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 .
Election/Restrictions
Claims 10, 11 and 14 are withdrawn from further consideration pursuant to 37 CFR 1.142(b), as being drawn to a nonelected invention and species, there being no allowable generic or linking claim. In addition, claims 8, 9 and 12 also fail to read on the elected species A1 (figure 1). Claim 8, does not read on fig. 1 – reads on figure 2 only. It requires region A of the LP column in a first column shell and region B in a second column shell, the two shells arranged next to one another (para. 0063), fig. 1 uses a single common shell 12’ for both regions A and B. The side-by-side divided column shell arrangement (shells 12a’ and 12b’) is exclusively the fig. 2 (species A2) embodiment (para. 0070). Claim 9 depends on claim 8 and claim 12 depends from claim 11. Therefore, claims 8-12 and 14 are withdrawn.
Applicant timely traversed the restriction (election) requirement in the reply filed on 04/16/2026. The traversal is on the ground(s) that Schaub et al. (US 6,543,253 B1) does not teach the two operating modes recited in claims 1 and 14, and that the ISR/WO-ISA acknowledged novelty over Schaub. These arguments are not persuasive and do not overcome the restriction.
The restriction was not predicated on Schaub teaching the operating modes. The examiner cited Schaub solely to establish that the common features shared between Group I and Group II — namely, a rectification column arrangement comprising a high-pressure column, a low-pressure column, an argon column, and transfer streams between them, including argon-enriched fluid withdrawn from the low-pressure column and introduced into the argon column — are not special technical features within the meaning of 37 CFR 1.475(a) and PCT Rule 13.2. Schaub plainly teaches these structural elements. See Schaub, Fig. 1, elements 201, 220, 12, streams 91–95.
The two operating modes and the specific pressure values of claims 1 and 14 are the distinguishing features of the claimed invention — not the common features linking the groups. A restriction under 37 CFR 1.475 requires only that the common linking features be disclosed in the prior art, not that the prior art anticipate the claims in their entirety. Applicant's argument conflates these two distinct inquiries. Applicant's reliance on the ISR and WO-ISA is also unavailing. A novelty finding under PCT procedures is directed to the claimed invention as a whole and does not constitute a determination that the common linking features are special technical features for purposes of unity of invention. The examiner is not bound by ISA conclusions in the national stage proceeding. See MPEP § 1893.03(d). The election of species between Species A1 (Figure 1) and Species A2 (Figure 2) is also maintained. The two species employ mutually exclusive column shell configurations and fluid routing arrangements — an undivided low-pressure column (Species A1) versus a divided, side-by-side column shell arrangement (Species A2) — and are not obvious variants on the current record. The requirement is still deemed proper and is therefore made FINAL.
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.
Claims 1-7, 13 and 15-17 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, with respect to the first operating mode, that the pressure in the argon column is set in "a pressure range that... corresponds to a pressure range at which the low-pressure column is operated, or... corresponds to a pressure range that is at least 50 mbar and/or up to 700 mbar or 900 mbar lower than the pressure range at which the low-pressure column is operated” renders the claim indefinite because the metes and bounds of this limitation are unclear for at least the following reasons: (i) The phrase "corresponds to a pressure range" does not define a particular pressure relationship; it is unclear whether the argon-column pressure must be equal to, within, overlapping with, or merely numerically associated with the low-pressure column pressure range. (ii) The use of "and/or" coupled with the alternative thresholds "up to 700 mbar or 900 mbar lower" renders the upper bound of the recited pressure offset ambiguous, such that one of ordinary skill cannot determine which of 700 mbar or 900 mbar establishes the outer limit of the claim, nor whether both alternatives are simultaneously required. (iii) The first-mode option (a) ("corresponds to a pressure range at which the low-pressure column is operated") and option (b) (at least 50 mbar lower) are presented as alternatives joined by "or," but the claim does not establish which alternative is to be used or how a reader is to determine whether option (a) or option (b) is met by a given embodiment. The same defects apply to the parallel recitations directed to the pure oxygen column pressure in the first operating mode (option (a) corresponding to the low-pressure column pressure range, or option (b) at least 50 mbar and/or up to 700/900 mbar lower).
Claim 1 further recites that, in the second operating mode, the argon column pressure is set "at least 50 mbar or 100 mbar and/or up to 700 mbar or 900 mbar" below the first-mode argon pressure range, and recites the same construction for the pure oxygen column renders the claim indefinite because the combination of "and/or" with multiple alternative numerical thresholds (50/100 mbar lower bounds and 700/900 mbar upper bounds) creates uncertainty as to which pressure relationship is required to fall within the scope of the claim.
Claim 2 recites that the valve in the line for feeding the first transfer quantity of the first transfer fluid into the argon column is "more closed" in the second operating mode than in the first operating mode. The phrase "more closed" is indefinite because the claim does not provide any objective metric, range of valve positions, percentage of nominal flow area, or other quantitative criterion by which the degree of closure can be measured or compared. Accordingly, one of ordinary skill in the art cannot ascertain the boundary between "closed" and "more closed" valve positions.
Claim 7 recites "the shell with the region C is arranged in particular above the shell of the pure oxygen column and connected thereto/integral" renders the claim indefinite because the phrase "in particular" is unclear whether the above/connected/integral arrangement is a required structural limitation of the claim or merely an exemplary or preferred arrangement, and the scope of the claim therefore cannot be ascertained. See MPEP § 2173.05(d).
Claims 3-6 and 15-17 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 1-7, 13, and 15-17 are rejected under 35 U.S.C. 103 as being unpatentable over DE 20 2021 000 696 U1 ("DE ‘696") in view of EP 3 327 393 A1 ("EP ‘393") in view of Victor et al. (US 4,838,913) in view of Al-Chalabi (US 4,784,677) and further in view of Kooijman, ChemSep Case Book: Air Separation Unit with Pure Argon Recovery (2006) ("Kooijman").
In regard to claim 1, DE ‘696 teaches a method for low-temperature air separation in an air separation plant (10) having a rectification column arrangement comprising a pressure column, (11), a low-pressure column (12), and an argon column (13 with further pure argon column 14), wherein the method comprises:
The low-pressure column (12) is designed in one or more parts and comprises a first rectification region and a second rectification region (see DE ‘696, fig. 1; DE ‘696 disclosure of streams B and D withdrawn from low-pressure column 12, wherein the low-pressure column 12 having distinct rectification regions, including a section above and a section below the side-draw location at which argon-enriched fluid D is removed), and the argon column is designed in one or more parts and comprises a first rectification region and a second rectification region (rectification apparatus 14, 15, 15a, 15b) (see DE ‘696, fig. 1 description of columns 13, 14, 15 and sections 15a, 15b; DE ‘696 teaches a crude argon column 13 cooperating with further rectification apparatus 14, 15, 15a, 15b that provide rectification regions corresponding to recited first and second regions C and D),
removing a first transfer fluid (D) enriched in argon from the low-pressure column (12) between the first and second rectification regions of the low-pressure column (12) (see fig. 1; stream D: DE ‘696 teaches withdrawing argon-enriched fluid D from low-pressure column 12 at an intermediate side-draw position between upper and lower rectification regions - stream D, 5-30 mol% Ar, <300 ppm N2),
feeding a first transfer quantity of the first transfer fluid (D) into the argon column below the first rectification region (DE ‘696 teaches, in the first operating mode, feeding fluid D to the further rectification columns/sections 13/14/15a/15b at a location below the crude argon rectification section (DE ‘696, first operating mode delivering stream D to columns 13/14/15)),
removing a second transfer fluid (E) depleted of argon from the argon column below the first rectification region of the argon column (DE ‘696 teaches withdrawing liquid E from crude argon column 13 circulated via pump 16 and a liquid F returned to the low-pressure column from the further separation apparatus (DE ‘696, streams E and F)),
feeding a second transfer quantity of the second transfer fluid (F) into the low-pressure column (12) between the first and second rectification regions (DE ‘696 teaches returning liquid F (depleted in argon) from the crude argon/further separation apparatus into low-pressure column 12 at a location between its rectification sections. (DE ‘696, return stream F)),
operating the plant in first and second operating modes; discharging the nitrogen product in the first operating mode in a larger product quantity than in the second operating mode (DE ‘696 teaches two operating modes: in the first mode, fluid D is rectified in the further columns 13/14/15 for full argon recovery and full nitrogen product output; in the second mode, fluid D is discharged/bypassed via bypass line 20 under control of control device 50, correspondingly reducing nitrogen product output (DE ‘696, first and second operating modes; control device 50; bypass line 20)),
operating the high-pressure and low-pressure columns at pressures consistent with conventional double-column ASUs (DE ‘696 teaches HP ≈ 4-7 bar (e.g., 5.3 bar) and LP ≈ 1-2 bar (e.g., 1.4 bar) (DE ‘696, pressure disclosures)).
DE ‘696 does not expressly teach (a) A pure oxygen column in the rectification arrangement that is operated with a liquid return flow removed from the argon column between regions C and D, and a head gas removed from the pure oxygen column and fed into the argon column between regions C and D (or D1/D2).
(b) Setting the argon-column and pure-oxygen-column pressures, in the first operating mode, to (a) correspond to the low-pressure column pressure range or (b) be at least 50 mbar and/or up to 700/900 mbar lower than the low-pressure column pressure range.
(c) Setting the argon-column and pure-oxygen-column pressures, in the second operating mode, at least 50 mbar or 100 mbar and/or up to 700/900 mbar below the corresponding first-mode pressures.
(d) A valve-based, mode-dependent control of the feedstream to the argon column responsive to the operating modes.
However, EP ‘393 teaches an auxiliary column system comprising a crude argon column (10) and a pure oxygen column (5), wherein: an argon-enriched stream (4) is drawn from the low-pressure column (3) and fed to the crude argon column (10); the pure oxygen column (5) has a sump evaporator (8); head gas (9) from the pure oxygen column is introduced into the bottom/sump of the crude argon column (10); crude argon sump liquid (15) is split, with a first part (17) fed to the top of pure oxygen column (5) and a second part (18) fed to a mass-transfer section of pure oxygen column (5); return flow (20) from the upper mass-transfer section drains back to low-pressure column (3); and a high-purity oxygen product 90 is withdrawn from the pure oxygen column (EP ‘393, abstract; claim 1; Fig. 1). EP ‘393 thereby teaches the pure oxygen column, the liquid return flow removed from the argon column between regions C and D, and the head gas removed from the pure oxygen column and fed into the argon column between regions C and D (or D1/D2), as recited in claim 1 and as identified above.
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 cryogenic air separation plant of DE ‘696 by incorporating the pure-oxygen-column/crude-argon-column integration of EP ‘393 because: (i) DE ‘696 and EP ‘393 are in the same field of cryogenic air separation and both employ a crude argon column fed from the low-pressure column; (ii) the integration of EP ‘393 represents a known way to obtain a high-purity oxygen product while reusing the head gas and crude-argon sump liquid for column reflux/feed, thereby improving recovery and thermodynamic efficiency; and (iii) the modification is a combination of known elements according to known methods to yield predictable results. See MPEP § 2143.
The modified DE ‘696 does not expressly teach (b) Setting the argon-column and pure-oxygen-column pressures, in the first operating mode, in a pressure range that corresponds to the low-pressure column pressure range or is at least 50 mbar and/or up to 700/900 mbar lower than the low-pressure column pressure range; and (c) setting those pressures in the second operating mode at least 50/100 mbar and/or up to 700/900 mbar below the first-mode pressures.
However, Victor teaches a double-column air separation process with a hybrid upper column in which the argon column operates at a pressure lower than the feed/low-pressure column point, with typical pressure differences on the order of 4 psi (≈275 mbar) and argon-column/LP-column pressures within the 12-30 psia range. The lower argon-column pressure is taught to improve thermodynamic efficiency and reduce compression duty. (see Victor, abstract; description of argon column operating pressures and oxygen-rich liquid return from argon column to LP column). Victor thereby teaches operating the argon column (and, by extension as further explained with respect to Kooijman below, the pure-oxygen column in fluid communication therewith per EP ‘393) at a pressure offset below the low-pressure column pressure within the recited 50 mbar to 700/900 mbar range, addressing (b) above.
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to further modify the modified DE ‘696 by operating the crude argon column (and the pure oxygen column of EP ‘393 in fluid communication therewith) at a pressure lower than the low-pressure column, within the range taught by Victor, in order to obtain the well-known thermodynamic efficiency and reduced compression-duty benefits taught by Victor. The selection of a pressure offset of at least 50 mbar and up to 700-900 mbar below the LP column is within or overlaps the offset taught by Victor and represents the routine result-effective optimization of a known operating variable. MPEP § 2144.05.
The modified DE ‘696 does not expressly teach (c) Setting the argon-column and pure-oxygen-column pressures specifically in the second operating mode at least 50/100 mbar and/or up to 700/900 mbar below the corresponding first-mode pressures; and (d) the valve-based, mode-dependent control of the argon-column feedstream and reflux/flow responsive to operating mode.
However, Al-Chalabi teaches a process and apparatus for controlling the argon-column feedstream, including a side stream from the LP column at the argon band to a crude argon stage, a return liquid from the crude argon column to the LP column near the takeoff, and control valves (e.g., valve 66) that adjust process variables (including argon production rate, feedstream flow to the crude argon column, and oxygen product withdrawal rate) responsive to plant conditions. (See Al-Chalabi, abstract; description of valve 66 and controlled variables: col. 6, ln 21-68; fig. 1-2c). Al-Chalabi thereby teaches the valve-based, mode-dependent control of the argon-column feedstream and the resulting differential operating-mode pressures in the argon column (and, in the integrated arrangement of EP ‘393, the pure oxygen column), addressing (c) and (d) above. Reducing the argon-column feed and operating pressure in the second (reduced-output) mode as taught by Al-Chalabi produces a corresponding reduction in argon-column and pure-oxygen-column operating pressure within the recited 50/100 mbar to 700/900 mbar offset between first and second modes.
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to further modify the modified DE ‘696 with the valve-based feedstream control of Al-Chalabi because: (i) DE ‘696 already employs control device (50) to switch between two operating modes by adjusting flow in bypass line (20), and Al-Chalabi provides additional, more specific control mechanisms for the same purpose; (ii) Al-Chalabi expressly identifies argon production rate, feedstream flow to the crude argon column, and oxygen product withdrawal rate as controlled variables, each of which directly affects argon-column and pure-oxygen-column operating pressure; and (iii) applying the known valve-based control of Al-Chalabi to the DE ‘696/EP ‘393/Victor plant yields the predictable result of differential operating-mode pressures within the recited ranges. KSR; MPEP § 2143.
Kooijman (NPL) further evidences the above and resolves any remaining gap: to the extent any limitation regarding the relative pressure relationships among the HP column, LP column, argon column, and pure oxygen column is not already expressly taught by the modified DE ‘696 above, Kooijman expressly teaches that, in a conventional ASU with pure argon recovery: the HP column operates at approximately 6 bar and the LP column at approximately 1.2 bar; the HP and LP columns share a shell and main condenser; the argon side rectifier is fed by a vapor side draw from the LP column; the argon column bottoms liquid is returned to the LP column by gravity; and the argon column operates at a pressure lower than the LP column (Kooijman, figures on page 1). Kooijman further teaches that internal flowrates are varied to obtain pure gaseous nitrogen and pure oxygen products, consistent with the recited mode-dependent operation (see Kooijman page 2, last paragraph). Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to rely on Kooijman as an evidentiary teaching that the recited pressure relationships are within the routine operating envelope of a conventional ASU with pure argon recovery, further supporting the obviousness of the claimed pressure ranges in the first and second operating modes.
In regard to claim 2, the modified DE ‘696 teaches the method according to claim 1, wherein a valve in the line for feeding the first transfer quantity of the first transfer fluid into the argon column is closed or more closed in the second operating mode than in the first operating mode (DE ‘696 teaches control device 50 operating a valve in bypass line 20 to selectively divert fluid D away from the further rectification columns 13/14/15 in the second operating mode, such that the valve in the line feeding fluid D to the crude argon column is closed (or more closed) in the second operating mode than in the first. (DE ‘696, control device 50 and bypass line 20)).
DE ‘696 does not expressly teach express disclosure of a graduated/partial-closure valve position responsive to plant conditions.
Al-Chalabi teaches use of control valves (e.g., valve 66) to adjust the feedstream to the crude argon column over a range of positions responsive to plant operating conditions. (Al-Chalabi, valve 66)). It would have been obvious to one of ordinary skill to apply the graduated valve control of Al-Chalabi to the mode-switching valve of DE ‘696 in order to obtain the predictable result of a "more closed" valve position in the reduced-output second mode, for the same reasons set forth above in claim 1.
In regard to claim 3, the modified DE ‘696 teaches the method according to claim 1, wherein DE ‘696 teaches the pressure column and low-pressure column are connected by a main condenser; the head gas from the low-pressure column is used to provide the nitrogen product (DE ‘696 teaches thermal coupling of HP column 11 and LP column 12 via a main condenser, with overhead gas B from LP column 12 providing the gaseous nitrogen product. (DE ‘696, main condenser; stream B)).
DE ‘696 does not expressly teach a recirculating stream formed using the head gas of the LP column, heated, compressed, cooled, passed at least partially through the main condenser and/or sump evaporator of a pure oxygen column, condensed at least partially, and fed back into the pressure column and/or low-pressure column.
EP ‘393 teaches a sump evaporator 8 of pure oxygen column 5 thermally integrated with the column system. (EP ‘393, sump evaporator 8). It would have been obvious to one of ordinary skill, in view of the EP ‘393 sump evaporator and the conventional recirculation of LP head gas, to form the recited recirculating stream using the LP head gas of DE ‘696 and pass it through the main condenser and/or sump evaporator of the pure oxygen column of EP ‘393, in order to recover refrigeration and improve plant efficiency.
The modified DE ‘696 is further evidenced by Kooijman: to the extent the heating/compressing/cooling and partial-condensation steps of the recirculating stream are not expressly enumerated, Kooijman evidences that such recirculation, compression, cooling, and partial condensation against the main condenser of an ASU are conventional operations in the field. (Kooijman.) Applying this conventional recirculation arrangement to the modified DE ‘696 would have been obvious as a combination of known elements yielding predictable results.
In regard to claim 4, the modified DE ‘696 teaches the method according to claim 1, wherein DE ‘696 teaches the nitrogen product quantity in the second operating mode is reduced relative to the first operating mode (DE ‘696 teaches that in the second operating mode fluid D is bypassed and the further rectification columns are bypassed/operated under reduced load, reducing nitrogen-product output relative to the first mode. (DE ‘696, bypass mode)).
DE ‘696 does not expressly teach the specific numerical recitation that the second-mode nitrogen product quantity is "at least 2.5%" less than the first-mode quantity. However, it would have been obvious to one of ordinary skill in the art before the filing date of the invention to modify the base reference De 696 or Linde to include the use of “specific numerical recitation that the second-mode nitrogen product quantity is "at least 2.5%" less than the first-mode quantity” as it constitutes an obvious mechanical expedient and falls within the realm of one of ordinary skill in the art as an obvious routine design optimization. And it has been recognized that Where the general conditions of a claim are disclosed in the prior art, discovering the optimum or workable range involves only routine skill in the art. MPEP § 2144.05.
In regard to claim 5, the modified DE ‘696 teaches the method according to claim 1, wherein DE ‘696 teaches the low-pressure column is operated at ≈ 1.4 bar across operating modes; the bypass of fluid D in the second mode does not require substantial change in HP/LP column pressures (DE ‘696 teaches LP ≈ 1-2 bar (e.g., 1.4 bar) and HP ≈ 4-7 bar (e.g., 5.3 bar) (DE ‘696, pressure disclosures)).
DE ‘696 does not expressly teach that the LP column pressure changes by "not more than 100 mbar" between the two modes.
However, Kooijman teaches that the HP and LP columns share a shell and main condenser, with the HP column operating at ≈6 bar and the LP column at ≈1.2 bar, such that the HP/LP thermal coupling across the main condenser requires the LP column to be maintained within a narrow operating-pressure band. (See claim 1 rejection in view of Kooijman). Victor likewise teaches LP-column operating pressures in the 12-30 psia range with controlled pressure differentials relative to the argon column. (See Victor, abstract; argon-column/LP pressure relationships). Together, Kooijman and Victor teach that the LP-column operating pressure is a result-effective variable that is held within a defined band during operation of a cryogenic ASU.
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention, to operate the modified DE ‘696 plant so that the pressure in the low-pressure column changes by not more than 100 mbar between the first and second operating modes, in order to maintain a substantially constant LP-column pressure while switching between the argon-recovery (first) and bypass/reduced-recovery (second) modes of DE ‘696 and to predictably preserve (i) rectification stability in the LP column, (ii) heat balance across the main condenser/reboiler that thermally couples the HP and LP columns, and (iii) overall column separation performance and product purity, while still permitting the mode-dependent reduction in nitrogen-product output expressly contemplated by DE ‘696.
DE ‘696 already teaches switching between argon-recovery and bypass/reduced-recovery operating modes while operating the LP column within a defined pressure range (LP ≈ 1-2 bar; e.g., 1.4 bar), and Victor and Kooijman teach pressure differentials and operating-pressure control as routine result-effective variables in ASU practice. Limiting the inter-mode LP pressure swing to ≤100 mbar is therefore an obvious operating choice yielding predictable results, and represents at most a routine optimization of a known result-effective variable. See MPEP §§ 2143, 2144.05.
In regard to claim 6, the modified DE ‘696 teaches the method according to claim 1, wherein DE ‘696 teaches regions A and B of the low-pressure column are accommodated in a common column shell, with region B above region A (DE ‘696 teaches LP column 12 as a single column shell having an upper rectification region (near overhead stream B) above the lower rectification region (below the side-draw of fluid D) (DE ‘696, LP column 12)).
In regard to claim 7, the modified DE ‘696 teaches the method according to claim 1, wherein DE ‘696 teaches regions C and D of the argon column are accommodated in separate column shells (DE ‘696 teaches crude argon column 13 and further separation apparatus 15 (sections 15a/15b) as separate shells in fluid communication. (DE ‘696, columns 13/15)). Note: claim 7 is evaluated on the merits in view of the 112(b) rejection above.
DE ‘696 does not expressly teach that the shell with region C is arranged above the shell of the pure oxygen column and connected thereto or integral therewith.
However, EP ‘393 teaches the crude argon column 10 arranged above and fluidly integrated with the pure oxygen column 5, with head gas 9 fed from the sump of pure oxygen column 5 into the bottom of crude argon column 10 (EP ‘393, Fig. 1; abstract)). It would have been obvious to one of ordinary skill to so arrange the C-region shell above and connected to/integral with the pure oxygen column shell to permit gravity-driven liquid return and direct head-gas transfer, as expressly taught by EP ‘393.
In regard to claim 13, the modified DE ‘696 teaches the method according to claim 1, wherein DE ‘696 teaches operating the HP and LP columns at conventional ASU pressures (DE ‘696 teaches HP ≈ 4-7 bar (e.g., 5.3 bar) and LP ≈ 1-2 bar (e.g., 1.4 bar). (DE ‘696, pressure disclosures)).
DE ‘696 does not expressly teach operating the pressure column at 9-14.5 bar and the LP column at 2-5 bar.
However, Victor teaches operating the HP/LP columns within the 12-30 psia range (≈0.83-2.07 bar absolute), with the argon column operated at a lower pressure than the LP/feed point, in order to improve thermodynamic efficiency and reduce compression duty (Victor, abstract; description of HP/LP/argon column pressure relationships). EP ‘393 teaches a main air compressor operating at approximately 6 bar with high-purity nitrogen product purity at approximately 1 ppm. See also EP ‘393, abstract; main air compressor disclosure. Kooijman further teaches HP ≈6 bar and LP ≈1.2 bar with HP and LP columns thermally coupled across a main condenser. Therefore, to the extent the cited art does not expressly disclose the exact recited ranges of 9 to 14.5 bar for the pressure column and 2 to 5 bar for the low-pressure column, it would nonetheless have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention, to select these pressure ranges as a matter of routine optimization and engineering expedient within the known cryogenic ASU pressure regime, in order to maintain main-condenser/reboiler duty, the HP/LP thermal coupling, the desired product withdrawal pressure for the gaseous nitrogen product, and overall rectification efficiency.
A person of ordinary skill in the art, recognizing absolute column pressure as a result-effective variable, would have routinely adjusted the absolute HP and LP operating pressures upward (e.g., to 9-14.5 bar and 2-5 bar, respectively) according to the desired nitrogen-product delivery pressure and plant load, while preserving the known HP/LP pressure-ratio relationship and the heat exchange through the main condenser as taught by the above prior arts. The recited ranges overlap and/or are immediately adjacent to the pressure regimes taught by the cited arts, and where the general conditions of a claim are disclosed in the prior art, discovery of the optimum or workable ranges involves only routine skill in the art.
In regard to claim 15, the modified DE ‘696 teaches the method according to claim 1, wherein DE ‘696 teaches substantial differences in argon-column/pure-oxygen-column duty between the first and second operating modes (DE ‘696 teaches mode-switching that reduces the load on the further rectification columns 13/14/15 in the second mode. (DE ‘696, modes 1 and 2)).
DE ‘696 does not expressly teach that the argon-column pressure and pure-oxygen-column pressure in the second mode are each at least 100 mbar and up to 700 mbar below the corresponding first-mode pressures.
However, Victor expressly teaches argon-column pressure offsets on the order of ≈275 mbar (4 psi) below the LP column. Al-Chalabi further teaches valve-based control producing different operating pressures between modes (see the rejection of claim 1 above). Operating with a 100-700 mbar pressure offset between first-mode and second-mode pressures falls within the same operating envelope and would have been obvious as a routine optimization for the reasons stated above in claim 1.
In regard to claim 16, the modified DE ‘696 teaches the method according to claim 1, wherein DE ‘696 teaches reduced nitrogen-product output in the second operating mode relative to the first (DE ‘696 teaches bypass of fluid D in the second mode, reducing nitrogen-product output. (DE ‘696, second operating mode)).
DE ‘696 does not expressly teach that the second-mode nitrogen product quantity is "10% to 60%" less than the first-mode quantity. However, it would have been obvious as a routine optimization: wherein a 10-60% turndown of nitrogen product is a routine operating turndown range consistent with the mode-switching expressly contemplated by DE ‘696 and would have been obvious to one of ordinary skill as a matter of routine optimization. MPEP § 2144.05.
In regard to claim 17, the modified DE ‘696 teaches the method according to claim 1, wherein DE ‘696 teaches regions C and D in separate column shells (See claim 7 above; DE ‘696 teaches separate shells for the crude argon column 13 and the further separation apparatus 15 (DE ‘696, columns 13/15)).
DE ‘696 does not expressly teach that the shell with region C is arranged above the shell of the pure oxygen column and connected thereto or integral therewith (without the "in particular" qualifier of claim 7).
EP ‘393 teaches, and it would have been obvious to modify DE ‘696 with EP ‘393, wherein EP ‘393 expressly teaches the crude argon column 10 arranged above and fluidly integrated with the pure oxygen column 5. (EP ‘393, Fig. 1; abstract). The combination is obvious for the reasons set forth above in claim 1 and claim 7.
Conclusion
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/W.M/Examiner, Art Unit 3763
/FRANTZ F JULES/Supervisory Patent Examiner, Art Unit 3763
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