Molten salts help capture carbon at high temperatures

Molten salts are famend for working at excessive temperatures and are supreme as a brand new technology of carbon seize media.

There are numerous energy-intensive industries the place the greenhouse gasoline, carbon dioxide (CO₂), is generated at excessive temperatures and in concentrated kind. A few of these embody cement, metal, energy, bioenergy, waste toenergy, pulp and paper, and hydrogen. 

This begs the query: Why not capture these emissions on the supply of those elevated manufacturing temperatures slightly than cooling them right down to the place conventional, source-point seize strategies prevail?

To this finish, revolutionary analysis has resulted in a sequence of pioneering papers which have enabled the founding of a new company to develop this concept. The central science underpinning the know-how relies upon CO₂ seize in a course of that includes flowing industrial greenhouse gasoline emissions by molten salts, which perform because the absorbent working within the excessive temperature vary of 500-700°C.

Molten salts for CO₂ seize

Molten salts are famend for working on the excessive temperatures that exist inside boilers, kilns, and furnaces with makes use of that embody thermal storage, warmth switch, and thermal energy vegetation. They’re deemed supreme as a brand new technology of absorption media for the seize of CO₂ emissions of a sort that has not hitherto been potential.

With this background, it has been found that molten ionic sodium borates and lithium substituted variations are perfect for high-temperature CO₂ seize functions. Optimum supplies are chosen based mostly on present data of their section diagrams, which offer data on how their construction, composition, and stable and liquid properties fluctuate with temperature.

The favored molten salt know-how relies on sodium orthoborate (Na₃BO₃) — the sodium salt of boric acid. Its section diagram is comprised of sodium metaborate (NaBO₂) at one excessive and disodium oxide (Na₂O) on the different. With this data, a fascinating liquid composition and temperature vary for the molten salt absorbent might be tailor-made that avoids the low efficiency noticed with the stable and solid-liquid phases.

The chemistry chargeable for absorbing CO₂ by the molten salt within the proof-of-concept case of sodium orthoborate might be described by the response equation:

Na₃BO₃ + CO₂ → NaBO₂ + Na₂CO₃

This response might be reversed by purging the soften with steam to desorb the CO₂ and regenerate the sodium orthoborate feedstock. Pure CO₂ can then be obtained by condensing the steam.

A promising future for this carbon seize know-how

The reproducibility and sturdiness of the CO₂ absorption-desorption cycle was discovered to be excessive, with the spectacular capacity to seize over 99.9% of incoming CO₂. The system has been proven to perform even at CO₂ concentrations as little as 1%, albeit with lesser effectivity.

It is very important be aware that the business viability of the method advantages from the favorable availability and price of the sodium orthoborate feedstock absorbent at an industrially vital scale. Remarkably, the precursor for the feedstock is the plentiful ore of boron colemanite (Ca₂B₆O₁₁), which is quickly transformed to borax (Na₂B₄O₇) by boiling in an aqueous answer of sodium carbonate (Na₂CO₃).

Mineral hydrochloric acid remedy of the borax yields boric acid (B(OH)₃), which upon mixing with aqueous sodium hydroxide yields the specified sodium orthoborate feedstock at scale to be used within the excessive temperature CO₂ seize course of.

The potential for scaling and integrating molten salt_{seize know-how into fossil-intensive industries represents an thrilling paradigm shift within the quest to scale back their carbon footprints. Whereas a single technology shouldn’t be doubtless a panacea for the challenges of worldwide warming and local weather change, using plentiful, lost-cost molten salts supplies one other promising software within the arsenal of rising approaches to attain this aim.}  

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