Sivert Vist et al.

Patent Trials and Appeals Board

Jun 24, 2020

2019001275 (P.T.A.B. Jun. 24, 2020)

UNITED STATES PATENT AND TRADEMARK OFFICE
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
13/580,977 11/06/2012 Sivert Vist 0312-0138PUS1 4422
127226 7590 06/24/2020
BIRCH, STEWART, KOLASCH & BIRCH, LLP
8110 Gatehouse Road
Suite 100 East
Falls Church, VA 22042-1248
EXAMINER
KING, BRIAN M
ART UNIT PAPER NUMBER
3763
NOTIFICATION DATE DELIVERY MODE
06/24/2020 ELECTRONIC
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
Notice of the Office communication was sent electronically on above-indicated "Notification Date" to the
following e-mail address(es):
mailroom@bskb.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte SIVERT VIST, TORE LØLAND, MORTEN SVENNING, and
SILJA ERIKSSON GYLSETH
Appeal 2019-001275
Application 13/580,977
Technology Center 3700
Before JENNIFER D. BAHR, DANIEL S. SONG, and
BENJAMIN D. M. WOOD, Administrative Patent Judges.
WOOD, Administrative Patent Judge.
DECISION ON APPEAL
STATEMENT OF THE CASE
Pursuant to 35 U.S.C. § 134(a), Appellant1 appeals from the
Examiner’s July 14, 2017 Non-Final Action rejecting claims 19–21. See
Non-Final Act. 1. Claims 1–18 have been canceled. Appeal Br., Claims
App. 1. We have jurisdiction under 35 U.S.C. § 6(b).
We REVERSE.

1 “Appellant” refers to the applicant as defined in 37 C.F.R. § 1.42.
Appellant identifies the real party in interest as Statoil Petroleum AS.
Appeal Br. 1.
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CLAIMED SUBJECT MATTER
The claims are directed to a method of operating a liquefied natural
gas (LNG) plant during turndown. Claim 19, reproduced below, is
illustrative of the claimed subject matter:
19. A method for operation of a liquefied natural gas (LNG)
plant, wherein the plant comprises:
an inlet for receiving natural gas;
a CO2 removal unit;
a drying and mercury-removal unit;
a pre-cooling or refrigeration unit;
a liquefaction unit;
an end flash or N2 stripping unit; and
an LNG storage tank;
wherein natural gas enters at the inlet, flows along a flow
path through the CO2 removal unit, the drying and mercury-
removal unit, the pre-cooling or refrigeration unit, the
liquefaction unit and end flash or N2 stripping unit in tum and is
stored as liquefied natural gas in the LNG storage tank and is
stored as liquefied natural gas in the storage tank;
the plant further comprising an LNG pump connected to
the end flash or N2 stripping unit; and
an LNG vaporizer connected to the LNG pump;
the method comprising the steps of:
removing LNG from the end flash or N2 stripping unit;
passing the removed LNG through the LNG pump, to
pump the removed LNG to a pressure of about 5–10 MPa;
passing the pressurized LNG to the LNG vaporizer to
vaporize the pressurized LNG so that the pressurized LNG is
transformed to gas phase; and
re-admitting the vaporized LNG to the flow path at a point
downstream of the inlet and upstream of the liquefaction unit;
and
wherein the method is carried out during turndown of the
LNG plant, when the LNG storage tank is full or when there is
an interruption in supply of natural gas through the inlet, and the
method is carried on until the LNG can be loaded from the LNG
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storage tank, or the supply of natural gas at the inlet is
recommenced.
REFERENCES
The prior art relied upon by the Examiner is:
Name Reference Date
Newton US 4,675,037 June 23, 1987
Kimble US 2003/0177785 A1 Sep. 25, 2003
Turner US 2007/0107465 A1 May 17, 2007
Martinez US 2009/0282865 A1 Nov. 19, 2009
Coyle US 2010/0011663 A1 Jan. 21, 2010
REJECTION
Claims 19–21 are rejected under pre–AIA 35 U.S.C. § 103(a) as
unpatentable over Kimble, Coyle, Newton, Turner, and Martinez.
OPINION
Independent claim 19 recites a method for operating an LNG plant
during turndown (reduced production) of the plant, comprising the steps of
removing LNG from the end flash or N2 stripping unit, recirculating it
through a LNG pump and vaporizer, and re-admitting the vaporized LNG
back to the natural-gas flow path downstream of the inlet and upstream of
the liquefaction unit. Appeal Br., Claims App. 1–2. According to the
Specification, recirculating LNG in this manner avoids having to shut the
plant down—thus saving time for re-start of the plant and wear of the plant
during shut-down and re-start—when full production is not possible because
natural gas supply is interrupted or storage for LNG is not available. Spec.,
1:20–2:7. Claim 19 specifically recites that the claimed method “is carried
out during turndown of the LNG plant, when the LNG storage tank is full or
when there is an interruption in supply of natural gas through the inlet, and
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the method is carried on until the LNG can be loaded from the LNG storage
tank, or the supply of natural gas at the inlet is recommenced.” Appeal Br.,
Claims App. 2 (emphasis added). There does not appear to be any dispute
that performing the claimed method “until the LNG can be loaded from the
LNG storage tank, or the supply of natural gas at the inlet is recommenced,”
means that the method is not performed when those conditions are met.
The Examiner finds that Kimble teaches most of the limitations of
claim 1, including an inlet; a liquefaction unit; an LNG pump connected to
an end flash unit; an LNG vaporizer connected to the LNG pump; and the
steps of removing LNG from the end flash unit, passing the removed LNG
to the LNG vaporizer to vaporize the pressurized LNG so that the
pressurized LNG is transformed to gas phase, and re-admitting the vaporized
LNG to the flow path at a point downstream of the inlet and upstream of the
liquefaction unit. Non-Final Act. 5. The Examiner acknowledges, however,
that Kimble does not teach, inter alia, that “the method is carried out during
turndown of the LNG plant.” Id. at 7 (citing Kimble ¶¶ 42–43, 45–46,
Abstract, Fig. 4). The Examiner therefore turns to Newton for this
limitation.
Newton teaches a system for reliquefying boiloff vapors from an LNG
storage container on an LNG tanker caused by heat leakage into the LNG
storage container. Newton, 1:12–14, 26–28, Fig. 2. Newton’s system may
experience reduced vapor flow due to, e.g., “reduced storage container liquid
inventory during a tanker return journey.” Id. at 2:23–28. Newton discloses
that “[i]n order to prevent the problems of shutdown and restart of the
reliquefier, it is proposed to artificially provide a constant load to the
reliquefier by revaporization of the condensed vapor.” Id. at 2:30–33; see
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also id. at 2:37–39 (“The use of [our] revaporizer in the present invention is
useful in preventing shutdown of the reliquefier at lower loadings.”).
According to the Examiner, “[w]hen [Newton’s revaporization
process] is not needed, the control valve (31) is closed” to stop redirecting
LNG through the revaporizer. Id. (citing Newton, 4:37). The Examiner
determines that it would have been obvious to one of ordinary skill in the art
to operate Kimble’s LNG recirculation process during turndown “to prevent
the problems of shutdown and restart of the liquefier by artificially providing
a constant load to the system.” Id. The Examiner acknowledges that
Kimble’s process for recirculation LNG provides some of the refrigeration
to the LNG plant during normal operation, but “in Kimble the refrigeration
provided by the vaporization of the LNG can be compensated for by the
addition of other refrigeration cycles.” Id. (citing Kimble ¶ 47).
Appellant responds that Kimble’s system recirculates LNG not during
turndown, but to provide a portion of the coolant during normal “steady
state” plant operation. Appeal Br. 7–8. Appellant asserts that:
[S]ome of the produced and cooled PLNG [pressurized liquefied
natural gas] is taken from a separation tank 80 and is passed
through heat exchangers 71 and 61 (as a refrigerant) to provide
some of the cooling of the natural gas flowing through the
cooling side of those heat exchangers from the source of Feed
Gas. Therefore, heat is transferred via the heat exchanger from
the feed gas to the already-liquefied gas. This is done to reduce
the cost of the refrigeration system and reduce the weight of the
liquefaction system to make it more suitable for offshore
applications. . . . Whilst this “refrigerant” gas is finally
recirculated back to the separation tank, this is purely incidental;
its use as a refrigerant is not reliant upon this.
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Id. at 8 (citing Kimble ¶ 5). Appellant further contends that “[a]lthough
Kimble briefly discusses that additional refrigeration cycles, heat exchangers
and expanders can be combined with the liquefaction system . . . the
recirculation of the PLNG as a refrigerant to provide a portion of the cooling
is a fundamental aspect of the disclosed system of Kimble.” Id.
In response to Appellant’s argument that Kimble’s LNG recirculation
is used to provide refrigeration to aid in liquefying natural gas during normal
plant operation, and therefore would not be terminated when the plant is not
in turndown as claim 19 requires, the Examiner asserts that “Kimble
considers having additional liquefaction systems including additional
refrigeration cycles to aid in liquefying the natural gas.” Ans. 13.
According to the Examiner, “[t]he systems as discussed by Kimble as being
additional are alone capable of producing LNG as they are standalone
systems and as such, one could use them instead of using that in Kimble to
produce the necessary PLNG and then use the method of Newton to
maintain conditions during start-up and turndown in the used liquefaction
system.” Id. at 14.
We do not sustain this rejection. As noted above, claim 19 requires
that its method be performed during turndown caused by insufficient supply
of feed gas or insufficient storage capacity for processed LNG, but ceases
when those conditions are not met (i.e., it would not be performed under
normal operating conditions). Kimble’s LNG recirculation process, on
which the Examiner relies, is used to provide a portion of the cooling of the
feed gas during normal plant operation. Kimble ¶¶ 42–46. The Examiner
determines that, based on Newton’s use of a “revaporizer” during turndown
operations, as well as Kimble’s suggestion that one of ordinary skill in the
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art “could add additional refrigeration cycles, heat exchangers and expanders
to the embodiments discussed above,” it would have been obvious to
discontinue use of Kimble’s LNG recirculation process during normal
operation. We do not consider these teachings as sufficient to render
obvious the cessation of a process under conditions for which it was
designed to operate. Newton may have suggested maintaining Kimble’s
LNG recirculation during turndown, but not its cessation when not in
turndown. Kimble’s teaching that “additional” refrigeration cycles may
have been used does not amount to a teaching that the LNG recirculation
system would not be used. This is particularly true given that the purpose of
using recirculated LNG to assist with cooling is to reduce the cost and
weight of cooling systems in offshore LNG plants. Kimble ¶ 5. It would be
contrary to this goal to have a system that assists in cooling but is not used.
Even if the Examiner is correct that the systems that Kimble refers to are
“standalone” systems that “are alone capable of producing LNG,” Kimble
does not teach using them as standalone systems, but only as “additional”
systems.
CONCLUSION
The Examiner’s rejection is reversed.
DECISION SUMMARY
Claims
Rejected
35 U.S.C. § Reference(s)/Basis Affirmed Reversed
19–21 103 Kimble, Coyle,
Newton, Turner,
Martinez
19–21

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REVERSED