钙镁复合助熔剂对长平煤灰熔融特性影响研究

Effect of Calcium and Magnesium Compound Flux on Changping Coal Ash Fusibility

以高灰熔融温度长平煤为对象,分别向其中添加单助熔剂CaO、MgO和钙镁复合助熔剂,在高温还原性气氛下,分别利用X-射线衍射仪(XRD)、扫描电子显微镜-能谱仪(SEM-EDX)研究钙镁复合助熔剂对煤灰熔渣晶体矿物转化过程、微观形貌和微区化学组成的影响,揭示钙镁复合助熔剂的助熔机理。结果表明:添加6%钙镁复合助熔剂(WCaO/WMgO=1),可将煤灰熔融温度降至1297℃,且助熔效果优于单助熔剂CaO、MgO;煤灰熔融过程中,离子半径较小的Ca^(2+)、Mg^(2+)容易进入空隙中,引起硅酸盐结构重组,分别形成架状硅酸盐钙长石、岛状硅酸盐镁橄榄石、镁堇青石等;钙长石与镁橄榄石等镁质矿物之间低温共熔体的生成,是钙镁复合助熔剂能够显著降低煤灰熔融温度的主要原因。

Changping coal with high fusion temperature was selected, to which add CaO, MgO and compound flux. The mineral composition, surface morphology and micro-chemical composition were investigated under reducing atmosphere at high temperature by X-ray diffraction （XRD）, scanning electron microscopy and energy dispersive X-ray spectroscopy （SEM-EDX）, respectively. The results indicate that when the percentage of addition dosage of flux is 6% and the mass ratio of CaO to MgO is 1, the flow temperature of Changping coal ash could be reduced to 1297℃, and the efftce of improving fusibility is better than that of CaO and MgO supplementation alone respectively. In the coal ash melting process, Ca2＋ and Mg2＋ whose ionic radius is smaller could enter into interspace easilier, resulting in the structure of silicate reeombining, then framework silicate anorthite and island-like silicate such as magnesium olivine, magnesium cordierite are formed. The formation of low-temperature eutectie between anorthite and magnesium olivine is the primary reason for calcium and magnesium compound flux could reduce coal ash fusion temperature remarkly.