颗粒的双极带电与气固流化床中的静电分布  

Bipolar charging of dielectric powder and electrostatic potential distribution in gas-solid fluidized beds

作　　者：王芳[1] 徐怡[1] 于恒修[1,2] 王靖岱[1] 阳永荣[1] 

机构地区：[1]浙江大学化学工程国家重点联合实验室聚合反应工程实验室,浙江杭州310027 [2]中石化长岭分公司军事代表室,湖南岳阳414012

出　　处：《浙江大学学报（工学版）》2008年第12期2166-2171,共6页Journal of Zhejiang University：Engineering Science

基　　金：国家自然科学基金资助项目(20490205)

摘　　要：对颗粒的双极带电现象和气固流化床中的静电分布进行了理论分析和实验研究.推导出了小颗粒上电荷量的计算公式,指出大小颗粒的带电极性由颗粒表面上的电荷载流子类型决定,若绝缘颗粒表面上的电荷载流子为电子或阴离子,则大颗粒带正电,小颗粒带负电;反之大颗粒带负电,小颗粒带正电.在150 mm的有机玻璃流化床冷模装置中,以干燥氮气为流化气体,对LLDPE、HDPE、PP1、PP2和PVC等5种聚合物粉料系统,测量了不同气速下流化床中不同床高处的静电压值.结果发现床内的静电场为非均匀电场,静电压沿床层轴向呈"Z"型或"S"型分布,且在床层稀密相分界面附近会发生极性的改变,实验验证了颗粒的双极带电理论.Theoretical analysis and experimental research on bipolar charging phenomena and electrostatic potential distribution in gas-solid fluidized beds were carried out. A formula for computing the charges on small particles was derived, and it was proposed that the sign of charge on particles is dependent on the type of transferable charge carriers residing on the surface of particles. If transferable charge carriers are electrons or negative ion, coarse particles charge positively, and small particles charge negatively. While charge carriers are positive ions, coarse particles charge negatively, and small particles charge positively. By measuring the electrostatic potential at different bed heights, electrostatic characteristics in PMMA gas- solid fluidized bed for five different kinds of polymer powder （LLDPE, HDPE, PP1,PP2 and PVC） were studied, and it was found that the electric field inside the bed is non-uniform. The axial profiles of potential are Z-shaped or S-shaped, and the voltage polarity will reverse near the interface between dense and dilute phases. Theory of particle bipolar charging was further validated through experimental results.

关 键 词：气固流化床 静电分布 摩擦起电 双极带电 

分 类 号：TQ021.8[化学工程]