Dimitris Sparis received his Diploma in Mining and Metallurgical Engineering from the National Technical University of Athens (NTUA) in 2011.  He has been working as a researcher at NTUA for nearly 15 years, contributing to a wide range of research projects focused on the optimization of pyrometallurgical processes, mineral processing, and soil remediation. His main area of expertise is extractive metallurgy, with a particular focus on pyrometallurgy. Dimitris has been part of HEPHAESTUS project since the very beginning, as he contributed to writing the project proposal. 

What is your role within HEPHAESTUS?
In HEPHAESTUS, I am responsible for evaluating the use of alternative raw materials to produce iron-based products like ferroalloys and pig iron. At NTUA, we focus on testing materials such as dust and slag from the ferronickel industry, as well as slags from lead and zinc production – not the original steelmaking dusts used in the main demos.
Our work involves a combination of thermodynamic analysis, laboratory experiments, and pilot-scale tests. I am specifically involved in Tasks 3.1, 3.4, and 3.5 of WP3.

The core of what we do is reductive smelting. We take these waste materials, add a carbon source, heat them above the liquidus point, and let the reactions occur. Once the process is done, we cool the material, slowly if we want a crystalline slag or rapidly for an amorphous one. Throughout the process, we are adjusting parameters like temperature, carbon content, and fluxes addition to optimize the alloy produced and the slag properties such as mineralogy etc.  slag formation and achieve efficient desulfurization.

We have run lab-scale tests and semi-pilot experiments using our in-house electric arc furnace (EAF). These efforts are now leading up to full-scale testing at the Greek demo site in METLEN.

What are your main results so far?
We have had promising results! We use different approaches: use industry wastes to produce supplementary cementitious materials, recycle it for making new steel or reuse it as an additive in steelmaking production.  
From a technical and chemical perspective, all these approaches work. But this is just the beginning. The next question is whether they make sense economically and from an environmental point of view. That is where life cycle assessment  and techno-economical assessment become crucial.

What part of your work within HEPHAESTUS are you most proud of?
Two things come to mind. First thing that is incredibly satisfying, is the ability to turn industrial waste into something useful and market-ready. Second, I am really proud of the small electric arc furnace we have added to our lab thanks to the HEPHAESTUS project. Ok, it is small for industrial standards –but compared to other laboratory furnaces it is a step-up. In fact, a whole room at the university is dedicated for this furnace. It is challenging to work with it but also fascinating and very rewarding.

How do you envision the future of steel production?
It is difficult to make predictions globally, but when it comes to Europe, I see a clear shift toward greener steel production. Everyone in this industry is working to reduce the carbon footprint of steelmaking, and that means moving away from traditional, carbon-intensive blast furnaces. The future likely lies in hydrogen-based direct reduction of iron (DRI) technology followed by electric arc furnaces (EAF), especially when those furnaces run on electricity from renewable sources.

On top of that, the integration of automation and AI is really changing the game. These technologies make production more efficient while also helping to reduce maintenance costs and carbon emissions.

Imagine you are running production of steel in an electric arc furnace. Every day you monitor the input of raw materials you use, how much energy you use, and what is the composition of the exhaust gases. If you collect all this data over time and analyze, the AI system can point out useful adjustments: maybe you are adding more carbon than needed, or the fluxes could be reduced, or the temperature could be lowered by 30 degrees without affecting the outcome. With this kind of insight, you can cut down on energy use, raw material consumption, and emissions. 
Moreover, AI helps predict equipment maintenance needs. Instead of waiting for something to break, you can fix it beforehand, which saves time and money. 

What makes HEPHAESTUS relevant today?
HEPHAESTUS addresses some of the most urgent challenges in the steel sector today.

First, we reduce dependency on virgin raw materials by reusing industrial by-products like dusts and slags. That is a major global issue. 

Second, by working with these secondary materials, we can significantly lower energy consumption. Each year, electric arc furnace (EAF) steel production generates up to 1.5 million tons of fine hazardous dust. The HEPHAESTUS process reduces energy use by about 0.8 MWh for every ton of dust processed.

Third, HEPHAESTUS technology enables a major reduction in CO₂ emissions—up to 3 tons of CO₂ saved for every ton of steelmaking dust treated. This is achieved in two ways. By avoiding traditional mining, we cut emissions at the source. At the same time, the project integrates a carbon capture and transformation process that captures CO₂ directly from furnace fumes and converts it into methanol. This part of the project is led by my colleague at NTUA, Professor Antonis Peppas, under task 3.2.

In short, HEPHAESTUS is not just another technological advancement; it is a crucial step towards a more sustainable, low-carbon future for the steel industry.

To learn more about TESMET, research group at National Technical University of Athens, visit their website.