CO2 capture of limestone modified by hydration–dehydration technology for carbonation/calcination looping

The hydration–dehydration technique was used to improve the cyclic performance of calcined natural limestone to make it highly suitable for carbonation/calcination looping. The modified CaO-based sorbents were tested for their cyclic carbonation behavior in a fixed bed reactor. Their morphology, pore structure and phase composition before and after carbonation/calcination cycles were determined by scanning electron microscopy, nitrogen adsorption, and X-ray diffraction. The modified sorbents exhibited significantly higher CO2 uptake than the calcined limestone under the same experimental conditions. The characterization results indicated that this synthesis offered a new calcium oxide with less crystallinity, greater porosity and higher surface area, which was the main contributor to enhance the reactivity of modified sorbents. Moreover, after the spent sorbents modified with hydration–dehydration technique again, the sorbents recovered their cyclic activity, which was also confirmed by XRD spectrum, nitrogen physisorption analyses and SEM analyses. These results showed that, with periodic hydration–dehydration steps, CaO-based sorbents can be used for extended times in CO2 looping cycles.

► The hydration–dehydration technique was used to improve the durability of limestone.
► This synthesis offered a CaO with less crystallinity and higher surface area.
► The modified sorbents exhibited significantly higher CO2 uptake than original one.
► This synthesis also restored the CO2 capture activity of spent sorbent.