Multi-stage direct capture of CO2 from air

A method for separation of CO2 from an input flow stream, comprising:

• exposing a first gas flow comprising 600 vppm or less of CO2 to at least one first contactor of a plurality of contactors to form a first CO2-depleted gas flow, the at least one first contactor comprising a first sorbent having selectivity for CO2 sorption supported on one or more first monoliths, the exposing the first gas flow further forming a first sorbent comprising sorbed CO2;
• exposing a second gas flow comprising 600 vppm or less of CO2 to at least one second contactor of the plurality of contactors to form a second CO2-depleted gas flow, the at least one second contactor comprising a sorbent having selectivity for CO2 sorption supported on one or more second monoliths, the exposing the second gas flow further forming a second sorbent comprising sorbed CO2;
• exposing the first sorbent comprising sorbed CO2 to a first heated working fluid to form a heated first sorbent and a first CO2-containing working fluid comprising 1.0 vol % or more of CO2, the first CO2-containing working fluid formed by desorbing at least a portion of the sorbed CO2 from the first sorbent comprising sorbed CO2;
• exposing the heated first sorbent to a first nitrogen-enriched gas comprising 95 vol % of N2 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 CO2 to at least a portion of the second heated working fluid to form a heated second sorbent and a second CO2-containing working fluid, the second CO2-containing working fluid formed by desorbing at least a portion of the sorbed CO2 from the second sorbent comprising sorbed CO2;
• exposing the heated second sorbent to a second nitrogen-enriched gas comprising 95 vol % or more of N2 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 CO2-containing working fluid to form at least a first product flow having a CO2 concentration of 80 vol % or more and a first output flow comprising 95 vol % or more of N2;
• and
• separating the second CO2-containing working fluid to form at least a second product flow having a CO2 concentration of 80 vol % or more and a second output flow comprising 95 vol % or more of N2.