氧化硅添加剂对准东煤高钙飞灰物相热转化作用的差示扫描量热分析

Investigation of the Role of Silica Additive in Thermal Transformation of Zhundong Coal High-calcium Fly Ash by DSC

为研究氧化硅添加剂粒径和掺加比对防治准东煤结渣沾污的影响,使用差示扫描量热仪(differentialscanning calorimeter,DSC)研究准东煤高钙飞灰和2种不同粒径氧化硅的掺混样品的升温热流特征,并使用X射线衍射分析加热样品的物相变化。结果表明准东煤飞灰中含钙相的显著热转化和氧化硅添加剂的作用均发生在810℃以上温度,添加剂促进高钙飞灰加热产物的钙黄长石向钙长石转化。2000目氧化硅的防治效果比100目氧化硅的更好。硅灰比为1:9时2000目氧化硅可使飞灰DSC吸热谷温度延后50℃,有效地减缓飞灰熔融物质的生成,但是硅灰比增加到1:1时,其减缓飞灰生成熔融物质的效果并不更显著。工程上使用氧化硅添加剂防治准东煤的结渣沾污时,选择粒径小的添加剂可能比增加氧化硅的掺加量更有效。

In order to study the influence of the particle size and ratio of silica additive on the prevention and control of slagging and fouling of Zhundong coal,a differential scanning calorimeter(DSC)was used to measure blended samples of a Zhundong coal high-calcium fly ash with two different sizes of silica,and the heat flux characteristics were investigated during heating process.X-ray diffraction was used to analyze phase transformation of the heated samples.The results shows that the significant thermal transformation of the calciumcontaining phases in Zhundong coal fly ash and the effect of the silica additive both occur at temperatures above 810℃.The additive promoted the conversion of gehlenite in the high-calcium fly ash thermal product to anorthite.The prevention effect of 2000-mesh silica is better than that of 100-mesh silica.With a silica-ash ratio of 1:9,2000-mesh silica can delay the temperature at which the fly ash reaches the DSC endothermic valley by 50℃,effectively slowing down the formation of molten matter in fly ash.However,when the silica-ash ratio is increased to 1:1,the additive role in slowing the generation of fly ash molten material is not more significant.In engineering practice of using silicon oxide additives to prevent slagging and fouling of Zhundong coal,selecting additives with smaller particle size may be more effective than increasing the amount of additives.