Multi-stage direct capture of CO
Systems and methods are provided for using a multi-stage capture process for capture of CO 2 from air. A first or initial sorption process is used to sorb CO 2 from air. After sorption from the air is complete, the desorption step of the initial stage is used to form a secondary CO 2 -containing stream that is passed into one or more additional sorption stages. This secondary CO 2 -containing stream can be at a concentration of roughly 1.0 vol % or more. Sorption of CO 2 from the secondary CO 2 -containing stream is performed using a different contacting method, such as a contacting method that is higher efficiency. The second or later CO 2 sorption stage can produce a CO 2 -containing output stream with a CO 2 concentration of 80 vol % or more, or 90 vol % or more, or 95 vol % or more. This high purity output stream can then be sequestered and/or used for further processing.
1 . A method for separation of CO 2 from an input flow stream, comprising:
exposing a first gas flow comprising 600 vppm or less of CO 2 to at least one first contactor of a plurality of contactors to form a first CO 2 -depleted gas flow, the at least one first contactor comprising a first sorbent having selectivity for CO 2 sorption supported on one or more first monoliths, the exposing the first gas flow further forming a first sorbent comprising sorbed CO 2 ;
exposing a second gas flow comprising 600 vppm or less of CO 2 to at least one second contactor of the plurality of contactors to form a second CO 2 -depleted gas flow, the at least one second contactor comprising a sorbent having selectivity for CO 2 sorption supported on one or more second monoliths, the exposing the second gas flow further forming a second sorbent comprising sorbed CO 2 ;
exposing the first sorbent comprising sorbed CO 2 to a first heated working fluid to form a heated first sorbent and a first CO 2 -containing working fluid comprising 1.0 vol % or more of CO 2 , the first CO 2 -containing working fluid formed by desorbing at least a portion of the sorbed CO 2 from the first sorbent comprising sorbed CO 2 ;
exposing the heated first sorbent to a first nitrogen-enriched gas comprising 95 vol % of N 2 or more to cool the heated first sorbent and to heat the first nitrogen-enriched gas to form a first partially heated working fluid;
heating the first partially heated working fluid to form a second heated working fluid;
exposing the second sorbent comprising sorbed CO 2 to at least a portion of the second heated working fluid to form a heated second sorbent and a second CO 2 -containing working fluid, the second CO 2 -containing working fluid formed by desorbing at least a portion of the sorbed CO 2 from the second sorbent comprising sorbed CO 2 ;
exposing the heated second sorbent to a second nitrogen-enriched gas comprising 95 vol % or more of N 2 to cool the heated second sorbent and to heat the second nitrogen-enriched gas to form a second partially heated working fluid;
separating the first CO 2 -containing working fluid to form at least a first product flow having a CO 2 concentration of 80 vol % or more and a first output flow comprising 95 vol % or more of N 2 ; and
separating the second CO 2 -containing working fluid to form at least a second product flow having a CO 2 concentration of 80 vol % or more and a second output flow comprising 95 vol % or more of N 2 .
2 . The method of claim 1 , wherein the first output flow comprises 0.08 vol % or more of CO 2 , or wherein the second output flow comprises 0.08 vol % or more of CO 2 , or a combination thereof.
3 . The method of claim 1 , wherein the first nitrogen-enriched gas comprises 0.08 vol % or more of CO 2 , or wherein the second nitrogen-enriched gas comprises 0.08 vol % or more of CO 2 , or a combination thereof.
4 . The method of claim 1 , wherein the volumetric flow rate of the first CO 2 -containing working fluid is 5.0% or less of the volumetric flow rate of the first gas flow, or wherein the volumetric flow rate of the second CO 2 -containing working fluid is 5.0% or less of the volumetric flow rate of the second gas flow.
5 . The method of claim 1 , further comprising:
exposing the first sorbent comprising sorbed CO 2 to a first pre-heating flow comprising 1.0 vol % or more of CO 2 and 95 vol % or more of N 2 , the exposing the first sorbent comprising sorbed CO 2 to a pre-heating flow being performed prior to exposing the first sorbent comprising sorbed CO 2 to the heated working fluid.
6 . The method of claim 5 , further comprising:
heating at least a portion of the first CO 2 -containing working fluid;
exposing a third gas flow comprising 600 vppm or less of CO 2 to at least one third contactor of a plurality of contactors to form a third CO 2 -depleted gas flow, the at least one third contactor comprising a third sorbent having selectivity for CO 2 sorption supported on one or more third monoliths, the exposing the third gas flow further forming a third sorbent comprising sorbed CO 2 ;
exposing the third sorbent comprising sorbed CO 2 to a third pre-heating flow comprising the at least a portion of the first CO 2 -containing working fluid after the heating of the at least a portion of the first CO 2 -containing working fluid;
exposing the third sorbent comprising sorbed CO 2 to a third heated working fluid to form a heated third sorbent and a third CO 2 -containing working fluid, the third CO 2 -containing working fluid formed by desorbing at least a portion of the sorbed CO 2 from the third sorbent comprising sorbed CO 2 ; and
exposing the heated third sorbent to a third nitrogen-enriched gas comprising 95 vol % of N 2 or more to cool the heated third sorbent and to heat the third nitrogen-enriched gas to form a third partially heated working fluid.
7 . The method of claim 1 , wherein the exposing the first sorbent comprising sorbed CO 2 to a first heated working fluid comprises exposing the first sorbent comprising sorbed CO 2 to the first heated working fluid at a pressure of 150 kPa-a or more.
8 . The method of claim 1 , wherein the first heated working fluid comprises a temperature of 100° C. to 170° C., or wherein the second heated working fluid comprises a temperature of 100° C. to 170° C., or a combination thereof.
9 . The method of claim 1 , wherein the first nitrogen-enriched gas comprises a temperature of 20° C. to 80° C., or wherein the second nitrogen-enriched gas comprises a temperature of 20° C. to 80° C., or a combination thereof.
10 . The method of claim 1 , wherein separating the first CO 2 -containing working fluid comprises separating the first CO 2 -containing working fluid using an amine scrubber; or wherein separating the first CO 2 -containing working fluid comprises performing a temperature swing separation; or wherein separating the first CO 2 -containing working fluid comprises performing a temperature swing vacuum-assisted separation using a sorbent supported on a solid support; or a combination thereof.
11 . The method of claim 1 , wherein the first sorbent comprises an amine-based sorbent, or wherein the second sorbent comprises an amine-based sorbent, or a combination thereof.
12 . The method of claim 1 , further comprising exposing the first sorbent comprising sorbed CO 2 to a purge flow prior to exposing the first sorbent comprising sorbed CO 2 to the first heated working fluid.
13 . The method of claim 1 , wherein the at least one first contactor comprises at least one rotary sorbent wheel.
14 . The method of claim 1 , wherein exposing the heated first sorbent to a first nitrogen-enriched gas comprising 95 vol % of N 2 further comprises exposing the heated first sorbent to a recycled portion of the first partially heated working fluid.
15 . The method of claim 1 , wherein the recycled portion of the first partially heated working fluid is cooled prior to exposing the recycled portion of the first partially heated working fluid to the heated first sorbent.
16 . The method of claim 1 , wherein the method further comprises:
exposing a fourth gas flow comprising 600 vppm or less of CO 2 to at least one fourth contactor of a plurality of contactors to form a fourth CO 2 -depleted gas flow, the at least one fourth contactor comprising a fourth sorbent having selectivity for CO 2 sorption supported on one or more fourth monoliths, the exposing the fourth gas flow further forming a fourth sorbent comprising sorbed CO 2 ;
exposing the fourth sorbent comprising sorbed CO 2 to a fourth heated working fluid to form a heated fourth sorbent and a fourth CO 2 -containing working fluid, the fourth CO 2 -containing working fluid formed by desorbing at least a portion of the sorbed CO 2 from the fourth sorbent comprising sorbed CO 2 ;
exposing the heated fourth sorbent to a fourth nitrogen-enriched gas comprising 95 vol % of N 2 or more to cool the heated fourth sorbent and to heat the fourth nitrogen-enriched gas to form a fourth partially heated working fluid, the fourth nitrogen-enriched gas comprising at least a portion of the first output flow.