Valverde J M, Quintanilla M A S, Espin M J, Castellanos A
Faculty of Physics, University of Seville, Avenida Reina Mercedes s/n, 41012 Seville, Spain.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Mar;77(3 Pt 1):031301. doi: 10.1103/PhysRevE.77.031301. Epub 2008 Mar 12.
Electrostatic charging of powders is a relevant phenomenon for a number of industrial applications. The design of new processes and the use of high resistivity materials and ultrafine powders may lead to higher charging rates and to higher levels of charge accumulation that can become a serious problem. In this work we investigate experimentally electrostatic charging in nanofluidization. The behavior of a fluidized bed of silica nanoparticles under the influence of an electrostatic field is studied. The electric field is applied in the horizontal direction and perpendicular to the gas flow. On one hand, we observe the influence of the electric field on the bulk behavior of the fluidized bed, which suffers a collapse when the electric field is turned on. For strong electric fields the stationary state of the fluidized bed reminds one of that of a spouted bed, with a solid layer adhered to the wall and a low density core region of local high gas velocity. On the other hand, and in order to gain additional insight, we look at the trajectories of nanoparticle agglomerates as affected by the electric field. This images analysis reveals that these agglomerates are horizontally deflected towards the wall as a consequence of being charged. From the analysis of agglomerate trajectories the charge per agglomerate is estimated. Using these measurements the electrostatic forces between agglomerates are calculated and compared to van der Waals attractive forces.
粉末的静电充电是许多工业应用中的一个相关现象。新工艺的设计以及高电阻率材料和超细粉末的使用可能导致更高的充电速率和更高的电荷积累水平，这可能成为一个严重问题。在这项工作中，我们对纳米流化中的静电充电进行了实验研究。研究了二氧化硅纳米颗粒流化床在静电场影响下的行为。电场沿水平方向施加且垂直于气流。一方面，我们观察电场对流化床整体行为的影响，当电场开启时，流化床会发生坍塌。对于强电场，流化床的稳态让人联想到喷动床的稳态，有一层固体附着在壁上，还有一个局部高气体速度的低密度核心区域。另一方面，为了获得更多见解，我们观察了受电场影响的纳米颗粒团聚体的轨迹。这种图像分析表明，这些团聚体由于带电而水平偏向壁面。通过对团聚体轨迹的分析，估算了每个团聚体的电荷量。利用这些测量结果，计算了团聚体之间的静电力，并与范德华吸引力进行了比较。
