Gaëlle Butin is originally from France. She studied geoscience engineering at the École Nationale Supérieure de Géologie in Nancy, where she specialised in mining and mineral processing. As part of her Master Thesis project, she worked on ore characterisation and lithium-bearing minerals recovery with Imerys. The thesis was one of the research works precursor to the EMILI project, which aims to recover lithium from Beauvoir granite in France.
In 2020, she joined KU Leuven for her PhD in the group of Prof. Bart Blanpain. While her background is in mineral processing, her research gradually moved towards pyrometallurgy, with a strong focus on slag crystallisation. Today, she continues her work as a postdoctoral researcher in the HiTemp group.
What are you currently working on?
I work together with Nyrstar’s zinc production plant in Balen. My research sits somewhere between ore characterisation and pyrometallurgy.
The process starts with zinc sulphide concentrates that were obtained after flotation from a mined ore. Before zinc can be recovered, these concentrates need to be roasted at around 900-1000 °C in an oxidizing atmosphere. During roasting, zinc sulphide is converted into zinc oxide, which can later be leached to recover the metal.
The challenge is that the concentrates are very complex. Besides zinc minerals, they often contain impurities such as lead minerals and silicates. My work focuses on understanding how all these different components interact inside the roaster.
What could possibly go wrong inside a zinc roaster?
During roasting, the concentrates are present within a fluidized bed through which air is flown. One of the biggest challenges is excessive agglomeration within this fluidized bed. Agglomeration can happen because impurities or mix of impurities can melt at the process temperature. When this happens, liquid bridges can form between particles, causing them to stick together.
If enough material agglomerates, the entire bed can defluidize and collapse. In the worst case, production needs to be stopped and the roaster cleaned, which is costly and disruptive. The industry already controls parameters such as concentrate blending and oxygen supply. However the key challenge lies in the variability of the concentrates. Each concentrate has its own mineralogical complexity and may behave differently during roasting.
The goal is therefore to understand agglomeration on a case-by-case basis and use these insights to build a broader understanding of the mechanisms that lead to defluidization.
Where does zinc in Europe come from?
Europe has relatively limited zinc resources compared to some other regions.
A significant share of zinc concentrates comes from Sweden, including material supplied by Boliden. There are also sources in Ireland, Portugal, and Poland. Beyond Europe, concentrates are mainly produced in China, Peru, Australia, India, USA, Mexico and Bolivia.
What is the most interesting part of your work?
I enjoy working with these complex systems. Every concentrate is different and comes with its own combination of minerals. The interesting part is figuring out how these different parameters interact and then testing my hypotheses through experiments.
In a way, it feels a bit like detective work. You cannot simply put a camera inside an industrial roaster and see what is happening. Instead, you collect clues from the raw materials, laboratory experiments, and plant observations, and slowly build the full picture.
That is what I enjoy most. With every experiment, the black box becomes a little less black.
What keeps you motivated when answers are difficult to find?
One thing I really enjoy is the close collaboration with industry. We work closely with Nyrstar and our partner Inspyro, so there is a constant exchange of ideas and results. It is motivating to know that the questions we are studying are not purely academic, but directly connected to real industrial challenges.
I also really appreciate the atmosphere at MTM. In my research group for instance, everyone works on different aspects of metallurgy, which means there is always someone who can offer a new perspective or help solve a problem. You learn something new almost every day, and that makes research both enjoyable and rewarding.
