Note: Descriptions are shown in the official language in which they were submitted.
2 Q ~
LIQUID FUELS FOR INTERNAL COMBUSTION ENGINES
AND PROCESS AND APPARATUS FOR MAKING SAME
Cross-Reference to Related APplications
This application is a continuation-in-part application of
Applicant's co-pending application Serial No. ~78,790, filed April
1, 1991, which is a continuation-in-part application of Applicant's
co-pending applications Serial No. 529,878, filed May 25, 1990 and
Serial No. 447,543, filed December 8, 1989, now U.S. Patent No.
5,004,850.
Field of the Inventlon
The present invention relates to liquid fuels, and more
particularly to liquid fuels for internal combustion engines and
processes and apparatus for making these fuels.
Backqround of the Invention
Petroleum reserves are decreasing, and the cost of locating
and recovering new liquid gasoline reserves is increasing. Large
amounts of low-weight hydrocarbon components and natural gasoline
are available, but have not been extensively utilized as fuels for
motor vehicles and other internal combustion engines. This is
despite the relatively low cost of these fuels. These fuels have
a high vapor pressure at standard temperatures and pressures, and
accordingly, vapor losses to the atmosphere by open-container
storage are environmentally unacceptable; These fuels are more
difficult to store and to dispense than currently available
gasolines, and would require modification of standard liquid
gasoline burning vehicles. Also, natural gasoline has a lower
octane than is acceptable for present day automotive engines.
- 2~2Q3
Summary of the Invention
It is an object of the invention to provide a liquid fuel for
internal combustion engines.
It is another ob3ect of the invention to provide a liquid fuel
for internal combustion engines which utilizes natural gasoline
resources.
It is still another object of the invention to provide a
liquid fuel for internal combustion engines with an environmentally
acceptable vapor pressure.
It is another object of the invention to provide a liquid fuel
for internal combustion engines with an acceptable octane rating.
It is yet another object of the invention to provide a fuel
for internal combustion engines which can be produced at relatively
low cost.
These and other objects are accomplished by blending at least
one natural gasoline component and at least one octane-enhancing
component. The natural gasoline component preferably contains
hydrocarbons having from about 4 to about 12 carbons. Most
preferably, the natural gasoline component contains at least 60
volume percent of 5 and 6 carbon hydrocarbons and at least 20
volume percent of hydrocarbons having 7 or more carbons.
The octane-enhancing component can be selected from several
suitable compounds, and can also include mixtures of compounds.
The octane-enhancing components will preferably have a high octane
rating with an (R+M)/2 octane of greater than about 85. The
octane-enhancing components should preferably also have a low vapor
2~2~3
pressure, with a Reid vapor pressure of less than about 8 psia, and
most preferably of about 1 psia or less.
Toluene, alone or in combination with other octane-enhancing
components, is a presently preferred octane-enhancing component.
The toluene component should be relatively pure, although up to
about 10 volume percent of the toluene component can be other
hydrocarbons. Other suitable octane-enhancing components include
methyl tertiary butyl ether (MTBE); tertiary anyl methyl ether
(TAME); ethyl tertiary butyl ether (ETBE); ethylbenzene; m-xylene;
p-xylene; o-xylene; eight carbon aromatic mixtures; nine carbon
aromatic ~ixtures; cumene (isopropylbenzene); n-propylbenzene; and
alkylates (isoparaffins). Catalytic cracked naphtha, catalytic
reformate, and pyrolysis gasoline can also be used, but will likely
result in increased emissions.
The octane-enhancing components are added and mixed with the
natural gasoline component. A vapor stream of light-weight
hydrocarbons is released from the natural gasoline, before, during
and/or after blending with the octane-enhancing component. The
natural gasoline mixture is agitated or otherwise caused to form
particles or droplets to increase the surface area of the liquid
and to facilitate the release of light-weight hydrocarbons from the
liquid. The light-weight hydrocarbons which are released from the
liquid blend can be burned to generate heat energy to power the
pumps and to provide for the other energy requirements of the
process. Alternatively, these light-weight hydrocarbons can be
stored for later use. The weathering process preferably continucs
~22~3
until a substantially homogeneous mixture is obtained with the
desired Reid vapor pressure, which is specified by government
regulations that are based upon seasonal and other considerations.
The resulting product normally will be a liquid fuel with
about 30-80 volume percent natural gasoline, about 20-50 volume
percent octane-enhancing components, and may also contain about 0-
35 volume percent low-weight hydrocarbons. The proportions of the
components can be adjusted to vary the octane rating and vapor
pressure of the product fuel.
S,~ ~ ~
Brief Description of the Drawinqs
There are shown in the drawings embodiments wh~ch are
presently preferred, it being understood, however, that the
invention is not limited to the precise arrangements and
instrumentalities shown, wherein:
Fig. 1 is a schematic view of a process and apparatus
according to the invention, partially broken away for clarity.
Fig. 2 is a cross-section taken along line 2-2 in Fig. 1.
~ J~
Detailed Description of the Preferred Embodiments
Blended gasolines according to the invention are produced by
blending a natural gasoline component with at least one octane-
enhancing componer,t, preferably toluene. The natural gasoline
component preferably comprises primarily hydrocarbons having about
4 to about 12 or more carbons. At least about 60 volume percent,
however, of the natural gasoline component should preferably be
pentanes and hexanes, and at least about 20 volume percent should
preferably have about 7 or more carbons. The natural gasoline
components can be extracted from raw natural gas sources consisting
mainly of methane. Most of the methane, together with ethane,
propane, and some butanes, exit from the process with only the
natural gasoline being condensed and collected by suitable methods
known in the art, including cascade refrigeration extraction
processes. These methane rich streams, free of natural gasoline
components, are used principally as a fuel in homes and in power
generating stations. Excess low-weight hydrocarbons can be sold
separately.
The octane-enhancing component can be selected from several
suitable compounds, and can also include mixtures of compounds.
The octane-enhancing components will preferably have a high octane
rating with an (R+M)/2 octane of greater than about 85. The
octane-enhancing components should preferably also have a low vapor
pressure, with a Reid vapor pressure of less than about 8 psia, and
most preferably of about 1 psia or less.
2 2 ~ ~
Toluene, alone ~r in combination with other octane-enhancing
components, is a presently preferred octane-enhancing component.
The toluene component should be relatively pure, although up to
about 10 volume percent of the toluene component can be other
hydrocarbon aromatics having six to nine carbon atoms. Other
suitable octane-enhancing components include methyl tertiary butyl
ether (MTBE); tertiary anyl methyl ether (TAME); ethyl tertiary
butyl ether (ETBE); ethylbenzene; m-xylene; p-xylene; o-xylene;
eight carbon aromatic mixtures; nine carbon aromatic mixtures;
cumene (isopropylbenzene); n-propylbenzene; alkylates
(isoparaffins); catalytic cracked naphtha: catalytic reformate; and
pyrolysis gasoline.
The product gasoline should have an (R+M)/2 octane rating of
at least 80 and a Reid vapor pressure of no more than about 12-14
psia in winter conditions, and about 8-10 psia in summer
conditions. A low-weight hydrocarbon component can be added to the
natural gasoline component and the octane-enhancing component in
order to more economically produce a merchantable liquid fuel for
internal combustion engines having a sufficiently low Reid vapor
pressure and a satisfactory octane rating. This will depend on
current commodity prices. The low-weight hydrocarbon component can
contain hydrocarbons having from about 1 to more than about 7
carbons, and in varying proportions. It is preferred, however,
that at least about 50 volume percent of the low-weight hydrocarbon
components be butanes and pentanes.
~22~3
If low-weight hydrocarbons are used, it is preferable to
initially blend the natural gasoline component with the low-weight
hydrocarbon component. It is anticipated that approximately 1-3
volume percent light-weight hydrocarbons will be weathered off in
the process. These will include methane, ethane, propane and some
butane. These light-weight hydrocarbons are weathered off during
the blending operation, and can be combusted to generate power and
to run pumps used in blending. Excess vapor can be stored by
suitable means such as underground storage wells or compressed-gas
vessels.
The components can be mixed together thoroughly by suitable
mixing apparatus, and the mixture is caused to attain a liquid form
having an extended surface area, such as droplets or a film-like
surface area. This has been found to facilitate the release of
light-weight hydrocarbons from the liquid. A vapor stream i5
withdrawn to remove these light-weight hydrocarbons including
methanes, ethanes, propanes and some butanes. The pressure is
preferably maintained àt about 2-15 psig, which allows the light-
weight hydrocarbon vapors to be released from the process and
passed to storage or a power generating station. The octane-
enhancing components, preferably toluene, are added to the low-
weight hydrocarbon/natural gasoline mixture, or to just the natural
gasoline component when the low-weight component is excluded, such
that the octane-enhancing components are approximately t5-55 volume
percent of the mixture.
~ 2~'~3
The liquid mix is preferably agitated, or otherwise caused to
take a liquid form having an extended surface area, in an enclosure
having a vapor space. Agitation will blend the components and will
cause the formation of droplets or a film-like surface area on the
side of a vertical vessel, such that the liquid will have an
increased surface area relative to the bulk liquid. The extended
surface area facilitates the release of light-weight hydrocarbon
vapors from the liquid. An enclosure formed as a tower or tank
will also provide for a stripping action, which action can also be
useful to facilitate the removal of light-weight hydrocarbons and
to minimize the escape of higher-weight hydrocarbons. Vapor flows
upward to a vapor space and liquid flows downward to a liquid space
of the enclosure. The vapor stream is withdrawn from the vapor
space. The contact of the rising vapors with the falling liquid
will help to retain heavier hydrocarbons in the falling liquid.
The high surface area form of the liquid can be created by
directing the liquid mixture into a dispersing, spraying or
splashing device positioned in the enclosure. Other known methods
for increasing the surface area of liquids, such as passing the
liquid through a packed column or over plates in a column, are also
possible. These structures will also act to blend the liquid
components together. It might also be possible to facilitate the
removal of light-weight hydrocarbons by the introduction of a
stripping gas, or by the application of heat. It is a feature of
the invention, however, that the natural gasoline can be
successfully processed in a substantially isothermal process,
Q~
without the introduction of heat.
The mixing process preferably continues as a batch process
until a substantially homogeneous mixture results with the desired
Reid vapor pressure. Intermediate storage tanks can be provided to
collect the mixture. Recirculation pumps can be utilized to return
the liquid from the intermediate storage tanks to the
agitation/mixing step.
Condensing or coalescing apparatus can be provided to condense
or coalesce low-weight hydrocarbons from the vapor stream, and
these low-weight hydrocarbons can be returned to the mixing
process. The condensing or coalescing apparatus can be of any
suitable design, but preferably has a large amount of condensing or
coalescing surface area such as would be provided by conventional
tower packing material. A ceramic packing is presently preferred,
although other materials, including stainless or carbon steel,
could also be useful.
The removal of light-weight hydrocarbons from the natural
gasoline component can occur before and/or after the introduction
of the octane-enhancing components. It is presently preferred that
at least some removal of light-weight hydrocarbons according to the
invention occur after the introduction of the octane-enhancing
components. It is possible to mix the natural gasoline component
with the octane-enhancing component in a separate operation,
however, a thorough mixing will usually result from the agitation
or other process used to remove the light-weight hydrocarbons from
the natural gasoline.
2~22~
A presently preferred mixing apparatus according to the
invention is shown in Figs. 1-2. A number of storage tanks lO-13
can be provided, although more or fewer storage tanks can be
provided if desired. The liquid components to be mixed can
initially be stored in the tanks 10-13. Liquid exits the tanks 10-
13 through a liquid return path 14 and by operation of valves 15-
18. Liquid from the return path 14 enters one or more high output
liquid pumps 20 through a pump suction or inlet path 22. The pump
20 moves the liquid to an agitating or high-surface area generating
apparatus, such as the mixing column or tank 24. A riser conduit
26 conducts the liquid to the top 25 of the column 24. The liquid
exits the riser conduit 26 in the do~nward direction, and can be
directed at a center surface 30 of a mechanical device such as the
splash tray 32. Liquids pass the splash tray 32 through openings
33. The mechanical device can be constructed from many alternative
designs, but is intended to agitate the liquid to promote mixing,
droplet and/or film formation, thus facilitating the release of
light-weight hydrocarbon vapors. Alternative means known in the
art for agitating liquids, causing the liquid to take on a high
surface area form, and for removing vapors from liquids, could also
be utilized, including impellers, pipe mixers, and packing. Known
optimization techniques can be utilized to further facilitate the
withdrawal of vapors from the liquid blends. The invention permits
the removal of light-weight hydrocarbons in a substantially
isothermal process, without the introduction of heat, however, heat
can also be utilized where deemed necessary.
Light hydrocarbon vapors released by this agitation and
increased surface area flow up-~ards through the vessel or tower
counter-current to the downward flowing liquid droplets and film.
There is an equilibrium exchange between this counter-current
liquid and vapor flow such that heavier components are knocked
downwards from the vapor and lighter components are liberated from
the liquid Vapors flow to, and are withdrawn from, a vapor space
at the top of the mixing column 24. The vapors exit the column 24
through a vapor outlet path 34. Some vapors will condense in the
vapor outlet path 34, and are returned to the tanks 10-13 through
a vapor manifold 36 and vapor return paths 38-41. Vapors exiting
the vapor manifold 36 are preferably processed in one or more
coalescing or condensation steps to return to the process any
heavier hydrocarbons which may be present in the vapor stream. A
coalescing or condenser apparatus 44 can be filled with a packing
46, which can be selected from several suitable materials and
designs, including ceramic spools, which will provide the requisite
surface area for coalescing or condensation of the low-weight
hydrocarbons. Vapors can enter tne coalescing or condenser
apparatus 44 through an inlet 48 and exit through a coalescing or
condenser outlet 50. Liquid hydrocarbons coalesced or condensed in
the coalescing or condenser apparatus 44 can fall under the
influence of gravity into the vapor manifold 36 and return to the
storage tanks 10-13 through the vapor return paths 38-41
Alternative coalescing or condensing operations are also possible
to coalesce or condense low-weight hydrocarbons from the light-
d ` ~ ~ '
weight hydrocarbon vapors.
The vapors leaving the coalescing or condenser apparatus 44through the coalescing or condenser outlet 50 will consist
primarily of light-weight hydrocarbons such as methanes, ethanes,
propanes and some butanes. These hydrocarbons can be combusted in
a suitable power generating station 35 to provide energy through a
path 37 to run the circulation pumps 20, and to provide for the
other energy requirements of the process. Excess vapor can be
stored by suitable means such as underground storage wells or
compressed-gas vessels.
Liquids passing through the openings 33 in the splash tray 32
can collect in a bottom portion 54 of mixing column or tank 24.
Liquid outlets 52 are preferably provided in the sides of the
mixing column 24, and are preferably located upwardly from the
bottom 54 of the column 24. Liquid hydrocarbons will accumulate in
the column to the level of the outlets 52, and will flow out of the
column through the outlets 52 into one or more liquid outlet
manifolds 58. Liquid in the liquid outlet manifolds 58 is returned
to the storage tanks 10-13 through liquid return paths 60-63. The
liquid outlets 52 may be positioned in a number of locations in the
column or tank 24 below the splash tray 32. The liquid outlets 52
are preferably positioned in the column 24 at a height greater than
that of the storage tanks 10-13 to permit gravity flow of the mix
from the liquid outlets 52 to the liquid return paths 60-63.
Mixture accumulated in the bottom 54 of the tank 24, below the
liquid outlets 52, can be recirculated to the pump 20 through a
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recirculation path 66, which can be controlled by operation of a
valve 68.
The product gasoline is pumped from the tanks 10-13 and the
column 24 when the weathering process is complete. A valve 72 in
the riser path 26 can be closed, and an exit path control valve 74
is opened. The pump 20 then operates to move the gasoline through
an exit path 78 to product storage tanks.
The apparatus according to the invention can be constructed
from other suitable process components. The number and layout of
the tanks 10-13 can be varied. Alternative pumping arrangements
are also possible. It is possible to replace the column or tank 24
with another mixing apparatus, for example, a pipe mixer apparatus,
and to provide alternative means for withdrawing a vapor stream
from the mixed product. The design must allow mixing to a
substantially homogeneous mixture and the release of enough of the
high vapor pressure, light-weight hydrocarbon components to obtain
a product with the desired Reid vapor pressure. It is also
possible to run the process as a continuous process, as contrasted
with the batch process described herein. It is also possible to
utilize alternative designs to the splash tray 32. The coalescing
or condenser apparatus 44 can be replaced with other suitable
coalescing or condenser means, including an artificially cooled
condenser, to remove heavier hydrocarbons from the vapor stream.
The proportions of natural gasoline, octane-enhancing
components, and any low-weight hydrocarbon components can be
adjusted to vary the resulting octane rating and Reid vapor
14
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pressure of gasoline products. A low octane gasoline product
according to the invention, of about 87 octane, and with a Reid
vapor pressure of about 12 psig and an initial boiling point of
about 80 degrees F, as might be useful in a winter gasoline, would
preferably have the following approximate composition:
Two Component Gasoline
55-85 volume percent natural gasoline
15-45 volume percent octane enhancing components
Three Component Gasoline
0-30 volume percent low-weight hydrocarbons
40-85 volume percent natural gasoline
15-45 volume percent octane-enhancing components (preferably
toluene)
A summer gasoline mix having an octane rating of a~out 87 and a
Reid vapor pressure of about 9 psig, together with an initial
boiling point of more than about 85 degrees F, would preferably
have the following composition:
Two Component Gasoline
50-85 volume percent natural gasoline
15-50 vol.ume percent octane-cnhancin~ componcnts
Three Com~ nt Gasoline
0-15 volume percent low-weight hydrocarbons
45-85 volume percent natural gasoline
15-45 volume percent octane-enhancing components ~preferably
toluene)
2 ~ ~
A winter mix gasoline having a high octane rating of approximately
92, together with a Reid vapor pressure of about 12 psig and an
initial boiling point of about 80 degrees F would preferably have
the following approximate composition:
Two Component Gasoline
45-85 volume percent natural gasoline
15-45 volume percent octane-enhancing components
Three Component Gasoline
0-20 volume percent low-weight hydrocarbons
45-85 volume percent natural gasoline
15-45 volume percent octane-enhancing components (preferably
toluene)
A summer gasoline mix having a high octane of about 92 and a Reid
vapor pressure of about 9 psig, with an initial boiling point of
more than about 85 degrees F, would preferably have the following
approxima~e composition:
Two Component Gasoline
45-85 volume percent natural gasoline
15-55 volume percent octane-enhancing components
Three Component Gasoline
0-25 volume percent low-weight hydrocarbon
45-85 volume percent natural gasoline
15-55 volume percent octane-enhancing components (preferably
toluene)
These proportions are preferred, but it will be understood that
additives can be included and the preferred proportions can vary
16
~ ~ ~ h '? Q ~3
depending upon the precise composition of the various low-weight
hydrocarbons, natural gasoline, and octane-enhancing components.
The natural gasoline product of the invention can be blended
with other components currently blended with petroleum-derived
gasolines. Ethanol in volume percentage up to about 10% or more,
if engine design permits, can be utilized to take advantage of
governmental incentives, and to improve environmental
characteristics through the usé of this alternative fuel. This
mode of operation also has the advantage of resulting in a normal
or low Reid vapor pressure for the finished gasoline. This process
is therefore particularly well suited for blending of the sub-
octane base fuel with 10% ethanol. The gasolines of the invention
can also be blended with methanol according to known methods.
EXAMPLES
The following examples are provided for purposes of
illustration, it being understood, however, that the invention is
not limited to the precise compositions disclosed therein.
Example 1
Feed compositions are provided having the following
characteristics:
2 2 Q 3
Low-weiqht Hydrocarbons
Weight %
ComponentLiquid Volume ~ t~lc~llated)
Propane 0.2 0.2
Isobutane 2.2 1.9
n-butane 25.1 23.0
Hydrocarbons having
5 or more carbons 72.5 74.9
100. 0 100. 0
Reid Vapor Pressure @ 100 degrees F 19 PSIA
(R~M)/2 Octane No. 76
Specific gravity @ 60 degrees F 0.64
Natural Gasoline
ComPonent Weight %
n-butane 4.0
i-pentane 15.0
n-pentane 23.0
hexanes 26.0
heptanes, and higher-
carbon hydrocarbons 32.0
1 00 . O
Reid Vapor Pressure @ 100 degrees F 9.5 PSIA
(R+M)/2 Octane No. 76
Specific gravity @ 60 degrees F. 0.68
s~
Toluene
Component Volume %
Toluene 99.9
Reid Vapor Pressure @ 100 degrees F 1.0 PSIA
(R+M)/2 Octane No. 109.5
Specific gravity @ 60 degrees F. 0.87
The above-described liquid components are blended by first
blending the low-weight hydrocarbon component with the natural
gasoline component in the proportions given in the preceding
formulations for various types of gasolines. This is true for the
blends containing the low-weight hydrocarbon component. It is
anticipated that 1-3 volume percent light hydrocarbons will be
weathered off in the process. These will include methane, ethane,
propane and some butanes. The toluene or other octane-enhancing
component is then added to the above natural gasoline component or
to the above mixture in the proportions given in the preceding
formulations for various types of gasolines. In the example
embodiment, the tanks 10-13 each have a 20,000 gallon capacity.
The column 24 is approximately 60 feet high, about 64 feet over
grade, and approximately 26 inches in diameter. The riser 26,
liquid manifolds 58, and conduit 14 are each 4 inch standard steel
pipe. The vapor line 36 is 2 inch standard steel pipe. The pump
20 is a high output, 900 gallon per minute pump. The size of all
equipment can be varied up or down to suit particular capacity
requirements.
19
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The pump 20 is operated to circulate the liquid components
from the tanks 10-13 to the top of the column 24. The liquid
components are directed onto the center 30 of the splash tray 32 to
agitate the liquid into droplets and to permit vapors to separate
from the liquid components. ~iquid vapors exit the column 24
through the vapor outlet path 34, and low-weight hydrocarbons are
recovered from the vapor in a coalescing or condenser unit 44.
Coalesced or condensed vapors and liquid from the column 24 are
returned to the tanks 10-13, and again are circulated by the pump
20. The column 24 is operated at a pressure of about 1-15 psig.
The mixing operation continues as a batch or continuous
process until the desired Reid vapor pressure is obtained for the
mixture, and the mixture is substantially homogeneous, at which
point the composition is approximately 15 volume percent low-weight
hydrocarbons, 55 volume percent natural gasoline, and about 30
volume percent toluene. The gasoline produced by the above-
described process will have a vapor pressure between about 9-12
psig, and an octane rating of between about ~7-92.
~_amPles 2-4
A natural gasoline component and toluene component are blended
together in approximately the following volume percentages to
attain the described octane rating:
Finished Gasoline Natural
Octane (R+M~2 Gasoline Toluene
Example 2 87 75 25
Example 3 90 65 35
Example 4 93 55 45
These components are blended in the tower in the manner
described in Example 1 to attain a product having a slightly
lowered volume percentage of natural gasoline, from 1-3%, due to
light hydrocarbon losses. The percentage of toluene will rise
proportionally.
This invention can be embodied in other specific forms without
departing from the spirit or essential attributes thereof, and
accordingly, reference should be had to the following claims,
rather than to the foregoing specification, as indicating the scope
of the invention.
