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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
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العدد
- 2017
أربعون
المجلد الثالث و ال
Re-refining of Used Lubricating Oil and its Economic and Environmental Implications
45
5.1
Treatment steps
i)
Primary treatments
Primary treatment is the first stage of any re-refining process. It is all too common for
re-refining technologies to start up with a primary treatment which is designed to
remove an important part of the used oil contaminants such as water, light
hydrocarbons, sludge, coarse particles, etc. For this, each technology uses a particular
method, or even a combination of several. Methods may include, but are not limited to,
the following: Filtration, settling, decantation, centrifugation, dehydration, heating,
thermal treatment, atmospheric distillation, demetallization , chemical treatment, etc.
ii)
Secondary (Separation) treatments:
In order to remove additives such as heavy metals, sludge, etc., each technology uses a
separation procedure. In the acid/clay technology, an acid is used to settle out the oil
followed by an earth (clay) treatment to remove other contaminants. Other technologies
use chemical processes such as solvent extraction (Interline, Rose/Kellog), or physical
methods such as vacuum distillation (PROP, KTI, IFP). Secondary treatment re-refining
technologies include, but are not limited to, the following: physical-chemical treatment,
thermal treatment, solvent extraction, vacuum distillation,
iii)
Tertiary (Finishing) treatments
While the earlier stages (i.e. primary and separation treatments) allow the re-refining
technology to achieve a contaminant-free base oil, a finishing step is necessary in order
to obtain a commercially viable base oil that is appropriate for the needs and conditions
of the market, especially in terms of odor and color characteristics. As in the previous
stages, each system uses a different unit operation to “finish off the look” of the end
product. Methods may include, but are not limited to, the following: Bleaching,
hydrotreating, fractionation, treatment with zeolites, vacuum distillation.
Table 3 summarizes re-refining technologies where the unit operations corresponding
to major steps are sequenced in order of occurrence.