Energy efficient removal of CO
A system has an alkaline capture stream as an input, an alkaline depleted stream as an output, a carbon dioxide removal unit operation having a return stream as an output, and a series of electrolyzers, each electrolyzer to receive a CO 2 -rich input stream and produce an acidified output stream that is more acidic than the CO 2 -rich input stream, and to receive a return stream and produce a basified output stream that is more alkaline than the input return stream. A method of removing carbon dioxide from an atmosphere and generating hydrogen includes capturing carbon dioxide from an atmosphere in an alkaline capture solution, sending the alkaline solution as a CO 2 -rich input solution to a series of electrolyzers in a CO 2 -rich path, removing carbon dioxide from the acidified CO 2 -rich solution at a removal unit to produce a CO 2 -poor solution, sending the CO 2 -poor solution to the series of electrolyzers in a return path, and returning the return solution to the alkaline capture stream. An electrolyzer is also discussed.
1. A system, comprising:
a carbon capture tower open to an atmosphere to capture CO 2 in a alkaline capture stream having a first pH, the carbon capture tower having an output configured to output the alkaline capture stream and an input configured to receive an alkaline depleted stream;
a carbon dioxide removal unit to remove carbon dioxide from a carbon dioxide unit input stream, the carbon dioxide removal unit having an input configured to receive the carbon dioxide unit input stream and an output configured to output a carbon dioxide unit output stream depleted of carbon dioxide, wherein the output stream is at second pH lower than the first pH; and
a series of electrolyzers, each electrolyzer having a first input configured to receive a CO 2 -rich input stream, a first output configured to output a CO 2 -rich output stream that is more acidic than the CO 2 -rich input stream, a second input configured to receive a CO 2 -poor input stream and a second output configured to output a CO 2 -poor output stream, each electrolyzer to apply a voltage to produce an output stream having a pH difference between the CO 2 -rich stream and the CO 2 -poor stream of less than 3 pH, wherein the series of electrolyzers comprises:
at least one electrolyzer connected to the carbon capture tower, the electrolyzer having an input configured to receive the alkaline capture stream as its CO 2 -rich input stream and an output configured to output its CO 2 -rich output stream to a next electrolyzer in the series;
at least one electrolyzer having the first input configured to receive its CO 2 -rich input stream from a previous electrolyzer in the series, the first output configured to send an acidified CO 2 -rich output stream to the carbon dioxide removal unit as the carbon dioxide unit input stream;
at least one electrolyzer connected to the carbon removal unit having the second input configured to receive the carbon dioxide removal unit output stream as its CO 2 -poor input stream, and the second output configured to output a basified CO 2 -poor output stream; and
at least one mixing vessel connected to at least the first output of the at least one electrolyzer.
2. The system of claim 1 , wherein the at least one electrolyzer connected to the carbon capture tower and the at least one electrolyzer connected to the carbon removal unit are the same electrolyzer.
3. The system of claim 1 , wherein the at least one electrolyzer connected to the carbon capture tower and the at least one electrolyzer connected to the carbon removal unit are different electrolyzers.
4. The system of claim 1 , further comprising at least one pump to provide pressure to the system, the pump comprising at least one of a system pump or an individual pump for each electrolyzer.
5. The system of claim 4 , wherein the at least one pump maintains a pressure in each electrolyzer greater than a desired partial pressure of carbon dioxide in each cell.
6. The system of claim 1 , wherein the electrolyzers contains at least one of either a cation exchange membrane or an anionic exchange membrane.
7. The system of claim 1 , wherein dissolved carbon in the alkaline capture stream is captured from one of ambient atmosphere, a mixture of gases, or an exhaust from a combustion process.
8. The system of claim 1 , further comprising at least one regenerator connected to at least one of the carbon dioxide removal unit input stream and the alkaline depleted stream.
9. The system of claim 1 , further comprising an oxygen-removal conduit connected to the electrolyzers in an initial flow.
10. The system of claim 1 , further comprising an electricity source for the electrolyzers comprising a renewable source of electricity.