用XPS研究高灰熔融温度煤灰的矿物结构转化

Study of Mineral Structure Transformation of Coal Ash with High Ash Melting Temperature by XPS

高灰熔点X煤通过添加钙镁复配(WCaO/WMgO=1)助熔剂降低灰熔点,在模拟煤气化过程中制备灰渣,用X射线光电子能谱(XPS)分析不同温度点灰渣中O,Si,Al,Ca,Mg的存在形态及演化过程。认为钙镁复配助熔剂降低灰熔点主要是作用在硅、铝、氧结构变化上,表现为铝元素结构中铝氧配位方式的变化,即四配位的铝氧四面体[AlO_4]和六配位的铝氧八面体[AlO_6]随温度的变化而变化;硅元素结构中SiO_2链的破坏,Ca^(2+)和Mg^(2+)加入会破坏SiO_2链,使得桥氧硅变为非桥氧硅;以及氧元素结构中桥氧键断裂和非桥氧键形成。结合Factsage热力学分析软件,分析了添加钙镁复配助熔剂后,煤灰渣的高温相平衡组成,从矿物的结构变化研究助熔剂的助熔机理。结果表明,添加钙镁复配助熔剂后,Ca^(2+)和Mg^(2+)易与硅氧和铝氧四面体以及铝氧八面体中非桥氧键结合,生成低熔点的长石类矿物和镁质矿物,从而降低煤灰熔融温度。

The ash melting temperature of X coal with high ash melting temperature was reduced by adding calcium-magnesium compound flux（WCaO/W MgO=1）.In the process of simulated coal gasification,the ash and slag were prepared,and the existence form and evolution process of oxygen,silicon,aluminum,calcium,magnesium at different temperature were analyzed by X-ray photoelectron spectroscopy（XPS）.Calcium-magnesium compound flux can reduce ash melting temperature and mainly affect structure change of silicon,aluminum and oxygen.The change of the coordination mode of aluminum and oxygen was shown,namely aluminum-oxide tetrahedrons[AlO4]and aluminum-oxide tetrahedrons[AlO6]varied with temperature changes.The addition of Ca^2＋and Mg^2＋can destroy the silica chain,making bridging oxygen silicon change into non bridge oxygen silicon;Bridged oxygen bond fracture was broken and non bridging oxygen bond was formed in oxygen element structure.Combined with the Factsage thermodynamic analysis software,the high temperature phase equilibrium composition of coal ash was analyzed after adding calcium-magnesium compound flux,and the fluxing mechanism of flux was studied from the change of mineral structure.The results showed that Ca^2＋and Mg^2＋were easy to combine with the non bridging oxygen bonds in the silicon-oxide and aluminum-oxide tetrahedrons and aluminum-oxide octahedrons to produce low melting temperature feldspar minerals and magnesia minerals.Therefore the ash melting temperatures were reduced.