Eco-friendly steelmaking slag solidification with energy ...

Eco-friendly steelmaking slag solidification with energy recovery to

produce a high quality slag product for a sustainable recycling

1

Agnieszka Morillon, David Algermissen, Dirk Mudrsbach, Susanne Schüler, Loredana Di Sante, Marta Guzzon, Filomena Giordano, Mirko

Piccolo, Johan Björkvall, Reza Safavi Nick, Virpi Leinonen, Inigo Unamuno, Leixuri Fernandez, Iñigo Ortega-Fernández , Luis González-

Fernández

www.ecoslag.eu

Green steel by EAF route workshop: a sustainable value chain in the EU Circular Economy scenario14 Nov 2019

2

1. International state-of-the art of heat recovery

2. Objectives of Ecoslag

3. Current slag handling

4. Slag characteristics

5. Current slag utilization

6. Direct recovery of heat from LF slag to EAF

7. Air granulation of EAF slag while recovering heat

8. RecHeat recovery system

9. Future work

Green steel by EAF route workshop - 14 Nov 2019

3

International state-of-the art of heat recovery


4

Heat recovery methods for steel slags

Worldwide several techniques for heat recovery exist, but none are really used in operational practice

• Air-blast-solidification

• Drum-solidification

• Rotating-cup-drum solidification

• Rotating-cup-solidification

• Other solidification-techniques


Air-blast-solidification

• Granulation of slag with air blast techniques was put into operational practice in early 1990’s in Japan. The reason for stopping is not clear, shortcomings include

– low heat recovery (~40%)

– scattering of the droplets

– energy intensiveness of the granulation process

• FEhS tried in 2000s to improve the process to decrease free lime in BOF slag produced, however after laboratory and pilot trials the resulting slag showed increased oxidation and unsuitable properties, so the project was not extended to recover heat

• Recently Ecomaister Ltd in South Korea developed a Slag Atomizer Plant for the air granulation of slag which produces PS Ball (Precious Slag Ball) below 5 mm, the process produces large amounts of fumes from which potentially heat could be recovered, but it is not in operational practice

Example:Air granulation, Nippon-Kokan

Green steel by EAF route workshop - 14 Nov 2019 5

Drum-solidification

• Rotating drum systems for slag granulation and heat recovery were investigated in the 1980’s by Ishikawajima-Harima Heavy Industries and Sumitomo Metal with a slag production of 40t/h with reported 50-60% heat recovery

– However the drum granulation impaired the amount of glossy BF slag produced

• In 2000s ASO Siderurgica with U. of Brescia developed slag drum cooling system “Slag-Rec”, which produces flat solid pieces by controlling the cooling cycle

– Shortcoming is the limitation of grain size by the width of the gap between the drums

• In 2000s JFE, Japan also developed a twin drum rollers indirectly cooled with coolant

– In laboratory tests about 30% of heat was recovered

Example:Drum solidification, SLAG-REC



Rotating-cup-drum-solidification

Example:Disk & drum atomizer, RIST

7

POSCO’s in South Korea target is “Global Green Growth Leader”

• In 2010s first laboratory tests were carried out at the Research Institute of Industrial Science and Technology (RIST) in Phang, for granulation and heat recovery of molten BF slag, but also of liquid steel slag using rotating cup-drum atomizer.

• Pilot trial at POSCO was produced with capacity of 35 kg/min

– More than 50% of the otherwise wasted heat was recovered


Rotating-cup-solidification

Example:Rotating Cup, PRIMETALS

8

Since 2010s few pilot plants for rotary cup atomizer with heat recovery have been investigated, but up to now none have been commercialized due to design difficulties.

• A full-scale rotating cup unit was installed at Tata Steel, Redcar No.1 BF by Siemens VAI UK, with possibility of heat recovery

• At CSIRO, Australia, in 2012 pilot plant was installed to process 100 kg of BF slag/min

• Pilot plant has been designed by Siemens VAI (today: PRIMETALS) and FEhS and tested at Montenauniversitat Loeoben, Austria. The rotating cup pilot plant has capacity of 2 t/min

– FEhS tested steel slag instead of BF slag and found insufficient properties of the solidified slag


Other solidification techniques

Example:Steel Balls, Paul Wurth

9

• In 1980s stirring of hot slag technique was investigated

– Failed to recover high amounts of heat or produce slag of high quality due to large grain size of slag produced

• In 2010s injection of steel spheres or cylinders into liquid slag was investigated by Paul Wurth

– Only 20% of heat recovery was achieved

• Chemical energy recovery from slag is being considered as possible method, but so far only conversion kinetics have been investigated

Expectations on heat recovery in steel industry

A heat recovery technique will never be implemented in operational practice, when

• the slag quality becomes worse

• the device / process is very complex and sensitive

• the benefit of using the recovered heat is low (technical and legislative barriers)


11

Objectives of Ecoslag


Objective of ECOSLAG

• Slag is almost the only heat source in a steel work without any application

• For BF slag, promising techniques exists but steelmaking slag has other challenging points

Hot LF-slag

Prevention of C2S disintegration

Granulation process

Quality check (marketability)

Hot EAF-slag

Hot mediumUse in steel

work

Hot BOF-slag RecHeat


13

Current slag


Current slag handling

• Each steelwork is different and needs an individual solution for slag handling, however similar steel works can learn from others and adopt the solutions being investigated in the project

• The physical restrictions to any solution due to the furnace layout is critical

• MAU

– 200k tons/y of EAF slag produced with 10-15 tons/ heat (2 EAF available)

– Slag sand or quartz sand as de-foaming material to slag pot

– 30k tons/y of LF slag produced with 1 ton/heat (2 LF available)

– 3-4 heats of LF slag in 1 slag pot

• ACP

– 25k tons/y of EAF slag produced with 15 tons/ heat (1 EAF available)

– Tapping EAF slag direct in pit under the furnace

• SIDENOR

– 80k tons/y of EAF slag produced with 15 tons/ heat (1 EAF available)

– Tapping in slag pots


Slag composition of slag from MAU, ACP and Sidenor

Parameter UnitMAU ACP Sidenor SSAB MAU

Slag sand Quarz sand via Swerim

Al2O3 wt.-% 2.3 1.8 4.72 5.57 0.57 17.19

CaO wt.-% 34.0 28.3 18.6 23.4 40.7 38.67

Cr2O3 wt.-% 2.3 1.8 4.19 2.90 0.3 0.12

Fetotal wt.-% 25.3 21.5 44.3 29.27 18.7 1.84

MgO wt.-% 4.4 5.4 2.58 7.46 11.8 13.28

MnO wt.-% 6.2 5.2 3.71 6.41 4.2 0.44

P2O5 wt.-% 0.4 0.3 0.31 0.37 0.7 0.03

SiO2 wt.-% 9.3 21.2 6.69 9.55 9.6 19.21

TiO2 wt.-% 0.4 0.5 0.33 0.41 1.3 0.25

V mg/kg 963 84 364 1,025 12,323 53

EAF BOF LF


C/S = 3.7 C/S = 1.3

Thermo-physical slag analysis of EAF slag, BOF slag and BF slag

Producer SlagApparent(kg/m3)

Skeletal(kg/m3)

Total porosity(%)

Sidenor(EAF)

A 3.83 4.05 5.43

B 3.91 4.16 6.01

SSAB (BOF)SSAB (BF)

C 3.42 3.64 6.04

D 2.04 2.99 31.77

Volume Variation Thermal Diffusivity Thermal Conductivity

Heat CapacityDensity


17

Current slag utilization


Current slag utilization

MAU

EAF

earthwork

roadconstruction

landfillconstruction

LF

deposit

ACP

EAF

civilengineering

roadconstruction

LF

deposit

Sidenor

EAF

civilengineering

roadconstruction

LF

deposit


19

Direct recovery of heat from LF slag to EAF


20

Direct recovery of heat from LF slag to EAF

• Due to specific design of LSW a tundish has to be used to transport LF slag to EAF

– Possibility to transport tundish

– Tundish size must allow for direct charging into EAF

– Tundish must be able to handle both metal and slag

– Slag must be kept from disintegrating


21

Modeling of tundish


• The figures shows the boundary where temperature of the slag is equal to 1610 K(~1337 °C).

• This represents the cooling patterns of the slag which is affected by the tundish geometry.

22

Modeling of tundish - After 50 seconds


• The cooling starts at the location where the slag, enviroment and tundish wall intersect

• Some small spots can be seen at the bottom centre

23



• The cooling continues at the location where the slag, enviroment and tundish wall intersectFaster cooling seems to appear at sides with smaller vertical wall

• Spots are enlarging and moving towards the top-left of the doman

24



• The cooling extends downwards at the location where the slag, enviroment and tundish wall intersect.Larger cooling seems to appear at side with smaller vertical wall

• Spots are even larger and are still mostly towards the top-left of the doman.

25

Lab tests for LF slag disintegration characteristics


26

Slag disintegration region


27

Air granulation of EAF slag while recovering heat


28

EAF slag granulation

Target

Air granulation of EAF slag directly on the slag pit in order to increase the cooling rate of the slag

Granulation model

Air flowrate is regulated based on a model of granulation and breakage mechanism theory

Typical slag droplet size was defined

• Simulation was performed in the laboratory

under the flow conditions (velocity at the gas

inlet) simulating industrial conductions

• Video recorded images were taken

• With the overall droplet analysis, the typical

size of the droplets formed were in the range

foreseen in the literature (within few mm)


29

Granulation of EAF slag directly on the slag pit in order to

increase the cooling rate of the slag

Main characteristics of the system

- Next to the furnace, just below the EAF slag door

- Dedicated valve stand

- Slag automatically detected by dedicated camera

- Station for heat recovery


Image analysis Laboratory test(1 kg slag)

Heat recovery station

EAF de-slaging below EAF Dry-granulationHeat-recovery✓ Bottom steel pipe to pipe panel✓ Top TEG panel✓ Top holed bricks panel

Handling

30

RecHeat recovery system


INNOVATION RecHeat – Recovery of Heat from Slag

• ModHeat enables drying of wet

materials e.g. slag, sludges etc.

• Heat for the drying process

(ModHeat) will be directly

recovered from the hot liquid slag

by RecHeat


32

Future work

• Construction of laboratory and industrial scale tests with tundish for LF slag

• Construction of laboratory and industrial scale tests with granulation of EAF slag

• Construction of a RecHeat with a new improved design and industrial trials with BOF slag

• Resulting slag analysis

• Feasibility evaluations


33

Thank you for your attention

The research leading to these results hasreceived funding from the European Union'sResearch Fund for Coal and Steel researchprogramme under grant agreement number:800762

Eco-friendly steelmaking slag solidification with energy ...

Documents

Transcript of Eco-friendly steelmaking slag solidification with energy ...