氯化钙焙烧法提取粉煤灰中的氧化铝

研究了以CaCl2为配料对粉煤灰进行焙烧活化,焙烧熟料水洗后,用硫酸溶液浸取以回收粉煤灰中氧化铝的方法,并考察了焙烧温度和时间、CaCl2加量、硫酸浓度和浸取时间等因素对氧化铝回收率的影响.采用添加CaCl2焙烧的方法,可高效率破坏粉煤灰中的刚玉和莫来石,生成能被无机酸分解的物相,如钙铝黄长石、硅铝酸钙等.结果表明,按CaCl2:粉煤灰=0.8的比例加入CaCl2,于900℃焙烧30min,熟料经水洗涤后,按照每g粉煤灰~30mmol硫酸的量加入1~4mol/L的硫酸溶液,常温浸取30min,氧化铝浸出率可达95%以上.

Extraction of alumina from coal fly ash by calcination with calcium chloride process

A method of recovery of alumina from coal fly ash (CFA) is reported in this article. The method includes activation of CFA by calcination with CaCl2, followed by washing with water to recover unreacted CaCl2 and leaching with sulfuric acid. The technological conditions which were considered to be key factors for the success of the procedure, including calcination temperature, calcination time, CaCl2 dosage, sulfuric acid concentration and leaching time, were investigated. The experimental results indicate that calcination with CaCl2 can effectively decompose the corundum and mullite particles, which can hardly be broken down by mineral acid leaching. When mixed with CaCl2 at a ratio of 0.8:1 (CaCl2:CFA) and the mixture calcined at 900℃ for 30min, the recovery of alumina can reach as high as >95% by sulfuric acid leaching.