TECHNOLOGIES TO TRANSFORM

STEELMAKING SLUDGE/DUST IN

BYPRODUCTS

Jorge Madias

ABM Week, Riocentro, Rio de Janeiro, Brazil, August 20th 2015

Round Table on Co-product and Waste Management

Content

Overview

Rotating Furnace (Waelz)

Rotating Hearth Furnaces (RHF)

Shaft Furnaces

Others

Process Evaluation

Conclusions

2

Overview

Presentation based on

Experimental work for BF/BOF slag and BOF sludge

carried out for Siderar while at IAS

Consulting work for Aceros Arequipa on EAF dust,

rolling scale and DRI plant waste, at metallon

Series of papers on slag, dust and sludge recycling for

Acero Latinoamericano, the ALACERO journal (2010-

2015)

Short course Recycling of Slags, Sludge & Dust, Buenos

Aires, March 2015

3

Overview

Eight worldsteel sustainability indicators

For raw materials conversion into products + byproducts: 96%

Efficiency in the use of materials

Decrease of specific consumption of raw materials and specific waste

generation

Efficient use of byproducts

Recycling (internal or external)

Use of wastes reinforce the sustainability of the industry

Prevents disposal

Reduces CO2 emissions

Helps in preserving natural resources

Sales of byproducts: economically sustainable

Generates income for steel producers

Forms the base for a lucrative world steel industry

4

Overview

Waste generation

Precise data is difficult to collect; reports are usually plant-based

or on a national/regional basis

Just as an example, for a gross estimation

Blast furnace slag: 320 kg/t hot metal

Blast furnace dust and sludge: 15 kg/t hot metal

BOF slag: 120 kg/t liquid steel

BOF sludge and dust: 40 kg/t liquid steel

EAF slag: 100 kg/t liquid steel

EAF dust: 17 kg/t liquid steel

Scale: 2 kg/t of rolled steel

5

Overview

Waste generation (gross estimation)

Taking into account 2014 world hot metal, BOF steel

and EAF steel production:

Blast furnace slag 370.000.000 t

Blast furnace dust and sludge 18.000.000 t

BOF slag 140.000.000 t

BOF sludge and dust 45.000.000 t

EAF slag 50.000.000 t

EAF dust 8.500.000 t

6

Overview

Possible use of wastes

Gangue recovery

The most important way (100% BF

slag; 80% BOF+EAF slag,

worldwide)

Metals recovery (Fe, Zn, Cd, Pb)

Not so popular, but carried out, at

some extent

Energy recovery (C, H2)

Just in particular cases

7

Overview 8

BOF

SLUDGE

&

DUST

ALTERNATIVES PRODUCTS

Landfill

Cement Industry

Blast Furnace (DK)

(Sinter)

Sinter Plants

Blast Furnace (Briquettes)

BOF (Briquettes, Lumps)

Cupola (Bricks, pellets)

RHF (Briquettes,

Pellets, Extrusion)

Clinker

Hot metal, ZnO,

BF slag

Sinter for blast furnace

(limited by Zn, alkalis,

size)

Hot metal; slag

Steel, slag

Hot metal, ZnO, Slag

DRI, ZnO

Overview 9

EAF

DUST

LOCATION/UNIT PRODUCTS

Landfill (Isolation / Insolubilization)

Injection in EAF

Waelz Kiln

Mitsui Furnace

Flame Reactor

Electro Thermical

ScanArc

RHF

Higher ZnO dust

ZnO conc., «slag»

ZnO conc., slag

ZnO conc.; slag

ZnO conc.; slag

Matte, Slag

DRI, ZnO conc.

Induction Hot metal, ZnO conc.

Overview

Standard tools for BOF / EAF sludge and dust

Fe/Zn/CaO units recovery (with 5 or more

references)

Waelz kiln for Zn rich byproducts, as EAF dust

Rotative Hearth Furnace (mostly for BF/BOF

sludge/dust)

Shaft Furnaces (Dedicated cupolas, blast furnace)

10

Waelz Process

Dominant for EAF dust recycling (80% market share)

Volatilization of non-ferrous metals as Zn, Pb, Cd, departing from a

mix of solid oxides, by means of reduction with small coke in a kiln,

without generation of liquid slag

Technology developed by Krupp in Germany, to use low Zn cinc ore

1925: first industrial plant

1940: application to wastes of neutral lixiviation, from cinc furnaces

1970: application to EAF dust

40,000 a 160,000 tpa of EAF dust in one kiln

11

Waelz Process

Typical lay out

12

Waelz Process

Raw material preparation

To insure homogeneous and even feeding

EAF dust of different plants

Small coke as reducing agent (180 to 350 kg/t dust)

Slag formers (sand 100-250 kg/t dust or lime 40-50 kg/t dust)

Power consumption 150-300 kWh/t dust

Kiln

The solid charge advances thanks to kiln rotation (1 rpm) and inclination (2-3%)

From the other end, air is suctioned and solid slag exits the kiln

The charge is dried, heated and starts to react

Endothermic reduction of Zn, vaporization, reoxidation

ZnO-containing gas passes through a deposition chamber, where it is cooled with

sprayed water and air ingress; separation in bag filters

Heat generated by coke combustion and oxidation of Zn vapor

Maximum temperature 1200 oC; air ingress at ambient temperature; gas exits at 700-

800ºC

13

Waelz Process

Main reactions

14

Waelz Process 15

Dust, Waelz Slag & Crude Waelz Oxide Chemistry

EAF Dust Waelz Slag Waelz Crude Oxide

Zinc (%) 14-35 0,2-2 55-58

Lead (%) 0-2 0,1-2 7-10

Cadmium (%) 0,1-0,2 <0,002 0,3-0,5

Chlorine (%) 1-5 0,1-0,5 4-8

FeO (%) 20-45 30-50 2-5

SiO2 (%) 3-6 25-40 0,5-1,5

CaO (%) 3-10 4-10 0,3-1

Waelz Process

Some references

16

Company Plant Country Units Capacity EAF

dust (tpa)

Company type

BEFESA

Duisburg Germany 1 Independent

Freiberg Germany 1 42,000 Independent

Erandío Spain 1 Independent

Harz-Metall Goslar-Oker Germany 1 60,000 Independent

Himeji Tekko Refine Himeji Japan 1 35,000 Independent

Horsehead Calumet, IL USA 2 Zn producer

Rockwood, TN USA 2 190,000 Zn producer

Palmerton, PA USA 3 Zn producer

Pontenossa Pontenossa, Bergamo Italy 1 100,000 Independent

Portovesme Portoscuso, Cerdeña Italy 1 75,000 Zn producer

Recytech Fouquières-lez-Lens France 1 80,000 Independent

Steel Dust Recycling Mobile, AL USA 1 120,000 Independent

Sotetsu Metal Aizu Japan 1 72,000 Zn producer

Sumitomo Shisakajima Japan 1 120,000 Zn producer

Zinc Nacional San Nicolás d.l. Garza México 1 ZnO producer

Votorantim Juiz de Fora, MG Brazil 1 Zn-Cd-Pb producer

Waelz Process

Summary

90 years old, well established process

References: 47 (more than 20 for EAF dust)

Needs high Zn dust (the higher the Zn content, the

higher the prize paid to steelmakers)

Slag not easy to commercialize (dangerous waste in

some countries)

Up to now, a business for Zn producers or waste

processors, not steelmakers

Coke, power and slag formers consumption

Sem sinergia entre produtores e consumidores de Zn

17

RHF

Initially proposed for DRI obtention departing from iron ore (then forgotten

as the gas-based DRI progressed)

Now used as a recycling tool for BF / BOF dust and sludge

Aglomeration as self-reducing pellets, briquettes or extrusions

A structural limitation, pointed out by Dr. Wei K. Lu

Low specific energy consumption and high metallization not compatible

Low quality DRI, not apt for EAF charge

Efficiency in Zn, K and Na separation

Very short reduction time: 12-10 minutes

Types

Single rotating hearth operated at normal temperature (the standard, there are

several suppliers)

Single rotating hearth operated at high temperature for iron nuggets (ITmk3)

Multiple hearths, operated at low temperature (PRIMUS)

18

RHF

Development

1960’: Midland-Ross creates the first RHF concept in the USA, the so-

called Heat-Fast, for DRI obtention departing from hot metal

1970’: Heat-Fast frozen al pilot scale due to the success of gas-based

MIDREX direct reduction process

1978: INMETCO kiln to recover Cr and Ni from stainless steel producers

wastes

2000: Start-up of an RHF (so called DRyIron) in Rouge Steel (Severstal

Dearborn), by a Midland-Ross heir, Maumee Research & Engineering

2000’: Nippon Steel Engineering (today Nippon Steel & Sumikin

Engineering) purchase RHFs to MRE, then presents its own patent, under

which most RHF plants have been built

19

RHF

The order of the reactions is inverted in comparison with blast

furnace

First, carbon reduce Fe oxide forming CO, within the self-reducing

agglomerate

Then, CO must be burned to CO2 in the free board to generate heat

and to increase temperature

The challenge is in transfering heat to the agglomerates without

oxidizing newly formed iron

A high CO/CO2 ratio, 2.3, is often used

It is possible to achieve high metallization or low energy consumption,

but not both simultaneously

20

RHF

NSSE

21

RHF

NSSE

Disk pelletizing (cold bonding with cement, self-curing)

Higher productivity

Sensitive to variation in raw materials properties and to mix

changes

For relatively dry and stable sludge and dust (most of them)

Extrusion in screw

Lower productividad, less sensitive to changes

For dust with high moisture or inconsistent physical properties

Rolls briquetting

Intermediate position

22

RHF

NSSE

23

RHF

Some references

24

Company Plant Country Start-

up

Capacity

(tpa)

Processed

Wastes

Agglome

-ration

DRI use Engineering

NSSMC Hirohata Japan 2000 210,000 BOF dust &

sludge

Pellets BOF Midrex

NSSMC Kimitsu Japan 2002 135,000 BF/BOF

sludge

Extrusions Blast Furnace MR&E, NSSE

CEVITAL Piombino Italy 2004 60,000 BF/BOF dust Pellets Blast Furnace SMS Siemag

China Steel Taiwan 2007 130,000 BF/BOF

sludge

Extrusions Blast Furnace

MR&E, NSSE

NSSNC Kimitsu Japan 2008 310,000 BF/BOF dust

Pellets Blast Furnace

MR&E, NSSE

Ma Steel Manshan China 2009 200,000 BF/BOF dust

Pellets Blast Furnace

MR&E, NSSE

POSCO Pohang Korea 2009 200,000 BF/BOF dust

Pellets Blast Furnace

MR&E, NSSE

POSCO Gwanyang Korea 2009 200,000 BF/BOF dust Pellets Blast Furnace MR&E, NSSE

Nittetsu

Shinko

Japan 2011 220,000 BF/BOF/EAF

dust

Briquettes BOF, EAF, BF

(HBI)

Midrex

RHF

Summary

50 years old, well established process

References: more than 10, worldwide

Either low energy consumption or high metallization

Agglomeration through pellets, briquettes or extrusions

Low quality DRI suitable only for blast furnace

Installed and operated within steel companies

Coal and power consumption; heat recovery

Till today, failed as a competitive alternative

ironmaking process

25

Shaft Furnaces

OXYCUP cupola

Conceived by Küttner and developed in SICARTSA (now ArcelorMittal

Lazaro Cardenas Long Carbon)

Very large cupola, with acid lining and Oxygen-enriched hot blast

Charge

Self-reducing bricks or pellets

BOF/BF sludge and BOF dust

Coal

Binder

Steel and pig iron skulls; big scrap pieces

Coke

Limestone

26

Shaft Furnaces

OXYCUP Cupola

27

Shaft Furnaces

OXYCUP Cupola

In comparison with conventional cupolas, OXYCUP has (for 85% bricks)

Coke rate very high (360 kg/t hot metal)

High slag generation (604 kg/t hot metal)

Blast furnace: Reduction below 800 oC

OXYCUP cupola: Reduction at more than 900 oC

28

Shaft Furnaces

OXYCUP Cupola

29

Shaft Furnaces

OXYCUP Cupola

Maximum Zn content in the brick, as function of the

percentage of bricks in the charge

To avoid the Zn accumulation problem typical of shaft

furnaces (low top temperature)

30

Maximum zinc oxide (%) Share of bricks in the charge (%)

10 20

6 40

3 80

Shaft Furnaces

OXYCUP Cupola

References

31

Company Country Melting capacity

(t hot metal/h)

Metallic

charge

Start-up

ArcelorMittal Mexico 80 t/h Bricks and

scrap

1998

ThyssenKrupp Germany 25-50 t/h Bricks and

scrap

2004

NSSMC Japan 60 t/h Pellets and

scrap

2005

JFE Steel Japan 80 t/h Bricks and

scrap

2008

TISCO Taiwan 3 x 50 t/h (1

being lined)

Bricks 2011

Shaft Furnaces

DK Process

DK Recycling und Roheisen (Duisburg, Germany)

Formerly owned by Rio Tinto, now property of the personnel

Sinter plant and two mini blast furnaces, operated under special

conditions

Waste processing for third parties, for a fee; pig iron ingots sold to

foundries

400.000 tpa of wastes from 9 plants of 6 European countries

Charge: more than 50% BOF dust; 5 % BOF sludge

Mixing with a clam crane, feeding several bins with a belt conveyor

below

Sinter cooling in the final third of the sinter belt

32

Shaft Furnaces

DK Process

Charging mix of the sinter plant

33

Shaft Furnaces

DK Process

Blast furnace charge 100% sinter

Zinc ≈ 38 kg/t hot metal (usually 0.02 – 0.2 kg/t hot

metal)

Top gas temperature relatively high, 350 oC

A heat each 2 hours

Hot metal is desulphurized

8-10 kg ingots cast in ingot casting machine, for the

foundry market

34

Others

Induction Furnace (Toho, Japan; PIZO, USA)

Plasma Arc Furnace (ScanArc, Norway)

Flash Smelter (Sumitomo, Japan; HorseHead, USA)

35

Process evaluation

Process Strengths Weaknesses Comments

Waelz Well known,

adaptable to

changes in raw

materials

Need for higher Zn content

Waste «slag» not always

saleable

Standard for EAF dust

RHF Good for Zn, Pb,

Cd separation

Low energy consumption

not compatible with high

metallization

Low quality DRI, mostly for

BF charge

Justified when landfill

cost is very expensive or

not possible and a blast

furnace is available

Oxycup Besides wastes, it

solves skulls

Production of hot

metal

Zn charge limited; high

coke consumption

Limited references

DK Flexible charge;

Production of hot

metal

Zn charge limited; high

coke consumption

Works well under

particular business

conditions

36

Conclusions

Several technologies are emerging for converting steelmaking

sludge and dust into byproducts

They are usually CAPEX intensive, with an important operating

cost

In some cases the product quality is low and asks for melting in

a blast furnace to separate the gangue

For EAF dust recycling the Waelz kiln is dominant; operated by

Zn producers or specialized waste processors, not steelmakers

Several of these process failed as alternative ironmaking

processes, but work well to convert wastes into byproducts

This has to do with the cost of landfilling, that pays for

inefficiences, high energy consumption, etc.

37