Abstract:

Aiming at the demand of ash deposition monitoring in industrial boiler, the capacitance characteristics of ash at high temperature were tested based on the principle of coplanar capacitance. The phase structure and microstructure of quenched ash were analyzed by XRD and SEM, and the effects of temperature, frequency and composition on the dielectric properties of ash were analyzed by broadband dielectric spectrometer. The results show that with the increase of temperature (>700℃), magnesia-iron spinel is formed in the ash phase and the grain size increases gradually. The complex impedance spectrum of the ash conforms to the IBLC dielectric model, resulting in a gradual increase in the dielectric constant and test capacitance of the ash slag. The capacitance value of the reference slag at 1200℃ is about 282.0 times that of 700℃. The change of Si/Al has little effect on the dielectric properties of ash. With the increase of Fe₂O₃ content or the decrease of CaO content, the grain size in ash gradually increases, resulting in the increase of dielectric constant, so the test capacitance value increases.

Key words: coplanar capacitance, ash, particle size, dielectric constant, component

摘要：

针对工业锅炉灰渣沉积监测的需求，基于共面电容原理对煤炭灰渣在高温下的电容特性进行测试，通过XRD与SEM分析淬冷灰渣的物相结构与微观形貌，并结合宽频介电谱仪研究温度、频率、组分对灰渣介电性能的影响规律。结果表明，随着温度的升高（>700℃），灰渣物相中形成镁铁尖晶石且晶粒尺寸逐渐增大，灰渣复阻抗谱符合IBLC电介质模型，导致灰渣介电常数和测试电容值逐渐增大，基准渣在1200℃时的电容值约为700℃的282.0倍；Si/Al的变化对灰渣的介电性能影响不大，随着Fe₂O₃含量的增加或CaO含量的减小，灰渣中的晶粒尺寸逐渐增大，导致介电常数增加，因此测试电容值增大。

关键词: 共面电容, 灰渣, 颗粒尺寸, 介电常数, 组分