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 Interpretation
The following is a quotation of 35 U.S.C. 112(f):
(f) Element in Claim for a Combination. – An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.
The following is a quotation of pre-AIA 35 U.S.C. 112, sixth paragraph:
An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.
This application includes one or more claim limitations that do not use the word “means,” but are nonetheless being interpreted under 35 U.S.C. 112(f) or pre-AIA 35 U.S.C. 112, sixth paragraph, because the claim limitation(s) uses a generic placeholder that is coupled with functional language without reciting sufficient structure to perform the recited function and the generic placeholder is not preceded by a structural modifier. Such claim limitation(s) is/are:
“a compression unit” in claims 1 and 11 is understood to be a compressor.
“an O2 depletion unit” in claim 4 and 7 is understood to be a deoxo/catalytic reactor (see ¶ 0103 of the publication).
Because this/these claim limitation(s) is/are being interpreted under 35 U.S.C. 112(f) or pre-AIA 35 U.S.C. 112, sixth paragraph, it/they is/are being interpreted to cover the corresponding structure described in the specification as performing the claimed function, and equivalents thereof.
If applicant does not intend to have this/these limitation(s) interpreted under 35 U.S.C. 112(f) or pre-AIA 35 U.S.C. 112, sixth paragraph, applicant may: (1) amend the claim limitation(s) to avoid it/them being interpreted under 35 U.S.C. 112(f) or pre-AIA 35 U.S.C. 112, sixth paragraph (e.g., by reciting sufficient structure to perform the claimed function); or (2) present a sufficient showing that the claim limitation(s) recite(s) sufficient structure to perform the claimed function so as to avoid it/them being interpreted under 35 U.S.C. 112(f) or pre-AIA 35 U.S.C. 112, sixth paragraph.
Claim Rejections - 35 USC § 112
The following is a quotation of the first paragraph of 35 U.S.C. 112(a):
(a) IN GENERAL.—The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention.
The following is a quotation of the first paragraph of pre-AIA 35 U.S.C. 112:
The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor of carrying out his invention.
Claims 1, 2 and 4-11 are rejected under 35 U.S.C. 112(a) or 35 U.S.C. 112 (pre-AIA ), first paragraph, as failing to comply with the written description requirement. The claim(s) contains subject matter which was not described in the specification in such a way as to reasonably convey to one skilled in the relevant art that the inventor or a joint inventor, or for applications subject to pre-AIA 35 U.S.C. 112, the inventor(s), at the time the application was filed, had possession of the claimed invention.
Claims 1 and 11 each recite the limitation: "wherein the booster further comprises a compressor capable to compress the first, low pressure (LP) methane enriched flow in order to mix the first, low pressure (LP) methane enriched flow with the first, medium pressure (MP) methane enriched flow, to produce a second, medium pressure methane enriched flow." This limitation lacks written description support in the specification. The specification and Figure 3 of the application publication (US 2024/0019205 A1) disclose two entirely separate elements with distinct functions at distinct locations in the process: Booster (9) is arranged upstream of the cryodistillation unit (8), between the CO₂ polishing unit (7) and the cryodistillation unit (8). Its disclosed function is to boost the pressure of the CO₂-depleted feed gas from the PTSA output (~110–230 psi) to the NRU feed pressure (~300–600 psi), enabling it to enter the nitrogen fractionation column. The booster (9) acts on the incoming feed gas before cryodistillation. (¶[0039]–[0040] of US 2024/0019205 A1; Fig. 3). Compressor (85) is a separate element arranged downstream of the cryodistillation unit (8). It receives LP gas flow (84), which is the LP methane product that exits the distillation column (61), passes through subcooler (80), and is vaporized in heat exchanger (59). Compressor (85) compresses LP gas flow (84) to produce second MP gas flow (86), which is then mixed (87) with first MP flow (75). (¶[0141]–[0143] of US 2024/0019205 A1; Fig. 3). The cryodistillation unit (8) is explicitly described in the specification as containing exactly four elements: heat exchanger (59), reboiler (60), distillation column (61), and subcooler (80). (¶[0132] of US 2024/0019205 A1.) Compressor (85) is identified as a separate element outside the cryodistillation unit and is never described as part of or comprised within booster (9). No paragraph, claim, or figure in the specification describes any embodiment in which booster (9) and compressor (85) constitute a single device, or in which booster (9) is said to "comprise" compressor (85) or any LP product compressor. Because booster (9) is positioned upstream of the cryodistillation unit, it cannot physically or functionally compress the LP methane product stream that only exists after the cryodistillation process is completed downstream. The specification provides no written description of any structure in which a single booster simultaneously serves as a feed-gas booster upstream of the cryodistillation unit and an LP product compressor downstream of the cryodistillation unit. Applicant has therefore not demonstrated possession of the invention as recited in claims 1 and 11. A person of ordinary skill in the art would not recognize, from the disclosure, that the inventors were in possession of the claimed arrangement.
Claims 2, 4–10 are also rejected under 35 U.S.C. § 112(a) for being dependent upon a rejected claim.
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.
Claims 1-10 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.
Claim 1 recites the limitation "the membrane" in line 14 lacks proper antecedent basis. Examiner read the limitation as –the at least one membrane separation--.
Claim 1 recites the limitation "the booster" in line 26 lacks proper antecedent basis. Examiner read the limitation as –the first booster--.
Claims 1 and 11 recites "booster…comprises a compressor" limitation discussed above under § 112(a). It is internally contradictory and indefinite to recite a booster placed "upstream the cryodistillation unit" that simultaneously "comprises a compressor capable to compress the first, low pressure (LP) methane enriched flow" - a flow that only exists as a product exiting the cryodistillation unit downstream. The claim language creates a logical impossibility: a component positioned upstream cannot operate on a stream produced downstream by that same unit. The scope of the claim is therefore unclear.
Claim 2 recites the limitation "the booster" in line 1 lacks proper antecedent basis.
Claim 10 recites the limitation "according to claim" without specifying the claim number on which it depends. As drafted, claim 10 does not identify the claim from which it depends, thereby failing to comply with 35 U.S.C. 112(b) and 37 C.F.R. 1.75(c). Appropriate correction identifying the parent claim number is required.
Claim 11 recites the limitation "wherein the first booster is arrange downstream of the CO₂ polishing unit and upstream the cryodistillation unit” in line 29-31 renders the claim indefinite because the verb phrase "is arrange" lacks the proper past-participle form and does not clearly define the positional relationship. The limitation should read — "wherein the first booster is arranged downstream of the CO₂ polishing unit and upstream the cryodistillation unit" — or be amended to eliminate the grammatical ambiguity.
Claims 4-10 are also rejected under 35 U.S.C. 112(b) for being dependent upon a rejected claim.
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, 2 and 9-11 are rejected under 35 U.S.C. § 103 as being unpatentable over Prince (US 2019/0001263 A1) view of Butts (US 2020/0072547 A1).
In regard to claim 1, Prince teaches a facility for producing biomethane by purifying biogas from non-hazardous waste storage facilities (NHWSF), which are landfills (Prince, ¶ 0087, 0001; Abstract), comprising:
a compression unit (4: in a form of lubricated screw compressor (18)) for compressing an initial gas (17) flow of the biogas (1) into a compressed initial flow of the biogas (20) to be purified (see Prince, ¶ 0090; fig. 1: the initial gas flow (17) of the biogas to a pressure of between 0.8 and 2.4 megapascals (8 and 24 bars) to produce a compressed gas flow (20)),
a volatile organic compound (VOC) purification unit (5: comprising two PSAs (21, 22)) arranged downstream of the compression unit (4) to receive the compressed initial flow of the biogas (20) and comprising at least one adsorber (21, 22) loaded with adsorbents capable of reversibly adsorbing VOCs to thereby produce a VOC-depleted gas flow (40) (see ¶ 0091-0092, 0095; fig. 1: Prince discloses two PSAs (21, 22) loaded with adsorbents specifically selected to allow reversible adsorption of VOCs (light hydrocarbons, mercaptans, siloxanes, etc.) during the adsorption phase and desorption during regeneration, operating alternately in production and regeneration mode to produce a VOC-purified gas flow directed to the CO₂ purification unit (6)),
a membrane separation unit (6) arranged downstream of the VOC purification unit (5) to receive the VOC-depleted gas flow (40) and subject the VOC-depleted gas flow (40) to at least one membrane separation (38, 39) to partially separate CO₂ and O₂ from the gas flow producing a methane rich retentate (42) (Prince, ¶ 0041, 0094-0095; fig. 1: Prince discloses selective membrane separation separates a large part of the CO₂ (more than 90%) and some of the O₂ (around 50%, and generally at least 30%) from the gas flow, producing a methane-rich retentate directed to the second CO₂ purification unit and a gas (42) with less than 3% CO₂ and a CH₄ yield greater than 90%),
a CO₂ polishing unit (7) arranged downstream of the membrane separation unit (6) to receive the methane rich retentate (42) from the membrane (38, 39), wherein the CO₂ polishing unit (7) comprises at least one adsorber loaded with adsorbents capable of reversibly adsorbing a majority of remaining CO₂ from the methane rich retentate (42) to produce a CO₂-depleted gas flow (52) (Prince, ¶ 0049-0051, 0096-0097; fig. 1: Prince discloses the gas flow (42) from the membrane alternately supplies PTSAs (43, 44) via pipes (45, 46) with valves (47, 48), wherein the CO₂-purified gas flow as single pipe (52) delivering CO₂-depleted gas flow to the next unit. The PTSAs reversibly adsorb the majority of remaining CO₂, and are dimensioned to avoid more than 2.5% CO₂ in the product),
a cryodistillation unit (8) comprising a heat exchanger (60) and a distillation column (62), arranged downstream of the CO₂ polishing unit (7) to receive the CO₂-depleted gas flow (52) and subject the CO₂-depleted gas flow (52) to a cryogenic separation to separate O₂ and N₂ from the CO₂-depleted gas flow (52) and to produce a gas distillate (68) (See Prince, ¶ 0098–0100, 0102; fig. 1: Prince discloses the heat exchanger (60) cools the CO₂-depleted gas flow (52) by thermal exchange with liquid methane (69) drawn off the bottom of the distillation column (62), partially liquefying the gas flow (63). The cryogenic separation separates the gas into a methane-rich liquid at the column bottom and a gas (68) loaded with CO₂ and O₂ at the column head, which is sent to the oxidation unit (10)),
Prince discloses the cryodistillation unit (8) uses external liquid nitrogen (9) to cool the condenser head of the column (62), and discloses only a single methane product stream (liquid methane (69)/gas (73)) (Prince, ¶ 0098-0104), but does not explicitly teach (a) a first booster (9) arranged between the membrane separation unit and the cryodistillation unit; (b) the cryodistillation unit further comprising a subcooler; (c) the cryodistillation unit producing two methane enriched flows at different pressures (LP and MP); and (d) the booster further comprises a compressor capable to compress the first, low pressure (LP) methane enriched flow in order to mix with the first, medium pressure (MP) methane enriched flow, to produce a second, medium pressure methane enriched flow.
Butts teaches an N₂ Fractionation Feed Subcooler (252) that receives stream (239) and further cools it into a subcooled state (stream 201) before the cooled stream enters the Nitrogen Fractionation Tower (253) (¶ 0046), wherein a 2nd JT Subcooler (256) that subcools stream (214) to stream (215) creating the internal condenser refrigerant for the Internal N₂ Reflux Exchanger (255) at the top of the Tower (253) ( ¶ 0049, fig. 5). Butts further teaches that the Nitrogen Fractionation Tower (253) produces three distinct methane product streams: (1) Low Pressure sales gas stream (221) (2) Intermediate Pressure (IP/MP) sales gas stream (225); and (3) High Pressure sales gas stream (231) (¶ 0049-0052; Table 1, streams 221/225/231; fig. 5). The LP stream (221) corresponds to the claimed "first, low pressure (LP) methane enriched flow" and the IP/MP stream (225) corresponds to the claimed "first, medium pressure (MP) methane enriched flow" (FIG. 4). Butts further teaches "successively compressing, through a series of compressors downstream of the first heat exchanger, the low pressure, intermediate pressure, and high pressure portions of the methane product stream" (¶ 0056 (11-d)), wherein stream (231) (HP sales gas) "may be blended with stream 221 and/or stream 225" — explicitly teaching the mixing of the LP and IP/MP portions of the methane product stream (¶ 0052). This series of downstream compressors, by compressing LP stream (221) and blending it with IP/MP stream (225), produces a combined higher-pressure methane product stream — directly corresponding to the claimed "second, medium pressure methane enriched flow."
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 Prince's facility by substituting its cryodistillation unit (8) — which uses external liquid nitrogen and produces a single methane stream — with the NRU Processing Section (195) of Butts, specifically incorporating Butts' Nitrogen Fractionation Tower (253) with its subcoolers (252, 256), LP/IP/HP methane product streams (221/225/231), and downstream compressors that compress the LP stream and blend it with IP/MP and HP streams to produce a combined methane product stream, in order to eliminate dependence on external liquid nitrogen supply, improve process energy efficiency, and produce a combined pipeline-pressure methane product stream.
Prince, as modified above, does not explicitly teaches a booster/compressor positioned between the membrane separation unit and the cryodistillation unit. However, the applicant's own specification at ¶[0039] of US 2024/0019205 A1 acknowledges that "an important first element of the design is the difference between the operating pressure of the membrane (between 110 psi to 230 psi) and the feed pressure requested by the single-column NRU (300 psi to 600 psi)." The inclusion of a booster/compressor between two process stages operating at different pressures is a routine engineering requirement that a person of ordinary skill in the art would implement as a matter of course when combining Prince's membrane-based front end with Butts' NRU back end.
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 Prince's facility by adding a booster between the membrane separation unit (6) and the cryodistillation unit (8), in order to increase the pressure of the CO₂-depleted retentate from the membrane output pressure (110–230 psi) to the NRU inlet pressure (300–600 psi) required by Butts' nitrogen fractionation tower (253), because Butts expressly acknowledges that intermediate recompression of the gas stream between a gas treatment section and an NRU was the standard prior art practice (Butts, ¶[0003]), and because the applicant's own specification identifies this exact pressure differential as the express rationale for the booster, stating: "an important first element of the design is the difference between the operating pressure of the membrane (between 110 psi to 230 psi) and the feed pressure requested by the single-column NRU (300 psi to 600 psi)." (See US 2024/0019205, ¶ 0039).
In regard to claim 2, Prince teaches a facility for producing biomethane by purifying biogas from landfill according to claim 1, wherein Prince teaches the membrane retentate flows directly into the PTSAs (Prince, ¶ 0095-0096), but does not explicitly teach that the booster is arranged downstream the membrane separation unit and upstream the CO₂ polishing unit.
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 Prince’s facility by positioning the booster upstream of the CO₂ polishing unit (7) and downstream of the membrane separation unit (6), as a routine skill in the art, in order to subject the PTSA adsorbents to a higher CO₂ partial pressure during adsorption and thereby improve CO₂ removal efficiency and reduce vessel size, because the adsorption capacity of zeolite adsorbents increases with the partial pressure of the adsorbed component, making it advantageous to boost the gas pressure before rather than after the CO₂ polishing step.
In regard to claim 9, Prince teaches a facility for producing biomethane by purifying biogas from landfill according to claim 1, characterized in that the volatile organic compound (VOC) purification unit (5) is a pressure swing adsorber (PSA) (21, 22) (See Prince, ¶ 0038-0039; ¶ 0091; claim 16 of Prince: Prince discloses the VOC purification unit (5) as comprising PSAs (21, 22) that operate by adsorption of VOCs under pressure and desorption during regeneration — the hallmark of pressure swing adsorption).
In regard to claim 10, Prince teaches a facility for producing biomethane by purifying biogas from landfill according to claim 1, characterized in that the CO₂ polishing unit (7) is a Pressure Temperature Swing Adsorption (PTSA) (see Prince, ¶ 0049, 0096; claim 16 of Prince).
In regard to claim 11, claim 11 recites the same facility as claim 1. The analysis for claim 1 applies to all shared limitations. The additional specific limitation of claim 11 is addressed below.
"wherein the first booster is arranged downstream of the CO₂ polishing unit and upstream the cryodistillation unit" This limitation places the booster in the specific position between the CO₂ polishing unit (7) and the cryodistillation unit (8). As discussed in claim 1, the booster is not explicitly taught by Prince or Butts in this specific placement. However, the applicant's specification at ¶[0073]–[0076] of US 2024/0019205 A1 identifies this as one of two equivalent embodiments (the other being the embodiment of claim 2, where the booster is upstream of the CO₂ polishing unit). Both embodiments serve the identical function of boosting the gas pressure from the membrane/PTSA output to the NRU feed pressure, differing only in whether this boosting occurs before or after the CO₂ polishing step. The selection between two equivalent, recognized placements of a known component — each achieving the same result through the same means — is an engineering expedient within the ordinary skill of a gas process engineer.
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 combined facility of Prince and Butts by positioning the booster downstream of the CO₂ polishing unit (7) and upstream of the cryodistillation unit (8), in order to increase the pressure of the CO₂-depleted gas flow exiting the PTSA to the NRU feed pressure before entering the nitrogen fractionation tower, because this placement is one of two equivalent and recognized booster positions that each achieve the same pressure increase by the same means, differing only in process location, as expressly disclosed by the applicant as an alternative embodiment at ¶[0073]–[0076] of US 2024/0019205 A1, and selecting between two such equivalent design options represents a routine engineering choice yielding predictable results.
Claim(s) 4-8 are rejected under 35 U.S.C. 103 as being unpatentable over Prince and Butts as applied to claim 1 or 2 above, and further in view of Whitley (US 2009/0193967 A1) and O'Brien (US 4,681,612).
In regard to claim 4, Prince teaches a facility for producing biomethane by purifying biogas from landfill according to claim 1, but does not teach an O₂ depletion unit arranged downstream the cryodistillation unit to receive the second, medium pressure methane enriched flow and capable of converting the O₂ present in the second, medium pressure methane enriched flow into CO₂ and H₂O to produce an O₂ depleted gas flow, and a dryer arranged downstream the O₂ depletion unit capable of removing H₂O from the O₂ depleted gas flow.
Whitley teaches a deoxo reactor (15) comprising Pd or Pt catalyst, heated to 200–500°F, that removes O₂ from a gas stream by catalytic oxidation with methane according to CH₄ + 2O₂ → CO₂ + 2H₂O, yielding an essentially oxygen-free intermediate gas containing additional water and CO₂ generated by the reaction (Whitley, ¶ 0036). O'Brien confirms that deoxo units are a recognized method for O₂ removal from landfill gas streams (O'Brien, col. 2, ll. 30–32). Whitley explicitly teaches that the intermediate gas exiting the deoxo reactor (15) via line (19) "contains essentially no oxygen and contains additional water and/or carbon dioxide generated in the oxidation reactions," and that downstream adsorber vessels in the PSA system (39) incorporate "a layer of activated alumina or silica gel or type NaX zeolite" to "adsorb water and carbon dioxide (some or all of which is formed in the deoxo and/or getter steps) (Whitley, ¶ 0036, 0045). Whitley therefore teaches that H₂O produced by the catalytic deoxo reaction must be removed downstream of the deoxo unit using an adsorbent-based drying step.
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 modified facility of Prince by adding a catalytic O₂ depletion unit downstream of the cryodistillation unit to receive the MP methane enriched flow, and a dryer downstream of the O₂ depletion unit, in view of teachings of Whitely and O’Brien, in order to: (i) remove residual O₂ from the methane product stream to meet pipeline O₂specifications, and (ii) remove the H₂O produced by the catalytic oxidation reaction before pipeline delivery to achieve complete O₂ removal, and because Whitley expressly teaches that water generated by the deoxo reaction must be removed downstream of the deoxo unit using an adsorbent (Whitley, ¶ 0036, 0045), with O'Brien confirming the use of deoxo units in landfill gas processing systems.
In regard to claim 5, Prince teaches a facility for producing biomethane by purifying biogas from landfill according to claim 4, wherein Prince, as modified by Whitley, teaches that the dryer is a TSA (Whitley, ¶ 0045). Whitley teaches that adsorbent vessels downstream of the deoxo step incorporate layers of alumina or silica gel to adsorb water produced by the deoxo reaction, which is the functional equivalent of the claimed TSA, an adsorbent-based dryer that removes H₂O from the gas stream.
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 modified dryer as a temperature swing adsorption (TSA) unit, in view of the teachings of Whitley, in order to remove H₂O from the O₂-depleted gas flow by adsorption at lower temperature and thermal regeneration at higher temperature, because TSA is a well-established and conventional technology for moisture removal from gas streams, as Whitley confirms through its teaching of alumina/silica gel adsorbent layers for water removal downstream a deoxo step (Whitley, ¶ 0045).
In regard to claim 6, the modified Prince teaches a facility for producing biomethane by purifying biogas from landfill according to claim 4, but does not teach further comprising a second booster arranged downstream the dryer.
O'Brien teaches that landfill gas processing systems include compression stages to deliver the methane product to pipeline pressure (O'Brien, Abstract; col. 2, ll. 19–27.) Butts teaches downstream compression of methane product streams to pipeline specification pressure (Butts, ¶ 0049-0052).
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 modified facility of Prince by adding a second booster downstream of the dryer, in view of teachings of O'Brien, in order to boost the purified O₂-depleted methane product from the dryer output pressure to the required pipeline delivery pressure (10–15 bar for gas supply networks, or 80–100 bar for transportation networks), because delivering a purified gas product at the required network pressure is a universal requirement in any gas upgrading system, as expressly confirmed by O'Brien's teaching of compression stages in landfill gas processing.
In regard to claim 7, the modified Prince teaches a facility for producing biomethane by purifying biogas from landfill according to claim 2, but does not teach an O₂ depletion unit (76) arranged downstream the first booster and upstream the CO₂ polishing unit.
Whitley teaches a deoxo reactor (15) comprising Pd or Pt catalyst, heated to 200–500°F, that removes O₂ from a gas stream by catalytic oxidation with methane (CH₄ + 2O₂ → CO₂ + 2H₂O), yielding an essentially oxygen-free product gas. (Whitley, ¶ 0036; claim 8; claim 18(b)). O’Brien confirms that deoxo units are a recognized method for O₂ removal from landfill gas streams (O’Brien, col. 2, ll. 30–32).
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 modified facility of Prince by adding a catalytic O₂ depletion unit downstream the first booster and upstream the CO₂ polishing unit, in view of the teachings of Whitley and O’Brien, in order to remove residual O₂ from the pressurized gas stream before it enters the PTSA and cryodistillation unit, because the presence of O₂ in the cryodistillation feed poses a recognized safety risk of oxygen enrichment in the cryogenic methane liquid phase as Whitley establish that catalytic deoxo was a well-known technique for residual O₂ removal from gas streams in the relevant field.
In regard to claim 8, the modified Prince teaches a facility for producing biomethane by purifying biogas from landfill according to claim 7, wherein Prince teaches that the CO₂ polishing unit (7) comprises PTSA adsorbers (43, 44) loaded with zeolite-type adsorbents (Prince, ¶ 0096). Zeolite adsorbents used in PTSA units adsorb both CO₂ and H₂O simultaneously, as zeolites have a strong affinity for polar molecules including water. Whitley further confirms, in the context of a multi-layer adsorber vessel, that a first layer of alumina or silica gel selectively adsorbs water and CO₂ from an incoming gas stream, demonstrating that adsorption-based units routinely remove H₂O from gas mixtures (Whitley, ¶ 0045). It would have been obvious to configure the zeolite-loaded PTSA of Prince to also adsorb H₂O from the incoming O₂-depleted stream, because this is an inherent and known capability of zeolite adsorbents, and doing so eliminates a separate drying step, reducing system complexity.
Response to Arguments
Applicant’s arguments with respect to the amended claims have been considered but are moot in view of the new ground(s) of rejection.
The drawing objection is withdrawn in view of amendments.
All § 112(b) rejections from the prior action that were directed to issues resolved by the amendments to claims 1–10 are withdrawn. New § 112(b) rejections are given to claims 1, 2 and 4-11 for the separate deficiencies identified in this action.
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.
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/W.M/Examiner, Art Unit 3763
/FRANTZ F JULES/Supervisory Patent Examiner, Art Unit 3763
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