CO₂ Sequestration by Indirect Carbonation of High-Calcium Coal Fly Ash

Abstract:

The use of coal fly ash for CO₂ sequestration has been proposed as a promising option for its utilization. However, research is quite necessary for advancing this technology. Indirect carbonation of high-calcium coal fly ash for CO₂ sequestration was investigated in this study. In these processes, calcium was first extracted from a high-calcium coal fly ash sample with NH₄Cl solution. The obtained leachate was subsequently carbonated by bubbling CO₂. It was shown that NH₄Cl could extract about 35% of the total calcium into the solution under the conditions investigated. The dissolution of calcium is nearly accomplished in half an hour. Further increasing the extraction solution temperature (10-90°C) and the concentration of NH₄Cl (0.5-3mol/L) only has subtle positive effects on the calcium extraction efficiency. The carbonation efficiency of the extraction leachate, namely the percentage of the calcium in the solution transformed into calcium carbonates is about 47%. The sharp drop in pH after bubbling CO₂ due to weak acid buffering capacity of the solution hinders the further precipitation of Ca²⁺. Calcium carbonate samples with a purity of up to 97% are obtained, meeting the purity requirements for industrial use.

• Periodical: Advanced Materials Research (Volumes 726-731)
• Pages: 2870-2874
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.726-731.2870
• Online since: August 2013
• Authors: Lan Lan He, Dun Xi Yu, Wei Zhi Lv, Jian Qun Wu, Ming Hou Xu
• Keywords: Ammonium Chloride, Carbonation Efficiency, CO₂ Sequestration, Coal Fly Ash, Extraction Efficiency

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