Claims:We Claim:
1. A process for lean iron ore fine based beneficiation and Iron making comprising :
subjecting lean iron ore fines along with low grade coal fines to reduction of the iron ore fines to form para magnetised iron ore fines containing magnetite as major phase such that the transformation of the iron ore fines into magnetite is accompanied with separation of gangue from the low grade iron ore fines and enabling its resulting beneficiation free of any sintering or pelletizing steps.
2. A process as claimed in claim 1 comprising reduction of iron ore fines in reduction roaster including static and/or fluidized bed furnace to form para-magnetized iron ore fines containing magnetite as major mineral phase under controlled atmosphere to restrict wustite formation followed by beneficiating the magnetite containing iron ore fines in low intensity magnetic separator in dry or dry-hot condition after pulverisation to separate out gangue locked in iron ore fines.
3. A process as claimed in anyone of claims 1 or 2 preferably involving mostly -1mm fines and wherein said magnetite containing iron ore fines are beneficiated in low intensity magnetic separator in dry or dry-hot condition after pulverisation to separate out gangue locked in iron ore fines, the beneficiated magnetite fines are downstream into metallic iron as direct reduced iron involving reducing gases in contact with magnetite ore fines resulting in 90-94 % metallization.
4. A process as claimed in anyone of claims 1 to 3 comprising converting DRI fines into hot metal in high temperature furnace preferably a flash melter operated above 20000C.
5. A process as claimed in anyone of claims 1 to 4 wherein said said lean iron ore fines include size range cumulatively 1mm 100% passing and 150micron 100% passing, and reducing gases (CO and H2), provided to kinematically react with the said lean iron ore fines to produce reduced iron ore phase (Magnetite) in the reduction roaster.

6. A process as claimed in anyone of claims 2 to 5 wherein said
reduction roaster is selected from static bed reduction roaster, fluidized bed reduction roaster, spiral path reduction roaster depending on the grade of said lean iron ore fines size distribution and its grade value.
7. A process as claimed in anyone of claims 1 to 6 wherein said reduction roaster converts oxidized phase (Hematite, Goethite, Limonite, Martite) of lean iron ore fines into reduced iron phase (Magnetite) in the temperature
range of 400-6500C with reducing gas composition comprising of CO 25-34%, H2 10 – 15 %, CO2 20 – 30 %, N2 12 -19%, H2O 15 – 22%, CH4 0-2% and SO2 0 – 1 % preferably providing for
conversion percentage of oxidized phase (Hematite, Goethite, Limonite, Martite) of lean iron ore fines into reduced iron phase (Magnetite) in the range of 60% to 85%.
8. A process as claimed in anyone of claims 1 to 7 wherein said phase conversion in reducing atmosphere is accompanied with volume expansion to generate strain on the interphase of gangue material and said iron oxide phases, the thus generated strain leading to ease in liberation, including the downstream flow process comprising of pulveriser for better liberation followed by dry magnetic separation for extracting the valuable magnetite as well as other iron phase.
9. A process as claimed in anyone of claims 1 to 8 involving dry magnetic separator to enhance the iron ore fines grade from 49-59% to 61- 65%, with the weighted yield percentage range between 60 to 85%.
10. A process as claimed in claim 9 wherein for hot condition of reduced iron ore fines the dry magnetic separation, the magnetic intensity of dry magnetic separator is maintained in range of 600gauss to 3000 gauss at higher belt speed 20-40 set point of magnetic separatorwhereas for room temperature condition of reduced iron ore fines the dry magnetic separation is operated in the range of 800 gauss to 4000 gauss at the belt speed 10-25 set point.
11. A process as claimed in anyone of claims 1 to 10 wherein based on the grade of iron ore fines the magnetic intensity and belt speed is selected wherein higher magnetic intensity and belt speed is required for treating the low grade said iron ore fines, whereas the lower magnetic intensity and belt speed is required for treating the high grade said iron or fines.
12. A process as claimed in anyone of claims 1 to 11 wherein output of dry magnetic separator is downstream towards the DRI and wherein the dry magnetic separation comprises single stage separation involving two product concentrate (higher magnetic susceptibility) and tails (reject or lower magnetic susceptibility)
13. A process as claimed in anyone of claims 1 to 11 wherein the product concentrate of dry magnetic separator are transformed into direct reduced iron in vertical metallic retort under reducing condition gasses mainly comprised of CO and H2 wherein the temperature of retort is maintained 850-900oC and involving CO of 55 to 65%, H2 of 25-35%, CO2 of 5 to 10%, H2O of 4 to 8%, N2 of maximum 1% and SO2 of max 1% enabling metallization of 91-94% and gangue load of 8-12%.
14. A process as claimed in anyone of claims 1 to 13 comprising subjecting the said DRI to further processing in melting softening unit involving softening start temperature in the range of 1350 to 1400 deg C, Primary slag forming temperature in the range of 1425 to 1475 deg C, melting start temperature in the range of 1475 to 1525 deg C and melting end temperature in the range of 1525 to 1570 deg C.
15. A process as claimed in anyone of claims 1 to 14 comprising blending DRI fines with flux material to attain the final slag chemistry which has the low melting temperature, capability to control S and Si % in the hot metal with maximum of 19.5% Al2O3 in final slag, with the temperature maintained at 1580-16000C under the reducing atmosphere comprising preferably 30% of CO and 70% of N2.
16. A process as claimed in anyone of claims 1 to 15 comprising solid flow sequence of iron making process from said lean iron ore fines following the iron ore fines first reduced in reduction roaster followed by dry beneficiation using magnetic separator then treated in reduction shaft for direct reduced iron followed by melting in flash melter.
17. A process as claimed in anyone of claims 1 to 16 which involve selectively to produce 1 ton of hot metal the lean iron ore quantity required in the range of 1900 – 2200 kg with Fe content in the range of 50 – 60% with gangue content of 8 to 20%;
the tailing loss in dry magnetic separator quantity ranges from 360 – 480 kg to produce 1 ton of hot metal;
the slag rate from the flash melter is in the range of 230 – 280 kg to produce 1 ton of hot metal;
, the slag temperature in the range of 1460 – 1520 oC with the B2 (CaO/ SiO2) in the range of 1 – 1.07, MgO of 7.5 to 8.5 % and Al2O3 of 19.5% maximum;
to achieve the slag rate and its chemical composition, the required flux is limestone of 85 to120 kg, dolomite of 70 to 100 kg and quartzite of 30 to 50 kg to produce 1 ton of hot metal;
the feed to DRI shaft contains Magnetite phase in the range of 70 – 85% against 70- 95% of hematite in iron ore pellets used in MIDREX, HYL and FINEX;
the hot reducing gas generated in coal gasifier of 65 – 85% is used to reduce predominant magnetite ore in DRI shaft;
the volume of gas required to produce 1 ton of DRI is in the range of 1450 to 1570 Nm3 ;
the volume of gas required to get predominantly magnetite phase in reduction roaster is in the range of 250 to 350 Nm3 to treat 1 ton of low grade lean iron fines;
the volume of tail gas is in the range of 250 to 350 Nm3 to treat 1 ton of low grade lean iron ore fines
18. A process as claimed in anyone of claims 1 to 17 wherein the tail gas composition comprises of CO of 20 to 30%, CO2 of 25 to 35%, H2 of 5 to 12%, N2 of 10 to 20%, H2O of 17 to 25%, CH4 of max 1% and SO2 of max 1%.
19. A process as claimed in anyone of claims 1 to 18 wherein the tail gas contains combustible gas in the range of 25 to 35% (CO + H2) can be utilized in iron and steel making preheaters and stoves
20. A process as claimed in anyone of claims 1 to 19 wherein the hot reducing gas generated from coal gasifier of 25 to 45% are used in flash melter as one of the fuel to produce hot metal.
21. A process as claimed in anyone of claims 1 to 20 wherein the tail gas generated from DRI Shaft is in the range of 1450 to 1570 Nm3 to produce one ton of DRI, said tail gas comprising of 50- 60% of combustible gas like CO and H2. 70 – 80% of this tail gas optionally utilized in iron and steel making preheaters and stove wherein 15 -25% of the tail gas are utilized in reduction roaster with mixing of N2 in the range of 35 – 85 Nm3 to treat 1 ton of low grade iron ore fines.

Dated this the 26th day of October, 2018
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)
IN/PA-199

, Description:FIELD OF THE INVENTION
The present invention relates to a process for production of hot pig iron using lean iron ore fines along with low grade coal fines having a wide particle size distribution without the need for sintering machines, pelletizing machines and coke ovens. During transformation of hematite, Goethite and limonitic iron ore fines into magnetite is accompanying with volume expansion resulting in crack formation at the interface of gangue basically (silica and alumina) that leads to liberation of gangue oxides. To separate gangue from the low grade iron ore fines, the present invention involves a reduction of iron ore fines in static or fluidized bed furnace to form para-magnetized iron ore fines containing magnetite as major mineral phase in a controlled atmosphere to restrict wustite formation. The magnetite containing iron ore fines are beneficiated in low intensity magnetic separator in dry or dry-hot condition after pulverisation to separate out gangue locked in iron ore fines. The beneficiated magnetite fines are downstream into metallic iron called as direct reduced iron in the shaft furnace where the reducing gases are in contact with magnetite ore fines resulting in 90-94 % metallization. The DRI fines are converted into hot metal in high temperature furnace basically a flash melter operated above 20000C.

The reduction gases basically CO and H2 are produced by burning low grade coal fines in coal gasifier. The said reducing gases are circulated from coal gasifier to DRI shaft furnace and flash melter with appropriate proportions of gases and top gases from DRI shaft mixed with nitrogen are passed to reduction roaster to induce magnetite transformation.

Maximum gas utilization will be achieved due to gas recirculation throughout the process and the remaining quantity of gases are called as export gas which will be utilized inside the plant for preheating heaters and stoves.

The hot metal quality so generated having similar chemical composition compared to Blast furnace and COREX furnace with low slag rate in the range of 230 to 280 kg/ton of hot metal.

BACKGROUND OF THE INVENTION
This field of invention associated with direct utilization iron ore fines to convert it into pig iron. This invention is encumbered with Roasting (Static and fluidized), beneficiation (Dry magnetic separation at hot as well as NTP condition) and flash melting process of any grade iron ore fines.
The blast furnace process uses globally as a counter current, high temperature reactor to reduce iron oxides and melt the iron for steel production. The majority of modern blast furnaces uses coke as the primary fuel as reductant and iron ore pellets or sinter as the primary iron rich feedstock. In summary, a modern blast furnace is characterized by the use of pulverized coal injection, oxygen enrichment, high blast temperatures, proper raw material loading (burdening) equipment, high quality coke, proper feedstock preparation, water cooled panels, and fully instrumented process control.
Electric arc furnace processes have evolved rather quickly in comparison to blast furnace processes and technological advances over the past twenty years or so have allowed this technology to increase its proportion of total steel production. The electric arc furnace process is a melting process only. Very little reduction takes place during the electric arc furnace process. Accordingly, the electric arc furnace process is largely dependent on cost effective and reliable sources of iron. The predominant feedstock is scrap. The amount of trace contaminants in the scrap determines the quality of the feed stock. Feedstock quality dictates hot metal quality and hence steel quality
ITmk3 furnace technology was developed by Kobe Steel, LTD of Osaka, Japan, to separate metal from iron ore using coal. Briefly, ITmk3 technology employs a pellet of finely ground iron ore compounded with coal dust and a binder, to metallize the iron oxide into iron, melt and express slag, and then a means to separate a hot iron nugget from the slag.
The finex iron making process is one of the emerging iron making process from the fines. A key feature of the FINEX® Process is that iron production is carried out in two separate process steps. In a series of fluidized-bed reactors, fine iron ore is reduced to direct reduced iron, compacted (HCI) and then transported to a melter-gasifier. Coal and coal briquettes charged to the melter-gasifier are gasified, providing the necessary energy for melting in addition to the reduction gas. Viewing the process from the ore route, a pneumatic conveying system transports the iron ore fines to the fluidized-bed reactor tower. The fine iron ore is then charged to a 3-stage fluidized-bed reactor series. A reduction gas generated in the melter-gasifier flows through each of the fluidized-bed reactors in counter flow to the ore direction. The fine iron ore is fluidized by the gas stream and the ore is increasingly reduced in each reactor step. Following the exit of the reduced iron from the final fluidized-bed reactor, it is then compacted to so-called hot compacted iron or HCI. The HCI is subsequently transported via a hot-transport system to the top of the melter-gasifier where it is directly charged together with coal into the melter-gasifier. Final reduction and melting of the HCI then takes place. In general, 100% of sinter feed fine ore is charged into fluidized bed reactors. 30-50% of pellet feed is also applicable. Brands and mix of iron ore are decided in consideration of chemical and physical properties such as total Fe content, composition structure, grain size, etc.
Hoffman, U.S. Pat. No. 4,731,112, discloses a method of making a molten ferroalloy product in a melting furnace by charging a briquette consisting essentially of metallized 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 charged to form a molten ferroalloy product. Fluxes and slag formers are also charged to the furnace as required.
The Sheet Material Inserting Metallization (SMIMET) study described in Production of direct reduced iron by a sheet material inserting metallization process, ISIJ International, Vol. 41 (2001), Supplement, pp. S13-S16 (Kamijo, C.,Hoshi, M., et. al.), investigated the possibility of using a rotary hearth furnace for production of Direct Reduced Iron (DRI) without the need for special preparation (pelletizing) of the raw materials. The SMIMET study was a laboratory study to determine the efficacy of mixing fine coal (94% of the particles having diameters less than 125 um), fine ore (both hematite and magnetite with 94% of the particles having diameters less than 125 um), and water, forming a 10 mm sheet of raw material in a nickel or alumina container, and placing this material into an inert atmosphere (N2 or CO2) electrically heated furnace at 13000 C. (23720 F.). The results of the SMIMET process study showed that iron reduction is possible using the volatile material devolatilized directly from coal, reduction occurs at a fairly fast rate (i.e., 10 mm converted in 15 min), and showed that a high degree of metallization (% metallic Fe divided by % total Fe) could be achieved in as little as 15 minutes. While the study showed promising results, the SMIMET process requires a rotary hearth furnace with all of its ancillary equipment. A rotary hearth furnace is quite expensive to build and the associated fuel/power costs are also substantial. Applicability of the DRI product as a blast furnace feed material is unknown and cannot be assumed because the SMIMET study makes no mention of the size, shape, or strength of the product. To date, no commercialization of the SMIMET process is known to the present inventor.
SaWa et al, U.S. Pat. No. 6,126,718, discloses a method of producing iron from a metal containing reducible material comprised of iron oxide compounded with metal reducing materials in a rotary hearth furnace. In the SaWa U.S. Pat. No. 6,126,718 method, 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. In the latter Zones of the rotating hearth furnace, the reducible mixture melts, forming liquid iron having a cap of slag. The iron and slag are cooled, and then separated by screening into iron and slag.

The High-Quality Iron Pebble (Hi-QIP) process described in US. Pat. No. 6,126,718 to SaWa, et. al. (the ’718 patent), represents an advancement on the SMIMET and COMET processes in that it does operate at temperatures sufficiently high to produce a form of pig iron. The product of the Hi-QIP process is referred to as iron pebble. As with the SMIMET and COMET processes, the Hi-QIP process uses a rotary hearth furnace with its attendant high capital cost and supplementary fuel requirements in order to operate at temperatures adequate to melt the iron. The ’718 patent discloses that the iron pebbles are suitable for both electric arc furnace and blast furnace operations. The article, “Hi-QIP, A New Ironmaking Process,” by SaWa, et al., in Iron and Steel Technology 87-94 (March 2008) describes problems associated with commercialization of this process. Most notably they cite the “furnace energy efficiency and reduction of fuel unit consumption.”
European Patent B1-0010627, a coal fluidized-bed with a high-temperature zone in the lower region is produced in a melter gasifier, to which iron sponge particles are added from above. On account of the impact pressure and buoyancy forces in the coal fluidized-bed, iron sponge particles having sizes greater than 3 mm are considerably braked and substantially elevated in temperature by the heat exchange with the fluidized bed. They impinge on the slag layer forming immediately below the high-temperature zone at a reduced speed and are melted on or in the same. The maximum melting performance of the melter gasifier, and thus the amount and temperature of the molten iron produced, not only depends on the geometric dimensions of the melter gasifier, but also are determined to a large extent by the quality of the coal used and by the portion of larger particles in the iron sponge added. When using low-grade coal, the heat supply to the slag bath, and thus the melting performance for the iron sponge particles, decline accordingly. In particular, with a large portion of iron sponge particles having grain sizes of about 3 mm, which cannot be heated to the same extent as smaller particles by the coal fluidized-bed when braked in their fall and which, therefore, necessitate a higher melting performance in the region of the slag layer, the reduced melting performance has adverse effects in case low-grade coal is used.
A melter gasifier is an advantageous method for producing molten iron or steel pre products and reduction gas are described in U.S. Pat. No. 4,588,437. Thus there is disclosed a method and a melter gasifier for producing molten iron or steel pre products and reduction gas. A first fluidized-bed zone is formed by coke particles, with a heavy motion of the particles, above a first blow-in plane by the addition of coal and by blowing in oxygen-containing gas. Iron sponge particles and/or pre-reduced iron ore particles with a substantial portion of particle sizes of more than 3 mm are added to the first fluidized-bed zone from above. A melter gasifier for carrying out the method is formed by a refractory lined vessel having openings for the addition of coal and ferrous material, openings for the emergence of the reduction gases produced, and openings for tapping the metal melt and the slag. Pipes or nozzles for injection of gases including oxygen enter into the melter gasifier above the slag level at at least two different heights.
U.S. Pat. No. 4,849,015 to Fassbinder et al. discloses a method for two-stage melt reduction of iron ore, in which iron ore is pre reduced substantially to wustite and at the same time melted down in a melting cyclone, and then liquid hot metal is produced in an iron bath reactor connected to the outlet of the melting cyclone and receiving the melted wustite by adding carbonaceous fuels and oxidizing gas to the melt. The resulting reaction gas from the melt is after burned, and the dust-laden, partly burned reaction gases from the iron bath reactor are accelerated and further after burned by adding a hot blast with a temperature of 800° C. to 1500° C., and at least a portion of such accelerated, after burned reaction gases are introduced into the melting cyclone to reduce and melt fresh iron ore.
Clearly, the fundamentals of reducing iron oxides into metallic iron are well established. An iron oxide in the presence of a reducing gas is heated to create the reducing reaction. In a laboratory setting, a process for reducing small quantities of most any iron oxide should be achievable if the practicalities necessary for economic sustainability in a commercial setting are ignored. In other words, a successful process developed and tested in a laboratory on small quantities of raw materials may prove the concept, yet fail to provide a solution to the real world problems faced by the iron and steel industry. Many proposed industrial technology development projects have historically failed due to scale up problems. Scale up problems occur in processes that have been proven at the bench scale level (laboratory scale), and even at the pilot plant level (nominally about 1% to 5% of full scale), but have failed at the full scale production level. In the very broadest of terms, a vast majority of these failures have occurred because the small scale process is a continuous process that cannot be sustained at an industrial level, the reactions occur in spherical or cylindrical reactors that are not reproducible at an industrial level, or the reduced scale reaction kinetics cannot be achieved in a full scale production facility.

A fundamental challenge is the production of sufficient quantities of quality raw materials to meet the demands of the iron and steel industry. In this context, sufficient quantities are measured in metric tons. In evaluating the solution, the efficiency and cost are significant factors. The cost includes the costs associated with obtaining and processing the raw material. A “successful” but energy inefficient laboratory reduction process is not a solution when scaled up to a commercial setting. In other words, if the operating costs of the scaled process offset the advantages of using a low cost raw material or if the scaled process cannot produce sufficient quantities of the iron/ steel product in a timely fashion, it amounts to little more than theory with no practical application.

This invention leads to generate similar specification hot pig iron as generated from other iron making reduction furnace. The achievement of this invention is to generate the lowest slag rate while treating the low grade iron ore fines and better utilization all reducing gas so it can restrict the environmental threats too.

The aforementioned inventions lead to generate only hot pig iron with substantial slag rate, but the present invention consisting hot condition beneficiation unit and better recirculation of the reducing gas inside flow circuit, thus this invention has more energy beneficial technology for conversion of iron ore fine into pig iron.

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to a method for producing pig iron by utilisation of low grade of iron ore fines involving the steps of reduction roasting, magnetic separation of reduced iron bearing fines from gangue oxides after pulverisation, and direct reduction followed by flash meting to produce hot metal by reduction gases basically CO and H2 produced by burning low grade coal fines in coal gasifier.

A further object of the present invention is directed to a method to produce molten iron from assayed iron ore fines cumulatively 100% passing from the sieve size of 1mm and 150 micron and consisting total Fe percentage ranging from 50% to 60% with accomplished gangue load varies from 8% to 20%.

Another object of the present invention is to provide a method of producing molten iron from lean iron ore fines by utilization of high ash coal, as high ash and low rank coal are very reactive in nature, thus this invention leads to economically utilize the reducing gases generated through gasification method by using assayed characteristic of coal, said low rank coal consisting the fixed Carbon value ranging from 45% to 65% and the ash value ranging from 10 to 35% with appropriate presence of volatile material in this ranking of coal.

A still further object of the present invention to provide a method for producing molten iron from lean iron ore fines is to carry out said step reduction roasting takes place by adopting static as well as fluidized bed techniques at the controlled temperature range with controlled reduction gas flow, retention time and restricted air availability to restrict the phase conversion from magnetite to hematite or other oxidized phases and to control the potential of CO and temperature to restrict the transformation of magnetite to wustite and metallic iron.

A still further object of the present invention to provide a method for producing molten iron from lean iron ore fines wherein the flash melter uses iron ore concentrate directly from DRI without further treatment whereby the fineness of the concentrate particles allows a very rapid reaction rate, thus requiring residence times measured in seconds instead of the minutes and hours it takes to reduce pellets and even iron ore fines.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a process for lean iron ore fine based beneficiation and iron making comprising:
subjecting lean iron ore fines along with low grade coal fines to reduction of the iron ore fines to form para magnetised iron ore fines containing magnetite as major phase such that the transformation of the iron ore fines into magnetite is accompanied with separation of gangue from the low grade iron ore fines and enabling its resulting beneficiation free of any sintering or pelletizing steps .
A further aspect of the present invention is directed to process comprising reduction of iron ore fines in reduction roaster including static and/or fluidized bed furnace to form para-magnetized iron ore fines containing magnetite as major mineral phase under controlled atmosphere to restrict wustite formation followed by beneficiating the magnetite containing iron ore fines in low intensity magnetic separator in dry or dry-hot condition after pulverisation to separate out gangue locked in iron ore fines.
A still further aspect of the present invention is directed to a process preferably involving mostly -1mm fines and wherein said magnetite containing iron ore fines are beneficiated in low intensity magnetic separator in dry or dry-hot condition after pulverisation to separate out gangue locked in iron ore fines, the beneficiated magnetite fines are downstream into metallic iron as direct reduced iron involving reducing gases in contact with magnetite ore fines resulting in 90-94 % metallization.
Another aspect of the present invention is directed to a process comprising converting DRI fines into hot metal in high temperature furnace preferably a flash melter operated above 20000C.
Yet another aspect of the present invention is directed to a process wherein said lean iron ore fines include size range cumulatively 1mm 100% passing and 150micron 100% passing, and reducing gases (CO and H2), provided to kinematically react with the said lean iron ore fines to produce reduced iron ore phase (Magnetite) in the reduction roaster.

A further aspect of the present invention is directed to a process wherein said
reduction roaster is selected from static bed reduction roaster, fluidized bed reduction roaster, spiral path reduction roaster depending on the grade of said lean iron ore fines size distribution and its grade value.
A still further aspect of the present invention is directed to a process wherein said reduction roaster converts oxidized phase (Hematite, Goethite, Limonite, Martite) of lean iron ore fines into reduced iron phase (Magnetite) in the temperature range of 400-6500C with reducing gas composition comprising of CO 25-34%, H2 10 – 15 %, CO2 20 – 30 %, N2 12 -19%, H2O 15 – 22%, CH4 0-2% and SO2 0 – 1 % preferably providing for conversion percentage of oxidized phase (Hematite, Goethite, Limonite, Martite) of lean iron ore fines into reduced iron phase (Magnetite) in the range of 60% to 85%.
A still further aspect of the present invention is directed to a process wherein said phase conversion in reducing atmosphere is accompanied with volume expansion to generate strain on the interphase of gangue material and said iron oxide phases , the thus generated strain leading to ease in liberation, including the downstream flow process comprising of pulveriser for better liberation followed by dry magnetic separation for extracting the valuable magnetite as well as other iron phase.
A still further aspect of the present invention is directed to a process as involving dry magnetic separator to enhance the iron ore fines grade from 49-59% to 61- 65%, with the weighted yield percentage range between 60 to 85%.
Another aspect of the present invention is directed to a process wherein for hot condition of reduced iron ore fines the dry magnetic separation ,the magnetic intensity of dry magnetic separator is maintained in range of 600 gauss to 3000 gauss at higher belt speed 20-40 set point of magnetic separator whereas for room temperature condition of reduced iron ore fines the dry magnetic separation is operated in the range of 800 gauss to 4000 gauss at the belt speed 10-25 set point.
Yet another aspect of the present invention is directed to a process wherein based on the grade of iron ore fines the magnetic intensity and belt speed is selected wherein higher magnetic intensity and belt speed is required for treating the low grade said iron ore fines, whereas the lower magnetic intensity and belt speed is required for treating the high grade said iron or fines.
A further aspect of the present invention is directed to a process wherein output of dry magnetic separator is downstream towards the DRI and wherein the dry magnetic separation comprises single stage separation involving two product concentrate (higher magnetic susceptibility) and tails (reject or lower magnetic susceptibility)
A still further aspect of the present invention is directed to a process wherein the product concentrate of dry magnetic separator are transformed into direct reduced iron in vertical metallic retort under reducing condition gasses mainly comprised of CO and H2 wherein the temperature of retort is maintained 850-900oC and involving CO of 55 to 65%, H2 of 25-35%, CO2 of 5 to 10%, H2O of 4 to 8%, N2 of maximum 1% and SO2 of max 1% enabling metallization of 91-94% and gangue load of 8-12%.
A still further aspect of the present invention is directed to a process comprising subjecting the said DRI to further processing in melting softening unit involving softening start temperature in the range of 1350 to 1400 deg C, primary slag forming temperature in the range of 1425 to 1475 deg C,Melting start temperature in the range of 1475 to 1525 deg C and Melting end temperature in the range of 1525 to 1570 deg C.
A still further aspect of the present invention is directed to a process comprising blending DRI fines with flux material to attain the final slag chemistry which has the low melting temperature, capability to control S and Si % in the hot metal with maximum of 19.5% Al2O3 in final slag, with the temperature maintained at 1580-16000C under the reducing atmosphere comprising preferably 30% of CO and 70% of N2.
A still further aspect of the present invention is directed to a process comprising solid flow sequence of iron making process from said lean iron ore fines following the iron ore fines first reduced in reduction roaster followed by dry beneficiation using magnetic separator then treated in reduction shaft for direct reduced iron followed by melting in flash melter.
A still further aspect of the present invention is directed to a process which involve selectively to produce 1 ton of hot metal the lean iron ore quantity required in the range of 1900 – 2200 kg with Fe content in the range of 50 – 60% with gangue content of 8 to 20%; the tailing loss in dry magnetic separator quantity ranges from 360 – 480 kg to produce 1 ton of hot metal;
the slag rate from the flash melter is in the range of 230 – 280 kg to produce 1 ton of hot metal ;
the slag temperature in the range of 1460 – 1520 oC with the B2 (CaO/ SiO2) in the range of 1 – 1.07, MgO of 7.5 to 8.5 % and Al2O3 of 19.5% maximum;
to achieve the slag rate and its chemical composition, the required flux is limestone of 85 to120 kg, dolomite of 70 to 100 kg and quartzite of 30 to 50 kg to produce 1 ton of hot metal;
the feed to DRI shaft contains Magnetite phase in the range of 70 – 85% against 70- 95% of hematite in iron ore pellets used in MIDREX, HYL and FINEX;
the hot reducing gas generated in coal gasifier of 65 – 85% is used to reduce predominant magnetite ore in DRI shaft ;
the volume of gas required to produce 1 ton of DRI is in the range of 1450 to 1570 Nm3 ;
the volume of gas required to get predominantly magnetite phase in reduction roaster is in the range of 250 to 350 Nm3 to treat 1 ton of low grade lean iron fines;
the volume of tail gas is in the range of 250 to 350 Nm3 to treat 1 ton of low grade lean iron ore fines.
Another aspect of the present invention is directed to a process wherein the tail gas composition comprises of CO of 20 to 30%, CO2 of 25 to 35%, H2 of 5 to 12%, N2 of 10 to 20%, H2O of 17 to 25%, CH4 of max 1% and SO2 of max 1%.
Yet another aspect of the present invention is directed to a process wherein the tail gas contains combustible gas in the range of 25 to 35% (CO + H2) can be utilized in iron and steel making preheaters and stoves.
An yet further aspect of the present invention is directed to a process wherein the hot reducing gas generated from coal gasifier of 25 to 45% are used in flash melter as one of the fuel to produce hot metal.
A still further aspect of the present invention is directed to a process wherein the tail gas generated from DRI Shaft is in the range of 1450 to 1570 Nm3 to produce one ton of DRI, said tail gas comprising of 50- 60% of combustible gas like CO and H2. 70 – 80% of this tail gas optionally utilized in iron and steel making preheaters and stove wherein 15 -25% of the tail gas are utilized in reduction roaster with mixing of N2 in the range of 35 – 85 Nm3 to treat 1 ton of low grade iron ore fines.
The above and other objects and advantages of the present invention are described hereunder in greater details with reference to the following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPNAYING DRAWINGS
Figure 1-Solid Flow and Gas Flow for converting iron ore fines in hot metal.
Figure 2- Laboratory set up for iron ore fines reduction, Beneficiation, DRI making and hot metal production.
Figure 3- Equilibrium gas composition diagram shows the same information as the Ellingham diagram, just expressed in terms of volume % CO. Also known as a “fish tail” diagram.
Figure 4- Overall process layout for hot metal making.
Figure 5-Ash fusion test for determination of melting temperature of slag and metal.
Figure 6-Graphical representation of differential pressure vs melting-softening temperature for Direct reduced iron in softening melting apparatus.
Figure 7: shows the phase transformation from oxidized iron phase to reduced magnetite phase, wherein(7a) shows Phase transformation of Sample A; (7b) shows Phase transformation of Sample B & (7c) shows Phase transformation of Sample C.
Fig. 8 a: shows Phase transformation of Sample A after roasting coal based and Gas based; Fig. 8 b: shows Phase transformation of Sample B after roasting coal based and Gas based; Fig. 8c: shows Phase transformation of Sample C after roasting coal based and Gas based.
Figure 9-11: shows the enrichment of Fe grade for the experimental trials carried out at NTP with variable magnetic intensity and variable belt drive speed wherein Fig 9(a) shows Fe(T) up gradation of sample A & Fig 9 (b) shows Fe Recovery % of sample A; Fig 10 (a) shows Fe(T) up gradation of sample B & Fig 10 (b) shows Fe Recovery % of sample B; and Fig 11 (a) shows Fe(T) up gradation of sample C & Fig 11 (b) shows Fe Recovery % of sample C.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
The present invention is directed to utilisation of low grade of iron ore fines and put a laser focus towards the direct reduction to produce hot metal from assay material by using high ash coal. This object is versed in accordance with the invention essentially with various range of size distribution in iron ore fines. The assayed iron ore fines are cumulatively 100% passing from the sieve size of 1mm and 150 micron. The chemical specification of iron ore fines consisting total Fe percentage ranging from 50% to 60% with accomplished gangue load varies from 8% to 20%. The major matrix associated phase with iron ore fines are Hematite, Magnetite, Goethite, Martite, Limonite with ranging 10 to 95% cumulatively, the minor matrix associated phase are Silica, Alumina, Kaolinite, Silicate-Alumina association etc.
The chemical physical and mineralogical specification of the said iron ore fines are briefly tabulated below:-
Chemical Specification of Iron Ore Fines
Attribute Occurrence %
Total.Fe 50 to 60
SiO2 3 to 16
Al2O3 2 to 10
LOI 4 to 10
Traces 0.5 to 2
Mineralogical Specification of Iron Ore Fines
Phases Occurrence %
Hematite 30 to 70
Magnetite 2 to 6
Goethite 6 to 22
Limonite 4 to 12
Silica 4 to 15
Alumina 2 to 10
Kaolinite 2 to 12
Others 5

Another object of the invention is to utilization of high ash coal, as high ash and low rank coal are very reactive in nature, thus this invention leads to economically utilize the reducing gases generated through gasification method by using assayed characteristic of coal. The specification of low rank coal consisting the fixed Carbon value ranging from 45% to 65% and the ash value is ranging from 10 to 35% with appropriate presence of volatile material in this ranking of coal.
The specification of said coal are tabulated below:-
Ultimate Analysis of Low Rank Coal
Attribute Symbol Wt% Range
Carbon C 60 to 75%
Hydrogen H 3.5 to 5%
Sulpher S 0.2 to 0.8%
Nitrogen N 1 to 1.5%
Oxygen O 4 to 15%
Heating Value HV 40 to 70 MJ/Kg
Proximate Analysis of Low Rank Coal
Attribute Symbol Wt% Range
Fixed Carbon FC 45-60
Volatile Matter VM 20-35
Ash A 10-35
Moisture M 5-15
Mineral Matter MM 2 to 8

According to an aspect of the present invention, reduction roasting of the said iron ore fines is effected with the gas generated through said coal material. The said reduction roasting is taken place by adopting static, moving bed as well as fluidized bed techniques at the temperature range 4500C to 6500C with appropriate concentration of CO and other activator gases (Nitrogen, Argon, and Air). The said iron ore fines are reduced in the experimental reactor in attempt to determine the degree of reduction that is attainable in a single-stage fluidized bed in which the reducing gas is supplied by the said combustion of coal.

In further aspects of this invention, it is based on the influence of retention time on reduction, the said iron ore fines passed through the reactor with different retention time interval of 10 to 60 min, it was necessary to add said activator gases and to decrease the flow of air because temperature control of the fluidized bed became difficult and to restrict the phase conversion from magnetite to hematite or other oxidized phases. It is necessary to control the potential of CO and temperature to restrict the transformation of magnetite to wustite and metallic iron. Further increase in temperature leads to formation of agglomerates of iron ore fines. A mineralogical investigation of the partly reduced particles revealed that the oxidised iron containing phases in the said iron ore fines ranging 70 to 90% contained both dense and porous particles are exhibit typical topochemical reduction behaviour and mostly converted to the magnetite phase conversion around 60 to 85% from other phases which results 70 to 85% magnetite phase. This whole invention leads to generate the reduced phases magnetite from the other oxidised phases of said iron ore fines with controlled time and temperature limit (10-60 min and 4000c to 6500C respectively) with acceptable concentration of CO gas i.e. 25 % to 34% with appropriate concentration of said activator gases.

In further aspects of this invention deals with effective utilization of roasting product, as the said iron ore fines are lean graded thus the reduced roasted product consisting measurable quantity of gangue elements also. As the magnetic susceptibility of reduced said iron ore fines are increases and so it is easy to facilitate this reduce iron ore towards the magnetic separation unit. As the mineralogy of this said mineral fines consisting both characteristic porous and dense structure where hematite, martite, goethite and other oxidized phases are entrapped. During the reduction roasting (Static and fluidized bed roaster) conversion of hematite and martite into magnetite can be easily observe at the temperature range of 400-5500C but at this temperature hydroxyl bearing iron phases (goethite or limonite) converted into hematite and at reducing atmosphere the nascent hematite converted into magnetite at the temperature range of 450-6500C. The decomposition of goethite started at 250 °C and concluded at about 370 °C. During the transformation, a dramatic decrease of lateral bond length was observed and determined the volume contraction while longitudinal bond length expanded which leads to net volume expansion. This is due to the relaxation around the vacancy generated by the proton migration from the structure while heating in reducing atmosphere.
For restricting the formation of magnetite to wustite the said minerals are treated in the reduction roaster for the time limit 10-60minute and at temperature range of 400-6500C with appropriate concentration of reducing and activator gases. This invention restricts the formation magnetite ranging from 60- 85% with no wustite generation from the said iron ore fines. The conversion of phases from said oxidized phases to reduce magnetite phase leads to the volumetric expansion around 20 to 22%, due to this expansion the interphase association of gangue and ore mineral become fragile.
So in this invention pulveriser unit is associated prior to magnetic separation for better liberation. The dry magnetic separator assisted in the concurrent circuit leads to separate out the magnetite and gangue minerals from the said reduced iron ore fines. The magnetic separator is encumbered with belt speed and variable magnetic intensity. This said reduce iron has yielded better in magnetic separator with variation in belt speed of 15 to 25 set point in room temperature condition and 20 to 40 set point belt speed if hot reduced said iron ore fines are treated. The magnetic intensity for the said reduced iron ore fines in the dry magnetic separator can vary from the rage of 800 gauss to 4000 gauss value. The optimal process variables for dry magnetic separation are tabulated below:

Condition Process Variable Limit of Process Variable
Room Temperature Belt Speed (Set point rpm) 10 to 25
Magnetic Intensity (Gauss) 800 to 4000
Hot Temperature Belt Speed (Set point rpm) 20 to 40
Magnetic Intensity (Gauss) 600 to 3000

The yield and recovery of concentrate generated from dry magnetic separator is ranging from 70 to 80% and 75 to 90% respectively with upgradation of Total Fe up to 65%. The gangue load generated from the tailing product of dry magnetic separator is ranging from 30 to 20%. The expected chemical specification of the concentrate from sais dry magnetic concentrator consisting total Fe value range are 61% to 65% with total gangue (Silica and Alumina) load in concentrate is 4 to 10%.

In the further aspect of this invention the said concentrate of dry magnetic separator is fed to the reducing vertical shaft furnace, where the counter current flow of reducing gases (CO and H2) are basically coming from coal gasifier is used for the reduction of said magnetite to metallic iron (Direct reduced iron making). The 65- 85% of the hot reducing gas generated from the coal gasifier are used as the reducing gas for DRI making.

Further aspect of this invention put a laser focus on utilization of 25 to 45% residual reducing gas from coal gasifier, which are directed towards flash melter. The oxygen is injected in order to maintain the temperature of hot metal in the range of 1450-1550 0C. Similarly, the high temperature is needed to maintain the slag in low viscosity range for continuous drainage of slag from the system.

The flash melter uses iron ore concentrate directly from DRI without further treatment. The fineness of the concentrate particles allows a very rapid reaction rate, thus requiring residence times measured in seconds instead of the minutes and hours it takes to reduce pellets and even iron ore fines.

Present invention is thus basically directed to the process for production of hot metal from lean iron ore fines and coal fines. The lean iron ore fines used for the process mainly contains different phases for example Goethite & Limonite etc. along with hematite which on conversion to hematite results in expansion of the lattice structure or change in c/a ratio which induce the strain in the interface of gangue and hematite matrix which helps in firm liberation of gangues oxide.

Accompanying Figure 1 shows the process of flow of solid and gases for making hot metal in novel route. The lean iron ore fines less than 1mm passing or 150 microns 100% passing size are processed in the reduction roaster furnace 111a which may be fluidized bed or in rotating counter current reduction reactor. The reducing gases mainly generated from coal gasification 111b contain CO and H2. The product from reduction roaster which mainly contains magnetite and gangue are passed through the low intensity magnetic separator 112b the magnetite gives better response to magnets compare to non-magnetic gangue.
The magnetic portion majorly magnetite is again passed through the reduction shaft furnace where the magnetite gets transform to metallic iron and wustite 113c. The gangue remains untransformed throughout the process of reduction roasting and DRI making.
Metallic iron fines passed through the flash melter 114d to convert DRI into hot metal and slag. The Flash melter process uses DRI fines directly without further treatment. The fineness of the concentrate particles allows a very rapid reaction rate, thus requiring residence times measured in seconds instead of the minutes and hours it takes to reduce pellets and even iron ore fines. Fluxes are added as per mass balance to combine with gangue to form the slag.

Accompanying Figure 2 shows the laboratory set up to prove the concept of iron making using fines and lean coal fines.
The CO generated by control burning of charcoal and passing CO2 in charcoal bed mix with nitrogen to get the required potential of CO gas. The temperature of retort maintained around 10500C. The Potential of gas is maintained is such a way that the reaction is restricted to magnetite generation only. The gases are control from controlling unit 201. The gases are passed to the reduction retort 202 for converting iron ore fines into magnetite concentrate fines. The iron ore fines are converted to magnetite were passed to pulveriser 204 to break any lump formed in reduction roasting process. The fines are treated in low intensity magnetic separator, the product of magnetic separator is magnetic portion 206 which is called as product or concentrate and 209 as tailing which is non-magnetic in nature.
The magnetic portion again transfer in to the vertical retort furnace 203 where the magnetite fines were transform into metallic iron at reduction gas composition of CO-55-65% H2- 35-45%.The temperature maintained around 850-900oC.
The Direct reduced iron ore fines are then mixed with required amount of fluxes to maintain the slag basicity of 1-1.2 in the apparatus called Melting softening unit 210.The DRI portion 208 in fines condition transferred to unit 210 for melting where the apparatus helps to tell the range of temperature for softening and melting of DRI fines. The product of unit 210 is slag and metal, Based on the rate of metal and slag generated and the amount of iron ore fines used for reduction roasting and DRI making were stoichiometric calculated to determine the overall efficiency of the iron making route.

Accompanying Figure 3 Equilibrium gas composition diagram shows the same information as the Ellingham diagram, just expressed in terms of volume % CO. Also known as a “fish tail” diagram. The diagram helps in determining the proper proportion of CO volume and temperature required to convert hematite into magnetite and magnetite to metallic iron. The diagram helps in providing the boundary line for the reduction roasting and DRI making process. It was estimated that the temperature required for hematite to magnetite is in range of 400-6500C with CO 25-30% however temperature for DRI making is more than 850-9000C at CO 53-63% concentration

Accompanying Figure 4 is a view illustrating an outline of a novel process method to produce hot metal from the low grade iron ore fines and coal fines with less amount of coke.
As shown in Figure 4, process method involves five major units namely coal gasifier 412, flash smelter 423, direct reduction fluidization process 431, reduction roasting 452 and magnetic concentrator 463.
Low grade coal fines are feed from the bunker 411 with the oxygen from the O2 line 461 to the coal gasifier 1. Oxygen are injected into the coal gasifier 1 system at three different locations to control the temperature inside the gasifier and also to maintain the producer gas temperature in the range of 950oC to 1080oC. Steam from the H2O line 462 are mixed with oxygen to quench the molten slag formed from coal ash and are injected in the bottom of the coal gasifier 1. The quenched molten slag is taken out from the bottom of the coal gasifier 414.
The hot reducing gas generated in the range of 2100 to 2300 Nm3/ton of coal from the coal gasifier 1 are feed to the dust cyclone 413 to remove the dust flying out from the coal gasifier 1 and for further usage in the following processes as a clean gas.
Iron ore fines are feed to reduction roaster 452 from the iron ore bunker 451. Reduction roaster has a rotary kind of setup (Moving bed reduction roaster) which will be rotating along its axis. In the reduction roaster, hematite to magnetite conversion are controlled with the input reducing gas temperature and its composition.
The top gas of direct reduction fluidization process is allowed to pass through wet scrubber 432 to remove dust and the clean gases are injected as the input/reducing gas 454 for the reduction roaster with proper mixing of N2 463 to control the gas temperature and its composition. The output of the reduction roaster gas is stored in the gas storage tank 453 for further usage like preheating of furnaces.
The solid output 455 of the reduction roaster 452 contains predominantly magnetite phase and rest will be hematite phase.
This roasted ore is conveyed through conveyor to dry magnetic separator 443. Roasted iron ore fines are transferred to the feeder 441 and then it passes through pulveriser 442 for further pulverisation to separate gangue from the iron oxides. The magnetized iron ores particles are stick with the magnetic conveyor belt and the magnetic particles are collected in the concentrate collection chamber 445 for further processing. The tailings are of mostly gangue contents which contains non-magnetic particles are collected in the tailing collection chamber 444.
Concentrates collected in chamber 445 are stored in the storage bunker 433 before charging into the direct reduction fluidization process 431. 65 - 85% of the hot reducing gas generated from the coal gasifier 412 is the major contribution as reducing gas and remaining reducing gases are from flash smelter cyclone 422 for the direct reduction fluidization process 431.
The top gas of the direct reduction fluidization process 431 are allowed to pass through wet scrubber 432 for cleaning of the gas. Some portion of the gases are used as the cooling gas to cool the hot DRI in case of emergency to store the DRI in the bunker 435. This cold DRI can be mixed with reducing gas, oxygen and hot DRI and injected into the system via dust burner 425.
The hot DRI produced from hot reducing fluidization process 431 are charged into the flash smelter 423 at hot condition through special conveyor 434 to avoid air oxidation.
Oxy-fuel burner 426 at the bottom of the flash smelter 423 to maintain the flame temperature and furnace temperature which helps for complete melting of slag and hot metal to meet the hot quality and slag quality.
The fluxes are added into the flash smelter 431 from the flux bunkers 427 to melt the gangues associated with iron ore fines. Coke from a bunker 421 are added in the sufficient quantity to the flash smelter 423 to have the bed permeability.
The hot metal and slag are tapped out from the tap hole 424 at the bottom of the flash smelter with regular interval.
Hot reducing gases are generated from coal gasifier process. The inputs are low grade thermal coals as a fuel with the addition of oxygen and steam to complete the combustion process and to control the flame temperature. Injection of oxygen with coal fines in dust burner at the top of the coal gasifier helps to maintain the dome/top gas temperature to crack the volatile matters and tar. The top gas temperature is maintained in the range of 1010 to 1080o C and the compositions are given in the table.
The molten coal ash is taken out from the bottom of the coal gasifier as a clinker which is subsequently cooled by water via quenching
H2 CO CO2 H2O SO2 N2
Actual 29.37 56.03 7.61 6.01 0.39 0.59
Range 25- 35 53 - 63 5 - 11 4 - 10 0.35 – 0.45 0.55 – 0.65

Accompanying Figure 5 is the ash fusion test to estimate the melting and softening temperature of DRI fines. At present DRI composition the softening of the DRI starts with the temperature of 13790C, where the actual deformation of DRI begins. At the temperature of 1423 0C primary slag formation begins and the deformation is continuing up-to the temperature of 15390 C, which is the indication of beginning of melting of DRI fines.
Accompanying Figure 6 show the graphical representation results of melting and softening of DRI fines. The DRI fines produced in the DRI process from the magnetized ore are taken for further melting to produce hot metal. To study the melting properties of the DRI fines, pellets are made from these fines and are mixed with sufficient flux to attain the final slag chemistry which has the low melting temperature, capability to control S and Si % in the hot metal with maximum of 19.5% Al2O3 in final slag. The results are as follows ; 1376 – Softening start temperature, 1448 – Primary slag forming temperature, 1497 – Melting start temperature and 1555 – Melting end temperature.

Experimental Results: -
The invention of the present process was established by conducting series of trials for reduction of iron ore fines using lean iron ore fines and coal fines. The fines were reduced by directly with low rank coal.

Assuming Ore is having 50-60 % of T (Fe) and coal is having 50-60% of carbon, calculations are made for production of 1 ton of Fe3O4. For production of 1ton of Fe3O4, 1.0346 ton of Fe2O3 is required, which can be obtained from 1.7243.and 47.1588 kg of coal is required assuming 100% indirect reduction by CO. Specific heat of ore, coal and air are taken as 960, 1380 and 1032 kcal/kg/K. Calorific value of coal is taken as 4.3151e+03 kcal/kg. The required amount of air is 148.9268 kg. The required amount of thermal energy to heat the charge material is 2.2396e+05 kcal. Reaction temperature is taken 873 K. Reduction of hematite to magnetite is mildly exothermic reaction. Oxidation of carbon to carbon monoxide is also an exothermic reduction. Heat generated due to the reactions 1.3936e+05 kcal.
Further, the gangue mineral content in this type of ore and ash content in coal are very high which will consume lot of heat. However, as these minerals will be separated in solid phase it is expected to consume less amount of heat (unlike molten slag in the blast furnace where lot of heat of about 28% of the total heat goes as waste).
A circulating fluidized bed reactor mechanism is hence proposed in the invention to enhance the reduction efficiency. It is also possible to recover the heat from the output of the reactor which can be used for drying/pre-heating the ore to reduce the overall heat input. This helps reduce the heat losses contributing to reduction in the cost of the production.
Further, the process proposed in the invention will save a lot of energy in the downstream process of iron making. The entire energy required in sintering and further in iron making units will be reduced to the extent of hematite reduction to magnetite as this is achieved outside the furnace.
The proposed process will also contribute to dry beneficiation of ore and helps in conservation of large amounts of precious water and eliminate subsequent contaminations. The waste output being dry solids can be briquetted /agglomerated and safely disposed of as landfills, brick manufacturing etc. This will help in mitigating the environmental impact and pollution.
However, the above process is combination of direct and indirect reduction of iron ore fines with the yield and recovery around 65% and 80% respectively. The gaseous reduction of said iron ore fines either in packed static bed or fluidized bed leads to enhance the better phase transformation and hence enhance the yield and recovery after dry magnetic separation up to 75% and 85% respectively in comparison of solid state reduction.
Analysis of Iron Ore Fines:
For this present invention, test trial was conducted on three different iron ore fine samples namely sample A, B and C. The chemical specification of represented said sample is tabulated below:
Sample ID Fe (T) % SiO2 % Al2O3 % LOI %
A 57.5 7.25 4.33 5.8
B 53.61 8.41 5.52 8.17
C 50.98 10.29 6.41 9.16

The representative samples with sample ID of A, B and C have different gangue load ( SiO2, Al2O3, LOI ), total iron ( Fe (T)) value. For the reduction roasting of said iron ore fine samples in fluidized bed reduction roaster, two size fractions were selected (a) -1mm and (b) -3+1 mm. The selection define size range sample is restricted for all said three sample in accordance of their terminal velocity criteria. The phase transformation of said three samples of two different size fractions from oxidized iron phase to reduced magnetite phase, are represented in Figure 7(a) to (c) wherein(7a) shows Phase transformation of Sample A; (7b) shows Phase transformation of Sample B & (7c) shows Phase transformation of Sample C.

The above figure 7a, 7b and 7c illustrate that the said samples consisting of size range -3+1 mm shows lesser reduction potential in comparison of -1mm sample. The total magnetite formation after reduction roasting from the parent feed material of sample A, B and C is in range of 45 to 68 % in -3+1 sample, whereas in -1mm samples the magnetite formation from parent feed hematite conversion is in the range of 70 to 88% due to increased surface area of the particle and higher exposure with reducing gases. Thus for generation of hot metal in this invention mostly -1mm 100% sample is preferred.
Accompanying Fig. 8 a shows Phase transformation of Sample A after roasting coal based and Gas based; Fig. 8 b shows Phase transformation of Sample B after roasting coal based and Gas based; and Fig. 8c shows Phase transformation of Sample C after roasting coal based and Gas based.
The better transformation from oxidized iron phases to reduce magnetite phases are seen with gaseous reduction process at temperature 4500 to 6500C with the time limit of 10-60 min. In sample A, as shown in figure 8a the phase transformation from hematite to magnetite attain maximum value in reaction time of 30 min and beyond that the phase transformation is marginal. But in sample B and C where the goethite constituent is high, the phase transformation from hematite to magnetite occurred with higher reaction time (40 min to 60 min) in comparison to sample A, as shown in figure 8b and 8c respectively. The goethite first converts into para-hematite and then to hematite which requires additional reaction time before final conversion to magnetite.
Dry Magnetic Separation: - The dry magnetic separator is used for separating the magnetite and gangue minerals. The product from reduction roasting reactor is further reduced in size in a pulveriser for liberation of iron particles and is processed on a belt feeder dry magnetic separator. The enrichment in Fe grade for the various samples by using the dry magnetic separation is ranging from 62 to 66% with recovery 70% to 87%. The experimental trial was carried out at NTP with variable magnetic intensity and variable belt drive speed (10- 25 rpm) whose values are shown in following accompanying figures: Fig 9 (a) shows Fe(T) up gradation of sample A & Fig 9 (b) shows Fe Recovery % of sample A; Fig 10 (a) shows Fe(T) up gradation of sample B & Fig 10 (b) shows Fe Recovery % of sample B; and Fig 11 (a) shows Fe(T) up gradation of sample C & Fig 11 (b) Fe Recovery % of sample C.

Several trials of dry magnetic separation were also conducted with the hot reduction roasted, pulverised material. It is observed that separation of iron from that of gangue material with hot feed material behaved similar at high belt speed (20-40 set point rpm) as that when the feed was cooled and treated at NTP. The above figure 9a,10a and 11a illustrate that maximum iron up gradation is achieved at 1600 gauss magnetic flux with 25 Set point belt speed and beyond that the recovery decreases because at higher intensity more gangue bounded magnetite are also attracted. In the similar condition figure 9b, 10b and 11b illustrate the maximum iron recovery is achieved at 1600 gauss value with belt speed 25 Set point (rpm).
From the experimental results, it is established that, the concentrate with roasting time in the range of 20 - 30min and magnetic separation at 1600 G flux intensity and 25 rpm belt speed provides better iron grade (chemical composition T(Fe) % - 65.8), with weighted fraction 78% and consisting 86.68% recovery and is most suited for further DRI making whose results are shown below: -

CHEMICAL ANALYSIS Gas Analysis
%SiO2 %Al2O3+others Total Gangue %T.Fe %M.Fe %Met H2 % N2% CH4% CO % CO2 %
4.28 3.76 8.04 88.94 82.21 92.98 35 1 0 60 0

The metallization obtained here with the representative sample which was treated with reduction roasting with gas composition 30% CO & 70% N2 up to 20 min and followed by magnetic concentration @ 1600G providing better metallization 92.98 % with reduced gangue load 10%.

%M.Fe %Met T.Fe SiO2 Al2O3 C CaO MgO K2O Na2O P S
82.21 92.98 88.94 4.28 3.76 0.45 0.68 0.28 0.022 0.03 0.08 0.003

M.Fe represents the metallic Fe, % Met stands for the metallization and T.Fe represents the total Fe. The formed DRI fines were processed in melting and softening unit to investigate the melting and softening range of DRI fines, and comparing the temperature range with ash fusion test.
The DRI fines are blend with the required amount of flux material to attain the final slag chemistry which has the low melting temperature, capability to control S and Si % in the hot metal with maximum of 19.5% Al2O3 in final slag. The temperature of apparatus maintained at 1580-16000C under the reducing atmosphere consisting 30% of CO and 70% of N2.
It is thus possible by way of the present invention to provide a process for production of hot pig iron using lean iron ore fines along with low grade coal fines having a wide particle size distribution without the need for sintering machines, pelletizing machines and coke ovens. During transformation of hematite, Goethite and limonitic iron ore fines into magnetite is accompanying with volume expansion resulting in crack formation at the interface of gangue basically (silica and alumina) that leads to liberation of gangue oxides. To separate gangue from the low grade iron ore fines, the present invention involves a reduction of iron ore fines in static or fluidized bed furnace to form para-magnetized iron ore fines containing magnetite as major mineral phase in a controlled atmosphere to restrict wustite formation. The magnetite containing iron ore fines are beneficiated in low intensity magnetic separator in dry or dry-hot condition after pulverisation to separate out gangue locked in iron ore fines. The beneficiated magnetite fines are converted into metallic iron called as direct reduced iron in the shaft furnace where the reducing gases are in contact with magnetite ore fines resulting in 90-94 % metallization. The DRI fines are converted into hot metal in high temperature furnace basically a flash melter operated above 20000C. The CO and H2 gases are product of coal gasifier, major portion of it transferred to DRI making as a reducing gas and remaining are utilized in flash melter as a combustible gas. The process is more energy intensive as the predominant tail gas quantity are used in process circuit and rest will be an export gas for external usage inside the plant. The intermediate beneficiation of iron ore fines after reduction roasting helps the process to produce less slag rate.