global slag magazine march 2008

gl bal slag MAGAZINE

Global slag news Adana Çimento Aumund 1st National Iranian EAF Slag Conference Review Borate slag stabilisation

MARCH 2008

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4 Global Slag News

12 Evaluation of the technical and economical aspects of

using type type CEM III cements in concrete

Researchers from Adana Çimento in Turkey compare and

contrast the relative strengths of CEM I cement with CEM III slag

cements.

17 Effi cient and reliable handling of GBFS and GGBFS at

grinding plants and cement works

Barry Woodbine of Aumund gives a broad overview of the range

of handling, conveying and storage options specially designed

for GBFS and GGBFS.

21 Global Cement Directory 07-08 Order Form

25 Borate stabilisation of air-cooled slags

The preventation of steel slag disintegration by borate addi-

tion has long been known. Here, Dirk Durinck and colleagues

from Leuven, Belgium, attempt to understand the underlying

mineralogical basis for this eff ect.

31 1st National Iranian EAF Slag Conference 2008 Review

Dr Hadi Sadrpour reports from Isfahan, Iran, and provides an

interesting review of the conference whose main themes were

processing, recycling and application of EAF slag.

34 Global Slag Magazine subscription form

35 Global Slag Magazine Advertiser Index and Reader

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CONTENTS MARCH2008

This month’s front cover...

The winner of the Global Slag Magazine Photo competition

is Steve Smith, a business improvement manager for H J

Enthoven & Sons, Darley Dale, Derbyshire, UK.

The winning entry is on the subject of furnace tapping, and

was taken in August 2007 whilst observing furnace opera-

tions at the Darley Dale lead smelter.

Mr Smith wins an iPod, in addition to his winning picture

appearing on the front cover of this month’s magazine.

A future edition of Global Slag Magazine will feature a photo

montage of the runner’s up, plus a selection of some of the

best entries in this year’s competition. Don’t miss it!



MARCH 2008

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NEWS

India/Netherlands: Tata Steel and Corus, which recently accel-erated their integration plan, have already started discovering the benefi ts in several areas of research and steel-making. Apart from the 15 R&D projects that the two sides have identifi ed for fast-track implementation, there are several ‘harvesting projects’ which could be exploited commercially by either side at short notice. Around 50% of the projects being exchanged by the two sides are said to be ‘harvesting’ projects, where each side puts the other’s intellectual property rights (IPR) directly into use for production.

Tata Steel chief technology offi cer T Venugopalan said, “It [Corus] has done something, and then we pick it up from there. We have also passed on all our developments, including IPRs and patents for whatever projects we have done in recent times to Corus.” Tata Steel has separate R&D and technology groups whereas Corus has a combined research, development and technology (RD&T) team.

“The integration is going quite well”, continued Venugopa-lan. Among several projects ready for Corus to take on is related

to ‘hydrogen harvesting’. Tata Steel has developed a process of cracking water into hydrogen and oxygen by way of sprinkling water on hot slag. While the heat in the slag will otherwise have gone to waste, hydrogen released in the process can now be collected for future use as fuel. “We started doing the project and had made some progress; now Corus also has taken up the project,” added the Tata Steel CTO. Likewise, Tata Steel has pio-neered the manufacture of a contemporary grade high-strength steel, which it calls HS-800. Corus has also tested HS-800 and declared it to be ‘far superior’ to most of the 800 tensile strength grades it has been producing. Having received all the know-how required to produce HS-800, Corus would now have to develop it and put it in the marketplace.

“They would fi rst of all test the market by producing a small quantity,” said Venugopalan. Similarly, Corus has advanced tech-nology when it comes to ‘metallic fuel tank’ grade steel. Tata Steel is going to develop the ‘fuel tank’ grade steel in India, using the knowledge available with Corus.

Tata and Corus partnership in rude health

Teluchamert works hard to clean up its act

Russia: In 2007 Tulachermet invested more than Euro4.5m in introducing nature-conservation meas-ures and low-waste technologies. The majority of this expenditure was spent on preparing for the planned renovation and repair of its blast-furnaces, scheduled for 2009.

Euro1.7m was spent on building the initial stages of a water rotation cycling system and gas purifi cation system at its blast-furnace No. 1. For the mounting of foundations for the electrostatic cleaners of the aspira-tion system inside the cast house and of the furance’s bin trestle, a total of Euro246,300 was spent. These im-provements led to a 500t decrease in the atmospheric release of contaminants compared to 2006.

One of Tulachermet’s priorities is in the area of waste recycling in order to protect the environment. In 2007, 215,000t of sludge was recycled, amounting to Euro1.1m of expenditure.

4 globalglobalslagslag MAGAZINE March 2008

Germano-Russian partnership aids the use of slag cement

Germany: KHD Humboldt Wedag Int Ltd announced that it has won contracts valued at approximately Euro$119m from two Russian ce-ment producers to develop new production lines. One of the new facilities is designed to use slag located near the building site as a component of the feedstock for the cement to be produced in the plant, thereby contributing to the local environmental remediation eff ort.

Under the fi rst contract, valued at US$56m, KHD will provide a 3000t per day production facility for Jugpk Novotoizk. The KHD por-tion of this contract includes the raw meal grinding section with KHD roller press RP 13-170/140; a pyro-processing section consisting of a fi ve-stage preheater with Pyroclon® calciner; Pyrorapid rotary kiln with Pyro-JRT burner; a Pyrofl oor clinker cooler PFC with clinker crusher; and the cement grinding section with a 0.5mx14.5m KHD ball mill with Sepmaster, type SKS-Z 3250.

Under the second contract, valued at US$63m, KHD will design, build and outfi t a new cement production line for OAO Ulanovskshifer. Ulanovskshifer is a subsidiary of Mordowcement, another major Rus-sian cement producer.

475,000t/y high-value Ti slag from ilmenite in Madagascar

Vietnam: Rio Tinto Plc has set aside US$1bn for a greenfi eld ilmenite operation in Madagascar and upgrade of associated processing facilities in Canada.

Phase one will involve ilmenite being smelted at the Canadian facility to produce 475,000t/y of a high grade (91% TiO2 content) chloride slag by 2012. Phase two and three could ultimately sup-port ilmenite output of 2Mt/y.

The news follows Rio Tinto’s iron and titanium division posting 2007 earnings of US$164m, a US$12m improvement compared to 2006. Demand for TiO2 chloride feedstock and zircon prod-ucts, and rising prices are the drivers of the results.

Construction of the site is underway, after a revision of the

budget in 2007. Rio Tinto are expecting the phase one produc-tion of 750,000t/y of ilmenite from the project by the end-2008.

MadagascarMadagascar

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NEWS

Ukraine: Metallurgical mill Dniprospet-sstal (Zaporizhia) intends to fully process slags on its waste sector in Serednia Balka (Volnianskyi district, Zaporizhia region) before 2013. According to the company’s board chairman, Daniel Valk, Dniprospet-sstal invested Euro3.3m into equipment made by US Amcom, which processes 6000t of slag per day. The installation makes it possible to produce scrap, or steel remains in whose production slag

was used. Any slag remaining after processing is used for the construction of roads. The plant also invested Euro1.3m in cleaning the riverbed of Nahirna Kanava, as required by environmental protection measures.

In 2007 Dniprospetsstal intended to launch a complex for the processing of slag residuals in Serednia Balka gorge. Serednia Zaporizhia is where the Zaporizh-stal metallurgical plant, Dniprospetsstal

metallurgical plant, Zaporizhia ferroalloy plant, and Zaporizhkoks coke plant dump their industrial waste as landfi ll.

Dniprospetsstal specialises in the production of special types of steels, including stainless steel, tool steel, high-speed steel, roller-bearing steel, construction steel. It also produces high-temperature nickel-based alloys.

Colombian slag workers demand extra pay and benefi ts in strike action

Colombia: Nickel production at Cerro Matoso SA in northern Colombia halted on 27 February 2008 when workers went on strike after contract talks broke down. All 1060 permanent workers and 2500 indirect workers are on strike, which may last up to 60 days under Colombian law, said Carlos Barroso, vice president of the Sintracerromatoso union and a mem-ber of the negotiating team.

The union is demanding that Cerro Matoso employs more contract workers, particularly those working under short-term contracts in the slag processing plant that began op-erating in January 2008. “The workers in the slag plant have contracts for either six or 12 months,” Barroso said. Sintracerromatoso is seeking a two-year contract for all of the operation’s unionized workers.

Workers, who earn an average of US$1085 a month, also have de-manded an 11% pay increase and improved health and education ben-efi ts in order to share in the profi ts generated by the nickel operation. Cerro Matoso has off ered an 8% pay rise. “The average nickel price in 2007 was US$20 a pound, and the cost of production was US$1.50 a pound,” Barroso said.

Cerro Matoso, owned by Anglo-Australian resources group BHP Billiton, produced 51,270t of nickel in 2007, and is studying whether to add a nickel leach plant to increase pro-duction. Company executives have declined to comment on the strike action.

Old slag heaps may be the cause of alleged lead poisoning in Mount Isa region

Australia: Controversial allegations of toxic lead levels in Mount Isa’s river soil have been rejected by mining giant Xstrata. The claims of lead-levels hundreds of times higher than government limits were made in the national media by environmental scientist Mark Taylor, of Sydney’s Macquarie University.

However, research from the University of Queensland’s Centre of Mined Land Reha-bilitation (CMLR) found a 70kg adult would have to dine daily on 2kg of dirt from certain hotspots in the Leichhardt River to be at risk of lead poisoning. A 14kg child would have to eat 400g everyday to get lead poisoning. CMLR samples from the local skate park, Kruttschnitt Oval and swimming pool, as well as downstream in the Leichhardt River show low levels of lead.

Lead in blood testing for children in the town was ordered after a senior Environ-mental Protection Agency offi cial claimed in 2006 the agency had failed to introduce air quality monitoring in Mount Isa because of commercial considerations with Xstrata. More than 400 children have been tested over about 12 months to determine the risk of lead exposure.

Tropical Population Health Unit director of Environmental Health John Piispanen said the report into the lead in blood sampling would be released by June 2008. The Tropical Population Health Unit has also run a public campaign reminding parents to wash their children’s hands after playing in the dirt and to wash fruit before eating it.

Xstrata will fi nish lead clean-up work in the Leichhardt River by May 2008. Remedia-tion of the river is expected to take two weeks and several areas of dirt with high lead levels, including one near the Grace St Bridge, will be dug out and the hole will be topped up with clean fi ll. The riverbed clean-up had been delayed by the wet season. Follow-up sampling and fi nal surveys of landform will also be done by the University of Queensland scientists supervised by Associate Professor Barry Noller.

Dr Taylor maintains his fi ndings show inadvertent metal run-off from the mine site catchment and the erosion of historical sources such as old slag heaps or tailings ponds. The original clean-up of the city was done by the former- MIM Holdings with Mount Isa City Council and the Queensland Government CHEM Unit between 1991 and 1994 on historical contamination in the river. The historical contamination was caused by mining activities and practices during the 1940s and 1950s.

Dr Taylor began his research in Mount Isa in 1991. His fi nding on metal toxicity in Mount Isa’s water and soil are expected to be published in the journal Marine and Freshwater Research. CMLR researchers are also investigating the mine’s emissions into the city’s water and air. The PhD study will look at how lead become present in the community, including its natural occurrence in the area.

Ukraine’s Dniprospetsstal intent on recycling slag

globalglobalslagslag MAGAZINE MAGAZINE March 2008March 2008 5

Pellets of leadPellets of lead

NEWS

6 globalslag MAGAZINE March 2008

News in Brief

China: Baosteel Group Corporation announced that for the fi rst time it has exported its new tech-nology for slag processing using rotary cylinders. Two rotary cylinders were recently transported to India’s JSW Steel. The exchange on slag process-ing technology between the two companies began in 2006 with JSW signing the technology purchase agreement in April 2007.

Brazil/Bulgaria/Finland: Finnish fi rm Outotec has been awarded two large minerals processing technology orders from Bulgaria and Brazil. The total value of the two contracts is over Euro21m.

Mirabela Mineração do Brasil has ordered a large technology package from Outotec for its new nickel sulphide concentrator in Brazil. Cumerio Med has ordered an expansion of its slag concentrator at the Pirdop copper smelter in Bulgaria.

Vietnam: Central Thua Thien-Hue province has given permission for a local company to inject US$6.37m in building a titanium slag factory in Phu Loc district. The 10,000t/y plant will be op-erational in April 2009, said Director Vo Quang Hien of the Thua Thien-Hue Minerals Company, the project investor. This will be the second tita-nium slag factory to be built in Vietnam after fi rst one located in central Binh Dinh province.

According to a survey, Thua Thien-Hue prov-ince has a deposit of around 7Mt of titanium ore, accounting for one-quarter of the country’s total reserves. The province plans to exploit titanium on an area of 618 hectares with the output ex-pected to reach 365,200t in the next few years.

India: Ajanta Limited proposes to set up a 3Mt/y slag cement facility at Kachchh in Gujarat at an investment of US$372m. It will include a 200MW coal-based power unit. Land acquisition is in progress.

US: A hearing has been set for 20 March 2008 in Franklin Furnace, Ohio, for public hearing on the subject of a proposed steel mill to be built by Russia’s OJSC Magnitogorsk Iron & Steel Works (MMK) in nearby Haverhill, Ohio. The plant would consist of melting, casting and fi nishing operations and would include processes such as continuous casting, vacuum degassing, acid pickling, hot- and cold-forming, hot-dip galvanis-ing and slag processing.

US: Tube City IMS LLC has announced that Hank Wilson has been appointed to the new position of Vice President - North American Sales and Business Development. He will work in the com-pany’s offi ces in Birmingham, Alabama.

Mercury emissions to be cut by Ash Grove Cement

US: The largest source of mercury pollution in Oregon could be cut by more than half by 2011 under a deal with state regulators. Ash Grove Cement near Baker City has reached a voluntary deal with regulators to cut its mercury emissions by 75% within 3 years.

The agreement with the Oregon Department of Environmental Quality requires the Overland Park-based company, which got help from North Dakota researchers, to install controls within two years for a cost estimated between US$15-20m. If the agreement is approved as expected, the com-pany and regulators say the cement plant would be the fi rst in the US with a specifi c deal to cut emissions of mercury, a potent toxic substance that accumulates in fi sh and can cause nervous system disorders in humans. Nei-ther the US Environmental Protection Agency (EPA) nor Oregon law requires cement plants to reduce mercury emissions, but the EPA is being sued over the issue and eventually could issue limits.

Mark Riskedahl, director of the Northwest Environmental Defense Center, was part of an advisory committee that recommended the Ash Grove deal. Riskedahl’s center frequently sues polluters who resist installing emissions controls. “This process is so diff erent,” Riskedahl said. “There’s no regulation mandating it, and nobody threatened them with litigation. It was of their own accord.” He said that Ash Grove would be the fi rst cement plant to use a carbon injection control system to capture mercury.

Ash Grove has set a mercury reduction goal of 85%, with a fallback target of 75%. If its capture rate falls below 75% the company could face civil penal-ties unless it can show the technology cannot achieve the reduction and applies for a lower reduction standard.

Ash Grove mines limestone, slate and clay from a quarry near its plant at Durkee, southeast of Baker City. It bakes those ingredients and iron slag in a kiln at temperatures approaching 3°C, producing about 1Mt of clinker, a precursor to cement, each year. The process sends gas containing mercury up the kiln’s 290ft-tall main smokestack. Levels vary, but the limestone is unusually high in naturally occurring mercury, the company says, and the plant emits about 2500 pounds of mercury a year. The level puts Ash Grove among the top US mercury polluters and more than 10 times the mercury emissions from Portland General Electric’s coal-fi red power plant in Board-man.

In Spring 2007, Ash Grove brought in experts from the University of North Dakota’s Energy and Environmental Research Center to try out an activated carbon control system. The center injected particles of activated carbon into the emission stream. The mercury attached to the carbon, which was then captured in a series of fi lters. The tests concluded that the technology, already used in coal power plants, would capture 65-90% of mercury emis-sions, depending on operating conditions.

Mercurial mercuryMercurial mercury

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Blast furnace slag · ground by the MPS 5600 BC vertical roller mill at Lafarge-Shui On's Chongqing works, China2006-12-21 · 10:30 local time

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Russia: An oxygen converter run by Nizhniy Tagil Iron and Steel Works is expected to reach its full capacity in 2008 thanks to the reconstruction of the oxygen converter shop, the spokesperson for Evraz Group said. Throughout the year, the company is plan-ning to upgrade two more steel-smelting units.

The fi rst one will probably be shut down for reconstruction as early as March 2008, while the equipment for the second

converter is already being shipped by European and Russian machine-building enterprises. The improved converters will be fi tted with a bottom blowing system and the slag fi lter unit that will remove the harmful impurities from the metal during pour-ing. This project will allow the company to produce more steel as well as minimise environmental hazards.

Oxygen converter upgrade by Evraz Group

Canada: It could take years to determine who is responsible for cleaning up the 26bn pounds of hazardous waste from a Canadian smelter that turned the reservoir behind eastern Washington’s Grand Coulee Dam into an environmental mess. The decision could have even broader implications for other emissions that cross national borders.

For nearly a century, slag from the Canadian smelter in Trail, British Columbia, 10 miles north of the US/Canadian border, was disposed of in the Columbia River. Gradually, heavy metals such as arsenic, cadmium, mercury, copper, lead and zinc leached out of the slag and accumulated in Lake Roosevelt, the 150-mile-long reservoir behind the dam.

Offi cials in the US Environmental Protection Agency’s (EPA)regional offi ce in Seattle tried to hold the owner of the smelter, Teck Cominco Metals Ltd, responsible. So far, US courts have agreed. But EPA and Justice Department lawyers in Washington DC have decided to rescind the EPA’s order, instead negotiating an agreement with Teck.

Administration offi cials deny there was any political interfer-ence, saying their motivation in negotiating the agreement was

to resolve a complicated environmental situation, not to pre-empt an adverse legal decision.

Under the agreement, Teck will set aside US$20m to pay for a voluntary study of the Lake Roosevelt contamination. In a statement sent by e-mail, the EPA said the agreement was “fully enforceable,” consistent with Superfund “models and poli-cies” and noted the agency retained full oversight authority.

Critics argue the agreement is virtu-ally unenforceable, riddled with loop-holes, could delay a clean-up for years and ultimately could allow the company to dodge its cleanup liabilities.

Canadian/US smelter pollution row rumbles on...

Slag cement the subject of a joint venture in India

India: The Steel Authority of India (SAIL) has signed a share-holder’s agreement with Jaypee Associates (JAL) to form a joint venture company for manufacturing cement at Bokaro. The deal is SAIL’s second joint venture for cement manufacturing, and is part of SAIL’s plans to diversify into cement production in a phased manner. The plant at Bokaro will be up and running in two years at an estimated cost of US$100.5m. It will manu-facture cement using blast furnace slag poduced at the Bokaro Steel Plant.

The plant, which will be run by a new company – Bokaro Jay-pee Cement (BJCL) – will have a capacity of 2.1Mt/y. The relative participation by the two partners, JAL and SAIL, will be in the ratio of 74:26 respectively. The initial authorised paid-up capital of the company will be US$12.4m.

SAIL is also exploring the formation of a similar joint venture for the utilisation of slag generated at the Rourkela steel plant. The search for a suitable partner is currently underway.

SAIL’s fi rst joint-venture cement company, Bhilai Jaypee Cement, began in April 2007 and involved setting up cement plants at Satna in Madhya Pradesh and Bhilai in Chhattisgarh. This plant, to be commissioned in 2010, will produce and mar-ket more than 2Mt/y of Portland slag cement.

Multiserv awarded three lucrative contracts

US: Harsco’s MultiServ mill services division has been awarded 10-year contract extensions at two steel plants that are ex-pected to generate more than US$75m in new revenue over the lives of the contracts. At the Nucor-Yamato sections mill in Arkansas, MultiServ will expand its operations to include on-site transport of ladles to the mill’s new strip casting facility, which is currently under construction.

MultiServ also received a contract extension at the Corus IJmuiden works in the Netherlands. In tandem with the sheet mill’s increased output plans, MultiServ’s responsibilities will include further development of its on-site slag handling and processing systems in concert with the Netherlands’ strin-gent environmental regulations. MultiServ will also use new Harsco investments in technology and equipment, enabling it to segregate slag by quality and type, thereby maximising its value to external markets.

In other news, MultiServ mill services division has been awarded a new, nine-year contract in Belgium from Arce-lorMittal’s ALZ Genk plant. The company said the contract is expected to generate new service revenues in excess of US$100m over its term. The agreement allows MultiServ to immediately assume on-site responsibilities for managing ALZ Genk’s complete scrap yard and slab yard operations.

Murray MemorialMurray Memorialbridge over Lake Washingtonbridge over Lake Washington

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NEWS


US: The government of India is likely to increase the import duty on ferro- and noble alloys from 5% to 7.5% to protect the do-mestic industry. The government expects large scale dumping of ferro and noble alloys from China, South Africa and Ukraine. Im-ports of ferro alloys have increased from US$65.3m in 2003-2004

to US$173.7m in 2006-2007. The Indian Ferro Alloy Producers’ Association has asked the Government to remove excise duty on manganese slag. The association has demanded zero import duty on petcoke with low ash and phosphorus content.

Indian government set to raise imports on metal slags in a bid to help the local market

Slag leak at Polokwane causes a head ache for Anglo PlatinumSouth Africa: Anglo Platinum announced that a minor slag run-out occurred just before 14.00 on Wednesday 13 February 2008 at its Polokwane smelter in Limpopo province. The smelter has been shut down and a detailed examination has commenced.

The slag caused damage to ancillary electrical equipment adjacent to the furnace. Repair work has commenced on this equip-ment and is expected to be completed in 4-6 weeks. While the extent of the damage to the furnace has yet to be fully quantifi ed early indications are that remedial work necessary to address the cause of the slag run-out will take less time than the electrical repairs.

Due to Anglo Platinum’s current excess smelting and refi ning capacity the 2008 forecast output of 2.4M ounces of refi ned platinum remains as announced on 11 Febru-ary 2008. This fi gure is inclusive of the impact of the 90% electricity constraint.

New deal adds value to precious metal slagUK: Weatherly International PLC said it is to sell its blast furnace and reverb slag dumps to Emerging Metals Ltd (EML) for a total of about Euro7.4m, payable in cash, shares and options in EML. Under the deal, Weatherly could emerge as a signifi cant shareholder in EML, which specialises in the extraction and marketing of minor metals important to new technology applications.

For completion of the deal, EML must list on a recognised exchange and complete a feasibility study to successfully reprocess the slag dumps, which are rich in zinc, gallium and other minor metals, within two years or ownership will revert back to Weatherly. Chief executive Rod Webster said the divest-ment of the furnace slag dumps is in line with Weatherly’s continuing strategy to maximise the value of non-core assets within the busi-ness.

The company added that this sale is un-related to an earlier deal with AIC, which is looking to reprocess the Tsumeb tailings dam and remains on schedule to construct a pilot plant during the second quarter of 2008.

Germany: Which feeder is best for which bulk material? In order to pro-vide customers with accurate answers to this question, Schenck Process GmbH is now off ering tests at its new, modern test centre in Darmstadt that are based on real life situations. Schenck invited its customers to the centre’s offi cial opening on 27 Feb-ruary 2008. More than 100 people attended the event to learn more about what the new centre has to off er. Just like at a trade fair, the event enabled them to view several highlights under one roof. More test rigs and an improved level of automation mean that the test centre can now run even more accurate tests, all very closely based on actual process-ing circumstances.

Just like real life tests in the four test labs can be run in paral-lel without impacting negatively on one another. Three of the test labs feature diff erent equipment for fi lling the feeders with bulk bags or pneu-matic feeding and complete cycle feeding. The fourth lab can be heated in a way that simulates diff erent am-bient conditions and can simulate the environments of hot climates. All this means that the test processes undertaken are very simple to run. For example, the centre includes:

Separate dust separation;• Separate preparation for tests in • the powder area;The test bulk material used being • stored locally;Liquid cleaning of dirty feeders and • equipment in the feeder wash with dirty water collection pan;Body and eye wash units that sat-• isfy the latest safety standards.

Customers can also benefi t from the test tower where bulk material can be supplied directly from the street. This features three diff erent bulk material test areas:

A material circuit with pneumatic • cycle feeding for dust or carbon dust with Multicor® S40;A granulate test area with Multist-• ream®;A Multidos® test area with Multi-• dos®.

Schenck Process opens new test centre

Various views of the Schenck test centreVarious views of the Schenck test centre

NEWS


JSW Steel group sets up cement plant to make use of slagIndia: Sajjan Jindal-owned JSW Steel Group plans to set up a 3Mt cement plant at Salboniin in West Bengal. The company has already decided to develop a 10Mt integrated steel plant with an investment of US$860m at the same place. JSW Bengal managing director Mr Biswadip Gupta, said: “JSW Bengal will construct the cement plant prior to the steel plant as part of the project.”

“As per the environmental clearance for the project we cannot throw any solid waste out of project area. To utilise the slag of the proposed steel plant we have decided to set up the cement plant,” Mr Gupta added.

The cement plant would become operational before the steel plant and would be fed with slag from other sources as long as the steel plant does not start operation. Mr Gupta could not give the exact project cost, saying it would not be less than Rs500 crore and depend on the technol-ogy used.

Highveld performs well in 2007

South Africa: Highveld Steel and Vanadium said profi t for 2007 increased by 73% from US$132m to US£228m. Headline earnings climbed 41% in the 12 months to the end of December 2007, boosted by the strong South African steel market. Turnover rose 9% from US$843m in 2006 to US$914m in 2007.

The crisis in the South African power industry and water supply problems meant Highveld lost about 2000t of fi nished rolled steel production in the second half of 2007. By the end of January 2008 it had lost another 150h of production, equivalent to approximately 8500t, because of renewed power shortages in the country.

On a more positive note, Highveld said the full commissioning of the third open slag bath furnace early in 2008 will improve effi ciencies in both steel and vanadium slag production. Highveld said it ex-pects the demand for steel to remain strong, both in the local and niche export markets. Vanadium prices and volumes are expected to strengthen.

In the medium term, the company hopes to achieve its goal of increasing steel output to more than 1Mt/y and to increase the production of vana-dium-bearing slag. “Investment in the fl at products mill will also contribute to improved product mix,” it said. Evraz, which is one of Russia’s largest steelmak-ers, became the controlling shareholder in Highveld Steel in May 2007.

Azovstal plans to export its slagUkraine: The Azovstal metallurgical plant is interested in exporting its slag, according to the plant director general Dmytro Livshits. Mr Livshits said: “Currently, a number of talks are being held with Lebanon, Russia, and the UAE on supplies of our slag.” He also said that success of one of the projects will allow Azovstal to avoid construction of new slag storage facility.

Livshits commented on the increase of slag supplies to consumers in the domestic market and said that it is linked with growth of construction in Ukraine. Azovstal ended 2006 with a net profi t of US$219m, increasing net revenues by 1.1% or US$27m, compared to 2005.

DIARY DATESFor further information and links, see www.propubs.com

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globalslag MAGAZINE


Oktay Kutlu, Meriç Demiriz OYAK Group Adana Cement Industry, İskenderun Plant

Evaluation of the technical and economical aspects of using type CEM III cements in concrete

Researchers at Adana Çimento in Turkey have undertaken a thorough investigation into the relative strengths of concretes made with normal Portland cement (CEM I) compares to those derived from GGBFS-based ce-ments (CEM III). The results of this investigation are presented in this paper, with the central conclusion being that concretes made with cements containing up to 65% by weight of GGBFS, have improved strength, lower unit costs and a more benign environmental footprint compared with concretes made from CEM I cements.


Cements containing ground granulated blast fur-nace slag (GGBFS) are usually manufactured in ce-

ment plants close to steel mills and are commonly used all over the world. Such cements contribute eff ectively to the high durability of concretes having good strength and water tightness. Th is paper summarises and com-pares the results of tests conducted on concretes con-taining local cements produced at Adana Cement Co.

Concretes made with CEM III/A 42.5 N type cementwere compared with those obtained with CEM II/B-S 42.5 R and CEM I 42.5 R types of cement. Th e compari-sons involved 2, 7, 28 day-compressive strengths, water requirement, chloride and water penetration proper-ties. In addition, similar tests were performed on self compacting concretes (SCC) produced with the same cements.

According to the results, concretes made with CEMIII/A 42.5 N cement had comparable 28 day strengths with concretes containing the other two cements. CEM III/A 42.5 N concretes were more resistant to water and chloride penetration and more economical based on unit strength. As well as containing less clinker, they are ‘environmentally friendly’.

IntroductionTh e addition of GGBFS either in cement or in concrete improves the following properties of concrete related to its durability as explained in various publications:1-4

Sulphate resistance: Cements with added GGBFS con-tain less alumina, Ca(OH)2 and C3A compared with normal Portland cement and they also have less water demand. Th is results in a more impermeable cement paste for penetration of sulphate ions and provides con-ditions to prevent ettrengite formation. Around 65% or more slag addition makes the cement comparable to sul-phate resisting cement.Resistance to chlorides: Th e permeability of concrete de-creases due to fi ne GGBFS particles and their hydration products in the cement paste. Such cement pastes also absorb more chloride ions. It has been determined that, compared with normal Portland cement pastes, slag ce-ment pastes are 100 times less permeable against potas-sium ions.

Alkali-silica reaction: Th e use of at least 50% GGBFSin cement is eff ective in reducing alkali-silica reactionexpansions.Acid resistance: Concretes containing GGBFS have beenfound to be more resistant to diluted acids comparedwith those containing normal Portland or sulphate re-sistant cements.Resistance to sea water: Concrete in sea water is subject-ed to sulphates and chlorides. Field studies in Belgium,Germany, Norway, England and France have been con-ducted on the performance of concrete structures builtwith diff erent types of cement in sea water. Th ere wasless spalling and reinforcement corrosion in concretesbuilt with slag cements (25-35% GGBFS). Slag cementswith more than 50% GGBFS performed even better.Reinforcement corrosion: Highly alkaline cement pastesprotect embedded steel bars against corrosion. Car-bonation or penetration of chloride ions into concretecan initiate corrosion. Cement pastes made with slag ce-ments can eff ectively block the entrance of chloride ionsand prolong the useful life of concrete structures.Th ermal behaviour and cracking: Th e hydration of ce-ggment is an exothermic process. Th e heat produced cancause temperature gradients and cracking in massivestructures and can also be harmful in rich concrete mix-es, in rapid curing and in hot weather concreting. In slagcements, the heat producing components of clinker ispartially replaced with GGBFS and heat of hydration iseff ectively reduced. Th us, adverse conditions mentionedabove that would otherwise serve to harm the durability of concrete do not take place.

In Turkey there are three main steel works, located inEreğli (Erdemir) Karabük (Kardemir) and İskenderun(İsdemir). Th e total granulated slag obtained from thesethree steel works currently stands at about 1.5Mt/y.İsdemir, located close to the plants of Adana CementCompany, currently produces 630,000t of granulatedslag per annum, and its output is expected to reach900,000t in 2008. Th e Adana Cement İskenderun plantuses granulated slag obtained from the İskenderun steelworks to produce slag cements CEM II/B-S 42.5R andCEM III/A 42.5R according to Turkish cement standardTS EN 197-1. Currently, about 17Mt of slag-containing

globalslag MAGAZINE


cements (CEM II, III and V) are produced annually in Turkey.

A comprehensive study was initiated by OYAK Group Adana Cement Co in collaboration with Turkish Cement Manufacturers’ Association (TÇMA) to confi rm some of the technical advan-tages of slag cements mentioned above using local materials, and also to make comparative economic assessments. Th is paper presents some of the fi nd-ings of that study.

Experimental work: MaterialsCementsTh e cements used in the study were produced by AdanaCement Co. Th ey were: Portland Cement CEM I 42.5 R,Portland Slag Cement CEM II/B-S 42.5 R (containingaround 33.5% mineral admixture) and blast furnace slagcement CEM III/A 42.5 N (containing around 55.5%mineral admixture). Th e other properties of these ce-ments are given in Table 1.Chemical admixturesDiff erent types of water-reducing chemical admixtureswere used in the concrete mixtures, depending on thetype of cement. A naphthalene sulfonate-based super-plasticiser, which showed good performance with slagcements, was used with CEM III/A 42.5 N. Anothersuperplasticiser was used with the othertwo cements. For self compacting con-crete a synthetic polymer-based hyper-plasticiser was chosen.

AggregateCrushed stone aggregate was used inthe concrete mixtures. For normal mix-tures the aggregate was composed fromfour size groups with a maximum parti-cle size of 22mm as shown below:

0.27 (0-2mm);•0.22 (0-4mm);•0.25 (4-15mm);•0.26 (15-22mm).•

For the self compacting concrete themaximum particle size was 15mm. Th ecombinations from three size groupswere as follows:

0.24 (0-2mm);•0.36 (0-4mm);•0.40 (4-15mm).•

Some physical properties of the aggregate are shown inTable 2.

Laboratory TestsConcrete mixturesNormal concrete mixtures were prepared using the threetypes of cement and fi ve levels of cement content: 270,280, 290, 300, 310kgm-3 for each of them. Th e chemi-cal admixture dos-ages were 1.2% by weight of cement.

Th e workability of the mixtures was kept constant at 21cm slump. Material quantities for the 15 concrete mixtures are given in Table 3.

For the self-compacting concrete, two mixtures were prepared. In one, CEM I 42.5R type cement was used at 500 kgm-3

and in the other CEM III/A 42.5 N type of ce-ment was used at 450kgm-3. Th e water/cement ra-tio was 0.40 and hyperplasticiser dosage was again 1.2% by weight of cement in both mixtures. Th e material quantities are shown in Table 4.

Test procedures and resultsTh e compressive strengths of all concrete mixtures were determined at 2, 7 and 28 days according to TS EN 12390-3 standard.5 Chloride and water penetration tests were performed on normal 28-day concrete mixtures with 300kgm-3 cement content and on self-compacting concrete mixtures.

Properties CEM I 42.5R CEM II/B-S 42.5R CEM III/A 42.5N

Insoluble residues (%) 0.24 0.50 0.38

SO3 (%) 2.56 2.47 1.83

MgO 1.68 3.48 4.22

Loss on ignition (%) 2.85 2.08 2.25

Specifi c gravity (g/cm3) 3.10 3.02 2.97

Specifi c surface (cm2/g) 3230 4660 4690

Aggregate type Specifi cgravity(gcm-3)

Water absorptioncapacity (%)

Crushed stone 0-2mm 2.65 2.20

Crushed stone 0-4mm 2.65 2.20

Fine aggregate 4-15mm 2.68 1.40

Coarse aggregate 15-22mm 2.70 1.20

MixtureNo.

Cement type Water-to-cement

ratio

Cement quantity (kgm-3)

Fineaggregates

(kgm-3)

Coarseaggregates

(kgm-3)

Chemical admixtures

(kgm-3)

1 CEM I 42.5R 0.74 270 920 957 3.24

2 CEM I 42.5R 0.71 280 917 954 3.36

3 CEM I 42.5R 0.68 290 915 952 3.48

4 CEM I 42.5R 0.66 300 909 946 3.60

5 CEM I 42.5R 0.64 310 904 941 3.72

6 CEM II/BS 42.5R 0.74 270 920 957 3.24

7 CEM II/BS 42.5R 0.71 280 917 954 3.36

8 CEM II/BS 42.5R 0.68 290 915 952 3.48

9 CEM II/BS 42.5R 0.66 300 909 946 3.60

10 CEM II/BS 42.5R 0.64 310 904 941 3.72

11 CEM III/A 42.5N 0.72 270 927 965 3.24

12 CEM III/A 42.5N 0.69 280 924 961 3.36

13 CEM III/A 42.5N 0.67 290 918 955 3.48

14 CEM III/A 42.5N 0.65 300 913 950 3.60

15 CEM III/A 42.5N 0.62 310 913 949 3.72

Mixture No.

Cement type Water-to-cement

ratio

Cementquantity(kgm-3)

Crushedsand

(kgm-3)

Crushed gravel

(kgm-3)

Plasticiser chemical additive

(kgm-3)

Flow(cm)

16 CEM I 42.5R 0.40 500 1001 668 6.0 65

17 CEM III/A 42.5N 0.40 450 1061 707 5.4 71

Table 1: Propertiesof cement.

Table 2: Propertiesof the aggregate.

Table 3: Materialquantities in normal

concrete mixtures.

Table 4: Mate-rial quantities inself-compacting

concrete mixtures.

Th e standard test to determine concrete’s ability toresist chloride penetration (ASTM C1202) involves measuring the electrical current passing through a satu-

rated concrete specimen placed between 3% NaCl and 0.3moldm-3 NaOH cells. Th e amount of current wasmeasured at 30min intervals for a total of 6 hours and plotted. Th e area under the curve was calculated as the total amount of current in coulombs.6

Th e depth of penetration of water under pressureinto concrete was determined according to TS EN 12390-8 standard. Oven-dried concrete specimens were subjected to water pressure for 48 hours under 1atm, 24 hours under 3atm and 24 hours under 7atm. Aft er-wards, specimens were split and depths of water pen-

etration were measured.7 Th e test results for normal and self-compacting concrete mixtures are listed in Tables 5 and 6, respectively.

DiscussionCompressive strengthTh e results of the compressive strength tests listedin Table 5 indicates that at early ages (days 2 and 7),concretes made with CEM I 42.5 R cement had high-er strengths than the the concretes made with CEMII/B-S 42.5 R and CEM III/A 42.5 N cements for allwater/cement ratios. However, the strengths at 28days of both concretes containing the slag cementsexceeded the strengths of CEM I concrete. At 28 days,concretes made with CEM III/A 42.5 N cement almostreached CEM II/B-S 42.5 R concrete values while ex-ceeding the strengths of CEM I 42.5 R concrete. Th edelay in strength gain of concretes containing slag ce-ments are attributed to the delayed hydration of blastfurnace slag. Slag cement concretes also showed fasterstrength gain from 2nd to 7th days compared withCEM I concrete.

Similar comments could be made for self compact-ing concretes studying the strength values in Table6. Again the strengths of concretes made with CEMIII/A 42.5 N cement remained below the strengths of

CEM I 42.5 R concrete at days 2 and 7, but exceededthem at 28 days.

Chloride penetrationAs seen from Tables 5 and 6, theability to resist chloride penetrationof concretes improved dramatically with the use of slag cements. CEMIII/A 42.5 N cement was the mosteff ective in this respect. Th is couldbe explained by the formation of the

additional pozzolanic gel in slag cement pastes, whichserves to close the pores and increase the fi neness of theslag cements.

Water penetrationWater penetration depths in Tables 5 and 6 indicate thatusing slag cements improved the resistance of concretesto the penetration of water under pressure. Again, CEMIII / A 42.5 N cement was the most eff ective and theresults could be explained in the same terms as for thepenetration of chloride ions.

Cost comparisons for concreteIn Table 7, raw material costs per unit volume of the nor-mal concrete mixtures having 300 kgm-3 cement contentare shown, as well as their 28 day compressive strengths,which are close to each other. In the last column, costs

(in Turkish Lira, YTL) per unit strength(1MPa) are calculated (1YTL = US$0.85/Euro0.59. It can be seen that using slagcements (mixtures 9 and 11) can lowerthe cost of concrete by about 11% as com-pared with the cost of CEM I cement con-crete (mixture 4).

Table 8 contains similar information for self-com-pacting concrete mixtures. Th is time, the cost of con-crete made with CEM I 42.5 R cement (mixture 16) isreduced by about 21% by using CEM III/A 42.5 N ce-


globalslag MAGAZINE

Mixture No.

Strength (MPa) Chloride penetration(Coulombs)

Waterpenetraton

(mm)2 days 7 days 28 days

1 12.9 18.7 25.3

2 14.2 19.7 27.7

3 14.9 21.5 28.0

4 17.2 22.6 28.5 >15,000 99

5 17.3 24.4 21.6

6 9.5 17.8 27.4

7 9.7 18.2 28.5

8 10.3 18.6 29.3

9 10.5 19.5 30.0 9392 53

10 10.7 22.8 33.5

11 8.4 16.7 26.1

12 9.4 17/0 26.9

13 9.5 18.3 27.4

14 9.7 18.8 29.4 2237 36

15 10.3 19.4 32.2

Mixture No.

Strength (MPa) Chloride penetration(Coulombs)

Water penetraton (mm)

2 days 7 days 28 days

16 32.6 42.8 51.0 7872 52

17 16.7 38.9 53.5 707 24

Mixture No.

Raw material cost (YTLm-3)

28 days compressive strength (MPa)

Price for 1Mpa(YTL)

4 50.95 28.5 1.79

9 48.25 30.0 1.61

14 46.91 29.4 1.60

Mixture No.

Cement quantity Raw material cost(YTLm-3)

28 days compressive strength (MPa)

Price for 1Mpa(YTL)

16 500 84.63 51.0 1.66

17 450 70.57 53.5 1.32

Table 5: Test resultsfor normal concrete mixtures.

Table 6: Test results for self-compacting concrete mixtures.

Table 7: costs of normal concrete mixtures per unit strength.

Table 8: Costs of self-compactingconcrete mixturesper unit strength.

14 15 APRIL 2008 SAS Radisson Düsseldorf, Germany

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PRo Publications International Ltd

Photo of Castle Cement’s Padeswood cement plant, courtesy of FLSmidth

http://www.propubs.com/gec

ment (mixture 17) on unit strength basis. It should be mentioned that in mixture 17, while obtaining higher strength at and beyond 28 days, 50kg less of cement was used per cubic metre of concrete. A larger fl ow value was also obtained.

Th e clinker percentages of the three cements used in this study and the clinker contents per cubic metre of normal concretes with 300kgm-3 cement content and self compacting concretes are listed in Table 9. It can be seen that by using CEM III/A 42.5 N cement instead of the other two cements, 66-157.5kg of clinker is saved per cubic metre of normal concrete mixtures. Th e sav-ing in clinker content is 285kgm-3 for self-compacting concrete mixtures.

ConclusionsTh e main results of the study could be summarised as follows: Concretes made with slag cements have lower 2nd and 7th day strengths compared with the ones made with CEM I cement. However, they gained strength faster aft erwards and reached or exceeded the strength of CEM I cement concrete by 28 days. Concretes made with CEM III/A 42.5 N cement, which had a slag con-tent of around 55.5%, almost reached the strength of concretes made with CEM II/B-S 42.5 R cement, having around 33.5% slag, and exceeded the strength of con-cretes made with CEM I 42.5 R cement at 28 days.

Using slag cements instead of CEM I cement im-proves the resistance to water and chloride penetration

of concrete and contrib-utes to its durability. In this respect CEM III/A 42.5 R cement was the most eff ective.

Using slag cements and especially CEM III/A 42.5 N in self-compacting concrete mixtures again resulted

in comparable or slightly higher 28 day strengths, im-proved water and chloride resistances and better fl ow characteristics, as compared with using CEM I 42.5 R cement.

An 11% reduction in the cost of concrete per 1MPa of strength was observed upon using a CEM III/A 42.5 N cement. Th is was achieved with a cement content of 300 kgm-3 at 28-days strength. Th is equated to a saving of 157.5kgm-3 in clinker content as compared to using CEM I 42.5 R cement. A higher cost reduction, around 21%, and a reduction in clinker content of 285 kgm-3 was possible in self-compacting concrete mixtures.

It can be concluded that concretes made with CEM III/A cements, which can contain up to 65% GGBFS, have improved strength and durability properties and lower unit costs as compared with CEM I cement concretes. Moreover, CEM III cements are also ‘en-vironmentally friendly’ as they make use of the main by-product of the steel industry. Th eir reduced clinker content means savings in natural raw materials and fuels and reduced CO2 emissions since the production of 1t of clinker results in the emission of almost 1t of CO2 into the atmosphere.

References1. American Concrete Institute, “Ground granulated blast furnace slag as a cementitious constitute in concrete”, ACI Manual of Concrete Practice, Part 1, 1994. 2. Higgins, Uron, “Concrete”, 25(6), 1991.3. M. Tokyay, K. Erdoğdu, “Cürufl ar ve Cürufl u Çimen-tolar”, TÇMB Ar-Ge Y 97-02, 2001.4. A. Yeğinobalı, T. Ertün, “Çimentoda yeni standardlar ve mineral katkılar”, TÇMB Ar-Ge Y 04-01, 2007.5. TS EN 12390-3 “Sertleşmiş beton deneyleri - bölüm 3: Deney numunelerinde basınç dayanımı tayini”, 2003.6. ASTM C 1202 “Standard test method for electrical in-dication of concrete’s ability to resist chloride penetration”, 1997.7. TS EN 12390-8 “Sertleşmiş beton deneyleri - bölüm 8: Basınç altında su işleme derinliği tayini”, 2002.8. Th is paper was published at 7th National Concrete Conference in Turkey.

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Mixture No.

Cement type Quantity (kgm-3) Amount of clinkerused in cement (%)

Clinker quantity(kgm-3)

Diff erence with CEM III

4 CEM I 42.5R 300 97.0 291.0 157.5

9 CEM II/BS 42.5R 300 66.5 199.5 66.0

14 CEM III/A 42.5N 300 44.5 133.5 –

16 CEM I 42.5R 500 97.0 485.0 285.5

17 CEM III/A 42.5N 450 44.5 44.5 –

Table 9: Clinkerquantity according to cement types and comparison with CEM III.

Below: Oyak Ce-ment Group facto-ries in Turkey, with colour-coded key tocolour-coded key toplants and offi ces.

Adana Çimento Bolu Çimento Ünye Cimento Mardin Çimento

1 - Headquarters 1 - Headquarters 1 - Headquarters

2 - Ìskenderun 1 2 - Ankara 2 - Çayeli

3 - Ìskenderun 2(operational in 2008)

3 - Ereğli (opened in 2007

4 - Ereğli (operationalin 2009)

globalslag MAGAZINEBarry Woodbine Aumund Group

Effi cient and reliable handling of GBFS andGGBFS at grinding plants and cement works

In this paper Aumund, recent winner of the Global Slag Equipment Innovation Award 2007, showcases its broad range of GBFS and GGBFS handling, conveying and storage options.


Above: Tipping of molten slag fromthe iron and steel

industries

Left: Aumund’s head-quarters in Rheinberg,

Germany

During recent years the cement industry has suff eredsignifi cant increases in operating costs driven in

particular by spiralling energy prices plus pressure fromenvironmental lobbies to reduce dependence on fossilfuels and reduce CO2 emissions overall. Consideringthat the production of a ton of conventional Portlandcement generates almost a ton of CO2, and in terms of total greenhouse gas emissions for all industries world-wide, this places cement second only to the power in-dustry in the scale of global polluters.

Th ese factors have generated an increased awarenessof alternative fuel possibilities for kiln fi ring and substi-tute raw material options for cement production, alsorefl ecting an increased demand for blended cementsparticularly including ground granulated blast furnaceslag (GGBFS). Th is last point is particularly important;for every ton of GGBFS included in the fi nal blended ce-ment the total CO2 production is reduced by around 1t.

Whilst the processes behind the use of GGBFS as asubstitute raw material is well understood, the applica-tion of the material represents a considerable challengefor the plant designer from the intake of the granulatedslag to the introduction of the ground material to theblended cement. In general these materials are diffi cultto handle, reliably varying from extremely free fl owing(GGBFS) to very sluggish and prone to bridging andblockage and liable to agglomerate in storage (GBFS).GBFS is also extremely abrasive, with wear rates somefi ve times greater than cement clinker in comparableinstallations.

Th e Aumund Group, including B&W and Schade,recognises these challenges. Over many years it has de-veloped innovative solutions for many of these handling

problems, including using special adapta-tions of existing designs that are tailored to suit the specifi c demands of these new ap-plications.

Combining the traditional strengths of the Aumund Group products with new concepts to improve plant design fl exibility and reduce project costs, Aumund off ers fast-track eff ec-tive solutions allowing clients to capitalise on short term market positions and maximise plant profi tability.

ProductionProductionGranulated blast furnace slag is a byproduct of the steel industry and is produced by rapid quenching in cold water of the molten slag recovered from the blast furnace; this process produces a granular, glassy, homogeneous, noncrystalline mate-rial that has cementitious properties.

Depending upon the process, around 25% or more of the raw material used in the blast furnace is tapped off as slag. Th is represents a vast quantity of material pro-duced worldwide and the market is eff ectively limited only by the availability of granulation equipment at the steel plant and the logistics of transportation to the ce-ment plant.

Th e granular material can then be dried and ground in a mill at a prescribed rate. Th e resulting powder, known as ground granulated blast furnace slag may be incorporated into concrete materials. GGBFS has been used for many years as a supplementary cementitious material in Portland cement concrete, either as a min-eral admixture or as a component of blended cement.GGBFS may replace 35–85% Portland cement in con-crete with corresponding reductions in CO2 emissions resulting in obvious environmental benefi ts.

Th e use of GGBFS as a partial Portland cement re-placement takes advantage of the energy invested in the slag-making process and its corresponding benefi ts with respect to the enhanced cementitious properties of the slag. Grinding slag for cement replacement requires only about 25% of the energy needed to manufacture

globalglobalslagslag MAGAZINEMAGAZINE March 2008 1717

globalslag MAGAZINE


normal Portland cement.Without the use of granulated

material the total volume of slagproduced could not be viably oreconomically utilised in other proc-esses, such as aggregate for example,and would inevitably go to landfi ll asin the past. Th erefore by maximis-ing the appropriate use of GGBFS incement, the industry is not only sig-nifi cantly reducing greenhouse gasproduction and energy consumptionbut also reducing landfi ll. Th is con-

stitutes a signifi cant reduction in total environmental pollution levels, in line with the general objectives of the Cement Sustainability Initiative.

Market conditionsMarket conditionsIn today’s rapidly changing international market the abil-ity to react quickly to market volatility and take advan-tage of short-term market positions is essential if opera-tors are to maximise profi tability and return on capital

invested. In this respect theuse of substitute raw mate-rials such as GBFS shouldbe considered as part of anoverall plan to reduce costsand improve the environ-ment. Oft en these are mu-tually exclusive demandsbut in the cement industry the combination of substi-tute raw materials and al-ternative fuels benefi ts all

and is truly a win-win situation.Th e use of these materials is also very much depend-

ent upon geography. In certain regions the cost of fuel and access to raw materials, as well as the demand for particular properties of the fi nish blended cement may signifi cantly aff ect the economic mix. Th is situation de-mands a fl exible and fast-trackable new plant solution. Similarly, other materials such as fl ue gas desulphurised gypsum (FGD), oft en known as synthetic gypsum, is

widely used in cement and other in-dustries. As such, pricing is market driven and the relative economies of use vary accordingly.

Where all of these conditions arefactored into the overall equation, market volatility may dramatically change the relative economy of spe-cifi c solutions in a short time. Under

these conditions the cement man-ufacturer has a diffi cult calcula-tion to make when evaluating the payback period of any new plant investments dedicated to the han-dling of alternative fuels or sub-stitute materials. As such reduced installation cost and fl exibility are key issues when making these de-

cisions. Similarly, the lead times to commissioning new plants once these decisions are resolved is critical in or-der to maximise the fi nancial benefi ts within a predictedcost and time-frame.

In this paper the handling requirements of granu-lated and ground materials in the cement industry willbe discussed, but similar solutions are also applicable forindependent grinding stations or grinding facilities in-stalled directly at the steel production plant.

Key plant design issuesKey plant design issuesIn addition to the suitability of the new plant for the in-tended application, there are other issues that can infl u-ence decision making. To maximise the fi nancial ben-efi ts relating to substitute raw materials or alternativefuels, the plant design criteria and budget constraintsare clearly substantially diff erent to what would be con-sidered for a mainline process demand. In addition,fl exibility in location and suitability for other materialsand applications is an attractive combination. Shouldthe relative economies of the intended project changesignifi cantly it is always useful if the plant may be reusedelsewhere and therefore the investment risk mitigated.Clearly civil works costs are also an important factor inany new plant and are not only expensive but obviously not re-usable and certainly incur delays in constructionwhere extensive design, planning and excavation may berequired.

With few exceptions the costs associated with railcar delivery of these alternative materials is prohibitive,meaning that delivery by road is generally the only op-tion. Intake by a tipping truck is always sensitive to fugi-tive dust pollution and necessary control measures aregenerally required to minimise any environmental im-pact. A successful and economic new plant installationmust address these key issues if the fi nancial rewards,environmental benefi ts and process demands are to berealised.

Aumund Group experienceAumund Group experienceWith over 80 years experience in designing specialisedbulk materials handling solutions for the steel and ce-ment industries, the Aumund Group off ers mechanicalconveying systems for GBFS both in its raw state andaft er grinding. Th is experience extends to the handlingof very hot materials in cement, sinter and pellet plantsusing the long established Aumund pan conveyor con-cept, as well as the use of highly developed designs spe-cifi cally tailored for these aggressive and demandingapplications.

As an example of the depth of engineering exper-tise available, Aumund has executed the largest bucketconveyor installation delivered thus far for handling hotcompacted iron with a lift height of 110m (150m centredistance) at a handling rate of 210t/h. Th ese conveyorsare designed to handle material at 900°C in an inert at-mosphere to maintain product quality.

Within the cement industry the name of Aumundis synonymous with quality and reliability, with over10,000 installations worldwide in over 100 countries.Aumund clinker transports and vertical bucket eleva-

Above: Hot materialtransport, a specialty of Aumund.

Below: Pellet coolingconveyor.

Below: Raw slag intake to a crushing plant (top); raw slagtransfer by belt con-veyor (bottom).

tors are market leaders in this industry with clear tech-nological benefi ts derived from continuous detaileddevelopment.

Developed from the pan conveyor concept, Aumundhas delivered special cooling conveyors for pellet plantsincorporating perforated pans using ambient air drawnthrough the pans and exhausted through comprehensiveducting systems to cool the pellets down from 250°C to100°C. In addition to the pan conveyors and vertical el-evators Aumund also delivers heavy duty feeder equip-ment and silo extractors, plus, with the addition of theSchade Group in 2001, a comprehensive range of stack-ers and chain scraper reclaimers bringing 125 years of continuous experience in this market. In 2002 also Au-mund acquired B&W Mechanical Handling Ltd of Eng-land, adding the Samson Surface Feeder and more fl ex-ible solutions based on mobile stacking and ship loadingequipment to an already comprehensive portfolio.

Th e experience gained in continuous process ap-plications operating under the most arduous workingconditions has been brought to bear on the detailed de-sign of equipment for the handling of GBFS, as will bediscussed herein.

From the standard Aumund range there exist a rangeof solutions from feeders for the intake of the raw orgranulated slag through to stacking and storage, recov-ery from storage and feeding of the material to the milland the raising of the fi nished ground material to thefi nal silo storage.

Tailored solution driven from experience:Tailored solution driven from experience:Intake and elevationntake and elevationTh e B&W range of Samson Surface Feeders off er theideal solution for the intake of both raw and granulatedslag. Th e Samson feeder receives raw slag direct fromthe steel works for processing at an off site crushingplant. Th e Samson discharges directly into a belt con-veyor mounted at 90° allowing an ideal transfer onto thebelt, minimising the risk of blockage as there is a highrisk of oversize and tramp materials. From the belt con-veyor the slag is fi rst screened to remove the tramp andthen crushed down to a particle size suitable for use asaggregate in road building.

Slag samples vary signifi cantly in their properties. Inorder to maximise the output of the system under any conditions the Samson output is automatically adjustedrelative to the actual handling rate (measured by beltweigher) and crusher current demand. Th e same Sam-son Surface Feeder design may also be utilised for theintake of granulated glag at a cement works or grindingplant, either directly from tipping trucks or from a load-ing shovel.

Th e new installation at the Holcim Carboneras plantin Spain receives imported granulated slag from tippingtrucks which discharge to a ground stockpile. From the

stockpile the ma-

terial is recovered by load-ing shovel using the Sam-son as a buff er hopper withfeed regulation (by level-ling blade) to the inclinedbelt conveyor which raisesthe slag to the mill bunkerat a high level.

Since the granulat-ed slag is liable to ag-glomerate in a groundstockpile creatinglarge hard lumps, theSamson must be fi t-ted with a reject grilleither at the entry or atthe discharge to pre-vent these large lumpsentering the mill bun-ker causing potentially catastrophic damage to the mill.

In some plants there simply is not suffi cient space to store large volumes of material and therefore the intake of granulated slag must be managed using road tipping trucks. Th is acts as a suitable alternative to the ground stockpile solution. In the road tipping scenario the Samson surface feeder is the ideal answer providing an intake, buff er storage and feed rate control in a single machine, whilst at the same time eliminating the need for deep pits and hoppers, thereby reducing civil works costs and improving fl exibility.

To overcome the problem of oversized agglomerated lumps a Samson with integral twin shaft rotary sizer can be mounted at the discharge. Th e rotary sizer is com-pact and may be accommodated between the Samson and the following conveyor. From the following con-veyor the material may be raised to the mill silo using an Aumund BWZ central chain bucket elevator as shall be describe later in this paper.

Th is particular plant layout is illustrated in the fol-lowing description of the Lafarge cement plant at Vil-laluenga in Spain. In this particular case the equipment is handling gypsum rock but the same basic equipment may be used to size agglomerated granulated slag lumps. Clearly this represents a considerably more arduous duty showing the local material stockpile. In addition to the integral rotary sizer other options are available to reject the oversize and tramp material aft er the Samson.

A Samson surface feeder can also be supplied with an inclined vibratory screen at the discharge arranged to al-low only the material passing the screen to be transferred to the mill bunkers. When the slag is recovered from a ground stockpileby shovel there isa strong possiblity of tramp material

globalslag MAGAZINE

globalglobalslagslag MAGAZINEMAGAZINE March 2008March 2008 1919

Above: Granulatedslag ground stockpile(top); granulated slag

intake to a cementplant (bottom).

Below: Aumund’sintegrated feederand primary sizer

(left); lumpy materialbefore sizing (centre);

integrated Samsonand screen (right).

being picked up and loaded to the feeder. To overcome this problem a magnetic separator plus metal detection systems is normally man-datory, mounted to the following belt conveyor system.

Belt conveying optionsBelt conveying optionsTh e combination of Samson and sizer is not new and naturally there are alternative solutions and as an example the Samson may be paired with a ‘side wall belt’ vertical conveyor system as used in the new installation for Holcim Germany handling granulated slag.

In this project the Samson receives the granulated slag direct from tipping trucks in the usual way with the output regulated us-ing the standard levelling blade system but the material is discharged direct to the horizontal loading section of the ‘S’ shaped side wall belt conveyor.

As shown in the fi gure on the left , a typical exposed side wall belt of the vertical section supported only from the head. However, these conveyors are notoriously diffi cult to clean, but the spillage returns conveyor is designed to pick up any spilt material and transfer this to the main conveyor feed boot.

As an alternative the Aumund Group off ers the type BWZ central chain bucket elevator. Th is off ers a totally enclosed and spillage-free handling system, rais-ing the granulated slag direct to storage silos. Th e verti-cal bucket elevator may be combined with any type of transfer or feeder conveyor system. When integrated to the Samson surface feeder the whole installation may be made compact and clean.

Th e Aumund chain bucket elevator is the ideal solu-tion for handling GBFS to silo storage, suitable for lift heights from 10-60m and handling rates of more than 600t/h. In other applications where required material

temperatures up to 400°C may also be accom-modated. Utilising a single central forged chain these machines are ideal for handling aggressive materials. However, for slag handling special features are included to ensure long term reli-ability. Th ese measures include:

Rubber lined head and boot;• Flexible rubber casing panels;• Fully lined buckets;• Toothed buckets (at 10th pitch);• Additional inspection access;• Seal pre-lubricated chains.•

Th e features are all geared to resist wear and provided extended machine life with minimum maintenance and minimum downtime. Devel-oped from our extensive experience in the ce-ment industry, handling hot cement clinker, these elevators off er proven reliability world-wide.

Rubber linings are the proven solution at the inlet and outlet of the machine, but for the ver-tical casing the conventional pressed steel sheet

sections are replaced by a fabricated lattice structure with fl exible rubber panels which resist wear and ma-terial adhesion. Each bucket is fully lined in wear-resisting steel plates applied to eve-ry plane of the bucket structure. In addition, on each 10th bucket, digging teeth are ap-plied which create a clear path through any residual material to minimise wear on the conveying strand as a whole.

However, the ma-jor feature of these elevators is the mas-sive forged conveyor chain with sealed and

prelubricated pins which forms the backbone of the unit and is the key to long term reliability. Th e labyrinth seals formed into chain-side plates eff ectively prevent materi-al ingress to the pin and bush and, when combined with eff ective pre-lubrication, extends the chain life by a mas-sive 60% compared to the traditional unsealed design without prelubrication. Th e chains are not relubricated in service and require no special routine maintenance but the choice of preinstalled lubricant is critical if the benefi t of this design is to be fully realised.

Th e chart below demonstrates the improvement in wear performance achievable with this design, eff ective-ly more than doubling the actual chain life. Th e blue line

globalslag MAGAZINE

20 20 globalglobalslagslag MAGAMAGAZINE March 2008

Above: Vertical elevation by a side-wall belt.

Below: Verticalelevation by a bucketelevator.

BW-Z central chain elevatorBW-Z central chain elevator

Forged bucket elevator chainsForged bucket elevator chains

Chain pre-lubricationChain pre-lubrication

Chain pin/bush labyrinth sealChain pin/bush labyrinth seal

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represents a stand-ard chain without a seal and without pre-lubrication; the red line represents a sealed chain with premium grade lu-brication. Th e inter-mediate lines repre-sent results obtained with other grades of lubricant.

When in operation minute traces of the conveyed material pass the seal and combine with the lubricant to form a mild grinding medium which polishes the pin/bush interface. It is this high level of surface fi nish that improves the long term wear life. Th is is the advantage of an eff ective research and development facility, a clear and demonstrable benefi t of the technological know-how of Aumund Group’s product where attention to detail is rigorously pursued with the goal of long term performance and reliability for the benefi t of its clients.

Silo dischargeSilo dischargeHaving raised the granulated slag to the storage silo or mill bunker, the stored material must be extracted and perhaps weighed for dosing. For the dosing of slag the Aumund weigh feeder combines accuracy with per-formance and reliability. It utilises a weigh rail mounted to load cells supporting the close pitch apron, or pan conveyor rollers to accurately measure the applied load. By measuring the material load over a known length, and by monitoring the chain speed, the desired output

rate may be continu-ously adjusted in real time to suit the process demands.

Based on the proven deep drawn pan conveyor princi-ple, these weigh feeders off er long term reliability while working un-

der the most diffi cult conditions.For handling cohesive materials the BPB-type

arched plate conveyor is the preferred solution, and is also available with weigh rails for proportional dosing or controlled rate feeding applications. With truly massive construction these feeders are suit-able for the most extreme duty applications.

For extracting cohesive materials from silo storage the Aumund Centrex® provides an eff ective solution eliminating bridging and blockage by recovering ma-

terial from the silo periph-ery using logarithmically shaped arms mounted to a rotating carrier. Th e Cen-trex® is off ered with a range of mounting options includ-ing the possibility of a rotat-

ing cone to ensure reliable discharge and fi rst in-fi rst out material fl ow. Since the discharge arm sweeps right out to the periphery of the silo, silo discharge is not impeded resulting in reliable extraction.

For larger silos the ‘rotating discharge machine’ is also an option comprising a multi-arm discharge wheel mounted to a rotating carrier. Th is arrangement caters for silo diameter up to 12m, enabling the handling of a wide range of cohesive materials. Th is has found a wide set of applications handling FGD gypsum, both in power plants and in cement plant as this type of gyp-sum may be utilised as a direct replacement for natural gypsum required to modify the cement properties at the fi nal grinding stage.

Stacking and reclaimStacking and reclaimFor larger projects where substantial volumes of gran-ulated slag are to be handled the Schade range of rail-mounted boom stackers and chain scraper-type portal reclaimers are an ideal solution. It receives the slag by a belt conveyor discharged by a tripper car to the travel-ling stacker boom at a handling rate of 600t/h to gener-ate a stockpile capacity of 35,000m3.

Reclaim from the stockpile is achieved by a Schade portal frame reclaimer fi tted with a special scraper chain. Th e material is fed to a belt conveyer running parallel to the stockpile at a rate of 300t/h to match the process requirements. Stockpiling and reclaim are fully automatic using onboard control systems with extensive fi eld and instrumentation and protection systems allow-ing unattended operation.

Recognising the potential wear problems handling this extremely abrasive material, Schade has developed the outboard bearing chain specifi cally for operation under these arduous conditions. Th e outboard roller is carried on an elongated chain pin using double preci-sion ball bearings plus a multipath labyrinth grease seal. Th e roller may be lubricated for life requiring no further

attention in service. Outboard roller chains also signifi -cantly reduced the machine noise level and are oft en used in applications located in sensitive areas close to urban developments. In addition to the special outboard bearing rollers special scraper shovels are also employed with wear-resisting digging face.

Schade off ers an extensive range of reclaimer designs and has over 50 years experience in this market. Schade was the fi rst company to deploy the chain scraper tech-nology in this manner. Schade has produced some of

2222 globalglobalslagslag MAGAZINEMAGAZINE March 2008March 2008

Above: Chart to show the relative chainlife as a function of lubrication.

Below: Aumund’s KZBweigh pan feeder.

Right: Schade’s portal reclaimer.

Below: The Centrex sweep arm silo dis-charger.

the world’s largest installations of this type with reclaim rates of 2400t/h and rail spans of 65m. In addition to the longitudinal portal reclaimer confi guration Schade also off ers the circular storage system comprising inte-grated stacker and reclaim boom mounted to a common column.

Th e Schade storage and reclaim systems may be sup-plied complete with rail or road intake equipment based on the Samson surface feeder or type BPB plate feeder as a complete handling package. Similarly the Schade stor-age system may be linked to the cement plant using, for example, Aumund bucket elevators and silo storage and extraction equipment and as such a complete package from intake to the mill.

In addition to the specifi c example illustrated herein Schade off ers many alternative designs such as the can-tilevered boom as described below. Th e semi-portal de-sign involves one side of the portal being supported on a raised building wall, which also acts as load-bearing containment to increase the eff ective storage capacity per metre of building length.

For the homogeneous blending of materials such as limestone at a cement plant, Schade also off ers the bridge reclaimer design with a reciprocating harrow ensuring material is recovered from the full face of the stockpile and thereby mixing samples for every layer. Bridge reclaim systems may be either longitudinal re-placing the portal design or may be based on a circular format. Schade produces some of the largest circular storage systems ever built. At 120m diameter these de-

signs represent the pinnacle of the market and demon-strate the capability and engineering prowess of Schade in this market.

Raising the ground slagRaising the ground slagTh e intake and storage of granulated slag as it is received from the steel works is not the full story. Aft er the slag is ground, typically in a vertical mill, the fi nished mate-rial generally known as GGBFS must be raised to silo storage before blending or direct dispatch. Th e handling characteristics of the ground slag are very similar to that of fi nished cement and in this situation Aumund is able to use the BWG-type belt bucket elevators. Units are in-stalled to over 140m lift height and conveying rates reach 1500t/h, with up to 450kW installed motor power.

As with the chain elevator, the belt elevator has been the subject of continuous development over many years culminating in a design of proven reliability on a 24/7 operational basis. Attention to detail is the key to success and every aspect of the design is the subject of ongoing development to maximise the benefi t of technological advances in materials and construction, typifi ed by the unique encapsulated clamping connection.

Th e Aumund belt bucket elevator uses a steel cord conveyor belt with close pitch buckets to reduce the in-dividual bucket size and therefore minimise the stress at the bucket fi xing. By minimising the bucket size the belt stress is also reduced at the terminal pulleys resulting in much improved belt life.

A typical installation at an independent grinding plant with adjacent storage silos and truck loading facil-ity includes a bucket elevator, mounted within the tower structure next to the silo. Th is raises the GGFBS from the grinding station. To convey the material to the el-evator and from the elevator to the storage silos, air slide conveyors are generally em-ployed in a simi-lar manner to that seen in a cement plant. Naturally there are alterna-tive solutions to raise the slag gen-erally based on pneumatic han-dling but this is extremely energy intensive and therefore expensive to operate.

Typically in a direct comparison the belt bucket el-evator has demonstrated a reduction of 75% in energy consumption, as shown in Graph 1. Not only is the bucket elevator energy effi cient it is also less prone to wear in comparison to pneumatic handling and off ers excellent long term reliability.

In the UK market the slag is typically ground by an independent company and supplied to the concrete manufacture, for fi nal blending in the concrete mix. Th ere are several such plants located close to the steel

globalslag MAGAZINE


Left: Circular storageand reclaim for slag.

Below: A bucketelevator for ground

slag transport.

Left: Circularstorage with a

bridge reclaimer.

globalslag MAGAZINE


works to minimise the logistics costs associated with the granulated slag delivery which is done invariably by tip-ping truck.

Th e ground slag is invariably delivered to the user by tanker truck using pneumatic discharge equipment which will generally ‘blow’ the ground slag directly to a local storage silo before blending to the concrete mix. For blended cements the slag grinding operation is gen-erally located at the cement plant and the ground slag is blended directly with Portland cement to obtain the desired characteristics and cement specifi cation.

Generally the integration of the slag grinding to the cement plant for the production of blended cements is the most popular solution internationally, and elimi-nates the need for separate independent plants with a clear economy of integration to an established opera-tion. Clearly logistics costs are important along with the expanded CO2 footprint that such transportation opera-tions bring to the total pollution envelope of the cement manufacturer as a whole. Th is issue must be considered alongside other sustainability issues. Th e location of such integrated plants must be market-driven but re-specting the environmental cost of transportation. Flexible mobile solutionsFlexible mobile solutionsWhere budget constraints will not permit the installa-tion of a dedicated fi xed handling system the mobile solutions off ered by B&W represent an economical an-swer to the storage and even export of slag. Th e Storma-jor receives granulated slag direct from the Corus steel works in South Wales (UK) delivered by tipping truck for a new grinding plant operated by Civil and Marine Slag Cement. Th e Stormajor comprises a Samson Sur-face Feeder to receive the material and a radial stacking boom to discharge direct to stockpile, all mounted to a common mobile chassis.

Th e machine, with a boom length of 23m, will pro-duce a stockpile height up to 12m allowing a large quan-tity of material to be stored with the minimum of ma-chine movements. First delivered in 1998, this particular machine has handed many thousands of tons of slag and has proven an eff ective solution. Th e Stormajor may also be eff ectively used for loading barges and railcars and as such represents a fl exible investment.

In addition to mobile stackers B&W also off ers mo-bile ship loading equipment incorporating the Samson surface feeder for direct loading from truck to ship. Th e use of mobile handling solutions eliminates costly civil

works and provides maximum fl exibility, allowing operators to take full advantage of short-term market conditions, therefore maximising fi nancial resources and minimising the investment risk without sacrifi c-ing performance or reliability.

Retrofi ts and upgradesRetrofi ts and upgradesIn addition to the design and execution of new plant and installations Aumund also off ers a unique up-grading service. Th is is not only the case for Aumund Group products but also for compatible machinery from other suppliers. When using the upgrade service clients have the option to convert existing machines using, for example, Aumund chains, buckets, shaft s,

pulleys, drives and other key components with mini-mal cost and plant disruption. Aumund off ers fast track availability of spare parts from its service centres world-wide guaranteeing the highest level of aft er-sales service and support.

ConclusionConclusionTh is paper has discussed a series of detailed innova-tions, resulting from Aumund’s commitment to ongoing R&D, which is specifi cally related to the handling of raw, granulated and ground blast furnace slag. Th ese prod-ucts may be integrated into plants, either as individual machines or as part of an integrated handling system where Aumund also off ers engineering support for the design and local manufacture of associated structures, conveyor bridges, transfer towers and similar ancillary services.

Aumund off ers a comprehensive service to its cli-ents from the conceptual plant layout through the de-sign stage to the fi nal commissioning of the plant. Th e ongoing service backup supported from its head offi ce in Germany, plus daughter companies and representa-tive offi ces in France, Switzerland, Poland, India, China, Brazil, Hong Kong, the US and the UK. Outside of these territories Aumund has an extensive network of agents, fully trained in Aumund Group products, providing lo-cal support and direct access to Aumund’s fi eld sales and service network.

Aumund is a truly international group with vast ex-perience and resources dedicated to the delivery of eff ec-tive and economical bulk materials handling solutions tailored to meet specifi c demands worldwide.

Graph 1: Chartto show the key operational and maintenance savings between pneumaticaland mechanicalhandling techniques.

globalslag MAGAZINE


Dirk Durinck, Sander Arnout, Dr Peter T Jones, Prof Bart Blanpain, Prof Patrick WollantsDepartment of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Belgium

Borate stabilisation of air-cooled slagsAir-cooled slags can exhibit a peculiar volume instability upon cooling and disintegrate into a fi ne powder. The outcomes of this are severe dust issues in the surroundings of the meltshop and forced landfi lling, since a powdery slag cannot be applied as an aggregate for construction applications. In this article, the causes of this disintegration is discussed, in addition to an evaluation of the dusting behaviour of a particular slag based on the overall slag composition, and how borates can be used to stabilise the slags.


Figure 1: Air-cooledslag disintegration

during cooling.

Certain types of slag disintegrate on cooling, (seeFigure 1. It is well known that this particular kind

of volume instability is caused by the presence of dical-cium silicate, 2CaO•SiO2, (C2S) in the slag structure.Th is mineral undergoes several phase transformationsduring the cooling of hot slag. Th e last transformationfrom the β to the γ polymorph at approximately 400°C isaccompanied by a 12% volume expansion, which causeshigh internal stresses in the slag and, subsequently, thedisintegration into a fi ne powder. Th e resulting particle

sizes are typically not larger than 100μm.Over time, this volume instability has been observed

with various slag types, ranging from blast furnace slags to steelmaking slags. At present, however, the prob-lematic disintegration is primarily encountered in two areas. Firstly, in stainless steelmaking, decarburisation slags are known to heavily disintegrate during cooling. EAF slags also display this behaviour, but to a lesser ex-tent. Secondly, aluminium-killed ladle refi ning slags in steelmaking may disintegrate as well.

globalslag MAGAZINE


What slags disintegrate?If one knows the slag composition, one can easily evalu-ate whether or not it will disintegrate. Already in 1942 the disintegration behaviour was described by composi-tional limits (wt%):

CaO + 0.8MgO ≤ 1.20SiO• 2 + 0.39Al2O3 (+1.75 S);CaO ≤ 0.93SiO• 2 + 0.55Al2O3 (+ 1.75S).

If the slag composition conforms to either one of these relations, the slag will be stable and will not disintegrate during cooling. Th ese limits were verifi ed extensively by laboratory experiments and industrial samples, and proved to describe the disintegration behaviour very well.

A recently developed Scheil-Gulliver solidifi cationmodel for air-cooled slags linked these limits directly to the C2S precipitation area in the CaO-Al2O3-SiO2-MgO

phase diagram. Th e correspondence between the previ-ous numerical relationships, indicated by the red linesin Figure 2, and the presence of C2S in the slag struc-ture, indicated by the surface plot, is excellent.

Compared to the compositional limits, the model hasseveral advantages. Firstly, it gives an indication of theactual C2S level in the slag structure, which is relevantinformation for possible countermeasures. Secondly,it also indicates the evolution of the mineralogy dur-ing solidifi cation. Th is allows one to see, for instance,in which temperature range the C2S forms. Th irdly, themodel can incorporate other slag components such asCrOx, FeOx or TiOx 2. Th is makes the model far more ver-satile than the simple numerical relations. Last but notleast, the model does not only check the presence of C2Sbut simulates the complete mineralogy of the slag aft ercooling. Th is makes it possible, for example, to rapidly verify whether or not the slag contains free CaO or freeMgO and requires a subsequent weathering treatmentto guarantee long term volume stability.

Regarding the disintegration behaviour of the air-cooled slags, it is clear that the relationship between slagstructure and slag properties is very well understood.Subsequently, measures can be developed to optimisethe slag mineralogy.

How to avoid disintegration?Th is particular kind of disintegration of air-cooled slagsis directly linked to the β → γ transformation of C2S.One possibility to avoid the dusting is to completely avoid the formation of C2S in the slag structure duringsolidifi cation.

Referring to the numerical relationships discussedabove, lowering the slag basicity by adding a substan-tial amount of SiO2 would be the best option to do this.As such a change would greatly aff ect the metallurgicalprocess, the SiO2 should be added aft er slag/metal sepa-ration. At this stage, however, it is by no means straight-forward to dissolve a large amount of additions into theslag.

Considering these practical diffi culties, a secondpathway has been developed, which focuses on the de-structive β → γ transformation rather than the presenceof C2S. From cement making, it is known that by incor-porating a small amount of doping agents in the C2Scrystal structure, the β-polymorph can be stabilised toambient temperatures.

In this regard borates have proven to be especially eff ective, particularly for slags as well. Even a smallamount of borate addition during or immediately aft erslag/metal separation resulted in a stable slag. Due to itspractical simplicity, borates have been used as a stabi-liser for metallurgical slags for several years in industrialpractice.

Recently, the scientifi c interest in the technique hasgrown because of several reasons. First of all, a borateslag treatment implies a signifi cant cost for the meltshop.Although this cost is minimal compared to the alterna-tive dust issues and valorisation problems, the ever-in-creasing competition in the market leads companies totry to further increase the borate effi ciency or even de-

Figure 2: Simulated C2S levels. The red lines indicatethe empiricalrelationshipsestablished in 1942.

1617 JUNE 2008 Thistle Charing Cross London

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velop alternative stabilisers. Secondly, although borates are generally not considered toxic, concerns have risen about the potential eff ects of boron leaching during the slag’s second life. In an attempt to anticipate changing regulations, alternative treatments are pursued.

Where do the borates go to?A fi rst question to be answered, is where the borates end up in the solidifi ed slag structure. Are they incorporated primarily in the C2S phase as intended, in other phases, or even in newly formed phases? Laboratory solidifi ca-

tion experiments on synthetic slags have led to surpris-ing results.

A disintegrating CaO-SiO2-MgO slag was treatedwith borates and solidifi ed in controlled conditions. Th eslag showed to be stable. Using a highly sensitive elec-tron microprobe, the slag structure was characterised.Six phases were identifi ed and analysed for their boratecontent. As expected from the macroscopic stabilisation,some B2O3 was found in solid solution with C2S. How-ever, B2O3 was also found in other phases (e.g. CS). Th ehighest concentration was detected in a CxSyBz phase


globalslag MAGAZINE

Figure 3:Microstructure of a slowly cooled CaO-SiO2-MgO slag (1.33C/S, 10% by wt. MgO) with 1.8% by wt. B2O3.

Figure 4: RelativeB2O3 concentrationsin the diff erent phases(indicated by the netpeak heights in the WDS wavescans).

(Figures 3 and 4), which was not found in the untreated slag structure. Similar results were observed in a borate treated industrial stainless steel decarburisation slag.

Th e obvious next question is what causes this par-ticular borate distribution. Th e thermodynamic solidifi -cation model provides some insight in the mechanism. One of the fi rst phases to form in most slags during so-lidifi cation is C2S (Figure 5). At this stage during cool-ing the borates are distributed amongst the C2S phase and the liquid phase. Th ermodynamic considerations stipulate that not the concentration but the activities of the borates in both phases are equal. For typical metal-lurgical slags, this means that the borate concentration in the liquid slag is roughly 5-10 times higher than in the C2S particles. Th erefore, only a minor part of the borate additions actually forms a solid solution with C2S and contributes to the stabilisation of the slag. Th e major part is taken up by the other phases, formed af-ter the C2S precipitation. Considering the controlling thermodynamics, however, it is not possible to increase this borate yield signifi cantly without changing the slag chemistry completely.

How much borate is required?Due to the relatively low yield, one could imagine a sub-stantial amount of borates is required to stabilise the dis-integrating slags. On the other hand, experiments have already shown that 0.1% by weight in solid solution with

pure C2S is suffi cient for the stabilisation. Looking at the required amount for slag stabilisation purposes, the available data is scarce and very fragmented. However, it does seems that an overall B2O3 concentration of 0.25% by weight leads in all cases to a stable slag. Recent labo-ratory experiments on disintegrating ladle refi ning slags have confi rmed this upper limit. In industrial practice a higher level is probably necessary due to diffi culties with mixing the borates homogeneously throughout the slag.

Th e eff ect of slag composition on the required borate level is not yet systematically studied. However, recent experiments on CaO-SiO2-MgO slags, presented in Fig-ure 6, have shown a clear dependence on slag basicity. First of all, the upper limit of 0.25% by weight B2O3 is confi rmed once more. Secondly, it is shown that certain slags can be stabilised using signifi cantly less B2O3. Es-pecially slags with a lower basicity require less borate ad-ditions. Also at higher basicity, less borates are needed. Th ough this may seem surprising, it is logical. As C2S levels are higher, less borates are lost to the other phas-es. From a scientifi c viewpoint, the observed empirical relationship at lower basicity can however not be fully explained. Seemingly, several stabilisation mechanisms do play a role as well.

From a pragmatic viewpoint, on the other hand, the observed relationship opens room for optimisation. By monitoring the exact slag composition, the added

globalslag MAGAZINE


Figure 5:Simulated

solidifi cationsequence of the

studied slag.

globalslag MAGAZINE


amount of borates could be fi ne-tuned to the particular slag, resulting in borate savings. It is recognised that an important premise needs to be fulfi lled before this opti-misation can be successful. Th e empirical relationship should be determined for the practical situation at the meltshop, taking into account the actual slag composi-tions, the cooling path and the method of borate addi-tion.

ConclusionsIncreasing environmental awareness has created incen-tives for metallurgical companies to tackle various slag issues. Regarding air-cooled slags, C2S-driven disinte-gration during cooling is one of the main issues, as it not only creates dust problems but also complicates the slag valorisation in construction applications.

Borate additions to the slag during or immediately aft er slag/metal separation have proven to be a eff ective and easy-to-implement method to stabilise these slags and avoid disintegration. Th e technique is commonly used for treating stainless steelmaking slags at the mo-ment, but its potential for treating ladle refi ning slags has also been shown. Actually, to the best of our knowl-edge, all slags prone to C2S-caused disintegration can be treated successfully with borates. To evaluate whether or not an air-cooled slag contains C2S, one can use simple numerical relationships. A more versatile thermody-namic solidifi cation model off ers a deeper understand-ing of the issue.

In an attempt to further increase the borate effi ciency and develop alternative stabilisers, the scientifi c com-munity is trying to unravel the exact mechanism of bo-rate stabilisation. It has been shown that only a fraction of the added borates forms a solid solution with C2S

and contributes to the chemical stabilisation of the slag. However, as this fraction is governed by thermodynam-ics, it is not possible to increase the borate yield without drastically changing the slag chemistry. On the other hand, it has also been shown that the required amount of borates depends heavily on the exact slag composi-tion. By close monitoring of the slags, the added amount of borates could be fi ne-tuned to the particular slag, re-sulting in signifi cant savings.

AcknowledgmentsTh is work was fi nancially supported by ArcelorMit-tal Stainless Genk, Rio Tinto Minerals and the IWT (050715). Th e authors also thank Pieter L’Hoëst for his help with the EPMA-WDS measurements.

Further reading1. D Durinck et al, ‘Slag solidifi cation modeling using the Scheil-Gulliver assumptions’, Journal of the American Ceramic Society, 2007, 90(4), p1177–1185.2. D Durinck et al, ‘Borate distribution in stabilised stain-less steel slags’, Journal of the American Ceramic Society, 2008, in press.3. D Durinck et al, ‘Prediction and prevention of the dis-integration of air-cooled slags’, Accepted in the 3rd In-ternational Conference on Process Development in Iron and Steelmaking (SCANMET III), Luleå, Sweden, 8-11 June 2008.4. D Durinck et al, ‘Review: Hot stage processing of met-allurgical slags’, Submitted to Resources, Conservation and Recycling, 2008. (see http://perswww.kuleuven.be/sander_arnout/).

Figure 6:Disintegration as afunction of slagbasicity inCaO-SiO2-MgO slags.



Above: The offi cialconference poster.

Th e Iranian steel industry began in the 1960s with theestablishment of a 1Mt/y capacity blast furnace. Duringtime this plant has been improved and the capacity in-creased to 4Mt/y. During the 1970s the new technolo-gies of direct reduction (DR), the electric arc furnace(EAF) and continuous casting were adopted. Currently,the annual capacity of steel production in Iran using theEAF method is approximately 8Mt.

Th e planned capacity for melting and casting basedmainly on EAF techniques is set to be 32Mt over thenext four years. As a result of this, the majority of slagproduced in Iran will be steel slag rather than that pro-duced from blast furnaces (BF). For example, at thepresent moment Iran produces 1.2Mt/y of blast furnaceslag, while the combined production of slag from EAFplants stands at 1.6Mt/y.

Th e majority of blast furnace slag is used in cement and road construction, but very little EAF slag has been adopted in Iran. Nevertheless, the situation is changing, mainly due to the increasing quantity of steel slag that has accumulated in steel mills during recent years (ap-proximately 10Mt).

With this background in mind, the aim of the 1st Iranian National EAF Slag Conference was to explore solutions for the application and processing of the ever-increasing quantities of Iranian steel slags, and in do-ing so to reduce the environmental problems associated with its long-term storage.

Conference reviewConference reviewTh e conference took place over the course of one day, and was attended by over 170 delegates from the steel,

1st National Iranian EAF Slag Conference 2008 Review

The fi rst Iranian National EAF Slag Conference was held on 19 December 2008 in Isfahan, famous for being the steel production capital of Iran. This event was sponsored by the Steel Institute of Isfahan University of Technology (IUT), and the Mobarakeh Steel Company (MSC), the largest steel producer in the Middle East. The main theme of the conference was ‘Processing, recycling and application of EAF slag.’

Hadi SadrpourIranGostaresh Technology Management Institute

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cement and construction industries, in addition to uni-versities and research institutes. A total of 14 papers were accepted for presentation on a variety of topics including processing technologies, applications of slag, and slag handling.

Th e conference was chaired by Dr Ashrafi zadeh.Moreover, a jury of fi ve experts from universities and industry were selected to evaluate the presentations.

Aft er the welcome address by Dr. Ashrafi zadeh thefi rst paper was presented by Prof. Youzbashi from the Sharif University of Technology (SUT), entitled ‘Diff er-ent types of slag, specifi cation and applications.’ Th en two keynote papers were presented by technical staff of the Mobarakeh Steel Company, entitled “Specifi ca-tion of EAF slag produced at MSC,” by E Moghadam and colleagues from the melting and casting depart-ment of MSC. Th is was followed by the second key-

note paper, entitled “Environmental eff ects of EAF slagat MSC.” Th is paper was delivered by M Sattari of theenvironmental control dept, MSC. Th e papers mainly focused on slag production and the environmental is-sues associated with the site and its vicinity.

Th e fourth paper (‘Molten slag processing apply-ing atomizing technique and the applications of prod-ucts’) was presented by Hadi Sadrpour of IranGostareshTechnology Management Institute in cooperation withEcomaister Co, Ltd of Korea. Dr Sadrpour discussed indetail the processing of molten slag utilising ‘slag atom-ising technology (SAT)’. According to Dr Sadrpour, theapplication of this technique will eliminate the environ-mental issues presently existing at mill sites and will pavethe way for profi table applications of a new generationof materials. Th e advantage of this process was identi-fi ed as converting a waste material into a high value andenvironmentally friendly by-product in a short time (15min process time), saving cost, landfi ll and removingany pollution issues.

Dr R Khodadadi then gave an interesting paper onthe application of slag in cement and concrete. He rec-ommended taking serious action to prepare standardsfor cements utilising slag as a key component of the ce-ment mixture.

Th e other paper titles and their contents that werepresented over the course of the day were as follows:

‘Processing techniques of steel slag;’ M Honarman•(RTC);A survey on how to reduce delays of steel produc-•tion by EAF due to unexpected constraints with slagcollection and transportation;’ A Bonakdar and HAbrishamkar, Imodro – MSC;‘Recognition of eff ective factors to control the con-•tent of EAF slag;’ S A Mozafari; Chemical IndustriesResearch Institute;

Above: Dr HadiSadrpour chairs asession.

Right: Delegatespose in front of theconference poster.

‘Th e eff ect of slag carrying pots confi guration on fi -• nal characteristics of carried slag;’ R Sangari and as-sociates, Saya Steel Co;‘Application of slag in cement and concrete produc-• tion;’ R Khodadadi, Civil Engineering School, Isfa-han University of Technology;‘Application of EAF slag to produce fl oor tiles;’ A. • Maghsoudi, Materials and Energy Research Center;‘Application of EAF slag to control environmental • pollution;’ N Mirghafari, College of Natural Re-sources, Environmental Dept, Isfahan University of Technology (IUT);‘Recovery of iron from slag and utilising it in EAF;’ • S Shahravan;‘Application of EAF slag in road construction;’ M R • Moghaddam, R&D Dept of Nemouneh Asphalt Co;‘Mathematical modeling for chemical quality control • of slag content cements;’ H Khani, Sepahan Cement Co;

Abstracts of each of these papers can be found at the Steel Institute web site, http://www.steel-institute.ir.

AwardsAwardsTh e awards for best presen-tation, article and exhibition were decided upon by the fi ve-panel jury. First place in the category of best presenta-tion was awarded to Dr Hadi Sadrpour. Th e same presenta-tion was also chosen as the best presentation as voted by the conference delegates. Dr Khodadadi came in second place in the same category.

In the category of best ex-hibition stand, fi rst prize went to Iran Gostaresh/Ecomaister Co, Ltd for their booth, which included live samples of slag generated from SAT.

Summary and potential Summary and potential future initiativesfuture initiativesTh e conference was warmly welcomed by all delegates, who encouraged the organis-ing committee to continue the event in the coming years. It was also highly recommend-ed to extend the scope of the seminar and invite compa-nies and individuals from across the world. Delegates also indicated a desire for fu-ture conferences to focus on research in order to discover new applications of slag.

Th e jury also advised the Mobarakeh Steel Company to establish a 300,000t/y slag at-omizing plant as soon as pos-

sible along the lines of Ecomaister’s SAT methodology.Other developments at the conference included the

recommendation to establish a joint marketing and research team between the IranGostaresh Technology Management Institute and the Steel Institute of Isfahan University of Technology. Th is venture should promote the commercial application of Ecomaister’s PS Balls.

globalslag MAGAZINE


Left: Some of thedelegates at this

year’s conference;plans are in place

to make the eventmore international

in scope.

Left: Thewinning team.

Ecomaister wasawarded fi rst prize

in the categoryof best exhibition

stand

1 globalcement MAGAZINE January 2007

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1 globalcement MAGAZINE January 2007

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Global Cement Directory 2007-2008 21

1st Global Cement Environmental Conference 2008, Düsseldorf 15

1st Global Cement Trade Conference 2008, London 27

4th Global Slag Conference 2008, Strasbourg OBC

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