David Pletinckx, Ruben Boeree, Koen Michielsen, Marcus Fox
The economics of newly developed flowsheets for zinc and zinc-lead smelters have created two
main challenges for zinc roasting. As the smelters developed their need for high value concentrate
feeds, the metal mines have adapted their way of working to newly developed technologies in
grinding and flotation. The trend for zinc concentrates to become finer will have a significant influence
on the fluidized bed roaster operation. Secondly, some larger high quality, low iron zinc mines
are closing their operations in this decade, for example MMG’s Century and Vendanta’s Lisheen in
2015. Newly developed concentrates are keen to be more challenging, directing more impurities to
the smelters and the roasting furnaces.
In order to meet the described challenges, a structural approach was needed, much more decisive
than basic technical networking and occasional problem solving. This article describes the strategy
of Nyrstar’s Metal Processing Segment towards knowledge development across the different smelters
at different sides of the world. Two facts were contributing to this necessity: the global transformation
of the Nyrstar’s smelters and the fact that two smelters were operating almost exclusively
on the Century zinc concentrate, with the latter to disappear end 2015. For these two smelters, projects
have been implemented in the course of 2015 enabling the treatment of concentrates containing
increased cadmium and iron volumes, following the introduction of a more complex feedbook
after the closure of the Century mine.
To prepare for the end of the Century concentrate, this approach of knowledge sharing was used to
develop extensive test work and process modifications at the Nyrstar Hobart (Australia) and Nyrstar
Budel (The Netherlands) zinc smelters.
The development of a technical network group for learning, research, testing and linked industrial
test campaigns has proven to be of great value for developing and understanding the control mechanisms
of fluidized bed roasting, especially separating and linking the physical/chemical properties
of the roaster feed to the physical and chemical aspects of roasting process control.