A System for Electrochemically Releasing Carbon Dioxide Being Captured in an Aqueous Solution to a Hydrogen Gas Stream

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This invention presents a system that captures carbon dioxide (CO2) from the air or gas streams using an aqueous alkaline solution, and then electrochemically releases the captured CO2 into a hydrogen gas stream while regenerating the alkaline capture solution. The system comprises a contactor to absorb CO2, an electrochemical cell with anion-exchange membrane, dedicated compartments for chemical reactions, and mechanisms to recycle hydrogen and extract the enriched CO2/H2 gas mixture. This process enables the continuous capture and utilization of atmospheric CO2, efficiently enriching hydrogen streams with CO2 for further chemical processing (for example, methanol synthesis) using less energy than conventional methods.

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• Direct air capture of atmospheric CO2 for use in chemical synthesis plants.
• Supplying concentrated CO2 and H2 mixtures for catalytic production of synthetic fuels such as methanol or synthetic natural gas.
• Integration with renewable-powered electrolysis plants to create carbon-neutral fuel cycles for transportation or industry.
• Utilization in industrial CO2 capture and recycling systems, e.g., for power plants or chemical factories.
• Decarbonization of hard-to-abate industrial sectors by providing non-fossil carbon feedstocks.

BenefitsContent extracted from patent full text and abstract with AI.

• Reduces overall energy consumption needed for CO2 capture and release compared to traditional thermal methods.
• Enables direct enrichment of hydrogen streams with high-purity CO2, facilitating efficient downstream fuel synthesis.
• Regenerates the CO2 capture solution in-line, allowing for continuous operation with minimal additional resources.
• Operates at ambient conditions and can be powered by renewable electricity, making the process more sustainable.
• Flexible control over the ratio of H2 and CO2 in the output stream, adaptable to various synthetic fuel production processes.
• Potential for integration into existing industrial infrastructure and scalability due to modular design.

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Patent Abstract

The use of atmospheric CO2 as a chemical feedstock is a promising way to decarbonize the chemical and transportation sectors, which currently rely heavily on fossil fuels. This transition requires new technologies to reduce the energy required to capture and separate CO2.Here, the present invention discloses a system for capturing carbon dioxide in an aqueous alkaline solution and electrochemically releasing the captured carbon dioxide to a hydrogen-comprising gas stream while simultaneously regenerating the aqueous alkaline solution, said system comprising:a) a contactor unit (8) for bringing air (10) or another carbon dioxide comprising gas stream into contact with the aqueous alkaline solution (12) thereby capturing carbon dioxide by the at least partial transformation of the aqueous alkaline solution (12) into a carbonate and/or bicarbonate comprising solution (14);b) an electrochemical cell (16) comprising an anion-exchange membrane (18) and a cathode compartment (20) and an anode compartment (22), said anion-exchange membrane (20) separating the cathode compartment (20) from the anode compartment (22);c) a first feeder (24) that supplies the carbonate and/or bicarbonate comprising solution (14) to the cathode compartment (20) thereby enabling a hydrogen evolution reaction to take place in order to generate hydroxide ions thus regenerating the aqueous alkaline solution (12) and transporting carbonate anions through the anion-exchange membrane (18) to the anode compartment (22);d) a second feeder (26) that supplies a hydrogen comprising gas stream (28) to the anode compartment (22) thereby providing the anode as hydrogen depolarized anode thus evolving gaseous carbon dioxide; ande) an exhaust gas duct (30) to evacuate the hydrogen depleted and carbon dioxide enriched gas stream (6) from the anode compartment (22) for further processing of the components of the hydrogen depleted and carbon dioxide enriched gas stream (6), preferably of the carbon dioxide content therein.This system and the process executed herewith simultaneously regenerates the CO2 capture solution on the feed side while enriching a stream of H2 with CO2 on the permeate side of the cell. The present results show a high CO2 transport faradaic efficiency when supplying an alkaline solution, such as a pure K2CO3 solution, at current densities up to 60 mA/cm2. A small cathode gap benefites cell operation by preventing membrane transport of OH-, although with an increased ohmic resistance. This represents a step forward in the application of electrochemistry to drive processes that are critical to CO2 valorization.