Detailed understanding of the mechanisms of the fast stage during CaO carbonation is important for the design of novel efficient CaO materials. This work systematically studies the formation of a CaCO 3 product layer on the outside surface of CaO grains during the fast reaction stage for carbon capture using two types of CaO adsorbents. The carbonation at 400 °C filled the small pores in the commercial CaO grains and no distinct product layer of CaCO 3 was observed. However, a distinct layer of CaCO 3 with a thickness around 90 nm was observed on the outside surface of the commercial CaO grains after the carbonation at 600 °C because the internal pores in the CaO grain had been filled and a layer of CaCO 3 product was deposited on the outside surface of the CaO grain. For sol-gel CaO, the carbonation reaction is limited by the availability of useful porosity for the growth of CaCO 3 product (confinement effect), instead of by the diffusion of ions in the critical layer of the CaCO 3 product. No surface product layer was observed. Therefore, fabricating nano-CaO having dimensions less than the critical thickness of the CaCO 3 layer (∼90 nm) is of potentially great significance if it can be done cheaply and in bulk.
ASJC Scopus subject areas
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)
Student thesis: Doctoral Thesis › Doctor of Philosophy