Conference and Exhibition

Reviewed by Dr Robert McCaffrey, conference convenor

Bangkok, Thailand

Royal Orchid Sheraton hotel, Bangkok, November 2006

 

The 2nd Global Slag Conference and Exhibition took place 20-21 November in Bangkok, Thailand, and attracted 110 delegates from 22 countries. Over two days, 17 presentations were given, on slag markets, on slag optimisation, on grinding options and on slag utilisation.

  

The 2nd Global Slag Conference started off with a field trip to the east of Thailand. Nearly 40 delegates traveled to see the operation of the Electric Arc Furnace at the Siam Construction Steel Company at Mab Ta Phut, Rayong. Slag is tapped using the eccentric bottom tapping method, leading to low slag volumes. Slag services at the plant are provided by Siam Steel Mill Services (SSMS), a joint venture with the Edw. C. Levy Group and Thai partners. After tapping, the slag pot is carried using a Kress slag pot transporter to a fully-enclosed slag tipping facility – one of the few in the world. Molten slag is tipped into the pit, and then the skull (the iron-rich plug at the bottom of the pot) is knocked from the pot once every two or three trips. Slag is allowed to cool for at least 8 hours (and more generally 24 hours) before being excavated. Front-end loaders equipped with tyre chains are used to load the slag into trucks for transport to the SSMS slag processing facility.

Above: Slag pouring in the fully-contained slag shed.

Right: Participants on the field trip

After a pleasant lunch at the Laemchabang Golf Club, delegates arrived at SSMS’s neat Bowin plant to view the facility. At the plant, slag from the various local steel mills is kept separately, so that each company’s recovered metal can be returned to it after processing. Skulls are shattered by dropping a giant steel ball on them from a height of 20m using a magnet-equipped crane, while some have to be cut using welding gear. Primary crushing of the slag is with a locally-manufactured jaw crusher, and secondary crushing to produce a cubical aggregate is with a cone crusher, again locally-manufactured (‘Nordberg might be good,’ says Sitthisak Wittayangkoon, SSMS chief operating officer, ‘but it is too expensive.’) Metal is recovered from the crushed slag by using overband and drum magnetic separators. Delegates were able to see a demonstration of volume stability testing at the facility, before departing to see the use of slag aggregates in the wearing course of a local highway. The field trip, organized with the kind cooperation of Mr Wittayangkoon, was a great success.

A convivial welcome reception took place on Sunday evening in the Global Slag exhibition area (including stands from Aumund, Kalenborn Kalprotect, Gebr. Pfeiffer, Prathyusha Shipping, Rexnord and RSG Inc). Through the conference, delegates used the exhibition area to meet contacts and to network, and the event was rated very highly for its potential for making new contacts in the global slag industry.


Conference commences

The conference itself commenced on the Monday morning. Craig Heidrich of the Australasian (iron and steel) Slag Association detailed Australia’s approach to lowering greenhouse gas emissions. Craig pointed out that Australia has a very carbon-intensive economy, and that its per capita emissions are actually twice those of even the famously carbon-profligate Americans. Australia has not ratified the Kyoto protocol, believing that it is not in Australia’s national interest, and has recently become a founding member of the AP6 group of Asian nations and America, which is moving towards a ‘Kyoto-lite’ approach to climate change. Even given these constraints, Australia will only be around 10% over its Kyoto commitments in the 2008-2012 period, so, as Craig says, ‘the target is within sight, but more needs to be done.’ The slag sector in Australia has made massive progress, with utilisation rates increasing from 21% in 1985 to 78% in 2005. Craig also stated that production of one tonne of GGBFS created 143kg of CO2, from drying, milling and transport (delivered up to 100km from the processing site), very significantly lower than cement clinker, and offering great potential for increased use as supplementary cementitious materials.


The second paper at the conference was given by Dr E. Y. Chen of EnGro Corporation, Singapore, on the subject of the growth of the application of GGBS in China. Starting only in 1997, with the commissioning of a 0.5Mt/year VRM at Baosteel in Shanghai, there are projected to be 49 VRMs in China grinding slag by the end of 2007, grinding a total of around 31Mt of GGBS, out of a total of around 100Mt of slag being produced in China. A significant proportion of the GGFS plants are operated by non-cement companies. Continuous expansion in the sector is foreseen in the future.


D. Venkateswaran of Indorama Cement, New Bombay, and his co-authors, then detailed a possible treatment method for the beneficiation of electric arc furnace (EAF) slag, for use as cementitious products. The laboratory-scale project heated EAF slag to 1500°C and then quenched it rapidly in water, to try to create a glass phase with improved cementitious properties. However, the authors frankly admitted that their treatment actually decreased the amount of glass in the samples, compared to untreated slag, although it did decrease the amount of iron oxides in the slag. The authors found that the treated slag was of comparable strength to normal GGBS slag in a Portland Slag Cement formulation.


Sang-tae Cha of Ecomaister, Korea, proceeded to give an impressive presentation on the industrial-scale beneficiation of EAF slag. In short, his patented process is a high-speed air blowing system using a catalyst and water, operating on the stream of molten EAF slag being poured out of the tundish. The slag stream is converted into spherical balls with a glassy finish, the size of which can be controlled by varying the operational parameters. As was later pointed out by one of the conference participants, the process also has the effect of separating out the metal-rich fraction of the slag, since heavier spherules will fall closer to the air-blowing apparatus than non-metal-rich spherules. The presentation created a huge amount of interest.

William Tan of Bulk Materials International then gave an excellent overview on the use of GGBS in the cement industry, and forcefully made the point that the increased use of slag as a clinker substitute will be a strong factor in decreasing the cement industry’s overall contribution to global warming through a reduction in the industry’s greenhouse gas production.


Barry Woodbine of Aumund outlined his company’s varied solutions to ‘efficient and reliable handling of GBFS and GGBFS at grinding plants and cement works.’ Included among the Aumund Group’s equipment are the Samson surface feeder, chain bucket elevator, Centrex silo extraction system, and Schade stacking and reclaim systems for slag and GGBFS.


Whereas Barry gave a general overview, Sikhil Supekar of Sterlite Industries (India) gave a very specific presentation, detailing the possible use of granulated copper slag in the manufacture of slag cement. The author found that the slag could be used as a source of iron in the cement raw mix, and that the amount of copper contained in the slag was not detrimental to clinker formation. Copper slag can also be used in the preparation of Portland Slag Cement, at up to 35% substitution, with no appreciable detrimental effects.

In the eighth paper presented to the conference, Kent Ege Jensen of Bangkok-based LV Technology detailed some of the parameters that must be taken into account when using converter slag as an alternative raw material for cement clinker. Kent concluded that it really is possible to substitute up to 20% of raw meal with converter slag, with the MgO content of the slag being the limiting factor in the case presented. With the addition of the slag, (paying attention to the capacity of the cooler to cope with extra throughput), cement production was increased by 23% at the plant in question.

Gala Dinner


Delegates were able to enjoy cocktails on the hotel terrace before embarking on a dining yacht for a nocturnal cruise down the Chao Phrya river, through the heart of Bangkok, accompanied by a Thai band - oddly-enough belting out country and western standards. Still, a good time was had by all.

 

Second day


The conference was honoured by the chairmanship, on its second morning, of industry stalwart Paul Ratcliffe, of Holcim Group Support, Switzerland, who brought his decades of experience to bear on the proceedings. The second day of the conference commenced with Stefan Seeman, a PhD candidate student, presenting his research into the impact of grinding technologies and conditions into the performance of slag cement. His compact paper condensed three or more years of research into just 25 minutes, but his conclusions were still fascinating: No significant differences were measured in strength developments of a BFS III cement ground to 3000 Blaine, created in a high-pressure grinding roll system, in a VRM or in a ball mill. However, grinding atmosphere had a marked effect on ground slag properties, with slag ground in humid air having lower strength development, and slag ground in high-CO2 conditions having lower compressive strength, possibly due to incipient carbonation reactions.

 

Ingo Engeln of Polysius AG then gave an eloquent presentation on the use of the Polysius roller mill for the grinding of slag, particularly with regard to the management of wear. The machines are already in use in China and Korea for the comminution of slag. York Reichardt of Gebr. Pfeiffer then outlined the features of the MPS vertical roller mill for slag and slag cement.


In a quietly controversial paper, author Hans Jorgen Nielsen of LV Technology concluded, amongst other things, that - after the study of more than 300 vertical roller mills - the use of secondary rollers in a vertical mill has a negative influence on the efficiency of mill operation, and that pressure should be applied to all rollers.


Next was Caroline Hacklaender-Woywadt of Loesche GmbH, who outlined the operation of the largest Loesche mill, the LM 56.3+3, at Rajganpur, India. She also mentioned the management of wear rates in the mill, but then proceeded to shock the delegates with an ‘exposé’ of the critical differences in the calculation of Blaine, according to EN and ASTM standards. As she pointed out, it can make around a 12% difference in Blaine value when using the different calculation methods, which could be a costly discrepancy when it comes to guarantee values: manufacturers and cement producers please take note.


Ho-Young Lee, CEO of VCEM Materials Co. Ltd., Korea, then gave a gracious presentation of his positive experiences with KHD’s roller grinding system.


The final two presentations at the conference diverged in topic somewhat. K. Sairaman of GE Energy, Pune, India, spoke about filtration challenges for the operators of air pollutions control equipment for venting slag grinding mills. Mr Sairaman gave details of a VRM in Zhangjiagang, China, which copes with a maximum temperature of 100°C and differential pressure of 800Pa, and which is at 105% of its design capacity.

The final presentation was given by Sitthisak Wittayangkoon, of Siam Steel Mill Services Limited. He gave an overview of Thailand’s economic growth over the years since the Asian Crisis of 1997, pointing out that GDP growth has been above 5% for the last few years, and pointing out that respectable amounts of capital are being spent on infrastructure projects, such as Bangkok’s fantastic new Suvarnabhumi airport. Siam Steel Mill Services provides slag pot, slag handling and slag processing services to a group of steel mills in the east of Thailand at Rayong, as well as in the Saraburi region, north of Bangkok.

Awards and prizes


Following the completion of the conference programme, delegates voted for their favourite presentations. Dr Chen’s presentation on slag grinding in China came a strong fourth, while Caroline Hacklaender-Woywadt’s paper on slag grinding with the LM56.3+3 mill (and Blaine calculation variations) came third. The Slag Atomisation Technology (SAT) detailed by Sang-Tae Cha garnered him the second prize, but the paper by Stefan Seeman (seen at right), co-authored with Dr Martin Schneider and Dr Michael Müller-Pfeiffer, both of the VDZ in Germany, was the worthy and popular winner of the Best Presentation Award at the second Global Slag Conference.

3rd Global Slag Conference


Following a show of hands at the farewell party, the 3rd Global Slag Conference, with the theme ‘Adding value to slag,’ will be held 19-20 November 2007, in Istanbul, Turkey. See you there!
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