Note: Descriptions are shown in the official language in which they were submitted.
7~7
COMBUSTION FUEL~E~ULSION
Summary of Invention
The present invention relates to petroleum fuels,
and more particularly to such fuels having small quantities
of water emulsified therein. By the term "petroleum fuels"
it is intended to include 211 grades of those products known
as fuel oils, as well as refined fractions, such as gasoline
and kerosene, which are used for burners in furnaces and
boilers, and for piston, turbine and jet engines,
It is known in the prior art that the intermix-
ture of a small percentage of water, such as up to about
10% by weight, with petroleum fuels can enhance the burning
qualities of the fuel and thereby improve the efficiency
of the fuel and reduce its noxious and undesirable
emissions and by products. It has fu~ther been observed
that the most efective way to incorporate the water in
the petroleum fuel is by emulsification, and the present
invention is directed to such water in petroleum fuel
emulsions. In accordance with the prior art processes and
procedures, these emulsions have been formed in-line, i.e.,
in the process of feed of the petroleum fuel ~o the combus-
tion chamber. Further, it has been a common practice to
incorporate emulsification aids, such as surfactants, in
the mixture to enhance the emulsification process. Hereto-
fore, such emulsified fuels have not been produced as stable
emulsions, and those emulsified fuels cannot be stored for
prolonged periods of time. Therefore, the in-line procedure
has necessitated the incorporation of emulsification equip-
nlent in combination with each combustion installation.
In accordance with the present invention, it
has been discovered that stable emulsions of small quantities
of water (i.e. up to about 15 or 20%) in petroleum fuels
can be produced, even without the use of stabiliæing
additives. By the term "stable emulsion" is meant emulsions
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that can be stored for three months, or more, without any
appreeiable change, or separation of the dispersed phase
~rom tne continuous phase. Because of the stability of
these emulsions, it is possible to produce ~hem at a central
processing sta~ion for normal distribution to consumption
locations, where the emulsified fuel may then be stored and
~ed to burners, or the like, as required, without additional
or ln-line emulsification treatment.
It has been discovered that such stable emulsions
are obtained when the droplet size of the~ter phase, i.e.
the dlsperse phase, is substantially entirely less than
about 0.5 micron. ~ereas the droplet size required for
stabllity varies somewhat with the viscosity of ~he petroleum
fuel used, it has been observed that with a residual oil
having a viscosity of 0.85 poises/sec.,0.5 micron water
droplets remain in suspension for well over 3 months without
any noticeable settlin~, while l micron droplets show
appreciable settling in only 7 days of storage, and 10
micron droplets in only 1 hour. Although more viscous
oils can obtain stability with larger droplets of wateir,
still such significant improvements in stability are had
with 0.5 micron or less droplets, that it is considered
optimum for all oils. It is believed that the emulsions of
the present invention are analogous to colloidal suspensions,
and the droplets are retained in stable suspension by the
thermal energy of the system~
Emulsions of the present invention are not easily
obtained. It has been found ~hat these emulsions can be
formed by passing oil and water in the desired ratio through
high speed or hi~h energy rotary impact mill. A rotary
impact mill of the type utili~ed for the practice of the
present inven~ion is shown in U.S. Patent 3,171,604 to ~.H.
Conley, et al. In the pa~ticular mill utilized for
the`speciic embodimen~s of the pre~ent ~pe~i~fi-
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cation, the rotor element had 6 concentric circular rows
of ;r!pact pins, interdi~itated with 5 concelltric circular
rows of i~npact pillS on the stator. The outer~nost row of
pins was located on a 35 inch diameter circle, on the rotor.
The dial7leter of the impact pins was 0.375 inch, and the
center to center spacing of adjacent pins in tne same
circular row was 1.6 inches, and the center to center
SpaCillg between interdigitated adjacent rows of pins was
0.625 inch. To produce an ennulsion in which the water
droplets were substantially all less than abou-t 0.5 ~icron,
the ~ill was operated at a rotor speed of 1650 rpm, producing
a li~-'ear peripheral speed of 15,119 feet per minute. In
this mill operating at t'ne stated speed, statistically
a water droplet ~as subject to about 102,000 impacts per'
s~cond. With the foregoing mill operating at the stated
par~net:eLs, the process is referred to herein as high energy
millilg. It is apparent that equivalent action can be
accomplisl-ed by such mills designed with different interrelated
parameters, and such equivalent milling is likewise embraced
by the term high energy milling,
It is therefore one object of the present invention
to provide a stable water and petrole-~ fuel emulsion.
Another object of the present invention is to
provide such an emulsion for use as a combustion fuel for
furnaces, boilers and en~ines.
And still another object of the invention is to
pr~vide such a combustion fuel w~ich can be stored for
significant periods of time without losing its el~ulsion
state.
Accordingly, there is provicled:
A stable combustion fuel emulsion comprising
a petrolewn fuel as the continuous phase and water droplets
dispersed therein, wherein said water is present in an
amount ~ess than about 20% by wei~ht, and wherein said water
droplets are substantially all of size less than about 0.5
micron.
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There is also provided:
A ~ethod of forming a stable combustion fuel
e ~ sion, o~ris~g ~x~s~g an ~unt less ~n 20~ b~ ~ic,ht ofwater
in a petroleum fuel by high energy rotary impact milling .
said petroleum fuel and water together until substantially
all of the droplets of wa~er dispersed in said petroleum
fuel have a size o less than about 0.5 micron,
Other objects and advantages of the present
invention will become apparent to those skilled in the art
from the following illustrative detailed description of the
invention had in conjunction wit~ the accompanying drawings.
In the accompanying drawings:
Fig. 1 is a graph plotting the emulsion stability
vs. droplet size of wa~er in oil emulsions, for residual
oil, low sulfur (0.5/O)~ viscosity at 100F. of 400 SSU
and 0.85 poises per second; and
Fig. 2 is a graph corresponding to Fig. 1, but
for residual oil, high sul~ur (2.5%~, viscosity at 100~
of 4000~SSU and 8.0 poises per second.
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Detailed ~escription
In each of the following specific examples of
~he invention, the rotary impact mill as above described
was utilized. Petroleum oil and water were each fed into
the mill at relative rates to provide approximately 10%
by weight of water in the mixture, Numerous samples of
water in petroleum oil emulsions were produced, and by
pro~ucîng various samples at different rotor speeds for
the mill, different water droplet sizes, and different size
distributions were obtained. From these samples, the
settling rates for various water droplet sizes were
determined. The reciprocal of the settling rate is used
as a measure of relative stability of the emulsions for
the various water droplet sizes.
Example I
In this example, the petroleum fuel used to form
the water in oil emulsions is a residual oil, lower sulfur
(0.5%), viscosity at lOO~F. of 400 SSU and 0.85 poises per
second. The following table sets forth the settling rate
(SR) in inches per month for different water droplet sizes
in the emulsion, and, as a relative measure of emulsion
stability for each droplet size, the reciprocal of the settling
rate (l/SR).
Water Droplet Size Settling Rate (SR) ~elative
(microns) Iinche_/month) Stability (l/SR)
0.5 0.39 2.6
1 1.6 0.6
2 6.2 0.16
3 14 0.07
4 25 0.04
39 0.03
156 0.006
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In Fig. 1, the relative stability values of the above
table are plotted against water droplet size.
Example II
In this example, the petroleum fuel used to
form the water in oil emulsion is a residual oil, high
~sul~ur (2.5%), viscosity at 100F of 4000 SSU
and 8.0 poises per second. The following table sets forth
the settling rates (SR) in inches per month for different
water droplet sizes in the emulsions, and, as a relative
measure of emulsion stability for each droplet size, the
reciprocal of the settling rate (l/S~).
Water Droplet Size Settling Rate ~SR)Relative
(mi.crons) (inches/month)Stability (l/SR)
0.5 0 0044 227
1 0.018 56
2 0.07 14
4 0 28 3.6
6 0.64 1.6
8 1.14 0.9
1.7~ 0.56
In Fig. 2, the relative stability values from the foregoing
table are pl~tted against water droplet size.
The foregoing illustrative examples of the invention
demonstrate the greatly enhanced stability of a water in
petroleum fuel emulsion when the water droplets are about
0.5 micron in size. To obtain the benefit of this stability,
it is of course necessary that substantially all the water
droplets be no greater than abou~ 0.5 micron. When the
water in oil emulsion is formed by a rotary impact mill as
above described, operating at a speed of 1650 rpm, or at
a peripheral linear speed of about 15,000 feet per minute,
approxiMately 95% of the water droplets formed are less than
about 0.5 micron in size. When said mill is operated at a
speed of 3500 rpm, or at a peripheral linear speed of about
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32,000 feet per minute, about 99.9% of the water droplets
ormed are less than about 0.5 micron in size.
Various modifications and variations of the
invention will become apparent to those skilled in the art,
and such as are embraced by the spirit and scope of the
appended claims are contemplated as within the purview of
the invention. For example, since the rotary impact mill
is an effective and efficient pulverizer for solids, solid
fuels such as coal or other carbonaceous materials can
be fed into the mi ll with the oil and water, and the solid
~uel will be pulverized and suspended in the water in oil
emulsion as the latter is formed in the mill. In this
manner there is produced an oil-solids-water slurry/emulsion.
