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Valorisation and dissemination of EAF technology
VALEAF
1st Workshop
State of the Art on EAF technology
Batch and continuous charge
Dalmine 12th March 2015
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Contents
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Scope of the presentation
Evolution of scrap management
EAF charging in modern plant configurations
Continuos charging in EAF
Scrap continuous charging
Innovations on scrap control and charging
On-line scrap analysis
Measurement of scrap density
Integration of scrap management and process adaptation
Reliability and development status
Emerging concepts for future EAF
Scope of the presentation
There is an evolution in progress concerning scrap treatment and control and EAF
charging strategy.
The importance of scrap quality and the needs for new techniques for scrap
selection and control emerged in ECSC research since begin ‘90th.
(e.g. Recycling of scrap for high quality products – ECSC 7210-CB/205 – 1997)
In the next 20 years at least 15 projects were mainly focused on scrap issues.
The developments on scrap management occurred in parallel with the evolution of
EAF furnace, especially with the introduction of system for scarp pre-heating and
continuous charging.
It is out of the scope of this presentation comparison and evaluation of commercial
solutions for such operations.
The presentation intends to illustrate some relevant contributions of European
research on development of modern scrap management and how important results
can be applied in different plant configurations.
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Evolution of scrap management
Scrap control and process optimization
A recent trend in EAF technology is dedicated to scrap selection, charge mix design and
process operation optimization taking into account scrap characteristics.
The evolution in progress
From a basic approach:
based on the select the most economical scrap mix for each produced steel grade while
keeping steel quality within specified limits;
Toward an advanced integrated approach, which includes:
• Selection of charged scrap and measurement of scrap characteristics
• Design of charge mix and related operating conditions in order to minimize (or maximize)
precise Key Performance Indexes – KPI (defined in terms of:
energy consumption, steel quality, productivity, environment, etc.)
• Monitoring of charge behaviour inside the furnace during the process
• Integration of scrap management, on-line measurement on the process, process modeling,
for global process optimization and control.
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Scrap management in modern furnace configurations
In a State–of-Art EAF about 25% (175/700 kWh/t) of
the total energy is lost with off gas and dust.
An obvious method for energy recovery is
scrap preheating.
First in-bucked pre-heating system have been
abandoned for practical problems and emissions.
Today industrial solutions are:
• shaft furnaces (about 30 in service)
• continuous charging furnaces (about 40 in service)
Contributions
electrical energy
chemical energy
metal oxidation
Liquid steel
off gas and dust
cooled panels
electrical losses
radiation and others
kWh/t
385
165
150
-455
-175
-40
-15
-15
Both solution imply the elimination of traditional bucked fro scrap charging.
Hence a there is an evolution in progress on the scrap management concepts.
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Scrap continuous charging
An important innovation in EAF technology has been the introduction of scrap
continuous charging.
The Consteel® plant has been the first commercial solution.
The ECSC demonstration project 7215-PP-027 supported the initial improvement of
the first Consteel® in Europe.
In the next years the Consteel® has evolved in many aspects.
Today more than 40 Consteel® have been built.
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Scrap continuous charging
The European project on Consteel demonstrated the effectiveness
of the technological solution for pre-heating the scrap
and for designing flexible operating conditions
optimizing the ratio chemical energy to electrical energy
1000
700
600
10 cm depth
500
400
300
200
30 cm depth
100
0
0
5
10
15
20
25
distance from the entrance of the scrap in the tunnel [m]
30
electrical energy requirement
[kWh/t]
800
temperature [°C]
carbon 12 kg/t
surface
900
460
440
420
400
carbon 22 kg/t
carbon 28 kg/t
380
360
340
320
300
0
0.2
0.4
0.6
0.8
CO2/CO in EAF
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Innovations on scrap control and charging
Main technological lines of development are:
• On-line chemical analysis of scrap
for scrap selection
• Measurement of scrap density and geometry in bucket
in order to define the best charging strategy that reduce the melting
time and the energy consumption;
• Integrated optimization of scrap charge management and process adaptation
for real-time adjustment of operating conditions taking into account
information on scrap chemical and physical characteristics
Common final aims are the improvement of performance and reduction of cost
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On-line scrap analysis
Calibration curves
Laser based analysis
Cu
Si
Comparison with plant analysis
Laser-induced breakdown spectroscopy for
advanced characterisation and sorting of
steel scrap (LCS).
Contract No RFSR-CT-2006-00035; 2006-2009
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Technique tested in both
batch and continuous charging
On-line scrap analysis
Scrap sorting and scrap recovery
In batch charge the technique is especially useful for scrap
sorting and purification and recovery of special scrap
Identification and separation
scrap
IronManganese
Stainless steel
Copper
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Scrap selection - example
Continuous EAF control
In continuous charging the technique is useful to determine specific scrap
components and adjusting consequently EAF operations
Comparison between Si concentration
by LIBS and from slag analysis
LIBS measurements
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Determination of scrap density
On-line measurement of
scrap density
Bulk density of scrap and apparent density of scrap
charge are important parameters in all the furnace
configurations:
conventional bucket, shaft pre-heating systems,
continuous charging.
For each configurations ‘best rules’ have been studied
and defined.
In any case measurement of the density is necessary to
apply the rules.
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Determination of scrap density
On-line measurement of
scrap density in bucket
Pictures of scrap layers
Camera for image acquisition
Characterisation of the scrap density.
Contract No 7210-PR/205; 2000-2003
Control and Optimisation of Scrap Charging
Strategies and Melting Operations to Increase
Steel Recycling Ratio
Contract RFSR-CT-2005-00003; 2005-2008
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Automated scrap images acquisition of the scrap
layers during the scrap basket charging operation.
The recorded images are processed to determine
the size distribution of each layer according to the
used scrap quality.
Image analysis and ultrasonic measurements were
used to determine an Density Index of scrap
charge
Determination of scrap density
On-line measurement of
scrap density in bucket
Camera measurements, ultrasonic and laser sensors have been used to determine scrap
volume during bucked charging with various scrap mixtures
Characterisation of the scrap density.
Contract No 7210-PR/205; 2000-2003
Control and Optimisation of Scrap Charging Strategies and
Melting Operations to Increase Steel Recycling Ratio
Contract RFSR-CT-2005-00003; 2005-2008
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Determination of scrap density
On-line measurement of
scrap density in bucket
The density of charged scrap affect the electrical and total energy consumption
Characterisation of the scrap density.
Contract No 7210-PR/205; 2000-2003
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Determination of scrap density
On-line measurement
of scrap density
The on-line measurement of the final scrap density gives a
valuable information in order to help for the melting
process control:
time to charge the second basket.
This recorded value is also useful for an off-line monitoring
of the scrap quality.
The continuous assessment of the instantaneous charged
scrap density can help for a final fine-tuning of the mix,
in order to avoid overfilling or underfilling of the bucket.
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Determination of scrap melting
On-line measurement of
scrap density in bucket
One of the dream of the EAF operators (in
batch charging) is to know exactly the
moment when the scarp is melted and a
new bucked can be charged.
Several attempts have been tried, based on
measurements and modeling.
An example of measurement is by means of
a sensor measuring intensity of Infra Red
(IR) and Ultra Violet (UV) radiation inside
the EAF.
CoSMes®
Control and Optimisation of Scrap Charging Strategies and Melting Operations to Increase Steel Recycling Ratio
Contract RFSR-CT-2005-00003; 2005-2008
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Determination of scrap melting
On-line measurement of
scrap melting
A combination of InfraRed
and UltraViolet sensors
(CoSMes) has been applied
to follow the scrap melting
progress.
The precise individuation
of melting phase for every
bucket is an essential
information to optimize
the operations
Control and Optimisation of Scrap Charging Strategies and Melting Operations to Increase Steel Recycling Ratio
Contract RFSR-CT-2005-00003; 2005-2008
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Integration of scrap management and
process adaptation
An important development trend is the integration of information on
characteristics of scrap and charge, with continuous measurements in EAF
and advanced modeling for a global optimization of the process.
The Conopt Scrap project is an example where systems for on-line
monitoring of the scrap charge and melting evolution have been applied
together with off-line simulation of process evolution depending on applied
operating practices.
This combination is a tool for optimization of melting conditions with
impact on furnace efficiency, iron yield and energy use.
The final aim of the project was to allow the most economic use of scrap,
especially increasing the use of lower scrap qualities for the EAF.
Control and Optimisation of Scrap Charging Strategies and Melting Operations to Increase Steel Recycling Ratio
Contract RFSR-CT-2005-00003; 2005-2008
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Integration of scrap management and
process adaptation
Data from charge
mix design and
charge monitoring
systems have been
coupled with
process model and
automatic optimizer
system to adjust the
EAF operations.
Control and Optimisation of Scrap Charging Strategies and Melting Operations to Increase Steel Recycling Ratio
Contract RFSR-CT-2005-00003; 2005-2008
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Reliability and development status
The presented examples concerns results of research of a
high degree of reliability.
Not all the examples can be considered mature technology
for direct industrial applications.
However, practical applications have been already
experimented and minor improvements are necessary for
their exploitation in routine operations.
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Reliability and development status
The most important emerging concept is that on-line
measurements are necessary for modern EAF.
This concept is true for batch charging, where accurate
information and optimization mathematical tools are
indispensable to allow flexibility of material use and
production maintaining quality consistency.
This is especially true because taking into account that the
increasing diffusion of continuous charging
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Emerging concepts for future EAF
The most important emerging concept is that on-line measurements are
necessary for modern EAF and must be integrated powerful modells and
optimization tools.
This concept is true for batch charging, where accurate information and
optimization mathematical tools are indispensable to allow flexibility of
material use and production maintaining quality consistency.
The concept is even more important in case of continuous charging system,
which are more and more diffuse.
Continuous charging requires to take decision in real time to adjust operating
conditions. Hence the need of reliable and accurate measurements.
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