Gist is to sorb acid-gas (like CO2) into a basic-solvent (e.g., aqueous monoethanolamine), then heat it up to release the acid-gas. Then the regenerated-solvent can be reused.
Making the process closed-loop may've been more of a focus around 1930. Before that, I think there were some patents showing open-loop designs (this is, designs where the solvent isn't regenerated-and-reused).
[Patent US1783901A](https://patents.google.com/patent/US1783901A/en ) (1930-ish) shows the basic closed-loop configuration that most folks build from.
Gist is to sorb acid-gas (like CO2) into a basic-solvent (e.g., aqueous monoethanolamine), then heat it up to release the acid-gas. Then the regenerated-solvent can be reused.
Making the process closed-loop may've been more of a focus around 1930. Before that, I think there were some patents showing open-loop designs (this is, designs where the solvent isn't regenerated-and-reused).