A new understanding of electric conduction in highly resistive dusts and bulk powders
A new understanding of electric conduction in highly resistive dusts and bulk powders
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DOI：
10.1016/j.powtec.2016.02.031
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发表时间：
2016-06
影响因子：
5.2
通讯作者：
Yury Aleksin;Alpesh Laxman Vora;U. Riebel
中科院分区：
文献类型：
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作者：
Yury Aleksin;Alpesh Laxman Vora;U. Riebel
从理论和实验两方面研究了高阻粉尘和颗粒材料的电学性质和电流输运机制，高阻粉尘具有明显的非欧姆特性，类似于半导体和驻极体材料。粉尘层的电阻率显示出非常强的时间效应，并且强烈依赖于粉尘层厚度、电流密度以及实验布置。电流传输通过注入两个极性的过量电荷而发生。对于不对称布置（例如，通过电晕充电），不对称注入导致高的过量电荷密度并引起强静电场。发现非对称注入布置测得的粉尘电阻率比对称注入布置测得的电阻率高几个数量级。粉尘电阻率对层厚和电流密度的依赖关系可以用类似于半导体和驻极体理论的空间电荷限制电流来解释。基于驻极体和半导体理论，建立了粉尘层中电流传输的模拟模型。该模型使用有效介质方法，因此可以通过文献中找到的均质材料的参考模拟进行验证。通过对动力学参数的经验调整，连续介质模型可以很好地描述多孔粉尘层的实验结果，但目前的实验验证仅限于理想情况，没有考虑吸附层的影响.尽管如此，研究结果使人们对静电除尘器中的反电晕效应有了新的认识。
The electric properties and current transport mechanisms in highly resistive dusts and granular materials are investigated both by theory and by experiments.Highly resistive dusts show markedly non-ohmic properties in analogy to semiconductor and electret materials. The resistivity of dust layers shows extremely strong time effects and is strongly dependent on the dust layer thickness, on current density and also on experimental arrangement. The current transport occurs by the injection of excess charges of both polarities. For asymmetric arrangements (e.g., charging by corona), asymmetric injection leads to high excess charge densities and induces strong electrostatic fields. Dust resistivity measured with asymmetric injection arrangement is found to be several orders of magnitude higher than resistivity measured with symmetric injection arrangement. The dependence of dust resistivity on layer thickness and current density can be explained as a result of space charge limited current in analogy to semiconductor and electret theory. Time effects are a result from charge carrier immobilization in combination with space charge limited conduction.Based on electret and semiconductor theory, a simulation model for current transport through dust layers was developed. The model uses an effective medium approach and therefore can be validated with reference simulations for homogeneous materials found in the literature. With an empirical adaptation of the kinetic parameters, the continuum approach seems to be well suited to describe the experimental results obtained with porous dust layers.So far, the experimental validation is limited to idealized situations and does not include effects from adsorption layers. Nevertheless, the results allow a new understanding of effects like back corona in electrostatic precipitators.