Issue 161-M

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البحـث الأول
مجلة النفط والتعاون العربي
161 العدد - 2017 أربعونالمجلد الثالث و ال
2016 أوابك العلمية لعام� ص لبحوث العلمية الفائزة بجائزة� عدد خا
65
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thought that mixing used oil with virgin fuel will lessen the environmental impact
of the former provided that ash content is limited and does not exceed some
regulation 4. In any case, the market for fuel oil far exceeds the availability of used
oil for the purpose.
There are two applications of burning used oil that do not need much treatment
except perhaps settling and dewatering which is known as mild processing 22.
Burning in cement kilns and hot mix asphalt plants does not cause too much
environmental worries. Both applications “operate at high temperatures and have
fairly long residence times to enable the destruction of most of the undesirable
chemical compounds in the oil1”. Therefore, the Polynuclear aromatics (PNA),
chlorinated hydrocarbons and heavy metals are destroyed in cement production
furnaces1 and asphalt mix plants. The metals are said to be locked in the produced
cement22. Especially in modern cement plants, there is efficient flue gas scrubbing
equipment to reduce emissions to atmosphere.
There are further logistical advantages that are relevant here. Cement plants and
asphalt mix plants are normally distributed around the country. Therefore, it is
beneficial for used lube oils collection and transportation to go to the nearest fuel
user. To show the extent of burning used oils in cement kilns, the Cement
Bureau104 said that 17% of fossil fuels used in the cement industry in Europe are
replaced by burning used oil in 2003. In Germany 600 thousand tons a year of
used oil is burned in cement kilns in 2002, which is equivalent to half of German
requirements while three quarters of French requirements are met by burning used
oil104.
Heavy fuel oil is not immune from contaminants such as metals, sulpher and
asphaltenes, which are detrimental to equipment in forming ash, slag and
corrosion. Equally, used lubricating oils contain higher levels of metals and ash
forming constituents. In applications other than cement kilns and asphalt mix
plants, it is often necessary to have access to landfill sites with permits to handle
the toxic ash 4, 9.
No matter what, it is important to reduce the risk of burning used oil by settling,
filtering and even centrifugation to remove solids and water. Distillation and
solvent extraction are more sophisticated methods of producing better fuels.
Mixing with virgin fuel and the installation of flue gas scrubbing systems reduces
the environmental risk to a large extent.
It is also important to know what fuel used oil is actually replacing in burning
applications. If it is replacing coal in a power station or any other application then
it is considered better for the environment 97. However, if used oil is replacing
gasoil in asphalt mix plants then environmentally the former is better 1,97. Perhaps