Canadian Patents Database / Patent 2618576 Summary

Third-party information liability

Some of the information on this Web page has been provided by external sources. The Government of Canada is not responsible for the accuracy, reliability or currency of the information supplied by external sources. Users wishing to rely upon this information should consult directly with the source of the information. Content provided by external sources is not subject to official languages, privacy and accessibility requirements.

Claims and Abstract availability

Any discrepancies in the text and image of the Claims and Abstract are due to differing posting times. Text of the Claims and Abstract are posted:

  • At the time the application is open to public inspection;
  • At the time of issue of the patent (grant).
(12) Patent: (11) CA 2618576
(54) English Title: NATURAL GAS LIQUEFACTION PROCESS FOR LNG
(54) French Title: PROCEDE DE LIQUEFACTION DE GAZ NATUREL DESTINE A PRODUIRE UN GNL
(51) International Patent Classification (IPC):
  • F25J 1/00 (2006.01)
(72) Inventors :
  • MINTA, MOSES (United States of America)
  • STANLEY, KEVIN N. (United States of America)
  • STONE, JOHN B. (United States of America)
  • BOWEN, RONALD R. (United States of America)
  • COTE, LINDA J. (United States of America)
(73) Owners :
  • EXXONMOBIL UPSTREAM RESEARCH COMPANY (United States of America)
(71) Applicants :
  • EXXONMOBIL UPSTREAM RESEARCH COMPANY (United States of America)
(74) Agent: BORDEN LADNER GERVAIS LLP
(74) Associate agent:
(45) Issued: 2014-05-27
(86) PCT Filing Date: 2006-05-24
(87) Open to Public Inspection: 2007-02-22
Examination requested: 2011-05-13
(30) Availability of licence: N/A
(30) Language of filing: English

(30) Application Priority Data:
Application No. Country/Territory Date
60/706,798 United States of America 2005-08-09
60/795,101 United States of America 2006-04-26

English Abstract




Embodiments of this invention relate to a process for liquefaction of natural
gas and other methane-rich gas streams, and more particularly to a process for
producing liquefied natural gas (LNG). In a first step of the process, a first
fraction of the feed gas is withdrawn, compressed to a pressure greater than
or equal to 1500 psia, cooled and expanded to a lower pressure to cool the
withdrawn first fraction. The remaining fraction of the feed stream is cooled
by indirect heat exchange with the expanded first fraction in a first heat
exchange process. In a second step a separate stream comprising flash vapor is
compressed, cooled and expanded to a lower pressure providing another cold
stream. This cold stream is used to cool the remaining feed gas stream in a
second indirect heat exchange process. The expanded stream exiting from the
second heat exchange process is used for supplemental cooling in the first
indirect heat exchange step. The remaining feed gas is subsequently expanded
to a lower pressure, thereby partially liquefying this feed gas stream. The
liquefied fraction of this stream is withdrawn from the process as LNG having
a temperature corresponding to the bubble point pressure.


French Abstract

L'invention concerne, selon des modes de réalisation, un procédé de liquéfaction de gaz naturel et autres flux gazeux riches en méthane, et plus particulièrement, un processus de production de gaz naturel liquéfié (GNL). Dans une première étape du processus, une première fraction du flux gazeux est retirée, comprimée à une pression supérieure ou égale à 1500 psia, refroidie puis dilatée à une pression inférieure afin de refroidir ladite première fraction retirée. La fraction restante du flux gazeux est refroidie par échange thermique indirect avec la première fraction dilatée, dans un premier processus d'échange thermique. Dans une seconde étape, un flux séparé comprenant de la vapeur instantanée est comprimée, refroidie puis dilatée à une pression inférieure afin de produire un autre flux froid. Ce flux froid est utilisé pour refroidir le flux gazeux d'alimentation restant, dans un second processus d'échange thermique. Le flux dilaté résultant du second processus d'échange thermique est utilisé pour réaliser un refroidissement supplémentaire dans la première étape d'échange thermique indirect. Le gaz d'alimentation restant est subséquemment dilaté à une pression inférieure pour liquéfier partiellement le flux gazeux d'alimentation. La fraction liquéfiée de ce flux est retirée du processus en tant que GNL dont la température correspond à la pression de point de bulle.


Note: Claims are shown in the official language in which they were submitted.


CLAIMS:
1. A process fat liquefying a gas stream, said process comprising:
providing said gas stream at a gas supply pressure less than 1,000 psia;
providing refrigerants by withdrawing portions of said gas stream, wherein
each of
the portions of said gas stream comprises one of the refrigerants and is rich
in methane;
compressing a first one of said refrigerants to a pressure greater than or
equal to
1500 psia to provide a compressed refrigerant;
cooling said compressed refrigerant by indirect heat exchange with a cooling
fluid;
expanding said compressed refrigerant to further cool said compressed
refrigerant,
thereby producing an expanded, cooled refrigerant;
passing said expanded, cooled refrigerant to a heat exchange area; and
passing said gas stream through said heat exchange area to cool at least part
of said
gas stream by indirect heat exchange with said expanded, cooled refrigerant,
thereby
forming a cooled gas stream,
wherein the gas stream is used as the only source for the refrigerants such
that no
external refrigerants are used, except for water or air.
2. The process of claim 1 wherein one of said portions of said gas stream
is
withdrawn before said gas stream is passed to said heat exchange area
3, The process of claim 1 wherein one of said portions of said gas stream
is
withdrawn from said heat exchange area.
4. The process of claim 1 further comprising providing at least a portion
of
refrigeration duty for said heat exchange area using a closed loop charged
with a flash
vapor produced in said process for liquefying a gas stream, the flash vapor
being a second
one of the refrigerants.
5. The process of claim 4 further comprising:
expanding at least a portion of said cooled gas stream to produce an expanded,

cooled gas stream; and
21

further cooling said expanded, cooled gas stream by indirect heat exchange
with
said closed loop charged with the flash vapor.
6. The process of claim 1 further comprising:
expanding at least a portion of said cooled gas stream to produce an expanded,

cooled gas stream; and
further cooling said expanded, cooled gas stream by indirect heat exchange in
one
or more additional heat exchange areas.
7. The process of claim 1 further comprising:
cooling said gas stream using a plurality of work expansion devices, each of
said
work expansion devices expanding a portion of the gas stream and thereby
cooling said
portion to form one or more expanded, cooled side streams, wherein said
portion of the
gas stream expanded in said work expansion devices is withdrawn from said gas
stream at
a different stage of gas stream cooling; and
cooling said gas stream by indirect heat exchange with said one or more
expanded,
cooled side streams.
8. The process of claim 1 further comprising:
withdrawing the portions of said gas stream;
passing each of the portions of said gas stream to one or more work expansion
devices and expanding each of the portions of said gas stream to expand and
cool said the
portions of said gas stream, thereby forming one or more expanded, cooled side
streams;
passing said expanded, cooled side streams to at least one heat exchange area;

passing said gas stream through said at least one heat exchange area; and
at least partially cooling said gas stream by indirect heat exchange with said
expanded, cooled side streams.
9. The process of any one of claims 5 to 8 wherein said gas stream is first
compressed
to a pressure above the gas supply pressure.
22

10. The process of claim 1 further comprising an expansion stage of said
cooled gas
stream before a final heat exchange step and prior to expansion to produce
LNG.
11. The process of claim 1 further comprising:
expanding at least a portion of said cooled gas stream before a final heat
exchange
step to produce an expanded, cooled gas stream;
passing a portion of said expanded, cooled gas stream to a work-producing
expander and further expanding said portion of said expanded, cooled gas
stream in said
work-producing expander; and
passing the stream emerging from said work-producing expander to a heat
exchange area to further cool the balance of said expanded, cooled gas stream
by indirect
heat exchange in said heat exchange area.
12. The process of claim 1 wherein the first one of said refrigerants is
compressed to a
pressure greater than or equal to 3,000 psia to provide said compressed
refrigerant.
13. The process of claim 1 wherein said heat exchange area comprises
multiple heat
exchange chambers.
14. The process of claim 1 further comprising:
a sub-cooling heat exchange area receiving said gas stream and cooled by
expansion of a second one of said refrigerants to provide a sub-cooled gas
stream;
followed by final expansion of said sub-cooled gas stream and recovery of LNG.
15. The process of claim 14 wherein said second one of said refrigerants is
sub-cooled
in said sub-cooling heat exchange area prior to expansion of said second one
of said
refrigerants.
16. The process of claim 14 wherein a portion of said sub-cooled gas stream
is
expanded and a portion thereof is said second one of said refrigerants.
23

17. The process of claim 16 wherein said portion of said sub-cooled gas
stream is split
into two partial streams, one of said partial streams is further expanded, and
both of said
partial streams comprise said second one of said refrigerants.
18. The process of claim 1 further comprising rejecting nitrogen with LNG
recovery.
24

Note: Descriptions are shown in the official language in which they were submitted.

CA 02618576 2008-02-08
NATURAL GAS LIQUEFACTION PROCESS FOR LNG
TECHNICAL FIELD
Embodiments of the invention relate to a process for liquefaction of
natural gas and other methane-rich gas streams, and more particularly to a
process for
producing liquefied natural gas (LNG).
BACKGROUND
Because of its clean burning qualities and convenience, natural gas has
become widely used in recent years. Many sources of natural gas are located in

remote areas, great distances from any commercial markets for the gas.
Sometimes a
pipeline is available for transporting produced natural gas to a commercial
market.
When pipeline transportation is not feasible, produced natural gas is often
processed
into liquefied natural gas (which is called "LNG") for transport to market.
In the design of an LNG plant, one of the most important
considerations is the process for converting the natural gas feed stream into
LNG.
Currently, the most common liquefaction processes use some form of
refrigeration
system. Although many refrigeration cycles have been used to liquefy natural
gas, the
three types most commonly used in LNG plants today are: (1) the "cascade
cycle,"
which uses multiple single component refrigerants in heat exchangers arranged
progressively to reduce the temperature of the gas to a liquefaction
temperature; (2)
the "multi-component refrigeration cycle," which uses a multi-component
refrigerant
in specially designed exchangers; and (3) the "expander cycle," which expands
gas
from feed gas pressure to a low pressure with a corresponding reduction in
temperature. Most natural gas liquefaction cycles use variations or
combinations of
these three basic types.
1

CA 02618576 2008-02-08
The refrigerants used may be a mixture of components such as
methane, ethane, propane, butane, and nitrogen in multi-component
refrigeration
cycles. The refrigerants may also be pure substances such as propane,
ethylene, or
nitrogen in "cascade cycles." Substantial volumes of these refrigerants with
close
control of composition are required. Further, such refrigerants may have to be

imported and stored imposing logistics requirements. Alternatively, some of
the
components of the refrigerant may be prepared, typically by a distillation
process
integrated with the liquefaction process.
The use of gas expanders to provide the feed gas cooling thereby
eliminating or reducing the logistical problems of refrigerant handling has
been of
interest to process engineers. The expander system operates on the principle
that the
feed gas can be allowed to expand through an expansion turbine, thereby
performing
work and reducing the temperature of the gas. The low temperature gas is then
heat
exchanged with the feed gas to provide the refrigeration needed. Supplemental
refrigeration is typically needed to fully liquefy the feed gas and this may
be provided
by a refrigerant system. The power obtained from the expansion is usually used
to
supply part of the main compression power used in the refrigeration cycle. The

typical expander cycle for making LNG operates at the feed gas pressure,
typically
under about 6,895 kPa (1,000 psia).
Previously proposed expander cycles have all been less efficient
thermodynamically, however, than the current natural gas liquefaction cycles
based
on refrigerant systems. Expander cycles have therefore not offered any
installed cost
advantage to date, and liquefaction cycles involving refrigerants are still
the preferred
option for natural gas liquefaction.
Because expander cycles result in a high recycle gas stream flow rate
and high inefficiency for the pre-cooling (warm) stage, gas expanders have
typically
been used to further cool feed gas after it has been pre-cooled to
temperatures well
below -20 C using an external refrigerant in a closed cycle, for example.
Thus, a
conunon factor in most proposed expander cycles is the requirement for a
second,
external refrigeration cycle to pre-cool the gas before the gas enters the
expander.
7

CA 02618576 2008-02-08
Such a combined external refrigeration cycle and expander cycle is sometimes
referred to as a "hybrid cycle." While such refrigerant-based pre-cooling
eliminates
a major source of inefficiency in the use of expanders, it significantly
reduces the
benefits of the expander cycle, namely the elimination of external
refrigerants.
Additional cooling may also be required after the expander cooling and may be
provided by another external refrigerant system, such as nitrogen or a cold
mixed
refrigerant.
Accordingly, there is still a need for an expander cycle that eliminates
the need for external refrigerants and has improved efficiency, at least
comparable to
that of technologies currently in use.
SUMMARY
Embodiments of the present invention provide a process for liquefying
natural gas and other methane-rich gas streams to produce liquefied natural
gas
(LNG) and/or other liquefied methane-rich gases. The term natural gas as used
in this
specification, including the appended claims, means a gaseous feed stock
suitable for
manufacturing LNG. The natural gas could comprise gas obtained from a crude
oil
well (associated gas) or from a gas well (non-associated gas). The composition
of
natural gas can vary significantly. As used herein, natural gas is a methane-
rich gas
containing methane (CI) as a major component.
In one or more embodiments of the method for producing LNG herein,
a first step is carried out in which a first fraction of the feed gas is
withdrawn,
compressed, cooled and expanded to a lower pressure to cool the withdrawn
first
fraction. The remaining fraction of the feed stream is cooled by indirect heat

exchange with the expanded first fraction in a first heat exchange process. In
a
second step, involving a sub-cooling loop, a separate stream comprised of the
flash
vapor is compressed, cooled and expanded to a lower pressure providing another
cold
stream. This cold stream is used to cool the remaining feed gas stream in a
second
indirect heat exchange process, which constitutes the sub-cooling heat
exchange
process. The expanded stream exiting from the second heat exchange process is
used
3

CA 02618576 2008-02-08
for supplemental cooling in the first indirect heat exchange step. The
remaining feed
gas is subsequently expanded to a lower pressure, thereby partially liquefying
this
feed gas stream. The liquefied fraction of this stream is withdrawn from the
process
as LNG having a temperature corresponding to the bubble point pressure. The
vapor
fraction of this stream is returned to supplement the cooling provided in the
indirect
heat exchange steps. The warmed cooling gases from the various sources are
compressed and recycled.
In one or more other embodiments according to the present invention,
a process for liquefying a gas stream rich in methane is provided, said
process
comprising providing a gas stream rich in methane at a pressure less than
1,000 psia;
providing a refrigerant at a pressure of less than 1,000 psia; compressing
said
refrigerant to a pressure greater than or equal to 1500 psia to provide a
compressed
refrigerant; cooling said compressed refrigerant by indirect heat exchange
with a
cooling fluid; expanding said compressed refrigerant to further cool said
compressed
refrigerant, thereby producing an expanded, cooled refrigerant; passing said
expanded, cooled refrigerant to a heat exchange area; and passing said gas
stream
through said heat exchange area to cool at least part of said gas stream by
indirect heat
exchange with said expanded, cooled refrigerant, thereby forming a cooled gas
stream. In one or more other specific embodiments, providing the refrigerant
at a
pressure of less than 1,000 psia comprises withdrawing a portion of the gas
for use as
the refrigerant. In other embodiments, the portion of the gas stream to be
used as the
refrigerant is withdrawn from the gas stream before the gas stream is passed
to the
heat exchange area. In still other embodiments, the process according to the
present
invention further comprises providing at least a portion of the refrigeration
duty for
the heat exchange area using a closed loop charged with flash vapor produced
in the
process for liquefying the gas stream rich in methane. Additional embodiments
according to the present invention will be apparent to those skilled in the
art.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic flow diagram of one embodiment for producing
LNG in accordance with the process of this invention.
4

CA 02618576 2008-02-08
FIG. 2 is a schematic flow diagram of a second embodiment for
producing LNG that is similar to the process shown in FIG. 1, except that the
gaseous
refrigerant in the compressed, cooled and expanded loop is de-coupled from the
feed
gas and may therefore have a different composition than the feed gas.
FIG. 3 is a schematic flow diagram of a third embodiment for
producing LNG in accordance with the process of this invention that uses a
plurality
of work expansion steps for improved efficiency.
FIG. 4 is a schematic flow diagram of a fourth embodiment for
producing LNG in accordance with the process of this invention that uses a
plurality
of work expansion steps similar to FIG. 3, but also incorporates an additional

expansion step as well as compression of the feed gas to improve performance
of the
expansion steps.
FIG. 5 is a schematic flow diagram of a fifth embodiment for
producing LNG in accordance with the process of this invention that is similar
to the
embodiment shown in FIG. 4, but utilizes an additional side stream and
expansion of
process gas to provide sub-cooling.
FIG. 6 is another embodiment similar to the embodiments shown in
FIG. 1 and FIG. 2 in which the refrigerant for the sub-cooling loop is cooled
in the
sub-cooling heat exchanger prior to expansion.
FIG. 7 is another embodiment in which the sub-cooling loop is coupled
to the feed gas.
FIG. 8 is another embodiment showing an alternative arrangement for
the sub-cooling loop.
FIG. 9 is a similar embodiment to that of FIG. 8 but using split
expanded streams through the sub-cooler wherein an expansion valve, Joules-
Thompson valve, or similar expansion device is used for improved efficiency in
the
sub-cooler.

CA 02618576 2008-02-08
FIG. 10 is another embodiment in which a nitrogen rejection stage has
been integrated for situations in which nitrogen rejection may be needed.
FIG. 11 is yet another embodiment in which the refrigerant for the
sub-cooling loop is derived from the flash vapor from the nitrogen rejection
unit and
is therefore rich in nitrogen content.
DETAILED DESCRIPTION
Embodiments of the present invention provide a process for natural gas
liquefaction using primarily gas expanders and eliminating the need for
external
refrigerants. That is, in some embodiments disclosed herein, the feed gas
itself (e.g.,
natural gas) is used as the refrigerant in all refrigeration cycles. Such
refrigeration
cycles do not require supplemental cooling using external refrigerants (i.e.,
refrigerants other than the feed gas itself or gas that is produced at or near
the LNG
process plant) as typical proposed gas expander cycles do, yet such
refrigeration
cycles have a higher efficiency. In one or more embodiments, cooling water or
air are
the only external sources of cooling fluids and are used for compressor inter-
stage or
after cooling.
FIG. 1 illustrates one embodiment of the present invention in which an
expander loop 5 (i.e., an expander cycle) and a sub-cooling loop 6 are used.
For
clarity, expander loop 5 and sub-cooling loop 6 are shown with double-width
lines in
FIG. 1. In this specification and the appended claims, the terms "loop" and
"cycle"
are used interchangeably. In FIG. 1, feed gas stream 10 enters the
liquefaction
process at a pressure less than about 1200 psia, or less than about 1100 psia,
or less
than about 1000 psia, or less than about 900 psia, or less than about 800
psia, or less
than about 700 psia, or less than about 600 psia. Typically, the pressure of
feed gas
stream 10 will be about 800 psia. Feed gas stream 10 generally comprises
natural gas
that has been treated to remove contaminants using processes and equipment
that are
well known in the art. Before it is passed to a heat exchanger, a portion of
feed gas
stream 10 is withdrawn to form side stream 11, thus providing, as will be
apparent
from the following discussion, a refrigerant at a pressure corresponding to
the
pressure of feed gas stream 10, namely any of the above pressures, including a
6

CA 02618576 2008-02-08
pressure of less than about 1000 psia. Thus, in the embodiment shown in FIG.
1, a
portion of the feed gas stream is used as the refrigerant for expander loop 5.
Although
the embodiment shown in FIG. 1 utilizes a side stream that is withdrawn from
feed
gas stream 10 before feed gas stream 10 is passed to a heat exchanger, the
side stream
of feed gas to be used as the refrigerant in expander loop 5 may be withdrawn
from
the feed gas after the feed gas has been passed to a heat exchange area. Thus,
in one
or more embodiments, the present method is any of the other embodiments herein

described, wherein the portion of the feed gas stream to be used as the
refrigerant is
withdrawn from the heat exchange area, expanded, and passed back to the heat
exchange area to provide at least part of the refrigeration duty for the heat
exchange
area.
Side stream 11 is passed to compression unit 20 where it is compressed
to a pressure greater than or equal to about 1500 psia, thus providing
compressed
refrigerant stream 12. Alternatively, side stream 11 is compressed to a
pressure
greater than or equal to about 1600 psia, or greater than or equal to about
1700 psia,
or greater than or equal to about 1800 psia, or greater than or equal to about
1900
psia, or greater than or equal to about 2000 psia, or greater than or equal to
about
2500 psia, or greater than or equal to about 3000 psia, thus providing
compressed
refrigerant stream 12. As used in this specification, including the appended
claims,
the term "compression unit" means any one type or combination of similar or
different types of compression equipment, and may include auxiliary equipment,

known in the art for compressing a substance or mixture of substances. A
"compression unit" may utilize one or more compression stages. Illustrative
compressors may include, but are not limited to, positive displacement types,
such as
reciprocating and rotary compressors for example, and dynamic types, such as
centrifugal and axial flow compressors, for example.
After exiting compression unit 20, compressed refrigerant stream 12 is
passed to cooler 30 where it is cooled by indirect heat exchange with a
suitable
cooling fluid to provide a compressed, cooled refrigerant. In one or more
embodiments, cooler 30 is of the type that provides water or air as the
cooling fluid,
although any type of cooler can be used. The temperature of compressed
refrigerant
7

CA 02618576 2008-02-08
stream 12 as it emerges from cooler 30 depends on the ambient conditions and
the
cooling medium used and is typically from about 35 F to about 105 F. Cooled
compressed refrigerant stream 12 is then passed to expander 40 where it is
expanded
and consequently cooled to form expanded refrigerant stream 13. In one or more

embodiments, expander 40 is a work-expansion device, such as gas expander
producing work that may be extracted and used for compression.
Expanded refrigerant stream 13 is passed to heat exchange area 50 to
provide at least part of the refrigeration duty for heat exchange area 50. As
used in
this specification, including the appended claims, the term "heat exchange
area"
means any one type or combination of similar or different types of equipment
known
in the art for facilitating heat transfer. Thus, a "heat exchange area" may be
contained
within a single piece of equipment, or it may comprise areas contained in a
plurality
of equipment pieces. Conversely, multiple heat exchange areas may be contained
in a
single piece of equipment.
Upon exiting heat exchange area 50, expanded refrigerant stream 13 is
fed to compression unit 60 for pressurization to form stream 14, which is then
joined
with side stream 11. It will be apparent that once expander loops has been
filled with
feed gas from side stream 11, only make-up feed gas to replace losses from
leaks is
required, the majority of the gas entering compressor unit 20 generally being
provided
by stream 14. The portion of feed gas stream 10 that is not withdrawn as side
stream
11 is passed to heat exchange area 50 where it is cooled, at least in part, by
indirect
heat exchange with expanded refrigerant stream 13. After exiting heat exchange
area
50, feed gas stream 10 is passed to heat exchange area 55. The principal
function of
heat exchange area 55 is to sub-cool the feed gas stream. Thus, in heat
exchange area
55 feed gas stream 10 is sub-cooled by sub-cooling loop 6 (described below) to

produce sub-cooled stream 10a. Sub-cooled stream 10a is then expanded to a
lower
pressure in expander 70, thereby partially liquefying sub-cooled stream 10a to
form a
liquid fraction and a remaining vapor fraction. Expander 70 may be any
pressure
reducing device, including, but not limited to a valve, control valve, Joule
Thompson
valve, Venturi device, liquid expander, hydraulic turbine, and the like.
Partially
liquefied sub-cooled stream 10a is passed to surge tank 80 where the liquefied
8

CA 02618576 2008-02-08
fraction 15 is withdrawn from the process as LNG having a temperature
corresponding to the bubble point pressure. The remaining vapor fraction
(flash
vapor) stream 16 is used as fuel to power the compressor units and/or as a
refrigerant
in sub-cooling loop 6 as described below. Prior to being used as fuel, all or
a portion
of flash vapor stream 16 may optionally be passed from surge tank 80 to heat
exchange areas 50 and 55 to supplement the cooling provided in such heat
exchange
areas.
Referring again to FIG. 1, a portion of flash vapor 16 is withdrawn
through line 17 to fill sub-cooling loop 6. Thus, a portion of the feed gas
from feed
gas stream 10 is withdrawn (in the form of flash gas from flash gas stream 16)
for use
as the refrigerant in sub-cooling loop 6. It will again be apparent that once
sub-
cooling loop 6 is fully charged with flash gas, only make-up gas (i.e.,
additional flash
vapor from line 17) to replace losses from leaks is required. In sub-cooling
loop 6,
expanded stream 18 is discharged from expander 41 and drawn through heat
exchange
areas 55 and 50. Expanded flash vapor stream 18 (the sub-cooling refrigerant
stream)
is then returned to compression unit 90 where it is re-compressed to a higher
pressure
and warmed. After exiting compression unit 90, the re-compressed sub-cooling
refrigerant stream is cooled in cooler 31, which can be of the same type as
cooler 30,
although any type of cooler may be used. After cooling, the re-compressed sub-
cooling refrigerant stream is passed to heat exchange area 50 where it is
further
cooled by indirect heat exchange with expanded refrigerant stream 13, sub-
cooling
refrigerant stream 18, and, optionally, flash vapor stream 16. After exiting
heat
exchange area 50, the re-compressed and cooled sub-cooling refrigerant stream
is
expanded through expander 41 to provide a cooled stream which is then passed
through heat exchange area 55 to sub-cool the portion of the feed gas stream
to be
finally expanded to produce LNG. The expanded sub-cooling refrigerant stream
exiting from heat exchange area 55 is again passed through heat exchange area
50 to
provide supplemental cooling before being re-compressed. In this manner the
cycle
in sub-cooling loop 6 is continuously repeated. Thus, in one or more
embodiments,
the present method is any of the other embodiments disclosed herein further
9

CA 02618576 2008-02-08
comprising providing cooling using a closed loop (e.g., sub-cooling loop 6)
charged
with flash vapor resulting from the LNG production (e.g., flash vapor 16).
It will be apparent that in the embodiment illustrated in FIG. 1 (and in
the other embodiments described herein) that as feed gas stream 10 passes from
one
heat exchange area to another, the temperature of feed gas stream 10 will be
reduced
until ultimately a sub-cooled stream is produced. In addition, as side streams
are
taken from feed gas stream 10, the mass flow rate of feed gas stream 10 will
be
reduced. Other modifications, such as compression, may also be made to feed
gas
stream 10. While each such modification to feed gas stream 10 could be
considered
to produce a new and different stream, for clarity and ease of illustration,
the feed gas
stream will be referred to as feed gas stream 10 unless otherwise indicated,
with the
understanding that passage through heat exchange areas, the taking of side
streams,
and other modifications will produce temperature, pressure, and/or flow rate
changes
to feed gas stream 10.
FIG. 2 illustrates another embodiment of the present invention that is
similar to the embodiment shown in FIG. 1, except that expander loop 5 has
been
replaced with expander loop 7. The other items in FIG. 2 have been previously
described above. Expander loop 7 is shown with double-width lines in FIG. 2
for
clarity. Expander loop 7 utilizes substantially the same equipment as expander
loop 5
(for example, compressor 20, cooler 30, and expander 40, all of which have
been
described above). The gaseous refrigerant in expander loop 7 however, is de-
coupled
from the feed gas and may therefore have a different composition than the feed
gas.
That is, expander loop 7 is essentially a closed loop and is not connected to
feed gas
stream 10. The refrigerant for expander loop 7 is therefore not necessarily
the feed
gas, although it may be. Expander loop 7 may be charged with any suitable
refrigerant gas that is produced at or near the LNG process plant in which
expander
loop 7 is utilized. For example, the refrigerant gas used to charge expander
loop 7
could be a feed gas, such as natural gas, that has only been partially treated
to remove
contaminants.

CA 02618576 2008-02-08
Like expander loop 5, expander loop 7 is a high pressure gas loop.
Stream 12a exits compression unit 20 at a pressure greater than or equal to
about 1500
psia, or greater than or equal to about 1600 psia, or greater than or equal to
about
1700 psia, or greater than or equal to about 1800 psia, or greater than or
equal to
about 1900 psia, or greater than or equal to about 2000 psia, or greater than
or equal
to about 2500 psia, or greater than or equal to about 3000 psia. The
temperature of
compressed refrigerant stream 12a as it emerges from cooler 30 depends on the
ambient conditions and the cooling medium used and is typically about from
about
35 F to about 105 F. Cooled compressed refrigerant stream 12a is then passed
to
expander 40 where it is expanded and further cooled to form expanded
refrigerant
stream 13a. Expanded refrigerant stream 13a is passed to heat exchange area 50
to
provide at least part of the refrigeration duty for heat exchange area 50,
where feed
gas stream 10 is at least partially cooled by indirect heat exchange with
expanded
refrigerant stream 13a. Upon exiting heat exchange area 50, expanded
refrigerant
stream 13a is returned to compression unit 20 for re-compression. hi any of
the
embodiments described herein, expander loops 5 and 7 may be used
interchangeably.
For example, in an embodiment utilizing expander loop 5, expander loop 7 may
be
substituted for expander loop 5.
FIG. 3 shows another embodiment for producing LNG in accordance
with the process of the invention. The process illustrated in FIG. 3 utilizes
a plurality
of work expansion cycles to provide supplemental cooling for the feed gas and
other
streams. The use of such work expansion cycles results in overall improved
efficiency for the liquefaction process. Referring to FIG. 3, feed gas stream
10 again
enters the liquefaction process at the pressures described above. In the
particular
embodiment shown in FIG. 3, side stream 11 is fed to expander loop 5 in the
manner
previously described, but it will be apparent that closed expander loop 7
could be
utilized in the place of expander loop 5, in which case side stream 11 would
not be
necessary. Expander loop 5 operates in the same manner as described above for
the
embodiment shown in FIG. 1, except that expanded refrigerant stream 13 is
passed
through heat exchange area 56, described in detail below, to provide at least
a part of
the refrigeration duty for heat exchange area 56.
11

CA 02618576 2008-02-08
=
The portion of feed gas stream 10 that is not withdrawn as side stream
11 is passed to heat exchange area 56 where it is cooled, at least in part, by
indirect
heat exchange with expanded refrigerant stream 13 and other streams described
below. After exiting heat exchange area 56, feed gas stream 10 is passed
through heat
exchange areas 57 and 58 where it is further cooled by indirect heat exchange
with
additional streams described below. In the present embodiment, first and
second
work expansion cycles are utilized for improved efficiency as follows: before
feed
gas stream 10 enters heat exchange area 57, side stream lib is taken from feed
gas
stream 10. After feed gas stream 10 exits heat exchange area 57, but before it
enters
heat exchange area 58, side stream 11c is taken from feed gas stream 10. Thus,
side
streams 11b and 11c are taken from feed gas stream 10 at different stages of
feed gas
stream cooling. That is, each side stream is withdrawn from the feed gas
stream at a
different point on the cooling curve of the feed gas such that each
successively
withdrawn side stream has a lower initial temperature than the previously
withdrawn
side stream.
Side stream 11b, which is part of the first work expansion cycle, is
passed to expander 42 where it is expanded and consequently cooled to form
expanded stream 13b. Expanded stream 13b is passed through heat exchange areas

56 and 57 to provide at least part of the refrigeration duty for heat exchange
areas 56
and 57. Similarly, side stream 11c, which is part of the second work expansion
cycle,
is passed to expander 43 where it is expanded and consequently cooled to form
expanded stream 13c. Expanded stream 13c is then passed through heat exchange
areas 56, 57, and 58 to provide at least part of the refrigeration duty for
heat exchange
areas 56, 57, and 58. Accordingly, feed gas stream 10 is also cooled in heat
exchange
areas 56 and 57 by indirect heat exchange with expanded streams 13b and 13c.
In
heat exchange area 58 feed gas stream 10 is also cooled by additional indirect
heat
exchange with expanded stream 13c.
Upon exiting heat exchange area 56, expanded streams 13b and 13c
are passed to compression units 61 and 62, respectively, where they are re-
compressed and combined to form stream 14a. Stream 14a is cooled by cooler 32
prior to being re-combined with feed gas stream 10. Cooler 32 can be the same
type
12

CA 02618576 2008-02-08
of cooler or cooler types as coolers 30 and 31. Expanders 42 and 43 are work
expansion devices of the type well know to those of skill in the art.
Illustrative, non-
limiting examples of suitable work expansion devices include liquid expanders
and
hydraulic turbines. Thus, in the embodiment shown in FIG. 3, the feed gas
stream is
further cooled using a plurality of work expansion devices. It will be
apparent to
those of ordinary skill in the art that additional work expansion cycles can
be added to
the embodiment illustrated in FIG. 3, or that a single work expansion cycle
could be
employed. Generally, therefore, one or more work expansion devices may be
employed in the manner described above. Each of the work expansion devices
expands a portion of the feed gas stream and thereby cools such portion,
wherein each
of the portions of the feed gas stream expanded in the work expansion devices
is
withdrawn from the feed gas stream at a different stage of feed gas stream
cooling
(i.e., at a different feed gas stream temperature).
In one or more other embodiments according to the present invention,
the work expansion devices are utilized by withdrawing one or more side
streams
from the feed gas stream; passing said one or more side streams to one or more
work
expansion devices; expanding said one of more side streams to expand and cool
said
one or more side streams, thereby forming one or more expanded, cooled side
streams; passing said one or more expanded, cooled side streams to at least
one heat
exchange area; passing said gas stream through said at least one heat exchange
area;
and at least partially cooling said gas stream by indirect heat exchange with
said one
or more expanded, cooled side streams.
Referring again to FIG. 3, feed gas stream 10, after being cooled in
heat exchange areas 56, 57, and 58, is then passed to heat exchange area 59
where it is
further cooled to produce sub-cooled stream 10a. The principal function of
heat
exchange area 59 is to sub-cool feed gas stream 10. Sub-cooled stream 10a is
then
expanded to a lower pressure in expander 85, thereby partially liquefying sub-
cooled
stream 10a to form a liquid fraction and a remaining vapor fraction. Expander
85
may be any pressure reducing device, including, but not limited to a valve,
control
valve, Joule Thompson valve, Venturi device, liquid expander, hydraulic
turbine, and
the like. Partially liquefied sub-cooled stream 10a is passed to surge tank 80
where
13

CA 02618576 2008-02-08
the liquefied fraction 15 is withdrawn from the process as LNG having a
temperature
corresponding to the bubble point pressure. The remaining vapor fraction
(flash
vapor) stream 16 is used as fuel to power the compressor units and/or as a
refrigerant
in sub-cooling loop 8 in a manner substantially the same as previously
described for
sub-cooling loop 6. As can be seen from FIG. 3, sub-cooling loop 8 is similar
to sub-
cooling loop 6, except that sub-cooling loop 8 supplies cooling to four heat
exchange
areas (heat exchange areas 56, 57, 58, and 59).
FIG. 4 illustrates yet another embodiment of the present invention.
The embodiment shown in FIG. 4 is substantially the same as the embodiment
shown
in FIG. 3, except that compression unit 25 and expander 35 have been added.
Expander 35 may be any type of liquid expander or hydraulic turbine. Expander
35 is
placed between heat exchange areas 58 and 59 such that feed gas stream 10
flows
from heat exchange area 58 into expander 35 where it is expanded, and
consequently
cooled to produce expanded feed gas stream 10b. Stream 10b then is passed to
heat
exchange area 59 where it is sub-cooled to produce sub-cooled stream 10c. By
expanding and consequently cooling feed gas stream 10 in expander 35 to
produce
stream lob, the overall cooling load on sub-cooling loop 8 is advantageously
reduced.
Thus, in one or more embodiments, the present method is any of the other
embodiments disclosed herein further comprising expanding at least a portion
of the
cooled feed gas stream to produce a cooled, expanded feed gas stream (e.g.,
stream
10b); and further cooling the cooled, expanded feed gas stream by indirect
heat
exchange with a closed loop (e.g., sub-cooling loop 6 or 8) charged with flash
vapor
resulting from the LNG production (e.g., flash vapor 16).
Continuing to refer to FIG. 4, compression unit 25 is utilized to
increase the pressure of feed gas stream 10 prior to entry into the
liquefaction process.
Thus, feed gas stream 10 is passed to compression unit 25 where it is
compressed to a
pressure above the feed gas supply pressure or, in one or more other
embodiments, to
a pressure greater than about 1200 psia. Alternatively, feed gas stream 10 is
compressed to a pressure greater than or equal to about 1300 psia, or greater
than or
equal to about 1400 psia, or greater than or equal to about 1500 psia, or
greater than
or equal to about 1600 psia, or greater than or equal to about 1700 psia, or
greater
14

CA 02618576 2008-02-08
than or equal to about 1800 psia, or greater than or equal to about 1900 psia,
or
greater than or equal to about 2000 psia, or greater than or equal to about
2500 psia,
or greater than or equal to about 3000 psia. After compression, feed gas
stream 10 is
passed to cooler 33 where it is cooled prior to being passed to heat exchange
area 56.
It will be appreciated that to the extent compression unit 25 is used to
compress feed
gas stream 10 (and, hence, side stream 11) to a lower pressure than that
desired for
compressed refrigerant stream 12, compression unit 20 may be used to boost the

pressure.
The compression of feed gas stream 10 as described above provides
three benefits. First, by increasing the pressure of the feed gas stream, the
pressures
of side streams 11b and 11c are also increased, with the result that the
cooling
performance of work expansion devices 42 and 43 is enhanced. Second, the heat
transfer coefficient in the heat exchange areas is improved. Thus, in one or
more
embodiments, the process for producing LNG described herein is carried out
according to any of the other embodiments describe herein wherein the feed gas
is
compressed to the pressures described above prior to entry into a heat
exchange area.
In still other embodiments, the present method comprises providing
supplemental
cooling for the feed gas stream from a plurality of work expansion devices,
each of
the work expansion devices expanding a portion of the feed gas stream and
thereby
cooling the portion to form one or more expanded, cooled side streams, wherein
each
of the portions of the feed gas stream expanded in the work expansion devices
is
withdrawn from the feed gas stream at a different stage of feed gas stream
cooling
(i.e., at a different feed gas stream temperature); and cooling said feed gas
stream by
indirect heat exchange with said one or more expanded, cooled side streams.
In still other embodiments, each of the above-described portions of
feed gas has a pressure, prior to expansion, greater than about 1200 psia, or
greater
than or equal to about 1300 psia, or greater than or equal to about 1400 psia,
or
greater than or equal to about 1500 psia, or greater than or equal to about
1600 psia,
or greater than or equal to about 1700 psia, or greater than or equal to about
1800
psia, or greater than or equal to about 1900 psia, or greater than or equal to
about
2000 psia, or greater than or equal to about 2500 psia, or greater than or
equal to

CA 02618576 2008-02-08
about 3000 psia. In yet other embodiments, the present method is any of the
other
embodiments described herein further comprising compressing the feed gas
stream to
any of the pressures described above to produce a pressurized feed gas stream;

feeding the pressurized feed gas stream to a work expansion device, or to a
plurality
of work expansion devices; expanding the compressed feed gas stream through
the
work expansion device, or through a plurality of work expansion devices, to
provide
supplemental cooling for the feed gas stream.
A third benefit obtained by compression the feed gas stream as
described above is that the cooling capacity of expander 35 is improved, with
the
result that expander 35 is able to even further reduce the cooling load on sub-
cooling
loop 8. It will be appreciated that compression unit 25 and/or expander 35
could also
be advantageously added to other embodiments described herein to provide
similar
reductions in the cooling load on the sub-cooling loops utilized in those
embodiments
or other improvements in cooling, and that compression unit 25 and expander 35
may
be used independently of each other in any embodiment herein. Moreover, it
will also
be appreciated that the cooling capacity of expander 35 (or the work expansion

devices 42 and 43) will be improved, even without compression of the feed
stream, to
the extent the feed stream is supplied at a pressure above the bubble point
pressure of
the LNG. For example, if the feed gas is supplied at any of the pressures
described
above resulting from compression of the feed gas, the benefit of such pressure
will
obviously be obtainable without additional compression. Therefore, in
interpreting
this specification, including the appended claims, the use of work expansion
devices
and/or expander 35 to expand streams having pressures above about 1200 psia
should
not be construed as requiring the use or presence of compression unit 25 or of
any
other compressor or compression step.
FIG. 5 is a schematic flow diagram of a fifth embodiment for
producing LNG in accordance with the process of this invention that is similar
to the
embodiment shown in FIG. 4, but utilizes yet another expansion step to provide
sub-
cooling. Referring to FIG. 5, it will be seen that sub-cooling loop 8 is not
present in
the embodiment shown in FIG. 5. Instead, side stream 11d is taken from stream
10b
and passed to expansion device 105 where it is expanded and consequently
cooled to
16

CA 02618576 2008-02-08
form expanded stream 13d. Expansion device 105 is a work-producing expander,
many types of which are readily available. Illustrative, non-limiting examples
of such
devices include liquid expanders and hydraulic turbines. Expanded stream 13d
is
passed through heat exchange areas 59, 58, 57, and 56 to provide at least part
of the
refrigeration duty for those heat exchange areas. As can be seen from FIG. 5,
stream
10b is also cooled by indirect heat exchange with expanded stream 13d, as well
as by
the flash vapor stream 16. Thus, in one or more embodiments, the inventive
process
further comprises expanding at least a portion of the cooled gas stream (feed
gas
stream 10) in expander 35 before the final heat exchange step (for example,
prior to
heat exchange area 59) to produce an expanded, cooled gas stream (for example,

stream 10b); passing a portion of said expanded, cooled gas stream to a work-
producing expander; further expanding said expanded, cooled gas stream in said

work-producing expander; and passing the stream emerging from said work-
producing expander (for example, stream 13d) to a heat exchange area to
further cool
said expanded, cooled gas stream by indirect heat exchange in said heat
exchange
area.
Upon exiting heat exchange area 56, expanded stream 13d is passed to
compression unit 95 where it is re-compressed and combined with the streams
emerging from compression units 61 and 62 to form part of stream 14a, which is

cooled and then re-cycled to feed stream 10 as before.
A further embodiment shown in FIG. 6 is similar to the embodiment
shown in FIG.1 and described above, except that sub-cooling loop 6 has been
modified such that after exiting heat exchange area 50, the re-compressed and
cooled
sub-cooling refrigerant stream is further cooled in heat exchange area 55
prior to
being expanded through expander 41. This embodiment is favorable where a
cooling
fluid is used that does not present much condensation after expander 41.
FIG. 7 depicts another embodiment in which sub-cooling loop 6a uses
a portion of feed gas 10. The portion of feed gas 10 is re-pressurized in
compressor
25 and cooled in cooler 33 from 201, in the same fashion as in FIG. 4.
17

CA 02618576 2008-02-08
FIG. 8 is another embodiment similar to FIG. 7 showing an alternative
arrangement for the sub-cooling loop 6. Depending on the composition of feed
gas
10, an additional compressor (not shown) may be used to prevent condensation
in the
sub-cooling loop or to ensure adequate line pressures.
FIG. 9 depicts an embodiment for use with certain feed gas 10
compositions and/or pressures. To better match the cooling curve of the feed
gas 10
being cooled for LNG collection, to the cooling curve of that portion of feed
gas 10
being used for cooling in sub-cooling heat exchange area 55, it may be
necessary to
further expand a split of the portion of the refrigerant gas going to the sub-
cooling
loop 6. This is accomplished using an expansion valve 82 or other expander
(e.g., a
Joules-Thompson valve) to provide supplemental cooling in sub-cooling loop 6.
FIG. 10 represents another embodiment showing the integration of a
nitrogen rejection stage using distillation column 81 or equivalent device,
for the case
where nitrogen rejection is needed, based on feed gas 10 composition. This may
be
needed to meet the nitrogen specification of product LNG for transmission and
end
use.
FIG. 11 represents another embodiment showing the integration of a
nitrogen rejection unit, where the flash vapor from the nitrogen rejection
unit is used
as refrigerant for the sub-cooling loop. The resulting refrigerant is
therefore rich in
nitrogen.
EXAMPLE
A hypothetical mass and energy balance was carried out to illustrate
the embodiment shown in FIG. 4, and the results are shown in the Table below.
The
data were obtained using a commercially available process simulation program
called
HYSYSTm (available from Hyprotech Ltd. of Calgary, Canada); however, other
commercially available process simulation programs can be used to develop the
data,
including for example HYSIMmi, PROIITM, and ASPEN PLUSTM, which are familiar
to those of ordinary skill in the art. This example assumed that feed gas
stream 10
had the following composition in mole percent: CI: 90.25%; C2: 5.70%; C3:
0.01%;
18

CA 02618576 2008-02-08
=
N2: 4.0%; He: 0.04%. The data presented in the Table are offered to provide a
better
understanding of the embodiment shown in FIG. 4, but the invention is not to
be
construed as unnecessarily limited thereto. The temperatures, pressures, and
flow
rates can have many variations in view of the teachings herein. The specific
temperature, pressure, and flow rate calculated for state points 201 through
214 (at the
locations shown in FIG. 4) are set forth in the Table.
In one embodiment of the inventive method, by controlling the
temperature of the stream emerging from the final heat exchange area, the
volume of
flash vapor stream 16 is controlled to match the fuel requirements of the
compression
units and other equipment. For example, referring to FIG. 4, the temperature
at state
point 207 can be controlled to produce more or less flash vapor (stream 16)
depending
on the fuel requirements. Higher temperatures at state point 207 will result
in the
production of more flash vapor (and hence more available fuel), and vice-
versa.
Alternatively, the temperature may be adjusted such that the flash vapor flow
rate is
higher than the fuel requirement, in which case the excess flow above the fuel
flow
requirement may be recycled after compression and cooling.
19

CA 02618576 2008-02-08
,
TABLE
Temperature Pressure Flow
State Point (deg. F) (psia) (lb-mole/hr)
201 262 985 3.35 x 10'
,
202 100 1500 1.08 x 106
203 -36 1480 4.85x 105
204 -130 1470 3.35x
205 -213 1460 3.35 x 105
206 -229 48 3.35 x 105
207 -236 42 3.35 x 105
208 -254 18 3.35x 105 -
209 -217 71 3.12x 105
210 -140 420 2.29x 104
211 100 126 2.57x 104
212 -240 44 2.57x 104
213 100 3000 8.57x 105
214 -40 895 8.57x 105
A person skilled in the art, particularly one having the benefit of the
teachings herein, will recognize many modifications and variations to the
specific
embodiments disclosed above. For example, features shown in one embodiment may

be added to other embodiments to form additional embodiments. Thus, the
specifically disclosed embodiments and example should not be used to limit or
restrict
the scope of the invention, which is to be determined by the claims that
follow.

A single figure which represents the drawing illustrating the invention.

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Admin Status

Title Date
Forecasted Issue Date 2014-05-27
(86) PCT Filing Date 2006-05-24
(87) PCT Publication Date 2007-02-22
(85) National Entry 2008-02-08
Examination Requested 2011-05-13
(45) Issued 2014-05-27

Abandonment History

There is no abandonment history.

Maintenance Fee

Description Date Amount
Last Payment 2020-04-21 $250.00
Next Payment if small entity fee 2021-05-25 $225.00
Next Payment if standard fee 2021-05-25 $450.00

Note : If the full payment has not been received on or before the date indicated, a further fee may be required which may be one of the following

  • the reinstatement fee set out in Item 7 of Schedule II of the Patent Rules;
  • the late payment fee set out in Item 22.1 of Schedule II of the Patent Rules; or
  • the additional fee for late payment set out in Items 31 and 32 of Schedule II of the Patent Rules.

Patent fees are adjusted on the 1st of January every year. The amounts above are the current amounts if received by December 31 of the current year.
Please refer to the CIPO Patent Fees web site to see the fee amounts that will be in effect as of January 1st next year.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Registration of Documents $100.00 2008-02-08
Registration of Documents $100.00 2008-02-08
Filing $400.00 2008-02-08
Maintenance Fee - Application - New Act 2 2008-05-26 $100.00 2008-04-14
Maintenance Fee - Application - New Act 3 2009-05-25 $100.00 2009-03-23
Maintenance Fee - Application - New Act 4 2010-05-25 $100.00 2010-03-25
Maintenance Fee - Application - New Act 5 2011-05-24 $200.00 2011-03-23
Request for Examination $800.00 2011-05-13
Maintenance Fee - Application - New Act 6 2012-05-24 $200.00 2012-03-23
Maintenance Fee - Application - New Act 7 2013-05-24 $200.00 2013-04-24
Final Fee $300.00 2014-03-17
Maintenance Fee - Application - New Act 8 2014-05-26 $200.00 2014-03-18
Maintenance Fee - Patent - New Act 9 2015-05-25 $200.00 2015-04-13
Maintenance Fee - Patent - New Act 10 2016-05-24 $250.00 2016-04-12
Maintenance Fee - Patent - New Act 11 2017-05-24 $250.00 2017-04-13
Maintenance Fee - Patent - New Act 12 2018-05-24 $250.00 2018-04-12
Maintenance Fee - Patent - New Act 13 2019-05-24 $250.00 2019-04-15
Maintenance Fee - Patent - New Act 14 2020-05-25 $250.00 2020-04-21
Current owners on record shown in alphabetical order.
Current Owners on Record
EXXONMOBIL UPSTREAM RESEARCH COMPANY
Past owners on record shown in alphabetical order.
Past Owners on Record
BOWEN, RONALD R.
COTE, LINDA J.
MINTA, MOSES
STANLEY, KEVIN N.
STONE, JOHN B.
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.

To view selected files, please enter reCAPTCHA code :




Filter Download Selected in PDF format (Zip Archive)
Document
Description
Date
(yyyy-mm-dd)
Number of pages Size of Image (KB)
Abstract 2008-02-08 2 80
Claims 2008-02-08 5 165
Description 2008-02-08 20 1,093
Drawings 2008-02-08 11 158
Representative Drawing 2008-02-08 1 11
Cover Page 2008-05-02 1 51
Claims 2008-02-09 5 152
Description 2008-02-09 20 941
Claims 2013-07-11 4 142
Representative Drawing 2014-05-02 1 7
Cover Page 2014-05-02 1 51
PCT 2008-02-08 2 68
Assignment 2008-02-08 8 292
Prosecution-Amendment 2008-02-08 31 1,299
Prosecution-Amendment 2011-05-13 1 30
Prosecution-Amendment 2013-01-21 2 78
Prosecution-Amendment 2013-07-11 7 281
Correspondence 2014-03-17 1 39