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أوابك العلمية لعام
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ص لبحوث العلمية الفائزة بجائزة
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عدد خا
مجلة النفط والتعاون العربي
161
العدد
- 2017
أربعون
المجلد الثالث و ال
Re-refining of Used Lubricating Oil and its Economic and Environmental Implications
1
1
Background
Lubricating oils have been primarily used for reducing friction between moving metal
parts of engines and machinery. As a result of the lubricating action, lube oil get
contaminated and degraded. Like most products, lubricating oils possess a life cycle
which is characterized by the end-of-life at which point the product reaches the end of
its useful life, and must be changed and safely disposed of. During normal use,
impurities such as dust, dirt, metal scrapings, water or chemicals, etc., can get mixed in
with the lubricating oil or be generated in it due to thermal degradation or oxidation.
Used lubrication oils contain water, salt, broken down additive components, varnish,
gum and other materials (Durrani et al, 2011). During operation, the lubricant loses its
initial properties; it becomes a “used lubricating oil” and must be replaced. The US
Environmental Protection Agency defines used oil as “any oil that has been refined
from crude oil or any synthetic oil that has been used and as a result of such use is
contaminated by physical or chemical impurities”. Basel convention states that “ used
oil, as referred to in these technical guidelines, is an oil from industrial and non
industrial sources which has been used for lubricating or other purposes and has
become unsuitable for its original purpose due to the presence of contaminants or
impurities or the loss of original properties”.
While many petroleum products such as gasoline, jet and diesel fuels are lost after
being used (i.e. combustion), lubricating oils can be recovered and regenerated to the
quality equal to or better than its original virgin form by using re-refining technologies
(Park, 2012).
The process by which the used lubricating oil is returned to a usable condition is called
re-refining. It is a process of repeating some of the basic refinery processes adapted to
upgrading the base oil to a usable condition. In reprocessing used oils, contaminants are
removed and the initial properties of the base oil restored. When re-refining is
conducted properly, the base oil properties are comparable with those of the virgin base
oil, as will be demonstrated later.
2
Historical overview of used lubricating oils re-refining processes.
The recycling of used lubricants has been practiced since the 1930s and particularly
during the Second World War when the scarcity of adequate supplies of crude oil
during the conflict encouraged recycling of all types of materials including used
lubricants (Tiwari et al, 2012). In the 1960s, the re-refining industry experienced a
slowdown due to the combined effect of the availability of large quantities of virgin