Electric arc furnaces have given space for a dynamic application of new technologies during this century. New ways for scrap preparation and alternative iron sources gave place to the conception of new equipment and experiences worldwide. Scrap preheating is the subject of changes overcoming previous limitations in maintenance and environment and promoting a better energy performance. Chemical energy for melting increases its action, requiring the development of equipment capable of rapid and precise application with large flowrate of gases and solids. New tools are offered to eliminate risks in the EAF working platform, making use of safer and long-lasting cooling systems, robots, automation of tap-hole operation, and automatic slag doors.

1. 27/09/2016
A CRITICAL REVIEW OF RECENT TECHNOLOGICAL
DEVELOPMENTS IN ELECTRIC ARC FURNACES
Jorge Madias, metallon, San Nicolas, Argentina
Sara Hornby, Global Strategic Solutions, Charlotte, USA
Francisco Torre, FACTS Ingenieria, Rosario, Argentina

2. • Content
– Introduction
– Metallic charge
– Scrap preheating
– Automatic process
control
– Safety in the platform
– Energy recovery
– Conclusions
2

3. • : technical services for the steel industry
in Latin America
– Technical assistance
– Short courses in company, self-learning, open
– Met lab services
– Library services
– Texts for specialized publications
– Brazilian customers: Gerdau, TK-CSA, CSN, ArcelorMittal,
Suncoke, MINITEC
3

4. • Introduction
– Lately, EAF share decreased (not total
production)
– In the future, as in Chine scrap
availability increases, and CO2 emissions
control be reinforced, EAF share will
increase, too
– IEA announced process route and
metallic consumption forecast till 2050,
EAF share close to 50%
– Challenge for technology development
• Enlarged thermal efficiency
• Increased productivity
• Decreased operating cost
• Improved environmental performance 4
Country
EAF
Production
EAF 2014 (t)
USA 55.174.000
India 50.211.000
China 49.938.000
Japan 25.679.000
Korea 24.197.000
Turkey 23.752.000
Russia 21.852.000
Italy 17.200.000
Iran 13.607.000
Mexico 13.311.000

5. • Metallic charge
– Scrap
• Main component of EAF charge
• Preparation: influence on furnace
efficiency
– Energy consumption
– Lime consumption
– Electrodes consumption
– Refractory consumption
– Metallic yield
– Chemistry achievement
• Schredder and baling equipment
being introduced by steelmakers
and scrap processors
• Schredderless concept
5

6. • Metallic charge
– Scrap
• Systems for analysis of scrap
on conveyor
– High speed X-ray fluorescence
» Analyze each lump
» Define if the lump must
be segregated
– Promt gamma neutron
activation analysis
» Analyzes the bulk of
the scrap
» Gives an idea of the
chemistry of the scrap
being processed
• Cu <0,20% guaranteed
6

7. • Metallic charge
– DRI/HBI
• Picked in 2013: 74.9 Mt
• 15 % of EAF metallic needs
• Melting requires more energy due to
gangue (and lime)
• But this can be counterweighed with
– High metallization
– Carbon content
– EAF operation
– Continuous charging
– Hot charging
7

8. • Metallic charge
– DRI/HBI
• Changes in
production and
application
– Natural gas reforming
in the furnace (make
miniplants feasible)
– Use of Corex gas,
coal gasification,
coke oven gas
– Come back of hot
charging
8

9. • Metallic charge
– Pig iron / Hot metal
• Introduction of EAF in
integrated plants
– China
» Low scrap
availability
» Week power
supply network
– A few plants in
Europe, North
America, and Brazil
• Electric energy savings
• CO2 emissions
increase
9

10. • Metallic charge
– Influence on energy consumption
10
150 EAF>30 t
Carbon & low alloy steel
TtT<100 minutes

11. 11
• Metallic charge
– Electric energy consumption
• <300 kWh/t
– 9 of the top ten consume 20% or more hot metal
• 300-400 kWh/t
– EAF consuming high pig iron charge
– 100% scrap EAF with high energy efficiency
• 400-450 kWh/t
– 100% scrap EAF with intermediate energy efficiency
– EAF with hot DRI charging
• >450 kWh/t
– 100% scrap EAF with low energy efficiency
– EAF with high cold DRI/HBI charge

12. • Optimization programs
– Charge calculation models for
lower cost charge, respecting
quality and availability
constraints
– Developed or improved by
consultants (Management
Science Associates Inc.),
scrap suppliers (TMS), EAF
builders and steelmakers
– Consider cost of all metallics,
value in use and liquid steel
chemistry
– Some of them include
procurement strategies
12

13. • Optimization programs
– Market factors, beyond cost and value in use, influence
purchasing decisions, and can be taken into account
– Factors that promote using high quality metallics despite their
higher cost
• Regional supply and demand balance
• Supplier history
• Savegard of future supplies
• Generation of internal scrap
• Alternative metallics supply
• Company policies regarding supplies, price and profits
• Inability to download products to secondary use
• Desire to guarantee specifications without trouble
13

14. • Scrap preheating
– Consteel evolution
• Burners in the scrap preheating tunnel
• Post combustion injectors in the furnace
• Off-gas analysis for EAF and tunnel burners
• First reference: Ori Martin, Italy 2016
14

15. • Scrap preheating
– SIMETAL EAF Quantum
• Changes to shaft furnace
design
– Charge of shaft with skip
and chute instead of
crane and bucket
(similar to JP Steel
Plantech’s Eco-Arc)
– Siphon for tapping, to
eliminate power-off time
during tapping, and to
promote slag-free
tapping (similar to
Stahlwerke Buderus)
– References: TYASA,
Mexico; Arvedi, Italy
(under construction)
15

16. • Scrap preheating
– Effect on electric energy consumption
• Only EAF charging 80% or more scrap
16
0
100
200
300
400
500
600
700
0 0.5 1 1.5 2 2.5
Specificpowerconsumption(kWh/t)
Specific installed power (MVA/t)
Estándar
Consteel
Twin Shell
Shaft

17. • One bucket charge: productivity
– As EAFs grow in size, buckets
required to fill them are more
– This means a loss in productivity,
as time is required to lift
electrodes, swing the roof, open
the bucket, etc.
– Good scrap preparation is helpful
in decreasing the number of
buckets
– Some new EAFS are designed
for single bucket charging
– Some existing furnaces are
modified to one bucket charging
17

18. • Bottom stirring
– Failed fashion in the 1990s
– New come back, promoted
by
• Production of special
steels
– Better thermal and
chemical homogeneity
• Furnaces with scrap
preheating in conveyor,
with large liquid heel
– To favor heat transfer
beween incoming scrap
and liquid steel
18

19. • Safety in the furnace
platform
– Robot for electrode
manipulation
– Robot for sampling and
temperature control
– Remotely controlled slag
door
– Robot for EBT cleaning
and refilling
– Waterleaks controlled by
EAF off-gas analysis
– Gunning robot

20. • Automatic process control
– Foaming slag assessment
systems, based on
– Measurement of electric
variables
– Measurement of noise
– Measurement of vibrations in
the furnace shell
• Data given by this system
can be employed by
operators for decision-
making
• But they can be utilized as a
base for in-line control of
carbon injection
20

21. • Automatic process control
– Foaming slag control
• Lech Stahlwerke
21

22. • Automatic process control
– Foaming slag control
• Lech Stahlwerke
22

23. • Dynamic control
– Steel Dynamics - Roanoke
• Off-gas analysis
• Measurement of off-gas rate and
speed
• Assessment of foaming slag
through measurement of
harmonics
• By using the three measurements,
and models, dynamic control is
carried out
– Oxygen injection for post-
combustion
– Oxy-gas burners
– Carbon injection for slag foaming
23

24. • Energy recovery
– First experiences
• Georgsmarienhütte,
Germany
• Elbe Stahlwerke Feralpi,
Germany
• Hyundai Steel Incheon,
Korea
• Ori Martin, Italy
• TISCO Taiyuan, China
• Arvedi, Italy (under
construction)
24

25. • Conclusions
– As scrap resources develop, and lower CO2 emissions are
enforced, EAF will capture a growing share of steel production
– Technical advances in the two latest decades give a sound
base for the leadership of this steelmaking tool
– Metallics availability influences performance
– Equipment choices influence performance
– Emphasis in safety
– Advances in process control
– Energy recovery being implemented

26. Thank you!
Jorge Madías – Sara Hornby – Francisco Torre
San Nicolás, Buenos Aires, Argentina
jorge.madias@metallon.com.ar
www.metallon.com.ar
26