3).
In the next step the calcium carbonate is thermally decomposed in a classical Calciner at 900°C. This is like the production of lime or cement and releases carbon dioxide (CaCO
3 CaO + CO
2). Unlike classical calciners, the CO
2is not released into the atmosphere, but separated from the process gases. The resultant high purity CO
2 is available for utilisation or sequestration.
The remaining calcium oxide is hydrated in a steam slaker at 300°C (CaO + H
2O Ca(OH)
2), and the regenerated calcium hydroxide is fed back into the pellet reactor in step two above.
The specific energy demand varies, depending on the Calciner input energy method and operating temperature. The total specific energy is 1,850 kWh/Tonne of CO
Author credit – Stephen B. Harrison, Managing Director, sbh4 consulting
Various mechanical direct air capture (DAC) processes have been developed to simulate the action of plants and capture carbon dioxide (CO2) directly from the air. In the past decade tremendous amount of research has been undertaken to scale up and commercialise these technologies.
Carbyon from the Netherlands, a Spin-Off from TNO, has a highly innovative and potentially efficient DAC technology. The proposed process is derived from photovoltaic research. It is based on a porous thin-film which is coated with amine- and/or bicarbonate-based adsorbents.
The combination of this thin-film, which is only a few microns thick, and a porous medium could prove to be very energy efficient. The pressure-drop for the air to cross the thin, porous medium is very small and the thermal mass of the thin film is low. These factors result in a very low heat demand for the process to capture CO2.