CaO含量对高钠煤灰熔融特性的影响

为研究CaO含量对高钠煤灰熔融特性的影响,配制了不同CaO含量的高钠合成灰并对灰熔融温度(AFTs)进行了测试,利用Fact Sage 7.0提供的热力学数据库对灰熔融过程进行了模拟,分析不同CaO含量的高钠合成灰的矿物质变化,利用X射线衍射(XRD)、扫描电子显微镜(SEM)对合成灰的矿物质组成及微观形貌进行了研究。结果表明,随着CaO含量的增加,灰熔融温度先降低后提高。添加CaO同时影响含钙矿物质与含钠矿物质的存在形式与相对含量。在1 000℃下,含钙矿物质由钙长石依次转化为钙铁榴石、硅灰石、钙黄长石、硅钙石和原硅酸钙,含钠矿物质由钠长石转化为霞石。二元相图和似三元相图的结果表明,液相线温度随CaO含量的变化趋势与灰熔融温度相同。对本研究中的煤种,当CaO含量高于40%时,可以有效提高灰熔融温度。

Effect of CaO content on the ash fusibility of high sodium coal

In order to study effect of CaO content on the ash fusibility of high sodium coal, high sodium synthetic coal ash samples with different CaO content were prepared and ash fusion temperatures (AFTs) were measured. Thermodynamic database FactSage 7.0 was applied to simulate the ash melting process, and the mineral conversion was analyzed. The minerals' composition and surface morphology of synthetic coal ash samples were investigated by X-ray diffraction (XRD) and scanning electronic microscope (SEM). The results show that the AFTs drop first and rise later with the increase of CaO content. CaO addition influences the existence form and relative mass of both calcium-containing and sodium-containing minerals. At 1 000℃, the calcium-containing minerals transform from anorthite to andradite, wollastonite, gehlenite, rankinite and larnite in turn. The sodium-containing minerals transform from albite to nepheline. The results of binary phase diagram and analogous ternary phase diagram indicate that variation of liquidus temperature is consistent with the AFTs with increasing CaO content. When the CaO content is higher than 40%, the AFTs could be improved efficiently for the coal sample.