8th Global Slag Conference 2012
12-13 November, Las Vegas, USA
Reviewed by Dr Robert McCaffrey, Global Cement Magazine
Image gallery for the 8th Global Slag Conference 2012
The 8th Global Slag Conference & Exhibition took place successfully at the Bellagio hotel in Las Vegas, USA on 12-13 November 2012. The 115 delegates from 26 countries heard a wide range of high-quality presentations on slag trends, performance, applications and markets and were able to speak with exhibitors in the busy exhibition area. The 9th Global Slag Conference & Exhibition will take place in Dubai, UAE on 10-11 December 2013.
The Global Slag Conference in 2012 took place in the US at the kind invitation of the US National Slag Association and also had the benefit of sponsorship and support from a number of important slag-related entities, including the Australasian Slag Association, the Slag Cement Association, the Nippon Slag Association and the Brazil Steel Institute.
Charles Zeynel of ZAG International opened the conference with a presentation on trends in global supply of cementitious materials, including ground granulated blast furnace slag (GGBFS). He suggested that there are a number of uncertainties that are currently impacting the situation including changes in the US energy mix, the global economic crisis, shifts in China, nuclear cutbacks, an increased emphasis on environmental regulations and changes in the availability of fly ash and other supplementary cementitious materials (SCMs).
He pointed out that the supply of SCMs is not within the power of the cement industry and that this makes the cement producers ‘somewhat uncomfortable.’ Charlie pointed out that the US is facing a medium- to long-term cement shortage, which will probably be partly filled by the use of slag and slag-based cements. He suggested that a combination of low gas prices and higher environmental regulation will mean less coal-fired power generation in the US and lower availability of fly ash. At the same time, Japan will also reduce slag exports, due to higher domestic demand and lower steel production.
SK Khoo, also of ZAG International, looked at the factors that influence the international trade in slag. In the 1980s, international freight went from boom to bust to boom again, but with relatively low levels of profitability. The 1990s saw a series of mini booms and busts, but the Asian Crisis led to widespread turmoil, with the world fleet cut in half... leading to increased profitability for the survivors. In 2003-2008, there was an unprecedented long period of growth, which has been called the Great Moderation, but which culminated in the gigantic bust of the 2008 global economic crisis. Freight rates, after the madness of inflated rates prior to the crisis, are now around what they were prior to 2003. SK suggested that there is a surplus of around 6% in global fleet tonnage, which will inevitably lead to a crash in freight prices. A new breed of super-eco ships may reduce the impact of dramatically increased costs of bunkers (fuel) on freight costs in the coming years.
Richard Lehman then gave a co-authored paper (with Karen Kiggins) on recent trends and happenings in the US slag industry. The (US) National Slag Association (NSA) is the representative body for American slag producers. The association has found that the US Environmental Protection Agency (EPA) has become considerably more difficult to work with, especially since the TVA Kingston ash lagoon spill of 2010, even though the Department of Transport is still open to the use of slag for road building. The new Steel Slag Coalition is trying to promote the acceptance of slag products as safe and environmentally benign products, rather than as a waste. The NSA is very active in promoting the use of slag products in a variety of applications. The regulation of slag varies widely, from state to state. The Steel Slag Coalition has looked at Europe’s REACH programme to provide a framework for the specification of slag products, which can then be taken to the standards organisations for their imprimatur. Slag use for transport infrastructure use is still being fought over on a state-by-state basis.
Hendrik van Oss of the USGS spoke about the latest results of the surveys of US slag and other construction materials. Air-cooled and granulated slag and steel slag production have all seen a dip during the economic crisis, but it seems that the bottom has been attained and some anaemic growth has been seen. He pointed out that in the US it is the concrete producers that tend to do the blending, rather than the cement industry (only 2% of cement sold in the US is blended), so that the use of slag in concrete, according to a survey of cement producers, is probably understated. Hendrik pointed out that a number of US iron and steel plants have been closed or idled, reducing the supply of slag. Only three blast furnaces out of the 25 in the US now have granulation facilities, while imports are readily available. Hendrik concluded that the use of alternative raw materials by the cement industry, such as GGBFS, must not create more problems than they solve.
Cassius Cerqueira next introduced the Brazil Steel Institute, which is a non-profit organisation that aims to bring together Brazilian steel companies and to promote their interests. Brazil produced 35Mt of steel in 2011, the world’s ninth largest producer, with an installed capacity of 48Mt. Considering that slag accounts for 60% of the co-products generated by the steel industry, finding value-added alternatives to landfilling them is the focus of the CCA Brazil (Brazil Steel Co-products Centre). Steel production is forecast to increase to around 58Mt of steel by 2017, with 36Mt of co-products. The four southeastern states of Brazil (Minas Gerais, São Paulo, Rio de Janeiro and Espirito Santo) produce 94% of Brazil’s steel. The use of slag faces an up-hill struggle and regulation seems to be tightening. However, the potential is massive: for example, 86% of Brazil’s roads are unpacked and tens of thousands of kilometres of new roads are currently planned. The CCA Brazil is working hard to have slag products designated as non-wastes.
Dave Berdusco of Paul Wurth next spoke about the INBA slag granulation system. (INBA coming from the initials of the inventor’s children). INBA is a fully automatic system and comes in hot water, cold water and cold water with steam condensation system configurations. Slag is granulated into a tank of water approximately 2m deep and is then taken to a rotating dewatering unit by gravity or slurry pumping. The cold water system incorporates a cooling tower. The INBA system has a compact design, high reliability, continuous filtering and evacuation, and low operation and maintenance costs. Using a granulation tank promotes a low water-to-slag ratio, good heat transfer and fast cooling of the slag with high slag density and low wear. A plant producing 6000t of metal per day will also produce 1600t of steam or 2.7Mm3 of steam in a day. If the steam is condensed, both H2S and SO2 emissions are reduced. Global Slag notes the huge potential for waste heat recovery (please see www.CemPower for details).
Joseph Zeno, CEO of ACS Industries, pointed out that the company developed a popular side attachment changeover technology and subsequently developed the first hot slag bucket. Joseph pointed out that bucket design and use of the correct materials are crucial to ensuring long service life for hot slag buckets. Heat compensation must also be used to avoid warping in the bucket during the digging of hot slag.
Sang Jin Nam of POSCO next spoke about slag optimisation for hearth protection and slag fluidity. Expanding the campaign life of a blast furnace is of great concern in the steelmaking industry and premature hearth erosion is one of the most important factors limiting campaign life. There are several measures to reduce the erosion of the blast furnace hearth, including the addition of titania-bearing materials into the charge of the blast furnace. This is believed to promote the formation of a protective layer on the refractory brick. Sang Jin Nam suggested that the optimum slag composition range can be identified using the composition of compounds and the measurement of viscosity in a given slag composition. As TiO2 content increases, both slag viscosity and critical temperatures are decreased and Mr Nam suggests that correct application of TiO2 compounds can increase hearth life.
Rick Comtois of Austin AI Inc next spoke about an image-enhanced induction sensing technique to process less slag and recover more metal from slag. He pointed out that around 90% of steel slag contains no metal, while perhaps 6% is bare metal and the rest is slag with encapsulated metal. Metal pieces are sensed using induction sensors and compressed air jets are used to separate desired from non-desired particles. An enhanced resolution image means that less raw slag is ejected from the process stream with the desired metal pieces.
Aaron Valencia of Dust Control Technology spoke about his company’s specialised fan for dust suppression. Water is forced through an atomising nozzle, so that dust is attracted to the droplet and the heavy droplet drops out of the atmosphere. Tower-based units have been successful in the slag industry. Aaron was realistic in stating that most users of the equipment wanted to instal the equipment and to forget about it. The equipment can be made to operate automatically and can also be controlled remotely. The units can also be mobile-mounted.
Gala dinner and Global Slag Awards
The Global Slag Conference Gala Dinner and Awards took place at the top of the Stratosphere Hotel, the tallest building in Las Vegas at an eye-popping 108 stories high. The Global Slag Awards were presented, following an online nomination and voting process. Plant of the Year was awarded to Phoenix Services’s Indiana Harbor East plant, while Product of the Year was awarded to slag-bonded wallboard. Paul Wurth was awarded the Technical Innovation of the Year award for the INBA process and Hendrik van Oss was awarded the Global Slag Personality of the Year, to rowdy applause. The conference convenor took the opportunity to jump from the top of the building (video here).
Second day
The second day of the conference started with a session on slag grinding, with Caroline Woywadt of Gebr. Pfeiffer going first. She gave details of her company’s MVR vertical roller mill (VRM). Two rollers are stationed next to each other on each support, providing a number of technical and economic advantages. The MVR mills feature the variable speed MultiDrive drive system, with self-aligning pinion, which are installed on rails and which achieve active redundancy. One or more rollers can be taken off-line and the production capacity of the mill will be only slightly reduced. The table support is designed to take unbalanced axial and radial forces. Caroline is convinced that the market share for VRMs for slag grinding will continue to grow. The need for integral drying and stand-alone grinding plants are also increasing. Caroline pointed out that the calculations for ASTM and EN 196 Blaine product fineness will come up with different answers. She pointed out that the grindability of slag is influenced by the granulation process, storage conditions, composition and mineralogy. The MVR mills can supply high Blaine ground slag at low specific energy consumption. The largest VRM in the world has been sold by Gebr. Pfeiffer to Holcim Barroso in Brazil, with a 6.7m table diameter and an installed power of 11,500 kW.
Jérôme Portal from Fives FCB spoke about the Horomill and TSV classifier for slag grinding. The Horomill consists of a horizontal rotating shell which uses bed compression grinding and four to six grinding passes before material is passed from the mill, via a bucket elevator, to the classifier. The internals are made of specialised wear-resistant materials, including chromium cast shell liners and tungsten carbide scrapers and roller sleeves. Typically, the Horomill is applied in locations with very high electrical costs and 56 Horomills have been sold worldwide, with more than 1,500,000 hours of operation. Fives FCB states that the Horomill system has the lowest specific grinding energy requirement of all grinding mill types, with a reduction of around 60% compared to an optimised ball mill. Six units have been sold into China, specifically for steel slag grinding. The zero-water injection units feature an external circulating loop, which makes iron removal easier, allowing a higher ground steel slag addition to cement (5-15%), due to the lower iron content.
Stefan Baaken next spoke on behalf of Loesche. He pointed out that Loesche has patented the 2+2 arrangement of rollers,,with a smaller roller preparing the grinding bed before the main roller. Loesche has sold 105 mills for slag grinding. He went on to speak about stainless steel slag grinding for fine metal recovery. The grinding process effectively separates the high metal fraction from the more finely ground and lower density slag fraction, which can then be used in the Carbstone block forming process. The first plant for processing stainless steel slag - incorporating a Carbstone pretreatment, shaping and carbonation-curing process - will be commissioned in 2013.
Moises Núnez from Cemengal next spoke on the Plug ‘n’ grind concept. Cemengal’s main business is supplying grinding stations for cement and slag and the company’s capabilities include all design and engineering, as well as installation and project management. The Plug ‘n’ grind system is a small slag grinding system (it would fit into a basketball court) and can be supplied in only seven months after the initial order. Production capacity is around 90,000t/yr for cement and around 60,000t/yr for slag. The system fits into just eight 40 foot containers. Only four or five people per shift are required to run it. The system uses a two-chamber 500kW ball mill for grinding. The system is ideal for traders and importers, who can avoid the high taxes and duties on the importation of finished products and which can manufacture in the target country: if markets fall, the plant can be dismantled and moved. Cemengal has already sold two units, one in Kenya and one in Saudi Arabia.
A ‘grinding panel’ composed of experts from grinding mill manufacturers subsequently answered audience questions, emphasising the companies’ differences - and similarities.
Dr Yixin Shao of McGill University, Montreal, next spoke about steel slag-bonded wallboard using carbonation activation. Steel slag is rich in calcium content, which can be activated by CO2 via carbonation, through the reaction with calcium silicates to produce calcium silicate hydrates while reducing free lime content. This leads to CO2 use and the reduction of embodied energy. A variety of commonly produced slags were tested and a BOF slag, a ladle slag and a GGBFS slag (although difficult to activate) were also used. Different slags had different carbonation reactivities and variations in compressive strength, largely due to mineralogical differences which also reflected the degree of weathering: an initial weathering phase made the slag less reactive. The binding capacity of one particularly promising slag was investigated with sawdust as a filler. Increasing sawdust content reduces carbonation uptake and reduces final compressive strength. The final boards used around 10% sawdust and 15% water content. Flexural and compressive strength of the slag sawdust boards were comparable to commercially-available boards. Moisture uptake of the boards did not greatly influence the strength characteristics of the boards.
Yasuhito Miyata of JFE Steel spoke about the use of steelmaking slag for environmental improvement in coastal areas. In areas of oxygen depletion, sulfate-reducing bacteria can decompose organic material to produce hydrogen sulphide, a toxic and very smelly gas. JFE steel tested out steelmaking slag in Fukuyama inner harbour to see if it would suppress sulphide production, after laboratory experiments indicated this possibility. Pollution control frames composed of slag were buried in the harbour sediments and the production of hydrogen sulphide measured by having divers disturb the sediments and collecting the gases given off. It was found, in short, that the area that the slag frames had been buried produced no hydrogen sulphide, compared to high levels from the control plots. Dr Miyata suggested that Fe ions on the surface of the steelmaking slag reacted with sulphide in the sediment to produce FeS, inhibiting the production of HS gas.
Akio Hiyashi of JFE steel Corporation went on to speak about the use of steelmaking slag in coastal areas, specifically for the absorption of CO2 to avoid ‘blue tides.’ Coastal ecosystems, such as seaweed beds, are recognised as an important CO2 sink, annually absorbing around 0.87-1.65bnt of CO2. The United Nations Environment Programme has called on all countries to make efforts to conserve coastal ecosystems, under the ‘blue carbon’ programme. Steelmaking slag is characterised by high levels of CaO and of total iron. A steelmaking slag and dredged soil embankment can be formed underwater, behind a submerged dyke and an extensive study was undertaken to determine whether this was a successful approach, at a test site in Kawasaki Port, closes to Tokyo. Extensive control points were used. It was found that seaweed grew very well on the slag-based mounds, to double the length of seaweed on control mounds with no slag. Inhibition of the settlement of other organisms was not observed in the areas of slag-mound-based seaweed beds.
Rich Russell of Tube City IMS next gave an introduction to the use of electric arc furnace (EAF) and basic oxygen furnace (BOF) slags as aggregates in asphalt, particularly with regards to use in the states of Illinois and Indiana. The slags provide resistance to rutting, shoving and polishing, they retain heat due to their dark colour and so are good for winter road use and they improve stopping distances due to the continued high angularity. Air-cooled slag is used in chip form and can be used in conjunction with natural aggregates. Slag passed through an impact crusher can provide well-shaped aggregate, but can produce a high proportion of fines. However, whatever gradation is produced, the keyword is consistency. It is critical to provide a high quality, consistent product and to keep exactly to all QC protocols. It may be costly and time-consuming to become a certified supplier to a state department of transportation (DOT) and substantial efforts, in terms of sampling, analysis and further QC controls, are required on an ongoing basis. DOTs are ‘broke’ and so they have put the responsibility for QC on the suppliers - if the product is not ‘in spec,’ the producer will be liable for rectification on the job site: “Tearing up a mile of highway might cost you $2m!” concluded Rich Russell.
Tim Stanfield, also of Tube City IMS, finally spoke about an application at a military facility which used steel slag for living and training areas, tank training roads, general purpose roads, erosion control, embankments, lay-down areas, shooting ranges, ‘treacherous’ roads and maintenance areas: as Tim said, “pretty much every possible application you could want.” The location used over 300,000t of air-cooled slag over six years and is set to use another 150,000t in the next two years.
Farewells and conclusions
At the farewell party, a number of honours were awarded. Tapojärvi won the ‘Best exhibition stand’ award, while the authors from JFE Steel - Yasuhito Miyata And Akio Hayashi - were awarded a special ‘environmental citation’ for their efforts to use steel slag to improve the environment.
Charles Zeynel was awarded fourth place in the best presentation awards (as voted by the delegates) while Dave Berdesco was third for his paper on the INBA slag granulation process. In second place was Rich Russell for his paper on the use of steel slag in hot-mix asphalt, but the winner of the ‘Best Presentation Award’ was Yixin Shao and co-authors for their paper on steel slag-bonded wallboard.
This particular edition of the Global Slag Conference was the highest-rated ever, and scored particularly highly in terms of networking opportunities, technical content and for the quality of the exhibition and the conference hotel.
The 9th Global Slag Conference, Exhibition and Awards will take place 10-11 December 2013 in Dubai, in the United Arab Emirates. We look forward to seeing you there!
