Note: Descriptions are shown in the official language in which they were submitted.
21 83433
WO95121902 PCT~S95tO1861
REMOVAL OF CONTAMINANTS FROM OIL
BACKGROUND
Field of Invention
This invention is concerned with the removal of
contaminants from crude or processed mineral oils and
in particular, is concerned with the removal of
contaminants from used motor oils. The invention is
concerned with a method and apparatus for removal of
contaminants from mineral oils.
Prior Art
A large number of processes for removal of
contaminants from mineral oils and waste lubricating
oils are known in the art. Indeed, this plethora of
prior art references is illustrative of continuing
endeavours to find a cost effective method of removal
of contaminants from oils.
Undesirable contaminants in crude oils typically
comprise a complex mixture of high molecular weight
hydrocarbons (including polycylics) known as
asphaltenes. Asphaltenes are recovered as a viscous
residuum in the vacuum distillation of petroleum and
are known to interfere with the efficiency of the
distillation process. Prior art processes for the
removal or reduction of asphaltenes by solvent
extraction of crude oil with a liquid solvent such as
propane or butane are well known.
Used motor oils contain a variety of undesirable
contaminants such as carbon, some asphaltenic
compounds and an additive "package" comprising organo-
metallic compounds in the form of rust inhibitors,
antioxidants, antiwear agents, a detergent-dispersant
and antifoaming agents as well as synthetic polymeric
pour-point depressants and viscosity index improvers.
Soluble and insoluble metal values in used motor oils
include lead tfrom gasoline), iron (from engine wear)
21 83433
WO95/21902 PCT~S95/01861
and varying amounts of càlcium, phosphorous, sulfur,
zinc, sodium and magnesium from the additive "package"
in addition to nitrogen containing organic compounds.
Removal of additive "packages" from used motor
oil is very difficult as the organo-metallic and
polymeric compounds are soluble in solvents used for
solvent extraction reclaiming processes and distil at
similar temperatures to the lubricant base oil.
In the recovery of bunker oil slops from ships
bilges, water and stable oil/water emulsions are
contaminants which are not readily removed on an
economical basis. Accordingly, bunker oil slops are
not employed as a refinery feed stock due to the risk
of refinery operating problems and traditional propane
extraction is not economical in view of the relatively
low volumes for processing.
United States Patent No. 2196989 describes a
process for separating asphaltic compounds from crude
oil to produce a lubricating oil. In this process the
crude oil is mixed with a light hydrocarbon solvent
such as liquid propane or butane and an inert gas such
as methane, ethane, hydrogen, carbon dioxide, nitrogen
or ammonia, the gases acting as a precipitant for oil
materials dissolved in the liquid solvent.
Asphaltic oil is contacted, at elevated
temperature and pressure with a liquid solution of the
oil and propane whereupon a large proportion of the
oil dissolves in the liquid propane solution and small
droplets of undissolved asphaltic impurities fall to
the bottom of the reaction vessel. A gas, soluble in
liquid propane but insoluble in the mineral oil is
introduced into the oil/propane liquid solution near
the top of the vessel under elevated pressure. The
precipitant gas is soluble in and dilutes the propane
solution, thereby decreasing the solubility of the
resinous asphaltic impurities and finally precipitates
the asphaltenes and a substantial proportion of the
2 1 83433
WO95/21902 PCT~S95/01861
oil from solution.
The precipitation of the oily impurities from the
propane solution by precipitant gas is said to be
effected by the principle of difference in
solubilities of the various components in one another.
A process for de-asphalting of residues from the
vacuum distillation of petroleum is described in
United States Patent No. 3870625. This process may
also be applied to reclaiming of used lubricating
oils.
The used oil or distillation residue is injected
under pressure into liquid propane in a pulsed manner
to facilitate dispersion of the oil material in the
solvent as fine droplets. The pulsed oil feedstock
flows countercurrent to the liquid propane which
dissolves the fraction of oil capable of being used as
a lubricant and allows precipitation of the insoluble
materials. The application of mechanical vibrations
to the apparatus is said to improve the output of the
apparatus.
United States Patent No. 4265734 concerns
improvements to the process of aforesaid Patent No.
3870625. As a preliminary step, polluted oil is
injected into reservoirs containing liquid propane to
form a mixture in the ratio of volume of polluted oil
to liquid propane of from 0.25:5 to 1:5. This mixture
is allowed to stand for about an hour to permit the
major part of the impurities in the polluted oil to
precipitate to the bottom of the reservoir. The
oil/propane solution is then withdrawn and treated as
described in earlier Patent No. 3870625.
United States Patent No. 5286380 to Mellen, a co-
inventor of the subject patent application, deals with
removal of contaminants from used motor.
In the '380 patent, used motor oil is fed into an
empty reaction vessel and a liquid aliphatic solvent
such as liquid propane is allowed to enter the
- 21 83433
WO95/21902 PCT~S95/01861
reaction vessel at the bottom thereof to mix with the
oil in the ratio of one part by volume of oil to ten
parts by volume of solvent whereupon the contaminants
precipitate. The oil/solvent solution is then
percolated down through a bed of activated charcoal to
remove lead and other metal contaminants. A glass or
plastics reaction vessel is preferred.
Traditional methods of propane extraction of
asphaltenes from crude oil stocks rely on a large
product upgrade, such as the production of light
stock, to justify high capital costs and high
operating overheads.
Processes employing propane as a solvent in both
crude oil asphaltene extraction and reprocessing of
used motor oils must use propane to oil ratios of from
between 10:1 and 15:1 in order to reduce the solution
viscosity and specific gravity sufficiently to permit
suspended microscopic solids to settle under the
influence of gravitational forces. This requirement
for high propane to oil ratios necessitates very high
energy requirements for propane recovery and large
settling vessels to permit sufficient residence times
for the settling of very fine particles.
Another method for reprocessing of used motor
oils which is currently employed in the United States
is a vacuum distillation process followed by
hydrotreating.
In this process, the waste oil is heated to about
150C to remove any water as well as light
hydrocarbons. The dewatered oil, containing the
additive package, is then heated to about 260C to
remove any diesel fractions.
The oil/additive package mixture is then heated
to about 370C in a distillation column operating at
about 5mm Hg absolute to separate the base oil from
the additive package and the base oil distillate is
then hydrotreated to improve colour and odour. The
21 83433
WO95/21902 PCT~S95/01861
hydrotreating step also removes a proportion of a
residual polycyclic aromatics.
While generally effective for its purpose, the
above described thin film vacuum distillation process
nevertheless suffers from a number of disadvantages.
The main problem with such distillation processes
is that the components of the additive package are not
removed until the last distillation step. At this
stage the oil (and additives) have been heated to over
370C at which temperatures, thermal cracking of the
polymeric compounds and thermal decomposition of the
organo-metallic compounds occurs resulting in severe
coking and corrosion in the distillation column and
ancillary plant. Coking and corrosion of the plant
not only interferes with throughput efficiencies but
also results in a poorer quality lube oil distillate
than otherwise might have been the case.
Although it is possible to pretreat the waste oil
with sodium hydroxide to reduce coking and corrosion
in the downstream region of the plant, this requires
expensive upgrading of the metallurgy in the upstream
region of the plant to reduce corrosion in this
region.
Even in the intermediate diesel distillation
column, plant maintenance is extremely costly due to
the need to replace the column packing every six to
eight months.
Generally speaking, thin film evaporators of the
type employed in the process described above are
expensive to construct and operate on a per unit
throughput capacity. Moreover, in this process, about
2% of the light oil (diesel) fraction is lost in the
water removal stage and about 3% of the available base
oil is lost in final distillation stage due to
retention in the asphaltic still bottoms.
United States Patents 4624763, 4624764, 4661226,
4634510, 4627901, 4622119 and 4622118 all deal with
21 83433
WOs~/21902 PCT~S95/01861
the removal of waxes from lubricating oil by the
induction of a high voltage charge into oil/solvent
mixes to obtain nucleation of wax particles before
precipitation.
Australian Patent No. 605288 describes a process
for extraction of oil from stable oil/water emulsions
by adding a liquefied hydrocarbon solvent to the
emulsion, separating portion of the oil which, on
standing forms an oil solvent phase, and then reducing
the pressure of the residual two phase system to allow
the pressurised liquid solvent to vaporise whereupon
the emulsion splits into oil and water phases.
Brief SummarY and Obiects of the Invention
It is an aim of the present invention to provide
a novel process and apparatus which overcome or
substantially alleviate at least some of the problems
associated with prior art methods and/or apparatus for
removal of contaminants from oil.
According to one aspect of the invention there is
provided a method of removal of contaminants from oil,
the method comprising the steps of:-
forming a solution of contaminated oil in a
liquid aliphatic solvent in the presence of a
flocculation enhancing reagent in a first pressure
vessel;
introducing in a lower region of said first
pressure vessel a gas in the form of fine bubbles
whereby said solution is agitated by the bubbles
rising through the solution and contaminants are
caused to separate from solution by a flocculation
reaction;
separating flocculated contaminants from the
liquid solution; and,
separating the solvent from the solution to
obtain an oil substantially free of contaminants.
Suitably the solvent comprises a C, to C, alkane.
Preferably the solvent comprises liquid propane
21 83433
WO95/21902 PCT~S95/01861
or butane or a mixture thereof.
The flocculation enhancing reagent may be
selected from water and/or an electrolyte solution.
Suitably at least 2% v/v of water is present in
the solution of oil and solvent during the
flocculation reaction.
Preferably at least 3% v/v of water is present in
the oil and solvent solution of oil and solvent during
the flocculation reaction.
Most preferably wacer is present in the oil and
solvent solution at a concentration in the range of
from about 3% to 6% v/v.
Alternatively or in addition to water as a
flocculation enhancing reagent, an electrolyte is
employed as a flocculation reagent.
Suitably the electrolyte comprises a strong acid
or alkali.
The electrolyte may be selected from H2SO4, HCl,
NaOH or KOH.
If required the flocculation reaction may be
carried out with an electrically conductive member in
physical contact with the oil and solvent solution.
The gas may comprise a polar or non polar gas.
Suitably the gas is selected from Co2, N2 or a C~
to C4 alkane.
Preferably the gas comprises propane or butane or
a mixture thereof.
Most preferably the gas comprises propane when
the aliphatic solvent is propane.
The flocculation reaction is carried out at a
temperature of between 15C and 45C.
Suitably the flocculation reaction is carried out
at a temperature of between 15C and 30C.
Most preferably the flocculation reaction is
carried out at a temperature between 18C and 25.
The method of removal of contaminants from oil
may comprise the further step of:
21 83433
WO95/21902 PCT~S95/01861
transferring, from the first pressure vessel to a
second pressure vessel, an oil and solvent solution
from which contaminants have been flocculated;
allowing any residual contaminants to settle from
the oil and solvent solution;
transferring from the second pressure vessel to a
solvent stripping vessel an oil and solvent solution
substantially free of contaminants; and
stripping solvent from the oil and solvent
solution to obtain a substantially contaminant free
oil fraction.
If required the substantially contaminant free
oil fraction may be further purified by a distillation
process.
Preferably the distillation process is carried
out under reduced pressure.
Before distillation, the substantially
contaminant free oil fraction may be subjected to a
stripping process to remove any residual solvent and
any light petroleum fractions therefrom.
If required, contaminant residues from the first
and/or second pressure vessels are subjected to a
stripping process to remove water and any residual
solvent.
Preferably, contaminant residues from which water
and any residual solvent have been removed are mixed
with a hot oil to obtain a flowable asphalt extender.
Most preferably the hot oil comprises a
distillation residue from the distillation process.
The contaminated oil may comprise automotive
drain oil.
Alternatively the contaminated oil may comprise
crude petroleum oil.
The contaminated oil may comprise residues from a
petroleum cracking and/or distillation process.
Alternatively the contaminated oil may comprise
bunker oil slops from ship~s bilges.
21 83433
WO95/21902 PCT~S95/01861
As a further alternative the contaminated oil may
comprise oil/water mixtures and or oil/water emulsions
obtained in petroleum drilling operations.
According to another aspect of the invention
there is provided a method of refining crude oils to
obtain a bright oil product, the method comprising
removal of contaminants from a crude oil feedstock
according to a first aspect of the invention and
subjecting the substantially contaminant free oil
feedstock to a subsequent refining process.
According to a further aspect of the invention
there is provided a method of beneficiating
distillation residues in a petroleum refining process,
the method comprising the steps of treating a
distillation residue in accordance with a first aspect
of the invention and separating lighter fractions from
a contaminated residue formed thereby.
In yet another aspect of the invention there is
provided a method of beneficiating water containing
oil residues from petroleum drilling operations, the
method comprising treatment of the water containing
residues according to the first aspect of the
invention to extract substantially contaminant free
oil fractions therefrom.
In still another aspect of the invention there is
provided a method of beneficiating bunker oil slops
comprising the treatment of bunker oil slops in
accordance with the method according to the first
aspect of the invention to extract substantially
contaminant free fuel oil fractions therefrom.
Preferably, in the beneficiation of water
containing oil residues from petroleum drilling
operations and/or bunker oil slops, the water content
of the oil containing residue to be treated is first
subjected to a water extraction process to reduce, the
water content of material to be treated to less than
10%.
21 83433
WO95/21902 PCT~S95/01861
1 0
According to a second aspect of the invention
there is provided an apparatus for removal of
contaminants from oil, said apparatus comprising:-
a first pressure vessel in fluid communication
with a source of contaminated oil and a solvent and,selectively, a source of flocculation enhancing
reagent comprising water and/or an electrolyte;
a source of pressurised gas selectively
introducible via an inlet port adjacent a lower
portion of said first pressure vessel to disperse fine
gas bubbles through an oil/solvent/flocculation
reagent contained therein;
an outlet port in fluid communication with said
inlet port to circulate gas introduced into said first
pressure vessel;
a decanting port to selectively remove an
oil/solvent solution substantially free of
contaminants from said first pressure vessel; and
a contaminant outlet port adjacent a lower region
of said first pressure vessel to selectively remove
flocculated contaminants settled in said lower region.
Suitably said apparatus includes a second
pressure vessel to accumulate a decanted substantially
contaminant free oil solvent solution from said first
pressure vessel, said second pressure vessel including
an outlet port for substantially continuous withdrawal
of a substantially contaminant free oil/solvent
solution therefrom and an outlet port in a lower
region of said second pressure vessel for removal of
accumulated flocculated contaminants settling therein.
The apparatus may include a solvent stripping
vessel to strip solvent from said substantially
contaminant free oil/solvent solution extracted from
said first and/or second pressure vessel, the solvent
so extracted being returned to said source of solvent.
Suitably said apparatus includes a further
stripping vessel to remove from a solvent stripped
2 1 83433
WO95t21902 PCT~S95/01861
1 1
material delivered from said stripping vessel any
residual solvent and light fuel oil fractions.
If required said apparatus may include a
distillation column to remove a base oil product from
said solvent stripped and light fuel oil stripped
fractions delivered from said further stripping
vessel.
Preferably said apparatus includes a residuum
collection vessel to collect contaminants from said
first and for said second pressure vessels.
Suitably said residuum collection vessel is
adapted to separate water and/or residual solvent from
residuum so collected.
If required said apparatus may further include a
residuum treatment vessel including heating means to
provide a flowable residuum material.
Suitably said residuum treatment vessel includes
a mixing apparatus to mix an oil with said residuum to
provide a flowable product.
Preferably said apparatus is in fluid
communication with said distillation column to provide
an oil distillation residue for mixing with said
residuum.
According to yet a further aspect of the
2S invention there is provided an apparatus for
production of bright oil from crude oil, said
apparatus comprising a decontamination apparatus
according to a second aspect of the invention for
pretreatment of crude oils upstream of a conventional
crude oil processing apparatus.
According to another aspect of the invention
there is provided an apparatus for processing of
distillation residues in a conventional petroleum
distillation apparatus said apparatus including an
apparatus according to a second aspect of the
invention to extract valuable petroleum fractions from
petroleum distillation residues.
2 1 83433
WO95121902 PCT~S95/01861
12
The invention provides yet another apparatus for
the beneficiation of water containing crude oils
obtained from petroleum drilling operations.
Still further the invention provides an apparatus
for beneficiation of bunker oil slops obtained from
ship's bilges.
If required, the invention in another aspect
provides an apparatus for treatment of oil containing
residues from commercial and public utilities for oil
separation from waste and/or storm water sources.
The present invention overcomes or substantially
alleviates the aforementioned prior art problems by
further providing a novel apparatus for removing
contaminants such as asphalts, additive packages and
other contaminants from drain oils; asphaltenes from
crude oils; asphaltenes, water and other contaminants
from bunker oil slops and the like.
In one embodiment, oil from an oil storage tank
is pumped by a pump into a solvent mix tank. This oil
is mixed with an aliphatic solvent such as methane,
ethane, propane, butane, pentane, hexane, heptane or
the like coming from a solvent storage tank via
another pump and an appropriate quantity of a
flocculation enhancing reagent is also added.
Advantageously, the solvent, reagent and oil are mixed
just prior to entering the solvent mix tank to form an
oil, reagent and solvent mixture at ambient or an
elevated temperature between 25C and about 40C.
Thereafter, gas, preferably propane, is dispersed into
the bottom of the solvent mix tank thus agitating the
mixture. This agitation is allowed to proceed for a
specified period of time after which the gas is shut
off and the mixture is allowed to separate via
gravity.
The oil/propane solution is then transferred to a
second tank using the pressure differential between
the two vessels as the driving force. Water, asphalt
21 83433
WO95/21902 PCT~S95/01861
residuum and some solvent are transferred from the
solvent mix tank into a residuum and water separation
tank.
When all of the material, both the
oil/solvent/reagent solution and the water and
residuum, have been transferred from the solvent mix
tank, it is once again ready to receive another batch
of, say, drain oil and propane solvent. The
oil/solvent solution in the solution feed tank allows
any residuum that may not have separated in the
solvent mix tank to separate out but primarily the
solution feed tank is a holding tank to allow a
continuous feed of oil/solvent solution into the
solvent oil recovery area, explained hereafter, so
that a continuous run is accomplished. The
oil/solvent solution is pumped via a stripper charge
pump which also increases the pressure up to the
solvent stripper operating pressure. Any residuum
settling out in the solution feed tank is transferred
to an asphalt mix tank. This transfer is accomplished
by the pressure differential between the two vessels.
The residuum and water separator is designed to
separate any oil/solvent solution that is transferred
from the bottom of the solvent mix tank from the
residuum and also from the water. Thus, this is a
three phase (oil, water and residuum) separator. The
interface of each phase is determined by pumping from
a specific level via a pump through a gage glass with
a viewport by detecting the difference in the colour
between the water and the residuum or by any other
suitable detection means. Once the level is detected,
then the water is taken off and disposed of, or if
required, portion of this water may be employed as a
flocculation enhancing reagent. The residuum which is
a solid with some propane and water trapped in the
solid is then transferred to the asphalt mix tank
where it is heated and mixed with the heavy oil from
; 21 83433
WO95/21902 PCT~S95/01861
14
the bottom of the vacuum distillation column.
The solvent stripper recovers in excess of 95
percent of all of the propane solvent that was
injected into the solvent mix tank. The remainder of
the propane solvent will be recovered in the
distillation preflash or light petroleum flash tank.
The oil/solvent solution from the solution feed tank
enters the solvent stripper at an increased pressure
because of the vane pump which facilitates the
transfer. The oil/solvent solution is then introduced
into a packed column in the solvent stripper, wherein
the oil and propane mixture flows across a packed bed
where propane vapours from the reboiler portion of the
solvent stripper strip out the propane solvent from
the oil. The propane then leaves the top portion of
the column and is subsequently condensed by a
condenser. From the condenser this propane solvent is
reintroduced into the solvent storage tank for future
reuse as needed.
The oil falls to the bottom of the solvent
stripper into the reboiler. This reboiler uses a hot
oil stream from the bottom of the distillation column,
heat being provided by the furnace, and the hot oil
stream is pumped through the reboiler heating the
mixture of oil to approximately 260C.
This hot oil is then transferred to the light
petroleum flash tank operating at a much lower
pressure. In the light petroleum flash tank the lower
pressure and high temperature allows light petroleum
fractions and whatever propane might remain in the oil
to vaporise.
The light petroleum fractions and propane solvent
that vaporises goes into an overhead condenser where
all of the light petroleum fraction condensed. The
light petroleum fraction and propane mixture then goes
to a light petroleum separation drum from where the
light petroleum is pumped to the light petroleum
21 83433
WO95/21902 PCT~S95/01861
storage facility via a pump. The propane vapour goes
to a two stage compressor with an intercooler where
the propane solvent is compressed and sent back to the
solvent storage tank.
The oil that did not flash in the light petroleum
flash tank is transferred to the vacuum distillation
column. By reducing the pressure on the oil, the
diesel and lubrication oil that remain in the liquid
state are vaporised and go into the upper part of the
distillation column. The liquid that does not
vaporise at that time, falls to the bottom of the
tower where it is heated to a temperature of
approximately 350C where further vaporisation happens
causing more of the oil to vaporise. The oil that
does not vaporise is transferred via a pump into the
hot oil loop where it provides the heat for both the
solvent stripper as described earlier and the asphalt
mix tank. When the oil has been cooled off by
rendering these services in the hot oil loop, it is
returned to the furnace where it is heated up to
approximately 350C and returned back to the bottom of
the distillation column.
A certain amount of heavy oil product that does
not vaporise in the distillation column is pumped to
the asphalt mix tank. It is this hot oil that
dissolves the residuum from the solvent mix tank and
solution feed tank.
The oil that vaporises in the distillation column
goes through the column and proceeds up to the section
of the column where it is condensed and drawn off by a
pump into the oil storage. A light petroleum fraction
which is still vaporising rises to the top packed
section of the column where it is condensed and drawn
off by a pump. Any noncondensibles that remain at
this time are pumped via a sliding vane vacuum pump to
a furnace where those vapours are burned.
These and other objects and features of the
- 2 1 83433
.
WO95/21902 PCT~S9S/01861
16
present invention will be apparent from the detailed
description and accompanying drawings.
Brief Description of the Drawinqs
In order that the various aspects of the
invention may be more fully understood and put into
practical effect, reference is made to preferred
embodiments illustrated in the accompanying drawings
in which:-
FIG 1 is a schematic view of a settlement
reaction vessel.
FIG 2 is a flow diagram representing an apparatus
for removal of contaminants from oil in accordance
with both method and apparatus aspects of the
invention.
FIG 3 is an enlarged schematic view of the
asphalt extraction system illustrated in FIG 2.
Detailed DescriPtion of the Illustrated Embodiments
FIG 1 illustrates a laboratory scale reaction
vessel employed in the generation of experimental data
discussed hereinafter.
In FIG 1 the vessel 201 comprises a clear
cylindrical acrylic plastics wall 202 with a top
closure member 203 and a generally frusto-conical
bottom closure member 204. Removably located within
vessel 201 is an expanded mild steel mesh tube 205,
the purpose of which will be explained later.
At the base of vessel 200 is an asphalt valve 206
to remove asphaltic residuum 207 which collects in
this region and a further valve 208 is provided in a
conduit 209 connected to a source of waste oil and
other additives (not shown).
A two way valve 209 is connected to conduit 210
providing a source (not shown) of liquid propane or a
pressurised gas such as CO2 or N2. Valve 209 is also
connected to a gas recirculation system comprising
21 83433
WO 95t21902 PCT/US95101861
17
conduit 211 in fluid communication with the upper
region of vessel 1, an isolating valve 212, a gas
compressor 213 and a heat exchanger 214. Gas is
dispersed in the vessel 201 via a sparging manifold
217 having a plurality of nozzles 218 to disperse the
gas as fine bubbles.
A take off conduit 215 with isolating valve 216
is connected to a solvent stripper/recovery system
(not shown).
The process according to a preferred aspect of
the invention involves mixing contaminated oil,
containing water and/or an electrolyte, with liquid
propane in the ratio of between 1:3 to 1:6 and then
sparging the mixture with fine bubbles of propane for
a period of 10 to 20 minutes at ambient temperature
and thereafter allowing the mixture to settle for
about 10 to 20 minutes.
The mixture separates into three distinct layers,
a clear oil/propane layer, a water layer and a residue
layer. Each of these layers are collected and propane
is removed from the clear oil fraction.
Examples
The reactor of FIG 1 was charged with 1000 ml of
oil and mixed with liquid propane in the ratio 1:6.
The propane/oil mix was agitated by pumping propane
vapour in fine bubbles through the liquid mixture for
a period of 10 minutes.
The sparging resulted in a high flow rate of gas
bubbles having a diameter of between 1 and 3mm which
provide a relatively gentle but turbulent mixing
action. After agitation for 10 minutes, the mixture
was allowed to settle and the rate of settling was
measured.
When the suspended solids had completely settled,
the clear oil/propane mixture layer was removed and
the propane was extracted therefrom under reduced
pressure. The remaining residue was removed and
` 21 ~3433
WO95121902 PCT~S95101861
18
entrained propane was allowed to boil off at
atmospheric pressure.
The oil used in the tests was automotive drain
oil which had an initial water content of 3.8%. This
oil was dehydrated by heating up to 140C to obtain an
oil with a water content of less than 0.2% and a
specific gravity of 0.887 kg/m3.
The clarity of the oil removed was measured by
diluting the oil in hexane in a 1:10 ratio of oil to
solvent and then measuring with a colour meter.
The residues from the tests were weighed and
visually compared with respect to viscosity and flow
characteristics and the water contents of the residue
was determined by standard ASTM methods.
All liquid additions to the oil such as H2O, 97%
H2SO4, 35% HCl and red water were on a volume to volume
basis whereas the additions of 45% KOH, CH3COOH, clay
and sodium hexametaphosphate were on a weight to
volume basis.
In all tests carried out the floc formation
appeared to occur during agitation with the stream of
gas bubbles. There may be some continued floc growth
after gas sparging is ceased at which time gentle
mixing of the liquid mixture/floc suspension occurs
due to entrained gas bubbles moving through the
liquid.
The following tables illustrate the effects of
varying concentrations of water in the oil/propane
mixture and the effects of electrolytes and other
chemicals in the settling properties of the treated
oil and the residue.
Table I
Effect of Water Content in DehYdrated Oil
(Metal Screen Present)
CONTENT SETTLING RATE OIL COLOUR RESIDUE (gm) H20 in
H20 (%) (MINUTES) residue (%)
2 1 83433
W O 95/21902 PC~rnUS95/01861
<0.2 Very slow 8.0 No solid N/A
14-18 residue 25mm
oil/sludge
1.0 Slow 7.5 No solid N/A
8-9 residue 1 2mm
oil/sludge
2.0 Slow 7.0 Traces of N/A
8-9 residue 1 2mm
oil/sludge
3.0 Medium 7.0 40-51 40
5-6
5.0 Medium 7.0 45-66 47
5-6
20.0 Medium 7.0 7200 64
5-6
TABLE IA
EFFECT OF WATER CONTENT IN DEHYDRATED OIL
(METAL SCREEN REMOVED)
10 H20 SETTLING OIL COLOUR RESIDUE (gm) H20 IN
CONTENT RATE RESIDUE
(%) (MIN) (%)
5.0 V.V. Slow 7.5 No Solid Residue N/A
~30 50 mm oil/Sludge
TABLE II
EFFECT OF KOH IN THE DEHYDRATED OIL
(METAL SCREEN PRESENT)
KOH SETTLING RATE OIL COLOUR RESIDUE H20 IN RESIDUE
(%) (MIN) (gm) (%)
0.2 V. Fast 5.5 28 12
2-3 Viscous
o.5 V. Fast 4.5 36 16
2-3 Viscous
0.5 Fast 5.5 39 30
3-4 Sticky
21 83433
WO95121902 PCT~S95/01861
TABLE IIA
EFFECT OF KOH IN THE DEHYDRATED OIL
(METAL SCREEN REMOVED)
KOH (%) SETTLING RATE OIL COLOUR RESIDUE H20 RESIDUE
(MIN) (gm) (%)
0.5 V. Fast 7.5 65 12
2-3 Viscous
TABLE III
EFFECT OF ACIDS IN THE DEHYDRATED OIL
CONCENTRATIONSETTLING OIL RESIDUE H20 IN
(%) RATE (MIN) COLOUR (gm) RESIDUE
(%)
0.2 H2SO~ (98%) V. Fast 2-3 4.5 21 6
V.V. Viscous
0.5 H2SO~ (98%) Fast 3-4 4.5 30 9
V.V. Viscous
0.5 HCl (35%) Medium 8-10 4.0 39 21
V.Viscous
0.5 CH3COOH Slow 10-12 6.5 29 3.5
Sticky
21 83433
WO95~1902 PCT~S95/01861
TABLE IV
EFFECT OF VARIOUS CHEMICALS IN THE DEHYDRATED OIL
CONCENTRATION SETTLING OIL RESIDUE H2O in
RATE COLOUR (gm) RESIDUE
(MIN) (%)
1% Calgon + 1%H2O Fast 5.5 120 Sticky 30
3-4
0 5% V. Slow - 34 Sticky 27
Hexametaphosphate 20-25
+ 2% H2O
5% red water Slow 7.5 47 Sticky
8-10
5% CH30H V. Slow 10 No Solid N/A
10-25 Residue
10 5% Clay Slow 7.S 65* 13
8-10
Some clay settled first followed by a mixture of clay and
residue as soft lumps.
The results show that a number of factors
contribute to the formation of large particles which
are capable of settling quickly in the propane/oil
mixture. Also it appears that there may be a number
of competing mechanisms which are responsible for the
formation of the large flocculant particles.
Without wishing to be bound by any particular
hypothesis as to the nature of the various competing
mechanisms, the following discussion is an attempt to
explain the basis of the various phenoma observed.
The stability of complex mixtures/dispersions of
surface active materials may, in addition to van der
Waals attractive forces and electrical double layer
repulsive forces, be influenced by a variety of
additional factors involving desorption energy,
entropic and bridging effects.
Given that there is no noticeable coagulation or
21 83433O95/21902 PCT~S95/01861
22
precipitation of the contaminants when drain oil is
simply mixed with liquid propane in the ratio of from
about 1:3 to 1:4 volume/volume of drain oil to liquid
propane, the introduction of the gas bubbles,
particularly in the presence of water or an
electrolyte, gives rise to circumstances which
destabilise the solution/dispersion. This is in stark
contrast to prior art propane treatment methods which
require oil/liquid propane ratios in the range 1:10 to
1:15 to reduce the viscosity and specific gravity of
the solution to permit precipitation of fine
particulate solids and insoluble oils with prolonged
settling periods.
In the process according to the invention, there
is no appreciable change in the oil/liquid propane
ratio with the introduction of propane gas bubbles as
the propane gas is withdrawn from the upper region of
the reaction vessel and recirculated.
Trials with other gases such as Co2 and N2 have
shown that although nowhere near as effective as
propane, agitation of the oil/liquid propane mixture,
in the presence of water and/or an electrolyte, with
these gases will also initiate a coagulation or
flocculation reaction. Accordingly, the dispersion of
fine gas bubbles through the oil/propane mixture may
involve the generation of a triboelectric charge on
the surface of the bubbles in the form of an
electrical double layer.
As drain oil is a mixture of ionic species such
as organo-metallic compounds and non-ionic macro-
molecular species such as synthetic polymeric
viscosity index modifiers as well as polar and non-
polar molecular species, it is believed that drain oil
behaves as a mixture of lyophilic and lyophobic
colloidal systems. This is borne out by the
inexplicable contribution of the metal screen to
solids formation and the contribution of strong
21 83433
WO95/21902 PCT~S95/01861
23
electrolytes to the process. On balance, the system
behaves like a lyophobic colloid system in which the
addition of a relatively small amount of electrolyte
causes flocculation. Although, strictly speaking,
water is not an electrolyte, it is believed that
contaminated oils contain water soluble impurities
which behave as electrolytes.
By examining the behaviour of the
coagulation/flocculation reaction, the settling rate
of the solids and the nature of the solids obtained
with the various chemicals added to dehydrated oil,
some insight into the complexity of the process may be
obtained.
WATER
In the absence of any other chemical, water plays
a vital role in the formation of large residue
particles. When the oil is dry (<0.2%) the insoluble
residue that is formed is very small in size, does not
flocculate and settles very slowly. The settled
residue does not form a viscous material that stays in
the bottom of the column, but remains concentrated in
the oil/propane mix and tends to redissolve in the oil
when the propane is removed.
With a propane to oil ratio of 6:1 at least 3%
water is required in the oil before a significant
change in the settling rate is achieved. At this
concentration larger residue particles are formed and
the residue can be easily separated from the
oil/propane mixture. The residue is viscous, and
tends to have a tar like structure. No viscosity
measurements were undertaken. The rate of settling of
the residue remains approximately constant with
increasing water contents above 3%, but the quantity
of residue increases with increasing water content.
This is mainly due to an increase in the water bound
up in the residue.
For the formation of these larger particles
21 ~3433
WO95/21902 PCT~S95/01861
sufficient water in the form of droplets needs to be
available so that the precipitated insolubles can be
attached to them. The minimum water content found in
this work is probably due to the solubility of water
in the propane-oil mixture and sufficient nuclei are
not available until the water content of the oil
reached about 3.0%. Although triboelectrically
charged gas bubbles may provide nuclei in their own
right, it is believed that a charge transfer may occur
between the gas bubbles and the water particles which
would explain the improved flocculation rates with
water/electrolyte nuclei.
However, without a metal mesh in the reactor an
oil containing 5.0% water did not form the large
particles and tended to settle in a manner similar to
dry oil. The particle size was small, it was very
slow in settling and did not produce a residue that
was readily separated from the oil-propane mixture.
It is believed that the metal screen provides an
electrically conductive matrix in an otherwise non-
conductive medium which assists in transference of the
electric charge from the gas bubbles to the aqueous
electrolyte or ionic and polar molecular species in
the mixture.
Since the insoluble residue produced in the dry
oil did not produce a fast settling residue the
presence of water and metal mesh whether iron or
copper, are necessary to form the large particles.
The most probable mechanism is that the turbulent
mixing created by the propane sparge creates a
triboelectric charge on the water droplets that
enables the precipitated residue to be attracted and
attached to it or that the gas bubbles are charged and
transfer this charge to the water droplets.
The mixing also provides greater droplet-particle
contact and this would assist in overcoming any double
layer repulsion. The residue will contain significant
21 83433
WO95/21902 PCT~S95/01861
ionic charges due to the presence of metal organics
but these alone do not explain the need for a metal
surface for the mixture to contact.
The metal mesh remains inert during the process
and there are no visible signs of it reacting or
eroding. The pilot plant described with reference to
FIGS 2 and 3 herein comprises mild steel reaction
vessels and operates in the same way as the laboratory
test with the metal mesh present.
ALKALIS
In the absence of water a 45% potassium hydroxide
solution added to the dry oil created large, fast
settling residues. Compared with the oil produced in
the process using water above, the colour was
significantly improved, the settling was much faster
and the viscosity of the settled residue increased
significantly.
The presence of 3% water with the 0.5% potassium
hydroxide slightly reduced the settling rate (but
better the 3% water only) and made the residue less
viscous. The amount of water in the residue appears
to have been reduced by the presence of potassium
hydroxide.
The formation of a fast settling residue was
independent of the presence of a metal mesh when KOH
was used. This shows that a different mechanism to
that for water alone is affecting the formation of the
large residue particles. The increase in viscosity of
the residue indicates greater bonding and cross-
linking may be occurring.
The strong alkali is reacting with the residue sothat when the particles come in contact with each
other due to the strong mixing they readily attach to
one another. The exact reaction is not known but both
potassium and sodium hydroxide work equally well
whereas ammonium and calcium hydroxide do not.
The test without the screen produced larger
21 83433
WO95/21902 PCT~S95/01861
26
amounts of residue and the colour of the oil was
darker.
ACIDS
In the absence of water a 0.2% or 0.5% sulphuric
acid solution created a large settling residue. The
colour of the oil was equal to that of 0.5% KOH. The
residue, however, was by far the most viscous
indicating considerable cross-linking. The presence
of water in the oil reduced the severity of the
reaction.
Similarly when 0.5% hydrochloric acid was used
the settling rate was moderate but faster than when
only water was present. However, the colour of the
oil was the best of all the tests. The water content
for this work was 2% due to the acid being a 35%
solution. From the previous work this would reduce
the settling rate.
A weak acid, such as acetic acid, produced a slow
settling residue that was difficult to separate from
the oil-propane mixture.
The strong acids tend to act in a similar manner
to strong alkalis by reacting with the residue to form
a material that attaches readily to other residue
particles or to create a cross-linking reaction
between the particles. The acids and alkalis may also
enhance the amount of insoluble material by
precipitating metal hydroxides and sulphates.
For this type of system the sparging by propane
or another gas may not be crucial and similar results
could be achieved by mechanical mixing.
DISPERSANT
Calgon, a commercial additive for water
treatment, and sodium hexametaphosphate showed
different effects. The calgon in high concentration
(1%) with 5% water produced a rapid settling residue
and an oil of moderate colour. The sodium
hexametaphosphate in 2% water produced a slow settling
2 1 83433
WO95/21902 PCT~S95/01861
residue which, unlike the 2~ water only test, could be
separated from the propane-oil mixture.
Both of these compounds act as particle
dispersant in an aqueous system and they were tested
in an attempt to keep the water from being tied up in
the residue. This was only partially successful and
the presence of highly charged ions appears to have
enhanced the growth of the residue particles. This
may be due to the precipitation of metal phosphates.
OTHER CHEMICALS
The addition of clay or red water did not
significantly change the particle size or the settling
rate of the residue. The clay improved the settling
characteristics by adsorbing some of the residue onto
its surface. The residue was drier and had poor flow
characteristics.
Whether used on automotive drain oils, raw crude
oil, petroleum distillation residues, bunker oil slops
or the like, the process according to the invention
has been found to remove up to 95% of contaminants,
including water, at the initial flocculation stage.
In the subsequent stripping and/or distillation stages
the light fuel fraction and the base oil fractions are
found to be substantially free of contaminants.
FIG 2 illustrates schematically a commercial
apparatus for the removal of contaminants from oils.
In FIG 2, the apparatus comprises a first
pressure vessel 10 for receiving solvent and
contaminated oil to form a solution, the first
pressure vessel 10 having top and bottom portions 12
and 14, respectively, the bottom portion 14 being
adapted for dispersing gas into the solution in the
first pressure vessel 10 through a line 15, and
recovery means in the form of a solvent stripper 16
whereby the solution is separated into a vaporised
solvent and oil, the vaporised solvent being
reintroduced by sparging through the bottom portion 14
21 83433
WO95/21902 PCT~S95/01861
of the first pressure vessel 10 through the line 15.
The apparatus also comprises a supply of
contaminated oil such as drain oil 18 in fluid
communication with the first pressure vessel through a
drain oil inlet line 20 and valve 22, a drain oil
charge pump 24 pumping the drain oil to the first
pressure vessel 10. Further, the apparatus includes a
supply of liquid solvent 26 which is introduced into
the first pressure vessel 10 through a liquid solvent
line 28 and a valve 30, a liquid solvent pump 32 being
provided for pumping the liquid solvent from the
supply 26 to the vessel 10.
Advantageously, the feed lines 20 and 28
intersect to form a third line 34 which leads to the
vessel 20 such that the third line 34 introduces
liquid solvent and drain oil simultaneously into the
vessel 10 to form a solution. An inlet port 152
permits selective introduction of a flocculation
enhancing reagent.
Additionally, the apparatus comprises a second
pressure vessel 36 in fluid communication with the
first vessel 10 through line 38, the second vessel 36
including top and bottom portions 40 and 42
respectively. Advantageously, the solvent and oil in
solution are removed from the first vessel 10 and
introduced into the second vessel 36 by a pressure
differential between the vessels.
The apparatus further includes a solution,
asphalt residuum and water separating tank 44 which
includes an inlet 46 in fluid communication with the
vessel 10 whereby solvent and oil in solution, asphalt
residuum and water are transferred from the bottom
portion 14 to the separating tank 44 by a pump 48.
The separating tank 44 also includes a first outlet 50
whereby water is removed from the tank 44, a second
outlet 52 whereby asphalt residuum is removed from the
tank 44, and a third outlet 54 whereby solvent and oil
21 83433
WO95/21902 PCT~S95/01861
29
in solution are returned to the first vessel 10.
Inside the tank 44 is found a weir 56 (not shown) over
which solvent and oil flows and also a water outlet
50.
The apparatus further comprises an asphalt
residuum mix tank 60 which includes an inlet 62 in
fluid communication with the second outlet 52 of the
tank 44 through which asphalt residuum is received
through line 64 and also an outlet 66 from which
asphalt product is removed. Advantageously, the
bottom portion 42 of the vessel 36 is in fluid
communication through line 68 with the inlet 62 of the
mix tank 60, whereby additional asphalt residuum is
removed from the vessel 36.
As mentioned, the apparatus includes a solvent
stripper 16 which serves as recovery means which is in
fluid communication through line 70 with the second
vessel 36. A charger pump 72 is included in the line
70 to facilitate transport of the solvent and oil
solution to the stripper 16. Also, the charger pump
72 increases the pressure differential between the
vessel 36 and the stripper 16. Preferably, the
stripper 16 comprises a packed column 74 into which
solvent and oil solution flows, the column 74 having
top and bottom portions 76 and 78 respectively, the
top portion 76 including an outlet 80 through which
most of the heated vaporised solvent is removed from
the stripper 16. The stripper 16 further comprises a
reboiler 82 integrally connected to and in fluid
communication with the bottom portion 78 of the column
74, the reboiler 82 including an outlet 84 through
which the oil and any remaining solvent are removed
from the stripper 16.
The apparatus further comprises a condenser 86
which is in fluid communication both with the top
portion 76 of the packed column 74 and with the supply
of solvent 26 through a line 88, whereby heated
21 83433
WO95/21902 PCT~S95/01861
vaporised solvent can be condensed into liquid form
and replaced into the solvent supply 26 for future
use.
The apparatus further comprises a gasoline flash
drum 90 having top and bottom portion 92 and 94
respectively, the top portion 92 including an outlet
96 and the bottom portion 94 including an outlet 98,
the drum 90 being in fluid communication through line
100 with the reboiler 82, such that oil and any
remaining solvent are transported from the solvent
stripper into the gasoline flash drum 90.
The apparatus also comprises another condenser
102 in fluid communication through line 104 with top
portion 92 of the drum 90, whereby the vaporised
gasoline is condensed into a liquid. The apparatus
further comprises a gasoline collection drum 106
having top and bottom portions 108 and 110
respectively, the top portion 108 including an outlet
112 for solvent and the bottom portion 110 including
outlet 114 for liquid gasoline, the drum 106 being in
fluid communication through line 116 with the
condenser 102, such that gasoline and solvent are
transported from the condenser 102 into the drum 106.
The apparatus further comprises a gasoline pump 118 in
fluid communication 120 with the outlet 114 of the
drum 106, whereby finished gasoline product is pumped
into a gasoline supply (not shown).
The apparatus further comprises a two stage
compressor and interstage cooler 122 in fluid
communication through line 124 with the outlet 112 in
the drum 106, such that the solvent in the drum 106
passes therethrough to be further compressed and
cooled. The compressor and cooler 122 are in fluid
communication through line 126 with the condenser 86,
such that solvent that has passed therethrough is
condensed and returned to the solvent supply 26 for
further use. An interstage suction scrubber (not
21 83433
WO95/21902 PCT~S95/01861
shown) is adjacent to and in fluid communication with
the cooler and compressor 122 such that liquid
condensed therein is returned to the drum 106.
The apparatus also comprises a vacuum
distillation column 128 having top, middle and bottom
portions 130, 132 and 134 respectively, the top
portion 130 including an outlet 136 for finished
diesel fuel product, middle portion 132 including an
outlet 138 for finished lubrication oil product and
the bottom portion 134 including an outlet 140 for
heavy oil and distillation residues, the column 128
being in fluid communication through line 142 with the
outlet 98 in the drum 90. The apparatus further
comprises a furnace 144 for heating the oil in the
column 128. Also, the column 128 is in fluid
communication through line 146 with the inlet 62 to
the tank 60, whereby heated heavy oil distillation
residues are introduced into the tank 60 to mix with
the asphalt residuum to create a final asphalt
product. An asphalt pump 148 preferably circulates
the residuum and oil to facilitate mixing. Line 150
is also provided between the tank 60 and the condenser
102 such that excess solvent vapour and water are
removed from the tank 60.
A flocculation enhancing reagent may be
introduced into the first pressure vessel 10 via an
introduction port 152 from a suitable storage means
(not shown). The flocculation enhancing reagent may
comprise water, an aqueous solution of a strong
electrolyte such as a strong acid or an alkaline earth
metal hydroxide or other suitable reagent or a mixture
thereof.
Sodium or potassium hydroxide solutions may, if
required, be introduced via either or both of ports
152 and 156 in an endeavour to improve the colour of
the finished base oil product.
Pilot scale operations conducted over prolonged
: 21 83433
WO9Sn1902 PCT~S95/01861
periods of operation have shown no reduction or change
in efficiency of any of the separating, stripping,
reboiling or vacuum distillation vessels and there is
little or no evidence of coking or corrosion in any of
the components of the apparatus other than the asphalt
mix tank which shows mild tar stains.
FIG 3 shows an alternative embodiment of the
asphalt residuum processing system shown generally as
60 in FIG 2 and for the sake of clarity, where
applicable, the same reference numerals have been
employed.
As the residuum from the propane extraction unit
44 is, under normal conditions when cooled, a solid
mass containing both water and entrained propane gas,
it would otherwise be unsuitable for sale as a
byproduct and generally difficult to handle for
disposition.
The process according to the invention combines
the heavy oil still residues from vacuum distillation
column 128 with the viscous residuum, water and
propane mix from propane extraction vessel 44 and
vessel 36 via conduits 146 and 64/68 respectively by
pumping both streams through a static mixer 300. The
mixture is then passed through a heat exchanger 301
where the temperature of the mix is raised to about
150C.
The heated mixture then flows via conduit 302 to
an inlet 303 associated with an extraction vessel 304.
A spray head 305 in fluid communication with inlet 303
sprays the mixture in a thin film over shed trays 306
to enhance the separation of propane and water vapours
from the mixture. An outlet 307 is in fluid
communication with conduit 150 tFIG 2) to recover and
separate the propane and water vapours.
The residuum/oil mixture then leaves vessel 304
via outlet 308 and asphalt pump 309 and is dispensed
from conduit 310 as a viscous liquid, free of water
21 83433
WO95/21902 PCT~S95/01861
33
and propane in the form of a saleable product as an
asphalt extender for roofing or paving applications or
the like.
Although the process and apparatus according to
the invention have been illustrated with reference to
the removal of contaminants from used motor vehicle
lubricating oils or "drain oils", it will be readily
apparent to a skilled addressee that the process and
apparatus, with no modification or some modifications,
are applicable to decontamination of other oils.
For example the process may be employed as an
upstream function in a petroleum cracking/distillation
plant to remove from the feedstock asphaltenes and
other contaminants which may reduce cracking
efficiencies by catalyst poisoning or the like and
otherwise reduce the efficiency of the vacuum
distillation process and lead to premature coking and
corrosion in the distillation column.
Similarly, still residues from conventional
cracking/distillation processes may also be treated in
accordance with the present invention to extract
valuable lighter fractions which otherwise cannot be
extracted economically from still residues and the
like.
The invention also permits the economic recovery
of valuable hydrocarbons from bunker oil slops
obtained from ship's bilges, oily wastes and emulsions
generated in tertiary crude extraction processes and
oil wastes and emulsions produced in sea bed
extraction of crude oils.
The byproduct of the process according to the
process according to the invention is a vendible
product in the form of an asphalt extender and where
heavy metals and other toxic materials are extracted
from the contaminated oils, the asphalt extender
material provides a safe, non water leachable binding
matrix which avoids the necessity and high costs and
- 2 1 83433
WO9S/21902 PCT~S95/01861
34
risks associated with other means for disposing of
toxic contaminants.
If required, the base oil product produced in
accordance with the invention may be upgraded even
further by a known hydrotreatment process.
It will be equally apparent to a skilled
addressee that many modifications and variations may
be made to the process and apparatus according to the
invention without departing from the spirit and scope
thereof.
