Finding a place for slag – review of EuroSlag 2017

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Putting two speakers from the European Commission front and centre at the start of this year’s European Slag Association Conference (EuroSlag) in Metz, France was always going to cause a ruck. Once Coal and Steel Research Unit head Hervé Martin and steel sector policy officer Gabriele Morgante said their pieces and the panel opened up then the verbal punches started flying. Okay, this may be slightly exaggerated, but after a bunch of policy-heavy presentations, suddenly the situation became crystal clear. Was the agricultural use of ferrous slag going to be allowed to continue? What would be the classification of the slag? And so on. One Russian delegate commented afterwards, “I thought we had environmental problems in Russia.”

Jérémie Domas, Centre Technique et de Promotion des Laitiers Sidérurgiques (CTPL) explained in a later presentation that the heart of the current debate goes back to the European Waste Framework Directive (2008/98/EC). This legislation created an ambiguity over the status of slag between classifying it, as a waste or as a by-product, that the European industry has been battling over ever since. A multi-coloured map in Aurelio Braconi of the European Steel Association’s (Eurofer) presentation depicted the disarray this has caused with the varied legal statuses of slag across Europe. To add to this, Braconi’s home country of Italy, for example, is split into designating slag as both a product and a waste. His response was to say that the ‘human factor’ was important back home for utilising slag. The European Union (EU) is now working on its Circular Economy Package, which includes revised legislative proposals on waste, and it has been consulting on various issues throughout the year. It is this process is that been making slag producers twitchy.

Other delegates on the first session’s panel provided a bit more context, with Thomas Reiche of the German Technical Association for Ferrous Slag (FEHS) saying that the waste legislation didn’t need to be changed but that public procurement laws did. Eric Seitz of the French Association of the Users of industrial By-products (AFOCO) added that slag products had been sold for decades without any problems. However, he definitely wanted ‘strong’ support from the EU on the issue.

Moving on, Craig Heidrich of the Australasian (Iron & Steel) Slag Association (ASA) provided some interesting figures in his presentation on worldwide slag production that differ from the data often reported by trading companies. Heidrich reckoned that 567Mt of slag was produced in 2015 with a breakdown of 347Mt blast furnace (BF) slag and 220Mt steel slag.

Andreas Ehrenberg of the FEHS presented research on converting electric arc furnace (EAF) slag into a hydraulic material that could be used in cement or concrete production. Given that, using Heidrich’s figures for example, about a third of ferrous slag production is steel slag often created in an EAF, the potential implications of this line of inquiry are important. Unfortunately, the main disadvantages of the original EAF slag analysed in Ehrenberg’s work compared to BF slag are the lower CaO and SiO2 contents and the higher MgO and Fe oxide contents. Laboratory-scale tests confirmed in principle the feasibility of forming clinker or ground blast furnace slag-like materials based on EAF slag. But the reduction and treatment steps in the process require a lot of effort and the economical value of the recovered metal is low. Taking the research further will require much more work on the semi-technical scale.

The other paper with particular relevance to the cement industry was Chris Poling of SCB International unveiling his company’s ground blast furnace slag (GBFS) micro-grinding mill, the Nutek Mill 2. The new mill is intended to allow slag grinding to take place in a much wider range of locations, along similar lines to the modular clinker grinding mills made by Cemengal or Gebr. Pfeiffer’s Ready2Grind line. The pilot project is being installed now in New York State, US. The mill has a GBFS capacity of 10 - 12t/hr with a target of 40 – 45kWh/t when fully optimised. Further units at the same location are planned for early 2018 with approval sought from the New York State Department of Transportation.

The 10th European Slag Conference is expected to take place in 2019. With more clarity expected from the EU on its Circular Economy Package there will be much to discuss.


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