Claims:We Claim:

1. Briquettes of Direct reduced iron (DRI) fines comprising:
DRI fines 85-93% preferably 90%, Molasses 5-10% preferably 8%, Hydrated lime 1-5% preferably 2%.
2. Briquettes as claimed in claim 1 wherein said DRI fines included comprises DRI fines of size range of 6-8 mm: 2.0%, 3-6 mm: 20%, 2-3 mm: 10%, 1-2 mm: 24%, 0.50-1.0 mm: 15%, 0.21-0.50 mm: 7.0%, 0.150-0.210 mm: 4.0%, 0.75-0.150 mm: 6.0%, 0.045-0.075 mm: 8%, below 0.045 mm: 4.0%.

3. Briquettes as claimed in anyone of claims 1 or 2 having Cold Compression Strength (CCS) of more than 100 kg/cm2 and moisture of below 4% preferably 2% with natural curing of 24-72 hours preferably 48 hrs.

4. Briquettes as claimed in anyone of claims 1 to 3 which is storage stable agglomerates of DRI fines favouring reduced heat emission, reoxidation thereby fire catching when maintained under 1 to 2 meter pile height preferably 1.5 meter height.

5. Briquettes as claimed in anyone of claims 1 to 4 suitable for use as coolant for BOF steel making.

6. A process for the manufacture of Briquettes of Direct reduced iron (DRI) fines as claimed in anyone of claims 1 to 5 comprising;
agglomerating the direct reduced iron (DRI) fines into briquettes involving selectively a blend ratio of DRI fines 85-93% preferably 90%, Molasses 5-10% preferably 8%, Hydrated lime 1-5% preferably 2%.
7. A process as claimed in claim 6 comprising
discharging DRI fines from the bunker initially followed by discharge of molasses and hydrated lime;
mixing preferably in a paddle mixer for uniform mixing of all the materials involving mixing time: 3-8 minutes preferably 5 minutes, and then discharge into the hopper ;
subjecting to briquetting in a briquetting machine involving press Roll pressure:100-500 kg/cm2 preferably 200 kg/cm2;

the briquettes thus obtained discharged into the storage area for curing.

8. A process as claimed in anyone of claims 6 or 7 wherein the briquettes are produced
involving (a) DRI fines of size range of 6-8 mm: 2.0%, 3-6 mm: 20%, 2-3 mm: 10%, 1-2 mm: 24%, 0.50-1.0 mm: 15%, 0.21-0.50 mm: 7.0%, 0.150-0.210 mm: 4.0%, 0.75-0.150 mm: 6.0%, 0.045-0.075 mm: 8%, below 0.045 mm: 4.0% (b) Molasses as binder 5-10%, preferably 8% and (c ) hydrated lime as hardener 1-5%, preferably 2%.
9. A process as claimed in anyone of claims 6 to 8 comprising involving natural curing of 24-72 hours preferably 48 hrs for producing Briquettes with Cold Compression Strength (CCS) of more than 100 kg/ cm2 and moisture of below 4% preferably 2%.

10. A process as claimed in anyone of claims 6 to 9 comprising step of storing of DRI fines briquettes to reduce heat emission, reoxidation thereby fire catching by maintaining 1 to 2 meter pile height preferably 1.5 meter height.

11. A process for steel making involving DRI fines based briquettes comprising :
providing steel scrap in convertor ;
pouring hot metal;
initiating oxygen blowing and monitoring liquid bath temperature ;
adding DRI fines based briquettes having DRI fines 85-93% preferably 90%, Molasses 5-10% preferably 8%, Hydrated lime 1-5% preferably 2%, as coolant when the bath temperature exceeds 17000C and in the process increasing metal yield through said DRI fines based briquettes as the coolant.
12. A process as claimed in claim 11 wherein by adding said. DRI fines based briquettes in the range of 0.75 to 4.5 % of liquid steel as coolant increase of metal yield of 0.73 to 4.4 preferably about 2.18 tons per heat is achieved.
13. A process as claimed in anyone of claims 11 or 12 involving in hot metal bath sulphur reduction only upto about 0.002% for additional desulphurization due to presence of excess CaO in the range of 0.001 to 0.005 % in the DRI briquettes contained in the form of hardener.
14. A process as claimed in anyone of claims 11 to 13 which is carried out following usual BOF process and steel quality free of any abnormalities with addition of DRI fines briquettes avoiding its loss as waste and environment issues and enabling
energy saving of 1.0 to 6.0 preferably about 4.07 Giga calorie per ton of DRI fine briquettes by effective utilization of DRI in the form of briquettes in BOF compared to sinter route.

Dated this the 26th day of September, 2019

Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199

, Description:FIELD OF THE INVENTION
The present invention relates to briquettes of Direct reduced iron (DRI) fines and a process for agglomeration of direct reduced iron(DRI) fines into briquettes for effective utilization in steel making. More particularly, the present invention is directed to developing of a suitable agglomeration process for briquetting the DRI fines into a dense metallized briquette for use as a coolant in primary steel making (i.e., basic oxygen furnace). Molasses and hydrated lime (slaked lime) is used as binder and hardener respectively in briquetting process. Initial lab scale experiments were done in pilot scale briquetting machine followed by industrial scale processing. The physical and chemical characteristics of these fines and briquettes were assessed at different stages. The cold compressive strength of the cured briquette was found more than 100 kg/cm2. In order to retard the reoxidation of DRI briquettes, the pile height is maintained 1.5 to 2 m. The present invention also describes the method of saving energy by making DRI fines into briquettes compared to usage in sinter making route.

BACKGROUND OF THE INVENTION

Direct reduced iron (DRI) production and its handling generate large amount of fines having less than 2 mm size particles. The iron content in DRI fines is more than 80%. Since these fines are extremely reactive and susceptible to oxidation, it reverts back into iron oxide. At JSW Steel, Vijayanagar Works around 50 to 70 tons of DRI fines (less than 2 mm size particles) gets generated. Presently, these fines are used in sinter base mix preparation as agglomeration feed.

Direct Reduced Iron [DRI] or sponge iron is a raw material popularly used in steel making in basic oxygen furnace (BOF) and Electric arc furnace (EAF). DRI is produced by the reduction of iron ore with reducing gases of H2 or CO gas generated from various carbon or hydrocarbon resources. The reaction follows, successive reduction of the iron oxides with gaseous reductant as per, Fe2O3? Fe3O4 ? FeO? Fe. The compacted and sintered briquette of iron oxide is used in sponge iron manufacturing processes of Midrex, HyL, SL/RN etc.

DRI is (also called as Sponge Iron) produced from direct reduction of Iron ore (in the form of lumps, pellets or fines) by a reducing gas produced from natural gas or Coal. The reducing gas is a mixture, the majority of which is H2, CO which act as reducing agents. This process of reducing the iron ore in solid from by reducing gases is called direct reduction. DRI fines produced are having iron content in metallic form up to 80%. Presently DRI fines generating are using in sintering process by mixing with sinter base mix raw materials. Sintering is a process of agglomeration of iron ore fines along with flux to make it solid compact mass which can be used as blast furnace feed. In general, hematite iron ore fines are used in this process. Usage of DRI fines which are already metallized in sintering process is not a logical process.

US 0268079 A1 describes the production of DRI briquettes from DRI fines, DRI sludge etc and usage of the produced briquettes in DRI process itself. Binders in this process are different compared to present invention.

European patent no 1425427 A4 describes a method for producing briquettes by mixing iron ore fines and flux and firing of same at 1200 -1380 oC. The application of produced briquettes are to use in Blast Furnaces or Direct Reduction Furnaces from the mixture of hydrated iron mineral and fluxes, being Goethite the preferred iron ore and limestone the preferred fluxes. Present invention is different where DRI fines are briquetted. Method of curing in the present invention is room temperature curing where as in cite document it is furnace curing at temperature of 1200 oC.

US Patent No.3125437 describes the process for the beneficiation of hematite ore fines comprising heating and partially reducing said ore fines at temperatures below 1500*f. in the presence of a suitable reducing agent to provide synthetic magnetite fines, and pressing said fines with contacting partially reduced interfaces into briquettes. Present invention is different from the cited document as present invention is briquetting of DRI fines and there is no heating of the briquettes.

US Patent. No.2865731A describes a method for producing cylindrical briquettes with a hydraulic piston from iron ore and paper pulp as binder, being the iron ore flotation concentrates of hematite which makes the difference from the present invention where DRI fines are used as base material for briquetting.

At JSW Steel, there is a Midrex based DRI manufacturing unit where DRI is produced. The typical DRI produced is 3200 tonnes/month. In the production of sponge iron briquettes, the hot DRI is handled and discharged. In the process, there is the generation of fines. Currently, the DRI fines generation is around 50-60 tons per day. It is very difficult to use the DRI fines generated. The DRI fines are iron based particulates with Fe content as high as >80%. It cannot be added in loose condition into the furnace, as it floats in the slag and is environmentally hazardous. Hence, DRI fines needs be used only in a compacted form. The as-reduced DRI fines are very reactive. It can react with atmospheric humidity readily and form ferric hydroxide which reverts further back to oxide form.

DRI can be used as a part of iron feed in sinter or it has to be used in agglomerated to a briquette form as soon as it is produced. In the sinter, the iron fines show less effect which may account for increase of 0.1% Fe of sinter.

Owing to high iron content, DRI fines in briquette form would be a suitable material to be used as coolant in primary steel making. In order to utilize the DRI fines in an effective manner it is proposed to make the cold briquettes from DRI fines by adding binders and hardeners and usage of same in the BOF converter as a coolant which utilizes the metallic iron content present in DRI fines directly in the steel making which will improve the metal yield. In the agglomerated form, the iron fines with suitable organic or inorganic binder can be made to briquettes, which can be added to the BOF as a coolant.

OBJECTS OF THE INVENTION

The basic objective of the present invention is directed to briquettes of Direct reduced iron (DRI) fines and a process for producing briquettes from DRI fines suitable for using in BOF steel making process by using molasses as binder and hydrated lime as hardener.

A further objective of the present invention is directed to a process for effective utilization of DRI fines through briquetting rather than using in sintering which save the energy.

A still further objective of the present invention is directed to a process for effective utilization of DRI whereby the metallic iron content present in DRI fines is used directly in the steel making which will improve the metal yield.

A still further objective of the present invention is directed to production of DRI briquettes which utilizes the microfines of DRI fines which protects environment by eliminating the disposal.

A still further objective of the present invention is directed to production of DRI briquettes which acts as coolant for BOF steel making without affecting the quality of liquid steel.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to provide briquettes of Direct reduced iron (DRI) fines comprising:
DRI fines 85-93% preferably 90%, Molasses 5-10% preferably 8%, Hydrated lime 1-5% preferably 2%.
A further aspect of the present invention is directed to said briquettes wherein said DRI fines included comprises DRI fines of size range of 6-8 mm: 2.0%, 3-6 mm: 20%, 2-3 mm: 10%, 1-2 mm: 24%, 0.50-1.0 mm: 15%, 0.21-0.50 mm: 7.0%, 0.150-0.210 mm: 4.0%, 0.75-0.150 mm: 6.0%, 0.045-0.075 mm: 8%, below 0.045 mm: 4.0%.
A still further aspect of the present invention is directed to said briquettes having Cold Compression Strength (CCS) of more than 100 kg/cm2 and moisture of below 4% preferably 2% with natural curing of 24-72 hours preferably 48 hrs.
A still further aspect of the present invention is directed to said briquettes which is storage stable agglomerates of DRI fines favouring reduced heat emission, reoxidation thereby fire catching when maintained under 1 to 2 meter pile height preferably 1.5 meter height.
A still further aspect of the present invention is directed to said briquettes which is suitable for use as coolant for BOF steel making.
Another aspect of the present invention is directed to a process for the manufacture of Briquettes of Direct reduced iron (DRI) fines as described above comprising;
agglomerating the direct reduced iron (DRI) fines into briquettes involving selectively a blend ratio of DRI fines 85-93% preferably 90%, Molasses 5-10% preferably 8%, Hydrated lime 1-5% preferably 2%.

Yet another aspect of the present invention is directed to said process comprising
discharging DRI fines from the bunker initially followed by discharge of molasses and hydrated lime;
mixing preferably in a paddle mixer for uniform mixing of all the materials involving mixing time: 3-8 minutes preferably 5 minutes, and then discharge into the hopper ;
subjecting to briquetting in a briquetting machine involving press Roll pressure:100-500 kg/cm2 preferably 200 kg/cm2;
the briquettes thus obtained discharged into the storage area for curing.

A further aspect of the present invention is directed to said process wherein the briquettes are produced
involving (a) DRI fines of size range of 6-8 mm: 2.0%, 3-6 mm: 20%, 2-3 mm: 10%, 1-2 mm: 24%, 0.50-1.0 mm: 15%, 0.21-0.50 mm: 7.0%, 0.150-0.210 mm: 4.0%, 0.75-0.150 mm: 6.0%, 0.045-0.075 mm: 8%, below 0.045 mm: 4.0% (b) Molasses as binder 5-10%, preferably 8% and (c ) hydrated lime as hardener 1-5%, preferably 2%.

A still further aspect of the present invention is directed to said process comprising involving natural curing of 24-72 hours preferably 48 hrs for producing Briquettes with Cold Compression Strength (CCS) of more than 100 kg/cm2 and moisture of below 4% preferably 2%.

A still further aspect of the present invention is directed to said process comprising step of storing of DRI fines briquettes to reduce heat emission, reoxidation thereby fire catching by maintaining 1 to 2 meter pile height preferably 1.5 meter height.

A further aspect of the present invention is directed to a process for steel making involving DRI fines based briquettes comprising:
providing steel scrap in convertor ;
pouring hot metal;
initiating oxygen blowing and monitoring liquid bath temperature ;
adding DRI fines based briquettes having DRI fines 85-93% preferably 90%, Molasses 5-10% preferably 8%, Hydrated lime 1-5% preferably 2%. as coolant when the bath temperature exceeds 17000C and in the process increasing metal yield through said DRI fines based briquettes as the coolant.

A still further aspect of the present invention is directed to said process wherein by adding said. DRI fines based briquettes in the range of 0.75 to 4.50 % of liquid steel as a coolant increase of metal yield of 0.73 to 4.4 preferably about 2.18 tons per heat is achieved.

A still further aspect of the present invention is directed to said process involving in hot metal bath sulphur reduction only upto about 0.002% for additional desulphurization due to presence of excess CaO in the range of 0.001 to 0.005 % in the DRI briquettes contained in the form of hardener.

A still further aspect of the present invention is directed to said process which is carried out following usual BOF process and steel quality free of any abnormalities with addition of DRI fines briquettes avoiding its loss as waste and environment issues and enabling
Energy saving of 1.0 to 6.0 preferably about 4.07 Giga calorie per ton of DRI fine briquettes by effective utilization of DRI in the form of briquettes in BOF compared to sinter route.

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1: Shows Comparison of present and proposed method of DRI fines agglomeration.
Fig. 2: Shows Schematic diagram of DRI fines briquetting and usage in steel making according to present invention.
Fig. 3: Shows Photograph and Microstructure of DRI fines.
Fig. 4: Shows Photograph of DRI fines briquettes.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The present invention is directed to briquettes of Direct reduced iron (DRI) fines and a process for producing briquettes from DRI fines suitable for using in BOF steel making process by using molasses as binder and hydrated lime as hardener. The process is for agglomeration of DRI fines to briquettes which can be directly used as coolant in primary steel making process. This is an energy saving process as compared to conventional utilization of DRI in sintering. Energy consumption for usage in both the process were compared and found that energy utilized by usage in steel making route is less compared to usage in sinter making. Details of present and proposed method of usage is described in accompanying Figure 1.

Accompanying Figure 2 describes the schematic diagram of the briquetting process for DRI briquettes. DRI fines are discharged from the bunker initially followed by discharging of molasses and hydrated lime. After conveying these material into paddle mixer, thorough mixing is carried out for 5 minutes to uniform mixing of all the materials and then discharge into the hopper and then into briquetting press. After briquetting press briquettes are discharged into the storage area for curing of 48 hrs. After curing, the briquettes will be transported to BOF shop and charged into the BOF converter based on the requirement. Following items are illustrated in Figure 2:
Sl. No. Material/equipment
101 DRI fines
102 Molasses
103 Hydrated lime
104 Water
105 Conveyor 1
106 Paddle mixer
107 Conveyor 1
108 Feeder
109 Roll tyre
110 Conveyor 1
111 DRI briquettes
112 BOF converter

Accompanying Figure 3 describes the image and micro structure of DRI fines. It is observed from microscopy that edges of the particles are sharp and it is mixture of fine and coarser particles. The fines particles go to the voids of coarser particles and bonded in the presence of binder and hardener during mixing and curing. Figure 4 describes the image of the DRI briquettes produced at plant scale which are discharge at storage yard.

The DRI fines were characterized for its size fraction using screens of size varying from 10 mm to 0.045 mm. The chemical analysis of the fines was determined using standard wet chemical analysis technique. The binders and hardeners used were obtained from sugar based process wastes and calcium based respectively. Ordinary water was used for the trials initially; laboratory scale trials were carried out followed by industrial scale trials. In the laboratory scale invention, the DRI fines were mixed with suitable organic binder and inorganic hardener in a mixer with water at appropriate proportion. The schematic diagram of the briquetting facility is shown in Figure 2. Following Table 1 shows the parameters used in experimental trials on lab scale and plant scale briquetting machines.

Table 1: Parameters of lab scale and plant scale briquetting machines

S. No. Features Lab scale Industrial scale
1 Type of briquetting press Roller type Roller type
2 Mixer type Paddle mixer Paddle mixer
3 Shape of the briquettes Pillow shape Pillow shape
4 Diameter of the rolls 500 mm 1000 mm
5 Briquetting Pressure, max 1000 kg/cm2 1000 kg/cm2
6 Pocket volume of briquette 25 cc 50 cc
7 Roller speed, max 50 rpm 50 rpm
8 Rate of production 1 tph 50 tph
9 Input for compaction DRI fines, moisture,
binder & hardener DRI fines, moisture,
binder & hardener

Based on the laboratory trial results, industrial scale trial was carried out in the mill scale briquetting plant with roller type briquetting of 750 tons per day capacity. The briquettes made at a scale of 200 tons were used in the primary steel making basic oxygen furnace at JSW. DRI briquettes charge of 3 tons was used as coolant in a steel making heat size of 133 tons.

The physical and chemical characterization of DRI fines was initially assessed. The size fraction of the fines as determined by size analysis of different screen sizes is shown in Table 2. The size analysis indicates that around 40% is below 1mm size which is difficult to handle. It is observed that below 2 mm size fraction is 68% due to which, fine particulate floats as dust cloud, when the material is used without compacting. Further, the finer fraction gets well locked into coarser fraction during compacting, which improves the briquette density. Tap density of the DRI fines is 1.8 gm/cc
Table 2: Size analysis of DRI fines
Size distribution %
+8 mm 0
+6 mm 2.0
+3 mm 20.0
+2 mm 10.0
+1 mm 24.0
+0.5 mm 15.0
+0.21 mm 7.0
+0.150 mm 4.0
+0.075 mm 6.0
+0.045 mm 8.0
-0.045 mm 4.0

The shape of the iron oxide particulates are porous fines, and are rounded with irregular shapes as shown in Fig.3. Hence, during compacting, the particles will get locked leading to better density and stability against crumbling.

The chemical analysis of the fines was assessed as shown in Table 3 (IS 15774-2007). It is seen that the total Fe is 84% and metallic Fe is 76%. Hence, the usage of agglomerated fines gives higher iron in put with the gangue content of around 14%.

Table 3: Chemical analysis of DRI fines
Constituent Wt. %
Fe(Total) 84.0
Fe(Metallic) 76.0
SiO2 6.39
Al2O3 4.99
CaO 2.02
MgO 0.46
Na2O 0.10
K2O 0.03
P 0.05
C 1.30
S 0.011

The briquettes were made in the laboratory scale of 10 kg batch size, as per the equipment process parameters shown in Table 1. Briquetting parameters of binder %, roll pressure, mixing time, curing time, curing type were optimized and given in Table 4. The typical laboratory scale green briquette made is shown in Figure 5. The briquette made from the fines was appearing metallic, dense and hard.

Table 4: Parameters of briquetting
Description Quantity
Mix proportion DRI fines - 92.25%. Organic binder- 5%,
Inorganic binder- 2%, Water- 0.75%
Iron fines 10 kg
Organic Binder 5%
Inorganic Hardener 2%
Mixing time 5 min
Roll pressure 340 kg/cm2
Roll tyre speed 4 rpm
Total moisture 4.0 %
Time for atmospheric
Curing 48 hrs
Briquette Shape Pillow shape
Density of briquette 2.4 gm/cc

Out of the various binders tried in pilot scale level, only combination of molasses and hydrated lime were established as binder and hardener respectively followed by mixing of 5 minutes gave satisfactory results with respect to both green briquette strength, and cured briquette strength, with minimum fines generation.

The main property required for briquette is cold compressive strength (CCS).The properties of the briquettes, was studied as a function of curing time and moisture content as shown in Table 5. CCS of the briquettes were measured by placing the briquettes in a compressive testing machine and applying load at a constant speed until the briquette breaks (IS: 8604 - 1977). The maximum load applied where the briquettes breaks is recorded in kilograms. The strength of the compacted briquette was studied as a function of moisture content. The CCS increases with increasing curing time and decreasing moisture content. It was found that 24 hours curing is adequate to achieve the required CCS.

Table 5: Properties of briquette (Lab scale result)
Curing time (hour) Moisture (%) CCS (kg/cm2)
0 3.5 155
24 1.3 347
48 1.0 472
72 0.9 512

The required CCS of the briquettes suitable for converter is more than 100 kg and required moisture should be of below 2% (based on plant optimization). The briquettes produced are having the required strength (CCS) of >100 kg and moisture should be of below 2% of 48 hrs of natural curing. It was observed that when water was used for the mixing of binders with DRI fines, high temperature fumes were observed due to exothermic reaction between water and DRI fines. So, it is recommended not to use water for mixing and moisture present (25%) in organic liquid binder was sufficient for the wetting of the surfaces of DRI fines during mixing. From this invention, the measures to prevent reoxidation, was obtained. The briquettes were spread and naturally cured for 2 days.

The chemical analysis of DRI briquette after compacting is shown in Table 6. It is seen that the total Fe content of 72.63% and the metallic Fe content of 63.47%.

Table 6: Chemical analysis of DRI briquettes
Constituent wt. %
Fe(Total) 72.63
Fe(Metallic) 63.47
C 4.50
S 0.04
P 0.06
SiO2 4.06
Al2O3 4.66
CaO 3.68
MgO 0.41
Na2O 0.14
K2O 0.52
ZnO 0.01

The total Fe and the metallic Fe in the briquette has decreased when compared to the original analysis of DRI fines. This decrease is due to addition of moisture and binders.

Plant Scale Trials
Based on the encouraging results of briquette making in the laboratory scale, plant scale feasibility trial was conducted producing around 200 tons of briquettes at the mill scale briquetting plant. Details of the plant trial are shown in Table 7. The process was run for 24 hours and about 200 tons was produced. A further improvement was introduced in the industrial scale trial by total elimination of water addition and the organic binder was found to be adequate to agglomerate. The properties of briquettes obtained on plant trial are shown in Table 8.

Table 7: Briquette manufacture at plant scale
Mix Proportion DRI fines - 90%, Organic binder - 8%, Inorganic binder -2%.
Briquettes Production Capacity 750 tons per day
Type of mixing Equipment Intense paddle mixer
Mixing time, min 5
Briquetting Machine Roll type with pillow shape
Roll pressure 340 kg/cm2
Roll tyre speed 4 rpm
Curing time, h 48 hr
Briquette dimensions 30mm*75mm*45mm
Briquette Shape Pillow shape
Briquette density 2.8 gm/cc
Total moisture 4.0%

Table 8: Properties of briquette (Plant scale result)
Curing time (hour) Moisture (%) CCS (kg/cm2)
0 3.5 350
24 1.1 750
48 0.9 1050
72 0.8 1200

The water addition resulted in oxidation of the DRI fines and the heat generation was directly felt. This was avoided in the industrial scale process. It is observed that the briquette formation during industrial scale trial was good with a fines generation less than 5%. The CCS of the briquette of more than 500 kg is achieved after 24 h of atmospheric curing. The CCS of the briquettes made at the plant scale shows much higher values in the industrial trials as compared to laboratory trials. This was attributed due to the bigger sizes of briquette which reduced the reactive area exposure to oxidation. The industrial scale briquettes had higher density (2.8gm/cc) compared to laboratory scale briquettes (2.4 gm/cc). The higher density is due to better compaction stress, more binder usage and absence of water addition in the process which promote formation of oxide particle around the DRI particulate. The stock pile of the briquette was maintained as a 2 m height pile to avoid reoxidation.

Usage of the Briquettes in SMS
Steel scrap, mill scale briquettes are used currently as coolant materials in the converter of steel making. In the present invention about 200 tons of DRI fine briquettes were used as coolant charged in about 60 heats of the primary steel making basic oxygen furnace in addition to the present coolant materials. The typical heat schedule is shown in Table 9. The briquette addition was done during the blowing process, when the temperature shoots up beyond 1700oC. The process behaved in a manner similar to that without the addition of DRI briquettes. The impurities present in steel such as sulphur, phosphorous, carbon and temperature were found normal during the usage of the DRI fines based briquettes in BOF trial. Details of the plant scale results were given in Table 8. The BOF process parameters were maintained especially with respect to bath temperature and composition of the steel bath. Hence, the byproduct fines of DRI plant could be effectively used for steel making. Theoretically, in each heat it was estimated that the iron in the fines about 2.18 tons could be recovered in the steel [based on 72.6% Fe in DRI]. Table 10 shows Converter parameters with and without DRI briquettes.

Table 9: Typical heat making parameter in the basic oxygen furnace, where DRI briquette was used.

Parameters Values
Furnace used Basic Oxygen furnace at SMS1
of JSW
Heat size 133 tons
Typical Charge mix, wt.
(tons per heat) Scrap =20.9, Mill scale briquettes= 3.5,
Cold DRI=3.2
Fluxes used (tons per heat) Calcined lime=7.2;calcined dolomite=4.8;
raw dolomite=1.1
Top lance Oxygen blow =6955 Nm3 per heat
Tap to tap time 50 min
Stage at which DRI briquette is
adding During blowing if temperature is beyond 1700oC
DRI briquettes Quantity in kg /
percent of total charge 3 tons / 2.3 % of total charge
Bath temperature 1655oC
Typical composition C= 0.027%; S =0.013%; Mn=0.062;
Si=0.060; P= 0.015; N2= 40 ppm

Table 10: Converter parameters with and without DRI briquettes
Parameter 2017-18 2018-19
Before DRI
Briquette addition
(Average value) After DRI
Briquette addition
(Average value)
Converter tap weight, Ton 133.1 132.4
Scrap weight, Ton 20.9 20.9
Lime (Tons) 7.2 6.9
Calcined Dolomite (Tons) 4.8 5.2
Converter metal bath Temperature, o C 1656 1654
Converter metal bath Carbon, % 0.027 0.029
Metal bath Manganese, % 0.062 0.065
Metal bath Sulphur, % 0.013 0.011
Metal bath Phosphorous, % 0.015 0.016
Total O2 consumption (NM 3 ) 6954.5 6955.0
Mill scale briquettes (Tons) 3.5 3.5
Iron Ore (Tons) 0.3 0.2
Cold DRI 3.0 3.0
DRI Briquette 0 3.0

Saving of energy due to process optimization
Due to effective utilization of DRI fines in the form of briquettes rather than using in sinter making, around 4 Gcal of energy is saved. Details of energy saving calculation is given in Table 11.

Table 11: Energy saving calculation breakup
Energy consumption details
Present route: Mixing with sintering Proposed route: Briquetting
Usage route Energy consumption
per ton of DRI fines, Gcal Usage route Energy consumption
per ton of DRI fines, Gcal
Sintering 0.146 DRI fines to
DRI briquettes 0.006
Melting in blast furnace 0.84% Sinter
(84.0% Fe total) 3.930 Blowing 1 ton of
DRI fine briquettes to liquid steel 0.500
converting 1 ton of hot metal/pig iron to
steel in BOF converter 0.500 - -
Total energy consumed 4.576 - 0.506
Energy saving per ton of
DRI fines briquette usage compared to sinter usage route (4.576 - 0.506 = 4.070), G Cal 4.070 - -

It is thus possible by way of the present invention to provide briquettes of Direct reduced iron (DRI) fines and a process for producing briquettes from DRI fines by using molasses as binder and hydrated lime as hardener suitable for using in BOF steel making process. The process is for agglomeration of DRI fines to briquettes which can be directly used as coolant in primary steel making process. This is an energy saving process as compared to conventional utilization of DRI fines in sintering. It is observed that the briquette formation during industrial scale trial was good with a fines generation less than 5%. The CCS of the briquette of more than 500 kg is achieved after 24 h of atmospheric curing. The CCS of the briquettes made at the plant scale shows much higher values in the industrial trials as compared to laboratory trials. This was attributed due to the bigger sizes of briquette which reduced the reactive area exposure to oxidation. The industrial scale briquettes had higher density (2.8gm/cc) compared to laboratory scale briquettes (2.4 gm/cc). The higher density is due to better compaction stress, more binder usage and absence of water addition in the process which promote formation of oxide particle around the DRI particulate. The stock pile of the briquette was maintained as a 2 m height pile to avoid reoxidation.