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مجلة النفط والتعاون العربي
161
العدد
- 2017
أربعون
المجلد الثالث و ال
2016
أوابك العلمية لعام
�
ص لبحوث العلمية الفائزة بجائزة
�
عدد خا
36
26
at elevated temperatures can form corrosive acids. Going forward, additives have
increased their share of finished lubricants and are likely to do so in the future.
Therefore, used oil contaminants are likely to increase with increasing additives
share. Table (3) shows typical composition of lubricating oils with respect to
additives.
Used engine oil is considered hazardous in Europe and in the US if contaminant
levels exceed certain parameters. The Waste Oil Directive of 2008 gives priority
to re-refining
as long as there are no technical, economic or organisational
obstacles
105
. Heat and energy recovery under environmentally acceptable and safe
destruction conditions are second in the hierarchy. Disposal is acceptable only if
the first two options are not practical
22
. This hierarchy is now the guideline in
many countries where dumping in landfills is avoided or prohibited.
A comparison between virgin and used oil properties at this point is important to
show the degree of deterioration of base oil as a result of its use under operating
conditions and the accumulation of contaminants in used oil. Table (4) shows just
that.
Impact of Synthetic lubricants:
Synthetic motor oils are manufactured or synthesized by “polymerising short
chain hydrocarbon molecules called alpha-olefins into longer chain hydrocarbon
polymers called polyalpha-olifins (PAO)
21
” and “PAOs do not contain the
impurities or waxes inherent in conventional mineral oils
21
”. PAO is mostly
synthesised from the products of naphtha or condensate steam cracking in
petrochemical plants
104
.
Synthetic lubricating oils are increasingly entering the market and due to their
superior performance they tend to increase the distances travelled before oil
changes and therefore reducing the volume of lube oil used and used oil
generated. From this point they have a positive role in reducing the impact on
the environment compared to traditional lubricants
21
. Re-refining, used oil
containing synthetic oils produces better re-refined base stock. However, their
high price and the limited production capacity are not supporting further inroads
into the market.