Detailed Action
This is a Final Office action based on application 17/425,639 filed on 23 July 2021. The application is a 371 of PCT/ EP2020/ 051747, with priority to EP 19153598.8 filed 24 January 2019.
Claims 1-14 are pending and have been fully considered.
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 .
Status of the Rejection
The §112(b) rejection of record is withdrawn, however, a new §112(b) ground of rejection is applied.
The §103 rejection of record is withdrawn responsive to Applicant’s amendment, however, new §103 grounds are established based on the same references in further view of Mayland et al (US 3,344,050 A).
Claim Interpretation
Claims 1 and 9 are amended to recite that the air stream, from which carbon dioxide is being removed by the method and apparatus of the claim, is “ambient atmosphere, having a carbon dioxide content of approximately 400 ppm”. Note that the scope of protection defined by Applicant’s claim depends on how broad the range “approximately 400 ppm” is. There is no exact definition for the bounds of the range “approximately 400 ppm” in the instant disclosure, however the specification at pg 21 Table 1 row 2, discloses that their method is practicable over a CO2 concentration range of from 190 ppm to 1000 ppm. For the purpose of further treatment in this action, Examiner interprets in light of the specification that the claimed range “approximately 400 ppm” can be read as a concentration range of from 190 ppm to 1000 ppm CO--2.
Claim Rejections - 35 USC § 112
The text of those sections of Title 35, U.S. Code not included in this action can be found in a prior Office action.
Claims 1-14 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 at step (c) recites the limitation, “the pH difference between the two solutions is no more than 2 during dialysis”. However, claim 1 recites five distinct solutions prior to that point. There is insufficient antecedent basis for the limitation “the two solutions” in Claim 1, because there is room for ambiguity about which two solutions are the intended antecedent; this makes claim 1 indefinite in scope. Claims 2-14 are indefinite by extension because they incorporate the text of claim 1 by reference.
Claim Rejections - 35 USC § 103
The text of those sections of Title 35, U.S. Code not included in this action can be found in a prior Office action.
Claims 9-14 are rejected under 35 U.S.C. 103 as being unpatentable over Littau et al (US 2010/0059377 A1) in view of Say (US 4,251,494 A).
Regarding claim 9, Littau teaches a facility for continuously executing a method for separating and recovering carbon dioxide from an ambient atmosphere (abstract; para [0024], “air and/or other gas 202 from a CO2 producing plant 204 is passed through ... at ambient conditions”), comprising the following devices or facility sections in fluid communication with one another via corresponding connecting conduits:
a) an absorber or a standing water body for bringing ambient air into contact with an aqueous solution of at least one alkali metal or alkaline earth metal cation for absorbing the carbon dioxide into the alkaline solution by forming the hydrogen carbonate or carbonate of the at least one metal (figure 2, spray tower 206; para [0024]-[0025], air stream 202 enters spray tower 206 where it is contacted with capture solution 208 comprising aqueous potassium carbonate / bicarbonate);
b) an electrodialysis separator (figure 2, electrodialysis unit 218; para [0025]-[0026], “The capture solution 208 is ... introduced into a bipolar membrane electrodialysis unit 218 ... capture solution 208 is partially depleted of bicarbonate through electrodialysis”) comprising a combination of bipolar ion exchanger membranes and ion exchanger membranes selective for mono- or multivalent anions for conducting ion exchange (figure 3, three chamber electrodialysis stack includes bipolar ion exchange membranes 308 and anion-selective ion exchange membranes 304 which selectively admit mono- and multi-valent anions; alternatively, two-chamber electrodialysis stack shown in figure 4 comprises bipolar exchange membranes 404 and anion selective membranes 40; para [0052]-[0055]) to obtain one solution enriched with (hydrogen) carbonate ions (figure 2, electrodialysis unit 218 produces carbonate-rich process stream 220; para [0026]) and one depleted thereof, as well as a conduit for recycling the solution depleted of (hydrogen) carbonate ions to a) (figure 2, para [0028], electrodialysis unit 218 produces regenerated capture solution stream 234, which is recycled via a conduit to absorber 206);
c) a desorption column for conducting steam stripping of the solution enriched with (hydrogen) carbonate ions to obtain a carbon dioxide/water steam mixture and a solution depleted of CO2 (figure 2, desorption chamber 224; para [0026], rich carbonate/bicarbonate solution is desorbed at chamber 224 to produce a CO2-steam mixture, which passes to condenser 226, and a depleted solution which passes via line 228 back to the electrodialysis stage), as well as a conduit for recycling the solution depleted of CO2 to b) (figure 2, conduit 228) and means for setting a specific pH value therein (para [0032]-[0034], “system adjusts process operations to ensure a desired pH value is maintained”); and
d) a condenser for separating water from the obtained carbon dioxide/water steam mixture through condensation (figure 2, condenser 226; para [0026], “Condenser 226 is then used to remove water vapor from the released CO2”).
However, Littau does not teach the desorption column is configured for conducting steam stripping.
Say is similarly directed to a facility for continuously executing a method for separating and recovering carbon dioxide (abstract), comprising the following devices or facility sections in fluid communication with one another via corresponding connecting conduits:
a) an absorber or a standing water body for bringing ambient air into contact with an aqueous solution of at least one alkali metal or alkaline earth metal cation for absorbing the carbon dioxide into the solution by forming the hydrogen carbonate or carbonate of the at least one metal (col 3 ln 8-40, figure 1: gas feed 12 contacts scrubbing solutions 16, 18 at absorption tower 10, yielding scrubbed gas stream 14 and CO2-loaded solution 22; col 4 ln 15-17, col 5 ln 45-61: the scrubbing solution comprises an alkali metal salt e.g. K2CO3);
c) a regeneration column for conducting steam stripping of the solution enriched with (hydrogen) carbonate ions (col 3 ln 40-66, col 5 ln 8-16, figure 1: CO2-loaded solution 22 is passed to regeneration tower 20 where it is stripped countercurrent by steam stream 32), to obtain a carbon dioxide/water steam mixture (col 3 ln 47-52, col 5 ln 13-16, figure 1: CO2 containing gas mix exits regeneration tower 20 at line 24, passes heat exchanger 40 and condenser 42, where it is separated into CO2 stream 44 and condensate stream 46) and a solution depleted of CO2 that is recycled to the absorption stage (col 3 ln 52-66, figure 1: liquid stream 28 from regeneration stage 20 is directed to reboiler 30, and from there is recycled to the absorption stage).
With respect to the steam stripping regenerator, Say teaches that “[r]egenerators are old and well-known in the art” (col 3 ln 42-43) and that the use of a steam stripping regenerator is suitable for desorbing carbon dioxide from an alkali carbonate absorption solution (col 5 ln 8-17).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention to use thermal desorption via steam stripping to separate the CO2 from the CO2-loaded potassium carbonate absorption solution in step (c) of Littau’s method, based on Say’s teaching that thermal regeneration via steam stripping is a suitable way of separating CO2 from CO2-loaded potassium carbonate absorption solution. The simple substitution of one known element for another (i.e., one desorption column for another) is likely to be obvious when predictable results are achieved (i.e., effective desorption of carbonate from an aqueous bicarbonate absorption solution) [MPEP § 2143(B)]. Furthermore, the selection of a known component, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art [MPEP § 2144.07].
Regarding claim 10, Littau and Say render obvious the facility of claim 9, and Littau teaches that the absorber is a spray washer (figure 2, spray tower 206; para [0024]-[0025], [0035]-[0038]).
Regarding claim 11, Littau and Say render obvious the facility of claim 9. Say further teaches that the relatively cold solution obtained in step b) and enriched with bicarbonate ions is, before steam stripping, heated in a heating device (figure 1, before relatively cold bicarbonate-rich stream 22 enters steam stripping tower 20, it is heated by exchange with relatively hot, lean streams 16, 18 at heat exchangers 60, 70; col 4 ln 9-14, “Exchangers 60, 70 disposed in lines 16, 18, respectively, preheat the scrubbing solution in line 22 to improve the desorption in regenerator 20”). Say teaches that such heat exchanging the relatively cold bicarbonate-rich solution before stripping is effective to improve the desorption in the subsequent stripping step (col 4 ln 9-14).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention, when modifying Littau to incorporate the steam stripping arrangement of Say, to also incorporate the feature of wherein the relatively cold bicarbonate-rich solution prior to stripping is heat exchanged with the relatively hot bicarbonate-lean solution that has already been stripped, based on Say’s teaching that such heat exchange is effective to improve desorption of CO2 in the stripping step (col 4 ln 9-14).
Regarding claim 12, Littau and Say render obvious the apparatus of claim 9, and Say further teaches that the desorption column is connected to an evaporator for introducing water steam (figure 1, reboiler 30; col 3 ln 55-60). Say also teaches that the desorption column is operated at underpressure (col 7 ln 55, “10 psia”), which implies that the regenerator is connected to an underpressure producing means such as a vacuum pump.
Regarding claim 13, Littau and Say render obvious the subject matter of claim 11, and Say further teaches that that the heating device is a heat exchanger to subject the relatively cold solution enriched with (hydrogen) carbonate ions in the electrodialysis separator to a heat exchange with the relatively hot solution that has already been subjected to steam stripping before recycling it, in order to heat the former solution and to cool the latter solution (figure 1, before relatively cold bicarbonate-rich stream 22 enters steam stripping tower 20, and before relatively hot, lean streams 16, 18 are recycled to the absorption tower 10, they are heat exchanged with each other at heat exchangers 60, 70; per col 4 ln 9-14, “Exchangers 60, 70 disposed in lines 16, 18, respectively, preheat the scrubbing solution in line 22 to improve the desorption in regenerator 20”, ergo, the solution in line 22 is relatively cold and is heated by the exchange, and the solutions in lines 16, 18 are relatively hot and are cooled by the exchange).
Regarding claim 14, Littau and Say render obvious the apparatus of claim 9, and Say further teaches that the condenser for recycling the condensate obtained during cooling of the carbon dioxide/water steam mixture is to the evaporator via a conduit to again produce water steam from the condensate (col 3 ln 50-60, “Condensibles from knock out pot 42 are returned to regenerator 20 through line 46. The partially desorbed solution passes downwardly through regenerator 20 and exits through line 28 at the bottom of the regenerator for transfer to reboiler 30. Reboiler 30, equipped with an external source of heat, such as steam flowing through inlet line 34 and return line 36, vaporizes a portion of this solution. The vapor is returned to regenerator 20 through line 32”).
Claims 1-3 and 5-7 are rejected under 35 U.S.C. 103 as being unpatentable over Littau and Say, in further view of Mayland et al (US 3,344,050 A).
Regarding claim 1, Littau teaches a method for separating and recovering carbon dioxide from ambient air (abstract; para [0024], “air and/or other gas 202 from a CO2 producing plant 204 is passed through ... at ambient conditions”), comprising the continuous execution of the following steps:
a) bringing ambient air into contact with an aqueous solution of at least one alkali metal or alkaline earth metal cation for absorbing the carbon dioxide into the solution, thus forming the bicarbonate or carbonate of the at least one metal (figure 2, air stream 202 enters spray tower 206 where it is contacted with capture solution 208; para [0024]-[0025], capture solution 208 comprises an aqueous solution of potassium carbonate/bicarbonate);
b) electrodialysis of the resulting solution (para [0025]-[0026], “The capture solution 208 is ... introduced into a bipolar membrane electrodialysis unit 218 ... capture solution 208 is partially depleted of bicarbonate through electrodialysis”) using a combination of bipolar ion-exchange membranes and ion-exchange membranes that are selective for mono- or multi-valent anions (figure 3, three chamber electrodialysis stack includes bipolar ion exchange membranes 308 and anion-selective ion exchange membranes 304; alternatively, two-chamber electrodialysis stack shown in figure 4 comprises bipolar exchange membranes 404 and anion selective membranes 40; para [0052]-[0055]) to obtain one solution enriched with (hydrogen) carbonate ions (figure 2, CO2 rich process stream 220; para [0026]) and one solution depleted of (hydrogen) carbonate ions (figure 2, regenerated capture solution stream 234), wherein the solution depleted of (hydrogen) carbonate ions is recycled to step a) (para [0028]);
c) desorption of the carbon dioxide from the solution obtained in step b) that is enriched with (hydrogen) carbonate ions (para [0026], “high pressure CO2 rich process stream 220 is transferred via P-regulator 222 to a gas evolution/separation tank 224 where the pressure is reduced with concomitant release of CO2”) in order to obtain a carbon dioxide – steam mixture (figure 2, gas stream from desorption chamber 224 to condenser 226) and a solution depleted of CO2 that is recycled to step (b) (figure 2, CO2-depleted solution 228 is recycled to electrodialysis device 218; para [0028]), wherein a pH between 7 and 8.5 or between 8 and 9.5 is set (claims 10-11; para [0032], “pH monitor 240 senses the pH value of capture solution 208 ... the system adjusts process operations to ensure a desired pH value is maintained”; para [0059], “In one situation where the system is optimized for energy efficiency, the capture stream will be approximately pH 8-9”); and
d) separating water from the obtained carbon dioxide-steam mixture by cooling to condense the steam, and optionally further drying of the carbon dioxide (para [0026], “Condenser 226 is then used to remove water vapor from the released CO2”).
Littau further teaches that, during the bipolar electrodialysis step, the pH difference between the two solutions on opposing sides of the bipolar membrane is a result effective variable, and the energy expenditure of the electrodialysis process can be reduced by reducing this pH difference (para [0045]-[0051]). Littau does not disclose that the pH difference between the two solutions on opposing sides of the bipolar membrane is 2 pH units or less. It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention to optimize the pH difference between these two solutions, based on Littau’s teaching that the energy cost of electrodialysis is directly related to this pH difference and the energy expenditure can therefore be reduced by optimization of this pH difference. (para [0045]-[0050]).
However:
Littau does not teach that the desorption of the carbon dioxide at step c) is thermal desorption by means of steam stripping.
Littau is primarily directed to separating and recovering carbon dioxide from a flue gas stream. Littau does not disclose separating carbon dioxide from ambient atmosphere having a CO-2 content of about 400 ppm.
Say is directed to a method of separating carbon dioxide from a gaseous mixture (abstract), comprising
bringing the gaseous mixture into contact with an aqueous solution of at least one alkali metal or alkaline earth metal cation for absorbing the carbon dioxide into the solution, thus forming the bicarbonate or carbonate of the at least one metal (col 3 ln 8-40, figure 1: gas feed 12 contacts scrubbing solutions 16, 18 at absorption tower 10, yielding scrubbed gas stream 14 and CO2-loaded solution 22; col 4 ln 15-17, col 5 ln 45-61: the scrubbing solution comprises an alkali metal salt e.g. K2CO3), and
thermal desorption of the carbon dioxide from the carbon-dioxide-loaded solution by way of a steam stripping regenerator (col 3 ln 40-66, col 5 ln 8-16, figure 1: CO2-loaded solution 22 is passed to regeneration tower 20 where it is stripped countercurrent by steam stream 32), in order to obtain a carbon dioxide-steam mixture which is subsequently cooled to condense the steam (col 3 ln 47-52, col 5 ln 13-16, figure 1: CO2 containing gas mix exits regeneration tower 20 at line 24, passes heat exchanger 40 and condenser 42, where it is separated into CO2 stream 44 and condensate stream 46), and a solution depleted of CO2 that is recycled to the absorption stage (col 3 ln 52-66, figure 1: liquid stream 28 from regeneration stage 20 is directed to reboiler 30, and from there is recycled to the absorption stage).
With respect to the steam stripping regenerator, Say teaches that “[r]egenerators are old and well-known in the art” (col 3 ln 42-43) and that the use of a steam stripping regenerator is suitable for desorbing carbon dioxide from an alkali carbonate absorption solution as required by the method (col 5 ln 8-17).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention to use thermal desorption via steam stripping to separate the CO2 from the CO2-loaded potassium carbonate absorption solution in step (c) of Littau’s method, based on Say’s teaching that thermal regeneration via steam stripping is a suitable way of separating CO2 from CO2-loaded potassium carbonate absorption solution. The simple substitution of one known element for another (i.e., one desorption column for another) is likely to be obvious when predictable results are achieved (i.e., effective desorption of carbonate from an aqueous bicarbonate absorption solution) [MPEP § 2143(B)]. Furthermore, the selection of a known component, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art [MPEP § 2144.07].
However, the atmosphere that Say is directed to scrubbing CO2 from is a petrochemical feedstock such as liquified natural gas (col 1 ln 20-35), having a typical CO2 content of about 8 vol% (col 7 ln 33-45). Say does not suggest removing CO-2 from ambient atmosphere with a CO2 concentration of about 400 ppm.
Mayland discloses a method for separating carbon dioxide from air, comprising
a) bringing ambient atmosphere into contact with an aqueous solution of at least one alkali metal or alkaline earth metal cation for absorbing the carbon dioxide into the solution, thus forming the bicarbonate or carbonate of the at least one metal (figure 2, air from line 1 is introduced into absorption column 2 where it is contacted by aqueous absorption solution from line 14; col 3 ln 55-75);
b) electrodialysis of the resulting solution to obtain one solution enriched with (hydrogen) carbonate ions and one solution depleted of (hydrogen) carbonate ions, wherein the solution depleted of (hydrogen) carbonate ions is recycled to step a) (figure 4, stream 38, taken from chambers 31 and 34 which are depleted of HCO3− ions, is returned via pump 39 to the absorber (col 5 ln 30-56);
c) thermal desorption of the carbon dioxide from the solution obtained in step b) that is enriched with (hydrogen) carbonate ions by means of steam stripping (figure 3, stripping steam line 44 is fed into the bicarbonate-enriched chambers 29, 32, 35, and desorbed CO2 is carried out by line 42; col 5 ln 42-51).
Mayland further teaches that a specific application their carbon dioxide absorption method is intended for is for maintaining a breathable atmosphere in a confined living space such as a submarine or a fallout shelter (col 1 ln 30-59).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention to adapt Littau’s CO2 separation method from the field of removing CO2 from flue gas to the related field of removing CO2 from breathable ambient atmosphere, i.e. one having a CO2 concentration of approximately 400 ppm, based on Mayland’s teaching that there is a need in the art for methods of CO2 removal from such an atmosphere (col 1 ln 30-59), and that a similar method based on absorbing CO2 into an aqueous alkaline absorption, concentrating bicarbonate ions from the loaded absorption solution via electrodialysis, and steam stripping the bicarbonate-concentrated stream to desorb CO2 therefrom, is appropriate for use with such an atmosphere. The court has found that it would be obvious for an inventor, knowing of work in one field of endeavor, to develop predictable variations of it for adaption to either the same field or a different field based on design incentives or other market forces. (MPEP 2143(F)).
Regarding claim 2, Littau in view of Say and Mayland renders obvious the method of claim 1. Littau further teaches that the solution of the at least one alkali metal or alkaline earth metal cation has a sufficiently high concentration of alkali metal or alkaline earth metal ions, and that the ion concentration is sufficient to result in a pH of the water of at least 7.5 and is optionally preset by the addition of a base (para [0032]-[0034], “system 200 includes monitors to sense various characteristics of the process. For example, ... pH monitor 240 senses the pH value of capture solution 208 coming out of spray tower 206. Using the readings from monitors 238 and 240, the system adjusts process operations to ensure a desired pH value is maintained ... if it is determined the pH of the capture solution that has come out of the spray tower needs to have additional capture solution, a makeup stream 244 (of for example potassium carbonate) may be added”; para [0055], [0059]). Littau is silent as to whether or not the water is lake water. However, the courts have held that a chemical composition and its properties are inseparable. Therefore, if the prior art teaches the identical chemical composition, the properties applicant claims are necessarily present (see MPEP 2112.01(II); In re Spada, 911 F.2d 705, 709, 15 USPQ2d 1655, 1658 (Fed. Cir. 1990)). Since a lake is not a positively recited element of the claimed method, and there is no apparent difference in composition between Littau’s water and the claimed lake water, the recitation of wherein the water is water of a natural or artificial lake does not patentably distinguish the claim from the prior art.
Regarding claim 3, Littau in view of Say and Mayland renders obvious the method of claim 1, and Littau teaches that, in step a), the aqueous solution of the at least one alkali metal or alkaline earth metal cation is brought into contact with ambient air in a spray washer or spray tower (figure 2, spray tower 206; para [0024]-[0025], [0035]-[0038]).
Regarding claim 5, Littau in view of Say and Mayland renders obvious the method of claim 1, and Say further teaches that the steam stripping is conducted in a packed column at underpressure (col 7 ln 52-56, “a packed tower ... operated at ... 10 psia”).
Regarding claim 6, Littau in view of Say and Mayland renders obvious the method of claim 5. Say further teaches that the relatively cold solution obtained in step b) and enriched with bicarbonate ions is, before steam stripping, subjected to a heat exchange with the relatively hot solution that has already been subjected to steam stripping, before it is recycled to step b), in order to heat the former solution and to cool the latter solution (figure 1, before relatively cold bicarbonate-rich stream 22 enters steam stripping tower 20, and before relatively hot, lean streams 16, 18 are recycled to the absorption tower 10, they are heat exchanged with each other at heat exchangers 60, 70; per col 4 ln 9-14, “Exchangers 60, 70 disposed in lines 16, 18, respectively, preheat the scrubbing solution in line 22 to improve the desorption in regenerator 20”, ergo, the solution in line 22 is relatively cold and is heated by the exchange, and the solutions in lines 16, 18 are relatively hot and are cooled by the exchange). Say teaches that such heat exchanging the relatively cold bicarbonate-rich solution before stripping is effective to improve the desorption in the subsequent stripping step (col 4 ln 9-14).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention, when modifying Littau to incorporate the steam stripping arrangement of Say, to also incorporate the feature of wherein the relatively cold bicarbonate-rich solution prior to stripping is heat exchanged with the relatively hot bicarbonate-lean solution that has already been stripped, based on Say’s teaching that such heat exchange is effective to improve desorption of CO2 in the stripping step (col 4 ln 9-14).
Regarding claim 7, Littau in view of Say and Mayland renders obvious the method of claim 1, and Say further teaches that the condensate obtained during cooling of the carbon dioxide/water steam mixture is recycled to step d) in order to again produce water steam for steam stripping therefrom (col 3 ln 50-60, “Condensibles from knock out pot 42 are returned to regenerator 20 through line 46. The partially desorbed solution passes downwardly through regenerator 20 and exits through line 28 at the bottom of the regenerator for transfer to reboiler 30. Reboiler 30, equipped with an external source of heat, such as steam flowing through inlet line 34 and return line 36, vaporizes a portion of this solution. The vapor is returned to regenerator 20 through line 32”).
Regarding claim 9, Littau teaches a facility for continuously executing a method for separating and recovering carbon dioxide from ambient air (abstract; para [0024], “air and/or other gas 202 from a CO2 producing plant 204 is passed through ... at ambient conditions”), comprising the following devices or facility sections in fluid communication with one another via corresponding connecting conduits:
a) an absorber or a standing water body for bringing ambient air into contact with an aqueous solution of at least one alkali metal or alkaline earth metal cation for absorbing the carbon dioxide into the solution by forming the hydrogen carbonate or carbonate of the at least one metal (figure 2, spray tower 206; para [0024]-[0025], air stream 202 enters spray tower 206 where it is contacted with capture solution 208 comprising aqueous of potassium carbonate / bicarbonate);
b) an electrodialysis separator (figure 2, electrodialysis unit 218; para [0025]-[0026], “The capture solution 208 is ... introduced into a bipolar membrane electrodialysis unit 218 ... capture solution 208 is partially depleted of bicarbonate through electrodialysis”) comprising a combination of bipolar ion exchanger membranes and ion exchanger membranes selective for mono- or multivalent anions for conducting ion exchange (figure 3, three chamber electrodialysis stack includes bipolar ion exchange membranes 308 and anion-selective ion exchange membranes 304 which selectively admit mono- and multi-valent anions; alternatively, two-chamber electrodialysis stack shown in figure 4 comprises bipolar exchange membranes 404 and anion selective membranes 40; para [0052]-[0055]) to obtain one solution enriched with (hydrogen) carbonate ions (figure 2, electrodialysis unit 218 produces carbonate-rich process stream 220; para [0026]) and one depleted thereof, as well as a conduit for recycling the solution depleted of (hydrogen) carbonate ions to a) (figure 2, para [0028], electrodialysis unit 218 produces regenerated capture solution stream 234, which is recycled via a conduit to absorber 206);
c) a desorption column for conducting steam stripping of the solution enriched with (hydrogen) carbonate ions to obtain a carbon dioxide/water steam mixture and a solution depleted of CO2 (figure 2, desorption chamber 224; para [0026], rich carbonate/bicarbonate solution is desorbed at chamber 224 to produce a CO2-steam mixture, which passes to condenser 226, and a depleted solution which passes via line 228 back to the electrodialysis stage), as well as a conduit for recycling the solution depleted of CO2 to b) (figure 2, conduit 228) and means for setting a pH value of between 7 and 8.5 or between 8 and 9.5 therein (para [0032]-[0034], “system adjusts process operations to ensure a desired pH value is maintained”); and
d) a condenser for separating water from the obtained carbon dioxide/water steam mixture through condensation (figure 2, condenser 226; para [0026], “Condenser 226 is then used to remove water vapor from the released CO2”).
However, Littau does not teach the desorption column is configured for conducting steam stripping.
Say is similarly directed to a facility for continuously executing a method for separating and recovering carbon dioxide (abstract), comprising the following devices or facility sections in fluid communication with one another via corresponding connecting conduits:
a) an absorber or a standing water body for bringing ambient air into contact with an aqueous solution of at least one alkali metal or alkaline earth metal cation for absorbing the carbon dioxide into the solution by forming the hydrogen carbonate or carbonate of the at least one metal (col 3 ln 8-40, figure 1: gas feed 12 contacts scrubbing solutions 16, 18 at absorption tower 10, yielding scrubbed gas stream 14 and CO2-loaded solution 22; col 4 ln 15-17, col 5 ln 45-61: the scrubbing solution comprises an alkali metal salt e.g. K2CO3);
c) a regeneration column for conducting steam stripping of the solution enriched with (hydrogen) carbonate ions (col 3 ln 40-66, col 5 ln 8-16, figure 1: CO2-loaded solution 22 is passed to regeneration tower 20 where it is stripped countercurrent by steam stream 32), to obtain a carbon dioxide/water steam mixture (col 3 ln 47-52, col 5 ln 13-16, figure 1: CO2 containing gas mix exits regeneration tower 20 at line 24, passes heat exchanger 40 and condenser 42, where it is separated into CO2 stream 44 and condensate stream 46) and a solution depleted of CO2 that is recycled to the absorption stage (col 3 ln 52-66, figure 1: liquid stream 28 from regeneration stage 20 is directed to reboiler 30, and from there is recycled to the absorption stage).
With respect to the steam stripping regenerator, Say teaches that “[r]egenerators are old and well-known in the art” (col 3 ln 42-43) and that the use of a steam stripping regenerator is suitable for desorbing carbon dioxide from an alkali carbonate absorption solution (col 5 ln 8-17).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention to use thermal desorption via steam stripping to separate the CO2 from the CO2-loaded potassium carbonate absorption solution in step (c) of Littau’s method, based on Say’s teaching that thermal regeneration via steam stripping is a suitable way of separating CO2 from CO2-loaded potassium carbonate absorption solution. The simple substitution of one known element for another (i.e., one desorption column for another) is likely to be obvious when predictable results are achieved (i.e., effective desorption of carbonate from an aqueous bicarbonate absorption solution) [MPEP § 2143(B)]. Furthermore, the selection of a known component, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art [MPEP § 2144.07].
Regarding claim 10, Littau and Say teach the facility of claim 9, and Littau teaches that the absorber is a spray washer (figure 2, spray tower 206; para [0024]-[0025], [0035]-[0038]).
Regarding claim 11, Littau and Say teach the facility of claim 9. Say further teaches that the relatively cold solution obtained in step b) and enriched with bicarbonate ions is, before steam stripping, heated in a heating device (figure 1, before relatively cold bicarbonate-rich stream 22 enters steam stripping tower 20, it is heated by exchange with relatively hot, lean streams 16, 18 at heat exchangers 60, 70; col 4 ln 9-14, “Exchangers 60, 70 disposed in lines 16, 18, respectively, preheat the scrubbing solution in line 22 to improve the desorption in regenerator 20”). Say teaches that such heat exchanging the relatively cold bicarbonate-rich solution before stripping is effective to improve the desorption in the subsequent stripping step (col 4 ln 9-14).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention, when modifying Littau to incorporate the steam stripping arrangement of Say, to also incorporate the feature of wherein the relatively cold bicarbonate-rich solution prior to stripping is heat exchanged with the relatively hot bicarbonate-lean solution that has already been stripped, based on Say’s teaching that such heat exchange is effective to improve desorption of CO2 in the stripping step (col 4 ln 9-14).
Regarding claim 12, Littau and Say teach the apparatus of claim 9, and Say further teaches that the desorption column is connected to an evaporator for introducing water steam (figure 1, reboiler 30; col 3 ln 55-60). Say also teaches that the desorption column is operated at underpressure (col 7 ln 55, “10 psia”), which implies that the regenerator is connected to an underpressure producing means such as a vacuum pump.
Regarding claim 13, Littau and Say teach the subject matter of claim 11, and Say further teaches that that the heating device is a heat exchanger to subject the relatively cold solution enriched with (hydrogen) carbonate ions in the electrodialysis separator to a heat exchange with the relatively hot solution that has already been subjected to steam stripping before recycling it, in order to heat the former solution and to cool the latter solution (figure 1, before relatively cold bicarbonate-rich stream 22 enters steam stripping tower 20, and before relatively hot, lean streams 16, 18 are recycled to the absorption tower 10, they are heat exchanged with each other at heat exchangers 60, 70; per col 4 ln 9-14, “Exchangers 60, 70 disposed in lines 16, 18, respectively, preheat the scrubbing solution in line 22 to improve the desorption in regenerator 20”, ergo, the solution in line 22 is relatively cold and is heated by the exchange, and the solutions in lines 16, 18 are relatively hot and are cooled by the exchange).
Regarding claim 14, Littau and Say teach the apparatus of claim 9, and Say further teaches that the condenser for recycling the condensate obtained during cooling of the carbon dioxide/water steam mixture is to the evaporator via a conduit to again produce water steam from the condensate (col 3 ln 50-60, “Condensibles from knock out pot 42 are returned to regenerator 20 through line 46. The partially desorbed solution passes downwardly through regenerator 20 and exits through line 28 at the bottom of the regenerator for transfer to reboiler 30. Reboiler 30, equipped with an external source of heat, such as steam flowing through inlet line 34 and return line 36, vaporizes a portion of this solution. The vapor is returned to regenerator 20 through line 32”).
Claim 4 is rejected under 35 U.S.C. 103 as being unpatentable over Littau and Say as applied to claim 1 above, and further in view of Wilkinson et al (US 2017/0014758 A1).
Regarding claim 4, Littau in view of Say and Mayland renders obvious the method of claim 1. Littau further teaches that there is a desire to control solution conditions in the capture solution to favor bicarbonate (HCO3−) over carbonate (CO3 2−) (see Littau at para [0059]). However, Littau and Say do not teach that the anion selective membranes used in the electrodialysis device are selective for monovalent anions.
Wilkinson is directed to a method for separating and recovering carbon dioxide, comprising:
a) bringing a gas stream into contact with an aqueous absorption solution for absorbing the carbon dioxide into the solution, thus forming a bicarbonate or carbonate solution (para [0037];
b) electrodialysis of the resulting solution using a combination of cation exchange membranes and anion exchange membranes, to obtain one solution enriched with hydrogen carbonate ions and one solution depleted of hydrogen carbonate ions (figure 1, absorption solution 120 is electrodialyzed thereby depleting the solution in chamber 103 of HCO3− anions, and enriching the solution in chamber 104 with HCO3− anions; para [0036]-[0040]; figure 3, a parallel stack of electrodialysis cells configured as in figure 1, with cation exchange membranes and anion exchange membranes), wherein the anion exchange membranes are selective for monovalent anions (para [0062], [0090]). Wilkinson teaches that the use of monovalent-selective anion exchange membranes in the electrodialysis device allows bicarbonate ions to permeate into the bicarbonate-concentrating chamber while blocking permeation of carbonate ions (para [0062], [0090]).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention to assemble the electrodialysis device of Littau using, as the anion exchange membranes, monovalent-selective anion exchange membranes as disclosed in Wilkinson, because Littau teaches that there is a desire to capture CO2 in the form of bicarbonate rather than carbonate (Littau at para [0059]), and Wilkinson teaches that the incorporation of monovalent anion exchange membranes in the electrodialysis unit would allow bicarbonate ions to permeate into the concentrating chamber while blocking permeation of carbonate ions (Wilkinson at para [0062], [0090]).
Claim 8 is rejected under 35 U.S.C. 103 as being unpatentable over Littau and Say as applied to claim 1 above, and further in view of Joh et al (US 2011/0139003 A1).
Regarding claim 8, Littau in view of Say and Mayland renders obvious the method of claim 1. Say further teaches that an external source of heat is used for producing the water steam in step c) (col 3 ln 55-58). Littau and Say do not specify, however, that the external source of heat is waste heat of a power plant or factory, or that the electrical power used for electrodialysis is DC from renewable energy sources.
Joh is directed to a continuous method for capturing CO2 from power plant flue gas (abstract; figure 2, para [0039]-[0041], power plant 14 (comprising burner 15 and steam turbine 25) generates flue gas stream 3 which is directed into CO2 capture apparatus 16), comprising
a) contacting the flue gas stream with an absorbent medium to absorb CO2 and thereby form a CO2-loaded absorbent medium (figure 2, flue gas 3 is directed to absorption unit 17 where it is contacted by an absorbent medium, thereby forming loaded absorbent medium stream 6 and scrubbed exhaust gas stream 39; para [0041]-[0043]);
c) steam stripping the CO2-loaded absorbent medium to desorb CO2 therefrom, generating a CO2-steam mixture and regenerating a lean absorbent medium, which is recycled to a) (para [0043]-[0045]; figure 2, loaded absorbent medium 6 passes through heat exchanger 35 and then into desorption column 18 where it is stripped by steam from steam injector 19, generating a CO2-steam mixture that exits via gas line 49, and a regenerated lean sorbent 11 via line 48);
d) separating water from the obtained carbon dioxide-steam mixture by cooling to condense the steam (para [0046]; figure 2, CO2-gas mixture in line 49 is condensed at condenser 38, and the condensate is returned via line 50).
Joh further teaches that the steam used in step c) is produced by waste heat of the power plant (per para [0045], a portion of the regenerated absorption medium 11 leaving the desorption unit 18 is heated via a heating device 26 to generate steam input to desorption unit 18; per figure 2, heating device 26 is a heat exchanger on the steam/condensate line 24 of the power plant 14, i.e., the heat source is waste heat from the power plant; per para [0044] and figure 2, overflow steam 23 line from the power plant may be directed into the steam injector 19 as well). Joh teaches that the injection of waste heat and steam from the power plant into the steam stripping step c) makes effective use of waste heat and low quality steam and thereby improves the efficiency of the carbon capture process (para [0013]-[0015], [0030], [0048]).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention, when implementing the method of Littau and Say, to use waste heat from a power plant as a heat source for the steam stripping step c), based on Joh’s teaching that, in the context of a process of capturing carbon dioxide with an absorbent and regenerating the absorbent by steam stripping, the process efficiency can be improved by using waste heat and steam from a power plant to provide the hot steam required by the steam stripping step. All the claimed elements were known in the prior art and one skilled in the art could have combined the elements as claimed by known methods with no change in their respective functions, and the combination yielded nothing more than predictable results. The incorporation of a predictable improvement into a known base invention, based on a finding that the prior art contained a comparable device that has been improved in the same way, is prima facie obvious as being part of the ordinary capabilities of one skilled in the art (MPEP 2143(C)).
Response to Arguments
Applicant’s arguments, see Remarks 14 October 2025, with respect to the grounds of rejection in the prior Office Action, have been fully considered and are persuasive partly. The §103 rejection of claim 9 is maintained. The §103 rejection of claim 1 is withdrawn, however upon further consideration, a new ground of rejection is made in view of the same references in further view of Mayland.
Applicant amends claims 1 and 9 to recite that the air from which carbon dioxide is removed is ambient atmosphere with a carbon dioxide content of about 400 ppm. Applicant argues that this feature distinguishes the claim from the Littau reference, because Littau is directed to removing CO2 from flue gas with a substantially higher CO-2- concentration than that.
Applicant’s argument is persuasive with respect to claim 1, but unpersuasive with respect to claim 9.
Claim 1 is a method claim which positively recites the step of “bringing ambient atmosphere, having a carbon dioxide content of approximately 400 ppm, into contact with” an aqueous capture solution. The CO2 content of the atmosphere that the method operates on is a feature of the method, and can be relied upon to distinguish Applicant’s method from Littau’s method. For this reason, Applicant’s argument is persuasive, the rejection of claim 1 is withdrawn. New grounds of rejection are presented based on the previously applied references in further view of Mayland.
By contrast, claim 9 claims an apparatus for performing the method of claim 1, said apparatus comprising “an absorber or a standing water body for bringing ambient atmosphere, having a carbon dioxide content of approximately 400 ppm, into contact with” an aqueous capture solution (emphasis added). Since claim 9 is an apparatus claim, the only limitations of the claim that carry patentable weight are those that define or limit the structure of the apparatus itself. A recitation with respect to the manner in which a claimed apparatus is intended to be employed does not differentiate the claimed apparatus from a prior art apparatus if the prior art teaches the structural features of the apparatus, because apparatus claims cover what a device is, not what a device does (MPEP 2114(II)). Nor is an apparatus limited by the composition of the material that the apparatus works upon (MPEP 2115). The recitation of the CO2 content of the air that is worked upon is therefore not a feature that can be relied upon to distinguish the device structure of claim 9 from the device structure of the prior art. Therefore the rejection of claim 9 is maintained.
Applicant also argues that it would be non-obvious to modify the method of Littau to include steam stripping as disclosed in Say, on the grounds that Littau at para [0056] allegedly teaches away from steam stripping.
This argument is unpersuasive because a reference does not teach away when it merely expresses a general preference for an alternative invention but does not criticize, discredit or otherwise discourage investigation into the invention claimed (MPEP 2145(X)(D)(1)). The only mention of steam anywhere in Littau’s disclosure is at para [0056] where they write:
Unlike traditional solvent systems, aqueous based carbonate absorption and BPMED regeneration does not require process steam to regenerate the solvent, nor is it sensitive to solvent loss.
Littau statement, that their preferred solvent regeneration method is one that does not require steam, is not a teaching away because it does not discredit steam stripping. Nor does Littau anywhere suggest that the addition of steam stripping would render their device unsatisfactory for its intended purpose (MPEP 2143.01(V)).
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
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/ANDREW KOLTONOW/Examiner, Art Unit 1795
/LUAN V VAN/Supervisory Patent Examiner, Art Unit 1795