'Waste recovery in ironmaking and steelmaking processes' 13 and ...

Conference report 

'Waste recovery in ironmaking and steelmaking 

processes' 13 and 14 December 2010 

V. Ludlow 1 , K. Linsley 2 , S. MiUman 3 , F. Abbott 3 and S. Drew 3 

The old adage says that 'What is a 

waste to one man is an opportunity to 

another'. Many today see waste 

recovery, not as an opportunity, but a 

necessity to minimise both the costs of 

disposal, i.e. dumping to landfill, and to 

recover valuable materials for recycling 

back into the ironmaking and 

steelmaking process route. Thus, the 

raison d'etre behind this two day 

international conference held at the 

Institute of Materials, Minerals and 

Mining (IOM3) in London was 'to 

stimulate interest and dialogue in the 

various ways and means that 

ironmaking and steelmaking wastes 

can be processed and their levels of 

utilisation increased'. 

The conference, sponsored by Paul 

Wurth, Harsco Metals and Tata Steel, 

was attended by a total of 75 delegates 

representing 40 companies and 

organisations from 15 countries. Steel 

companies, steel service companies, 

universities and steel research 

organisations provided the majority of 

the attendees. During the two days 

there were 27 presentations divided 

over four sessions and at the end of 

day 1 there was an opportunity for the 

delegates to network at wine and 

cheese reception held in the library at 1 

Carlton House Terrace. 

In his welcome and introduction to 

the conference, Chairman of the 

Organising Committee K. Linsley gave 

an example that illustrated that even 

after 150 years of significant technical 

progress, there are today still problems 

using some waste materials that 

contain over twice as much iron as 

found in prime raw material in the 

nineteenth century. Consequently 

these may be regarded as wastes, with 

1 

Consultant and Assistant Editor Ironmaking 

and Steelmaking, UK 

2 

Chairman of the Conference Organising 

Committee, Teesside Technology Centre, Tata 

Steel RD&T, UK 

3 

Steelmaking and Casting Department, 

Teesside Technology Centre, Tata Steel RD&T, 

UK 

the subsequent loss of a potential 

source of iron units and an addition cost 

of dumping. He asked, 'Is it really a 

waste or a wasted opportunity?' 

Session 1: waste strategy and 

thermal processes 

Session Chairmen: Mike Copeland 

and Kevin Linsley 

This session was opened by Dr P. 

Brooks, Group Director Environment, 

Tata Steel, with his keynote paper; 'Is 

waste just a dirty word or an asset to 

be exploited?' The paper gave an 

insight into some of the legal, financial 

and technical drivers and barriers for 

increasing waste utilisation. The paper 

also introduced the psychology of 

dealing with wastes. Dr Brooks stated 

that many manufacturers often see 

waste as exactly that; 'something 

inevitable arising from the process 

route that can be tolerated and which is 

handled by someone else, either inside 

or outside of the organisation'. Also, 

and to make matters worse, he 

considered that the costs of handling 

Waste are rarely transparent. To 

highlight disposal costs, Dr Brooks 

gave a breakdown in landfill charges for 

Tata Steel UK for 2010/2011 as 8% 

transport, 23% gate fee, 31% lost 

value and 31 % government tax. With 

landfill charges of £80/t and upwards, 

depending on possible hazardous 

content, the 31 % lost value can mean a. 

significant saving to the organisation. 

Dr Brooks continued by arguing that 

there is a need to treat some wastes as 

a 'secondary' raw material as primary 

resources are depleted or competition 

for these resources increases and he 

gave an indication of some resource 

availability, for example coal at 150 to 

200 years. In conclusion, he stated that 

in order to recover valuable iron units, 

reduce mineral and raw material costs 

and minimise landfill, there is a need to 

improve the usage of by-products from 

coke making, slags and flue dusts from 

ironmaking and steelmaking and sludge 

form casting and rolling. 

The second paper in this first 

session, 'Helping iron and steelmakers 

towards the zero waste goal', was 

given by Daniel Devid of Harsco Metals 

Group Ltd. For the steelmaker, zero 

waste or resource recovery translates 

into greater efficiency and through 

recovery of by-products; significant 

tangible economic benefits can be 

achieved. This is the philosophy behind 

the recovery process developments 

and specific engineered solutions 

provided by the Harsco Metal Group. 

Mr Devid stated that according to the 

World Steef Organisation, every tonne 

of steel produced generates 200 kg of 

by-products via the electric arc furnace 

(EAF) route and approximately double 

this figure from the biast furnace (ВF}/ 

basic oxygen furnace (BOF) route. 

Environmental regulations, as weli as 

the economics associated with the 

process are making land filling of such 

by-products an increasingly expensive 

option. The Harsco Metals Group has 

developed a variety of proprietary 

technologies to solve many of the : 

problems created by the by-products of 

the steel industry,: Slags, dusts, fines, 

slurries and various scales are all 

processed to recover the valuable Iron 

units from the carbon steel route and Ni 

and Cr units from the stainless steel 

route and these include; 

micropelletising, plasma smelting and 

adding value (valorisation) to otherwise 

waste slag. Three specific examples 

were given: (i) the processing of all 

slag, dusts and sludges for Hadeed in 

Saudi Arabia, (ii) briquetting/peiletising 

of dusts and sludges for US Steel in 

Kosice, Slovakia. From this technology, 

Harsco have developed a specialist : 

additive mixture that can be recycled 

into the cement making industry, and 

(iii) the smelting of stainless steel dusts 

in a DC plasma arc furnace (termed the 

Plasminox process) at TKS Terni, Italy. 

Mr Devid concluded by stating that 'the 

positives of resource recovery of byproducts 

extend beyond simple 

economics, recycling and recovery of 

steelmaking by-products greatly 

© 2011 Institute of Materials, Minerals and Mining 

Published by Maney on behalf of the Institute 

DOE 10.1179/030192311X13135947813771 Ironmaking and Steelmaking 2011 VOL 38 NO 7 481

CONFERENCE REPORT 

reduces the environmental impact of 

steelmaking in a number of ways by 

reduced land fill of materials, reduced 

usage of natural resources, reduced 

transport footprint and reduced C02 

emissions'. 

The third paper in session 1, entitled 

'By-products in iron & steelmaking - 

troublesome materials or secondary 

raw materials?' was given by Dr Peter 

Drissen of the FEhS Building Materials 

Institute of Germany. Recycled BF and 

steelmaking slags do not always meet 

the end-user requirements and there is 

also considerable scope for 

improvement in metal recovery and 

properties of ceramic material 

produced from slags. This has been the 

scope of the work of the Institute for a 

number of years. Dr Drissen's 

presentation gave four specific 

examples of the treatment of iron and 

steel slag aiming at improved building 

materials, on metal recovery from slag 

and the internal recycling of 

steelmaking slag: 

• pneumatic injection of lime into the 

BF runner to modify the slag 

composition prior to granulation to 

effect improvements in cement/ 

concrete compressive strength 

• silica/sand injection into the BOF slag 

ladle to modify chemistry and 

thereby reduce free lime and free 

MgO in the final product, thus 

increasing product stabilisation and 

improved potential utilisation of this 

by-product 

• stimulation of complex spinel 

formation in EAF slag by Al/Al203 

addition resulting in a reduction in 

the levels of Cr that leaches from the 

slag 

• substitution of lime by ladle slag 

(80% ladle slag/20% spent dolomite) 

in EAF steelmaking. 

In his paper, 'Recycling of solid wastes, 

Tata Steel's experience'. Tapas 

Chakraborty reported that in the last 

five years up to 2009/2010, solid waste 

utilisation increased from 80-2 to 

91-1 % at Tata Steel Jamshedpur. As 

with most integrated works the sinter 

plant bears the brunt of the recycling. 

92% of BOF sludge, 7-9% of BOF slag, 

68% of flue dusts, 100% mill scale and 

97% of mill sludge are recycled via the 

sinter plant with little or no pretreatment 

or enhancement, other than 

being incorporated into the piles ready 

for sintering. Currently, BF sludge is not 

recycled due to its alkali material 

content, but recent efforts to lower the 

alkali input to the BF means that it is 

now possible to recycle a proportion of 

Ironmaking and Steelmaking 20.11 VOL 38 NO 7 487 

this material. Miliscale and sludge 

recycling to the sinter plant has an oil 

contamination limit of 5%- due to the 

potential for glow fires to occur in the 

electrostatic precipitator dusts. Cost 

savings by utilisation of wastes through 

the sinter plant are estimated at $2'66/t 

of sinter, equivalent to S222M for an 

8 Mtpa sinter plant. Energy recovery 

was also thought important and as such 

Tata Steel, Jamshedpur is investigating 

the possibilities of selective waste gas 

recovery and heat recovery from the 

sinter cooler. 

In the paper, 'The plasma processing 

of steel plant wastes', Dr David Deegan 

of Tetronics limited described the use 

plasma-fired carbothermic reduction 

furnaces to recover metals from EAF 

and argon oxygen decarburisation 

(AOD) dusts. Although the technology 

is aimed primarily at the stainless 

steelmaking production route it is 

equally applicable to the carbon steel 

route. The combined fly ash by-product 

from EAF melting, the AOD process 

and vacuum refining operations is 

typically in the range of 1 -5 to 2-5% of 

the total metal production. In addition, 

significant amounts of residue 

materials are generated in finishing 

processes, such as grinding and flame 

cutting, which may represent a further 

1 -0 to 1 -5% of metal production. These 

stainless steel plant dusts contain a 

range of valuable, but leachable toxic 

metal species including chromium, 

nickel, lead and cadmium, which 

prevent them from being disposed of in 

open land-fill sites. Typically these 

dusts contain 32%Fe203, 13%Cr02, 

13-6%ZnO and 3-5%NiO. As well as 

recovering the high value metals, 

hazardous wastes are converted into 

inert, vitrified products, which avoids 

punitive landfill liabilities; these vitrified 

products also have an end-user 

application. The recovered ferroalloy 

can be returned to the melt shop or, in 

the case of zinc and lead recovery, sold 

on as oxide products. The net 

economic benefit of the technology 

was quoted as typically £100 s per 

tonne of waste, with payback within 

five years. 

In April 2010, the first European 

waste treatment facility based on rotary 

hearth furnace (RHF) technology was 

started successfully at the integrated 

steel plant at Lucchini Piombino Italy. 

The plant and process were described 

in the paper 'Redlron technology for the 

recycling of iron-bearing residues at the 

Lucchini Piombino iron and steel plant' 

given by Piergiorgio Fontana. The aim 

of the facility is a target of zero iron and 

steel plant waste,- recycling all of the BF 

sludges and BOF dusts arising at the 

plant; totalling about 60 000 metric tpa 

(dry-basis). The recycling p!ant4s basedon 

the Paul Wurth Redlron technology 

and consists of three main steps: 

(i) sludge drying, mixing and pelletising, 

(ii) iron pre-reduction and zinc removal 

at the RHF, and (iii) hot briquetting of 

the pre-reduced pellets. The hot 

briquetted iron is then recycled to the 

BF. The off-gas and briquetting system 

were recycled from another operation 

and a balling disk, rather than 

briquetting, was chosen as it is a onepass 

operation. The plant uses 

630 Nm 3 h" 1 natural gas and the hot air 

flow is 7500 Nm 3 h~ 1 . The operation 

costs are approximately €100/t. At the 

time of the conference, the plant was 

experiencing operational problems due 

to fouling within the recuperator 

exchange surface in the heat 

exchanger, caused by the condensation 

of alkalis within the off-gas system. 

The final paper in session 1 entitled 

'The DK process; a proven technology 

for the sustainable recovery of iron and 

zinc from BOF dusts and sludges', was 

given by Dr Carston Hillman of DK 

Recycling und Roheisen GmbH, 

Germany. DK Recycling und Roheisen 

GmbH was formed in 1991 to recycle 

sinter plant, BF, BOF and EAF dusts 

and BF and BOF sludges and today 

treats some 400 300 tpa of wastes 

from integrated steel plants within 

Europe. The wastes are recycled via 

the sinter plant. As the sinter plant has 

no mixing beds, the raw mix is made 

using weigh hoppers rather than beds. 

There is a secondary gas cleaning 

system installed at the sinter plant, 

which includes lime and lignite injection 

to aid S02 and dioxin reduction 

respectively. The plant is allowed tó bypass 

temporally the bag filter on startup 

due to the high temperatures. The 

finished sinter contains 2%Zn and 

0'06%Pb. DK operate only one BF that 

has a Zn loading of 38 kg/t of hot metal 

and an alkali loading of 8 5 kg/t of hot 

metal. Of the BF Zn input, 40% is lost 

to the flue dust, 4% to bucket conveyor 

dust, 56% as Zn concentrate (BF gas 

cleaning sludges) and

connected to the high emissions in the 

sinter plant, and (iii) zinc in the BF, 

which increases coke consumption. 

Alkali content, rather than Zn, limits the 

DK feed raw mix due to the swelling 

effect on pellets in the BF. Less than 

1 % of DK's output is classified as 

waste and subsequently disposed offsite, 

electrostatic precipitator dust 

being the main waste and this is sent 

for disposal at an underground mine. 

Session 2: further processing 

and practical solutions 

Session Chairmen: Mike Copeland 

and Richard Reasbeck 

The keynote paper for the second 

session, entitled 'Overview of baosteel 

waste management and utilisation', 

was given by Mr Exefu Hu from 

Baosteel Headquarters. In 2009, 

Baosteel produced a total of 

14-605 million tons of solid wastes 

including dusts, sludges, slags, fly ash 

and refractories. Of these BF slag, steel 

slag and Fe-bearing dusts and sludges 

were the three major wastes and these 

accounted for 80% of the total. The 

total utilisation rate was 98-4% of 

which 3-55 million tons (24-3%) were 

recovered for internal processing. 

20-1 % of the waste processing was of 

high value added products. Baosteel 

use hydro cyclones to produce low/high 

zinc fractions of the BF slurry. The low 

zinc fraction is reused in sintering and 

the high zinc fraction sent with EAF and 

BOF dusts to smaller external plants 

with smaller BFs that can utilise these 

materials. BOF slag is processed 

through the Baosteel BSSF process to 

effect free lime reduction in the 

product. Of the 200 к tons of used 

refractories, some are reused after 

internal treatment, but most are sold to 

refractory plant manufacturers for 

recycling. Baosteel plans to build up a 

production base with capacity of 22 к 

tons for used refractories, all the used 

refractories will be processed and 

recovered by Baosteel itself. In 

addition, Baosteel have recently 

announced that they are planning to 

invest 2-76 billion Yuan on solid waste 

management systems and processes. 

Nippon Steel Engineering Co. Ltd 

(NSEC) RHF process for steel dust and 

sludge recycling was described by Mr 

Daisaku Johbe of NSEC in his paper 

'RHF process for dust recycling 

system'. To date eight plants have 

been supplied to treat a wide range of 

sludges and dusts with the 

agglomerated product in pellet, 

briquette or extruded form. The 

process is based around a rotary hearth 

furnace that consists of four zones, 

feeding, heating, reduction, and 

discharging. The hearth floor rotates at 

a constant speed carryinglhë 

agglomerates, in the opposite direction 

to the gas flow. Burners are set onto 

the walls and inject air and fuel to 

control the atmosphere and the 

temperature. The agglomerates on the 

floor are at first heated, reduced and on 

completion of reduction discharged into 

a DRI cooler. Zinc oxide in the 

agglomerates reacts with the charge 

carbon to produce zinc vapour that 

leaves the furnace with the off-gasses 

(80 to 90% of the Zn in the charge is 

removed). The off-gas dusts and 

condensates consist mainly of Zn and 

BP oxides and alkaline halides. As the 

latter are very viscous there is patented 

NSC technology to ensure no off-gas 

problems. Total process time was 

quoted as 10 to 12 min. At Kimitsu, 

three RHF furnaces treat 1800 tons of 

dusts and sludges to produce 

1000 tons of DRI per day. 

In the paper 'The adaption of three 

pyro-technologles for recycling ironand 

steelmaking residues', Mr Ingo 

Both of Paul Wurth described three 

thermal based technologies for 

recycling. The use of the rotary hearth 

furnace technology Redlron was 

described earlier in the conference in 

paper by Piergiorgio Fontana. This is a 

stand-alone reduction tool that 

produces DRI, but the process can be 

combined with a smelter in the 

RedSmelt process. The Paul Wurth 

Primus® process is based on a multiple 

hearth furnace. Based on a 

conventional EAF, and using 

submerged charging, the i-Meltor 

process can be used to process dusts 

and sludges from carbon, high alloy and 

stainless steel manufacture, slag and 

sludge from the ZU industry and, under 

development, solid residues containing 

valuable metals from spent catalysts. 

One problem of the treatment of oily 

sludges and scales is the possible 

formation of dioxins and the risk of 

VOC deflagration (slow burning of 

volatile organic compounds) in the offgas 

system. To enable the treatment of 

these wastes, Paul Wurth and Lhoist 

have developed the PLD process, 

which is similar in principle to the 

Primus process except that lime is 

added to the oily mill scale and sludge 

producing a quick temperature rise that 

is followed by complete oxidation of 

the organic compounds at a 


temperature of


refractories include medium range 

castables and precast shapes, tundish 

spray and furnace gunning repair 

products. Other possible uses of 

reclaimed refractories are slag 

conditioning in EAF and ladle slag 

chemistry. 

Ms Cristina Lausin from Global 

ArcelorMittal R&D, presented the final 

paper of the session, 'Win-win 

approach between steel and ceramics 

industries'. The presentation reported 

on a project on the valorisation of 

steelmaking by-products, namely LD 

slag and BF sludge, as raw materials 

with an added value for the ceramics 

industry, specifically, structural bricks. 

The project partners were Global 

ArcelorMittal R&D, ArcelorMittal 

Environmental Department, 

ArcelorMittal by-products department 

and University of Oviedo, with 

characterisation of the bricks done by 

Cerámica La Espina. LD sludge was 

investigated as a degreasing agent 

replacement, due to its drying capacity 

from the free lime content and BF 

sludge as an organic component and 

flux, due to the Fe and high С content. 

It was noted that under Spanish 

legislation BF sludge is classified as a 

non-hazardous material, though it does 

contain 3%Zn and 48%C. At pilot scale 

it was found that up to 10% of byproducts 

could be added successfully 

to the bricks without any detriment the 

properties of the bricks. Test work, 

undertaken by a brick manufacturer, 

showed that the addition of LD slag can 

be up to 20% of the degreasing agent 

and BF sludge could substitute up 2-5- 

3%. ArcelorMittal consider that the 

recycling of BF sludge via the sinter 

strand is not viable due to its Zn content 

and its consequential detrimental effect 

on the BF process. 

Day 2, Session 3: 

environmental issues, 

alternative approaches and 

research 

Session Chairmen: Mark Sexton and 

Richard Thackray 

Session 3 started with a very thought 

provoking keynote paper from Dr Jean- 

Pierre Birat of ArcelorMittal, entitled 

'The sustainability footprint of 

steelmaking by-products'. To 

summarise this particular paper is very 

difficult and to it do full justice the- best 

way is to quote verbatim Jean-Pierre's 

conclusions (A full version of this paper 

will be published in Ironmaking and 

Steelmaking). Quote: 


'The Steel Industry is not only 

producing steel, it also delivers 

secondary raw materials to other 

sectors: 

• slags are the largest output in terms 

of volume (1/3 of the mass o¡ stoei 

produced!) 

• but there are also metal-bearing 

residues, such as home scrap, mill 

scale and dusts, some of which are 

used internally in the steel mill, 

whilst others are sold to other 

industries 

• carbon-bearing residues, like BF 

sludge. 

By- and co-products usually command 

low prices in their markets, because 

they retain the image of a waste, which 

they are not. Legislation and practice 

are slowly changing their image and the 

scarcity of raw materials adds to the 

trend, especially when this causes 

prices to increase. With higher prices, 

more preparation of the co-products is 

possible in order to turn them into true 

and sophisticated secondary raw 

materials. 

Beyond their economic value, these 

co-products have a sustainability value 

related to the fact that they avoid using 

primary raw materials and often involve 

less preparation (less process steps) in 

the client industries and, thus, exhibit a 

smaller overall ecological footprint. 

We have dealt with this issue in the 

particular case of BF slag, which is both 

a large volume example of existing 

commercial connections between the 

steel and the cement sectors and a 

clear case where this industrial ecology 

synergy can indeed bring significant 

energy savings and cuts in C02 

emissions. This is intuitive and this is 

true. It shows particularly clearly when 

one compares the two sectors as 

separate entities or as synergistic ones: 

the coupling of a large integrated steel 

mill with a large cement kiln saves 

0-24 t of C02 per ton of steel produced 

or 0-64 t per ton of cement produced. 

It is however difficult to allocate C02 

shared in this manner to any of the two 

sectors, because beyond the apparent 

win-win strategy, there are issues due 

to the fact that C02 will very soon 

command prices that may rise to very 

high levels, so high actually that the 

price of cement, and to a lesser extent 

of steel, may change radically. With this 

perspective, it is not so simple to 

choose the proper allocation method, 

especially since the method which 

seems most appropriate for doing this¿ 

life cycle analysis (LCA), is actually not 

capable of doing it in a fair manner: LCA 

has not been developed to make such 

strategic decisions. 

This is a serious methodological 

difficulty, which leads to serious 

practical-hurdles in areas where slag is 

discussed. There are several ways out 

of this conundrum: 

• in the long term, the problem will 

necessarily find a solution in line with 

the internalisation of externality cost of 

C02 in materials an energy markets 

• in the short term, it is probably naïve 

to believe that a single solution can 

be found that does not displease one 

or the other sector involved. 

Therefore, living with different low 

carbon inventories in different 

networks or communities might be a 

solution; after all, LCA has not yet 

made up its mind on other serious 

and disturbing Issues, like 

accounting for end of life or for 

materials recycling. Moreover, 

society has entered a post-modern 

world, a definition of which it is a 

world where several temporalities 

coexist; the analysis of this renewed 

complexity should not be left to soft/ 

subtle scientists, like sociologists or 

literary critics, but has to be taken on 

board in applying sustainability tools, 

when difficult issues like that of 

sustainability footprint of co-products 

come to the front 

• the 'best' allocation method, if the 

criteria for defining 'best' relates to 

how well it describes real physical 

emissions, is certainly a physical 

allocation. Weight allocations are not 

fair to the user of the co-product, 

because it is almost always of a 

lesser value than the main product. 

Price allocation is not fair either, for 

the opposite reason that it dumps 

cheap secondary raw material on the 

market. 

Going back to the planet-wide picture 

from which this paper started, it is clear 

that the collision between the 

anthroposphere and the ecosphere is 

under way; the noise and the furore of 

the clash is all around us! Climate 

Change is the most obvious of the 

consequences of this 'cosmic' event, 

but one should also be wary of the 

loss of biodiversity or of the threat to 

water resources. Since economics 

mediates between the two worlds, 

the consequence of this shock is an 

eruption of environmental issues in 

the economic sphere, the econosphere. 

This is happening slowly, but 

irreversibly, like a catastrophe movie 

shown in slow motion; a price of 

externalities is being introduced in the

system, except that the scenario is not 

yet fully written and its timeline is 

fuzzy. This introduces the kind of 

uncertainty, which the economy and 

business dislike most. 

To make things more complex, not 

only environmental externalities, but 

social ones as well are entering the 

stage. In the middle or long terms, it 

means that more synergies will 

develop between sectors, that the 

amount of waste will dwindle and that 

by-products will be used more 

extensively as secondary raw 

materials. 

The transition may be confusing as 

the set is not fully reorganised, in terms 

of tools and methodologies in 

particular, to yet let the new show run 

smoothly. 

One may also wonder at the 

distinction between products, coproducts, 

by-products, residues and 

waste, which has been introduced in 

the fields of law and regulation (the 

legislosphere or the regulatosphere?) 

to solve important international trade 

issues in an opportunistic way. Nature 

does not abide with these different 

concepts related to the anthroposphere 

and the technosphere; it might just 

touch upon the subject through the 

concept of ecotoxicity, with the 

important caveat that, of course, all 

waste is not toxic! ! All outputs from an 

industrial process have, in the long-run, 

the same fate of going back eventually 

to the environment, directly or after 

being used by consumers or by an 

industry, at some end-of-llfe or after 

one or several steps of recycling. They 

may go back in their chemical form, or 

be transformed into other compounds. 

The anthroposphere is thus giving back 

these products to the ecosphere, after 

borrowing them for a while. 

The concept of 'bio-slag' to restore 

seaweed beds in venerable coastal 

locations in Korea was introduced by Dr 

Sungkil Park of POSCO, Germany in 

the paper 'Response to coastal climate 

change by steelmaking slag'. Coral 

'bleaching' (whitening due to the death 

of algae living in symbiosis with the 

polyps) occurs when seawater 

temperature rises, especially due to 

global warming. This phenomenon is 

also known as coralline flat or 

desertification of seaweed bed and 

characterised by the disappearance of 

valuable algae such as brown . 

seaweeds, sea tangles, and sargassos 

from the rock mass of the coastal 

water and the surface of rock turning 

white due to white crustose coralline 

algae. Eventually it will reduce the 

growth of fish and shellfish populations 

that use the seaweed bed as breeding 

grounds or for feeding. On Jeju Island 

located in the South Sea of Korea, 

about 31 % of coastal fisheries round 

were found to be influenced by the 

coralline flat. Treated BOF slag has 

been used to create 179 artificial reefs 

in trials ranging from the application of 

between 5 to 25 000 tons. The slag is 

stabilised by cooling after the 

steelmaking process. The Fe content ' 

within the BOF slag promotes the 

growth algae/seaweed blooms and as a 

result there has been an increase in the 

mass of seaweed forests in the test 

areas than compared to other areas. 

This is a great result as the seaweed 

and algae act as a C02 sink, via 

photosynthesis; a sink estimated at 

0-3 t C02/t slag. The bio-slag has 

proved more effective than any other 

materials due to the calcining of the 

CaO in the BOF slag. 

The advent of hot dip galvanising or 

electrolytic galvanising of low carbon 

strip for packaging applications has had 

the consequence of an increased Zn load 

in recycled scrap. Zn evaporates during 

the steelmaking process and condenses 

in the off-gas, producing flue dusts and 

sludges rich in Zn. Mr Gerald Stubbe of 

VDEh-Betriebsforschungsinstitut 

GmbH, in a paper entitled 'Zinc and iron 

recovery from filter dust by submerged 

injection in hot metal' gave a summary of 

the sources of Zn in the recycling route, 

especially the recycling of Zn galvanised 

low carbon steel. In a relatively simple 

process being developed by VDEh- 

Betriebsforschungsinstitut GmbH and 

DK Recycling und Roheisen GmbH, Zn 

containing dusts and sludges are 

Injected into a molten iron bath held in an 

induction furnace. The dried dusts and 

sludges, including BF sludge, BOF 

sludge and zinc leaching residues are 

injected at a rate of between 8 and 

40 kg min -1 . The injectants must be 

conveyable pneumatically. By reduction 

with carbon, metallic iron and zinc is 

produced in the hot metal. The zinc 

evaporates and after reoxidation 

generates a high quality ZnO product 

dust, which is separated in the off-gas 

system. The results are a very good with 

zinc yield into a zinc oxide product >84% 

and a 66% Fe yield into the hot metal. 

In the fourth paper of session 3, 

Professor A. Saidi from Isfahan 

University of Technology presented the 

paper 'Investigation of possible usage 

of electric arc furnace dust in cement 

industry'. This work has been done 


using EAF dusts from the Mobarakeh 

Steel Company, which utilises a mainly 

DRI charge (70 to 80%) and very low 

scrap usage. Thus, EAF dusts are 

significantly löwer in Zn and Pb thantrorn 

many other EAF plants. However 

alkali content can be high in the dusts 

and because of this two separate trials 

were done; one using mixtures of the 

EAF dust and Portland cement and the 

other using mixtures of Portland 

cement and EAF dust treated to reduce 

the high alkali levels by soaking the 

dust in water. Tests done on the 

mixtures were to investigate the most 

important properties of cement, 

namely hydration heat, water 

coefficient, viscosity, initial and final 

setting time, strength development and 

leachability of heavy metals. The 

results revealed that the EAF dust 

alters characteristics of cement 

unfavourably. However, the addition of 

the water treated EAF dust was not 

detrimental and enhanced some of the 

cement's characteristics due to the low 

alkaline compounds that are 

responsible for unfavourable alternation 

of cement characteristics. Leaching 

tests also proved that heavy metals can 

be effectively removed. 

In 2009, a £60 m investment was 

undertaken at Tata Steel's Port Talbot 

Plant to collect and use internally BOS 

gas (BOSG). Already collected and used 

on-site for electricity generation, were 

coke oven gas (COG) änd BF gas (BFG). 

Following the BOSG recovery project 

electricity generation was planned 

using BFG and BOSG: and the COG to 

be used for reheating in the Hot Mill, 

thus reducing the requirement for 

purchased natural gas. Projected saving 

are £30 m pa and an estimated 

reduction in CO2 emissions of around 

3%. One drawback of using mixed 

gasses for electricity generation' is the 

variable calorific value, for example 

BFG can vary between 2-7 and 

4 MJ Nm~ 3 . In addition, with the BOS 

being a batch process there could be 

gas availability problems due to plant 

operation and schedules. In the paper 

'Dynamic support tool for optimised 

use of process gases', Mrs Zoe 

Hughes of Tata Steel Strip Products, 

UK, described the further development 

of 'Discrete Event Simulation' 

modelling, in use prior to the BOSG 

recovery project for mixing COG and 

BFG, for application of the new gas mix 

for electricity generation. The dynamic 

model, which forecasts the volume of 

process gas produced, and then 

recommends the optimum method of 

Ironmaking and Steelmaking 20.11 VOL 38 NO 7 487


use has been well received by the 

process operators. Future development 

of the model will include a modification 

to the assumed calorific value as In 

practice this has been found to be 

greater that assumed in the model. The 

main limitation of the model is that it is 

totally dependent on the BOS Plant 

schedule. The schedule must be 

always updated to reflect exactly what 

will be happening at the BOS Plant, so 

that the volume of gas into the holder 

can be calculated correctly. Problems 

that occur are changes to the schedule 

without the database being updated. 

This leads to errors in gas production 

calculations and in turn hourly flow to 

the Power Plant is incorrect and may 

result in too little or too much gas 

leaving the gasholder. 

The penultimate paper in this 

session, 'Iron and steel process wastes 

as resource' was presented by Dr R 

Vasant Kumar of Cambridge University. 

The paper described three innovative 

applications to utilising waste products. 

In laboratory experiments, 1 -5 kg of 

baled Sn coated steel scrap in a packed 

bed reactor was treated by chlorination 

in an air gas mixture (10:1 air chlorine) 

rate of 330 cm 3 min -1 . The amount 

of tin in the sample was reduced from 

an average value of 0-25to 0-04 wt-% 

after several hours. In a second example, 

the potential possibility of using 

zinc oxide bearing dust for desulphurising 

hot metal was explored; 

this being shown to be feasible 

thermodynamically. In the final 

example, the potential for recycling 

BF top gas (approximately 25%CO 

and 2%H2) was described using 

mathematical modelling. The modelling 

illustrated the need for injection of 

oxygen in the BF rather than air, i.e. 

a nitrogen-free BF. 

One of the main drivers for recycling 

wastes is to reduce costs. This was 

particularly the case when the former 

Tata Steel plant on Teesside [Teesside 

Cast Products (TCP)] was facing closure. 

One possible large source of iron 

units on site was slag skim arising 

scrap recovered from the hot metal 

desulphurisation plant. The use of such 

material was described by Dr S Millman 

in his paper, 'Internal arisings and recovered 

scrap'. At TCP approximately 

100 kt/a of iron scrap was recovered 

from hot metal desulphurisation skimmings. 

Historically, TCP had set a . 

directive that the recovered smaller 

lump size fraction of hot metal desulphurisation 

skimmings were to be 

processed to a 55% Fe yield using 


a range of screening and magnetic 

separation techniques. This meant that 

approximately 45% of high sulphur 

bearing skimming slag remained 

attached to the recovered desulphurised 

BF iron. Therefore, addition of 

this material to the BOS charge when It 

was returned to the steelmaking 

process route inevitably led to high 

sulphur pick-up levels during converter 

processing. As a consequence of this, 

plant operations management were 

always reluctant to use these materials 

except on steel qualities with high 

sulphur or no sulphur specification. 

Using a combination of drop balling 

and magnetic recovery techniques, 

the larger lump size fractions could be 

processed to an iron scrap with Fe yield 

of >90%, but at an increasing process 

cost. However, it was still perceived 

by steel plant operators that these 

materials produced high amounts of 

sulphur pick-up when used in the 

steelmaking process. Due to these 

perceptions, very little of this material 

was used in the BOF. This meant that 

large quantities of recovered iron 

arisings were not returned to the 

steelmaking process and instead, 

they were left to accumulate on site. 

In a joint project, Tata Research 

Development and Technology, Tata 

TCP and Harsco Metals, who were 

contracted to handle all slag and 

scrap processing on the TCP site, 

investigated the effect of higher yield 

recovered iron scrap on the BOF 

process, resulting sulphur levels in the 

steel and whether the increased cost of 

recovery outweighed the benefits of its 

use. The trial work illustrated that the 

extra processing of the skimming slag 

iron led to a substantial increase in its 

value-in-use, together with a significant 

financial advantage when it was subsequently 

charged to the converter as a 

substitute for merchant scrap. 

Session 4: slag utilisation and 

marketing 

Session Chairmen: Louis 

Brimacombe and Kevin Linsley 

The session was opened by Mr 

Jonathan Aylen, Manchester Institute 

of Innovation Research, with his 

keynote paper 'Instituting New 

Markets for Recovered Waste'. An 

ever increasing recovery of metals and 

slags from steelmaking production 

route wastes means that new markets 

have to be found for these recovered 

products. As many of these new markets 

do not exist, they must be created 

and developed. For example, a market 

for the recycling of aluminium beverage 

cans was created and done with 

incentives for the cans' recycling. Once 

a market is defined and before«tt carr 

be developed, the recycled product 

must be shown to meet legislation, 

have value in use, be inert and not 

detrimental to human health. End of life 

legislation means increasing quantities 

of scrap and Jonathan questioned 

whether the current scrap market was 

capable of segregating scrap from 

different sources (white goods, cars 

and construction) in order to maintain 

their value. He also questioned the 

need to re-melt, why not reuse, for 

example sections? However, any 

recycled section would need to meet all 

standards and may not be possible to 

verify these. An alternative option is 

to lease the steel and an example of 

leased piling was given, 

'If steel slags can be fully utilised, 

there is a win-win situation for both the 

environment and the steel producers as 

it maximises utilisation of a resource 

and minimises a costly waste'. This 

was an opening quote of Nick Jones 

of Harsco Metals Group Limited on his 

paper 'Utilisation of steelmaking slag - 

an environmental and sustainable 

solution'. Harsco currently handle and 

market between 8 and 10 million 

tonnes of iron and steel making slags 

per annum; of this just over 50% is 

steelmaking slag from integrated 

plants. These slags are generated 

from 50 sites in 16 countries and are 

processed and sold as products into 

more than 20 different applications. 

There have been concerns over slag 

derived products due to free lime with 

its expansion and instability. Processing 

of the slags has developed such 

that some slag products are now 

considered a better option to natural 

aggregates; more abrasive, more 

robust and no 'polishing' finish. Other 

uses of slag derived products have 

involved embankments (low value and 

high quantity slags), gabion boxes, 

percolating filters in reservoirs, landfill 

drainage layers (the shape helping this), 

cement, metallurgical additives (via 

bagging or briquetting), abrasives and 

agricultural additions. On the marketing 

side, Nick Jones stated that the potential 

for the development of markets for 

significant volumes of slag derived 

products depends primarily on the 

properties of the slag, location of the 

steel plant with respect to the location 

of both processing facilities and the 

customer and the slag volume.

In China the generation of stainless 

steel slag is in excess of 3 mt and there 

is an issue of how to use effectively, or 

dispose of the slag. In his paper, Dr 

Ruyi Wang of the Baosteel Research 

Institute, Iron and Steel Co Ltd, 

'Beneficial use of stainless steel AOD 

slag as composite cement admixture 

and its safety risks', discussed some of 

the options for the use of this type of 

slag. Intensive laboratory testing was 

done on the raw and prepared AOD 

slags followed by trials where the 

treated slag was added to mixtures 

of Portland cement. It was shown 

that stainless steel AOD slag, mainly 

Ca2.Si04 with some Cr containing 

minerals, has cement like activity so 

it can be used as composite cement 

mixture. In addition, the results also 

showed that most heavy metals in 

the stainless steel AOD slag existed 

as stable forms and consequently the 

leaching concentration is far lower than 

the limit values of the identification 

standards for hazardous waste and 

lower the limit values of national 

Chinese standards for chromium slag 

used as cement admixture. Therefore, 

the heavy metals in the stainless steel 

AOD slags posed little pollution risk and 

the stainless steel AOD slag can be 

safely used as admixture of Portland 

cement to produce composite cement. 

A new and successful method for the 

recovery of Cr from the slag during the 

stainless steelmaking process was 

reported by Mr Gerald Stubbe, VDEh- 

Betriebsforschungsinstitut GmbH. The 

paper 'New technology for recovery of 

chromium from EAF stainless steelmaking 

slag', details the cooperative 

research programme between VDEh- 

Betriebsforschungsinstitut and BGH 

Edelstahl Siegen, (with industrial plant 

trials at the BGH stainless), in which AI 

is added (injected) into the slag to 

reduce the Cr. The addition of AI also 

releases large amounts of heat, which 

decreases significantly the electric 

energy consumption for steel melting 

and enables increased productivity. 

The most commonly employed method 

of reducing chromium loss via the 

EAF slag is through the addition of 

ferrosilicon (FeSi). The FeSi usually 

added as reducing agent in a balanced 

quantity when the furnace is charged, 

but a disadvantage of the slag reduction 

treatment by FeSi is the often difficult 

dosage and the influence of the reaction 

product Si02 on the basicity of 

the slag. This requires increased lime 

addition in order to maintain the 

slag basicity to the required level of 

approximately 1 -3 to 1 -7 and in this way 

prevent excessive refractory attack by 

the slag. An alternative reductant is 

carbon or calcium carbide, but the Cr 

recovery from the EAF stainless steel 

making slag is often poor.The alumi-nium 

may be added as secondary raw 

material by injection in the form of 

mechanically processed granulated 

metal and in this way the overall 

primary energy input and the raw 

material costs are minimised. Quoted 

improvements to the EAF process 

for stainless steelmaking were a 

chromium recovery yield from the 

slag of up to 87%, electric energy 

consumption reduced by about 10% 

and a decreased power-on time of 

about 17%. 

In the paper 'Long term stability of 

steel slags from EAF processes', Dr 

Caisa Samuelsson of Lulea University 

presented interesting data on the 

stability of recycled steelmaking slag 

used for road construction. Over a 

24 month period two different recycled 

EAF slags were monitored for leaching 

and change to its mineralogy using 

SEM, XRD and a standard test for 

leaching. The pH and the conductivity 

decreased with time for all samples. 

The leaching of calcium, chromium and 

aluminium decreased with time whilst 

the leaching of magnesium increased. 

CaC03 formed on slag surfaces as 

calcium rich minerals reacted with 

moisture and C02 from the air. 

The final paper of the conference, 

'Dry slag granulation - the environmentally 

friendly way to making 

cement', was presented by Mr Ian 

McDonald of Siemens VAI Metals 

Technologies Ltd. The traditional 

method for processing BF slag is wet 

granulation where the liquid slag is 

quenched quickly in a granulation plant 

using large quantities of water. The 

fine grained, amorphous and very wet 

product is known as 'slag sand'. Due 

to the frozen crystallisation energy, 

the slag sand when ground to cement 

fines, form hydration products in 

conjunction with water that correspond 

to the hydration products of Portland 

cement clinker, the main component 

of Portland cement. Thus the key 

prerequisite for the use of slag sand 

as a binding agent in the building 

material industry is satisfied. Despite 

mechanical dewatering, 10 to 12% 

moisture remains in the slag sand, thus 

drying is required. The glass content of 

the slag sand (target >95%) is the key 

parameter for its reactivity and has a 

direct impact on the strength of the 


cements and concretes. However, the 

required glass content can only be 

achieved by sudden cooling below 

the transformation temperature of 

approximately 900°C. Due-fo the less 

efficient cooling mechanism of waterfree 

quenching, the dry process is 

technically more challenging than 

conventional water based granulation. 

Dry granulation does produce a larger 

sieve size product, but grinding times 

are with industry standards. Prior to its 

mothballing, the BF at TCP utilised a dry 

granulation process. The substitution of 

cement clinker by BF slag sand is an 

attractive economic alternative for the 

cement industry, because it reduces 

high energy costs and reduces C02 

emissions. Approximately 1 ton of C02 

can be saved for each tonne of clinker 

substituted by slag sand because not 

only is primary energy saved, but also 

the release of the C02 bound chemically 

in the limestone is avoided. Dry 

granulation requires no subsequent 

drying of the slag sand and this leads to 

a C02 reduction of roughly 30 kg/t in 

comparison with wet process. Given 

global production of approximately 

210 mt of slag sand (2007), this is 

equivalent to a potential C02 reduction 

of over 6-3 mta. 

Discussion sessions 

These took place at the end of each 

group of papers and were generally 

of the question and answer type, 

clarifying points in the presented 

papers. However, there were some 

interesting discussions worthy of 

summary. 

What is a waste? The Oxford English 

Dictionary quotes, 'superfluous, leftover, 

no longer serving a purpose', and 

thus this is a simple definition. As the 

conference illustrated, what once 

was a waste and dumped now has 

some residual value, but only whilst it 

contains some value such as iron units, 

or can be transformed into a useful byproduct. 

At the regulatory level, the 

definition of the terms 'Waste' and 'Byproduct' 

are exceedingly complex and 

vary from country to country. One 

Swedish delegate stated that waste land 

by-products require careful definition, as 

in Sweden, there has to be careful use 

of the definition 'by-products'. The third 

speaker of session 1, Daniel Devid, 

stated that a waste product goes out 

from the steel industry for disposal, 

whereas a by-product is used as a 

product in the industry or marketed 

externally. One delegate added that 

there needed to be more stringent 

Ironmaking and Steelmaking 20.11 VOL 38 NO 7 487


criteria assigned to by-products, in that 

they must be fit-for-purpose, have 

positive market value and not be 

detrimental to human health. Another 

delegate stated that all waste arising byproducts 

must have REACH registration 

(European Union regulation of 2007 - 

'Registration, evaluation, authorisation 

and registration of chemicals'). It 

appears that many at the conference are 

aware of the regulations and legislations, 

especially, when the waste and/or byproducts 

leave site, but unclear as to 

how it affects the in-house use of say 

recovered metalloid units. 

The 'value' of an iron and/or steel 

scrap generated considerable discussion. 

Dr Millman explained that the 

market price for scrap did not always 

reflect its value in use. In fact, there 

could be substantial differences 

between the market price and the 

relative value that individual scrap types 

bring to the process. It is the latter that 

needs to be considered for an individual 

process route, as this will take account 

of gas, flux and energy usage, iron unit 

processing costs and resulting steel 

residual levels. Following Dr Brooks' 

keynote paper, one delegate asked 

why there was so much emphasis on 

re-melting prime scrap, rather than reworking, 

the example given being rails. 

Jonathan Aylen continued the debate 

with his example of the re-use of 

sections. For rail steels, melting is the 

preferred option because it is a high 

value, consistent and low residual 

charge material. However, in this area 

of recycling, governance and fit-forpurpose 

are issues. Should we be 

serious about Jonathan Aylen's 


suggestion of stopping selling steel and 

just rent it out on lease and then 

buyback at the end of its useful life? 

Jonathan does not believe so, but, we 

should talk to bankers and financers 

about leasing and buyback ••- — " 

arrangements and other new 

innovative ways of reusing and 

recycling the steel we have. On the 

issues of scrap quality, Jean-Pierre 

Birat commented that about 15 years 

ago, the EU set out standards and 

created close cooperation between 

scrap buyers and sellers and after 10 

years, scrap standards were well 

controlled and met requirements. 

However, interest was lost as people 

changed and now, scrap controls are 

back to where they were. If there is an 

interest in improving scrap quality then 

maybe we should develop a two tier 

market where we would pay a 

premium price for guaranteed high 

quality scrap and a nominal price for 

normal quality. 

'How can people's perceptions of 

waste be changed?' was a question 

asked at the very outset of the 

conference. The answers from both 

authors and delegates can be 

summarised in three statements: 

• demonstrate the benefits that are 

available (economic and environmental) 

to the whole work force 

• underlining the 'real cost' of failure to 

meet both in-house and Legislative 

requirements 

• educating to a can do/must do 

attitude. 

As illustrated in a number of the papers, 

one of the good things to come out of 

the recession was a stronger emphasis 

on waste reduction and the real costs 

associated with waste. 

Summary 

This~very enjoyable and informative 

conference illustrated that steel 

companies are taking the issue of 

waste seriously. On the one hand, 

this is being driven through punitive 

tax penalties for disposing of waste, 

limited, and decreasing, landfill 

availability, and legislation, whereas, 

on the other hand, the companies 

are recycling to reduce costs by 

substituting primary raw materials 

by recycled iron and other high value 

metal units and to reduce energy 

consumption. This is being supported 

by technology and knowhow provided 

by research centres and Universities, 

commercial materials handling and 

recycling companies and plant builders. 

Environmental improvements also 

act as a driver, no more so than C02 

reductions. It was interesting to note 

the continued development of the most 

mature usage of steelmaking wastes, 

that of the recycling of BF, BOF and 

EAF slags, with their by-products being 

used in more critical applications. 

Some papers from the conference 

will be published in full in Ironmaking 

and Steelmaking. The journal is also 

looking for more papers on the topics 

covered at the conference; so if you 

wish please submit a manuscript (this 

will be subject to the normal peer 

review). Further information about the 

journal is available at 

www.maney.co.uk/journals/irs.

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