10th Global Slag Conference, Exhibition & Awards 2014
8 - 9 December, Aachen, Germany
Reviewed by Dr Robert McCaffrey, Global Cement Magazine
Image gallery for the 10th Global Slag Conference 2014 (large gallery - may take time to load)
The 10th Global Slag Conference, Exhibition and Awards 2014 have successfully taken place in Aachen, Germany, attracting 170 delegates from 35 countries to attend 16 presentations and more than 12 hours of networking and business opportunities, including 12 exhibitors. The 11th Global Slag Conference will take place in November 2015 in Bangkok, Thailand.
Welcome!
On the evening before the conference, the 10th Global Slag Conference started off with a convivial welcome party in the event's exhibition area, which was graced with 12 slag industry supplier-exhibitors.
Conference first day
After a welcome to the conference from the event convenor Robert McCaffrey, the first speaker, Charlie Zeynel of ZAG International, started the conference by saying that we are just entering into a major boom in the cement industry. Charlie pointed out that the global cement scene has changed a great deal since the first Global Slag Conference in Düsseldorf in 2005. Chinese companies have burst into the global top ten cement producers, while the European cement companies have been fighting back through mergers and acquisitions. Slag supply and demand have shifted over the decade and now slag products are in increased demand. Charlie suggested that the US will become the largest importer of raw materials over the next decade. Indeed, imports are set to resume in 2015, mostly into the Gulf Coast, with 10Mt set to be landed in 2015, and 20Mt/year expected by 2020 (possibly more if environmental regulations lead to plant shutdowns in the US). Other supplementary cementitious materials (SCMs) such as flyash, are set to be sucked in at the same time.
Africa's population is set to double over the next couple of decades and will be a 'great place to be,' in terms of business and trade, according to Charlie. At the same time, China has a huge 'overhang' of production capacity, equal perhaps to 1.6t of cement production capacity per person per year, compared to a long term average demand in developed countries of around 500kg per person. Along with Europe, we could see a 'Japan-like' rationalisation of production capacity, with capacity being cut by around 50% over as little as a decade. Charlie reminded delegates that ten countries control 96% of blast furnace iron production worldwide, with a total of around 361Mt of slag produced, but with only 273Mt of slag being granulated. Blast furnace production capacity expansion is slowing, as mini-mills replace integrated blast furnace complexes. The reactivity of granulated blast furnace slag (GBFS) varies around the world, according to the source. Charlie underlined the fact that the global supply of slag products and of fly ash is insufficient to meet global demand.
Next, Michael Connolly of Tube City IMS showed delegates a video extolling the virtues of slag products. He said that Nebraska had legislated so that slag which is not 'discarded' is now regarded as a product rather than as a waste. Tennessee and Iowa have both followed along the same regulatory path, with additional states being targeted for similar legislation including South Carolina, Indiana and Texas. The regulatory trend in the US seems to be to try to ensure that cooled-slag and slag products are classified as products rather than as by-products or as waste, and also to specify product characteristics and performance to ensure that slag products can compete with other building materials. Ohio has stipulated that, in essence, if a material is treated like a waste, then it is a waste; If, on the other hand, it is treated as a valuable resource, and is managed as such, then it can be classified as a co-product. Michael concluded that the treatment of cooled-slag or slag products varies from state to state, but that the best way forward is to work with state legislators to ensure that slag products are classified as products rather than as waste. Manganese has come into the sights of legislators and the slag products industry is fighting legislation on this on a number of fronts.
Winnie Matthes of Holcim Technology spoke about Holcim's long history of the use of slag products in the cement industry. In 1995 Holcim had a clinker factor of over 80%, but this is now lower than 70%, partly thanks to increasing use of slag but also due to the use of other SCMs. The company makes a variety of products with varying amounts of slag substitution, from low-slag with elevated early strengths, to higher slag contents with improved workability, lower heat of hydration, increased late strength, improved ASR and chemical resistance and a lighter colour but with lower early strengths. Robusto (slag and burnt oil shale), Opticeo (cement, slag and silica fume - Opticeo is a CEM II/A-S (slag composite cement) - offered as an alternative to the conventional solution of OPC + silica fume) and Spinor (slag-based finely-ground micro-cements for oilwell cementing and ground rehabilitation) are just three of the new slag-containing products from Holcim. Winnie pointed out that the higher the content of GBFS in the product, the higher the effect on performance of the quality of the GBFS.
Slag from different regions in the world varies in general composition, with slag from Asia being high in alumina, slag from North America being low alumina and Russian and Eastern European slags tending to have low alumina and with C/S being medium to high. With increasing C/S ratio, the strength of the final product tends to increase. Elevated levels of titanium, Winnie said, should be considered as deleterious to cement strength, so that Ti concentration should be reduced to as low a level as possible in the GBFS, also given that higher Ti levels lead to lower grindability of the granulated slag. Glass content, chloride content, bulk density, moisture content, loss on ignition and the state of prehydration are all important factors influencing granulated slag quality. Lower granulated slag quality tends to increase cement production cost, through adjustment of cement composition, blending, the use of additives and possible pre-treatment of the GBFS before use.
SK Khoo of ZAG International spoke about short and long term drivers of freight rates influencing the costs of international SCM trade. He pointed out that China is rapidly reaching a crisis point in its economy, including an ongoing collapse in house prices, which may lead to a rapid reduction in the amount of freight capacity that is required to service the country. India is having to import more coal, due to the inefficiency and bureaucracy of its own coal industry. SK told delegates that a large number of new ships is on order, and that they are going to be larger ships than in the past. The average age of a ship when it is scrapped is also coming down, due to the oversupply in the freight market. In the 20 years to 2008, shipowners added 200Mt of shipping capacity, whereas 200Mt was added to the global freight fleet in just four years, in the period 2008-2012. A reduction in slow steaming (due to the fall in fuel prices) has also effectively added to the availability of freight capacity. This imbalance in supply and demand has led to a near-collapse in the profitability of freight operators, but on the other hand the cost of shipping materials over considerable distances has reduced for producers, shippers and users.
Sander Arnout of InsPyro, a Belgian university spin off, spoke about the feasibility of re-melting for the recovery of metal and to upgrade slag. Sander spoke about his company's thermodynamic approach to process modelling, which is not just based on theory, but which also includes 'real-world' lessons from practical process technology. The slag melting and crystallisation model can take input compositions and can then predict - with a given cooling profile - compositions and mineralogy of the resultant cooled slag. The validation of the models using real-world slag sampling is crucial.
Stefan Baaken spoke about the latest Loesche technologies for processing by-products from the steel industry. Stefan spoke about a new installation at the Charleroi plant in Belgium which takes pre-crushed stainless steel slag and grinds it in a specially-modified Loesche mill, to liberate even fine particles of stainless steel enclosed by slag. The mill produces a fine slag-based mineral filler product and a very high purity metal recovery fraction. The plant has a capacity of 20t/hr, with a feedstock of 3-15% stainless steel, and it produces a stainless steel raw material product with a metal content of 90%. The fine filler is mixed with water and additives, moulded into the appropriate form such as blocks or kerb stones, and is then processed in an autoclave to create high specification 'CarbStone' building materials.
In the second part of his presentation, Stefan spoke about the co-grinding of GBFS and concrete rubble in a Loesche mill, the aim being to disaggregate the inputs to create aggregates at least equal in quality to natural aggregates. The waste material needs to be pre-crushed and the rebar removed, along with other contaminants. The material is ground in a specially-adapted Loesche mill, which effectively separates out the cement component to produce a dry powder of 4500-5000 Blaine. Gravel and sand are produced as a 'reject' fraction, which after classification can be used as products or fed back into the mill for further processing. The recycled aggregate lends a higher strength to produced concretes compared to the use of natural aggregate, possibly due to crystallisation promotion through a fine coating of cement minerals of the recycled gravels. The finely-ground cement filler powder produced by the mill can be used as a filler for concrete.
In the third part of his presentation, Stefan spoke about the processing of LD steel slag to a highly reactive cement component and recovery of metal. Three steps are used to optimise the final product: a thermal phase is used to react the remaining metal in the hot slag to a more useable phase, which at the same time optimises the composition of the slag towards a more reactive set of phases akin to the composition of clinker - with alite increasing and belite, C4AF and amorphous phases decreasing. A dry granulation process is used to optimise the crystal structure of the product and to allow energy recovery, and finally the milling process increases the reactive surface area of the product and allows a final fine separation of metal content. Mortar tests show that the new clinker replacement material provides equivalent or higher strengths compared to OPC, particularly when the clinker replacement material is finely ground. Stefan concluded by stating that the next step is to find a parent for a prototype installation.
In the first of a pair of presentations both on the topic of dry slag granulation, Ian McDonald of Siemens VAI Metals Technologies spoke about his company's project to recoup the 1.5Gj of heat energy in each tonne of hot blast furnace slag. The solution is to pour molten slag onto a spinning cup, with the air in the chamber heated to 600°C by the cooling slag and then subject to heat exchange for steam generation and power production. The slag cools quickly in the cooling chamber and the aim is to produce at least 98% glass phase, with granulate size of 1-3mm and in a dry state. Ian pointed out the cost reduction in dry slag granulation compared to wet slag granulation. He also described a 'eureka moment' of realisation that the molten slag droplets in the cooler could still be allowed to be molten when they hit the water-cooled wall of the cooling vessels: The impacting droplets would be distorted but would reform as droplets due to surface tension, while still not being hot enough to agglomerate and instead to form a granular material of mostly between 1-3mm. The technology will be proven in a pilot plant at the VoestalpineStahl Linz blast furnace, which is currently under construction and which is due to come into operation in late 2015.
In the second paper on dry granulation, Daniel Michels of Paul Wurth spoke about his own company's unique approach to dry slag granulation. The company's INBA slag granulation plant, common around the world, uses water for granulation and has no energy recovery. Dry slag granulation saves the 700kg of water per cooled tonne of slag, but is also able to recover energy from the slag and at the same time reduce sulphurous emissions. Dry slag granulation saves on transportation costs owing to the dry product, involves no drying at the cement factory, the dry granules do not freeze in winter thanks to low water content and the granulated slag has a higher bulk density (1.3-1.4t/m3) than water-cooled granulated slag (1.0-1.1t/m3). All blast furnace dry slag granulation technologies must cope with surges in slag volumes and the new technology from Paul Wurth is able to do this. In the Paul Wurth technology, cold steel balls are tipped into the molten slag which is contained in large moulds, which leads to a fast cooling of the slag, down to 650°C within 30 seconds. The mixed balls and hot but not molten slag are placed into a buffer vessel which is used to heat air for heat exchange. The mix is then crushed and the slag balls separated out using magnets, with the steel balls then reused. Grindability of the produced granulated slag is akin to water-cooled slag, the glass content is generally above 95% and the compression strength of BF slag cements produced with the dry granulated slag is the same as cements made with water-cooled slags.
The first phase of a pilot plant was built at Dillinger Hütte BF 4, coming into operation in November 2013, but excluding the waste heat recovery phase. Daniel showed an impressive video of the plant in operation and mentioned that the process is appropriate for BF, BOF, EAF and FeNi slags. At the moment the vitrification rate from the process is still too low at around 90%, partly due to heat losses in the 35m-long slag runner. Once these issues have been addressed, the waste heat recovery phase of the pilot project will be undertaken.
Gala Dinner and Global Slag Awards
In the evening of the first day of the conference, delegates were transported by coach to Chateau Neercanne, literally right on the border between Belgium and Netherlands, to enjoy an evening of music, networking, fine wines, business and superb cuisine. During the evening, the Global Slag Awards were presented, after a two-stage on-line nomination and voting process which was open to all participants in the global slag industry. Slag company of the year was Tata Steel; Slag user of the year was Holcim; Equipment supplier of the year was Loesche; Slag plant of the year was the Calvert, Alabama, plant of Tube City IMS; Slag product of the year was heavily-bound EAF steel slag ER-MB20 road-base from SCE Materials and Recycling in Australia; the technical innovation of the year was the dry slag granulation and energy recovery process from Paul Wurth and finally the Global Slag personality of the year was a surprised and delighted David Ball, chairman of the David Ball Group, Cambridge. Slag discussions continued late into the night back at the hotel bar.
Second day
On the second day of the conference, Anil Parashar of Binani Cement in Dubai spoke about his company's management of slag. Binani Cement was the first company to grind slag in the UAE, back in 1999, as a contract grinder. Now the company grinds and markets GGBFS in the UAE and it accounts for around 30% of the market volume. Binani's production is expected to amount to 500,000t of GGBFS product within the next two or three years. The plant in Dubai operates three ball mills with a combined grinding capacity of 2Mt per year. The company faces a number of challenges, including slag storage, increasing slag prices and competitive pressures. Anil pointed out that the ball mills produce practically half the tonnage when grinding slag when compared to grinding OPC clinker. The factory has a constrained area for slag storage, particularly after a portion of the factory's land was appropriated by the Dubai municipality. Slag prices have increased by approximately 30% over the last two years, particularly for quality slag from Japan. Anil stated that the construction materials market in the UAE totally collapsed after 2008, but that it is coming back slowly, starting in 2012. The company has switched its production to its largest ball mill to achieve economies of scale and sufficient production tonnage. The company now also blends Japanese, Indian and Chinese slags, although the Japanese slags form the basis of the mix, with a maximum of 25% of other GBF slags. Some Indian slags were approaching Japanese slags in terms of reactivity. The plant had found that the use of a hot air generator was costing the equivalent of $7/t of slag ground, so that since 2012, the use of the generator was banned: the plant has coped nonetheless, albeit at lower production capacity.
Anil concluded that a variety of infrastructure projects in the Gulf States will continue to boost cement demand. In order to cope with future expected increases in demand, the Binani Cement Factory is considering the installation of a roller press for pre-grinding, with an investment of around US$8m and a payback time of 48 months. Anil repeatedly lamented the fact that the company had bought ball mills instead of vertical roller mills, but he shrugged and concluded, "We are where we are."
Rudolf Schulze of technical representative company Schulze & Partner spoke about the use of ACT's EcoSafe fire-resistant HFDU hydraulic fluid for slag and steel mill equipment. EcoSafe is a fully-synthetic fluid on a butol base, with lubricity over a wide temperature range, from -45°C to around 150°C, which can be used for slag-handling vehicles.
Caroline Woywadt of Gebr. Pfeiffer then spoke about her company's solutions for slag grinding. The grindability of a slag is controlled by many factors, including the mineralogy of the slag, the glass content and the weathering extent of the slag. The company still needs to undertake trial grinds of large (1000kg) samples to characterise the materials before proposing a design for a vertical roller mill. The company uses smaller scale mills for its tests, which require the test samples to be pre-crushed 'to scale'. The test mill can determine the throughput, the friction factor, the absorbed power and specific power consumption, the wear rate, dust load at the classifier and the range of fineness for all materials. The test results from the small test mills are continuously compared to results from full scale mills in order to validate the scaling of results. Caroline showed the construction of a major cement and slag grinding mill in Australia, with a guaranteed throughout of 190t/h at residual moisture of 0.5% and Blaine4200.
Franz Muschaweck of Dalog pointed out that every third VRM gearbox of above 2000kW is currently destined to fail, but that condition monitoring can avoid early gearbox failure and also allow production optimisation through the diagnosis of a variety of equipment anomalies such as a cracked table liner.
Emad Ewais of the Refractory and Ceramic Materials Division of the Central Metallurgical Research and Development Institute of Egypt next spoke about the conversion of slag into a ceramic foam as a new feedstock for industry, through a simple rapid quenching technique. He pointed out that some slags accord to the composition of highly valuable calcium aluminate cements, and with higher levels of manganese they trend towards highly valuable ceramic materials. Emad has created a brittle low-density amorphous foam-like ceramic material from slag, with many possible industrial applications, including as a raw material for insulating bricks or as monolithic castables.
The next presentation came from Muhammad Kalimur Rahman of the King Fahd University of Petroleum and Minerals from Dhahran, Saudi Arabia, who spoke on the use of slag cement in mass concrete blocks subject to marine environments. He pointed out that the development of microcracks in the young concrete - due to volume changes caused by hydration - create pathways for chloride and sulphate ingress and eventual reinforcement failure. Seawater in the Gulf has very high salinity, and temperatures are extreme, leading to short durability of reinforced concrete structures, partly due to corrosion of rebar. The King Abdullah Cultural Centre is to be built on reclaimed land, and concrete for the project is required to be highly sulphate- and chloride-resistant. Of course, slag cement, microsilica, flyash and corrosion inhibiting additives can all be used to mitigate this harsh environment. In one model, the use of 65% BFS compared to a zero BFS cement, the service life of the concrete jumped from a calculated three years to 22 years, due to reduction in microcracking, partly due to a lower heat of hydration, and subsequent chemical ingress and corrosion. Mohammad said that it was important to insulate the top and sides of castings to prevent the formation of cracking due to thermal gradient formation.
David Ball of the David Ball Group, Cambridge, spoke about using slag to reduce concrete's carbon legacy in the built environment. David's company manufactures CemFree binder through the blending of GGBFS and/or PFA with a lime-based proprietary patented activator. The CemFree binder can be used as a replacement for the OPC in structural concrete mix designs. The new binder has a number of advantages over OPC, according to David, including having negligible associated CO2 emission, enhanced long-term durability of concrete structures, a reduced requirement for steel reinforcement, low water demand, a reduced number of required joints in large areas and high volume jobs, and increased thermal mass due to higher density of concrete, all the time making use of existing concrete industry infrastructure and practices.
Marc Fixaris of ArcelorMittal finished the speaker programme at the conference by speaking about the use of converter and secondary metallurgical slags as liming agents for the control of soil pH, and as the supplier of silica and micronutrients for agricultural applications. Basic Oxygen Furnace steel slag is already used as a soil improvement agent, for example in the UK, to aggregate fine soil particles, to help nitrogen-fixation, to increase crop fungal resistance and to increase yields through phosphorous absorption. Marc reminded delegates that the chemistry of the slag is important to determine its efficacy as a soil improver. To use the slags as a soil improver, a very finely-ground material must be used, typically after screening and grinding with a roller press, for example in France to 96% below 630µm and 75% less than 160µm. A number of countries have been identified with market development potential, including Spain, Ukraine, Romania, Kazakhstan, South Africa and Brazil.
Farewell and prizes
At the conference farewell party a number of prizes were awarded the first of which went to Sennebogen for the best exhibition stand. David Ball came third in the best presentation awards, with Winnie Matthes of Holcim the runner-up. However, the first prize went to Charlie Zeynel for his update and overview on the global slag industry.
What the delegates said in 2014
- The organisation and time schedule was perfect - well done.
- Well done! A great event.
- Great team. Thanks a lot. Merci beaucoup.
- All good - format very balanced. Keep up the good work.
- Great conference!!!
- Very good quality of the conference overall.
- Good job.
- Good show.
- This is a must-attend for a cement company, I need to attend it all the time.
- Networking opportunities were directed perfectly, with meet the delegates and speed dating session, lunches, gala dinner, etc.
- Thank you. Overall, it was a very productive and focussed conference.
- Very friendly 'family' atmosphere.
