METHOD FOR REMOVING POLLUTANTS FROM USED OIL

METHODE POUR L'EXTRACTION DE POLLUANTS D'HUILES USEES

English Abstract

21766-614
ABSTRACT
The invention provides a method for removing polluting
constituents from used oil by heating the used oil to an
elevated temperature below 100°C; adding water to the oil; adding
sulphuric acid to the oil; thoroughly mixing the oil and the
sulphuric acid; allowing the oil-sulphuric acid mixture to react;
adding a demulsifier to the oil-sulphuric acid mixture;
thoroughly mixing the oil-sulphuric acid-demulsifier mixture;
allowing the oil-sulphuric acid-demulsifier mixture to stand in
order to allow formation of a water phase containing the
pollutants and a purified oil phase; and separating the water
phase from the purified oil phase. The sulphuric acid is added
to the oil to dissolve heavy metals present in the oil. The
dissolved heavy metals will go into the water phase, which water
phase is separated from the oil using the demulsifier. After a
treatment according to the invention the purified oil may contain
less than 0.1% heavy metals and therefore be suitable for
combustion or for reuse for refining purposes.

Claims

21766-61
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Method for removing polluting constituents from used
oil comprising the steps of:
a) heating the used oil to an elevated temperature
below 100°C;
b) adding water to the oil;
c) adding sulphuric acid to the oil;
d) thoroughly mixing the oil and the sulphuric acid;
e) adding a demulsifier to the oil-sulphuric acid
mixture;
f) thoroughly mixing the oil-sulphuric acid-demulsifier
mixture;
g) allowing the oil-sulphuric acid-demulsifier mixture
to stand to allow forming of a water phase containing the
pollutants and a purified oil phase; and
h) separating the water phase from the purified oil
phase.
2. Method as claimed in claim 1, characterized in that
the used oil is heated to a temperature between 50 and 100°C.
3. Method as claimed in claim 2, characterized in that
the used oil is heated to a temperature of 80°C.
4. Method as claimed in claim 1, characterized in that a
minimum of 15% water is present in the used oil.
5. Method as claimed in claim 1, characterized in that
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21766-614
sulphuric acid is added to a final concentration of between 0.3
and 1%.
6. Method as claimed in claim 5, characterized in that
sulphuric acid is added to a final concentration of 0.5%.
7. Method as claimed in any one of the claims 1 - 6,
characterized in that the oil-sulphuric acid mixture is allowed
to be mixed for at least two hours before the demulsifier is
added.
8. Method as claimed in any one of the claims 1 - 6,
characterized in that the demulsifier is added to the oil-
sulphuric acid mixture to a final concentration of a maximum
of 0.5%.
9. Method as claimed in any one of the claims 1 - 6,
wherein the demulsifier is a mixture of a non-ionic, cationic,
surface active agents in an organic solvent that can destabilize
water-in-oil emulsions.
10. Method as claimed in claim 9, characterized in that
the demulsifier is SOT-826.
11. Method as claimed in any one of the claims 1 - 6,
characterized in that the oil-sulphuric acid-demulsifier mixture
is mixed for at least approximately two hours.
12. Method as claimed in any one of the claims 1 - 6,
characterized in that the oil-sulphuric acid-demulsifier mixture
is allowed to stand for at least about twenty-four hours for
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21766-614
separation of the water phase containing the pollutants and the
purified oil phase.
13. Method for removing polluting constituents from used
oil, comprising:
treating the used oil, which oil is at an elevated
temperature below 100°C and contains water, with sulphuric acid;
treating the oil, sulphuric acid and water mixture
with a demulsifier;
allowing the mixture to form a water phase and an oil
phase; and
separating the water phase from the oil phase.
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Description

21766-614
20~077
METHOD FOR REMOVING POLLUTANTS FROM USED OIL
.
The invention relates to a method for removing polluting
constituents from used oil.
After a determined period of use, various pollutants
such as heavy metals and water collect in oil, for instance motor
oil. The heavy metals come for example from the engine block,
from additives or from petrol (such as lead).
A requirement set down in the treatment for instance of
used motor oil is that the ash content thereof, that is, the
percentage of heavy metals remaining after burning of the oil,
must amount to less than 0.25%. The ash content of oil types
used at this moment in time varies after use between 0.6 and
1.4%.
A number of methods have been proposed to decrease this
ash content. According to one of the known methods the oil is
heated under vacuum to 80C in order to allow water and light
fractions to evaporate. Between 7.5 and 15% sulphuric acid is
subsequently added to the water-free oil formed in this way in
order to dissolve heavy metals. So-called acid tar is hereby
formed. Finally, the oil is passed over a so-called china-clay
filter.
The above-described method has a number of drawbacks~
The first of these is the formation of the acid tar. Acid tar
is chemical waste and undesirable as such. The formation of acid
tar further results in up to 10% loss of oil. In addition, the
whole procedure is performed in an acid environment due to the
comparatively high sulphuric acid content. This acid has inter
alia a corrosive effect on the containers in which the procedure
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1077
is carried out.
Furthermore, neither wi-th this or any other of the
known methods are ash contents achieved which comply with the
legal requirements.
It is an object of the present invention to provide a
method for removi~g polluting constituents from used oil with
whic~l the above-stated drawbacks are alleviated or obviated and
with which oil can be obtained, the ash content of which complies
with the legally required norms.
This is achieved according to the invention by a
method comprising the steps of:
a) heating the used oil to an elevated temperature
below 100C;
b) adding water to the oil;
c) adding sulphuric acid to the oil;
d) thoroughly mixing the oil and sulphuric acid;
e) adding a demulsifier to the oil-sulphuric acid
mixture;
f) thoroughly mixing the oil-sulphuric acid-demulsifier
mixture;
g) allowing the oil-sulphuric acid-demulsifier mixture
to stand to allow forming of a water phase containing the
pollutants and a purified oil phase; and
h) separating the water phase from the purified oil
phase.
The temperature to which the oil is heated lies
preferably between 50 and 100C. A temperature below 50C is
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217 ~ o 7 7
likewise possible but the viscosity of particular oil types is
often too high in this temperature range for an optimum removal
of pollutants. When the oil is heated above 100C the water
phase will evaporate. Most preferred is a temperature of
approximately 80C.
In preference a minimum of 15~ water is present in the
oil. The presence of water is essential for optimal functioning
of the method according to the invention because the pollutant
heavv metals and the like will go into the water.
The heavy metals present in the oil are dissolved
through use of sulphuric acid. The dissolved metals collect in
the water phase. The quantity of sulphuric acid to be added is
subject to the total ash content of the motor oil. It has been
found that a final sulphuric acid concentration of between 0.3
and 1% will be sufficient for effectively removing the heavy
metals.
The time for which the oil-sulphuric acid mixture is
allowed to react is preferably at least about two hours.
Any suitable demulsifier can in principle be used. It
has been found however that optimum results can be obtained with
the demulsifier SOT-826 (S&D Oil Technics B.V., Groot-Ammers).
SOT-826 is a mixture of non-lonic and cationic surface active
agents in an organic solvent. It destabiliz~s water in-oil
emulsions.
The mixing of the oil-sulphuric acid-demulsifier
mixture can be carried out in different ways. It is for instance
possible to pump the mixture through the container or to stir it
or to blow air into the container from below. Mixing preferably
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21766-61~06~,~77
takes place for at least about two hours.
The time for which the oil-sulphuric acid-demulsifier
mixture is allowed to stand is preferably at least about twenty-
four hours. During this time the heavier water phase containing
the pollutants will sink to the bottom of the container, while
the phase with the purified oil will float on top. After a
check has been made as to whether the oil layer complies with
the requirements, that is, has a BS~W (Bottom Sediments & Water)
~alue of less than 1%, either the purified oil can be removed
from the top by means of pumping or the underlying water phase
can be drained from below.
It has been found that with the method according to
the invention ash contents of less than 0.1% can be achieved.
Oil cleaned in the said manner not only complies with the require-
ments but can, if desired, also be reused for refining purposes.
The invention is further illustrated in the following
example.
EXAMP _
Was~e/slob oil is mixed and brought to a temperature of
80C and then mixed with an adequate amount of (tap)water to
increase the water content of the oil to 15-20~. Subsequently
5,000 ppm sulphuric acid (technical grade; > 90~) is added to
the oil/water mixture. The thus obtained oil-sulphuric acid
mixture is kept at 80C and mixed or at least two hours. After
this, 5,000 ppm of the demulsifier SOT-826 (S&D Oil Technics) is
added and the oil-sulphuric acid-demulsifier mixture is mixed
thoroughly for another two hours at 80C. The mixture is then
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2l7~ 7
allowed to settle for eighteen to twenty-four hours, forming a
water-free oil layer, an interface layer and a bottom layer of
water.
The initial water content of the waste/slob oil was
6.8%, whereas the initial ash content was 0.97~. After the
above-described treatment an ash content of 0.058% was found.
The water content of the purified oil was found to be 0.19~.
The acidity (according to IP-l standard (=IP-139= ASTM D~74))
was 3.65.
The water contains sulphates of heavy metals, that can
be removed by adding barium chloride at 80C, mixing for at
least fifteen minutes, adding sodium hydroxide to obtain a pH
> 13, again mixing for fifteen minutes and then removing the
heavy metals by using a filter-press.
The ash reduction was found to be 94%. The reduction
was never higher than 4. The reduction,of the water content in
the oil was more than 97%. The oil content of the water layer
was ~ 50 ppm.