Separation of alumina and silica from metakaolinite by reduction roasting-alkaline leaching process: Effect of CaSO_(4) and CaO  

还原焙烧-碱浸工艺实现偏高岭石中氧化铝和氧化硅的分离:CaSO_(4)和CaO的影响

作　　者：Hong-yang WANG Xiao-xue ZHANG Si-yuan YANG Cheng LIU Li-qun LUO 王洪阳;张晓雪;杨思原;刘诚;罗立群(武汉理工大学资源与环境工程学院,武汉430070;武汉理工大学矿物资源加工与环境湖北省重点实验室,武汉430070)

机构地区：[1]School of Resources and Environmental Engineering,Wuhan University of Technology,Wuhan 430070,China [2]Hubei Key Laboratory of Mineral Resources Processing and Environment,Wuhan University of Technology,Wuhan 430070,China

出　　处：《Transactions of Nonferrous Metals Society of China》2022年第3期999-1009,共11页中国有色金属学报（英文版）

基　　金：the financial supports from the National Natural Science Foundation of China (Nos. 52004194, 51874219);the China Postdoctoral Science Foundation (No. 2019M662733)。

摘　　要：Limestone(CaCO3),which could promote sulfur fixation,was added to coal gangue during roasting in a circulating fluidized bed(CFB)boiler.CaO and CaSO_(4) were the main Ca-bearing minerals while metakaolinite was the major Al-bearing mineral in CFB slag.The effect of CaSO_(4) and CaO on the separation of alumina and silica from metakaolinite by reduction roasting−alkaline leaching process was studied.Results showed that metakaolinite was completely converted into hercynite and silica solid solutions(i.e.,quartz and cristobalite solid solutions)by reduction roasting with hematite.More than 95%of silica in the reduced specimen was removed by alkaline leaching.The addition of CaSO_(4) and CaO remarkably decreased the separation efficiency of alumina and silica in metakaolinite,which could be attributed to the formation of Si-bearing minerals:(1)Fayalite and anorthite were formed during the reduction roasting process;(2)Fayalite was stable while anorthite was converted into sodalite and wollastonite during the alkaline leaching process.This study demonstrates that sulfur in coal gangue should be fixed by treating the exhaust gas instead of controlling the combustion process of CFB to achieve the comprehensive recovery of silica and alumina from the CFB slag.采用循环流化床技术处理高铝煤矸石时会添加石灰石以起到固硫作用。此时,循环流化床渣中的主要含钙矿物为CaO和CaSO_(4),含铝矿物为偏高岭石。研究CaSO_(4)和CaO对还原焙烧−碱浸工艺实现偏高岭石中氧化铝和氧化硅分离的影响。结果表明,添加氧化铁还原焙烧可将偏高岭石完全转变为铝酸亚铁和二氧化硅固溶体(石英固溶体和方石英固溶体)。随后经碱浸可脱除还原焙烧产物中95%以上的二氧化硅。CaSO_(4)和CaO的添加可显著降低偏高岭石中氧化铝和氧化硅的分离效率,其主要原因为含硅物相的形成:(1)还原焙烧过程中生成铁橄榄石和钙长石;(2)碱浸过程中铁橄榄石稳定存在,而钙长石转变为方钠石和硅灰石。为实现循环流化床渣中氧化铝和氧化硅的综合提取,高铝煤矸石中的硫应该在烟气中进行脱除,而不适于在循环流化床燃烧过程中进行钙化固定。

关 键 词：circulating fluidized bed slag METAKAOLINITE Ca-bearing minerals reduction roasting alkaline leaching 

分 类 号：TD849.5[矿业工程—煤矿开采]