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

jorge.madias@metallon.com.ar

www.metallon.com.ar

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