高温还原性气氛下钙镁助熔剂对莫来石熔融性的影响

Effects of Calcium and Magnesium Compound Flux on Meltability of Mullite in High Temperature Reducing Atmosphere

以莫来石为研究对象,向其中添加单助熔剂CaO,MgO和钙镁复配助熔剂,在模拟煤高温还原性气氛下,利用X-射线衍射仪研究了钙镁复合助熔剂对矿物转化的影响,借助FactSage热力学软件分析了添加钙镁复配助熔剂后灰渣在高温下的相平衡组成及矿物的组成含量变化,结合量子化学软件Material Studio 7.0对莫来石的建模优化,从分子水平揭示了钙镁复配助熔剂的助熔机理。结果表明:添加质量为莫来石质量20%的钙镁复配助熔剂(mCaO/mMgO=1)后,可将流动温度降至1 426℃,且助熔效果优于单助熔剂的助熔效果;莫来石熔融过程中,Ca^(2+)和Mg^(2+)易从莫来石晶格中的Al(6)—O(8)和Al(5)—O(7)两处进入铝氧八面体,引起硅酸盐结构重组,生成的低熔点长石类矿物和镁质矿物是钙镁复合助熔剂显著降低熔融温度的主要原因。

Taking mullite as the research object, adding single fluxes CaO, MgO and calcium-magnesium compound flux to study the mineral transformation of calcium-magnesium compound flux by X-ray diffraction spectroscopy in simulated high temperature reducing atmosphere of coal, with the help of thermodynamic software FactSage, the phase equilibrium composition and mineral composition change of ash at high temperature after adding calcium-magnesium compound flux were analyzed, combined with quantum chemistry software Material Studio 7.0 to optimize the modeling of mullite, from molecular level the fluxing mechanism of the calcium-magnesium compound flux was revealed. The results show that the addition of 20% calcium-magnesium compound flux ( m CaO / m MgO =1) can reduce the flow temperature to 1 426 ℃, and the fluxing effect is better than that of single flux;during the mullite melting process, Ca^2+ and Mg^2+ are easy to enter the silicon oxide and aluminum oxide tetrahedron, and the aluminum oxide octahedron causes the silicate structure to recombine. The low- melting feldspar minerals and magnesia minerals produced by the calcium- magnesium compound flux are the main reasons for the significant reduction of the melting temperature.