphosphate and magnesia as binders. It is further claimed mat the product finds use as a replacement in whole or part for metal sources in a steel making process.
In Patent No. RU 2150514, use of charge briquettes, containing 63-75% metallic iron, 18-29% iron oxides, 5-7% carbon and balance gangue, in steel making is disclosed. The quality of these briquettes is claimed to be comparable to iron-rich pellets.
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US Patent No. 4032352 discloses a binder composition for agglomerating directly reduced metallized particles and mineral ore particles comprising of pitch, hydrated lime, sodium silicate and water.
Patent No. SU 1127907 mentions use of metallized pellets in quantity 20-30% of the weight of pig iron in low carbon steel converter smelting process to produce high grade, high plasticity steel.
US patent No. 4497661 claims a process for forming the briquettes from metal and / or carbon containing wastes at room temperature using reactible isocynate group containing materials, hydroxyl group containing materials and magnesia as binders. It is further claimed that the product is of use as partial or complete replacement of metal and / or carbon sources in steel making,
US Patent No. 3953196 discloses a process for direct reduction of metal oxides by heating metal oxide - carbonaceous agglomerates in a shaft furnace by flow of hot gases.
US Patent No. 5833735 claims a method for production of briquettes from iron oxide containing steel plant residues and carbon carriers, which can be used up to 30% as converter feed as a scrap substitute.
In none of the inventions mentioned above, direct charging of cold briquettes into the induction furnace for single step manufacturing of liquid iron & steel is claimed.
3. Objects of the Invention
(i) Utilisation of the waste materials obtained in the manufacture of iron and steel like iron ore fines, coke fines, steel mill waste, etc. which otherwise are to be
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disposed off. The preservation of the waste and the process of disposal of such waste are very difficult to due to environmental reasons.
(ii) Use of the raw material like iron ore fines, coke fines, steel mill waste, etc. for the manufacture of steel by the new invented process wherein (hey are directly processed in the induction furnace thereby having advantage of energy conservation and utilization of the waste fines, which are otherwise posing economic and environmental problems, for the manufacture and the production of value added products.
(iii) Utilization of commonly available equipments like briquetting plants and induction heating/melting furnaces for the manufacture of iron and steel from fines / wastes without resorting to complicated intermediate processes / equipments.
(iv) Utilization of iron bearing wastes / fines in place of pig iron in small and medium scale steel making units as pig iron is one of the costliest inputs in such steel making units through induction furnace route thereby achieving the economic advantage even in smaller units.
Detailed Description
In the present invention, briquettes containing iron bearing wastes / fines and carbonaceous materials are charged into induction furnace to produce liquid iron and steel. Sponge iron is produced within the furnace in the intermediate stage.
Iron bearing wastes / fines for use in briquettes could be iron ore fines, mill scale or steel plant wastes (which may include EAF dust or open hearth flue dust, etc.) having at least 50% iron content The carbonaceous material is preferably coke dust with more than 70% fixed carbon content. The binder could be tar or molasses. The briquettes could be formed in one of the commonly available briquetting presses. It is
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advisable to add some electrically conductive material, such as cast iron dust, up to 5% to the raw material for briquetting. This reduces the requirement of scrap during smelting stage. Carbon content in the briquette will depend upon the composition of iron bearing waste / fines and that of other charge materials to be added during the induction smelting stage. The quantity of carbonaceous material is calculated to account for complete reduction of oxides as well as carbon required in the output metal plus the expected carbon losses. The briquettes could be in the size range of 25-100 mm. For best results, the size of briquettes should be of 25-50 mm. The briquettes are sun dried. For faster production or in the regions / seasons of non¬availability of sunshine., mechanized drying can be resorted to.
Briquettes are charged manually or by grab buckets into the induction furnace. If conductive material is added during briquetting stage, then briquettes can be charged alone into the induction furnace to begin the process. Otherwise, iron / steel scrap is charged along with briquettes in layers.
As the power input to the induction furnace is gradually increased, the briquettes are first reduced to direct reduced iron (sponge iron) when fiimace / charge temperature reaches 850-950 C. The carbon monoxide liberated during the reduction process protects the reduced iron even in hot stage from its re-oxidation while in furnace.
While it is possible to transfer the direct reduced iron in hot stage from the induction furnace into a cooler to produce saleable sponge iron, during the experiments of the present invention, it was preferred to proceed to liquid iron stage by further increasing the power input to the induction furnace. At this stage, sponge iron / steel scrap is added to the molten liquid iron to proceed to steel making phase of the process, Finally other additives (such as ferro-alloys) are added and steel is tapped into ingots or into ladles for further processing.
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Thus, this invention enables steel making in a single step process in induction furnace from iron-carbon briquettes containing iron bearing and carbonaceous materials.
7. Claims
I claim:
(i) A process for manufacturing of direct reduced iron (sponge iron), liquid iron and liquid steel, in that sequence, in an induction furnace by charging briquettes (made of iron bearing wastes /fines, carbonaceous materials, with or without electrically conductive materials as constituents of the briquettes) with or without iron / steel scrap as a first step, heating the charge in the induction furnace gradually to first convert briquettes into direct reduced iron (sponge iron) and then to liquid iron, subsequently adding sponge iron / steel scrap / other additives and further heating to produce liquid steel.
(li) A process as per claim (i), wherein the conductivity required for smelting briquettes in the induction furnace is achieved by adding up to 5% conductive material as a constituent of the briquette or charging iron / steel scrap along with briquettes, in layers, into the induction furnace.
(iii) A process as per claim (i), wherein briquettes made of low value iron bearing materials are smelted directly in the induction furnace without going through an intermediate reduction process.
(iv) A process as per claim (i), wherein during the first stage of heating the briquettes in the induction furnace, direct reduced iron (sponge iron) is produced between 850-950°C, which is protected from re-oxidation by the evolving carbon monoxide and which can be transferred to a cooler to produce saleable direct reduced iron (sponge iron).
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(v) A process as per claim (i), wherein direct reduced iron produced as in claim (iv) is allowed to remain in the induction furnace and power input is further increased to produce liquid iron, which can be poured into pigs to produce pig iron.
(vi) A process as per claim (i), wherein the liquid iron produced as in claim (v) is allowed to remain in the induction furnace, power input to further increased, additional sponge iron I steel scrap and other additives charged to the liquid iron melt to produce liquid steel, which can be poured into saleable ingots or transferred into ladles to be taken to continuous casting machine.

Nayan Rawal
Constituted Attorney
For Applicant
Patent Agent

To:
The Controller of Patents,
The Patent Office, at Mumbai, India.

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