Mg2+和Na+对高熔点煤灰熔融性的影响

以山西阳泉固庄高熔点煤灰为研究对象,通过向煤灰中添加不同量的MgO与Na₂CO₃,研究了Mg²⁺与Na⁺在高温下对煤灰熔融性的影响。研究结果表明,煤灰熔融温度随氧化镁的添加(5%~25%)单调下降;而随氧化钠添加(5%~25%)出现先降后升现象,在氧化钠添加量为15% 时,灰熔点达到最低。XRD分析表明,阳泉固庄煤灰熔融温度高(大于1 750℃)的原因是高温条件下耐熔矿物莫来石、方英石的存在。添加外加剂后,高温时外加剂与硅酸盐矿物反应,生成了更多的低共熔矿物霞石、堇青石等。同时,Mg²⁺和Na⁺的加入会使得非桥氧数量增多,高温煤灰低聚物增多,降低了煤灰的熔融温度。通过三元相图以及SEM分析,高温条件下煤灰中部分元素的富集以及团聚现象是导致Mg²⁺和Na⁺对煤灰熔融温度影响不同的原因。

Study on the effect of Mg2+ and Na+ on the fusibility of coal ash with high ash fusion point

Adjustment of coal ash fusibility of high fusion point coal has been attracted by attention of many researchers in coal gasification and combustion. The effect of Mg²⁺ and Na⁺ on the fusibility behavior of the high fusion temperature coal ash from Yangquan Guzhuang was studied in this paper, using the method of adding different amount of MgO and Na₂CO₃ (5%~25%) to the coal ash. The result shown that the ash fusion temperature monotonically decreases with increasing addition amount of MgO, while the ash fusion temperatures exhibit low valley and reach the minimum when the addition amount of Na₂CO₃ is 15%. Investigated by XRD, mullite and cristobalite are detected in the Yangquan Guzhuang coal ash, which results in the ash fusion temperature of the coal ash higher than 1 750℃. Additions reacting with silicate minerals can form more low-melting eutectic minerals, such as cordierite and nepheline, etc. Meanwhile, the additions of Mg²⁺ and Na⁺ cause non-bridged oxygen and oligomers increasing, then the ash fusion temperature reduce. Ternary phase diagram and SEM micrograph confirm that the local clustering of partial elements and reunited phenomenon of coal ash under high temperature condition result in the different effect of Mg²⁺ and Na⁺ on the coal ash fusibility behavior.