a critical review of recent technological developments in electric arc furnaces
TRANSCRIPT
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, USAFrancisco Torre, FACTS Ingenieria, Rosario, Argentina
• Content
– Introduction
– Metallic charge
– Scrap preheating
– Automatic process
control
– Safety in the platform
– Energy recovery
– Conclusions
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• : 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
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• 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 performance4
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
• 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
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• 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
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• 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
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• Metallic charge
– DRI/HBI• Changes in
production and application– Natural gas reforming
in the furnace (makeminiplants feasible)
– Use of Corex gas, coal gasification, coke oven gas
– Come back of hotcharging
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• Metallic charge– Pig iron / Hot metal
• Introduction of EAF in integrated plants– China
» Low scrapavailability
» Week powersupply network
– A few plants in Europe, North America, and Brazil
• Electric energy savings
• CO2 emissionsincrease
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• Metallic charge
– Influence on energy consumption
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150 EAF>30 t
Carbon & low alloy steel
TtT<100 minutes
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• 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
• Optimization programs
– Charge calculation models forlower cost charge, respectingquality and availabilityconstraints
– Developed or improved byconsultants (Management Science Associates Inc.), scrap suppliers (TMS), EAF builders and steelmakers
– Consider cost of all metallics, value in use and liquid steelchemistry
– Some of them includeprocurement strategies
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• 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
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• 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
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• Scrap preheating– SIMETAL EAF Quantum
• Changes to shaft furnacedesign
– Charge of shaft with skipand chute instead of crane and bucket(similar to JP Steel Plantech’s Eco-Arc)
– Siphon for tapping, toeliminate power-off time during tapping, and topromote slag-free tapping (similar toStahlwerke Buderus)
– References: TYASA, Mexico; Arvedi, Italy(under construction)
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• Scrap preheating
– Effect on electric energy consumption
• Only EAF charging 80% or more scrap
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0
100
200
300
400
500
600
700
0 0.5 1 1.5 2 2.5
Sp
ecif
ic p
ow
er
co
nsu
mp
tio
n (
kW
h/t
)
Specific installed power (MVA/t)
Estándar
Consteel
Twin Shell
Shaft
• 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 liftelectrodes, swing the roof, open the bucket, etc.
– Good scrap preparation is helpfulin decreasing the number of buckets
– Some new EAFS are designedfor single bucket charging
– Some existing furnaces are modified to one bucket charging
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• 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
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• Safety in the furnaceplatform– Robot for electrode
manipulation
– Robot for sampling and temperature control
– Remotely controlled slagdoor
– Robot for EBT cleaningand refilling
– Waterleaks controlled byEAF off-gas analysis
– Gunning robot
• 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 systemcan be employed byoperators for decision-making
• But they can be utilized as a base for in-line control of carbon injection
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• Automatic process control
– Foaming slag control
• Lech Stahlwerke
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• Automatic process control
– Foaming slag control
• Lech Stahlwerke
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• 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
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• Energy recovery
– First experiences
• Georgsmarienhütte,
Germany
• Elbe Stahlwerke Feralpi,
Germany
• Hyundai Steel Incheon,
Korea
• Ori Martin, Italy
• TISCO Taiyuan, China
• Arvedi, Italy (under
construction)
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• 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
Thank you!
Jorge Madías – Sara Hornby – Francisco Torre
San Nicolás, Buenos Aires, Argentina
www.metallon.com.ar
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