Dr. Jelena Lukić

The project under the acronym “GreenCleanS” aims to develop a new technology for removing elemental sulfur, in a form of eight atom molecule of suphur, S₈, from mineral insulating oils. Under the acronym GreenCleanS, a unique technology is being developed based on low-temperature eco-friendly treatment, which does not emit pollution while efficiently removing elemental sulfur from mineral insulating oils, unlike existing technologies worldwide which can be pollutant emitters (if polychlorinated biphenyls are present in the oil), do not remove elemental sulfur, and, moreover create it as a by-product of the reactivation procedures of the adsorbents used. The development of this technology for removing elemental sulfur from transformer oils will involve treatments of insulating oil under laboratory conditions and at a pilot scale experiments, followed by a demonstration of the developed technology in operational environments on-site at the mobile facility of the Institute Nikola Tesla. The procedure is based on the application a small amount of iron particles coated with copper on its surface as a key component of the reagent mixture which is dispersed in polyethylene glycol. Intensive mixing of the reagent mixture with mineral insulating oil at temperatures below 100 °C enables the complete removal of S₈ from the oil. High process efficiency, the removal of S₈ from the initial 15 mg/kg to levels below the detection limit, is achieved by using a small amount of the reagent mixture relative to the oil mass (<0.2 wt.%), in laboratory conditions and on a pilot scale experiments. Applying this process and subsequent treatment with adsorbents, insulating oils with improved physical, chemical and electrical characteristics are obtained, suitable for further use in power transformers. Integration of the GreenCleanS desulfurization procedure with a previously developed and patented technology for removing polychlorinated biphenyls and corrosive dibenzyl disulfide will create a unique multifunctional technology enabling simultaneous removal of all unwanted compounds from mineral insulating oils. This technology represents a significant advancement over existing procedures that can be pollutants or inefficient in removing elemental sulfur, providing an extremely efficient solution with minimal environmental impact.

Keywords: elemental sulfur, corrosive sulfur, green technology, power transformers, mineral insulating oil