煤灰熔融特性与灰成分之间关系的矿物变化研究

通过在一种真实煤灰中添加不同的氧化物或直接用氧化物配制合成灰,探究了不同灰成分对灰熔融特性的影响规律。利用Fact Sage 7.0对不同灰分的熔融过程进行了热力学模拟,通过熔融过程中的矿物质变化为各种灰成分对熔融特性的影响规律提供理论依据。结果表明,氧化钠对灰熔点的降低作用源于钠长石和霞石对钙长石的取代;氧化镁含量的增加对灰熔点起先降低后升高的作用,当氧化镁含量超过一定时,产生的镁橄榄石能够升高灰熔点;硫对灰熔点的升高作用源于镁橄榄石和硫酸钙对透辉石的取代;氧化钙含量的增加对灰熔点起到先降低后升高的作用,当氧化钙含量超过一定时,硅从熔点较低的矿物质迁移到熔点较高的矿物质中,升高了灰熔点。在与硅氧单元体结合的过程中,氧化钠优先于氧化钙;与氧化钙和硅氧单元体结合的氧化物的优先级为:氧化铝氧化镁氧化铁。

Relationship between coal ash fusibility and ash composition in terms of mineral changes

Coal ash and synthetic ash samples were used to detect effect of different ash components on ash fusion temperatures (AFTs). Thermodynamic database FactSage 7.0 was applied to simulate the melting process of ashes with different compositions, in order to provide theoretical basis for effect of ash components on ash fusibility. The reducing effect of Na₂O on AFTs is due to the replacement of anorthite by albite and nepheline. The increasing content of MgO can initially lower and then raise the AFTs. When MgO exceeds certain content, forsterite is generated and raise the AFTs. The raising effect of sulfur on AFTs is due to the replacement of diopside by forsterite and calcium sulfate. The increasing content of CaO can also initially lower and then raise the AFTs. When CaO exceeds certain level, Si migrates from minerals with low melting points to those with higher melting points, thus raising the AFTs. Na₂O is prior to CaO when being bound with silica-oxygen units to form minerals. The priority order of the oxides when being bound with CaO and silica-oxygen units is: Al₂O₃ > MgO > Fe₂O₃.