U.S. patent application number 12/185677 was filed with the patent office on 2008-11-20 for method of dissolving a gaseous hydrocarbon into a liquid hydrocarbon.
Invention is credited to Carlos Borras, Richard G. Mallinson, Mauricio A. Sanchez, William H. Sutton.
Application Number | 20080283141 12/185677 |
Document ID | / |
Family ID | 34636336 |
Filed Date | 2008-11-20 |
United States Patent
Application |
20080283141 |
Kind Code |
A1 |
Sutton; William H. ; et
al. |
November 20, 2008 |
Method of Dissolving A Gaseous Hydrocarbon Into A Liquid
Hydrocarbon
Abstract
The present invention is directed to a method of dissolving a
gaseous hydrocarbon into a liquid hydrocarbon to re-circulate
gaseous components, which have separated from the liquid fuel
mixture, back into the liquid fuel mixture, as well as, a method
for making batch or continuous process amounts of mixed hydrocarbon
fuels. The mixed hydrocarbon fuel is produced by introducing a
volume of a liquid hydrocarbon into a vessel, and introducing a
volume of a gaseous hydrocarbon into the vessel by bubbling the
gaseous hydrocarbon into the liquid hydrocarbon at a gravitational
low point of the vessel such that the bubbled gaseous hydrocarbon
is dissolved into the liquid hydrocarbon to produce a liquid fuel
solution. The vessel may be a mixing tank from which the liquid
fuel is pumped into a vehicle fuel tank, or the vessel may be the
vehicle fuel tank.
Inventors: |
Sutton; William H.;
(Tuscaloosa, AL) ; Borras; Carlos; (Norman,
OK) ; Sanchez; Mauricio A.; (Edmond, OK) ;
Mallinson; Richard G.; (Norman, OK) |
Correspondence
Address: |
DUNLAP CODDING, P.C.
PO BOX 16370
OKLAHOMA CITY
OK
73113
US
|
Family ID: |
34636336 |
Appl. No.: |
12/185677 |
Filed: |
August 4, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10973007 |
Oct 25, 2004 |
|
|
|
12185677 |
|
|
|
|
60514392 |
Oct 24, 2003 |
|
|
|
Current U.S.
Class: |
141/1 ;
585/6 |
Current CPC
Class: |
C10L 3/00 20130101 |
Class at
Publication: |
141/1 ;
585/6 |
International
Class: |
B65B 1/04 20060101
B65B001/04; C10L 3/00 20060101 C10L003/00 |
Claims
1. A method of mixing a two phase fuel mixture comprising a vapor
component and a liquid component in a vessel to reduce
stratification of the fuel mixture, the method comprising:
providing the two phase fuel mixture in the vessel, the two phase
fuel mixture comprising a gaseous methane and at least one other
hydrocarbon and a mole percent of methane from about 50 percent to
about 80 percent, the mixture of methane and the at least one other
hydrocarbon maintained at a temperature of about -1.degree. C. or
greater and at a pressure of about 8.0 Mpa or greater withdrawing
at least a portion of the vapor component of the mixture from the
vessel; and re-introducing the withdrawn vapor component into the
vessel by bubbling the withdrawn vapor component into the liquid
component of the fuel mixture at a gravitational low point of the
vessel such that the bubbled vapor component is dissolved into the
liquid component and the fuel mixture is sufficiently agitated to
effectively mix the two phase fuel mixture.
2. The method of claim 1 wherein the vapor component is bubbled
into the liquid component of the fuel mixture at a downward angle
of from about 5 degrees to about 45 degrees relative to a vertical
axis of the vessel.
3. A method of mixing a two phase fuel mixture comprising a vapor
component and a liquid component in a vessel to reduce
stratification of the fuel mixture, the method comprising the steps
of: providing the two phase fuel mixture in the vessel, the two
phase fuel mixture comprising a gaseous methane and at least one
other hydrocarbon and a mole percent of methane from about 50
percent to about 80 percent, the mixture of methane and the at
least one other hydrocarbon maintained at a temperature of about
-1.degree. C. or greater and at a pressure of about 8.0 Mpa or
greater withdrawing at least a portion of the vapor component of
the mixture from the vessel; and re-introducing the withdrawn vapor
component into the vessel by bubbling the withdrawn vapor component
into the liquid component of the fuel mixture in a downward
direction such that the bubbled vapor component is dissolved into
the liquid component and the fuel mixture is sufficiently agitated
to effectively mix the two phase fuel mixture.
4. The method of claim 3 wherein the vapor component is bubbled
into the liquid component of the fuel mixture at a downward angle
of from about 5 degrees to about 45 degrees relative to a vertical
axis of the vessel.
5. A method of producing a liquid fuel solution, the method
comprising: introducing a volume of a liquid hydrocarbon into a
fuel storage tank mounted on a vehicle to provide fuel to the
vehicle; and introducing a volume of a gaseous hydrocarbon into the
vessel by bubbling the gaseous hydrocarbon into the liquid
hydrocarbon at a gravitational low point of the vessel such that
the bubbled gaseous hydrocarbon is dissolved into the liquid
hydrocarbon to produce a liquid fuel solution.
6. The method of claim 5 wherein the gaseous hydrocarbon is bubbled
into the liquid hydrocarbon at a downward angle of from about 5
degrees to about 45 degrees relative to a vertical axis of the fuel
storage tank.
7. The method of claim 5 wherein the liquid hydrocarbon is propane
and wherein the gaseous hydrocarbon is methane.
8. A method of fueling a vehicle, the method comprising:
introducing a volume of a liquid hydrocarbon into a mixing tank;
and (a) introducing a volume of a gaseous hydrocarbon into the
mixing tank by bubbling the gaseous hydrocarbon into the liquid
hydrocarbon at a gravitational low point of the vessel such that
the bubbled gaseous hydrocarbon is dissolved into the liquid
hydrocarbon to produce a liquid fuel solution; (b) introducing a
second volume of the gaseous hydrocarbon into a fuel storage tank
mounted on a vehicle to provide fuel to the vehicle; and (c)
passing a volume of the liquid fuel solution from the mixing tank
and introducing the liquid fuel solution into the fuel storage
tank.
9. The method of claim 8 wherein the gaseous hydrocarbon is bubbled
into the liquid hydrocarbon at a downward angle of from about 5
degrees to about 45 degrees relative to a vertical axis of the
mixing tank.
10. The method of claim 8 wherein the second volume of gaseous
hydrocarbon introduced into the fuel storage tank is sufficient to
pressurize the fuel storage tank to prevent flash vaporization of
the liquid fuel solution upon the liquid fuel solution being
introduced into the fuel storage tank.
11. The method of claim 10 wherein the fuel storage tank is
pressurized to about 1,000 psig by the second volume of gaseous
hydrocarbon.
12. The method of claim 8 wherein the liquid hydrocarbon is propane
and wherein the gaseous hydrocarbon is methane.
13. The method of claim 8 wherein the mixing tank includes an open
loop connecting a top of the mixing tank with a bottom of the
mixing tank and wherein the method further comprises: sensing the
level of the liquid hydrocarbon in the open loop to determine the
level of liquid hydrocarbon in the mixing tank.
14. The method of claim 8 wherein steps (a)-(c) are performed
automatically.
15. The method of claim 14 further comprising using a ladder logic
algorithm.
16. The method of claim 8 wherein the liquid hydrocarbon and the
liquid fuel solution are conveyed with a hydraulically driven
piston pump.
17. The method of claim 16 wherein the hydraulically driven piston
pump is controlled by a programmable logic controller.
18. The method of claim 8 further comprising: determining the
amount of liquid fuel solution in the vehicle fuel tank prior to
passing liquid fuel solution into the vehicle fuel tank.
19. The method of claim 18 wherein the step of determining the
amount of liquid fuel solution further comprises: venting a fixed
volume of vapor from the vehicle fuel tank; and measuring the
pressure of the vented vapor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No.
10/973,007 filed on Oct. 25, 2004, which claims the benefit of U.S.
Provisional Application Ser. No. 60/514,392, filed Oct. 24, 2003.
The entire contents of both patent applications are hereby
expressly incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to methods of
producing liquid fuel solutions, and more particularly, but not by
way of limitation, to an improved method of dissolving a gaseous
hydrocarbon into a liquid hydrocarbon to produce a liquid fuel
mixture and to recirculate gaseous components, which have separated
from the liquid fuel mixture, back into the liquid fuel
mixture.
[0004] 2. Brief Description of the Related Art
[0005] Most hydrocarbon fuels are composed of multiple hydrocarbons
with varying degrees of volatility. Even gasoline has a composite
of several hydrocarbons that vary between refineries and between
locations to account for cold or hot conditions, or differences in
altitude. Current fuels may be stored and handled in liquid, liquid
plus vapor, or vapor phases. The liquid phase of a liquid or liquid
plus vapor mixture tends to stratify or separate out with
increasingly heavier components migrating toward the bottom of the
storage vessel when the fuel mixture remains stationary over an
extended period of time.
[0006] Examples of common fuels that have liquid plus vapor
components are commercial propane (LPG) and commercial liquid
natural gas (LNG). Commercial propane contains propane, ethane,
butanes, and other hydrocarbons in a liquid plus vapor form due to
the pressure at which these compounds are stored and handled (about
150 psig). Commercial liquid natural gas contains mostly methane in
liquid plus vapor phase, with five percent or more of various
heavier hydrocarbons contained mostly in the liquid parts of the
fuel stored at cryogenic conditions (about -200.degree. F.) in
insulated tanks. Finally, commercial compressed natural gas (CNG)
contains mostly methane with varying degrees of other compounds,
such as nitrogen or carbon dioxide, and is completely gaseous, thus
remaining fairly well mixed.
[0007] Liquid and liquid plus vapor fuels have higher energy
densities (energy content per unit volume) than gaseous fuels. This
allows the storage of a greater quantity of useful energy in the
fuel tank of a vehicle. However, the more volatile compounds, which
are the lighter compounds such as methane, will tend to slowly
leave the liquid mixture as a gas primarily due to heat transfer
into the fuel tank. If the fuel tank remains stationary for a long
period of time, significant stratification of the liquid combined
with the vapor leaving the liquid tends to result in the various
liquid components to stratify with the heavier components migrating
to the bottom of the tank and the lighter components migrating
toward the top of the tank. This phenomena is commonly referred to
as "weathering". Weathering occurs for all mixed hydrocarbon fuels
with a liquid phase under certain thermodynamic conditions which
are specific to the composition of the particular fuel mixture. The
problems associated with weathering have generally been overcome by
reprocessing the fuel. However, this requires significant handling
of the fuel and thus significantly increases the production cost of
the fuel.
[0008] To this end, a need exists for an improved method of
dissolving a gaseous hydrocarbon into a liquid hydrocarbon to
re-circulate gaseous components, which have separated from the
liquid fuel mixture, back into the liquid fuel mixture, as well as,
a method for making batch or continuous process amounts of mixed
hydrocarbon fuels. It is to such methods that the present invention
is directed.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0009] FIG. 1 is a cross-sectional view of a mixing and storage
tank constructed in accordance with the present invention.
[0010] FIG. 2 is a cross-sectional view of a lower portion of a
liquid inlet tube looking left to right horizontally in FIG. 1.
[0011] FIG. 3 is a cross-sectional view of another embodiment of a
mixing and storage tank constructed in accordance with the present
invention.
[0012] FIG. 4 is a schematic flow diagram of a process for
manufacturing a two-phase composite fuel within a vehicle storage
tank.
[0013] FIG. 5 is a schematic flow diagram of another embodiment of
a process for manufacturing a two-phase composite fuel.
[0014] FIGS. 6A and 6B are a block diagram of a control algorithm
for use in the process of FIG. 5.
DETAILED DESCRIPTION OF THE INVENTION
[0015] It has been found that a fuel composed of an approximately
50/50 mass mixture of liquid petroleum gas (LPG) and compressed
natural gas (CNG) offers a variety of advantages over other types
of alternative fuels, such as vehicle mileage range while
maintaining both economical and environmental superiority. The
composite fuel has been shown to reduce some of the problems
associated with the use of commercial compressed natural gas (CNG)
or commercial liquid petroleum gas (LPG). For example, the fuel is
stored at approximately half the pressure of CNG (approximately
1500 psig), but retains the high energy density of LPG. An example
of a fuel composed of a 50/50 mass mixture of liquid petroleum gas
(LPG) and compressed natural gas (CNG) is disclosed in U.S. Pat.
Nos. 5,900,515 and 6,111,154 issued to Mallinson et al., each of
which is hereby incorporated herein by reference. Preferably, the
two phase fuel mixture comprises a gaseous methane and at least one
other hydrocarbon and a mole percent of methane from about 50
percent to about 80 percent. The mixture of methane and the at
least one other hydrocarbon maintained at a temperature of about
-1.degree. C. or greater and at a pressure of about 8.0 Mpa or
greater. As mentioned above, due to the effects of weathering,
problems are encountered when attempts are made to store composite
fuels.
[0016] Referring now to the drawings, and more particularly to FIG.
1, a vessel 10 for mixing and storing a two phase fuel composite,
such as in a vehicle, in accordance with the present invention is
illustrated. The vessel 10 is an example of a standard natural gas
storage vessel having a single point of entry. However, double
ended tanks may also be used. The vessel 10 is provided with an
inlet tube 12, a liquid outlet tube 14, and a vapor outlet tube 16.
In a manner to be discussed in greater detail below, the composite
fuel may either be mixed within the vessel 10 or mixed outside the
vessel 10 and then conveyed to the vessel 10. In either case, the
gaseous fuel component is first introduced into the vessel 10 via
the inlet tube 12 to raise the pressure in the vessel 10 above the
known vaporization pressure of the liquid fuel component. When the
composite fuel is mixed outside the vessel 10, the composite fuel
is introduced to the vessel through the inlet tube 12.
[0017] When the composite fuel is mixed in the vessel 10, the
constituent fuel that is normally liquid at the lowest pressure is
then introduced into the vessel 10 via the inlet tube 12. The more
volatile, gaseous fuel component is next introduced into the vessel
10 via the inlet tube 12. The inlet tube 12 has a lower portion 18
positioned near the gravitational low point of the vessel 10. The
gaseous fuel component is slowly added by bubbling the gaseous fuel
component into the liquid fuel component. The bubbles are routed by
the inlet tube 12 to the lowest gravitational point, and released
downward through a series of openings 20 (FIG. 2) oriented at
angles just off straight downward (5 to 45 degrees, depending on
the downward velocity). This downward directional release of the
bubbles ensures that a dead layer of heavier hydrocarbon does not
become fixated in the tank (it is also possible to release the gas
from the bottom wall upward, but the key is to avoid dead layers).
The openings 20 of the inlet tube 12 should be sufficiently small
(or pass to a device such as a porous block that does have
sufficiently small orifices) to allow collapse of the bubbles
rising from the inlet tube 12 over the available length of liquid
height above the inlet tube 12.
[0018] The entire mixture is blended by bubbling until the pressure
exists at a point sufficiently over the critical pressure for the
mixture to overcome pressure losses that might occur in handling
the mix. For example, a 50/50 molar percent mix of methane and
propane would be mixed to about 1350 psig at standard temperature
conditions; a projected ultimate pressure for the mix would be to
exceed 1265 psig. All bubbles tend to collapse above the critical
pressure, enforcing a uniform resultant mixture. The bubbling
serves to avoid large deviation in additional heavy hydrocarbon by
avoiding unmixed regions in the tank.
[0019] If the mixture may be fully utilized at above the critical
pressure of the mixture, then the feed from the vessel 10 should be
located at the lowest gravitational point on the vessel 10. If the
contents of the vessel 10 involves only pressures below the
critical pressure, then several extraction points may be needed. To
this end, the extraction tube 14 is provided with a series of
openings 22 extending along a portion of the extraction tube 14.
The inlet tube 12 and the liquid outlet tube 14 may be combined,
although this may restrict the process time and flow rate.
Preferably, the extraction tube 14 extends to nearly touch the
bottom of the vessel 10.
[0020] As the vessel 10 is emptied by extracting liquid, vapor will
be produced in the handling process. Some vapor may be utilized to
maintain the necessary pressure conditions in the vessel 10.
Additionally, vapor may be periodically captured by the vapor
outlet tube 16 positioned at gravitationally high points in the
vessel 10 and circulated back into the vessel 10 by bubbling the
vapor into the liquid via the inlet tube 12 to maintain a uniform
composition. Alternatively, the captured vapor may be metered to a
vehicle engine (not shown).
[0021] FIG. 3 illustrates another embodiment of a vessel 10a for
mixing and storing a two phase composite fuel in accordance with
the present invention. The vessel 10a is similar to the vessel 10
described above with the exception that the vessel 10a has a
horizontal configuration as opposed to a vertical configuration.
The vessel 10a is provided with an inlet tube 12a, and a liquid
outlet tube 14a, and a vapor outlet tube 16a. The bubbles are
routed by the inlet tube 12a to the lowest gravitational point, and
released downward at angles just off straight downward (5 to 45
degrees, depending on the downward velocity). This downward
directional release of the bubbles ensures that a dead layer of
heavier hydrocarbon does not become fixated in the tank (it is also
possible to release the gas from the bottom wall upward, but the
key is to avoid dead layers).
[0022] The holes 20a of the inlet tube 12a direct flow downward and
should be sufficiently small (or pass to a device such as a porous
block that does have sufficiently small orifices) to allow collapse
of the bubbles rising from that tube over the available length of
liquid height above the inlet tube 12a.
[0023] As the vessel 10a is emptied by extracting liquid, vapor
will be produced in the handling process. Some vapor may be
utilized to maintain the necessary pressure conditions in the
vessel 10a. This vapor may be captured by the vapor outlet tube 16a
positioned at gravitationally high points in the vessel 10a. The
captured vapor may then be fed back into the vessel 10a if captured
at a high enough pressure or metered to a vehicle engine (not
shown) if captured on board a vehicle at lower pressure.
[0024] FIG. 4 is a schematic illustration of a process of making a
mixed composite fuel within a vehicle fuel tank, such as the
vessels 10 and 10a described above, in accordance with the present
invention. This process depends on the thermodynamic end state
required relative to the mixed phase. The pressure associated with
the usual state of individual constituents does not match the end
state of the mixed fuel. To use the contents of vessels 10 or 10a
fully down to lowest pressure, the volatile component of the
mixture is first injected, if the tank/vessel pressure is lower
than the thermodynamic vaporization point of the liquid
constituent. Once the vaporization pressure of the liquid is
reached, the constituent fuel that is normally liquid at the lowest
pressure is first introduced into a sufficiently high pressure,
vented vessel, such as the vessels 10 and 10a described above. The
more volatile, gaseous fuel is next introduced at the gravitational
low point of the vessel as described above. The more volatile fuel
is usually stored at higher pressure than the final mixture, thus
simple mixing of the gas into the liquid is possible. Positive
compression is only needed if the gaseous component is at a
pressure less than or equal to the final required state (target
pressure). As the higher pressure, gaseous component is slowly
added, the pressure is allowed to build up in the mixture, until
the final pressure that is required is met. After manufacture of
the mixture, re-circulation is then performed periodically to
maintain a uniform composition using the concepts described
above.
[0025] Again, in order to use the contents of vessels 10 or 10a
fully down to lowest pressure, the volatile component of the
mixture is first injected, if the tank/vessel pressure is lower
than the thermodynamic vaporization point of the liquid
constituent. Once the vaporization pressure of the liquid is
reached, the system then operates by first pumping LPG, such as
propane, into the vessel 10 from a storage tank 30 via a liquid
stream 32. Once the desired amount of LPG is pumped into the vessel
10, CNG is allowed to flow from a storage tank 34 into the vessel
10 via a gas stream 36 bubbling through the LPG that is already
disposed in the vessel 10. By these means, the fuel is formulated
on board the vehicle. The desired amount varies depending on the
size of the vessel 10.
[0026] The storage tanks 30 and 34 are located at a fueling site
and are constructed to be watertight to ensure maximum isolation.
The storage tanks 30 and 34 are preferably enclosed in an insulated
housing (not shown).
[0027] As shown in FIG. 4, the system includes a pump 38 and a
compressor 39. The pump 38 is an 8 gpm Hydra-Cell D10 pump or other
positive displacement pumping device similar to that shown and
described in reference to FIG. 5, driven by an explosion proof
motor 40. A pressure relief loop 41 is installed to protect against
over pressurization of the pump 38. A fill line 42 is provided with
a coupling 43 for connection with the vessel 10.
[0028] A controller (not shown) is used to monitor and control all
functions of the system in a manner well known in the art. An
example of a suitable controller is a Direct Logic 205 programmable
logic computer (PLC). The controller monitors a pair of axial
turbine flow meters 45 and 46 or other precision flow devices, such
as coriolis flow meters, and controls two valves 47 and 48, the
pump 38, a pressure switch 50, and a pressure transducer 52. The
pressure switch 50 is used to indicate to the controller when the
required pressure has been reached. The pressure transducer 52 is
used to keep track of the pressure in the CNG storage tank 34 in
order to maintain correct flow meter calibration. The storage tanks
30 and 34 should be electrically isolated, and all wiring enclosed
in rigid conduit and sealed junction boxes.
[0029] It has been found that fueling times are greatly reduced
when the pressure in the vessel 10 is low (e.g., <100 psig). The
fueling time has been greatly reduced when this condition is
present since the pump 38 functions as a transfer pump. Also, the
methane and propane content of the mixture is greatly enhanced due
to turbulent convection mass transfer produced by the fast bubbling
of CNG into the propane. To improve the speed of propane delivering
to the vessel 10, the inlet downstream piping is preferably at
least about 0.75 inches. The FIG. 4 process is termed a
"bubble-on-board" process because the mixed fuel is processed
onboard a vehicle. This processing method may be suitable for lost
fuel handling for small captive vehicle fleets or where the
constituent fuel compositions added to a vehicle are regulated.
[0030] FIG. 5 is a schematic illustration of a process for making
and storing a mixed two-phase composite fuel for fueling of a
vehicle storage tank constructed in accordance with the present
invention. The process illustrated in FIG. 5 is termed a
"fast-fill" process because the constituent components are
premixed, allowing for faster transfer to a vehicle. The process
also allows the filling of a vehicle that has any residual fuel
onboard the vehicle, at any pressure within the design of the
present invention. The process involves three primary steps: (1)
pumping a liquid hydrocarbon, such as propane, from a storage tank
60 into a mixing tank 62, (2) passing a gaseous hydrocarbon, such
as compressed natural gas, from a storage tank 64 into the mixing
tank 62, and (3) pumping the composite fuel from the mixing tank 62
to a vehicle fuel tank 66. This is accomplished through a series of
valves and sensors illustrated in FIG. 5. A secondary process is
the identification of the contents of the vehicle tank to be
filled, after sufficient inventory of mixed fuel is available.
[0031] Propane, which is stored in the storage tank 60 at
approximately 150 psig, is conveyed from the propane storage tank
60 to the mixing tank 62 with a pump 70. A 3-way valve 72
positioned upstream of the pump 70 and a 3-way valve 74 positioned
downstream of the pump 70 cooperate to direct the propane to the
mixing tank 62 along a conduit 76. Upstream of the valve 72, the
propane is passed through a filter 78 to remove debris and a flow
meter 80.
[0032] The propane inlet of the mixing tank 62 is at the bottom of
the mixing tank 62. The mixing tank 62 preferably is a tank that is
rated for 5000 psig. The mixing tank 62 is provided with an open
loop 82 connecting a top cap 84 with a bottom cap 86. Pressure
equalizes the liquid level in the mixing tank 62 with the liquid
level in the loop 82. A capacitive sensor 88 detects the liquid
level of propane. The capacitive sensor 88 is mounted outside the
loop 82 at the maximum height of propane needed to prepare the
composite fuel. When the liquid level reaches the preselected
height, the capacitive sensor 88 produces a signal which causes the
valves 72 and 74 to close and operation of the pump 70 to be
terminated. Subsequently, a 3-way valve 90 interposed in a conduit
92 opens permitting compressed natural gas (CNG) to pass from the
gas storage tank 64 to the mixing tank 62.
[0033] The CNG, which is stored in the gas storage tank 64 at about
3000 psig, flows by regulated pressure (above the critical pressure
as described earlier) into the mixing tank 62. The 3-way valve 90
controls the flow of the CNG between a pre-filling conduit 94 and a
mixing tank conduit 96. The pre-filling conduit 94 permits the
vehicle fuel tank 66 to be pre-filled with CNG before filling the
vehicle fuel tank 66 with the composite fuel to avoid flash
vaporization. The mixing tank conduit 96 is connected to the top of
the mixing tank 62 and is the bubbling line for manufacturing the
composite fuel. The mixing tank conduit 96 extends into the mixing
tank 62 and down to near the gravitational low point of the mixing
tank 62 for bubbling purposes in a manner similar to that described
above in relation to the vessel 10. The CNG is passed through a
flow meter 98 and bubbled into the mixing tank 62 until it reaches
a pressure above 1265 psig, at which time a pressure transducer 100
produces a signal to close the valve 90 and thus terminate the flow
of gas from the CNG storage tank. The composite fuel in the mixing
tank 62 is now ready to be transferred to the vehicle fuel tank
66.
[0034] The vehicle fuel tank 66, when empty, has a much lower
pressure than the mixing tank 62. Therefore, to avoid flashing, the
vehicle fuel tank 66 is preferably pre-filled with CNG to a
pressure near 1000 psig via the pre-filling conduit 94. A pressure
transducer 101 located at the end of the pre-filling conduit 94
produces a signal to start and stop the pre-filling process.
[0035] With the vehicle fuel tank 66 pre-filled with CNG, the pump
70 is actuated and the valves 72 and 74 are operated to cause the
composite fuel to pass from the mixing tank 62 via the conduit 76.
The composite fuel then travels through a conduit 102, the valve
72, the pump 70, the valve 74, and a conduit 104 and into the
vehicle fuel tank 66. A flow meter 106 measures the liquid volume
of composite fuel delivered to the vehicle fuel tank 66. When the
fuel capacity of the vehicle fuel tank 66 is reached, a capacitive
sensor 108 produces a signal to stop the pump 70 and to close the
valves 72 and 74.
[0036] For safety purposes, the process preferably includes a
venting loop 110 to prevent overfilling of the vehicle fuel tank
66. The venting loop 110 includes a vapor extraction conduit 112
connectable to the vehicle fuel tank 66 for capturing vapor and
transferring the captured vapor into a recycle tank 114. The
capacitive sensor 108 detects when the vehicle fuel tank 66 is full
and overflows into the conduit 112 to the recycle tank 114. The
capacitive sensor 108 produces a signal to terminate the pump 70
and to close a valve 116 interposed in the conduit 112. The
collected vapor in the recycle tank 114 may then be compressed and
bubbled back into the mixing tank 62 via a conduit 118. a valve 119
is interposed in the conduit 118 to control the flow of the vapor.
Knowing the target conditions of the thermodynamic mixture
(pressure/temperature, which are unique at this design point), this
constitutes the secondary sensing to reliably fill a partially full
vehicle tank with a nominal 50/50 molar mix of the composite
fuel.
[0037] The mixing tank 62 should be rated for at least 3000 psi.
meeting appropriate federal and state standards. The mixing tank 62
might either be U-Stamped for 3000 psi, meet AMSE code for 3000
psi, or be made of rated composite designed to the appropriate
standard. The dimensions of the mixing tank 62 may be, by way of
example, a length of about 74 inches, an outer diameter of about 16
inches, and a volume of about 30 US gallons (water volume). The
mixing tank 62 is preferably a double ended tank.
[0038] The pump 70 is preferably a hydraulic piston pump powered by
a hydraulic power assembly 120 and consists of a hydraulic cylinder
122 and a pump cylinder 124. A suitable pump is commercially
available from Parker Hannifin Corporation with the hydraulic
cylinder 122 being model no. 2.5 inches CJB2HKTV34AC10 (Parker or
equivalent) and the pump cylinder being model no. 3.25 inch
JB2HKTV14A110/2 (Parker or equivalent). The example hydraulic
cylinder has a 2.50 inch bore, a cushioned head and cap, and a 10
inch stroke. The pump cylinder has a 3.25 inch bore and 10.5 inch
stroke. The pump operates using proximity sensors to signal when
the cylinders should change direction. In production, larger
cylinders and steam/water/hydraulics/electrics or other driven
engines might power the pumping process.
[0039] The valves and pump described herein are preferably
controlled with a programmable logic controller. Control valves and
controllers constructed to operate in the manner described herein
are well known in the art. Thus, a detailed description of such
components is not believed necessary to enable one skilled in the
art to understand the operation of the system of the present
invention. An example of a suitable controller is a Direct Logic
205 with a CPU 240 made by Koyo.
[0040] FIG. 6 shows a control algorithm for the process shown in
FIG. 5. The control algorithm is written using ladder programming
RLL Plus. The program is composed of three main stages: filling
propane into the mixing tank 62, injecting CNG into the mixing tank
62 to a pressure of 1500 psi, and transferring the mixture into the
vehicle fuel tank.
[0041] From the above description it is clear that the present
invention is well adapted to carry out the objects and to attain
the advantages mentioned herein as well as those inherent in the
invention. While presently preferred embodiments of the invention
have been described for purposes of this disclosure, it will be
understood that numerous changes may be made which will readily
suggest themselves to those skilled in the art and which are
accomplished within the spirit of the invention disclosed and as
defined in the appended claims.
* * * * *