NextGenSøderberg - Next generation Søderberg electrode for Mn production

One of the most significant industrial inventions in Norway, the self-baking Søderberg electrode, celebrated its 100th anniversary in 2019. The Søderberg electrode is still the dominant technology to produce ferroalloys, and Eramet Norway (ENO), a world-leading producer of refined manganese alloys, operates some of the industry's largest electrodes at its three Norwegian processing plants. The main challenge with the technology is the use of coal tar pitch (CTP) as a binder in the electrode paste. Coal tar pitch contains polycyclic aromatic hydrocarbons (PAH), a group of substances that can have negative effects on health and the environment. It is therefore important to find environmentally friendly binder alternatives without negative operational impacts. In 2017 the European Commission decided that all uses of CTP are prohibited in Europe as of October 2020. The European metallurgical industry benefits currently from an exemption since it has not yet been possible to find good replacements for CTP for electrode use, but more stringent regulations are expected. ENO aims to be the most climate and environmentally friendly producer of manganese alloys in the industry and has in recent years actively sourced alternative electrode pastes with lower PAH footprints. In 2017, a breakthrough came when one of the suppliers introduced the first commercially available PAH-free electrode paste to the market. Taking a huge technical risk, ENO was the first producer to carry out industrial experiments with PAH-free technology on large electrodes. However, there are still major technical challenges to be solved before the full conversion can be done. In NextGenSøderberg, ENO will collaborate with SINTEF to develop the next generation of Søderberg technology for manganese alloys production, targeting improved environmentally friendly electrode performance contribution to secure a sustainable Mn-industry in Norway. In 2021, the following results have been achieved in the project: A workshop has been carried out with Eramet's Norske Elektrodegruppe where challenges related to the use of PAH free electrode mass were discussed in relation to planned activities in the NextGenSøderberg project. An important focus area was HSE and especially odor issues related to the use of the new PAH-free electrode masses. Methods for identifying odor components in the exhaust gases from the electrode reversal have been established and tested both on a lab-scale and through analysis of gas samples obtained from the working atmosphere at work. Several full-scale operational tests with PAH-free electrode mass have been carried out at Eramet's plants in Norway. Sampling has been carried out from a baked electrode from an oven that has been in operation. Here, physical properties are analyzed to better understand and characterize the baking process. A similar sampling program from full-scale electrodes from Kvinesdal has also been completed in 2021. Data from these works will be an important basis for modeling the baking process in the electrodes, as well as increasing understanding of the property differences in laboratory-made electrodes and full-scale electrodes. Work on developing simulation models as future decision support tools for the operation of furnaces has started with the establishment of an initial model specification that also defines the necessary data from the characterization of PAH free electrode mass as well as geometric and process technical boundary conditions from furnace design. A meeting has been held with Eramet's modeling community in France (Eramet Ideas) for the exchange of ideas and model basis.

The NextGenSøderberg project will enable full scale conversion of the electrodes at Eramet Norway (ENO) Mn-alloy smelting furnaces to less toxic Søderberg electrode paste without negative impact on furnace operation and overall costs. Current Søderberg technology face health, environment and safety (HES) issues related to polycyclic aromatic hydrocarbons (PAH) present in the coal tar pitch (CTP) used as binder in the self-baking electrodes. In June 2017 the European Commission decided that all uses of CTP is prohibited in Europe from October 2020. The European metallurgical industry is currently exempt, but more stringent regulations are expected. To meet the environmental challenge suppliers of electrode paste have started developing PAH free electrode paste materials. Introduction of new electrode binder materials is likely to introduce operational challenges and risks of sub-optimal operation of existing Søderberg furnaces. ENO has three production sites with seven closed submerged electric arc furnaces operating with self-baking Søderberg electrodes. If a complete prohibition is enforced without a replacement to coal tar pitch, plant closures are unavoidable. The impact on the communities will be severe as the plants are in rural and semi-rural areas, employs about 600 people and support about four times as many jobs indirectly. ENO has a turnover of 6-7000 MNOK/y and is a world-leading supplier of essential products to the steel industry, contributing to improved sustainability. In order to secure safe operational performance, material characterization methods and mathematical simulation tools need to be developed to allow introduction of new environmentally friendly binder materials. New analysis technologies will be used to evaluate and document the HES and toxicological performance. The performance of new materials will be verified systematically by critical investigations in full scale and used to develop optimal design and operational procedures.