DETAILED ACTION
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Election/Restrictions
In rehearsal, in response to the restriction requirement dated 04/22/2024, the Applicant elected Group I (claims 1-6, 21-23, 25), Species 4 (Fig. 4), Subspecies A, Subspecies E, and Subspecies C without traverse in the reply filed on 10/31/24. New Claim(s) 28 is/are withdrawn from further consideration pursuant to 37 CFR 1.142(b) as being drawn to a nonelected species or subspecies, there being no allowable generic or linking claim. Claim 28 does not read on the elected species and subspecies because in the elected species the condensed boil-off gas stream is returned to a top of the storage tank not a bottom of the storage tank.
Examiner Comment
The applicant is thanked for providing line numbers to the claims.
Claim Rejections - 35 USC § 112
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION.—The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph:
The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.
Claim(s) 4-6, 21-23, 27 is/are rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention.
In regard to claim 4, the recitations, “it” (page 3, line 10, 13) are indefinite for being unclear what “it” references.
In regard to claim 6, the recitation, “of step (a)” (page 3, line 21) is indefinite for improperly reintroducing step (a) and it not understood why the step is not referenced properly.
In regard to claim 21, the recitation, “step (b)” (page 4, line 1) is indefinite as it is not clear if this is a reference to the step (b) or introduces some other step (b), the recitation should properly reference the step (b).
In regard to claim 23, the recitation, “prior to filling of the storage tank, performing a cooldown of the storage tank using the pump and spray header” is indefinite for not being clear how any “cooldown” operation could be performed with the pump before or prior to filling the storage tank, since prior to filling, there is no liquid natural gas in the tank. The recitation is logically inconsistent and unclear.
In regard to claim 27, the recitation, “the top” (line 27, page 4) lacks proper antecedent basis.
All of the claims have been evaluated under the three-prong test set forth in MPEP § 2181, subsection I, and it is considered that none of the claim recitations should be interpreted under 35 U.S.C. 112(f) or pre-AIA 35 U.S.C. 112, sixth paragraph.
Claim Rejections - 35 USC § 102
The following is a quotation of the appropriate paragraphs of 35 U.S.C. 102 that form the basis for the rejections under this section made in this Office action:
A person shall be entitled to a patent unless –
(a)(1) the claimed invention was patented, described in a printed publication, or in public use, on sale or otherwise available to the public before the effective filing date of the claimed invention.
Claim(s) 1, 2, 21 is/are rejected under 35 U.S.C. 102(a)(1) as being anticipated by Limb (GB 2069119).
In regard to claim 1, Limb teaches a method for re-condensing a boil-off gas stream (21) comprising natural gas from a storage tank (1), the method comprising:
(a) at least partially condensing the boil-off gas stream (21) in a first heat exchanger (at least 3) against a two phase refrigerant stream (30) to form an at least partially condensed boil-off gas stream (22) and a gaseous refrigerant stream (at least part of 28), the two phase refrigerant stream (30) comprising no more than 5 mol% hydrocarbons and at least 90 mol% of nitrogen (page, 2, line 60-65, refrigerant is nitrogen; note that the claim does not require any hydrocarbons in the refrigerant since 0% hydrocarbons is within the scope of no more than 5% and Limb explicitly teaches that the refrigerant is Nitrogen and therefore, the nitrogen identified in Limb is at least 90% nitrogen, since the refrigerant identified is only nitrogen), the two-phase refrigerant stream (30) having a gas phase portion (gas) and a liquid phase portion (liquid) in the first heat exchanger (3) (page 2, line 120-125; see that the fluid 30 is vaporized in 3 by cooling the boil-off 21 and thus gas and liquid are present in the first heat exchanger 3);
(b) returning the at least partially condensed boil-off gas stream (22) to the storage tank (1);
(c) heating the gaseous refrigerant stream (part of 28) in a second heat exchanger (4, 5, 6) against a high pressure refrigerant stream (25) (interpreted as merely higher in pressure than any recited low or medium pressure stream) to form a warmed refrigerant stream (28, 23);
(d) compressing the warmed refrigerant stream (28, 23) in a compression system (7, 9) to form a compressed refrigerant stream (after 9 at least);
(e) cooling the compressed refrigerant stream (after 9 at least) in a third heat exchanger (11) to form the high pressure refrigerant stream (25);
(f) cooling the high pressure refrigerant stream (25) against the gaseous refrigerant stream (part of 28) in the second heat exchanger (4, 5, 6) to form a cooled high pressure refrigerant stream (25 after at least some cooling);
(g) separating the cooled high pressure refrigerant stream (25 after at least some cooling) into a first portion (toward 29) and a second portion (26);
(h) expanding the second portion (26) of the cooled high pressure refrigerant stream (25 after at least some cooling) to form an expanded refrigerant stream (27).
In regard to claim 2, Limb teaches (i) combining the expanded refrigerant stream (27) with the gaseous refrigerant stream (part of 28) before performing at least a portion of the step (c) (see figure).
In regard to claim 21, Limb teaches that the step (b) comprises returning the at least partially condensed boil-off gas stream (22) to a vapor space (top of 1) of the storage tank (1) and the at least partially condensed boil-off gas stream is only partially condensed during the performance of the step (b) (natural heat leak into the liquid will cause at least some vapor formation; in addition, during an initial phase of recondensing of the BOG, not all BOG will be condensed).
In regard to claim 26, Limb teaches that the at least partially condensed boil-off gas stream (22) is returned to the storage tank by gravity (see that gravity aides in the return; note that the recitation does not exclude the use of pump(s)).
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries set forth in Graham v. John Deere Co., 383 U.S. 1, 148 USPQ 459 (1966), that are applied for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
Claim(s) 5, 22, 23, 27 is/are rejected under 35 U.S.C. 103 as being unpatentable over Limb (GB 2069119) in view of Pozivil (US 2007/0068176).
In regard to claim 5, Limb teaches most of the claim limitations but does not explicitly teach maintaining the boil-off gas at a pressure that is no more than 110% of a pressure of the storage tank during the performance of the steps (a) and (b). However, by returning the at least partially condensed boil-off gas stream to the storage tank (1), this reduces boil-off and thereby prevents an increase of the pressure of the storage tank (1). Further, Pozivil explicitly teaches that it is well known that providing cooling to a natural gas storage tank maintains the pressure of natural gas within a storage tank (para. 29). Therefore it would have been obvious to a person of ordinary skill in the art to maintain the pressure of the storage tank at the tank pressure (this being 100%) and operate the pump of Limb so as to maintain the desired pressure and temperature conditions of the natural gas in the storage tank.
In regard to claim 22, Limb teaches most claim limitations but does not explicitly teach pumping liquefied natural gas from the storage tank (1) through a spray header located in the vapor space using a pump, thereby preventing enrichment of nitrogen in the vapor space. However, Pozivil teaches pumping liquefied natural gas (para. 29) from a storage tank (10; para. 29) through a spray header (at least 44) located in a vapor space (top region of 10) using a pump (16). Such operation facilitates stable conditions in the tank (para. 15). Therefore it would have been obvious to those of ordinary skill in the art at the time the invention was made to modify Limb with the pump and spray header of Pozivil for the purpose of improving the stability of the stored fluid and avoid problems with uncontrolled stratification (para. 15, 11, 10). Note that such mixing would induce mixing and thereby reduce enrichment of nitrogen in the vapor space.
In regard to claim 23, Limb, as modified above, does not explicitly teach performing an operation using the pump (Pozivil-16) and spray header (Pozivil - at least 44) prior to a filling operation with liquefied natural gas. However, Pozivil explicitly teaches that LNG tankers retain a volume of liquid to reduce evaporation of liquid upon refilling (para. 26). In view of these teachings and the rest of the teachings of Pozivil showing that operation of the pump (16) and spray header (44) permit more stable storage conditions, these teachings suggest operating the pump (16) and spray header (44) prior to a filling operation with liquefied natural gas to further ensure stratification and warmer gases in a top of the storage tank do not lead to undue evaporation during a filling operation. Therefore it would have been obvious to those of ordinary skill in the art at the time the invention was made to operate the pump (Pozivil-16) and spray header (Pozivil-44) prior to a filling operation to further ensure stratification and warmer gases in a top of the storage tank do not lead to undue evaporation during a filling operation.
In regard to claim 27, Limb teaches most of the claim limitations, including that the at least partially condensed boil-off gas stream (22) is returned to a top of the storage tank (1), but does not explicitly teach that the at least partially condensed boil-off gas stream (22) is only partially condensed. However, it is routine for initial operations to employ cool down transitions, and therefore when boil-off gas is first being condensed, it would have been obvious to those of ordinary skill in the art at the time the invention was made to only partially condense the boil-off stream as a routine part of getting to steady state condensing operation and to prevent the need for venting during initial cooling down time periods.
Claim(s) 4, 26 is/are rejected under 35 U.S.C. 103 as being unpatentable over Limb (GB 2069119) in view of Lee (US 8959930) and Oka (US 2010/0170297).
In regard to claim 4, Limb teaches most of the claim limitations, but does not explicitly teach a temperature difference between the boil-off gas stream (21) entering the first heat exchanger (3) and the at least partially condensed boil-off gas stream (22) exiting the first heat exchanger (3) is less than 2 degrees Celsius.
However, Limb explicitly teaches that the LNG is stored at a pressure slightly about atmospheric pressure and a temperature of about -160 C (page, 3 line 50-55) and Lee explicitly teaches that when LNG is stored in LNG storage tanks (column 9, line 10-15) it is routine to maintain a pressure very near atmospheric pressure (column 9, line 47-55) and teaches that at such pressures, the temperature of the LNG may raise only to -159 C (column 9, line 55) and further teaches (column 11, line 20-30) that by pumping (via 11) the LNG into a spray bar (13) at the top of the tank that a uniform temperature can be maintained in the storage tank thereby reducing generation of boil-off gas (column 11, line 50) and requiring a temperature change for recondensation of only a few degrees Celsius.
In addition, Oka explicitly teaches that by providing a recondenser (12, Fig. 2B) at a location near and above an storage LNG tank (3) recondensing a boil-off stream (BOG, para. 44) is improved by reducing a rise the in the temperature of the BOG due to heat leak (para. 74).
In view of these teachings, it would have been obvious to those of ordinary skill in the art at the time the invention was made to modify Limb with pumping of LNG to a top of the storage tank to improve the temperature uniformity of the fluid in the tank and reduce boil-off gas generation and to further relocate the recondenser near to and above the storage tank for the purpose of minimizing any temperature gain of the boil-off gas so that the refrigeration provided to the recondenser can be used for recondensation and less for returning the boil-off vapor to saturated vapor conditions and hence it would be obvious to operate with a temperature difference of less than 2 degrees Celsius for these benefits.
In regard to claim 26, Limb, as modified above, teaches that the at least partially condensed boil-off gas stream (22) is returned to the storage tank (1) by gravity per the relocation of the recondenser to be near and on top of the storage tank in view of the teachings of Oka for the additional obvious purpose of removing a need for a pump to return the liquid (see Oka -para. 77).
Claim(s) 6 is/are rejected under 35 U.S.C. 103 as being unpatentable over Limb (GB 2069119) in view of Lofredo (US 3780534).
Limb teaches most of the claim limitations, but does not explicitly teach that the at least partially condensing the boil-off gas stream of the step (a) comprises the at least partially condensing of the boil-off gas stream in a first vessel of the first heat exchanger (3) against the two phase refrigerant stream (30) flowing through a second vessel to form the at least partially condensed boil-off gas stream (22) and the gaseous refrigerant stream (part of 28), the first vessel being contained within the second vessel. However, providing a first vessel within a second vessel for heat exchangers is ordinary and routine as taught by Lofredo.
Lofredo teaches flowing a two phase refrigerant stream (vaporizing nitrogen refrigerant flow from 106 to 109, see fig. 2, column 6, line 60) through a vessel (shell of 107) to cool boil off gas (from 108, column 6, line 65) in a first vessel (flow channel of 107, see figure 2) of a first heat exchanger (107); the first vessel (flow channel in 107) being contained within a second vessel (shell of 107); and thereby forming an at least partially condensed boil-off gas stream (toward 74) and a gaseous refrigerant stream (109).
Therefore it would have been obvious to those of ordinary skill in the art at the time of the invention to modify the first heat exchanger structure (3) of Limb to have a first vessel contained in a second vessel as taught by Lofredo for the purpose of providing immersion of the boil off gas in the vaporizing refrigerant and to provide good thermal contact between the boil off gas and the refrigerant and to provide an economical and well understood heat exchanger structure.
Claim(s) 30 is/are rejected under 35 U.S.C. 103 as being unpatentable over Limb (GB 2069119) in view of Becker (US 3511058).
Limb teaches most of the claim limitations but does not appear to explicitly teach that the refrigerant is argon. However, argon is a well known alternative for refrigerant as taught by Becker (column 2, line 25-26). Therefore it would have been obvious to those of ordinary skill in the art at the time the invention was made to employ argon refrigerant in place of the nitrogen for the purpose of providing an inert refrigerant with the well known thermal performance of argon.
Claim(s) 29 is/are rejected under 35 U.S.C. 103 as being unpatentable over Limb (GB 2069119) in view of Brostow (US 2004/0231359).
Limb teaches most of the claim limitations but does not appear to explicitly teach that the refrigerant has hydrocarbons of more than 0% and less than 5%. However, employing nitrogen refrigerant that has a small amount of a hydrocarbon is routine and ordinary. Brostow explicitly teaches that it is routine and ordinary to employ a nitrogen refrigerant that is between having 1% - 5% methane (para. 84, 108, 118) and being 90-99% nitrogen. Therefore it would have been obvious to those of ordinary skill in the art at the time the invention was made to modify employ a nitrogen refrigerant having hydrocarbons as such minor amounts would not make the nitrogen unsuitable as a refrigerant and further for the purpose of obtaining nitrogen refrigerant from natural gas on hand so as to eliminate or reduce the need to purchase or procure nitrogen from an outside source.
Response to Arguments
Applicant's arguments filed 4/28/2025 have been fully considered but they are not persuasive.
Applicant's arguments (page 8) are an allegation that Limb does not teach at least partially condensing the boil off gas stream (21) against “liquid and vapor”.
In response, the allegation is unpersuasive as since the claim does not limit how the recited two phase stream is heat exchanged and the identified fluid does provide the claimed at least partial condensation.
Applicant's arguments (page 9) are an allegation that there is no evidence of heat leak. In response, the allegation is unpersuasive since such real world operations inherently have such imperfections and the alleging that such are not present is a denial of basic physics. The claims make no requirements for the amount of vapor present and therefore the real world performance of moving such fluid read on the claim.
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to JOHN F PETTITT whose telephone number is (571)272-0771. The examiner can normally be reached on M-F, 9-5p. Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR): http://www.uspto.gov/interviewpractice. The examiner’s supervisor, Frantz Jules can be reached on 571-272-6681. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300. Information regarding the status of an application may be obtained from the Patent Application Information Retrieval (PAIR) system. Status information for published applications may be obtained from either Private PAIR or Public PAIR. Status information for unpublished applications is available through Private PAIR only. For more information about the PAIR system, see http://pair-direct.uspto.gov. Should you have questions on access to the Private PAIR system, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative or access to the automated information system, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000.
/JOHN F PETTITT, III/Primary Examiner, Art Unit 3763
JFPIII
August 15, 2025