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
Applicant’s election without traverse of invention I (encompassing claims 1-10 and 20) in the reply filed on 05/26/2026 is acknowledged. Claims 11-19 are withdrawn from further consideration pursuant to 37 CFR 1.142(b) as being drawn to a nonelected invention, there being no allowable generic or linking claim.
Specification
The title is objected to as containing a typographical error: “COMSUMPTION” appears in place of “CONSUMPTION.” A corrected title is required. See 37 C.F.R. § 1.72(a); MPEP § 606.
The disclosure is objected to because of the following informalities:
Reference numeral (215) is used for three different streams: the flow from the outlet of the refrigerant tank (212) to the inlet of the chiller (208), the flow received at the inlet of the refrigerant compressor, and the flow through the recycle valve (¶¶ 0037, 0055, 0061). A single reference character may not designate three streams. See 37 C.F.R. § 1.84(p)(4); MPEP § 608.01(o).
The specification defines Cp in the cooling-duty expression as “specific gravity of the production fluid” (¶ 0062). Cp is the conventional symbol for specific heat capacity, and the recited product of volumetric flow rate, density, Cp and a temperature difference yields a rate of heat transfer only if Cp is a specific heat capacity. Specific gravity is dimensionless and yields no unit of power. This informality is further addressed under 35 U.S.C. § 112 below. Appropriate correction is required.
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:
the monitoring system (120) and production control system (107) in claim 1, is understood to be as hardware and/or software on plant servers or a programmable logic controller corresponding to the computer (402), and the control logic (135) as software executing the algorithm of FIG. 3 (¶¶ 0025, 0029, 0042, 0052, 0067–0075).
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 1-10 and 20 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 enablement requirement. The claim(s) contains subject matter which was not described in the specification in such a way as to enable one skilled in the art to which it pertains, or with which it is most nearly connected, to make and/or use the invention.
Claim 1 recites “calculating, using the plurality of production parameters, an isentropic efficiency value for the primary compressor if the production flow rate is less than a production threshold”; “comparing each of the plurality of isentropic efficiency values”; “determining from the comparing each of the plurality of isentropic efficiency values, a primary compressor having a lowest isentropic efficiency value”; and “selecting the respective primary compressor having the lowest isentropic efficiency value.” Claim 2 further recites “calculating, using the recycle valve opening measurement and the driver power value, the isentropic efficiency value.” Claim 5 further recites “selecting the respective primary compressor with next lowest isentropic efficiency value.” Claims 3, 4, 6–10 and 20 incorporate the above limitations of claim 1 by dependency. The specification discloses one manner of obtaining the recited value, Equation (1) at ¶ 0055, described in connection with step (305) of FIG. 3:
eff = [(total flow − recycle flow) ÷ total flow] × [ΔHisen ÷ Driver Power]
where total flow is the total refrigerant flow through the compressor inlet, recycle flow is the flow through the recycle valve, ΔHisen is the change in enthalpy at the inlet and outlet of the compressor given by the temperature of the fluid at the inlet and outlet, and driver power is the power required to power the compressor (¶ 0055).
Equation (1) does not yield an isentropic efficiency. The leading bracketed term is a ratio of two flows and is dimensionless. The trailing bracketed term is a specific enthalpy change divided by a power — energy per unit mass divided by energy per unit time: having dimensions of time per unit mass. Their product therefore has dimensions of time per unit mass. An isentropic efficiency is the dimensionless ratio of the ideal to the actual work of compression and takes a value between zero and one.
The defect is not notational. Recovering a dimensionless efficiency requires multiplying the specific enthalpy change by a mass flow rate; dividing the net flow by the total flow instead introduces a reciprocal mass flow having no counterpart in any art-recognized definition. The specification supplies no worked example, numerical value, units, or expected magnitude for “eff.” Nor does it identify the thermodynamic state at which ΔHisen is evaluated, stating only that it is given by the inlet and outlet temperatures, whereas an isentropic enthalpy change is evaluated at the compressor discharge pressure and the compressor suction entropy and cannot be obtained from those temperatures alone.
Considering the Wands factors, the invention is a control method whose entire operation turns on this value; the claims reach any refrigerant compressor in any production train; the direction provided is the single defective expression at ¶ 0055; and no working example is provided. One of ordinary skill would be required to reconstruct by trial and error the computation on which every subsequent step of claim 1 depends. Undue experimentation would therefore be required to practice the limitations identified in part (A). See MPEP §§ 2164.01(a), 2164.06.
Claim 8 recites “calculating a cooling duty of the refrigeration system for liquefying the production fluids” and “determining whether the cooling duty is greater than a cooling threshold.” The specification discloses one manner of obtaining the recited duty, Equation (3) at ¶ 0062, which recites the product of the production flow rate V, the production fluid density ρfl, Cp, and a temperature difference ΔT, and defines Cp as “specific gravity of the production fluid.” Specific gravity is a dimensionless ratio of densities. The recited product therefore yields a quantity having dimensions of mass per unit time multiplied by temperature, which is not a duty. No other disclosure enables the claimed cooling duty, and no cooling threshold value, or basis for selecting one, is disclosed anywhere in the specification (¶ 0063). Undue experimentation would therefore be required to practice the limitations identified in claim 8.
Any amendment addressing this rejection must be supported by the disclosure as originally filed and must not introduce new matter. See MPEP § 2163.06.
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 and 20 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 “an isentropic efficiency value” in line 15-16 renders the claim indefinite. Isentropic efficiency has a settled meaning in the art: the dimensionless ratio of ideal to actual work of compression. As shown above, the only disclosed computation does not produce a dimensionless ratio. It cannot be determined whether the claimed value is the art-recognized isentropic efficiency, the quantity produced by Equation (1), or some third quantity. See MPEP §§ 2173.05(a), 2111.01(IV).
Claim 1 the determining step recites “a production threshold” in line 13 and the calculating step again recites “a production threshold,” in line 17 raising the question whether the “production threshold” of the calculating step refers to the same production threshold of the determining step, or entirely different threshold.
Claim 1 recites “the plurality of isentropic efficiency values” lacks proper antecedent basis. Only “an isentropic efficiency value for the primary compressor” is previously recited. The same defect attends “each of the plurality of isentropic efficiency values,” “one of the plurality of isentropic efficiency values,” and “all other isentropic efficiency values.”
Claim 1 recites “the one of the plurality of production trains.” Insufficient antecedent basis in the reducing and redirecting steps. No particular train has been identified; claim 1 identifies only a primary compressor.
Claim 1 recites “a production flow therethrough.” It is unclear whether the singular flow is a single aggregate flow to the trains collectively or a respective flow through each train. The ambiguity is material: the claim obtains a production flow rate “for each production train” and compares it to a threshold, whereas the specification describes the threshold as a total facility feed rate of 1450 mmscfd (¶ 0054).
Claim 1 recites “the primary compressor.” Each train “respectively comprises a primary compressor,” establishing a plurality; it is unclear which is intended in the calculating step.
Claim 5 recites “the lowest isentropic” in line 5 is incomplete and lacking antecedent basis. Claim 1 recites “a lowest isentropic efficiency value.”
Claim 5 affirmatively requires shutting down the secondary compressor and, in the same claim, conditions deselection on that secondary compressor being “already shutdown.” The condition is necessarily satisfied by the claim's own antecedent step, and it is unclear whether the deselection is intended to be contingent at all.
Claim 5 recites “the selected primary compressor”, in the final step, renders the claim indefinite because it is ambiguous whether this refers to the compressor selected in claim 1, which claim 5 has just deselected, or to the compressor with the next lowest value selected in the preceding clause.
Claim 6 recites step within a “wherein” clause. It is unclear whether claim 6 requires an initiating step in addition to that of claim 1, or merely specifies the source of the input for the initiating step of claim 1.
Claim 8 recites “the production fluids” in line 2 lacks proper antecedent basis.
Claim 8 recites determining whether the cooling duty is greater than a cooling threshold and deselecting the selected primary compressor, without stating whether the deselecting occurs when the duty exceeds the threshold, when it does not, or without regard to the outcome. The specification describes continuing normal operations when the duty is greater than or equal to the threshold and proceeding toward shutdown when it is less (¶ 0063), which is the opposite of the ordering the claim language suggests.
Claim 9 recites “optimizing.” A relative term of degree. Neither the claim nor the specification provides a standard for what degree of improvement constitutes optimizing, or the baseline against which it is measured. See MPEP § 2173.05(b).
Claim 9 recites “wherein optimizing energy consumption reduces carbon dioxide emissions” in line 3 renders the claim indefinite because the limitation recited result rather than a manipulative step; no carbon dioxide emission is recited or measured by any step. It is unclear what the recitation requires.
Claims 10 and 20 recites “the lowest isentropic value.” Insufficient antecedent basis. Claim 1 recites “a lowest isentropic efficiency value” and attributes it to a primary compressor, not to a production train. The excluded train cannot be identified.
Claims 2, 3, 4 and 7 are also rejected under 35 U.S.C. § 112(b) for being dependent upon a rejected claim.
The following is a quotation of 35 U.S.C. 112(d):
(d) REFERENCE IN DEPENDENT FORMS.—Subject to subsection (e), a claim in dependent form shall contain a reference to a claim previously set forth and then specify a further limitation of the subject matter claimed. A claim in dependent form shall be construed to incorporate by reference all the limitations of the claim to which it refers.
The following is a quotation of pre-AIA 35 U.S.C. 112, fourth paragraph:
Subject to the following paragraph [i.e., the fifth paragraph of pre-AIA 35 U.S.C. 112], a claim in dependent form shall contain a reference to a claim previously set forth and then specify a further limitation of the subject matter claimed. A claim in dependent form shall be construed to incorporate by reference all the limitations of the claim to which it refers.
Claim 20 is rejected under 35 U.S.C. 112(d) or pre-AIA 35 U.S.C. 112, 4th paragraph, as being of improper dependent form for failing to further limit the subject matter of the claim upon which it depends, or for failing to include all the limitations of the claim upon which it depends.
Claim 20 depends from method claim 1 and recites only that “the production control system is configured to redistribute production flow equally…” a “configured to” recitation requires only capability, not performance. Claim 20 therefore adds no step that must be carried out in practicing claim 1 and does not narrow its scope. See MPEP §§ 2111.04, 608.01(n)(III).
Claim 20 is further substantially duplicative of claim 10, which recites the same redistribution as an affirmative step. Applicant may cancel the claim(s), amend the claim(s) to place the claim(s) in proper dependent form, rewrite the claim(s) in independent form, or present a sufficient showing that the dependent claim(s) complies with the statutory requirements.
Claim Interpretation — Conditional Limitations
Claim 1 conditions the calculating step on “if the production flow rate is less than a production threshold.” Claims 5 and 8 likewise recite contingent limitations.
Under the broadest reasonable interpretation, a method step conditioned on an event need not be performed if the condition does not occur. See MPEP § 2111.04(II). Because every subsequent step of claim 1 operates on the isentropic efficiency values produced by the conditional calculating step, the broadest reasonable interpretation of claim 1 encompasses a performance in which the production flow rate is not less than the threshold and none of those steps is carried out. This interpretation is noted for the record; the art applied below is shown to teach the conditional steps themselves.
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, 4-7, 9, 10 and 20 are rejected under 35 U.S.C. § 103 as being unpatentable over Taha (US 2009/0248174) in view of Singh (US 2007/0089440), Staroselsky (US 5,743,715) and Van de Rijt (US 2019/0195555).
In regard to claim 1, Taha teaches a method for monitoring and controlling energy consumption of a refrigeration system (first refrigeration system 34, second refrigeration system 54, third refrigeration system 64, each compressing a working fluid by compressors 35, 55, 65, the refrigeration load comprising the electricity required to operate them) operatively connected to a plurality of production trains (liquid recovery trains 1–n; trains 72, 74, 76, 78) (¶¶ 0022–0026, 0030; figs. 1–3), the method comprising:
using a monitoring system (controller 71 communicating with each train over links 73, 75, 77, 79, with output 82 providing a readout of compressor electricity usage in amperes, the flow rate to each individual train, and percent recovery), initiating a control logic configured to control a production control system pertaining to the refrigeration system (optimal targets fed to a multivariable controller algorithm or entered in the plant distributed control system, with mixed integer optimizers determining the number of deactivated refrigeration compressors) (¶¶ 0027, 0030; fig. 3);
wherein the plurality of production trains includes a production flow therethrough (compressed feed gas stream 3 delivered by a header manifold system through feed lines 4, 5, 6, 7, 8 to the individual trains, natural gas feed stream 9 entering each train) (¶¶ 0015–0016; figs. 1–2);
wherein each of the production trains respectively comprises a primary compressor (compressor 35 of first refrigeration system 34; four trains carrying eight propane compressors of 40,000 horsepower each) (¶¶ 0023, 0033; fig. 2);
for each production train, obtaining a plurality of production parameters, wherein one comprises a production flow rate (output 82 providing the flow rate to each individual train alongside its compressor electricity usage; input values including total feed to the facility, ambient temperature and feed composition) (¶¶ 0030–0031; fig. 3);
determining whether the production flow rate is less than a production threshold (one C3 compressor may be shut down without loss of recovery if total feed is less than 1,470 MMSCFD; six compressors suffice below 1,260 MMSCFD) (¶ 0033);
reducing the production flow to the one of the plurality of production trains which includes the selected primary compressor (the train with a deactivated compressor receives a proportionally reduced feed) (¶ 0033);
redirecting the production flow from the one of the plurality of production trains including the selected primary compressor to at least one other of the plurality of production trains (redirecting a portion of the flow from the train with a deactivated compressor and distributing it to other trains; splitters added to redirect flow) (¶¶ 0032, 0035; claim 1, step (h)); and
shutting down the selected primary compressor (deactivating a refrigeration compressor of the functioning facility, whereby compressor load and operating cost are reduced) (¶¶ 0007, 0032).
Taha does not explicitly teach calculating, using the plurality of production parameters, an isentropic efficiency value for the primary compressor.
However, Singh teaches a refrigeration system (100) having a plurality of compressors (104) in a rack (110), each with its own discharge temperature sensor (114) and suction temperature sensor (115), together with suction pressure sensor (118) and discharge pressure sensor (124), a controller (140) that switches the individual compressors on and off through input/output module (142), and energy sensors (150) monitoring each component's energy consumption (¶¶ 0051, 0055, 0058, 0062; figs. 1, 3). Singh calculates an isentropic efficiency for the compressor from those measurements as NCMP = (hID − hsuc)/(hDIS − hsuc) × 100, the enthalpies being obtained from the measured suction and discharge pressures and temperatures (¶¶ 0095–0096; fig. 25, steps 2500, 2502). Singh teaches that a lower isentropic efficiency identifies a compressor operating inefficiently and consuming more energy than required (¶¶ 0093–0094).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the method of Taha to calculate an isentropic efficiency value for each of the primary compressors as taught by Singh, in order to identify the compressor that is operating inefficiently and consuming more energy than required, as Singh teaches that a lower isentropic efficiency so identifies a compressor and that closely monitoring compressor performance in this manner maximizes efficiency and thereby reduces operational costs (Singh ¶¶ 0004, 0093–0094). One of ordinary skill would have been motivated to make this modification because Taha seeks to minimize the refrigeration system's electricity usage and expressly contemplates an equipment performance monitor for the refrigeration compressors without specifying the metric that monitor is to report (Taha ¶¶ 0006, 0026–0027), and because Singh's computation relies on suction and discharge pressures and temperatures already measured in Taha's plant.
Taha, as modified, does not explicitly teach comparing each of the plurality of isentropic efficiency values, determining from the comparing a primary compressor whose value is quantitatively extreme relative to all other such values, and selecting that compressor.
However, Staroselsky teaches a control method for a network of two or more compressors, expressly applicable to compressors in parallel, comprising defining a parameter characterizing the operating point of a compressor, calculating a value of that parameter for each of the compressors, and determining from all of the calculated values the single value that is extreme relative to all others, that determined value then governing the control action taken (claims 19–21, steps (a)–(c); claims 26, 45; Best Mode). Staroselsky performs the comparison for the purpose of distributing load among the compressors so as to operate them efficiently and to avoid the energy penalty of recycling (Disclosure of the Invention; Best Mode, Region 2).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have further modified the method of Taha in view of Singh to compare each of the isentropic efficiency values calculated for the several primary compressors and to determine therefrom the compressor whose value is extreme relative to all others, and to select that compressor, as taught by Staroselsky, in order to distribute the load among the compressors so as to operate them efficiently and to avoid the energy penalty of recycling, as Staroselsky teaches (Staroselsky, Disclosure of the Invention; Best Mode, Region 2).
In this case, one of ordinary skill would have been motivated to make this modification because Taha determines that one compressor may be deactivated at reduced facility feed but does not identify which of the several nominally identical compressors is to be deactivated (Taha ¶¶ 0027, 0033), and because Taha's output 82 already presents the per-train figures side by side for comparison across the four trains (Taha ¶ 0030; fig. 3). That Staroselsky determines a maximum rather than a minimum reflects only the polarity of its parameter, which increases toward the undesired condition; an efficiency is undesirable at its minimum, so one of ordinary skill applying Staroselsky's comparison step to Singh's isentropic efficiency values would determine the smallest.
Taha as modified by Singh and Staroselsky does not explicitly teach a primary compressor comprising a first recycle valve, or opening that recycle valve to fully opened.
However, Van de Rijt teaches, for refrigerant compressors serving parallel liquefaction trains, a refrigerant compressor unit (200) having suction side (201) and discharge side (202), with recycle line (211) and controllable compressor recycle valve (212) connecting discharge to suction, each compressor of a multi-compressor unit having its own recycle valve and line, and teaches that controlling the recycle valve means controlling it to a closed position, a fully opened position, or an intermediate position, the control scheme being triggered by a decrease in feed gas flow rate exceeding a predetermined threshold (¶¶ 0032–0036, 0052, 0109; figs. 1–5; claim 1). A liquid knock-out vessel (205) accumulates incidental liquid to allow shutdown of the compressor before liquid can enter it, and an uncontrolled response to a rapid feed-flow reduction results in train trip, flaring and mechanical damage (¶¶ 0013–0014, 0108).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the primary compressors of Taha to include the recycle line and controllable compressor recycle valve of Van de Rijt, and to drive that recycle valve to its fully opened position when taking the selected compressor out of service, in order to protect the compressor against surge and against liquid entering it as its process flow is withdrawn, and thereby to avoid the train trip, flaring and mechanical damage that Van de Rijt identifies as the consequence of an uncontrolled response to a rapid feed-flow reduction (Van de Rijt ¶¶ 0013–0014, 0052, 0108).
In regard to claim 2, the modified Taha teaches the method of claim 1 wherein the plurality of production parameters further comprises a recycle valve opening measurement (recycle valve stem position transmitter 24 supplying the valve stem position v, from which the valve flow coefficient Cv = fv(v) and the relative mass flow through the recycle valve mv are obtained, mv entering the per-compressor balancing parameter Sp* = [1 − β(1 − S)][1 + mv]) and a driver power value (power P computed from measured suction and discharge pressures and temperatures and a reduced head, or sensed directly by a power measuring device), and calculating, using the recycle valve opening measurement and the driver power value, the isentropic efficiency value (Staroselsky, Best Mode, Regions 2–3; claims 8–10, 19, 20, 23, 25–26, 38–40; Singh ¶¶ 0095–0096; fig. 25; Van de Rijt ¶¶ 0037, 0061, 0125).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the efficiency calculation of the modified Taha to use the recycle valve opening measurement and the driver power value as taught by Staroselsky, in order to avoid the energy penalty of recycling, which Staroselsky teaches is wasteful from an energy consumption standpoint and is the condition the control is designed to minimize (Staroselsky, Disclosure of the Invention; Best Mode, Region 2). One of ordinary skill would have recognized that recycled flow returns to suction and performs no net compression duty, and that driver power is the energy input against which any useful output must be normalized, and would further have been motivated by Van de Rijt, which monitors recycle valve opening as a percentage of maximum and identifies reduced driver power as the visible signature of a successful efficiency optimization (Van de Rijt ¶¶ 0037, 0061, 0125).
In regard to claim 4, the modified Taha teaches the method of claim 1 wherein each production train comprises a secondary compressor (second refrigeration compressor 55 of second refrigeration system 54, in parallel with system 34 and independently operable; eight propane compressors across four trains) comprising a second recycle valve (second recycle valve 212' and recycle line 211' over second compressor 203'), and closing the second recycle valve of the secondary compressor of the train having the selected primary compressor (the recycle valve being controllable to a closed position; the controller closing recycle valve 212 when a compressor unit efficiency optimization is performed) (Taha ¶¶ 0024, 0033; fig. 2; Van de Rijt ¶¶ 0034–0035, 0125, 0134; figs. 2, 5).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have closed the second recycle valve of the secondary compressor remaining in service while opening the recycle valve of the primary compressor being shut down, in order to obtain the most energy efficient operation of the refrigerant loop, as Van de Rijt teaches that closed-recycle operation affords the most energy efficient normal operation because of minimum pressure loss, and that automatic closing of the recycle valve is the visible signature of a successful compressor unit efficiency optimization (Van de Rijt ¶¶ 0052, 0125).
In regard to claim 5, the modified Taha teaches the method of claim 4 further comprising shutting down the secondary compressor of the train having the selected primary compressor (deactivating one or more refrigeration compressors; six of eight compressors operating below 1,260 MMSCFD, that is, two deactivated), deselecting the primary compressor having the lowest isentropic efficiency value if that train's secondary compressor is already shut down, selecting the primary compressor with the next lowest isentropic efficiency value, and shutting it down (Taha ¶¶ 0032–0033; claim 1, step (g); Singh ¶¶ 0095–0096).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have deselected the primary compressor of a train whose secondary compressor is already shut down and to have proceeded to the primary compressor bearing the next lowest isentropic efficiency value, in order to maintain the recovery and product specification on which Taha conditions any deactivation, since a train stripped of both of its refrigeration compressors would retain no refrigeration capacity (Taha ¶¶ 0032–0033). One of ordinary skill would have been motivated to do so because Taha teaches that successively more compressors are deactivated at successively lower facility feed rates, and because the comparison already performed identifies the next smallest value without further computation. See KSR, 550 U.S. 398; MPEP § 2143(I)(G).
In regard to claim 6, the modified Taha teaches the method of claim 1 wherein the monitoring system comprises a user interface (output 82 providing an operator readout of compressor electricity usage, per-train flow rate, and percent recovery), and initiating the control logic from input from the user interface (optimal targets implemented directly by plant operators entering them in the distributed control system; an automated controller or manual operator identifying the process scenario and deactivating one or more refrigeration compressors) (Taha ¶¶ 0027, 0030, 0032; fig. 3).
In regard to claim 7, the modified Taha teaches the method of claim 1 wherein the production threshold is a total facility feed rate in million standard cubic feet per day below which a refrigeration compressor may be shut down without loss of recovery, disclosed as 1,470 MMSCFD for four trains each limited to 420 MMSCFD, derived as three times 420 plus one half of 420 (Taha ¶ 0033).
Taha does not explicitly teach a production threshold of 1450 mmscfd. However, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have arrived at a production threshold of 1450 mmscfd, in order to set the threshold at the total facility feed rate below which a refrigeration compressor may be deactivated without loss of recovery for the particular facility at hand, as Taha teaches that threshold to be computed from the number of trains and the per-train capacity (Taha ¶ 0033). Taha's 1,470 MMSCFD differs from the claimed 1450 mmscfd by approximately 1.4 percent, and a prima facie case of obviousness exists where the claimed and prior art values are so close that one skilled in the art would have expected them to have the same properties. See Titanium Metals Corp. of America v. Banner, 778 F.2d 775, 227 USPQ 773 (Fed. Cir. 1985); MPEP § 2144.05(I). The threshold is further a result-effective variable whose optimum value involves only routine skill. See In re Aller, 220 F.2d 454, 105 USPQ 233 (CCPA 1955); MPEP § 2144.05(II)(B). The instant specification discloses no criticality for 1450 mmscfd, describing it as a numerical constant that may be a value or a range and may be entered by a user (¶ 0054).
In regard to claim 9, the modified Taha teaches the method of claim 1 further comprising optimizing energy consumption of the refrigeration system (optimizing operation by minimizing the refrigeration load, which comprises the electricity required to operate the refrigeration systems; minimizing overall electricity or energy usage; deactivation reducing compressor load and operating cost) (Taha ¶¶ 0002, 0006, 0026, 0032; Singh ¶ 0004).
The recitation requiring that optimizing energy consumption reduces carbon dioxide emissions recites a result rather than a manipulative step, and that result flows inherently from the recited act: reducing the electricity consumed by a refrigeration compressor necessarily reduces the carbon dioxide emitted in generating it where generation is fossil-fired. The instant specification asserts the same relationship without reciting any additional act (¶¶ 0063, 0077). A recitation of an inherent result does not distinguish the claim. See MPEP § 2112(I)–(II).
In regard to claim 10, the modified Taha teaches the method of claim 1 further comprising redistributing production flow among the production trains other than the one having the compressor of lowest efficiency (redirecting a portion of the flow from the train with a deactivated compressor and distributing it to other trains; splitters added to redirect or control amounts of flow; optimizing the feed flow rate distribution to each train; the worked example allocating a total feed below 1,470 MMSCFD as three trains at the full 420 MMSCFD plus one at half) (Taha ¶¶ 0032–0033, 0035; claim 1, step (h); claim 19).
Taha does not explicitly recite that the redistribution is equal. However, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have redistributed the withdrawn flow equally among the remaining production trains, in order to carry out Taha's instruction to optimize the feed flow rate distribution to each train while keeping every remaining train within its 420 MMSCFD rated capacity (Taha ¶ 0033; claim 1, step (h)). Taha's trains are nominally identical parallel units of equal rated capacity, and Taha's worked example allocates the redistributed flow so that each unaffected train carries the same full 420 MMSCFD. Equal division among identical parallel units is one of a finite number of identified, predictable distribution schemes and the only one leaving each remaining train the same margin below its rated capacity. See MPEP § 2143(I)(E).
In regard to claim 20, the modified Taha teaches the method of claim 1 wherein the production control system is configured to redistribute production flow equally among the production trains other than the one having the compressor of lowest efficiency, for the reasons given as to claim 10. As set forth under 35 U.S.C. § 112(d), the “configured to” recitation requires only capability; Taha's controller 71, which communicates with each of the four trains over links 73, 75, 77, 79 and optimizes the feed flow rate distribution to each train, possesses that capability (Taha ¶¶ 0030, 0032; fig. 3; claim 1, step (h); claim 19).
Claim(s) 3 is rejected under 35 U.S.C. 103 as being unpatentable over Taha, Singh, Staroselsky and Van de Rijt as applied to claim 2 above, and further in view of Jayanth (US 2016/0190799).
In regard to claim 3, the combination teaches the method of claim 2 comprising determining the driver power value using the monitoring system (output 82 providing a readout of compressor electricity usage in amperes; energy sensors 150 monitoring compressor energy consumption and reporting to controller 140; power sensed by a power measuring device or computed from measured suction and discharge pressures and temperatures) (Taha ¶ 0030; Singh ¶¶ 0058, 0062; Staroselsky claims 9–10).
The modified Taha does not explicitly teach determining the driver power value from at least a measured voltage, a measured current, and a power factor.
However, Jayanth teaches a compressor monitoring system comprising a current monitor measuring the current drawn by a compressor motor, a voltage monitor measuring the voltage of the motor, and a power factor monitor (606, 708) calculating the power factor from the measured current and voltage and generating power factor values, the power factor being the ratio of real power to the volt-ampere product of the supplied current and voltage (¶¶ 0012, 0019, 0091–0092, 0102–0104; figs. 8–9).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the driver power determination of Taha to use at least a measured voltage, a measured current and a power factor as taught by Jayanth, in order to obtain the real power drawn by the compressor motor rather than the apparent power, as Jayanth teaches that the power factor is the ratio of the real power consumed by the load to the volt-ampere product of the actual supplied current and voltage, and monitors that power factor on a compressor motor for control purposes (Jayanth ¶¶ 0012, 0019, 0091–0092).
Claim(s) 8 is rejected under 35 U.S.C. 103 as being unpatentable over Taha, Singh, Staroselsky and Van de Rijt as applied to claim 1 above, and further in view of Kang (US 2020/0025407).
In regard to claim 8, the combination teaches the method of claim 1 in which process heat exchanger duty is among the input variables of the optimization, and in which the scenario is classified as a compressor on scenario- the compressor not being deactivated, and therefore retained in or returned to service - if the modeled recovery falls below the baseline (Taha ¶¶ 0026, 0032; claims 2, 6).
The modified Taha does not explicitly teach calculating a cooling duty and determining whether it is greater than a cooling threshold.
However, Kang teaches, for a plant of plural refrigeration machines each comprising a compressor (12), calculating the delivered cooling capacity as Cap = cw × mchw × ΔTchw, the product of the specific heat of the cooled medium, its flow rate through the machine, and the difference between its inlet and outlet temperatures, and alternatively estimating capacity from refrigerant flow rate and evaporator inlet and outlet enthalpies (¶¶ 0038, 0041–0042). Kang compares the result against a reference, a machine scoring below the reference being considered inefficient, gives low operating priority to a machine unable to deliver the required cooling relative to setpoint, and brings the next machine online where the first cannot produce the cooling for the load (¶¶ 0043, 0045, 0055; figs. 2–3).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the method of Taha to calculate a cooling duty and to determine whether it is greater than a cooling threshold as taught by Kang, and to deselect the primary compressor otherwise selected for shutdown, in order to verify that a machine can be removed from service without compromising the cooling delivered, as Kang teaches giving low operating priority to a machine unable to deliver the required cooling relative to setpoint and bringing the next machine online where the first cannot produce the cooling for the load (Kang ¶¶ 0043, 0045, 0055). One of ordinary skill would have been motivated to make this modification because Taha permits deactivation of a compressor only where recovery and product specification are maintained, and otherwise classifies the scenario as a compressor on scenario in which the compressor is not deactivated (Taha ¶ 0032; claim 2).
Conclusion
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/W.M/Examiner, Art Unit 3763
/FRANTZ F JULES/Supervisory Patent Examiner, Art Unit 3763
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