Systems and methods for capturing carbon dioxide and regenerating a capture solution
Techniques according to the present disclosure include capturing carbon dioxide from a dilute gas source with a CO 2 capture solution to form a carbonate-rich capture solution; separating at least a portion of carbonate from the carbonate-rich capture solution; forming an electrodialysis (ED) feed solution; flowing a water stream and the ED feed solution to a bipolar membrane electrodialysis (BPMED) unit; applying an electric potential to the BPMED unit to form at least two ED product streams including a first ED product stream including a hydroxide; and flowing the first ED product stream to use in the capturing the carbon dioxide from the dilute gas source with the CO 2 capture solution.
1 . A method comprising:
capturing carbon dioxide from a dilute gas source with a CO 2 capture solution to form a carbonate-rich capture solution;
increasing a concentration of carbonate in the carbonate-rich capture solution by crystallizing the carbonate-rich capture solution to form a mother liquor and a crystalline carbonate hydrate;
forming an electrodialysis (ED) feed solution;
flowing a water stream and the ED feed solution to a bipolar membrane electrodialysis (BPMED) unit;
applying an electric potential to the BPMED unit to form at least two ED product streams including a first ED product stream that includes a hydroxide; and
flowing the first ED product stream to use in capturing the carbon dioxide from the dilute gas source with the CO 2 capture solution.
2 . The method of claim 1 , wherein applying the electric potential to the BPMED unit includes applying at least a portion of the electric potential to the BPMED unit to form the first ED product stream and a second ED product stream.
3 . The method of claim 2 , wherein the second ED product stream includes carbonic acid, the method further comprising recovering at least a portion of a carbon dioxide gas stream from the second ED product stream.
4 . The method of claim 3 , wherein recovering the portion of the carbon dioxide gas stream from the second ED product stream includes recovering at least the portion of the carbon dioxide gas stream from the second ED product stream to form a brine stream, the method comprising:
dissolving the crystalline carbonate hydrate and mixing the dissolved crystalline carbonate hydrate with the brine stream to form the ED feed solution before flowing the water and the ED feed solution to the BPMED unit.
5 . The method of claim 4 , wherein recovering the portion of the carbon dioxide gas stream from the second ED product stream to form the brine stream includes recovering the portion of the carbon dioxide gas stream in a flash tank, the method further comprising:
flowing the brine stream from the flash tank to use in the dissolving the crystalline carbonate hydrate and mixing the dissolved crystalline carbonate hydrate with the brine stream to form the ED feed solution.
6 . The method of claim 4 , comprising:
flowing the carbon dioxide gas stream to a downstream process comprising at least one of: a compression unit, a fuel synthesis system, a syngas generation reactor, or an electrolyzer cell; and
yielding one or more downstream products comprising at least one of: syngas, CO, H 2 , or water.
7 . The method of claim 2 , wherein the second ED product stream includes a proton-shuttling species, the method further comprising:
reacting the second ED product stream with the portion of carbonate to recover the carbon dioxide gas and to form the ED feed solution.
8 . The method of claim 7 , wherein reacting the second ED product stream with the portion of carbonate to recover the carbon dioxide gas includes reacting the proton-shuttling species of the second ED product stream with the portion of carbonate to form carbonic acid and the ED feed solution.
9 . The method of claim 7 , comprising:
flowing the carbon dioxide gas to a downstream process comprising at least one of: a compression unit, a fuel synthesis system, a syngas generation reactor, or an electrolyzer cell; and
yielding one or more downstream products comprising at least one of: syngas, CO, H 2 , or water.
10 . The method of claim 7 , wherein reacting the second ED product stream with the portion of carbonate includes reacting the proton-shuttling species comprising bisulfate with the portion of carbonate.
11 . The method of claim 1 , comprising flowing the ED feed solution through an ion exchanger before flowing the water and the ED feed solution to the BPMED unit.
12 . The method of claim 1 , comprising separating a BPMED recycle stream from the first ED product stream, and returning the BPMED recycle stream to the BPMED unit.
13 . The method of claim 2 , comprising:
flowing the carbonate-rich capture solution through a nanofiltration unit to form a nanofiltration (NF) retentate stream comprising a carbonate-rich mixture, and to form a NF permeate stream comprising a hydroxide-rich mixture, and flowing the water and the ED feed solution to the BPMED unit includes flowing the ED feed solution comprising at least a portion of the NF retentate stream to the BPMED unit, the method further comprising:
recovering a carbon dioxide gas from the second ED product stream to form a brine stream;
flowing the brine stream to a reverse osmosis (RO) unit to form an RO retentate stream comprising a bicarbonate-rich solution and to form an RO permeate stream comprising water; and
combining the RO retentate stream with the NF retentate stream to form the ED feed solution.
14 . The method of claim 13 , comprising flowing at least a portion of the NF permeate stream to use in the capturing the carbon dioxide from the dilute gas source with the CO 2 capture solution.
15 . The method of claim 13 , comprising flowing the NF retentate stream to an ion exchanger downstream of the nanofiltration unit to form an ion exchange regenerate waste stream and at least a portion of the ED feed solution.
16 . The method of claim 13 , comprising combining at least a portion of the RO permeate stream comprising water with the first ED product stream to form a BPMED recycle stream.
17 . The method of claim 1 , comprising increasing a concentration of hydroxide in the first ED product stream to form the CO 2 capture solution before capturing the carbon dioxide from the dilute gas source with the CO 2 capture solution.
18 . The method of claim 1 , comprising:
dissolving at least a portion of the crystalline carbonate hydrate to form a portion of carbonate; and
mixing the portion of carbonate with a brine stream to form the ED feed solution.
19 . The method of claim 2 , comprising;
dissolving at least a portion of the crystalline carbonate hydrate to form a portion of carbonate; and
reacting the portion of carbonate with a proton-shuttling species in the second ED product stream to form the ED feed solution.
20 . The method of claim 1 , comprising evaporating water from the carbonate-rich capture solution to increase a concentration of carbonate before crystallizing the carbonate-rich capture solution.
21 . The method of claim 1 , comprising combining at least a portion of the mother liquor with at least a portion of the CO 2 capture solution for use in the capturing the carbon dioxide from the dilute gas source with the CO 2 capture solution.
22 . The method of claim 1 , wherein increasing the concentration of carbonate in the carbonate-rich capture solution comprises crystallizing the carbonate-rich capture solution to form a low solids stream and a high solids stream comprising the crystalline carbonate hydrate, the low solids stream having a higher liquid-to-solid ratio than the high solids stream, the method further comprising:
dissolving the crystalline carbonate hydrate of the high solids stream in an aqueous solution and mixing with a brine stream to form the ED feed solution; and
returning the low solids stream to use in the crystallizing of the carbonate-rich capture solution.
23 . A method comprising:
capturing carbon dioxide from air with a CO 2 capture solution to form a carbonate-rich capture solution;
separating at least a portion of carbonate from the carbonate-rich capture solution;
reacting a proton-shuttling species with the portion of carbonate to recover carbon dioxide gas from the portion of carbonate and to form a feed solution;
flowing a water stream and the feed solution to an electrochemical cell;
applying an electric potential to the electrochemical cell to form a first product stream that includes a hydroxide and a second product stream comprising the proton-shuttling species;
flowing the second product stream comprising the proton-shuttling species to react the proton-shuttling species with the portion of carbonate; and
flowing the first product stream to use in capturing the carbon dioxide from the air with the CO2 capture solution.
24 . The method of claim 23 , wherein:
reacting the proton-shuttling species with the portion of carbonate comprises reacting the proton-shuttling species with the portion of carbonate to form carbonic acid and the feed solution; and
degassing the carbon dioxide gas from the carbonic acid.
25 . The method of claim 24 , wherein reacting the proton-shuttling species with the portion of carbonate comprises reacting the proton-shuttling species comprising at least one of sulfuric acid and bisulfate with the portion of carbonate to form the carbonic acid and the feed solution.
26 . The method of claim 23 , wherein separating the portion of carbonate from the carbonate-rich capture solution comprises crystallizing the portion of carbonate to form a crystalline carbonate hydrate.
27 . The method of claim 26 , wherein reacting the proton-shuttling species with the portion of carbonate comprises:
dissolving the crystalline carbonate hydrate to form a dissolved inorganic carbon; and
reacting the dissolved inorganic carbon with the proton-shuttling species to form the feed solution and carbon dioxide gas, before the flowing the water stream and the feed solution to the electrochemical cell.
28 . The method of claim 26 , wherein reacting the proton-shuttling species with the portion of carbonate comprises:
dissolving the crystalline carbonate hydrate to form a dissolved inorganic carbon;
flowing the dissolved inorganic carbon to a flash tank; and
reacting the dissolved inorganic carbon with the proton-shuttling species in the flash tank to form the feed solution and carbon dioxide gas, before the flowing the water stream and the feed solution to the electrochemical cell.
29 . The method of claim 23 , wherein flowing the water stream and the feed solution to the electrochemical cell comprises:
separating a recycle stream including hydroxide from the first product stream; and
flowing the recycle stream to the electrochemical cell.
30 . The method of claim 23 , wherein flowing the water stream and the feed solution to the electrochemical cell comprises:
flowing the water to an alkaline regeneration compartment of the electrochemical cell, the alkaline regeneration compartment defined between a cathode and a cation exchange membrane of the electrochemical cell; and
flowing the feed solution to a feed compartment of the electrochemical cell separate from the alkaline regeneration compartment.
31 . The method of claim 30 , wherein flowing the feed solution to the feed compartment comprises flowing the feed solution to the feed compartment defined between an anode of the electrochemical cell and the cation exchange membrane.
32 . The method of claim 30 , wherein:
flowing the feed solution to the feed compartment comprises flowing the feed solution to the feed compartment defined between an anion exchange membrane of the electrochemical cell and the cation exchange membrane; and
applying the electric potential to the electrochemical cell comprises moving the proton-shuttling species across the anion exchange membrane into an acid compartment defined between the anion exchange membrane and an anode of the electrochemical cell.
33 . The method of claim 30 , wherein flowing the first product stream to use in capturing the carbon dioxide from the air comprises flowing the first product stream from the alkaline regeneration compartment of the electrochemical cell.
34 . The method of claim 23 , wherein flowing the first product stream to use in capturing the carbon dioxide from the air comprises:
separating the first product stream into a hydrogen stream and into the CO2 capture solution; and
flowing the CO2 capture solution to use in capturing the carbon dioxide from the air.
35 . The method of claim 23 , wherein flowing the second product stream comprising the proton-shuttling species to react the proton-shuttling species with the portion of carbonate comprises:
separating the second product stream into an oxygen stream and into a proton-shuttling species stream; and
flowing the proton-shuttling species stream to react the proton-shuttling species with the portion of carbonate.
36 . The method of claim 26 , wherein crystallizing the portion of the carbonate comprises crystallizing the portion of carbonate to form a mother liquor, the method comprising:
combining at least a portion of the mother liquor with at least a portion of the CO 2 capture solution for use in the capturing of carbon dioxide from the air with the CO 2 capture solution.