Quality of Raw Materials - a Key to Cost Reduction

M P Srivastava, Non-member
S K Pan, Non-member
S K Mukherjee, Non-member
R N Singh, Non-member
The integrated iron and steel plants are raw material intensive and the quality and cost of raw materials influence the
techno-economic performance of the plants significantly. Under Indian conditions, the role of raw materials is more critical
on account of their intrinsic quality consideration which are unique compared to global scenario. It has been well estab-
lished that the cost of steel can be brought down considerably by improving the physical and chemical quality of raw
materials. Indian iron ores are generally quite high in iron content and low in gangue but are characterized by high
alumina content. Alumina in iron ore fines affects the process of sintering and quality of sinter. Reduction in cost of hot
metal production can be achieved by lowering the cost of iron ore produced, as well as improving the granulometry and
quality of iron ore. As regards coal, wide fluctuations in ash, volatile matter and coking properties are observed. Wide
variation in quality of coal and erratic supply results in inconsistency in coal blend. In view of the decline in supply and
inconsistency in coal from indigenous sources, good quality coking coals are imported to reduce ash and improve other
metallurgical properties. Limestone is consumed in lesser quality, but its quality has significant impact on the cost of hot
metal. Steel plants, particularly under SAIL, use limestone from captive sources which have high silica content. In order to
sweeten the limestone, high grade limestone is purchased from Rajasthan, Uttar Pradesh and Himachal Pradesh. This paper
looks into potential areas such as alumina reduction in iron ore fines, productivity constraints at ore mines, reduction of
slime loss which has direct impact on cost of hot metal and also future plan to improve quality and quantity of iron ore with
special reference to SAIL mines.
Keywords: Raw material quality; Cost reduction; Beneficiation

INTRODUCTION production. The per capita consumption of steel in India, which

indicates the economic growth of a country, is only 27 kg,
Iron ore and coking coal are the principal raw materials in the which is much lower compared to world average as shown in
manufacture of iron and steel. Production of one tonne of hot Figure1.With the present trend of growth of steel industry, it
metal requires around 1.65 t of iron ore, 0.45t of fluxes and has become necessary to produce hot metal at lower cost so as
1.0 t of coking coal. Cost of hot metal is strongly influenced to compete in the world and domestic market. The production
by the consumption of iron ore and coking coal per tonne of cost of steel can be brought down considerably by using raw
hot metal produced. While cost of iron ore and flux account materials of consistent quality, lowering gangue content, using
for 20% of the raw material cost, coke accounts for about 50% calibrated ore and use of low alumina ore fines for sinter
of the total cost of production of hot metal. Iron ore and coking
coal become the key factor for cost reduction in iron and steel
Table 1 Cost of production during 2002-2003 for mines in India

4 22 .4 Mines Iron ore Cost, Rs/t

4 50
4 00 Kiriburu Lump 221.00
Per-c apita c onsum ption

3 50 Fine 217.00
3 00 Meghahatuburu Lump 209.00
2 39 .6
2 50 Fine 204.00
2 00
1 20 .9 Bolani Lump 267.00
1 50
8 7.2 9 5.9 Fine 263.00
1 00
50 27 Barsua Lump 495.00
0 Fine 490.00
C hina U SA UK Brazil Avg.W orld Ind ia Kalta Lump 383.00
N am e o f the c ou ntries Fine 378.00
Figure 1 Per-capita consumption of finished steel Rajhara and Dalli Lump 353.91
Fine 191.37
M P Srivastava, S K Pan, S K Mukherjee and R N Singh are with Gua Lump 493.00
Research & Development Centre for Iron & Steel, SAIL,Ranchi Chiria Lump 564.00
834002.1 TISCO(procurement rate incl.tax) Lump 485.00
This paper was awarded the Dr M Visvesvaraya Award for the year 2003. OMDC(procurement rate incl.tax) Lump 365.00

Vol 85, October 2004 71

burden. To meet the quality requirement of iron ore, the Table-2 Landed cost of coal in SAIL plants during 2002-2003, Rs/t
present ore mines and processing plants will have to gear up Category BSP DSP RSP BSL
not only for higher production by better mine planning but BCCL(Sudamdih) 3513 2805 2923 2801
also systematic development of large capacity mechanized mines. CCL (Kathara ) 3261 2669 2784 2502
Cost of production of iron ore can be reduced by increasing WCL 2517
the rated capacity of mines. The cost of production of iron ore SECL 1750 2035 1788 1999
lump and fines in India in various mines ranges from Rs 190/t TISCO (Bhelatand) 3605 2990 3112 2941
Rs 350/t as indicated in Table 1. Cost of production at Barsua TISCO(Jamadoba) 3590 2976 3097 2969
mines is high because of low productivity whereas at Chiria and
Imported (Hard), Australia
Kalta it is due to manual mining.Gua mines, a captive mine to
Vizag 4050 4261 3936 4333
IISCO, produces only iron ore lump as there is no sintering
Haldia 4287 3753 3750 3779
plant at IISCO. As a result, cost of production at Gua mine is
Paradip 4208 3900 3836 4047
very high.
Imported (Hard),
For the last few years, the quality and quantity of coking coal New Zealand
from indigenous sources has deteriorated and will continue to Vizag 4079 4288 3963 4360
be a problem in future. The price of imported coking coal is Haldia 4315 3780 3777 3806
increasing at a fast rate and its availability in the international Paradip 4236 3927 3863 4074
market is also becoming difficult. Since the cost of hot metal is Imported (Soft)
strongly influenced by consumption of coking coal per tonne Vizag 3305 3551 3226 3623
of hot metal produced, it is necessary to examine various issues Haldia 3541 3043 3040 3069
involved and take specific action to reduce consumption of coke Paradip 3462 3190 3126 3337
in blast furnace.Coke quality can be improved by ensuring
desired quality of raw feed coal to the washeries and better
beneficiation facilities. The ash content of indigenous coking
Low productivity in mines is also attributed to factors such as
coals is quite high ( more than 21 %).As indigenous supply from
non-availability of heavy mining equipment, under-utilization of
Coal India Ltd (CIL) has not only wide fluctuation but also
dumpers etc. Cost reduction may be achieved not only by
erratic supply, regular interaction with CIL at various levels may quality improvement of raw materials but also giving stress to
improve the situation. Proper blend of imported coal with areas such as bedding and blending facility, proper size of iron
indigenous coal will also result in significant cost saving. Besides ore lump and fines, recovery of iron values from slime, better
quality parameters of coking coal, measures such as reduction mine planning and also giving serious thought to using pellets
in transportation loss from mines to plant and handling loss at made of high quality iron concentrate in blast furnace.
steel plants, avoiding loss of +25 mm fraction coke due to
damage of screens will result in appreciable cost reduction. IRON ORE RESERVES
Table 2 gives landed cost of coals at SAIL plants during 2002-
2003. It is clear that some plants pay about Rs 1000/t more Indian Perspective
due to transportation cost. The benefit obtained with low ash Indian ranks fifth in the iron ore producers of the world. India
and better properties of imported coals in comparison with exported 48 Mt of ore valued at Rs 58 000 million during
indigenous coals and also blending soft coal would reduce the 2002-2003 out of which China’s share was 20 Mt worth
cost of coke. Rs 24 000 million. The output gradually increased to 78 Mt
Limestone quality available in captive mines of SAIL has gone in 2002-2003 from an ouput of 58 Mt in the year 1992-
down because of the selective mining practice followed earlier. 1993. Iron ore production has mostly been confined to the
Mining at Bhawanathpur and Purnapani has been reduced to states of Jharkhand, Orissa, Karnataka, Goa and Chattisgarh.
almost 10000 t/month. The silica content varies from 5%–6.5 State-wise reserves of hematite and magnetite iron ore in India
% and CaO is about 43 %.Mostly the limestone from are shown in the Table 3.
Kuteshwar mines is supplied to Bokaro Steel Plant which has The onset of liberalisation and economic reforms in the early
silica about 3.5 %. Low silica limestones are available in Uttar 90’s, India witnessed rapid strides in the iron ore mining and
Pradesh, Rajasthan and Himachal Pradesh. The landed cost of steel industry and more so with entry of large public sector
limestone at steel plants becomes very high due to high mining companies like NMDC and KIOCL which helped in
transportation cost. Techno-economics and logistic of linkage the introduction of modern techniques of open cast mining and
plan should be worked out to reduce the landed cost at various beneficiation. About 56% of the output of iron ore is from
mines. Proper blending of various sources would help in getting Public Sector mines and 44% being contributed by private
the desired quality of blast furnace and steel melting shops. sector. Almost 67.5% of the ore production is from Chattisgarh,

72 IE(I) Journal-MM
Table 3 Reserves of iron ore in India alumina (more than 2.6 %) are processed through washing and
Grade / State Total reserve, Mt beneficiation circuit. Typical flowsheet of few Indian mines are
Hematite : shown in Figure 3-8.
Andhra Pradesh 51
Global Perspective
Jharkhand 2657
Goa 745 The estimated world reserve of iron ore is 229 000 Mt and
Karnataka 1072 more than 85% of the reserves are located in eight countries,
Chattisgarh 1998 namely, CIS, Australia, Brazil, Canada, USA, India, South
Maharashtra 227 Africa and China as shown in Table 5. It may be observed that
Orissa 3294 reserve of iron ore in India is 5.46% of the total world reserve.
Rajasthan 9 The share of world ore production by different countries is
Magnetite : indicated in Figure 2. India ranks 5th in the world iron ore
Andhra Pradesh 418 production and its share is about 7%. More than 80% of the
Jharkhand 5 total world’s iron ore production is by China, Brazil, Australia,
Goa 164 CIS countries, India and USA and the leading producer is
Karnataka 2784 China.
Kerala 36
Most of the iron ore mined worldwide are mainly hematite and
Tamil Nadu 1 magnetite. Fe content of the iron ore worldwide is much lower
as compared to that in Indian ore deposits. In order to process
Table 4 Production quantity from different mines, Mtpa iron ore containing low Fe and high gangue, intensive
Mine Rated Actual Projected beneficiation circuit comprising gravimetric, magnetic
capacity production production separation, flotation, heavy media separation and hydrocyclone
in 2002-2003 by 2006-2007
Rajhara 3.50 2.68 5.01
O ther C hina
Dalli 5.50 4.25 5.05
16% 23%
USA
Kiriburu 4.25 3.60 4.17
6%
Meghahatuburu 4.30 3.18 3.86
India
Bolani 3.00 3.08 4.24
7% B razil
Barsua 2.01 1.03 1.08 19%
C IS A ustralia
Kalta 0.5 0.93 1.05 14% 15%
Figure 2 : Share of different countries in World’s iron ore production

Goa and Jharkhand. Most of the integrated steel plants have Table 5 World reserves of iron ore
their captive iron ore mines. The production capacity of iron
Country Reserves
ore ranges from 2 Mt/annum-5.5 Mt/annum. Actual
Mt %
production during 2002-2003 with rated capacities are
indicated in Table 4. CIS 78 000 33.54
Australia 28 100 12.08
The iron ore analysis varies widely in these plants depending Canada 25 500 10.97
upon the iron ore reserves. TISCO has comparatively better iron USA 25 200 10.84
ore deposit (Noamundi and Joda). The iron ore processing Brazil 17 300 7.44
circuits in SAIL and TISCO mines primarily consists of two India 12 700 5.46
stage crushing, wet/dry screening, classification. In some South Africa 9 300 4.00
processing circuit, facilities for treatment of slimes have been China 9 000 3.87
provided using hydrocyclone and slow speed spiral classifier. Sweden 4 600 1.98
Venezuela 3 300 1.42
Processing circuit at different mines varies depending upon the
type of ore available ie, hematite or magnetite. India has mostly France 2 200 0.95
hematite deposit except Kudremukh mine which has magnetite Liberia 1 600 0.69
as well as hematite deposit. In SAIL ores are broadly classified Mauritania 700 0.30
as direct ore and beneficiable ore. Good quality run-of mines Other Countries 12 500 5.37
categorized as direct ore are dry processed and ore with high World total 229 000 100.00

Vol 85, October 2004 73

 ROM (1600t /h) Fe, % = 37-40
ROM
SiO2, % = 40
Al2O3 % = 1.5-2.0

PRIMARY CRUSHER

Gyratory Crusher
WET AUTOGENEOUS
MILL
-300 mm

SCALPING SCREEN
Cone Crusher

-50 mm SIZING SCREEN

Drum Scrubber Backflow NON MAGNETIC PRIMARY MAGNETIC

SEPARATOR (LIMS)
SPIRAL

CONCENTRATE REGRINDING BALL

Lump MILL
(-50mm + 10 mm) Double Deck Screen
REGRINDING BALL MILL

SECONDARY MAGNETIC
-10 mm MECHANICAL FLOTATION SEPARATOR

Rake Classifiers
COLUMN FLOTATION

-10mm+0.2 mm -0.2 mm
TAILING THICKNER CONCENTRATE THICKENER

Fines Slimes to Tailing Pond

IRON ORE CONCENTRATE

Figure 3 Flowsheet of Bolani Ore Processing Plant Fe, % = 68
SiO2, % = 3-3.5
Al2O3 % = 0.5
R. O. M. (- 40mm)
Figure 5 Flow sheet of Kudremukh iron ore beneficiation plant
WATER

D/D SCREEN (3 No’s)

ROM
U/F O/F
Fe, % = 59–60

RAKE CLASSIFIERS PRODUCT SCREEN

(3 No’s of 400t/h each) LUMP (+ 10 mm) +4 mm
-4 mm
O/F +4 mm
SAND 30 mm SCREEN
-4 mm
D/W SCREEN
U/F (3 Nos) TROMMEL IMPACT CRUSHER ATTRITION JET SCRUBBER

O/F
LOG WASHER FINES SCREW WASHER
SLIME PRODUCT
DISTRIBUTOR TANK FINES (- 10mm)

DOUBLE DECK ATTRITION JET SCRUBBER

SCREEN
10 & 5 mm
SLURRY HYDROCYCLONES
PUMPS (6 Nos) (12 No’s / 24 inch)
3
(6.00 m /h cap)
3
(@ 300 m /h cap)
Fines screw washer
-30mm+10 mm -10mm+5 mm
O/F Despatch Despatch CONCENTRATE
U/F
Fe, % = 64–65
HYDROCYCLONE
O/F S S S CLASSIFIER
(2 No’s @ 90 t/h) SAND THICKNER

THICKENERS WLIMS
(2 No’s) TAILINGS
F
Fe, % =40–45
HGMS
Figure 4 Material flow diagram of Miom washing plant

CONCENTRATE
are used in the processing circuit. The capacity of these mines Fe, % = 64–65

are more than 10 Mt/year. The low grade iron ore are crushed Figure 6 Flow sheet of iron ore beneficiation plant of Fomento, Goa

74 IE(I) Journal-MM
 ROM 1500 t/h

Primary Crusher

+70 mm, 490 t/h -70 mm, 1010 t/h

Scalping Screen

Sec Cone Cr. Sec Gyratory Cr.

Primary Screen Primary Screen Primary Screen

+40 mm -40 mm + 4 mm -4 mm +40 mm -40 mm + 4 mm -4 mm +40 mm -40 mm + 4 mm -4 mm

Tertiary Crusher

Tertiary Screen Secondary Screen Spiral classifier

+30 mm -30 mm + 10 mm -10 mm -40 mm+10mm -10 mm + 4 mm -4 mm

Sand Slime, 2251

Quat. Crusher
To Thickener

Screen, 10 mm Lump ore, 390 t Fine Ore, 885 t

+10 mm -10 mm
Figure 7 Flow-sheet of Kiriburu mines

to liberation size followed by a series of beneficiation processes of steel plants. Huge dumps of low grade limestone have
so as to get a product in the Fe range 63%-66%. Depending accumulated at pit heads. Due to selective mining overall
upon the type of processing circuit used, tailings may be 10%- quality of the deposits have gone down and Bhawnathpur mines
25% of the ROM. Some of the processing circuit used was forced to reduce its production.
worldwide are shown in Figures 9-11.
Limestone available in SAIL mines contain very high amount
LIMESTONE of acid insolubles – silica and other deletrious oxides. This
results in low availability of free lime in the furnace. For better
SAIL is operating three mines namely Bhawnathpur, Purnapani efficiency of iron making, furnace operators demand low silica
and Nandini for Bokaro, Rourkela and Bhilai Steel Plants, limestone. Availability of such limestone is very low and these
respectively. Over the years the chemical quality with respect deposits are situated in distant areas from steel plants such as
to acid insolubles and alkalies has deteriorated and as a result Rajasthan, Uttar Pradesh and Himachal Pradesh. Procurement
selective mining was resorted to satisfy stringent quality needs of limestone from these involves high transportation cost. The
Vol 85, October 2004 75
 The quality upgradation of limestone can be done by two ways.
Primary Crushing One alternative is to use crush limestone to –3mm size and
Single Deck Rod process it in scrubber and classifier, while the other entails
Screen
Gyratory grinding of raw feed to less than 200 mesh and carry out
Crusher
Secondary Crushing beneficiation by froth flotation method. The concentrate thus
-300mm +40 mm obtained will have to be micro-pelletized for utilization in sinter
feed due to its ultra fine nature. This process needs to be done
in detail to evaluate its techno-economics. Very low silica
limestone in the range 0.3%-0.5% are also available in China,
Saudi Arabia,Iran and Indonesia. Government has recently
reduced duties on high quality limestone by 10%. The techno-
-40mm
Scrubber economics of imported low silica limestone vis-a-vis indigenously
OH Lump
+40 mm available limestone from Katni-Maiher Region of Madhya
BF Lump Sinter Fines Pradesh should be worked out.
DD Wet Screen Classifier
+10 mm -10 mm
INFLUENCE OF IRON ORE FINES QUALITY ON
Figure 8 Dalli mechanised mines processing circuit SINTER PROPERTIES

The alumina content in iron ore fines used for sinter making
cost of limestone from Rajasthan (Jaisalmer) is Rs 310 whereas all over the world is mostly below 1%. In contrast, the alumina
transportation cost is about Rs 1275. content in Indian iron ores fines is as high as 2.5%-4.5%. On

RUN OF MINE ORE

PRIMARY CRUSHING

-200 mm

SCREEN

+100 mm
-100 mm
SECONDARY CRUSHING

-100 mm

DRY SCREENING PLANT

Make-up -100 mm + 6 mm
water -6 mm + 0 mm
-1 mm
WET SCREENING PLANT HEAVY MEDIUM
-0.06 mm -6 CYCLONE PLANT
CLARIFIED DESLIMING +1 mm
WATER
TANK THICKENER REICHERT HEAVY MEDIUM
CONES PLANT DRUM PLANT

Tailing Concentrate Float Sink Float Sink

To Plant
SLIMES DAM

DEWATERING BUNKER SAMPLE

WASTE STATION
STOCKPILE SURGE BIN

-100 mm+0.06 mm

TRAIN LOADOUT STOCKPILE

Figure 9 Flowsheet of the Mt Whaieback beneficiation plant of BHP Iron Ore, WA

76 IE(I) Journal-MM
 LGO
Keeping in view the demand for good quality iron ore fines in
STOCKPILE SAIL plants, investigations were carried out in Barsua and
Meghahatuburu mines to reduce alumina in ore fines and also
CRUSHING AND SCREENING PLANT
recover iron values from slimes. The washing plant of
Meghahatuburu mines has three parallel circuits of 400 t/h
–30mm +6 mm –6 mm
capacity each. It consists of wet screening of –10 mm iron ore
LUMP FINES fines followed by treatment in rake classifier. The product of
STOCKPILE STOCKPILE
rake classifier is dewatered and then taken as fines product
(-10mm). The overflow of the classifier is pumped to
WET WET SCREEN hydrocyclone. Underflow of hydrocyclone is dewatered in a slow
SCREEN –6mm +1 mm
–1 mm speed spiral classifier whereas overflow of the hydrocyclone is
sent to tailing pond.
+6 mm –6 mm CYCLONES

Processing circuit of washing plant of MIOM is shown in

LUMP JIG FINES JIG SPIRALS SLIMES
Figure 4. The quality of iron ore fines produced during
2002-2003 averaged 63.12% Fe, 2.89% SiO 2 , and
Conc. Mld. Tail. Conc. Mld. Tail. Conc. Tail.
2.84% Al2O3, which is beyond the norm of 2.7%. In order to
reduce the alumina content of iron ore fines by optimizing
CRUSHER ROD MILL WHIMS process parameter, technological audit was conducted which
revealed that :
Conc. Tail.
• Proper water to ore ratio was not maintained in the feed
Figure 10 Flowsheet of the finucane island iron ore beneficiation plant of
BHP iron ore (Goldsworthy) Ltd, WA. of rake classifier which was causing good quality fines
below 0.2 mm being discarded through the overflow of
crushing and sizing Indian ores, the high alumina bearing the rake classifier.
laterites and the friable portion break up preferentially into a
finer size. This leads to concentration of alumina in iron ore • Rake classifier overflow which was going to slime
fines, the slimes (-100 mesh fraction) being the richest in distributor tank prior to being pumped to hydrocyclone
alumina (6%-10%). were operated in surge mode due to erratic feed to
hydrocyclone, causing poor performance of the
The sinter produced from such high alumina bearing iron ore equipment.
fines, therefore, contain between 4%-7% alumina which is very
high compared to other countries where the alumina in sinter • Water was being sprayed on dewatering screen causing
seldom exceeds 2%. High alumina sinter contributes about 40% good quality iron ore fines to pass through the screen
of the total alumina input into an Indian blast furnace using and getting discarded to tailing pond. Process parameters
70% sinter. It also makes the blast furnace slag highly viscous, of rake classifier was optimized by maintaining proper
which is normally tackled by resorting to relatively high slag ore to water ratio which resulted in cleaner product with
volumes operation (350 kg/thm- 500 kg/thm). This decreases 0.5 units reduction in alumina.
the productivity of Indian blast furnace and also results in
increased fuel rates. A decrease in sinter alumina from 3.1% Experimental Work
to 2.5% can improve the RDI of sinter by at least 6 points To achieve less than 2% Al2O3 in hydrocyclone product, experi-
which in turn, lower blast furnace coke rate by about 14 kg/ ments were conducted at RDCIS laboratory using stub/water
thm and increase productivity by about 3% under Indian
operating conditions. Two major factors which influence blast
Table 6 Quality of raw materials presently used by integrated steel plants
furnace productivity are coke quality and sinter properties and
in turn influence cost of production of hot metal. The adverse BSP BSL DSP RSP TISCO VSP
role of alumina on sinter strength and reduction-degradation Iron ore lumps
properties has now been conclusively established. Fe, % 65.46 63.37 62.84 63.0 67.21 66.99
Al2O3, % 1.63 2.41 2.20 3.0 1.41 1.6
QUALITY IMPROVEMENT IN IRON ORE FINES SiO2, % 2.00 1.89 1.79 1.7 0.85 0.9
Iron ore fines
Since most Indian iron ores contain high alumina, the only
Fe, % 63.76 62.90 61.8 62.3 65.67 64.83
option left to obtain lower alumina in fines is by
beneficiation.Table 6 shows the analysis of iron ore and fines Al2O3, % 2.48 2.54 2.8 3.1 2.6 1.81
used by integrated steel plants in India. SiO2, % 3.38 3.14 2.3 2.8 0.9 2.07

Vol 85, October 2004 77

 LOW GRADE ORE

GRIZZLYS

–200 mm +200 mm

STOCKPILE PRIMARY CRUSHER

GRIZZLY SCREENS To high grade ore plant

–80 mm +80 mm

SECONDARY CRUSHERS TERTIARY CRUSHERS

PRIMARY WET SCREENS PRODUCT SCREENS

–6 mm –30mm+6 mm +30 mm –30 mm +30 mm

SECONDARY WET SCREENS FEED PREPARATION SCREENS

–0.5 mm +0.5 mm US OS

DEWATERING SCREENS
US OS

HYDROCYCLONES FEED PREPARATION SCREENS

OF UF US OS

THICKENER FEED PROTECTION SCREEN HEAVY MEDIUM CYCLONES HEAVY MEDIUM DRUMS

US OS UF OF Sinks Floats
OF UF MEDIUM MEDIUM MEDIUM MEDIUM
RECOVERY RECOVERY RECOVERY RECOVERY
WHIMS DEWATERING SCREENS SCREENS SCREENS SCREENS
Recycle SCREEN

Mag Non-mag Hematite Medium Medium Shale Hematite Medium Medium Shale

PAN FILTERS Recycle Recycle

DEWATERING
BUNKERS

To To
talling Fines To To
dam product coarse tailing lump
disposal product

Figure 11 Flowsheet of hamersley iron ore plant at Mount Tom Price, WA.

only cyclone. A comparative study was made to see the 3.4% Al2O3) could be upgraded to 63.9% Fe, 2.46% SiO2 and
effectiveness of the water only cyclone over normal hydro- 1.93% Al2O3 at a recovery of 60% with the water only cyclone.
cyclone. Meghahatuburu slime (60.5% Fe, 3.7% SiO2 and Using conventional hydrocyclone, the enrichment was observed

78 IE(I) Journal-MM
Table 7 Results of stub and conventional hydrocyclone –8+2mm fraction along with the classifier sand (–2 mm). Ample
Sample type Chemical analysis % water was used for proper fluidization of the jig bed and with
Fe SiO2 Al2O3 the cut point adjusted, the quality of processed fines product
Slime 60.50 3.66 3.40 could be brought up to 62.75% Fe, 2.07% SiO2 and 3.06%
Stub cyclone product 63.90 2.46 1.93 Al2O3 from an earlier yearly average of 3.6 % Al2O3
Conventional hydrocyclone product 63.70 2.69 2.25
EFFECT OF RAW MATERIAL QUALITY ON BLAST
FURNACE PERFORMANCE
as 63.7% Fe, 2.69% SiO2 and 2.25% Al2O3 in its underflow
product.Table 7 gives the comparison of results obtained Blast furnace technology has improved significantly during last
through stub and conventional cyclone. The granulometry data few decades and with respect to changing steel scenario and
of the stub cyclone product clearly shows that the water only marketing competitiveness, it needs further improvement to
cyclone behaves as gravity separation unit apart from size reach international standards. Improvement in physical,
classification. Based on the laboratory investigations, existing chemical and metallurgical properties of coke and iron ore,
hydrocyclones were replaced by stub cyclones at increase in hot blast temperature, use of fuel injectants, adoption
Meghahatuburu washing plant. of efficient process control and recently the application of
artificial intelligence have led to significant decrease in coke rate,
Operational results of stub cyclone at MIOM indicate that increase in productivity, improved hot metal quality and increase
additional recovery of about 65 t/h of enriched fines with in furnace campaign life. Of all these developments, the
alumina about 2% is being produced. If the washing plant is improvement in raw materials quality is the most essential and
operated five months in a year, the estimated value of iron ore has contributed to a great extent.
fines recovered will be more than Rs 20 million/year. Use of
stub cyclone not only recovers additional enriched iron ore As the raw material play the most decisive role in bringing
fines, it’s granulometry are also favourable for improving sinter about improvement in blast furnace performance and reduce
quality as the micro fines (300 mesh) are discarded during cost of hot metal, improvement in raw material quality and
process. reduction in their specific consumption rates received most
attention.
Alumina Reduction in Ore Fines at Barsua Mine.
Properties of raw materials desired for blast furnaces are :
The beneficiation plant of Barsua mines was commissioned in
1969 with the equipment such as wet screen, spiral classifiers • high reducibility of iron ore, low alumina content
and Remer jigs for upgradation of quality of iron ore fines
(10mm). The circuit consists of two spiral classifiers of capacity • low reactivity of coke and ash
150 t/h each and eight jigs of 32 t/h each to reduce the • uniform size range to promote uniform gas distribution.
gangue minerals, especially Al2O3 from the fines. Remer jigs • sufficient cold and hot strength of materials.
were not in operation for a long time. The average quality of
iron ore fines product of Barsua plant during 2002-2003 was • uniformity of chemical and physical properties.
63.1 % Fe, 1.8% SiO2 and 3.6 % Al2O3 and does not meet As regards iron ore, enough scope exists to improve on uniform
the quality norms of 62.5% Fe, 2.5% SiO2 and 3.0% Al2O3 size range of iron ore by minimising over and undersize in iron
for Rourkela Steel Plant. One of the reasons being the jigs are ore lump and uniformity in chemical and physical properties
not operated continuously due to various operating problems. by proper bedding and blending. Screening efficiency at mines
Quality of run-of-mine ore of Barsua mine, which is very and steel plants can be improved by optimizing feed rate, screen
aluminous in nature, needs very high operational efficiency of aperture, amplitude and replacement of wire mesh screen with
the processing equipment to meet the quality target of steel
polyurethane screen (PU) mat. PU mat gives very long life
plant. Desired technological parameters for the operation of
compared to the wire mesh mat. Consistency in iron ore lump
classifiers and jigs could not be maintained, resulting in inferior
and fines can be improved by providing facilities in mines for
quality of iron ore fines.
proper blending and reclaiming. At steel plants also, standard
Efforts were taken by RDCIS and RMD mines personnel to operating procedures should be followed to ensure minimum
revamp the jigs for their continuous operation and optimize the deviation in the chemical and physical quality of the reclaimed
classifier parameters. It was observed that percentage solid in ore from the bed.
classifier overflow was very high resulting in losses of very good
Cost Implications
quality fines through the slime. The pulp density of the feed
to classifier was optimized by the addition of water such that The benefits reported by various research organization and in
the classifier product alumina reduced by 0.5 unit-1 unit. Also literature in respect to quality improvement in raw materials
six numbers of jigs were fully revamped and operated with are :
Vol 85, October 2004 79
• Increase in Fe in iron ore burden by 1% will increase Replacement of 2 dumpers, 1 drill and 1 dozer every
productivity of hot metal by 1.5%-2% and decrease coke year and 1 excavator every 2 years at every mine is
rate by 0.8%-1.2%. In terms of Rupees, it amounts to a cost proposed to improve the age mix of earth moving
reduction in hot metal by Rs 60/thm-Rs 70/thm. equipment. This would lead to improvement in
availability, reliability and utilisation of heavy earth
• Lowering of alumina in iron ore burden by 1% will reduce
moving equipment:
the cost of hot metal by Rs 200/thm-Rs 250/thm.
• Besides breakdown maintenance , preventive
• Lowering of silica in iron ore burden by 1% will reduce the maintenance and house keeping needs to be looked into.
cost of hot metal by Rs 50/thm-Rs 100/thm.
• Emphasis needs to be given with respect to annual
• Reduction in undersize in iron ore lump by 1% will reduce maintenance/ repair schedule and spare-part planning in
the cost of hot metal by Rs 50/thm-Rs 60/thm. the mine.
• Reduction in fluctuation in Fe chemistry by 1% will reduce • Most of the delays can be reduced by installation of
the cost of hot metal by Rs 40/thm-Rs 50/thm. radio communication system in dumpers, shovels, drills
This data clearly shows the impact of quality, consistency and and dozers,
uniform granulometry becomes a key factor to cost reduction
in hot metal production. • HRD interventions for upgradation of skill for
maintenance group needs to be restored immediately .
With the present mining and beneficiation facilities,
improvement in Fe percent in iron ore lump is expected to be • Maintenance contract with original equipment
marginal. Only scope remains in reducing alumina in iron ore manufacturers (OEM) may be looked into till such time
fines. Even if 0.5% reduction in alumina in the burden to BF, the skill development takes place among the mine’s
5% reduction in undersize and improvement in chemical and maintenance crew.
physical consistency is achieved, it is expected that saving to the
tune of Rs 150 crore per year can be achieved for a 4 Mtpa • Absenteeism of operators in mines is high. Immediate
hot metal production plant. steps need to be taken up to discourage the same.
SHORT TERM PLAN • Some of the equipment are kept idle because of non-
Strategy for Increasing Production availability and absenteeism of operators. Immediate
steps should be taken up for posting/recruitment of
To achieve the projected 24.0 Mtpa iron ore production by earth moving equipment operators in general and
2006 in SAIL, the following measures/actions need to be taken dumper operators in particular.
up at all producing mines. Some specific measures pertinent to
respective mines: • Improvement of excavator and dumper productivity by
well fragmented blasted mass inventory of 15 days.
• Development of a mine is the primary necessity for
effecting any improvement in quantity and quality. The • Construction of new haulage roads on shorter routes,
upper benches should normally be advanced sufficiently maintenance of haul roads,
ahead of lower benches. This will facilitate to maintain
wide and long benches in the lower levels. The main Quality Control Strategy:
advantages are better haulage roads, large drilling blocks
and large blasted faces. Quick advancement of upper • One exclusive drill machine for quality control advance
benches will facilitate to plan and implement bench wise drilling at 25m × 25m grid upto 20 m depth.
excavations for blending of ROM.
• Sequential dumping of ore either in pre-crusher
• The age mix of equipment in all the mines is in adverse stockpile or in hopper for effecting ore blending. The
condition. It is desirable to take immediate action for sequence to be decided based on quality of available
replacement of surveyed off equipment (worked beyond blasted inventory and position of excavation equipment.
economic life). Since replacement of all surveyed off
equipment would be a very expensive proposition, it is • Pre-crusher stock pile to ensure uniform ROM feed to
suggested to be implemented at regular interval. crusher

80 IE(I) Journal-MM
 • The existing control and monitoring system should be concentrate would not affect sinter production but would
modernized by introducing centralized control and improve the quality of sinter resulting in better blast furnace
monitoring of the mining operation including ore feed/productivity. Some of the plant like Corus, Dofasco, USS
processing and loading operations and mobile equipment Fairfield, Algoma in North America, Europe, Japan and Asia
tracking system at all the mines. donot use lump at all in their blast furnace. Use of 10% lump
along with 70%-80 % sinter and 10%-20 % pellet is reported
Global positioning system (GPS) should be provided for tracking in the plants like Posco, China Steel, Sollac and other plants.
the mobile equipment in the mining and loading area. GPS is
a satellite based locating and navigating system that determines CONCLUSIONS
the precise location of the moving object by indicating the
latitude, longitude and altitude of the object equipped with a • Iron ore being principal raw material in the iron and steel
receiver. industry, quality improvement with respect to physical,
chemical and consistency becomes the key factor for cost
LONG TERM PLAN reduction in hot metal.

It is estimated that the demand for iron ore for SAIL would • Al2O3 quality of iron ore fines can be improved by 0.5
go up to 30 Mt/year by the year 2012. Life of unit-1unit as alumina reduction a short term plan by
Meghahatuburu, Kiriburu and Dalli-Rajhara mines is about 8 installation of a slime recovery system, better mine planning
to 12 years. As development of a new mine would take about and optimizing the existing processing circuit.
10 years, planning for development of Chiria and Rowghat
mines and opening of South Block and Central Block as Al2O3 as alumina is the most deleterious mineral in iron ore
substitute for Kiriburu and Meghahatuburu mines, respectively and maximum benefit comes by removing this gangue, inte-
should be taken up immediately. By increasing the production nsive beneficiation technique like Batac jig, spirals and
of Kiriburu and Meghahatuburu mines nearing to its rated magnetic separator need to be installed to reduce this
capacity and providing additional facility to increase production gangue to 1% from the existing 2.5%-3% in iron ore fines
capacity of Bolani mines to 5 Mt, production target of 25 Mtpa
can be achieved. In order to meet the future requirement of REFERENCES
30 Mtpa, it is suggested to open Chiria and Rowghat mines, 1. M K Deshmukh et al. ‘Strategies for Turn-around in Indian Steel
particularly Chiria mines to 10 Mtpa. Higher production Industry.’ Jounral of The Institution of Engineers (I) Pt MM, Vol.84,
capacity would reduce the cost of production as well as it would April 2003.
provide an opportunity for revenue generation by in-house 2. V G K Murty et al. ‘Reduction in Alumina in Iron Ore Classifier
selling or exporting additional quantity of ore. Fines and its Influence on Sinter Properties’. Tata Search, 1994.
3. A W Pradhan et al. ‘Evaluation of Iron Ore Property for an
TECHNOLOGY STRATEGY Integrated Steel Plant with Case Studies’. TISCO report.
4. Raw Materials Scenario of SAIL – SAIL Corporate Report.
Keeping in view the deposit quality, the existing beneficiation 5. Tata Search, 1994, pp 7-13.
6. Humboldt Wedag Report on Batch Stratification Test with Bolani
facilities are grossly inadequate to meet the enhanced quality
Ore Fines. Report No. B09-0962-7001, February 2003.
requirement. The long term solution would be to upgrade the 7. Design and Operating Experience with the Goldsworthy Mining
ore in a full fledged concentrator with world class beneficiation Ltd. Batac jig and Spiral Concentrator Iron Ore Beneficiation Plant
technique involving grinding the ore to liberation size followed by D J Milter, Report of Goldsworthy Mine.
by concentration through suitable means. The concentrate thus 8. Beneficiation of Iron and Manganese Ores and Recycling by Means
generated need to be micro-pelletised/pelletised for use in of Air Pulsated Jigs – International. Seminar on Mineral Beneficiation,
Nagpur, October.’1994.
existing sinter plant/blast furnace. Prior to adopting such system,
9. S K Ojha and R N Singh. ‘Effect of Raw Materials Characteristics
economics thereof need to be established. on Blast Furnace Performance’. TAP Programme, Ranchi, June 2002.
10. A K Satsangi, et al. ‘Beneficiation of Low Grade Limestone for
While the beneficiation circuit would be located in each mine, Use in Iron Making Processes for SAIL Mines’. – Conference on Mineral
it is proposed to have a centralized concentrator, designed to Processing – Received Advances and Futures Trends.
process ore from different mines. This would make the plant 11. Independent Review of Iron Ore Supply to Bhilai Steel Plant-
more cost effective. The product filter/concentrate thus Report by Woodward–Clyde, Australia.
produced would be of the desired quality. 12. Optimal Utilization of Coking Coals in SAIL Plants,
RDCIS Report.
Micro-pellets for sinter making with lime as binder using a 13. RDCIS Internal Report – June 2002.
balling drum is nowadays practised. Use of filter cake/

Vol 85, October 2004 81