Note: Descriptions are shown in the official language in which they were submitted.
CA 02795410 2012-11-13
MARINE ENGINE LUBRICATION
FIELD OF THE INVENTION
This invention relates to a trunk piston marine engine lubricating composition
for a
medium-speed four-stroke compression-ignited (diesel) marine engine and
lubrication of
such an engine.
BACKGROUND OF THE INVENTION
Marine trunk piston engines generally use Heavy Fuel Oil ('HF0') for offshore
running. Heavy Fuel Oil is the heaviest fraction of petroleum distillate and
comprises a
complex mixture of molecules including up to 15% of asphaltenes, defined as
the fraction
of petroleum distillate that is insoluble in an excess of aliphatic
hydrocarbon (e.g. heptane)
but which is soluble in aromatic solvents (e.g. toluene). Asphaltenes can
enter the engine
lubricant as contaminants either via the cylinder or the fuel pumps and
injectors, and
asphaltene precipitation can then occur, manifested in 'black paint' or 'black
sludge' in the
engine. The presence of such carbonaceous deposits on a piston surface can act
as an
insulating layer which can result in the formation of cracks that then
propagate through the
piston. If a crack travels through the piston, hot combustion gases can enter
the crankcase,
possibly resulting in a crankcase explosion.
It is therefore highly desirable that trunk piston engine oils ('TPEO's)
prevent or
inhibit asphaltene precipitation. The prior art describes ways of doing this.
WO 96/26995 (`995) discloses the use of a hydrocarbyl-substituted phenol to
reduce 'black paint' in a diesel engine. Specifically, it mentions a
lubricating oil for
lubricating a medium-speed 4-stroke diesel engine, such oils also being known
in the art as
TPEO's. It mentions use of alkyl phenols to reduce black paint formation in
use of such
oils with fuel oils with a residual oil content, also known in the art as
HFO's. '995 further
mentions that the lubricating oil may contain detergents such as hydrocarbyl-
substituted
alkaline earth metal phenates, salicylates, napththenates, sulphonates or
carboxylates,
which may be normal or overbased.
'995 also mentions that the lubricating oil has a TBN of 8-50, provided by
adjusting the amount of detergent, for use in a 4-stroke engine, and 0.5 to
10% by weight
of the phenol. Its examples describe sediments tests on TPEO's of 30 TBN
containing a
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CA 02795410 2012-11-13
calcium phenate detergent and either no or varying amounts of a branched chain
alkyl
phenol.
'995 is not, however, concerned with the economics of treating TPEO's to
inhibit
'black paint' formation. A considerable cost arises from the amount of
detergent soap that
is used, i.e. the detergent other than the basic material. It is now found
that, when the
detergent is a salicylate, there is a relationship between 'black paint'
reducing performance
and the respective concentrations of salicylate soap and of alkyl phenol. This
relationship
is such that the level of soap may be reduced, and cost reduced, without any
deleterious
effect on 'black paint' reducing performance.
WO 2010/124859 describes trunk piston marine engine lubrication where, to
prevent or inhibit asphaltene precipitation, the lubricant comprises a Group
II basestock
and respective minor amounts of an overbased metal salicylate detergent and an
alkyl-
substituted phenol, other than a hindered phenol.
SUMMARY OF THE INVENTION The following are now found when a salicylate
detergent/alkyl phenol system is
used in TPEO's in attempting to reduce or eliminate 'black paint'. When the
salicylate
soap concentration is high, addition of alkyl phenol does not substantially
affect
performance. However, when the salicylate soap level is lower, additions of
low levels of
alkyl phenol, for example below those stated in '995 to be preferred (i.e.
2.0% by weight)
and even below those stated generally in '995 (i.e. 0.5% by weight), are found
to improve
performance.
A first aspect of the invention is a trunk piston marine engine lubricating
oil
composition of TBN in the range of 20 to 60, such as, 30 to 55, for improving
asphaltene
handling in use thereof, in operation of the engine when fuelled by a heavy
fuel oil, which
composition comprises or is made by admixing an oil of lubricating viscosity,
in a major
amount, containing 50 mass % or more of a Group 1 basestock, and, in
respective minor
amounts:
(A) an overbased calcium alkyl salicylate detergent
providing 40 to 90, such as,
50 to 85, mmol of calcium alkyl salicylate per kg of the composition, as
determined by titration; and
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CA 02795410 2012-11-13
(B) 0.1 to 10, such as 0.1 to less than 2.0, for
example to 1.5, mass % active
ingredient, based on the mass of the composition, of an oil-soluble linear
(straight chain) alkyl-substituted phenol.
A second aspect of the invention is the use of a detergent (A) in combination
with
a component (B) as defined in, and in the amounts stated in, the first aspect
of the
invention in a trunk piston marine lubricating oil composition of TBN in the
range of 20 to
60, such as, 30 to 55, for a medium-speed compression-ignited marine engine,
which
composition comprises an oil of lubricating viscosity in a major amount and
contains 50
mass % or more of a Group 1 basestock, to improve asphaltene handling during
operation
of the engine, fueled by a heavy fuel oil and its lubrication by the
composition.
A third aspect of the invention is a method of operating a trunk piston medium-
speed compression-ignited marine engine comprising
(i) fueling the engine with a heavy fuel oil; and
(ii) lubricating the crankcase of the engine with a
composition as defined in the
first aspect of the invention.
A fourth aspect of the invention is a method of dispersing asphaltenes in a
trunk
piston marine lubricating oil composition during its lubrication of surfaces
of the
combustion chamber of a medium-speed compression-ignited marine engine and
operation
of the engine, which method comprises
(i) providing a composition as defined in the first
aspect of the invention;
(ii) providing the composition in the combustion
chamber;
(iii) providing heavy fuel oil in the combustion chamber;
and
(iv) combusting the heavy fuel oil in the combustion
chamber.
the meanings ascribed below:In this specification, the following words and
expressions, if and when used, have
"active ingredients" or "(a.i.)" refers to additive material that is not
diluent or
solvent;
"comprising" or any cognate word specifies the presence of stated features,
steps,
or integers or components, but does not preclude the presence or addition of
one or
more other features, steps, integers, components or groups thereof; the
expressions
"consists of' or "consists essentially of' or cognates may be embraced within
"comprises" or cognates, wherein "consists essentially of' permits inclusion
of
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CA 02795410 2012-11-13
substances not materially affecting the characteristics of the composition to
which
it applies;
"major amount" means 50 mass % or more of a composition;
"minor amount" means less than 50 mass % of a composition;
"TBN" means total base number as measured by ASTM D2896.
Furthermore in this specification, if and when used:
"calcium content" is as measured by ASTM 4951;
"phosphorus content" is as measured by ASTM D5185;
"sulphated ash content" is as measured by ASTM D874;
"sulphur content" is as measured by ASTM D2622;
"KV100" means kinematic viscosity at 100 C as measured by ASTM D445.
Also, it will be understood that various components used, essential as well as
optimal and customary, may react under conditions of formulation, storage or
use and that
the invention also provides the product obtainable or obtained as a result of
any such
reaction.
Further, it is understood that any upper and lower quantity, range and ratio
limits
set forth herein may be independently combined.
DETAILED DESCRIPTION OF THE INVENTION
The features of the invention will now be discussed in more detail below.
OIL OF LUBRICATING VISCOSITY
The lubricating oils may range in viscosity from light distillate mineral oils
to
heavy lubricating oils. Generally, the viscosity of the oil ranges from 2 to
40 mm2/sec, as
measured at 100 C.
Natural oils include animal oils and vegetable oils (e.g., castor oil, lard
oil); liquid
petroleum oils and hydrorefined, solvent-treated or acid-treated mineral oils
of the
paraffinic, naphthenic and mixed paraffinic-naphthenic types. Oils of
lubricating viscosity
derived from coal or shale also serve as useful base oils.
Synthetic lubricating oils include hydrocarbon oils and halo-substituted
hydrocarbon oils such as polymerized and interpolymerized olefins (e.g.,
polybutylenes,
polypropylenes, propylene-isobutylene copolymers, chlorinated polybutylenes,
poly(1-
hexenes), poly(1-octenes), poly(1-decenes)); alkybenzenes (e.g.,
dodecylbenzenes,
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CA 02795410 2012-11-13
tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)benzenes); polyphenyls
(e.g.,
biphenyls, terphenyls, alkylated polyphenols); and alkylated diphenyl ethers
and alkylated
diphenyl sulphides and derivative, analogues and homologues thereof.
Alkylene oxide polymers and interpolymers and derivatives thereof where the
terminal hydroxyl groups have been modified by esterification, etherification,
etc.,
constitute another class of known synthetic lubricating oils. These are
exemplified by
polyoxyalkylene polymers prepared by polymerization of ethylene oxide or
propylene
oxide, and the alkyl and aryl ethers of polyoxyalkylene polymers (e.g., methyl-
polyiso-
propylene glycol ether having a molecular weight of 1000 or diphenyl ether of
poly-
ethylene glycol having a molecular weight of 1000 to 1500); and mono- and
polycarboxylic esters thereof, for example, the acetic acid esters, mixed C3-
C8 fatty acid
esters and C13 oxo acid diester of tetraethylene glycol.
Another suitable class of synthetic lubricating oils comprises the esters of
dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids
and alkenyl
succinic acids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric
acid, adipic
acid, linoleic acid dimer, malonic acid, alkylmalonic acids, alkenyl malonic
acids) with a
variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-
ethylhexyl
alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol).
Specific
examples of such esters includes dibutyl adipate, di(2-ethylhexyl) sebacate,
di-n-hexyl
fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl
phthalate, didecyl
phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid
dimer, and the
complex ester formed by reacting one mole of sebacic acid with two moles of
tetraethylene glycol and two moles of 2-ethylhexanoic acid.
Esters useful as synthetic oils also include those made from C5 to C I 2
monocarboxylic acids and polyols and polyol esters such as neopentyl glycol,
trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol.
Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy- or
polyaryloxysilicone oils and silicate oils comprise another useful class of
synthetic
lubricants; such oils include tetraethyl silicate, tetraisopropyl silicate,
tetra-(2-
ethylhexyl)silicate, tetra-(4-methyl-2-ethylhexyl)silicate, tetra-(p-tert-
butyl-phenyl)
silicate, hexa-(4-methyl-2-ethylhexyl)disiloxane, poly(methyl)siloxanes
and
poly(methylphenyl)siloxanes. Other synthetic lubricating oils include liquid
esters of
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CA 02795410 2012-11-13
phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate,
diethyl ester of
decylphosphonie acid) and polymeric tetrahydrofurans.
Unrefined, refined and re-refined oils can be used in lubricants of the
present
invention. Unrefined oils are those obtained directly from a natural or
synthetic source
without further purification treatment. For example, a shale oil obtained
directly from
retorting operations; petroleum oil obtained directly from distillation; or
ester oil obtained
directly from esterification and used without further treatment, are unrefined
oils. Refined
oils are similar to unrefined oils except that the oil is further treated in
one or more
purification steps to improve one or more properties. Many such purification
techniques,
such as distillation, solvent extraction, acid or base extraction, filtration
and percolation,
are known to those skilled in the art. Re-refined oils are obtained by
processes similar to
those used to provide refined oils but begin with oil that has already been
used in service.
Such re-refined oils are also known as reclaimed or reprocessed oils and are
often
subjected to additional processing using techniques for removing spent
additives and oil
breakdown products.
The American Petroleum Institute (API) publication "Engine Oil Licensing and
Certification System", Industry Services Department, Fourteenth Edition,
December 1996,
Addendum 1, December 1998 categorizes Group 1 base stocks as follows:
Group I base stocks contain less than 90 percent saturates and/or greater than
0.03
percent sulphur and have a viscosity index greater than or equal to 80 and
less than
120 using the test methods specified in Table E-1.
Analytical Methods for Base Stock are tabulated below:
PROPERTY TEST METHOD
Saturates ASTM D 2007
Viscosity Index ASTM D 2270
Sulphur ASTM D 2622
ASTM D 4294
ASTM D 4927
ASTM D 3120
As stated, the oil of lubricating viscosity in this invention contains 50 mass
% or
more of the defined basestock or a mixture thereof. Preferably, it contains
60, such as 70,
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CA 02795410 2012-11-13
80 or 90, mass % or more of the defined basestock or a mixture thereof. The
oil of
lubricating viscosity may be substantially all the defined basestock or a
mixture thereof.
OVERBASED CALCIUM ALKYL SALICYLATE DETERGENT (A)
A metal detergent is an additive based on so-called metal "soaps", that is
metal
salts of acidic organic compounds, sometimes referred to as surfactants. They
generally
comprise a polar head with a long hydrophobic tail. Overbased metal
detergents, which
comprise neutralized metal detergents as the outer layer of a metal base (e.g.
carbonate)
micelle, may be provided by including large amounts of metal base by reacting
an excess
of a metal base, such as an oxide or hydroxide, with an acidic gas such as
carbon dioxide.
In the present invention, (A) are overbased calcium alkyl-substituted
salicylates.
The overbased detergent typically has the structure shown:
/ OH
R `07 Ca2+
wherein R is a linear alkyl group. There may be more than one R group attached
to the
benzene ring. The C00- group can be in the ortho, meta or para position with
respect to
the hydroxyl group; the ortho position is preferred. The R group can be in the
ortho, meta
or para position with respect to the hydroxyl group.
Salicylic acids are typically prepared by the carboxylation, by the Kolbe-
Schmitt
process, of phenoxides, and in that case, will generally be obtained (normally
in a diluent)
in admixture with uncarboxylated phenol. Salicylic acids may be non-
sulphurized or
sulphurized, and may be chemically modified and/or contain additional
substituents.
Processes for sulphurizing an alkyl salicylic acid are well known to those
skilled in the art,
and are described, for example, in US 2007/0027057.
14 to 24, carbon atoms.The alkyl groups advantageously contain 5 to 100,
preferably 9 to 30, especially
The term "overbased" is generally used to describe metal detergents in which
the
ratio of the number of equivalents of the metal moiety to the number of
equivalents of the
acid moiety is greater than one. The term low-based' is used to describe metal
detergents
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, CA 02795410 2012-11-13
in which the equivalent ratio of metal moiety to acid moiety is greater than
1, and up to
about 2.
By an "overbased calcium salt of surfactants" is meant an overbased detergent
in
which the metal cations of the oil-insoluble metal salt are essentially
calcium cations.
Small amounts of other cations may be present in the oil-insoluble metal salt,
but typically
at least 80, more typically at least 90, for example at least 95, mole %, of
the cations in the
oil-insoluble metal salt, are calcium ions. Cations other than calcium may be
derived, for
example, from the use in the manufacture of the overbased detergent of a
surfactant salt in
which the cation is a metal other than calcium. Preferably, the metal salt of
the surfactant
is also calcium.
Carbonated overbased metal detergents typically comprise amorphous
nanoparticles. Additionally, there are disclosures of nanoparticulate
materials comprising
carbonate in the crystalline calcite and vaterite forms.
The basicity of the detergents may be expressed as a total base number (TBN).
A
total base number is the amount of acid needed to neutralize all of the
basicity of the
overbased material. The TBN may be measured using ASTM standard D2896 or an
equivalent procedure. The detergent may have a low TBN (i.e. a TBN of less
than 50), a
medium TBN (i.e. a TBN of 50 to 150) or a high TBN (i.e. a TBN of greater than
150,
such as 150-500).
As stated, 40-90, such as, 50-85, mmol of calcium alkyl salicylate per kg of
the
composition is provided, the values being determined by titration. Preferably,
the values
are in the range of 50-80, more preferably 50-70, mmol/kg.
LINEAR ALKYL-SUBSTITUTED PHENOL (B)
As stated, the phenol constitutes 0.1 to 10, preferably 0.1 to less than 2.0,
such as
0.1 to 1.5, mass % of the mass of the composition. Also, it may constitute
from 0.1 or
from 0.25 to less than 0.5, mass % of the mass of the composition. It may be
present in
the range of 0.2 or 0.25 to 5 or 10 mass %.
The alkyl substitution in (B) may be mono, for example by way of a straight
chain
alkyl group having from 9 to 30, preferably 14 to 24, carbon atoms.
As an example of alkylphenol (B) there may be mentioned an alkyl benzenol
where the alkyl substitution is, for example, in the 2-position or in the 4-
position.
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CA 02795410 2012-11-13
(A) and (B) may be provided for the purpose of the invention by blending them
together, or, they may be provided individually.
CO-ADDITIVES
The lubricating oil composition of the invention may comprise further
additives,
different from and additional to (A) and (B). Such additional additives may,
for example
include ashless dispersants, other metal detergents, anti-wear agents such as
zinc
dihydrocarbyl dithiophosphates, anti-oxidants and demulsifiers. In some cases,
an ashless
dispersant need not be provided.
It may be desirable, although not essential, to prepare one or more additive
packages or concentrates comprising the additives, whereby additives (A) and
(B) can be
added simultaneously to the base oil to form the lubricating oil composition.
Dissolution
of the additive package(s) into the lubricating oil may be facilitated by
solvents and by
mixing accompanied with mild heating, but this is not essential. The additive
package(s)
will typically be formulated to contain the additive(s) in proper amounts to
provide the
desired concentration, and/or to carry out the intended function in the final
formulation
when the additive package(s) is/are combined with a predetermined amount of
base
lubricant. Thus, additives (A) and (B), in accordance with the present
invention, may be
admixed with small amounts of base oil or other compatible solvents together
with other
desirable additives to form additive packages containing active ingredients in
an amount,
based on the additive package, of, for example, from 2.5 to 90, preferably
from 5 to 75,
most preferably from 8 to 60, mass % of additives in the appropriate
proportions, the
remainder being base oil.
The final formulations as a trunk piston engine oil may typically contain 30,
preferably 10 to 28, more preferably 12 to 24, mass % of the additive
package(s), the
remainder being base oil. The trunk piston engine oil has a compositional TBN
(using
ASTM D2896) of 20 to 60, such as, 30 to 55. For example, it may be 40 to 55 or
35 to 50.
When the TBN is high, for example 45-55, the concentration of (A) may be high
such as
up to 80 mmol/kg. When the TBN is lower, for example 30 to below 45, the
concentration
of (A) may be low such as up to 70 mmol/kg.
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EXAMPLES
The present invention is illustrated by but in no way limited to the following
examples.
COMPONENTS
The following components were used:
Component (A): one or more calcium alkyl salicylate detergents having basicity
indices of 3-6
Component (B): a mixed 2- and 4- (linear C16 alkyl) benzenol (2:1)
Base oil I: solvent-extracted API Group I base oil
HFO: a heavy fuel oil (ISO-F-RMK 380)
LUBRICANTS
Selections of the above components were blended to give a range of trunk
piston
marine engine lubricants. Some of the lubricants are examples of the
invention; others are
reference examples for comparison purposes. The compositions of the lubricants
tested
when each contained HFO are shown in the tables below under the "Results"
heading.
TESTING
Light Scattering
Test lubricants were evaluated for asphaltene dispersancy using light
scattering
according to the Focused Beam Reflectance Method ("FBRM"), which predicts
asphaltene
agglomeration and hence 'black sludge' formation.
The FBRM test method was disclosed at the 7th International Symposium on
Marine Engineering, Tokyo, 24th - 28th October 2005, and was published in 'The
Benefits
of Salicylate Detergents in TPEO Applications with a Variety of Base Stocks',
in the
Conference Proceedings. Further details were disclosed at the CIMAC Congress,
Vienna,
21st -24t11 May 2007 and published in "Meeting the Challenge of New Base
Fluids for the
Lubrication of Medium Speed Marine Engines ¨ An Additive Approach" in the
Congress
Proceedings. In the latter paper it is disclosed that by using the FBRM method
it is
possible to obtain quantitative results for asphaltene dispersancy that
predict performance
for lubricant systems based on base stocks containing greater than or less
than 90%
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CA 02795410 2012-11-13
saturates, and greater than or less than 0.03% sulphur. The predictions of
relative
performance obtained from FBRM were confirmed by engine tests in marine diesel
engines.
The FBRM probe contains fibre optic cables through which laser light travels
to
reach the probe tip. At the tip, an optic focuses the laser light to a small
spot. The optic is
rotated so that the focussed beam scans a circular path between the window of
the probe
and the sample. As particles flow past the window, they intersect the scanning
path,
giving backscattered light from the individual particles.
The scanning laser beam travels much faster than the particles; this means
that the
particles are effectively stationary. As the focussed beam reaches one edge of
the particle
the amount of backscattered light increases; the amount will decrease when the
focussed
beam reaches the other edge of the particle.
The instrument measures the time of the increased backscatter. The time period
of
backscatter from one particle is multiplied by the scan speed and the result
is a distance or
chord length. A chord length is a straight line between any two points on the
edge of a
particle. This is represented as a chord length distribution, a graph of
numbers of chord
lengths (particles) measured as a function of the chord length dimensions in
microns. As
the measurements are performed in real time, the statistics of a distribution
can be
calculated and tracked. FBRM typically measures tens of thousands of chords
per second,
resulting in a robust number-by-chord length distribution. The method gives an
absolute
measure of the particle size distribution of the asphaltene particles.
The Focused beam Reflectance Probe (FBRM), model Lasentec D600L, was
supplied by Mettler Toledo, Leicester, UK. The instrument was used in a
configuration to
give a particle size resolution of I um to 1 mm. Data from FBRM can be
presented in
several ways. Studies have suggested that the average counts per second can be
used as a
quantitative determination of asphaltene dispersancy. This value is a function
of both the
average size and level of agglomerate. In this application, the average count
rate (over the
entire size range) was monitored using a measurement time of 1 second per
sample.
The test lubricant formulations were heated to 60 C and stirred at 400rpm,
when
the temperature reached 60 C the FBRM probe was inserted into the sample and
measurements made for 15 minutes. An aliquot of heavy fuel oil (10% w/w) was
introduced into the lubricant formulation under stirring using a four blade
stirrer (at 400
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CA 02795410 2012-11-13
rpm). A value for the average counts per second was taken when the count rate
had
reached an equilibrium value (typically overnight).
RESULTS
Light Scattering
The results of the FBRM tests are summarized in TABLES 1, 2 and 3 below,
where lower particle count indicates better performance.
Comparative examples are designated "Ref' and examples of the invention
designated by a number alone.
TABLE 1
Ex Soap Phenol Particle Counts
(mmol/kg) (mass %)
Ref 1 80 - 15.78
Ref 2 80 1.5 13.58
Ref 3 80 3.0 14.83
Ref 4 70 - 37.68
1 70 1.5 12.25
2 70 3.0 11.96
Ref 5 60 - 136.96
3 60 1.5 15.31
4 60 3.0 12.4
Ref 1, Ref 2 and Ref 3 show that, at high soap levels, the presence or absence
of
the phenol has little effect on performance. At lower soap levels (Ref 4, 1,
2; and Ref 5, 3,
4), the absence of phenol gives poor results, but performance is restored to
about those at
80 mmol/kg (i.e. Ref 1, Ref 2 and Ref 3) when phenol is present.
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TABLE 2
Ex Soap Phenol Particle Counts
(mmol/kg) (mass %)
Ref 6 80 18.82
Ref 7 70 22.23
Ref 8 60 77.16
60 0.25 47.42
6 60 0.5 43.38
7 60 1.0 34.48
Ref 6, Ref 7, Ref 8 show that, in the absence of phenol, performance
deteriorates
5 as soap level decreases. 5, 6, 7 show that, at a low soap level of 60
mmol/kg, performance
is improved by progressive additions of phenol.
TABLE 3
These results are obtained using a higher asphaltene content heavy fuel oil,
which
is accordingly more difficult to treat.
Ex Soap Phenol Particle Counts
(mmol/kg) (mass %)
Ref 9 80 517
Ref 10 70 1675
Ref 11 60 3916
8 60 0.25 3043
9 60 0.5 1926
10 60 1.0 1896
The same trend as in Table 2 is shown, but less exaggerated. Ref 9, Ref 10,
Ref
11 show that, in the absence of phenol, performance deteriorates with
decreasing soap
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level. 8, 9 and 10 show that, at a low soap level of 60 mmol/kg, performance
is partly
restored by progressive additions of phenol.
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