Patent Publication Number: US-11638902-B2

Title: Apparatus and method for direct air capture of carbon dioxide from the atmosphere

Description:
RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 16/662,594 filed on Oct. 24, 2019 and issued on Feb. 15, 2022 as U.S. Pat. No. 11,247,176 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to direct capture of carbon dioxide from the atmosphere utilizing membranes operating under vacuum, enriching the carbon dioxide concentration and forwarding the enriched carbon dioxide to a sequestration facility. Embodiments of the present invention may be utilized to reduce the overall concentration of carbon dioxide in the atmosphere. The term “sequestration facility” is defined herein as anyone of a variety of mechanisms which sequester the carbon dioxide thereby preventing immediate release back into the atmosphere. The term may include systems which utilize bio-sequestration, such as orchards, crops, forests, and other photosynthetic organisms which either convert carbon dioxide utilizing photosynthesis or store the carbon dioxide in the organism. The sequestration facility may also include manufacturing processes which utilize carbon dioxide. The sequestration facility may also include a system which injects carbon dioxide into petroleum reservoirs for purposes of enhanced oil recovery such as miscible flooding. 
     This application further relates to the utilization of membranes under vacuum for providing an enriched oxygen stream to a flue gas generator thereby decreasing fuel consumption and reducing the output of flue gas emissions. The carbon dioxide concentration in the flue gas, as compared to a flue gas generator without oxygen enrichment of the air supply, is highly enriched and thus suitable for various commercial uses, which may include enhanced oil recovery operations, agricultural use, medical applications, and other known commercial applications. 
     It is known that carbon dioxide is a major contributor to global warming. Global warming is a result of increasing concentrations of greenhouse gases (“GHG”) in the atmosphere. Among the primary greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, perfluorocarbons, hydrofluorocarbons, and sulfur hexafluoride. Of these, carbon dioxide is the primary anthropogenic (i.e., manmade) GHG, accounting for a substantial portion of the human contribution to the greenhouse effect in recent years. 
     There is an ongoing and critical need for additional mechanisms and methods for reducing consumption of non-renewable fuels and reducing atmospheric carbon dioxide. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention exploit the unique property of membranes to economically achieve direct air capture of carbon dioxide from the atmosphere and separating carbon dioxide, oxygen, and water vapor from nitrogen and producing a permeate comprising enriched concentration of carbon dioxide, oxygen and water, and a reduced concentration of nitrogen. Instead of using processes which yield highly purified concentrations of carbon dioxide and oxygen at significant capital expense and significant operating costs, embodiments of the present invention utilize low pressure “leaf” membrane units to remove nitrogen from the atmospheric air and thereby mildly or moderately increasing the concentrations of the carbon dioxide and the oxygen in the permeate. The resulting permeate stream does not have to be highly purified to attain significant benefits. 
     Embodiments of the present invention may utilize membrane materials having properties similar to those of the cellulose acetate based sheet or spiral wound type membrane units used in the Separex™ membrane product as manufactured by Honeywell/UOP, or other polymeric based membrane products such as “plate and frame” type Polaris™ membranes as manufactured by MTR, Inc., or hollow fiber type membrane units such as Cynara™ membranes manufactured by Schlumberger, or PRISM™ membranes as manufactured by Air Products. However, these known membrane devices have significant supporting structure and require blowers or compressors for operation of the systems. 
     The use of the above listed membrane materials and products enrich the oxygen and carbon dioxide concentrations of a gas stream processed through the membrane units. Carbon dioxide and oxygen pass or permeate more rapidly through the membrane relative to nitrogen, thereby forming a permeate stream which is more concentrated or enriched in oxygen and carbon dioxide than the “feed” stream. It is noted that the term “feed” is used somewhat loosely for purposes of this disclosure and does not refer to a stream delivered to the membrane via an intake or similar structure. With embodiments of the presently disclosed leaf membranes, a “feed” side of the membrane (which may also be referred to as the “outer side” but should not be thereby limited to an exterior position) is exposed to a gas, i.e., air, which is brought into the membrane unit by a vacuum applied to the membrane unit. Gas components which pass relatively slowly through the membrane in comparison to oxygen, carbon dioxide and water, such as nitrogen, remain mostly on the same side of the membrane as the “feed” stream and disbursed into the atmosphere. 
     In one embodiment of the invention, a flue gas generator may be disposed between the membrane unit and the sequestration facility. The combustion processes utilized in flue gas generators conventionally use atmospheric air to produce a flue gas that contains carbon dioxide concentrations well above that found in atmospheric air. As indicated above, the permeate stream generated from the disclosed membrane units has higher concentrations of carbon dioxide and oxygen than atmospheric air. When the permeate stream is introduced into a combustion process in place of atmospheric air, the result is a flue gas having a carbon dioxide concentration well above that from using conventional combustion air. This carbon dioxide enriched flue gas may then be utilized in the sequestration facilities discussed above. In some embodiments of the invention the flue gas generator may be pressurized thereby eliminating the need for downstream pressurization. 
     Embodiments of the present invention may also comprise a secondary (or tertiary) enrichment system which utilizes the permeate from a first stage membrane unit as a feed for secondary membrane units contained within enclosures such as conduit or piping or as feed for a cryogenic oxygen enrichment system. 
     A unique vacuum system may be utilized for application of vacuum to the membrane units. The disclosed bellows system is relatively simple and requires low power input to generate the vacuum necessary to process a feed gas through the disclosed leaf membranes. 
     A method of direct air capture of carbon dioxide utilizing membrane members under vacuum is also disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    depicts a configuration for a bank or array of leaf membrane units which may be utilized for direct air capture of atmospheric air. 
         FIG.  2    depicts an exploded view of an embodiment of a leaf membrane unit which may be utilized for low pressure direct air capture of carbon dioxide. 
         FIG.  3    shows a system which may utilize embodiments of leaf membranes for low pressure enrichment of a gas stream comprising oxygen and carbon dioxide flowing into a flue gas source. 
         FIG.  4    depicts a system which may utilize embodiments of leaf membranes for low pressure enrichment and a separate system for secondary enrichment of a gas stream comprising oxygen and carbon dioxide flowing into a flue gas source. 
         FIG.  5    depicts a system which may utilize embodiments of leaf membranes for low pressure enrichment of a gas stream comprising oxygen and carbon dioxide flowing into a pressurized flue gas source. 
         FIG.  6    depicts a system which may utilize embodiments of leaf membranes for lower pressure enrichment and a separate system for secondary enrichment of a gas stream comprising oxygen and carbon dioxide flowing into a pressurized flue gas source. 
         FIG.  7    depicts an embodiment of a configuration of membrane units mounted within enclosed conduits which may be utilized for secondary (and tertiary) enrichment of a permeate stream in embodiments of the invention. 
         FIG.  8    depicts an alternative embodiment of a configuration of membrane units mounted within enclosed conduits which may be utilized for secondary (and tertiary) enrichment of a permeate stream in embodiments of the invention. 
         FIG.  9    depicts an embodiment of a membrane unit which may be utilized in a system as depicted in  FIG.  8   . 
         FIG.  10    depicts a piping configuration which may be utilized for a secondary and tertiary enrichment of a permeate stream. 
         FIG.  11    schematically depicts an embodiment of a bellows vacuum system for alternatively applying vacuum to a permeate stream in a low-pressure membrane and for generating pressure to deliver the permeate for further processing. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG.  1    depicts a configuration for an array or bank  100  formed by a plurality of leaf membrane units  102  for direct air capture of components of atmospheric air, specifically oxygen, nitrogen, water vapor, and, most importantly, carbon dioxide. It is to be appreciated that a plurality of banks  100  as depicted in  FIG.  1    may be deployed to increase the direct air capture of carbon dioxide. Once captured, leaf membrane units  102  separate oxygen, carbon dioxide and water from nitrogen, forming a permeate comprising enriched concentrations of oxygen, carbon dioxide and water, but a depleted level of nitrogen. The separated nitrogen simply returns to the atmosphere while the permeate, flows into delivery conduit  104  and into headers  106 . A vacuum generating device  108  applies a vacuum to the leaf membrane units  102  of bank  100 . Vacuum generating device applies a strong vacuum to the leaf membrane units. Among the acceptable vacuum generating devices  108  are blowers, liquid ring compressors, or the bellows vacuum system described below and schematically depicted in  FIG.  11   . 
     It is to be appreciated that multiple membrane banks  100  may be utilized to increase the capture of carbon dioxide from the atmosphere. Because the disclosed systems, including the membranes, the conduits, and the vacuum generating devices can be produced at relatively low cost, the only significant detriment in utilizing a substantial number of membrane banks  100  is the amount of area required for placement of the units. 
       FIG.  2    shows an exploded view of a leaf membrane unit  102  from the membrane bank  100 . Leaf membrane unit  102  comprises surface membrane sheets  110  which are disposed on either side of barrier ribbed sheet  112 . Each side of the barrier ribbed sheet  112  comprises a plurality or ribs  114 . Barrier ribbed sheet  112  comprises edges  116  which are attached to corresponding edges of the sides  118  of each surface membrane sheet  110  which are in facing relation to each side the barrier ribbed sheet  112 . Leaf membrane unit  102  takes neat (meaning ambient atmospheric) air allows oxygen, carbon dioxide and water to pass through surface membrane sheets  110 , thereby producing a lower total volume of and significantly higher concentration in the permeate stream of oxygen, carbon dioxide and water, and significantly lower concentration of nitrogen. The elimination of most or all of the nitrogen than in the air results in a permeate stream of enriched concentrations of oxygen, carbon dioxide and water. The permeate flows into the respective envelopes created between the opposing faces of each surface membrane sheet  110  and the barrier ribbed sheet  112  defining, with respect only to the orientation shown in  FIG.  2   , an upper envelope and a lower envelope, with conjoined edges  116 ,  118  enclosing all but one side of the upper envelope and the lower envelope. 
     The permeate is directed by ribs  114  towards an open side of the upper envelope and an open side of the lower envelope at unattached edges  120  of the surface membrane sheets  110  and unattached edge  122  of the barrier ribbed sheet  112 . The open side at unattached edges  120 ,  122  is inserted into slot  124  of permeate conduit  104 . 
       FIGS.  3 - 6    depict different generalized configurations of a flue gas generator  300 ,  400 ,  500 ,  600  which may be utilized in the various embodiments of the invention.  FIG.  3    depicts a base embodiment  300  which utilizes a membrane bank  100  upstream of the flue gas generator  300 .  FIG.  4    depicts an alternative embodiment  400  which utilizes a membrane bank  100  but also includes structure for secondary enrichment of the permeate stream.  FIG.  5    depicts an alternative embodiment  500  which utilizes membrane bank  100  but also utilizes a pressurized flue gas generator.  FIG.  6    depicts an alternative embodiment  600  which utilizes a membrane bank  100 , the structure for secondary enrichment of the permeate stream, and utilizes a pressurized flue gas generator. 
     For the base embodiment, flue gas generator  300  may have a stack  302  which may be capped with a closure device  304  at the tip. Flue gas generator  300  may have an economizer  306 , which is a heat exchanger which saves on fuel gas by preheating boiler feed water from ambient temperature on the tube side up to approximately 200 degrees Fahrenheit, utilizing hot stack gas on the shell side, utilizing a boiler feed water pump  308 . Fuel for the boiler  310  is delivered through fuel inlet  312 . “Air” for the boiler  310  is delivered through air inlet  314 , although the “air” provided through the inlet will comprise permeate provided by membrane bank  100 . Discharge from flue gas generator  300 , which may comprise an enriched concentration of carbon dioxide, may be delivered to a cooler  316  with the cooled gas dehydrated with liquids removal equipment (not shown) and then pressurized by a compressor or blower  318  for delivery to a sequestration facility  5000 , which may include systems which utilize bio-sequestration, such as orchards, crops, forests, and other photosynthetic organisms which either convert carbon dioxide utilizing photosynthesis or store the carbon dioxide in the organism. The sequestration facility  5000  may also include manufacturing processes which utilize carbon dioxide. The sequestration facility  5000  may also include a system which injects carbon dioxide into petroleum reservoirs for purposes of enhanced oil recovery such as miscible flooding. 
     Air provided to the boiler  310  first passes through membrane bank  100 . Membrane bank  100  utilizes a vacuum generating device  108  to draw ambient or atmospheric air into contact with the individual leaf membrane units  102 , and to pull the permeate through each membrane. The vacuum generating device  108  may be a blower or a liquid ring compressor, although both types of devices require liquid separation. Alternatively, a bellows vacuum device  1100  as schematically depicted in  FIG.  11    may be utilized. Vacuum generating device  108  discharges a permeate stream which, after being dehydrated as necessary by separator  324 , is delivered to air inlet  114 . 
     The bellows vacuum device  1100  uses less energy than a blower or a liquid ring compressor. The bellows vacuum device may be fabricated from a large enclosure, such as a tank. It is to be noted that because of the low speeds at which the bellows vacuum system operates, and the lubrication to be provided between the cylinder walls and piston, that little or no heat will be generated at the discharge of the device. 
     As shown in  FIG.  11   , double-acting piston  1102  is set within a large cylinder  1104 . Piston  1102  may have graphite rings and/or the cylinder walls  1106  may comprise graphite. Actuation devices  1108 ,  1110  respectively utilize connectors  1112 ,  1114  to actuate piston  1102  in either direction within the cylinder  1104 . It is to be appreciated that large cylinder  1104  need not be a pressure vessel and that actuation devices  1108 ,  1110  may be small winches driven by small motors and connectors  1112 ,  1114  may be light rods or small diameter cables. Double-acting piston  1102  may be diamond-shaped to provide additional structural integrity under vacuum conditions. 
     As indicated in  FIG.  11   , bellows vacuum device  1100  applies vacuum to membrane banks  100  on each upstroke (relative to the position of the oxygen enrichment membrane) of the piston  1102  within cylinder  1104 , thereby causing permeate to be pulled into cylinder  1104 . On the downstroke, with the action of check valves  1116 , permeate is pushed out of cylinder  1104  and into air inlets  314 ,  414 ,  514 ,  614  and into the boilers  310 ,  410 ,  510 ,  610  of the respective flue gas generators  300 ,  400 ,  500 ,  600   
     For the alternative embodiment depicted in  FIG.  4   , flue gas generator  400  may have a stack  402  which may be capped with a closure device  404  at the tip. Flue gas generator  400  may have an economizer  406 , which is a heat exchanger which saves on fuel gas by preheating boiler feed water from ambient temperature on the tube side up to approximately 200 degrees Fahrenheit, utilizing hot stack gas on the shell side, utilizing a boiler feed water pump  408 . Fuel for the boiler  410  is delivered through fuel inlet  412 . “Air” for the boiler  410  is delivered through air inlet  414 , although the “air” provided through the inlet will have enriched concentrations of oxygen, carbon dioxide and water and a reduced concentration if nitrogen, as described below. Discharge from flue gas generator  400 , which may comprise an enriched concentration of carbon dioxide, may be delivered to a cooler  416  with the cooled gas dehydrated with liquids removal equipment (not shown) and then pressurized by a compressor or blower  418  for delivery to a sequestration facility  5000 . 
     Air provided to the boiler  410  first passes through membrane bank  100 . Membrane bank  100  utilizes a vacuum-generating device  108  to draw ambient air into contact with the individual leaf membrane units  102  and pull the permeate through each individual membrane. As previously discussed, the vacuum generating device may be any of the various types described for the embodiment depicted in  FIG.  3   . Vacuum generating device  108  discharges a permeate stream which, after being dehydrated as necessary by separator  424  may be delivered to air inlet  414  and/or routed to inlet  426  to secondary enrichment mechanism  700 ,  800 , embodiments of which are described in greater detail below and depicted, respectively, in  FIGS.  7 - 8   . Alternatively, the secondary enrichment mechanism may comprise a known cryogenic oxygen enrichment system. 
     For the alternative embodiment depicted in  FIG.  5   , flue gas generator  500  is pressurized. The flue gas generator  500  has a stack  502  which is capped with a closure device  504  at the tip. Flue gas generator  500  may have an economizer  506 , which is a heat exchanger which saves on fuel gas by preheating boiler feed water from ambient temperature on the tube side up to approximately 200 degrees Fahrenheit, utilizing hot stack gas on the shell side, utilizing a boiler feed water pump  508 . Fuel for the boiler  510  is delivered through fuel inlet  512 . “Air” for the boiler  510  is delivered through air inlet  514 , although the “air” provided through the inlet will have enriched concentrations of oxygen, carbon dioxide and water and a reduced concentration of nitrogen. Discharge from flue gas generator  500  is emitted at a pressure in excess of atmospheric pressure and therefore may have a highly enriched concentration of carbon dioxide. The discharge may be routed to separator  550 , with enriched carbon dioxide discharged to sequestration facility  5000  and liquids discharged through outlet  554 . 
     Air provided to the boiler  510  first passes through membrane bank  100 . Membrane bank  100  utilizes a vacuum-generating device  108  to draw ambient air into contact with the individual leaf membrane units  102  and pull the permeate through each individual membrane. As previously discussed, the vacuum generating device may be any of the various types described for the embodiment depicted in  FIG.  3   . Vacuum generating device  108  discharges a permeate stream which, after being dehydrated as necessary by separator  524 , is delivered to air inlet  514 . 
     For the alternative embodiment depicted in  FIG.  6   , flue gas generator  600  is pressurized. The flue gas generator  600  has a stack  602  which is capped with a closure device  604  at the tip. Flue gas generator  600  may have an economizer  606 , which is a heat exchanger which saves on fuel gas by preheating boiler feed water from ambient temperature on the tube side up to approximately 200 degrees Fahrenheit, utilizing hot stack gas on the shell side, utilizing a boiler feed water pump  608 . Fuel for the boiler  610  is delivered through fuel inlet  612 . “Air” for the boiler  610  is delivered through air inlet  614 , although the “air” provided through the inlet will have enriched concentrations of oxygen, carbon dioxide and water. Discharge from flue gas generator  600  is emitted at a pressure in excess of atmospheric pressure and therefore may have a highly enriched concentration of carbon dioxide. The discharge may be routed to separator  650 , with enriched carbon dioxide discharged to sequestration facility  5000  and liquids discharged through outlet  654 . 
     Air provided to the boiler  610  first passes through membrane bank  100 . Membrane bank  100  utilizes a vacuum-generating device  108  to draw ambient air into contact with the individual leaf membrane units  102  and pull the permeate through each individual membrane. As previously discussed, the vacuum generating device may be any of the various types described for the embodiment depicted in  FIG.  3   . Vacuum generating device  108  discharges a permeate stream which, after being dehydrated as necessary by separator  624  may be delivered to air inlet  614  and/or routed to inlet  626  to secondary enrichment mechanism  700 ,  800 , embodiments of which are described in greater detail below and depicted, respectively, in  FIGS.  7 - 8   . Alternatively, the secondary enrichment mechanism may comprise a known cryogenic oxygen enrichment system. 
       FIG.  7    depicts an embodiment of a secondary enrichment mechanism  700 . Secondary oxygen enrichment mechanism  700  receives “feed” (i.e., permeate from membrane bank  100 ) through inlets  426 ,  626 . The feed flows into enclosed conduit  702  where the feed encounters membrane units  704 . In this embodiment of the secondary oxygen enrichment mechanism  700 , the membrane units  704  may be the leaf membrane units  102  described above and depicted in  FIG.  2   . However, instead of being exposed to the atmosphere, the membrane units  704  of secondary enrichment mechanism  700  are entirely enclosed and the feed is provided under pressure, with a pressure differential created at headers  706  by blower  708 , which delivers the permeate either to a tertiary enrichment mechanism, such as another membrane system as depicted in  FIGS.  7 ,  8    and shown schematically in  FIG.  10   , or to air inlets  414 ,  614  for boilers  410 ,  610 . Residue from the secondary enrichment mechanism  700  remains within enclosed conduit  702  and may be discharge through an outlet, not shown. 
       FIG.  8    depicts an embodiment of a secondary enrichment mechanism  800 . Secondary enrichment mechanism  800  receives “feed” (i.e., permeate from membrane bank  100 ) through inlets  426 ,  626 . The feed flows under pressure into enclosed conduit  802  where the feed encounters membrane units  804 . 
     In this embodiment of the secondary enrichment mechanism  800 , the membrane units  804  may be spiral wound membrane units  900  as depicted in  FIG.  9   , with the feed entering into the front face  902  of each unit and the residue stream leaving the rear face  904  of each unit. Spiral wound membrane unit  900  is fabricated from alternating sheets of membrane sheets and spacer sheets. An expanded detail of an unwound membrane unit is shown in detail A of  FIG.  9   , where the spiral membrane unit has the following elements: (1) a bottom feed/residue spacer  1 ; (2) a bottom membrane sheet  2 ; (3) a permeate spacer  3 ; (4) a top membrane sheet  4 ; (5) a top feed/residue spacer  5 ; (6) a bottom feed/residue channel  6 ; (7) a bottom feed permeate channel  7 ; (8) a top permeate channel  8 ; and (9) a top feed/residue channel  9 . The membrane sheet layers  2 ,  4  are glued to the feed/residue spacers  1 ,  5  at the front edges only and glued to the permeate spacer  3  at the front and the side edges. The open ends of permeate channels  7 ,  8  are attached over perforations in the permeate collection pipe  908 . The top feed/residue spacer  5  is longitudinally ribbed on the bottom of the spacer and the bottom feed/residue spacer  1  is longitudinally ribbed on the top of the spacer. Permeate spacer  3  is laterally ribbed on the top and bottom of the spacer. 
     Gas flows in a spiral pattern through the spiral wound membrane with the permeate received by permeate collection pipe  910 . The ends of permeate collection pipe  910  may threaded so that the spiral wound membrane units may be attached in an end-to-end configuration for collection of the permeate. Permeate collection pipes  910  are connected to permeate collection header  806   
     The membrane units  904  for secondary enrichment mechanism  900  are entirely enclosed and the feed is provided under pressure, with a pressure differential created at permeate collection header  806  by blower  808 , which delivers the permeate either to a tertiary enrichment mechanism, such as another membrane system as depicted in  FIGS.  7 ,  8    or to air inlets  414 ,  614  for boilers  410 ,  610 . Residue from the secondary enrichment mechanism  800  will remain within enclosed conduit  802  and may be discharge through an outlet, not shown. 
       FIG.  10    schematically depicts a configuration of a secondary and tertiary enrichment structures which may be utilized in embodiments of the invention. As indicated in the figures, vacuum-generating devices  708 ,  808 , as described herein are required to pull the feed gas through the membranes of secondary enrichment mechanisms  700 ,  800  and pressurize the post membrane permeate to service destinations which may include sequestration facility  5000 . For secondary enrichment mechanisms  700 ,  800  a strong vacuum blower  708 ,  808 , usually a liquid ring compression device, is needed to pull the permeate through. Dehydration and liquid separation devices  1024  are required. 
     With the embodiments of the invention disclosed herein, the flue gas stream from the flue gas generator  300 ,  400 ,  500 ,  600  is reduced in volume and thus more economical to transport because ducts and permeate blower systems may be substantially reduced in size. 
     While the above is a description of various embodiments of the present invention, further modifications may be employed without departing from the spirit and scope of the present invention. Thus the scope of the invention should not be limited according to these factors, but according to the following appended claims.