1
CHAPTER 1
INTRODUCTION
Iron and Steel rank amongst the most important materials of our
times. The iron and steel industry remains a viable and dynamic industry;
thanks to creative engineers and enterprising investors. Competition, the
driving force of invention and innovation, has forced steel makers to adopt
new technologies that reduce costs without sacrificing quality.
1.1
HISTORICAL BACKGROUNDS
OF
STEEL
MAKING
TECHNOLOGY
Production of hot metal in the Blast Furnaces (BF) followed by
steel making through Bessemer Converters or Open Hearth Furnaces (OHF)
was the main steel making process for mass production from 1850 to 1960.
From the early 1960s, while blast furnaces continued to be the source of
supply of hot metal to steel melting shops, the OHF started getting replaced
by LD converters where pure oxygen blowing in a specially designed vessel
was carried out in order to shorten the blowing period. Typically, the
processing time in the OHF was 12 to 14 hours while the LD cut short the
processing time to less than one hour. Hence, from 1960 onwards all new
facilities for steel melting came up with LD converters for large capacity
integrated steels plants. For lower capacity new installations, normally
Electric Arc Furnace (EAF) was installed, especially in the areas where
scrap/sponge iron and power at economic price was available. The OHF were
normally having ingot casting arrangement for converting liquid steel to solid
product suitable for rolling. However, in high speed LD converter and EAF
2
shops, continuous casting machines were installed to handle large quantities
of liquid steel for casting into solid products at the matching speed.
During the period mid 1960s up to the end of 1970s, a lot of work
was done to reduce the cycle time of the OHF in order to compete with the
new installations having LD converters and EAF. This was mainly achieved
through oxygen blowing in the OHF through the roof and also through
submerged tuyeres. Through various efforts, the cycle time of OHF was
reduced from 12 hours to as low as 4 to 5 hours. Due to the basic construction
of the OHF, it was difficult to reduce the cycle time below 4 hours and
therefore OHF was not able to compete with the LD converters or EAF with
regard to productivity as well as cost of production. Hence, a number of OHF
in the existing steel plants either closed down or were replaced by more
efficient steel making equipments.
The steel manufacturing companies were faced with the situation to
replace the less efficient OHF by LD Converters, EAF or by a new process in
order to remain competitive. New capacities for steel production, which were
emerging primarily in the developing countries, also had to make a choice
between one of the three options specified above. Each option has its own
merit and it is suitable in a given local condition. The raw material and the
major inputs in iron and steel making are location specific depending on the
cost of material and transportation cost. Therefore, a steel maker has to select
the most economical process in order to convert the local raw materials into
the finished steel. Such decisions are based on the capital investments as well
as operational costs.
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1.2
DEVELOPMENT OF ENERGY OPTIMIZING FURNACE IN
BRAZIL
At CS Pains, Divinopolis, Brazil, KORF Group had a 200,000 MT
per annum steel plant, having three numbers working and one stand-by OHF.
During late 1970s to meet the competition of LD converters and EAF, the
KORF group developed the Energy Optimizing Furnace (EOF) which was
designed to have the advantages of both the LD converter and EAF. The
(EOF) is a combined blowing, basic oxygen steel making furnace where a
combination of hot metal and solid scrap is converted to liquid steel suitable
for secondary refining and continuous casting. The schematic view of the first
EOF developed at C.S.Pains is shown in Figure 1.1 - Weber et al (1984).
1. Furnace Vessel
6. Combustion Air (cold)
2. Scrap Preheating
7. Combustion Air (preheated)
3. Recuperator
8. Additional Oxygen
4. Oxygen Nozzles Beneath Bath
9. Scrap (cold)
5. Oil-Oxygen Burner
10. Scrap (preheated)
Figure 1.1 Energy optimizing furnace overview
4
The quality of steel produced through EOF was comparable with
OHF- Weber et al (1984). The shape of the EOF is like EAF, which facilitates
continuous slag removal, and efficient slag free tapping. The top and side
oxygen blowing in EOF is like LD converters where it facilitates very high
turbulence of the bath in order to achieve short blowing time of about thirty
minutes. C S Pains, not only wanted to increase the steel production in their
works, but also to market EOF technology all over the world with flexibility
of hot metal to scrap ratio in order to produce steel economically.
The first EOF installed at CS Pains in 1982 and then replaced by
the tilting type modern EOF in 1988, presently having capacity of 35 / 40 MT,
is still in operation and presently producing 0.5 million MT steel per annum.
Thereafter, a number of EOF’s were installed worldwide but most of them
were not commercially successful for one reason or the other as shown in
Table 1.1.
By the mid 1990s, when 80 MT EOF at TATA Iron & Steel
Company Ltd (TISCO) was shut down, this technology almost appeared to be
technically not sound for mass production. This is the reason why in the book
“Making, Shaping and Treating of Steel” in Chapter 13, ‘Alternative Oxygen
Steel Making Process’, page 746, EOF is also appearing as One of the
processes under development along with other new processes such as
IRSID (France), WORCA (Australia), COSMOS (U.S) etc.
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Table 1.1 EOF Installations
EOF PLANTS
Capacity
Heat size
(MT per
(MT)
annum)
S.No.
Location
1
CS.PAINS, Brazil
30
220,000 in operation from 12/1/1982 to
1998.
2
CS.PAINS, Brazil
30
220,000 in operation since 3/1/1988
3
ALIPERTI, Brazil
60
400,000 Start-up, 8/1/1988 CLOSED
4
RIFS, USA
40
250,000 Start-up late 1989 CLOSED
5
TISCO (TATA),
Jamshedpur
80
520,000
6
AFS, Italy
60
450,000 start-up early 1991 CLOSED
7
SISCOL, Salem
8
Hospet Steels,
Karnataka
1.3
40/45
40
Status
start-up early 1990 CLOSED
4,00,000 in operation since 1998
3,50,000
in operation since 1998
INSTALLATION OF ENERGY OPTIMIZING FURNACES
IN INDIA
In the 1990s two EOF, of 35/40 MT capacity were planned in India
in two mini mills. Here the choice was between LD converter, EAF using
60% hot metal and 40% scrap, or to install EOF. The decision was taken in
favour of EOF since the capital investment in EOF was less than half of the
LD converter and the processing cost was envisaged to be significantly lower
than EAF.
In 1998 one 40 MT EOF was installed at Hospet Steels Ltd.,
Hospet, India and another 35 MT capacity EOF was installed at Southern Iron
And Steel Co. Ltd, (SISCOL) at Salem, Tamil Nadu, India. The scholar was
responsible for putting up 300,000 MT integrated steel plant through EOF
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route for manufacturing special steels at Hospet Steels Ltd. The EOF
operating at CS Pains was studied in detail, which was producing only
commercial grade of steel. Through literature survey the reasons for failure of
the other EOF in the other parts of the world were also studied in order to take
corrective measures. The EOF for manufacturing special steels under Indian
conditions at Hospet Steels Ltd was a good success and that gave a new life to
the EOF technology. Hospet Steels Ltd operates at the productivity of
400,000 MT per annum for special steels through EOF route. The quality of
the product is well accepted by the customers and the cost of production was
as per the norms.
At SISCOL, EOF was producing 200,000 MT of steel per annum
but the over all operation was not profitable. In 2004 the scholar took the
responsibility to turn around the SISCOL operation into a successful venture.
By increasing the EOF capacity to 45 MT and through technical upgradation
of the upstream and downstream facilities, the steel productivity was doubled
to 400,000 MT per annum. In addition, one 65 MT EOF, the largest in the
world, was put up at SISCOL for the second line of production, having
capacity of 600,000 MT per annum. Today SISCOL is a one million ton
capacity steel plant where the capacity enhancement has been done at a low
investment compared to industry norms. The quality of special steels
produced at SISCOL is well accepted by the customers. The cost of
production is very similar to the plants making steel through LD converters.
In India up to December 2007, 4.42 million ton of steel (Hospet Steels –
2.68 million ton, SISCOL – 1.74 million ton) has been produced as shown in
Figures 1.2 and 1.3. This proves that the EOF technology has good potential
in India especially for the steel plants of capacity up to one million MT per
annum of carbon and special steels. This is also true for other countries where
conditions are similar to Indian conditions. Today, SISCOL is the largest
integrated steel plant in the world having entire steel production through the
EOF route.
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500000
PRODUCTION (MT)
450000
400000
350000
300000
250000
200000
150000
100000
50000
0
PROD ( MT)
1998-99
1999 2000
9791
64395
2000 - 01 2001- 02 2002- 03 2003 - 04 2004 - 05 2005 - 06 2006 - 07 2007 - 08
67621
46194
213885
171073
161954
YEAR
228104
320402
460878
TOTAL = 1744297
Figure 1.2 Steel productions per annum – SISCOL
450000
PRODUCTION (MT)
400000
350000
300000
250000
200000
150000
100000
50000
0
PROD ( MT)
1998-99
1999 2000
2000 01
2001 2003 2002- 03
02
04
2004 05
2005 06
2006 07
2007 08
27664
127608
195195
250010 279359
273894 347822
351756
408000
417744
YEAR
TOTAL = 2679052
Figure 1.3 Steel productions per annum – Hospet Steels
1.4
ORGANIZATION OF THESIS
The critical analysis of all the papers published in the field of
Energy Optimizing Furnace (EOF) and related steel making processes have
been explained in Literature Survey – chapter 2. Literature Survey also gave
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an insight into the missing links in the technology, which paved the way for
further work in the area of EOF based on which the objectives and scope of
research for the present work has been defined. Chapter 3 briefly describes
the various equipments of EOF. Chapter 4 explains the steel making process
through EOF for proper understanding. In Chapter 5, important modifications
and design changes carried out in the EOF equipment to suit the Indian
conditions have been explained. Chapter 6 deals with improvement in cost of
production through the EOF route. Chapter 7 highlights the commissioning
of World’s largest 65 MT capacity EOF at SISCOL, Salem, India. Chapter 8
deals with the implementation of catch carbon process in EOF, which has
been the most important contribution of the present research work.
The
results of the present research work and the analysis of the results have been
discussed in chapter 9.
The main conclusions of this research work are
presented in the last chapter 10.