Issue 161-M

البحـث الأول

مجلة النفط والتعاون العربي

161

العدد

- 2017

أربعون

المجلد الثالث و ال

2016

أوابك العلمية لعام

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ص لبحوث العلمية الفائزة بجائزة

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عدد خا

Chapter 3 - Virgin and Used Oil Processing

Re-refining is defined as the chemical and physical processes that extract the

lubricating base stock from used lubricants where water, fuels, additives remnants

and sludge are separated from the base stock.

But it is perhaps better to consider first the steps to produce virgin base oils before

embarking on the processes of re-refining used lubricants. There are some

similarities between the two manufacturing processes that may be useful for the

overall understanding.

Virgin Base Oil Processing:

1, 2,49,84,85

Base oil is the name given to lubricants grade oils which are produced, in the

modern industry, in a complex sequence of steps in a refinery as shown in Fig

(1). Their boiling ranges between 300 and 565

and are produced normally by

feeding reduced crude oil from the atmospheric distillation unit to a vacuum unit

column to lower the boiling points and obtain distillates side streams. The vacuum

residue bottoms still contain valuable high viscosity oil that cannot be distilled

and have to be recovered by using a propane solvent in a de-asphalting unit (PDA)

where the propane dissolves the oil leaving heavy asphalt cut to be produced. The

oil produced so is de-asphalted oil (DAO) and propane is recovered and recycled.

The vacuum side streams and the DAO contain components that are undesirable

in lube base stocks. Therefore they are sent in turn to an extraction unit, usually

with a furfural solvent where the solvent absorbs the undesirables especially

aromatics and gives a raffinate with an improved viscosity characteristic ready

for the next step. The furfural solvent is recovered and the extract product is

returned to be used as asphalt cutter or blended with fuel oil or as feed to

conversion processes.

To get rid of the wax the lube streams are sent in turn to a dewaxing unit which

separates the wax, to improve the pour point, either by refrigeration and filtration

or by solvent, refrigeration and filtration. The solvent is often a mixture of MEK

and toluene.