Direct capture of carbon dioxide from air via lime-based sorbents

Abstract

Direct air capture (DAC) is a developing technology for removing carbon dioxide (CO 2 ) from the atmosphere or from low-CO 2 -containing sources. In principle, it could be used to remove sufficient CO 2 from the atmosphere to compensate for hard-to-decarbonize sectors, such as aviation, or even for polishing gas streams containing relatively low CO 2 concentrations. In this paper, the performance of lime-based sorbents for CO 2 capture from air in a fixed bed was investigated. The effects of sorbent type, particle diameter, air flow rate, and relative humidity on the breakthrough time, breakthrough shape, and global reaction rate over a series of capture and regeneration cycles were examined. The greatest reaction rates and conversions were obtained when the sorbents were pre-hydrated and inlet air was humidified to 55% relative humidity. Humidifying the air alone leads to axial carbonation gradients since there is competition between CO 2 and water with the available CaO. Negligible conversion, over the duration of the experiment, is obtained in a dry system without pre-hydration and humid air. A shrinking-core gas-solid reaction model was fitted to the breakthrough curves in order to estimate the surface reaction and effective diffusion constants. Although the surface reaction constants of the two sorbents were similar, the pelletized limestone had a greater effective diffusivity due to its greater porosity. At mild calcination conditions with air at 850°C, the pelletized particles maintained their activity over nine carbonation-calcination cycles with a conversion drop of only 9% points. However, calcination under oxy-fuel conditions (CO 2 at 920°C) reduced the pellet carbonation conversion from 81 to 59% and pore surface area from 12.01 to 3.20 m 2 /g after only 4 cycles. This research clearly shows that DAC using lime-based

Towards Indicators for a Negative Emissions Climate Stabilisation Index: Problems and Prospects

“…Some store carbon in stocks that require maintenance to remain unoxidised. Others are more maintenance-free with more or less perpetual storage [12,14], see Table 1. To, for example, execute the full technology chain of BECCS and DACCS means that most of the carbon dioxide injected into suitable geological storage formations is stored permanently or for long periods of time.…”

“…For overviews of NETs, see, for example, IPCC [4], Fuss et al [19], Minx et al [12], and McLaren [20]. [12] with additions from Samari et al [14], Iordan et al [21], and Fuss et al [19].…”

Materials and techniques used for the “Vienna Moamin”: multianalytical investigation of a book about hunting with falcons from the thirteenth century

“…The detection of calcium carbonate (CaCO 3 ) by rFTIR and Raman on the parchment surface argues for the use of lime for dehairing of the skins, as residues of lime may react with atmospheric CO 2 to form CaCO 3 [ 17 ] and/or whitening of the parchment with chalk. The bands with maxima at 1450 cm −1 and 875 cm −1 in the absorption index spectra match with the IRUG reference calcite MP00108, and were assigned to ν 3 -asymmetric CO 3 stretching and ν 2 -asymmetric CO 3 deformation, respectively [ 18 ].…”

Investigation and Possibilities of Reuse of Carbon Dioxide Absorbent Used in Anesthesiology

“…In addition, calcium bicarbonate may be formed on the surface of the sorbent particles. The higher solubility of bicarbonate enhances CO 2 diffusion through the bulk of the particle [24]. Soda lime is exhausted when all hydroxides become carbonates.…”