基于共面电容原理的煤炭灰渣介电特性实验研究

doi:10.11949/0438-1157.20230339

摘要/Abstract

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

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

中图分类号:

TK 39

张孟斌, 李锐, 张嘉杰, 马素霞, 张建胜. 基于共面电容原理的煤炭灰渣介电特性实验研究[J]. 化工学报, 2023, 74(7): 3028-3037.

Mengbin ZHANG, Rui LI, Jiajie ZHANG, Suxia MA, Jiansheng ZHANG. Experimental study on dielectric properties of coal ash based on coplanar capacitance principle[J]. CIESC Journal, 2023, 74(7): 3028-3037.

图/表 17

图1 共面电容传感器

Fig.1 Coplanar capacitance sensor

图2 实验系统图

Fig.2 Schematic diagram of experimental system

表1 灰渣样品组分

Table 1 Components of ash sample

灰样	SiO₂/% (质量)	Al₂O₃/% (质量)	CaO/% (质量)	Fe₂O₃/% (质量)	MgO/% (质量)
#1	38.56	15.03	20.08	19.29	7.04
#2	17.86	35.73	20.08	19.29	7.04
#3	43.85	9.74	20.08	19.29	7.04
#4	43.00	16.76	22.39	10.00	7.85
#5	33.43	13.04	17.42	30.00	6.11
#6	43.42	16.93	10.00	21.72	7.93
#7	33.77	13.16	30.00	16.90	6.17

图3 基准渣的电容特性曲线

Fig.3 Capacitance characteristic curve of reference ash

图4 淬冷基准渣的介电常数随测试频率的变化曲线

Fig.4 Variation of dielectric constant of quenched reference ash with test frequency

图5 淬冷基准渣的XRD谱图1—石英 (SiO2); 2—赤铁矿(Fe2O3); 3—方镁石(MgO); 4—镁铁尖晶石(MgFe2O4); 5—镁硅钙石[Ca3Mg(SiO4)2]

Fig.5 XRD patterns of quenched reference ash

图6 基准渣的复阻抗谱

Fig.6 Complex impedance spectrum of reference ash

图7 淬冷基准渣的SEM图像

Fig.7 SEM images of quenched reference ash

图8 Si/Al对灰渣电容及介电常数的影响

Fig.8 Effect of Si/Al on capacitance and dielectric constant of ash

图9 不同Si/Al淬冷灰渣的XRD谱图1—石英(SiO2); 2—赤铁矿(Fe2O3); 3—方镁石(MgO); 4—镁铁尖晶石(MgFe2O4); 5—镁硅钙石[Ca3Mg(SiO4)2]

Fig.9 XRD patterns of quenched ash with different Si/Al

图10 不同Si/Al淬冷灰渣的SEM图像(1200℃)

Fig.10 SEM images of quenched ash with different Si/Al (1200℃)

图11 Fe2O3比例对灰渣电容及介电常数的影响

Fig.11 Effect of Fe2O3 ratio on capacitance and dielectric constant of ash

图12 不同Fe2O3比例淬冷灰渣的XRD谱图1—石英(SiO2); 2—赤铁矿(Fe2O3); 3—方镁石(MgO); 4—镁铁尖晶石(MgFe2O4); 5—镁硅钙石[Ca3Mg(SiO4)2]

Fig.12 XRD patterns of ash with different Fe2O3 ratios

图13 不同Fe2O3比例淬冷灰渣的SEM图像(1200℃)

Fig.13 SEM images of quenched ash with different Fe2O3 ratios (1200℃)

图14 CaO比例对灰渣电容及介电常数的影响

Fig.14 Effect of CaO ratio on capacitance and dielectric constant of ash

图15 不同CaO比例淬冷灰渣的XRD谱图1—石英(SiO2); 2—赤铁矿(Fe2O3); 3—方镁石(MgO); 4—镁铁尖晶石(MgFe2O4); 5—镁硅钙石[Ca3Mg(SiO4)2]; 6—透辉石(CaMgSi2O6); 7—钙铝黄长石(Ca2Al2SiO7)

Fig.15 XRD patterns of quenched ash with different CaO ratios

图16 不同CaO比例淬冷灰渣的SEM图像(1200℃)

Fig.16 SEM images of quenched ash with different CaO ratios(1200℃)

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