Slag treatment solutions for non-ferrous metals


In every pyrometallurgical process, slag is produced. The slag can then be charged back into the existing process lines or in settling units recovering valuable metals. Alternatively it is discarded and either sold to off-takers (in the cement or construction industry) or needs to be dumped in costly deposits. Dumping of the slag will become the most undesirable solution and shall be avoided. SMS developed several possibilities to convert the slag into products. The slag treatment solutions are a central part of circular economy approach as part of our BlueTechnology philosophy.

Electric slag settling and slag cleaning furnaces

As one of the leading suppliers of electric slag cleaning and matte settling furnaces, Metix as part of SMS group has gone a step further and developed a new generation of these furnaces. In continuous operation, the novel, rectangular furnace design boasts significant advantages compared to conventional circular furnaces. The electrodes are arranged in-line to ensure uniform power distribution and cover the whole furnace vessel. The system also has additional positive effects during the cleaning and settling process, ensuring that the copper content in the cleaned slag is reduced to a minimum. SMS group offers its customers cooling and lining concepts that increase the lifetime of the furnace significantly.

Moreover, SMS group is working on innovative concepts to boost recycling rates. Electric slag cleaning furnaces are primarily used in the nickel, copper, lead, and PGM (Platinum Group Metals) industries recovering metals from slags. This began in the 1950s when SMS group installed its first units. They are so successful that SMS group/Metix has supplied more than 40 units to date. Depending on the slag properties and volumes, rectangular or circular solutions are possible.

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Rectangular slag cleaning furnace


  • Outstanding reference track record for rectangular and circular furnaces
  • High metals recovery rates
  • Reliable, energy efficient electrode column system with either prebaked or Soederberg electrodes
  • Optimized refractory lining and sidewall cooling concept
  • Robust vessel design

BlueSlag process – slag conditioning technology

The non-ferrous metals industry produces large amounts of various slag types. The objective of many producers is to sell the slag as a premium product avoiding dumping costs. Due to tighter legislation, this is becoming more challenging for certain types of slag, because the benchmark for undesired elements/ components in the slag is too high. SMS group has been working on the optimization of the slag conditioning process for decades.

The BlueSlag-Process follows a two-step principle, ladle treatment station + slag settling furnace, and was primarily developed for the treatment of copper and nickel slag. In the ladle treatment station, the slag is heated and purged/stirred with gaseous reduction media. Fluxing and addition of solids is also possible. During operation, the liquid metal droplets, which are entrapped in the slag, grow as a result of the stirring and enhanced coagulation effects in the stirred melt.

The treated slag is then charged into a rectangular settling furnace, where the enlarged droplets fall onto the furnace hearth and are tapped separately from the slag. Our goal is to reduce Cu content in discard slag to under 0.3 %. Impurities in Cu slag, such as Zn, Pb, or As, are also reduced to obtain slag as a product.

The following main reactions occur:

  • Joule’s heat liberation for additional temperature increase by electrodes
  • Additional chemical reduction
  • Injection of reduction gases to accelerate the rate of reduction (optional)
  • Forced migration of metal/matte droplets under stirring conditions
  • Coalescence of metal/matte inclusions due to stirring
  • Settling of the larger metal/matte inclusions under gravity
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BlueSlag process


SMSgroup Degel,Dr. Rolf

Dr. Rolf Degel

SMS group GmbH
Vice President Non-Ferrous Metals
Eduard-Schloemann-Straße 4
40237 Düsseldorf

Phone : +49 211 881 6372