Removal of carbon dioxide from air

Abstract

The present invention provides a method and apparatus for removing a contaminant, such as carbon dioxide, from a gas stream, such as ambient air. The contaminant is removed from the gas stream by a sorbent which may be regenerated using a humidity swing, a thermal swing, or a combination thereof. The sorbent may comprise a substrate having embedded positive ions and individually mobile negative ions wherein the positive ions are sufficiently spaced to prevent interactions between the negative ions. Where a thermal swing is used, heat may be conserved by employing a heat exchanger to transfer heat from the regenerated sorbent to an amount of sorbent that is loaded with the contaminant prior to regeneration.

1 - 18 . (canceled) 
     
     
         19 . A method for extracting a contaminant from a gas stream, comprising the steps of:
 a) bringing the gas stream in contact with a sorbent which captures the contaminant from the gas stream, so as to at least partially saturate the sorbent with contaminant;   b) placing the contaminant carrying sorbent in a regeneration unit for releasing the contaminant from the sorbent and regenerate the sorbent, wherein the regeneration unit is maintained at a temperature that is higher than the temperature of the gas stream;   c) removing the regenerated sorbent from the regeneration unit; and   d) capturing heat from the regenerated sorbent as the sorbent is removed from the regeneration unit.   
     
     
         20 . The method of  claim 19 , wherein the heat captured from the sorbent regeneration is used to raise the temperature of the contaminant carrying sorbent prior to the step (b) of placing the sorbent in the regeneration unit. 
     
     
         21 . The method of  claim 19 , wherein the contaminant is carbon dioxide. 
     
     
         22 . The method of  claim 19 , wherein the gas stream is an exhaust stream or ambient air. 
     
     
         24 . The method of  claim 19 , wherein the sorbent is a liquid or a solid. 
     
     
         25 . (canceled) 
     
     
         26 . The method of  claim 19 , wherein heat is captured from the regenerated sorbent using a heat exchanger in a refrigeration cycle, wherein water preferably is employed as refrigerant in the refrigeration cycle, the refrigerant water optionally is evaporated using heat exchanged from the regenerate, and the evaporated water optionally is condensed on the contaminant carrying sorbent. 
     
     
         27 - 29 . (canceled) 
     
     
         30 . The method of  claim 26 , wherein the heat exchanger uses carbon dioxide as a refrigerant. 
     
     
         31 . The method of  claim 26 , wherein the heat exchanger utilizes a refrigerant that is isolated from having contact with the sorbent. 
     
     
         32 . The method of  claim 19 , wherein the regeneration unit is maintained at an elevated temperature using heat from a source that is one from a group consisting of: solar energy, geothermal energy, and waste heat from an industrial process. 
     
     
         33 . An apparatus for extracting a contaminant from a gas stream using a sorbent employing a thermal swing, comprising:
 a sorbent for capturing the contaminant;   a capture unit, wherein the sorbent is exposed to the gas stream and becomes at least partially saturated with the contaminant;   a regeneration unit, wherein the sorbent is exposed to elevated temperatures thereby causing the sorbent to release the contaminant according to a thermal swing; and   a heat exchanger for extracting heat retained from the sorbent in the regeneration unit.   
     
     
         34 . The apparatus of  claim 33 , wherein heat extracted by the heat exchanger is used to raise the temperature of the at least partially saturated sorbent prior to placing the at least partially saturated sorbent in the regeneration unit. 
     
     
         35 . The apparatus of  claim 33 , wherein the contaminant is carbon dioxide or ambient air. 
     
     
         36 . (canceled) 
     
     
         37 . The apparatus of  claim 33 , wherein the sorbent is a liquid or a solid. 
     
     
         38 . (canceled) 
     
     
         39 . The apparatus of  claim 33 , (a) wherein the heat exchanger uses water or carbon dioxide as a refrigerant, and/or (b) wherein the heat exchanger utilizes a refrigerant that is isolated from having contact with the sorbent. 
     
     
         40 - 41 . (canceled) 
     
     
         42 . A method for extracting CO 2  from a gas stream comprising the steps of:
 (a) bringing a sorbent in contact with said gas stream, so as to at least partially saturate said sorbent with CO 2 ;   (b) releasing CO 2  from said sorbent at a temperature that is higher than the temperature of said gas stream, thereby regenerating said sorbent;   (c) capturing heat retained by said sorbent using a working fluid; and   (d) recycling captured heat for use in step (b).   
     
     
         43 . The method of  claim 42 , wherein said gas stream is ambient air. 
     
     
         44 . The method of  claim 42 , wherein said sorbent is selected from the group consisting of: a sodium hydroxide solution, a sodium carbonate solution, an amine solution, a solid amine resin, an ion exchange resin, a functionalized mineral, a functionalized inorganic matter, a zeolite, a metal oxide, a metal hydroxide, a high surface powder, a sodium silicate, a foam material, and a functionalized foam. 
     
     
         45 . The method of  claim 44 , wherein said high surface power is formed from sodium carbonate, aluminum hydroxide, magnesium hydroxide, iron(III) oxide, activated alumina, activated magnesia, and activated iron oxide. 
     
     
         46 . The method of  claim 42 , characterized by one or more of the following features:
 (a) wherein said working fluid is water, CO 2 , R-12, or R-22;   (b) said working fluid contacts said sorbent; and   (c) said working fluid is isolated from said sorbent.   
     
     
         47 . The method of  claim 46 , wherein CO 2  released from said sorbent is collected in a vessel.