DETAILED ACTION
Claim Status
Former Claim 41 is added to Claim 28.
Response to Arguments
Applicant's arguments filed 3/2/26 have been fully considered but they are not persuasive.
On pages 9-10, the remarks argue the following:
On page 9 of the Office Action, the Examiner concedes that Hoefer and Find do not teach that the amount of CO2 absorbed in step b is greater than the amount of CO2 absorbed in step e.
However, the Examiner alleges that Horizoe discloses the following:
*Citing to page 9 of the office action*
Horize's paragraph [0019] (cited by the Examiner on page 9 of the Office Action) merely recites an absorber without specifying which of the top portion 13a, middle stage 13b or bottom portion 13c is being referred to.
The remarks are respectfully not persuasive. The paragraphs cited in the office action include paragraphs 19, 21 and 51. Paragraph 51, which in the context is describing the absorbent removed at the middle stage 13b, which is adjusted to lower the CO2 absorption rate. This absorption solution, as shown in the figures, is returned at 12b, which is the upper portion of the second absorbent. Horizoe explains in the background that this is designed to increase the H2S removal rate, relative to the CO2 recovery (para. 10).
Next, pages 10-11 of the remarks argue the following:
Horize's paragraph [0051] recites the following:
*citing to para. 51 of Horize*
Horize's paragraph [0021] (cited by the Examiner on page 9 of the Office Action) merely recites it is possible to lower the CO2 absorption amount, but fails to specify where the such lowering is occurring. Horize's lowering of the amount of CO2 absorption fails to disclose, teach or suggest how much or relative to what magnitude of CO2 absorption that the CO2 absorption is lowered. For example, Horize fails to disclose whether the extraction of a part of the absorbent from the vicinity of the middle stage of the absorber effects or lowers the CO2 absorption in the top portion 13a or the bottom portion 13c, or both portions. Based on the foregoing, the proposed combination of Hoefer, Find and Horizoe fails to disclose, teach, or suggest all the limitations of claim 28.
The remarks are respectfully not persuasive. As explained above, Horizoe explains where the lowering of CO2 occurs. As to the amount of CO2 absorption and the magnitude of CO2 absorption, this feature is narrower than the claims. The claims do not require an amount of CO2 absorption. Therefore, this is outside of the scope of the claims.
Next, the remarks argue on pages 11-12, the following:
Unlike amended claim 28, Hoefer in view of Find, in view of Horizoe fails to disclose, teach, or suggest "increasing the pressure of the first gas effluent, to obtain a pressurized biogas stream or "d. feeding the pressurized biogas stream and a second liquid absorption stream to a second absorber of the second absorption step of a second absorption step."
On page 6 of the Office Action, the Examiner concedes the following:
*Citing to page 6 of the Office Action*
Applicant respectfully submits that Find merely discloses "compressing the provided stream (para [0008]), that when pressure is at or above 30 bar the gas can be condensed (para [0009]) and condensation does not require low temperature which are normally necessary at 15-20 bar. Find fails to disclose pressurization at the second absorption step recited in amended claim 28 and the Examiner's reasoning is merely based on hindsight reconstruction of what is recited in claim 28.
Applicant also points out that compression and pressurization are not the same.
Specifically, compression involves a reduction in volume while pressurization is directed to an increase in pressure. Thus, Find's disclosure of compression does not specifically disclose pressurization, as recited in claim 28.
Based upon the foregoing, the proposed combination of Hoefer, Find and Horizoe fails to disclose, teach or suggest all the limitations of amended claim 28. Accordingly claim 28 is allowable over the proposed combination of Hoefer, Find and Horizoe. Accordingly, Applicant respectfully requests reconsideration and withdrawal of the Hoefer, Find and Horizoe based section 103 rejection of claim 28.
In addition, one skilled in the relevant art would not have been motivated to consider pressurization at the second absorption step at least because if flow rate were to be lowered (as suggested by the Examiner) increasing pressure would work against lowering flow rate.
These remarks are respectfully not persuasive. Hoefer, the primary reference, already establishes that the absorption steps are pressurized at a range of 0.5 to 20 bar. Find explains the reason why pressurizing the absorber (continuing to pressurize) prior to absorption into the second absorber is desired and beneficial. As to the use of the word “compression”, it is respectfully argued that the current specification also uses the word “compression” interchangeably with “pressure”, see paragraph 27 of the published specification “. .. ..The pressure of the biogas stream is typically provided at about atmospheric pressure or slightly compressed. . “ (also see para. 49 and other instances of this).
Next, the remarks argue the following on pages 12-14:
In addition, there is inadequate motivation to combine Hoefer, Find and Horizoe. "If the proposed modification or combination of the prior art would change the principle of operation of the prior art invention being modified, then the teachings of the references are not sufficient to render the claims prima facie obvious." MPEP $2143.01 VI. Here, Hoefer is directed to a two stage absorber having a crude absorber 1 and a pure absorber 2 wherein a regenerated absorption medium is applied via line 4 to the top of the crude absorber 1, as shown in Hoefer's FIG. 2, reproduced below, and disclosed in Hoefer's paragraph [0091].
In contrast, Horizoe discloses an absorber 13 that includes a top portion 13a and a bottom portion 13c, with part of the absorbent 12 being extracted at a middle stage 13b between the top portion 13a and the bottom portion 13c via line L3. (See Horizoe paras. [0027] and [0048] and Horizoe's FIG. 1, reproduced below.
On page 9 of the Office Action, the Examiner refers to paragraph [0021] of Horizoe,
which states: *Cites to paragraph 21*
Thus, Horizoe teaches that for lower CO2 absorption there must be an extraction between the first and second stage.
Based on the foregoing, the addition of Horizoe's extraction feature to Hoefer's two stage absorber would change the principle of operation Hoefer because of the incompatibility of such extraction feature with Hoefer's input of regenerated absorption medium. Likewise, the addition of Hoefer's input of regenerated absorption medium to Horizoe's absorber 13 would change the principle of operation of Horizoe's absorber because of the incompatibility of such extraction feature with Hoefer's input of regenerated absorption medium. Based on the foregoing the proposed combination of Hoefer, Find and Horizoe is improper and insufficient to render claim 28 prima facie obvious. Accordingly, Applicant respectfully requests reconsideration and withdrawal of the Hoefer, Find and Horizoe based section 103 rejection of claim 28.
The remarks are respectfully not persuasive. Hoefer describes use of two absorbers, which can be in at least two configurations—individual and separated or connected and attached (see Fig. 1 and 2). In the connected and attached configuration, Hoefer teaches use of absorber (1) where the stream is removed from the bottom for regeneration (para. 91) and that it includes a second absorber stream up top (2), where new absorption solution is added at the top and used absorber is removed also via line 7 (from absorber 1).
Similarly, Horizoe describes a two-tier absorber that uses a first absorber (13B) and removes used absorber solution at the bottom for regeneration (Fig. 1, 12A). The system also includes a second absorber stream up top (at 13A), where fresh absorption solution is fed at 12 (Fig. 1). The primary difference is that in Horizoe, used absorber from the second absorber is removed at 12C. Horizoe addresses this difference in the background discussion. Horizoe explains that in the prior art, the systems used are effective for CO2 recovery, but not as effective with H2S recovery. As a solution to this, Horizoe proposes extracting part of the absorbent from the middle of the absorption portion of the absorber (para. 11). That is, removing absorbent from the middle of the absorber, the primary difference between Hoefer and Horizoe, is the contemplated improvement of Horizoe designed to improve H2S recovery from the gas stream.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries 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.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claim(s) 28, 29, 30, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 43, 49, 50, 54 is/are rejected under 35 U.S.C. 103 as being unpatentable over Hoefer (US Pub.: 2005/0202967) and in view of Find (US Pub.: 2013/0133363) and further in view of Horizoe (US Pub.: 2015/0361364).
As to Claims 28, 39, 40 and 54, Hoefer describes use of absorption medium (title) in treated acid gases (para. 1), such as those derived from biogas plants (para. 22) and other gases (para. 15, 19) from bacterial decomposition of organic substances (para. 18). These gases can all be considered types of biogases.
In their treatment steps, Hoefer describes feeding the gas to a first crude absorber 1 (para. 91) and then feeding the gas to a pure absorber 2 (para. 91). As to the absorption of CO2 and H2S, Hoefer teaches that the flashing of the absorption solution releases CO2 and H2S from the absorption medium (para. 90). Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that the absorption solution is used to sorb CO2 and H2S from the gas stream.
As to the regeneration step, Hoefer teaches that acid-gas loaded absorption medium is regenerated in a regeneration step and then the regenerated absorption medium is then recirculated back to the absorption step (para. 83). In Fig. 2, absorption medium leaves at 7 to be regenerated and then is returned via lines 4 and line 5, to both the first absorption reactor and the second absorption reactor (para. 91).
Hoefer teaches that the pressure in the absorption step is from 0.5 to 20 bar (para. 80, but Hoefer does not specifically teach that the gas stream entering the pure absorber 2, the second absorber reactor, is compressed.
Find describes a method of removing CO2 from a gaseous stream from a fermentation process using absorption (abstract). Find explains that the gaseous stream is compressed prior to absorption (para. 8). Find explains that it has been found that when the pressure of the gaseous stream is at least 30 bar, the gas can subsequently be condensed using fluids (para. 9). Furthermore, when the pressure is high, the amount of water necessary to obtain the desired purity (para. 11). Finally, Find explains the condensation following absorption does not require the lower temperature, which are normally necessary in order to condense CO2 when present at 15-20 bar (para. 11).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to compress the gas stream entering the second absorber, as taught by Find for use with the process of Hoefer because Find explains that compressing a gas stream prior to entering a second absorber reduces the amount of water necessary to obtain the desired purity and does not require as low of a temperature to condense the absorption solution.
The references do not teach that the amount of CO2 absorbed in step b is greater than the amount of CO2 absorbed in step e in the second liquid absorption stream (claim 41) or that the flow rate of the first liquid absorption stream is greater than the flow rate of the second liquid absorption stream (Claim 42).
Horizoe describes a system that employs a CO2 and H2S absorption column (para. 15), which has an upper part and a lower part (see Fig. 1, 13A and 13B). These can be considered two absorbers. The system absorbs CO2 and H2S with an absorbent (para. 17) and then the absorbent is fed to a regenerator to extract the absorbed CO2 and H2S from the absorbent (para. 17). The system can be designed to lower the amount of CO2 absorbed after the initial absorption in order to absorb more H2S by adjusting the flow rate of the absorbent (para. 21 and 19). As to the amount of CO2 absorbed in the second absorber, Horizoe explains that the CO2 absorption amount is lowered after first absorption in order to increase the amount of H2S absorbed (para. 51).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to lower the amount of CO2 absorbed into the second absorber, as taught by Horizoe for use with the dual absorber system of Hoefer and Find
because Horizoe explains that this then increases the amount of H2S absorbed into the absorption solution.
As to the flow rate, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to adjust the flow rate, as taught by Horizoe in order to adjust the amount of CO2 and H2S absorbed into the absorption solution in Hoefer and Find because Horizoe explains that this can be performed by varying the flow rate in order to remove more H2S from the stream.
As to Claim 29, the upgraded system can be considered the absorption systems described in Figure 2. The rejection of Claim 28 is re-iterated here.
As to Claim 30, Hoefer explains that the regenerated stream is fed back to the absorbers (see the rejection to Claim 28, which is re-iterated here).
As to Claims 32 and 33, Hoefer teaches that the absorption solution from the first and second absorbers are fed to the regenerator (see Fig. 2, 2, 1 and 8). Since both liquids are fed to the regenerator 8, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that they are mixed.
As to Claim 34, Hoefer teaches that some of the spent absorption solution is fed from the second absorber to the regenerator (see Fig. 2, 7, 8). The solution is returned, some of which are returned to the first absorber (Fig. 2, 5). Therefore, since the absorber solutions of both absorber columns are mixed in the regenerator, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention that some of the absorption solution from the second absorber is sent to the first absorber.
As to Claim 35, Hoefer teaches that the absorbent solution is fed to the upper absorber (see Fig. 2) and passes to the lower absorber (see Fig. 2) prior to exiting to the regenerator (see Fig. 2, 7). The rest of the claim is optional.
As to Claim 36, Hoefer teaches that the stripper column 21 releases CO2, as well as the upstream regenerator 8 (para. 92, 93).
As to Claim 37, Hoefer teaches that steam is used to strip out the gases from the absorption solution (para. 93). This is part of the regenerator system. The steam is generated using a reboiler (para. 93). Therefore, use of steam is considered a heating step of the absorber solution.
As to Claim 38, Hoefer explains that part of the regeneration system includes a stripper column with a reboiler (para. 93).
As to Claims 42 and 43, Horizoe describes a system that employs a CO2 and H2S absorption column (para. 15), which has an upper part and a lower part (see Fig. 1, 13A and 13B). These can be considered two absorbers. The system absorbs CO2 and H2S with an absorbent (para. 17) and then the absorbent is fed to a regenerator to extract the absorbed CO2 and H2S from the absorbent (para. 17). The system can be designed to lower the amount of CO2 absorbed after the initial absorption in order to absorb more H2S by adjusting the flow rate of the absorbent (para. 21 and 19). As to the amount of CO2 absorbed in the second absorber, Horizoe explains that the CO2 absorption amount is lowered after first absorption in order to increase the amount of H2S absorbed (para. 51).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to lower the amount of CO2 absorbed into the second absorber, as taught by Horizoe for use with the dual absorber system of Hoefer and Find
because Horizoe explains that this then increases the amount of H2S absorbed into the absorption solution.
As to the flow rate, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to adjust the flow rate, as taught by Horizoe in order to adjust the amount of CO2 and H2S absorbed into the absorption solution in Hoefer and Find because Horizoe explains that this can be performed by varying the flow rate in order to remove more H2S from the stream.
As to Claim 43, Horizoe describes adjusting the flow rate of the second liquid absorption stream so that it is reduces the CO2 absorption and increases the H2S absorption (para. 19, 28, 48, 50). Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to adjust the flow rate, as taught by Horizoe in order to adjust the amount of CO2 and H2S absorbed into the absorption solution in Hoefer and Find because Horizoe explains that this can be performed by varying the flow rate in order to remove more H2S from the stream.
As to Claims 49 and 50, Hoefer teaches that the absorption media used can be one of those listed in para. 32, which include MEA, TEA, DEEA, DIPA and MDEA (para. 32). The claims describe these as chemical absorbers (see Claim 50, which depends on Claim 49 that describes the compounds in Claim 50 as chemical absorbers).
It is well settled that determination of optimum values of cause effective variables such as these process parameters is within the skill of one practicing in the art. In re Boesch, 205 USPQ 215 (CCPA 1980).
Claim(s) 44, 45, 46 is/are rejected under 35 U.S.C. 103 as being unpatentable over Hoefer, Find and Horizoe as applied to claim 28 above, and in view of Singh (US Pub.: 2013/0280152).
The references do not teach that the different flow rate features of Claims 44, 45 and 46.
Horizoe describes a system that employs a CO2 and H2S absorption column (para. 15), which has an upper part and a lower part (see Fig. 1, 13A and 13B). These can be considered two absorbers. The system absorbs CO2 and H2S with an absorbent (para. 17) and then the absorbent is fed to a regenerator to extract the absorbed CO2 and H2S from the absorbent (para. 17). The system can be designed to lower the amount of CO2 absorbed after the initial absorption in order to absorb more H2S by adjusting the flow rate of the absorbent (para. 21 and 19). As to the amount of CO2 absorbed in the second absorber, Horizoe explains that the CO2 absorption amount is lowered after first absorption in order to increase the amount of H2S absorbed (para. 51).
Horizoe describes adjusting the flow rate of the second liquid absorption stream so that it is reduces the CO2 absorption and increases the H2S absorption (para. 19, 28, 48, 50).
As to adjusting the flow rate of the incoming feed gas as compared to the flow rate of the absorbent, Singh teaches a method for removing CO2 from a gas stream (title). Singh teaches that the ratio of the flow rate of the absorbing solution to the flow rate of the flue gas is referred to as l/G ratio (para. 39) and is used for determining the desired amount of CO2 removal from the flue gas (para. 38).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to adjust the flow rate of the absorbing solution and the flow rate of the flue gas, as taught by Singh in order to optimize the CO2 adsorption in the flue gas, as taught by Singh and to further reduce the H2S, as taught by Horizoe in the CO2 and H2S absorption removing systems of Hoefer and Find because these methods are known to be effective and lead to predictable and expected results.
It would have been obvious to one having ordinary skill in the art to have determined the optimum value of a cause effective variable such as absorption solution flow rate through routine experimentation in the absence of a showing of criticality. In re Woodruff, 16 USPQ2d 1934, 1936 (Fed. Cir. 1990).
Claim(s) 47 and 48 is/are rejected under 35 U.S.C. 103 as being unpatentable over Hoefer, Find and Horizoe as applied to claim 28 above, and further in view of Matton (US Pub.: 2017/0081604).
Hoefer describes use of amine absorbents, which can include MDEA and other amine-based acid gas absorbents (para. 4, 32).
The references describe operating the second absorption as an elevated pressure (see Find in the rejection of Claim 28), but the reference does not recite a pressure described in Claims 47 and 48.
Matton describes a method of removing acid gases from a gas stream using absorption liquids (abstract). The reference explains that the absorbent solution is used at a pressure of 7-9 bar because applicants have found that the absorbents are particularly effective and efficient under these higher absorbent pressures (para. 68). The absorbents used can include amines (para. 37), such as MDEA (para. 37).
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 absorption steps of Hoefer, Find and Horizoe at the elevated pressure of 7-9 bar, as taught by Matton because Matton explains that operating the absorbers at these elevated pressures are particularly effective and efficient.
Claim(s) 52 is/are rejected under 35 U.S.C. 103 as being unpatentable over Hoefer, Find and Horizoe as applied to claim 28 above, and further in view of Gal (US Pub.: 2014/0234176).
The references do not disclose that the biogas stream after treatment contains less than 50ppm CO2 and less than 4ppm H2S.
Gal describes a method of capturing CO2 and H2S from a gas stream (title). The method uses absorbers to capture the CO2 and H2S gases (para. 20). The system includes two absorbers in series (abstract). The first stage absorber may include a multistage vessel 300 with at least two absorption stages each designed to achieve optimal results (para. 29). Downstream of the first absorber stage is a second stage absorber vessel, which is designed to lower the CO2 and H2S concentration (para. 38).
Gal explains that after treatment, the CO2 concentration is less than 10ppm and the H2S concentration is less than 1ppm (para. 20). It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to adjust the process conditions, as taught by Gal for use in the process of Hoefer, Find and Horizoe to achieve the desired CO2 and H2S concentrations.
Claim(s) 53 is/are rejected under 35 U.S.C. 103 as being unpatentable over Hoefer, Find and Horizoe as applied to claim 28 above, and further in view of Cao (CN 103881778).
The references do not teach that the processed biogas is liquified.
Cao describes a method of purifying biogas (title), which involves compressing, cooling and condensing the gas stream to produce a liquified biogas stream (Equivalent Abstract , Organic Chemistry, para. 1).
It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to further liquify the biogas, as taught by Cao for use with the purified biogas of Hoefer, Find and Horizoe because this is another form of converting biogas for further use.
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to SHENG HAN DAVIS whose telephone number is (571)270-5823. The examiner can normally be reached 9-5:30. Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR) at http://www.uspto.gov/interviewpractice. If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Fung Coris can be reached at 571-270-5713. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300. Information regarding the status of published or unpublished applications may be obtained from Patent Center. Unpublished application information in Patent Center is available to registered users. To file and manage patent submissions in Patent Center, visit: https://patentcenter.uspto.gov. Visit https://www.uspto.gov/patents/apply/patent-center for more information about Patent Center and https://www.uspto.gov/patents/docx for information about filing in DOCX format. For additional questions, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000.
/SHENG H DAVIS/
Primary Examiner, Art Unit 1732 April 15, 2026
Prosecution Insights