铝土矿中明矾石的结晶形貌和熔融反应

Morphology and melting reaction of alunite in bauxite

为了探明豫西地区铝土矿的部分矿石煅烧时易胀裂的原因，借助于扫描电镜和能谱分析，确认了含K2O较多的豫西铝土矿中赋存明矾石，研究了其赋存状态及其在受热过程中的变化。明矾石的典型结晶形状显示为立方体，多在5μm以下，EDS分析测得化学组成（ω）范围为：Al2O3 43．4％～44．4％，SO3 44．6％～46．3％，K2O7．0％～8．8％，Na2O2．3％～3．4％。明矾石多呈不均态富集或与云母、高岭石呈共生结构，借助形貌特征易于分辨。铝土矿经1000℃3h热处理后，其中的明矾石熔融，形成玻璃相，经EDS分析显示，S元素消失殆尽，表明以SO3形式燃烧掉；但K元素尚存，构成了玻璃相的成分。经1200℃ 3h热处理后，明矾石完全熔融形成较稀薄的液相，从中析出细微的柱状刚玉，液相的典型组成（ω）为：Al2O3 47．7％，SiO2 43．8％，K2O 4．9％，TiO2 3．6％。含有明矾石的铝土矿经1400℃ 3h热处理后严重爆裂成碎片，是因硫的激剧燃烧所致。

In order to research the reason that some bauxite in the west of Henan Province is easy to spall during calcination,alunite crystallized in bauxite containing more K2O （ 〉 1% ,in mass,the same hereinafter） from the west of Henan Province was confirmed, and its crystallization state and its change during heating were researched by SEM and EDS. The typical alunite crystals are cubic and are smaller than 5 μm in size mostly. The chemical compositions of alunite determined by EDS are.Al2O3 43.4% -44.4%, SO3 44.6 % - 46.3 %, K2O 7.0% - 8.8 %, and Na2O 2.3 % - 3.4 %. Alunite is in uneven enrichment state or coexists with muscovite or kaolinite,which can be distinguished by their morphology features. When the bauxite is heated at 1 000℃ for 3 h,the alunite melts and forms glassy phase. EDS analysis shows that element sulfur disappears completely,which means it＇s burned out in the form of SO3 ,but element potassium dissolves in glassy phase. With temperature rising to 1 200℃ and soaking for 3 h,the alunite melts completely forming dilute glassy phase and from which small columnar corundum crystallizes. The typical compositions of the glassy phase are：Al2O3 47.7% ,SiO2 43.8% ,K2O 4.9% ,and TiO2 3.6%. When heated at 1 400 ℃ for 3 h,the bauxite containing alunite cracks into pieces seriously, which is resulted from the intense burning of sulfur.