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Concept
Carbon dioxide scrubber
Résumé
A carbon dioxide scrubber is a piece of equipment that absorbs carbon dioxide (CO2). It is used to treat exhaust gases from industrial plants or from exhaled air in life support systems such as rebreathers or in spacecraft, submersible craft or airtight chambers. Carbon dioxide scrubbers are also used in controlled atmosphere (CA) storage. They have also been researched for carbon capture and storage as a means of combating climate change.
Amine gas treating
The primary application for CO2 scrubbing is for removal of CO2 from the exhaust of coal- and gas-fired power plants. Virtually the only technology being seriously evaluated involves the use of various amines, e.g. monoethanolamine. Cold solutions of these organic compounds bind CO2, but the binding is reversed at higher temperatures:
CO2 + 2 HOCH2CH2NH2 ↔ HOCH2CH2NH3+ + HOCH2CH2NHCO2−
this technology has only been lightly implemented because of capital costs of installing the facility and the operating costs of utilizing it.
Several minerals and mineral-like materials reversibly bind CO2. Most often, these minerals are oxides or hydroxides, and often the CO2 is bound as carbonate. Carbon dioxide reacts with quicklime (calcium oxide) to form limestone (calcium carbonate), in a process called carbonate looping. Other minerals include serpentinite, a magnesium silicate hydroxide, and olivine. Molecular sieves also function in this capacity.
Various (cyclical) scrubbing processes have been proposed to remove CO2 from the air or from flue gases and release them in a controlled environment, reverting the scrubbing agent. These usually involve using a variant of the Kraft process which may be based on sodium hydroxide. The CO2 is absorbed into such a solution, transfers to lime (via a process called causticization) and is released again through the use of a kiln. With some modifications to the existing processes (mainly changing to an oxygen-fired kiln) the resulting exhaust becomes a concentrated stream of CO2, ready for storage or use in fuels.
Source officielle
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