Direct capture of CO
Systems and methods are provided for integrating direct air capture of carbon dioxide with capture of carbon dioxide from a point source. The systems and methods can include exposing an adsorbent to a low CO 2 content gas flow (e.g., air) at conditions similar to ambient conditions to perform an initial amount of sorption of CO 2 . The initial sorption results in a partially loaded sorbent having a first sorbent loading. The partially loaded sorbent can then be exposed to a flue gas and/or other gas flow that contains a higher CO 2 content. This allows a second sorption step to be performed using a higher CO 2 content gas, resulting in an additionally loaded sorbent having a second (higher) sorbent loading. The sorbed CO 2 can then be desorbed from the sorbent.
1 . A method of sorbing CO2, comprising:
exposing a first gas flow comprising 15 vol % to 25 vol % O 2 and 100 vppm to 800 vppm CO 2 to one or more amine sorbents in a sorbent environment at a first temperature of 10° C. to 35° C. to form one or more partially loaded amine sorbents comprising a first sorbent loading of CO2 sorbed during the exposing the first gas flow;
exposing a second gas flow comprising 1.0 vol % to 20 vol % CO 2 and a second temperature higher than the first temperature to the one or more partially loaded amine sorbents in the sorbent environment to form one or more additionally loaded amine sorbents comprising a second sorbent loading of CO 2 sorbed during the exposing the second gas flow, a ratio of the second sorbent loading to the first sorbent loading being 0.02 or more;
passing a purge gas flow through the sorbent environment; and
heating the sorbent environment to a temperature of 85° C. or higher to desorb at least a portion of the CO 2 from the one or more additionally loaded amine sorbents;
wherein the second gas flow comprises a second O 2 concentration, wherein during the exposing the second gas flow, a ratio of a time for the sorbent environment to reach a maximum temperature of 80° C. or higher versus a time for the sorbent environment to reach the second O 2 concentration is 4.0 or more, the maximum temperature being the highest temperature in the sorbent environment.
2 . The method of claim 1 , wherein a pressure of the sorbent environment at a beginning of the exposing the second gas flow is 50 kPa-a or higher.
3 . The method of claim 1 , wherein the second temperature is 85° C. to 100° C.
4 . A method of sorbing CO2, comprising:
exposing a first gas flow comprising 15 vol % to 25 vol % O 2 and 100 vppm to 800 vppm CO 2 to one or more amine sorbents in a sorbent environment at a first temperature of 10° C. to 35° C. to form one or more partially loaded amine sorbents comprising a first sorbent loading of CO 2 sorbed during the exposing the first gas flow;
exposing a second gas flow comprising 1.0 vol % to 20 vol % CO 2 and a second temperature higher than the first temperature to the one or more partially loaded amine sorbents in the sorbent environment to form one or more additionally loaded amine sorbents comprising a second sorbent loading of CO 2 sorbed during the exposing the second gas flow, a ratio of the second sorbent loading to the first sorbent loading being 0.02 or more;
passing a purge gas flow through the sorbent environment; and
heating the sorbent environment to a temperature of 85° C. or higher to desorb at least a portion of the CO 2 from the one or more additionally loaded amine sorbents;
wherein desorbing at least a portion of the CO 2 from the one or more additionally loaded amine sorbents forms one or more regenerated amine sorbents, the method further comprising:
cooling the sorbent environment to a temperature of less than 90° C. and above the temperature of the first gas flow; and
exposing another portion of the first gas flow to the one or more regenerated amine sorbents;
wherein a time for the exposing another portion of the first gas flow is greater than a time for the exposing the first gas flow, or wherein a time for the exposing another portion of the first gas flow is less than a time for the exposing the first gas flow.
5 . The method of claim 1 , wherein the first sorbent loading is greater than the second sorbent loading.
6 . The method of claim 1 , wherein the one or more amine sorbents comprise at least one aminopolymer.
7 . The method of claim 6 , wherein the one or more amine sorbents have an absolute loading of 3.0 mmol-CO 2 /g-aminopolymer or less prior to exposing the first gas flow to the one or more amine sorbents.
8 . The method of claim 6 , wherein the first sorbent loading is 0.2 mmol-CO 2 /g-aminopolymer or more.
9 . The method of claim 6 , wherein the first sorbent loading is 0.2 mmol-CO 2 /g-aminopolymer to 4.5 mmol-CO 2 /g-aminopolymer.
10 . The method of claim 6 , wherein the second sorbent loading is 1.0 mmol-CO 2 /g-aminopolymer to 4.0 mmol-CO 2 /g-aminopolymer.
11 . The method of claim 6 , wherein the second sorbent loading is 4.0 mmol-CO 2 /g-aminopolymer to 7.0 mmol-CO 2 /g-aminopolymer.
12 . The method of claim 1 , wherein desorbing at least a portion of the CO 2 from the one or more additionally loaded amine sorbents forms one or more regenerated amine sorbents, the method further comprising:
cooling the sorbent environment to a temperature of less than 90° C. and above the temperature of the first gas flow; and
exposing another portion of the first gas flow to the one or more regenerated amine sorbents.
13 . The method of claim 4 , wherein cooling the sorbent environment comprises cooling the sorbent environment to a temperature of less than 70° C.
14 . The method of claim 4 , the second gas flow comprising a second O 2 concentration, wherein during the exposing the second gas flow, a ratio of a time for the sorbent environment to reach a maximum temperature of 80° C. or higher versus a time for the sorbent environment to reach the second O 2 concentration is 4.0 or more, the maximum temperature being the highest temperature in the sorbent environment.
15 . The method of claim 1 , wherein heating the sorbent environment comprises passing the purge gas flow through the sorbent environment, the purge gas flow comprising a temperature of 85° C. or higher.
16 . The method of claim 1 , wherein the first gas flow comprises air; or wherein the second gas flow comprises at least a portion of a combustion flue gas; or a combination thereof.
17 . The method of claim 1 , wherein 95 vol % or more of the volume of CO 2 in the second gas flow during the exposing the second gas flow is sorbed by the one or more partially loaded amine sorbents.
18 . The method of claim 1 , the second gas flow comprising at least a portion of a combustion flue gas from a power plant, wherein
i) the purge gas flow comprises steam generated by the power plant,
ii) at least a portion of the power for performing the method of sorbing CO 2 is provided by the power plant, or
iii) a combination of i) and ii).