FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
1 TITLE OF THE INVENTION :
IRON ENRICHED DRI AND ITS PROCESS OF MANUFACTURE USING IRON RICH WASTES.


2 APPLICANT (S)
Name : Nationality : Address :
JSW Steel Limited.
An Indian Company.
Jindal Mansion, 5-A, Dr. G. Deshmukh Marg, Mumbai - 400 026, State of Maharastra, India.
3 PREAMBLE TO THE DESCRIPTION
COMPLETE

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


FIELD OF THE INVENTION
The present invention relates to production of iron-rich DRI adapted to substantially replace the use of costly steel scrap as coolant in steel making in LD Converter or in Electric Arc Furnace and/or Induction furnace and a process for its production. Importantly, the Fe content is enriched in DRI by the recycling of iron rich steel plant wastes, in order that the DRI has low gangue content and less reliance on iron content in iron ore fines as the only input for DRI making process. More particularly, the present invention is directed to produce the DRI rich in iron particularly utilizing the wastes/by¬products generated from different unit processes in large integrated steel plants e.g. mill scale, CRM oxide, BOF sludge, iron making sludge dust etc that are rich in iron content, so as to on one hand avoid use of iron ore fines or lump ores which are often having limited iron content and on the other hand effectively replace use of costly steel scrap in steel production in LD converter or arc/induction furnaces. Advantageously, recycling of the iron rich steel plant wastes to produce iron rich DRI according to the present process also eliminates the environmental problem posed other wise from handling and disposal of such wastes, containing mineral values. Iron rich waste materials are mixed with requisite amount of carbon material, flux and moisture before sending to balling disc for agglomeration and then sent to furnace having reducing or inert conditions in presence of sufficient coal/coke fines so as to produce DRI of desired strength and properties for transporting and use in steel making. The present invention is thus having the potential of recycling of iron rich steel plant wastes for production of iron rich DRI to effectively substitute use of costly scrap in steel making process in integrated steel plants in cost effective and environment friendly manner.
BACKGROUND ART
It is well known in the art of steel making that steel scrap is conventionally used as a coolant in steel making through LD converter and also via Electric Arc Furnace and Induction Furnace. A number of attempts have been made in the past to replace the expensive steel scrap addition in steel making in a variety of ways while also maintaining the desired yield and quality of steel free of any undesired impurities/inclusions. In order
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to replace use of costly scrap to some extent and in particular scrap with unknown impurities, part of the scrap has been replaced by DRI. The DRI used in steel making is produced from iron ore fines/pellet or lump iron ore in kilns. The quality of this DRI depends to a large extent on the quality of iron ore used for conversion to DRI. Due to the limitation of availability of iron ore fines rich in Iron, the DRI produced has high gangue content and consequently the replacement of steel scrap with this DRI is also found to be limited.
There has thus been a continuing need in the art to use iron rich DRI containing low gangue content in order to replace the costly steel scrap to a maximum extent. Attempt has been made by way of the present invention for enhancing the Fe content in DRI through recycling of iron rich steel plant wastes derived from different unit processes in large integrated steel plants. It is well known in the art that integrated steel plants process iron ore, coal, coke, and fluxes to produce iron and steel comprising steps carried out through various unit processes, i.e., agglomeration, coke making, iron making, steel making, casting, rolling etc. wherefrom one or more wastes or by-products are generated. These wastes on one hand contain considerable mineral values and on the other hand pose environmental concern from handling and disposal. The DRI made through conventional route using iron ore fines or from lump ore that is often low in iron content and with high gangue content, is replaced with stated iron rich plant wastes such as mill scale, BOF sludge, iron making sludge / dust, CRM oxide etc.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide for an iron-rich DRI by a process involving conversion of wastes generated from various unit processes in integrated steel plants for advantageously replacing use of steel scrap in steel making.
Another object of the present invention is directed to producing iron rich DRI by a process of conversion of steel plant wastes comprising the iron rich wastes like the mill scale, BOF sludge, iron making sludge/dust, CRM oxide etc. generated from various unit processes in
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steel plants are used in place of iron ore fines to produce DRI so that the recycling of such wastes having mineral value is gainfully utilized.
A further object of the present invention is directed to producing iron rich DRI by a process of conversion of wastes comprising the iron rich wastes like the mill scale, BOF sludge, iron making sludge/dust, CRM oxide in steel plants so as to avoid environmental concern posed due to handling and disposal of such wastes.
A still further object of the present invention is directed to producing iron rich DRI by a process of conversion of iron rich wastes generated in steel plants wherein the DRI produced has low gangue content and is thus capable of replacing use of costly steel scrap in steel making to a maximum extent.
A still further object of the present invention is directed to producing iron rich DRI by a process of conversion of iron rich wastes generated in steel plants wherein the process of producing the iron rich DRI as agglomerates exhibit strong affinity to magnet favoring ease of handling/charging in converter/furnace for steel making.
A still further object of the present invention is directed to producing iron rich DRI by a process of conversion of iron rich wastes generated in steel plants wherein the process ensure production of iron rich DRI with good metallization and sufficient strength for handling and transporting to steel making converter/furnace without breakage.
A further object of the present invention is directed to producing iron rich DRI by a process of conversion of iron rich wastes generated in steel plants wherein the DRI produced by the conversion, exhibit high Fe content at reasonably low cost by recycling of iron rich wastes generated in steel plants.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided for an Iron enriched DRI comprising
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obtaining from iron rich steel plant waste and having
Fe(T) in the range of 70 to 100
Fe(Met) in the range of 60 to 100
strength in the range of 0 to 150 kg/pellet; and
metallization properties of 60 to 100 %.
Another aspect of the present invention is directed to Iron enriched DRI wherein said steel plant waste comprises:
iron ore fines - 0-100 wt. %;
mill scale -0 100 wt %;
CRM Oxide - 0-80 %;
BOF sludge - 0-80 %;
Iron making sludge - 0-80%.
A further aspect of the present invention is directed to said Iron enriched DRI comprising: Fe(T): 70 to 100 % preferably about 84 ; Fe(Met): 60 to 100 % preferably about 73; FeO : 0 to 30 % preferably about 12; C : 0 to 4 % preferably about 0.2;

S: 0 to 1.0 % preferably about 0.28
According to yet another aspect of the present invention is directed to a process for the manufacture of iron enriched DRI comprising the steps of:
(i) providing iron ore fines, iron rich steel plant waste , coal fines and lime fines and
mixing thoroughly , followed by grounding such as to maintain about -325 #
greater than 50% in the total mix; (ii) adding water to the above mix to maintain moisture content in the range of 5 to 15
% preferably 8-10%; (iii) obtaining green pellets of the size ranging from 5-20 mm; (iv) mixing the green pellets with coal fines in the range of 10-50% and (v) obtaining the DRI by heating in the furnace in the temperature range of 800 to
1300°C for a period of 10 -40 hrs preferably about 20hrs.
A still further aspect of the present invention is directed to said process comprising screening the DRI to remove the ash and any un-burnt coal fines.
A still further aspect of the present invention is directed to said process comprising utilizing the following as blend for pellet making:
iron ore fines - 0-100 wt. %;
mill scale -0 100 wt %;
CRM Oxide - 0-80 %;
BOF sludge - 0-80 %;
Iron making sludge - 0-80%;
Lime fines: 0-20%;
Carbon in green pellets 0-5%; and
Coal fines,% of green pellets: 10-50 %.


A still further aspect of the present invention is directed to said process wherein the steel plant waste material containing iron is recycled into the process for generation of the iron enriched DRI.
The present invention and its objectives and advantages are described in greater details with reference to the following accompanying non limiting exemplary embodiment.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING EXAMPLE
The present invention is directed to use iron rich wastes generated in steel plants as input material replacing the conventional for conversion to DRI so as to enrich the DRI produced by maximizing the iron content. To enrich the DRI with Fe, iron rich wastes such as mill scale, CRM oxide, BOF sludge etc are used as a replacement to either iron ore fines or lump ore conventionally used to produce DRI which are often having limited iron content. According to the process of the present invention, the iron rich wastes are mixed with requisite amount of carbon material, flux and moisture, before sending to balling disc. The green agglomerates are then sent to a furnace having reducing or inert conditions along with sufficient amount of coal/coke fines. The agglomerates obtained from such process exhibit strong affinity to magnet, with good metallization and sufficient strength for handling and transporting to converter/furnace for steel making. The DRI made through this route exhibit high Fe and at low cost.
The process for producing the iron rich DRI by conversion of iron rich plant wastes according to the present invention has been experimentally conducted through lab scale trial comprising the sequential steps as illustrated in the accompanying non-limiting Example I:
EXAMPLE I:
The steps followed in the present process of the invention include;


(i) providing the initial charge of iron ore fines, iron rich wastes, coal fines and lime fines in desired proportions that are measured and mixed thoroughly. The raw material proportion used in the process and analysis thereof are given in following Table 1 and Table 2;
(ii) the above proportionate mix of input materials including the iron rich wastes are ground in grinder so as to selectively maintain the particle sizes of -325# greater than 50% in the total mix;
(iii) water is added to the above mix to maintain moisture content in the range of 5 to 15% and preferably 8-10%;
(iv) the mix is then sent to balling disc to make green pellets of size range 5-20 mm;
(v) the green pellets are then mixed with coal fines in the range of 10-50% and sent to furnace to produce DRI for a firing time duration in the range of 10-40 hr and preferably 20 hr.
(vi) the DRI is then screened to remove the ash and any un-burnt coal fines;
(vii) the DRI so produced is then sent for chemical analysis and for physical testing results of which are shown in the following accompanying Table-3;
(viii) the DRI produced having specific properties now used as a replacement of scrap in steel making according to requirement of the properties of iron enriched DRI for desired substitution of costly steel scrap for steel making.
Utilization of the iron rich solid wastes and their proportion into the blend for pellet making as described in step (i) above has been shown in the accompanying Table-1 as follows:
Table I:

Material Composition wt. percent
Iron ore fines, % 0-100
Mill Scale, % 0-100
CRM Oxide, % 0-80
BOF Sludge, % 0-80
Iron making Sludqe, % 0-80
Lime fines, % 0-20
Carbon in green pellets, % 0-5
Coal fines, % of green pellets 10-50


Typical analysis of iron ore fines along with other iron rich waste materials in the mix used as input in lab scale trials for producing iron enriched DRI, has been illustrated in terms of the particle size and chemical composition in the accompanying Table-2:
Table 2:

Blue dust Iron ore Iron making Sludge BOF Sludge Mill Scale CRM Oxide Lime Dust
Size Analysis
+2mm, % 14 - - 100 - 14
+lmm, % 22 - - - - 28
+0.5mm, % 14 10 12 - - 16
-0.5mm, % 50 90 88 - 100 42
Chemical Analysis
Fe (Total), % 64.67 31.0 65 76.0 69.3 0.91
Fe Cm), % - - 22 1.5 -
Si02, % 3.32 9.0 1.8 - 0.18 3.47
AI203, % 1.63 6.5 0.6 - 0.16 2.18
CaO, % 0.08 2.5 14.0 - 0.032 68.6
MqO, % 0.015 1.0 1.1 - - 4.03
C o/0 - 36.0 1.5 0.1 - -
Analysis of DRI has been conducted and its metallurgical properties analysed to ascertain achievement of desired metallisation and strength properties capable of making good quality steel at less cost with the use of iron rich DRI, is as illustrated in the following accompanying Table 3:
Table 3;

DRI
Fe(Total), % 84.1
Fe(Met), % 73.9
FeO, % 12.7
C, % 0.2
S, % 0.28
Metallisation, % 87.8
CCS, kg/DRI pellet 50
Time, h 19


The results of the experiments and analysis of the DRI produced using the iron rich wastes from the unit processes in steel plants comprising iron making sludge, BOF sludge, Mill scale, CRM oxide etc. along with iron ore fines and lime fines in ground and mixed in required proportions, shows
(a) That the iron rich wastes generated in the integrated steel plant can be converted into DRI with high iron content and resultantly low gangue content in steel making.
(b) The green pellets could be converted to DRI having good strength of more than 75 kg/pellet with a metallization as high as 85% on optimizing the ratio of coal fines and green pellets.
(c) The product exhibited strong affinity to magnet, indicating reduction of hematite ore to metallic form.
It is thus possible by way of the present invention to developing a process for production of iron enriched DRI by recycling iron rich wastes generated from various unit operations in an integrated steel plant replacing the use of iron ore fines or lump iron ore such that the iron rich DRI produced is having on one hand good metallisation and strength properties adapted to ease of handling and transporting to steel making and on the other hand ensure low gangue content and producing good quality steel in converter or arc/induction furnace with reliability, effectively substituting the use of costly steel scrap as coolant. The iron rich DRI produced following the process according to the present invention is thus having prospects of wide scale industrial application in steel making by recycling of iron rich wastes having substantial mineral value generated from unit processes in large integrated steel plants, avoiding environmental concern for handling and disposal of such wastes. The iron rich DRI obtained using the process of the invention ensure production of superior quality steel at lower cost with less reliance on the iron content of the iron ore fines/lump ores usually available and used.


WE CLAIM:
1. Iron enriched DRI comprising
obtaining from iron rich steel plant waste and having
Fe(T) in the range of 70 to 100
Fe(Met) in the range of 60 to 100
strength in the range of 0 to 150 kg/pellet; and
metallization properties of 60 to 100 %.
2. Iron enriched DRI as claimed in claim 1 wherein said steel plant waste comprises:
iron ore fines - 0-100 wt. %;
mill scale -0 100 wt %; CRM Oxide - 0-80 %; BOF sludge - 0-80 %; Iron making sludge - 0-80%.
3. Iron enriched DRI as claimed in anyone of claims 1 or 2 comprising:
Fe(T): 70 to 100 % preferably about 84 ;
Fe(Met): 60 to 100 % preferably about 73; FeO : 0 to 30 % preferably about 12;

C : 0 to 4 % preferably about 0.2; S: 0 to 1.0 % preferably about 0.28
4. A process for the manufacture of iron enriched DRI as claimed in anyone of claims 1 to
3 comprising the steps of:
(vi) providing iron ore fines, iron rich steel plant waste , coal fines and lime fines
and mixing thoroughly , followed by grounding such as to maintain about -325
# greater than 50% in the total mix; (vii) adding water to the above mix to maintain moisture content in the range of 5 to
15 % preferably 8-10%; (viii) obtaining green pellets of the size ranging from 5-20 mm; (ix) mixing the green pellets with coal fines in the range of 10-50% and (x) obtaining the DRI by heating in the furnace in the temperature range of 800 to
1300°C for a period of 10 -40 hrs preferably about 20hrs.
5. A process as claimed in claim 4 comprising screening the DRI to remove the ash and any un-burnt coal fines.
6. A process as claimed in anyone of claims 4 or 5 comprising utilizing the following as blend for pellet making:
iron ore fines - 0-100 wt. %; mill scale -0 100 wt %; CRM Oxide - 0-80 %; BOF sludge - 0-80 %;


Iron making sludge - 0-80%;
Lime fines: 0-20%;
Carbon in green pellets 0-5%; and
Goal fines,% of green pellets: 10-50 %.
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7. A process as claimed in anyone of claims 4 to 6 wherein the steel plant waste material containing iron is recycled into the process for generation of the iron enriched DRI.
8. Iron enriched DRI and its process of manufacture substantially as here in described and illustrated with reference to the accompanying examples.