solutions for internal recycling of steelmaking dusts and
TRANSCRIPT
K1-MET ǀ 2020-11-13 ǀ 1
Johannes Rieger, K1-MET
2020-11-13
ESTEP workshop “Resi4Future”
Co-authors: Wolfgang Reiter (K1-MET), Harald Raupenstrauch (Montanuniversität Leoben), Laura Lohmeier, Hans-Werner Schröder (both TU Bergakademie Freiberg), Christoph Thaler (voestalpine Stahl)
Solutions for internal recycling of steelmaking dusts and sludges
K1-MET ǀ 2020-11-13 ǀ 2
(1) K1-MET in a glance
• Research on residue treatment and recycling solutions
(2) Treatment of BOF dust for internal recycling
• Project partners and methodology
(3) Treatment of DR dusts and sludges for internal recycling
• Project partners and methodology
• Process concept
(4) Summary and outlook
• Next steps in the process developments
Agenda
K1-MET ǀ 2020-11-13 ǀ 3
K1-MET in a glance
Research Areas
Four symbiotic areas:
➢ Area 1: Raw Materials and Recycling
• Endeavours the best possible utilisation of all resources and
searches for residue treatment and recycling solutions
➢ Area 2: Metallurgical Processes
• Unites the core topics of metallurgical process
developments.
➢ Area 3: Low Carbon Energy Systems
• Is dedicated to the developments of carbon-lean steal
production.
➢ Area 4: Simulation and Analyses
• Represents the enveloping area for numerical developments
and data analyses.
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K1-MET Research Area 1
Recycling of residues from primary steelmaking
Blast Furnace –
Basic Oxygen Furnace
MIDREX® Direct
Reduction Process
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(1) K1-MET in a glance
• Research on residue treatment and recycling solutions
(2) Treatment of BOF dust for internal recycling – RecoDust process
• Project partners and methodology
(3) Treatment of DR dusts and sludges for internal recycling
• Project partners and methodology
• Process concept
(4) Summary and outlook
• Next steps in the process developments
Agenda
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Treatment of BOF dust for internal recycling
RecoDust (Flash-Reactor)
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Small-scale lab trials [1]
- Conveying behaviour of BOF dust
Computational Fluid Dynamics [2]
- Gas-solid reaction kinetics
- Design studies for reactor and burner
Pilot plant operation [1]
(Flash-Reactor)
- BOF dust treatment
- Definition of process
parameters
RecoDust Process
Project partners and methodology
[1] Montanuniversität Leoben, Chair of Thermal Processing Technology
[2] K1-MET
Project
partners
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Reduction/slaggingT ~ 1,700 °C
λ = 0.7
DosingT ~ 40 °C
Steps of the RecoDust process Way of BOF dust within the
RecoDust process
BOF dust
RecoDust Slag
(Iron)
Crude zinc
oxideCoolingT ~ 800 - 150 °C
Post-combustionT ~ 1,700 - 800 °C
λ = 1.4
Gas cleaningT < 250 °C
Bag filter
Clean gas
RecoDust process concept
Pilot plant at Montanuniversität Leoben
[1] Reiter, W. et al.: The
RecoDust process -
Upscale of a pilot plant,
Steel Research
International, published
online, 2020
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• Requirements of the dust input [1]
• Free flowing
• Grain size <1 mm
• Dry
• Product 1 → Crude zinc oxide ZnO [2]
• Zinc extraction >95 %
• Washing process to remove halides
• Product 2 → Fe-rich fraction (= RecoDust slag [1, 2])
• Hard material, not leachable
• Low Zn content (0.1-0.5 wt.-%);
Fe~50 wt.-% (= FeO + Fe2O3);
slag formers ~40 wt.-% (B2 ~3)
RecoDust process
Feed requirements and products
Typical composition of the crude ZnO product (left)
and the iron rich RecoDust slag product from the
RecoDust process (right, [2])
[1] Raupenstrauch, H. et al.: RecoDust - an efficient way of processing steel mill dusts, J Sustainable Metallurgy 5(3), 310-318
[2] Geier, B. et al.: RecoDust-process for the recycling of steel mill dusts, METEC & 2nd European Steel Technology and
Application Days (ESTAD), Düsseldorf, 2015
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Possible internal use of the RecoDust slag
• Sinter plant or BF (iron substitute material)
• Energy for slag grinding important for added-value
• Material hardness and abrasivity depend on slag granulation
• Crushing energy ~ 25 kWh/t (compare with ore ~ 1kWh/t)
• Extremely abrasive (1,600 - 2,000 acc. to LCPC test [3])
Grinding process needs to be optimized
• Combination of crushing and sieving steps
Iron-enriched product (RecoDust slag)
Comparison RecoDust vs. Waelz and possible internal use
Species
(extraction from
the composition)
RecoDust
slag [1]
Waelz
slag [2]
FeO [wt.-%] 37.0 45.0
Zn [wt.-%] <0.5 <5.0
MgO [wt.-%] ~4.0 <6.0
SiO2 [wt.-%] ~4.0 <10.0
CaO [wt.-%] ~19.0 <26.0
Cl [wt.-%] n.a. <0.1
• Some species not directly comparable (BOF dust used for RecoDust, EAF dust for Waelz)
• High separation degree of zinc and iron with RecoDust process
[1] Geier, B. et al.: METEC & 2nd European Steel Technology and Application Days (ESTAD), Düsseldorf (Germany), 2015
[2] Von Billerbeck, E. et al., book contribution „Treatment of electric steelmaking filter dusts with the Waelz process“, 2014
[3] Kurosch, T. et al.: 1st Canada-US Rock Mechanics Symposium, Vancouver, 2007
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(1) K1-MET in a glance
• Research on residue treatment and recycling solutions
(2) Treatment of BOF dust for internal recycling – RecoDust process
• Project partners and methodology
(3) Treatment of DR dusts and sludges for internal recycling
• Project partners and methodology
• Process concept
(4) Summary and outlook
• Next steps in the process developments
Agenda
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Treatment of DR dusts and sludges for internal recycling
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MIDREX® residue briquetting
• Cold-bonded agglomeration of MIDREX® waste products for a reuse in the process
• Project partners beside K1-MET
• voestalpine Stahl
• TU Bergakademie Freiberg, Institute of Thermal-, Environmental- and Resources' Process Engineering
Methodology
Project partners and methodologyProject
partners
Abrasion
resistance R30
(100) [%]
Briquette strength measurements [1]
- Compressive and abrasive strength
[1] TU Bergakademie Freiberg, Institute of Thermal-, Environmental- and Resources' Process Engineering
Briquetting of MIDREX® residues [1]
- Hydraulic stamp press
- Screening of binder systems
Reducibility prediction (left) and
thermochemic stability (right) [1] +
low temperature disintegration tests
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• Screened oxide fines➔ Fine-grained residue from iron ore pellet feed (Fetot 67.2%, Femet 0%)
• Dried sludge➔ By-product from top gas cleaning (Fetot 74.0%, Femet 29.5%)
• HBI screened fines➔ Fine-grained residue fraction (Fetot 88.7%, Femet 74.9%)
Quality requirements for materials to be used in the MIDREX® process
• Composition, stability, and metallurgical properties must be within certain value ranges
• Composition: Fe~67%; 3-4% gangue (especially low contents on silicon, alumina)
• Stability: compressive strength >35 MPa (green strength), abrasive strength R30 (100) >85%
MIDREX® residue treatment concept
Iron bearing residue fractions & quality requirements
[1] Lohmeier et al.: Briquetting of fine-grained residues from iron and steel production using organic and inorganic binders,
Steel Research International, published online, 2020
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• Fe-carrier mixture (wt-%)
• 30% screened oxide fines / 40% dried sludge / 30% HBI & process residues (dust, fines)
• Tested binder systems: Organic (cellulose, starch) and inorganic (bentonite clay) materials
Test procedure
(1) Material mixing (Eirich-Mixer) with varying contents of binder and water
(2) Material preheating (60°C) and briquetting (hydraulic stamp press)
• Briquetting parameters: 140 MPa, pressing time 3s, pressing temperature 60°C
• Briquette dimensions: cylindric shape, 3 cm diameter, 1.5 cm height
(3) Briquette hardening under ambient air (1 day)
(4) Executed tests: compressive strength, abrasion resistance, shatter strength, apparent density, low-
temperature disintegration, reduction test
MIDREX® residue treatment concept
Case study
[1] Lohmeier et al.: Briquetting of fine-grained residues from iron and steel production using organic and inorganic binders,
Steel Research International, published online, 2020
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Case study
Main results – Mechanical + metallurgical properties
[1] Lohmeier et al.: Briquetting of fine-grained residues from iron and steel production using organic and inorganic binders,
Steel Research International, published online, 2020
Design of Experiments (DoE, [1])
+ Primary blend
* Binary blend
o Tertiary blend
x Additional runs
Results for bentonite (extraction from [1])
Compressive strength Abrasion resistance R30 (100)
Metallurgical properties
+ Small low-temperature disintegration tendency (positive)
- Slow reduction, 80% red. degree after 300 min (negative)
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• Test parameters
• Sample mass: 2,100 g (53 briquettes)
• Temperature: 820 °C
• Reduction agent: H2 (12 L/min gas flow)
• Similar oxygen content in the sample after
3h reduction test duration
Case study
Main results – Reduction test
B1, B2…Bentonite-bounded briquette samples, P2…Ore pellet sample
[1] TU Bergakademie Freiberg, Institute of Thermal-, Environmental- and Resources' Process Engineering
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(1) K1-MET in a glance
• Research on residue treatment and recycling solutions
(2) Treatment of BOF dust for internal recycling – RecoDust process
• Project partners and methodology
(3) Treatment of DR dusts and sludges for internal recycling
• Project partners and methodology
• Process concept
(4) Summary and outlook
• Next steps in the process developments
Agenda
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• No complex dust-pretreatment necessary
• Small facility
• No further additives to be charged
• Use of gaseous reducing agents
• Variable input quality (treatment of EAF
dusts also possible)
• High dezincification rate (separation Zn-Fe)
• Processing of RecoDust slag important to
reach added-value (iron substitute)
The RecoDust process
A concept for increased circular economy
Life cylce in steel industry (voestalpine)
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• Mixture of different waste materials processable via
cold-bonded briquetting
• High mechanical strength reached for all tested
binders
• Optimal recipes for high briquette strengths
• Bentonite: Binder 3.0 - 5.5% / H2O 3.7 - 7.0%
• Starch: Binder 3.0 - 8.0% / H2O 3.0 - 4.0%
• Cellulose: Binder 3.0 - 5.5% / H2O 5.0 - 8.0%
• Small resistance for low-temperature disintegration
of organic-bounded briquettes
• Low reduction speed of bentonite-bounded
briquettes
MIDREX® residue briquetting
A concept for increased circular economy
Life cylce in steel industry (voestalpine)
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Outlook
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RecoDust process
• Upscale of the pilot plant (300 kg/h ➔ 1,000 kg/h)
• Optimized dust feeding system
• Increased process and energy efficiency
• Optimized product properties
MIDREX® residue briquetting
• Increased thermal stability and quantify effect of better
reducibility for organic-bounded briquettes
• Quantify optimum size of bentonite-bounded briquettes
• Impact on reducibility has to be proven
• Concept of continuous agglomeration
• Transfer of hydraulic stamp press to a roller press
Open challenges
Next steps in the research projects
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Questions?Dr. Johannes Rieger
K1-MET
Franz-Josef-Strasse 18, Leoben 8700, Austria
T.: +43 / 3842 / 402-2280
M: +43 / 664 / 88 32 24 99
Dr. Christoph Thaler
voestalpine Stahl
voestalpine-Strasse 3, Linz 4020, Austria
T.: +43 / 50304 / 15-73316
M.: +43 / 664 / 61 572 34
Project partners
- Montanuniversität Leoben, Chair of Thermal Processing Technology (Austria)
- TU Bergakademie Freiberg, Institute of Thermal-, Environmental- and
Resources' Process Engineering (Germany)
The research program of the competence center
K1-MET is running within COMET - Competence
Center for Excellent Technologies and is funded by:
• The Federal Ministry for Climate Action,
Environment, Energy, Mobility, Innovation and
Technology
• The Federal Ministry for Digital and Economic
Affairs
• The provinces of Upper Austria, Tyrol and Styria
Beside the public funding from COMET, the
research projects are partially financed by industrial
partners. Continuous support is given by
Upper Austrian Research GmbH