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Chemical formula for carbon dioxide11/24/2023 ![]() Regenerative carbon dioxide removal system This material offers considerable performance advantages although it requires high temperatures for the formation of carbonate to take place. In recent years lithium orthosilicate has attracted much attention towards CO 2capture, as well as energy storage. Lithium peroxide can also be used as it absorbs more CO 2 per unit weight with the added advantage of releasing oxygen. Lithium hydroxide may offer some safety and convenience benefits over the older calcium based products. Anesthesia machines which provide life support and inhaled agents during surgery typically employ a closed circuit necessitating the removal of carbon dioxide exhaled by the patient. Recently lithium hydroxide absorbent technology has been adapted for use in anesthesia machines. It reacts with carbon dioxide to form lithium carbonate. In particular, lithium hydroxide was used aboard spacecraft, such as in the Apollo program, to remove carbon dioxide from the atmosphere. Other strong bases such as soda lime, sodium hydroxide, potassium hydroxide, and lithium hydroxide are able to remove carbon dioxide by chemically reacting with it. Using water, it is a liquid/solid reaction as shown here:Ģ(s) ΔH° = -64.5 kJ/mol Lithium hydroxide Lime hydration is an exothermic reaction that can be performed with water or steam. Hydration of the lime (CaO) completes the cycle. The thermal decomposition of calcite is performed in a lime kiln fired with oxygen in order to avoid an additional gas separation step. The calcination reaction is the only endothermic reaction in the process and is shown here:ģ(s) → CaO(s) + CO 2(g) ΔH° = + 179.2 kJ/mol Subsequently, the calcium carbonate precipitate is filtered from solution and thermally decomposed to produce gaseous CO 2. The absorption reaction is a gas liquid reaction, strongly exothermic, here:Ĭausticization is performed ubiquitously in the pulp and paper industry and readily transfers 94% of the carbonate ions from the sodium to the calcium cation. įirst, CO 2 is absorbed by an alkaline NaOH solution to produce dissolved sodium carbonate. Zeman and Lackner outlined a specific method of air capture. ![]() Some thermal CO 2 capture systems use heat generated on-site, which reduces the inefficiencies resulting from off-site electricity production, but it still needs a source of (green) heat, which nuclear power or concentrated solar power could provide. Early incarnations of environmentally motivated CO 2 capture used electricity as the energy source and were therefore dependent on green energy. To prevent negating the environmental benefit of using electrolysis over the kiln method, the electricity should come from a renewable (or less emissive than the otherwise needed kiln) source. While simpler, this electrical process consumes more energy as electrolysis, also splits water. An alternative to this thermo-chemical process is an electrical one which releases the CO 2 through electrolyzing of the carbonate solution. With some modifications to the existing processes (mainly changing to an oxygen-fired kiln) the resulting exhaust becomes a concentrated stream of CO 2, ready for storage or use in fuels. The CO 2 is absorbed into such a solution, transfers to lime (via a process called causticization) and is released again through the use of a kiln. These usually involve using a variant of the Kraft process which may be based on sodium hydroxide. Various (cyclical) scrubbing processes have been proposed to remove CO 2 from the air or from flue gases and release them in a controlled environment, reverting the scrubbing agent. ![]() Molecular sieves also function in this capacity. Other minerals include serpentinite, a magnesium silicate hydroxide, and olivine. Carbon dioxide reacts with quicklime (calcium oxide) to form limestone ( calcium carbonate), in a process called carbonate looping. Most often, these minerals are oxides or hydroxides, and often the CO 2 is bound as carbonate. Several minerals and mineral-like materials reversibly bind CO 2. Cold solutions of these organic compounds bind CO 2, but the binding is reversed at higher temperatures:Īs of 2009, this technology has only been lightly implemented because of capital costs of installing the facility and the operating costs of utilizing it. Virtually the only technology being seriously evaluated involves the use of various amines, e.g. The primary application for CO 2 scrubbing is for removal of CO 2 from the exhaust of coal- and gas-fired power plants.
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