Note: Descriptions are shown in the official language in which they were submitted.
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
1
LNG TRANSPORTATION VESSEL AND
METHOD FOR TRANSPORTING HYDROCARBONS
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application
60/625,388, filed 5 November, 2004.
BACKGROUND
Field of the Inventions
[0002] Embodiments of the present invention generally relate to the
transportation
of hydrocarbons. More particularly, embodiments of the present invention
relate to an
integrated design for a liquefied natural gas transportation vessel. In
addition,
embodiments of the present invention relate to a method for combining
liquefaction,
transportation and regasification processes.
Description of Related Art
[0003] Clean burning natural gas has become the fuel of choice in many
industrial
and consumer markets around the world. However, natural gas sources are often
located in remote locations relative to the commercial markets desiring the
gas. This
means that the natural gas must sometimes be produced in remote geographic
locations, and then transported across oceans using large-volume marine
vessels.
[0004] To maximize gas volumes for transportation, the gas may be taken
through
a liquefaction process. The liquefied natural gas ("LNG") is formed by
chilling very
light hydrocarbons, e.g., gases containing methane, to approximately -160 C.
The
liquefied gas may be stored at ambient pressure in special, cryogenic tanks
disposed
on large ships. Alternatively, LNG may be liquefied at an increased pressure
and at a
warmer temperature, i.e., above -160 C, in which case it is known as
Pressurized
LNG ("PLNG"). For purposes of the present disclosure, PLNG and LNG may be
referred to collectively as "LNG."
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
2
[0005] The transportation of LNG to the importing nation or locale is
expensive.
As currently developed, gas is taken through a liquefaction process at a
location
proximate the point of production. This means that a large gathering and
liquefaction
center is erected in the producing country. Alternatively, the liquefaction
process may
take place offshore on a platform or vessel, such as a floating production,
storage and
offloading (FPSO) vessel. From there, the hydrocarbon product is loaded in its
liquefied state onto marine transport vessels. Such vessels are known as LNG
tankers.
[0006] Upon arrival at a destination country, the LNG product is offloaded at
a
receiving terminal. The receiving terminal may be onshore or "near shore"
relative to
the importing nation. In some cases, the gas is temporarily maintained in
storage in
its chilled and liquefied state. Liquefaction enables larger volumes of gas to
be stored
in insulated tanks until introduced into the gas grid, or delivered to a
customer. In
some instances, the chilled gas is transported in specially insulated vessels
on the back
of a trailer and hauled over-the-road to markets. In some instances, the
imported
LNG is "vaporized" into the grid for the market.
[0007] LNG technology generally requires large investments of capital and
resources at the export and import terminals. It also requires cryogenic
transfer of
liquids at each end. In many locations, natural gas resources are present in
insufficient quantities to justify the expense of building a gas liquefaction
processing
facility in the producing country or at the producing site. In addition, the
transfer of
cryogenic material, particularly from an FPSO, is difficult. Alternatively,
consumer
demand at the importing location may not economically justify the fabrication
of a
regasification facility. Therefore, there is a need for an integrated vessel
that is
capable of receiving a light hydrocarbon product at an export terminal of a
producing
country, chilling the gas to a liquefied state, and then transporting the gas
to a location
in greater proximity to the desired market. In addition, there is a need for a
vessel that
is capable of regasifying the light hydrocarbon upon arrival at a location for
offloading, or import terminal. There is further a need for such a vessel that
travels
the oceans, on a river, or over the road.
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
3
[0008] Additional information relating to LNG liquefaction, transportation,
and/or
regasification technology can be found in U.S. patent no. 5,878,814 (to
Breivik et al.),
DE 32 00 958 (Linde AG), U.S. patent no. 5,025,860 (to Mandrin et al.), U.S.
patent
no. 6,517,286 (to Latchem), WO 2004/081441 (Conversion Gas Imports),
US2003/185631 (Bliault et al.), WO 2004/000638 (ABB Lummus Global, Inc.), U.S.
patent no. 3,766,583 (to Phelps), US2003/182948 (Nierenberg), US 2002/174662
(Frimm et al.), and U.S. patent no. 6,089,022 (to Zednik et al.).
SUMMARY
[0009] First, a method for transporting liquefied natural gas is provided. The
method includes the steps of on-loading natural gas in a substantially gaseous
phase
onto a vessel at a first location; cooling the natural gas on the vessel so as
to convert it
substantially into liquefied natural gas; storing the liquefied gas in an
insulated
container; transporting the liquefied natural gas on the vessel from the first
location to
a second location; heating the liquefied natural gas on the vessel so as to
reconvert it
back into a substantially gaseous phase; and off-loading the natural gas from
the
vessel at the second location. Preferably, the steps of cooling the natural
gas and
heating the liquefied natural gas are each accomplished by using a gas
processing
facility. More preferably, the same gas processing facility is used for both
cooling
(liquefying) the natural gas and heating the liquefied natural gas.
[0010] The method for transporting LNG may be accomplished on a variety of
vessels. Examples include a marine vessel, a barge vessel, and an over-the-
road
trailer vessel.
[0011] In another aspect, a method is provided for transporting liquefied
natural
gas on a vessel. The method generally comprises the steps of providing a gas
transfer
system for the vessel; on-loading the natural gas onto the vessel through the
gas
transfer system, the natural gas being in essentially a gaseous phase;
providing a gas
processing facility on the vessel, the gas processing facility selectively
cooling and
heating the natural gas; flowing the natural gas through the gas processing
facility so
as to cool the natural gas to a lower temperature where the natural gas is in
a
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
4
substantially liquefied phase, and providing a containment structure on the
vessel for
containing the liquefied natural gas during transport.
[0012] In addition, a vessel for transporting liquefied natural gas is
provided. In
one embodiment, the vessel includes a gas transfer system for on-loading and
off-
loading natural gas to and from the vessel in its essentially gaseous phase; a
gas
processing facility for selectively (i) cooling the natural gas from a
temperature where
the natural gas is in a gaseous phase, to a lower temperature where the
natural gas is
in a substantially liquefied phase; and (ii) heating the natural gas from a
temperature
where the natural gas is in a substantially liquefied phase, to a temperature
where the
natural gas is converted back to its gaseous phase; a power generator for
providing
power to the gas processing facility; and a containment structure for
containing the
liquefied natural gas during transport.
[0013] The vessel again may be any type of transport vessel, including for
example a marine vessel, a barge vessel, or an over-the-road trailer vessel.
Where the
vessel is a marine vessel, the gas transfer system may further comprise a
buoyed line
for placing the gas processing facility in fluid communication with a marine
jumper
line. Where the vessel is a land-based vessel such as a vessel on a trailer,
the gas
transfer system may further comprise a line for placing the gas processing
facility in
fluid communication with a land hose.
[0014] Where the containment structure is a marine vessel, the containrnent
structure may be one or more Moss sphere tanks, it may be a membrane tank, or
it
may be a plurality of pressurized bottles in fluid communication. The
plurality of
bottles maintain the LNG under pressures greater than ambient.
[0015] In one aspect, the gas processing facility comprises at least one heat
exchanger through which the natural gas thermally contacts a heat exchanger
fluid;
and at least one fluid movement device. The fluid movement device may be
either a
compressor or a pump.
[0016] In one arrangement, the gas processing facility cools the natural gas
by
providing a first heat exchanger for cooling the natural gas by thermal
contact
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
between the natural gas and a heat exchanger fluid; a compressor wherein the
heat
exchanger fluid is compressed and temporarily warmed after flowing through the
first
heat exchanger; a second heat exchanger wherein the compressed heat exchanger
fluid is cooled; and an expander wherein the compressed heat exchanger fluid
is
further cooled, and decompressed before returning through the first heat
exchanger.
Alternatively, the gas processing facility heats the natural gas by providing
a first heat
exchanger for warming the natural gas by thermal contact between the natural
gas and
a heat exchanger fluid; and a second heat exchanger wherein the heat exchanger
fluid
is warmed after flowing through the first heat exchanger. The heat exchanger
fluid
movement device may be a compressor wherein the heat exchanger fluid is
compressed and further warmed after flowing through the second heat exchanger
and
before returning through the first heat exchanger. Alternatively, the fluid
movement
device is a pump disposed in line between the first and second heat exchangers
for
pressurizing the liquefied heat exchanger fluid.
[0017] Preferably, the power generator is configured to selectively provide
power
to propel the vessel when the natural gas is stored in the containment
structure, and to
provide power to the gas processing facility when the natural gas is being
cooled or
heated. Optionally, the vessel may further have an ancillary compressor for
circulating and cooling the heat exchanger fluid while the vessel is
transporting the
LNG in order to recondense any natural gas that becomes vaporized during
transport,
or to generally keep the heat exchanger fluid and system equipment cool.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The following drawings are provided as an aid in understanding the
various inventions described herein.
[0019] Figure lA presents a plan view of the main deck of a fluid
transportation
vessel. The exemplary vessel is a marine vessel. Visible in this view are a
bridge, a
cargo storage area, and a gas processing facility. The cargo storage area
represents
one or more individual tanks within a liquefied gas containment structure.
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
6
[0020] Figure 1B presents an alternate marine vessel for transporting fluids
in a
temperature-controlled environment. The containment structure of the LNG
transportation vessel of Figure 1B is a Moss sphere tank.
[0021] Figure IC presents yet an additional alternate marine vessel for
transporting fluids in a temperature-controlled environment. The containment
structure of the LNG transportation vessel of Figure 1 C is a membrane tank.
The
illustrative vessel is again a marine vessel.
[0022] Figure 2 is a side view of the vessel of Figure 1 A. The profile of the
vessel can be seen. Visible in this view is a side of the containment
structure of
Figure 1A.
[0023] Figure 3 presents a schematic view of the gas processing facility of
Figure
1A, in one embodiment. Arrows depict the process of liquefaction for the light
hydrocarbons.
[0024] Figure 4A presents another schematic view of the gas processing
facility
of Figure 1 A. In this view, arrows depict the process of regasification for
the light
hydrocarbons.
[0025] Figure 4B presents an alternate arrangement for the regasification
facility
of Figure 4A. In this view, arrows again depict the process of regasification
for the
light hydrocarbons.
[0026] Figure 5A demonstrates an LNG transportation vessel as a barge vessel.
The barge vessel is being towed by a tug boat.
[0027] Figure 5B demonstrates the LNG transportation vessel as a trailer
vessel.
The trailer vessel is being pulled by an over-the-road rig.
DETAILED DESCRIPTION
[0028] The following words and phrases are specifically defined for purposes
of
the descriptions and claims herein. To the extent that a term has not been
defined, it
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
7
should be given its broadest definition that persons in the pertinent art have
given that
term as reflected in printed publications, dictionaries and/or issued patents.
[0029] "Natural gas" means a light hydrocarbon gas or a mixture including two
or
more light hydrocarbon gases that includes greater than 25 molar percent
methane on
a hydrocarbon species basis. For example, natural gas may contain methane
along
with other hydrocarbon components such as, but not limited to, ethane,
propane,
butane, or isomers thereof Natural gas may also include non-hydrocarbon
contaminant species such as, for example, carbon dioxide, hydrogen sulfide,
water,
carbonyl sulfide, mercaptans and nitrogen.
[0030] "LNG" or "liquefied natural gas" means natural gas or a portion thereof
that has been liquefied. The term collectively includes any light hydrocarbon
or
mixture of two or more light hydrocarbons in substantially liquid form that
includes
greater than 25 molar percent methane on a hydrocarbon species molar basis.
LNG
includes, for example, natural gas induced into a liquid form through cooling
at about
atmospheric pressure and by both cooling and application of increased pressure
over
ambient pressure such as "PLNG."
[0031] "Vessel" means any fluid transportation structure. Non-limiting
examples
of a vessel include a marine vessel, a barge vessel, or a trailer vessel.
[0032] "Marine vessel" means a vessel configured to transport volumes of
fluids
such as LNG over an ocean or other large water body.
[0033] "Barge vessel" means a vessel configured to transport volumes of fluids
such as LNG over a river or within a marine inlet or bay.
[0034] "Trailer vessel" means a vessel configured to transport volumes of
fluids
such as LNG on a trailer. The trailer is pulled by a truck, a rig, or other
mechanized
vehicle over-the-road.
[0035] The terms "on-loading" and "off-loading" refer to the movement of
fluids
onto and off of a vessel, respectively. The terms are not limited as to the
manner in
which fluid movement is accomplished.
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
8
[0036] "Gas transfer system" means a system for on-loading or off-loading of
fluids in at least a partially gaseous phase. Non-limiting examples of
features for a
gas transfer system include compressors, valves, conduits and pumps.
[0037] "Ambient temperature" refers to the temperature prevailing at any
particular location.
[0038] "Expander" means any device capable of reducing pressure in a fluid
line,
including but not limited to an expansion valve or turboexpander.
[0039] Some embodiments of the invention include apparatus and methods for
liquefying natural gas. In some embodiments natural gas includes a light
hydrocarbon gas or a mixture including two or more light hydrocarbon gases
that
includes greater than 25 molar percent methane. Alternatively, natural gas may
include greater than 40 molar percent methane or greater than 70 molar percent
methane on a hydrocarbon species basis.
[0040] Some embodiments of the invention include apparatus and methods for
liquefying natural gas to form LNG or regasifying LNG to reform natural gas.
In
some embodiments LNG includes natural gas or a portion thereof that has been
liquefied. LNG may include any light hydrocarbon or mixture of two or more
light
hydrocarbons in substantially liquid form that includes greater than 25 molar
percent
methane on a hydrocarbon species basis. Alternatively, LNG may include greater
than 40 molar percent methane or greater than 70 molar percent methane on a
hydrocarbon species basis.
[0041] The following provides a description of specific embodiments shown in
the drawings:
[0042] Figure 1A presents a plan view of a fluid transportation vessel 100.
The
illustrative fluid transportation vessel 100 is a marine vessel. The vessel
100 is
specifically configured to carry liquefied natural gas, or "LNG," over an
ocean or
other large water body. In one aspect, the vessel 100 is nominally 300 meters
in
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
9
length. The vessel 100 includes a main deck 12, visible in the plan view of
Figure
1A.
[0043] Figure 2 provides a side view of the vessel 100 of Figure 1A. A profile
of the vessel 100 can be seen, defined by a hull 16. The hull 16 is generally
under the
main deck 12. The hull 16 provides for a "ship-shaped" vessel that is
preferably self-
propelled. However, it is understood that the scope of the present inventions
is not
limited to vessels that are ship-shaped or self-propelled.
[0044] The marine vessel 100 includes a bridge 20. The bridge 20 is typically
at
either the fore or aft sections of the vessel. The bridge 20 is seen in both
FIGS. 1A
and 2 at the bow of the ship 100. The bridge 20 is positioned on the deck 12,
and
provides living quarters for the ship's officers and crew members. The bridge
20 also
provides navigational and operational controls for the ship 100. It is
understood that
the vessel will also have a navigation system that will include a steering or
guidance
mechanism, a rudder and instrumentation (all not shown).
[0045] The marine vessel 100 further includes a cargo storage area 30, or
"containment structure." The containment structure 30 is shown schematically
in
Figures 1A and 2, and is intended to represent a single "insulated
compartment." The
illustrative containment structure 30 includes a plurality of containers 30A
configured
to hold a cryogenic fluid such as LNG under pressure. The containment
structure 30
is cut away in each of Figures 1A and 2 to expose a sampling of containers
30A. It is
understood that the containment structure 30 is not limited to a single
"insulated
compartment;" the containers 30A may be individually insulated.
[0046] Selected sets of bottles 30A are in fluid communication with one
another
to form a "tank." The bottles 30A have appropriate valving 32 for moving LNG
into
and out of the bottles 30A. In one aspect, four-inch piping connections are
provided
for moving cryogenic fluids into and out of the containers 30A, though it is
understood that other dimensions may be employed. The containers 30A may be at
ambient pressure or slightly higher, and contain natural gas chilled to a
temperature of
approximately -160 F(-106.7 C) or less to provide liquefaction. Alternately
the
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
natural gas may be chilled to a temperature of approximately -190 F(-123.3
C) or
less. Alternatively, the containers may be at ambient pressure or slightly
higher, and
contain natural gas chilled to a temperature of between approximately -200 F
to -
270 F(-128.9 C to -167.8 C). The containers 30A may alternatively be stored
at a
higher pressure above approximately 150 psi, and at temperature of
approximately -
193 F(-125 C) or more. Alternatively, the containers may be stored at a
pressure in
the range of approximately 250 - 450 psi, and at temperature between about -
175 F
and -130 F(-115 C to -90 C). Those of ordinary skill in the art will
understand that
the liquefaction temperature of a hydrocarbon will depend upon its pressure
and
composition.
[0047] The bottles 30A are preferably cylindrical in shape, and are typically
fabricated from a steel material. Where the containers 30A serve as a pressure
vessel,
they are preferably fabricated from a steel material having walls of
appropriate
thickness. One or more bottles 30A in fluid communication together form a
single
"tank."
[0048] Various other LNG containment structures are known for marine vessels.
Examples are provided in Figures 1B and 1C. Figure 1B presents a containment
structure for an LNG transportation vessel 100B as a plurality of Moss sphere
tanks
30B. The exemplary vessel 10 is again a marine vessel. The Moss sphere tanks
30B
are semispherical or elongated in shape, and may have a diameter of up to 40
or more
meters. Typically, three to five Moss sphere tanks will be placed on a single
marine
vessel. LNG is stored in the Moss sphere tanks at ambient pressure.
[0049] Figure 1C presents a containment structure 30C for an LNG
transportation vessel 100C as a membrane tank. The exemplary vessel 100C is
again
a marine vessel. A membrane tank is typically a square or rectangular
structure
having steel lining (not shown) for providing a fluid-tight compartment. The
lining is
structurally supported by a frame that is insulated. The framing forms an
insulated
cargo hold. Each membrane tank 30C may be 40 meters x 40 meters in footprint,
for
example.
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
11
[0050] Each illustrative marine vessel 100, 100B, 100C also includes a gas
processing facility. The gas processing facility is shown schematically at 40,
and is
intended to represent any facility that can selectively cool or heat fluids
such as
natural gas. Preferably, the gas processing facility 40 will first cool the
natural gas
from an essentially ambient temperature where the natural gas is in a gaseous
phase,
to a lower temperature where the natural gas is in a substantially liquefied
phase. This
occurs in connection with a procedure for on-loading of natural gas onto the
vessel,
e.g., vessel 100. In addition, the gas processing facility 40 will preferably
also heat
the natural gas from a temperature where the natural gas is in a substantially
liquefied
phase, to an essentially ambient temperature where the natural gas is
converted back
to its gaseous phase. This occurs in connection with a procedure for off-
loading of
natural gas from the vessel 100, 100B or 100C.
[0051] Figure 3 presents a more detailed view of the gas processing facility
40, in
one embodiment. In this view, the gas processing facility 40 is set up for the
cooling
of fluids, or "liquefaction." Arrows depict the flow of fluids for the process
of
cooling the natural gas. More specifically, arrow G shows the movement of gas
through the gas processing facility 40 located on the vessel 100, while arrow
C
demonstrates the pumping of a coolant to cryogenically refrigerate the gas.
[0052] Figures 4A and 4B present other schematic views of the gas processing
facility 40 of Figures 1, 1B and 1C. In these views, the gas processing
facility 40 is
set up for the heating of fluids, or "regasification." Arrows depict the flow
of fluids
for a process of regasification of light hydrocarbons. Arrow G shows the
movement
of gas through the gas processing facility 40 located on the vessel 100, while
arrow H
demonstrates the pumping of a heat exchanger fluid to warm the gas. Figures 4A
and
4B provide alternate gas processing systems for regasification.
[0053] The gas processing facility of Figure 3 is an intermediate facility
between
the reception of natural gas from the field, and the storage of LNG in the
containment
structure 30 for transport. Similarly, the gas processing facilities of
Figures 4A and
4B each provide an intermediate facility between the offloading of natural gas
from
the containment structure 30 to an import terminal. To accommodate the
movement
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
12
of hydrocarbons onto and off of the vessel, a gas transfer system is provided.
The gas
transfer system is represented schematically by line 50 in Figures 3, 4A and
4B. In
practice, the gas transfer system 50 will comprise a line that provides fluid
communication between the gas processing facility 40 and a line (not shown)
external
to the vessel 100. For example, where the fluid transportation vessel is a
marine
vessel (such as the vessel 100 of Figure 1A) or a barge vessel (seen in Figure
5A),
the line will connect to a marine jumper. The marine jumper will preferably be
buoyed with either integral or attached buoys. Where the fluid transportation
vessel is
a trailer vessel (seen in Figure 5B), the line will connect to a land hose.
[0054] Figure 5A demonstrates an LNG transportation vessel as a barge vessel
500A. The barge vessel 500A is being towed by a tug boat 510A. The vessel 500A
includes a gas transfer system 502A, a gas processing facility 504A, and a
fluid
containment structure 506A. The gas transfer system 502A will typically define
a
hose configured to connect to a marine jumper line (not shown). The barge
vessel
500A is preferably pulled by a tug 510A. The vessel 500A may be integral to
the tug
510A, but is preferably a separate floating apparatus that can be hitched and
unhitched. Figure 5A shows a hitching line 501A. The tug 510A, of course,
includes
an engine and propeller (not shown). The engine is typically diesel or
gasoline
powered, and operates to drive the propeller in the water W. The barge 510A
may
also include a battery (not shown) for powering electrical equipment such as
lights.
Preferably, the gas processing facility 504A is powered by either the engine
or the
battery of the tug 510A.
[0055] Figure 5B demonstrates the LNG transportation vessel as a trailer
vessel
500B. The vessel 500B includes a gas transfer system 502B, a gas processing
facility
504B, and a fluid containment structure 506B. The gas transfer system 502B
will
typically define a valve and, perhaps, a hose configured to connect to a
supply line
(not shown). The trailer vessel 500B is being pulled by an over-the-road rig
510B.
The trailer vessel 500B is disposed on a multi-axle trailer 520B for land-
based
transport.
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
13
[0056] The trailer vesse1500B is propelled by being pulled behind the rig
510B,
or "truck." The vesse1500B may be integral to the truck 510B, but is
preferably on a
separate trailer 520B that can be hitched and unhitched. The truck 510B, of
course,
includes an engine and shaft (not shown). The engine is typically diesel or
gasoline
powered, and operates to drive a shaft that transmits rotational motion to a
transmission. The truck 510B also includes a battery (not shown) for powering
electrical equipment. Preferably, the gas processing facility 504B is powered
by the
engine of the truck 510B, reducing equipment requirements. The engine may
drive an
electrical generator for creating electrical power for the gas processing
facility 504B.
[0057] In practice, a volume of fluid such as natural gas is brought from the
field
to a gathering center. The gathering center may be on land, near shore, or
offshore.
The natural gas is stored at an essentially ambient temperature. In the case
of a
marine vessel such as vessels 100, 100B, and 100C, the vessel is offshore and
receives natural gas pumped from the gathering facility (not shown) onto the
vessel
through the gas transfer system 50. The natural gas is not stored directly in
the
containment structure 30 of the vessel 100; rather, it is pumped through the
gas
processing facility 40 for liquefaction in accordance with Figure 3.
[0058] Referring again to Figure 3, a gas process facility 40 is again shown.
The
gas process facility 40 is used for the purpose of condensing a fluid, such as
natural
gas. Arrow G depicts the flow of gas during liquefaction, as described above.
[0059] The gas process facility 40 includes a first heat exchanger 42. The
first
heat exchanger 42 acts to cool the natural gas by thermal contact between the
natural
gas and a heat exchanger fluid. The first heat exchanger 42 provides suitable
adjacent
fluid channels (not shown) for directing hydrocarbons and a heat exchanger
fluid,
respectively, so that the two channels are in thermal contact with one
another. In this
sequence, the heat exchanger fluid acts as a refrigerant flowing through lines
"C."
[0060] The gas process facility 40 also includes a compressor 44. The
compressor 44 receives the heat exchanger fluid, or refrigerant, as it cycles
from the
first heat exchanger 42, and compresses the refrigerant. The process of
compressing
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
14
the refrigerant also acts to temporarily warm the refrigerant as it moves
through the
compressor 44. In one arrangement, the refrigerant is approximately 35 F(1.7
C)
upon exiting the first heat exchanger 42, and is 300 F(148.9 C) upon exiting
the
compressor 44.
[0061] The gas process facility 40 also includes a second heat exchanger 46.
The
compressed refrigerant is cooled in the second heat exchanger 46. The second
heat
exchanger 46 provides adjacent fluid channels (not shown) through which the
refrigerant and a coolant fluid flow. The coolant fluid acts to chill the
refrigerant
through thermal contact. In the context of a marine vessel such as the vessel
100 of
Figure 1A, the coolant may be the abundantly available sea water or air. In
the
context of a barge vessel (such as vessel 500A seen in Figure 5A), the coolant
may be
fresh water or air. In the context of a trailer vessel (such as vesse1500B
seen in
Figure 5B), the coolant is most typically air.
[0062] The gas process facility 40 also includes an expander 48. The expander
48
acts to expand the compressed refrigerant. The expander 48 may be an expansion
valve, a turboexpander, or any other device for expanding fluid. The process
of
expanding the compressed refrigerant acts not only to decompress the
refrigerant, but
also to further chill it. In one arrangement, the refrigerant is at a
temperature of
approximately 65 F upon exiting the second heat exchanger 46, but is -170 F
upon
exiting the expander 48. The significantly chilled refrigerant is then cycled
back
through the first heat exchanger 42 where it again acts to refrigerate the
natural gas.
Ultimately, the natural gas is condensed into a substantially liquid phase.
Thus, the
gas process facility 40 of Figure 3 acts as a liquefaction facility.
[0063] Referring now to Figure 4A, the gas process facility 40 is again shown.
However, in this arrangement the gas process facility 40 is used for the
purpose of
heating a fluid, such as natural gas. Arrow G depicts the process of
regasification for
the light hydrocarbons as described above. The arrows are generally directed
in
opposite directions from the arrows of Figure 3.
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
[0064] The gas process facility 40 again includes a first heat exchanger 42.
In this
instance, however, the first heat exchanger 42 acts to warm the natural gas by
thermal
contact between the natural gas and the heat exchanger fluid. In this
sequence, the
heat exchanger fluid acts as a heating fluid flowing through lines "H." The
first heat
exchanger 42 provides suitable fluid channels (not shown) for directing
natural gas in
its liquid phase, and a heat exchanger fluid, so that the two channels are in
thermal
contact with one another. In this sequence, the heat exchanger fluid acts as a
heating
fluid.
[0065] After cycling through the first heat exchanger 42, the heat exchanger
fluid
moves to the second heat exchanger 46. The heat exchanger fluid bypasses the
expander 48. It can be seen in Figure 4A that the arrows do not indicate the
flow of
fluids through the expander 48.
[0066] In the regasification process shown in Figure 4A, the second heat
exchanger 46 now acts to warm the heat exchanger fluid. In this respect, the
process
of cycling the heat exchanger fluid through the first heat exchanger 42 has
produced a
cooling of the heat exchanger fluid. The heat exchanger fluid is now very cold
upon
exiting the exchanger 42. Thus, the heat exchanger fluid is warmed in the
second heat
exchanger 46. The second heat exchanger 46 provides adjacent fluid channels
(not
shown) through which the heat exchanger fluid and a warming fluid flow. The
warming fluid acts to warm the heat exchanger fluid through thermal contact.
In the
context of a marine vessel such as the vessel 100 of Figure 1A, the warming
fluid
may be sea water. Alternatively, the warming fluid is fresh water maintained
on the
vessel at ambient temperature by a combustion or other warming process not
shown.
Alternatively, the second heat exchanger 46 may be a tank which receives and
heats
fresh water directly, such as through combustion. In the context of a barge
vessel
(such as vessel 500A seen in Figure 5A), or in the context of a trailer vessel
(such as
vessel 500B seen in Figure 5B), the warming fluid may be either air or water.
[0067] From the second heat exchanger 46, the heat exchanger fluid moves
through the compressor 44. The compressor 44 compresses the heating fluid, and
delivers it to the first heat exchanger 42 in a further warmed state. As noted
above,
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
16
the process of compressing the fluid also acts to warm the fluid as it moves
through
the compressor 44. In one arrangement, the heat exchanger fluid is
approximately 55
F upon exiting the second heat exchanger 46, but is approximately 300 F upon
exiting the compressor 44. The significantly warmed heat exchanger fluid is
then
cycled back through the first heat exchanger 42 where it again acts to warm
the
natural gas. Ultimately, the natural gas is vaporized into a substantially
gaseous phase
for offloading. Thus, the gas process facility 40 of Figure 4 acts as a
regasification
facility.
[0068] Specific temperatures have been provided in connection with certain
components of the gas process facility 40. However, it is understood that the
scope of
the present inventions is not limited to any particular temperatures, so long
as the
temperature of the heat exchanger fluid as it enters the first heat exchanger
is
sufficiently low to liquefy the natural gas (or other fluid) in the
liquefaction process,
and sufficiently high to vaporize the natural gas (or other fluid) in the
gasification
process. It is noted, however, that the gas processing facility 40 operates
more
efficiently where water is available in the second heat exchanger 46 that is
warm, i.e.,
five degrees Fahrenheit or more above freezing. In an environment that lacks a
suitable ambient temperature warming medium, integration of the liquefaction
and
vaporization heat exchangers is difficult. In this scenario, the gas
processing facility
40 would preferably employ a vaporization means heated through combustion of a
portion of the natural gas product. The fired vaporization facilities would
benefit
from the integration of utilities like water supply and fuel gas systems with
the
liquefaction process.
[0069] As noted above, Figure 4B presents an alternate arrangement for the gas
processing facility of Figure 4A. In this view, arrows again depict the
process of
regasification for the light hydrocarbons. The system is now shown at 40'. In
the
arrangement of Figure 4B, the heat exchanger fluid is again cycled through the
first
heat exchanger 42 in order to warm ("regasify") the LNG. The regasified
hydrocarbons exit the gas processing facility 40' through line 50. Ultimately,
the
natural gas is vaporized into a substantially gaseous phase for offloading.
Thus, the
gas process facility 40' of Figure 4B also acts as a regasification facility.
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
17
[0070] The process of cycling the heat exchanger fluid through the first heat
exchanger 42 has produced a cooling of the heat exchanger fluid, substantially
liquefying it. To reheat the heat exchanger fluid, the heat exchanger fluid is
first
moved through a pump 49. The pump 49 serves as an alternate fluid movement
device vis-a-vis the compressor 44. It can again be seen that the heat
exchanger fluid
again bypasses the expander 48. The pump 49 is provided after the first 42
heat
exchanger in order to energize and warm the heat exchanger fluid. The pump 49
also
transfers the liquid heat exchanger fluid, e.g., sea water, towards the second
heat
exchanger 46.
[0071] As with facility 40 of FIG. 4A, the second heat exchanger 46 acts to
further warm the heat exchanger fluid. The second heat exchanger 46 provides
adjacent fluid channels (not shown) through which the heat exchanger fluid and
a
warming fluid flow. The warming fluid acts to warm the heat exchanger fluid
through thermal contact. In the context of a marine vessel such as the vessel
100 of
Figure 1A, the warming fluid may again be seawater or fresh water that has
been
warmed through a direct combustion process. In the context of a barge vessel
(such
as vesse1500A seen in Figure 5A), or in the context of a trailer vessel (such
as vessel
500B seen in Figure 5B), the warming fluid may be either air or water.
[0072] From the second heat exchanger 46, the heat exchanger fluid returns
directly to the first heat exchanger 42 where it again acts to warm the
natural gas. It
can be seen that the compressor 44 has been bypassed in FIG 4B. The compressor
44
is optionally not used when a pump 49 is employed. The process of pumping the
fluid through pump 44 provides the pressure needed to cycle the heat exchanger
fluid
through the system 40'.
[0073] It can be seen from the arrangements of Figures 3, 4A and 4B that
substantially the same physical equipment and heat exchange fluids for both
the
liquefaction operation and the regasification operation may be employed. By
modifying the refrigeration system operation as shown in Figure 3, it is
possible to
use the same heat exchangers and heat transfer fluids for vaporization of the
gas via
systems 40, 40' of Figures 4A and 4B. This results in equipment savings on the
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
18
vessel. Where the vessel is a marine vessel, if the water temperature at the
import
location is warm, i.e., approximately five degrees Fahrenheit or more above
freezing,
or if ambient heating medium of any type is available from a source near the
import
location, it is possible to install the liquefaction and regasification
equipment 40 on
the vessel, e.g., vessel 100, in a more cost-effective manner.
[0074] In the gas process facility 40 shown in Figures 3 and 4A, the heat
exchanger fluid is moved through the system 40 by compression. Compression may
be accomplished by using the compressor 44 as the fluid movement device. In
the gas
process facility 40' shown in Figure 4B, the heat exchanger fluid is moved
through
the system by pumping. Pumping may be accomplished in connection with pump 49
as the fluid movement device. Power is provided to either the compressor 44 or
the
pump 49 (and other mechanical parts of the gas process facilities 40 and 40')
by a
power generator. A power generator is shown schematically at 41 in Figures 3,
4A
and 4B.
[0075] The power generator 41 is preferably an engine. The engine may be gas-
powered, with the gas being provided from either naturally-occurring boil-off
of
natural gas from the LNG stored in the containment structure 30, or from an
independent fuel supply (not shown). Alternatively, the engine may be diesel
powered. In this instance, a diesel supply (not shown) would be provided on
the ship.
In the arrangement of Figures 3 and 4A, it can be seen that the power
generator 41
drives a motor 43m. Arrow "e" indicates an electric line providing power to
the
motor 43m. The motor 43m in turn, provides mechanical power to run the
vessel's
propulsion system, shown schematically at 43. Arrow "s" is indicative of a
mechanical shaft going to the propulsion system 43.
[0076] It is preferred that the ship's propulsion system 43 be integrated with
the
power system for powering the gas processing facility 40 or 40'. Thus, when
the ship
is not in transit, the power generator may be used to drive separate motors
44m and
49m (49m not shown). The motors 44m and 49m, in turn, provide mechanical power
to either the compressor 44 (in the arrangement of FIGS. 3 and 4A and B) or
the
pump 49 (in the arrangement of FIG. 4B), respectively.
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
19
[0077] In order for the gas processing facility 40 to share a power generator
41
with the ship's propulsion system 43, the power requirements should be
generally
comparable. With propulsion and gas processing power requirements being
comparable, a single, integrated power generation plant and electric or
hydrocarbon
motor drive may be installed to provide the power needed for both operations.
In this
arrangement, the gas compression 44 and ship propulsion 43 are preferably not
used
at the same time so as to minimize the overall power generation needs for the
ship. In
one embodiment, the power generator 41 is a power generation plant that feeds
a
single variable frequency drive (VFD). The VFD is used to alternately control
the
ship's propulsion 43 and to power refrigeration motors 44m and 49m. It is
understood that the present inventions are not limited to the way in which
power is
shared or transferred between the propulsion system 43 and the gas processing
facility
40. Other power arrangements may be used, such as the modification of motor
windings, or the use of a gear box system that employs mechanical shafts.
[0078] In another embodiment, the ship's power generator 41 may be used for
initial liquefaction of the natural gas, as described above in connection with
Figure 3.
However, a smaller separate compressor 45 may optionally be provided to
provide
power to the gas processing facility 40 during the transport stage. In this
respect,
natural gas that vaporizes during transport due to an increase in temperature
within
the containment structure 30 would be captured in the first heat exchanger 42.
The
compressor 45 would be activated by an ancillary smaller motor 45m to
temporarily
operate the condensing process in order to re-cool the natural gas without
interrupting
the ship's propulsion power 43. The ancillary motor 45m draws a smaller amount
of
power from the power generator 41. An electric line "e" is shown between the
power
generator 41 and the smaller generator 45m. Further, a mechanical shaft "s" is
shown
going into the compressor 45. Finally, a bypass loop "b" is provided to
circulate heat
exchanger fluid through the smaller compressor 45 rather than the primary
compressor 44.
[0079] The use of a smaller, ancillary compressor 45 has many advantages.
First,
this arrangement allows reliquefaction of hydrocarbons during transit. This,
in turn,
accommodates a much higher boil-off gas rate from the containment structure
30.
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
This also reduces the insulation requirements for the cryogenic storage.
Further, the
use of a smaller, ancillary compressor 45 keeps the heat exchanger fluid and
system
equipment cold during transit, allowing the vessel to be prepared more quickly
to
receive natural gas more quickly upon docking at an export terminal for
liquefaction.
[0080] In yet another embodiment, two independent power generation systems are
provided. One system operates to power the ship's propulsion system 43, while
the
other system operates the gas processing facility 40 along with the
miscellaneous
process equipment associated with liquefaction and vaporization. Such process
equipment may include firefighting equipment, gas processing controls, fluid
pumps,
and drain valves.
[0081] A method for transporting liquefied natural gas on a vessel is also
provided. The vessel may be a marine vessel such as vessel 100 of Figure 1A, a
barge vessel such as vessel 500A of Figure 5A, or a trailer vessel such as
vessel 500B
of Figure 5B. A gas transfer system, such as system 50 of Figure 3, is
provided on
the vessel. Further, a containment structure is provided on the vessel for
containing
the liquefied natural gas. The containment structure may be, by example, one
of the
structures shown in Figures 1A, 1B, IC, 5A or 5B. In addition, a gas
processing
facility is provided on the vessel. The gas processing facility may be such as
facility
40 of Figures 3 and 4A or facility 40' of Figure 4B, and may selectively cool
and
heat the natural gas.
[0082] As part of the method, the natural gas is on-loaded onto the outfitted
vessel
at an export terminal. The natural gas is on-loaded through a gas transfer
system at
essentially ambient temperature and in a gaseous phase. The transport vessel
may
optionally be integrated with the natural gas production system. The transport
vehicle
would receive raw fluids from the well, and provide the facilities to process
the fluids
into gas, ambient hydrocarbon liquid, and produced water. The production
facilities
would receive utility and operating benefits through integration with the
liquefaction
and vaporization facilities. The transport vehicle would also have the storage
capacity
to transport and deliver any ambient liquid hydrocarbon products created in
the
production system.
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
21
[0083] The natural gas flows through the first heat exchanger 42 of the gas
processing facility 40 so as to cool the natural gas from its ambient
temperature. The
natural gas is brought to a lower temperature where it is in a substantially
liquefied
phase. Thus, the natural gas is "liquefied." The liquefied natural gas is then
stored in
the containment structure 30, and is ready for transport on the vessel to an
import
terminal.
[0084] During the on-loading process, the ship's propulsion system 43 is
preferably shut down. The ship's power generator 41 diverts power to the
liquefaction process facilities 40. Once the ship cargo is full, the gas
processing
system 40 is shut down, and the ship propulsion system 43 is started. The
vessel 100
then transports the cryogenic cargo to the import location.
[0085] Upon arrival at an import terminal, the gas is off-loaded. In order to
off-
load the gas, the gas is pumped through the gas processing facility 40 so as
to heat the
natural gas from a temperature where the natural gas is in its substantially
liquefied
phase, to a temperature where the natural gas is converted back to its gaseous
phase.
The natural gas is then off-loaded through the gas transfer system 50. While
on
station at the import location, the ship's propulsion system 43 is again shut
down, and
the cryogenic cargo is regasified as it is unloaded from the vessel 100. This
allows
for optionally an integrated power generator for both the ship's propulsion
system 43
and the gas processing facility 40.
[0086] In one embodiment of the method invention, partially regasified fluids
are
pumped into a gas storage device on land. An example is a salt dome cavern
facility.
The gas storage device is integrated with the vessel to store pressurized gas
off-loaded
at the gas receiving terminal. The facility can be sized to supply continuous
gas at the
average delivery rate between deliveries. Pressurized gas storage is ideal
because the
cryogenic fluid can be inexpensively pumped to storage pressures before
vaporization
rather than having expensive gas compression with the storage facility.
[0087] It can thus be seen that an LNG transportation vessel is provided, and
that
a method for transporting LNG or other hydrocarbon fluids is also provided.
The
CA 02585211 2007-04-24
WO 2006/052392 PCT/US2005/037245
22
method of transporting, in one aspect, combines liquefaction, transportation
and
regasification processes. In addition, it can be seen that an integrated
system is
provided for transporting natural gas.
[0088] Conventional gas transportation means require large transfer rates over
a
period of 25-30 years to be economically attractive. As a result, many
resources
containing under approximately 5 TSCF (trillion standard cubic feet) of gas
currently
go undeveloped. The disclosed technology may allow an investor to monetize
these
smaller hydrocarbon reserves. The three functions of liquefaction, transport
and
regasification may be integrated into a single re-deployable unit for cost-
effective
transport of natural gas to consumer markets from remote locations. Stated
another
way, the integration of liquefaction, vaporization and transport means enables
recovery of otherwise stranded hydrocarbon resources, and also decreases the
overall
manpower required for operations and maintenance, thus reducing operating
expenses
and crew requirements. The vessel allows monetization of small gas resources,
and
enables development of a series of small resources as it is re-deployable.
