中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 24 No. 4 April 2014 |
（1. Key Laboratory of Green Process and Engineering, Institute of Process Engineering,
Chinese Academy of Sciences, Beijing 100190, China;
2. College of Environmental Engineering, North China Institute of Science and Technology, Beijing 101601, China）
Abstract:To utilize CFBC Al-rich fly ash, a mild hydrochemical extraction process was investigated for recovery of alumina. An alumina extraction efficiency of 92.31% was attained using a 45% NaOH solution, an original caustic ratio (molar ratio of Na2O to Al2O3 in the sodium aluminate solution) of 25, a molar ratio of CaO to SiO2 in the fly ash of 1.1, a liquid volume to solid mass ratio of 9, a reaction temperature of 280 °C, and a residence time of 1 h when treating fly ash with an alumina to silica mass ratio (A/S) of 0.78 and an alumina content of 32.43%. Additionally, the alumina leaching mechanism was explored via structural and chemical analysis, which revealed that after alkaline digestion, the main solid phase containing silica was NaCaHSiO4 with a theoretical A/S of zero.
Key words: recovery of alumina; fly ash; phase transformation; circulating fluidized bed combustion (CFBC)
