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البحـث الثاني
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2016
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
2
lube oils and the failure of the re-refining industry to provide consumers with high
quality products (Cukor et al, 1973). In those days, acid/clay based technologies- which
were based on the use of large amounts of acid and clay to reprocess the used oil- were
for many years the standard method for regenerating used lubricating oil. These acid-
based technologies not only produced base oils with lower properties than virgin base
oils, but also were the source of environmental pollution. During the re-refining
processes (e.g. acidification, clay treatment), hazardous by-products were produced,
including acid tar and oil saturated clay, thereby creating waste disposal problems and
environmental drawbacks. Consequently, the technology failed to find widespread
acceptance for various reasons including high processing costs, and therefore high
selling prices, and inadequate removal of impurities (Avaduth, 2011).
The energy crisis of the seventies has generated renewed interest in re-refining. A series
of technical innovations based on technologies borrowed from crude oil refining were
introduced in the re-refining industry. Vacuum distillation, for example, was adapted to
re-refining through the use of specialized equipment (Rudnick L, 2011). Also,
developments in catalysts and hydrofinishing technology have enabled the industry to
partially overcome the environmental challenge so that re-refiners were able to produce
good quality base oils.
In the 1980s, the level of awareness on environmental issues increased significantly as
more stringent environmental regulations were introduced in developed countries. As a
result, many re-refiners, not being able to abide by those costly-to-implement-
regulations, were pushed out of business (Wolfe, 1992). In particular, acid/clay re-
refining plants, mainly in the USA, were the main casualty of these new tough
environmental regulations as many were forced to shut down (EC, 2006).
The re-refining industry has come a long way since the early days of acid-based
technologies. Today, re-refining processes are considerably different, and much more
advanced, than when re-refining first began back in the 1930s. Over the years the re-
refining technology has evolved from simple distillation over clay and sulfuric acid, to
thin film evaporation with solvent extraction, through to the hydro-treatment process
technology of today. Thanks to advanced technologies such as hydrogenation-based
technologies and solvent-based technologies but also to adequate state-sponsored
legislations, re-refined used oil is starting to be accepted as equivalent in quality and
price to most virgin lubricating oils.