The GreenCleanS project, funded under the Green Program of Cooperation between Science and Industry of the Science Fund of the Republic of Serbia, is being implemented by the Institute of Electrical Engineering Nikola Tesla Joint Stock Company, Belgrade, as the lead institution, in partnership with the Faculty of Technology and Metallurgy and the Institute of Chemistry, Technology and Metallurgy of the University of Belgrade.
Within the GreenCleanS project, an innovative low-temperature technology has been developed for removing elemental sulfur from mineral transformer oils. The presence of elemental sulfur in mineral oil, even at very low concentrations, leads to the formation of conductive deposits of silver (I) sulfide on the silver contacts of the tap selector of the load tap changer, especially at low operating temperatures. This results in the formation of electrically conductive paths, which can ultimately lead to failures of power equipment.
The motivation for developing this innovative technology stems from the need to abandon the risky practice of oil regeneration using reactivated adsorbents, which cause multiple adverse effects. One of them is the generation of dioxin and furan emissions, substances that are extremely toxic to human health and the environment. In addition to the environmental and health hazards associated with oil regeneration, one must also not overlook the technical risks that technologies using reactivating adsorbents carry. Namely, to remove dibenzyl disulfide, these technologies generate elemental sulfur as a byproduct, thus creating a new and escalating problem.
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The development of the GreenCleanS technology involved several successive phases, beginning with laboratory oil treatment, followed by the optimization of process parameters in a pilot plant (TRL 4), and culminating in a final demonstration of the new technology under real-world conditions at the Kolubara A Thermal Power Plant site. This was achieved through the treatment of 3 tons of corrosive oil using a mobile unit developed by the Nikola Tesla Institute (INT), resulting in a higher level of technological readiness — TRL 7. The mobile oil treatment unit is shown in Figure 1.
The newly developed patented GreenCleanS technology, combined with previously patented procedures by the Nikola Tesla Institute for the removal of polychlorinated biphenyls (PCBs) and corrosive compounds (DBDS), forms the 3PINT — a unique multifunctional technology.
The INT technology enables PCB decontamination, desulfurization, and re-refining of oil, while also helping to prevent transformer failures caused by the presence of corrosive sulfur.
By implementing the GreenCleanS technology, following regulatory requirements, and the principles of the circular economy, the service life of transformers is extended. The chemical conversion process developed within this technology complies with the principles of Best Environmental Practice (BEP). The competitive advantage of the GreenCleanS technology lies in its significantly lower carbon and overall environmental footprint compared to the competing practice of replacing corrosive oils.
The integration of GreenCleanS technology into standard maintenance procedures for power equipment contributes to the green and sustainable production, distribution, and delivery of electricity.
Institute of Electrical Engineering Nikola Tesla
The story was published in Energy portal Magazine PURE ENERGY.
