Quantitative effects of physical encapsulation during carbonation process based on scaled up simulation of fly ash particles

• Published in: Journal of the Energy Institute Vol. 115; p. 101679
• Main Authors: Yuan, Qixin, Lu, Hairong, Guo, Xuemao, Ma, Suxia
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-08-2024
• Subjects: Carbonation; Coal fly ash; Heavy metal stabilization; Physical containment; Quantitative analysis; Coal fly ash; Heavy metal stabilization; Carbonation; Physical containment; Quantitative analysis
• ISSN: 1743-9671
• DOI: 10.1016/j.joei.2024.101679

Accelerated carbonation of fly ash can effectively stabilize heavy metals. The mechanism can be divided into physical stabilization and chemical stabilization. However, the effect of the mechanisms has not been quantitatively studied at present. In order to exclude the influence of other substances, smooth and non-porous CaO spheres which simulated fly ash particles were used to research the mechanism. After carbonation, CaO spheres were encapsulated by CaCO3, and physical containment played a major role. 1h carbonation experiment showed that the maximum physical stabilization effect on Pb and Zn was 12.90 % and 17.41 %. With the increase of carbonation time, the thickness of CaCO3 could promote the solidification of heavy metals. Then carbonation experiments were carried out on fly ash. Effect of physical containment on stabilizing heavy metals was eliminated by ball milling to crush carbonate shell. Quantitative effects of physical stabilization on Pb and Zn are 8.61 % and 7.68 %, and quantitative effects of chemical stabilization on Pb and Zn are 70.48 % and 61.94 %. Chemical stabilization plays a major role, because fly ash has many pores, and CO2 can diffuse in and react with internal heavy metals. And the content of CaO in fly ash is small, which is not enough to encapsulate particles. Increasing the CaO content in fly ash can effectively reduce the leaching of heavy metals, indicating that composition in fly ash play an important role in carbonation.
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•The formation process of carbonate layers has been revealed.•Quantitative impact of physical encapsulation is calculated.•Chemical stabilization plays a major role because of many pores in fly ash.