DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
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 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.
Claims 1, 10, 13 and 14 are rejected under 35 U.S.C. § 103 as being unpatentable over Masaru (JP 2009-204026 A) in view of JP 2009-501896 A (LNG BOG Reliquefaction Equipment) hereinafter "JP 896", and further in view of Mostello (US 7,581,411 B2).
Regarding claim 1, Masaru teaches a boil-off gas reliquefaction system for a vessel comprising:
a boil-off gas compressor (61) configured to compress boil-off gas (13) generated in a storage tank (3) storing liquefied gas (Masaru: BOG compressor 61 configured to compress boil-off gas 13 generated in storage tank 3 storing LNG 11; fig. 1; ¶0034);
a reliquefaction line (55, 57) extending from the boil-off gas compressor (61) to the storage tank (3) and configured to reliquefy the compressed boil-off gas and deliver the reliquefied gas to the storage tank (Masaru: BOG supply pipe 55 and reliquefied gas pipe 57 extending from compressor 61 through condenser 35 to storage tank 3; fig. 1; ¶0034);
a heat exchanger (35) provided to the reliquefaction line and configured to receive and cool the compressed boil-off gas (condenser 35 provided to the reliquefaction line configured to receive and cool compressed BOG 13; fig. 1; ¶0035–0036);
a first refrigerant compressor (21) configured to compress a refrigerant discharged from the heat exchanger after cooling the compressed boil-off gas (refrigerant compressor 21 compresses the low-temperature low-pressure refrigerant returned through cooling piping section 43 after providing cooling in condenser 35; fig. 1; ¶0031–0033);
a second refrigerant compressor (27) configured to further compress the refrigerant compressed in the first refrigerant compressor (21) (booster compressor 27 further compresses the refrigerant introduced from first aftercooler 25 following compression by refrigerant compressor 21; fig. 1; ¶0031–0033);
a refrigerant expander (31) configured to expand and cool the refrigerant compressed through the first and second refrigerant compressors and supply the refrigerant to the heat exchanger (35) (expander 31 expands the refrigerant compressed through refrigerant compressor 21 and booster compressor 27 by decompression to form low-temperature, low-pressure gaseous refrigerant supplied to condenser 35; fig. 1; ¶0030–0031, ¶0043–0044);
a refrigerant circulation line (line 19 from tank 40) to which the first (21) and second (27) refrigerant compressors and the refrigerant expander are provided and in which the refrigerant supplied to the heat exchanger circulates (Masaru: refrigeration pipe 19 forming a closed system connecting refrigerant compressor 21, booster compressor 27, and expander 31, in which refrigerant circulates; fig. 1; ¶0030);
a refrigerant inventory part (configured to supply the refrigerant circulating in the refrigerant circulation line (19) (Masaru: refrigerant storage tank 40 connected to refrigeration pipe 19 via supply and extraction lines; fig. 1; ¶0050);
a refrigerant supply line (line 19 from tank 40) extending from the refrigerant inventory part (40) to an upstream side of the first refrigerant compressor (21) of the refrigerant circulation line to replenish the refrigerant to the refrigerant circulation line (fig. 1; ¶0050);
a refrigerant discharge line (the line extending from refrigerant line 43 to refrigerant storage tank 40) extending from a downstream side of the second refrigerant compressor (27) of the refrigerant circulation line (40) to the refrigerant inventory part to discharge the refrigerant of the refrigerant circulation line (Masaru: extraction line extending from a downstream side of booster compressor 27 to refrigerant storage tank 40 to discharge refrigerant from the circulation line; fig. 1; ¶0050);
wherein the refrigerant compressed through the first and second refrigerant compressors is pre-cooled in the heat exchanger, expanded and cooled in the refrigerant expander, and supplied as a cold heat source to the heat exchanger (Masaru: refrigerant compressed by refrigerant compressor 21 and booster compressor 27 is pre-cooled in condenser 35, expanded and cooled in expander 31, and supplied as a cold heat source to condenser 35 via cooling piping section 43; fig. 1; ¶0030–0032, ¶0043–0044).
However, Masaru does not explicitly teach the limitation "wherein either the first refrigerant compressor or the second refrigerant compressor is axially connected to the refrigerant expander to be driven by expansion energy of the refrigerant delivered from the refrigerant expander, and the other is driven by an external electric power."
Masaru discloses at ¶0032 that expander (31) generates rotational force when the refrigerant expands, which rotates booster compressor (27), and at ¶0031 that refrigerant compressor (21) is driven by drive motor (23), i.e., external electric power — thus expressly teaching the functional arrangement of one compressor driven by the expansion energy of the expander and the other driven by external electric power. However, Masaru does not expressly describe the mechanical connection between expander (31) and booster compressor (27) as a shaft connection or axial connection.
However, Mostello teaches a nitrogen refrigerant reliquefaction system for LNG boiloff gas, comprising a single-stage main refrigerant compressor and one or two turboexpanders. Mostello explicitly discloses that in LNG BOG reliquefaction systems for LNG carriers, further compression may take place in compressors which are shaft-connected to turboexpanders (Background Art section). Mostello further explicitly discloses in the Detailed Description (FIGS. 1 & 2) that "power recovery from the turboexpander 8 may be by mechanical shaft connection to the single-stage nitrogen compressor or by means of an electric generator." Mostello's FIG. 5 and its accompanying Example depict and describe turboexpander 8 driving compressor 81 via shaft connection — i.e., a turboexpander-driven compressor that is shaft-connected to the expander — while the single-stage main compressor 2 is driven externally, with the two compressors operating in series in the nitrogen refrigeration cycle for shipboard LNG BOG reliquefaction. Mostello's Summary of Invention further confirms that "turboexpander energy recovery by mechanical loading, compressor drive, or electric generator" are the known alternative implementations for turboexpander output in nitrogen BOG reliquefaction systems for LNG carriers.
Therefore, it would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to implement the expander-to-booster-compressor drive arrangement of Masaru using a mechanical shaft connection, in view of the teachings of Mostello, in order to establish that shaft-connecting the turboexpander to its driven compressor is the well-known and standard means of implementing such a mechanical drive arrangement and such shaft connection yields a predictable results of efficient transfer of expansion energy to compression duty with reduced equipment count and improved system efficiency. MPEP §§ 2143, 2143.02.
Masaru does not explicitly teach the limitation "wherein a load of a reliquefaction cycle is adjusted by replenishing the refrigerant to the refrigerant circulation line through the refrigerant supply line upon an increase in an amount of the compressed boil-off gas to be reliquefied, and discharging the refrigerant from the refrigerant circulation line through the refrigerant discharge line upon a decrease in an amount of the compressed boil-off gas to be reliquefied."
However, JP 896 teaches a nitrogen reverse Brayton cycle BOG reliquefaction system for an LNG carrier vessel that includes a nitrogen buffer tank (120) performing a mass flow rate adjustment function. Specifically, JP 896 explicitly discloses that "The nitrogen buffer tank (120) performs the function of adjusting the mass flow rate of the nitrogen cycle in accordance with the change in the BOG reliquefaction amount, that is, the change in the cooling load of the nitrogen cycle" (see at least pages 6, 10, 14, and 16 of the translation). Thus, JP 896 directly teaches adjusting the refrigerant mass flow rate based on variation in the amount of BOG to be reliquefied — the precise control trigger recited in the claim. JP 896 also discloses an optional external nitrogen makeup supply source connected to the buffer tank for replenishment when nitrogen quantity decreases.
Therefore, it would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to modify the reliquefaction system of Masaru to adjust the refrigerant inventory through the supply and discharge lines based on the amount of compressed boil-off gas to be reliquefied, in view of JP 896, because JP 896 explicitly establishes that the BOG reliquefaction amount is the proper control variable for adjusting refrigerant mass flow rate, and applying this teaching to Masaru's existing supply and discharge line structure to implement BOG-amount-triggered refrigerant replenishment and discharge represents the straightforward combination of a known structural framework (Masaru) with a known and directly applicable control principle (JP 896), yielding only predictable results. See MPEP §§ 2143, 2143.02.
Regarding claim 10, see the rejection of claim 1 above. Claim 10 recites a boil-off gas reliquefaction method whose steps correspond directly to the structural elements and functional limitations of claim 1. The same prior art teachings of Masaru, JP 896, and Mostello, and the same rationale, apply with equal force.
In regard to claim 13, the modified Masaru teaches the boil-off reliquefacation system according to claim 1 and further recites the limitation that the first refrigerant compressor is axially connected to the refrigerant expander to be driven by expansion energy of the refrigerant delivered from the refrigerant expander, and the second refrigerant compressor is driven by the external electric power (Masaru: expander 31 generates rotational force that rotates booster compressor 27, while refrigerant compressor 21 is driven by drive motor 23, i.e., external electric power; fig. 1; ¶0031–0032; Masaru at ¶0053 further expressly contemplating that the first refrigerant compressor (21) or the second refrigerant compressor (27) is driven by expansion energy of expander 31).
Masaru does not explicitly use the term "axially connected" to describe the mechanical linkage between expander (31) and booster compressor (27), and Masaru's first embodiment (fig. 1) shows the booster compressor (27) — not refrigerant compressor (21) — as the expander-driven unit. Claim 13 specifically requires that it is the first refrigerant compressor that is axially connected to the expander.
However, Mostello teaches that in nitrogen refrigerant BOG reliquefaction systems, compressors that are driven by turboexpanders are implemented by shaft-connecting the compressor to the turboexpander (Background Art; Detailed Description, FIGS. 1 & 2: power recovery from the turboexpander 8 may be by mechanical shaft connection to the single-stage nitrogen compressor or by means of an electric generator; FIG. 5 and Example: turboexpander 8 shaft-drives compressor 81 while single-stage main compressor 2 is driven externally). Mostello further discloses that the turboexpander-driven compressor and the externally-driven main compressor operate together in the same nitrogen refrigerant closed cycle for BOG reliquefaction aboard LNG carrier vessels.
Therefore, it would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to implement the expander-driven compressor arrangement of Masaru in the specific configuration— with the first refrigerant compressor axially shaft-connected to expander (31) while the second refrigerant compressor is driven by external electric power — because: (1) Masaru at ¶0032 and ¶0053 expressly contemplates both the first and second refrigerant compressor as equally available alternatives for expander-driven operation; (2) Mostello explicitly teaches that shaft-connecting a compressor to a turboexpander is the known and standard implementation for turboexpander-driven compression in nitrogen BOG reliquefaction systems for LNG carrier vessels, with the remaining compressor driven by an external source — the identical technical field and refrigerant as Masaru; (3) the applicant's own specification (¶0049, ¶0051; fig. 1 and fig. 2) expressly discloses both the first-compressor-shaft-connected and second-compressor-shaft-connected configurations as interchangeable design alternatives achieving the same result; and (4) selecting which compressor is shaft-connected to the expander is a routine design choice in the art yielding only predictable results. See KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007); MPEP §§ 2143, 2143.02.
In regard to claim 14, see the rejection of claim 13 above. The same analysis applies, as claim 14 recites the corresponding method steps.
Claim(s) 2, 9, and 11 are rejected under 35 U.S.C. § 103 as being unpatentable over Masaru, JP 896, and Mostello as applied to claims 1 or 10 above, and further in view of Bernard (WO 2019/145643 A1).
In regard to claim 2, the modified Masaru teaches the boil-off gas reliquefaction system according to amended claim 1, as set forth above, but does not explicitly teach that four streams are heat exchanged in the heat exchanger, and specifically does not teach a stream of uncompressed boil-off gas supplied from the storage tank to the boil-off gas compressor as one of those four streams. Masaru's condenser (35) processes three streams: the compressed boil-off gas (line 55), the refrigerant compressed through the first and second refrigerant compressors through precooling piping section (41), and the expanded/cooled refrigerant downstream of expander (31) through cooling piping section (43), but does not route uncompressed boil-off gas through the heat exchanger prior to compression.
However, Bernard teaches a boil-off gas reliquefaction system comprising a heat exchanger (E2) in which four streams are heat exchanged: (1) a stream of uncompressed boil-off gas supplied from the storage tank to the compressor; (2) a stream of the compressed boil-off gas through the compressor; (3) a stream of a refrigerant compressed through a refrigerant compressor; and (4) a stream of the refrigerant expanded and cooled through a refrigerant expander (see fig. 33 and 34 of Bernard).
Therefore, it would have been obvious to one of ordinary skill in the art to modify the arrangement of the modified Masaru to route the uncompressed boil-off gas through the heat exchanger prior to compression, in view of Bernard, as a well-established cryogenic processing principle — pre-cooling the uncompressed BOG before compression, in order to avoid cryogenic compressor inlet temperature extremes, ensure stable compressor operation, and facilitates more effective subsequent liquefaction.
Regarding claim 9, the modified Masaru teaches the boil-off gas reliquefaction system according to claim 1 but does not explicitly teach that the compressed boil-off gas is supplied as fuel to an engine or generator of the vessel and the boil-off gas not supplied as fuel is reliquefied through the reliquefaction line. Bernard teaches that compressed boil-off gas is supplied as fuel to an engine or generator of the vessel (streams 58, 64), while the portion not supplied as fuel is reliquefied (¶0142, 0155–0156; fig. 33 and 34). Therefore, it would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to supply the compressed boil-off gas as a fuel and the gas not supplied as fuel is reliquefied, in view of the teachings of Bernard, in order to efficiently utilize the compressed BOG for the dual purposes as fuel and as reliquefaction feedstock.
Regarding claim 11, see the rejection of claim 2 above. The same analysis applies, as claim 11 recites the corresponding method steps.
Claim(s) 8 is rejected under 35 U.S.C. § 103 as being unpatentable over Masaru, JP 896, and Mostello as applied to claim 1 above, in view of Bernard (WO 2019/145643 A1) and further in view of Lee et al. (US 2016/0114876 A1).
In regard to claim 8, the modified Masaru teaches the boil-off gas reliquefaction system according to claim 1 but does not teach: (a) a boil-off gas supply line extending from the storage tank to the boil-off gas compressor through the heat exchanger; and (b) a preheater branched upstream of the heat exchanger in the boil-off gas supply line to heat all or part of the boil-off gas and supply the heated boil-off gas to an upstream side of the heat exchanger.
Bernard teaches a boil-off gas supply line extending from the storage tank (24) to the compressor through the heat exchanger (E2), such that the BOG is pre-cooled in the heat exchanger before compression (fig. 33 and 34). Therefore, it would have been obvious to one of ordinary skill in the art to modify the arrangement of Masaru (as modified by JP 896 and Mostello) to route the uncompressed boil-off gas through the heat exchanger prior to compression, in view of Bernard, as pre-cooling the uncompressed BOG before compression in order to avoid cryogenic compressor inlet temperature extremes, ensures stable compressor operation, and facilitates more effective subsequent liquefaction.
The modified Masaru, does not explicitly teach a preheater branched upstream of the heat exchanger in the boil-off gas supply line.
However, Lee et al. teaches a preheater (21) branched upstream of the heat exchanger in a boil-off gas supply line (L12) to heat all or part of the boil-off gas (L1) and supply the heated boil-off gas to an upstream side of the heat exchanger (fig. 6).
Therefore, it would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to modify the boil-off gas reliquefaction system of Masaru by reheating a portion of the boil-off gas upstream of the heat exchanger, in view of Lee, in order to prevent inlet temperature extremes at the heat exchanger, provide supplemental refrigeration capacity, and maintain controlled operating conditions across varying load conditions.
Response to Arguments
Applicant’s arguments with respect the amended claims have been considered but are moot in view of the new ground(s) of rejections (in view Mostello US 7,581,411 B2).
Conclusion
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/W.M/Examiner, Art Unit 3763
/FRANTZ F JULES/Supervisory Patent Examiner, Art Unit 3763
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