PCBs are persistent organic pollutants that have intentionally and unintentionally (through
contamination) been added to mineral insulating oil to improve its insulating and cooling
properties within electrical equipment. The Stockholm Convention on Persistent Organic
Pollutants (2001) orders the eradication of PCBs from use by 2025.
Sodium based dechlorination is a PCB destruction process that is non-thermal, relatively cost
effective and allows for the recovery of a reusable end product. A comparative benefits
study, contained in chapter 2 of this dissertation, describes the increased financial and
environmental impact associated with incinerating large volumes of PCB contaminated
mineral oil. The results of the comparative analysis indicate a cost ratio of 1: 2.5, in favour of
sodium dechlorination.
In addition to the financial benefit, the sodium based PCB dechlorination process is versatile
and can be either batched or skid mounted and is typically combined with an oil regeneration
step, allowing for transformers to be treated onsite and whilst energised. Eskom is currently
considering obtaining the mobile dechlorination unit for the purpose of conducting
dechlorination and regeneration on its PCB contaminated transformers while energised.
Mineral insulating oil is considered a strategic asset within most industries. Eskom uses
mainly uninhibited mineral oil in its older transformers and the effects of PCB dechlorination
on the natural inhibitor content of the oil is uncertain.
The objective of this study was to investigate the effects of sodium dechlorination on the
oxidation stability and thereby indirectly the natural inhibitor content of uninhibited
naphthenic based mineral oil. The study involved the dechlorination, regeneration and
subsequent chemical analyses of PCB contaminated oils in the PCB ranges <50ppm, 50 to
500 ppm and >500 ppm as stipulated by the Stockholm Convention on Persistent Organic
Pollutants (2001).
The study confirmed the reduction in oxidation stability and thereby the natural inhibitor
content of the mineral oil after sodium dechlorination. Based on the results obtain a
preliminary algorithm was established to predict the reduction in oxidation stability after
sodium dechlorination, as a function of the PCB concentration prior to dechlorination. This
will provide an indirect indication of the rate of natural inhibitor depletion of the oil, based on
its exposure to the sodium dechlorination reagents and process conditions. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/5119 |
| Date | January 2010 |
| Creators | Nassiep, Sumaya. |
| Contributors | Arnold, Dave R. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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